Science.gov

Sample records for amorphous biophotonic nanostructure

  1. Self-assembly of amorphous biophotonic nanostructures by phase separation

    SciTech Connect

    Dufresne, Eric R.; Noh, Heeso; Saranathan, Vinodkumar; Mochrie, Simon G.J.; Cao, Hui; Prum, Richard O.

    2009-04-23

    Some of the most vivid colors in the animal kingdom are created not by pigments, but by wavelength-selective scattering of light from nanostructures. Here we investigate quasi-ordered nanostructures of avian feather barbs which produce vivid non-iridescent colors. These {beta}-keratin and air nanostructures are found in two basic morphologies: tortuous channels and amorphous packings of spheres. Each class of nanostructure is isotropic and has a pronounced characteristic length scale of variation in composition. These local structural correlations lead to strong backscattering over a narrow range of optical frequencies and little variation with angle of incidence. Such optical properties play important roles in social and sexual communication. To be effective, birds need to precisely control the development of these nanoscale structures, yet little is known about how they grow. We hypothesize that multiple lineages of birds have convergently evolved to exploit phase separation and kinetic arrest to self-assemble spongy color-producing nanostructures in feather barbs. Observed avian nanostructures are strikingly similar to those self-assembled during the phase separation of fluid mixtures; the channel and sphere morphologies are characteristic of phase separation by spinodal decomposition and nucleation and growth, respectively. These unstable structures are locked-in by the kinetic arrest of the {beta}-keratin matrix, likely through the entanglement or cross-linking of supermolecular {beta}-keratin fibers. Using the power of self-assembly, birds can robustly realize a diverse range of nanoscopic morphologies with relatively small physical and chemical changes during feather development.

  2. Electron tomography, three-dimensional Fourier analysis and colour prediction of a three-dimensional amorphous biophotonic nanostructure

    PubMed Central

    Shawkey, Matthew D.; Saranathan, Vinodkumar; Pálsdóttir, Hildur; Crum, John; Ellisman, Mark H.; Auer, Manfred; Prum, Richard O.

    2009-01-01

    Organismal colour can be created by selective absorption of light by pigments or light scattering by photonic nanostructures. Photonic nanostructures may vary in refractive index over one, two or three dimensions and may be periodic over large spatial scales or amorphous with short-range order. Theoretical optical analysis of three-dimensional amorphous nanostructures has been challenging because these structures are difficult to describe accurately from conventional two-dimensional electron microscopy alone. Intermediate voltage electron microscopy (IVEM) with tomographic reconstruction adds three-dimensional data by using a high-power electron beam to penetrate and image sections of material sufficiently thick to contain a significant portion of the structure. Here, we use IVEM tomography to characterize a non-iridescent, three-dimensional biophotonic nanostructure: the spongy medullary layer from eastern bluebird Sialia sialis feather barbs. Tomography and three-dimensional Fourier analysis reveal that it is an amorphous, interconnected bicontinuous matrix that is appropriately ordered at local spatial scales in all three dimensions to coherently scatter light. The predicted reflectance spectra from the three-dimensional Fourier analysis are more precise than those predicted by previous two-dimensional Fourier analysis of transmission electron microscopy sections. These results highlight the usefulness, and obstacles, of tomography in the description and analysis of three-dimensional photonic structures. PMID:19158016

  3. Structural Diversity of Self-Assembled Iridescent Arthropod Biophotonic Nanostructures

    NASA Astrophysics Data System (ADS)

    Saranathan, Vinod Kumar; Prum, Richard O.

    2015-03-01

    Many organisms, especially arthropods, produce vivid interference colors using diverse mesoscopic (100-350 nm) integumentary biophotonic nanostructures that are increasingly being investigated for technological applications. Despite a century of interest, we lack precise structural knowledge of many biophotonic nanostructures and mechanisms controlling their development, when such knowledge can open novel biomimetic routes to facilely self-assemble tunable, multi-functional materials. Here, we use synchrotron small angle X-ray scattering and electron microscopy to characterize the photonic nanostructure of 140 iridescent integumentary scales and setae from 127 species of terrestrial arthropods in 85 genera from 5 orders. We report a rich nanostructural diversity, including triply-periodic bicontinuous networks, close-packed spheres, inverse columnar, perforated lamellar, and disordered sponge-like morphologies, commonly observed as stable phases of amphiphilic surfactants, block copolymer, and lyotropic lipid-water systems. Diverse arthropod lineages appear to have independently evolved to utilize the self-assembly of infolding bilayer membranes to develop biophotonic nanostructures that span the phase-space of amphiphilic morphologies, but at optical length scales.

  4. Structural Diversity of Arthropod Biophotonic Nanostructures Spans Amphiphilic Phase-Space

    SciTech Connect

    Saranathan, Vinod Kumar; Seago, Ainsley E.; Sandy, Alec; Narayanan, Suresh; Mochrie, Simon G.J.; Dufresne, Eric R.; Cao, Hui; Osuji, Chinedum O.; Prum, Richard Owen

    2015-05-04

    Many organisms, especially arthropods, produce vivid interference colors using diverse mesoscopic (100-350 nm) integumentary biophotonic nanostructures that are increasingly being investigated for technological applications. Despite a century of interest, precise structural knowledge of many biophotonic nanostructures and the mechanisms controlling their development remain tentative, when such knowledge can open novel biomimetic routes to facilely self-assemble tunable, multifunctional materials. Here, we use synchrotron small-angle X-ray scattering and electron microscopy to characterize the photonic nanostructure of 140 integumentary scales and setae from ~127 species of terrestrial arthropods in 85 genera from 5 orders. We report a rich nanostructural diversity, including triply periodic bicontinuous networks, close-packed spheres, inverse columnar, perforated lamellar, and disordered spongelike morphologies, commonly observed as stable phases of amphiphilic surfactants, block copolymer, and lyotropic lipid-water systems. Diverse arthropod lineages appear to have independently evolved to utilize the self-assembly of infolding lipid-bilayer membranes to develop biophotonic nanostructures that span the phase-space of amphiphilic morphologies, but at optical length scales.

  5. Structural Diversity of Arthropod Biophotonic Nanostructures Spans Amphiphilic Phase-Space.

    PubMed

    Saranathan, Vinodkumar; Seago, Ainsley E; Sandy, Alec; Narayanan, Suresh; Mochrie, Simon G J; Dufresne, Eric R; Cao, Hui; Osuji, Chinedum O; Prum, Richard O

    2015-06-10

    Many organisms, especially arthropods, produce vivid interference colors using diverse mesoscopic (100-350 nm) integumentary biophotonic nanostructures that are increasingly being investigated for technological applications. Despite a century of interest, precise structural knowledge of many biophotonic nanostructures and the mechanisms controlling their development remain tentative, when such knowledge can open novel biomimetic routes to facilely self-assemble tunable, multifunctional materials. Here, we use synchrotron small-angle X-ray scattering and electron microscopy to characterize the photonic nanostructure of 140 integumentary scales and setae from ∼127 species of terrestrial arthropods in 85 genera from 5 orders. We report a rich nanostructural diversity, including triply periodic bicontinuous networks, close-packed spheres, inverse columnar, perforated lamellar, and disordered spongelike morphologies, commonly observed as stable phases of amphiphilic surfactants, block copolymer, and lyotropic lipid-water systems. Diverse arthropod lineages appear to have independently evolved to utilize the self-assembly of infolding lipid-bilayer membranes to develop biophotonic nanostructures that span the phase-space of amphiphilic morphologies, but at optical length scales.

  6. Nanostructures having crystalline and amorphous phases

    DOEpatents

    Mao, Samuel S; Chen, Xiaobo

    2015-04-28

    The present invention includes a nanostructure, a method of making thereof, and a method of photocatalysis. In one embodiment, the nanostructure includes a crystalline phase and an amorphous phase in contact with the crystalline phase. Each of the crystalline and amorphous phases has at least one dimension on a nanometer scale. In another embodiment, the nanostructure includes a nanoparticle comprising a crystalline phase and an amorphous phase. The amorphous phase is in a selected amount. In another embodiment, the nanostructure includes crystalline titanium dioxide and amorphous titanium dioxide in contact with the crystalline titanium dioxide. Each of the crystalline and amorphous titanium dioxide has at least one dimension on a nanometer scale.

  7. Nanostructural characterization of amorphous diamondlike carbon films

    SciTech Connect

    SIEGAL,MICHAEL P.; TALLANT,DAVID R.; MARTINEZ-MIRANDA,L.J.; BARBOUR,J. CHARLES; SIMPSON,REGINA L.; OVERMYER,DONALD L.

    2000-01-27

    Nanostructural characterization of amorphous diamondlike carbon (a-C) films grown on silicon using pulsed-laser deposition (PLD) is correlated to both growth energetic and film thickness. Raman spectroscopy and x-ray reflectivity probe both the topological nature of 3- and 4-fold coordinated carbon atom bonding and the topographical clustering of their distributions within a given film. In general, increasing the energetic of PLD growth results in films becoming more ``diamondlike'', i.e. increasing mass density and decreasing optical absorbance. However, these same properties decrease appreciably with thickness. The topology of carbon atom bonding is different for material near the substrate interface compared to material within the bulk portion of an a-C film. A simple model balancing the energy of residual stress and the free energies of resulting carbon topologies is proposed to provide an explanation of the evolution of topographical bonding clusters in a growing a-C film.

  8. Domain morphology, boundaries, and topological defects in biophotonic gyroid nanostructures of butterfly wing scales

    PubMed Central

    Singer, Andrej; Boucheron, Leandra; Dietze, Sebastian H.; Jensen, Katharine E.; Vine, David; McNulty, Ian; Dufresne, Eric R.; Prum, Richard O.; Mochrie, Simon G. J.; Shpyrko, Oleg G.

    2016-01-01

    Many organisms in nature have evolved sophisticated cellular mechanisms to produce photonic nanostructures and, in recent years, diverse crystalline symmetries have been identified and related to macroscopic optical properties. However, because we know little about the distributions of domain sizes, the orientations of photonic crystals, and the nature of defects in these structures, we are unable to make the connection between the nanostructure and its development and functionality. We report on nondestructive studies of the morphology of chitinous photonic crystals in butterfly wing scales. Using spatially and angularly resolved x-ray diffraction, we find that the domains are highly oriented with respect to the whole scale, indicating growth from scale boundaries. X-ray coherent diffractive imaging reveals two types of crystalline domain interfaces: abrupt changes between domains emerging from distinct nucleation sites and smooth transitions with edge dislocations presumably resulting from internal stresses during nanostructure development. Our study of the scale structure reveals new aspects of photonic crystal growth in butterfly wings and shows their similarity to block copolymer materials. It opens new avenues to exploration of fundamental processes underlying the growth of biological photonic nanostructures in a variety of species. PMID:27386575

  9. Double scattering of light from Biophotonic Nanostructures with short-range order.

    PubMed

    Noh, Heeso; Liew, Seng Fatt; Saranathan, Vinodkumar; Prum, Richard O; Mochrie, Simon G J; Dufresne, Eric R; Cao, Hui

    2010-05-24

    We investigate the physical mechanism for color production by isotropic nanostructures with short-range order in bird feather barbs. While the primary peak in optical scattering spectra results from constructive interference of singly-scattered light, many species exhibit secondary peaks with distinct characteristic. Our experimental and numerical studies show that these secondary peaks result from double scattering of light by the correlated structures. Without an analog in periodic or random structures, such a phenomenon is unique for short-range ordered structures, and has been widely used by nature for non-iridescent structural coloration.

  10. Double scattering of light from Biophotonic Nanostructures with short-range order

    SciTech Connect

    Noh, Heeso; Liew, Seng Fatt; Saranathan, Vinodkumar; Prum, Richard O.; Mochrie, Simon G.J.; Dufresne, Eric R.; Cao, Hui

    2010-07-28

    We investigate the physical mechanism for color production by isotropic nanostructures with short-range order in bird feather barbs. While the primary peak in optical scattering spectra results from constructive interference of singly-scattered light, many species exhibit secondary peaks with distinct characteristic. Our experimental and numerical studies show that these secondary peaks result from double scattering of light by the correlated structures. Without an analog in periodic or random structures, such a phenomenon is unique for short-range ordered structures, and has been widely used by nature for non-iridescent structural coloration.

  11. Unusually High and Anisotropic Thermal Conductivity in Amorphous Silicon Nanostructures.

    PubMed

    Kwon, Soonshin; Zheng, Jianlin; Wingert, Matthew C; Cui, Shuang; Chen, Renkun

    2017-02-02

    Amorphous Si (a-Si) nanostructures are ubiquitous in numerous electronic and optoelectronic devices. Amorphous materials are considered to possess the lower limit to the thermal conductivity (κ), which is ∼1 W·m(-1) K(-1) for a-Si. However, recent work suggested that κ of micrometer-thick a-Si films can be greater than 3 W·m(-1) K(-1), which is contributed to by propagating vibrational modes, referred to as "propagons". However, precise determination of κ in a-Si has been elusive. Here, we used structures of a-Si nanotubes and suspended a-Si films that enabled precise in-plane thermal conductivity (κ∥) measurement within a wide thickness range of 5 nm to 1.7 μm. We showed unexpectedly high κ∥ in a-Si nanostructures, reaching ∼3.0 and 5.3 W·m(-1) K(-1) at ∼100 nm and 1.7 μm, respectively. Furthermore, the measured κ∥ is significantly higher than the cross-plane κ on the same films. This unusually high and anisotropic thermal conductivity in the amorphous Si nanostructure manifests the surprisingly broad propagon mean free path distribution, which is found to range from 10 nm to 10 μm, in the disordered and atomically isotropic structure. This result provides an unambiguous answer to the century-old problem regarding mean free path distribution of propagons and also sheds light on the design and performance of numerous a-Si based electronic and optoelectronic devices.

  12. Amorphous nanostructuralization in HOPG by 1014 W cm-2 laser

    NASA Astrophysics Data System (ADS)

    NISHIMURA, Yasuhiko; KITAGAWA, Yoneyoshi; MORI, Yoshitaka; ISHII, Katsuhiro; HANAYAMA, Ryohei; AZUMA, Hirozumi; HIOKI, Tatsumi; NISHI, Teppei; MOTOHIRO, Tomoyoshi; KOMEDA, Osamu; SEKINE, Takashi; SATO, Nakahiro; KURITA, Takashi; KAWASHIMA, Toshiyuki; KAN, Hirofumi; SUNAHARA, Atsushi; SENTOKU, Yasuhiko; MIURA, Eisuke

    2016-05-01

    This reports provide an amorphous nanostructuralization technique on the surface modification in Highly Oriented Pyrolytic Graphite (HOPG) by using a femtosecond laser. We showed, for the first time, that the surface of HOPG is changed to the amorphous nanostructuralization graphite by using a femtosecond laser-driven compression technique. Our results also suggest that the HOPG surface is changed until the deeper area from the surface by the laser-driven shock wave. A single shot of a femtosecond laser beam (1.27 ∼ 1.33×1014 Wcm∼2 in intensity, with 2 mm-diameter, and 110 fs in pulse width) is irradiated under the vacuum ambience onto a 2 mm-thick of HOPG. The calculated impact pressures on a sample was 8.3 ∼ 8.7 GPa. Crystal structure in the HOPG were analyzed using a Raman spectroscopy and an X-ray diffraction, those analyzing depth from the surface were 50 nm and 350 μm, respectively.

  13. Amorphous mixed-metal hydroxide nanostructures for advanced water oxidation catalysts

    NASA Astrophysics Data System (ADS)

    Gao, Y. Q.; Liu, X. Y.; Yang, G. W.

    2016-02-01

    The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm-2 at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec-1, while no deactivation is detected in the CV testing even up to 30 000 cycles, which suggests the promising application of these amorphous nanomaterials in electrochemical oxidation. Meanwhile, the distinct catalytic activities among these amorphous Ni-Fe hydroxide nanostructures prompts us to take notice of the composition of the alloy hydroxides/oxides when studying their catalytic properties, which opens an avenue for the rational design and controllable preparation of such amorphous nanomaterials as advanced OER electrocatalysts.The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm-2 at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec-1, while no deactivation is detected in the CV

  14. Amorphous mixed-metal hydroxide nanostructures for advanced water oxidation catalysts.

    PubMed

    Gao, Y Q; Liu, X Y; Yang, G W

    2016-03-07

    The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm(-2) at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec(-1), while no deactivation is detected in the CV testing even up to 30 000 cycles, which suggests the promising application of these amorphous nanomaterials in electrochemical oxidation. Meanwhile, the distinct catalytic activities among these amorphous Ni-Fe hydroxide nanostructures prompts us to take notice of the composition of the alloy hydroxides/oxides when studying their catalytic properties, which opens an avenue for the rational design and controllable preparation of such amorphous nanomaterials as advanced OER electrocatalysts.

  15. Nanostructure formation by dynamic densification and recrystallization of amorphous Ti-Si alloy

    NASA Astrophysics Data System (ADS)

    Counihan, P. J.; Crawford, A.; Thadhani, N. N.

    1998-07-01

    Dynamic densification was used to consolidate mechanically amorphized Ti-Si alloy powders, using a 3-capsule, plate-impact, gas-gun loading system at velocities of 300 and 500 m/s. The recovered amorphous compacts were subsequently annealed above the crystallization temperature. A single-phase nano-structured (50-90 nm) Ti5Si3 compound was produced, as revealed by TEM and XRD analysis. In this paper, the influence of dynamic densification on the crystallization behavior of amorphous Ti-Si, and the formation of nano-crystals will be discussed.

  16. In Situ Mechanical Property Measurements of Amorphous Carbon-Boron Nitride Nanotube Nanostructures

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Woo; Lin, Yi; Nunez, Jennifer Carpena; Siochi, Emilie J.; Wise, Kristopher E.; Connell, John W.; Smith, Michael W.

    2011-01-01

    To understand the mechanical properties of amorphous carbon (a-C)/boron nitride nanotube (BNNT) nanostructures, in situ mechanical tests are conducted inside a transmission electron microscope equipped with an integrated atomic force microscope system. The nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation. We demonstrate multiple in situ tensile, compressive, and lap shear tests with a-C/BNNT hybrid nanostructures. The tensile strength of the a-C/BNNT hybrid nanostructure is 5.29 GPa with about 90 vol% of a-C. The tensile strength and strain of the end-to-end joint structure with a-C welding is 0.8 GPa and 5.2% whereas the lap shear strength of the side-by-side joint structure with a-C is 0.25 GPa.

  17. Amorphous and nanostructured silica and aluminosilicate spray-dried microspheres

    NASA Astrophysics Data System (ADS)

    Todea, M.; Turcu, R. V. F.; Frentiu, B.; Tamasan, M.; Mocuta, H.; Ponta, O.; Simon, S.

    2011-08-01

    Amorphous silica and aluminosilicate microspheres with diameters in the 0.1-20 μm range were produced by spray drying method. SEM, TEM and AFM images showed the spherical shape of the obtained particles. Based on thermal analysis data, several heat treatments have been applied on the as-prepared samples in order to check the amorphous state stability of the microspheres and to develop nanosized crystalline phases. As-prepared microspheres remain amorphous up to 1400 °C. By calcination at 1400 °C, cristobalite type nanocrystals are developed on silica sample, while in aluminosilicate sample first are developed mullite type nanocrystals and only after prolonged treatment are developed also cristobalite type nanocrystals. 29Si and 27Al MAS NMR results show that the local order around aluminum and silicon atoms strongly depend on the thermal history of the microspheres.

  18. A field effect glucose sensor with a nanostructured amorphous In-Ga-Zn-O network.

    PubMed

    Du, Xiaosong; Li, Yajuan; Herman, Gregory S

    2016-11-03

    Amorphous indium gallium zinc oxide (IGZO) field effect transistors (FETs) are a promising technology for a wide range of electronic applications. Herein, we fabricated and characterized FETs with a nanostructured IGZO network as a sensing transducer. The IGZO was patterned using colloidal lithography and electrohydrodynamic printing, where an 8 μm wide nanostructured close-packed hexagonal IGZO network was obtained. Electrical characterization of the nanostructured IGZO network FET demonstrated a drain-source current on-off ratio of 6.1 × 10(3) and effective electron mobilities of 3.6 cm(2) V(-1) s(-1). The nanostructured IGZO network was functionalized by aminosilane groups with cross-linked glucose oxidase. The devices demonstrated a decrease in drain-source conductance and a more positive VON with increasing glucose concentration. These changes are ascribed to the acceptor-like surface states associated with positively charged aminosilane groups attached to the nanostructured IGZO surface. Continuous monitoring of the drain-source current indicates a stepwise and fully reversible response to glucose concentrations with a short response time. The specific catalytic reaction between the GOx enzyme and glucose eliminates interference from acetaminophen/ascorbic acid. We demonstrate that nanostructured IGZO FETs have improved sensitivity compared to non-nanostructured IGZO for sensing glucose and can be potentially extended to other biosensor technologies.

  19. Nanostructuring of GeTiO amorphous films by pulsed laser irradiation.

    PubMed

    Teodorescu, Valentin Serban; Ghica, Cornel; Maraloiu, Adrian Valentin; Vlaicu, Mihai; Kuncser, Andrei; Ciurea, Magdalena Lidia; Stavarache, Ionel; Lepadatu, Ana M; Scarisoreanu, Nicu Doinel; Andrei, Andreea; Ion, Valentin; Dinescu, Maria

    2015-01-01

    Laser pulse processing of surfaces and thin films is a useful tool for amorphous thin films crystallization, surface nanostructuring, phase transformation and modification of physical properties of thin films. Here we show the effects of nanostructuring produced at the surface and under the surface of amorphous GeTiO films through laser pulses using fluences of 10-30 mJ/cm(2). The GeTiO films were obtained by RF magnetron sputtering with 50:50 initial atomic ratio of Ge:TiO2. Laser irradiation was performed by using the fourth harmonic (266 nm) of a Nd:YAG laser. The laser-induced nanostructuring results in two effects, the first one is the appearance of a wave-like topography at the film surface, with a periodicity of 200 nm and the second one is the structure modification of a layer under the film surface, at a depth that is related to the absorption length of the laser radiation. The periodicity of the wave-like relief is smaller than the laser wavelength. In the modified layer, the Ge atoms are segregated in spherical amorphous nanoparticles as a result of the fast diffusion of Ge atoms in the amorphous GeTiO matrix. The temperature estimation of the film surface during the laser pulses shows a maximum of about 500 °C, which is much lower than the melting temperature of the GeTiO matrix. GeO gas is formed at laser fluences higher than 20 mJ/cm(2) and produces nanovoids in the laser-modified layer at the film surface. A glass transition at low temperatures could happen in the amorphous GeTiO film, which explains the formation of the wave-like topography. The very high Ge diffusivity during the laser pulse action, which is characteristic for liquids, cannot be reached in a viscous matrix. Our experiments show that the diffusivity of atomic and molecular species such as Ge and GeO is very much enhanced in the presence of the laser pulse field. Consequently, the fast diffusion drives the formation of amorphous Ge nanoparticles through the segregation of Ge atoms

  20. Coherent fiber supercontinuum for biophotonics

    PubMed Central

    Tu, Haohua; Boppart, Stephen A.

    2013-01-01

    Biophotonics and nonlinear fiber optics have traditionally been two independent fields. Since the discovery of fiber-based supercontinuum generation in 1999, biophotonics applications employing incoherent light have experienced a large impact from nonlinear fiber optics, primarily because of the access to a wide range of wavelengths and a uniform spatial profile afforded by fiber supercontinuum. However, biophotonics applications employing coherent light have not benefited from the most well-known techniques of supercontinuum generation for reasons such as poor coherence (or high noise), insufficient controllability, and inadequate portability. Fortunately, a few key techniques involving nonlinear fiber optics and femtosecond laser development have emerged to overcome these critical limitations. Despite their relative independence, these techniques are the focus of this review, because they can be integrated into a low-cost portable biophotonics source platform. This platform can be shared across many different areas of research in biophotonics, enabling new applications such as point-of-care coherent optical biomedical imaging. PMID:24358056

  1. Coherent fiber supercontinuum for biophotonics.

    PubMed

    Tu, Haohua; Boppart, Stephen A

    2013-09-01

    Biophotonics and nonlinear fiber optics have traditionally been two independent fields. Since the discovery of fiber-based supercontinuum generation in 1999, biophotonics applications employing incoherent light have experienced a large impact from nonlinear fiber optics, primarily because of the access to a wide range of wavelengths and a uniform spatial profile afforded by fiber supercontinuum. However, biophotonics applications employing coherent light have not benefited from the most well-known techniques of supercontinuum generation for reasons such as poor coherence (or high noise), insufficient controllability, and inadequate portability. Fortunately, a few key techniques involving nonlinear fiber optics and femtosecond laser development have emerged to overcome these critical limitations. Despite their relative independence, these techniques are the focus of this review, because they can be integrated into a low-cost portable biophotonics source platform. This platform can be shared across many different areas of research in biophotonics, enabling new applications such as point-of-care coherent optical biomedical imaging.

  2. Biophotonics: a European perspective

    NASA Astrophysics Data System (ADS)

    Robin, Thierry; Cochard, Jacques; Breussin, Frédéric

    2013-03-01

    The objective of the present work is to determine the opportunities and challenges for Biophotonics business development in Europe for the next five years with a focus on sensors and systems: for health diagnostics and monitoring; for air, water and food safety and quality control. The development of this roadmap was initiated and supported by EPIC (The European Photonics Industry Consortium). We summarize the final roadmap data: market application segments and trends, analysis of the market access criteria, analysis of the technology trends and major bottlenecks and challenges per application.

  3. Synthesis and characterization of large specific surface area nanostructured amorphous silica materials.

    PubMed

    Marquez-Linares, Francisco; Roque-Malherbe, Rolando M A

    2006-04-01

    Large specific surface area materials attract wide attention because of their applications in adsorption, catalysis, and nanotechnology. In the present study, we describe the synthesis and characterization of nanostructured amorphous silica materials. These materials were obtained by means of a modification of the Stobe-Fink-Bohn (SFB) method. The morphology and essential features of the synthesized materials have been studied using an automated surface area and pore size analyzer and scanning electron microscopy. The existence of a micro/mesoporous structure in the obtained materials has been established. It was also found that the obtained particle packing materials show large specific surface area up to 1,600 m2/g. (To our best knowledge, there is no any reported amorphous silica material with such a higher specific surface area.) The obtained materials could be useful in the manufacture of adsorbents, catalyst supports, and other nanotechnological applications.

  4. Management in biophotonics and biotechnologies

    NASA Astrophysics Data System (ADS)

    Meglinski, I. V.; Tuchin, V. V.

    2005-10-01

    Biophotonics, one of the most exciting and rapidly growing areas, offers vast potential for changing traditional approaches to meeting many critical needs in medicine, biology, pharmacy, food, health care and cosmetic industries. Follow the market trends we developed new MSc course Management in Biophotonics and Biotechnologies (MBB) that provide students of technical disciplines with the necessary training, education and problem-solving skills to produce professionals and managers who are better equipped to handle the challenges of modern science and business in biophotonics and biotechnology. A major advantage of the course is that it provides skills not currently available to graduates in other Master programs.

  5. Comparison of microstructure and magnetic properties of 3% Si-steel, amorphous and nanostructure Finemet

    NASA Astrophysics Data System (ADS)

    Yousefi, M.; Rahmani, Kh.; Amiri Kerahroodi, M. S.

    2016-12-01

    This paper presents a comparison of microstructure and magnetic properties of polycrystalline 3%Si-steel, amorphous and nano-crystalline alloy Fe73.5Cu1Nb3Si13.5B9 (known as Finemet). Si-steels are industrially produced by casting, hot and cold rolling, annealing and coating. Samples of thin amorphous ribbons were prepared by the planar flow casting (PFC) method. Nano-crystalline samples are obtained after annealing in vacuum furnace at 560 °C for 1 h. The structure of specimens was investigated by XRD, SEM and FE-SEM. Also, magnetic properties were measured using vibrating sample magnetometer (VSM). The results showed that, hysteresis losses in as-quenched and nano-crystalline ribbons were by 94.75% and 96.06% less than 3%Si-steel, respectively. After the heat treatment of amorphous specimens, hysteresis area was decreased by 25% in comparison with heat treated specimen. This decreasing is occurred due to the formation of Fe3Si nanostructure with size of 10-17 nm and removing segregation after heat treatment.

  6. Synthesis of bulk nanostructured aluminum containing in situ crystallized amorphous particles

    NASA Astrophysics Data System (ADS)

    Zhang, Zhihui

    5083 Al containing in situ crystallized Al85Ni10La 5 amorphous particles (10% and 20% in volume fraction) was synthesized through a powder metallurgy route consisting of cold isostatic pressing, degassing and hot extrusion. The nanostructured 5083 Al powders (grain size ˜28 nm) were produced through mechanical milling in liquid nitrogen. The Al 85Ni10La5 powders were produced via gas atomization using helium gas and the fraction in the size range of <500 mesh (<25 mum), which appeared to be fully amorphous on the basis of X-ray diffraction studies, was isolated for further investigation. The amorphous Al85Ni10La5 alloy exhibited a glass transition at ˜259°C (at a heating rate of 40°C/min) and nanoscale crystallites (< 100 nm) with an equiaxed morphology formed during the subsequent crystallization reactions. At temperatures higher than 283°C, only the equilibrium phases Al, Al3Ni and Al11La 3 were formed. An unusually high nucleation density (1021-22 /m3) was recorded in the crystallization process. The copious nucleation sites were rationalized from the presence of quenched-in Al nuclei, which were evidenced by isothermal calorimetric tracing (235°C) and a direct HRTEM observation of the amorphous Al85Ni10La 5 powders. The feasibility of preparation of nanocrystalline/amorphous particles via melt spinning followed by ball milling was also studied. In the as-extruded composites, the amorphous Al85Ni10 La5 particles underwent complete crystallization resulting in a grain size of 100 ˜ 200 nm; the 5083 Al matrix had a grain size around 200 nm in the fine-grained region interspersed by coarse-grained region with a grain size of 600 ˜ 1500 nm. A metallurgical bond formed between the 5083 Al matrix and Al85Ni10La5 particles showing a grain-boundary-like interface. The compressive fracture strength of the as-extruded 10% and 20% Al85Ni10La5 composites were determined to be 1025 MPa and 837 MPa, respectively. The influence of secondary processing, i.e., swaging

  7. Fabrication of single-crystalline plasmonic nanostructures on transparent and flexible amorphous substrates

    PubMed Central

    Mori, Tomohiro; Mori, Takeshi; Tanaka, Yasuhiro; Suzaki, Yoshifumi; Yamaguchi, Kenzo

    2017-01-01

    A new experimental technique is developed for producing a high-performance single-crystalline Ag nanostructure on transparent and flexible amorphous substrates for use in plasmonic sensors and circuit components. This technique is based on the epitaxial growth of Ag on a (001)-oriented single-crystalline NaCl substrate, which is subsequently dissolved in ultrapure water to allow the Ag film to be transferred onto a wide range of different substrates. Focused ion beam milling is then used to create an Ag nanoarray structure consisting of 200 cuboid nanoparticles with a side length of 160 nm and sharp, precise edges. This array exhibits a strong signal and a sharp peak in plasmonic properties and Raman intensity when compared with a polycrystalline Ag nanoarray. PMID:28216626

  8. Fabrication of ZnO photonic amorphous diamond nanostructure from parrot feathers for modulated photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengli; Yu, Ke; Liao, Na; Yin, Haihong; Lou, Lei; Yu, Qian; Liao, Yuanyuan; Zhu, Ziqiang

    2011-12-01

    A ZnO photonic amorphous diamond nanostructure was successfully synthesised using a feather barb of the Rosy-Faced Lovebird as supporting template via a facile sol-gel process. Different from ordered structures, an isotropic PBG around 500 nm was evidenced from reflectance spectra and an optical metallurgical microscopy image, which overlaps with the visible emission peak of ZnO. As a result, the inhibition of visible emission inside the PBG and the enhancement of UV emission at the PBG edges have both been observed, which is independent from the incident angle. Moreover, the rapid thermal annealing can also help improve the crystallinity of ZnO and raise the UV/visible emission ratio without affecting the structure. These results can be very useful for the study of the modification of the optical emission properties of ZnO and other semiconductor materials as well as research on ZnO random lasing.

  9. Fabrication of single-crystalline plasmonic nanostructures on transparent and flexible amorphous substrates

    NASA Astrophysics Data System (ADS)

    Mori, Tomohiro; Mori, Takeshi; Tanaka, Yasuhiro; Suzaki, Yoshifumi; Yamaguchi, Kenzo

    2017-02-01

    A new experimental technique is developed for producing a high-performance single-crystalline Ag nanostructure on transparent and flexible amorphous substrates for use in plasmonic sensors and circuit components. This technique is based on the epitaxial growth of Ag on a (001)-oriented single-crystalline NaCl substrate, which is subsequently dissolved in ultrapure water to allow the Ag film to be transferred onto a wide range of different substrates. Focused ion beam milling is then used to create an Ag nanoarray structure consisting of 200 cuboid nanoparticles with a side length of 160 nm and sharp, precise edges. This array exhibits a strong signal and a sharp peak in plasmonic properties and Raman intensity when compared with a polycrystalline Ag nanoarray.

  10. Thermally induced transformations of amorphous carbon nanostructures fabricated by electron beam induced deposition.

    PubMed

    Kulkarni, Dhaval D; Rykaczewski, Konrad; Singamaneni, Srikanth; Kim, Songkil; Fedorov, Andrei G; Tsukruk, Vladimir V

    2011-03-01

    We studied the thermally induced phase transformations of electron-beam-induced deposited (EBID) amorphous carbon nanostructures by correlating the changes in its morphology with internal microstructure by using combined atomic force microscopy (AFM) and high resolution confocal Raman microscopy. These carbon deposits can be used to create heterogeneous junctions in electronic devices commonly known as carbon-metal interconnects. We compared two basic shapes of EBID deposits: dots/pillars with widths from 50 to 600 nm and heights from 50 to 500 nm and lines with variable heights from 10 to 150 nm but having a constant length of 6 μm. We observed that during thermal annealing, the nanoscale amorphous deposits go through multistage transformation including dehydration and stress-relaxation around 150 °C, dehydrogenation within 150-300 °C, followed by graphitization (>350 °C) and formation of nanocrystalline, highly densified graphitic deposits around 450 °C. The later stage of transformation occurs well below commonly observed graphitization for bulk carbon (600-800 °C). It was observed that the shape of the deposits contribute significantly to the phase transformations. We suggested that this difference is controlled by different contributions from interfacial footprints area. Moreover, the rate of graphitization was different for deposits of different shapes with the lines showing a much stronger dependence of its structure on the density than the dots.

  11. Glucose oxidase-loaded amorphous FeNi-Pt fan-shaped nanostructures and their electrochemical behaviors.

    PubMed

    Wang, Na; Wen, Ming; Wu, Qingsheng

    2013-11-01

    Glucose oxidase (GOD) loaded amorphous FeNi-Pt fan-shaped nanostructures with the average length of ∼ 7 μm have been synthesized for improving the electrochemical activity of enzyme electrode materials. The electrochemical oxidation of glucose solution has been successfully facilitated using FeNi-Pt fan-shaped nanostructures to load GOD due to their fan-shaped constitution and amorphous nanostructure. Chitosan could provide better response of nanostructure electrode than nafion. Compared with glassy carbon electrode (GCE) modified by chitosan/Fe(40)Ni(40)-Pt(20)/GOD/GCE (GOD-loaded Fe(40)Ni(40)-Pt(20) nanoalloys using chitosan as immobilization-agent), chitosan/Fe(45)Ni(45)-Pt(10)/GOD/GCE presents smaller oxidation and reduction peak potential separation at 0.2912 V. No any electrochemical response can be observed when FeNi-Pt was absent in this electrode system. Additionally, a group of parallel experiments were tested when chitosan was changed to nafion. When Fe(40)Ni(40)-Pt(20) nanostructure was employed to the electrode system, the oxidation and reduction peaks potentials were -0.7341 V and -0.4943 V, respectively, with a peak potential separation of 0.3371 V.

  12. Intrinsic nanostructural domains: Possible origin of weaklinkless superconductivity in the quenched reaction product of Mg and amorphous B

    NASA Astrophysics Data System (ADS)

    Li, S.; Prabhakar, O.; Tan, T. T.; Sun, C. Q.; Wang, X. L.; Soltanian, S.; Horvat, J.; Dou, S. X.

    2002-07-01

    Smooth modulation structure of Mg-B alloy in the quenched reaction product of Mg and amorphous B was studied. It indicates that the MgB2 formed possibly in spinodal decomposition, thus resulting in MgB2 nanodomains. It was found that the nanodomains with small angle boundaries of atomic-scale width were distributed within the subgrains that constitute the clusters in MgB2 grains. This nanostructural characteristic may be intrinsic in the quenched reaction product of Mg and amorphous B. It makes the nanodomain boundaries not act as barriers to the current percolation path, thus exhibiting no weak-link problem in the MgB2.

  13. Band-gap engineering by molecular mechanical strain-induced giant tuning of the luminescence in colloidal amorphous porous silicon nanostructures.

    PubMed

    Mughal, A; El Demellawi, J K; Chaieb, Sahraoui

    2014-12-14

    Nano-silicon is a nanostructured material in which quantum or spatial confinement is the origin of the material's luminescence. When nano-silicon is broken into colloidal crystalline nanoparticles, its luminescence can be tuned across the visible spectrum only when the sizes of the nanoparticles, which are obtained via painstaking filtration methods that are difficult to scale up because of low yield, vary. Bright and tunable colloidal amorphous porous silicon nanostructures have not yet been reported. In this letter, we report on a 100 nm modulation in the emission of freestanding colloidal amorphous porous silicon nanostructures via band-gap engineering. The mechanism responsible for this tunable modulation, which is independent of the size of the individual particles and their distribution, is the distortion of the molecular orbitals by a strained silicon-silicon bond angle. This mechanism is also responsible for the amorphous-to-crystalline transformation of silicon.

  14. Fullerene nanostructure-induced excellent mechanical properties in hydrogenated amorphous carbon

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Wang, Chengbing; Wang, Zhou; Zhang, Junyan; He, Deyan

    2007-10-01

    Hydrogenated amorphous carbon films were deposited by dc-pulse plasma chemical vapor deposition. The structure of as-prepared films, characterized by transmission electron microscopy, Raman spectra, and x-ray photoelectron spectra, is considered as nanocomposite thin films with C60 and fullerene crystalline nanoparticles embedded in amorphous sp2 and sp3 carbon matrices. The high hardness and high elastic recovery of as-prepared films are attributed to the unique structure that C60 and fullerene nanocrystalline grains (soft) dispersed in amorphous carbon phase (hard) to form a network structure, which restrains the dislocation migration, assists the stress relaxation, and hence, enhances the mechanical properties of the films.

  15. Biophotons Contribute to Retinal Dark Noise.

    PubMed

    Li, Zehua; Dai, Jiapei

    2016-06-01

    The discovery of dark noise in retinal photoreceptors resulted in a long-lasting controversy over its origin and the underlying mechanisms. Here, we used a novel ultra-weak biophoton imaging system (UBIS) to detect biophotonic activity (emission) under dark conditions in rat and bullfrog (Rana catesbeiana) retinas in vitro. We found a significant temperature-dependent increase in biophotonic activity that was completely blocked either by removing intracellular and extracellular Ca(2+) together or inhibiting phosphodiesterase 6. These findings suggest that the photon-like component of discrete dark noise may not be caused by a direct contribution of the thermal activation of rhodopsin, but rather by an indirect thermal induction of biophotonic activity, which then activates the retinal chromophore of rhodopsin. Therefore, this study suggests a possible solution regarding the thermal activation energy barrier for discrete dark noise, which has been debated for almost half a century.

  16. Nanostructure Formation by Dynamic Densification and Recrystallization of Amorphous Ti-Si Alloy

    NASA Astrophysics Data System (ADS)

    Counihan, P. J.; Thadhani, N. N.

    1997-07-01

    Dynamic densification was used to consolidate mechanically amorphized Ti-Si alloy powders. A 3-capsule, plate-impact, gas-gun loading system was used to densify the powders at impact velocities of 300 and 500 m/s. The recovered compacts were observed to retain the amorphous structure as evidenced by x-ray diffraction (XRD) and transmission microscopy (TEM) analysis. The densified material was subsequently annealed at various temperatures (above the crystallization temperature) to produce a nanocrystalline Ti_5Si3 microstructure. TEM and XRD analysis revealed retention of a nano-grain microstructure (< 100 nm) in the crystallized compacts. In this presentation the influence of dynamic densification on the crystallization of the amorphous compound and retention of the nano-scale grain size in the crystallized compacts will be discussed.

  17. Structure and optical function of amorphous photonic nanostructures from avian feather barbs: a comparative small angle X-ray scattering (SAXS) analysis of 230 bird species

    PubMed Central

    Saranathan, Vinodkumar; Forster, Jason D.; Noh, Heeso; Liew, Seng-Fatt; Mochrie, Simon G. J.; Cao, Hui; Dufresne, Eric R.; Prum, Richard O.

    2012-01-01

    Non-iridescent structural colours of feathers are a diverse and an important part of the phenotype of many birds. These colours are generally produced by three-dimensional, amorphous (or quasi-ordered) spongy β-keratin and air nanostructures found in the medullary cells of feather barbs. Two main classes of three-dimensional barb nanostructures are known, characterized by a tortuous network of air channels or a close packing of spheroidal air cavities. Using synchrotron small angle X-ray scattering (SAXS) and optical spectrophotometry, we characterized the nanostructure and optical function of 297 distinctly coloured feathers from 230 species belonging to 163 genera in 51 avian families. The SAXS data provided quantitative diagnoses of the channel- and sphere-type nanostructures, and confirmed the presence of a predominant, isotropic length scale of variation in refractive index that produces strong reinforcement of a narrow band of scattered wavelengths. The SAXS structural data identified a new class of rudimentary or weakly nanostructured feathers responsible for slate-grey, and blue-grey structural colours. SAXS structural data provided good predictions of the single-scattering peak of the optical reflectance of the feathers. The SAXS structural measurements of channel- and sphere-type nanostructures are also similar to experimental scattering data from synthetic soft matter systems that self-assemble by phase separation. These results further support the hypothesis that colour-producing protein and air nanostructures in feather barbs are probably self-assembled by arrested phase separation of polymerizing β-keratin from the cytoplasm of medullary cells. Such avian amorphous photonic nanostructures with isotropic optical properties may provide biomimetic inspiration for photonic technology. PMID:22572026

  18. Label-free direct electronic detection of biomolecules with amorphous silicon nanostructures.

    PubMed

    Lund, John; Mehta, Ranjana; Parviz, Babak A

    2006-12-01

    We present the fabrication and characterization of a nano-scale sensor made of amorphous silicon for the label-free, electronic detection of three classes of biologically important molecules: ions, oligonucleotides, and proteins. The sensor structure has an active element which is a 50 nm wide amorphous silicon semicircle and has a total footprint of less than 4 microm2. We demonstrate the functionalization of the sensor with receptor molecules and the electronic detection of three targets: H(+) ions, short single-stranded DNAs, and streptavidin. The sensor is able to reliably distinguish single base-pair mismatches in 12 base long strands of DNA and monitor the introduction and identification of straptavidin in real-time. The versatile sensor structure can be readily functionalized with a wide range of receptor molecules and is suitable for integration with high-speed electronic circuits as a post-process on an integrated circuit chip.

  19. Feature issue introduction: biophotonic materials and applications

    PubMed Central

    Lee, Kwang-Sup; Andraud, Chantal; Tamada, Kaoru; Sokolov, Konstantin; Kotz, Kenneth T.; Zheng, Gang

    2016-01-01

    Biophotonics can be defined as the interplay of light and biological matter. The percolation of new optical technology into the realm of biology has literally shed new light into the inner workings of biological systems. This has revealed new applications for optics in biology. In a parallel trend, biomolecules have been investigated for their optical applications. Materials are playing a central role in the development of biophotonics. New materials, fabrication methods, and structures are enabling new biosensors, contrast agents, imaging strategies, and assay methods. Similarly, biologic materials themselves can be used in photonic devices. In this context, two open-access, rapid-publication journals from The Optical Society of America (OSA), Optical Materials Express and Biomedical Optics Express, will publish a joint feature issue covering advances in biophotonics materials. PMID:27231644

  20. Feature issue introduction: biophotonic materials and applications.

    PubMed

    Lee, Kwang-Sup; Andraud, Chantal; Tamada, Kaoru; Sokolov, Konstantin; Kotz, Kenneth T; Zheng, Gang

    2016-05-01

    Biophotonics can be defined as the interplay of light and biological matter. The percolation of new optical technology into the realm of biology has literally shed new light into the inner workings of biological systems. This has revealed new applications for optics in biology. In a parallel trend, biomolecules have been investigated for their optical applications. Materials are playing a central role in the development of biophotonics. New materials, fabrication methods, and structures are enabling new biosensors, contrast agents, imaging strategies, and assay methods. Similarly, biologic materials themselves can be used in photonic devices. In this context, two open-access, rapid-publication journals from The Optical Society of America (OSA), Optical Materials Express and Biomedical Optics Express, will publish a joint feature issue covering advances in biophotonics materials.

  1. 2.5 D Transrotational Microcrystals and Nanostructures Revealed by TEM in Crystallizing Amorphous Films

    NASA Astrophysics Data System (ADS)

    Kolosov, Vladimir

    2015-03-01

    Unexpected transrotational microcrystals can be grown in thin 10-100 nm amorphous films. Crystals of different morphology (from nanowhiskers to spherulites, complex textures) and chemical nature (oxides, chalcogenides, metals and alloys) grown in thin films prepared by various methods are studied by transmission electron microscopy (TEM). We use primarily our TEM bend-contour method and SAED (HREM, AFM are also performed). The phenomenon resides in strong (up to 300 degrees/ μm) regular internal bending of crystal lattice planes in a growing crystal. It can be traced inside TEM in situ. Usual translation is complicated by slight regular rotation of the crystal unit cell (transrotation) most prominent at the mesoscale. Different geometries of transrotation of positive and negative curvature are revealed. Transrotational crystal resembles ideal single crystal enclosed in a curved space. It can be also considered similar to hypothetical endless 2.5 D analogy of MW nanotube/nano-onion halves. Transrotation is strongly increasing as the film gets thinner in the range 100-15 nm. Transrotations supplement dislocations and disclinations. New transrotational nanocrystalline model of amorphous state is proposed. Support of Ministry of Higher Education and Science is acknowledged.

  2. Nanostructured and amorphous-like tungsten films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Dellasega, D.; Merlo, G.; Conti, C.; Bottani, C. E.; Passoni, M.

    2012-10-01

    An experimental investigation of nanostructured, micrometer-thick, tungsten films deposited by pulsed laser deposition is presented. The films are compact and pore-free, with crystal grain sizes ranging from 14 nm to less than 2 nm. It is shown how, by properly tailoring deposition rate and kinetic energy of ablated species, it is possible to achieve a detailed and separate control of both film morphology and structure. The role of the main process parameters, He background pressure, laser fluence, and energy, is elucidated. In contrast with W films produced with other PVD techniques, β-phase growth is avoided and the presence of impurities and contaminants, like oxygen, is not correlated with film structure. These features make these films interesting for the development of coatings with improved properties, like increased corrosion resistance and enhanced diffusion barriers.

  3. High-strength and high-ductility nanostructured and amorphous metallic materials.

    PubMed

    Kou, Hongning; Lu, Jian; Li, Ying

    2014-08-20

    The development of materials with dual properties of high strength and high ductility has been a constant challenge since the foundation of the materials science discipline. The rapid progress of nanotechnology in recent decades has further brought this challenge to a new era. This Research News highlights a few newly developed strategies to optimize advanced nanomaterials and metallic glasses with exceptional dual mechanical properties of high strength and high ductility. A general concept of strain non-localization is presented to describe the role of multiscale (i.e., macroscale, microscale, nanoscale, and atomic scale) heterogeneities in the ductility enhancement of materials reputed to be intrinsically brittle, such as nanostructured metallic materials and bulk metallic glasses. These nanomaterials clearly form a new group of materials that display an extraordinary relationship between yield strength and the uniform elongation with the same chemical composition. Several other examples of nanomaterials such as those reinforced by nanoprecipitates will also be described.

  4. Dual-Layer Nanostructured Flexible Thin-Film Amorphous Silicon Solar Cells with Enhanced Light Harvesting and Photoelectric Conversion Efficiency.

    PubMed

    Lin, Yinyue; Xu, Zhen; Yu, Dongliang; Lu, Linfeng; Yin, Min; Tavakoli, Mohammad Mahdi; Chen, Xiaoyuan; Hao, Yuying; Fan, Zhiyong; Cui, Yanxia; Li, Dongdong

    2016-05-04

    Three-dimensional (3-D) structures have triggered tremendous interest for thin-film solar cells since they can dramatically reduce the material usage and incident light reflection. However, the high aspect ratio feature of some 3-D structures leads to deterioration of internal electric field and carrier collection capability, which reduces device power conversion efficiency (PCE). Here, we report high performance flexible thin-film amorphous silicon solar cells with a unique and effective light trapping scheme. In this device structure, a polymer nanopillar membrane is attached on top of a device, which benefits broadband and omnidirectional performances, and a 3-D nanostructure with shallow dent arrays underneath serves as a back reflector on flexible titanium (Ti) foil resulting in an increased optical path length by exciting hybrid optical modes. The efficient light management results in 42.7% and 41.7% remarkable improvements of short-circuit current density and overall efficiency, respectively. Meanwhile, an excellent flexibility has been achieved as PCE remains 97.6% of the initial efficiency even after 10 000 bending cycles. This unique device structure can also be duplicated for other flexible photovoltaic devices based on different active materials such as CdTe, Cu(In,Ga)Se2 (CIGS), organohalide lead perovskites, and so forth.

  5. Center for Biophotonics Science and Technology (CBST).

    PubMed

    Chuang, Frank

    2004-01-01

    The Center for Biophotonics Science and Technology (CBST) is the only center in the country funded by the National Science Foundation and devoted to the study of light and radiant energy in biology and medicine. Our consortium of 10 world-class academic institutions and research laboratories is comprised of physical and life scientists, physicians and engineers - along with industry participants, educators and community leaders - working together to bring biophotonics to the forefront of mainstream science. The three main arms of CBST are (1) Science and Technology, (2) Education, and (3) Knowledge Transfer. The research sponsored by the center focuses on critical themes that are expected to have significant impact on current biomedical science and technology. Projects include the development of new methods in optical microscopy that work well beyond the diffraction limit; ultrafast, high-intensity X-ray lasers to resolve the structure of single biomolecules, and new devices and sensors for minimally - or noninvasive medical applications. CBST is developing a new curriculum, along with training materials, internships and research fellowships to introduce biophotonics to students and teachers at all educational levels. Finally, the knowledge transfer component of CBST is seeking to catalyze the rapid growth of biophotonics as a new technology sector by supplying intellectual capital and tools to stimulate the growth of new products and new companies. By coupling the center's biophotonics research projects with industry partners and sponsors, a unique R&D environment is created to expand the use of photons in the development of life sciences, bioengineering and health care.

  6. Photo-induced oxidation and amorphization of trigonal tellurium: A means to engineer hybrid nanostructures and explore glass structure under spatial confinement

    SciTech Connect

    Vasileiadis, Thomas; Yannopoulos, Spyros N.

    2014-09-14

    Controlled photo-induced oxidation and amorphization of elemental trigonal tellurium are achieved by laser irradiation at optical wavelengths. These processes are monitored in situ by time-resolved Raman scattering and ex situ by electron microscopies. Ultrathin TeO₂ films form on Te surfaces, as a result of irradiation, with an interface layer of amorphous Te intervening between them. It is shown that irradiation, apart from enabling the controllable transformation of bulk Te to one-dimensional nanostructures, such as Te nanotubes and hybrid core-Te/sheath-TeO₂ nanowires, causes also a series of light-driven (athermal) phase transitions involving the crystallization of the amorphous TeO₂ layers and its transformation to a multiplicity of crystalline phases including the γ-, β-, and α-TeO₂ crystalline phases. The kinetics of the above photo-induced processes is investigated by Raman scattering at various laser fluences revealing exponential and non-exponential kinetics at low and high fluence, respectively. In addition, the formation of ultrathin (less than 10 nm) layers of amorphous TeO₂ offers the possibility to explore structural transitions in 2D glasses by observing changes in the short- and medium-range structural order induced by spatial confinement.

  7. Identical particle model on biophoton emission

    NASA Astrophysics Data System (ADS)

    Liu, T. C.; Liu, Songhao; Popp, Fritz A.; Tang, Ao-Qing

    1996-09-01

    Biophoton emission (PE) method is a non-invasive way revealing biophysical interactions in living tissues. Since its mechanism is not very clear, its acceptance is limited. Gu has presented the quantum theory on biophoton emission according to the Dicke model. However, the Dicke model does not apply to biological system. In this paper, we studied PE by using the identical particle model, the interaction of identical particles by quantum chemistry, as well as the transition of the system interacting with radiation by the time quantum theory on radiation-matter interaction put forward by the first author and his cooperators. It was shown that the identical particles form coherent states, the photon emission probability of the superradiant state is a liner function of N and N2, and the one of the subradiant state is zero. In other words, the photon emission intensity represents the coherent states of the identical particle system. The linear relationship of N and N2 agrees with the PE experiment results on early drosophila embryos. The research on the cell division cycle showed that the superradiant states correspond to the late S phase. This is why PE can be used to differentiate human tumor tissues from normal ones. We also studied induced PE.

  8. Electronic structure and phase composition of dielectric interlayers in multilayer amorphous nanostructure [(CoFeB)60C40/SiO2]200

    NASA Astrophysics Data System (ADS)

    Domashevskaya, E. P.; Builov, N. S.; Terekhov, V. A.; Barkov, K. A.; Sitnikov, V. G.

    2017-01-01

    The multilayer amorphous nanostructure [(CoFeB)60C40/SiO2]200 of alternating composite and dielectric layers was obtained by ion-beam sputtering on a rotating pyroceramic substrate of two targets, one of which was a Co40Fe40B20 metal alloy plate with graphite inserts. The dielectric interlayers of SiO2 were sputtered from a quartz plate (second target). The thicknesses of bilayers of the multilayered nanostructure (MNS) (6 nm), consisting of metal-carbon composite layers (CoFeB)60C40 approximately 4 nm in thickness and a silicon oxide dielectric interlayers with a thickness of approximately 2 nm, were determined by small-angle diffraction. The results of experimental layer-by-layer study without destroying the MNS by ultrasoft X-ray spectroscopy (USXES) showed a significant deviation of the stoichiometric composition of the dielectric interlayers from stoichiometry sputtered quartz towards decreasing oxygen concentration with the formation of SiO1.3 suboxide. As a result of simulation of the Si L 2,3 spectra of silicon using reference spectra of known phases, the concentration of the silicon suboxide phase in the amorphous dielectric interlayers reaches about half of the interlayer content, the second half of which is accounted for SiO 2 dioxide. A "shielding" effect of carbon in the metal layers is manifested in the absence of silicide formation at the interfaces of the multilayer structure under study and should help to increase the anisotropy of their electromagnetic properties.

  9. A near-frictionless and extremely elastic hydrogenated amorphous carbon film with self-assembled dual nanostructure.

    PubMed

    Liu, Xiaoqiang; Yang, Jun; Hao, Junying; Zheng, Jianyun; Gong, Qiuyu; Liu, Weimin

    2012-09-04

    A highly crosslinking network combined with a fullerene-like structure is disclosed in a hydrogenated amorphous carbon film. The very soft carbon film exhibits super-low friction and excellent wear resistance even under a Hertzian contact pressure comparable to its hardness under vacuum, which is an extraordinary tribological behavior in the filed of solid lubrication films or coatings.

  10. Enhanced photocurrent in thin-film amorphous silicon solar cells via shape controlled three-dimensional nanostructures.

    PubMed

    Hilali, Mohamed M; Yang, Shuqiang; Miller, Mike; Xu, Frank; Banerjee, Sanjay; Sreenivasan, S V

    2012-10-12

    In this paper, we have explored manufacturable approaches to sub-wavelength controlled three-dimensional (3D) nano-patterns with the goal of significantly enhancing the photocurrent in amorphous silicon solar cells. Here we demonstrate efficiency enhancement of about 50% over typical flat a-Si thin-film solar cells, and report an enhancement of 20% in optical absorption over Asahi textured glass by fabricating sub-wavelength nano-patterned a-Si on glass substrates. External quantum efficiency showed superior results for the 3D nano-patterned thin-film solar cells due to enhancement of broadband optical absorption. The results further indicate that this enhanced light trapping is achieved with minimal parasitic absorption losses in the deposited transparent conductive oxide for the nano-patterned substrate thin-film amorphous silicon solar cell configuration. Optical simulations are in good agreement with experimental results, and also show a significant enhancement in optical absorption, quantum efficiency and photocurrent.

  11. Micro/nanostructures formation by femtosecond laser surface processing on amorphous and polycrystalline Ni60Nb40

    NASA Astrophysics Data System (ADS)

    Peng, Edwin; Tsubaki, Alfred; Zuhlke, Craig A.; Wang, Meiyu; Bell, Ryan; Lucis, Michael J.; Anderson, Troy P.; Alexander, Dennis R.; Gogos, George; Shield, Jeffrey E.

    2017-02-01

    Femtosecond laser surface processing is a technology that can be used to functionalize many surfaces, imparting specialized properties such as increased broadband optical absorption or superhydrophilicity/superhydrophobicity. In this study, two unique classes of surface structures, below surface growth (BSG) and above surface growth (ASG) mounds, were formed by femtosecond laser surface processing on amorphous and polycrystalline Ni60Nb40 with two different grain sizes. Cross sectional imaging of these mounds revealed thermal evidence of the unique formation processes for each class of surface structure. BSG mounds formed on all three substrates using the same laser parameters had similar surface morphology. The microstructures in the mounds were unaltered compared with the substrate before laser processing, suggesting their formation was dominated by preferential valley ablation. ASG mounds had similar morphology when formed on the polycrystalline Ni60Nb40 substrates with 100 nm and 2 μm grain size. However, the ASG mounds had significantly wider diameter and higher peak-to-valley heights when the substrate was amorphous Ni60Nb40. Hydrodynamic melting was primarily responsible for ASG mound formation. On amorphous Ni60Nb40 substrates, the ASG mounds are most likely larger due to lower thermal diffusivity. There was clear difference in growth mechanism of femtosecond laser processed BSG and ASG mounds, and grain size does not appear to be a factor.

  12. Role of Inelastic Electron–Phonon Scattering in Electron Transport through Ultra-Scaled Amorphous Phase Change Material Nanostructures

    SciTech Connect

    Liu, Jie; Xu, Xu; Anantram, M.P.

    2014-09-01

    The electron transport through ultra-scaled amorphous phase change material (PCM) GeTe is investigated by using ab initio molecular dynamics, density functional theory, and non-equilibrium Green’s function, and the inelastic electron–phonon scattering is accounted for by using the Born approximation. It is shown that, in ultra-scaled PCM device with 6 nm channel length, < 4 % of the energy carried by the incident electrons from the source is transferred to the atomic lattice before reaching the drain, indicating that the electron transport is largely elastic. Our simulation results show that the inelastic electron–phonon scattering, which plays an important role to excite trapped electrons in bulk PCM devices, exerts very limited influence on the current density value and the shape of current–voltage curve of ultra-scaled PCM devices. The analysis reveals that the Poole–Frenkel law and the Ohm’s law, which are the governing physical mechanisms of the bulk PCM devices, cease to be valid in the ultra-scaled PCM devices.

  13. New master program in management in biophotonics and biotechnologies

    NASA Astrophysics Data System (ADS)

    Meglinski, I. V.; Tuchin, V. V.

    2006-08-01

    We develop new graduate educational highly interdisciplinary program that will be useful for addressing problems in worldwide biotechnologies and related biomedical industries. This Master program called Management in Biophotonics and Biotechnologies provides students with the necessary training, education and problem-solving skills to produce managers who are better equipped to handle the challenges of modern business in modern biotechnologies. Administered jointly by Cranfield University (UK) and Saratov State University, Russia) graduates possess a blend of engineering, biotechnologies, business and interpersonal skills necessary for success in industry. The Master courses combine a regular year program in biophotonics & biotechnologies disciplines with the core requirements of a Master degree. A major advantage of the program is that it will provide skills not currently available to graduates in any other program, and it will give the graduates an extra competitive edge for getting a job then.

  14. Biophoton signal transmission and processing in the brain.

    PubMed

    Tang, Rendong; Dai, Jiapei

    2014-10-05

    The transmission and processing of neural information in the nervous system plays a key role in neural functions. It is well accepted that neural communication is mediated by bioelectricity and chemical molecules via the processes called bioelectrical and chemical transmission, respectively. Indeed, the traditional theories seem to give valuable explanations for the basic functions of the nervous system, but difficult to construct general accepted concepts or principles to provide reasonable explanations of higher brain functions and mental activities, such as perception, learning and memory, emotion and consciousness. Therefore, many unanswered questions and debates over the neural encoding and mechanisms of neuronal networks remain. Cell to cell communication by biophotons, also called ultra-weak photon emissions, has been demonstrated in several plants, bacteria and certain animal cells. Recently, both experimental evidence and theoretical speculation have suggested that biophotons may play a potential role in neural signal transmission and processing, contributing to the understanding of the high functions of nervous system. In this paper, we review the relevant experimental findings and discuss the possible underlying mechanisms of biophoton signal transmission and processing in the nervous system.

