Optical Property Characterization of Novel Graphene-X (X=Ag, Au and Cu Nanoparticle Hybrids

Directory of Open Access Journals (Sweden)

Sumit Ranjan Sahu

2013-01-01

Full Text Available The present investigation reports new results on optical properties of graphene-metal nanocomposites. These composites were prepared by a solution-based chemical approach. Graphene has been prepared by thermal reduction of graphene oxide (GO at 90°C by hydrazine hydrate in an ammoniacal medium. This ammoniacal solution acts as a solvent as well as a basic medium where agglomeration of graphene can be prevented. This graphene solution has further been used for functionalization with Ag, Au, and Cu nanoparticles (NPs. The samples were characterized by X-ray diffraction (XRD, Raman spectroscopy, UV-Vis spectroscopy, scanning electron microscopy (SEM, and transmission electron microscopy (TEM to reveal the nature and type of interaction of metal nanoparticles with graphene. The results indicate distinct shift of graphene bands both in Raman and UV-Vis spectroscopies due to the presence of the metal nanoparticles. Raman spectroscopic analysis indicates blue shift of D and G bands in Raman spectra of graphene due to the presence of metal nanoparticles except for the G band of Cu-G, which undergoes red shift, reflecting the charge transfer interaction between graphene sheets and metal nanoparticles. UV-Vis spectroscopic analysis also indicates blue shift of graphene absorption peak in the hybrids. The plasmon peak position undergoes blue shift in Ag-G, whereas red shift is observed in Au-G and Cu-G.

Fabrication of fine spongy nanoporous Ag-Au alloys with improved catalysis properties

Directory of Open Access Journals (Sweden)

Cuiting Li

2017-12-01

Full Text Available Fine NP-AgAu (nanoporous AgAu alloys with spongy structure was fabricated by chemical dealloying from rapidly solidified amorphous precursors Ag38.75−xCu38.75Si22.5Aux (x=0, 0.5, 1 and 5. The results indicate that the addition of small content Au in precursor can refine both the ligaments and pores obviously. Among the present components of the precursors, NP-AgAu alloys dealloying from Ag37.75Cu38.75Si22.5Au1 had the finest spongy structure. The size of pores was 5–10 nm and the grain size of ligaments was 10–20 nm. It also had the highest surface area of 106.83 m2g−1 and the best catalytic activity towards electro-oxidation of formaldehyde with the peak current of 665 mA mg−1.

Geology and mineralogy of the Au-As (Ag-Pb-Zn-Cu-Sb polymetallic deposit of Valiña-Azúmara (Lugo, NW Spain

Directory of Open Access Journals (Sweden)

Martínez-Abad, I.

2015-12-01

Full Text Available Valiña-Azúmara is a polymetallic Au-As (Ag-Pb-Zn-Cu-Sb deposit, located in the province of Lugo (NW Spain, that was mined for arsenic at the beginning of the 20th century. The mineralization is hosted in a Variscan thrust fault with a dip direction of N247-261ºE, and N-S and NE-SW Late-Variscan faults. These structures are hosted in black slates, Cambrian in age. To a lesser extent, the mineralization also occurs disseminated within narrow, weakly silicified and sericited selvages. Mineralization is divided into two hypogene stages. The first consists of quartz, calcite, rutile, sericite, arsenopyrite and pyrite. Two types of pyrite (Py-I and Py-II are defined according to their chemical and textural characteristics. Py-II occurs as overgrowth of previous Py-I crystals. Py-II is As-rich (≤1.7 wt.% and often contains traces of Te, Zn, Cu, Bi, Sb and Au. The mineralized drill core sections show a significant correlation between Au and As. This is due to Au occurring as invisible Au within the Py-II grains, with contents of up to 176 ppm. The Au/As ratios of Py-II indicate that Au was deposited as Au1+, as solid solution within the pyrite structure. The second stage of mineralization is enriched in Ag-Pb-Zn-Cu-Sb, replacing the first stage, and consists of quartz, calcite, chlorite, sphalerite, jamesonite, Ag-rich tetrahedrite, freibergite, chalcopyrite, pyrrhotite and galena. Although jamesonite shows traces of Ag, the Cu-Ag sulfosalts are the main carriers of the Ag mineralization in the deposit, with contents that vary from 13.7 to 23.9 wt.% of Ag. In the most superficial levels of the area, secondary Fe oxide and hydroxide, scorodite and anglesite developed due to the oxidation of the ore.Valiña-Azúmara es un yacimiento filoniano de Au-As (Ag-Pb-Zn-Cu-Sb situado en la provincia de Lugo (NO España, que fue explotado por arsénico a principios del siglo XX. La mineralización se encuentra encajada en un cabalgamiento Varisco de direcci

N-Heterocyclic carbenes on close-packed coinage metal surfaces: bis-carbene metal adatom bonding scheme of monolayer films on Au, Ag and Cu.

Science.gov (United States)

Jiang, Li; Zhang, Bodong; Médard, Guillaume; Seitsonen, Ari Paavo; Haag, Felix; Allegretti, Francesco; Reichert, Joachim; Kuster, Bernhard; Barth, Johannes V; Papageorgiou, Anthoula C

2017-12-01

By means of scanning tunnelling microscopy (STM), complementary density functional theory (DFT) and X-ray photoelectron spectroscopy (XPS) we investigate the binding and self-assembly of a saturated molecular layer of model N -heterocyclic carbene (NHC) on Cu(111), Ag(111) and Au(111) surfaces under ultra-high vacuum (UHV) conditions. XPS reveals that at room temperature, coverages up to a monolayer exist, with the molecules engaged in metal carbene bonds. On all three surfaces, we resolve similar arrangements, which can be interpreted only in terms of mononuclear M(NHC) 2 (M = Cu, Ag, Au) complexes, reminiscent of the paired bonding of thiols to surface gold adatoms. Theoretical investigations for the case of Au unravel the charge distribution of a Au(111) surface covered by Au(NHC) 2 and reveal that this is the energetically preferential adsorption configuration.

Phenomenological approach to the spin glass state of (Cu-Mn, Ag-Mn, Au-Mn and Au-Fe) alloys at low temperatures

International Nuclear Information System (INIS)

Al-Jalali, Muhammad A.; Kayali, Fawaz A.

2000-01-01

Full text.The spin glass of: (Cu-Mn, Ag-Mn, Au-Mn, Au-Fe) alloys has been extensively studied. The availability of published and assured experimental data on the susceptibility x(T) of this alloys has enabled the design and application of phenomenological approach to the spin glass state of these interesting alloys. The use of and advanced (S.P.S.S) computer software has resulted revealing some important features of the spin glass in these alloys, the most important of which is that the spin glass state do not represent as phase change

Theoretical study of PTCDA adsorbed on the coinage metal surfaces, Ag(111), Au(111) and Cu(111)

International Nuclear Information System (INIS)

Romaner, L; Nabok, D; Puschnig, P; Ambrosch-Draxl, C; Zojer, E

2009-01-01

A thorough understanding of the adsorption of molecules on metallic surfaces is a crucial prerequisite for the development and improvement of functionalized materials. A prominent representative within the class of π-conjugated molecules is 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) which, adsorbed on the Ag(111), Au(111) or Cu(111) surfaces, shows characteristic trends for work-function modification, alignment of molecular levels with the substrate Fermi energy and binding distances. We carried out density functional theory (DFT) calculations to investigate to what extent these trends can be rationalized on a theoretical basis. We used different density functionals (DF) including a fully non-local van der Waals (vdW) DF capable of describing dispersion interactions. We show that, rather independent of the DF, the calculations yield level alignments and work-function modifications consistent with ultra-violet photoelectron spectroscopy when the monolayer is placed onto the surfaces at the experimental distances (as determined from x-ray standing wave experiments). The lowest unoccupied molecular orbital is occupied on the Ag and Cu surfaces, whereas it remains unoccupied on the Au surface. Simultaneously, the work function increases for Ag but decreases for Cu and Au. Adsorption distances and energies, on the other hand, depend very sensitively on the choice of the DF. While calculations in the local density approximation bind the monolayer consistently with the experimental trends, the generalized gradient approximation in several flavors fails to reproduce realistic distances and energies. Calculations employing the vdW-DF reveal that substantial bonding contributions arise from dispersive interactions. They yield reasonable binding energies but larger binding distances than the experiments.

The Shear Strength and Fracture Behavior of Sn-Ag- xSb Solder Joints with Au/Ni-P/Cu UBM

Science.gov (United States)

Lee, Hwa-Teng; Hu, Shuen-Yuan; Hong, Ting-Fu; Chen, Yin-Fa

2008-06-01

This study investigates the effects of Sb addition on the shear strength and fracture behavior of Sn-Ag-based solders with Au/Ni-P/Cu underbump metallization (UBM) substrates. Sn-3Ag- xSb ternary alloy solder joints were prepared by adding 0 wt.% to 10 wt.% Sb to a Sn-3.5Ag alloy and joining them with Au/Ni-P/Cu UBM substrates. The solder joints were isothermally stored at 150°C for up to 625 h to study their microstructure and interfacial reaction with the UBM. Single-lap shear tests were conducted to evaluate the mechanical properties, thermal resistance, and failure behavior. The results show that UBM effectively suppressed intermetallic compound (IMC) formation and growth during isothermal storage. The Sb addition helped to refine the Ag3Sn compounds, further improving the shear strength and thermal resistance of the solders. The fracture behavior evolved from solder mode toward the mixed mode and finally to the IMC mode with increasing added Sb and isothermal storage time. However, SnSb compounds were found in the solder with 10 wt.% Sb; they may cause mechanical degradation of the solder after long-term isothermal storage.

Femtosecond Laser Fabricated Ag@Au and Cu@Au Alloy Nanoparticles for Surface Enhanced Raman Spectroscopy Based Trace Explosives Detection

Directory of Open Access Journals (Sweden)

Moram Sree Satya Bharati

2018-03-01

Full Text Available Herein we present results from our detailed studies on the fabrication of Ag@Au and Cu@Au alloy nanoparticles (NPs using the femtosecond laser ablation in liquid technique. The NPs were obtained by ablating the pure Ag, Cu targets (bulk in HAuCl4 (5 mM solution. The absorption properties of the obtained NPs colloids were characterized using UV-Visible absorption spectrometer and their size, shape, and crystallinity were investigated using the XRD, FESEM and TEM techniques. The fabricated NPs were utilized for sensing of explosive molecules such as 2,4,6-trinitrophenol (PA, 2,4-dinitrotoluene (DNT and a common dye methylene blue (MB using the surface enhanced Raman spectroscopy (SERS technique. The detection limit in terms of weight was as low as few nano-grams in the case of nitroaromatic explosive compounds (PA, DNT and few picograms in the case of a common dye molecule (MB. Typical enhancement factors achieved were estimated to be ~104, ~105, and ~107, respectively, for PA, DNT, and MB. The significance of the present work lies in exploring the performance of the prepared NPs being used as SERS substrates for explosives detection using a portable Raman instrument. Such capability enables one to carry the spectrometer to the point of interest in the field and evaluate any hazardous samples within a short period of time.

Mass and velocity of fragments from the reaction 17-115 MeV/u 40Ar + Cu, Ag and Au

International Nuclear Information System (INIS)

Colin, E.; Guinet, D.; Stern, M.

1998-01-01

Measurements are reported for fragment masses and velocities from the reactions 17-115 MeV/u 40 Ar + Cu, Ag and Au. High momentum and energy deposition are reported for selected events, even for higher incident energy. Further study is needed to understand their origin. (authors)

A comparative study of Cu, Ag and Au doped CeO_2 in the total oxidation of volatile organic compounds (VOCs)

International Nuclear Information System (INIS)

Aboukaïs, Antoine; Skaf, Mira; Hany, Sara; Cousin, Renaud; Aouad, Samer; Labaki, Madona; Abi-Aad, Edmond

2016-01-01

Total oxidation of two Volatile Organic Compounds (VOCs), propylene and toluene, was investigated over M/CeO_2 catalysts, where M is a metal from IB group (i.e. Au, Ag, Cu), prepared by two different methods: the conventional wet impregnation and the deposition-precipitation. The catalysts have been characterized by means of total surface area (BET), X-ray diffraction (XRD), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), diffuse reflectance ultra-violet-visible spectroscopy (DR-UV/Vis), and temperature-programmed reduction (TPR), in order to explain the differences observed in their catalytic activity towards the studied reactions. By comparing the two different preparation methods, the presence of metal in high oxidation state for gold and silver, and the presence of clusters for copper were the main factors responsible for the high catalytic activity. This latter was also found to be related, when comparing the different IB metals, to the values of the oxidation/reduction potential of the redox couples of the different metals. - Highlights: • IB metals (Au, Ag and Cu) were supported on ceria (CeO_2) by two different methods. • The solids were tested as catalysts for total oxidation of propylene and toluene. • The deposition-precipitation is better for Au whereas for Ag and Cu it is the impregnation. • High oxidation states of gold and silver and clusters of copper enhanced catalytic behavior. • Catalytic activity is linked to the oxidation/reduction potential of the redox IB couples.

Brazing of zirconia to titanium using Ag-Cu and Au-Ni filler alloys

Directory of Open Access Journals (Sweden)

Jean S. Pimenta

2013-12-01

Full Text Available Advanced ceramic is usually joined to metal by the well-known direct brazing process, where costly active filler alloys can be considered a limitation. Brazing using active-metal-free filler alloy as insert between the joint components is an attempt to overcome it. The active metal diffusion from the titanium member through the bulk of molten filler to the ceramic was responsible to produce an active filler alloy in loco and promote reduction of the zirconium oxide to improve wetting on the ceramic surface. Unalloyed titanium was joined in a high-vacuum furnace (<3x10-5 mbar to yttria-tetragonal zirconia polycristals (Y-TZP and zirconia partially stabilized with magnesia (Mg-PSZ, where commercial fillers Ag-28Cu and Au-18Ni with respective thermal cycles were evaluated. Helium gas leak detection test was performed at the ceramic/metal interface at room temperature; samples from reliable vacuum tight joints were examined by microstructural analysis techniques and energy dispersive X-ray analysis at the joint cross-section. Tight joints were produced with eutectic Ag-Cu filler, revealing an intermetallic layer and a dark reaction layer near the ceramic surface; titanium diffusion was efficient for superficial chemical interactions between individual components. Brazing joints were also tested using three-point flexure testing.

A comparative study of Cu, Ag and Au doped CeO{sub 2} in the total oxidation of volatile organic compounds (VOCs)

Energy Technology Data Exchange (ETDEWEB)

Aboukaïs, Antoine, E-mail: aboukais@univ-littoral.fr [Unité de Chimie Environnementale et Interactions sur le Vivant EA 4492, ULCO, Equipe de Catalyse-UCEIV, MREI, 59140, Dunkerque (France); Skaf, Mira, E-mail: miraskaf@hotmail.com [Unité de Chimie Environnementale et Interactions sur le Vivant EA 4492, ULCO, Equipe de Catalyse-UCEIV, MREI, 59140, Dunkerque (France); Department of Chemistry, Faculty of Sciences, University of Balamand, P.O. Box 100, Deir El Balamand, Kelhat-Tripoli (Lebanon); Hany, Sara, E-mail: sarahani@hotmail.com [Unité de Chimie Environnementale et Interactions sur le Vivant EA 4492, ULCO, Equipe de Catalyse-UCEIV, MREI, 59140, Dunkerque (France); Cousin, Renaud, E-mail: Renaud.Cousin@univ-littoral.fr [Unité de Chimie Environnementale et Interactions sur le Vivant EA 4492, ULCO, Equipe de Catalyse-UCEIV, MREI, 59140, Dunkerque (France); Aouad, Samer, E-mail: Samer.Aouad@balamand.edu.lb [Department of Chemistry, Faculty of Sciences, University of Balamand, P.O. Box 100, Deir El Balamand, Kelhat-Tripoli (Lebanon); Labaki, Madona, E-mail: mlabaki@ul.edu.lb [Laboratory of Physical Chemistry of Materials (LCPM)/PR2N, Faculty of Sciences, Lebanese University, Fanar, PO Box 90656, Jdeidet El Metn (Lebanon); Abi-Aad, Edmond, E-mail: abiaad@univ-littoral.fr [Unité de Chimie Environnementale et Interactions sur le Vivant EA 4492, ULCO, Equipe de Catalyse-UCEIV, MREI, 59140, Dunkerque (France)

2016-07-01

Total oxidation of two Volatile Organic Compounds (VOCs), propylene and toluene, was investigated over M/CeO{sub 2} catalysts, where M is a metal from IB group (i.e. Au, Ag, Cu), prepared by two different methods: the conventional wet impregnation and the deposition-precipitation. The catalysts have been characterized by means of total surface area (BET), X-ray diffraction (XRD), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), diffuse reflectance ultra-violet-visible spectroscopy (DR-UV/Vis), and temperature-programmed reduction (TPR), in order to explain the differences observed in their catalytic activity towards the studied reactions. By comparing the two different preparation methods, the presence of metal in high oxidation state for gold and silver, and the presence of clusters for copper were the main factors responsible for the high catalytic activity. This latter was also found to be related, when comparing the different IB metals, to the values of the oxidation/reduction potential of the redox couples of the different metals. - Highlights: • IB metals (Au, Ag and Cu) were supported on ceria (CeO{sub 2}) by two different methods. • The solids were tested as catalysts for total oxidation of propylene and toluene. • The deposition-precipitation is better for Au whereas for Ag and Cu it is the impregnation. • High oxidation states of gold and silver and clusters of copper enhanced catalytic behavior. • Catalytic activity is linked to the oxidation/reduction potential of the redox IB couples.

Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

Directory of Open Access Journals (Sweden)

M. Vinod

2014-12-01

Full Text Available Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation. The dependence of laser fluence on the surface plasmon characteristics of the nanoparticles was investigated. Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids. The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process. The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones. The surface enhanced Raman scattering activity of the Au, Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules. Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.

Stopping Power of Be, Al, Cu, Ag, Pt, and Au for 5-12-MeV Protons and Deuterons

DEFF Research Database (Denmark)

Andersen, H.H.; Hanke, C.; Sørensen, H.

1967-01-01

Recent measurements on stopping power of aluminum have been continued with the stopping materials Be, Cu, Ag, Pt, and Au. The method of measuring stopping powers utilizing a thermometric compensation technique working at liquid-helium temperature has been used. Results are obtained with a standard...... deviation of 0.3%, and agree with other published experimental results and with Bichsel's tabulated values within their stated errors....

Induced accumulation of Au, Ag and Cu in Brassica napus grown in a mine tailings with the inoculation of Aspergillus niger and the application of two chemical compounds.

Science.gov (United States)

González-Valdez, Eduardo; Alarcón, Alejandro; Ferrera-Cerrato, Ronald; Vega-Carrillo, Héctor René; Maldonado-Vega, María; Salas-Luévano, Miguel Ángel; Argumedo-Delira, Rosalba

2018-06-15

This study evaluated the ability of Brassica napus for extracting gold (Au), silver (Ag) and copper (Cu) from a mine tailings, with the inoculation of two Aspergillus niger strains, and the application of ammonium thiocyanate (NH 4 SCN) or ammonium thiosulfate [(NH 4 ) 2 S 2 O 3 ]. After seven weeks of growth inoculated or non-inoculated plants were applied with 1 or 2 g kg -1 of either NH 4 SCN or (NH 4 ) 2 S 2 O 3 , respectively. Eight days after the application of the chemical compounds, plants were harvested for determining the total dry biomass, and the content of Au, Ag, and Cu in plant organs. Application of (NH 4 ) 2 S 2 O 3 or NH 4 SCN resulted in enhanced Au-accumulation in stems (447% and 507%, respectively), while either (NH 4 ) 2 S 2 O 3 +Aspergillus, or NH 4 SCN increased the Au-accumulation in roots (198.5% and 404%, respectively) when compared to the control. Treatments with (NH 4 ) 2 S 2 O 3 or (NH 4 ) 2 S 2 O 3 +Aspergillus significantly increased (P ≤ 0.001) the accumulation of Ag in leaves (677% and 1376%, respectively), while NH 4 SCN + Aspergillus, and (NH 4 ) 2 S 2 O 3 enhanced the accumulation in stems (7153% and 6717.5%). The Ag-accumulation in roots was stimulated by NH 4 SCN+ Aspergillus, and (NH 4 ) 2 S 2 O 3 + Aspergillus (132.5% and 178%, respectively), when compared to the control. The combination of NH 4 SCN+Aspergillus significantly enhanced the Cu-accumulation in leaves (228%); whereas NH 4 SCN+ Aspergillus, or (NH 4 ) 2 S 2 O 3 + Aspergillus resulted in greater accumulation of Cu in stems (1233.5% and 1580%, respectively) than the control. Results suggest that either NH 4 SCN or (NH 4 ) 2 S 2 O 3 (with or without Aspergillus) improved the accumulation of Au and Ag by B. napus. Accumulation of Au and Ag in plant organs overpassed the hyperaccumulation criterion (> 1 mg kg -1 of plant biomass); whereas Cu-accumulation in stems and roots also overpassed such criterion (> 1000 mg kg -1 ) by applying

Energy Reflection Coefficients for 5-10 keV He Ions Incident on Au, Ag, and Cu

DEFF Research Database (Denmark)

Schou, Jørgen; Sørensen, H.; Littmark, U.

1978-01-01

The calorimetric deuterium-film method was used for measurements of the energy reflection coefficient γ for normal incidence of 5-10 keV He ions on Cu, Ag and Au. A theoretical calculation of γ by means of transport theory gives fair agreement with the experimental results. The experimental data...... the experimental and theoretical results for the He ions are in acceptable agreement with other experimental and theoretical results. For He ions, the experimental γ-values are 20-30% above the values for hydrogen ions for the same value of ε...

Effect of Isothermal Aging on the Long-Term Reliability of Fine-Pitch Sn-Ag-Cu and Sn-Ag Solder Interconnects With and Without Board-Side Ni Surface Finish

Science.gov (United States)

Lee, Tae-Kyu; Duh, Jeng-Gong

2014-11-01

The combined effects on long-term reliability of isothermal aging and chemically balanced or unbalanced surface finish have been investigated for fine-pitch ball grid array packages with Sn-3.0Ag-0.5Cu (SAC305) (wt.%) and Sn-3.5Ag (SnAg) (wt.%) solder ball interconnects. Two different printed circuit board surface finishes were selected to compare the effects of chemically balanced and unbalanced structure interconnects with and without board-side Ni surface finish. NiAu/solder/Cu and NiAu/solder/NiAu interconnects were isothermally aged and thermally cycled to evaluate long-term thermal fatigue reliability. Weibull plots of the combined effects of each aging condition and each surface finish revealed lifetime for NiAu/SAC305/Cu was reduced by approximately 40% by aging at 150°C; less degradation was observed for NiAu/SAC305/NiAu. Further reduction of characteristic life-cycle number was observed for NiAu/SnAg/NiAu joints. Microstructure was studied, focusing on its evolution near the board and package-side interfaces. Different mechanisms of aging were apparent under the different joint configurations. Their effects on the fatigue life of solder joints are discussed.

Preparation and electric and photoelectric properties of thin deposits of Fe, Co, Ni, Cu, Ag, Au and Pd

International Nuclear Information System (INIS)

Heras, J.M.; Albano, E.V.; Asensio, M.C.; Viscido, L.

1984-01-01

The physics chemical properties of desordered metallic thin films of Fe, Co, Ni, Pd, Ag, Cu and Au are of great interest for its catalitic activity and for its application in radiation absorption of solar cells and micro electronic devices. This work has the purpose of reporting the experimental results obtained by evaporated films of these metals, which present desordered characteristics, small crystal size and high surface-volume rate. (A.C.A.S.) [pt

Specific composition of native silver from the Rogovik Au-Ag deposit, Northeastern Russia

Science.gov (United States)

Kravtsova, R. G.; Tauson, V. L.; Palyanova, G. A.; Makshakov, A. S.; Pavlova, L. A.

2017-09-01

The first data on native silver from the Rogovik Au-Ag deposit in northeastern Russia are presented. The deposit is situated in central part of the Okhotsk-Chukchi Volcanic Belt (OCVB) in the territory of the Omsukchan Trough, unique in its silver resources. Native silver in the studied ore makes up finely dispersed inclusions no larger than 50 μm in size, which are hosted in quartz; fills microfractures and interstices in association with küstelite, electrum, acanthite, silver sulfosalts and selenides, argyrodite, and pyrite. It has been shown that the chemical composition of native silver, along with its typomorphic features, is a stable indication of the various stages of deposit formation and types of mineralization: gold-silver (Au-Ag), silver-base metal (Ag-Pb), and gold-silver-base metal (Au-Ag-Pb). The specificity of native silver is expressed in the amount of trace elements and their concentrations. In Au-Ag ore, the following trace elements have been established in native silver (wt %): up to 2.72 S, up to 1.86 Au, up to 1.70 Hg, up to 1.75 Sb, and up to 1.01 Se. Native silver in Ag-Pb ore is characterized by the absence of Au, high Hg concentrations (up to 12.62 wt %), and an increase in Sb, Se, and S contents; the appearance of Te, Cu, Zn, and Fe is notable. All previously established trace elements—Hg, Au, Sb, Se, Te, Cu, Zn, Fe, and S—are contained in native silver of Au-Ag-Pb ore. In addition, Pb appears, and silver and gold amalgams are widespread, as well as up to 24.61 wt % Hg and 11.02 wt % Au. Comparison of trace element concentrations in native silver at the Rogovik deposit with the literature data, based on their solubility in solid silver, shows that the content of chalcogenides (S, Se, Te) exceeds saturated concentrations. Possible mechanisms by which elevated concentrations of these elements are achieved in native silver are discussed. It is suggested that the appearance of silver amalgams, which is unusual for Au-Ag mineralization

Ammonia synthesis on Au modified Fe(111) and Ag and Cu modified Fe(100) surfaces

DEFF Research Database (Denmark)

Lytken, Ole; Waltenburg, Hanne Neergaard; Chorkendorff, Ib

2003-01-01

In order to investigate any influence of steps and possible positive effects of making surface alloys the ammonia synthesis has been investigated over Au modified Fe(111) and Ag and Cu modified Fe(100) single crystals in the temperature range 603-773 K, using a system combining ultra-high vacuum...... and a high-pressure cell. Ammonia was synthesized from a stoichiometric (N-2:3H(2)) gas mixture at a pressure of 2 bar. By deposition of small amounts of An, the ammonia production activity of the Fe(1 1 1) surface can be enhanced. More important, for the gold modified surface, the reaction order in ammonia...

Porphyry Cu-Au mineralization in the Mirkuh Ali Mirza magmatic complex, NW Iran

Science.gov (United States)

Maghsoudi, A.; Yazdi, M.; Mehrpartou, M.; Vosoughi, M.; Younesi, S.

2014-01-01

The Mirkuh Ali Mirza Cu-Au porphyry system in East Azerbaijan Province is located on the western part of the Cenozoic Alborz-Azerbaijan volcanic belt. The belt is also an important Cu-Mo-Au metallogenic province in northwestern Iran. The exposed rocks in the study area consist of a volcaniclastic sequence, subvolcanic rocks and intermediate to mafic lava flows of Neogene age. The volcanic rocks show a typical subduction-related magmatic arc geological and geochemical signature, with low concentration of Nb, Ta, and Ti. Mineralization is hosted by Neogene dacitic tuff and porphyritic dacite situated at the intersections of northeast and northwest faults. Field observations, alteration zonation, geochemical haloes and isotopic data of the Mirkuh Ali Mirza magmatic complex show similarities with typical convergent margin Cu-Au porphyry type deposits. The following features confirm the classic model for Cu-Au porphyry systems: (a) close spatial association with high-K calcalkaline to shoshonitic rock related to post-collision extensional setting (b) low grade Cu (0.57%) (c) stockworks as well as disseminated sulfides (c) zonality of the alteration patterns from intense phyllic at the center to outward weak-phyllic, argillic, and propylitic (d) the presence of a pyritic halo (e) accompanied by sheeted veins and low-sulfidation epithermal gold (f) mineralization spatially associated with intersection of structures, (g) genetically related to diorite porphyry stocks at depth (h) geochemical zonation of (Cu ± Au ± Ag ± Bi) → (Cu + Mo ± Bi ± Au ± Pb ± Zn ± As) → (Au + Mo ± Pb ± Zn) → (As + Ag + Sb + Mn + Ba + Pb + Zn + Hg) → Hg from center to outwards (i) The range of sulfur isotopic values is approximately zero (interpreted to have magmatic source) and similar to other subduction-related porphyry Cu deposits.

Pentacene on Au(1 1 1), Ag(1 1 1) and Cu(1 1 1): From physisorption to chemisorption.

Science.gov (United States)

Lu, Meng-Chao; Wang, Rong-Bin; Yang, Ao; Duhm, Steffen

2016-03-09

We measured the electronic and the molecular surface structure of pentacene deposited on the (1 1 1)-surfaces of coinage metals by means of ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction (LEED). Pentacene is almost flat-lying in monolayers on all three substrates and highly ordered on Au(1 1 1) and on Cu(1 1 1). On Ag(1 1 1), however, weak chemisorption leads to almost disordered monolayers, both, at room temperature and at 78 K. On Cu(1 1 1) pentacene is strongly chemisorbed and the lowest unoccupied molecular orbital becomes observable in UPS by a charge transfer from the substrate. On Ag(1 1 1) and Cu(1 1 1) multilayers adopt a tilted orientation and a high degree of crystallinity. On Au(1 1 1), most likely, also in multilayers the molecular short and long axes are parallel to the substrate, leading to a distinctively different electronic structure than on Ag(1 1 1) and Cu(1 1 1). Overall, it could be demonstrated that the substrate not only determines the geometric and electronic characteristics of molecular monolayer films but also plays a crucial role for multilayer film growth.

Development of casting investment preventing blackening of noble metal alloys part 1. Application of developed investment for Ag-Pd-Cu-Au alloy.

Science.gov (United States)

Kakuta, Kiyoshi; Nakai, Akira; Goto, Shin-ichi; Wakamatsu, Yasushi; Yara, Atushi; Miyagawa, Yukio; Ogura, Hideo

2003-03-01

The objective of this study is to develop a casting investment that prevents the blackening of the cast surface of noble metal alloys. The experimental investments were prepared using a gypsum-bonded investment in which the metallic powders such as boron (B), silicon (Si), aluminum (Al) and titanium (Ti) were added as oxidizing agents. An Ag-Pd-Cu-Au alloy was cast into the mold made of the prepared investment. The effect of the addition of each metal powder was evaluated from the color difference between the as-cast surface and the polished surface of the cast specimen. The color of the as-cast surface approached that of the polished surface with increasing B and Al content. A lower mean value in the color difference was obtained at 0.25-1.00 mass% B content. B and Al are useful as an additive in a gypsum-bonded investment to prevent the blackening of an Ag-Pd-Cu-Au alloy. The effects of Si and Ti powder addition could not be found.

Copper-based alloys, crystallographic and crystallochemical parameters of alloys in binary systems Cu-Me (Me=Co, Rh, Ir, Cu, Ag, Au, Ni, Pd, Pt)

Energy Technology Data Exchange (ETDEWEB)

Porobova, Svetlana, E-mail: porobova.sveta@yandex.ru; Loskutov, Oleg, E-mail: lom58@mail.ru [Tomsk State University of Architecture and Building, Russia, Tomsk, 2 Solyanaya sq, Tomsk, 634003 (Russian Federation); Markova, Tat’jana, E-mail: patriot-rf@mail.ru [Siberian State Industrial University. 42 Kirov St., Novokuznetsk, 654007 (Russian Federation); Klopotov, Vladimir, E-mail: vdklopotov@mail.ru [Research Tomsk Polytechnic University, 30 Lenin Ave., Tomsk, 634050 (Russian Federation); Klopotov, Anatoliy, E-mail: klopotovaa@tsuab.ru [Tomsk State University of Architecture and Building, Russia, Tomsk, 2 Solyanaya sq, Tomsk, 634003 (Russian Federation); National Research Tomsk State University, 36, Lenin Ave., Tomsk, 634050 (Russian Federation); Vlasov, Viktor, E-mail: vik@tsuab.ru [Tomsk State University of Architecture and Building, Russia, Tomsk, 2 Solyanaya sq, Tomsk, 634003 (Russian Federation); Research Tomsk Polytechnic University, 30 Lenin Ave., Tomsk, 634050 (Russian Federation)

2016-01-15

The article presents the results of the analysis of phase equilibrium of ordered phases in binary systems based on copper Cu- Me (where Me - Co, Rh, Ir, Ag, Au, Ni, Pd, Pt) to find correlations of crystallochemical and crystallographic factors. It is established that the packing index in disordered solid solutions in binary systems based on copper is close to the value of 0.74 against the background of an insignificant deviation of atomic volumes from the Zen’s law.

Microstructure of Co/X (X=Cu,Ag,Au) epitaxial thin films grown on Al2O3(0001) substrates

International Nuclear Information System (INIS)

Ohtake, Mitsuru; Akita, Yuta; Futamoto, Masaaki; Kirino, Fumiyoshi

2007-01-01

Epitaxial thin films of Co/X (X=Cu,Ag,Au) were prepared on Al 2 O 3 (0001) substrates at substrate temperatures of 100 and 300 degree sign C by UHV molecular beam epitaxy. A complicated microstructure was realized for the epitaxial thin films. In-situ reflection high-energy electron diffraction observation has shown that X atoms of the buffer layer segregated to the surface during Co layer deposition, and it yielded a unique epitaxial granular structure. The structure consists of small Co grains buried in the X buffer layer, where both the magnetic small Co grains and the nonmagnetic X layer are epitaxially grown on the single crystal substrate. The structure varied depending on the X element and the substrate temperature. The crystal structure of Co grains is influenced by the buffer layer material and determined to be hcp and fcc structures for the buffer layer materials of Au and Cu, respectively

Measurement of antiproton annihilation on Cu, Ag and Au with emulsion films

International Nuclear Information System (INIS)

Aghion, S.; Consolati, G.; Evans, C.; Ferragut, R.; Amsler, C.; Ariga, A.; Ariga, T.; Ereditato, A.; Bonomi, G.; Bräunig, P.; Demetrio, A.; Brusa, R.S.; Cabaret, L.; Comparat, D.; Caccia, M.; Castelli, F.; Caravita, R.; Noto, L. Di; Cerchiari, G.; Doser, M.

