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Sample records for 2d bn nanostructures

  1. 2D nanostructures for water purification: graphene and beyond.

    PubMed

    Dervin, Saoirse; Dionysiou, Dionysios D; Pillai, Suresh C

    2016-08-18

    Owing to their atomically thin structure, large surface area and mechanical strength, 2D nanoporous materials are considered to be suitable alternatives for existing desalination and water purification membrane materials. Recent progress in the development of nanoporous graphene based materials has generated enormous potential for water purification technologies. Progress in the development of nanoporous graphene and graphene oxide (GO) membranes, the mechanism of graphene molecular sieve action, structural design, hydrophilic nature, mechanical strength and antifouling properties and the principal challenges associated with nanopore generation are discussed in detail. Subsequently, the recent applications and performance of newly developed 2D materials such as 2D boron nitride (BN) nanosheets, graphyne, molybdenum disulfide (MoS2), tungsten chalcogenides (WS2) and titanium carbide (Ti3C2Tx) are highlighted. In addition, the challenges affecting 2D nanostructures for water purification are highlighted and their applications in the water purification industry are discussed. Though only a few 2D materials have been explored so far for water treatment applications, this emerging field of research is set to attract a great deal of attention in the near future.

  2. 2D nanostructures for water purification: graphene and beyond.

    PubMed

    Dervin, Saoirse; Dionysiou, Dionysios D; Pillai, Suresh C

    2016-08-18

    Owing to their atomically thin structure, large surface area and mechanical strength, 2D nanoporous materials are considered to be suitable alternatives for existing desalination and water purification membrane materials. Recent progress in the development of nanoporous graphene based materials has generated enormous potential for water purification technologies. Progress in the development of nanoporous graphene and graphene oxide (GO) membranes, the mechanism of graphene molecular sieve action, structural design, hydrophilic nature, mechanical strength and antifouling properties and the principal challenges associated with nanopore generation are discussed in detail. Subsequently, the recent applications and performance of newly developed 2D materials such as 2D boron nitride (BN) nanosheets, graphyne, molybdenum disulfide (MoS2), tungsten chalcogenides (WS2) and titanium carbide (Ti3C2Tx) are highlighted. In addition, the challenges affecting 2D nanostructures for water purification are highlighted and their applications in the water purification industry are discussed. Though only a few 2D materials have been explored so far for water treatment applications, this emerging field of research is set to attract a great deal of attention in the near future. PMID:27506268

  3. Synthesis and processing of nanostructured BN and BN/Ti composites

    NASA Astrophysics Data System (ADS)

    Horvath, Robert Steven

    Superhard materials, such as cubic-BN, are widely used in machine tools, grinding wheels, and abrasives. Low density combined with high hardness makes c-BN and its composites attractive candidate materials for personnel and vehicular armor. However, improvements in toughness, and ballistic-impact performance, are needed to meet anticipated performance requirements. To achieve such improvements, we have targeted for development nanostructured c-BN, and its composites with Ti. Current research utilizes an experimental high pressure/high temperature (HPHT) method to produce these materials on a laboratory scale. Results from this work should transfer well into the industrial arena, utilizing high-tonnage presses used in the production of synthetic diamond and c-BN. Progress has been made in: (1) HPHT synthesis of cBN powder using Mg as catalyst; (2) HPHT consolidation of cBN powder to produce nanostructured cBN; (3) reactive-HPHT consolidation of mixed cBN/Ti powder to produce nanostructured Ti- or TiB2/TiN-bonded cBN; and (4) reactive-HPHT consolidation of mixed hBN/Ti powder to produce nanostructured Ti-bonded TiB2/TiN or TiB2/TiN. Even so, much remains to be done to lay a firm scientific foundation to enable the reproducible fabrication of large-area panels for armor applications. To this end, Rutgers has formed a partnership with a major producer of hard and superhard materials. The ability to produce hard and superhard nanostructured composites by reacting cBN or hBN with Ti under high pressure also enables multi-layered structures to be developed. Such structures may be designed to satisfy impedance-mismatch requirements for high performance armor, and possibly provide a multi-hit capability. A demonstration has been made of reactive-HPHT processing of multi-layered composites, consisting of alternating layers of superhard Ti-bonded cBN and tough Ti. It is noteworthy that the pressure requirements for processing Ti-bonded cBN, Ti-bonded TiB2/TiN, and their

  4. Raman 2D response of graphene in hBN sandwich as a function of doping

    NASA Astrophysics Data System (ADS)

    Wang, Xuanye; Christopher, Jason; Swan, Anna

    Graphene on SiO2 is plagued by accidental strain and charge doping which cause significant deterioration in electrical, thermal and optical properties. The stacking of Van der Waals layers can not only provide better properties, e.g., electrical mobility, but can also be used for novel interactions between layers. Here we use gated and contacted hBN-graphene-hBN heterostructures to calibrate the 2D Raman response to doping, particularly the low doping region less than 1 ×1012 cm-2 . This will enable the use of the correlation between Raman G and 2D band to determine effects from doping and strain or compression separately. The dielectric environment of hBN as compared to SiO2 affects the phonon dispersion and the Fermi velocity which results in approximately 7 cm-1 blue shift in 2D band per side of graphene contacted with hBN. Charge dependent Raman measurements of the G band provide the means to determine the electron-phonon coupling and the Fermi velocity for graphene in an hBN sandwich. NSF DMR 1411008.

  5. Thermally induced formation of 2D hexagonal BN nanoplates with tunable characteristics

    NASA Astrophysics Data System (ADS)

    Nersisyan, Hayk; Lee, Tae-Hyuk; Lee, Kap-Ho; Jeong, Seong-Uk; Kang, Kyung-Soo; Bae, Ki-Kwang; Lee, Jong-Hyeon

    2015-05-01

    We have investigated a thermally induced combustion route for preparing 2D hexagonal BN nanoplates from B2O3+(3+0.5k)Mg+kNH4Cl solid system, for k=1-4 interval. Temperature-time profiles recorded by thermocouples indicated the existence of two sequential exothermic processes in the combustion wave leading to the BN nanoplates formation. The resulting BN nanoplates were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy, PL spectrometry, and Brunauer-Emmett-Teller surface area analysis. It was found that B2O3 was converted into BN completely (by XRD) at 1450-1930 °C within tens of seconds in a single-step synthesis process. The BN prepared at a k=1-4 interval comprised well-shaped nanoplates with an average edge length ranging from 50 nm to several micrometer and thickness from 5 to 100 nm. The specific surface area of BN nanoplates was 13.7 g/m2 for k=2 and 28.4 m2/g for k=4.

  6. Thermally induced formation of 2D hexagonal BN nanoplates with tunable characteristics

    SciTech Connect

    Nersisyan, Hayk; Lee, Tae-Hyuk; Lee, Kap-Ho; Jeong, Seong-Uk; Kang, Kyung-Soo; Bae, Ki-Kwang; Lee, Jong-Hyeon

    2015-05-15

    We have investigated a thermally induced combustion route for preparing 2D hexagonal BN nanoplates from B{sub 2}O{sub 3}+(3+0.5k)Mg+kNH{sub 4}Cl solid system, for k=1–4 interval. Temperature–time profiles recorded by thermocouples indicated the existence of two sequential exothermic processes in the combustion wave leading to the BN nanoplates formation. The resulting BN nanoplates were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy, PL spectrometry, and Brunauer–Emmett–Teller surface area analysis. It was found that B{sub 2}O{sub 3} was converted into BN completely (by XRD) at 1450–1930 °C within tens of seconds in a single-step synthesis process. The BN prepared at a k=1–4 interval comprised well-shaped nanoplates with an average edge length ranging from 50 nm to several micrometer and thickness from 5 to 100 nm. The specific surface area of BN nanoplates was 13.7 g/m{sup 2} for k=2 and 28.4 m{sup 2}/g for k=4. - Graphical abstract: 2D hexagonal BN nanoplates with an average edge length ranging from 50 nm to several micrometer and thickness from 5 to 100 nm were prepared by combustion of B{sub 2}O{sub 3}+(3+0.5k)Mg+kNH{sub 4}Cl solid mixture in nitrogen atmosphere. - Highlights: • Thermally induced combustion route was developed for synthesizing BN nanoplates from B{sub 2}O{sub 3}. • Mg was used as reductive agent and NH{sub 4}Cl as an effective nitrogen source. • Temperature–time profiles and the combustion parameters were recorded and discussed. • BN with an average edge length from 50 nm to several micrometer and thickness from 5 to 100 nm were prepared. • Our study clarifies the formation mechanism of BN in the combustion wave.

  7. Morphology-driven nonwettability of nanostructured BN surfaces.

    PubMed

    Pakdel, Amir; Bando, Yoshio; Golberg, Dmitri

    2013-06-18

    Designing geometrical structures is an effective route to tailoring the wettability of a surface. BN-based hierarchical nano- and microstructures, in particular, vertically aligned and randomly distributed tubes and cones, were synthesized and employed as a platform for studying the influence of surface morphology on their static and dynamic interactions with water droplets. The variation of the contact angle in different hierarchical BN films is attributed to the combined effects of surface roughness and partial liquid-solid contact at the interface. Moreover, the impact response of water droplets impinging on BN arrays with different wetting properties is distinct. In the case of superhydrophobic films, the water droplet bounces off the surface several times whereas in less hydrophobic films it does not rebound and remains pinned to the surface. These results provide a facile route for the selective preparation of hierarchical BN nanostructure array films and a better understanding of their tunable water-repelling behavior, for which a number of promising applications in microelectronics and optics can be envisaged.

  8. Molecular Dynamics implementation of BN2D or 'Mercedes Benz' water model

    NASA Astrophysics Data System (ADS)

    Scukins, Arturs; Bardik, Vitaliy; Pavlov, Evgen; Nerukh, Dmitry

    2015-05-01

    Two-dimensional 'Mercedes Benz' (MB) or BN2D water model (Naim, 1971) is implemented in Molecular Dynamics. It is known that the MB model can capture abnormal properties of real water (high heat capacity, minima of pressure and isothermal compressibility, negative thermal expansion coefficient) (Silverstein et al., 1998). In this work formulas for calculating the thermodynamic, structural and dynamic properties in microcanonical (NVE) and isothermal-isobaric (NPT) ensembles for the model from Molecular Dynamics simulation are derived and verified against known Monte Carlo results. The convergence of the thermodynamic properties and the system's numerical stability are investigated. The results qualitatively reproduce the peculiarities of real water making the model a visually convenient tool that also requires less computational resources, thus allowing simulations of large (hydrodynamic scale) molecular systems. We provide the open source code written in C/C++ for the BN2D water model implementation using Molecular Dynamics.

  9. Nanostructured BN-Mg composites: features of interface bonding and mechanical properties.

    PubMed

    Kvashnin, Dmitry G; Krasheninnikov, Arkady V; Shtansky, Dmitry; Sorokin, Pavel B; Golberg, Dmitri

    2016-01-14

    Magnesium (Mg) is one of the lightest industrially used metals. However, wide applications of Mg-based components require a substantial enhancement of their mechanical characteristics. This can be achieved by introducing small particles or fibers into the metal matrix. Using first-principles calculations, we investigate the stability and mechanical properties of a nanocomposite made of magnesium reinforced with boron nitride (BN) nanostructures (BN nanotubes and BN monolayers). We show that boron vacancies at the BN/Mg interface lead to a substantial increase in BN/Mg bonding establishing an efficient route towards the development of BN/Mg composite materials with enhanced mechanical properties. PMID:26662205

  10. Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology

    PubMed Central

    Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr

    2016-01-01

    The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct “beyond graphene” domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials. PMID:26861346

  11. Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology.

    PubMed

    Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr

    2016-01-01

    The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct "beyond graphene" domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials.

  12. h-BN Nanosheets as 2D Substrates to Load 0D Fe3O4 Nanoparticles: A Hybrid Anode Material for Lithium-Ion Batteries.

    PubMed

    Duan, Zhi-Qiang; Liu, Yi-Tao; Xie, Xu-Ming; Ye, Xiong-Ying; Zhu, Xiao-Dong

    2016-03-18

    h-BN, as an isoelectronic analogue of graphene, has improved thermal mechanical properties. Moreover, the liquid-phase production of h-BN is greener since harmful oxidants/reductants are unnecessary. Here we report a novel hybrid architecture by employing h-BN nanosheets as 2D substrates to load 0D Fe3O4 nanoparticles, followed by phenol/formol carbonization to form a carbon coating. The resulting carbon-encapsulated h-BN@Fe3O4 hybrid architecture exhibits synergistic interactions: 1) The h-BN nanosheets act as flexible 2D substrates to accommodate the volume change of the Fe3O4 nanoparticles; 2) The Fe3O4 nanoparticles serve as active materials to contribute to a high specific capacity; and 3) The carbon coating not only protects the hybrid architecture from deformation but also keeps the whole electrode highly conductive. The synergistic interactions translate into significantly enhanced electrochemical performances, laying a basis for the development of superior hybrid anode materials. PMID:26833884

  13. Free-Standing 2-D Graphene Carbon Nanostructures

    NASA Astrophysics Data System (ADS)

    Holloway, Brian; Quinlan, Ronald; Hou, Kun

    2008-03-01

    Carbon nanosheets -- a new, free-standing, two-dimensional carbon nanostructure -- have been deposited on a metal, semiconductor, and insulating substrates by RF PECVD. Raman, SEM, TEM, SAED, XPS, AES, FTIR, and XRD all indicate that nanosheets are graphite sheets up to 8 μm in height but <=1 nm in edge thickness. The nanosheets stand off the growth substrate in a manner similar to aligned nanotubes grown by CVD. In contrast to nanotubes, nanosheets do not require catalyst for growth and can be patterned after deposition using standard lithographic techniques. Hydrogen etching promotes the formation of the atomically thin structures while the anisotropic dipole created in the graphene planes by the plasma sheath promotes the vertical orientation. Due to their uniform height and the large number of edge emission sites, nanosheets have proven to be excellent field emitters. Nanosheet samples have produced up to 33 mA of current (32 mm^2 sample area); similar nanosheet samples have sustained 1.3 mA of current over 200 hours of testing with no degradation.

  14. Role of 2-D periodic symmetrical nanostructures in improving efficiency of thin film solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Jiang, Liyong; Li, Xiangyin

    2016-01-01

    We systematically investigated several different nanostructures in crystalline silicon (c-Si) thin film solar cells and then proposed a brand-new structure with two dimensional (2-D) periodic dielectric cylinders on the top and annular metal columns on bottom surface to enhance the optical harvesting. The periodic symmetrical nanostructures affect the solar cell efficiency due to the grating diffraction effect of dielectric columns and surface plasmon polaritons (SPPs) effect induced by metal nanostructures at the dielectric-metal interface. About 52.1% more optical absorption and 33.3% more power conversion efficiency are obtained, and the maximum short current reaches to 33.24 mA/cm2.

  15. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways.

    PubMed

    Wang, Zenghui; Feng, Philip X-L

    2016-01-01

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout. PMID:27464908

  16. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways.

    PubMed

    Wang, Zenghui; Feng, Philip X-L

    2016-07-28

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout.

  17. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways

    NASA Astrophysics Data System (ADS)

    Wang, Zenghui; Feng, Philip X.-L.

    2016-07-01

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout.

  18. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways

    PubMed Central

    Wang, Zenghui; Feng, Philip X.-L.

    2016-01-01

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout. PMID:27464908

  19. Synthesis of tailored 2D SiC f/SiC ceramic matrix composites with BN/C interphase through ICVI

    NASA Astrophysics Data System (ADS)

    Udayakumar, A.; Raole, P. M.; Balasubramanian, M.

    2011-10-01

    Synthesis of 2D SiC f /SiC composites for applications in fusion reactors is a challenging task due to the stringent specification requirements on various mechanical and thermo-mechanical properties, chemical compatibility (with Pb-Li), oxidation resistance and irradiation resistance. Three types of SiC f/SiC composites with C interface and BN interface, with and without intermediate heat treatment are prepared through isothermal and isobaric chemical vapor infiltration process. Dense SiC seal coat applied to the composites has improved their oxidation resistance. The tensile, flexural and fracture toughness values of composite with BN interface were found to be improved by stabilizing the BN interface through thermal treatment. The electrical and thermal conductivity values obtained for composites with C interface are in the range of 10-29 S/m and 2.5-3.25 W/mK for the temperature range 500-900 °C as required for fusion reactor applications.

  20. Scalable synthesis of WS2 on graphene and h-BN: an all-2D platform for light-matter transduction

    NASA Astrophysics Data System (ADS)

    Rossi, Antonio; Büch, Holger; Di Rienzo, Carmine; Miseikis, Vaidotas; Convertino, Domenica; Al-Temimy, Ameer; Voliani, Valerio; Gemmi, Mauro; Piazza, Vincenzo; Coletti, Camilla

    2016-09-01

    By exhibiting a measurable bandgap and exotic valley physics, atomically thick tungsten disulfide (WS2) offers exciting prospects for optoelectronic applications. The synthesis of continuous WS2 films on other two-dimensional (2D) materials would greatly facilitate the implementation of novel all-2D photoactive devices. In this work we demonstrate the scalable growth of WS2 on graphene and hexagonal boron nitride (h-BN) via a chemical vapor deposition approach. Spectroscopic and microscopic analysis reveal that the film is bilayer-thick, with local monolayer inclusions. Photoluminescence measurements show a remarkable conservation of polarization at room temperature peaking 74% for the entire WS2 film. Furthermore, we present a scalable bottom-up approach for the design of photoconductive and photoemitting patterns. In memory of Carmine Di Rienzo, who passed away on 5 July 2016.

  1. A facile route for 3D aerogels from nanostructured 1D and 2D materials

    PubMed Central

    Jung, Sung Mi; Jung, Hyun Young; Dresselhaus, Mildred S.; Jung, Yung Joon; Kong, Jing

    2012-01-01

    Aerogels have numerous applications due to their high surface area and low densities. However, creating aerogels from a large variety of materials has remained an outstanding challenge. Here, we report a new methodology to enable aerogel production with a wide range of materials. The method is based on the assembly of anisotropic nano-objects (one-dimensional (1D) nanotubes, nanowires, or two-dimensional (2D) nanosheets) into a cross-linking network from their colloidal suspensions at the transition from the semi-dilute to the isotropic concentrated regime. The resultant aerogels have highly porous and ultrafine three-dimensional (3D) networks consisting of 1D (Ag, Si, MnO2, single-walled carbon nanotubes (SWNTs)) and 2D materials (MoS2, graphene, h-BN) with high surface areas, low densities, and high electrical conductivities. This method opens up a facile route for aerogel production with a wide variety of materials and tremendous opportunities for bio-scaffold, energy storage, thermoelectric, catalysis, and hydrogen storage applications. PMID:23152940

  2. A facile route for 3D aerogels from nanostructured 1D and 2D materials.

    PubMed

    Jung, Sung Mi; Jung, Hyun Young; Dresselhaus, Mildred S; Jung, Yung Joon; Kong, Jing

    2012-01-01

    Aerogels have numerous applications due to their high surface area and low densities. However, creating aerogels from a large variety of materials has remained an outstanding challenge. Here, we report a new methodology to enable aerogel production with a wide range of materials. The method is based on the assembly of anisotropic nano-objects (one-dimensional (1D) nanotubes, nanowires, or two-dimensional (2D) nanosheets) into a cross-linking network from their colloidal suspensions at the transition from the semi-dilute to the isotropic concentrated regime. The resultant aerogels have highly porous and ultrafine three-dimensional (3D) networks consisting of 1D (Ag, Si, MnO(2), single-walled carbon nanotubes (SWNTs)) and 2D materials (MoS(2), graphene, h-BN) with high surface areas, low densities, and high electrical conductivities. This method opens up a facile route for aerogel production with a wide variety of materials and tremendous opportunities for bio-scaffold, energy storage, thermoelectric, catalysis, and hydrogen storage applications.

  3. 2D Hybrid Nanostructure of Reduced Graphene Oxide-CdS Nanosheet for Enhanced Photocatalysis.

    PubMed

    Bera, Rajesh; Kundu, Simanta; Patra, Amitava

    2015-06-24

    Graphene-based hybrid nanostructures have recently emerged as a new class of functional materials for light-energy conversion and storage. Here, we have synthesized reduced graphene oxide (RGO)-semiconductor composites to improve the efficiency of photocatalysis. Zero-dimensional CdS nanoparticles (0D), one-dimensional CdS nanorods (1D), and two-dimensional CdS nanosheets (2D) are grafted on the RGO sheet (2D) by a surface modification method using 4-aminothiophenol (4-ATP). Structural analysis confirms the attachment of CdS nanocrystals with RGO, and the strong electronic interaction is found in the case of a CdS nanosheet and RGO, which has an influence on photocatalytic properties. The degradation of dye under visible light varies with changing the dimension of nanocrystals, and the catalytic activity of the CdS NS/RGO composite is ∼4 times higher than that of CdS nanoparticle/RGO and 3.4 times higher than that of CdS nanorod/RGO composite samples. The catalytic activity of the CdS nanosheet/RGO composite is also found to be ∼2.5 times than that of pure CdS nanosheet samples. The unique 2D-2D nanoarchitecture would be effective to harvest photons from solar light and transport electrons to reaction sites with respect to other 0D-2D and 1D-2D hybrid systems. This observation can be extended to other graphene-based inorganic semiconductor composites, which can provide a valuable opportunity to explore novel hybrid materials with superior visible-light-induced catalytic activity.

  4. Metal induced self-assembly of designed V-shape protein into 2D wavy supramolecular nanostructure

    NASA Astrophysics Data System (ADS)

    Qiao, S. P.; Lang, C.; Wang, R. D.; Li, X. M.; Yan, T. F.; Pan, T. Z.; Zhao, L. L.; Fan, X. T.; Zhang, X.; Hou, C. X.; Luo, Q.; Xu, J. Y.; Liu, J. Q.

    2015-12-01

    In order to understand and imitate the more complex bio-processes and fascinating functions in nature, protein self-assembly has been studied and has attracted more and more interest in recent years. Artificial self-assemblies of proteins have been constructed through many strategies. However, the design of complicated protein self-assemblies utilizing the special profile of building blocks remains a challenge. We herein report linear and 2D nanostructures constructed from a V shape SMAC protein and induced by metal coordination. Zigzag nanowires and wavy 2D nanostructures have been demonstrated by AFM and TEM. The zigzag nanowires can translate to a 2D nanostructure with an excess of metal ions, which reveals the step by step assembly process. Fluorescence and UV/Vis spectra have also been obtained to further study the mechanism and process of self-assembly. Upon the protein nanostructure, fluorescence resonance energy transfer (FRET) could also be detected using fluorescein modified proteins as building blocks. This article provides an approach for designing and controlling self-assembled protein nanostructures with a distinctive topological morphology.In order to understand and imitate the more complex bio-processes and fascinating functions in nature, protein self-assembly has been studied and has attracted more and more interest in recent years. Artificial self-assemblies of proteins have been constructed through many strategies. However, the design of complicated protein self-assemblies utilizing the special profile of building blocks remains a challenge. We herein report linear and 2D nanostructures constructed from a V shape SMAC protein and induced by metal coordination. Zigzag nanowires and wavy 2D nanostructures have been demonstrated by AFM and TEM. The zigzag nanowires can translate to a 2D nanostructure with an excess of metal ions, which reveals the step by step assembly process. Fluorescence and UV/Vis spectra have also been obtained to further

  5. Coupled leaky mode theory for light absorption in 2D, 1D, and 0D semiconductor nanostructures.

    PubMed

    Yu, Yiling; Cao, Linyou

    2012-06-18

    We present an intuitive, simple theoretical model, coupled leaky mode theory (CLMT), to analyze the light absorption of 2D, 1D, and 0D semiconductor nanostructures. This model correlates the light absorption of nanostructures to the optical coupling between incident light and leaky modes of the nanostructure. Unlike conventional methods such as Mie theory that requests specific physical features of nanostructures to evaluate the absorption, the CLMT model provides an unprecedented capability to analyze the absorption using eigen values of the leaky modes. Because the eigenvalue shows very mild dependence on the physical features of nanostructures, we can generally apply one set of eigenvalues calculated using a real, constant refractive index to calculations for the absorption of various nanostructures with different sizes, different materials, and wavelength-dependent complex refractive index. This CLMT model is general, simple, yet reasonably accurate, and offers new intuitive physical insights that the light absorption of nanostructures is governed by the coupling efficiency between incident light and leaky modes of the structure.

  6. Controlled synthesis of 2-D and 3-D dendritic platinum nanostructures.

    SciTech Connect

    Brinker, C. Jeffrey; Shelnutt, John Allen; Yang, Yi; van Swol, Frank B.; Pereira, Eulalia; Jiang, Ying-Bing; Medforth, Craig John; Xu, Huifang; Song, Yujiang; Singh, Anup K.

    2004-06-01

    Seeding and autocatalytic reduction of platinum salts in aqueous surfactant solution using ascorbic acid as the reductant leads to remarkable dendritic metal nanostructures. In micellar surfactant solutions, spherical dendritic metal nanostructures are obtained, and the smallest of these nanodendrites resemble assemblies of joined nanoparticles and the nanodendrites are single crystals. With liposomes as the template, dendritic platinum sheets in the form of thin circular disks or solid foam-like nanomaterials can be made. Synthetic control over the morphology of these nanodendrites, nanosheets, and nanostructured foams is realized by using a tin-porphyrin photocatalyst to conveniently and effectively produce a large initial population of catalytic growth centers. The concentration of seed particles determines the ultimate average size and uniformity of these novel two- and three-dimensional platinum nanostructures.

  7. Relation between 2D/3D chirality and the appearance of chiroptical effects in real nanostructures.

    PubMed

    Arteaga, Oriol; Sancho-Parramon, Jordi; Nichols, Shane; Maoz, Ben M; Canillas, Adolf; Bosch, Salvador; Markovich, Gil; Kahr, Bart

    2016-02-01

    The optical activity of fabricated metallic nanostructures is investigated by complete polarimetry. While lattices decorated with nanoscale gammadia etched in thin metallic films have been described as two dimensional, planar nanostructures, they are better described as quasi-planar structures with some three dimensional character. We find that the optical activity of these structures arises not only from the dissymmetric backing by a substrate but, more importantly, from the selective rounding of the nanostructure edges. A true chiroptical response in the far-field is only allowed when the gammadia contain these non-planar features. This is demonstrated by polarimetric measurements in conjunction with electrodynamical simulations based on the discrete dipole approximation that consider non-ideal gammadia. It is also shown that subtle planar dissymmetries in gammadia are sufficient to generate asymmetric transmission of circular polarized light.

  8. Enhanced photon absorption in spiral nanostructured solar cells using layered 2D materials.

    PubMed

    Tahersima, Mohammad H; Sorger, Volker J

    2015-08-28

    Recent investigations of semiconducting two-dimensional (2D) transition metal dichalcogenides have provided evidence for strong light absorption relative to its thickness attributed to high density of states. Stacking a combination of metallic, insulating, and semiconducting 2D materials enables functional devices with atomic thicknesses. While photovoltaic cells based on 2D materials have been demonstrated, the reported absorption is still just a few percent of the incident light due to their sub-wavelength thickness leading to low cell efficiencies. Here we show that taking advantage of the mechanical flexibility of 2D materials by rolling a molybdenum disulfide (MoS(2))/graphene (Gr)/hexagonal boron nitride stack to a spiral solar cell allows for optical absorption up to 90%. The optical absorption of a 1 μm long hetero-material spiral cell consisting of the aforementioned hetero stack is about 50% stronger compared to a planar MoS(2) cell of the same thickness; although the volumetric absorbing material ratio is only 6%. A core-shell structure exhibits enhanced absorption and pronounced absorption peaks with respect to a spiral structure without metallic contacts. We anticipate these results to provide guidance for photonic structures that take advantage of the unique properties of 2D materials in solar energy conversion applications.

  9. Synthesis by pulsed laser ablation of 2D nanostructures for advanced biomedical sensing

    NASA Astrophysics Data System (ADS)

    Trusso, S.; Zanchi, C.; Bombelli, A.; Lucotti, A.; Tommasini, M.; de Grazia, U.; Ciusani, E.; Romito, L. M.; Ossi, P. M.

    2016-05-01

    Au nanoparticle arrays with controlled nanostructure were produced by pulsed laser ablation on glass. Such substrates were optimized for biomedical sensing by means of SERS keeping fixed all process parameters but the laser pulse (LP) number that is a key deposition parameter. It allows to fine-tune the Au surface nanostructure with a considerable improvement in the SERS response towards the detection of apomorphine in blood serum (3.3 × 10-6 M), when LP number is increased from 1 × 104 to 2 × 104. This result is the starting point to correlate the intensity of selected SERS signals of apomorphine to its concentration in the blood of patients with Parkinson's disease.

  10. Interfacial polymerization of conductive polymers: Generation of polymeric nanostructures in a 2-D space.

    PubMed

    Dallas, Panagiotis; Georgakilas, Vasilios

    2015-10-01

    In the recent advances in the field of conductive polymers, the fibrillar or needle shaped nanostructures of polyaniline and polypyrrole have attracted significant attention due to the potential advantages of organic conductors that exhibit low-dimensionality, uniform size distribution, high crystallinity and improved physical properties compared to their bulk or spherically shaped counterparts. Carrying the polymerization reaction in a restricted two dimensional space, instead of the three dimensional space of the one phase solution is an efficient method for the synthesis of polymeric nanostructures with narrow size distribution and small diameter. Ultra-thin nanowires and nanofibers, single crystal nanoneedles, nanocomposites with noble metals or carbon nanotubes and layered materials can be efficiently synthesized with high yield and display superior performance in sensors and energy storage applications. In this critical review we will focus not only on the interfacial polymerization methods that leads to polymeric nanostructures and composites and their properties, but also on the mechanism and the physico-chemical processes that govern the diffusion and reactivity of molecules and nanomaterials at an interface. Recent advances for the synthesis of conductive polymer composites with an interfacial method for energy storage applications and future perspectives are presented. PMID:26272721

  11. Interfacial polymerization of conductive polymers: Generation of polymeric nanostructures in a 2-D space.

    PubMed

    Dallas, Panagiotis; Georgakilas, Vasilios

    2015-10-01

    In the recent advances in the field of conductive polymers, the fibrillar or needle shaped nanostructures of polyaniline and polypyrrole have attracted significant attention due to the potential advantages of organic conductors that exhibit low-dimensionality, uniform size distribution, high crystallinity and improved physical properties compared to their bulk or spherically shaped counterparts. Carrying the polymerization reaction in a restricted two dimensional space, instead of the three dimensional space of the one phase solution is an efficient method for the synthesis of polymeric nanostructures with narrow size distribution and small diameter. Ultra-thin nanowires and nanofibers, single crystal nanoneedles, nanocomposites with noble metals or carbon nanotubes and layered materials can be efficiently synthesized with high yield and display superior performance in sensors and energy storage applications. In this critical review we will focus not only on the interfacial polymerization methods that leads to polymeric nanostructures and composites and their properties, but also on the mechanism and the physico-chemical processes that govern the diffusion and reactivity of molecules and nanomaterials at an interface. Recent advances for the synthesis of conductive polymer composites with an interfacial method for energy storage applications and future perspectives are presented.

  12. A Theoretical Study of Single-Atom Catalysis of CO Oxidation Using Au Embedded 2D h-BN Monolayer: A CO-Promoted O2 Activation

    PubMed Central

    Mao, Keke; Li, Lei; Zhang, Wenhua; Pei, Yong; Zeng, Xiao Cheng; Wu, Xiaojun; Yang, Jinlong

    2014-01-01

    The CO oxidation behaviors on single Au atom embedded in two-dimensional h-BN monolayer are investigated on the basis of first-principles calculations, quantum Born-Oppenheim molecular dynamic simulations (BOMD) and micro-kinetic analysis. We show that CO oxidation on h-BN monolayer support single gold atom prefers an unreported tri-molecular Eley-Rideal (E-R) reaction, where O2 molecule is activated by two pre-adsorbed CO molecules. The formed OCOAuOCO intermediate dissociates into two CO2 molecules synchronously, which is the rate-limiting step with an energy barrier of 0.47 eV. By using the micro-kinetic analysis, the CO oxidation following the tri-molecular E-R reaction pathway entails much higher reaction rate (1.43 × 105 s−1) than that of bimolecular Langmuir-Hinshelwood (L-H) pathway (4.29 s−1). Further, the quantum BOMD simulation at the temperature of 300 K demonstrates the complete reaction process in real time. PMID:24962006

  13. A theoretical study of single-atom catalysis of CO oxidation using Au embedded 2D h-BN monolayer: a CO-promoted O₂ activation.

    PubMed

    Mao, Keke; Li, Lei; Zhang, Wenhua; Pei, Yong; Zeng, Xiao Cheng; Wu, Xiaojun; Yang, Jinlong

    2014-01-01

    The CO oxidation behaviors on single Au atom embedded in two-dimensional h-BN monolayer are investigated on the basis of first-principles calculations, quantum Born-Oppenheim molecular dynamic simulations (BOMD) and micro-kinetic analysis. We show that CO oxidation on h-BN monolayer support single gold atom prefers an unreported tri-molecular Eley-Rideal (E-R) reaction, where O2 molecule is activated by two pre-adsorbed CO molecules. The formed OCOAuOCO intermediate dissociates into two CO2 molecules synchronously, which is the rate-limiting step with an energy barrier of 0.47 eV. By using the micro-kinetic analysis, the CO oxidation following the tri-molecular E-R reaction pathway entails much higher reaction rate (1.43 × 10(5) s(-1)) than that of bimolecular Langmuir-Hinshelwood (L-H) pathway (4.29 s(-1)). Further, the quantum BOMD simulation at the temperature of 300 K demonstrates the complete reaction process in real time. PMID:24962006

  14. Engineering of lead chalcogenide nanostructures for carrier multiplication: Core/shell, 1D, and 2D

    NASA Astrophysics Data System (ADS)

    Lin, Qianglu

    Near infrared emitting semiconductors have been used widely in industry especially in solar-cell fabrications. The efficiency of single junction solar-cell can reach the Shockley-Queisser limit by using optimum band gap material such as silicon and cadmium telluride. The theoretical efficiency can be further enhanced through carrier multiplication, in which a high energy photon is absorbed and more than one electron-hole pair can be generated, reaching more than 100% quantum efficiency in the high energy region of sunlight. The realization of more than unity external quantum efficiency in lead selenide quantum dots solar cell has motivated vast investigation on lowering the carrier multiplication threshold and further improving the efficiency. This dissertation focuses on synthesis of lead chalcogenide nanostructures for their optical spectroscopy studies. PbSe/CdSe core/shell quantum dots were synthesized by cation exchange to obtain thick shells (up to 14 monolayers) for studies of visible and near infrared dual band emissions and carrier multiplication efficiency. By examining the reaction mechanism, a thermodynamic and a kinetic model are introduced to explain the vacancy driven cation exchange. As indicated by the effective mass model, PbSe/CdSe core/shell quantum dots has quasi-type-II band alignment, possessing electron delocalized through the entire quantum dot and hole localized in the core, which breaks down the symmetry of energy levels in the conduction and valence band, leading to hot-hole-assisted efficient multi-exciton generation and a lower carrier multiplication threshold to the theoretical value. For further investigation of carrier multiplication study, PbTe, possessing the highest efficiency among lead chalcogenides due to slow intraband cooling, is synthesized in one-dimensional and two-dimensional nanostructures. By using dodecanethiol as the surfactant, PbTe NRs can be prepared with high uniformity in width and resulted in fine quantum

  15. Optical nanostructures in 2D for wide-diameter and broadband beam collimation

    PubMed Central

    Clark, James; Anguita, José V.; Chen, Ying; Silva, S. Ravi P.

    2016-01-01

    Eliminating curved refracting lensing components used in conventional projection, imaging and sensing optical assemblies, is critical to enable compactness and miniaturisation of optical devices. A suitable means is replacing refracting lenses with two-dimensional optical media in flat-slab form, to achieve an equivalent optical result. One approach, which has been the focus of intense research, uses a Veselago lens which features a negative-index metamaterial. However, practical implementations rely on resonance techniques, thus broadband operation at optical frequencies imposes significant technical challenges that have been difficult to overcome. Here, we demonstrate a highly-collimated, broadband, wide-diameter beam from a compact source in flat-slab form, based on light collimation using nanomaterials ordered in patterns and embedded into flexible polymers. These provide a highly anisotropic absorption coefficient due to patterns created by vertical carbon nanotube structures grown on glass, and the anisotropic electrical conductivity of the nanotubes. We show this nanostructure strongly absorbs unwanted off-axis light rays, whilst transmitting the desired on-axis rays, to achieve the required optical effect over broadband, from visible to short-infrared, thus circumventing some technical limitations of negative-index metamaterials. We further show a low substrate-temperature system for nanotube growth, allowing direct implementation into heat-sensitive large-area devices. PMID:26732851

  16. Optical nanostructures in 2D for wide-diameter and broadband beam collimation

    NASA Astrophysics Data System (ADS)

    Clark, James; Anguita, José V.; Chen, Ying; Silva, S. Ravi P.

    2016-01-01

    Eliminating curved refracting lensing components used in conventional projection, imaging and sensing optical assemblies, is critical to enable compactness and miniaturisation of optical devices. A suitable means is replacing refracting lenses with two-dimensional optical media in flat-slab form, to achieve an equivalent optical result. One approach, which has been the focus of intense research, uses a Veselago lens which features a negative-index metamaterial. However, practical implementations rely on resonance techniques, thus broadband operation at optical frequencies imposes significant technical challenges that have been difficult to overcome. Here, we demonstrate a highly-collimated, broadband, wide-diameter beam from a compact source in flat-slab form, based on light collimation using nanomaterials ordered in patterns and embedded into flexible polymers. These provide a highly anisotropic absorption coefficient due to patterns created by vertical carbon nanotube structures grown on glass, and the anisotropic electrical conductivity of the nanotubes. We show this nanostructure strongly absorbs unwanted off-axis light rays, whilst transmitting the desired on-axis rays, to achieve the required optical effect over broadband, from visible to short-infrared, thus circumventing some technical limitations of negative-index metamaterials. We further show a low substrate-temperature system for nanotube growth, allowing direct implementation into heat-sensitive large-area devices.

  17. Nanostructured 2D Diporphyrin Honeycomb Film: Photoelectrochemistry, Photodegradation, and Antibacterial Activity.

    PubMed

    Zhao, Yuewu; Shang, Qiuwei; Yu, Jiachao; Zhang, Yuanjian; Liu, Songqin

    2015-06-10

    Surface patterns of well-defined nanostructures play important roles in fabrication of optoelectronic devices and applications in catalysis and biology. In this paper, the diporphyrin honeycomb film, composed of titanium dioxide, protoporphyrin IX, and hemin (TiO2/PPIX/Hem), was synthesized using a dewetting technique with the well-defined polystyrene (PS) monolayer as a template. The TiO2/PPIX/Hem honeycomb film exhibited a higher photoelectrochemical response than that of TiO2 or TiO2/PPIX, which implied a high photoelectric conversion efficiency and a synergistic effect between the two kinds of porphyrins. The TiO2/PPIX/Hem honeycomb film was also a good photosensitizer due to its ability to generate singlet oxygen ((1)O2) under irradiation by visible light. This led to the use of diporphyrin TiO2/PPIX/Hem honeycomb film for the photocatalytic inactivation of bacteria. In addition, the photocatalytic activities of other metal-diporphyrin-based honeycomb films, such as TiO2/MnPPIX/Hem, TiO2/CoPPIX/Hem, TiO2/NiPPIX/Hem, TiO2/CuPPIX/Hem, and TiO2/ZnPPIX/Hem, were investigated. The result demonstrated that the photoelectric properties of diporphyrin-based film could be effectively enhanced by further coupling of porphyrin with metal ions. Such enhanced performance of diporphyrin compounds opened a new way for potential applications in various photoelectrochemical devices and medical fields. PMID:25992484

  18. Nanostructured 2D Diporphyrin Honeycomb Film: Photoelectrochemistry, Photodegradation, and Antibacterial Activity.

    PubMed

    Zhao, Yuewu; Shang, Qiuwei; Yu, Jiachao; Zhang, Yuanjian; Liu, Songqin

    2015-06-10

    Surface patterns of well-defined nanostructures play important roles in fabrication of optoelectronic devices and applications in catalysis and biology. In this paper, the diporphyrin honeycomb film, composed of titanium dioxide, protoporphyrin IX, and hemin (TiO2/PPIX/Hem), was synthesized using a dewetting technique with the well-defined polystyrene (PS) monolayer as a template. The TiO2/PPIX/Hem honeycomb film exhibited a higher photoelectrochemical response than that of TiO2 or TiO2/PPIX, which implied a high photoelectric conversion efficiency and a synergistic effect between the two kinds of porphyrins. The TiO2/PPIX/Hem honeycomb film was also a good photosensitizer due to its ability to generate singlet oxygen ((1)O2) under irradiation by visible light. This led to the use of diporphyrin TiO2/PPIX/Hem honeycomb film for the photocatalytic inactivation of bacteria. In addition, the photocatalytic activities of other metal-diporphyrin-based honeycomb films, such as TiO2/MnPPIX/Hem, TiO2/CoPPIX/Hem, TiO2/NiPPIX/Hem, TiO2/CuPPIX/Hem, and TiO2/ZnPPIX/Hem, were investigated. The result demonstrated that the photoelectric properties of diporphyrin-based film could be effectively enhanced by further coupling of porphyrin with metal ions. Such enhanced performance of diporphyrin compounds opened a new way for potential applications in various photoelectrochemical devices and medical fields.

  19. The formation of Colloidal 2D/3D MoS2 Nanostructures in Organic Liquid Environment

    NASA Astrophysics Data System (ADS)

    Durgun, Engin; Sen, H. Sener; Oztas, Tugba; Ortac, Bulend

    2015-03-01

    2D MoS2 nanosheets (2D MoS2 NS) and fullerene-like MoS2 nanostructures (3D MoS2 NS) with varying sizes are synthesized by nanosecond laser ablation of hexagonal crystalline 2H-MoS2 powder in methanol. Structural, chemical, and optical properties of MoS2 NS are characterized by optical microscopy, SEM, TEM, XRD, Raman and UV/VIS/NIR absorption spectroscopy techniques. Results of structural analysis show that the obtained MoS2 NS mainly present layered morphology from micron to nanometer surface area. Detailed analysis of the product also proves the existence of inorganic polyhedral fullerene-like 3D MoS2 NS generated by pulsed laser ablation in methanol. The possible factors which may lead to formation of both 2D and 3D MoS2 NS in methanol are examined by ab initio calculations and shown that it is correlated with vacancy formation. The hexagonal crystalline structure of MoS2 NS was determined by XRD analysis. The colloidal MoS2 NS solution presents broadband absorption edge tailoring from UV region to NIR region. Investigations of MoS2 NS show that the one step physical process of pulsed laser ablation-bulk MoS2 powder interaction in organic solution opens doors to the formation of ``two scales'' micron- and nanometer-sized layered and fullerene-like morphology MoS2 structures. This work was partially supported by TUBITAK under the Project No. 113T050 and Bilim Akademisi - The Science Academy, Turkey under the BAGEP program.

  20. 2D quasi-planar or 3D structures? A comparison between CrBn(n = 2 - 10) wheel-like clusters and their corresponding 3D pyramidal clusters, and their hydrogen storage capability

    NASA Astrophysics Data System (ADS)

    Yildirim, E. K.

    2015-09-01

    In this study, we investigated stable structures for a transition metal atom-boron (CrB) wheel-like clusters and compared them with their corresponding 3D counterparts by means of density functional theory (DFT). In addition, hydrogen storage capability of the wheel-like system was investigated. All simulations were performed at the B3LYP/TZVP level of theory. We set out a complete route to the formation of CrB wheel-like clusters. Our results showed that, some of the clusters, investigated in this work (CrBn; n = 4, 6, 7, 8), either prefer to be in a 3D geometry rather than 2D quasi-planar or planar geometry. However, hydrogen doping has an interesting effect on both 2D quasi-planar and 3D geometries of this system. Simply it transforms the 3D structure, first, into a 2D quasi-planar, then a planar geometry. Furthermore, our results show that H-cluster interaction is too high for reversible hydrogen storage for these clusters.

  1. Nanostructures of the binary nitrides, BN, TiN, and NbN, prepared by the urea-route

    SciTech Connect

    Gomathi, A.; Rao, C.N.R. . E-mail: cnrrao@jncasr.ac.in

    2006-05-25

    By heating mixtures of H{sub 3}BO{sub 3}, TiCl{sub 4}, and NbCl{sub 5} with urea in 1:6 molar ratios in the 900-1000 deg. C range, nanoparticles of BN, TiN, and NbN have been obtained, respectively. The nanoparticles are crystalline and have been characterized by electron microscopy and other techniques. By carrying out the urea reaction over Au islands deposited on Si substrates, nanowires of TiN could be obtained.

  2. Continuous fabrication of scalable 2-dimensional (2D) micro- and nanostructures by sequential 1D mechanical patterning processes.

    PubMed

    Ok, Jong G; Panday, Ashwin; Lee, Taehwa; Jay Guo, L

    2014-12-21

    We present a versatile and simple methodology for continuous and scalable 2D micro/nano-structure fabrication via sequential 1D patterning strokes enabled by dynamic nano-inscribing (DNI) and vibrational indentation patterning (VIP) as well as a 'single-stroke' 2D patterning using a DNI tool in VIP. PMID:25363145

  3. New ways to synthesize lead sulfide nanosheets-substituted alkanes direct the growth of 2D nanostructures.

    PubMed

    Bielewicz, Thomas; Klein, Eugen; Klinke, Christian

    2016-09-01

    Two-dimensional colloidal nanosheets represent very attractive optoelectronic materials. They combine good lateral conductivity with solution-processability and geometry-tunable electronic properties. In the case of PbS nanosheets, so far synthesis has been driven by the addition of chloroalkanes as coligands. Here, we demonstrate how to synthesize two-dimensional lead sulfide nanostructures using other halogen alkanes and primary amines. Further, we show that at a reaction temperature of 170 °C a coligand is not even necessary and the only ligand, oleic acid, controls the anisotropic growth of the two-dimensional structures. Also, using thiourea as a sulfide source, nanosheets with lateral dimensions of over 10 μm are possible.

  4. New ways to synthesize lead sulfide nanosheets—substituted alkanes direct the growth of 2D nanostructures

    NASA Astrophysics Data System (ADS)

    Bielewicz, Thomas; Klein, Eugen; Klinke, Christian

    2016-09-01

    Two-dimensional colloidal nanosheets represent very attractive optoelectronic materials. They combine good lateral conductivity with solution-processability and geometry-tunable electronic properties. In the case of PbS nanosheets, so far synthesis has been driven by the addition of chloroalkanes as coligands. Here, we demonstrate how to synthesize two-dimensional lead sulfide nanostructures using other halogen alkanes and primary amines. Further, we show that at a reaction temperature of 170 °C a coligand is not even necessary and the only ligand, oleic acid, controls the anisotropic growth of the two-dimensional structures. Also, using thiourea as a sulfide source, nanosheets with lateral dimensions of over 10 μm are possible.

  5. Bn and Si-Doped Bn Coatings on Woven Fabrics

    NASA Technical Reports Server (NTRS)

    Hurwitz, Frances I.; Scott, John M.; Wheeler, Donald R.; Chayka, Paul V.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    A computer controlled, pulsed chemical vapor infiltration (CVI) system has been developed to deposit BN from a liquid borazine (B3N3H6) source, as well as silicon doped BN coatings using borazine and a silicon source, into 2-D woven ceramic fabric preforms. The coating process was evaluated as a function of deposition temperature, pressure, and precursor flow rate. Coatings were characterized by field emission scanning electron microscopy, electron dispersive spectroscopy and Auger spectroscopy. By controlling the reactant feed ratios, Si incorporation could be controlled over the range of 6-24 atomic percent.

  6. Raman Study of Uncoated and p-BN/SiC-Coated Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites. Part 1; Distribution and Nanostructure of Different Phases

    NASA Technical Reports Server (NTRS)

    Gouadec, Gwenael; Colomban, Philippe; Bansal, Narottam P.

    2000-01-01

    Hi-Nicalon fiber reinforced celsian matrix composites were characterized by Raman spectroscopy and imaging, using several laser wavelengths. Composite #1 is reinforced by as-received fibers while coatings of p-BN and SiC protect the fibers in composite #2. The matrix contains traces of the hexagonal phase of celsian, which is concentrated in the neighborhood of fibers in composite #1. Some free silicon was evident in the coating of composite #2 which might involve a {BN + SiC yields BNC + Si} "reaction" at the p-BN/SiC interface. Careful analysis of C-C peaks revealed no abnormal degradation of the fiber core in the composites.

  7. Synthesis of silver nanostructures by simple redox under electrodeposited copper microcubes and the orient attachment growth of 2D silver

    NASA Astrophysics Data System (ADS)

    Wu, Guoxing; Yang, Sanjun; Liu, Qiming

    2015-12-01

    Copper microcubes about 500 nm were electrodeposited on ITO glasses. Silver nanoparticles, netty consist of short nanorods or nanowires, nanosheets with thickness about 40 nm, were successfully obtained by immersing ITOs with different concentration of AgNO3 solution. XRD, SEM and TEM were applied to characterize the products. Silver ions were initially reduced on the surface of copper, and then gradually decomposed the copper. Cuprous oxide intermediate was found to participate in the redox reaction. Both agglomerates on the cubes and escaped reductant nanoparticles act as the positions for anisotropic growth. Based on the experimental results, the roles of three kinds of cubes are discussed in preparing the nanosheets before proposing the possible growth process. Oriented attachment influenced and controlled the final shapes, such as layered nanonets, nanoplates and nanosheets. Big nanoparticles were inclined to link as nanowires, netty and even 2D porous structure consisted of 'nanosnakes', small reductant nanoparticles with silver around absorbed on the edge of silver nanoplate and further accelerated the extension of nanoplate until worked out, holes on the nanoplate confirmed that the adsorbed matters could be reductant nanoparticles. Reductant nanoparticles can also be exhausted before silver nanoparticles and nanoflakes absorbed on the growth positions.

  8. 75 FR 79990 - Airworthiness Directives; B-N Group Ltd. Model BN-2, BN-2A, BN-2A-2, BN-2A-3, BN-2A-6, BN-2A-8...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-21

    ... Procedures (44 FR 11034, February 26, 1979); and 3. Will not have a significant economic impact, positive or.... Model BN-2, BN-2A, BN- 2A-2, BN-2A-3, BN-2A-6, BN-2A-8, BN-2A-9, BN-2A-20, BN-2A-21, BN-2A-26, BN-2A-27, BN-2B-20, BN-2B-21, BN-2B-26, BN-2B-27, BN-2T, and BN-2T-4R Airplanes AGENCY: Federal...

  9. Multifunctional Nanofluids with 2D Nanosheets for thermal management and tribological applications

    NASA Astrophysics Data System (ADS)

    Taha Tijerina, Jose Jaime

    Conventional heat-transfer fluids such as water, ethylene glycol, standard oils and other lubricants are typically low-efficiency heat-transfer fluids. Thermal management plays a critical factor in many applications where these fluids can be used, such as in motors/engines, solar cells, biopharmaceuticals, fuel cells, high voltage power transmission systems, micro/nanoelectronics mechanical systems (MEMS/NEMS), and nuclear cooling among others. These insulating fluids require superb filler dispersion, high thermal conduction, and for certain applications as in electrical/electronic devices also electrical insulation. The miniaturization and high efficiency of electrical/electronic devices in these fields demand successful heat management and energy-efficient fluid-based heat-transfer systems. Recent advances in layered materials enable large scale synthesis of various two-dimensional (2D) structures. Some of these 2D materials are good choices as nanofillers in heat transfer fluids; mainly due to their inherent high thermal conductivity (TC) and high surface area available for thermal energy transport. Among various 2D-nanostructures, hexagonal boron nitride (h-BN) and graphene (G) exhibit versatile properties such as outstanding TC, excellent mechanical stability, and remarkable chemical inertness. The following research, even though investigate various conventional fluids, will focus on dielectric insulating nanofluids (mineral oil -- MO) with significant thermal performance. It is presented the plan for synthesis and characterization of stable high-thermal conductivity nanofluids using 2D-nanostructures of h-BN, which will be further incorporated at diverse filler concentrations to conventional fluids for cooling applications, without compromising its electrical insulating property. For comparison, properties of h-BN based fluids are compared with conductive fillers such as graphene; where graphene has similar crystal structure of h-BN and also has similar bulk

  10. Postsynthesis of h‐BN/Graphene Heterostructures Inside a STEM

    PubMed Central

    Tizei, Luiz H. G.; Sato, Yohei; Lin, Yung‐Chang; Yeh, Chao‐Hui; Chiu, Po‐Wen; Terauchi, Masami; Iijima, Sumio

    2015-01-01

    Combinations of 2D materials with different physical properties can form heterostructures with modified electrical, mechanical, magnetic, and optical properties. The direct observation of a lateral heterostructure synthesis is reported by epitaxial in‐plane graphene growth from the step‐edge of hexagonal BN (h‐BN) within a scanning transmission electron microscope chamber. Residual hydrocarbon in the chamber is the carbon source. The growth interface between h‐BN and graphene is atomically identified as largely N–C bonds. This postgrowth method can form graphene nanoribbons connecting two h‐BN domains with different twisting angles, as well as isolated carbon islands with arbitrary shapes embedded in the h‐BN layer. The electronic properties of the vertically stacked h‐BN/graphene heterostructures are investigated by electron energy‐loss spectroscopy (EELS). Low‐loss EELS analysis of the dielectric response suggests a robust coupling effect between the graphene and h‐BN layers. PMID:26618896

  11. Creating a Nanospace under an h-BN Cover for Adlayer Growth on Nickel(111).

    PubMed

    Yang, Yang; Fu, Qiang; Li, Haobo; Wei, Mingming; Xiao, Jianping; Wei, Wei; Bao, Xinhe

    2015-12-22

    Heterostructures of two-dimensional (2D) atomic crystals have attracted increasing attention, while fabrication of the 2D stacking structures remains a challenge. In this work, we present a route toward formation of 2D heterostructures via confined growth of a 2D adlayer underneath the other 2D overlayer. Taking a hexagonal boron nitride (h-BN) monolayer on Ni(111) as a model system, both epitaxial and nonepitaxial h-BN islands have been identified on the Ni surface. Surface science studies combined with density functional theory calculations reveal that the nonepitaxial h-BN islands interact weakly with the Ni(111) surface, which creates a 2D nanospace underneath the h-BN islands. An additional h-BN or graphene layer can be grown in the space between the nonepitaxial h-BN islands and Ni(111) surface, forming h-BN/h-BN bilayer structures and h-BN/graphene heterostructures. These results suggest that confined growth under 2D covers may provide an effective route to obtain stacks of 2D atomic crystals.

  12. Electrical transport properties of (BN)-rich hexagonal (BN)C semiconductor alloys

    SciTech Connect

    Uddin, M. R.; Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.; Ziemer, K. S.

    2014-08-15

    The layer structured hexagonal boron nitride carbon semiconductor alloys, h-(BN)C, offer the unique abilities of bandgap engineering (from 0 for graphite to ∼6.4 eV for h-BN) and electrical conductivity control (from semi-metal for graphite to insulator for undoped h-BN) through alloying and have the potential to complement III-nitride wide bandgap semiconductors and carbon based nanostructured materials. Epilayers of (BN)-rich h-(BN){sub 1-x}(C{sub 2}){sub x} alloys were synthesized by metal-organic chemical vapor deposition (MOCVD) on (0001) sapphire substrates. Hall-effect measurements revealed that homogeneous (BN)-rich h-(BN){sub 1-x}(C{sub 2}){sub x} alloys are naturally n-type. For alloys with x = 0.032, an electron mobility of about 20 cm{sup 2}/Vs at 650 °K was measured. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition and analyze chemical bonding states. Both composition and chemical bonding analysis confirm the formation of alloys. XPS results indicate that the carbon concentration in the alloys increases almost linearly with the flow rate of the carbon precursor (propane (C{sub 3}H{sub 8})) employed during the epilayer growth. XPS chemical bonding analysis showed that these MOCVD grown alloys possess more C-N bonds than C-B bonds, which possibly renders the undoped h-(BN){sub 1-x}(C{sub 2}){sub x} alloys n-type and corroborates the Hall-effect measurement results.

  13. A theoretical study on monoatomic BN nanochains and nanorings.

    PubMed

    Rizi, Rouhollah Namazi; Noei, Maziar

    2016-09-01

    Boron nitride (BN) nanochains were successfully synthesized recently. In this work, we investigate the electronic, energetic, and structural properties of BN nanochains and nanorings by means of density functional theory calculations. Our calculations support the experimental findings and offer additional physical insights into these new nanostructured materials. We show that BN nanochains are biracial compounds that tend to be closed and form a ring. They have single and double bonds alternately throughout the chain. The boron atoms are not saturated and are strong Lewis acids. Increase in the length of the chain tends to result in the conversion from a semiconductor to a semimetal material. The ring structures are stabler than the corresponding chains, and unlike the chains these structures are predicted to be insulators. The binding energy of the chains and rings increases with an increase in their size. Rings with odd or even numbers of BN units show different electronic properties. PMID:27497865

  14. A single-stage functionalization and exfoliation method for the production of graphene in water: stepwise construction of 2D-nanostructured composites with iron oxide nanoparticles.

    PubMed

    Ihiawakrim, Dris; Ersen, Ovidiu; Melin, Frédéric; Hellwig, Petra; Janowska, Izabela; Begin, Dominique; Baaziz, Walid; Begin-Colin, Sylvie; Pham-Huu, Cuong; Baati, Rachid

    2013-10-01

    A practically simple top-down process for the exfoliation of graphene (GN) and few-layer graphene (FLG) from graphite is described. We have discovered that a biocompatible amphiphilic pyrene-based hexahistidine peptide is able to exfoliate, functionalize, and dissolve few layer graphene flakes in pure water under exceptionally mild, sustainable and virtually innocuous low intensity cavitation conditions. Large area functionalized graphene flakes with the hexahistidine oligopeptide (His₆-TagGN = His₆@GN) have been produced efficiently at room temperature and characterized by TEM, Raman, and UV spectroscopy. Conductivity experiments carried out on His₆-TagGN samples revealed superior electric performances as compared to reduced graphene oxide (rGO) and non-functionalized graphene, demonstrating the non-invasive features of our non-covalent functionalization process. We postulated a rational exfoliation mechanism based on the intercalation of the peptide amphiphile under cavitational chemistry. We also demonstrated the ability of His6-TagGN nanoassemblies to self-assemble spontaneously with inorganic iron oxide nanoparticles generating magnetic two-dimensional (2D) His₆-TagGN/Fe₃O₄ nanocomposites under mild and non-hydrothermal conditions. The set of original experiments described here open novel perspectives in the facile production of water dispersible high quality GN and FLG sheets that will improve and facilitate the interfacing, processing and manipulation of graphene for promising applications in catalysis, nanocomposite construction, integrated nanoelectronic devices and bionanotechnology.

  15. A single-stage functionalization and exfoliation method for the production of graphene in water: stepwise construction of 2D-nanostructured composites with iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Ihiawakrim, Dris; Ersen, Ovidiu; Melin, Frédéric; Hellwig, Petra; Janowska, Izabela; Begin, Dominique; Baaziz, Walid; Begin-Colin, Sylvie; Pham-Huu, Cuong; Baati, Rachid

    2013-09-01

    A practically simple top-down process for the exfoliation of graphene (GN) and few-layer graphene (FLG) from graphite is described. We have discovered that a biocompatible amphiphilic pyrene-based hexahistidine peptide is able to exfoliate, functionalize, and dissolve few layer graphene flakes in pure water under exceptionally mild, sustainable and virtually innocuous low intensity cavitation conditions. Large area functionalized graphene flakes with the hexahistidine oligopeptide (His6-TagGN = His6@GN) have been produced efficiently at room temperature and characterized by TEM, Raman, and UV spectroscopy. Conductivity experiments carried out on His6-TagGN samples revealed superior electric performances as compared to reduced graphene oxide (rGO) and non-functionalized graphene, demonstrating the non-invasive features of our non-covalent functionalization process. We postulated a rational exfoliation mechanism based on the intercalation of the peptide amphiphile under cavitational chemistry. We also demonstrated the ability of His6-TagGN nanoassemblies to self-assemble spontaneously with inorganic iron oxide nanoparticles generating magnetic two-dimensional (2D) His6-TagGN/Fe3O4 nanocomposites under mild and non-hydrothermal conditions. The set of original experiments described here open novel perspectives in the facile production of water dispersible high quality GN and FLG sheets that will improve and facilitate the interfacing, processing and manipulation of graphene for promising applications in catalysis, nanocomposite construction, integrated nanoelectronic devices and bionanotechnology.A practically simple top-down process for the exfoliation of graphene (GN) and few-layer graphene (FLG) from graphite is described. We have discovered that a biocompatible amphiphilic pyrene-based hexahistidine peptide is able to exfoliate, functionalize, and dissolve few layer graphene flakes in pure water under exceptionally mild, sustainable and virtually innocuous low

  16. Synthesis and Oxidation Resistance of h-BN Thin Films

    NASA Astrophysics Data System (ADS)

    Stewart, David; Meulenberg, Robert; Lad, Robert

    Hexagonal boron nitride (h-BN) is an exciting 2D material for use in sensors and other electronic devices that operate in harsh, high temperature environments. Not only is h-BN a wide band gap material with excellent wear resistance and high temperature stability, but recent reports indicate that h-BN can prevent metallic substrates from oxidizing above 600°C in low O2 pressures. However, the PVD of highly crystalline h-BN films required for this oxidation protection has proven challenging. In this work, we have explored the growth of h-BN thin films by reactive RF magnetron sputtering from an elemental B target in an Ar/N2 atmosphere. The film growth rate is extremely slow and the resulting films are atomically smooth and homogeneous. Using DC biasing during deposition and high temperature annealing treatments, the degree of film crystallinity can be controlled. The oxidation resistance of h-BN films deposited on inert sapphire and reactive metal substrates such as Zr and ZrB2 has been examined by techniques such as XPS, XRD, and SEM after oxidation between 600 and 1200°C under varying oxygen pressures. The success of h-BN as a passivation layer for metallic substrates in harsh environments is shown to depend greatly on its crystalline quality and defects. Supported by the NSF SusChEM program.

  17. Nanostructures having high performance thermoelectric properties

    DOEpatents

    Yang, Peidong; Majumdar, Arunava; Hochbaum, Allon I; Chen, Renkun; Delgado, Raul Diaz

    2014-05-20

    The invention provides for a nanostructure, or an array of such nanostructures, each comprising a rough surface, and a doped or undoped semiconductor. The nanostructure is an one-dimensional (1-D) nanostructure, such a nanowire, or a two-dimensional (2-D) nanostructure. The nanostructure can be placed between two electrodes and used for thermoelectric power generation or thermoelectric cooling.

  18. Nanostructures having high performance thermoelectric properties

    DOEpatents

    Yang, Peidong; Majumdar, Arunava; Hochbaum, Allon I.; Chen, Renkun; Delgado, Raul Diaz

    2015-12-22

    The invention provides for a nanostructure, or an array of such nanostructures, each comprising a rough surface, and a doped or undoped semiconductor. The nanostructure is an one-dimensional (1-D) nanostructure, such a nanowire, or a two-dimensional (2-D) nanostructure. The nanostructure can be placed between two electrodes and used for thermoelectric power generation or thermoelectric cooling.

  19. Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

    NASA Astrophysics Data System (ADS)

    Narayan, Jagdish; Bhaumik, Anagh

    2016-04-01

    pulsed laser evaporation of carbon and obtained cBN/diamond composites, where cBN acts as template for diamond growth. Both diamond and cBN grown from super undercooled liquid can be alloyed with both p- and n-type dopants. This process allows carbon to diamond and hBN to cBN conversions and formation of useful nanostructures and microstructures at ambient temperatures in air at atmospheric pressure on practical and heat-sensitive substrates in a controlled way without need for any catalysts and hydrogen to stabilize sp3 bonding for diamond and cBN phases.

