Sample records for nanostructured palladium-gold alloy

  1. Electrocatalysts having platium monolayers on palladium, palladium alloy, and gold alloy core-shell nanoparticles, and uses thereof

    DOEpatents

    Adzic, Radoslav; Mo, Yibo; Vukmirovic, Miomir; Zhang, Junliang

    2010-12-21

    The invention relates to platinum-coated particles useful as fuel cell electrocatalysts. The particles are composed of a noble metal or metal alloy core at least partially encapsulated by an atomically thin surface layer of platinum atoms. The invention particularly relates to such particles having a palladium, palladium alloy, gold alloy, or rhenium alloy core encapsulated by an atomic monolayer of platinum. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

  2. Potentiodynamic polarization study of the in vitro corrosion behavior of 3 high-palladium alloys and a gold-palladium alloy in 5 media.

    PubMed

    Sun, Desheng; Monaghan, Peter; Brantley, William A; Johnston, William M

    2002-01-01

    Corrosion of cast alloy restorations may lead to their failure or adversely affect their biocompatibility. Although some documentation of the corrosion behavior of the high-palladium dental alloys exists, questions remain about their corrosion resistance and mechanisms. This study compared the in vitro corrosion characteristics of 3 high-palladium alloys and 1 gold-palladium alloy in simulated body fluid and oral environments. Two Pd-Cu-Ga alloys and 1 Pd-Ga alloy were selected; an Au-Pd alloy served as the control. The corrosion behavior for the as-cast and simulated porcelain-firing (heat-treated) conditions of each alloy (N = 5) was evaluated in 0.9% NaCl, 0.09% NaCl, and Fusayama solutions. Heat-treated specimens of each alloy (N = 5) were also tested in N(2)-deaerated 0.09% NaCl and Fusayama solutions (pH 4). After immersion in the electrolyte for 24 hours, the open-circuit potential (OCP) was measured, and linear polarization was performed from -20 mV to +20 mV (vs. OCP) at a scanning rate of 0.125 mV/s. Cyclic polarization was performed from -300 mV to +1000 mV and back to -300 mV (vs. OCP) at a scanning rate of 1 mV/s. Data were evaluated with analysis of variance and the Ryan-Einot-Gabriel-Welsch multiple-range test (alpha=.05). The OCP of each alloy varied with the condition (as-cast or heat-treated) and electrolyte used. Corrosion resistance was similar for the 4 alloys tested. For cyclic polarization, all alloys showed active-passive or spontaneous passive behavior in nearly all electrolytes. During some reverse scans, the 3 high-palladium alloys displayed 3 or 5 anodic peaks. No positive hysteresis was observed for any of the alloy/electrolyte combinations evaluated. The corrosion resistances of the 3 high-palladium alloys in simulated body fluid and oral environments were comparable to that of the gold-palladium alloy. The similar corrosion resistance for the 3 high-palladium alloys was attributed to their high noble metal content and theorized stable

  3. On the corrosion behavior and biocompatibility of palladium-based dental alloys

    NASA Astrophysics Data System (ADS)

    Sun, Desheng

    Palladium-based alloys have been used as dental restorative materials for about two decades with good clinical history. But there have been clinical case reports showing possible allergy effects from these alloys. The aim of this study was to characterize the corrosion behavior and mechanisms of several palladium-based dental alloys by potentiodynamic polarization methods, electrochemical impedance spectroscopy (EIS), and scanning Kelvin probe force microscopy/atomic force microscopy (SKPFM/AFM), and to evaluate their biocompatibility by a cell culture technique and an animal model. Using SKPFM/AFM and scanning electron microscopy, the Ru-enriched phase from the use of ruthenium as a grain-refining element was identified as being slightly more noble than the palladium solid solution matrix in a high-palladium alloy. Other secondary precipitates that exist in the microstructures of these high-palladium alloys have minimal differences in Volta potential compared to the matrix. For high-palladium alloys, corrosion is generally uniform due to the predominant palladium content in the different phases. Potentiodynamic polarization and EIS have shown that representative palladium-silver alloys have low corrosion tendency and high corrosion resistance, which are equivalent to a well-known high-noble gold-palladium alloy in simulated body fluid and oral environments. The palladium-silver alloys tested are resistant to chloride ion corrosion. Passivation and dealloying have been identified for all of the tested palladium-silver alloys. The great similarity in corrosion behavior among the palladium-silver alloys is attributed to their similar chemical compositions. The variation in microstructures of palladium-silver alloys tested does not cause significant difference in corrosion behavior. The corrosion resistance of these palladium-silver alloys at elevated potentials relevant to oral environment is still satisfactory. The release of elements from representative dental

  4. Gold-nickel-titanium brazing alloy

    DOEpatents

    Mizuhara, Howard

    1995-01-03

    A brazing alloy in accordance with this invention has the following composition, by weight: 91 to 99 gold, 0.5 to 7% nickel; 0.10 to 2% titanium. Alternatively, with palladium present, the composition is as follows, by weight: 83 to 96% gold; 3 to 10% palladium; 0.5 to 5% nickel; 0.10 to 2% titanium.

  5. Gold-nickel-titanium brazing alloy

    DOEpatents

    Mizuhara, Howard

    1990-07-03

    A brazing alloy in accordance with this invention has the following composition, by weight: 91 to 99% gold, 0.5 to 7% nickel; 0.10 to 2% titanium. Alternatively, with palladium present, the composition is as follows, by weight: 83 to 96% gold; 3 to 10% palladium; 0.5 to 5% nickel; 0.10 to 2% titanium.

  6. Preparation and characterization of carbon-supported sub-monolayer palladium decorated gold nanoparticles for the electro-oxidation of ethanol in alkaline media

    NASA Astrophysics Data System (ADS)

    Zhu, L. D.; Zhao, T. S.; Xu, J. B.; Liang, Z. X.

    Carbon-supported gold nanoparticles (Au/C) are successfully decorated with mono- or sub-monolayer palladium atoms with different Pd/Au atomic ratios by a chemically epitaxial seeded growth method. TEM, UV-vis spectrometry and XRD techniques are used to characterize the particle size, dispersion, palladium coverage on gold seeds and crystal structures of the prepared catalysts. Cyclic voltammetric tests show that the Pd-decorated Au/C (denoted by Pd@Au/C) have higher specific activities than that of Pd/C for the oxidation of ethanol in alkaline media. This suggests that the Pd utilization is improved with such a surface-alloyed nanostructure. In addition, stable chronoamperometric responses are achieved with the so-prepared electrocatalysts during ethanol oxidation.

  7. Microwave-assisted synthesis of gold, silver, platinum and palladium nanostructures and their use in electrocatalytic applications.

    PubMed

    Safavi, Afsaneh; Tohidi, Maryam

    2014-09-01

    Microwave-assisted ionic liquid method was used for synthesis of various noble metals, such as gold, silver, platinum and palladium nanomaterials. This route does not employ any template agent, surface capping agents or reducing agents. The process is fast, simple and of high yield. Different metal precursors in various ionic liquids media (1-butyl-3-methylimidazolium tetrafluoroborate, octyl pyridinium hexaflurophosphate and 1-octyl-3-methylimidazolium hexaflurophosphate) were applied to produce metal nanomaterials. Silver, platinium and palladium nanoparticles exhibit spherical morphology while nanosheets with high aspect ratio were obtained for gold. These metal nanostructures were incorporated into a carbon ionic liquid electrode to investigate their electrocatalytic properties. It was found that synthesis in different ionic liquids result in different activity. Excellent electrocatalytic effects toward adenine, hydrazine, formaldehyde and ethanol were observed for the modified electrodes with different nanoparticles synthesized in 1-butyl-3-methylimidazolium tetrafluoroborate. The high conductivity, large surface-to-volume ratio and active sites of nanosized metal particles are responsible for their electrocatalytic activity. In contrast, the carbon ionic liquid electrode modified with synthesized metal nanoparticles in octyl pyridinium hexaflurophosphate and 1-octyl-3-methylimidazolium hexaflurophosphate showed negligible activity for detection of these probes.

  8. Hydrogen absorption induced metal deposition on palladium and palladium-alloy particles

    DOEpatents

    Wang, Jia X [East Setauket, NY; Adzic, Radoslav R [East Setauket, NY

    2009-03-24

    The present invention relates to methods for producing metal-coated palladium or palladium-alloy particles. The method includes contacting hydrogen-absorbed palladium or palladium-alloy particles with one or more metal salts to produce a sub-monoatomic or monoatomic metal- or metal-alloy coating on the surface of the hydrogen-absorbed palladium or palladium-alloy particles. The invention also relates to methods for producing catalysts and methods for producing electrical energy using the metal-coated palladium or palladium-alloy particles of the present invention.

  9. Nanostructuring of Palladium with Low-Temperature Helium Plasma

    PubMed Central

    Fiflis, P.; Christenson, M.P.; Connolly, N.; Ruzic, D.N.

    2015-01-01

    Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium. PMID:28347109

  10. Nanostructuring of Palladium with Low-Temperature Helium Plasma.

    PubMed

    Fiflis, P; Christenson, M P; Connolly, N; Ruzic, D N

    2015-11-25

    Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium.

  11. Gold-promoted structurally ordered intermetallic palladium cobalt nanoparticles for the oxygen reduction reaction.

    PubMed

    Kuttiyiel, Kurian A; Sasaki, Kotaro; Su, Dong; Wu, Lijun; Zhu, Yimei; Adzic, Radoslav R

    2014-11-06

    Considerable efforts to make palladium and palladium alloys active catalysts and a possible replacement for platinum have had a marginal success. Here we report on a structurally ordered Au10Pd₄₀Co₅₀ catalyst that exhibits comparable activity to conventional platinum catalysts in both acid and alkaline media. Electron microscopic techniques demonstrate that, at elevated temperatures, palladium cobalt nanoparticles undergo an atomic structural transition from core-shell to a rare intermetallic ordered structure with twin boundaries forming stable {111}, {110} and {100} facets via addition of gold atoms. The superior stability of this catalyst compared with platinum after 10,000 potential cycles in alkaline media is attributed to the atomic structural order of PdCo nanoparticles along with protective effect of clusters of gold atoms on the surface. This strategy of making ordered palladium intermetallic alloy nanoparticles can be used in diverse heterogeneous catalysis where particle size and structural stability matter.

  12. Effects of soldering methods on tensile strength of a gold-palladium metal ceramic alloy.

    PubMed

    Ghadhanfari, Husain A; Khajah, Hasan M; Monaco, Edward A; Kim, Hyeongil

    2014-10-01

    The tensile strength obtained by conventional postceramic application soldering and laser postceramic welding may require more energy than microwave postceramic soldering, which could provide similar tensile strength values. The purpose of the study was to compare the tensile strength obtained by microwave postceramic soldering, conventional postceramic soldering, and laser postceramic welding. A gold-palladium metal ceramic alloy and gold-based solder were used in this study. Twenty-seven wax specimens were cast in gold-palladium noble metal and divided into 4 groups: laser welding with a specific postfiller noble metal, microwave soldering with a postceramic solder, conventional soldering with the same postceramic solder used in the microwave soldering group, and a nonsectioned control group. All the specimens were heat treated to simulate a normal porcelain sintering sequence. An Instron Universal Testing Machine was used to measure the tensile strength for the 4 groups. The means were analyzed statistically with 1-way ANOVA. The surface and fracture sites of the specimens were subjectively evaluated for fracture type and porosities by using a scanning electron microscope. The mean (standard deviation) ultimate tensile strength values were as follows: nonsectioned control 818 ±30 MPa, microwave 516 ±34 MPa, conventional 454 ±37 MPa, and laser weld 191 ±39 MPa. A 1-way ANOVA showed a significant difference in ultimate tensile strength among the groups (F3,23=334.5; P<.001). Follow-up multiple comparisons showed a significant difference among all the groups. Microwave soldering resulted in a higher tensile strength for gold and palladium noble metals than either conventional soldering or laser welding. Conventional soldering resulted in a higher tensile strength than laser welding. Under the experimental conditions described, either microwave or conventional postceramic soldering would appear to satisfy clinical requirements related to tensile strength

  13. External-beam PIXE spectrometry for the study of Punic jewellery (SW Spain): The geographical provenance of the palladium-bearing gold

    NASA Astrophysics Data System (ADS)

    Ontalba Salamanca, M. Á.; Gómez-Tubío, B.; Ortega-Feliu, I.; Respaldiza, M. Á.; Luisa de la Bandera, M.; Ovejero Zappino, G.; Bouzas, A.; Gómez-Morón, A.

    2006-08-01

    This paper presents the study of a set of Punic gold items (400 B.C.), from the Museum of Cádiz (Spain). An external beam set-up has been employed for the absolutely non-destructive analysis of the objects. PIXE spectrometry has been performed in order to characterize the metallic alloys and the manufacturing techniques. Compositional differences have been found and soldering procedures have been identified. By comparison with the rings and other coetaneous jewellery, the presence of palladium in the bulk alloy of the earrings can be pointed out. The geographical provenance of the palladium-bearing gold is discussed based on geological and archaeological considerations.

  14. Controlled deposition of palladium nanodendrites on the tips of gold nanorods and their enhanced catalytic activity.

    PubMed

    Su, Gaoxing; Jiang, Huaqiao; Zhu, Hongyan; Lv, Jing-Jing; Yang, Guohai; Yan, Bing; Zhu, Jun-Jie

    2017-08-31

    Plasmonic Au-Pd nanostructures have drawn significant attention for use in heterogeneous catalysis. In this study, palladium nanodendrite-tipped gold nanorods (PdND-T-AuNRs) were subjected to a facile fabrication under mild reaction conditions. The palladium amounts on the two tips were tunable. In the preparation of PdND-T-AuNRs, dense capped AuNRs, a low reaction temperature, and suitable stabilizing agents were identified as critical reaction parameters for controlling palladium nanodendrites deposited on both ends of AuNRs. After overgrowth with palladium nanodendrites, the longitudinal surface plasmonic resonance peaks of PdND-T-AuNRs were red-shifted from 810 nm to 980 nm. The electrocatalytic activity of PdND-T-AuNRs for ethanol oxidation was examined, which was a bit weaker than that of cuboid core-shell Au-Pd nanodendrites; however, PdND-T-AuNRs were more stable in ethanol electrooxidation. Moreover, the photocatalytic activity of PdND-T-AuNRs for Suzuki cross-coupling reactions was investigated. At room temperature, nearly 100% yield was obtained under laser irradiation. The results can further enhance our capability of fine-tuning the optical, electronic, and catalytic properties of the bimetallic Au-Pd nanostructures.

  15. Strategies for the synthesis of supported gold palladium nanoparticles with controlled morphology and composition.

    PubMed

    Hutchings, Graham J; Kiely, Christopher J

    2013-08-20

    The discovery that supported gold nanoparticles are exceptionally effective catalysts for redox reactions has led to an explosion of interest in gold nanoparticles. In addition, incorporating a second metal as an alloy with gold can enhance the catalyst performance even more. The addition of small amounts of gold to palladium, in particular, and vice versa significantly enhances the activity of supported gold-palladium nanoparticles as redox catalysts through what researchers believe is an electronic effect. In this Account, we describe and discuss methodologies for the synthesis of supported gold-palladium nanoparticles and their use as heterogeneous catalysts. In general, three key challenges need to be addressed in the synthesis of bimetallic nanoparticles: (i) control of the particle morphology, (ii) control of the particle size distribution, and (iii) control of the nanoparticle composition. We describe three methodologies to address these challenges. First, we discuss the relatively simple method of coimpregnation. Impregnation allows control of particle morphology during alloy formation but does not control the particle compositions or the particle size distribution. Even so, we contend that this method is the best preparation method in the catalyst discovery phase of any project, since it permits the investigation of many different catalyst structures in one experiment, which may aid the identification of new catalysts. A second approach, sol-immobilization, allows enhanced control of the particle size distribution and the particle morphology, but control of the composition of individual nanoparticles is not possible. Finally, a modified impregnation method can allow the control of all three of these crucial parameters. We discuss the effect of the different methodologies on three redox reactions: benzyl alcohol oxidation, toluene oxidation, and the direct synthesis of hydrogen peroxide. We show that the coimpregnation method provides the best reaction

  16. Low-cost method for fabricating palladium and palladium-alloy thin films on porous supports

    DOEpatents

    Lee, Tae H; Park, Chan Young; Lu, Yunxiang; Dorris, Stephen E; Balachandran, Uthamalingham

    2013-11-19

    A process for forming a palladium or palladium alloy membrane on a ceramic surface by forming a pre-colloid mixture comprising a powder palladium source, carrier fluid, dispersant and a pore former and a binder. Ultrasonically agitating the precolloid mixture and applying to a substrate with an ultrasonic nozzle and heat curing the coating form a palladium-based membrane.

  17. Chemiresistive hydrogen gas sensors from gold-palladium nanopeapods

    NASA Astrophysics Data System (ADS)

    Moon, Chung Hee; Myung, Nosang V.; Haberer, Elaine D.

    2014-12-01

    Gold-palladium (Au-Pd) nanopeapod-based H2 chemiresistors were fabricated using a gold binding M13 viral template. Peptides displayed along the length of this biological template served as affinity binding sites to direct gold nanoparticle assembly under ambient conditions in an aqueous environment. In addition, the geometry of this filamentous biomolecule readily facilitated the formation of the highly anisotropic nanopeapod structure. Pd electroless deposition controlled peapod diameter, as well as electrical resistance. Sensor performance was determined by overall peapod morphology. Thicker nanopeapods (i.e., ˜15 nm Pd layer) with fully encapsulated Au nanoparticle seeds showed strong evidence of oxygen inclusion during or after Pd deposition, and a modest response (i.e., 0.04%-2.6%) at 2000 ppmv H2 after device conditioning through extended H2 exposure. Thinner nanopeapods (i.e., ˜5 nm Pd layer) with discontinuous Au nanoparticle coverage showed superior performance with a response of 117% at 2000 ppmv H2 in air, a 70% response time (t70%) within 1 min, and a low detection limit of 25 ppmv. The bio-directed formation of these unique thin-shelled, Au-Pd peapod nanostructures and the development of a highly sensitive H2 detector advance both the fields of nanoassembly and gas sensing.

  18. Platinum- and platinum alloy-coated palladium and palladium alloy particles and uses thereof

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang; Mo, Yibo; Vukmirovic, Miomir Branko

    2010-04-06

    The present invention relates to particle and nanoparticle composites useful as oxygen-reduction electrocatalysts. The particle composites are composed of a palladium or palladium-alloy particle or nanoparticle substrate coated with an atomic submonolayer, monolayer, bilayer, or trilayer of zerovalent platinum atoms. The invention also relates to a catalyst and a fuel cell containing the particle or nanoparticle composites of the invention. The invention additionally includes methods for oxygen reduction and production of electrical energy by using the particle and nanoparticle composites of the invention.

  19. Sorption of silver, gold and palladium with a polythioether foam.

    PubMed

    Khan, A S; Chow, A

    1986-02-01

    Silver, gold and palladium can be sorbed by a thiopolymer of the type [HO(CH(2)CH(2)CH(2)SS)(n)CH(2)CH(2)OH]. The distribution coefficient for palladium increases with halide concentration, with iodide having the largest effect. Silver can be extracted from chloride, nitrate or picrate media. The different distribution coefficients for gold in hydrochloric acid and in sodium chloride suggest that different sorption mechanisms predominate.

  20. DNAzyme-functionalized gold-palladium hybrid nanostructures for triple signal amplification of impedimetric immunosensor.

    PubMed

    Hou, Li; Gao, Zhuangqiang; Xu, Mingdi; Cao, Xia; Wu, Xiaoping; Chen, Guonan; Tang, Dianping

    2014-04-15

    A highly sensitive and selective impedimetric immunosensor with triple signal amplification was designed for ultrasensitive detection of prostate-specific antigen (PSA) by using anti-PSA antibody and DNAzyme-functionalized gold-palladium hybrid nanotags (Ab2-AuPd-DNA). The signal was amplified based on the Ab2-AuPd-DNA toward the catalytic precipitation of 4-choloro-1-naphthol (4-CN). DNAzyme (as a kind of peroxidase mimic) could catalyze the oxidation of 4-CN, whilst AuPd hybrid nanostructures could not only provide a large surface coverage for immobilization of biomolecules but also promote 4-CN oxidation to some extent. The produced insoluble benzo-4-chlorohexadienone via 4-CN was coated on the electrode surface, and hindered the electron transfer between the solution and the electrode, thereby increasing the Faradaic impedance of the base electrode. Three labeling strategies including Ab2-AuNP, Ab2-AuPd and Ab2-AuPd-DNA were investigated for determination of PSA, and improved analytical features were obtained with the Ab2-AuPd-DNA strategy. Under optimal conditions, the dynamic concentration range of the impedimetric immunosensor spanned from 1.0 pg mL(-1) to 50 ng mL(-1) PSA with a detection limit of 0.73 pg mL(-1). Intra- and inter-assay coefficients of variation were below 8.5% and 9.5%, respectively. Importantly, no significant differences at the 0.05 significance level were encountered in the analysis of 6 clinical serum specimens and 6 diluted standards between the impedimetric immunosensor and the commercialized electrochemiluminescent method for PSA detection. © 2013 Published by Elsevier B.V.

  1. Evolution of silver/gold triangular nanoframes from prismatic silver/gold core/shell nanostructures and their SERS properties

    NASA Astrophysics Data System (ADS)

    Parthiban, P.; Sakar, M.; Balakumar, S.

    2013-02-01

    We report the evolution of Ag/Au triangular nanoframes from nano core/shell of Ag/Au and their surface enhanced Raman scattering (SERS) properties. The Ag/Au prismatic core/shell nanostructures were synthesized using chemical reduction method. It was observed that, on the addition of excess gold chloride (HAuCl4) solution, the morphology of nano core/shell was changed to alloy like triangular nanoframes. Accordingly, a shift was found towards higher wavelengths in the UV-Visible absorption peaks of Ag/Au nanoframes compare to Ag/Au nano core/shell. Consequently, the SERS effect of these Ag/Au anisotropic nanostructures were studied on methylene blue. The Ag/Au alloy like prismatic nanoframes showed improved SERS effect than that of prismatic core/shell nanostructures. The experimental findings were revealed that the improved SERS effect could be resulted from the enhanced surface plasmon resonance (SPR) due to the alloy like construction of Ag/Au system.

  2. Ultrafine nanoporous palladium-aluminum film fabricated by citric acid-assisted hot-water-treatment of aluminum-palladium alloy film

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

    Harumoto, Takashi; Tamura, Yohei; Ishiguro, Takashi, E-mail: ishiguro@rs.noda.tus.ac.jp

    Hot-water-treatment has been adapted to fabricate ultrafine nanoporous palladium-aluminum film from aluminum-palladium alloy film. Using citric acid as a chelating agent, a precipitation of boehmite (aluminum oxide hydroxide, AlOOH) on the nanoporous palladium-aluminum film was suppressed. According to cross-sectional scanning transmission electron microscopy observations, the ligament/pore sizes of the prepared nanoporous film were considerably small (on the order of 10 nm). Since this fabrication method only requires aluminum alloy film and hot-water with chelating agent, the ultrafine nanoporous film can be prepared simply and environmentally friendly.

  3. Structure evolution of self-catalyzed grown Au, Ag and their alloy nanostructure

    NASA Astrophysics Data System (ADS)

    Zhu, Zhu; Chen, Feng; Xu, Chunxiang; Yang, Guangcan; Zhu, Ye; Luo, Zhaoxu

    2017-12-01

    Monitoring the nucleation and growth of nanomaterials is a key technique for material synthesis design and control. An efficient fabrication method can be realized deeply understanding the growth mechanisms. Here, noble metal nanostructures, gold (Au) nanoparticles, silver nanostructures (Ag nanoparticles/Ag nanowires) and gold-silver alloy nanoparticles were prepared in a facile method at room temperature. The growth processes of the Au nanoparticles, Ag nanowires and Au-Ag alloy nanoparticles can be monitored real-timely through the ultraviolet visible absorption (UV-vis), dynamic light scattering (DLS) and transmission electron microscopy (TEM). It is found that the whole formation involved Digestive ripening and Ostwald ripening cooperative mechanism. Furthermore, the self-assembly growth is noticed in the oriented attachment of precursor Ag monomers into nanowires under the same synthetic conditions without external templates or rigorous conditions. This result can provide a platform to discover the underlying growth mechanism of wet-chemistry methods for metal nanostructure fabrication.

  4. Ultrafast studies of gold, nickel, and palladium nanorods

    NASA Astrophysics Data System (ADS)

    Sando, Gerald M.; Berry, Alan D.; Owrutsky, Jeffrey C.

    2007-08-01

    Steady state and ultrafast transient absorption studies have been carried out for gold, nickel, and palladium high aspect ratio nanorods. For each metal, nanorods were fabricated by electrochemical deposition into ˜6μm thick polycarbonate templates. Two nominal pore diameters(10 and 30nm, resulting in nanorod diameters of about 40 and 60nm, respectively) were used, yielding nanorods with high aspect ratios (>25). Static spectra of nanorods of all three metals reveal both a longitudinal surface plasmon resonance (SPRL) band in the mid-infrared as well as a transverse band in the visible for the gold and larger diameter nickel and palladium nanorods. The appearance of SPRL bands in the infrared for high aspect ratio metal nanorods and the trends in their maxima for the different aspect ratios and metals are consistent with calculations based on the Gans theory. For the gold and nickel samples, time resolved studies were performed with a subpicosecond resolution using 400nm excitation and a wide range of probe wavelengths from the visible to the mid-IR as well as for infrared excitation (near 2000cm-1) probed at 800nm. The dynamics observed for nanorods of both metals and both diameters include transients due to electron-phonon coupling and impulsively excited coherent acoustic breathing mode oscillations, which are similar to those previously reported for spherical and smaller rod-shaped gold nanoparticles. The dynamics we observe are the same within the experimental uncertainty for 400nm and infrared (5μm) excitation probed at 800nm. The transient absorption using 400nm excitation and 800nm probe pulses of the palladium nanorods also reveal coherent acoustic oscillations. The results demonstrate that the dynamics for high aspect ratio metal nanorods are similar to those for smaller nanoparticles.

  5. Platinum-ruthenium-palladium alloys for use as a fuel cell catalyst

    DOEpatents

    Gorer, Alexander

    2002-01-01

    A noble metal alloy composition for a fuel cell catalyst, a ternary alloy composition containing platinum, ruthenium and palladium. The alloy shows increased activity as compared to well-known catalysts.

  6. Monodisperse gold-palladium alloy nanoparticles and their composition-controlled catalysis in formic acid dehydrogenation under mild conditions.

    PubMed

    Metin, Önder; Sun, Xiaolian; Sun, Shouheng

    2013-02-07

    Monodisperse 4 nm AuPd alloy nanoparticles with controlled composition were synthesized by co-reduction of hydrogen tetrachloroaurate(III) hydrate and palladium(II) acetylacetonate with a borane-morpholine complex in oleylamine. These NPs showed high activity (TOF = 230 h(-1)) and stability in catalyzing formic acid dehydrogenation and hydrogen production in water at 50 °C without any additives.

  7. Emerging advances in nanomedicine with engineered gold nanostructures.

    PubMed

    Webb, Joseph A; Bardhan, Rizia

    2014-03-07

    Gold nanostructures possess unique characteristics that enable their use as contrast agents, as therapeutic entities, and as scaffolds to adhere functional molecules, therapeutic cargo, and targeting ligands. Due to their ease of synthesis, straightforward surface functionalization, and non-toxicity, gold nanostructures have emerged as powerful nanoagents for cancer detection and treatment. This comprehensive review summarizes the progress made in nanomedicine with gold nanostructures (1) as probes for various bioimaging techniques including dark-field, one-photon and two-photon fluorescence, photothermal optical coherence tomography, photoacoustic tomography, positron emission tomography, and surface-enhanced Raman scattering based imaging, (2) as therapeutic components for photothermal therapy, gene and drug delivery, and radiofrequency ablation, and (3) as a theranostic platform to simultaneously achieve both cancer detection and treatment. Distinct from other published reviews, this article also discusses the recent advances of gold nanostructures as contrast agents and therapeutic actuators for inflammatory diseases including atherosclerotic plaque and arthritis. For each of the topics discussed above, the fundamental principles and progress made in the past five years are discussed. The review concludes with a detailed future outlook discussing the challenges in using gold nanostructures, cellular trafficking, and translational considerations that are imperative for rapid clinical viability of plasmonic nanostructures, as well as the significance of emerging technologies such as Fano resonant gold nanostructures in nanomedicine.

  8. Emerging advances in nanomedicine with engineered gold nanostructures

    NASA Astrophysics Data System (ADS)

    Webb, Joseph A.; Bardhan, Rizia

    2014-02-01

    Gold nanostructures possess unique characteristics that enable their use as contrast agents, as therapeutic entities, and as scaffolds to adhere functional molecules, therapeutic cargo, and targeting ligands. Due to their ease of synthesis, straightforward surface functionalization, and non-toxicity, gold nanostructures have emerged as powerful nanoagents for cancer detection and treatment. This comprehensive review summarizes the progress made in nanomedicine with gold nanostructures (1) as probes for various bioimaging techniques including dark-field, one-photon and two-photon fluorescence, photothermal optical coherence tomography, photoacoustic tomography, positron emission tomography, and surface-enhanced Raman scattering based imaging, (2) as therapeutic components for photothermal therapy, gene and drug delivery, and radiofrequency ablation, and (3) as a theranostic platform to simultaneously achieve both cancer detection and treatment. Distinct from other published reviews, this article also discusses the recent advances of gold nanostructures as contrast agents and therapeutic actuators for inflammatory diseases including atherosclerotic plaque and arthritis. For each of the topics discussed above, the fundamental principles and progress made in the past five years are discussed. The review concludes with a detailed future outlook discussing the challenges in using gold nanostructures, cellular trafficking, and translational considerations that are imperative for rapid clinical viability of plasmonic nanostructures, as well as the significance of emerging technologies such as Fano resonant gold nanostructures in nanomedicine.

  9. Low-Field-Triggered Large Magnetostriction in Iron-Palladium Strain Glass Alloys.

    PubMed

    Ren, Shuai; Xue, Dezhen; Ji, Yuanchao; Liu, Xiaolian; Yang, Sen; Ren, Xiaobing

    2017-09-22

    Development of miniaturized magnetostriction-associated devices requires low-field-triggered large magnetostriction. In this study, we acquired a large magnetostriction (800 ppm) triggered by a low saturation field (0.8 kOe) in iron-palladium (Fe-Pd) alloys. Magnetostriction enhancement jumping from 340 to 800 ppm was obtained with a slight increase in Pd concentration from 31.3 to 32.3 at. %. Further analysis showed that such a slight increase led to suppression of the long-range ordered martensitic phase and resulted in a frozen short-range ordered strain glass state. This strain glass state possessed a two-phase nanostructure with nanosized frozen strain domains embedded in the austenite matrix, which was responsible for the unique magnetostriction behavior. Our study provides a way to design novel magnetostrictive materials with low-field-triggered large magnetostriction.

  10. Selective growth of palladium and titanium dioxide nanostructures inside carbon nanotube membranes.

    PubMed

    Hevia, Samuel; Homm, Pía; Cortes, Andrea; Núñez, Verónica; Contreras, Claudia; Vera, Jenniffer; Segura, Rodrigo

    2012-06-25

    Hybrid nanostructured arrays based on carbon nanotubes (CNT) and palladium or titanium dioxide materials have been synthesized using self-supported and silicon-supported anodized aluminum oxide (AAO) as nanoporous template. It is well demonstrated that carbon nanotubes can be grown using these membranes and hydrocarbon precursors that decompose at temperatures closer to 600°C without the use of a metal catalyst. In this process, carbonic fragments condensate to form stacked graphitic sheets, which adopt the shape of the pores, yielding from these moulds' multi-walled carbon nanotubes. After this process, the ends of the tubes remain open and accessible to other substances, whereas the outer walls are protected by the alumina. Taking advantage of this fact, we have performed the synthesis of palladium and titanium dioxide nanostructures selectively inside carbon nanotubes using these CNT-AAO membranes as nanoreactors.

  11. Selective growth of palladium and titanium dioxide nanostructures inside carbon nanotube membranes

    PubMed Central

    2012-01-01

    Hybrid nanostructured arrays based on carbon nanotubes (CNT) and palladium or titanium dioxide materials have been synthesized using self-supported and silicon-supported anodized aluminum oxide (AAO) as nanoporous template. It is well demonstrated that carbon nanotubes can be grown using these membranes and hydrocarbon precursors that decompose at temperatures closer to 600°C without the use of a metal catalyst. In this process, carbonic fragments condensate to form stacked graphitic sheets, which adopt the shape of the pores, yielding from these moulds' multi-walled carbon nanotubes. After this process, the ends of the tubes remain open and accessible to other substances, whereas the outer walls are protected by the alumina. Taking advantage of this fact, we have performed the synthesis of palladium and titanium dioxide nanostructures selectively inside carbon nanotubes using these CNT-AAO membranes as nanoreactors. PMID:22731888

  12. Selective growth of palladium and titanium dioxide nanostructures inside carbon nanotube membranes

    NASA Astrophysics Data System (ADS)

    Hevia, Samuel; Homm, Pía; Cortes, Andrea; Núñez, Verónica; Contreras, Claudia; Vera, Jenniffer; Segura, Rodrigo

    2012-06-01

    Hybrid nanostructured arrays based on carbon nanotubes (CNT) and palladium or titanium dioxide materials have been synthesized using self-supported and silicon-supported anodized aluminum oxide (AAO) as nanoporous template. It is well demonstrated that carbon nanotubes can be grown using these membranes and hydrocarbon precursors that decompose at temperatures closer to 600°C without the use of a metal catalyst. In this process, carbonic fragments condensate to form stacked graphitic sheets, which adopt the shape of the pores, yielding from these moulds' multi-walled carbon nanotubes. After this process, the ends of the tubes remain open and accessible to other substances, whereas the outer walls are protected by the alumina. Taking advantage of this fact, we have performed the synthesis of palladium and titanium dioxide nanostructures selectively inside carbon nanotubes using these CNT-AAO membranes as nanoreactors.

  13. DETERMINATION OF GOLD, PLATINUM AND PALLADIUM IN BELGIAN CONGO ORES

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

    Crowther, A.B. et al.

    1955-01-31

    A survey of analytical methods for determination of gold, platinum, and palladium in urauium ore is presented. A fire assay method to obtain a silver load in which the other elements are determined appears feasible. (J.R.D.)

  14. Low-Dimensional Palladium Nanostructures for Fast and Reliable Hydrogen Gas Detection

    PubMed Central

    Noh, Jin-Seo; Lee, Jun Min; Lee, Wooyoung

    2011-01-01

    Palladium (Pd) has received attention as an ideal hydrogen sensor material due to its properties such as high sensitivity and selectivity to hydrogen gas, fast response, and operability at room temperature. Interestingly, various Pd nanostructures that have been realized by recent developments in nanotechnologies are known to show better performance than bulk Pd. This review highlights the characteristic properties, issues, and their possible solutions of hydrogen sensors based on the low-dimensional Pd nanostructures with more emphasis on Pd thin films and Pd nanowires. The finite size effects, relative strengths and weaknesses of the respective Pd nanostructures are discussed in terms of performance, manufacturability, and practical applicability. PMID:22346605

  15. Gold–promoted structurally ordered intermetallic palladium cobalt nanoparticles for the oxygen reduction reaction

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

    Kuttiyiel, Kurian A.; Sasaki, Kotaro; Su, Dong

    2014-11-06

    Considerable efforts to make palladium and palladium alloys active catalysts and a possible replacement for platinum have had a marginal success. Here, we report on a structurally ordered Au₁₀Pd₄₀Co₅₀ catalyst that exhibits comparable activity to conventional platinum catalysts in both acid and alkaline media. Electron microscopic techniques demonstrate that via addition of gold atoms PdCo nanoparticles undergo at elevated temperatures an atomic structural transition from core-shell to a rare intermetallic ordered structure with twin boundaries forming stable {111}, {110} and {100} facets. The superior stability of this catalyst compared to platinum after 10,000 potential cycles in alkaline media is attributedmore » to the atomic structural order of PdCo nanoparticles along with protective effect of clusters of gold atoms on the surface. This strategy of making ordered palladium intermetallic alloy nanoparticles can be used in diverse heterogeneous catalysis where particle size and structural stability matters.« less

  16. A close-space sublimation driven pathway for the manipulation of substrate-supported micro- and nanostructures

    NASA Astrophysics Data System (ADS)

    Sundar, Aarthi

    gold beneath the grid selectively attaches to it due to the surface energy gradient which drives gold from the low surface energy oxide surface to the higher surface energy nickel mesh. With this process being confined to areas adjacent to and in contact with the grid surface the film ruptures at well-defined locations to form isolated islands of gold and subsequently, a periodic array of microstructures. The process can be carried out on substrates of different crystallographic orientations leading to nanostructures which are formed epitaxially and have orientations based on underlying substrate orientations. The process can be extended by placing a metallic foil of Pt or Ni over preformed templates, in which case a reduction in the size of the initial structures is observed. Placing a foil on structures with random placement and a wide size distribution results, not only in a size reduction, but also a narrowed size distribution. Additive processes are carried out by using materials which possess high vapor pressures much below the sublimation temperature of the template materials. In this case a germanium substrate was used as a source of germanium adatoms while gold or silver nanostructures were used as heterogeneous nucleation sites. At elevated temperatures the adatoms collect in sufficient quantities to transform each site into a liquid alloy which, upon cooling, phase separates into elemental components sharing a common interface and, hence, resulting in the formation of heterodimers and hollowed metal nanocrescents upon etching away the Ge. A process which combined aspects of the additive and subtractive process was carried out by using a metallic foil with a high vapor pressure and higher surface energy than the substrate surface (in this case Pd foil). This process resulted in the initial preformed gold templates being annihilated and replaced by nanostructures of palladium, thereby altering their chemical composition. The assembly process relies on the

  17. Library of electrocatalytic sites in nano-structured domains: electrocatalysis of hydrogen peroxide.

    PubMed

    Pandey, Prem C; Singh, Bhupendra

    2008-12-01

    Electrochemical detection of hydrogen peroxide at eight types of ormosil-modified electrodes, referred as hexacyanoferrate-system; Prussian blue systems (PB-1, PB-2, and PB-3), palladium (Pd-) system, graphite (Gr-) system, gold nanoparticle (AuNPs) system and palladium-gold nanoparticle (Pd-AuNPs) system were studied. The results on electrochemical detection suggested that hydrogen peroxide does not undergo homogeneous electrochemical mediation; however, the presence of redox mediator within nano-structured domains facilitates the electro-analysis of the same via redox electrocatalysis. Four approaches causing manipulation in nano-structured domains are described: (a) increase in the molecular size of the components generating nano-structured domains; (b) modulation via chemical reactivity; (c) modulation by non-reactive moieties and known nanoparticles; and (d) modulation by mixed approaches (a-c), all leading to decrease in a nano-structured domains. The results demonstrated that an increase in the size of nano-structured domains or decrease in micro-porous geometry increases the efficiency of electrocatalysis. The basic reaction protocol adopted in generating nano-structured domains, followed by manipulation protocols, supported the introduction of a library for creating electrocatalytic sites with varying electrocatalytic efficiency within the same basic nano-structured platform.

  18. Synthesis, Structure, Stability and Redispersion of Gold-based Nanoparticles

    NASA Astrophysics Data System (ADS)

    Tiruvalam, Ram Chandra

    Nanoscale gold has been shown to possess an intriguing combination of unexpected optical, photochemical and catalytic properties. The ability to control the size, shape, morphology, composition and dispersion of gold-based nanostructures is key to optimizing their performance for nanotechnology applications. The advanced electron microscopy studies described in this thesis analyze three important aspects of gold and gold-palladium alloy nanoparticles: namely, (i) the ability to synthesize gold nanoparticles of controlled size and shape in an aqueous medium; (ii) the colloidal preparation of designer gold-palladium alloys for selective oxidation catalysis; and (iii) the ability to disperse gold as finely and homogeneously as possible on a metal oxide or carbon support. The ability to exploit the nanoscale properties of gold for various engineering applications often depends on our ability to control size and shape of the nanoscale entity by careful manipulation of the synthesis parameters. We have explored an aqueous based synthesis route, using oleylamine as both a reductant and surfactant, for preparing gold nanostructures. By systematically varying synthesis parameters such as oleylamine concentration, reaction temperature, and aging time it is possible to identify processing regimens that generate Au nanostructures having either pseudo-spherical, faceted polyhedral, nanostar or wire shaped morphologies. Furthermore, by quenching the reaction partway through it is possible to create a class of metastable Au-containing structures such as nanocubes, nanoboxes and nanowires. Possible formation mechanisms for these gold based nano-objects are discussed. There is a growing interest in using supported bimetallic AuPd alloy nanoparticles for selective oxidation reactions. In this study, a systematic series of size controlled AuPd bimetallic particles have been prepared by colloidal synthesis methods. Particles having random alloy structures, as well as `designer

  19. Bond Strength of Gold Alloys Laser Welded to Cobalt-Chromium Alloy

    PubMed Central

    Watanabe, Ikuya; Wallace, Cameron

    2008-01-01

    The objective of this study was to investigate the joint properties between cast gold alloys and Co-Cr alloy laser-welded by Nd:YAG laser. Cast plates were fabricated from three types of gold alloys (Type IV, Type II and low-gold) and a Co-Cr alloy. Each gold alloy was laser-welded to Co-Cr using a dental laser-welding machine. Homogeneously-welded and non-welded control specimens were also prepared. Tensile testing was conducted and data were statistically analyzed using ANOVA. The homogeneously-welded groups showed inferior fracture load compared to corresponding control groups, except for Co-Cr. In the specimens welded heterogeneously to Co-Cr, Type IV was the greatest, followed by low-gold and Type II. There was no statistical difference (P<0.05) in fracture load between Type II control and that welded to Co-Cr. Higher elongations were obtained for Type II in all conditions, whereas the lowest elongation occurred for low-gold welded to Co-Cr. This study indicated that, of the three gold alloys tested, the Type IV gold alloy was the most suitable alloy for laser-welding to Co-Cr. PMID:19088892

  20. Metallurgical characterization of new palladium-containing cobalt chromium and nickel chromium alloys

    NASA Astrophysics Data System (ADS)

    Puri, Raghav

    Recently introduced to the market has been an entirely new subclass of casting alloy composition whereby palladium (˜25 wt%) is added to traditional base metal alloys such as CoCr and NiCr. Objectives. The purpose of this study was to evaluate the microstructure and Vickers hardness of two new CoPdCr and one new NiPdCr alloy and compare them to traditional CoCr and NiCr alloys. Methods. The casting alloys investigated were: CoPdCr-A (Noble Crown NF, The Argen Corporation), CoPdCr-I (Callisto CP+, Ivoclar Vivadent), NiPdCr (Noble Crown, Argen), CoCr (Argeloy N.P. Special, Argen), and NiCr (Argeloy N.P. Star, Argen). As-cast cylindrical alloy specimens were mounted in epoxy resin and prepared with standard metallographic procedures, i.e. grinding with successive grades of SiC paper and polishing with alumina suspensions. The alloys were examined with an optical microscope, SEM/EPMA, and XRD to gain insight into their microstructure, composition, and crystal structure. Vickers hardness (VHN) was measured and statistically analyzed by one way ANOVA and Tukey's HSD test (alpha=0.05). Results. Optical microscopy showed a dendritic microstructure for all alloys. The Pd-containing alloys appear to possess a more complex microstructure. SEM/EPMA showed Cr to be rather uniformly distributed in the matrix with palladium tending to be segregated apart from Mo and Ni or Co. Areas of different composition may explain the poor electrochemical results noted in previous studies. XRD suggested the main phase in the Ni-containing solutions was a face centered cubic Ni solid solution, whereas the CoCr exhibited a hexagonal crystal structure that was altered to face centered cubic when Pd was included in the composition. For Vickers hardness, the Co-containing alloys possessed a greater hardness than the Ni-containing alloys. However, the incorporation of Pd in CoCr and NiCr had only a slight effect on microhardness. Conclusion. Overall, the inclusion of palladium increases the

  1. High performing and stable supported nano-alloys for the catalytic hydrogenation of levulinic acid to γ-valerolactone

    PubMed Central

    Luo, Wenhao; Sankar, Meenakshisundaram; Beale, Andrew M.; He, Qian; Kiely, Christopher J.; Bruijnincx, Pieter C. A.; Weckhuysen, Bert M.

    2015-01-01

    The catalytic hydrogenation of levulinic acid, a key platform molecule in many biorefinery schemes, into γ-valerolactone is considered as one of the pivotal reactions to convert lignocellulose-based biomass into renewable fuels and chemicals. Here we report on the development of highly active, selective and stable supported metal catalysts for this reaction and on the beneficial effects of metal nano-alloying. Bimetallic random alloys of gold-palladium and ruthenium-palladium supported on titanium dioxide are prepared with a modified metal impregnation method. Gold-palladium/titanium dioxide shows a marked,~27-fold increase in activity (that is, turnover frequency of 0.1 s−1) compared with its monometallic counterparts. Although ruthenium-palladium/titanium dioxide is not only exceptionally active (that is, turnover frequency of 0.6 s−1), it shows excellent, sustained selectivity to γ-valerolactone (99%). The dilution and isolation of ruthenium by palladium is thought to be responsible for this superior catalytic performance. Alloying, furthermore, greatly improves the stability of both supported nano-alloy catalysts. PMID:25779385

  2. Further studies on gold alloys used in fabrication of porcelain-fused-to-metal restorations.

    PubMed

    Civjan, S; Huget, E F; Dvivedi, N; Cosner, H J

    1975-03-01

    Composition, microstructure, castability, mechanical properties, and heat treatment characteristics of two gold-palladium-silver-based alloys were studied. The materials exhibited compositional as well as microstructural differences. Clinically acceptable castings could not be obtained when manufacturers' recommended casting temperatures were used. Ultimate tensile strength, yield strength, modulus of elasticity, and Brinell hardness values for the alloys were comparable. The elastic limit of Cameo, however, was significantly higher than that of vivo-star. Maximum rehardening of annealed castings occurred on reheat treatment at temperatures between 1,200 and 1,300 F. As-cast specimens, however, were not heat hardenable. The sequence of heat treatments used in the application of porcelain reduced slightly the hardness of both alloys. Hardness of the metal substructures was not increased by return of porcelain-coated specimens to a 1,250 F oven for final heat treatment.

  3. Silver and palladium alloy nanoparticle catalysts: reductive coupling of nitrobenzene through light irradiation.

    PubMed

    Peiris, Sunari; Sarina, Sarina; Han, Chenhui; Xiao, Qi; Zhu, Huai-Yong

    2017-08-15

    Silver-palladium (Ag-Pd) alloy nanoparticles strongly absorb visible light and exhibit significantly higher photocatalytic activity compared to both pure palladium (Pd) and silver (Ag) nanoparticles. Photocatalysts of Ag-Pd alloy nanoparticles on ZrO 2 and Al 2 O 3 supports are developed to catalyze the nitroaromatic coupling to the corresponding azo compounds under visible light irradiation. Ag-Pd alloy NP/ZrO 2 exhibited the highest photocatalytic activity for nitrobenzene coupling to azobenzene (yield of ∼80% in 3 hours). The photocatalytic efficiency could be optimized by altering the Ag : Pd ratio of the alloy nanoparticles, irradiation light intensity, temperature and wavelength. The rate of the reaction depends on the population and energy of the excited electrons, which can be improved by increasing the light intensity or by using a shorter wavelength. The knowledge developed in this study may inspire further studies on Ag alloy photocatalysts and organic syntheses using Ag-Pd nanoparticle catalysts driven under visible light Irradiation.

  4. Comparative Corrosion Behavior of Two Palladium Containing Titanium Alloys

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

    Lian, T; Yashiki, T; Nakayama, T

    2006-02-05

    The ASTM standard B 265 provides the requirements for the chemical composition of titanium (Ti) alloys. It is planned to use corrosion resistant and high strength titanium alloys to fabricate the drip shield at the proposed Yucca Mountain Repository. Titanium grade (Gr) 7 (R52400) and other Ti alloys are currently being characterized for this application. Ti Gr 7 contains 0.15% Palladium (Pd) to increase its corrosion performance. In this article we report results on the comparative short term corrosion behavior of Ti Gr 7 and a Ruthenium (Ru) containing alloy (Ti Gr 33). Ti Gr 33 also contains a smallmore » amount of Pd. Limited electrochemical testing such as polarization resistance and cyclic potentiodynamic curves showed that both alloys have a similar corrosion behavior in the tested environments.« less

  5. COMPARATIVE CORROSION BEHAVIOR OF TWO PALLADIUM CONTAINING TITANIUM ALLOYS

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

    T. Lian, T. Yashiki, T. Nakayama, T. Nakanishi, R. B. Rebak

    2006-07-23

    The ASTM standard B 265 provides the requirements for the chemical composition of titanium (Ti) alloys. It is planned to use corrosion resistant and high strength titanium alloys to fabricate the drip shield at the proposed Yucca Mountain Repository. Titanium grade (Gr) 7 (R52400) and other Ti alloys are currently being characterized for this application. Ti Gr 7 contains 0.15% Palladium (Pd) to increase its corrosion performance. In this article we report results on the comparative short term corrosion behavior of Ti Gr 7 and a Ruthenium (Ru) containing alloy (Ti Gr 33). Ti Gr 33 also contains a smallmore » amount of Pd. Limited electrochemical testing such as polarization resistance and cyclic potentiodynamic curves showed that both alloys have a similar corrosion behavior in the tested environments.« less

  6. Effects of Palladium Content, Quaternary Alloying, and Thermomechanical Processing on the Behavior of Ni-Ti-Pd Shape Memory Alloys for Actuator Applications

    NASA Technical Reports Server (NTRS)

    Bigelow, Glen

    2008-01-01

    The need for compact, solid-state actuation systems for use in the aerospace, automotive, and other transportation industries is currently driving research in high-temperature shape memory alloys (HTSMA) having transformation temperatures above 100 C. One of the basic high temperature systems under investigation to fill this need is NiTiPd. Prior work on this alloy system has focused on phase transformations and respective temperatures, no-load shape memory behavior (strain recovery), and tensile behavior for selected alloys. In addition, a few tests have been done to determine the effect of boron additions and thermomechanical treatment on the aforementioned properties. The main properties that affect the performance of a solid state actuator, namely work output, transformation strain, and permanent deformation during thermal cycling under load have mainly been neglected. There is also no consistent data representing the mechanical behavior of this alloy system over a broad range of compositions. For this thesis, ternary NiTiPd alloys containing 15 to 46 at.% palladium were processed and the transformation temperatures, basic tensile properties, and work characteristics determined. However, testing reveals that at higher levels of alloying addition, the benefit of increased transformation temperature begins to be offset by lowered work output and permanent deformation or "walking" of the alloy during thermal cycling under load. In response to this dilemma, NiTiPd alloys have been further alloyed with gold, platinum, and hafnium additions to solid solution strengthen the martensite and parent austenite phases in order to improve the thermomechanical behavior of these materials. The tensile properties, work behavior, and dimensional stability during repeated thermal cycling under load for the ternary and quaternary alloys were compared and discussed. In addition, the benefits of more advanced thermomechanical processing or training on the dimensional stability of

  7. 21 CFR 872.3060 - Noble metal alloy.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Noble metal alloy. 872.3060 Section 872.3060 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3060 Noble metal alloy. (a) Identification. A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver, that...

  8. 21 CFR 872.3060 - Noble metal alloy.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Noble metal alloy. 872.3060 Section 872.3060 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3060 Noble metal alloy. (a) Identification. A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver, that...

  9. Gallium arsenide/gold nanostructures deposited using plasma method

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

    Mangla, O.; Physics Department, Hindu College, University of Delhi, Delhi, 110007; Roy, S.

    2016-05-23

    The fabrication of gallium arsenide (GaAs) nanostructures on gold coated glass, quartz and silicon substrates using the high fluence and highly energetic ions has been reported. The high fluence and highly energetic ions are produced by the hot, dense and extremely non-equilibrium plasma in a modified dense plasma focus device. The nanostructures having mean size about 14 nm, 13 nm and 18 nm are deposited on gold coated glass, quartz and silicon substrates, respectively. The optical properties of nanostructures studied using absorption spectra show surface plasmon resonance peak of gold nanoparticles. In addition, the band-gap of GaAs nanoparticles is more than that ofmore » bulk GaAs suggesting potential applications in the field of optoelectronic and sensor systems.« less

  10. Precipitate strengthening of nanostructured aluminium alloy.

    PubMed

    Wawer, Kinga; Lewandowska, Malgorzata; Kurzydlowski, Krzysztof J

    2012-11-01

    Grain boundaries and precipitates are the major microstructural features influencing the mechanical properties of metals and alloys. Refinement of the grain size to the nanometre scale brings about a significant increase in the mechanical strength of the materials because of the increased number of grain boundaries which act as obstacles to sliding dislocations. A similar effect is obtained if nanoscale precipitates are uniformly distributed in coarse grained matrix. The development of nanograin sized alloys raises the important question of whether or not these two mechanisms are "additive" and precipitate strengthening is effective in nanostructured materials. In the reported work, hydrostatic extrusion (HE) was used to obtain nanostructured 7475 aluminium alloy. Nanosized precipitates were obtained by post-HE annealing. It was found that such annealing at the low temperatures (100 degrees C) results in a significant increase in the microhardness (HV0.2) and strength of the nanostructured 7475 aluminium alloy. These results are discussed in terms of the interplay between the precipitation and deformation of nanocrystalline metals.

  11. Passive fit of frameworks in titanium and palladium-silver alloy submitted the laser welding.

    PubMed

    de Sousa, S A; de Arruda Nobilo, M A; Henriques, G E P; Mesquita, M F

    2008-02-01

    This study evaluated the precision of fit of implant frameworks cast in titanium (cp Ti) and palladium-silver alloy (Pd-Ag), made by the one-piece cast and laser welding techniques. From a metal matrix with five implants, 20 master casts were obtained, to which replicas of implants were incorporated. On these masters 10 frameworks were made for each type of material (cp Ti and Pd-Ag alloy). Half of these were made by the one-piece cast technique and the other half by the laser welding technique. The implant/prosthesis interface was analysed and measured in the vestibular and lingual regions of the central and distal implants with the help of a measuring microscope. The results indicated that in the central cylinders, the Tukey test (P<0.0005) showed a significant difference in the passive fit between the laser-welded frameworks (34.73 microm) and those one-piece cast frameworks (151.39 microm), and as regards materials, the palladium-silver alloy (66.30 microm) showed better results than the titanium (119.83 microm). In the distal cylinders there was no significant difference between the frameworks cast in titanium and palladium-silver by the one-piece technique. However, after laser welding, there was a significant difference for the frameworks cast in titanium (31.37 microm) and palladium-silver (106.59 microm).

  12. Cu-Au alloy nanostructures coated with aptamers: a simple, stable and highly effective platform for in vivo cancer theranostics

    NASA Astrophysics Data System (ADS)

    Ye, Xiaosheng; Shi, Hui; He, Xiaoxiao; Yu, Yanru; He, Dinggeng; Tang, Jinlu; Lei, Yanli; Wang, Kemin

    2016-01-01

    As a star material in cancer theranostics, photoresponsive gold (Au) nanostructures may still have drawbacks, such as low thermal conductivity, irradiation-induced melting effect and high cost. To solve the problem, copper (Cu) with a much higher thermal conductivity and lower cost was introduced to generate a novel Cu-Au alloy nanostructure produced by a simple, gentle and one-pot synthetic method. Having the good qualities of both Cu and Au, the irregularly-shaped Cu-Au alloy nanostructures showed several advantages over traditional Au nanorods, including a broad and intense near-infrared (NIR) absorption band from 400 to 1100 nm, an excellent heating performance under laser irradiation at different wavelengths and even a notable photostability against melting. Then, via a simple conjugation of fluorophore-labeled aptamers on the Cu-Au alloy nanostructures, active targeting and signal output were simultaneously introduced, thus constructing a theranostic platform based on fluorophore-labeled, aptamer-coated Cu-Au alloy nanostructures. By using human leukemia CCRF-CEM cancer and Cy5-labeled aptamer Sgc8c (Cy5-Sgc8c) as the model, a selective fluorescence imaging and NIR photothermal therapy was successfully realized for both in vitro cancer cells and in vivo tumor tissues. It was revealed that Cy5-Sgc8c-coated Cu-Au alloy nanostructures were not only capable of robust target recognition and stable signal output for molecular imaging in complex biological systems, but also killed target cancer cells in mice with only five minutes of 980 nm irradiation. The platform was found to be simple, stable, biocompatible and highly effective, and shows great potential as a versatile tool for cancer theranostics.As a star material in cancer theranostics, photoresponsive gold (Au) nanostructures may still have drawbacks, such as low thermal conductivity, irradiation-induced melting effect and high cost. To solve the problem, copper (Cu) with a much higher thermal conductivity

  13. Comparative study of label-free electrochemical immunoassay on various gold nanostructures

    NASA Astrophysics Data System (ADS)

    Rafique, S.; Gao, C.; Li, C. M.; Bhatti, A. S.

    2013-10-01

    Electrochemical methods such as amperometry and impedance spectroscopy provide the feasibility of label-free immunoassay. However, the performance of electrochemical interfaces varies with the shape of gold nanostructures. In the present work three types of gold nanostructures including pyramid, spherical, and rod-like nanostructures were electrochemically synthesized on the gold electrode and were further transformed into immunosensor by covalent binding of antibodies. As a model protein, a cancer biomarker, Carcinoembryonic Antigen (CEA) was detected using amperometric and impedimetric techniques on three nanostructured electrodes, which enabled to evaluate and compare the immunoassay's performance. It was found that all three immunosensors showed improved linear electrochemical response to the concentration of CEA compared to bare Au electrode. Among all the spherical gold nanostructure based immunosensors displayed superior performance. Under optimal condition, the immunosensors exhibited a limit of detection of 4.1 pg ml-1 over a concentration range of five orders of magnitude. This paper emphasizes that fine control over the geometry of nanostructures is essentially important for high-performance electrochemical immunoassay.

  14. Mechanical, electrical, and thermal expansion properties of carbon nanotube-based silver and silver-palladium alloy composites

    NASA Astrophysics Data System (ADS)

    Pal, Hemant; Sharma, Vimal

    2014-11-01

    The mechanical, electrical, and thermal expansion properties of carbon nanotube (CNT)-based silver and silver-palladium (10:1, w/w) alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver-palladium nanocomposite with CNT resulted in increases in the hardness and Young's modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion (CTE). The hardness and Young's modulus of the nanocomposites were increased by 30%-40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver-palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.

  15. Nanostructured gold microelectrodes for extracellular recording from electrogenic cells.

    PubMed

    Brüggemann, D; Wolfrum, B; Maybeck, V; Mourzina, Y; Jansen, M; Offenhäusser, A

    2011-07-01

    We present a new biocompatible nanostructured microelectrode array for extracellular signal recording from electrogenic cells. Microfabrication techniques were combined with a template-assisted approach using nanoporous aluminum oxide to develop gold nanopillar electrodes. The nanopillars were approximately 300-400 nm high and had a diameter of 60 nm. Thus, they yielded a higher surface area of the electrodes resulting in a decreased impedance compared to planar electrodes. The interaction between the large-scale gold nanopillar arrays and cardiac muscle cells (HL-1) was investigated via focused ion beam milling. In the resulting cross-sections we observed a tight coupling between the HL-1 cells and the gold nanostructures. However, the cell membranes did not bend into the cleft between adjacent nanopillars due to the high pillar density. We performed extracellular potential recordings from HL-1 cells with the nanostructured microelectrode arrays. The maximal amplitudes recorded with the nanopillar electrodes were up to 100% higher than those recorded with planar gold electrodes. Increasing the aspect ratio of the gold nanopillars and changing the geometrical layout can further enhance the signal quality in the future.

  16. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction

    PubMed Central

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E.; Lowe, Michael A.; Lin, Feng; Nordlund, Dennis; Liu, Hongfang; Muller, David A.; Xin, Huolin L.; Abruña, Héctor D.

    2016-01-01

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd–Co–Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications. PMID:27336795

  17. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction

    DOE PAGES

    Wang, Deli; Liu, Sufen; Wang, Jie; ...

    2016-06-23

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd–Co–Cu lattice and distributes uniformly within the particles. Themore » uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications.« less

  18. Gold Nanostructures as a Platform for Combinational Therapy in Future Cancer Therapeutics

    PubMed Central

    Jelveh, Salomeh; Chithrani, Devika B.

    2011-01-01

    The field of nanotechnology is currently undergoing explosive development on many fronts. The technology is expected to generate innovations and play a critical role in cancer therapeutics. Among other nanoparticle (NP) systems, there has been tremendous progress made in the use of spherical gold NPs (GNPs), gold nanorods (GNRs), gold nanoshells (GNSs) and gold nanocages (GNCs) in cancer therapeutics. In treating cancer, radiation therapy and chemotherapy remain the most widely used treatment options and recent developments in cancer research show that the incorporation of gold nanostructures into these protocols has enhanced tumor cell killing. These nanostructures further provide strategies for better loading, targeting, and controlling the release of drugs to minimize the side effects of highly toxic anticancer drugs used in chemotherapy and photodynamic therapy. In addition, the heat generation capability of gold nanostructures upon exposure to UV or near infrared light is being used to damage tumor cells locally in photothermal therapy. Hence, gold nanostructures provide a versatile platform to integrate many therapeutic options leading to effective combinational therapy in the fight against cancer. In this review article, the recent progress in the development of gold-based NPs towards improved therapeutics will be discussed. A multifunctional platform based on gold nanostructures with targeting ligands, therapeutic molecules, and imaging contrast agents, holds an array of promising directions for cancer research. PMID:24212654

  19. Inductively coupled plasma-mass spectroscopy measurements of elemental release from 2 high-palladium dental casting alloys into a corrosion testing medium.

    PubMed

    Tufekci, Eser; Mitchell, John C; Olesik, John W; Brantley, William A; Papazoglou, Efstratios; Monaghan, Peter

    2002-01-01

    The biocompatibility of high-palladium alloy restorations has been of some concern due to the release of palladium into the oral environment and sensitivity reactions in patients. This study measured the in vitro elemental release from a Pd-Cu-Ga alloy and a Pd-Ga alloy into a corrosion testing medium. Both alloys were cast into 12-mm-diameter x 1-mm-thick disks, subjected to heat treatment that simulated porcelain firing cycles, polished to a 0.05-mm surface finish, and ultrasonically cleaned in ethanol. Two specimens of each alloy were immersed 3 times (at 7, 70, and 700 hours) in an aqueous lactic acid/NaCl solution used for in vitro corrosion testing and maintained at 37 degrees C. The specimens were removed after each immersion time, and the elemental compositions of the solutions were analyzed with inductively coupled plasma-mass spectroscopy (ICP-MS). Elemental concentrations for the 2 alloys at each immersion time were compared with Student t test (alpha=.05). No significant differences in palladium release were found for the 7- and 70-hour solutions, but significant differences were found for the 700-hour solutions. Mean concentrations of palladium and gallium in the 700-hour solutions, expressed as mass per unit area of alloy surface, were 97 (Pd) and 46 (Ga) microg/cm(2) for the Pd-Cu-Ga alloy and 5 (Pd) and 18 (Ga) microg/cm(2) for the Pd-Ga alloy. Relative proportions of the elements in the solutions were consistent with the release of palladium and breakdown of microstructural phases found in the alloys. The results suggest that there may be a lower risk of adverse biological reactions with the Pd-Ga alloy than with the Pd-Cu-Ga alloy tested.

  20. Synthesis of fullerene@gold core-shell nanostructures.

    PubMed

    Ren, Yupeng; Paira, Priyankar; Nayak, Tapas Ranjan; Ang, Wee Han; Pastorin, Giorgia

    2011-07-21

    A "direct encapsulation" method was developed for the synthesis of highly stable water-soluble fullerene@gold core-shell nanostructures, with gold nanoshells showing either closed or porous morphology. This gold nano-shell coating formed a "nano-oven", capable of decomposing encapsulated fullerene molecules rapidly when irradiated by laser. We envisaged this being a useful tool for chemical reactions as well as a novel scaffold for nano-material synthesis.

  1. Method for forming gold-containing catalyst with porous structure

    DOEpatents

    Biener, Juergen; Hamza, Alex V; Baeumer, Marcus; Schulz, Christian; Jurgens, Birte; Biener, Monika M.

    2014-07-22

    A method for forming a gold-containing catalyst with porous structure according to one embodiment of the present invention includes producing a starting alloy by melting together of gold and at least one less noble metal that is selected from the group consisting of silver, copper, rhodium, palladium, and platinum; and a dealloying step comprising at least partial removal of the less noble metal by dissolving the at least one less noble metal out of the starting alloy. Additional methods and products thereof are also presented.

  2. Rational geometrical engineering of palladium sulfide multi-arm nanostructures as a superior bi-functional electrocatalyst.

    PubMed

    Nandan, R; Nanda, K K

    2017-08-31

    Geometrical tunability offers sharp edges and an open-armed structure accompanied with a high electrochemical active surface area to ensure the efficient and effective utilization of materials by exposing the electrochemical active sites for facile accessibility of reactant species. Herein, we report a one-step, single-pot, surfactant-free, electroless, and economic route to synthesize palladium sulfide nanostructures with different geometries at mild temperatures and their catalytic properties towards the oxygen reduction reaction (ORR) and methanol electro-oxidation (MOR). For ORR, the positive on-set, half wave potentials, smaller Tafel slope, high electrochemical active surface area, large roughness factor, and better cyclic stability of the proposed nanostructures as compared to those of the commercial state-of-the-art Pt-C/PdS catalysts suggest their superiority in an alkaline medium. In addition, high mass activity (J f ∼ 715 mA mg -1 ), in comparison with that of the commercial state-of-the-art Pt-C/PdS catalysts (J f ∼ 138/41 mA mg -1 , respectively), and high J f /J b (1.52) along with the superior operational stability of the multi-arm palladium sulfide nanostructures towards MOR advocates the bi-functional behavior of the catalyst and its potential as a promising Pt-free anode/cathode electrocatalyst in fuel cells.

  3. NANOSTRUCTURED MATERIAL DESIGN FOR HG, AS, AND SE CAPTURE

    EPA Science Inventory

    The goal of this research project is to identify potential materials that can be used as multipollutant sorbents using a hierarchy of computational modeling approaches. Palladium (Pd) and gold (Au) alloys were investigated and the results show that the addition of a small amou...

  4. Gold in minerals and the composition of native gold

    USGS Publications Warehouse

    Jones, Robert Sprague; Fleischer, Michael

    1969-01-01

    Gold occurs in nature mainly as the metal and as various alloys. It forms complete series of solid solutions with silver, copper, nickel, palladium, and platinum. In association with the platinum metals, gold occurs as free gold as well as in solid solution. The native elements contain the most gold, followed by the sulfide minerals. Several gold tellurides are known, but no gold selenides have been reported, and only one sulfide, the telluride-sulfide mineral nagyagite, is known. The nonmetallic minerals carry the least gold, and the light-colored minerals generally contain less gold than the dark minerals. Some conclusions in the literature are conflicting in regard to the relation of fineness of native gold to its position laterally and vertically within a lode, the nature of the country rocks, and the location and size of nuggets in a streambed, as well as to the variation of fineness within an individual nugget.

  5. Gold coated metal nanostructures grown by glancing angle deposition and pulsed electroplating

    NASA Astrophysics Data System (ADS)

    Grüner, Christoph; Reeck, Pascal; Jacobs, Paul-Philipp; Liedtke, Susann; Lotnyk, Andriy; Rauschenbach, Bernd

    2018-05-01

    Nickel based nanostructures are grown by glancing angle deposition (GLAD) on flat and pre-patterned substrates. These fabricated porous thin films were subsequently coated by pulsed electroplating with gold. The morphology and conformity of the gold coating were investigated by scanning electron microscopy and X-ray diffraction. Controlled growth of closed gold layers on the nanostructures could be achieved, while the open-pore structure of the nanosculptured thin films was preserved. Such gold coated nanostructures are a candidate for optical sensing and catalysis applications. The demonstrated method can be applied for numerous material combinations, allowing to provide GLAD thin films with new surface properties.

  6. Gold/silver/gold trilayer films on nanostructured polycarbonate substrates for direct and label-free nanoplasmonic biosensing.

    PubMed

    López-Muñoz, Gerardo A; Estévez, M-Carmen; Vázquez-García, Marc; Berenguel-Alonso, Miguel; Alonso-Chamarro, Julián; Homs-Corbera, Antoni; Lechuga, Laura M

    2018-05-01

    Ultrasmooth gold/silver/gold trilayer nanostructured plasmonic sensors were obtained using commercial Blu-ray optical discs as nanoslits-based flexible polymer substrates. A thin gold film was used as an adhesion and nucleation layer to improve the chemical stability and reduce the surface roughness of the overlying silver film, without increasing ohmic plasmon losses. The structures were physically and optically characterized and compared with nanostructures of single gold layer. Ultrasmooth and chemically stable trilayer nanostructures with a surface roughness <0.5 nm were obtained following a simple and reproducible fabrication process. They showed a figure of merit (FOM) value up to 69.2 RIU -1 which is significantly higher (more than 95%) than the gold monolayer counterpart. Their potential for biosensing was demonstrated by employing the trilayer sensor for the direct and refractometric (label-free) detection of C-reactive protein (CRP) biomarker in undiluted urine achieving a Limit of Detection (LOD) in the pM order. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Exploring the Efficacy of Platinum and Palladium Nanostructures for Organic Molecule Detection via Raman Spectroscopy

    PubMed Central

    Tran, Minh; Whale, Alison

    2018-01-01

    Noble transition metals, like palladium (Pd) and platinum (Pt), have been well-known for their excellent catalytic and electrochemical properties. However, they have been considered non-active for surface enhanced Raman spectroscopy (SERS). In this work, we explore the scattering contributions of Pd and Pt for the detection of organic molecules. The Pd and Pt nanostructures were synthesized on silicon substrate using a modified galvanic displacement method. The results show Pt nanoparticles and dendritic Pd nanostructures with controlled density and size. The influence of surfactants, including sodium dodecyl sulfate and cetyltrimethylammonium bromide, on the size and morphology of the nanostructures was investigated. The Pd and Pt nanostructures with a combination of large size and high density were then used to explore their applicability for the detection of 10−5 M Rhodamine 6G and 10−2 M paraoxon. PMID:29316659

  8. Influence of gold content on copper oxidation from silver-gold-copper alloys

    NASA Astrophysics Data System (ADS)

    Swinbourne, D. R.; Barbante, G. G.; Strahan, A.