2017-01-01

The characteristics of low energy antiproton annihilations on nuclei (e.g. hadronization and product multiplicities) are not well known, and Monte Carlo simulation packages that use different models provide different descriptions of the annihilation events. In this study, we measured the particle multiplicities resulting from antiproton annihilations on nuclei. The results were compared with predictions obtained using different models in the simulation tools GEANT4 and FLUKA. For this study, we exposed thin targets (Cu, Ag and Au) to a very low energy antiproton beam from CERN's Antiproton Decelerator, exploiting the secondary beamline available in the AEgIS experimental zone. The antiproton annihilation products were detected using emulsion films developed at the Laboratory of High Energy Physics in Bern, where they were analysed at the automatic microscope facility. The fragment multiplicity measured in this study is in good agreement with results obtained with FLUKA simulations for both minimally and heavily ionizing particles.

Measurement of antiproton annihilation on Cu, Ag and Au with emulsion films

Science.gov (United States)

Aghion, S.; Amsler, C.; Ariga, A.; Ariga, T.; Bonomi, G.; Bräunig, P.; Brusa, R. S.; Cabaret, L.; Caccia, M.; Caravita, R.; Castelli, F.; Cerchiari, G.; Comparat, D.; Consolati, G.; Demetrio, A.; Di Noto, L.; Doser, M.; Ereditato, A.; Evans, C.; Ferragut, R.; Fesel, J.; Fontana, A.; Gerber, S.; Giammarchi, M.; Gligorova, A.; Guatieri, F.; Haider, S.; Hinterberger, A.; Holmestad, H.; Huse, T.; Kawada, J.; Kellerbauer, A.; Kimura, M.; Krasnický, D.; Lagomarsino, V.; Lansonneur, P.; Lebrun, P.; Malbrunot, C.; Mariazzi, S.; Matveev, V.; Mazzotta, Z.; Müller, S. R.; Nebbia, G.; Nedelec, P.; Oberthaler, M.; Pacifico, N.; Pagano, D.; Penasa, L.; Petracek, V.; Pistillo, C.; Prelz, F.; Prevedelli, M.; Ravelli, L.; Rienaecker, B.; RØhne, O. M.; Rotondi, A.; Sacerdoti, M.; Sandaker, H.; Santoro, R.; Scampoli, P.; Simon, M.; Smestad, L.; Sorrentino, F.; Testera, G.; Tietje, I. C.; Vamosi, S.; Vladymyrov, M.; Widmann, E.; Yzombard, P.; Zimmer, C.; Zmeskal, J.; Zurlo, N.

2017-04-01

The characteristics of low energy antiproton annihilations on nuclei (e.g. hadronization and product multiplicities) are not well known, and Monte Carlo simulation packages that use different models provide different descriptions of the annihilation events. In this study, we measured the particle multiplicities resulting from antiproton annihilations on nuclei. The results were compared with predictions obtained using different models in the simulation tools GEANT4 and FLUKA. For this study, we exposed thin targets (Cu, Ag and Au) to a very low energy antiproton beam from CERN's Antiproton Decelerator, exploiting the secondary beamline available in the AEgIS experimental zone. The antiproton annihilation products were detected using emulsion films developed at the Laboratory of High Energy Physics in Bern, where they were analysed at the automatic microscope facility. The fragment multiplicity measured in this study is in good agreement with results obtained with FLUKA simulations for both minimally and heavily ionizing particles.

High-temperature stability of Au/Pd/Cu and Au/Pd(P)/Cu surface finishes

Science.gov (United States)

Ho, C. E.; Hsieh, W. Z.; Lee, P. T.; Huang, Y. H.; Kuo, T. T.

2018-03-01

Thermal reliability of Au/Pd/Cu and Au/Pd(4-6 wt.% P)/Cu trilayers in the isothermal annealing at 180 °C were investigated by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and transmission electron microscopy (TEM). The pure Pd film possessed a nanocrystalline structure with numerous grain boundaries, thereby facilitating the interdiffusion between Au and Cu. Out-diffusion of Cu through Pd and Au grain boundaries yielded a significant amount of Cu oxides (CuO and Cu2O) over the Au surface and gave rise to void formation in the Cu film. By contrast, the Pd(P) film was amorphous and served as a good diffusion barrier against Cu diffusion. The results of this study indicated that amorphous Pd(P) possessed better oxidation resistance and thermal reliability than crystalline Pd.

Corrosion of Dental Au-Ag-Cu-Pd Alloys in 0.9 % Sodium Chloride Solution

International Nuclear Information System (INIS)

Chiba, Atsushi; Kusayanagi, Yukiharu

2005-01-01

Two Au-Ag-Cu-Pd dental casting alloys (Au:12% and 20%) used. The test solutions used 0.9 % NaCl solution (isotonic sodium chloride solution), 0.9 % NaCl solution containing 1 % lactic acid, and 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol dm -3 Na 2 S. The surface of two samples in three sample solutions was not natural discoloration during one year. The alloy containing 12 % gold was easily alloyed and the composition was uniform comparing with the alloy containing 20 % gold. The rest potentials have not a little effect after three months. The kinds of metals could not definitely from the oxidation and reduction waves of metal on the cyclic voltammograms. The dissolutions of gold and palladium were 12 % Au sample in the 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol dm -3 Na 2 S. The pH of solution had an affect on dissolution of copper, and sulfur ion had an affect on dissolution of silver. The copper dissolved amount from 20 % gold sample was about 26 times comparing with that of 12 % gold sample in the 0.9 % solution containing 1 % lactic acid. Corrosion products were silver chloride and copper chloride in NaCl solution, and silver sulfide and copper sulfide in NaCl solution containing Na 2 S

The role of Ag precipitates in Cu-12 wt% Ag

Energy Technology Data Exchange (ETDEWEB)

Yao, D.W.; Song, L.N. [Department of Materials Science and Engineering, Zhejiang University, Zheda Road No.38, Hangzhou, Zhejiang 310027 (China); Dong, A.P.; Wang, L.T. [China Railway Construction Electrification Bureau Group Co.,Ltd., Beijing 100036 (China); Zhang, L. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Meng, L., E-mail: mengliang@zju.edu.cn [Department of Materials Science and Engineering, Zhejiang University, Zheda Road No.38, Hangzhou, Zhejiang 310027 (China)

2012-12-15

The Cu-12 wt% Ag was prepared to investigate the role of Ag precipitates on the properties of the alloy. Two kinds of heat treatment procedures were adopted to produce different amount of Ag precipitates in the Cu-12 wt% Ag. The microstructure of Ag precipitates was systematically observed by optical microscopy and electron microscopy. The Cu-12 wt% Ag with more Ag precipitates exhibits higher strength and lower electrical conductivity. More Ag precipitates results in more phase interface and less Ag atoms dissolved in Cu matrix. By comparing the strengthening effect and electron scattering effect of phase interface and dissolved Ag atoms, it is conclude that the interface between Cu matrix and Ag precipitates could significantly block dislocation movement and enhance electron scattering in Cu-Ag alloys.

Computer simulation of displacement cascade structures in D-T neutron-irradiated Au, Ag, Cu, Ni and Al with the MARLOWE code

International Nuclear Information System (INIS)

Watanabe, N.; Nishiguchi, R.; Shimomura, Y.

1991-01-01

Spatial distribution of point defects in displacement damage cascades at the early stage of their formation was simulated with the MARLOWE code for primary knock-on atoms which is relevant to D-T neutron irradiation. Calculations were carried out for Au, Ag, Cu, Ni and Al. Computer-simulated results were analyzed with complement of TEM observations of D-T neutron-irradiated metals at low temperature. The spatial configuration of displacement cascades, the size of small vacancy aggregates and the size of displacement damage cascade were examined. Results suggest that most of vacancy clusters which were formed in damage cascades may be as small as below 20 vacancies. The remarkable difference in defect yield of cascade damage in Ni and Cu is due to interstitial cluster formation and main contribution of cascade energy overlapping observed in cryotransfer TEM of D-T neutron-irradiated Au is due to ejected interstitials from cascade cores. (orig.)

The behaviour of the elements Ni, Co, Cu, Pb, Zn, Au, Ag, Mo, Sn, W and U in the magmatic, hydrothermal, sedimentary and weathering environments

International Nuclear Information System (INIS)

Anderson, J.R.

1978-01-01

In the last two decades much has been published on the behaviour of certain elements in the magmatic, hydrothermal, sedimentary and weathering environments, but the information is scattered throughout the literature. This situation prompted the present study on the elements Ni, Co, Cu, Pb, Zn, Au, Ag, Mo, Sn, W and U. The behaviour of the elements Ni, Cu, Pb, Zn, Au, Sn, W and U has been studied experimentally in some depth. Ag has been moderately studied, but there is very little information about Co and Mo. Studies on the complexes formed by the elements within the hydrothermal and aqueous environment are often inconclusive and controversial, but conclusions are drawn as to the more likely complexes formed. A genetic classification of ore deposits is used as a framework for the discussion. The source of the elements is regarded as being the mantle, and therefore discussion on other possible sources is beyond the scope of this dissertation. The crystal chemistry and geochemistry of the elements are presented and the essay concludes with a discussion on the elements within their depositional environments

The extraction characteristic of Au-Ag from Au concentrate by thiourea solution

Science.gov (United States)

Kim, Bongju; Cho, Kanghee; On, Hyunsung; Choi, Nagchoul; Park, Cheonyoung

2013-04-01

The cyanidation process has been used commercially for the past 100 years, there are ores that are not amenable to treatment by cyanide. Interest in alternative lixiviants, such as thiourea, halogens, thiosulfate and malononitrile, has been revived as a result of a major increase in gold price, which has stimulated new developments in extraction technology, combined with environmental concern. The Au extraction process using the thiourea solvent has many advantages over the cyanidation process, including higher leaching rates, faster extraction time and less than toxicity. The purpose of this study was investigated to the extraction characteristic of Au-Ag from two different Au concentrate (sulfuric acid washing and roasting) under various experiment conditions (thiourea concentration, pH of solvent, temperature) by thiourea solvent. The result of extraction experiment showed that the Au-Ag extraction was a fast extraction process, reaching equilibrium (maximum extraction rate) within 30 min. The Au-Ag extraction rate was higher in the roasted concentrate than in the sulfuric acid washing. The higher the Au-Ag extraction rate (Au - 70.87%, Ag - 98.12%) from roasted concentrate was found when the more concentration of thiourea increased, pH decreased and extraction temperature increased. This study informs extraction method basic knowledge when thiourea was a possibility to eco-/economic resources of Au-Ag utilization studies including the hydrometallurgy.

Study on antibacterial activity of chemically synthesized PANI-Ag-Au nanocomposite

Energy Technology Data Exchange (ETDEWEB)

Boomi, Pandi [Department of Industrial Chemistry, School of Chemical Sciences, Alagappa University, Karaikudi 630 003, Tamil Nadu (India); Prabu, Halliah Gurumallesh, E-mail: hgprabu2010@gmail.com [Department of Industrial Chemistry, School of Chemical Sciences, Alagappa University, Karaikudi 630 003, Tamil Nadu (India); Manisankar, Paramasivam [Department of Industrial Chemistry, School of Chemical Sciences, Alagappa University, Karaikudi 630 003, Tamil Nadu (India); Ravikumar, Sundaram [Department of Oceanography and Coastal Area Studies, School of Marine Sciences, Alagappa University, Thondi Campus 623 409, Tamil Nadu (India)

2014-05-01

Graphical abstract: - Highlights: • New method of synthesizing PANI-Ag-Au nanocomposite. • Surface Plasmon resonance and formation of composite at nano level were analyzed. • HR-TEM study revealed uniform distribution of nanoparticles. • PANI-Ag-Au nanocomposite exhibited good antibacterial activity. - Abstract: Pristine polyaniline (PANI), PANI-Ag, PANI-Au and PANI-Ag-Au nanocomposites have been successfully synthesized by chemical oxidative polymerization method using aniline as monomer, ammonium persulphate as oxidant and metal (Ag, Au and Ag-Au) colloids. UV-Vis analysis exhibited surface Plasmon resonances of Ag, Au, Ag-Au nanoparticles. FT-IR spectra revealed the shift in peak position of N-H stretching. X-ray diffraction (XRD) results confirm the presence of Ag, Au and Au-Ag nanoparticles. HR-TEM images show nanosizes of Ag, Au, Ag-Au and the incorporation of such nanoparticles into the PANI matrix. Pristine PANI, PANI-Ag, PANI-Au and PANI-Ag-Au nanocomposites were tested for antibacterial activity by agar well diffusion method. PANI-Ag-Au nanocomposite exhibited higher antibacterial activity against both gram-positive [Streptococcus sp. (MTCC 890), Staphylococcus sp. (MTCC 96)] and gram-negative bacteria [Escherichia coli (MTCC 1671) and Klebsiella sp. (MTCC 7407)] when compared with PANI-Ag nanocomposite, PANI-Au nanocomposite and pristine PANI. The novelty of this study is the polymer-bimetal synthesis and its antibacterial potential.

Controlled Synthesis of Au@AgAu Yolk-Shell Cuboctahedra with Well-Defined Facets.

Science.gov (United States)

Londono-Calderon, Alejandra; Bahena, Daniel; Yacaman, Miguel J

2016-08-02

The synthesis of Au@AgAu yolk-shell cuboctahedra nanoparticles formed by galvanic replacement in a seed-mediated method is described. Initially, single-crystal Au seeds are used for the formation of Au@Ag core-shell nanocubes, which serve as the template material for the deposition of an external Au layer. The well-controlled synthesis yields the formation of cuboctahedra nanoparticles with smooth inner and outer Au/Ag surfaces. The deposition/oxidation process is described to understand the formation of cuboctahedra and octahedra nanoparticles. The Au core maintains the initial morphology of the seed and remains static at the center of the yolk-shell because of residual Ag. Structural analysis of the shell indicates intrinsic stacking faults (SFs) near the surface. Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) compositional analysis show an Au-Ag nonordered alloy forming the shell. The three-dimensional structure of the nanoparticles presented open facets on the [111] as observed by electron tomography SIRT reconstruction over a stack of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images. The geometrical model was validated by analyzing the direction of streaks in coherent nanobeam diffraction (NBD). The catalytic activity was evaluated using a model reaction based on the reduction of 4-nitrophenol (4-NTP) by NaBH4 in the presence of Au@AgAu yolk-shell nanoparticles.

Transformation of Ag nanocubes into Ag-Au hollow nanostructures with enriched Ag contents to improve SERS activity and chemical stability.

Science.gov (United States)

Yang, Yin; Zhang, Qiang; Fu, Zheng-Wen; Qin, Dong

2014-03-12

We report a strategy to complement the galvanic replacement reaction between Ag nanocubes and HAuCl4 with co-reduction by ascorbic acid (AA) for the formation of Ag-Au hollow nanostructures with greatly enhanced SERS activity. Specifically, in the early stage of synthesis, the Ag nanocubes are sharpened at corners and edges because of the selective deposition of Au and Ag atoms at these sites. In the following steps, the pure Ag in the nanocubes is constantly converted into Ag(+) ions to generate voids owing to the galvanic reaction with HAuCl4, but these released Ag(+) ions are immediately reduced back to Ag atoms and are co-deposited with Au atoms onto the nanocube templates. We observe distinctive SERS properties for the Ag-Au hollow nanostructures at visible and near-infrared excitation wavelengths. When plasmon damping is eliminated by using an excitation wavelength of 785 nm, the SERS activity of the Ag-Au hollow nanostructures is 15- and 33-fold stronger than those of the original Ag nanocubes and the Ag-Au nanocages prepared by galvanic replacement without co-reduction, respectively. Additionally, Ag-Au hollow nanostructures embrace considerably improved stability in an oxidizing environment such as aqueous H2O2 solution. Collectively, our work suggests that the Ag-Au hollow nanostructures will find applications in SERS detection and imaging.

Fabricating a Homogeneously Alloyed AuAg Shell on Au Nanorods to Achieve Strong, Stable, and Tunable Surface Plasmon Resonances

KAUST Repository

Huang, Jianfeng

2015-08-13

Colloidal metal nanocrystals with strong, stable, and tunable localized surface plasmon resonances (SPRs) can be useful in a corrosive environment for many applications including field-enhanced spectroscopies, plasmon-mediated catalysis, etc. Here, a new synthetic strategy is reported that enables the epitaxial growth of a homogeneously alloyed AuAg shell on Au nanorod seeds, circumventing the phase segregation of Au and Ag encountered in conventional synthesis. The resulting core–shell structured bimetallic nanorods (AuNR@AuAg) have well-mixed Au and Ag atoms in their shell without discernible domains. This degree of mixing allows AuNR@AuAg to combine the high stability of Au with the superior plasmonic activity of Ag, thus outperforming seemingly similar nanostructures with monometallic shells (e.g., Ag-coated Au NRs (AuNR@Ag) and Au-coated Au NRs (AuNR@Au)). AuNR@AuAg is comparable to AuNR@Ag in plasmonic activity, but that it is markedly more stable toward oxidative treatment. Specifically, AuNR@AuAg and AuNR@Ag exhibit similarly strong signals in surface-enhanced Raman spectroscopy that are some 30-fold higher than that of AuNR@Au. When incubated with a H2O2 solution (0.5 m), the plasmonic activity of AuNR@Ag immediately and severely decayed, whereas AuNR@AuAg retained its activity intact. Moreover, the longitudinal SPR frequency of AuNR@AuAg can be tuned throughout the red wavelengths (≈620–690 nm) by controlling the thickness of the AuAg alloy shell. The synthetic strategy is versatile to fabricate AuAg alloyed shells on different shaped Au, with prospects for new possibilities in the synthesis and application of plasmonic nanocrystals.

Formation and evolution of nanoporous bimetallic Ag-Cu alloy by electrochemically dealloying Mg-(Ag-Cu)-Y metallic glass

International Nuclear Information System (INIS)

Li, Ran; Wu, Na; Liu, Jijuan; Jin, Yu; Chen, Xiao-Bo; Zhang, Tao

2017-01-01

Highlights: • Uniform nanoporous Ag-Cu alloy was fabricated by dealloying Mg-based metallic glass. • The nanoporous structure was built up with numerous Ag-Cu ligaments. • The nanoporous ligaments show two-stage coarsening behavior with dealloying time. • The formation and evolution mechanisms of the nanoporous structure were clarified. • It could provide new guidance to the synthesis of nanoporous multi-component alloys. - Abstract: A three-dimensional nanoporous bimetallic Ag-Cu alloy with uniform chemical composition has been fabricated by dealloying Mg_6_5Ag_1_2_._5Cu_1_2_._5Y_1_0 metallic glass in dilute (0.04 M) H_2SO_4 aqueous solution under free-corrosion conditions. The nanoporous Ag-Cu evolves through two distinct stages. First, ligaments of the nanoporous structure, consisting of supersaturated Ag(Cu) solid solution with a constant Ag/Cu mole ratio of 1:1, are yielded. Second, with excessive immersion, some Cu atoms separate from the metastable nanoporous matrix and form spherical Cu particles on the sample surface. Formation and evolution mechanisms of the nanoporous structure are proposed.

Growth of intermetallics between Sn/Ni/Cu, Sn/Ag/Cu and Sn/Cu layered structures

International Nuclear Information System (INIS)

Horváth, Barbara; Illés, Balázs; Shinohara, Tadashi

2014-01-01

Intermetallic growth mechanisms and rates are investigated in Sn/Ni/Cu, Sn/Ag/Cu and Sn/Cu layer systems. An 8–10 μm thick Sn surface finish layer was electroplated onto a Cu substrate with a 1.5–2 μm thick Ni or Ag barrier layer. In order to induce intermetallic layer growth, the samples were aged in elevated temperatures: 50 °C and 125 °C. Intermetallic layer growth was checked by focused ion beam–scanning ion microscope. The microstructures and chemical compositions of the intermetallic layers were observed with a transmission electron microscope. It has been found that Ni barrier layers can effectively block the development of Cu 6 Sn 5 intermetallics. The intermetallic growth characteristics in the Sn/Cu and Sn/Ni/Cu systems are very similar. The intermetallic layer grows towards the Sn layer and forms a discrete layer. Differences were observed only in the growth gradients and surface roughness of the intermetallic layer which may explain the different tin whiskering properties. It was observed that the intermetallic layer growth mechanisms are completely different in the Ag barrier layers compared to the Ni layers. In the case of Sn/Ag/Cu systems, the Sn and Cu diffused through the Ag layer, formed Cu 6 Sn 5 intermetallics mainly at the Sn/Ag interface and consumed the Ag barrier layer. - Highlights: • Intermetallic growth was characterised in Sn/Ni/Cu, Sn/Ag/Cu and Sn/Cu layer systems. • Intermetallic growth rates and roughness are similar in the Sn/Cu and Sn/Ni/Cu systems. • Sn/Ni/Cu system contains the following intermetallic layer structure Sn–Ni3Sn4–Ni3Sn2–Ni3Sn–Ni. • In the case of Sn/Ag/Cu systems the Sn and Cu diffusion consumes the Ag barrier layer. • When Cu reaches the Sn/Ag interface a large amount of Cu 6 Sn 5 forms above the Ag layer

Facile synthesis of Ag nanocubes and Au nanocages.

Science.gov (United States)

Skrabalak, Sara E; Au, Leslie; Li, Xingde; Xia, Younan

2007-01-01

This protocol describes a method for the synthesis of Ag nanocubes and their subsequent conversion into Au nanocages via the galvanic replacement reaction. The Ag nanocubes are prepared by a rapid (reaction time nanocubes. With this method, Ag nanocubes can be prepared and isolated for use within approximately 3 h. The Ag nanocubes can then serve as sacrificial templates for the preparation of Au nanocages, with a method for their preparation also described herein. The procedure for Au nanocage preparation and isolation requires approximately 5 h.

A label-free electrochemical immunosensor based on the novel signal amplification system of AuPdCu ternary nanoparticles functionalized polymer nanospheres.

Science.gov (United States)

Yan, Qin; Yang, Yuying; Tan, Zhaoling; Liu, Qing; Liu, Hui; Wang, Ping; Chen, Lei; Zhang, Daopeng; Li, Yueyun; Dong, Yunhui

2018-04-30

A sensitive label-free electrochemical immunosensor was designed using a novel signal amplification system for quantitative detecting hepatitis B surface antigen (HBsAg). Nitrogen-doped graphene quantum dots (N-GQDs) supported surfactant-free AuPdCu ternary nanoparticles (AuPdCu/N-GQDs), which featured with good conductivity and excellent catalytic properties for the reduction of hydrogen peroxide (H 2 O 2 ), was synthesized by a simple and benign hydrothermal procedure. At the same time, the electroactive polymer nanospheres (PS) was synthesized by infinite coordination polymers of ferrocenedicarboxylic acid, which could play as carrier and electronic mediator to load AuPdCu/N-GQDs. The PS not only improved the ability to load antibodies because of the good biocompatibility, but also accelerated electron transport of the electrode interface attribute to plentiful ferrocene unit. Thus, the prepared AuPdCu/N-GQDs@PS has abilities of good biocompatibility, catalytic activity and electrical conductivity to be applied as transducing materials to amplify electrochemical signal in detection of HBsAg. Under optimal conditions, the fabricated immunosensor exhibited high sensitivity and stability in the detection of HBsAg. A linear relationship between current signals and the concentrations of HBsAg was obtained in the range from 10fg/mL to 50ng/mL and the detection limit of HBsAg was 3.3fg/mL (signal-to-noise ratio of 3). Moreover, the designed immunosensor with excellent selectivity, reproducibility and stability shows excellent performance in detection of human serum samples. Furthermore, this label-free electrochemical immunosensor has promising application in clinical diagnosis of HBsAg. Copyright © 2017 Elsevier B.V. All rights reserved.

In-situ STM study of phosphate adsorption on Cu(111), Au(111) and Cu/Au(111) electrodes

DEFF Research Database (Denmark)

Schlaup, Christian; Horch, Sebastian

2013-01-01

The interaction of Cu(111), Au(111) and Cu-covered Au(111) electrodes with a neutral phosphate buffer solution has been studied by means of cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (EC-STM). Under low potential conditions, both the Cu(111) and the Au(111......) surface appear apparently adsorbate free, indicated by the presence of a (4×4) structure and the herringbone surface reconstruction, respectively. Upon potential increase, phosphate anions adsorb on both surfaces and for Cu(111) the formation of a (√3×√3)R30° structure is found, whereas on Au(111) a "(√3......×√7)" structure is formed. For a Cu-submonolayer on Au(111), coadsorption of phosphate anions leads to the formation of a (2×2) vacancy structure within an assumed pseudomorphic structure of the Cu-submonolayer with the phosphate anions occupying the vacancies. When desorbing the phosphate anions at low...

Surface chemistry of 2-butanol and furfural on Cu, Au and Cu/Au single crystals

OpenAIRE

Megginson, Rory

2016-01-01

In this study, the adsorption of 2-butanol and furfural was investigated on Au (111), Cu (111) and Cu/Au (111) surfaces. It was hoped that by studying how these species adsorbed on these surfaces , insight would be provided into the roles of Cu and Au in the “hydrogen free” hydrogenation of furfural to furfuryl alcohol. This is a valuable process as currently furfuryl alcohol is derived from crude oil but it is possible to derive furfural from corn husk making it a greener process...

Surface structure and morphology of Cu-free and Cu-covered Au(100) and Au(111) electrodes in alkaline solution

Energy Technology Data Exchange (ETDEWEB)

Schlaup, Christian [Technical University of Denmark, Department of Physics, Fysikvey, DK-2800 Kongens Lyngby (Denmark); Friebel, Daniel [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd, Menlo Park, CA 94025 (United States); Wandelt, Klaus [University of Bonn, Institute for Physical und Theoretical Chemistry, Wegelerstr. 12, D-53115 Bonn (Germany)

2011-07-01

For both Cu-free Au-electrodes three different phases were observed as a function of the applied electrode potential. While at low potentials the onset of surface reconstruction points towards an apparently adsorbate free surface and, thus, a weak interaction with species from the electrolyte, a Au-hydroxide and a Au-oxide phase are formed subsequently during potential increase. A similar phase behavior was also found for Cu-covered Au-electrodes, while at low potentials an apparently adsorbate free Cu layer is observed, a Cu-hydroxide coadsorbate phase and a Cu-oxide phase are formed under increased potential conditions. In addition the apparently adsorbate free Cu-film tends to form a Cu-Au alloy phase while keeping the electrode for a sufficient long time at low potential conditions.

A simple approach for facile synthesis of Ag, anisotropic Au and bimetallic (Ag/Au) nanoparticles using cruciferous vegetable extracts

Energy Technology Data Exchange (ETDEWEB)

Jacob, Jasmine; Mukherjee, Tulsi; Kapoor, Sudhir, E-mail: sudhirk@barc.gov.in

2012-10-01

We present a simple and straightforward approach for the synthesis and stabilization of relatively monodisperse Ag, Au and bimetallic (Ag/Au) nanoparticles by using cruciferous vegetable (green/red) extracts by simply adjusting the pH environment in the aqueous medium. The vegetable extracts act both as reducing and capping agents. The monometallic and bimetallic nanoparticles of Ag and Au so obtained were characterized by UV-visible spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM). It is shown that red cabbage extract can be used for the preparation of anisotropic Au nanoparticles. The formation of Au anisotropic nanoparticles was found to depend on a number of environmental factors, such as the pH of the reaction medium, reaction time, and initial reactant concentrations. Additionally, it is shown that these extract-stabilized Au and Ag nanoparticles can be used as a seed for preparation of bimetallic Au/Ag nanoparticles. For bimetallic alloy nanoparticles the absorption peak was observed between the two maxima of the corresponding metallic particles. The surface plasmon absorption maxima for bimetallic nanoparticles changed linearly with increasing Au mole ratio content in various alloy compositions. It has been shown that the formation of hollow Au spheres depends on the experimental conditions. - Graphical abstract: TEM image of gold nanoparticles at pH 3.27 formed by red cabbage extract. Highlights: Black-Right-Pointing-Pointer First report on the reactivity of the extracts toward metal ions using a spectrophotometric technique. Black-Right-Pointing-Pointer Red cabbage extract has better reducing properties than green cabbage extract. Black-Right-Pointing-Pointer Red cabbage extract can reduce metal ions at any pH. Black-Right-Pointing-Pointer Reduction of metal ions can have important consequences in the study of soil chemistry.

A simple approach for facile synthesis of Ag, anisotropic Au and bimetallic (Ag/Au) nanoparticles using cruciferous vegetable extracts

International Nuclear Information System (INIS)

Jacob, Jasmine; Mukherjee, Tulsi; Kapoor, Sudhir

2012-01-01

We present a simple and straightforward approach for the synthesis and stabilization of relatively monodisperse Ag, Au and bimetallic (Ag/Au) nanoparticles by using cruciferous vegetable (green/red) extracts by simply adjusting the pH environment in the aqueous medium. The vegetable extracts act both as reducing and capping agents. The monometallic and bimetallic nanoparticles of Ag and Au so obtained were characterized by UV–visible spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM). It is shown that red cabbage extract can be used for the preparation of anisotropic Au nanoparticles. The formation of Au anisotropic nanoparticles was found to depend on a number of environmental factors, such as the pH of the reaction medium, reaction time, and initial reactant concentrations. Additionally, it is shown that these extract-stabilized Au and Ag nanoparticles can be used as a seed for preparation of bimetallic Au/Ag nanoparticles. For bimetallic alloy nanoparticles the absorption peak was observed between the two maxima of the corresponding metallic particles. The surface plasmon absorption maxima for bimetallic nanoparticles changed linearly with increasing Au mole ratio content in various alloy compositions. It has been shown that the formation of hollow Au spheres depends on the experimental conditions. - Graphical abstract: TEM image of gold nanoparticles at pH 3.27 formed by red cabbage extract. Highlights: ► First report on the reactivity of the extracts toward metal ions using a spectrophotometric technique. ► Red cabbage extract has better reducing properties than green cabbage extract. ► Red cabbage extract can reduce metal ions at any pH. ► Reduction of metal ions can have important consequences in the study of soil chemistry.

Cu-Zr-Ag bulk metallic glasses based on Cu8Zr5 icosahedron

International Nuclear Information System (INIS)

Xia Junhai; Qiang Jianbing; Wang Yingmin; Wang Qing; Dong Chuang

2007-01-01

Based on the cluster line criterion, the Ag addition into the Cu 8 Zr 5 cluster composition is investigated for the search of ternary Cu-Zr-Ag bulk metallic glasses with high glass forming abilities. Two initial binary compositions Cu 0.618 Zr 0.382 and Cu 0.64 Zr 0.36 are selected. The former one corresponds to a deep eutectic point; it is also the composition of the Cu 8 Zr 5 icosahedron, which is derived from the Cu 8 Zr 3 structure. The latter one, which can be regarded as the Cu 8 Zr 5 cluster plus a glue atom Cu, is the best glass-forming composition in the Cu-Zr binary system. Two composition lines (Cu 0.618 Zr 0.382 ) 1-x Ag x and (Cu 0.64 Zr 0.36 ) 1-x Ag x are thus constructed in the Cu-Zr-Ag system by linking these two compositions with the third constitute Ag. A series of Cu-Zr-Ag bulk metallic glasses are found with 2-8 at.% Ag contents in both composition lines. The optimum composition (Cu 0.618 Zr 0.382 ) 0.92 Ag 0.08 within the searched region with the highest T g /T l = 0.633, is located along the cluster line (Cu 0.618 Zr 0.382 ) 1-x Ag x , where the deep eutectic Cu 0.618 Zr 0.382 exactly corresponds to the dense packing cluster Cu 8 Zr 5 . The alloying mechanism is discussed in the light of atomic size and electron concentration factors

Microstructure evolution during 300 °C storage of sintered Ag nanoparticles on Ag and Au substrates

Energy Technology Data Exchange (ETDEWEB)

Paknejad, S.A. [King’s College London, Physics Department, Strand, London WC2R 2LS (United Kingdom); Dumas, G. [Eltek Semiconductors Ltd, Nelson Road Industrial Estate, Dartmouth, Devon TQ6 9LA (United Kingdom); West, G. [Loughborough University, Materials Department, Loughborough LE11 3TU (United Kingdom); Lewis, G. [Eltek Semiconductors Ltd, Nelson Road Industrial Estate, Dartmouth, Devon TQ6 9LA (United Kingdom); Mannan, S.H., E-mail: samjid.mannan@kcl.ac.uk [King’s College London, Physics Department, Strand, London WC2R 2LS (United Kingdom)

2014-12-25

Highlights: • Shear strength of pressure-free sintered Ag found to increase during ageing at 300 °C on Ag substrate. • Rapid collapse of void number density after 24 h ageing in the sintered Ag layer. • Higher porosity at edge of joint compared to the middle. • Shear strength of pressure-free sintered Ag decreases during ageing at 300 °C due to high porosity layer growth. • Void free layer and high porosity layer growth explained in terms of atomic diffusion and grain boundary migration. - Abstract: A silver nanoparticle based die attach material was used in a pressure free process to bond 2.5 mm square Ag plated Si die to Ag and Au plated substrates. The assemblies were stored at 300 °C for up to 500 h and the morphology of the sintered Ag and the shear strength were monitored as a function of time. On Ag substrate it was found that die shear strength increased and that the Ag grains grew in size and porosity decreased over time. There was also a clear difference in morphology between sintered Ag at the die edge and centre. On Au substrate, it was observed that the initially high die shear strength decreased with storage time and that voids migrated away from the Ag/Au interface and into the Ag joint. This has led to the formation of a void free layer at the interface followed by a high porosity region, which weakened the joint. The microstructure reveals a high density of grain and twin boundaries which facilitate the Ag and Au atomic diffusion responsible. The grain structure of the plated Au led to diffusion of Au into the Ag via high-angle tilt grain boundaries, and grain boundary migration further dispersed the Au into the Ag layer.