  20. Atomistic Interrogation of B-N Co-dopant Structures and Their Electronic Effects in Graphene.

    PubMed

    Schiros, Theanne; Nordlund, Dennis; Palova, Lucia; Zhao, Liuyan; Levendorf, Mark; Jaye, Cherno; Reichman, David; Park, Jiwoong; Hybertsen, Mark; Pasupathy, Abhay

    2016-07-26

    Chemical doping has been demonstrated to be an effective method for producing high-quality, large-area graphene with controlled carrier concentrations and an atomically tailored work function. The emergent optoelectronic properties and surface reactivity of carbon nanostructures are dictated by the microstructure of atomic dopants. Co-doping of graphene with boron and nitrogen offers the possibility to further tune the electronic properties of graphene at the atomic level, potentially creating p- and n-type domains in a single carbon sheet, opening a gap between valence and conduction bands in the 2-D semimetal. Using a suite of high-resolution synchrotron-based X-ray techniques, scanning tunneling microscopy, and density functional theory based computation we visualize and characterize B-N dopant bond structures and their electronic effects at the atomic level in single-layer graphene grown on a copper substrate. We find there is a thermodynamic driving force for B and N atoms to cluster into BNC structures in graphene, rather than randomly distribute into isolated B and N graphitic dopants, although under the present growth conditions, kinetics limit segregation of large B-N domains. We observe that the doping effect of these BNC structures, which open a small band gap in graphene, follows the B:N ratio (B > N, p-type; B < N, n-type; B═N, neutral). We attribute this to the comparable electron-withdrawing and -donating effects, respectively, of individual graphitic B and N dopants, although local electrostatics also play a role in the work function change. PMID:27327863

  1. 2D materials: Graphene and others

    NASA Astrophysics Data System (ADS)

    Bansal, Suneev Anil; Singh, Amrinder Pal; Kumar, Suresh

    2016-05-01

    Present report reviews the recent advancements in new atomically thick 2D materials. Materials covered in this review are Graphene, Silicene, Germanene, Boron Nitride (BN) and Transition metal chalcogenides (TMC). These materials show extraordinary mechanical, electronic and optical properties which make them suitable candidates for future applications. Apart from unique properties, tune-ability of highly desirable properties of these materials is also an important area to be emphasized on.

  2. Boron Nitride Nanostructures: Fabrication, Functionalization and Applications.

    PubMed

    Yin, Jun; Li, Jidong; Hang, Yang; Yu, Jin; Tai, Guoan; Li, Xuemei; Zhang, Zhuhua; Guo, Wanlin

    2016-06-01

    Boron nitride (BN) structures are featured by their excellent thermal and chemical stability and unique electronic and optical properties. However, the lack of controlled synthesis of quality samples and the electrically insulating property largely prevent realizing the full potential of BN nanostructures. A comprehensive overview of the current status of the synthesis of two-dimensional hexagonal BN sheets, three dimensional porous hexagonal BN materials and BN-involved heterostructures is provided, highlighting the advantages of different synthetic methods. In addition, structural characterization, functionalizations and prospective applications of hexagonal BN sheets are intensively discussed. One-dimensional BN nanoribbons and nanotubes are then discussed in terms of structure, fabrication and functionality. In particular, the existing routes in pursuit of tunable electronic and magnetic properties in various BN structures are surveyed, calling upon synergetic experimental and theoretical efforts to address the challenges for pioneering the applications of BN into functional devices. Finally, the progress in BN superstructures and novel B/N nanostructures is also briefly introduced. PMID:27073174

  3. Graphene/h-BN/ZnO van der Waals tunneling heterostructure based ultraviolet photodetector.

    PubMed

    Wu, Zhiqian; Li, Xiaoqiang; Zhong, Huikai; Zhang, Shengjiao; Wang, Peng; Kim, Tae-ho; Kwak, Sung Soo; Liu, Cheng; Chen, Hongsheng; Kim, Sang-Woo; Lin, Shisheng

    2015-07-27

    We report a novel ultraviolet photodetector based on graphene/h-BN/ZnO van der Waals heterostructure. Graphene/ZnO heterostructure shows poor rectification behavior and almost no photoresponse. In comparison, graphene/h-BN/ZnO structure shows improved electrical rectified behavior and surprising high UV photoresponse (1350AW(-1)), which is two or three orders magnitude larger than reported GaN UV photodetector (0.2~20AW(-1)). Such high photoresponse mainly originates from the introduction of ultrathin two-dimensional (2D) insulating h-BN layer, which behaves as the tunneling layer for holes produced in ZnO and the blocking layer for holes in graphene. The graphene/h-BN/ZnO heterostructure should be a novel and representative 2D heterostructure for improving the performance of 2D materials/Semiconductor heterostructure based optoelectronic devices.

  4. Spin and band-gap engineering in copper-doped BN sheet

    SciTech Connect

    Zhou, Yungang; Jiang, Xiao-dong; Duan, G.; Gao, Fei; Zu, Xiaotao T.

    2010-05-01

    We perform first-principles calculations on single- or dimer-Cu absorbed BN sheet. It was found that the band gap of BN sheet was reduced due to the emergence of certain impurity states arisen from Cu atom. The value of band gap depends on the adsorption configuration. Unpaired electron in absorbed single-Cu atom is polarized causing a magnetic moment of 1.0 μB, while no magnetic moment has been detected after dimer-Cu adsorption. Comparing the analogous carbon nanostructures, Cu-absorbed BN sheet is more resistant to oxidation and thereby is more experimentally accessible.

  5. Interplay between intercalated oxygen superstructures and monolayer h -BN on Cu(100)

    DOE PAGES

    Ma, Chuanxu; Park, Jewook; Liu, Lei; Kim, Yong-Sung; Yoon, Mina; Baddorf, Arthur P.; Gu, Gong; Li, An-Ping

    2016-08-18

    The confinement effect of intercalated atoms in van der Waals heterostructures can lead to interesting interactions between the confined atoms or molecules and the overlaying two-dimensional (2D) materials. In this paper, we report the formation of ordered Cu(100) p(2×2) oxygen superstructures by oxygen intercalation under the monolayer hexagonal boron nitride (h-BN) on Cu after annealing. By using scanning tunneling microscopy and x-ray photoelectron spectroscopy, we identify the superstructure and reveal its roles in passivating the exposed Cu surfaces, decoupling h-BN and Cu, and disintegrating h-BN monolayers. The oxygen superstructure appears as a 2D pattern on the exposed Cu surface ormore » quasi-1D stripes of paired oxygen intercalated in the interface of h-BN and Cu predominantly oriented along the moiré modulations. The oxygen superstructure is shown to etch the overlaying h-BN monolayer in a thermal annealing process. After extended annealing, the h-BN monolayer disintegrates into nanoislands with zigzag edges. Finally, we discuss the implications of these findings on the stability and oxidation resistance of h-BN and relate them to challenges in process integration and 2D heterostructures.« less

  6. Interplay between intercalated oxygen superstructures and monolayer h -BN on Cu(100)

    NASA Astrophysics Data System (ADS)

    Ma, Chuanxu; Park, Jewook; Liu, Lei; Kim, Yong-Sung; Yoon, Mina; Baddorf, Arthur P.; Gu, Gong; Li, An-Ping

    2016-08-01

    The confinement effect of intercalated atoms in van der Waals heterostructures can lead to interesting interactions between the confined atoms or molecules and the overlaying two-dimensional (2D) materials. Here we report the formation of ordered Cu(100) p (2 ×2 ) oxygen superstructures by oxygen intercalation under the monolayer hexagonal boron nitride (h -BN) on Cu after annealing. By using scanning tunneling microscopy and x-ray photoelectron spectroscopy, we identify the superstructure and reveal its roles in passivating the exposed Cu surfaces, decoupling h -BN and Cu, and disintegrating h -BN monolayers. The oxygen superstructure appears as a 2D pattern on the exposed Cu surface or quasi-1D stripes of paired oxygen intercalated in the interface of h -BN and Cu predominantly oriented along the moiré modulations. The oxygen superstructure is shown to etch the overlaying h -BN monolayer in a thermal annealing process. After extended annealing, the h -BN monolayer disintegrates into nanoislands with zigzag edges. We discuss the implications of these findings on the stability and oxidation resistance of h -BN and relate them to challenges in process integration and 2D heterostructures.

  7. 2D materials for nanophotonic devices

    NASA Astrophysics Data System (ADS)

    Xu, Renjing; Yang, Jiong; Zhang, Shuang; Pei, Jiajie; Lu, Yuerui

    2015-12-01

    Two-dimensional (2D) materials have become very important building blocks for electronic, photonic, and phononic devices. The 2D material family has four key members, including the metallic graphene, transition metal dichalcogenide (TMD) layered semiconductors, semiconducting black phosphorous, and the insulating h-BN. Owing to the strong quantum confinements and defect-free surfaces, these atomically thin layers have offered us perfect platforms to investigate the interactions among photons, electrons and phonons. The unique interactions in these 2D materials are very important for both scientific research and application engineering. In this talk, I would like to briefly summarize and highlight the key findings, opportunities and challenges in this field. Next, I will introduce/highlight our recent achievements. We demonstrated atomically thin micro-lens and gratings using 2D MoS2, which is the thinnest optical component around the world. These devices are based on our discovery that the elastic light-matter interactions in highindex 2D materials is very strong. Also, I would like to introduce a new two-dimensional material phosphorene. Phosphorene has strongly anisotropic optical response, which creates 1D excitons in a 2D system. The strong confinement in phosphorene also enables the ultra-high trion (charged exciton) binding energies, which have been successfully measured in our experiments. Finally, I will briefly talk about the potential applications of 2D materials in energy harvesting.

  8. Direct conversion of h-BN into c-BN and formation of epitaxial c-BN/diamond heterostructures

    NASA Astrophysics Data System (ADS)

    Narayan, Jagdish; Bhaumik, Anagh; Xu, Weizong

    2016-05-01

    We have created a new state of BN (named Q-BN) through rapid melting and super undercooling and quenching by using nanosecond laser pulses. Phase pure c-BN is formed either by direct quenching of super undercooled liquid or by nucleation and growth from Q-BN. Thus, a direct conversion of hexagonal boron nitride (h-BN) into phase-pure cubic boron nitride (c-BN) is achieved by nanosecond pulsed laser melting at ambient temperatures and atmospheric pressure in air. According to the P-T phase diagram, the transformation from h-BN into c-BN under equilibrium processing can occur only at high temperatures and pressures, as the hBN-cBN-Liquid triple point is at 3500 K/9.5 GPa or 3700 K/7.0 GPa with a recent theoretical refinement. Using nonequilibrium nanosecond laser melting, we have created super undercooled state and shifted this triple point to as low as 2800 K and atmospheric pressure. The rapid quenching from super undercooled state leads to the formation of a new phase, named as Q-BN. We present detailed characterization of Q-BN and c-BN layers by using Raman spectroscopy, high-resolution scanning electron microscopy, electron-back-scatter diffraction, high-resolution TEM, and electron energy loss spectroscopy, and discuss the mechanism of formation of nanodots, nanoneedles, microneedles, and single-crystal c-BN on sapphire substrate. We have also deposited diamond by pulsed laser deposition of carbon on c-BN and created c-BN/diamond heterostructures, where c-BN acts as a template for epitaxial diamond growth. We discuss the mechanism of epitaxial c-BN and diamond growth on lattice matching c-BN template under pulsed laser evaporation of amorphous carbon, and the impact of this discovery on a variety of applications.

  9. All Chemical Vapor Deposition Growth of MoS2:h-BN Vertical van der Waals Heterostructures.

    PubMed

    Wang, Shanshan; Wang, Xiaochen; Warner, Jamie H

    2015-05-26

    Vertical van der Waals heterostructures are formed when different 2D crystals are stacked on top of each other. Improved optical properties arise in semiconducting transition metal dichalcogenide (TMD) 2D materials, such as MoS2, when they are stacked onto the insulating 2D hexagonal boron nitride (h-BN). Most work to date has required mechanical exfoliation of at least one of the TMDs or h-BN materials to form these semiconductor:insulator structures. Here, we report a direct all-CVD process for the fabrication of high-quality monolayer MoS2:h-BN vertical heterostructured films with isolated MoS2 domains distributed across 1 cm. This is enabled by the use of few-layer h-BN films that are more robust against decomposition than monolayer h-BN during the MoS2 growth process. The MoS2 domains exhibit different growth dynamics on the h-BN surfaces compared to bare SiO2, confirming that there is strong interaction between the MoS2 and underlying h-BN. Raman and photoluminescence spectroscopies of CVD-grown MoS2 are compared to transferred MoS2 on both types of substrates, and our results show directly grown MoS2 on h-BN films have smaller lattice strain, lower doping level, cleaner and sharper interfaces, and high-quality interlayer contact.

  10. Metrology for graphene and 2D materials

    NASA Astrophysics Data System (ADS)

    Pollard, Andrew J.

    2016-09-01

    The application of graphene, a one atom-thick honeycomb lattice of carbon atoms with superlative properties, such as electrical conductivity, thermal conductivity and strength, has already shown that it can be used to benefit metrology itself as a new quantum standard for resistance. However, there are many application areas where graphene and other 2D materials, such as molybdenum disulphide (MoS2) and hexagonal boron nitride (h-BN), may be disruptive, areas such as flexible electronics, nanocomposites, sensing and energy storage. Applying metrology to the area of graphene is now critical to enable the new, emerging global graphene commercial world and bridge the gap between academia and industry. Measurement capabilities and expertise in a wide range of scientific areas are required to address this challenge. The combined and complementary approach of varied characterisation methods for structural, chemical, electrical and other properties, will allow the real-world issues of commercialising graphene and other 2D materials to be addressed. Here, examples of metrology challenges that have been overcome through a multi-technique or new approach are discussed. Firstly, the structural characterisation of defects in both graphene and MoS2 via Raman spectroscopy is described, and how nanoscale mapping of vacancy defects in graphene is also possible using tip-enhanced Raman spectroscopy (TERS). Furthermore, the chemical characterisation and removal of polymer residue on chemical vapour deposition (CVD) grown graphene via secondary ion mass spectrometry (SIMS) is detailed, as well as the chemical characterisation of iron films used to grow large domain single-layer h-BN through CVD growth, revealing how contamination of the substrate itself plays a role in the resulting h-BN layer. In addition, the role of international standardisation in this area is described, outlining the current work ongoing in both the International Organization of Standardization (ISO) and the

  11. Fabrication of AlN/BN bishell hollow nanofibers by electrospinning and atomic layer deposition

    SciTech Connect

    Haider, Ali; Kayaci, Fatma; Uyar, Tamer; Biyikli, Necmi; Ozgit-Akgun, Cagla; Okyay, Ali Kemal

    2014-09-01

    Aluminum nitride (AlN)/boron nitride (BN) bishell hollow nanofibers (HNFs) have been fabricated by successive atomic layer deposition (ALD) of AlN and sequential chemical vapor deposition (CVD) of BN on electrospun polymeric nanofibrous template. A four-step fabrication process was utilized: (i) fabrication of polymeric (nylon 6,6) nanofibers via electrospinning, (ii) hollow cathode plasma-assisted ALD of AlN at 100 °C onto electrospun polymeric nanofibers, (iii) calcination at 500 °C for 2 h in order to remove the polymeric template, and (iv) sequential CVD growth of BN at 450 °C. AlN/BN HNFs have been characterized for their chemical composition, surface morphology, crystal structure, and internal nanostructure using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction. Measurements confirmed the presence of crystalline hexagonal BN and AlN within the three dimensional (3D) network of bishell HNFs with relatively low impurity content. In contrast to the smooth surface of the inner AlN layer, outer BN coating showed a highly rough 3D morphology in the form of BN nano-needle crystallites. It is shown that the combination of electrospinning and plasma-assisted low-temperature ALD/CVD can produce highly controlled multi-layered bishell nitride ceramic hollow nanostructures. While electrospinning enables easy fabrication of nanofibrous template, self-limiting reactions of plasma-assisted ALD and sequential CVD provide control over the wall thicknesses of AlN and BN layers with sub-nanometer accuracy.

  12. Studies on antibiotics BN-227 and BN-227-F, new antibiotics. I. Taxonomy, isolation and characterization.

    PubMed

    Itoh, J; Miyadoh, S; Takahasi, S; Amano, S; Ezaki, N; Yamada, Y

    1979-11-01

    The two new antibiotics, BN-227 and BN-227-F, were isolated from the fermentation broth of Pseudomonas sp. BN-227. BN-227 has a molecular formula C7H9NO3, and melts at 115 degrees C. BN-227-F has a molecular formula C21H24N3O9Fe, and melts at 156 degrees C. BN-227-F is a chelate compound consisting of three similar ligands (antibiotic BN-227) and ferric ion. The two antibiotics have antimicrobial activity against Gram-positive and Gram-negative bacteria. PMID:528378

  13. Van der Waals stacked 2D layered materials for optoelectronics

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjing; Wang, Qixing; Chen, Yu; Wang, Zhuo; Wee, Andrew T. S.

    2016-06-01

    The band gaps of many atomically thin 2D layered materials such as graphene, black phosphorus, monolayer semiconducting transition metal dichalcogenides and hBN range from 0 to 6 eV. These isolated atomic planes can be reassembled into hybrid heterostructures made layer by layer in a precisely chosen sequence. Thus, the electronic properties of 2D materials can be engineered by van der Waals stacking, and the interlayer coupling can be tuned, which opens up avenues for creating new material systems with rich functionalities and novel physical properties. Early studies suggest that van der Waals stacked 2D materials work exceptionally well, dramatically enriching the optoelectronics applications of 2D materials. Here we review recent progress in van der Waals stacked 2D materials, and discuss their potential applications in optoelectronics.

  14. High-Yield Synthesis of Stoichiometric Boron Nitride Nanostructures

    DOE PAGES

    Nocua, José E.; Piazza, Fabrice; Weiner, Brad R.; Morell, Gerardo

    2009-01-01

    Boron nimore » tride (BN) nanostructures are structural analogues of carbon nanostructures but have completely different bonding character and structural defects. They are chemically inert, electrically insulating, and potentially important in mechanical applications that include the strengthening of light structural materials. These applications require the reliable production of bulk amounts of pure BN nanostructures in order to be able to reinforce large quantities of structural materials, hence the need for the development of high-yield synthesis methods of pure BN nanostructures. Using borazine ( B 3 N 3 H 6 ) as chemical precursor and the hot-filament chemical vapor deposition (HFCVD) technique, pure BN nanostructures with cross-sectional sizes ranging between 20 and 50 nm were obtained, including nanoparticles and nanofibers. Their crystalline structure was characterized by (XRD), their morphology and nanostructure was examined by (SEM) and (TEM), while their chemical composition was studied by (EDS), (FTIR), (EELS), and (XPS). Taken altogether, the results indicate that all the material obtained is stoichiometric nanostructured BN with hexagonal and rhombohedral crystalline structure.« less

  15. Aniso2D

    2005-07-01

    Aniso2d is a two-dimensional seismic forward modeling code. The earth is parameterized by an X-Z plane in which the seismic properties Can have monoclinic with x-z plane symmetry. The program uses a user define time-domain wavelet to produce synthetic seismograms anrwhere within the two-dimensional media.

  16. Towards 2D nanocomposites

    NASA Astrophysics Data System (ADS)

    Jang, Hyun-Sook; Yu, Changqian; Hayes, Robert; Granick, Steve

    2015-03-01

    Polymer vesicles (``polymersomes'') are an intriguing class of soft materials, commonly used to encapsulate small molecules or particles. Here we reveal they can also effectively incorporate nanoparticles inside their polymer membrane, leading to novel ``2D nanocomposites.'' The embedded nanoparticles alter the capacity of the polymersomes to bend and to stretch upon external stimuli.

  17. (Fuzzy) Ideals of BN-Algebras

    PubMed Central

    Walendziak, Andrzej

    2015-01-01

    The notions of an ideal and a fuzzy ideal in BN-algebras are introduced. The properties and characterizations of them are investigated. The concepts of normal ideals and normal congruences of a BN-algebra are also studied, the properties of them are displayed, and a one-to-one correspondence between them is presented. Conditions for a fuzzy set to be a fuzzy ideal are given. The relationships between ideals and fuzzy ideals of a BN-algebra are established. The homomorphic properties of fuzzy ideals of a BN-algebra are provided. Finally, characterizations of Noetherian BN-algebras and Artinian BN-algebras via fuzzy ideals are obtained. PMID:26125050

  18. Mesh2d

    2011-12-31

    Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assignsmore » an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.« less

  19. Factors controlling the CO intercalation of h-BN overlayers on Ru(0001).

    PubMed

    Dong, Aiyi; Fu, Qiang; Wu, Hao; Wei, Mingming; Bao, Xinhe

    2016-09-21

    The space between a two-dimensional (2D) material overlayer and a metal surface can be regarded as a nanoreactor, in which molecule adsorption and surface reaction may occur. In this work, we present CO intercalation under a hexagonal boron nitride (h-BN) overlayer on Ru(0001) at room temperature, observed using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and scanning tunneling microscopy. Critical factors influencing the interfacial process have been investigated, including CO partial pressure, h-BN coverage, and oxygen pre-adsorption on the Ru surface. It has been identified that CO adsorption on the bare Ru surface region plays an important role in CO intercalation. Comparative studies of CO intercalation at h-BN/Ru(0001) and graphene/Ru(0001) interfaces indicate that CO starts to intercalate h-BN overlayers more easily than graphene. Temperature-programmed CO desorption experiments from h-BN/CO/Ru(0001) and graphene/CO/Ru(0001) surfaces reveal a similar confinement effect of the 2D cover on CO adsorption, which results in a more abrupt and quick CO desorption in comparison with the CO/Ru(0001) surface. PMID:27530273

  20. Bandgap modulation and hydrogen storage with Cr-doped BN sheets

    NASA Astrophysics Data System (ADS)

    Ma, Shengqian

    2015-08-01

    The theoretical calculations indicate that the metal-doped boron nitride (BN) sheets are potential materials to store the hydrogen and tune the bandgap. It is all known that the BN sheet is a nonmagnetic wide-bandgap semiconductor. Using density function theory (DFT), the lattice parameters of Cr-doped BN sheets are optimized, which are still kept on two-dimensional (2D) planar geometry, and the bandgap and H2 storage are studied. The simulation results show that the H2 molecule can be easily absorbed by Cr-doped N in BN sheet. As the adsorption energy was greatly decreasing with the increasing number of Cr-doped N, B had an affinity for adsorption of H2. With the increase of Cr doping, the bandgap of Cr-doped BN sheet is decreasing. The bandgap decreases from 4.705 eV to 0.08 eV. So Cr-doped BN sheet is a promising material in storing H2 and tuning the bandgap.

  1. The interface between ferroelectric and 2D material for a Ferroelectric Field-Effect Transistor

    NASA Astrophysics Data System (ADS)

    Park, Nahee; Kang, Haeyong; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    We have studied electrical property of ferroelectric field-effect transistor which consists of graphene on hexagonal Boron-Nitride (h-BN) gated by a ferroelectric, PMN-PT (i.e. (1-x)Pb(Mg1/3Nb2/3) O3-xPbTiO3) single-crystal substrate. The PMN-PT was expected to have an effect on polarization field into the graphene channel and to induce a giant amount of surface charge. The hexagonal Boron-Nitride (h-BN) flake was directly exfoliated on the PMN-PT substrate for preventing graphene from directly contacting on the PMN-PT substrate. It can make us to observe the effect of the interface between ferroelectric and 2D material on the device operation. Monolayer graphene as 2D channel material, which was confirmed by Raman spectroscopy, was transferred on top of the hexagonal Boron-Nitride (h-BN) by using the conventional dry-transfer method. Here, we can demonstrate that the structure of graphene/hexagonal-BN/ferroelectric field-effect transistor makes us to clearly understand the device operation as well as the interface between ferroelectric and 2D materials by inserting h-BN between them. The phenomena such as anti-hysteresis, current saturation behavior, and hump-like increase of channel current, will be discussed by in terms of ferroelectric switching, polarization-assisted charge trapping.

  2. A new apparatus for direct transformation from hBN to cBN

    SciTech Connect

    Kuroyama, Y.; Itoh, K.; Liu, Z. Y.; Fujita, M.; Itoh, S.

    1998-07-10

    A new apparatus was devised for direct phase transformation from hBN to cBN by using the cylindrical explosion. The apparatus consisted of multiple thin-metal foils in a metal tube surrounded by a high efficiency explosive and the spaces between the multiple thin-metal foils were filled with hBN containing a small amount of copper powder. This apparatus was expected to produce higher pressure and temperature than the ordinary cylindrical method. These high pressure and temperature has been proved to be satisfactory to result in the direct phase transformation from hBN into cBN.

  3. Microwave Assisted 2D Materials Exfoliation

    NASA Astrophysics Data System (ADS)

    Wang, Yanbin

    Two-dimensional materials have emerged as extremely important materials with applications ranging from energy and environmental science to electronics and biology. Here we report our discovery of a universal, ultrafast, green, solvo-thermal technology for producing excellent-quality, few-layered nanosheets in liquid phase from well-known 2D materials such as such hexagonal boron nitride (h-BN), graphite, and MoS2. We start by mixing the uniform bulk-layered material with a common organic solvent that matches its surface energy to reduce the van der Waals attractive interactions between the layers; next, the solutions are heated in a commercial microwave oven to overcome the energy barrier between bulk and few-layers states. We discovered the minutes-long rapid exfoliation process is highly temperature dependent, which requires precise thermal management to obtain high-quality inks. We hypothesize a possible mechanism of this proposed solvo-thermal process; our theory confirms the basis of this novel technique for exfoliation of high-quality, layered 2D materials by using an as yet unknown role of the solvent.

  4. Laser-based diagnostics applied to the study of BN nanotubes synthesis.

    PubMed

    Cau, M; Dorval, N; Attal-Trétout, B; Cochon, J L; Cao, B; Bresson, L; Jaffrennou, P; Silly, M; Loiseau, A; Obraztsova, E D

    2008-11-01

    The boron nitride nanotubes (BNNTs) synthesis, using CO2-laser vaporization of a BN target under nitrogen gas, is investigated by UV-laser induced fluorescence (LIF) of the vapor phase and UV-Rayleigh scattering (RS) of the gas-suspended nanoparticles. The LIF signal from B atoms is mainly detected in the 1.5 mm-thick region above the BN target. It originates from a boron-rich vapor region confined near the hot boron droplet formed at the target surface. Then, recombination between hot boron and N2 gas occurs through a fast condensation process as revealed by both the depletion of B atoms from the vapor phase and the RS signal arising from the grown BN nanoparticles. Fluorescence spectra exhibit a strong peak at 250 nm due to boron fluorescence and mainly to nanoparticles Rayleigh scattering. A narrow peak is observed at 210 nm and a broader peak at 189 nm. These bands are tentatively assigned to fluorescence or photoluminescence (PL) from gaseous or solid BN species respectively since both gas and solid phases coexist in the plume due to the rapid cooling process. Two very weak bands occur at 308 nm and 350 nm. They are related to PL of defects bands from BN nanostructures on the basis of ex situ PL spectra of h-BN crystallites and multi-wall BNNTs. Detection of oxygen impurities is shown feasible through LIF from BO radical which is detected just above the BN target evaporated under vacuum pressure (approximately 1 mbar). An optical diagnostic strategy is demonstrated from these first in situ observations during BNNTs synthesis. PMID:19198355

  5. Negative Refraction with Superior Transmission in Graphene-Hexagonal Boron Nitride (hBN) Multilayer Hyper Crystal

    PubMed Central

    Sayem, Ayed Al; Rahman, Md. Masudur; Mahdy, M. R. C.; Jahangir, Ifat; Rahman, Md. Saifur

    2016-01-01

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride (hBN) multilayer structure (hyper crystal) to demonstrate all angle negative refraction along with superior transmission. hBN, one of the latest natural hyperbolic materials, can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hBN can exhibit negative refraction, the transmission is generally low due to its high reflectivity. Whereas due to graphene’s 2D nature and metallic characteristics in the frequency range where hBN behaves as a type-I hyperbolic material, we have found graphene-hBN hyper-crystals to exhibit all angle negative refraction with superior transmission. Interestingly, superior transmission from the whole structure can be fully controlled by the tunability of graphene without hampering the negative refraction originated mainly from hBN. We have also presented an effective medium description of the hyper crystal in the low-k limit and validated the proposed theory analytically and with full wave simulations. Along with the current extensive research on hybridization of graphene plasmon polaritons with (hyperbolic) hBN phonon polaritons, this work might have some substantial impact on this field of research and can be very useful in applications such as hyper-lensing. PMID:27146561

  6. Negative Refraction with Superior Transmission in Graphene-Hexagonal Boron Nitride (hBN) Multilayer Hyper Crystal.

    PubMed

    Sayem, Ayed Al; Rahman, Md Masudur; Mahdy, M R C; Jahangir, Ifat; Rahman, Md Saifur

    2016-05-05

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride (hBN) multilayer structure (hyper crystal) to demonstrate all angle negative refraction along with superior transmission. hBN, one of the latest natural hyperbolic materials, can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hBN can exhibit negative refraction, the transmission is generally low due to its high reflectivity. Whereas due to graphene's 2D nature and metallic characteristics in the frequency range where hBN behaves as a type-I hyperbolic material, we have found graphene-hBN hyper-crystals to exhibit all angle negative refraction with superior transmission. Interestingly, superior transmission from the whole structure can be fully controlled by the tunability of graphene without hampering the negative refraction originated mainly from hBN. We have also presented an effective medium description of the hyper crystal in the low-k limit and validated the proposed theory analytically and with full wave simulations. Along with the current extensive research on hybridization of graphene plasmon polaritons with (hyperbolic) hBN phonon polaritons, this work might have some substantial impact on this field of research and can be very useful in applications such as hyper-lensing.

  7. Negative Refraction with Superior Transmission in Graphene-Hexagonal Boron Nitride (hBN) Multilayer Hyper Crystal

    NASA Astrophysics Data System (ADS)

    Sayem, Ayed Al; Rahman, Md. Masudur; Mahdy, M. R. C.; Jahangir, Ifat; Rahman, Md. Saifur

    2016-05-01

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride (hBN) multilayer structure (hyper crystal) to demonstrate all angle negative refraction along with superior transmission. hBN, one of the latest natural hyperbolic materials, can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hBN can exhibit negative refraction, the transmission is generally low due to its high reflectivity. Whereas due to graphene’s 2D nature and metallic characteristics in the frequency range where hBN behaves as a type-I hyperbolic material, we have found graphene-hBN hyper-crystals to exhibit all angle negative refraction with superior transmission. Interestingly, superior transmission from the whole structure can be fully controlled by the tunability of graphene without hampering the negative refraction originated mainly from hBN. We have also presented an effective medium description of the hyper crystal in the low-k limit and validated the proposed theory analytically and with full wave simulations. Along with the current extensive research on hybridization of graphene plasmon polaritons with (hyperbolic) hBN phonon polaritons, this work might have some substantial impact on this field of research and can be very useful in applications such as hyper-lensing.

  8. Graphene/h-BN/GaAs sandwich diode as solar cell and photodetector.

    PubMed

    Li, Xiaoqiang; Lin, Shisheng; Lin, Xing; Xu, Zhijuan; Wang, Peng; Zhang, Shengjiao; Zhong, Huikai; Xu, Wenli; Wu, Zhiqian; Fang, Wei

    2016-01-11

    In graphene/semiconductor heterojunction, the statistic charge transfer between graphene and semiconductor leads to decreased junction barrier height and limits the Fermi level tuning effect in graphene, which greatly affects the final performance of the device. In this work, we have designed a sandwich diode for solar cells and photodetectors through inserting 2D hexagonal boron nitride (h-BN) into graphene/GaAs heterostructure to suppress the static charge transfer. The barrier height of graphene/GaAs heterojunction can be increased from 0.88 eV to 1.02 eV by inserting h-BN. Based on the enhanced Fermi level tuning effect with interface h-BN, through adopting photo-induced doping into the device, power conversion efficiency (PCE) of 10.18% has been achieved for graphene/h-BN/GaAs compared with 8.63% of graphene/GaAs structure. The performance of graphene/h-BN/GaAs based photodetector is also improved with on/off ratio increased by one magnitude compared with graphene/GaAs structure.

  9. Heterostructured hBN-BP-hBN Nanodetectors at Terahertz Frequencies.

    PubMed

    Viti, Leonardo; Hu, Jin; Coquillat, Dominique; Politano, Antonio; Consejo, Christophe; Knap, Wojciech; Vitiello, Miriam S

    2016-09-01

    By reassembling thin isolated atomic planes of hexagonal borum nitride (hBN) with a few layer phosphorene black phosphorus (BP), hBN/BP/hBN heterostructures are mechanically stacked to devise high-efficiency THz photodetectors operating in the 0.3-0.65 THz range, from 4 K to 300 K, with a record signal-to-noise ratio of 20 000.

  10. Anisotropic Effective Mass, Optical Property, and Enhanced Band Gap in BN/Phosphorene/BN Heterostructures.

    PubMed

    Hu, Tao; Hong, Jisang

    2015-10-28

    Phosphorene is receiving great research interests because of its peculiar physical properties. Nonetheless, the phosphorus has a trouble of degradation due to oxidation. Hereby, we propose that the electrical and optical anisotropic properties can be preserved by encapsulating into hexagonal boron nitride (h-BN). We found that the h-BN contributed to enhancing the band gap of the phosphorene layer. Comparing the band gap of the pristine phosphorene layer, the band gap of the phosphorene/BN(1ML) system was enhanced by 0.15 eV. It was further enhanced by 0.31 eV in the BN(1ML)/phosphorene/BN(1ML) trilayer structure. However, the band gap was not further enhanced when we increased the thickness of the h-BN layers even up to 4 MLs. Interestingly, the anisotropic effective mass and optical property were still preserved in BN/phosphorene/BN heterostructures. Overall, we predict that the capping of phosphorene by the h-BN layers can be an excellent solution to protect the intrinsic properties of the phosphorene.

  11. Cellulose nanofibrils (CNF) filled boron nitride (BN) nanocomposites

    SciTech Connect

    Sulaiman, Hanisah Syed; Hua, Chia Chin; Zakaria, Sarani

    2015-09-25

    In this study, nanocomposite using cellulose nanofibrils filled with different percentage of boron nitride (CNF-BN) were prepared. The objective of this research is to study the effect of different percentage of BN to the thermal conductivity of the nanocomposite produced. The CNF-BN nanocomposite were characterization by FT-IR, SEM and thermal conductivity. The FT-IR analysis of the CNF-BN nanocomposite shows all the characteristic peaks of cellulose and BN present in all samples. The dispersion of BN in CNF were seen through SEM analysis. The effect of different loading percentage of BN to the thermal conductivity of the nanocomposite were also investigated.

  12. Plasma as a tool for growth of 1D and 2D nanomaterials and their conversions

    NASA Astrophysics Data System (ADS)

    Cvelbar, Uros

    2015-09-01

    The growth of 1D and 2D nanostructures in low pressure oxygen plasma is presented with the special stress on metal-oxide nanowires and their deterministic growth mechanisms. Since the resulting nanostructures not always have required properties for applications their modifications are required. Therefore their conversions into different oxides or sulphites/nitrides are required with either molecules, atoms, electrons or photons.

  13. Research Update: Direct conversion of h-BN into pure c-BN at ambient temperatures and pressures in air

    NASA Astrophysics Data System (ADS)

    Narayan, Jagdish; Bhaumik, Anagh

    2016-02-01

    We report a direct conversion of hexagonal boron nitride (h-BN) into pure cubic boron nitride (c-BN) by nanosecond laser melting at ambient temperatures and atmospheric pressure in air. According to the phase diagram, the transformation from h-BN into c-BN can occur only at high temperatures and pressures, as the hBN-cBN-Liquid triple point is at 3500 K/9.5 GPa. Using nanosecond laser melting, we have created super undercooled state and shifted this triple point to as low as 2800 K and atmospheric pressure. The rapid quenching from super undercooled state leads to formation of super undercooled BN (Q-BN). The c-BN phase is nucleated from Q-BN depending upon the time allowed for nucleation and growth.

  14. Effect of B[sub 2]O[sub 3] and hBN crystallinity on cBN synthesis

    SciTech Connect

    Junyoup Choi; Kang, S.J.L. . Dept of Ceramic Science and Engineering); Fukunaga, O. . Dept. of Inorganic Materials); Jongku Park; Eun, K.Y. . Div. of Ceramics)

    1993-10-01

    Four kinds of BN powders--amorphous BN with B[sub 2]O[sub 3], partially crystallized BN without B[sub 2]O[sub 3], well-crystallized hBN with B[sub 2]O[sub 3], and well-crystallized hBN without B[sub 2]O[sub 3]--were prepared to determine the effect of B[sub 2]O[sub 3] on the crystallization of amorphous BN and the effect of BN crystallinity on the formation of cBN under high pressure (4--5 GPa) and at high temperature (1,350--1,450 C). The amorphous BN with B[sub 2]O[sub 3] easily crystallized and transformed to cBN in the presence of AlN catalyst, while the partially crystallized Bn without B[sub 2]O[sub 3] did not. The well-crystallized hBN transformed very slowly to cBN without B[sub 2]O[sub 3], in contrast to fast transformation with B[sub 2]O[sub 3]. It is thus found that the transformation from hBN to cBN in the presence of AlN catalyst is determined by the degree of BN crystallinity as well as the presence of B[sub 2]O[sub 3]. Cubic BN can be synthesized only from crystallized hBN under the experimental conditions used. The formation of cBN from amorphous BN is possible through its prior crystallization, which can occur in the presence of B[sub 2]O[sub 3].

  15. Low energy cluster beam deposited BN films as the cascade for field emission

    NASA Astrophysics Data System (ADS)

    Song, F.; Zhang, L.; Zhu, L.; Ge, J.; Wang, G.

    2005-07-01

    The atomic deposited BN films with the thickness of nanometers (ABN) were prepared by radio frequency magnetron sputtering method and the nanostructured BN films (CBN) were prepared by Low Energy Cluster Beam Deposition. UV-Vis Absorption measurement proves the band gap of 4.27 eV and field emission of the BN films were carried out. F-N plots of all the samples give a good fitting and demonstrate the F-N tunneling of the emission process. The emission of ABN begins at the electric field of 14.6 V/μ m while that of CBN starts at 5.10 V/μ m. Emission current density of 1 mA/cm2 for ABN needs the field of 20 V/μ m while that of CBN needs only 12.1 V/μ m. The cluster-deposited BN on n-type Silicon substrate proves a good performance in terms of the lower gauge voltage, more emission sites and higher electron intensity and seems a promising substitute for the cascade of field emission.

  16. First-principles calculation of electronic structure and optical absorption of BN ZnO

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao; Schleife, Andre

    2015-03-01

    The α-BN structure of ZnO, a nonequilibrium phase with a transition pressure of 25 GPa, has been found in nano structures of ZnO. The structural difference between the BN structure and the equilibrium wurtzite structure can play an important role for applications of nanostructured ZnO. In order to understand the difference, first principles calculations have been performed on both phases. The electronic structure is computed using the GW method based on Density Functional Theory and HSE hybrid functional calculations. The GW method includes the quasiparticle effects due to the screened electron-electron interaction which gives an accurate description of the electronic band structure and density of states. After that, by solving the Bethe-Salpeter Equation for the optical polarization function, which take excitonic effects into account, we have achieved an accurate description of optical absorption spectra for both structures. We find a good agreement with experimental and previous computational results for WZ structure, and predict the absorption for the BN structure. The BN structure shows a larger band gap and we found a very large optical anisotropy: The gap for extraordinary light polarization is almost 0.7eV larger than that for ordinary light polarization.

  17. The reconstructed edges of the hexagonal BN

    NASA Astrophysics Data System (ADS)

    Zhao, Ruiqi; Gao, Junfeng; Liu, Zhongfan; Ding, Feng

    2015-05-01

    As an important two-dimensional material which shows exceptional mechanical and chemical stability, superior electronic properties, along with broad applications, the hexagonal-BN (h-BN) has drawn great attention recently. Here we report a systematic study on the structural stability, electronic and magnetic properties of various h-BN edges, including both bare and hydrogen-terminated ones. It is found that along the armchair (AC) direction, the pristine edge is the most stable one because of the formation of a triple B\\z.tbd N bond, while, along the zigzag (ZZ) directions, the reconstructed ones, ZZB + N and ZZN57 are more stable. The pristine edges are more stable in bare BN in most cases if saturated with hydrogen. By applying the theory of Wulff construction, we predicted that an unpassivated BN domain prefers the hexagonal shape enclosed with bare AC edges i.e., AC-Ns, AC, AC-Bs if the feedstock varies from N-rich to B-rich. However, the evolution from ZZN edged triangular domain, to hexagonal domain enclosed with AC edges, and ZZB edged triangle may occur if the edges are terminated by hydrogen atoms. Further calculation shows that these edges present rich type-dependent properties and thus are important for various applications. This theoretical study showed that controlling the morphologies of BN domains and BN edges is crucial for various applications.As an important two-dimensional material which shows exceptional mechanical and chemical stability, superior electronic properties, along with broad applications, the hexagonal-BN (h-BN) has drawn great attention recently. Here we report a systematic study on the structural stability, electronic and magnetic properties of various h-BN edges, including both bare and hydrogen-terminated ones. It is found that along the armchair (AC) direction, the pristine edge is the most stable one because of the formation of a triple B\\z.tbd N bond, while, along the zigzag (ZZ) directions, the reconstructed ones, ZZB + N

  18. High divergent 2D grating

    NASA Astrophysics Data System (ADS)

    Wang, Jin; Ma, Jianyong; Zhou, Changhe

    2014-11-01

    A 3×3 high divergent 2D-grating with period of 3.842μm at wavelength of 850nm under normal incidence is designed and fabricated in this paper. This high divergent 2D-grating is designed by the vector theory. The Rigorous Coupled Wave Analysis (RCWA) in association with the simulated annealing (SA) is adopted to calculate and optimize this 2D-grating.The properties of this grating are also investigated by the RCWA. The diffraction angles are more than 10 degrees in the whole wavelength band, which are bigger than the traditional 2D-grating. In addition, the small period of grating increases the difficulties of fabrication. So we fabricate the 2D-gratings by direct laser writing (DLW) instead of traditional manufacturing method. Then the method of ICP etching is used to obtain the high divergent 2D-grating.

  19. Functionalized 2D atomic sheets with new properties

    NASA Astrophysics Data System (ADS)

    Sun, Qiang; Zhou, Jian; Wang, Qian; Jena, Puru

    2011-03-01

    Due to the unique atomic structure and novel physical and chemical properties, graphene has sparked tremendous theoretical and experimental efforts to explore other 2D atomic sheets like B-N, Al-N, and Zn-O, where the two components offer much more complexities and flexibilities in surface modifications. Using First principles calculations based on density functional theory, we have systematically studied the semi- and fully-decorated 2D sheets with H and F and Cl. We have found that the electronic structures and magnetic properties can be effectively tuned, and the system can be a direct or an indirect semiconductor or even a half-metal, and the system can be made ferromagnetic, antiferromagnetic, or magnetically degenerate depending upon how the surface is functionalized. Discussions are made for the possible device applications.

  20. Cheap, Gram-Scale Fabrication of BN Nanosheets via Substitution Reaction of Graphite Powders and Their Use for Mechanical Reinforcement of Polymers

    PubMed Central

    Liu, Fei; Mo, Xiaoshu; Gan, Haibo; Guo, Tongyi; Wang, Xuebin; Chen, Bin; Chen, Jun; Deng, Shaozhi; Xu, Ningsheng; Sekiguchi, Takashi; Golberg, Dmitri; Bando, Yoshio

    2014-01-01

    As one of the most important two-dimensional (2D) materials, BN nanosheets attracted intensive interest in the past decade. Although there are many methods suitable for the preparation of BN sheets, finding a cheap and nontoxic way for their mass and high-quality production is still a challenge. Here we provide a highly effective and cheap way to synthesize gram-scale-level well-structured BN nanosheets from many common graphite products as source materials. Single-crystalline multi-layered BN sheets have a mean lateral size of several hundred nanometers and a thickness ranging from 5 nm to 40 nm. Cathodoluminescence (CL) analysis shows that the structures exhibit a near band-edge emission and a broad emission band from 300 nm to 500 nm. Utilization of nanosheets for the reinforcement of polymers revealed that the Young's modulus of BN/PMMA composite had increased to 1.56 GPa when the BN's fraction was only 2 wt.%, thus demonstrating a 20% gain compared to a blank PMMA film. It suggests that the BN nanosheet is an ideal mechanical reinforcing material for polymers. In addition, this easy and nontoxic substitution method may provide a universal route towards high yields of other 2D materials. PMID:24572725

  1. Multipurpose Black-Phosphorus/hBN Heterostructures.

    PubMed

    Constantinescu, Gabriel C; Hine, Nicholas D M

    2016-04-13

    Black phosphorus (BP) has recently emerged as a promising semiconducting two-dimensional material. However, its viability is threatened by its instability in ambient conditions and by the significant decrease of its band gap in multilayers. We show that one could solve all the aforementioned problems by interfacing BP with hexagonal boron nitride (hBN). To this end, we simulate large, rotated hBN/BP interfaces using linear-scaling density functional theory. We predict that hBN-encapsulation preserves the main electronic properties of the BP monolayer, while hBN spacers can be used to counteract the band gap reduction in stacked BP. Finally, we propose a model for a tunneling field effect transistor (TFET) based on hBN-spaced BP bilayers. Such BP TFETs would sustain both low-power and fast-switching operations, including negative differential resistance behavior with peak-to-valley ratios of the same order of magnitude as those encountered in transition metal dichalcogenide TFETs. PMID:27028122

  2. Multipurpose Black-Phosphorus/hBN Heterostructures.

    PubMed

    Constantinescu, Gabriel C; Hine, Nicholas D M

    2016-04-13

    Black phosphorus (BP) has recently emerged as a promising semiconducting two-dimensional material. However, its viability is threatened by its instability in ambient conditions and by the significant decrease of its band gap in multilayers. We show that one could solve all the aforementioned problems by interfacing BP with hexagonal boron nitride (hBN). To this end, we simulate large, rotated hBN/BP interfaces using linear-scaling density functional theory. We predict that hBN-encapsulation preserves the main electronic properties of the BP monolayer, while hBN spacers can be used to counteract the band gap reduction in stacked BP. Finally, we propose a model for a tunneling field effect transistor (TFET) based on hBN-spaced BP bilayers. Such BP TFETs would sustain both low-power and fast-switching operations, including negative differential resistance behavior with peak-to-valley ratios of the same order of magnitude as those encountered in transition metal dichalcogenide TFETs.

  3. Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Singh, Bikramjeet; Singh, Paviter; Kumar, Manjeet; Thakur, Anup; Kumar, Akshay

    2015-05-01

    Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H3BO3). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications as well boron neutron capture therapy (BNCT).

  4. Ultrafast 2D IR microscopy

    PubMed Central

    Baiz, Carlos R.; Schach, Denise; Tokmakoff, Andrei

    2014-01-01

    We describe a microscope for measuring two-dimensional infrared (2D IR) spectra of heterogeneous samples with μm-scale spatial resolution, sub-picosecond time resolution, and the molecular structure information of 2D IR, enabling the measurement of vibrational dynamics through correlations in frequency, time, and space. The setup is based on a fully collinear “one beam” geometry in which all pulses propagate along the same optics. Polarization, chopping, and phase cycling are used to isolate the 2D IR signals of interest. In addition, we demonstrate the use of vibrational lifetime as a contrast agent for imaging microscopic variations in molecular environments. PMID:25089490

  5. AnisWave 2D

    2004-08-01

    AnisWave2D is a 2D finite-difference code for a simulating seismic wave propagation in fully anisotropic materials. The code is implemented to run in parallel over multiple processors and is fully portable. A mesh refinement algorithm has been utilized to allow the grid-spacing to be tailored to the velocity model, avoiding the over-sampling of high-velocity materials that usually occurs in fixed-grid schemes.

  6. p-Phosphonic acid calix[8]arene assisted exfoliation and stabilization of 2D materials in water.

    PubMed

    Chen, Xianjue; Boulos, Ramiz A; Eggers, Paul K; Raston, Colin L

    2012-12-01

    Exfoliated 2D materials including graphene, BN, MoS(2) and WS(2) are accessible in water over a wide range of pH for a synergistic process involving sonication in the presence of p-phosphonic acid calix[8]arene.

  7. Germany unveils €18bn research plan

    NASA Astrophysics Data System (ADS)

    Banks, Michael

    2009-07-01

    The German government has unveiled an ambitious plan to inject a total of €18bn into teaching and research over the next decade. The German chancellor Angela Merkel, who has a degree in physics, announced that she was releasing the funds despite concerns from her social-democrat coalition partners that financing the package could be difficult in the economic downturn.

  8. Fully dry PMMA transfer of graphene on h-BN using a heating/cooling system

    NASA Astrophysics Data System (ADS)

    Uwanno, T.; Hattori, Y.; Taniguchi, T.; Watanabe, K.; Nagashio, K.

    2015-12-01

    The key to achieve high-quality van der Waals heterostructure devices made of stacking various two-dimensional (2D) layered materials lies in the clean interface without bubbles and wrinkles. Although polymethylmethacrylate (PMMA) is generally used as a sacrificial transfer film due to its strong adhesion property, it is always dissolved in the solvent after the transfer, resulting in the unavoidable PMMA residue on the top surface. This makes it difficult to locate clean interface areas. In this work, we present a fully dry PMMA transfer of graphene onto h-BN using a heating/cooling system which allows identification of clean interface area for high quality graphene/h-BN heterostructure fabrication. The mechanism lies in the utilization of the large difference in thermal expansion coefficients between polymers (PMMA/PDMS) and inorganic materials (graphene/h-BN substrate) to mechanically peel off PMMA from graphene by the thermal shrinkage of polymers, leaving no PMMA residue on the graphene surface. This method can be applied to all types of 2D layered materials.

  9. Atomically precise semiconductor--graphene and hBN interfaces by Ge intercalation.

    PubMed

    Verbitskiy, N I; Fedorov, A V; Profeta, G; Stroppa, A; Petaccia, L; Senkovskiy, B; Nefedov, A; Wöll, C; Usachov, D Yu; Vyalikh, D V; Yashina, L V; Eliseev, A A; Pichler, T; Grüneis, A

    2015-01-01

    The full exploration of the potential, which graphene offers to nanoelectronics requires its integration into semiconductor technology. So far the real-world applications are limited by the ability to concomitantly achieve large single-crystalline domains on dielectrics and semiconductors and to tailor the interfaces between them. Here we show a new direct bottom-up method for the fabrication of high-quality atomically precise interfaces between 2D materials, like graphene and hexagonal boron nitride (hBN), and classical semiconductor via Ge intercalation. Using angle-resolved photoemission spectroscopy and complementary DFT modelling we observed for the first time that epitaxially grown graphene with the Ge monolayer underneath demonstrates Dirac Fermions unaffected by the substrate as well as an unperturbed electronic band structure of hBN. This approach provides the intrinsic relativistic 2D electron gas towards integration in semiconductor technology. Hence, these new interfaces are a promising path for the integration of graphene and hBN into state-of-the-art semiconductor technology. PMID:26639608

  10. Engineering of hydrogenated two-dimensional h-BN/C superlattices as electrostatic substrates.

    PubMed

    Liu, Zhun; Zhong, Xiaoliang; Yan, Hui; Wang, Ru-Zhi

    2016-01-14

    Hybridized two-dimensional materials incorporating domains from the hexagonal boron nitride (h-BN) and graphene is an interesting branch of materials science due to their highly tunable electronic properties. In the present study, we investigate the hydrogenated two-dimensional (2D) h-BN/C superlattices (SLs) with zigzag edges using first-principles calculations. We found that the domain width, the phase ratio, and the vertical dipole orientation all have significant influence on the stability of SLs. The electronic reconstruction is associated with the lateral polar discontinuities at the zigzag edges and the vertically polarized (B2N2H4)(m) domains, which modifies the electronic structures and the spatial potential of the SLs significantly. Furthermore, we demonstrate that the hydrogenated 2D h-BN/C SLs can be applied in engineering the electronic structure of graphene: laterally-varying doping can be achieved by taking advantage of the spatial variation of the surface potential of the SLs. By applying an external vertical electric field on these novel bidirectional heterostructures, graphene doping levels and band offsets can be tuned to a wide range, such that the graphene doping profile can be switched from the bipolar (p-n junction) to unipolar (n(+)-n junction) mode. It is expected that such bidirectional heterostructures provide an effective approach for developing novel nanoscale electronic devices and improving our understanding of the fundamentals of low-dimensional materials. PMID:26661743

  11. Atomically precise semiconductor--graphene and hBN interfaces by Ge intercalation.

    PubMed

    Verbitskiy, N I; Fedorov, A V; Profeta, G; Stroppa, A; Petaccia, L; Senkovskiy, B; Nefedov, A; Wöll, C; Usachov, D Yu; Vyalikh, D V; Yashina, L V; Eliseev, A A; Pichler, T; Grüneis, A

    2015-01-01

    The full exploration of the potential, which graphene offers to nanoelectronics requires its integration into semiconductor technology. So far the real-world applications are limited by the ability to concomitantly achieve large single-crystalline domains on dielectrics and semiconductors and to tailor the interfaces between them. Here we show a new direct bottom-up method for the fabrication of high-quality atomically precise interfaces between 2D materials, like graphene and hexagonal boron nitride (hBN), and classical semiconductor via Ge intercalation. Using angle-resolved photoemission spectroscopy and complementary DFT modelling we observed for the first time that epitaxially grown graphene with the Ge monolayer underneath demonstrates Dirac Fermions unaffected by the substrate as well as an unperturbed electronic band structure of hBN. This approach provides the intrinsic relativistic 2D electron gas towards integration in semiconductor technology. Hence, these new interfaces are a promising path for the integration of graphene and hBN into state-of-the-art semiconductor technology.

  12. Atomically precise semiconductor—graphene and hBN interfaces by Ge intercalation

    PubMed Central

    Verbitskiy, N. I.; Fedorov, A. V.; Profeta, G.; Stroppa, A.; Petaccia, L.; Senkovskiy, B.; Nefedov, A.; Wöll, C.; Usachov, D. Yu.; Vyalikh, D. V.; Yashina, L. V.; Eliseev, A. A.; Pichler, T.; Grüneis, A.

    2015-01-01

    The full exploration of the potential, which graphene offers to nanoelectronics requires its integration into semiconductor technology. So far the real-world applications are limited by the ability to concomitantly achieve large single-crystalline domains on dielectrics and semiconductors and to tailor the interfaces between them. Here we show a new direct bottom-up method for the fabrication of high-quality atomically precise interfaces between 2D materials, like graphene and hexagonal boron nitride (hBN), and classical semiconductor via Ge intercalation. Using angle-resolved photoemission spectroscopy and complementary DFT modelling we observed for the first time that epitaxially grown graphene with the Ge monolayer underneath demonstrates Dirac Fermions unaffected by the substrate as well as an unperturbed electronic band structure of hBN. This approach provides the intrinsic relativistic 2D electron gas towards integration in semiconductor technology. Hence, these new interfaces are a promising path for the integration of graphene and hBN into state-of-the-art semiconductor technology. PMID:26639608

  13. Superstructure formation in SrBa8[BN2]6 and EuBa8[BN2]6.

    PubMed

    Seidel, Stefan; Dierkes, Tobias; Jüstel, Thomas; Benndorf, Christopher; Eckert, Hellmut; Pöttgen, Rainer

    2016-07-26

    X-ray pure samples of SrBa8[BN2]6 and EuBa8[BN2]6 were synthesized from appropriate amounts of binary nitrides (Sr3N2, Ba3N2 and BN in sealed niobium ampoules and EuN, Ba3N2 and BN in BN crucibles, respectively) at temperatures up to 1370 K. The structure of SrBa8[BN2]6 was refined from single crystal X-ray diffractometer data: Fd3[combining macron]m, a = 1595.1(1) pm, wR(F(2)) = 0.0515, 387 F(2) values and 21 variables. EuBa8[BN2]6 has a lattice parameter of 1595.00(9) pm. Both nitridoborates adopt a new 2 × 2 × 2 superstructure variant of the LiCa4[BN2]3 type, realized through ordering of vacancies and Sr(2+) and Eu(2+) cations, respectively. The structures of SrBa8[BN2]6 and LiCa4[BN2]3 are related by a group-subgroup scheme. The Sr(2+)/vacancy ordering leads to an asymmetric coordination (1 × Sr(2+) and 8 × Ba(2+) in a distorted, mono-capped square prism) for the [BN2](3-) units with B-N distances of 132 and 136 pm. Vibrational spectra of SrBa8[BN2]6 and EuBa8[BN2]6 confirm the discrete linear [BN2](3-) units and (11)B solid state MAS NMR spectra are compatible with single crystallographic sites for the boron atoms. In EuBa8[BN2]6 the spectra are profoundly influenced by interactions of the (11)B nuclei with the unpaired electrons of the paramagnetic Eu(2+) ions. PMID:27397545

  14. Superstructure formation in SrBa8[BN2]6 and EuBa8[BN2]6.

    PubMed

    Seidel, Stefan; Dierkes, Tobias; Jüstel, Thomas; Benndorf, Christopher; Eckert, Hellmut; Pöttgen, Rainer

    2016-07-26

    X-ray pure samples of SrBa8[BN2]6 and EuBa8[BN2]6 were synthesized from appropriate amounts of binary nitrides (Sr3N2, Ba3N2 and BN in sealed niobium ampoules and EuN, Ba3N2 and BN in BN crucibles, respectively) at temperatures up to 1370 K. The structure of SrBa8[BN2]6 was refined from single crystal X-ray diffractometer data: Fd3[combining macron]m, a = 1595.1(1) pm, wR(F(2)) = 0.0515, 387 F(2) values and 21 variables. EuBa8[BN2]6 has a lattice parameter of 1595.00(9) pm. Both nitridoborates adopt a new 2 × 2 × 2 superstructure variant of the LiCa4[BN2]3 type, realized through ordering of vacancies and Sr(2+) and Eu(2+) cations, respectively. The structures of SrBa8[BN2]6 and LiCa4[BN2]3 are related by a group-subgroup scheme. The Sr(2+)/vacancy ordering leads to an asymmetric coordination (1 × Sr(2+) and 8 × Ba(2+) in a distorted, mono-capped square prism) for the [BN2](3-) units with B-N distances of 132 and 136 pm. Vibrational spectra of SrBa8[BN2]6 and EuBa8[BN2]6 confirm the discrete linear [BN2](3-) units and (11)B solid state MAS NMR spectra are compatible with single crystallographic sites for the boron atoms. In EuBa8[BN2]6 the spectra are profoundly influenced by interactions of the (11)B nuclei with the unpaired electrons of the paramagnetic Eu(2+) ions.

  15. Large-roll growth of 25-inch hexagonal BN monolayer film for self-release buffer layer of free-standing GaN wafer

    PubMed Central

    Wu, Chenping; Soomro, Abdul Majid; Sun, Feipeng; Wang, Huachun; Huang, Youyang; Wu, Jiejun; Liu, Chuan; Yang, Xiaodong; Gao, Na; Chen, Xiaohong; Kang, Junyong; Cai, Duanjun

    2016-01-01

    Hexagonal boron nitride (h-BN) is known as promising 2D material with a wide band-gap (~6 eV). However, the growth size of h-BN film is strongly limited by the size of reaction chamber. Here, we demonstrate the large-roll synthesis of monolayer and controllable sub-monolayer h-BN film on wound Cu foil by low pressure chemical vapor deposition (LPCVD) method. By winding the Cu foil substrate into mainspring shape supported by a multi-prong quartz fork, the reactor size limit could be overcome by extending the substrate area to a continuous 2D curl of plane inward. An extremely large-size monolayer h-BN film has been achieved over 25 inches in a 1.2” tube. The optical band gap of h-BN monolayer was determined to be 6.0 eV. The h-BN film was uniformly transferred onto 2” GaN or 4” Si wafer surfaces as a release buffer layer. By HVPE method, overgrowth of thick GaN wafer over 200 μm has been achieved free of residual strain, which could provide high quality homo-epitaxial substrate. PMID:27756906

  16. Raman enhancement effect on two-dimensional layered materials: graphene, h-BN and MoS2.

    PubMed

    Ling, Xi; Fang, Wenjing; Lee, Yi-Hsien; Araujo, Paulo T; Zhang, Xu; Rodriguez-Nieva, Joaquin F; Lin, Yuxuan; Zhang, Jin; Kong, Jing; Dresselhaus, Mildred S

    2014-06-11

    Realizing Raman enhancement on a flat surface has become increasingly attractive after the discovery of graphene-enhanced Raman scattering (GERS). Two-dimensional (2D) layered materials, exhibiting a flat surface without dangling bonds, were thought to be strong candidates for both fundamental studies of this Raman enhancement effect and its extension to meet practical applications requirements. Here, we study the Raman enhancement effect on graphene, hexagonal boron nitride (h-BN), and molybdenum disulfide (MoS2), by using the copper phthalocyanine (CuPc) molecule as a probe. This molecule can sit on these layered materials in a face-on configuration. However, it is found that the Raman enhancement effect, which is observable on graphene, hBN, and MoS2, has different enhancement factors for the different vibrational modes of CuPc, depending strongly on the surfaces. Higher-frequency phonon modes of CuPc (such as those at 1342, 1452, 1531 cm(-1)) are enhanced more strongly on graphene than that on h-BN, while the lower frequency phonon modes of CuPc (such as those at 682, 749, 1142, 1185 cm(-1)) are enhanced more strongly on h-BN than that on graphene. MoS2 demonstrated the weakest Raman enhancement effect as a substrate among these three 2D materials. These differences are attributed to the different enhancement mechanisms related to the different electronic properties and chemical bonds exhibited by the three substrates: (1) graphene is zero-gap semiconductor and has a nonpolar C-C bond, which induces charge transfer (2) h-BN is insulating and has a strong B-N bond, while (3) MoS2 is semiconducting with the sulfur atoms on the surface and has a polar covalent bond (Mo-S) with the polarity in the vertical direction to the surface. Therefore, the different Raman enhancement mechanisms differ for each material: (1) charge transfer may occur for graphene; (2) strong dipole-dipole coupling may occur for h-BN, and (3) both charge transfer and dipole-dipole coupling may

  17. Raman enhancement effect on two-dimensional layered materials: graphene, h-BN and MoS2.

    PubMed

    Ling, Xi; Fang, Wenjing; Lee, Yi-Hsien; Araujo, Paulo T; Zhang, Xu; Rodriguez-Nieva, Joaquin F; Lin, Yuxuan; Zhang, Jin; Kong, Jing; Dresselhaus, Mildred S

    2014-06-11

    Realizing Raman enhancement on a flat surface has become increasingly attractive after the discovery of graphene-enhanced Raman scattering (GERS). Two-dimensional (2D) layered materials, exhibiting a flat surface without dangling bonds, were thought to be strong candidates for both fundamental studies of this Raman enhancement effect and its extension to meet practical applications requirements. Here, we study the Raman enhancement effect on graphene, hexagonal boron nitride (h-BN), and molybdenum disulfide (MoS2), by using the copper phthalocyanine (CuPc) molecule as a probe. This molecule can sit on these layered materials in a face-on configuration. However, it is found that the Raman enhancement effect, which is observable on graphene, hBN, and MoS2, has different enhancement factors for the different vibrational modes of CuPc, depending strongly on the surfaces. Higher-frequency phonon modes of CuPc (such as those at 1342, 1452, 1531 cm(-1)) are enhanced more strongly on graphene than that on h-BN, while the lower frequency phonon modes of CuPc (such as those at 682, 749, 1142, 1185 cm(-1)) are enhanced more strongly on h-BN than that on graphene. MoS2 demonstrated the weakest Raman enhancement effect as a substrate among these three 2D materials. These differences are attributed to the different enhancement mechanisms related to the different electronic properties and chemical bonds exhibited by the three substrates: (1) graphene is zero-gap semiconductor and has a nonpolar C-C bond, which induces charge transfer (2) h-BN is insulating and has a strong B-N bond, while (3) MoS2 is semiconducting with the sulfur atoms on the surface and has a polar covalent bond (Mo-S) with the polarity in the vertical direction to the surface. Therefore, the different Raman enhancement mechanisms differ for each material: (1) charge transfer may occur for graphene; (2) strong dipole-dipole coupling may occur for h-BN, and (3) both charge transfer and dipole-dipole coupling may

  18. PROBING THE EARLIEST STAGE OF PROTOSTELLAR EVOLUTION-BARNARD 1-bN AND BARNARD 1-bS

    SciTech Connect

    Huang, Yun-Hsin; Hirano, Naomi

    2013-04-01

    Two submm/mm sources in the Barnard 1b (B1-b) core, B1-bN and B1-bS, have been observed with the Submillimeter Array (SMA) and the Submillimeter Telescope (SMT). The 1.1 mm continuum map obtained with the SMA reveals that the two sources contain spatially compact components, suggesting that they harbor protostars. The N{sub 2}D{sup +} and N{sub 2}H{sup +} J = 3-2 maps were obtained by combining the SMA and SMT data. The N{sub 2}D{sup +} map clearly shows two peaks at the continuum positions. The N{sub 2}H{sup +} map also peaks at the continuum positions, but is more dominated by the spatially extended component. The N{sub 2}D{sup +}/N{sub 2}H{sup +} ratio was estimated to be {approx}0.2 at the positions of both B1-bN and B1-bS. The derived N{sub 2}D{sup +}/N{sub 2}H{sup +} ratio is comparable to those of the prestellar cores in the late evolutionary stage and the class 0 protostars in the early evolutionary stage. Although B1-bN is bright in N{sub 2}H{sup +} and N{sub 2}D{sup +}, this source was barely seen in H{sup 13}CO{sup +}. This implies that the depletion of carbon-bearing molecules is significant in B1-bN. The chemical property suggests that B1-bN is in the earlier evolutionary stage as compared to B1-bS with the H{sup 13}CO{sup +} counterpart. The N{sub 2}H{sup +} and N{sub 2}D{sup +} lines show that the radial velocities of the two sources are different by {approx}0.9 km s{sup -1}. However, the velocity pattern along the line through B1-bN and B1-bS suggests that these two sources were not formed out of a single rotating cloud. It is likely that the B1-b core consists of two velocity components, each of which harbors a very young source.