    1996-10-01

    In the final stages of the smelting of copper anode slimes, a silver alloy, known as “doré,” is produced. Oxidation refining is used to remove copper since this element interferes with subsequent electroparting of the small amounts of gold and platinum group metals in the doré. The gold content of doré can be greatly increased by gold scrap additions and this may affect the minimum achievable copper content of doré. In this work, silver-gold-copper alloys were oxidized by injecting pure oxygen at 1100 °C in the absence of any slag cover. For the gold contents expected in practice, the equilibrium copper content of the doré did not increase significantly as the gold content increased. However, at the other extreme of composition, the equilibrium copper content was a very strong function of the silver content of the gold bullion. The activity coefficient of copper in silver-gold alloys was calculated and compared to those predicted from a ternary subregular solution model of the system Ag-Au-Cu. Satisfactory agreement was found.

  9. Plasmonic Switches and Sensors Based on PANI-Coated Gold Nanostructures

    NASA Astrophysics Data System (ADS)

    Jiang, Nina

    Gold nanostructures have been received intense and growing attention due to their unique properties associated with localized surface plasmon resonance (LSPR). The frequency and strength of the LSPR are highly dependent on the dielectric properties of the surrounding environment around gold nanostructures. Such dependence offers the essential basis for the achievement of plasmonic switching and sensing. While the plasmonic response of gold nanostructures is tuned by changing their dielectric environment, the external stimuli inducing the changes in the dielectric environment will be read out through the plasmonic response of gold nanostructures. As a consequence, plasmonic sensors and switches can be engineered by integrating active media that can respond to external stimuli with gold nanostructures. In this thesis research, I have achieved the coating of polyaniline (PANI) ' a conductive polymer, on gold nanostructures, and exploited the application of the core/shell nanostructures in plasmonic switching and sensing. Large modulation of the longitudinal plasmon resonance of single gold nanorods is achieved by coating PANI shell onto gold nanorods to produce colloidal plasmonic switches. The dielectric properties of PANI shell can be tuned by changing the proton-doping levels, which allows for the modulation of the plasmonic response of gold nanorods. The coated nanorods are sparsely housed in a simple microfluidic chamber. HCl and NaOH solutions are alternately pumped through the chamber for the realization of proton doping and dedoping. The plasmonic switching behavior is examined by monitoring the single-particle scattering spectra under the proton-doped and dedoped state of PANI. The coated nanorods exhibit a remarkable switching performance, with the modulation depth and scattering peak shift reaching 10 dB and 100 nm, respectively. Electrodynamic simulations are employed to confirm the plasmon switching behavior. I have further investigated the modulation of

  10. Enhanced Hydrogen Transport over Palladium Ultrathin Films through Surface Nanostructure Engineering.

    PubMed

    Abate, Salvatore; Giorgianni, Gianfranco; Gentiluomo, Serena; Centi, Gabriele; Perathoner, Siglinda

    2015-11-01

    Palladium ultrathin films (around 2 μm) with different surface nanostructures are characterized by TEM, SEM, AFM, and temperature programmed reduction (TPR), and evaluated in terms of H2 permeability and H2-N2 separation. A change in the characteristics of Pd seeds by controlled oxidation-reduction treatments produces films with the same thickness, but different surface and bulk nanostructure. In particular, the films have finer and more homogeneous Pd grains, which results in lower surface roughness. Although all samples show high permeo-selectivity to H2 , the samples with finer grains exhibit enhanced permeance and lower activation energy for H2 transport. The analysis of the data suggests that grain boundaries between the Pd grains at the surface favor H2 transfer from surface to subsurface. Thus, the surface nanostructure plays a relevant role in enhancing the transport of H2 over the Pd ultrathin film, which is an important aspect to develop improved membranes that function at low temperatures and toward new integrated process architectures in H2 and syngas production with enhanced sustainability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Role of nanostructured gold surfaces on monocyte activation and Staphylococcus epidermidis biofilm formation

    PubMed Central

    Svensson, Sara; Forsberg, Magnus; Hulander, Mats; Vazirisani, Forugh; Palmquist, Anders; Lausmaa, Jukka; Thomsen, Peter; Trobos, Margarita

    2014-01-01

    The role of material surface properties in the direct interaction with bacteria and the indirect route via host defense cells is not fully understood. Recently, it was suggested that nanostructured implant surfaces possess antimicrobial properties. In the current study, the adhesion and biofilm formation of Staphylococcus epidermidis and human monocyte adhesion and activation were studied separately and in coculture in different in vitro models using smooth gold and well-defined nanostructured gold surfaces. Two polystyrene surfaces were used as controls in the monocyte experiments. Fluorescent viability staining demonstrated a reduction in the viability of S. epidermidis close to the nanostructured gold surface, whereas the smooth gold correlated with more live biofilm. The results were supported by scanning electron microscopy observations, showing higher biofilm tower formations and more mature biofilms on smooth gold compared with nanostructured gold. Unstimulated monocytes on the different substrates demonstrated low activation, reduced gene expression of pro- and anti-inflammatory cytokines, and low cytokine secretion. In contrast, stimulation with opsonized zymosan or opsonized live S. epidermidis for 1 hour significantly increased the production of reactive oxygen species, the gene expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, and IL-10, as well as the secretion of TNF-α, demonstrating the ability of the cells to elicit a response and actively phagocytose prey. In addition, cells cultured on the smooth gold and the nanostructured gold displayed a different adhesion pattern and a more rapid oxidative burst than those cultured on polystyrene upon stimulation. We conclude that S. epidermidis decreased its viability initially when adhering to nanostructured surfaces compared with smooth gold surfaces, especially in the bacterial cell layers closest to the surface. In contrast, material surface properties neither strongly

  12. New Gold Nanostructures for Sensor Applications: A Review

    PubMed Central

    Zhang, Yuanchao; Chu, Wendy; Foroushani, Alireza Dibaji; Wang, Hongbin; Li, Da; Liu, Jingquan; Barrow, Colin J.; Wang, Xin; Yang, Wenrong

    2014-01-01

    Gold based structures such as nanoparticles (NPs) and nanowires (NWs) have widely been used as building blocks for sensing devices in chemistry and biochemistry fields because of their unusual optical, electrical and mechanical properties. This article gives a detailed review of the new properties and fabrication methods for gold nanostructures, especially gold nanowires (GNWs), and recent developments for their use in optical and electrochemical sensing tools, such as surface enhanced Raman spectroscopy (SERS). PMID:28788124

  13. A new electrochemical sensor for the simultaneous determination of acetaminophen and codeine based on porous silicon/palladium nanostructure.

    PubMed

    Ensafi, Ali A; Ahmadi, Najmeh; Rezaei, Behzad; Abarghoui, Mehdi Mokhtari

    2015-03-01

    A porous silicon/palladium nanostructure was prepared and used as a new electrode material for the simultaneous determination of acetaminophen (ACT) and codeine (COD). Palladium nanoparticles were assembled on porous silicon (PSi) microparticles by a simple redox reaction between the Pd precursor and PSi in an aqueous solution of hydrofluoric acid. This novel nanostructure was characterized by different spectroscopic and electrochemical techniques including scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, fourier transform infrared spectroscopy and cyclic voltammetry. The high electrochemical activity, fast electron transfer rate, high surface area and good antifouling properties of this nanostructure enhanced the oxidation peak currents and reduced the peak potentials of ACT and COD at the surface of the proposed sensor. Simultaneous determination of ACT and COD was explored using differential pulse voltammetry. A linear range of 1.0-700.0 µmol L(-1) was achieved for ACT and COD with detection limits of 0.4 and 0.3 µmol L(-1), respectively. Finally, the proposed method was used for the determination of ACT and COD in blood serum, urine and pharmaceutical compounds. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. [Microanalytical determinations of gold alloys for fixed dentures].

    PubMed

    Lotito, M; Negri, P; Fraschini, M

    1993-01-01

    In this work the authors analyse gold alloys for fixed prosthesis by X-ray spectrometry in energy dispersion (EDS). The results of this analysis, given in graphic and table form, show remarkable differences in alloy composition. For this reason recommended dentists are to be attentive and severe in the control of gold alloys for fixed prosthesis.

  15. Comparison of the metal-to-ceramic bond strengths of four noble alloys with press-on-metal and conventional porcelain layering techniques.

    PubMed

    Khmaj, Mofida R; Khmaj, Abdulfatah B; Brantley, William A; Johnston, William M; Dasgupta, Tridib

    2014-11-01

    New noble alloys for metal ceramic restorations introduced by manufacturers are generally lower-cost alternatives to traditional higher-gold alloys. Information about the metal-to-ceramic bond strength for these alloys, which is needed for rational clinical selection, is often lacking. The purpose of this study was to evaluate the bond strength of 4 recently introduced noble alloys by using 2 techniques for porcelain application. Aquarius Hard (high-gold: 86.1 gold, 8.5 platinum, 2.6 palladium, 1.4 indium; values in wt. %), Evolution Lite (reduced-gold: 40.3 gold, 39.3 palladium, 9.3 indium, 9.2 silver, 1.8 gallium), Callisto 75 Pd (palladium-silver containing gold: 75.2 palladium, 7.1 silver, 2.5 gold, 9.3 tin, 1.0 indium), and Aries, (conventional palladium-silver: 63.7 palladium, 26.0 silver, 7.0 tin, 1.8 gallium, 1.5 indium) were selected for bonding to leucite-containing veneering porcelains. Ten metal ceramic specimens that met dimensional requirements for International Organization for Standardization (ISO) Standard 9693 were prepared for each alloy by using conventional porcelain layering and press-on-metal methods. The 3-point bending test in ISO Standard 9693 was used to determine bond strength. Values were compared with 2-way ANOVA (maximum likelihood analysis, SAS Mixed Procedure) and the Tukey test (α=.05). Means (standard deviations) for bond strength with conventional porcelain layering were as follows: Aquarius Hard (50.7 ±5.5 MPa), Evolution Lite (40.2 ±3.3 MPa), Callisto 75 Pd (37.2 ±3.9 MPa), and Aries (34.0 ±4.9 MPa). For the press-on-metal technique, bond strength results were as follows: Aquarius Hard (33.7 ±11.5 MPa), Evolution Lite (34.9 ±4.5 MPa), Callisto 75 Pd (37.2 ±11.9 MPa), and Aries (30.7 ±10.8 MPa). From statistical analyses, the following 3 significant differences were found for metal-to-ceramic bond strength: the bond strength for Aquarius Hard was significantly higher for conventional porcelain layers compared with

  16. Crack injection in silver gold alloys

    NASA Astrophysics Data System (ADS)

    Chen, Xiying

    Stress corrosion cracking (SCC) is a materials degradation phenomena resulting from a combination of stress and a corrosive environment. Among the alphabet soup of proposed mechanism of SCC the most important are film-rupture, film-induced cleavage and hydrogen embrittlement. This work examines various aspects of film-induced cleavage in gold alloys for which the operation of hydrogen embrittlement processes can be strictly ruled out on thermodynamic grounds. This is so because in such alloys SCC occurs under electrochemical conditions within which water is stable to hydrogen gas evolution. The alloy system examined in this work is AgAu since the corrosion processes in this system occur by a dealloying mechanism that results in the formation of nanoporous gold. The physics behind the dealloying process as well as the resulting formation of nanoporous gold is today well understood. Two important aspects of the film-induced cleavage mechanism are examined in this work: dynamic fracture in monolithic nanoporous gold and crack injection. In crack injection there is a finite thickness dealloyed layer formed on a AgAu alloy sample and the question of whether or not a crack that nucleates within this layer can travel for some finite distance into the un-corroded parent phase alloy is addressed. Dynamic fracture tests were performed on single edge-notched monolithic nanoporous gold samples as well as "infinite strip" sample configurations for which the stress intensity remains constant over a significant portion of the crack length. High-speed photography was used to measure the crack velocity. In the dynamic fracture experiments cracks were observed to travel at speeds as large as 270 m/s corresponding to about 68% of the Raleigh wave velocity. Crack injection experiments were performed on single crystal Ag77Au23, polycrystalline Ag72Au28 and pure gold, all of which had thin nanoporous gold layers on the surface of samples. Through-thickness fracture was seen in both the

  17. Stability of suspended gold and silver alloy monatomic chains

    NASA Astrophysics Data System (ADS)

    Fa, Wei; Dong, Jinming

    2008-06-01

    Using the first-principles plane wave pseudopotential method, we have studied the structures and stability of gold and silver alloy monatomic chains. It is found that minimizing system's enthalpy instead of its energy is critical to identify the stability of stretched alloy chains at zero temperature since the string tension can efficiently suppress the self-purification. Our simulations show that all the gold-containing chains do exhibit a local enthalpy minimum, giving a reasonable interpretation for the experimental observations of gold and silver alloy chains with different Ag concentrations [Bettini et al., Nat. Nanotechnol. 1, 182 (2006)]. These alloy chains are stabilized by the combined actions of the gold's relativistic effect and the string tension applied by the tip contacts, having similar geometrical structures to those of the pure gold chains.

  18. Hydrogen sorption characteristics of nanostructured Pd–10Rh processed by cryomilling

    DOE PAGES

    Yang, Nancy; Yee, Joshua K.; Zhang, Zhihui; ...

    2014-10-03

    Palladium and its alloys are model systems for studying solid-state storage of hydrogen. Mechanical milling is commonly used to process complex powder systems for solid-state hydrogen storage; however, milling can also be used to evolve nanostructured powder to modify hydrogen sorption characteristics. In the present study, cryomilling (mechanical attrition milling in a cryogenic liquid) is used to produce nanostructured palladium-rhodium alloy powder. Characterization of the cryomilled Pd-10Rh using electron microscopy, X-ray diffraction, and surface area analysis reveals that (i) particle morphology evolves from spherical to flattened disk-like particles; while the (ii) crystallite size decreases from several microns to less thanmore » 100 nm and (iii) dislocation density increases with increased cryomilling time. Hydrogen absorption and desorption isotherms as well as the time scales for absorption were measured for cryomilled Pd-10Rh, and correlated with observed microstructural changes induced by the cryomilling process. In short, as the microstructure of the Pd-10Rh alloy is refined by cryomilling: (i) the maximum hydrogen concentration in the α-phase increases, (ii) the pressure plateau becomes flatter, and (iii) the equilibrium hydrogen capacity at 760 Torr increases. In addition, the rate of hydrogen absorption was reduced by an order of magnitude compared to non-cryomilled (atomized) powder.« less

  19. One-pot synthesis of keto thioethers by palladium/gold-catalyzed click and pinacol reactions.

    PubMed

    Cadu, Alban; Watile, Rahul A; Biswas, Srijit; Orthaber, Andreas; Sjöberg, Per J R; Samec, Joseph S M

    2014-11-07

    An atom-efficient synthesis of keto thioethers was devised via tandem gold/palladium catalysis. The reaction proceeds through a regioselective thiol attack at the β-position of the alcohol, followed by an alkyl, aryl, or benzyl 1,2-shift. Both acyclic and cyclic systems were studied, in the latter case leading to the ring expansion of cyclic substrates.

  20. [Clinical evaluation of the effect of gold alloy and Ni-Cr alloy porcelain fused metal crown restorations].

    PubMed

    Sun, Wei-ge; Liu, Xiang-hui; Zhang, Ling; Zhang, Chun; Xie, Ming-yi; Zhou, Wen-juan

    2009-02-01

    To observe the clinical effect of gold alloy porcelain fused metal (PFM) crown restoration and Ni-Cr alloy PFM crown restoration. A total of 168 teeth from 48 patients were restored with gold alloy PFM crown. The other 48 patients, with a total of 179 teeth were restored with Ni-Cr alloy PFM crown. They were examined in integrality, retention, shade, cervical margin, and gingival health immediately, 6 months, one year, two years ,and three years after restoration. The date was analyzed by rank sum test using SPSS12.0 software package. The clinical effect of Ni-Cr alloy PFM crown was as good as gold alloy PFM crown when checked up after cementation at once. However, when they were examined 6 months, one year, two years ,and three years after restoration, the clinical effect of gold alloy PFM crown group was significantly better than that of Ni-Cr alloy PFM crown, P<0.05. The gold alloy PFM crown has better properties than Ni-Cr alloy PFM crown as a kind of long-term restoration, especially on the aspect of shade.

  1. Aqueous Black Colloids of Reticular Nanostructured Gold

    NASA Astrophysics Data System (ADS)

    Stanca, S. E.; Fritzsche, W.; Dellith, J.; Froehlich, F.; Undisz, A.; Deckert, V.; Krafft, C.; Popp, J.

    2015-01-01

    Since ancient times, noble gold has continuously contributed to several aspects of life from medicine to electronics. It perpetually reveals its new features. We report the finding of a unique form of gold, reticular nanostructured gold (RNG), as an aqueous black colloid, for which we present a one-step synthesis. The reticules consist of gold crystals that interconnect to form compact strands. RNG exhibits high conductivity and low reflection, and these features, coupled with the high specific surface area of the material, could prove valuable for applications in electronics and catalysis. Due to high absorption throughout the visible and infrared domain, RNG has the potential to be applied in the construction of sensitive solar cells or as a substrate for Raman spectroscopy.

  2. Correlation between theoretical descriptor and catalytic oxygen reduction activity of graphene supported palladium and palladium alloy electrocatalysts

    NASA Astrophysics Data System (ADS)

    Seo, Min Ho; Choi, Sung Mook; Lee, Dong Un; Kim, Won Bae; Chen, Zhongwei

    2015-12-01

    The oxygen reduction reaction, ORR, performances of graphene-supported palladium (Pd) and palladium alloys (Pd3X: X = Ag, Co and Fe) catalysts with highly dispersed catalyst particles are investigated in acidic and alkaline conditions using a rotating disk electrode, RDE. Graphene nanosheet, GNS, supported Pd based catalysts are fabricated without surfactant through the impregnation of Pd and 2nd metal precursors on GNS, leading to small and uniformly dispersed nanoparticles, even when high metal loading of up to 60 wt.% are deposited on supports. The ab-initio density functional theory, DFT, calculations, which are based on the d-band center theory, have been applied to correlate with the results of the ORR performances obtained by half-cell tests. Additionally, the cohesive energy, Ecoh, and dissolution potential, Um, for the Pd nanoparticles have been calculated to understand thermodynamic stability. To elucidate the d-band center shift, the Pd 3d5/2 core-level binding energies for Pd/GNS, Pd3Ag/GNS, Pd3Fe/GNS and Pd3Co/GNS have been investigated by X-ray photoelectron spectroscopy, XPS. The GNS-supported Pd, or Pd-based alloy-nanoparticle catalyst shows good ORR activity under acidic and alkaline conditions, suggesting it may offer potential replacement for Pt for use in cathode electrodes of anion-exchange membrane fuel cell, AEMFC, and acid based polymer electrolyte fuel cell, PEMFC.

  3. Gold nanostructure materials in diabetes management

    NASA Astrophysics Data System (ADS)

    Si, Satyabrata; Pal, Arttatrana; Mohanta, Jagdeep; Sagar Satapathy, Smith

    2017-04-01

    Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia, and is now one of the most non-communicable diseases globally and can be lethal if not properly controlled. Prolonged exposure to chronic hyperglycemia, without proper management, can lead to various vascular complications and represents the main cause of morbidity and mortality in diabetes patients. Studies have indicated that major long-term complications of diabetes arise from persistent oxidative-nitrosative stress and dysregulation in multiple metabolic pathways. Presently, the main focus for diabetes management is to optimize the available techniques to ensure adequate blood sugar level, blood pressure and lipid profile, thereby minimizing the diabetes complications. In this regard, nanomedicine utilizing gold nanostructures has great potential and seems to be a promising option. The present review highlights the basic concepts and up-to-date literature survey of gold nanostructure materials in management of diabetes in several ways, which include sensing, imaging, drug delivery and therapy. The work can be of interest to various researchers working on basic and applied sciences including nanosciences.

  4. Effective and selective recovery of gold and palladium ions from metal wastewater using a sulfothermophilic red alga, Galdieria sulphuraria.

    PubMed

    Ju, Xiaohui; Igarashi, Kensuke; Miyashita, Shin-Ichi; Mitsuhashi, Hiroaki; Inagaki, Kazumi; Fujii, Shin-Ichiro; Sawada, Hitomi; Kuwabara, Tomohiko; Minoda, Ayumi

    2016-07-01

    The demand for precious metals has increased in recent years. However, low concentrations of precious metals dissolved in wastewater are yet to be recovered because of high operation costs and technical problems. The unicellular red alga, Galdieria sulphuraria, efficiently absorbs precious metals through biosorption. In this study, over 90% of gold and palladium could be selectively recovered from aqua regia-based metal wastewater by using G. sulphuraria. These metals were eluted from the cells into ammonium solutions containing 0.2M ammonium salts without other contaminating metals. The use of G. sulphuraria is an eco-friendly and cost-effective way of recovering low concentrations of gold and palladium discarded in metal wastewater. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  5. High Strength and Thermally Stable Nanostructured Magnesium Alloys and Nanocomposites

    NASA Astrophysics Data System (ADS)

    Chang, Yuan-Wei

    Magnesium and its alloys are currently in the spotlight of global research because of the need to limit energy consumption and reduce the environmental impact. In particular, their low densities compared to other structural metals make them a very attractive alternative in the automobile and aerospace industries. However, their low strength compared to other structural materials (e.g. Al and steels) has limited their widespread application. This dissertation presents the results of developing and investigation of a high strength nanostructured magnesium-aluminum alloy and composite. The nanostructured magnesium alloy is prepared by cryomilling and consolidated by spark-plasma-sintering. Focused ion beam is used to prepare micropillars with different diameters ranging from 1.5 to 8 mum and micro-compression test is conducted by nanoindenter in order to evaluate the mechanical properties. The yield strength obtained in the present study is around three times higher than conventional magnesium alloys (120 MPa vs. 370 MPa). The yield strength of the nanostructured magnesium alloy is further improved through hot extrusion, resulting in a yield strength of 550 MPa and an ultimate strength of 580 MPa. The nanostructured magnesium alloy exhibits a strong size-dependence, and a significant improvement in strength is observed when the pillar diameter is reduced to below 3.5 mum. The deformation mechanisms of the compressed pillars were characterized using transmission electron microscopy. The size-induced strengthening is attributed to a less number of dislocation sources along with a higher activity of non-basal deformation mechanisms. We have also developed a high strength and thermally stable nanostructured magnesium composite by adding diamantane. A yield strength of 500 MPa is achieved, moreover, excellent thermal stability is demonstrated in the magnesium alloy containing diamantanes. The strength and grain size are thermally stable after annealing at 400°C for 100

  6. High Temperature Fracture Characteristics of a Nanostructured Ferritic Alloy (NFA)

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

    Byun, Thak Sang; Kim, Jeoung H; Ji Hyun, Yoon

    2010-01-01

    High temperature fracture behavior has been investigated for the nanostructured ferritic alloy 14YWT (SM10). The fracture toughness of the alloy was above 140 MPa m at low temperatures, room temperature (RT) and 200 C, but decreased to a low fracture toughness range of 52 82 MPa m at higher temperatures up to 700 C. This behavior was explained by the fractography results indicating that the unique nanostructure of 14YWT alloy produced shallow plasticity layers at high temperatures and a low-ductility grain boundary debonding occurred at 700 C.

  7. Atomically flat single-crystalline gold nanostructures for plasmonic nanocircuitry.

    PubMed

    Huang, Jer-Shing; Callegari, Victor; Geisler, Peter; Brüning, Christoph; Kern, Johannes; Prangsma, Jord C; Wu, Xiaofei; Feichtner, Thorsten; Ziegler, Johannes; Weinmann, Pia; Kamp, Martin; Forchel, Alfred; Biagioni, Paolo; Sennhauser, Urs; Hecht, Bert

    2010-01-01

    Deep subwavelength integration of high-definition plasmonic nanostructures is of key importance in the development of future optical nanocircuitry for high-speed communication, quantum computation and lab-on-a-chip applications. To date, the experimental realization of proposed extended plasmonic networks consisting of multiple functional elements remains challenging, mainly because of the multi-crystallinity of commonly used thermally evaporated gold layers. This can produce structural imperfections in individual circuit elements that drastically reduce the yield of functional integrated nanocircuits. In this paper we demonstrate the use of large (>100 μm(2)) but thin (<80 nm) chemically grown single-crystalline gold flakes that, after immobilization, serve as an ideal basis for focused ion beam milling and other top-down nanofabrication techniques on any desired substrate. Using this methodology we obtain high-definition ultrasmooth gold nanostructures with superior optical properties and reproducible nano-sized features over micrometre-length scales. Our approach provides a possible solution to overcome the current fabrication bottleneck and realize high-definition plasmonic nanocircuitry.

  8. Development of second generation gold-supported palladium material with low-leaching and recyclable characteristics in aromatic amination.

    PubMed

    Al-Amin, Mohammad; Arai, Satoshi; Hoshiya, Naoyoki; Honma, Tetsuo; Tamenori, Yusuke; Sato, Takatoshi; Yokoyama, Mami; Ishii, Akira; Takeuchi, Masashi; Maruko, Tomohiro; Shuto, Satoshi; Arisawa, Mitsuhiro

    2013-08-02

    An improved process for the preparation of sulfur-modified gold-supported palladium material [SAPd, second generation] is presented. The developed preparation method is safer and generates less heat (aqueous Na2S2O8 and H2SO4) for sulfur fixation on a gold surface, and it is superior to the previous method of preparing SAPd (first generation), which requires the use of the more heat-generating and dangerous piranha solution (concentrated H2SO4 and 35% H2O2) in the sulfur fixation step. This safer and improved preparation method is particularly important for the mass production of SAPd (second generation) for which the catalytic activity was examined in ligand-free Buchwald-Hartwig cross-coupling reactions. The catalytic activities were the same between the first and second generation SAPds in aromatic aminations, but the lower palladium leaching properties and safer preparative method of second generation SAPd are a significant improvement over the first generation SAPd.

  9. Accelerated sintering in phase-separating nanostructured alloys

    PubMed Central

    Park, Mansoo; Schuh, Christopher A.

    2015-01-01

    Sintering of powders is a common means of producing bulk materials when melt casting is impossible or does not achieve a desired microstructure, and has long been pursued for nanocrystalline materials in particular. Acceleration of sintering is desirable to lower processing temperatures and times, and thus to limit undesirable microstructure evolution. Here we show that markedly enhanced sintering is possible in some nanocrystalline alloys. In a nanostructured W–Cr alloy, sintering sets on at a very low temperature that is commensurate with phase separation to form a Cr-rich phase with a nanoscale arrangement that supports rapid diffusional transport. The method permits bulk full density specimens with nanoscale grains, produced during a sintering cycle involving no applied stress. We further show that such accelerated sintering can be evoked by design in other nanocrystalline alloys, opening the door to a variety of nanostructured bulk materials processed in arbitrary shapes from powder inputs. PMID:25901420

  10. Synthesis of gold nanostructures using fruit extract of Garcinia Indica

    NASA Astrophysics Data System (ADS)

    Krishnaprabha, M.; Pattabi, Manjunatha

    2016-05-01

    Gold nanoparticles having different shapes are synthesized using extract of fresh fruit rinds of Garcinia Indica. The onset of growth and formation of gold nanostructures is confirmed from UV-Vis spectroscopy. Morphological studies are done using FESEM. Size dependent catalytic activity is evaluated with the model reduction reaction of 4-nitrophenol to 4-aminophenol.

  11. Nanostructural hierarchy increases the strength of aluminium alloys.

    PubMed

    Liddicoat, Peter V; Liao, Xiao-Zhou; Zhao, Yonghao; Zhu, Yuntian; Murashkin, Maxim Y; Lavernia, Enrique J; Valiev, Ruslan Z; Ringer, Simon P

    2010-09-07

    Increasing the strength of metallic alloys while maintaining formability is an interesting challenge for enabling new generations of lightweight structures and technologies. In this paper, we engineer aluminium alloys to contain a hierarchy of nanostructures and possess mechanical properties that expand known performance boundaries-an aerospace-grade 7075 alloy exhibits a yield strength and uniform elongation approaching 1 GPa and 5%, respectively. The nanostructural architecture was observed using novel high-resolution microscopy techniques and comprises a solid solution, free of precipitation, featuring (i) a high density of dislocations, (ii) subnanometre intragranular solute clusters, (iii) two geometries of nanometre-scale intergranular solute structures and (iv) grain sizes tens of nanometres in diameter. Our results demonstrate that this novel architecture offers a design pathway towards a new generation of super-strong materials with new regimes of property-performance space.

  12. The influence of a hyperbaric environment and increased oxygen partial pressure on the corrosion of dental alloys.

    PubMed

    Mehl, Christian; Heblich, Frank; Lenz, Rudolf; Ludwig, Klaus; Kern, Matthias

    2011-09-01

    The purpose of this in-vitro study was to determine whether there is a correlation between a hyperbaric environment or increased oxygen partial pressure and the corrosion of dental alloys used for dental restorations in divers. Samples of three commercially available dental alloys (palladium-based, reduced-gold-content and high-gold-content) were tested in the DIN EN ISO 1562 static immersion test and the amount of dissolved ions measured by atomic absorption spectrometry. The specimens were exposed to one of the following three conditions: normobaric and normoxic conditions (PO2 21 kPa); 608 kPa (6 bar, PO2 127 kPa) pressurised air in a pressure chamber or 506 kPa (5 bar, PO2 304 kPa) pressurised nitrox in a pressure chamber. None of the exposures suggested a correlation between increased ion solubility as a measure of corrosion and increased ambient pressure of the three alloys. The reduced-gold-content alloy released zinc ions at twice the weekly recommended dose. When the palladium-based alloy was exposed to a hyperbaric or hyperbaric/hyperoxic environment, ion solubility increased only slightly for gallium and silver. Within the limited sample size of the current study it can be concluded that hyperbaric and/or hyperoxic conditions do not seem to be a risk for increased corrosion for any of the three tested alloys.

  13. Characteristics of Iron-Palladium alloy thin films deposited by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Chiu, Y.-J.; Shen, C.-Y.; Chang, H.-W.; Jian, S.-R.

    2018-06-01

    The microstructural features, magnetic, nanomechanical properties and wettability behaviors of Iron-Palladium (FePd) alloy thin films are investigated by using X-ray diffraction (XRD), atomic force microscopy (AFM), vibrating sample magnetometer (VSM), nanoindentation and water contact angle (CA) techniques, respectively. The FePd alloy thin films were deposited on glass substrates using a magnetron sputtering system. The post-annealing processes of FePd alloy thin films were carried out at 400 °C and 750 °C and resulted in a significant increase of both the average grain size and surface roughness. The XRD analysis showed that FePd alloy thin films exhibited a predominant (1 1 1) orientation. The magnetic field dependence of magnetization of all FePd thin films are measured at room temperature showed the ferromagnetic characteristics. The nanoindentation with continuous stiffness measurement (CSM) is used to measure the hardness and Young's modulus of present films. The contact angle (θCA) increased with increasing surface roughness. The maximum θCA of 75° was achieved for the FePd alloy thin film after annealing at 750 °C and a surface roughness of 4.2 nm.

  14. Low gravity containerless processing of immiscible gold rhodium alloys

    NASA Technical Reports Server (NTRS)

    Andrews, J. Barry

    1986-01-01

    Under normal one-g conditions immiscible alloys segregate extensively during solidification due to sedementation of the more dense of the immiscible liquid phases. However, under low-g conditions it should be possible to form a dispersion of the two immiscible liquids and maintain this dispersed structure during solidification. Immiscible (hypermonotectic) gold-rhodium alloys were processed in the Marshall Space Flight Center 105 meter drop tube in order to investigate the influence of low gravity, containerless solidification on their microstructure. Hypermonotectic alloys composed of 65 atomic % rhodium exhibited a tendency for the gold rich liquid to wet the outer surface of the containerless processed samples. This tendency led to extensive segregation in several cases. However, well dispersed microstructures consisting of 2 to 3 micron diameter rhodium-rich spheres in a gold-rich matrix were produced in 23.4 atomic % rhodium alloys. This is one of the best dispersions obtained in research on immiscible alloy-systems to data.

  15. A low-cost hierarchical nanostructured beta-titanium alloy with high strength

    PubMed Central

    Devaraj, Arun; Joshi, Vineet V.; Srivastava, Ankit; Manandhar, Sandeep; Moxson, Vladimir; Duz, Volodymyr A.; Lavender, Curt

    2016-01-01

    Lightweighting of automobiles by use of novel low-cost, high strength-to-weight ratio structural materials can reduce the consumption of fossil fuels and in turn CO2 emission. Working towards this goal we achieved high strength in a low cost β-titanium alloy, Ti–1Al–8V–5Fe (Ti185), by hierarchical nanostructure consisting of homogenous distribution of micron-scale and nanoscale α-phase precipitates within the β-phase matrix. The sequence of phase transformation leading to this hierarchical nanostructure is explored using electron microscopy and atom probe tomography. Our results suggest that the high number density of nanoscale α-phase precipitates in the β-phase matrix is due to ω assisted nucleation of α resulting in high tensile strength, greater than any current commercial titanium alloy. Thus hierarchical nanostructured Ti185 serves as an excellent candidate for replacing costlier titanium alloys and other structural alloys for cost-effective lightweighting applications. PMID:27034109

  16. A low-cost hierarchical nanostructured beta-titanium alloy with high strength

    DOE PAGES

    Devaraj, Arun; Joshi, Vineet V.; Srivastava, Ankit; ...

    2016-04-01

    Lightweighting of automobiles by use of novel low-cost, high strength-to-weight ratio structural materials can reduce the consumption of fossil fuels and in turn CO 2 emission. Working towards this goal we achieved high strength in a low cost β-titanium alloy, Ti-1Al-8V-5Fe (Ti185), by hierarchical nanostructure consisting of homogenous distribution of micron-scale and nanoscale α-phase precipitates within the β-phase matrix. The sequence of phase transformation leading to this hierarchical nanostructure is explored using electron microscopy and atom probe tomography. Our results suggest that the high number density of nanoscale α-phase precipitates in the β-phase matrix is due to ω assisted nucleationmore » of α resulting in high tensile strength, greater than any current commercial titanium alloy. Furthermore hierarchical nanostructured Ti185 serves as an excellent candidate for replacing costlier titanium alloys and other structural alloys for cost-effective lightweighting applications.« less

  17. A low-cost hierarchical nanostructured beta-titanium alloy with high strength

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

    Devaraj, Arun; Joshi, Vineet V.; Srivastava, Ankit

    Lightweighting of automobiles by use of novel low-cost, high strength-to-weight ratio structural materials can reduce the consumption of fossil fuels and in turn CO 2 emission. Working towards this goal we achieved high strength in a low cost β-titanium alloy, Ti-1Al-8V-5Fe (Ti185), by hierarchical nanostructure consisting of homogenous distribution of micron-scale and nanoscale α-phase precipitates within the β-phase matrix. The sequence of phase transformation leading to this hierarchical nanostructure is explored using electron microscopy and atom probe tomography. Our results suggest that the high number density of nanoscale α-phase precipitates in the β-phase matrix is due to ω assisted nucleationmore » of α resulting in high tensile strength, greater than any current commercial titanium alloy. Furthermore hierarchical nanostructured Ti185 serves as an excellent candidate for replacing costlier titanium alloys and other structural alloys for cost-effective lightweighting applications.« less

  18. Highly conductive and pure gold nanostructures grown by electron beam induced deposition

    PubMed Central

    Shawrav, Mostafa M.; Taus, Philipp; Wanzenboeck, Heinz D.; Schinnerl, M.; Stöger-Pollach, M.; Schwarz, S.; Steiger-Thirsfeld, A.; Bertagnolli, Emmerich

    2016-01-01

    This work introduces an additive direct-write nanofabrication technique for producing extremely conductive gold nanostructures from a commercial metalorganic precursor. Gold content of 91 atomic % (at. %) was achieved by using water as an oxidative enhancer during direct-write deposition. A model was developed based on the deposition rate and the chemical composition, and it explains the surface processes that lead to the increases in gold purity and deposition yield. Co-injection of an oxidative enhancer enabled Focused Electron Beam Induced Deposition (FEBID)—a maskless, resistless deposition method for three dimensional (3D) nanostructures—to directly yield pure gold in a single process step, without post-deposition purification. Gold nanowires displayed resistivity down to 8.8 μΩ cm. This is the highest conductivity achieved so far from FEBID and it opens the possibility of applications in nanoelectronics, such as direct-write contacts to nanomaterials. The increased gold deposition yield and the ultralow carbon level will facilitate future applications such as the fabrication of 3D nanostructures in nanoplasmonics and biomolecule immobilization. PMID:27666531

  19. Fabrication of polystyrene/gold nanotubes and nanostructure-controlled growth of aluminate.

    PubMed

    Zhu, Haifeng; Ai, Sufen; He, Qiang; Cui, Yue; Li, Junbai

    2007-07-01

    Direct adsorption of gold nanoparticles in the inner of alumina template and following immersion of polystyrene (PS) dichloromethane solution in the template resulted in the fabrication of composite nanotubes of PS and gold nanoparticles. Several methods have been used to characterize the tubular structure. Nanostructured sodium aluminates were formed when the anodic alumina oxide membrane was dissolved by the sodium hydroxide. A "flower" shape was found after etching the template while the synthesis process was recorded as function of a time. The results demonstrate that the shape and size of the aluminates nanostructure can be controlled by etching time and the pore diameter of the alumina membrane.

  20. Direct writing of gold nanostructures with an electron beam: On the way to pure nanostructures by combining optimized deposition with oxygen-plasma treatment

    PubMed Central

    Belić, Domagoj; Shawrav, Mostafa M; Bertagnolli, Emmerich

    2017-01-01

    This work presents a highly effective approach for the chemical purification of directly written 2D and 3D gold nanostructures suitable for plasmonics, biomolecule immobilisation, and nanoelectronics. Gold nano- and microstructures can be fabricated by one-step direct-write lithography process using focused electron beam induced deposition (FEBID). Typically, as-deposited gold nanostructures suffer from a low Au content and unacceptably high carbon contamination. We show that the undesirable carbon contamination can be diminished using a two-step process – a combination of optimized deposition followed by appropriate postdeposition cleaning. Starting from the common metal-organic precursor Me2-Au-tfac, it is demonstrated that the Au content in pristine FEBID nanostructures can be increased from 30 atom % to as much as 72 atom %, depending on the sustained electron beam dose. As a second step, oxygen-plasma treatment is established to further enhance the Au content in the structures, while preserving their morphology to a high degree. This two-step process represents a simple, feasible and high-throughput method for direct writing of purer gold nanostructures that can enable their future use for demanding applications. PMID:29259868

  1. High pressure/temperature equation of state of gold-silver alloys

    NASA Astrophysics Data System (ADS)

    Evans, W. J.; Jenei, Zs.; Sinogeikin, S. V.; Yang, W.; Shebanova, O.

    2010-03-01

    It has been reported previously (McKeehan Phys.Rev. 20 p424) that gold-silver alloys crystallize in face centered cubic structures, like their constituant pure elements and the cell parameter of the alloy has a linear relationship with the ratios of Ag/Au in the alloy. We investigate the high-pressure/temperature behavior of gold-silver alloys with different Au/Ag ratios. Powder x-ray diffraction experiments performed at HPCAT/Advanced Photon Source confirm the stability of the alloy's fcc structure to pressures/temperatures exceeding 100 GPa/1000 K. We will present isothermal EOS of the alloys from ambient temperature up to 1000 K, discuss the thermal expansion and its variation with pressure.

  2. High pressure/temperature equation of state of gold silver alloys

    NASA Astrophysics Data System (ADS)

    Jenei, Zsolt; Lipp, Magnus J.; Klepeis, Jae-Hyun P.; Cynn, Hyunchae; Evans, William J.; Park, Changyong

    2012-02-01

    Gold-silver alloys crystallize in face centered cubic structures, like their constituent pure elements [McKeehan -- Phys.Rev. 20, 424 (1922)]. The cell parameter of the alloys does not scale linearly with the ratio of Ag/Au. In this work we investigate the high-pressure/temperature behavior of gold-silver alloys with different Au/Ag ratios. Powder x-ray diffraction experiments performed at HPCAT/Advanced Photon Source confirm the stability of the alloy's fcc structure to pressures/temperatures exceeding 100 GPa/1000 K. We will present isothermal EOS of the alloys from ambient temperature up to 1000 K, discuss the thermal expansion and its variation with pressure.

  3. Superfast assembly and synthesis of gold nanostructures using nanosecond low-temperature compression via magnetic pulsed power

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

    Li, Binsong; Bian, Kaifu; Lane, J. Matthew D.

    Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearlymore » establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. As a result, this nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales.« less

  4. Superfast assembly and synthesis of gold nanostructures using nanosecond low-temperature compression via magnetic pulsed power

    DOE PAGES

    Li, Binsong; Bian, Kaifu; Lane, J. Matthew D.; ...

    2017-03-16

    Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearlymore » establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. As a result, this nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales.« less

  5. Superfast assembly and synthesis of gold nanostructures using nanosecond low-temperature compression via magnetic pulsed power

    NASA Astrophysics Data System (ADS)

    Li, Binsong; Bian, Kaifu; Lane, J. Matthew D.; Salerno, K. Michael; Grest, Gary S.; Ao, Tommy; Hickman, Randy; Wise, Jack; Wang, Zhongwu; Fan, Hongyou

    2017-03-01

    Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearly establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. This nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales.

  6. Superfast assembly and synthesis of gold nanostructures using nanosecond low-temperature compression via magnetic pulsed power.

    PubMed

    Li, Binsong; Bian, Kaifu; Lane, J Matthew D; Salerno, K Michael; Grest, Gary S; Ao, Tommy; Hickman, Randy; Wise, Jack; Wang, Zhongwu; Fan, Hongyou

    2017-03-16

    Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearly establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. This nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales.

  7. Superfast assembly and synthesis of gold nanostructures using nanosecond low-temperature compression via magnetic pulsed power

    PubMed Central

    Li, Binsong; Bian, Kaifu; Lane, J. Matthew D.; Salerno, K. Michael; Grest, Gary S.; Ao, Tommy; Hickman, Randy; Wise, Jack; Wang, Zhongwu; Fan, Hongyou

    2017-01-01

    Gold nanostructured materials exhibit important size- and shape-dependent properties that enable a wide variety of applications in photocatalysis, nanoelectronics and phototherapy. Here we show the use of superfast dynamic compression to synthesize extended gold nanostructures, such as nanorods, nanowires and nanosheets, with nanosecond coalescence times. Using a pulsed power generator, we ramp compress spherical gold nanoparticle arrays to pressures of tens of GPa, demonstrating pressure-driven assembly beyond the quasi-static regime of the diamond anvil cell. Our dynamic magnetic ramp compression approach produces smooth, shockless (that is, isentropic) one-dimensional loading with low-temperature states suitable for nanostructure synthesis. Transmission electron microscopy clearly establishes that various gold architectures are formed through compressive mesoscale coalescences of spherical gold nanoparticles, which is further confirmed by in-situ synchrotron X-ray studies and large-scale simulation. This nanofabrication approach applies magnetically driven uniaxial ramp compression to mimic established embossing and imprinting processes, but at ultra-short (nanosecond) timescales. PMID:28300067

  8. Scalable creation of gold nanostructures on high performance engineering polymeric substrate

    NASA Astrophysics Data System (ADS)

    Jia, Kun; Wang, Pan; Wei, Shiliang; Huang, Yumin; Liu, Xiaobo

    2017-12-01

    The article reveals a facile protocol for scalable production of gold nanostructures on a high performance engineering thermoplastic substrate made of polyarylene ether nitrile (PEN) for the first time. Firstly, gold thin films with different thicknesses of 2 nm, 4 nm and 6 nm were evaporated on a spin-coated PEN substrate on glass slide in vacuum. Next, the as-evaporated samples were thermally annealed around the glass transition temperature of the PEN substrate, on which gold nanostructures with island-like morphology were created. Moreover, it was found that the initial gold evaporation thickness and annealing atmosphere played an important role in determining the morphology and plasmonic properties of the formulated Au NPs. Interestingly, we discovered that isotropic Au NPs can be easily fabricated on the freestanding PEN substrate, which was fabricated by a cost-effective polymer solution casting method. More specifically, monodispersed Au nanospheres with an average size of ∼60 nm were obtained after annealing a 4 nm gold film covered PEN casting substrate at 220 °C for 2 h in oxygen. Therefore, the scalable production of Au NPs with controlled morphology on PEN substrate would open the way for development of robust flexible nanosensors and optical devices using high performance engineering polyarylene ethers.

  9. Formation, Characteristics and Electrocatalytic Properties of Nanoporous Metals Formed by Dealloying of Ternary-Noble Alloys

    NASA Astrophysics Data System (ADS)

    Vega Zuniga, Adrian A.

    Nanoporous metals formed by electrochemical dealloying of silver from Ag-Au-Pt alloys, with 77 at.% silver and platinum contents of 1, 2 and 3 at.%, have been studied. The presence of platinum, which is immobile relative to gold, refine the ligament size and stabilized the nanostructure against coarsening, even under experimental conditions that would be expected to promote coarsening (e.g., exposure to high temperature, longer dealloying times). By adding only 1 at.% Pt to the alloy precursor, the ligament/pore size was reduced by 50% with respect to that in nanoporous gold (NPG), which was formed on a Ag-Au alloy with the same silver content as ternary alloys. A further decrease in the ligament size was observed by increasing the platinum content of the precursor; however, most of the improvement occurred with 1 at.% Pt. The adsorbate-induced surface segregation of platinum was also investigated for these nanoporous metals. By exposing freshly-dealloyed nanostructures to moderate temperatures in the presence of air, platinum segregated to the ligament surface; in contrast, in an inert atmosphere (Ar-H 2), platinum mostly reverted to the bulk of the ligaments. This thermally activated process was thermodynamically driven by the interaction between platinum and oxygen; however, at the desorption temperature of oxygen, platinum de-segregated from the surface. Moreover, the co-segregation of platinum and oxygen hindered the thermal coarsening of the ligaments. Finally, the electrocatalytic abilities of these nanostructures were studied towards methanol and ethanol electro-oxidation, in alkaline and acidic media, showing significantly improved response in comparison to that observed in NPG. The synergistic effect between gold and platinum atoms and the smaller feature size of the nanostructures were directly associated with this behaviour. In alkaline electrolyte, the nanostructure formed on the alloy with 1 at.% Pt showed higher catalytic response than the other two

  10. A comparative study on the bond strength of porcelain to the millingable Pd-Ag alloy

    PubMed Central

    Hong, Jun-Tae

    2014-01-01

    PURPOSE The porcelain fused to gold has been widely used as a restoration both with the natural esthetics of the porcelain and durability and marginal fit of metal casting. However, recently, due to the continuous rise in the price of gold, an interest towards materials to replace gold alloy is getting higher. This study compared the bond strength of porcelain to millingable palladium-silver (Pd-Ag) alloy, with that of 3 conventionally used metal-ceramic alloys. MATERIALS AND METHODS Four types of metal-ceramic alloys, castable nonprecious nickel-chrome alloy, castable precious metal alloys containing 83% and 32% of gold, and millingable Pd-Ag alloy were used to make metal specimens (n=40). And porcelain was applied on the center area of metal specimen. Three-point bending test was performed with universal testing machine. The bond strength data were analyzed with a one-way ANOVA and post hoc Scheffe's tests (α=.05). RESULTS The 3-point bending test showed the strongest (40.42 ± 5.72 MPa) metal-ceramic bond in the nonprecious Ni-Cr alloy, followed by millingable Pd-Ag alloy (37.71 ± 2.46 MPa), precious metal alloy containing 83% of gold (35.89 ± 1.93 MPa), and precious metal alloy containing 32% of gold (34.59 ± 2.63 MPa). Nonprecious Ni-Cr alloy and precious metal alloy containing 32% of gold showed significant difference (P<.05). CONCLUSION The type of metal-ceramic alloys affects the bond strength of porcelain. Every metal-ceramic alloy used in this study showed clinically applicable bond strength with porcelain (25 MPa). PMID:25352959

  11. Hybrid framework with cobalt-chromium alloy and gold cylinder for implant superstructure: Bond strength and corrosion resistance.

    PubMed

    Yoshinari, Masao; Uzawa, Shinobu; Komiyama, Yataro

    2016-10-01

    The aim of this in vitro study was to evaluate tensile bond strengths and corrosion resistance of CoCr alloys joined with gold cylinder by a soldering system in comparison with the conventional cast-joining system. CoCr alloys joined with gold cylinder by a soldering system using a high-fusing gold solder (CoCr/Solder/Gold cylinder), gold alloy joined with gold cylinder by a cast joining system (Gold alloy/Gold cylinder) and CoCr castings were fabricated. The tensile bond strength and corrosion resistance in 0.9% NaCl solution (pH 7.4 and pH 2.3) were evaluated. Scanning electron microscopy (SEM) of the fractured surface and electron probe microanalysis (EPMA) of the joined interfaces were also performed. The tensile bond strengths of the CoCr/Solder/Gold cylinder specimens showed similar values as the Gold alloy/Gold cylinder specimens. SEM observation and EPMA analyses suggested firm bonding between the CoCr alloy and gold cylinder. The released elements from the CoCr/Solder/Gold cylinder specimens were similar to ones from CoCr castings. Results showed that superstructures made of CoCr alloys joined with the gold cylinder using a high-fusing gold solder had sufficient bond strength and high corrosion resistance. These hybrid frameworks with cobalt-chromium alloy and gold cylinder are promising prosthesis for implant superstructures with the low cost and favorable mechanical properties instead of conventional high-gold alloys. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  12. Dissolution and uptake of cadmium from dental gold solder alloy implants.

    PubMed

    Bergman, B; Bergman, M; Söremark, R

    1977-11-01

    Pure metallic cadmium was irradiated by means of thermal neutrons. The irradiated cadmium (115Cd) was placed in bags of gold foil and the bags were implanted subcutaneously in the neck region of mice. Two and 3d respectively after implantation the mice were killed, the bags removed and the animals subjected to whole-body autoradiography. The autoradiograms revealed an uptake of 115Cd in liver and kidney. In another experiment specimens of a cadmium-containing dental gold solder alloy, a cadmium-free dental casting gold alloy and soldered assemblies made of these two alloys were implanted subcutaneously in the neck region of mice. The animals were killed after 6 months; cadmium analysis showed significant increases in the cadmium concentration in liver and kidney of those mice which had been given implants of gold solder alloy. The study clearly shows that due to electrochemical corrosion cadmium can be released from implants and accumulated in the kidneys and the liver.

  13. Effect of different high-palladium metal-ceramic alloys on the color of opaque and dentin porcelain.

    PubMed

    Stavridakis, Minos M; Papazoglou, Efstratios; Seghi, Robert R; Johnston, William M; Brantley, William A

    2004-08-01

    The color of dental porcelain depends on the type of metal substrate. Little research has been done to document the effects of different types of high-palladium alloys on the color of dental porcelain. The purpose of this in vitro study was to evaluate the effects of different high-palladium alloys on the resulting color of dentin porcelain, as well as on that of opaque porcelain after simulated dentin and glazing firing cycles. Three Pd-Cu-Ga alloys, Spartan Plus (S), Liberty (B), and Freedom Plus (F), and 5 Pd-Ga alloys, Legacy (L), IS 85 (I), Protocol (P), Legacy XT (X), and Jelenko No.1 (N), were examined. A Pd-Ag alloy, Super Star (T), was included for comparison to the high-palladium alloys, and the Au-Pd alloy, Olympia (O), served as the control. Six cast discs (16 x 1 mm) were prepared from each of the alloys. Shade B1 opaque porcelain (Vita-Omega) was applied at a final thickness of 0.1 mm. After 2 opaque porcelain firing cycles, the surfaces were airborne-particle abraded, and the specimens were divided into 2 groups. In the first group, 0.9 mm of B1 dentin porcelain was applied. The other group of specimens with only opaque porcelain underwent the same dentin porcelain and glazing firing cycles. Color differences (DeltaE) were determined with a colorimeter between the control and each experimental group, after the second opaque porcelain, second dentin porcelain, and glazing firing cycles. One-way analysis of variance and Dunnett's multiple range test were performed on the DeltaE data (alpha=.05). After the application of dentin porcelain, the 3 Pd-Cu-Ga alloys showed significantly different (P<.05) DeltaE values (S=2.3 +/- 0.5, B=1.4 +/- 0.3, and F=1.3 +/- 0.7) than the control group. After the glazing cycle of this group, the 3 Pd-Cu-Ga alloys and the Pd-Ag alloy exhibited significantly different (P<.05) DeltaE values (S=2.8 +/- 0.8, B=2.2 +/- 0.3, F=1.9 +/- 1.0, and T=1.4 +/- 0.5) than the control group. After the simulated dentin porcelain firing

  14. Gold and palladium adsorption from leached electronic scrap using ordered mesoporous carbon nanoscaffolds

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

    McDowell, Rocklan; Dutech, Guy

    2014-09-01

    Ordered mesoporous carbon (OMC) nanoscaffolds are engineered agglomerates of carbon nanotubes held together by small carbon nanofibers with uniform pore sizes, high pore volume, and high channel permeability. These materials exhibit very high affinity for the adsorption of gold from aqueous acidic mixtures. The efficiency of gold recovery is comparable to those typically accomplished using biopolymer-based adsorbents. The adsorption efficiency for other precious metals such as palladium and platinum is lower. Studies on the precious metal (Au, Pd) adsorption on OMC materials from actual liquors of leached electronics will be presented. Adsorption properties will be compared for several different sorbentsmore » used for the recovery of precious metals. The leach liquor compositions for three different types of electronic scrap materials (personal computer board, cell phone and tv input/output board) will be presented. The sorption efficiencies for Au, Pd, together with a spectrum of competing and non-competing metals, from such leach mixtures will be compared.« less

  15. Powering the programmed nanostructure and function of gold nanoparticles with catenated DNA machines

    NASA Astrophysics Data System (ADS)

    Elbaz, Johann; Cecconello, Alessandro; Fan, Zhiyuan; Govorov, Alexander O.; Willner, Itamar

    2013-06-01

    DNA nanotechnology is a rapidly developing research area in nanoscience. It includes the development of DNA machines, tailoring of DNA nanostructures, application of DNA nanostructures for computing, and more. Different DNA machines were reported in the past and DNA-guided assembly of nanoparticles represents an active research effort in DNA nanotechnology. Several DNA-dictated nanoparticle structures were reported, including a tetrahedron, a triangle or linear nanoengineered nanoparticle structures; however, the programmed, dynamic reversible switching of nanoparticle structures and, particularly, the dictated switchable functions emerging from the nanostructures, are missing elements in DNA nanotechnology. Here we introduce DNA catenane systems (interlocked DNA rings) as molecular DNA machines for the programmed, reversible and switchable arrangement of different-sized gold nanoparticles. We further demonstrate that the machine-powered gold nanoparticle structures reveal unique emerging switchable spectroscopic features, such as plasmonic coupling or surface-enhanced fluorescence.

  16. Preparation and characterization of Fe50Co50 nanostructured alloy

    NASA Astrophysics Data System (ADS)

    Yepes, N.; Orozco, J.; Caamaño, Z.; Mass, J.; Pérez, G.

    2014-04-01

    Nanostructured Fe50Co50 alloy was prepared by mechanical alloying of Fe and Co powders in a planetary high energy ball milling. The microstructure and structural evolution of the alloy have been investigated as a function of milling time (0 h, 8 h, 20 h and 35 h) by scanning electron microscopy (SEM) and X-Ray diffraction (XRD) characterization techniques. SEM micrographs showed different powder particles morphologies during the mechanical alloying stages. By XRD analysis it could be identified the structural phases of the alloy and the crystallite size was calculated as a function of the milling time.

  17. Gold-Based Nanostructures for Ultrafast Dynamic Nanothermometer

    NASA Astrophysics Data System (ADS)

    Sun, Hongtao

    Nano-scale temperature measurements are of significance for fundamental understanding of functional applications and nanosystems, requiring ultimate miniaturization of thermometers with reduced size, maintained sensitivity, simplicity and accuracy of temperature reading. Particularly, grand challenges exist for scenarios of combustion or thermal shock where materials may be subjected to drastic temperature variations and extreme thermal flux, and dynamic thermal sensors with an ultrafast response (seconds to milliseconds) are yet to be developed. Targeting the developments of advanced nano-scale thermal sensors with a fast time response and rapid readout, this thesis reports innovative designs of high surface-to-volume ratio gold nanostructures including ultrathin gold island films on transparent quartz substrates and silica-gold core-shell (SiO2 Au) nanospheres as potential dynamic thermal sensors for accurate temperature determination. The sensing mechanism is based on strong temperature dependences of the thermally-dewetting-induced morphological self-reorganization and characteristic surface plasmon (SP) absorption of the gold nanostructures. The irreversible thermally-induced morphological and optical signatures behave as characteristic "fingerprints" for temperature recording, allowing the retrieval of thermal history ex-situ. The fundamental studies of thermal-induced dewetting process and its corresponding unique optical properties were extensively investigated by high resolution scanning electron microscopy (HR-SEM), atomic force microscopy (AFM), and UV-vis-NIR spectroscopy, which illustrate temperature and time dependent variations. As compared with current nanothermometer technologies such as metal-filled nanotubes, our thermo-sensor offers positively synergistic advantages of ultrafast time response, permanent recording and fast readout of thermal history, and ex-situ capability for effective temperature measurements. In addition, SiO2 Au nanospheres

  18. Facile synthesis of dendritic gold nanostructures with hyperbranched architectures and their electrocatalytic activity toward ethanol oxidation.

    PubMed

    Huang, Jianshe; Han, Xinyi; Wang, Dawei; Liu, Dong; You, Tianyan

    2013-09-25

    Gold dendritic nanostructures with hyperbranched architectures were synthesized by the galvanic replacement reaction between nickel wire and HAuCl4 in aqueous solution. The study revealed that the morphology of the obtained nanostructures strongly depended on experimental parameters such as the HAuCl4 solution concentration, reaction temperature, and time, as well as stirring or not. According to the investigation of the growth process, it was proposed that gold nanoparticles with rough surfaces were first deposited on the nickel substrate and that subsequent growth preferentially occurred on the preformed gold nanoparticles, finally leading to the formation of hyperbranched gold dendrites via a self-organization process under nonequilibrium conditions. The electrochemical experiment results demonstrated that the as-obtained gold dendrites exhibited high catalytic activity toward ethanol electrooxidation in alkaline solution, indicating that this nanomaterial may be a potential catalyst for direct ethanol fuel cells.

  19. Transition from poor ductility to room-temperature superplasticity in a nanostructured aluminum alloy.

    PubMed

    Edalati, Kaveh; Horita, Zenji; Valiev, Ruslan Z

    2018-04-30

    Recent developments of nanostructured materials with grain sizes in the nanometer to submicrometer range have provided ground for numerous functional properties and new applications. However, in terms of mechanical properties, bulk nanostructured materials typically show poor ductility despite their high strength, which limits their use for structural applications. The present article shows that the poor ductility of nanostructured alloys can be changed to room-temperature superplastisity by a transition in the deformation mechanism from dislocation activity to grain-boundary sliding. We report the first observation of room-temperature superplasticity (over 400% tensile elongations) in a nanostructured Al alloy by enhanced grain-boundary sliding. The room-temperature grain-boundary sliding and superplasticity was realized by engineering the Zn segregation along the Al/Al boundaries through severe plastic deformation. This work introduces a new boundary-based strategy to improve the mechanical properties of nanostructured materials for structural applications, where high deformability is a requirement.

  20. MO-FG-BRA-03: A Monte-Carlo Study of Cellular Dosimetry of Radioactive Gold-Palladium Nanoparticles

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

    Ma, Y; Michaud, F; Fortin, M

    Purpose: Radioactive gold-palladium nanoparticles ({sup 103}Pd:Pd@Au NPs) are being developed for prostate cancer brachytherapy. Photons emitted by the radioisotope palladium (photon energy: 20.1 and 23.0 keV), interacting with gold-coating of NPs, lead to enhanced energy distribution in nucleus. Here, a simple cellular model was studied using detailed track-structure method. Methods: Geant4-DNA was used with auger electrons enabled. Biological cell was modeled as a sphere of radius r=5 µm that were immersed in a fluid containing large number of NPs at different concentrations (S=1, 2.15, 5.1, 17.2 mg-Au/g-H2O). Nucleus was modeled as a concentric sphere (r=3µm). Thickness of gold-coating on {supmore » 103}Pd core was 15nm, 20nm and 25nm, respectively. A scenario of NP diffusion was investigated, where S=5.1 mg-Au/g-H2O outside cell and S=1 mg-Au/g-H2O in cytoplasm. 10{sup 10} {sup 103}Pd decays were simulated for each combination of NP concentration and gold-coating. Results: A uniform increase in energy deposition (Edep) is observed in cell nucleus and the energy enhancement ratio (EER) is 1.16, 1.22 and 1.3 for 15nm, 20nm and 25nm of gold -coatings, respectively. Edep at the center of nucleus is increased by a factor of 1.47, 2.51 and 5.54 when the NP concentration in the cytoplasm increases from 1 mg-Au/g-H2O to 2.15, 5.10 and 17.2 mg-Au/g-H2O, respectively. When NPs diffuse into cytoplasm, the mean value of Edep in nucleus increases from 0.42 to 1.13 MeV per 10{sup 9} decays (GBq-Second) of {sup 103}Pd and the maximum value increases from 0.54 to 2.5 MeV per GBq-Second. Conclusion: These results suggest that {sup 103}Pd:Pd@Au NPs constitute a promising nanotherapeutic agent. Ongoing studies use transmission electron microscopy (TEM) images of prostate cancer.« less

  1. Photoelectrochemical Water Splitting Properties of Ti-Ni-Si-O Nanostructures on Ti-Ni-Si Alloy

    PubMed Central

    Dong, Zhenbiao; Ning, Congqin

    2017-01-01

    Ti-Ni-Si-O nanostructures were successfully prepared on Ti-1Ni-5Si alloy foils via electrochemical anodization in ethylene glycol/glycerol solutions containing a small amount of water. The Ti-Ni-Si-O nanostructures were characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and diffuse reflectance absorption spectra. Furthermore, the photoelectrochemical water splitting properties of the Ti-Ni-Si-O nanostructure films were investigated. It was found that, after anodization, three different kinds of Ti-Ni-Si-O nanostructures formed in the α-Ti phase region, Ti2Ni phase region, and Ti5Si3 phase region of the alloy surface. Both the anatase and rutile phases of Ti-Ni-Si-O oxide appeared after annealing at 500 °C for 2 h. The photocurrent density obtained from the Ti-Ni-Si-O nanostructure photoanodes was 0.45 mA/cm2 at 0 V (vs. Ag/AgCl) in 1 M KOH solution. The above findings make it feasible to further explore excellent photoelectrochemical properties of the nanostructure-modified surface of Ti-Ni-Si ternary alloys. PMID:29088083

  2. Photoelectrochemical Water Splitting Properties of Ti-Ni-Si-O Nanostructures on Ti-Ni-Si Alloy.

    PubMed

    Li, Ting; Ding, Dongyan; Dong, Zhenbiao; Ning, Congqin

    2017-10-31

    Ti-Ni-Si-O nanostructures were successfully prepared on Ti-1Ni-5Si alloy foils via electrochemical anodization in ethylene glycol/glycerol solutions containing a small amount of water. The Ti-Ni-Si-O nanostructures were characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and diffuse reflectance absorption spectra. Furthermore, the photoelectrochemical water splitting properties of the Ti-Ni-Si-O nanostructure films were investigated. It was found that, after anodization, three different kinds of Ti-Ni-Si-O nanostructures formed in the α-Ti phase region, Ti₂Ni phase region, and Ti₅Si₃ phase region of the alloy surface. Both the anatase and rutile phases of Ti-Ni-Si-O oxide appeared after annealing at 500 °C for 2 h. The photocurrent density obtained from the Ti-Ni-Si-O nanostructure photoanodes was 0.45 mA/cm² at 0 V (vs. Ag/AgCl) in 1 M KOH solution. The above findings make it feasible to further explore excellent photoelectrochemical properties of the nanostructure-modified surface of Ti-Ni-Si ternary alloys.

  3. Macrocyclic Receptor for Precious Gold, Platinum, or Palladium Coordination Complexes.

    PubMed

    Liu, Wenqi; Oliver, Allen G; Smith, Bradley D

    2018-06-06

    Two macrocyclic tetralactam receptors are shown to selectively encapsulate anionic, square-planar chloride and bromide coordination complexes of gold(III), platinum(II), and palladium(II). Both receptors have a preorganized structure that is complementary to its precious metal guest. The receptors do not directly ligate the guest metal center but instead provide an array of arene π-electron donors that interact with the electropositive metal and hydrogen-bond donors that interact with the outer electronegative ligands. This unique mode of supramolecular recognition is illustrated by six X-ray crystal structures showing receptor encapsulation of AuCl 4 - , AuBr 4 - , PtCl 4 -2 , or Pd 2 Cl 6 -2 . In organic solution, the 1:1 association constants correlate with specific supramolecular features identified in the solid state. Technical applications using these receptors are envisioned in a wide range of fields that involve precious metals, including mining, recycling, catalysis, nanoscience, and medicine.

  4. The adsorption of gold, palladium and platinum from acidic chloride solutions on mesoporous carbons.

    DOE PAGES

    Zalupski, Peter R.; McDowell, Rocklan; Dutech, Guy

    2014-08-05

    Studies on the adsorption characteristics of gold, palladium and platinum on mesoporous carbon (CMK-3) and sulfur-impregnated mesoporous carbon (CMK-3/S) evaluated the benefits/drawbacks of the presence of a layer of elemental sulfur inside mesoporous carbon structures. Adsorption isotherms collected for Au(III), Pd(II) and Pt(IV) on those materials suggest that sulfur does enhance the adsorption of those metal ions in mildly acidic environment (pH 3). The isotherms collected in 1 M HCl show that the benefit of sulfur disappears due to the competing influence of large concentration of hydrogen ions on the ion-exchanging mechanism of metal ions sorption on mesoporous carbon surfaces.more » The collected acid dependencies illustrate similar adsorption characteristics for CMK-3 and CMK-3/S in 1-5 M HCl concentration range. Sorption of metal ions from diluted aqueous acidic mixtures of actual leached electronic waste demonstrated the feasibility of recovery of gold from such liquors.« less

  5. Corrosion behavior of as-received and previously cast type III gold alloy.

    PubMed

    Ayad, Mohamed F; Ayad, Ghada M

    2010-04-01

    The rationale for using gold alloys is based largely upon their alleged ability to resist corrosion, but little information is available to determine the corrosion behavior of recast alloys. This study characterized the elemental composition of as-received and recast type III gold alloy and examined the in vitro corrosion behavior in two media using a potentiodynamic polarization technique. Seventy-eight disk-shaped specimens were prepared from a type III gold alloy under three casting protocols according to the proportion of as-received and recast gold alloy (n = 26). (1) Group as received (100% as-received metal), (2) group 50% to 50% (50% wt. new metal, 50% wt. once recast metal), and (3) group recast (100% once recast metal). The surface structures of 20 specimens from each group were examined under scanning electron microscopy, and their elemental compositions were determined using X-ray energy-dispersive spectroscopy. Further, the potentiodynamic cyclic polarization between -1000 and +1000 mV (SCE) were performed for six specimens from each casting protocol in 0.09% NaCl solution (n = 3) and Fusayama artificial saliva (n = 3) at 37 degrees C. Zero-current potential and corrosion current density were determined. The data were analyzed with 1-way ANOVA and the Ryan-Einot-Gabriel-Welsch multiple-range test t (alpha= 0.05). Elemental composition was significantly different among the casting groups (p < 0.001). The mean weight percentage values were 72.4 to 75.7% Au, 4.5 to 7.0% Pd, 10.7 to 11.1% Ag, 7.8 to 8.4% Cu, and 1.0 to 1.4% Zn. The mean values for Zero-current potential and corrosion current density for all casting protocols were not significant (p > 0.05); however, the difference between the electrolytes was significant (p < 0.001). Fusayama artificial saliva seemed to offer the most corrosive environment. Type III gold alloy in any casting protocol retained passivity under electrochemical conditions similar to the oral environment. Moreover, high-gold

  6. Synthesis and antimicrobial activity of gold/silver-tellurium nanostructures.

    PubMed

    Chang, Hsiang-Yu; Cang, Jinshun; Roy, Prathik; Chang, Huan-Tsung; Huang, Yi-Cheng; Huang, Chih-Ching

    2014-06-11

    Gold-tellurium nanostructures (Au-Te NSs), silver-tellurium nanostructures (Ag-Te NSs), and gold/silver-tellurium nanostructures (Au/Ag-Te NSs) have been prepared through galvanic reactions of tellurium nanotubes (Te NTs) with Au(3+), Ag(+), and both ions, respectively. Unlike the use of less environmentally friendly hydrazine, fructose as a reducing agent has been used to prepare Te NTs from TeO2 powders under alkaline conditions. The Au/Ag-Te NSs have highly catlaytic activity to convert nonfluorescent Amplex Red to form fluorescent product, revealing their great strength of generating reactive oxygen species (ROS). Au/Ag-Te NSs relative to the other two NSs exhibit greater antimicrobial activity toward the growth of E. coli, S. enteritidis, and S. aureus; the minimal inhibitory concentration (MIC) values of Au/Ag-Te NSs were much lower (>10-fold) than that of Ag-Te NSs and Au-Te NSs. The antibacterial activity of Au/Ag-Te NSs is mainly due to the release of Ag(+) ions and Te-related ions and also may be due to the generated ROS which destroys the bacteria membrane. In vitro cytotoxicity and hemolysis analyses have revealed their low toxicity in selected human cell lines and insignificant hemolysis in red blood cells. In addition, inhibition zone measurements using a Au/Ag-Te NSs-loaded konjac jelly film have suggested that it has great potential in practial application such as wound dressing for reducing bacterial wound infection. Having great antibacterial activitiy and excellent biocompatibility, the low-cost Au/Ag-Te NSs hold great potential as effective antimicrobial drugs.