Texturization of diamond-wire-sawn multicrystalline silicon wafer using Cu, Ag, or Ag/Cu as a metal catalyst

Science.gov (United States)

Wang, Shing-Dar; Chen, Ting-Wei

2018-06-01

In this work, Cu, Ag, or Ag/Cu was used as a metal catalyst to study the surface texturization of diamond-wire-sawn (DWS) multi-crystalline silicon (mc-Si) wafer by a metal-assisted chemical etching (MACE) method. The DWS wafer was first etched by standard HF-HNO3 acidic etching, and it was labeled as AE-DWS wafer. The effects of ratios of Cu(NO3)2:HF, AgNO3:HF, and AgNO3:Cu(NO3)2 on the morphology of AE-DWS wafer were investigated. After the process of MACE, the wafer was treated with a NaF/H2O2 solution. In this process, H2O2 etched the nanostructure, and NaF removed the oxidation layer. The Si {1 1 1} plane was revealed by etching the wafer in a mixture of 0.03 M Cu(NO3)2 and 1 M HF at 55 °C for 2.5 min. These parallel Si {1 1 1} planes replaced some parallel saw marks on the surface of AE-DWS wafers without forming a positive pyramid or an inverted pyramid structure. The main topography of the wafer is comprised of silicon nanowires grown in direction when Ag or Ag/Cu was used as a metal catalyst. When silicon is etched in a mixed solution of Cu(NO3)2, AgNO3, HF and H2O2 at 55 °C with a concentration ratio of [Cu2+]/[Ag+] of 50 or at 65 °C with a concentration ratio of [Cu2+]/[Ag+] of 33, a quasi-inverted pyramid structure can be obtained. The reflectivity of the AE-DWS wafers treated with MACE is lower than that of the multiwire-slurry-sawn (MWSS) mc-Si wafers treated with traditional HF + HNO3 etching.

Formation of Cu, Ag and Au nanofiims under the influence of hydrogen atoms

Directory of Open Access Journals (Sweden)

Zhavzharov E. L.

2015-12-01

Full Text Available Due to their electrical properties, thin metallic films are widely used in modern micro- and nanoelectronics. These properties allow solving fundamental problems of surface and solid state physics. Up-to-date methods of producing thin films involve high vacuum or multi-stage processes, which calls for complicated equipment. The authors propose an alternative method of producing thin metallic films using atomic hydrogen. Exothermal reaction of atoms recombination in a molecule (about 4.5 eV / recombination act initiated on the solid surface by atomic hydrogen may stimulate local heating, spraying and surface atoms transfer. We investigated the process of atomic hydrogen treatment of Cu, Ag and Au metal films, obtained by thermal vacuum evaporation. There are two methods of obtaining nanofilms using atomic hydrogen treatment: sputtering and vapor-phase epitaxy. In the first method, a film is formed by reducing the thickness of the starting film. This method allows obtaining a film as thick as the monolayer. In the second method, a nanofilm is formed by deposition of metal atoms from the vapor phase. This method allows obtaining a film thickness from monolayer to ~10 nm. These methods allow creating nanofilms with controlled parameters and metal thickness. Such films would be technologically pure and have good adhesion.

Site-Selective Carving and Co-Deposition: Transformation of Ag Nanocubes into Concave Nanocrystals Encased by Au-Ag Alloy Frames.

Science.gov (United States)

Ahn, Jaewan; Wang, Daniel; Ding, Yong; Zhang, Jiawei; Qin, Dong

2018-01-23

We report a facile synthesis of Ag nanocubes with concave side faces and Au-Ag alloy frames, namely Ag@Au-Ag concave nanocrystals, by titrating HAuCl 4 solution into an aqueous mixture of Ag nanocubes, ascorbic acid (H 2 Asc), NaOH, and cetyltrimethylammonium chloride (CTAC) at an initial pH of 11.6 under ambient conditions. Different from all previous studies involving poly(vinylpyrrolidine), the use of CTAC at a sufficiently high concentration plays an essential role in carving away Ag atoms from the side faces through galvanic replacement. Concurrent co-deposition of Au and Ag atoms via chemical reduction at orthogonal sites on the surface of Ag nanocubes leads to the generation of Ag@Au-Ag concave nanocrystals with well-defined and controllable structures. Specifically, in the presence of CTAC-derived Cl - ions, the titrated HAuCl 4 is maintained in the AuCl 4 - species, enabling its galvanic replacement with the Ag atoms located on the side faces of nanocubes. The released Ag + ions can be retained in the soluble form of AgCl 2 - by complexing with the Cl - ions. Both the AuCl 4 - and AgCl 2 - in the solution are then reduced by ascorbate monoanion, a product of the neutralization reaction between H 2 Asc and NaOH, to Au and Ag atoms for their preferential co-deposition onto the edges and corners of the Ag nanocubes. Compared with Ag nanocubes, the Ag@Au-Ag concave nanocrystals exhibit much stronger SERS activity at an excitation of 785 nm, making it feasible to monitor the Au-catalyzed reduction of 4-nitrothiophenol by NaBH 4 in situ. When the Ag cores are removed, the concave nanocrystals evolve into Au-Ag nanoframes with controllable ridge thicknesses.

Equilibrium phase diagram of the Ag-Au-Pb ternary system

International Nuclear Information System (INIS)

Hassam, S.; Bahari, Z.

2005-01-01

The phase diagram of the ternary system Ag-Au-Pb has been established using differential thermal analysis and X-ray powder diffraction analysis. Four vertical sections were studied: X Pb = 0.40, X Au /X Pb = 1/3, X Ag /X Au = 4/1 and X Ag /X Au = 1/1. Two ternary transitory peritectics and one ternary eutectic were characterized. A schematic representation of the ternary equilibria is given

Temperature stability of AgCu nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Sopoušek, Jiří, E-mail: sopousek@mail.muni.cz; Zobač, Ondřej; Vykoukal, Vít [Masaryk University, Department of Chemistry, Faculty of Science (Czech Republic); Buršík, Jiří; Roupcová, Pavla [Institute of Physics of Materials ASCR (Czech Republic); Brož, Pavel; Pinkas, Jiří [Masaryk University, Department of Chemistry, Faculty of Science (Czech Republic); Vřešťál, Jan [Masaryk University, Central European Institute of Technology, CEITEC (Czech Republic)

2015-12-15

The colloidal solutions of the Ag–Cu nanoparticles (NPs, 10–32 nm) were prepared by solvothermal reactions. The samples of dried AgCu NPs and the resulting microstructures after heat treatment in air were investigated by various methods including electron microscopy (TEM, SEM) and high-temperature X-ray powder diffraction (HTXRD). The AgCu randomly mixed, Cu-rich, and Ag-rich face centred cubic crystal lattices were detected during the experiments. The temperature induced sintering was observed experimentally by HTXRD at 250 °C. The phase transformations at high temperatures were monitored by differential scanning calorimetry. The formation of the Ag-rich grains during heating in air and evolution of copper oxide microstructure were detected.Graphical abstract.

CHARGED PARTICLE MULTIPLICITIES IN ULTRA-RELATIVISTIC AU+AU AND CU+CU COLLISIONS

Science.gov (United States)

Back, B. B.; Alver, B.; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Busza, W.; Carroll, A.; Chai, Z.; Chetluru, V.; Decowski, M. P.; Garcia, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Halliwell, C.; Hamblen, J.; Harnarine, I.; Hauer, M.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holynski, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Khan, N.; Kulinich, P.; Kuo, C. M.; Li, W.; Lin, W. T.; Loizides, C.; Manly, S.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Reed, C.; Richardson, E.; Roland, C.; Roland, G.; Sagerer, J.; Seals, H.; Sedykh, I.; Smith, C. E.; Stankiewicz, M. A.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Szostak, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; Vannieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Walters, P.; Wenger, E.; Willhelm, D.; Wolfs, F. L. H.; Wosiek, B.; Wozniak, K.; Wyngaardt, S.; Wyslouch, B.

The PHOBOS collaboration has carried out a systematic study of charged particle multiplicities in Cu+Cu and Au+Au collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. A unique feature of the PHOBOS detector is its ability to measure charged particles over a very wide angular range from 0.5° to 179.5° corresponding to |η| <5.4. The general features of the charged particle multiplicity distributions as a function of pseudo-rapidity, collision energy and centrality, as well as system size, are discussed.

Retrieval of Au, Ag, Cu precious metals coupled with electric energy production via an unconventional coupled redox fuel cell reactor.

Science.gov (United States)

Zhang, Hui-Min; Fan, Zheng; Xu, Wei; Feng, Xiao; Wu, Zu-Cheng

2017-09-15

The recovery of heavy metals from aqueous solutions or e-wastes is of upmost importance. Retrieval of Au, Ag, and Cu with electricity generation through building an ethanol-metal coupled redox fuel cells (CRFCs) is demonstrated. The cell was uniquely assembled on PdNi/C anode the electro-oxidation of ethanol takes place to give electrons and then go through the external circuit reducing metal ions to metallic on the cathode, metals are recovered. Taking an example of removal of 100mgL -1 gold in 0.5M HAc-NaAc buffer solution as the catholyte, 2.0M ethanol in 1.0M alkaline solution as the anolyte, an open circuit voltage of 1.4V, more than 96% of gold removal efficiency in 20h, and equivalent energy production of 2.0kWhkg -1 of gold can be readily achieved in this system. When gold and copper ions coexist, it was confirmed that metallic Cu is formed on the cathodic electrode later than metallic Au formation by XPS analysis. Thus, this system can achieve step by step electrodeposition of gold and copper while the two metal ions coexisting. This work develops a new approach to retrieve valuable metals from aqueous solution or e-wastes. Copyright © 2017 Elsevier B.V. All rights reserved.

Zr-(Cu,Ag)-Al bulk metallic glasses

International Nuclear Information System (INIS)

Jiang, Q.K.; Wang, X.D.; Nie, X.P.; Zhang, G.Q.; Ma, H.; Fecht, H.-J.; Bendnarcik, J.; Franz, H.; Liu, Y.G.; Cao, Q.P.; Jiang, J.Z.

2008-01-01

In this paper, we report the formation of a series Zr-(Cu,Ag)-Al bulk metallic glasses (BMGs) with diameters at least 20 mm and demonstrate the formation of about 25 g amorphous metallic ingots in a wide Zr-(Cu,Ag)-Al composition range using a conventional arc-melting machine. The origin of high glass-forming ability (GFA) of the Zr-(Cu,Ag)-Al alloy system has been investigated from the structural, thermodynamic and kinetic points of view. The high GFA of the Zr-(Cu,Ag)-Al system is attributed to denser local atomic packing and the smaller difference in Gibbs free energy between amorphous and crystalline phases. The thermal, mechanical and corrosion properties, as well as elastic constants for the newly developed Zr-(Cu,Ag)-Al BMGs, are also presented. These newly developed Ni-free Zr-(Cu,Ag)-Al BMGs exhibit excellent combined properties: strong GFA, high strength, high compressive plasticity, cheap and non-toxic raw materials and biocompatible property, as compared with other BMGs, leading to their potential industrial applications

Influence of Au Nanoparticle Shape on Au@Cu2O Heterostructures

Directory of Open Access Journals (Sweden)

Jie Zhu

2015-01-01

Full Text Available Synthesis of metal-semiconductor heterostructures may allow the combination of function of the corresponding components and/or the enhanced performance resulting from the interactions between all the components. In this paper, Au@Cu2O core-shell heterostructures are prepared by a seed-growth method, using different-shaped Au nanocrystals as the seeds such as nanorods, octahedra, decahedra, dots, and nanocubes. The results revealed that the final structure of Au@Cu2O was greatly influenced by the shape of the seeds used. Exposure of Cu2O{111} and Cu2O{001} favored when the overgrowth happened on Au{111} and Au{001} surface, respectively. The size of the product can also be tuned by the amount of the seeds. The results reported here provide a thinking clue to modulate the shape and size of core-shell nanocrystals, which is useful in developing new materials with desired performance.

Comparison of Au and Ag nanoshells' metal-enhanced fluorescence

International Nuclear Information System (INIS)

Liaw, Jiunn-Woei; Chen, Huang-Chih; Kuo, Mao-Kuen

2014-01-01

The average enhancement factors of Au and Ag nanoshells (NSs) were analyzed theoretically to compare their overall performances on metal-enhanced fluorescence. We used the Mie theory and dyadic Green's functions to calculate the excitation rate and apparent quantum yield of NS interacting with a plane wave and a dipole, respectively, and then to obtain the enhancement factor. Moreover, the average enhancement factor (AEF) of NS on the fluorescence of a nearby molecule was obtained by averaging all possible orientations and locations of the molecule with a constant distance from NS. Our results show that the maximum AEF of Au NS occurs at the wavelength of the dipole mode, which is broadband. In contrast, the maximum AEF of Ag NS is at the narrowband quadrupole mode. In addition, the Stokes shift effect on AEF was studied for Au and Ag NSs. - Highlights: • The average enhancement factors of Au and Ag nanoshells were analyzed theoretically. • The maximum AEF of Au NS occurs at the wavelength of the dipole mode. • The maximum AEF of Ag NS is at the narrowband quadrupole mode. • The Stokes shift effect on AEF is discussed for Au and Ag NSs

Spin and orbital magnetism of coinage metal trimers (Cu3, Ag3, Au3: A relativistic density functional theory study

Directory of Open Access Journals (Sweden)

Mahdi Afshar

2013-11-01

Full Text Available We have demonstrated electronic structure and magnetic properties of Cu3, Ag3 and Au3 trimers using a full potential local orbital method in the framework of relativistic density functional theory. We have also shown that the non-relativistic generalized gradient approximation for the exchange-correlation energy functional gives reliable magnetic properties in coinage metal trimers compared to experiment. In addition we have indicated that the spin-orbit coupling changes the structure and magnetic properties of gold trimer while the structure and magnetic properties of copper and silver trimers are marginally affected. A significant orbital moment of 0.21μB was found for most stable geometry of the gold trimer whereas orbital magnetism is almost quenched in the copper and silver trimers.

Leaching of Au, Ag, and Pd from waste printed circuit boards of mobile phone by iodide lixiviant after supercritical water pre-treatment

International Nuclear Information System (INIS)

Xiu, Fu-Rong; Qi, Yingying; Zhang, Fu-Shen

2015-01-01

Highlights: • We report a novel process for recovering Au, Ag, and Pd from waste PCBs. • The effect of SCWO on the leaching of Au, Ag, and Pd in waste PCBs was studied. • SCWO was highly efficient for enhancing the leaching of Au, Ag, and Pd. • The optimum leaching parameters for Au, Ag, and Pd in iodine–iodide were studied. - Abstract: Precious metals are the most attractive resources in waste printed circuit boards (PCBs) of mobile phones. In this work, an alternative process for recovering Au, Ag, and Pd from waste PCBs of mobile phones by supercritical water oxidation (SCWO) pre-treatment combined with iodine–iodide leaching process was developed. In the process, the waste PCBs of mobile phones were pre-treated in supercritical water, then a diluted hydrochloric acid leaching (HL) process was used to recovery the Cu, whose leaching efficiency was approximately 100%, finally the resulting residue was subjected to the iodine–iodide leaching process for recovering the Au, Ag, and Pd. Experimental results indicated that SCWO pre-treatment temperature, time, and pressure had significant influence on the Au, Ag, and Pd leaching from (SCWO + HL)-treated waste PCBs. The optimal SCWO pre-treatment conditions were 420 °C and 60 min for Au and Pd, and 410 °C and 30 min for Ag. The optimum dissolution parameters for Au, Pd, and Ag in (SCWO + HL)-treated PCBs with iodine–iodide system were leaching time of 120 min (90 min for Ag), iodine/iodide mole ratio of 1:5 (1:6 for Ag), solid-to-liquid ratio (S/L) of 1:10 g/mL (1:8 g/mL for Ag), and pH of 9, respectively. It is believed that the process developed in this study is environment friendly for the recovery of Au, Ag, and Pd from waste PCBs of mobile phones by SCWO pre-treatment combined with iodine–iodide leaching process

Leaching of Au, Ag, and Pd from waste printed circuit boards of mobile phone by iodide lixiviant after supercritical water pre-treatment

Energy Technology Data Exchange (ETDEWEB)

Xiu, Fu-Rong, E-mail: xiu_chem@hotmail.com [College of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou 350108 (China); Qi, Yingying [College of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou 350108 (China); Zhang, Fu-Shen [Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China)

2015-07-15

Highlights: • We report a novel process for recovering Au, Ag, and Pd from waste PCBs. • The effect of SCWO on the leaching of Au, Ag, and Pd in waste PCBs was studied. • SCWO was highly efficient for enhancing the leaching of Au, Ag, and Pd. • The optimum leaching parameters for Au, Ag, and Pd in iodine–iodide were studied. - Abstract: Precious metals are the most attractive resources in waste printed circuit boards (PCBs) of mobile phones. In this work, an alternative process for recovering Au, Ag, and Pd from waste PCBs of mobile phones by supercritical water oxidation (SCWO) pre-treatment combined with iodine–iodide leaching process was developed. In the process, the waste PCBs of mobile phones were pre-treated in supercritical water, then a diluted hydrochloric acid leaching (HL) process was used to recovery the Cu, whose leaching efficiency was approximately 100%, finally the resulting residue was subjected to the iodine–iodide leaching process for recovering the Au, Ag, and Pd. Experimental results indicated that SCWO pre-treatment temperature, time, and pressure had significant influence on the Au, Ag, and Pd leaching from (SCWO + HL)-treated waste PCBs. The optimal SCWO pre-treatment conditions were 420 °C and 60 min for Au and Pd, and 410 °C and 30 min for Ag. The optimum dissolution parameters for Au, Pd, and Ag in (SCWO + HL)-treated PCBs with iodine–iodide system were leaching time of 120 min (90 min for Ag), iodine/iodide mole ratio of 1:5 (1:6 for Ag), solid-to-liquid ratio (S/L) of 1:10 g/mL (1:8 g/mL for Ag), and pH of 9, respectively. It is believed that the process developed in this study is environment friendly for the recovery of Au, Ag, and Pd from waste PCBs of mobile phones by SCWO pre-treatment combined with iodine–iodide leaching process.

Synthesis of biocompatible AuAgS/Ag2S nanoclusters and their applications in photocatalysis and mercury detection

International Nuclear Information System (INIS)

Zhao, Qian; Chen, Shenna; Zhang, Lingyang; Huang, Haowen; Liu, Fengping; Liu, Xuanyong

2014-01-01

In this paper, a facile approach for preparation of AuAgS/Ag 2 S nanoclusters was developed. The unique AuAgS/Ag 2 S nanoclusters capped with biomolecules exhibit interesting excellent optical and catalytic properties. The fluorescent AuAgS/Ag 2 S nanoclusters show tunable luminescence depending on the nanocluster size. The apoptosis assay demonstrated that the AuAgS/Ag 2 S nanoclusters showed low cytotoxicity and good biocompatibility. Therefore, the nanoclusters can be used not only as a probe for labeling cells but also for their photocatalytic activity for photodegradation of organic dye. Moreover, a highly selective and sensitive assay for detection of mercury including Hg 2+ and undissociated mercury complexes was developed based on the quenching fluorescent AuAgS/Ag 2 S nanoclusters, which provides a promising approach for determining various forms of Hg in the mercury-based compounds in environment. These unique nanoclusters may have potential applications in biological labeling, sensing mercury, and photodegradation of various organic pollutants in waste water.Graphical Abstract

Photoreduction of Ag{sup +} in Ag/Ag{sub 2}S/Au memristor

Energy Technology Data Exchange (ETDEWEB)

Mou, N.I.; Tabib-Azar, M., E-mail: azar.m@utah.edu

2015-06-15

Highlights: • The effect of illumination on the operating voltages and switching speed of Ag/Ag{sub 2}S/Au memristors is studied • Illumination decreased the average switching time from high to low resistance states by ∼19% and decreased the turn-off voltages dramatically from −0.8 V to −0.25 V. • Photo-induced reduction of silver in Ag{sub 2}S may be used in three dimensional optical memories that can be electronically read and reset. • Illumination changed sulfur's valency and modified its oxidation/reduction potential. - Abstract: Silver halides and chalcogenides are excellent memristor materials that have been extensively used in the past as photosensitive layers in photography. Here we examine the effect of illumination on the operating voltages and switching speed of Ag/Ag{sub 2}S/Au memristors using a green laser (473–523 nm). Our results indicate that illumination decreases the average switching time from high to low resistance states by ∼19% and decreases the turn-off voltages dramatically from −0.8 V to −0.25 V that we attribute to the change in sulfur valency and a photo-induced change in its oxidation/reduction potential. Photo-induced reduction of silver in Ag{sub 2}S may be used in three dimensional optical memories that can be electronically read and reset.

Cubic-to-Tetragonal Phase Transitions in Ag-Cu Nano rods

International Nuclear Information System (INIS)

Delogu, F.; Mascia, M.

2012-01-01

Molecular dynamics simulations have been used to investigate the structural behavior of nano rods with square cross section. The nano rods consist of pure Ag and Cu phases or of three Ag and Cu domains in the sequence Ag-Cu-Ag or Cu-Ag-Cu. Ag and Cu domains are separated by coherent interfaces. Depending on the side length and the size of individual domains, Ag and Cu can undergo a transition from the usual face-centered cubic structure to a body-centered tetragonal one. Such transition can involve the whole nano rod, or only the Ag domains. In the latter case, the transition is accompanied by a loss of coherency at the Ag-Cu interfaces, with a consequent release of elastic energy. The observed behaviors are connected with the stresses developed at the nano rod surfaces.

Synthesis of Ag-Cu and Ag-Cu{sub 2}O alloy nanoparticles using a seed-mediated polyol process, thermodynamic and kinetic aspects

Energy Technology Data Exchange (ETDEWEB)

Niknafs, Yasaman; Amirjani, Amirmostafa; Marashi, Pirooz, E-mail: pmarashi@aut.ac.ir; Fatmehsari, Davoud Haghshenas

2017-03-01

In this paper, Ag, Ag-Cu and Ag-Cu{sub 2}O nanoparticles were synthesized using a modified polyol method. Size, shape and composition of the obtained nanostructures were effectively controlled by adjusting the kinetic and thermodynamic conditions. Response surface methodology was employed to consider the interaction of parameters and to develop a polynomial equation for predicting the size of the silver nanoparticles. The precisely controlled silver nanoaprticles were used as the seeds for the formation of alloyed nanoparticles. By manipulating the involved parameters, both spherical and cubical Ag-Cu and Ag-Cu{sub 2}O nanostructures are obtainable in the size range of 90–100 nm. The morphological, optical and compositional characteristics of the obtained nanostructures were studied using SEM, FE-SEM, UV–Vis, EDS and XRD. - Highlights: • Synthesis of Ag, Ag-Cu and Ag-Cu{sub 2}O alloy nanostructures. • RSM was successfully employed for predicting the size of the AgNPs. • Size and composition tuning by adjusting the kinetic and thermodynamic conditions.

Fabrication and stability investigation of ultra-thin transparent and flexible Cu-Ag-Au tri-layer film on PET

Science.gov (United States)

Prakasarao, Ch Surya; D'souza, Slavia Deeksha; Hazarika, Pratim; Karthiselva N., S.; Ramesh Babu, R.; Kovendhan, M.; Kumar, R. Arockia; Joseph, D. Paul

2018-04-01

The need for transparent conducting electrodes with high transmittance, low sheet resistance and flexibility to replace Indium Tin Oxide is ever growing. We have deposited and studied the performance of ultra-thin Cu-Ag-Au tri-layer films over a flexible poly-ethylene terephthalate substrate. Scotch tape test showed good adhesion of the metallic film. Transmittance of the tri-layer was around 40 % in visible region. Optical profiler measurements were done to study the surface features. The XRD pattern revealed that film was amorphous. Sheet resistance measured by four probe technique was around 7.7 Ohm/Δ and was stable up to 423 K. The transport parameters by Hall effect showed high conductivity and carrier concentration with a mobility of 5.58 cm2/Vs. Tests performed in an indigenously designed bending unit indicated the films to be stable both mechanically and electrically even after 50,000 bending cycles.

Bimetallic AgCu/Cu2O hybrid for the synergetic adsorption of iodide from solution.

Science.gov (United States)

Mao, Ping; Liu, Ying; Liu, Xiaodong; Wang, Yuechan; Liang, Jie; Zhou, Qihang; Dai, Yuexuan; Jiao, Yan; Chen, Shouwen; Yang, Yi

2017-08-01

To further improve the capacity of Cu 2 O to absorb I - anions from solution, and to understand the difference between the adsorption mechanisms of Ag/Cu 2 O and Cu/Cu 2 O adsorbents, bimetallic AgCu was doped into Cu 2 O through a facile solvothermal route. Samples were characterized and employed to adsorb I - anions under different experimental conditions. The results show that the Cu content can be tuned by adding different volumes of Ag sols. After doping bimetallic AgCu, the adsorption capacity of the samples can be increased from 0.02 mmol g -1 to 0.52 mmol g -1 . Moreover, the optimal adsorption is reached within only 240 min. Meanwhile, the difference between the adsorption mechanisms of Ag/Cu 2 O and Cu/Cu 2 O adsorbents was verified, and the cooperative adsorption mechanism of the AgCu/Cu 2 O hybrid was proposed and verified. In addition, the AgCu/Cu 2 O hybrid showed excellent selectivity, e.g., its adsorption efficiencies are 85.1%, 81.9%, 85.9% and 85.7% in the presence of the Cl - , CO 3 2- , SO 4 2- and NO 3 - competitive anions, respectively. Furthermore, the AgCu/Cu 2 O hybrid can worked well in other harsh environments (e.g., acidic, alkaline and seawater environments). Therefore, this study is expected to promote the development of Cu 2 O into a highly efficient adsorbent for the removal of iodide from solution. Copyright © 2017 Elsevier Ltd. All rights reserved.

Influence of Au Nanoparticle Shape on Au@Cu2O Heterostructures

OpenAIRE

Zhu, Jie; Lu, Na; Chen, Wei; Kong, Lina; Yang, Yun; Ma, Dekun; Huang, Shaoming

2015-01-01

Synthesis of metal-semiconductor heterostructures may allow the combination of function of the corresponding components and/or the enhanced performance resulting from the interactions between all the components. In this paper, Au@Cu2O core-shell heterostructures are prepared by a seed-growth method, using different-shaped Au nanocrystals as the seeds such as nanorods, octahedra, decahedra, dots, and nanocubes. The results revealed that the final structure of Au@Cu2O was greatly influenced by ...

Interfacial Reaction of Sn-Ag-Cu Lead-Free Solder Alloy on Cu: A Review

Directory of Open Access Journals (Sweden)

Liu Mei Lee

2013-01-01

Full Text Available This paper reviews the function and importance of Sn-Ag-Cu solder alloys in electronics industry and the interfacial reaction of Sn-Ag-Cu/Cu solder joint at various solder forms and solder reflow conditions. The Sn-Ag-Cu solder alloys are examined in bulk and in thin film. It then examines the effect of soldering conditions to the formation of intermetallic compounds such as Cu substrate selection, structural phases, morphology evolution, the growth kinetics, temperature and time is also discussed. Sn-Ag-Cu lead-free solder alloys are the most promising candidate for the replacement of Sn-Pb solders in modern microelectronic technology. Sn-Ag-Cu solders could possibly be considered and adapted in miniaturization technologies. Therefore, this paper should be of great interest to a large selection of electronics interconnect materials, reliability, processes, and assembly community.

Formation of Ag2, Au2 and AgAu particles on MgO(1 0 0): DFT study on the role of support-induced charge transfer in metal-metal interactions

International Nuclear Information System (INIS)

Fuente, Silvia A.; Belelli, Patricia G.; Branda, Maria M.; Ferullo, Ricardo M.; Castellani, Norberto J.

2009-01-01

The formation of Ag 2 , Au 2 and AgAu particles oriented perpendicularly to the MgO(1 0 0) surface was studied using the density functional theory. While the support induces a slight enhancement of the Ag-Ag bond (by 0.3-0.4 eV), the Au-Au bond is strongly enhanced (by 0.8-1.1 eV). Concerning the bimetallic particle, the Ag-Au bond stabilization depends on the relative position of each atom. Thus, in general terms, the strength of the metal-metal bond is determined by the nature of the terminal atom; the bond is stronger in Au-terminal particles. The partial electronic charge transfer to the terminal Au atom and its ability to polarize this charge are responsible for this energetic stabilization.

Toward hybrid Au nanorods @ M (Au, Ag, Pd and Pt) core-shell heterostructures for ultrasensitive SERS probes

Science.gov (United States)

Xie, Xiaobin; Gao, Guanhui; Kang, Shendong; Lei, Yanhua; Pan, Zhengyin; Shibayama, Tamaki; Cai, Lintao

2017-06-01

Being able to precisely control the morphologies of noble metallic nanostructures is of essential significance for promoting the surface-enhanced Raman scattering (SERS) effect. Herein, we demonstrate an overgrowth strategy for synthesizing Au @ M (M = Au, Ag, Pd, Pt) core-shell heterogeneous nanocrystals with an orientated structural evolution and highly improved properties by using Au nanorods as seeds. With the same reaction condition system applied, we obtain four well-designed heterostructures with diverse shapes, including Au concave nanocuboids (Au CNs), Au @ Ag crystalizing face central cube nanopeanuts, Au @ Pd porous nanocuboids and Au @ Pt nanotrepangs. Subsequently, the exact overgrowth mechanism of the above heterostructural building blocks is further analysed via the systematic optimiziation of a series of fabrications. Remarkably, the well-defined Au CNs and Au @ Ag nanopeanuts both exhibit highly promoted SERS activity. We expect to be able to supply a facile strategy for the fabrication of multimetallic heterogeneous nanostructures, exploring the high SERS effect and catalytic activities.

Contrasting fluids and reservoirs in the contiguous Marcona and Mina Justa iron oxide-Cu (-Ag-Au) deposits, south-central Perú

Science.gov (United States)

Chen, Huayong; Kyser, T. Kurtis; Clark, Alan H.

2011-10-01

The Marcona-Mina Justa deposit cluster, hosted by Lower Paleozoic metaclastic rocks and Middle Jurassic shallow marine andesites, incorporates the most important known magnetite mineralization in the Andes at Marcona (1.9 Gt at 55.4% Fe and 0.12% Cu) and one of the few major iron oxide-copper-gold (IOCG) deposits with economic Cu grades (346.6 Mt at 0.71% Cu, 3.8 g/t Ag and 0.03 g/t Au) at Mina Justa. The Middle Jurassic Marcona deposit is centred in Ica Department, Perú, and the Lower Cretaceous Mina Justa Cu (Ag, Au) prospect is located 3-4 km to the northeast. New fluid inclusion studies, including laser ablation time-of-flight inductively coupled plasma mass spectrometry (LA-TOF-ICPMS) analysis, integrated with sulphur, oxygen, hydrogen and carbon isotope analyses of minerals with well-defined paragenetic relationships, clarify the nature and origin of the hydrothermal fluid responsible for these contiguous but genetically contrasted deposits. At Marcona, early, sulphide-free stage M-III magnetite-biotite-calcic amphibole assemblages are inferred to have crystallized from a 700-800°C Fe oxide melt with a δ18O value from +5.2‰ to +7.7‰. Stage M-IV magnetite-phlogopite-calcic amphibole-sulphide assemblages were subsequently precipitated from 430-600°C aqueous fluids with dominantly magmatic isotopic compositions (δ34S = +0.8‰ to +5.9‰; δ18O = +9.6‰ to +12.2‰; δD = -73‰ to -43‰; and δ13C = -3.3‰). Stages M-III and M-IV account for over 95% of the magnetite mineralization at Marcona. Subsequent non-economic, lower temperature sulphide-calcite-amphibole assemblages (stage M-V) were deposited from fluids with similar δ34S (+1.8‰ to +5.0‰), δ18O (+10.1‰ to +12.5‰) and δ13C (-3.4‰), but higher δD values (average -8‰). Several groups of lower (200°C) fluids can be recognized in the main polymetallic (Cu, Zn, Pb) sulphide stage M-V and may record the involvement of modified seawater. At Mina Justa, early magnetite

Preparation of Ag{sub core}/Au{sub shell} bimetallic nanoparticles from physical mixtures of Au clusters and Ag ions under dark conditions and their catalytic activity for aerobic glucose oxidation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Haijun, E-mail: zhanghaijun@wust.edu.cn [College of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei Province 430081 (China); Toshima, Naoki; Takasaki, Kanako [Department of Applied Chemistry, Tokyo University of Science Yamaguchi, SanyoOnoda-shi, Yamaguchi 756-0884 (Japan); Okumura, Mitsutaka [Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)

2014-02-15

Graphical abstract: The synthesis, characterization and catalytic activities for glucose oxidation of AgAu bimetallic nanoparticles (BNPs) with size of less than 2 nm are reported. The catalytic activity of Ag{sub 10}Au{sub 90} BNPs was about two times higher than that of Au NPs, even the BNPs have a larger particle size than that of Au NPs. -- Highlights: • Ag{sub core}/Au{sub shell} BNPs with size of less than 2.0 nm were prepared. • No any reducing reagents and lights were used for the preparation of the BNPs. • The catalytic activity of the BNPs is about two times higher than that of Au NPs. -- Abstract: AgAu bimetallic nanoparticles (BNPs), one of the most extensively studied bimetallic systems in the literatures, could have various structures and compositions depending on their preparation conditions. In the present work, catalytically highly active PVP-protected Ag{sub core}/Au{sub shell} BNPs of about 2.5 nm in diameter were fabricated from physical mixtures of aqueous dispersions of Au nanoparticles and Ag{sup +} ions under dark conditions without using any reducing agents. The prepared Ag{sub core}/Au{sub shell} BNP colloidal catalysts, which possessed a high activity for aerobic glucose oxidation, were characterized by Ultraviolet–visible spectrophotometry (UV–Vis), Inductive coupled plasma emission spectrometer (ICP), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Energy disperse spectroscopy (EDS) in High-resolution scanning transmission electron microscopy (HR-STEM). The highest activity (11,360 mol-glucose h{sup −1} mol-metal{sup −1}) was observed for the BNPs with the Ag/Au atomic ratio of 1/9, the TOF value of which is about two times higher than that of Au nanoparticles with the particle size of 1.3 nm. The enhanced catalytic activity of the prepared Ag{sub core}/Au{sub shell} BNPs compared to Au NPs can be ascribed to the presence of negatively charged Au atoms resulted from electron donations

Plasmon enhanced water splitting mediated by hybrid bimetallic Au-Ag core-shell nanostructures.