  19. Structure of boron clusters revisited, Bn with n = 14-20

    NASA Astrophysics Data System (ADS)

    Tai, Truong Ba; Tam, Nguyen Minh; Nguyen, Minh Tho

    2012-03-01

    We reinvestigate the structures of neutral boron clusters Bn, with n = 14-20. G3B3 calculations confirm that a transition between 2D and 3D shape occurs at B20, which has a tubular form. In disagreement with Boustani et al. (Phys. Rev. B, 83 (2011) 193405), we find a planar B19 cluster. Standard heats of formation are obtained and used to evaluate the clusters stability. The average binding energy tends to increase with increasing size toward a limit. Higher stability is found B14, B16, B18 and B20. All Bn have negative NICS-values. The bonding nature and electron delocalization of B20 are re-examined using CMO and LOL.

  20. Prevention of Transition Metal Dichalcogenide Photodegradation by Encapsulation with h-BN Layers.

    PubMed

    Ahn, Seongjoon; Kim, Gwangwoo; Nayak, Pramoda K; Yoon, Seong In; Lim, Hyunseob; Shin, Hyun-Joon; Shin, Hyeon Suk

    2016-09-27

    Transition metal dichalcogenides (TMDs) have recently received increasing attention because of their potential applications in semiconducting and optoelectronic devices exhibiting large optical absorptions in the visible range. However, some studies have reported that the grain boundaries of TMDs can be easily degraded by the presence of oxygen in water and by UV irradiation, ozone, and heating under ambient conditions. We herein demonstrate the photodegradation of WSe2 and MoSe2 by laser exposure (532 nm) and the subsequent prevention of this photodegradation by encapsulation with hexagonal boron nitride (h-BN) layers. The photodegradation was monitored by variation in peak intensities in the Raman and photoluminescence spectra. The rapid photodegradation of WSe2 under air occurred at a laser power of ≥0.5 mW and was not observed to any extent at ≤0.1 mW. However, in the presence of a water droplet, the photodegradation of WSe2 was accelerated and took place even at 0.1 mW. We examined the encapsulation of WSe2 with h-BN and found that this prevented photodegradation. However, a single layer of h-BN was not sufficient to fully prevent this photodegradation, and so a triple layer of h-BN was employed. We also demonstrated that the photodegradation of MoSe2 was prevented by encapsulation with h-BN layers. On the basis of X-ray photoelectron spectroscopy and scanning photoemission microscopy data, we determined that this degradation was caused by the photoinduced oxidation of TMDs. These results can be used to develop a general strategy for improving the stability of 2D materials in practical applications. PMID:27563804

  1. Prevention of Transition Metal Dichalcogenide Photodegradation by Encapsulation with h-BN Layers.

    PubMed

    Ahn, Seongjoon; Kim, Gwangwoo; Nayak, Pramoda K; Yoon, Seong In; Lim, Hyunseob; Shin, Hyun-Joon; Shin, Hyeon Suk

    2016-09-27

    Transition metal dichalcogenides (TMDs) have recently received increasing attention because of their potential applications in semiconducting and optoelectronic devices exhibiting large optical absorptions in the visible range. However, some studies have reported that the grain boundaries of TMDs can be easily degraded by the presence of oxygen in water and by UV irradiation, ozone, and heating under ambient conditions. We herein demonstrate the photodegradation of WSe2 and MoSe2 by laser exposure (532 nm) and the subsequent prevention of this photodegradation by encapsulation with hexagonal boron nitride (h-BN) layers. The photodegradation was monitored by variation in peak intensities in the Raman and photoluminescence spectra. The rapid photodegradation of WSe2 under air occurred at a laser power of ≥0.5 mW and was not observed to any extent at ≤0.1 mW. However, in the presence of a water droplet, the photodegradation of WSe2 was accelerated and took place even at 0.1 mW. We examined the encapsulation of WSe2 with h-BN and found that this prevented photodegradation. However, a single layer of h-BN was not sufficient to fully prevent this photodegradation, and so a triple layer of h-BN was employed. We also demonstrated that the photodegradation of MoSe2 was prevented by encapsulation with h-BN layers. On the basis of X-ray photoelectron spectroscopy and scanning photoemission microscopy data, we determined that this degradation was caused by the photoinduced oxidation of TMDs. These results can be used to develop a general strategy for improving the stability of 2D materials in practical applications.

  2. An open canvas--2D materials with defects, disorder, and functionality.

    PubMed

    Zou, Xiaolong; Yakobson, Boris I

    2015-01-20

    CONSPECTUS: While some exceptional properties are unique to graphene only (its signature Dirac-cone gapless dispersion, carrier mobility, record strength), other features are common to other two-dimensional materials. The broader family "beyond graphene" offers greater choices to be explored and tailored for various applications. Transition metal dichalcogenides (TMDCs), hexagonal boron nitride (h-BN), and 2D layers of pure elements, like phosphorus or boron, can complement or even surpass graphene in many ways and uses, ranging from electronics and optoelectronics to catalysis and energy storage. Their availability greatly relies on chemical vapor deposition growth of large samples, which are highly polycrystalline and include interfaces such as edges, heterostructures, and grain boundaries, as well as dislocations and point defects. These imperfections do not always degrade the material properties, but they often bring new physics and even useful functionality. It turns particularly interesting in combination with the sheer openness of all 2D sheets, fully exposed to the environment, which, as we show herein, can change and tune the defect structures and consequently all their qualities, from electronic levels, conductivity, magnetism, and optics to structural mobility of dislocations and catalytic activities. In this Account, we review our progress in understanding of various defects. We begin by expressing the energy of an arbitrary graphene edge analytically, so that the environment is regarded by "chemical phase shift". This has profound implications for graphene and carbon nanotube growth. Generalization of this equation to heteroelemental BN gives a method to determine the energy for arbitrary edges of BN, depending on the partial chemical potentials. This facilitates the tuning of the morphology and electronic and magnetic properties of pure BN or hybrid BN|C systems. Applying a similar method to three-atomic-layer TMDCs reveals more diverse edge

  3. An open canvas--2D materials with defects, disorder, and functionality.

    PubMed

    Zou, Xiaolong; Yakobson, Boris I

    2015-01-20

    CONSPECTUS: While some exceptional properties are unique to graphene only (its signature Dirac-cone gapless dispersion, carrier mobility, record strength), other features are common to other two-dimensional materials. The broader family "beyond graphene" offers greater choices to be explored and tailored for various applications. Transition metal dichalcogenides (TMDCs), hexagonal boron nitride (h-BN), and 2D layers of pure elements, like phosphorus or boron, can complement or even surpass graphene in many ways and uses, ranging from electronics and optoelectronics to catalysis and energy storage. Their availability greatly relies on chemical vapor deposition growth of large samples, which are highly polycrystalline and include interfaces such as edges, heterostructures, and grain boundaries, as well as dislocations and point defects. These imperfections do not always degrade the material properties, but they often bring new physics and even useful functionality. It turns particularly interesting in combination with the sheer openness of all 2D sheets, fully exposed to the environment, which, as we show herein, can change and tune the defect structures and consequently all their qualities, from electronic levels, conductivity, magnetism, and optics to structural mobility of dislocations and catalytic activities. In this Account, we review our progress in understanding of various defects. We begin by expressing the energy of an arbitrary graphene edge analytically, so that the environment is regarded by "chemical phase shift". This has profound implications for graphene and carbon nanotube growth. Generalization of this equation to heteroelemental BN gives a method to determine the energy for arbitrary edges of BN, depending on the partial chemical potentials. This facilitates the tuning of the morphology and electronic and magnetic properties of pure BN or hybrid BN|C systems. Applying a similar method to three-atomic-layer TMDCs reveals more diverse edge

  4. High-performance polyimide nanocomposites with core-shell AgNWs@BN for electronic packagings

    NASA Astrophysics Data System (ADS)

    Zhou, Yongcun; Liu, Feng

    2016-08-01

    The increasing density of electronic devices underscores the need for efficient thermal management. Silver nanowires (AgNWs), as one-dimensional nanostructures, possess a high aspect ratio and intrinsic thermal conductivity. However, high electrical conductivity of AgNWs limits their application for electronic packaging. We synthesized boron nitride-coated silver nanowires (AgNWs@BN) using a flexible and fast method followed by incorporation into synthetic polyimide (PI) for enhanced thermal conductivity and dielectric properties of nanocomposites. The thinner boron nitride intermediate nanolayer on AgNWs not only alleviated the mismatch between AgNWs and PI but also enhanced their interfacial interaction. Hence, the maximum thermal conductivity of an AgNWs@BN/PI composite with a filler loading up to 20% volume was increased to 4.33 W/m K, which is an enhancement by nearly 23.3 times compared with that of the PI matrix. The relative permittivity and dielectric loss were about 9.89 and 0.015 at 1 MHz, respectively. Compared with AgNWs@SiO2/PI and Ag@BN/PI composites, boron nitride-coated core-shell structures effectively increased the thermal conductivity and reduced the permittivity of nanocomposites. The relative mechanism was studied and discussed. This study enables the identification of appropriate modifier fillers for polymer matrix nanocomposites.

  5. DYNA2D96. Explicit 2-D Hydrodynamic FEM Program

    SciTech Connect

    Whirley, R.G.

    1992-04-01

    DYNA2D is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.

  6. Role of hexagonal boron nitride in protecting ferromagnetic nanostructures from oxidation

    NASA Astrophysics Data System (ADS)

    Zihlmann, Simon; Makk, Péter; Vaz, Carlos A. F.; Schönenberger, Christian

    2016-03-01

    Ferromagnetic contacts are widely used to inject spin polarized currents into non-magnetic materials such as semiconductors or 2-dimensional materials like graphene. In these systems, oxidation of the ferromagnetic materials poses an intrinsic limitation on device performance. Here we investigate the role of ex situ transferred chemical vapour deposited hexagonal boron nitride (hBN) as an oxidation barrier for nanostructured cobalt and permalloy electrodes. The chemical state of the ferromagnets was investigated using x-ray photoemission electron microscopy because of its high sensitivity and lateral resolution. We have compared the oxide thickness formed on ferromagnetic nanostructures covered by hBN to uncovered reference structures. Our results show that hBN reduces the oxidation rate of ferromagnetic nanostructures suggesting that it could be used as an ultra-thin protection layer in future spintronic devices.

  7. MOSS2D V1

    2001-01-31

    This software reduces the data from two-dimensional kSA MOS program, k-Space Associates, Ann Arbor, MI. Initial MOS data is recorded without headers in 38 columns, with one row of data per acquisition per lase beam tracked. The final MOSS 2d data file is reduced, graphed, and saved in a tab-delimited column format with headers that can be plotted in any graphing software.

  8. Impact of diet on ozone-induced pulmonary and systemic effects in female Brown Norway (BN) rats

    EPA Science Inventory

    Impact of diet on ozone-induced pulmonary and systemic effects in female Brown Norway (BN) ratsV.L. Bass1, M.C. Schladweiler2, S. Snow5, C.J. Gordon4, K.A. Jarema4, P. Phillips4, A.D. Ledbetter2, D.B. Miller3, J.E. Richards2, U.P. Kodavanti2. 1. SPH, UNC, Chapel Hill2. EPHD, NHE...

  9. From Saturated BN Compounds to Isoelectronic BN/CC Counterparts: An Insight from Computational Perspective.

    PubMed

    Sagan, Filip; Piękoś, Łukasz; Andrzejak, Marcin; Mitoraj, Mariusz Paweł

    2015-10-19

    In the present study, the inorganic analogues of alkanes as well as their isoelectronic BN/CC counterparts that bridge the gap between organic and inorganic chemistry are comparatively studied on the grounds of static DFT and Car-Parrinello molecular dynamics simulations. The BN/CC butanes CH3 CH2 BH2 NH3 , BH3 CH2 NH2 CH3 , and NH3 CH2 BH2 CH3 were considered and compared with their isoelectronic counterparts NH3 BH2 NH2 BH3 and CH3 CH2 CH2 CH3 . In addition, systematical replacement of the NH2 BH2 fragment by the isoelectronic CH2 CH2 moiety is studied in the molecules H3 N(NH2 BH2 )3-m (CH2 CH2 )m BH3 (for m=0, 1, 2, or 3) and H3 N(NH2 BH2 )2-m (CH2 CH2 )m BH3 (for m=0, 1, or 2). The DFT and Car-Parrinello simulations show that the isosteres of the BN/CC butanes CH3 CH2 BH2 NH3 , BH3 CH2 NH2 CH3 , and NH3 CH2 BH2 CH3 and of larger oligomers of the type (BN)k (CC)l where k≥l are stable compounds. The BN/CC butane H3 NCH2 CH2 BH3 spontaneously produces molecular hydrogen at room temperature. The reaction, prompted by very strong dihydrogen bonding NH⋅⋅⋅HB, undergoes through the neutral, hypervalent, pentacoordinated boron dihydrogen complex RBH2 (H2 ) [R=(CH2 CH2 )n NH2 ]. The calculations suggest that such intermediate and the other BN/CC butanes CH3 CH2 BH2 NH3 , BH3 CH2 NH2 CH3 , and NH3 CH2 BH2 CH3 as well as larger BN/CC oligomers are viable experimentally. A simple recipe for the synthesis of CH3 CH2 BH2 NH3 is proposed. The strength of the dihydrogen bonding appeared to be crucial for the overall stability of the saturated BN/CC derivatives.

  10. Progress on BN and Doped-BN Coatings on Woven Fabrics

    NASA Technical Reports Server (NTRS)

    Hurwitz, Frances I.; Scott, John M.; Chayka, Paul V.

    2001-01-01

    A novel, multistep process for applying interface coatings to woven structures using a pulsed CVD process is being evaluated. Borazine (B3N3H6), a neat liquid, and several Si precursors are used in the process to produce BN and SiBN coatings on Hi- Nicalon fabrics and preforms. A three variable, two level, full factorial matrix is proposed to define the influence of processing parameters. Coating morphology, uniformity and chemistry are characterized by field emission scanning electron microscopy (FESEM), energy dispersive (EDS) and Auger spectroscopies.

  11. Superhydrophilic nanostructure

    DOEpatents

    Mao, Samuel S; Zormpa, Vasileia; Chen, Xiaobo

    2015-05-12

    An embodiment of a superhydrophilic nanostructure includes nanoparticles. The nanoparticles are formed into porous clusters. The porous clusters are formed into aggregate clusters. An embodiment of an article of manufacture includes the superhydrophilic nanostructure on a substrate. An embodiment of a method of fabricating a superhydrophilic nanostructure includes applying a solution that includes nanoparticles to a substrate. The substrate is heated to form aggregate clusters of porous clusters of the nanoparticles.

  12. Large-Scale Graphene on Hexagonal-BN Hall Elements: Prediction of Sensor Performance without Magnetic Field.

    PubMed

    Joo, Min-Kyu; Kim, Joonggyu; Park, Ji-Hoon; Nguyen, Van Luan; Kim, Ki Kang; Lee, Young Hee; Suh, Dongseok

    2016-09-27

    A graphene Hall element (GHE) is an optimal system for a magnetic sensor because of its perfect two-dimensional (2-D) structure, high carrier mobility, and widely tunable carrier concentration. Even though several proof-of-concept devices have been proposed, manufacturing them by mechanical exfoliation of 2-D material or electron-beam lithography is of limited feasibility. Here, we demonstrate a high quality GHE array having a graphene on hexagonal-BN (h-BN) heterostructure, fabricated by photolithography and large-area 2-D materials grown by chemical vapor deposition techniques. A superior performance of GHE was achieved with the help of a bottom h-BN layer, and showed a maximum current-normalized sensitivity of 1986 V/AT, a minimum magnetic resolution of 0.5 mG/Hz(0.5) at f = 300 Hz, and an effective dynamic range larger than 74 dB. Furthermore, on the basis of a thorough understanding of the shift of charge neutrality point depending on various parameters, an analytical model that predicts the magnetic sensor operation of a GHE from its transconductance data without magnetic field is proposed, simplifying the evaluation of each GHE design. These results demonstrate the feasibility of this highly performing graphene device using large-scale manufacturing-friendly fabrication methods.

  13. Large-Scale Graphene on Hexagonal-BN Hall Elements: Prediction of Sensor Performance without Magnetic Field.

    PubMed

    Joo, Min-Kyu; Kim, Joonggyu; Park, Ji-Hoon; Nguyen, Van Luan; Kim, Ki Kang; Lee, Young Hee; Suh, Dongseok

    2016-09-27

    A graphene Hall element (GHE) is an optimal system for a magnetic sensor because of its perfect two-dimensional (2-D) structure, high carrier mobility, and widely tunable carrier concentration. Even though several proof-of-concept devices have been proposed, manufacturing them by mechanical exfoliation of 2-D material or electron-beam lithography is of limited feasibility. Here, we demonstrate a high quality GHE array having a graphene on hexagonal-BN (h-BN) heterostructure, fabricated by photolithography and large-area 2-D materials grown by chemical vapor deposition techniques. A superior performance of GHE was achieved with the help of a bottom h-BN layer, and showed a maximum current-normalized sensitivity of 1986 V/AT, a minimum magnetic resolution of 0.5 mG/Hz(0.5) at f = 300 Hz, and an effective dynamic range larger than 74 dB. Furthermore, on the basis of a thorough understanding of the shift of charge neutrality point depending on various parameters, an analytical model that predicts the magnetic sensor operation of a GHE from its transconductance data without magnetic field is proposed, simplifying the evaluation of each GHE design. These results demonstrate the feasibility of this highly performing graphene device using large-scale manufacturing-friendly fabrication methods. PMID:27580305

  14. Surface Tension Components Based Selection of Cosolvents for Efficient Liquid Phase Exfoliation of 2D Materials.

    PubMed

    Shen, Jianfeng; Wu, Jingjie; Wang, Man; Dong, Pei; Xu, Jingxuan; Li, Xiaoguang; Zhang, Xiang; Yuan, Junhua; Wang, Xifan; Ye, Mingxin; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M

    2016-05-01

    A proper design of direct liquid phase exfoliation (LPE) for 2D materials as graphene, MoS2 , WS2 , h-BN, Bi2 Se3 , MoSe2 , SnS2 , and TaS2 with common cosolvents is carried out based on considering the polar and dispersive components of surface tensions of various cosolvents and 2D materials. It has been found that the exfoliation efficiency is enhanced by matching the ratio of surface tension components of cosolvents to that of the targeted 2D materials, based on which common cosolvents composed of IPA/water, THF/water, and acetone/water can be designed for sufficient LPE process. In this context, the library of low-toxic and low-cost solvents with low boiling points for LPE is infinitely enlarged when extending to common cosolvents. Polymer-based composites reinforced with a series of different 2D materials are compared with each other. It is demonstrated that the incorporation of cosolvents-exfoliated 2D materials can substantially improve the mechanical and thermal properties of polymer matrices. Typically, with the addition of 0.5 wt% of such 2D material as MoS2 nanosheets, the tensile strength and Young's modulus increased up to 74.85% and 136.97%, respectively. The different enhancement effect of 2D materials is corresponded to the intrinsic properties and LPE capacity of 2D materials. PMID:27059403

  15. Surface Tension Components Based Selection of Cosolvents for Efficient Liquid Phase Exfoliation of 2D Materials.

    PubMed

    Shen, Jianfeng; Wu, Jingjie; Wang, Man; Dong, Pei; Xu, Jingxuan; Li, Xiaoguang; Zhang, Xiang; Yuan, Junhua; Wang, Xifan; Ye, Mingxin; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M

    2016-05-01

    A proper design of direct liquid phase exfoliation (LPE) for 2D materials as graphene, MoS2 , WS2 , h-BN, Bi2 Se3 , MoSe2 , SnS2 , and TaS2 with common cosolvents is carried out based on considering the polar and dispersive components of surface tensions of various cosolvents and 2D materials. It has been found that the exfoliation efficiency is enhanced by matching the ratio of surface tension components of cosolvents to that of the targeted 2D materials, based on which common cosolvents composed of IPA/water, THF/water, and acetone/water can be designed for sufficient LPE process. In this context, the library of low-toxic and low-cost solvents with low boiling points for LPE is infinitely enlarged when extending to common cosolvents. Polymer-based composites reinforced with a series of different 2D materials are compared with each other. It is demonstrated that the incorporation of cosolvents-exfoliated 2D materials can substantially improve the mechanical and thermal properties of polymer matrices. Typically, with the addition of 0.5 wt% of such 2D material as MoS2 nanosheets, the tensile strength and Young's modulus increased up to 74.85% and 136.97%, respectively. The different enhancement effect of 2D materials is corresponded to the intrinsic properties and LPE capacity of 2D materials.

  16. A straightforward strategy toward large BN-embedded π-systems: synthesis, structure, and optoelectronic properties of extended BN heterosuperbenzenes.

    PubMed

    Wang, Xiao-Ye; Zhuang, Fang-Dong; Wang, Rui-Bo; Wang, Xin-Chang; Cao, Xiao-Yu; Wang, Jie-Yu; Pei, Jian

    2014-03-12

    A straightforward strategy has been used to construct large BN-embedded π-systems simply from azaacenes. BN heterosuperbenzene derivatives, the largest BN heteroaromatics to date, have been synthesized in three steps. The molecules exhibit curved π-surfaces, showing two different conformations which are self-organized into a sandwich structure and further packed into a π-stacking column. The assembled microribbons exhibit good charge transport properties and photoconductivity, representing an important step toward the optoelectronic applications of BN-embedded aromatics.

  17. Pure & crystallized 2D Boron Nitride sheets synthesized via a novel process coupling both PDCs and SPS methods

    NASA Astrophysics Data System (ADS)

    Yuan, Sheng; Linas, Sébastien; Journet, Catherine; Steyer, Philippe; Garnier, Vincent; Bonnefont, Guillaume; Brioude, Arnaud; Toury, Bérangère

    2016-02-01

    Within the context of emergent researches linked to graphene, it is well known that h-BN nanosheets (BNNSs), also referred as 2D BN, are considered as the best candidate for replacing SiO2 as dielectric support or capping layers for graphene. As a consequence, the development of a novel alternative source for highly crystallized h-BN crystals, suitable for a further exfoliation, is a prime scientific issue. This paper proposes a promising approach to synthesize pure and well-crystallized h-BN flakes, which can be easily exfoliated into BNNSs. This new accessible production process represents a relevant alternative source of supply in response to the increasing need of high quality BNNSs. The synthesis strategy to prepare pure h-BN is based on a unique combination of the Polymer Derived Ceramics (PDCs) route with the Spark Plasma Sintering (SPS) process. Through a multi-scale chemical and structural investigation, it is clearly shown that obtained flakes are large (up to 30 μm), defect-free and well crystallized, which are key-characteristics for a subsequent exfoliation into relevant BNNSs.

  18. Unparticle example in 2D.

    PubMed

    Georgi, Howard; Kats, Yevgeny

    2008-09-26

    We discuss what can be learned about unparticle physics by studying simple quantum field theories in one space and one time dimension. We argue that the exactly soluble 2D theory of a massless fermion coupled to a massive vector boson, the Sommerfield model, is an interesting analog of a Banks-Zaks model, approaching a free theory at high energies and a scale-invariant theory with nontrivial anomalous dimensions at low energies. We construct a toy standard model coupling to the fermions in the Sommerfield model and study how the transition from unparticle behavior at low energies to free particle behavior at high energies manifests itself in interactions with the toy standard model particles.

  19. Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

    PubMed

    Park, Nahee; Kang, Haeyong; Park, Jeongmin; Lee, Yourack; Yun, Yoojoo; Lee, Jeong-Ho; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    2015-11-24

    The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics.

  20. Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

    PubMed

    Park, Nahee; Kang, Haeyong; Park, Jeongmin; Lee, Yourack; Yun, Yoojoo; Lee, Jeong-Ho; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    2015-11-24

    The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics. PMID:26487348

  1. Photocurrent measurements in Coupled Quantum Well van der Waals Heterostructures made of 2D Transition Metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Joe, Andrew; Jauregui, Luis; High, Alex; Dibos, Alan; Gulpinar, Elgin; Pistunova, Kateryna; Park, Hongkun; Kim, Philip

    , Luis A. Jauregui, Alex A. High, Alan Dibos, Elgin Gulpinar, Kateryna Pistunova, Hongkun Park, Philip Kim Harvard University, Physics Department -abstract- Single layer transition metal dichalcogenides (TMDC) are 2-dimensional (2D) semiconductors van der Waals (vdW) characterized by a direct optical bandgap in the visible wavelength (~2 eV). Characterization of the band alignment between TMDC and the barrier is important for the fabrication of tunneling devices. Here, we fabricate coupled quantum well (CQW) heterostructures made of 2D TMDCs with hexagonal Boron nitride (hBN) as an atomically thin barrier and gate dielectric and with top and bottom metal (or graphite) as gate electrodes. We observe a clear dependence of the photo-generated current with varying hBN thickness, electrode workfunctions, electric field, laser excitation power, excitation wavelength, and temperature. We will discuss the implication of photocurrent in relation to quantum transport process across the vdW interfaces.

  2. Dimensional Crossover of Thermal Transport in Hybrid Boron Nitride Nanostructures.

    PubMed

    Sakhavand, Navid; Shahsavari, Rouzbeh

    2015-08-26

    Although boron nitride nanotubes (BNNT) and hexagonal-BN (hBN) are superb one-dimensional (1D) and 2D thermal conductors respectively, bringing this quality into 3D remains elusive. Here, we focus on pillared boron nitride (PBN) as a class of 3D BN allotropes and demonstrate how the junctions, pillar length and pillar distance control phonon scattering in PBN and impart tailorable thermal conductivity in 3D. Using reverse nonequilibrium molecular dynamics simulations, our results indicate that although a clear phonon scattering at the junctions accounts for the lower thermal conductivity of PBN compared to its parent BNNT and hBN allotropes, it acts as an effective design tool and provides 3D thermo-mutable features that are absent in the parent structures. Propelled by the junction spacing, while one geometrical parameter, e.g., pillar length, controls the thermal transport along the out-of-plane direction of PBN, the other parameter, e.g., pillar distance, dictates the gross cross-sectional area, which is key for design of 3D thermal management systems. Furthermore, the junctions have a more pronounced effect in creating a Kapitza effect in the out-of-plane direction, due to the change in dimensionality of the phonon transport. This work is the first report on thermo-mutable properties of hybrid BN allotropes and can potentially impact thermal management of other hybrid 3D BN architectures. PMID:26158661

  3. Side-gate modulation effects on high-quality BN-Graphene-BN nanoribbon capacitors

    SciTech Connect

    Wang, Yang; Chen, Xiaolong; Ye, Weiguang; Wu, Zefei; Han, Yu; Han, Tianyi; He, Yuheng; Cai, Yuan; Wang, Ning

    2014-12-15

    High-quality BN-Graphene-BN nanoribbon capacitors with double side-gates of graphene have been experimentally realized. The double side-gates can effectively modulate the electronic properties of graphene nanoribbon capacitors. By applying anti-symmetric side-gate voltages, we observed significant upward shifting and flattening of the V-shaped capacitance curve near the charge neutrality point. Symmetric side-gate voltages, however, only resulted in tilted upward shifting along the opposite direction of applied gate voltages. These modulation effects followed the behavior of graphene nanoribbons predicted theoretically for metallic side-gate modulation. The negative quantum capacitance phenomenon predicted by numerical simulations for graphene nanoribbons modulated by graphene side-gates was not observed, possibly due to the weakened interactions between the graphene nanoribbon and side-gate electrodes caused by the Ga{sup +} beam etching process.

  4. Electronic and magnetic properties of functionalized BN sheet

    NASA Astrophysics Data System (ADS)

    Sun, Qiang; Zhou, Jian; Wang, Qian; Jena, Puru

    2010-03-01

    First principles calculations based on density functional theory reveal some unusual properties of BN sheet functionalized with hydrogen and fluorine. These properties differ from those of similarly functionalized graphene even though both share the same honeycomb structure. (1) Unlike graphene which undergoes a metal to insulator transition when fully hydrogenated, the band gap of the BN sheet significantly narrows when fully saturated with hydrogen. Furthermore, the band gap of the BN sheet can be tuned from 4.7 eV to 0.6 eV and the system can be a direct or an indirect semiconductor or even a half-metal depending upon surface coverage. (2) Unlike graphene, BN sheet, due to its hetero-atomic composition, permits the surface to be co-decorated with H and F, thus leading to anisotropic structures with rich electronic and magnetic properties. (3) Unlike graphene, BN sheets can be made ferromagnetic, antiferromagnetic, or magnetically degenerate depending upon how the surface is functionalized. (4) Unlike graphene, the stability of magnetic coupling of functionalized BN sheet can be modulated by applying external strain. Our study highlights the potential of functionalized BN sheets for novel applications.

  5. Diamond-cBN alloy: A universal cutting material

    SciTech Connect

    Wang, Pei; He, Duanwei Kou, Zili; Li, Yong; Hu, Qiwei; Xu, Chao; Lei, Li; Wang, Qiming; Wang, Liping; Zhao, Yusheng; Xiong, Lun; Liu, Jing

    2015-09-07

    Diamond and cubic boron nitride (cBN) as conventional superhard materials have found widespread industrial applications, but both have inherent limitations. Diamond is not suitable for high-speed cutting of ferrous materials due to its poor chemical inertness, while cBN is only about half as hard as diamond. Because of their affinity in structural lattices and covalent bonding character, diamond and cBN could form alloys that can potentially fill the performance gap. However, the idea has never been demonstrated because samples obtained in the previous studies were too small to be tested for their practical performance. Here, we report the synthesis and characterization of transparent bulk diamond-cBN alloy compacts whose diameters (3 mm) are sufficiently large for them to be processed into cutting tools. The testing results show that the diamond-cBN alloy has superior chemical inertness over polycrystalline diamond and higher hardness than single crystal cBN. High-speed cutting tests on hardened steel and granite suggest that diamond-cBN alloy is indeed a universal cutting material.

  6. Diamond-cBN alloy: A universal cutting material

    NASA Astrophysics Data System (ADS)

    Wang, Pei; He, Duanwei; Wang, Liping; Kou, Zili; Li, Yong; Xiong, Lun; Hu, Qiwei; Xu, Chao; Lei, Li; Wang, Qiming; Liu, Jing; Zhao, Yusheng

    2015-09-01

    Diamond and cubic boron nitride (cBN) as conventional superhard materials have found widespread industrial applications, but both have inherent limitations. Diamond is not suitable for high-speed cutting of ferrous materials due to its poor chemical inertness, while cBN is only about half as hard as diamond. Because of their affinity in structural lattices and covalent bonding character, diamond and cBN could form alloys that can potentially fill the performance gap. However, the idea has never been demonstrated because samples obtained in the previous studies were too small to be tested for their practical performance. Here, we report the synthesis and characterization of transparent bulk diamond-cBN alloy compacts whose diameters (3 mm) are sufficiently large for them to be processed into cutting tools. The testing results show that the diamond-cBN alloy has superior chemical inertness over polycrystalline diamond and higher hardness than single crystal cBN. High-speed cutting tests on hardened steel and granite suggest that diamond-cBN alloy is indeed a universal cutting material.

  7. Influence of rotation on BN separation in binary particle system

    NASA Astrophysics Data System (ADS)

    Wu, Ping; Wang, Shuang; Xie, Ziang; Huang, Yuming; Tong, Lige; Zhang, Peikun; Yin, Shaowu; Liu, Chuanping; Wang, Li

    2013-06-01

    Granular particles systems under vertical vibration exhibit Brazilian Nut separation (BN), Reversed BN (RBN) separation or transitional phases at different vibrating conditions. In the present work, we investigate the influence of rotation on the BN separation of a binary granular particle system by changing rotational speed. 13X molecular sieve particles with diameter 6.00 mm and 0.60 mm are used. Vibration frequency f is 30 Hz and dimensionless acceleration Γ is 1.52 or 1.75, in which the particle system mainly exhibits BN separation tendency. Rotational speed ω varies from 0 to 150rpm, while the upper surface of the particle system maintains flat. We took the pictures of the particles distribution and measured the particles mass layer by layer to obtain the 3-D distribution of the particles. The results show that rotation enhances the BN separation tendency at slow rotational speed. The BN separation becomes strongest when ω is approximately 50rpm, then the BN separation tendency reduces as ω continues to increase. A butterfly pattern appears in the middle particles layer under the simultaneous stimulations of vibration and rotation.

  8. Broadband THz Spectroscopy of 2D Nanoscale Materials

    NASA Astrophysics Data System (ADS)

    Chen, Lu; Tripathi, Shivendra; Huang, Mengchen; Hsu, Jen-Feng; D'Urso, Brian; Lee, Hyungwoo; Eom, Chang-Beom; Irvin, Patrick; Levy, Jeremy

    Two-dimensional (2D) materials such as graphene and transition-metal dichalcogenides (TMDC) have attracted intense research interest in the past decade. Their unique electronic and optical properties offer the promise of novel optoelectronic applications in the terahertz regime. Recently, generation and detection of broadband terahertz (10 THz bandwidth) emission from 10-nm-scale LaAlO3/SrTiO3 nanostructures created by conductive atomic force microscope (c-AFM) lithography has been demonstrated . This unprecedented control of THz emission at 10 nm length scales creates a pathway toward hybrid THz functionality in 2D-material/LaAlO3/SrTiO3 heterostructures. Here we report initial efforts in THz spectroscopy of 2D nanoscale materials with resolution comparable to the dimensions of the nanowire (10 nm). Systems under investigation include graphene, single-layer molybdenum disulfide (MoS2), and tungsten diselenide (WSe2) nanoflakes. 1. Y. Ma, et al., Nano Lett. 13, 2884 (2013). We gratefully acknowledge financial support from the following agencies and grants: AFOSR (FA9550-12-1-0268 (JL, PRI), FA9550-12-1-0342 (CBE)), ONR (N00014-13-1-0806 (JL, CBE), N00014-15-1-2847 (JL)), NSF DMR-1124131 (JL, CBE) and DMR-1234096 (CBE).

  9. Unusual dimensionality effects and surface charge density in 2D Mg(OH)2

    PubMed Central

    Suslu, Aslihan; Wu, Kedi; Sahin, Hasan; Chen, Bin; Yang, Sijie; Cai, Hui; Aoki, Toshihiro; Horzum, Seyda; Kang, Jun; Peeters, Francois M.; Tongay, Sefaattin

    2016-01-01

    We present two-dimensional Mg(OH)2 sheets and their vertical heterojunctions with CVD-MoS2 for the first time as flexible 2D insulators with anomalous lattice vibration and chemical and physical properties. New hydrothermal crystal growth technique enabled isolation of environmentally stable monolayer Mg(OH)2 sheets. Raman spectroscopy and vibrational calculations reveal that the lattice vibrations of Mg(OH)2 have fundamentally different signature peaks and dimensionality effects compared to other 2D material systems known to date. Sub-wavelength electron energy-loss spectroscopy measurements and theoretical calculations show that Mg(OH)2 is a 6 eV direct-gap insulator in 2D, and its optical band gap displays strong band renormalization effects from monolayer to bulk, marking the first experimental confirmation of confinement effects in 2D insulators. Interestingly, 2D-Mg(OH)2 sheets possess rather strong surface polarization (charge) effects which is in contrast to electrically neutral h-BN materials. Using 2D-Mg(OH)2 sheets together with CVD-MoS2 in the vertical stacking shows that a strong change transfer occurs from n-doped CVD-MoS2 sheets to Mg(OH)2, naturally depleting the semiconductor, pushing towards intrinsic doping limit and enhancing overall optical performance of 2D semiconductors. Results not only establish unusual confinement effects in 2D-Mg(OH)2, but also offer novel 2D-insulating material with unique physical, vibrational, and chemical properties for potential applications in flexible optoelectronics. PMID:26846617

  10. Unusual dimensionality effects and surface charge density in 2D Mg(OH)2

    NASA Astrophysics Data System (ADS)

    Suslu, Aslihan; Wu, Kedi; Sahin, Hasan; Chen, Bin; Yang, Sijie; Cai, Hui; Aoki, Toshihiro; Horzum, Seyda; Kang, Jun; Peeters, Francois M.; Tongay, Sefaattin

    2016-02-01

    We present two-dimensional Mg(OH)2 sheets and their vertical heterojunctions with CVD-MoS2 for the first time as flexible 2D insulators with anomalous lattice vibration and chemical and physical properties. New hydrothermal crystal growth technique enabled isolation of environmentally stable monolayer Mg(OH)2 sheets. Raman spectroscopy and vibrational calculations reveal that the lattice vibrations of Mg(OH)2 have fundamentally different signature peaks and dimensionality effects compared to other 2D material systems known to date. Sub-wavelength electron energy-loss spectroscopy measurements and theoretical calculations show that Mg(OH)2 is a 6 eV direct-gap insulator in 2D, and its optical band gap displays strong band renormalization effects from monolayer to bulk, marking the first experimental confirmation of confinement effects in 2D insulators. Interestingly, 2D-Mg(OH)2 sheets possess rather strong surface polarization (charge) effects which is in contrast to electrically neutral h-BN materials. Using 2D-Mg(OH)2 sheets together with CVD-MoS2 in the vertical stacking shows that a strong change transfer occurs from n-doped CVD-MoS2 sheets to Mg(OH)2, naturally depleting the semiconductor, pushing towards intrinsic doping limit and enhancing overall optical performance of 2D semiconductors. Results not only establish unusual confinement effects in 2D-Mg(OH)2, but also offer novel 2D-insulating material with unique physical, vibrational, and chemical properties for potential applications in flexible optoelectronics.

  11. Steady propagation of Bingham plugs in 2D channels

    NASA Astrophysics Data System (ADS)

    Zamankhan, Parsa; Takayama, Shuichi; Grotberg, James

    2009-11-01

    The displacement of the yield-stress liquid plugs in channels and tubes occur in many biological systems and industrial processes. Among them is the propagation of mucus plugs in the respiratory tracts as may occur in asthma, cystic fibrosis, or emphysema. In this work the steady propagation of mucus plugs in a 2D channel is studied numerically, assuming that the mucus is a pure Bingham fluid. The governing equations are solved by a mixed-discontinuous finite element formulation and the free surface is resolved with the method of spines. The constitutive equation for a pure Bingham fluid is modeled by a regularization method. Fluid inertia is neglected, so the controlling parameters in a steady displacement are; the capillary number, Ca, Bingham number ,Bn, and the plug length. According to the numerical results, the yield stress behavior of the plug modifies the plug shape, the pattern of the streamlines and the distribution of stresses in the plug domain and along the walls in a significant way. The distribution along the walls is a major factor in studying cell injuries. This work is supported through the grant NIH HL84370.

  12. MOCVD grown hexagonal BN epilayers for DUV photonics

    NASA Astrophysics Data System (ADS)

    Majety, Sashikanth; Li, Jing; Lin, Jingyu; Jiang, Hongxing

    2013-03-01

    Hexagonal boron nitride (hBN) has attracted a lot of interest recently owing to its excellent physical properties and its potential use as a template in graphene electronics. We report on the successful growth of hBN epilayers using metal organic chemical vapor deposition (MOCVD) on sapphire and n-AlGaN substrates. P-type conductivity control was also achieved by in-situ Mg doping. This provides us with an opportunity to solve the problem of low quantum efficiency of DUV devices using Al-rich AlGaN alloys due to their extremely low p-type conductivity. Mg doped hBN epilayers grown on insulating templates were p-type with an in-plane resistivity of 2.3 Ω cm. Diode behavior in the p-n structures of p-hBN/n-Al0.62Ga0.38N has been demonstrated. Our results indicate that hBN epilayers have potential for DUV optoelectronic devices and also demonstrate the feasibility of using highly conductive p-type hBN as electron blocking and p-contact layers for AlGaN based deep UV emitters. This work is supported by DOE.

  13. Energetics and Electronic Structure of h-BN Nanoflakes.

    PubMed

    Yamanaka, Ayaka; Okada, Susumu

    2016-01-01

    We studied the energetics and electronic structure of hexagonal boron nitride (h-BN) nanoribbons with hydrogenated and clean edges with respect to the detailed edge shapes using density functional theory. Our calculations showed that the stability of h-BN edges strongly depends on the edge termination. In the case of hydrogenated edges, the formation energy is constant for all edge angles ranging from armchair to zigzag, indicating that h-BN may exhibit rich variation in their edge atomic arrangements under static conditions. The hydrogenated h-BN nanoribbons are insulators with an energy gap of 4 eV irrespective of edge shape, in which the lowest branch of the conduction band exhibits nearly free electron states nature distributed in the vacuum region outside the ribbons. In contrast, the formation energy of h-BN nanoribbons with clean edges monotonically increases as the edge angle is changed from armchair to zigzag. Our analysis reveals that the increase of density of states at the Fermi level arising from dangling bond states leads to this monotonic increase of edge formation energy in h-BN nanoribbons with clean edges. PMID:27481626

  14. Energetics and Electronic Structure of h-BN Nanoflakes

    NASA Astrophysics Data System (ADS)

    Yamanaka, Ayaka; Okada, Susumu

    2016-08-01

    We studied the energetics and electronic structure of hexagonal boron nitride (h-BN) nanoribbons with hydrogenated and clean edges with respect to the detailed edge shapes using density functional theory. Our calculations showed that the stability of h-BN edges strongly depends on the edge termination. In the case of hydrogenated edges, the formation energy is constant for all edge angles ranging from armchair to zigzag, indicating that h-BN may exhibit rich variation in their edge atomic arrangements under static conditions. The hydrogenated h-BN nanoribbons are insulators with an energy gap of 4 eV irrespective of edge shape, in which the lowest branch of the conduction band exhibits nearly free electron states nature distributed in the vacuum region outside the ribbons. In contrast, the formation energy of h-BN nanoribbons with clean edges monotonically increases as the edge angle is changed from armchair to zigzag. Our analysis reveals that the increase of density of states at the Fermi level arising from dangling bond states leads to this monotonic increase of edge formation energy in h-BN nanoribbons with clean edges.

  15. Energetics and Electronic Structure of h-BN Nanoflakes

    PubMed Central

    Yamanaka, Ayaka; Okada, Susumu

    2016-01-01

    We studied the energetics and electronic structure of hexagonal boron nitride (h-BN) nanoribbons with hydrogenated and clean edges with respect to the detailed edge shapes using density functional theory. Our calculations showed that the stability of h-BN edges strongly depends on the edge termination. In the case of hydrogenated edges, the formation energy is constant for all edge angles ranging from armchair to zigzag, indicating that h-BN may exhibit rich variation in their edge atomic arrangements under static conditions. The hydrogenated h-BN nanoribbons are insulators with an energy gap of 4 eV irrespective of edge shape, in which the lowest branch of the conduction band exhibits nearly free electron states nature distributed in the vacuum region outside the ribbons. In contrast, the formation energy of h-BN nanoribbons with clean edges monotonically increases as the edge angle is changed from armchair to zigzag. Our analysis reveals that the increase of density of states at the Fermi level arising from dangling bond states leads to this monotonic increase of edge formation energy in h-BN nanoribbons with clean edges. PMID:27481626

  16. Tunable localized surface plasmon resonances in one-dimensional h-BN/graphene/h-BN quantum-well structure

    NASA Astrophysics Data System (ADS)

    Kaibiao, Zhang; Hong, Zhang; Xinlu, Cheng

    2016-03-01

    The graphene/hexagonal boron-nitride (h-BN) hybrid structure has emerged to extend the performance of graphene-based devices. Here, we investigate the tunable plasmon in one-dimensional h-BN/graphene/h-BN quantum-well structures. The analysis of optical response and field enhancement demonstrates that these systems exhibit a distinct quantum confinement effect for the collective oscillations. The intensity and frequency of the plasmon can be controlled by the barrier width and electrical doping. Moreover, the electron doping and the hole doping lead to very different results due to the asymmetric energy band. This graphene/h-BN hybrid structure may pave the way for future optoelectronic devices. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474207 and 11374217) and the Scientific Research Fund of Sichuan University of Science and Engineering, China (Grant No. 2014PY07).

  17. Perspectives for spintronics in 2D materials

    NASA Astrophysics Data System (ADS)

    Han, Wei

    2016-03-01

    The past decade has been especially creative for spintronics since the (re)discovery of various two dimensional (2D) materials. Due to the unusual physical characteristics, 2D materials have provided new platforms to probe the spin interaction with other degrees of freedom for electrons, as well as to be used for novel spintronics applications. This review briefly presents the most important recent and ongoing research for spintronics in 2D materials.

  18. Quantitative 2D liquid-state NMR.

    PubMed

    Giraudeau, Patrick

    2014-06-01

    Two-dimensional (2D) liquid-state NMR has a very high potential to simultaneously determine the absolute concentration of small molecules in complex mixtures, thanks to its capacity to separate overlapping resonances. However, it suffers from two main drawbacks that probably explain its relatively late development. First, the 2D NMR signal is strongly molecule-dependent and site-dependent; second, the long duration of 2D NMR experiments prevents its general use for high-throughput quantitative applications and affects its quantitative performance. Fortunately, the last 10 years has witnessed an increasing number of contributions where quantitative approaches based on 2D NMR were developed and applied to solve real analytical issues. This review aims at presenting these recent efforts to reach a high trueness and precision in quantitative measurements by 2D NMR. After highlighting the interest of 2D NMR for quantitative analysis, the different strategies to determine the absolute concentrations from 2D NMR spectra are described and illustrated by recent applications. The last part of the manuscript concerns the recent development of fast quantitative 2D NMR approaches, aiming at reducing the experiment duration while preserving - or even increasing - the analytical performance. We hope that this comprehensive review will help readers to apprehend the current landscape of quantitative 2D NMR, as well as the perspectives that may arise from it.

  19. Vibrational Properties of h-BN and h-BN-Graphene Heterostructures Probed by Inelastic Electron Tunneling Spectroscopy

    NASA Astrophysics Data System (ADS)

    Jung, Suyong; Park, Minkyu; Park, Jaesung; Jeong, Tae-Young; Kim, Ho-Jong; Watanabe, Kenji; Taniguchi, Takashi; Ha, Dong Han; Hwang, Chanyong; Kim, Yong-Sung

    2015-11-01

    Inelastic electron tunneling spectroscopy is a powerful technique for investigating lattice dynamics of nanoscale systems including graphene and small molecules, but establishing a stable tunnel junction is considered as a major hurdle in expanding the scope of tunneling experiments. Hexagonal boron nitride is a pivotal component in two-dimensional Van der Waals heterostructures as a high-quality insulating material due to its large energy gap and chemical-mechanical stability. Here we present planar graphene/h-BN-heterostructure tunneling devices utilizing thin h-BN as a tunneling insulator. With much improved h-BN-tunneling-junction stability, we are able to probe all possible phonon modes of h-BN and graphite/graphene at Γ and K high symmetry points by inelastic tunneling spectroscopy. Additionally, we observe that low-frequency out-of-plane vibrations of h-BN and graphene lattices are significantly modified at heterostructure interfaces. Equipped with an external back gate, we can also detect high-order coupling phenomena between phonons and plasmons, demonstrating that h-BN-based tunneling device is a wonderful playground for investigating electron-phonon couplings in low-dimensional systems.

  20. Vibrational Properties of h-BN and h-BN-Graphene Heterostructures Probed by Inelastic Electron Tunneling Spectroscopy

    PubMed Central

    Jung, Suyong; Park, Minkyu; Park, Jaesung; Jeong, Tae-Young; Kim, Ho-Jong; Watanabe, Kenji; Taniguchi, Takashi; Ha, Dong Han; Hwang, Chanyong; Kim, Yong-Sung

    2015-01-01

    Inelastic electron tunneling spectroscopy is a powerful technique for investigating lattice dynamics of nanoscale systems including graphene and small molecules, but establishing a stable tunnel junction is considered as a major hurdle in expanding the scope of tunneling experiments. Hexagonal boron nitride is a pivotal component in two-dimensional Van der Waals heterostructures as a high-quality insulating material due to its large energy gap and chemical-mechanical stability. Here we present planar graphene/h-BN-heterostructure tunneling devices utilizing thin h-BN as a tunneling insulator. With much improved h-BN-tunneling-junction stability, we are able to probe all possible phonon modes of h-BN and graphite/graphene at Γ and K high symmetry points by inelastic tunneling spectroscopy. Additionally, we observe that low-frequency out-of-plane vibrations of h-BN and graphene lattices are significantly modified at heterostructure interfaces. Equipped with an external back gate, we can also detect high-order coupling phenomena between phonons and plasmons, demonstrating that h-BN-based tunneling device is a wonderful playground for investigating electron-phonon couplings in low-dimensional systems. PMID:26563740

  1. Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

    SciTech Connect

    Singh, Bikramjeet; Singh, Paviter; Kumar, Akshay; Kumar, Manjeet; Thakur, Anup

    2015-05-15

    Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H{sub 3}BO{sub 3}). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications as well boron neutron capture therapy (BNCT)

  2. Substituent Directed Phototransformations of BN-Heterocycles: Elimination vs Isomerization via Selective B-C Bond Cleavage.

    PubMed

    Yang, Deng-Tao; Mellerup, Soren K; Peng, Jin-Bao; Wang, Xiang; Li, Quan-Song; Wang, Suning

    2016-09-14

    Electron-rich and -poor BN-heterocycles with benzyl-pyridyl backbones and two bulky aryls on the boron (Ar = tipp, BN-1, Ar = MesF, BN-2) have been found to display distinct molecular transformations upon irradiation by UV light. BN-1 undergoes an efficient photoelimination reaction forming a BN-phenanthrene with ΦPE = 0.25, whereas BN-2 undergoes a thermally reversible, stereoselective, and quantitative isomerization to a dark colored BN-1,3,5-cyclooctatriene (BN-1,3,5-COT, BN-2a). This unusual photoisomerization persists for other BN-heterocycles with electron-deficient aryls such as BN-3 with a benzyl-benzothiazolyl backbone and Mes(F) substituents or BN-4 with a benzyl-pyridyl backbone and two C6F5 groups on the boron. The photoisomerization of BN-4 goes beyond BN-1,3,5-COT (BN-4a), forming a new species (BN-1,3,6-COT, BN-4b) via C-F bond cleavage and [1,3]-F atom sigmatropic migration. Computational studies support that BN-4a is an intermediate in the formation of BN-4b. This work establishes that steric and electronic factors can effectively control the transformations of BN-heterocycles, allowing access to important and previously unknown BN-embedded species. PMID:27580241

  3. Band engineering in a van der Waals heterostructure using a 2D polar material and a capping layer

    NASA Astrophysics Data System (ADS)

    Cho, Sung Beom; Chung, Yong-Chae

    2016-06-01

    Van der Waals (vdW) heterostructures are expected to play a key role in next-generation electronic and optoelectronic devices. In this study, the band alignment of a vdW heterostructure with 2D polar materials was studied using first-principles calculations. As a model case study, single-sided fluorographene (a 2D polar material) on insulating (h-BN) and metallic (graphite) substrates was investigated to understand the band alignment behavior of polar materials. Single-sided fluorographene was found to have a potential difference along the out-of-plane direction. This potential difference provided as built-in potential at the interface, which shift the band alignment between h-BN and graphite. The interface characteristics were highly dependent on the interface terminations because of this built-in potential. Interestingly, this band alignment can be modified with a capping layer of graphene or BN because the capping layer triggered electronic reconstruction near the interface. This is because the bonding nature is not covalent, but van der Waals, which made it possible to avoid Fermi-level pinning at the interface. The results of this study showed that diverse types of band alignment can be achieved using polar materials and an appropriate capping layer.

  4. Staring 2-D hadamard transform spectral imager

    DOEpatents

    Gentry, Stephen M.; Wehlburg, Christine M.; Wehlburg, Joseph C.; Smith, Mark W.; Smith, Jody L.

    2006-02-07

    A staring imaging system inputs a 2D spatial image containing multi-frequency spectral information. This image is encoded in one dimension of the image with a cyclic Hadamarid S-matrix. The resulting image is detecting with a spatial 2D detector; and a computer applies a Hadamard transform to recover the encoded image.

  5. Carbon-rich hexagonal (BN)C alloys

    SciTech Connect

    Uddin, M. R.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2015-06-07

    Thin films of hexagonal boron nitride carbon, h-(BN){sub 1−x}(C{sub 2}){sub x}, alloys in the C-rich side have been synthesized by metal-organic chemical vapor deposition (MOCVD) on c-plane sapphire substrates. X-ray diffraction measurements confirmed single hexagonal phase of h-(BN){sub 1−x}(C{sub 2}){sub x} epilayers. Electrical transport and Raman spectroscopy measurements results revealed evidences that homogenous h-(BN){sub 1−x}(C{sub 2}){sub x} alloys with x ≥ 95% can be synthesized by MOCVD at a growth temperature of 1300 °C. The variable temperature Hall-effect measurements suggested that a bandgap opening of about 93 meV with respect to graphite has been obtained for h-(BN){sub 1−x}(C{sub 2}){sub x} with x = 0.95, which is consistent with the expected value deduced from the alloy dependence of the energy gap of homogenous h-(BN){sub 1−x}(C{sub 2}){sub x} alloys. Atomic composition results obtained from x-ray photoelectron spectroscopy measurements revealed that the carrier type in C-rich h-(BN){sub 1−x}(C{sub 2}){sub x} alloys is controlled by the stoichiometry ratio between the B and N via changing the V/III ratio during the growth. The demonstration of bandgap opening and conductivity control in C-rich h-(BN){sub 1−x}(C{sub 2}){sub x} alloys provide feasibilities for realizing technologically significant devices including infrared (IR) emitters and detectors active from near to far IR and multi-spectral IR emitters and detectors.

  6. Low-dimensional hyperthin FeS2 nanostructures for efficient and stable hydrogen evolution electrocatalysis

    DOE PAGES

    Jasion, Daniel; Qiao, Qiao; Barforoush, Joseph M.; Zhu, Yimei; Ren, Shenqiang; Leonard, Kevin C.

    2015-10-05

    We report a scalable, solution-processing method for synthesizing low-dimensional hyperthin FeS2 nanostructures, and we show that 2D FeS2 disc nanostructures are an efficient and stable hydrogen evolution electrocatalyst. By changing the Fe:S ratio in the precursor solution, we were able to preferentially synthesize either 1D wire or 2D disc nanostructures. The 2D FeS2 disc structure has the highest electrocatalytic activity for the hydrogen evolution reaction, comparable to platinum in neutral pH conditions. Moreover, the ability of the FeS2 nanostructures to generate hydrogen was confirmed by scanning electrochemical microscopy, and the 2D disc nanostructures were able to generate hydrogen for overmore » 125 h.« less

  7. Magnetic Properties of Nanostructures

    NASA Astrophysics Data System (ADS)

    Ciraldo, John

    2007-10-01

    The recent development of the superlattice nanowire pattern transfer (SNAP) technique has enabled the fabrication of complex molecular-electronic circuits at unprecedented densities. In this project, we explore the possibility of extending this technique to generate comparably dense arrays of nanoscale giant magnetoresistive (GMR) and tunneling magnetoresistive (TMR) devices. My primary contribution to this project has focused on using a vibrating sample magnetometer (VSM), as well as a superconducting interference device (SQUID) magnetometer to monitor the magnetic properties of the devices as they are processed from thin 2D films into nanostructure arrays. This investigation allows us to investigate both fundamental and technological aspects of the nanopatterning process. For example, the effects of changing surface to volume ratios on the ferromagnetic exchange interaction and the role of various patterning techniques in determining surface chemistry and oxidation of the final nanostructures, respectively. Additionally I have worked on simulations of the materials using NIST's OOMF program, allowing me to compare actual results with theoretical expectations. I am also designing a magneto-optical Kerr effect (MOKE) detector, which will allow faster approximations of magnetic behavior.

  8. Tuning the Growth Pattern in 2D Confinement Regime of Sm2O3 and the Emerging Room Temperature Unusual Superparamagnetism

    PubMed Central

    Guria, Amit K.; Dey, Koushik; Sarkar, Suresh; Patra, Biplab K.; Giri, Saurav; Pradhan, Narayan

    2014-01-01

    Programming the reaction chemistry for superseding the formation of Sm2O3 in a competitive process of formation and dissolution, the crystal growth patterns are varied and two different nanostructures of Sm2O3 in 2D confinement regime are designed. Among these, the regular and self-assembled square platelets nanostructures exhibit paramagnetic behavior analogous to the bulk Sm2O3. But, the other one, 2D flower like shaped nanostructure, formed by irregular crystal growth, shows superparamagnetism at room temperature which is unusual for bulk paramagnet. It has been noted that the variation in the crystal growth pattern is due to the difference in the binding ability of two organic ligands, oleylamine and oleic acid, used for the synthesis and the magnetic behavior of the nanostructures is related to the defects incorporated during the crystal growth. Herein, we inspect the formation chemistry and plausible origin of contrasting magnetism of these nanostructures of Sm2O3. PMID:25269458

  9. PREFACE: Ultrathin layers of graphene, h-BN and other honeycomb structures Ultrathin layers of graphene, h-BN and other honeycomb structures

    NASA Astrophysics Data System (ADS)

    Geber, Thomas; Oshima, Chuhei

    2012-08-01

    Since ancient times, pure carbon materials have been familiar in human society—not only diamonds in jewellery and graphite in pencils, but also charcoal and coal which have been used for centuries as fuel for living and industry. Carbon fibers are stronger, tougher and lighter than steel and increase material efficiency because of their lower weight. Today, carbon fibers and related composite materials are used to make the frames of bicycles, cars and even airplane parts. The two-dimensional allotrope, now called graphene, is just a single layer of carbon atoms, locked together in a strongly bonded honeycomb lattice. In plane, graphene is stiffer than diamond, but out-of-plane it is soft, like rubber. It is virtually invisible, may conduct electricity (heat) better than copper and weighs next to nothing. Carbon compounds with two carbon atoms as a base, such as graphene, graphite or diamond, have isoelectronic sister compounds made of boron-nitrogen pairs: hexagonal and cubic boron nitride, with almost the same lattice constant. Although the two 2D sisters, graphene and h-BN, have the same number of valence electrons, their electronic properties are very different: freestanding h-BN is an insulator, while charge carriers in graphene are highly mobile. The past ten years have seen a great expansion in studies of single-layer and few-layer graphene. This activity has been concerned with the π electron transport in graphene, in electric and magnetic fields. More than 30 years ago, however, single-layer graphene and h-BN on solid surfaces were widely investigated. It was noted that they drastically changed the chemical reactivity of surfaces, and they were known to 'poison' heterogeneous catalysts, to passivate surfaces, to prevent oxidation of surfaces and to act as surfactants. Also, it was realized that the controlled growth of h-BN and graphene on substrates yields the formation of mismatch driven superstructures with peculiar template functionality on the

  10. Hydrogen-bond-assisted "gold cold fusion" for fabrication of 2D web structures.

    PubMed

    Mandal, Saikat; Shundo, Atsuomi; Acharya, Somobrata; Hill, Jonathan P; Ji, Qingmin; Ariga, Katsuhiko

    2009-07-01

    Keeping their cool: Fabrication of a 2D weblike nanonetwork of gold was successfully demonstrated through a two-step procedure including complexation of gold precursors to a weblike supramolecular assembly of surfactant followed by in situ reduction of the precursors to gold. Molecular assemblies stabilized by hydrogen bonding provided a sound template, leading to the highly integrated structure of gold through room-temperature (cold) nanostructure fusion.

  11. Internal Photoemission Spectroscopy of 2-D Materials

    NASA Astrophysics Data System (ADS)

    Nguyen, Nhan; Li, Mingda; Vishwanath, Suresh; Yan, Rusen; Xiao, Shudong; Xing, Huili; Cheng, Guangjun; Hight Walker, Angela; Zhang, Qin

    Recent research has shown the great benefits of using 2-D materials in the tunnel field-effect transistor (TFET), which is considered a promising candidate for the beyond-CMOS technology. The on-state current of TFET can be enhanced by engineering the band alignment of different 2D-2D or 2D-3D heterostructures. Here we present the internal photoemission spectroscopy (IPE) approach to determine the band alignments of various 2-D materials, in particular SnSe2 and WSe2, which have been proposed for new TFET designs. The metal-oxide-2-D semiconductor test structures are fabricated and characterized by IPE, where the band offsets from the 2-D semiconductor to the oxide conduction band minimum are determined by the threshold of the cube root of IPE yields as a function of photon energy. In particular, we find that SnSe2 has a larger electron affinity than most semiconductors and can be combined with other semiconductors to form near broken-gap heterojunctions with low barrier heights which can produce a higher on-state current. The details of data analysis of IPE and the results from Raman spectroscopy and spectroscopic ellipsometry measurements will also be presented and discussed.

  12. 2D materials: to graphene and beyond.

    PubMed

    Mas-Ballesté, Rubén; Gómez-Navarro, Cristina; Gómez-Herrero, Julio; Zamora, Félix

    2011-01-01

    This review is an attempt to illustrate the different alternatives in the field of 2D materials. Graphene seems to be just the tip of the iceberg and we show how the discovery of alternative 2D materials is starting to show the rest of this iceberg. The review comprises the current state-of-the-art of the vast literature in concepts and methods already known for isolation and characterization of graphene, and rationalizes the quite disperse literature in other 2D materials such as metal oxides, hydroxides and chalcogenides, and metal-organic frameworks.

  13. Synergic nitrogen source route to inorganic fullerene-like boron nitride with vessel, hollow sphere, onion, and peanut nanostructures.

    PubMed

    Xu, Fen; Xie, Yi; Zhang, Xu; Zhang, Shuyuan; Liu, Xianming; Tian, Xiaobo

    2004-01-26

    In this paper we describe the large-scale synthesis of inorganic fullerene-like (IF-like) hexagonal boron nitride with vessel, hollow sphere, peanut, and onion structures by reacting BBr(3) with the synergic nitrogen sources NaNH(2) and NH(4)Cl at 400-450 degrees C for 6-12 h. The composition of products could be confirmed to be pure boron nitride with hexagonal structures by the XRD patterns and FT-IR, XPS, and EDXA spectra. The representative HRTEM images clearly reveal the layerlike features of the products. Here, the peanut-like structure of the IF-like BN is reported for the first time, and added to the list as one kind of new morphology of BN nanomaterials. The similarity in the structure between h-BN and graphite is responsible for the formation of IF-like BN with nanostructures of vessels, hollow spheres, peanuts, and onions. PMID:14731047

  14. Electronic properties of T graphene-like C-BN sheets: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Majidi, R.

    2015-11-01

    We have used density functional theory to study the electronic properties of T graphene-like C, C-BN and BN sheets. The planar T graphene with metallic property has been considered. The results show that the presence of BN has a considerable effect on the electronic properties of T graphene. The T graphene-like C-BN and BN sheets show semiconducting properties. The energy band gap is increased by enhancing the number of BN units. The possibility of opening and controlling band gap opens the door for T graphene in switchable electronic devices.