  7. Triblock copolymer-mediated synthesis of catalytically active gold nanostructures

    NASA Astrophysics Data System (ADS)

    Santos, Douglas C.; de Souza, Viviane C.; Vasconcelos, Diego A.; Andrade, George R. S.; Gimenez, Iara F.; Teixeira, Zaine

    2018-04-01

    The design of nanostructures based on poly(ethylene oxide)-poly(propylene)-poly(ethylene oxide) (PEO-PPO-PEO) and metal nanoparticles is becoming an important research topic due to their multiple functionalities in different fields, including nanomedicine and catalysis. In this work, water-soluble gold nanoparticles have been prepared through a green aqueous synthesis method using Pluronic F127 as both reducing and stabilizing agents. The size dependence (varying from 2 to 70 nm) and stability of gold nanoparticles were systematically studied by varying some parameters of synthesis, which were the polymer concentration, temperature, and exposure to UV-A light, being monitored by UV-Vis spectroscopy and TEM. Also, an elaborated study regarding to the kinetic of formation (nucleation and growth) was presented. Finally, the as-prepared Pluronic-capped gold nanoparticles have shown excellent catalytic activity towards the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride, in which a higher catalytic performance was exhibited when compared with gold nanoparticles prepared by classical reduction method using sodium citrate. [Figure not available: see fulltext.

  8. Electroplating Gold-Silver Alloys for Spherical Capsules for NIF Double-Shell Targets

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

    Bhandarkar, N.; Horwood, C.; Bunn, T.

    For Inertial Confinement Fusion (ICF) implosions, a design based on gradients of high and mid Z materials could potentially be more robust than single element capsule systems. To that end, gold and silver alloys were electroplated on 2.0 mm diameter surrogate brass spheres using a new flow–based pulsed plating method specifically designed to minimize surface roughness without reducing plating rates. The coatings were analyzed by scanning electron microscope (SEM) and white light interferometry for surface topography, and by energy dispersive x-ray spectroscopy (EDX) to determine near-surface gold and silver compositions. The alloy range attainable was 15 to 85 weight percentmore » gold using 1:1 and 1:3 silver to gold ratio plating baths at applied potentials of -0.7 volts to -1.8 volts. This range was bounded by the open circuit potential of the system and hydrogen evolution, and in theory could be extended by using ionic liquids or aprotic solutions. Preliminary gradient trials proved constant composition alloy data could be translated to smooth gradient plating, albeit at higher gold compositions.« less

  9. Gold-Copper alloy "nano-dumplings" with tunable compositions and plasmonic properties

    NASA Astrophysics Data System (ADS)

    Verma, Manoj; Kedia, Abhitosh; Kumar, P. Senthil

    2016-05-01

    The unique yet tunable optical properties of plasmonic metal nanoparticles have made them attractive targets for a wide range of applications including nanophotonics, molecular sensing, catalysis etc. Such diverse applications that require precisely stable / reproducible plasmonic properties depend sensitively on the particle morphology ie. the shape, size and constituents. Herein, we systematically study the size / shape controlled synthesis of gold-copper "dumpling" shaped alloy nanoparticles by simultaneous reduction of gold and copper salts in the PVP-methanol solute-solvent system, by effectively utilizing the efficient but mild reduction as well as capping abilities of Poly (N-vinylpyrrolidone). Introduction of copper salts not only yielded the alloy nanoparticles, but also slowed down the growth process to maintain high mono-dispersity of the new shapes evolved. Copper and gold has different lattice constants (0.361 and 0.408 nm respectively) and hence doping/addition/replacement of copper atoms to gold FCC unit cell introduces strain into the lattice which is key parameter to the shape evolution in anisotropic nanoparticles. Synthesized alloy nanoparticles were characterized by UV-visible absorption spectroscopy, XRD and TEM imaging.

  10. Modulation of Morphology and Optical Property of Multi-Metallic PdAuAg and PdAg Alloy Nanostructures.

    PubMed

    Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil; Lee, Jihoon

    2018-05-16

    In this work, the evolution of PdAg and PdAuAg alloy nanostructures is demonstrated on sapphire (0001) via the solid-state dewetting of multi-metallic thin films. Various surface configurations, size, and arrangements of bi- and tri-metallic alloy nanostructures are fabricated as a function of annealing temperature, annealing duration, film thickness, and deposition arrangements such as bi-layers (Pd/Ag), tri-layers (Pd/Au/Ag), and multi-layers (Pd/Au/Ag × 5). Specifically, the tri-layers film shows the gradual evolution of over-grown NPs, voids, wiggly nanostructures, and isolated PdAuAg alloy nanoparticles (NPs) along with the increased annealing temperature. In contrast, the multi-layers film with same thickness show the enhanced dewetting rate, which results in the formation of voids at relatively lower temperature, wider spacing, and structural regularity of alloy NPs at higher temperature. The dewetting enhancement is attributed to the increased number of interfaces and reduced individual layer thickness, which aid the inter-diffusion process at the initial stage. In addition, the time evolution of the Pd 150 nm /Ag 80 nm bi-layer films at constant temperature show the wiggly-connected and isolated PdAg alloy NPs. The overall evolution of alloy NPs is discussed based on the solid-state dewetting mechanism in conjunction with the diffusion, inter-diffusion, alloying, sublimation, Rayleigh instability, and surface energy minimization. Depending upon their surface morphologies, the bi- and tri-metallic alloy nanostructures exhibit the dynamic reflectance spectra, which show the formation of dipolar (above 700 nm) and quadrupolar resonance peaks (~ 380 nm) and wide dips in the visible region as correlated to the localized surface plasmon resonance (LSPR) effect. An absorption dip is readily shifted from ~ 510 to ~ 475 nm along with the decreased average size of alloy nanostructures.

  11. Modulation of Morphology and Optical Property of Multi-Metallic PdAuAg and PdAg Alloy Nanostructures

    NASA Astrophysics Data System (ADS)

    Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil; Lee, Jihoon

    2018-05-01

    In this work, the evolution of PdAg and PdAuAg alloy nanostructures is demonstrated on sapphire (0001) via the solid-state dewetting of multi-metallic thin films. Various surface configurations, size, and arrangements of bi- and tri-metallic alloy nanostructures are fabricated as a function of annealing temperature, annealing duration, film thickness, and deposition arrangements such as bi-layers (Pd/Ag), tri-layers (Pd/Au/Ag), and multi-layers (Pd/Au/Ag × 5). Specifically, the tri-layers film shows the gradual evolution of over-grown NPs, voids, wiggly nanostructures, and isolated PdAuAg alloy nanoparticles (NPs) along with the increased annealing temperature. In contrast, the multi-layers film with same thickness show the enhanced dewetting rate, which results in the formation of voids at relatively lower temperature, wider spacing, and structural regularity of alloy NPs at higher temperature. The dewetting enhancement is attributed to the increased number of interfaces and reduced individual layer thickness, which aid the inter-diffusion process at the initial stage. In addition, the time evolution of the Pd150 nm/Ag80 nm bi-layer films at constant temperature show the wiggly-connected and isolated PdAg alloy NPs. The overall evolution of alloy NPs is discussed based on the solid-state dewetting mechanism in conjunction with the diffusion, inter-diffusion, alloying, sublimation, Rayleigh instability, and surface energy minimization. Depending upon their surface morphologies, the bi- and tri-metallic alloy nanostructures exhibit the dynamic reflectance spectra, which show the formation of dipolar (above 700 nm) and quadrupolar resonance peaks ( 380 nm) and wide dips in the visible region as correlated to the localized surface plasmon resonance (LSPR) effect. An absorption dip is readily shifted from 510 to 475 nm along with the decreased average size of alloy nanostructures.

  12. Detection and quantification of solute clusters in a nanostructured ferritic alloy

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

    Miller, Michael K.; Larson, David J.; Reinhard, D. A.

    2014-12-26

    A series of simulated atom probe datasets were examined with a friends-of-friends method to establish the detection efficiency required to resolve solute clusters in the ferrite phase of a 14YWT nanostructured ferritic alloy. The size and number densities of solute clusters in the ferrite of the as-milled mechanically-alloyed condition and the stir zone of a friction stir weld were estimated with a prototype high-detection-efficiency (~80%) local electrode atom probe. High number densities, 1.8 × 10 24 m –3 and 1.2 × 10 24 m –3, respectively of solute clusters containing between 2 and 9 solute atoms of Ti, Y andmore » O and were detected for these two conditions. Furthermore, these results support first principle calculations that predicted that vacancies stabilize these Ti–Y–O– clusters, which retard diffusion and contribute to the excellent high temperature stability of the microstructure and radiation tolerance of nanostructured ferritic alloys.« less

  13. Reconfigurable Three-Dimensional Gold Nanorod Plasmonic Nanostructures Organized on DNA Origami Tripod.

    PubMed

    Zhan, Pengfei; Dutta, Palash K; Wang, Pengfei; Song, Gang; Dai, Mingjie; Zhao, Shu-Xia; Wang, Zhen-Gang; Yin, Peng; Zhang, Wei; Ding, Baoquan; Ke, Yonggang

    2017-02-28

    Distinct electromagnetic properties can emerge from the three-dimensional (3D) configuration of a plasmonic nanostructure. Furthermore, the reconfiguration of a dynamic plasmonic nanostructure, driven by physical or chemical stimuli, may generate a tailored plasmonic response. In this work, we constructed a 3D reconfigurable plasmonic nanostructure with controllable, reversible conformational transformation using bottom-up DNA self-assembly. Three gold nanorods (AuNRs) were positioned onto a reconfigurable DNA origami tripod. The internanorod angle and distance were precisely tuned through operating the origami tripod by toehold-mediated strand displacement. The transduction of conformational change manifested into a controlled shift of the plasmonic resonance peak, which was studied by dark-field microscopy, and agrees well with electrodynamic calculations. This new 3D plasmonic nanostructure not only provides a method to study the plasmonic resonance of AuNRs at prescribed 3D conformations but also demonstrates that DNA origami can serve as a general self-assembly platform for constructing various 3D reconfigurable plasmonic nanostructures with customized optical properties.

  14. Development of casting investment preventing blackening of noble metal alloys Part 2. Application of developed investment for type 4 gold alloy.

    PubMed

    Nakai, Akira; Kakuta, Kiyoshi; Goto, Shin-ichi; Kato, Katuma; Yara, Atushi; Ogura, Hideo

    2003-09-01

    The objective of this study was to evaluate the efficacy of the developed investment for the prevention of blackening of a cast Type 4 gold and to analyze the oxides on its surface in relation to the blackening of the alloy. The experimental investments were prepared using a gypsum-bonded investment in which boron (B) or aluminum (Al) was added as a reducing agent. A Type 4 gold alloy was cast into the mold made of the prepared investment. The effect of the additives was evaluated from the color difference (deltaE*) between the as-cast surface and the polished surface of the cast specimen. B and Al were effective to prevent the blackening of a Type 4 gold alloy and the color of the as-cast surface approached that of the polished surface with increasing B and Al content. The prevention of the blackening of the gold alloy can be achieved by restraining the formation of CuO.

  15. Detecting Airborne Mercury by Use of Palladium Chloride

    NASA Technical Reports Server (NTRS)

    Ryan, Margaret; Shevade, Abhijit; Kisor, Adam; Homer, Margie; Jewell, April; Manatt, Kenneth; Torres, Julia; Soler, Jessica; Taylor, Charles

    2009-01-01

    Palladium chloride films have been found to be useful as alternatives to the gold films heretofore used to detect airborne elemental mercury at concentrations of the order of parts per billion (ppb). Somewhat more specifically, when suitably prepared palladium chloride films are exposed to parts-per-billion or larger concentrations of airborne mercury, their electrical resistances change by amounts large enough to be easily measurable. Because airborne mercury adversely affects health, it is desirable to be able to detect it with high sensitivity, especially in enclosed environments in which there is a risk of leakage of mercury from lamps or other equipment. The detection of mercury by use of gold films involves the formation of gold/mercury amalgam. Gold films offer adequate sensitivity for detection of airborne mercury and could easily be integrated into an electronic-nose system designed to operate in the temperature range of 23 to 28 C. Unfortunately, in order to regenerate a gold-film mercury sensor, one must heat it to a temperature of 200 C for several minutes in clean flowing air. In preparation for an experiment to demonstrate the present sensor concept, palladium chloride was deposited from an aqueous solution onto sets of gold electrodes and sintered in air to form a film. Then while using the gold electrodes to measure the electrical resistance of the films, the films were exposed, at a temperature of 25 C, to humidified air containing mercury at various concentrations from 0 to 35 ppb (see figure). The results of this and other experiments have been interpreted as signifying that sensors of this type can detect mercury in room-temperature air at concentrations of at least 2.5 ppb and can readily be regenerated at temperatures <40 C.

  16. Diffusion and surface alloying of gradient nanostructured metals

    PubMed Central

    Lu, Ke

    2017-01-01

    Gradient nanostructures (GNSs) have been optimized in recent years for desired performance. The diffusion behavior in GNS metals is crucial for understanding the diffusion mechanism and relative characteristics of different interfaces that provide fundamental understanding for advancing the traditional surface alloying processes. In this paper, atomic diffusion, reactive diffusion, and surface alloying processes are reviewed for various metals with a preformed GNS surface layer. We emphasize the promoted atomic diffusion and reactive diffusion in the GNS surface layer that are related to a higher interfacial energy state with respect to those in relaxed coarse-grained samples. Accordingly, different surface alloying processes, such as nitriding and chromizing, have been modified significantly, and some diffusion-related properties have been enhanced. Finally, the perspectives on current research in this field are discussed. PMID:28382244

  17. Kinetic Monte Carlo Simulation of the Growth of Various Nanostructures through Atomic and Cluster Deposition: Application to Gold Nanostructure Growth on Graphite

    NASA Astrophysics Data System (ADS)

    Claassens, C. H.; Hoffman, M. J. H.; Terblans, J. J.; Swart, H. C.

    2006-01-01

    A Kinetic Monte Carlo (KMC) method is presented to describe the growth of metallic nanostructures through atomic and cluster deposition in the mono -and multilayer regime. The model makes provision for homo- and heteroepitaxial systems with small lattice mismatch. The accuracy of the model is tested with simulations of the growth of gold nanostructures on HOPG and comparisons are made with existing experimental data.

  18. Evolution of Nano-structured Quasicrystals from Amorphous alloys

    NASA Astrophysics Data System (ADS)

    Xing, L. Q.; Kelton, K. F.

    2002-03-01

    Ta shows a significant effect on the precipitation of quasicrystals in (Zr_1-xTa_x)_64Cu_18Ni_8Al_10 amorphous alloys. The amorphous alloy made without Ta forms precipitates of tetragonal Zr_2Cu primary phases upon annealing. The addition of a small amount of Ta ( ~ 3 at%) to the alloy initiates the precipitation of primary icosahedral quasicrystal phases. Moreover, as the Ta concentration increases, the size of the precipitates decreases dramatically. To study the effect of Ta in this alloy system and to understand the mechanism for the precipitation of nano-structured quasicrystals, we have investigated the crystallization characteristics of the alloys made with different Ta concentration using DSC, checked the structures of the annealed samples with TEM and X-ray diffraction, and analyzed the kinetics of the crystallization processes. The kinetic parameter and the measured crystal size distribution will be compared with theoretical predictions from conventional nucleation and growth model and from a new model for nucleation that couples the long-range diffusion flux with the interfacial attachment processes.

  19. Theoretical study of surface plasmon resonance sensors based on 2D bimetallic alloy grating

    NASA Astrophysics Data System (ADS)

    Dhibi, Abdelhak; Khemiri, Mehdi; Oumezzine, Mohamed

    2016-11-01

    A surface plasmon resonance (SPR) sensor based on 2D alloy grating with a high performance is proposed. The grating consists of homogeneous alloys of formula MxAg1-x, where M is gold, copper, platinum and palladium. Compared to the SPR sensors based a pure metal, the sensor based on angular interrogation with silver exhibits a sharper (i.e. larger depth-to-width ratio) reflectivity dip, which provides a big detection accuracy, whereas the sensor based on gold exhibits the broadest dips and the highest sensitivity. The detection accuracy of SPR sensor based a metal alloy is enhanced by the increase of silver composition. In addition, the composition of silver which is around 0.8 improves the sensitivity and the quality of SPR sensor of pure metal. Numerical simulations based on rigorous coupled wave analysis (RCWA) show that the sensor based on a metal alloy not only has a high sensitivity and a high detection accuracy, but also exhibits a good linearity and a good quality.

  20. Gold nanostructure-integrated silica-on-silicon waveguide for the detection of antibiotics in milk and milk products

    NASA Astrophysics Data System (ADS)

    Ozhikandathil, Jayan; Badilescu, Simona; Packirisamy, Muthukumaran

    2012-10-01

    Antibiotics are extensively used in veterinary medicine for the treatment of infectious diseases. The use of antibiotics for the treatment of animals used for food production raised the concern of the public and a rapid screening method became necessary. A novel approach of detection of antibiotics in milk is reported in this work by using an immunoassay format and the Localized Surface Plasmon Resonance property of gold. An antibiotic from the penicillin family that is, ampicillin is used for testing. Gold nanostructures deposited on a glass substrate by a novel convective assembly method were heat-treated to form a nanoisland morphology. The Au nanostructures were functionalized and the corresponding antibody was absorbed from a solution. Solutions with known concentrations of antigen (antibiotics) were subsequently added and the spectral changes were monitored step by step. The Au LSPR band corresponding to the nano-island structure was found to be suitable for the detection of the antibody antigen interaction. The detection of the ampicillin was successfully demonstrated with the gold nano-islands deposited on glass substrate. This process was subsequently adapted for the integration of gold nanostructures on the silica-on-silicon waveguide for the purpose of detecting antibiotics.

  1. Stability of Y–Ti–O precipitates in friction stir welded nanostructured ferritic alloys

    DOE PAGES

    Yu, Xinghua; Mazumder, B.; Miller, M. K.; ...

    2015-01-19

    Nanostructured ferritic alloys, which have complex microstructures which consist of ultrafine ferritic grains with a dispersion of stable oxide particles and nanoclusters, are promising materials for fuel cladding and structural applications in the next generation nuclear reactor. This paper evaluates microstructure of friction stir welded nanostructured ferritic alloys using electron microscopy and atom probe tomography techniques. Atom probe tomography results revealed that nanoclusters are coarsened and inhomogeneously distributed in the stir zone and thermomechanically affected zone. Three hypotheses on coarsening of nanoclusters are presented. Finally, the hardness difference in different regions of friction stir weld has been explained.

  2. Engineering Defect-Free Nanoporous Pd from Optimized Pd-Ni Precursor Alloy by Understanding Palladium-Hydrogen Interactions During Dealloying

    NASA Astrophysics Data System (ADS)

    Schoop, Julius; Balk, T. John

    2014-04-01

    Thin films of nanoporous palladium (np-Pd) were produced from binary palladium-nickel (Pd-Ni) precursor alloys. A suitable precursor alloy and a method of dealloying to yield optimum nanoporosity (average pore/ligament size of 7 nm) were developed by studying the effects of various processing parameters on final microstructure. To obtain crack-free np-Pd, a 100 nm thin film of 20 at. pct Pd (80 at. pct Ni) can be dealloyed for ~5 hours in a 1 M solution of sulfuric acid, with oleic acid and oleylamine added as surfactants. Both shorter and longer dealloying times, as well as heating, inhibit the formation of crack-free np-Pd. Stress measurements at different stages of dealloying revealed that the necessary dealloying time is determined by the diffusion-controlled corrosion reaction occurring within the thin film during dealloying. Strong interaction between hydrogen and np-Pd was reflected in the stress evolution during dealloying. A mechanism is proposed for the formation of a Ni-rich dense top layer that results from H-induced swelling during initial dealloying and permits the development of defect-free np-Pd beneath, by limiting the speed of dealloying.

  3. Gold-based thin multilayers for ohmic contacts in RF-MEMS switches

    NASA Astrophysics Data System (ADS)

    Mulloni, V.; Iannacci, J.; Bartali, R.; Micheli, V.; Colpo, S.; Laidani, N.; Margesin, B.

    2011-06-01

    In RF-MEMS switches many reliability issues are related to the metal contacts in the switching area. The characteristics of this contact influence not only contact resistance and insertion loss, but also the most relevant switch failure mechanisms that are wear of ohmic contact, adhesion and stiction. Gold is widely used for this purpose because of its good conductivity and chemical inertness, but is a soft metal, and the development of hard contact materials with low resistivity is of great interest for RF-MEMS switch reliability. It is possible to increase the contact hardness preserving the convenient gold properties alternating gold layers with thin layers of different metals. The material becomes harder not only by simple alloying but also by the presence of interfaces which act as barriers for mechanical dislocation migration. A detailed study of mechanical, electrical and morphological properties of gold-chromium, gold-platinum and gold-palladium multilayers is presented and discussed. It is found that the annealing treatments are important for tuning hardness values, and a careful choice of the alloying metal is essential when the material is inserted in a real switch fabrication cycle, because hardness improvements can vanish during oxygen plasma treatments usually involved in RF-switches fabrication. Platinum is the only metal tested that is unaffected by oxidation, and also modifies the chromium adhesion layer diffusion on the contact surface.

  4. Gold-silver alloy nanoshells: a new candidate for nanotherapeutics and diagnostics

    NASA Astrophysics Data System (ADS)

    Gheorghe, Dana E.; Cui, Lili; Karmonik, Christof; Brazdeikis, Audrius; Penaloza, Jose M.; Young, Joseph K.; Drezek, Rebekah A.; Bikram, Malavosklish

    2011-10-01

    We have developed novel gold-silver alloy nanoshells as magnetic resonance imaging (MRI) dual T 1 (positive) and T 2 (negative) contrast agents as an alternative to typical gadolinium (Gd)-based contrast agents. Specifically, we have doped iron oxide nanoparticles with Gd ions and sequestered the ions within the core by coating the nanoparticles with an alloy of gold and silver. Thus, these nanoparticles are very innovative and have the potential to overcome toxicities related to renal clearance of contrast agents such as nephrogenic systemic fibrosis. The morphology of the attained nanoparticles was characterized by XRD which demonstrated the successful incorporation of Gd(III) ions into the structure of the magnetite, with no major alterations of the spinel structure, as well as the growth of the gold-silver alloy shells. This was supported by TEM, ICP-AES, and SEM/EDS data. The nanoshells showed a saturation magnetization of 38 emu/g because of the presence of Gd ions within the crystalline structure with r 1 and r 2 values of 0.0119 and 0.9229 mL mg-1 s-1, respectively (Au:Ag alloy = 1:1). T 1- and T 2-weighted images of the nanoshells showed that these agents can both increase the surrounding water proton signals in the T 1-weighted image and reduce the signal in T 2-weighted images. The as-synthesized nanoparticles exhibited strong absorption in the range of 600-800 nm, their optical properties being strongly dependent upon the thickness of the gold-silver alloy shell. Thus, these nanoshells have the potential to be utilized for tumor cell ablation because of their absorption as well as an imaging agent.

  5. Preparation, characterization, and optical properties of gold, silver, and gold-silver alloy nanoshells having silica cores.

    PubMed

    Kim, Jun-Hyun; Bryan, William W; Lee, T Randall

    2008-10-07

    This report describes the structural and optical properties of a series of spherical shell/core nanoparticles in which the shell is comprised of a thin layer of gold, silver, or gold-silver alloy, and the core is comprised of a monodispersed silica nanoparticle. The silica core particles were prepared using the Stöber method, functionalized with terminal amine groups, and then seeded with small gold nanoparticles (approximately 2 nm in diameter). The gold-seeded silica particles were coated with a layer of gold, silver, or gold-silver alloy via solution-phase reduction of an appropriate metal ion or mixture of metal ions. The size, morphology, and elemental composition of the composite nanoparticles were characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The optical properties of the nanoparticles were analyzed by UV-vis spectroscopy, which showed strong absorptions ranging from 400 nm into the near-IR region, where the position of the plasmon band reflected not only the thickness of the metal shell, but also the nature of the metal comprising the shell. Importantly, the results demonstrate a new strategy for tuning the position of the plasmon resonance without having to vary the core diameter or the shell thickness.

  6. Effect of surface nanostructuring on corrosion behavior of Ti–6Al–4V alloy

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

    Kumar, Sanjeev, E-mail: sanjeevphy85@gmail.com; Ch

    Surface nanostructure was induced in Ti–6Al–4V alloy by ultrasonic shot peening (USSP) for different durations, from 15 s to 30 min, and the modified surface was characterized by optical, scanning, atomic force and transmission electron microscopy. Nano size grains were observed to form on surface of the USSPed samples and surface roughness was increased with duration of USSP. Polarization study was carried out in Ringer's solution to examine the effect of surface nanostructuring on corrosion resistance of this alloy. Electrochemical corrosion was carried out for all the USSPed specimens as well as the non-USSPed sample in Ringer's solution. Surface morphologymore » of the corroded samples was examined by SEM. In general, corrosion resistance was improved by USSP up to the duration of 15 min and there was maximum improvement in the specimen USSPed for 1 min. However, corrosion resistance was drastically reduced due to USSP for long duration of 30 min. - Highlights: •Nanostructure was induced by USSP on alloy Ti–6Al–4V of about 28 nm. •Grain refinement was confirmed by XRD and TEM. •USSP is an effective technique for the improvement in corrosion resistance. •Nanostructured surface promotes formation of protective surface layer of TiO{sub 2}.« less

  7. Effects of metal primers on the bonding of an adhesive resin cement to noble metal ceramic alloys after thermal cycling.

    PubMed

    Minami, Hiroyuki; Murahara, Sadaaki; Suzuki, Shiro; Tanaka, Takuo

    2011-12-01

    Although the effectiveness of primers for resin bonding to noble alloys has been demonstrated, no effective clinical technique for bonding to noble metal ceramic alloys has been established. The purpose of this study was to evaluate the effects of metal primers on the shear bond strength of an adhesive resin to noble metal ceramic alloys after thermal cycling. Sixty-three disk-shaped specimens (10 × 2.5 mm) were cast from high-gold-content alloys (Super Metal W-85: W85 or IFK88 GR: IFK88), a high-palladium-content alloy (Super Metal N-40: N40), and an Ag-Pd-Cu-Au alloy (Castwell M.C.12: MC12). Smaller-sized disk-shaped specimens (8 × 2.5 mm) were fabricated with MC12. Bonding surfaces were finished with 600-grit SiC-paper and airborne-particle abraded with 50-μm alumina. Pairs of disks were primed (V-Primer: VP; ML Primer: ML; or Metaltite: MT) and bonded with an adhesive resin (Super-Bond C&B). The bond strengths were determined before and after 20,000 and 50,000 thermal cycles (n=7). Data were analyzed by using a 3-way ANOVA and the Bonferroni test (α=.05). Failure modes were determined by optical microscope and SEM observation. Bond strengths to high-gold-content alloys with VP and MT significantly decreased after the thermal cycling (P<.001). Bond strengths to W85 (35.27 ±4.25 MPa) and IFK88 (33.57 ±3.56 MPa) after 50,000 thermal cycles obtained by ML were the highest (P<.001), and these groups showed combination failures. Bond strengths to N40 significantly decreased after 50,000 thermal cycles (P<.001), regardless of primers. Shear bond strengths (SBS) to high-gold-content alloys were not degraded up to 50,000 thermal cycles when primed with ML. None of the primers evaluated was effective for high-palladium-content alloy. Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  8. Nanostructured gold microelectrodes for SERS and EIS measurements by incorporating ZnO nanorod growth with electroplating

    PubMed Central

    Zong, Xianli; Zhu, Rong; Guo, Xiaoliang

    2015-01-01

    In this paper, a fine gold nanostructure synthesized on selective planar microelectrodes in micro-chip is realized by using an advanced hybrid fabrication approach incorporating growth of nanorods (NRs) with gold electroplating. By this developed nanostructure, integration of in-situ surface-enhanced Raman spectroscopy (SERS) detection with electrochemical impedance spectroscopy (EIS) measurement for label-free, nondestructive, real-time and rapid monitoring on a single cell has been achieved. Moreover, parameters of Au nanostructures such as size of nanoholes/nanogaps can be controllably adjusted in the fabrication. We have demonstrated a SERS enhancement factor of up to ~2.24 × 106 and double-layer impedance decrease ratio of 90% ~ 95% at low frequency range below 200 kHz by using nanostructured microelectrodes. SERS detection and in-situ EIS measurement of a trapped single cell by using planar microelectrodes are realized to demonstrate the compatibility, multi-functions, high-sensitivity and simplicity of the micro-chip system. This dual function platform integrating SERS and EIS is of great significance in biological, biochemical and biomedical applications. PMID:26558325

  9. Insights into biogenic and chemical production of inorganic nanomaterials and nanostructures.

    PubMed

    Faramarzi, Mohammad Ali; Sadighi, Armin

    2013-03-01

    The synthesis of inorganic nanomaterials and nanostructures by the means of diverse physical, chemical, and biological principles has been developed in recent decades. The nanoscale materials and structures creation continue to be an active area of researches due to the exciting properties of the resulting nanomaterials and their innovative applications. Despite physical and chemical approaches which have been used for a long time to produce nanomaterials, biological resources as green candidates that can replace old production methods have been focused in recent years to generate various inorganic nanoparticles (NPs) or other nanoscale structures. Cost-effective, eco-friendly, energy efficient, and nontoxic produced nanomaterials using diverse biological entities have been received increasing attention in the last two decades in contrast to physical and chemical methods owe using toxic solvents, generate unwanted by-products, and high energy consumption which restrict the popularity of these ways employed in nanometric science and engineering. In this review, the biosynthesis of gold, silver, gold-silver alloy, magnetic, semiconductor nanocrystals, silica, zirconia, titania, palladium, bismuth, selenium, antimony sulfide, and platinum NPs, using bacteria, actinomycetes, fungi, yeasts, plant extracts and also informational bio-macromolecules including proteins, polypeptides, DNA, and RNA have been reported extensively to mention the current status of the biological inorganic nanomaterial production. In other hand, two well-known wet chemical techniques, namely chemical reduction and sol-gel methods, used to produce various types of nanocrystalline powders, metal oxides, and hybrid organic-inorganic nanomaterials have presented. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Microstructure and mechanical properties of thermoelectric nanostructured n-type silicon-germanium alloys synthesized employing spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Bathula, Sivaiah; Gahtori, Bhasker; Jayasimhadri, M.; Tripathy, S. K.; Tyagi, Kriti; Srivastava, A. K.; Dhar, Ajay

    2014-08-01

    Owing to their high thermoelectric (TE) figure-of-merit, nanostructured Si80Ge20 alloys are evolving as a potential replacement for their bulk counterparts in designing efficient radio-isotope TE generators. However, as the mechanical properties of these alloys are equally important in order to avoid in-service catastrophic failure of their TE modules, we report the strength, hardness, fracture toughness, and thermal shock resistance of nanostructured n-type Si80Ge20 alloys synthesized employing spark plasma sintering of mechanically alloyed nanopowders of its constituent elements. These mechanical properties show a significant enhancement, which has been correlated with the microstructural features at nano-scale, delineated by transmission electron microscopy.

  11. Gold-Copper alloy “nano-dumplings” with tunable compositions and plasmonic properties

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

    Verma, Manoj, E-mail: duplasmonic@gmail.com; Kedia, Abhitosh; Kumar, P. Senthil

    The unique yet tunable optical properties of plasmonic metal nanoparticles have made them attractive targets for a wide range of applications including nanophotonics, molecular sensing, catalysis etc. Such diverse applications that require precisely stable / reproducible plasmonic properties depend sensitively on the particle morphology ie. the shape, size and constituents. Herein, we systematically study the size / shape controlled synthesis of gold-copper “dumpling” shaped alloy nanoparticles by simultaneous reduction of gold and copper salts in the PVP-methanol solute-solvent system, by effectively utilizing the efficient but mild reduction as well as capping abilities of Poly (N-vinylpyrrolidone). Introduction of copper salts notmore » only yielded the alloy nanoparticles, but also slowed down the growth process to maintain high mono-dispersity of the new shapes evolved. Copper and gold has different lattice constants (0.361 and 0.408 nm respectively) and hence doping/addition/replacement of copper atoms to gold FCC unit cell introduces strain into the lattice which is key parameter to the shape evolution in anisotropic nanoparticles. Synthesized alloy nanoparticles were characterized by UV-visible absorption spectroscopy, XRD and TEM imaging.« less

  12. Helium sequestration at nanoparticle-matrix interfaces in helium + heavy ion irradiated nanostructured ferritic alloys

    DOE PAGES

    Parish, Chad M.; Unocic, Kinga A.; Tan, Lizhen; ...

    2016-10-24

    Here we irradiated four ferritic alloys with energetic Fe and He ions: one castable nanostructured alloy (CNA) containing Ti-W-Ta-carbides, and three nanostructured ferritic alloys (NFAs). The NFAs were: 9Cr containing Y-Ti-O nanoclusters, and two Fe-12Cr-5Al NFAs containing Y-Zr-O or Y-Hf-O clusters. All four were subjected to simultaneous dual-beam Fe + He ion implantation (650 °C, ~50 dpa, ~15 appm He/dpa), simulating fusion-reactor conditions. Examination using scanning/transmission electron microscopy (STEM) revealed high-number-density helium bubbles of ~8 nm, ~10 21 m -3 (CNA), and of ~3 nm, 10 23 m -3 (NFAs). STEM combined with multivariate statistical analysis data mining suggests thatmore » the precipitate-matrix interfaces in all alloys survived ~50 dpa at 650 °C and serve as effective helium trapping sites. All alloys appear viable structural material candidates for fusion or advanced fission energy systems. Finally, among these developmental alloys the NFAs appear to sequester the helium into smaller bubbles and away from the grain boundaries more effectively than the early-generation CNA.« less

  13. Mechanical alloying of lanthana-bearing nanostructured ferritic steels

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

    Somayeh Paseban; Indrajit Charit; Yaqiao Q. Wu

    2013-09-01

    A novel nanostructured ferritic steel powder with the nominal composition Fe–14Cr–1Ti–0.3Mo–0.5La2O3 (wt.%) was developed via high energy ball milling. La2O3 was added to this alloy instead of the traditionally used Y2O3. The effects of varying the ball milling parameters, such as milling time, steel ball size and ball to powder ratio, on the mechanical properties and micro structural characteristics of the as-milled powder were investigated. Nanocrystallites of a body-centered cubic ferritic solid solution matrix with a mean size of approximately 20 nm were observed by transmission electron microscopy. Nanoscale characterization of the as-milled powder by local electrode atom probe tomographymore » revealed the formation of Cr–Ti–La–O-enriched nanoclusters during mechanical alloying. The Cr:Ti:La:O ratio is considered “non-stoichiometric”. The average size (radius) of the nanoclusters was about 1 nm, with number density of 3.7 1024 m3. The mechanism for formation of nanoclusters in the as-milled powder is discussed. La2O3 appears to be a promising alternative rare earth oxide for future nanostructured ferritic steels.« less

  14. Silver, gold, and alloyed silver-gold nanoparticles: characterization and comparative cell-biologic action

    NASA Astrophysics Data System (ADS)

    Mahl, Dirk; Diendorf, Jörg; Ristig, Simon; Greulich, Christina; Li, Zi-An; Farle, Michael; Köller, Manfred; Epple, Matthias

    2012-10-01

    Silver, gold, and silver-gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly( N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15-25 nm), gold (5-6 nm), and silver-gold (50:50; 10-12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver-gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver-gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver-gold nanoparticles in the concentration range of 5-20 μg mL-1 induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

  15. Novel ascorbic acid based ionic liquids for the in situ synthesis of quasi-spherical and anisotropic gold nanostructures in aqueous medium.

    PubMed

    Dinda, Enakshi; Si, Satyabrata; Kotal, Atanu; Mandal, Tarun K

    2008-01-01

    A series of newly designed ascorbic acid based room temperature ionic liquids were successfully used to prepare quasi-spherical and anisotropic gold nanostructures in an aqueous medium at ambient temperature. The synthesis of these room temperature ionic liquids involves, first, the preparation of a 1-alkyl (such as methyl, ethyl, butyl, hexyl, octyl, and decyl) derivative of 3-methylimidazolium hydroxide followed by the neutralization of the derivatised product with ascorbic acid. These ionic liquids show significantly better thermal stability and their glass transition temperature (Tg) decreases with increasing alkyl chain length. The ascorbate counter anion of these ionic liquids acts as a reducing agent for HAuCl4 to produce metallic gold and the alkylated imidazolium counter cation acts as a capping/shape-directing agent. It has been found that the nature of the ionic liquids and the mole ratio of ionic liquid to HAuCl4 has a significant effect on the morphology of the formed gold nanostructures. If an equimolar mixture of ionic liquid and HAuCl4 is used, predominantly anisotropic gold nanostructures are formed and by varying the alkyl chain length attached to imidazolium cation of the ionic liquids, various particle morphologies can formed, such as quasispherical, raspberry-like, flakes or dendritic. A probable formation mechanism for such anisotropic gold nanostructures has been proposed, which is based on the results of some control experiments.

  16. Gold and palladium minerals (including empirical PdCuBiSe3) from the former Roter Bär mine, St. Andreasberg, Harz Mountains, Germany: a result of low-temperature, oxidising fluid overprint

    NASA Astrophysics Data System (ADS)

    Cabral, Alexandre Raphael; Ließmann, Wilfried; Lehmann, Bernd

    2015-10-01

    At Roter Bär, a former underground mine in the polymetallic deposits of St. Andreasberg in the middle-Harz vein district, Germany, native gold and palladium minerals occur very locally in clausthalite-hematite pockets of few millimetres across in carbonate veinlets. The native gold is a Au-Ag intermetallic compound and the palladium minerals are characterised as mertieite-II [Pd8(Sb,As)3] and empirical PdCuBiSe3 with some S. The latter coexists with bohdanowiczite (AgBiSe2), a mineral that is stable below 120 °C. The geological setting of Roter Bär, underneath a post-Variscan unconformity, and its hematite-selenide-gold association suggest that oxidising hydrothermal brines of low temperature were instrumental to the Au-Pd mineralisation. The Roter Bär Au-Pd mineralisation can be explained by Permo-Triassic, red-bed-derived brines in the context of post-Variscan, unconformity-related fluid overprint.

  17. Improve the refractive index sensitivity of coaxial-cable type gold nanostructure: the effect of dielectric polarization from the separate layer

    NASA Astrophysics Data System (ADS)

    Zhu, Jian; Li, Jian-Jun; Zhao, Jun-Wu

    2013-06-01

    The separate layer refractive index sensitivity of a coaxial-cable type three-layered gold nanotube has been studied. Theoretical calculation results based on quasi-static model show that the coaxial-cable type gold nanostructure has higher refractive index sensitivity than that of single-layered gold nanotube. This sensitivity could be improved by increasing the inner wire radius or decreasing the total radius of the tube, and the maximum sensitivity may exceed 1,000 nm per refractive index unit. The physical origin was also investigated based on the coupling of the dielectric media induced polarizations and the local electric fields in separate layer and outer surrounding. These separate layer refractive index sensing properties of coaxial-cable type gold nanostructure present well potential for plasmonic biosensing applications.

  18. Modeling Ultra-fast assembly and sintering of gold nanostructures

    NASA Astrophysics Data System (ADS)

    Lane, J. Matthew D.; Salerno, K. Michael; Grest, Gary S.; Fan, Hongyou

    We use fully atomistic simulations to understand the role of extreme pressure in the assembly and sintering of fcc superlattices of alkanethiol-coated gold nanocrystals into larger nanostructures. Recent quasi-isentropic experiments have shown that 1D, 2D and 3D nanostructures can be formed and recovered from dynamic compression experiments on Sandia's Veloce pulsed power accelerator. Here, we describe the role of coating properties, such as ligand length and grafting density, on ligand migration and deformation processes during pressure-driven coalescence of metal nano cores into permanent nanowires, nanosheets and 3D structures. The role of uniaxial vs isotropic pressure and the effects of compression along various superlattice orientations will be discussed. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  19. Functionalization of nanostructured gold substrates with chiral chromophores for SERS applications: The case of 5-Aza[5]helicene.

    PubMed

    Zanchi, Chiara; Lucotti, Andrea; Cancogni, Damiano; Fontana, Francesca; Trusso, Sebastiano; Ossi, Paolo M; Tommasini, Matteo

    2018-05-31

    Nanostructured gold thin films can be fabricated by controlled pulsed laser deposition to get efficient sensors, with uniform morphology and optimized plasmon resonance, to be employed as plasmonic substrates in surface enhanced Raman scattering spectroscopy. By attaching 5-aza[5]helicen-6-yl-6-hexanethiol to such gold nanostructures, used in a previous work for label-free drug sensing with biomedical purposes, we successfully prepared functionalized substrates with remarkable surface enhanced Raman scattering activity. The long-term motivation is to develop probes for drug detection at low concentrations, where sensitivity to specific chiral targets is required. © 2018 Wiley Periodicals, Inc.

  20. Coating of biodegradable magnesium alloy bone implants using nanostructured diopside (CaMgSi2O6)

    NASA Astrophysics Data System (ADS)

    Razavi, Mehdi; Fathi, Mohammadhossein; Savabi, Omid; Beni, Batoul Hashemi; Razavi, Seyed Mohammad; Vashaee, Daryoosh; Tayebi, Lobat

    2014-01-01

    Magnesium alloys with their biodegradable characteristic can be a very good candidate to be used in orthopedic implants. However, magnesium alloys may corrode and degrade too fast for applications in the bone healing procedure. In order to enhance the corrosion resistance and the in vitro bioactivity of a magnesium alloy, a nanostructured diopside (CaMgSi2O6) film was coated on AZ91 magnesium alloy through combined micro-arc oxidation (MAO) and electrophoretic deposition (EPD) methods. The crystalline structures, morphologies and compositions of the coated and uncoated substrates were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy. Polarization, electrochemical impedance spectroscopy, and immersion test in simulated body fluid (SBF) were employed to evaluate the corrosion resistance and the in vitro bioactivity of the samples. The results of our investigation showed that the nanostructured diopside coating deposited on the MAO layer increases the corrosion resistance and improves the in vitro bioactivity of the biodegradable magnesium alloy.

  1. Gold-nanoparticle-based catalysts for the oxidative esterification of 1,4-butanediol into dimethyl succinate.

    PubMed

    Brett, Gemma L; Miedziak, Peter J; He, Qian; Knight, David W; Edwards, Jennifer K; Taylor, Stuart H; Kiely, Christopher J; Hutchings, Graham J

    2013-10-01

    The oxidation of 1,4-butanediol and butyrolactone have been investigated by using supported gold, palladium and gold-palladium nanoparticles. The products of such reactions are valuable chemical intermediates and, for example, can present a viable pathway for the sustainable production of polymers. If both gold and palladium were present, a significant synergistic effect on the selective formation of dimethyl succinate was observed. The support played a significant role in the reaction, with magnesium hydroxide leading to the highest yield of dimethyl succinate. Based on structural characterisation of the fresh and used catalysts, it was determined that small gold-palladium nanoalloys supported on a basic Mg(OH)2 support provided the best catalysts for this reaction. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Self-assembly of metal nanostructures on binary alloy surfaces

    PubMed Central

    Duguet, T.; Han, Yong; Yuen, Chad; Jing, Dapeng; Ünal, Barış; Evans, J. W.; Thiel, P. A.

    2011-01-01

    Deposition of metals on binary alloy surfaces offers new possibilities for guiding the formation of functional metal nanostructures. This idea is explored with scanning tunneling microscopy studies and atomistic-level analysis and modeling of nonequilibrium island formation. For Au/NiAl(110), complex monolayer structures are found and compared with the simple fcc(110) bilayer structure recently observed for Ag/NiAl(110). We also consider a more complex codeposition system, (Ni + Al)/NiAl(110), which offers the opportunity for fundamental studies of self-growth of alloys including deviations for equilibrium ordering. A general multisite lattice-gas model framework enables analysis of structure selection and morphological evolution in these systems. PMID:21097706

  3. Microbial synthesis of core/shell gold/palladium nanoparticles for applications in green chemistry

    PubMed Central

    Deplanche, Kevin; Merroun, Mohamed L.; Casadesus, Merixtell; Tran, Dung T.; Mikheenko, Iryna P.; Bennett, James A.; Zhu, Ju; Jones, Ian P.; Attard, Gary A.; Wood, J.; Selenska-Pobell, Sonja; Macaskie, Lynne E.

    2012-01-01

    We report a novel biochemical method based on the sacrificial hydrogen strategy to synthesize bimetallic gold (Au)–palladium (Pd) nanoparticles (NPs) with a core/shell configuration. The ability of Escherichia coli cells supplied with H2 as electron donor to rapidly precipitate Pd(II) ions from solution is used to promote the reduction of soluble Au(III). Pre-coating cells with Pd(0) (bioPd) dramatically accelerated Au(III) reduction, with the Au(III) reduction rate being dependent upon the initial Pd loading by mass on the cells. Following Au(III) addition, the bioPd–Au(III) mixture rapidly turned purple, indicating the formation of colloidal gold. Mapping of bio-NPs by energy dispersive X-ray microanalysis suggested Au-dense core regions and peripheral Pd but only Au was detected by X-ray diffraction (XRD) analysis. However, surface analysis of cleaned NPs by cyclic voltammetry revealed large Pd surface sites, suggesting, since XRD shows no crystalline Pd component, that layers of Pd atoms surround Au NPs. Characterization of the bimetallic particles using X-ray absorption spectroscopy confirmed the existence of Au-rich core and Pd-rich shell type bimetallic biogenic NPs. These showed comparable catalytic activity to chemical counterparts with respect to the oxidation of benzyl alcohol, in air, and at a low temperature (90°C). PMID:22399790

  4. A micromachined calorimetric gas sensor: an application of electrodeposited nanostructured palladium for the detection of combustible gases.

    PubMed

    Bartlett, Philip N; Guerin, Samuel

    2003-01-01

    Palladium films with regular nanoarchitectures were electrochemically deposited from the hexagonal (H1) lyotropic liquid crystalline phase of the nonionic surfactant octaethyleneglycol monohexadecyl ether (C16EO8) onto micromachined silicon hotplate structures. The H1-e Pd films were shown to have high surface areas (approximately 28 m2 g(-1)) and to act as effective and stable catalysts for the detection of methane in air on heating to 500 degrees C. The response of the H1-e Pd-coated planar pellistors was found to be linearly proportional to the concentration of methane between 0 and 2.5% in air with a detection limit below 0.125%. Our results show that the electrochemical deposition of nanostructured metal films offers a promising approach to the fabrication of micromachined calorimetric gas sensors for combustible gases.

  5. Tunable synthesis and acetylation of dendrimer-entrapped or dendrimer-stabilized gold-silver alloy nanoparticles.

    PubMed

    Liu, Hui; Shen, Mingwu; Zhao, Jinglong; Guo, Rui; Cao, Xueyan; Zhang, Guixiang; Shi, Xiangyang

    2012-06-01

    In this study, amine-terminated generation 5 poly(amidoamine) dendrimers were used as templates or stabilizers to synthesize dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy nanoparticles (NPs) with different gold atom/silver atom/dendrimer molar ratios with the assistance of sodium borohydride reduction chemistry. Following a one-step acetylation reaction to transform the dendrimer terminal amines to acetyl groups, a series of dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs with terminal acetyl groups were formed. The formed Au-Ag alloy NPs before and after acetylation reaction were characterized using different techniques. We showed that the optical property and the size of the bimetallic NPs were greatly affected by the metal composition. At the constant total metal atom/dendrimer molar ratio, the size of the alloy NPs decreased with the gold content. The formed Au-Ag alloy NPs were stable at different pH (pH 5-8) and temperature (4-50°C) conditions. X-ray absorption coefficient measurements showed that the attenuation of the binary NPs was dependent on both the gold content and the surface modification. With the increase of gold content in the binary NPs, their X-ray attenuation intensity was significantly enhanced. At a given metal composition, the X-ray attenuation intensity of the binary NPs was enhanced after acetylation. Cytotoxicity assays showed that after acetylation, the cytocompatibility of Au-Ag alloy NPs was significantly improved. With the controllable particle size and optical property, metal composition-dependent X-ray attenuation characteristics, and improved cytocompatibility after acetylation, these dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs should have a promising potential for CT imaging and other biomedical applications. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores.

    PubMed

    El-Safty, Sherif A; Shenashen, Mohamed A; Sakai, Masaru; Elshehy, Emad; Halada, Kohmei

    2015-12-06

    Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

  7. Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

    PubMed Central

    El-Safty, Sherif A.; Shenashen, Mohamed A.; Sakai, Masaru; Elshehy, Emad; Halada, Kohmei

    2015-01-01

    Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobaltmetals. PMID:26709467

  8. Affibody Modified and Radiolabeled Gold-Iron Oxide Hetero-nanostructures for Tumor PET, Optical and MR Imaging

    PubMed Central

    Yang, Meng; Cheng, Kai; Qi, Shibo; Liu, Hongguang; Jiang, Yuxin; Jiang, Han; Li, Jinbo; Chen, Kai; Zhang, Huimao; Cheng, Zhen

    2013-01-01

    A highly monodispersed hetero-nanostructure with two different functional nanomaterials (gold (Au) and iron oxide (Fe3O4, IO)) within one structure was successfully developed as Affibody based trimodality nanoprobe (positron emission tomography, PET; optical imaging; and magnetic resonance imaging, MRI) for imaging of epidermal growth factor receptor (EGFR) positive tumors. Unlike other regular nanostructures with a single component, the Au-IO hetero-nanostructures (Au-IONPs) with unique chemical and physical properties have capability to combine several imaging modalities together to provide complementary information. The IO component within hetero-nanostructures serve as a T2 reporter for MRI; and gold component serve as both optical and PET reporters. Moreover, such hetero-nanoprobes could provide a robust nano-platform for surface-specific modification with both targeting molecules (anti-EGFR Affibody protein) and PET imaging reporters (radiometal 64Cu chelators) in highly efficient and reliable manner. In vitro and in vivo study showed that the resultant nanoprobe provided high specificity, sensitivity, and excellent tumor contrast for both PET and MRI imaging in the human EGFR-expressing cells and tumors. Our study data also highlighted the EGFR targeting efficiency of hetero-nanoparticles and the feasibility for their further theranostic applications. PMID:23343632

  9. Method for producing electricity using a platinum-ruthenium-palladium catalyst in a fuel cell

    DOEpatents

    Gorer, Alexander

    2004-01-27

    A method for producing electricity using a fuel cell that utilizes a ternary alloy composition as a fuel cell catalyst, the ternary alloy composition containing platinum, ruthenium and palladium. The alloy shows increased activity as compared to well-known catalysts.

  10. Palladium coated porous anodic alumina membranes for gas reforming processes

    NASA Astrophysics Data System (ADS)

    Wu, Jeremy P.; Brown, Ian W. M.; Bowden, Mark E.; Kemmitt, Timothy

    2010-11-01

    Nanostructured ceramic membranes with ultrathin coatings of palladium metal have been demonstrated to separate hydrogen gas from a gas mixture containing nitrogen with 10% carbon dioxide and 10% hydrogen at temperatures up to 550 °C. The mechanically robust and thermally durable membranes were fabricated using a combination of conventional and high-efficiency anodisation processes on high purity aluminium foils. A pH-neutral plating solution has also been developed to enable electroless deposition of palladium metal on templates which were normally prone to chemical corrosion in strong acid or base environment. Activation and thus seeding of palladium nuclei on the surface of the template were essential to ensure uniform and fast deposition, and the thickness of the metal film was controlled by time of deposition. The palladium coated membranes showed improved hydrogen selectivity with increased temperature as well as after prolonged exposure to hydrogen, demonstrating excellent potential for gas separation technologies.

  11. Mace-like gold hollow hierarchical micro/nanostructures fabricated by co-effect of catalytic etching and electrodeposition and their SERS performance

    NASA Astrophysics Data System (ADS)

    Zhang, Haibao; Wang, Jingjing; Wang, Hua; Tian, Xingyou

    2017-09-01

    In this paper, we presented the fabrication of mace-like gold hollow hierarchical micro/nanostructures (HMNs) grafted on ZnO nanorods array by using an electrochemical deposition in chloroauric acid solution on gold layer pre-coated ZnO nanorods array. Different from general electrochemical deposition process, the catalytic etching to ZnO and electrodeposition of gold are co-existed in our case, which lead to an inner hollow structure and an outer gold shell. Due to the appropriate electrodeposition conditions, the outer gold shell was built of many wimble-like nanoparticles, and the hierarchical micro/nanostructures were thus formed. In addition, because of the deposition rate is decreased gradually away from the top of ZnO nanorods, the final structures show mace-like appearance. The surface-enhanced Raman scattering (SERS) effect of the as-prepared gold hollow HMNs was further studied by using rhodamine 6G as probe molecule. It is demonstrated that these structures show ultrahigh SERS activity, and the detecting low limit of R6G solution can be to 10-10 M on single mace-like gold HMNs, which is quite important for their potential application in SERS-based surface analysis and sensors.

  12. HYDROGENATION OF OLEFINS USING PALLADIUM NANOPARTICLES PREPARED WITH PULSE ELECTROCHEMICAL DEPOSITION

    EPA Science Inventory

    Electrochemistry has been used to synthesize nano-structured materials. In this project, we have conducted the application of electrochemistry for the synthesis of nano-palladium catalysts that may have application in the area of green chemistry. The electrochemical technique use...

  13. Nanostructured β-type titanium alloy fabricated by ultrasonic nanocrystal surface modification.

    PubMed

    Kheradmandfard, Mehdi; Kashani-Bozorg, Seyed Farshid; Kim, Chang-Lae; Hanzaki, Abbas Zarei; Pyoun, Young-Shik; Kim, Jung-Hyong; Amanov, Auezhan; Kim, Dae-Eun

    2017-11-01

    The surface of β-type Ti-Nb-Ta-Zr (TNTZ) alloy, which is a promising material for biomedical applications, was treated with the ultrasonic nanocrystal surface modification (UNSM) technique to enhance its hardness. As a result, a gradient nanostructured (GNS) layer was generated in the surface; the microstructure of the top surface layer consisted of nanoscale lamellae with a width of about 60-200nm. In addition, there were lamellar grains consisting of nanostructured subgrains having unclear and wavy boundaries. The treated surface exhibited a hardness value of ∼385HV compared to 190HV for the untreated alloy. It was further determined that highly dense deformation twins were generated at a depth of ∼40-150µm below the UNSM-treated surface. These deformation twins led to a significant work hardening effect which aided in enhancing the mechanical properties. It was also found that UNSM treatment resulted in the formation of micropatterns on the surface, which would be beneficial for high bioactivity and bone regeneration performance of TNTZ implants. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Hollow raspberry-like PdAg alloy nanospheres: High electrocatalytic activity for ethanol oxidation in alkaline media

    NASA Astrophysics Data System (ADS)

    Peng, Cheng; Hu, Yongli; Liu, Mingrui; Zheng, Yixiong

    2015-03-01

    Palladium-silver (PdAg) alloy nanospheres with unique structure were prepared using a one-pot procedure based on the galvanic replacement reaction. Their electrocatalytic activity for ethanol oxidation in alkaline media was evaluated. The morphology and crystal structure of the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Electrochemical characterization techniques, including cyclic voltammetry (CV) and chronoamperometry (CA) measurements were used to analyze the electrochemical performance of the PdAg alloy nanospheres. The SEM and TEM images showed that the PdAg alloy nanospheres exhibit a hierarchical nanostructure with hollow interiors and porous walls. Compared to the commercial Pd/C catalyst, the as-prepared PdAg alloy nanospheres exhibit superior electrocatalytic activity and stability towards ethanol electro-oxidation in alkaline media, showing its potential as a new non-Pt electro-catalyst for direct alcohol fuel cells (DAFCs).

  15. SUPERCONDUCTING VANADIUM BASE ALLOY

    DOEpatents

    Cleary, H.J.

    1958-10-21

    A new vanadium-base alloy which possesses remarkable superconducting properties is presented. The alloy consists of approximately one atomic percent of palladium, the balance being vanadium. The alloy is stated to be useful in a cryotron in digital computer circuits.

  16. Microwave-assisted green synthesis of silver nanostructures.

    PubMed

    Nadagouda, Mallikarjuna N; Speth, Thomas F; Varma, Rajender S

    2011-07-19

    Over the past 25 years, microwave (MW) chemistry has moved from a laboratory curiosity to a well-established synthetic technique used in many academic and industrial laboratories around the world. Although the overwhelming number of MW-assisted applications today are still performed on a laboratory (mL) scale, we expect that this enabling technology may be used on a larger, perhaps even production, scale in conjunction with radio frequency or conventional heating. Microwave chemistry is based on two main principles, the dipolar mechanism and the electrical conductor mechanism. The dipolar mechanism occurs when, under a very high frequency electric field, a polar molecule attempts to follow the field in the same alignment. When this happens, the molecules release enough heat to drive the reaction forward. In the second mechanism, the irradiated sample is an electrical conductor and the charge carriers, ions and electrons, move through the material under the influence of the electric field and lead to polarization within the sample. These induced currents and any electrical resistance will heat the sample. This Account summarizes a microwave (MW)-assisted synthetic approach for producing silver nanostructures. MW heating has received considerable attention as a promising new method for the one-pot synthesis of metallic nanostructures in solutions. Researchers have successfully demonstrated the application of this method in the preparation of silver (Ag), gold (Au), platinum (Pt), and gold-palladium (Au-Pd) nanostructures. MW heating conditions allow not only for the preparation of spherical nanoparticles within a few minutes but also for the formation of single crystalline polygonal plates, sheets, rods, wires, tubes, and dendrites. The morphologies and sizes of the nanostructures can be controlled by changing various experimental parameters, such as the concentration of metallic salt precursors, the surfactant polymers, the chain length of the surfactant polymers

  17. Template-Free Electroless Plating of Gold Nanowires: Direct Surface Functionalization with Shape-Selective Nanostructures for Electrochemical Applications.

    PubMed

    Muench, Falk; Schaefer, Sandra; Hagelüken, Lorenz; Molina-Luna, Leopoldo; Duerrschnabel, Michael; Kleebe, Hans-Joachim; Brötz, Joachim; Vaskevich, Alexander; Rubinstein, Israel; Ensinger, Wolfgang

    2017-09-13

    Metal nanowires (NWs) represent a prominent nanomaterial class, the interest in which is fueled by their tunable properties as well as their excellent performance in, for example, sensing, catalysis, and plasmonics. Synthetic approaches to obtain metal NWs mostly produce colloids or rely on templates. Integrating such nanowires into devices necessitates additional fabrication steps, such as template removal, nanostructure purification, or attachment. Here, we describe the development of a facile electroless plating protocol for the direct deposition of gold nanowire films, requiring neither templates nor complex instrumentation. The method is general, producing three-dimensional nanowire structures on substrates of varying shape and composition, with different seed types. The aqueous plating bath is prepared by ligand exchange and partial reduction of tetrachloroauric acid in the presence of 4-dimethylaminopyridine and formaldehyde. Gold deposition proceeds by nucleation of new grains on existing nanostructure tips and thus selectively produces curvy, polycrystalline nanowires of high aspect ratio. The nanofabrication potential of this method is demonstrated by producing a sensor electrode, whose performance is comparable to that of known nanostructures and discussed in terms of the catalyst architecture. Due to its flexibility and simplicity, shape-selective electroless plating is a promising new tool for functionalizing surfaces with anisotropic metal nanostructures.

  18. Large-area, freestanding, single-layer graphene-gold: a hybrid plasmonic nanostructure.

    PubMed

    Iyer, Ganjigunte R Swathi; Wang, Jian; Wells, Garth; Guruvenket, Srinivasan; Payne, Scott; Bradley, Michael; Borondics, Ferenc

    2014-06-24

    Graphene-based plasmonic devices have recently drawn great attention. However, practical limitations in fabrication and device architectures prevent studies from being carried out on the intrinsic properties of graphene and their change by plasmonic structures. The influence of a quasi-infinite object (i.e., the substrate) on graphene, being a single sheet of carbon atoms, and the plasmonic device is overwhelming. To address this and put the intrinsic properties of the graphene-plasmonic nanostructures in focus, we fabricate large-area, freestanding, single-layer graphene-gold (LFG-Au) sandwich structures and Au nanoparticle decorated graphene (formed via thermal treatment) hybrid plasmonic nanostructures. We observed two distinct plasmonic enhancement routes of graphene unique to each structure via surface-enhanced Raman spectroscopy. The localized electronic structure variation in the LFG due to graphene-Au interaction at the nanoscale is mapped using scanning transmission X-ray microscopy. The measurements show an optical density of ∼0.007, which is the smallest experimentally determined for single-layer graphene thus far. Our results on freestanding graphene-Au plasmonic structures provide great insight for the rational design and future fabrication of graphene plasmonic hybrid nanostructures.

  19. Effect of heat treatments on machinability of gold alloy with age-hardenability at intraoral temperature.

    PubMed

    Watanabe, I; Baba, N; Watanabe, E; Atsuta, M; Okabe, T

    2004-01-01

    This study investigated the effect of heat treatment on the machinability of heat-treated cast gold alloy with age-hardenability at intraoral temperature using a handpiece engine with SiC wheels and an air-turbine handpiece with carbide burs and diamond points. Cast gold alloy specimens underwent various heat treatments [As-cast (AC); Solution treatment (ST); High-temperature aging (HA), Intraoral aging (IA)] before machinability testing. The machinability test was conducted at a constant machining force of 0.784N. The three circumferential speeds used for the handpiece engine were 500, 1,000 and 1,500 m/min. The machinability index (M-index) was determined as the amount of metal removed by machining (volume loss, mm(3)). The results were analyzed by ANOVA and Scheffé's test. When an air-turbine handpiece was used, there was no difference in the M-index of the gold alloy among the heat treatments. The air-turbine carbide burs showed significantly (p<0.05) higher M-indexes than the diamond points after any heat treatments. With the SiC wheels, increasing the circumferential speed increased the M-index values for each heat treatment. The specimens heat-treated with AC, HA and IA had similar M-indexes at the lower speeds (500 and 1,000 m/min). The ST specimens exhibited the lowest M-index at the lower speeds. However, at the highest speed (1,500 m/min), there were no significant differences in the M-indexes among the heat treatments except for HA, which showed the highest M-index. There was no effect of heat treatment on the machinability of the gold alloy using the air-turbine handpiece. The heat treatments had a small effect on the M-index of the gold alloy machined with a SiC wheel for a handpiece engine.

  20. Processing of Ni30Pt20Ti50 High-Temperature Shape-Memory Alloy Into Thin Rod Demonstrated

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.; Draper, Susan L.; Biles, Tiffany A.; Leonhardt, Todd

    2005-01-01

    High-temperature shape-memory alloys (HTSMAs) based on nickel-titanium (NiTi) with significant ternary additions of palladium (Pd), platinum (Pt), gold (Au), or hafnium (Hf) have been identified as potential high-temperature actuator materials for use up to 500 C. These materials provide an enabling technology for the development of "smart structures" used to control the noise, emissions, or efficiency of gas turbine engines. The demand for these high-temperature versions of conventional shape-memory alloys also has been growing in the automotive, process control, and energy industries. However these materials, including the NiPtTi alloys being developed at the NASA Glenn Research Center, will never find widespread acceptance unless they can be readily processed into useable forms.

  1. The Study and Application of Hydrometallurgical Gold Leaching in the Analysis of Refractory Precious Metals

    NASA Astrophysics Data System (ADS)

    Yang, M.; Geng, X.; Wang, Y. L.; Li, D. X.

    2017-05-01

    Three orthogonal tests are separately designed for each hydrometallurgical gold leaching process to finding the optimum reaction conditions of melting gold and palladium in each process. Under the optimum condition, the determination amount of gold and palladium in aqua regia—hydrofluoric acid, Sodium thiosulfate, and potassium iodide reaches 2.87g/kg and 8.34 g/kg, 2.39g/kg and 8.12 g/kg, 2.51g/kg and 7.84g/kg. From the result, the content of gold and palladium using the leaching process of combining Aqua regia, hydrofluoric acid and hydrogen peroxide is relatively higher than the other processes. In addition, the experiment procedure of aqua regia digestion operates easily, using less equipment, and its period is short.

  2. Controlled growth of hexagonal gold nanostructures during thermally induced self-assembling on Ge(001) surface

    PubMed Central

    Jany, B. R.; Gauquelin, N.; Willhammar, T.; Nikiel, M.; van den Bos, K. H. W.; Janas, A.; Szajna, K.; Verbeeck, J.; Van Aert, S.; Van Tendeloo, G.; Krok, F.

    2017-01-01

    Nano-sized gold has become an important material in various fields of science and technology, where control over the size and crystallography is desired to tailor the functionality. Gold crystallizes in the face-centered cubic (fcc) phase, and its hexagonal closed packed (hcp) structure is a very unusual and rare phase. Stable Au hcp phase has been reported to form in nanoparticles at the tips of some Ge nanowires. It has also recently been synthesized in the form of thin graphene-supported sheets which are unstable under electron beam irradiation. Here, we show that stable hcp Au 3D nanostructures with well-defined crystallographic orientation and size can be systematically created in a process of thermally induced self-assembly of thin Au layer on Ge(001) monocrystal. The Au hcp crystallite is present in each Au nanostructure and has been characterized by different electron microscopy techniques. We report that a careful heat treatment above the eutectic melting temperature and a controlled cooling is required to form the hcp phase of Au on a Ge single crystal. This new method gives scientific prospects to obtain stable Au hcp phase for future applications in a rather simple manner as well as redefine the phase diagram of Gold with Germanium. PMID:28195226

  3. Controlled growth of hexagonal gold nanostructures during thermally induced self-assembling on Ge(001) surface

    NASA Astrophysics Data System (ADS)

    Jany, B. R.; Gauquelin, N.; Willhammar, T.; Nikiel, M.; van den Bos, K. H. W.; Janas, A.; Szajna, K.; Verbeeck, J.; van Aert, S.; van Tendeloo, G.; Krok, F.

    2017-02-01

    Nano-sized gold has become an important material in various fields of science and technology, where control over the size and crystallography is desired to tailor the functionality. Gold crystallizes in the face-centered cubic (fcc) phase, and its hexagonal closed packed (hcp) structure is a very unusual and rare phase. Stable Au hcp phase has been reported to form in nanoparticles at the tips of some Ge nanowires. It has also recently been synthesized in the form of thin graphene-supported sheets which are unstable under electron beam irradiation. Here, we show that stable hcp Au 3D nanostructures with well-defined crystallographic orientation and size can be systematically created in a process of thermally induced self-assembly of thin Au layer on Ge(001) monocrystal. The Au hcp crystallite is present in each Au nanostructure and has been characterized by different electron microscopy techniques. We report that a careful heat treatment above the eutectic melting temperature and a controlled cooling is required to form the hcp phase of Au on a Ge single crystal. This new method gives scientific prospects to obtain stable Au hcp phase for future applications in a rather simple manner as well as redefine the phase diagram of Gold with Germanium.

  4. Theoretical model for plasmonic photothermal response of gold nanostructures solutions

    NASA Astrophysics Data System (ADS)

    Phan, Anh D.; Nga, Do T.; Viet, Nguyen A.

    2018-03-01

    Photothermal effects of gold core-shell nanoparticles and nanorods dispersed in water are theoretically investigated using the transient bioheat equation and the extended Mie theory. Properly calculating the absorption cross section is an extremely crucial milestone to determine the elevation of solution temperature. The nanostructures are assumed to be randomly and uniformly distributed in the solution. Compared to previous experiments, our theoretical temperature increase during laser light illumination provides, in various systems, both reasonable qualitative and quantitative agreement. This approach can be a highly reliable tool to predict photothermal effects in experimentally unexplored structures. We also validate our approach and discuss itslimitations.

  5. Method of making sulfur-resistant composite metal membranes

    DOEpatents

    Way, J Douglas [Boulder, CO; Lusk, Mark [Golden, CO; Thoen, Paul [Littleton, CO

    2012-01-24

    The invention provides thin, hydrogen-permeable, sulfur-resistant membranes formed from palladium or palladium-alloy coatings on porous, ceramic or metal supports. Also disclosed are methods of making these membranes via sequential electroless plating techniques, wherein the method of making the membrane includes decomposing any organic ligands present on the substrate, reducing the palladium crystallites on the substrate to reduced palladium crystallites, depositing a film of palladium metal on the substrate and then depositing a second, gold film on the palladium film. These two metal films are then annealed at a temperature between about 200.degree. C. and about 1200.degree. C. to form a sulfur-resistant, composite PdAu alloy membrane.