  15. Spatiotemporal Imaging of Glutamate-Induced Biophotonic Activities and Transmission in Neural Circuits

    PubMed Central

    Tang, Rendong; Dai, Jiapei

    2014-01-01

    The processing of neural information in neural circuits plays key roles in neural functions. Biophotons, also called ultra-weak photon emissions (UPE), may play potential roles in neural signal transmission, contributing to the understanding of the high functions of nervous system such as vision, learning and memory, cognition and consciousness. However, the experimental analysis of biophotonic activities (emissions) in neural circuits has been hampered due to technical limitations. Here by developing and optimizing an in vitro biophoton imaging method, we characterize the spatiotemporal biophotonic activities and transmission in mouse brain slices. We show that the long-lasting application of glutamate to coronal brain slices produces a gradual and significant increase of biophotonic activities and achieves the maximal effect within approximately 90 min, which then lasts for a relatively long time (>200 min). The initiation and/or maintenance of biophotonic activities by glutamate can be significantly blocked by oxygen and glucose deprivation, together with the application of a cytochrome c oxidase inhibitor (sodium azide), but only partly by an action potential inhibitor (TTX), an anesthetic (procaine), or the removal of intracellular and extracellular Ca2+. We also show that the detected biophotonic activities in the corpus callosum and thalamus in sagittal brain slices mostly originate from axons or axonal terminals of cortical projection neurons, and that the hyperphosphorylation of microtubule-associated protein tau leads to a significant decrease of biophotonic activities in these two areas. Furthermore, the application of glutamate in the hippocampal dentate gyrus results in increased biophotonic activities in its intrahippocampal projection areas. These results suggest that the glutamate-induced biophotonic activities reflect biophotonic transmission along the axons and in neural circuits, which may be a new mechanism for the processing of neural

  16. 77 FR 19744 - Advanced BioPhotonics, Inc., Advanced Viral Research Corp., Brantley Capital Corp., Brilliant...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-02

    ... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION Advanced BioPhotonics, Inc., Advanced Viral Research Corp., Brantley Capital Corp., Brilliant... information concerning the securities of Advanced BioPhotonics, Inc. because it has not filed any...

  17. The spectrum of courses offered by the Center for Biophotonics Science and Technology (CBST)

    NASA Astrophysics Data System (ADS)

    Molinaro, Marco; Shackelford, James F.

    2007-06-01

    The National Science Foundation (NSF) funded Center for Biophotonics Science and Technology CBST) provides a number of short to full-length courses on the subject of biophotonics. A middle school summer camp and various versions of multi-year high school courses are currently in progress. Two courses define a Biophotonics Option within the Photonics Technology Degree Program at the Central New Mexico Community College. CBST also collaborates with the Integrated Studies Honors Program (ISHP) at UC Davis to provide an introductory course to some of the top students in the freshman class. Advanced undergraduate and graduate courses are provided at UC Davis and sister institutions within CBST.

  18. Biophotonics and immune responses-Highlights from a new SPIE photonics west conference (BIOS 2006).

    PubMed

    Chen, Wei R; Huang, Zheng

    2006-09-01

    This report summarizes some highlights from the "Biophotonics and Immune Responses", a new 2006 SPIE Photonics West Biomedical Optics (BIOS 2006) Conference. Some exciting recent progresses in host immune responses elicited by photodynamic therapy and other novel phototherapies are discussed.

  19. Solid hemoglobin-polymer phantoms for evaluation of biophotonic systems.

    PubMed

    Jang, Hyounguk; Pfefer, T Joshua; Chen, Yu

    2015-09-15

    Stable tissue phantoms that incorporate the spectral absorption properties of hemoglobin would benefit a wide range of biophotonic technologies. Toward this end, we have developed and validated a novel polymer material incorporating hemoglobin. Our solid hemoglobin-polymer (SHP) material is fabricated by mixing liquid silicone base with a hemoglobin solution, followed by sonication and low temperature curing. The optical properties of samples were determined over 450-1000 nm using the inverse adding-doubling method and the Beer-Lambert law. Measurements indicated SHP optical stability over four months. Near-infrared spectroscopy and hyperspectral imaging measurements of SHP samples were performed to demonstrate the utility of this approach. SHP materials have the potential to improve tissue-simulating phantoms used for development, evaluation, and standardization of optical devices for oximetry and other applications.

  20. Biophotonics in diagnosis and modeling of tissue pathologies

    NASA Astrophysics Data System (ADS)

    Serafetinides, A. A.; Makropoulou, M.; Drakaki, E.

    2008-12-01

    Biophotonics techniques are applied to several fields in medicine and biology. The laser based techniques, such as the laser induced fluorescence (LIF) spectroscopy and the optical coherence tomography (OCT), are of particular importance in dermatology, where the laser radiation could be directly applied to the tissue target (e.g. skin). In addition, OCT resolves architectural tissue properties that might be useful as tumour discrimination parameters for skin as well as for ocular non-invasive visualization. Skin and ocular tissues are complex multilayered and inhomogeneous organs with spatially varying optical properties. This fact complicates the quantitative analysis of the fluorescence and/or light scattering spectra, even from the same tissue sample. To overcome this problem, mathematical simulation is applied for the investigation of the human tissue optical properties, in the visible/infrared range of the spectrum, resulting in a better discrimination of several tissue pathologies. In this work, we present i) a general view on biophotonics applications in diagnosis of human diseases, ii) some specific results on laser spectroscopy techniques, as LIF measurements, applied in arterial and skin pathologies and iii) some experimental and theoretical results on ocular OCT measurements. Regarding the LIF spectroscopy, we examined the autofluorescence properties of several human skin samples, excised from humans undergoing biopsy examination. A nitrogen laser was used as an excitation source, emitting at 337 nm (ultraviolet excitation). Histopathology examination of the samples was also performed, after the laser spectroscopy measurements and the results from the spectroscopic and medical analysis were compared, to differentiate malignancies, e.g. basal cell carcinoma tissue (BCC), from normal skin tissue. Regarding the OCT technique, we correlated human data, obtained from patients undergoing OCT examination, with Monte Carlo simulated cornea and retina tissues

  1. Development of a biophotonics technician-training program: directions for the 21st Century

    NASA Astrophysics Data System (ADS)

    Shackelford, James F.; Gellman, Joel; Vasan, Srini; Hall, Robert A.; Goodwin, Don E.; Molinaro, Marco; Matthews, Dennis

    2005-06-01

    Albuquerque Technical Vocational Institute (TVI) is collaborating with the National Science Foundation (NSF) funded Center for Biophotonics Science and Technology (CBST) headquartered at the University of California, Davis in order to develop a biophotonics curriculum for community colleges nationwide. TVI began the formal collaboration to bring about critically needed training and education that will ultimately create new jobs and employment opportunities in the field of biophotonics. "Biophotonics" is the science of generating and harnessing light to detect, image and manipulate biological materials. CBST chose TVI as a partner because of the Institute's current high-level photonics and biotechnology programs. In addition, TVI is a part of the "Albuquerque Model" that involves exposure to photonics education from the middle school level through graduate education at the University of New Mexico. Three middle schools feed into the West Mesa High School Photonics Academy, whose students then move on to TVI for advanced training. CBST brings together scientists, industry, educators and the community to research and develop applications for biophotonics. Roughly 100 researchers-including physical scientists, life scientists, physicians and engineers from UC Davis, Lawrence Livermore National Laboratory, UC Berkeley, UC San Francisco, Alabama A&M University, Stanford University, University of Texas at San Antonio, Fisk University and Mills College-are collaborating in this rapidly developing area of research. Applications of biophotonics range from using light to image or selectively treat tumors, to sequencing DNA and identifying single biomolecules within cells.

  2. Introducing biophotonics to first year undergraduates in science and non-science majors: approaches and lessons learned

    NASA Astrophysics Data System (ADS)

    Molinaro, Marco; Shackelford, James

    2010-08-01

    Engaging students in photonics can be challenging as the field appears lesser known compared to standard majors offered at US Colleges and Universities. At the University of California Davis we teach a well-received introductory biophotonics course that attracts 20-25 honors freshman students yearly. The 40-hour course attracts science, engineering, and humanities majors alike. The course is a basic interdisciplinary exploration of the intersection of biology, physics, medicine, optics and technology with light. In addition to an overview of biophotonics, class participants do hands-on experiments, practice peer-review, interact with biophotonics scientists, and carry out projects to communicate biophotonics to others.

  3. Human high intelligence is involved in spectral redshift of biophotonic activities in the brain

    PubMed Central

    Wang, Niting; Li, Zehua; Xiao, Fangyan; Dai, Jiapei

    2016-01-01

    Human beings hold higher intelligence than other animals on Earth; however, it is still unclear which brain properties might explain the underlying mechanisms. The brain is a major energy-consuming organ compared with other organs. Neural signal communications and information processing in neural circuits play an important role in the realization of various neural functions, whereas improvement in cognitive function is driven by the need for more effective communication that requires less energy. Combining the ultraweak biophoton imaging system (UBIS) with the biophoton spectral analysis device (BSAD), we found that glutamate-induced biophotonic activities and transmission in the brain, which has recently been demonstrated as a novel neural signal communication mechanism, present a spectral redshift from animals (in order of bullfrog, mouse, chicken, pig, and monkey) to humans, even up to a near-infrared wavelength (∼865 nm) in the human brain. This brain property may be a key biophysical basis for explaining high intelligence in humans because biophoton spectral redshift could be a more economical and effective measure of biophotonic signal communications and information processing in the human brain. PMID:27432962

  4. Noninvasive biophotonic imaging for studies of infectious disease

    PubMed Central

    Andreu, Nuria; Zelmer, Andrea; Wiles, Siouxsie

    2011-01-01

    According to World Health Organization estimates, infectious organisms are responsible for approximately one in four deaths worldwide. Animal models play an essential role in the development of vaccines and therapeutic agents but large numbers of animals are required to obtain quantitative microbiological data by tissue sampling. Biophotonic imaging (BPI) is a highly sensitive, nontoxic technique based on the detection of visible light, produced by luciferase-catalysed reactions (bioluminescence) or by excitation of fluorescent molecules, using sensitive photon detectors. The development of bioluminescent/fluorescent microorganisms therefore allows the real-time noninvasive detection of microorganisms within intact living animals. Multiple imaging of the same animal throughout an experiment allows disease progression to be followed with extreme accuracy, reducing the number of animals required to yield statistically meaningful data. In the study of infectious disease, the use of BPI is becoming widespread due to the novel insights it can provide into established models, as well as the impact of the technique on two of the guiding principles of using animals in research, namely reduction and refinement. Here, we review the technology of BPI, from the instrumentation through to the generation of a photonic signal, and illustrate how the technique is shedding light on infection dynamics in vivo. PMID:20955395

  5. Optics and biophotonics of nanoparticles with a plasmon resonance

    SciTech Connect

    Khlebtsov, N G

    2008-06-30

    A brief review of the state of the art in theoretical and experimental studies of the optical properties of metal particles with dipole and multipole plasmon resonances is presented. Metal spheres, nanorods, spherical and elliptic metal nanoshells are considered. The tuning of plasmon resonances of nanoparticles by varying their size, shape, structure, and dielectric environment is described. A large amount of spectrophotometric data on dimensional characteristics of gold colloidal particles is critically analysed and a new calibration of the dependence of their average size on the extinction plasmon resonance wavelength is proposed. A drastic difference between gold and silver colloids in the region of small deviations of their form from spherical is discussed. An example of the excess over not only the Rayleigh limit for the scattering depolarisation factor for dielectric needles (1/3) but also over the plasmon-resonance limit for metal thin rods (3/4) is presented for the first time. The multipole properties of nanorods and universal linear wavelength scaling of multipole resonances are considered depending on the axial ratio of nanoparticles. The outlook for modern trends in biomedical applications of nanoparticles with plasmon resonances is discussed. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)

  6. Biophotonics for imaging and cell manipulation: quo vadis?

    NASA Astrophysics Data System (ADS)

    Serafetinides, Alexandros A.; Makropoulou, Mirsini; Kotsifaki, Domna G.; Tsigaridas, Giorgos

    2016-01-01

    As one of the major health problems for mankind is cancer, any development for the early detection and effective treatment of cancer is crucial to saving lives. Worldwide, the dream for the anti-cancer procedure of attack is the development of a safe and efficient early diagnosis technique, the so called "optical biopsy". As early diagnosis of cancer is associated with improved prognosis, several laser based optical diagnostic methods were developed to enable earlier, non-invasive detection of human cancer, as Laser Induced Fluorescence spectroscopy (LIFs), Diffuse Reflectance spectroscopy (DRs), confocal microscopy, and Optical Coherence Tomography (OCT). Among them, Optical Coherence Tomography (OCT) imaging is considered to be a useful tool to differentiate healthy from malignant (e.g. basal cell carcinoma, squamous cell carcinoma) skin tissue. If the demand is to perform imaging in sub-tissular or even sub-cellular level, optical tweezers and atomic force microscopy have enabled the visualization of molecular events underlying cellular processes in live cells, as well as the manipulation and characterization of microscale or even nanoscale biostructures. In this work, we will present the latest advances in the field of laser imaging and manipulation techniques, discussing some representative experimental data focusing on the 21th century biophotonics roadmap of novel diagnostic and therapeutical approaches. As an example of a recently discussed health and environmental problem, we studied both experimentally and theoretically the optical trapping forces exerted on yeast cells and modified with estrogen-like acting compounds yeast cells, suspended in various buffer media.

  7. Lab-on-a-chip biophotonics: its application to assisted reproductive technologies.

    PubMed

    Lai, David; Smith, Gary D; Takayama, Shuichi

    2012-08-01

    With the benefits of automation, sensitivity and precision, microfluidics has enabled complex and otherwise tedious experiments. Lately, lab-on-a-chip (LOC) has proven to be a useful tool for enhancing non-invasive assisted reproductive technology (ART). Non-invasive gamete and embryo assessment has largely been through periodic morpohological assessment using optical microscopy and early LOC ART was the same. As we realize that morphological assessment is a poor indication of gamete or embryo health, more advanced biophotonics has emerged in LOC ART to assay for metabolites or gamete separation via optoelectrical tweezers. Off-chip, even more advanced biophotonics with broad spectrum analysis of metabolites and secretomes has been developed that show even higher accuracy to predicting reproductive potential. The integration of broad spectrum metabolite analysis into LOC ART is an exciting future that merges automation and sensitivity with the already highly accurate and strong predictive power of biophotonics.

  8. Growth of biophotonic Escherichia coli O157:H7 (ATCC #43888) within rumen fluid media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of biophotonic microbes can allow researchers to gain a better understanding of mechanisms utilized by bacteria to grow and colonize within the ruminant gastrointestinal tract, thus allowing the investigation of how stress management and nutrition impact pathogen shedding in ruminants. Howev...

  9. Genomic instantiation of consciousness in neurons through a biophoton field theory.

    PubMed

    Cacha, Lleuvelyn A; Poznanski, Roman R

    2014-06-01

    A theoretical framework is developed based on the premise that brains evolved into sufficiently complex adaptive systems capable of instantiating genomic consciousness through self-awareness and complex interactions that recognize qualitatively the controlling factors of biological processes. Furthermore, our hypothesis assumes that the collective interactions in neurons yield macroergic effects, which can produce sufficiently strong electric energy fields for electronic excitations to take place on the surface of endogenous structures via alpha-helical integral proteins as electro-solitons. Specifically the process of radiative relaxation of the electro-solitons allows for the transfer of energy via interactions with deoxyribonucleic acid (DNA) molecules to induce conformational changes in DNA molecules producing an ultra weak non-thermal spontaneous emission of coherent biophotons through a quantum effect. The instantiation of coherent biophotons confined in spaces of DNA molecules guides the biophoton field to be instantaneously conducted along the axonal and neuronal arbors and in-between neurons and throughout the cerebral cortex (cortico-thalamic system) and subcortical areas (e.g., midbrain and hindbrain). Thus providing an informational character of the electric coherence of the brain - referred to as quantum coherence. The biophoton field is realized as a conscious field upon the re-absorption of biophotons by exciplex states of DNA molecules. Such quantum phenomenon brings about self-awareness and enables objectivity to have access to subjectivity in the unconscious. As such, subjective experiences can be recalled to consciousness as subjective conscious experiences or qualia through co-operative interactions between exciplex states of DNA molecules and biophotons leading to metabolic activity and energy transfer across proteins as a result of protein-ligand binding during protein-protein communication. The biophoton field as a conscious field is

  10. Amorphic complexity

    NASA Astrophysics Data System (ADS)

    Fuhrmann, G.; Gröger, M.; Jäger, T.

    2016-02-01

    We introduce amorphic complexity as a new topological invariant that measures the complexity of dynamical systems in the regime of zero entropy. Its main purpose is to detect the very onset of disorder in the asymptotic behaviour. For instance, it gives positive value to Denjoy examples on the circle and Sturmian subshifts, while being zero for all isometries and Morse-Smale systems. After discussing basic properties and examples, we show that amorphic complexity and the underlying asymptotic separation numbers can be used to distinguish almost automorphic minimal systems from equicontinuous ones. For symbolic systems, amorphic complexity equals the box dimension of the associated Besicovitch space. In this context, we concentrate on regular Toeplitz flows and give a detailed description of the relation to the scaling behaviour of the densities of the p-skeletons. Finally, we take a look at strange non-chaotic attractors appearing in so-called pinched skew product systems. Continuous-time systems, more general group actions and the application to cut and project quasicrystals will be treated in subsequent work.

  11. Imaging of biophoton emission from electrostimulated skin acupuncture point jg4: effect of light enhancers.

    PubMed

    Slawinski, Janusz; Gorski, Zbigniew

    2008-05-01

    Using an ultrasensitive CCD camera, an extremely low light intensity from the acupuncture-sensitive point JG4 at the left hand was recorded. As the intensity of the light was very weak and the time of electrostimulation exceeded the recommended period, the quality of biophoton images was poor. Chemiluminescent and fluorescent hydrophilic, hydrophobic and amphyphilic molecular probes were used to: (i) ensure penetration of probes into skin, (ii) enhance the intensity of BP emission, (iii) shorten time and (iv) obtain information about mechanisms of biophotons generation in EAP-sensitive points and channels. The results obtained partially fulfilled expectations and indicate on the necessity to elaborate special techniques of probes deposition on the skin.

  12. Involvement of Reactive Oxygen Species and Mitochondrial Proteins in Biophoton Emission in Roots of Soybean Plants under Flooding Stress.

    PubMed

    Kamal, Abu Hena Mostafa; Komatsu, Setsuko

    2015-05-01

    To understand the mechanism of biophoton emission, ROS and mitochondrial proteins were analyzed in soybean plants under flooding stress. Enzyme activity and biophoton emission were increased in the flooding stress samples when assayed in reaction mixes specific for antioxidant enzymes and reactive oxygen species; although the level of the hydroxyl radicals was increased at day 4 (2 days of flooding) compared to nonflooding at day 4, the emission of biophotons did not change. Mitochondria were isolated and purified from the roots of soybean plants grown under flooding stress by using a Percoll gradient, and proteins were analyzed by a gel-free proteomic technique. Out of the 98 mitochondrial proteins that significantly changed abundance under flooding stress, 47 increased and 51 decreased at day 4. The mitochondrial enzymes fumarase, glutathione-S-transferase, and aldehyde dehydrogenase increased at day 4 in protein abundance and enzyme activity. Enzyme activity and biophoton emission decreased at day 4 by the assay of lipoxygenase under stress. Aconitase, acyl CoA oxidase, succinate dehydrogenase, and NADH ubiquinone dehydrogenase were up-regulated at the transcription level. These results indicate that oxidation and peroxide scavenging might lead to biophoton emission and oxidative damage in the roots of soybean plants under flooding stress.

  13. Amorphous metal composites

    DOEpatents

    Byrne, Martin A.; Lupinski, John H.

    1984-01-01

    An improved amorphous metal composite and process of making the composite. The amorphous metal composite comprises amorphous metal (e.g. iron) and a low molecular weight thermosetting polymer binder. The process comprises placing an amorphous metal in particulate form and a thermosetting polymer binder powder into a container, mixing these materials, and applying heat and pressure to convert the mixture into an amorphous metal composite.

  14. Capturing structure and function in an embryonic heart with biophotonic tools

    PubMed Central

    Karunamuni, Ganga H.; Gu, Shi; Ford, Matthew R.; Peterson, Lindsy M.; Ma, Pei; Wang, Yves T.; Rollins, Andrew M.; Jenkins, Michael W.; Watanabe, Michiko

    2014-01-01

    Disturbed cardiac function at an early stage of development has been shown to correlate with cellular/molecular, structural as well as functional cardiac anomalies at later stages culminating in the congenital heart defects (CHDs) that present at birth. While our knowledge of cellular and molecular steps in cardiac development is growing rapidly, our understanding of the role of cardiovascular function in the embryo is still in an early phase. One reason for the scanty information in this area is that the tools to study early cardiac function are limited. Recently developed and adapted biophotonic tools may overcome some of the challenges of studying the tiny fragile beating heart. In this chapter, we describe and discuss our experience in developing and implementing biophotonic tools to study the role of function in heart development with emphasis on optical coherence tomography (OCT). OCT can be used for detailed structural and functional studies of the tubular and looping embryo heart under physiological conditions. The same heart can be rapidly and quantitatively phenotyped at early and again at later stages using OCT. When combined with other tools such as optical mapping (OM) and optical pacing (OP), OCT has the potential to reveal in spatial and temporal detail the biophysical changes that can impact mechanotransduction pathways. This information may provide better explanations for the etiology of the CHDs when interwoven with our understanding of morphogenesis and the molecular pathways that have been described to be involved. Future directions for advances in the creation and use of biophotonic tools are discussed. PMID:25309451

  15. Thermal transport in amorphous materials: a review

    NASA Astrophysics Data System (ADS)

    Wingert, Matthew C.; Zheng, Jianlin; Kwon, Soonshin; Chen, Renkun

    2016-11-01

    Thermal transport plays a crucial role in performance and reliability of semiconductor electronic devices, where heat is mainly carried by phonons. Phonon transport in crystalline semiconductor materials, such as Si, Ge, GaAs, GaN, etc, has been extensively studied over the past two decades. In fact, study of phonon physics in crystalline semiconductor materials in both bulk and nanostructure forms has been the cornerstone of the emerging field of ‘nanoscale heat transfer’. On the contrary, thermal properties of amorphous materials have been relatively less explored. Recently, however, a growing number of studies have re-examined the thermal properties of amorphous semiconductors, such as amorphous Si. These studies, which included both computational and experimental work, have revealed that phonon transport in amorphous materials is perhaps more complicated than previously thought. For instance, depending on the type of amorphous materials, thermal transport occurs via three types of vibrations: propagons, diffusons, and locons, corresponding to the propagating, diffusion, and localized modes, respectively. The relative contribution of each of these modes dictates the thermal conductivity of the material, including its magnitude and its dependence on sample size and temperature. In this article, we will review the fundamental principles and recent development regarding thermal transport in amorphous semiconductors.

  16. Shock induced crystallization of amorphous Nickel powders

    NASA Astrophysics Data System (ADS)

    Cherukara, Mathew; Strachan, Alejandro

    2015-06-01

    Recent experimental work has shown the efficacy of amorphous Ni/crystalline Al composites as energetic materials, with flame velocities twice that of a comparable crystalline Ni/crystalline Al system. Of further interest is the recrystallization mechanisms in the pure amorphous Ni powders, both thermally induced and mechanically induced. We present large-scale molecular dynamics simulations of shock-induced recrystallization in loosely packed amorphous Nickel powders. We study the time dependent nucleation and growth processes by holding the shocked samples at the induced pressures and temperatures for extended periods following the passage of the shock (up to 6 ns). We find that the nanostructure of the recrystallized Ni and time scales of recrystallization are dependent on the piston velocity. At low piston velocities, nucleation events are rare, leading to long incubation times and a relatively coarse nanostructure. At higher piston velocities, local variations in temperature due to jetting phenomena and void collapse, give rise to multiple nucleation events on time scales comparable to the passage of the shock wave, leading to the formation of a fine-grained nanostructure. Interestingly, we observe that the nucleation and growth process occurs in two steps, with the first nuclei crystallizing into the BCC structure, before evolving over time into the expected FCC structure. U.S. Defense Threat Reduction Agency, HDTRA1-10-1-0119 (Program Manager Suhithi Peiris).

  17. Synthesis and Characterization of Luminescent Amorphous Porous Silicon (ap-Si) Nanoparticles via unconventional Stain Etching

    NASA Astrophysics Data System (ADS)

    Tchalala, M. R.; El-Demellawi, J. K.; Mughal, A. J.; Chaieb, S.

    2016-10-01

    Starting from crystalline silicon we synthesised bright suspensions of amorphous porous silicon nanoparticles through unconventional stain etching. Upon excitation with UV light, this novel nanostructured material gives rise to an intense red photoluminescence (PL) which resembles that of some silicon nanostructures. We studied the properties of the prepared nanoparticles using a number of cutting-edge characterization techniques such as TEM, SEM and EDX. The complete crystalline-to-amorphous phase transition, confirmed by the morphological studies, seems fortuitous.

  18. Low-bandgap biophotonic nanoblend: a platform for systemic disease targeting and functional imaging.

    PubMed

    Seo, Young Hun; Cho, Min Ju; Cheong, Oug Jae; Jang, Woo-Dong; Ohulchanskyy, Tymish Y; Lee, Sangyoup; Choi, Dong Hoon; Prasad, Paras N; Kim, Sehoon

    2015-01-01

    Photonic nanomaterials have found wide applications in theranostics. We introduce here a design of all-organic photonic nanoparticles, different from traditional ones, in which we utilize nanoblend of a low-bandgap π-conjugated polymer (LB-CP) and polystyrene as the photonic core, surrounded by an FDA-approved polymeric surfactant. This design provides capability for efficient deep tissue imaging using highly penetrating near-infrared (NIR) excitation and emission of LB-CP and also allows us to incorporate a NIR phosphorescent oxygen-sensitive dye in the core to serve as a dual-emissive probe for hypoxia imaging. These biophotonic nanoblend (BNB) particles (∼20 nm in diameter) show facile blood circulation, efficient disease targeting and minimal liver filtration as well as sustained renal excretion in the intravenously administered mouse models, as noninvasively visualized by the NIR emission signals. In diseased mouse models, pathological tissue deoxygenation at hypoxic sites was successfully detected with ratiometric spectral information. We also show that our nanoformulation exhibits no apparent toxicity, thus serving as a versatile biophotonics platform for diagnostic imaging.

  19. Porphysome nanovesicles generated by porphyrin bilayers for use as multimodal biophotonic contrast agents

    NASA Astrophysics Data System (ADS)

    Lovell, Jonathan F.; Jin, Cheng S.; Huynh, Elizabeth; Jin, Honglin; Kim, Chulhong; Rubinstein, John L.; Chan, Warren C. W.; Cao, Weiguo; Wang, Lihong V.; Zheng, Gang

    2011-04-01

    Optically active nanomaterials promise to advance a range of biophotonic techniques through nanoscale optical effects and integration of multiple imaging and therapeutic modalities. Here, we report the development of porphysomes; nanovesicles formed from self-assembled porphyrin bilayers that generated large, tunable extinction coefficients, structure-dependent fluorescence self-quenching and unique photothermal and photoacoustic properties. Porphysomes enabled the sensitive visualization of lymphatic systems using photoacoustic tomography. Near-infrared fluorescence generation could be restored on dissociation, creating opportunities for low-background fluorescence imaging. As a result of their organic nature, porphysomes were enzymatically biodegradable and induced minimal acute toxicity in mice with intravenous doses of 1,000 mg kg-1. In a similar manner to liposomes, the large aqueous core of porphysomes could be passively or actively loaded. Following systemic administration, porphysomes accumulated in tumours of xenograft-bearing mice and laser irradiation induced photothermal tumour ablation. The optical properties and biocompatibility of porphysomes demonstrate the multimodal potential of organic nanoparticles for biophotonic imaging and therapy.

  20. Dynamic biophotonics: female squid exhibit sexually dimorphic tunable leucophores and iridocytes.

    PubMed

    DeMartini, Daniel G; Ghoshal, Amitabh; Pandolfi, Erica; Weaver, Aaron T; Baum, Mary; Morse, Daniel E

    2013-10-01

    Loliginid squid use tunable multilayer reflectors to modulate the optical properties of their skin for camouflage and communication. Contained inside specialized cells called iridocytes, these photonic structures have been a model for investigations into bio-inspired adaptive optics. Here, we describe two distinct sexually dimorphic tunable biophotonic features in the commercially important species Doryteuthis opalescens: bright stripes of rainbow iridescence on the mantle just beneath each fin attachment and a bright white stripe centered on the dorsal surface of the mantle between the fins. Both of these cellular features are unique to the female; positioned in the same location as the conspicuously bright white testis in the male, they are completely switchable, transitioning between transparency and high reflectivity. The sexual dimorphism, location and tunability of these features suggest that they may function in mating or reproduction. These features provide advantageous new models for investigation of adaptive biophotonics. The intensely reflective cells of the iridescent stripes provide a greater signal-to-noise ratio than the adaptive iridocytes studied thus far, while the cells constituting the white stripe are adaptive leucophores--unique biological tunable broadband scatterers containing Mie-scattering organelles activated by acetylcholine, and a unique complement of reflectin proteins.

  1. Biophotonic low-coherence sensors with boron-doped diamond thin layer

    NASA Astrophysics Data System (ADS)

    Milewska, D.; Karpienko, K.; Sobaszek, M.; Jedrzejewska-Szczerska, M.

    2016-03-01

    Low-coherence sensors using Fabry-Perot interferometers are finding new applications in biophotonic sensing, especially due to the rapid technological advances in the development of new materials. In this paper we discuss the possibility of using boron-doped nanodiamond layers to protect mirror in a Fabry-Perot interferometer. A low-coherence sensor using Fabry-Perot interferometer with a boron-doped nanodiamond (B-NCD) thin protective layer has been developed. B-NCD layers with different boron doping level were investigated. The boron level, expressed as the boron to carbon (/[C]) ratio in the gas phase, was: 0, 2000, 5000 or 10000 ppm. B-NCD layers were grown by chemical vapor deposition (CVD). The sensing Fabry-Perot interferometer, working in the reflective mode, was connected to the source and to the optical processor by single-mode fibers. Superluminescent diodes with Gaussian spectral density were used as sources, while an optical spectrum analyzer was used as an optical processor. The design of the sensing interferometer was optimized to attain the maximum interference contrast. The experiment has shown that B-NCD thin layers can be successfully used in biophotonic sensors.

  2. 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.

  3. Proteins involved in biophoton emission and flooding-stress responses in soybean under light and dark conditions.

    PubMed

    Kamal, Abu Hena Mostafa; Komatsu, Setsuko

    2016-02-01

    To know the molecular systems basically flooding conditions in soybean, biophoton emission measurements and proteomic analyses were carried out for flooding-stressed roots under light and dark conditions. Photon emission was analyzed using a photon counter. Gel-free quantitative proteomics were performed to identify significant changes proteins using the nano LC-MS along with SIEVE software. Biophoton emissions were significantly increased in both light and dark conditions after flooding stress, but gradually decreased with continued flooding exposure compared to the control plants. Among the 120 significantly identified proteins in the roots of soybean plants, 73 and 19 proteins were decreased and increased in the light condition, respectively, and 4 and 24 proteins were increased and decreased, respectively, in the dark condition. The proteins were mainly functionally grouped into cell organization, protein degradation/synthesis, and glycolysis. The highly abundant lactate/malate dehydrogenase proteins were decreased in flooding-stressed roots exposed to light, whereas the lysine ketoglutarate reductase/saccharopine dehydrogenase bifunctional enzyme was increased in both light and dark conditions. Notably, however, specific enzyme assays revealed that the activities of these enzymes and biophoton emission were sharply increased after 3 days of flooding stress. This finding suggests that the source of biophoton emission in roots might involve the chemical excitation of electron or proton through enzymatic or non-enzymatic oxidation and reduction reactions. Moreover, the lysine ketoglutarate reductase/saccharopine dehydrogenase bifunctional enzyme may play important roles in responses in flooding stress of soybean under the light condition and as a contributing factor to biophoton emission.

  4. Exosomes are released by bystander cells exposed to radiation-induced biophoton signals: Reconciling the mechanisms mediating the bystander effect

    PubMed Central

    Fernandez-Palomo, Cristian; McNeill, Fiona E.; Seymour, Colin B.; Rainbow, Andrew J.; Mothersill, Carmel E.

    2017-01-01

    Objective The objective of our study was to explore a possible molecular mechanism by which ultraviolet (UV) biophotons could elicit bystander responses in reporter cells and resolve the problem of seemingly mutually exclusive mechanisms of a physical UV signal & a soluble factor-mediated bystander signal. Methods The human colon carcinoma cell line, HCT116 p53 +/+, was directly irradiated with 0.5 Gy tritium beta particles to induce ultraviolet biophoton emission. Bystander cells were not directly irradiated but were exposed to the emitted UV biophotons. Medium was subsequently harvested from UV-exposed bystander cells. The exosomes extracted from this medium were incubated with reporter cell populations. These reporter cells were then assayed for clonogenic survival and mitochondrial membrane potential with and without prior treatment of the exosomes with RNase. Results Clonogenic cell survival was significantly reduced in reporter cells incubated with exosomes extracted from cells exposed to secondarily-emitted UV. These exosomes also induced significant mitochondrial membrane depolarization in receiving reporter cells. Conversely, exosomes extracted from non-UV-exposed cells did not produce bystander effects in reporter cells. The treatment of exosomes with RNase prior to their incubation with reporter cells effectively abolished bystander effects in reporter cells and this suggests a role for RNA in mediating the bystander response elicited by UV biophotons and their produced exosomes. Conclusion This study supports a role for exosomes released from UV biophoton-exposed bystander cells in eliciting bystander responses and also indicates a reconciliation between the UV-mediated bystander effect and the bystander effect which has been suggested in the literature to be mediated by soluble factors. PMID:28278290

  5. Amorphous carbon for photovoltaics

    NASA Astrophysics Data System (ADS)

    Risplendi, Francesca; Grossman, Jeffrey C.

    2015-03-01

    All-carbon solar cells have attracted attention as candidates for innovative photovoltaic devices. Carbon-based materials such as graphene, carbon nanotubes (CNT) and amorphous carbon (aC) have the potential to present physical properties comparable to those of silicon-based materials with advantages such as low cost and higher thermal stability.In particular a-C structures are promising systems in which both sp2 and sp3 hybridization coordination are present in different proportions depending on the specific density, providing the possibility of tuning their optoelectronic properties and achieving comparable sunlight absorption to aSi. In this work we employ density functional theory to design suitable device architectures, such as bulk heterojunctions (BHJ) or pn junctions, consisting of a-C as the active layer material.Regarding BHJ, we study interfaces between aC and C nanostructures (such as CNT and fullerene) to relate their optoelectronic properties to the stoichiometry of aC. We demonstrate that the energy alignment between the a-C mobility edges and the occupied and unoccupied states of the CNT or C60 can be widely tuned by varying the aC density to obtain a type II interface.To employ aC in pn junctions we analyze the p- and n-type doping of a-C focusingon an evaluation of the Fermi level and work function dependence on doping.Our results highlight promising features of aC as the active layer material of thin-film solar cells.

  6. Theory of amorphous ices

    PubMed Central

    Limmer, David T.; Chandler, David

    2014-01-01

    We derive a phase diagram for amorphous solids and liquid supercooled water and explain why the amorphous solids of water exist in several different forms. Application of large-deviation theory allows us to prepare such phases in computer simulations. Along with nonequilibrium transitions between the ergodic liquid and two distinct amorphous solids, we establish coexistence between these two amorphous solids. The phase diagram we predict includes a nonequilibrium triple point where two amorphous phases and the liquid coexist. Whereas the amorphous solids are long-lived and slowly aging glasses, their melting can lead quickly to the formation of crystalline ice. Further, melting of the higher density amorphous solid at low pressures takes place in steps, transitioning to the lower-density glass before accessing a nonequilibrium liquid from which ice coarsens. PMID:24858957

  7. Growth Control and Biophoton Radiation by Plant Hormones in Red Bean

    NASA Astrophysics Data System (ADS)

    Kai, Shoichi; Moriya, Tomoyuki; Fujimoto, Tokio

    1995-12-01

    The growth kinetics of seeds of red beans ( Phaseolus angularis ) was investigated by externally adding various hormones (gibberellin (GA3)), abscisic acid (ABA) and indole acetic acid (IAA)) during germination. For root growth of red beans, GA3 always acted as an activator while ABA as an inhibitor. IAA was both an activator and an inhibitor depending on its concentration. Root growth could be described by a stochastic logistic equation. The hormone concentration dependences of coefficients of the equation were determined. The hormone influences on biophoton radiation were also investgated. With GA3, the intensity of spontaneous bioluminescence increased with time and showed two strong radiation periods, in which strong localization of bioluminescence was induced. However with ABA and IAA, weaker bioluminescences were observed. The location of the strong radiation induced by GA3 was determined as the growing point near a root cap, by use of a two-dimensional photon counting system.

  8. Aqueous phase synthesis of CdTe quantum dots for biophotonics.

    PubMed

    Yong, Ken-Tye; Law, Wing-Cheung; Roy, Indrajit; Jing, Zhu; Huang, Huijie; Swihart, Mark T; Prasad, Paras N

    2011-01-01

    Over the past few years, CdTe quantum dots have been demonstrated as powerful probes for biophotonics applications. The aqueous phase synthesis technique remains the best approach to make high quality CdTe QDs in a single-pot process. CdTe QDs prepared directly in the aqueous phase can have quantum yield as high as 80%. In addition, the surface of CdTe QDs prepared using the aqueous phase technique is functionalized with reactive groups that enable them to be directly conjugated with specific ligands for targeted delivery and sensing. In this contribution, we review recent progress in fabricating aqueous CdTe QDs and exploiting their optical properties in novel approaches to biomedical imaging and sensing applications.

  9. Biophotonics Master studies: teaching and training experience at University of Latvia

    NASA Astrophysics Data System (ADS)

    Spigulis, Janis

    2007-06-01

    Two-year program for Master's studies on Biophotonics (Biomedical Optics) has been originally developed and carried out at University of Latvia since 1995. The Curriculum contains basic subjects like Fundamentals of Biomedical Optics, Medical Lightguides, Anatomy and Physiology, Lasers and Non-coherent Light Sources, Basic Physics, etc. Student laboratories, special English Terminology and Laboratory-Clinical Praxis are also involved as the training components, and Master project is the final step for the degree award. Life-long learning is supported by several E-courses and an extensive short course for medical laser users "Lasers and Bio-optics in Medicine". Recently a new inter-university European Social Fund project was started to adapt the program accordingly to the Bologna Declaration guidelines.

  10. Detecting presence of cardiovascular disease through mitochondria respiration as depicted through biophotonic emission

    PubMed Central

    Rizzo, Nancy R.; Hank, Nicole C.; Zhang, Jian

    2015-01-01

    Aims Increased production of reactive oxygen species (ROS) in mitochondria, play an important role in the cardiovascular system. Furthermore, oxidative metabolism of mitochondria comprised of biophoton emissions, are linked to ROS and oxidative stress. In this review we investigated the association between the ability of ClearViewTM system (ClearView) to indicate the presence or absence of cardiovascular disease through mitochondria respiration as depicted through biophotonic emission. Methods and results One hundred and ninety-five out of the three hundred and fifty-three human subjects enrolled in this prospective, single site study had at least one cardiovascular related diagnosis. Measurements with ClearView consisted of scanning all 10 fingers twice. Images were captured through the ClearView software and analyzed to produce a scale that indicates the presence or absence of cardiovascular disease. The association of ClearView's ability to indicate the presence or absence of cardiovascular disease with a physician's diagnosis was assessed using odds ratios (OR) and area under ROC curve (AUC). Adjusting for age, OR of ClearView measurements conducted with capacitive barrier was 3.44 (95%CI: 2.13, 5.55) and the OR without the capacitive barrier was 2.15 (95%CI: 1.42, 3.23). The OR in men were 5.91 (95%CI: 2.35, 14.85) and 2.88 (95%CI: 1.38, 6.01), adjusting for age and corresponding to with and without capacitive barrier. The OR in women were 3.50 (95%CI: 1.86, 6.59) and 2.09 (95%CI: 1.20, 3.64) with and without capacitive barrier. AUCs for measurements with capacitive barrier were >0.90. Conclusion ClearView detected the presence or absence of cardiovascular disease independent of other conditions. PMID:26722839

  11. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  12. Nanostructured materials

    NASA Astrophysics Data System (ADS)

    Moriarty, Philip

    2001-03-01

    Nanostructured materials may be defined as those materials whose structural elements - clusters, crystallites or molecules - have dimensions in the 1 to 100 nm range. The explosion in both academic and industrial interest in these materials over the past decade arises from the remarkable variations in fundamental electrical, optical and magnetic properties that occur as one progresses from an `infinitely extended' solid to a particle of material consisting of a countable number of atoms. This review details recent advances in the synthesis and investigation of functional nanostructured materials, focusing on the novel size-dependent physics and chemistry that results when electrons are confined within nanoscale semiconductor and metal clusters and colloids. Carbon-based nanomaterials and nanostructures including fullerenes and nanotubes play an increasingly pervasive role in nanoscale science and technology and are thus described in some depth. Current nanodevice fabrication methods and the future prospects for nanostructured materials and nanodevices are discussed.

  13. The mechanism and properties of bio-photon emission and absorption in protein molecules in living systems

    NASA Astrophysics Data System (ADS)

    Pang, Xiao-feng

    2012-05-01

    The mechanism and properties of bio-photon emission and absorption in bio-tissues were studied using Pang's theory of bio-energy transport, in which the energy spectra of protein molecules are obtained from the discrete dynamic equation. From the energy spectra, it was determined that the protein molecules could both radiate and absorb bio-photons with wavelengths of <3 μm and 5-7 μm, consistent with the energy level transitions of the excitons. These results were consistent with the experimental data; this consisted of infrared absorption data from collagen, bovine serum albumin, the protein-like molecule acetanilide, plasma, and a person's finger, and the laser-Raman spectra of acidity I-type collagen in the lungs of a mouse, and metabolically active Escherichia coli. We further elucidated the mechanism responsible for the non-thermal biological effects produced by the infrared light absorbed by the bio-tissues, using the above results. No temperature rise was observed; instead, the absorbed infrared light promoted the vibrations of amides as well the transport of the bio-energy from one place to other in the protein molecules, which changed their conformations. These experimental results, therefore, not only confirmed the validity of the mechanism of bio-photon emission, and the newly developed theory of bio-energy transport mentioned above, but also explained the mechanism and properties of the non-thermal biological effects produced by the absorption of infrared light by the living systems.

  14. Femtosecond laser crystallization of amorphous Ge

    SciTech Connect

    Salihoglu, Omer; Aydinli, Atilla; Kueruem, Ulas; Gul Yaglioglu, H.; Elmali, Ayhan

    2011-06-15

    Ultrafast crystallization of amorphous germanium (a-Ge) in ambient has been studied. Plasma enhanced chemical vapor deposition grown a-Ge was irradiated with single femtosecond laser pulses of various durations with a range of fluences from below melting to above ablation threshold. Extensive use of Raman scattering has been employed to determine post solidification features aided by scanning electron microscopy and atomic force microscopy measurements. Linewidth of the Ge optic phonon at 300 cm{sup -1} as a function of laser fluence provides a signature for the crystallization of a-Ge. Various crystallization regimes including nanostructures in the form of nanospheres have been identified.

  15. Femtosecond laser crystallization of amorphous Ge

    NASA Astrophysics Data System (ADS)

    Salihoglu, Omer; Kürüm, Ulaş; Yaglioglu, H. Gul; Elmali, Ayhan; Aydinli, Atilla

    2011-06-01

    Ultrafast crystallization of amorphous germanium (a-Ge) in ambient has been studied. Plasma enhanced chemical vapor deposition grown a-Ge was irradiated with single femtosecond laser pulses of various durations with a range of fluences from below melting to above ablation threshold. Extensive use of Raman scattering has been employed to determine post solidification features aided by scanning electron microscopy and atomic force microscopy measurements. Linewidth of the Ge optic phonon at 300 cm-1 as a function of laser fluence provides a signature for the crystallization of a-Ge. Various crystallization regimes including nanostructures in the form of nanospheres have been identified.

  16. Effect of Amorphisation on the Thermal Properties of Nanostructured Membranes

    NASA Astrophysics Data System (ADS)

    Termentzidis, Konstantinos; Verdier, Maxime; Lacroix, David

    2017-02-01

    The majority of the silicon devices contain amorphous phase and amorphous/crystalline interfaces which both considerably affect the transport of energy carriers as phonons and electrons. In this article, we investigate the impact of amorphous phases (both amorphous silicon and amorphous SiO2) of silicon nanoporous membranes on their thermal properties via molecular dynamics simulations. We show that a small fraction of amorphous phase reduces dramatically the thermal transport. One can even create nanostructured materials with subamorphous thermal conductivity, while keeping an important crystalline fraction. In general, the a-SiO2 shell around the pores reduces the thermal conductivity by a factor of five to ten compared to a-Si shell. The phonon density of states for several systems is also given to give the impact of the amorphisation on the phonon modes.

  17. Trehalose amorphization and recrystallization.

    PubMed

    Sussich, Fabiana; Cesàro, Attilio

    2008-10-13

    The stability of the amorphous trehalose prepared by using several procedures is presented and discussed. Amorphization is shown to occur by melting (T(m)=215 degrees C) or milling (room temperature) the crystalline anhydrous form TRE-beta. Fast dehydration of the di-hydrate crystalline polymorph, TRE-h, also produces an amorphous phase. Other dehydration procedures of TRE-h, such as microwave treatment, supercritical extraction or gentle heating at low scan rates, give variable fractions of the polymorph TRE-alpha, that undergo amorphization upon melting (at lower temperature, T(m)=130 degrees C). Additional procedures for amorphization, such as freeze-drying, spray-drying or evaporation of trehalose solutions, are discussed. All these procedures are classified depending on the capability of the undercooled liquid phase to undergo cold crystallization upon heating the glassy state at temperatures above the glass transition temperature (T(g)=120 degrees C). The recrystallizable amorphous phase is invariably obtained by the melt of the polymorph TRE-alpha, while other procedures always give an amorphous phase that is unable to crystallize above T(g). The existence of two different categories is analyzed in terms of the transformation paths and the hypothesis that the systems may exhibit different molecular mobilities.

  18. Hydrogen in amorphous silicon

    SciTech Connect

    Peercy, P. S.

    1980-01-01

    The structural aspects of amorphous silicon and the role of hydrogen in this structure are reviewed with emphasis on ion implantation studies. In amorphous silicon produced by Si ion implantation of crystalline silicon, the material reconstructs into a metastable amorphous structure which has optical and electrical properties qualitatively similar to the corresponding properties in high-purity evaporated amorphous silicon. Hydrogen studies further indicate that these structures will accomodate less than or equal to 5 at.% hydrogen and this hydrogen is bonded predominantly in a monohydride (SiH/sub 1/) site. Larger hydrogen concentrations than this can be achieved under certain conditions, but the excess hydrogen may be attributed to defects and voids in the material. Similarly, glow discharge or sputter deposited amorphous silicon has more desirable electrical and optical properties when the material is prepared with low hydrogen concentration and monohydride bonding. Results of structural studies and hydrogen incorporation in amorphous silicon were discussed relative to the different models proposed for amorphous silicon.

  19. Biophotonic effect of diode laser irradiance on tensile strength of diabetic rats.

    PubMed

    Lau, Pik Suan; Bidin, Noriah; Krishnan, Ganesan; Nassir, Zaleha; Bahktiar, Hazri

    2015-04-01

    Low-energy laser irradiance at certain wavelengths is able to stimulate the tissue bio-reaction and enhance the healing process. Collagen deposition is one of the important aspects in healing process because it can increase the strength of the skin. This study was designed to examine the biophotonic effect of irradiance on collagen production of diabetic wound in rat model. The tensile strength of skin was employed as a parameter to describe the wound. Diabetic rat models were induced by streptozotocin via intravenous injection. Skin-breaking strength was measured using an Instron tensile test machine. The experimental animals were treated with 808-nm diode laser at two different powers-0.1 and 0.5 W/cm(2)-and 30, 60, and 120 s for each session. The tensile strength was optimized after treated with high-power diode laser. The photostimulation effect was revealed by accelerated healing process and enhanced tensile strength of wound. Laser photostimulation on tensile strength in diabetic wound suggests that such therapy facilitates collagen production in diabetic wound healing.

  20. Cyclable Condensation and Hierarchical Assembly of Metastable Reflectin Proteins, the Drivers of Tunable Biophotonics*

    PubMed Central

    Levenson, Robert; Bracken, Colton; Bush, Nicole; Morse, Daniel E.

    2016-01-01

    Reversible changes in the phosphorylation of reflectin proteins have been shown to drive the tunability of color and brightness of light reflected from specialized cells in the skin of squids and related cephalopods. We show here, using dynamic light scattering, electron microscopy, and fluorescence analyses, that reversible titration of the excess positive charges of the reflectins, comparable with that produced by phosphorylation, is sufficient to drive the reversible condensation and hierarchical assembly of these proteins. The results suggest a two-stage process in which charge neutralization first triggers condensation, resulting in the emergence of previously cryptic structures that subsequently mediate reversible, hierarchical assembly. The extent to which cyclability is seen in the in vitro formation and disassembly of complexes estimated to contain several thousand reflectin molecules suggests that intrinsic sequence- and structure-determined specificity governs the reversible condensation and assembly of the reflectins and that these processes are therefore sufficient to produce the reversible changes in refractive index, thickness, and spacing of the reflectin-containing subcellular Bragg lamellae to change the brightness and color of reflected light. This molecular mechanism points to the metastability of reflectins as the centrally important design principle governing biophotonic tunability in this system. PMID:26719342

  1. Investigation on dynamics of red blood cells through their behavior as biophotonic lenses

    NASA Astrophysics Data System (ADS)

    Memmolo, Pasquale; Merola, Francesco; Miccio, Lisa; Mugnano, Martina; Ferraro, Pietro

    2016-12-01

    The possibility to adopt biological matter as photonic optical elements can open scenarios in biophotonics research. Recently, it has been demonstrated that a red blood cell (RBC) can be seen as an optofluidic microlens by showing its imaging capability as well as its focal tunability. Moreover, correlation between an RBC's morphology and its behavior as a refractive optical element has been established and its exploitation for biomedical diagnostic purposes has been foreseen. In fact, any deviation from the healthy RBC morphology can be seen as additional aberration in the optical wavefront passing through the cell. By this concept, accurate localization of focal spots of RBCs can become very useful in the blood disorders identification. We investigate the three-dimensional positioning of such focal spots over time for samples with two different osmolarity conditions, i.e., when they assume discocyte and spherical shapes, respectively. We also demonstrate that a temporal variation of an RBC's focal points along the optical axis is correlated to the temporal fluctuations in the RBC's thickness maps. Furthermore, we show a sort of synchronization of the whole erythrocytes ensemble.

  2. Transmission matrix of a scattering medium and its applications in biophotonics.

    PubMed

    Kim, Moonseok; Choi, Wonjun; Choi, Youngwoon; Yoon, Changhyeong; Choi, Wonshik

    2015-05-18

    A conventional lens has well-defined transfer function with which we can form an image of a target object. On the contrary, scattering media such as biological tissues, multimode optical fibers and layers of disordered nanoparticles have highly complex transfer function, which makes them impractical for the general imaging purpose. In recent studies, we presented a method of experimentally recording the transmission matrix of such media, which is a measure of the transfer function. In this review paper, we introduce two major applications of the transmission matrix: enhancing light energy delivery and imaging through scattering media. For the former, we identified the eigenchannels of the transmission matrix with large eigenvalues and then coupled light to those channels in order to enhance light energy delivery through the media. For the latter, we solved matrix inversion problem to reconstruct an object image from the distorted image by the scattering media. We showed the enlargement of the numerical aperture of imaging systems with the use of scattering media and demonstrated endoscopic imaging through a single multimode optical fiber working in both reflectance and fluorescence modes. Our approach will pave the way of using scattering media as unique optical elements for various biophotonics applications.

  3. Infrared Thermography-based Biophotonics: Integrated Diagnostic Technique for Systemic Reaction Monitoring

    NASA Astrophysics Data System (ADS)

    Vainer, Boris G.; Morozov, Vitaly V.

    A peculiar branch of biophotonics is a measurement, visualisation and quantitative analysis of infrared (IR) radiation emitted from living object surfaces. Focal plane array (FPA)-based IR cameras make it possible to realize in medicine the so called interventional infrared thermal diagnostics. An integrated technique aimed at the advancement of this new approach in biomedical science and practice is described in the paper. The assembled system includes a high-performance short-wave (2.45-3.05 μm) or long-wave (8-14 μm) IR camera, two laser Doppler flowmeters (LDF) and additional equipment and complementary facilities implementing the monitoring of human cardiovascular status. All these means operate synchronously. It is first ascertained the relationship between infrared thermography (IRT) and LDF data in humans in regard to their systemic cardiovascular reactivity. Blood supply real-time dynamics in a narcotized patient is first visualized and quantitatively represented during surgery in order to observe how the general hyperoxia influences thermoregulatory mechanisms; an abrupt increase in temperature of the upper limb is observed using IRT. It is outlined that the IRT-based integrated technique may act as a take-off runway leading to elaboration of informative new methods directly applicable to medicine and biomedical sciences.

  4. One-Dimensional Peptide Nanostructure Templated Growth of Iron Phosphate Nanostructures for Lithium-Ion Battery Cathodes.

    PubMed

    Susapto, Hepi Hari; Kudu, O Ulas; Garifullin, Ruslan; Yılmaz, Eda; Guler, Mustafa O

    2016-07-13

    Template-directed synthesis of nanomaterials can provide benefits such as small crystalline size, high surface area, large surface-to-volume ratio, and structural stability. These properties are important for shorter distance in ion/electron movement and better electrode surface/electrolyte contact for energy storage applications. Here nanostructured FePO4 cathode materials were synthesized by using peptide nanostructures as a template inspired by biomineralization process. The amorphous, high surface area FePO4 nanostructures were utilized as a cathode for lithium-ion batteries. Discharge capacity of 155 mAh/g was achieved at C/20 current rate. The superior properties of biotemplated and nanostructured amorphous FePO4 are shown compared to template-free crystalline FePO4.

  5. Amorphous diamond films

    DOEpatents

    Falabella, S.

    1998-06-09

    Amorphous diamond films having a significant reduction in intrinsic stress are prepared by biasing a substrate to be coated and depositing carbon ions thereon under controlled temperature conditions. 1 fig.

  6. Amorphous pharmaceutical solids.

    PubMed

    Vranić, Edina

    2004-07-01

    Amorphous forms are, by definition, non-crystalline materials which possess no long-range order. Their structure can be thought of as being similar to that of a frozen liquid with the thermal fluctuations present in a liquid frozen out, leaving only "static" structural disorder. The amorphous solids have always been an essential part of pharmaceutical research, but the current interest has been raised by two developments: a growing attention to pharmaceutical solids in general, especially polymorphs and solvates and a revived interest in the science of glasses and the glass transition. Amorphous substances may be formed both intentionally and unintentionally during normal pharmaceutical manufacturing operations. The properties of amorphous materials can be exploited to improve the performance of pharmaceutical dosage forms, but these properties can also give rise to unwanted effects that need to be understood and managed in order for the systems to perform as required.

  7. Amorphous metal alloy

    DOEpatents

    Wang, R.; Merz, M.D.

    1980-04-09

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  8. Characterisation of amorphous and nanocrystalline molecular materials by total scattering

    SciTech Connect

    Billinge, Simon J.L.; Dykhne, Timur; Juhás, Pavol; Boin, Emil; Taylor, Ryan; Florence, Alastair J.; Shankland, Kenneth

    2010-09-17

    The use of high-energy X-ray total scattering coupled with pair distribution function analysis produces unique structural fingerprints from amorphous and nanostructured phases of the pharmaceuticals carbamazepine and indomethacin. The advantages of such facility-based experiments over laboratory-based ones are discussed and the technique is illustrated with the characterisation of a melt-quenched sample of carbamazepine as a nanocrystalline (4.5 nm domain diameter) version of form III.

  9. Advanced biosensing methodologies developed for evaluating performance quality and safety of emerging biophotonics technologies and medical devices (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Ilev, Ilko K.; Walker, Bennett; Calhoun, William; Hassan, Moinuddin

    2016-03-01

    Biophotonics is an emerging field in modern biomedical technology that has opened up new horizons for transfer of state-of-the-art techniques from the areas of lasers, fiber optics and biomedical optics to the life sciences and medicine. This field continues to vastly expand with advanced developments across the entire spectrum of biomedical applications ranging from fundamental "bench" laboratory studies to clinical patient "bedside" diagnostics and therapeutics. However, in order to translate these technologies to clinical device applications, the scientific and industrial community, and FDA are facing the requirement for a thorough evaluation and review of laser radiation safety and efficacy concerns. In many cases, however, the review process is complicated due the lack of effective means and standard test methods to precisely analyze safety and effectiveness of some of the newly developed biophotonics techniques and devices. There is, therefore, an immediate public health need for new test protocols, guidance documents and standard test methods to precisely evaluate fundamental characteristics, performance quality and safety of these technologies and devices. Here, we will overview our recent developments of novel test methodologies for safety and efficacy evaluation of some emerging biophotonics technologies and medical devices. These methodologies are based on integrating the advanced features of state-of-the-art optical sensor technologies and approaches such as high-resolution fiber-optic sensing, confocal and optical coherence tomography imaging, and infrared spectroscopy. The presentation will also illustrate some methodologies developed and implemented for testing intraocular lens implants, biochemical contaminations of medical devices, ultrahigh-resolution nanoscopy, and femtosecond laser therapeutics.

  10. Sub-amorphous thermal conductivity in ultrathin crystalline silicon nanotubes.

    PubMed

    Wingert, Matthew C; Kwon, Soonshin; Hu, Ming; Poulikakos, Dimos; Xiang, Jie; Chen, Renkun

    2015-04-08

    Thermal transport behavior in nanostructures has become increasingly important for understanding and designing next generation electronic and energy devices. This has fueled vibrant research targeting both the causes and ability to induce extraordinary reductions of thermal conductivity in crystalline materials, which has predominantly been achieved by understanding that the phonon mean free path (MFP) is limited by the characteristic size of crystalline nanostructures, known as the boundary scattering or Casimir limit. Herein, by using a highly sensitive measurement system, we show that crystalline Si (c-Si) nanotubes (NTs) with shell thickness as thin as ∼5 nm exhibit a low thermal conductivity of ∼1.1 W m(-1) K(-1). Importantly, this value is lower than the apparent boundary scattering limit and is even about 30% lower than the measured value for amorphous Si (a-Si) NTs with similar geometries. This finding diverges from the prevailing general notion that amorphous materials represent the lower limit of thermal transport but can be explained by the strong elastic softening effect observed in the c-Si NTs, measured as a 6-fold reduction in Young's modulus compared to bulk Si and nearly half that of the a-Si NTs. These results illustrate the potent prospect of employing the elastic softening effect to engineer lower than amorphous, or subamorphous, thermal conductivity in ultrathin crystalline nanostructures.

  11. TEM study of annealed Pt nanostructures grown by electron beam-induced deposition

    NASA Astrophysics Data System (ADS)

    Frabboni, S.; Gazzadi, G. C.; Spessot, A.

    2007-03-01

    In this paper we report on the microstructural characterization of Pt nanostructures fabricated by electron beam-induced deposition in a dual beam system and subsequently annealed in furnace. The as-deposited nanostructures are made of a mixture of nanocrystalline Pt and amorphous carbon. We show by transmission electron microscopy and electron energy loss spectroscopy that the annealing in presence of oxygen at 550 °C for 30 min is able to remove the amorphous carbon from the nanostructure, leaving polycrystalline Pt grains.