  15. Nanostructured photovoltaics

    NASA Astrophysics Data System (ADS)

    Fu, Lan; Tan, H. Hoe; Jagadish, Chennupati

    2013-01-01

    Energy and the environment are two of the most important global issues that we currently face. The development of clean and sustainable energy resources is essential to reduce greenhouse gas emission and meet our ever-increasing demand for energy. Over the last decade photovoltaics, as one of the leading technologies to meet these challenges, has seen a continuous increase in research, development and investment. Meanwhile, nanotechnology, which is considered to be the technology of the future, is gradually revolutionizing our everyday life through adaptation and incorporation into many traditional technologies, particularly energy-related technologies, such as photovoltaics. While the record for the highest efficiency is firmly held by multijunction III-V solar cells, there has never been a shortage of new research effort put into improving the efficiencies of all types of solar cells and making them more cost effective. In particular, there have been extensive and exciting developments in employing nanostructures; features with different low dimensionalities, such as quantum wells, nanowires, nanotubes, nanoparticles and quantum dots, have been incorporated into existing photovoltaic technologies to enhance their performance and/or reduce their cost. Investigations into light trapping using plasmonic nanostructures to effectively increase light absorption in various solar cells are also being rigorously pursued. In addition, nanotechnology provides researchers with great opportunities to explore the new ideas and physics offered by nanostructures to implement advanced solar cell concepts such as hot carrier, multi-exciton and intermediate band solar cells. This special issue of Journal of Physics D: Applied Physics contains selected papers on nanostructured photovoltaics written by researchers in their respective fields of expertise. These papers capture the current excitement, as well as addressing some open questions in the field, covering topics including the

  16. A new kind of 2D topological insulators BiCN with a giant gap and its substrate effects.

    PubMed

    Fu, Botao; Ge, Yanfeng; Su, Wenyong; Guo, Wei; Liu, Cheng-Cheng

    2016-01-01

    Based on DFT calculation, we predict that BiCN, i.e., bilayer Bi films passivated with -CN group, is a novel 2D Bi-based material with highly thermodynamic stability, and demonstrate that it is also a new kind of 2D TI with a giant SOC gap (~1 eV) by direct calculation of the topological invariant Z2 and obvious exhibition of the helical edge states. Monolayer h-BN and MoS2 are identified as good candidate substrates for supporting the nontrivial topological insulating phase of the 2D TI films, since the two substrates can stabilize and weakly interact with BiCN via van der Waals interaction and thus hardly affect the electronic properties, especially the band topology. The topological properties are robust against the strain and electric field. This may provide a promising platform for realization of novel topological phases. PMID:27444954

  17. A new kind of 2D topological insulators BiCN with a giant gap and its substrate effects

    PubMed Central

    Fu, Botao; Ge, Yanfeng; Su, Wenyong; Guo, Wei; Liu, Cheng-Cheng

    2016-01-01

    Based on DFT calculation, we predict that BiCN, i.e., bilayer Bi films passivated with -CN group, is a novel 2D Bi-based material with highly thermodynamic stability, and demonstrate that it is also a new kind of 2D TI with a giant SOC gap (~1 eV) by direct calculation of the topological invariant Z2 and obvious exhibition of the helical edge states. Monolayer h-BN and MoS2 are identified as good candidate substrates for supporting the nontrivial topological insulating phase of the 2D TI films, since the two substrates can stabilize and weakly interact with BiCN via van der Waals interaction and thus hardly affect the electronic properties, especially the band topology. The topological properties are robust against the strain and electric field. This may provide a promising platform for realization of novel topological phases. PMID:27444954

  18. A new kind of 2D topological insulators BiCN with a giant gap and its substrate effects

    NASA Astrophysics Data System (ADS)

    Fu, Botao; Ge, Yanfeng; Su, Wenyong; Guo, Wei; Liu, Cheng-Cheng

    2016-07-01

    Based on DFT calculation, we predict that BiCN, i.e., bilayer Bi films passivated with -CN group, is a novel 2D Bi-based material with highly thermodynamic stability, and demonstrate that it is also a new kind of 2D TI with a giant SOC gap (~1 eV) by direct calculation of the topological invariant Z2 and obvious exhibition of the helical edge states. Monolayer h-BN and MoS2 are identified as good candidate substrates for supporting the nontrivial topological insulating phase of the 2D TI films, since the two substrates can stabilize and weakly interact with BiCN via van der Waals interaction and thus hardly affect the electronic properties, especially the band topology. The topological properties are robust against the strain and electric field. This may provide a promising platform for realization of novel topological phases.

  19. Anisotropy of BN and Be x-ray-emission bands

    NASA Astrophysics Data System (ADS)

    Mansour, A.; Schnatterly, S. E.

    1987-12-01

    We present measurements of the K emission spectra of hexagonal Be and BN (h-Be and h-BN). The anisotropy of the emission allows us to separate the bands into their σ and π components, enabling us to demonstrate the unambiguous π character of the B core exciton. We find that the exciton presents a double-peaked structure which we attribute to phonon ringing. For the first time we are able to separate into π and σ components the doubly ionized K emission bands of B and N in h-BN and of Be in h-Be, revealing the effect of the spectator core hole on the shape of the density of states. Such an effect is in qualitative agreement with the final-state rule, although the local p density of states is distorted more than has previously been reported.

  20. First principles study of trilayers of graphene-BN-graphene

    NASA Astrophysics Data System (ADS)

    Zhong, Xiaoliang; Amorim, Rodrigo; Pandey, Ravindra; Karna, Shashi

    2012-02-01

    The stability, electronic structure and electronic transport properties of graphene-BN-graphene (C-BN-C) trilayers are studied in the framework of density functional theory. Different stacking formats, i.e., AAA, ABA and ABC stackings are considered. The ABA stacking is found to be most energetically favorable, followed by ABC and AAA stackings. The interlayer spacing of trilayers are close to those of corresponding C-BN bilayers, while the intralayer bond length can be regarded as the weighted mean of constituent layers. All considered configurations are found to be metallic, independent of stacking formats. When an external electric field is applied perpendicularly, electronic band structures undergo stacking-dependent variations. While both AAA and ABA stackings show good tunability of energy gap, ABC stacking shows less flexibility of gap tuning. We will also present the results of the electronic transport properties which are modeled by sandwiching trilayers between gold contact electrodes.

  1. Heterodimer Formation of BnPKSA or BnPKSB with BnACOS5 Constitutes a Multienzyme Complex in Tapetal Cells and is Involved in Male Reproductive Development in Brassica napus.

    PubMed

    Qin, Maomao; Tian, Tiantian; Xia, Shengqian; Wang, Zhixin; Song, Liping; Yi, Bin; Wen, Jing; Shen, Jinxiong; Ma, Chaozhi; Fu, Tingdong; Tu, Jinxing

    2016-08-01

    Multienzyme associations localized to specific subcellular sites are involved in several critical functions in cellular metabolism, such as plant survival and reproduction. To date, few multienzyme complexes involved in male fertility have been examined in Brassica napus Here, we reported that in B. napus, the members of a multienzyme complex work in an interaction pattern different from that in Arabidopsis thaliana for sporopollenin biosynthesis. 7365A, a male-sterile mutant with a relatively smooth anther cuticle, was found to have a dramatic reduction in both cutin monomers and wax composition. Proteomic comparison between the mutant 7365A and wild-type 7365B showed down-regulation of three sporopollenin biosynthetic enzymes, namely BnPKSA, BnPKSB and BnTKPR; these enzymes were tightly co-expressed with BnACOS5. BnPKSA and BnPKSB showed similar expression patterns but distinct accumulation levels, suggesting that they had partially distinct functions during sporopollenin biosynthesis. In vitro and in vivo analyses demonstrated that BnPKSB directly interacted with BnPKSA and BnACOS5, but no such interactions were found in the present investigation for BnTKPR1. Interestingly, the interaction between PKSA and PKSB has not been discovered in Arabidopsis, which may indicate a new interaction representing an additional efficient regulation method in B. napus Taken together, we propose that BnPKSA and BnPKSB may comprise a heterodimer combined with BnACOS5, constituting a sporopollenin metabolon in tapetal cells that is related to male reproductive development in B. napus. PMID:27335346

  2. Rapid Changes in the Structure of the BN Object

    NASA Technical Reports Server (NTRS)

    Danchi, William C.; Gezari, D. Y.; Greenhill, L. J.; Najita, J.; Monnier, J. D.; Tuthill, P. G.; Wishnow, E. H.; Townes, C. H.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    The BN/KL region in Orion is the archetypal region of high-mass star formation, radiating approx. 10(sup)5 Lsun and displaying promininent bulk outflows. In particular, there is no certain identification of the sources responsible for the high luminosity and outflows, and is the origin of a major explosive event (Shultz et al. 1999, ApJ, 511, 282). Using 18.7 and 12.5 micron data from observations in December 1999 and October 2000 made at the Keck I telescope, we discovered that the BN Object has a companion previously seen only at radio wavelengths (Menten & Reid 1995, ApJ, 445, L157). We call this companion B2 and it is about 1.5 arcsec West of the bright component. We also see changes in the shape of BN and the emission of "blobs" or "bullets" of material. While B2 remains unchanged and in the same place between the two epochs, there is an additional structure in BN to the South-South-East and the North-East, as well as a finger of material pointing North from B2 itself. Such a change has not been seen before in the infrared. We have looked very carefully at these images, calibrator images taken within a few minutes of the source images, as well as our previous images and cannot find any technical faults with the data. We explore the implications of these results, in particular, can these features be connected with previously observed "bullets" or "fingers" (see Allen & Burton 1993, for example), making BN a source for the bullets, implying they are not from IRc2 as previously thought? Or could they be produced by an interaction between material from BN and other sources such as IRc2?

  3. 2-d Finite Element Code Postprocessor

    1996-07-15

    ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forcesmore » along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.« less

  4. Matrix models of 2d gravity

    SciTech Connect

    Ginsparg, P.

    1991-01-01

    These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.

  5. Matrix models of 2d gravity

    SciTech Connect

    Ginsparg, P.

    1991-12-31

    These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.

  6. Brittle damage models in DYNA2D

    SciTech Connect

    Faux, D.R.

    1997-09-01

    DYNA2D is an explicit Lagrangian finite element code used to model dynamic events where stress wave interactions influence the overall response of the system. DYNA2D is often used to model penetration problems involving ductile-to-ductile impacts; however, with the advent of the use of ceramics in the armor-anti-armor community and the need to model damage to laser optics components, good brittle damage models are now needed in DYNA2D. This report will detail the implementation of four brittle damage models in DYNA2D, three scalar damage models and one tensor damage model. These new brittle damage models are then used to predict experimental results from three distinctly different glass damage problems.

  7. Thermoelectric effects in graphene nanostructures

    NASA Astrophysics Data System (ADS)

    Dollfus, Philippe; Nguyen, Viet Hung; Saint-Martin, Jérôme

    2015-04-01

    The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages. It is gapless, which leads to a small Seebeck coefficient due to the opposite contributions of electrons and holes, and it is an excellent thermal conductor. The thermoelectric figure of merit ZT of a two-dimensional (2D) graphene sheet is thus very limited. However, many works have demonstrated recently that appropriate nanostructuring and bandgap engineering of graphene can concomitantly strongly reduce the lattice thermal conductance and enhance the Seebeck coefficient without dramatically degrading the electronic conductance. Hence, in various graphene nanostructures, ZT has been predicted to be high enough to make them attractive for energy conversion. In this article, we review the main results obtained experimentally and theoretically on the thermoelectric properties of graphene and its nanostructures, emphasizing the physical effects that govern these properties. Beyond pure graphene structures, we discuss also the thermoelectric properties of some hybrid graphene structures, as graphane, layered carbon allotropes such as graphynes and graphdiynes, and graphene/hexagonal boron nitride heterostructures which offer new opportunities. Finally, we briefly review the recent activities on other atomically thin 2D semiconductors with finite bandgap, i.e. dichalcogenides and phosphorene, which have attracted great attention for various kinds of applications, including thermoelectrics.

  8. Thermoelectric effects in graphene nanostructures.

    PubMed

    Dollfus, Philippe; Hung Nguyen, Viet; Saint-Martin, Jérôme

    2015-04-10

    The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages. It is gapless, which leads to a small Seebeck coefficient due to the opposite contributions of electrons and holes, and it is an excellent thermal conductor. The thermoelectric figure of merit ZT of a two-dimensional (2D) graphene sheet is thus very limited. However, many works have demonstrated recently that appropriate nanostructuring and bandgap engineering of graphene can concomitantly strongly reduce the lattice thermal conductance and enhance the Seebeck coefficient without dramatically degrading the electronic conductance. Hence, in various graphene nanostructures, ZT has been predicted to be high enough to make them attractive for energy conversion. In this article, we review the main results obtained experimentally and theoretically on the thermoelectric properties of graphene and its nanostructures, emphasizing the physical effects that govern these properties. Beyond pure graphene structures, we discuss also the thermoelectric properties of some hybrid graphene structures, as graphane, layered carbon allotropes such as graphynes and graphdiynes, and graphene/hexagonal boron nitride heterostructures which offer new opportunities. Finally, we briefly review the recent activities on other atomically thin 2D semiconductors with finite bandgap, i.e. dichalcogenides and phosphorene, which have attracted great attention for various kinds of applications, including thermoelectrics.

  9. Chemical Approaches to 2D Materials.

    PubMed

    Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang

    2016-08-01

    Chemistry plays an ever-increasing role in the production, functionalization, processing and applications of graphene and other 2D materials. This special issue highlights a selection of enlightening chemical approaches to 2D materials, which nicely reflect the breadth of the field and convey the excitement of the individuals involved in it, who are trying to translate graphene and related materials from the laboratory into a real, high-impact technology. PMID:27478083

  10. Chemical Approaches to 2D Materials.

    PubMed

    Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang

    2016-08-01

    Chemistry plays an ever-increasing role in the production, functionalization, processing and applications of graphene and other 2D materials. This special issue highlights a selection of enlightening chemical approaches to 2D materials, which nicely reflect the breadth of the field and convey the excitement of the individuals involved in it, who are trying to translate graphene and related materials from the laboratory into a real, high-impact technology.

  11. Glitter in a 2D monolayer.

    PubMed

    Yang, Li-Ming; Dornfeld, Matthew; Frauenheim, Thomas; Ganz, Eric

    2015-10-21

    We predict a highly stable and robust atomically thin gold monolayer with a hexagonal close packed lattice stabilized by metallic bonding with contributions from strong relativistic effects and aurophilic interactions. We have shown that the framework of the Au monolayer can survive 10 ps MD annealing simulations up to 1400 K. The framework is also able to survive large motions out of the plane. Due to the smaller number of bonds per atom in the 2D layer compared to the 3D bulk we observe significantly enhanced energy per bond (0.94 vs. 0.52 eV per bond). This is similar to the increase in bond strength going from 3D diamond to 2D graphene. It is a non-magnetic metal, and was found to be the global minima in the 2D space. Phonon dispersion calculations demonstrate high kinetic stability with no negative modes. This 2D gold monolayer corresponds to the top monolayer of the bulk Au(111) face-centered cubic lattice. The close-packed lattice maximizes the aurophilic interactions. We find that the electrons are completely delocalized in the plane and behave as 2D nearly free electron gas. We hope that the present work can inspire the experimental fabrication of novel free standing 2D metal systems.

  12. 2d index and surface operators

    NASA Astrophysics Data System (ADS)

    Gadde, Abhijit; Gukov, Sergei

    2014-03-01

    In this paper we compute the superconformal index of 2d (2, 2) supersymmetric gauge theories. The 2d superconformal index, a.k.a. flavored elliptic genus, is computed by a unitary matrix integral much like the matrix integral that computes the 4d superconformal index. We compute the 2d index explicitly for a number of examples. In the case of abelian gauge theories we see that the index is invariant under flop transition and under CY-LG correspondence. The index also provides a powerful check of the Seiberg-type duality for non-abelian gauge theories discovered by Hori and Tong. In the later half of the paper, we study half-BPS surface operators in = 2 super-conformal gauge theories. They are engineered by coupling the 2d (2, 2) supersymmetric gauge theory living on the support of the surface operator to the 4d = 2 theory, so that different realizations of the same surface operator with a given Levi type are related by a 2d analogue of the Seiberg duality. The index of this coupled system is computed by using the tools developed in the first half of the paper. The superconformal index in the presence of surface defect is expected to be invariant under generalized S-duality. We demonstrate that it is indeed the case. In doing so the Seiberg-type duality of the 2d theory plays an important role.

  13. PREFACE: Ultrathin layers of graphene, h-BN and other honeycomb structures Ultrathin layers of graphene, h-BN and other honeycomb structures

    NASA Astrophysics Data System (ADS)

    Geber, Thomas; Oshima, Chuhei

    2012-08-01

    Since ancient times, pure carbon materials have been familiar in human society—not only diamonds in jewellery and graphite in pencils, but also charcoal and coal which have been used for centuries as fuel for living and industry. Carbon fibers are stronger, tougher and lighter than steel and increase material efficiency because of their lower weight. Today, carbon fibers and related composite materials are used to make the frames of bicycles, cars and even airplane parts. The two-dimensional allotrope, now called graphene, is just a single layer of carbon atoms, locked together in a strongly bonded honeycomb lattice. In plane, graphene is stiffer than diamond, but out-of-plane it is soft, like rubber. It is virtually invisible, may conduct electricity (heat) better than copper and weighs next to nothing. Carbon compounds with two carbon atoms as a base, such as graphene, graphite or diamond, have isoelectronic sister compounds made of boron-nitrogen pairs: hexagonal and cubic boron nitride, with almost the same lattice constant. Although the two 2D sisters, graphene and h-BN, have the same number of valence electrons, their electronic properties are very different: freestanding h-BN is an insulator, while charge carriers in graphene are highly mobile. The past ten years have seen a great expansion in studies of single-layer and few-layer graphene. This activity has been concerned with the π electron transport in graphene, in electric and magnetic fields. More than 30 years ago, however, single-layer graphene and h-BN on solid surfaces were widely investigated. It was noted that they drastically changed the chemical reactivity of surfaces, and they were known to 'poison' heterogeneous catalysts, to passivate surfaces, to prevent oxidation of surfaces and to act as surfactants. Also, it was realized that the controlled growth of h-BN and graphene on substrates yields the formation of mismatch driven superstructures with peculiar template functionality on the

  14. Band-gap engineering of the h-BN/MoS2/h-BN sandwich heterostructure under an external electric field

    NASA Astrophysics Data System (ADS)

    Huang, Zongyu; Qi, Xiang; Yang, Hong; He, Chaoyu; Wei, Xiaolin; Peng, Xiangyang; Zhong, Jianxin

    2015-05-01

    Based on first-principles calculations in the framework of van der Waals density functional theory, we investigate the structural, electronic properties and band-gap tuning of the h-BN/MoS2/h-BN sandwich heterostructure under an external electric field. We find that, different from the suspended monolayer MoS2 with a direct band-gap, h-BN/MoS2/h-BN has an indirect band-gap. Particular attention has been focused on the engineering of the band-gap of the h-BN/MoS2/h-BN heterostructure via application of an external electric field. With the increase of electric field, the band-gap of the h-BN/MoS2/h-BN heterostructure undergoes an indirect-to-direct band-gap transition. Once the electric field intensity is larger than 0.1 V Å-1, the gap value of direct band-gap shrinks almost linearly with the field-strength, which indicates that the h-BN/MoS2/h-BN heterostructure is a viable candidate for optoelectronic applications.

  15. Atomic Layer Epitaxy of h-BN(0001) Multilayers on Co(0001) and Molecular Beam Epitaxy Growth of Graphene on h-BN(0001)/Co(0001).

    PubMed

    Driver, M Sky; Beatty, John D; Olanipekun, Opeyemi; Reid, Kimberly; Rath, Ashutosh; Voyles, Paul M; Kelber, Jeffry A

    2016-03-22

    The direct growth of hexagonal boron nitride (h-BN) by industrially scalable methods is of broad interest for spintronic and nanoelectronic device applications. Such applications often require atomically precise control of film thickness and azimuthal registry between layers and substrate. We report the formation, by atomic layer epitaxy (ALE), of multilayer h-BN(0001) films (up to 7 monolayers) on Co(0001). The ALE process employs BCl3/NH3 cycles at 600 K substrate temperature. X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) data show that this process yields an increase in h-BN average film thickness linearly proportional to the number of BCl3/NH3 cycles, with BN layers in azimuthal registry with each other and with the Co(0001) substrate. LEED diffraction spot profile data indicate an average BN domain size of at least 1900 Å. Optical microscopy data indicate the presence of some domains as large as ∼20 μm. Transmission electron microscopy (TEM) and ambient exposure studies demonstrate macroscopic and microscopic continuity of the h-BN film, with the h-BN film highly conformal to the Co substrate. Photoemission data show that the h-BN(0001) film is p-type, with band bending near the Co/h-BN interface. Growth of graphene by molecular beam epitaxy (MBE) is observed on the surface of multilayer h-BN(0001) at temperatures of 800 K. LEED data indicate azimuthal graphene alignment with the h-BN and Co(0001) lattices, with domain size similar to BN. The evidence of multilayer BN and graphene azimuthal alignment with the lattice of the Co(0001) substrate demonstrates that this procedure is suitable for scalable production of heterojunctions for spintronic applications.

  16. Plasma-assisted interface engineering of boron nitride nanostructure films.

    PubMed

    Pakdel, Amir; Bando, Yoshio; Golberg, Dmitri

    2014-10-28

    Today many aspects of science and technology are progressing into the nanoscale realm where surfaces and interfaces are intrinsically important in determining properties and performances of materials and devices. One familiar phenomenon in which interfacial interactions play a major role is the wetting of solids. In this work we use a facile one-step plasma method to control the wettability of boron nitride (BN) nanostructure films via covalent chemical functionalization, while their surface morphology remains intact. By tailoring the concentration of grafted hydroxyl groups, superhydrophilic, hydrophilic, and hydrophobic patterns are created on the initially superhydrophobic BN nanosheet and nanotube films. Moreover, by introducing a gradient of the functional groups, directional liquid spreading toward increasing [OH] content is achieved on the films. The resulting insights are meant to illustrate great potentials of this method to tailor wettability of ceramic films, control liquid flow patterns for engineering applications such as microfluidics and biosensing, and improve the interfacial contact and adhesion in nanocomposite materials.

  17. Band-gap control in phosphorene/BN structures from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Marsoner Steinkasserer, Lukas Eugen; Suhr, Simon; Paulus, Beate

    2016-09-01

    Using both DFT as well as G0W0 calculations, we investigate static and dynamic effects on the phosphorene band gap upon deposition and encapsulation on/in BN multilayers. We demonstrate how competing long- and short-range effects cause the phosphorene band gap to increase at low P -BN interlayer spacings, while the band gap is found to drop below that of isolated phosphorene in the BN/P bilayer at intermediate distances around 4 Å. Subsequent stacking of BN layers, i.e., BN/BN/P and BN/BN/BN/P is found to have a negligible effect at the DFT level while at the G0W0 level, increased screening lowers the band gap as compared to the BN/P bilayer. Encapsulation between two BN layers, on the other hand, is found to further increase the phosphorene band gap with respect to the BN/P bilayer. Lastly we investigate the use of the GLLB-SC functional as a starting point for G0W0 calculations showing it to, in the case of phosphorene, yield results close to those obtained from G W0@P B E .

  18. 49 CFR 178.39 - Specification 3BN seamless nickel cylinders.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Specification 3BN seamless nickel cylinders. 178... FOR PACKAGINGS Specifications for Cylinders § 178.39 Specification 3BN seamless nickel cylinders. (a) Type, size and service pressure. A DOT 3BN cylinder is a seamless nickel cylinder with a water...

  19. 49 CFR 178.39 - Specification 3BN seamless nickel cylinders.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Specification 3BN seamless nickel cylinders. 178... FOR PACKAGINGS Specifications for Cylinders § 178.39 Specification 3BN seamless nickel cylinders. (a) Type, size and service pressure. A DOT 3BN cylinder is a seamless nickel cylinder with a water...

  20. 49 CFR 178.39 - Specification 3BN seamless nickel cylinders.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Specification 3BN seamless nickel cylinders. 178... FOR PACKAGINGS Specifications for Cylinders § 178.39 Specification 3BN seamless nickel cylinders. (a) Type, size and service pressure. A DOT 3BN cylinder is a seamless nickel cylinder with a water...

  1. 49 CFR 178.39 - Specification 3BN seamless nickel cylinders.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Specification 3BN seamless nickel cylinders. 178... FOR PACKAGINGS Specifications for Cylinders § 178.39 Specification 3BN seamless nickel cylinders. (a) Type, size and service pressure. A DOT 3BN cylinder is a seamless nickel cylinder with a water...

  2. 49 CFR 178.39 - Specification 3BN seamless nickel cylinders.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Specification 3BN seamless nickel cylinders. 178... FOR PACKAGINGS Specifications for Cylinders § 178.39 Specification 3BN seamless nickel cylinders. (a) Type, size and service pressure. A DOT 3BN cylinder is a seamless nickel cylinder with a water...

  3. Orthotropic Piezoelectricity in 2D Nanocellulose

    NASA Astrophysics Data System (ADS)

    García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.

    2016-10-01

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V‑1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies.

  4. Orthotropic Piezoelectricity in 2D Nanocellulose

    PubMed Central

    García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.

    2016-01-01

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V−1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies. PMID:27708364

  5. 2D microwave imaging reflectometer electronics

    SciTech Connect

    Spear, A. G.; Domier, C. W. Hu, X.; Muscatello, C. M.; Ren, X.; Luhmann, N. C.; Tobias, B. J.

    2014-11-15

    A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program.

  6. Optical modulators with 2D layered materials

    NASA Astrophysics Data System (ADS)

    Sun, Zhipei; Martinez, Amos; Wang, Feng

    2016-04-01

    Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that 2D layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this Review, we cover the state of the art of optical modulators based on 2D materials, including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as 2D heterostructures, plasmonic structures, and silicon and fibre integrated structures. We also take a look at the future perspectives and discuss the potential of yet relatively unexplored mechanisms, such as magneto-optic and acousto-optic modulation.

  7. Inkjet printing of 2D layered materials.

    PubMed

    Li, Jiantong; Lemme, Max C; Östling, Mikael

    2014-11-10

    Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials. PMID:25169938

  8. Inkjet printing of 2D layered materials.

    PubMed

    Li, Jiantong; Lemme, Max C; Östling, Mikael

    2014-11-10

    Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials.

  9. Tuning and synthesis of metallic nanostructures by mechanical compression

    DOEpatents

    Fan, Hongyou; Li, Binsong

    2015-11-17

    The present invention provides a pressure-induced phase transformation process to engineer metal nanoparticle architectures and to fabricate new nanostructured materials. The reversible changes of the nanoparticle unit cell dimension under pressure allow precise control over interparticle separation in 2D or 3D nanoparticle assemblies, offering unique robustness for interrogation of both quantum and classic coupling interactions. Irreversible changes above a threshold pressure of about 8 GPa enables new nanostructures, such as nanorods, nanowires, or nanosheets.

  10. Thermal Stability of Microstructure and Hardness of Cold-Sprayed cBN/NiCrAl Nanocomposite Coating

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-Tao; Li, Chang-Jiu

    2012-06-01

    cBN/NiCrAl nanocomposite coatings were deposited by cold spraying using mechanically alloyed composite powders. To examine their thermal stability, the nanocomposite coatings were annealed at different temperatures up to 1000 °C. The microstructure of composite coatings was characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that the nanostructure can be retained when the annealing temperature is not higher than 825 °C, which is 0.7 times of the melting point of the NiCrAl matrix. The dislocation density was significantly reduced when the annealing temperature was higher than 750 °C. The reaction between cBN particles and the NiCrAl matrix became noticeable when the annealing temperature was higher than 825 °C. The effects of grain refinement and work-hardening strengthening mechanisms were quantitatively estimated as a function of annealing temperature. The influence of annealing temperature on the contribution of different strengthening mechanisms to coating hardness was discussed.

  11. Nano-structured interface of graphene and h-BN for sensing applications.

    PubMed

    de Souza, Fábio A L; Amorim, Rodrigo G; Scopel, Wanderlã L; Scheicher, Ralph H

    2016-09-01

    The atomically-precise controlled synthesis of graphene stripes embedded in hexagonal boron nitride opens up new possibilities for the construction of nanodevices with applications in sensing. Here, we explore properties related to the electronic structure and quantum transport of a graphene nanoroad embedded in hexagonal boron nitride, using a combination of density functional theory and the non-equilibrium Green's functions method to calculate the electric conductance. We find that the graphene nanoribbon signature is preserved in the transmission spectra and that the local current is mainly confined to the graphene domain. When a properly sized nanopore is created in the graphene part of the system, the electronic current becomes restricted to a carbon chain running along the border with hexagonal boron nitride. This circumstance could allow the hypothetical nanodevice to become highly sensitive to the electronic nature of molecules passing through the nanopore, thus opening up ways to detect gas molecules, amino acids, or even DNA sequences based on a measurement of the real-time conductance modulation in the graphene nanoroad. PMID:27485857

  12. Nano-structured interface of graphene and h-BN for sensing applications

    NASA Astrophysics Data System (ADS)

    de Souza, Fábio A. L.; Amorim, Rodrigo G.; Scopel, Wanderlã L.; Scheicher, Ralph H.

    2016-09-01

    The atomically-precise controlled synthesis of graphene stripes embedded in hexagonal boron nitride opens up new possibilities for the construction of nanodevices with applications in sensing. Here, we explore properties related to the electronic structure and quantum transport of a graphene nanoroad embedded in hexagonal boron nitride, using a combination of density functional theory and the non-equilibrium Green's functions method to calculate the electric conductance. We find that the graphene nanoribbon signature is preserved in the transmission spectra and that the local current is mainly confined to the graphene domain. When a properly sized nanopore is created in the graphene part of the system, the electronic current becomes restricted to a carbon chain running along the border with hexagonal boron nitride. This circumstance could allow the hypothetical nanodevice to become highly sensitive to the electronic nature of molecules passing through the nanopore, thus opening up ways to detect gas molecules, amino acids, or even DNA sequences based on a measurement of the real-time conductance modulation in the graphene nanoroad.

  13. Overexpression of BnWRKY33 in oilseed rape enhances resistance to Sclerotinia sclerotiorum.

    PubMed

    Wang, Zheng; Fang, Hedi; Chen, Yu; Chen, Keping; Li, Guanying; Gu, Shoulai; Tan, Xiaoli

    2014-09-01

    Sclerotinia sclerotiorum causes a devastating disease in oilseed rape (Brassica napus) resulting in a tremendous yield loss worldwide. Studies on various host-pathogen interactions have shown that plant WRKY transcription factors are essential for defence. For the B. napus-S. sclerotiorum interaction, little direct evidence has been found with regard to the biological roles of specific WRKY genes in host resistance. In this study, we isolated a B. napus WRKY gene, BnWRKY33, and found that the gene is highly responsive to S. sclerotiorum infection. Transgenic B. napus plants overexpressing BnWRKY33 showed markedly enhanced resistance to S. sclerotiorum, constitutive activation of the expression of BnPR1 and BnPDF1.2, and inhibition of H2 O2 accumulation in response to pathogen infection. Further, we isolated a mitogen-activated protein (MAP) kinase substrate gene, BnMKS1, and found that not only can BnWRKY33 interact with BnMKS1, which can also interact with BnMPK4, using the yeast two-hybrid assay, consistent with their collective nuclear localization, but also BnWRKY33, BnMKS1 and BnMPK4 are substantially and synergistically expressed in response to S. sclerotiorum infection. In contrast, the three genes showed differential expression in response to phytohormone treatments. Together, these results suggest that BnWRKY33 plays an important role in B. napus defence to S. sclerotiorum, which is most probably associated with the activation of the salicylic acid (SA)- and jasmonic acid (JA)-mediated defence response and inhibition of H2 O2 accumulation, and we propose a potential mechanism in which BnMPK4-BnMKS1-BnWRKY33 exist in a nuclear localized complex to regulate resistance to S. sclerotiorum in oilseed rape.

  14. Hoop Tensile Characterization Of SiC/SiC Cylinders Fabricated From 2D Fabric

    NASA Technical Reports Server (NTRS)

    Verrilli, Michael J.; Yun, HeeMann; DiCarlo, James A.; Barnett, Terry R.

    2002-01-01

    Tensile stress-strain properties in the hoop direction were obtained for 100-mm diameter SiC/SiC cylinders using ring specimens machined from the cylinder ends. The cylinders were fabricated from 2D balanced fabric with several material variants, including wall thickness (6, 8, and 12 plies), Sic fiber type (Sylramic, Sylramic-iBN, Hi-Nicalon, and Hi-Nicalon S), fiber sizing type, and matrix type (full CVI Sic, and partial CVI plus melt-infiltrated SiC-Si). Fiber ply splices existed in the all the hoops. Tensile hoop measurements were made at room temperature and 1200 C using hydrostatic ring test facilities. The hoop results are compared with in-plane data measured on flat panels using same material variants, but containing no splices.

  15. Parallel stitching of 2D materials

    DOE PAGES

    Ling, Xi; Wu, Lijun; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; et al

    2016-01-27

    Diverse parallel stitched 2D heterostructures, including metal–semiconductor, semiconductor–semiconductor, and insulator–semiconductor, are synthesized directly through selective “sowing” of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. Lastly, the methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.

  16. Parallel Stitching of 2D Materials.

    PubMed

    Ling, Xi; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; Hsu, Allen L; Bie, Yaqing; Lee, Yi-Hsien; Zhu, Yimei; Wu, Lijun; Li, Ju; Jarillo-Herrero, Pablo; Dresselhaus, Mildred; Palacios, Tomás; Kong, Jing

    2016-03-23

    Diverse parallel stitched 2D heterostructures, including metal-semiconductor, semiconductor-semiconductor, and insulator-semiconductor, are synthesized directly through selective "sowing" of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. The methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.

  17. Low-dimensional hyperthin FeS2 nanostructures for efficient and stable hydrogen evolution electrocatalysis

    SciTech Connect

    Jasion, Daniel; Qiao, Qiao; Barforoush, Joseph M.; Zhu, Yimei; Ren, Shenqiang; Leonard, Kevin C.

    2015-10-05

    We report a scalable, solution-processing method for synthesizing low-dimensional hyperthin FeS2 nanostructures, and we show that 2D FeS2 disc nanostructures are an efficient and stable hydrogen evolution electrocatalyst. By changing the Fe:S ratio in the precursor solution, we were able to preferentially synthesize either 1D wire or 2D disc nanostructures. The 2D FeS2 disc structure has the highest electrocatalytic activity for the hydrogen evolution reaction, comparable to platinum in neutral pH conditions. Moreover, the ability of the FeS2 nanostructures to generate hydrogen was confirmed by scanning electrochemical microscopy, and the 2D disc nanostructures were able to generate hydrogen for over 125 h.

  18. Stabilities and mechanical and electronic properties on BN doped zigzag single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Vongachariya, Arthit; Parasuk, Vudhichai

    2015-12-01

    Electronic structures of undoped and BN doped zigzag (8,0) single-walled carbon nanotube (SWCNT) were investigated using density functional theoretical calculations. Their stabilities due to BN doping and spin states were considered and those with the shortest B-N distance and singlet spin is the most stable. The BN substitution also causes the reduction of the band gap energy. While the BN doping reduces the band gap energy from 0.606 to 0.183 eV, it has no effect on the Young's modulus value. The band gap energy of SWCNTs can be varied upon applying stress. At high stress ratio, SWCNT could become metallic.

  19. R.F. magnetron sputtering of multilayered c-BN films on cemented carbide tool.

    PubMed

    Park, Sungtae; Jeong, Sehoon; Lee, Kwangmin

    2011-02-01

    A c-BN thin film was deposited using a B4C target in a r.f. magnetron sputtering system. The c-BN layer was coated with a TiAIN adhesion layer (approximately 2 microm), boron carbide (approximately 1 microm) and BCN (10 approximately 15 nm) nano-gradient layer system. The c-BN layers with thicknesses of more than 0.5 microm were successfully deposited onto cemented carbide substrates. The high resolution XPS spectra analysis of B1s and N1s revealed that the c-BN film was mainly composed of sp3 BN bonds.

  20. Storage of molecular hydrogen in B-N cage: energetics and thermal stability.

    PubMed

    Sun, Qiang; Wang, Qian; Jena, Puru

    2005-07-01

    Using first principles theory based on density functional formulation we have studied the energetics and thermal stability of storing hydrogen in B-N-based nanostructures. We show that hydrogen molecule enters through the hexagonal face of the B36N36 cage and prefers to remain inside the cage in molecular form. The energy barriers for the hydrogen molecule to enter into or escape from the cage are respectively 1.406 eV and 1.516 eV. As the concentration of hydrogen inside the cage increases, the cage expands and the bond length of the hydrogen molecule contracts, resulting in significant energy cost. At zero temperature, up to 18 hydrogen molecules can be stored inside a B36N36 cage corresponding to a gravimetric density of 4 wt %. However, molecular dynamics simulation by using Nose algorithm at room temperature (T = 300 K) indicates that high weight percentage hydrogen storage cannot be achieved in B-N cage structures and thus these materials may not be good for practical applications.

  1. Biological Efficacy of Streptomyces sp. Strain BN1 against the Cereal Head Blight Pathogen Fusarium graminearum

    PubMed Central

    Jung, Boknam; Park, Sook-Young; Lee, Yin-Won; Lee, Jungkwan

    2013-01-01

    Fusarium head blight (FHB) caused by the filamentous fungus Fusarium graminearum is one of the most severe diseases threatening the production of small grains. Infected grains are often contaminated with mycotoxins such as zearalenone and trichothecences. During survey of contamination by FHB in rice grains, we found a bacterial isolate, designated as BN1, antagonistic to F. graminearum. The strain BN1 had branching vegetative hyphae and spores, and its aerial hyphae often had long, straight filaments bearing spores. The 16S rRNA gene of BN1 had 100% sequence identity with those found in several Streptomyces species. Phylogenetic analysis of ITS regions showed that BN1 grouped with S. sampsonii with 77% bootstrap value, suggesting that BN1 was not a known Streptomyces species. In addition, the efficacy of the BN1 strain against F. graminearum strains was tested both in vitro and in vivo. Wheat seedling length was significantly decreased by F. graminearum infection. However, this effect was mitigated when wheat seeds were treated with BN1 spore suspension prior to F. graminearum infection. BN1 also significantly decreased FHB severity when it was sprayed onto wheat heads, whereas BN1 was not effective when wheat heads were point inoculated. These results suggest that spraying of BN1 spores onto wheat heads during the wheat flowering season can be efficient for plant protection. Mechanistic studies on the antagonistic effect of BN1 against F. graminearum remain to be analyzed. PMID:25288928

  2. Profile Grinding of Superalloys with Ultrafine-Crystalline cBN Wheels

    NASA Astrophysics Data System (ADS)

    Ichida, Yoshio; Sato, Ryunosuke; Morimoto, Yoshitaka; Inoue, Yoshihiro

    This paper deals with the grinding characteristics of newly developed polycrystalline cBN (cBN-U) abrasives in creep feed profile grinding of nickel-based superalloys. Experiments for producing a V-shaped groove on a flat surface in one pass by creep feed grinding have been carried out using the new polycrystalline cBN-U and representative conventional cBN (cBN-B) grits. When grinding with cBN-U abrasives, both radial wear and profile wear are less, and hence the grinding ratio is around 10 times higher than that with the conventional cBN-B abrasives. Grinding forces in grinding with cBN-U abrasives are reduced by 20-30% compared with those in Grinding with cBN-B abrasives. The cBN-U abrasive is suitable for the applications with a high dimensional accuracy in creep feed profile grinding for nickel-based superalloys, because it gives less profile wear, and hence better form retention, than conventional cBN abrasive.

  3. Profile Grinding of High-Speed Steel using Ultrafine-Crystalline cBN Wheels

    NASA Astrophysics Data System (ADS)

    Ichida, Yoshio

    This paper deals with the grinding characteristics of newly developed ultrafine-crystalline cBN (cBN-U) abrasive grains in creep feed profile grinding of high-speed steels. Experiments for producing a V-shaped groove on a flat surface in one pass by creep feed grinding have been carried out using new polycrystalline cBN-U and representative conventional cBN (cBN-B) abrasive grains. When grinding with the cBN-U wheel, both radial wear and profile wear are less, and hence the grinding ratio is around 4 times higher than that with conventional cBN-B wheel. Grinding force in grinding with the cBN-U wheel is reduced by 5˜15 % compared with that in grinding with the cBN-B wheel. The cBN-U abrasive grain is suitable for application with a high dimensional accuracy in creep feed profile grinding for high-speed steel, because it gives less profile wear, and hence better form retention of the wheel, than conventional cBN abrasive grain.

  4. In situ high pressure synthesis of cBN-based composites

    NASA Astrophysics Data System (ADS)

    Xue, Yanan; Qin, Jiaqian; Zhang, Xinyu; Ma, Mingzhen; He, Duanwei; Liu, Riping

    2014-05-01

    Vickers hardness, phase combination, elastic modulus and cutting performance of the cubic boron nitride (cBN) based composites with different cBN weight ratios sintered at high pressure and high temperature were investigated. During high-pressure sintering, reactions occurred between cBN and Ti3SiC2, then new compounds, TiB2, C0.7N0.3Ti, SiC and SiB4 were formed, and no hBN phase was observed. Bulk modulus and hardness of the cBN composites decreased with increasing Ti3SiC2 contents in raw mixture, and the highest hardness of 35.9 GPa was achieved for 95 wt.% cBN-5 wt.% Ti3SiC2 composition specimen sintered at 1600°C. In addition, the present cBN-based composites exhibited good cutting performance.

  5. Chemically engineered graphene-based 2D organic molecular magnet.

    PubMed

    Hong, Jeongmin; Bekyarova, Elena; de Heer, Walt A; Haddon, Robert C; Khizroev, Sakhrat

    2013-11-26

    Carbon-based magnetic materials and structures of mesoscopic dimensions may offer unique opportunities for future nanomagnetoelectronic/spintronic devices. To achieve their potential, carbon nanosystems must have controllable magnetic properties. We demonstrate that nitrophenyl functionalized graphene can act as a room-temperature 2D magnet. We report a comprehensive study of low-temperature magnetotransport, vibrating sample magnetometry (VSM), and superconducting quantum interference (SQUID) measurements before and after radical functionalization. Following nitrophenyl (NP) functionalization, epitaxially grown graphene systems can become organic molecular magnets with ferromagnetic and antiferromagnetic ordering that persists at temperatures above 400 K. The field-dependent, surface magnetoelectric properties were studied using scanning probe microscopy (SPM) techniques. The results indicate that the NP-functionalization orientation and degree of coverage directly affect the magnetic properties of the graphene surface. In addition, graphene-based organic magnetic nanostructures were found to demonstrate a pronounced magneto-optical Kerr effect (MOKE). The results were consistent across different characterization techniques and indicate room-temperature magnetic ordering along preferred graphene orientations in the NP-functionalized samples. Chemically isolated graphene nanoribbons (CINs) were observed along the preferred functionality directions. These results pave the way for future magnetoelectronic/spintronic applications based on promising concepts such as current-induced magnetization switching, magnetoelectricity, half-metallicity, and quantum tunneling of magnetization.

  6. 2D:4D Ratio in children at familial high-risk for eating disorders: The role of prenatal testosterone exposure

    PubMed Central

    Kothari, Radha; Gafton, Joseph; Treasure, Janet; Micali, Nadia

    2014-01-01

    Objectives Markers of prenatal hormone exposure have been associated with the development of eating disorder (ED) behaviors. Our aim was to determine whether 2D:4D ratio, a marker for in utero testosterone exposure, is associated with risk for ED in a large population-based cohort: the Avon Longitudinal Study of Parents and Children (ALSPAC). Methods This is the first study to investigate prenatal testosterone exposure in children at high-risk for ED, using 2D:4D as a marker. We compared children whose mothers reported a lifetime ED (anorexia, bulimia, or both; N = 446) to children whose mothers did not (n = 5,367). Results Daughters of women with lifetime bulimia nervosa (BN) had lower 2D:4D ratio (B: −0.01, 95% CI: −0.02 to −0.002, P = 0.02), indicating higher prenatal testosterone exposure, than daughters of mothers unaffected by ED. No differences were observed in the male children of women with an ED. Conclusions Findings suggest that children at high-risk for BN may be exposed to higher levels of testosterone in utero. Fetal exposure to androgen excess is thought to be causal in the development of polycystic ovary syndrome (PCOS), a disorder which is highly comorbid with binge eating and BN. Future research should investigate the potential role of testosterone exposure in utero as a risk factor for BN and binge eating. Am. J. Hum. Biol. 26:176–182, 2014. © 2013 Wiley Periodicals, Inc. PMID:24323736

  7. Identification and Characterization of 1,2-BN Cyclohexene Using Microwave Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kukolich, Stephen G.; Sun, Ming; Daly, Adam M.; Ishibashi, Jacob S. A.; Liu, Shih-Yuan

    2016-06-01

    1,2-BN Cyclohexene was produced from 1,2-BN Cyclohexane through the loss of H_2 and characterized and identified using a pulsed-beam Fourier-transform microwave spectrometer. The first microwave spectra for 1,2-10BN Cyclohexene 1,2-11BN Cyclohexene have been measured in the frequency range of 5.5-12.5 GHz, providing accurate rotational constants and nitrogen and boron quadrupole coupling strengths for two isotopologues. High-level ab initio calculations provided rotational constants and quadrupole coupling strengths for the precursor 1,2-BN Cyclohexane (C_4H12BN) and 1,2-BN Cyclohexene(C_4H10BN). Calculated molecular properties for 1,2-BN Cyclohexene are in very good agreement with measured parameters. Calculated parameters for the starting material, 1,2-BN Cyclohexane do not agree with the experimental data. Rotational constants for 1,2-11BN Cyclohexene are A = 4702.058(2) MHz, B = 4360.334(1) MHz and C = 2494.407(1) MHz. The inertial defect is Δ_0 = -20.78 amu-Å^2 clearly indicating a nonplanar structure. These microwave experiments show that heating the initial compound, 1,2-BN Cyclohexane, to 60 C in a 1 atm neon stream results in the loss of H_2 and conversion to 1,2-BN Cyclohexene. This appears to be the first characterization of the 1,2-BN Cyclohexene monomer. Supported by the NSF CHE-1057796 and DOE DE-EE-0005658

  8. Solid Oxide Fuel Cell Seal Glass - BN Nanotubes Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Choi, Sung R.; Hurst, Janet B.; Garg, Anita

    2005-01-01

    Solid oxide fuel cell seal glass G18 composites reinforced with approx.4 weight percent of BN nanotubes were fabricated via hot pressing. Room temperature strength and fracture toughness of the composite were determined by four-point flexure and single edge V-notch beam methods, respectively. The strength and fracture toughness of the composite were higher by as much as 90% and 35%, respectively, than those of the glass G18. Microscopic examination of the composite fracture surfaces using SEM and TEM showed pullout of the BN nanotubes, similar in feature to fiber-reinforced ceramic matrix composites with weak interfaces. Other mechanical and physical properties of the composite will also be presented.

  9. Electrodeposition and characterization of Co-BN (h) nanocomposite coatings

    NASA Astrophysics Data System (ADS)

    Shahri, Z.; Allahkaram, S. R.; Zarebidaki, A.

    2013-07-01

    Co-BN (h) nanocomposite coatings were prepared by means of the conventional electrodeposition in a chloride solution containing different concentrations of hexagonal boron nitride particles, and pure Co coating was also prepared as a comparison. Morphology of the coatings and the effect of incorporated particles on metal matrix structure and composition were investigated via scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction analysis. Microhardness, roughness, friction coefficient and wear resistance of the coatings were also evaluated using Vickers microhardness, stylus profilometer and pin-on disk machine. The results showed that Co-BN (h) nanocomposite coatings exhibit higher hardness and lower friction coefficient. Roughness and wear resistance compared with that of the pure Co coating obtained under the same electrodeposition condition and the wear mechanism of the coatings were also discussed.

  10. Stochastic Inversion of 2D Magnetotelluric Data

    SciTech Connect

    Chen, Jinsong

    2010-07-01

    The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function is explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows

  11. Explicit 2-D Hydrodynamic FEM Program

    1996-08-07

    DYNA2D* is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D* contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. Themore » isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.« less

  12. Stochastic Inversion of 2D Magnetotelluric Data

    2010-07-01

    The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function ismore » explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows« less

  13. Static & Dynamic Response of 2D Solids

    1996-07-15

    NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surfacemore » contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.« less

  14. Static & Dynamic Response of 2D Solids

    SciTech Connect

    Lin, Jerry

    1996-07-15

    NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surface contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.

  15. Explicit 2-D Hydrodynamic FEM Program

    SciTech Connect

    Lin, Jerry

    1996-08-07

    DYNA2D* is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D* contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.

  16. 2D photonic-crystal optomechanical nanoresonator.

    PubMed

    Makles, K; Antoni, T; Kuhn, A G; Deléglise, S; Briant, T; Cohadon, P-F; Braive, R; Beaudoin, G; Pinard, L; Michel, C; Dolique, V; Flaminio, R; Cagnoli, G; Robert-Philip, I; Heidmann, A

    2015-01-15

    We present the optical optimization of an optomechanical device based on a suspended InP membrane patterned with a 2D near-wavelength grating (NWG) based on a 2D photonic-crystal geometry. We first identify by numerical simulation a set of geometrical parameters providing a reflectivity higher than 99.8% over a 50-nm span. We then study the limitations induced by the finite value of the optical waist and lateral size of the NWG pattern using different numerical approaches. The NWG grating, pierced in a suspended InP 265-nm thick membrane, is used to form a compact microcavity involving the suspended nanomembrane as an end mirror. The resulting cavity has a waist size smaller than 10 μm and a finesse in the 200 range. It is used to probe the Brownian motion of the mechanical modes of the nanomembrane. PMID:25679837

  17. Compact 2-D graphical representation of DNA

    NASA Astrophysics Data System (ADS)

    Randić, Milan; Vračko, Marjan; Zupan, Jure; Novič, Marjana

    2003-05-01

    We present a novel 2-D graphical representation for DNA sequences which has an important advantage over the existing graphical representations of DNA in being very compact. It is based on: (1) use of binary labels for the four nucleic acid bases, and (2) use of the 'worm' curve as template on which binary codes are placed. The approach is illustrated on DNA sequences of the first exon of human β-globin and gorilla β-globin.

  18. Layer Engineering of 2D Semiconductor Junctions.

    PubMed

    He, Yongmin; Sobhani, Ali; Lei, Sidong; Zhang, Zhuhua; Gong, Yongji; Jin, Zehua; Zhou, Wu; Yang, Yingchao; Zhang, Yuan; Wang, Xifan; Yakobson, Boris; Vajtai, Robert; Halas, Naomi J; Li, Bo; Xie, Erqing; Ajayan, Pulickel

    2016-07-01

    A new concept for junction fabrication by connecting multiple regions with varying layer thicknesses, based on the thickness dependence, is demonstrated. This type of junction is only possible in super-thin-layered 2D materials, and exhibits similar characteristics as p-n junctions. Rectification and photovoltaic effects are observed in chemically homogeneous MoSe2 junctions between domains of different thicknesses. PMID:27136275

  19. Realistic and efficient 2D crack simulation

    NASA Astrophysics Data System (ADS)

    Yadegar, Jacob; Liu, Xiaoqing; Singh, Abhishek

    2010-04-01

    Although numerical algorithms for 2D crack simulation have been studied in Modeling and Simulation (M&S) and computer graphics for decades, realism and computational efficiency are still major challenges. In this paper, we introduce a high-fidelity, scalable, adaptive and efficient/runtime 2D crack/fracture simulation system by applying the mathematically elegant Peano-Cesaro triangular meshing/remeshing technique to model the generation of shards/fragments. The recursive fractal sweep associated with the Peano-Cesaro triangulation provides efficient local multi-resolution refinement to any level-of-detail. The generated binary decomposition tree also provides efficient neighbor retrieval mechanism used for mesh element splitting and merging with minimal memory requirements essential for realistic 2D fragment formation. Upon load impact/contact/penetration, a number of factors including impact angle, impact energy, and material properties are all taken into account to produce the criteria of crack initialization, propagation, and termination leading to realistic fractal-like rubble/fragments formation. The aforementioned parameters are used as variables of probabilistic models of cracks/shards formation, making the proposed solution highly adaptive by allowing machine learning mechanisms learn the optimal values for the variables/parameters based on prior benchmark data generated by off-line physics based simulation solutions that produce accurate fractures/shards though at highly non-real time paste. Crack/fracture simulation has been conducted on various load impacts with different initial locations at various impulse scales. The simulation results demonstrate that the proposed system has the capability to realistically and efficiently simulate 2D crack phenomena (such as window shattering and shards generation) with diverse potentials in military and civil M&S applications such as training and mission planning.

  20. 2D Spinodal Decomposition in Forced Turbulence

    NASA Astrophysics Data System (ADS)

    Fan, Xiang; Diamond, Patrick; Chacon, Luis; Li, Hui

    2015-11-01

    Spinodal decomposition is a second order phase transition for binary fluid mixture, from one thermodynamic phase to form two coexisting phases. The governing equation for this coarsening process below critical temperature, Cahn-Hilliard Equation, is very similar to 2D MHD Equation, especially the conserved quantities have a close correspondence between each other, so theories for MHD turbulence are used to study spinodal decomposition in forced turbulence. Domain size is increased with time along with the inverse cascade, and the length scale can be arrested by a forced turbulence with direct cascade. The two competing mechanisms lead to a stabilized domain size length scale, which can be characterized by Hinze Scale. The 2D spinodal decomposition in forced turbulence is studied by both theory and simulation with ``pixie2d.'' This work focuses on the relation between Hinze scale and spectra and cascades. Similarities and differences between spinodal decomposition and MHD are investigated. Also some transport properties are studied following MHD theories. This work is supported by the Department of Energy under Award Number DE-FG02-04ER54738.

  1. MAGNUM-2D computer code: user's guide

    SciTech Connect

    England, R.L.; Kline, N.W.; Ekblad, K.J.; Baca, R.G.

    1985-01-01

    Information relevant to the general use of the MAGNUM-2D computer code is presented. This computer code was developed for the purpose of modeling (i.e., simulating) the thermal and hydraulic conditions in the vicinity of a waste package emplaced in a deep geologic repository. The MAGNUM-2D computer computes (1) the temperature field surrounding the waste package as a function of the heat generation rate of the nuclear waste and thermal properties of the basalt and (2) the hydraulic head distribution and associated groundwater flow fields as a function of the temperature gradients and hydraulic properties of the basalt. MAGNUM-2D is a two-dimensional numerical model for transient or steady-state analysis of coupled heat transfer and groundwater flow in a fractured porous medium. The governing equations consist of a set of coupled, quasi-linear partial differential equations that are solved using a Galerkin finite-element technique. A Newton-Raphson algorithm is embedded in the Galerkin functional to formulate the problem in terms of the incremental changes in the dependent variables. Both triangular and quadrilateral finite elements are used to represent the continuum portions of the spatial domain. Line elements may be used to represent discrete conduits. 18 refs., 4 figs., 1 tab.

  2. Engineering light outcoupling in 2D materials.

    PubMed

    Lien, Der-Hsien; Kang, Jeong Seuk; Amani, Matin; Chen, Kevin; Tosun, Mahmut; Wang, Hsin-Ping; Roy, Tania; Eggleston, Michael S; Wu, Ming C; Dubey, Madan; Lee, Si-Chen; He, Jr-Hau; Javey, Ali

    2015-02-11

    When light is incident on 2D transition metal dichalcogenides (TMDCs), it engages in multiple reflections within underlying substrates, producing interferences that lead to enhancement or attenuation of the incoming and outgoing strength of light. Here, we report a simple method to engineer the light outcoupling in semiconducting TMDCs by modulating their dielectric surroundings. We show that by modulating the thicknesses of underlying substrates and capping layers, the interference caused by substrate can significantly enhance the light absorption and emission of WSe2, resulting in a ∼11 times increase in Raman signal and a ∼30 times increase in the photoluminescence (PL) intensity of WSe2. On the basis of the interference model, we also propose a strategy to control the photonic and optoelectronic properties of thin-layer WSe2. This work demonstrates the utilization of outcoupling engineering in 2D materials and offers a new route toward the realization of novel optoelectronic devices, such as 2D LEDs and solar cells.

  3. On-Surface Synthesis of BN-Substituted Heteroaromatic Networks.

    PubMed

    Sánchez-Sánchez, Carlos; Brüller, Sebastian; Sachdev, Hermann; Müllen, Klaus; Krieg, Matthias; Bettinger, Holger F; Nicolaï, Adrien; Meunier, Vincent; Talirz, Leopold; Fasel, Roman; Ruffieux, Pascal

    2015-09-22

    We report on the bottom-up fabrication of BN-substituted heteroaromatic networks achieved by surface-assisted polymerization and subsequent cyclodehydrogenation of specifically designed BN-substituted precursor monomers based on a borazine core structural element. To get insight into the cyclodehydrogenation pathway and the influence of molecular flexibility on network quality, two closely related precursor monomers with different degrees of internal cyclodehydrogenation have been employed. Scanning tunneling microscopy shows that, for both monomers, surface-assisted cyclodehydrogenation allows for complete monomer cyclization and the formation of covalently interlinked BN-substituted polyaromatic hydrocarbon networks on the Ag(111) surface. In agreement with experimental observations, density functional theory calculations reveal a significantly lower energy barrier for the cyclodehydrogenation of the conformationally more rigid precursor monomer, which is also reflected in a higher degree of long-range order of the obtained heteroaromatic network. Our proof-of-concept study will allow for the fabrication of atomically precise substitution patterns within BNC heterostructures.

  4. Orientation-dependence of elastic strain energy in hexagonal and cubic boron nitride layers in energetically deposited BN films

    SciTech Connect

    Cardinale, G.F.; Medlin, D.L.; Mirkarimi, P.B.; McCarty, K.F.; Howitt, D.G.

    1997-01-01

    Using anisotropic elasticity theory, we analyze the relative thermodynamic stabilities of strained graphitic (hexagonal) BN and cubic BN (cBN) single-crystal structures for all orientations of biaxial stress and strain fields relative to the crystallographic directions. In hBN, the most thermodynamically stable orientation has the graphitic basal planes oriented roughly 45{degree} relative to either the plane of stress or strain. For cBN, the lowest-energy configuration differs for the constant stress or constant strain assumptions. Importantly, these most-stable orientations of hBN and cBN differ from those found experimentally for graphitic BN and cBN in polycrystalline BN films produced by energetic deposition processes. Therefore, the observed textures are not those that minimize elastic strain energy. We discuss possible origins other than elastic strain{endash}energy effects for the observed textures. {copyright} {ital 1997 American Vacuum Society.}

  5. Development of a High Performance Vitrified Grinding Wheel using Ultrafine-Crystalline cBN Abrasive Grains

    NASA Astrophysics Data System (ADS)

    Ichida, Yoshio; Fujimoto, Masakazu; Inoue, Yuichiro; Matsui, Keisuke

    This paper describes the development of a high-performance vitrified bonded cBN grinding wheel using a new type of ultrafine-crystalline cBN (cBN-U) abrasive grain. Surface plunge grinding experiments using a vitrified wheel made of the cBN-U grains with a mesh size of #80/100 were carried out, and the wheel’s grinding performance was compared with those of cBN vitrified wheels made of representative conventional monocrystalline and polycrystalline cBN abrasive grains. This new cBN-U abrasive grain was found to possess a higher fracture strength than these conventional cBN grains. Therefore, the cBN-U wheel exhibits a higher grinding ratio and longer grinding wheel life than conventional cBN wheels.

  6. Present perspectives of broadband photodetectors based on nanobelts, nanoribbons, nanosheets and the emerging 2D materials.

    PubMed

    Dhanabalan, Sathish Chander; Ponraj, Joice Sophia; Zhang, Han; Bao, Qiaoliang

    2016-03-28

    Recent research on photodetectors has been mainly focused on nanostructured materials that form the building blocks of device fabrication. The selection of a suitable material with well-defined properties forms the key issue for the fabrication of photodetectors that cover different ranges of the electromagnetic spectrum. In this review, the latest progress in light detection using nanobelts, nanoribbons, nanosheets and the emerging two-dimensional (2D) materials is reviewed. Particular emphasis is placed on the detection of light by the hybrid structures of the mentioned nanostructured materials in order to enhance the efficiency of the light-matter interaction. The booming research area of black phosphorus based photo-detection is also reviewed. This review provides an overview of basic concepts and new directions towards photodetectors, and highlights potential for the future development of high performance broadband photodetectors. PMID:26935809

  7. Present perspectives of broadband photodetectors based on nanobelts, nanoribbons, nanosheets and the emerging 2D materials.

    PubMed

    Dhanabalan, Sathish Chander; Ponraj, Joice Sophia; Zhang, Han; Bao, Qiaoliang

    2016-03-28

    Recent research on photodetectors has been mainly focused on nanostructured materials that form the building blocks of device fabrication. The selection of a suitable material with well-defined properties forms the key issue for the fabrication of photodetectors that cover different ranges of the electromagnetic spectrum. In this review, the latest progress in light detection using nanobelts, nanoribbons, nanosheets and the emerging two-dimensional (2D) materials is reviewed. Particular emphasis is placed on the detection of light by the hybrid structures of the mentioned nanostructured materials in order to enhance the efficiency of the light-matter interaction. The booming research area of black phosphorus based photo-detection is also reviewed. This review provides an overview of basic concepts and new directions towards photodetectors, and highlights potential for the future development of high performance broadband photodetectors.

  8. The genes BnSCT1 and BnSCT2 from Brassica napus encoding the final enzyme of sinapine biosynthesis: molecular characterization and suppression.

    PubMed

    Weier, Diana; Mittasch, Juliane; Strack, Dieter; Milkowski, Carsten

    2008-01-01

    This study describes the molecular characterization of the genes BnSCT1 and BnSCT2 from oilseed rape (Brassica napus) encoding the enzyme 1-O-sinapoyl-beta-glucose:choline sinapoyltransferase (SCT; EC 2.3.1.91). SCT catalyzes the 1-O-beta-acetal ester-dependent biosynthesis of sinapoylcholine (sinapine), the most abundant phenolic compound in seeds of B. napus. GUS fusion experiments indicated that seed specificity of BnSCT1 expression is caused by an inducible promoter confining transcription to embryo tissues and the aleurone layer. A dsRNAi construct designed to silence seed-specifically the BnSCT1 gene was effective in reducing the sinapine content of Arabidopsis seeds thus defining SCT genes as targets for molecular breeding of low sinapine cultivars of B. napus. Sequence analyses revealed that in the allotetraploid genome of B. napus the gene BnSCT1 represents the C genome homologue from the B. oleracea progenitor whereas BnSCT2 was derived from the Brassica A genome of B. rapa. The BnSCT1 and BnSCT2 loci showed colinearity with the homologous Arabidopsis SNG2 gene locus although the genomic microstructure revealed the deletion of a cluster of three genes and several coding regions in the B. napus genome.

  9. Comparative study of metal atom adsorption on free-standing h-BN and h-BN/Ni (1 1 1) surfaces

    NASA Astrophysics Data System (ADS)

    Hwang, Yubin; Chung, Yong-Chae

    2014-04-01

    In this paper, a comparative study of the adsorption behavior of single metal atoms (Li, Sc, Ti, Co, Ni, and Cu) on two systems, a free-standing hexagonal boron nitride (h-BN) sheet and an h-BN/Ni (1 1 1) surface, was performed using density functional theory calculations. It was found that the Ni (1 1 1) supporting layer under the h-BN sheet could significantly improves the adsorption energies for single metal adatoms with h-BN. In particular, in the case of Li and Sc, the improved adsorption energies were higher than the cohesive energies of their atoms. The mechanism for these strong adsorptions was primarily due to the charge transfer increases from the adsorbed metal atoms to the h-BN, except for the case of Ni. On the other hand, the adsorption behavior was greatly affected by the interface interaction between the h-BN and Ni (1 1 1) for the adsorption of a single Ni atom. These results may provide fundamental information on the interaction between the adsorbed metal atoms between the h-BN based systems, and suggest that the use of a metal-adsorbed h-BN/Ni (1 1 1) system has good potential for nanosensors and nanocatalysts.