  6. Synergetic effect of palladium-ruthenium nanostructures for ethanol electrooxidation in alkaline media

    NASA Astrophysics Data System (ADS)

    Monyoncho, Evans A.; Ntais, Spyridon; Soares, Felipo; Woo, Tom K.; Baranova, Elena A.

    2015-08-01

    Palladium-ruthenium nanoparticles supported on carbon PdxRu1-x/C (x = 1, 0.99, 0.95, 0.90, 0.80, 0.50) were prepared using a polyol method for ethanol electrooxidation in alkaline media. The resulting bimetallic catalysts were found to be primarily a mix of Pd metal, Ru oxides and Pd oxides. Their electrocatalytic activity towards ethanol oxidation reaction (EOR) in 1M KOH was studied using cyclic voltammetry and chronoamperometry techniques. Addition of 1-10 at.% Ru to Pd not only lowers the onset oxidation potential for EOR but also produces higher current densities at lower potentials compared to Pd by itself. Thus, Pd90Ru10/C and Pd99Ru1/C provide the current densities of up to six times those of Pd/C at -0.96 V and -0.67 V vs MSE, respectively. The current density at different potentials was found to be dependent on the surface composition of PdxRu1-x/C nanostructures. Pd90Ru10/C catalyst with more surface oxides was found to be active at lower potential compared to Pd99Ru1/C with less surface oxides, which is active at higher potentials. The steady-state current densities of the two best catalysts, Pd90Ru10/C and Pd99Ru1/C, showed minimal surface deactivation from EOR intermediates/products during chronoamperometry.

  7. Biogenic Growth of Alloys and Core-Shell Nanostructures Using Urease as a Nanoreactor at Ambient Conditions

    PubMed Central

    Sharma, Bhagwati; Mandani, Sonam; Sarma, Tridib K.

    2013-01-01

    Biomineralization is an extremely efficient biologically guided process towards the advancement of nano-bio integrated materials. As a prime module of the natural world, enzymes are expected to play a major role in biogenic growth of inorganic nanostructures. Although there have been developments in designing enzyme-responsive nanoparticle systems or generation of inorganic nanostructures in an enzyme-stimulated environment, reports regarding action of enzymes as reducing agents themselves for the growth of inorganic nanoparticles still remains elusive. Here we present a mechanistic investigation towards the synthesis of metal and metallic alloy nanoparticles using a commonly investigated enzyme, Jack bean urease (JBU), as a reducing as well as stabilizing agent under physiological conditions. The catalytic functionality of urease was taken advantage of towards the development of metal-ZnO core-shell nanocomposites, making urease an ideal bionanoreactor for synthesizing higher order nanostructures such as alloys and core- shell under ambient conditions. PMID:24018831

  8. Influence of gold additives on the stability and phase transformation of titanate nanostructures.

    PubMed

    Pusztai, P; Puskás, R; Varga, E; Erdőhelyi, A; Kukovecz, Á; Kónya, Z; Kiss, J

    2014-12-28

    Gold nanoparticles were prepared and characterized on protonated (H-form) titanate nanotubes (TiONTs) and nanowires (TiONWs). The chemical nature and morphology of gold particles were monitored by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD) and high resolution electron microscopy (HRTEM). The optical properties of Au-containing titanate nanowires were explored by means of ultraviolet-visible diffuse reflectance spectroscopy. The size distribution and homogeneity of gold particles depend on the reduction mode from the corresponding gold salt to metal particles. Smaller clusters (3-8 nm) were obtained with the NaBH4 reactant at 293 K than with molecular hydrogen reduction. An unexpectedly high binding energy gold state was found by XPS in gold-loaded titanate nanostructures. This state was absent from the spectra of gold-loaded TiO2(110). A likely explanation for this phenomenon, supported also by the characteristic decrease of band gap energy from 3.10 eV to 2.74 eV with increasing Au content, is that depending on the metal loading and titanate structure, Au is stabilized on titanate nanowires partially in positively charged gold form by ion exchange and also as Au clusters. Our important new finding is that the thermal annealing behavior of Au-loaded titanate nanotubes and nanowires is different. The former lose their tubular morphology and are readily transformed into anatase even at a very low temperature of 473 K. On the other hand, gold stabilizes the layered structure of titanate nanowires up to 873 K.

  9. In vitro comparative analysis of the fit of gold alloy or commercially pure titanium implant-supported prostheses before and after electroerosion.

    PubMed

    Sartori, Ivete Aparecida de Mattias; Ribeiro, Ricardo Faria; Francischone, Carlos Eduardo; de Mattos, Maria da Gloria Chiarello

    2004-08-01

    For implant-supported prostheses, passive fit is critical for the success of rehabilitation, especially when alternative materials are used. The purpose of this study was to compare interfacial fit of implant-supported prostheses cast in titanium to those cast in gold alloy. Five 3-unit fixed partial dentures were fabricated in gold alloy (Degudent U) as 1-piece castings, and 5 others were similarly cast in commercially pure titanium (Grade 1). The interfacial gaps between the prostheses and the abutments were evaluated with an optical microscope, before and after electroerosion. Readings were made with both screws tightened (10 N.cm torque), and with only 1 side tightened, so as to also evaluate the passive fit of the prostheses. Data were compared statistically by 2-way analysis of variance and the post hoc Tukey multiple range test (alpha=.05). Before electroerosion, the interfacial gaps for the 1-piece prostheses were significantly smaller (P<.001) in the gold alloy group when the screws were tightened (Au=12.6 +/- 3.0 microm, compared to Ti=30.1 +/- 6.4 microm). When the side opposite the tightened side was analyzed, there was no significant difference between the gold alloy and titanium groups (Au=69.2 +/- 24.9 microm and Ti=94.2 +/- 39.6 microm). The electroerosion procedure significantly (P<.001) reduced the gaps at the interfaces for both groups under all conditions. Comparison between groups after electroerosion did not present significant differences when the side opposite the tightened side was analyzed, but the gold alloy group showed better fit when the tightened side was analyzed (12.8 +/- 1.4 microm for gold alloy; 29.6 +/- 4.4 microm for titanium) and when both screws were tightened (5.4 +/- 2.3 microm for gold alloy; 16.1 +/- 5.5 microm for titanium). Cast titanium prostheses, despite showing larger interfacial gaps between the prosthesis and abutment than those obtained with gold alloy, had improved fit after being subjected to electroerosion.

  10. Effect of Systematic Control of Pd Thickness and Annealing Temperature on the Fabrication and Evolution of Palladium Nanostructures on Si (111) via the Solid State Dewetting.

    PubMed

    Kunwar, Sundar; Pandey, Puran; Sui, Mao; Zhang, Quanzhen; Li, Ming-Yu; Lee, Jihoon

    2017-12-01

    Si-based optoelectronic devices embedded with metallic nanoparticles (NPs) have demonstrated the NP shape, size, spacing, and crystallinity dependent on light absorption and emission induced by the localized surface plasmon resonance. In this work, we demonstrate various sizes and configurations of palladium (Pd) nanostructures on Si (111) by the systematic thermal annealing with the variation of Pd thickness and annealing temperature. The evolution of Pd nanostructures are systematically controlled by the dewetting of thin film by means of the surface diffusion in conjunction with the surface and interface energy minimization and Volmer-Weber growth model. Depending on the control of deposition amount ranging between 0.5 and 100 nm at various annealing temperatures, four distinctive regimes of Pd nanostructures are demonstrated: (i) small pits and grain formation, (ii) nucleation and growth of NPs, (iii) lateral evolution of NPs, and (iv) merged nanostructures. In addition, by the control of annealing between 300 and 800 °C, the Pd nanostructures show the evolution of small pits and grains, isolated NPs, and finally, Pd NP-assisted nanohole formation along with the Si decomposition and Pd-Si inter-diffusion. The Raman analysis showed the discrepancies on phonon modes of Si (111) such that the decreased peak intensity with left shift after the fabrication of Pd nanostructures. Furthermore, the UV-VIS-NIR reflectance spectra revealed the existence of surface morphology dependent on absorption, scattering, and reflectance properties.

  11. Effect of Systematic Control of Pd Thickness and Annealing Temperature on the Fabrication and Evolution of Palladium Nanostructures on Si (111) via the Solid State Dewetting

    NASA Astrophysics Data System (ADS)

    Kunwar, Sundar; Pandey, Puran; Sui, Mao; Zhang, Quanzhen; Li, Ming-Yu; Lee, Jihoon

    2017-05-01

    Si-based optoelectronic devices embedded with metallic nanoparticles (NPs) have demonstrated the NP shape, size, spacing, and crystallinity dependent on light absorption and emission induced by the localized surface plasmon resonance. In this work, we demonstrate various sizes and configurations of palladium (Pd) nanostructures on Si (111) by the systematic thermal annealing with the variation of Pd thickness and annealing temperature. The evolution of Pd nanostructures are systematically controlled by the dewetting of thin film by means of the surface diffusion in conjunction with the surface and interface energy minimization and Volmer-Weber growth model. Depending on the control of deposition amount ranging between 0.5 and 100 nm at various annealing temperatures, four distinctive regimes of Pd nanostructures are demonstrated: (i) small pits and grain formation, (ii) nucleation and growth of NPs, (iii) lateral evolution of NPs, and (iv) merged nanostructures. In addition, by the control of annealing between 300 and 800 °C, the Pd nanostructures show the evolution of small pits and grains, isolated NPs, and finally, Pd NP-assisted nanohole formation along with the Si decomposition and Pd-Si inter-diffusion. The Raman analysis showed the discrepancies on phonon modes of Si (111) such that the decreased peak intensity with left shift after the fabrication of Pd nanostructures. Furthermore, the UV-VIS-NIR reflectance spectra revealed the existence of surface morphology dependent on absorption, scattering, and reflectance properties.

  12. High-capacity nanostructured germanium-containing materials and lithium alloys thereof

    DOEpatents

    Graetz, Jason A.; Fultz, Brent T.; Ahn, Channing; Yazami, Rachid

    2010-08-24

    Electrodes comprising an alkali metal, for example, lithium, alloyed with nanostructured materials of formula Si.sub.zGe.sub.(z-1), where 0

  13. Electromagnetic plasmon propagation and coupling through gold nanoring heptamers: a route to design optimized telecommunication photonic nanostructures.

    PubMed

    Ahmadivand, Arash; Golmohammadi, Saeed

    2014-06-20

    In this work, a configuration of bulk gold nanorings with certain geometrical sizes has been utilized for designing efficient photonic subwavelength nanostructures. We verify that adjacent heptamers based on gold nanorings are able to couple and transport magnetic plasmon resonance along a nanoring array in chrysene and triphenylene molecule orientations. This magnetic resonance transmission is caused by an antiphase circular current through the heptamer arrays. An orientation model of nanoring heptamers helps us to provide efficient optical structures with a remarkable decay length and a trivial ratio of destructive interferences. Exploiting the robust magnetic plasmon resonance coupling effect between heptamers arrays, we would be able to propose a practical plasmonic waveguide, a Y-shaped optical power divider (splitter), and an ON/OFF router that is operating based on destructive and constructive interferences. The quality of power splitting has been discussed comprehensively and also, the effect of undesirable occasions on the functioning performance of the proposed router has been investigated numerically. Ultimately, we verify that employing heptamers based on gold nanorings leads us to propose efficient plasmonic nanostructures and devices that are able to work in the telecommunication spectrum.

  14. Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

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

    Miller, Michael K.; Parish, Chad M.; Bei, Hongbin

    Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti–Y–O-enriched nanoclusters and solute clusters, which drives themore » mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. Furthermore, the result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.« less

  15. Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

    DOE PAGES

    Miller, Michael K.; Parish, Chad M.; Bei, Hongbin

    2014-12-18

    Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti–Y–O-enriched nanoclusters and solute clusters, which drives themore » mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. Furthermore, the result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.« less

  16. Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

    NASA Astrophysics Data System (ADS)

    Miller, M. K.; Parish, C. M.; Bei, H.

    2015-07-01

    Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti-Y-O-enriched nanoclusters and solute clusters, which drives the mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. The result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.

  17. COST-EFFECTIVE METHOD FOR PRODUCING SELF SUPPORTED PALLADIUM ALLOY MEMBRANES FOR USE IN EFFICIENT PRODUCTION OF COAL DERIVED HYDROGEN

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

    B. Lanning; J. Arps

    2004-04-01

    Extending upon development efforts last quarter to produce ''free-standing'', copper and palladium alloy films, the goal this quarter has been to produce pinhole-free, Pd-Cu alloy films up to 5 x 5 inches in area (1-3 microns thick) using both magnetron sputtering and e-beam evaporation on PVA (Solublon) and polystyrene backing materials. A set of experiments were conducted to assess processing methods/solutions chemistry for removing the polymer backing material from the Pd-Cu film. For all of the alloy films produced to this point, we were unable to produce pinhole-free films on plastic although we were able to produce free-standing Pd-Cu filmsmore » at less than 0.5 microns thick with minimal intrinsic stress. Subsequently, to evaluate gas permeation and leakage across the films, two films were sandwiched together on top of a porous Monel support disc (25 mm in diameter) and then tested in a leak test apparatus. Using two Cu films (10 micron thickness total) in the sandwich configuration, leak rates were about 20% of the background leak rate.« less

  18. XPS and NRA investigations during the fabrication of gold nanostructured functionalized screen-printed sensors for the detection of metallic pollutants

    NASA Astrophysics Data System (ADS)

    Jasmin, Jean-Philippe; Miserque, Frédéric; Dumas, Eddy; Vickridge, Ian; Ganem, Jean-Jacques; Cannizzo, Caroline; Chaussé, Annie

    2017-03-01

    An all covalent nanostructured lead sensor was built by the successive grafting of gold nanoparticles and carboxylic ligands at the surface of self-adhesive carbon screen-printed electrodes (SPEs). Surface analysis techniques were used in each step in order to investigate the structuration of this sensor. The self-adhesive surfaces were made from the electrochemical grafting of p-phenylenediamine at the surface of the SPEs via diazonium salts chemistry. The quantity of grafted aniline functions, estimated by Nuclear Reaction Analysis (NRA) performed with p-phenylenediamine labelled with 15N isotope, is in agreement with an almost complete coverage of the electrode surface. The subsequent diazotization of the aniline functions at the surface of the SPEs was performed; X-ray Photoelectron Spectroscopy (XPS) allowed us to consider a quantitative conversion of the aniline functions into diazonium moieties. The spontaneous grafting of gold nanoparticles on the as-obtained reactive surfaces ensures the nanostructuration of the material, and XPS studies showed that the covalent bonding of the gold nanoparticles at the surface of the SPEs induces a change both in the Au-4f (gold nanoparticles) and Cl-2p (carbon ink) core level signals. These unusual observations are explained by an interaction between the carbon ink constituting the substrate and the gold nanoparticles. Heavy and toxic metals are considered of major environmental concern because of their non-biodegradability. In a final step, the grafting of the carboxylic ligands at the surface of the SPEs and an accumulation step in the presence of lead(II) cations allowed us to evidence the interest of nanostructured materials as metallic pollutants sensors.

  19. Influence of ceramic surface texture on the wear of gold alloy and heat-pressed ceramics.

    PubMed

    Saiki, Osamu; Koizumi, Hiroyasu; Nogawa, Hiroshi; Hiraba, Haruto; Akazawa, Nobutaka; Matsumura, Hideo

    2014-01-01

    The purpose of this study was to evaluate the influence of ceramic surface texture on the wear of rounded rod specimens. Plate specimens were fabricated from zirconia (ZrO2), feldspathic porcelain, and lithium disilicate glass ceramics (LDG ceramics). Plate surfaces were either ground or polished. Rounded rod specimens with a 2.0-mm-diameter were fabricated from type 4 gold alloy and heat-pressed ceramics (HP ceramics). Wear testing was performed by means of a wear testing apparatus under 5,000 reciprocal strokes of the rod specimen with 5.9 N vertical loading. The results were statistically analyzed with a non-parametric procedure. The gold alloy showed the maximal height loss (90.0 µm) when the rod specimen was abraded with ground porcelain, whereas the HP ceramics exhibited maximal height loss (49.8 µm) when the rod specimen was abraded with ground zirconia. There was a strong correlation between height loss of the rod and surface roughness of the underlying plates, for both the gold alloy and HP ceramics.

  20. Tessellated gold nanostructures from Au144(SCH2CH2Ph)60 molecular precursors and their use in organic solar cell enhancement

    NASA Astrophysics Data System (ADS)

    Bauld, Reg; Hesari, Mahdi; Workentin, Mark S.; Fanchini, Giovanni

    2014-06-01

    We report for the first time the fabrication of nanocomposite hole-blocking layers consisting of poly-3,4-ethylene-dioxythiophene:poly-styrene-sulfonate (PEDOT:PSS) thin films incorporating networks of gold nanoparticles assembled from Au144(SCH2CH2Ph)60, a molecular gold precursor. These thin films can be prepared reproducibly on indium tin oxide by spinning on it Au144(SCH2CH2Ph)60 solutions in chlorobenzene, annealing the resulting thin film at 400 °C, and subsequently spinning PEDOT:PSS on top. The use of our nanocomposite hole-blocking layers for enhancing the photoconversion efficiency of bulk heterojunction organic solar cells is demonstrated. By varying the concentration of Au144(SCH2CH2Ph)60 in the starting solution and the annealing time, different gold nanostructures were obtained ranging from individual gold nanoparticles (AuNPs) to tessellated networks of gold nanostructures (Tess-AuNPs). Improvement in organic solar cell efficiencies up to 10% relative to a reference cell is demonstrated with Tess-AuNPs embedded in PEDOT:PSS.

  1. 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.

  2. Measurements of thermoelectric power in annealed and quenched gold-platinum alloys

    NASA Technical Reports Server (NTRS)

    Baarle, C. V.; Huebener, R. P.

    1969-01-01

    Report gives measurements of absolute thermoelectric powers of dilute gold-platinum alloys and influence of quenched-in lattice vacancies on their thermoelectric powers. It investigates phonon-drag component of thermoelectric power as a function of platinum concentration, and change in phonon-drag thermoelectric power by lattice vacancies.

  3. High performance SERS on nanoporous gold substrates synthesized by chemical de-alloying a Au-based metallic glass

    NASA Astrophysics Data System (ADS)

    Xue, Yanpeng; Scaglione, Federico; Rizzi, Paola; Battezzati, Livio

    2017-12-01

    A Au20Cu48Ag7Pd5Si20 metallic glass precursor has been used to synthesize nanoporous gold by chemical de-alloying in a mixture of HNO3 and HF. Gold ligaments of size ranging from 45 to 100 nm were obtained as a function of HNO3 concentration, electrolyte temperature and de-alloying time. The as-prepared nanoporous gold exhibited strong surface enhanced Raman scattering (SERS) effect using 4,4‧-bi-pyridine as probe molecule. For application in melamine sensing, the detection limit of 10-6 M was achieved, which indicated that this biocompatible material has great potential as SERS active substrate.

  4. Effect of S-phase precipitates on deformation nanostructuring and hardening of 2xxx aluminum alloy

    NASA Astrophysics Data System (ADS)

    Markushev, Michael; Krymskiy, Stanislav; Avtokratova, Elena; Ilyasov, Rafis; Sitdikov, Oleg

    2017-12-01

    The influence of preliminary heat treatment, involving quenching and further aging at 190°C for 10 h, on the grain structure, hardness, and tensile strength of hot-pressed commercial D16 alloy severely deformed via room-temperature high pressure torsion (HPT) (10 revolutions under P = 6 GPa) was investigated. In spite of higher deformation strengthening, owing to the formation of a more developed nanostructure in the prequenched material, the alloy hardness and strength in both HPT conditions (i.e. after quenching and further aging) were quite similar. The nature of the alloy structure-property relations found is discussed.

  5. Control of both particle and pore size in nanoporous palladium alloy powders

    DOE PAGES

    Jones, Christopher G.; Cappillino, Patrick J.; Stavila, Vitalie; ...

    2014-07-15

    Energy storage materials often involve chemical reactions with bulk solids. Porosity within the solids can enhance reaction rates. The porosity can be either within or between individual particles of the material. Greater control of the size and uniformity of both types of pore should lead to enhancements of charging and discharging rates in energy storage systems. Furthermore, to control both particle and pore size in nanoporous palladium (Pd)-based hydrogen storage materials, first we created uniformly sized copper particles of about 1 μm diameter by the reduction of copper sulfate with ascorbic acid. In turn, these were used as reducing agentsmore » for tetrachloropalladate in the presence of a block copolymer surfactant. The copper reductant particles are geometrically self-limiting, so the resulting Pd particles are of similar size. The surfactant induces formation of 10 nm-scale pores within the particles. Some residual copper is alloyed with the Pd, reducing hydrogen storage capacity; use of a more reactive Pd salt can mitigate this. The reaction is conveniently performed in gram-scale batches.« less

  6. Redbed-type gold mineralisation, Kupferschiefer, south-west Poland

    NASA Astrophysics Data System (ADS)

    Piestrzyński, Adam; Pieczonka, Jadwiga; Głuszek, Adam

    2002-06-01

    A new type of gold mineralisation containing minor amounts of platinum and palladium has been found proximal to the secondary redox interface located below the Cu-Ag Kupferschiefer orebody of the Polkowice-Sieroszowice mine in the south-western part of the Lubin-Sieroszowice district, Poland. This deposit can be classified as redbed-type gold. Our study shows that gold, platinum and palladium occur in secondary red-coloured sections of the basal Zechstein sedimentary rocks and in the uppermost Weissliegendes sandstone. Noble metal mineralisation occurs within an average interval of 0.22 m, which lies directly below the copper ores. The average grade of the horizon is 2.25 ppm Au, 0.138 ppm Pt and 0.082 ppm Pd with a metal content of several tens of tonnes of gold. A transition zone has been recognised between the gold-bearing horizon and the copper deposit. This transition zone is characterised by the presence of low grades of copper (<0.2 wt%) and elevated gold contents (>0.5 ppm). Native gold accompanied by electrum, mercury-bearing gold, haematite, covellite, chalcocite, bornite and chalcopyrite has been identified in the gold-bearing horizon. In some sections, Pd-arsenides, tetra-auricupride, Co-arsenides, clausthalite, tennantite, digenite, yarrowite, spionkopite and galena have also been noted.

  7. Nanostructured enzymatic biosensor based on fullerene and gold nanoparticles: preparation, characterization and analytical applications.

    PubMed

    Lanzellotto, C; Favero, G; Antonelli, M L; Tortolini, C; Cannistraro, S; Coppari, E; Mazzei, F

    2014-05-15

    In this work a novel electrochemical biosensing platform based on the coupling of two different nanostructured materials (gold nanoparticles and fullerenols) displaying interesting electrochemical features, has been developed and characterized. Gold nanoparticles (AuNPs) exhibit attractive electrocatalytic behavior stimulating in the last years, several sensing applications; on the other hand, fullerene and its derivatives are a very promising family of electroactive compounds although they have not yet been fully employed in biosensing. The methodology proposed in this work was finalized to the setup of a laccase biosensor based on a multilayer material consisting in AuNPs, fullerenols and Trametes versicolor Laccase (TvL) assembled layer by layer onto a gold (Au) electrode surface. The influence of different modification step procedures on the electroanalytical performance of biosensors has been evaluated. Cyclic voltammetry, chronoamperometry, surface plasmon resonance (SPR) and scanning tunneling microscopy (STM) were used to characterize the modification of surface and to investigate the bioelectrocatalytic biosensor response. This biosensor showed fast amperometric response to gallic acid, which is usually considered a standard for polyphenols analysis of wines, with a linear range 0.03-0.30 mmol L(-1) (r(2)=0.9998), with a LOD of 0.006 mmol L(-1) or expressed as polyphenol index 5.0-50 mg L(-1) and LOD 1.1 mg L(-1). A tentative application of the developed nanostructured enzyme-based biosensor was performed evaluating the detection of polyphenols either in buffer solution or in real wine samples. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. High permeance sulfur tolerant Pd/Cu alloy membranes

    DOEpatents

    Ma, Yi Hua; Pomerantz, Natalie

    2014-02-18

    A method of making a membrane permeable to hydrogen gas (H.sub.2.uparw.) is disclosed. The membrane is made by forming a palladium layer, depositing a layer of copper on the palladium layer, and galvanically displacing a portion of the copper with palladium. The membrane has improved resistance to poisoning by H.sub.2S compared to a palladium membrane. The membrane also has increased permeance of hydrogen gas compared to palladium-copper alloys. The membrane can be annealed at a lower temperature for a shorter amount of time.

  9. Palladium-tin catalysts for the direct synthesis of H 2O 2 with high selectivity

    DOE PAGES

    Freakley, Simon J.; He, Qian; Harrhy, Jonathan H.; ...

    2016-02-25

    The direct synthesis of hydrogen peroxide (H 2O 2 ) from H 2 and O 2 represents a potentially atom-efficient alternative to the current industrial indirect process. We show that the addition of tin to palladium catalysts coupled with an appropriate heat treatment cycle switches off the sequential hydrogenation and decomposition reactions, enabling selectivities of >95% toward H 2O 2 . This effect arises from a tin oxide surface layer that encapsulates small Pd-rich particles while leaving larger Pd-Sn alloy particles exposed. In conclusion, we show that this effect is a general feature for oxide-supported Pd catalysts containing an appropriatemore » second metal oxide component, and we set out the design principles for producing high-selectivity Pd-based catalysts for direct H 2O 2 production that do not contain gold.« less

  10. Detection of bacteria using bacteriophage with hollow gold nanostructures immobilized fiber optic sensor

    NASA Astrophysics Data System (ADS)

    Halkare, Pallavi; Punjabi, Nirmal; Wangchuk, Jigme; Kondabagil, Kiran; Mukherji, Soumyo

    2016-04-01

    Hollow gold nanostructures (HGNS) have been used in variety of optical biosensors due to their inherent advantage of operating at near infra red (NIR) wavelength, large extinction coefficient and high dielectric sensitivity. The absorption wavelength of these nanostructures can be modulated by changing the ratio of hollow region to the core shell thickness. The aim of the present study is to incorporate the properties of HGNS, to develop LSPR based U-bent fiber optic sensor for detection of pathogens. The detection was carried out using an experimental set up consisting of a white light source, 200 μm diameter optical fiber having bend diameter of 1.6 mm +/- 0. 2 mm and a spectrometer. The HGNS were immobilized on the decladded portion of the fiber optic probe by chemisorptions. The effective plasmon penetration depth of the HGNS immobilized fiber optic sensor was approximated by using alternating layers of positively and negatively charged polyelectrolytes. The HGNS immobilized U-bent fiber optic sensor was used for detection of E.coli B40 strain using bacteriophage T4. The preliminary experiments were carried out with 104 cfu/ml of E.coli B40 and the change in absorbance obtained was approx. 0.042 +/- 0.0045 abs. units (n = 3). The response of this sensor was found to be better than spherical gold nanoparticle immobilized sensing platforms.

  11. GREENER SYNTHESIS OF ALIGNED PALLADIUM NANOBELTS AND NANOPLATES IN AQUEOUS MEDIUM USING VITAMIN B1

    EPA Science Inventory

    Palladium (Pd) plays an important role in many industrial and technological applications such as reduction of automobile pollutants, and Suzuki, Heck, and Stille coupling reactions. Consequently, a great deal of effort has been devoted to the synthesis of Pd nanostructures. Her...

  12. Hermetic diamond capsules for biomedical implants enabled by gold active braze alloys.

    PubMed

    Lichter, Samantha G; Escudié, Mathilde C; Stacey, Alastair D; Ganesan, Kumaravelu; Fox, Kate; Ahnood, Arman; Apollo, Nicholas V; Kua, Dunstan C; Lee, Aaron Z; McGowan, Ceara; Saunders, Alexia L; Burns, Owen; Nayagam, David A X; Williams, Richard A; Garrett, David J; Meffin, Hamish; Prawer, Steven

    2015-01-01

    As the field of biomedical implants matures the functionality of implants is rapidly increasing. In the field of neural prostheses this is particularly apparent as researchers strive to build devices that interact with highly complex neural systems such as vision, hearing, touch and movement. A retinal implant, for example, is a highly complex device and the surgery, training and rehabilitation requirements involved in deploying such devices are extensive. Ideally, such devices will be implanted only once and will continue to function effectively for the lifetime of the patient. The first and most pivotal factor that determines device longevity is the encapsulation that separates the sensitive electronics of the device from the biological environment. This paper describes the realisation of a free standing device encapsulation made from diamond, the most impervious, long lasting and biochemically inert material known. A process of laser micro-machining and brazing is described detailing the fabrication of hermetic electrical feedthroughs and laser weldable seams using a 96.4% gold active braze alloy, another material renowned for biochemical longevity. Accelerated ageing of the braze alloy, feedthroughs and hermetic capsules yielded no evidence of corrosion and no loss of hermeticity. Samples of the gold braze implanted for 15 weeks, in vivo, caused minimal histopathological reaction and results were comparable to those obtained from medical grade silicone controls. The work described represents a first account of a free standing, fully functional hermetic diamond encapsulation for biomedical implants, enabled by gold active alloy brazing and laser micro-machining. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. New electrocatalysts for hydrogen-oxygen fuel cells

    NASA Technical Reports Server (NTRS)

    Cattabriga, R. A.; Giner, J.; Parry, J.; Swette, L. L.

    1970-01-01

    Platinum-silver, palladium-gold, and platinum-gold alloys serve as oxygen reduction catalysts in high-current-density cells. Catalysts were tested on polytetrafluoroethylene-bonded cathodes and a hydrogen anode at an operating cell temperature of 80 degrees C.

  14. Electrochemical synthesis of nanostructured gold film for the study of carbohydrate–lectin interactions using localized surface plasmon resonance spectroscopy

    PubMed Central

    Bhattarai, Jay K.; Sharma, Abeera; Fujikawa, Kohki; Demchenko, Alexei V.; Stine, Keith J.

    2014-01-01

    Localized surface plasmon resonance (LSPR) spectroscopy is a label-free chemical and biological molecular sensing technique whose sensitivity depends upon development of nanostructured transducers. Herein, we report an electrodeposition method for fabricating nanostructured gold films (NGFs) that can be used as transducers in LSPR spectroscopy. The NGF was prepared by electrodepositing gold from potassium dicyanoaurate solution onto a flat gold surface using two sequential controlled potential steps. Imaging by scanning electron microscopy reveals a morphology consisting of randomly configured block-like nanostructures. The bulk refractive index sensitivity of the prepared NGF is 100 ± 2 nm RIU−1 and the initial peak in the reflectance spectrum is at 518 ± 1 nm under N2(g). The figure of merit is 1.7. In addition, we have studied the interaction between carbohydrate (mannose) and lectin (Concanavalin A) on the NGF surface using LSPR spectroscopy by measuring the interaction of 8-mercaptooctyl-α-D-mannopyranoside (αMan-C8-SH) with Concanavalin A by first immobilizing αMan-C8-SH in mixed SAMs with 3,6-dioxa-8-mercaptooctanol (TEG-SH) on the NGF surface. The interaction of Con A with the mixed SAMs is confirmed using electrochemical impedance spectroscopy. Finally, the NGF surface was regenerated to its original sensitivity by removing the SAM and the bound biomolecules. The results from these experiments contribute toward the development of inexpensive LSPR based sensors that could be useful for studying glycan–protein interactions and other bioanalytical purposes. PMID:25442712

  15. The Effects of Size, Shape, and Surface Functional Group of Gold Nanostructures on Their Adsorption and Internalization by Cells

    PubMed Central

    Cho, Eun Chul; Au, Leslie; Zhang, Qiang; Xia, Younan

    2010-01-01

    In this study, we examined the effects of size, shape, and surface chemistry of gold nanostructures on their uptake (including both adsorption and internalization) by SK-BR-3 breast cancer cells. We used both spherical and cubic Au nanostructures (nanospheres and nanocages, respectively) of two different sizes, and their surface was modified with poly(ethylene glycol) (PEG), antibody anti-HER2, or poly(allyamine hydrochloride) (PAA). Our results showed that the size of the Au nanostructures influenced their uptake by the cells in a similar way regardless of the surface chemistry, while the shape dependency could vary depending on the surface functional group. In addition, the cells preferred to take up the Au nanostructures covered by different surface groups in the following order: PAA>> anti-HER2> PEG. The fraction of Au nanostructures attached to the cell surface was also dependent on the aforementioned parameters. PMID:20029850

  16. Pulsed laser deposition of plasmonic nanostructured gold on flexible transparent polymers at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    McCann, Ronán; Hughes, Cian; Bagga, Komal; Stalcup, Apryll; Vázquez, Mercedes; Brabazon, Dermot

    2017-06-01

    In this paper, we outline a novel technique for the deposition of nanostructured thin films utilizing a modified form of pulsed laser deposition (PLD). We demonstrate confined atmospheric PLD (CAP) for the deposition of gold on cyclic olefin polymer substrates. The deposition process is a simplified form of conventional PLD, with deposition conducted under atmospheric conditions and the substrate and target in close proximity. It was found that this confinement results in the deposition of nanostructured thin films on the substrate. Infrared spectroscopy showed no significant change of polymer surface chemistry as a result of the deposition process, and optical spectroscopy revealed plasmonic behavior of the resulting thin film. The effect of laser fluence on the deposition process was also examined with more uniform films deposited at higher fluences.

  17. Gold-Copper Nanoparticles: Nanostructural Evolution and Bifunctional Catalytic Sites

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

    Yin, Jun; Shan, Shiyao; Yang, Lefu

    2012-12-12

    Understanding of the atomic-scale structure is essential for exploiting the unique catalytic properties of any nanoalloy catalyst. This report describes novel findings of an investigation of the nanoscale alloying of gold-copper (AuCu) nanoparticles and its impact on the surface catalytic functions. Two pathways have been explored for the formation of AuCu nanoparticles of different compositons, including wet chemical synthesis from mixed Au- and Cu-precursor molecules, and nanoscale alloying via an evolution of mixed Au- and Cu-precursor nanoparticles near the nanoscale melting temperatures. For the evolution of mixed precursor nanoparticles, synchrotron x-ray based in-situ real time XRD was used to monitormore » the structural changes, revealing nanoscale alloying and reshaping towards an fcc-type nanoalloy (particle or cube) via a partial melting–resolidification mechanism. The nanoalloys supported on carbon or silica were characterized by in-situ high-energy XRD/PDFs, revealing an intriguing lattice "expanding-shrinking" phenomenon depending on whether the catalyst is thermochemically processed under oxidative or reductive atmosphere. This type of controllable structural changes is found to play an important role in determining the catalytic activity of the catalysts for carbon monoxide oxidation reaction. The tunable catalytic activities of the nanoalloys under thermochemically oxidative and reductive atmospheres are also discussed in terms of the bifunctional sites and the surface oxygenated metal species for carbon monoxide and oxygen activation.« less

  18. Surface functionalized Cu2Zn1- x Cd x SnS4 quinternary alloyed nanostructure for DNA sensing

    NASA Astrophysics Data System (ADS)

    Ibraheam, A. S.; Al-Douri, Y.; Voon, C. H.; Foo, K. L.; Azizah, N.; Gopinath, S. C. B.; Ameri, M.; Ibrahim, Sattar S.

    2017-03-01

    A sensing plate of extended Cu2Zn1- x Cd x SnS4 quinternary alloy nanostructures, fabricated on an oxidized silicon substrate by the sol-gel method, is reported in this paper. The fabricated device was characterized and analyzed via field emission-scanning electron microscopy, X-ray diffraction (XRD), and photoluminescence (PL). The XRD peaks shifted towards the lower angle side alongside increasing concentration of cadmium. The average diameter of the Cu2Zn1- x Cd x SnS4 quinternary alloy nanostructures falls between 21.55 and 43.12 nm, while the shift of the PL bandgap was from 1.81 eV ( x = 0) to 1.72 eV ( x = 1). The resulting Cu2Zn1- x Cd x SnS4 quinternary alloy nanostructures components were functionalized with oligonucleotides probe DNA molecules and interacted with the target, exhibiting good sensing capabilities due to its large surface-to-volume ratio. The fabrication, immobilization, and hybridization processes were analyzed via representative current-voltage ( I- V) plots. Its electrical profile shows that the device is capable to distinguish biomolecules. Its high performance was evident from the linear relationship between the probe DNA from cervical cancer and the target DNA, showing its applicability for medical applications.

  19. Oxide mediated liquid-solid growth of high aspect ratio aligned gold silicide nanowires on Si(110) substrates.

    PubMed

    Bhatta, Umananda M; Rath, Ashutosh; Dash, Jatis K; Ghatak, Jay; Yi-Feng, Lai; Liu, Chuan-Pu; Satyam, P V

    2009-11-18

    Silicon nanowires grown using the vapor-liquid-solid method are promising candidates for nanoelectronics applications. The nanowires grow from an Au-Si catalyst during silicon chemical vapor deposition. In this paper, the effect of temperature, oxide at the interface and substrate orientation on the nucleation and growth kinetics during formation of nanogold silicide structures is explained using an oxide mediated liquid-solid growth mechanism. Using real time in situ high temperature transmission electron microscopy (with 40 ms time resolution), we show the formation of high aspect ratio ( approximately 15.0) aligned gold silicide nanorods in the presence of native oxide at the interface during in situ annealing of gold thin films on Si(110) substrates. Steps observed in the growth rate and real time electron diffraction show the existence of liquid Au-Si nano-alloy structures on the surface besides the un-reacted gold nanostructures. These results might enable us to engineer the growth of nanowires and similar structures with an Au-Si alloy as a catalyst.

  20. Thin metal bilayer for surface plasmon resonance sensors in a multimode plastic optical fiber: the case of palladium and gold metal films

    NASA Astrophysics Data System (ADS)

    Cennamo, Nunzio; Zuppella, Paola; Bacco, Davide; Corso, Alain J.; Pelizzo, Maria G.; Pesavento, Maria; Zeni, Luigi

    2016-05-01

    A novel sensing platform based on thin metal bilayer for surface plasmon resonance (SPR) in a D-shaped plastic optical fiber (POF) has been designed, implemented and tested. The experimental results are congruent with the numerical studies. This platform has been properly optimized to work in the 1.38 -1.42 refractive index range and it exhibits excellent sensitivity. This refractive index range is very interesting for bio-chemical applications, where the polymer layer are used as receptors (e.g. molecularly imprinted polymer) or to immobilize the bio-receptor on the metal surface. The proposed metallic bilayer is based on palladium and gold films and replaces the traditional gold by exhibiting higher performances. Furthermore, the deposition of the thin bilayer is a single process and no further manufacturing step is required. In fact, in this case the photoresist buffer layer between the POF core and the metal layer, usually required to increase the refractive index range, is no longer necessary.

  1. Precise Control Over Morphology and Density of Metal and Transition Metal Nanostructures for Sensing and Energy Related Applications

    NASA Astrophysics Data System (ADS)

    Tran, Minh

    Metallic nanostructures are of great interest due to their applicability in various modern technologies, such as catalysis, sensing, and optoelectronics. In this work, we employed three solution-based methods, including colloidal suspension synthesis, modified galvanic displacement, and electrodeposition, to synthesize nanostructured metals and transition metals, including gold (Au), copper (Cu), platinum (Pt), palladium (Pd), nickel (Ni), and cobalt (Co). Our focus was to establish process-structure-property relationship and explore their applicability in the field of sensing and clean energy generation. More precisely we established relationships between experimental parameters, such as temperature, applied potential, electrolyte pH, reactant concentration, additive, and the number of deposition cycles, and the characteristics of the nanostructures, such as morphology, density, size, and size distribution. Our results indicated that the nanostructures were tunable by adjusting the process parameters. This provided insight into the growth mechanisms of the metallic nanostructures. Since properties of the nanostructures are tunable by controlling the structure, our results provided researchers with additional tools to obtain nanomaterials with desired properties for specific applications. The materials synthesized by our methods were utilized to as substrates for surface enhanced Raman spectroscopy (SERS) and as photocathodes for photoelectrochemical production of hydrogen. The results showed that the performances of our materials were either promising or compatible with those reported in the literature, thus bringing new opportunities to the development of low-cost, high-performance, and flexible nanomaterials for the current and future technologies.

  2. Enhancing the reactivity of gold: Nanostructured Au(111) adsorbs CO

    DOE PAGES

    Hoffmann, F. M.; Hrbek, J.; Ma, S.; ...

    2015-12-02

    Low-coordinated sites are surface defects whose presence can transform a surface of inert or noble metal such as Au into an active catalyst. We prepared gold surfaces modified by pits, starting with a well-ordered Au(111) surface; we then used microscopy (STM) for their structural characterization and CO spectroscopy (IRAS and NEXAFS) for probing reactivity of surface defects. In contrast to the Au(111) surface CO adsorbs readily on the pitted surfaces bonding to low-coordinated sites identified as step atoms forming {111} and {100} microfacets. Finally, pitted nanostructured surfaces can serve as interesting and easily prepared models of catalytic surfaces with definedmore » defects that offer an attractive alternative to vicinal surfaces or nanoparticles commonly employed in catalysis science.« less

  3. Annealing of Co-Cr dental alloy: effects on nanostructure and Rockwell hardness.

    PubMed

    Ayyıldız, Simel; Soylu, Elif Hilal; Ide, Semra; Kılıç, Selim; Sipahi, Cumhur; Pişkin, Bulent; Gökçe, Hasan Suat

    2013-11-01

    The aim of the study was to evaluate the effect of annealing on the nanostructure and hardness of Co-Cr metal ceramic samples that were fabricated with a direct metal laser sintering (DMLS) technique. Five groups of Co-Cr dental alloy samples were manufactured in a rectangular form measuring 4 × 2 × 2 mm. Samples fabricated by a conventional casting technique (Group I) and prefabricated milling blanks (Group II) were examined as conventional technique groups. The DMLS samples were randomly divided into three groups as not annealed (Group III), annealed in argon atmosphere (Group IV), or annealed in oxygen atmosphere (Group V). The nanostructure was examined with the small-angle X-ray scattering method. The Rockwell hardness test was used to measure the hardness changes in each group, and the means and standard deviations were statistically analyzed by one-way ANOVA for comparison of continuous variables and Tukey's HSD test was used for post hoc analysis. P values of <.05 were accepted as statistically significant. The general nanostructures of the samples were composed of small spherical entities stacked atop one another in dendritic form. All groups also displayed different hardness values depending on the manufacturing technique. The annealing procedure and environment directly affected both the nanostructure and hardness of the Co-Cr alloy. Group III exhibited a non-homogeneous structure and increased hardness (48.16 ± 3.02 HRC) because the annealing process was incomplete and the inner stress was not relieved. Annealing in argon atmosphere of Group IV not only relieved the inner stresses but also decreased the hardness (27.40 ± 3.98 HRC). The results of fitting function presented that Group IV was the most homogeneous product as the minimum bilayer thickness was measured (7.11 Å). After the manufacturing with DMLS technique, annealing in argon atmosphere is an essential process for Co-Cr metal ceramic substructures. The dentists should be familiar with

  4. Annealing of Co-Cr dental alloy: effects on nanostructure and Rockwell hardness

    PubMed Central

    Soylu, Elif Hilal; İde, Semra; Kılıç, Selim; Sipahi, Cumhur; Pişkin, Bulent; Gökçe, Hasan Suat

    2013-01-01

    PURPOSE The aim of the study was to evaluate the effect of annealing on the nanostructure and hardness of Co-Cr metal ceramic samples that were fabricated with a direct metal laser sintering (DMLS) technique. MATERIALS AND METHODS Five groups of Co-Cr dental alloy samples were manufactured in a rectangular form measuring 4 × 2 × 2 mm. Samples fabricated by a conventional casting technique (Group I) and prefabricated milling blanks (Group II) were examined as conventional technique groups. The DMLS samples were randomly divided into three groups as not annealed (Group III), annealed in argon atmosphere (Group IV), or annealed in oxygen atmosphere (Group V). The nanostructure was examined with the small-angle X-ray scattering method. The Rockwell hardness test was used to measure the hardness changes in each group, and the means and standard deviations were statistically analyzed by one-way ANOVA for comparison of continuous variables and Tukey's HSD test was used for post hoc analysis. P values of <.05 were accepted as statistically significant. RESULTS The general nanostructures of the samples were composed of small spherical entities stacked atop one another in dendritic form. All groups also displayed different hardness values depending on the manufacturing technique. The annealing procedure and environment directly affected both the nanostructure and hardness of the Co-Cr alloy. Group III exhibited a non-homogeneous structure and increased hardness (48.16 ± 3.02 HRC) because the annealing process was incomplete and the inner stress was not relieved. Annealing in argon atmosphere of Group IV not only relieved the inner stresses but also decreased the hardness (27.40 ± 3.98 HRC). The results of fitting function presented that Group IV was the most homogeneous product as the minimum bilayer thickness was measured (7.11 Å). CONCLUSION After the manufacturing with DMLS technique, annealing in argon atmosphere is an essential process for Co-Cr metal ceramic

  5. Enhancement of antibiotic effect via gold:silver-alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    dos Santos, Margarida Moreira; Queiroz, Margarida João; Baptista, Pedro V.

    2012-05-01

    A strategy for the development of novel antimicrobials is to combine the stability and pleiotropic effects of inorganic compounds with the specificity and efficiency of organic compounds, such as antibiotics. Here we report on the use of gold:silver-alloy (Au:Ag-alloy) nanoparticles, obtained via a single-step citrate co-reduction method, combined to conventional antibiotics to enhance their antimicrobial effect on bacteria. Addition of the alloy nanoparticles considerably decreased the dose of antibiotic necessary to show antimicrobial effect, both for bacterial cells growing in rich medium in suspension and for bacterial cells resting in a physiological buffer on a humid cellulose surface. The observed effect was more pronounced than the sum of the individual effects of the nanoparticles and antibiotic. We demonstrate the enhancement effect of Au:Ag-alloy nanoparticles with a size distribution of 32.5 ± 7.5 nm mean diameter on the antimicrobial effect of (i) kanamycin on Escherichia coli (Gram-negative bacterium), and (ii) a β-lactam antibiotic on both a sensitive and resistant strain of Staphylococcus aureus (Gram-positive bacterium). Together, these results may pave the way for the combined use of nanoparticle-antibiotic conjugates towards decreasing antibiotic resistance currently observed for certain bacteria and conventional antibiotics.

  6. MICROWAVE-ASSISTED SYNTHESIS OF NOBLE NANOSTRUCTURES

    EPA Science Inventory

    Microwave-assisted (MW) spontaneous reduction of noble metal salts, silver (Ag), gold (Au), platinum (Pt) and palladium (Pd) is reported using sugar solutions such as -D glucose, sucrose and maltose, etc. to generate nanomaterials. These MW-assisted reactions, conducted in aqueo...

  7. Plasma boriding of a cobalt-chromium alloy as an interlayer for nanostructured diamond growth

    NASA Astrophysics Data System (ADS)

    Johnston, Jamin M.; Jubinsky, Matthew; Catledge, Shane A.

    2015-02-01

    Chemical vapor deposited (CVD) diamond coatings can potentially improve the wear resistance of cobalt-chromium medical implant surfaces, but the high cobalt content in these alloys acts as a catalyst to form graphitic carbon. Boriding by high temperature liquid baths and powder packing has been shown to improve CVD diamond compatibility with cobalt alloys. We use the microwave plasma-enhanced (PE) CVD process to deposit interlayers composed primarily of the borides of cobalt and chromium. The use of diborane (B2H6) in the plasma feedgas allows for the formation of a robust boride interlayer for suppressing graphitic carbon during subsequent CVD of nano-structured diamond (NSD). This metal-boride interlayer is shown to be an effective diffusion barrier against elemental cobalt for improving nucleation and adhesion of NSD coatings on a CoCrMo alloy. Migration of elemental cobalt to the surface of the interlayer is significantly reduced and undetectable on the surface of the subsequently-grown NSD coating. The effects of PECVD boriding are compared for a range of substrate temperatures and deposition times and are evaluated using glancing-angle X-ray diffraction (XRD), cross-sectional scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and micro-Raman spectroscopy. Boriding of CoCrMo results in adhered nanostructured diamond coatings with low surface roughness.

  8. Sb-Te alloy nanostructures produced on a graphite surface by a simple annealing process

    NASA Astrophysics Data System (ADS)

    Kuwahara, Masashi; Uratsuji, Hideaki; Abe, Maho; Sone, Hayato; Hosaka, Sumio; Sakai, Joe; Uehara, Yoichi; Endo, Rie; Tsuruoka, Tohru

    2015-08-01

    We have produced Sb-Te alloy nanostructures from a thin Sb2Te3 layer deposited on a highly oriented pyrolytic graphite substrate using a simple rf-magnetron sputtering and annealing technique. The size, shape, and chemical composition of the structures were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectrometry (EDX), respectively. The shape of the nanostructures was found to depend on the annealing temperature; nanoparticles appear on the substrate by annealing at 200 °C, while nanoneedles are formed at higher temperatures. Chemical composition analysis has revealed that all the structures were in the composition of Sb:Te = 1:3, Te rich compared to the target composition Sb2Te3, probably due to the higher movability of Te atoms on the substrate compared with Sb. We also tried to observe the production process of nanostructures in situ using SEM. Unfortunately, this was not possible because of evaporation in vacuum, suggesting that the formation of nanostructures is highly sensitive to the ambient pressure.

  9. Multifunctional substrate of Al alloy based on general hierarchical micro/nanostructures: superamphiphobicity and enhanced corrosion resistance.

    PubMed

    Li, Xuewu; Shi, Tian; Liu, Cong; Zhang, Qiaoxin; Huang, Xingjiu

    2016-10-24

    Aluminum alloys are vulnerable to penetrating and peeling failures in seawater and preparing a barrier coating to isolate the substrate from corrosive medium is an effective anticorrosion method. Inspired by the lotus leaves effect, a wetting alloy surface with enhanced anticorrosion behavior has been prepared via etch, deposition, and low-surface-energy modification. Results indicate that excellent superamphiphobicity has been achieved after the modification of the constructed hierarchical labyrinth-like microstructures and dendritic nanostructures. The as-prepared surface is also found with good chemical stability and mechanical durability. Furthermore, superior anticorrosion behaviors of the resultant samples in seawater are investigated by electrochemical measurements. Due to trapped air in micro/nanostructures, the newly presented solid-air-liquid contacting interface can help to resist the seawater penetration by greatly reducing the interface interaction between corrosive ions and the superamphiphobic surface. Finally, an optimized two-layer perceptron artificial neural network is set up to model and predict the cause-and-effect relationship between preparation conditions and the anticorrosion parameters. This work provides a great potential to extend the applications of aluminum alloys especially in marine engineering fields.

  10. Multifunctional substrate of Al alloy based on general hierarchical micro/nanostructures: superamphiphobicity and enhanced corrosion resistance

    PubMed Central

    Li, Xuewu; Shi, Tian; Liu, Cong; Zhang, Qiaoxin; Huang, Xingjiu

    2016-01-01

    Aluminum alloys are vulnerable to penetrating and peeling failures in seawater and preparing a barrier coating to isolate the substrate from corrosive medium is an effective anticorrosion method. Inspired by the lotus leaves effect, a wetting alloy surface with enhanced anticorrosion behavior has been prepared via etch, deposition, and low-surface-energy modification. Results indicate that excellent superamphiphobicity has been achieved after the modification of the constructed hierarchical labyrinth-like microstructures and dendritic nanostructures. The as-prepared surface is also found with good chemical stability and mechanical durability. Furthermore, superior anticorrosion behaviors of the resultant samples in seawater are investigated by electrochemical measurements. Due to trapped air in micro/nanostructures, the newly presented solid-air-liquid contacting interface can help to resist the seawater penetration by greatly reducing the interface interaction between corrosive ions and the superamphiphobic surface. Finally, an optimized two-layer perceptron artificial neural network is set up to model and predict the cause-and-effect relationship between preparation conditions and the anticorrosion parameters. This work provides a great potential to extend the applications of aluminum alloys especially in marine engineering fields. PMID:27775053

  11. Multifunctional substrate of Al alloy based on general hierarchical micro/nanostructures: superamphiphobicity and enhanced corrosion resistance

    NASA Astrophysics Data System (ADS)

    Li, Xuewu; Shi, Tian; Liu, Cong; Zhang, Qiaoxin; Huang, Xingjiu

    2016-10-01

    Aluminum alloys are vulnerable to penetrating and peeling failures in seawater and preparing a barrier coating to isolate the substrate from corrosive medium is an effective anticorrosion method. Inspired by the lotus leaves effect, a wetting alloy surface with enhanced anticorrosion behavior has been prepared via etch, deposition, and low-surface-energy modification. Results indicate that excellent superamphiphobicity has been achieved after the modification of the constructed hierarchical labyrinth-like microstructures and dendritic nanostructures. The as-prepared surface is also found with good chemical stability and mechanical durability. Furthermore, superior anticorrosion behaviors of the resultant samples in seawater are investigated by electrochemical measurements. Due to trapped air in micro/nanostructures, the newly presented solid-air-liquid contacting interface can help to resist the seawater penetration by greatly reducing the interface interaction between corrosive ions and the superamphiphobic surface. Finally, an optimized two-layer perceptron artificial neural network is set up to model and predict the cause-and-effect relationship between preparation conditions and the anticorrosion parameters. This work provides a great potential to extend the applications of aluminum alloys especially in marine engineering fields.

  12. Hybrid systems based on gold nanostructures and porphyrins as promising photosensitizers for photodynamic therapy.

    PubMed

    Ferreira, Daniele C; Monteiro, Camila S; Chaves, Claudilene R; Sáfar, Gustavo A M; Moreira, Roberto L; Pinheiro, Maurício V B; Martins, Dayse C S; Ladeira, Luiz Orlando; Krambrock, Klaus

    2017-02-01

    Gold nanostructures of two different shapes (spheres and rods) were synthesized to form a colloidal hybrid system with 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin tosylate salt (H 2 TM4PyP(OTs) 4 ) (POR) for applications in photodynamic therapy (PDT) using light in the visible spectral range. Electron paramagnetic resonance (EPR) experiments in combination with spin trapping were used for the detection of reactive oxygen species (ROS) and evaluation of the efficiency of these novel hybrid systems as photosensitizers. It is shown that the hybrid system consisting of gold nanorods (AuNR) and porphyrin (POR) is by far more efficient than its isolated components. This enhanced efficiency is explained by a synergetic effect between the AuNR and the porphyrin, wherein a rapid energy transfer from the former to the latter produces a large amount of singlet oxygen followed by its conversion into hydroxyl radicals. The mechanism was investigated using different spin traps and different ROS inhibitors. On the other hand, spherical gold nanoparticles (AuNP) do not show this synergetic effect. The synergetic effect for gold nanorods/POR hybrid is attributed to a larger field enhancement close to the gold nanorod surface in addition to the electrostatic attraction between the components of the hybrid system. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. A novel luminol chemiluminescent method catalyzed by silver/gold alloy nanoparticles for determination of anticancer drug flutamide.

    PubMed

    Chaichi, Mohammad Javad; Azizi, Seyed Naser; Heidarpour, Maryam

    2013-12-01

    It was found that silver/gold alloy nanoparticles enhance the chemiluminescence (CL) of the luminol-H2O2 system in alkaline solution. The studies of UV-Vis spectra, CL spectra, effects of concentrations luminol, hydrogen peroxide and silver/gold alloy nanoparticles solutions were carried out to explore the CL enhancement mechanism. Flutamide was found to quench the CL signals of the luminol-H2O2 reaction catalyzed by silver/gold alloy nanoparticles, which made it applicable for the determination of flutamide. Under the optimum conditions, the CL intensity is proportional to the concentration of the flutamide in solution over the range 5.0 × 10(-7) to 1.0 × 10(-4)mol L(-1). Detection limit was obtained 1.2 × 10(-8)mol L(-1)and the relative standard deviation (RSD) γ5%. This work is introduced as a new method for the determination of flutamide in commercial tablets. Box-Behnken experimental design is applied to investigate and validate the CL measurement parameters. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Engineered Metallic Nanostructures: Fabrication, Characterization, and Applications

    NASA Astrophysics Data System (ADS)

    Bohloul, Arash

    Metallic nanostructures have garnered a great deal of attention due to their fascinating optical properties, which differ from the bulk metal. They have been proven to exceed expectations in wide variety of applications including chemical and biological sensing. Nevertheless, high-throughput and low cost nanofabrication techniques are required to implant metallic nanostructures in widespread applications. With that vision, this thesis presents a versatile and reliable method for scalable fabrication of gold nanostructures. In this approach, a plasma-treated ordered array of polystyrene nanospheres acts as an initial mask. The key step in this process is the vapor-deposition of nickel as a sacrificial mask. Thereby, gold nanostructures are directly formed on the substrate through the nickel mask. This is an easy, powerful, and straightforward method that offers several degrees of freedom to precisely control the shape and size of nanostructures. We made a library of nanostructures including gold nanocrescents, double crescents, nanorings, and nanodisks with the ability to tune the size in the range of 150 to 650 nm. The fabricated nanostructures are highly packed and uniformly cover the centimeter scale substrate. The optical properties of metallic nanostructures were extensively studied by a combination of UV-Vis-NIR and Fourier transform infrared (FTIR) spectroscopies, and correlation between optical response and geometrical parameters were investigated. In the next part of this thesis, highly sensitive surface enhanced infrared absorption (SEIRA) analysis was demonstrated on gold nanocrescent arrays. Theoretical modeling was confirmed that these substrates provide highly dense and strong hot-spots over the substrate, which is required for surface enhanced spectroscopic studies. Gold nanocrescent arrays exhibit highly tunable plasmon resonance to cover desired molecular vibrational bands. These substrates experimentally illustrated 3 orders of magnitude

  15. Facile preparation of gold nanocages and hollow gold nanospheres via solvent thermal treatment and their surface plasmon resonance and photothermal properties.

    PubMed

    Wang, Haifei; Han, Jing; Lu, Wensheng; Zhang, Jianping; Li, Jinru; Jiang, Long

    2015-02-15

    Although template etching method is one of the most common ways of preparation of hollow gold nanostructures, this approach still requires further improvements to avoid the collapse of gold shells after the cores were removed. In this work, an improved template etching method, with which hollow gold nanostructure is fabricated by etching Polystyrene (PS) cores from PS@Au core-shell nanospheres with solvent thermal treatment in N,N-Dimethylformamide (DMF), is demonstrated. When PS cores were removed by a thermal treatment process, gold nanoshells reconstruct and the collapse of the nanoshells is avoided. Gold nanocages and hollow gold nanospheres are easily obtained from the various structures of PS@Au core-shell nanospheres. These hollow nanostructures represent special near infrared (NIR) optical property and photothermal property. Compared with hollow gold nanospheres, the gold nanocages show higher temperature increase at the same particle concentration. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. III-Nitride Digital Alloy: Electronics and Optoelectronics Properties of the InN/GaN Ultra-Short Period Superlattice Nanostructures.

    PubMed

    Sun, Wei; Tan, Chee-Keong; Tansu, Nelson

    2017-07-27

    The III-Nitride digital alloy (DA) is comprehensively studied as a short-period superlattice nanostructure consisting of ultra-thin III-Nitride epitaxial layers. By stacking the ultra-thin III-Nitride epitaxial layers periodically, these nanostructures are expected to have comparable optoelectronic properties as the conventional III-Nitride alloys. Here we carried out numerical studies on the InGaN DA showing the tunable optoelectronic properties of the III-Nitride DA. Our study shows that the energy gap of the InGaN DA can be tuned from ~0.63 eV up to ~2.4 eV, where the thicknesses and the thickness ratio of each GaN and InN ultra-thin binary layers within the DA structure are the key factors for tuning bandgap. Correspondingly, the absorption spectra of the InGaN DA yield broad wavelength tunability which is comparable to that of bulk InGaN ternary alloy. In addition, our investigation also reveals that the electron-hole wavefunction overlaps are remarkably large in the InGaN DA structure despite the existence of strain effect and build-in polarization field. Our findings point out the potential of III-Nitride DA as an artificially engineered nanostructure for optoelectronic device applications.

  17. Kinetic Characteristics of Hydrogen Transfer Through Palladium-Modified Membrane

    NASA Astrophysics Data System (ADS)

    Petriev, I. S.; Frolov, V. Yu.; Bolotin, S. N.; Baryshev, M. G.; Kopytov, G. F.

    2018-01-01

    The paper deals with hydrogen transfer through Pd-23%Ag alloy membrane, the surface of which is modified by the electrolytic deposition of highly dispersed palladium. The dependence between the density of hydrogen flow and its excess pressure on the input surface of membrane is well approximated by the first-order curve. This fact indicates that the process of hydrogen permeability is defined by its dissociation on the input surface. Activation energy of this process is 47.9 kJ/mol which considerably exceeds that of the process of hydrogen transfer through palladium (22-30 kJ/mol). This confirms the fact that the chemisorption is a rate-controlling step of the hydrogen transfer through membrane.

  18. The Effect of Palladium Additions on the Solidus/Liquidus Temperatures and Wetting Properties of Ag-CuO Based Air Brazes

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

    Darsell, Jens T.; Weil, K. Scott

    2007-05-16

    As a means of increasing the use temperature of ceramic-ceramic and ceramic-metal air brazes, palladium was investigated as possible ternary addition to the currently employed silver - copper oxide system. The silver component was directly substituted with palladium to form the following series of alloys: (100-y)[(100-z)Pd - (z)Ag] - (y)CuOx where y = 0 - 34 mol% CuOx, z = 50 - 100 mol% silver, and x = 0, 0.5, and 1, denoting copper metal, Cu2O, or CuO. From differential scanning calorimetry, it was determined that the addition of palladium causes an increase in the solidus and liquidus temperatures ofmore » the resulting Pd-Ag-CuO brazes. In general, the liquidus was found to increase by approximately 220°C for the (100-y)(25Pd - 75Ag) - (z)CuOx filler metal compositions relative to comparable Ag-CuOx alloys. Likewise, the solidus was found to increase for these alloys, respectively by 185°C and 60°C, respectively for CuOx contents of y = 0 - 1mol% and 4 - 10 mol%. For the (100-y)(50Pd - 50Ag) - (y)CuOx alloys, the solidus increased between 280 - 390°C over a copper oxide compositional range of x = 0 to 8 mol%. It was determined from sessile drop experiments conducted on alumina substrates that in all cases the palladium causes an increase in the wetting angle relative to the corresponding binary braze. Alloy compositions of (100-y)(25Pd - 75Ag) - (y)CuOx displayed increased wetting angles of 5-20° relative to comparable binary compositions. (100-y)(50Pd - 50Ag) - (y)CuOx alloys exhibited an increase in contact angle of 10-60° and compositions containing less than 10 mol% CuOx were not able to wet the substrate. Scanning electron microscopy indicated that the microstructure of the braze consists of discrete CuOx precipitates in an alloyed silver-palladium matrix. In both the binary and ternary filler metal formulations, a reaction layer consisting of CuAlO2 was observed along the interface with the alumina substrate. This reaction product appears to be

  19. Structure of dental gallium alloys.

    PubMed

    Herø, H; Simensen, C J; Jørgensen, R B

    1996-07-01

    The interest in gallium alloys as a replacement for amalgam has increased in recent years due to the risk of environmental pollution from amalgam. Alloy powders with compositions close to those for alloys of amalgam are mixed with a liquid gallium alloy. The mix is condensed into a prepared cavity in much the same way as for amalgam. The aim of the present work was to study the structure of: (1) two commercial alloy powders containing mainly silver, tin and copper, and (2) the phases formed by mixing these powders with a liquid alloy of gallium, indium and tin. One of the alloy powders contained 9 wt% palladium. Cross-sections of cylindrical specimens made by these gallium mixes were investigated by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Discrete grains of the following phases were found to be present in both gallium alloys: hexagonal Ag2Ga, tetragonal Cu(Pd)Ga2, cubic Ag9In4 and tetragonal beta-Sn. Indications of hexagonal or orthorhombic Ag2Sn were found in the remaining, unreacted alloy particles. In the palladium-containing alloy the X-ray reflections indicate a minor fraction of cubic Cu9Ga4 in addition to the Cu(Pd)Ga2 phase. Particles of beta-Sn are probably precipitated because Sn-Ga phases cannot be formed according to the binary phase diagram.

  20. Noble Hybrid Nanostructures as Efficient Anti-Proliferative Platforms for Human Breast Cancer Cell.

    PubMed

    Tavangar, Amirhossein; Premnath, Priyatha; Tan, Bo; Venkatakrishnan, Krishnan

    2016-04-27

    Nanomaterials have proven to possess great potential in biomaterials research. Recently, they have suggested considerable promise in cancer diagnosis and therapy. Among others, silicon (Si) nanomaterials have been extensively employed for various biomedical applications; however, the utilization of Si for cancer therapy has been limited to nanoparticles, and its potential as anticancer substrates has not been fully explored. Noble nanoparticles have also received considerable attention owing to unique anticancer properties to improve the efficiency of biomaterials for numerous biological applications. Nevertheless, immobilization and control over delivery of the nanoparticles have been challenge. Here, we develop hybrid nanoplatforms to efficiently hamper breast cancer cell adhesion and proliferation. Platforms are synthesized by femtosecond laser processing of Si into multiphase nanostructures, followed by sputter-coating with gold (Au)/gold-palladium (Au-Pd) nanoparticles. The performance of the developed platforms was then examined by exploring the response of normal fibroblast and metastatic breast cancer cells. Our results from the quantitative and qualitative analyses show a dramatic decrease in the number of breast cancer cells on the hybrid platform compared to untreated substrates. Whereas, fibroblast cells form stable adhesion with stretched and elongated cytoskeleton and actin filaments. The hybrid platforms perform as dual-acting cytophobic/cytostatic stages where Si nanostructures depress breast cancer cell adhesion while immobilized Au/Au-Pd nanoparticles are gradually released to affect any surviving cell on the nanostructures. The nanoparticles are believed to be taken up by breast cancer cells via endocytosis, which subsequently alter the cell nucleus and may cause cell death. The findings suggest that the density of nanostructures and concentration of coated nanoparticles play critical roles on cytophobic/cytostatic properties of the platforms on

  1. An electrochemical biosensor based on nanoporous stainless steel modified by gold and palladium nanoparticles for simultaneous determination of levodopa and uric acid.

    PubMed

    Rezaei, Behzad; Shams-Ghahfarokhi, Leila; Havakeshian, Elaheh; Ensafi, Ali A

    2016-09-01

    In this paper, an electrochemical biosensor based on gold and palladium nano particles-modified nanoporous stainless steel (Au-Pd/NPSS) electrode has been introduced for the simultaneous determination of levodopa (LD) and uric acid (UA). To prepare the electrode, the stainless steel was anodized to fabricate NPSS and then Cu was electrodeposited onto the nanoporous steel by applying the multiple step potential. Finally, the electrode was immersed into a gold and palladium precursor's solution by the atomic ratio of 9:1 to form Au-Pd/NPSS through the galvanic replacement reaction. Morphological aspects, structural properties and the electroanalytical behavior of the Au-Pd/NPSS electrode were studied using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS) and voltammetric techniques. Also, differential pulse voltammetry (DPV) was used for the simultaneous determination of LD and UA. According to results, the surface of Au-Pd/NPSS electrode contained Au and Pd nanoparticles with an average diameter of 75nm. The electrode acted better than Au/NPSS and Pd/NPSS electrodes for the simultaneous determination of LD and UA, with the peak separation potential of about 220mV. Also, the calibration plot for LD was in two linear concentration ranges of 5.0-10.0 and 10.0-55.0μmolL(-1) and for UA, it was in the range of 100-1200μmolL(-1). The detection limit for LD and UA was 0.2 and 15μmolL(-1), respectively. The modified electrode had a good performance for LD and UA detection in urine, blood serum and levodopa C-Forte tablet. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. METAL COMPOSITIONS

    DOEpatents

    Seybolt, A.U.

    1959-02-01

    Alloys of uranium which are strong, hard, and machinable are presented, These alloys of uranium contain bctween 0.1 to 5.0% by weight of at least one noble metal such as rhodium, palladium, and gold. The alloys may be heat treated to obtain a product with iniproved tensile and compression strengths,

  3. Preparation and Photocatalytic Activity of Potassium-Incorporated Titanium Oxide Nanostructures Produced by the Wet Corrosion Process Using Various Titanium Alloys

    PubMed Central

    Lee, So Yoon; Lee, Choong Hyun; Kim, Do Yun; Locquet, Jean-Pierre; Seo, Jin Won

    2015-01-01

    Nanostructured potassium-incorporated Ti-based oxides have attracted much attention because the incorporated potassium can influence their structural and physico-chemical properties. With the aim of tuning the structural and physical properties, we have demonstrated the wet corrosion process (WCP) as a simple method for nanostructure fabrication using various Ti-based materials, namely Ti–6Al–4V alloy (TAV), Ti–Ni (TN) alloy and pure Ti, which have 90%, 50% and 100% initial Ti content, respectively. We have systematically investigated the relationship between the Ti content in the initial metal and the precise condition of WCP to control the structural and physical properties of the resulting nanostructures. The WCP treatment involved various concentrations of KOH solutions. The precise conditions for producing K-incorporated nanostructured titanium oxide films (nTOFs) were strongly dependent on the Ti content of the initial metal. Ti and TAV yielded one-dimensional nanowires of K-incorporated nTOFs after treatment with 10 mol/L-KOH solution, whereas TN required a higher concentration (20 mol/L-KOH solution) to produce comparable nanostructures. The obtained nanostructures revealed a blue-shift in UV absorption spectra due to the quantum confinement effects. A significant enhancement of the photocatalytic activity was observed via the chromomeric change and the intermediate formation of methylene blue molecules under UV irradiation. This study demonstrates the WCP as a simple, versatile and scalable method for the production of nanostructured K-incorporated nTOFs to be used as high-performance photocatalysts for environmental and energy applications. PMID:28347071

  4. Oxygen reduction of several gold alloys in 1-molar potassium hydroxide

    NASA Technical Reports Server (NTRS)

    Miller, R. O.