Science.gov (United States)

Erwin, William R; Coppola, Andrew; Zarick, Holly F; Arora, Poorva; Miller, Kevin J; Bardhan, Rizia

2014-11-07

In this work, we employed wet chemically synthesized bimetallic Au-Ag core-shell nanostructures (Au-AgNSs) to enhance the photocurrent density of mesoporous TiO2 for water splitting and we compared the results with monometallic Au nanoparticles (AuNPs). While Au-AgNSs incorporated photoanodes give rise to 14× enhancement in incident photon to charge carrier efficiency, AuNPs embedded photoanodes result in 6× enhancement. By varying nanoparticle concentration in the photoanodes, we observed ∼245× less Au-AgNSs are required relative to AuNPs to generate similar photocurrent enhancement for solar fuel conversion. Power-dependent measurements of Au-AgNSs and AuNPs showed a first order dependence to incident light intensity, relative to half-order dependence for TiO2 only photoanodes. This indicated that plasmonic nanostructures enhance charge carriers formed on the surface of the TiO2 which effectively participate in photochemical reactions. Our experiments and simulations suggest the enhanced near-field, far-field, and multipolar resonances of Au-AgNSs facilitating broadband absorption of solar radiation collectively gives rise to their superior performance in water splitting.

Picosecond laser fabricated Ag, Au and Ag-Au nanoparticles for detecting ammonium perchlorate using a portable Raman spectrometer

Science.gov (United States)

Byram, Chandu; Moram, Sree Sathya Bharathi; Soma, Venugopal Rao

2018-04-01

In this paper, we present the results from fabrication studies of Ag, Au, and Ag-Au alloy nanoparticles (NPs) using picosecond laser ablation technique in the presence of liquid media. The alloy formation in the NPs was confirmed from UV-Visible measurements. The shape and crystallinity of NPs were investigated by using high resolution transmission electron microscopy (HRTEM), selected area diffraction pattern (SAED) and energy dispersive spectroscopy (EDS). The SERS effect of fabricated NPs was tested with methylene blue and an explosive molecule (ammonium perchlorate) using a portable Raman spectrometer and achieved EFs of ˜106.

Leaching of Au, Ag, and Pd from waste printed circuit boards of mobile phone by iodide lixiviant after supercritical water pre-treatment.

Science.gov (United States)

Xiu, Fu-Rong; Qi, Yingying; Zhang, Fu-Shen

2015-07-01

Precious metals are the most attractive resources in waste printed circuit boards (PCBs) of mobile phones. In this work, an alternative process for recovering Au, Ag, and Pd from waste PCBs of mobile phones by supercritical water oxidation (SCWO) pre-treatment combined with iodine-iodide leaching process was developed. In the process, the waste PCBs of mobile phones were pre-treated in supercritical water, then a diluted hydrochloric acid leaching (HL) process was used to recovery the Cu, whose leaching efficiency was approximately 100%, finally the resulting residue was subjected to the iodine-iodide leaching process for recovering the Au, Ag, and Pd. Experimental results indicated that SCWO pre-treatment temperature, time, and pressure had significant influence on the Au, Ag, and Pd leaching from (SCWO+HL)-treated waste PCBs. The optimal SCWO pre-treatment conditions were 420°C and 60min for Au and Pd, and 410°C and 30min for Ag. The optimum dissolution parameters for Au, Pd, and Ag in (SCWO+HL)-treated PCBs with iodine-iodide system were leaching time of 120min (90min for Ag), iodine/iodide mole ratio of 1:5 (1:6 for Ag), solid-to-liquid ratio (S/L) of 1:10g/mL (1:8g/mL for Ag), and pH of 9, respectively. It is believed that the process developed in this study is environment friendly for the recovery of Au, Ag, and Pd from waste PCBs of mobile phones by SCWO pre-treatment combined with iodine-iodide leaching process. Copyright © 2015 Elsevier Ltd. All rights reserved.

Computational investigation of CO adsorbed on Aux, Agx and (AuAg)x nanoclusters (x = 1 - 5, 147) and monometallic Au and Ag low-energy surfaces*

Science.gov (United States)

Gould, Anna L.; Catlow, C. Richard A.; Logsdail, Andrew J.

2018-02-01

Density functional theory calculations have been performed to investigate the use of CO as a probe molecule for the determination of the structure and composition of Au, Ag and AuAg nanoparticles. For very small nanoclusters (x = 1 - 5), the CO vibrational frequencies can be directly correlated to CO adsorption strength, whereas larger 147-atom nanoparticles show a strong energetic preference for CO adsorption at a vertex position but the highest wavenumbers are for the bridge positions. We also studied CO adsorption on Au and Ag (100) and (111) surfaces, for a 1 monolayer coverage, which proves to be energetically favourable on atop only and bridge positions for Au (100) and atop for Ag (100); vibrational frequencies of the CO molecules red-shift to lower wavenumbers as a result of increased metal coordination. We conclude that CO vibrational frequencies cannot be solely relied upon in order to obtain accurate compositional analysis, but we do propose that elemental rearrangement in the core@shell nanoclusters, from Ag@Au (or Au@Ag) to an alloy, would result in a shift in the CO vibrational frequencies that indicate changes in the surface composition. Contribution to the Topical Issue "Shaping Nanocatalysts", edited by Francesca Baletto, Roy L. Johnston, Jochen Blumberger and Alex Shluger.Supplementary material in the form of one pdf file available from the Journal web page at http://https://doi.org/10.1140/epjb/e2017-80280-7

Dual structural transition in small nanoparticles of Cu-Au alloy

Science.gov (United States)

Gafner, Yuri; Gafner, Svetlana; Redel, Larisa; Zamulin, Ivan

2018-02-01

Cu-Au alloy nanoparticles are known to be widely used in the catalysis of various chemical reactions as it was experimentally defined that in many cases the partial substitution of copper with gold increases catalytic activity. However, providing the reaction capacity of alloy nanoparticles the surface electronic structure strongly depends on their atomic ordering. Therefore, to theoretically determine catalytic properties, one needs to use a most real structural model complying with Cu-Au nanoparticles under various external influences. So, thermal stability limits were studied for the initial L12 phase in Cu3Au nanoalloy clusters up to 8.0 nm and Cu-Au clusters up to 3.0 nm at various degrees of Au atom concentration, with molecular dynamics method using a modified tight-binding TB-SMA potential. Dual structural transition L12 → FCC and further FCC → Ih is shown to be possible under the thermal factor in Cu3Au and Cu-Au clusters with the diameter up to 3.0 nm. The temperature of the structural transition FCC → Ih is established to decrease for small particles of Cu-Au alloy under the increase of Au atom concentration. For clusters with this structural transition, the melting point is found to be a linear increasing function of concentration, and for clusters without FCC → Ih structural transition, the melting point is a linear decreasing function of Au content. Thus, the article shows that doping Cu nanoclusters with Au atoms allows to control the forming structure as well as the melting point.

Effect of Ag film thickness on the optical and the electrical properties in CuAlO2/Ag/CuAlO2 multilayer films grown on glass substrates

International Nuclear Information System (INIS)

Oh, Dohyun; No, Young Soo; Kim, Su Youn; Cho, Woon Jo; Kwack, Kae Dal; Kim, Tae Whan

2011-01-01

Research highlights: The CuAlO 2 /Ag/CuAlO 2 multilayer films were grown on glass substrates using radio-frequency magnetron sputtering at room temperature. Effects of Ag film thickness on the optical and the electrical properties in CuAlO 2 /Ag/CuAlO 2 multilayer films grown on glass substrates were investigated. X-ray diffraction patterns showed that the phase of the CuAlO 2 layer was amorphous. Atomic force microscopy images showed that Ag films with a thickness of a few nanometers had island structures. The morphology Ag films with a thickness of 8 nm was uniform. The morphology of the Ag films inserted in the CuAlO 2 films significantly affected the optical transmittance and the resistivity of the CuAlO 2 films deposited on glass substrates. The maximum transmittance of the CuAlO 2 /Ag/CuAlO 2 multilayer films with a thickness of 8 nm was 89.16%. The resistivity of the CuAlO 2 /Ag/CuAlO 2 multilayer films with an Ag film thickness of 18 nm was as small as about 2.8 x 10 -5 Ω cm. The resistivity of the CuAlO 2 /Ag/CuAlO 2 multilayer films was decreased as a result of the thermal annealing treatment. These results indicate that CuAlO 2 /Ag/CuAlO 2 multilayer films grown on glass substrates hold promise for potential applications as TCO films in solar cells. - Abstract: Effects of Ag film thickness on the optical and the electrical properties in CuAlO 2 /Ag/CuAlO 2 multilayer films grown on glass substrates were investigated. Atomic force microscopy images showed that Ag films with a thickness of a few nanometers had island structures. X-ray diffraction patterns showed that the phase of the CuAlO 2 layer was amorphous. The resistivity of the 40 nm-CuAlO 2 /18 nm-Ag/40 nm-CuAlO 2 multilayer films was 2.8 x 10 -5 Ω cm, and the transmittance of the multilayer films with an Ag film thickness of 8 nm was approximately 89.16%. These results indicate that CuAlO 2 /Ag/CuAlO 2 multilayer films grown on glass substrates hold promise for potential applications as

Energy and system size dependence of phi meson production in Cu+Cu and Au+Au collisions

Energy Technology Data Exchange (ETDEWEB)

STAR Coll

2008-10-28

We study the beam-energy and system-size dependence of {phi} meson production (using the hadronic decay mode {phi} {yields} K{sup +}K{sup -}) by comparing the new results from Cu + Cu collisions and previously reported Au + Au collisions at {radical}s{sub NN} = 62.4 and 200 GeV measured in the STAR experiment at RHIC. Data presented are from midrapidity (|y| < 0.5) for 0.4 < p{sub T} < 5 GeV/c. At a given beam energy, the transverse momentum distributions for {phi} mesons are observed to be similar in yield and shape for Cu + Cu and Au + Au colliding systems with similar average numbers of participating nucleons. The {phi} meson yields in nucleus-nucleus collisions, normalized by the average number of participating nucleons, are found to be enhanced relative to those from p + p collisions with a different trend compared to strange baryons. The enhancement for {phi} mesons is observed to be higher at {radical}s{sub NN} = 200 GeV compared to 62.4 GeV. These observations for the produced {phi}(s{bar s}) mesons clearly suggest that, at these collision energies, the source of enhancement of strange hadrons is related to the formation of a dense partonic medium in high energy nucleus-nucleus collisions and cannot be alone due to canonical suppression of their production in smaller systems.

Physicochemical and antibacterial characterization of ionocity Ag/Cu powder nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Nowak, A., E-mail: ana.maria.nowak@gmail.com [A. Chełkowski Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Silesian Center for Education and Interdisciplinary Research, 75 Pułku Piechoty 1A, 41-500 Chorzów (Poland); Szade, J. [A. Chełkowski Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Silesian Center for Education and Interdisciplinary Research, 75 Pułku Piechoty 1A, 41-500 Chorzów (Poland); Talik, E. [A. Chełkowski Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Zubko, M. [Silesian Center for Education and Interdisciplinary Research, 75 Pułku Piechoty 1A, 41-500 Chorzów (Poland); Institute of Material Science, University of Silesia, 75 Pułku Piechoty 1a, 41-500 Chórzow (Poland); Wasilkowski, D. [Department of Biochemistry, University of Silesia, Jagiellońska 28, 40-032 Katowice (Poland); Dulski, M. [Silesian Center for Education and Interdisciplinary Research, 75 Pułku Piechoty 1A, 41-500 Chorzów (Poland); Institute of Material Science, University of Silesia, 75 Pułku Piechoty 1a, 41-500 Chórzow (Poland); Balin, K. [A. Chełkowski Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Silesian Center for Education and Interdisciplinary Research, 75 Pułku Piechoty 1A, 41-500 Chorzów (Poland); and others

2016-07-15

Metal ion in bimetallic nanoparticles has shown vast potential in a variety of applications. In this paper we show the results of physical and chemical investigations of powder Ag/Cu nanoparticles obtained by chemical synthesis. Transmission electron microscopy (TEM) experiment indicated the presence of bimetallic nanoparticles in the agglomerated form. The average size of silver and copper nanoparticles is 17.1(4) nm (Ag) and 28.9(2) nm (Cu) basing on the X-ray diffraction (XRD) data. X-ray photoelectron (XPS) and Raman spectroscopies revealed the existence of metallic silver and copper as well as Cu{sub 2}O and CuO being a part of the nanoparticles. Moreover, UV–Vis spectroscopy showed surface alloy of Ag and Cu while Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) and Energy Dispersive X-ray Spectroscopy (EDX) showed heterogeneously distributed Ag structures placed on spherical Cu nanoparticles. The tests of antibacterial activity show promising killing/inhibiting growth behaviour for Gram positive and Gram negative bacteria. - Highlights: • Ag/Cu nanoparticles were obtained in the powder form. • The average size of nanoparticles is 17.1(4) nm (Ag) and 28.9(2) nm (Cu). • Ag/Cu powder nanoparticle shows promising antibacterial properties.

The enhancing of Au-Ag-Te content in tellurium-bearing ore mineral by bio-oxidation-leaching

Science.gov (United States)

Kim, PyeongMan; Kim, HyunSoo; Myung, EunJi; Kim, YoonJung; Lee, YongBum; Park*, CheonYoung

2015-04-01

The purpose of this study is to enhance the content of valuable metals such as Au-Ag-Te in tellurium-bearing minerals by bio-oxidation-leaching. It was confirmed that pyrite, chalcopyrite, sphalerite and galena were produced together with tellurium-bearing minerals including hessite, sylvanite and tellurobismuthite from ore minerals and concentrates through microscopic observation and SEM/EDS analysis. In a bio-oxidation-leaching experiment, with regard to Au, Ag, Te, Cu and Fe, the changes in the amount of leaching and the content of leaching residues were compared and analyzed with each other depending on the adaptation of an indigenous microbe identified as Acidithiobacillus ferrooxidans. As a result of the experiment, the Au-Ag-Te content in tellurium-bearing ore mineral was enhanced in the order of physical oxidation leaching, physical/non-adaptive bio-oxidation-leaching and physical/adaptive biological leaching. It suggests that the bio-oxidation-leaching using microbes adapted in tellurium-bearing ore mineral can be used as a pre-treatment and a main process in a recovery process of valuable metals. "This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(NRF-2013R1A1A2004898)"

Comparative efficiencies of photothermal destruction of malignant cells using antibody-coated silica-Au nanoshells, hollow Au/Ag nanospheres and Au nanorods

Energy Technology Data Exchange (ETDEWEB)

Cheng, Fong-Yu; Chen, Chen-Tai; Yeh, Chen-Sheng, E-mail: csyeh@mail.ncku.edu.t [Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan (China)

2009-10-21

Three Au-based nanomaterials (silica-Au nanoshells, hollow Au/Ag nanospheres and Au nanorods) were evaluated for their comparative photothermal efficiencies at killing three types of malignant cells (A549 lung cancer cells, HeLa cervix cancer cells and TCC bladder cancer cells) using a CW NIR laser. Photodestructive efficiency was evaluated as a function of the number of nanoparticles required to destroy the cancer cells under 808 nm laser wavelength at fixed laser power. Of the three nanomaterials, silica/Au nanoshells needed the minimum number of particles to produce effective photodestruction, whereas Au nanorods needed the largest number of particles. Together with the calculated photothermal conversion efficiency, the photothermal efficiency rankings are silica-Au nanoshells > hollow Au/Ag nanospheres > Au nanorods. Additionally, we found that HeLa cells seem to present better heat tolerance than the other two cancer cell lines.

Studies on L-histidine capped Ag and Au nanoparticles for dopamine detection

Energy Technology Data Exchange (ETDEWEB)

Nivedhini Iswarya, Chandrasekaran; Kiruba Daniel, S.C.G. [Division of Nanoscience and Technology, Anna University-BIT Campus, Tiruchirappalli 620024 (India); Sivakumar, Muthusamy, E-mail: muthusiva@gmail.com [Division of Nanoscience and Technology, Anna University-BIT Campus, Tiruchirappalli 620024 (India); Department of Chemistry, Anna University-BIT Campus, Tiruchirappalli 620024 (India)

2017-06-01

This work demonstrates the effective surface functionalization of Ag, Au and bimetallic Ag-Au nanoparticles using L-histidine for colorimetric detection of dopamine (DA) which plays majorly in recognizing the neurological disorder. L-Histidine (L-His) capped Ag, Au, and bimetallic Ag-Au nanoparticles are characterized using physico-chemical techniques. The optical behaviour of nanoparticles has been analysed at various time intervals using UV–Vis absorption spectroscopy. FT-IR results provide the evidence of chemical bonding between L-histidine and metal nanoparticles. Its structure with the capping of L-His was clearly shown in HR-TEM images. The average size of nanoparticles has calculated from TEM image fringes are 11 nm, 5 nm and 6.5 nm respectively, matches with crystals size calculated from X-ray diffraction pattern. Enhanced optical nature of nanoparticles provides the best platform to develop a colorimetric-based biosensor for DA detection. After addition of DA, a rapid colour change has been noted in colloids of nanoparticles. The substantial changes in absorbance and λ{sub max} in metal nanoparticles respect to DA concentration have been observed and formulated. This is one of the successive methods for trace level determination of DA and will be going to a significant material for designing biosensor to determine DA in real extracellular body fluids. - Highlights: • L-His functionalized Ag, Au and bimetallic Ag-Au nanoparticles were prepared and its properties were studied. • L-His based Ag, Au, Ag-Au nanoparticles have characterized by spectroscopy, XRD and microscopic studies. • Enhanced optical nature of nanoparticles delivers the best platform to develop a biosensor for DA detection. • For qualitative determination of dopamine, SPR of metal nanoparticles plays a major role in dopamine determination. • This basic finding can be utilized for further identification of imbalanced DA concentration in body fluids.

Facile preparation of Ag-Cu bifunctional electrocatalysts for zinc-air batteries

International Nuclear Information System (INIS)

Jin, Yachao; Chen, Fuyi

2015-01-01

Highlights: • Ag-Cu dendrites are observed for the first time to exhibit high catalytic activity for oxygen reduction reaction. • Ag-Cu dendrites are directly synthesized through galvanic displacement on the current collector layer made of Ni foams. • A bifunctional air cathode is fabricated using Ag-Cu dendrites as a carbon-free, binder-free catalyst layer. • Both the primary and rechargeable zinc–air batteries fabricated by Ag-Cu catalysts exhibit excellent performance. - ABSTRACT: An inexpensive, facile galvanic displacement reaction for the direct growth of silver–copper (Ag-Cu) catalysts on nickel foams is developed for the first time. The resulting Ag-Cu catalysts exhibit dendritic morphologies. Ag and Cu atoms are in their metallic state while the presence of CuO and Cu 2 O are limited on the surface of catalyst. The catalysts demonstrate high catalytic activity for oxygen reduction reaction (ORR) in alkaline solution, as evaluated by both linear scanning voltammetry and rotating disk electrode polarization measurements. The ORR catalysed by Ag-Cu catalyst in alkaline solution proceeds through a four-electron pathway. An air cathode is fabricated using Ag-Cu catalyst as a carbon-free, binder-free catalyst layer. Using this Ag-Cu catalyst based air cathode, both the primary and rechargeable zinc-air batteries show excellent battery performance. The specific capacity of the primary zinc-air battery is 572 mAh g −1 . Especially, the rechargeable zinc-air battery shows high round-trip efficiency, appealing stability at a long charge-discharge cycle period

Direct measurement of time dependent diffusion for Ag and Au under ambient conditions

Energy Technology Data Exchange (ETDEWEB)

Yoo, Pil Sun; Jo, Han Yeol; Kim, Tae Kyeong [Hankuk University of Foreign Studies, Yongin (Korea, Republic of)

2014-12-15

Time-dependent diffusion for Ag and Au metal atoms was measured using the scanning tunneling microscope break-junction technique in ambient conditions. We observed that Ag contacts do not form long single-atomic chains compared to Au contacts during the elongation of each metal electrode, and Ag atoms diffuse more quickly than Au atoms after metal contact rupture. This is consistent with previous results of molecular dynamic simulations. Further, we found a correlation between diffusion length and the evolution time on an atomic scale to reveal the time-dependent diffusion for Ag and Au metal atoms.

Binding Affinity of a Highly Sensitive Au/Ag/Au/Chitosan-Graphene Oxide Sensor Based on Direct Detection of Pb2+ and Hg2+ Ions

Directory of Open Access Journals (Sweden)

Nur Hasiba Kamaruddin

2017-10-01

Full Text Available The study of binding affinity is essential in surface plasmon resonance (SPR sensing because it allows researchers to quantify the affinity between the analyte and immobilised ligands of an SPR sensor. In this study, we demonstrate the derivation of the binding affinity constant, K, for Pb2+ and Hg2+ ions according to their SPR response using a gold/silver/gold/chitosan–graphene oxide (Au/Ag/Au/CS–GO sensor for the concentration range of 0.1–5 ppm. The higher affinity of Pb2+ to binding with the CS–GO sensor explains the outstanding sensitivity of 2.05 °ppm−1 against 1.66 °ppm−1 of Hg2+. The maximum signal-to-noise ratio (SNR upon detection of Pb2+ is 1.53, and exceeds the suggested logical criterion of an SNR. The Au/Ag/Au/CS–GO SPR sensor also exhibits excellent repeatability in Pb2+ due to the strong bond between its functional groups and this cation. The adsorption data of Pb2+ and Hg2+ on the CS–GO sensor fits well with the Langmuir isotherm model where the affinity constant, K, of Pb2+ and Hg2+ ions is computed. The affinity of Pb2+ ions to the Au/Ag/Au/CS–GO sensor is significantly higher than that of Hg2+ based on the value of K, 7 × 105 M−1 and 4 × 105 M−1, respectively. The higher shift in SPR angles due to Pb2+ and Hg2+ compared to Cr3+, Cu2+ and Zn2+ ions also reveals the greater affinity of the CS–GO SPR sensor to them, thus supporting the rationale for obtaining K for these two heavy metals. This study provides a better understanding on the sensing performance of such sensors in detecting heavy metal ions.

Relativity-Induced Bonding Pattern Change in Coinage Metal Dimers M2 (M = Cu, Ag, Au, Rg).

Science.gov (United States)

Li, Wan-Lu; Lu, Jun-Bo; Wang, Zhen-Ling; Hu, Han-Shi; Li, Jun

2018-05-07

The periodic table provides a fundamental protocol for qualitatively classifying and predicting chemical properties based on periodicity. While the periodic law of chemical elements had already been rationalized within the framework of the nonrelativistic description of chemistry with quantum mechanics, this law was later known to be affected significantly by relativity. We here report a systematic theoretical study on the chemical bonding pattern change in the coinage metal dimers (Cu 2 , Ag 2 , Au 2 , Rg 2 ) due to the relativistic effect on the superheavy elements. Unlike the lighter congeners basically demonstrating ns- ns bonding character and a 0 g + ground state, Rg 2 shows unique 6d-6d bonding induced by strong relativity. Because of relativistic spin-orbit (SO) coupling effect in Rg 2 , two nearly degenerate SO states, 0 g + and 2 u , exist as candidate of the ground state. This relativity-induced change of bonding mechanism gives rise to various unique alteration of chemical properties compared with the lighter dimers, including higher intrinsic bond energy, force constant, and nuclear shielding. Our work thus provides a rather simple but clear-cut example, where the chemical bonding picture is significantly changed by relativistic effect, demonstrating the modified periodic law in heavy-element chemistry.

Devitrification behavior and glass-forming ability of Cu-Zr-Ag alloys

International Nuclear Information System (INIS)

Louzguine-Luzgin, Dmitri V.; Xie, Guoqiang; Zhang, Wei; Inoue, Akihisa

2007-01-01

This paper presents an influence of Ag addition on the glass-forming ability and devitrification behavior of Cu-Zr glassy alloys on heating. The crystallization kinetics and structure changes in Cu 45 Zr 45 Ag 10 and Cu 35 Zr 45 Ag 20 glassy alloys on heating were studied by X-ray diffraction, transmission electron microscopy, differential scanning and isothermal calorimetry methods. Based on the results obtained one can assume that the improvement of the glass-forming ability of the Cu-Zr alloys by the addition of Ag is connected with a particular crystallization mechanism and a higher reduced glass-transition temperature of the Cu 45 Zr 45 Ag 10 ternary alloy compared to the binary Cu 55 Zr 45 counterpart. As observed in the present work crystallization of the Cu-Zr-Ag alloys is found to cause embitterment of the samples and should be avoided as these alloys are considered to be used as structural materials. The Cu 35 Zr 45 Ag 20 alloy shows possible submicron-scale phase separation upon annealing

Strain Distribution of Au and Ag Nanoparticles Embedded in Al2O3 Thin Film

Directory of Open Access Journals (Sweden)

Honghua Huang

2014-01-01

Full Text Available Au and Ag nanoparticles embedded in amorphous Al2O3 matrix are fabricated by the pulsed laser deposition (PLD method and rapid thermal annealing (RTA technique, which are confirmed by the experimental high-resolution transmission electron microscope (HRTEM results, respectively. The strain distribution of Au and Ag nanoparticles embedded in the Al2O3 matrix is investigated by the finite-element (FE calculations. The simulation results clearly indicate that both the Au and Ag nanoparticles incur compressive strain by the Al2O3 matrix. However, the compressive strain existing on the Au nanoparticle is much weaker than that on the Ag nanoparticle. This phenomenon can be attributed to the reason that Young’s modulus of Au is larger than that of Ag. This different strain distribution of Au and Ag nanoparticles in the same host matrix may have a significant influence on the technological potential applications of the Au-Ag alloy nanoparticles.

Efficient low-temperature soot combustion by bimetallic Ag-Cu/SBA-15 catalysts.

Science.gov (United States)

Wen, Zhaojun; Duan, Xinping; Hu, Menglin; Cao, Yanning; Ye, Linmin; Jiang, Lilong; Yuan, Youzhu

2018-02-01

In this study, the effects of copper (Cu) additive on the catalytic performance of Ag/SBA-15 in complete soot combustion were investigated. The soot combustion performance of bimetallic Ag-Cu/SBA-15 catalysts was higher than that of monometallic Ag and Cu catalysts. The optimum catalytic performance was acquired with the 5Ag 1 -Cu 0.1 /SBA-15 catalyst, on which the soot combustion starts at T ig =225°C with a T 50 =285°C. The temperature for 50% of soot combustion was lower than that of conventional Ag-based catalysts to more than 50°C (Aneggi et al., 2009). Physicochemical characterizations of the catalysts indicated that addition of Cu into Ag could form smaller bimetallic Ag-Cu nanolloy particles, downsizing the mean particle size from 3.7nm in monometallic catalyst to 2.6nm in bimetallic Ag-Cu catalyst. Further experiments revealed that Ag and Cu species elicited synergistic effects, subsequently increasing the content of surface active oxygen species. As a result, the structure modifications of Ag by the addition of Cu strongly intensified the catalytic performance. Copyright © 2017. Published by Elsevier B.V.

Effects of Ag addition on solid–state interfacial reactions between Sn–Ag–Cu solder and Cu substrate

International Nuclear Information System (INIS)

Yang, Ming; Ko, Yong-Ho; Bang, Junghwan; Kim, Taek-Soo; Lee, Chang-Woo; Li, Mingyu

2017-01-01

Low–Ag–content Sn–Ag–Cu (SAC) solders have attracted much recent attention in electronic packaging for their low cost. To reasonably reduce the Ag content in Pb–free solders, a deep understanding of the basic influence of Ag on the SAC solder/Cu substrate interfacial reaction is essential. Previous studies have discussed the influence of Ag on the interfacial intermetallic compound (IMC) thickness. However, because IMC growth is the joint result of multiple factors, such characterizations do not reveal the actual role of Ag. In this study, changes in interfacial IMCs after Ag introduction were systemically and quantitatively characterized in terms of coarsening behaviors, orientation evolution, and growth kinetics. The results show that Ag in the solder alloy affects the coarsening behavior, accelerates the orientation concentration, and inhibits the growth of interfacial IMCs during solid–state aging. The inhibition mechanism was quantitatively discussed considering the individual diffusion behaviors of Cu and Sn atoms, revealing that Ag inhibits interfacial IMC growth primarily by slowing the diffusion of Cu atoms through the interface. - Highlights: •Role of Ag in IMC formation during Sn–Ag–Cu soldering was investigated. •Ag affects coarsening, crystallographic orientation, and IMC growth. •Diffusion pathways of Sn and Cu are affected differently by Ag. •Ag slows Cu diffusion to inhibit IMC growth at solder/substrate interface.

Effects of Ag addition on solid–state interfacial reactions between Sn–Ag–Cu solder and Cu substrate

Energy Technology Data Exchange (ETDEWEB)

Yang, Ming [Micro-Joining Center, Korea Institute of Industrial Technology (KITECH), Incheon 21999 (Korea, Republic of); Ko, Yong-Ho [Micro-Joining Center, Korea Institute of Industrial Technology (KITECH), Incheon 21999 (Korea, Republic of); Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291, Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Bang, Junghwan [Micro-Joining Center, Korea Institute of Industrial Technology (KITECH), Incheon 21999 (Korea, Republic of); Kim, Taek-Soo [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291, Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Lee, Chang-Woo, E-mail: cwlee@kitech.re.kr [Micro-Joining Center, Korea Institute of Industrial Technology (KITECH), Incheon 21999 (Korea, Republic of); Li, Mingyu, E-mail: myli@hit.edu.cn [Shenzhen Key Laboratory of Advanced Materials, Harbin Institute of Technology Shenzhen Graduate School, Shenzhen 518055 (China)

2017-02-15

Low–Ag–content Sn–Ag–Cu (SAC) solders have attracted much recent attention in electronic packaging for their low cost. To reasonably reduce the Ag content in Pb–free solders, a deep understanding of the basic influence of Ag on the SAC solder/Cu substrate interfacial reaction is essential. Previous studies have discussed the influence of Ag on the interfacial intermetallic compound (IMC) thickness. However, because IMC growth is the joint result of multiple factors, such characterizations do not reveal the actual role of Ag. In this study, changes in interfacial IMCs after Ag introduction were systemically and quantitatively characterized in terms of coarsening behaviors, orientation evolution, and growth kinetics. The results show that Ag in the solder alloy affects the coarsening behavior, accelerates the orientation concentration, and inhibits the growth of interfacial IMCs during solid–state aging. The inhibition mechanism was quantitatively discussed considering the individual diffusion behaviors of Cu and Sn atoms, revealing that Ag inhibits interfacial IMC growth primarily by slowing the diffusion of Cu atoms through the interface. - Highlights: •Role of Ag in IMC formation during Sn–Ag–Cu soldering was investigated. •Ag affects coarsening, crystallographic orientation, and IMC growth. •Diffusion pathways of Sn and Cu are affected differently by Ag. •Ag slows Cu diffusion to inhibit IMC growth at solder/substrate interface.

Diffusion and aggrigation of implanted Ag and Au in a lithia-alumina-silica glass

International Nuclear Information System (INIS)

Arnold, G.W.; Borders, J.A.

1976-01-01

Optical extinction and Rutherford backscattering (RBS) techniques have been employed to obtain information on the size and spatial distribution of Au and Ag colloids in implanted (Au + ,Ag + )lithia-alumina-silica glass. The formation of metallic aggregates (colloids), necessary for preparation of a glass-ceramic surface layer, proceeds readily with annealing temperature for Au-implanted samples but not for Ag-implanted material. The optical and RBS spectra show that the particle size and spatial distribution in Ag-implanted samples are sensitive to sample temperature and ion-beam heating effects, while these parameters for Au-implanted samples are relatively insensitive to temperature and beam current. It is suggested that this behaviour is related to differences in the dissolution energies of Ag and Au aggregates. A two-peaked spatial distribution for Ag implanted at room temperature at a dose rate of approximately 1 μA cm -2 is observed which may result from the trappings of Ag in the ion displacement damage region of the glass during implantation. (author)

Surface tension estimation of high temperature melts of the binary alloys Ag-Au

Science.gov (United States)

Dogan, Ali; Arslan, Hüseyin

2017-11-01

Surface tension calculation of the binary alloys Ag-Au at the temperature of 1381 K, where Ag and Au have similar electronic structures and their atomic radii are comparable, are carried out in this study using several equations over entire composition range of Au. Apparently, the deviations from ideality of the bulk solutions, such as activities of Ag and Au are small and the maximum excess Gibbs free energy of mixing of the liquid phase is for instance -4500 J/mol at XAu = 0.5. Besides, the results obtained in Ag-Au alloys that at a constant temperature the surface tension increases with increasing composition while the surface tension decreases as the temperature increases for entire composition range of Au. Although data about surface tension of the Ag-Au alloy are limited, it was possible to make a comparison for the calculated results for the surface tension in this study with the available experimental data. Taken together, the average standard error analysis that especially the improved Guggenheim model in the other models gives the best agreement along with the experimental results at temperature 1383 K although almost all models are mutually in agreement with the other one.