  10. The genes BnSCT1 and BnSCT2 from Brassica napus encoding the final enzyme of sinapine biosynthesis: molecular characterization and suppression.

    PubMed

    Weier, Diana; Mittasch, Juliane; Strack, Dieter; Milkowski, Carsten

    2008-01-01

    This study describes the molecular characterization of the genes BnSCT1 and BnSCT2 from oilseed rape (Brassica napus) encoding the enzyme 1-O-sinapoyl-beta-glucose:choline sinapoyltransferase (SCT; EC 2.3.1.91). SCT catalyzes the 1-O-beta-acetal ester-dependent biosynthesis of sinapoylcholine (sinapine), the most abundant phenolic compound in seeds of B. napus. GUS fusion experiments indicated that seed specificity of BnSCT1 expression is caused by an inducible promoter confining transcription to embryo tissues and the aleurone layer. A dsRNAi construct designed to silence seed-specifically the BnSCT1 gene was effective in reducing the sinapine content of Arabidopsis seeds thus defining SCT genes as targets for molecular breeding of low sinapine cultivars of B. napus. Sequence analyses revealed that in the allotetraploid genome of B. napus the gene BnSCT1 represents the C genome homologue from the B. oleracea progenitor whereas BnSCT2 was derived from the Brassica A genome of B. rapa. The BnSCT1 and BnSCT2 loci showed colinearity with the homologous Arabidopsis SNG2 gene locus although the genomic microstructure revealed the deletion of a cluster of three genes and several coding regions in the B. napus genome. PMID:17882453

  11. High pressure sintering behavior and mechanical properties of cBN-Ti3Al and cBN-Ti3Al-Al composite materials

    NASA Astrophysics Data System (ADS)

    Li, Yu; Kou, Zili; Wang, Haikuo; Wang, Kaixue; Tang, Hongchang; Wang, Yanfei; Liu, Shenzhuo; Ren, Xiangting; Meng, Chuanming; Wang, Zhigang

    2012-12-01

    The sintering behavior and mechanical properties of cubic boron nitride (cBN) composites, using the mixture of cBN-Ti3Al and cBN-Ti3Al-Al as the starting material respectively, were investigated under high pressure and high temperature (HPHT) conditions. The results show that the samples of cBN-Ti3Al-Al sintering system have more homogeneous microstructures. Young's modulus, shear modulus, and bulk modulus of samples measured by ultrasonic measurements can reach to 782±3 GPa, 344±1 GPa, and 348±2 GPa, respectively. The hardness increases remarkably with the sintering temperature rising, and reaches to the highest value of 35.04±0.51 GPa. For the cBN-Ti3Al sintering system, the X-ray diffraction patterns of composites reveal that the chemical reactions between cBN and Ti3Al occurred at 5.0 GPa and 1300°C. The reaction mechanisms of both cBN-Ti3Al and cBN-Ti3Al-Al sintering systems are discussed in this paper.

  12. Microstructure, Mechanical Properties, and Two-Body Abrasive Wear Behavior of Cold-Sprayed 20 vol.% Cubic BN-NiCrAl Nanocomposite Coating

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-Tao; Yang, Er-Juan; Shang, Fu-Lin; Yang, Guan-Jun; Li, Chen-Xin; Li, Chang-Jiu

    2014-10-01

    20 vol.% cubic boron nitride (cBN) dispersoid reinforced NiCrAl matrix nanocomposite coating was prepared by cold spray using mechanically alloyed nanostructured composite powders. The as-sprayed nanocomposite coating was annealed at a temperature of 750 °C to enhance the inter-particle bonding. Microstructure of spray powders and coatings was characterized. Vickers microhardness of the coatings was measured. Two-body abrasive wear behavior of the coatings was examined on a pin-on-disk test. It was found that, in mechanically alloyed composite powders, nano-sized and submicro-sized cBN particles are uniformly distributed in nanocrystalline NiCrAl matrix. Dense coating was deposited by cold spray at a gas temperature of 650 °C with the same phases and grain size as those of the starting powder. Vickers hardness test yielded a hardness of 1063 HV for the as-sprayed 20 vol.% cBN-NiCrAl coating. After annealed at 750 °C for 5 h, unbonded inter-particle boundaries were partially healed and evident grain growth of nanocrystalline NiCrAl was avoided. Wear resistance of the as-sprayed 20 vol.% cBN-NiCrAl nanocomposite coating was comparable to the HVOF-sprayed WC-12Co coating. Annealing of the nanocomposite coating resulted in the improvement of wear resistance by a factor of ~33% owing to the enhanced inter-particle bonding. Main material removal mechanisms during the abrasive wear are also discussed.

  13. Band gap engineering of chemical vapor deposited graphene by in situ BN doping.

    PubMed

    Chang, Cheng-Kai; Kataria, Satender; Kuo, Chun-Chiang; Ganguly, Abhijit; Wang, Bo-Yao; Hwang, Jeong-Yuan; Huang, Kay-Jay; Yang, Wei-Hsun; Wang, Sheng-Bo; Chuang, Cheng-Hao; Chen, Mi; Huang, Ching-I; Pong, Way-Faung; Song, Ker-Jar; Chang, Shoou-Jinn; Guo, Jing-Hua; Tai, Yian; Tsujimoto, Masahiko; Isoda, Seiji; Chen, Chun-Wei; Chen, Li-Chyong; Chen, Kuei-Hsien

    2013-02-26

    Band gap opening and engineering is one of the high priority goals in the development of graphene electronics. Here, we report on the opening and scaling of band gap in BN doped graphene (BNG) films grown by low-pressure chemical vapor deposition method. High resolution transmission electron microscopy is employed to resolve the graphene and h-BN domain formation in great detail. X-ray photoelectron, micro-Raman, and UV-vis spectroscopy studies revealed a distinct structural and phase evolution in BNG films at low BN concentration. Synchrotron radiation based XAS-XES measurements concluded a gap opening in BNG films, which is also confirmed by field effect transistor measurements. For the first time, a significant band gap as high as 600 meV is observed for low BN concentrations and is attributed to the opening of the π-π* band gap of graphene due to isoelectronic BN doping. As-grown films exhibit structural evolution from homogeneously dispersed small BN clusters to large sized BN domains with embedded diminutive graphene domains. The evolution is described in terms of competitive growth among h-BN and graphene domains with increasing BN concentration. The present results pave way for the development of band gap engineered BN doped graphene-based devices.

  14. Removing Impurity of cBN Crystal Prepared at High Pressure and High Temperature

    NASA Astrophysics Data System (ADS)

    Ji, Xiao-Rui; Yang, Xiao-Hong

    2012-03-01

    The black cubic boron nitride (cBN) single crystal is synthesized by using hBN-LiH and hBN-Li3N-B as the raw materials at high temperature and high pressure (HTHP). The colors of the cBN crystal synthesized in an hBN-Li3N-B system vary from transparent yellow, half-transparent and then opaque black with the increasing B content in the raw materials. It is worth noting that a trigonal shadow is presented at the center of the cBN crystal synthesized in the hBN-Li3N-B system but can not be found in the hBN-LiH system. Analyzing the Raman spectrum, we find that the darkening and the trigonal shadow in the cBN crystal may be due to the presence of excess B atoms. The above-mentioned phenomenon can be determined by removing impurity capacity and growth environment of the cBN crystal.

  15. Direct Growth of MoS₂/h-BN Heterostructures via a Sulfide-Resistant Alloy.

    PubMed

    Fu, Lei; Sun, Yangyong; Wu, Nian; Mendes, Rafael G; Chen, Linfeng; Xu, Zhen; Zhang, Tao; Rümmeli, Mark H; Rellinghaus, Bernd; Pohl, Darius; Zhuang, Lin; Fu, Lei

    2016-02-23

    Improved properties arise in transition metal dichalcogenide (TMDC) materials when they are stacked onto insulating hexagonal boron nitride (h-BN). Therefore, the scalable fabrication of TMDCs/h-BN heterostructures by direct chemical vapor deposition (CVD) growth is highly desirable. Unfortunately, to achieve this experimentally is challenging. Ideal substrates for h-BN growth, such as Ni, become sulfides during the synthesis process. This leads to the decomposition of the pregrown h-BN film, and thus no TMDCs/h-BN heterostructure forms. Here, we report a thoroughly direct CVD approach to obtain TMDCs/h-BN vertical heterostructures without any intermediate transfer steps. This is attributed to the use of a nickel-based alloy with excellent sulfide-resistant properties and a high catalytic activity for h-BN growth. The strategy enables the direct growth of single-crystal MoS2 grains of up to 200 μm(2) on h-BN, which is approximately 1 order of magnitude larger than that in previous reports. The direct band gap of our grown single-layer MoS2 on h-BN is 1.85 eV, which is quite close to that for free-standing exfoliated equivalents. This strategy is not limited to MoS2-based heterostructures and so allows the fabrication of a variety of TMDCs/h-BN heterostructures, suggesting the technique has promise for nanoelectronics and optoelectronic applications.

  16. GBL-2D Version 1.0: a 2D geometry boolean library.

    SciTech Connect

    McBride, Cory L. (Elemental Technologies, American Fort, UT); Schmidt, Rodney Cannon; Yarberry, Victor R.; Meyers, Ray J.

    2006-11-01

    This report describes version 1.0 of GBL-2D, a geometric Boolean library for 2D objects. The library is written in C++ and consists of a set of classes and routines. The classes primarily represent geometric data and relationships. Classes are provided for 2D points, lines, arcs, edge uses, loops, surfaces and mask sets. The routines contain algorithms for geometric Boolean operations and utility functions. Routines are provided that incorporate the Boolean operations: Union(OR), XOR, Intersection and Difference. A variety of additional analytical geometry routines and routines for importing and exporting the data in various file formats are also provided. The GBL-2D library was originally developed as a geometric modeling engine for use with a separate software tool, called SummitView [1], that manipulates the 2D mask sets created by designers of Micro-Electro-Mechanical Systems (MEMS). However, many other practical applications for this type of software can be envisioned because the need to perform 2D Boolean operations can arise in many contexts.

  17. Periodically sheared 2D Yukawa systems

    SciTech Connect

    Kovács, Anikó Zsuzsa; Hartmann, Peter; Donkó, Zoltán

    2015-10-15

    We present non-equilibrium molecular dynamics simulation studies on the dynamic (complex) shear viscosity of a 2D Yukawa system. We have identified a non-monotonic frequency dependence of the viscosity at high frequencies and shear rates, an energy absorption maximum (local resonance) at the Einstein frequency of the system at medium shear rates, an enhanced collective wave activity, when the excitation is near the plateau frequency of the longitudinal wave dispersion, and the emergence of significant configurational anisotropy at small frequencies and high shear rates.

  18. ENERGY LANDSCAPE OF 2D FLUID FORMS

    SciTech Connect

    Y. JIANG; ET AL

    2000-04-01

    The equilibrium states of 2D non-coarsening fluid foams, which consist of bubbles with fixed areas, correspond to local minima of the total perimeter. (1) The authors find an approximate value of the global minimum, and determine directly from an image how far a foam is from its ground state. (2) For (small) area disorder, small bubbles tend to sort inwards and large bubbles outwards. (3) Topological charges of the same sign repel while charges of opposite sign attract. (4) They discuss boundary conditions and the uniqueness of the pattern for fixed topology.

  19. Nanostructuring Mixed-Dimensional Perovskites: A Route Toward Tunable, Efficient Photovoltaics.

    PubMed

    Koh, Teck Ming; Shanmugam, Vignesh; Schlipf, Johannes; Oesinghaus, Lukas; Müller-Buschbaum, Peter; Ramakrishnan, N; Swamy, Varghese; Mathews, Nripan; Boix, Pablo P; Mhaisalkar, Subodh G

    2016-05-01

    2D perovskites is one of the proposed strategies to enhance the moisture resistance, since the larger organic cations can act as a natural barrier. Nevertheless, 2D perovskites hinder the charge transport in certain directions, reducing the solar cell power conversion efficiency. A nanostructured mixed-dimensionality approach is presented to overcome the charge transport limitation, obtaining power conversion efficiencies over 9%.

  20. Metal-dielectric photonic crystal superlattice: 1D and 2D models and empty lattice approximation

    NASA Astrophysics Data System (ADS)

    Kichin, G.; Weiss, T.; Gao, H.; Henzie, J.; Odom, T. W.; Tikhodeev, S. G.; Giessen, H.

    2012-10-01

    Periodic nanostructures are one of the main building blocks in modern nanooptics. They are used for constructing photonic crystals and metamaterials and provide optical properties that can be changed by adjusting the geometrical parameters of the structures. In this paper the optical properties of a photonic crystal slab with a 2D superlattice are discussed. The structure consists of a gold layer with a finite periodic pattern of air holes that is itself repeated periodically with a larger superperiod. We propose simplified 1D and 2D models to understand the physical nature of Wood's anomalies in the optical spectra of the investigated structure. The latter are attributed to the Rayleigh anomalies, surface plasmon Bragg resonances and the hole-localized plasmons.

  1. h-BN monolayer on the Ni(111) surface: a potential catalyst for oxidation.

    PubMed

    Wasey, A H M Abdul; Chakrabarty, Soubhik; Das, G P; Majumder, C

    2013-11-13

    The hexagonal boron nitride (h-BN) is traditionally considered to be inert. In sharp contrast to the inert behavior of free-standing hexagonal boron nitride (h-BN), we propose the catalytic property of h-BN monolayer on Ni(111) substrate using first-principles density functional theory investigation. The interaction of O2 molecule with the h-BN/Ni(111) substrate results in nondissociative adsorption of the molecule along with elongation of the O-O bond. This can be considered as the activated state of the O2 molecule. Further interaction of this complex viz O2-h-BN/Ni(111) with an incoming CO molecule leads to the spontaneous formation of CO2. Interestingly, the CO adsorption on the h-BN/Ni(111) substrate was found to be unfavorable, thereby implying the oxidation of CO selectively through Eley-Rideal (ER) mechanism. PMID:24127935

  2. Raman spectroscopy and time-resolved photoluminescence of BN and BxCyNz nanotubes

    SciTech Connect

    Wu, J.; Han, Wei-Qiang; Walukiewicz, W.; Ager III, J.W.; Shan, W.; Haller,E.E.; Zettl, A.

    2004-01-21

    We report Raman and time-resolved photoluminescence spectroscopic studies of multiwalled BN and B{sub x}C{sub y}N{sub z} nanotubes. The Raman spectroscopy shows that the as-grown B{sub x}C{sub y}N{sub z} charge recombination, respectively. Comparison of the photoluminescence of BN nanotubes to that decay process is characterized by two time constants that are attributed to intra- and inter-BN sheet nanotubes as predicted by theory. nanotubes are radially phase separated into BN shells and carbon shells. The photoluminescence of hexagonal BN is consistent with the existence of a spatially indirect band gap in multi-walled BN.

  3. The effects on the electronic properties of BN nanoribbon with C-chain substitution doping

    NASA Astrophysics Data System (ADS)

    Wang, Zhiyong; Zhao, Yayun; Sun, Mengyao; Xiao, Jianrong; Lu, Maowang; Wang, Liu; Zeng, Yaping; Long, Mengqiu

    2016-08-01

    The electronic properties of Boron-Nitrogen (BN) nanoribbon with Carbon (C)-chain substitution doping are investigated by performing first-principle calculations based on density functional theory. For the zigzag BN nanoribbon, the spin-unpolarized calculated results exhibit the insulator-semiconductor-metal transition with the number of substitution C-chain increasing. But for the armchair BN nanoribbon in the spin-unpolarized calculations, it is found that it appears the insulator-metal-semiconductor transition. The band gap of BN nanoribbon can be tuned according to the C-chain doping ratio. Interestingly, spin-polarized calculations exhibiting half-metallic may be tuned by changing the number of C-chain in the zigzag BN nanoribbon, opening a possibility in spintronics device based on BN nanoribbon.

  4. Self-forming TiBN Nanocomposite Multilayer Coating Prepared by Pulse Cathode Arc Method

    NASA Astrophysics Data System (ADS)

    Cao, Yongzhi; Hu, Zhenjiang; Yan, Leilei; Yu, Fuli; Tu, Wendi

    2016-07-01

    Novel multilayer structured TiBN coatings were deposited on Si (100) substrate using TiBN complex cathode plasma immersion ion implantation and deposition technique (PIIID). The coatings were characterized by X-ray diffraction (XRD), high-resolution transmission electron microcopy (HRTEM), energy-dispersive spectrometer (EDS) and ball-on-disk test. XRD results reveal that both samples of TiBN coatings have the main diffraction peak of TiN (200) and (220). Cross-section TEM images reveal that these coatings have the character of self-forming multilayer and consists of face-centered cubic TiN and hexagonal BN nanocrystalline embedded in amorphous matrix. Because of the existence of hexagonal BN, the friction coefficient of the new TiBN coating in room temperature is obviously lower than that of the monolithic TiN nanocrystalline coating.

  5. WFR-2D: an analytical model for PWAS-generated 2D ultrasonic guided wave propagation

    NASA Astrophysics Data System (ADS)

    Shen, Yanfeng; Giurgiutiu, Victor

    2014-03-01

    This paper presents WaveFormRevealer 2-D (WFR-2D), an analytical predictive tool for the simulation of 2-D ultrasonic guided wave propagation and interaction with damage. The design of structural health monitoring (SHM) systems and self-aware smart structures requires the exploration of a wide range of parameters to achieve best detection and quantification of certain types of damage. Such need for parameter exploration on sensor dimension, location, guided wave characteristics (mode type, frequency, wavelength, etc.) can be best satisfied with analytical models which are fast and efficient. The analytical model was constructed based on the exact 2-D Lamb wave solution using Bessel and Hankel functions. Damage effects were inserted in the model by considering the damage as a secondary wave source with complex-valued directivity scattering coefficients containing both amplitude and phase information from wave-damage interaction. The analytical procedure was coded with MATLAB, and a predictive simulation tool called WaveFormRevealer 2-D was developed. The wave-damage interaction coefficients (WDICs) were extracted from harmonic analysis of local finite element model (FEM) with artificial non-reflective boundaries (NRB). The WFR-2D analytical simulation results were compared and verified with full scale multiphysics finite element models and experiments with scanning laser vibrometer. First, Lamb wave propagation in a pristine aluminum plate was simulated with WFR-2D, compared with finite element results, and verified by experiments. Then, an inhomogeneity was machined into the plate to represent damage. Analytical modeling was carried out, and verified by finite element simulation and experiments. This paper finishes with conclusions and suggestions for future work.

  6. Multienzyme Inkjet Printed 2D Arrays.

    PubMed

    Gdor, Efrat; Shemesh, Shay; Magdassi, Shlomo; Mandler, Daniel

    2015-08-19

    The use of printing to produce 2D arrays is well established, and should be relatively facile to adapt for the purpose of printing biomaterials; however, very few studies have been published using enzyme solutions as inks. Among the printing technologies, inkjet printing is highly suitable for printing biomaterials and specifically enzymes, as it offers many advantages. Formulation of the inkjet inks is relatively simple and can be adjusted to a variety of biomaterials, while providing nonharmful environment to the enzymes. Here we demonstrate the applicability of inkjet printing for patterning multiple enzymes in a predefined array in a very straightforward, noncontact method. Specifically, various arrays of the enzymes glucose oxidase (GOx), invertase (INV) and horseradish peroxidase (HP) were printed on aminated glass surfaces, followed by immobilization using glutardialdehyde after printing. Scanning electrochemical microscopy (SECM) was used for imaging the printed patterns and to ascertain the enzyme activity. The successful formation of 2D arrays consisting of enzymes was explored as a means of developing the first surface confined enzyme based logic gates. Principally, XOR and AND gates, each consisting of two enzymes as the Boolean operators, were assembled, and their operation was studied by SECM. PMID:26214072

  7. Twisted Graphene Nanostructures

    NASA Astrophysics Data System (ADS)

    Gani, Satrio; Virgus, Yudistira; Rossi, Enrico

    2015-03-01

    Recent advances in fabrication techniques have made possible the realization of graphene nanostructures with atomic precision. Some of the nanostructures realized are completely novel. We study the electronic properties of such novel graphene nanostructures when deposited on two dimensional crystals. In particular we study the case when the two dimensional crystal is graphene, or bilayer graphene. We obtain results for the nanostructure electronic spectrum and find how the spectrum is affected by the coupling between the nanostructure and the two-dimensional substrate. In particular we study how the ``twist'' angle between the graphene nanostructure and the two-dimensional crystal affects the spectrum of the nanostructure. Work supported by ONR-N00014-13-1-0321 and ACS-PRF # 53581-DNI5.

  8. 2-D or not 2-D, that is the question: A Northern California test

    SciTech Connect

    Mayeda, K; Malagnini, L; Phillips, W S; Walter, W R; Dreger, D

    2005-06-06

    Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regions of approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. The complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Using the same station and event distribution, we compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7{le} f {le} 8.0-Hz), the 2-D approach resulted in inter-station scatter that was generally 10-30% smaller. For complex regions where data are plentiful, a 2-D approach can significantly improve upon the simple 1-D assumption. In regions where only 1-D coda correction is available it is still preferable over 2

  9. First-principles studies of boron nanostructures

    NASA Astrophysics Data System (ADS)

    Lau, Kah Chun

    Boron is an 'electron deficient' element which has a rather fascinating chemical versatility. In the solid state, the elemental boron has neither a pure covalent nor a pure metallic character. As a result, its vast structural dimensionality and peculiar bonding features hold a unique place among other elements in the periodic table. In order to understand and properly describe these unusual bonding features, a detailed and systematic theoretical study is needed. In this work, I will show that some of the qualitative features of boron nanostructures, including clusters, sheets and nanotubes can easily be extracted from the results of first principles calculations based on density functional theory. Specifically, the size-dependent evolution of topological structures and bonding characteristics of boron clusters, Bn will be discussed. Based on the scenario observed in the boron clusters, the unique properties of boron sheets and boron nanotubes will be described. Moreover, the ballistic electron transport in single-walled boron nanotube relative to that of single-walled carbon nanotubes will be considered. It is expected that the theoretical results obtained in the present thesis will initiate further studies on boron nanostructures, which will be helpful in understanding, designing and realizing boron-based nanoscale devices.

  10. Self-leveling 2D DPN probe arrays

    NASA Astrophysics Data System (ADS)

    Haaheim, Jason R.; Val, Vadim; Solheim, Ed; Bussan, John; Fragala, J.; Nelson, Mike

    2010-02-01

    Dip Pen Nanolithography® (DPN®) is a direct write scanning probe-based technique which operates under ambient conditions, making it suitable to deposit a wide range of biological and inorganic materials. Precision nanoscale deposition is a fundamental requirement to advance nanoscale technology in commercial applications, and tailoring chemical composition and surface structure on the sub-100 nm scale benefits researchers in areas ranging from cell adhesion to cell-signaling and biomimetic membranes. These capabilities naturally suggest a "Desktop Nanofab" concept - a turnkey system that allows a non-expert user to rapidly create high resolution, scalable nanostructures drawing upon well-characterized ink and substrate pairings. In turn, this system is fundamentally supported by a portfolio of MEMS devices tailored for microfluidic ink delivery, directed placement of nanoscale materials, and cm2 tip arrays for high-throughput nanofabrication. Massively parallel two-dimensional nanopatterning is now commercially available via NanoInk's 2D nano PrintArray™, making DPN a high-throughput (>3×107 μm2 per hour), flexible and versatile method for precision nanoscale pattern formation. However, cm2 arrays of nanoscopic tips introduce the nontrivial problem of getting them all evenly touching the surface to ensure homogeneous deposition; this requires extremely precise leveling of the array. Herein, we describe how we have made the process simple by way of a selfleveling gimbal attachment, coupled with semi-automated software leveling routines which bring the cm^2 chip to within 0.002 degrees of co-planarity. This excellent co-planarity yields highly homogeneous features across a square centimeter, with <6% feature size standard deviation. We have engineered the devices to be easy to use, wire-free, and fully integrated with both of our patterning tools: the DPN 5000, and the NLP 2000.

  11. nBn Infrared Detector Containing Graded Absorption Layer

    NASA Technical Reports Server (NTRS)

    Gunapala, Sarath D.; Ting, David Z.; Hill, Cory J.; Bandara, Sumith V.

    2009-01-01

    It has been proposed to modify the basic structure of an nBn infrared photodetector so that a plain electron-donor- type (n-type) semiconductor contact layer would be replaced by a graded n-type III V alloy semiconductor layer (i.e., ternary or quarternary) with appropriate doping gradient. The abbreviation nBn refers to one aspect of the unmodified basic device structure: There is an electron-barrier ("B" ) layer between two n-type ("n" ) layers, as shown in the upper part of the figure. One of the n-type layers is the aforementioned photon-absorption layer; the other n-type layer, denoted the contact layer, collects the photocurrent. The basic unmodified device structure utilizes minority-charge-carrier conduction, such that, for reasons too complex to explain within the space available for this article, the dark current at a given temperature can be orders of magnitude lower (and, consequently, signal-to-noise ratios can be greater) than in infrared detectors of other types. Thus, to obtain a given level of performance, less cooling (and, consequently, less cooling equipment and less cooling power) is needed. [In principle, one could obtain the same advantages by means of a structure that would be called pBp because it would include a barrier layer between two electron-acceptor- type (p-type) layers.] The proposed modifications could make it practical to utilize nBn photodetectors in conjunction with readily available, compact thermoelectric coolers in diverse infrared- imaging applications that could include planetary exploration, industrial quality control, monitoring pollution, firefighting, law enforcement, and medical diagnosis.

  12. FePt/BN granular films with texture

    NASA Astrophysics Data System (ADS)

    Daniil, M.; Farber, P.; Okumura, H.; Hadjipanayis, G. C.

    2001-03-01

    The driving force for higher magnetic recording density leads to future materials with very small sizes, below 10 nm. At these sizes thermal fluctuations lead to the superparamagnetic effect, resulting in unstable magnetization. This obstacle can be overcome by using materials with higher anisotropy, such as CoPt and FePt, which have magnetocrystalline anisotropy above 10^7 erg/cc. Another vital requirement for low noise recording media is the isolation of the grains, to reduce the intergrain interactions. This can be succeeded by growing the FePt/CoPt nanoparticles in a non magnetic matrix. In the present work we report on the effect of BN matrix in the structure, microstructure and magnetic properties of FePt nanoparticles. FePt particles with the highly anisotropic L10 structure were obtained by annealing the as-deposited multilayers at temperatures above 600^oC. Films with thicker bilayer thickness were found to have a strong [111] texture, which is less developed in thinner bilayer films. For special bilayer thickness (FePt(20 ÅBN(40 Åa special type of ordering is observed, in which the c-axis of all particles has an out of plane component, that makes these materials promising for both perpendicular and longitudinal recording. Magnetic measurements showed that a wide range of coercivities (2-18 kOe) can be obtained by varying the annealing temperature and time and the layer thickness. The coercivity increases with the annealing temperature and time, due to the increase of average grain size, which according to TEM studies it was ranged from 3 to 15 nm. The amount of BN was found to control the intergrain interactions, which for higher concentrations lead to decoupling of the FePt grains. This work has been supported by NSF-DMR 9972035.

  13. DFT study of geometries and stability of Bn clusters (n=2-8)

    NASA Astrophysics Data System (ADS)

    Li, Dong-Mei; Xiong, Zhi-Hua; Wan, Qi-Xin; Liu, Guo-Dong; Zhang, Wen-Rui; Ren, Zhong

    2008-12-01

    With density functional theory (DFT), the structures and stability of Bn clusters with n=2-8 have been studied. By using the all electron basis, all the geometries have been globally optimized without any symmetry constraint. It is found that all the small Bn (n=2-8) clusters prefer to form planar structures with sp2 bonds, which are in good agreement with others' related studies. Bn and Bn- are also compared. In contrast with the neutral Bn clusters, although B-B distances in Bn - have slight differences, but addition of one electron does not change their structures significantly. As for energies, all the anions are lying lower than their corresponding neutral clusters. In addition, calculations of energetic and electronic properties for all the neutral clusters have been presented. Both of these two properties show that in Bn (n=2-8), B3 and B5 are more stable than others. Vibrational spectra of Bn (n=3-8) clusters have also been discussed. In each spectrum, intensity peaks which are associated with the vibration of boron clusters related to B-B bond stretching can be observed and they are highest. However, among all the Bn clusters, such peaks of B3 and B5 show lower intensity than others. This results suggest that B3 and B5 are relatively more stable, which further demonstrates the conclusion above.

  14. Ultrahard stitching of nanotwinned diamond and cubic boron nitride in C2-BN composite.

    PubMed

    Liu, Xiaobing; Chen, Xin; Ma, Hong-An; Jia, Xiaopeng; Wu, Jinsong; Yu, Tony; Wang, Yanbin; Guo, Jiangang; Petitgirard, Sylvain; Bina, Craig R; Jacobsen, Steven D

    2016-01-01

    Materials combining the hardness and strength of diamond with the higher thermal stability of cubic boron nitride (cBN) have broad potential value in science and engineering. Reacting nanodiamond with cBN at moderate pressures and high temperatures provides a pathway to such materials. Here we report the fabrication of Cx-BN nanocomposites, measuring up to 10 mm in longest dimension, by reacting nanodiamond with pre-synthesized cBN in a large-volume press. The nanocomposites consist of randomly-oriented diamond and cBN domains stitched together by sp(3)-hybridized C-B and C-N bonds, leading to p-type semiconductivity. Dislocations near the sutures accommodate lattice mismatch between diamond and cBN. Nanotwinning within both diamond and cBN domains further contributes to a bulk hardness ~50% higher than sintered cBN. The nanocomposite of C2-BN exhibits p-type semiconductivity with low activation energy and high thermal stability, making it a functional, ultrahard substance. PMID:27461889

  15. Electrocatalytic activity of various types of h-BN for the oxygen reduction reaction.

    PubMed

    Elumalai, Ganesan; Noguchi, Hidenori; Uosaki, Kohei

    2014-07-21

    The electrocatalytic activities of various types of h-BN, i.e., spin coated BN nanotubes (BNNTs) and BN nanosheets (BNNSs) and sputter deposited BN, on Au electrodes as well as those of BNNS modified glassy carbon (GC) and Pt electrodes for the oxygen reduction reaction (ORR) were examined in O2 saturated 0.5 M H2SO4 solution based on the theoretical prediction that monolayered BN on a metal substrate may act as an electrocatalyst for ORR even though bulk BN is an insulator with a wide band gap. The overpotential for ORR at Au electrodes was reduced by ca. 100, ca. 270, and ca. 150 mV by spin coating of the dispersion of BNNT and liquid exfoliated BNNS, and sputter deposition of BN, respectively, proving the theoretical prediction. On the other hand, no change in the overpotential was observed at the glassy carbon electrode with BNNS modification and the overpotential even increased at the Pt electrode, suggesting that the interaction between BN and Au plays an important role in BN becoming ORR active.

  16. Ultrahard stitching of nanotwinned diamond and cubic boron nitride in C2-BN composite

    PubMed Central

    Liu, Xiaobing; Chen, Xin; Ma, Hong-An; Jia, Xiaopeng; Wu, Jinsong; Yu, Tony; Wang, Yanbin; Guo, Jiangang; Petitgirard, Sylvain; Bina, Craig R.; Jacobsen, Steven D.

    2016-01-01

    Materials combining the hardness and strength of diamond with the higher thermal stability of cubic boron nitride (cBN) have broad potential value in science and engineering. Reacting nanodiamond with cBN at moderate pressures and high temperatures provides a pathway to such materials. Here we report the fabrication of Cx-BN nanocomposites, measuring up to 10 mm in longest dimension, by reacting nanodiamond with pre-synthesized cBN in a large-volume press. The nanocomposites consist of randomly-oriented diamond and cBN domains stitched together by sp3-hybridized C-B and C-N bonds, leading to p-type semiconductivity. Dislocations near the sutures accommodate lattice mismatch between diamond and cBN. Nanotwinning within both diamond and cBN domains further contributes to a bulk hardness ~50% higher than sintered cBN. The nanocomposite of C2-BN exhibits p-type semiconductivity with low activation energy and high thermal stability, making it a functional, ultrahard substance. PMID:27461889

  17. Ultrahard stitching of nanotwinned diamond and cubic boron nitride in C2-BN composite

    NASA Astrophysics Data System (ADS)

    Liu, Xiaobing; Chen, Xin; Ma, Hong-An; Jia, Xiaopeng; Wu, Jinsong; Yu, Tony; Wang, Yanbin; Guo, Jiangang; Petitgirard, Sylvain; Bina, Craig R.; Jacobsen, Steven D.

    2016-07-01

    Materials combining the hardness and strength of diamond with the higher thermal stability of cubic boron nitride (cBN) have broad potential value in science and engineering. Reacting nanodiamond with cBN at moderate pressures and high temperatures provides a pathway to such materials. Here we report the fabrication of Cx-BN nanocomposites, measuring up to 10 mm in longest dimension, by reacting nanodiamond with pre-synthesized cBN in a large-volume press. The nanocomposites consist of randomly-oriented diamond and cBN domains stitched together by sp3-hybridized C-B and C-N bonds, leading to p-type semiconductivity. Dislocations near the sutures accommodate lattice mismatch between diamond and cBN. Nanotwinning within both diamond and cBN domains further contributes to a bulk hardness ~50% higher than sintered cBN. The nanocomposite of C2-BN exhibits p-type semiconductivity with low activation energy and high thermal stability, making it a functional, ultrahard substance.

  18. Ultrahard stitching of nanotwinned diamond and cubic boron nitride in C2-BN composite.

    PubMed

    Liu, Xiaobing; Chen, Xin; Ma, Hong-An; Jia, Xiaopeng; Wu, Jinsong; Yu, Tony; Wang, Yanbin; Guo, Jiangang; Petitgirard, Sylvain; Bina, Craig R; Jacobsen, Steven D

    2016-01-01

    Materials combining the hardness and strength of diamond with the higher thermal stability of cubic boron nitride (cBN) have broad potential value in science and engineering. Reacting nanodiamond with cBN at moderate pressures and high temperatures provides a pathway to such materials. Here we report the fabrication of Cx-BN nanocomposites, measuring up to 10 mm in longest dimension, by reacting nanodiamond with pre-synthesized cBN in a large-volume press. The nanocomposites consist of randomly-oriented diamond and cBN domains stitched together by sp(3)-hybridized C-B and C-N bonds, leading to p-type semiconductivity. Dislocations near the sutures accommodate lattice mismatch between diamond and cBN. Nanotwinning within both diamond and cBN domains further contributes to a bulk hardness ~50% higher than sintered cBN. The nanocomposite of C2-BN exhibits p-type semiconductivity with low activation energy and high thermal stability, making it a functional, ultrahard substance.

  19. Ultrahard stitching of nanotwinned diamond and cubic boron nitride in C2-BN composite

    DOE PAGES

    Liu, Xiaobing; Chen, Xin; Ma, Hong-An; Jia, Xiaopeng; Wu, Jinsong; Yu, Tony; Wang, Yanbin; Guo, Jiangang; Petitgirard, Sylvain; Bina, Craig R.; et al

    2016-07-27

    Materials combining the hardness and strength of diamond with the higher thermal stability of cubic boron nitride (cBN) have broad potential value in science and engineering. Reacting nanodiamond with cBN at moderate pressures and high temperatures provides a pathway to such materials. Here we report the fabrication of Cx-BN nanocomposites, measuring up to 10 mm in longest dimension, by reacting nanodiamond with pre-synthesized cBN in a large-volume press. The nanocomposites consist of randomly-oriented diamond and cBN domains stitched together by sp3-hybridized C-B and C-N bonds, leading to p-type semiconductivity. Dislocations near the sutures accommodate lattice mismatch between diamond and cBN.more » Nanotwinning within both diamond and cBN domains further contributes to a bulk hardness ~50% higher than sintered cBN. We find the nanocomposite of C2-BN exhibits p-type semiconductivity with low activation energy and high thermal stability, making it a functional,ultrahard substance.« less

  20. Electronic properties of complex nanostructures

    NASA Astrophysics Data System (ADS)

    Zhu, Zhen

    Nanostructured materials have brought an unprecedented opportunity for advancement in many fields of human endeavor and in applications. Nanostructures are a new research field which may revolutionize people's everyday life. In the Thesis, I have used theoretical methods including density functional theory (DFT), molecular dynamic simulations (MD) and tight-binding methods to explore the structural, mechanical and electronic properties of various nanomaterials. In all this, I also paid attention to potential applications of these findings. First, I will briefly introduce the scientific background of this Thesis, including the motivation for the study of a boron enriched aluminum surface, novel carbon foam structures and my research interest in 2D electronics. Then I will review the computational techniques I used in the study, mostly DFT methods. In Chapter 3, I introduce an effective way to enhance surface hardness of aluminum by boron nanoparticle implantation. Using boron dimers to represent the nanoparticles, the process of boron implantation is modeled in a molecular dynamics simulation of bombarding the aluminum surface by energetic B 2 molecules. Possible metastable structures of boron-coated aluminum surface are identified. Within these structures, I find that boron atoms prefer to stay in the subsurface region of aluminum. By modeling the Rockwell indentation process, boron enriched aluminum surface is found to be harder than the pristine aluminum surface by at least 15%. In Chapter 4, I discuss novel carbon structures, including 3D carbon foam and related 2D slab structures. Carbon foam contains both sp 2 and sp3 hybridized carbon atoms. It forms a 3D honeycomb lattice with a comparable stability to fullerenes, suggesting possible existence of such carbon foam structures. Although the bulk 3D foam structure is semiconducting, an sp2 terminated carbon surface could maintain a conducting channel even when passivated by hydrogen. To promote the experimental

  1. The transition metal surface passivated edges of hexagonal boron nitride (h-BN) and the mechanism of h-BN's chemical vapor deposition (CVD) growth.

    PubMed

    Zhao, Ruiqi; Li, Feifei; Liu, Zhirong; Liu, Zhongfan; Ding, Feng

    2015-11-21

    Edge structure and stability are crucial in determining both the morphology and the growth behaviours of hexagonal boron nitride (h-BN) domains in chemical vapour deposition (CVD) growth under near thermal equilibrium conditions. In this study, various edges of h-BN on three typical transition metal surfaces used for h-BN's CVD growth, Cu(111), Ni(111) and Rh(111), are explored with density functional theory calculations. Different from that in vacuum, our study shows that the formation of non-hexagonal rings, such as pentagon, heptagon or their pairs, is energetically not preferred and both zigzag (ZZ) edges are more stable than the armchair (AC) edge on all the explored catalyst surfaces under typical conditions of h-BN's CVD growth, which explains the broad experimental observation of triangular h-BN domains. More importantly, our results indicate that, instead of the pristine ZZ edge terminated with nitrogen atoms (ZZN), the triangular BN domains observed in experiments are likely to be enclosed with ZZ Klein edges having dangling atoms, ZZB + N or ZZN + B. By applying the theory of Wulff construction, we predicted that the equilibrium shape of a BN domain could be a hexagon enclosed with nitrogen-rich AC edges, triangles enclosed with two different types of ZZ Klein edges or a hexagon enclosed with boron-rich AC edges if the growth is in a N-rich, neutral or B-rich environment, respectively. This study presents how the edges and equilibrium shapes of h-BN domains can be controlled during the CVD synthesis and provides guidelines for further exploring the growth behaviours and improving the quality of CVD-prepared h-BN films. PMID:26469316

  2. Two-Dimensional Nanostructure- Reinforced Biodegradable Polymeric Nanocomposites for Bone Tissue Engineering

    PubMed Central

    Lalwani, Gaurav; Henslee, Allan M.; Farshid, Behzad; Lin, Liangjun; Kasper, F. Kurtis; Qin, Yi-Xian; Mikos, Antonios G.; Sitharaman, Balaji

    2013-01-01

    This study investigates the efficacy of two dimensional (2D) carbon and inorganic nanostructures as reinforcing agents of crosslinked composites of the biodegradable and biocompatible polymer polypropylene fumarate (PPF) as a function of nanostructure concentration. PPF composites were reinforced using various 2D nanostructures: single- and multi-walled graphene oxide nanoribbons (SWGONRs, MWGONRs), graphene oxide nanoplatelets (GONPs), and molybdenum di-sulfite nanoplatelets (MSNPs) at 0.01–0.2 weight% concentrations. Cross-linked PPF was used as the baseline control, and PPF composites reinforced with single- or multi-walled carbon nanotubes (SWCNT, MWCNT) were used as positive controls. Compression and flexural testing show a significant enhancement (i.e., compressive modulus = 35–108%, compressive yield strength = 26–93%, flexural modulus = 15–53%, and flexural yield strength = 101–262% greater than the baseline control) in the mechanical properties of the 2D-reinforced PPF nanocomposites. MSNPs nanocomposites consistently showed the highest values among the experimental or control groups in all the mechanical measurements. In general, the inorganic nanoparticle MSNPs showed a better or equivalent mechanical reinforcement compared to carbon nanomaterials, and 2-D nanostructures (GONP, MSNP) are better reinforcing agents compared to 1-D nanostructures (e.g. SWCNTs). The results also indicate that the extent of mechanical reinforcement is closely dependent on the nanostructure morphology and follows the trend nanoplatelets > nanoribbons > nanotubes. Transmission electron microscopy of the cross-linked nanocomposites indicates good dispersion of nanomaterials in the polymer matrix without the use of a surfactant. The sol-fraction analysis showed significant changes in the polymer cross-linking in the presence of MSNP (0.01–0.2 wt %) and higher loading concentrations of GONP and MWGONR (0.1–0.2 wt%). The analysis of surface area and aspect ratio of

  3. Latent heat induced rotation limited aggregation in 2D ice nanocrystals.

    PubMed

    Bampoulis, Pantelis; Siekman, Martin H; Kooij, E Stefan; Lohse, Detlef; Zandvliet, Harold J W; Poelsema, Bene

    2015-07-21

    The basic science responsible for the fascinating shapes of ice crystals and snowflakes is still not understood. Insufficient knowledge of the interaction potentials and the lack of relevant experimental access to the growth process are to blame for this failure. Here, we study the growth of fractal nanostructures in a two-dimensional (2D) system, intercalated between mica and graphene. Based on our scanning tunneling spectroscopy data, we provide compelling evidence that these fractals are 2D ice. They grow while they are in material contact with the atmosphere at 20 °C and without significant thermal contact to the ambient. The growth is studied in situ, in real time and space at the nanoscale. We find that the growing 2D ice nanocrystals assume a fractal shape, which is conventionally attributed to Diffusion Limited Aggregation (DLA). However, DLA requires a low mass density mother phase, in contrast to the actual currently present high mass density mother phase. Latent heat effects and consequent transport of heat and molecules are found to be key ingredients for understanding the evolution of the snow (ice) flakes. We conclude that not the local availability of water molecules (DLA), but rather them having the locally required orientation is the key factor for incorporation into the 2D ice nanocrystal. In combination with the transport of latent heat, we attribute the evolution of fractal 2D ice nanocrystals to local temperature dependent rotation limited aggregation. The ice growth occurs under extreme supersaturation, i.e., the conditions closely resemble the natural ones for the growth of complex 2D snow (ice) flakes and we consider our findings crucial for solving the "perennial" snow (ice) flake enigma. PMID:26203037

  4. Latent heat induced rotation limited aggregation in 2D ice nanocrystals

    NASA Astrophysics Data System (ADS)

    Bampoulis, Pantelis; Siekman, Martin H.; Kooij, E. Stefan; Lohse, Detlef; Zandvliet, Harold J. W.; Poelsema, Bene

    2015-07-01

    The basic science responsible for the fascinating shapes of ice crystals and snowflakes is still not understood. Insufficient knowledge of the interaction potentials and the lack of relevant experimental access to the growth process are to blame for this failure. Here, we study the growth of fractal nanostructures in a two-dimensional (2D) system, intercalated between mica and graphene. Based on our scanning tunneling spectroscopy data, we provide compelling evidence that these fractals are 2D ice. They grow while they are in material contact with the atmosphere at 20 °C and without significant thermal contact to the ambient. The growth is studied in situ, in real time and space at the nanoscale. We find that the growing 2D ice nanocrystals assume a fractal shape, which is conventionally attributed to Diffusion Limited Aggregation (DLA). However, DLA requires a low mass density mother phase, in contrast to the actual currently present high mass density mother phase. Latent heat effects and consequent transport of heat and molecules are found to be key ingredients for understanding the evolution of the snow (ice) flakes. We conclude that not the local availability of water molecules (DLA), but rather them having the locally required orientation is the key factor for incorporation into the 2D ice nanocrystal. In combination with the transport of latent heat, we attribute the evolution of fractal 2D ice nanocrystals to local temperature dependent rotation limited aggregation. The ice growth occurs under extreme supersaturation, i.e., the conditions closely resemble the natural ones for the growth of complex 2D snow (ice) flakes and we consider our findings crucial for solving the "perennial" snow (ice) flake enigma.

  5. Canard configured aircraft with 2-D nozzle

    NASA Technical Reports Server (NTRS)

    Child, R. D.; Henderson, W. P.

    1978-01-01

    A closely-coupled canard fighter with vectorable two-dimensional nozzle was designed for enhanced transonic maneuvering. The HiMAT maneuver goal of a sustained 8g turn at a free-stream Mach number of 0.9 and 30,000 feet was the primary design consideration. The aerodynamic design process was initiated with a linear theory optimization minimizing the zero percent suction drag including jet effects and refined with three-dimensional nonlinear potential flow techniques. Allowances were made for mutual interference and viscous effects. The design process to arrive at the resultant configuration is described, and the design of a powered 2-D nozzle model to be tested in the LRC 16-foot Propulsion Wind Tunnel is shown.

  6. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Kelly, Daniel P.; Kutyrev, Alexander S.; Moseley, Samuel H.

    2015-01-01

    Electrostatically actuated microshutter arrays consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutters demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.

  7. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Jones, Justin S.; Kelly, Daniel P.; Zheng, Yun; Kutyrev, Alexander S.; Moseley, Samuel H.

    2015-01-01

    An electrostatically actuated microshutter array consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutter arrays demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.

  8. 2D quantum gravity from quantum entanglement.

    PubMed

    Gliozzi, F

    2011-01-21

    In quantum systems with many degrees of freedom the replica method is a useful tool to study the entanglement of arbitrary spatial regions. We apply it in a way that allows them to backreact. As a consequence, they become dynamical subsystems whose position, form, and extension are determined by their interaction with the whole system. We analyze, in particular, quantum spin chains described at criticality by a conformal field theory. Its coupling to the Gibbs' ensemble of all possible subsystems is relevant and drives the system into a new fixed point which is argued to be that of the 2D quantum gravity coupled to this system. Numerical experiments on the critical Ising model show that the new critical exponents agree with those predicted by the formula of Knizhnik, Polyakov, and Zamolodchikov.

  9. Graphene suspensions for 2D printing

    NASA Astrophysics Data System (ADS)

    Soots, R. A.; Yakimchuk, E. A.; Nebogatikova, N. A.; Kotin, I. A.; Antonova, I. V.

    2016-04-01

    It is shown that, by processing a graphite suspension in ethanol or water by ultrasound and centrifuging, it is possible to obtain particles with thicknesses within 1-6 nm and, in the most interesting cases, 1-1.5 nm. Analogous treatment of a graphite suspension in organic solvent yields eventually thicker particles (up to 6-10 nm thick) even upon long-term treatment. Using the proposed ink based on graphene and aqueous ethanol with ethylcellulose and terpineol additives for 2D printing, thin (~5 nm thick) films with sheet resistance upon annealing ~30 MΩ/□ were obtained. With the ink based on aqueous graphene suspension, the sheet resistance was ~5-12 kΩ/□ for 6- to 15-nm-thick layers with a carrier mobility of ~30-50 cm2/(V s).

  10. CYP2D6*36 gene arrangements within the cyp2d6 locus: association of CYP2D6*36 with poor metabolizer status.

    PubMed

    Gaedigk, Andrea; Bradford, L Dianne; Alander, Sarah W; Leeder, J Steven

    2006-04-01

    Unexplained cases of CYP2D6 genotype/phenotype discordance continue to be discovered. In previous studies, several African Americans with a poor metabolizer phenotype carried the reduced function CYP2D6*10 allele in combination with a nonfunctional allele. We pursued the possibility that these alleles harbor either a known sequence variation (i.e., CYP2D6*36 carrying a gene conversion in exon 9 along the CYP2D6*10-defining 100C>T single-nucleotide polymorphism) or novel sequences variation(s). Discordant cases were evaluated by long-range polymerase chain reaction (PCR) to test for gene rearrangement events, and a 6.6-kilobase pair PCR product encompassing the CYP2D6 gene was cloned and entirely sequenced. Thereafter, allele frequencies were determined in different study populations comprising whites, African Americans, and Asians. Analyses covering the CYP2D7 to 2D6 gene region established that CYP2D6*36 did not only exist as a gene duplication (CYP2D6*36x2) or in tandem with *10 (CYP2D6*36+*10), as previously reported, but also by itself. This "single" CYP2D6*36 allele was found in nine African Americans and one Asian, but was absent in the whites tested. Ultimately, the presence of CYP2D6*36 resolved genotype/phenotype discordance in three cases. We also discovered an exon 9 conversion-positive CYP2D6*4 gene in a duplication arrangement (CYP2D6*4Nx2) and a CYP2D6*4 allele lacking 100C>T (CYP2D6*4M) in two white subjects. The discovery of an allele that carries only one CYP2D6*36 gene copy provides unequivocal evidence that both CYP2D6*36 and *36x2 are associated with a poor metabolizer phenotype. Given a combined frequency of between 0.5 and 3% in African Americans and Asians, genotyping for CYP2D6*36 should improve the accuracy of genotype-based phenotype prediction in these populations.

  11. Nanostructured Boron Nitride With High Water Dispersibility For Boron Neutron Capture Therapy

    PubMed Central

    Singh, Bikramjeet; Kaur, Gurpreet; Singh, Paviter; Singh, Kulwinder; Kumar, Baban; Vij, Ankush; Kumar, Manjeet; Bala, Rajni; Meena, Ramovatar; Singh, Ajay; Thakur, Anup; Kumar, Akshay

    2016-01-01

    Highly water dispersible boron based compounds are innovative and advanced materials which can be used in Boron Neutron Capture Therapy for cancer treatment (BNCT). Present study deals with the synthesis of highly water dispersible nanostructured Boron Nitride (BN). Unique and relatively low temperature synthesis route is the soul of present study. The morphological examinations (Scanning/transmission electron microscopy) of synthesized nanostructures showed that they are in transient phase from two dimensional hexagonal sheets to nanotubes. It is also supported by dual energy band gap of these materials calculated from UV- visible spectrum of the material. The theoretically calculated band gap also supports the same (calculated by virtual nano lab Software). X-ray diffraction (XRD) analysis shows that the synthesized material has deformed structure which is further supported by Raman spectroscopy. The structural aspect of high water disperse ability of BN is also studied. The ultra-high disperse ability which is a result of structural deformation make these nanostructures very useful in BNCT. Cytotoxicity studies on various cell lines (Hela(cervical cancer), human embryonic kidney (HEK-293) and human breast adenocarcinoma (MCF-7)) show that the synthesized nanostructures can be used for BNCT. PMID:27759052

  12. Modeling the Elastic Modulus of 2D Woven CVI SiC Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.

    2006-01-01

    The use of fiber, interphase, CVI SiC minicomposites as structural elements for 2D-woven SiC fiber reinforced chemically vapor infiltrated (CVI) SiC matrix composites is demonstrated to be a viable approach to model the elastic modulus of these composite systems when tensile loaded in an orthogonal direction. The 0deg (loading direction) and 90deg (perpendicular to loading direction) oriented minicomposites as well as the open porosity and excess SiC associated with CVI SiC composites were all modeled as parallel elements using simple Rule of Mixtures techniques. Excellent agreement for a variety of 2D woven Hi-Nicalon(TradeMark) fiber-reinforced and Sylramic-iBN reinforced CVI SiC matrix composites that differed in numbers of plies, constituent content, thickness, density, and number of woven tows in either direction (i.e, balanced weaves versus unbalanced weaves) was achieved. It was found that elastic modulus was not only dependent on constituent content, but also the degree to which 90deg minicomposites carried load. This depended on the degree of interaction between 90deg and 0deg minicomposites which was quantified to some extent by composite density. The relationships developed here for elastic modulus only necessitated the knowledge of the fractional contents of fiber, interphase and CVI SiC as well as the tow size and shape. It was concluded that such relationships are fairly robust for orthogonally loaded 2D woven CVI SiC composite system and can be implemented by ceramic matrix composite component modelers and designers for modeling the local stiffness in simple or complex parts fabricated with variable constituent contents.

  13. Mechanical property characterization of multidirectional Si{sub 3}N{sub 4}/BN fibrous monoliths.

    SciTech Connect

    Tlustochowicz, M.

    1999-06-29

    Fibrous monoliths (FMs) of Si{sub 3}N{sub 4}/BN ({approx}85 vol% Si{sub 3}N{sub 4}/15 vol% BN) with three different cell architectures (unidirectional, 0{degree}/90{degree}, and {+-}45{degree}) were tested in four-point-bend mode under ambient conditions. The FM constituents (hot-pressed monolithic Si{sub 3}N{sub 4} and BN) were also characterized. The unidirectional Si{sub 3}N{sub 4}/BN FM demonstrated the best properties, with ultimate strength of 476 {+-} 30 MPa and work-of-fracture of 12.6 {+-} 1.9 kJ/m{sup 2}, while Si{sub 3}N{sub 4}/BN FM with {+-}45{degree} cell architecture had the lowest strength (175 {+-} 13 MPa) and work-of-fracture (2.7 {+-} 1.7 kJ/m{sup 2}). The 0{degree}/90{degree} FM had intermediate values of 379 {+-} 86 MPa and 4.9 {+-} 2.2 kJ/m{sup 2}. High work-of-fracture for the unidirectional Si{sub 3}N{sub 4}/BN was correlated to toughening mechanisms such as extensive delamination and crack deflection. Predictions for the elastic moduli of the Si{sub 3}N{sub 4}/BN FMs based on laminate theory correlated well with the observed elastic moduli for the unidirectional and 0{degree}/90{degree} Si{sub 3}N{sub 4}/BN FMs. However, large discrepancies were observed between predictions and observed values for the {+-}45{degree} Si{sub 3}N{sub 4}/BN FMs, possibly due to the increasing role of the BN phase on mechanical properties in these FMs. Mechanical properties of monolithic Si{sub 3}N{sub 4} and BN compared well with literature values.

  14. Wear Characteristics of Vitrified cBN Grinding Wheels

    NASA Astrophysics Data System (ADS)

    Fujimoto, Masakazu; Ichida, Yoshio; Sato, Ryunosuke

    To clarify the wheel wear characteristics in grinding process using vitrified cBN wheels, we have investigated the change in wheel wear behavior when the load on the grain cutting edge is increased by increasing work speed. Wheel wear behavior in the grinding process may be classified into two main types, a) wheel wear process-type 1, that is consists of initial and steady-state wheel wear regions, and b) wheel wear process-type 2, that is consists of initial, steady-state and abnormal wheel wear regions. In the steady-state wear region of wheel wear process-type 1, lower wheel wear rate, lower stable grinding forces and good finished surface roughness are obtained, because self-sharpening due to micro fractures of the cutting edges takes place. In grinding with wheel wear process-type 2, it is very hard to obtain good finished surface and high grinding ratio, because of occurrences of fracture or releasing of cBN grains.

  15. A new inversion method for (T2, D) 2D NMR logging and fluid typing

    NASA Astrophysics Data System (ADS)

    Tan, Maojin; Zou, Youlong; Zhou, Cancan

    2013-02-01

    One-dimensional nuclear magnetic resonance (1D NMR) logging technology has some significant limitations in fluid typing. However, not only can two-dimensional nuclear magnetic resonance (2D NMR) provide some accurate porosity parameters, but it can also identify fluids more accurately than 1D NMR. In this paper, based on the relaxation mechanism of (T2, D) 2D NMR in a gradient magnetic field, a hybrid inversion method that combines least-squares-based QR decomposition (LSQR) and truncated singular value decomposition (TSVD) is examined in the 2D NMR inversion of various fluid models. The forward modeling and inversion tests are performed in detail with different acquisition parameters, such as magnetic field gradients (G) and echo spacing (TE) groups. The simulated results are discussed and described in detail, the influence of the above-mentioned observation parameters on the inversion accuracy is investigated and analyzed, and the observation parameters in multi-TE activation are optimized. Furthermore, the hybrid inversion can be applied to quantitatively determine the fluid saturation. To study the effects of noise level on the hybrid method and inversion results, the numerical simulation experiments are performed using different signal-to-noise-ratios (SNRs), and the effect of different SNRs on fluid typing using three fluid models are discussed and analyzed in detail.

  16. Nanostructured composite reinforced material

    DOEpatents

    Seals, Roland D.; Ripley, Edward B.; Ludtka, Gerard M.

    2012-07-31

    A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

  17. Modeling energy transport in nanostructures

    NASA Astrophysics Data System (ADS)

    Pattamatta, Arvind

    interaction between the energy carriers namely electrons/carriers with phonons which lead to a significant non-equilibrium at the semiconductor-metal contacts. This dissertation aims to focus on these three important topics. The first topic is addressed by modeling the thermal transport in 2-D and 3-D nanocomposites. The Boltzmann transport equation (BTE) for the phonon intensity is solved in conjunction with suitable boundary and interface treatment. Unlike in bulk composites, the results show a strong dependence of thermal conductivity, temperature, and heat flux on the wire size, wire atomic ratio, and interface specularity parameter. The second topic is addressed through a computational study for modeling the interfacial thermal resistance in carbon nanotube (CNT) contacts. A detailed parametric study is conducted by varying the dimensions of the CNT. The results of this study are compared with experimental data and the theory developed for nanoscale contacts. The third topic is addressed by modeling the non-equilibrium between energy carriers in metals and semiconductors. The Boltzmann transport model (BTM) has been introduced to study the electron-phonon non-equilibrium due to short pulsed laser interaction with thin gold and silicon films. A three stage Runge Kutta (RK) time stepping and a higher order Discontinuous Galerkin (DG) scheme using two Legendre basis functions are implemented for temporal and spatial discretization of the BTM. A parametric study is conducted by varying the laser parameters and studying their effect on electron/carrier and phonon thermal characteristics.

  18. Radiofrequency Spectroscopy and Thermodynamics of Fermi Gases in the 2D to Quasi-2D Dimensional Crossover

    NASA Astrophysics Data System (ADS)

    Cheng, Chingyun; Kangara, Jayampathi; Arakelyan, Ilya; Thomas, John

    2016-05-01

    We tune the dimensionality of a strongly interacting degenerate 6 Li Fermi gas from 2D to quasi-2D, by adjusting the radial confinement of pancake-shaped clouds to control the radial chemical potential. In the 2D regime with weak radial confinement, the measured pair binding energies are in agreement with 2D-BCS mean field theory, which predicts dimer pairing energies in the many-body regime. In the qausi-2D regime obtained with increased radial confinement, the measured pairing energy deviates significantly from 2D-BCS theory. In contrast to the pairing energy, the measured radii of the cloud profiles are not fit by 2D-BCS theory in either the 2D or quasi-2D regimes, but are fit in both regimes by a beyond mean field polaron-model of the free energy. Supported by DOE, ARO, NSF, and AFOSR.

  19. Competing coexisting phases in 2D water

    PubMed Central

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-01-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules. PMID:27185018

  20. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations. PMID:27099950

  1. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations.

  2. Competing coexisting phases in 2D water

    NASA Astrophysics Data System (ADS)

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-05-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules.

  3. The BnALMT1 and BnALMT2 genes from rape encode aluminum-activated malate transporters that enhance the aluminum resistance of plant cells.

    PubMed

    Ligaba, Ayalew; Katsuhara, Maki; Ryan, Peter R; Shibasaka, Mineo; Matsumoto, Hideaki

    2006-11-01

    The release of organic anions from roots can protect plants from aluminum (Al) toxicity and help them overcome phosphorus (P) deficiency. Our previous findings showed that Al treatment induced malate and citrate efflux from rape (Brassica napus) roots, and that P deficiency did not induce the efflux. Since this response is similar to the malate efflux from wheat (Triticum aestivum) that is controlled by the TaALMT1 gene, we investigated whether homologs of TaALMT1 are present in rape and whether they are involved in the release of organic anions. We isolated two TaALMT1 homologs from rape designated BnALMT1 and BnALMT2 (B. napus Al-activated malate transporter). The expression of these genes was induced in roots, but not shoots, by Al treatment but P deficiency had no effect. Several other cations (lanthanum, ytterbium, and erbium) also increased BnALMT1 and BnALMT2 expression in the roots. The function of the BnALMT1 and BnALMT2 proteins was investigated by heterologous expression in cultured tobacco (Nicotiana tabacum) cells and in Xenopus laevis oocytes. Both transfection systems showed an enhanced capacity for malate efflux but not citrate efflux, when exposed to Al. Smaller malate fluxes were also activated by ytterbium and erbium treatment. Transgenic tobacco cells grew significantly better than control cells following an 18 h treatment with Al, indicating that the expression of BnALMT1 and BnALMT2 increased the resistance of these plant cells to Al stress. This report demonstrates that homologs of the TaALMT1 gene from wheat perform similar functions in other species.

  4. Electronic and magnetic properties of a BN sheet decorated with hydrogen and fluorine

    NASA Astrophysics Data System (ADS)

    Zhou, Jian; Wang, Qian; Sun, Qiang; Jena, Puru

    2010-02-01

    First-principles calculations based on density-functional theory reveal some unusual properties of BN sheet functionalized with hydrogen and fluorine. These properties differ from those of similarly functionalized graphene even though both share the same honeycomb structure. (1) Unlike graphene which undergoes a metal to insulator transition when fully hydrogenated, the band gap of the BN sheet significantly narrows when fully saturated with hydrogen. Furthermore, the band gap of the BN sheet can be tuned from 4.7 to 0.6 eV and the system can be a direct or an indirect semiconductor or even a half-metal depending on surface coverage. (2) Unlike graphene, the hydrogenation of BN sheet is endothermic. (3) Unlike graphene, BN sheet has heteroatomic composition. When codecorated with H and F, it can lead to anisotropic structures with rich electronic and magnetic properties. (4) Unlike graphene, BN sheets can be made ferromagnetic, antiferromagnetic, or magnetically degenerate depending on how the surface is functionalized. (5) The stability of magnetic coupling of functionalized BN sheet can be further modulated by applying external strain. Our study highlights the potential of functionalized BN sheets for unusual applications.