    1975-01-01

    With rotated disk-and-ring equipment, polarograms and other electrochemical measurements were made of oxygen reduction in 1-molar potassium hydroxide on an equiatomic gold-copper (Au-Cu) alloy and a Au-Cu alloy doped with either indium (In) or cobalt (Co) and on Au doped with either nickel (Ni) or platinum (Pt). The results were compared with those for pure Au and pure Pt. The two-electron reaction dominated on all Au alloys as it did on Au. The polarographic results at lower polarization potentials were compared, assuming exclusively a two-step reduction. A qualified ranking of cathodic electrocatalytic activity on the freshly polished reduced disks was indicated: anodized Au Au-Cu-In Au-Cu Au-Cu-Co is equivalent or equal to Au-Pt Au-Ni. Aging in distilled water improved the electrocatalytic efficiency of Au-Cu-Co, Au-Cu, and (to a lesser extent) Au-Cu-In.

  5. Platinum nanoparticles decorated dendrite-like gold nanostructure on glassy carbon electrodes for enhancing electrocatalysis performance to glucose oxidation

    NASA Astrophysics Data System (ADS)

    Jia, Hongmei; Chang, Gang; Lei, Ming; He, Hanping; Liu, Xiong; Shu, Honghui; Xia, Tiantian; Su, Jie; He, Yunbin

    2016-10-01

    Platinum nanoparticles decorated dendrite-like gold nanostructure, bimetal composite materials on glassy carbon electrode (Pt/DGNs/GC) for enhancing electrocatalysis to glucose oxidation was designed and successfully fabricated by a facile two-step deposition method without any templates, surfactants, or stabilizers. Dendrite-like gold nanostructure was firstly deposited on the GC electrode via the potentiostatic method, and then platinum nanoparticles were decorated on the surface of gold substrate through chemical reduction deposition. X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) were applied to characterize the evolution of morphology and structure of the as-prepared Pt/DGNs/GC. Based on electrochemical measurements such as cyclic voltammetry, linear voltammetry and chronoamperometry, Pt/DGNs/GC exhibited significantly enhanced electrocatalytic performance to glucose oxidation compared those of pure dendrite-like Au nanoparticles in our previous report. Controlling chemical reduction deposition time, the amount of platinum nanoparticles on Au surface could be regulated, which further tuned electrocatalytic properties toward glucose oxidation. The dendrite-like gold surface partially covered by platinum nanoparticles dramatically enhanced the electrocatalytic performance for the oxidation of glucose because of excellent synergetic effects between gold and platinum species and the increased electrochemical active area from Pt nanoparticles loading. The non-enzymatic glucose biosensor based on Pt/DGNs/GC showed a rapid respond time (within 2 s), wide linear range (from 0.1 mM to 14 mM), low detection limit (0.01 mM), supernal sensitivity (275.44 μA cm-2 mM-1, R = 0.993), satisfactory reproducibility and good stability for glucose sensing. It was demonstrated that Pt/DGNs/GC could work as promising candidate for factual non-enzymatic glucose detection.

  6. Cadmium effect on structural properties of Cu{sub 2}Zn{sub 1-x}Cd{sub x}SnS{sub 4} quinternary alloys nanostructures

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

    Ibraheam, A. S.; Al-Douri, Y., E-mail: yaldouri@yahoo.com; Hashim, U.

    The study report novel sensing plat of extended quinternart materials, Cu{sub 2}Zn{sub 1-x}d{sub x}SnS{sub 4} quinternary alloy nanostructures were fabricated onto oxidized silicon substrate by sol-gel method and characterized were synthesized by X-ray diffraction (XRD). The XRD peaks were shifted towered the lower angle side with increasing cadmium content. The practical size average of the Cu{sub 2}Zn{sub 1-x}d{sub x}SnS{sub 4} quinternary alloy nanostructures between 34.55 to 63.30 nm.

  7. Nanostructured Fe-Cr Alloys for Advanced Nuclear Energy Applications

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

    Scattergood, Ronald O.

    2016-04-26

    We have completed research on the grain-size stabilization of model nanostructured Fe14Cr base alloys at high temperatures by the addition of non-equilibrium solutes. Fe14Cr base alloys are representative for nuclear reactor applications. The neutron flux in a nuclear reactor will generate He atoms that coalesce to form He bubbles. These can lead to premature failure of the reactor components, limiting their lifetime and increasing the cost and capacity for power generation. In order to mitigate such failures, Fe14Cr base alloys have been processed to contain very small nano-size oxide particles (less than 10 nm in size) that trap He atomsmore » and reduce bubble formation. Theoretical and experimental results indicate that the grain boundaries can also be very effective traps for He atoms and bubble formation. An optimum grain size will be less than 100 nm, ie., nanocrystalline alloys must be used. Powder metallurgy methods based on high-energy ball milling can produce Fe-Cr base nanocrystalline alloys that are suitable for nuclear energy applications. The problem with nanocrystalline alloys is that excess grain-boundary energy will cause grains to grow at higher temperatures and their propensity for He trapping will be lost. The nano-size oxide particles in current generation nuclear alloys provide some grain size stabilization by reducing grain-boundary mobility (Zener pinning – a kinetic effect). However the current mitigation strategy minimizing bubble formation is based primarily on He trapping by nano-size oxide particles. An alternate approach to nanoscale grain size stabilization has been proposed. This is based on the addition of small amounts of atoms that are large compared to the base alloy. At higher temperatures these will diffuse to the grain boundaries and will produce an equilibrium state for the grain size at higher temperatures (thermodynamic stabilization – an equilibrium effect). This would be preferred compared to a kinetic effect

  8. Synthesis and characterization of palladium-cobalt alloy for new medical micro-devices

    NASA Astrophysics Data System (ADS)

    Kafrouni, Lina

    According to Canadian Cancer Statistics, it is estimated that 196,900 Canadians will develop cancer and 78,000 will die of cancer in 2015. Given that tumor cells are more sensitive to a temperature increase than healthy ones, this property can be used in vivo to destroy the cancerous cells by elevation of body temperature, otherwise known as hyperthermia. Magnetic hyperthermia is a promising technique for cancer treatment because of ease in targeting the cancerous cells using magnetic nanoparticles (MNPs) and hence having fewer side effects than chemotherapy and radiotherapy. Despite the use of magnetic hyperthermia to treat cancer for thousands of years, the challenge of only heating malignant cells remains daunting. Thus, oncologists often use the heat treatment in combination with radiotherapy or chemotherapy or both. The combined approach results in eliminating many cancer cells in addition to making the resistant cancer cells more vulnerable to other treatments. To use stand-alone magnetic hyperthermia therapy, difficulties in surface modification of magnetic particles for selective uptake by cancerous cells and stability as well as magnetic properties for high heating capacity (> 1000 W/g) must be overcome. The ultimate objective of this thesis is to synthesize an excellent candidate for a powerful magnetic hyperthermia. Due to rapid advances in nanotechnology, a synthesis method of nanoparticles (NPs) with the ability to rigorously control the structure and morphology, such as size, shape and crystallinity, is needed. Electrodeposition is a versatile method for the synthesis of metal NPs directly and selectively onto conductive substrates, simply by regulating applied current or voltage. Furthermore, the particles size and the shape are easily controllable. Besides, studies have shown that the electrodeposition technique is of great utility in the fabrication of nanocrystalline palladium-cobalt (PdCo) alloys. The primary goal of this project is to synthesize

  9. Nanostructuring of Aluminum Alloy Powders by Cryogenic Attrition with Hydrogen-Free Process Control Agent

    DTIC Science & Technology

    2015-02-01

    Nanostructuring of Aluminum Alloy Powders by Cryogenic Attrition with Hydrogen-Free Process Control Agent by Frank Kellogg , Clara Hofmeister...Process Control Agent Frank Kellogg Bowhead Science and Technology Clara Hofmeister Advanced Materials Processing and Analysis Center...NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Frank Kellogg , Clara Hofmeister, Anit Giri, and Kyu Cho 5d. PROJECT NUMBER 5e

  10. Facile synthesis of hierarchical gold nanostructures and their catalytic application

    NASA Astrophysics Data System (ADS)

    Ma, Ying; Siang Yi, Edward Ng

    2016-08-01

    We demonstrate a one-step, surfactant-free method to prepare gold (Au) nanostructures using a synthesized aniline (ANI) derivative N-(3-amidino)-aniline (NAAN) as a reducing agent. By simply mixing NAAN with a Au precursor, raspberry-like Au particles (RSPs) were formed. The presence of Ag+ resulted in the formation of Au nanoflowers (AuNFs). The size and shape of the AuNFs can be tuned by the reaction conditions such as the NAAN/HAuCl4 ratio, the temperature and the solvent composition. Under the same reaction conditions, bowling-pin-like particles (BPLPs) were reported for the first time using commercial ANI as a reducing agent. The AuNFs exhibited good ability to oxidize peroxidase substrate 3, 3‧, 5, 5‧-tetramethylbenzidine (TMB) by H2O2, allowing them as a peroxidase mimetic.

  11. An experimental palladium-103 seed (OptiSeedexp) in a biocompatible polymer without a gold marker: characterization of dosimetric parameters including the interseed effect.

    PubMed

    Abboud, F; Scalliet, P; Vynckier, S

    2008-12-01

    Permanent implantation of 125I (iodine) or 103Pd (palladium) sources is a popular treatment option in the management of early stage prostate cancer. New sources are being developed, some of which are being marketed for different clinical applications. A new technique of adjuvant stereotactic permanent seed breast implant, similar to that used in the treatment of prostate cancer, has been proposed by [N. Jansen et al., Int. J. Radiat. Oncol. Biol. Phys. 67, 1052-1058 (2007)] with encouraging results. The presence of artifacts from the metallic seeds, however, can disturb follow-up imaging. The development of plastic seeds has reduced these artifacts. This paper presents a feasibility study of the advantages of palladium-103 seeds, encapsulated with a biocompatible polymer, for future clinical applications, and on the effect of the gold marker on the dosimetric characteristics of such seeds. Experimental palladium seeds, OptiSeedexp, were manufactured by International Brachytherapy (IBt), Seneffe, Belgium, from a biocompatible polymer, including the marker. Apart from the absence of a gold marker, the studied seed has an identical design to the OptiSeed103 [Phys. Med. Biol. 50, 1493-1504 (2005)]; [Appl. Radiat. Isot. 63, 311-321 (2005)]. Polymer encapsulation was preferred by IBt in order to reduce the quantity of radioactive material needed for a given dose rate and to reduce the anisotropy of the radiation field around the seed. In addition, this design is intended to decrease the interseed effects that can occur as a result of the marker and the encapsulation. Dosimetric measurements were performed using LiF thermoluminescent dosimeters (1 mm3) in solid water phantoms (WT1). Measured data were compared to Monte Carlo simulated data in solid water using the MCNP code, version 4C. Updated cross sections [Med. Phys. 30, 701-711 (2003)] were used. As the measured and calculated data were in agreement, Monte Carlo calculations were then performed in liquid water to

  12. Colloidal lithography nanostructured Pd/PdO x core-shell sensor for ppb level H2S detection.

    PubMed

    Benedict, Samatha; Lumdee, Chatdanai; Dmitriev, Alexandre; Anand, Srinivasan; Bhat, Navakanta

    2018-06-22

    In this work we report on plasma oxidation of palladium (Pd) to form reliable palladium/palladium oxide (Pd/PdO x ) core-shell sensor for ppb level H 2 S detection and its performance improvement through nanostructuring using hole-mask colloidal lithography (HCL). The plasma oxidation parameters and the sensor operating conditions are optimized to arrive at a sensor device with high sensitivity and repeatable response for H 2 S. The plasma oxidized palladium/palladium oxide sensor shows a response of 43.1% at 3 ppm H 2 S at the optimum operating temperature of 200 °C with response and recovery times of 24 s and 155 s, respectively. The limit of detection (LoD) of the plasma oxidised beam is 10 ppb. We further integrate HCL, a bottom-up and cost-effective process, to create nanodiscs of fixed diameter of 100 nm and varying heights (10, 15 and 20 nm) on 10 nm thin Pd beam which is subsequently plasma oxidized to improve the H 2 S sensing characteristics. The nanostructured Pd/PdO x sensor with nanodiscs of 100 nm diameter and 10 nm height shows an enhancement in sensing performance by 11.8% at same operating temperature and gas concentration. This nanostructured sensor also shows faster response and recovery times (15 s and 100 s, respectively) compared to the unstructured Pd/PdO x counterpart together with an experimental LoD of 10 ppb and the estimated limit going all the way down to 2 ppb. Material characterization of the fabricated Pd/PdO x sensors is done using UV-vis spectroscopy and x-ray photoemission spectroscopy.

  13. Colloidal lithography nanostructured Pd/PdO x core–shell sensor for ppb level H2S detection

    NASA Astrophysics Data System (ADS)

    Benedict, Samatha; Lumdee, Chatdanai; Dmitriev, Alexandre; Anand, Srinivasan; Bhat, Navakanta

    2018-06-01

    In this work we report on plasma oxidation of palladium (Pd) to form reliable palladium/palladium oxide (Pd/PdO x ) core–shell sensor for ppb level H2S detection and its performance improvement through nanostructuring using hole-mask colloidal lithography (HCL). The plasma oxidation parameters and the sensor operating conditions are optimized to arrive at a sensor device with high sensitivity and repeatable response for H2S. The plasma oxidized palladium/palladium oxide sensor shows a response of 43.1% at 3 ppm H2S at the optimum operating temperature of 200 °C with response and recovery times of 24 s and 155 s, respectively. The limit of detection (LoD) of the plasma oxidised beam is 10 ppb. We further integrate HCL, a bottom-up and cost-effective process, to create nanodiscs of fixed diameter of 100 nm and varying heights (10, 15 and 20 nm) on 10 nm thin Pd beam which is subsequently plasma oxidized to improve the H2S sensing characteristics. The nanostructured Pd/PdO x sensor with nanodiscs of 100 nm diameter and 10 nm height shows an enhancement in sensing performance by 11.8% at same operating temperature and gas concentration. This nanostructured sensor also shows faster response and recovery times (15 s and 100 s, respectively) compared to the unstructured Pd/PdO x counterpart together with an experimental LoD of 10 ppb and the estimated limit going all the way down to 2 ppb. Material characterization of the fabricated Pd/PdO x sensors is done using UV–vis spectroscopy and x-ray photoemission spectroscopy.

  14. Nano-structured surface plasmon resonance sensor for sensitivity enhancement

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Ho; Kim, Hyo-Sop; Kim, Jin-Ho; Choi, Sung-Wook; Cho, Yong-Jin

    2008-08-01

    A new nano-structured SPR sensor was devised to improve its sensitivity. Nano-scaled silica particles were used as the template to fabricate nano-structure. The surface of the silica particles was modified with thiol group and a single layer of the modified silica particles was attached on the gold or silver thin film using Langmuir-Blodgett (LB) method. Thereafter, gold or silver was coated on the template by an e-beam evaporator. Finally, the nano-structured surface with basin-like shape was obtained after removing the silica particles by sonication. Applying the new developed SPR sensor to a model food of alcoholic beverage, the sensitivities for the gold and silver nano-structured sensors, respectively, had 95% and 126% higher than the conventional one.

  15. Iron Oxide and Gold Based Magneto-Plasmonic Nanostructures for Medical Applications: A Review

    PubMed Central

    Mammeri, Fayna; Ammar, Souad

    2018-01-01

    Iron oxide and gold-based magneto-plasmonic nanostructures exhibit remarkable optical and superparamagnetic properties originating from their two different components. As a consequence, they have improved and broadened the application potential of nanomaterials in medicine. They can be used as multifunctional nanoprobes for magneto-plasmonic heating as well as for magnetic and optical imaging. They can also be used for magnetically assisted optical biosensing, to detect extreme traces of targeted bioanalytes. This review introduces the previous work on magneto-plasmonic hetero-nanostructures including: (i) their synthesis from simple “one-step” to complex “multi-step” routes, including seed-mediated and non-seed-mediated methods; and (ii) the characterization of their multifunctional features, with a special emphasis on the relationships between their synthesis conditions, their structures and their properties. It also focuses on the most important progress made with regard to their use in nanomedicine, keeping in mind the same aim, the correlation between their morphology—namely spherical and non-spherical, core-satellite and core-shell, and the desired applications. PMID:29518969

  16. Effect of laser irradiation conditions on the laser welding strength of cobalt-chromium and gold alloys.

    PubMed

    Kikuchi, Hisaji; Kurotani, Tomoko; Kaketani, Masahiro; Hiraguchi, Hisako; Hirose, Hideharu; Yoneyama, Takayuki

    2011-09-01

    Using tensile tests, this study investigated differences in the welding strength of casts of cobalt-chromium and gold alloys resulting from changes in the voltage and pulse duration in order to clarify the optimum conditions of laser irradiation for achieving favorable welding strength. Laser irradiation was performed at voltages of 150 V and 170 V with pulse durations of 4, 8, and 12 ms. For cobalt-chromium and gold alloys, it was found that a good welding strength could be achieved using a voltage of 170 V, a pulse duration of 8 ms, and a spot diameter of 0.5 mm. However, when the power density was set higher than this, defects tended to occur, suggesting the need for care when establishing welding conditions.

  17. Energy and charge transfer effects in two-dimensional van der Waals hybrid nanostructures on periodic gold nanopost array

    NASA Astrophysics Data System (ADS)

    Kim, Jun Young; Kim, Sun Gyu; Youn, Jong Won; Lee, Yongjun; Kim, Jeongyong; Joo, Jinsoo

    2018-05-01

    Two-dimensional (2D) semiconducting MoS2 and WSe2 flakes grown by chemical vapor deposition were mechanically hybridized. A hexagonal boron nitride (h-BN) dielectric flake was inserted between MoS2 and WSe2 flakes to investigate the nanoscale optical properties of 2D van der Waals hybrid nanostructures. The fabricated MoS2/WSe2 and MoS2/h-BN/WSe2 van der Waals hybrid nanostructures were loaded on a periodic gold nanopost (Au-NPo) array to study energy and charge transfer effects at the surface plasmon resonance (SPR) condition. Nanoscale photoluminescence (PL) spectra of the 2D hybrid nanostructures were measured using a high-resolution laser confocal microscope (LCM). A shift of the LCM PL peak of the MoS2/WSe2 n-p hybrid nanostructures was observed owing to the charge transfer. In contrast, the shift of the LCM PL peak of the MoS2/h-BN/WSe2 n-insulator-p hybrid nanostructure was not considerable, as the inserted h-BN dielectric layer prevented the charge transfer. The intensity of the LCM PL peak of the MoS2/h-BN/WSe2 hybrid nanostructure considerably increased once the nanostructure was loaded on the Au-NPo array, owing to the energy transfer between the 2D materials and the Au-NPo array at the SPR condition, which was confirmed by the increase in the LCM Raman intensity.

  18. Unsupported palladium alloy membranes and methods of making same

    DOEpatents

    Way, J. Douglas; Thoen, Paul; Gade, Sabina K.

    2015-06-02

    The invention provides support-free palladium membranes and methods of making these membranes. Single-gas testing of the unsupported foils produced hydrogen permeabilities equivalent to thicker membranes produced by cold-rolling. Defect-free films as thin as 7.2 microns can be fabricated, with ideal H.sub.2/N.sub.2 selectivities as high as 40,000. Homogeneous membrane compositions may also be produced using these methods.

  19. Gold nanostructures and methods of use

    DOEpatents

    Zhang, Jin Z [Santa Cruz, CA; Schwartzberg, Adam [Santa Cruz, CA; Olson, Tammy Y [Santa Cruz, CA

    2012-03-20

    The invention is drawn to novel nanostructures comprising hollow nanospheres and nanotubes for use as chemical sensors, conduits for fluids, and electronic conductors. The nanostructures can be used in microfluidic devices, for transporting fluids between devices and structures in analytical devices, for conducting electrical currents between devices and structure in analytical devices, and for conducting electrical currents between biological molecules and electronic devices, such as bio-microchips.

  20. Gold nanostructures and methods of use

    DOEpatents

    Zhang, Jin Z.; Schwartzberg, Adam; Olson, Tammy Y.

    2016-03-01

    The invention is drawn to novel nanostructures comprising hollow nanospheres and nanotubes for use as chemical sensors, conduits for fluids, and electronic conductors. The nanostructures can be used in microfluidic devices, for transporting fluids between devices and structures in analytical devices, for conducting electrical currents between devices and structure in analytical devices, and for conducting electrical currents between biological molecules and electronic devices, such as bio-microchips.

  1. Application of a Nanostructured Enzymatic Biosensor Based on Fullerene and Gold Nanoparticles to Polyphenol Detection.

    PubMed

    Tortolini, Cristina; Sanzò, Gabriella; Antiochia, Riccarda; Mazzei, Franco; Favero, Gabriele

    2017-01-01

    Electrochemical biosensors provide an attractive means of analyzing the content of a biological sample due to the direct conversion of a biological event to an electronic signal. The signal transduction and the general performance of electrochemical biosensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor. We show herein a novel electrochemical biosensing platform based on the coupling of two different nanostructured materials (gold nanoparticles and fullerenols) displaying interesting electrochemical features. The use of these nanomaterials improved the electrochemical performance of the proposed biosensor.An application of the nanostructured enzyme-based biosensor has been developed for evaluating the detection of polyphenols either in buffer solution or in real wine samples.

  2. Silver-palladium catalysts for the direct synthesis of hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Khan, Zainab; Dummer, Nicholas F.; Edwards, Jennifer K.

    2017-11-01

    A series of bimetallic silver-palladium catalysts supported on titania were prepared by wet impregnation and assessed for the direct synthesis of hydrogen peroxide, and its subsequent side reactions. The addition of silver to a palladium catalyst was found to significantly decrease hydrogen peroxide productivity and hydrogenation, but crucially increase the rate of decomposition. The decomposition product, which is predominantly hydroxyl radicals, can be used to decrease bacterial colonies. The interaction between silver and palladium was characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The results of the TPR and XPS indicated the formation of a silver-palladium alloy. The optimal 1% Ag-4% Pd/TiO2 bimetallic catalyst was able to produce approximately 200 ppm of H2O2 in 30 min. The findings demonstrate that AgPd/TiO2 catalysts are active for the synthesis of hydrogen peroxide and its subsequent decomposition to reactive oxygen species. The catalysts are promising for use in wastewater treatment as they combine the disinfectant properties of silver, hydrogen peroxide production and subsequent decomposition. This article is part of a discussion meeting issue 'Providing sustainable catalytic solutions for a rapidly changing world'.

  3. Sub-parts per million NO2 chemi-transistor sensors based on composite porous silicon/gold nanostructures prepared by metal-assisted etching.

    PubMed

    Sainato, Michela; Strambini, Lucanos Marsilio; Rella, Simona; Mazzotta, Elisabetta; Barillaro, Giuseppe

    2015-04-08

    Surface doping of nano/mesostructured materials with metal nanoparticles to promote and optimize chemi-transistor sensing performance represents the most advanced research trend in the field of solid-state chemical sensing. In spite of the promising results emerging from metal-doping of a number of nanostructured semiconductors, its applicability to silicon-based chemi-transistor sensors has been hindered so far by the difficulties in integrating the composite metal-silicon nanostructures using the complementary metal-oxide-semiconductor (CMOS) technology. Here we propose a facile and effective top-down method for the high-yield fabrication of chemi-transistor sensors making use of composite porous silicon/gold nanostructures (cSiAuNs) acting as sensing gate. In particular, we investigate the integration of cSiAuNs synthesized by metal-assisted etching (MAE), using gold nanoparticles (NPs) as catalyst, in solid-state junction-field-effect transistors (JFETs), aimed at the detection of NO2 down to 100 parts per billion (ppb). The chemi-transistor sensors, namely cSiAuJFETs, are CMOS compatible, operate at room temperature, and are reliable, sensitive, and fully recoverable for the detection of NO2 at concentrations between 100 and 500 ppb, up to 48 h of continuous operation.

  4. Well-ordered large-area arrays of epitaxial ferroelectric (Bi,La)4Ti3O12 nanostructures fabricated by gold nanotube-membrane lithography

    NASA Astrophysics Data System (ADS)

    Lee, Sung Kyun; Lee, Woo; Alexe, Marin; Nielsch, Kornelius; Hesse, Dietrich; Gösele, Ulrich

    2005-04-01

    Two-dimensionally well-ordered, large-area arrays of epitaxial, ferroelectric, La-substituted Bi4Ti3O12 (BLT) nanostructures are prepared using gold nanotube membranes as a liftoff mask. Epitaxial nanostructures with a height of about 65nm and a lateral size of about 150nm, with either (001) ("c-axis") orientation, or mixed (118)/(100) ("non-c-axis") orientation, are obtained on (001)- and (011)-oriented SrTiO3 substrates, respectively. The ferroelectric properties are probed by piezoresponse scanning force microscopy. Non-c-axis-oriented BLT nanostructures show an effective piezoresponse coefficient (2dzz) of about 38.0pm /V, whereas c-axis-oriented structures show one of only about 4.9pm/V.

  5. Dental implant suprastructures using cobalt-chromium alloy compared with gold alloy framework veneered with ceramic or acrylic resin: a retrospective cohort study up to 18 years.

    PubMed

    Teigen, Kyrre; Jokstad, Asbjørn

    2012-07-01

    An association between the long-term success and survival of implant-supported prostheses as a function of biomaterial combinations has not been established. The use of cast cobalt-chromium for the suprastructure framework may be an alternative to the conventional approach of using type 3 gold alloys. A retrospective chart audit of all patients who had received implant-supported fixed dental prostheses (FDP) before 1996 was identified in a private practice clinic. Data were recorded for FDPs made from four combinations of alloy frameworks and veneering material, i.e. type 3 gold and cobalt-chromium with ceramic or prefabricated acrylic teeth. The extracted data from the charts were subjected to explorative statistical tests including Kaplan-Meier survival analyses. Patients (n=198) with 270 short and extensive FDPs supported entirely by 1117 implants were identified. The average follow-up observation periods varied between 4 and 220 months, with an average of 120 months. The success and survival, as well as event rates and types of biological and technical complications, were similar for implant-supported FDPs using cobalt-chromium and type 3 gold alloy frameworks veneered with ceramics or prefabricated acrylic teeth. An influence of the suprastructure biomaterial combination on the clinical performance of the individual supporting implants could not be established. Implant-supported FDPs made from type 3 gold or cobalt-chromium frameworks and veneered with ceramic or prefabricated acrylic teeth demonstrate comparable clinical performance. The biomaterial combinations do not appear to influence the success or survival of the individual implants. © 2011 John Wiley & Sons A/S.

  6. Catalytic property of fiber media supported palladium containing alloy nanoparticles and electrospun ceramic fibers biodurability study

    NASA Astrophysics Data System (ADS)

    Shin, Hyeon Ung

    The nanoscale of the supporting fibers may provide enhancements such as restricting the migration of metal catalyst particles. In this work, palladium nanoparticle doped alumina fibers were electrospun into template submicron fibers. These fibers were calcined at temperatures between 650°C and 1150°C to vary the crystal structures of the calcined fibers with the Pd particle size. Higher calcination temperatures led to higher reaction temperatures from 250 to about 450°C for total conversion, indicating the effective reactivity of the fiber-supported catalysts decreased with increase in calcination temperature. Pd-Au alloy nanoparticle doped titania fibers were also fabricated using an electrospinning method and assembled into a fibrous porous medium structure by a vacuum molding process. In reactor tests, the fiber media with Pd-Au alloy nanoparticle catalyst had greater reactivity in conversion of NO and CO gases than that of fiber media with Pd monometallic catalyst alone, attributed to a lower activation energy of the Pd-Au catalyst particles. In carbon monoxide oxidation reaction tests, the results showed that the performance was optimal for a catalyst of composition Pd2Au1 molar ratio that was active at 125°C, which had higher dispersion of active components and better catalytic performance compared to monometallic particle Au/TiO 2 and Pd/TiO2 fiber media. Moreover, the improved reaction activity of Pd2Au1/TiO2 fiber medium was attributed to a decreased in the activation energy. Further experiments were conducted using the electrospun ceramic fibers biodurability study. The properties of nano-sized fiber structures have attracted the attention of recent research on ceramic nanostructures as nonwoven media for applications in hazardous chemical and high temperature environments. However, health and safety concerns of micro and nano scale ceramic materials have not been fully investigated. Little is known about the physicochemical effects of the properties

  7. A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

    NASA Astrophysics Data System (ADS)

    Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; Maloy, Stuart A.

    2017-02-01

    The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This study aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide a comparative assessment of their high-temperature structural performance. The KJQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.

  8. Copper-Based Electrochemical Sensor with Palladium Electrode for Cathodic Stripping Voltammetry of Manganese

    PubMed Central

    2015-01-01

    In this work, we report on the development of a palladium-based, microfabricated point-of-care electrochemical sensor for the determination of manganese using square wave cathodic stripping voltammetry. Heavy metals require careful monitoring, yet current methods are too complex for a point-of-care system. Voltammetry offers an attractive approach to metal detection on the microscale, but traditional carbon, gold, or platinum electrodes are difficult or expensive to microfabricate, preventing widespread use. Our sensor uses palladium working and auxiliary electrodes and integrates them with a copper-based reference electrode for simple fabrication and compatibility with microfabrication and printed circuit board processing, while maintaining competitive performance in electrochemical detection. Copper electrodes were prepared on glass substrate using a combination of microfabrication procedures followed by electrodeposition of palladium. The disposable sensor system was formed by bonding a poly(dimethylsiloxane) (PDMS) well to the glass substrate. Cathodic stripping voltammetry of manganese using our new disposable palladium-based sensors exhibited 334 nM (18.3 ppb) limit of detection in borate buffer. The sensor was used to demonstrate manganese determination in natural water samples from a pond in Burnet Woods, located in Cincinnati, OH, and the Ohio River. PMID:25476591

  9. Copper-based electrochemical sensor with palladium electrode for cathodic stripping voltammetry of manganese.

    PubMed

    Kang, Wenjing; Pei, Xing; Bange, Adam; Haynes, Erin N; Heineman, William R; Papautsky, Ian

    2014-12-16

    In this work, we report on the development of a palladium-based, microfabricated point-of-care electrochemical sensor for the determination of manganese using square wave cathodic stripping voltammetry. Heavy metals require careful monitoring, yet current methods are too complex for a point-of-care system. Voltammetry offers an attractive approach to metal detection on the microscale, but traditional carbon, gold, or platinum electrodes are difficult or expensive to microfabricate, preventing widespread use. Our sensor uses palladium working and auxiliary electrodes and integrates them with a copper-based reference electrode for simple fabrication and compatibility with microfabrication and printed circuit board processing, while maintaining competitive performance in electrochemical detection. Copper electrodes were prepared on glass substrate using a combination of microfabrication procedures followed by electrodeposition of palladium. The disposable sensor system was formed by bonding a poly(dimethylsiloxane) (PDMS) well to the glass substrate. Cathodic stripping voltammetry of manganese using our new disposable palladium-based sensors exhibited 334 nM (18.3 ppb) limit of detection in borate buffer. The sensor was used to demonstrate manganese determination in natural water samples from a pond in Burnet Woods, located in Cincinnati, OH, and the Ohio River.

  10. Real-time monitoring of H2O2 release from single cells using nanoporous gold microelectrodes decorated with platinum nanoparticles.

    PubMed

    Xiao, Chong; Liu, Yan-Ling; Xu, Jia-Quan; Lv, Song-Wei; Guo, Shan; Huang, Wei-Hua

    2015-06-07

    Here, we report a self-supported nanoporous gold microelectrode decorated with well-dispersed and tiny platinum nanoparticles as an electrochemical nonenzymatic hydrogen peroxide biosensor. Nanoporous gold was fabricated by electrochemical alloying/dealloying and then small-sized platinum nanoparticles were electrodeposited uniformly on them. This novel hybrid nanostructure endows the sensor with high sensitivity and selectivity towards the reduction of hydrogen peroxide with a low detection limit of 0.3 nM. The sensor has been successfully applied for the measurement of H2O2 release from a single isolated human breast cancer cell, demonstrating its great potential for further physiological and pathological applications.

  11. An experimental palladium-103 seed (OptiSeed{sup exp}) in a biocompatible polymer without a gold marker: Characterization of dosimetric parameters including the interseed effect

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

    Abboud, F.; Scalliet, P.; Vynckier, S.

    Permanent implantation of {sup 125}I (iodine) or {sup 103}Pd (palladium) sources is a popular treatment option in the management of early stage prostate cancer. New sources are being developed, some of which are being marketed for different clinical applications. A new technique of adjuvant stereotactic permanent seed breast implant, similar to that used in the treatment of prostate cancer, has been proposed by [N. Jansen et al., Int. J. Radiat. Oncol. Biol. Phys. 67, 1052-1058 (2007)] with encouraging results. The presence of artifacts from the metallic seeds, however, can disturb follow-up imaging. The development of plastic seeds has reduced thesemore » artifacts. This paper presents a feasibility study of the advantages of palladium-103 seeds, encapsulated with a biocompatible polymer, for future clinical applications, and on the effect of the gold marker on the dosimetric characteristics of such seeds. Experimental palladium seeds, OptiSeed{sup exp}, were manufactured by International Brachytherapy (IBt), Seneffe, Belgium, from a biocompatible polymer, including the marker. Apart from the absence of a gold marker, the studied seed has an identical design to the OptiSeed{sup 103}[Phys. Med. Biol. 50, 1493-1504 (2005)]; [Appl. Radiat. Isot. 63, 311-321 (2005)]. Polymer encapsulation was preferred by IBt in order to reduce the quantity of radioactive material needed for a given dose rate and to reduce the anisotropy of the radiation field around the seed. In addition, this design is intended to decrease the interseed effects that can occur as a result of the marker and the encapsulation. Dosimetric measurements were performed using LiF thermoluminescent dosimeters (1 mm{sup 3}) in solid water phantoms (WT1). Measured data were compared to Monte Carlo simulated data in solid water using the MCNP code, version 4C. Updated cross sections [Med. Phys. 30, 701-711 (2003)] were used. As the measured and calculated data were in agreement, Monte Carlo calculations were

  12. Pentacle gold-copper alloy nanocrystals: a new system for entering male germ cells in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Lin, Yu; He, Rong; Sun, Liping; Yang, Yushan; Li, Wenqing; Sun, Fei

    2016-12-01

    Gold-based nanocrystals have attracted considerable attention for drug delivery and biological applications due to their distinct shapes. However, overcoming biological barriers is a hard and inevitable problem, which restricts medical applications of nanomaterials in vivo. Seeking for an efficient transportation to penetrate biological barriers is a common need. There are three barriers: blood-testis barrier, blood-placenta barrier, and blood-brain barrier. Here, we pay close attention to the blood-testis barrier. We found that the pentacle gold-copper alloy nanocrystals not only could enter GC-2 cells in vitro in a short time, but also could overcome the blood-testis barrier and enter male germ cells in vivo. Furthermore, we demonstrated that the entrance efficiency would become much higher in the development stages. The results also suggested that the pentacle gold-copper alloy nanocrystals could easier enter to germ cells in the pathological condition. This system could be a new method for theranostics in the reproductive system.

  13. Palladium-bacterial cellulose membranes for fuel cells.

    PubMed

    Evans, Barbara R; O'Neill, Hugh M; Malyvanh, Valerie P; Lee, Ida; Woodward, Jonathan

    2003-07-01

    Bacterial cellulose is a versatile renewable biomaterial that can be used as a hydrophilic matrix for the incorporation of metals into thin, flexible, thermally stable membranes. In contrast to plant cellulose, we found it catalyzed the deposition of metals within its structure to generate a finely divided homogeneous catalyst layer. Experimental data suggested that bacterial cellulose possessed reducing groups capable of initiating the precipitation of palladium, gold, and silver from aqueous solution. Since the bacterial cellulose contained water equivalent to at least 200 times the dry weight of the cellulose, it was dried to a thin membranous structure suitable for the construction of membrane electrode assemblies (MEAs). Results of our study with palladium-cellulose showed that it was capable of catalyzing the generation of hydrogen when incubated with sodium dithionite and generated an electrical current from hydrogen in an MEA containing native cellulose as the polyelectrolyte membrane (PEM). Advantages of using native and metallized bacterial cellulose membranes in an MEA over other PEMs such as Nafion 117 include its higher thermal stability to 130 degrees C and lower gas crossover.

  14. A biodegradable AZ91 magnesium alloy coated with a thin nanostructured hydroxyapatite for improving the corrosion resistance.

    PubMed

    Mukhametkaliyev, T M; Surmeneva, M A; Vladescu, A; Cotrut, C M; Braic, M; Dinu, M; Vranceanu, M D; Pana, I; Mueller, M; Surmenev, R A

    2017-06-01

    The main aim of this study was to investigate the properties of an AZ91 alloy coated with nanostructured hydroxyapatite (HA) prepared by radio frequency (RF) magnetron sputtering. The bioactivity and biomineralization of the AZ91 magnesium alloy coated with HA were investigated in simulated body fluid (SBF) via an in vitro test. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analyses were performed. The samples were immersed in SBF to study the ability of the surface to promote the formation of an apatite layer as well as corrosion resistance and mass change of the HA-coated AZ91 alloy. Electrochemical tests were performed to estimate the corrosion behaviour of HA-coated and uncoated samples. The results revealed the capability of the HA coating to significantly improve the corrosion resistance of the uncoated AZ91 alloy. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Effect of heat treatment on mechanical properties of age-hardenable gold alloy at intraoral temperature.

    PubMed

    Watanabe, I; Watanabe, E; Cai, Z; Okabe, T; Atsuta, M

    2001-09-01

    The aim of this study was to investigate the effect of various heat treatments on the mechanical properties of gold alloys capable of age-hardening at intraoral temperature. Dumbbell-shaped patterns (ISO 6871) were cast with three gold alloys (Sofard; NC Type-IV; Aurum Cast, NihombashiTokuriki Co.). The Sofard alloy is age-hardenable at intraoral temperature. The castings underwent various heat treatments [as-cast (AC); solution treatment (ST); high-temperature aging (HA); intraoral aging (IA)]. After these heat treatments, ultimate tensile strength (UTS), 0.2% offset yield strength (YS), and elongation (EL) were measured at a strain rate of 1.7x10(-4)/s. Fracture surfaces of the specimens after tensile testing were observed using SEM. Vickers hardness was also measured after heat treating. After IA, the hardness values of the Sofard alloy increased and reached values similar to the hardness of the Sofard specimens aged at high temperature (HA). The hardness values of the NC Type-IV and Aurum Cast specimens slightly increased after IA, but did not reach the values of the specimens after HA. All the Sofard, NC Type-IV and Aurum Cast specimens showed significantly (P<0.05) greater hardness values after HA, compared with the values after any other heat treatments (AC, ST and IA). The UTS and YS of the specimens indicated a tendency similar to the results obtained for hardness. The Sofard specimens with ST showed the greatest elongation compared to the corresponding NC Type-IV and Aurum Cast specimens. However, the elongation of the Sofard specimens was abruptly reduced after intraoral aging. Intraoral aging significantly improved the mechanical properties and hardness of the Sofard alloy.

  16. Biomolecular Assembly of Gold Nanocrystals

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

    Micheel, Christine Marya

    2005-05-20

    Over the past ten years, methods have been developed to construct discrete nanostructures using nanocrystals and biomolecules. While these frequently consist of gold nanocrystals and DNA, semiconductor nanocrystals as well as antibodies and enzymes have also been used. One example of discrete nanostructures is dimers of gold nanocrystals linked together with complementary DNA. This type of nanostructure is also known as a nanocrystal molecule. Discrete nanostructures of this kind have a number of potential applications, from highly parallel self-assembly of electronics components and rapid read-out of DNA computations to biological imaging and a variety of bioassays. My research focused inmore » three main areas. The first area, the refinement of electrophoresis as a purification and characterization method, included application of agarose gel electrophoresis to the purification of discrete gold nanocrystal/DNA conjugates and nanocrystal molecules, as well as development of a more detailed understanding of the hydrodynamic behavior of these materials in gels. The second area, the development of methods for quantitative analysis of transmission electron microscope data, used computer programs written to find pair correlations as well as higher order correlations. With these programs, it is possible to reliably locate and measure nanocrystal molecules in TEM images. The final area of research explored the use of DNA ligase in the formation of nanocrystal molecules. Synthesis of dimers of gold particles linked with a single strand of DNA possible through the use of DNA ligase opens the possibility for amplification of nanostructures in a manner similar to polymerase chain reaction. These three areas are discussed in the context of the work in the Alivisatos group, as well as the field as a whole.« less

  17. Designing supported palladium-on-gold bimetallic nano-catalysts for controlled hydrogenation of acetylene in large excess of ethylene

    NASA Astrophysics Data System (ADS)

    Malla, Pavani

    Ethylene is used as a starting point for many chemical intermediates in the petrochemical industry. It is predominantly produced through steam cracking of higher hydrocarbons (ethane, propane, butane, naphtha, and gas oil). During the cracking process, a small amount of acetylene is produced as a side product. However, acetylene must be removed since it acts as a poison for ethylene polymerization catalysts at even ppm concentrations (>5 ppm). Thus, the selective hydrogenation of acetylene to ethylene is an important process for the purification of ethylene. Conventional, low weight loading Pd catalysts are used for this selective reaction in high concentration ethylene streams. Gold was initially considered to be catalytically inactive for a long time. This changed when gold was seen in the context of the nanometric scale, which has indeed shown it to have excellent catalytic activity as a homogeneous or a heterogeneous catalyst. Gold is proved to have high selectivity to ethylene but poor at conversion. Bimetallic Au and Pd catalysts have exhibited superior activity as compared to Pd particles in semi-hydrogenation. Hydrogenation of acetylene was tested using this bimetallic combination. The Pd-on-Au bimetallic catalyst structure provides a new synthesis approach in improving the catalytic properties of monometallic Pd materials. TiO 2 as a support material and 0.05%Pd loading on 1%Au on titania support and used different treatment methods like washing plasma and reduction between the two metal loadings and was observed under 2:1 ratio. In my study there were two set of catalysts which were prepared by a modified incipient wetness impregnation technique. Out of all the reaction condition the catalyst which was reduced after impregnating gold and then impregnating palladium which was further treated in non-thermal hydrogen plasma and then pretreated in hydrogen till 250°C for 1 hour produced the best activity of 76% yield at 225°C. Stability tests were conducted

  18. Alloy solution hardening with solute pairs

    DOEpatents

    Mitchell, John W.

    1976-08-24

    Solution hardened alloys are formed by using at least two solutes which form associated solute pairs in the solvent metal lattice. Copper containing equal atomic percentages of aluminum and palladium is an example.

  19. High Sensitivity and High Detection Specificity of Gold-Nanoparticle-Grafted Nanostructured Silicon Mass Spectrometry for Glucose Analysis.

    PubMed

    Tsao, Chia-Wen; Yang, Zhi-Jie

    2015-10-14

    Desorption/ionization on silicon (DIOS) is a high-performance matrix-free mass spectrometry (MS) analysis method that involves using silicon nanostructures as a matrix for MS desorption/ionization. In this study, gold nanoparticles grafted onto a nanostructured silicon (AuNPs-nSi) surface were demonstrated as a DIOS-MS analysis approach with high sensitivity and high detection specificity for glucose detection. A glucose sample deposited on the AuNPs-nSi surface was directly catalyzed to negatively charged gluconic acid molecules on a single AuNPs-nSi chip for MS analysis. The AuNPs-nSi surface was fabricated using two electroless deposition steps and one electroless etching step. The effects of the electroless fabrication parameters on the glucose detection efficiency were evaluated. Practical application of AuNPs-nSi MS glucose analysis in urine samples was also demonstrated in this study.

  20. Designing Hollow Nano Gold Golf Balls

    PubMed Central

    2015-01-01

    Hollow/porous nanoparticles, including nanocarriers, nanoshells, and mesoporous materials have applications in catalysis, photonics, biosensing, and delivery of theranostic agents. Using a hierarchical template synthesis scheme, we have synthesized a nanocarrier mimicking a golf ball, consisting of (i) solid silica core with a pitted gold surface and (ii) a hollow/porous gold shell without silica. The template consisted of 100 nm polystyrene beads attached to a larger silica core. Selective gold plating of the core followed by removal of the polystyrene beads produced a golf ball-like nanostructure with 100 nm pits. Dissolution of the silica core produced a hollow/porous golf ball-like nanostructure. PMID:24937196

  1. Liquid metal ion source and alloy

    DOEpatents

    Clark, Jr., William M.; Utlaut, Mark W.; Behrens, Robert G.; Szklarz, Eugene G.; Storms, Edmund K.; Santandrea, Robert P.; Swanson, Lynwood W.

    1988-10-04

    A liquid metal ion source and alloy, wherein the species to be emitted from the ion source is contained in a congruently vaporizing alloy. In one embodiment, the liquid metal ion source acts as a source of arsenic, and in a source alloy the arsenic is combined with palladium, preferably in a liquid alloy having a range of compositions from about 24 to about 33 atomic percent arsenic. Such an alloy may be readily prepared by a combustion synthesis technique. Liquid metal ion sources thus prepared produce arsenic ions for implantation, have long lifetimes, and are highly stable in operation.

  2. Method of depositing a protective layer over a biaxially textured alloy substrate and composition therefrom

    DOEpatents

    Goyal, Amit; Kroeger, Donald M.; Paranthaman, Mariappan; Lee, Dominic F.; Feenstra, Roeland; Norton, David P.

    2002-01-01

    A laminate article consists of a substrate and a biaxially textured protective layer over the substrate. The substrate can be biaxially textured and also have reduced magnetism over the magnetism of Ni. The substrate can be selected from the group consisting of nickel, copper, iron, aluminum, silver and alloys containing any of the foregoing. The protective layer can be selected from the group consisting of gold, silver, platinum, palladium, and nickel and alloys containing any of the foregoing. The protective layer is also non-oxidizable under conditions employed to deposit a desired, subsequent oxide buffer layer. Layers of YBCO, CeO.sub.2, YSZ, LaAlO.sub.3, SrTiO.sub.3, Y.sub.2 O.sub.3, RE.sub.2 O.sub.3, SrRuO.sub.3, LaNiO.sub.3 and La.sub.2 ZrO.sub.3 can be deposited over the protective layer. A method of forming the laminate article is also disclosed.

  3. Ambient ammonia synthesis via palladium-catalyzed electrohydrogenation of dinitrogen at low overpotential.

    PubMed

    Wang, Jun; Yu, Liang; Hu, Lin; Chen, Gang; Xin, Hongliang; Feng, Xiaofeng

    2018-05-15

    Electrochemical reduction of N 2 to NH 3 provides an alternative to the Haber-Bosch process for sustainable, distributed production of NH 3 when powered by renewable electricity. However, the development of such process has been impeded by the lack of efficient electrocatalysts for N 2 reduction. Here we report efficient electroreduction of N 2 to NH 3 on palladium nanoparticles in phosphate buffer solution under ambient conditions, which exhibits high activity and selectivity with an NH 3 yield rate of ~4.5 μg mg -1 Pd h -1 and a Faradaic efficiency of 8.2% at 0.1 V vs. the reversible hydrogen electrode (corresponding to a low overpotential of 56 mV), outperforming other catalysts including gold and platinum. Density functional theory calculations suggest that the unique activity of palladium originates from its balanced hydrogen evolution activity and the Grotthuss-like hydride transfer mechanism on α-palladium hydride that lowers the free energy barrier of N 2 hydrogenation to *N 2 H, the rate-limiting step for NH 3 electrosynthesis.

  4. Photonics of 2D gold nanolayers on sapphire surface

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

    Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Nabatov, B. V.

    Gold layers with thicknesses of up to several nanometers, including ordered and disordered 2D nanostructures of gold particles, have been formed on sapphire substrates; their morphology is described; and optical investigations are carried out. The possibility of increasing the accuracy of predicting the optical properties of gold layers and 2D nanostructures using quantum-mechanical models based on functional density theory calculation techniques is considered. The application potential of the obtained materials in photonics is estimated.

  5. Is It Real Gold?

    ERIC Educational Resources Information Center

    Harris, Harold H.

    1999-01-01

    Features acid tests for determining whether jewelry is "real" gold or simply gold-plated. Describes the carat system of denoting gold content and explains how alloys are used to create various shades of gold jewelry. Addresses the question of whether gold jewelry can turn a wearer's skin green by considering various oxidation reactions.…

  6. A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

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

    Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han

    The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This paper aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide amore » comparative assessment of their high-temperature structural performance. The K JQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Finally, irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.« less

  7. A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

    DOE PAGES

    Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; ...

    2016-12-07

    The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This paper aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide amore » comparative assessment of their high-temperature structural performance. The K JQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Finally, irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.« less

  8. Directing self-assembly of gold nanoparticles in diblock copolymer scaffold

    NASA Astrophysics Data System (ADS)

    Li, Qifang; He, Jinbo; Glogowski, Elizabeth; Emrick, Todd; Russell, Thomas

    2007-03-01

    A versatile hierarchical approach for directing self -assembly of gold nanostructures with size 2-3nm in diblock copolymer scaffolds is found. Diblock copolymer polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) is used to form a regular scaffold of highly anisotropic, stripe-like domains, and controlled differential wetting by dichloromethane and thermal annealing guides gold nanoparticles with half hydrophilic ligand to aggregate selectively along the scaffold, producing highly organized metal nanostructures. In as-cast block-copolymer and gold nanoparticles thin films, micelle structure and gold nanoparticles random distribution on scaffold are typically observed. However, samples annealed in dichloromethane exhibit well-defined short-range ordered nanostructure with gold nanoparticles located at the interface of PS and P2VP nanoscale domain. After annealing at 170 C, the gold nanoparticles at interface migrated into the middle of P2VP phase and exhibited long-range ordered hierarchical structures. Synergistic interactions between the gold nanoparticles and the PS-b-P2VP caused an orientation of the microdomains normal to the film surface.

  9. Determination of palladium and platinum by atomic absorption

    USGS Publications Warehouse

    Schnepfe, M.M.; Grimaldi, F.S.

    1969-01-01

    Palladium and platinum are determined by atomic absorption after fire-assay concentration into a gold bead. The limit of determination is ~0??06 ppm in a 20-g sample. Serious depressive interelement interferences are removed by buffering the solutions with a mixture of cadmium and copper sulphates with cadmium and copper concentrations each at 0??5%. Substantial amounts of Ag, Al, Au, Bi, Ca, Co, Cr, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn, and the platinum metals do not interfere in the atomic-absorption determination. ?? 1969.

  10. CONTROL ROD ALLOY CONTAINING NOBLE METAL ADDITIONS

    DOEpatents

    Anderson, W.K.; Ray, W.E.

    1960-05-01

    Silver-base alloys suitable for use in the fabrication of control rods for neutronic reactors are given. The alloy consists of from 0.5 wt.% to about 1.5 wt.% of a noble metal of platinum, ruthenium, rhodium, osmium, or palladium, up to 10 wt.% of cadmium, from 2 to 20 wt.% indium, the balance being silver.

  11. Pitting and Stress Corrosion Cracking Susceptibility of Nanostructured Al-Mg Alloys in Natural and Artificial Environments

    NASA Astrophysics Data System (ADS)

    Sharma, Mala M.; Ziemian, Constance W.

    2008-12-01

    The stress corrosion cracking (SCC) behavior of two developmental nanocrystalline 5083 alloys with varied composition and processing conditions was studied. The results were compared to a commercial aluminum AA 5083 (H111) alloy. The pitting densities, size and depths, and residual tensile strengths were measured after alternate immersion in artificial seawater and atmospheric exposure under different loading conditions. Optical and scanning electron microscopy (SEM) with EDX was used to analyze the fracture surfaces of failed specimen after removal at selected intervals and tensile testing. One of the nanostructured Al-Mg alloys exhibited significantly superior pitting resistance when compared to conventional microstructured AA 5083. Under conditions where pitting corrosion showed up as local tunnels toward phase inclusions, transgranular cracking was observed, whereas under conditions when pitting corrosion evolved along grain boundaries, intergranular cracking inside the pit was observed. Pit initiation resistance of the nano alloys appears to be better than that of the conventional alloys. However, long-term pit propagation is a concern and warrants further study. The objective of this investigation was to obtain information regarding the role that ultra-fine microstructures play in their degradation in marine environments and to provide insight into the corrosion mechanisms and damage processes of these alloys.

  12. Surface microstructure and in vitro analysis of nanostructured akermanite (Ca2MgSi2O7) coating on biodegradable magnesium alloy for biomedical applications.

    PubMed

    Razavi, Mehdi; Fathi, Mohammadhossein; Savabi, Omid; Hashemi Beni, Batoul; Vashaee, Daryoosh; Tayebi, Lobat

    2014-05-01

    Magnesium (Mg) alloys, owing to their biodegradability and good mechanical properties, have potential applications as biodegradable orthopedic implants. However, several poor properties including low corrosion resistance, mechanical stability and cytocompatibility have prevented their clinical application, as these properties may result in the sudden failure of the implants during the bone healing. In this research, nanostructured akermanite (Ca2MgSi2O7) powder was coated on the AZ91 Mg alloy through electrophoretic deposition (EPD) assisted micro arc oxidation (MAO) method to modify the properties of the alloy. The surface microstructure of coating, corrosion resistance, mechanical stability and cytocompatibility of the samples were characterized with different techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical corrosion test, immersion test, compression test and cell culture test. The results showed that the nanostructured akermanite coating can improve the corrosion resistance, mechanical stability and cytocompatibility of the biodegradable Mg alloy making it a promising material to be used as biodegradable bone implants for orthopedic applications. Published by Elsevier B.V.

  13. The role of processing route on the microstructure of 14YWT nanostructured ferritic alloy

    NASA Astrophysics Data System (ADS)

    Mazumder, B.; Parish, C. M.; Bei, H.; Miller, M. K.

    2015-10-01

    Nanostructured ferritic alloys have outstanding high temperature creep properties and enhanced tolerance to radiation damage over conventional ferritic alloys. To achieve these properties, NFAs are fabricated by mechanical alloying of metallic and yttria powders. Atom probe tomography has demonstrated that milling times of at least 40 h are required to produce a uniform distribution of solutes in the flakes. After milling and hot extrusion, the microstructure consists of α-Fe, high number densities of Ti-Y-O-vacancy-enriched nanoclusters, and coarse Y2Ti2O7 and Ti(O,C,N) precipitates on the grain boundaries. In contrast, the as-cast condition consists of α-Fe with 50-100 μm irregularly-shaped Y2Ti2O7 pyrochlore precipitates with smaller embedded precipitates with the Y3Al5O12 (yttrium-aluminum garnet) crystal structure indicating that this traditional processing route is not a viable approach to achieve the desired microstructure. The nano-hardnesses were also substantially different, i.e., 4 and 8 GPa for the as-cast and as-extruded conditions, respectively. These variances can be explained by the microstructural differences and the effects of the high vacancy content introduced by mechanical alloying, and the strong binding energy of vacancies with O, Ti, and Y atoms that retard diffusion.

  14. A rapid and practical strategy for the determination of platinum, palladium, ruthenium, rhodium, iridium and gold in large amounts of ultrabasic rock by inductively coupled plasma optical emission spectrometry combined with ultrasound extraction

    NASA Astrophysics Data System (ADS)

    Zhang, Gai; Tian, Min

    2015-04-01

    This proposed method regulated the determination of platinum, palladium, ruthenium, rhodium, iridium and gold in platinum-group ores by nickel sulfide fire assay—inductively coupled plasma optical emission spectrometry (ICP-OES) combined with ultrasound extraction for the first time. The quantitative limits were 0.013-0.023μg/g. The samples were fused to separate the platinum-group elements from matrix. The nickel sulfide button was then dissolved with hydrochloric acid and the insoluble platinum-group sulfide residue was dissolved with aqua regia by ultrasound bath and finally determined by ICP-OES. The proposed method has been applied into the determination of platinum-group element and gold in large amounts of ultrabasic rocks from the Great Dyke of Zimbabwe.

  15. Electrophoretic deposition of nanostructured hydroxyapatite coating on AZ91 magnesium alloy implants with different surface treatments

    NASA Astrophysics Data System (ADS)

    Rojaee, Ramin; Fathi, Mohammadhossein; Raeissi, Keyvan

    2013-11-01

    Bio-absorbable magnesium (Mg) based alloys have been introduced as innovative orthopedic implants during recent years. It has been specified that rapid degradation of Mg based alloys in physiological environment should be restrained in order to be utilized in orthopedic trauma fixation and vascular intervention. In this developing field of healthcare materials, micro-arc oxidation (MAO), and MgF2 conversion coating were exploited as surface pre-treatment of AZ91 magnesium alloy to generate a nanostructured hydroxyapatite (n-HAp) coating via electrophoretic deposition (EPD) method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM) techniques were used to characterize the obtained powder and coatings. The potentiodynamic polarization tests were carried out to evaluate the corrosion behavior of the coated and uncoated specimens, and in vitro bioactivity evaluation were performed in simulated body fluid. Results revealed that the MAO/n-HAp coated AZ91 Mg alloy samples with a rough topography and lower corrosion current density leads to a lower Mg degradation rate accompanied by high bioactivity.

  16. Sputter target

    DOEpatents

    Gates, Willard G.; Hale, Gerald J.

    1980-01-01

    The disclosure relates to an improved sputter target for use in the deposition of hard coatings. An exemplary target is given wherein titanium diboride is brazed to a tantalum backing plate using a gold-palladium-nickel braze alloy.

  17. Laser-induced damage thresholds of gold, silver and their alloys in air and water

    NASA Astrophysics Data System (ADS)

    Starinskiy, Sergey V.; Shukhov, Yuri G.; Bulgakov, Alexander V.

    2017-02-01

    The nanosecond-laser-induced damage thresholds of gold, silver and gold-silver alloys of various compositions in air and water have been measured for single-shot irradiation conditions. The experimental results are analyzed theoretically by solving the heat flow equation for the samples irradiated in air and in water taking into account vapor nucleation at the solid-water interface. The damage thresholds of Au-Ag alloys are systematically lower than those for pure metals, both in air and water that is explained by lower thermal conductivities of the alloys. The thresholds measured in air agree well with the calculated melting thresholds for all samples. The damage thresholds in water are found to be considerably higher, by a factor of ∼1.5, than the corresponding thresholds in air. This cannot be explained, in the framework of the used model, neither by the conductive heat transfer to water nor by the vapor pressure effect. Possible reasons for the high damage thresholds in water such as scattering of the incident laser light by the vapor-liquid interface and the critical opalescence in the superheated water are suggested. Optical pump-probe measurements have been performed to study the reflectance dynamics of the surface irradiated in air and water. Comparison of the transient reflectance signal with the calculated nucleation dynamics provides evidence that the both suggested scattering mechanisms are likely to occur during metal ablation in water.

  18. Photoelectron spectroscopic study on the electronic structures of the dental gold alloys and their interaction with L-cysteine

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

    Ogawa, Koji; Takahashi, Kazutoshi; Azuma, Junpei

    The valence electronic structures of the dental gold alloys, type 1, type 3, and K14, and their interaction with L-cysteine have been studied by ultraviolet photoelectron spectroscopy with synchrotron radiation. It was found that the electronic structures of the type-1 and type-3 dental alloys are similar to that of polycrystalline Au, while that of the K14 dental alloy is much affected by Cu. The peak shift and the change in shape due to alloying are observed in all the dental alloys. It is suggested that the new peak observed around 2 eV for the L-cysteine thin films on all themore » dental alloys may be due to the bonding of S 3sp orbitals with the dental alloy surfaces, and the Cu-S bond, as well as the Au-S and Au-O bonds, may cause the change in the electronic structure of the L-cysteine on the alloys.« less

  19. Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

    PubMed Central

    Zhang, Z. W.; Yao, L.; Wang, X.-L.; Miller, M. K.

    2015-01-01

    A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. Here we report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using a combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters. PMID:26023747

  20. Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys

    DOE PAGES

    Zhang, Z. W.; Yao, L.; Wang, X. -L.; ...

    2015-05-29

    A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. We report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using amore » combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters.« less

  1. The effect of Mn and B on the magnetic and structural properties of nanostructured Fe60Al40 alloys produced by mechanical alloying.

    PubMed

    Rico, M M; Alcázar, G A Pérez; Zamora, L E; González, C; Greneche, J M

    2008-06-01

    The effect of Mn and B on the magnetic and structural properties of nanostructured samples of the Fe60Al40 system, prepared by mechanical alloying, was studied by 57Fe Mössbauer spectrometry, X-ray diffraction and magnetic measurements. In the case of the Fe(60-x)Mn(x)Al40 system, 24 h milling time is required to achieve the BCC ternary phase. Different magnetic structures are observed according to the temperature and the Mn content for alloys milled during 48 h: ferromagnetic, antiferromagnetic, spin-glass, reentrant spin-glass and superparamagnetic behavior. They result from the bond randomness behaviour induced by the atomic disorder introduced by the MA process and from the competitive interactions of the Fe-Fe ferromagnetic interactions and the Mn-Mn and Fe-Mn antiferromagnetic interactions and finally the presence of Al atoms acting as dilutors. When B is added in the Fe60Al40 alloy and milled for 12 and 24 hours, two crystalline phases were found: a prevailing FeAl BCC phase and a Fe2B phase type. In addition, one observes an additional contribution attributed to grain boundaries which increases when both milling time and boron composition increase. Finally Mn and B were added to samples of the Fe60Al40 system prepared by mechanical alloying during 12 and 24 hours. Mn content was fixed to 10 at.% and B content varied between 0 and 20 at.%, substituting Al. X-ray patterns show two crystalline phases, the ternary FeMnAl BCC phase, and a (Fe,Mn)2B phase type. The relative proportion of the last phase increases when the B content increases, in addition to changes of the grain size and the lattice parameter. Such behavior was observed for both milling periods. On the other hand, the magnetic hyperfine field distributions show that both phases exhibit chemical disorder, and that the contribution attributed to the grain boundaries is less important when the B content increases. Coercive field values of about 10(2) Oe slightly increase with boron content

  2. Preparation of multifunctional Al-Mg alloy surface with hierarchical micro/nanostructures by selective chemical etching processes

    NASA Astrophysics Data System (ADS)

    Shi, Tian; Kong, Jianyi; Wang, Xingdong; Li, Xuewu

    2016-12-01

    A superamphiphobic aluminum magnesium alloy surface with enhanced anticorrosion behavior has been prepared in this work via a simple and low-cost method. By successively polishing, etching and boiling treatments, the multifunctional hierarchical binary structures composed of the labyrinth-like concave-convex microstructures and twisty nanoflakes have been prepared. Results indicate that a superhydrophobic contact angle of 160.5° and superoleophobic contact angle larger than 150° as well as low adhesive property to liquids are achieved after such structures being modified with fluoroalkyl-silane. Furthermore, the anticorrosion behaviors in seawater of as-prepared samples are characterized by electrochemical tests including the impedance spectroscopies, equivalent circuits fittings and polarization curves. It is found that the hierarchical micro/nanostructures accompanying with the modified coating are proved to possess the maximal coating coverage rate of 90.0% larger than microstructures of 85.9%, nanostructures of 83.8% and bare polished surface of 67.1% suggesting the optimal anticorrosion. Finally, a great potential application in concentrators for surface-enhanced Raman scattering (SERS) analysis of toxic and pollutive ions on the superamphiphobic surface is also confirmed. This work has wider significance in extending further applications of alloys in engineering and environmental detecting fields.

  3. 21 CFR 872.3580 - Preformed gold denture tooth.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a) Identification. A preformed gold denture tooth is a device composed of austenitic alloys or alloys containing 75...

  4. 21 CFR 872.3580 - Preformed gold denture tooth.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a) Identification. A preformed gold denture tooth is a device composed of austenitic alloys or alloys containing 75...

  5. 21 CFR 872.3580 - Preformed gold denture tooth.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a) Identification. A preformed gold denture tooth is a device composed of austenitic alloys or alloys containing 75...

  6. 21 CFR 872.3580 - Preformed gold denture tooth.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a) Identification. A preformed gold denture tooth is a device composed of austenitic alloys or alloys containing 75...

  7. 21 CFR 872.3580 - Preformed gold denture tooth.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Preformed gold denture tooth. 872.3580 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3580 Preformed gold denture tooth. (a) Identification. A preformed gold denture tooth is a device composed of austenitic alloys or alloys containing 75...

  8. Acoustic vibrations of single suspended gold nanostructures

    NASA Astrophysics Data System (ADS)

    Major, Todd A.

    The acoustic vibrations for single gold nanowires and gold plates were studied using time-resolved ultrafast transient absorption. The objective of this work was to remove the contribution of the supporting substrate from the damping of the acoustic vibrations of the metal nano-objects. This was achieved by suspending the nano-objects across trenches created by photolithography and reactive ion etching. Transient absorption measurements for single suspended gold nanowires were initially completed in air and water environments. The acoustic vibrations for gold nanowires over the trench in air last typically for several nanoseconds, whereas gold nanowires in water are damped more quickly. Continuum mechanics models suggest that the acoustic impedance mismatch between air and water dominates the damping rate. Later transient absorption studies on single suspended gold nanowires were completed in glycerol and ethylene glycol environments. However, our continuum mechanical model suggests nearly complete damping in glycerol due to its high viscosity, but similar damping rates are seen between the two liquids. The continuum mechanics model thus incorrectly addresses high viscosity effects on the lifetimes of the acoustic vibrations, and more complicated viscoelastic interactions occur for the higher viscosity liquids. (Abstract shortened by UMI.).

  9. Rolling up gold nanoparticle-dressed DNA origami into three-dimensional plasmonic chiral nanostructures.

    PubMed

    Shen, Xibo; Song, Chen; Wang, Jinye; Shi, Dangwei; Wang, Zhengang; Liu, Na; Ding, Baoquan

    2012-01-11

    Construction of three-dimensional (3D) plasmonic architectures using structural DNA nanotechnology is an emerging multidisciplinary area of research. This technology excels in controlling spatial addressability at sub-10 nm resolution, which has thus far been beyond the reach of traditional top-down techniques. In this paper, we demonstrate the realization of 3D plasmonic chiral nanostructures through programmable transformation of gold nanoparticle (AuNP)-dressed DNA origami. AuNPs were assembled along two linear chains on a two-dimensional rectangular DNA origami sheet with well-controlled positions and particle spacing. By rational rolling of the 2D origami template, the AuNPs can be automatically arranged in a helical geometry, suggesting the possibility of achieving engineerable chiral nanomaterials in the visible range. © 2011 American Chemical Society

  10. Thermal tuning of infrared resonant absorbers based on hybrid gold-VO{sub 2} nanostructures

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

    Kocer, Hasan; Department of Electrical Engineering, Turkish Military Academy, 06654 Ankara; Butun, Serkan

    2015-04-20

    Resonant absorbers based on plasmonic materials, metamaterials, and thin films enable spectrally selective absorption filters, where absorption is maximized at the resonance wavelength. By controlling the geometrical parameters of nano/microstructures and materials' refractive indices, resonant absorbers are designed to operate at wide range of wavelengths for applications including absorption filters, thermal emitters, thermophotovoltaic devices, and sensors. However, once resonant absorbers are fabricated, it is rather challenging to control and tune the spectral absorption response. Here, we propose and demonstrate thermally tunable infrared resonant absorbers using hybrid gold-vanadium dioxide (VO{sub 2}) nanostructure arrays. Absorption intensity is tuned from 90% to 20%more » and 96% to 32% using hybrid gold-VO{sub 2} nanowire and nanodisc arrays, respectively, by heating up the absorbers above the phase transition temperature of VO{sub 2} (68 °C). Phase change materials such as VO{sub 2} deliver useful means of altering optical properties as a function of temperature. Absorbers with tunable spectral response can find applications in sensor and detector applications, in which external stimulus such as heat, electrical signal, or light results in a change in the absorption spectrum and intensity.« less

  11. Nanomolar electrochemical detection of caffeic acid in fortified wine samples based on gold/palladium nanoparticles decorated graphene flakes.