Atomistic study of self-diffusion in Cu-Ag immiscible alloy system

International Nuclear Information System (INIS)

Zhang Jianmin; Chen Gouxiang; Xu Kewei

2006-01-01

Combining molecular dynamic (MD) simulation with modified analytic embedded-atom method (MAEAM) potential, the formation, migration and activation energies have been calculated for four-kind migrations of Cu vacancy and three-kind migrations of Ag vacancy in Cu-Ag immiscible alloy system. The equilibrium concentration of Cu vacancies is greater than that of Ag vacancies owing to the formation energy of Cu vacancy (1.012 eV) is lower than that of Ag vacancy (1.169 eV). Comparing the migration or activation energy needed for four-kind migrations of Cu vacancy and three-kind migrations of Ag vacancy show that the favorable migration mechanism is the nearest-neighbor (NN) jump for Cu vacancy, while the straight [0 1 0] six-jump cycle (6JC) for Ag vacancy. Furthermore, the activation energy of the NN jump of Cu vacancy (2.164 eV) is lower than that of straight [0 1 0] 6JC of Ag vacancy (2.404 eV) also show that the former is more favorable. We conclude accordingly that the primary migration mechanism is the NN jump of an abundance of Cu vacancies

SERS-active Ag, Au and Ag–Au alloy nanoparticles obtained by laser ablation in liquids for sensing methylene blue

Energy Technology Data Exchange (ETDEWEB)

Olea-Mejía, Oscar, E-mail: oleaoscar@yahoo.com.mx [Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Universidad Autónoma del Estado de México, km 14.5 Carretera Toluca-Atlacomulco, San Cayetano 50200, México (Mexico); Fernández-Mondragón, Mariana; Rodríguez-de la Concha, Gabriela [Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Universidad Autónoma del Estado de México, km 14.5 Carretera Toluca-Atlacomulco, San Cayetano 50200, México (Mexico); Camacho-López, Marco [Laboratorio de Investigación y Desarrollo de Materiales Avanzados, Universidad Autónoma del Estado de México, Km 14.5 Carretera Toluca-Atlacomulco, San Cayetano 50925, México (Mexico)

2015-09-01

Highlights: • We synthesized Ag/Au nanoparticles by laser ablation in liquids. • We characterized such particles by UV–vis, TEM and EDS/STEM. • The SERS effect was studied for the obtained nanoparticles. • Pure silver nanoparticles showed the highest SERS signals. • We can sense methylene blue at a concentration of 10{sup −10} mole/L. - Abstract: We have synthesized Ag–Au nanoparticles by laser ablation in liquids using five different targets: 100% Ag, 80%Ag/20%Au, 50%Ag/50%Au, 20%Ag/80%Au and 100% Au (weight percentages). We used ethanol and methylene blue solutions in ethanol as the liquid media. The nanoparticles were mostly spherical with diameters 15, 19, 18, 23 and 11 nm, respectively. When alloyed targets were used, the resulting nanoparticles were completely alloyed forming solid solutions as evidenced by UV–vis Spectroscopy and Scanning Transmission Electron Microscopy. The obtained nanoparticles were employed to study the SERS effect of the methylene blue molecule. All the samples showed good SERS activity, however the ones composed of pure silver showed the greatest Raman signal enhancement. Finally, pure Ag nanoparticles were used for sensing methylene blue at different concentrations. While almost no signal can be discerned from the Raman spectrum when no particles are used at a concentration of methylene blue of 1 × 10{sup −2} M (∼3000 ppm), when Ag nanoparticles are used one can observe the characteristic peak of the molecule at concentrations as low as 1 × 10{sup −10} M (∼3 × 10{sup −5} ppm)

An experimental investigation of ionic transport properties in CuI-Ag2WO4 and CuI-Ag2CrO4 mixed systems

International Nuclear Information System (INIS)

Suthanthiraraj, S. Austin; Premchand, Y. Daniel

2004-01-01

The phenomenon of ionic transport in the case of two different mixed systems (CuI) (1-x) -(Ag 2 WO 4 ) x (0.15= (1-y) -(Ag 2 CrO 4 ) y (0.15= -3 Scm -1 for the composition (CuI) 0.45 -(Ag 2 WO 4 ) 0.55 and 1.1x10 -4 Scm -1 in the case of (CuI) 0.55 -(Ag 2 CrO 4 ) 0.45 at room temperature has been discussed in terms of the observed characteristics

Study of Ag and Au Nanoparticles Synthesized by Arc Discharge in Deionized Water

Directory of Open Access Journals (Sweden)

Der-Chi Tien

2010-01-01

Full Text Available The paper presents a study of Ag and Au nanofluids synthesized by the arc discharge method (ADM in deionized water. The metallic Ag nanoparticle (Ag0 and ionic Ag (Ag+ have played an important role in the battle against germs which are becoming more drug-resistant every year. Our study indicates that Ag nanoparticle suspension (SNPS fabricated by using ADM without added surfactants exclusively contains the metallic Ag nanoparticle and ionic Ag. Besides that, the ADM in deionized water has also been employed for the fabrication process of Au nanoparticles. The experimental results indicate that the prepared Ag nanoparticles can react with the dissolved H2CO3 in deionized water, leading to the formation of Ag2CO3. Significantly different to Ag, the prepared Au nanoparticles with their surfaces bonded by oxygen are suspended in deionized water by the formation of hydrogen bonded with the neighboring water molecules.

Templated Atom-Precise Galvanic Synthesis and Structure Elucidation of a [Ag 24 Au(SR) 18 ] − Nanocluster

KAUST Repository

Bootharaju, Megalamane Siddaramappa

2015-11-27

Synthesis of atom-precise alloy nanoclusters with uniform composition is challenging when the alloying atoms are similar in size (for example, Ag and Au). A galvanic exchange strategy has been devised to produce a compositionally uniform [Ag24Au(SR)18]- cluster (SR: thiolate) using a pure [Ag25(SR)18]- cluster as a template. Conversely, the direct synthesis of Ag24Au cluster leads to a mixture of [Ag25-xAux(SR)18]-, x=1-8. Mass spectrometry and crystallography of [Ag24Au(SR)18]- reveal the presence of the Au heteroatom at the Ag25 center, forming Ag24Au. The successful exchange of the central Ag of Ag25 with Au causes perturbations in the Ag25 crystal structure, which are reflected in the absorption, luminescence, and ambient stability of the particle. These properties are compared with those of Ag25 and Ag24Pd clusters with same ligand and structural framework, providing new insights into the modulation of cluster properties with dopants at the single-atom level.

Centrality, Rapidity And Transverse-Momentum Dependence of Cold Nuclear Matter Effects on J/Psi Production in D Au, Cu Cu And Au Au Collisions at S(NN)**(1/2)

Energy Technology Data Exchange (ETDEWEB)

Ferreiro, E.G.; /Santiago de Compostela U.; Fleuret, F.; /Ecole Polytechnique; Lansberg, J.P.; /Ecole Polytechnique /SLAC; Rakotozafindrabe, A.; /SPhN, DAPNIA, Saclay

2011-11-11

We have carried out a wide study of Cold Nuclear Matter (CNM) effects on J/{Psi} = production in dAu, CuCu and AuAu collisions at {radical}s{sub NN} = 200 GeV. We have studied the effects of three different gluon-shadowing parameterizations, using the usual simplified kinematics for which the momentum of the gluon recoiling against the J/{Psi} is neglected as well as an exact kinematics for a 2 {yields} 2 process, namely g + g {yields} J/{psi} + g as expected from LO pQCD. We have shown that the rapidity distribution of the nuclear modification factor R{sub dAu}, and particularly its anti-shadowing peak, is systematically shifted toward larger rapidities in the 2 {yields} 2 kinematics, irrespective of which shadowing parameterization is used. In turn, we have noted differences in the effective final-state nuclear absorption needed to fit the PHENIX dAu data. Taking advantage of our implementation of a 2 {yields} 2 kinematics, we have also computed the transverse momentum dependence of the nuclear modification factor, which cannot be predicted with the usual simplified kinematics. All the corresponding observables have been computed for CuCu and AuAu collisions and compared to the PHENIX and STAR data. Finally, we have extracted the effective nuclear absorption from the recent measurements of RCP in dAu collisions by the PHENIX collaboration.

J /ψ production at low pT in Au + Au and Cu + Cu collisions at √sNN =200 GeV with the STAR detector

Science.gov (United States)

Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Alford, J.; Anson, C. D.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Averichev, G. S.; Banerjee, A.; Beavis, D. R.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Borowski, W.; Bouchet, J.; Brandin, A. V.; Brovko, S. G.; Bültmann, S.; Bunzarov, I.; Burton, T. P.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Cendejas, R.; Cervantes, M. C.; Chaloupka, P.; Chang, Z.; Chattopadhyay, S.; Chen, H. F.; Chen, J. H.; Chen, L.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Chwastowski, J.; Codrington, M. J. M.; Contin, G.; Cramer, J. G.; Crawford, H. J.; Cui, X.; Das, S.; Davila Leyva, A.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Derradi de Souza, R.; di Ruzza, B.; Didenko, L.; Dilks, C.; Ding, F.; Djawotho, P.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Engle, K. S.; Eppley, G.; Eun, L.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Fedorisin, J.; Filip, P.; Fisyak, Y.; Flores, C. E.; Gagliardi, C. A.; Gangadharan, D. R.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Gliske, S.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Haag, B.; Hamed, A.; Han, L.-X.; Haque, R.; Harris, J. W.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Hofman, D. J.; Horvat, S.; Huang, B.; Huang, H. Z.; Huang, X.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Kesich, A.; Khan, Z. H.; Kikola, D. P.; Kisel, I.; Kisiel, A.; Koetke, D. D.; Kollegger, T.; Konzer, J.; Koralt, I.; Kosarzewski, L. K.; Kotchenda, L.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulakov, I.; Kumar, L.; Kycia, R. A.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, C.; Li, W.; Li, X.; Li, X.; Li, Y.; Li, Z. M.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Ma, G. L.; Ma, Y. G.; Mahapatra, D. P.; Majka, R.; Margetis, S.; Markert, C.; Masui, H.; Matis, H. S.; McDonald, D.; McShane, T. S.; Minaev, N. G.; Mioduszewski, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nigmatkulov, G.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Ohlson, A.; Okorokov, V.; Oldag, E. W.; Olvitt, D. L.; Page, B. S.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlak, T.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Planinic, M.; Pluta, J.; Poljak, N.; Poniatowska, K.; Porter, J.; Poskanzer, A. M.; Powell, C. B.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Raniwala, R.; Raniwala, S.; Ray, R. L.; Riley, C. K.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ross, J. F.; Roy, A.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sangaline, E.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, B.; Shen, W. Q.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Simko, M.; Skoby, M. J.; Smirnov, D.; Smirnov, N.; Solanki, D.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stevens, J. R.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Sun, X.; Sun, X. M.; Sun, Y.; Sun, Z.; Surrow, B.; Svirida, D. N.; Symons, T. J. M.; Szelezniak, M. A.; Takahashi, J.; Tang, A. H.; Tang, Z.; Tarnowsky, T.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Trzeciak, B. A.; Tsai, O. D.; Turnau, J.; Ullrich, T.; Underwood, D. G.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Vanfossen, J. A.; Varma, R.; Vasconcelos, G. M. S.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Viyogi, Y. P.; Vokal, S.; Vossen, A.; Wada, M.; Wang, F.; Wang, G.; Wang, H.; Wang, J. S.; Wang, X. L.; Wang, Y.; Wang, Y.; Webb, G.; Webb, J. C.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y. F.; Xiao, Z.; Xie, W.; Xin, K.; Xu, H.; Xu, J.; Xu, N.; Xu, Q. H.; Xu, Y.; Xu, Z.; Yan, W.; Yang, C.; Yang, Y.; Yang, Y.; Ye, Z.; Yepes, P.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, J. B.; Zhang, J. L.; Zhang, S.; Zhang, X. P.; Zhang, Y.; Zhang, Z. P.; Zhao, F.; Zhao, J.; Zhong, C.; Zhu, X.; Zhu, Y. H.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

2014-08-01

The J /ψ pT spectrum and nuclear modification factor (RAA) are reported for pT<5GeV /c and |y|<1 from 0% to 60% central Au +Au and Cu +Cu collisions at √sNN =200GeV at STAR. A significant suppression of pT-integrated J /ψ production is observed in central Au +Au events. The Cu +Cu data are consistent with no suppression, although the precision is limited by the available statistics. RAA in Au +Au collisions exhibits a strong suppression at low transverse momentum and gradually increases with pT. The data are compared to high-pT STAR results and previously published BNL Relativistic Heavy Ion Collider results. Comparing with model calculations, it is found that the invariant yields at low pT are significantly above hydrodynamic flow predictions but are consistent with models that include color screening and regeneration.

Misfit dislocations in (001) Cu/(111) Ag epitaxial bilayers

Energy Technology Data Exchange (ETDEWEB)

Vook, R W; Chao, S S

1979-01-01

Two sets of elongated epitaxial (111) Ag islands rotated by 90/sup 0/ with respect to each other were observed to grow on (001) Cu substrates. In addition, two sets of edge misfit dislocations lay parallel to (110) Cu and (110) Cu or equivalently along (110) Ag and (112) Ag. Their Burgers vectors were determined, together with the elastic strains in these two directions. The island elongation was interpreted as arising from a lower strain energy in the preferred direction of growth.

Fe-U-PGE-Au-Ag-Cu Deposits of the Udokan-Chiney Region (East Siberia, Russia)

Science.gov (United States)

Gongalskiy, B.; Krivolutskaya, N.; Murashov, K.; Nistratov, S.; Gryazev, S.

2012-04-01

Introduction. Cupriferous sandstones-shales and magmatic copper-nickel deposits mark out the western and southern boundaries of the Siberian Craton accordingly. Of special interest are the Paleoproterozoic deposits of the Udokan-Chiney mining district (Gongalskiy, Krivolutskaya, 2008). Copper reserves and resources of this region are estimated at more than 50 Mt. Half of them is concentrated at the unique Udokan Deposit and the second half is distributed among sedimentary (Unkur, Pravoingamakitskoye, Sakinskoye, Krasnoye, Burpala) and magmatic deposits of the Chiney (Rudnoye, Verkhnechineyskoye, Kontaktovoye), Luktur and Maylav massifs. Results. It was established that the ores are characterized by similarity in chemical composition (main, major and rare elements that are Ag, Au, PGE) and mineral assemblages with varying proportions. It is important to emphasize that Fe role in mineralization was previously ignored. Meanwhile the Udokan deposit contains 10 Mt of magnetite metacrystals so as chalcocite ores may contain up to 50% magnetite too. It has been recently found that the Chiney titanomagnetite ores comprise commercially significant uranium and rare-earth metal concentrations (Makaryev et al., 2011). Thus the Udokan-Chiney region comprises Cu, Fe, Ti, V, U, REE, Ag, Au, PGE. These deposits differ from similar objects, the Olympic Dam in particular, by a much smaller content of fluid-bearing minerals. Copper mineralization at the Udokan is represented by chalcocite-bornite ores. They occur as ore beds conformable with sedimentary structures or as cross-cutting veins. The central zones of the former are often brecciated. They are rimmed by fine magnetite, bornite, and chalcocite dissemination. Bornite-chalcopyrite and chalcopyrite-pyrite veins are known at the lower levels of the Udokan ore bed. Such ore compositions are predominant in other ore deposits in sedimentary rocks (Pravoingamakitskoye, Unkur) and have a hydrothermal origin. Silver grades are up to

Geochemistry of the Patricia Zn-Pb-Ag Deposit (paguanta, NE Chile)

Science.gov (United States)

Chinchilla Benavides, D.; Merinero Palomares, R.; Piña García, R.; Ortega Menor, L.; Lunar Hernández, R.

2013-12-01

The Patricia Zn-Pb-Ag ore deposit is located within the Paguanta mining project, situated at the northern end of the Andean Oligocene Porphyry Copper Belt of Chile. The sulfide mineralization occurs as W-E oriented veins hosted in volcanic rocks, mainly andesite (pyroclastic, ash and lavas), of Upper Cretaceous to Middle Tertiary age. The ore mineralogy (obtained by EMPA analyses) comprises in order of abundance, pyrite, sphalerite (5.5 - 10.89 wt % Fe, 9.8-19 % molar FeS and 0.52 wt % Cd), galena, arsenopyrite, chalcopyrite and Ag-bearing sulfosalts. The veins show a zoned and banded internal structure with pyrite at the edges and sphalerite in the center. The Ag occurs mostly as Ag-Cu-Sb sulfosalts, in order of abundance: series freibergite - argentotennantite -polybasite and stephanite. Other minor Ag phases such as argentite, pyrargirite and diaphorite were also identified. These Ag phases are typically associated with the base-metal sulfides. Freibergite occurs filling voids within sphalerite, chalcopyrite and at the contact between sphalerite and galena. Polybasite, stephanite, pyrargirite and argentite are mostly in close association with freibergite. In the case of diaphorite, it commonly occurs filling voids between galena crystals or as inclusions within galena. Some minor Ag-bearing sulfosalts are also identified between pyrite crystals. The alteration minerals are dominated by chlorite, illite and kaolinite. The gangue minerals consist of quartz and carbonates identified by XRD as kutnahorite. We obtained linear correlation statistically significant only for Ag, As Au, Cd, Cu, Pb, Sb and Zn and therefore we generated an enhanced scatter plot matrix of these elements. Bulk rock analyses (ICP/MS and XRF) of drill cores show that Ag is strongly and positively correlated with Pb and As, moderately with Cd, Sb, Au and Zn and weakly with Cu, while Au is moderately and positively correlated with Ag, As, Cd, Sb and Zn and weakly with Cu and Pb. These results

Diffusion and aggregation of implanted Ag and Au in a lithia--alumina--silica glass

International Nuclear Information System (INIS)

Arnold, G.W.; Borders, J.A.

1975-01-01

Optical extinction and Rutherford backscattering (RBS) techniques were employed to obtain information on the size and spatial distribution of Au- and Ag-colloids in implanted (Au + , Ag + ) lithia-alumina-silica glass. The formation of metallic aggregates (colloids), necessary for preparation of a glass-ceramic surface layer, proceeds readily with annealing temperature for Au-implanted samples but not for Ag-implanted material. The optical and RBS spectra show that the particle size and spatial distribution in as-implanted samples are sensitive to sample temperature and ion-beam heating effects, while these parameters for Au-implanted samples are relatively insensitive to temperature and beam current. It is suggested that this behavior is related to differences in the dissolution energies of Ag and Au aggregates. A two-peaked spatial distribution for Ag implanted at room temperature at a dose rate of approximately 1 μA/cm 2 is observed which may result from the trapping of Ag in the compacted damage region of the glass during implantation. (auth)

Aging properties studies in a Cu-Ag-Cr Alloy

International Nuclear Information System (INIS)

Jia, S.G.; Zheng, M.S.; Liu, P.; Ren, F.Z.; Tian, B.H.; Zhou, G.S.; Lou, H.F.

2006-01-01

A Cu-Ag-Cr alloy was produced by means of vacuum induction melting. The effects of aging processes on microhardness and conductivity of Cu-Ag-Cr alloy were studied. The microstructure of the alloy was examined using transmission electron microscope (TEM). Aging at 450 deg. C for 4 h, the alloy has an excellent combination of microhardness and conductivity, the microhardness and conductivity reach 132 HV and 80% IACS, respectively. The precipitates responsible for the age-hardening effect are fcc Cr. The fine and dispersed precipitates are fully coherent with the Cu matrix and make the Cu-Ag-Cr alloy possesses higher hardness and conductivity

Wear behavior of Cu-Ag-Cr alloy wire under electrical sliding

International Nuclear Information System (INIS)

Jia, S.G.; Liu, P.; Ren, F.Z.; Tian, B.H.; Zheng, M.S.; Zhou, G.S.

2005-01-01

The wear behavior of a Cu-Ag-Cr alloy contact wire against a copper-base sintered alloy strip was investigated. Wear tests were conducted under laboratory conditions with a special sliding wear apparatus that simulated train motion under electrical current conditions. The initial microstructure of the Cu-Ag-Cr alloy contact wire was analyzed by transmission electron microscopy. Worn surfaces of the Cu-Ag-Cr alloy wire were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). The results indicate that the wear rate of the Cu-Ag-Cr wire increased with increasing electrical current and sliding. Within the studied range of electrical current, the wear rate increases with increasing electrical current and sliding speed. Compared with the Cu-Ag contact wire under the same testing conditions, the Cu-Ag-Cr alloy wire has much better wear resistance. Adhesive, abrasive, and electrical erosion wear are the dominant mechanisms during the electrical sliding processes

Crystal Structural Effect of AuCu Alloy Nanoparticles on Catalytic CO Oxidation

International Nuclear Information System (INIS)

Zhan, Wangcheng; Wang, Jinglin; Wang, Haifeng; Zhang, Jinshui; Liu, Xiaofei

2017-01-01

Controlling the physical and chemical properties of alloy nanoparticles (NPs) is an important approach to optimize NP catalysis. Unlike other tuning knobs, such as size, shape, and composition, crystal structure has received limited attention and not been well understood for its role in catalysis. This deficiency is mainly due to the difficulty in synthesis and fine-tuning of the NPs’ crystal structure. Here, Exemplifying by AuCu alloy NPs with face centered cubic (fcc) and face centered tetragonal (fct) structure, we demonstrate a remarkable difference in phase segregation and catalytic performance depending on the crystal structure. During the thermal treatment in air, the Cu component in fcc-AuCu alloy NPs segregates more easily onto the alloy surface as compared to that in fct-AuCu alloy NPs. As a result, after annealing at 250 °C in air for 1 h, the fcc- and fct-AuCu alloy NPs are phase transferred into Au/CuO and AuCu/CuO core/shell structures, respectively. More importantly, this variation in heterostructures introduces a significant difference in CO adsorption on two catalysts, leading to a largely enhanced catalytic activity of AuCu/CuO NP catalyst for CO oxidation. Furthermore, the same concept can be extended to other alloy NPs, making it possible to fine-tune NP catalysis for many different chemical reactions.

Crystal Structural Effect of AuCu Alloy Nanoparticles on Catalytic CO Oxidation

Energy Technology Data Exchange (ETDEWEB)

Zhan, Wangcheng [East China Univ. of Science and Technology, Shanghai (China); Wang, Jinglin [East China Univ. of Science and Technology, Shanghai (China); Wang, Haifeng [East China Univ. of Science and Technology, Shanghai (China); Zhang, Jinshui [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Liu, Xiaofei [East China Univ. of Science and Technology, Shanghai (China); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Zhang, Pengfei [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chi, Miaofang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Guo, Yanglong [East China Univ. of Science and Technology, Shanghai (China); Guo, Yun [East China Univ. of Science and Technology, Shanghai (China); Lu, Guanzhong [East China Univ. of Science and Technology, Shanghai (China); Sun, Shouheng [Brown Univ., Providence, RI (United States); Dai, Sheng [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States); Zhu, Huiyuan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-06-07

Controlling the physical and chemical properties of alloy nanoparticles (NPs) is an important approach to optimize NP catalysis. Unlike other tuning knobs, such as size, shape, and composition, crystal structure has received limited attention and not been well understood for its role in catalysis. This deficiency is mainly due to the difficulty in synthesis and fine-tuning of the NPs’ crystal structure. Here, Exemplifying by AuCu alloy NPs with face centered cubic (fcc) and face centered tetragonal (fct) structure, we demonstrate a remarkable difference in phase segregation and catalytic performance depending on the crystal structure. During the thermal treatment in air, the Cu component in fcc-AuCu alloy NPs segregates more easily onto the alloy surface as compared to that in fct-AuCu alloy NPs. As a result, after annealing at 250 °C in air for 1 h, the fcc- and fct-AuCu alloy NPs are phase transferred into Au/CuO and AuCu/CuO core/shell structures, respectively. More importantly, this variation in heterostructures introduces a significant difference in CO adsorption on two catalysts, leading to a largely enhanced catalytic activity of AuCu/CuO NP catalyst for CO oxidation. Furthermore, the same concept can be extended to other alloy NPs, making it possible to fine-tune NP catalysis for many different chemical reactions.

Self-standing corrugated Ag and Au-nanorods for plasmonic applications

DEFF Research Database (Denmark)

Habouti, S.; Mátéfi-Tempfli, M.; Solterbeck, C.-H.

2011-01-01

We use home-made Si-supported anodized alumina thin film templates for the electrodeposition of large area self-standing Ag- and Au-nanorod (Au-NR) arrays. The deposition conditions chosen, i.e. electrolyte composition and deposition voltage, lead to a corrugated rod morphology, particularly for Au...

Phase composition of rapidly solidified Ag-Sn-Cu dental alloys

International Nuclear Information System (INIS)

Lecong Dzuong; Do Minh Nghiep; Nguyen van Dzan; Cao the Ha

1996-01-01

The phase composition of some rapidly solidified Ag-Sn-Cu dental alloys with different copper contents (6.22 wtpct) has been studied by XRD, EMPA and optical microscopy. The samples were prepared from melt-spun ribbons. The microstructure of the as-quenched ribbons was microcrystalline and consisted of the Ag sub 3 Sn, Ag sub 4 Sn, Cu sub 3 Sn and Cu sub 3 Sn sub 8 phases. Mixing with mercury (amalgamation) led to formation of the Ag sub 2 Hg sub 3, Sn sub 7 Hg and Cu sub 6 Sn sub 5 phases. The amount of copper atoms in the alloys played an important role in phase formation in the amalgams

Physical Properties Of Some Pd-Au-Ag Ternary Alloys: A Md Study

International Nuclear Information System (INIS)

Aydin, G.

2010-01-01

Mechanical properties of palladium (Pd), gold (Au) and silver (Ag) and their ternary alloys in the following concentrations (Au 5 0Ag 2 5Pd 2 5, Au 4 0Ag 2 0Pd 4 0) are studied by using by using molecular dynamics with Quantum Sutton-Chen (Q-SC) potential. Cell constants, densities, enthalpies, elastic constants and heat capacities are investigated. Calculations are performed in the solid phase. Rafii-Tabar combination rules are used and it is showed that these combination rules are valid for ternary alloys also. Additionally, temperature dependence of mechanical properties of alloys are investigated.

Production of φ mesons in Au-Au collisions at the AGS

International Nuclear Information System (INIS)

Back, B. B.; Betts, R. R.; Chang, J.; Gillitzer, A.; Henning, W. F.; Hofman, D. J.; Nanal, V.; Seto, R.; Wuosmaa, A. H.; Xiang, H.

1999-01-01

The first measurements of φ meson production in Au-Au collisions at AGS energies are presented via the decay to K + K - . A measurement of the centrality dependence of the yield shows an increase similar to that seen for the K - with a spectral shape consistent with a relativistic Breit-Wigner distribution within the statistical errors of the present data set. Future analysis using the full data set with 4 times the statistics will allow a more accurate determination of the yields, slopes and spectral shapes

Deformation of Ag clusters deposited on Au(111) - Experiment and molecular dynamics

Energy Technology Data Exchange (ETDEWEB)

Miroslawski, Natalie; Groenhagen, Niklas; Hoevel, Heinz [TU Dortmund, Experimentelle Physik I (Germany); Issendorff, Bernd von [Universitaet Freiburg, Fakultaet Physik (Germany); Jaervi, Tommi [Fraunhofer Institut fuer Werkstoffmechanik, Freiburg (Germany); Moseler, Michael [Universitaet Freiburg, Fakultaet Physik (Germany); Fraunhofer Institut fuer Werkstoffmechanik, Freiburg (Germany); Freiburger Materialforschungszentrum (Germany)

2011-07-01

Mass selected clusters from Ag{sup +}{sub 55} to Ag{sup +}{sub 147{+-}}{sub 2} were deposited with different deposition energies at 77 K on Au(111) and imaged with STM at 77 K. We observed a deformation of the cluster shape due to the strong metallic interaction between the cluster and the substrate. The clusters became epitaxial and developed a structure composed of several Ag monolayers. The number of these monolayers depends on the number of atoms in the cluster and the deposition energy. The larger the cluster mass the more monolayers the cluster develops on Au(111) and the larger the deposition energy the fewer monolayers occur. These results were verified by molecular dynamic simulations. Additionally the behaviour of Ag{sub N} clusters on Au(111) after different annealing steps was investigated.

Comparison of partial structures of melts of superionic AgI and CuI and non-superionic AgCl

Energy Technology Data Exchange (ETDEWEB)

Kawakita, Yukinobu [Department of Physics, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan); Tahara, Shuta [Department of Condensed Matter Chemistry and Physics, Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Chuo-ku, Fukuoka 810-8560 (Japan); Fujii, Hiroyuki [Department of Condensed Matter Chemistry and Physics, Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Chuo-ku, Fukuoka 810-8560 (Japan); Kohara, Shinji [Research and Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8), 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Takeda, Shin' ichi [Department of Physics, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan)

2007-08-22

Neutron and high-energy x-ray diffraction analyses of molten AgI have been performed and the partial structures are discussed in detail with the aid of the structural modelling procedure of the reverse Monte Carlo (RMC) technique by comparison with those of molten CuI and AgCl. It is well known that AgI and CuI have a superionic solid phase below the melting point, in which the cations favour a tetrahedral configuration, while solid AgCl has a rock-salt structure with an octahedral environment around both Ag and Cl atoms. Even in the molten states, there is a significant difference between superionic and non-superionic melts. The cation is located on the triangular plain formed by three iodine ions in molten AgCl and CuI, while molten AgCl favours a 90 deg. Cl-Ag-Cl bond angle, which is understood to maintain a similar local environment to that in the solid state. The atomic configurations of the RMC model suggest that the cation distributions in superionic melts of CuI and AgI exhibit large fluctuations, while Ag ions in the non-superionic melts of AgCl are distributed much more uniformly.

Anchoring of Ag-Au alloy nanoparticles on reduced graphene oxide sheets for the reduction of 4-nitrophenol

Energy Technology Data Exchange (ETDEWEB)

Hareesh, K., E-mail: appi.2907@gmail.com [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Joshi, R.P. [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Sunitha, D.V. [School of Physics, Reva University, Bangalore 560064 (India); Bhoraskar, V.N. [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Dhole, S.D., E-mail: sanjay@physics.unipune.ac.in [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India)

2016-12-15

Highlights: • Ag-Au-rGO nanocomposite was synthesized by gamma radiation assisted method. • Ag-Au nanoparticles of size (5–19) nm were decorated on rGO. • Ag-Au-rGO showed enhanced catalytic activity for reduction of 4-Nitrophenol. - Abstract: One-step gamma radiation assisted method has been used for the synthesis of Silver-Gold (Ag-Au) alloy nanoparticles with simultaneous reduction of graphene oxide (GO). UV–vis spectroscopic results along with X-ray diffraction analysis, X-ray Photoelectron spectroscopy and Transmission electron microscopy confirmed the decoration face centered cubic structured Ag-Au nanoparticles of size (5–19) nm on reduced graphene oxide (rGO) sheets. The increase in disorder parameter in Raman spectroscopy indicates the formation of more number of small sp{sup 2} domains. The synthesized Ag-Au-rGO nanocomposite showed enhanced catalytic activity towards the reduction of 4-Nitrophenol compared to individual Ag-Au and rGO components.

Ultrasonic friction power during thermosonic Au and Cu ball bonding

International Nuclear Information System (INIS)

Shah, A; Mayer, M; Zhou, Y; Qin, I; Huynh, C; Meyer, M

2010-01-01

The ultrasonic friction power during thermosonic ball bonding with Au and Cu wires, both 25 μm in diameter, is derived with an improved method from experimental measurements during the bonding process. Experimental data include the current delivered to the ultrasonic transducer and the tangential force measured using piezoresistive microsensors integrated close to the Al bonding pad. The improvement results from a new, more accurate method to derive the mechanical compliance of the ultrasonic system. The method employs a bond process modification in which the ultrasonic current is ramped up sequentially in three steps. In the first two steps, the ultrasonic current is set to levels that are too low to cause sliding. The bonding takes place during the third step, when the current is ramped up to the optimum value required for making good quality bonds. The ultrasonic compliance values are derived from the first two steps and are 8.2 ± 0.5 μm N -1 and 7.7 ± 0.5 μm N -1 for the Au and Cu processes, respectively. These values are determined within an average error estimate of ±6%, substantially lower than the ±10% estimated with a previously reported method. The ultrasonic compliance in the case of Au is 6% higher due to the lower elastic modulus of Au compared with that of Cu. Typical maximum values of relative sliding amplitude of ultrasonic friction at the interface are 655 nm and 766 nm for the Au and Cu processes. These values are 81% of the free-air vibration amplitude of the bonding capillary tip for the respective ultrasonic current settings. Due to bond growth, which damps relative motion between the ball and the pad, the final relative amplitude at the bond interface is reduced to 4% of the equivalent free-air amplitude. Even though the maximum value of relative amplitude is 17% higher in the Cu process compared with the Au process, the average total interfacial sliding is 519 μm in the Cu process, which is 31% lower than that in the Au process (759 �

Wettability of zirconium diboride ceramics by Ag, Cu and their alloys with Zr

International Nuclear Information System (INIS)

Muolo, M.L.; Ferrera, E.; Novakovic, R.; Passerone, A.

2003-01-01

Sintered ZrB 2 ceramics, pure and with 4 wt.% Ni as sintering aid, have been tested in contact with liquid Ag, Cu, Ag-Cu and Ag-Cu-Zr. ''Pure'' ZrB 2 ceramics are wetted by Ag-Zr alloys, and ZrB 2 /Ni ceramics also by pure Cu. The wetting behaviour is briefly discussed in terms of existing wetting theories

Development of Au-Ag nanowire mesh fabrication by UV-induced approach

Energy Technology Data Exchange (ETDEWEB)

Saggar, Siddhartha [Laboratory for Molecular Photonics and Electronics, Department of Physics, National Institute of Technology, Calicut, Kerala, India and School of Nanoscience and Technology, National Institute of Technology, Calicut, Kerala (India); Predeep, Padmanabhan, E-mail: predeep@nitc.ac.in

2014-10-15

In an attempt to overcome the limitations of the presently prevailing transparent conducting electrode (TCE) - indium tin oxide (ITO) - many materials have been considered for replacing ITO. Recently, a novel method has been reported for the synthesis of Au-Ag nanowire (NW) mesh, and tested successfully for organic-light-emitting-diodes (OLEDs). It employs UV-induced reduction of gold- and silver- precursors to form Au-Ag NW mesh. In this report, Au-Ag NW mesh thin films are synthesized on glass substrates with an objective for use as facing-electrode for Organic Photovoltaics. Various issues and factors affecting the fabrication-process have been improved, and are also discussed here. The electrode showed good transmitivity, of around 95% (excluding that of glass substrate). The advantage of the technique is its simple processing method and cost-effectiveness.

Alloy formation during the electrochemical growth of a Ag-Cd ultrathin film on Au(1 1 1)

International Nuclear Information System (INIS)

Barrio, M.C. del; Garcia, S.G.; Salinas, D.R.

2009-01-01

The electrodeposition of a Ag/Cd ultrathin film on a Au(1 1 1) surface and the formation of a surface alloy during this process have been studied using classical electrochemical techniques and in situ Scanning Tunneling Microscopy (STM). The films were obtained from separate electrolytes containing Ag + or Cd 2+ ions and from a multicomponent solution containing both ions. First, the polarization conditions were adjusted in order to form a Ag film by overpotential deposition. Afterwards, a Cd monolayer was formed onto this Au(1 1 1)/Ag modified surface by underpotential deposition. The voltammetric behavior of the Cd UPD and the in situ STM images indicated that the ultrathin Ag films were uniformly deposited and epitaxially oriented with respect to the Au(1 1 1) surface. Long time polarization experiments showed that a significant Ag-Cd surface alloying accompanied the formation of the Cd monolayer on the Au(1 1 1)/Ag modified surface, independent of the Ag film thickness. In the case of an extremely thin Ag layer (1 Ag ML) the STM images and long time polarization experiments revealed a solid state diffusion process of Cd, Ag, and Au atoms which can be responsible for the formation of different Ag-Cd or Au-Ag-Cd alloy phases.