  5. Seamless Rim-Functionalization of h-BN with Silica-Experiment and Theoretical Modeling.

    PubMed

    Furlotti, Michele; Caputo, Riccarda; Krumeich, Frank; Nesper, Reinhard

    2015-05-18

    Boron nitride contains six-ring layers, which are isostructural to graphene, and it exhibits similar extraordinary mechanical strength. Unlike graphene, hexagonal boron nitride (h-BN) is an insulator and has some polar features that make it a perfect material for those applications graphene is not suitable for, for example, purely ionic conductors, insulating membranes, transparent coatings, composite ceramics, high oxidation resistance materials. We report here a selective rim-functionalization of h-BN with SiO2 by using the Stöber process. A closed, protruding ring of SiO2 is formed covering all edges perpendicular to the [001] zones of the h-BN stacks and thus shield the most reactive centers of BN layers. SEM and HAADF-STEM images, X-ray spectroscopy, and atomic force microscopy confirm the rim-functionalization by SiO2 . XRD demonstrates the absence of any intercalation phenomenon of BN and reveals the glassy nature of the SiO2 rims. Selected variations of synthesis and theoretical modeling both confirm that rim activation by water prior to the Stöber condensation is crucial. First-principles calculations also confirm that dangling bonds of clean BN edges merge to give interlayer bonds that make further functionalization much more difficult. The reported reaction pathway should allow for other new functionalizations of pure BN and of the rimmed SiO2 /h-BN composites. PMID:25873400

  6. BnNHL18A shows a localization change by stress-inducing chemical treatments

    SciTech Connect

    Lee, Suk-Bae; Ham, Byung-Kook; Park, Jeong Mee; Kim, Young Jin; Paek, Kyung-Hee . E-mail: khpaek95@korea.ac.kr

    2006-01-06

    The two genes, named BnNHL18A and BnNHL18B, showing sequence homology with Arabidopsis NDR1/HIN1-like (NHL) genes, were isolated from cDNA library prepared with oilseed rape (Brassica napus) seedlings treated with NaCl. The transcript level of BnNHL18A was increased by sodium chloride, ethephon, hydrogen peroxide, methyl jasmonate, or salicylic acid treatment. The coding regions of BnNHL18A and BnNHL18B contain a sarcolipin (SLN)-like sequence. Analysis of the localization of smGFP fusion proteins showed that BnNHL18A is mainly localized to endoplasmic reticulum (ER). This result suggests that the SLN-like sequence plays a role in retaining proteins in ER membrane in plants. In response to NaCl, hydrogen peroxide, ethephon, and salicylic acid treatments, the protein localization of BnNHL18A was changed. Our findings suggest a common function of BnNHL18A in biotic and abiotic stresses, and demonstrate the presence of the shared mechanism of protein translocalization between the responses to plant pathogen and to osmotic stress.

  7. BnWRI1 coordinates fatty acid biosynthesis and photosynthesis pathways during oil accumulation in rapeseed.

    PubMed

    Wu, Xue-Long; Liu, Zhi-Hong; Hu, Zhang-Hua; Huang, Rui-Zhi

    2014-06-01

    Photosynthesis in "green" seeds, such as rapeseed, soybean, and Arabidopsis, plays a substantial role in the improved efficiency of oil accumulation. However, the molecular mechanism underpinning the coordinated expression of fatty acid (FA) biosynthesis- and photosynthesis-related genes in such developing seeds remains to be elucidated. Here, we found that seed-specific overexpression of BnWRI1, a WRI1 homolog from rapeseed (Brassica napus cv. ZGY2), results in enhanced chlorophyll content in developing seeds and increased oil content and seed mass in matured seeds. BnWRI1 was co-expressed with BnBCCP and BnCAB, two marker genes of FA biosynthesis and photosynthesis during seed development, respectively. Overexpression of BnWRI1 increased expression of both marker genes. Further, the nuclear-localized BnWRI1 protein was found to act as a transcription activator. It could bind to the GT1-element and/or GCC-box, which are widespread in the upstream regions of genes involved in FA biosynthesis and photosynthesis pathways. Accordingly, BnWRI1 could interact with promoters of BCCP2 and LHB1B2 in vivo. These results suggested that BnWRI1 may coordinate FA biosynthesis and photosynthesis pathways in developing seeds via directly stimulating expression of GT1-element and/or GCC-box containing genes.

  8. Engineering the plasmonic optical properties of cubic silver nanostructures based on Fano resonance

    NASA Astrophysics Data System (ADS)

    Yang, Zhi; Wang, Minqiang; Song, Xiaohui; Deng, Jianping; Yao, Xi

    2013-10-01

    The plasmonic optical properties of nanostructures including a dimer, a linear chain, a T-shaped nanostructure, and a 2D array consisting of Ag nanocubes have been investigated using the discrete dipole approximation method. The simulation results indicate that both the interparticle gap and polarization have an important impact on far-field and near-field characteristics. With decreasing interparticle distance for four nanostructures, the plasmon resonance peak is monotonically red-shifted and the electric intensity enhancement factor increases rapidly due to increased interparticle coupling interaction. Moreover, we also find that a T-shaped nanostructure has the largest electric intensity enhancement factor compared with other three nanostructures due to the coupling interaction at the intersection. This coupling is caused by the radiative interference between subradiant and superradiant resulting in Fano resonance. These results show how nanostructure arrangement design, gap adjustment, and polarization control can be used to achieve high field enhancements.

  9. 2-D Animation's Not Just for Mickey Mouse.

    ERIC Educational Resources Information Center

    Weinman, Lynda

    1995-01-01

    Discusses characteristics of two-dimensional (2-D) animation; highlights include character animation, painting issues, and motion graphics. Sidebars present Silicon Graphics animations tools and 2-D animation programs for the desktop computer. (DGM)

  10. Substrate-induced magnetism in BN layer: A first-principles study

    SciTech Connect

    Zhou, Yungang; Zu, Xiaotao T.; Gao, Fei

    2011-06-01

    We predict an accepted configuration of hexagonal boron nitride (BN) layer on Co(111) surface by first-principles calculations. The calculated adsorption energy of this configuration is around -0.51 eV with a corrugation close to 0.1 Å. Polarized spin states are induced in BN layer due to the hybridization of the BN layer with the substrate Co, which gives rise to a magnetic moment of 0.2 μB on each pair of BN. The finding of high spin polarization on the absorbed BN layer ensures a high degree of passage of the preferred spin and is important in the development of nanoscale devices for spintronics applications.

  11. Incorporation of small BN domains in graphene during CVD using methane, boric acid and nitrogen gas.

    PubMed

    Bepete, George; Voiry, Damien; Chhowalla, Manish; Chiguvare, Zivayi; Coville, Neil J

    2013-07-21

    Chemical doping of graphene with small boron nitride (BN) domains has been shown to be an effective way of permanently modulating the electronic properties in graphene. Herein we show a facile method of growing large area graphene doped with small BN domains on copper foils using a single step CVD route with methane, boric acid powder and nitrogen gas as the carbon, boron and nitrogen sources respectively. This facile and safe process avoids the use of boranes and ammonia. Optical microscopy confirmed that continuous films were grown and Raman spectroscopy confirmed changes in the electronic structure of the grown BN doped graphene. Using XPS studies we find that both B and N can be substituted into the graphene structure in the form of small BN domains to give a B-N-C system. A novel structure for the BN doped graphene is proposed. PMID:23759928

  12. Incorporation of small BN domains in graphene during CVD using methane, boric acid and nitrogen gas.

    PubMed

    Bepete, George; Voiry, Damien; Chhowalla, Manish; Chiguvare, Zivayi; Coville, Neil J

    2013-07-21

    Chemical doping of graphene with small boron nitride (BN) domains has been shown to be an effective way of permanently modulating the electronic properties in graphene. Herein we show a facile method of growing large area graphene doped with small BN domains on copper foils using a single step CVD route with methane, boric acid powder and nitrogen gas as the carbon, boron and nitrogen sources respectively. This facile and safe process avoids the use of boranes and ammonia. Optical microscopy confirmed that continuous films were grown and Raman spectroscopy confirmed changes in the electronic structure of the grown BN doped graphene. Using XPS studies we find that both B and N can be substituted into the graphene structure in the form of small BN domains to give a B-N-C system. A novel structure for the BN doped graphene is proposed.

  13. Incorporation of small BN domains in graphene during CVD using methane, boric acid and nitrogen gas

    NASA Astrophysics Data System (ADS)

    Bepete, George; Voiry, Damien; Chhowalla, Manish; Chiguvare, Zivayi; Coville, Neil J.

    2013-06-01

    Chemical doping of graphene with small boron nitride (BN) domains has been shown to be an effective way of permanently modulating the electronic properties in graphene. Herein we show a facile method of growing large area graphene doped with small BN domains on copper foils using a single step CVD route with methane, boric acid powder and nitrogen gas as the carbon, boron and nitrogen sources respectively. This facile and safe process avoids the use of boranes and ammonia. Optical microscopy confirmed that continuous films were grown and Raman spectroscopy confirmed changes in the electronic structure of the grown BN doped graphene. Using XPS studies we find that both B and N can be substituted into the graphene structure in the form of small BN domains to give a B-N-C system. A novel structure for the BN doped graphene is proposed.

  14. First principles study on B/N pairs co-doping zigzag single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yao, Xinhua; Li, Kejing; Ye, Jinqian; Shao, Qing Yi

    2016-06-01

    The B/N pairs co-doping (5, 0) single-walled carbon nanotubes (SWCNTs) have been investigated by using density functional theory. We gradually increase B/N doping concentration to simulate the growth of B/N pairs doping. We find that B/N pairs prefer to form a B/N hexagonal ring and then B/N rings successively grow around the axis until they are end to end. All B/N pairs doped tubes are turned to semiconducting and the five BN rings co-doped (5, 0) tube shows the occurrence of magnetism. Moreover, the increase of the doping concentration in a particular law may not change electrical properties obviously.

  15. Generates 2D Input for DYNA NIKE & TOPAZ

    SciTech Connect

    Hallquist, J. O.; Sanford, Larry

    1996-07-15

    MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  16. MAZE96. Generates 2D Input for DYNA NIKE & TOPAZ

    SciTech Connect

    Sanford, L.; Hallquist, J.O.

    1992-02-24

    MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  17. 2d PDE Linear Symmetric Matrix Solver

    1983-10-01

    ICCG2 (Incomplete Cholesky factorized Conjugate Gradient algorithm for 2d symmetric problems) was developed to solve a linear symmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as resistive MHD, spatial diffusive transport, and phase space transport (Fokker-Planck equation) problems. These problems share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized withmore » finite-difference or finite-element methods,the resulting matrix system is frequently of block-tridiagonal form. To use ICCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. The incomplete Cholesky conjugate gradient algorithm is used to solve the linear symmetric matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For matrices lacking symmetry, ILUCG2 should be used. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  18. 2d PDE Linear Asymmetric Matrix Solver

    1983-10-01

    ILUCG2 (Incomplete LU factorized Conjugate Gradient algorithm for 2d problems) was developed to solve a linear asymmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as plasma diffusion, equilibria, and phase space transport (Fokker-Planck equation) problems. These equations share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized with finite-difference or finite-elementmore » methods, the resulting matrix system is frequently of block-tridiagonal form. To use ILUCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. A generalization of the incomplete Cholesky conjugate gradient algorithm is used to solve the matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For problems having a symmetric matrix ICCG2 should be used since it runs up to four times faster and uses approximately 30% less storage. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source, containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  19. Position control using 2D-to-2D feature correspondences in vision guided cell micromanipulation.

    PubMed

    Zhang, Yanliang; Han, Mingli; Shee, Cheng Yap; Ang, Wei Tech

    2007-01-01

    Conventional camera calibration that utilizes the extrinsic and intrinsic parameters of the camera and the objects has certain limitations for micro-level cell operations due to the presence of hardware deviations and external disturbances during the experimental process, thereby invalidating the extrinsic parameters. This invalidation is often neglected in macro-world visual servoing and affects the visual image processing quality, causing deviation from the desired position in micro-level cell operations. To increase the success rate of vision guided biological micromanipulations, a novel algorithm monitoring the changing image pattern of the manipulators including the injection micropipette and cell holder is designed and implemented based on 2 dimensional (2D)-to 2D feature correspondences and can adjust the manipulator and perform position control simultaneously. When any deviation is found, the manipulator is retracted to the initial focusing plane before continuing the operation.

  20. High Temperature Si-doped BN Interphases for Woven SiC/SiC Composites

    NASA Technical Reports Server (NTRS)

    Morscher, Gregory N.; Hurwitz, Frances; Yun, Hee Mann; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    The hydrolytic stability of high-temperature deposited Si-doped BN has been shown in the past to be superior in comparison to "pure" BN processed at similar or even higher temperatures. This type of material would be very desirable as a SiC/SiC composite interphase that is formed by chemical infiltration into multi-ply woven preform. However, due to rapid deposition on the preform outer surface at the high processing temperature, this has proven very difficult. To overcome this issue, single plies of woven fabric were infiltrated with Si-doped BN. Three composite panels of different SiC fiber types were fabricated with Si-doped BN interphases including Sylramic, Hi-Nicalon Type S and Sylramic-iBN fiber-types. The latter fiber-type possesses a thin in-situ grown BN layer on the fiber surface. High Si contents (approx. 7 to 10 a/o) and low oxygen contents (less than 1 a/o) were achieved. All three composite systems demonstrated reasonable debonding and sliding properties. The coated Sylramic fabric and composites were weak due to fiber degradation apparently caused during interphase processing by the formation of TiN crystals on the fiber surface. The Hi-Nicalon Type S composites with Si-doped BN interphase were only slightly weaker than Hi-Nicalon Type S composites with conventional BN when the strength on the load-bearing fibers at failure was compared. On the other hand, the Sylramic-iBN fabric and composites with Si-doped BN showed excellent composite and intermediate temperature stress-rupture properties. Most impressive was the lack of any significant interphase oxidation on the fracture surface of stress-ruptured specimens tested well above matrix cracking at 815C.

  1. Process-Induced Carbon and Sub-Layer in SiC/BN/SiC Composites: Characterization and Consequences

    NASA Technical Reports Server (NTRS)

    Ogbuji, L. U. J. T; Wheeler, D. R.; McCue, T. R.

    2001-01-01

    Following our detection of films of elemental carbon in the Hi-Nicalon TM/BN/SiC composite and its deleterious effect on oxidative durability, we have examined other SiC/BN/SiC systems. The problem is pervasive, and significant residues of free carbon are confirmed in Sylramic /BN/SiC materials. Effective techniques for routine detection and characterization of adventitious carbon in SiC/BN/SiC composites are discussed.

  2. A Planar Quantum Transistor Based on 2D-2D Tunneling in Double Quantum Well Heterostructures

    SciTech Connect

    Baca, W.E.; Blount, M.A.; Hafich, M.J.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.

    1998-12-14

    We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional -- two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DELTT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D, the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets ({approximately} 21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 K. Finally, we briefly discuss the prospects for room temperature operation, increases in gain, and high-speed.

  3. 'Brukin2D': a 2D visualization and comparison tool for LC-MS data

    PubMed Central

    Tsagkrasoulis, Dimosthenis; Zerefos, Panagiotis; Loudos, George; Vlahou, Antonia; Baumann, Marc; Kossida, Sophia

    2009-01-01

    Background Liquid Chromatography-Mass Spectrometry (LC-MS) is a commonly used technique to resolve complex protein mixtures. Visualization of large data sets produced from LC-MS, namely the chromatogram and the mass spectra that correspond to its compounds is the focus of this work. Results The in-house developed 'Brukin2D' software, built in Matlab 7.4, which is presented here, uses the compound data that are exported from the Bruker 'DataAnalysis' program, and depicts the mean mass spectra of all the chromatogram compounds from one LC-MS run, in one 2D contour/density plot. Two contour plots from different chromatograph runs can then be viewed in the same window and automatically compared, in order to find their similarities and differences. The results of the comparison can be examined through detailed mass quantification tables, while chromatogram compound statistics are also calculated during the procedure. Conclusion 'Brukin2D' provides a user-friendly platform for quick, easy and integrated view of complex LC-MS data. The software is available at . PMID:19534737

  4. Inhibition of human cytochrome P450 2D6 (CYP2D6) by methadone.

    PubMed Central

    Wu, D; Otton, S V; Sproule, B A; Busto, U; Inaba, T; Kalow, W; Sellers, E M

    1993-01-01

    1. In microsomes prepared from three human livers, methadone competitively inhibited the O-demethylation of dextromethorphan, a marker substrate for CYP2D6. The apparent Ki value of methadone ranged from 2.5 to 5 microM. 2. Two hundred and fifty-two (252) white Caucasians, including 210 unrelated healthy volunteers and 42 opiate abusers undergoing treatment with methadone were phenotyped using dextromethorphan as the marker drug. Although the frequency of poor metabolizers was similar in both groups, the extensive metabolizers among the opiate abusers tended to have higher O-demethylation metabolic ratios and to excrete less of the dose as dextromethorphan metabolites than control extensive metabolizer subjects. These data suggest inhibition of CYP2D6 by methadone in vivo as well. 3. Because methadone is widely used in the treatment of opiate abuse, inhibition of CYP2D6 activity in these patients might contribute to exaggerated response or unexpected toxicity from drugs that are substrates of this enzyme. PMID:8448065

  5. Characterization of Wheel Surface Topography in cBN Grinding

    NASA Astrophysics Data System (ADS)

    Fujimoto, Masakazu; Ichida, Yoshio; Sato, Ryunosuke; Morimoto, Yoshitaka

    The wheel surface topography in the grinding process with vitrified cBN wheels has been investigated on the basis of 3-dimensional analysis using a multi-probe SEM, and the relationships between these results and the grinding characteristic parameters have been discussed. Moreover, the change of the wheel surface profile in the grinding process has been evaluated using fractal analysis. There are two regions: an initial wear region and a steady-state wear region, in the grinding process. In the initial wear region, a rapid decrease of grinding force and a rapid increase of wheel wear occur with increasing stock removal. In the steady-state wear region, the micro self-sharpening phenomenon owing to the micro fracture as well as the attritious wear of cutting edge occurs. The change in fractal dimension of the wheel surface is closely related to the change of grinding force dominated by the wear behavior of grain cutting edges.

  6. Prediction of a new graphenelike Si2BN solid

    NASA Astrophysics Data System (ADS)

    Andriotis, Antonis N.; Richter, Ernst; Menon, Madhu

    2016-02-01

    While the possibility to create a single-atom-thick two-dimensional layer from any material remains, only a few such structures have been obtained other than graphene and a monolayer of boron nitride. Here, based upon ab initio theoretical simulations, we propose a new stable graphenelike single-atomic-layer Si2BN structure that has all of its atoms with s p2 bonding with no out-of-plane buckling. The structure is found to be metallic with a finite density of states at the Fermi level. This structure can be rolled into nanotubes in a manner similar to graphene. Combining first- and second-row elements in the Periodic Table to form a one-atom-thick material that is also flat opens up the possibility for studying new physics beyond graphene. The presence of Si will make the surface more reactive and therefore a promising candidate for hydrogen storage.

  7. Correlated Electron Phenomena in 2D Materials

    NASA Astrophysics Data System (ADS)

    Lambert, Joseph G.

    In this thesis, I present experimental results on coherent electron phenomena in layered two-dimensional materials: single layer graphene and van der Waals coupled 2D TiSe2. Graphene is a two-dimensional single-atom thick sheet of carbon atoms first derived from bulk graphite by the mechanical exfoliation technique in 2004. Low-energy charge carriers in graphene behave like massless Dirac fermions, and their density can be easily tuned between electron-rich and hole-rich quasiparticles with electrostatic gating techniques. The sharp interfaces between regions of different carrier densities form barriers with selective transmission, making them behave as partially reflecting mirrors. When two of these interfaces are set at a separation distance within the phase coherence length of the carriers, they form an electronic version of a Fabry-Perot cavity. I present measurements and analysis of multiple Fabry-Perot modes in graphene with parallel electrodes spaced a few hundred nanometers apart. Transition metal dichalcogenide (TMD) TiSe2 is part of the family of materials that coined the term "materials beyond graphene". It contains van der Waals coupled trilayer stacks of Se-Ti-Se. Many TMD materials exhibit a host of interesting correlated electronic phases. In particular, TiSe2 exhibits chiral charge density waves (CDW) below TCDW ˜ 200 K. Upon doping with copper, the CDW state gets suppressed with Cu concentration, and CuxTiSe2 becomes superconducting with critical temperature of T c = 4.15 K. There is still much debate over the mechanisms governing the coexistence of the two correlated electronic phases---CDW and superconductivity. I will present some of the first conductance spectroscopy measurements of proximity coupled superconductor-CDW systems. Measurements reveal a proximity-induced critical current at the Nb-TiSe2 interfaces, suggesting pair correlations in the pure TiSe2. The results indicate that superconducting order is present concurrently with CDW in

  8. CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6*15 and *35 Genotyping

    PubMed Central

    Riffel, Amanda K.; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C.; Leeder, J. Steven; Rosenblatt, Kevin P.; Gaedigk, Andrea

    2016-01-01

    TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6*15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6*15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6*35) which is also located in exon 1. Although alternative CYP2D6*15 and *35 assays resolved the issue, we discovered a novel CYP2D6*15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6*15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6*43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer and/or probe regions can impact

  9. CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6 (*) 15 and (*) 35 Genotyping.

    PubMed

    Riffel, Amanda K; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C; Leeder, J Steven; Rosenblatt, Kevin P; Gaedigk, Andrea

    2015-01-01

    TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6 (*) 15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6 (*) 15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6 (*) 35) which is also located in exon 1. Although alternative CYP2D6 (*) 15 and (*) 35 assays resolved the issue, we discovered a novel CYP2D6 (*) 15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6 (*) 15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6 (*) 43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer

  10. First-Principles Simulations of Chemical Reactions in an HCl Molecule Embedded inside a C or BN Nanotube Induced by Ultrafast Laser Pulses

    NASA Astrophysics Data System (ADS)

    Miyamoto, Yoshiyuki; Zhang, Hong; Rubio, Angel

    2010-12-01

    We show by first-principles simulations that ultrafast laser pulses induce different chemical reactions in a molecule trapped inside a nanotube. A strong laser pulse polarized perpendicular to the tube axis induces a giant bond stretch of an encapsulated HCl molecule in semiconducting carbon nanotube or in a BN nanotube. Depending on the initial orientation of the HCl molecule, the subsequent laser-induced dynamics is different: either complete disintegration or rebonding of the HCl molecule. Radial motion of the nanotube is always observed and a vacancy appears on the tube wall when the HCl is perpendicular to the tube axis. Those results are important to analyze confined nanochemistry and to manipulate molecules and nanostructures encapsulated in organic and inorganic nanotubes.

  11. First-principles simulations of chemical reactions in an HCl molecule embedded inside a C or BN nanotube induced by ultrafast laser pulses.

    PubMed

    Miyamoto, Yoshiyuki; Zhang, Hong; Rubio, Angel

    2010-12-10

    We show by first-principles simulations that ultrafast laser pulses induce different chemical reactions in a molecule trapped inside a nanotube. A strong laser pulse polarized perpendicular to the tube axis induces a giant bond stretch of an encapsulated HCl molecule in semiconducting carbon nanotube or in a BN nanotube. Depending on the initial orientation of the HCl molecule, the subsequent laser-induced dynamics is different: either complete disintegration or rebonding of the HCl molecule. Radial motion of the nanotube is always observed and a vacancy appears on the tube wall when the HCl is perpendicular to the tube axis. Those results are important to analyze confined nanochemistry and to manipulate molecules and nanostructures encapsulated in organic and inorganic nanotubes.

  12. First-Principles Simulations of Chemical Reactions in an HCl Molecule Embedded inside a C or BN Nanotube Induced by Ultrafast Laser Pulses

    SciTech Connect

    Miyamoto, Yoshiyuki; Zhang Hong; Rubio, Angel

    2010-12-10

    We show by first-principles simulations that ultrafast laser pulses induce different chemical reactions in a molecule trapped inside a nanotube. A strong laser pulse polarized perpendicular to the tube axis induces a giant bond stretch of an encapsulated HCl molecule in semiconducting carbon nanotube or in a BN nanotube. Depending on the initial orientation of the HCl molecule, the subsequent laser-induced dynamics is different: either complete disintegration or rebonding of the HCl molecule. Radial motion of the nanotube is always observed and a vacancy appears on the tube wall when the HCl is perpendicular to the tube axis. Those results are important to analyze confined nanochemistry and to manipulate molecules and nanostructures encapsulated in organic and inorganic nanotubes.

  13. Efficient many-body calculations for two-dimensional materials using exact limits for the screened potential: Band gaps of MoS2, h -BN, and phosphorene

    NASA Astrophysics Data System (ADS)

    Rasmussen, Filip A.; Schmidt, Per S.; Winther, Kirsten T.; Thygesen, Kristian S.

    2016-10-01

    Calculating the quasiparticle (QP) band structure of two-dimensional (2D) materials within the GW self-energy approximation has proven to be a rather demanding computational task. The main reason is the strong q dependence of the 2D dielectric function around q =0 that calls for a much denser sampling of the Brillouin zone (BZ) than is necessary for similar three-dimensional solids. Here, we use an analytical expression for the small q limit of the 2D response function to perform the BZ integral over the critical region around q =0 . This drastically reduces the requirements on the q -point mesh and implies a significant computational speedup. For example, in the case of monolayer MoS2, convergence of the G0W0 band gap to within ˜0.1 eV is achieved with 12 ×12 q points rather than the 36 ×36 mesh required with discrete BZ sampling techniques. We perform a critical assessment of the band gap of the three prototypical 2D semiconductors, MoS2, h -BN, and phosphorene, including the effect of self-consistency at the GW0 level. The method is implemented in the open source code gpaw.

  14. Mapping of BnMs4 and BnRf to a common microsyntenic region of Arabidopsis thaliana chromosome 3 using intron polymorphism markers.

    PubMed

    Xia, Shengqian; Cheng, Ling; Zu, Feng; Dun, Xiaoling; Zhou, Zhengfu; Yi, Bin; Wen, Jing; Ma, Chaozhi; Shen, Jinxiong; Tu, Jinxing; Fu, Tingdong

    2012-05-01

    A recessive epistatic genic male sterile two-type line, 7365AB (Bnms3ms3ms4msRrfRf/BnMs3ms3ms4ms4RfRf), combined with the fertile interim-maintainer 7365C (Bnms3ms3ms4ms4rfrf) is an effective pollination control system in hybrid rapeseed production. We report an effective strategy used to fine map BnMs4 and BnRf. The two genes were both defined to a common microsyntenic region with Arabidopsis chromosome 3 using intron polymorphism (IP) markers developed according to Arabidopsis genome information and published genome organization of the A genome. The near-isogenic lines 7365AC (Bnms3ms3ms4ms4Rfrf/Bnms3ms3ms4ms4rfrf) of BnRf and 736512AB (Bnms3ms3Ms4ms4RfRf/Bnms3ms3ms4ms4RfRf) of BnMs4 were constructed to screen developed markers and create genetic linkage maps. Nine polymorphic IP markers (P1-P9) were identified. Of these, P2, P3, P4, and P6 were linked to both BnMs4 and BnRf with genetic distances <0.6 cM. Three simple sequence repeat markers, SR2, SR3, and SR5, were also identified by using public information. Subsequently, all markers linked to the two genes were used to compare the micro-collinearity of the regions flanking the two genes with Brassica rapa and Arabidopsis. The flanking regions showed rearrangements and inversion with fragments of different Arabidopsis chromosomes, but a high collinearity with B. rapa. This collinearity provided extremely valuable reference for map-based cloning in polyploid Brassica species. These IP markers could be exploited for comparative genomic studies within and between Brassica species, providing an economically feasible approach for molecular marker-assisted selection breeding, accelerating the process of gene cloning, and providing more direct evidence for the presence of multiple alleles between BnMs4 and BnRf.

  15. Mapping of BnMs4 and BnRf to a common microsyntenic region of Arabidopsis thaliana chromosome 3 using intron polymorphism markers.

    PubMed

    Xia, Shengqian; Cheng, Ling; Zu, Feng; Dun, Xiaoling; Zhou, Zhengfu; Yi, Bin; Wen, Jing; Ma, Chaozhi; Shen, Jinxiong; Tu, Jinxing; Fu, Tingdong

    2012-05-01

    A recessive epistatic genic male sterile two-type line, 7365AB (Bnms3ms3ms4msRrfRf/BnMs3ms3ms4ms4RfRf), combined with the fertile interim-maintainer 7365C (Bnms3ms3ms4ms4rfrf) is an effective pollination control system in hybrid rapeseed production. We report an effective strategy used to fine map BnMs4 and BnRf. The two genes were both defined to a common microsyntenic region with Arabidopsis chromosome 3 using intron polymorphism (IP) markers developed according to Arabidopsis genome information and published genome organization of the A genome. The near-isogenic lines 7365AC (Bnms3ms3ms4ms4Rfrf/Bnms3ms3ms4ms4rfrf) of BnRf and 736512AB (Bnms3ms3Ms4ms4RfRf/Bnms3ms3ms4ms4RfRf) of BnMs4 were constructed to screen developed markers and create genetic linkage maps. Nine polymorphic IP markers (P1-P9) were identified. Of these, P2, P3, P4, and P6 were linked to both BnMs4 and BnRf with genetic distances <0.6 cM. Three simple sequence repeat markers, SR2, SR3, and SR5, were also identified by using public information. Subsequently, all markers linked to the two genes were used to compare the micro-collinearity of the regions flanking the two genes with Brassica rapa and Arabidopsis. The flanking regions showed rearrangements and inversion with fragments of different Arabidopsis chromosomes, but a high collinearity with B. rapa. This collinearity provided extremely valuable reference for map-based cloning in polyploid Brassica species. These IP markers could be exploited for comparative genomic studies within and between Brassica species, providing an economically feasible approach for molecular marker-assisted selection breeding, accelerating the process of gene cloning, and providing more direct evidence for the presence of multiple alleles between BnMs4 and BnRf. PMID:22246313

  16. Wafer-scale controlled exfoliation of metal organic vapor phase epitaxy grown InGaN/GaN multi quantum well structures using low-tack two-dimensional layered h-BN

    NASA Astrophysics Data System (ADS)

    Ayari, Taha; Sundaram, Suresh; Li, Xin; El Gmili, Youssef; Voss, Paul L.; Salvestrini, Jean Paul; Ougazzaden, Abdallah

    2016-04-01

    Recent advances in epitaxial growth have led to the growth of III-nitride devices on 2D layered h-BN. This advance has the potential for wafer-scale transfer to arbitrary substrates, which could improve the thermal management and would allow III-N devices to be used more flexibly in a broader range of applications. We report wafer scale exfoliation of a metal organic vapor phase epitaxy grown InGaN/GaN Multi Quantum Well (MQW) structure from a 5 nm thick h-BN layer that was grown on a 2-inch sapphire substrate. The weak van der Waals bonds between h-BN atomic layers break easily, allowing the MQW structure to be mechanically lifted off from the sapphire substrate using a commercial adhesive tape. This results in the surface roughness of only 1.14 nm on the separated surface. Structural characterizations performed before and after the lift-off confirm the conservation of structural properties after lift-off. Cathodoluminescence at 454 nm was present before lift-off and 458 nm was present after. Electroluminescence near 450 nm from the lifted-off structure has also been observed. These results show that the high crystalline quality ultrathin h-BN serves as an effective sacrificial layer—it maintains performance, while also reducing the GaN buffer thickness and temperature ramps as compared to a conventional two-step growth method. These results support the use of h-BN as a low-tack sacrificial underlying layer for GaN-based device structures and demonstrate the feasibility of large area lift-off and transfer to any template, which is important for industrial scale production.

  17. Study of the second harmonic generation and optical rectification in a cBN crystal

    SciTech Connect

    Dou Qingping; Ma Haitao; Jia Gang; Chen Zhanguo; Cao Kun; Zhang Tiechen

    2007-02-28

    Cubic boron nitride (cBN) - a kind of an artificial (synthetic) crystal with the band gap of {approx}6.3 eV, which has the zinc blende structure and the 4-bar 3m symmetry, is studied. The optical rectification is obtained and the second harmonic generation (SHG) is observed in the cBN crystal for the first time by using a 1064-nm Q-switched Nd:YAG laser. The green light at 532 nm from the cBN sample can be seen with a naked eye. (nonlinear optical phenomena)

  18. Sensitivity of BN nano-cages to caffeine and nicotine molecules

    NASA Astrophysics Data System (ADS)

    Soltani, Alireza; Baei, Mohammad T.; Tazikeh Lemeski, E.; Shahini, Malihe

    2014-12-01

    Adsorption of caffeine and nicotine molecules over B12N12 and B16N16 nano-cages were investigated by using first-principles calculations to define whether BN nano-cages are applicable for filtering or sensing caffeine and nicotine molecules. The chemisorption energy of nicotine molecule on BN nano-cages is very stronger than caffeine molecule. Upon the adsorption of caffeine and nicotine molecules, the electronic properties of the BN nano-cages can be significantly changed, being too much sensitized on the caffeine and nicotine adsorptions.

  19. Synthesis, Characterization, Physical Properties, and OLED Application of Single BN-Fused Perylene Diimide.

    PubMed

    Li, Gang; Zhao, Yongbiao; Li, Junbo; Cao, Jun; Zhu, Jia; Sun, Xiao Wei; Zhang, Qichun

    2015-01-01

    It is very challenging to introduce azaborine into an electron-deficient arene system because of unfavorable intramolecular electrophilic borylation reaction. In this report, we adopted a straightforward methodology to construct a large BN-embedded π-system based on perylene diimide (PDI), which is the first BN-annulation example with highly electron-withdrawing polycyclic aromatic hydrocarbons. The physical properties of the as-prepared N,N-dicyclohexyl-1-aza-12-bora-benzoperylene diimide (PDI-1BN) have been fully studied, and its sensing behavior to fluoride ion as well as its OLED performance was also investigated.

  20. 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.

  1. Stoichiometric controlling of boroncarbonitride thin films with using BN-C dual-targets

    SciTech Connect

    Zhang, Song; Wu, Jun; Yang, Qiong; Tu, Rong; Wang, Chuanbin Shen, Qiang; Zhang, Lianmeng

    2015-04-15

    High carbon-rich boroncarbonitride thin films have been grown by pulsed laser deposition (PLD) technique with using BN-C dual-targets. Fourier-transform infrared (FTIR) spectroscopy results presented B-N, B-C and C-N bonds, indicating the as-deposited thin films were new ternary compounds. B-N, B-C and C-N bonding structures were also detected by X-ray photoelectron spectroscopy (XPS), and carbon content fell into a large range of 45.8 to 85.9%. The films exhibited good thermalstability in vacuum, whereas were oxidized at 600 {sup o}C in air.

  2. Mechanical characterization of 2D, 2D stitched, and 3D braided/RTM materials

    NASA Technical Reports Server (NTRS)

    Deaton, Jerry W.; Kullerd, Susan M.; Portanova, Marc A.

    1993-01-01

    Braided composite materials have potential for application in aircraft structures. Fuselage frames, floor beams, wing spars, and stiffeners are examples where braided composites could find application if cost effective processing and damage tolerance requirements are met. Another important consideration for braided composites relates to their mechanical properties and how they compare to the properties of composites produced by other textile composite processes being proposed for these applications. Unfortunately, mechanical property data for braided composites do not appear extensively in the literature. Data are presented in this paper on the mechanical characterization of 2D triaxial braid, 2D triaxial braid plus stitching, and 3D (through-the-thickness) braid composite materials. The braided preforms all had the same graphite tow size and the same nominal braid architectures, (+/- 30 deg/0 deg), and were resin transfer molded (RTM) using the same mold for each of two different resin systems. Static data are presented for notched and unnotched tension, notched and unnotched compression, and compression after impact strengths at room temperature. In addition, some static results, after environmental conditioning, are included. Baseline tension and compression fatigue results are also presented, but only for the 3D braided composite material with one of the resin systems.

  3. The near-Surface Region of Cubic Boron Nitride Single Crystal from the Li3N-hBN System

    NASA Astrophysics Data System (ADS)

    Guo, Xiao-Fei; Xu, Bin; Wen, Zhen-Xing; Fan, Xiao-Hong; Tian, Bin

    2014-04-01

    Cubic boron nitride single crystals are synthesized with lithium nitride as a catalyst under high pressure and high temperature. The main phases in the near-surface region, which around the single crystal are determined as a mixture of hexagonal boron nitride (hBN), cubic boron nitride (cBN) and lithium boron nitride (Li3BN2). High resolution transmission electron microscopy examinations show that there exist lots of nanometer-sized cubic boron nitride nuclei in this region. The interface phase structures of cubic boron nitride crystal and its near-surface region are investigated by means of transmission electron microscopy. The growth mechanism of cubic boron nitride crystal is analyzed briefly. It is supposed that Li3BN2 impels the direct conversion of hBN to cBN as a real catalyst, and cBN is homogeneously nucleated in the molten state under high pressure and high temperature.

  4. Synergistic Behavior of Tubes, Junctions, and Sheets Imparts Mechano-Mutable Functionality in 3D Porous Boron Nitride Nanostructures

    PubMed Central

    2015-01-01

    One-dimensional (1D) boron nitride nanotube (BNNT) and 2D hexagonal BN (h-BN) are attractive for demonstrating fundamental physics and promising applications in nano-/microscale devices. However, there is a high anisotropy associated with these BN allotropes as their excellent properties are either along the tube axis or in-plane directions, posing an obstacle in their widespread use in technological and industrial applications. Herein, we report a series of 3D BN prototypes, namely, pillared boron nitride (PBN), by fusing single-wall BNNT and monolayer h-BN aimed at filling this gap. We use density functional theory and molecular dynamics simulations to probe the diverse mechano-mutable properties of PBN prototypes. Our results demonstrate that the synergistic effect of the tubes, junctions, and sheets imparts cooperative deformation mechanisms, which overcome the intrinsic limitations of the PBN constituents and provide a number of superior characteristics including 3D balance of strength and toughness, emergence of negative Poisson’s ratio, and elimination of strain softening along the armchair orientation. These features, combined with the ultrahigh surface area and lightweight structure, render PBN as a 3D multifunctional template for applications in graphene-based nanoelectronics, optoelectronics, gas storage, and functional composites with fascinating in-plane and out-of-plane tailorable properties. PMID:25289114

  5. Methoxylation of Singly Bonded 1,4-1',4'-BnC60-C60Bn Dimer: Preferential Formation of 1,4-C60 Adduct with Sterically Less Demanding Addends and Stability Difference between 1,2- and 1,4-OMe(Bn)C60.

    PubMed

    He, Fa-Gui; Li, Zong-Jun; Gao, Xiang

    2016-08-01

    Methoxylation of the singly bonded 1,4-1',4'-BnC60-C60Bn dimer afforded 1,4-OMe(Bn)C60, a 1,4-C60 adduct with sterically less demanding addends, as the major adduct. The situation was different from that of direct functionalization of C60, where 1,2-OMe(Bn)C60 was obtained as the major product. The reaction was studied with in situ vis-NIR spectroscopy and computational calculations to obtain a better understanding of this unusual regioselectivity. The stability difference between 1,2- and 1,4-OMe(Bn)C60 was studied. PMID:27387300

  6. Computational Screening of 2D Materials for Photocatalysis.

    PubMed

    Singh, Arunima K; Mathew, Kiran; Zhuang, Houlong L; Hennig, Richard G

    2015-03-19

    Two-dimensional (2D) materials exhibit a range of extraordinary electronic, optical, and mechanical properties different from their bulk counterparts with potential applications for 2D materials emerging in energy storage and conversion technologies. In this Perspective, we summarize the recent developments in the field of solar water splitting using 2D materials and review a computational screening approach to rapidly and efficiently discover more 2D materials that possess properties suitable for solar water splitting. Computational tools based on density-functional theory can predict the intrinsic properties of potential photocatalyst such as their electronic properties, optical absorbance, and solubility in aqueous solutions. Computational tools enable the exploration of possible routes to enhance the photocatalytic activity of 2D materials by use of mechanical strain, bias potential, doping, and pH. We discuss future research directions and needed method developments for the computational design and optimization of 2D materials for photocatalysis.

  7. Design of Advanced Photocatalysis System by Adatom Decoration in 2D Nanosheets of Group-IV and III–V Binary Compounds

    PubMed Central

    Jin, Hao; Dai, Ying; Huang, Bai-Biao

    2016-01-01

    Searching for novel photocatalysts is one of the most important topic in photocatalytic fields. In the present work, we propose a feasible approach to improve the photocatalytic activities of 2D bilayers through surface decoration, i.e. hydrogenation, halogenation, and hydroxylation. Our investigations demonstrate that after surface modification, the optical adsorption expands into the visible region, while a built-in electric field is induced due to the interlayer coupling, which can promote the charge separation for photogenerated electron-hole pairs. Our results show that the indirect-direct band gap transition of SiC, SnC, BN and GaN can be realised through adatom decoration. Furthermore, the surface-modified 2D bilayers have suitable VBM and CBM alignments with the oxidation and reduction potentials for water splitting, suggesting powerful potentials in energy and environmental applications. PMID:26983908

  8. High-efficiency exfoliation of layered materials into 2D nanosheets in switchable CO2/Surfactant/H2O system

    NASA Astrophysics Data System (ADS)

    Wang, Nan; Xu, Qun; Xu, Shanshan; Qi, Yuhang; Chen, Meng; Li, Hongxiang; Han, Buxing

    2015-11-01

    Layered materials present attractive and important properties due to their two-dimensional (2D) structure, allowing potential applications including electronics, optoelectronics, and catalysis. However, fully exploiting the outstanding properties will require a method for their efficient exfoliation. Here we present that a series of layered materials can be successfully exfoliated into single- and few-layer nanosheets using the driving forces coming from the phase inversion, i.e., from micelles to reverse micelles in the emulsion microenvironment built by supercritical carbon dioxide (SC CO2). The effect of variable experimental parameters including CO2 pressure, ethanol/water ratio, and initial concentration of bulk materials on the exfoliation yield have been investigated. Moreover, we demonstrate that the exfoliated 2D nanosheets have their worthwhile applications, for example, graphene can be used to prepare conductive paper, MoS2 can be used as fluorescent label to perform cellular labelling, and BN can effectively reinforce polymers leading to the promising mechanical properties.

  9. Synthetic Covalent and Non-Covalent 2D Materials.

    PubMed

    Boott, Charlotte E; Nazemi, Ali; Manners, Ian

    2015-11-16

    The creation of synthetic 2D materials represents an attractive challenge that is ultimately driven by their prospective uses in, for example, electronics, biomedicine, catalysis, sensing, and as membranes for separation and filtration. This Review illustrates some recent advances in this diverse field with a focus on covalent and non-covalent 2D polymers and frameworks, and self-assembled 2D materials derived from nanoparticles, homopolymers, and block copolymers.

  10. BnSGS3 Has Differential Effects on the Accumulation of CMV, ORMV and TuMV in Oilseed Rape.

    PubMed

    Chen, Quan; Wang, Jie; Hou, Mingsheng; Liu, Shengyi; Huang, Junyan; Cai, Li

    2015-08-01

    Virus diseases greatly affect oilseed rape (Brassica napus) production. Investigating antiviral genes may lead to the development of disease-resistant varieties of oilseed rape. In this study, we examined the effects of the suppressor of gene silencing 3 in Brassica napus (BnSGS3, a putative antiviral gene) with different genus viruses by constructing BnSGS3-overexpressing (BnSGS3-Ov) and BnSGS3-silenced (BnSGS3-Si) oilseed rape (cv. Zhongshuang No. 6) plants. These three viruses are Oilseed rape mosaic virus (ORMV), Turnip mosaic virus (TuMV) and Cucumber mosaic virus (CMV). The native BnSGS3 expressed in all examined tissues with the highest expression in siliques. All three viruses induced BnSGS3 expression, but ORMV induced a dramatic increase in the BnSGS3-Ov plants, followed by TuMV and CMV. Upon inoculation with three different viruses, transcript abundance of BnSGS3 gene follows: BnSGS3-Ov > non-transgenic plants > BnSGS3-Si. The accumulation quantities of ORMV and TuMV exhibited a similar trend. However, CMV accumulation showed an opposite trend where virus accumulations were negatively correlated with BnSGS3 expression. The results suggest that BnSGS3 selectively inhibits CMV accumulation but promotes ORMV and TuMV accumulation. BnSGS3 should be used in different ways (up- and down-regulation) for breeding virus-resistant oilseed rape varieties. PMID:26225990

  11. Building gold nanonetworks from 2-D to quasi-3-D: thickness depended properties

    NASA Astrophysics Data System (ADS)

    Yu, Xiaojing; Wan, Xiaowen; Wang, Liqun; Yang, Zhimao; Ding, Bingjun; Yang, Shengchun

    2014-03-01

    In this work, an effective approach to control the thickness and porosity of porous gold nanonetworks (PGNs) was demonstrated. The 3-dimensional (3-D) PGNs were accomplished by repeated overlaying of two-dimensional (2-D) monolayer gold nanonetworks which assembled at the pentanol/water interface. The porosity of the PGNs can be improved by increasing the number of layers, which greatly enhances the intralayer and interlayer plasmon coupling and the mass diffusion of the analyte molecules, resulting in an improved sensitivity for SERS and glucose detection. In addition, the current approach also offered an effect method to produce 3-D porous nanostructures through the self-assembly of the isolated nanoparticles (NPs).

  12. A Geometric Boolean Library for 2D Objects

    2006-01-05

    The 2D Boolean Library is a collection of C++ classes -- which primarily represent 2D geometric data and relationships, and routines -- which contain algorithms for 2D geometric Boolean operations and utility functions. Classes are provided for 2D points, lines, arcs, edgeuses, loops, surfaces and mask sets. Routines are provided that incorporate the Boolean operations Union(OR), XOR, Intersection and Difference. Various analytical geometry routines and routines for importing and exporting the data in various filemore » formats, are also provided in the library.« less

  13. VizieR Online Data Catalog: The 2dF Galaxy Redshift Survey (2dFGRS) (2dFGRS Team, 1998-2003)

    NASA Astrophysics Data System (ADS)

    Colless, M.; Dalton, G.; Maddox, S.; Sutherland, W.; Norberg, P.; Cole, S.; Bland-Hawthorn, J.; Bridges, T.; Cannon, R.; Collins, C.; Couch, W.; Cross, N.; Deeley, K.; de Propris, R.; Driver, S. P.; Efstathiou, G.; Ellis, R. S.; Frenk, C. S.; Glazebrook, K.; Jackson, C.; Lahav, O.; Lewis, I.; Lumsden, S.; Madgwick, D.; Peacock, J. A.; Peterson, B. A.; Price, I.; Seaborne, M.; Taylor, K.

    2007-11-01

    The 2dF Galaxy Redshift Survey (2dFGRS) is a major spectroscopic survey taking full advantage of the unique capabilities of the 2dF facility built by the Anglo-Australian Observatory. The 2dFGRS is integrated with the 2dF QSO survey (2QZ, Cat. VII/241). The 2dFGRS obtained spectra for 245591 objects, mainly galaxies, brighter than a nominal extinction-corrected magnitude limit of bJ=19.45. Reliable (quality>=3) redshifts were obtained for 221414 galaxies. The galaxies cover an area of approximately 1500 square degrees selected from the extended APM Galaxy Survey in three regions: a North Galactic Pole (NGP) strip, a South Galactic Pole (SGP) strip, and random fields scattered around the SGP strip. Redshifts are measured from spectra covering 3600-8000 Angstroms at a two-pixel resolution of 9.0 Angstrom and a median S/N of 13 per pixel. All redshift identifications are visually checked and assigned a quality parameter Q in the range 1-5; Q>=3 redshifts are 98.4% reliable and have an rms uncertainty of 85 km/s. The overall redshift completeness for Q>=3 redshifts is 91.8% but this varies with magnitude from 99% for the brightest galaxies to 90% for objects at the survey limit. The 2dFGRS data base is available on the World Wide Web at http://www.mso.anu.edu.au/2dFGRS/. (6 data files).

  14. Measuring Strong Nanostructures

    ScienceCinema

    Andy Minor

    2016-07-12

    Andy Minor of Berkeley Lab's National Center for Electron Microscopy explains measuring stress and strain on nanostructures with the In Situ Microscope. More information: http://newscenter.lbl.gov/press-relea...

  15. Measuring Strong Nanostructures

    SciTech Connect

    Andy Minor

    2008-10-16

    Andy Minor of Berkeley Lab's National Center for Electron Microscopy explains measuring stress and strain on nanostructures with the In Situ Microscope. More information: http://newscenter.lbl.gov/press-relea...

  16. Bioinspired chemistry: Rewiring nanostructures

    NASA Astrophysics Data System (ADS)

    Ulijn, Rein V.; Caponi, Pier-Francesco

    2010-07-01

    The cell's dynamic skeleton, a tightly regulated network of protein fibres, continues to provide inspiration for the design of synthetic nanostructures. Genetic engineering has now been used to encode non-biological functionality within these structures.

  17. First-principles study of ferromagnetism in Pd-doped and Pd- Cu-codoped BN

    NASA Astrophysics Data System (ADS)

    Wang, Q.; Wang, S.; Dai, J. F.; Li, W. X.

    2016-07-01

    In this paper, we aimed at probing the ferromagnetism properties of Pd and Pd-Cu- codoped supercell BN based on the first-principles methods. The formation energy, lattice constants, energy band structures, spin density of state, energy difference between ferromagnetism (FM) and autiferromagnetism (AFM) orderings were calculated. Formation energy calculations showed that Pd atom tended to replace B atom in the supercell. Pd-doped BN exhibited a half-metallic ferromagnetic. And the ferromagnetism arised form the strong hybridization between the Pd4d and N2p state. Pd-Cu-codoped BN also displayed a half-metallic ferromagnetic. The incorporation of Pd and Pd-Cu induced some impurity energy differences between FM and AFM orderings. It also showed that FM state was the ground state, and room temperature ferromagnetism may be expected. These results pointed out the possibility of fabricating BN based on dilute magnetic semiconductors (DMS) by doping with Pd and Pd-Cu.

  18. Enhancing the mechanical properties of BN nanosheet-polymer composites by uniaxial drawing.

    PubMed

    Jan, Rahim; May, Peter; Bell, Alan P; Habib, Amir; Khan, Umar; Coleman, Jonathan N

    2014-05-01

    We have used liquid exfoliation of hexagonal Boron-Nitride (BN) to prepare composites of BN nanosheets of three different sizes in polyvinylchloride matrices. These composites show low levels of reinforcement, consistent with poor alignment of the nanosheets as-described by a modified version of Halpin-Tsai theory. However, drawing of the composites to 300% strain results in a considerable increase in mechanical properties with the maximum composite modulus and strength both ∼×3 higher than that of the pristine polymer. In addition, the rate of increase of modulus with BN volume fraction was up to 3-fold larger than for the unstrained composites. This is higher than can be explained by drawing-induced alignment using Halpin-Tsai theory. However, the data was consistent with a combination of alignment and strain-induced de-aggregation of BN multilayers.

  19. Turnable perfect absorption at infrared frequencies by a Graphene-hBN Hyper Crystal.

    PubMed

    Wu, Jipeng; Jiang, Leyong; Guo, Jun; Dai, Xiaoyu; Xiang, Yuanjiang; Wen, Shuangchun

    2016-07-25

    In this article, we have theoretically demonstrated that the perfect absorption at infrared frequencies can be achieved and controlled by using a graphene-hexagonal Boron Nitride (hBN) hyper crystal. hBN, the latest natural hyperbolic material, can be regarded as an excellent substrate to form a hyper crystal with graphene. Although the perfect absorption by a half-space of hBN crystal can be achieved due to its high optical anisotropy, but the perfect absorption can only appear at certain fixed wavenumber and incidence angle. By introducing a graphene-hBN hyper crystal, we can get perfect absorption at different wavenumbers and incidence angles by varying the Fermi energy level of graphene sheets via electrostatic biasing. We show that the perfect absorption can be realized at different Fermi energies for TM waves. PMID:27464161

  20. Highly sensitive hBN/graphene hot electron bolometers with a Johnson noise readout

    NASA Astrophysics Data System (ADS)

    Efetov, Dmitri; Gao, Yuanda; Walsh, Evan; Shiue, Ren-Jye; Grosso, Gabriele; Peng, Cheng; Hone, James; Fong, Kin Chun; Englund, Dirk

    Graphene has remarkable opto-electronic and thermo-electric properties that make it an exciting functional material for various photo-detection applications. In particular, owed to graphenes unique combination of an exceedingly low electronic heat capacity and a strongly suppressed electron-phonon thermal conductivity Gth, the electronic and phononic temperatures are highly decoupled allowing an operation principle as a hot electron bolometer (HEB). Here we demonstrate highly sensitive HEBs made of high quality hBN/graphene/hBN stacks and employ a direct electronic temperature read out scheme via Johnson noise thermometry (JNT). We perform combined pump-probe and JNT measurements to demonstrate strongly damped Ce and Gth in the ultra-low impurity σi = 109 cm-2 hBN/G/hBN stacks, which result in unprecedented photo-detection sensitivity and noise equivalent power for graphene HEBs.

  1. Klassifikation von Standardebenen in der 2D-Echokardiographie mittels 2D-3D-Bildregistrierung

    NASA Astrophysics Data System (ADS)

    Bergmeir, Christoph; Subramanian, Navneeth

    Zum Zweck der Entwicklung eines Systems, das einen unerfahrenen Anwender von Ultraschall (US) zur Aufnahme relevanter anatomischer Strukturen leitet, untersuchen wir die Machbarkeit von 2D-US zu 3D-CT Registrierung. Wir verwenden US-Aufnahmen von Standardebenen des Herzens, welche zu einem 3D-CT-Modell registriert werden. Unser Algorithmus unterzieht sowohl die US-Bilder als auch den CT-Datensatz Vorverarbeitungsschritten, welche die Daten durch Segmentierung auf wesentliche Informationen in Form von Labein für Muskel und Blut reduzieren. Anschließend werden diese Label zur Registrierung mittels der Match-Cardinality-Metrik genutzt. Durch mehrmaliges Registrieren mit verschiedenen Initialisierungen ermitteln wir die im US-Bild sichtbare Standardebene. Wir evaluierten die Methode auf sieben US-Bildern von Standardebenen. Fünf davon wurden korrekt zugeordnet.

  2. Epitaxial 2D SnSe2/ 2D WSe2 van der Waals Heterostructures.

    PubMed

    Aretouli, Kleopatra Emmanouil; Tsoutsou, Dimitra; Tsipas, Polychronis; Marquez-Velasco, Jose; Aminalragia Giamini, Sigiava; Kelaidis, Nicolaos; Psycharis, Vassilis; Dimoulas, Athanasios

    2016-09-01

    van der Waals heterostructures of 2D semiconductor materials can be used to realize a number of (opto)electronic devices including tunneling field effect devices (TFETs). It is shown in this work that high quality SnSe2/WSe2 vdW heterostructure can be grown by molecular beam epitaxy on AlN(0001)/Si(111) substrates using a Bi2Se3 buffer layer. A valence band offset of 0.8 eV matches the energy gap of SnSe2 in such a way that the VB edge of WSe2 and the CB edge of SnSe2 are lined up, making this materials combination suitable for (nearly) broken gap TFETs. PMID:27537619

  3. CVMAC 2D Program: A method of converting 3D to 2D

    SciTech Connect

    Lown, J.

    1990-06-20

    This paper presents the user with a method of converting a three- dimensional wire frame model into a technical illustration, detail, or assembly drawing. By using the 2D Program, entities can be mapped from three-dimensional model space into two-dimensional model space, as if they are being traced. Selected entities to be mapped can include circles, arcs, lines, and points. This program prompts the user to digitize the view to be mapped, specify the layers in which the new two-dimensional entities will reside, and select the entities, either by digitizing or windowing. The new two-dimensional entities are displayed in a small view which the program creates in the lower left corner of the drawing. 9 figs.

  4. Thermoelectric Transport Measurements of Graphene on hBN

    NASA Astrophysics Data System (ADS)

    Duan, Junxi; Wang, Xiaoming; Li, Guohong; Lai, Xinyuan; Zebarjadi, Mona; Andrei, Eva Y.

    The unique electronic transport properties of graphene, arising from massless charge carriers whose sign and density can be tuned by gating, have been studied extensively. Much less work was devoted to graphene's thermal properties. Unlike electrical transport which depends on total carrier density, the thermopower is determined by the net charge transferred and not by the carrier density. This leads to profound differences between the two phenomena. For example, when the Fermi level is close to the Dirac point (DP) where electron-hole (e-h) puddles are populated symmetrically, the electron and hole contributions to the thermopower cancel out. In contrast, their contributions to the electrical current add up. We studied the thermoelectric properties of high quality graphene supported on an hBN substrate, where the e-h puddle regime is significantly reduced compared to that on SiO2 substrates, which allows closer access to the DP. At room temperature we find that the maximum Seebeck coefficient close to the DP reaches up to twice the values on SiO2 substrates. Upon cooling down to 77K it decreases in a non-linear fashion with temperature. We will discuss possible origins of this behavior. Work Supported by DOE-FG02-99ER45742, NSF DMR 1207108 and FA9550-14-1-0316.

  5. Sepsis Patient Detection and Monitor Based on Auto-BN.

    PubMed

    Jiang, Yu; Sha, Lui; Rahmaniheris, Maryam; Wan, Binhua; Hosseini, Mohammad; Tan, Pengliu; Berlin, Richard B

    2016-04-01

    Sepsis is a life-threatening condition caused by an inappropriate immune response to infection, and is a leading cause of elderly death globally. Early recognition of patients and timely antibiotic therapy based on guidelines improve survival rate. Unfortunately, for those patients, it is often detected late because it is too expensive and impractical to perform frequent monitoring for all the elderly. In this paper, we present a risk driven sepsis screening and monitoring framework to shorten the time of onset detection without frequent monitoring of all the elderly. Within this framework, the sepsis ultimate risk of onset probability and mortality is calculated based on a novel temporal probabilistic model named Auto-BN, which consists of time dependent state, state dependent property, and state dependent inference structures. Then, different stages of a patient are encoded into different states, monitoring frequency is encoded into the state dependent property, and screening content is encoded into different state dependent inference structures. In this way, the screening and monitoring frequency and content can be automatically adjusted when encoding the sepsis ultimate risk into the guard of state transition. This allows for flexible manipulation of the tradeoff between screening accuracy and frequency. We evaluate its effectiveness through empirical study, and incorporate it into existing medical guidance system to improve medical healthcare.

  6. 2D Four-Channel Perfect Reconstruction Filter Bank Realized with the 2D Lattice Filter Structure

    NASA Astrophysics Data System (ADS)

    Sezen, S.; Ertüzün, A.

    2006-12-01

    A novel orthogonal 2D lattice structure is incorporated into the design of a nonseparable 2D four-channel perfect reconstruction filter bank. The proposed filter bank is obtained by using the polyphase decomposition technique which requires the design of an orthogonal 2D lattice filter. Due to constraint of perfect reconstruction, each stage of this lattice filter bank is simply parameterized by two coefficients. The perfect reconstruction property is satisfied regardless of the actual values of these parameters and of the number of the lattice stages. It is also shown that a separable 2D four-channel perfect reconstruction lattice filter bank can be constructed from the 1D lattice filter and that this is a special case of the proposed 2D lattice filter bank under certain conditions. The perfect reconstruction property of the proposed 2D lattice filter approach is verified by computer simulations.

  7. Single-molecule mechanochemical sensing using DNA origami nanostructures.

    PubMed

    Koirala, Deepak; Shrestha, Prakash; Emura, Tomoko; Hidaka, Kumi; Mandal, Shankar; Endo, Masayuki; Sugiyama, Hiroshi; Mao, Hanbin

    2014-07-28

    While single-molecule sensing offers the ultimate detection limit, its throughput is often restricted as sensing events are carried out one at a time in most cases. 2D and 3D DNA origami nanostructures are used as expanded single-molecule platforms in a new mechanochemical sensing strategy. As a proof of concept, six sensing probes are incorporated in a 7-tile DNA origami nanoassembly, wherein binding of a target molecule to any of these probes leads to mechanochemical rearrangement of the origami nanostructure, which is monitored in real time by optical tweezers. Using these platforms, 10 pM platelet-derived growth factor (PDGF) are detected within 10 minutes, while demonstrating multiplex sensing of the PDGF and a target DNA in the same solution. By tapping into the rapid development of versatile DNA origami nanostructures, this mechanochemical platform is anticipated to offer a long sought solution for single-molecule sensing with improved throughput.

  8. Microstructure and resistivity of machinable AIN/h-BN ceramic nanocomposites.

    PubMed

    Jin, Haiyun; Huang, Yinmao; Gao, Naikui; Peng, Zongren; Li, Shengtao; He, Bo

    2011-12-01

    The microstructure and resistivity of AIN/BN ceramic nano-composites and micro-composites were investigated. The results showed that because the nano-BN crystals were homogeneously dispersed around the AIN grains of the matrix, the conductive glass phase surround AIN grains were separated, and it was difficult to form the electric conductible consecutive passageway (than micro composites), the leakage conductance of nano-composites was far lower than micro-composites.

  9. BnNAC485 is involved in abiotic stress responses and flowering time in Brassica napus.

    PubMed

    Ying, Lu; Chen, Haiying; Cai, Weiming

    2014-06-01

    NAC domain proteins are plant-specific transcription factors that play important roles in plant growth and development. In this present study, we isolated BnNAC485 from Brassica napus L. (cv. HuYou15) and found that it showed high homology (84% at the amino acid level) with a NAC protein called AtRD26/ANAC072. BnNAC485 was specifically expressed in cotyledons and leaves of young seedlings, and expression was induced by abiotic stress and abscisic acid (ABA) treatment. The BnNAC485 protein localized to the nucleus. Over-expression of BnNAC485 enhanced tolerance to abiotic stress compared with wild-type plants in both B. napus and Arabidopsis thaliana. Furthermore, under exogenous ABA stress, BnNAC485 over-expression lines showed hypersensitivity to this treatment compared with wild-type B. napus and A. thaliana plants. Moreover, exogenous ABA treatment enhanced stomatal closing in B. napus plants over-expressing BnNAC485. Real-time RT-PCR assays showed that some abiotic- or ABA-responsive genes were up-regulated in A. thaliana plants over-expressing BnNAC485. Additionally, the transgenic lines flowered earlier than the wild-type B. napus and A. thaliana plants and the expression patterns of certain circadian clock genes were found to have changed. These results suggest that BnNAC485 acts in response to abiotic stress in plants via an ABA-mediated pathway and this gene can also alter plant flowering time.

  10. 1,2-Azaborine, the BN derivative of ortho-benzyne

    PubMed Central

    Edel, Klara; Brough, Sarah; Lamm, Ashley N.; Liu, Shih-Yuan

    2015-01-01

    The BN analogue of ortho-benzyne, 1,2-azaborine, is generated by flash vacuum pyroylsis, trapped under cryogenic conditions, and studied by direct spectroscopic techniques. The parent BN-aryne spontaneously binds N2 and CO2, demonstrating its highly reactive nature. The interaction with N2 is photochemically reversible. The CO2 adduct of 1,2-azaborine is a cyclic lactam that undergoes photocleavage thus resulting in overall CO2 splitting. PMID:26095444

  11. Substrate surface effect on the structure of cubic BN thin films from synchrotron-based X-ray diffraction and reflection

    NASA Astrophysics Data System (ADS)

    Zhang, X. M.; Wen, W.; Li, X. L.; He, Q.; Zhou, X. T.

    2013-02-01

    Cubic BN (cBN) thin films prepared by mass-selected ion beam deposition technique (MSIBD) on Si substrates with different surface roughness were studied by synchrotron-based grazing incidence X-ray diffraction (GI-XRD) and X-ray reflectivity (XRR) measurements. The BN films are mostly composed of two phases. One is cBN phase, the other is hexagonal BN (hBN) phase. The cubic phase content of the thin films is dependent on the roughness of their corresponding substrates. The smooth substrate surface is helpful for the nucleation of the cBN phase. cBN phase is mostly grown in the near surface region of the films and there is a hBN interlayer at the film-substrate interface. GIXRD and XRR are proved to be powerful tools for analyzing the structure of the cBN thin films.