    PubMed

    Thangavelu, Kokulnathan; Raja, Nehru; Chen, Shen-Ming; Liao, Wei-Cheng

    2017-09-01

    Amalgamation of noble metal nanomaterials on graphene flakes potentially paves one way to improve their physicochemical properties. This paper deals with the simultaneous electrochemical deposition of gold and palladium nanoparticles on graphene flakes (Au/PdNPs-GRF) for the sensitive determination of caffeic acid (CA). The physiochemical properties of the prepared Au/PdNPs-GRF was characterized by using numerous analytical techniques such as scanning electron microscopy, electron dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy and electrochemical impedance spectroscopy. The enhanced electrochemical determination of CA at Au/PdNPs deposition on GRF were studied by using cyclic voltammetry and differential pulse voltammetry. In results, Au/PdNPs-GRF electrode exhibited an excellent electrocatalytic activity towards CA with wide linear range and low limit of detection of 0.03-938.97µM and 6nM, respectively. Eventually, the Au/PdNPs-GRF was found as a selective and stable active material for the sensing of CA. In addition, the proposed sensor showed the adequate results in real sample analysis. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Study of self-ion irradiated nanostructured ferritic alloy (NFA) and silicon carbide-nanostructured ferritic alloy (SiC-NFA) cladding materials

    NASA Astrophysics Data System (ADS)

    Ning, Kaijie; Bai, Xianming; Lu, Kathy

    2018-07-01

    Silicon carbide-nanostructured ferritic alloy (SiC-NFA) materials are expected to have the beneficial properties of each component for advanced nuclear claddings. Fabrication of pure NFA (0 vol% SiC-100 vol% NFA) and SiC-NFAs (2.5 vol% SiC-97.5 vol% NFA, 5 vol% SiC-95 vol% NFA) has been reported in our previous work. This paper is focused on the study of radiation damage in these materials under 5 MeV Fe++ ion irradiation with a dose up to ∼264 dpa. It is found that the material surfaces are damaged to high roughness with irregularly shaped ripples, which can be explained by the Bradley-Harper (B-H) model. The NFA matrix shows ion irradiation induced defect clusters and small dislocation loops, while the crystalline structure is maintained. Reaction products of Fe3Si and Cr23C6 are identified in the SiC-NFA materials, with the former having a partially crystalline structure but the latter having a fully amorphous structure upon irradiation. The different radiation damage behaviors of NFA, Fe3Si, and Cr23C6 are explained using the defect reaction rate theory.

  13. Modeling, Fabrication and Characterization of Scalable Electroless Gold Plated Nanostructures for Enhanced Surface Plasmon Resonance

    NASA Astrophysics Data System (ADS)

    Jang, Gyoung Gug

    The scientific and industrial demand for controllable thin gold (Au) film and Au nanostructures is increasing in many fields including opto-electronics, photovoltaics, MEMS devices, diagnostics, bio-molecular sensors, spectro-/microscopic surfaces and probes. In this study, a novel continuous flow electroless (CF-EL) Au plating method is developed to fabricate uniform Au thin films in ambient condition. The enhanced local mass transfer rate and continuous deposition resulting from CF-EL plating improved physical uniformity of deposited Au films and thermally transformed nanoparticles (NPs). Au films and NPs exhibited improved optical photoluminescence (PL) and surface plasmon resonance (SPR), respectively, relative to batch immersion EL (BI-EL) plating. Suggested mass transfer models of Au mole deposition are consistent with optical feature of CF-EL and BI-EL films. The prototype CF-EL plating system is upgraded an automated scalable CF-EL plating system with real-time transmission UV-vis (T-UV) spectroscopy which provides the advantage of CF-EL plating, such as more uniform surface morphology, and overcomes the disadvantages of conventional EL plating, such as no continuous process and low deposition rate, using continuous process and controllable deposition rate. Throughout this work, dynamic morphological and chemical transitions during redox-driven self-assembly of Ag and Au film on silica surfaces under kinetic and equilibrium conditions are distinguished by correlating real-time T-UV spectroscopy with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) measurements. The characterization suggests that four previously unrecognized time-dependent physicochemical regimes occur during consecutive EL deposition of silver (Ag) and Au onto tin-sensitized silica surfaces: self-limiting Ag activation; transitory Ag NP formation; transitional Au-Ag alloy formation during galvanic replacement of Ag by Au; and uniform morphology formation under

  14. Palladium/kieselguhr composition and method

    DOEpatents

    Mosley, W.C. Jr.

    1993-09-28

    A hydrogen-absorbing composition and method for making such a composition are described. The composition comprises a metal hydride, preferably palladium, deposited onto a porous substrate such as kieselguhr, for use in hydrogen-absorbing processes. The composition is made by immersing a substrate in a concentrated solution containing palladium, such as tetra-amine palladium nitrate. Palladium from the solution is deposited onto the porous substrate, which is preferably in the form of kieselguhr particles. The substrate is then removed from the solution, calcined, and heat treated. This process is repeated until the desired amount of palladium has been deposited onto the substrate.

  15. Palladium/kieselguhr composition and method

    DOEpatents

    Mosley, Jr., Wilbur C.

    1993-01-01

    A hydrogen-absorbing composition and method for making such a composition. The composition comprises a metal hydride, preferably palladium, deposited onto a porous substrate such as kieselguhr, for use in hydrogen-absorbing processes. The composition is made by immersing a substrate in a concentrated solution containing palladium, such as tetra-amine palladium nitrate. Palladium from the solution is deposited onto the porous substrate, which is preferably in the form of kieselguhr particles. The substrate is then removed from the solution, calcined, and heat treated. This process is repeated until the desired amount of palladium has been deposited onto the substrate.

  16. Laccases as palladium oxidases.

    PubMed

    Mekmouche, Yasmina; Schneider, Ludovic; Rousselot-Pailley, Pierre; Faure, Bruno; Simaan, A Jalila; Bochot, Constance; Réglier, Marius; Tron, Thierry

    2015-02-01

    The first example of a coupled catalytic system involving an enzyme and a palladium(ii) catalyst competent for the aerobic oxidation of alcohol in mild conditions is described. In the absence of dioxygen, the fungal laccase LAC3 is reduced by a palladium(0) species as evidenced by the UV/VIS and ESR spectra of the enzyme. During the oxidation of veratryl alcohol performed in water, at room temperature and atmospheric pressure, LAC3 regenerates the palladium catalyst, is reduced and catalyzes the four-electron reduction of dioxygen into water with no loss of enzyme activity. The association of a laccase with a water-soluble palladium complex results in a 7-fold increase in the catalytic efficiency of the complex. This is the first step in the design of a family of renewable palladium catalysts for aerobic oxidation.

  17. Interaction of palladium ions with the skin.

    PubMed

    Santucci, B; Cristaudo, A; Cannistraci, C; Picardo, M

    1995-08-01

    87 subjects sensitive to both nickel sulfate and palladium-chloride pet., were contemporaneously patch retested to nickel sulfate 5% pet., metallic palladium chloride 1% pet. and to palladium chloride 1% aq. Whilst all subjects reacted to nickel sulfate and palladium chloride pet., only 3 reacted to palladium chloride aq. No positive reactions were found to metallic palladium. The negative results to palladium chloride aq. are probably due to the formation of a new palladium ion (PdCl4)2-, achieved on adding an amount of hydrocloric acid to the aqueous solution of PdCl2. The findings seem to demonstrate that the allergic reaction to palladium depends on the arrangement of the metal electrons. The sensitization to palladium does not seem to be dependent on the element itself but on the complexes formed by the different compounds. The concomitant reactions to nickel and palladium ions could be dependent on the generation of similar complexes between the ions and the skin proteins.

  18. Computational investigation of single-wall carbon nanotube functionalized with palladium nanoclusters as hydrogen sulfide gas sensor

    NASA Astrophysics Data System (ADS)

    Bagherzadeh-Nobari, S.; Hosseini-Istadeh, K.; Kalantarinejad, R.; Elahi, S. M.; Shokri, A. A.

    2018-03-01

    Our aim is to study theoretically, the sensitivity of a hydrogen sulfide gas sensor, with regard to electrical conductance behavior. Our senor consists of a semiconductor single-wall carbon nanotube (SWCNT), functionalized with palladium nanoclusters, sandwiched between two gold electrodes. Initially, we have computed the optimized structure of the sensor, via molecular dynamic simulations. Then by using non-equilibrium Green's function method, combined with density functional theory, the electronic and transport properties of the sensor were calculated, and compared before and after adsorption of H2S gas, at different bias voltages. The highest sensitivity is achieved at 40 mV bias voltage. In this bias voltage, H2S gas adsorption causes a significant decrease of current, because as a result of charge transfer from the CNT and palladium nanoclusters, to H2S gas, majority carriers (electrons) decrease. The results show that CNT decorated with palladium nanoclusters can be a promising candidate in gas-sensorics.

  19. Alloy-assisted deposition of three-dimensional arrays of atomic gold catalyst for crystal growth studies

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

    Fang, Yin; Jiang, Yuanwen; Cherukara, Mathew J.

    Large-scale assembly of individual atoms over smooth surfaces is difficult to achieve. A configuration of an atom reservoir, in which individual atoms can be readily extracted, may successfully address this challenge. In this work, we demonstrate that a liquid gold-silicon alloy established in classical vapor-liquid-solid growth can deposit ordered and three-dimensional rings of isolated gold atoms over silicon nanowire sidewalls. Here, we perform ab initio molecular dynamics simulation and unveil a surprising single atomic gold-catalyzed chemical etching of silicon. Experimental verification of this catalytic process in silicon nanowires yields dopant-dependent, massive and ordered 3D grooves with spacing down to similarmore » to 5 nm. Finally, we use these grooves as self-labeled and ex situ markers to resolve several complex silicon growths, including the formation of nodes, kinks, scale-like interfaces, and curved backbones.« less

  20. Alloy-assisted deposition of three-dimensional arrays of atomic gold catalyst for crystal growth studies

    DOE PAGES

    Fang, Yin; Jiang, Yuanwen; Cherukara, Mathew J.; ...

    2017-12-08

    Large-scale assembly of individual atoms over smooth surfaces is difficult to achieve. A configuration of an atom reservoir, in which individual atoms can be readily extracted, may successfully address this challenge. In this work, we demonstrate that a liquid gold-silicon alloy established in classical vapor-liquid-solid growth can deposit ordered and three-dimensional rings of isolated gold atoms over silicon nanowire sidewalls. Here, we perform ab initio molecular dynamics simulation and unveil a surprising single atomic gold-catalyzed chemical etching of silicon. Experimental verification of this catalytic process in silicon nanowires yields dopant-dependent, massive and ordered 3D grooves with spacing down to similarmore » to 5 nm. Finally, we use these grooves as self-labeled and ex situ markers to resolve several complex silicon growths, including the formation of nodes, kinks, scale-like interfaces, and curved backbones.« less

  1. Morphologic evolution and optical properties of nanostructured gold based on mesoporous silica

    NASA Astrophysics Data System (ADS)

    Kan, Caixia; Cai, Weiping; Li, Cuncheng; Fu, Ganhua; Zhang, Lide

    2004-11-01

    In this paper, we report the morphologic evolution and optical properties of nanostructured gold dispersed in monolithic mesoporous silica induced by soaking the silica into a HAuCl4 aqueous solution and subsequent treatments. It has been shown that the morphology of nanostructured Au depends on the subsequent treatments after soaking. If the HAuCl4-soaked mesoporous silica was dried at <100°C for enough time (>10h) and annealed at <300°C without any special reduction treatment, Au nanowires/silica assembly can be formed. Corresponding optical-absorption spectra exhibit a broad absorption band around 1000nm. Subsequent step annealing from 300°C to 800°C results in a blueshift of the absorption band down to the visible region, accompanied by a decrease of the bandwidth. The corresponding morphology of the nanostructured Au evolves from the wire, rodlike to a spherical shape. This means that we can control the optical properties of this assembly in a large region by such a simple way. Further experiments reveal that the pore walls of silica have significant reduction effect on AuCl4- ions at a low temperature (<100°C). The interconnected channels in the silica host and drying at <100°C for enough time after soaking are crucial to form such Au nanowire/silica assembly and hence to show tunable optical properties by subsequent step annealing. Not a single one of these conditions can be dispensed with. Otherwise, direct annealing the soaked monolithic silica at a high temperature (>300°C) or treating the soaked porous silica powders only leads to nearly spherical Au nanoparticles highly dispersed in silica, accompanying a normal surface plasmon resonance of Au around 540nm. It has been confirmed that the surface-mediated reducing groups (≡Si -OH) on the silica pore wall are responsible for the low-temperature reduction of Au3+ ions. The formation of the Au nanowires is attributed to the low nucleation rate, unidirectional diffusion of Au atoms along the pore

  2. The relationship between structure and magnetic properties in ultra-fine grained/nanostructured FePd alloys

    NASA Astrophysics Data System (ADS)

    Okumura, Hideyuki

    In this study, the magnetic behavior including coercivity and the magnetic phase transition (ferromagnetic ↔ paramagnetic) and related phenomena were qualitatively and quantitatively investigated in ultra-fine grained/nanostructured FePd permanent magnet alloys, in relation to the microstructure and defect structure, and the results were compared with bulk FePd. Most of the alloy specimens investigated were in the form of epoxybonded magnets or isostatically-pressed pellets, formed from powders which were produced with high energy ball milling. Some results of thin films and ribbons produced with sputtering and melt-spinning, respectively, are also included in this thesis. Characterization of the materials was performed by using X-ray diffraction techniques with texture measurement, transmission electron microscopy with Lorentz microscopy, scanning electron microscopy with EDS analysis, optical microscopy and vibrating sample magnetometry. X-ray line broadening analysis was utilized for the quantitative characterization of the nanoscale microstructure, and it was found that the Cauchy-Gaussian profile assumption best describes the broadening data. Enhanced coercivities ˜10 times those of the bulk FePd obtained using conventional heat treatments were explained as the result of statistical (stochastic) unpinning of interaction domain walls out of the potential well at the grain boundary, and there is also an additional effect ascribed to an increase of the magnetocrystalline anisotropy, which is mainly due to the metastable c/a ratio of the nanostructured ordered phase and possibly to stress anisotropy. At the same time, there is also a decrease of the coercivity for smaller grain sizes because of the "magnetically soft" grain boundary phase. A semi-quantitative theoretical model is proposed, which includes the effect of exchange coupling between the ordered grains. The so-called Kronmuller analysis based on the wall pinning model was self-consistent, supporting

  3. Surface-enhanced Raman scattering of amorphous TiO2 thin films by gold nanostructures: Revealing first layer effect with thickness variation

    NASA Astrophysics Data System (ADS)

    Degioanni, S.; Jurdyc, A.-M.; Bessueille, F.; Coulm, J.; Champagnon, B.; Vouagner, D.

    2013-12-01

    In this paper, amorphous titanium dioxide (TiO2) thin films have been deposited on a commercially available Klarite substrate using the sol-gel process to produce surface-enhanced Raman scattering (SERS). The substrate consists of square arrays of micrometer-sized pyramidal pits in silicon with a gold coating. Several thin TiO2 layers have been deposited on the surface to study the influence of film thickness. Ultimately, we obtained information on SERS of an amorphous TiO2 layer by gold nanostructures, whose range is less than a few nanometers. Mechanisms responsible for the enhancement are the product of concomitant chemical and electromagnetic effects with an important contribution from plasmon-induced charge transfer.

  4. Two-Photon Vibrational Spectroscopy using local optical fields of gold and silver nanostructures

    NASA Astrophysics Data System (ADS)

    Kneipp, Katrin; Kneipp, Janina; Kneipp, Harald

    2007-03-01

    Spectroscopic effects can be strongly affected when they take place in the immediate vicinity of metal nanostructures due to coupling to surface plasmons. We introduce a new approach that suggests highly efficient two-photon labels as well as two-photon vibrational spectroscopy for non-destructive chemical probing. The underlying spectroscopic effect is the incoherent inelastic scattering of two photons on the vibrational quantum states performed in the enhanced local optical fields of gold nanoparticles, surface enhanced hyper Raman scattering (SEHRS). We infer effective two-photon cross sections for SEHRS on the order of 10^5 GM, similar or higher than the best known cross sections for two-photon fluorescence. SEHRS combines the advantages of two-photon spectroscopy with the structural information of vibrational spectroscopy, and the high sensitivity and nanometer-scale local confinement of plasmonics-based spectroscopy.

  5. 21 CFR 872.3350 - Gold or stainless steel cusp.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Gold or stainless steel cusp. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel cusp. (a) Identification. A gold or stainless steel cusp is a prefabricated device made of austenitic alloys or alloys...

  6. 21 CFR 872.3350 - Gold or stainless steel cusp.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Gold or stainless steel cusp. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel cusp. (a) Identification. A gold or stainless steel cusp is a prefabricated device made of austenitic alloys or alloys...

  7. 21 CFR 872.3350 - Gold or stainless steel cusp.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Gold or stainless steel cusp. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel cusp. (a) Identification. A gold or stainless steel cusp is a prefabricated device made of austenitic alloys or alloys...

  8. 21 CFR 872.3350 - Gold or stainless steel cusp.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Gold or stainless steel cusp. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel cusp. (a) Identification. A gold or stainless steel cusp is a prefabricated device made of austenitic alloys or alloys...

  9. 21 CFR 872.3350 - Gold or stainless steel cusp.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Gold or stainless steel cusp. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel cusp. (a) Identification. A gold or stainless steel cusp is a prefabricated device made of austenitic alloys or alloys...

  10. Low energy milling method, low crystallinity alloy, and negative electrode composition

    DOEpatents

    Le, Dihn B; Obrovac, Mark N; Kube, Robert Y; Landucci, James R

    2012-10-16

    A method of making nanostructured alloy particles includes milling a millbase in a pebble mill containing milling media. The millbase comprises: (i) silicon, and (ii) at least one of carbon or a transition metal, and wherein the nanostructured alloy particles are substantially free of crystalline domains greater than 50 nanometers in size. A method of making a negative electrode composition for a lithium ion battery including the nanostructured alloy particles is also disclosed.

  11. Degradation of TATP, TNT, and RDX using mechanically alloyed metals

    NASA Technical Reports Server (NTRS)

    Geiger, Cherie (Inventor); Sigman, Michael (Inventor); Fidler, Rebecca (Inventor); Clausen, Christian (Inventor)

    2012-01-01

    Bimetallic alloys prepared in a ball milling process, such as iron nickel (FeNi), iron palladium (FePd), and magnesium palladium (MgPd) provide in situ catalyst system for remediating and degrading nitro explosive compounds. Specifically, munitions, such as, 2,4,6-trinitrotoluene (TNT), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), nitrocellulose and nitroglycerine that have become contaminants in groundwater, soil, and other structures are treated on site to remediate explosive contamination.

  12. Not All That Glitters is Gold: Gold Imitations in History.

    PubMed

    Karpenko, Vladimír

    2007-07-01

    When gold became considered as a precious metal for decorative purposes and later for coinage, attempts at producing imitations soon began to appear. There were two motives behind this activity: to make a metal that could pass as gold, and to quite openly imitate this precious metal for people who could not afford true gold. Imitation gold was produced by metallurgists, and later also by alchemists. This paper is about gold imitations that did not contain any precious metal. Gold-like alloys of silver are thus excluded. An attempt is further undertaken to classify into separate groups the various gold imitations that have appeared in different cultures throughout time, with an emphasis on brass as a typical imitation of gold.

  13. The role of processing route on the microstructure of 14YWT nanostructured ferritic alloy

    DOE PAGES

    Mazumder, B.; Parish, C. M.; Bei, H.; ...

    2015-06-03

    Nanostructured ferritic alloys (NFAs) have outstanding high temperature creep properties and extreme tolerance to radiation damage. To achieve these properties, NFAs are fabricated by mechanical alloying of metallic and yttria powders. Atom probe tomography has demonstrated that milling times of at least 40 h are required to produce a uniform distribution of solutes in the flakes. After milling and hot extrusion, the microstructure consists of -Fe, high number densities of Ti-Y-O-vacancy-enriched nanoclusters, and coarse Y2Ti2O7 and Ti(O,C,N) precipitates on the grain boundaries. In contrast, the as-cast condition consists of -Fe with 50-100 m irregularly-shaped Y2Ti2O7 pyrochlore precipitates with smaller embeddedmore » precipitates with the Al5Y3O12 (yttrium-aluminum garnet) crystal structure indicating that this traditional processing route is not a viable approach to achieve the desired microstructure. The nano-hardnesses were also substantially different, i.e., 4 and 8 GPa for the as-cast and as-extruded conditions, respectively. These differences can be explained by the differences in the microstructure and the effects of the high vacancy content introduced by mechanical alloying, and the strong binding energy of vacancies with O, Ti, and Y atoms retarding diffusion.« less

  14. Fluorometric imaging methods for palladium and platinum and the use of palladium for imaging biomolecules.

    PubMed

    Tracey, Matthew P; Pham, Dianne; Koide, Kazunori

    2015-07-21

    Neither palladium nor platinum is an endogenous biological metal. Imaging palladium in biological samples, however, is becoming increasingly important because bioorthogonal organometallic chemistry involves palladium catalysis. In addition to being an imaging target, palladium has been used to fluorometrically image biomolecules. In these cases, palladium species are used as imaging-enabling reagents. This review article discusses these fluorometric methods. Platinum-based drugs are widely used as anticancer drugs, yet their mechanism of action remains largely unknown. We discuss fluorometric methods for imaging or quantifying platinum in cells or biofluids. These methods include the use of chemosensors to directly detect platinum, fluorescently tagging platinum-based drugs, and utilizing post-labeling to elucidate distribution and mode of action.

  15. Stable and Efficient CuO Based Photocathode through Oxygen-Rich Composition and Au-Pd Nanostructure Incorporation for Solar-Hydrogen Production.

    PubMed

    Masudy-Panah, Saeid; Siavash Moakhar, Roozbeh; Chua, Chin Sheng; Kushwaha, Ajay; Dalapati, Goutam Kumar

    2017-08-23

    Enhancing stability against photocorrosion and improving photocurrent response are the main challenges toward the development of cupric oxide (CuO) based photocathodes for solar-driven hydrogen production. In this paper, stable and efficient CuO-photocathodes have been developed using in situ materials engineering and through gold-palladium (Au-Pd) nanoparticles deposition on the CuO surface. The CuO photocathode exhibits a photocurrent generation of ∼3 mA/cm 2 at 0 V v/s RHE. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis and X-ray spectroscopy (XPS) confirm the formation of oxygen-rich (O-rich) CuO film which demonstrates a highly stable photocathode with retained photocurrent of ∼90% for 20 min. The influence of chemical composition on the photocathode performance and stability has been discussed in detail. In addition, O-rich CuO photocathodes deposited with Au-Pd nanostructures have shown enhanced photoelectrochemical performance. Linear scan voltammetry characteristic shows ∼25% enhancement in photocurrent after Au-Pd deposition and reaches ∼4 mA/cm 2 at "0" V v/s RHE. Hydrogen evolution rate significantly depends on the elemental composition of CuO and metal nanostructure. The present work has demonstrated a stable photocathode with high photocurrent for visible-light-driven water splitting and hydrogen production.

  16. Comparing nanostructured hydroxyapatite coating on AZ91 alloy samples via sol-gel and electrophoretic deposition for biomedical applications.

    PubMed

    Rojaee, Ramin; Fathi, Mohammadhossein; Raeissi, Keyvan

    2014-12-01

    Magnesium is one of the most critical elements in hard tissues regeneration and therefore causes speeding up the restoration of harmed bones, while high deterioration rate of magnesium in body fluid restricts it to be used as biodegradable implants. Alloying magnesium with some relatively nobler metals such as aluminium, zinc, rare earth elements, magnesium-bioceramics composites, and surface modification techniques are some of the routes to control magnesium corrosion rate. In this study AZ91 magnesium alloy had been coated by nanostructured hydroxyapatite via sol-gel dip coating and electrophoretical methods to survey the final barricade properties of the obtained coatings. In order to perform electrophoretic coating, powders were prepared by sol-gel method, and then the powders deposited on substrates utilizing direct current electricity. Zeta potentials of the electrophoresis suspensions were measured to determine a best mode for good quality coatings. Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM) were used to confirm nanoscale dimension, and the uniformity of the nanostructured hydroxyapatite coating, respectively. Fourier Transform-Infrared and X-ray diffraction analysis were utilized for functional group and phase structure evaluation of the prepared coatings, correspondingly. Electrochemical corrosion tests were performed in SBF at 37±1 (°)C which revealed considerable increase in corrosion protection resistivity and corrosion current density for electrophoretic coated specimens versus sol-gel coated specimens. Results showed that both sol-gel and electrophoretical techniques seem to be suitable to coat magnesium alloys for biomedical applications but electrophoretic coating technique is a better choice due to the more homogeneity and more crystalline structure of the coating.

  17. Large-scale atomistic simulations of helium-3 bubble growth in complex palladium alloys

    DOE PAGES

    Hale, Lucas M.; Zimmerman, Jonathan A.; Wong, Bryan M.

    2016-05-18

    Palladium is an attractive material for hydrogen and hydrogen-isotope storage applications due to its properties of large storage density and high diffusion of lattice hydrogen. When considering tritium storage, the material’s structural and mechanical integrity is threatened by both the embrittlement effect of hydrogen and the creation and evolution of additional crystal defects (e.g., dislocations, stacking faults) caused by the formation and growth of helium-3 bubbles. Using recently developed inter-atomic potentials for the palladium-silver-hydrogen system, we perform large-scale atomistic simulations to examine the defect-mediated mechanisms that govern helium bubble growth. Our simulations show the evolution of a distribution of materialmore » defects, and we compare the material behavior displayed with expectations from experiment and theory. In conclusion, we also present density functional theory calculations to characterize ideal tensile and shear strengths for these materials, which enable the understanding of how and why our developed potentials either meet or confound these expectations.« less

  18. Platinum and palladium nano-structured catalysts for polymer electrolyte fuel cells and direct methanol fuel cells.

    PubMed

    Long, Nguyen Viet; Thi, Cao Minh; Yong, Yang; Nogami, Masayuki; Ohtaki, Michitaka

    2013-07-01

    In this review, we present the synthesis and characterization of Pt, Pd, Pt based bimetallic and multi-metallic nanoparticles with mixture, alloy and core-shell structure for nano-catalysis, energy conversion, and fuel cells. Here, Pt and Pd nanoparticles with modified nanostructures can be controllably synthesized via chemistry and physics for their uses as electro-catalysts. The cheap base metal catalysts can be studied in the relationship of crystal structure, size, morphology, shape, and composition for new catalysts with low cost. Thus, Pt based alloy and core-shell catalysts can be prepared with the thin Pt and Pt-Pd shell, which are proposed in low and high temperature proton exchange membrane fuel cells (PEMFCs), and direct methanol fuel cells (DMFCs). We also present the survey of the preparation of Pt and Pd based catalysts for the better catalytic activity, high durability, and stability. The structural transformations, quantum-size effects, and characterization of Pt and Pd based catalysts in the size ranges of 30 nm (1-30 nm) are presented in electro-catalysis. In the size range of 10 nm (1-10 nm), the pure Pt catalyst shows very large surface area for electro-catalysis. To achieve homogeneous size distribution, the shaped synthesis of the polyhedral Pt nanoparticles is presented. The new concept of shaping specific shapes and morphologies in the entire nano-scale from nano to micro, such as polyhedral, cube, octahedra, tetrahedra, bar, rod, and others of the nanoparticles is proposed, especially for noble and cheap metals. The uniform Pt based nanosystems of surface structure, internal structure, shape, and morphology in the nanosized ranges are very crucial to next fuel cells. Finally, the modifications of Pt and Pd based catalysts of alloy, core-shell, and mixture structures lead to find high catalytic activity, durability, and stability for nano-catalysis, energy conversion, fuel cells, especially the next large-scale commercialization of next

  19. Palladium and platinum based solid and hollow nanoparticles: An ab-initio study of structural and electronic properties

    NASA Astrophysics Data System (ADS)

    Yildizhan, Gulsum; Caliskan, Serkan; Ozturk, Ramazan

    2018-04-01

    Nanoparticles composed of palladium and platinum are particularly interesting for catalytic purposes, for instance, selective hydrogenation and alcohol oxidation. The reactivity and selectivity of nanostructures are mostly based on the size and shape of the nanocrystals in catalytic reactions. In this work, we studied the structural stabilities of Pd and Pt based nanocubes and nanocages and adsorption strength of chemisorbed species on these nanostructures to investigate their structure dependent catalytic activities. Solid cubic and hollow cage like nanostructures of different sizes were designed with Pd and Pt atoms. The volume of the crystal cavity in nanocage structures was tuned by removing of atoms from solid cubic structure. The effect of size and shape on the formation energies and HOMO-LUMO energy gap of nanostructures were elucidated and correlated to structural stabilities, hardness-softness, electronegativity and electrophilicity index. The relationship between size and chemical reactivity clearly showed that increasing the number of atoms participating in a catalyst enhances the activity. For further understanding of the catalytic activity we employed 4-nitro thiophenol, as an S-donor representative molecule, to evaluate the adsorption characteristics of the nanostructures.

  20. Orthogonal chemical functionalization of patterned gold on silica surfaces

    PubMed Central

    Léonard, Didier; Le Mogne, Thierry; Zuttion, Francesca; Chevalier, Céline; Phaner-Goutorbe, Magali; Souteyrand, Éliane

    2015-01-01

    Summary Single-step orthogonal chemical functionalization procedures have been developed with patterned gold on silica surfaces. Different combinations of a silane and a thiol were simultaneously deposited on a gold/silica heterogeneous substrate. The orthogonality of the functionalization (i.e., selective grafting of the thiol on the gold areas and the silane on the silica) was demonstrated by X-ray photoelectron spectroscopy (XPS) as well as time-of-flight secondary ion mass spectrometry (ToF–SIMS) mapping. The orthogonal functionalization was used to immobilize proteins onto gold nanostructures on a silica substrate, as demonstrated by atomic force microscopy (AFM). These results are especially promising in the development of future biosensors where the selective anchoring of target molecules onto nanostructured transducers (e.g., nanoplasmonic biosensors) is a major challenge. PMID:26734519

  1. Electrogenerative gold recovery from cyanide solutions using a flow-through cell with activated reticulated vitreous carbon.

    PubMed

    Yap, Chin Yean; Mohamed, Norita

    2008-10-01

    An electrogenerative flow-through reactor with an activated reticulated vitreous carbon cathode was developed. The influence of palladium-tin activation of the cathode towards gold deposition was studied by cyclic voltammetry. The reactor proved to be efficient in recovering more than 99% of gold within 4 h of operation. The performance of the reactor was evaluated with initial gold concentrations of 10, 100 and 500 mg L-1 and various electrolyte flow rates. Gold recovery was found to be strongly dependent on electrolyte flow rate and initial gold concentration in the cyanide solution under the experimental conditions used.

  2. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    DOE PAGES

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; ...

    2016-02-19

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for twomore » interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. Lastly, the co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.« less

  3. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    PubMed Central

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

    2016-01-01

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications. PMID:26892834

  4. Design of Janus nanoparticles with atomic precision: tungsten-doped gold nanostructures.

    PubMed

    Sun, Qiang; Wang, Qian; Jena, Puru; Kawazoe, Yoshiyuki

    2008-02-01

    Janus nanoparticles, characterized by their anisotropic structure and interactions, have added a new dimension to nanoscience because of their potential applications in biomedicine, sensors, catalysis, and assembled materials. The technological applications of these nanoparticles, however, have been limited as the current chemical, physical, and biosynthetic methods lack sufficient size and shape selectivity. We report a technique where gold clusters doped with tungsten can serve as a seed that facilitates the natural growth of anisotropic nanostructures whose size and shape can be controlled with atomic precision. Using ab initio simulated annealing and molecular dynamics calculations on AunW (n > 12) clusters, we discovered that the W@Au12 cage cluster forms a very stable core with the remaining Au atoms forming patchy structures on its surface. The anisotropic geometry gives rise to anisotropies in vibrational spectra, charge distributions, electronic structures, and reactivity, thus making it useful to have dual functionalities. In particular, the core-patch structure is shown to possess a hydrophilic head and a hydrophobic tail. The W@Au12 clusters can also be used as building blocks of a nanoring with novel properties.

  5. Implantation and growth of dendritic gold nanostructures on graphene derivatives: electrical property tailoring and Raman enhancement.

    PubMed

    Jasuja, Kabeer; Berry, Vikas

    2009-08-25

    Interfacing electron-rich metal nanoparticles with graphene derivatives can sensitively regulate the properties of the resultant hybrid with potential applications in metal-doped graphene field-effect transistors (FETs), surface-enhanced Raman spectroscopy, and catalysis. Here, we show that by controlling the rate of diffusion and catalytic reduction of gold ions on graphene oxide (GO), dendritic "snowflake-shaped" gold nanostructures (SFGNs) can be templated on graphene. The structural features of the SFGNs and their interfacing mechanism with GO were characterized by microscopic analysis and Raman-scattering. We demonstrate that (a) SFGNs grow on GO-surface via diffusion limited aggregation; (b) SFGN's morphology (dendritic to globular), size (diameter of 150-500 nm and a height of 45-55 nm), coverage density, and dispersion stability can be controlled by regulating the chemiophysical forces; (c) SFGNs enhance the Raman signal by 2.5 folds; and (d) SFGNs act as antireduction resist during GO-SFGN's chemical reduction. Further, the SFGNs interfacing with graphene reduces the apparent band gap (from 320 to 173 meV) and the Schottky barrier height (from 126 to 56 meV) of the corresponding FET.

  6. The effect of oxidizing water on metallic restorations in the mouth: in vitro reduction behavior of oxidizing water.

    PubMed

    Nishida, T

    1997-03-01

    Mouth-rinsing with oxydized water which contains electrolytically generated chlorine is known to hinder dental plaque formation and growth, but it also accelerates the deterioration of metallic restorations in the mouth. The present work consists of an in vitro study to elucidate the electrochemical reactions involved in the reduction of oxydized water on dental alloys through a systematic investigation of the potentiostatic polarization behavior of dental alloy electrodes. The five dental alloys selected for investigation were gold alloy, gold alloy containing platinum, silver-palladium-gold alloy, conventional amalgam and high copper amalgam. The corrosion potentials of all dental alloy electrodes were shown to be more noble in oxydized water than in 0.1N sodium chloride solution. The potential differences between the corrosion potentials were relatively small in the case of amalgam electrodes. The polarization curves for all of the dental alloy electrodes in oxydized water revealed reduction currents of chlorine, hypochlorous acid, dissolved oxygen and oxonium ion. The reduction of chlorine and hypochlorous acid started at a more noble potential than that of dissolved oxygen. The dental alloys studied, except the amalgams, did not dissolve excessively at the corrosion potentials in oxydized water.

  7. Oxidation of Palladium-Chromium Alloys for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Piltch, Nancy D.; Jih-Fen, Lei; Zeller, Mary V.

    1994-01-01

    An alloy consisting of Pd with 13 wt % Cr is a promising material for high temperature applications. High temperature performance is degraded by the oxidation of the material, which is more severe in the fine wires and thin films used for sensor applications than in the bulk. The present study was undertaken to improve our understanding of the physical and chemical changes occurring at these temperatures and to identify approaches to limit oxidation of the alloy. The alloy was studied in both ribbon and wire forms. Ribbon samples were chosen to examine the role of grain boundaries in the oxidation process because of the convenience of handling for the oxidation studies. Wire samples 25 microns in diameter which are used in resistance strain gages were studied to correlate chemical properties with observed electrical, physical, and structural properties. Overcoating the material with a metallic Cr film did prevent the segregation of Pd to the surface; however, it did not eliminate the oxidation of the alloy.

  8. Containerless low gravity processing of glass forming and immiscible alloys

    NASA Technical Reports Server (NTRS)

    Andrews, J. Barry; Briggs, Craig; Robinson, M. B.

    1990-01-01

    Under normal one-g conditions immiscible alloys segregate extensively during solidification due to sedimentation of the more dense of the immiscible liquid phases. Immiscible (hypermonotectic) gold-rhodium alloys were processed in the 100 meter drop tube under low gravity, containerless conditions to determine the feasibility of producing dispersed structures. Three alloy compositions were utilized. Alloys containing 10 percent by volume of the gold-rich hypermonotectic phase exhibited a tendency for the gold-rich liquid to wet the outer surface of the samples. This wetting tendency led to extensive segregation in several cases. Alloys containing 80 and 90 percent by volume of the gold-rich phase possessed completely different microstructures from the 10 percent samples when processed under low-g, containerless conditions. Several samples exhibited microstructures consisting of well dispersed 2 to 3 microns diameter rhodium-rich spheres in a gold-rich matrix.

  9. Demonstration of Ultra High-Strength Nanocrystalline Copper Alloys for Military Applications

    DTIC Science & Technology

    2012-01-22

    Powder Processing vi Acknowledgements The development of these Cu -Ta alloys was accomplished with assistance from the following...nanostructured Cu -Ta based alloy powders with a unique ability to retain their ultrahigh strength properties to temperatures nearing the melting point of the Cu ...nanostructured Cu -Ta based alloy powders with the unique ability to retain their ultrahigh strength properties to temperatures

  10. NEUTRON DIFFRACTION INVESTIGATIONS OF FERROMAGNETIC PALLADIUM AND IRON GROUP ALLOYS

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

    Cable, J.W.; Wollan, E.O.; Koehler, W.C.

    1962-03-01

    In order to account for the magnetic properties of alloys It becomes important to determine the individual magnetic moments of the constituent atoms. This determination can be accomplished by means of neutron diffraction and magnetic induction measurements. Such measurements are made on the ferromagnetic alloys Pd/sub 3/Fe, PdFe, Pd/sub 3/Co, PdCo, Ni/sub 3/Co, and NiCo. The average moment values are obtained from magnetic induction measurements while the differences in the atomic moments are determined from either the ferromagnetic diffuse scattering by the disordered alloys or the superlattice reflections by the ordered alloys. (auth)

  11. Preparation of nanostructured materials having improved ductility

    DOEpatents

    Zhao, Yonghao; Zhu, Yuntian T.

    2010-04-20

    A method for preparing a nanostructured aluminum alloy involves heating an aluminum alloy workpiece at temperature sufficient to produce a single phase coarse grained aluminum alloy, then refining the grain size of the workpiece at a temperature at or below room temperature, and then aging the workpiece to precipitate second phase particles in the nanosized grains of the workpiece that increase the ductility without decreasing the strength of the workpiece.

  12. Tunable Electromagnetic Coupling in Plasmonic Nanostructures Mediated by Thermoresponsive Polymer Brushes.

    PubMed

    Nguyen, Mai; Kanaev, Andrei; Sun, Xiaonan; Lacaze, Emmanuelle; Lau-Truong, Stéphanie; Lamouri, Aazdine; Aubard, Jean; Felidj, Nordin; Mangeney, Claire

    2015-11-24

    A smart and highly SERS-active plasmonic platform was designed by coupling regular arrays of nanotriangles to colloidal gold nanorods via a thermoresponsive polymer spacer (poly(N-isopropylacrylamide), PNIPAM). The substrates were prepared by combining a top-down and a bottom-up approach based on nanosphere lithography, surface-initiated controlled radical polymerization, and colloidal assembly. This multistep strategy provided regular hexagonal arrays of nanotriangles functionalized by polymer brushes and colloidal gold nanorods, confined exclusively on the nanotriangle surface. Interestingly, one could finely tune the gold nanorod impregnation on the polymer-coated nanostructures by adjusting the polymer layer thickness, leading to highly coupled plasmonic systems for intense SERS signal. Moreover, the thermoresponsive properties of the PNIPAM brushes could be wisely handled in order to monitor the SERS activity of the nanostructures coupled via this polymer spacer. The coupled hybrid plasmonic nanostructures designed in this work are therefore very promising smart platforms for the sensitive detection of analytes by SERS.

  13. Experimental and theoretical photoluminescence studies in nucleic acid assembled gold-upconverting nanoparticle clusters.

    PubMed

    He, Liangcan; Mao, Chenchen; Cho, Suehyun; Ma, Ke; Xi, Weixian; Bowman, Christopher N; Park, Wounjhang; Cha, Jennifer N

    2015-11-07

    Combinations of rare earth doped upconverting nanoparticles (UCNPs) and gold nanostructures are sought as nanoscale theranostics due to their ability to convert near infrared (NIR) photons into visible light and heat, respectively. However, because the large NIR absorption cross-section of the gold coupled with their thermo-optical properties can significantly hamper the photoluminescence of UCNPs, methods to optimize the ratio of gold nanostructures to UCNPs must be developed and studied. We demonstrate here nucleic acid assembly methods to conjugate spherical gold nanoparticles (AuNPs) and gold nanostars (AuNSs) to silica-coated UCNPs and probe the effect on photoluminescence. These studies showed that while UCNP fluorescence enhancement was observed from the AuNPs conjugated UCNPs, AuNSs tended to quench fluorescence. However, conjugating lower ratios of AuNSs to UCNPs led to reduced quenching. Simulation studies both confirmed the experimental results and demonstrated that the orientation and distance of the UCNP with respect to the core and arms of the gold nanostructures played a significant role in PL. In addition, the AuNS-UCNP assemblies were able to cause rapid gains in temperature of the surrounding medium enabling their potential use as a photoimaging-photodynamic-photothermal agent.

  14. Geometric effect on second harmonic generation from gold grating

    NASA Astrophysics Data System (ADS)

    Lu, Jiao; Ding, Baoyong; Huo, Yanyan; Ning, Tingyin

    2018-05-01

    We numerically investigate second harmonic generation from gold gratings of an ideal rectangular and ladder-shaped cross-section. The SHG efficiency from the gold gratings of the ladder-shaped cross-section is significantly enhanced compared with that from the ideal rectangular cross-section with a maximum enhancement factor of around two. The enhancement is ascribe to the nanostructure dependent local fundamental electric field, the nonlinear sources and thus the far field radiation. Our results have a practical meaning in the explanation of experimental SHG measurement, and the modulation of SHG response in the metallic nanostructure.

  15. Shape-controlled continuous synthesis of metal nanostructures

    NASA Astrophysics Data System (ADS)

    Sebastian, Victor; Smith, Christopher D.; Jensen, Klavs F.

    2016-03-01

    A segmented flow-based microreactor is used for the continuous production of faceted nanocrystals. Flow segmentation is proposed as a versatile tool to manipulate the reduction kinetics and control the growth of faceted nanostructures; tuning the size and shape. Switching the gas from oxygen to carbon monoxide permits the adjustment in nanostructure growth from 1D (nanorods) to 2D (nanosheets). CO is a key factor in the formation of Pd nanosheets and Pt nanocubes; operating as a second phase, a reductant, and a capping agent. This combination confines the growth to specific structures. In addition, the segmented flow microfluidic reactor inherently has the ability to operate in a reproducible manner at elevated temperatures and pressures whilst confining potentially toxic reactants, such as CO, in nanoliter slugs. This continuous system successfully synthesised Pd nanorods with an aspect ratio of 6; thin palladium nanosheets with a thickness of 1.5 nm; and Pt nanocubes with a 5.6 nm edge length, all in a synthesis time as low as 150 s.A segmented flow-based microreactor is used for the continuous production of faceted nanocrystals. Flow segmentation is proposed as a versatile tool to manipulate the reduction kinetics and control the growth of faceted nanostructures; tuning the size and shape. Switching the gas from oxygen to carbon monoxide permits the adjustment in nanostructure growth from 1D (nanorods) to 2D (nanosheets). CO is a key factor in the formation of Pd nanosheets and Pt nanocubes; operating as a second phase, a reductant, and a capping agent. This combination confines the growth to specific structures. In addition, the segmented flow microfluidic reactor inherently has the ability to operate in a reproducible manner at elevated temperatures and pressures whilst confining potentially toxic reactants, such as CO, in nanoliter slugs. This continuous system successfully synthesised Pd nanorods with an aspect ratio of 6; thin palladium nanosheets with a

  16. Synthesis of gold nanostructures with optical properties within the near-infrared window for biomedical applications

    NASA Astrophysics Data System (ADS)

    Garcia-Soto, Mariano de Jesus

    The work reported in this dissertation describes the design and synthesis of different gold nanoshells with strong absorption coefficients at the near-infrared region (NIR) of the spectrum, and includes preliminary studies of their use for the photo-induced heating of pancreatic cancer cells and ex vivo tissues. As the emphasis was on gold nanoshells with maximum extinctions located at 800 nm, the methods explored for their synthesis led us to the preparation of silica-core and hollow gold nanoshells of improved stability, with maximum extinctions at or beyond the targeted within the near-infrared window. The synthesis of silica-core gold nanoshells was investigated first given its relevance as one of the pioneering methods to produce gold nanostructures with strong absorption and scattering coefficients in the visible and the near-infrared regions of the spectrum. By using a classical method of synthesis, we explored the aging of the precursor materials and the effect of using higher concentrations than the customary for the reduction of gold during the shell growth. We found that the aging for one week of the as-prepared or purified precursors, namely, the gold cluster suspensions, and the seeded silica particles, along with higher concentrations of gold in the plating solution, produced fully coated nanoshells of 120 nm in size with smooth surfaces and maximum extinctions around 800 nm. Additional work carried out to reduce the time and steps in the synthesis of silica-core gold nanoshells, led us to improve the seeding step by increasing the ionic strength of the cluster suspension, and also to explore the growth of gold on tin-seeded silica nanoparticles. The synthesis of hollow gold nanoshells (HGS) of with maximum extinctions at the NIR via the galvanic replacement of silver nanoparticles for gold in solution was explored next. A first method explored led us to obtain HGS with maximum extinctions between 650 and 800 nm and sizes between 30 and 80 nm from

  17. Lowering coefficient of friction in Cu alloys with stable gradient nanostructures

    PubMed Central

    Chen, Xiang; Han, Zhong; Li, Xiuyan; Lu, K.

    2016-01-01

    The coefficient of friction (COF) of metals is usually high, primarily because frictional contacts induce plastic deformation underneath the wear surface, resulting in surface roughening and formation of delaminating tribolayers. Lowering the COF of metals is crucial for improving the reliability and efficiency of metal contacts in engineering applications but is technically challenging. Refining the metals’ grains to nanoscale cannot reduce dry-sliding COFs, although their hardness may be elevated many times. We report that a submillimeter-thick stable gradient nanograined surface layer enables a significant reduction in the COF of a Cu alloy under high-load dry sliding, from 0.64 (coarse-grained samples) to 0.29, which is smaller than the COFs of many ceramics. The unprecedented stable low COF stems from effective suppression of sliding-induced surface roughening and formation of delaminating tribolayer, owing to the stable gradient nanostructures that can accommodate large plastic strains under repeated sliding for more than 30,000 cycles. PMID:27957545

  18. Determination of palladium, platinum and rhodium in geologic materials by fire assay and emission spectrography

    USGS Publications Warehouse

    Hapfty, J.; Riley, L.B.

    1968-01-01

    A method is described for the determination of palladium down to 4ppb (parts per billion, 109), platinum down to 10 ppb and rhodium down to 5 ppb in 15 g of sample. Fire-assay techniques are used to preconcentrate the platinum metals into a gold bead, then the bead is dissolved in aqua regia and diluted to volume with 1M hydrochloric acid. The solution is analysed by optical emission spectrography of the residue from 200 ??l of it evaporated on a pair of flat-top graphite electrodes. This method requires much less sample handling than most published methods for these elements. Data are presented for G-1, W-1, and six new standard rocks of the U.S. Geological Survey. The values for palladium in W-1 are in reasonable agreement with previously published data. ?? 1968.

  19. Metal precursor induced shape controlled synthesis of gold nanostructures

    NASA Astrophysics Data System (ADS)

    Verma, Manoj; Kathy, Annu Dahiya; Kumar, P. Senthil

    2018-05-01

    Anisotropic gold nanoparticles have excellent properties which enables them to utilize in exciting applications in plasmonics as well as in nanophotonics, catalysis etc. In this report we have synthesized/tune shape of gold nanoparticles by utilizing in situ polymer halide interaction. Our quest for achieving shape control of gold nanoparticles succeeded even under ambient conditions by utilizing the mild but effective reducing power of versatile polymer, polyvinyl pyrrolidone(PVP) on different precursor more specifically on Hydrochloroauric acid and Potassiumbromoauric acid. The significant shape dependent optical plasmonic signature agrees in excellent manner with TEM observations as shown below. Moreover, as prepared gold nanocrystals having different morphology were studied with XRD measurements and a beautiful conclusion was drawn between crystallographic facets and shapes of gold nanoparticles.

  20. Formation and electronic properties of palladium hydrides and palladium-rhodium dihydride alloys under pressure.

    PubMed

    Yang, Xiao; Li, Huijian; Ahuja, Rajeev; Kang, Taewon; Luo, Wei

    2017-06-14

    We present the formation possibility for Pd-hydrides and Pd-Rh hydrides system by density functional theory (DFT) in high pressure upto 50 GPa. Calculation confirmed that PdH 2 in face-centered cubic (fcc) structure is not stable under compression that will decomposition to fcc-PdH and H 2 . But it can be formed under high pressure while the palladium is involved in the reaction. We also indicate a probably reason why PdH 2 can not be synthesised in experiment due to PdH is most favourite to be formed in Pd and H 2 environment from ambient to higher pressure. With Rh doped, the Pd-Rh dihydrides are stabilized in fcc structure for 25% and 75% doping and in tetragonal structure for 50% doping, and can be formed from Pd, Rh and H 2 at high pressure. The electronic structural study on fcc type Pd x Rh 1-x H 2 indicates the electronic and structural transition from metallic to semi-metallic as Pd increased from x = 0 to 1.

  1. The use of bipolar electrochemistry in nanoscience: Contact free methods for the site selective modification of nanostructured carbon materials

    NASA Astrophysics Data System (ADS)

    Ndungu, Patrick Gathura

    Bipolar electrochemistry occurs when an isolated conductive substrate inside an electric field supports both oxidation and reduction reactions. The method requires no direct contact between the power supply and the substrate. In the following thesis bipolar electrochemistry has been used to deposit palladium onto isolated graphite platelets, carbon nanofibers (CNF), and carbon nanotubes (CNT), as well as, various metals, a semiconductor, and an electropolymer on CNTs. Initial work used pulsed DC electric fields to deposit palladium onto isolated graphite platelets. Transmission electron microscopy (TEM) studies on the platelets found palladium metal on one area, indicative of a bipolar mechanism, and palladium deposits that varied from surface bound to highly ramified deposits. No correlation was found between the frequency used to prepare the deposits and the palladium metal dispersion. The same field intensities and frequencies used on the graphite platelets were used to produce CNFs with palladium on one tip. The amount of palladium deposited on one tip of a CNF was controlled by adjusting how long the electric field was applied. Preliminary experiments to produce bulk quantities of CNFs with palladium bipolar electrodeposits used CNFs ball milled with silica, and CNFs suspended in tetrahydrofuran or methylene chloride. The palladium content, measured by atomic absorption spectroscopy, of the functionalized CNFs in silica showed no difference with increased CNF loading; however, TEM studies found a small number of functionalized chloride used suspensions with high loadings of CNFs which led to small percentages of CNFs with bipolar electrodeposited palladium. Finally CNTs obtained commercially and CNTs grown using chemical vapor deposition were successfully functionalized using bipolar electrodeposition. These experiments demonstrate a reliable and controlled method to modify nanostructured materials.

  2. Synthesis of palladium@gold nanoalloys/nitrogen and sulphur-functionalized multiple graphene aerogel for electrochemical detection of dopamine.

    PubMed

    Li, Ruiyi; Yang, Tingting; Li, Zaijun; Gu, Zhiguo; Wang, Guangli; Liu, Junkang

    2017-02-15

    Integration of noble metal nanomaterials on graphene nanosheets potentially paves one way to improve their electronic, chemical and electrochemical properties. The study reported synthesis of palladium@gold nanoalloys/nitrogen and sulphur-functionalized multiple graphene aerogel composite (Pd@Au/N,S-MGA). The as-prepared composite offers a well-defined three-dimensional architecture with rich of mesopores. The Pd@Au nanoalloys were dispersed on the graphene framework networks and their active sites were fully exposed. The unique structure achieves to ultra high electron/ion conductivity, electrocatalytic activity and structural stability. The sensor based on the Pd@Au/N,S-MGA creates ultrasensitive electrochemical response towards dopamine due to significantly electrochemical synergy between Pd, Au and N,S-MGA. Its differential pulse voltammetric signal linearly increases with the increase of dopamine concentration in the range from 1.0 × 10 -9  M to 4.0 × 10 -5  M with the detection limit of 3.6 × 10 -10  M (S/N = 3). The analytical method provides the advantage of sensitivity, reproducibility, rapidity and long-term stability. It has been successfully applied in the detection of trace dopamine in biological samples. The study also opens a window on the electronic properties of graphene aerogel and metal nanomaterials as well their nanohybrids to meet needs of further applications as nanoelectronics in diagnosis, bioanalysis and catalysis. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Analysis and characterization of Cu2CdSnS4 quaternary alloy nanostructures deposited on GaN

    NASA Astrophysics Data System (ADS)

    Odeh, Ali Abu; Al-Douri, Y.; Ameri, M.; Bouhemadou, A.

    2018-06-01

    Through using spin coating technique, Cu2CdSnS4 (CCTS) quaternary alloy nanostructures were successfully deposited on GaN substrate using a wide range of spin coating speeds; 1500, 2000, 2500, 3000 and 3500 RPM at annealing temperature 300 °C. The optical properties were investigated through UV-vis which revealed the changing of energy band gap as the spin coating speed increases, in addition, to verify specific models of refractive index and optical dielectric constant. The structural properties were studied by X-ray diffraction which indicated that the number and intensity of the peaks were changed as the spin coating speed changes. The morphological and topographical studies of CCTS were elaborated by field emission-scanning electron microscopy and atomic force microscopy. The obtained results suggest that CCTS nanostructures deposited on GaN substrate are very suitable for optoelectronic applications, that are in accordance with the available theoretical and experimental data.

  4. Development and Characterization of Improved NiTiPd High-Temperature Shape-Memory Alloys by Solid-Solution Strengthening and Thermomechanical Processing

    NASA Technical Reports Server (NTRS)

    Bigelow, Glen; Noebe, Ronald; Padula, Santo, II; Garg, Anita; Olson, David

    2006-01-01

    The need for compact, solid-state actuation systems for use in the aerospace, automotive, and other transportation industries is currently motivating research in high-temperature shape-memory alloys (HTSMA) with transformation temperatures greater than 100 C. One of the basic high-temperature alloys investigated to fill this need is Ni(19.5)Ti(50.5)Pd30. Initial testing has indicated that this alloy, while having acceptable work characteristics, suffers from significant permanent deformation (or ratcheting) during thermal cycling under load. In an effort to overcome this deficiency, various solid-solution alloying and thermomechanical processing schemes were investigated. Solid-solution strengthening was achieved by substituting 5at% gold or platinum for palladium in Ni(19.5)Ti(50.5)Pd30, the so-called baseline alloy, to strengthen the martensite and austenite phases against slip processes and improve thermomechanical behavior. Tensile properties, work behavior, and dimensional stability during repeated thermal cycling under load for the ternary and quaternary alloys were compared. The relative difference in yield strength between the martensite and austenite phases and the dimensional stability of the alloy were improved by the quaternary additions, while work output was only minimally impacted. The three alloys were also thermomechanically processed by cycling repeatedly through the transformation range under a constant stress. This so-called training process dramatically improved the dimensional stability in these samples and also recovered the slight decrease in work output caused by quaternary alloying. An added benefit of the solid-solution strengthening was maintenance of enhanced dimensional stability of the trained material to higher temperatures compared to the baseline alloy, providing a greater measure of over-temperature capability.

  5. Liquid metal ion source and alloy for ion emission of multiple ionic species

    DOEpatents

    Clark, Jr., William M.; Utlaut, Mark W.; Wysocki, Joseph A.; Storms, Edmund K.; Szklarz, Eugene G.; Behrens, Robert G.; Swanson, Lynwood W.; Bell, Anthony E.

    1987-06-02

    A liquid metal ion source and alloy for the simultaneous ion evaporation of arsenic and boron, arsenic and phosphorus, or arsenic, boron and phosphorus. The ionic species to be evaporated are contained in palladium-arsenic-boron and palladium-arsenic-boron-phosphorus alloys. The ion source, including an emitter means such as a needle emitter and a source means such as U-shaped heater element, is preferably constructed of rhenium and tungsten, both of which are readily fabricated. The ion sources emit continuous beams of ions having sufficiently high currents of the desired species to be useful in ion implantation of semiconductor wafers for preparing integrated circuit devices. The sources are stable in operation, experience little corrosion during operation, and have long operating lifetimes.

  6. Cu assisted synthesis of self-supported PdCu alloy nanowires with enhanced performances toward ethylene glycol electrooxidation

    NASA Astrophysics Data System (ADS)

    Yan, Bo; Xu, Hui; Zhang, Ke; Li, Shujin; Wang, Jin; Shi, Yuting; Du, Yukou

    2018-03-01

    Self-supported PdCu alloy nanowires fabricated by a facile one-pot method have been reported, which copper assists in the morphological transformation from graininess to nanowires. The copper incorporated with palladium to form alloy structures cannot only cut down the usage of noble metal but also enhance their catalytic performances. The catalysts with self-supported structure and proper ratio of palladium to copper show great activity and long-term stability for the electrooxidation of ethylene glycol in alkaline solution. Especially for Pd43Cu57, its mass activity reaches to 5570.83 mA mg-1, which is 3.12 times as high as commercial Pd/C. This study highlights an accessible strategy to prepare self-supported PdCu alloy nanowires and their potential applications in renewable energy fields.

  7. Synthesis and pH-dependent assembly of isotropic and anisotropic gold nanoparticles functionalized with hydroxyl-bearing amino acids

    NASA Astrophysics Data System (ADS)

    Swami, Anuradha; Mittal, Sherry; Chopra, Adity; Sharma, Rohit K.; Wangoo, Nishima

    2018-03-01

    In recent years, the synthesis of gold nanostructures of controllable shapes and dimensions has become a subject of intensive and interesting studies. Especially, anisotropic gold nanostructures such as nanoplates, nanoribbons, nanoprisms and nanorods have attracted much attention due to their striking optical properties and promising applications in electronics, photonics, sensing and biomedicine. Keeping this in mind, in the present report, an unprecedented, facile and one pot synthesis of isotropic (spherical) and anisotropic (triangular, pentagonal, hexagonal, rod shaped) gold nanomaterials via pH controlled shape modulation using hydroxyl moeity containing α-amino acids (Serine, Threonine, Tyrosine) as both reducing and capping agents is reported. The synthesized nanostructures have been further characterized by UV-Vis spectroscopy and transmission electron microscopy. It was deduced from these studies that pH played a key role in the anisotropic growth of gold nanostructures. These gold nanoparticles can be further used for applications in biosensing, plasmonics, and electrocatalysis and others involving surface enhanced raman scattering. This study is therefore, important from the point of view of using amino acids for the synthesis of gold nanoparticles of different shapes and sizes leading towards the development of inventive biosensors and biocompatible nanoconstructs.

  8. 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.

  9. Superhydrophobic SERS substrates based on silicon hierarchical nanostructures

    NASA Astrophysics Data System (ADS)

    Chen, Xuexian; Wen, Jinxiu; Zhou, Jianhua; Zheng, Zebo; An, Di; Wang, Hao; Xie, Weiguang; Zhan, Runze; Xu, Ningsheng; Chen, Jun; She, Juncong; Chen, Huanjun; Deng, Shaozhi

    2018-02-01

    Silicon nanostructures have been cultivated as promising surface enhanced Raman scattering (SERS) substrates in terms of their low-loss optical resonance modes, facile functionalization, and compatibility with today’s state-of-the-art CMOS techniques. However, unlike their plasmonic counterparts, the electromagnetic field enhancements induced by silicon nanostructures are relatively small, which restrict their SERS sensing limit to around 10-7 M. To tackle this problem, we propose here a strategy for improving the SERS performance of silicon nanostructures by constructing silicon hierarchical nanostructures with a superhydrophobic surface. The hierarchical nanostructures are binary structures consisted of silicon nanowires (NWs) grown on micropyramids (MPs). After being modified with perfluorooctyltriethoxysilane (PFOT), the nanostructure surface shows a stable superhydrophobicity with a high contact angle of ˜160°. The substrate can allow for concentrating diluted analyte solutions into a specific area during the evaporation of the liquid droplet, whereby the analytes are aggregated into a small volume and can be easily detected by the silicon nanostructure SERS substrate. The analyte molecules (methylene blue: MB) enriched from an aqueous solution lower than 10-8 M can be readily detected. Such a detection limit is ˜100-fold lower than the conventional SERS substrates made of silicon nanostructures. Additionally, the detection limit can be further improved by functionalizing gold nanoparticles onto silicon hierarchical nanostructures, whereby the superhydrophobic characteristics and plasmonic field enhancements can be combined synergistically to give a detection limit down to ˜10-11 M. A gold nanoparticle-functionalized superhydrophobic substrate was employed to detect the spiked melamine in liquid milk. The results showed that the detection limit can be as low as 10-5 M, highlighting the potential of the proposed superhydrophobic SERS substrate in

  10. Au-thiol interaction chemistry to influence the structural transformation of semiconductor nanocrystals and formation of giant nanostructures.

    PubMed

    Bose, Riya; Manna, Goutam; Pradhan, Narayan

    2014-04-09

    Giant nanostructures which are difficult to design by the classical growth process can be fabricated in a facilitated and well programmed surface ligand removal protocol employing the thiol-gold strong interaction chemistry. When thiol capped small ZnSe seed nanocrystals are treated with amine capped gold particles, gold snatches the thiol ligands from ZnSe and forces them to agglomerate leading to the giant crystalline ZnSe nanostructures. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Structural Engineering of Carbon and Metal Nanostructures for Antibacterial Applications

    NASA Astrophysics Data System (ADS)

    Rojas-Andrade, Mauricio D.

    Cu alloy nanoparticles is presented. A comprehensive characterization of Ag, Cu, and AgCu alloy nanoparticle structures is first presented, followed by a thorough analysis of their antibacterial activities. AgCu alloy nanoparticles with an average size of 5 nm and an equal composition of Ag and Cu were found to be the most effective at inhibiting bacterial growth. The mechanisms of Ag, Cu, and AgCu alloy nanoparticles cytotoxicity is then further investigated using fluorescence microscopy and electron paramagnetic resonance (EPR) experiments. AgCu alloy nanoparticles are concluded to exhibit their marked activity due to enhanced reactive oxygen species (ROS) generation resulting from increased Fenton reactions catalyzed by copper species stabilized in the homogenous bimetallic alloy structure. Finally, in chapter 3, the antibacterial activity of graphene oxide quantum dots (GOQD) is reported. The as-prepared structures were synthesized through an established top-down approach, and a sodium borohydride-reduced derivative (rGOQD) was synthesized using these as the precursor. Using a variety of spectroscopic techniques, the structural properties are characterized and differences between as-prepared and reduced GOQD established. Their cytotoxicity toward bacterial cells with and without light irradiation is presented, with GOQDs demonstrating apparent activity under dark conditions, and rGOQD only under light irradiation. A mechanism of cytotoxicity and phototoxicty is proposed, which can be used to establish a foundation by which the cytotoxicity of all carbon nanostructures can be understood.

  12. Analyses of gold artifacts from Slovenia

    NASA Astrophysics Data System (ADS)

    Šmit, Ž.; Budnar, M.; Pelicon, P.; Zorko, B.; Knific, T.; Istenič, J.; Trampuž-Orel, N.; Demortier, G.

    2000-03-01

    The method of particle-induced X-ray emission (PIXE) was used for the study of two gold archaeological finds: a Norico-Pannonian brooch, presumably a votive item, and a pair of earrings and a ring from a Slavic female grave. The analysis was performed by an external proton millibeam and aimed to identify the manufacturing techniques. The brooch, including the spring, was made of a rather pure 98% gold. This may indicate that the brooch was produced for votive purposes, as a more flexible spring would suit an object to be worn. The Slavic ring was made of a different alloy than the earrings; moreover, its inhomogeneous alloy reveals the exploitation of local gold sources.

  13. Study of palladium plating components

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Palladium deposits were prepared by electrolysis for evaluation as catalytic materials. Electrolysis was carried out in acidic solutions consisting of either 1.0 M in NaCl and 0.01 M PdCl2 or 1.0 M NaCl and 0.04 M PdCl2. It was during the preparation of the palladium deposits that unexpected observations were made that led to the request for analytical services. The analyses did not, nor were they intended to, answer all of the questions. They did, however, shed light on the nature and magnitude of some of the contaminants in the solutions and in the palladium electrodes, as well as characterize the forms of the palladium deposits. Results of analyses are grouped into solution, deposit, and electrode categories for comparison purposes.

  14. l-Glutamic acid assisted eco-friendly one-pot synthesis of sheet-assembled platinum-palladium alloy networks for methanol oxidation and oxygen reduction reactions.

    PubMed

    Shi, Ya-Cheng; Mei, Li-Ping; Wang, Ai-Jun; Yuan, Tao; Chen, Sai-Sai; Feng, Jiu-Ju

    2017-10-15

    In this work, bimetallic platinum-palladium sheet-assembled alloy networks (PtPd SAANs) were facilely synthesized by an eco-friendly one-pot aqueous approach under the guidance of l-glutamic acid at room temperature, without any additive, seed, toxic or organic solvent involved. l-Glutamic acid was served as the green shape-director and weak-stabilizing agent. A series of characterization techniques were employed to examine the morphology, structure and formation mechanism of the product. The architectures exhibited improved electrocatalytic activity and durable ability toward methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in contrast with commercial Pt black and Pd black catalysts. This is ascribed to the unique structures of the obtained PtPd SAANs and the synergistic effects of the bimetals. These results demonstrate the potential application of the prepared catalyst in fuel cells. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Etude de l'electrocatalyse de la reduction de l'oxygene sur des alliages de palladium cuivre

    NASA Astrophysics Data System (ADS)

    Fouda-Onana, Frederic

    This thesis is on the development of the ORR on Pd-Cu alloys in acid medium. Density Functional Theory (DFT) was used to determine the intrinsic properties of the alloys. The alloys were fabricated by RF sputtering on glassy carbon support and chemical salt reduction on carbon support. They characterised by electrochemical methods and correlations were made between the intrinsic properties and the experimental electrochemical parameters. These correlations were used to explain the electrocatalytic performance of the ORR on these aklooys and to determine the mechanism of this reaction on these electrocatalysts. Accordingly the following aspects were studied in details. In the first step, ab initio investigations of the effect of the intermediate adsorption on the variation of the reversible potential of the ORR on Pt(100) was shown. Density Functional Theory (DFT) was used to determine the energies and the geometry parameters of the intermediates which can be adsorbed on Pt(100) during the oxygen reduction reaction (ORR) and their effect on the . The Comparison of these energies and parameters using the Bridge or the Griffiths sites adsorption mechanism suggests that the two paths are feasible. In both mechanisms, the total adsorption energies of the intermediates species continuously decrease. Moreover, according to the geometry analysis, the O-O bond distance in H2O2 is higher in both (Bridge and Griffiths) processes compared to the gas phase. Such a result suggests a dissociative H2O2 adsorption whatever the type of the involved mechanism involved. In the second step, the Oxygen reduction reaction (ORR) on palladium-copper alloys was studied through two approaches. The first one is based on the correlations between the surface chemical composition and the kinetics parameters of the ORR. The second approach is focused on the correlations between the adsorption energies of O2 and OH of Pd-Cu(111) surfaces and the electronic properties of the alloys. The adsorbtion

  16. Formation of neutral and charged gold carbonyls on highly facetted gold nanostructures

    NASA Astrophysics Data System (ADS)

    Chau, Thoi-Dai; Visart de Bocarmé, Thierry; Kruse, Norbert; Wang, Richard L. C.; Kreuzer, Hans Jürgen

    2003-12-01

    We show that gold mono- and di-carbonyls are formed on gold field emitter tips during interaction with carbon monoxide gas at room temperature and in the presence of high electrostatic fields. The experiments are done in a time-of-flight atom probe to obtain mass spectra. The yield of monocarbonyl cations is about twice that of di-carbonyl ions. Density functional theory calculations are reported that explain the field stabilization of adsorbed carbonyls and the desorption yield of their cations.

  17. Hierarchical concave layered triangular PtCu alloy nanostructures: rational integration of dendritic nanostructures for efficient formic acid electrooxidation.

    PubMed

    Wu, Fengxia; Lai, Jianping; Zhang, Ling; Niu, Wenxin; Lou, Baohua; Luque, Rafael; Xu, Guobao

    2018-05-08

    The rational construction of multi-dimensional layered noble metal nanostructures is a great challenge since noble metals are not layer-structured materials. Herein, we report a one-pot hydrothermal synthetic method for PtCu hierarchical concave layered triangular (HCLT) nanostructures using dl-carnitine, KI, poly(vinylpyrrolidone), CuCl2, and H2PtCl6. The PtCu HCLT nanostructure is comprised of multilayered triangular dendrites. Its layer number is tunable by changing dl-carnitine concentrations, and the concavity/convexity of the PtCu triangle nanostructures is tunable by changing the H2PtCl6/CuCl2 ratio or KI concentrations. Hierarchical trigonal bipyramid nanoframes are also obtained under certain conditions. Because of its advantageous nanostructure and bimetallic synergetic effect, the obtained PtCu HCLT nanostructure exhibits enhanced electrocatalytic activity and prolonged stability to formic acid oxidation compared to commercial Pt black, Pd/C and some other nanostructures.

  18. Nanoporous Gold as a Neural Interface Coating: Effects of Topography, Surface Chemistry, and Feature Size

    DOE PAGES

    Chapman, Christopher A. R.; Chen, Hao; Stamou, Marianna; ...