Photoconductive properties of organic-inorganic Ag/p-CuPc/n-GaAs/Ag cell

Energy Technology Data Exchange (ETDEWEB)

Karimov, Khasan Sanginovich; Saeed, Muhammad Tariq; Khalid, Fazal Ahmad [GIK Institute of Engineering Sciences and Technology, Top 23640, Swabi, Khyber Pakhtunkhwa (Pakistan); Karieva, Zioda Mirzoevna, E-mail: tariqchani@hotmail.com [Tajik Technical University, Rajabov St.10, Dushanbe, 734000 (Tajikistan)

2011-07-15

A thin film of copper phthalocyanine (CuPc), a p-type semiconductor, was deposited by thermal evaporation in vacuum on an n-type gallium arsenide (GaAs) single-crystal semiconductor substrate. Then semi-transparent Ag thin film was deposited onto the CuPc film also by thermal evaporation to fabricate the Ag/p-CuPc/n-GaAs/Ag cell. Photoconduction of the cell was measured in photoresistive and photodiode modes of operation. It was observed that with an increase in illumination, the photoresistance decreased in reverse bias while it increased in forward bias. The photocurrent was increased in reverse bias operation. In forward bias operation with an increase in illumination, the photocurrent showed a different behavior depending on the voltage applied. (semiconductor physics)

Microstructural evaluation of interfacial intermetallic compounds in Cu wire bonding with Al and Au pads

International Nuclear Information System (INIS)

Kim, Hyung Giun; Kim, Sang Min; Lee, Jae Young; Choi, Mi Ri; Choe, Si Hyun; Kim, Ki Hong; Ryu, Jae Sung; Kim, Sangshik; Han, Seung Zeon; Kim, Won Yong; Lim, Sung Hwan

2014-01-01

A comparative study on the difference in interfacial behavior of thermally aged Cu wire bonding with Al and Au pads was conducted using transmission electron microscopy. During high-temperature lifetime testing of Cu wire bonding with Al and Au pads at 175 °C for up to 2000 h, different growth rates and growth characteristics were investigated in the Cu–Al intermetallic compounds (IMCs), including CuAl 2 , CuAl and Cu 9 Al 4 , and in the Cu–Au IMCs, including (Au,Cu), Cu 3 Au and (Cu,Au). Because of the lower growth rates and greater ductility of Cu–Au IMCs compared to those of Cu–Al IMCs, the Cu wire bonding with the Au pad showed relatively better thermal aging properties of bond pull strength and ball shear strength than those with the Al pad counterpart. In this study, the coherent interfaces were found to retard the growth of IMCs, and a variety of orientation relationships between wire, pad and interfacial IMCs were identified

Co-Cu-Au deposits in metasedimentary rocks-A preliminary report

Science.gov (United States)

Slack, J.F.; Causey, J.D.; Eppinger, R.G.; Gray, J.E.; Johnson, C.A.; Lund, K.I.; Schulz, K.J.

2010-01-01

A compilation of data on global Co-Cu-Au deposits in metasedimentary rocks refines previous descriptive models for their occurrence and provides important information for mineral resource assessments and exploration programs. This compilation forms the basis for a new classification of such deposits, which is speculative at this early stage of research. As defined herein, the Co-Cu-Au deposits contain 0.1 percent or more by weight of Co in ore or mineralized rock, comprising disseminated to semi-massive Co-bearing sulfide minerals with associated Fe- and Cu-bearing sulfides, and local gold, concentrated predominantly within rift-related, siliciclastic metasedimentary rocks of Proterozoic age. Some deposits have appreciable Ag ? Bi ? W ? Ni ? Y ? rare earth elements ? U. Deposit geometry includes stratabound and stratiform layers, lenses, and veins, and (or) discordant veins and breccias. The geometry of most deposits is controlled by stratigraphic layering, folds, axial-plane cleavage, shear zones, breccias, or faults. Ore minerals are mainly cobaltite, skutterudite, glaucodot, and chalcopyrite, with minor gold, arsenopyrite, pyrite, pyrrhotite, bismuthinite, and bismuth; some deposits have appreciable tetrahedrite, uraninite, monazite, allanite, xenotime, apatite, scheelite, or molybdenite. Magnetite can be abundant in breccias, veins, or stratabound lenses within ore or surrounding country rocks. Common gangue minerals include quartz, biotite, muscovite, K-feldspar, albite, chlorite, and scapolite; many deposits contain minor to major amounts of tourmaline. Altered wall rocks generally have abundant biotite or albite. Mesoproterozoic metasedimentary successions constitute the predominant geologic setting. Felsic and (or) mafic plutons are spatially associated with many deposits and at some localities may be contemporaneous with, and involved in, ore formation. Geoenvironmental data for the Blackbird mining district in central Idaho indicate that weathering of

Synthesis, characterization and catalytic property of CuO and Ag/CuO nanoparticles for the epoxidation of styrene

Energy Technology Data Exchange (ETDEWEB)

Lashanizadegan, Maryam; Erfaninia, Nasrin [Alzahra University, Tehran (Iran, Islamic Republic of)

2013-11-15

CuO nanorodes, CuO nanoplates and Ag/CuO nanoparticles were synthesized in the presence of polyethylene glycol by depositional in alkaline environment. Oxide nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared absorption spectra (FT-IR). CuO and Ag/CuO nanoparticles show high catalytic activity for the selective epoxidation of styrene to styrene oxide by TBHP. Under the optimized reaction condition, the oxidation of styrene catalyzed by CuO nanorods gave 100% conversion with 60 and 35% styrene oxide and benzaldehyde, respectively. Ag/CuO gave 99% conversion and styrene oxide (71%) and benzaldehyde (12%) being the major product.

Damage behavior of SnAgCu/Cu solder joints subjected to thermomechanical cycling

International Nuclear Information System (INIS)

Xiao, H.; Li, X.Y.; Hu, Y.; Guo, F.; Shi, Y.W.

2013-01-01

Highlights: •A creep–fatigue damage model based on CDM was proposed. •Designed system includes load frame, strain measure device and damage test device. •Damage evolution of solder joints was a function of accumulated inelastic strain. •Damage of solder joints is an interaction between creep and low-cycle fatigue. -- Abstract: Thermomechanical fatigue damage is a progressive process of material degradation. The objective of this study was to investigate the damage behavior of SnAgCu/Cu solder joints under thermomechanical cycling. A damage model was proposed based on continuum damage mechanics (CDM). Based upon an analysis of displacements for flip-chip solder joints subjected to thermal cycling, a special bimetallic loading frame with single-solder joint samples was designed to simulate the service conditions of actual joints in electronic packages. The assembly, which allowed for strain measurements of an individual solder joint during temperature cycling, was used to investigate the impact of stress–strain cycling on the damage behavior of SnAgCu/Cu solder joints. The characteristic parameters of the damage model were determined through thermomechanical cycling and strain measurement tests. The damage variable D = 1 − R 0 /R was selected, and values for it were obtained using a four-probe method for the single-solder joint samples every dozen cycles during thermomechanical cycling tests to verify the model. The results showed that the predicted damage was in good agreement with the experimental results. The damage evolution law proposed here is a function of inelastic strain, and the results showed that the damage rate of SnAgCu/Cu solder joints increased as the range of the applied strain increased. In addition, the microstructure evolution of the solder joints was analyzed using scanning electron microscopy, which provided the microscopic explanation for the damage evolution law of SnAgCu/Cu solder joints

Damage behavior of SnAgCu/Cu solder joints subjected to thermomechanical cycling

Energy Technology Data Exchange (ETDEWEB)

Xiao, H., E-mail: xiaohui2013@yahoo.com.cn; Li, X.Y.; Hu, Y.; Guo, F.; Shi, Y.W.

2013-11-25

Highlights: •A creep–fatigue damage model based on CDM was proposed. •Designed system includes load frame, strain measure device and damage test device. •Damage evolution of solder joints was a function of accumulated inelastic strain. •Damage of solder joints is an interaction between creep and low-cycle fatigue. -- Abstract: Thermomechanical fatigue damage is a progressive process of material degradation. The objective of this study was to investigate the damage behavior of SnAgCu/Cu solder joints under thermomechanical cycling. A damage model was proposed based on continuum damage mechanics (CDM). Based upon an analysis of displacements for flip-chip solder joints subjected to thermal cycling, a special bimetallic loading frame with single-solder joint samples was designed to simulate the service conditions of actual joints in electronic packages. The assembly, which allowed for strain measurements of an individual solder joint during temperature cycling, was used to investigate the impact of stress–strain cycling on the damage behavior of SnAgCu/Cu solder joints. The characteristic parameters of the damage model were determined through thermomechanical cycling and strain measurement tests. The damage variable D = 1 − R{sub 0}/R was selected, and values for it were obtained using a four-probe method for the single-solder joint samples every dozen cycles during thermomechanical cycling tests to verify the model. The results showed that the predicted damage was in good agreement with the experimental results. The damage evolution law proposed here is a function of inelastic strain, and the results showed that the damage rate of SnAgCu/Cu solder joints increased as the range of the applied strain increased. In addition, the microstructure evolution of the solder joints was analyzed using scanning electron microscopy, which provided the microscopic explanation for the damage evolution law of SnAgCu/Cu solder joints.

Au@Ag core-shell nanocubes with finely tuned and well-controlled sizes, shell thicknesses, and optical properties.

Science.gov (United States)

Ma, Yanyun; Li, Weiyang; Cho, Eun Chul; Li, Zhiyuan; Yu, Taekyung; Zeng, Jie; Xie, Zhaoxiong; Xia, Younan

2010-11-23

This paper describes a facile method for generating Au@Ag core-shell nanocubes with edge lengths controllable in the range of 13.4-50 nm. The synthesis involved the use of single-crystal, spherical Au nanocrystals of 11 nm in size as the seeds in an aqueous system, with ascorbic acid serving as the reductant and cetyltrimethylammonium chloride (CTAC) as the capping agent. The thickness of the Ag shells could be finely tuned from 1.2 to 20 nm by varying the ratio of AgNO(3) precursor to Au seeds. We also investigated the growth mechanism by examining the effects of seeds (capped by CTAC or cetyltrimethylammonium bromide(CTAB)) and capping agent (CTAC vs CTAB) on both size and shape of the resultant core-shell nanocrystals. Our results clearly indicate that CTAC worked much better than CTAB as a capping agent in both the syntheses of Au seeds and Au@Ag core-shell nanocubes. We further studied the localized surface plasmon resonance properties of the Au@Ag nanocubes as a function of the Ag shell thickness. By comparing with the extinction spectra obtained from theoretical calculations, we derived a critical value of ca. 3 nm for the shell thickness at which the plasmon excitation of the Au cores would be completely screened by the Ag shells. Moreover, these Au@Ag core-shell nanocubes could be converted into Au-based hollow nanostructures containing the original Au seeds in the interiors through a galvanic replacement reaction.

AgCuO2: Preparationand Electrochemical Behaviors in Alkaline Electrolytes%AgCuO2:制备及其在碱性溶液中的电化学行为

Institute of Scientific and Technical Information of China (English)

张婷锦; 张校刚; 胡风平

2005-01-01

The silver cuprate AgCuO2 powder was prepared by a chemical co-precipitation method and characterized by XRD, SEM and TEM techniques. The electrochemical behaviors of AgCuO2 electrodes and AgCuO2 modified by sulfur were studied by means of galvanostatic discharge and line sweep voltammetry experiments. The resuits indicated that the specific capacity of AgCuO2 could reach 422.32 mAh·g-1 at middle discharge rate and the addition of sulfur could significantly improve the discharge performance of AgCuO2. The mechanism for this modified effect was also discussed.

An Atomically Precise Au10 Ag2 Nanocluster with Red-Near-IR Dual Emission.

Science.gov (United States)

Lei, Zhen; Guan, Zong-Jie; Pei, Xiao-Li; Yuan, Shang-Fu; Wan, Xian-Kai; Zhang, Jin-Yuan; Wang, Quan-Ming

2016-08-01

A red-near-IR dual-emissive nanocluster with the composition [Au10 Ag2 (2-py-C≡C)3 (dppy)6 ](BF4 )5 (1; 2-py-C≡C is 2-pyridylethynyl, dppy=2-pyridyldiphenylphosphine) has been synthesized. Single-crystal X-ray structural analysis reveals that 1 has a trigonal bipyramidal Au10 Ag2 core that contains a planar Au4 (2-py-C≡C)3 unit sandwiched by two Au3 Ag(dppy)3 motifs. Cluster 1 shows intense red-NIR dual emission in solution. The visible emission originates from metal-to-ligand charge transfer (MLCT) from silver atoms to phosphine ligands in the Au3 Ag(dppy)3 motifs, and the intense NIR emission is associated with the participation of 2-pyridylethynyl in the frontier orbitals of the cluster, which is confirmed by a time-dependent density functional theory (TD-DFT) calculation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Syntheses and crystal structures of BaAgTbS{sub 3}, BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and CsAgUTe{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Prakash, Jai; Beard, Jessica C.; Ibers, James A. [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113 (United States); Mesbah, Adel [Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113 (United States); ICSM-UMR 5257 CNRS/CEA/UM2/ENSCM, Bat 426, BP 17171, 30207 Bagnols/Ceze (France)

2015-06-15

Five new quaternary chalcogenides of the 1113 family, namely BaAgTbS{sub 3}, BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and CsAgUTe{sub 3}, were synthesized by the reactions of the elements at 1173-1273 K. For CsAgUTe{sub 3} CsCl flux was used. Their crystal structures were determined by single-crystal X-ray diffraction studies. The sulfide BaAgTbS{sub 3} crystallizes in the BaAgErS{sub 3} structure type in the monoclinic space group C{sup 3},{sub 2h}-C2/m, whereas the tellurides BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and CsAgUTe{sub 3} crystallize in the KCuZrS{sub 3} structure type in the orthorhombic space group D{sup 1},{sub 2}{sup 7},{sub h}-Cmcm. The BaAgTbS{sub 3} structure consists of edge-sharing [TbS{sub 6}{sup 9-}] octahedra and [AgS{sub 5}{sup 9-}] trigonal pyramids. The connectivity of these polyhedra creates channels that are occupied by Ba atoms. The telluride structure features {sup 2}{sub ∞}[MLnTe{sub 3}{sup 2-}] layers for BaCuGdTe{sub 3}, BaCuTbTe{sub 3}, BaAgTbTe{sub 3}, and {sup 2}{sub ∞}[AgUTe{sub 3}{sup 1-}] layers for CsAgUTe{sub 3}. These layers comprise [MTe{sub 4}] tetrahedra and [LnTe{sub 6}] or [UTe{sub 6}] octahedra. Ba or Cs atoms separate these layers. As there are no short Q..Q (Q = S or Te) interactions these compounds achieve charge balance as Ba{sup 2+}M{sup +}Ln{sup 3+}(Q{sup 2-}){sub 3} (Q = S and Te) and Cs{sup +}Ag{sup +}U{sup 4+}(Te{sup 2-}){sub 3}. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

AuCu@Pt Nanoalloys for Catalytic Application in Reduction of 4-Nitrophenol

Directory of Open Access Journals (Sweden)

Sadia Mehmood

2016-01-01

Full Text Available To enhance and optimize nanocatalyst ability for nitrophenol (4-NP reduction reaction we look beyond Au-metal nanoparticles and describe a new class of Au nanoalloys with controlled composition for core of AuCu-metals and Pt-metal shell. The reduction of 4-NP was investigated in aqueous media spectroscopically on 7.8 nm Au nanospheres (AuNSs, 8.3 nm AuCuNSs, and 9.1 nm AuCu@Pt core-shell NSs in diameter. The rate constants of the catalyzed reaction at room temperature, activation energies, and entropies of activation of reactions catalyzed by the AuCu@Pt core-shell NSs are found to have different values to those of the pure metal NSs. The results strongly support the proposal that catalysis by nanoparticles is taking place efficiently on the surface of NSs. These core-shell nanocatalysts exhibited stability throughout the reduction reaction and proved that heterogonous type mechanisms are most likely to be dominant in nanoalloy based catalysis if the surface of the NSs is not defected upon shell incorporation.

A colorimetric nitrite detection system with excellent selectivity and high sensitivity based on Ag@Au nanoparticles.

Science.gov (United States)

Li, Tianhua; Li, Yonglong; Zhang, Yujie; Dong, Chen; Shen, Zheyu; Wu, Aiguo

2015-02-21

Excessive uptake of NO2(-) is detrimental to human health, but the currently available methods used to sensitively detect this ion in the environment are cumbersome and expensive. In this study, we developed an improved NO2(-) detection system based on a redox etching strategy of CTAB-stabilized Ag-Au core-shell nanoparticles (Ag@AuNPs). The detection mechanism was verified by UV-Vis spectroscopy, TEM and XPS. The detection system produces a color change from purple to colorless in response to an increase of NO2(-) concentration. The selectivity of detection of NO2(-), both with the unaided eye and by measurement of UV-Vis spectra, is excellent in relation to other ions, including Cu(2+), Co(2+), Ni(2+), Cr(3+), Al(3+), Pb(2+), Cd(2+), Ca(2+), Ba(2+), Zn(2+), Mn(2+), Mg(2+), Fe(3+), Hg(2+), Ag(+), K(+), F(-), PO4(3-), C2O4(2-), SO3(2-), CO3(2-), SO4(2-), NO3(-) and CH3-COO(-) (Ac(-)). The limit of detection (LOD) for NO2(-) is 1.0 μM by eye and 0.1 μM by UV-Vis spectroscopy. The LOD by eye is lower than the lowest previously reported value (4.0 μM). There is a good linear relationship between A/A0 and the concentration of NO2(-) from 1.0 to 20.0 μM NO2(-), which permits a quantitative assay. The applicability of our detection system was also verified by analysis of NO2(-) in tap water and lake water. The results demonstrate that our Ag@AuNP-based detection system can be used for the rapid colorimetric detection of NO2(-) in complex environmental samples, with excellent selectivity and high sensitivity.

The Effect of Cu:Ag Atomic Ratio on the Properties of Sputtered Cu–Ag Alloy Thin Films

Directory of Open Access Journals (Sweden)

Janghsing Hsieh

2016-11-01

Full Text Available Cu–Ag thin films with various atomic ratios were prepared using a co-sputtering technique, followed by rapid thermal annealing at various temperatures. The films’ structural, mechanical, and electrical properties were then characterized using X-ray diffractometry (XRD, atomic force microscopy (AFM, FESEM, nano-indentation, and TEM as functions of compositions and annealing conditions. In the as-deposited condition, the structure of these films transformed from a one-phase to a dual-phase state, and the resistivity shows a twin-peak pattern, which can be explained in part by Nordheim’s Rule and the miscibility gap of Cu–Ag alloy. After being annealed, the films’ resistivity followed the mixture rule in general, mainly due to the formation of a dual-phase structure containing Ag-rich and Cu-rich phases. The surface morphology and structure also varied as compositions and annealing conditions changed. The recrystallization of these films varied depending on Ag–Cu compositions. The annealed films composed of 40 at % to 60 at % Cu had higher hardness and lower roughness than those with other compositions. Particularly, the Cu50Ag50 film had the highest hardness after being annealed. From the dissolution testing, it was found that the Cu-ion concentration was about 40 times higher than that of Ag. The galvanic effect and over-saturated state could be the cause of the accelerated Cu dissolution and the reduced dissolution of the Ag.

Enzyme-free hydrogen peroxide sensor based on Au@Ag@C core-double shell nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Li, Yancai, E-mail: liyancai@mnnu.edu.cn [College of Chemistry & Environment, Minnan Normal University, Zhangzhou 363000 (China); Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China); Zhang, Yayun; Zhong, Yanmei [College of Chemistry & Environment, Minnan Normal University, Zhangzhou 363000 (China); Li, Shunxing [College of Chemistry & Environment, Minnan Normal University, Zhangzhou 363000 (China); Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou 363000 (China)

2015-08-30

Graphical abstract: - Highlights: • A facile method was designed to synthesize Au@Ag@C core-double shell nanocomposites. • Carbon nanomaterials at the outermost layer could protect Au and Ag nanoparticles from oxidation and aggregation. • The Au@Ag@C core-double shell nanocomposites showed high sensitivity and selectivity to electrocatalytic reduction of hydrogen peroxide. • The hydrogen peroxide sensor has a wide linear range of 5.0 μM to 4.75 mM and a limit of detection as low as 0.14 μM. - Abstract: The well-designed Au@Ag@C core-double shell nanocomposites were synthesized via a facile method, and were used to fabricate an enzyme-free amperometric hydrogen peroxide (H{sub 2}O{sub 2}) sensor. The size, shape, elementary composition and structure of the nanocomposites were characterized by transmission electron microscope (TEM), energy-dispersed spectrum (EDS) and X-ray diffraction (XRD). The outermost layer of the nanocomposites was amorphous carbon, the second layer was Ag and the core was Au. The Au@Ag@C core-double shell nanocomposites exhibit attractive activity for electrocatalytic reduction of H{sub 2}O{sub 2} according to the electrochemical experiments. It also demonstrates the H{sub 2}O{sub 2} sensor possess well performance with a wide linear range of 5.0 μM to 4.75 mM and a limit of detection (LOD) as low as 0.14 μM (S/N = 3). Furthermore, the interference from the common interfering species, such as glucose, ascorbic acid, dopamine and uric acid can be effectively avoided. In a word, the Au@Ag@C nanocomposites are promising candidates for enzyme-free H{sub 2}O{sub 2} sensor.

Fabrication of Cu-Ag core-shell bimetallic superfine powders by eco-friendly reagents and structures characterization

Science.gov (United States)

Zhao, Jun; Zhang, Dongming; Zhao, Jie

2011-09-01

Superfine bimetallic Cu-Ag core-shell powders were synthesized by reduction of copper sulfate pentahydrate and silver nitrate with eco-friendly ascorbic acid as a reducing agent and cyclodextrins as a protective agent in an aqueous system. The influence of Ag/Cu ratio on coatings was investigated. Ag was homogeneously distributed on the surface of Cu particles at a mole ratio of Ag/Cu=1. FE-SEM showed an uniformity of Ag coatings on Cu particles. Antioxidation of Cu particles was improved by increasing Ag/Cu ratio. TEM-EDX and UV-vis spectra also revealed that Cu cores were covered by Ag nanoshells on the whole. The surface composition analysis by XPS indicated that only small parts of Cu atoms in the surface were oxidized. It was noted that the hindrance of cyclodextrins chemisorbed on particles plays an important role in forming high quality and good dispersity Cu-Ag (Cu@Ag) core-shell powders.

Silver contents and Cu/Ag ratios in Martian meteorites and the implications for planetary differentiation

Science.gov (United States)

Wang, Zaicong; Becker, Harry

2017-11-01

Silver and Cu show very similar partitioning behavior in sulfide melt-silicate melt and metal-silicate systems at low and high pressure-temperature (P-T) experimental conditions, implying that mantle melting, fractional crystallization and core-mantle differentiation have at most modest (within a factor of 3) effects on Cu/Ag ratios. For this reason, it is likely that Cu/Ag ratios in mantle-derived magmatic products of planetary bodies reflect that of the mantle and, in some circumstances, also the bulk planet composition. To test this hypothesis, new Ag mass fractions and Cu/Ag ratios in different groups of Martian meteorites are presented and compared with data from chondrites and samples from the Earth's mantle. Silver contents in lherzolitic, olivine-phyric and basaltic shergottites and nakhlites range between 1.9 and 12.3 ng/g. The data display a negative trend with MgO content and correlate positively with Cu contents. In spite of displaying variable initial Ɛ143Nd values and representing a diverse spectrum of magmatic evolution and physiochemical conditions, shergottites and nakhlites display limited variations of Cu/Ag ratios (1080 ± 320, 1 s, n = 14). The relatively constant Cu/Ag suggests limited fractionation of Ag from Cu during the formation and evolution of the parent magmas, irrespectively of whether sulfide saturation was attained or not. The mean Cu/Ag ratio of Martian meteorites thus reflects that of the Martian mantle and constrains its Ag content to 1.9 ± 0.7 ng/g (1 s). Carbonaceous and enstatite chondrites display a limited range of Cu/Ag ratios of mostly 500-2400. Ordinary chondrites show a larger scatter of Cu/Ag up to 4500, which may have been caused by Ag redistribution during parent body metamorphism. The majority of chondrites have Cu/Ag ratios indistinguishable from the Martian mantle value, indicating that Martian core formation strongly depleted Cu and Ag contents, but probably did not significantly change the Cu/Ag ratio of the

Laser ablation of Au-CuO core-shell nanocomposite in water for optoelectronic devices

Science.gov (United States)

Ismail, Raid A.; Abdul-Hamed, Ryam S.

2017-12-01

Core-shell gold-copper oxide Au-CuO nanocomposites were synthesized using laser ablation of CuO target in colloidal solution of Au nanoparticles (NPs). The effect of laser fluence on the structural, morphological, electrical, and optical properties of Au-CuO nanocomposites was investigated using x-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), transmission electron microscope (TEM), photoluminescence (PL), Fourier transformed infrared spectroscopy (FTIR), Hall measurement, and UV-vis spectroscopy. X-ray diffraction results confirm the formation of polycrystalline Au-CuO NPs with monoclinic structure. The optical energy gap for CuO was 4 eV and for the Au-CuO core-shell nanocomposites was found to be in the range of 3.4-3.7 eV. SEM and TEM investigations revealed that the structure and morphology of Au-CuO core-shell nanocomposites were strongly depending on the laser fluence. A formation of Au-CuO nanospheres and platelets structures was observed. The photoluminescence data showed an emission of broad visible peaks between 407 and 420 nm. The effect of laser fluence on the dark and illuminated I-V characteristics of Au-CuO/n-Si heterojunction photodetectors was investigated and analyzed. The experimental data demonstrated that the photodetector prepared at optimum laser fluence exhibited photosensitivity of 0.6 AW-1 at 800 nm.

Collagen-chitosan scaffold modified with Au and Ag nanoparticles: Synthesis and structure

International Nuclear Information System (INIS)

Rubina, M.S.; Kamitov, E.E.; Zubavichus, Ya. V.; Peters, G.S.; Naumkin, A.V.; Suzer, S.; Vasil’kov, A.Yu.

2016-01-01

Graphical abstract: - Highlights: • Biocompatible collagen-chitosan scaffolds were modified by Au and Ag nanoparticles via the metal-vapor synthesis. • Structural and morphological parameters of the nanocomposites were assessed using a set of modern instrumental techniques, including electron microscopy, X-ray diffraction, small-angle X-ray scattering, EXAFS, XPS. • Potential application of the nanocomposites are envisaged. - Abstract: Nowadays, the dermal biomimetic scaffolds are widely used in regenerative medicine. Collagen-chitosan scaffold one of these materials possesses antibacterial activity, good compatibility with living tissues and has been already used as a wound-healing material. In this article, collagen-chitosan scaffolds modified with Ag and Au nanoparticles have been synthesized using novel method - the metal-vapor synthesis. The nanocomposite materials are characterized by XPS, TEM, SEM and synchrotron radiation-based X-ray techniques. According to XRD data, the mean size of the nanoparticles (NPs) is 10.5 nm and 20.2 nm in Au-Collagen-Chitosan (Au-CollCh) and Ag-Collagen-Chitosan (Ag-CollCh) scaffolds, respectively in fair agreement with the TEM data. SAXS analysis of the composites reveals an asymmetric size distribution peaked at 10 nm for Au-CollCh and 25 nm for Ag-CollCh indicative of particle's aggregation. According to SEM data, the metal-carrying scaffolds have layered structure and the nanoparticles are rather uniformly distributed on the surface material. XPS data indicate that the metallic nanoparticles are in their unoxidized/neutral states and dominantly stabilized within the chitosan-rich domains.

Collagen-chitosan scaffold modified with Au and Ag nanoparticles: Synthesis and structure

Energy Technology Data Exchange (ETDEWEB)

Rubina, M.S.; Kamitov, E.E. [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russian Federation (Russian Federation); Zubavichus, Ya. V.; Peters, G.S. [National Research center «Kurchatov Institute», Moscow, 123182 Russian Federation (Russian Federation); Naumkin, A.V. [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russian Federation (Russian Federation); Suzer, S. [Department of Chemistry, Bilkent University, Ankara, 06800 Turkey (Turkey); Vasil’kov, A.Yu., E-mail: alexandervasilkov@yandex.ru [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russian Federation (Russian Federation)

2016-03-15

Graphical abstract: - Highlights: • Biocompatible collagen-chitosan scaffolds were modified by Au and Ag nanoparticles via the metal-vapor synthesis. • Structural and morphological parameters of the nanocomposites were assessed using a set of modern instrumental techniques, including electron microscopy, X-ray diffraction, small-angle X-ray scattering, EXAFS, XPS. • Potential application of the nanocomposites are envisaged. - Abstract: Nowadays, the dermal biomimetic scaffolds are widely used in regenerative medicine. Collagen-chitosan scaffold one of these materials possesses antibacterial activity, good compatibility with living tissues and has been already used as a wound-healing material. In this article, collagen-chitosan scaffolds modified with Ag and Au nanoparticles have been synthesized using novel method - the metal-vapor synthesis. The nanocomposite materials are characterized by XPS, TEM, SEM and synchrotron radiation-based X-ray techniques. According to XRD data, the mean size of the nanoparticles (NPs) is 10.5 nm and 20.2 nm in Au-Collagen-Chitosan (Au-CollCh) and Ag-Collagen-Chitosan (Ag-CollCh) scaffolds, respectively in fair agreement with the TEM data. SAXS analysis of the composites reveals an asymmetric size distribution peaked at 10 nm for Au-CollCh and 25 nm for Ag-CollCh indicative of particle's aggregation. According to SEM data, the metal-carrying scaffolds have layered structure and the nanoparticles are rather uniformly distributed on the surface material. XPS data indicate that the metallic nanoparticles are in their unoxidized/neutral states and dominantly stabilized within the chitosan-rich domains.

Stability enhancement of Cu2S against Cu vacancy formation by Ag alloying

Science.gov (United States)

Barman, Sajib K.; Huda, Muhammad N.

2018-04-01

As a potential solar absorber material, Cu2S has proved its importance in the field of renewable energy. However, almost all the known minerals of Cu2S suffer from spontaneous Cu vacancy formation in the structure. The Cu vacancy formation causes the structure to possess very high p-type doping that leads the material to behave as a degenerate semiconductor. This vacancy formation tendency is a major obstacle for this material in this regard. A relatively new predicted phase of Cu2S which has an acanthite-like structure was found to be preferable than the well-known low chalcocite Cu2S. However, the Cu-vacancy formation tendency in this phase remained similar. We have found that alloying silver with this structure can help to reduce Cu vacancy formation tendency without altering its electronic property. The band gap of silver alloyed structure is higher than pristine acanthite Cu2S. In addition, Cu diffusion in the structure can be reduced with Ag doped in Cu sites. In this study, a systematic approach is presented within the density functional theory framework to study Cu vacancy formation tendency and diffusion in silver alloyed acanthite Cu2S, and proposed a possible route to stabilize Cu2S against Cu vacancy formations by alloying it with Ag.

Synthesis, characterization of Ag-Au core-shell bimetal nanoparticles and its application for electrocatalytic oxidation/sensing of L-methionine

Energy Technology Data Exchange (ETDEWEB)

Murugavelu, M.; Karthikeyan, B., E-mail: bkarthi_au@yahoo.com

2017-01-01

The Ag-Au core-shell bimetal nanoparticles (BNPs) was prepared using chemical reduction method. The prepared Ag-Au core-shell BNPs were characterized by UV–Visible (UV–Vis) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) pattern. These results showed the Ag-Au BNPs exhibited core-shell shape. The Ag-Au core-shell BNPs was examined towards electrocatalytic oxidation of L-methionine (L-Met) by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. According to the results, L-Met is determined with detection limit of 30 μM. Interference studies in biological buffer was also studied. - Highlights: • The Ag-Au core-shell BNPs are synthesized and characterized • Ag-Au core-shell BNPs modified (Ag-Au/GCE) has been examined for L-methionine oxidation/sensing by using electrochemical method. • The Ag-Au/GCE exhibited good performance for the detection of L-methionine.

Fabrication of Cu-Ag core-shell bimetallic superfine powders by eco-friendly reagents and structures characterization

International Nuclear Information System (INIS)

Zhao Jun; Zhang Dongming; Zhao Jie

2011-01-01

Superfine bimetallic Cu-Ag core-shell powders were synthesized by reduction of copper sulfate pentahydrate and silver nitrate with eco-friendly ascorbic acid as a reducing agent and cyclodextrins as a protective agent in an aqueous system. The influence of Ag/Cu ratio on coatings was investigated. Ag was homogeneously distributed on the surface of Cu particles at a mole ratio of Ag/Cu=1. FE-SEM showed an uniformity of Ag coatings on Cu particles. Antioxidation of Cu particles was improved by increasing Ag/Cu ratio. TEM-EDX and UV-vis spectra also revealed that Cu cores were covered by Ag nanoshells on the whole. The surface composition analysis by XPS indicated that only small parts of Cu atoms in the surface were oxidized. It was noted that the hindrance of cyclodextrins chemisorbed on particles plays an important role in forming high quality and good dispersity Cu-Ag (Cu-Ag) core-shell powders. - Graphical abstract: Mechanism of fabricating Cu-Ag particles with good dispersibility using β-CDs as a protective agent was studied because of its special structure. Highlights: → Green supramolecular β-CD used as a protective agent and ascorbic acid(Vc) as a reducing agent to fabricate Cu-Ag powders. → Particles are monodisperse and the diameter is close to nanoscale(100-150 nm). → Resistance of Cu particles to oxidation was higher. → Formation mechanism explained.