  12. Quantitative assessment of biophotonic imaging system performance with phantoms fabricated by rapid prototyping

    NASA Astrophysics Data System (ADS)

    Wang, Jianting; Coburn, James; Woolsey, Nicholas; Liang, Chia-Pin; Ramella-Roman, Jessica; Chen, Yu; Pfefer, Joshua

    2014-03-01

    In biophotonic imaging, turbid phantoms that are low-cost, biologically-relevant, and durable are desired for standardized performance assessment. Such phantoms often contain inclusions of varying depths and sizes in order to quantify key image quality characteristics such as penetration depth, sensitivity and contrast detectability. The emerging technique of rapid prototyping with three-dimensional (3D) printers provides a potentially revolutionary way to fabricate these structures. Towards this goal, we have characterized the optical properties and morphology of phantoms fabricated by two 3D printing approaches: thermosoftening and photopolymerization. Material optical properties were measured by spectrophotometry while the morphology of phantoms incorporating 0.2-1.0 mm diameter channels was studied by μCT, optical coherence tomography (OCT) and optical microscopy. A near-infrared absorbing dye and nanorods at several concentrations were injected into channels to evaluate detectability with a near-infrared hyperspectral reflectance imaging (HRI) system (650-1100 nm). Phantoms exhibited biologically-relevant scattering and low absorption across visible and near-infrared wavelengths. Although limitations in resolution were noted, channels with diameters of 0.4 mm or more could be reliably fabricated. The most significant problem noted was the porosity of phantoms generated with the thermosoftening-based printer. The aforementioned three imaging methods provided a valuable mix of insights into phantom morphology and may also be useful for detailed structural inspection of medical devices fabricated by rapid prototyping, such as customized implants. Overall, our findings indicate that 3D printing has significant potential as a method for fabricating well-characterized, standard phantoms for medical imaging modalities such as HRI.

  13. Metallic glass nanostructures: fabrication, properties, and applications.

    PubMed

    Liu, Lianci; Hasan, Molla; Kumar, Golden

    2014-02-21

    Remarkable progress has been made in fabrication and characterization of metal nanostructures because of their crucial role in energy conversion, nanophotonics, nanoelectronics, and biodiagnostics. Less emphasis has been placed on the synthesis of nanostructures from metallic alloys, which are better suited than elemental metals for certain applications such as fuel-cell catalysts. The main challenges in fabrication of alloy nanostructures are controlling their chemical stoichiometry, crystal structures, and shapes because of anisotropic nucleation and growth rates. These limitations can be overcome by using metallic glasses (amorphous metal alloys) which are isotropic and provide additional control handles through their tunable compositions and degree of crystallinity. Here, we review the recent developments in fabrication and characterization of metallic glass (MG) nanostructures. The focus is on sub-micron structures synthesized by unconventional thermoplastic techniques. A concept of self-assembly is introduced for fashioning functional structures using MG nanostructures as building blocks. The article concludes with a brief discussion about unique properties and prospective applications of MG nanostructures.

  14. Formation of amorphous materials

    DOEpatents

    Johnson, William L.; Schwarz, Ricardo B.

    1986-01-01

    Metastable amorphous or fine crystalline materials are formed by solid state reactions by diffusion of a metallic component into a solid compound or by diffusion of a gas into an intermetallic compound. The invention can be practiced on layers of metals deposited on an amorphous substrate or by intermixing powders with nucleating seed granules. All that is required is that the diffusion of the first component into the second component be much faster than the self-diffusion of the first component. The method is practiced at a temperature below the temperature at which the amorphous phase transforms into one or more crystalline phases and near or below the temperature at which the ratio of the rate of diffusion of the first component to the rate of self-diffusion is at least 10.sup.4. This anomalous diffusion criteria is found in many binary, tertiary and higher ordered systems of alloys and appears to be found in all alloy systems that form amorphous materials by rapid quenching. The method of the invention can totally convert much larger dimensional materials to amorphous materials in practical periods of several hours or less.

  15. A Novel Nanofabrication Technique of Silicon-Based Nanostructures.

    PubMed

    Meng, Lingkuan; He, Xiaobin; Gao, Jianfeng; Li, Junjie; Wei, Yayi; Yan, Jiang

    2016-12-01

    A novel nanofabrication technique which can produce highly controlled silicon-based nanostructures in wafer scale has been proposed using a simple amorphous silicon (α-Si) material as an etch mask. SiO2 nanostructures directly fabricated can serve as nanotemplates to transfer into the underlying substrates such as silicon, germanium, transistor gate, or other dielectric materials to form electrically functional nanostructures and devices. In this paper, two typical silicon-based nanostructures such as nanoline and nanofin have been successfully fabricated by this technique, demonstrating excellent etch performance. In addition, silicon nanostructures fabricated above can be further trimmed to less than 10 nm by combing with assisted post-treatment methods. The novel nanofabrication technique will be expected a new emerging technology with low process complexity and good compatibility with existing silicon integrated circuit and is an important step towards the easy fabrication of a wide variety of nanoelectronics, biosensors, and optoelectronic devices.

  16. A Novel Nanofabrication Technique of Silicon-Based Nanostructures

    NASA Astrophysics Data System (ADS)

    Meng, Lingkuan; He, Xiaobin; Gao, Jianfeng; Li, Junjie; Wei, Yayi; Yan, Jiang

    2016-11-01

    A novel nanofabrication technique which can produce highly controlled silicon-based nanostructures in wafer scale has been proposed using a simple amorphous silicon (α-Si) material as an etch mask. SiO2 nanostructures directly fabricated can serve as nanotemplates to transfer into the underlying substrates such as silicon, germanium, transistor gate, or other dielectric materials to form electrically functional nanostructures and devices. In this paper, two typical silicon-based nanostructures such as nanoline and nanofin have been successfully fabricated by this technique, demonstrating excellent etch performance. In addition, silicon nanostructures fabricated above can be further trimmed to less than 10 nm by combing with assisted post-treatment methods. The novel nanofabrication technique will be expected a new emerging technology with low process complexity and good compatibility with existing silicon integrated circuit and is an important step towards the easy fabrication of a wide variety of nanoelectronics, biosensors, and optoelectronic devices.

  17. 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

  18. Structural Amorphous Steels

    NASA Astrophysics Data System (ADS)

    Lu, Z. P.; Liu, C. T.; Thompson, J. R.; Porter, W. D.

    2004-06-01

    Recent advancement in bulk metallic glasses, whose properties are usually superior to their crystalline counterparts, has stimulated great interest in fabricating bulk amorphous steels. While a great deal of effort has been devoted to this field, the fabrication of structural amorphous steels with large cross sections has remained an alchemist’s dream because of the limited glass-forming ability (GFA) of these materials. Here we report the discovery of structural amorphous steels that can be cast into glasses with large cross-section sizes using conventional drop-casting methods. These new steels showed interesting physical, magnetic, and mechanical properties, along with high thermal stability. The underlying mechanisms for the superior GFA of these materials are discussed.

  19. Biophotonic endoscopy: a review of clinical research techniques for optical imaging and sensing of early gastrointestinal cancer

    PubMed Central

    Coda, Sergio; Siersema, Peter D.; Stamp, Gordon W. H.; Thillainayagam, Andrew V.

    2015-01-01

    Detection, characterization, and staging constitute the fundamental elements in the endoscopic diagnosis of gastrointestinal diseases, but histology still remains the diagnostic gold standard. New developments in endoscopic techniques may challenge histopathology in the near future. An ideal endoscopic technique should combine a wide-field, “red flag” screening technique with an optical contrast or microscopy method for characterization and staging, all simultaneously available during the procedure. In theory, biophotonic advances have the potential to unite these elements to allow in vivo “optical biopsy.” These techniques may ultimately offer the potential to increase the rates of detection of high risk lesions and the ability to target biopsies and resections, and so reduce the need for biopsy, costs, and uncertainty for patients. However, their utility and sensitivity in clinical practice must be evaluated against those of conventional histopathology. This review describes some of the most recent applications of biophotonics in endoscopic optical imaging and metrology, along with their fundamental principles and the clinical experience that has been acquired in their deployment as tools for the endoscopist. Particular emphasis has been placed on translational label-free optical techniques, such as fluorescence spectroscopy, fluorescence lifetime imaging microscopy (FLIM), two-photon and multi-photon microscopy, second harmonic generation (SHG) and third harmonic generation (THG) imaging, optical coherence tomography (OCT), diffuse reflectance, Raman spectroscopy, and molecular imaging. PMID:26528489

  20. Development of immobilized biophotonic beads consisting of Photobacterium leiognathi for the detection of heavy metals and pesticide.

    PubMed

    Ranjan, Rajeev; Rastogi, Navin K; Thakur, M S

    2012-07-30

    The present communication deals with construction of immobilized robust biophotonic bead using P. leiognathi, a marine luminescent bacterium for their possible application in monitoring of environmental toxicants. Immobilization efficiency of agar, carrageenan and sodium alginate was evaluated separately in terms of luminescence response and was recorded as 30.3, 77.4 or 99.5%, respectively. Under optimized storage conditions, the luminescent response of P. leiognathi in the immobilized state was studied over a period of 30 days. These biophotonic beads were further used as a rapid and reliable optical biosensing tool for the detection of heavy metals [Hg(II), As(V) or Cd(II)] and pesticide [2,4-dichlorophenoxyacetic acid (2,4-D)] in water systems. The concentration range for the detection of Hg(II), As(V), Cd(II) and 2,4-D was 2-32ppm, 4-128ppm, 16-512ppm and 100-600ppm, respectively, while corresponding sensitivity threshold was 2.0ppm, 4.0ppm, 16.0ppm and 100ppm. A comparison of inhibition constant (K(d)) (or EC(20)) values indicated that the sensitivity thresholds rank as Hg(II)>As(V)>Cd(II)>2,4-D. Moreover, the time taken for the detection of heavy metals and pesticide was less than 30min. Using the bioluminescence inhibition method, the concentration of heavy metals and pesticide could be predicted.

  1. Lightweight Beryllium Free Nanostructured Nanostructured Composites

    DTIC Science & Technology

    2007-11-02

    Plasma Processes, Inc. Lightweight Beryllium Free Nanostructured Composites SBIR Contract DASG60-02-P-41 Phase I Final Report 1/15/03 Submitted by...Report Type N/A Dates Covered (from... to) - Title and Subtitle Lightweight Beryllium Free Nanostructured Nanostructured Composites Contract

  2. Interface of Physics and Biology: Engineering Virus-Based Nanoparticles for Biophotonics

    PubMed Central

    2015-01-01

    Virus-based nanoparticles (VNPs) have been used for a wide range of applications, spanning basic materials science and translational medicine. Their propensity to self-assemble into precise structures that offer a three-dimensional scaffold for functionalization has led to their use as optical contrast agents and related biophotonics applications. A number of fluorescently labeled platforms have been developed and their utility in optical imaging demonstrated, yet their optical properties have not been investigated in detail. In this study, two VNPs of varying architectures were compared side-by-side to determine the impact of dye density, dye localization, conjugation chemistry, and microenvironment on the optical properties of the probes. Dyes were attached to icosahedral cowpea mosaic virus (CPMV) and rod-shaped tobacco mosaic virus (TMV) through a range of chemistries to target particular side chains displayed at specific locations around the virus. The fluorescence intensity and lifetime of the particles were determined, first using photochemical experiments on the benchtop, and second in imaging experiments using tissue culture experiments. The virus-based optical probes were found to be extraordinarily robust under ultrashort, pulsed laser light conditions with a significant amount of excitation energy, maintaining structural and chemical stability. The most effective fluorescence output was achieved through dye placement at optimized densities coupled to the exterior surface avoiding conjugated ring systems. Lifetime measurements indicate that fluorescence output depends not only on spacing the fluorophores, but also on dimer stacking and configurational changes leading to radiationless relaxation—and these processes are related to the conjugation chemistry and nanoparticle shape. For biological applications, the particles were also examined in tissue culture, from which it was found that the optical properties differed from those found on the benchtop

  3. Interface of physics and biology: engineering virus-based nanoparticles for biophotonics.

    PubMed

    Wen, Amy M; Infusino, Melissa; De Luca, Antonio; Kernan, Daniel L; Czapar, Anna E; Strangi, Giuseppe; Steinmetz, Nicole F

    2015-01-21

    Virus-based nanoparticles (VNPs) have been used for a wide range of applications, spanning basic materials science and translational medicine. Their propensity to self-assemble into precise structures that offer a three-dimensional scaffold for functionalization has led to their use as optical contrast agents and related biophotonics applications. A number of fluorescently labeled platforms have been developed and their utility in optical imaging demonstrated, yet their optical properties have not been investigated in detail. In this study, two VNPs of varying architectures were compared side-by-side to determine the impact of dye density, dye localization, conjugation chemistry, and microenvironment on the optical properties of the probes. Dyes were attached to icosahedral cowpea mosaic virus (CPMV) and rod-shaped tobacco mosaic virus (TMV) through a range of chemistries to target particular side chains displayed at specific locations around the virus. The fluorescence intensity and lifetime of the particles were determined, first using photochemical experiments on the benchtop, and second in imaging experiments using tissue culture experiments. The virus-based optical probes were found to be extraordinarily robust under ultrashort, pulsed laser light conditions with a significant amount of excitation energy, maintaining structural and chemical stability. The most effective fluorescence output was achieved through dye placement at optimized densities coupled to the exterior surface avoiding conjugated ring systems. Lifetime measurements indicate that fluorescence output depends not only on spacing the fluorophores, but also on dimer stacking and configurational changes leading to radiationless relaxation-and these processes are related to the conjugation chemistry and nanoparticle shape. For biological applications, the particles were also examined in tissue culture, from which it was found that the optical properties differed from those found on the benchtop due

  4. Amorphous silicon photovoltaic devices

    DOEpatents

    Carlson, David E.; Lin, Guang H.; Ganguly, Gautam

    2004-08-31

    This invention is a photovoltaic device comprising an intrinsic or i-layer of amorphous silicon and where the photovoltaic device is more efficient at converting light energy to electric energy at high operating temperatures than at low operating temperatures. The photovoltaic devices of this invention are suitable for use in high temperature operating environments.

  5. Anomalous hopping conduction in nanocrystalline/amorphous composites and amorphous semiconductor thin films

    NASA Astrophysics Data System (ADS)

    Kakalios, James; Bodurtha, Kent

    Composite nanostructured materials consisting of nanocrystals (nc) embedded within a thin film amorphous matrix can exhibit novel opto-electronic properties. Composite films are synthesized in a dual-chamber co-deposition PECVD system capable of producing nanocrystals of material A and embedding then within a thin film matrix of material B. Electronic conduction in composite thin films of hydrogenated amorphous silicon (a-Si:H) containing nc-germanium or nc-silicon inclusions, as well as in undoped a-Si:H, does not follow an Arrhenius temperature dependence, but rather is better described by an anomalous hopping expression (exp[-(To/T)3/4) , as determined from the ``reduced activation energy'' proposed by Zabrodskii and Shlimak. This temperature dependence has been observed in other thin film resistive materials, such as ultra-thin disordered films of Ag, Bi, Pb and Pd; carbon-black polymer composites; and weakly coupled Au and ZnO quantum dot arrays. There is presently no accepted theoretical understanding of this expression. The concept of a mobility edge, accepted for over four decades, appears to not be necessary to account for charge transport in amorphous semiconductors. Supported by NSF-DMR and the Minnesota Nano Center.

  6. Shockwave Consolidation of Nanostructured Thermoelectric Materials

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.; Taylor, Patrick; Nemir, David

    2014-01-01

    Nanotechnology based thermoelectric materials are considered attractive for developing highly efficient thermoelectric devices. Nano-structured thermoelectric materials are predicted to offer higher ZT over bulk materials by reducing thermal conductivity and increasing electrical conductivity. Consolidation of nano-structured powders into dense materials without losing nanostructure is essential towards practical device development. Using the gas atomization process, amorphous nano-structured powders were produced. Shockwave consolidation is accomplished by surrounding the nanopowder-containing tube with explosives and then detonating. The resulting shock wave causes rapid fusing of the powders without the melt and subsequent grain growth. We have been successful in generating consolidated nano-structured bismuth telluride alloy powders by using the shockwave technique. Using these consolidated materials, several types of thermoelectric power generating devices have been developed. Shockwave consolidation is anticipated to generate large quantities of nanostructred materials expeditiously and cost effectively. In this paper, the technique of shockwave consolidation will be presented followed by Seebeck Coefficient and thermal conductivity measurements of consolidated materials. Preliminary results indicate a substantial increase in electrical conductivity due to shockwave consolidation technique.

  7. Enhancement in optical absorption of silicon fibrous nanostructure produced using femtosecond laser ablation

    SciTech Connect

    Mahmood, Abdul Salam; Venkatakrishnan, Krishnan; Sivakumar, M.; Tan, Bo

    2009-07-20

    Fibrous nanostructures are proposed for the application of solar cell. Irradiation of silicon surface with a few hundred femtosecond laser pulses of fluence 13 kJ/m{sup 2} at 13 MHz pulse frequency in air atmosphere results in the formation of fibrous nanostructure layer on the treated surface that leads to a significant decrease in the reflection of visible radiation. For the visible wavelength, the decreased reflection is a result of the nature of the nanostructure. The Raman peak shift in the irradiated surface confirms that the surface is changed to amorphous silicon due to fibrous nanostructure formation.

  8. DNA nanostructure meets nanofabrication.

    PubMed

    Zhang, Guomei; Surwade, Sumedh P; Zhou, Feng; Liu, Haitao

    2013-04-07

    Recent advances in DNA nanotechnology have made it possible to construct DNA nanostructures of almost arbitrary shapes with 2-3 nm of precision in their dimensions. These DNA nanostructures are ideal templates for bottom-up nanofabrication. This review highlights the challenges and recent advances in three areas that are directly related to DNA-based nanofabrication: (1) fabrication of large scale DNA nanostructures; (2) pattern transfer from DNA nanostructure to an inorganic substrate; and (3) directed assembly of DNA nanostructures.

  9. Amorphous silicon radiation detectors

    DOEpatents

    Street, Robert A.; Perez-Mendez, Victor; Kaplan, Selig N.

    1992-01-01

    Hydrogenated amorphous silicon radiation detector devices having enhanced signal are disclosed. Specifically provided are transversely oriented electrode layers and layered detector configurations of amorphous silicon, the structure of which allow high electric fields upon application of a bias thereby beneficially resulting in a reduction in noise from contact injection and an increase in signal including avalanche multiplication and gain of the signal produced by incoming high energy radiation. These enhanced radiation sensitive devices can be used as measuring and detection means for visible light, low energy photons and high energy ionizing particles such as electrons, x-rays, alpha particles, beta particles and gamma radiation. Particular utility of the device is disclosed for precision powder crystallography and biological identification.

  10. Amorphous silicon radiation detectors

    DOEpatents

    Street, R.A.; Perez-Mendez, V.; Kaplan, S.N.

    1992-11-17

    Hydrogenated amorphous silicon radiation detector devices having enhanced signal are disclosed. Specifically provided are transversely oriented electrode layers and layered detector configurations of amorphous silicon, the structure of which allow high electric fields upon application of a bias thereby beneficially resulting in a reduction in noise from contact injection and an increase in signal including avalanche multiplication and gain of the signal produced by incoming high energy radiation. These enhanced radiation sensitive devices can be used as measuring and detection means for visible light, low energy photons and high energy ionizing particles such as electrons, x-rays, alpha particles, beta particles and gamma radiation. Particular utility of the device is disclosed for precision powder crystallography and biological identification. 13 figs.

  11. Amorphous metallic foam

    NASA Astrophysics Data System (ADS)

    Schroers, Jan; Veazey, Chris; Johnson, William L.

    2003-01-01

    The bulk glass forming alloy Pd43Ni10Cu27P20 is processed into a low-density amorphous metallic foam. Pd43Ni10Cu27P20 is mixed with hydrated B2O3, which releases gas at elevated temperature and/or low pressure. Very homogeneous foams are achieved due to the high viscosity of the alloy even at its liquidus temperature. By processing at the liquidus temperature and decreasing the pressure to 10-2 mbar, well-distributed bubbles expand to foam the material. Foam densities as low as 1.4×103 kg/m3 were obtained, corresponding to a bubble volume fraction of 84%. The bubble diameter ranges between 2×10-4 and 1×10-3 m. Thermal analysis by differential scanning calorimetry confirms the amorphous nature of the foam. Furthermore, it reveals that the foam's thermal stability is comparable to the bulk material.

  12. Defects in Amorphous Metals.

    DTIC Science & Technology

    1982-07-01

    this map with a similar plot of the experimental data. An experimental deformation data map for Pd-based amorphous al- loys is shown in fig. 10. In the...Masumoto. I Mat. Sci. 12 (1977) 1927, [IgI T M Ha.es. J. W Allen. J. Tauc . B. C. Giessen and J. J. Hauser. Phys. Re. Lett. 41 i197s) 1282 [191 J

  13. Defect studies on as-synthesized and purified carbon nanostructures produced by arc-discharge in solution process.

    PubMed

    Bera, Debasis; Perrault, Jean-Philippe; Heinrich, Helge; Seal, Sudipta

    2006-04-01

    Carbon nanostructures are synthesized using a novel arc-discharge in solution process. A multitude of defects on nanotubes and nanostructures is found. Evidence of these defects in as-synthesized carbon nanostructures is explored using high-resolution transmission electron microscopy (HRTEM). Tri-, tetra-, penta-, hexa-, heptagonal, toroidal, oval, and spherical nanoshells are found in HRTEM investigation along with carbon nanotubes, carbon nanohorns, carbon rods, nanoporous carbon, dislodged graphene sheets, and amorphous carbon. Purifications are carried out through two oxidation methods to eliminate the amorphous carbon. Several different defects caused by oxidations are also found in purified samples.

  14. The Stabilization of Amorphous Zopiclone in an Amorphous Solid Dispersion.

    PubMed

    Milne, Marnus; Liebenberg, Wilna; Aucamp, Marique

    2015-10-01

    Zopiclone is a poorly soluble psychotherapeutic agent. The aim of this study was to prepare and characterize an amorphous form of zopiclone as well as the characterization and performance of a stable amorphous solid dispersion. The amorphous form was prepared by the well-known method of quench-cooling of the melt. The solid dispersion was prepared by a solvent evaporation method of zopiclone, polyvinylpyrrolidone-25 (PVP-25), and methanol, followed by freeze-drying. The physico-chemical properties and stability of amorphous zopiclone and the solid dispersion was studied using differential scanning calorimetry (DSC), infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), hot-stage microscopy (HSM), X-ray diffractometry (XRD), solubility, and dissolution studies. The zopiclone amorphous solid-state form was determined to be a fragile glass; it was concluded that the stability of the amorphous form is influenced by both temperature and water. Exposure of amorphous zopiclone to moisture results in rapid transformation of the amorphous form to the crystalline dihydrated form. In comparison, the amorphous solid dispersion proved to be more stable with increased aqueous solubility.

  15. Compensated amorphous silicon solar cell

    DOEpatents

    Carlson, David E.

    1980-01-01

    An amorphous silicon solar cell incorporates a region of intrinsic hydrogenated amorphous silicon fabricated by a glow discharge wherein said intrinsic region is compensated by P-type dopants in an amount sufficient to reduce the space charge density of said region under illumination to about zero.

  16. Compensated amorphous silicon solar cell

    DOEpatents

    Devaud, Genevieve

    1983-01-01

    An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon over said substrate and having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the electrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF.sub.3 doped intrinsic layer.

  17. Bulk amorphous materials

    SciTech Connect

    Schwarz, R.B.; Archuleta, J.I.; Sickafus, K.E.

    1998-12-01

    This is the final report for a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this work was to develop the competency for the synthesis of novel bulk amorphous alloys. The authors researched their synthesis methods and alloy properties, including thermal stability, mechanical, and transport properties. The project also addressed the development of vanadium-spinel alloys for structural applications in hostile environments, the measurement of elastic constants and thermal expansion in single-crystal TiAl from 300 to 750 K, the measurement of elastic constants in gallium nitride, and a study of the shock-induced martensitic transformations in NiTi alloys.

  18. Radial distribution function imaging by STEM diffraction: Phase mapping and analysis of heterogeneous nanostructured glasses.

    PubMed

    Mu, Xiaoke; Wang, Di; Feng, Tao; Kübel, Christian

    2016-09-01

    Characterizing heterogeneous nanostructured amorphous materials is a challenging topic, because of difficulty to solve disordered atomic arrangement in nanometer scale. We developed a new transmission electron microscopy (TEM) method to enable phase analysis and mapping of heterogeneous amorphous structures. That is to combine scanning TEM (STEM) diffraction mapping, radial distribution function (RDF) analysis, and hyperspectral analysis. This method was applied to an amorphous zirconium oxide and zirconium iron multilayer system, and showed extreme sensitivity to small atomic packing variations. This approach helps to understand local structure variations in glassy composite materials and provides new insights to correlate structure and properties of glasses.

  19. Gold nanoparticle-embedded silk protein-ZnO nanorod hybrids for flexible bio-photonic devices

    NASA Astrophysics Data System (ADS)

    Gogurla, Narendar; Kundu, Subhas C.; Ray, Samit K.

    2017-04-01

    Silk protein has been used as a biopolymer substrate for flexible photonic devices. Here, we demonstrate ZnO nanorod array hybrid photodetectors on Au nanoparticle-embedded silk protein for flexible optoelectronics. Hybrid samples exhibit optical absorption at the band edge of ZnO as well as plasmonic energy due to Au nanoparticles, making them attractive for selective UV and visible wavelength detection. The device prepared on Au-silk protein shows a much lower dark current and a higher photo to dark-current ratio of ∼105 as compared to the control sample without Au nanoparticles. The hybrid device also exhibits a higher specific detectivity due to higher responsivity arising from the photo-generated hole trapping by Au nanoparticles. Sharp pulses in the transient photocurrent have been observed in devices prepared on glass and Au-silk protein substrates due to the light induced pyroelectric effect of ZnO, enabling the demonstration of self-powered photodetectors at zero bias. Flexible hybrid detectors have been demonstrated on Au-silk/polyethylene terephthalate substrates, exhibiting characteristics similar to those fabricated on rigid glass substrates. A study of the performance of photodetectors with different bending angles indicates very good mechanical stability of silk protein based flexible devices. This novel concept of ZnO nanorod array photodetectors on a natural silk protein platform provides an opportunity to realize integrated flexible and self-powered bio-photonic devices for medical applications in near future.

  20. Bio-photonic detection method for morphological analysis of anthracnose disease and physiological disorders of Diospyros kaki

    NASA Astrophysics Data System (ADS)

    Wijesinghe, Ruchire Eranga; Lee, Seung-Yeol; Ravichandran, Naresh Kumar; Shirazi, Muhammad Faizan; Moon, Byungin; Jung, Hee-Young; Jeon, Mansik; Kim, Jeehyun

    2016-10-01

    The pathological and physiological defects in various types of fruits lead to large amounts of economical waste. It is well recognized that internal fruit defects due to pathological infections and physiological disorders can be effectively visualized at an initial stage of the disease using a well-known bio-photonic detection method called optical coherence tomography (OCT). This work investigates the use of OCT for identifying the morphological variations of anthracnose (bitter rot) disease infected and physiologically disordered Diospyros kaki (Asian Persimmon) fruits. An experiment was conducted using fruit samples that were carefully selected from persimmon orchards. Depth-resolved images with a high axial resolution were acquired using 850-nm-based spectral-domain OCT (SD-OCT) system. The obtained exemplary high-resolution two-dimensional and volumetric three-dimensional images revealed complementary morphological differences between healthy and defected samples. Moreover, the obtained depth-profile analysis results confirmed the disappearance of the healthy cell layers among the healthy-infected boundary regions. Thus, the proposed method has the potential to increase the diagnostic accuracy of the OCT technique used in agricultural plantations.

  1. Gold nanoparticle-embedded silk protein-ZnO nanorod hybrids for flexible bio-photonic devices.

    PubMed

    Gogurla, Narendar; Kundu, Subhas C; Ray, Samit K

    2017-04-07

    Silk protein has been used as a biopolymer substrate for flexible photonic devices. Here, we demonstrate ZnO nanorod array hybrid photodetectors on Au nanoparticle-embedded silk protein for flexible optoelectronics. Hybrid samples exhibit optical absorption at the band edge of ZnO as well as plasmonic energy due to Au nanoparticles, making them attractive for selective UV and visible wavelength detection. The device prepared on Au-silk protein shows a much lower dark current and a higher photo to dark-current ratio of ∼10(5) as compared to the control sample without Au nanoparticles. The hybrid device also exhibits a higher specific detectivity due to higher responsivity arising from the photo-generated hole trapping by Au nanoparticles. Sharp pulses in the transient photocurrent have been observed in devices prepared on glass and Au-silk protein substrates due to the light induced pyroelectric effect of ZnO, enabling the demonstration of self-powered photodetectors at zero bias. Flexible hybrid detectors have been demonstrated on Au-silk/polyethylene terephthalate substrates, exhibiting characteristics similar to those fabricated on rigid glass substrates. A study of the performance of photodetectors with different bending angles indicates very good mechanical stability of silk protein based flexible devices. This novel concept of ZnO nanorod array photodetectors on a natural silk protein platform provides an opportunity to realize integrated flexible and self-powered bio-photonic devices for medical applications in near future.

  2. Optical probing of long-range spatial correlation and symmetry in complex biophotonic architectures on transparent insect wings

    NASA Astrophysics Data System (ADS)

    Kumar, Pramod; Shamoon, Danish; Singh, Dhirendra P.; Mandal, Sudip; Singh, Kamal P.

    2015-02-01

    We experimentally probe the structural organization of complex bio-photonic architecture on transparent insect wings by a simple, non-invasive, real-time optical technique. A stable and reproducible far-field diffraction pattern in transmission was observed using collimated cw and broadband fs laser pulses. A quantitative analysis of the observed diffraction pattern unveiled long-range quasi-periodic order in the arrangement of the microstructures over mm scale. These observations agree well with the Fourier analysis of SEM images of the wing taken at various length scales. We propose a simple quantitative model based on optical diffraction by an array of non overlapping microstructures with minimal disorder which supports our experimental observations. We observed a rotation of the original diffraction profile by scanning the laser beam across the wing sample which gives direct signature of organizational symmetry in microstructure arrangements at various length scales. In addition, we report the first optical detection of reorganization in the photonic architecture on the Drosophila wings by various genetic mutations. These results have potential for the design and development of diffractive optical components for applied photonics and may open up new opportunities in biomimetic device research.

  3. Containerless processing of amorphous ceramics

    NASA Technical Reports Server (NTRS)

    Weber, J. K. Richard; Krishnan, Shankar; Schiffman, Robert A.; Nordine, Paul C.

    1990-01-01

    The absence of gravity allows containerless processing of materials which could not otherwise be processed. High melting point, hard materials such as borides, nitrides, and refractory metals are usually brittle in their crystalline form. The absence of dislocations in amorphous materials frequently endows them with flexibility and toughness. Systematic studies of the properties of many amorphous materials have not been carried out. The requirements for their production is that they can be processed in a controlled way without container interaction. Containerless processing in microgravity could permit the control necessary to produce amorphous forms of hard materials.

  4. Process flow to integrate nanostructures on silicon grass in surface micromachined systems

    NASA Astrophysics Data System (ADS)

    Mehner, H.; Müller, L.; Biermann, S.; Hänschke, F.; Hoffmann, M.

    2016-10-01

    The process flow to integrate metallic nanostructures in surface micromachining processes is presented. The nanostructures are generated by evaporation of microstructured silicon grass with metal. The process flow is based on the lift-off of a thin amorphous silicon layer deposited using a CVD process. All steps feature a low temperature load beneath 120 °C and high compatibility with many materials as only well-established chemicals are used. As a result metallic nanostructures usable for optical applications can be generated as part of multilayered microsystems fabricated in surface micromachining.

  5. Nanostructured composite reinforced material

    DOEpatents

    Seals, Roland D [Oak Ridge, TN; Ripley, Edward B [Knoxville, TN; Ludtka, Gerard M [Oak Ridge, TN

    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.

  6. Amorphous and Ultradisperse Crystalline Materials,

    DTIC Science & Technology

    The book sums up experimental and theoretical findings on amorphous and ultradisperse crystalline materials , massive and film types. Present-day... crystalline materials of metallic systems are presented. Emphasis is placed on inorganic film materials.

  7. Fabrication of amorphous diamond films

    DOEpatents

    Falabella, S.

    1995-12-12

    Amorphous diamond films having a significant reduction in intrinsic stress are prepared by biasing a substrate to be coated and depositing carbon ions thereon under controlled temperature conditions. 1 fig.

  8. Gold nanostructuring on Si substrate by selective electroless deposition.

    PubMed

    Bhuvana, T; Kulkarni, G U

    2007-06-01

    Gold deposition on Si(111) substrates has been carried out by electroless process from KAuCl4 in a fluorinated solution and the resulting nanostructures have been characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Deposition carried out under normal plating conditions produces an Au film with (111) orientation. The effect of additives such as poly(vinylpyrrolidone) (PVP) and mercaptoundecanoic acid (MUA) to the plating solution has been examined. While PVP induces amorphous deposition, MUA gives rise to flat (111) oriented islands. In order to produce individual nanostructures, we made use of octadecyltrichlorosilane (OTS) as a masking agent and carried out electroless deposition with an intermittent dip in OTS. By varying the durations of dip in the two solutions, various Au nanostructures-islands, cellular networks, and nanowires are obtained.

  9. Characterization Techniques for Amorphous Alloys

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 2 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from B-Be-Fe to Co-W-Zr' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter '2 Characterization Techniques for Amorphous Alloys' with the content:

  10. Amorphous metal alloy and composite

    DOEpatents

    Wang, Rong; Merz, Martin D.

    1985-01-01

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  11. Magnetic carbon nanostructures: microwave energy-assisted pyrolysis vs. conventional pyrolysis.

    PubMed

    Zhu, Jiahua; Pallavkar, Sameer; Chen, Minjiao; Yerra, Narendranath; Luo, Zhiping; Colorado, Henry A; Lin, Hongfei; Haldolaarachchige, Neel; Khasanov, Airat; Ho, Thomas C; Young, David P; Wei, Suying; Guo, Zhanhu

    2013-01-11

    Magnetic carbon nanostructures from microwave assisted- and conventional-pyrolysis processes are compared. Unlike graphitized carbon shells from conventional heating, different carbon shell morphologies including nanotubes, nanoflakes and amorphous carbon were observed. Crystalline iron and cementite were observed in the magnetic core, different from a single cementite phase from the conventional process.

  12. Hydrogenated amorphous silicon photonics

    NASA Astrophysics Data System (ADS)

    Narayanan, Karthik

    2011-12-01

    Silicon Photonics is quickly proving to be a suitable interconnect technology for meeting the future goals of on-chip bandwidth and low power requirements. However, it is not clear how silicon photonics will be integrated into CMOS chips, particularly microprocessors. The issue of integrating photonic circuits into electronic IC fabrication processes to achieve maximum flexibility and minimum complexity and cost is an important one. In order to minimize usage of chip real estate, it will be advantageous to integrate in three-dimensions. Hydrogenated amorphous silicon (a-Si:H) is emerging as a promising material for the 3-D integration of silicon photonics for on-chip optical interconnects. In addition, a-Si:H film can be deposited using CMOS compatible low temperature plasma-enhanced chemical vapor deposition (PECVD) process at any point in the fabrication process allowing maximum flexibility and minimal complexity. In this thesis, we demonstrate a-Si:H as a high performance alternate platform to crystalline silicon, enabling backend integration of optical interconnects in a hybrid photonic-electronic network-on-chip architecture. High quality passive devices are fabricated on a low-loss a-Si:H platform enabling wavelength division multiplexing schemes. We demonstrate a broadband all-optical modulation scheme based on free-carrier absorption effect, which can enable compact electro-optic modulators in a-Si:H. Furthermore, we comprehensively characterize the optical nonlinearities in a-Si:H and observe that a-Si:H exhibits enhanced nonlinearities as compared to crystalline silicon. Based on the enhanced nonlinearities, we demonstrate low-power four-wave mixing in a-Si:H waveguides enabling high speed all-optical devices in an a-Si:H platform. Finally, we demonstrate a novel data encoding scheme using thermal and all-optical tuning of silicon waveguides, increasing the spectral efficiency in an interconnect link.

  13. Aqueous ultracapacitors using amorphous MnO2 and reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Mery, Adrien; Ghamouss, Fouad; Autret, Cécile; Farhat, Douaa; Tran-Van, François

    2016-02-01

    Herein, synthesis and characterization of amorphous MnO2 and application in asymmetric aqueous ultracapacitors are reported. Different amorphous manganese oxide (MnO2) materials were synthesized from the reduction of KMnO4 in different media such as ethanol (EtOH) or dimethylformamide (DMF). The electrochemical behavior of amorphous MnO2, labeled MnO2-Et and MnO2-DMF, were studied by using cyclic voltammetry, impedance spectroscopy, and galvanostatic cycling in aqueous electrolyte. XRD, BET, TEM, and SEM characterizations highlighted the amorphous nature and the nanostructuration of these MnO2 materials. BET measurement established that these amorphous MnO2 are mesoporous. In addition, MnO2-Et exhibits a larger specific surface area (168 m2 g-1), a narrower pore diameters distribution with lower diameters compared to MnO2-DMF. These results are in agreement with the electrochemical results. Indeed, MnO2-Et shows a higher specific capacitance and lower impedance in aqueous K2SO4 electrolyte. Furthermore, aqueous asymmetric ultracapacitors were assembled and studied using amorphous MnO2 as positive electrode and reduced graphene oxide (rGO) as negative electrode. These asymmetric systems exhibit an electrochemical stability for more than 20,000 galvanostatic cycles at current density of 1 A g-1 with an operating voltage of 2 V.

  14. Microstructure, thermal, and mechanical properties of nanostructured Cu-9.5Ni-4.0Sn-7.5P

    NASA Astrophysics Data System (ADS)

    Li, J.; Wang, T. M.

    1995-04-01

    Nanostructured Cu-9.5Ni-4.0Sn-7.5P samples represent a polycrystal microstructure of nanometer-sized α-Cu and Cu3P crystallites for crystallite sizes less than 20 nm and of nanometer-sized α-Cu, Cu3P, and Ni2P crystallites for crystallite sizes greater than 20 nm. The specific heat values between 300 K and 400 K for the nanostructured sample with crystallite size of 10 nm are about 20% higher than for the amorphous sample and about 40% higher than for the coarse-grained sample. The hardness of the nanostructured sample with crystallite size of 10 nm is 30% higher than that of the amorphous sample and 110% higher than that of the coarse-grained sample. The variation in hardness with the crystallite size for the nanostructured samples follows the Hall-Petch relationship.

  15. Nanostructured Protective Coatings

    DTIC Science & Technology

    2006-01-01

    potential superior wear resistance properties. The Nanostructured Protective Coatings (NPC) program was designed to establish a collaborative team of...understanding of PVD parameters, depositing coatings on practical substrates such as the Ti6Al4V used for turbine blades , and developing a versatile...Nanostructured Protective Coatings (NPC) program was designed to establish a collaborative team of three entities (Pennsylvania State University

  16. Enhanced photocatalytic performance of TiO2-ZnO hybrid nanostructures

    PubMed Central

    Cheng, Chun; Amini, Abbas; Zhu, Chao; Xu, Zuli; Song, Haisheng; Wang, Ning

    2014-01-01

    We studied the photocatalytic properties of rational designed TiO2-ZnO hybrid nanostructures, which were fabricated by the site-specific deposition of amorphous TiO2 on the tips of ZnO nanorods. Compared with the pure components of ZnO nanorods and amorphous TiO2 nanoparticles, these TiO2-ZnO hybrid nanostructures demonstrated a higher catalytic activity. The strong green emission quenching observed from photoluminescence of TiO2-ZnO hybrid nanostructures implied an enhanced charge transfer/separation process resulting from the novel type II heterostructures with fine interfaces. The catalytic performance of annealing products with different TiO2 phase varied with the annealing temperatures. This is attributed to the combinational changes in Eg of the TiO2 phase, the specific surface area and the quantity of surface hydroxyl groups. PMID:24566978

  17. Allotropic composition of amorphous carbon

    SciTech Connect

    Yastrebov, S. G. Ivanov-Omskii, V. I.

    2007-08-15

    Using the concept of an inhomogeneous broadening of spectral lines of the basic oscillators responsible for forming the spectrum, the experimental dependences of the dispersion of the imaginary part of permittivity are analyzed for amorphous carbon. It turned out that four types of oscillators contribute to this dependence. The first three types represent the electron transitions from the energy-spectrum ground state for {pi} and {sigma} electrons of amorphous carbon to an excited state. The fourth type is related to the absorption of electromagnetic radiation by free charge carriers. The absolute values of squared plasma frequencies of oscillators are estimated, and, using them, the relative fraction of sp{sup 2}-bonded atoms forming the amorphous-carbon skeleton is calculated. This estimate agrees closely with the theoretical predictions for amorphous carbon of the same density as the material under study. The dependence of the relative fraction of sp{sup 2}-bonded atoms contained in amorphous hydrogenised carbon on annealing temperature is determined. The developed method is also applied to the analysis of the normalized curve for the light extinction in the interstellar medium. The contribution to the extinction of two varieties of interstellar matter is detected.

  18. Amorphous-diamond electron emitter

    DOEpatents

    Falabella, Steven

    2001-01-01

    An electron emitter comprising a textured silicon wafer overcoated with a thin (200 .ANG.) layer of nitrogen-doped, amorphous-diamond (a:D-N), which lowers the field below 20 volts/micrometer have been demonstrated using this emitter compared to uncoated or diamond coated emitters wherein the emission is at fields of nearly 60 volts/micrometer. The silicon/nitrogen-doped, amorphous-diamond (Si/a:D-N) emitter may be produced by overcoating a textured silicon wafer with amorphous-diamond (a:D) in a nitrogen atmosphere using a filtered cathodic-arc system. The enhanced performance of the Si/a:D-N emitter lowers the voltages required to the point where field-emission displays are practical. Thus, this emitter can be used, for example, in flat-panel emission displays (FEDs), and cold-cathode vacuum electronics.

  19. Imprinting bulk amorphous alloy at room temperature

    PubMed Central

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-01-01

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. Our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment. PMID:26563908

  20. Imprinting bulk amorphous alloy at room temperature

    SciTech Connect

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-11-13

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. In conclusion, our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment.

  1. Chalcogenide glass nanostructures

    DOEpatents

    Johnson, Bradley R.; Schweiger, Michael J.; MacIsaac, Brett D.; Sundaram, S. Kamakshi

    2007-05-01

    Chalcogenide nanowires and other micro-and nano scale structures are grown on a preselected portion of on a substrate. They are amorphous and of uniform composition and can be grown by a sublimation-condensation process onto the surface of an amorphous substrate. Among other uses, these structures can be used as coatings on optical fibers, as coatings on implants, as wispering galleries, in electrochemical devices, and in nanolasers.

  2. Model for amorphous aggregation processes

    NASA Astrophysics Data System (ADS)

    Stranks, Samuel D.; Ecroyd, Heath; van Sluyter, Steven; Waters, Elizabeth J.; Carver, John A.; von Smekal, Lorenz

    2009-11-01

    The amorphous aggregation of proteins is associated with many phenomena, ranging from the formation of protein wine haze to the development of cataract in the eye lens and the precipitation of recombinant proteins during their expression and purification. While much literature exists describing models for linear protein aggregation, such as amyloid fibril formation, there are few reports of models which address amorphous aggregation. Here, we propose a model to describe the amorphous aggregation of proteins which is also more widely applicable to other situations where a similar process occurs, such as in the formation of colloids and nanoclusters. As first applications of the model, we have tested it against experimental turbidimetry data of three proteins relevant to the wine industry and biochemistry, namely, thaumatin, a thaumatinlike protein, and α -lactalbumin. The model is very robust and describes amorphous experimental data to a high degree of accuracy. Details about the aggregation process, such as shape parameters of the aggregates and rate constants, can also be extracted.

  3. Amorphous titanium-oxide supercapacitors

    PubMed Central

    Fukuhara, Mikio; Kuroda, Tomoyuki; Hasegawa, Fumihiko

    2016-01-01

    The electric capacitance of an amorphous TiO2-x surface increases proportionally to the negative sixth power of the convex diameter d. This occurs because of the van der Waals attraction on the amorphous surface of up to 7 mF/cm2, accompanied by extreme enhanced electron trapping resulting from both the quantum-size effect and an offset effect from positive charges at oxygen-vacancy sites. Here we show that a supercapacitor, constructed with a distributed constant-equipment circuit of large resistance and small capacitance on the amorphous TiO2-x surface, illuminated a red LED for 37 ms after it was charged with 1 mA at 10 V. The fabricated device showed no dielectric breakdown up to 1,100 V. Based on this approach, further advances in the development of amorphous titanium-dioxide supercapacitors might be attained by integrating oxide ribbons with a micro-electro mechanical system. PMID:27767103

  4. Amorphous rare earth magnet powders

    SciTech Connect

    Sellers, C.H.; Branagan, D.J.; Hyde, T.A.; Lewis, L.H.; Panchanathan, V.

    1996-08-01

    Gas atomization (GA) processing does not generally have a high enough cooling rate to produce the initial amorphous microstructure needed to obtain optimal magnetic properties in RE{sub 2}Fe{sub 14}B alloys. Phase separation and an underquenched microstructure result from detrimental {alpha}-Fe precipitation, and the resulting magnetic domain structure is very coarse. Additionally, there is a dramatic dependence of the magnetic properties on the cooling rate (and therefore the particle size) and the powders can be sensitive to environmental degradation. Alloy compositions designed just for GA (as opposed to melt spinning) are necessary to produce an amorphous structure that can be crystallized to result in a fine structure with magnetic properties which are independent of particle size. The addition of titanium and carbon to the melt has been found to change the solidification process sufficiently to result in an ``overquenched`` state in which most of the powder size fractions have an amorphous component. Crystallization with a brief heat treatment produces a structure which has improved magnetic properties, in part due to the ability to use compositions with higher Fe contents without {alpha}-Fe precipitation. Results from magnetometry, magnetic force microscopy, and x-ray analyses will be used to contrast the microstructure, domain structure, and magnetic properties of this new generation of amorphous powders with their multiphase predecessors.

  5. Amorphous titanium-oxide supercapacitors

    NASA Astrophysics Data System (ADS)

    Fukuhara, Mikio; Kuroda, Tomoyuki; Hasegawa, Fumihiko

    2016-10-01

    The electric capacitance of an amorphous TiO2-x surface increases proportionally to the negative sixth power of the convex diameter d. This occurs because of the van der Waals attraction on the amorphous surface of up to 7 mF/cm2, accompanied by extreme enhanced electron trapping resulting from both the quantum-size effect and an offset effect from positive charges at oxygen-vacancy sites. Here we show that a supercapacitor, constructed with a distributed constant-equipment circuit of large resistance and small capacitance on the amorphous TiO2-x surface, illuminated a red LED for 37 ms after it was charged with 1 mA at 10 V. The fabricated device showed no dielectric breakdown up to 1,100 V. Based on this approach, further advances in the development of amorphous titanium-dioxide supercapacitors might be attained by integrating oxide ribbons with a micro-electro mechanical system.

  6. Crystallized Silicon Nanostructures - Experimental Characterization and Atomistic Simulations

    SciTech Connect

    Agbo, Solomon; Sutta, Pavol; Calta, Pavel; Biswas, Rana; Pan, Bicai

    2014-07-01

    We have synthesized silicon nanocrystalline structures from thermal annealing of thin film amorphous silicon-based multilayers. The annealing procedure that was carried out in vacuum at temperatures up to 1100 °C is integrated in a X-ray diffraction (XRD) setup for real-time monitoring of the formation phases of the nanostructures. The microstructure of the crystallized films is investigated through experimental measurements combined with atomistic simulations of realistic nanocrystalline silicon (nc-Si) models. The multilayers consisting of uniformly alternating thicknesses of hydrogenated amorphous silicon and silicon oxide (SiO2) were deposited by plasma enhanced chemical vapor deposition on crystalline silicon and Corning glass substrates. The crystallized structure consisting of nc-Si structures embedded in an amorphous matrix were further characterized through XRD, Raman spectroscopy, and Fourier transform infrared measurements. We are able to show the different stages of nanostructure formation and how the sizes and the crystallized mass fraction can be controlled in our experimental synthesis. The crystallized silicon structures with large crystalline filling fractions exceeding 50% have been simulated with a robust classical molecular dynamics technique. The crystalline filling fractions and structural order of nc-Si obtained from this simulation are compared with our Raman and XRD measurements.

  7. 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...

  8. 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...

  9. Ion irradiation induced element-enriched and depleted nanostructures in Zr-Al-Cu-Ni metallic glass

    SciTech Connect

    Chen, H. C.; Liu, R. D.; Yan, L. E-mail: zhouxingtai@sinap.ac.cn; Zhou, X. T. E-mail: zhouxingtai@sinap.ac.cn; Cao, G. Q.; Wang, G.

    2015-07-21

    The microstructural evolution of a Zr-Al-Cu-Ni metallic glass induced by irradiation with Ar ions was investigated. Under ion irradiation, the Cu- and Ni-enriched nanostructures (diameter of 30–50 nm) consisted of crystalline and amorphous structures were formed. Further, Cu- and Ni-depleted nanostructures with diameters of 5–20 nm were also observed. The formation of these nanostructures can be ascribed to the migration of Cu and Ni atoms in the irradiated metallic glass.

  10. Nanostructured Carbon Coatings

    DTIC Science & Technology

    2000-01-01

    carbon coatings and explores a very broad range of potentially important carbon nanostructures that may be used in future technologies. A new method ...for the synthesis of nanostructured carbon coatings on the surface of SiC and other metal carbides is described. This method is accomplished through the...With the fall in cost of fullerene powders, this method may become important in the future as a method to produce nanocrystalline diamond free of metal

  11. Local Crystalline Structure in an Amorphous Protein Dense Phase.

    PubMed

    Greene, Daniel G; Modla, Shannon; Wagner, Norman J; Sandler, Stanley I; Lenhoff, Abraham M

    2015-10-20

    Proteins exhibit a variety of dense phases ranging from gels, aggregates, and precipitates to crystalline phases and dense liquids. Although the structure of the crystalline phase is known in atomistic detail, little attention has been paid to noncrystalline protein dense phases, and in many cases the structures of these phases are assumed to be fully amorphous. In this work, we used small-angle neutron scattering, electron microscopy, and electron tomography to measure the structure of ovalbumin precipitate particles salted out with ammonium sulfate. We found that the ovalbumin phase-separates into core-shell particles with a core radius of ∼2 μm and shell thickness of ∼0.5 μm. Within this shell region, nanostructures comprised of crystallites of ovalbumin self-assemble into a well-defined bicontinuous network with branches ∼12 nm thick. These results demonstrate that the protein gel is comprised in part of nanocrystalline protein.

  12. Local Crystalline Structure in an Amorphous Protein Dense Phase

    PubMed Central

    Greene, Daniel G.; Modla, Shannon; Wagner, Norman J.; Sandler, Stanley I.; Lenhoff, Abraham M.

    2015-01-01

    Proteins exhibit a variety of dense phases ranging from gels, aggregates, and precipitates to crystalline phases and dense liquids. Although the structure of the crystalline phase is known in atomistic detail, little attention has been paid to noncrystalline protein dense phases, and in many cases the structures of these phases are assumed to be fully amorphous. In this work, we used small-angle neutron scattering, electron microscopy, and electron tomography to measure the structure of ovalbumin precipitate particles salted out with ammonium sulfate. We found that the ovalbumin phase-separates into core-shell particles with a core radius of ∼2 μm and shell thickness of ∼0.5 μm. Within this shell region, nanostructures comprised of crystallites of ovalbumin self-assemble into a well-defined bicontinuous network with branches ∼12 nm thick. These results demonstrate that the protein gel is comprised in part of nanocrystalline protein. PMID:26488663

  13. Architectures for Nanostructured Batteries

    NASA Astrophysics Data System (ADS)

    Rubloff, Gary

    2013-03-01

    Heterogeneous nanostructures offer profound opportunities for advancement in electrochemical energy storage, particularly with regard to power. However, their design and integration must balance ion transport, electron transport, and stability under charge/discharge cycling, involving fundamental physical, chemical and electrochemical mechanisms at nano length scales and across disparate time scales. In our group and in our DOE Energy Frontier Research Center (www.efrc.umd.edu) we have investigated single nanostructures and regular nanostructure arrays as batteries, electrochemical capacitors, and electrostatic capacitors to understand limiting mechanisms, using a variety of synthesis and characterization strategies. Primary lithiation pathways in heterogeneous nanostructures have been observed to include surface, interface, and both isotropic and anisotropic diffusion, depending on materials. Integrating current collection layers at the nano scale with active ion storage layers enhances power and can improve stability during cycling. For densely packed nanostructures as required for storage applications, we investigate both ``regular'' and ``random'' architectures consistent with transport requirements for spatial connectivity. Such configurations raise further important questions at the meso scale, such as dynamic ion and electron transport in narrow and tortuous channels, and the role of defect structures and their evolution during charge cycling. Supported as part of the Nanostructures for Electrical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DESC0001160

  14. Aragonite nanorods in calcium carbonate/polymer hybrids formed through self-organization processes from amorphous calcium carbonate solution.

    PubMed

    Kajiyama, Satoshi; Nishimura, Tatsuya; Sakamoto, Takeshi; Kato, Takashi

    2014-04-24

    Nanostructured inorganic/polymer hybrid thin films comprising aragonite nanorods derived from aqueous suspensions of amorphous calcium carbonate (ACC) are prepared. For the formation of calcium carbonate (CaCO₃)/polymer hybrids, spincoated and annealed films of poly(vinyl alcohol) (PVA) that function as polymer matrices are soaked in aqueous colloidal solutions dispersing ACC stabilized by poly(acrylic acid) (PAA). In the initial stage, calcite thin films form on the surface. Subsequently, aragonite crystals start to form inside the PVA matrix that contains PVA crystallites which induce aragonite nucleation. Nanostructured hybrids composed of calcite thin films consisting of nanoparticles and assembled aragonite nanorods are formed in the matrices of PVA.

  15. Flexible amorphous metal films with high stability

    NASA Astrophysics Data System (ADS)

    Liu, M.; Cao, C. R.; Lu, Y. M.; Wang, W. H.; Bai, H. Y.

    2017-01-01

    We report the formation of amorphous Cu50Zr50 films with a large-area of more than 100 cm2. The films were fabricated by ion beam assisted deposition with a slow deposition rate at moderate temperature. The amorphous films have markedly enhanced thermal stability, excellent flexibility, and high reflectivity with atomic level smoothness. The multifunctional properties of the amorphous films are favorites in the promising applications of smart skin or wearable devices. The method of preparing highly stable amorphous metal films by tuning the deposition rate instead of deposition temperature could pave a way for exploring amorphous metal films with unique properties.

  16. 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.

  17. 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.

  18. Excimer laser crystallization of amorphous silicon on metallic substrate

    NASA Astrophysics Data System (ADS)

    Delachat, F.; Antoni, F.; Slaoui, A.; Cayron, C.; Ducros, C.; Lerat, J.-F.; Emeraud, T.; Negru, R.; Huet, K.; Reydet, P.-L.

    2013-06-01

    An attempt has been made to achieve the crystallization of silicon thin film on metallic foils by long pulse duration excimer laser processing. Amorphous silicon thin films (100 nm) were deposited by radiofrequency magnetron sputtering on a commercial metallic alloy (N42-FeNi made of 41 % of Ni) coated by a tantalum nitride (TaN) layer. The TaN coating acts as a barrier layer, preventing the diffusion of metallic impurities in the silicon thin film during the laser annealing. An energy density threshold of 0.3 J cm-2, necessary for surface melting and crystallization of the amorphous silicon, was predicted by a numerical simulation of laser-induced phase transitions and witnessed by Raman analysis. Beyond this fluence, the melt depth increases with the intensification of energy density. A complete crystallization of the layer is achieved for an energy density of 0.9 J cm-2. Scanning electron microscopy unveils the nanostructuring of the silicon after laser irradiation, while cross-sectional transmission electron microscopy reveals the crystallites' columnar growth.

  19. Thermal decomposition of fullerene nanowhiskers protected by amorphous carbon mask

    PubMed Central

    Guo, Hongxuan; Wang, Chengxiang; Miyazawa, Kun’ichi; Wang, Hongxin; Masuda, Hideki; Fujita, Daisuke

    2016-01-01

    Fullerene nanostructures are well known for their unique morphology, physical and mechanical properties. The thermal stability of fullerene nanostructures, such as their sublimation at high temperature is also very important for studying their structures and applications. In this work, We observed fullerene nanowhiskers (FNWs) in situ with scanning helium ion microscopy (HIM) at elevated temperatures. The FNWs exhibited different stabilities with different thermal histories during the observation. The pristine FNWs were decomposed at the temperatures higher than 300 °C in a vacuum environment. Other FNWs were protected from decomposition with an amorphous carbon (aC) film deposited on the surface. Based on high spacial resolution, aC film with periodic structure was deposited by helium ion beam induced deposition (IBID) on the surface of FNWs. Annealed at the high temperature, the fullerene molecules were selectively sublimated from the FNWs. The periodic structure was formed on the surface of FNWs and observed by HIM. Monte Carlo simulation and Raman characterization proved that the morphology of the FNWs was changed by helium IBID at high temperature. This work provides a new method of fabricating artificial structure on the surface of FNWs with periodic aC film as a mask. PMID:27991498

  20. Thermal decomposition of fullerene nanowhiskers protected by amorphous carbon mask

    NASA Astrophysics Data System (ADS)

    Guo, Hongxuan; Wang, Chengxiang; Miyazawa, Kun’Ichi; Wang, Hongxin; Masuda, Hideki; Fujita, Daisuke

    2016-12-01

    Fullerene nanostructures are well known for their unique morphology, physical and mechanical properties. The thermal stability of fullerene nanostructures, such as their sublimation at high temperature is also very important for studying their structures and applications. In this work, We observed fullerene nanowhiskers (FNWs) in situ with scanning helium ion microscopy (HIM) at elevated temperatures. The FNWs exhibited different stabilities with different thermal histories during the observation. The pristine FNWs were decomposed at the temperatures higher than 300 °C in a vacuum environment. Other FNWs were protected from decomposition with an amorphous carbon (aC) film deposited on the surface. Based on high spacial resolution, aC film with periodic structure was deposited by helium ion beam induced deposition (IBID) on the surface of FNWs. Annealed at the high temperature, the fullerene molecules were selectively sublimated from the FNWs. The periodic structure was formed on the surface of FNWs and observed by HIM. Monte Carlo simulation and Raman characterization proved that the morphology of the FNWs was changed by helium IBID at high temperature. This work provides a new method of fabricating artificial structure on the surface of FNWs with periodic aC film as a mask.

  1. Nanohole Structuring for Improved Performance of Hydrogenated Amorphous Silicon Photovoltaics.

    PubMed

    Johlin, Eric; Al-Obeidi, Ahmed; Nogay, Gizem; Stuckelberger, Michael; Buonassisi, Tonio; Grossman, Jeffrey C

    2016-06-22

    While low hole mobilities limit the current collection and efficiency of hydrogenated amorphous silicon (a-Si:H) photovoltaic devices, attempts to improve mobility of the material directly have stagnated. Herein, we explore a method of utilizing nanostructuring of a-Si:H devices to allow for improved hole collection in thick absorber layers. This is achieved by etching an array of 150 nm diameter holes into intrinsic a-Si:H and then coating the structured material with p-type a-Si:H and a conformal zinc oxide transparent conducting layer. The inclusion of these nanoholes yields relative power conversion efficiency (PCE) increases of ∼45%, from 7.2 to 10.4% PCE for small area devices. Comparisons of optical properties, time-of-flight mobility measurements, and internal quantum efficiency spectra indicate this efficiency is indeed likely occurring from an improved collection pathway provided by the nanostructuring of the devices. Finally, we estimate that through modest optimizations of the design and fabrication, PCEs of beyond 13% should be obtainable for similar devices.

  2. Programmable SERS active substrates for chemical and biosensing applications using amorphous/crystalline hybrid silicon nanomaterial

    NASA Astrophysics Data System (ADS)

    Powell, Jeffery Alexander; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-01

    We present the creation of a unique nanostructured amorphous/crystalline hybrid silicon material that exhibits surface enhanced Raman scattering (SERS) activity. This nanomaterial is an interconnected network of amorphous/crystalline nanospheroids which form a nanoweb structure; to our knowledge this material has not been previously observed nor has it been applied for use as a SERS sensing material. This material is formed using a femtosecond synthesis technique which facilitates a laser plume ion condensation formation mechanism. By fine-tuning the laser plume temperature and ion interaction mechanisms within the plume, we are able to precisely program the relative proportion of crystalline Si to amorphous Si content in the nanospheroids as well as the size distribution of individual nanospheroids and the size of Raman hotspot nanogaps. With the use of Rhodamine 6G (R6G) and Crystal Violet (CV) chemical dyes, we have been able to observe a maximum enhancement factor of 5.38 × 106 and 3.72 × 106 respectively, for the hybrid nanomaterial compared to a bulk Si wafer substrate. With the creation of a silicon-based nanomaterial capable of SERS detection of analytes, this work demonstrates a redefinition of the role of nanostructured Si from an inactive to SERS active role in nano-Raman sensing applications.