  12. Functional characterization of CYP2D6 enhancer polymorphisms

    PubMed Central

    Wang, Danxin; Papp, Audrey C.; Sun, Xiaochun

    2015-01-01

    CYP2D6 metabolizes nearly 25% of clinically used drugs. Genetic polymorphisms cause large inter-individual variability in CYP2D6 enzyme activity and are currently used as biomarker to predict CYP2D6 metabolizer phenotype. Previously, we had identified a region 115 kb downstream of CYP2D6 as enhancer for CYP2D6, containing two completely linked single nucleotide polymorphisms (SNPs), rs133333 and rs5758550, associated with enhanced transcription. However, the enhancer effect on CYP2D6 expression, and the causative variant, remained to be ascertained. To characterize the CYP2D6 enhancer element, we applied chromatin conformation capture combined with the next-generation sequencing (4C assays) and chromatin immunoprecipitation with P300 antibody, in HepG2 and human primary culture hepatocytes. The results confirmed the role of the previously identified enhancer region in CYP2D6 expression, expanding the number of candidate variants to three highly linked SNPs (rs133333, rs5758550 and rs4822082). Among these, only rs5758550 demonstrated regulating enhancer activity in a reporter gene assay. Use of clustered regularly interspaced short palindromic repeats mediated genome editing in HepG2 cells targeting suspected enhancer regions decreased CYP2D6 mRNA expression by 70%, only upon deletion of the rs5758550 region. These results demonstrate robust effects of both the enhancer element and SNP rs5758550 on CYP2D6 expression, supporting consideration of rs5758550 for CYP2D6 genotyping panels to yield more accurate phenotype prediction. PMID:25381333

  13. Synthesis and Characterization of Large-Area Graphene Directly CVD-Grown on h-BN

    NASA Astrophysics Data System (ADS)

    Kim, Minwoo; Song, Young; Wang, Min; Jang, Seong-Kyu; Lee, Sungjoo; Jang, Won-Jun; Kahng, Se-Jong; Graphene synthesis Collaboration; Characterization Collaboration

    2013-03-01

    As an ideal substrate for graphene, hexagonal boron nitride (h-BN) has been utilized and studied extensively by transfer technique, which still has a high chance to have impurities at the graphene/h-BN interface. Here we report direct CVD growth of graphene on large area h-BN film. AFM and Raman spectroscopy measurements show that there is only one monolayer of graphene, and whose unperturbed electronic structures are also confirmed by electron transport measurements and scanning tunneling spectroscopy. High resolution TEM images for cross-section taken before and after transferring graphene/h-BN on to SiO2 indicate this CVD-grown hybrid structure is robust enough. Based on this new method, high quality and large area graphene on h-BN film with a clean interface can be synthesized for the application of electronic devices, and can fill the missing steps to grow fully CVD-grown super-structure of graphene and h-BN. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Grant Numbers: 2009-0083540, 2012R1A1A2020089 and 2012R1A1A1041416).

  14. Theoretical predictions for hexagonal BN based nanomaterials as electrocatalysts for the oxygen reduction reaction.

    PubMed

    Lyalin, Andrey; Nakayama, Akira; Uosaki, Kohei; Taketsugu, Tetsuya

    2013-02-28

    The catalytic activity for the oxygen reduction reaction (ORR) of both the pristine and defect-possessing hexagonal boron nitride (h-BN) monolayer and H-terminated nanoribbon have been studied theoretically using density functional theory. It is demonstrated that an inert h-BN monolayer can be functionalized and become catalytically active by nitrogen doping. It is shown that the energetics of adsorption of O(2), O, OH, OOH, and H(2)O on N atom impurities in the h-BN monolayer (N(B)@h-BN) is quite similar to that known for a Pt(111) surface. The specific mechanism of destructive and cooperative adsorption of ORR intermediates on the surface point defects is discussed. It is demonstrated that accounting for entropy and zero-point energy (ZPE) corrections results in destabilization of the ORR intermediates adsorbed on N(B)@h-BN, while solvent effects lead to their stabilization. Therefore, entropy, ZPE and solvent effects partly cancel each other and have to be taken into account simultaneously. Analysis of the free energy changes along the ORR pathway allows us to suggest that a N-doped h-BN monolayer can demonstrate catalytic properties for the ORR under the condition that electron transport to the catalytically active center is provided. PMID:23338859

  15. Vibration responses of h-BN sheet to charge doping and external strain

    SciTech Connect

    Yang, Wei; Yang, Yu; Zheng, Fawei; Zhang, Ping

    2013-12-07

    Based on density functional theory and density functional perturbation theory calculations, we systematically investigate the vibration responses of h-BN sheet to charge doping and external strains. It is found that under hole doping, the phonon frequencies of the ZO and TO branches at different wave vector q shift linearly with different slopes. Under electron doping, although the phonon frequencies shift irregularly, the shifting values are different at different phonon wave vectors. Interestingly, we find that external strain can restrain the irregular vibration responses of h-BN sheet to electron doping. The critical factor is revealed to be the relative position of the nearly free electron and boron p{sub z} states of h-BN sheet. Under external strains, the vibration responses of h-BN sheet are also found to be highly dependent on the phonon branches. Different vibration modes at different q points are revealed to be responsible for the vibration responses of h-BN sheet to charge doping and external strain. Our results point out a new way to detect the doping or strain status of h-BN sheet by measuring the vibration frequencies at different wave vector.

  16. Modification of the electronic properties of hexagonal boron-nitride in BN/graphene vertical heterostructures

    DOE PAGES

    Pan, Minghu; Liang, Liangbo; Lin, Wenzhi; Kim, Soo Min; Li, Qing; Kong, Jing; Dresselhaus, Mildred S.; Meunier, Vincent

    2016-09-28

    Van der Waals (vdW) heterostructures consist of isolated atomic planar structures, assembled layer- by-layer into desired structures in a well-defined sequence. Graphene deposited on hexagonal boron nitride (h-BN) has been first considered as a testbed system for vdW heterostructures, and many others have been demonstrated both theoretically and experimentally, revealing many attractive properties and phenomena. However, much less emphasis has been placed on how graphene actively affects h-BN properties. Here, we perform local probe measurements on single-layer h-BN grown over graphene and highlight the manifestation of a proximity effect that significantly affects the electronic properties of h-BN due to itsmore » coupling with the underlying graphene. We find electronic states originating from the graphene layer and the Cu substrate to be injected into the wide electronic gap of the h-BN top layer. Such proximity effect is further confirmed in a study of the variation of h-BN in-gap states with interlayer couplings, elucidated using a combination of topographical/ spectroscopic measurements and first-principles density functional theory calculations. In conclusion, the findings of this work indicate the potential of mutually engineering electronic properties of the components of vdW heterostructures.« less

  17. Structural and electronic properties of epitaxial multilayer h-BN on Ni(111) for spintronics applications.

    PubMed

    Tonkikh, A A; Voloshina, E N; Werner, P; Blumtritt, H; Senkovskiy, B; Güntherodt, G; Parkin, S S P; Dedkov, Yu S

    2016-03-24

    Hexagonal boron nitride (h-BN) is a promising material for implementation in spintronics due to a large band gap, low spin-orbit coupling, and a small lattice mismatch to graphene and to close-packed surfaces of fcc-Ni(111) and hcp-Co(0001). Epitaxial deposition of h-BN on ferromagnetic metals is aimed at small interface scattering of charge and spin carriers. We report on the controlled growth of h-BN/Ni(111) by means of molecular beam epitaxy (MBE). Structural and electronic properties of this system are investigated using cross-section transmission electron microscopy (TEM) and electron spectroscopies which confirm good agreement with the properties of bulk h-BN. The latter are also corroborated by density functional theory (DFT) calculations, revealing that the first h-BN layer at the interface to Ni is metallic. Our investigations demonstrate that MBE is a promising, versatile alternative to both the exfoliation approach and chemical vapour deposition of h-BN.

  18. Catalytic synthesis of bamboo-like multiwall BN nanotubes via SHS-annealing process

    SciTech Connect

    Zhang, L.P.; Gu, Y.L.; Wang, J.L.; Zhao, G.W.; Qian, Q.L.; Li, J.; Pan, X.Y.; Zhang, Z.H.

    2011-03-15

    Bamboo-like multiwall boron nitride (BN) nanotubes were synthesized via annealing porous precursor prepared by self-propagation high temperature synthesis (SHS) method. The as-synthesized BN nanotubes were characterized by the field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), Raman and Fourier transform infrared (FTIR) spectroscopy. These nanotubes have uniform diameters of about 60 nm and an average length of about 10 {mu}m. Four growth models, including tip, base, based tip and base-tip growth models, are proposed based on the catalytic vapor-liquid-solid (VLS) growth mechanism for explaining the formation of the as-synthesized bamboo-like BN nanotubes. Chemical reactions and annealing mechanism are also discussed. -- Graphical Abstract: A novel and effective annealing porous precursor route to bulk synthesis of bamboo-like multiwall BN nanotubes. Four growth models of VLS growth mechanism for these nanotubes are proposed. Display Omitted Research highlights: {yields} Bulk bamboo-like BN nanotubes were synthesized by SHS-annealing method. {yields} Boron-containing, porous precursor played a crucial role in bulk synthesis process. {yields} Four possible growth models were proposed to explain the formation of the bamboo-like BN nanotubes.

  19. Structural and electronic properties of epitaxial multilayer h-BN on Ni(111) for spintronics applications

    PubMed Central

    Tonkikh, A. A.; Voloshina, E. N.; Werner, P.; Blumtritt, H.; Senkovskiy, B.; Güntherodt, G.; Parkin, S. S. P.; Dedkov, Yu. S.

    2016-01-01

    Hexagonal boron nitride (h-BN) is a promising material for implementation in spintronics due to a large band gap, low spin-orbit coupling, and a small lattice mismatch to graphene and to close-packed surfaces of fcc-Ni(111) and hcp-Co(0001). Epitaxial deposition of h-BN on ferromagnetic metals is aimed at small interface scattering of charge and spin carriers. We report on the controlled growth of h-BN/Ni(111) by means of molecular beam epitaxy (MBE). Structural and electronic properties of this system are investigated using cross-section transmission electron microscopy (TEM) and electron spectroscopies which confirm good agreement with the properties of bulk h-BN. The latter are also corroborated by density functional theory (DFT) calculations, revealing that the first h-BN layer at the interface to Ni is metallic. Our investigations demonstrate that MBE is a promising, versatile alternative to both the exfoliation approach and chemical vapour deposition of h-BN. PMID:27009238

  20. An Incompressible 2D Didactic Model with Singularity and Explicit Solutions of the 2D Boussinesq Equations

    NASA Astrophysics Data System (ADS)

    Chae, Dongho; Constantin, Peter; Wu, Jiahong

    2014-09-01

    We give an example of a well posed, finite energy, 2D incompressible active scalar equation with the same scaling as the surface quasi-geostrophic equation and prove that it can produce finite time singularities. In spite of its simplicity, this seems to be the first such example. Further, we construct explicit solutions of the 2D Boussinesq equations whose gradients grow exponentially in time for all time. In addition, we introduce a variant of the 2D Boussinesq equations which is perhaps a more faithful companion of the 3D axisymmetric Euler equations than the usual 2D Boussinesq equations.

  1. Adaptation algorithms for 2-D feedforward neural networks.

    PubMed

    Kaczorek, T

    1995-01-01

    The generalized weight adaptation algorithms presented by J.G. Kuschewski et al. (1993) and by S.H. Zak and H.J. Sira-Ramirez (1990) are extended for 2-D madaline and 2-D two-layer feedforward neural nets (FNNs).

  2. Integrating Mobile Multimedia into Textbooks: 2D Barcodes

    ERIC Educational Resources Information Center

    Uluyol, Celebi; Agca, R. Kagan

    2012-01-01

    The major goal of this study was to empirically compare text-plus-mobile phone learning using an integrated 2D barcode tag in a printed text with three other conditions described in multimedia learning theory. The method examined in the study involved modifications of the instructional material such that: a 2D barcode was used near the text, the…

  3. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density. PMID:27334788

  4. CYP2D6: novel genomic structures and alleles

    PubMed Central

    Kramer, Whitney E.; Walker, Denise L.; O’Kane, Dennis J.; Mrazek, David A.; Fisher, Pamela K.; Dukek, Brian A.; Bruflat, Jamie K.; Black, John L.

    2010-01-01

    Objective CYP2D6 is a polymorphic gene. It has been observed to be deleted, to be duplicated and to undergo recombination events involving the CYP2D7 pseudogene and surrounding sequences. The objective of this study was to discover the genomic structure of CYP2D6 recombinants that interfere with clinical genotyping platforms that are available today. Methods Clinical samples containing rare homozygous CYP2D6 alleles, ambiguous readouts, and those with duplication signals and two different alleles were analyzed by long-range PCR amplification of individual genes, PCR fragment analysis, allele-specific primer extension assay, and DNA sequencing to characterize alleles and genomic structure. Results Novel alleles, genomic structures, and the DNA sequence of these structures are described. Interestingly, in 49 of 50 DNA samples that had CYP2D6 gene duplications or multiplications where two alleles were detected, the chromosome containing the duplication or multiplication had identical tandem alleles. Conclusion Several new CYP2D6 alleles and genomic structures are described which will be useful for CYP2D6 genotyping. The findings suggest that the recombination events responsible for CYP2D6 duplications and multiplications are because of mechanisms other than interchromosomal crossover during meiosis. PMID:19741566

  5. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density.

  6. Initial stages of growth and the influence of temperature during chemical vapor deposition of sp{sup 2}-BN films

    SciTech Connect

    Chubarov, Mikhail; Pedersen, Henrik; Högberg, Hans; Henry, Anne; Czigány, Zsolt

    2015-11-15

    Knowledge of the structural evolution of thin films, starting by the initial stages of growth, is important to control the quality and properties of the film. The authors present a study on the initial stages of growth and the temperature influence on the structural evolution of sp{sup 2} hybridized boron nitride (BN) thin films during chemical vapor deposition (CVD) with triethyl boron and ammonia as precursors. Nucleation of hexagonal BN (h-BN) occurs at 1200 °C on α-Al{sub 2}O{sub 3} with an AlN buffer layer (AlN/α-Al{sub 2}O{sub 3}). At 1500 °C, h-BN grows with a layer-by-layer growth mode on AlN/α-Al{sub 2}O{sub 3} up to ∼4 nm after which the film structure changes to rhombohedral BN (r-BN). Then, r-BN growth proceeds with a mixed layer-by-layer and island growth mode. h-BN does not grow on 6H-SiC substrates; instead, r-BN nucleates and grows directly with a mixed layer-by-layer and island growth mode. These differences may be caused by differences in substrate surface temperature due to different thermal conductivities of the substrate materials. These results add to the understanding of the growth process of sp{sup 2}-BN employing CVD.

  7. 2D materials and van der Waals heterostructures.

    PubMed

    Novoselov, K S; Mishchenko, A; Carvalho, A; Castro Neto, A H

    2016-07-29

    The physics of two-dimensional (2D) materials and heterostructures based on such crystals has been developing extremely fast. With these new materials, truly 2D physics has begun to appear (for instance, the absence of long-range order, 2D excitons, commensurate-incommensurate transition, etc.). Novel heterostructure devices--such as tunneling transistors, resonant tunneling diodes, and light-emitting diodes--are also starting to emerge. Composed from individual 2D crystals, such devices use the properties of those materials to create functionalities that are not accessible in other heterostructures. Here we review the properties of novel 2D crystals and examine how their properties are used in new heterostructure devices.

  8. Low-cost chemiresistive sensor for volatile amines based on a 2D network of a zinc(II) Schiff-base complex

    NASA Astrophysics Data System (ADS)

    Mirabella, S.; Oliveri, I. P.; Ruffino, F.; Maccarrone, G.; Di Bella, S.

    2016-10-01

    A marked chemiresistive behavior is revealed in a nanostructured material obtained by spin-coating a solution of a bis(salycilaldiminato)Zn(II) Schiff-base (ZnSB) complex. The resulting submicron 2D network exhibits reversible changes in absorbance and resistance under the cycles of absorption and desorption of a volatile amine. These results are explained in terms of a Lewis donor-acceptor interaction between the ZnSB (acceptor) and the chemisorbed amine (donor). The 2D network of ZnSB was employed as a sensing element to fabricate a low-cost device for the volatile amines detection, showing promising results for food spoilage detection.

  9. Estrogen-Induced Cholestasis Leads to Repressed CYP2D6 Expression in CYP2D6-Humanized Mice

    PubMed Central

    Pan, Xian

    2015-01-01

    Cholestasis activates bile acid receptor farnesoid X receptor (FXR) and subsequently enhances hepatic expression of small heterodimer partner (SHP). We previously demonstrated that SHP represses the transactivation of cytochrome P450 2D6 (CYP2D6) promoter by hepatocyte nuclear factor (HNF) 4α. In this study, we investigated the effects of estrogen-induced cholestasis on CYP2D6 expression. Estrogen-induced cholestasis occurs in subjects receiving estrogen for contraception or hormone replacement, or in susceptible women during pregnancy. In CYP2D6-humanized transgenic (Tg-CYP2D6) mice, cholestasis triggered by administration of 17α-ethinylestradiol (EE2) at a high dose led to 2- to 3-fold decreases in CYP2D6 expression. This was accompanied by increased hepatic SHP expression and subsequent decreases in the recruitment of HNF4α to CYP2D6 promoter. Interestingly, estrogen-induced cholestasis also led to increased recruitment of estrogen receptor (ER) α, but not that of FXR, to Shp promoter, suggesting a predominant role of ERα in transcriptional regulation of SHP in estrogen-induced cholestasis. EE2 at a low dose (that does not cause cholestasis) also increased SHP (by ∼50%) and decreased CYP2D6 expression (by 1.5-fold) in Tg-CYP2D6 mice, the magnitude of differences being much smaller than that shown in EE2-induced cholestasis. Taken together, our data indicate that EE2-induced cholestasis increases SHP and represses CYP2D6 expression in Tg-CYP2D6 mice in part through ERα transactivation of Shp promoter. PMID:25943116

  10. Nanostructuring Mixed-Dimensional Perovskites: A Route Toward Tunable, Efficient Photovoltaics.

    PubMed

    Koh, Teck Ming; Shanmugam, Vignesh; Schlipf, Johannes; Oesinghaus, Lukas; Müller-Buschbaum, Peter; Ramakrishnan, N; Swamy, Varghese; Mathews, Nripan; Boix, Pablo P; Mhaisalkar, Subodh G

    2016-05-01

    2D perovskites is one of the proposed strategies to enhance the moisture resistance, since the larger organic cations can act as a natural barrier. Nevertheless, 2D perovskites hinder the charge transport in certain directions, reducing the solar cell power conversion efficiency. A nanostructured mixed-dimensionality approach is presented to overcome the charge transport limitation, obtaining power conversion efficiencies over 9%. PMID:26990287

  11. Bonding-restricted structure search for novel 2D materials with dispersed C2 dimers.

    PubMed

    Zhang, Cunzhi; Zhang, Shunhong; Wang, Qian

    2016-01-01

    Currently, the available algorithms for unbiased structure searches are primarily atom-based, where atoms are manipulated as the elementary units, and energy is used as the target function without any restrictions on the bonding of atoms. In fact, in many cases such as nanostructure-assembled materials, the structural units are nanoclusters. We report a study of a bonding-restricted structure search method based on the particle swarm optimization (PSO) for finding the stable structures of two-dimensional (2D) materials containing dispersed C2 dimers rather than individual C atoms. The C2 dimer can be considered as a prototype of nanoclusters. Taking Si-C, B-C and Ti-C systems as test cases, our method combined with density functional theory and phonon calculations uncover new ground state geometrical structures for SiC2, Si2C2, BC2, B2C2, TiC2, and Ti2C2 sheets and their low-lying energy allotropes, as well as their electronic structures. Equally important, this method can be applied to other complex systems even containing f elements and other molecular dimers such as S2, N2, B2 and Si2, where the complex orbital orientations require extensive search for finding the optimal orientations to maximize the bonding with the dimers, predicting new 2D materials beyond MXenes (a family of transition metal carbides or nitrides) and dichalcogenide monolayers. PMID:27403589

  12. Bonding-restricted structure search for novel 2D materials with dispersed C2 dimers

    PubMed Central

    Zhang, Cunzhi; Zhang, Shunhong; Wang, Qian

    2016-01-01

    Currently, the available algorithms for unbiased structure searches are primarily atom-based, where atoms are manipulated as the elementary units, and energy is used as the target function without any restrictions on the bonding of atoms. In fact, in many cases such as nanostructure-assembled materials, the structural units are nanoclusters. We report a study of a bonding-restricted structure search method based on the particle swarm optimization (PSO) for finding the stable structures of two-dimensional (2D) materials containing dispersed C2 dimers rather than individual C atoms. The C2 dimer can be considered as a prototype of nanoclusters. Taking Si-C, B-C and Ti-C systems as test cases, our method combined with density functional theory and phonon calculations uncover new ground state geometrical structures for SiC2, Si2C2, BC2, B2C2, TiC2, and Ti2C2 sheets and their low-lying energy allotropes, as well as their electronic structures. Equally important, this method can be applied to other complex systems even containing f elements and other molecular dimers such as S2, N2, B2 and Si2, where the complex orbital orientations require extensive search for finding the optimal orientations to maximize the bonding with the dimers, predicting new 2D materials beyond MXenes (a family of transition metal carbides or nitrides) and dichalcogenide monolayers. PMID:27403589

  13. Bonding-restricted structure search for novel 2D materials with dispersed C2 dimers.

    PubMed

    Zhang, Cunzhi; Zhang, Shunhong; Wang, Qian

    2016-07-12

    Currently, the available algorithms for unbiased structure searches are primarily atom-based, where atoms are manipulated as the elementary units, and energy is used as the target function without any restrictions on the bonding of atoms. In fact, in many cases such as nanostructure-assembled materials, the structural units are nanoclusters. We report a study of a bonding-restricted structure search method based on the particle swarm optimization (PSO) for finding the stable structures of two-dimensional (2D) materials containing dispersed C2 dimers rather than individual C atoms. The C2 dimer can be considered as a prototype of nanoclusters. Taking Si-C, B-C and Ti-C systems as test cases, our method combined with density functional theory and phonon calculations uncover new ground state geometrical structures for SiC2, Si2C2, BC2, B2C2, TiC2, and Ti2C2 sheets and their low-lying energy allotropes, as well as their electronic structures. Equally important, this method can be applied to other complex systems even containing f elements and other molecular dimers such as S2, N2, B2 and Si2, where the complex orbital orientations require extensive search for finding the optimal orientations to maximize the bonding with the dimers, predicting new 2D materials beyond MXenes (a family of transition metal carbides or nitrides) and dichalcogenide monolayers.

  14. Bonding-restricted structure search for novel 2D materials with dispersed C2 dimers

    NASA Astrophysics Data System (ADS)

    Zhang, Cunzhi; Zhang, Shunhong; Wang, Qian

    2016-07-01

    Currently, the available algorithms for unbiased structure searches are primarily atom-based, where atoms are manipulated as the elementary units, and energy is used as the target function without any restrictions on the bonding of atoms. In fact, in many cases such as nanostructure-assembled materials, the structural units are nanoclusters. We report a study of a bonding-restricted structure search method based on the particle swarm optimization (PSO) for finding the stable structures of two-dimensional (2D) materials containing dispersed C2 dimers rather than individual C atoms. The C2 dimer can be considered as a prototype of nanoclusters. Taking Si-C, B-C and Ti-C systems as test cases, our method combined with density functional theory and phonon calculations uncover new ground state geometrical structures for SiC2, Si2C2, BC2, B2C2, TiC2, and Ti2C2 sheets and their low-lying energy allotropes, as well as their electronic structures. Equally important, this method can be applied to other complex systems even containing f elements and other molecular dimers such as S2, N2, B2 and Si2, where the complex orbital orientations require extensive search for finding the optimal orientations to maximize the bonding with the dimers, predicting new 2D materials beyond MXenes (a family of transition metal carbides or nitrides) and dichalcogenide monolayers.

  15. Enhancing superplasticity of engineering ceramics by introducing BN nanotubes

    NASA Astrophysics Data System (ADS)

    Huang, Qing; Bando, Yoshio; Xu, Xin; Nishimura, Toshiyuki; Zhi, Chunyi; Tang, Chengchun; Xu, Fangfang; Gao, Lian; Golberg, Dmitri

    2007-12-01

    Introducing carbon nanotubes (CNTs) into polymer or ceramic matrices has been a promising approach to obtain ultra-strong, extra-toughened materials as well as multifunctional composites. Most of the previous work on CNT composites has focused on strengthening and toughening of matrix materials at ambient conditions. However, so far there is a lack of information on the mechanical behavior of these composites at elevated temperature. Recently, single-walled CNTs were found to undergo a superplastic deformation with an appealing 280% elongation at a high temperature (Huang et al 2006 Nature 439 281). This discovery implies the high probability for the potential usage of CNTs as reinforcing agents in engineering high-temperature ceramics with improved ductility. Here, for the first time, we demonstrate that a small addition of boron nitride nanotubes (BNNTs) can dramatically enhance the high-temperature superplastic deformation (SPD) of engineering ceramics. More specifically, 0.5 wt% addition of BNNTs leads to an inspiring brittle-to-ductile transition in Al2O3 ceramics even at a moderate temperature (1300 °C). For Si3N4 ceramics, 0.5 wt% addition of BNNTs could also decrease the true stress by 75% under the same deformation conditions. In contrast, addition of micro-sized or nano-sized BN powders has no or a negative effect on the superplasticity of these ceramics. The underlying SPD-enhancement mechanism is discussed in terms of the inhibition of static and dynamic grain growth of the matrix and the energy-absorption mechanism of BNNTs. The unraveled capability of BNNTs to enhance the SPD behavior will make BNNTs promising components in cost-effective complex ceramics with good comprehensive mechanical properties.

  16. Targeted fluorescence imaging enhanced by 2D materials: a comparison between 2D MoS2 and graphene oxide.

    PubMed

    Xie, Donghao; Ji, Ding-Kun; Zhang, Yue; Cao, Jun; Zheng, Hu; Liu, Lin; Zang, Yi; Li, Jia; Chen, Guo-Rong; James, Tony D; He, Xiao-Peng

    2016-08-01

    Here we demonstrate that 2D MoS2 can enhance the receptor-targeting and imaging ability of a fluorophore-labelled ligand. The 2D MoS2 has an enhanced working concentration range when compared with graphene oxide, resulting in the improved imaging of both cell and tissue samples.

  17. Efficient 2D MRI relaxometry using compressed sensing

    NASA Astrophysics Data System (ADS)

    Bai, Ruiliang; Cloninger, Alexander; Czaja, Wojciech; Basser, Peter J.

    2015-06-01

    Potential applications of 2D relaxation spectrum NMR and MRI to characterize complex water dynamics (e.g., compartmental exchange) in biology and other disciplines have increased in recent years. However, the large amount of data and long MR acquisition times required for conventional 2D MR relaxometry limits its applicability for in vivo preclinical and clinical MRI. We present a new MR pipeline for 2D relaxometry that incorporates compressed sensing (CS) as a means to vastly reduce the amount of 2D relaxation data needed for material and tissue characterization without compromising data quality. Unlike the conventional CS reconstruction in the Fourier space (k-space), the proposed CS algorithm is directly applied onto the Laplace space (the joint 2D relaxation data) without compressing k-space to reduce the amount of data required for 2D relaxation spectra. This framework is validated using synthetic data, with NMR data acquired in a well-characterized urea/water phantom, and on fixed porcine spinal cord tissue. The quality of the CS-reconstructed spectra was comparable to that of the conventional 2D relaxation spectra, as assessed using global correlation, local contrast between peaks, peak amplitude and relaxation parameters, etc. This result brings this important type of contrast closer to being realized in preclinical, clinical, and other applications.

  18. Nanostructured materials in potentiometry.

    PubMed

    Düzgün, Ali; Zelada-Guillén, Gustavo A; Crespo, Gastón A; Macho, Santiago; Riu, Jordi; Rius, F Xavier

    2011-01-01

    Potentiometry is a very simple electrochemical technique with extraordinary analytical capabilities. It is also well known that nanostructured materials display properties which they do not show in the bulk phase. The combination of the two fields of potentiometry and nanomaterials is therefore a promising area of research and development. In this report, we explain the fundamentals of potentiometric devices that incorporate nanostructured materials and we highlight the advantages and drawbacks of combining nanomaterials and potentiometry. The paper provides an overview of the role of nanostructured materials in the two commonest potentiometric sensors: field-effect transistors and ion-selective electrodes. Additionally, we provide a few recent examples of new potentiometric sensors that are based on receptors immobilized directly onto the nanostructured material surface. Moreover, we summarize the use of potentiometry to analyze processes involving nanostructured materials and the prospects that the use of nanopores offer to potentiometry. Finally, we discuss several difficulties that currently hinder developments in the field and some future trends that will extend potentiometry into new analytical areas such as biology and medicine.

  19. Adsorption of alkali and alkaline-earth metal atoms on the reconstructed graphene-like BN single sheet

    NASA Astrophysics Data System (ADS)

    Hao, Jun-Hua; Wang, Zheng-Jia; Wang, Yu-Fang; Yin, Yu-Hua; Jiang, Run; Jin, Qing-Hua

    2015-12-01

    A graphene-like BN single sheet with absorbed alkali and alkaline-earth metal atoms have been investigated by using a first-principles method within the framework of density functional theory (DFT). The electronic structure of BN sheet with adsorbed metal atoms is mainly determined by the metal electronic state which is near to the Fermi level owing to the wide band gap of pure BN sheet. So, we calculated the adsorption energy, charge transfer and work function after the metal adsorbed on BN sheet. We found that the interaction between the metal atoms and BN surface was very strong, and the stable adsorption site for all the adsorbed atoms concluded was high-coordination surface site (H-center) rather than the surface dangling bond sites from the perspective of simple bond-counting arguments. Our results indicate that the interaction of BN sheet with metal atoms could help in the development of metallic nanoscale devices.

  20. Synthesis and characterization of cBN/WCCo composites obtained by the pulse plasma sintering (PPS) method

    NASA Astrophysics Data System (ADS)

    Michalski, A.; Rosiński, M.; Płocińska, M.; Szawłowski, J.

    2011-10-01

    The cBN/cemented carbide containing 30vol% of cBN particles was produced using a mixture of a 6wt% Co added-WC powder, with a WC grain size of 0.4 μm and a cBN powder with a grain size ranging from 4 to 40 μm. The mixture was sintered to produce a plate, 20 mm in diameter, 3 mm thick. The sintering processes were conducted at temperature of 1100°C under a load of 100 MPa. The phase composition, density, hardness and micro structure of the sintered parts thus obtained were examined. The fractures through the WCCo/cBN composite showed the cBN particles torn out from the cemented carbide matrix were only few, whereas most of them have cleaved along the fracture plane. This gives evidence that the bond at the WCCo/cBN interface is mechanically strong.

  1. Practical Algorithm For Computing The 2-D Arithmetic Fourier Transform

    NASA Astrophysics Data System (ADS)

    Reed, Irving S.; Choi, Y. Y.; Yu, Xiaoli

    1989-05-01

    Recently, Tufts and Sadasiv [10] exposed a method for computing the coefficients of a Fourier series of a periodic function using the Mobius inversion of series. They called this method of analysis the Arithmetic Fourier Transform(AFT). The advantage of the AFT over the FN 1' is that this method of Fourier analysis needs only addition operations except for multiplications by scale factors at one stage of the computation. The disadvantage of the AFT as they expressed it originally is that it could be used effectively only to compute finite Fourier coefficients of a real even function. To remedy this the AFT developed in [10] is extended in [11] to compute the Fourier coefficients of both the even and odd components of a periodic function. In this paper, the improved AFT [11] is extended to a two-dimensional(2-D) Arithmetic Fourier Transform for calculating the Fourier Transform of two-dimensional discrete signals. This new algorithm is based on both the number-theoretic method of Mobius inversion of double series and the complex conjugate property of Fourier coefficients. The advantage of this algorithm over the conventional 2-D FFT is that the corner-turning problem needed in a conventional 2-D Discrete Fourier Transform(DFT) can be avoided. Therefore, this new 2-D algorithm is readily suitable for VLSI implementation as a parallel architecture. Comparing the operations of 2-D AFT of a MxM 2-D data array with the conventional 2-D FFT, the number of multiplications is significantly reduced from (2log2M)M2 to (9/4)M2. Hence, this new algorithm is faster than the FFT algorithm. Finally, two simulation results of this new 2-D AFT algorithm for 2-D artificial and real images are given in this paper.

  2. Thermal Conductivity of Epoxy Resin Composites Filled with Combustion Synthesized h-BN Particles.

    PubMed

    Chung, Shyan-Lung; Lin, Jeng-Shung

    2016-01-01

    The thermal conductivity of epoxy resin composites filled with combustion-synthesized hexagonal boron nitride (h-BN) particles was investigated. The mixing of the composite constituents was carried out by either a dry method (involving no use of solvent) for low filler loadings or a solvent method (using acetone as solvent) for higher filler loadings. It was found that surface treatment of the h-BN particles using the silane 3-glycidoxypropyltrimethoxysilane (GPTMS) increases the thermal conductivity of the resultant composites in a lesser amount compared to the values reported by other studies. This was explained by the fact that the combustion synthesized h-BN particles contain less -OH or active sites on the surface, thus adsorbing less amounts of GPTMS. However, the thermal conductivity of the composites filled with the combustion synthesized h-BN was found to be comparable to that with commercially available h-BN reported in other studies. The thermal conductivity of the composites was found to be higher when larger h-BN particles were used. The thermal conductivity was also found to increase with increasing filler content to a maximum and then begin to decrease with further increases in this content. In addition to the effect of higher porosity at higher filler contents, more horizontally oriented h-BN particles formed at higher filler loadings (perhaps due to pressing during formation of the composites) were suggested to be a factor causing this decrease of the thermal conductivity. The measured thermal conductivities were compared to theoretical predictions based on the Nielsen and Lewis theory. The theoretical predictions were found to be lower than the experimental values at low filler contents (< 60 vol %) and became increasing higher than the experimental values at high filler contents (> 60 vol %). PMID:27213325

  3. Thermal Conductivity of Epoxy Resin Composites Filled with Combustion Synthesized h-BN Particles.

    PubMed

    Chung, Shyan-Lung; Lin, Jeng-Shung

    2016-05-20

    The thermal conductivity of epoxy resin composites filled with combustion-synthesized hexagonal boron nitride (h-BN) particles was investigated. The mixing of the composite constituents was carried out by either a dry method (involving no use of solvent) for low filler loadings or a solvent method (using acetone as solvent) for higher filler loadings. It was found that surface treatment of the h-BN particles using the silane 3-glycidoxypropyltrimethoxysilane (GPTMS) increases the thermal conductivity of the resultant composites in a lesser amount compared to the values reported by other studies. This was explained by the fact that the combustion synthesized h-BN particles contain less -OH or active sites on the surface, thus adsorbing less amounts of GPTMS. However, the thermal conductivity of the composites filled with the combustion synthesized h-BN was found to be comparable to that with commercially available h-BN reported in other studies. The thermal conductivity of the composites was found to be higher when larger h-BN particles were used. The thermal conductivity was also found to increase with increasing filler content to a maximum and then begin to decrease with further increases in this content. In addition to the effect of higher porosity at higher filler contents, more horizontally oriented h-BN particles formed at higher filler loadings (perhaps due to pressing during formation of the composites) were suggested to be a factor causing this decrease of the thermal conductivity. The measured thermal conductivities were compared to theoretical predictions based on the Nielsen and Lewis theory. The theoretical predictions were found to be lower than the experimental values at low filler contents (< 60 vol %) and became increasing higher than the experimental values at high filler contents (> 60 vol %).

  4. 2D electron cyclotron emission imaging at ASDEX Upgrade (invited)

    SciTech Connect

    Classen, I. G. J.; Boom, J. E.; Vries, P. C. de; Suttrop, W.; Schmid, E.; Garcia-Munoz, M.; Schneider, P. A.; Tobias, B.; Domier, C. W.; Luhmann, N. C. Jr.; Donne, A. J. H.; Jaspers, R. J. E.; Park, H. K.; Munsat, T.

    2010-10-15

    The newly installed electron cyclotron emission imaging diagnostic on ASDEX Upgrade provides measurements of the 2D electron temperature dynamics with high spatial and temporal resolution. An overview of the technical and experimental properties of the system is presented. These properties are illustrated by the measurements of the edge localized mode and the reversed shear Alfven eigenmode, showing both the advantage of having a two-dimensional (2D) measurement, as well as some of the limitations of electron cyclotron emission measurements. Furthermore, the application of singular value decomposition as a powerful tool for analyzing and filtering 2D data is presented.

  5. Comparison of 2D and 3D gamma analyses

    SciTech Connect

    Pulliam, Kiley B.; Huang, Jessie Y.; Howell, Rebecca M.; Followill, David; Kry, Stephen F.; Bosca, Ryan; O’Daniel, Jennifer

    2014-02-15

    Purpose: As clinics begin to use 3D metrics for intensity-modulated radiation therapy (IMRT) quality assurance, it must be noted that these metrics will often produce results different from those produced by their 2D counterparts. 3D and 2D gamma analyses would be expected to produce different values, in part because of the different search space available. In the present investigation, the authors compared the results of 2D and 3D gamma analysis (where both datasets were generated in the same manner) for clinical treatment plans. Methods: Fifty IMRT plans were selected from the authors’ clinical database, and recalculated using Monte Carlo. Treatment planning system-calculated (“evaluated dose distributions”) and Monte Carlo-recalculated (“reference dose distributions”) dose distributions were compared using 2D and 3D gamma analysis. This analysis was performed using a variety of dose-difference (5%, 3%, 2%, and 1%) and distance-to-agreement (5, 3, 2, and 1 mm) acceptance criteria, low-dose thresholds (5%, 10%, and 15% of the prescription dose), and data grid sizes (1.0, 1.5, and 3.0 mm). Each comparison was evaluated to determine the average 2D and 3D gamma, lower 95th percentile gamma value, and percentage of pixels passing gamma. Results: The average gamma, lower 95th percentile gamma value, and percentage of passing pixels for each acceptance criterion demonstrated better agreement for 3D than for 2D analysis for every plan comparison. The average difference in the percentage of passing pixels between the 2D and 3D analyses with no low-dose threshold ranged from 0.9% to 2.1%. Similarly, using a low-dose threshold resulted in a difference between the mean 2D and 3D results, ranging from 0.8% to 1.5%. The authors observed no appreciable differences in gamma with changes in the data density (constant difference: 0.8% for 2D vs 3D). Conclusions: The authors found that 3D gamma analysis resulted in up to 2.9% more pixels passing than 2D analysis. It must

  6. Recent advances in 2D materials for photocatalysis.

    PubMed

    Luo, Bin; Liu, Gang; Wang, Lianzhou

    2016-04-01

    Two-dimensional (2D) materials have attracted increasing attention for photocatalytic applications because of their unique thickness dependent physical and chemical properties. This review gives a brief overview of the recent developments concerning the chemical synthesis and structural design of 2D materials at the nanoscale and their applications in photocatalytic areas. In particular, recent progress on the emerging strategies for tailoring 2D material-based photocatalysts to improve their photo-activity including elemental doping, heterostructure design and functional architecture assembly is discussed.

  7. Massively parallel patterning of complex 2D and 3D functional polymer brushes by polymer pen lithography.

    PubMed

    Xie, Zhuang; Chen, Chaojian; Zhou, Xuechang; Gao, Tingting; Liu, Danqing; Miao, Qian; Zheng, Zijian

    2014-08-13

    We report the first demonstration of centimeter-area serial patterning of complex 2D and 3D functional polymer brushes by high-throughput polymer pen lithography. Arbitrary 2D and 3D structures of poly(glycidyl methacrylate) (PGMA) brushes are fabricated over areas as large as 2 cm × 1 cm, with a remarkable throughput being 3 orders of magnitudes higher than the state-of-the-arts. Patterned PGMA brushes are further employed as resist for fabricating Au micro/nanostructures and hard molds for the subsequent replica molding of soft stamps. On the other hand, these 2D and 3D PGMA brushes are also utilized as robust and versatile platforms for the immobilization of bioactive molecules to form 2D and 3D patterned DNA oligonucleotide and protein chips. Therefore, this low-cost, yet high-throughput "bench-top" serial fabrication method can be readily applied to a wide range of fields including micro/nanofabrication, optics and electronics, smart surfaces, and biorelated studies.

  8. Nanostructured materials for hydrogen storage

    DOEpatents

    Williamson, Andrew J.; Reboredo, Fernando A.

    2007-12-04

    A system for hydrogen storage comprising a porous nano-structured material with hydrogen absorbed on the surfaces of the porous nano-structured material. The system of hydrogen storage comprises absorbing hydrogen on the surfaces of a porous nano-structured semiconductor material.

  9. Synthesis of porphyrin nanostructures

    DOEpatents

    Fan, Hongyou; Bai, Feng

    2014-10-28

    The present disclosure generally relates to self-assembly methods for generating porphyrin nanostructures. For example, in one embodiment a method is provided that includes preparing a porphyrin solution and a surfactant solution. The porphyrin solution is then mixed with the surfactant solution at a concentration sufficient for confinement of the porphyrin molecules by the surfactant molecules. In some embodiments, the concentration of the surfactant is at or above its critical micelle concentration (CMC), which allows the surfactant to template the growth of the nanostructure over time. The size and morphology of the nanostructures may be affected by the type of porphyrin molecules used, the type of surfactant used, the concentration of the porphyrin and surfactant the pH of the mixture of the solutions, and the order of adding the reagents to the mixture, to name a few variables.

  10. Half-metallicity modulation of hybrid BN-C nanotubes by external electric fields: A first-principles study

    SciTech Connect

    Liang, Yunye; Kawazoe, Yoshiyuki

    2014-06-21

    On the basis of density functional theory, we systematically investigate the electronic and magnetic properties of hybrid BN-C nanotubes, C{sub x}(BN){sub y} where x + y = 12, with and without an external electric field. The BN-C nanotubes are totally distinct from pristine boron-nitride and carbon nanotubes. The electronic properties of C{sub x}(BN){sub y} change significantly with composition: from the nonmagnetic semiconductors to the half-metals. The half-metallicity is attributed to the competition among the band gap, which is related to the width of C domain, the width of BN domain, and the intrinsic polarization field. Application of the external fields can enhance or counterbalance the polarization fields and change the band gaps. The half-metallicity can be modulated. In BN-rich tubes, such as C{sub 2}(BN){sub 10}, the energy gap can be engineered from 0.50 eV to 0.95 eV and in C{sub 3}(BN){sub 9}, the ground state is converted from the nonmagnetic state into the anti-ferro-magnetic one. In other tubes, the half-metallicity can be enhanced or destroyed by different external fields. The modulation indicates that hybrid BN-C nanotubes can work as the components of the spin-filter devices.

  11. Half-metallicity modulation of hybrid BN-C nanotubes by external electric fields: a first-principles study.

    PubMed

    Liang, Yunye; Kawazoe, Yoshiyuki

    2014-06-21

    On the basis of density functional theory, we systematically investigate the electronic and magnetic properties of hybrid BN-C nanotubes, Cx(BN)y where x + y = 12, with and without an external electric field. The BN-C nanotubes are totally distinct from pristine boron-nitride and carbon nanotubes. The electronic properties of Cx(BN)y change significantly with composition: from the nonmagnetic semiconductors to the half-metals. The half-metallicity is attributed to the competition among the band gap, which is related to the width of C domain, the width of BN domain, and the intrinsic polarization field. Application of the external fields can enhance or counterbalance the polarization fields and change the band gaps. The half-metallicity can be modulated. In BN-rich tubes, such as C2(BN)10, the energy gap can be engineered from 0.50 eV to 0.95 eV and in C3(BN)9, the ground state is converted from the nonmagnetic state into the anti-ferro-magnetic one. In other tubes, the half-metallicity can be enhanced or destroyed by different external fields. The modulation indicates that hybrid BN-C nanotubes can work as the components of the spin-filter devices.

  12. Layered Graphene-Hexagonal BN Nanocomposites: Experimentally Feasible Approach to Charge-Induced Switchable CO2 Capture.

    PubMed

    Tan, Xin; Kou, Liangzhi; Smith, Sean C

    2015-09-01

    Recently, inducing negative charge density on hexagonal boron nitride (h-BN) has been predicted as an effective strategy for controllable, selective, and reversible CO2 capture. However, h-BN is a wide-gap semiconductor and it is not clear how to effectively induce the requisite negative charge density. In this paper, we employ first-principle calculations to propose hybrid h-BN-graphene (hybrid BN/G) nanosheets as an experimentally feasible strategy to induce charge on h-BN for charge-controlled CO2 capture. The results indicate that the charge density is effectively transferred from the graphene layer with high electronic mobility into the h-BN layer on the surface, regardless of the thickness of BN layers, such that CO2 capture/release can be simply controlled by switching on/off the charge states of hybrid BN/G system. In addition, these negatively charged hybrid BN/G are highly selective for separating CO2 from mixtures with CH4 , N2 , and/or H2 . PMID:26073178

  13. Effects of Processing Parameters on Internal Stress of BN Films Prepared by Ion Mixing and Vapor Deposition

    SciTech Connect

    Hanaki, Satoshi; Leng, Bo; Uchida, Hitoshi

    2010-10-13

    Boron nitride (BN) films have been attractive due to their excellent properties such as high hardness, thermal conductivity and chemical stability. In this study, BN films were prepared by depositing B vapor under simultaneous irradiation of N ions, that is ion mixing and vapor deposition (IVD) technique. The effects of processing parameters such as, acceleration voltage of N ions, transport ratio B/N and substrate temperature, on the internal stress of BN films were investigated. As a result, compressive internal stress increases at low acceleration voltage and high transport ratio B/N, which corresponded to the condition for formation of cBN phase. The hardness also becomes high at this condition and there is a strong correlation between internal stress and hardness of BN film. In addition to that, relaxation of internal stress by inserting inner layer between substrate and cBN layer has been carried out. It is confirmed that internal stress can be decreased by inner layer. Especially, relaxation of internal stress without degradation of high hardness can be achieved when the crystal structure of inner layer is hBN.

  14. The Effect of Processing Parameters on the Performance of Spark Plasma Sintered cBN-WC-Co Composites

    NASA Astrophysics Data System (ADS)

    Mao, Cong; Zhang, Mingjun; Zhang, Jian; Tang, Kun; Gan, Hangyu; Zhang, Gaofeng

    2015-12-01

    Cubic boron nitride (cBN) particles were mixed into superfine tungsten carbide (WC), and then cBN-WC-cobalt (Co) composites were prepared using spark plasma sintering method. The influence of the processing parameters on the microstructures and the mechanical properties of the cBN-WC-Co composites were investigated. The results indicated that the cBN particles arranged uniformly and had an excellent adhesion with WC matrix. There was no evidence of phase transformation from cBN to hBN. With the increasing of the sintering temperature, the liquid-phase Co was increased and entered the micro-pores between WC and cBN particles easily. Correspondingly, the density, the flexural strength, and the hardness of the cBN-WC-Co composites also increased. With the further increasing of the sintering temperature, WC grains grew leading to the reduction of the hardness. Therefore, the hardness of the samples increased to a maximum value of 2978 HV at 1250 °C, and then decreased with the sintering temperature. The experimental results also showed that the density, the flexural strength, and the hardness of cBN-WC-Co composites increased with the holding time, whereas the hardness presented a decreasing tendency when the holding time exceeded 7 min.

  15. Simulation of Semiconductor Nanostructures

    SciTech Connect

    Williamson, A J; Grossman, J C; Puzder, A; Benedict, L X; Galli, G

    2001-07-19

    The field of research into the optical properties of silicon nanostructures has seen enormous growth over the last decade. The discovery that silicon nanoparticles exhibit visible photoluminescence (PL) has led to new insights into the mechanisms responsible for such phenomena. The importance of understanding and controlling the PL properties of any silicon based material is of paramount interest to the optoelectronics industry where silicon nanoclusters could be embedded into existing silicon based circuitry. In this talk, we present a combination of quantum Monte Carlo and density functional approaches to the calculation of the electronic, structural, and optical properties of silicon nanostructures.

  16. Plasmonic nanostructures: artificial molecules.

    PubMed

    Wang, Hui; Brandl, Daniel W; Nordlander, Peter; Halas, Naomi J

    2007-01-01

    This Account describes a new paradigm for the relationship between the geometry of metallic nanostructures and their optical properties. While the interaction of light with metallic nanoparticles is determined by their collective electronic or plasmon response, a compelling analogy exists between plasmon resonances of metallic nanoparticles and wave functions of simple atoms and molecules. Based on this insight, an entire family of plasmonic nanostructures, artificial molecules, has been developed whose optical properties can be understood within this picture: nanoparticles (nanoshells, nanoeggs, nanomatryushkas, nanorice), multi-nanoparticle assemblies (dimers, trimers, quadrumers), and a nanoparticle-over-metallic film, an electromagnetic analog of the spinless Anderson model. PMID:17226945

  17. Plasmonics in nanostructures.

    PubMed

    Fang, Zheyu; Zhu, Xing

    2013-07-26

    Plasmonics has developed into one of the rapidly growing research topics for nanophotonics. With advanced nanofabrication techniques, a broad variety of nanostructures can be designed and fabricated for plasmonic devices at nanoscale. Fundamental properties for both surface plasmon polaritons (SPP) and localized surface plasmons (LSP) arise a new insight and understanding for the electro-optical device investigations, such as plasmonic nanofocusing, low-loss plasmon waveguide and active plasmonic detectors for energy harvesting. Here, we review some typical functional plasmonic nanostructures and nanosmart devices emerging from our individual and collaborative research works.

  18. 3D visualization of polymer nanostructure

    SciTech Connect

    Werner, James H

    2009-01-01

    Soft materials and structured polymers are extremely useful nanotechnology building blocks. Block copolymers, in particular, have served as 2D masks for nanolithography and 3D scaffolds for photonic crystals, nanoparticle fabrication, and solar cells. F or many of these applications, the precise 3 dimensional structure and the number and type of defects in the polymer is important for ultimate function. However, directly visualizing the 3D structure of a soft material from the nanometer to millimeter length scales is a significant technical challenge. Here, we propose to develop the instrumentation needed for direct 3D structure determination at near nanometer resolution throughout a nearly millimeter-cubed volume of a soft, potentially heterogeneous, material. This new capability will be a valuable research tool for LANL missions in chemistry, materials science, and nanoscience. Our approach to soft materials visualization builds upon exciting developments in super-resolution optical microscopy that have occurred over the past two years. To date, these new, truly revolutionary, imaging methods have been developed and almost exclusively used for biological applications. However, in addition to biological cells, these super-resolution imaging techniques hold extreme promise for direct visualization of many important nanostructured polymers and other heterogeneous chemical systems. Los Alamos has a unique opportunity to lead the development of these super-resolution imaging methods for problems of chemical rather than biological significance. While these optical methods are limited to systems transparent to visible wavelengths, we stress that many important functional chemicals such as polymers, glasses, sol-gels, aerogels, or colloidal assemblies meet this requirement, with specific examples including materials designed for optical communication, manipulation, or light-harvesting Our Research Goals are: (1) Develop the instrumentation necessary for imaging materials

  19. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices.

  20. Emerging and potential opportunities for 2D flexible nanoelectronics

    NASA Astrophysics Data System (ADS)

    Zhu, Weinan; Park, Saungeun; Akinwande, Deji

    2016-05-01

    The last 10 years have seen the emergence of two-dimensional (2D) nanomaterials such as graphene, transition metal dichalcogenides (TMDs), and black phosphorus (BP) among the growing portfolio of layered van der Waals thin films. Graphene, the prototypical 2D material has advanced rapidly in device, circuit and system studies that has resulted in commercial large-area applications. In this work, we provide a perspective of the emerging and potential translational applications of 2D materials including semiconductors, semimetals, and insulators that comprise the basic material set for diverse nanosystems. Applications include RF transceivers, smart systems, the so-called internet of things, and neurotechnology. We will review the DC and RF electronic performance of graphene and BP thin film transistors. 2D materials at sub-um channel length have so far enabled cut-off frequencies from baseband to 100GHz suitable for low-power RF and sub-THz concepts.

  1. 2D hexagonal quaternion Fourier transform in color image processing

    NASA Astrophysics Data System (ADS)

    Grigoryan, Artyom M.; Agaian, Sos S.

    2016-05-01

    In this paper, we present a novel concept of the quaternion discrete Fourier transform on the two-dimensional hexagonal lattice, which we call the two-dimensional hexagonal quaternion discrete Fourier transform (2-D HQDFT). The concept of the right-side 2D HQDFT is described and the left-side 2-D HQDFT is similarly considered. To calculate the transform, the image on the hexagonal lattice is described in the tensor representation when the image is presented by a set of 1-D signals, or splitting-signals which can be separately processed in the frequency domain. The 2-D HQDFT can be calculated by a set of 1-D quaternion discrete Fourier transforms (QDFT) of the splitting-signals.

  2. Technical Review of the UNET2D Hydraulic Model

    SciTech Connect

    Perkins, William A.; Richmond, Marshall C.

    2009-05-18

    The Kansas City District of the US Army Corps of Engineers is engaged in a broad range of river management projects that require knowledge of spatially-varied hydraulic conditions such as velocities and water surface elevations. This information is needed to design new structures, improve existing operations, and assess aquatic habitat. Two-dimensional (2D) depth-averaged numerical hydraulic models are a common tool that can be used to provide velocity and depth information. Kansas City District is currently using a specific 2D model, UNET2D, that has been developed to meet the needs of their river engineering applications. This report documents a tech- nical review of UNET2D.

  3. Double resonance rotational spectroscopy of CH2D+

    NASA Astrophysics Data System (ADS)

    Töpfer, Matthias; Jusko, Pavol; Schlemmer, Stephan; Asvany, Oskar

    2016-09-01

    Context. Deuterated forms of CH are thought to be responsible for deuterium enrichment in lukewarm astronomical environments. There is no unambiguous detection of CH2D+ in space to date. Aims: Four submillimetre rotational lines of CH2D+ are documented in the literature. Our aim is to present a complete dataset of highly resolved rotational lines, including millimetre (mm) lines needed for a potential detection. Methods: We used a low-temperature ion trap and applied a novel IR-mm-wave double resonance method to measure the rotational lines of CH2D+. Results: We measured 21 low-lying (J ≤ 4) rotational transitions of CH2D+ between 23 GHz and 1.1 THz with accuracies close to 2 ppb.

  4. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices. PMID:26839956

  5. ORION96. 2-d Finite Element Code Postprocessor

    SciTech Connect

    Sanford, L.A.; Hallquist, J.O.

    1992-02-02

    ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forces along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  6. Phylogenetic tree construction based on 2D graphical representation

    NASA Astrophysics Data System (ADS)

    Liao, Bo; Shan, Xinzhou; Zhu, Wen; Li, Renfa

    2006-04-01

    A new approach based on the two-dimensional (2D) graphical representation of the whole genome sequence [Bo Liao, Chem. Phys. Lett., 401(2005) 196.] is proposed to analyze the phylogenetic relationships of genomes. The evolutionary distances are obtained through measuring the differences among the 2D curves. The fuzzy theory is used to construct phylogenetic tree. The phylogenetic relationships of H5N1 avian influenza virus illustrate the utility of our approach.

  7. Generating a 2D Representation of a Complex Data Structure

    NASA Technical Reports Server (NTRS)

    James, Mark

    2006-01-01

    A computer program, designed to assist in the development and debugging of other software, generates a two-dimensional (2D) representation of a possibly complex n-dimensional (where n is an integer >2) data structure or abstract rank-n object in that other software. The nature of the 2D representation is such that it can be displayed on a non-graphical output device and distributed by non-graphical means.

  8. Anisotropic 2D Materials for Tunable Hyperbolic Plasmonics.

    PubMed

    Nemilentsau, Andrei; Low, Tony; Hanson, George

    2016-02-12

    Motivated by the recent emergence of a new class of anisotropic 2D materials, we examine their electromagnetic modes and demonstrate that a broad class of the materials can host highly directional hyperbolic plasmons. Their propagation direction can be manipulated on the spot by gate doping, enabling hyperbolic beam reflection, refraction, and bending. The realization of these natural 2D hyperbolic media opens up a new avenue in dynamic control of hyperbolic plasmons not possible in the 3D version.

  9. A simultaneous 2D/3D autostereo workstation

    NASA Astrophysics Data System (ADS)

    Chau, Dennis; McGinnis, Bradley; Talandis, Jonas; Leigh, Jason; Peterka, Tom; Knoll, Aaron; Sumer, Aslihan; Papka, Michael; Jellinek, Julius

    2012-03-01

    We present a novel immersive workstation environment that scientists can use for 3D data exploration and as their everyday 2D computer monitor. Our implementation is based on an autostereoscopic dynamic parallax barrier 2D/3D display, interactive input devices, and a software infrastructure that allows client/server software modules to couple the workstation to scientists' visualization applications. This paper describes the hardware construction and calibration, software components, and a demonstration of our system in nanoscale materials science exploration.

  10. QUENCH2D. Two-Dimensional IHCP Code

    SciTech Connect

    Osman, A.; Beck, J.V.

    1995-01-01

    QUENCH2D* is developed for the solution of general, non-linear, two-dimensional inverse heat transfer problems. This program provides estimates for the surface heat flux distribution and/or heat transfer coefficient as a function of time and space by using transient temperature measurements at appropriate interior points inside the quenched body. Two-dimensional planar and axisymmetric geometries such as turnbine disks and blades, clutch packs, and many other problems can be analyzed using QUENCH2D*.

  11. Superior machinability of steel enhanced with BN and MnS particles

    NASA Astrophysics Data System (ADS)

    Chen, Ya-nan; Bao, Yan-ping; Wang, Min; Cai, Xiao-feng; Wang, Lin-jing; Zhao, Li-hua

    2016-03-01

    The strategy that replacing part of MnS with BN was proposed in order to decrease the sulfur content in sulfur based free-cutting steel. The effects of BN and MnS inclusions on the microstructure and machinability of the steel were systematically investigated. The results show that most of the BN and MnS inclusions exist individually in the steel and only a small amount of them are in a composite state forming either isolated particles or clusters of particles. In the case of multi-phased steel, the theoretical calculation predicts that the volume of large BN particles should be 0.7 times of the volume of large MnS particles. The machinability of this type of BN and MnS alloy steel over a wide range of cutting speeds ranging from a low speed appropriate for drilling to a high speed appropriate for turning is confirmed as being equal to or superior to that of an MnS reference steel, even though the sulfur content in the composite steel is only half that of the MnS steel. The aptitude for cutting effect of 240 ppm nitrogen and 115 ppm boron in the composite steel is demonstrated to be equivalent or even better than 1000 ppm sulfur in MnS free-cutting steel.

  12. Template-free synthesis of functional 3D BN architecture for removal of dyes from water.

    PubMed

    Liu, Dan; Lei, Weiwei; Qin, Si; Chen, Ying

    2014-01-01

    Three-dimensional (3D) architectures are of interest in applications in electronics, catalysis devices, sensors and adsorption materials. However, it is still a challenge to fabricate 3D BN architectures by a simple method. Here, we report the direct synthesis of 3D BN architectures by a simple thermal treatment process. A 3D BN architecture consists of an interconnected flexible network of nanosheets. The typical nitrogen adsorption/desorption results demonstrate that the specific surface area for the as-prepared samples is up to 1156 m(2) g(-1), and the total pore volume is about 1.17 cm(3) g(-1). The 3D BN architecture displays very high adsorption rates and large capacities for organic dyes in water without any other additives due to its low densities, high resistance to oxidation, good chemical inertness and high surface area. Importantly, 88% of the starting adsorption capacity is maintained after 15 cycles. These results indicate that the 3D BN architecture is potential environmental materials for water purification and treatment. PMID:24663292

  13. Reduction of interfacial friction in commensurate graphene/h-BN heterostructures by surface functionalization

    NASA Astrophysics Data System (ADS)

    Guo, Yufeng; Qiu, Jiapeng; Guo, Wanlin

    2015-12-01

    The reduction of interfacial friction in commensurately stacked two-dimensional layered materials is important for their application in nanoelectromechanical systems. Our first-principles calculations on the sliding energy corrugation and friction at the interfaces of commensurate fluorinated-graphene/h-BN and oxidized-graphene/h-BN heterostructures show that the sliding energy barriers and shear strengths for these heterostructures are approximately decreased to 50% of those of commensurate graphene/h-BN. The adsorbed F and O atoms significantly suppress the interlayer electrostatic and van der Waals energy corrugations by modifying the geometry and charge redistribution of the graphene layers. Our empirical registry index models further reveal the difference between the roles of the F and O atoms in affecting the sliding energy landscapes, and are also utilized to predict the interlayer superlubricity in a large-scale oxidized-graphene/h-BN system. Surface functionalization is a valid way to control and reduce the interlayer friction in commensurate graphene/h-BN heterostructures.

  14. Precipitation behavior of BN type inclusions in 42CrMo steel

    NASA Astrophysics Data System (ADS)

    Wang, Yu-nan; Bao, Yan-ping; Wang, Min; Zhang, Le-chen

    2013-01-01

    Automobile crankshaft steel 42CrMo, which requires excellent machinability and mechanical properties, cannot be manufactured by traditional methods. To achieve these qualities, the formation behavior of boron nitride (BN) inclusions in 42CrMo steel was studied in this article. First, the precipitation temperature and the amount of BN type inclusions with different contents of boron and nitrogen in molten steel were calculated thermodynamically by FactSage software. Then the morphology and the size of BN type inclusions as well as the influence of cooling methods on them were investigated by scanning electron microscopy. Furthermore, the effects of cooling rate and the contents of B and N in molten steel on the morphology, size, and distribution of BN type inclusions were studied quantitatively and detailedly by directional solidification experiments. It is found that different BN inclusions in molten steel can form by controlling the cooling rate and the contents of B and N, which is important for obtaining the excellent machinability of 42CrMo steel.

  15. Computational and Spectroscopic Study of the B-N Dative Bond in Ammonia Borane

    NASA Astrophysics Data System (ADS)

    Wright, Ashley M.; Tschumper, Gregory S.; Hammer, Nathan I.

    2011-06-01

    Ammonia borane is the archetypal small molecule employed to study dative bonds (also known as coordinate covalent or dipolar bonds) theoretically. We analyze the sensitivity of the B-N dative bond to method and basis set by computing the B-N bond length and the B-N stretching frequency. Our goal is to find the least computationally demanding method and basis set combination that yields trustworthy results. Previous researchers have demonstrated the inaccuracy of the B3LYP method for describing this type of bond. Here, we compare results using the M06-2X hybrid density functional with ab initio methods including MP2, CCSD, and CCSD(T) with different sized basis sets. We compare these results to experimental solid state and gas phase Raman spectra. Monomer calculations overestimate the B-N bond length and underestimate the B-N stretch in ammonia borane when compared to experimental values. However, calculations performed on clusters of ammonia borane molecules do a better job of reproducing the solid state experimental results. This agreement could be due to dihydrogen bonding between the ammonia borane molecules.

  16. Effect of substrate temperature and gas flow ratio on the nanocomposite TiAlBN coating

    NASA Astrophysics Data System (ADS)

    Rosli, Z. M.; Kwan, W. L.; Juoi, J. M.

    2016-07-01

    Nanocomposite TiAlBN (nc-TiAlBN) coatings were successfully deposited via RF magnetron sputtering by varying the nitrogen-to-total gas flow ratio (RN), and substrate temperature (TS). All coatings were deposited on AISI 316 substrates using single Ti-Al-BN hot-pressed disc as a target. The grain size, phases, and chemical composition of the coatings were evaluated using glancing angle X-ray diffraction analysis (GAXRD) and X-ray photoelectron spectroscopy (XPS). Results showed that the grains size of the deposited nc-TiAlBN coatings were in the range of 3.5 to 5.7 nm and reached a nitride saturation state as early as 15 % RN. As the nitrogen concentration decreases, boron concentration increased from 9 at.% to 16.17 at.%. and thus, increase the TiB2 phase within the coatings. The TS, however, showed no significant effect either on the crystallographic structure, grain size, or in the chemical composition of the deposited nc-TiAlBN coating.

  17. Chemical Exfoliation of Layered Superconductors: An Avenue to Synthesize Boron-rich Quasi Two Dimensional Nanostructures

    NASA Astrophysics Data System (ADS)

    Das, Saroj Kumar; Liza James, Asha; Jasuja, Kabeer

    2015-03-01

    Zero-dimensional and one-dimensional boron based nanostructures have presented excellent avenues in the past for utilizing the fascinating science of boron at the atomic level. The research on synthesizing two-dimensional (2-D) boron-based nanostructures is currently in its incipient stages. In this talk, we demonstrate two chemical approaches that yield quasi 2-D boron-rich nanostructures by enabling an exfoliation of a layered boron-based superconductor. While one approach employs the simple tool of ultrasonication in an aqueous phase, the other approach utilizes a chelation mediated strategy based on coordination of metal ions and organic ligands. Both these synthetic routes are shown to result in a processable colloidal dispersion of nanosheets. This talk will present details of the two exfoliation approaches and a comprehensive study of the morphological, chemical and optical properties of the dispersed nanosheets. We will demonstrate that the exfoliated nanosheets undergo an in-situ chemical modification with ionizable functional groups derived from solvent that enable electrostatic stabilization. We will further shown that this functionalization modifies the band structure of the nanosheets which gives rise to photoluminescence and result in physico-chemical properties distinct from the parent superconductor. This ability to synthesize quasi 2-D boron rich nanostructures significantly adds to the current state of literature on born-based quasi-planar nanostructures.