Dealloying of Cu{sub x}Au studied by hard X-ray photoelectron spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Rajput, Parasmani, E-mail: parasmani.rajput@northwestern.edu [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France); Gupta, Ajay [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452 017 (India); Detlefs, Blanka [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France); Kolb, Dieter M. [Institute for Electrochemistry, University of Ulm, D-89069 Ulm (Germany); Potdar, Satish [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452 017 (India); Zegenhagen, Jörg [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France)

2013-10-15

Highlights: ► The shift in binding energy of Cu and Au lines in CuAu alloys is opposite to expected from the nobility of the elements. ► The magnitude of the chemical shifts of the metal lines in CuAu alloys is strongly influenced by finite size effects and disorder. ► Cu 3s and/or Au 4f cross-sections are not well described by theory (Scofield). The Cu 3s photoabsorption cross-section seems to be strongly overestimated. ► We find/confirm that (CuAu) dealloying proceeds into depth like a spinodal decomposition. -- Abstract: We studied pristine and leached ultra-thin Cu{sub x}Au (x ≈ 4) films by hard X-ray photoelectron spectroscopy. The Au 4f and Cu 3s core levels show a shift in binding energy which is opposite to expected from the nobility of the elements, which is explained by charge transfer involving differently screening s and d valence levels of the elements [W. Eberhardt, S.C. Wu, R. Garrett, D. Sondericker, F. Jona, Phys. Rev. B 31 (1985) 8285]. The magnitude of the chemical shifts of the metal lines is strongly influenced by the finite size and disorder of the films. Angular dependent photoelectron emission allowed to assess the alloy composition as a function of depth larger than 5 nm. The potential controlled dealloying proceeds into depth like a spinodal decomposition with Cu going into solution and the remaining Au accumulating in the surface region. The compositional gradient did not lead to a significant broadening of the metal photoelectron lines suggesting a non-local screening mechanism.

TL and OSL studies on lithium borate single crystals doped with Cu and Ag

International Nuclear Information System (INIS)

Rawat, N.S.; Kulkarni, M.S.; Tyagi, M.; Ratna, P.; Mishra, D.R.; Singh, S.G.; Tiwari, B.; Soni, A.; Gadkari, S.C.; Gupta, S.K.

2012-01-01

Lithium borate (LBO) single crystals doped with Cu and Ag (0.25 mol% each) (Li 2 B 4 O 7 :Cu,Ag) are grown by the Czochralski method. The thermoluminescence readout on Li 2 B 4 O 7 :Cu,Ag crystals showed three glow peaks at∼375, 441 and 516 K for the heating rate of 1 K/s. The thermoluminescence sensitivity of the grown Li 2 B 4 O 7 :Cu,Ag single crystals is found to be 5 times TLD-100 and a linear dose response in the range 1 mGy to 1 kGy. The glow curve deconvolution reveals nearly first order kinetics for all the three peaks with trap depths 0.77, 1.25 and 1.34 eV respectively and corresponding frequency factors 1.6×10 9 , 1.3×10 13 and 6.8×10 11 s −1 . The continuous wave optically stimulated luminescence (CW-OSL) measurements were performed on the LBO:Cu,Ag single crystals using blue light stimulation. The traps responsible for the three thermoluminescence peaks in Li 2 B 4 O 7 :Cu,Ag are found to be OSL sensitive. The qualitative correlation between TL peaks and CW-OSL response is established. The photoluminescence studies show that in case of co-doping of Ag in LBO:Cu the emission at 370 nm in Cu states dominates over the transitions in Ag states implying doping of Ag plays a role as sensitizer when co-doped with Cu and increases overall emission. - Highlights: ► Growth of crack free single crystals of Li2B4O7 :Cu and Ag. ► Study of TL and OSL parameters for Li2B4O7 :Cu and Ag. ► Correlation of OSL with TL peaks. ► Optimization of OSL readout time with respect to residual TL.

Schottky barrier height measurements of Cu/Si(001), Ag/Si(001), and Au/Si(001) interfaces utilizing ballistic electron emission microscopy and ballistic hole emission microscopy

International Nuclear Information System (INIS)

Balsano, Robert; Matsubayashi, Akitomo; LaBella, Vincent P.

2013-01-01

The Schottky barrier heights of both n and p doped Cu/Si(001), Ag/Si(001), and Au/Si(001) diodes were measured using ballistic electron emission microscopy and ballistic hole emission microscopy (BHEM), respectively. Measurements using both forward and reverse ballistic electron emission microscopy (BEEM) and (BHEM) injection conditions were performed. The Schottky barrier heights were found by fitting to a linearization of the power law form of the Bell-Kaiser BEEM model. The sum of the n-type and p-type barrier heights are in good agreement with the band gap of silicon and independent of the metal utilized. The Schottky barrier heights are found to be below the region of best fit for the power law form of the BK model, demonstrating its region of validity

Synthesis of triangular Au core-Ag shell nanoparticles

International Nuclear Information System (INIS)

Rai, Akhilesh; Chaudhary, Minakshi; Ahmad, Absar; Bhargava, Suresh; Sastry, Murali

2007-01-01

In this paper, we demonstrate a simple and reproducible method for the synthesis of triangular Au core-Ag shell nanoparticles. The triangular gold core is obtained by the reduction of gold ions by lemongrass extract. Utilizing the negative charge on the gold nanotriangles, silver ions are bound to their surface and thereafter reduced by ascorbic acid under alkaline conditions. The thickness of the silver shell may be modulated by varying the pH of the reaction medium. The formation of the Au core-Ag shell triangular nanostructures has been followed by UV-vis-NIR Spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements. The sharp vertices of the triangles coupled with the core-shell structure is expected to have potential for application in surface enhanced Raman spectroscopy and in the sensitive detection of biomolecules

Au@Ag core/shell cuboids and dumbbells: Optical properties and SERS response

Science.gov (United States)

Khlebtsov, Boris N.; Liu, Zhonghui; Ye, Jian; Khlebtsov, Nikolai G.

2015-12-01

Recent studies have conclusively shown that the plasmonic properties of Au nanorods can be finely controlled by Ag coating. Here, we investigate the effect of asymmetric silver overgrowth of Au nanorods on their extinction and surface-enhanced Raman scattering (SERS) properties for colloids and self-assembled monolayers. Au@Ag core/shell cuboids and dumbbells were fabricated through a seed-mediated anisotropic growth process, in which AgCl was reduced by use of Au nanorods with narrow size and shape distribution as seeds. Upon tailoring the reaction rate, monodisperse cuboids and dumbbells were synthesized and further transformed into water-soluble powders of PEGylated nanoparticles. The extinction spectra of AuNRs were in excellent agreement with T-matrix simulations based on size and shape distributions of randomly oriented particles. The multimodal plasmonic properties of the Au@Ag cuboids and dumbbells were investigated by comparing the experimental extinction spectra with finite-difference time-domain (FDTD) simulations. The SERS efficiencies of the Au@Ag cuboids and dumbbells were compared in two options: (1) individual SERS enhancers in colloids and (2) self-assembled monolayers formed on a silicon wafer by drop casting of nanopowder solutions mixed with a drop of Raman reporters. By using 1,4-aminothiophenol Raman reporter molecules, the analytical SERS enhancement factor (AEF) of the colloidal dumbbells was determined to be 5.1×106, which is an order of magnitude higher than the AEF=4.0×105 for the cuboids. This difference can be explained by better fitting of the dumbbell plasmon resonance to the excitation laser wavelength. In contrast to the colloidal measurements, the AEF=5×107 of self-assembled cuboid monolayers was almost twofold higher than that for dumbbell monolayers, as determined with rhodamine 6G Raman reporters. According to TEM data and electromagnetic simulations, the better SERS response of the self-assembled cuboids is due to uniform

Radiation annealing in Ag and Au due to energetic displacement cascades

International Nuclear Information System (INIS)

Averback, R.S.; Merkle, K.L.

1975-01-01

Radiation annealing due to energetic displacement cascades has been studied in Ag and Au. Thin film specimens, 2500 A, were doped to various concentrations of Frenkel pair defects by irradiating with 150 keV protons at temperatures below 10 K. Subsequently, the specimens were irradiated below 10 K with energetic, approximately 540 keV, self-ions. Electrical resistivity measurements were used to monitor the concentration of defects as a function of dose. In Au, approximately 5 percent of the doped-in Frenkel pairs, annealed during the 540 keV Au irradiation. The annealing volume associated with individual cascades was found to be 2.1 x 10 -16 cm 3 . In Ag approximately 5 percent of the doped-in defects annealed during a 500 keV Ag irradiation and the annealing volume of the cascade was found to be 5 x 10 -16 cm 3 . In addition, the effects of doping concentration and specimen temperature during doping were investigated

Charged hadron multiplicity fluctuations in Au+Au and Cu+Cu collisions from √s.sub.NN./sub. = 22.5 to 200 GeV

Czech Academy of Sciences Publication Activity Database

Adare, A.; Adler, S. S.; Afanasiev, S.; Kubart, J.; Mašek, L.; Mikeš, P.; Tomášek, Lukáš; Vrba, Václav

2008-01-01

Roč. 78, č. 4 (2008), 044902/1-044902/15 ISSN 0556-2813 R&D Projects: GA MŠk LA08015; GA MŠk 1P04LA211; GA ČR GA202/05/0653 Institutional research plan: CEZ:AV0Z10100502 Keywords : charged hadron * multiplicity fluctuations * Au+Au * Cu+Cu Subject RIV: BF - Elementary Particles and High Energy Physics Impact factor: 3.124, year: 2008

Antimicrobial activity and biocompatibility of Ag+- and Cu2+-doped biphasic hydroxyapatite/α-tricalcium phosphate obtained from hydrothermally synthesized Ag+- and Cu2+-doped hydroxyapatite

International Nuclear Information System (INIS)

Radovanović, Željko; Jokić, Bojan; Veljović, Djordje; Dimitrijević, Suzana; Kojić, Vesna; Petrović, Rada; Janaćković, Djordje

2014-01-01

Hydroxyapatite (HAp) powders doped with Ag + or Cu 2+ were synthesized by a hydrothermal method in order to obtain biomaterial with an antimicrobial effect. The synthesis was performed with two contents of dopant (Ag + or Cu 2+ ) by considering both the antimicrobial activities and biocompatibility of the powders. The doped HAp was annealed at 1200 °C for 2 h with the intention of investigating the influence of doping with Ag + and Cu 2+ on the creation of the biphasic HAp/α-tricalcium phosphate (HAp/α-TCP) and determining the antimicrobial activity and biocompatibility of the obtained biphasic powders. Analyses of all powders, undoped and doped HAp and HAp/α-TCP, were performed by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic absorption spectroscopy (AAS) and energy-dispersive X-ray spectroscopy (EDS). The in vitro antibacterial activities of the powders were evaluated against: Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. All powders showed good antimicrobial activity but generally the powders of doped HAp/α-TCP had more uniform results against all pathogenic microorganisms than the powders of doped HAp. In vitro biocompatibility tests, MTT and DET, were used to evaluate the biocompatibility of Ag + - and Cu 2+ -doped HAp/α-TCP with MRC-5 human fibroblast cells. These tests confirmed that powders do not have a cytotoxic effect. The HAp/α-TCP powders doped with the lower content of Ag + and Cu 2+ showed especially good biocompatibility. Antimicrobial and biocompatibility tests recommend the Ag + - and Cu 2+ -doped HAp/α-TCP as promising material for use in reconstructive surgery of bone.

Preparation of dendritic Ag/Au bimetallic nanostructures and their application in surface-enhanced Raman scattering

International Nuclear Information System (INIS)

Yi Zao; Chen Shanjun; Chen Yan; Luo Jiangshan; Wu Weidong; Yi Yougen; Tang Yongjian

2012-01-01

Dendritic Ag/Au bimetallic nanostructures have been synthesized via a multi-stage galvanic replacement reaction of Ag dendrites in a chlorauric acid (HAuCl 4 ) solution at room temperature. After five stages of replacement reaction, one obtains structures with protruding nanocubes; these will mature into many porous structures with a few Ag atoms that are left over dendrites. The morphological and compositional changes which evolved with reaction stages were analyzed by using scanning electron microscopy, transmission electron microscopy, UV–visible spectroscopy, selected area electron diffraction and energy-dispersive X-ray spectrometry. The replacement of Ag with Au was confirmed. A formation mechanism involving the original development of Ag dendrites into porous structures with the growth of Au nanocubes on this underlying structure as the number of reaction stages is proposed. This was confirmed by surface-enhanced Raman scattering (SERS). The dendritic Ag/Au bimetallic nanostructures could be used as efficient SERS active substrates. It was found that the SERS enhancement ability was dependent on the stage of galvanic replacement reaction. - Highlights: ► Dendritic Ag/Au bimetallic nanostructures have been synthesized. ► Protruding cubic nanostructures obtained after 5 stages mature into porous structures. ► SERS results allow confirm the proposed formation mechanism. ► The nanostructures could be used as efficient SERS active substrates.

Au and AuCu Nanoparticles Supported on SBA-15 Ordered Mesoporous Titania-Silica as Catalysts for Methylene Blue Photodegradation

Directory of Open Access Journals (Sweden)

Isabel Barroso-Martín

2018-05-01

Full Text Available The photocatalytic degradation of methylene blue (MB dye has been performed under UV irradiation in aqueous suspension, employing photocatalysts based on Au (1.5 wt % and AuCu (Au/Cu = 1, 2.0 wt %, and supported on SBA-15-ordered mesoporous silica, with and without titania (Si/Ti = 3, in order to evaluate the versatility of this mesoporous support in this type of reaction of great impact from the environmental point of view. Samples were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, N2 adsorption-desorption at −196 °C, and X-ray photoelectron spectroscopy (XPS, so as to study their structural, optical, and chemical properties. All the prepared catalysts were found to be active in the test reaction. The bimetallic AuCu-based catalysts attained very high MB degradation values, in particular AuCu/SBA-15 titania-silica sample reached 100% of dye oxidation after the monitored reaction period (120 min.

Evidence for rapid epithermal mineralization and coeval bimodal volcanism, Bruner Au-Ag property, NV USA

Science.gov (United States)

Baldwin, Dylan

The character of Au-Ag mineralization and volcanic/hydrothermal relationships at the underexplored Miocene-age Bruner low-sulfidation epithermal Au-Ag deposit are elucidated using field and laboratory studies. Bruner is located in central Nevada within the Great Basin extensional province, near several major volcanic trends (Western Andesite, Northern Nevada Rift) associated with world-class Miocene-age epithermal Au-Ag provinces. Despite its proximity to several >1 Moz Au deposits, and newly discovered high-grade drill intercepts (to 117 ppm Au/1.5m), there is no published research on the deposit, the style of mineralization has not been systematically characterized, and vectors to mineralization remain elusive. By investigating the nature of mineralization and time-space relationships between volcanic/hydrothermal activity, the deposit has been integrated into a regional framework, and exploration targeting improved. Mineralization occurs within narrow quartz + adularia +/- pyrite veins that manifest as sheeted/stockwork zones, vein swarms, and rare 0.3-2 m wide veins hosted by two generations of Miocene high-K, high-silica rhyolite flow dome complexes overlying an andesite flow unit. The most prominent structural controls on veining are N­striking faults and syn-mineral basalt/rhyolite dikes. Productive veins have robust boiling indicators (high adularia content, bladed quartz after calcite, recrystallized colloform quartz bands), lack rhythmic banding, and contain only 1-2 stages; these veins overprint, or occur separately from another population of barren to weakly mineralized rhythmically banded quartz-only veins. Ore minerals consist of coarse Au0.5Ag 0.5 electrum, fine Au0.7Ag0.3 electrum, acanthite, uytenbogaardtite (Ag3AuS2) and minor embolite Ag(Br,Cl). Now deeply oxidized, veins typically contain Bruner appears to belong to a small subset of mid-Miocene epithermal deposits in Nevada with low base metal contents and low to no Se, related to calc

Ag- and Cu-doped multifunctional bioactive nanostructured TiCaPCON films

Energy Technology Data Exchange (ETDEWEB)

Shtansky, D.V., E-mail: shtansky@shs.misis.ru [National University of Science and Technology “MISIS”, Leninsky prospekt 4, Moscow 119049 (Russian Federation); Batenina, I.V.; Kiryukhantsev-Korneev, Ph.V.; Sheveyko, A.N.; Kuptsov, K.A. [National University of Science and Technology “MISIS”, Leninsky prospekt 4, Moscow 119049 (Russian Federation); Zhitnyak, I.Y.; Anisimova, N.Yu.; Gloushankova, N.A. [N.N. Blokhin Russian Cancer Research Center of RAMS, Kashirskoe shosse 24, Moscow 115478 (Russian Federation)

2013-11-15

A key property of multicomponent bioactive nanostructured Ti(C,N)-based films doped with Ca, P, and O (TiCaPCON) that can be improved further is their antibacterial effect that should be achieved without compromising the implant bioactivity and biocompatibility. The present work is focused on the study of structure, chemical, mechanical, tribological, and biological properties of Ag- and Cu-doped TiCaPCON films. The films with Ag (0.4–4 at.%) and Cu (13 at.%) contents were obtained by simultaneous sputtering of a TiC{sub 0.5}–Ca{sub 3}(PO{sub 4}){sub 2} target and either an Ag or a Cu target. The film structure was studied using X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy, and Raman-shift and IR spectroscopy. The films were characterized in terms of their hardness, elastic modulus, dynamic impact resistance, friction coefficient and wear rate (both in air and normal saline), surface wettability, electrochemical behavior and Ag or Cu ion release in normal saline. Particular attention was paid to the influence of inorganic bactericides (Ag and Cu ions) on the bactericidal activity against unicellular yeast fungus Saccharomyces cerevisiae and gram-positive bacteria Lactobacillus acidophilus, as well as on the attachment, spreading, actin cytoskeleton organization, focal adhesions, and early stages of osteoblastic cell differentiation. The obtained results show that the Ag-doped films are more suitable for the protection of metallic surfaces against bacterial infection compared with their Cu-doped counterpart. In particular, an excellent combination of mechanical, tribological, and biological properties makes Ag-doped TiCaPCON film with 1.2 at.% of Ag very attractive material for bioengineering and modification of load-bearing metal implant surfaces.

A first principles study on the electronic origins of silver segregation at the Ag-Au (111) surface

Science.gov (United States)

Hoppe, Sandra; Müller, Stefan

2017-12-01

The special electronic structure of gold gives rise to many interesting phenomena, such as its color. The surface segregation of the silver-gold system has been the subject of numerous experimental and theoretical studies, yielding conflicting results ranging from strong Ag surface enrichment to Au surface segregation. Via a combined approach of density functional theory (DFT) and statistical physics, we have analyzed the segregation at the Ag-Au (111) surface with different Ag bulk concentrations. Interestingly, we observe a moderate Au surface segregation, which is due to a charge transfer from the less electronegative Ag to Au. Canonical Monte Carlo simulations suggest that the calculated concentration profile with a Au-enriched surface layer remains stable up to higher temperatures. However, the presence of adsorbed oxygen reverses the segregation behavior and leads to strong Ag enrichment of the surface layer.

Coupled growth of Al-Al2Cu eutectics in Al-Cu-Ag alloys

International Nuclear Information System (INIS)

Hecht, U; Witusiewicz, V; Drevermann, A

2012-01-01

Coupled eutectic growth of Al and Al 2 Cu was investigated in univariant Al-Cu-Ag alloys during solidification with planar and cellular morphology. Experiments reveal the dynamic selection of small spacings, below the minimum undercooling spacing and show that distinct morphological features pertain to nearly isotropic or anisotropic Al-Al 2 Cu interfaces.

Electrical resistivity of liquid Ag-Au alloy

International Nuclear Information System (INIS)

Anis Alam, M.; Tomak, M.

1983-01-01

Calculations of the dependence of the electrical resistivity in liquid Ag-Au binary alloy on composition are reported. The structure of the binary alloy is described as a hard-sphere system. A one-parameter local pseudopotential, which incorporates s-d hybridization effects phenomenologically, is employed in the resistivity calculation. A reasonable agreement with experimental trend is observed. (author)

Mixed Cu(i)/Au(i) coordination polymers as reversible turn-on vapoluminescent sensors for volatile thioethers.

Science.gov (United States)

Varju, Bryton R; Ovens, Jeffrey S; Leznoff, Daniel B

2017-06-13

Vapour-phase thioethers play an important role in a wide number of fields, including plant biology, chemical weapon disposal, and brewing but few sensor materials are known. The emissive coordination polymer Cu 1/2 Au 1/2 CN does not react with vapour phase dimethyl sulphide (DMS) or diethyl sulphide (DES) despite the independent synthesis of emissive [Cu 1/2 Au 1/2 CN] 2 (DMS) and [Cu 1/2 Au 1/2 CN] 2 (DES) from their constituent components in solution. However, the doped Cu 2/3 Au 1/3 CN rapidly reacts in the solid state with both of these vapour phase thioethers reversibly, with a change in emission from 380/560 nm to 460 nm (DMS) or 420 nm (DES), illustrating that doping the inactive parent Cu 1/2 Au 1/2 CN with Cu(i) generates an active sensor material. This response can be thermally cycled with little to no loss in functionality. [Cu 1/2 Au 1/2 CN] 2 (DMS), [Cu 2/3 Au 1/3 CN] 2 (DMS), and [Cu 2/3 Au 1/3 CN] 2 (DES) were structurally characterized as 3-D network structures supported by aurophilic interactions.

Nucleon shadowing effects in Cu + Cu and Au + Au collisions at RHIC within the HIJING code

Science.gov (United States)

Abdel-Waged, Khaled; Felemban, Nuha

2018-02-01

The centrality dependence of pseudorapidity density of charged particles ({{{d}}{N}}{{ch}}/{{d}}η ) in Cu + Cu (Au + Au) collisions at Relativistic Heavy Ion Collider energy of \\sqrt{{s}{{NN}}}=22.4, 62.4 and 200 (19.6, 62.4 and 200) GeV, is investigated within an improved HIJING code. The standard HIJING model is enhanced by a prescription for collective nucleon-nucleon (NN) interactions and more modern parton distribution functions. The collective NN-interactions are used to induce both cascade and nucleon shadowing effects. We find collective cascade broadens the pseudorapidity distributions in the tails (at | η | > {y}{beam}) above 25%-30% collision centrality to be consistent with the {{{d}}{N}}{{ch}}/{{d}}η data at \\sqrt{{s}{{NN}}} =19.6,22.4,62.4 {GeV}. The overall contribution of nucleon shadowing is shown to depress the whole shape of {{{d}}{N}}{{ch}}/{{d}}η in the primary interaction region (at | η | data.

Improving the mechanical performance of Sn57.6Bi0.4Ag solder joints on Au/Ni/Cu pads during aging and electromigration through the addition of tungsten (W) nanoparticle reinforcement

Energy Technology Data Exchange (ETDEWEB)

Li, Yi, E-mail: yili64-c@my.cityu.edu.hk [Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Luo, Kaiming; Lim, Adeline B.Y.; Chen, Zhong [School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Wu, Fengshun [School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan (China); Chan, Y.C. [Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong)

2016-07-04

Sn57.6Bi0.4Ag solder has been reinforced successfully through the addition of tungsten (W) nanoparticles at a concentration of 0.5 wt%. With the addition of W nanoparticles, the solder matrix lamellar interphase spacing was reduced by 31.0%. Due to the dispersion of W nanoparticles and the consequently refined microstructure, the mechanical properties of the solder alloy were enhanced, as indicated by a 6.2% improvement in the microhardness. During the reflow of solder on Au/Ni/Cu pads, the entire Au layer dissolved into the molten solder rapidly and a large number of (Au,Ni)(Sn,Bi){sub 4} particles were formed. The fracture path of the as-reflowed joint was within the solder region, showing ductile characteristic, and the shear strength was reinforced by 8.2%, due to the enhanced mechanical properties of the solder. During the subsequent aging process, the Au migrated back towards the interface and a thick layer of interfacial (Au,Ni)(Sn,Bi){sub 4} IMC was formed, leading to the shift of the fracture path to the interfacial IMC region, the transformation to brittle fracture and the deterioration of the strength of the joint, due to Au embrittlement. By adding W nanoparticles, the migration of Au was mitigated and the thickness of the (Au,Ni)(Sn,Bi){sub 4} layer was reduced significantly, which reduced the Au embrittlement-induced deterioration of the strength of the joint. During electromigration, the segregation of the Bi-rich and Sn-rich phases and the accumulation of the (Au,Ni)(Sn,Bi){sub 4} layer at cathode interface were mitigated by the addition of W nanoparticles, which improved the electromigration resistance.

Stopping power measurements for 4-5MeV/nucleon 16O, 40Ar, 63Cu and 84Kr in C, Al, Ni, Ag and Au

International Nuclear Information System (INIS)

Bimbot, R.; Della Negra, S.; Gardes, D.; Gauvin, H.; Fleury, A.; Hubert, F.

1977-01-01

The stopping powers for (4 and 5 MeV/nucleon) 16 O, 40 Ar, 63 Cu and 84 Kr have been measured in C, Al, Ni, Ag and Au media. The experimental technique consists in measuring accurately the energy of protons elastically scattered at zero degree by the incident and degraded beams. The experimental results have been compared with stopping powers calculated in different ways. Discrepancies as large as 30% have been observed for the heaviest ions in light media (C, Al), the experimental values being higher than the calculated ones. Moreover, this comparison indicates that, from these calculations, no agreement can be obtained in the whole range of incident ions and stopping media. On the contrary, a quantitative agreement was obtained by a new calculation mode which takes into account the variation of the moving ion effective charge with the atomic number of the stopping medium

1-Hexadecylamine as both reducing agent and stabilizer to synthesize Au and Ag nanoparticles and their SERS application

International Nuclear Information System (INIS)

Hou Xiaomiao; Zhan, Xiaoling; Fang Yan; Chen Shutang; Li Na; Zhou Qi

2011-01-01

1-Hexadecylamine (HDA)-capped Au and Ag nanoparticles (NPs) have been successfully prepared by a one-pot solution growth method. The HDA is used as both reducing agent and stabilizer in the synthetic process is favorable for investigating the capping mechanism of Au and Ag NPs’ surface. The growth process and characterization of Au and Ag NPs are determined by Ultraviolet–visible (UV–vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Experimental results demonstrate that the HDA-capped Au and Ag NPs are highly crystalline and have good optical properties. Furthermore, surface-enhanced Raman scattering (SERS) spectra of 2-thionaphthol are obtained on the Au and Ag NPs modified glass surface, respectively, indicating that the as-synthesized noble metal NPs have potentially high sensitive optical detection application.

1-Hexadecylamine as both reducing agent and stabilizer to synthesize Au and Ag nanoparticles and their SERS application

Energy Technology Data Exchange (ETDEWEB)

Hou Xiaomiao; Zhan, Xiaoling, E-mail: zhangxl@bit.edu.cn [Beijing Institute of Technology, Department of Chemistry, School of Science (China); Fang Yan, E-mail: fangyan@mail.cnu.edu.cn [Capital Normal University, Beijing Key Lab for Nano-Photonics and Nano-Structure (NPNS), Department of Physics (China); Chen Shutang; Li Na; Zhou Qi [Beijing Institute of Technology, Department of Chemistry, School of Science (China)

2011-05-15

1-Hexadecylamine (HDA)-capped Au and Ag nanoparticles (NPs) have been successfully prepared by a one-pot solution growth method. The HDA is used as both reducing agent and stabilizer in the synthetic process is favorable for investigating the capping mechanism of Au and Ag NPs' surface. The growth process and characterization of Au and Ag NPs are determined by Ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Experimental results demonstrate that the HDA-capped Au and Ag NPs are highly crystalline and have good optical properties. Furthermore, surface-enhanced Raman scattering (SERS) spectra of 2-thionaphthol are obtained on the Au and Ag NPs modified glass surface, respectively, indicating that the as-synthesized noble metal NPs have potentially high sensitive optical detection application.

Grindability of dental cast Ti-Ag and Ti-Cu alloys.

Science.gov (United States)

Kikuchi, Masafumi; Takahashi, Masatoshi; Okabe, Toru; Okuno, Osamu

2003-06-01

Experimental Ti-Ag alloys (5, 10, and 20 mass% Ag) and Ti-Cu alloys (2, 5, and 10 mass% Cu) were cast into magnesia molds using a dental casting machine, and their grindability was investigated. At the lowest grinding speed (500 m min(-1)), there were no statistical differences among the grindability values of the titanium and titanium alloys. The grindability of the alloys increased as the grinding speed increased. At the highest grinding speed (1500 m x min(-1)), the grindability of the 20% Ag, 5% Cu, and 10% Cu alloys was significantly higher than that of titanium. It was found that alloying with silver or copper improved the grindability of titanium, particularly at a high speed. It appeared that the decrease in elongation caused by the precipitation of small amounts of intermetallic compounds primarily contributed to the favorable grindability of the experimental alloys.

High-pressure x-ray diffraction of icosahedral Zr-Al-Ni-Cu-Ag quasicrystals

DEFF Research Database (Denmark)

Jiang, Jianzhong; Saksl, Karel; Rasmussen, Helge Kildahl

2001-01-01

temperature using synchrotron radiation. The icosahedral quasicrystal structure is retained up to the highest hydrostatic pressure used (approximately 28 GPa) and is reversible after decompression. The bulk modulus at zero pressure and its pressure derivative of the icosahedral Zr-Al-Ni-Cu-Ag quasicrystal......The effect of pressure on the structural stability of icosahedral Zr-Al-Ni-Cu-Ag quasicrystals forming from a Zr65Al7.5Ni10Cu7.5Ag10 metallic glass with a supercooled liquid region of 44 K has been investigated by in situ high-pressure angle-dispersive x-ray powder diffraction at ambient......-Al-Ni-Cu-Ag quasicrystals induced by pressure....

Recombination luminescence of Cu and/or Ag doped lithium tetraborate single crystals

Energy Technology Data Exchange (ETDEWEB)

Romet, I. [Institute of Physics, University of Tartu, W. Ostwaldi Str. 1, 50411 Tartu (Estonia); Aleksanyan, E. [Institute of Physics, University of Tartu, W. Ostwaldi Str. 1, 50411 Tartu (Estonia); A. Alikhanyan National Science Laboratory, 2 Br. Alikhanyan Str., 0036 Yerevan (Armenia); Brik, M.G. [Institute of Physics, University of Tartu, W. Ostwaldi Str. 1, 50411 Tartu (Estonia); College of Sciences, Chongqing University of Posts and Telecommunications, 400065 Chongqing (China); Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200 Czestochowa (Poland); Corradi, G. [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Konkoly-Thege M. út 29-33, H-1121 Budapest (Hungary); Kotlov, A. [Photon Science at DESY, Notkestrasse 85, 22607 Hamburg (Germany); Nagirnyi, V., E-mail: vitali.nagirnoi@ut.ee [Institute of Physics, University of Tartu, W. Ostwaldi Str. 1, 50411 Tartu (Estonia); Polgár, K. [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Konkoly-Thege M. út 29-33, H-1121 Budapest (Hungary)

2016-09-15

Complex investigations of thermostimulated luminescence (TSL) and radioluminescence properties of Li{sub 2}B{sub 4}O{sub 7} (LTB), LTB:Cu, LTB:Ag and LTB:Cu, Ag crystals suitable for tissue equivalent dosimeters were carried out in the temperature range 4.2–700 K. TSL, cathodoluminescence and X-ray excited luminescence spectra are compared to those measured under photoexcitation. The emission band at 4.6 eV in LTB:Ag is reliably related to Ag{sup +} ions based on the comparison of the results of optical spectroscopy studies and first principle calculations. Energy transfer from the relaxed exited state of the Ag{sup +} ion to the Cu{sup +} ion in double-doped LTB:Cu, Ag crystals is demonstrated. Thermostimulated recombination of charge carriers in irradiated crystals is seen to take place mainly at oxygen sites at low temperatures and at impurity sites at high temperatures. For the first time, the appearance of the low-temperature TSL peak at 90 K is assigned to ionic processes in LTB crystals. The appearance of pyroelectric flashes due to the lattice relaxation in the temperature region 90–240 K is demonstrated and their surface-related nature clarified. In accordance with EPR studies the dosimetric TSL peaks in copper and silver doped LTB crystals are attributed to thermally released electrons recombining with Cu{sup 2+} and Ag{sup 2+} centres.

Spectroscopy of microcrystals of CuI-AgI system

International Nuclear Information System (INIS)

Voll, V.A.; Barmasov, A.V.; Struts, A.V.

1994-01-01

By means of comparison of absorption and luminescence spectra analysis for samples with different relative component concentrations is considered obtaining in a gelatin matrix and the structure of CuI-AgI system composite microcrystals. Resonant character of excitation and its localization in the region of the interphase boundary of substrate/epitaxy is established. The most probable composition of thermally stable photolytic centers is discussed in dependence on the Cu and Ag relative content t. 25 refs

Studying the Range of Incident Alpha Particles on Cu , Ge , Ag , Cd , Te and Au, With Energy (4-15 MeV)

International Nuclear Information System (INIS)

Kadhim, R.O.; Jasim, W.N.

2015-01-01

In this paper theoretical calculation of the range for alpha particles with the energy range (4 – 15)MeV when passing in some metallic media (Cu , Ge , Ag , Cd , Te and Au).Semi empirical formula was used in addition to (SRIM-2012) program. The Semi empirical equation was programmed to calculate the range using Matlab Language.The results of the range in these media were compared with the results obtained from SRIM-2012 and )(2011)Andnet) results.There was good agreement among the semi empirical equation result , SRIM- 2012 results and with )(2011)Andnet) results in the low energy.The results showed exponential relation between the range of alpha particles in these media and the velocity of the particles.By recourse with SRIM- 2012 results and application them in Matlab program and by using Curve Fitting Tool we extraction equation with its constants to calculate the range of alpha particles in any element of these six elements with the energy range (4 – 15)MeV.The maximum deviation between the results from the semi empirical calculation and SRIM-2012 results was calculated the statistical test ( kstest2) in Matlab program

Synthesis of Au and Au/Cu alloy nanoparticles on multiwalled carbon nanotubes by using microwave irradiation

International Nuclear Information System (INIS)

Rangari, Vijaya K.; Dey, Sanchita; Jeelani, Shaik

2010-01-01

Gold nanoparticles and gold-copper alloy nanoparticles were synthesized by reduction of chloroauric acid (HAuCl_4.xH_2O) and co-reduction of chloroauric acid (HAuCl_4.xH_2O) and Copper(II) acetate [(CH_3COO)_2Cu.H_2O] by ethylene glycol through microwave irradiation technique. In this reaction ethylene glycol used as a solvent and also reducing agent. The cetyltrimethyl ammonium bromide (CTAB) used as surfactant. Au nanoparticles and Au-Cu nanoparticles on the surface of multiwalled carbon nanotube also produced by using same procedure. The XRD analysis confirmed the formation of Au and Au-Cu alloy nanoparticles on multiwalled carbon nanotubes(CNTs). The morphology and size of the particles were examined by the transmission electron microscopy. The EDS analysis on individual particles confirmed that the presence of two metals in a particle in case of alloy nanoparticle. The results presented here show that a variety of well defined metal and metal alloy nanoparticles can be produced by using the microwave polyol process with in a short period of time. (author)

Computer simulation of the structure of liquid metal halides RbBr, CuCl, CuBr, CuI, and AgBr

International Nuclear Information System (INIS)

Belashchenko, D.K.; Ostrovskij, O.I.