  3. Programmable SERS active substrates for chemical and biosensing applications using amorphous/crystalline hybrid silicon nanomaterial

    PubMed Central

    Powell, Jeffery Alexander; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-01

    We present the creation of a unique nanostructured amorphous/crystalline hybrid silicon material that exhibits surface enhanced Raman scattering (SERS) activity. This nanomaterial is an interconnected network of amorphous/crystalline nanospheroids which form a nanoweb structure; to our knowledge this material has not been previously observed nor has it been applied for use as a SERS sensing material. This material is formed using a femtosecond synthesis technique which facilitates a laser plume ion condensation formation mechanism. By fine-tuning the laser plume temperature and ion interaction mechanisms within the plume, we are able to precisely program the relative proportion of crystalline Si to amorphous Si content in the nanospheroids as well as the size distribution of individual nanospheroids and the size of Raman hotspot nanogaps. With the use of Rhodamine 6G (R6G) and Crystal Violet (CV) chemical dyes, we have been able to observe a maximum enhancement factor of 5.38 × 106 and 3.72 × 106 respectively, for the hybrid nanomaterial compared to a bulk Si wafer substrate. With the creation of a silicon-based nanomaterial capable of SERS detection of analytes, this work demonstrates a redefinition of the role of nanostructured Si from an inactive to SERS active role in nano-Raman sensing applications. PMID:26785682

  4. 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.

  5. Structure and physical properties of Fe6 O8/ba Fe6 O11 nanostructure

    NASA Astrophysics Data System (ADS)

    Naseri, Mahmoud; Ghasemi, Rahmat

    2016-05-01

    The thermal treatment method was employed to prepare barium hexaferrite (Fe6 O8/Ba Fe6 O11) nanostructure. This method was attempted to achieve higher homogeneity of the final product. Specimens of barium hexaferrite nanostructure were characterized by various experimental techniques including X-ray diffraction (XRD), high resolution Field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FT-IR). X-ray diffraction results showed that there was no crystallinity in the predecessor and it had still amorphous phase. The formations of crystalline phases of barium hexaferrite nanostructures started from 673 to 973 K and the final products had different crystallite sizes ranging from 29 to 48 nm. The chemical analysis of the barium hexaferrite nanostructures was performed by energy dispersion X-ray analysis (EDXA), demonstrated that the barium hexaferrite nanostructures contained the elements of Ba, Fe, and O. The effect of calcination temperature on band gap energy was studied by UV-vis absorption spectra disclosed when calcination temperature increased, the appraised band gap energy values of the BaFe12O19 nanostructures decreased. The formed nanostructures exhibited ferromagnetic behaviors which were confirmed by using a vibrating sample magnetometer (VSM). The technique of the Electron paramagnetic resonance (EPR) spectroscopy was carried out at 300 K on the calcined specimens that exhibited the variation of the line-shapes of the spectra of with calcination temperature.

  6. Development of colour-producing β-keratin nanostructures in avian feather barbs

    PubMed Central

    Prum, Richard O.; Dufresne, Eric R.; Quinn, Tim; Waters, Karla

    2009-01-01

    The non-iridescent structural colours of avian feather barbs are produced by coherent light scattering from amorphous (i.e. quasi-ordered) nanostructures of β-keratin and air in the medullary cells of feather barb rami. Known barb nanostructures belong to two distinct morphological classes. ‘Channel’ nanostructures consist of β-keratin bars and air channels of elongate, tortuous and twisting forms. ‘Spherical’ nanostructures consist of highly spherical air cavities that are surrounded by thin β-keratin bars and sometimes interconnected by tiny passages. Using transmission electron microscopy, we observe that the colour-producing channel-type nanostructures of medullary β-keratin in feathers of the blue-and-yellow macaw (Ara ararauna, Psittacidae) develop by intracellular self-assembly; the process proceeds in the absence of any biological prepattern created by the cell membrane, endoplasmic reticulum or cellular intermediate filaments. We examine the hypothesis that the shape and size of these self-assembled, intracellular nanostructures are determined by phase separation of β-keratin protein from the cytoplasm of the cell. The shapes of a broad sample of colour-producing channel-type nanostructures from nine avian species are very similar to those self-assembled during the phase separation of an unstable mixture, a process called spinodal decomposition (SD). In contrast, the shapes of a sample of spherical-type nanostructures from feather barbs of six species show a poor match to SD. However, spherical nanostructures show a strong morphological similarity to morphologies produced by phase separation of a metastable mixture, called nucleation and growth. We propose that colour-producing, intracellular, spongy medullary β-keratin nanostructures develop their characteristic sizes and shapes by phase separation during protein polymerization. We discuss the possible role of capillary flow through drying of medullary cells in the development of the hollow

  7. Molecular dynamics simulations of nanostructures

    NASA Astrophysics Data System (ADS)

    Yuan, Zaoshi

    This dissertation is focused on multimillion-atom molecular dynamics (MD) simulations of nanoscale materials. In the past decade, nanoscale materials have made significant commercial impacts, which will potentially lead to the next industrial revolution. The interest lies in the novel and promising features nanoscale materials exhibit due to their confined sizes. However, not all novel behaviors are understood or controllable. Many uncontrollable parameters, e.g. defects and dangling bonds, are known to hinder the performance of nanodevices. Solutions to these problems rely on our understanding of fundamental elements in nanoscience: isolated individual nanostructures and their assemblies. In this dissertation, we will address atomistic foundations of several problems of technological importance in nanoscience. Specifically, three basic problems are discussed: (1) embrittlement of nanocrystalline metal; (2) novel thermo-mechanical behaviors of nanowires (NWs); and (3) planar defect generation in NWs. With a scalable algorithm implemented on massively parallel computing platforms and various data mining methods, MD simulations can provide valuable insights into these problems. An essential role of sulfur segregation-induced amorphization of crystalline nickel was recently discovered experimentally, but the atomistic mechanism of the amorphization remains unexplained. Our MD simulations reveal that the large steric size of sulfur impurity causes strong sulfur-sulfur interaction mediated by lattice distortion, which leads to amorphization near the percolation threshold at the sulfur-sulfur network in nickel crystal. The generality of the mechanism due to the percolation of an impurity network is further confirmed by a model binary system. In our study of novel behaviors of semiconductor NWs, MD simulations construct a rich size-temperature `phase diagram' for the mechanical response of a zinc-oxide NW under tension. For smaller diameters and higher temperatures, novel

  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. Formation of nanostructures from colloidal solutions of silicon dioxide and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhukalin, D. A.; Tuchin, A. V.; Goloshchapov, D. L.; Bityutskaya, L. A.

    2015-02-01

    The formation of nanostructures from colloidal solutions of amorphous silicon dioxide (SiO2) and carbon nanotubes (CNTs) in evaporating drops at room temperature has been studied. It is established that spherical aggregates with an average diameter of ˜2 μm and rodlike nanostructures with diameters within 250-300 nm and lengths of ˜4 μm are formed under these conditions. The mechanisms of covalent and van der Waals interaction between CNTs and SiO2 are considered in the framework of a phenomenological model of the active center of a closed CNT.

  10. Nanostructured Biomaterials for Regeneration**

    PubMed Central

    Wei, Guobao; Ma, Peter X.

    2009-01-01

    Biomaterials play a pivotal role in regenerative medicine, which aims to regenerate and replace lost/dysfunctional tissues or organs. Biomaterials (scaffolds) serve as temporary 3D substrates to guide neo tissue formation and organization. It is often beneficial for a scaffolding material to mimic the characteristics of extracellular matrix (ECM) at the nanometer scale and to induce certain natural developmental or/and wound healing processes for tissue regeneration applications. This article reviews the fabrication and modification technologies for nanofibrous, nanocomposite, and nanostructured drug-delivering scaffolds. ECM-mimicking nanostructured biomaterials have been shown to actively regulate cellular responses including attachment, proliferation, differentiation and matrix deposition. Nano-scaled drug delivery systems can be successfully incorporated into a porous 3D scaffold to enhance the tissue regeneration capacity. In conclusion, nano-structured biomateials are a very exciting and rapidly expanding research area, and are providing new enabling technologies for regenerative medicine. PMID:19946357

  11. 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.

  12. Biophotonics and Bone Biology

    NASA Technical Reports Server (NTRS)

    Zimmerli, Gregory; Fischer, David; Asipauskas, Marius; Chauhan, Chirag; Compitello, Nicole; Burke, Jamie; Tate, Melissa Knothe

    2004-01-01

    One of the more-serious side effects of extended space flight is an accelerated bone loss [Bioastronautics Critical Path Roadmap, http://research.hq.nasa.gov/code_u/bcpr/index.cfm]. Rates of bone loss are highest in the weight-bearing bones of the hip and spine regions, and the average rate of bone loss as measured by bone mineral density measurements is around 1.2% per month for persons in a microgravity environment. It shows that an extrapolation of the microgravity induced bone loss rates to longer time scales, such as a 2.5 year round-trip to Mars (6 months out at 0 g, 1.5 year stay on Mars at 0.38 g, 6 months back at 0 g), could severely compromise the skeletal system of such a person.

  13. Biophotonics and Bone Biology

    NASA Technical Reports Server (NTRS)

    Zimmerli, Gregory; Fischer, David; Asipauskas, Marius; Chauhan, Chirag; Compitello, Nicole; Burke, Jamie; Tate, Melissa Knothe

    2004-01-01

    One of the more serious side effects of extended space flight is an accelerated bone loss. Rates of bone loss are highest in the weight-bearing bones of the hip and spine regions, and the average rate of bone loss as measured by bone mineral density measurements is around 1.2% per month for persons in a microgravity environment. It is well known that bone remodeling responds to mechanical forces. We are developing two-photon microscopy techniques to study bone tissue and bone cell cultures to better understand the fundamental response mechanism in bone remodeling. Osteoblast and osteoclast cell cultures are being studied, and the goal is to use molecular biology techniques in conjunction with Fluorescence Lifetime Imaging Microscopy (FLIM) to study the physiology of in-vitro cell cultures in response to various stimuli, such as fluid flow induced shear stress and mechanical stress. We have constructed a two-photon fluorescence microscope for these studies, and are currently incorporating FLIM detection. Current progress will be reviewed. This work is supported by the NASA John Glenn Biomedical Engineering Consortium.

  14. Nanostructured Solar Cells.

    PubMed

    Chen, Guanying; Ning, Zhijun; Ågren, Hans

    2016-08-09

    We are glad to announce the Special Issue "Nanostructured Solar Cells", published in Nanomaterials. This issue consists of eight articles, two communications, and one review paper, covering major important aspects of nanostructured solar cells of varying types. From fundamental physicochemical investigations to technological advances, and from single junction solar cells (silicon solar cell, dye sensitized solar cell, quantum dots sensitized solar cell, and small molecule organic solar cell) to tandem multi-junction solar cells, all aspects are included and discussed in this issue to advance the use of nanotechnology to improve the performance of solar cells with reduced fabrication costs.

  15. 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.

  16. Nanostructured Solar Cells

    PubMed Central

    Chen, Guanying; Ning, Zhijun; Ågren, Hans

    2016-01-01

    We are glad to announce the Special Issue “Nanostructured Solar Cells”, published in Nanomaterials. This issue consists of eight articles, two communications, and one review paper, covering major important aspects of nanostructured solar cells of varying types. From fundamental physicochemical investigations to technological advances, and from single junction solar cells (silicon solar cell, dye sensitized solar cell, quantum dots sensitized solar cell, and small molecule organic solar cell) to tandem multi-junction solar cells, all aspects are included and discussed in this issue to advance the use of nanotechnology to improve the performance of solar cells with reduced fabrication costs.

  17. Narrow band gap amorphous silicon semiconductors

    DOEpatents

    Madan, A.; Mahan, A.H.

    1985-01-10

    Disclosed is a narrow band gap amorphous silicon semiconductor comprising an alloy of amorphous silicon and a band gap narrowing element selected from the group consisting of Sn, Ge, and Pb, with an electron donor dopant selected from the group consisting of P, As, Sb, Bi and N. The process for producing the narrow band gap amorphous silicon semiconductor comprises the steps of forming an alloy comprising amorphous silicon and at least one of the aforesaid band gap narrowing elements in amount sufficient to narrow the band gap of the silicon semiconductor alloy below that of amorphous silicon, and also utilizing sufficient amounts of the aforesaid electron donor dopant to maintain the amorphous silicon alloy as an n-type semiconductor.

  18. Amorphous silicon solar cell allowing infrared transmission

    DOEpatents

    Carlson, David E.

    1979-01-01

    An amorphous silicon solar cell with a layer of high index of refraction material or a series of layers having high and low indices of refraction material deposited upon a transparent substrate to reflect light of energies greater than the bandgap energy of the amorphous silicon back into the solar cell and transmit solar radiation having an energy less than the bandgap energy of the amorphous silicon.

  19. Amorphous-Amorphous Phase Separation in API/Polymer Formulations.

    PubMed

    Luebbert, Christian; Huxoll, Fabian; Sadowski, Gabriele

    2017-02-15

    The long-term stability of pharmaceutical formulations of poorly-soluble drugs in polymers determines their bioavailability and therapeutic applicability. However, these formulations do not only often tend to crystallize during storage, but also tend to undergo unwanted amorphous-amorphous phase separations (APS). Whereas the crystallization behavior of APIs in polymers has been measured and modeled during the last years, the APS phenomenon is still poorly understood. In this study, the crystallization behavior, APS, and glass-transition temperatures formulations of ibuprofen and felodipine in polymeric PLGA excipients exhibiting different ratios of lactic acid and glycolic acid monomers in the PLGA chain were investigated by means of hot-stage microscopy and DSC. APS and recrystallization was observed in ibuprofen/PLGA formulations, while only recrystallization occurred in felodipine/PLGA formulations. Based on a successful modeling of the crystallization behavior using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT), the occurrence of APS was predicted in agreement with experimental findings.

  20. Amorphous silicon based radiation detectors

    SciTech Connect

    Perez-Mendez, V.; Cho, G.; Drewery, J.; Jing, T.; Kaplan, S.N.; Qureshi, S.; Wildermuth, D. ); Fujieda, I.; Street, R.A. )

    1991-07-01

    We describe the characteristics of thin(1 {mu}m) and thick (>30{mu}m) hydrogenated amorphous silicon p-i-n diodes which are optimized for detecting and recording the spatial distribution of charged particles, x-rays and {gamma} rays. For x-ray, {gamma} ray, and charged particle detection we can use thin p-i-n photosensitive diode arrays coupled to evaporated layers of suitable scintillators. For direct detection of charged particles with high resistance to radiation damage, we use the thick p-i-n diode arrays. 13 refs., 7 figs.

  1. Preparation of amorphous sulfide sieves

    DOEpatents

    Siadati, Mohammad H.; Alonso, Gabriel; Chianelli, Russell R.

    2006-11-07

    The present invention involves methods and compositions for synthesizing catalysts/porous materials. In some embodiments, the resulting materials are amorphous sulfide sieves that can be mass-produced for a variety of uses. In some embodiments, methods of the invention concern any suitable precursor (such as thiomolybdate salt) that is exposed to a high pressure pre-compaction, if need be. For instance, in some cases the final bulk shape (but highly porous) may be same as the original bulk shape. The compacted/uncompacted precursor is then subjected to an open-flow hot isostatic pressing, which causes the precursor to decompose and convert to a highly porous material/catalyst.

  2. Structural study of amorphous polyaniline

    NASA Astrophysics Data System (ADS)

    Laridjani, M.; Pouget, J. P.; MacDiarmid, A. G.; Epstein, A. J.

    1992-06-01

    Many materials, especially polymers, have a substantial volume fraction with no long range crystalline order. Through these regions are often termed amorphous, they frequently have a specific local order. We describe and use here a method, base on a non-energy dispersive X-ray diffraction technique, to obtain good quality interference functions and, by Fourier transform, radial distribution functions of the amorphous structure of polymers. We apply this approach to members of a family of electronic polymers of current interest : polyaniline emeraldine bases. We show that the local order exhibits significant differences in type I and type II materials, precipitated as salt and base respectively. These studies demonstrate the importance of sample preparation in evaluating the physical properties of polyaniline, and provide a structural origin for memory effects observed in the doping-dedoping processes. Beaucoup de matériaux, spécialement les polymères, ont une importante fraction de leur volume sans ordre cristallin à longue portée. Bien que ces régions soient souvent appelées amorphes, elles présentent fréquemment un ordre local caractéristique. Nous décrivons et utilisons dans ce papier une méthode, basée sur une technique de diffraction de rayons X non dispersive en énergie, pour obtenir des fonctions d'interférence de bonne qualité et, par transformée de Fourier, la fonction de distribution radiale des polymères amorphes. Nous appliquons cette technique à plusieurs éléments d'une même famille de polymères électroniques d'intérêt actuel : les polyanilines éméraldine bases. Nous montrons que l'ordre local présente d'appréciables différences dans les matériaux de type I et II, préparés respectivement sous forme de sel et de base. Cette étude démontre l'importance des conditions de préparation sur les propriétés physiques du polyaniline et donne une base structurale aux effets observés dans les processus de dopage-dédopage de

  3. Building Nanostructures with Drugs

    PubMed Central

    Ma, Wang; Cheetham, Andrew G.

    2016-01-01

    The convergence of nanoscience and drug delivery has prompted the formation of the field of nanomedicine, one that exploits the novel physicochemical and biological properties of nanostructures for improved medical treatments and reduced side effects. Until recently, this nanostructure-mediated strategy considered the drug to be solely a biologically active compound to be delivered, and its potential as a molecular building unit remained largely unexplored. A growing trend within nanomedicine has been the use of drug molecules to build well-defined nanostructures of various sizes and shapes. This strategy allows for the creation of self-delivering supramolecular nanomedicines containing a high and fixed drug content. Through rational design of the number and type of the drug incorporated, the resulting nanostructures can be tailored to assume various morphologies (e.g. nanospheres, rods, nanofibers, or nanotubes) for a particular mode of administration such as systemic, topical, and local delivery. This review covers the recent advances in this rapidly developing field, with the aim of providing an in-depth evaluation of the exciting opportunities that this new field could create to improve the current clinical practice of nanomedicine. PMID:27066106

  4. 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.

  5. Atomically Traceable Nanostructure Fabrication.

    PubMed

    Ballard, Josh B; Dick, Don D; McDonnell, Stephen J; Bischof, Maia; Fu, Joseph; Owen, James H G; Owen, William R; Alexander, Justin D; Jaeger, David L; Namboodiri, Pradeep; Fuchs, Ehud; Chabal, Yves J; Wallace, Robert M; Reidy, Richard; Silver, Richard M; Randall, John N; Von Ehr, James

    2015-07-17

    Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process being used in order to maintain exquisite control over both feature size and feature density. Here, we demonstrate a method for tracking atomically resolved and controlled structures from initial template definition through final nanostructure metrology, opening up a pathway for top-down atomic control over nanofabrication. Hydrogen depassivation lithography is the first step of the nanoscale fabrication process followed by selective atomic layer deposition of up to 2.8 nm of titania to make a nanoscale etch mask. Contrast with the background is shown, indicating different mechanisms for growth on the desired patterns and on the H passivated background. The patterns are then transferred into the bulk using reactive ion etching to form 20 nm tall nanostructures with linewidths down to ~6 nm. To illustrate the limitations of this process, arrays of holes and lines are fabricated. The various nanofabrication process steps are performed at disparate locations, so process integration is discussed. Related issues are discussed including using fiducial marks for finding nanostructures on a macroscopic sample and protecting the chemically reactive patterned Si(100)-H surface against degradation due to atmospheric exposure.

  6. Emerging double helical nanostructures.

    PubMed

    Zhao, Meng-Qiang; Zhang, Qiang; Tian, Gui-Li; Wei, Fei

    2014-08-21

    As one of the most important and land-mark structures found in nature, a double helix consists of two congruent single helices with the same axis or a translation along the axis. This double helical structure renders the deoxyribonucleic acid (DNA) the crucial biomolecule in evolution and metabolism. DNA-like double helical nanostructures are probably the most fantastic yet ubiquitous geometry at the nanoscale level, which are expected to exhibit exceptional and even rather different properties due to the unique organization of the two single helices and their synergistic effect. The organization of nanomaterials into double helical structures is an emerging hot topic for nanomaterials science due to their promising exceptional unique properties and applications. This review focuses on the state-of-the-art research progress for the fabrication of double-helical nanostructures based on 'bottom-up' and 'top-down' strategies. The relevant nanoscale, mesoscale, and macroscopic scale fabrication methods, as well as the properties of the double helical nanostructures are included. Critical perspectives are devoted to the synthesis principles and potential applications in this emerging research area. A multidisciplinary approach from the scope of nanoscience, physics, chemistry, materials, engineering, and other application areas is still required to the well-controlled and large-scale synthesis, mechanism, property, and application exploration of double helical nanostructures.

  7. Nanostructured catalyst supports

    DOEpatents

    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.

  8. Complex WS 2 nanostructures

    NASA Astrophysics Data System (ADS)

    Whitby, R. L. D.; Hsu, W. K.; Lee, T. H.; Boothroyd, C. B.; Kroto, H. W.; Walton, D. R. M.

    2002-06-01

    A range of elegant tubular and conical nanostructures has been created by template growth of (WS 2) n layers on the surfaces of single-walled carbon nanotube bundles. The structures exhibit remarkably perfect straight segments together with interesting complexities at the intersections, which are discussed here in detail in order to enhance understanding of the structural features governing tube growth.

  9. Crystalline-Amorphous Silicon Nanocomposites with Reduced Thermal Conductivity for Bulk Thermoelectrics.

    PubMed

    Miura, Asuka; Zhou, Shu; Nozaki, Tomohiro; Shiomi, Junichiro

    2015-06-24

    Responding to the need for thermoelectric materials with high efficiency in both conversion and cost, we developed a nanostructured bulk silicon thermoelectric materials by sintering silicon crystal quantum dots of several nanometers in diameters synthesized by plasma-enhanced chemical vapor deposition (PECVD). The material consists of hybrid structures of nanograins of crystalline silicon and amorphous silicon oxide. The percolated nanocrystalline region gives rise to high power factor with the high doping concentration realized by PECVD, and the binding amorphous region reduces thermal conductivity. Consequently, the nondimensional figure of merit reaches 0.39 at 600 °C, equivalent to the best reported value for silicon thermoelectrics. The thermal conductivity of the densely packed material is as low as 5 W m(-1) K(-1) in a wide temperature range from room temperature to 1000 °C, which is beneficial not only for the conversion efficiency but also for material cost by requiring less material to establish certain temperature gradient.

  10. Direct tunneling through high-κ amorphous HfO{sub 2}: Effects of chemical modification

    SciTech Connect

    Wang, Yin Yu, Zhizhou; Zahid, Ferdows; Wang, Jian; Liu, Lei; Zhu, Yu; Guo, Hong

    2014-07-14

    We report first principles modeling of quantum tunneling through amorphous HfO{sub 2} dielectric layer of metal-oxide-semiconductor (MOS) nanostructures in the form of n-Si/HfO{sub 2}/Al. In particular, we predict that chemically modifying the amorphous HfO{sub 2} barrier by doping N and Al atoms in the middle region—far from the two interfaces of the MOS structure—can reduce the gate-to-channel tunnel leakage by more than one order of magnitude. Several other types of modification are found to enhance tunneling or induce substantial band bending in the Si, both are not desired from leakage point of view. By analyzing transmission coefficients and projected density of states, the microscopic physics of electron traversing the tunnel barrier with or without impurity atoms in the high-κ dielectric is revealed.

  11. Core-shell amorphous silicon-carbon nanoparticles for high performance anodes in lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Sourice, Julien; Bordes, Arnaud; Boulineau, Adrien; Alper, John P.; Franger, Sylvain; Quinsac, Axelle; Habert, Aurélie; Leconte, Yann; De Vito, Eric; Porcher, Willy; Reynaud, Cécile; Herlin-Boime, Nathalie; Haon, Cédric

    2016-10-01

    Core-shell silicon-carbon nanoparticles are attractive candidates as active material to increase the capacity of Li-ion batteries while mitigating the detrimental effects of volume expansion upon lithiation. However crystalline silicon suffers from amorphization upon the first charge/discharge cycle and improved stability is expected in starting with amorphous silicon. Here we report the synthesis, in a single-step process, of amorphous silicon nanoparticles coated with a carbon shell (a-Si@C), via a two-stage laser pyrolysis where decomposition of silane and ethylene are conducted in two successive reaction zones. Control of experimental conditions mitigates silicon core crystallization as well as formation of silicon carbide. Auger electron spectroscopy and scanning transmission electron microscopy show a carbon shell about 1 nm in thickness, which prevents detrimental oxidation of the a-Si cores. Cyclic voltammetry demonstrates that the core-shell composite reaches its maximal lithiation during the first sweep, thanks to its amorphous core. After 500 charge/discharge cycles, it retains a capacity of 1250 mAh.g-1 at a C/5 rate and 800 mAh.g-1 at 2C, with an outstanding coulombic efficiency of 99.95%. Moreover, post-mortem observations show an electrode volume expansion of less than 20% and preservation of the nanostructuration.

  12. Nanostructured Porous Silicon: The Winding Road from Photonics to Cell Scaffolds – A Review

    PubMed Central

    Hernández-Montelongo, Jacobo; Muñoz-Noval, Alvaro; García-Ruíz, Josefa Predestinación; Torres-Costa, Vicente; Martín-Palma, Raul J.; Manso-Silván, Miguel

    2015-01-01

    For over 20 years, nanostructured porous silicon (nanoPS) has found a vast number of applications in the broad fields of photonics and optoelectronics, triggered by the discovery of its photoluminescent behavior in 1990. Besides, its biocompatibility, biodegradability, and bioresorbability make porous silicon (PSi) an appealing biomaterial. These properties are largely a consequence of its particular susceptibility to oxidation, leading to the formation of silicon oxide, which is readily dissolved by body fluids. This paper reviews the evolution of the applications of PSi and nanoPS from photonics through biophotonics, to their use as cell scaffolds, whether as an implantable substitute biomaterial, mainly for bony and ophthalmological tissues, or as an in vitro cell conditioning support, especially for pluripotent cells. For any of these applications, PSi/nanoPS can be used directly after synthesis from Si wafers, upon appropriate surface modification processes, or as a composite biomaterial. Unedited studies of fluorescently active PSi structures for cell culture are brought to evidence the margin for new developments. PMID:26029688

  13. Effect of medium range order on pulsed laser crystallization of amorphous germanium thin films

    SciTech Connect

    Li, T. T.; Bayu Aji, L. B.; Heo, T. W.; Santala, M. K.; Kucheyev, S. O.; Campbell, G. H.

    2016-06-03

    Sputter deposited amorphous Ge thin films had their nanostructure altered by irradiation with high-energy Ar+ ions. The change in the structure resulted in a reduction in medium range order (MRO) characterized using fluctuation electron microscopy. The pulsed laser crystallization kinetics of the as-deposited versus irradiated materials were investigated using the dynamic transmission electron microscope operated in the multi-frame movie mode. In conclusion, the propagation rate of the crystallization front for the irradiated material was lower; the changes were correlated to the MRO difference and formation of a thin liquid layer during crystallization.

  14. Transformations induced in bulk amorphous silica by ultrafast laser direct writing.

    PubMed

    Oliveira, Vitor; Sharma, Sahendra P; Herrero, Pilar; Vilar, Rui

    2013-12-01

    A transmission electron microscopy study of nanogratings formed in bulk amorphous silica by direct writing with an ultrafast pulsed laser with a radiation wavelength of 1030 nm and pulse duration of 560 fs is presented. The results achieved show that the nanogratings are composed of planar nanostructures with an average periodicity of 250 nm and typical thickness of about 30 nm, consisting of alternating layers of heavily damaged material and layers of material where a dense precipitation of nanocrystals occurred. The crystallization of silica to form these nanocrystals can be explained by the large pressures and temperatures reached in these regions as a result of nanoplasma formation and recombination.

  15. Effect of medium range order on pulsed laser crystallization of amorphous germanium thin films

    DOE PAGES

    Li, T. T.; Bayu Aji, L. B.; Heo, T. W.; ...

    2016-06-03

    Sputter deposited amorphous Ge thin films had their nanostructure altered by irradiation with high-energy Ar+ ions. The change in the structure resulted in a reduction in medium range order (MRO) characterized using fluctuation electron microscopy. The pulsed laser crystallization kinetics of the as-deposited versus irradiated materials were investigated using the dynamic transmission electron microscope operated in the multi-frame movie mode. In conclusion, the propagation rate of the crystallization front for the irradiated material was lower; the changes were correlated to the MRO difference and formation of a thin liquid layer during crystallization.

  16. Is Mg-stabilized amorphous calcium carbonate a homogeneous mixture of amorphous magnesium carbonate and amorphous calcium carbonate?

    PubMed

    Yang, Sheng-Yu; Chang, Hsun-Hui; Lin, Cang-Jie; Huang, Shing-Jong; Chan, Jerry C C

    2016-10-04

    We find two types of carbonate ions in Mg stabilized amorphous calcium carbonate (Mg-ACC), whose short-range orders are identical to those of ACC and amorphous magnesium carbonate (AMC). Mg-ACC comprises a homogeneous mixture of the nano-clusters of ACC and AMC. Their relative amount varies systematically at different pH.

  17. Laser surface treatment of amorphous metals

    NASA Astrophysics Data System (ADS)

    Katakam, Shravana K.

    Amorphous materials are used as soft magnetic materials and also as surface coatings to improve the surface properties. Furthermore, the nanocrystalline materials derived from their amorphous precursors show superior soft magnetic properties than amorphous counter parts for transformer core applications. In the present work, laser based processing of amorphous materials will be presented. Conventionally, the nanocrystalline materials are synthesized by furnace heat treatment of amorphous precursors. Fe-based amorphous/nanocrystalline materials due to their low cost and superior magnetic properties are the most widely used soft magnetic materials. However, achieving nanocrystalline microstructure in Fe-Si-B ternary system becomes very difficult owing its rapid growth rate at higher temperatures and sluggish diffusion at low temperature annealing. Hence, nanocrystallization in this system is achieved by using alloying additions (Cu and Nb) in the ternary Fe-Si-B system. Thus, increasing the cost and also resulting in reduction of saturation magnetization. laser processing technique is used to achieve extremely fine nanocrystalline microstructure in Fe-Si-B amorphous precursor. Microstructure-magnetic Property-laser processing co-relationship has been established for Fe-Si-B ternary system using analytical techniques. Laser processing improved the magnetic properties with significant increase in saturation magnetization and near zero coercivity values. Amorphous materials exhibit excellent corrosion resistance by virtue of their atomic structure. Fe-based amorphous materials are economical and due to their ease of processing are of potential interest to synthesize as coatings materials for wear and corrosion resistance applications. Fe-Cr-Mo-Y-C-B amorphous system was used to develop thick coatings on 4130 Steel substrate and the corrosion resistance of the amorphous coatings was improved. It is also shown that the mode of corrosion depends on the laser processing

  18. Fluorination of amorphous thin-film materials with xenon fluoride

    DOEpatents

    Weil, R.B.

    1987-05-01

    A method is disclosed for producing fluorine-containing amorphous semiconductor material, preferably comprising amorphous silicon. The method includes depositing amorphous thin-film material onto a substrate while introducing xenon fluoride during the film deposition process.

  19. Fluorination of amorphous thin-film materials with xenon fluoride

    DOEpatents

    Weil, Raoul B.

    1988-01-01

    A method is disclosed for producing fluorine-containing amorphous semiconductor material, preferably comprising amorphous silicon. The method includes depositing amorphous thin-film material onto a substrate while introducing xenon fluoride during the film deposition process.

  20. Method of making amorphous metal composites

    DOEpatents

    Byrne, Martin A.; Lupinski, John H.

    1982-01-01

    The process comprises placing an amorphous metal in particulate form and a low molecular weight (e.g., 1000-5000) thermosetting polymer binder powder into a container, mixing these materials, and applying heat and pressure to convert the mixture into an amorphous metal composite.

  1. Co amorphous systems: A product development perspective.

    PubMed

    Chavan, Rahul B; Thipparaboina, Rajesh; Kumar, Dinesh; Shastri, Nalini R

    2016-12-30

    Solubility is one of the major problems associated with most of the new chemical entities that can be reasonably addressed by drug amorphization. However, being a high-energy form, it usually tends to re-crystallize, necessitating new formulation strategies to stabilize amorphous drugs. Polymeric amorphous solid dispersion (PASD) is one of the widely investigated strategies to stabilize amorphous drug, with major limitations like limited polymer solubility and hygroscopicity. Co amorphous system (CAM), a new entrant in amorphous arena is a promising alternative to PASD. CAMs are multi component single phase amorphous solid systems made up of two or more small molecules that may be a combination of drugs or drug and excipients. Excipients explored for CAM preparation include amino acids, carboxylic acids, nicotinamide and saccharine. Advantages offered by CAM include improved aqueous solubility and physical stability of amorphous drug, with a potential to improve therapeutic efficacy. This review attempts to address different aspects in the development of CAM as drug products. Criterion for co-former selection, various methods involved in CAM preparation, characterization tools, stability, scale up and regulatory requirements for the CAM product development are discussed.

  2. Electron tunnelling into amorphous germanium and silicon.

    NASA Technical Reports Server (NTRS)

    Smith, C. W.; Clark, A. H.

    1972-01-01

    Measurements of tunnel conductance versus bias, capacitance versus bias, and internal photoemission were made in the systems aluminum-oxide-amorphous germanium and aluminium-oxide-amorphous silicon. A function was extracted which expresses the deviation of these systems from the aluminium-oxide-aluminium system.

  3. Electron beam recrystallization of amorphous semiconductor materials

    NASA Technical Reports Server (NTRS)

    Evans, J. C., Jr.

    1968-01-01

    Nucleation and growth of crystalline films of silicon, germanium, and cadmium sulfide on substrates of plastic and glass were investigated. Amorphous films of germanium, silicon, and cadmium sulfide on amorphous substrates of glass and plastic were converted to the crystalline condition by electron bombardment.

  4. Imprinting bulk amorphous alloy at room temperature

    DOE PAGES

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; ...

    2015-11-13

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the abilitymore » of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. In conclusion, our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment.« less

  5. 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

  6. Compensated amorphous-silicon solar cell

    DOEpatents

    Devaud, G.

    1982-06-21

    An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the elecrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF/sub 3/ doped intrinsic layer.

  7. Neutron irradiation induced amorphization of silicon carbide

    SciTech Connect

    Snead, L.L.; Hay, J.C.

    1998-09-01

    This paper provides the first known observation of silicon carbide fully amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60 C to a total fast neutron fluence of 2.6 {times} 10{sup 25} n/m{sup 2}. Amorphization was seen in both materials, as evidenced by TEM, electron diffraction, and x-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density ({minus}10.8%), elastic modulus as measured using a nanoindentation technique ({minus}45%), hardness as measured by nanoindentation ({minus}45%), and standard Vickers hardness ({minus}24%). Similar property changes are observed for the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than 130 C.

  8. Amorphization of sugar hydrates upon milling.

    PubMed

    Willart, J F; Dujardin, N; Dudognon, E; Danède, F; Descamps, M

    2010-07-19

    The possibility to amorphize anhydrous crystalline sugars, like lactose, trehalose and glucose, by mechanical milling was previously reported. We test here the possibility to amorphize the corresponding crystalline hydrates: lactose monohydrate, trehalose dihydrate and glucose monohydrate using fully identical milling procedures. The results show that only the first hydrate amorphizes while the other two remain structurally invariant. These different behaviours are attributed to the plasticizing effect of the structural water molecules which can decrease the glass transition temperature below the milling temperature. The results reveal clearly the fundamental role of the glass transition in the solid-state amorphization process induced by milling, and they also explain why crystalline hydrates are systematically more difficult to amorphize by milling than their anhydrous counterpart. The investigations have been performed by differential scanning calorimetry and powder X-ray diffraction.

  9. Structure, thermodynamics, and crystallization of amorphous hafnia

    SciTech Connect

    Luo, Xuhui; Demkov, Alexander A.

    2015-09-28

    We investigate theoretically amorphous hafnia using the first principles melt and quench method. We identify two types of amorphous structures of hafnia. Type I and type II are related to tetragonal and monoclinic hafnia, respectively. We find type II structure to show stronger disorder than type I. Using the phonon density of states, we calculate the specific heat capacity for type II amorphous hafnia. Using the nudged elastic band method, we show that the averaged transition barrier between the type II amorphous hafnia and monoclinic phase is approximately 0.09 eV/HfO{sub 2}. The crystallization temperature is estimated to be 421 K. The calculations suggest an explanation for the low thermal stability of amorphous hafnia.

  10. Locomotion of Amorphous Surface Robots

    NASA Technical Reports Server (NTRS)

    Bradley, Arthur T. (Inventor)

    2016-01-01

    An amorphous robot includes a compartmented bladder containing fluid, a valve assembly, and an outer layer encapsulating the bladder and valve assembly. The valve assembly draws fluid from a compartment(s) and discharges the drawn fluid into a designated compartment to displace the designated compartment with respect to the surface. Another embodiment includes elements each having a variable property, an outer layer that encapsulates the elements, and a control unit. The control unit energizes a designated element to change its variable property, thereby moving the designated element. The elements may be electromagnetic spheres with a variable polarity or shape memory polymers with changing shape and/or size. Yet another embodiment includes an elongated flexible tube filled with ferrofluid, a moveable electromagnet, an actuator, and a control unit. The control unit energizes the electromagnet and moves the electromagnet via the actuator to magnetize the ferrofluid and lengthen the flexible tube.

  11. Locomotion of Amorphous Surface Robots

    NASA Technical Reports Server (NTRS)

    Bradley, Arthur T. (Inventor)

    2014-01-01

    An amorphous robot includes a compartmented bladder containing fluid, a valve assembly, and an outer layer encapsulating the bladder and valve assembly. The valve assembly draws fluid from a compartment(s) and discharges the drawn fluid into a designated compartment to displace the designated compartment with respect to the surface. Another embodiment includes elements each having a variable property, an outer layer that encapsulates the elements, and a control unit. The control unit energizes a designated element to change its variable property, thereby moving the designated element. The elements may be electromagnetic spheres with a variable polarity or shape memory polymers with changing shape and/or size. Yet another embodiment includes an elongated flexible tube filled with ferrofluid, a moveable electromagnet, an actuator, and a control unit. The control unit energizes the electromagnet and moves the electromagnet via the actuator to magnetize the ferrofluid and lengthen the flexible tube.

  12. Biologically formed amorphous calcium carbonate.

    PubMed

    Weiner, Steve; Levi-Kalisman, Yael; Raz, Sefi; Addadi, Lia

    2003-01-01

    Many organisms from a wide variety of taxa produce amorphous calcium carbonate (ACC), despite the fact that it is inherently unstable and relatively soluble in its pure state. These properties also make it difficult to detect and characterize ACC. Raman spectroscopy is a particularly useful method for investigating ACC because the sample can be examined wet, and extended X-ray absorption fine structure (EXAFS) analysis can provide detailed information on the short-range order. Other methods for characterizing ACC include infrared spectroscopy, thermogravimetric analysis and differential thermal analysis (TGA and DTA), transmission electron microscopy (TEM), and electron and X-ray diffraction. Because of the difficulties involved, we suspect that ACC is far more widely distributed than is presently known, and a comparison of EXAFS spectra shows that different biogenic ACC phases have different short-range order structures. We also suspect that ACC fulfils many different functions, including as a transient precursor phase during the formation of crystalline calcium carbonate.

  13. Surface properties and biocompatibility of nanostructured TiO2 film deposited by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Majeed, Asif; He, Jie; Jiao, Lingrui; Zhong, Xiaoxia; Sheng, Zhengming

    2015-02-01

    Nanostructured TiO2 films are deposited on a silicon substrate using 150-W power from the RF magnetron sputtering at working pressures of 3 to 5 Pa, with no substrate bias, and at 3 Pa with a substrate bias of -50 V. X-ray diffraction (XRD) analysis reveals that TiO2 films deposited on unbiased as well as biased substrates are all amorphous. Surface properties such as surface roughness and wettability of TiO2 films, grown in a plasma environment, under biased and unbiased substrate conditions are reported according to the said parameters of RF power and the working pressures. Primary rat osteoblasts (MC3T3-E1) cells have been cultured on nanostructured TiO2 films fabricated at different conditions of substrate bias and working pressures. The effects of roughness and hydrophilicity of nanostructured TiO2 films on cell density and cell spreading have been discussed.

  14. Enhanced photocatalytic activity of C@ZnO core-shell nanostructures and its photoluminescence property

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Yu, Shanwen; Fang, Xiaoxin; Huang, Honghong; Li, Lun; Wang, Xiuyuan; Wang, Huihu

    2016-12-01

    An ultrathin layer of amorphous carbon coated C@ZnO core-shell nanostructures were synthesized via a facile hydrothermal carbonization process using glucose as precursor in this work. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance UV-vis spectroscopy (DRS) were used for the characterization of as-prepared samples. Photoluminescence (PL) properties of C@ZnO samples were investigated using PL spectroscopy. The microstructure analysis results show that the glucose content has a great influence on the size, morphology, crystallinity and surface chemical states of C@ZnO nanostructures. Moreover, the as-prepared C@ZnO core-shell nanostructures exhibit the enhanced photocatalytic activity and good photostability for methyl orange dye degradation due to its high adsorption ability and its improved optical characteristics.

  15. Surface properties and biocompatibility of nanostructured TiO2 film deposited by RF magnetron sputtering.

    PubMed

    Majeed, Asif; He, Jie; Jiao, Lingrui; Zhong, Xiaoxia; Sheng, Zhengming

    2015-01-01

    Nanostructured TiO2 films are deposited on a silicon substrate using 150-W power from the RF magnetron sputtering at working pressures of 3 to 5 Pa, with no substrate bias, and at 3 Pa with a substrate bias of -50 V. X-ray diffraction (XRD) analysis reveals that TiO2 films deposited on unbiased as well as biased substrates are all amorphous. Surface properties such as surface roughness and wettability of TiO2 films, grown in a plasma environment, under biased and unbiased substrate conditions are reported according to the said parameters of RF power and the working pressures. Primary rat osteoblasts (MC3T3-E1) cells have been cultured on nanostructured TiO2 films fabricated at different conditions of substrate bias and working pressures. The effects of roughness and hydrophilicity of nanostructured TiO2 films on cell density and cell spreading have been discussed.

  16. Nanostructured Superhydrophobic Coatings

    SciTech Connect

    2009-03-01

    This factsheet describes a research project that deals with the nanostructured superhydrophobic (SH) powders developed at ORNL. This project seeks to (1) improve powder quality; (2) identify binders for plastics, fiberglass, metal (steel being the first priority), wood, and other products such as rubber and shingles; (3) test the coated product for coating quality and durability under operating conditions; and (4) application testing and production of powders in quantity.

  17. Planar plasmonic chiral nanostructures

    NASA Astrophysics Data System (ADS)

    Zu, Shuai; Bao, Yanjun; Fang, Zheyu

    2016-02-01

    A strong chiral optical response induced at a plasmonic Fano resonance in a planar Au heptamer nanostructure was experimentally and theoretically demonstrated. The scattering spectra show the characteristic narrow-band feature of Fano resonances for both left and right circular polarized lights, with a chiral response reaching 30% at the Fano resonance. Specifically, we systematically investigate the chiral response of planar heptamers with gradually changing the inter-particle rotation angles and separation distance. The chiral spectral characteristics clearly depend on the strength of Fano resonances and the associated near-field optical distributions. Finite element method simulations together with a multipole expansion method demonstrate that the enhanced chirality is caused by the excitation of magnetic quadrupolar and electric toroidal dipolar modes. Our work provides an effective method for the design of 2D nanostructures with a strong chiral response.A strong chiral optical response induced at a plasmonic Fano resonance in a planar Au heptamer nanostructure was experimentally and theoretically demonstrated. The scattering spectra show the characteristic narrow-band feature of Fano resonances for both left and right circular polarized lights, with a chiral response reaching 30% at the Fano resonance. Specifically, we systematically investigate the chiral response of planar heptamers with gradually changing the inter-particle rotation angles and separation distance. The chiral spectral characteristics clearly depend on the strength of Fano resonances and the associated near-field optical distributions. Finite element method simulations together with a multipole expansion method demonstrate that the enhanced chirality is caused by the excitation of magnetic quadrupolar and electric toroidal dipolar modes. Our work provides an effective method for the design of 2D nanostructures with a strong chiral response. Electronic supplementary information (ESI) available

  18. Alternative nanostructures for thermophones.

    PubMed

    Aliev, Ali E; Mayo, Nathanael K; Jung de Andrade, Monica; Robles, Raquel O; Fang, Shaoli; Baughman, Ray H; Zhang, Mei; Chen, Yongsheng; Lee, Jae Ah; Kim, Seon Jeong

    2015-05-26

    Thermophones are highly promising for applications such as high-power SONAR arrays, flexible loudspeakers, and noise cancellation devices. So far, freestanding carbon nanotube aerogel sheets provide the most attractive performance as a thermoacoustic heat source. However, the limited accessibility of large-size freestanding carbon nanotube aerogel sheets and other even more exotic materials recently investigated hampers the field. We describe alternative materials for a thermoacoustic heat source with high-energy conversion efficiency, additional functionalities, environmentally friendly, and cost-effective production technologies. We discuss the thermoacoustic performance of alternative nanostructured materials and compare their spectral and power dependencies of sound pressure in air. We demonstrate that the heat capacity of aerogel-like nanostructures can be extracted by a thorough analysis of the sound pressure spectra. The study presented here focuses on engineering thermal gradients in the vicinity of nanostructures and subsequent heat dissipation processes from the interior of encapsulated thermoacoustic projectors. Applications of thermoacoustic projectors for high-power SONAR arrays, sound cancellation, and optimal thermal design, regarding enhanced energy conversion efficiency, are discussed.

  19. Plasmonic Nanostructured Cellular Automata

    NASA Astrophysics Data System (ADS)

    Alkhazraji, Emad; Ghalib, A.; Manzoor, K.; Alsunaidi, M. A.

    2017-03-01

    In this work, we have investigated the scattering plasmonic resonance characteristics of silver nanospheres with a geometrical distribution that is modelled by Cellular Automata using time-domain numerical analysis. Cellular Automata are discrete mathematical structures that model different natural phenomena. Two binary one-dimensional Cellular Automata rules are considered to model the nanostructure, namely rule 30 and rule 33. The analysis produces three-dimensional scattering profiles of the entire plasmonic nanostructure. For the Cellular Automaton rule 33, the introduction of more Cellular Automata generations resulted only in slight red and blue shifts in the plasmonic modes with respect to the first generation. On the other hand, while rule 30 introduced significant red shifts in the resonance peaks at early generations, at later generations however, a peculiar effect is witnessed in the scattering profile as new peaks emerge as a feature of the overall Cellular Automata structure rather than the sum of the smaller parts that compose it. We strongly believe that these features that emerge as a result adopting the different 256 Cellular Automata rules as configuration models of nanostructures in different applications and systems might possess a great potential in enhancing their capability, sensitivity, efficiency, and power utilization.

  20. Strength, Deformation and Fracture in Metallic Nanostructures

    NASA Astrophysics Data System (ADS)

    Gu, Xun Wendy

    An understanding of the mechanics of nanoscale metals and semiconductors is necessary for the safe and prolonged operation of nanostructured devices from transistors to nanowire- based solar cells to miniaturized electrodes. This is a fascinating but challenging pursuit because mechanical properties that are size-invariant in conventional materials, such as strength, ductility and fracture behavior, can depend critically on sample size when materials are reduced to sub-micron dimensions. In this thesis, the effect of nanoscale sample size, microstructure and structural geometry on mechanical strength, deformation and fracture are explored for several classes of solid materials. Nanocrystalline platinum nano-cylinders with diameters of 60 nm to 1 μm and 12 nm sized grains are fabricated and tested in compression. We find that nano-sized metals containing few grains weaken as sample diameter is reduced relative to grain size due to a change from deformation governed by internal grains to surface grain governed deformation. Fracture at the nanoscale is explored by performing in-situ SEM tension tests on nanocrystalline platinum and amorphous, metallic glass nano-cylinders containing purposely introduced structural flaws. It is found that failure location, mechanism and strength are determined by the stress concentration with the highest local stress whether this is at the structural flaw or a microstructural feature. Principles of nano-mechanics are used to design and test mechanically robust hierarchical nanostructures with structural and electrochemical applications. 2-photon lithography and electroplating are used to fabricate 3D solid Cu octet meso-lattices with micron-scale features that exhibit strength higher than that of bulk Cu. An in-situ SEM lithiation stage is developed and used to simultaneously examine morphological and electrochemical changes in Si-coated Cu meso-lattices that are of interest as high energy capacity electrodes for Li-ion batteries.

  1. Nanostructured FeZrCuB alloys prepared by mechanosynthesis

    SciTech Connect

    Pereira, R. D.; Passamani, E. C.; Larica, C.; Freitas, J. C. C.; Takeuchi, A. Y.

    2007-08-01

    Nanostructured Fe{sub 84}Zr{sub 9}B{sub 6}Cu{sub 1} alloys were prepared by the mechanosynthesis method, following two alternative routes. In the first procedure, the alloy was directly obtained from the milling of the powder mixture of all elemental components. The resulting alloy was partially nanocrystalline, with dispersion of nanograins in an amorphous matrix. In the second route, Cu and B elemental powders were progressively added to a previously milled Fe{sub 90}Zr{sub 10} alloy. A nearly single amorphous phase was consequently obtained. The dispersion of nanograins was easily recovered in this case, after annealing the milled alloy. The hyperfine magnetic properties of the amorphous phase prepared by milling were comparable to those found in similar melt-spun alloys. The crystallization temperatures and activation energies, associated with the first and second crystallization stages, were found to be lower for the milled alloy when compared with the corresponding melt-spun alloy, an effect associated with the larger number of defects induced by the mechanosynthesis process.

  2. Nanostructured diamond-TiC composites with high fracture toughness

    NASA Astrophysics Data System (ADS)

    Wang, Haikuo; He, Duanwei; Xu, Chao; Tang, Mingjun; Li, Yu; Dong, Haini; Meng, Chuanmin; Wang, Zhigang; Zhu, Wenjun

    2013-01-01

    We report the preparation of nanostructured diamond-TiC composites with high fracture toughness and high hardness starting from a ball-milled mixture of nano-sized Ti3SiC2 and submicron-sized diamond by simultaneously tuning the pressure-temperature conditions. The phase segregation of Ti3SiC2 at pressure of 5.5 GPa were investigated by X-ray diffraction and high resolution transmission electron microscopy, we found that the Ti3SiC2 could decompose into nanosized TiC and amorphous Ti-Si at 600-700 °C. The subsequent reaction between diamond and Ti-Si led to an amorphous Ti-Si-C matrix in which diamond and TiC crystals are embedded. With a loading force of 98 N, the measured fracture toughness KIC and Vicker's hardness HV of the synthesized composites reach up to 14 MPa m1/2 and 45.5 GPa, respectively. Our results demonstrate that the nanocrystalline/amorphous bonding matrix could largely enhance the toughness of the brittle composites.

  3. Microstructural Evolution and Optical Properties of (InGa)(AsN) Nanostructures Synthesized by Ion Implantation

    NASA Astrophysics Data System (ADS)

    Weng, X.; Clarke, S.; Kumar, S.; Goldman, R. S.; Rotberg, V. H.; Krishna, S.; Bhattacharya, P. K.; Holt, J.; Sipowska, J.; Francis, A.; Daniel, A.; Clarke, R.

    2001-03-01

    Mixed anion nitride-arsenide compound semiconductor heterostructures are promising for light-emitting devices operating throughout the near infrared range. However, due to the large N-As size difference, a limited miscibility of (InGa)(AsN) on the anion sublattice is predicted. Furthermore, alloy phase separation resulting in the formation of quantum dot-like nanostructures has been reported in GaAsN/GaAs [1] and InGaAsN/GaAs [2] superlattices. We have investigated the evolution of the microstructure and optical properties of (InGa)(AsN) quantum dot-like nanostructures synthesized by N ion implantation into GaAs and InAs, using a variety of implantation and rapid thermal annealing conditions. For 50keV N ion implanted GaAs and InAs substrates, high-resolution cross-sectional transmission electron microscopy reveals ~5 nm diameter amorphous nanostructures surrounded by crystalline matrices. For 100keV N ion implanted GaAs epilayers, ~10 nm diameter crystalline nanostructures surrounded by amorphous matrices are apparent. Electron diffraction indicates that these crystallites are mostly randomly-oriented cubic phases, with lattice parameters close to that of pure GaN. Furthermore, the crystalline nanostructures exhibit significant photoluminescence in the near-infrared range. The apparent lowering of the fundamental band gap is consistent with strain-induced band gap narrowing of a GaN-rich spherical cluster [1]. We will discuss the mechanisms of formation and coarsening of these nanostructures, as well as correlations between their optical and structural properties. [1] R. S. Goldman, R. M. Feenstra, B. G. Briner, M. L. O'Steen, and R. J. Hauenstein, Appl. Phys. Lett. 69, 3698 (1996), J. Electr. Mater. 26, 1342 (1997). [2] H. P. Xin, K. L. Kavanagh, Z. Q. Zhu, and C. W. Tu, Appl. Phys. Lett. 74, 2337 (1999).

  4. Crystalline to amorphous transformation in silicon

    SciTech Connect

    Cheruvu, S.M.

    1982-09-01

    In the present investigation, an attempt was made to understand the fundamental mechanism of crystalline-to-amorphous transformation in arsenic implanted silicon using high resolution electron microscopy. A comparison of the gradual disappearance of simulated lattice fringes with increasing Frenkel pair concentration with the experimental observation of sharp interfaces between crystalline and amorphous regions was carried out leading to the conclusion that when the defect concentration reaches a critical value, the crystal does relax to an amorphous state. Optical diffraction experiments using atomic models also supported this hypothesis. Both crystalline and amorphous zones were found to co-exist with sharp interfaces at the atomic level. Growth of the amorphous fraction depends on the temperature, dose rate and the mass of the implanted ion. Preliminary results of high energy electron irradiation experiments at 1.2 MeV also suggested that clustering of point defects occurs near room temperature. An observation in a high resolution image of a small amorphous zone centered at the core of a dislocation is presented as evidence that the nucleation of an amorphous phase is heterogeneous in nature involving clustering or segregation of point defects near existing defects.

  5. Low Temperature Growth of Nanostructured Diamond Films on Metals

    NASA Technical Reports Server (NTRS)

    Baker, Paul A.; Catledge, Shane A.; Vohra, Yogesh K.

    2001-01-01

    The field of nanocrystalline diamond and tetrahedral amorphous carbon films has been the focus of intense experimental activity in the last few years for applications in field emission display devices, optical windows, and tribological coatings, The choice of substrate used in most studies has typically been silicon. For metals, however, the thermal expansion mismatch between the diamond film and substrate gives rise to thermal stress that often results in delamination of the film. To avoid this problem in conventional CVD deposition low substrate temperatures (less than 700 C) have been used, often with the incorporation of oxygen or carbon monoxide to the feedgas mixture. Conventionally grown CVD diamond films are also rough and would require post-deposition polishing for most applications. Therefore, there is an obvious need to develop techniques for deposition of well-adhered, smooth nano-structured diamond films on metals for various tribological applications. In our work, nanostructured diamond films are grown on a titanium alloy substrate using a two-step deposition process. The first step is performed at elevated temperature (820 C) for 30 minutes using a H2/CH4/N2 gas mixture in order to grow a thin (approx. 600 nm) nanostructured diamond layer and improve film adhesion. The remainder of the deposition involves growth at low temperature (less than 600 C) in a H2/CH4/O2 gas mixture. Laser reflectance Interferometry (LRI) pattern during growth of a nanostructured diamond film on Ti-6Al-4V alloy. The first 30 minutes are at a high temperature of 820 C and the rest of the film is grown at a low temperature of 580 T. The fringe pattern is observed till the very end due to extremely low surface roughness of 40 nm. The continuation of the smooth nanostructured diamond film growth during low temperature deposition is confirmed by in-situ laser reflectance interferometry and by post-deposition micro-Raman spectroscopy and surface profilometry. Similar experiments

  6. Laser irradiation to produce amorphous pharmaceuticals.

    PubMed

    Titapiwatanakun, Varin; Tankul, Junlathip; Basit, Abdul W; Gaisford, Simon

    2016-11-30

    Using a high-power CO2 laser to irradiate powder beds, it was possible to induce phase transformation to the amorphous state. Irradiation of a model drug, indometacin, resulted in formation of a glass. Varying the settings of the laser (power and raster speed) was shown to change the physicochemical properties of the glasses produced and all irradiated glasses were found to be more stable than a reference glass produced by melt-quenching. Irradiation of a powder blend of paracetamol and polyvinylpyrrolidone K30 was found to produce a solid amorphous dispersion. The results suggest that laser-irradiation might be a useful method for making amorphous pharmaceuticals.

  7. Method of producing hydrogenated amorphous silicon film

    DOEpatents

    Wiesmann, Harold J.

    1980-01-01

    This invention relates to hydrogenated amorphous silicon produced by thermally decomposing silane (SiH.sub.4) or other gases comprising H and Si, from a tungsten or carbon foil heated to a temperature of about 1400.degree.-1600.degree. C., in a vacuum of about 10.sup.-6 to 19.sup.-4 torr, to form a gaseous mixture of atomic hydrogen and atomic silicon, and depositing said gaseos mixture onto a substrate independent of and outside said source of thermal decomposition, to form hydrogenated amorphous silicon. The presence of an ammonia atmosphere in the vacuum chamber enhances the photoconductivity of the hydrogenated amorphous silicon film.

  8. Characterization of mechanical heterogeneity in amorphous solids

    NASA Astrophysics Data System (ADS)

    Peng, H. L.; Li, M. Z.; Sun, B. A.; Wang, W. H.

    2012-07-01

    The structural geometry and size distribution of the local atomic rearrangements induced by external stress in amorphous solids are investigated by molecular dynamics studies. We find that the size distribution exhibits a generic power-law behavior and their structural geometry shows fractal feature. This indicates that the local atomic rearrangements in amorphous solids are self-organized during deformation. A simple theoretical model based on the interaction of the heterogeneous elastic field sources is proposed which predicts the power-law scaling and characterizes the properties of the local atomic rearrangements in amorphous solids.

  9. Origin of Magnetic Properties in Amorphous Metals.

    DTIC Science & Technology

    1979-12-01

    Magnetic Properties of Fe-Ni-B Amorphous Alloys," F. E. Luborsky, J. L. Walter, and H. H. Liebermann , IEEE Trans. on Magnetics MAG-15, 909 (1979). Also GE...Report 78CRD132. 2. "Formation and Magnetic Properties of Fe-B-Si Amorphous Alloys," F. E. Luborsky, J. J. Becker, J. L. Walter, and H. H. Liebermann ...Amorphous Alloys," F. E. Luborsky and H. H. Liebermann , J. Appl. Phys., to appear. Also GE Report 79CRD177. 4. "The Effect of Temperature on Magnetic

  10. Photonic crystals, amorphous materials, and quasicrystals

    PubMed Central

    Edagawa, Keiichi

    2014-01-01

    Photonic crystals consist of artificial periodic structures of dielectrics, which have attracted much attention because of their wide range of potential applications in the field of optics. We may also fabricate artificial amorphous or quasicrystalline structures of dielectrics, i.e. photonic amorphous materials or photonic quasicrystals. So far, both theoretical and experimental studies have been conducted to reveal the characteristic features of their optical properties, as compared with those of conventional photonic crystals. In this article, we review these studies and discuss various aspects of photonic amorphous materials and photonic quasicrystals, including photonic band gap formation, light propagation properties, and characteristic photonic states. PMID:27877676

  11. Effects of CO2-induced pH reduction on the exoskeleton structure and biophotonic properties of the shrimp Lysmata californica

    PubMed Central

    Taylor, Jennifer R. A.; Gilleard, Jasmine M.; Allen, Michael C.; Deheyn, Dimitri D.

    2015-01-01

    The anticipated effects of CO2-induced ocean acidification on marine calcifiers are generally negative, and include dissolution of calcified elements and reduced calcification rates. Such negative effects are not typical of crustaceans for which comparatively little ocean acidification research has been conducted. Crustaceans, however, depend on their calcified exoskeleton for many critical functions. Here, we conducted a short-term study on a common caridean shrimp, Lysmata californica, to determine the effect of CO2-driven reduction in seawater pH on exoskeleton growth, structure, and mineralization and animal cryptic coloration. Shrimp exposed to ambient (7.99 ± 0.04) and reduced pH (7.53 ± 0.06) for 21 days showed no differences in exoskeleton growth (percent increase in carapace length), but the calcium weight percent of their cuticle increased significantly in reduced pH conditions, resulting in a greater Ca:Mg ratio. Cuticle thickness did not change, indicating an increase in the mineral to matrix ratio, which may have mechanical consequences for exoskeleton function. Furthermore, there was a 5-fold decrease in animal transparency, but no change in overall shrimp coloration (red). These results suggest that even short-term exposure to CO2-induced pH reduction can significantly affect exoskeleton mineralization and shrimp biophotonics, with potential impacts on crypsis, physical defense, and predator avoidance. PMID:26030212

  12. Effects of CO2-induced pH reduction on the exoskeleton structure and biophotonic properties of the shrimp Lysmata californica.