    2015-02-23

    We report that designing neural interfaces that maintain close physical coupling of neurons to an electrode surface remains a major challenge for both implantable and in vitro neural recording electrode arrays. Typically, low-impedance nanostructured electrode coatings rely on chemical cues from pharmaceuticals or surface-immobilized peptides to suppress glial scar tissue formation over the electrode surface (astrogliosis), which is an obstacle to reliable neuron–electrode coupling. Nanoporous gold (np-Au), produced by an alloy corrosion process, is a promising candidate to reduce astrogliosis solely through topography by taking advantage of its tunable length scale. In the present in vitro study on np-Au’s interactionmore » with cortical neuron–glia co-cultures, we demonstrate that the nanostructure of np-Au achieves close physical coupling of neurons by maintaining a high neuron-to-astrocyte surface coverage ratio. Atomic layer deposition-based surface modification was employed to decouple the effect of morphology from surface chemistry. Additionally, length scale effects were systematically studied by controlling the characteristic feature size of np-Au through variations in the dealloying conditions. In conclusion, our results show that np-Au nanotopography, not surface chemistry, reduces astrocyte surface coverage while maintaining high neuronal coverage and may enhance neuron–electrode coupling through nanostructure-mediated suppression of scar tissue formation.« less

  19. M13 Virus-Incorporated Biotemplates on Electrode Surfaces To Nucleate Metal Nanostructures by Electrodeposition.

    PubMed

    Manivannan, Shanmugam; Kang, Inhak; Seo, Yeji; Jin, Hyo-Eon; Lee, Seung-Wuk; Kim, Kyuwon

    2017-09-27

    We report a virus-incorporated biological template (biotemplate) on electrode surfaces and its use in electrochemical nucleation of metal nanocomposites as an electrocatalytic material for energy applications. The biotemplate was developed with M13 virus (M13) incorporated in a silicate sol-gel matrix as a scaffold to nucleate Au-Pt alloy nanostructures by electrodeposition, together with reduced graphene oxide (rGO). The phage when engineered with Y3E peptides could nucleate Au-Pt alloy nanostructures, which ensured adequate packing density, simultaneous stabilization of rGO, and a significantly increased electrochemically active surface area. Investigation of the electrocatalytic activity of the resulting sol-gel composite catalyst toward methanol oxidation in an alkaline medium showed that this catalyst had mass activity greater than that of the biotemplate containing wild-type M13 and that of monometallic Pt and other Au-Pt nanostructures with different compositions and supports. M13 in the nanocomposite materials provided a close contact between the Au-Pt alloy nanostructures and rGO. In addition, it facilitated the availability of an OH - -rich environment to the catalyst. As a result, efficient electron transfer and a synergistic catalytic effect of the Au and Pt in the alloy nanostructures toward methanol oxidation were observed. Our nanocomposite synthesis on the novel biotemplate and its application might be useful for developing novel clean and green energy-generating and energy-storage materials.

  20. The optical, photothermal, and facile surface chemical properties of gold and silver nanoparticles in biodiagnostics, therapy, and drug delivery

    PubMed Central

    Austin, Lauren A.; Mackey, Megan A.; Dreaden, Erik C.

    2014-01-01

    Nanotechnology is a rapidly growing area of research in part due to its integration into many biomedical applications. Within nanotechnology, gold and silver nanostructures are some of the most heavily utilized nanomaterial due to their unique optical, photothermal, and facile surface chemical properties. In this review, common colloid synthesis methods and biofunctionalization strategies of gold and silver nanostructures are highlighted. Their unique properties are also discussed in terms of their use in biodiagnostic, imaging, therapeutic, and drug delivery applications. Furthermore, relevant clinical applications utilizing gold and silver nanostructures are also presented. We also provide a table with reviews covering related topics. PMID:24894431

  1. Synthesis of vanadium-doped palladium nanoparticles for hydrogen storage materials

    NASA Astrophysics Data System (ADS)

    Yamamoto, Yuki; Miyachi, Mariko; Yamanoi, Yoshinori; Minoda, Ai; Maekawa, Shunsuke; Oshima, Shinji; Kobori, Yoshihiro; Nishihara, Hiroshi

    2011-12-01

    Palladium-vanadium (Pd/V) alloy nanoparticles stabilized with n-pentyl isocyanide were prepared as new hydrogen storage materials by a facile polyol-based synthetic route with tetraethylene glycol and NaOH at 250 °C. The size distribution of the nanoparticles thus obtained featured two peaks at 4.0 ± 1.1 and 1.4 ± 0.3 nm in diameter, which were the mixture of Pd/V alloy and Pd nanoparticles. The ratio between the number of Pd/V and that of Pd nanoparticles was 51:49, and the Pd:V ratio of the overall product was 9:1 in wt%, indicating that the 4.0 nm Pd/V nanoparticles were composed of 81% Pd and 19% V. The inclusion of vanadium caused the increase in the d-spacing and thus expansion of lattice constant. A rapid increase in hydrogen content at low H2 pressures was observed for the Pd/V nanoparticles, and a 0.47 wt% H2 adsorption capacity was achieved under a H2 pressure of 10 MPa at 303 K. Hydrogen storage performances of Pd/V alloy nanoparticles was superior compared with Pd nanoparticles.

  2. Facile synthesis of gold coated copper(II) hydroxide pine-needle-like micro/nanostructures for surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Long, Kailin; Du, Deyang; Luo, Xiaoguang; Zhao, Weiwei; Wu, Zhangting; Si, Lifang; Qiu, Teng

    2014-08-01

    This work reports a facile method to fabricate gold coated copper(II) hydroxide pine-needle-like micro/nanostructures for surface-enhanced Raman scattering (SERS) application. The effects of reaction parameters on the shape, size and surface morphology of the products are systematically investigated. The as-prepared 3D hierarchical structures have the advantage of a large surface area available for the formation of hot spots and the adsorption of target analytes, thus dramatically improving the Raman signals. The finite difference time domain calculations indicate that the pine-needle-like model pattern may demonstrate a high quality SERS property owing to the high density and abundant hot spot characteristic in closely spaced needle-like arms.

  3. How can we make stable linear monoatomic chains? Gold-cesium binary subnanowires as an example of a charge-transfer-driven approach to alloying.

    PubMed

    Choi, Young Cheol; Lee, Han Myoung; Kim, Woo Youn; Kwon, S K; Nautiyal, Tashi; Cheng, Da-Yong; Vishwanathan, K; Kim, Kwang S

    2007-02-16

    On the basis of first-principles calculations of clusters and one dimensional infinitely long subnanowires of the binary systems, we find that alkali-noble metal alloy wires show better linearity and stability than either pure alkali metal or noble metal wires. The enhanced alternating charge buildup on atoms by charge transfer helps the atoms line up straight. The cesium doped gold wires showing significant charge transfer from cesium to gold can be stabilized as linear or circular monoatomic chains.

  4. Influence of the microstructure on the physicomechanical properties of the aluminum alloy Al-Mg-Si nanostructured under severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Mavlyutov, A. M.; Kasatkin, I. A.; Murashkin, M. Yu.; Valiev, R. Z.; Orlova, T. S.

    2015-10-01

    The microstructural features, strength, and electrical conductivity of the electrotechnical aluminum alloy 6201 of the Al-Mg-Si system was investigated. The alloy was nanostructured using severe plastic deformation by high pressure torsion at different temperatures and in different deformation regimes. As a result, the samples had an ultrafine-grain structure with nanoinclusions of secondary phases, which provided an excellent combination of high strength (conventional yield strength σ0.2 = 325-410 MPa) and electrical conductivity (55-52% IACS). The contributions from different mechanisms to the strengthening were analyzed. It was experimentally found that the introduction of an additional dislocation density (an increase from 2 × 1013 to 5 × 1013 m-2) with the same basic parameters of the ultrafine-grain structure (grain size, size and distribution of particles of secondary strengthening phases) leads to an increase in the strength of the alloy by ~15%, while the electrical conductivity of the material changes insignificantly. The contribution from grain boundaries to the electrical resistivity of the alloy with an ultrafine-grain structure upon the change in their state, most likely, due to a change in the degree of nonequilibrium was estimated.

  5. Directed assembly of gold nanowires on silicon via reorganization and simultaneous fusion of randomly distributed gold nanoparticles.

    PubMed

    Reinhardt, Hendrik M; Bücker, Kerstin; Hampp, Norbert A

    2015-05-04

    Laser-induced reorganization and simultaneous fusion of nanoparticles is introduced as a versatile concept for pattern formation on surfaces. The process takes advantage of a phenomenon called laser-induced periodic surface structures (LIPSS) which originates from periodically alternating photonic fringe patterns in the near-field of solids. Associated photonic fringe patterns are shown to reorganize randomly distributed gold nanoparticles on a silicon wafer into periodic gold nanostructures. Concomitant melting due to optical heating facilitates the formation of continuous structures such as periodic gold nanowire arrays. Generated patterns can be converted into secondary structures using directed assembly or self-organization. This includes for example the rotation of gold nanowire arrays by arbitrary angles or their fragmentation into arrays of aligned gold nanoparticles.

  6. A new generation of alloyed/multimetal chalcogenide nanowires by chemical transformation

    PubMed Central

    Yang, Yuan; Wang, Kai; Liang, Hai-Wei; Liu, Guo-Qiang; Feng, Mei; Xu, Liang; Liu, Jian-Wei; Wang, Jin-Long; Yu, Shu-Hong

    2015-01-01

    One-dimensional metal chalcogenide nanostructures are important candidates for many technological applications such as photovoltaic and thermoelectric devices. However, the design and synthesis of one-dimensional metal chalcogenide nanostructured materials with controllable components and properties remain a challenge. We report a general chemical transformation process for the synthesis of more than 45 kinds of one-dimensional alloyed/hybrid metal chalcogenide nanostructures inherited from mother template TexSey@Se core-shell nanowires with tunable compositions. As many as nine types of monometal chalcogenide alloy nanowires (including AgSeTe, HgSeTe, CuSeTe, BiSeTe, PbSeTe, CdSeTe, SbSeTe, NiSeTe, and CoSeTe) can be synthesized. Alloyed and hybrid nanowires integrated with two or more alloyed metal chalcogenide phases can also be prepared. The compositions of all of these metal chalcogenide nanowires are tunable within a wide range. This protocol provides a new general route for the controllable synthesis of a new generation of one-dimensional metal chalcogenide nanostructures. PMID:26601137

  7. A new generation of alloyed/multimetal chalcogenide nanowires by chemical transformation.

    PubMed

    Yang, Yuan; Wang, Kai; Liang, Hai-Wei; Liu, Guo-Qiang; Feng, Mei; Xu, Liang; Liu, Jian-Wei; Wang, Jin-Long; Yu, Shu-Hong

    2015-11-01

    One-dimensional metal chalcogenide nanostructures are important candidates for many technological applications such as photovoltaic and thermoelectric devices. However, the design and synthesis of one-dimensional metal chalcogenide nanostructured materials with controllable components and properties remain a challenge. We report a general chemical transformation process for the synthesis of more than 45 kinds of one-dimensional alloyed/hybrid metal chalcogenide nanostructures inherited from mother template Te x Se y @Se core-shell nanowires with tunable compositions. As many as nine types of monometal chalcogenide alloy nanowires (including AgSeTe, HgSeTe, CuSeTe, BiSeTe, PbSeTe, CdSeTe, SbSeTe, NiSeTe, and CoSeTe) can be synthesized. Alloyed and hybrid nanowires integrated with two or more alloyed metal chalcogenide phases can also be prepared. The compositions of all of these metal chalcogenide nanowires are tunable within a wide range. This protocol provides a new general route for the controllable synthesis of a new generation of one-dimensional metal chalcogenide nanostructures.

  8. Palladium-cobalt particles as oxygen-reduction electrocatalysts

    DOEpatents

    Adzic, Radoslav [East Setauket, NY; Huang, Tao [Manorville, NY

    2009-12-15

    The present invention relates to palladium-cobalt particles useful as oxygen-reducing electrocatalysts. The invention also relates to oxygen-reducing cathodes and fuel cells containing these palladium-cobalt particles. The invention additionally relates to methods for the production of electrical energy by using the palladium-cobalt particles of the invention.

  9. A comparative analysis of metal allergens associated with dental alloy prostheses and the expression of HLA-DR in gingival tissue

    PubMed Central

    ZHANG, XIN; WEI, LI-CHENG; WU, BIN; YU, LI-YING; WANG, XIAO-PING; LIU, YUE

    2016-01-01

    The present study aimed to provide guidance for the selection of prosthodontic materials and the management of patients with a suspected metal allergy. This included a comparison of the sensitivity of patients to alloys used in prescribed metal-containing prostheses, and correlation analysis between metal allergy and accompanying clinical symptoms of sensitized patients using a patch test. The results from the patch test and metal component analyses were processed to reach a final diagnosis. In the present study, four dental alloys were assessed. Subsequent to polishing the surface of a metal restoration, the components were analyzed using an X-ray fluorescence microscopy and spectrometry. Immunohistochemical analysis, reverse transcription-polymerase chain reaction and western blotting were used to detect the expression levels of human leukocyte antigen (HLA)-DR in gingival tissues affected by alloy restoration, and in normal gingival tissue samples. Positive allergens identified in the patch test were consistent with the components of the metal prostheses. The prevalence of nickel (Ni) allergy was highest (22.8%), and women were significantly more allergic to palladium and Ni than men (P<0.05). The protein and gene expression levels of HLA-DR in the Ni-chromium (Cr) prosthesis group were significantly higher, compared with those in the other groups (P<0.01); followed by cobalt-Cr alloy, gold alloy and titanium alloy. In conclusion, dentists require an understanding of the corrosion and allergy rates of prescribed alloys, in order to reduce the risk of allergic reactions. Patch testing for hypersensitive patients is recommended and caution is required when planning to use different alloys in the mouth. PMID:26573458

  10. Silica coatings formed on noble dental casting alloy by the sol-gel dipping process.

    PubMed

    Yoshida, K; Tanagawa, M; Kamada, K; Hatada, R; Baba, K; Inoi, T; Atsuta, M

    1999-08-01

    The sol-gel dipping process, in which liquid silicon alkoxide is transformed into the solid silicon-oxygen network, can produce a thin film coating of silica (SiO2). The features of this method are high homogeneity and purity of the thin SiO2 film and a low sinter temperature, which are important in preparation of coating films that can protect from metallic ion release from the metal substrate and prevent attachment of dental plaque. We evaluated the surface characteristics of the dental casting silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy coated with a thin SiO2 film by the sol-gel dipping process. The SiO2 film bonded strongly (over 40 MPa) to Ti-implanted Ag-Pd-Cu-Au alloy substrate as demonstrated by a pull test. Hydrophobilization of Ti-implanted/SiO2-coated surfaces resulted in a significant increase of the contact angle of water (80.5 degrees) compared with that of the noncoated alloy specimens (59.3 degrees). Ti-implanted/SiO2-coated specimens showed the release of many fewer metallic ions (192 ppb/cm2) from the substrate than did noncoated specimens (2,089 ppb/cm2). The formation of a thin SiO2 film by the sol-gel dipping process on the surface of Ti-implanted Ag-Pd-Cu-Au alloy after casting clinically may be useful for minimizing the possibilities of the accumulation of dental plaque and metal allergies caused by intraoral metal restorations.

  11. Advanced composite alloys for constructional parts of robots

    NASA Astrophysics Data System (ADS)

    Issin, D. K.; Zholdubayeva, Zh D.; Neshina, Y. G.; Alkina, A. D.; Khuangan, N.; Rahimova, G. M.

    2018-05-01

    In recent years all over the world special attention has been paid to the development and implementation of nanostructured materials possessing unique properties and opening fascinating prospects for the development of technical progress in various fields of human activities. A special place can be given to the development of service robots, the market of which is actively developing. There is problem associated mainly with the lack of heat-strengthened alloys which consists in low thermal stability of the alloy properties under the conditions of elevated variable temperatures and loads. The article presents studies to assess the effect of composition, the amounts of refractory nanoscale particles and methods for their introduction into the melt on the structure and properties in nanostructured composite aluminum alloys. The powders of metals, alloys, as well as silicon carbide and aluminum oxide were used to produce the nanostructured powder composite materials. As a result of the research, NPCM compositions containing micro-size particles of transition metals that are carriers of nanosized reinforcing particles and initiators of the formation of an intermetallide of endogenous origin in a melt.

  12. Corrosion analysis of NiCu and PdCo thermal seed alloys used as interstitial hyperthermia implants.

    PubMed

    Paulus, J A; Parida, G R; Tucker, R D; Park, J B

    1997-12-01

    Ferromagnetic materials with low Curie temperatures are being investigated for use as interstitial implants for fractionated hyperthermia treatment of prostatic disease. Previous investigations of the system have utilized alloys, such as NiCu, with inadequate corrosion resistance, requiring the use of catheters for removal of the implants following treatment or inert surface coatings which may interfere with thermal characteristics of the implants. We are evaluating a palladium-cobalt (PdCo) binary alloy which is very similar to high palladium alloys used in dentistry. Electrochemical corrosion tests and immersion tests at 37 degrees C for both NiCu and PdCo alloy samples in mammalian Ringer's solution were performed. Long-term corrosion rates are 5.8 x 10(-5) microm per year (NiCu) and 7.7 x 10(-8) microm per year (PdCo) from average immersion test results, indicating higher corrosion resistance of PdCo (P < 0.02); immersion corrosion rates were much lower than initial corrosion rates found electrochemically. Both alloys had significantly lower corrosion rates than standard surgical implant rates of 0.04 microm per year (P < 0.001 for both alloys). Scanning electron microscopy illustrates changes in the NiCu alloy surface due to pitting corrosion; no difference is observed for PdCo. The data indicate that the PdCo alloy may be suitable as a long-term implant for use in fractionated hyperthermia.

  13. Assessment of exposures and potential risks to the US adult population from the leaching of elements from gold and ceramic dental restorations.

    PubMed

    Richardson, G Mark; James, Kyle Jordan; Peters, Rachel Elizabeth; Clemow, Scott Richard; Siciliano, Steven Douglas

    2016-01-01

    Using data from the 2001 to 2004 US National Health and Nutrition Examination Survey (NHANES) on the number and placement of tooth restorations in adults, we quantified daily doses due to leaching of elements from gold (Au) alloy and ceramic restorative materials. The elements with the greatest leaching rates from these materials are often the elements of lowest proportional composition. As a result, exposure due to wear will predominate for those elements of relatively high proportional composition, while exposure due leaching may predominate for elements of relatively low proportional composition. The exposure due to leaching of silver (Ag) and palladium (Pd) from Au alloys exceeded published reference exposure levels (RELs) for these elements when multiple full surface crowns were present. Six or more molar crowns would result in exceeding the REL for Ag, whereas three or more crowns would be necessary to exceed the REL for Pd. For platinum (Pt), the majority of tooth surfaces, beyond just molar crowns, would be necessary to exceed the REL for Pd. Exposures due to leaching of elements from ceramic dental materials were less than published RELs for all components examined here, including having all restorations composed of ceramic.

  14. Corrosion resistance and durability of superhydrophobic surface formed on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution.

    PubMed

    Ishizaki, Takahiro; Masuda, Yoshitake; Sakamoto, Michiru

    2011-04-19

    The corrosion resistant performance and durability of the superhydrophobic surface on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution were investigated using electrochemical and contact angle measurements. The durability of the superhydrophobic surface in corrosive 5 wt% NaCl aqueous solution was elucidated. The corrosion resistant performance of the superhydrophobic surface formed on magnesium alloy was estimated by electrochemical impedance spectroscopy (EIS) measurements. The EIS measurements and appropriate equivalent circuit models revealed that the superhydrophobic surface considerably improved the corrosion resistant performance of magnesium alloy AZ31. American Society for Testing and Materials (ASTM) standard D 3359-02 cross cut tape test was performed to investigate the adhesion of the superhydrophobic film to the magnesium alloy surface. The corrosion formation mechanism of the superhydrophobic surface formed on the magnesium alloy was also proposed. © 2011 American Chemical Society

  15. A Nanostructured Sensor Based on Gold Nanoparticles and Nafion for Determination of Uric Acid

    PubMed Central

    Stozhko, Natalia; Bukharinova, Maria; Galperin, Leonid; Brainina, Khiena

    2018-01-01

    The paper discusses the mechanism of uric acid (UA) electrooxidation occurring on the surface of gold nanoparticles. It has been shown that the electrode process is purely electrochemical, uncomplicated with catalytic stages. The nanoeffects observed as the reduction of overvoltage and increased current of UA oxidation have been described. These nanoeffects are determined by the size of particles and do not depend on the method of particle preparation (citrate and “green” synthesis). The findings of these studies have been used to select a modifier for carbon screen-printed electrode (CSPE). It has been stated that CSPE modified with gold nanoparticles (5 nm) and 2.5% Nafion (Nf) may serve as non-enzymatic sensor for UA determination. The combination of the properties of nanoparticles and Nafion as a molecular sieve at the selected pH 5 phosphate buffer solution has significantly improved the resolution of the sensor compared to unmodified CSPE. A nanostructured sensor has demonstrated good selectivity in determining UA in the presence of ascorbic acid. The detection limit of UA is 0.25 μM. A linear calibration curve has been obtained over a range of 0.5–600 μM. The 2.5%Nf/Au(5nm)/CSPE has been successfully applied to determining UA in blood serum and milk samples. The accuracy and reliability of the obtained results have been confirmed by a good correlation with the enzymatic spectrophotometric analysis (R2 = 0.9938) and the “added−found” technique (recovery close to 100%). PMID:29509718

  16. 16 CFR 23.4 - Misrepresentation as to gold content.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 1 2014-01-01 2014-01-01 false Misrepresentation as to gold content. 23.4... JEWELRY, PRECIOUS METALS, AND PEWTER INDUSTRIES § 23.4 Misrepresentation as to gold content. (a) It is unfair or deceptive to misrepresent the presence of gold or gold alloy in an industry product, or the...

  17. 16 CFR 23.4 - Misrepresentation as to gold content.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Misrepresentation as to gold content. 23.4... JEWELRY, PRECIOUS METALS, AND PEWTER INDUSTRIES § 23.4 Misrepresentation as to gold content. (a) It is unfair or deceptive to misrepresent the presence of gold or gold alloy in an industry product, or the...

  18. Controllable growth of GeSi nanostructures by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Ma, Yingjie; Zhou, Tong; Zhong, Zhenyang; Jiang, Zuimin

    2018-06-01

    We present an overview on the recent progress achieved on the controllable growth of diverse GeSi alloy nanostructures by molecular beam epitaxy. Prevailing theories for controlled growth of Ge nanostructures on patterned as well as inclined Si surfaces are outlined firstly, followed by reviews on the preferential growth of Ge nanoislands on patterned Si substrates, Ge nanowires and high density nanoislands grown on inclined Si surfaces, and the readily tunable Ge nanostructures on Si nanopillars. Ge nanostructures with controlled geometries, spatial distributions and densities, including two-dimensional ordered nanoislands, three-dimensional ordered quantum dot crystals, ordered nanorings, coupled quantum dot molecules, ordered nanowires and nanopillar alloys, are discussed in detail. A single Ge quantum dot-photonic crystal microcavity coupled optical emission device demonstration fabricated by using the preferentially grown Ge nanoisland technique is also introduced. Finally, we summarize the current technology status with a look at the future development trends and application challenges for controllable growth of Ge nanostructures. Project supports by the Natural Science Foundation of China (Nos. 61605232, 61674039) and the Open Research Project of State Key Laboratory of Surface Physics from Fudan University (Nos. KF2016_15s, KF2017_05).

  19. Palladium nanoparticles exposure: Evaluation of permeation through damaged and intact human skin.

    PubMed

    Larese Filon, Francesca; Crosera, Matteo; Mauro, Marcella; Baracchini, Elena; Bovenzi, Massimo; Montini, Tiziano; Fornasiero, Paolo; Adami, Gianpiero

    2016-07-01

    The intensified use of palladium nanoparticles (PdNPs) in many chemical reactions, jewellery, electronic devices, in car catalytic converters and in biomedical applications lead to a significant increase in palladium exposure. Pd can cause allergic contact dermatitis when in contact with the skin. However, there is still a lack of toxicological data related to nano-structured palladium and information on human cutaneous absorption. In fact, PdNPs, can be absorbed through the skin in higher amounts than bulk Pd because NPs can release more ions. In our study, we evaluated the absorption of PdNPs, with a size of 10.7 ± 2.8 nm, using intact and damaged human skin in Franz cells. 0.60 mg cm(-2) of PdNPs were applied on skin surface for 24 h. Pd concentrations in the receiving solutions at the end of experiments were 0.098 ± 0.067 μg cm(-2) and 1.06 ± 0.44 μg cm(-2) in intact skin and damaged skin, respectively. Pd flux permeation after 24 h was 0.005 ± 0.003 μg cm(-2) h(-1) and 0.057 ± 0.030 μg cm(-2) h(-1) and lag time 4.8 ± 1.7 and 4.2 ± 3.6 h, for intact and damaged skin respectively. This study indicates that Pd can penetrate human skin. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Dynamic restructuring drives catalytic activity on nanoporous gold–silver alloy catalysts

    DOE PAGES

    Zugic, Branko; Wang, Lucun; Heine, Christian; ...

    2016-12-19

    Bimetallic, nanostructured materials hold promise for improving catalyst activity and selectivity, yet little is known about the dynamic compositional and structural changes that these systems undergo during pretreatment that leads to efficient catalyst function. Here we use ozone-activated silver–gold alloys in the form of nanoporous gold as a case study to demonstrate the dynamic behaviour of bimetallic systems during activation to produce a functioning catalyst. We show that it is these dynamic changes that give rise to the observed catalytic activity. Advanced in situ electron microscopy and X-ray photoelectron spectroscopy are used to demonstrate that major restructuring and compositional changesmore » occur along the path to catalytic function for selective alcohol oxidation. Transient kinetic measurements correlate the restructuring to three types of oxygen on the surface. The direct influence of changes in surface silver concentration and restructuring at the nanoscale on oxidation activity is demonstrated. Finally, our results demonstrate that characterization of these dynamic changes is necessary to unlock the full potential of bimetallic catalytic materials.« less

  1. Dynamic restructuring drives catalytic activity on nanoporous gold–silver alloy catalysts

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

    Zugic, Branko; Wang, Lucun; Heine, Christian

    Bimetallic, nanostructured materials hold promise for improving catalyst activity and selectivity, yet little is known about the dynamic compositional and structural changes that these systems undergo during pretreatment that leads to efficient catalyst function. Here we use ozone-activated silver–gold alloys in the form of nanoporous gold as a case study to demonstrate the dynamic behaviour of bimetallic systems during activation to produce a functioning catalyst. We show that it is these dynamic changes that give rise to the observed catalytic activity. Advanced in situ electron microscopy and X-ray photoelectron spectroscopy are used to demonstrate that major restructuring and compositional changesmore » occur along the path to catalytic function for selective alcohol oxidation. Transient kinetic measurements correlate the restructuring to three types of oxygen on the surface. The direct influence of changes in surface silver concentration and restructuring at the nanoscale on oxidation activity is demonstrated. Finally, our results demonstrate that characterization of these dynamic changes is necessary to unlock the full potential of bimetallic catalytic materials.« less

  2. Morphology modification of gold nanoparticles from nanoshell to C-shape: Improved surface enhanced Raman scattering

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

    Xing, Ting-Yang; Zhu, Jian; Li, Jian-Jun

    Morphology modification of nanostructures is of great interest, because it can be used to fabricate nanostructures which are hard to be done using other methods. Different from traditional lithographic technique which is slow and expensive, morphology modification is easy, cheap, and reproducible. In this paper, modification of the optical and morphological properties of a hollow gold nanoshell (HGNS) is achieved by using H{sub 2}O{sub 2} as an oxidizer. The reshaping of these nanostructures has been demonstrated as a consequence of an oxidation process in which HGNSs are dissolved by H{sub 2}O{sub 2} under the acidic conditions provided by HCl. Wemore » investigate the oxidation process by a transmission electron microscope and propose a reshaping model involving four different shapes (HGNS, HGNS with hole, gold nanoring, and C-shaped gold nanoparticle) which are corresponding to the oxidation products of HGNSs at different pH values. Besides, the surface enhanced Raman scattering (SERS) activity of each oxidation product has been evaluated by using rhodamine 6G as the Raman active probe. It has been observed that the C-shaped gold nanoparticles which are corresponding to the oxidation products at the minimum pH value have the highest SERS activity and this result can also be interpreted by discrete-dipole approximation simulations. We demonstrate that the morphology modification of HGNSs becomes possible in a controlled manner using wet chemistry and can be used in preparation of gold nanoparticles such as HGNS with hole, gold nanoring, and C-shaped gold nanoparticle with large SERS activity. These nanostructures must have potential use in many plasmonic areas, including sensing, catalysis, and biomedicine.« less

  3. Electrochemical properties of nanostructured porous gold electrodes in biofouling solutions.

    PubMed

    Patel, Jay; Radhakrishnan, Logudurai; Zhao, Bo; Uppalapati, Badharinadh; Daniels, Rodney C; Ward, Kevin R; Collinson, Maryanne M

    2013-12-03

    The effect of electrode porosity on the electrochemical response of redox active molecules (potassium ferricyanide, ruthenium(III) hexammine, and ferrocene methanol) in the presence of bovine serum albumin or fibrinogen was studied at macroporous (pore diameter: 1200 nm), hierarchical (1200/60 nm), and nanoporous (<50 nm) gold. These electrodes were prepared using standard templating or dealloying techniques, and cyclic voltammetry (CV) was utilized to evaluate the effect of protein adsorption on the electron transfer of the diffusing redox probes. Following exposure to albumin (or fibrinogen) under near neutral pH conditions, planar gold electrodes showed an immediate reduction in Faradaic peak current and increase in peak splitting for potassium ferricyanide. The rate at which the CV curves changed was highly dependent on the morphology of the electrode. For example, the time required for the Faradaic current to drop to one-half of its original value was 3, 12, and 38 min for planar gold, macroporous gold, and hierarchical gold, respectively. Remarkably, for nanoporous gold, only a few percent drop in the peak Faradaic current was observed after an hour in solution. A similar suppression in the voltammetry at planar gold was also noted for ruthenium hexammine at pH 3 after exposure to albumin for several hours. At nanoporous gold, no significant loss in response was observed. The order of performance of the electrodes as judged by their ability to efficiently transfer electrons in the presence of biofouling agents tracked porosity with the electrode having the smallest pore size and largest surface area, providing near ideal results. Nanoporous gold electrodes when immersed in serum or heparinized blood containing potassium ferricyanide showed ideal voltammetry while significant fouling was evident in the electrochemical response at planar gold. The small nanopores in this 3D open framework are believed to restrict the transport of large biomolecules, thus

  4. Biosynthesis of extracellular and intracellular gold nanoparticles by Aspergillus fumigatus and A. flavus.

    PubMed

    Gupta, Saurabh; Bector, Shruti

    2013-05-01

    Green chemistry is a boon for the development of safe, stable and ecofriendly nanostructures using biological tools. The present study was carried out to explore the potential of selected fungal strains for biosynthesis of intra- and extracellular gold nanostructures. Out of the seven cultures, two fungal strains (SBS-3 and SBS-7) were selected on the basis of development of dark pink colour in cell free supernatant and fungal beads, respectively indicative of extra- and intracellular gold nanoparticles production. Both biomass associated and cell free gold nanoparticles were characterized using X-ray diffractogram (XRD) analysis and transmission electron microscopy (TEM). XRD analysis confirmed crystalline, face-centered cubic lattice of metallic gold nanoparticles along with average crystallite size. A marginal difference in average crystallite size of extracellular (17.76 nm) and intracellular (26 and 22 nm) Au-nanostructures was observed using Scherrer equation. In TEM, a variety of shapes (triangles, spherical, hexagonal) were observed in both extra- and intracellular nanoparticles. 18S rRNA gene sequence analysis by multiple sequence alignment (BLAST) indicated 99 % homology of SBS-3 to Aspergillus fumigatus with 99 % alignment coverage and 98 % homology of SBS-7 to Aspergillus flavus with 98 % alignment coverage respectively. Native-PAGE and activity staining further confirmed enzyme linked synthesis of gold nanoparticles.

  5. Electrocatalysts having gold monolayers on platinum nanoparticle cores, and uses thereof

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang

    2010-04-27

    The invention relates to gold-coated particles useful as fuel cell electrocatalysts. The particles are composed of an electrocatalytically active core at least partially encapsulated by an outer shell of gold or gold alloy. The invention more particularly relates to such particles having a noble metal-containing core, and more particularly, a platinum or platinum alloy core. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

  6. Interference of Steroidogenesis by Gold Nanorod Core/Silver Shell Nanostructures: Implications for Reproductive Toxicity of Silver Nanomaterials.

    PubMed

    Jiang, Xiumei; Wang, Liming; Ji, Yinglu; Tang, Jinglong; Tian, Xin; Cao, Mingjing; Li, Jingxuan; Bi, Shuying; Wu, Xiaochun; Chen, Chunying; Yin, Jun-Jie

    2017-03-01

    As a widely used nanomaterial in daily life, silver nanomaterials may cause great concern to female reproductive system as they are found to penetrate the blood-placental barrier and gain access to the ovary. However, it is largely unknown about how silver nanomaterials influence ovarian physiology and functions such as hormone production. This study performs in vitro toxicology study of silver nanomaterials, focusing especially on cytotoxicity and steroidogenesis and explores their underlying mechanisms. This study exposes primary rat granulosa cells to gold nanorod core/silver shell nanostructures (Au@Ag NRs), and compares outcomes with cells exposed to gold nanorods. The Au@Ag NRs generate more reactive oxygen species and reduce mitochondrial membrane potential and less production of adenosine triphosphate. Au@Ag NRs promote steroidogenesis, including progesterone and estradiol, in a time- and dose-dependent manner. Chemical reactivity and transformation of Au@Ag NRs are then studied by electron spin resonance spectroscopy and X-ray absorption near edge structure, which analyze the generation of free radical and intracellular silver species. Results suggest that both particle-specific activity and intracellular silver ion release of Au@Ag NR contribute to the toxic response of granulosa cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Functionalization of indium-tin-oxide electrodes by laser-nanostructured gold thin films for biosensing applications

    NASA Astrophysics Data System (ADS)

    Grochowska, Katarzyna; Siuzdak, Katarzyna; Karczewski, Jakub; Śliwiński, Gerard

    2015-12-01

    The production and properties of the indium-tin-oxide (ITO) electrodes functionalized by Au nanoparticle (NP) arrays of a relatively large area formed by pulsed laser nanostructuring of thin gold films are reported and discussed. The SEM inspection of modified electrodes reveals the presence of the nearly spherical and disc-shaped particles of dimensions in the range of 40-120 nm. The NP-array geometry can be controlled by selection of the laser processing conditions. It is shown that particle size and packing density of the array are important factors which determine the electrode performance. In the case of NP-modified electrodes the peak current corresponding to the glucose direct oxidation process shows rise with increasing glucose concentration markedly higher comparing to the reference Au disc electrode. The detection limit reaches 12 μM and linear response of the sensor is observed from 0.1 to 47 mM that covers the normal physiological range of the blood sugar detection.

  8. Phase structuring in metal alloys: Ultrasound-assisted top-down approach to engineering of nanostructured catalytic materials.

    PubMed

    Cherepanov, Pavel V; Andreeva, Daria V

    2017-03-01

    High intensity ultrasound (HIUS) is a novel and efficient tool for top-down nanostructuring of multi-phase metal systems. Ultrasound-assisted structuring of the phase in metal alloys relies on two main mechanisms including interfacial red/ox reactions and temperature driven solid state phase transformations which affect surface composition and morphology of metals. Physical and chemical properties of sonication medium strongly affects the structuring pathways as well as morphology and composition of catalysts. HIUS can serve as a simple, fast, and effective approach for the tuning of structure and surface properties of metal particles, opening the new perspectives in design of robust and efficient catalysts. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Nanoporous gold membranes: From morphological control to fuel cell catalysis

    NASA Astrophysics Data System (ADS)

    Ding, Yi

    Porous noble metals are particularly attractive for scientific research and industrial applications such as catalysis, sensing, and filtration. In this thesis, I will discuss the fabrication, characterization, and application of a new class of porous metals, called nanoporous metals (NPM). NPM is made during selective dissolution (also called dealloying) of reactive components (e.g., silver) from multi-component alloys (e.g., Ag/Au alloy). Commercially available white gold leaf (Ag65Au35) can, for example, be etched into nanoporous gold (NPG) membrane by simply floating the leaf on concentrated nitric acid for periods of a few minutes. NPG leaf adopts a single crystal porous structure within individual grains. The microstructure of NPG, such as the pore size, is tunable between a few nanometers to sub-micron length scale by either thermal annealing or post-treatment in nitric acid for extended period of time. A new gas-liquid-solid interface electroless plating technique is developed to uniformly cover the NPG surface with other metals, such as silver and platinum. This technique allows new opportunities of making functionalized nanostructures. We show that a combination of silver plating and dealloying can be used to make multimodal porous metals, which are expected to have application in sensing field. Electroless platinum plating onto NPG shows very usual growth mode. TEM observation indicates that the platinum layer on NPG surface takes a novel form of layer-islanding growth (Stranski-Krastanov growth). Annealing the Pt/NPG composite smoothens the Pt islands and forms a 1 nm coherent Pt layer on the NPG backbone, possibly with dislocation formation at the Pt/Au interface. Furthermore, it was found that we could dissolve the gold away in aqueous gold etchant, leaving behind the 1 nm-thick Pt shell, a structure we call nanotubular mesoporous platinum (NMP). Pt plated NPG has a series of unique structural properties, such as high active surface area, thermally

  10. Quantitative biokinetics and systemic translocation of various gold nanostructures are highly dependent on their size and shape.

    PubMed

    Zhang, Jiajing; Nie, Xin; Ji, Yinglu; Liu, Ying; Wu, Xiaochun; Chen, Chunying; Fang, Xiaohong

    2014-06-01

    Gold nanostructures with promising applications in biomedical field have attracted great attention. However, some fundamental questions other than the development of novel applications should be elucidated before they can actually serve as biomedicines in the clinic. Bio-safety is one of the most important issues. Since numerous modifications (e.g., surface coating and composites) have been designed on gold nanoparticles (GNPs) to extend their application, there would be hundreds of GNPs synthesized in the lab although the prototypes of GNPs (i.e., cluster, shell, rod, sphere, cage, and star) are rather limited. Thus, in the present work we aim to conduct our experiments only on the most basic types of GNPs--including gold nanocluster (GNC), gold nanorod (GNR) and gold nanosphere (GNS), to investigate their biodistribution and toxicities in vivo, in the hope of revealing some basic rules which could be further extended to other complicated situations. Bovine serum albumin (BSA) was coated at the surface to increase their plasma stability and of the same BSA coating would help to compare the fate and behaviors of various GNPs in vivo. After intravenous administration of different GNPs with an equal content of gold element at 0.5 mg/kg in mice, samples were harvested at a series of time points. Biodistribution was compared among different GNPs and the process of accumulation-retention-clearance of each kind of GNP was also observed through quantification analysis by inductively coupled plasma-mass spectrometry (ICP-MS). The results showed, with the same BSA coating at the surface and similar negative charge, size rather than shape was dominating the in vivo fate of GNPs. Even between GNC and hydrolyzed GNC with their size at 7.1 and 3.2 nm, huge difference in the kidney accumulation was observed. Totally, GNR and GNS in relative large size preferred to accumulate in liver and spleen whereas GNC in relative small size tended to accumulate in liver and kidney. GNPs

  11. Nanostructured Platinum Alloys for Use as Catalyst Materials

    NASA Technical Reports Server (NTRS)

    Narayan, Sri R. (Inventor); Hays, Charles C. (Inventor)

    2015-01-01

    A series of binary and ternary Pt-alloys, that promote the important reactions for catalysis at an alloy surface; oxygen reduction, hydrogen oxidation, and hydrogen and oxygen evolution. The first two of these reactions are essential when applying the alloy for use in a PEMFC.

  12. Nanostructured Platinum Alloys for Use as Catalyst Materials

    NASA Technical Reports Server (NTRS)

    Hays, Charles C. (Inventor); Narayan, Sri R. (Inventor)

    2013-01-01

    A series of binary and ternary Pt-alloys, that promote the important reactions for catalysis at an alloy surface; oxygen reduction, hydrogen oxidation, and hydrogen and oxygen evolution. The first two of these reactions are essential when applying the alloy for use in a PEMFC.

  13. Aluminium-gold reference material for the k0-standardisation of neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Ingelbrecht, C.; Peetermans, F.; De Corte, F.; De Wispelaere, A.; Vandecasteele, C.; Courtijn, E.; D'Hondt, P.

    1991-05-01

    Gold is an excellent comparator material for the k0-standardisation of neutron activation analysis because of its convenient and well defined nuclear properties. The most suitable form for a reference material is a dilute aluminium-gold alloy, for which the self-shielding effect for neutrons is small. Castings of composition Al-0.1 wt.% Au were prepared by crucible-less levitation melting, which gives close control of ingot composition with minimal contamination of the melt. The alloy composition was checked using induction-coupled plasma source emission spectrometry. The homogeneity of the alloy was measured by neutron activation analysis and a relative standard deviation of the gold content of 0.30% was found (10 mg samples). Metallography revealed a homogeneous distribution of AuAl 2 particles. The alloy was certified as Reference Material CBNM-530, with certified gold mass fraction 0.100±0.002 wt.%.

  14. Single-molecule optical-trapping measurements with DNA anchored to an array of gold nanoposts.

    PubMed

    Paik, D Hern; Perkins, Thomas T

    2012-01-01

    Gold-thiol chemistry is one of the most successful chemistries for conjugating biomolecules to surfaces, but such chemistry has not been exploited in optical-trapping experiments because of laser-induced ablation of gold. In this work, we describe a method to combine these two separate technologies without undue heating using DNA anchored to gold nanostructures (r = 50-250 nm; h ≈ 20 nm). Moreover, we demonstrate a quantitative and mechanically robust (>100 pN) optical-trapping assay. By using three dithiol phosphoramidites (DTPAs) incorporated into a polymerase chain reaction (PCR) primer, the gold-DNA bond remained stable in the presence of excess thiolated compounds. This chemical robustness allowed us to reduce nonspecific sticking by passivating the unreacted gold with methoxy-(polyethylene glycol)-thiol (mPEG-SH). Overall, this surface conjugation of biomolecules onto an ordered array of gold nanostructures by chemically and mechanically robust bonds provides a unique way to carry out spatially controlled, repeatable measurements of single molecules.

  15. Effect of silver on the shape of palladium nanoparticles

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

    Gupta, Dikshita, E-mail: dgmonugupta@gmail.com; Barman, P. B.; Hazra, S. K.

    We report a facile route to prepare palladium-silver nanoparticles at considerably low temperature. First the controlled synthesis of palladium nanoparticles was performed via reduction of sodium tetrachloropalladate (II) in ethylene glycol in the presence of PVP(polyvinylpyrrolidone) as capping agent. The reaction was carried out at three different temperatures-80°C, 100°C and 120°C for one hour. Short reaction time and low synthesis temperature adds advantage to this method over others. Formed palladium nanoparticles were nearly spherical with the average particle size of 7.5±0.5 nm, 9.5±0.5 nm and 10.5±0.5 nm at 80°C, 100°C and 120°C respectively. Secondly, the palladium-silver nanoparticles were prepared bymore » the simultaneous reduction of palladium and silver from their respective precursors in ethylene glycol at 100°C (optimized temperature). The shape and size distribution was studied by TEM (Transmission Electron Microscopy). The role of silver in transforming the shape of palladium nanoparticles from spherical to triangular has been discussed. Spherical symmetry of palladium nanoparticles is disturbed by the interaction of silver ions on the crystal facets of palladium nanoparticles. From UV-vis spectra, the absorption maxima of palladium nanoparticles at 205 nm and absorption maxima of palladium-silver nanoparticles at 272 nm revealed the partial evidence of their formation.« less

  16. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1963-02-26

    A brazing alloy which, in the molten state, is characterized by excellent wettability and flowability, said alloy being capable of forming a corrosion resistant brazed joint wherein at least one component of said joint is graphite and the other component is a corrosion resistant refractory metal, said alloy consisting essentially of 20 to 50 per cent by weight of gold, 20 to 50 per cent by weight of nickel, and 15 to 45 per cent by weight of molybdenum. (AEC)

  17. Surface analysis and biocorrosion properties of nanostructured surface sol-gel coatings on Ti6Al4V titanium alloy implants.

    PubMed

    Advincula, Maria C; Petersen, Don; Rahemtulla, Firoz; Advincula, Rigoberto; Lemons, Jack E

    2007-01-01

    Surfaces of biocompatible alloys used as implants play a significant role in their osseointegration. Surface sol-gel processing (SSP), a variant of the bulk sol-gel technique, is a relatively new process to prepare bioreactive nanostructured titanium oxide for thin film coatings. The surface topography, roughness, and composition of sol-gel processed Ti6Al4V titanium alloy coatings was investigated by atomic force microscopy (AFM) and X-ray electron spectroscopy (XPS). This was correlated with corrosion properties, adhesive strength, and bioreactivity in simulated body fluids (SBF). Electroimpedance spectroscopy (EIS) and polarization studies indicated similar advantageous corrosion properties between sol-gel coated and uncoated Ti6Al4V, which was attributed to the stable TiO2 composition, topography, and adhesive strength of the sol-gel coating. In addition, inductive coupled plasma (ICP) and scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) analysis of substrates immersed in SBF revealed higher deposition of calcium and phosphate and low release rates of alloying elements from the sol-gel modified alloys. The equivalent corrosion behavior and the definite increase in nucleation of calcium apatite indicate the potential of the sol-gel coating for enhanced bioimplant applications. 2006 Wiley Periodicals, Inc.

  18. Direct and indirect measurement of the magnetocaloric effect in bulk and nanostructured Ni-Mn-In Heusler alloy

    NASA Astrophysics Data System (ADS)

    Ghahremani, Mohammadreza; Aslani, Amir; Hosseinnia, Marjan; Bennett, Lawrence H.; Della Torre, Edward

    2018-05-01

    A systematic study of the magnetocaloric effect of a Ni51Mn33.4In15.6 Heusler alloy converted to nanoparticles via high energy ball-milling technique in the temperature range of 270 to 310 K has been performed. The properties of the particles were characterized by x-ray diffraction, electron microscopy, and magnetometer techniques. Isothermal magnetic field variation of magnetization exhibits field hysteresis in bulk Ni51Mn33.4In15.6 alloy across the martensitic transition which significantly lessened in the nanoparticles. The magnetocaloric effects of the bulk and nanoparticle samples were measured both with direct method, through our state of the art direct test bed apparatus with controllability over the applied fields and temperatures, as well as an indirect method through Maxwell and thermodynamic equations. In direct measurements, nanoparticle sample's critical temperature decreased by 6 K, but its magnetocaloric effect enhanced by 17% over the bulk counterpart. Additionally, when comparing the direct and indirect magnetocaloric curves, the direct method showed 14% less adiabatic temperature change in the bulk and 5% less adiabatic temperature change in the nanostructured sample.

  19. Palladium Coated Copper Nanowires as a Hydrogen Oxidation Electrocatalyst in Base

    DOE PAGES

    Alia, Shaun M.; Yan, Yushan

    2015-05-09

    The palladium (Pd) nanotubes we synthesized by the spontaneous galvanic displacement of copper (Cu) nanowires, are forming extended surface nanostructures highly active for the hydrogen oxidation reaction (HOR) in base. The synthesized catalysts produce specific activities in rotating disk electrode half-cells 20 times greater than Pd nanoparticles and about 80% higher than polycrystalline Pd. Although the surface area of the Pd nanotubes was low compared to conventional catalysts, partial galvanic displacement thrifted the noble metal layer and increased the Pd surface area. Moreover, the use of Pd coated Cu nanowires resulted in a HOR mass exchange current density 7 timesmore » greater than the Pd nanoparticles. The activity of the Pd coated Cu nanowires further nears Pt/C, producing 95% of the mass activity.« less

  20. An Optical Sensor with Polyaniline-Gold Hybrid Nanostructures for Monitoring pH in Saliva.

    PubMed

    Luo, Chongdai; Wang, Yangyang; Li, Xuemeng; Jiang, Xueqin; Gao, Panpan; Sun, Kang; Zhou, Jianhua; Zhang, Zhiguang; Jiang, Qing

    2017-03-17

    Saliva contains important personal physiological information that is related to some diseases, and it is a valuable source of biochemical information that can be collected rapidly, frequently, and without stress. In this article, we reported a new and simple localized surface plasmon resonance (LSPR) substrate composed of polyaniline (PANI)-gold hybrid nanostructures as an optical sensor for monitoring the pH of saliva samples. The overall appearance and topography of the substrates, the composition, and the wettability of the LSPR surfaces were characterized by optical and scanning electron microscope (SEM) images, infrared spectra, and contact angles measurement, respectively. The PANI-gold hybrid substrate readily responded to the pH. The response time was very short, which was 3.5 s when the pH switched from 2 to 7, and 4.5 s from 7 to 2. The changes of visible-near-infrared (NIR) spectra of this sensor upon varying pH in solution showed that-for the absorption at given wavelengths of 665 nm and 785 nm-the sensitivities were 0.0299 a.u./pH (a.u. = arbitrary unit) with a linear range of pH = 5-8 and 0.0234 a.u./pH with linear range of pH = 2-8, respectively. By using this new sensor, the pH of a real saliva sample was monitored and was consistent with the parallel measurements with a standard laboratory method. The results suggest that this novel LSPR sensor shows great potential in the field of mobile healthcare and home medical devices, and could also be modified by different sensitive materials to detect various molecules or ions in the future.

  1. Constructing, connecting and soldering nanostructures by environmental electron beam deposition

    NASA Astrophysics Data System (ADS)

    Mølhave, Kristian; Nørgaard Madsen, Dorte; Dohn, Søren; Bøggild, Peter

    2004-08-01

    Highly conductive nanoscale deposits with solid gold cores can be made by electron beam deposition in an environmental scanning electron microscope (ESEM), suggesting the method to be used for constructing, connecting and soldering nanostructures. This paper presents a feasibility study for such applications. We identify several issues related to contamination and unwanted deposition, relevant for deposition in both vacuum (EBD) and environmental conditions (EEBD). We study relations between scan rate, deposition rate, angle and line width for three-dimensional structures. Furthermore, we measure the conductivity of deposits containing gold cores, and find these structures to be highly conductive, approaching the conductivity of solid gold and capable of carrying high current densities. Finally, we study the use of the technique for soldering nanostructures such as carbon nanotubes. Based on the presented results we are able to estimate limits for the applicability of the method for the various applications, but also demonstrate that it is a versatile and powerful tool for nanotechnology within these limits.

  2. [A study on the color difference between Au-Pt alloy porcelain and Ni-Cr alloy porcelain].

    PubMed

    Li, Yong; Zhao, Yunfeng; Li, Hong

    2003-06-01

    To investigate the color difference between Au-Pt alloy porcelain and Ni-Cr alloy porcelain. 30 metal-ceramic specimens with different dentin porcelain thickness were fabricated with two types of metal-ceramic alloy, each type of alloy had 15 specimens. L*, a*, b* were measured after opaque porcelain was applied, and dentin porcelain was fired 1, 3, 5, 7 times by MINOLTA CR-100. Then delta E was calculated which reflected the color difference between high-gold alloy porcelain and Ni-Cr alloy porcelain. Comparing with Ni-Cr alloy porcelain, the color of Au-Pt alloy porcelain was reddish, yellowish and less bright. The delta E between high-gold alloy porcelain and Ni-Cr alloy porcelain in shade A2 was largest when opaque porcelain was applied. It decreased when dentin porcelain was applied. It became smallest when fired 3 times, and increased along with the increase of fire times. It was larger than 1.5 except firing 3 times. When dentin porcelain was applied, delta E which was larger than 1.5 among different dentin porcelain thickness decreased along with the increase of dentin porcelain thickness. The color difference between the two types of metal-ceramic alloy should be carefully taken into account in order to improve the quality of color matching.

  3. Inhibitory effect of Ti-Ag alloy on artificial biofilm formation.

    PubMed

    Nakajo, Kazuko; Takahashi, Masatoshi; Kikuchi, Masafumi; Takada, Yukyo; Okuno, Osamu; Sasaki, Keiichi; Takahashi, Nobuhiro

    2014-01-01

    Titanium-silver (Ti-Ag) alloy has been improved for machinability and mechanical properties, but its anti-biofilm properties have not been elucidated yet. Thus, this study aimed to evaluate the effects of Ti-Ag alloy on biofilm formation and bacterial viability in comparison with pure Ti, pure Ag and silver-palladium (Ag-Pd) alloy. Biofilm formation on the metal plates was evaluated by growing Streptococcus mutans and Streptococcus sobrinus in the presence of metal plates. Bactericidal activity was evaluated using a film contact method. There were no significant differences in biofilm formation between pure Ti, pure Ag and Ag-Pd alloy, while biofilm amounts on Ti-20% Ag and Ti-25% Ag alloys were significantly lower (p<0.05). In addition, Ti-Ag alloys and pure Ti were not bactericidal, although pure Ag and Ag-Pd alloy killed bacteria. These results suggest that Ti-20% Ag and Ti-25% Ag alloys are suitable for dental material that suppresses biofilm formation without disturbing healthy oral microflora.

  4. Synthesis of icosahedral gold nanocrystals: a thermal process strategy.

    PubMed

    Zhou, Min; Chen, Shenhao; Zhao, Shiyong

    2006-03-16

    We demonstrate a one-step thermal process route to the synthesis of icosahedral gold nanocrystals. By regulating the concentrations of poly(vinyl pyrrolidone) (PVP) and HAuCl4 or changing the temperature, we can readily access the shapes of icosahedral nanocrystals with good uniformity. These gold nanostructures, with unique geometrical shapes, might find use in areas that include photonics, optoelectronics, and optical sensing. We also observed that these gold nanocrystals have a strong tendency to be immobilized spontaneously on the glass substrate.

  5. Enhanced chemiluminescence-based detection on gold substrate after electrografting of diazonium precursor-coated gold nanoparticles.

    PubMed

    Houmed Adabo, Ali; Zeggari, Rabah; Mohamed Saïd, Nasser; Bazzi, Rana; Elie-Caille, Céline; Marquette, Christophe; Martini, Matteo; Tillement, Olivier; Perriat, Pascal; Chaix, Carole; Boireau, Wilfrid; Roux, Stéphane

    2016-04-01

    Since it was demonstrated that nanostructured surfaces are more efficient for the detection based on the specific capture of analytes, there is a real need to develop strategies for grafting nanoparticles onto flat surfaces. Among the different routes for the functionalization of a surface, the reduction of diazonium salts appears very attractive for the covalent immobilization of nanoparticles because this method does not require a pre-treatment of the surface. For achieving this goal, gold nanoparticles coated by precursor of diazonium salts were synthesized by reduction of gold salt in presence of mercaptoaniline. These mercaptoaniline-coated gold nanoparticles (Au@MA) were successfully immobilized onto various conducting substrates (indium tin oxide (ITO), glassy carbon (GC) and gold electrodes with flat terraces) after addition of sodium nitrite at fixed potential. When applied onto the gold electrodes, such a grafting strategy led to an obvious enhancement of the luminescence of luminol used for the biodetection. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Liquid-phase pulsed laser ablation synthesis of graphitized carbon-encapsulated palladium core-shell nanospheres for catalytic reduction of nitrobenzene to aniline

    NASA Astrophysics Data System (ADS)

    Kim, Yu-jin; Ma, Rory; Reddy, D. Amaranatha; Kim, Tae Kyu

    2015-12-01

    Graphitized carbon-encapsulated palladium (Pd) core-shell nanospheres were produced via pulsed laser ablation of a solid Pd foil target submerged in acetonitrile. The microstructural features and optical properties of these nanospheres were characterized via high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy. Microstructural analysis indicated that the core-shell nanostructures consisted of single-crystalline cubic metallic Pd spheres that serve as the core material, over which graphitized carbon was anchored as a heterogeneous shell. The absorbance spectrum of the synthesized nanostructures exhibited a broad (absorption) band at ∼264 nm; this band corresponded to the typical inter-band transition of a metallic system and resulted possibly from the absorbance of the ionic Pd2+. The catalytic properties of the Pd and Pd@C core-shell nanostructures were investigated using the reduction of nitrobenzene to aniline by an excess amount of NaBH4 in an aqueous solution at room temperature, as a model reaction. Owing to the graphitized carbon-layered structure and the high specific surface area, the resulting Pd@C nanostructures exhibited higher conversion efficiencies than their bare Pd counterparts. In fact, the layered structure provided access to the surface of the Pd nanostructures for the hydrogenation reaction, owing to the synergistic effect between graphitized carbon and the nanostructures. Their unique structure and excellent catalytic performance render Pd@C core-shell nanostructures highly promising candidates for catalysis applications.

  7. Fabrication of a nanostructured gold-polymer composite material.

    PubMed

    Mallick, K; Witcomb, M; Scurrell, M

    2006-07-01

    A facile synthesis route is described for the preparation of a poly-(o-aminophenol)-gold nanoparticle composite material by polymerization of o-aminophenol (AP) monomer using HAuCl(4) as the oxidant. The synthesis was carried out in a methanol medium so that it could serve a dual solvent role, a solvent for both the AP and the water solution of HAuCl(4). It was found that oxidative polymerization of AP leads to the formation of poly-AP with a diameter of 50+/-10nm, while the reduction of AuCl(4) (-) results in the formation of gold nanoparticles ( approximately 2nm). The gold nanoparticles were uniformly dispersed and highly stabilized throughout the macromolecular chain that formed a uniform metal-polymer composite material. The resultant composite material was characterized by means of different techniques, such as UV-vis, IR and Raman spectroscopy, which offered the information about the chemical structure of polymer, whereas electron microscopy images provided information regarding the morphology of the composite material and the distribution of the metal particles in the composite material.

  8. Doped palladium containing oxidation catalysts

    DOEpatents

    Mohajeri, Nahid

    2014-02-18

    A supported oxidation catalyst includes a support having a metal oxide or metal salt, and mixed metal particles thereon. The mixed metal particles include first particles including a palladium compound, and second particles including a precious metal group (PMG) metal or PMG metal compound, wherein the PMG metal is not palladium. The oxidation catalyst may also be used as a gas sensor.

  9. Nanostructures based on alumina hydroxides inhibit tumor growth

    NASA Astrophysics Data System (ADS)

    Fomenko, A. N.; Korovin, M. S.

    2017-09-01

    Nanoparticles and nanostructured materials are one of the most promising developments for cancer therapy. Gold nanoparticles, magnetic nanoparticles based on iron and its oxides and other metal oxides have been widely used in diagnosis and treatment of cancer. Much less research attention has been payed to nanoparticles and nanostructures based on aluminum oxides and hydroxides as materials for cancer diagnosis and treatment. However recent investigations have shown promising results regarding these objects. Here, we review the antitumor results obtained with AlOOH nanoparticles.

  10. Compression of freestanding gold nanostructures: from stochastic yield to predictable flow

    NASA Astrophysics Data System (ADS)

    Mook, W. M.; Niederberger, C.; Bechelany, M.; Philippe, L.; Michler, J.

    2010-02-01

    Characterizing the mechanical response of isolated nanostructures is vitally important to fields such as microelectromechanical systems (MEMS) where the behaviour of nanoscale contacts can in large part determine system reliability and lifetime. To address this challenge directly, single crystal gold nanodots are compressed inside a high resolution scanning electron microscope (SEM) using a nanoindenter equipped with a flat punch tip. These structures load elastically, and then yield in a stochastic manner, at loads ranging from 16 to 110 µN, which is up to five times higher than the load necessary for flow after yield. Yielding is immediately followed by displacement bursts equivalent to 1-50% of the initial height, depending on the yield point. During the largest displacement bursts, strain energy within the structure is released while new surface area is created in the form of localized slip bands, which are evident in both the SEM movies and still-images. A first order estimate of the apparent energy release rate, in terms of fracture mechanics concepts, for bursts representing 5-50% of the structure's initial height is on the order of 10-100 J m-2, which is approximately two orders of magnitude lower than bulk values. Once this initial strain burst during yielding has occurred, the structures flow in a ductile way. The implications of this behaviour, which is analogous to a brittle to ductile transition, are discussed with respect to mechanical reliability at the micro- and nanoscales.

  11. Size and shape-dependent cytotoxicity profile of gold nanoparticles for biomedical applications.

    PubMed

    Woźniak, Anna; Malankowska, Anna; Nowaczyk, Grzegorz; Grześkowiak, Bartosz F; Tuśnio, Karol; Słomski, Ryszard; Zaleska-Medynska, Adriana; Jurga, Stefan

    2017-06-01

    Metallic nanoparticles, in particular gold nanoparticles (AuNPs), offer a wide spectrum of applications in biomedicine. A crucial issue is their cytotoxicity, which depends greatly on various factors, including morphology of nanoparticles. Because metallic nanoparticles have an effect on cell membrane integrity, their shape and size may affect the viability of cells, due to their different geometries as well as physical and chemical interactions with cell membranes. Variations in the size and shape of gold nanoparticles may indicate particular nanoparticle morphologies that provide strong cytotoxicity effects. Synthesis of different sized and shaped bare AuNPs was performed with spherical (~ 10 nm), nanoflowers (~ 370 nm), nanorods (~ 41 nm), nanoprisms (~ 160 nm) and nanostars (~ 240 nm) morphologies. These nanostructures were characterized and interacting with cancer (HeLa) and normal (HEK293T) cell lines and cell viability tests were performed by WST-1 tests and fluorescent live/dead cell imaging experiments. It was shown that various shapes and sizes of gold nanostructures may affect the viability of the cells. Gold nanospheres and nanorods proved to be more toxic than star, flower and prism gold nanostructures. This may be attributed to their small size and aggregation process. This is the first report concerning a comparison of cytotoxic profile in vitro with a wide spectrum of bare AuNPs morphology. The findings show their possible use in biomedical applications.

  12. Method for wetting a boron alloy to graphite

    DOEpatents

    Storms, E.K.

    1987-08-21

    A method is provided for wetting a graphite substrate and spreading a a boron alloy over the substrate. The wetted substrate may be in the form of a needle for an effective ion emission source. The method may also be used to wet a graphite substrate for subsequent joining with another graphite substrate or other metal, or to form a protective coating over a graphite substrate. A noneutectic alloy of boron is formed with a metal selected from the group consisting of nickel (Ni), palladium (Pd), and platinum (Pt) with excess boron, i.e., and atomic percentage of boron effective to precipitate boron at a wetting temperature of less than the liquid-phase boundary temperature of the alloy. The alloy is applied to the substrate and the graphite substrate is then heated to the wetting temperature and maintained at the wetting temperature for a time effective for the alloy to wet and spread over the substrate. The excess boron is evenly dispersed in the alloy and is readily available to promote the wetting and spreading action of the alloy. 1 fig.

  13. 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.

  14. Nanostructured severe plastic deformation processed titanium for orthodontic mini-implants.

    PubMed

    Serra, Glaucio; Morais, Liliane; Elias, Carlos Nelson; Semenova, Irina P; Valiev, Ruslan; Salimgareeva, Gulnaz; Pithon, Matheus; Lacerda, Rogério

    2013-10-01

    Titanium mini-implants have been successfully used as anchorage devices in Orthodontics. Commercially pure titanium (cpTi) was recently replaced by Ti-6Al-4V alloy as the mini-implant material base due to the higher strength properties of the alloy. However, the lower corrosion resistance and the lower biocompatibility have been lowering the success rate of Ti-6Al-4V mini-implants. Nanostructured titanium (nTi) is commercially pure titanium that was nanostructured by a specific technique of severe plastic deformation. It is bioinert, does not contain potentially toxic or allergic additives, and has higher specific strength properties than any other titanium applied in medical implants. The higher strength properties associated to the higher biocompatibility make nTi potentially useful for orthodontic mini-implant applications, theoretically overcoming cpTi and Ti-6Al-4V mini-implants. The purposes of the this work were to process nTi, to mechanically compare cpTi, Ti-6Al-4V, and nTi mini-implants by torque test, and to evaluate both the surface morphology and the fracture surface characteristics of them by SEM. Torque test results showed significant increase in the maximum torque resistance of nTi mini-implants when compared to cpTi mini-implants, and no statistical difference between Ti-6Al-4V and nTi mini-implants. SEM analysis demonstrated smooth surface morphology and transgranular fracture aspect for nTi mini-implants. Since nanostructured titanium mini-implants have mechanical properties comparable to titanium alloy mini-implants, and biocompatibility comparable to commercially pure titanium mini-implants, it is suggestive that nanostructured titanium can replace Ti-6Al-4V alloy as the material base for mini-implants. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. Tellurium nano-structure based NO gas sensor.

    PubMed

    Kumar, Vivek; Sen, Shashwati; Sharma, M; Muthe, K P; Jagannath; Gaur, N K; Gupta, S K

    2009-09-01

    Tellurium nanotubes were grown on bare and silver/gold nanoparticle (nucleation centers) deposited silicon substrates by vacuum deposition technique at a substrate temperature of 100 degrees C under high vacuum conditions. Silver and gold nanoparticles prepared on (111) oriented silicon substrates were found to act as nucleation centers for growth of Tellurium nanostructures. Density of nanotubes was found to increase while their diameter reduced when grown using metallic nanoparticle template. These Te nanostructures were investigated for their gas sensitivity. Tellurium nanotubes on Ag templates showed better response to NO in comparison to H2S and NH3 gases. Selectivity in response to NO was improved in comparison to Te thin film sensors reported earlier. The gas sensing mechanism was investigated using Raman and X-ray photoelectron spectroscopy techniques. The interaction of NO is seen to yield increased adsorption of oxygen that in turn increases hole density and conductivity in the material.

  16. Elastic moduli of cast Ti-Au, Ti-Ag, and Ti-Cu alloys.

    PubMed

    Kikuchi, Masafumi; Takahashi, Masatoshi; Okuno, Osamu

    2006-07-01

    This study investigated the effect of alloying titanium with gold, silver, or copper on the elastic properties of the alloys. A series of binary titanium alloys was made with four concentrations of gold, silver, or copper (5, 10, 20, and 30 mass%) in an argon-arc melting furnace. The Young's moduli and Poisson's ratios of the alloy castings were determined with an ultrasonic-pulse method. The density of each alloy was previously measured by the Archimedes' principle. Results were analyzed using one-way ANOVA and the Scheffé's test. The densities of Ti-Au, Ti-Ag, and Ti-Cu alloys monotonically increased as the concentration of alloying elements increased. As the concentration of gold or silver increased to 20%, the Young's modulus significantly decreased, followed by a subsequent increase in value. As the concentration of copper increased, the Young's modulus monotonically increased. The Young's moduli of all the Ti-Cu alloys were significantly higher than that of the titanium. The density of all the experimental alloys was virtually independent of the alloy phases, while the Young's moduli and Poisson's ratios of the alloys were dependent. The addition of gold or silver slightly reduced the Young's modulus of the titanium when the alloy phase was single alpha. The increase in the Young's modulus of the Ti-Cu alloys is probably due to the precipitation of intermetallic compound Ti2Cu. Copper turned out to be a moderate stiffener that gains a Young's modulus of titanium up to 20% at the copper concentration of 30 mass%.

  17. [Studies on high temperature oxidation of noble metal alloys for dental use. (III) On high temperature oxidation resistance of noble metal alloys by adding small amounts of alloying elements. (author's transl)].

    PubMed

    Ohno, H

    1976-11-01

    The previous report pointed out the undesirable effects of high temperature oxidation on the casting. The influence of small separate additions of Zn, Mg, Si, Be and Al on the high temperature oxidation of the noble metal alloys was examined. These alloying elements were chosen because their oxide have a high electrical resistivity and they have much higher affinity for oxygen than Cu. The casting were oxidized at 700 degrees C for 1 hour in air. The results obtained were as follows: 1. The Cu oxides are not observed on the as-cast surface of noble metal alloys containing small amounts of Zn, Mg, Si, Be, and Al. The castings have gold- or silver-colored surface. 2. After heating of the unpolished and polished castings, the additions of Si, Be and Al are effective in preventing oxidation of Cu in the 18 carats gold alloys. Especially the golden surface is obtained by adding Be and Al. But there is no oxidation-resistance on the polished castings in the alloys containing Zn and Mg. 3. The zinc oxide film formed on the as-cast specimen is effective in preventing of oxidation Cu in 18 carats gold alloys. 4. It seems that the addition of Al is most available in dental application.

  18. Metal Alloy ICF Capsules Created by Electrodeposition

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

    Horwood, Corie; Stadermann, Michael; Bunn, Thomas L.

    Electrochemical deposition is an attractive alternative to physical vapor deposition and micromachining to produce metal capsules for inertial confinement fusion (ICF). Electrochemical deposition (also referred to as electrodeposition or plating) is expected to produce full-density metal capsules without seams or inclusions of unwanted atomic constituents, the current shortcomings of micromachine and physical vapor deposition, respectively. In this paper, we discuss new cathode designs that allow for the rapid electrodeposition of gold and copper alloys on spherical mandrels by making transient contact with the constantly moving spheres. Electrodeposition of pure gold, copper, platinum, and alloys of gold-copper and gold-silver are demonstrated,more » with nonporous coatings of >40 µm achieved in only a few hours of plating. The surface roughness of the spheres after electrodeposition is comparable to the starting mandrel, and the coatings appear to be fully dense with no inclusions. A detailed understanding of the electrodeposition conditions that result in different alloy compositions and plating rates will allow for the electrodeposition of graded alloys on spheres in the near future. Finally, this report on the electrodeposition of metals on spherical mandrels is an important first step toward the fabrication of graded-density metal capsules for ICF experiments at the National Ignition Facility.« less

  19. Metal Alloy ICF Capsules Created by Electrodeposition

    DOE PAGES

    Horwood, Corie; Stadermann, Michael; Bunn, Thomas L.