  18. Simulating MEMS Chevron Actuator for Strain Engineering 2D Materials

    NASA Astrophysics Data System (ADS)

    Vutukuru, Mounika; Christopher, Jason; Bishop, David; Swan, Anna

    2D materials pose an exciting paradigm shift in the world of electronics. These crystalline materials have demonstrated high electric and thermal conductivities and tensile strength, showing great potential as the new building blocks of basic electronic circuits. However, strain engineering 2D materials for novel devices remains a difficult experimental feat. We propose the integration of 2D materials with MEMS devices to investigate the strain dependence on material properties such as electrical and thermal conductivity, refractive index, mechanical elasticity, and band gap. MEMS Chevron actuators, provides the most accessible framework to study strain in 2D materials due to their high output force displacements for low input power. Here, we simulate Chevron actuators on COMSOL to optimize actuator design parameters and accurately capture the behavior of the devices while under the external force of a 2D material. Through stationary state analysis, we analyze the response of the device through IV characteristics, displacement and temperature curves. We conclude that the simulation precisely models the real-world device through experimental confirmation, proving that the integration of 2D materials with MEMS is a viable option for constructing novel strain engineered devices. The authors acknowledge support from NSF DMR1411008.

  19. Configuration space method for calculating binding energies of exciton complexes in quasi-1D/2D semiconductors

    NASA Astrophysics Data System (ADS)

    Bondarev, Igor

    A configuration space method, pioneered by Landau and Herring in studies of molecular binding and magnetism, is developed to obtain universal asymptotic relations for lowest energy exciton complexes (trion, biexciton) in confined semiconductor nanostructures such as nanowires and nanotubes, as well as coupled quantum wells. Trions are shown to be more stable (have greater binding energy) than biexcitons in strongly confined quasi-1D structures with small reduced electron-hole masses. Biexcitons are more stable in less confined quasi-1D structures with large reduced electron-hole masses. The theory predicts a crossover behavior, whereby trions become less stable than biexcitons as the transverse size of the quasi-1D nanostructure increases, which might be observed on semiconducting carbon nanotubes of increasing diameters. This method is also efficient in calculating binding energies for trion-type electron-hole complexes formed by indirect excitons in double coupled quantum wells, quasi-2D nanostructures that show new interesting electroabsorption/refraction phenomena. Supported by DOE-DE-SC0007117.

  20. Final report: high resolution lensless 3D imaging of nanostructures with coherent x-rays

    SciTech Connect

    Jacobsen, Chris

    2011-04-14

    This project helped pioneer the core capabilities of coherent diffraction imaging (CDI) using X rays at synchrotron light source facilities. We developed an apparatus that was used for CDI at the Advanced Light Source, and applied it to 2D and 3D imaging of nanostructures. We also explored a number of conceptual and computational issues on the reconstruction of CDI data.

  1. One-Dimensional Nanostructures for Neutron Detection

    SciTech Connect

    Zhu, Yong; Eapen, Jacob; Hawari, Ayman

    2015-05-04

    This report consists of four parts in addition to a publication/presentation list. Part I is on electronic structure simulations on boron nitride (BN) and BCxN nanotubes using density function theory (DFT), Part II is on fabrication and characterization of nanowire sensors, Part III is on irradiation response of BN nanotubes using molecular dynamics (MD) simulations, and Part IV is on the in-situ transmission electron microscopy (TEM) study of irradiation response of BN nanotubes.

  2. Nanostructured catalyst supports

    SciTech Connect

    Zhu, Yimin; Goldman, Jay L.; Qian, Baixin; Stefan, Ionel C.

    2015-09-29

    The present invention relates to SiC nanostructures, including SiC nanopowder, SiC nanowires, and composites of SiC nanopowder and nanowires, which can be used as catalyst supports in membrane electrode assemblies and in fuel cells. The present invention also relates to composite catalyst supports comprising nanopowder and one or more inorganic nanowires for a membrane electrode assembly.

  3. Measuring Strong Nanostructures

    SciTech Connect

    Minor, Andy

    2008-01-01

    Andy Minor of Berkeley Lab's National Center for Electron Microscopy explains measuring stress and strain on nanostructures with the In Situ Microscope. More information:http://newscenter.lbl.gov/press-releases/2008/10/20/engineering-nanoparticles-for-maximum-strength/

  4. Combustion Synthesis of Nanostructures

    NASA Astrophysics Data System (ADS)

    Huczko, A.; Lange, H.; Chojecki, G.; Cudziłło, S.; Zhu, Y. Q.; Walton, D. R. M.; Kroto, H. W.; Presz, A.; Diduszko, R.

    2002-10-01

    Novel carbon and inorganic 1D nanostructures were prepared by combustion of metal-polytetrafluoroethylene (PTFE) systems in a calorimetric bomb. The high carbon yield from silicon-containing PTFE starting materials is due to the production and volatility of SiF4.

  5. Nanostructured catalyst supports

    DOEpatents

    Zhu, Yimin; Goldman, Jay L.; Qian, Baixin; Stefan, Ionel C.

    2012-10-02

    The present invention relates to SiC nanostructures, including SiC nanopowder, SiC nanowires, and composites of SiC nanopowder and nanowires, which can be used as catalyst supports in membrane electrode assemblies and in fuel cells. The present invention also relates to composite catalyst supports comprising nanopowder and one or more inorganic nanowires for a membrane electrode assembly.

  6. Use of the 'Precessions' process for prepolishing and correcting 2D & 2(1/2)D form.

    PubMed

    Walker, David D; Freeman, Richard; Morton, Roger; McCavana, Gerry; Beaucamp, Anthony

    2006-11-27

    The Precessions process polishes complex surfaces from the ground state preserving the ground-in form, and subsequently rectifies measured form errors. Our first paper introduced the technology and focused on the novel tooling. In this paper we describe the unique CNC machine tools and how they operate in polishing and correcting form. Experimental results demonstrate both the '2D' and '2(1/2)D' form-correction modes, as applied to aspheres with rotationally-symmetric target-form.

  7. Structure, Vibrational and Electronic Spectra of Heterofullerene C48(BN)6

    SciTech Connect

    Manaa, M R; Xie, R; Smith, Jr., V H

    2004-01-15

    We report the geometrical structure, vibrational, and excitation spectra of novel, fullerene - analog C{sub 48}(BN){sub 6} using density functional calculations. The lowest energy structure is one in which B-N bonding is present as boron and nitrogen occupy each of the twelve pentagons of the fullerene cage. The cluster is polar with a net dipole moment of 0.55 Debye, which indicates an enhanced tendency toward reactivity with other media. The excitation spectrum shows that the lowest transition of 1.75 eV is dipole-allowed. The optical gap of C{sub 48}(BN){sub 6} is redshifted by 1.17 eV relative to that of C{sub 60}, suggesting possible use as single-molecule fluorescent probes for various applications.

  8. Detection of genes for alkane and naphthalene catabolism in Rhodococcus sp. strain 1BN.

    PubMed

    Andreoni, V; Bernasconi, S; Colombo, M; van Beilen, J B; Cavalca, L

    2000-10-01

    Rhodococcus sp. 1BN was isolated from a contaminated site and showed various biodegradative capabilities. Besides naphthalene, strain 1BN degraded medium- (C6) and long-chain alkanes (C16-C28), benzene and toluene, alone or when the hydrocarbons were mixed in equal proportions. The nucleotide sequence of an alk polymerase chain reaction (PCR) fragment revealed a 59% nucleotide homology to the Pseudomonas oleovorans alkB gene. The nar fragments were highly homologous to genes coding for large and small subunits of cis-naphthalene 1,2-dioxygenase (narAa and narAb) and to cis-naphthalene dihydrodiol dehydrogenase (narB) from other rhodococci. The oxidation of indene to cis-(1S,2R)-1,2-dihydroxyindan by toluene-induced cells allows to hypothesize that strain 1BN also carries a toluene dioxygenase-like system. PMID:11233165

  9. Indirect doping effects from impurities in MoS2/h-BN heterostructures

    NASA Astrophysics Data System (ADS)

    Gillen, Roland; Robertson, John; Maultzsch, Janina

    2014-08-01

    We performed density functional theory calculations on heterostructures of single layers of hexagonal BN and MoS2 to assess the effect of doping in the BN sheet and of interstitial Na atoms on the electronic properties of the adjacent MoS2 layer. Our calculations predict that n doping of the boron nitride subsystem by oxygen, carbon, and sulfur impurities causes noticeable charge transfer into the conduction band of the MoS2 sheet, while p doping by beryllium and carbon leaves the molybdenum disulphide layer largely unaffected. Intercalated sodium atoms lead to a significant increase of the interlayer distance in the heterostructure and to a metallic ground state of the MoS2 subsystem. The presence of such n dopants leads to a distinct change of valence-band and conduction-band offsets, suggesting that doped h-BN remains a suitable substrate and gate material for applications of n-type MoS2.

  10. InSb photodetectors with PIN and nBn designs

    NASA Astrophysics Data System (ADS)

    Evirgen, A.; Abautret, J.; Perez, J. P.; Aït-Kaci, H.; Christol, P.; Fleury, J.; Sik, H.; Nedelcu, A.; Cluzel, R.; Cordat, A.

    2013-12-01

    InSb pin photodiodes and nBn photodetectors were fabricated by Molecular Beam epitaxy (MBE) on InSb (100) n-type substrate and characterized. MBE Growth conditions were carefully studied to obtain high quality InSb layers, exhibiting in pin photodiode design dark current density values as low as 13nA.cm-2 at -50mV and R0A product as high as 6x106 WΩcm2 at 77K. Then, a new unipolar nBn InSb/InAlSb/InSb detector structure on InSb substrate were designed in order to suppress generation-recombination dark current. The first InSb nBn devices were fabricated and preliminary electrical characterizations are reported.

  11. Growth kinetics of white graphene (h-BN) on a planarised Ni foil surface

    PubMed Central

    Cho, Hyunjin; Park, Sungchan; Won, Dong-Il; Kang, Sang Ook; Pyo, Seong-Soo; Kim, Dong-Ik; Kim, Soo Min; Kim, Hwan Chul; Kim, Myung Jong

    2015-01-01

    The morphology of the surface and the grain orientation of metal catalysts have been considered to be two important factors for the growth of white graphene (h-BN) by chemical vapour deposition (CVD). We report a correlation between the growth rate of h-BN and the orientation of the nickel grains. The surface of the nickel (Ni) foil was first polished by electrochemical polishing (ECP) and subsequently annealed in hydrogen at atmospheric pressure to suppress the effect of the surface morphology. Atmospheric annealing with hydrogen reduced the nucleation sites of h-BN, which induced a large crystal size mainly grown from the grain boundary with few other nucleation sites in the Ni foil. A higher growth rate was observed from the Ni grains that had the {110} or {100} orientation due to their higher surface energy. PMID:26156068

  12. Surface Integrity in Grinding Medium Carbon Steel with Miniature Electroplated Monolayer cBN Wheel

    NASA Astrophysics Data System (ADS)

    Vashista, Meghanshu; Kumar, Shobhit; Ghosh, Amitava; Paul, Soumitra

    2010-12-01

    An experimental study was undertaken to investigate the role of process parameters on grindability of medium carbon steel with particular emphasis on surface integrity. Grinding with miniature monolayer electroplated cBN wheels provided compressive residual stress throughout the experimental domain unlike conventional grinding. This can be attributed to desirable temperature control as the wheel takes away substantial part of grinding heat flux owing to its better thermal conductivity. Micromagnetic or Barkhausen Noise (BN) parameters correlated linearly with the residual stress indicating its applicability in assessing surface integrity of cBN ground products. Increase in maximum grit depth of cut ( h m) provided more grain elongation and surface hardness due to more chip load during chip formation.

  13. Dielectric Response and Born Dynamic Charge of BN Nanotubes from Ab Initio Finite Electric Field Calculations

    NASA Astrophysics Data System (ADS)

    Guo, Guang-Yu; Ishibashi, Shoji; Tamura, Tomoyuki; Terakura, Kiyoyuki

    2007-03-01

    Since the discovery of carbon nanotubes (CNTs) in 1991 by Iijima, carbon and other nanotubes have attracted considerable interest worldwide because of their unusual properties and also great potentials for technological applications. Though CNTs continue to attract great interest, other nanotubes such as BN nanotubes (BN-NTs) may offer different opportunities that CNTs cannot provide. In this contribution, we present the results of our recent systematic ab initio calculations of the static dielectric constant, electric polarizability, Born dynamical charge, electrostriction coefficient and piezoelectric constant of BN-NTs using the latest crystalline finite electric field theory [1]. [1] I. Souza, J. Iniguez, and D. Vanderbilt, Phys. Rev. Lett. 89, 117602 (2002); P. Umari and A. Pasquarello, Phys. Rev. Lett. 89, 157602 (2002).

  14. All-printed capacitors from graphene-BN-graphene nanosheet heterostructures

    NASA Astrophysics Data System (ADS)

    Kelly, Adam G.; Finn, David; Harvey, Andrew; Hallam, Toby; Coleman, Jonathan N.

    2016-07-01

    This work aims to develop methodologies to print pinhole-free, vertically stacked heterostructures by sequential deposition of conductive graphene and dielectric h-BN nanosheet networks. We achieve this using a combination of inkjet printing and spray-coating to fabricate dielectric capacitors in a stacked graphene/BN/graphene arrangement. Impedance spectroscopy shows such heterostructures to act as series combinations of a capacitor and a resistor, with the expected dimensional dependence of the capacitance. The areal capacitance ranges from 0.24 to 1.1 nF/cm2 with an average series resistance of ˜120 kΩ. The sprayed BN dielectrics are pinhole-free for thicknesses above 1.65 μm. This development paves the way toward fabrication of all-printed, vertically integrated, multilayer devices.

  15. Blue native polyacrylamide gel electrophoresis (BN-PAGE) for analysis of multiprotein complexes from cellular lysates.

    PubMed

    Fiala, Gina J; Schamel, Wolfgang W A; Blumenthal, Britta

    2011-01-01

    Multiprotein complexes (MPCs) play a crucial role in cell signalling, since most proteins can be found in functional or regulatory complexes with other proteins (Sali, Glaeser et al. 2003). Thus, the study of protein-protein interaction networks requires the detailed characterization of MPCs to gain an integrative understanding of protein function and regulation. For identification and analysis, MPCs must be separated under native conditions. In this video, we describe the analysis of MPCs by blue native polyacrylamide gel electrophoresis (BN-PAGE). BN-PAGE is a technique that allows separation of MPCs in a native conformation with a higher resolution than offered by gel filtration or sucrose density ultracentrifugation, and is therefore useful to determine MPC size, composition, and relative abundance (Schägger and von Jagow 1991); (Schägger, Cramer et al. 1994). By this method, proteins are separated according to their hydrodynamic size and shape in a polyacrylamide matrix. Here, we demonstrate the analysis of MPCs of total cellular lysates, pointing out that lysate dialysis is the crucial step to make BN-PAGE applicable to these biological samples. Using a combination of first dimension BN- and second dimension SDS-PAGE, we show that MPCs separated by BN-PAGE can be further subdivided into their individual constituents by SDS-PAGE. Visualization of the MPC components upon gel separation is performed by standard immunoblotting. As an example for MPC analysis by BN-PAGE, we chose the well-characterized eukaryotic 19S, 20S, and 26S proteasomes. PMID:21403626

  16. Vacuolar Iron Transporter BnMEB2 Is Involved in Enhancing Iron Tolerance of Brassica napus.

    PubMed

    Zhu, Wei; Zuo, Rong; Zhou, Rongfang; Huang, Junyan; Tang, Minqiang; Cheng, Xiaohui; Liu, Yueying; Tong, Chaobo; Xiang, Yang; Dong, Caihua; Liu, Shengyi

    2016-01-01

    Iron toxicity is a nutrient disorder that severely affects crop development and yield in some soil conditions. Vacuolar detoxification of metal stress is an important strategy for plants to survive and adapt to this adverse environment. Vacuolar iron transporter (VIT) members are involved in this process and play essential roles in iron storage and transport. In this study, we identified a rapeseed VIT gene BnMEB2 (BnaC07g30170D) homologs to Arabidopsis MEB2 (At5g24290). Transient expression analysis revealed that BnMEB2 was localized to the vacuolar membrane. Q-PCR detection showed a high expression of BnMEB2 in mature (60-day-old) leaves and could be obviously induced by exogenous iron stress in both roots and leaves. Over-expressed BnMEB2 in both Arabidopsis wild type and meb2 mutant seedlings resulted in greatly improved iron tolerability with no significant changes in the expression level of other VIT genes. The mutant meb2 grew slowly and its root hair elongation was inhibited under high iron concentration condition while BnMEB2 over-expressed transgenic plants of the mutant restored the phenotypes with apparently higher iron storage in roots and dramatically increased iron content in the whole plant. Taken together, these results suggested that BnMEB2 was a VIT gene in rapeseed which was necessary for safe storage and vacuole detoxification function of excess iron to enhance the tolerance of iron toxicity. This research sheds light on a potentially new strategy for attenuating hazardous metal stress from environment and improving iron biofortification in Brassicaceae crops.

  17. Vacuolar Iron Transporter BnMEB2 Is Involved in Enhancing Iron Tolerance of Brassica napus

    PubMed Central

    Zhu, Wei; Zuo, Rong; Zhou, Rongfang; Huang, Junyan; Tang, Minqiang; Cheng, Xiaohui; Liu, Yueying; Tong, Chaobo; Xiang, Yang; Dong, Caihua; Liu, Shengyi

    2016-01-01

    Iron toxicity is a nutrient disorder that severely affects crop development and yield in some soil conditions. Vacuolar detoxification of metal stress is an important strategy for plants to survive and adapt to this adverse environment. Vacuolar iron transporter (VIT) members are involved in this process and play essential roles in iron storage and transport. In this study, we identified a rapeseed VIT gene BnMEB2 (BnaC07g30170D) homologs to Arabidopsis MEB2 (At5g24290). Transient expression analysis revealed that BnMEB2 was localized to the vacuolar membrane. Q-PCR detection showed a high expression of BnMEB2 in mature (60-day-old) leaves and could be obviously induced by exogenous iron stress in both roots and leaves. Over-expressed BnMEB2 in both Arabidopsis wild type and meb2 mutant seedlings resulted in greatly improved iron tolerability with no significant changes in the expression level of other VIT genes. The mutant meb2 grew slowly and its root hair elongation was inhibited under high iron concentration condition while BnMEB2 over-expressed transgenic plants of the mutant restored the phenotypes with apparently higher iron storage in roots and dramatically increased iron content in the whole plant. Taken together, these results suggested that BnMEB2 was a VIT gene in rapeseed which was necessary for safe storage and vacuole detoxification function of excess iron to enhance the tolerance of iron toxicity. This research sheds light on a potentially new strategy for attenuating hazardous metal stress from environment and improving iron biofortification in Brassicaceae crops. PMID:27679642

  18. Vacuolar Iron Transporter BnMEB2 Is Involved in Enhancing Iron Tolerance of Brassica napus

    PubMed Central

    Zhu, Wei; Zuo, Rong; Zhou, Rongfang; Huang, Junyan; Tang, Minqiang; Cheng, Xiaohui; Liu, Yueying; Tong, Chaobo; Xiang, Yang; Dong, Caihua; Liu, Shengyi

    2016-01-01

    Iron toxicity is a nutrient disorder that severely affects crop development and yield in some soil conditions. Vacuolar detoxification of metal stress is an important strategy for plants to survive and adapt to this adverse environment. Vacuolar iron transporter (VIT) members are involved in this process and play essential roles in iron storage and transport. In this study, we identified a rapeseed VIT gene BnMEB2 (BnaC07g30170D) homologs to Arabidopsis MEB2 (At5g24290). Transient expression analysis revealed that BnMEB2 was localized to the vacuolar membrane. Q-PCR detection showed a high expression of BnMEB2 in mature (60-day-old) leaves and could be obviously induced by exogenous iron stress in both roots and leaves. Over-expressed BnMEB2 in both Arabidopsis wild type and meb2 mutant seedlings resulted in greatly improved iron tolerability with no significant changes in the expression level of other VIT genes. The mutant meb2 grew slowly and its root hair elongation was inhibited under high iron concentration condition while BnMEB2 over-expressed transgenic plants of the mutant restored the phenotypes with apparently higher iron storage in roots and dramatically increased iron content in the whole plant. Taken together, these results suggested that BnMEB2 was a VIT gene in rapeseed which was necessary for safe storage and vacuole detoxification function of excess iron to enhance the tolerance of iron toxicity. This research sheds light on a potentially new strategy for attenuating hazardous metal stress from environment and improving iron biofortification in Brassicaceae crops.

  19. Vacuolar Iron Transporter BnMEB2 Is Involved in Enhancing Iron Tolerance of Brassica napus.

    PubMed

    Zhu, Wei; Zuo, Rong; Zhou, Rongfang; Huang, Junyan; Tang, Minqiang; Cheng, Xiaohui; Liu, Yueying; Tong, Chaobo; Xiang, Yang; Dong, Caihua; Liu, Shengyi

    2016-01-01

    Iron toxicity is a nutrient disorder that severely affects crop development and yield in some soil conditions. Vacuolar detoxification of metal stress is an important strategy for plants to survive and adapt to this adverse environment. Vacuolar iron transporter (VIT) members are involved in this process and play essential roles in iron storage and transport. In this study, we identified a rapeseed VIT gene BnMEB2 (BnaC07g30170D) homologs to Arabidopsis MEB2 (At5g24290). Transient expression analysis revealed that BnMEB2 was localized to the vacuolar membrane. Q-PCR detection showed a high expression of BnMEB2 in mature (60-day-old) leaves and could be obviously induced by exogenous iron stress in both roots and leaves. Over-expressed BnMEB2 in both Arabidopsis wild type and meb2 mutant seedlings resulted in greatly improved iron tolerability with no significant changes in the expression level of other VIT genes. The mutant meb2 grew slowly and its root hair elongation was inhibited under high iron concentration condition while BnMEB2 over-expressed transgenic plants of the mutant restored the phenotypes with apparently higher iron storage in roots and dramatically increased iron content in the whole plant. Taken together, these results suggested that BnMEB2 was a VIT gene in rapeseed which was necessary for safe storage and vacuole detoxification function of excess iron to enhance the tolerance of iron toxicity. This research sheds light on a potentially new strategy for attenuating hazardous metal stress from environment and improving iron biofortification in Brassicaceae crops. PMID:27679642

  20. In situ study of the growth of two-dimensional palladium dendritic nanostructures using liquid-cell electron microscopy.

    PubMed

    Zhu, Guomin; Jiang, Yingying; Lin, Fang; Zhang, Hui; Jin, Chuanhong; Yuan, Jun; Yang, Deren; Zhang, Ze

    2014-08-28

    We investigated the growth of two-dimensional (2D) palladium dendritic nanostructures (DNSs) using in situ liquid-cell transmission electron microscopy (TEM). Detailed in situ and ex situ high-resolution scanning TEM (S/TEM) characterization and fractal dimension analyses reveal that the diffusion-limited aggregation and direct atomic deposition are responsible for the growth of palladium dendritic nanostructures. PMID:24938863

  1. Interaction between serotonin transporter and dopamine D2/D3 receptor radioligand measures is associated with harm avoidant symptoms in anorexia and bulimia nervosa.

    PubMed

    Bailer, Ursula F; Frank, Guido K; Price, Julie C; Meltzer, Carolyn C; Becker, Carl; Mathis, Chester A; Wagner, Angela; Barbarich-Marsteller, Nicole C; Bloss, Cinnamon S; Putnam, Karen; Schork, Nicholas J; Gamst, Anthony; Kaye, Walter H

    2013-02-28

    Individuals with anorexia nervosa (AN) and bulimia nervosa (BN) have alterations of measures of serotonin (5-HT) and dopamine (DA) function, which persist after long-term recovery and are associated with elevated harm avoidance (HA), a measure of anxiety and behavioral inhibition. Based on theories that 5-HT is an aversive motivational system that may oppose a DA-related appetitive system, we explored interactions of positron emission tomography (PET) radioligand measures that reflect portions of these systems. Twenty-seven individuals recovered (REC) from eating disorders (EDs) (7 AN-BN, 11 AN, 9 BN) and nine control women (CW) were analyzed for correlations between [(11)C]McN5652 and [(11)C]raclopride binding. There was a significant positive correlation between [(11)C]McN5652 binding potential (BP(non displaceable(ND))) and [(11)C]Raclopride BP(ND) for the dorsal caudate, antero-ventral striatum (AVS), middle caudate, and ventral and dorsal putamen. No significant correlations were found in CW. [(11)C]Raclopride BP(ND), but not [(11)C]McN5652 BP(ND), was significantly related to HA in REC EDs. A linear regression analysis showed that the interaction between [(11)C]McN5652 BP(ND) and [(11)C]raclopride BP(ND) in the dorsal putamen significantly predicted HA. This is the first study using PET and the radioligands [(11)C]McN5652 and [(11)C]raclopride to show a direct relationship between 5-HT transporter and striatal DA D2/D3 receptor binding in humans, supporting the possibility that 5-HT and DA interactions contribute to HA behaviors in EDs.

  2. B=N Units as Part of Extended π-Conjugated Oligomers and Polymers.

    PubMed

    Helten, Holger

    2016-09-01

    The replacement of C=C units by their isoelectronic and isosteric B=N units (BN/CC isosterism) in π-conjugated organic compounds, as a strategy to produce novel organic-inorganic hybrid materials, has recently been successfully transferred to π-conjugated polymers. This Concept provides an overview of the recent advances in this quickly evolving field, with a focus on synthesis, photophysical and electrochemical properties of the new polymers and related oligomers, as well as possible future applications in organic electronics and optoelectronics.

  3. Postfunctionalization of BN-embedded polycyclic aromatic compounds for fine-tuning of their molecular properties.

    PubMed

    Wang, Xiao-Ye; Yang, Dong-Chu; Zhuang, Fang-Dong; Liu, Jia-Jie; Wang, Jie-Yu; Pei, Jian

    2015-06-01

    New BN-embedded, thiophene-fused, polycyclic aromatic compounds with planar geometry were designed and synthesized. The molecules showed excellent stability and chemical robustness. Postfunctionalization on this skeleton was demonstrated with a series of electrophilic bromination, palladium-catalyzed cross-coupling, and Knoevenagel condensation reactions. The π skeleton remained intact during these late-stage transformations. The optical and electronic properties have been well tuned through incorporation of electron-rich and -deficient groups on the backbone. This work shows the great advantage of the postfunctionalization strategy on BN-containing polycyclic aromatic compounds for fast diversification and materials screening. PMID:25955825

  4. High Angular Resolution Mid-Infrared Imaging of Young Stars in Orion BN/KL

    NASA Technical Reports Server (NTRS)

    Greenhill, L. J.; Gezari, D. Y.; Danchi, W. C.; Najita, J.; Monnier, J. D.

    2004-01-01

    The authors present Keck LWS images of the Orion BN/KL star forming region obtained in the first multi-wavelength study to have 0.3--0.5 resolution from 4.7 (micro)m to 22 (micro)m. The young stellar objects designed infrared source n and radio source I are believed to dominate the BN/KL region. They have detected extended emission from a probable accretion disk around source n but infer a stellar luminosity on the order of only 2000 L(sub (center-dot)).

  5. Experimental and theoretical approach to chemical beam epitaxy of cBN

    SciTech Connect

    Komatsu, Shojiro; Satoh, Yoichiro

    1995-12-31

    Chemical beam epitaxy(CBE) method is introduced to carry out the study of cBN deposition on well-defined surfaces and the in-situ observation of the surfaces using an RHEED (reflection high energy electron diffraction)-TRAXS (total reflection angle X-ray spectroscopy) system. The CBE study is theoretically assisted by semiempirical MO calculations of nanocrystals to model hydrogenated surfaces of cBN. The (100)N was found unique because it stabilizes as fully-hydrogenated dihydride structure. On the other hand, the (100)B was predicted to stabilize as monohydride structure, which is similar to hydrogenated surface of diamond(100).

  6. Study of vibrational modes and specific heat of wurtzite phase of BN

    NASA Astrophysics Data System (ADS)

    Singh, Daljit; Sinha, M. M.

    2016-05-01

    In these days of nanotechnology the materials like BN is of utmost importance as in hexagonal phase it is among hardest materials. The phonon mode study of the materials is most important factor to find structural and thermodynamcal properties. To study the phonons de launey angular force (DAF) constant model is best suited as it involves many particle interactions. Therefore in this presentation we have studied the lattice dynamical properties and specific heat of BN in wurtzite phase using DAF model. The obtained results are in excellent agreement with existing results.

  7. Ultrafast 2D-IR spectroelectrochemistry of flavin mononucleotide

    NASA Astrophysics Data System (ADS)

    El Khoury, Youssef; Van Wilderen, Luuk J. G. W.; Bredenbeck, Jens

    2015-06-01

    We demonstrate the coupling of ultrafast two-dimensional infrared (2D-IR) spectroscopy to electrochemistry in solution and apply it to flavin mononucleotide, an important cofactor of redox proteins. For this purpose, we designed a spectroelectrochemical cell optimized for 2D-IR measurements in reflection and measured the time-dependent 2D-IR spectra of the oxidized and reduced forms of flavin mononucleotide. The data show anharmonic coupling and vibrational energy transfer between different vibrational modes in the two redox species. Such information is inaccessible with redox-controlled steady-state FTIR spectroscopy. The wide range of applications offered by 2D-IR spectroscopy, such as sub-picosecond structure determination, IR band assignment via energy transfer, disentangling reaction mixtures through band connectivity in the 2D spectra, and the measurement of solvation dynamics and chemical exchange can now be explored under controlled redox potential. The development of this technique furthermore opens new horizons for studying the dynamics of redox proteins.

  8. Ultrafast 2D-IR spectroelectrochemistry of flavin mononucleotide.

    PubMed

    El Khoury, Youssef; Van Wilderen, Luuk J G W; Bredenbeck, Jens

    2015-06-01

    We demonstrate the coupling of ultrafast two-dimensional infrared (2D-IR) spectroscopy to electrochemistry in solution and apply it to flavin mononucleotide, an important cofactor of redox proteins. For this purpose, we designed a spectroelectrochemical cell optimized for 2D-IR measurements in reflection and measured the time-dependent 2D-IR spectra of the oxidized and reduced forms of flavin mononucleotide. The data show anharmonic coupling and vibrational energy transfer between different vibrational modes in the two redox species. Such information is inaccessible with redox-controlled steady-state FTIR spectroscopy. The wide range of applications offered by 2D-IR spectroscopy, such as sub-picosecond structure determination, IR band assignment via energy transfer, disentangling reaction mixtures through band connectivity in the 2D spectra, and the measurement of solvation dynamics and chemical exchange can now be explored under controlled redox potential. The development of this technique furthermore opens new horizons for studying the dynamics of redox proteins.

  9. Mean flow and anisotropic cascades in decaying 2D turbulence

    NASA Astrophysics Data System (ADS)

    Liu, Chien-Chia; Cerbus, Rory; Gioia, Gustavo; Chakraborty, Pinaki

    2015-11-01

    Many large-scale atmospheric and oceanic flows are decaying 2D turbulent flows embedded in a non-uniform mean flow. Despite its importance for large-scale weather systems, the affect of non-uniform mean flows on decaying 2D turbulence remains unknown. In the absence of mean flow it is well known that decaying 2D turbulent flows exhibit the enstrophy cascade. More generally, for any 2D turbulent flow, all computational, experimental and field data amassed to date indicate that the spectrum of longitudinal and transverse velocity fluctuations correspond to the same cascade, signifying isotropy of cascades. Here we report experiments on decaying 2D turbulence in soap films with a non-uniform mean flow. We find that the flow transitions from the usual isotropic enstrophy cascade to a series of unusual and, to our knowledge, never before observed or predicted, anisotropic cascades where the longitudinal and transverse spectra are mutually independent. We discuss implications of our results for decaying geophysical turbulence.

  10. Sparse radar imaging using 2D compressed sensing

    NASA Astrophysics Data System (ADS)

    Hou, Qingkai; Liu, Yang; Chen, Zengping; Su, Shaoying

    2014-10-01

    Radar imaging is an ill-posed linear inverse problem and compressed sensing (CS) has been proved to have tremendous potential in this field. This paper surveys the theory of radar imaging and a conclusion is drawn that the processing of ISAR imaging can be denoted mathematically as a problem of 2D sparse decomposition. Based on CS, we propose a novel measuring strategy for ISAR imaging radar and utilize random sub-sampling in both range and azimuth dimensions, which will reduce the amount of sampling data tremendously. In order to handle 2D reconstructing problem, the ordinary solution is converting the 2D problem into 1D by Kronecker product, which will increase the size of dictionary and computational cost sharply. In this paper, we introduce the 2D-SL0 algorithm into the reconstruction of imaging. It is proved that 2D-SL0 can achieve equivalent result as other 1D reconstructing methods, but the computational complexity and memory usage is reduced significantly. Moreover, we will state the results of simulating experiments and prove the effectiveness and feasibility of our method.

  11. Ultrafast 2D NMR: an emerging tool in analytical spectroscopy.

    PubMed

    Giraudeau, Patrick; Frydman, Lucio

    2014-01-01

    Two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy is widely used in chemical and biochemical analyses. Multidimensional NMR is also witnessing increased use in quantitative and metabolic screening applications. Conventional 2D NMR experiments, however, are affected by inherently long acquisition durations, arising from their need to sample the frequencies involved along their indirect domains in an incremented, scan-by-scan nature. A decade ago, a so-called ultrafast (UF) approach was proposed, capable of delivering arbitrary 2D NMR spectra involving any kind of homo- or heteronuclear correlation, in a single scan. During the intervening years, the performance of this subsecond 2D NMR methodology has been greatly improved, and UF 2D NMR is rapidly becoming a powerful analytical tool experiencing an expanded scope of applications. This review summarizes the principles and main developments that have contributed to the success of this approach and focuses on applications that have been recently demonstrated in various areas of analytical chemistry--from the real-time monitoring of chemical and biochemical processes, to extensions in hyphenated techniques and in quantitative applications. PMID:25014342

  12. Electrostatic and electrodynamic response properties of nanostructures

    NASA Astrophysics Data System (ADS)

    Ayaz, Yuksel

    1999-11-01

    This thesis addresses the problem of nanostructure dielectric response to excitation by electric fields, both in the electrostatic c→infinity and the electrodynamic regimes. The nanostructures treated include planar quantum wells and quantum wires embedded in the vicinity of the bounding surface of the host semiconductor medium. Various cases are analyzed, including a single well or wire, a double well or wire, a lattice of N wells or wires and an infinite superlattice of wells or wires. The host medium is considered to have phonons and/or a bulk semiconductor plasma which interact with the plasmons of the embedded quantum wells or wires, and the host plasma is treated in both the local "cold" plasma regime and the nonlocal "hot" plasma regime. New hybridized quantum plasma collective modes emerge from these studies. The techniques employed here include the variational differential formulation of integral equations for the inverse dielectric function (in electrostatic case) and the dyadic Green's function (in the electrodynamic case) for the various systems described above. These integral equations are then solved in frequency-position representation by a variety of techniques depending on the geometrical features of the particular problem. Explicit closed form solutions for the inverse dielectric function or dyadic Green's function facilitate identification of the coupled collective modes in terms of their frequency poles, and the residues at the pole positions provide the relative amplitudes with which these normal modes respond to external excitation. Interesting features found include, for example, explicit formulas showing the transference of coupling of a two dimensional (2D) quantum well plasmon from a surface phonon to a bulk phonon as the 2D quantum well is displaced away from the bounding surface, deeper into the medium.

  13. Divacancy-assisted transition metal adsorption on the BN graphene and its interaction with hydrogen molecules: a theoretical study

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Wang, Hongmei; Wang, Hongxia; Zhao, Jing-xiang; Cai, Qing-hai; Wang, Xiao-Guang; Ding, Yi-hong

    2013-05-01

    We have performed first-principles calculations to study the chemical functionalization of the BN graphene with divacancy (DV) defect by 12 different transition metal (TM) atoms, including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pt, and Au. The results indicate that the DV defect can assist the adsorption of TM atoms on BN graphene. Moreover, some impurity bands are induced within the band gap of DV-BN graphene, leading to the modification of its electronic properties in various ways. Interestingly, Ti- and Co-adsorbed DV-BN graphenes are found to possess ferromagnetic characteristic, while antiferromagnetic state is preferred for V-, Mn-, and Fe-functionalized DV-BN graphenes, and the paramagnetic state is the ground state for Sc-, Cr-, Ni-, Cu, Zn-, Pt-, and Au-decorated DV-BN graphenes. Finally, aiming at evaluating the potential of these functionalized BN graphenes in hydrogen storage, we study their interaction with H2 molecules. It is found that the dispersed Sc, V, and Cr on DV-BN graphene are able to adsorb up to three H2 molecules as strongly as 0.25-0.58 eV/H2, suggesting that the three nanomaterials may be suitable candidates for hydrogen storage.

  14. Graphene based 2D-materials for supercapacitors

    NASA Astrophysics Data System (ADS)

    Palaniselvam, Thangavelu; Baek, Jong-Beom

    2015-09-01

    Ever-increasing energy demands and the depletion of fossil fuels are compelling humanity toward the development of suitable electrochemical energy conversion and storage devices to attain a more sustainable society with adequate renewable energy and zero environmental pollution. In this regard, supercapacitors are being contemplated as potential energy storage devices to afford cleaner, environmentally friendly energy. Recently, a great deal of attention has been paid to two-dimensional (2D) nanomaterials, including 2D graphene and its inorganic analogues (transition metal double layer hydroxides, chalcogenides, etc), as potential electrodes for the development of supercapacitors with high electrochemical performance. This review provides an overview of the recent progress in using these graphene-based 2D materials as potential electrodes for supercapacitors. In addition, future research trends including notable challenges and opportunities are also discussed.

  15. Perception-based reversible watermarking for 2D vector maps

    NASA Astrophysics Data System (ADS)

    Men, Chaoguang; Cao, Liujuan; Li, Xiang

    2010-07-01

    This paper presents an effective and reversible watermarking approach for digital copyright protection of 2D-vector maps. To ensure that the embedded watermark is insensitive for human perception, we only select the noise non-sensitive regions for watermark embedding by estimating vertex density within each polyline. To ensure the exact recovery of original 2D-vector map after watermark extraction, we introduce a new reversible watermarking scheme based on reversible high-frequency wavelet coefficients modification. Within the former-selected non-sensitive regions, our watermarking operates on the lower-order vertex coordinate decimals with integer wavelet transform. Such operation further reduces the visual distortion caused by watermark embedding. We have validated the effectiveness of our scheme on our real-world city river/building 2D-vector maps. We give extensive experimental comparisons with state-of-the-art methods, including embedding capability, invisibility, and robustness over watermark attacking.

  16. Secretory pathways generating immunosuppressive NKG2D ligands

    PubMed Central

    Baragaño Raneros, Aroa; Suarez-Álvarez, Beatriz; López-Larrea, Carlos

    2014-01-01

    Natural Killer Group 2 member D (NKG2D) activating receptor, present on the surface of various immune cells, plays an important role in activating the anticancer immune response by their interaction with stress-inducible NKG2D ligands (NKG2DL) on transformed cells. However, cancer cells have developed numerous mechanisms to evade the immune system via the downregulation of NKG2DL from the cell surface, including the release of NKG2DL from the cell surface in a soluble form. Here, we review the mechanisms involved in the production of soluble NKG2DL (sNKG2DL) and the potential therapeutic strategies aiming to block the release of these immunosuppressive ligands. Therapeutically enabling the NKG2D-NKG2DL interaction would promote immunorecognition of malignant cells, thus abrogating disease progression. PMID:25050215

  17. 2D bifurcations and Newtonian properties of memristive Chua's circuits

    NASA Astrophysics Data System (ADS)

    Marszalek, W.; Podhaisky, H.

    2016-01-01

    Two interesting properties of Chua's circuits are presented. First, two-parameter bifurcation diagrams of Chua's oscillatory circuits with memristors are presented. To obtain various 2D bifurcation images a substantial numerical effort, possibly with parallel computations, is needed. The numerical algorithm is described first and its numerical code for 2D bifurcation image creation is available for free downloading. Several color 2D images and the corresponding 1D greyscale bifurcation diagrams are included. Secondly, Chua's circuits are linked to Newton's law φ ''= F(t,φ,φ')/m with φ=\\text{flux} , constant m > 0, and the force term F(t,φ,φ') containing memory terms. Finally, the jounce scalar equations for Chua's circuits are also discussed.

  18. Focusing surface wave imaging with flexible 2D array

    NASA Astrophysics Data System (ADS)

    Zhou, Shiyuan; Fu, Junqiang; Li, Zhe; Xu, Chunguang; Xiao, Dingguo; Wang, Shaohan

    2016-04-01

    Curved surface is widely exist in key parts of energy and power equipment, such as, turbine blade cylinder block and so on. Cycling loading and harsh working condition of enable fatigue cracks appear on the surface. The crack should be found in time to avoid catastrophic damage to the equipment. A flexible 2D array transducer was developed. 2D Phased Array focusing method (2DPA), Mode-Spatial Double Phased focusing method (MSDPF) and the imaging method using the flexible 2D array probe are studied. Experiments using these focusing and imaging method are carried out. Surface crack image is obtained with both 2DPA and MSDPF focusing method. It have been proved that MSDPF can be more adaptable for curved surface and more calculate efficient than 2DPA.

  19. Manganese Nanostructures and Magnetism

    NASA Astrophysics Data System (ADS)

    Simov, Kirie Rangelov

    The primary goal of this study is to incorporate adatoms with large magnetic moment, such as Mn, into two technologically significant group IV semiconductor (SC) matrices, e.g. Si and Ge. For the first time in the world, we experimentally demonstrate Mn doping by embedding nanostructured thin layers, i.e. delta-doping. The growth is observed by in-situ scanning tunneling microscopy (STM), which combines topographic and electronic information in a single image. We investigate the initial stages of Mn monolayer growth on a Si(100)(2x1) surface reconstruction, develop methods for classification of nanostructure types for a range of surface defect concentrations (1.0 to 18.2%), and subsequently encapsulate the thin Mn layer in a SC matrix. These experiments are instrumental in generating a surface processing diagram for self-assembly of monoatomic Mn-wires. The role of surface vacancies has also been studied by kinetic Monte Carlo modeling and the experimental observations are compared with the simulation results, leading to the conclusion that Si(100)(2x1) vacancies serve as nucleation centers in the Mn-Si system. Oxide formation, which happens readily in air, is detrimental to ferromagnetism and lessens the magnetic properties of the nanostructures. Therefore, the protective SC cap, composed of either Si or Ge, serves a dual purpose: it is both the embedding matrix for the Mn nanostructured thin film and a protective agent for oxidation. STM observations of partially deposited caps ensure that the nanostructures remain intact during growth. Lastly, the relationship between magnetism and nanostructure types is established by an in-depth study using x-ray magnetic circular dichroism (XMCD). This sensitive method detects signals even at coverages less than one atomic layer of Mn. XMCD is capable of discerning which chemical compounds contribute to the magnetic moment of the system, and provides a ratio between the orbital and spin contributions. Depending on the amount

  20. Antibacterial Au nanostructured surfaces

    NASA Astrophysics Data System (ADS)

    Wu, Songmei; Zuber, Flavia; Brugger, Juergen; Maniura-Weber, Katharina; Ren, Qun

    2016-01-01

    We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It was found that all the Au nanostructures, regardless their shapes, exhibited similar excellent antibacterial properties. A comparison of live cells attached to nanotopographic surfaces showed that the number of live S. aureus cells was <1% of that from flat and rough reference surfaces. Our micro/nanofabrication process is a scalable approach based on cost-efficient self-organization and provides potential for further developing functional surfaces to study the behavior of microbes on nanoscale topographies.We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It

  1. Engineering DNA self-assemblies as templates for functional nanostructures.

    PubMed

    Wang, Zhen-Gang; Ding, Baoquan

    2014-06-17

    CONSPECTUS: DNA is a well-known natural molecule that carries genetic information. In recent decades, DNA has been used beyond its genetic role as a building block for the construction of engineering materials. Many strategies, such as tile assembly, scaffolded origami and DNA bricks, have been developed to design and produce 1D, 2D, and 3D architectures with sophisticated morphologies. Moreover, the spatial addressability of DNA nanostructures and sequence-dependent recognition enable functional elements to be precisely positioned and allow for the control of chemical and biochemical processes. The spatial arrangement of heterogeneous components using DNA nanostructures as the templates will aid in the fabrication of functional materials that are difficult to produce using other methods and can address scientific and technical challenges in interdisciplinary research. For example, plasmonic nanoparticles can be assembled into well-defined configurations with high resolution limit while exhibiting desirable collective behaviors, such as near-field enhancement. Conducting metallic or polymer patterns can be synthesized site-specifically on DNA nanostructures to form various controllable geometries, which could be used for electronic nanodevices. Biomolecules can be arranged into organized networks to perform programmable biological functionalities, such as distance-dependent enzyme-cascade activities. DNA nanostructures can carry multiple cytoactive molecules and cell-targeting groups simultaneously to address medical issues such as targeted therapy and combined administration. In this Account, we describe recent advances in the functionalization of DNA nanostructures in different fashions based on our research efforts in nanophotonics, nanoelectronics, and nanomedicine. We show that DNA origami nanostructures can guide the assembly of achiral, spherical, metallic nanoparticles into nature-mimicking chiral geometries through hybridization between complementary DNA

  2. Radiative heat transfer in 2D Dirac materials.

    PubMed

    Rodriguez-López, Pablo; Tse, Wang-Kong; Dalvit, Diego A R

    2015-06-01

    We compute the radiative heat transfer between two sheets of 2D Dirac materials, including topological Chern insulators and graphene, within the framework of the local approximation for the optical response of these materials. In this approximation, which neglects spatial dispersion, we derive both numerically and analytically the short-distance asymptotic of the near-field heat transfer in these systems, and show that it scales as the inverse of the distance between the two sheets. Finally, we discuss the limitations to the validity of this scaling law imposed by spatial dispersion in 2D Dirac materials. PMID:25965703

  3. Quantum process tomography by 2D fluorescence spectroscopy

    SciTech Connect

    Pachón, Leonardo A.; Marcus, Andrew H.; Aspuru-Guzik, Alán

    2015-06-07

    Reconstruction of the dynamics (quantum process tomography) of the single-exciton manifold in energy transfer systems is proposed here on the basis of two-dimensional fluorescence spectroscopy (2D-FS) with phase-modulation. The quantum-process-tomography protocol introduced here benefits from, e.g., the sensitivity enhancement ascribed to 2D-FS. Although the isotropically averaged spectroscopic signals depend on the quantum yield parameter Γ of the doubly excited-exciton manifold, it is shown that the reconstruction of the dynamics is insensitive to this parameter. Applications to foundational and applied problems, as well as further extensions, are discussed.

  4. On 2D bisection method for double eigenvalue problems

    SciTech Connect

    Ji, X.

    1996-06-01

    The two-dimensional bisection method presented in (SIAM J. Matrix Anal. Appl. 13(4), 1085 (1992)) is efficient for solving a class of double eigenvalue problems. This paper further extends the 2D bisection method of full matrix cases and analyses its stability. As in a single parameter case, the 2D bisection method is very stable for the tridiagonal matrix triples satisfying the symmetric-definite condition. Since the double eigenvalue problems arise from two-parameter boundary value problems, an estimate of the discretization error in eigenpairs is also given. Some numerical examples are included. 42 refs., 1 tab.

  5. Design of the LRP airfoil series using 2D CFD

    NASA Astrophysics Data System (ADS)

    Zahle, Frederik; Bak, Christian; Sørensen, Niels N.; Vronsky, Tomas; Gaudern, Nicholas

    2014-06-01

    This paper describes the design and wind tunnel testing of a high-Reynolds number, high lift airfoil series designed for wind turbines. The airfoils were designed using direct gradient- based numerical multi-point optimization based on a Bezier parameterization of the shape, coupled to the 2D Navier-Stokes flow solver EllipSys2D. The resulting airfoils, the LRP2-30 and LRP2-36, achieve both higher operational lift coefficients and higher lift to drag ratios compared to the equivalent FFA-W3 airfoils.

  6. Laboratory Experiments On Continually Forced 2d Turbulence

    NASA Astrophysics Data System (ADS)

    Wells, M. G.; Clercx, H. J. H.; Van Heijst, G. J. F.

    There has been much recent interest in the advection of tracers by 2D turbulence in geophysical flows. While there is a large body of literature on decaying 2D turbulence or forced 2D turbulence in unbounded domains, there have been very few studies of forced turbulence in bounded domains. In this study we present new experimental results from a continuously forced quasi 2D turbulent field. The experiments are performed in a square Perspex tank filled with water. The flow is made quasi 2D by a steady background rotation. The rotation rate of the tank has a small (<8 %) sinusoidal perturbation which leads to the periodic formation of eddies in the corners of the tank. When the oscillation period of the perturbation is greater than an eddy roll-up time-scale, dipole structures are observed to form. The dipoles can migrate away from the walls, and the interior of the tank is continually filled with vortexs. From experimental visualizations the length scale of the vortexs appears to be largely controlled by the initial formation mechanism and large scale structures are not observed to form at large times. Thus the experiments provide a simple way of cre- ating a continuously forced 2D turbulent field. The resulting structures are in contrast with most previous laboratory experiments on 2D turbulence which have investigated decaying turbulence and have observed the formations of large scale structure. In these experiments, decaying turbulence had been produced by a variety of methods such as the decaying turbulence in the wake of a comb of rods (Massen et al 1999), organiza- tion of vortices in thin conducting liquids (Cardoso et al 1994) or in rotating systems where there are sudden changes in angular rotation rate (Konijnenberg et al 1998). Results of dye visualizations, particle tracking experiments and a direct numerical simulation will be presented and discussed in terms of their oceanographic application. Bibliography Cardoso,O. Marteau, D. &Tabeling, P

  7. EM 2dV1.0.F

    2012-01-05

    Code is for a layered electric medium with 2d structure. Includes air-earth interface at node z=2.. The electric ex and ez fields are calculated on edges of elemental grid and magnetic field hy is calculated on the face of the elemental grid. The code allows for a layered earth with 2d structures. Solutions of coupled first order Maxwell's equations are solved in the two dimensional environment using a finite- difference scheme on a staggered spationamore » and temporal grid.« less

  8. Noninvasive deep Raman detection with 2D correlation analysis

    NASA Astrophysics Data System (ADS)

    Kim, Hyung Min; Park, Hyo Sun; Cho, Youngho; Jin, Seung Min; Lee, Kang Taek; Jung, Young Mee; Suh, Yung Doug

    2014-07-01

    The detection of poisonous chemicals enclosed in daily necessaries is prerequisite essential for homeland security with the increasing threat of terrorism. For the detection of toxic chemicals, we combined a sensitive deep Raman spectroscopic method with 2D correlation analysis. We obtained the Raman spectra from concealed chemicals employing spatially offset Raman spectroscopy in which incident line-shaped light experiences multiple scatterings before being delivered to inner component and yielding deep Raman signal. Furthermore, we restored the pure Raman spectrum of each component using 2D correlation spectroscopic analysis with chemical inspection. Using this method, we could elucidate subsurface component under thick powder and packed contents in a bottle.

  9. Self-dual strings and 2D SYM

    NASA Astrophysics Data System (ADS)

    Hosomichi, Kazuo; Lee, Sungjay

    2015-01-01

    We study the system of M2-branes suspended between parallel M5-branes using ABJM model with a natural half-BPS boundary condition. For small separation between M5-branes, the worldvolume theory is shown to reduce to a 2D super Yang-Mills theory with some similarity to q-deformed Yang-Mills theory. The gauge coupling is related to the position of the branes in an interesting manner. The theory is considerably different from the 2D theory proposed for multiple "M-strings". We make a detailed comparison of elliptic genus of the two descriptions and find only a partial agreement.

  10. Finite temperature corrections in 2d integrable models

    NASA Astrophysics Data System (ADS)

    Caselle, M.; Hasenbusch, M.

    2002-09-01

    We study the finite size corrections for the magnetization and the internal energy of the 2d Ising model in a magnetic field by using transfer matrix techniques. We compare these corrections with the functional form recently proposed by Delfino and LeClair-Mussardo for the finite temperature behaviour of one-point functions in integrable 2d quantum field theories. We find a perfect agreement between theoretical expectations and numerical results. Assuming the proposed functional form as an input in our analysis we obtain a relevant improvement in the precision of the continuum limit estimates of both quantities.

  11. 2dF grows up: Echidna for the AAT

    NASA Astrophysics Data System (ADS)

    McGrath, Andrew; Barden, Sam; Miziarski, Stan; Rambold, William; Smith, Greg

    2008-07-01

    We present the concept design of a new fibre positioner and spectrograph system for the Anglo-Australian Telescope, as a proposed enhancement to the Anglo-Australian Observatory's well-known 2dF facility. A four-fold multiplex enhancement is accomplished by replacing the 400-fibre 2dF fibre positioning robot with a 1600-fibre Echidna unit, feeding three clones of the AAOmega optical spectrograph. Such a facility has the capability of a redshift 1 survey of a large fraction of the southern sky, collecting five to ten thousand spectra per night for a million-galaxy survey.

  12. Radiative heat transfer in 2D Dirac materials

    DOE PAGES

    Rodriguez-López, Pablo; Tse, Wang -Kong; Dalvit, Diego A. R.

    2015-05-12

    We compute the radiative heat transfer between two sheets of 2D Dirac materials, including topological Chern insulators and graphene, within the framework of the local approximation for the optical response of these materials. In this approximation, which neglects spatial dispersion, we derive both numerically and analytically the short-distance asymptotic of the near-field heat transfer in these systems, and show that it scales as the inverse of the distance between the two sheets. In conclusion, we discuss the limitations to the validity of this scaling law imposed by spatial dispersion in 2D Dirac materials.

  13. Nomenclature for human CYP2D6 alleles.

    PubMed

    Daly, A K; Brockmöller, J; Broly, F; Eichelbaum, M; Evans, W E; Gonzalez, F J; Huang, J D; Idle, J R; Ingelman-Sundberg, M; Ishizaki, T; Jacqz-Aigrain, E; Meyer, U A; Nebert, D W; Steen, V M; Wolf, C R; Zanger, U M

    1996-06-01

    To standardize CYP2D6 allele nomenclature, and to conform with international human gene nomenclature guidelines, an alternative to the current arbitrary system is described. Based on recommendations for human genome nomenclature, we propose that alleles be designated by CYP2D6 followed by an asterisk and a combination of roman letters and arabic numerals distinct for each allele with the number specifying the key mutation and, where appropriate, a letter specifying additional mutations. Criteria for classification as a separate allele and protein nomenclature are also presented. PMID:8807658

  14. Spreading dynamics of 2D dipolar Langmuir monolayer phases.

    PubMed

    Heinig, P; Wurlitzer, S; Fischer, Th M

    2004-07-01

    We study the spreading of a liquid 2D dipolar droplet in a Langmuir monolayer. Interfacial tensions (line tensions) and microscopic contact angles depend on the scale on which they are probed and obey a scaling law. Assuming rapid equilibration of the microscopic contact angle and ideal slippage of the 2D solid/liquid and solid/gas boundary, the driving force of spreading is merely expressed by the shape-dependent long-range interaction integrals. We obtain good agreement between experiment and numerical simulations using this theory. PMID:15278693

  15. Evaluation of 2D ceramic matrix composites in aeroconvective environments

    NASA Technical Reports Server (NTRS)

    Riccitiello, Salvatore R.; Love, Wendell L.; Balter-Peterson, Aliza

    1992-01-01

    An evaluation is conducted of a novel ceramic-matrix composite (CMC) material system for use in the aeroconvective-heating environments encountered by the nose caps and wing leading edges of such aerospace vehicles as the Space Shuttle, during orbit-insertion and reentry from LEO. These CMCs are composed of an SiC matrix that is reinforced with Nicalon, Nextel, or carbon refractory fibers in a 2D architecture. The test program conducted for the 2D CMCs gave attention to their subsurface oxidation.

  16. Quantum process tomography by 2D fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Pachón, Leonardo A.; Marcus, Andrew H.; Aspuru-Guzik, Alán

    2015-06-01

    Reconstruction of the dynamics (quantum process tomography) of the single-exciton manifold in energy transfer systems is proposed here on the basis of two-dimensional fluorescence spectroscopy (2D-FS) with phase-modulation. The quantum-process-tomography protocol introduced here benefits from, e.g., the sensitivity enhancement ascribed to 2D-FS. Although the isotropically averaged spectroscopic signals depend on the quantum yield parameter Γ of the doubly excited-exciton manifold, it is shown that the reconstruction of the dynamics is insensitive to this parameter. Applications to foundational and applied problems, as well as further extensions, are discussed.

  17. Synthesis and determination of the structural and optical characteristics of cBN micropowder with Eu{sup 3+} ions

    SciTech Connect

    Leonchik, S. V. Karotki, A. V.

    2013-10-15

    Cubic boron-nitride micropowder with Eu{sup 3+} ions (cBN:Eu) is synthesized under conditions of high pressures and temperatures. The structural, morphological, chemical, and optical characteristics of the cBN:Eu micropowder are studied using X-ray diffraction, energy-dispersive X-ray spectral microanalysis, photoluminescence, and optical transmission methods. It is found that the cBN:Eu lattice parameter is {approx}3.615 A. The intense red luminescence of the cBN:Eu micropowder (red glow), measured in the visible region of the spectrum in the range from 550 to 750 nm, is attributed to intracenter 4f-electron transitions of the Eu{sup 3+} ions. The possible nature of the cBN:Eu micropowder luminescence is discussed.

  18. 2D molybdenum disulphide (2D-MoS2) modified electrodes explored towards the oxygen reduction reaction.

    PubMed

    Rowley-Neale, Samuel J; Fearn, Jamie M; Brownson, Dale A C; Smith, Graham C; Ji, Xiaobo; Banks, Craig E

    2016-08-21

    Two-dimensional molybdenum disulphide nanosheets (2D-MoS2) have proven to be an effective electrocatalyst, with particular attention being focused on their use towards increasing the efficiency of the reactions associated with hydrogen fuel cells. Whilst the majority of research has focused on the Hydrogen Evolution Reaction (HER), herein we explore the use of 2D-MoS2 as a potential electrocatalyst for the much less researched Oxygen Reduction Reaction (ORR). We stray from literature conventions and perform experiments in 0.1 M H2SO4 acidic electrolyte for the first time, evaluating the electrochemical performance of the ORR with 2D-MoS2 electrically wired/immobilised upon several carbon based electrodes (namely; Boron Doped Diamond (BDD), Edge Plane Pyrolytic Graphite (EPPG), Glassy Carbon (GC) and Screen-Printed Electrodes (SPE)) whilst exploring a range of 2D-MoS2 coverages/masses. Consequently, the findings of this study are highly applicable to real world fuel cell applications. We show that significant improvements in ORR activity can be achieved through the careful selection of the underlying/supporting carbon materials that electrically wire the 2D-MoS2 and utilisation of an optimal mass of 2D-MoS2. The ORR onset is observed to be reduced to ca. +0.10 V for EPPG, GC and SPEs at 2D-MoS2 (1524 ng cm(-2) modification), which is far closer to Pt at +0.46 V compared to bare/unmodified EPPG, GC and SPE counterparts. This report is the first to demonstrate such beneficial electrochemical responses in acidic conditions using a 2D-MoS2 based electrocatalyst material on a carbon-based substrate (SPEs in this case). Investigation of the beneficial reaction mechanism reveals the ORR to occur via a 4 electron process in specific conditions; elsewhere a 2 electron process is observed. This work offers valuable insights for those wishing to design, fabricate and/or electrochemically test 2D-nanosheet materials towards the ORR. PMID:27448174

  19. A novel improved method for analysis of 2D diffusion-relaxation data--2D PARAFAC-Laplace decomposition.

    PubMed

    Tønning, Erik; Polders, Daniel; Callaghan, Paul T; Engelsen, Søren B

    2007-09-01

    This paper demonstrates how the multi-linear PARAFAC model can with advantage be used to decompose 2D diffusion-relaxation correlation NMR spectra prior to 2D-Laplace inversion to the T(2)-D domain. The decomposition is advantageous for better interpretation of the complex correlation maps as well as for the quantification of extracted T(2)-D components. To demonstrate the new method seventeen mixtures of wheat flour, starch, gluten, oil and water were prepared and measured with a 300 MHz nuclear magnetic resonance (NMR) spectrometer using a pulsed gradient stimulated echo (PGSTE) pulse sequence followed by a Carr-Purcell-Meiboom-Gill (CPMG) pulse echo train. By varying the gradient strength, 2D diffusion-relaxation data were recorded for each sample. From these double exponentially decaying relaxation data the PARAFAC algorithm extracted two unique diffusion-relaxation components, explaining 99.8% of the variation in the data set. These two components were subsequently transformed to the T(2)-D domain using 2D-inverse Laplace transformation and quantitatively assigned to the oil and water components of the samples. The oil component was one distinct distribution with peak intensity at D=3 x 10(-12) m(2) s(-1) and T(2)=180 ms. The water component consisted of two broad populations of water molecules with diffusion coefficients and relaxation times centered around correlation pairs: D=10(-9) m(2) s(-1), T(2)=10 ms and D=3 x 10(-13) m(2) s(-1), T(2)=13 ms. Small spurious peaks observed in the inverse Laplace transformation of original complex data were effectively filtered by the PARAFAC decomposition and thus considered artefacts from the complex Laplace transformation. The oil-to-water ratio determined by PARAFAC followed by 2D-Laplace inversion was perfectly correlated with known oil-to-water ratio of the samples. The new method of using PARAFAC prior to the 2D-Laplace inversion proved to have superior potential in analysis of diffusion-relaxation spectra, as it

  20. 2D molybdenum disulphide (2D-MoS2) modified electrodes explored towards the oxygen reduction reaction.

    PubMed

    Rowley-Neale, Samuel J; Fearn, Jamie M; Brownson, Dale A C; Smith, Graham C; Ji, Xiaobo; Banks, Craig E

    2016-08-21

    Two-dimensional molybdenum disulphide nanosheets (2D-MoS2) have proven to be an effective electrocatalyst, with particular attention being focused on their use towards increasing the efficiency of the reactions associated with hydrogen fuel cells. Whilst the majority of research has focused on the Hydrogen Evolution Reaction (HER), herein we explore the use of 2D-MoS2 as a potential electrocatalyst for the much less researched Oxygen Reduction Reaction (ORR). We stray from literature conventions and perform experiments in 0.1 M H2SO4 acidic electrolyte for the first time, evaluating the electrochemical performance of the ORR with 2D-MoS2 electrically wired/immobilised upon several carbon based electrodes (namely; Boron Doped Diamond (BDD), Edge Plane Pyrolytic Graphite (EPPG), Glassy Carbon (GC) and Screen-Printed Electrodes (SPE)) whilst exploring a range of 2D-MoS2 coverages/masses. Consequently, the findings of this study are highly applicable to real world fuel cell applications. We show that significant improvements in ORR activity can be achieved through the careful selection of the underlying/supporting carbon materials that electrically wire the 2D-MoS2 and utilisation of an optimal mass of 2D-MoS2. The ORR onset is observed to be reduced to ca. +0.10 V for EPPG, GC and SPEs at 2D-MoS2 (1524 ng cm(-2) modification), which is far closer to Pt at +0.46 V compared to bare/unmodified EPPG, GC and SPE counterparts. This report is the first to demonstrate such beneficial electrochemical responses in acidic conditions using a 2D-MoS2 based electrocatalyst material on a carbon-based substrate (SPEs in this case). Investigation of the beneficial reaction mechanism reveals the ORR to occur via a 4 electron process in specific conditions; elsewhere a 2 electron process is observed. This work offers valuable insights for those wishing to design, fabricate and/or electrochemically test 2D-nanosheet materials towards the ORR.