    PubMed

    Taylor, Jennifer R A; Gilleard, Jasmine M; Allen, Michael C; Deheyn, Dimitri D

    2015-06-01

    The anticipated effects of CO2-induced ocean acidification on marine calcifiers are generally negative, and include dissolution of calcified elements and reduced calcification rates. Such negative effects are not typical of crustaceans for which comparatively little ocean acidification research has been conducted. Crustaceans, however, depend on their calcified exoskeleton for many critical functions. Here, we conducted a short-term study on a common caridean shrimp, Lysmata californica, to determine the effect of CO2-driven reduction in seawater pH on exoskeleton growth, structure, and mineralization and animal cryptic coloration. Shrimp exposed to ambient (7.99 ± 0.04) and reduced pH (7.53 ± 0.06) for 21 days showed no differences in exoskeleton growth (percent increase in carapace length), but the calcium weight percent of their cuticle increased significantly in reduced pH conditions, resulting in a greater Ca:Mg ratio. Cuticle thickness did not change, indicating an increase in the mineral to matrix ratio, which may have mechanical consequences for exoskeleton function. Furthermore, there was a 5-fold decrease in animal transparency, but no change in overall shrimp coloration (red). These results suggest that even short-term exposure to CO2-induced pH reduction can significantly affect exoskeleton mineralization and shrimp biophotonics, with potential impacts on crypsis, physical defense, and predator avoidance.

  13. Engineering hybrid nanostructures of active materials: Applications as electrode materials in lithium ion rechargeable batteries

    NASA Astrophysics Data System (ADS)

    Huang, Huan

    stability by hindering the tin from aggregation, and also to reduce their capacity loss by the enhancement of electronic contact. The Sn2P2O7/C nanocomposite shows much improved stability with Q50/Q2 = 71%, compared to 27% for bulk amorphous Sn2P2O7. Furthermore, this nanostructured composite leads to much better rate capability. As the rate increases by 20 fold (from C/10 to 2C), close to 90% of the total capacity is still accessible. Similar improvement of the stability is also observed for some SnO-B 2O3-P2O5/C nanocomposites.

  14. Non-crosslinked, amorphous, block copolymer electrolyte for batteries

    DOEpatents

    Mayes, Anne M.; Ceder, Gerbrand; Chiang, Yet-Ming; Sadoway, Donald R.; Aydinol, Mehmet K.; Soo, Philip P.; Jang, Young-Il; Huang, Biying

    2006-04-11

    Solid battery components are provided. A block copolymeric electrolyte is non-crosslinked and non-glassy through the entire range of typical battery service temperatures, that is, through the entire range of at least from about 0.degree. C. to about 70.degree. C. The chains of which the copolymer is made each include at least one ionically-conductive block and at least one second block immiscible with the ionically-conductive block. The chains form an amorphous association and are arranged in an ordered nanostructure including a continuous matrix of amorphous ionically-conductive domains and amorphous second domains that are immiscible with the ionically-conductive domains. A compound is provided that has a formula of Li.sub.xM.sub.yN.sub.zO.sub.2. M and N are each metal atoms or a main group elements, and x, y and z are each numbers from about 0 to about 1. y and z are chosen such that a formal charge on the M.sub.yN.sub.z portion of the compound is (4-x). In certain embodiments, these compounds are used in the cathodes of rechargeable batteries. The present invention also includes methods of predicting the potential utility of metal dichalgogenide compounds for use in lithium intercalation compounds. It also provides methods for processing lithium intercalation oxides with the structure and compositional homogeneity necessary to realize the increased formation energies of said compounds. An article is made of a dimensionally-stable, interpenetrating microstructure of a first phase including a first component and a second phase, immiscible with the first phase, including a second component. The first and second phases define interphase boundaries between them, and at least one particle is positioned between a first phase and a second phase at an interphase boundary. When the first and second phases are electronically-conductive and ionically-conductive polymers, respectively, and the particles are ion host particles, the arrangement is an electrode of a battery.

  15. Amorphous to Amorphous Form Transitions of Water Ice and Astrophysical Implications

    NASA Technical Reports Server (NTRS)

    Jenniskens, Peter; Blake, David F.; Chang, Sherwood (Technical Monitor)

    1994-01-01

    We have combined Selected Area Electron Diffraction (SAED) and cryogenic techniques in an instrumental configuration that allows observing the structure of vapor deposited ice as it evolves during warmup. The ice is deposited in-situ inside an Hitachi H-500 H transmission electron microscope at a base pressure of 1-5 x 10(exp -7) torr on a thin amorphous carbon substrate at 15K or 86K and warmed up at a rate of 1-2 K/min. We find a progression of amorphous forms and well defined amorphous to amorphous transitions. Apart from the well known low-density form of ice, we confirm the presence of a high-density form and find a third amorphous form that coexists with cubic ice. We will report too on the amorphous to crystalline transition and the implications of these results for radical diffusion and gas retention observed in laboratory analog studies of interstellar and cometary ices.

  16. Formation of quasi-single crystalline porous ZnO nanostructures with a single large cavity

    NASA Astrophysics Data System (ADS)

    Cho, Seungho; Kim, Semi; Jung, Dae-Won; Lee, Kun-Hong

    2011-09-01

    We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space.We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space. Electronic supplementary information (ESI) available: TEM images and the corresponding SAED image of a Zn

  17. Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals

    DOEpatents

    Farmer, Joseph C.; Wong, Frank M. G.; Haslam, Jeffery J.; Yang, Nancy; Lavernia, Enrique J.; Blue, Craig A.; Graeve, Olivia A.; Bayles, Robert; Perepezko, John H.; Kaufman, Larry; Schoenung, Julie; Ajdelsztajn, Leo

    2009-11-17

    A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

  18. Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals

    DOEpatents

    Farmer, Joseph C.; Wong, Frank M.G.; Haslam, Jeffery J.; Yang, Nancy; Lavernia, Enrique J.; Blue, Craig A.; Graeve, Olivia A.; Bayles, Robert; Perepezko, John H.; Kaufman, Larry; Schoenung, Julie; Ajdelsztajn, Leo

    2014-07-15

    A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

  19. Amorphization of Silicon Carbide by Carbon Displacement

    SciTech Connect

    Devanathan, Ram; Gao, Fei; Weber, William J.

    2004-05-10

    We have used molecular dynamics simulations to examine the possibility of amorphizing silicon carbide (SiC) by exclusively displacing C atoms. At a defect generation corresponding to 0.2 displacements per atom, the enthalpy surpasses the level of melt-quenched SiC, the density decreases by about 15%, and the radial distribution function shows a lack of long-range order. Prior to amorphization, the surviving defects are mainly C Frenkel pairs (67%), but Si Frenkel pairs (18%) and anti-site defects (15%) are also present. The results indicate that SiC can be amorphized by C sublattice displacements. Chemical short-range disorder, arising mainly from interstitial production, plays a significant role in the amorphization.

  20. Nanostructures for peroxidases

    PubMed Central

    Carmona-Ribeiro, Ana M.; Prieto, Tatiana; Nantes, Iseli L.

    2015-01-01

    Peroxidases are enzymes catalyzing redox reactions that cleave peroxides. Their active redox centers have heme, cysteine thiols, selenium, manganese, and other chemical moieties. Peroxidases and their mimetic systems have several technological and biomedical applications such as environment protection, energy production, bioremediation, sensors and immunoassays design, and drug delivery devices. The combination of peroxidases or systems with peroxidase-like activity with nanostructures such as nanoparticles, nanotubes, thin films, liposomes, micelles, nanoflowers, nanorods and others is often an efficient strategy to improve catalytic activity, targeting, and reusability. PMID:26389124

  1. Amorphous Phases on the Surface of Mars

    NASA Technical Reports Server (NTRS)

    Rampe, E. B.; Morris, R. V.; Ruff, S. W.; Horgan, B.; Dehouck, E.; Achilles, C. N.; Ming, D. W.; Bish, D. L.; Chipera, S. J.

    2014-01-01

    Both primary (volcanic/impact glasses) and secondary (opal/silica, allophane, hisingerite, npOx, S-bearing) amorphous phases appear to be major components of martian surface materials based on orbital and in-situ measurements. A key observation is that whereas regional/global scale amorphous components include altered glass and npOx, local scale amorphous phases include hydrated silica/opal. This suggests widespread alteration at low water-to-rock ratios, perhaps due to snow/ice melt with variable pH, and localized alteration at high water-to-rock ratios. Orbital and in-situ measurements of the regional/global amorphous component on Mars suggests that it is made up of at least three phases: npOx, amorphous silicate (likely altered glass), and an amorphous S-bearing phase. Fundamental questions regarding the composition and the formation of the regional/global amorphous component(s) still remain: Do the phases form locally or have they been homogenized through aeolian activity and derived from the global dust? Is the parent glass volcanic, impact, or both? Are the phases separate or intimately mixed (e.g., as in palagonite)? When did the amorphous phases form? To address the question of source (local and/or global), we need to look for variations in the different phases within the amorphous component through continued modeling of the chemical composition of the amorphous phases in samples from Gale using CheMin and APXS data. If we find variations (e.g., a lack of or enrichment in amorphous silicate in some samples), this may imply a local source for some phases. Furthermore, the chemical composition of the weathering products may give insight into the formation mechanisms of the parent glass (e.g., impact glasses contain higher Al and lower Si [30], so we might expect allophane as a weathering product of impact glass). To address the question of whether these phases are separate or intimately mixed, we need to do laboratory studies of naturally altered samples made

  2. Ion-beam amorphization of semiconductors: A physical model based on the amorphous pocket population

    SciTech Connect

    Mok, K.R.C.; Jaraiz, M.; Martin-Bragado, I.; Rubio, J.E.; Castrillo, P.; Pinacho, R.; Barbolla, J.; Srinivasan, M.P.

    2005-08-15

    We introduce a model for damage accumulation up to amorphization, based on the ion-implant damage structures commonly known as amorphous pockets. The model is able to reproduce the silicon amorphous-crystalline transition temperature for C, Si, and Ge ion implants. Its use as an analysis tool reveals an unexpected bimodal distribution of the defect population around a characteristic size, which is larger for heavier ions. The defect population is split in both size and composition, with small, pure interstitial and vacancy clusters below the characteristic size, and amorphous pockets with a balanced mixture of interstitials and vacancies beyond that size.

  3. Analysing and Manipulating the Nanostructure of Geopolymers

    NASA Astrophysics Data System (ADS)

    Provis, J. L.; Hajimohammadi, A.; Rees, C. A.; van Deventer, J. S. J.

    Geopolymer concretes are currently being commercialised in Australia and elsewhere around the world, with a view towards enhancing the sustainability of the world’s construction industry. The fundamental geopolymer binder is an aluminosilicate gel which displays key structural features on every length scale from Ångstroms up to centimetres, meaning that multiscale analysis is key to the development of a detailed understanding of geopolymer formation and performance. Here, we present results from investigations of geopolymer nanostructure, focusing on the use of infrared spectroscopy as an analytical tool. The effects of different combinations of precursors in geopolymer formation provides critical information, in particular with regard to the rate of reaction and its impact on the final distribution of elements and structures within the geopolymer binder. Formulations are designed so that the same composition is obtained by the use of precursors which release their constituent elements at very different rates under alkaline attack during geopolymerisation, and this provides essential information regarding the role of different elements in forming strong and durable geopolymer structures. Seeding the geopolymer mixture with very low doses of oxide nanoparticles presents several unexpected effects, both in terms of reaction kinetics and also in altering the nature of the zeolitic crystallites formed within the predominantly X-ray amorphous geopolymer binder.

  4. Tests Of Amorphous-Silicon Photovoltaic Modules

    NASA Technical Reports Server (NTRS)

    Ross, Ronald G., Jr.

    1988-01-01

    Progress in identification of strengths and weaknesses of amorphous-silicon technology detailed. Report describes achievements in testing reliability of solar-power modules made of amorphous-silicon photovoltaic cells. Based on investigation of modules made by U.S. manufacturers. Modules subjected to field tests, to accelerated-aging tests in laboratory, and to standard sequence of qualification tests developed for modules of crystalline-silicon cells.

  5. A Magnetic Sensor with Amorphous Wire

    PubMed Central

    He, Dongfeng; Shiwa, Mitsuharu

    2014-01-01

    Using a FeCoSiB amorphous wire and a coil wrapped around it, we have developed a sensitive magnetic sensor. When a 5 mm long amorphous wire with the diameter of 0.1 mm was used, the magnetic field noise spectrum of the sensor was about 30 pT/√Hz above 30 Hz. To show the sensitivity and the spatial resolution, the magnetic field of a thousand Japanese yen was scanned with the magnetic sensor. PMID:24940865

  6. Picosecond Electronic Relaxations In Amorphous Semiconductors

    NASA Astrophysics Data System (ADS)

    Tauc, Jan

    1983-11-01

    Using the pump and probe technique the relaxation processes of photogenerated carriers in amorphous tetrahedral semiconductors and chalcogenide glasses in the time domain from 0.5 Ps to 1.4 ns have been studied. The results obtained on the following phenomena are reviewed: hot carrier thermalization in amorphous silicon; trapping of carriers in undoped a-Si:H; trapping of carriers in deep traps produced by doping; geminate recombination in As2S3-xSex glasses.

  7. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    NASA Technical Reports Server (NTRS)

    Kim, Jae Woo (Inventor); Siochi, Emilie J. (Inventor); Wise, Kristopher E. (Inventor); Lin, Yi (Inventor); Connell, John (Inventor)

    2016-01-01

    A method for joining or repairing boron nitride nanotubes (BNNTs). In joining BNNTs, the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures. In repairing BNNTs, the damaged site of the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures at the damage site.

  8. Electronic and Mechanical Properties of Hydrogenated Irradiated and Amorphous Graphene

    NASA Astrophysics Data System (ADS)

    Weerasinghe, Asanka; Ramasubramaniam, Ashwin; Maroudas, Dimitrios

    Defect engineering and chemical functionalization of graphene are promising routes for fabrication of carbon nanostructures and 2D metamaterials with unique properties and function. Here, we use hydrogenation of irradiated, including irradiation-induced amorphous, graphene as a means of studying chemical functionalization effects on its electronic structure and mechanical response. We use molecular-dynamics simulations based on a reliable bond-order potential to prepare the hydrogenated configurations and carry out dynamic deformation tests at constant strain rate and temperature. Our mechanical tests show that hydrogenation does not affect the ultimate tensile strength (UTS) of the irradiated graphene sheet if the hydrogenated C atoms remain sp2-hybridized; however, upon inducing sp3 hybridization of these C atoms, UTS decreases by about 10 GPa. Furthermore, the fracture strain of the irradiated structure decreases by up to 30% upon hydrogenation independent of the hybridization type. We also report results for the electronic structure of hydrogenated configurations based on a density-functional tight-binding approach and assess the potential for tuning the electronic properties of these defective, functionalized graphenes.

  9. Neutron irradiation induced amorphization of silicon carbide

    NASA Astrophysics Data System (ADS)

    Snead, L. L.; Hay, J. C.

    1999-07-01

    This paper provides the properties of bulk stoichiometric silicon carbide which has been amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60°C to a total fast neutron fluence of 2.6 × 10 25 n/m 2. Amorphization was seen in both materials as evidenced by TEM, electron diffraction and X-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density (-10.8%), elastic modulus as measured using a nanoindentation technique (-45%), hardness as measured by nanoindentation (-45%), and standard Vickers hardness (-24%). Similar property changes are observed for the amorphized CVD SiC. Using measured thermal conductivity data for the CVD SiC sample, the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than ˜125°C.

  10. Wear Resistant Amorphous and Nanocomposite Steel Coatings

    SciTech Connect

    Branagan, Daniel James; Swank, William David; Haggard, Delon C; Fincke, James Russell; Sordelet, D.

    2001-10-01

    In this article, amorphous and nanocomposite thermally deposited steel coatings have been formed by using both plasma and high-velocity oxy-fuel (HVOF) spraying techniques. This was accomplished by developing a specialized iron-based composition with a low critical cooling rate (?104 K/s) for metallic glass formation, processing the alloy by inert gas atomization to form micron-sized amorphous spherical powders, and then spraying the classified powder to form coatings. A primarily amorphous structure was formed in the as-sprayed coatings, independent of coating thickness. After a heat treatment above the crystallization temperature (568°C), the structure of the coatings self-assembled (i.e., devitrified) into a multiphase nanocomposite microstructure with 75 to 125 nm grains containing a distribution of 20 nm second-phase grain-boundary precipitates. Vickers microhardness testing revealed that the amorphous coatings were very hard (10.2 to 10.7 GPa), with further increases in hardness after devitrification (11.4 to 12.8 GPa). The wear characteristics of the amorphous and nanocomposite coatings were determined using both two-body pin-on-disk and three-body rubber wheel wet-slurry sand tests. The results indicate that the amorphous and nanocomposite steel coatings are candidates for a wide variety of wear-resistant applications.

  11. Amorphous boron nitride at high pressure

    NASA Astrophysics Data System (ADS)

    Durandurdu, Murat

    2016-06-01

    The pressure-induced phase transformation in hexagonal boron nitrite and amorphous boron nitrite is studied using ab initio molecular dynamics simulations. The hexagonal-to-wurtzite phase transformation is successfully reproduced in the simulation with a transformation mechanism similar to one suggested in experiment. Amorphous boron nitrite, on the other hand, gradually transforms to a high-density amorphous phase with the application of pressure. This phase transformation is irreversible because a densified amorphous state having both sp3 and sp2 bonds is recovered upon pressure release. The high-density amorphous state mainly consists of sp3 bonds and its local structure is quite similar to recently proposed intermediate boron nitrite phases, in particular tetragonal structure (P42/mnm), rather than the known the wurtzite or cubic boron nitrite due to the existence of four membered rings and edge sharing connectivity. On the basis of this finding we propose that amorphous boron nitrite might be best candidate as a starting structure to synthesize the intermediate phase(s) at high pressure and temperature (probably below 800 °C) conditions.

  12. EDITORIAL: Nanostructured solar cells Nanostructured solar cells

    NASA Astrophysics Data System (ADS)

    Greenham, Neil C.; Grätzel, Michael

    2008-10-01

    Conversion into electrical power of even a small fraction of the solar radiation incident on the Earth's surface has the potential to satisfy the world's energy demands without generating CO2 emissions. Current photovoltaic technology is not yet fulfilling this promise, largely due to the high cost of the electricity produced. Although the challenges of storage and distribution should not be underestimated, a major bottleneck lies in the photovoltaic devices themselves. Improving efficiency is part of the solution, but diminishing returns in that area mean that reducing the manufacturing cost is absolutely vital, whilst still retaining good efficiencies and device lifetimes. Solution-processible materials, e.g. organic molecules, conjugated polymers and semiconductor nanoparticles, offer new routes to the low-cost production of solar cells. The challenge here is that absorbing light in an organic material produces a coulombically bound exciton that requires dissociation at a donor-acceptor heterojunction. A thickness of at least 100 nm is required to absorb the incident light, but excitons only diffuse a few nanometres before decaying. The problem is therefore intrinsically at the nano-scale: we need composite devices with a large area of internal donor-acceptor interface, but where each carrier has a pathway to the respective electrode. Dye-sensitized and bulk heterojunction cells have nanostructures which approach this challenge in different ways, and leading research in this area is described in many of the articles in this special issue. This issue is not restricted to organic or dye-sensitized photovoltaics, since nanotechnology can also play an important role in devices based on more conventional inorganic materials. In these materials, the electronic properties can be controlled, tuned and in some cases completely changed by nanoscale confinement. Also, the techniques of nanoscience are the natural ones for investigating the localized states, particularly at

  13. Electrons and phonons in amorphous semiconductors

    NASA Astrophysics Data System (ADS)

    Prasai, Kiran; Biswas, Parthapratim; Drabold, D. A.

    2016-07-01

    The coupling between lattice vibrations and electrons is one of the central concepts of condensed matter physics. The subject has been deeply studied for crystalline materials, but far less so for amorphous and glassy materials, which are among the most important for applications. In this paper, we explore the electron-lattice coupling using current tools of a first-principles computer simulation. We choose three materials to illustrate the phenomena: amorphous silicon (a-Si), amorphous selenium (a-Se) and amorphous gallium nitride (a-GaN). In each case, we show that there is a strong correlation between the localization of electron states and the magnitude of thermally induced fluctuations in energy eigenvalues obtained from the density-functional theory (i.e. Kohn-Sham eigenvalues). We provide a heuristic theory to explain these observations. The case of a-GaN, a topologically disordered partly ionic insulator, is distinctive compared to the covalent amorphous examples. Next, we explore the consequences of changing the charge state of a system as a proxy for tracking photo-induced structural changes in the materials. Where transport is concerned, we lend insight into the Meyer-Neldel compensation rule and discuss a thermally averaged Kubo-Greenwood formula as a means to estimate electrical conductivity and especially its temperature dependence. We close by showing how the optical gap of an amorphous semiconductor can be computationally engineered with the judicious use of Hellmann-Feynman forces (associated with a few defect states) using molecular dynamics simulations. These forces can be used to close or open an optical gap, and identify a structure with a prescribed gap. We use the approach with plane-wave density functional methods to identify a low-energy amorphous phase of silicon including several coordination defects, yet with a gap close to that of good quality a-Si models.

  14. Mechanical design of DNA nanostructures.

    PubMed

    Castro, Carlos E; Su, Hai-Jun; Marras, Alexander E; Zhou, Lifeng; Johnson, Joshua

    2015-04-14

    Structural DNA nanotechnology is a rapidly emerging field that has demonstrated great potential for applications such as single molecule sensing, drug delivery, and templating molecular components. As the applications of DNA nanotechnology expand, a consideration of their mechanical behavior is becoming essential to understand how these structures will respond to physical interactions. This review considers three major avenues of recent progress in this area: (1) measuring and designing mechanical properties of DNA nanostructures, (2) designing complex nanostructures based on imposed mechanical stresses, and (3) designing and controlling structurally dynamic nanostructures. This work has laid the foundation for mechanically active nanomachines that can generate, transmit, and respond to physical cues in molecular systems.

  15. Formation of nanostructured TiO{sub 2} by femtosecond laser irradiation of titanium in O{sub 2}

    SciTech Connect

    Landis, Elizabeth C.; Phillips, Katherine C.; Mazur, Eric; Friend, Cynthia M.

    2012-09-15

    We used femtosecond laser irradiation of titanium metal in an oxidizing environment to form a highly stable surface layer of nanostructured amorphous titanium dioxide (TiO{sub 2}). We studied the influence of atmospheric composition on these surface structures and found that gas composition and pressure affect the chemical composition of the surface layer but not the surface morphology. Incorporation of nitrogen is only possible when no oxygen is present in the surrounding atmosphere.

  16. Iron-based amorphous alloys and methods of synthesizing iron-based amorphous alloys

    DOEpatents

    Saw, Cheng Kiong; Bauer, William A.; Choi, Jor-Shan; Day, Dan; Farmer, Joseph C.

    2016-05-03

    A method according to one embodiment includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %; and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. Several amorphous iron-based metal alloys are also presented, including corrosion-resistant amorphous iron-based metal alloys and radiation-shielding amorphous iron-based metal alloys.

  17. Alternative nanostructures for thermophones

    NASA Astrophysics Data System (ADS)

    Mayo, Nathanael; Aliev, Ali; Baughman, Ray

    2015-03-01

    There is a large promise for thermophones in high power sonar arrays, flexible loudspeakers, and noise cancellation devices. So far, freestanding aerogel-like carbon nanotube sheets demonstrate the best performance as a thermoacoustic heat source. However, the limited accessibility of large size freestanding carbon nanotube sheets and other even more exotic materials published recently, hampers the field. We present here new alternative materials for a thermoacoustic heat source with high energy conversion efficiency, additional functionalities, environmentally friendly and cost effective production technologies. We discuss the thermoacoustic performance of alternative nanoscale materials and compare their spectral and power dependencies of sound pressure in air. The study presented here focuses on engineering thermal gradients in the vicinity of nanostructures and subsequent heat dissipation processes from the interior of encapsulated thermoacoustic projectors. Applications of thermoacoustic projectors for high power SONAR arrays, sound cancellation, and optimal thermal design, regarding enhanced energy conversion efficiency, are discussed.

  18. Amorphous Silicon Based Neutron Detector

    SciTech Connect

    Xu, Liwei

    2004-12-12

    Various large-scale neutron sources already build or to be constructed, are important for materials research and life science research. For all these neutron sources, neutron detectors are very important aspect. However, there is a lack of a high-performance and low-cost neutron beam monitor that provides time and temporal resolution. The objective of this SBIR Phase I research, collaboratively performed by Midwest Optoelectronics, LLC (MWOE), the University of Toledo (UT) and Oak Ridge National Laboratory (ORNL), is to demonstrate the feasibility for amorphous silicon based neutron beam monitors that are pixilated, reliable, durable, fully packaged, and fabricated with high yield using low-cost method. During the Phase I effort, work as been focused in the following areas: 1) Deposition of high quality, low-defect-density, low-stress a-Si films using very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) at high deposition rate and with low device shunting; 2) Fabrication of Si/SiO2/metal/p/i/n/metal/n/i/p/metal/SiO2/ device for the detection of alpha particles which are daughter particles of neutrons through appropriate nuclear reactions; and 3) Testing of various devices fabricated for alpha and neutron detection; As the main results: · High quality, low-defect-density, low-stress a-Si films have been successfully deposited using VHF PECVD on various low-cost substrates; · Various single-junction and double junction detector devices have been fabricated; · The detector devices fabricated have been systematically tested and analyzed. · Some of the fabricated devices are found to successfully detect alpha particles. Further research is required to bring this Phase I work beyond the feasibility demonstration toward the final prototype devices. The success of this project will lead to a high-performance, low-cost, X-Y pixilated neutron beam monitor that could be used in all of the neutron facilities worldwide. In addition, the technologies

  19. Synthesis of graphene and graphene nanostructures by ion implantation and pulsed laser annealing

    NASA Astrophysics Data System (ADS)

    Wang, Xiaotie; Berke, Kara; Rudawski, Nicholas G.; Venkatachalam, Dinesh K.; Elliman, Robert G.; Fridmann, Joel; Hebard, Arthur F.; Ren, Fan; Gila, Brent P.; Appleton, Bill R.

    2016-07-01

    In this paper, we report a systematic study that shows how the numerous processing parameters associated with ion implantation (II) and pulsed laser annealing (PLA) can be manipulated to control the quantity and quality of graphene (G), few-layer graphene (FLG), and other carbon nanostructures selectively synthesized in crystalline SiC (c-SiC). Controlled implantations of Si- plus C- and Au+ ions in c-SiC showed that both the thickness of the amorphous layer formed by ion damage and the doping effect of the implanted Au enhance the formation of G and FLG during PLA. The relative contributions of the amorphous and doping effects were studied separately, and thermal simulation calculations were used to estimate surface temperatures and to help understand the phase changes occurring during PLA. In addition to the amorphous layer thickness and catalytic doping effects, other enhancement effects were found to depend on other ion species, the annealing environment, PLA fluence and number of pulses, and even laser frequency. Optimum II and PLA conditions are identified and possible mechanisms for selective synthesis of G, FLG, and carbon nanostructures are discussed.

  20. Repairable, nanostructured biomimetic hydrogels

    NASA Astrophysics Data System (ADS)

    Firestone, M.; Brombosz, S.; Grubjesic, S.

    2013-03-01

    Proteins facilitate many key cellular processes, including signal recognition and energy transduction. The ability to harness this evolutionarily-optimized functionality could lead to the development of protein-based systems useful for advancing alternative energy storage and conversion. The future of protein-based, however, requires the development of materials that will stabilize, order and control the activity of the proteins. Recently we have developed a synthetic approach for the preparation of a durable biomimetic chemical hydrogel that can be reversibly swollen in water. The matrix has proven ideal for the stable encapsulation of both water- and membrane-soluble proteins. The material is composed of an aqueous dispersion of a diacrylate end-derivatized PEO-PPO-PEO macromer, a saturated phospholipid and a zwitterionic co-surfactant that self-assembles into a nanostructured physical gel at room temperature as determined by X-ray scattering. The addition of a water soluble PEGDA co-monomer and photoinitator does not alter the self-assembled structure and UV irradiation serves to crosslink the acrylate end groups on the macromer with the PEGDA forming a network within the aqueous domains as determined by FT-IR. More recently we have begun to incorporate reversible crosslinks employing Diels-Alder chemistry, allowing for the extraction and replacement of inactive proteins. The ability to replenish the materials with active, non-denatured forms of protein is an important step in advancing these materials for use in nanostructured devices This work was supported by the Office of Basic Energy Sciences, Division of Materials Sciences, USDoE under Contract No. DE-AC02-06CH11357.

  1. @AuAg nanostructures

    NASA Astrophysics Data System (ADS)

    Singh, Rina; Soni, R. K.

    2014-09-01

    Bimetallic and trimetallic nanoparticles have attracted significant attention in recent times due to their enhanced electrochemical and catalytic properties compared to monometallic nanoparticles. The numerical calculations using Mie theory has been carried out for three-layered metal nanoshell dielectric-metal-metal (DMM) system consisting of a particle with a dielectric core (Al@Al2O3), a middle metal Ag (Au) layer and an outer metal Au (Ag) shell. The results have been interpreted using plasmon hybridization theory. We have also prepared Al@Al2O3@Ag@Au and Al@Al2O3@AgAu triple-layered core-shell or alloy nanostructure by two-step laser ablation method and compared with calculated results. The synthesis involves temporal separations of Al, Ag, and Au deposition for step-by-step formation of triple-layered core-shell structure. To form Al@Ag nanoparticles, we ablated silver for 40 min in aluminium nanoparticle colloidal solution. As aluminium oxidizes easily in water to form alumina, the resulting structure is core-shell Al@Al2O3. The Al@Al2O3 particle acts as a seed for the incoming energetic silver particles for multilayered Al@Al2O3@Ag nanoparticles is formed. The silver target was then replaced by gold target and ablation was carried out for different ablation time using different laser energy for generation of Al@Al2O3@Ag@Au core-shell or Al@Al2O3@AgAu alloy. The formation of core-shell and alloy nanostructure was confirmed by UV-visible spectroscopy. The absorption spectra show shift in plasmon resonance peak of silver to gold in the range 400-520 nm with increasing ablation time suggesting formation of Ag-Au alloy in the presence of alumina particles in the solution.

  2. SURVIVAL OF AMORPHOUS WATER ICE ON CENTAURS

    SciTech Connect

    Guilbert-Lepoutre, Aurelie

    2012-10-01

    Centaurs are believed to be Kuiper Belt objects in transition between Jupiter and Neptune before possibly becoming Jupiter family comets. Some indirect observational evidence is consistent with the presence of amorphous water ice in Centaurs. Some of them also display a cometary activity, probably triggered by the crystallization of the amorphous water ice, as suggested by Jewitt and this work. Indeed, we investigate the survival of amorphous water ice against crystallization, using a fully three-dimensional thermal evolution model. Simulations are performed for varying heliocentric distances and obliquities. They suggest that crystallization can be triggered as far as 16 AU, though amorphous ice can survive beyond 10 AU. The phase transition is an efficient source of outgassing up to 10-12 AU, which is broadly consistent with the observations of the active Centaurs. The most extreme case is 167P/CINEOS, which barely crystallizes in our simulations. However, amorphous ice can be preserved inside Centaurs in many heliocentric distance-obliquity combinations, below a {approx}5-10 m crystallized crust. We also find that outgassing due to crystallization cannot be sustained for a time longer than 10{sup 4}-10{sup 4} years, leading to the hypothesis that active Centaurs might have recently suffered from orbital changes. This could be supported by both observations (although limited) and dynamical studies.

  3. Amorphous silicon detectors in positron emission tomography

    SciTech Connect

    Conti, M. Lawrence Berkeley Lab., CA ); Perez-Mendez, V. )

    1989-12-01

    The physics of the detection process is studied and the performances of different Positron Emission Tomography (PET) system are evaluated by theoretical calculation and/or Monte Carlo Simulation (using the EGS code) in this paper, whose table of contents can be summarized as follows: a brief introduction to amorphous silicon detectors and some useful equation is presented; a Tantalum/Amorphous Silicon PET project is studied and the efficiency of the systems is studied by Monte Carlo Simulation; two similar CsI/Amorphous Silicon PET projects are presented and their efficiency and spatial resolution are studied by Monte Carlo Simulation, light yield and time characteristics of the scintillation light are discussed for different scintillators; some experimental result on light yield measurements are presented; a Xenon/Amorphous Silicon PET is presented, the physical mechanism of scintillation in Xenon is explained, a theoretical estimation of total light yield in Xenon and the resulting efficiency is discussed altogether with some consideration of the time resolution of the system; the amorphous silicon integrated electronics is presented, total noise and time resolution are evaluated in each of our applications; the merit parameters {epsilon}{sup 2}{tau}'s are evaluated and compared with other PET systems and conclusions are drawn; and a complete reference list for Xenon scintillation light physics and its applications is presented altogether with the listing of the developed simulation programs.

  4. Laser processing and in-situ diagnostics for crystallization: from thin films to nanostructures

    NASA Astrophysics Data System (ADS)

    Yoo, Jae-Hyuck; In, Jung Bin; Zheng, Andy Cheng; Ryu, Sang-Gil; Hwang, David J.; Xiang, Bin; Minor, Andrew M.; Grigoropoulos, Costas P.

    2014-10-01

    Recent work on laser-induced crystallization of thin films and nanostructures is presented. Characterization of the morphology of the crystallized area reveals the optimum conditions for sequential lateral growth in a-Si thin films under high-pulsed laser irradiation. Silicon crystal grains of several micrometers in lateral dimensions can be obtained reproducibly. Laser-induced grain morphology change is observed in silicon nanopillars under a transmission electron microscopy (TEM) environment. The TEM is coupled with a near-field scanning optical microscopy (NSOM) pulsed laser processing system. This combination enables immediate scrutiny on the grain morphologies that the pulsed laser irradiation produces. The tip of the amorphous or polycrystalline silicon pillar is transformed into a single crystalline domain via melt-mediated crystallization. The microscopic observation provides a fundamental basis for laser-induced conversion of amorphous nanostructures into coarse-grained crystals. A laser beam shaping strategy is introduced to control the stochastic dewetting of ultrathin silicon film on a foreign substrate under thermal stimulation. Upon a single pulse irradiation of the shaped laser beam, the thermodynamically unstable ultrathin silicon film is dewetted from the glass substrate and transformed to a nanodome. The results suggest that the laser beam shaping strategy for the thermocapillary-induced de-wetting combined with the isotropic etching is a simple alternative for scalable manufacturing of array of nanostructures.

  5. Modeling of amorphous SiCxO6/5 by classical molecular dynamics and first principles calculations.

    PubMed

    Liao, Ningbo; Zhang, Miao; Zhou, Hongming; Xue, Wei

    2017-02-14

    Polymer-derived silicon oxycarbide (SiCO) presents excellent performance for high temperature and lithium-ion battery applications. Current experiments have provided some information on nano-structure of SiCO, while it is very challenging for experiments to take further insight into the molecular structure and its relationship with properties of materials. In this work, molecular dynamics (MD) based on empirical potential and first principle calculation were combined to investigate amorphous SiCxO6/5 ceramics. The amorphous structures of SiCO containing silicon-centered mix bond tetrahedrons and free carbon were successfully reproduced. The calculated radial distribution, angular distribution and Young's modulus were validated by current experimental data, and more details on molecular structure were discussed. The change in the slope of Young's modulus is related to the glass transition temperature of the material. The proposed modeling approach can be used to predict the properties of SiCO with different compositions.

  6. Nanostructured Materials for Renewable Energy

    SciTech Connect

    2009-11-01

    This factsheet describes a research project whose overall objective is to advance the fundamental understanding of novel photoelectronic organic device structures integrated with inorganic nanostructures, while also expanding the general field of nanomaterials for renewable energy devices and systems.

  7. Microscopic characterization of peptide nanostructures.

    PubMed

    Mammadov, Rashad; Tekinay, Ayse B; Dana, Aykutlu; Guler, Mustafa O

    2012-02-01

    Peptide-based nanomaterials have been utilized for various applications from regenerative medicine to electronics since they provide several advantages including easy synthesis methods, numerous routes for functionalization and biomimicry of secondary structures of proteins which leads to design of self-assembling peptide molecules to form nanostructures. Microscopic characterization at nanoscale is critical to understand processes directing peptide molecules to self-assemble and identify structure-function relationship of the nanostructures. Here, fundamental studies in microscopic characterization of peptide nanostructures are discussed to provide insights in widely used microscopy tools. In this review, we will encompass characterization studies of peptide nanostructures with modern microscopes, such as TEM, SEM, AFM, and advanced optical microscopy techniques. We will also mention specimen preparation methods and describe interpretation of the images.

  8. Factor analysis of 27Al MAS NMR spectra for identifying nanocrystalline phases in amorphous geopolymers.

    PubMed

    Urbanova, Martina; Kobera, Libor; Brus, Jiri

    2013-11-01

    Nanostructured materials offer enhanced physicochemical properties because of the large interfacial area. Typically, geopolymers with specifically synthesized nanosized zeolites are a promising material for the sorption of pollutants. The structural characterization of these aluminosilicates, however, continues to be a challenge. To circumvent complications resulting from the amorphous character of the aluminosilicate matrix and from the low concentrations of nanosized crystallites, we have proposed a procedure based on factor analysis of (27)Al MAS NMR spectra. The capability of the proposed method was tested on geopolymers that exhibited various tendencies to crystallize (i) completely amorphous systems, (ii) X-ray amorphous systems with nanocrystalline phases, and (iii) highly crystalline systems. Although the recorded (27)Al MAS NMR spectra did not show visible differences between the amorphous systems (i) and the geopolymers with the nanocrystalline phase (ii), the applied factor analysis unambiguously distinguished these materials. The samples were separated into the well-defined clusters, and the systems with the evolving crystalline phase were identified even before any crystalline fraction was detected by X-ray powder diffraction. Reliability of the proposed procedure was verified by comparing it with (29)Si MAS NMR spectra. Factor analysis of (27)Al MAS NMR spectra thus has the ability to reveal spectroscopic features corresponding to the nanocrystalline phases. Because the measurement time of (27)Al MAS NMR spectra is significantly shorter than that of (29)Si MAS NMR data, the proposed procedure is particularly suitable for the analysis of large sets of specifically synthesized geopolymers in which the formation of the limited fractions of nanocrystalline phases is desired.

  9. Characterization of Nanostructured Polymer Films

    DTIC Science & Technology

    2014-12-23

    of the film for complete polymer chain relaxation, including relaxation of surface features . The presence of intact surface globules at a substrate...AFRL-OSR-VA-TR-2015-0059 Characterization of Nanostructured Polymer Films RODNEY PRIESTLEY TRUSTEES OF PRINCETON UNIVERSITY Final Report 12/23/2014...Report 3. DATES COVERED (From - To) 06/01/2012-08/31/2014 4. TITLE AND SUBTITLE Characterization of Nanostructured Polymer Films 5a. CONTRACT

  10. Nanostructure-induced DNA condensation

    NASA Astrophysics Data System (ADS)

    Zhou, Ting; Llizo, Axel; Wang, Chen; Xu, Guiying; Yang, Yanlian

    2013-08-01

    The control of the DNA condensation process is essential for compaction of DNA in chromatin, as well as for biological applications such as nonviral gene therapy. This review endeavours to reflect the progress of investigations on DNA condensation effects of nanostructure-based condensing agents (such as nanoparticles, nanotubes, cationic polymer and peptide agents) observed by using atomic force microscopy (AFM) and other techniques. The environmental effects on structural characteristics of nanostructure-induced DNA condensates are also discussed.

  11. Amorphous metallic films in silicon metallization systems

    NASA Astrophysics Data System (ADS)

    So, F.; Kolawa, E.; Nicolet, M. A.

    1985-06-01

    Diffusion barrier research was focussed on lowering the chemical reactivity of amorphous thin films on silicon. An additional area of concern is the reaction with metal overlays such as aluminum, silver, and gold. Gold was included to allow for technology transfer to gallium arsenide PV cells. Amorphous tungsten nitride films have shown much promise. Stability to annealing temperatures of 700, 800, and 550 C were achieved for overlays of silver, gold, and aluminum, respectively. The lower results for aluminum were not surprising because there is an eutectic that can form at a lower temperature. It seems that titanium and zirconium will remove the nitrogen from a tungsten nitride amorphous film and render it unstable. Other variables of research interest were substrate bias and base pressure during sputtering.

  12. Nanocrystalline silicon/amorphous silicon dioxide superlattices

    SciTech Connect

    Fauchet, P.M.; Tsybeskov, L.; Zacharias, M. |; Hirschman, K. |

    1998-12-31

    Thin layers made of densely packed silicon nanocrystals sandwiched between amorphous silicon dioxide layers have been manufactured and characterized. An amorphous silicon/amorphous silicon dioxide superlattice is first grown by CVD or RF sputtering. The a-Si layers are recrystallized in a two-step procedure (nucleation + growth) for form layers of nearly identical nanocrystals whose diameter is given by the initial a-Si layer thickness. The recrystallization is monitored using a variety of techniques, including TEM, X-Ray, Raman, and luminescence spectroscopies. When the a-Si layer thickness decreases (from 25 nm to 2.5 nm) or the a-SiO{sub 2} layer thickness increases (from 1.5 nm to 6 nm), the recrystallization temperature increases dramatically compared to that of a single a-Si film. The removal of the a-Si tissue present between the nanocrystals, the passivation of the nanocrystals, and their doping are discussed.

  13. Phase transitions in biogenic amorphous calcium carbonate

    PubMed Central

    Gong, Yutao U. T.; Killian, Christopher E.; Olson, Ian C.; Appathurai, Narayana P.; Amasino, Audra L.; Martin, Michael C.; Holt, Liam J.; Wilt, Fred H.; Gilbert, P. U. P. A.

    2012-01-01

    Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amorphous calcium carbonate (ACC·H2O) → dehydrated amorphous calcium carbonate (ACC) → calcite. Unexpectedly, we find ACC·H2O-rich nanoparticles that persist after the surrounding mineral has dehydrated and crystallized. Protein matrix components occluded within the mineral must inhibit ACC·H2O dehydration. We devised an in vitro, also using XANES-PEEM, assay to identify spicule proteins that may play a role in stabilizing various mineral phases, and found that the most abundant occluded matrix protein in the sea urchin spicules, SM50, stabilizes ACC·H2O in vitro. PMID:22492931

  14. Amorphous metallic films in silicon metallization systems

    NASA Technical Reports Server (NTRS)

    So, F.; Kolawa, E.; Nicolet, M. A.

    1985-01-01

    Diffusion barrier research was focussed on lowering the chemical reactivity of amorphous thin films on silicon. An additional area of concern is the reaction with metal overlays such as aluminum, silver, and gold. Gold was included to allow for technology transfer to gallium arsenide PV cells. Amorphous tungsten nitride films have shown much promise. Stability to annealing temperatures of 700, 800, and 550 C were achieved for overlays of silver, gold, and aluminum, respectively. The lower results for aluminum were not surprising because there is an eutectic that can form at a lower temperature. It seems that titanium and zirconium will remove the nitrogen from a tungsten nitride amorphous film and render it unstable. Other variables of research interest were substrate bias and base pressure during sputtering.

  15. Amorphous/epitaxial superlattice for thermoelectric application

    NASA Astrophysics Data System (ADS)

    Ishida, Akihiro; Thao, Hoang Thi Xuan; Shibata, Mamoru; Nakashima, Seisuke; Tatsuoka, Hirokazu; Yamamoto, Hidenari; Kinoshita, Yohei; Ishikiriyama, Mamoru; Nakamura, Yoshiaki

    2016-08-01

    An amorphous/epitaxial superlattice system is proposed for application to thermoelectric devices, and the superlattice based on a PbGeTeS system was prepared by the alternate deposition of PbS and GeTe using a hot wall epitaxy technique. The structure was analyzed by high-resolution transmission electron microscopy (HRTEM) and X-ray analysis, and it was found that the superlattice consists of an epitaxial PbTe-based layer and a GeS-based amorphous layer by the reconstruction of the constituents. A reduction in thermal conductivity due to the amorphous/epitaxial system was confirmed by a 2ω method. Electrical and thermoelectric properties were measured for the samples.

  16. Atomic Bond Deficiency Defects in Amorphous Metals

    NASA Astrophysics Data System (ADS)

    Zhu, Aiwu; Shiflet, Gary J.; Poon, S. Joseph

    2012-10-01

    Atomic bond deficiency (BD) is considered to be characteristic structural defects in amorphous metals. They are the necessary feature of local atomic configurations that facilitate various atomic transports under different driving forces. Compared with vacancies in crystalline solids, they are "small" in terms of their formation energies, volume costs, and elementary steps involved in atomic transport. This article reviews the authors' recent efforts made to analyze how various local configurations containing BD are related to amorphous metal's unique characteristics, such as glass transition, diffusion, shear flow, and structural relaxation.

  17. Thermal conductivity of sputtered amorphous Ge films

    SciTech Connect

    Zhan, Tianzhuo; Xu, Yibin; Goto, Masahiro; Tanaka, Yoshihisa; Kato, Ryozo; Sasaki, Michiko; Kagawa, Yutaka

    2014-02-15

    We measured the thermal conductivity of amorphous Ge films prepared by magnetron sputtering. The thermal conductivity was significantly higher than the value predicted by the minimum thermal conductivity model and increased with deposition temperature. We found that variations in sound velocity and Ge film density were not the main factors in the high thermal conductivity. Fast Fourier transform patterns of transmission electron micrographs revealed that short-range order in the Ge films was responsible for their high thermal conductivity. The results provide experimental evidences to understand the underlying nature of the variation of phonon mean free path in amorphous solids.

  18. Neutron scattering studies of amorphous Invar alloys

    SciTech Connect

    Fernandez-Baca, J.A.

    1989-01-01

    This paper reviews recent inelastic neutron scattering experiments performed to study the spin dynamics of two amorphous Invar systems: Fe/sub 100-x/B/sub x/ and Fe/sub 90-x/Ni/sub x/Zr/sub 10/. As in crystalline Invar Fe/sub 65/Ni/sub 35/ and Fe/sub 3/Pt, the excitation of conventional long-wavelength spin waves in these amorphous systems cannot account for the relatively rapid change of their magnetization with temperature. These results are discussed in terms of additional low-lying excitations which apparently have a density of states similar to the spin waves.

  19. Nanostructured photovoltaic materials using block polymer assemblies

    NASA Astrophysics Data System (ADS)

    Mastroianni, Sarah Elizabeth

    Despite its potential as an abundant, sustainable alternative to non-renewable energy sources, solar energy currently is underutilized. Photovoltaics, which convert energy from sunlight into electricity, commonly are made from inorganic semiconductor materials that require expensive manufacturing and processing techniques. Alternatively, organic materials can be used to produce flexible and lightweight organic photovoltaic (OPV) devices, which can be prepared using solution-based processing techniques. However, OPV devices are limited by low efficiencies and short lifetimes compared to their inorganic counterparts. In OPV systems, charge carriers are generated in the active layer via the separation of excitons (electron-hole pairs) at interfaces between donor and acceptor materials. Because excitons have a limited diffusion length (˜10 nm), they may recombine before reaching a donor-acceptor interface if domain sizes are large. This exciton recombination can limit device efficiency; thus, the design parameters for improved active layer morphologies include large interfacial areas, small size scales, and continuous conducting pathways. Currently, most OPV devices are prepared by blending donor and acceptor materials in bulk heterojunction (BHJ) devices, often resulting in non-ideal, process-dependent morphologies. Alternatively, the self-assembly of block polymers (BP)s offers a reproducible means to generate nanostructured active layers. The work presented in this dissertation examines the synthetic approaches to preparing BPs containing different electroactive materials: non-conjugated, amorphous poly(vinyl-m-triphenylamine) [PVmTPA] and conjugated poly(3-alkythiophene) [P3AT] p-type materials as well as fullerene-based n-type materials. The synthesis and self-assembly of a model poly(methyl methacrylate)- b-PVmTPA system is presented. This work was extended to synthesize PVmTPA BPs with complementary poly(methyl methacrylate- co-hydroxyethyl methacrylate) [P

  20. Chemically enabled nanostructure fabrication

    NASA Astrophysics Data System (ADS)

    Huo, Fengwei

    The first part of the dissertation explored ways of chemically synthesizing new nanoparticles and biologically guided assembly of nanoparticle building blocks. Chapter two focuses on synthesizing three-layer composite magnetic nanoparticles with a gold shell which can be easily functionalized with other biomolecules. The three-layer magnetic nanoparticles, when functionalized with oligonucleotides, exhibit the surface chemistry, optical properties, and cooperative DNA binding properties of gold nanoparticle probes, while maintaining the magnetic properties of the Fe3O4 inner shell. Chapter three describes a new method for synthesizing nanoparticles asymmetrically functionalized with oligonucleotides and the use of these novel building blocks to create satellite structures. This synthetic capability allows one to introduce valency into such structures and then use that valency to direct particle assembly events. The second part of the thesis explored approaches of nanostructure fabrication on substrates. Chapter four focuses on the development of a new scanning probe contact printing method, polymer pen lithography (PPL), which combines the advantages of muCp and DPN to achieve high-throughput, flexible molecular printing. PPL uses a soft elastomeric tip array, rather than tips mounted on individual cantilevers, to deliver inks to a surface in a "direct write" manner. Arrays with as many as ˜11 million pyramid-shaped pens can be brought into contact with substrates and readily leveled optically in order to insure uniform pattern development. Chapter five describes gel pen lithography, which uses a gel to fabricate pen array. Gel pen lithography is a low-cost, high-throughput nanolithography method especially useful for biomaterials patterning and aqueous solution patterning which makes it a supplement to DPN and PPL. Chapter 6 shows a novel form of optical nanolithography, Beam Pen Lithography (BPL), which uses an array of NSOM pens to do nanoscale optical

  1. Multiple Exciton Generation in Semiconductor Nanostructures: DFT-based Computation

    NASA Astrophysics Data System (ADS)

    Mihaylov, Deyan; Kryjevski, Andrei; Kilin, Dmitri; Kilina, Svetlana; Vogel, Dayton

    Multiple exciton generation (MEG) in nm-sized H-passivated Si nanowires (NWs), and quasi 2D nanofilms depends strongly on the degree of the core structural disorder as shown by the perturbation theory calculations based on the DFT simulations. In perturbation theory, we work to the 2nd order in the electron-photon coupling and in the (approximate) RPA-screened Coulomb interaction. We also include the effect of excitons for which we solve Bethe-Salpeter Equation. To describe MEG we calculate exciton-to-biexciton as well as biexciton-to-exciton rates and quantum efficiency (QE). We consider 3D arrays of Si29H36 quantum dots, NWs, and quasi 2D silicon nanofilms, all with both crystalline and amorphous core structures. Efficient MEG with QE of 1.3 up to 1.8 at the photon energy of about 3Egap is predicted in these nanoparticles except for the crystalline NW and film where QE ~=1. MEG in the amorphous nanoparticles is enhanced by the electron localization due to structural disorder. The exciton effects significantly red-shift QE vs. photon energy curves. Nm-sized a-Si NWs and films are predicted to have effective MEG within the solar spectrum range. Also, we find efficient MEG in the chiral single-wall Carbon nanotubes and in a perovskite nanostructure.

  2. Inverted amorphous silicon solar cell utilizing cermet layers

    DOEpatents

    Hanak, Joseph J.

    1979-01-01

    An amorphous silicon solar cell incorporating a transparent high work function metal cermet incident to solar radiation and a thick film cermet contacting the amorphous silicon opposite to said incident surface.

  3. Amorphization and nanocrystallization of silcon under shock compression

    SciTech Connect

    Remington, B. A.; Wehrenberg, C. E.; Zhao, S.; Hahn, E. N.; Kad, B.; Bringa, E. M.; Meyers, M. A.

    2015-11-06

    High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon unveiled remarkable structural changes above a pressure threshold. Two distinct amorphous regions were identified: (a) a bulk amorphous layer close to the surface and (b) amorphous bands initially aligned with {111} slip planes. Further increase of the laser energy leads to the re-crystallization of amorphous silicon into nanocrystals with high concentration of nano-twins. This amorphization is produced by the combined effect of high magnitude hydrostatic and shear stresses under dynamic shock compression. Shock-induced defects play a very important role in the onset of amorphization. Calculations of the free energy changes with pressure and shear, using the Patel-Cohen methodology, are in agreement with the experimental results. Molecular dynamics simulation corroborates the amorphization, showing that it is initiated by the nucleation and propagation of partial dislocations. As a result, the nucleation of amorphization is analyzed qualitatively by classical nucleation theory.

  4. Silver/zinc oxide self-assembled nanostructured bolometer

    NASA Astrophysics Data System (ADS)

    Sanchez, John E.; González, Gabriel; Vera-Reveles, Gustavo; Velazquez-Salazar, J. Jesus; Bazan-Diaz, Lourdes; Gutiérrez-Hernández, José M.; José-Yacaman, Miguel; Ponce, Arturo; González, Francisco J.

    2017-03-01

    Temperature coefficient of resistance (TCR) is the main figure of merit for bolometric detectors. Reports show that zinc oxide can have TCR values higher than vanadium oxide (VOx) and amorphous silicon (a-Si), which are the most common materials used in bolometric applications, however its high resistivity makes it difficult to match it to read-out electronics. In this work, self-assembled nanostructures of Silver/Zinc oxide (Ag/ZnO) have been fabricated as well as their electrical and optical properties were measured as function of the Ag/ZnO concentration ratio. It was found that the nanostructures with the highest ZnO concentration exhibited a temperature coefficient of resistance as high as -11.8% K-1 near room temperature. Moreover, the TCR values and conductivity of the material can be tuned with the Ag/ZnO concentration ratio. This tuning flexibility allows this material to be better matched to read-out integrated circuits.

  5. Phonon engineering for nanostructures.

    SciTech Connect

    Aubry, Sylvie; Friedmann, Thomas Aquinas; Sullivan, John Patrick; Peebles, Diane Elaine; Hurley, David H.; Shinde, Subhash L.; Piekos, Edward Stanley; Emerson, John Allen

    2010-01-01

    Understanding the physics of phonon transport at small length scales is increasingly important for basic research in nanoelectronics, optoelectronics, nanomechanics, and thermoelectrics. We conducted several studies to develop an understanding of phonon behavior in very small structures. This report describes the modeling, experimental, and fabrication activities used to explore phonon transport across and along material interfaces and through nanopatterned structures. Toward the understanding of phonon transport across interfaces, we computed the Kapitza conductance for {Sigma}29(001) and {Sigma}3(111) interfaces in silicon, fabricated the interfaces in single-crystal silicon substrates, and used picosecond laser pulses to image the thermal waves crossing the interfaces. Toward the understanding of phonon transport along interfaces, we designed and fabricated a unique differential test structure that can measure the proportion of specular to diffuse thermal phonon scattering from silicon surfaces. Phonon-scale simulation of the test ligaments, as well as continuum scale modeling of the complete experiment, confirmed its sensitivity to surface scattering. To further our understanding of phonon transport through nanostructures, we fabricated microscale-patterned structures in diamond thin films.

  6. Ultrahard magnetic nanostructures

    NASA Astrophysics Data System (ADS)

    Sahota, P. K.; Liu, Y.; Skomski, R.; Manchanda, P.; Zhang, R.; Franchin, M.; Fangohr, H.; Hadjipanayis, G. C.; Kashyap, A.; Sellmyer, D. J.

    2012-04-01

    The performance of hard-magnetic nanostructures is investigated by analyzing the size and geometry dependence of thin-film hysteresis loops. Compared to bulk magnets, weight and volume are much less important, but we find that the energy product remains the main figure of merit down to very small features sizes. However, hysteresis loops are much easier to control on small length scales, as epitomized by Fe-Co-Pt thin films with magnetizations of up to 1.78 T and coercivities of up to 2.52 T. Our numerical and analytical calculations show that the feature size and geometry have a big effect on the hysteresis loop. Layered soft regions, especially if they have a free surface, are more harmful to coercivity and energy product than spherical inclusions. In hard-soft nanocomposites, an additional complication is provided by the physical properties of the hard phases. For a given soft phase, the performance of a hard-soft composite is determined by the parameter (Ms - Mh)/Kh.

  7. Nanostructures in photovoltaics.

    PubMed

    Catchpole, Kylie R

    2006-12-15

    The world has recently been waking up to the urgent need to move away from fossil fuels and towards a low-carbon economy. To achieve this, we need a way of producing electricity that is efficient, widely applicable and cheap. At the same time, there has recently been an appreciation of the tremendous scope for making entirely new types of devices, and even seeing new physics, by structuring matter at the nanoscale. Furthermore, the occurrence of self-assembly in nature suggests that a range of types of nanoscale structures could be made simply and cheaply. The application of nanostructures to photovoltaics combines a field of almost limitless possibilities with a problem of vital urgency. In this paper, some of the newer ideas emerging from this trend are described, along with how they challenge our ideas on what a solar cell looks like. We are at the beginning of a time of radically rethinking the design of the solar cell, which may lead to the exploitation of completely new physical ideas in achieving a sustainable energy future.

  8. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, Auda K.

    1986-01-01

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  9. TRANSIENT AMORPHOUS CALCIUM PHOSPHATE IN FORMING ENAMEL

    PubMed Central

    Beniash, Elia; Metzler, Rebecca A.; Lam, Raymond S.K.; Gilbert, P.U.P.A.

    2009-01-01

    Enamel, the hardest tissue in the body, begins as a three-dimensional network of nanometer size mineral particles, suspended in a protein gel. This mineral network serves as a template for mature enamel formation. To further understand the mechanisms of enamel formation we characterized the forming enamel mineral at an early secretory stage using x-ray absorption near-edge structure (XANES) spectromicroscopy, transmission electron microscopy (TEM), FTIR microspectroscopy and polarized light microscopy. We show that the newly formed enamel mineral is amorphous calcium phosphate (ACP), which eventually transforms into apatitic crystals. Interestingly, the size, shape and spatial organization of these amorphous mineral particles and older crystals are essentially the same, indicating that the mineral morphology and organization in enamel is determined prior to its crystallization. Mineralization via transient amorphous phases has been previously reported in chiton teeth, mollusk shells, echinoderm spicules and spines, and recent reports strongly suggest the presence transient amorphous mineral in forming vertebrate bones. The present finding of transient ACP in murine tooth enamel suggests that this strategy might be universal. PMID:19217943

  10. High resolution amorphous silicon radiation detectors

    DOEpatents

    Street, Robert A.; Kaplan, Selig N.; Perez-Mendez, Victor

    1992-01-01

    A radiation detector employing amorphous Si:H cells in an array with each detector cell having at least three contiguous layers (n type, intrinsic, p type), positioned between two electrodes to which a bias voltage is applied. An energy conversion layer atop the silicon cells intercepts incident radiation and converts radiation energy to light energy of a wavelength to which the silicon cells are responsive. A read-out device, positioned proximate to each detector element in an array allows each such element to be interrogated independently to determine whether radiation has been detected in that cell. The energy conversion material may be a layer of luminescent material having a columnar structure. In one embodiment a column of luminescent material detects the passage therethrough of radiation to be detected and directs a light beam signal to an adjacent a-Si:H film so that detection may be confined to one or more such cells in the array. One or both electrodes may have a comb structure, and the teeth of each electrode comb may be interdigitated for capacitance reduction. The amorphous Si:H film may be replaced by an amorphous Si:Ge:H film in which up to 40 percent of the amorphous material is Ge. Two dimensional arrays may be used in X-ray imaging, CT scanning, crystallography, high energy physics beam tracking, nuclear medicine cameras and autoradiography.

  11. High resolution amorphous silicon radiation detectors

    DOEpatents

    Street, R.A.; Kaplan, S.N.; Perez-Mendez, V.

    1992-05-26

    A radiation detector employing amorphous Si:H cells in an array with each detector cell having at least three contiguous layers (n-type, intrinsic, p-type), positioned between two electrodes to which a bias voltage is applied. An energy conversion layer atop the silicon cells intercepts incident radiation and converts radiation energy to light energy of a wavelength to which the silicon cells are responsive. A read-out device, positioned proximate to each detector element in an array allows each such element to be interrogated independently to determine whether radiation has been detected in that cell. The energy conversion material may be a layer of luminescent material having a columnar structure. In one embodiment a column of luminescent material detects the passage therethrough of radiation to be detected and directs a light beam signal to an adjacent a-Si:H film so that detection may be confined to one or more such cells in the array. One or both electrodes may have a comb structure, and the teeth of each electrode comb may be interdigitated for capacitance reduction. The amorphous Si:H film may be replaced by an amorphous Si:Ge:H film in which up to 40 percent of the amorphous material is Ge. Two dimensional arrays may be used in X-ray imaging, CT scanning, crystallography, high energy physics beam tracking, nuclear medicine cameras and autoradiography. 18 figs.

  12. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, A.K.

    1979-07-18

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  13. Structural modeling of amorphous conducting carbon film

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Somnath; Pati, Swapan K.; Subramanyam, S. V.

    1998-04-01

    Amorphous conducting carbon films are prepared using plasma assisted polymerization process. SEM and TEM shows random aggregate of globular clusters of micron size inside the samples. Electrical measurements indicate a near metallic nature. A tendency of saturation of resistivity at low temperature is observed. From spectroscopic analysis we find some unusual features. Based on these observations a structural model of this carbon is proposed.