    2017-12-04

    Electrochemical deposition is an attractive alternative to physical vapor deposition and micromachining to produce metal capsules for inertial confinement fusion (ICF). Electrochemical deposition (also referred to as electrodeposition or plating) is expected to produce full-density metal capsules without seams or inclusions of unwanted atomic constituents, the current shortcomings of micromachine and physical vapor deposition, respectively. In this paper, we discuss new cathode designs that allow for the rapid electrodeposition of gold and copper alloys on spherical mandrels by making transient contact with the constantly moving spheres. Electrodeposition of pure gold, copper, platinum, and alloys of gold-copper and gold-silver are demonstrated,more » with nonporous coatings of >40 µm achieved in only a few hours of plating. The surface roughness of the spheres after electrodeposition is comparable to the starting mandrel, and the coatings appear to be fully dense with no inclusions. A detailed understanding of the electrodeposition conditions that result in different alloy compositions and plating rates will allow for the electrodeposition of graded alloys on spheres in the near future. Finally, this report on the electrodeposition of metals on spherical mandrels is an important first step toward the fabrication of graded-density metal capsules for ICF experiments at the National Ignition Facility.« less

  20. Mecanismes d'ablation du silicium par laser ultrarapide amplifie par des nanostructures plasmoniques

    NASA Astrophysics Data System (ADS)

    Robitaille, Alexandre

    Ultrafast laser interaction with gold nanostructures deposited onto a silicon surface produces considerable field amplification that can result in the ablation of features with dimensions smaller than the diffraction limit. This field amplification in the near field of the nanostructures has been thoroughly investigated in the literature. However, while this is the main phenomenon that permits this nanoablation, energy deposition and diffusion processes cannot be neglected to interpret experimental results. In this work, we study plasmon-enhanced femtosecond laser ablation of silicon using gold nanorods and gold nanospheres to produce sub-diffraction limit holes. Atomic force microscopy and scanning electron microscopy of such features are done and hole depth as a function of fluence is measured. Especially for gold nanorods, hole shape is inconsistent with calculated field distribution. Field distribution alone would let us believe that each nanorod would produce two holes at its both ends. We show that using a model based on a differential equations system describing carriers excitation and diffusion, both shape and depth of the nanoholes can be predicted. Importance of the diffusion process is shown to arise from the extreme localization of the deposited energy around the nanostructure, compared to what is usually the case for conventional ablation of a surface. The characteristic shape of holes is revealed as a striking signature of the energy distribution through the electron-phonon carrier density dependant interaction.

  1. Ceramic-metal composite article and joining method

    DOEpatents

    Kang, Shinhoo; Selverian, John H.; Kim, Hans J.; Dunn, Edmund M.; Kim, Kyung S.

    1992-01-01

    A ceramic-metal article including a ceramic rod, a metal rod, and a braze joining the ceramic and metal rods at a braze area of a coaxial bore in the metal rod. The bore gradually decreases in diameter, having an inward seat area sized for close sliding fit about the ceramic, a larger brazing area near the joint end, and a void area intermediate the braze and seat areas. The ceramic is seated without brazing in the bore seat area. The side wall between the brazing area and the metal outer surface is about 0.030-0.080 inch. The braze includes an inner braze layer, an outer braze layer, and an interlayer about 0.030-0.090 inch thick. A shoulder between the brazing and void areas supports the interlayer during bonding while preventing bonding between the void area and the ceramic member, leaving a void space between the void area and the ceramic member. A venting orifice extends generally radially through the metal member from the outer surface to the void space. The braze layers are palladium, platinum, gold, silver, copper, nickel, indium, chromium, molybdenum, niobium, iron, aluminum, or alloys thereof. Preferred is a gold-palladium-nickel brazing alloy. The interlayer is nickel, molybdenum, copper, tantalum, tungsten, niobium, aluminum, cobalt, iron, or an alloy thereof.

  2. Ceramic-metal composite article and joining method

    DOEpatents

    Kang, S.; Selverian, J.H.; Kim, H.J.; Dunn, E.M.; Kim, K.S.

    1992-04-28

    A ceramic-metal article including a ceramic rod, a metal rod, and a braze joining the ceramic and metal rods at a braze area of a coaxial bore in the metal rod is described. The bore gradually decreases in diameter, having an inward seat area sized for close sliding fit about the ceramic, a larger brazing area near the joint end, and a void area intermediate the braze and seat areas. The ceramic is seated without brazing in the bore seat area. The side wall between the brazing area and the metal outer surface is about 0.030-0.080 inch. The braze includes an inner braze layer, an outer braze layer, and an interlayer about 0.030-0.090 inch thick. A shoulder between the brazing and void areas supports the interlayer during bonding while preventing bonding between the void area and the ceramic member, leaving a void space between the void area and the ceramic member. A venting orifice extends generally radially through the metal member from the outer surface to the void space. The braze layers are palladium, platinum, gold, silver, copper, nickel, indium, chromium, molybdenum, niobium, iron, aluminum, or alloys thereof. Preferred is a gold-palladium-nickel brazing alloy. The interlayer is nickel, molybdenum, copper, tantalum, tungsten, niobium, aluminum, cobalt, iron, or an alloy thereof. 4 figs.

  3. Integrating a high-force optical trap with gold nanoposts and a robust gold-DNA bond.

    PubMed

    Paik, D Hern; Seol, Yeonee; Halsey, Wayne A; Perkins, Thomas T

    2009-08-01

    Gold-thiol chemistry is widely used in nanotechnology but has not been exploited in optical-trapping experiments due to laser-induced ablation of gold. We circumvented this problem by using an array of gold nanoposts (r = 50-250 nm, h approximately 20 nm) that allowed for quantitative optical-trapping assays without direct irradiation of the gold. DNA was covalently attached to the gold via dithiol phosphoramidite (DTPA). By using three DTPAs, the gold-DNA bond was not cleaved in the presence of excess thiolated compounds. This chemical robustness allowed us to reduce nonspecific sticking by passivating the unreacted gold with methoxy-(polyethylene glycol)-thiol. We routinely achieved single beads anchored to the nanoposts by single DNA molecules. We measured DNA's elasticity and its overstretching transition, demonstrating moderate- and high-force optical-trapping assays using gold-thiol chemistry. Force spectroscopy measurements were consistent with the rupture of the strepavidin-biotin bond between the bead and the DNA. This implied that the DNA remained anchored to the surface due to the strong gold-thiol bond. Consistent with this conclusion, we repeatedly reattached the trapped bead to the same individual DNA molecule. Thus, surface conjugation of biomolecules onto an array of gold nanostructures by chemically and mechanically robust bonds provides a unique way to carry out spatially controlled, repeatable measurements of single molecules.

  4. Probing Interfacial Friction and Dissipation in Granular Gold­ Nickel Alloys with a Quartz Crystal Oscillator in an External Magnetic Field

    NASA Astrophysics Data System (ADS)

    Stevens, K. M.; Krim, J.

    2015-03-01

    We present here a quartz crystal microbalance study of two-phase gold nickel alloys whose internal granular properties are probed by exposure to a fluctuating external magnetic field. The work is motivated by prior studies demonstrating that granular two-phase materials exhibited lower friction and wear than solid solution alloys with identical compositions. In particular, we report a ``flexing'' effect which appears when an external magnetic field is applied, and is manifested as a decrease in the magnitude of oscillation amplitude that is synchronized with the applied field; the effect is not seen on the complimentary solid solution samples. The effect is consistent with internal interfacial friction between nickel and gold grains, indicating a degree of freedom which may decrease friction even in the absence of an external magnetic field. This is supported through analysis of energy dissipation in the system, using the Butterworth­-Van Dyke equivalent circuit model. Data and interpretation are also presented that rule out alternate explanations such as giant magnetoresistance and/or other resistive phenomenon within the film. Funding provided by NSF DMR0805204. Thanks to L. Pan for sample preparation.

  5. Multipole Plasmon Resonances in Gold Nanorods

    PubMed Central

    Payne, Emma Kathryn; Shuford, Kevin L.; Park, Sungho; Schatz, George C.

    2011-01-01

    The optical properties of gold rods electrochemically deposited in anodic aluminum oxide templates have been investigated. Homogeneous suspensions of rods with average diameter of 85 nm and varying lengths of 96, 186, 321, 465, 495, 578, 641, 735, and 1175 nm were fabricated. The purity and dimensions of these rod nanostructures allowed us to observe higher order multipole resonances for the first time in a colloidal suspension. The experimental optical spectra agree with discrete dipole approximation calculations that have been modeled from the dimensions of the gold nanorods. PMID:16471797

  6. Toxicity of porcelain-fused-to-metal substrate to zebrafish (Danio rerio) embryos and larvae.

    PubMed

    Zhao, Libo; Si, Jing; Wei, Yuan; Li, Sirui; Jiang, Yanjiao; Zhou, Rong; Liu, Bin; Zhang, Hong

    2018-06-15

    Porcelain-fused-to-metal (PFM) crowns are a standard restoration technique in dentistry, but toxicity of PFM in vivo has not been systematically evaluated. The present study evaluated the effects of various metal alloy shells of PFM crowns on the development of zebrafish embryos and larvae in order to determine the safety of these materials. Gold palladium (Au-Pd), silver palladium (Ag-Pd), Nickel chromium (Ni-Cr), cobalt chromium (Co-Cr), titanium (Ti) alloy porcelain crowns were immersed in artificial saliva for 1, 4, and 7 weeks, and the leach solution was collected and used to treat zebrafish embryos at 4-144 h PFM. Toxicity was assessed based on mortality, spontaneous movement, heart rate, hatchability, malformation, and swimming behavior. The 1-week leachates of the five PFMs were not toxic to zebrafish. The rates of mortality and malformation of zebrafish in the Ni-Cr alloy group were increased whereas spontaneous movement, heart rate, and swimming behavior were decreased for 4- and 7-week leachates. Among metal substrates commonly used in dental work, Ni-Cr alloy was most toxic, followed by Co-Cr and Ag-Pd alloys. Ti and Au-Pd alloys showed good biocompatibility and are therefore the most suitable materials for clinical applications. Copyright © 2018 Elsevier Inc. All rights reserved.

  7. SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Agarwal, N. R.; Tommasini, M.; Fazio, E.; Neri, F.; Ponterio, R. C.; Trusso, S.; Ossi, P. M.

    2014-10-01

    Nanostructured Au and Ag thin films were obtained by nanosecond pulsed laser ablation in presence of a controlled Ar atmosphere. Keeping constant other deposition parameters such as target-to-substrate distance, incidence angle, laser wavelength and laser fluence, the film morphology, revealed by SEM, ranges from isolated NPs to island structures and sensibly depends on gas pressure (10-100 Pa) and on the laser pulse number (500-3 × 10). The control of these two parameters allows tailoring the morphology and correspondingly the optical properties of the films. The position and width of the surface plasmon resonance peak, in fact, can be varied with continuity. The films showed remarkable surface-enhanced Raman activity (SERS) that depends on the adopted deposition conditions. Raman maps were acquired on micrometer-sized areas of both silver and gold substrates selected among those with the strongest SERS activity. Organic dyes of interest in cultural heritage studies (alizarin, purpurin) have been also considered for bench marking the substrates produced in this work. Also the ability to detect the presence of biomolecules was tested using lysozyme in a label free configuration.

  8. Palladium Gate All Around - Hetero Dielectric -Tunnel FET based highly sensitive Hydrogen Gas Sensor

    NASA Astrophysics Data System (ADS)

    Madan, Jaya; Chaujar, Rishu

    2016-12-01

    The paper presents a novel highly sensitive Hetero-Dielectric-Gate All Around Tunneling FET (HD-GAA-TFET) based Hydrogen Gas Sensor, incorporating the advantages of band to band tunneling (BTBT) mechanism. Here, the Palladium supported silicon dioxide is used as a sensing media and sensing relies on the interaction of hydrogen with Palladium-SiO2-Si. The high surface to volume ratio in the case of cylindrical GAA structure enhances the fortuities for surface reactions between H2 gas and Pd, and thus improves the sensitivity and stability of the sensor. Behaviour of the sensor in presence of hydrogen and at elevated temperatures is discussed. The conduction path of the sensor which is dependent on sensors radius has also been varied for the optimized sensitivity and static performance analysis of the sensor where the proposed design exhibits a superior performance in terms of threshold voltage, subthreshold swing, and band to band tunneling rate. Stability of the sensor with respect to temperature affectability has also been studied, and it is found that the device is reasonably stable and highly sensitive over the bearable temperature range. The successful utilization of HD-GAA-TFET in gas sensors may open a new door for the development of novel nanostructure gas sensing devices.

  9. Gold coatings on polymer laser induced periodic surface structures: assessment as substrates for surface-enhanced Raman scattering.

    PubMed

    Rebollar, Esther; Sanz, Mikel; Pérez, Susana; Hernández, Margarita; Martín-Fabiani, Ignacio; Rueda, Daniel R; Ezquerra, Tiberio A; Domingo, Concepción; Castillejo, Marta

    2012-12-05

    We report on the fabrication of gold coated nanostructured polymer thin films and on their characterization as substrates for surface enhanced Raman spectroscopy (SERS). Laser induced periodic surface structures (LIPSS) were obtained on thin polymer films of poly(trimethylene terephthalate) (PTT) upon laser irradiation with the fourth harmonic of a Nd:YAG laser (266 nm, pulse duration 6 ns) resulting in a period close to the incident wavelength. The nanostructured polymer substrates were coated with a nanoparticle assembled gold layer by pulsed laser deposition using the fifth harmonic of a Nd:YAG laser (213 nm, pulse duration 15 ns). Different deposition times resulted in thicknesses from a few nanometres up to several tens of nanometres. Analysis by atomic force microscopy and grazing incident small angle X-ray scattering showed that gold coating preserved the LIPSS relief. The capabilities of the produced nanostructures as substrates for SERS have been investigated using benzenethiol as a test molecule. The SERS signal is substantially larger than that observed for a gold-coated flat substrate. Advantages of this new type of SERS substrates are discussed.

  10. MONTANA PALLADIUM RESEARCH INITIATIVE

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

    Peters, John; McCloskey, Jay; Douglas, Trevor

    2012-05-09

    Project Objective: The overarching objective of the Montana Palladium Research Initiative is to perform scientific research on the properties and uses of palladium in the context of the U.S. Department of Energy's Hydrogen, Fuel Cells and Infrastructure Technologies Program. The purpose of the research will be to explore possible palladium as an alternative to platinum in hydrogen-economy applications. To achieve this objective, the Initiatives activities will focus on several cutting-edge research approaches across a range of disciplines, including metallurgy, biomimetics, instrumentation development, and systems analysis. Background: Platinum-group elements (PGEs) play significant roles in processing hydrogen, an element that shows highmore » potential to address this need in the U.S. and the world for inexpensive, reliable, clean energy. Platinum, however, is a very expensive component of current and planned systems, so less-expensive alternatives that have similar physical properties are being sought. To this end, several tasks have been defined under the rubric of the Montana Palladium Research Iniative. This broad swath of activities will allow progress on several fronts. The membrane-related activities of Task 1 employs state-of-the-art and leading-edge technologies to develop new, ceramic-substrate metallic membranes for the production of high-purity hydrogen, and develop techniques for the production of thin, defect-free platinum group element catalytic membranes for energy production and pollution control. The biomimetic work in Task 2 explores the use of substrate-attached hydrogen-producing enzymes and the encapsulation of palladium in virion-based protein coats to determine their utility for distributed hydrogen production. Task 3 work involves developing laser-induced breakdown spectroscopy (LIBS) as a real-time, in situ diagnostic technique to characterize PGEs nanoparticles for process monitoring and control. The systems engineering work in task 4

  11. Block-copolymer assisted fabrication of anisotropic plasmonic nanostructures.

    PubMed

    Gunder, Calbi J; Dhara, Pijush Kanti; Manna, Uttam; Biswas, Mahua

    2018-05-30

    The anisotropic nanostructures of noble metals are of great interest for plasmonic applications due to the possibility of tuning the localized surface plasmon resonance (LSPR) across the UV-VIS-NIR without sacrificing the linewidth as well as to achieve larger local field enhancement. Here, we report a simple and promising fabrication method of anisotropic gold nanostructures film using polystyrene-b-2-vinylpyridine (PS-b-P2VP) block copolymers (BCP) as a template. In this approach, PS-b-P2VP spherical micelles were first synthesized as a template followed by selective deposition of Au precursor inside P2VP core of the micelles using ethanol solution of Au salt. Subsequently, heat treatment of the precursor deposited BCP films followed by removal of the BCP template produced anisotropic gold nanostructures of various shapes, such as octahedron, decahedron, tetrahedron, triangles, and triangular prism. A temperature and time dependent annealing of the fabricated nanostructures led to the formation of clusters at higher temperature. Furthermore, measurement of ensemble extinction spectra of the anisotropic Au nanoparticle films showed two broad distinct LSPR peaks; one in the visible range (~ 660 nm), and the other in the NIR range (~ 875 nm). The electrodynamic simulation showed that octahedron and decahedron nanoparticles are responsible for the LSPR response in the visible; whereas the triangular shapes are responsible for the LSPR response in the NIR. Our work is expected to open up a new direction of synthesis of anisotropic nanostructures of noble metals that can be utilized to tune the LSPR response across the UV-VIS-NIR range using a simple BCP template-based method. © 2018 IOP Publishing Ltd.

  12. Detector and energy analyzer for energetic-hydrogen in beams and plasmas

    DOEpatents

    Bastasz, Robert J.; Hughes, Robert C.; Wampler, William R.

    1988-01-01

    A detector for detecting energetic hydrogen ions and atoms ranging in energy from about 1 eV up to 1 keV in an evacuated environment includes a Schottky diode with a palladium or palladium-alloy gate metal applied to a silicondioxide layer on an n-silicon substrate. An array of the energetic-hydrogen detectors having a range of energy sensitivities form a plasma energy analyzer having a rapid response time and a sensitivity for measuring fluxes of energetic hydrogen. The detector is sensitive to hydrogen and its isotopes but is insensitive to non-hydrogenic particles. The array of energetic-hydrogen detectors can be formed on a single silicon chip, with thin-film layers of gold metal applied in various thicknesses to successive detectors in the array. The gold layers serve as particle energy-filters so that each detector is sensitive to a different range of hydrogen energies.

  13. Detector and energy analyzer for energetic-hydrogen in beams and plasmas

    DOEpatents

    Bastasz, R.J.; Hughes, R.C.; Wampler, W.R.

    1988-11-01

    A detector for detecting energetic hydrogen ions and atoms ranging in energy from about 1 eV up to 1 keV in an evacuated environment includes a Schottky diode with a palladium or palladium-alloy gate metal applied to a silicon-dioxide layer on an n-silicon substrate. An array of the energetic-hydrogen detectors having a range of energy sensitivities form a plasma energy analyzer having a rapid response time and a sensitivity for measuring fluxes of energetic hydrogen. The detector is sensitive to hydrogen and its isotopes but is insensitive to non-hydrogenic particles. The array of energetic-hydrogen detectors can be formed on a single silicon chip, with thin-film layers of gold metal applied in various thicknesses to successive detectors in the array. The gold layers serve as particle energy-filters so that each detector is sensitive to a different range of hydrogen energies. 4 figs.

  14. Direct writing of metal nanostructures: lithographic tools for nanoplasmonics research.

    PubMed

    Leggett, Graham J

    2011-03-22

    Continued progress in the fast-growing field of nanoplasmonics will require the development of new methods for the fabrication of metal nanostructures. Optical lithography provides a continually expanding tool box. Two-photon processes, as demonstrated by Shukla et al. (doi: 10.1021/nn103015g), enable the fabrication of gold nanostructures encapsulated in dielectric material in a simple, direct process and offer the prospect of three-dimensional fabrication. At higher resolution, scanning probe techniques enable nanoparticle particle placement by localized oxidation, and near-field sintering of nanoparticulate films enables direct writing of nanowires. Direct laser "printing" of single gold nanoparticles offers a remarkable capability for the controlled fabrication of model structures for fundamental studies, particle-by-particle. Optical methods continue to provide a powerful support for research into metamaterials.

  15. High temperature static strain gage alloy development program

    NASA Technical Reports Server (NTRS)

    Hulse, C. O.; Bailey, R. S.; Lemkey, F. D.

    1985-01-01

    The literature, applicable theory and finally an experimental program were used to identify new candidate alloy systems for use as the electrical resistance elements in static strain gages up to 1250K. The program goals were 50 hours of use in the environment of a test stand gas turbine engine with measurement accuracies equal to or better than 10 percent of full scale for strains up to + or - 2000 microstrain. As part of this effort, a computerized electrical resistance measurement system was constructed for use at temperatures between 300K and 1250K and heating and cooling rates of 250K/min and 10K/min. The two best alloys were an iron-chromium-aluminum alloy and a palladium base alloy. Although significant progress was made, it was concluded that a considerable additional effort would be needed to fully optimize and evaluate these candidate systems.

  16. Gold silver alloy nanoparticles (GSAN): an imaging probe for breast cancer screening with dual-energy mammography or computed tomography

    NASA Astrophysics Data System (ADS)

    Naha, Pratap C.; Lau, Kristen C.; Hsu, Jessica C.; Hajfathalian, Maryam; Mian, Shaameen; Chhour, Peter; Uppuluri, Lahari; McDonald, Elizabeth S.; Maidment, Andrew D. A.; Cormode, David P.

    2016-07-01

    Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various analytical methods. DEM and computed tomography (CT) phantom imaging showed that GSAN produced robust contrast that was comparable to silver alone. Cell viability, reactive oxygen species generation and DNA damage results revealed that the formulations with 30% or higher gold content are cytocompatible to Hep G2 and J774A.1 cells. In vivo imaging was performed in mice with and without breast tumors. The results showed that GSAN produce strong DEM and CT contrast and accumulated in tumors. Furthermore, both in vivo imaging and ex vivo analysis indicated the excretion of GSAN via both urine and feces. In summary, GSAN produce strong DEM and CT contrast, and has potential for both blood pool imaging and for breast cancer screening.Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various

  17. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1962-02-20

    A brazing alloy is described which, in the molten state, is characterized by excellent wettability and flowability and is capable of forming a corrosion-resistant brazed joint. At least one component of said joint is graphite and the other component is a corrosion-resistant refractory metal. The brazing alloy consists essentially of 40 to 90 wt % of gold, 5 to 35 wt% of nickel, and 1 to 45 wt% of tantalum. (AEC)

  18. Galvanic coupling of steel and gold alloy lingual brackets with orthodontic wires.

    PubMed

    Polychronis, Georgios; Al Jabbari, Youssef S; Eliades, Theodore; Zinelis, Spiros

    2018-03-06

    The aim of this research was to assess galvanic behavior of lingual orthodontic brackets coupled with representative types of orthodontic wires. Three types of lingual brackets: Incognito (INC), In-Ovation L (IOV), and STb (STB) were combined with a stainless steel (SS) and a nickel-titanium (NiTi) orthodontic archwire. All materials were initially investigated by scanning electron microscopy / x-ray energy dispersive spectroscopy (SEM/EDX) while wires were also tested by x-ray diffraction spectroscopy (XRD). All bracket-wire combinations were immersed in acidic 0.1M NaCl 0.1M lactic acid and neutral NaF 0.3% (wt) electrolyte, and the potential differences were continuously recorded for 48 hours. The SEM/EDX analysis revealed that INC is a single-unit bracket made of a high gold (Au) alloy while IOV and STB are two-piece appliances in which the base and wing are made of SS alloys. The SS wire demonstrated austenite and martensite iron phase, while NiTi wire illustrated an intense austenite crystallographic structure with limited martensite. All bracket wire combinations showed potential differences below the threshold of galvanic corrosion (200 mV) except for INC and STB coupled with NiTi wire in NaF media. The electrochemical results indicate that all brackets tested demonstrated galvanic compatibility with SS wire, but fluoride treatment should be used cautiously with NiTi wires coupled with Au and SS brackets.

  19. An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation

    NASA Astrophysics Data System (ADS)

    Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Boykin, Timothy; Klimeck, Gerhard

    2014-03-01

    Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.

  20. Mechanistic insight into oxide-promoted palladium catalysts for the electro-oxidation of ethanol.

    PubMed

    Martinez, Ulises; Serov, Alexey; Padilla, Monica; Atanassov, Plamen

    2014-08-01

    Recent advancements in the development of alternatives to proton exchange membrane fuel cells utilizing less-expensive catalysts and renewable liquid fuels, such as alcohols, has been observed for alkaline fuel cell systems. Alcohol fuels present the advantage of not facing the challenge of storage and transportation encountered with hydrogen fuel. Oxidation of alcohols has been improved by the promotion of alloyed or secondary phases. Nevertheless, currently, there is no experimental understanding of the difference between an intrinsic and a synergistic promotion effect in high-pH environments. This report shows evidence of different types of promotion effects on palladium electrocatalysts obtained from the presence of an oxide phase for the oxidation of ethanol. The correlation of mechanistic in situ IR spectroscopic studies with electrochemical voltammetry studies on two similar electrocatalytic systems allow the role of either an alloyed or a secondary phase on the mechanism of oxidation of ethanol to be elucidated. Evidence is presented for the difference between an intrinsic effect obtained from an alloyed system and a synergistic effect produced by the presence of an oxide phase. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Effects of electronic excitation on cascade dynamics in nickel–iron and nickel–palladium systems

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

    Zarkadoula, Eva; Samolyuk, German; Weber, William J.

    Using molecular dynamics simulations and the two-temperature model, we provide in this paper a comparison of the surviving damage from single ion irradiation events in nickel-based alloys, for cascades with and without taking into account the effects of the electronic excitations. We find that including the electronic effects impacts the amount of the resulting damage and the production of isolated defects. Finally, irradiation of nickel–palladium systems results in larger numbers of defects compared to nickel–iron systems, with similar numbers of isolated defects. We additionally investigate the mass effect on the two-temperature model in molecular dynamics simulations of cascades.

  2. Effects of electronic excitation on cascade dynamics in nickel–iron and nickel–palladium systems

    DOE PAGES

    Zarkadoula, Eva; Samolyuk, German; Weber, William J.

    2017-06-10

    Using molecular dynamics simulations and the two-temperature model, we provide in this paper a comparison of the surviving damage from single ion irradiation events in nickel-based alloys, for cascades with and without taking into account the effects of the electronic excitations. We find that including the electronic effects impacts the amount of the resulting damage and the production of isolated defects. Finally, irradiation of nickel–palladium systems results in larger numbers of defects compared to nickel–iron systems, with similar numbers of isolated defects. We additionally investigate the mass effect on the two-temperature model in molecular dynamics simulations of cascades.

  3. Formation of gold grating structures on fused silica substrates by femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Takami, Akihiro; Nakajima, Yasutaka; Terakawa, Mitsuhiro

    2017-05-01

    Despite the attractive optical properties of gold nanostructures for emerging applications, the formation of sharp laser-induced periodic gold structures has not been reported. In this study, we experimentally demonstrate the formation of micro- and nanoscale periodic gold grating structures on fused silica substrates using a femtosecond laser. The experimental and calculated results show good agreement, indicating that the gold grating structures were formed by a beat formed in a gold thin film. We also propose that the beat was formed by interference of two surface plasmon polaritons with different periods excited in a gold thin film and calculated their periods.

  4. Tensile deformation and fracture properties of a 14YWT nanostructured ferritic alloy

    DOE PAGES

    Alam, M. Ershadul; Pal, Soupitak; Fields, Kirk; ...

    2016-08-13

    Here, a new larger heat of a 14YWT nanostructured ferritic alloy (NFA), FCRD NFA-1, was synthesized by ball milling FeO and argon atomized Fe-14Cr-3W-0.4Ti-0.2Y (wt%) powders, followed by hot extrusion, annealing and cross rolling to produce an ≈10 mm-thick plate. NFA-1 contains a bimodal size distribution of pancake-shaped, mostly very fine scale, grains. The as-processed plate also contains a large population of microcracks running parallel to its broad surfaces. The small grains and large concentration of Y–Ti–O nano-oxides (NOs) result in high strength up to 800 °C. The uniform and total elongations range from ≈1–8%, and ≈10–24%, respectively. The strengthmore » decreases more rapidly above ≈400 °C and deformation transitions to largely viscoplastic creep by ≈600 °C. While the local fracture mechanism is generally ductile-dimple microvoid nucleation, growth and coalescence, perhaps the most notable feature of tensile deformation behavior of NFA-1 is the occurrence of periodic delamination, manifested as fissures on the fracture surfaces.« less

  5. Effect of surface reaction layer on grindability of cast titanium alloys.

    PubMed

    Ohkubo, Chikahiro; Hosoi, Toshio; Ford, J Phillip; Watanabe, Ikuya

    2006-03-01

    The purpose of this study was to investigate the effect of the cast surface reaction layer on the grindability of titanium alloys, including free-machining titanium alloy (DT2F), and to compare the results with the grindability of two dental casting alloys (gold and Co-Cr). All titanium specimens (pure Ti, Ti-6Al-4V and DT2F) were cast using a centrifugal casting machine in magnesia-based investment molds. Two specimen sizes were used to cast the titanium metals so that the larger castings would be the same size as the smaller gold and Co-Cr alloy specimens after removal of the surface reaction layer (alpha-case). Grindability was measured as volume loss ground from a specimen for 1 min using a handpiece engine with a SiC abrasive wheel at 0.1 kgf and four circumferential wheel speeds. For the titanium and gold alloys, grindability increased as the rotational speed increased. There was no statistical difference (p>0.05) in grindability for all titanium specimens either with or without the alpha-case. Of the titanium metals tested, Ti-6 Al-4V had the greatest grindability at higher speeds, followed by DT2F and CP Ti. The grindability of the gold alloy was similar to that of Ti-6 Al-4V, whereas the Co-Cr alloy had the lowest grindability. The results of this study indicated that the alpha-case did not significantly affect the grindability of the titanium alloys. The free-machining titanium alloy had improved grindability compared to CP Ti.

  6. Synthesis of copper oxide nanowires and nanoporous copper via environmentally friendly transformation of bulk copper-calcium alloys.

    PubMed

    Zhang, X; Turcheniuk, K; Zusmann, B; Benson, J; Nelson, S; Luo, S; Magasinski, A; Yushin, G

    2018-05-24

    In this work, we report a novel, one-step, inexpensive and environmentally friendly synthesis of Cu nanostructures by means of chemical de-alloying of bulk Cu-Ca alloys in aqueous solutions. By controlling the synthesis conditions, we tune the morphology of the nanostructured Cu from nanoporous Cu to copper oxide nanowires.

  7. SrZnO nanostructures grown on templated <0001> Al2O3 substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Labis, Joselito P.; Alanazi, Anwar Q.; Albrithen, Hamad A.; El-Toni, Ahmed Mohamed; Hezam, Mahmoud; Elafifi, Hussein Elsayed; Abaza, Osama M.

    2017-09-01

    The parameters of pulsed laser deposition (PLD) have been optimized to design different nanostructures of Strontium-alloyed zinc oxide (SrZnO). In this work, SrZnO nanostructures are grown on <0001>Al2O3 substrates via two-step templating/seeding approach. In the temperature range between 300 - 750 oC and O2 background pressures between 0.01 and 10 Torr, the growth conditions have been tailored to grow unique pointed leaf-like- and pitted olive-like nanostructures. Prior to the growth of the nanostructures, a thin SrZnO layer that serves as seed layer/template is first deposited on the Al2O3 substrates at ˜300oC and background oxygen pressure of 10 mTorr. The optical properties of the nanostructures were examined by UV/Vis spectroscopy and photoluminescence (PL), while the structures/morphologies were examined by SEM, TEM, and XRD. The alloyed SrZnO nanostructures, grown by ablating ZnO targets with 5, 10, 25% SrO contents, have in common a single-crystal hexagonal nanostructure with (0002) preferential orientation and have shown remarkable changes in the morphological and optical properties of the materials. To date, this is the only reported work on optimization of laser ablation parameters to design novel SrZnO nanostructures in the 5-25% alloying range, as most related Sr-doped ZnO studies were done below 7% doping. Although the physical properties of ZnO are modified via Sr doping, the mechanism remains unclear. The PLD-grown SrZnO nanostructures were directly grown onto the Al2O3 substrates; thus making these nanomaterials very promising for potential applications in biosensors, love-wave filters, solar cells, and ultrasonic oscillators.

  8. Lattice dynamics and thermoelectric properties of nanocrystalline silicon-germanium alloys: Lattice dynamics and thermoelectric properties of nc Si-Ge alloys

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

    Claudio, Tania; Stein, Niklas; Petermann, Nils

    2015-10-26

    The lattice dynamics and thermoelectric properties of sintered phosphorus-doped nanostructured silicon–germanium alloys obtained by gas-phase synthesis were studied. Measurements of the density of phonon states by inelastic neutron scattering were combined with measurements of the elastic constants and the low-temperature heat capacity. A strong influence of nanostructuring and alloying on the lattice dynamics was observed. The thermoelectric transport properties of samples with different doping as well as samples sintered at different temperature were characterized between room temperature and 1000°C. A peak figure of merit zT=0.88 at 900°C is observed and is comparatively insensitive to the aforementioned parameter variations.

  9. Molecular origin of the selectivity differences between palladium and gold-palladium in benzyl alcohol oxidation: Different oxygen adsorption properties

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

    Savara, Aditya Ashi; Chan-Thaw, Carine E.; Sutton, Jonathan E.

    The same mechanism and microkinetic model used for benzyl alcohol oxidation over Pd/C was shown to apply to benzyl alcohol oxidation over AuPd/C. Almost all of the selectivity differences could be explained by a decrease in oxygen adsorption on AuPd. After isolating oxygen adsorption as being the origin of the selectivity differences, density functional theory was used to investigate the oxygen adsorption properties of a pure Pd surface, a pure Au surface, and an alloyed AuPd surface. Finally, the calculations showed that Au–Pd alloying decreased the oxygen adsorption properties relative to pure Pd, which explained the selectivity differences, consistent withmore » the microkinetic modeling.« less

  10. Application of nanodimensional particles and aluminum hydroxide nanostructures for cancer diagnosis and therapy

    NASA Astrophysics Data System (ADS)

    Korovin, M. S.; Fomenko, A. N.

    2017-09-01

    Nanoparticles and nanostructured materials are one of the most promising developments for cancer therapy. Gold nanoparticles, magnetic nanoparticles based on iron and its oxides and other metal oxides have been widely used in diagnosis and treatment of cancer. Much less researchers' attention has been paid to nanoparticles and nanostructures based on aluminum oxides and hydroxides as materials for cancer diagnosis and treatment. However, recent investigations have shown promising results regarding these objects. Here, we review the antitumor results obtained with different aluminum oxide/hydroxide nanoparticles and nanostructures.

  11. Role of alloying elements in adhesive transfer and friction of copper-base alloys

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1978-01-01

    Sliding friction experiments were conducted in a vacuum with binary-copper alloy riders sliding against a conventional bearing-steel surface with normal residual oxides present. The binary alloys contained 1 atomic percent of various alloying elements. Auger spectroscopy analysis was used to monitor the adhesive transfer of the copper alloys to the bearing-steel surface. A relation was found to exist between adhesive transfer and the reaction potential and free energy of formation of the alloying element in the copper. The more chemically active the element and the more stable its oxide, the greater was the adhesive transfer and wear of the copper alloy. Transfer occurred in all the alloys except copper-gold after relatively few (25) passes across the steel surface.

  12. Engineering on-chip nanoporous gold material libraries via precision photothermal treatment

    NASA Astrophysics Data System (ADS)

    Chapman, Christopher A. R.; Wang, Ling; Biener, Juergen; Seker, Erkin; Biener, Monika M.; Matthews, Manyalibo J.

    2015-12-01

    Libraries of nanostructured materials on a single chip are a promising platform for high throughput and combinatorial studies of structure-property relationships in the fields of physics and biology. Nanoporous gold (np-Au), produced by an alloy corrosion process, is a nanostructured material specifically suited for such studies because of its self-similar thermally induced coarsening behavior. However, traditional heat application techniques for the modification of np-Au are bulk processes that cannot be used to generate a library of different pore sizes on a single chip. Here, laser micro-processing offers an attractive solution to this problem by providing a means to apply energy with high spatial and temporal resolution. In the present study we use finite element multiphysics simulations to predict the effects of laser mode (continuous-wave vs. pulsed) and thermal conductivity of the supporting substrate on the local np-Au film temperatures during photothermal annealing. Based on these results we discuss the mechanisms by which the np-Au network is coarsened. Thermal transport simulations predict that continuous-wave mode laser irradiation of np-Au thin films on a silicon substrate supports the widest range of morphologies that can be created through photothermal annealing of np-Au. Using the guidance provided by simulations, we successfully fabricate an on-chip material library consisting of 81 np-Au samples of 9 different morphologies for use in the parallel study of structure-property relationships.Libraries of nanostructured materials on a single chip are a promising platform for high throughput and combinatorial studies of structure-property relationships in the fields of physics and biology. Nanoporous gold (np-Au), produced by an alloy corrosion process, is a nanostructured material specifically suited for such studies because of its self-similar thermally induced coarsening behavior. However, traditional heat application techniques for the modification

  13. On Delamination Toughening of a 14YWT Nanostructured Ferritic Alloy

    DOE PAGES

    Alam, M.E.; Pal, S.; Maloy, Stuart Andrew; ...

    2017-06-22

    The FCRD NFA-1 is a high strength, irradiation tolerant nanostructured ferritic alloy (NFA) produced by ball milling argon atomized Fe-14Cr-3W-0.35Ti-0.25Y (wt.%) and FeO powders, followed by hot extrusion at 850 °C, and subsequent annealing and cross-rolling at 1000 °C. The microstructure of the resulting ≈10 mm thick NFA-1 plate is dominated by ultrafine sub-micron pancake shaped grains, and a large population of microcracks lying on planes parallel to the plate faces. Pre-cracked fracture toughness tests in four different orientations (L-T, T-L, L-S and T-S) show stable crack growth by ductile tearing, with peak load K Jc from ≈ 88 tomore » 154 MPa√m at ambient temperature. Stable crack tearing persists down to ≈ -175 °C and is accompanied by extensive delamination due to the propagation of the microcracks. Depending on the specimen orientation, this unusual toughening mechanism is either due to a reduction of crack tip stresses in thin ligaments formed by the delaminations (L-T and T-L), or 90° deflection of cracks initially running normal to the delaminations (L-S and T-S), thereby suppressing cleavage in both cases. Lastly, understanding the fracture processes in NFA-1 is also important to its irradiation tolerance in nuclear service as well as its fabricability in making defect-free components such as thin-walled tubing.« less

  14. Gold dendrites Co-deposited with M13 virus as a biosensor platform for nitrite ions.

    PubMed

    Seo, Yeji; Manivannan, Shanmugam; Kang, Inhak; Lee, Seung-Wuk; Kim, Kyuwon

    2017-08-15

    We developed a biosensor for nitrite ion on an electrode surface modified with M13 viruses and gold nanostructures. Gold dendritic nanostructures (Au-DNs) are electrochemically co-deposited from 4E peptides engineered M13 virus (M13 4E ) mixed electrolyte on to the ITO electrode. The M13 4E could specifically nucleate Au precursor (Gold (III) chloride), which enable the efficient growth of dendritic nanostructures, whereas such dendritic structures were not obtained in the presence of wild-type and Y3E peptides engineered M13 viruses. The structural features of the Au-DNs and their interfacing mechanism with ITO electrode are characterized by SEM, EDX and XRD analyses. The growth of Au-DNs at ITO electrode has been monitored by time dependent SEM study. The M13 4E induces the formation and plays a crucial role in shaping the dendritic morphology for Au. Biosensor electrode was constructed using Au-DNs modified electrode for nitrite ions and found improved sensitivity relative to the sensor electrode prepared from wild-type M13, Y3E peptides engineered M13 and without M13. Sensor electrode exhibited good selectivity toward target analyte from the possible interferences. Furthermore, 4E native peptides were used as additive to deposit Au nanostructures and it is compared with the structure and reactivity of the Au nanostructures prepared in the presence of M13 4E . Our novel biosensor fabrication can be extended to other metal and metal oxide nanostructures and its application might be useful to develop novel biosensor electrode for variety of biomolecules. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Construction and DNA condensation of cyclodextrin-coated gold nanoparticles with anthryl grafts.

    PubMed

    Zhao, Di; Chen, Yong; Liu, Yu

    2014-07-01

    The condensation of DNA in a controlled manner is one of the key steps in gene delivery and gene therapy. For this purpose, a water-soluble supramolecular nanostructure is constructed by coating 14 β-cyclodextrins onto the surface of a gold nanoparticle, followed by the noncovalent association of different amounts of anthryl-modified adamantanes with coated β-cyclodextrins. The strong binding of β-cyclodextrins with anthryl adamantanes (K(S) =8.61×10(4)  M(-1)) efficiently stabilizes the supramolecular nanostructure. Spectrophotometric fluorescence spectra and microscopic studies demonstrated that, with many anthryl grafts that can intercalate in the outer space of the DNA double helix, this supramolecular nanostructure showed good condensation abilities to calf thymus DNA. Significantly, the condensation efficiency of supramolecular nanostructure towards DNA could be conveniently controlled by adjusting the ratio between gold nanoparticles and anthryl adamantane grafts, leading to the formation of DNA condensates of a size that are suitable for the endocytosis of hepatoma cells, which will make it potentially applicable in many fields of medicinal science and biotechnology. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. A review of advantages of high-efficiency X-ray spectrum imaging for analysis of nanostructured ferritic alloys

    DOE PAGES

    Parish, Chad M.; Miller, Michael K.

    2014-12-09

    Nanostructured ferritic alloys (NFAs) exhibit complex microstructures consisting of 100-500 nm ferrite grains, grain boundary solute enrichment, and multiple populations of precipitates and nanoclusters (NCs). Understanding these materials' excellent creep and radiation-tolerance properties requires a combination of multiple atomic-scale experimental techniques. Recent advances in scanning transmission electron microscopy (STEM) hardware and data analysis methods have the potential to revolutionize nanometer to micrometer scale materials analysis. The application of these methods is applied to NFAs as a test case and is compared to both conventional STEM methods as well as complementary methods such as scanning electron microscopy and atom probe tomography.more » In this paper, we review past results and present new results illustrating the effectiveness of latest-generation STEM instrumentation and data analysis.« less

  17. Intermetallic Compound Growth between Electroless Nickel/Electroless Palladium/Immersion Gold Surface Finish and Sn-3.5Ag or Sn-3.0Ag-0.5Cu Solder

    NASA Astrophysics Data System (ADS)

    Oda, Yukinori; Fukumuro, Naoki; Yae, Shinji

    2018-04-01

    Using an electroless nickel/electroless palladium/immersion gold (ENEPIG) surface finish with a thick palladium-phosphorus (Pd-P) layer of 1 μm, the intermetallic compound (IMC) growth between the ENEPIG surface finish and lead-free solders Sn-3.5Ag (SA) or Sn-3.0Ag-0.5Cu (SAC) after reflow soldering and during solid-state aging at 150°C was investigated. After reflow soldering, in the SA/ENEPIG and SAC/ENEPIG interfaces, thick PdSn4 layers of about 2 μm to 3 μm formed on the residual Pd-P layers ( 0.5 μm thick). On the SA/ENEPIG interface, Sn was detected on the upper side of the residual Pd-P layer. On the SAC/ENEPIG interface, no Sn was detected in the residual Pd-P layer, and Cu was detected in the interface between the Pd-P and PdSn4 layers. After 300 h of aging at 150°C, the residual Pd-P layers had diffused completely into the solders. In the SA/ENEPIG interface, an IMC layer consisting of Ni3Sn4 and Ni3SnP formed between the PdSn4 layer and the nickel-phosphorus (Ni-P) layer, and a (Pd,Ni)Sn4 layer formed on the lower side of the PdSn4 layer. On the SAC/ENEPIG interface, a much thinner (Pd,Ni)Sn4 layer was observed, and a (Cu,Ni)6Sn5 layer was observed between the PdSn4 and Ni-P layers. These results indicate that Ni diffusion from the Ni-P layer to the PdSn4 layer produced a thick (Pd,Ni)Sn4 layer in the SA solder case, but was prevented by formation of (Cu,Ni)6Sn5 in the SAC solder case. This causes the difference in solder joint reliability between SA/ENEPIG and SAC/ENEPIG interfaces in common, thin Pd-P layer cases.

  18. Nanostructured calcium phosphate coatings on magnesium alloys: characterization and cytocompatibility with mesenchymal stem cells

    PubMed Central

    Iskandar, Maria Emil; Aslani, Arash; Tian, Qiaomu

    2016-01-01

    This article reports the deposition and characterization of nanostructured calcium phosphate (nCaP) on magnesium–yttrium alloy substrates and their cytocompatibility with bone marrow derived mesenchymal stem cells (BMSCs). The nCaP coatings were deposited on magnesium and magnesium–yttrium alloy substrates using proprietary transonic particle acceleration process for the dual purposes of modulating substrate degradation and BMSC adhesion. Surface morphology and feature size were analyzed using scanning electron microscopy and quantitative image analysis tools. Surface elemental compositions and phases were analyzed using energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. The deposited nCaP coatings showed a homogeneous particulate surface with the dominant feature size of 200–500 nm in the long axis and 100–300 nm in the short axis, and a Ca/P atomic ratio of 1.5–1.6. Hydroxyapatite was the major phase identified in the nCaP coatings. The modulatory effects of nCaP coatings on the sample degradation and BMSC behaviors were dependent on the substrate composition and surface conditions. The direct culture of BMSCs in vitro indicated that multiple factors, including surface composition and topography, and the degradation-induced changes in media composition, influenced cell adhesion directly on the sample surface, and indirect adhesion surrounding the sample in the same culture. The alkaline pH, the indicator of Mg degradation, played a role in BMSC adhesion and morphology, but not the sole factor. Additional studies are necessary to elucidate BMSC responses to each contributing factor. PMID:25917827

  19. Nanostructured calcium phosphate coatings on magnesium alloys: characterization and cytocompatibility with mesenchymal stem cells.

    PubMed

    Iskandar, Maria Emil; Aslani, Arash; Tian, Qiaomu; Liu, Huinan

    2015-05-01

    This article reports the deposition and characterization of nanostructured calcium phosphate (nCaP) on magnesium-yttrium alloy substrates and their cytocompatibility with bone marrow derived mesenchymal stem cells (BMSCs). The nCaP coatings were deposited on magnesium and magnesium-yttrium alloy substrates using proprietary transonic particle acceleration process for the dual purposes of modulating substrate degradation and BMSC adhesion. Surface morphology and feature size were analyzed using scanning electron microscopy and quantitative image analysis tools. Surface elemental compositions and phases were analyzed using energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. The deposited nCaP coatings showed a homogeneous particulate surface with the dominant feature size of 200-500 nm in the long axis and 100-300 nm in the short axis, and a Ca/P atomic ratio of 1.5-1.6. Hydroxyapatite was the major phase identified in the nCaP coatings. The modulatory effects of nCaP coatings on the sample degradation and BMSC behaviors were dependent on the substrate composition and surface conditions. The direct culture of BMSCs in vitro indicated that multiple factors, including surface composition and topography, and the degradation-induced changes in media composition, influenced cell adhesion directly on the sample surface, and indirect adhesion surrounding the sample in the same culture. The alkaline pH, the indicator of Mg degradation, played a role in BMSC adhesion and morphology, but not the sole factor. Additional studies are necessary to elucidate BMSC responses to each contributing factor.

  20. Brazing open cell reticulated copper foam to stainless steel tubing with vacuum furnace brazed gold/indium alloy plating

    DOEpatents

    Howard, Stanley R [Windsor, SC; Korinko, Paul S [Aiken, SC

    2008-05-27

    A method of fabricating a heat exchanger includes brush electroplating plated layers for a brazing alloy onto a stainless steel tube in thin layers, over a nickel strike having a 1.3 .mu.m thickness. The resultant Au-18 In composition may be applied as a first layer of indium, 1.47 .mu.m thick, and a second layer of gold, 2.54 .mu.m thick. The order of plating helps control brazing erosion. Excessive amounts of brazing material are avoided by controlling the electroplating process. The reticulated copper foam rings are interference fit to the stainless steel tube, and in contact with the plated layers. The copper foam rings, the plated layers for brazing alloy, and the stainless steel tube are heated and cooled in a vacuum furnace at controlled rates, forming a bond of the copper foam rings to the stainless steel tube that improves heat transfer between the tube and the copper foam.

  1. Engineering optical properties using plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Tamma, Venkata Ananth

    Plasmonic nanostructures can be engineered to take on unusual optical properties not found in natural materials. The optical responses of plasmonic materials are functions of the structural parameters and symmetry of the nanostructures, material parameters of the nanostructure and its surroundings and the incidence angle, frequency and polarization state of light. The scattering and hence the visibility of an object could be reduced by coating it with a plasmonic material. In this thesis, presented is an optical frequency scattering cancelation device composed of a silicon nanorod coated by a plasmonic gold nanostructure. The principle of operation was theoretically analyzed using Mie theory and the device design was verified by extensive numerical simulations. The device was fabricated using a combination of nanofabrication techniques such as electron beam lithography and focused ion beam milling. The optical responses of the scattering cancelation device and a control sample of bare silicon rod were directly visualized using near-field microscopy coupled with heterodyne interferometric detection. The experimental results were analyzed and found to match very well with theoretical prediction from numerical simulations thereby validating the design principles and our implementation. Plasmonic nanostructures could be engineered to exhibit unique optical properties such as Fano resonance characterized by narrow asymmetrical lineshape. We present dynamic tuning and symmetry lowering of Fano resonances in plasmonic nanostructures fabricated on flexible substrates. The tuning of Fano resonance was achieved by application of uniaxial mechanical stress. The design of the nanostructures was facilitated by extensive numerical simulations and the symmetry lowering was analyzed using group theoretical methods. The nanostructures were fabricated using electron beam lithography and optically characterized for various mechanical stress. The experimental results were in good

  2. Reshaping, Fragmentation, and Assembly of Gold Nanoparticles Assisted by Pulse Lasers

    PubMed Central

    2016-01-01

    Conspectus The vast majority of the outstanding applications of metal nanoparticles (NPs) developed during the last two decades have arisen from their unique optical properties. Within this context, rational synthesis and assembly of gold NPs have been the main research focus, aiming at the design of nanoplasmonic devices with tailored optical functionalities. The progress made in this field is thus to be ascribed to the understanding of the origin of the interaction between light and such gold nanostructures, the dynamics of which have been thoroughly investigated with significant contributions from short and ultrashort pulse laser technologies. We focus this Account on the potential of pulse lasers to provide new fundamental insights into the electron dynamics involved in the interaction of light with the free conduction electrons of Au NPs, that is, localized surface plasmon resonances (LSPRs). The excitation of LSPRs with a femtosecond pulse laser is followed by thermalization of the Au NP electrons and the subsequent relaxation of the nanocrystal lattice and the surrounding environment, which generally results in surface melting. By contrast, nanosecond irradiation usually induces AuNP fragmentation and uncontrolled melting due to overlapping excitation and relaxation phenomena. These concepts have been exploited toward the preparation of highly monodisperse gold nanospheres via pulse laser irradiation of polyhedral nanocrystal colloids, or in the fabrication of nanostructures with “written-in” optical properties. The applicability of pulsed coherent light has been extended toward the direct synthesis and manipulation of Au NPs. Through ablation of a gold target in a liquid with pulse lasers, spherical Au NPs can be synthesized with no need of stabilizing ligands, which is a great advantage in terms of reducing toxicity, rendering these NPs particularly suitable for medical applications. In addition, femtosecond laser irradiation has been proven a unique

  3. Electrocatalytic oxidation of small organic molecules in acid medium: enhancement of activity of noble metal nanoparticles and their alloys by supporting or modifying them with metal oxides.

    PubMed

    Kulesza, Pawel J; Pieta, Izabela S; Rutkowska, Iwona A; Wadas, Anna; Marks, Diana; Klak, Karolina; Stobinski, Leszek; Cox, James A

    2013-11-01

    Different approaches to enhancement of electrocatalytic activity of noble metal nanoparticles during oxidation of small organic molecules (namely potential fuels for low-temperature fuel cells such as methanol, ethanol and formic acid) are described. A physical approach to the increase of activity of catalytic nanoparticles (e.g. platinum or palladium) involves nanostructuring to obtain highly dispersed systems of high surface area. Recently, the feasibility of enhancing activity of noble metal systems through the formation of bimetallic (e.g. PtRu, PtSn, and PdAu) or even more complex (e.g. PtRuW, PtRuSn) alloys has been demonstrated. In addition to possible changes in the electronic properties of alloys, specific interactions between metals as well as chemical reactivity of the added components have been postulated. We address and emphasize here the possibility of utilization of noble metal and alloyed nanoparticles supported on robust but reactive high surface area metal oxides (e.g. WO 3 , MoO 3 , TiO 2 , ZrO 2 , V 2 O 5 , and CeO 2 ) in oxidative electrocatalysis. This paper concerns the way in which certain inorganic oxides and oxo species can act effectively as supports for noble metal nanoparticles or their alloys during electrocatalytic oxidation of hydrogen and representative organic fuels. Among important issues are possible changes in the morphology and dispersion, as well as specific interactions leading to the improved chemisorptive and catalytic properties in addition to the feasibility of long time operation of the discussed systems.

  4. Electrocatalytic oxidation of small organic molecules in acid medium: enhancement of activity of noble metal nanoparticles and their alloys by supporting or modifying them with metal oxides

    PubMed Central

    Kulesza, Pawel J.; Pieta, Izabela S.; Rutkowska, Iwona A.; Wadas, Anna; Marks, Diana; Klak, Karolina; Stobinski, Leszek; Cox, James A.

    2013-01-01

    Different approaches to enhancement of electrocatalytic activity of noble metal nanoparticles during oxidation of small organic molecules (namely potential fuels for low-temperature fuel cells such as methanol, ethanol and formic acid) are described. A physical approach to the increase of activity of catalytic nanoparticles (e.g. platinum or palladium) involves nanostructuring to obtain highly dispersed systems of high surface area. Recently, the feasibility of enhancing activity of noble metal systems through the formation of bimetallic (e.g. PtRu, PtSn, and PdAu) or even more complex (e.g. PtRuW, PtRuSn) alloys has been demonstrated. In addition to possible changes in the electronic properties of alloys, specific interactions between metals as well as chemical reactivity of the added components have been postulated. We address and emphasize here the possibility of utilization of noble metal and alloyed nanoparticles supported on robust but reactive high surface area metal oxides (e.g. WO3, MoO3, TiO2, ZrO2, V2O5, and CeO2) in oxidative electrocatalysis. This paper concerns the way in which certain inorganic oxides and oxo species can act effectively as supports for noble metal nanoparticles or their alloys during electrocatalytic oxidation of hydrogen and representative organic fuels. Among important issues are possible changes in the morphology and dispersion, as well as specific interactions leading to the improved chemisorptive and catalytic properties in addition to the feasibility of long time operation of the discussed systems. PMID:24443590

  5. Reliable contact fabrication on nanostructured Bi2Te3-based thermoelectric materials.

    PubMed

    Feng, Shien-Ping; Chang, Ya-Huei; Yang, Jian; Poudel, Bed; Yu, Bo; Ren, Zhifeng; Chen, Gang

    2013-05-14

    A cost-effective and reliable Ni-Au contact on nanostructured Bi2Te3-based alloys for a solar thermoelectric generator (STEG) is reported. The use of MPS SAMs creates a strong covalent binding and more nucleation sites with even distribution for electroplating contact electrodes on nanostructured thermoelectric materials. A reliable high-performance flat-panel STEG can be obtained by using this new method.

  6. Ultrafast Non-thermal Response of Plasmonic Resonance in Gold Nanoantennas

    NASA Astrophysics Data System (ADS)

    Soavi, Giancarlo; Valle, Giuseppe Della; Biagioni, Paolo; Cattoni, Andrea; Longhi, Stefano; Cerullo, Giulio; Brida, Daniele

    Ultrafast thermalization of electrons in metal nanostructures is studied by means of pump-probe spectroscopy. We track in real-time the plasmon resonance evolution, providing a tool for understanding and controlling gold nanoantennas non-linear optical response.

  7. Selective isolation of gold facilitated by second-sphere coordination with α-cyclodextrin.

    PubMed

    Liu, Zhichang; Frasconi, Marco; Lei, Juying; Brown, Zachary J; Zhu, Zhixue; Cao, Dennis; Iehl, Julien; Liu, Guoliang; Fahrenbach, Albert C; Botros, Youssry Y; Farha, Omar K; Hupp, Joseph T; Mirkin, Chad A; Fraser Stoddart, J

    2013-01-01

    Gold recovery using environmentally benign chemistry is imperative from an environmental perspective. Here we report the spontaneous assembly of a one-dimensional supramolecular complex with an extended {[K(OH₂)₆][AuBr₄](α-cyclodextrin)₂}n chain superstructure formed during the rapid co-precipitation of α-cyclodextrin and KAuBr₄ in water. This phase change is selective for this gold salt, even in the presence of other square-planar palladium and platinum complexes. From single-crystal X-ray analyses of six inclusion complexes between α-, β- and γ-cyclodextrins with KAuBr₄ and KAuCl₄, we hypothesize that a perfect match in molecular recognition between α-cyclodextrin and [AuBr₄](-) leads to a near-axial orientation of the ion with respect to the α-cyclodextrin channel, which facilitates a highly specific second-sphere coordination involving [AuBr₄](-) and [K(OH₂)₆](+) and drives the co-precipitation of the 1:2 adduct. This discovery heralds a green host-guest procedure for gold recovery from gold-bearing raw materials making use of α-cyclodextrin-an inexpensive and environmentally benign carbohydrate.

  8. Synthesis of one-dimensional gold nanostructures and the electrochemical application of the nanohybrid containing functionalized graphene oxide for cholesterol biosensing.

    PubMed

    Nandini, Seetharamaiah; Nalini, Seetharamaiah; Reddy, M B Madhusudana; Suresh, Gurukar Shivappa; Melo, Jose Savio; Niranjana, Pathappa; Sanetuntikul, Jakkid; Shanmugam, Sangaraju

    2016-08-01

    This manuscript reports a new approach for the synthesis of one dimensional gold nanostructure (AuNs) and its application in the development of cholesterol biosensor. Au nanostructures have been synthesized by exploiting β-diphenylalanine (β-FF) as an sacrificial template, whereas the Au nanoparticles (AuNPs) were synthesized by ultrasound irradiation. X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive analysis of X-rays (EDAX) have been employed to characterize the morphology and composition of the prepared samples. With the aim to develop a highly sensitive cholesterol biosensor, cholesterol oxidase (ChOx) was immobilized on AuNs which were appended on the graphite (Gr) electrode via chemisorption onto thiol-functionalized graphene oxide (GO-SH). This Gr/GO-SH/AuNs/ChOx biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy and chronoamperometry. CV results indicated a direct electron transfer between the enzyme and the electrode surface. A new potentiostat intermitant titration technique (PITT) has been studied to determine the diffusion coefficient and maxima potential value. The proposed biosensor showed rapid response, high sensitivity, wide linear range and low detection limit. Furthermore, our AuNs modified electrode showed excellent selectivity, repeatability, reproducibility and long term stability. The proposed electrode has also been used successfully to determine cholesterol in serum samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Process for recovery of palladium from nuclear fuel reprocessing wastes

    DOEpatents

    Campbell, D.O.; Buxton, S.R.

    1980-06-16

    Palladium is selectively removed from spent nuclear fuel reprocessing waste by adding sugar to a strong nitric acid solution of the waste to partially denitrate the solution and cause formation of an insoluble palladium compound. The process includes the steps of: (a) adjusting the nitric acid content of the starting solution to about 10 M; (b) adding 50% sucrose solution in an amount sufficient to effect the precipitation of the palladium compound; (c) heating the solution at reflux temperature until precipitation is complete; and (d) centrifuging the solution to separate the precipitated palladium compound from the supernatant liquid.

  10. Process for recovery of palladium from nuclear fuel reprocessing wastes

    DOEpatents

    Campbell, David O.; Buxton, Samuel R.

    1981-01-01

    Palladium is selectively removed from spent nuclear fuel reprocessing waste by adding sugar to a strong nitric acid solution of the waste to partially denitrate the solution and cause formation of an insoluble palladium compound. The process includes the steps of: (a) adjusting the nitric acid content of the starting solution to about 10 M, (b) adding 50% sucrose solution in an amount sufficient to effect the precipitation of the palladium compound, (c) heating the solution at reflux temperature until precipitation is complete, and (d) centrifuging the solution to separate the precipitated palladium compound from the supernatant liquid.

  11. Tuning Surface Chemistry of Polyetheretherketone by Gold Coating and Plasma Treatment

    NASA Astrophysics Data System (ADS)

    Novotná, Zdeňka; Rimpelová, Silvie; Juřík, Petr; Veselý, Martin; Kolská, Zdeňka; Hubáček, Tomáš; Borovec, Jakub; Švorčík, Václav

    2017-06-01

    Polyetheretherketone (PEEK) has good chemical and biomechanical properties that are excellent for biomedical applications. However, PEEK exhibits hydrophobic and other surface characteristics which cause limited cell adhesion. We have investigated the potential of Ar plasma treatment for the formation of a nanostructured PEEK surface in order to enhance cell adhesion. The specific aim of this study was to reveal the effect of the interface of plasma-treated and gold-coated PEEK matrices on adhesion and spreading of mouse embryonic fibroblasts. The surface characteristics (polarity, surface chemistry, and structure) before and after treatment were evaluated by various experimental techniques (gravimetry, goniometry, X-ray photoelectron spectroscopy (XPS), and electrokinetic analysis). Further, atomic force microscopy (AFM) was employed to examine PEEK surface morphology and roughness. The biological response of cells towards nanostructured PEEK was evaluated in terms of cell adhesion, spreading, and proliferation. Detailed cell morphology was evaluated by scanning electron microscopy (SEM). Compared to plasma treatment, gold coating improved PEEK wettability. The XPS method showed a decrease in the carbon concentration with increasing time of plasma treatment. Cell adhesion determined on the interface between plasma-treated and gold-coated PEEK matrices was directly proportional to the thickness of a gold layer on a sample. Our results suggest that plasma treatment in a combination with gold coating could be used in biomedical applications requiring enhanced cell adhesion.

  12. Fission product palladium-silicon carbide interaction in htgr fuel particles

    NASA Astrophysics Data System (ADS)

    Minato, Kazuo; Ogawa, Toru; Kashimura, Satoru; Fukuda, Kousaku; Shimizu, Michio; Tayama, Yoshinobu; Takahashi, Ishio

    1990-07-01

    Interaction of fission product palladium (Pd) with the silicon carbide (SiC) layer was observed in irradiated Triso-coated uranium dioxide particles for high temperature gas-cooled reactors (HTGR) with an optical microscope and electron probe microanalyzers. The SiC layers were attacked locally or the reaction product formed nodules at the attack site. Although the main element concerned with the reaction was palladium, rhodium and ruthenium were also detected at the corroded areas in some particles. Palladium was detected on both the hot and cold sides of the particles, but the corroded areas and the palladium accumulations were distributed particularly on the cold side of the particles. The observed Pd-SiC reaction depths were analyzed on the assumption that the release of palladium from the fuel kernel controls the whole Pd-SiC reaction.

  13. Ultra-high Strength Nanostructured Mg

    DTIC Science & Technology

    2014-03-31

    27709-2211 Nanostructured Mg and Mg alloys, Mg metallic glass, Cryomilling, Powder consolidation, Spark plasma sintering , Deformation mechanisms REPORT...mechanically milled powder and high pressure on spark plasma sintering of Mg-Cu-Gd metallic glasses; (9) microstructure and mechanical behavior of Mg-10Li-3Al...pressure on spark plasma sintering of Mg– Cu–Gd metallic glasses, Acta Materialia , (07 2013): 4414. doi: Baolong Zheng, Ying Li, Weizong Xu

  14. Increased Phonon Scattering by Nanograins and Point Defects in Nanostructured Silicon with a Low Concentration of Germanium

    NASA Astrophysics Data System (ADS)

    Zhu, G. H.; Lee, H.; Lan, Y. C.; Wang, X. W.; Joshi, G.; Wang, D. Z.; Yang, J.; Vashaee, D.; Guilbert, H.; Pillitteri, A.; Dresselhaus, M. S.; Chen, G.; Ren, Z. F.

    2009-05-01

    The mechanism for phonon scattering by nanostructures and by point defects in nanostructured silicon (Si) and the silicon germanium (Ge) alloy and their thermoelectric properties are investigated. We found that the thermal conductivity is reduced by a factor of 10 in nanostructured Si in comparison with bulk crystalline Si. However, nanosize interfaces are not as effective as point defects in scattering phonons with wavelengths shorter than 1 nm. We further found that a 5at.% Ge replacing Si is very efficient in scattering phonons shorter than 1 nm, resulting in a further thermal conductivity reduction by a factor of 2, thereby leading to a thermoelectric figure of merit 0.95 for Si95Ge5, similar to that of large grained Si80Ge20 alloys.

  15. Scanning the potential energy surface for synthesis of dendrimer-wrapped gold clusters: design rules for true single-molecule nanostructures.

    PubMed

    Thompson, Damien; Hermes, Jens P; Quinn, Aidan J; Mayor, Marcel

    2012-04-24

    The formation of true single-molecule complexes between organic ligands and nanoparticles is challenging and requires careful design of molecules with size, shape, and chemical properties tailored for the specific nanoparticle. Here we use computer simulations to describe the atomic-scale structure, dynamics, and energetics of ligand-mediated synthesis and interlinking of 1 nm gold clusters. The models help explain recent experimental results and provide insight into how multidentate thioether dendrimers can be employed for synthesis of true single-ligand-nanoparticle complexes and also nanoparticle-molecule-nanoparticle "dumbbell" nanostructures. Electronic structure calculations reveal the individually weak thioether-gold bonds (325 ± 36 meV), which act collectively through the multivalent (multisite) anchoring to stabilize the ligand-nanoparticle complex (∼7 eV total binding energy) and offset the conformational and solvation penalties involved in this "wrapping" process. Molecular dynamics simulations show that the dendrimer is sufficiently flexible to tolerate the strained conformations and desolvation penalties involved in fully wrapping the particle, quantifying the subtle balance between covalent anchoring and noncovalent wrapping in the assembly of ligand-nanoparticle complexes. The computed preference for binding of a single dendrimer to the cluster reveals the prohibitively high dendrimer desolvation barrier (1.5 ± 0.5 eV) to form the alternative double-dendrimer structure. Finally, the models show formation of an additional electron transfer channel between nitrogen and gold for ligands with a central pyridine unit, which gives a stiff binding orientation and explains the recently measured larger interparticle distances for particles synthesized and interlinked using linear ligands with a central pyridine rather than a benzene moiety. The findings stress the importance of organic-inorganic interactions, the control of which is central to the

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

    PubMed

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

    2008-08-20

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

  17. Synthesis of ultrasmall, homogeneously alloyed, bimetallic nanoparticles on silica supports

    NASA Astrophysics Data System (ADS)

    Wong, A.; Liu, Q.; Griffin, S.; Nicholls, A.; Regalbuto, J. R.

    2017-12-01

    Supported nanoparticles containing more than one metal have a variety of applications in sensing, catalysis, and biomedicine. Common synthesis techniques for this type of material often result in large, unalloyed nanoparticles that lack the interactions between the two metals that give the particles their desired characteristics. We demonstrate a relatively simple, effective, generalizable method to produce highly dispersed, well-alloyed bimetallic nanoparticles. Ten permutations of noble and base metals (platinum, palladium, copper, nickel, and cobalt) were synthesized with average particle sizes from 0.9 to 1.4 nanometers, with tight size distributions. High-resolution imaging and x-ray analysis confirmed the homogeneity of alloying in these ultrasmall nanoparticles.

  18. Recovery of cesium and palladium from nuclear reactor fuel processing waste

    DOEpatents

    Campbell, David O.

    1976-01-01

    A method of recovering cesium and palladium values from nuclear reactor fission product waste solution involves contacting the solution with a source of chloride ions and oxidizing palladium ions present in the solution to precipitate cesium and palladium as Cs.sub.2 PdCl.sub.6.

  19. Gold-Catalyzed Enantio- and Diastereoselective Syntheses of Left Fragments of Azadirachtin/Meliacarpin-Type Limonoids.

    PubMed

    Shi, Hang; Tan, Ceheng; Zhang, Weibin; Zhang, Zichun; Long, Rong; Gong, Jianxian; Luo, Tuoping; Yang, Zhen

    2016-02-05

    Meliacarpin-type limonoids are an important class of organic insecticides. Their syntheses are challenging due to their chemical complexity. Here, we report the highly enantio- and diastereoselective synthesis of the left fragments of azadirachtin I and 1-cinnamoylmelianolone, being two important family members of meliacarpin-type limonoids, via pairwise palladium- and gold-catalyzed cascade reactions. Gold-catalyzed reactions of 1,7-diynes were performed as model studies, and the efficient construction of tetracyclic late-stage intermediates was achieved on the basis of this key transformation. Our unique route gave both of the left fragments in 23 steps from the commercially available chiral starting material (-)-carvone. This study significantly advances research on the synthesis of the meliacarpin-type limonoids.

  20. Palladium coupling catalysts for pharmaceutical applications.

    PubMed

    Doucet, Henri; Hierso, Jean-Cyrille

    2007-11-01

    This review discusses recent advances made in the area of palladium-catalyzed coupling reactions and describes a selection of the catalytic systems that are useful in the preparation of valuable compounds for the pharmaceutical industry. Most of these types of syntheses have used either simple palladium salts or palladium precursors associated with electron-rich mono- or bidentate phosphine ligands as catalysts. For some reactions, ligands such as triphenyl phosphine, 1,1'-bis(diphenylphosphino)ferrocene, a carbene or a bipyridine have also been employed. Several new procedures for the Suzuki cross-coupling reaction, the activation of aryl chlorides, the functionalization of aromatics and the synthesis of heteroaromatics are discussed. The C-H activation/ functionalization reactions of aryl and heteroaryl derivatives have emerged as powerful tools for the preparation of biaryl compounds, and the recent procedures and catalysts employed in this promising field are also highlighted herein.