  14. Low temperature internal friction of amorphous silicon

    NASA Astrophysics Data System (ADS)

    Liu, Xiao; Metcalf, Thomas; Jernigan, Glenn; Jugdersuren, Battogtokh; Kearney, Brian; Culberston, James

    The ubiquitous low-energy excitations, known as two-level tunnelling systems (TLS), are one of the universal phenomena of amorphous solids. These excitations dominate the acoustic, dielectric, and thermal properties of structurally disordered solids. Using the double-paddle oscillator internal friction measurement technique, we have shown that TLS can be made to almost completely disappear in e-beam deposited amorphous silicon (a-Si) as the growth temperature increased to 400°C. However, there is a mysterious broad maximum in internal friction at 2-3K, which we suspect to come from metallic contamination of our oscillators and is not related to a-Si. Our new result of a-Si, deposited in a different UHV system and on oscillators with a different type of metallic electrodes, confirms our suspicion. This lowers the upper bound of possible TLS content in a-Si, in terms of tunnelling strength, to below 10-6. Our results offer an encouraging opportunity to use growth temperature to improve the structure order of amorphous thin films and to develop high quality amorphous dielectrics for applications, such as in modern quantum devices. Work supported by the Office of Naval Research.

  15. Metal electrode for amorphous silicon solar cells

    DOEpatents

    Williams, Richard

    1983-01-01

    An amorphous silicon solar cell having an N-type region wherein the contact to the N-type region is composed of a material having a work function of about 3.7 electron volts or less. Suitable materials include strontium, barium and magnesium and rare earth metals such as gadolinium and yttrium.

  16. Amorphous Molecular Organic Solids for Gas Adsorption

    SciTech Connect

    Tian, Jian; Thallapally, Praveen K.; Dalgarno, Scott J.; McGrail, B. Peter; Atwood, Jerry L.

    2009-07-06

    We show that molecular organic compounds with large accessible internal cavities, as part of their rigid molecular structure, display exceptional ability for gas storage and separation in the amorphous solid state. This finding suggests for the first time that long-range molecular order is not a prerequisite for organic molecules to be engineered as porous materials

  17. Improving the capacity of sodium ion battery using a virus-templated nanostructured composite cathode.

    PubMed

    Moradi, Maryam; Li, Zheng; Qi, Jifa; Xing, Wenting; Xiang, Kai; Chiang, Yet-Ming; Belcher, Angela M

    2015-05-13

    In this work we investigated an energy-efficient biotemplated route to synthesize nanostructured FePO4 for sodium-based batteries. Self-assembled M13 viruses and single wall carbon nanotubes (SWCNTs) have been used as a template to grow amorphous FePO4 nanoparticles at room temperature (the active composite is denoted as Bio-FePO4-CNT) to enhance the electronic conductivity of the active material. Preliminary tests demonstrate a discharge capacity as high as 166 mAh/g at C/10 rate, corresponding to composition Na0.9FePO4, which along with higher C-rate tests show this material to have the highest capacity and power performance reported for amorphous FePO4 electrodes to date.

  18. Improving the Capacity of Sodium Ion Battery Using a Virus-Templated Nanostructured Composite Cathode

    SciTech Connect

    Moradi, M; Li, Z; Qi, JF; Xing, WT; Xiang, K; Chiang, YM; Belcher, AM

    2015-05-01

    In this work we investigated an energy-efficient biotemplated route to synthesize nanostructured FePO4 for sodium-based batteries. Self-assembled M13 viruses and single wall carbon nanotubes (SWCNTs) have been used as a template to grow amorphous FePO4 nanoparticles at room temperature (the active composite is denoted as Bio-FePO4-CNT) to enhance the electronic conductivity of the active material. Preliminary tests demonstrate a discharge capacity as high as 166 mAh/g at C/10 rate, corresponding to composition Na0.9FePO4, which along with higher C-rate tests show this material to have the highest capacity and power performance reported for amorphous FePO4 electrodes to date.

  19. Thermal Conductivity Suppression in Nanostructured Silicon and Germanium Nanowires

    NASA Astrophysics Data System (ADS)

    Özden, Ayberk; Kandemir, Ali; Ay, Feridun; Perkgöz, Nihan Kosku; Sevik, Cem

    2016-03-01

    The inherent low lattice thermal conductivity (TC) of semiconductor nanowires (s-NW) due to one-dimensional phonon confinement might provide a solution for the long-lasting figure-of-merit problem for highly efficient thermoelectric (TE) applications. Standalone diameter modulation or alloying of s-NW serve as a toolkit for TC control, but realizing the full potential of nanowires requires new atomic-scale designs, growth, characterization, and understanding of the physical mechanisms behind the structure-property (TC) relationship. Before undertaking time-consuming and expensive experimental work, molecular dynamics (MD) simulations serve as an excellent probe to investigate new designs and understand how nanostructures affect thermal transport properties through their capability to capture various phenomena such as phonon boundary scattering, phonon coherence resonance, and phonon backscattering. On the other hand, because different research groups use different structural and MD parameters in their simulations, it is rather difficult to make comparisons between different nanostructures and select appropriate ones for potential TE applications. Therefore, in this work, we systematically investigated pristine, core-shell (C-S), holey (H-N), superlattice (SL), sawtooth (ST), and superlattice sawtooth (SL-ST) nanowires with identical structural parameters. Specifically, we aim to compare the relative TC reduction achieved by these nanostructures with respect to pristine nanowires in order to propose the best structural design with the lowest lattice TC, using Green-Kubo method-based equilibrium molecular dynamics simulations at 300 K. Our results show that the TC can be minimized by changing specific parameters such as the core diameter and monolayer separation for C-S, H-N, and ST structures. In the case of SL structures, the TC is found to be independent of these parameters. However, surface roughness in the form of a ST morphology provides a TC value below 2 W

  20. Nanostructured catalysts for organic transformations.

    PubMed

    Chng, Leng Leng; Erathodiyil, Nandanan; Ying, Jackie Y

    2013-08-20

    The development of green, sustainable and economical chemical processes is one of the major challenges in chemistry. Besides the traditional need for efficient and selective catalytic reactions that will transform raw materials into valuable chemicals, pharmaceuticals and fuels, green chemistry also strives for waste reduction, atomic efficiency and high rates of catalyst recovery. Nanostructured materials are attractive candidates as heterogeneous catalysts for various organic transformations, especially because they meet the goals of green chemistry. Researchers have made significant advances in the synthesis of well-defined nanostructured materials in recent years. Among these are novel approaches that have permitted the rational design and synthesis of highly active and selective nanostructured catalysts by controlling the structure and composition of the active nanoparticles (NPs) and by manipulating the interaction between the catalytically active NP species and their support. The ease of isolation and separation of the heterogeneous catalysts from the desired organic product and the recovery and reuse of these NPs further enhance their attractiveness as green and sustainable catalysts. This Account reviews recent advances in the use of nanostructured materials for catalytic organic transformations. We present a broad overview of nanostructured catalysts used in different types of organic transformations including chemoselective oxidations and reductions, asymmetric hydrogenations, coupling reactions, C-H activations, oxidative aminations, domino and tandem reactions, and more. We focus on recent research efforts towards the development of the following nanostructured materials: (i) nanostructured catalysts with controlled morphologies, (ii) magnetic nanocomposites, (iii) semiconductor-metal nanocomposites, and (iv) hybrid nanostructured catalysts. Selected examples showcase principles of nanoparticle design such as the enhancement of reactivity, selectivity

  1. Carbon nanostructures for orthopedic medical applications.

    PubMed

    Yang, Lei; Zhang, Lijuan; Webster, Thomas J

    2011-09-01

    Carbon nanostructures (including carbon nanofibers, nanostructured diamond, fullerene materials and so forth) possess extraordinary physiochemical, mechanical and electrical properties attractive to bioengineers and medical researchers. In the past decade, numerous developments towards the fabrication and biological studies of carbon nanostructures have provided opportunities to improve orthopedic applications. Therefore, the aim of this article is to provide an up-to-date review on carbon nanostructure advances in orthopedic research. Orthopedic medical device applications of carbon nanotubes/carbon nanofibers and nanostructured diamond (including particulate nanodiamond and nanocrystalline diamond coatings) are emphasized here along with other carbon nanostructures that have promising potential. In addition, widely used fabrication techniques for producing carbon nanostructures in both the laboratory and in industry are briefly introduced. In conclusion, carbon nanostructures have demonstrated tremendous promise for orthopedic medical device applications to date, and although some safety, reliability and durability issues related to the manufacturing and implantation of carbon nanomaterials remain, their future is bright.

  2. Integrated three-dimensional photonic nanostructures for achieving near-unity solar absorption and superhydrophobicity

    NASA Astrophysics Data System (ADS)

    Kuang, Ping; Hsieh, Mei-Li; Lin, Shawn-Yu

    2015-06-01

    In this paper, we proposed and realized 3D photonic nanostructures consisting of ultra-thin graded index antireflective coatings (ARCs) and woodpile photonic crystals. The use of the integrated ARC and photonic crystal structure can achieve broadband, broad-angle near unity solar absorption. The amorphous silicon based photonic nanostructure experimentally shows an average absorption of ˜95% for λ = 400-620 nm over a wide angular acceptance of θ = 0°-60°. Theoretical studies show that a Gallium Arsenide (GaAs) based structure can achieve an average absorption of >95% for λ = 400-870 nm. Furthermore, the use of the slanted SiO2 nanorod ARC surface layer by glancing angle deposition exhibits Cassie-Baxter state wetting, and superhydrophobic surface is obtained with highest water contact angle θCB ˜ 153°. These properties are fundamentally important for achieving maximum solar absorption and surface self-cleaning in thin film solar cell applications.

  3. Amorphous silica-like carbon dioxide

    NASA Astrophysics Data System (ADS)

    Santoro, Mario; Gorelli, Federico A.; Bini, Roberto; Ruocco, Giancarlo; Scandolo, Sandro; Crichton, Wilson A.

    2006-06-01

    Among the group IV elements, only carbon forms stable double bonds with oxygen at ambient conditions. At variance with silica and germania, the non-molecular single-bonded crystalline form of carbon dioxide, phase V, only exists at high pressure. The amorphous forms of silica (a-SiO2) and germania (a-GeO2) are well known at ambient conditions; however, the amorphous, non-molecular form of CO2 has so far been described only as a result of first-principles simulations. Here we report the synthesis of an amorphous, silica-like form of carbon dioxide, a-CO2, which we call `a-carbonia'. The compression of the molecular phase III of CO2 between 40 and 48GPa at room temperature initiated the transformation to the non-molecular amorphous phase. Infrared spectra measured at temperatures up to 680K show the progressive formation of C-O single bonds and the simultaneous disappearance of all molecular signatures. Furthermore, state-of-the-art Raman and synchrotron X-ray diffraction measurements on temperature-quenched samples confirm the amorphous character of the material. Comparison with vibrational and diffraction data for a-SiO2 and a-GeO2, as well as with the structure factor calculated for the a-CO2 sample obtained by first-principles molecular dynamics, shows that a-CO2 is structurally homologous to the other group IV dioxide glasses. We therefore conclude that the class of archetypal network-forming disordered systems, including a-SiO2, a-GeO2 and water, must be extended to include a-CO2.

  4. Self-organized ordering of nanostructures produced by ion-beam sputtering.

    PubMed

    Castro, Mario; Cuerno, Rodolfo; Vázquez, Luis; Gago, Raúl

    2005-01-14

    We study the self-organized ordering of nanostructures produced by ion-beam sputtering of targets amorphizing under irradiation. By introducing a model akin to models of pattern formation in aeolian sand dunes, we extend consistently the current continuum theory of erosion by IBS. We obtain new nonlinear effects responsible for the in-plane ordering of the structures, whose strength correlates with the degree of ordering found in experiments. Our results highlight the importance of redeposition and surface viscous flow to this nanopattern formation process.

  5. Key Physical Mechanisms in Nanostructured Solar Cells

    SciTech Connect

    Dr Stephan Bremner

    2010-07-21

    The objective of the project was to study both theoretically and experimentally the excitation, recombination and transport properties required for nanostructured solar cells to deliver energy conversion efficiencies well in excess of conventional limits. These objectives were met by concentrating on three key areas, namely, investigation of physical mechanisms present in nanostructured solar cells, characterization of loss mechanisms in nanostructured solar cells and determining the properties required of nanostructured solar cells in order to achieve high efficiency and the design implications.

  6. Nanoporosity induced by ion implantation in deposited amorphous Ge thin films

    SciTech Connect

    Romano, L.; Impellizzeri, G.; Ruffino, F.; Miritello, M.; Grimaldi, M. G.; Bosco, L.

    2012-06-01

    The formation of a nano-porous structure in amorphous Ge thin film (sputter-deposited on SiO{sub 2}) during ion irradiation at room temperature with 300 keV Ge{sup +} has been observed. The porous film showed a sponge-like structure substantially different from the columnar structure reported for ion implanted bulk Ge. The voids size and structure resulted to be strongly affected by the material preparation, while the volume expansion turned out to be determined only by the nuclear deposition energy. In SiGe alloys, the swelling occurs only if the Ge concentration is above 90%. These findings rely on peculiar characteristics related to the mechanism of voids nucleation and growth, but they are crucial for future applications of active nanostructured layers such as low cost chemical and biochemical sensing devices or electrodes in batteries.

  7. Computational design of surfaces, nanostructures and optoelectronic materials

    NASA Astrophysics Data System (ADS)

    Choudhary, Kamal

    Properties of engineering materials are generally influenced by defects such as point defects (vacancies, interstitials, substitutional defects), line defects (dislocations), planar defects (grain boundaries, free surfaces/nanostructures, interfaces, stacking faults) and volume defects (voids). Classical physics based molecular dynamics and quantum physics based density functional theory can be useful in designing materials with controlled defect properties. In this thesis, empirical potential based molecular dynamics was used to study the surface modification of polymers due to energetic polyatomic ion, thermodynamics and mechanics of metal-ceramic interfaces and nanostructures, while density functional theory was used to screen substituents in optoelectronic materials. Firstly, polyatomic ion-beams were deposited on polymer surfaces and the resulting chemical modifications of the surface were examined. In particular, S, SC and SH were deposited on amorphous polystyrene (PS), and C2H, CH3, and C3H5 were deposited on amorphous poly (methyl methacrylate) (PMMA) using molecular dynamics simulations with classical reactive empirical many-body (REBO) potentials. The objective of this work was to elucidate the mechanisms by which the polymer surface modification took place. The results of the work could be used in tailoring the incident energy and/or constituents of ion beam for obtaining a particular chemistry inside the polymer surface. Secondly, a new Al-O-N empirical potential was developed within the charge optimized many body (COMB) formalism. This potential was then used to examine the thermodynamic stability of interfaces and mechanical properties of nanostructures composed of aluminum, its oxide and its nitride. The potentials were tested for these materials based on surface energies, defect energies, bulk phase stability, the mechanical properties of the most stable bulk phase, its phonon properties as well as with a genetic algorithm based evolution theory of

  8. Semiconductor nanostructure-based photovoltaic solar cells.

    PubMed

    Zhang, Genqiang; Finefrock, Scott; Liang, Daxin; Yadav, Gautam G; Yang, Haoran; Fang, Haiyu; Wu, Yue

    2011-06-01

    Substantial efforts have been devoted to design, synthesize, and integrate various semiconductor nanostructures for photovoltaic (PV) solar cells. In this article, we will review the recent progress in this exciting area and cover the material chemistry and physics related to all-inorganic nanostructure solar cells, hybrid inorganic nanostructure-conductive polymer composite solar cells, and dye-sensitized solar cells.

  9. Nanostructured materials in electroanalysis of pharmaceuticals.

    PubMed

    Rahi, A; Karimian, K; Heli, H

    2016-03-15

    Basic strategies and recent developments for the enhancement of the sensory performance of nanostructures in the electroanalysis of pharmaceuticals are reviewed. A discussion of the properties of nanostructures and their application as modified electrodes for drug assays is presented. The electrocatalytic effect of nanostructured materials and their application in determining low levels of drugs in pharmaceutical forms and biofluids are discussed.

  10. Semiconductor nanostructure-based photovoltaic solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Genqiang; Finefrock, Scott; Liang, Daxin; Yadav, Gautam G.; Yang, Haoran; Fang, Haiyu; Wu, Yue

    2011-06-01

    Substantial efforts have been devoted to design, synthesize, and integrate various semiconductor nanostructures for photovoltaic (PV) solar cells. In this article, we will review the recent progress in this exciting area and cover the material chemistry and physics related to all-inorganic nanostructure solar cells, hybrid inorganic nanostructure-conductive polymer composite solar cells, and dye-sensitized solar cells.

  11. Method of fabrication of anchored nanostructure materials

    DOEpatents

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2013-11-26

    Methods for fabricating anchored nanostructure materials are described. The methods include heating a nano-catalyst under a protective atmosphere to a temperature ranging from about 450.degree. C. to about 1500.degree. C. and contacting the heated nano-catalysts with an organic vapor to affix carbon nanostructures to the nano-catalysts and form the anchored nanostructure material.

  12. Interfacing nanostructures to biological cells

    DOEpatents

    Chen, Xing; Bertozzi, Carolyn R.; Zettl, Alexander K.

    2012-09-04

    Disclosed herein are methods and materials by which nanostructures such as carbon nanotubes, nanorods, etc. are bound to lectins and/or polysaccharides and prepared for administration to cells. Also disclosed are complexes comprising glycosylated nanostructures, which bind selectively to cells expressing glycosylated surface molecules recognized by the lectin. Exemplified is a complex comprising a carbon nanotube functionalized with a lipid-like alkane, linked to a polymer bearing repeated .alpha.-N-acetylgalactosamine sugar groups. This complex is shown to selectively adhere to the surface of living cells, without toxicity. In the exemplified embodiment, adherence is mediated by a multivalent lectin, which binds both to the cells and the .alpha.-N-acetylgalactosamine groups on the nanostructure.

  13. Nanostructure Neutron Converter Layer Development

    NASA Technical Reports Server (NTRS)

    Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Kang, Jin Ho (Inventor); Lowther, Sharon E. (Inventor); Thibeault, Sheila A. (Inventor); Bryant, Robert G. (Inventor)

    2016-01-01

    Methods for making a neutron converter layer are provided. The various embodiment methods enable the formation of a single layer neutron converter material. The single layer neutron converter material formed according to the various embodiments may have a high neutron absorption cross section, tailored resistivity providing a good electric field penetration with submicron particles, and a high secondary electron emission coefficient. In an embodiment method a neutron converter layer may be formed by sequential supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In another embodiment method a neutron converter layer may be formed by simultaneous supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In a further embodiment method a neutron converter layer may be formed by in-situ metalized aerogel nanostructure development.

  14. Zinc stannate nanostructures: hydrothermal synthesis

    PubMed Central

    Baruah, Sunandan; Dutta, Joydeep

    2011-01-01

    Nanostructured binary semiconducting metal oxides have received much attention in the last decade owing to their unique properties rendering them suitable for a wide range of applications. In the quest to further improve the physical and chemical properties, an interest in ternary complex oxides has become noticeable in recent times. Zinc stannate or zinc tin oxide (ZTO) is a class of ternary oxides that are known for their stable properties under extreme conditions, higher electron mobility compared to its binary counterparts and other interesting optical properties. The material is thus ideal for applications from solar cells and sensors to photocatalysts. Among the different methods of synthesizing ZTO nanostructures, the hydrothermal method is an attractive green process that is carried out at low temperatures. In this review, we summarize the conditions leading to the growth of different ZTO nanostructures using the hydrothermal method and delve into a few of its applications reported in the literature. PMID:27877377

  15. PREFACE: Self-organized nanostructures

    NASA Astrophysics Data System (ADS)

    Rousset, Sylvie; Ortega, Enrique

    2006-04-01

    In order to fabricate ordered arrays of nanostructures, two different strategies might be considered. The `top-down' approach consists of pushing the limit of lithography techniques down to the nanometre scale. However, beyond 10 nm lithography techniques will inevitably face major intrinsic limitations. An alternative method for elaborating ultimate-size nanostructures is based on the reverse `bottom-up' approach, i.e. building up nanostructures (and eventually assemble them to form functional circuits) from individual atoms or molecules. Scanning probe microscopies, including scanning tunnelling microscopy (STM) invented in 1982, have made it possible to create (and visualize) individual structures atom by atom. However, such individual atomic manipulation is not suitable for industrial applications. Self-assembly or self-organization of nanostructures on solid surfaces is a bottom-up approach that allows one to fabricate and assemble nanostructure arrays in a one-step process. For applications, such as high density magnetic storage, self-assembly appears to be the simplest alternative to lithography for massive, parallel fabrication of nanostructure arrays with regular sizes and spacings. These are also necessary for investigating the physical properties of individual nanostructures by means of averaging techniques, i.e. all those using light or particle beams. The state-of-the-art and the current developments in the field of self-organization and physical properties of assembled nanostructures are reviewed in this issue of Journal of Physics: Condensed Matter. The papers have been selected from among the invited and oral presentations of the recent summer workshop held in Cargese (Corsica, France, 17-23 July 2005). All authors are world-renowned in the field. The workshop has been funded by the Marie Curie Actions: Marie Curie Conferences and Training Courses series named `NanosciencesTech' supported by the VI Framework Programme of the European Community, by

  16. Fabricating amorphous silicon solar cells by varying the temperature _of the substrate during deposition of the amorphous silicon layer

    DOEpatents

    Carlson, David E.

    1982-01-01

    An improved process for fabricating amorphous silicon solar cells in which the temperature of the substrate is varied during the deposition of the amorphous silicon layer is described. Solar cells manufactured in accordance with this process are shown to have increased efficiencies and fill factors when compared to solar cells manufactured with a constant substrate temperature during deposition of the amorphous silicon layer.

  17. Defect-induced solid state amorphization of molecular crystals

    NASA Astrophysics Data System (ADS)

    Lei, Lei; Carvajal, Teresa; Koslowski, Marisol

    2012-04-01

    We investigate the process of mechanically induced amorphization in small molecule organic crystals under extensive deformation. In this work, we develop a model that describes the amorphization of molecular crystals, in which the plastic response is calculated with a phase field dislocation dynamics theory in four materials: acetaminophen, sucrose, γ-indomethacin, and aspirin. The model is able to predict the fraction of amorphous material generated in single crystals for a given applied stress. Our results show that γ-indomethacin and sucrose demonstrate large volume fractions of amorphous material after sufficient plastic deformation, while smaller amorphous volume fractions are predicted in acetaminophen and aspirin, in agreement with experimental observation.

  18. Nanostructured Substrates for Optical Sensing

    PubMed Central

    Kemling, Jonathan W.; Qavi, Abraham J.; Bailey, Ryan C.

    2011-01-01

    Sensors that change color have the advantages of versatility, ease of use, high sensitivity, and low cost. The recent development of optically based chemical sensing platforms has increasingly employed substrates manufactured with advanced processing or fabrication techniques to provide precise control over shape and morphology of the sensor micro- and nano-structure. New sensors have resulted with improved capabilities for a number of sensing applications, including the detection of biomolecules and environmental monitoring. This perspective focuses on recent optical sensor devices that utilize nanostructured substrates. PMID:22174955

  19. Vortex ice in nanostructured superconductors

    SciTech Connect

    Reichhardt, Charles; Reichhardt, Cynthia J; Libal, Andras J

    2008-01-01

    We demonstrate using numerical simulations of nanostructured superconductors that it is possible to realize vortex ice states that are analogous to square and kagome ice. The system can be brought into a state that obeys either global or local ice rules by applying an external current according to an annealing protocol. We explore the breakdown of the ice rules due to disorder in the nanostructure array and show that in square ice, topological defects appear along grain boundaries, while in kagome ice, individual defects appear. We argue that the vortex system offers significant advantages over other artificial ice systems.

  20. Atomic-scale disproportionation in amorphous silicon monoxide

    PubMed Central

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-01-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material. PMID:27172815

  1. Amorphous-crystalline transition in thermoelectric NbO2

    NASA Astrophysics Data System (ADS)

    Music, Denis; Chen, Yen-Ting; Bliem, Pascal; Geyer, Richard W.

    2015-06-01

    Density functional theory was employed to design enhanced amorphous NbO2 thermoelectrics. The covalent-ionic nature of Nb-O bonding is identical in amorphous NbO2 and its crystalline counterpart. However, the Anderson localisation occurs in amorphous NbO2, which may affect the transport properties. We calculate a multifold increase in the absolute Seebeck coefficient for the amorphous state. These predictions were critically appraised by measuring the Seebeck coefficient of sputtered amorphous and crystalline NbO2 thin films with the identical short-range order. The first-order phase transition occurs at approximately 550 °C, but amorphous NbO2 possesses enhanced transport properties at all temperatures. Amorphous NbO2, reaching  -173 μV K-1, exhibits up to a 29% larger absolute Seebeck coefficient value, thereby validating the predictions.

  2. Atomic-scale disproportionation in amorphous silicon monoxide.

    PubMed

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-05-13

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material.

  3. One-dimensional ZnO nanostructures.

    PubMed

    Jayadevan, K P; Tseng, T Y

    2012-06-01

    The wide-gap semiconductor ZnO with nanostructures such as nanoparticle, nanorod, nanowire, nanobelt, nanotube has high potential for a variety of applications. This article reviews the fundamentals of one-dimensional ZnO nanostructures, including processing, structure, property, application and their processing-microstructure-property correlation. Various fabrication methods of the ZnO nanostructures including vapor-liquid-solid process, vapor-solid growth, solution growth, solvothermal growth, template-assisted growth and self-assembly are introduced. The characterization and properties of the ZnO nanostructures are described. The possible applications of these nanostructures are also discussed.

  4. Modification of semiconductor or metal nanoparticle lattices in amorphous alumina by MeV heavy ions

    NASA Astrophysics Data System (ADS)

    Bogdanović Radović, I.; Buljan, M.; Karlušić, M.; Jerčinović, M.; Dražič, G.; Bernstorff, S.; Boettger, R.

    2016-09-01

    In the present work we investigate effects of MeV heavy ions (from 0.4 MeV Xe to 15 MeV Si) on regularly ordered nanoparticle (NP) lattices embedded in amorphous alumina matrix. These nanostructures were produced by self-assembling growth using magnetron-sputtering deposition. From grazing incidence small-angle x-ray scattering measurements we have found that the used MeV heavy ions do not change the NP sizes, shapes or distances among them. However, ions cause a tilt of the entire NP lattice in the direction parallel to the surface. The tilt angle depends on the incident ion energy, type and the applied fluence and a nearly linear increase of the tilt angle with the ion fluence and irradiation angle was found. This way, MeV heavy ion irradiation can be used to design custom-made NP lattices. In addition, grazing incidence small-angle x-ray scattering can be effectively used as a method for the determination of material redistribution/shift caused by the ion hammering effect. For the first time, the deformation yield in amorphous alumina was determined for irradiation performed at the room temperature.

  5. Direct growth of single-crystalline III–V semiconductors on amorphous substrates

    PubMed Central

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager III, Joel W.; Chrzan, Daryl C.; Javey, Ali

    2016-01-01

    The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III–V's on application-specific substrates by direct growth. PMID:26813257

  6. Carbon-assisted growth and high visible-light optical reflectivity of amorphous silicon oxynitride nanowires

    PubMed Central

    2011-01-01

    Large amounts of amorphous silicon oxynitride nanowires have been synthesized on silicon wafer through carbon-assisted vapor-solid growth avoiding the contamination from metallic catalysts. These nanowires have the length of up to 100 μm, with a diameter ranging from 50 to 150 nm. Around 3-nm-sized nanostructures are observed to be homogeneously distributed within a nanowire cross-section matrix. The unique configuration might determine the growth of ternary amorphous structure and its special splitting behavior. Optical properties of the nanowires have also been investigated. The obtained nanowires were attractive for their exceptional whiteness, perceived brightness, and optical brilliance. These nanowires display greatly enhanced reflection over the whole visible wavelength, with more than 80% of light reflected on most of the wavelength ranging from 400 to 700 nm and the lowest reflectivity exceeding 70%, exhibiting performance superior to that of the reported white beetle. Intense visible photoluminescence is also observed over a broad spectrum ranging from 320 to 500 nm with two shoulders centered at around 444 and 468 nm, respectively. PMID:21787429

  7. Direct growth of single-crystalline III–V semiconductors on amorphous substrates

    DOE PAGES

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; ...

    2016-01-27

    The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V’s on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V’s of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. Themore » patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. In conclusion, the work presents an important advance towards universal integration of III–V’s on application-specific substrates by direct growth.« less

  8. Optical and transport properties correlation driven by amorphous/crystalline disorder in InP nanowires

    NASA Astrophysics Data System (ADS)

    Kamimura, H.; Gouveia, R. C.; Carrocine, S. C.; Souza, L. D.; Rodrigues, A. D.; Teodoro, M. D.; Marques, G. E.; Leite, E. R.; Chiquito, A. J.

    2016-11-01

    Indium phosphide nanowires with a single crystalline zinc-blend core and polycrystalline/amorphous shell were grown from a reliable route without the use of hazardous precursors. The nanowires are composed by a crystalline core covered by a polycrystalline shell, presenting typical lengths larger than 10 μm and diameters of 80-90 nm. Raman spectra taken from as-grown nanowires exhibited asymmetric line shapes with broadening towards higher wave numbers which can be attributed to phonon localization effects. It was found that optical phonons in the nanowires are localized in regions with average size of 3 nm, which seems to have the same order of magnitude of grain sizes in the polycrystalline shell. Regardless of the fact that the nanowires exhibit a crystalline core, any considerable degree of disorder can lead to a localized behaviour of carriers. In consequence, the variable range hopping was observed as the main transport instead of the usual thermal excitation mechanisms. Furthermore the hopping length was ten times smaller than nanowire cross-sections, confirming that the nanostructures do behave as a 3D system. Accordingly, the V-shape observed in PL spectra clearly demonstrates a very strong influence of the potential fluctuations on the exciton optical recombination. Such fluctuations can still be observed at low temperature regime, confirming that the amorphous/polycrystalline shell of the nanowires affects the exciton recombination in every laser power regime tested.

  9. Direct growth of single-crystalline III–V semiconductors on amorphous substrates

    SciTech Connect

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager III, Joel W.; Chrzan, Daryl C.; Javey, Ali

    2016-01-27

    The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V’s on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V’s of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. In conclusion, the work presents an important advance towards universal integration of III–V’s on application-specific substrates by direct growth.

  10. Directed dewetting of amorphous silicon film by a donut-shaped laser pulse

    NASA Astrophysics Data System (ADS)

    Yoo, Jae-Hyuck; In, Jung Bin; Zheng, Cheng; Sakellari, Ioanna; Raman, Rajesh N.; Matthews, Manyalibo J.; Elhadj, Selim; Grigoropoulos, Costas P.

    2015-04-01

    Irradiation of a thin film with a beam-shaped laser is proposed to achieve site-selectively controlled dewetting of the film into nanoscale structures. As a proof of concept, the laser-directed dewetting of an amorphous silicon thin film on a glass substrate is demonstrated using a donut-shaped laser beam. Upon irradiation of a single laser pulse, the silicon film melts and dewets on the substrate surface. The irradiation with the donut beam induces an unconventional lateral temperature profile in the film, leading to thermocapillary-induced transport of the molten silicon to the center of the beam spot. Upon solidification, the ultrathin amorphous silicon film is transformed to a crystalline silicon nanodome of increased height. This morphological change enables further dimensional reduction of the nanodome as well as removal of the surrounding film material by isotropic silicon etching. These results suggest that laser-based dewetting of thin films can be an effective way for scalable manufacturing of patterned nanostructures.

  11. Silicon and aluminum doping effects on the microstructure and properties of polymeric amorphous carbon films

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoqiang; Hao, Junying; Xie, Yuntao

    2016-08-01

    Polymeric amorphous carbon films were prepared by radio frequency (R.F. 13.56 MHz) magnetron sputtering deposition. The microstructure evolution of the deposited polymeric films induced by silicon (Si) and aluminum(Al) doping were scrutinized through infrared spectroscopy, multi-wavelength Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The comparative results show that Si doping can enhance polymerization and Al doping results in an increase in the ordered carbon clusters. Si and Al co-doping into polymeric films leads to the formation of an unusual dual nanostructure consisting of cross-linked polymer-like hydrocarbon chains and fullerene-like carbon clusters. The super-high elasticity and super-low friction coefficients (<0.002) under a high vacuum were obtained through Si and Al co-doping into the films. Unconventionally, the co-doped polymeric films exhibited a superior wear resistance even though they were very soft. The relationship between the microstructure and properties of the polymeric amorphous carbon films with different elements doping are also discussed in detail.

  12. Thermoluminescence characteristics of hydrogenated amorphous zirconia

    NASA Astrophysics Data System (ADS)

    Montalvo, T. R.; Tenorio, L. O.; Nieto, J. A.; Salgado, M. B.; Estrada, A. M. S.; Furetta, C.

    2005-05-01

    This paper reports the experimental results concerning the thermoluminescent (TL) characteristics of hydrogenated amorphous zirconium oxide (a-Zr:H) powder prepared by the sol-gel method. The advantages of this method are the homogeneity and the purity of the gels associated with a relatively low sintering temperature. Hydrogenated amorphous powder was characterized by thermal analysis and X-ray diffraction. The main TL characteristics investigated were the TL response as a function of the absorbed dose, the reproducibility of the TL readings and the fading. The undoped a-Zr:H powder presents a TL glow curve with two peaks centered at 150 and 260 degrees C, respectively, after beta irradiation. The TL response a-Zr:H as a function of the absorbed dose showed a linear behavior over a wide range. The results presented open the possibility to use this material as a good TL dosimeter.

  13. Computer models for amorphous silicon hydrides

    NASA Astrophysics Data System (ADS)

    Mousseau, Normand; Lewis, Laurent J.

    1990-02-01

    A procedure for generating fully coordinated model structures appropriate to hydrogenated amorphous semiconductors is described. The hydrogen is incorporated into an amorphous matrix using a bond-switching process similar to that proposed by Wooten, Winer, and Weaire, which ensures that fourfold coordination is preserved. After each inclusion of hydrogen, the structure is relaxed using a finite-temperature Monte Carlo algorithm. The method is applied to a-Si:H at various hydrogen concentrations. The resulting model structures are found to be in excellent agreement with recent neutron-scattering measurements on a sample with 12 at. % H. Our prescription, which is essentially nonlocal, allows great flexibility and can easily be extended to related systems.

  14. Wear Resistant Amorphous and Nanocomposite Coatings

    SciTech Connect

    Racek, O

    2008-03-26

    Glass forming materials (critical cooling rate <10{sup 4}K.s{sup -1}) are promising for their high corrosion and wear resistance. During rapid cooling, the materials form an amorphous structure that transforms to nanocrystalline during a process of devitrification. High hardness (HV 1690) can be achieved through a controlled crystallization. Thermal spray process has been used to apply coatings, which preserves the amorphous/nanocomposite structure due to a high cooling rate of the feedstock particles during the impact on a substrate. Wear properties have been studied with respect to process conditions and feedstock material properties. Application specific properties such as sliding wear resistance have been correlated with laboratory tests based on instrumented indentation and scratch tests.

  15. Structural characterization of stable amorphous silicon films

    NASA Astrophysics Data System (ADS)

    Zhang, Shibin; Kong, Guanglin; Wang, Yongqian; Sheng, Shuran; Liao, Xianbo

    2002-05-01

    A kind of hydrogenated diphasic silicon films has been prepared by a new regime of plasma enhanced chemical vapor deposition (PECVD) in the region adjacent to the phase transition from amorphous to crystalline state. The photoelectronic and microstructural properties of the films have been investigated by the constant photocurrent method (CPM), Raman scattering and nuclear magnetic resonance (NMR). Our experimental results and corresponding analyses showed that the diphasic films, incorporated with a subtle boron compensation, could gain both the fine photosensitivity and high stability, provided the crystalline fraction ( f) was controlled in the range of 0< f<0.3. When compared with the conventional hydrogenated amorphous silicon (a-Si:H), the diphasic films are more ordered and robust in the microstructure, and have a less clustered phase in the Si-H bond configurations.

  16. Reversibility and criticality in amorphous solids

    DOE PAGES

    Regev, Ido; Weber, John; Reichhardt, Charles; ...

    2015-11-13

    The physical processes governing the onset of yield, where a material changes its shape permanently under external deformation, are not yet understood for amorphous solids that are intrinsically disordered. Here, using molecular dynamics simulations and mean-field theory, we show that at a critical strain amplitude the sizes of clusters of atoms undergoing cooperative rearrangements of displacements (avalanches) diverges. We compare this non-equilibrium critical behaviour to the prevailing concept of a ‘front depinning’ transition that has been used to describe steady-state avalanche behaviour in different materials. We explain why a depinning-like process can result in a transition from periodic to chaoticmore » behaviour and why chaotic motion is not possible in pinned systems. As a result, these findings suggest that, at least for highly jammed amorphous systems, the irreversibility transition may be a side effect of depinning that occurs in systems where the disorder is not quenched.« less

  17. Reversibility and criticality in amorphous solids

    SciTech Connect

    Regev, Ido; Weber, John; Reichhardt, Charles; Dahmen, Karin A.; Lookman, Turab

    2015-11-13

    The physical processes governing the onset of yield, where a material changes its shape permanently under external deformation, are not yet understood for amorphous solids that are intrinsically disordered. Here, using molecular dynamics simulations and mean-field theory, we show that at a critical strain amplitude the sizes of clusters of atoms undergoing cooperative rearrangements of displacements (avalanches) diverges. We compare this non-equilibrium critical behaviour to the prevailing concept of a ‘front depinning’ transition that has been used to describe steady-state avalanche behaviour in different materials. We explain why a depinning-like process can result in a transition from periodic to chaotic behaviour and why chaotic motion is not possible in pinned systems. As a result, these findings suggest that, at least for highly jammed amorphous systems, the irreversibility transition may be a side effect of depinning that occurs in systems where the disorder is not quenched.

  18. Breakdown of elasticity in amorphous solids

    NASA Astrophysics Data System (ADS)

    Biroli, Giulio; Urbani, Pierfrancesco

    2016-12-01

    What characterizes a solid is the way that it responds to external stresses. Ordered solids, such as crystals, exhibit an elastic regime followed by a plastic regime, both understood microscopically in terms of lattice distortion and dislocations. For amorphous solids the situation is instead less clear, and the microscopic understanding of the response to deformation and stress is a very active research topic. Several studies have revealed that even in the elastic regime the response is very jerky at low temperature, resembling very much the response of disordered magnetic materials. Here we show that in a very large class of amorphous solids this behaviour emerges upon decreasing temperature, as a phase transition, where standard elastic behaviour breaks down. At the transition all nonlinear elastic moduli diverge and standard elasticity theory no longer holds. Below the transition, the response to deformation becomes history- and time-dependent.

  19. Disappearance and Creation of Constrained Amorphous Phase

    NASA Astrophysics Data System (ADS)

    Cebe, Peggy; Lu, Sharon X.

    1997-03-01

    We report observation of the disappearance and recreation of rigid, or constrained, amorphous phase by sequential thermal annealing. Tempera- ture modulated differential scanning calorimetry (MDSC) is used to study the glass transition and lower melting endotherm after annealing. Cold crystallization of poly(phenylene sulfide), PPS, at a temperature just above Tg creates an initial large fraction of rigid amorphous phase (RAP). Brief, rapid annealing to a higher temperature causes RAP almost to disappear completely. Subsequent reannealing at the original lower temperature restores RAP to its original value. At the same time that RAP is being removed, Tg decreases; when RAP is restored, Tg also returns to its initial value. The crystal fraction remains unaffected by the annealing sequence.

  20. Germanium detector passivated with hydrogenated amorphous germanium

    DOEpatents

    Hansen, William L.; Haller, Eugene E.

    1986-01-01

    Passivation of predominantly crystalline semiconductor devices (12) is provided for by a surface coating (21) of sputtered hydrogenated amorphous semiconductor material. Passivation of a radiation detector germanium diode, for example, is realized by sputtering a coating (21) of amorphous germanium onto the etched and quenched diode surface (11) in a low pressure atmosphere of hydrogen and argon. Unlike prior germanium diode semiconductor devices (12), which must be maintained in vacuum at cryogenic temperatures to avoid deterioration, a diode processed in the described manner may be stored in air at room temperature or otherwise exposed to a variety of environmental conditions. The coating (21) compensates for pre-existing undesirable surface states as well as protecting the semiconductor device (12) against future impregnation with impurities.

  1. Annealing behavior of high permeability amorphous alloys

    SciTech Connect

    Rabenberg, L.

    1980-06-01

    Effects of low temperature annealing on the magnetic properties of the amorphous alloy Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ were investigated. Annealing this alloy below 400/sup 0/C results in magnetic hardening; annealing above 400/sup 0/C but below the crystallization temperature results in magnetic softening. Above the crystallization temperature the alloy hardens drastically and irreversibly. Conventional and high resolution transmission electron microscopy were used to show that the magnetic property changes at low temperatures occur while the alloy is truly amorphous. By imaging the magnetic microstructures, Lorentz electron microscopy has been able to detect the presence of microscopic inhomogeneities in this alloy. The low temperature annealing behavior of this alloy has been explained in terms of atomic pair ordering in the presence of the internal molecular field. Lorentz electron microscopy has been used to confirm this explanation.

  2. Phonon stop bands in amorphous superlattices

    NASA Astrophysics Data System (ADS)

    Koblinger, O.; Mebert, J.; Dittrich, E.; Döttinger, S.; Eisenmenger, W.; Santos, P. V.; Ley, L.

    1987-06-01

    In periodically layered media the phonon-dispersion relation shows energy ranges in which phonon propagation is not possible. The existence of such phonon stop bands in crystalline superlattices has been observed in work by V. Narayanamurti, H. L. Störmer, M. A. Chin, A. C. Gossard, and W. Wiegman [Phys. Rev. Lett. 43, 2012 (1979)]. In this Communication we report the observation of phonon stop bands in amorphous superlattices. The filter characteristic of these amorphous superlattices is much sharper than in the case of the crystalline superlattices studied earlier. The investigated superlattices have been prepared by alternating evaporation of Si and SiO2 layers as well as by plasma-enhanced chemical vapor deposition of a-Si:H/a-SiNx:H films in a glow-discharge reactor.

  3. New transformations between crystalline and amorphous ice

    NASA Technical Reports Server (NTRS)

    Hemley, R. J.; Chen, L. C.; Mao, H. K.

    1989-01-01

    High-pressure optical and spectroscopic techniques were used to obtain directly the ice I(h) - hda-ice transformation in a diamond-anvil cell, and the stability of the amorphous form is examined as functions of pressure and temperature. It is demonstrated that hda-ice transforms abruptly at 4 GPa and 77 K to a crystalline phase close in structure to orientationally disordered ice-VII and to a more highly ordered, ice-VIII-like structure at higher temperatures. This is the first time that an amorphous solid is observed to convert to a crystalline solid at low temperatures by compression alone. Phase transitions of this type may be relevant on icy planetary satellites, and there may also be implications for the high-pressure behavior of silica.

  4. Conductance fluctuations in nanostructures

    NASA Astrophysics Data System (ADS)

    Zhu, Ningjia

    1997-12-01

    In this Ph.D thesis the conductance fluctuations of different physical origins in semi-conductor nanostructures were studied using both diagrammatic analytical methods and large scale numerical techniques. In the "mixed" transport regime where both mesoscopic and ballistic features play a role, for the first time I have analytically calculated the non-universal conductance fluctuations. This mixed regime is reached when impurities are distributed near the walls of a quantum wire, leaving the center region ballistic. I have discovered that the existence of a ballistic region destroys the universal conductance fluctuations. The crossover behavior of the fluctuation amplitude from the usual quasi-1D situation to that of the mixed regime is clearly revealed, and the role of various length scales are identified. My analytical predictions were confirmed by a direct numerical simulation by evaluating the Landauer formula. In another direction, I have made several studies of conductance or resistance oscillations and fluctuations in systems with artificial impurities in the ballistic regime. My calculation gave explanations of all the experimental results concerning the classical focusing peaks of the resistance versus magnetic field, the weak localization peak in a Sinai billiard system, the formation of a chaotic billiard, and predicted certain transport features which were indeed found experimentally. I have further extended the calculation to study the Hall resistance in a four-terminal quantum dot in which there is an antidot array. From my numerical data I analyzed the classical paths of electron motion and its quantum oscillations. The results compare well with recent experimental studies on similar systems. Since these billiard systems could provide quantum chaotic dynamics, I have made a detailed study of the consequence of such dynamics. In particular I have investigated the resonant transmission of electrons in these chaotic systems, and found that the level

  5. Tribological properties, corrosion resistance and biocompatibility of magnetron sputtered titanium-amorphous carbon coatings

    NASA Astrophysics Data System (ADS)

    Dhandapani, Vishnu Shankar; Subbiah, Ramesh; Thangavel, Elangovan; Arumugam, Madhankumar; Park, Kwideok; Gasem, Zuhair M.; Veeraragavan, Veeravazhuthi; Kim, Dae-Eun

    2016-05-01

    Amorphous carbon incorporated with titanium (a-C:Ti) was coated on 316L stainless steel (SS) by magnetron sputtering technique to attain superior tribological properties, corrosion resistance and biocompatibility. The morphology, topography and functional groups of the nanostructured a-C:Ti coatings in various concentrations were analyzed using atomic force microscopy (AFM), Raman, X-Ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Raman and XPS analyses confirmed the increase in sp2 bonds with increasing titanium content in the a-C matrix. TEM analysis confirmed the composite nature of the coating and the presence of nanostructured TiC for Ti content of 2.33 at.%. This coating showed superior tribological properties compared to the other a-C:Ti coatings. Furthermore, electrochemical corrosion studies were performed against stimulated body fluid medium in which all the a-C:Ti coatings showed improved corrosion resistance than the pure a-C coating. Preosteoblasts proliferation and viability on the specimens were tested and the results showed that a-C:Ti coatings with relatively high Ti (3.77 at.%) content had better biocompatibility. Based on the results of this work, highly durable coatings with good biocompatibility could be achieved by incorporation of optimum amount of Ti in a-C coatings deposited on SS by magnetron sputtering technique.

  6. Flexible a-Si:H Solar Cells with Spontaneously Formed Parabolic Nanostructures on a Hexagonal-Pyramid Reflector.

    PubMed

    Dong, Wan Jae; Yoo, Chul Jong; Cho, Hyoung Won; Kim, Kyoung-Bo; Kim, Moojin; Lee, Jong-Lam

    2015-04-24

    Flexible amorphous silicon (a-Si:H) solar cells with high photoconversion efficiency (PCE) are demonstrated by embedding hexagonal pyramid nanostructures below a Ag/indium tin oxide (ITO) reflector. The nanostructures constructed by nanoimprint lithography using soft materials allow the top ITO electrode to spontaneously form parabolic nanostructures. Nanoimprint lithography using soft materials is simple, and is conducted at low temperature. The resulting structure has excellent durability under repeated bending, and thus, flexible nanostructures are successfully constructed on flexible a-Si:H solar cells on plastic film. The nanoimprinted pyramid back reflector provides a high angular light scattering with haze reflectance >98% throughout the visible spectrum. The spontaneously formed parabolic nanostructure on the top surface of the a-Si:H solar cells both reduces reflection and scatters incident light into the absorber layer, thereby elongating the optical path length. As a result, the nanopatterned a-Si:H solar cells, fabricated on polyethersulfone (PES) film, exhibit excellent mechanical flexibility and PCE increased by 48% compared with devices on a flat substrate.

  7. Controlled placement and orientation of nanostructures

    DOEpatents

    Zettl, Alex K; Yuzvinsky, Thomas D; Fennimore, Adam M

    2014-04-08

    A method for controlled deposition and orientation of molecular sized nanoelectromechanical systems (NEMS) on substrates is disclosed. The method comprised: forming a thin layer of polymer coating on a substrate; exposing a selected portion of the thin layer of polymer to alter a selected portion of the thin layer of polymer; forming a suspension of nanostructures in a solvent, wherein the solvent suspends the nanostructures and activates the nanostructures in the solvent for deposition; and flowing a suspension of nanostructures across the layer of polymer in a flow direction; thereby: depositing a nanostructure in the suspension of nanostructures only to the selected portion of the thin layer of polymer coating on the substrate to form a deposited nanostructure oriented in the flow direction. By selectively employing portions of the method above, complex NEMS may be built of simpler NEMSs components.

  8. Magnetostatic interactions between wire-tube nanostructures

    NASA Astrophysics Data System (ADS)

    Salazar-Aravena, D.; Palma, J. L.; Escrig, J.

    2015-05-01

    We have investigated the magnetostatic interactions between wire-tube nanostructures. We have observed that the coercivity of the array decreases when the distance between the nanostructures decreases. Besides, when the external magnetic field is applied along the axis of the nanostructures, the two Barkhausen jumps observed for an isolated wire-tube nanostructure give rise to several minor jumps for a weakly interacting array, which eventually become a single jump for the most interacting case. Additionally, the angle θ at which maximum coercivity is obtained varies as a function of the center-to-center distance between the nanostructures, while those remanences obtained for arrays with different distances between the nanostructures coincide. In this way, the study of magnetostatic interactions between wire-tube nanostructures is an interesting topic of research in connection with potential applications where it is usually desirable to avoid such interactions or at least control them.

  9. Carbon-coated Si nanoparticles/reduced graphene oxide multilayer anchored to nanostructured current collector as lithium-ion battery anode

    NASA Astrophysics Data System (ADS)

    Liu, Zhengjiao; Guo, Pengqian; Liu, Boli; Xie, Wenhe; Liu, Dequan; He, Deyan

    2017-02-01

    Silicon is the most promising anode material for the next-generation lithium-ion batteries (LIBs). However, the large volume change during lithiation/delithiation and low intrinsic conductivity hamper its electrochemical performance. Here we report a well-designed LIB anode in which carbon-coated Si nanoparticles/reduced graphene oxide (Si/rGO) multilayer was anchored to nanostructured current collector with stable mechanical support and rapid electron conduction. Furthermore, we improved the integral stability of the electrode through introducing amorphous carbon. The designed anode exhibits superior cyclability, its specific capacity remains above 800 mAh g-1 after 350 cycles at a current density of 2.0 A g-1. The excellent electrochemical performance can be attributed to the fact that the Si/rGO multilayer is reinforced by the nanostructured current collector and the formed amorphous carbon, which can maintain the structural and electrical integrities of the electrode.

  10. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, R.C.

    1985-02-11

    Disclosed are: amorphous metallic precipitates having the formula (M/sub 1/)/sub a/(M/sub 2/)/sub b/ wherein M/sub 1/ is at least one transition metal, M/sub 2/ is at least one main group metal and the integers ''a'' and ''b'' provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  11. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, Robert C.

    1988-01-01

    Amorphous metallic precipitates having the formula (M.sub.1).sub.a (M.sub.2).sub.b wherein M.sub.1 is at least one transition metal, M.sub.2 is at least one main group metal and the integers "a" and "b" provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  12. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, Robert C.

    1986-01-01

    Amorphous metallic precipitates having the formula (M.sub.1).sub.a (M.sub.2).sub.b wherein M.sub.1 is at least one transition metal, M.sub.2 is at least one main group metal and the integers "a" and "b" provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  13. Magnetic and magnetoelastic properties of amorphous ribbons

    SciTech Connect

    Chiriac, H.; Ciobotaru, I.; Mohorianu, S.

    1994-03-01

    A phenomenological model for the magnetic and magnetoelastic behavior of the field-annealed magnetostrictive ribbon is proposed. The basic hypothesis is that the magnetic domain coupling energy due to the inhomogeneity inherent to amorphous state is dependent on the reduced magnetization. The model takes into account the anisotropy energy, Zeeman energy, magnetoelastic energy and magnetic domain coupling energy. The magnetization, engineering magnetostriction and Young`s modulus are derived as continuous functions of the applied magnetic field and stress.

  14. Design Requirements for Amorphous Piezoelectric Polymers

    NASA Technical Reports Server (NTRS)

    Ounaies, Z.; Young, J. A.; Harrison, J. S.

    1999-01-01

    An overview of the piezoelectric activity in amorphous piezoelectric polymers is presented. The criteria required to render a polymer piezoelectric are discussed. Although piezoelectricity is a coupling between mechanical and electrical properties, most research has concentrated on the electrical properties of potentially piezoelectric polymers. In this work, we present comparative mechanical data as a function of temperature and offer a summary of polarization and electromechanical properties for each of the polymers considered.

  15. Ultrathin amorphous coatings on lunar dust grains.

    PubMed

    Bibring, J P; Duraud, J P; Durrieu, L; Jouret, C; Maurette, M; Meunier, R

    1972-02-18

    UItrathin amorphous coatings have been observed by high-voltage electron microscopy on micrometer-sized dust grains from the Apollo 11, Apollo 12, Apollo 14, and Luna 16 missions. Calibration experiments show that these coatings result from an "ancient" implantation of solar wind ions in the grains. This phenomenon has interdisciplinary applications concerning the past activity of the sun, the lunar albedo, the ancient lunar atmosphere and magnetic field, the carbon content of lunar soils, and lunar dynamic processes.

  16. Computer model of tetrahedral amorphous diamond

    NASA Astrophysics Data System (ADS)

    Djordjević, B. R.; Thorpe, M. F.; Wooten, F.

    1995-08-01

    We computer generate a model of amorphous diamond using the Wooten-Weaire method, with fourfold coordination everywhere. We investigate two models: one where four-membered rings are allowed and the other where the four-membered rings are forbidden; each model consisting of 4096 atoms. Starting from the perfect diamond crystalline structure, we first randomize the structure by introducing disorder through random bond switches at a sufficiently high temperature. Subsequently, the temperature is reduced in stages, and the topological and geometrical relaxation of the structure takes place using the Keating potential. After a long annealing process, a random network of comparatively low energy is obtained. We calculate the pair distribution function, mean bond angle, rms angular deviation, rms bond length, rms bond-length deviation, and ring statistics for the final relaxed structures. We minimize the total strain energy by adjusting the density of the sample. We compare our results with similar computer-generated models for amorphous silicon, and with experimental measurement of the structure factor for (predominantly tetrahedral) amorphous carbon.

  17. Interactions of hydrogen with amorphous hafnium oxide

    NASA Astrophysics Data System (ADS)

    Kaviani, Moloud; Afanas'ev, Valeri V.; Shluger, Alexander L.

    2017-02-01

    We used density functional theory (DFT) calculations to study the interaction of hydrogen with amorphous hafnia (a -HfO2 ) using a hybrid exchange-correlation functional. Injection of atomic hydrogen, its diffusion towards electrodes, and ionization can be seen as key processes underlying charge instability of high-permittivity amorphous hafnia layers in many applications. Hydrogen in many wide band gap crystalline oxides exhibits negative-U behavior (+1 and -1 charged states are thermodynamically more stable than the neutral state) . Our results show that in a -HfO2 hydrogen is also negative-U, with charged states being the most thermodynamically stable at all Fermi level positions. However, metastable atomic hydrogen can share an electron with intrinsic electron trapping precursor sites [Phys. Rev. B 94, 020103 (2016)., 10.1103/PhysRevB.94.020103] forming a [etr -+O -H ] center, which is lower in energy on average by about 0.2 eV. These electron trapping sites can affect both the dynamics and thermodynamics of the interaction of hydrogen with a -HfO2 and the electrical behavior of amorphous hafnia films in CMOS devices.

  18. Amorphous molybdenum silicon superconducting thin films

    SciTech Connect

    Bosworth, D. Sahonta, S.-L.; Barber, Z. H.; Hadfield, R. H.

    2015-08-15

    Amorphous superconductors have become attractive candidate materials for superconducting nanowire single-photon detectors due to their ease of growth, homogeneity and competitive superconducting properties. To date the majority of devices have been fabricated using W{sub x}Si{sub 1−x}, though other amorphous superconductors such as molybdenum silicide (Mo{sub x}Si{sub 1−x}) offer increased transition temperature. This study focuses on the properties of MoSi thin films grown by magnetron sputtering. We examine how the composition and growth conditions affect film properties. For 100 nm film thickness, we report that the superconducting transition temperature (Tc) reaches a maximum of 7.6 K at a composition of Mo{sub 83}Si{sub 17}. The transition temperature and amorphous character can be improved by cooling of the substrate during growth which inhibits formation of a crystalline phase. X-ray diffraction and transmission electron microscopy studies confirm the absence of long range order. We observe that for a range of 6 common substrates (silicon, thermally oxidized silicon, R- and C-plane sapphire, x-plane lithium niobate and quartz), there is no variation in superconducting transition temperature, making MoSi an excellent candidate material for SNSPDs.

  19. Phase transitions in biogenic amorphous calcium carbonate

    NASA Astrophysics Data System (ADS)

    Gong, Yutao

    Geological calcium carbonate exists in both crystalline phases and amorphous phases. Compared with crystalline calcium carbonate, such as calcite, aragonite and vaterite, the amorphous calcium carbonate (ACC) is unstable. Unlike geological calcium carbonate crystals, crystalline sea urchin spicules (99.9 wt % calcium carbonate and 0.1 wt % proteins) do not present facets. To explain this property, crystal formation via amorphous precursors was proposed in theory. And previous research reported experimental evidence of ACC on the surface of forming sea urchin spicules. By using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), we studied cross-sections of fresh sea urchin spicules at different stages (36h, 48h and 72h after fertilization) and observed the transition sequence of three mineral phases: hydrated ACC → dehydrated ACC → biogenic calcite. In addition, we unexpectedly found hydrated ACC nanoparticles that are surrounded by biogenic calcite. This observation indicates the dehydration from hydrated ACC to dehydrated ACC is inhibited, resulting in stabilization of hydrated ACC nanoparticles. We thought that the dehydration was inhibited by protein matrix components occluded within the biomineral, and we designed an in vitro assay to test the hypothesis. By utilizing XANES-PEEM, we found that SM50, the most abundant occluded matrix protein in sea urchin spicules, has the function to stabilize hydrated ACC in vitro.

  20. Formation of iron disilicide on amorphous silicon

    NASA Astrophysics Data System (ADS)

    Erlesand, U.; Östling, M.; Bodén, K.

    1991-11-01

    Thin films of iron disilicide, β-FeSi 2 were formed on both amorphous silicon and on crystalline silicon. The β-phase is reported to be semiconducting with a direct band-gap of about 0.85-0.89 eV. This phase is known to form via a nucleation-controlled growth process on crystalline silicon and as a consequence a rather rough silicon/silicide interface is usually formed. In order to improve the interface a bilayer structure of amorphous silicon and iron was sequentially deposited on Czochralski <111> silicon in an e-gun evaporation system. Secondary ion mass spectrometry profiling (SIMS) and scanning electron micrographs revealed an improvement of the interface sharpness. Rutherford backscattering spectrometry (RBS) and X-ray diffractiometry showed β-FeSi 2 formation already at 525°C. It was also observed that the silicide growth was diffusion-controlled, similar to what has been reported for example in the formation of NiSi 2 for the reaction of nickel on amorphous silicon. The kinetics of the FeSi 2 formation in the temperature range 525-625°C was studied by RBS and the activation energy was found to be 1.5 ± 0.1 eV.

  1. Multiple cell photoresponsive amorphous alloys and devices

    SciTech Connect

    Ovshinsky, S.R.; Adler, D.

    1990-01-02

    This patent describes an improved photoresponsive tandem multiple solar cell device. The device comprising: at least a first and second superimposed cell of various materials. The first cell being formed of a silicon alloy material. The second cell including an amorphous silicon alloy semiconductor cell body having an active photoresponsive region in which radiation can impinge to produce charge carriers, the amorphous cell body including at least one density of states reducing element. The element being fluorine. The amorphous cell body further including a band gap adjusting element therein at least in the photoresponsive region to enhance the radiation absorption thereof, the adjusting element being germanium: the second cell being a multi-layer body having deposited semiconductor layers of opposite (p and n) conductivity type; and the first cell being formed with the second cell in substantially direct Junction contact therebetween. The first and second cells designed to generate substantially matched currents from each cell from a light source directed through the first cell and into the second cell.

  2. Newtonian Flow in Bulk Amorphous Alloys

    SciTech Connect

    Wadsworth, J.; Nieh, T.G.

    2000-09-27

    Bulk amorphous alloys have many unique properties, e.g., superior strength and hardness, excellent corrosion resistance, reduced sliding friction and improved wear resistance, and easy formability in a viscous state. These properties, and particularly easy formability, are expected to lead to applications in the fields of near-net-shape fabrication of structural components. Whereas large tensile ductility has generally been observed in the supercooled liquid region in metallic glasses, the exact deformation mechanism, and in particular whether such alloys deform by Newtonian viscous flow, remains a controversial issue. In this paper, existing data are analyzed and an interpretation for the apparent controversy is offered. In addition, new results obtained from an amorphous alloy (composition: Zr-10Al-5TI-17.9Cu-14.6Ni, in at. %) are presented. Structural evolution during plastic deformation is particularly characterized. It is suggested that the appearance of non-Newtonian behavior is a result of the concurrent crystallization of the amorphous structure during deformation.

  3. Crystalline-amorphous transition in silicate perovskites

    SciTech Connect

    Hemmati, M.; Chizmeshya, A. |; Wolf, G.H.; Poole, P.H.; Shao, J.; Angell, C.A.

    1995-06-01

    CaSiO{sub 3} and MgSiO{sub 3} perovskites are known to undergo solid-state crystal to amorphous transitions near ambient pressure when decompressed from their high-pressure stability fields. In order to elucidate the mechanistic aspects of this transition we have performed detailed molecular-dynamics simulations and lattice-dynamical calculations on model silicate perovskite systems using empirical rigid-ion pair potentials. In the simulations at low temperatures, the model perovskite systems transform under tension to a low-density glass composed of corner shared chains of tetrahedral silicon. The amorphization is initiated by a thermally activated step involving a soft polar optic mode in the perovskite phase at the Brillouin zone center. Progression of the system along this reaction coordinate triggers, in succession, multiple barrierless modes of instability ultimately producing a catastrophic decohesion of the lattice. An important intermediary along the reaction path is a crystalline phase where silicon is in a five-coordinate site and the alkaline-earth metal atom is in eightfold coordination. At the onset pressure, this transitory phase is itself dynamically unstable to a number of additional vibrational modes, the most relevant being those which result in transformation to a variety of tetrahedral chain silicate motifs. These results support the conjecture that stress-induced amorphization arises from the near simultaneous accessibility of multiple modes of instability in the highly metastable parent crystalline phase.

  4. Computer Code for Nanostructure Simulation

    NASA Technical Reports Server (NTRS)

    Filikhin, Igor; Vlahovic, Branislav

    2009-01-01

    Due to their small size, nanostructures can have stress and thermal gradients that are larger than any macroscopic analogue. These gradients can lead to specific regions that are susceptible to failure via processes such as plastic deformation by dislocation emission, chemical debonding, and interfacial alloying. A program has been developed that rigorously simulates and predicts optoelectronic properties of nanostructures of virtually any geometrical complexity and material composition. It can be used in simulations of energy level structure, wave functions, density of states of spatially configured phonon-coupled electrons, excitons in quantum dots, quantum rings, quantum ring complexes, and more. The code can be used to calculate stress distributions and thermal transport properties for a variety of nanostructures and interfaces, transport and scattering at nanoscale interfaces and surfaces under various stress states, and alloy compositional gradients. The code allows users to perform modeling of charge transport processes through quantum-dot (QD) arrays as functions of inter-dot distance, array order versus disorder, QD orientation, shape, size, and chemical composition for applications in photovoltaics and physical properties of QD-based biochemical sensors. The code can be used to study the hot exciton formation/relation dynamics in arrays of QDs of different shapes and sizes at different temperatures. It also can be used to understand the relation among the deposition parameters and inherent stresses, strain deformation, heat flow, and failure of nanostructures.

  5. A transparent nanostructured optical biosensor.

    PubMed

    He, Yuan; Li, Xiang; Que, Long

    2014-05-01

    Herein we report a new transparent nanostructured Fabry-Perot interferometer (FPI) device. The unique features of the nanostructured optical device can be summarized as the following: (i) optically transparent nanostructured optical device; (ii) simple and inexpensive for fabrication; (iii) easy to be fabricated and scaled up as an arrayed format. These features overcome the existing barriers for the current nanopore-based interferometric optical biosensors by measuring the transmitted optical signals rather than the reflected optical signals, thereby facilitating the optical testing significantly for the arrayed biosensors and thus paving the way for their potential for high throughput biodetection applications. The optically transparent nanostructures (i.e., anodic aluminum oxide nanopores) inside the FPI devices are fabricated from 2.2 microm thick lithographically patterned Al thin film on an indium tin oxide (ITO) glass substrate using a two-step anodization process. Utilizing the binding between Protein A and porcine immunoglobulin G (IgG) as a model, the detection of the bioreaction between biomolecules has been demonstrated successfully. Experiments found that the lowest detection concentration of proteins is in the range of picomolar level using current devices, which can be easily tuned into the range of femtomolar level by optimizing the performance of devices.

  6. Characterization of Amorphous and Co-Amorphous Simvastatin Formulations Prepared by Spray Drying.

    PubMed

    Craye, Goedele; Löbmann, Korbinian; Grohganz, Holger; Rades, Thomas; Laitinen, Riikka

    2015-12-03

    In this study, spray drying from aqueous solutions, using the surface-active agent sodium lauryl sulfate (SLS) as a solubilizer, was explored as a production method for co-amorphous simvastatin-lysine (SVS-LYS) at 1:1 molar mixtures, which previously have been observed to form a co-amorphous mixture upon ball milling. In addition, a spray-dried formulation of SVS without LYS was prepared. Energy-dispersive X-ray spectroscopy (EDS) revealed that SLS coated the SVS and SVS-LYS particles upon spray drying. X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) showed that in the spray-dried formulations the remaining crystallinity originated from SLS only. The best dissolution properties and a "spring and parachute" effect were found for SVS spray-dried from a 5% SLS solution without LYS. Despite the presence of at least partially crystalline SLS in the mixtures, all the studied formulations were able to significantly extend the stability of amorphous SVS compared to previous co-amorphous formulations of SVS. The best stability (at least 12 months in dry conditions) was observed when SLS was spray-dried with SVS (and LYS). In conclusion, spray drying of SVS and LYS from aqueous surfactant solutions was able to produce formulations with improved physical stability for amorphous SVS.

  7. Nanostructure fabrication using inorganic sols and electron beam lithography

    NASA Astrophysics Data System (ADS)

    Donthu, Suresh Kumar

    Dimensionally constrained material systems are at the forefront of current materials research because of their novel and often enhanced physical, chemical and biological properties. The dimensionality effects are pervasive through different classes of materials including ceramics, metals and polymers. Often times dimensionality effects are manifested as internal structure variations in polycrystalline materials. This is evident from some recent reports indicating that "internal" microstructural inhomogenities such as grain boundaries and porosity even in dimensionally constrained systems can further enhance their performance metrics such as gas sensitivity, for example. These results, coupled with the maxim that "microstructure is a material's DNA" underscore the need for novel approaches to enable tailoring of the "internal" microstructure of constrained nanopatterned systems and their characterization. This dissertation reports one such approach. We have developed an enabling nanopatterning technique termed as soft-electron beam lithography (soft-eBL) which utilizes liquid precursors (e.g., sol) as the material source for patterning variety of materials and composites with dimensional control down to 30 nm. Among several advantages, soft-eBL is capable of patterning structures on almost any substrate - single crystals, fragile ultra-thin membranes and insulators. We have exploited these unique attributes of soft-eBL to fabricate nanopatterns of simple and complex functional oxides with defined sizes and shapes. For example, we showed that by controlling the width of ZnO nanopatterned lines on an amorphous substrate, it is possible to define the number of grains per unit line length, such as a beaded (or a bamboo) structure where a single grain spans the entire line width. Using Soft-eBL we were able to demonstrate the effect of dimension, line-width to be specific, on the reduced crystallization rate in ceramic oxide nanostructures. The average grain size in

  8. Amorphous Silica- and Carbon- rich nano-templated surfaces as model interstellar dust surfaces for laboratory astrochemistry

    NASA Astrophysics Data System (ADS)

    Pascual, Natalia; Dawes, Anita; González-Posada, Fernando; Thompson, Neil; Chakarov, Dinko; Mason, Nigel J.; Fraser, Helen Jane

    2015-08-01

    Experimental studies on surface astrochemistry are vital to our understanding of chemical evolution in the interstellar medium (ISM). Laboratory surface-astrochemists have recently begun to study chemical reactions on interstellar dust-grain mimics, ranging from graphite, HOPG and graphene (representative of PAHs or large C-grains in the ISM) to amorphous olivine (representative of silicate dust) and ablated meteoritic samples (representative of interplanetary dust). These pioneering experiments show that the nature of the surface fundamentally affects processes at the substrate surface, substrate-ice interface, and ice over-layer. What these experiments are still lacking is the ability to account for effects arising from the discrete nano-scale of ISM grains, which might include changes to electronic structure, optical properties and surface-kinetics in comparison to bulk materials. The question arises: to what extent are the chemical and optical properties of interstellar ices affected by the size, morphology and material of the underlying ISM dust?We have designed, fabricated and characterised a set of nano-structured surfaces, where nanoparticles, representative of ISM grains, are adhered to an underlying support substrate. Here we will show the nanoparticles that have been manufactured from fused-silica (FS), glassy carbon (GC) and amorphous-C (aC). Our optical characterisation data shows that the nanostructured surfaces have different absorption cross-sections and significant scattering in comparison to the support substrates, which has implications for the energetic processing of icy ISM dust. We have been able to study how water-ice growth differs on the nanoparticles in comparison to the “flat” substrates, indicating increased ice amorphicity when nanoparticles are present, and on C-rich surfaces, compared to Si-rich particles. These data will be discussed in the context of interstellar water-ice features.

  9. Characterizing Amorphous Silicates in Extraterrestrial Materials

    NASA Astrophysics Data System (ADS)

    Fu, X.; Wang, A.; Krawczynski, M. J.

    2015-12-01

    Amorphous silicates are common in extraterrestrial materials. They are seen in the matrix of carbonaceous chondrites as well as in planetary materials. Tagish Lake is one of the most primitive carbonaceous meteorites in which TEM and XRD analyses found evidence for poorly crystalline phyllosilicate-like species; Raman spectra revealed amorphous silicates with variable degree of polymerization and low crystallinity. On Mars, CheMin discovered amorphous phases in all analyzed samples, and poorly crystalline smectite in mudstone samples. These discoveries pose questions on the crystallinity of phyllosilicates found by remote sensing on Mars, which is directly relevant to aqueous alteration during geologic history of Mars. Our goal is to use spectroscopy to better characterize amorphous silicates. We use three approaches: (1) using silicate glasses synthesized with controlled chemistry to study the effects of silicate polymerization and (2) using phyllosilicates synthesized with controlled hydrothermal treatment to study the effect of crystallinity on vibrational spectroscopy, finally (3) to use the developed correlations in above two steps to study amorphous phases in meteorites, and those found in future missions to Mars. In the 1st step, silicate glasses were synthesized from pure oxides in a range of NBO/T ratios (from 0 to 4). Depending on the targeted NBO/T and composition of mixed oxides, temperatures for each experiment fell in a range from 1260 to 1520 °C, run for ~ 4 hrs. The melt was quenched in liquid N2 or water. Homogeneity of glass was checked under optical microscopy. Raman spectra were taken over 100 spots on small chips free of bubbles and crystals. We have observed that accompanying an increase of NBO/T, there is a strengthening and a position shift of the Raman peak near 1000 cm-1 (Si-Onon-bridging stretching mode), and the weakening of broad Raman peaks near 500 cm-1 (ring breathing mode) and 700cm-1 (Si-Obridging-Si mode). We are building the

  10. Fabrication of zein nanostructure

    NASA Astrophysics Data System (ADS)

    Luecha, Jarupat

    resins. The soft lithography technique was mainly used to fabricate micro and nanostructures on zein films. Zein material well-replicated small structures with the smallest size at sub micrometer scale that resulted in interesting photonic properties. The bonding method was also developed for assembling portable zein microfluidic devices with small shape distortion. Zein-zein and zein-glass microfluidic devices demonstrated sufficient strength to facilitate fluid flow in a complex microfluidic design with no leakage. Aside from the fabrication technique development, several potential applications of this environmentally friendly microfluidic device were investigated. The concentration gradient manipulation of Rhodamine B solution in zein-glass microfluidic devices was demonstrated. The diffusion of small molecules such as fluorescent dye into the wall of the zein microfluidic channels was observed. However, with this formulation, zein microfluidic devices were not suitable for cell culture applications. This pioneer study covered a wide spectrum of the implementation of the two nanotechnology approaches to advance zein biomaterial which provided proof of fundamental concepts as well as presenting some limitations. The findings in this study can lead to several innovative research opportunities of advanced zein biomaterials with broad applications. The information from the study of zein nanocomposite structure allows the packaging industry to develop the low cost biodegradable materials with physical property improvement. The information from the study of the zein microfluidic devices allows agro-industry to develop the nanotechnology-enabled microfluidic sensors fabricated entirely from biodegradable polymer for on-site disease or contaminant detection in the fields of food and agriculture.

  11. Phase transformation and microstructural evolution of nanostructured oxides and nitrides under ion irradiations

    NASA Astrophysics Data System (ADS)

    Lu, Fengyuan

    Material design at the nanometer scale is an effective strategy for developing advanced materails with enhanced radiation tolerance for advanced nuclear energy systems as high densities of surfaces and interfaces of the nanostructured materials may behave as effective sinks for defect recovery. However, nanostructured materials may not be intrinsically radiation tolerant, and the interplay among the factors of crystal size, temperature, chemical composition, surface energy and radiation conditions may eventually determine material radiation behaviors. Therefore, it is necessary to understand the radiation effects of nanostructured materials and the underlying physics for the design of advanced nanostructured nuclear materials. The main objective of this doctoral thesis is to study the behavior of nanostructured oxides and nitrides used as fuel matrix and waste forms under extreme radiation conditions with the focus of phase transformation, microstructural evolution and damage mechanisms. Radiation experiments were performed using energetic ion beam techniques to simulate radiation damage resulting from energetic neutrons, alpha-decay events and fission fragments, and various experimental approaches were employed to characterize materials’ microstructural evolution and phase stability upon intense radiation environments including transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. Thermal annealing experiments indicated that nanostructured ZrO2 phase stability is strongly affected by the grain size. Radiation results on nanostructured ZrO2 indicated that thermodynamically unstable or metastable high temperature phases can be induced by energetic beam irradiation at room temperature. Various phase transformation among different polymorphs of monoclinic, tetragonal and amorphous states can be induced, and different mechanisms are responsible for structural transformations including oxygen vacancies accumulation upon displacive

  12. Integrated biophotonics in endoscopic oncology

    NASA Astrophysics Data System (ADS)

    Muguruma, Naoki; DaCosta, Ralph S.; Wilson, Brian C.; Marcon, Norman E.

    2009-02-01

    Gastrointestinal endoscopy has made great progress during last decade. Diagnostic accuracy can be enhanced by better training, improved dye-contrast techniques method, and the development of new image processing technologies. However, diagnosis using conventional endoscopy with white-light optical imaging is essentially limited by being based on morphological changes and/or visual attribution: hue, saturation and intensity, interpretation of which depends on the endoscopist's eye and brain. In microlesions in the gastrointestinal tract, we still rely ultimately on the histopathological diagnosis from biopsy specimens. Autofluorescence imaging system has been applied for lesions which have been difficult to morphologically recognize or are indistinct with conventional endoscope, and this approach has potential application for the diagnosis of dysplastic lesions and early cancers in the gastrointestinal tract, supplementing the information from white light endoscopy. This system has an advantage that it needs no administration of a photosensitive agent, making it suitable as a screening method for the early detection of neoplastic tissues. Narrow band imaging (NBI) is a novel endoscopic technique which can distinguish neoplastic and non-neoplastic lesions without chromoendoscopy. Magnifying endoscopy in combination with NBI has an obvious advantage, namely analysis of the epithelial pit pattern and the vascular network. This new technique allows a detailed visualization in early neoplastic lesions of esophagus, stomach and colon. However, problems remain; how to combine these technologies in an optimum diagnostic strategy, how to apply them into the algorithm for therapeutic decision-making, and how to standardize several classifications surrounding them. 'Molecular imaging' is a concept representing the most novel imaging methods in medicine, although the definition of the word is still controversial. In the field of gastrointestinal endoscopy, the future of endoscopic diagnosis is likely to be impacted by a combination of biomarkers and technology, and 'endoscopic molecular imaging' should be defined as "visualization of molecular characteristics with endoscopy". These innovations will allow us not only to locate a tumor or dysplastic lesion but also to visualize its molecular characteristics (e.g., DNA mutations and polymorphisms, gene and/or protein expression), and the activity of specific molecules and biological processes that affect tumor behavior and/or its response to therapy. In the near future, these methods should be promising technologies that will play a central role in gastrointestinal oncology.

  13. Synthesis of nanostructured WC-12 pct Co coating using mechanical milling and high velocity oxygen fuel thermal spraying

    SciTech Connect

    He, J. Ice, M.; Dallek, S.; Lavernia, E.J.

    2000-02-01

    A nanostructured WC-12 pct Co coating was synthesized using mechanical milling and high velocity oxygen fuel (HVOF) thermal spraying. The variation of powder characteristics with milling time and the performance of the coatings were investigated using scanning electron microscope (SEM), X-ray, transmission electron microscope (TEM), thermogravimetric analyzer (TGA), and microhardness measurements. There is no evidence that indicates the presence of an amorphous phase in the sintered WC-12 pct Co powder, and the binder phase in this powder is still crystalline Co. Mechanical milling of up to 20 hours did not lead to the formation of an amorphous phase in the sintered WC-12 pct Co powder. During the initial stages of the milling, the brittle carbide particles were first fractured into fragments and then embedded into the binder phase. This process gradually formed polycrystal nanocomposite powders of the Co binder phase and W carbide particles. The conventional cold welding and fracturing processes primarily occurred among the Co binder powders and polycrystal composite powders. The nanostructured WC-12 pct Co coatings, synthesized in the present study, consist of an amorphous matrix and carbides with an average particle diameter of 35 nm. The coating possesses an average microhardness of 1135 HV and higher resistance to indentation fracture than that of its conventional counterpart.

  14. Formation of amorphous silicon by light ion damage

    SciTech Connect

    Shih, Y.C.

    1985-12-01

    Amorphization by implantation of boron ions (which is the lightest element generally used in I.C. fabrication processes) has been systematically studied for various temperatures, various voltages and various dose rates. Based on theoretical considerations and experimental results, a new amorphization model for light and intermediate mass ion damage is proposed consisting of two stages. The role of interstitial type point defects or clusters in amorphization is emphasized. Due to the higher mobility of interstitials out-diffusion to the surface particularly during amorphization with low energy can be significant. From a review of the idealized amorphous structure, diinterstitial-divacancy pairs are suggested to be the embryos of amorphous zones formed during room temperature implantation. The stacking fault loops found in specimens implanted with boron at room temperature are considered to be the origin of secondary defects formed during annealing.

  15. Polyamorphous transition in amorphous fullerites C{sub 70}

    SciTech Connect

    Borisova, P. A.; Agafonov, S. S.; Glazkov, V. P.; D'yakonova, N. P.; Somenkov, V. A.

    2011-12-15

    Samples of amorphous fullerites C{sub 70} have been obtained by mechanical activation (grinding in a ball mill). The structure of the samples has been investigated by neutron and X-ray diffraction. The high-temperature (up to 1200 Degree-Sign C) annealing of amorphous fullerites revealed a polyamorphous transition from molecular to atomic glass, which is accompanied by the disappearance of fullerene halos at small scattering angles. Possible structural versions of the high-temperature amorphous phase are discussed.

  16. Switching in coplanar amorphous hydrogenated silicon devices

    NASA Astrophysics Data System (ADS)

    Avila, A.; Asomoza, R.

    2000-01-01

    Switching has been observed in a wide variety of materials and devices. Hydrogenated amorphous silicon has become one of the most important cases because of interest in neural network applications. Although there are many reports regarding this phenomenon, not all of the physical processes involved are still determined precisely. Therefore, some more experimental information is needed in order to achieve this task. Much of the behavior of the devices has been ascribed to the existence of a filamentary region which is produced after the first switching process, called forming. We observed this filamentary region in its full extension by producing forming in amorphous silicon devices with coplanar metallic contacts placed near each other (˜5 μm). The I-V characteristics, filament optical and atomic force microscopy images and chemical etching led us to correlate changes in resistance to metal inclusion into the amorphous film. There are two stages: the first is related to contact stabilization, the second to metal transport into the film bulk. Optical images show a permanent filamentary region after forming. AFM images of these filaments showed that they are formed essentially by material accumulation between the contacts. This material tends to get some atomic arrangement, becoming a polycrystalline solid. If the device was led to breakdown, such accumulation becomes either a hillock or a thin conducting channel connecting both contacts. In the case of a switching filament, the accumulation tends to be a chain of smaller hillocks along the conduction path. Metal from the contacts remains in the conduction path after forming and chemical etching indicated that it is placed near the path core. Before forming, a tunneling transport process can be ascribed to the non-ohmic behavior of the samples during the first stage of metallic inclusion.

  17. Chemical Sensors Based on Metal Oxide Nanostructures

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Xu, Jennifer C.; Evans, Laura J.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Mike J.; Liu, Chung-Chiun

    2006-01-01

    This paper is an overview of sensor development based on metal oxide nanostructures. While nanostructures such as nanorods show significan t potential as enabling materials for chemical sensors, a number of s ignificant technical challenges remain. The major issues addressed in this work revolve around the ability to make workable sensors. This paper discusses efforts to address three technical barriers related t o the application of nanostructures into sensor systems: 1) Improving contact of the nanostructured materials with electrodes in a microse nsor structure; 2) Controling nanostructure crystallinity to allow co ntrol of the detection mechanism; and 3) Widening the range of gases that can be detected by using different nanostructured materials. It is concluded that while this work demonstrates useful tools for furt her development, these are just the beginning steps towards realizati on of repeatable, controlled sensor systems using oxide based nanostr uctures.

  18. Composite materials formed with anchored nanostructures

    DOEpatents

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2015-03-10

    A method of forming nano-structure composite materials that have a binder material and a nanostructure fiber material is described. A precursor material may be formed using a mixture of at least one metal powder and anchored nanostructure materials. The metal powder mixture may be (a) Ni powder and (b) NiAl powder. The anchored nanostructure materials may comprise (i) NiAl powder as a support material and (ii) carbon nanotubes attached to nanoparticles adjacent to a surface of the support material. The process of forming nano-structure composite materials typically involves sintering the mixture under vacuum in a die. When Ni and NiAl are used in the metal powder mixture Ni.sub.3Al may form as the binder material after sintering. The mixture is sintered until it consolidates to form the nano-structure composite material.

  19. Raman Studies of Carbon Nanostructures

    NASA Astrophysics Data System (ADS)

    Jorio, Ado; Souza Filho, Antonio G.

    2016-07-01

    This article reviews recent advances on the use of Raman spectroscopy to study and characterize carbon nanostructures. It starts with a brief survey of Raman spectroscopy of graphene and carbon nanotubes, followed by recent developments in the field. Various novel topics, including Stokes-anti-Stokes correlation, tip-enhanced Raman spectroscopy in two dimensions, phonon coherence, and high-pressure and shielding effects, are presented. Some consequences for other fields—quantum optics, near-field electromagnetism, archeology, materials and soil sciences—are discussed. The review ends with a discussion of new perspectives on Raman spectroscopy of carbon nanostructures, including how this technique can contribute to the development of biotechnological applications and nanotoxicology.

  20. Nanorice: a new hybrid nanostructure

    NASA Astrophysics Data System (ADS)

    Nordlander, P.; Brandl, D.; Le, F.; Wang, H.; Halas, N. J.

    2006-03-01

    The plasmon hybridization method [1] is applied to nanorice, a new metallic nanostructure which combines the properties of two popular tunable plasmonic nanoparticle geometries: nanorods and nanoshells. The particle consists of a prolate spheroidal dielectric core and a thin metallic shell, bearing a remarkable resemblance to a rice grain. The nanorice particle shows far greater geometric tunability of the optical resonance, larger local field intensity enhancements and far greater sensitivity as a surface plasmon resonance (SPR) nanosensor than any previously reported dielectric-metal nanostructure. The tunability of the nanorice particle arises from the interaction of primitive plasmons associated with the inner and outer surfaces of the shell. The results from plasmon hybridization are compared to FDTD simulations. [1] E. Prodan and P. Nordlander, J. Chem. Phys. 120(2004)5444-5454

  1. Nanostructured materials for thermoelectric applications.

    PubMed

    Bux, Sabah K; Fleurial, Jean-Pierre; Kaner, Richard B

    2010-11-28

    Recent studies indicate that nanostructuring can be an effective method for increasing the dimensionless thermoelectric figure of merit (ZT) in materials. Most of the enhancement in ZT can be attributed to large reductions in the lattice thermal conductivity due to increased phonon scattering at interfaces. Although significant gains have been reported, much higher ZTs in practical, cost-effective and environmentally benign materials are needed in order for thermoelectrics to become effective for large-scale, wide-spread power and thermal management applications. This review discusses the various synthetic techniques that can be used in the production of bulk scale nanostructured materials. The advantages and disadvantages of each synthetic method are evaluated along with guidelines and goals presented for an ideal thermoelectric material. With proper optimization, some of these techniques hold promise for producing high efficiency devices.

  2. Nanostructured Biomaterials and Their Applications

    PubMed Central

    Parratt, Kirsten; Yao, Nan

    2013-01-01

    Some of the most important advances in the life sciences have come from transitioning to thinking of materials and their properties on the nanoscale rather than the macro or even microscale. Improvements in imaging technology have allowed us to see nanofeatures that directly impact chemical and mechanical properties of natural and man-made materials. Now that these can be imaged and quantified, substantial advances have been made in the fields of biomimetics, tissue engineering, and drug delivery. For the first time, scientists can determine the importance of nanograins and nanoasperities in nacre, direct the nucleation of apatite and the growth of cells on nanostructured scaffolds, and pass drugs tethered to nanoparticles through the blood-brain barrier. This review examines some of the most interesting materials whose nanostructure and hierarchical organization have been shown to correlate directly with favorable properties and their resulting applications.

  3. Dispersive interactions in graphitic nanostructures

    NASA Astrophysics Data System (ADS)

    Woods, L. M.; Popescu, A.; Drosdoff, D.; Bondarev, I. V.

    2013-02-01

    The Casimir interaction between graphitic nanostructures, such as carbon nanotubes and graphene sheets, is investigated at the quantum mechanical limit (T = 0 K) using a quantum electrodynamical approach for absorbing and dispersive media. It is found that the nanotube/nanotube interaction in a double wall carbon nanotube configuration is profoundly affected by the collective low frequency excitations of individual nanotubes. It is shown that pronounced, low frequency peaks in the nanotube electron energy loss spectra are a main factor contributing to the strength of the intertube attraction. The graphene/graphene force is also investigated. It is obtained that the graphene optical transparency is the main reason for the reduced attraction as compared to the one for perfect metals. This study presents a unified approach for electromagnetic interactions in graphitic nanostructures, which is able to account for their unique electronic and response properties and geometry configurations.

  4. Recent advances in co-amorphous drug formulations.

    PubMed

    Dengale, Swapnil Jayant; Grohganz, Holger; Rades, Thomas; Löbmann, Korbinian

    2016-05-01

    Co-amorphous drug delivery systems have recently gained considerable interest in the pharmaceutical field because of their potential to improve oral bioavailability of poorly water-soluble drugs through drug dissolution enhancement as a result of the amorphous nature of the material. A co-amorphous system is characterized by the use of only low molecular weight components that are mixed into a homogeneous single-phase co-amorphous blend. The use of only low molecular weight co-formers makes this approach very attractive, as the amount of amorphous stabilizer can be significantly reduced compared with other amorphous stabilization techniques. Because of this, several research groups started to investigate the co-amorphous formulation approach, resulting in an increasing amount of scientific publications over the last few years. This study provides an overview of the co-amorphous field and its recent findings. In particular, we investigate co-amorphous formulations from the viewpoint of solid dispersions, describe their formation and mechanism of stabilization, study their impact on dissolution and in vivo performance and briefly outline the future potentials.

  5. Delivery of poorly soluble compounds by amorphous solid dispersions.

    PubMed

    Lee, Thomas W Y; Boersen, Nathan A; Hui, H W; Chow, S F; Wan, K Y; Chow, Albert H L

    2014-01-01

    Solid state manipulation by amorphous solid dispersion has been the subject of intensive research for decades due to their excellent potential for dissolution and bioavailability enhancement. The present review aims to highlight the latest advancement in this area, with focus on the fundamentals, characterization, formulation development and manufacturing of amorphous solid dispersions as well as the new generation amorphization technologies. Additionally, specific applications of amorphous solid dispersion in the formulation of herbal drugs or bioactive natural products are reviewed to reflect the growing interest in this relatively neglected area.

  6. Irreversible Enthalpic Relaxation of Rigid Amorphous Fraction in Isotactic Polystyrene

    NASA Astrophysics Data System (ADS)

    Xu, Hui; Cebe, Peggy

    2004-03-01

    The crystalline, rigid amorphous, and mobile amorphous fractions in isotactic polystyrene (iPS) were studied using: 1. quasi-isothermal temperature-modulated differential scanning calorimetry (TMDSC) (i.e., with step-wise increase of temperature), and 2. regular TMDSC (i.e., with constant rate of temperature increase). The crystal fraction was determined from wide angle X-ray scattering and endotherm analysis; mobile amorphous fraction was determined from heat capacity measurements at the glass transition. The validity of a three-phase model for iPS (comprising crystals, mobile and rigid amorphous fractions) is confirmed by heat capacity measurements made during quasi-isothermal cold crystallization. At the same time, we prove the rigid amorphous fraction to be established at the crystallization temperature and not during subsequent cooling. The rigid amorphous fraction is thus stable below the crystallization temperature Tc, and relaxes at a temperature Ta, between Tc and the melting point of the lowest melting crystals. Upon relaxing, the rigid amorphous fraction undergoes a phase transition to mobile amorphous fraction. For cold-crystallized iPS the relaxation of the rigid amorphous fraction is found to be an enthalpy involved, non-reversible relaxation occurring before the melting of the crystals.

  7. Thermally induced evolution of hydrogenated amorphous carbon

    NASA Astrophysics Data System (ADS)

    Mangolini, Filippo; Rose, Franck; Hilbert, James; Carpick, Robert W.

    2013-10-01

    The thermally induced structural evolution of hydrogenated amorphous carbon (a-C:H) films was investigated in situ by X-ray photoelectron spectroscopy for annealing temperatures up to 500 °C. A model for the conversion of sp3- to sp2-hybridized carbon in a-C:H vs. temperature and time was developed and applied to determine the ranges of activation energies for the thermally activated processes occurring. The energies are consistent with ordering and clustering of sp2 carbon, scission of sp3 carbon-hydrogen bonds and formation of sp2 carbon, and direct transformation of sp3- to sp2-hybridized carbon.

  8. Caltech Center for Structural and Amorphous Metals

    DTIC Science & Technology

    2005-05-10

    fracture resistance and subcritical-crack growth behavior in BMG’s and their composites. We have shown that hydrogen significantly increases the glass...Science des Materiaux , 2713], 2002 L. Shadowspeaker, M. B. Shah and R. Busch, "On the crystalline equilibrium phases of the Zr5 7 Nb 5 Cu 15 .4Ni12.6 A lI0...Lowhaphandu, L.A. Ludrosky, and J.J. Lewandowski "Fracture Resistance of Zr-Ti-Ni-Cu-Be Bulk Amorphous Alloy",, TMS-AIME Fall Meeting, Cincinnati, OH

  9. Optical multilayers with an amorphous fluoropolymer

    NASA Astrophysics Data System (ADS)

    Chow, Robert; Loomis, Gary E.; Lindsey, Edward F.

    1994-09-01

    Multilayered coatings were made by physical vapor deposition (PVD) of a perfluorinated amorphous polymer, Teflon AF2400, together with other optical materials. A high reflector at 1064 nm was made with ZnS and AF2400. An all-organic 1064-nm reflector was made from AF2400 and polyethylene. Oxide (HfO2, SiO2) compatibility was also tested. Each multilayer system adhered to itself. The multilayers were influenced by coating stress and unintentional temperature rises during PVD deposition.

  10. On the crystallization of amorphous germanium films

    NASA Astrophysics Data System (ADS)

    Edelman, F.; Komem, Y.; Bendayan, M.; Beserman, R.

    1993-06-01

    The incubation time for crystallization of amorphous Ge (a-Ge) films, deposited by e-gun, was studied as a function of temperature between 150 and 500°C by means of both in situ transmission electron microscopy and Raman scattering spectroscopy. The temperature dependence of t0 follows an Arrhenius curve with an activation energy of 2.0 eV for free-sustained a-Ge films. In the case where the a-Ge films were on Si 3N 4 substrate, the activation energy of the incubation process was 1.3 eV.

  11. Continuous synthesis of amorphous carbonated apatites.

    PubMed

    Tadic, D; Peters, F; Epple, M

    2002-06-01

    Amorphous carbonated hydroxyapatite was prepared by rapid mixing of aqueous solutions of a continuous computer-controlled reactor. The variation of the carbonate content in the solid product is possible by adjustment of the ratios of phosphate to carbonate in the initial solution. The principal reaction parameters (temperature, pH, stirrer speed, solution composition and supersaturation) are controlled and monitored. By controlling these processing parameters, a non-stoichiometric hydroxyapatite with fine-tuned crystallinity, morphology, and carbonate content can be reproducibly prepared. The higher solubility under the conditions of osteoclastic resorption was tested in vitro at constant pH (4.4).

  12. Radiation resistance studies of amorphous silicon films

    NASA Technical Reports Server (NTRS)

    Woodyard, James R.; Payson, J. Scott

    1989-01-01

    Hydrogenated amorphous silicon thin films were irradiated with 2.00 MeV helium ions using fluences ranging from 1E11 to 1E15 cm(-2). The films were characterized using photothermal deflection spectroscopy and photoconductivity measurements. The investigations show that the radiation introduces sub-band-gap states 1.35 eV below the conduction band and the states increase supralinearly with fluence. Photoconductivity measurements suggest the density of states above the Fermi energy is not changing drastically with fluence.

  13. Giant magnetoresistive nanostructured materials by electrodeposition

    NASA Astrophysics Data System (ADS)

    Myung, No Sang

    NiFe/Cu and CoFe/Cu multilayers and NiFe compositional modulated alloys (CMA) electrodeposited by newly developed flow-through electrochemical reactor. Sub-micron (Ni)Cu and nano-size (CoFe)Cu granular alloys have been electrodeposited by magneto-electrodeposition method. These two methods eliminate the problems confronted by conventional methods and provide a new direction in fabrication of nanostructured materials by electrodeposition. Prior to fabrication of GMR materials, electrodeposition kinetics of individual metals (Co, NiFe, Cu) were studied. In Co electrodeposition and dissolution from sulfate bath, substrates have a great impact on the initial growth mode of film. On polycrystalline platinum metal, cobalt film grew in hemispherical shape (nodule) where it grew in right conical shape on amorphous glass carbon. In NiFe alloys electrodeposition, the effects of applied current density, solution composition, substrate and solution hydrodynamics on current efficiency, film composition, crystal structure, corrosion resistant, and magnetic properties of NiFe alloys from all-chloride and citrate-sulfate-chloride bath have been studied. Citrate ions enhance the anomalous codeposition phenomena in NiFe electrodeposition. In crystal structure studies on electrodeposited. NiFe, the narrow mixed phase solid region was noted around 50% Fe. In addition, the smallest grain size were also observed in that region. In corrosion studies, the maximum corrosion resistance was observed at 50% Fe in naturally aerated 0.5 M NaCl. In Ni/Cu and Co/Cu multilayers by single bath technique, the optimum deposition potential ranges of pure copper and nickel (cobalt) were determined to minimize copper codeposition during nickel (cobalt) deposition and to minimize cobalt dissolution during copper deposition. Well defined laminated NiFe/Cu and CoFe/Cu multilayers and NiFe compositional modulated alloys (CMA) were successfully electrodeposited by utilizing flow-through electrochemical

  14. Integration of nanostructured titania into microsystems

    NASA Astrophysics Data System (ADS)

    Abu Samah, Zuruzi

    2005-07-01

    This thesis describes research on a novel process to fabricate integrated nanostructured titanic (NST) features as functional components in microsystems devices. NST features were formed by oxidizing Ti films in aqueous hydrogen peroxide followed by thermal annealing. The oxidation kinetics and properties of NST formed were investigated. The process developed is compatible with current microelectronics manufacturing practices for Si and plastic substrates. Amorphous hydrated titanic gels form when hydrogen peroxide (H2 O2) reacts with Ti. Oxidation of a blanket (unpatterned) Ti surface with hydrogen peroxide results in a titanic layer with high crack density. In this study, NST was formed by reacting pre-patterned Ti thin films with H2O2 solution. Crack elimination was achieved when exposed Ti films were below a threshold dimension. Hydrated titanic gel crystallizes into anatase after annealing at 300°C for 8 hr. Crack elimination is thought to result from stress reduction in titanic gels due to patterning. Oxidation of Ti films occurs by nucleation and growth mechanism. During growth, oxidation of Ti films with thickness 50 nm and below proceeds at a constant rate until films are fully consumed. For Ti films with thickness 100 nm or thicker oxidation rate reduces significantly after a period of growth. This reduction is attributed to a change in mechanism controlling growth of the hydrated titania gel layer. Functionality of NST formed and compatibility of the process with current microelectronics manufacturing practices were demonstrated by exploring three applications. First, a prototype conductometric gas sensor was fabricated that used micrometer-scale NST pad arrays as sensing elements. This sensor is capable of detecting hydrogen and oxygen gas at concentration of a few parts per million (ppm). Second, micrometer scale Au-NST interpenetrating network nanocomposite contacts in micro-switches were fabricated by infiltrating NST features with Au using

  15. 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.

  16. Chemical elimination of amorphous carbon on amorphous carbon nanotubes and its electrochemical performance

    NASA Astrophysics Data System (ADS)

    He, Xiaojun; Jiang, Li; Fan, Chuangang; Lei, Jiangwei; Zheng, Mingdong

    2007-04-01

    Chemical elimination of amorphous carbon on amorphous carbon nanotubes (ACNTs) was for the first time investigated by different treatment processes. Electrochemical performance of the modified ACNTs/carbon paste electrode (ACNTs/CPE) was measured by cyclic voltammetry. Field emission scanning and transmission electron microscope (STEM) observation reveals that the diameter of ACNTs is in the range of 60-100 nm. The amorphous nature of ACNTs was proved by the result of Raman analysis. FT-IR spectra showed that it might be one of the low-cost ways to eliminate amorphous carbon on the surface of ACNTs to treat ACNTs with HNO 3 in microwave oven. Further oxidation in air would lead to the decrease of electron transfer rate on the ACNTs/CPE because OH groups on the wall of ACNTs were partly eliminated by oxidation in air. The results of cyclic voltammetry showed that ACNTs/CPE treated with HNO 3 in microwave oven has optimal peak in relation to the highest redox peak current.

  17. Local probing of structure and property in dimensionally confined amorphous and crystalline structures by S/TEM

    NASA Astrophysics Data System (ADS)

    Yan, Aiming

    The characterization of materials' microstructure has been brought up to a new level since the invention and broad application of transmission electron microscope (TEM) thanks to the high-energy electron beam source which guarantees an unsurpassable spatial resolution and theoretical study of interaction between electron and matter. The advent of nano-world has imposed an urgent request to characterize nano-assemblies in nano- or even sub-nano-scale and scanning transmission electron microscopy (STEM) which typically utilizes an electron probe with a size of 1nm or even smaller has found its unique advantage to unravel the local structure, chemical and physical properties of these emerging nanostructures. Dimensionally constrained nanostructures such as thin films and nanopatterned systems have attracted people's attention for decades due to their novel chemical and physical properties and popularity in energy storage, biological integration and etc. This dissertation focuses on the unique characterization capability of S/TEM to study the local order in amorphous transparent conducting oxide thin films, disordering in 2-D layered materials, localized surface plasmons in nanoporous gold patterns on 2-D layered structures and crystallization process in dimensionally and spatially constrained oxide nanopatterns observed by in-situ TEM. Electron diffraction and x-ray diffraction are commonly used techniques to study the crystallinity in a certain material - crystalline or amorphous. In amorphous materials which lack long-range order, normal electron diffraction and x-ray diffraction techniques won't be able to extract any useful information regarding the ordering or disordering in the materials. We have developed a unique set of electron diffraction methods in both TEM and STEM, combined with density functional theory molecular dynamics of liquid quench to study the short-range (< 1 nm) and medium-range order (between 1 nm and 3 nm) in amorphous transparent oxide films

  18. Dielectric nanostructures with high laser damage threshold

    NASA Astrophysics Data System (ADS)

    Ngo, C. Y.; Hong, L. Y.; Deng, J.; Khoo, E. H.; Liu, Z.; Wu, R. F.; Teng, J. H.

    2017-02-01

    Dielectric-based metamaterials are proposed to be the ideal candidates for low-loss, high-efficiency devices. However, to employ dielectric nanostructures for high-power applications, the dielectric material must have a high laser-induced damaged threshold (LIDT) value. In this work, we investigated the LIDT values of dielectric nanostructures for high-power fiber laser applications. Consequently, we found that the fabricated SiO2 nanostructured lens can withstand laser fluence exceeding 100 J/cm2.

  19. Nanostructured conducting polymers and their biomedical applications.

    PubMed

    Wang, G W; Lu, Y N; Wang, L P; Wang, H J; Wang, J Y

    2014-01-01

    Much attention has been paid to nanostructured conducting polymers due to their unique properties, which arise from their nanoscale size, such as their large surface area, high electrical conductivity, electrochemical stability and quantum effects. This article reviews three methods to synthesize nanostructured conducting polymers and their applications in the biomedical field, focusing specifically on neural probes, biosensors, artificial muscles or actuators and controlled drug release. Challenges and future directions of these nanostructured conducting polymer are also discussed.

  20. Sintering and ripening resistant noble metal nanostructures

    DOEpatents

    van Swol, Frank B; Song, Yujiang; Shelnutt, John A; Miller, James E; Challa, Sivakumar R

    2013-09-24

    Durable porous metal nanostructures comprising thin metal nanosheets that are metastable under some conditions that commonly produce rapid reduction in surface area due to sintering and/or Ostwald ripening. The invention further comprises the method for making such durable porous metal nanostructures. Durable, high-surface area nanostructures result from the formation of persistent durable holes or pores in metal nanosheets formed from dendritic nanosheets.

  1. Synthesis, characterization, and properties of low-dimensional nanostructured materials

    NASA Astrophysics Data System (ADS)

    Hu, Xianluo

    2007-05-01

    Nanometer scale structures represent an exciting and rapidly expanding area of research. Studies on new physical/chemical properties and applications of nanomaterials and nanostructures are possible only when nanostructured materials are made available with desired size, morphology, crystal and microstructure, and composition. Thus, controlled synthesis of nanomaterials is the essential aspect of nanotechnology. This thesis describes the development of simple and versatile solution-based approaches to synthesize low-dimensional nanostructures. The first major goal of this research is to design and fabricate morphology-controlled alpha-Fe 2O3 nanoarchitectures in aqueous solution through a programmed microwave-assisted hydrothermal route, taking advantage of microwave irradiation and hydrothermal effects. Free-standing alpha-Fe2O3 nanorings are prepared by hydrolysis of FeCl3 in the presence of phosphate ions. The as-formed architecture of alpha-Fe2O 3 nanorings is an exciting new member in the family of iron oxide nanostructures. Our preliminary results demonstrate that sensors made of the alpha-Fe 2O3 nanorings exhibit high sensitivity not only for bio-sensing of hydrogen peroxide in a physiological solution but also for gas-sensing of alcohol vapor at room temperature. Moreover, monodisperse alpha-Fe 2O3 nanocrystals with continuous aspect-ratio tuning and fine shape control are achieved by controlling the experimental conditions. The as-formed alpha-Fe2O3 exhibits shape-dependent infrared optical properties. The growth process of colloidal alpha-Fe 2O3 crystals in the presence of phosphate ions is discussed. In addition, through an efficient microwave-assisted hydrothermal process, self-assembled hierarchical alpha-Fe2O3 nanoarchitectures are synthesized on a large scale. The second major goal of this research is to develop convenient microwave-hydrothermal approaches for the fabrication of carbon-based nanocomposites: (1) A one-pot solution-phase route, namely

  2. Optical properties of chiral nanostructures

    NASA Astrophysics Data System (ADS)

    Cecilia, Noguez; Román-Velázquez, Carlos E.; Garzón, Ignacio L.

    2004-03-01

    We present a computational model to study the optical properties chiral nanostructures[1] . In this work the nanostructures of interest are composed by N atoms, where each one is represented by a polarizable point dipole located at theposition of the atom. We assume that the dipole located is characterized by a polarizability. The nanostructure is excited by a circularly polarized incident wave, such that, each dipole is subject to a total electric field due to: (i) the incident radiation field, plus (ii) the radiation field resulting from all of the other induced dipoles. Once we solve the complex-linear equations, the dipole moment on each atom in the cluster can be determined and we can find the extinction cross section of the whole nanoparticle. Circular dichroism (CD) spectra of chiral bare and thiol-passivated gold nanoclusters have been calculated within the dipole approximation. The calculated CD spectra show features that allow us to distinguish between clusters with different indexes of chirality. The main factor responsible of the differences in the CD lineshapes is the distribution of interatomic distances that characterize the chiral cluster geometry. These results provide theoretical support for the quantification of chirality and its measurement, using the CD lineshapes of chiral metal nanoclusters. [1] C. E. Roman-Velazquez, et al., J. of Phys. Chem. B (Letter) 107, 12035 (2003) This work has been partly supported by DGAPA-UNAM grants No. IN104201 and IN104402, and by CONACyT grant 36651-E.

  3. Photoinduced magnetic force between nanostructures

    NASA Astrophysics Data System (ADS)

    Guclu, Caner; Tamma, Venkata Ananth; Wickramasinghe, Hemantha Kumar; Capolino, Filippo

    2015-12-01

    Photoinduced magnetic force between nanostructures, at optical frequencies, is investigated theoretically. Till now optical magnetic effects were not used in scanning probe microscopy because of the vanishing natural magnetism with increasing frequency. On the other hand, artificial magnetism in engineered nanostructures led to the development of measurable optical magnetism. Here two examples of nanoprobes that are able to generate strong magnetic dipolar fields at optical frequency are investigated: first, an ideal magnetically polarizable nanosphere and then a circular cluster of silver nanospheres that has a looplike collective plasmonic resonance equivalent to a magnetic dipole. Magnetic forces are evaluated based on nanostructure polarizabilities, i.e., induced magnetic dipoles, and magnetic-near field evaluations. As an initial assessment on the possibility of a magnetic nanoprobe to detect magnetic forces, we consider two identical magnetically polarizable nanoprobes and observe magnetic forces on the order of piconewtons, thereby bringing it within detection limits of conventional atomic force microscopes at ambient pressure and temperature. The detection of magnetic force is a promising method in studying optical magnetic transitions that can be the basis of innovative spectroscopy applications.

  4. Physical electrochemistry of nanostructured devices.

    PubMed

    Bisquert, Juan

    2008-01-07

    This Perspective reviews recent developments in experimental techniques and conceptual methods applied to the electrochemical properties of metal-oxide semiconductor nanostructures and organic conductors, such as those used in dye-sensitized solar cells, high-energy batteries, sensors, and electrochromic devices. The aim is to provide a broad view of the interpretation of electrochemical and optoelectrical measurements for semiconductor nanostructures (sintered colloidal particles, nanorods, arrays of quantum dots, etc.) deposited or grown on a conducting substrate. The Fermi level displacement by potentiostatic control causes a broad change of physical properties such as the hopping conductivity, that can be investigated over a very large variation of electron density. In contrast to traditional electrochemistry, we emphasize that in nanostructured devices we must deal with systems that depart heavily from the ideal, Maxwell-Boltzmann statistics, due to broad distributions of states (energy disorder) and interactions of charge carriers, therefore the electrochemical analysis must be aided by thermodynamics and statistical mechanics. We discuss in detail the most characteristic densities of states, the chemical capacitance, and the transport properties, specially the chemical diffusion coefficient, mobility, and generalized Einstein relation.

  5. Biological insertion of nanostructured germanium and titanium oxides into diatom biosilica

    NASA Astrophysics Data System (ADS)

    Jeffryes, Clayton S.

    There is significant interest in titanium oxide and germanium-silicon oxide nanocomposites for optoelectronic, photocatalytic, and solar cell applications. The ability of the marine diatom Pinnularia sp. to uptake soluble metal oxides from cell culture medium, and incorporate them into the micro- and nano-structure of their amorphous silica cell walls, called frustules, was evaluated using an engineered photobioreactor system. The effects of metal oxides on the structural and elemental properties of the frustule were also evaluated. Diatom cell cultures grown in 5 L photobioreactors were initially charged with 0.5 mM of soluble silicon, Si(OH)4, an obligate substrate required for frustule fomation. Upon exhaustion of Si(OH)4 cells were exposed to the mixed pulse-addition of soluble silicon and germanium or co-perfusion addition of soluble silicon and titanium, which were incorporated into the frustules. Metals composition of the cell culture medium, diatom biomass and purified frustules were measured, as was the local elemental composition within the frustule pores and the metal oxide crystallinity. Diatom frustules having a germanium composition of 1.6 wt % were devoid of the native intra-pore structures and possessed enhanced photoluminescence and electroluminescence when compared to frustules without Ge. Diatoms cultivated in the presence of soluble titanium incorporated amorphous titania into the frustule, which maintained native structure even when local TiO2 concentrations within the nanopores approached 60 wt. %. Titanium oxide could also be biomimetically deposited directly within the diatom nanopores by adsorbing poly-L-lysine to the diatom biosilica where it catalyzed the soluble titanium precursor Ti-BALDH into amorphous titania nanoparticles. Both biogenic and biomimetic titania could be converted to anatase titanium by thermal annealing. It was determined that nanostructured metal oxide composites can be fabricated biomimetically or in cell culture to

  6. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    NASA Astrophysics Data System (ADS)

    Abdulraheem, Yaser; Gordon, Ivan; Bearda, Twan; Meddeb, Hosny; Poortmans, Jozef

    2014-05-01

    An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H) layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si) wafers by plasma enhanced chemical vapor deposition (PECVD). The layer thicknesses along with their optical properties -including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE) in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc) bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause of the observed

  7. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    SciTech Connect

    Abdulraheem, Yaser; Gordon, Ivan; Bearda, Twan; Meddeb, Hosny; Poortmans, Jozef

    2014-05-15

    An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H) layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si) wafers by plasma enhanced chemical vapor deposition (PECVD). The layer thicknesses along with their optical properties –including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE) in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc) bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause of the observed

  8. Quantum confinement in Si and Ge nanostructures: effect of crystallinity

    NASA Astrophysics Data System (ADS)

    Barbagiovanni, Eric G.; Lockwood, David J.; Costa Filho, Raimundo N.; Goncharova, Lyudmila V.; Simpson, Peter J.

    2013-10-01

    We look at the relationship between the preparation method of Si and Ge nanostructures (NSs) and the structural, electronic, and optical properties in terms of quantum confinement (QC). QC in NSs causes a blue shift of the gap energy with decreasing NS dimension. Directly measuring the effect of QC is complicated by additional parameters, such as stress, interface and defect states. In addition, differences in NS preparation lead to differences in the relevant parameter set. A relatively simple model of QC, using a `particle-in-a-box'-type perturbation to the effective mass theory, was applied to Si and Ge quantum wells, wires and dots across a variety of preparation methods. The choice of the model was made in order to distinguish contributions that are solely due to the effects of QC, where the only varied experimental parameter was the crystallinity. It was found that the hole becomes de-localized in the case of amorphous materials, which leads to stronger confinement effects. The origin of this result was partly attributed to differences in the effective mass between the amorphous and crystalline NS as well as between the electron and hole. Corrections to our QC model take into account a position dependent effective mass. This term includes an inverse length scale dependent on the displacement from the origin. Thus, when the deBroglie wavelength or the Bohr radius of the carriers is on the order of the dimension of the NS the carriers `feel' the confinement potential altering their effective mass. Furthermore, it was found that certain interface states (Si-O-Si) act to pin the hole state, thus reducing the oscillator strength.

  9. Precise replication of antireflective nanostructures from biotemplates

    NASA Astrophysics Data System (ADS)

    Gao, Hongjun; Liu, Zhongfan; Zhang, Jin; Zhang, Guoming; Xie, Guoyong

    2007-03-01

    The authors report herein a new type of nanonipple structures on the cicada's eye and the direct structural replication of the complex micro- and nanostructures for potential functional emulation. A two-step direct molding process is developed to replicate these natural micro- and nanostructures using epoxy resin with high fidelity, which demonstrates a general way of fabricating functional nanostructures by direct replication of natural biotemplates via a suitable physicochemical process. Measurements of spectral reflectance showed that this kind of replicated nanostructure has remarkable antireflective property, suggestive of its potential applications to optical devices.

  10. Particle Lithography Enables Fabrication of Multicomponent Nanostructures

    PubMed Central

    Lin, Wei-feng; Swartz, Logan A.; Li, Jie-Ren; Liu, Yang; Liu, Gang-yu

    2014-01-01

    Multicomponent nanostructures with individual geometries have attracted much attention because of their potential to carry out multiple functions synergistically. The current work reports a simple method using particle lithography to fabricate multicomponent nanostructures of metals, proteins, and organosiloxane molecules, each with its own geometry. Particle lithography is well-known for its capability to produce arrays of triangular-shaped nanostructures with novel optical properties. This paper extends the capability of particle lithography by combining a particle template in conjunction with surface chemistry to produce multicomponent nanostructures. The advantages and limitations of this approach will also be addressed. PMID:24707328

  11. Processing Nanostructured Sensors Using Microfabrication Techniques

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; VanderWal, Randall L.; Evans, Laura J.; Xu, Jennifer C.

    2010-01-01

    Standard microfabrication techniques can be implemented and scaled to help assemble nanoscale microsensors. Currently nanostructures are often deposited onto materials primarily by adding them to a solution, then applying the solution in a thin film. This results in random placement of the nanostructures with no controlled order, and no way to accurately reproduce the placement. This method changes the means by which microsensors with nanostructures are fabricated. The fundamental advantage to this approach is that it enables standard microfabrication techniques to be applied in the repeated manufacture of nanostructured sensors on a microplatform.

  12. Is there a shift to "active nanostructures"?

    NASA Astrophysics Data System (ADS)

    Subramanian, Vrishali; Youtie, Jan; Porter, Alan L.; Shapira, Philip

    2010-01-01

    It has been suggested that an important transition in the long-run trajectory of nanotechnology development is a shift from passive to active nanostructures. Such a shift could present different or increased societal impacts and require new approaches for risk assessment. An active nanostructure "changes or evolves its state during its operation," according to the National Science Foundation's (2006) Active Nanostructures and Nanosystems grant solicitation. Active nanostructure examples include nanoelectromechanical systems (NEMS), nanomachines, self-healing materials, targeted drugs and chemicals, energy storage devices, and sensors. This article considers two questions: (a) Is there a "shift" to active nanostructures? (b) How can we characterize the prototypical areas into which active nanostructures may emerge? We build upon the NSF definition of active nanostructures to develop a research publication search strategy, with a particular intent to distinguish between passive and active nanotechnologies. We perform bibliometric analyses and describe the main publication trends from 1995 to 2008. We then describe the prototypes of research that emerge based on reading the abstracts and review papers encountered in our search. Preliminary results suggest that there is a sharp rise in active nanostructures publications in 2006, and this rise is maintained in 2007 and through to early 2008. We present a typology that can be used to describe the kind of active nanostructures that may be commercialized and regulated in the future.

  13. Anchored nanostructure materials and method of fabrication

    DOEpatents

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2012-11-27

    Anchored nanostructure materials and methods for their fabrication are described. The anchored nanostructure materials may utilize nano-catalysts that include powder-based or solid-based support materials. The support material may comprise metal, such as NiAl, ceramic, a cermet, or silicon or other metalloid. Typically, nanoparticles are disposed adjacent a surface of the support material. Nanostructures may be formed as anchored to nanoparticles that are adjacent the surface of the support material by heating the nano-catalysts and then exposing the nano-catalysts to an organic vapor. The nanostructures are typically single wall or multi-wall carbon nanotubes.

  14. Synthesis of Silver Nanostructures by Multistep Methods

    PubMed Central

    Zhang, Tong; Song, Yuan-Jun; Zhang, Xiao-Yang; Wu, Jing-Yuan

    2014-01-01

    The shape of plasmonic nanostructures such as silver and gold is vital to their physical and chemical properties and potential applications. Recently, preparation of complex nanostructures with rich function by chemical multistep methods is the hotspot of research. In this review we introduce three typical multistep methods to prepare silver nanostructures with well-controlled shapes, including the double reductant method, etching technique and construction of core-shell nanostructures. The growth mechanism of double the reductant method is that different favorable facets of silver nanocrystals are produced in different reductants, which can be used to prepare complex nanostructures such as nanoflags with ultranarrow resonant band bandwidth or some silver nanostructures which are difficult to prepare using other methods. The etching technique can selectively remove nanoparticles to achieve the aim of shape control and is widely used for the synthesis of nanoflowers and hollow nanostructures. Construction of core-shell nanostructures is another tool to control shape and size. The three methods can not only prepare various silver nanostructures with well-controlled shapes, which exhibit unique optical properties, such as strong surface-enhanced Raman scattering (SERS) signal and localized surface plasmon resonance (LSPR) effect, but also have potential application in many areas. PMID:24670722

  15. Synthesis, electronic and optical properties of Si nanostructures

    SciTech Connect

    Dinh, L.N.

    1996-09-01

    Silicon and silicon oxide nanostructures have been deposited on solid substrates, in an ultra high vacuum (UHV) chamber, by laser ablation or thermal vaporization. Laser ablation followed by substrate post annealing produced Si clusters with average size of a few nanometers, on highly oriented pyrolytic graphite (HOPG) surfaces. This technique, which is based on surface diffusion, is limited to the production of less than one layer of clusters on a given surface. The low coverage of Si clusters and the possibility of nonradiative decay of excitation in the Si cores to the HOPG substrates in these samples rendered them unsuitable for many optical measurements. Thermal vaporization of Si in an Ar buffer gas, on the contrary, yielded multilayer coverage of Si nanoclusters with a fairly narrow size distribution of about 2 nm, full width at half maximum (FWHM). As a result, further study was performed only on Si nanoclusters synthesized by thermal vaporization in a buffer gas. High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) revealed that these nanoclusters were crystalline. However, during synthesis, if oxygen was the buffer gas, a network of amorphous Si oxide nanostructures (an-SiO{sub x}) with occasional embedded Si dots was formed. All samples showed strong infrared and/or visible photoluminescence (PL) with varying decay times from nanoseconds to microseconds depending on synthesis conditions. There were differences in PL spectra for hydrogen and oxygen passivated nc-Si, while many common PL properties between oxygen passivated nc-Si and an SiO{sub x} were observed. The observed experimental results can be best explained by a model involving absorption between quantum confined states in the Si cores and emission for which the decay times are very sensitive to surface and/or interface states.

  16. The structure, conductive properties, and reflective properties of amorphous granulated (Co45Fe45Zr10) x (ZrO)1 - x composite films

    NASA Astrophysics Data System (ADS)

    Antonets, I. V.; Kotov, L. N.; Golubev, E. A.; Kalinin, Yu. E.; Sitnikov, A. V.

    2017-02-01

    The micro- and nanostructure of 328-772-nm-thick amorphous granulated (Co45Fe45Zr10) x (ZrO)1 - x (0.27 < x < 0.61) composite films deposited in argon on a lavsan substrate has been examined using atomic force microscopy, magnetic force microscopy, and scanning electron microscopy. It has been shown that the mean sizes of the grain and the metallic phase content govern the conductive and reflective properties of the films in the microwave range.

  17. Bottom-up multiferroic nanostructures

    NASA Astrophysics Data System (ADS)

    Ren, Shenqiang

    Multiferroic and especially magnetoelectric (ME) nanocomposites have received extensive attention due to their potential applications in spintronics, information storage and logic devices. The extrinsic ME coupling in composites is strain mediated via the interface between the piezoelectric and magnetostrictive components. However, the design and synthesis of controlled nanostructures with engineering enhanced coupling remain a significant challenge. The purpose of this thesis is to create nanostructures with very large interface densities and unique connectivities of the two phases in a controlled manner. Using inorganic solid state phase transformations and organic block copolymer self assembly methodologies, we present novel self assembly "bottom-up" techniques as a general protocol for the nanofabrication of multifunctional devices. First, Lead-Zirconium-Titanate/Nickel-Ferrite (PZT/NFO) vertical multilamellar nanostructures have been produced by crystallizing and decomposing a gel in a magnetic field below the Curie temperature of NFO. The ensuing microstructure is nanoscopically periodic and anisotropic. The wavelength of the PZT/NFO alternation, 25 nm, agrees within a factor of two with the theoretically estimated value. The macroscopic ferromagnetic and magnetoelectric responses correspond qualitatively and semi-quantitatively to the features of the nanostructure. The maximum of the field dependent magnetoelectric susceptibility equals 1.8 V/cm Oe. Second, a magnetoelectric composite with controlled nanostructures is synthesized using co-assembly of two inorganic precursors with a block copolymer. This solution processed material consists of hexagonally arranged ferromagnetic cobalt ferrite (CFO) nano-cylinders within a matrix of ferroelectric Lead-Zirconium-Titanate (PZT). The initial magnetic permeability of the self-assembled CFO/PZT nanocomposite changes by a factor of 5 through the application of 2.5 V. This work may have significant impact on the

  18. Emergent interparticle interactions in thermal amorphous solids

    NASA Astrophysics Data System (ADS)

    Gendelman, Oleg; Lerner, Edan; Pollack, Yoav G.; Procaccia, Itamar; Rainone, Corrado; Riechers, Birte

    2016-11-01

    Amorphous media at finite temperatures, be them liquids, colloids, or glasses, are made of interacting particles that move chaotically due to thermal energy, continuously colliding and scattering off each other. When the average configuration in these systems relaxes only at long times, one can introduce effective interactions that keep the mean positions in mechanical equilibrium. We introduce a framework to determine the effective force laws that define an effective Hessian that can be employed to discuss stability properties and the density of states of the amorphous system. We exemplify the approach with a thermal glass of hard spheres; these experience zero forces when not in contact and infinite forces when they touch. Close to jamming we recapture the effective interactions that at temperature T depend on the gap h between spheres as T /h [C. Brito and M. Wyart, Europhys. Lett. 76, 149 (2006), 10.1209/epl/i2006-10238-x]. For hard spheres at lower densities or for systems whose binary bare interactions are longer ranged (at any density), the emergent force laws include ternary, quaternary, and generally higher-order many-body terms, leading to a temperature-dependent effective Hessian.

  19. The future of amorphous silicon photovoltaic technology

    SciTech Connect

    Crandall, R; Luft, W

    1995-06-01

    Amorphous silicon modules are commercially available. They are the first truly commercial thin-film photovoltaic (PV) devices. Well-defined production processes over very large areas (>1 m{sup 2}) have been implemented. There are few environmental issues during manufacturing, deployment in the field, or with the eventual disposal of the modules. Manufacturing safety issues are well characterized and controllable. The highest measured initial efficiency to date is 13.7% for a small triple-stacked cell and the highest stabilized module efficiency is 10%. There is a consensus among researchers, that in order to achieve a 15% stabilized efficiency, a triple-junction amorphous silicon structure is required. Fundamental improvements in alloys are needed for higher efficiencies. This is being pursued through the DOE/NREL Thin-Film Partnership Program. Cost reductions through improved manufacturing processes are being pursued under the National Renewable Energy Laboratory/US Department of Energy (NREL/DOE)-sponsored research in manufacturing technology (PVMaT). Much of the work in designing a-Si devices is a result of trying to compensate for the Staebler-Wronski effect. Some new deposition techniques hold promise because they have produced materials with lower stabilized defect densities. However, none has yet produced a high efficiency device and shown it to be more stable than those from standard glow discharge deposited material.

  20. Anisotropic mechanical amorphization drives wear in diamond

    NASA Astrophysics Data System (ADS)

    Pastewka, Lars; Moser, Stefan; Gumbsch, Peter; Moseler, Michael

    2011-01-01

    Diamond is the hardest material on Earth. Nevertheless, polishing diamond is possible with a process that has remained unaltered for centuries and is still used for jewellery and coatings: the diamond is pressed against a rotating disc with embedded diamond grit. When polishing polycrystalline diamond, surface topographies become non-uniform because wear rates depend on crystal orientations. This anisotropy is not fully understood and impedes diamond’s widespread use in applications that require planar polycrystalline films, ranging from cutting tools to confinement fusion. Here, we use molecular dynamics to show that polished diamond undergoes an sp3-sp2 order-disorder transition resulting in an amorphous adlayer with a growth rate that strongly depends on surface orientation and sliding direction, in excellent correlation with experimental wear rates. This anisotropy originates in mechanically steered dissociation of individual crystal bonds. Similarly to other planarization processes, the diamond surface is chemically activated by mechanical means. Final removal of the amorphous interlayer proceeds either mechanically or through etching by ambient oxygen.

  1. Anisotropic mechanical amorphization drives wear in diamond.

    PubMed

    Pastewka, Lars; Moser, Stefan; Gumbsch, Peter; Moseler, Michael

    2011-01-01

    Diamond is the hardest material on Earth. Nevertheless, polishing diamond is possible with a process that has remained unaltered for centuries and is still used for jewellery and coatings: the diamond is pressed against a rotating disc with embedded diamond grit. When polishing polycrystalline diamond, surface topographies become non-uniform because wear rates depend on crystal orientations. This anisotropy is not fully understood and impedes diamond's widespread use in applications that require planar polycrystalline films, ranging from cutting tools to confinement fusion. Here, we use molecular dynamics to show that polished diamond undergoes an sp(3)-sp(2) order-disorder transition resulting in an amorphous adlayer with a growth rate that strongly depends on surface orientation and sliding direction, in excellent correlation with experimental wear rates. This anisotropy originates in mechanically steered dissociation of individual crystal bonds. Similarly to other planarization processes, the diamond surface is chemically activated by mechanical means. Final removal of the amorphous interlayer proceeds either mechanically or through etching by ambient oxygen.

  2. Structural Characteristics of Synthetic Amorphous Calcium Carbonate

    SciTech Connect

    Michel, F. Marc; MacDonald, Jason; Feng, Jian; Phillips, Brian L.; Ehm, Lars; Tarabrella, Cathy; Parise, John B.; Reeder, Richard J.

    2008-08-06

    Amorphous calcium carbonate (ACC) is an important phase involved in calcification by a wide variety of invertebrate organisms and is of technological interest in the development of functional materials. Despite widespread scientific interest in this phase a full characterization of structure is lacking. This is mainly due to its metastability and difficulties in evaluating structure using conventional structure determination methods. Here we present new findings from the application of two techniques, pair distribution function analysis and nuclear magnetic resonance spectroscopy, which provide new insight to structural aspects of synthetic ACC. Several important results have emerged from this study of ACC formed in vitro using two common preparation methods: (1) ACC exhibits no structural coherence over distances > 15 {angstrom} and is truly amorphous; (2) most of the hydrogen in ACC is present as structural H{sub 2}O, about half of which undergoes restricted motion on the millisecond time scale near room temperature; (3) the short- and intermediate-range structure of ACC shows no distinct match to any known structure in the calcium carbonate system; and (4) most of the carbonate in ACC is monodentate making it distinctly different from monohydrocalcite. Although the structure of synthetic ACC is still not fully understood, the results presented provide an important baseline for future experiments evaluating biogenic ACC and samples containing certain additives that may play a role in stabilization of ACC, crystallization kinetics, and final polymorph selection.

  3. Cryoflotation: densities of amorphous and crystalline ices.

    PubMed

    Loerting, Thomas; Bauer, Marion; Kohl, Ingrid; Watschinger, Katrin; Winkel, Katrin; Mayer, Erwin

    2011-12-08

    We present an experimental method aimed at measuring mass densities of solids at ambient pressure. The principle of the method is flotation in a mixture of liquid nitrogen and liquid argon, where the mixing ratio is varied until the solid hovers in the liquid mixture. The temperature of such mixtures is in the range of 77-87 K, and therefore, the main advantage of the method is the possibility of determining densities of solid samples, which are instable above 90 K. The accessible density range (~0.81-1.40 g cm(-3)) is perfectly suitable for the study of crystalline ice polymorphs and amorphous ices. As a benchmark, we here determine densities of crystalline polymorphs (ices I(h), I(c), II, IV, V, VI, IX, and XII) by flotation and compare them with crystallographic densities. The reproducibility of the method is about ±0.005 g cm(-3), and in general, the agreement with crystallographic densities is very good. Furthermore, we show measurements on a range of amorphous ice samples and correlate the density with the d spacing of the first broad halo peak in diffraction experiments. Finally, we discuss the influence of microstructure, in particular voids, on the density for the case of hyperquenched glassy water and cubic ice samples prepared by deposition of micrometer-sized liquid droplets.

  4. Photoswitching and Thermoresponsive Properties of Conjugated Multi-chromophore Nanostructured Materials.

    PubMed

    Bhattacharyya, Santanu; Jana, Bikash; Sain, Sumanta; Barman, Monoj Kumar; Pradhan, Swapan Kumar; Patra, Amitava

    2015-12-16

    Conjugated multi-chromophore organic nanostructured materials have recently emerged as a new class of functional materials for developing efficient light-harvesting, photosensitization, photocatalysis, and sensor devices because of their unique photophysical and photochemical properties. Here, we demonstrate the formation of various nanostructures (fibers and flakes) related to the molecular arrangement (H-aggregation) of quaterthiophene (QTH) molecules and their influence on the photophysical properties. XRD studies confirm that the fiber structure consists of >95% crystalline material, whereas the flake structure is almost completely amorphous and the microstrain in flake-shaped QTH is significantly higher than that of QTH in solution. The influence of the aggregation of the QTH molecules on their photoswitching and thermoresponsive photoluminescence properties is revealed. Time-resolved anisotropic studies further unveil the relaxation dynamics and restricted chromophore properties of the self-assembled nano/microstructured morphologies. Further investigations should pave the way for the future development of organic electronics, photovoltaics, and light-harvesting systems based on π-conjugated multi-chromophore organic nanostructured materials.

  5. UV-black rutile TiO{sub 2}: An antireflective photocatalytic nanostructure

    SciTech Connect

    Sanz, Ruy Zimbone, Massimo; Buccheri, Maria Antonietta; Scuderi, Viviana; Impellizzeri, Giuliana; Privitera, Vittorio; Romano, Lucia; Scuderi, Mario; Nicotra, Giuseppe; Jensen, Jens

    2015-02-21

    This work presents an experimental study on the specific quantitative contributions of antireflective and effective surface areas on the photocatalytic and antibacterial properties of rutile TiO{sub 2} nanospikes. They are studied when continuously distributed over the whole surface and when integrated into well-defined microstructures. The nanospikes were produced following MeV ion beam irradiation of bulk rutile TiO{sub 2} single crystals and subsequent chemical etching. The ion beam irradiation generated embedded isolated crystalline nanoparticles inside an etchable amorphous TiO{sub 2} layer, and nanospikes fixed to the not etchable TiO{sub 2} bulk substrate. The produced nanospikes are shown to resist towards aggressive chemical environments and act as an efficient UV antireflective surface. The photocatalytic activity experiments were performed under the ISO 10678:2010 protocol. The photonic and quantum efficiency are reported for the studied samples. The combined micro- and nanostructured surface triples the photonic efficiency compared to the initial flat surface. Results also revealed that the antireflective effect, due to the nanostructuring, is the dominating factor compared to the increase of surface area, for the observed photocatalytic response. The obtained results may be taken as a general strategy to design and precisely evaluate photoactive nanostructures.

  6. CORROSION STUDY OF AMORPHOUS METAL RIBBONS

    SciTech Connect

    Lian, T; Day, S D; Farmer, J C

    2006-07-31

    Corrosion costs the Department of Defense billions of dollars every year, with an immense quantity of material in various structures undergoing corrosion. For example, in addition to fluid and seawater piping, ballast tanks, and propulsions systems, approximately 345 million square feet of structure aboard naval ships and crafts require costly corrosion control measures. The use of advanced corrosion-resistant materials to prevent the continuous degradation of this massive surface area would be extremely beneficial. The potential advantages of amorphous metals have been recognized for some time [Latanison 1985]. Iron-based corrosion-resistant, amorphous-metal coatings under development may prove important for maritime applications [Farmer et al. 2005]. Such materials could also be used to coat the entire outer surface of containers for the transportation and long-term storage of spent nuclear fuel, or to protect welds and heat affected zones, thereby preventing exposure to environments that might cause stress corrosion cracking [Farmer et al. 1991, 2000a, 2000b]. In the future, it may be possible to substitute such high-performance iron-based materials for more-expensive nickel-based alloys, thereby enabling cost savings in a wide variety of industrial applications. It should be noted that thermal-spray ceramic coatings have also been investigated for such applications [Haslam et al. 2005]. This report focuses on the corrosion resistance of iron-based melt-spun amorphous metal ribbons. Melt-Spun ribbon is made by rapid solidification--a stream of molten metal is dropped onto a spinning copper wheel, a process that enables the manufacture of amorphous metals which are unable to be manufactured by conventional cold or hot rolling techniques. The study of melt-spun ribbon allows quick evaluation of amorphous metals corrosion resistance. The melt-spun ribbons included in this study are DAR40, SAM7, and SAM8, SAM1X series, and SAM2X series. The SAM1X series ribbons have

  7. Modeling energy transport in nanostructures

    NASA Astrophysics Data System (ADS)

    Pattamatta, Arvind

    Heat transfer in nanostructures differ significantly from that in the bulk materials since the characteristic length scales associated with heat carriers, i.e., the mean free path and the wavelength, are comparable to the characteristic length of the nanostructures. Nanostructure materials hold the promise of novel phenomena, properties, and functions in the areas of thermal management and energy conversion. Example of thermal management in micro/nano electronic devices is the use of efficient nanostructured materials to alleviate 'hot spots' in integrated circuits. Examples in the manipulation of heat flow and energy conversion include nanostructures for thermoelectric energy conversion, thermophotovoltaic power generation, and data storage. One of the major challenges in Metal-Oxide Field Effect Transistor (MOSFET) devices is to study the 'hot spot' generation by accurately modeling the carrier-optical phonon-acoustic phonon interactions. Prediction of hotspot temperature and position in MOSFET devices is necessary for improving thermal design and reliability of micro/nano electronic devices. Thermoelectric properties are among the properties that may drastically change at nanoscale. The efficiency of thermoelectric energy conversion in a material is measured by a non-dimensional figure of merit (ZT) defined as, ZT = sigmaS2T/k where sigma is the electrical conductivity, S is the Seebeck coefficient, T is the temperature, and k is the thermal conductivity. During the last decade, advances have been made in increasing ZT using nanostructures. Three important topics are studied with respect to energy transport in nanostructure materials for micro/nano electronic and thermoelectric applications; (1) the role of nanocomposites in improving the thermal efficiency of thermoelectric devices, (2) the interfacial thermal resistance for the semiconductor/metal contacts in thermoelectric devices and for metallic interconnects in micro/nano electronic devices, (3) the

  8. Nanoparticle Decorated Ultrathin Porous Nanosheets as Hierarchical Co3O4 Nanostructures for Lithium Ion Battery Anode Materials

    PubMed Central

    Mujtaba, Jawayria; Sun, Hongyu; Huang, Guoyong; Mølhave, Kristian; Liu, Yanguo; Zhao, Yanyan; Wang, Xun; Xu, Shengming; Zhu, Jing

    2016-01-01

    We report a facile synthesis of a novel cobalt oxide (Co3O4) hierarchical nanostructure, in which crystalline core-amorphous shell Co3O4 nanoparticles with a bimodal size distribution are uniformly dispersed on ultrathin Co3O4 nanosheets. When tested as anode materials for lithium ion batteries, the as-prepared Co3O4 hierarchical electrodes delivered high lithium storage properties comparing to the other Co3O4 nanostructures, including a high reversible capacity of 1053.1 mAhg−1 after 50 cycles at a current density of 0.2 C (1 C = 890 mAg−1), good cycling stability and rate capability. PMID:26846434

  9. Growth and characterization of branched carbon nanostructures arrays in nano-patterned surfaces from porous silicon substrates.

    PubMed

    Solá, Francisco; Resto, Oscar; Biaggi-Labiosa, Azlin; Fonseca, Luis F

    2009-01-01

    A method to grow branched carbon nanostructures arrays is presented. We employ the electron-beam-induced deposition method using a transmission electron microscope in poor vacuum conditions where hydrocarbons are present in the chamber. The hydrocarbons are attracted to the substrates by the local electric fields. Saw-tooth nano-patterns were made with a focused ion beam in porous silicon substrates with high porosity in order to create sites with high-local electric fields. We found that the adequate ion dose to create well-defined saw-tooth nano-patterns was between 8 and 10 nC/microm(2). Raman and electron energy-loss spectroscopy on the branched carbon nanostructures show a high concentration of sp(2) sites suggesting that they are made of graphite-like hydrogenated amorphous carbon. Selected area electron diffraction, high-resolution images and energy dispersive X-ray analysis (EDS) are also presented.

  10. Endurance Tests Of Amorphous-Silicon Photovoltaic Modules

    NASA Technical Reports Server (NTRS)

    Ross, Ronald G., Jr.; Sugimura, Russell S.

    1989-01-01

    Failure mechanisms in high-power service studied. Report discusses factors affecting endurance of amorphous-silicon solar cells. Based on field tests and accelerated aging of photovoltaic modules. Concludes that aggressive research needed if amorphous-silicon modules to attain 10-year life - value U.S. Department of Energy established as goal for photovoltaic modules in commercial energy-generating plants.

  11. Optical conductivity of amorphous Ta and beta-Ta films

    NASA Technical Reports Server (NTRS)

    Nestell, J. E., Jr.; Scoles, K. J.; Christy, R. W.

    1982-01-01

    Tantalum films evaporated in high vacuum onto liquid-nitrogen-cooled substrates had an amorphous structure that persisted even after warming to room temperature. The optical conductivity (as well as the dc conductivity) of the amorphous films differed significantly from that of the bcc films.

  12. Amorphization of SiC under ion and neutron irradiation

    NASA Astrophysics Data System (ADS)

    Snead, L. L.; Zinkle, S. J.; Hay, J. C.; Osborne, M. C.

    1998-05-01

    This paper presents results on the microstructure and physical properties of SiC amorphized by both ion and neutron irradiation. Specifically, 0.56 MeV Si ions have been implanted in single crystal 6H-SiC from ambient through >200°C and the critical threshold for amorphization was measured as a function of the irradiation temperature. From a high resolution transmission electron microscopy (HRTEM) study of the crystalline to amorphous transition region in these materials, elongated pockets of amorphous material oriented parallel to the free surface are observed. Single crystal 6H-SiC and hot pressed and sintered 6H and 3C SiC were neutron irradiated at approximately 70°C to a dose of ˜2.56 dpa causing complete amorphization. Property changes resulting from the crystal to amorphous transition in SiC include a density decrease of 10.8%, a hardness decrease from 38.7 to 21.0 GPa, and a decrease in elastic modulus from 528 to 292 GPa. Recrystallization of the amorphized, single crystal 6H-SiC appears to occur in two stages. In the temperature range of ˜800-1000°C, crystallites nucleate and slowly grow. In the temperature range of 1125-1150°C spontaneous nucleation and rapid growth of crystallites occur. It is further noted that amorphized 6H (alpha) SiC recrystallizes to highly faulted fcc (beta) SiC.

  13. Quantifying Nanoscale Order in Amorphous Materials via Fluctuation Electron Microscopy

    ERIC Educational Resources Information Center

    Bogle, Stephanie Nicole

    2009-01-01

    Fluctuation electron microscopy (FEM) has been used to study the nanoscale order in various amorphous materials. The method is explicitly sensitive to 3- and 4-body atomic correlation functions in amorphous materials; this is sufficient to establish the existence of structural order on the nanoscale, even when the radial distribution function…

  14. Addressing the amorphous content issue in quantitative phase analysis

    NASA Astrophysics Data System (ADS)

    Cline, J. P.; Dreele, R. B. Von; Winburn, R.; Stephens, P. W.; Filliben, J. J.

    2011-07-01

    A novel method is used to determine the amorphous content in the certification of NIST standard reference material (SRM) 676a (corundum). Extrapolation of diffraction measurements from mixtures with Si powders of varying surface-to-volume ratio show that approximately 1% by weight of SRM 676a is amorphous.

  15. Magnetic flux distribution in the amorphous modular transformers

    NASA Astrophysics Data System (ADS)

    Tomczuk, B.; Koteras, D.

    2011-06-01

    3D magnetic fluxes in one-phase and three-phase transformers with amorphous modular cores have been studied. Scalar potentials were implemented for the 3D Finite Element field calculation. Due to the inability to simulate each thin amorphous layer, we introduced supplementary permeabilities along the main directions of magnetization. The calculated fluxes in the cores were tested on the prototypes.

  16. Thermodynamic properties and amorphization of Zr-Si melts

    NASA Astrophysics Data System (ADS)

    Arutyunyan, N. A.; Zaitsev, A. I.; Dunaev, S. F.; Shaposhnikov, N. G.

    2016-02-01

    The relationship between the thermodynamic properties of Zr-Si liquid alloys and their propensity to amorphization is studied. The temperature-concentration dependences of the thermodynamic properties of melts are presented using the concept of associated solutions. It is shown that the range of amorphization coincides with the range of the predominant concentration of Zr3Si associative groups with low formation entropy.

  17. Superlattice doped layers for amorphous silicon photovoltaic cells

    DOEpatents

    Arya, Rajeewa R.

    1988-01-12

    Superlattice doped layers for amorphous silicon photovoltaic cells comprise a plurality of first and second lattices of amorphous silicon alternatingly formed on one another. Each of the first lattices has a first optical bandgap and each of the second lattices has a second optical bandgap different from the first optical bandgap. A method of fabricating the superlattice doped layers also is disclosed.

  18. Polarization effects in femtosecond laser induced amorphization of monocrystalline silicon

    NASA Astrophysics Data System (ADS)

    Bai, Feng; Li, Hong-Jin; Huang, Yuan-Yuan; Fan, Wen-Zhong; Pan, Huai-Hai; Wang, Zhuo; Wang, Cheng-Wei; Qian, Jing; Li, Yang-Bo; Zhao, Quan-Zhong

    2016-10-01

    We have used femtosecond laser pulses to ablate monocrystalline silicon wafer. Raman spectroscopy and X-ray diffraction analysis of ablation surface indicates horizontally polarized laser beam shows an enhancement in amorphization efficiency by a factor of 1.6-1.7 over the circularly polarized laser ablation. This demonstrates that one can tune the amorphization efficiency through the polarization of irradiation laser.

  19. Electrically conducting ternary amorphous fully oxidized materials and their application

    NASA Technical Reports Server (NTRS)

    Giauque, Pierre (Inventor); Nicolet, Marc (Inventor); Gasser, Stefan M. (Inventor); Kolawa, Elzbieta A. (Inventor); Cherry, Hillary (Inventor)

    2004-01-01

    Electrically active devices are formed using a special conducting material of the form Tm--Ox mixed with SiO2 where the materials are immiscible. The immiscible materials are forced together by using high energy process to form an amorphous phase of the two materials. The amorphous combination of the two materials is electrically conducting but forms an effective barrier.

  20. Amorphization and nanocrystallization of silcon under shock compression

    DOE PAGES

    Remington, B. A.; Wehrenberg, C. E.; Zhao, S.; ...

    2015-11-06

    High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon unveiled remarkable structural changes above a pressure threshold. Two distinct amorphous regions were identified: (a) a bulk amorphous layer close to the surface and (b) amorphous bands initially aligned with {111} slip planes. Further increase of the laser energy leads to the re-crystallization of amorphous silicon into nanocrystals with high concentration of nano-twins. This amorphization is produced by the combined effect of high magnitude hydrostatic and shear stresses under dynamic shock compression. Shock-induced defects play a very important role in the onset of amorphization. Calculations of the free energymore » changes with pressure and shear, using the Patel-Cohen methodology, are in agreement with the experimental results. Molecular dynamics simulation corroborates the amorphization, showing that it is initiated by the nucleation and propagation of partial dislocations. As a result, the nucleation of amorphization is analyzed qualitatively by classical nucleation theory.« less

  1. Tritiated amorphous silicon films and devices

    NASA Astrophysics Data System (ADS)

    Kosteski, Tome

    The do saddle-field glow discharge deposition technique has been used to bond tritium within an amorphous silicon thin film network using silane and elemental tritium in the glow discharge. The concentration of tritium is approximately 7 at. %. Minimal outgassing of tritium from tritiated hydrogenated amorphous silicon (a-Si:H:T) at room temperature suggests that tritium is bonded stably. Tritium effusion only occurred at temperatures above the film's growth temperature. The radioactive decay of tritium results in the production of high-energy beta particles. Each beta particle can generate on average approximately 1300 electron-hole pairs in a-Si:H:T. Electrical conductivity of a-Si:H:T is shown to be due to a thermally activated process and due to the generation of excess carriers by the beta particles. p-i-n betavoltaic devices have been made with a-Si:H:T in the intrinsic (i-) region. The i-region consisted of either a-Si:H:T, or a thin section of a-Si:H:T (a Delta layer) sandwiched between undoped hydrogenated amorphous silicon (a-Si:H). The excess carriers generated in the i-region are separated by the device's built-in electric field. Short-circuit currents (Isc ), open-circuit voltages (Voc), and power have been measured and correlated to the generation of excess carriers in the i-region. Good devices were made at a substrate temperature of 250°C and relatively large flow rates of silane and tritium; this ensures that there are more monohydride bonds than dihydride bonds. Under dark conditions, Isc, and Voc have been found to decrease rapidly. This is consistent with the production of silicon neutral dangling bonds (5 x 1017cm-3 per day) from the loss of tritium due to its transmutation into helium. Dangling bonds reduce carrier lifetime and weaken the electric field in the i-region. The short-circuit current from Delta layer devices decreased more slowly and settled to higher values for narrower Delta layers. This is because the dangling bonds are

  2. Amorphous molybdenum sulfides as hydrogen evolution catalysts.

    PubMed

    Morales-Guio, Carlos G; Hu, Xile

    2014-08-19

    Providing energy for a population projected to reach 9 billion people within the middle of this century is one of the most pressing societal issues. Burning fossil fuels at a rate and scale that satisfy our near-term demand will irreversibly damage the living environment. Among the various sources of alternative and CO2-emission-free energies, the sun is the only source that is capable of providing enough energy for the whole world. Sunlight energy, however, is intermittent and requires an efficient storage mechanism. Sunlight-driven water splitting to make hydrogen is widely considered as one of the most attractive methods for solar energy storage. Water splitting needs a hydrogen evolution catalyst to accelerate the rate of hydrogen production and to lower the energy loss in this process. Precious metals such as Pt are superior catalysts, but they are too expensive and scarce for large-scale applications. In this Account, we summarize our recent research on the preparation, characterization, and application of amorphous molybdenum sulfide catalysts for the hydrogen evolution reaction. The catalysts can be synthesized by electrochemical deposition under ambient conditions from readily available and inexpensive precursors. The catalytic activity is among the highest for nonprecious catalysts. For example, at a loading of 0.2 mg/cm(2), the optimal catalyst delivers a current density of 10 mA/cm(2) at an overpotential of 160 mV. The growth mechanism of the electrochemically deposited film catalysts was revealed by an electrochemical quartz microcrystal balance study. While different electrochemical deposition methods produce films with different initial compositions, the active catalysts are the same and are identified as a "MoS(2+x)" species. The activity of the film catalysts can be further promoted by divalent Fe, Co, and Ni ions, and the origins of the promotional effects have been probed. Highly active amorphous molybdenum sulfide particles can also be prepared

  3. Construction and characterization of amorphous-silicon test structures

    SciTech Connect

    Koppel, L.N.; Milgram, A.A.

    1987-08-01

    Semiconductor device fabrication and characterization work indicates that construction of amorphous-Si photoconductive radiation detectors is feasible. Amorphous Si films are mechanically stable and adhere well to candidate electrode materials; form Schottky-type rectifying junctions with several electrode metals. Materials exist for forming ohmic contacts on amorphous-Si films. Fabrication facilities accessible to ARACOR produce material of nominal band-gap energy, dangling bond density, and dielectric constant. Modification of amorphous-Si conductivity is feasible and supports the construction of PIN devices. Significant photoconductive response is observed for both Schottky-type and PIN devices, with the latter providing superior performance. It is recommended that construction and experimental evaluation of prototype amorphous-Si radiation detectors be persued in Phase II.

  4. Atomistic simulation of damage accumulation and amorphization in Ge

    SciTech Connect

    Gomez-Selles, Jose L. Martin-Bragado, Ignacio; Claverie, Alain; Benistant, Francis

    2015-02-07

    Damage accumulation and amorphization mechanisms by means of ion implantation in Ge are studied using Kinetic Monte Carlo and Binary Collision Approximation techniques. Such mechanisms are investigated through different stages of damage accumulation taking place in the implantation process: from point defect generation and cluster formation up to full amorphization of Ge layers. We propose a damage concentration amorphization threshold for Ge of ∼1.3 × 10{sup 22} cm{sup −3} which is independent on the implantation conditions. Recombination energy barriers depending on amorphous pocket sizes are provided. This leads to an explanation of the reported distinct behavior of the damage generated by different ions. We have also observed that the dissolution of clusters plays an important role for relatively high temperatures and fluences. The model is able to explain and predict different damage generation regimes, amount of generated damage, and extension of amorphous layers in Ge for different ions and implantation conditions.

  5. Pressure-Induced Structural Transformation in Radiation-Amorphized Zircon

    SciTech Connect

    Trachenko, Kostya; Dove, Martin T.; Salje, E. K. H.; Brazhkin, V. V.; Tsiok, O. B.

    2007-03-30

    We study the response of a radiation-amorphized material to high pressure. We have used zircon ZrSiO{sub 4} amorphized by natural radiation over geologic times, and have measured its volume under high pressure, using the precise strain-gauge technique. On pressure increase, we observe apparent softening of the material, starting from 4 GPa. Using molecular dynamics simulation, we associate this softening with the amorphous-amorphous transformation accompanied by the increase of local coordination numbers. We observe permanent densification of the quenched sample and a nontrivial 'pressure window' at high temperature. These features point to a new class of amorphous materials that show a response to pressure which is distinctly different from that of crystals.

  6. Pressure-induced structural transformation in radiation-amorphized zircon.

    PubMed

    Trachenko, Kostya; Brazhkin, V V; Tsiok, O B; Dove, Martin T; Salje, E K H

    2007-03-30

    We study the response of a radiation-amorphized material to high pressure. We have used zircon ZrSiO4 amorphized by natural radiation over geologic times, and have measured its volume under high pressure, using the precise strain-gauge technique. On pressure increase, we observe apparent softening of the material, starting from 4 GPa. Using molecular dynamics simulation, we associate this softening with the amorphous-amorphous transformation accompanied by the increase of local coordination numbers. We observe permanent densification of the quenched sample and a nontrivial "pressure window" at high temperature. These features point to a new class of amorphous materials that show a response to pressure which is distinctly different from that of crystals.

  7. Direct-patterned optical waveguides on amorphous silicon films

    DOEpatents

    Vernon, Steve; Bond, Tiziana C.; Bond, Steven W.; Pocha, Michael D.; Hau-Riege, Stefan

    2005-08-02

    An optical waveguide structure is formed by embedding a core material within a medium of lower refractive index, i.e. the cladding. The optical index of refraction of amorphous silicon (a-Si) and polycrystalline silicon (p-Si), in the wavelength range between about 1.2 and about 1.6 micrometers, differ by up to about 20%, with the amorphous phase having the larger index. Spatially selective laser crystallization of amorphous silicon provides a mechanism for controlling the spatial variation of the refractive index and for surrounding the amorphous regions with crystalline material. In cases where an amorphous silicon film is interposed between layers of low refractive index, for example, a structure comprised of a SiO.sub.2 substrate, a Si film and an SiO.sub.2 film, the formation of guided wave structures is particularly simple.

  8. Salt Fog Testing Iron-Based Amorphous Alloys

    SciTech Connect

    Rebak, Raul B.; Aprigliano, Louis F.; Day, S. Daniel; Farmer, Joseph C.

    2007-07-01

    Iron-based amorphous alloys are hard and highly corrosion resistant, which make them desirable for salt water and other applications. These alloys can be produced as powder and can be deposited as coatings on any surface that needs to be protected from the environment. It was of interest to examine the behavior of these amorphous alloys in the standard salt-fog testing ASTM B 117. Three different amorphous coating compositions were deposited on 316L SS coupons and exposed for many cycles of the salt fog test. Other common engineering alloys such as 1018 carbon steel, 316L SS and Hastelloy C-22 were also tested together with the amorphous coatings. Results show that amorphous coatings are resistant to rusting in salt fog. Partial devitrification may be responsible for isolated rust spots in one of the coatings. (authors)

  9. Fabrication and Characterization of Amorphous/Nanocrystalline Thin Film Composite

    NASA Astrophysics Data System (ADS)

    Newton, Benjamin S.

    Combining the absorption abilities of amorphous silicon and the electron transport capabilities of crystalline silicon would be a great advantage to not only solar cells but other semiconductor devices. In this work composite films were created using molecular beam epitaxy and electron beam deposition interchangeably as a method to create metallic precursors. Aluminum induced crystallization techniques were used to convert an amorphous silicon film with a capping layer of aluminum nanodots into a film composed of a mixture of amorphous silicon and nanocrystalline silicon. This layer was grown into the amorphous layer by cannibalizing a portion of the amorphous silicon material during the aluminum induced crystallization. Characterization was performed on films and metallic precursors utilizing SEM, TEM, ellipsometry and spectrophotometer.

  10. Mechanism of solid state amorphization of glucose upon milling.

    PubMed

    Dujardin, N; Willart, J F; Dudognon, E; Danède, F; Descamps, M

    2013-02-07

    Crystalline α-glucose is known to amorphize upon milling at -15 °C while it remains structurally invariant upon milling at room temperature. We have taken advantage of this behavior to compare the microstructural evolutions of the material in both conditions in order to identify the essential microstructural features which drive the amorphization process upon milling. The investigations have been performed by differential scanning calorimetry and by powder X-ray diffraction. The results indicate that two different amorphization mechanisms occur upon milling: an amorphization at the surface of crystallites due to the mechanical shocks and a spontaneous amorphization of the crystallites as they reach a critical size, which is close to 200 Å in the particular case of α-glucose.

  11. Recent achievements in nanostructured photovoltaic devices.

    PubMed

    Khlyap, Halyna M; Laptev, Viktor I

    2011-06-01

    This mini-review summarizes some key interesting applications and perspectives of nanostructured devices for future nanoelectronics, among them are photonic circuits, carbon nanostructures for chemisensors, unique Ag-Cu-nanocluster contacts for high-effective solar cells. Recent patents in the field are also discussed.

  12. Vertically aligned nanostructure scanning probe microscope tips

    DOEpatents

    Guillorn, Michael A.; Ilic, Bojan; Melechko, Anatoli V.; Merkulov, Vladimir I.; Lowndes, Douglas H.; Simpson, Michael L.

    2006-12-19

    Methods and apparatus are described for cantilever structures that include a vertically aligned nanostructure, especially vertically aligned carbon nanofiber scanning probe microscope tips. An apparatus includes a cantilever structure including a substrate including a cantilever body, that optionally includes a doped layer, and a vertically aligned nanostructure coupled to the cantilever body.

  13. Metal oxide nanostructures with hierarchical morphology

    SciTech Connect

    Ren, Zhifeng; Lao, Jing Yu; Banerjee, Debasish

    2007-11-13

    The present invention relates generally to metal oxide materials with varied symmetrical nanostructure morphologies. In particular, the present invention provides metal oxide materials comprising one or more metallic oxides with three-dimensionally ordered nanostructural morphologies, including hierarchical morphologies. The present invention also provides methods for producing such metal oxide materials.

  14. Processing of Nanostructured Devices Using Microfabrication Techniques

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W (Inventor); Xu, Jennifer C (Inventor); Evans, Laura J (Inventor); Kulis, Michael H (Inventor); Berger, Gordon M (Inventor); Vander Wal, Randall L (Inventor)

    2014-01-01

    Systems and methods that incorporate nanostructures into microdevices are discussed herein. These systems and methods can allow for standard microfabrication techniques to be extended to the field of nanotechnology. Sensors incorporating nanostructures can be fabricated as described herein, and can be used to reliably detect a range of gases with high response.

  15. High-Density Amorphous Ice, the Frost on Interstellar Grains

    NASA Technical Reports Server (NTRS)

    Jenniskens, P.; Blake, D. F.; Wilson, M. A.; Pohorille, A.

    1995-01-01

    Most water ice in the universe is in a form which does not occur naturally on Earth and of which only minimal amounts have been made in the laboratory. We have encountered this 'high-density amorphous ice' in electron diffraction experiments of low-temperature (T less than 30 K) vapor-deposited water and have subsequently modeled its structure using molecular dynamics simulations. The characteristic feature of high-density amorphous ice is the presence of 'interstitial' oxygen pair distances between 3 and 4 A. However, we find that the structure is best described as a collapsed lattice of the more familiar low-density amorphous form. These distortions are frozen in at temperatures below 38 K because, we propose, it requires the breaking of one hydrogen bond, on average, per molecule to relieve the strain and to restructure the lattice to that of low-density amorphous ice. Several features of astrophysical ice analogs studied in laboratory experiments are readily explained by the structural transition from high-density amorphous ice into low-density amorphous ice. Changes in the shape of the 3.07 gm water band, trapping efficiency of CO, CO loss, changes in the CO band structure, and the recombination of radicals induced by low-temperature UV photolysis all covary with structural changes that occur in the ice during this amorphous to amorphous transition. While the 3.07 micrometers ice band in various astronomical environments can be modeled with spectra of simple mixtures of amorphous and crystalline forms, the contribution of the high-density amorphous form nearly always dominates.

  16. Characteristics of amorphous kerogens fractionated from terrigenous sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Suzuki, Noriyuki

    1984-02-01

    A preliminary attempt to fractionate amorphous kerogens from terrigenous bulk kerogen by a benzene-water two phase partition method under acidic condition was made. Microscopic observation revealed that amorphous kerogens and structured kerogens were fractionated effectively by this method. Characteristics of the amorphous and structured kerogens fractionated by this method were examined by some chemical analyses and compared with those of the bulk kerogen and humic acid isolated from the same rock sample (Haizume Formation, Pleistocene, Japan). The elemental and infrared (IR) analyses showed that the amorphous kerogen fraction had the highest atomic H/C ratio and the lowest atomic N/C ratio and was the richest in aliphatic structures and carbonyl and carboxyl functional groups. Quantities of fatty acids from the saponification products of each geopolymer were in agreement with the results of elemental and IR analyses. Distribution of the fatty acids was suggestive that more animal lipids participate in the formation of amorphous kerogens because of the abundance of relatively lower molecular weight fatty acids (such as C 16 and C 18 acids) in saponification products of amorphous kerogens. On the other hand, although the amorphous kerogen fraction tends to be rich in aliphatic structures compared with bulk kerogen of the same rock samples, van Krevelen plots of elemental compositions of kerogens from the core samples (Nishiyama Oil Field, Tertiary, Japan) reveal that the amorphous kerogen fraction is not necessarily characterized by markedly high atomic H/C ratio. This was attributed to the oxic environment of deposition and the abundance of biodegraded terrestrial amorphous organic matter in the amorphous kerogen fraction used in this work.

  17. "Spontaneous Growth of ZnCO3 Nanowires on ZnO Nanostructures in Normal Ambient Environment: Unstable ZnO Nanostructures:

    SciTech Connect

    Pan, Zhengwei; Tao, Jing; Zhu, Yimei; Huang, Jing-Fang; Paranthaman, Mariappan Parans

    2010-01-01

    ZnO nanowires, one of the most investigated nanostructures that promise numerous applications in nanophotonics, opto-electronics, and energy, are generally thought to be highly stable under ambient conditions because of their oxide nature. Here, we report that ZnO nanowires are actually extremely unstable even in normal ambient environment (70% RH, and 350 ppm CO2) because of atmospheric corrosion.When placed on an oxide substrate (e.g., glass slide) and exposed in air, ZnO nanowires tend to react with airborne moisture and CO2 to form amorphous ZnCO3 thin films and nanowires. The factors that specially affect the corrosion of ZnO nanowires in a laboratory environment include CO2, humidity, and substrates. Our results suggest that a CO2- and/or moisture-free environment are required in order for optimal applications of ZnO nanowires.

  18. Spontaneous Growth of ZnCO3 Nanowires on ZnO Nanostructures in Normal Ambient Environment: Unstable ZnO Nanostructures

    SciTech Connect

    Pan, Z.; Tao, J.; Zhu, Y.; Huang, J.-F.; Paranthaman, M.P.

    2009-12-09

    ZnO nanowires, one of the most investigated nanostructures that promise numerous applications in nanophotonics, opto-electronics, and energy, are generally thought to be highly stable under ambient conditions because of their oxide nature. Here, we report that ZnO nanowires are actually extremely unstable even in normal ambient environment (70% RH, and {approx}350 ppm CO{sub 2}) because of atmospheric corrosion. When placed on an oxide substrate (e.g., glass slide) and exposed in air, ZnO nanowires tend to react with airborne moisture and CO{sub 2} to form amorphous ZnCO{sub 3} thin films and nanowires. The factors that specially affect the corrosion of ZnO nanowires in a laboratory environment include CO{sub 2}, humidity, and substrates. Our results suggest that a CO{sub 2}{sup -} and/or moisture-free environment are required in order for optimal applications of ZnO nanowires.

  19. Theoretical studies of amorphous silicon and hydrogenated amorphous silicon with molecular dynamics simulations

    SciTech Connect

    Kwon, I.

    1991-12-20

    Amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) have been studied with molecular dynamics simulations. The structural, vibrational, and electronic properties of these materials have been studied with computer-generated structural models and compare well with experimental observations. The stability of a-si and a-Si:H have been studied with the aim of understanding microscopic mechanisms underlying light-induced degradation in a-Si:H (the Staebler-Wronski effect). With a view to understanding thin film growth processes, a-Si films have been generated with molecular dynamics simulations by simulating the deposition of Si-clusters on a Si(111) substrate. A new two- and three-body interatomic potential for Si-H interactions has been developed. The structural properties of a-Si:H networks are in good agreement with experimental measurements. The presence of H atoms reduces strain and disorder relative to networks without H.

  20. High-performance nanostructured MR contrast probes

    PubMed Central

    Hu, Fengqin; Joshi, Hrushikesh M.; Dravid, Vinayak P.; Meade, Thomas J.

    2011-01-01

    Magnetic resonance imaging (MRI) has become a powerful technique in biological molecular imaging and clinical diagnosis. With the rapid progress in nanoscale science and technology, nanostructure-based MR contrast agents are undergoing rapid development. This is in part due to the tuneable magnetic and cellular uptake properties, large surface area for conjugation and favourable biodistribution. In this review, we describe our recent progress in the development of high-performance nanostructured MR contrast agents. Specifically, we report on Gd-enriched nanostructured probes that exhibit T1 MR contrast and superparamagnetic Fe3O4 and CoFe2O4 nanostructures that display T2 MR contrast enhancement. The effects of nanostructure size, shape, assembly and surface modification on relaxivity are described. The potential of these contrast agents for in vitro and in vivo MR imaging with respect to colloidal stability under physiological conditions, biocompatibility, and surface functionality are also evaluated. PMID:20694208

  1. Supramolecular Nanostructures Formed by Anticancer Drug Assembly

    PubMed Central

    Cheetham, Andrew G.; Zhang, Pengcheng; Lin, Yi-an; Lock, Lye Lin; Cui, Honggang

    2013-01-01

    We report here a supramolecular strategy to directly assemble the small molecular hydrophobic anticancer drug camptothecin (CPT) into discrete, stable, well-defined nanostructures with a high and quantitative drug loading. Depending on the number of CPTs in the molecular design, the resulting nanostructures can be either nanofibers or nanotubes, and have a fixed CPT loading content ranging from 23% to 38%. We found that formation of nanostructures provides protection for both the CPT drug and the biodegradable linker from the external environment and thus offers a mechanism for controlled release of CPT. Under tumor-relevant conditions, these drug nanostructures can release the bioactive form of CPT and show in vitro efficacy against a number of cancer cell lines. This strategy can be extended to construct nanostructures of other types of anticancer drugs, and thus presents new opportunities for the development of self-delivering drugs for cancer therapeutics. PMID:23379791

  2. Nanostructures, systems, and methods for photocatalysis

    SciTech Connect

    Reece, Steven Y.; Jarvi, Thomas D.

    2015-12-08

    The present invention generally relates to nanostructures and compositions comprising nanostructures, methods of making and using the nanostructures, and related systems. In some embodiments, a nanostructure comprises a first region and a second region, wherein a first photocatalytic reaction (e.g., an oxidation reaction) can be carried out at the first region and a second photocatalytic reaction (e.g., a reduction reaction) can be carried out at the second region. In some cases, the first photocatalytic reaction is the formation of oxygen gas from water and the second photocatalytic reaction is the formation of hydrogen gas from water. In some embodiments, a nanostructure comprises at least one semiconductor material, and, in some cases, at least one catalytic material and/or at least one photosensitizing agent.

  3. Structural relaxation of vacancies in amorphous silicon

    SciTech Connect

    Kim, E.; Lee, Y.H.; Chen, C.; Pang, T.

    1997-07-01

    The authors have studied the structural relaxation of vacancies in amorphous silicon (a-Si) using a tight-binding molecular-dynamics method. The most significant difference between vacancies in a-Si and those in crystalline silicon (c-Si) is that the deep gap states do not show up in a-Si. This difference is explained through the unusual behavior of the structural relaxation near the vacancies in a-Si, which enhances the sp{sup 2} + p bonding near the band edges. They have also observed that the vacancies do not migrate below 450 K although some of them can still be annihilated, particularly at high defect density due to large structural relaxation.

  4. Polarization Stability of Amorphous Piezoelectric Polyimides

    NASA Technical Reports Server (NTRS)

    Park, C.; Ounaies, Z.; Su, J.; Smith, J. G., Jr.; Harrison, J. S.

    2000-01-01

    Amorphous polyimides containing polar functional groups have been synthesized and investigated for potential use as high temperature piezoelectric sensors. The thermal stability of the piezoelectric effect of one polyimide was evaluated as a function of various curing and poling conditions under dynamic and static thermal stimuli. First, the polymer samples were thermally cycled under strain by systematically increasing the maximum temperature from 50 C to 200 C while the piezoelectric strain coefficient was being measured. Second, the samples were isothermally aged at an elevated temperature in air, and the isothermal decay of the remanent polarization was measured at room temperature as a function of time. Both conventional and corona poling methods were evaluated. This material exhibited good thermal stability of the piezoelectric properties up to 100 C.

  5. Amorphous materials molded IR lens progress report

    NASA Astrophysics Data System (ADS)

    Hilton, A. R., Sr.; McCord, James; Timm, Ronald; Le Blanc, R. A.

    2008-04-01

    Amorphous Materials began in 2000 a joint program with Lockheed Martin in Orlando to develop molding technology required to produce infrared lenses from chalcogenide glasses. Preliminary results were reported at this SPIE meeting by Amy Graham1 in 2003. The program ended in 2004. Since that time, AMI has concentrated on improving results from two low softening glasses, Amtir 4&5. Both glasses have been fully characterized and antireflection coatings have been developed for each. Lenses have been molded from both glasses, from Amtir 6 and from C1 Core glass. A Zygo unit is used to evaluate the results of each molded lens as a guide to improving the molding process. Expansion into a larger building has provided room for five production molding units. Molded lens sizes have ranged from 8 mm to 136 mm in diameter. Recent results will be presented

  6. Negative Magnetoresistance in Amorphous Indium Oxide Wires

    NASA Astrophysics Data System (ADS)

    Mitra, Sreemanta; Tewari, Girish C.; Mahalu, Diana; Shahar, Dan

    2016-11-01

    We study magneto-transport properties of several amorphous Indium oxide nanowires of different widths. The wires show superconducting transition at zero magnetic field, but, there exist a finite resistance at the lowest temperature. The R(T) broadening was explained by available phase slip models. At low field, and far below the superconducting critical temperature, the wires with diameter equal to or less than 100 nm, show negative magnetoresistance (nMR). The magnitude of nMR and the crossover field are found to be dependent on both temperature and the cross-sectional area. We find that this intriguing behavior originates from the interplay between two field dependent contributions.

  7. Extracting Crystal Chemistry from Amorphous Carbon Structures.

    PubMed

    Deringer, Volker L; Csányi, Gábor; Proserpio, Davide M

    2017-03-08

    Carbon allotropes have been explored intensively by ab initio crystal structure prediction, but such methods are limited by the large computational cost of the underlying density functional theory (DFT). Here we show that a novel class of machine-learning-based interatomic potentials can be used for random structure searching and readily predicts several hitherto unknown carbon allotropes. Remarkably, our model draws structural information from liquid and amorphous carbon exclusively, and so does not have any prior knowledge of crystalline phases: it therefore demonstrates true transferability, which is a crucial prerequisite for applications in chemistry. The method is orders of magnitude faster than DFT and can, in principle, be coupled with any algorithm for structure prediction. Machine-learning models therefore seem promising to enable large-scale structure searches in the future.

  8. Thermomechanical behavior of amorphous tactic methacrylate polymers

    NASA Technical Reports Server (NTRS)

    Kiran, E.; Gillham, J. K.; Gipstein, E.

    1974-01-01

    Dynamic mechanical spectra of amorphous stereoregular poly(methyl methacrylate)s and poly(t-butyl methacrylate)s with assigned microtacticities are presented and discussed. An intermolecular argument is invoked to account for the higher glass transition temperature of syndiotactic vis a vis isotactic PMMA, in spite of the higher density of the latter at 30 C. An argument is presented to show that the ratio of glassy-region relaxation temperature to glass transition temperature is not only a measure of the degree of coupling of the beta and glass transition processes, but also of the degree to which intermolecular factors influence these processes. The greater extent of the low-temperature irreversibilities observed in the thermomechanical spectra of poly(t-butyl methacrylate)s is attributed to the brittle character induced by the bulky side groups which presumably weaken cohesive forces.

  9. Tunable plasticity in amorphous silicon carbide films.

    PubMed

    Matsuda, Yusuke; Kim, Namjun; King, Sean W; Bielefeld, Jeff; Stebbins, Jonathan F; Dauskardt, Reinhold H

    2013-08-28

    Plasticity plays a crucial role in the mechanical behavior of engineering materials. For instance, energy dissipation during plastic deformation is vital to the sufficient fracture resistance of engineering materials. Thus, the lack of plasticity in brittle hybrid organic-inorganic glasses (hybrid glasses) often results in a low fracture resistance and has been a significant challenge for their integration and applications. Here, we demonstrate that hydrogenated amorphous silicon carbide films, a class of hybrid glasses, can exhibit a plasticity that is even tunable by controlling their molecular structure and thereby leads to an increased and adjustable fracture resistance in the films. We decouple the plasticity contribution from the fracture resistance of the films by estimating the "work-of-fracture" using a mean-field approach, which provides some insight into a potential connection between the onset of plasticity in the films and the well-known rigidity percolation threshold.

  10. Radiation resistance studies of amorphous silicon films

    NASA Technical Reports Server (NTRS)

    Payson, J. Scott; Woodyard, James R.

    1988-01-01

    A study of hydrogenated amorphous silicon thin films irradiated with 2.00 MeV helium ions using fluences ranging from 1E11 to 1E15/sq cm is presented. The films were characterized using photothermal deflection spectroscopy, transmission and reflection spectroscopy, and photoconductivity and annealing measurements. Large changes were observed in the subband-gap optical absorption for energies between 0.9 and 1.7 eV. The steady-state photoconductivity showed decreases of almost five orders of magnitude for a fluence of 1E15/sq cm, but the slope of the intensity dependence of the photoconductivity remained almost constant for all fluences. Substantial annealing occurs even at room temperature, and for temperatures greater than 448 K the damage is completely annealed. The data are analyzed to describe the defects and the density of states function.

  11. Energy landscape of relaxed amorphous silicon

    NASA Astrophysics Data System (ADS)

    Valiquette, Francis; Mousseau, Normand

    2003-09-01

    We analyze the structure of the energy landscape of a well-relaxed 1000-atom model of amorphous silicon using the activation-relaxation technique (ART nouveau). Generating more than 40 000 events starting from a single minimum, we find that activated mechanisms are local in nature, that they are distributed uniformly throughout the model, and that the activation energy is limited by the cost of breaking one bond, independently of the complexity of the mechanism. The overall shape of the activation-energy-barrier distribution is also insensitive to the exact details of the configuration, indicating that well-relaxed configurations see essentially the same environment. These results underscore the localized nature of relaxation in this material.

  12. Negative Magnetoresistance in Amorphous Indium Oxide Wires

    PubMed Central

    Mitra, Sreemanta; Tewari, Girish C; Mahalu, Diana; Shahar, Dan

    2016-01-01

    We study magneto-transport properties of several amorphous Indium oxide nanowires of different widths. The wires show superconducting transition at zero magnetic field, but, there exist a finite resistance at the lowest temperature. The R(T) broadening was explained by available phase slip models. At low field, and far below the superconducting critical temperature, the wires with diameter equal to or less than 100 nm, show negative magnetoresistance (nMR). The magnitude of nMR and the crossover field are found to be dependent on both temperature and the cross-sectional area. We find that this intriguing behavior originates from the interplay between two field dependent contributions. PMID:27876859

  13. Spray drying formulation of amorphous solid dispersions.

    PubMed

    Singh, Abhishek; Van den Mooter, Guy

    2016-05-01

    Spray drying is a well-established manufacturing technique which can be used to formulate amorphous solid dispersions (ASDs) which is an effective strategy to deliver poorly water soluble drugs (PWSDs). However, the inherently complex nature of the spray drying process coupled with specific characteristics of ASDs makes it an interesting area to explore. Numerous diverse factors interact in an inter-dependent manner to determine the final product properties. This review discusses the basic background of ASDs, various formulation and process variables influencing the critical quality attributes (CQAs) of the ASDs and aspects of downstream processing. Also various aspects of spray drying such as instrumentation, thermodynamics, drying kinetics, particle formation process and scale-up challenges are included. Recent advances in the spray-based drying techniques are mentioned along with some future avenues where major research thrust is needed.

  14. Tailored magnetic anisotropy in an amorphous trilayer

    NASA Astrophysics Data System (ADS)

    Fu, Yu; Barsukov, I.; Raanaei, H.; Spasova, M.; Lindner, J.; Meckenstock, R.; Farle, M.; Hjörvarsson, B.

    2011-06-01

    An amorphous Co68Fe24Zr8(3 nm)/Al70Zr30(3 nm)/Co68Fe24Zr8(3 nm) trilayer system has been investigated using in-plane and out-of-plane angular dependent ferromagnetic resonance at different frequencies. The in-plane magnetic anisotropy is uniaxial, retaining its value of (2.9 ± 0.1) × 103 J/m3 for each magnetic layer, whereas its direction was tailored independently in an arbitrary manner by applying an external magnetic field during the film deposition. The perpendicular anisotropy constant, supposed to reflect the interface quality, is nearly identical for both layers. Furthermore, the magnetic layers act independently upon each other due to the absence of interlayer coupling.

  15. Spectrometric characterization of amorphous silicon PIN detectors

    NASA Astrophysics Data System (ADS)

    Leyva, A.; Ramírez, F. J.; Ortega, Y.; Estrada, M.; Cabal, A.; Cerdeira, A.; Díaz, A.

    2000-10-01

    During the last years, much interest has been dedicated to the use of amorphous silicon PIN diodes as particle and radiation detectors for medical applications. This work presents the spectrometric characterization of PECVD high deposition rate diodes fabricated at our laboratory, with thickness up to 17.5 μm. Results show that the studied devices detect the Am241 alpha particles and the medical X-rays generated by a mammograph model Senographe 700T from General Electric Possible reasons of the observed energy losses are discussed in the text. Using the SRIM2000 program, the transit of 5.5 MeV alpha particles through a diode was simulated, determining the optimum thickness for these particles to deposit their energy in the intrinsic layer of the diode.

  16. Bulk amorphous steels based on Fe alloys

    DOEpatents

    Lu, ZhaoPing; Liu, Chain T.

    2006-05-30

    A bulk amorphous alloy has the approximate composition: Fe.sub.(100-a-b-c-d-e)Y.sub.aMn.sub.bT.sub.cM.sub.dX.sub.e wherein: T includes at least one of the group consisting of: Ni, Cu, Cr and Co; M includes at least one of the group consisting of W, Mo, Nb, Ta, Al and Ti; X includes at least one of the group consisting of Co, Ni and Cr; a is an atomic percentage, and a<5; b is an atomic percentage, and b.ltoreq.25; c is an atomic percentage, and c.ltoreq.25; d is an atomic percentage, and d.ltoreq.25; and e is an atomic percentage, and 5.ltoreq.e.ltoreq.30.

  17. Microwave properties of ferromagnetic nanostructures.

    PubMed

    Valenzuela, R; Alvarez, G; Mata-Zamora, M E

    2008-06-01

    A review of the dynamic properties of nanostructured ferromagnetic materials at microwave frequencies (1-40 GHz) is presented. Since some confusion has recently appeared between giant magnetoimpedance (GMI) and ferromagnetic resonance (FMR), a detailed analysis is made in order to establish their differences. A brief review of a novel microwave absorption mode, the low-field microwave absorption (LFA) is then presented, together with a discussion about its similarities with GMI. Recent results on high-frequency measurements on nanogranular thin films and FMR in nanowire arrays are finally addressed.

  18. 3D Nanostructuring of Semiconductors

    NASA Astrophysics Data System (ADS)

    Blick, Robert

    2000-03-01

    Modern semiconductor technology allows to machine devices on the nanometer scale. I will discuss the current limits of the fabrication processes, which enable the definition of single electron transistors with dimensions down to 8 nm. In addition to the conventional 2D patterning and structuring of semiconductors, I will demonstrate how to apply 3D nanostructuring techniques to build freely suspended single-crystal beams with lateral dimension down to 20 nm. In transport measurements in the temperature range from 30 mK up to 100 K these nano-crystals are characterized regarding their electronic as well as their mechanical properties. Moreover, I will present possible applications of these devices.

  19. Phyllosilicates and Amorphous Gel in the Nakhlites

    NASA Astrophysics Data System (ADS)

    Hicks, L. J.; Bridges, J. C.; Gurman, S. J.

    2013-09-01

    Previous studies of the nakhlite martian meteorites have revealed hydrothermal minerals present within the fractures of the olivine minerals and the mesostasis. The olivine fractures of the Lafayette nakhlite reveal variations with initial deposits of siderite on the fracture walls, followed by crystalline phyllosilicates (smectite), and finishing with a rapidly cooled amorphous silicate gel within the central regions of the fractures. The mesostasis fractures of Lafayette also contain a crystalline phyllosilicate (serpentine). The amorphous gel is the most abundant secondary phase within the fractures of the other nakhlites [1, 2]. By studying nine nakhlite samples, including Lafayette, Governador Valadares, Nakhla, Y-000593, Y-000749, Miller-Range 03346, NWA 817, NWA 998, and NWA 5790, our aim is to constrain the identity of the phyllosilicate secondary phase minerals found throughout the nakhlite martian meteorites. This is achieved using methods including Electron Probe Micro-analysis (EPMA); X-ray Absorption Near-Edge Structure (Fe-K XANES) spectroscopy measured using Beamline I-18 at the Diamond Light Source synchrotron; and the use of Transmission Electron Microscopy (TEM) at the University of Leicester for High-Resolution (HR) imaging and Selected Area Electron Diffraction (SAED). BF studying nine nakhlite samples, including Lafayette, Governador Valadares, Nakhla, Y-000593, Y-000749, Miller-Range 03346, NWA 817, NWA 998, and NWA 5790, our aim is to constrain the identity of the phyllosilicate secondary phase minerals found throughout the nakhlite martian meteorites. This is achieved using methods including Electron Probe Micro-analysis (EPMA); X-ray Absorption Near-Edge Structure (Fe-K XANES) spectroscopy measured using Beamline I-18 at the Diamond Light Source synchrotron; and the use of Transmission Electron Microscopy (TEM) at the University of Leicester for High-Resolution (HR) imaging and Selected Area Electron Diffraction (SAED).

  20. Castable Amorphous Metal Mirrors and Mirror Assemblies

    NASA Technical Reports Server (NTRS)

    Hofmann, Douglas C.; Davis, Gregory L.; Agnes, Gregory S.; Shapiro, Andrew A.

    2013-01-01

    A revolutionary way to produce a mirror and mirror assembly is to cast the entire part at once from a metal alloy that combines all of the desired features into the final part: optical smoothness, curvature, flexures, tabs, isogrids, low CTE, and toughness. In this work, it has been demonstrated that castable mirrors are possible using bulk metallic glasses (BMGs, also called amorphous metals) and BMG matrix composites (BMGMCs). These novel alloys have all of the desired mechanical and thermal properties to fabricate an entire mirror assembly without machining, bonding, brazing, welding, or epoxy. BMGs are multi-component metal alloys that have been cooled in such a manner as to avoid crystallization leading to an amorphous (non-crystalline) microstructure. This lack of crystal structure and the fact that these alloys are glasses, leads to a wide assortment of mechanical and thermal properties that are unlike those observed in crystalline metals. Among these are high yield strength, carbide-like hardness, low melting temperatures (making them castable like aluminum), a thermoplastic processing region (for improving smoothness), low stiffness, high strength-to-weight ratios, relatively low CTE, density similar to titanium alloys, high elasticity and ultra-smooth cast parts (as low as 0.2-nm surface roughness has been demonstrated in cast BMGs). BMGMCs are composite alloys that consist of a BMG matrix with crystalline dendrites embedded throughout. BMGMCs are used to overcome the typically brittle failure observed in monolithic BMGs by adding a soft phase that arrests the formation of cracks in the BMG matrix. In some cases, BMGMCs offer superior castability, toughness, and fatigue resistance, if not as good a surface finish as BMGs. This work has demonstrated that BMGs and BMGMCs can be cast into prototype mirrors and mirror assemblies without difficulty.