2003-01-01

The computerized models of the RbBr, AgBr, CuCl, CuBr and CuI liquid ion systems of 498 ions dimension are simulated at the temperatures of 753-960 K on the basis of the known diffraction data through the BELION algorithm. Good agreement of diffraction and model partial pair correlation functions (PPCF), excluding the PPCF first peaks heights, is obtained in all the cases. The simulation is carried out by the varied ion charges (the atomization energy values, close to the real ones, are obtained by ion charges ±1.00 for the RbBr, ±1.15 for AgBr, ±1.20 for CuCl, ±1.48 for CuBr and ±1.367 for CuI). The noncoulomb contributions in the interparticle potentials are calculated [ru

Highly open bowl-like PtAuAg nanocages as robust electrocatalysts towards ethylene glycol oxidation

Science.gov (United States)

Xu, Hui; Yan, Bo; Li, Shumin; Wang, Jin; Song, Pingping; Wang, Caiqin; Guo, Jun; Du, Yukou

2018-04-01

A novel combined seed mediated and galvanic replacement method has been demonstrated to synthesize a new class of trimetallic PtAuAg nanocatalysts with highly open bowl-like nanocage structure. The newly-generated PtAuAg nanocages catalysts exhibit superior electrocatalytic performances towards ethylene glycol oxidation with the mass activity of 6357.1 mA mg-1, 5.5 times higher than that of commercial Pt/C (1151.1 mA mg-1). This work demonstrates the first example of designing shape-controlled architectures of trimetallic bowl-like PtAuAg nanocages for liquid fuel electrooxidation.

Size and composition tunable Ag-Au alloy nanoparticles by replacement reactions

International Nuclear Information System (INIS)

Zhang Qingbo; Lee, J Y; Yang Jun; Boothroyd, Chris; Zhang Jixuan

2007-01-01

Ag-Au alloy nanoparticles with tunable size and composition were prepared by a replacement reaction between Ag nanoparticles and HAuCl 4 at elevated temperatures. The formation of homogeneous alloy nanoparticles was confirmed by selected-area energy-dispersive x-ray spectroscopy (SAEDX), UV-visible absorption spectroscopy, high resolution transmission electron microscopy (HRTEM) and electron diffraction. This method leverages upon the rapid interdiffusion of Ag and Au atoms in the reduced dimension of a nanoparticle, elevated temperatures and the large number of vacancy defects created in the replacement reaction. This method of preparation has several notable advantages: (1) independent tuning of the size and composition of alloy nanoparticles; (2) production of alloy nanoparticles in high concentrations; (3) general utility in the synthesis of alloy nanoparticles that cannot be obtained by the co-reduction method

Au-CuO core-shell nanoparticles design and development for the selective determination of Vitamin B6

International Nuclear Information System (INIS)

Kumar, Deivasigamani Ranjith; Manoj, Devaraj; Santhanalakshmi, Jayadevan; Shim, Jae-Jin

2015-01-01

Highlights: • Seed mediated growth of Au-CuO core-shell nanoparticle. • Au-CuO core-shell nanoparticle provided good peak current for pyridoxine. • Au-CuO/MWCNTs/GC exhibited excellent vitamin B 6 peak separation with other vitamin. - Abstract: This paper reports the synthesis of gold (core)-copper oxide (shell) nanoparticles using a simple seed mediated growth method. Pre-synthesized Au nanoparticles were used as seed materials for copper oxide shell growth, which were shown to be effective for Au-CuO core-shell formation. The novelty of this assembly strategy is that the exploitation of the Cu-ligand, which is thermolyzed on the Au nanoseed surface, results in the formation of CuO. Au-CuO core-shell nanoparticles were characterized by UV-visible spectroscopy, high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The as prepared Au-CuO was used to fabricate a Au-CuO/MWCNTs/GC-modified electrode, which was applied to Vitamin B 6 (pyridoxine) determination by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The MWCNTs enhance the pyridoxine oxidation rate by increasing the peak current with Au-CuO, hence pyridoxine oxidized lower operating potentials. The Au-CuO/MWCNTs/GC-modified electrode showed excellent electrochemical performance towards pyridoxine (PY) in the presence of other typical vitamins, such as riboflavin, ascorbic acid and uric acid. The linear calibration graph was obtained over the PY concentration range of 0.79 μM–18.4 μM and the detection limit (S/N = 3) was 0.15 μM. The Au-CuO/MWCNTs/GC-modified electrode showed good stability, repeatability and recovery of real sample analysis

Some recent results in Au+Au collisions at AGS

International Nuclear Information System (INIS)

Chen, Z.

1996-01-01

Many interesting results have been obtained for Au + Au reactions at AGS. The basic information about the reaction dynamics comes from the hadronic distribution. and this article reviews the recent progress of these distributions in details. The proton rapidity distribution shows significantly increased stopping compared to lighter systems, implying the formation of a state of high baryon density. Unlike reactions at this energy induced by lighter heavy ions, at low m t - m 0 the proton invariant spectra deviate from a single exponential shape and become fear,. while pion spectra are found to rise in this region, with the π - spectra rising faster than the π + spectra. The inverse slope parameter increases faster for particles of larger mass as the number of participants in the reaction increases, an indication of increased effect of radial expansion in central collision. Anti-proton Needs have been measured recently, and unfortunately a comparison among current results from different experiments indicates discrepancy

Microstructures and coherent phase diagram for the pseudobinary system (AuCu)1-xPd x with x ≤ 0.10

International Nuclear Information System (INIS)

Luciano, Rhodora H.; Shiraishi, Takanobu; Udoh, Koh-ichi; Tanaka, Yasuhiro; Hisatsune, Kunihiro

2005-01-01

A coherent phase diagram for the pseudobinary system (AuCu) 1-x Pd x with x ≤ 0.10 was constructed based on phase identification and microstructural analysis by transmission electron microscopy. It was confirmed that the addition of palladium exceeding 1.0 at.% to the equiatomic AuCu eliminated the AuCu II long-period superstructure from the phase equilibria and stabilized the AuCu I superstructure. The AuCu-0.5 at.% Pd and AuCu-1.0 at.% Pd alloys isothermally aged for long time at temperatures ranging from 380 to 420 deg. C exhibited seven distinguishable regions; a single-phase region of disordered solid solution (α); a single-phase region of AuCu I ordered phase; a single-phase region of AuCu II ordered phase; a region of the coexisting AuCu I and AuCu II ordered phases; a region of the coexisting AuCu I ordered and α phases; a region of the coexisting AuCu II ordered and α phases; and a region of the coexisting AuCu I and AuCu II ordered and α phases

The effect of copper and silver on the properties of Au-ZnO catalyst and its activity in glycerol oxidation

Science.gov (United States)

Kaskow, Iveta; Decyk, Piotr; Sobczak, Izabela

2018-06-01

The goal of this work was to use ZnO as a support for gold and copper (Au-Cu system) or gold and silver (Au-Ag system) and comparison of the effect of copper and silver on the properties of gold and its activity in glycerol oxidation with oxygen in the liquid phase. The samples prepared were fully characterized by XRD, TEM techniques and UV-vis, XPS, ESR spectroscopic methods. It was found that the introduction of copper and silver changed the electronic state of gold loaded on ZnO by the electron transfer between metals. Three different metallic gold species were identified in calcined catalysts: (Au°)δ- (Au-ZnO), (Au°)η- (AuCu-ZnO) and (Au°)γ- (AuAg-ZnO), where δ-,η-,γ- indicate a different partial negative charge on metallic gold and γ > δ > η. The results showed that (Au°)η- centers (metallic gold with the lowest negative charge) formed on AuCu-ZnO were the most active in glycerol oxidation. The increase in the negative charge on metallic gold loaded on AuAg-ZnO reduced the gold activity in silver containing sample. The glyceric acid adsorption and desorption rate influenced the selectivity of the catalysts.

Synthesis and characterization of Ag@Cu nano/microstructure ordered arrays as SERS-active substrates

Science.gov (United States)

Zhang, Pinhua; Cui, Guangliang; Xiao, Chuanhai; Zhang, Mingzhe; Chen, Li; Shi, Changmin

2016-06-01

We fabricated an Ag decorated Cu (Ag@Cu) nano/microstructure ordered array by facile template-free 2D electrodeposition combined with a galvanic reduction method for SERS applications. The Cu nano/microstructure ordered arrays were first synthesized by a 2D electrodeposition method, then Ag nanocubes were decorated on the arrays by galvanic reduction without any capping agent. The pollution-free surface and edge-to-face heterostructure of Ag nanocubes and Cu nano/microstructure arrays provide the powerful field-enhancements for SERS performance. The results verified that the Ag@Cu nano/microstructure ordered arrays have excellent activity for 4-Mercaptopyridine, and the sensitivity limit is as low as 10-8 M. Therefore, this facile route provides a useful platform for the fabrication of a SERS substrate based on nano/microstructure ordered arrays.

Ag-Cu Bimetallic Nanoparticles Prepared by Microemulsion Method as Catalyst for Epoxidation of Styrene

Directory of Open Access Journals (Sweden)

Hong-Kui Wang

2012-01-01

Full Text Available Ag/Cu bimetallic nanocatalysts supported on reticulate-like γ-alumina were prepared by a microemulsion method using N2H4·H2O as the reducing agent. The catalysts were activated by calcination followed with hydrogen reduction at 873K, and the properties were confirmed using various characterization techniques. Compared with metal oxides particles, Ag-Cu particles exhibited smaller sizes (<5 nm after calcination in H2 at 873K. XPS results indicated that the binding energies changed with the Ag/Cu ratios, suggesting that increasing the copper content gave both metals a greater tendency to lose electrons. Furthermore, Ag-Cu bimetallic nanoparticles supported on γ-alumina showed better catalytic activity on the epoxidation of styrene as compared with the corresponding monometallic silver or copper. The styrene oxide selectivity could reach 76.6% at Ag/Cu molar ratio of 3/1, while the maximum conversion (up to 94.6% appeared at Ag/Cu molar ratio of 1/1 because of the maximum interaction between silver and copper.

Electronic structure of disordered Cu-Ag alloys

International Nuclear Information System (INIS)

Razee, S.S.A.

1994-08-01

We present a self-consistent-field Korringa-Kohn-Rostoker coherent potential approximation study of the electronic structure of disordered Cu x Ag 1-x alloys for x=0.0, 0.25, 0.50, 0.75 and 1.0. In particular, we focus on the Fermi surface, density of states, and Bloch spectral density, and study how they evolve as a function of x. We find that, Fermi surface dimensions have a non-linear composition dependence. The disorder-induced smearing of the Fermi surface, as expected, is very high along the direction; both the Cu and Ag Fermi surfaces have a neck in this direction. Whenever possible we have compared our results with the available experimental data. (author). 34 refs, 4 figs

Cu2O-directed in situ growth of Au nanoparticles inside HKUST-1 nanocages.

Science.gov (United States)

Liu, Yongxin; Liu, Ting; Tian, Long; Zhang, Linlin; Yao, Lili; Tan, Taixing; Xu, Jin; Han, Xiaohui; Liu, Dan; Wang, Cheng

2016-12-07

Controllable integration of metal nanoparticles (MNPs) and metal-organic frameworks (MOFs) is attracting considerable attention as the obtained composite materials always show synergistic effects in applications of catalysis, delivery, as well as sensing. Herein, a Cu 2 O-directed in situ growth strategy was developed to integrate Au nanoparticles and HKUST-1. In this strategy, Cu 2 O@HKUST-1 core-shell heterostructures, HKUST-1 nanocages, Cu 2 O@Au@HKUST-1 sandwich core-shell heterostructures and Au@HKUST-1 balls-in-cage heterostructures were successfully synthesized. Cu 2 O@HKUST-1 core-shell heterostructures were synthesized by soaking Cu 2 O nanocrystals in benzene-1,3,5-tricarboxylic acid solution. The well-defined Cu 2 O@HKUST-1 core-shell heterostructures were demonstrated to be dominated by the ratio of Cu 2+ cations to btc 3- ligands in solution during the period of HKUST-1 formation. Cu 2 O@Au@HKUST-1 sandwich core-shell or Au@HKUST-1 balls-in-cage heterostructures were obtained by impregnating HAuCl 4 into Cu 2 O@HKUST-1 core-shell heterostructures. Due to the porosity of HKUST-1 and reducibility of Cu 2 O, HAuCl 4 could pass through the HKUST-1 shell and be reduced by the Cu 2 O core in situ forming Au nanoparticles. Finally, CO oxidation reaction at high temperatures was carried out to assess the catalytic functionality of the obtained composite heterostructures. This strategy can circumvent some drawbacks of the existing approaches for integrating MNPs and MOFs, such as nonselective deposition of MNPs at the outer surface of the MOF matrices, extreme treatment conditions and additional surface modifications.

Enhanced photocatalytic, electrochemical and photoelectrochemical properties of TiO2 nanotubes arrays modified with Cu, AgCu and Bi nanoparticles obtained via radiolytic reduction

International Nuclear Information System (INIS)

Nischk, Michał; Mazierski, Paweł; Wei, Zhishun; Siuzdak, Katarzyna; Kouame, Natalie Amoin; Kowalska, Ewa; Remita, Hynd; Zaleska-Medynska, Adriana

2016-01-01

Highlights: • TiO 2 nanotubes were modified with Cu, AgCu, Bi nanoparticles via gamma radiolysis. • Excessive amount of deposited metal decreased photocatalytic activity. • AgCu-modified samples were more active than Cu-modified (with the same Cu content). • AgCu nanoparticles exist in a core (Ag) -shell (Cu) form. • Examined photocatalysts were resistant towards photocorrosion processes. - Abstract: TiO 2 nanotubes arrays (NTs), obtained via electrochemical anodization of Ti foil, were modified with monometallic (Cu, Bi) and bimetallic (AgCu) nanoparticles. Different amounts of metals’ precursors were deposited on the surface of NTs by the spin-coating technique, and the reduction of metals was performed via gamma radiolysis. Surface modification of titania was studied by EDS and XPS analysis. The results show that AgCu nanoparticles exist in a Ag core -Cu shell form. Photocatalytic activity was examined under UV irradiation and phenol was used as a model pollutant of water. Over 95% of phenol degradation was achieved after 60 min of irradiation for almost all examined samples, but only slight difference in degradation efficiency (about 3%) between modified and bare NTs was observed. However, the initial phenol degradation rate and TOC removal efficiency was significantly enhanced for the samples modified with 0.31 and 0.63 mol% of Bi as well as for all the samples modified with Cu and AgCu nanoparticles in comparison with bare titania nanotubes. The saturated photocurrent, under the influence of simulated solar light irradiation, for the most active Bi- and AgCu-modified samples, was over two times higher than for pristine NTs. All the examined materials were resistant towards photocorrosion processes that enables their application for long term processes induced by light.

Single-molecule conductance with nitrile and amino contacts with Ag or Cu electrodes

International Nuclear Information System (INIS)

Li, Dong-Fang; Mao, Jin-Chuan; Chen, De-Li; Chen, Fang; Ze-Wen, Hong; Zhou, Xiao-Yi; Wang, Ya-Hao; Zhou, Xiao-Shun; Niu, Zhen-Jiang; Maisonhaute, Emmanuel

2015-01-01

The single-molecule conductance of 1,4-dicyanobenzene (DCB), 1,4-benzenediamine (BDA) and 4,4'-biphenyldicarbonitrile (BPDC) with Ag and/or Cu electrodes is measured by electrochemical jump-to-contact STM-break junction. All single-molecule junctions present three sets of conductance values revealing different contact geometries. We observe that the single-molecule conductance of Ag-BDA-Ag junction is larger that of Ag-DCB-Ag junction, and DCB with Ag contacts are more conductive than that with Cu ones. This is related to a different electronic coupling between the molecules and the electrodes. Tunneling decay constants of 1.70 and 1.68 per phenyl group were found for Ag and Cu electrodes, respectively. The present study therefore shows that nitrile and amino groups can also be used as effective anchors for other metals than gold

Origin of the Distinct Diffusion Behaviors of Cu and Ag in Covalent and Ionic Semiconductors.

Science.gov (United States)

Deng, Hui-Xiong; Luo, Jun-Wei; Li, Shu-Shen; Wei, Su-Huai

2016-10-14

It is well known that Cu diffuses faster than Ag in covalent semiconductors such as Si, which has prevented the replacement of Ag by Cu as a contact material in Si solar cells for reducing the cost. Surprisingly, in more ionic materials such as CdTe, Ag diffuses faster than Cu despite that it is larger than Cu, which has prevented the replacement of Cu by Ag in CdTe solar cells to improve the performance. But, so far, the mechanisms behind these distinct diffusion behaviors of Cu and Ag in covalent and ionic semiconductors have not been addressed. Here we reveal the underlying mechanisms by combining the first-principles calculations and group theory analysis. We find that the symmetry controlled s-d coupling plays a critical role in determining the diffusion behaviors. The s-d coupling is absent in pure covalent semiconductors but increases with the ionicity of the zinc blende semiconductors, and is larger for Cu than for Ag, owing to its higher d orbital energy. In conjunction with Coulomb interaction and strain energy, the s-d coupling is able to explain all the diffusion behaviors from Cu to Ag and from covalent to ionic hosts. This in-depth understanding enables us to engineer the diffusion of impurities in various semiconductors.

On interface dipole layers between C60 and Ag or Au

NARCIS (Netherlands)

Veenstra, Sjoerd; Heeres, A.; Hadziioannou, G.; Sawatzky, G.A.; Jonkman, H.T.

2002-01-01

C60 layers on polycrystalline Ag and Au are studied by photoelectron spectroscopy. At these metal/C60 interfaces an electron transfer occurs from the metal to the lowest unoccupied orbital of C60. We found in the case of the polycrystalline Ag/C60 interface a dipolar layer with its associated

Preparation and use of Cu nanoclusters as fluorescent probes to determine Au(III) ions

Energy Technology Data Exchange (ETDEWEB)

Liu, Jinshui, E-mail: jsliu@sina.com; Wang, Bin; Xu, Meijiao; Wang, Lizhen; Zhou, Zihan

2017-05-15

Polyethyleneimine-capped Cu nanoclusters (PEI-CuNCs) with a mean diameter of 2.5 nm and that emitted blue light at 485 nm were synthesized. The fluorescence of PEI-CuNCs was strongly quenched when Au(III) ions were present. Because of this specific response, a PEI-CuNC-based fluorescent turn-off sensor was developed. Under optimum conditions, a good linear relationship (R{sup 2}=0.993) was found between the relative fluorescence intensity (F{sub 0}/F) and the Au(III) ion concentration between 0.5 and 15 µM. The detection limit for Au(III) ions was 0.06 µM. The quenching mechanism was assessed by performing X-ray photoelectron spectroscopy spectra studies. The fluorescence quenching was ascribed to photo-induced electron transfer from the PEI-CuNCs to the AuCl{sub 4}{sup −} occur. Using The method described is a new way of quantifying Au(III) ions.

Diffusion-induced grain boundary migration during ion beam mixing of Au/Cu bilayers

International Nuclear Information System (INIS)

Alexander, D.E.; Baldo, P.M.; Rehn, L.E.

1992-09-01

Experiments were performed to evaluate the effect of 1.5 MeV Kr irradiation on diffusion-induced grain boundary migration (DIGM) in Au/Cu bilayers in the temperature range of 300≤T≤050K. The experimental results were consistent with DIGM occurring in bilayers both during irradiation and during annealing treatments. Rutherford backscattering spectrometry showed a nearly uniform distribution of Cu present through the entire thickness of appropriately prepared polycrystalline Au films irradiated or annealed at temperatures ≥400K. No parallel effect was seen in similarly treated single-crystal films. In each polycrystalline sample studied, irradiation resulted in greater amounts of Cu present uniformly in the Au compared to annealing-only. The magnitudes of measured Cu compositions were substantially greater than that expected solely from grain boundary diffusion. A simple analysis of the process indicated that ion irradiation affects DIGM by increasing the composition of Cu present in alloyed zones and/or by increasing the grain boundary velocity in the Au

Covellite CuS as a matrix for "invisible" gold: X-ray spectroscopic study of the chemical state of Cu and Au in synthetic minerals

Science.gov (United States)

Tagirov, Boris R.; Trigub, Alexander L.; Kvashnina, Kristina O.; Shiryaev, Andrey A.; Chareev, Dmitriy A.; Nickolsky, Maximilian S.; Abramova, Vera D.; Kovalchuk, Elena V.

2016-10-01

Geological processes leading to formation of sulfide ores often result in precipitation of gold-bearing sulfides which can contain high concentrations of this metal in ;invisible; (or ;refractory;) state. Covellite (CuS) is ubiquitous mineral in many types of the ore deposits, and numerous studies of the natural ores show that covellite can contain high concentrations of Au. At the same time, Au-bearing covellite withstands cooling in contrast to other minerals of the Cu-Fe-S system (chalcocite, bornite, chalcopyrite), where Au exsolves at low temperatures. This makes covellite a convenient model system for investigation of the chemical state (local environment and valence) of the ;invisible; Au in copper-sulfide ores (copper-porphyry, epithermal, volcanogenic massive sulfide, SEDEX deposits). Therefore, it is necessary to determine the location of Au in the covellite matrix as it will have important implications for the methods employed by mineral processing industry to extract Au from sulfide ores. Here we investigate the chemical state of Cu and Au in synthetic covellite containing up to 0.3 wt.% of Au in the ;invisible; state. The covellite crystals were synthesized by hydrothermal and salt flux methods. Formation of the chemically bound Au is indicated by strong dependence of the concentration of Au in covellite on the sulfur fugacity in the experimental system (d(log C(Au))/d(log f(S2)) ∼ 0.65). The Au concentration of covellite grows with increasing temperature from 400 to 450 °C, whereas further temperature increase to 500 °C has only minor effect. The synthesized minerals were studied using X-ray absorption fine structure spectroscopy (XAFS) in high energy resolution fluorescence detection (HERFD) mode. Ab initio simulations of Cu K edge XANES spectra show that the Cu oxidation state in two structural positions in covellite (tetrahedral and triangular coordination with S atoms) is identical: the total loss of electronic charge for the 3d shell is ∼0

Charged-particle multiplicity and pseudorapidity distributions measured with the PHOBOS detector in Au+Au, Cu+Cu, d+Au, and p+p collisions at ultrarelativistic energies

Science.gov (United States)

Alver, B.; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Chai, Z.; Chetluru, V.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kotuła, J.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Li, W.; Lin, W. T.; Loizides, C.; Manly, S.; McLeod, D.; Michałowski, J.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Sedykh, I.; Skulski, W.; Smith, C. E.; Steadman, S. G.; Steinberg, P.; Stephans, G. S. F.; Stodulski, M.; Sukhanov, A.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Wadsworth, B.; Walters, P.; Wenger, E.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wuosmaa, A. H.; Wysłouch, B.

2011-02-01

Pseudorapidity distributions of charged particles emitted in Au+Au, Cu+Cu, d+Au, and p+p collisions over a wide energy range have been measured using the PHOBOS detector at the BNL Relativistic Heavy-Ion Collider (RHIC). The centrality dependence of both the charged particle distributions and the multiplicity at midrapidity were measured. Pseudorapidity distributions of charged particles emitted with |η|<5.4, which account for between 95% and 99% of the total charged-particle emission associated with collision participants, are presented for different collision centralities. Both the midrapidity density dNch/dη and the total charged-particle multiplicity Nch are found to factorize into a product of independent functions of collision energy, sNN, and centrality given in terms of the number of nucleons participating in the collision, Npart. The total charged particle multiplicity, observed in these experiments and those at lower energies, assumes a linear dependence of (lnsNN)2 over the full range of collision energy of sNN=2.7-200 GeV.

Atomic-scale investigation of interface-facilitated deformation twinning in severely deformed Ag-Cu nanolamellar composites

International Nuclear Information System (INIS)

An, X. H.; Cao, Y.; Liao, X. Z.; Zhu, S. M.; Nie, J. F.; Kawasaki, M.; Ringer, S. P.; Langdon, T. G.; Zhu, Y. T.

2015-01-01

We report an atomic-scale investigation of interface-facilitated deformation twinning behaviour in Ag-Cu nanolamellar composites. Profuse twinning activities in Ag supply partial dislocations to directly transmit across the Ag-Cu lamellar interface that promotes deformation twinning in the neighbouring Cu lamellae although the interface is severely deformed. The trans-interface twin bands change the local structure at the interface. Our analysis suggests that the orientation relationship and interfacial structure between neighbouring Ag-Cu lamellae play a crucial role in such special interface-facilitated twinning behaviour

Biocorrosion Evaluation on a Zr-Cu-Ag-Ti Metallic Glass

Science.gov (United States)

Kumar, Shresh; Anwar, Rebin; Ryu, Wookha; Park, E. S.; Vincent, S.

2018-04-01

Metallic glasses are in high demand for fabrication of variety of innovative products, in particular surgical and biomedical tools and devices owing to its excellent biocompatible properties. In the present investigation, a novel Zr39.5Cu50.5Ag4Ti6 metallic glass composition was synthesized using melt spinning technique. Potentiodynamic polarization studies were conducted to investigate bio-corrosion behaviour of Zr39.5Cu50.5Ag4Ti6 metallic glass. The test were conducted in various simulated artificial body conditions such as artificial saliva solution, phosphate-buffered saline solution, artificial blood plasma solution, and Hank’s balanced saline solution. The bio-corrosion results of metallic glass were compared with traditional biomaterials. The study aims to provide bio-compatible properties of Zr39.5Cu50.5Ag4Ti6 metallic glass.

Bifunctional Interface of Au and Cu for Improved CO2 Electroreduction.

Science.gov (United States)

Back, Seoin; Kim, Jun-Hyuk; Kim, Yong-Tae; Jung, Yousung

2016-09-07

Gold is known currently as the most active single-element electrocatalyst for CO2 electroreduction reaction to CO. In this work, we combine Au with a second metal element, Cu, to reduce the amount of precious metal content by increasing the surface-to-mass ratio and to achieve comparable activity to Au-based catalysts. In particular, we demonstrate that the introduction of a Au-Cu bifunctional "interface" is more beneficial than a simple and conventional homogeneous alloying of Au and Cu in stabilizing the key intermediate species, *COOH. The main advantages of the proposed metal-metal bifunctional interfacial catalyst over the bimetallic alloys include that (1) utilization of active materials is improved, and (2) intrinsic properties of metals are less affected in bifunctional catalysts than in alloys, which can then facilitate a rational bifunctional design. These results demonstrate for the first time the importance of metal-metal interfaces and morphology, rather than the simple mixing of the two metals homogeneously, for enhanced catalytic synergies.

Formation and Schottky barrier height of Au contacts to CuInSe2

International Nuclear Information System (INIS)

Nelson, A.J.; Gebhard, S.; Kazmerski, L.L.; Colavita, E.; Engelhardt, M.; Hoechst, H.

1991-01-01

Synchrotron radiation soft x-ray photoemission spectroscopy was used to investigate the development of the electronic structure at the Au/CuInSe 2 interface. Au overlayers were deposited in steps on single-crystal p and n-type CuInSe 2 at ambient temperature. Reflection high-energy electron diffraction analysis before and during growth of the Au overlayers indicated that the Au overlayer was amorphous. Photoemission measurements were acquired after each growth in order to observe changes in the valence band electronic structure as well as changes in the In 4d and Se 3d core lines. The results were used to correlate the interface chemistry with the electronic structure at these interfaces and to directly determine the Au/CuInSe 2 Schottky barrier height

Stepwise synthesis of cubic Au-AgCdS core-shell nanostructures with tunable plasmon resonances and fluorescence.

Science.gov (United States)

Liu, Xiao-Li; Liang, Shan; Nan, Fan; Pan, Yue-Yue; Shi, Jun-Jun; Zhou, Li; Jia, Shuang-Feng; Wang, Jian-Bo; Yu, Xue-Feng; Wang, Qu-Quan

2013-10-21

Cubic Au-AgCdS core-shell nanostructures were synthesized through cation exchange method assisted by tributylphosphine (TBP) as a phase-transfer agent. Among intermediate products, Au-Ag core-shell nanocubes exhibited many high-order plasmon resonance modes related to the special cubic shape, and these plasmon bands red-shifted along with the increasing of particle size. The plasmon band of Au core first red-shifted and broadened at the step of Au-Ag₂S and then blue-shifted and narrowed at the step of Au-AgCdS. Since TBP was very crucial for the efficient conversion from Ag₂S to CdS, we found that both absorption and fluorescence of the final products could be controlled by TBP.

Structure and photoelectrochemistry of silver-copper-indium-diselenide ((AgCu)InSe2) thin film

Science.gov (United States)

Zhang, Lin Rui; Li, Tong; Wang, Hao; Pang, Wei; Chen, Yi Chuan; Song, Xue Mei; Zhang, Yong Zhe; Yan, Hui

2018-02-01

In this work, silver (Ag) precursors with different thicknesses were sputtered on the surfaces of CuIn alloys, and (AgCu)InSe2 (ACIS) films were formed after selenization at 550 °C under nitrogen condition using a rapid thermal process furnace. The structure and electrical properties of the ACIS films were investigated. The result showed that the distribution of Ag+ ion was more uniform with increasing the thickness of Ag precursor, and the surface of the thin-film became more homogeneous and denser. When Ag/Cu ratio ≥0.249, the small grain particles disappeared. The band gap can be rationally controlled by adjusting Ag content. When (Ag + Cu)/In ratio ≥ 1.15, the surface of the ACIS thin-film mainly exhibited n-type semiconductor. Through the photoelectrochemistry measurement, it was observed that the incorporation of Ag+ ions could improve photocurrent by adjusting the band gap. With the Ag precursor thickness increased, the dark current decreased at the more negative potential.

Particle growth mechanisms in Ag-ZrO2 and Au-ZrO2 granular films obtained by pulsed laser deposition

International Nuclear Information System (INIS)

Konstantinovic, Zorica; Muro, Montserrat Garcia del; Varela, Manuel; Batlle, Xavier; Labarta, AmIlcar

2006-01-01

Thin films consisting of Ag and Au nanoparticles embedded in amorphous ZrO 2 matrix were grown by pulsed laser deposition in a wide range of metal volume concentrations in the dielectric regime (0.08 Ag Au c (Ag)∼0.28 and x c (Au)∼0.52)

Enhanced photocatalytic, electrochemical and photoelectrochemical properties of TiO{sub 2} nanotubes arrays modified with Cu, AgCu and Bi nanoparticles obtained via radiolytic reduction

Energy Technology Data Exchange (ETDEWEB)

Nischk, Michał [Department of Chemical Technology, Faculty of Chemistry, Gdansk University of Technology, 11/12 G. Narutowicza 11/12 St., 80-233 Gdansk (Poland); Department of Environmental Technology, Faculty of Chemistry, University of Gdansk, 63 Wita Stwosza St., 80-308 Gdansk (Poland); Mazierski, Paweł [Department of Environmental Technology, Faculty of Chemistry, University of Gdansk, 63 Wita Stwosza St., 80-308 Gdansk (Poland); Wei, Zhishun [Institute for Catalysis, Hokkaido University, N21, W10, 001-0021, Sapporo (Japan); Siuzdak, Katarzyna [Centre for Plasma and Laser Engineering, The Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences, 14 Fiszera St., 80-231 Gdansk (Poland); Kouame, Natalie Amoin [Laboratoire de Chimie Physique, CNRS—UMR 8000,Université Paris-Sud, Université Paris-Saclay, Bâtiment 349, 91405 Orsay (France); Kowalska, Ewa [Institute for Catalysis, Hokkaido University, N21, W10, 001-0021, Sapporo (Japan); Remita, Hynd [Laboratoire de Chimie Physique, CNRS—UMR 8000,Université Paris-Sud, Université Paris-Saclay, Bâtiment 349, 91405 Orsay (France); Zaleska-Medynska, Adriana, E-mail: adriana.zaleska@ug.edu.pl [Department of Environmental Technology, Faculty of Chemistry, University of Gdansk, 63 Wita Stwosza St., 80-308 Gdansk (Poland)

2016-11-30

Highlights: • TiO{sub 2} nanotubes were modified with Cu, AgCu, Bi nanoparticles via gamma radiolysis. • Excessive amount of deposited metal decreased photocatalytic activity. • AgCu-modified samples were more active than Cu-modified (with the same Cu content). • AgCu nanoparticles exist in a core{sub (Ag)}-shell{sub (Cu)} form. • Examined photocatalysts were resistant towards photocorrosion processes. - Abstract: TiO{sub 2} nanotubes arrays (NTs), obtained via electrochemical anodization of Ti foil, were modified with monometallic (Cu, Bi) and bimetallic (AgCu) nanoparticles. Different amounts of metals’ precursors were deposited on the surface of NTs by the spin-coating technique, and the reduction of metals was performed via gamma radiolysis. Surface modification of titania was studied by EDS and XPS analysis. The results show that AgCu nanoparticles exist in a Ag{sub core}-Cu{sub shell} form. Photocatalytic activity was examined under UV irradiation and phenol was used as a model pollutant of water. Over 95% of phenol degradation was achieved after 60 min of irradiation for almost all examined samples, but only slight difference in degradation efficiency (about 3%) between modified and bare NTs was observed. However, the initial phenol degradation rate and TOC removal efficiency was significantly enhanced for the samples modified with 0.31 and 0.63 mol% of Bi as well as for all the samples modified with Cu and AgCu nanoparticles in comparison with bare titania nanotubes. The saturated photocurrent, under the influence of simulated solar light irradiation, for the most active Bi- and AgCu-modified samples, was over two times higher than for pristine NTs. All the examined materials were resistant towards photocorrosion processes that enables their application for long term processes induced by light.

Wetting Behavior of Ternary Au-Ge-X (X = Sb, Sn) Alloys on Cu and Ni

Science.gov (United States)

Jin, S.; Valenza, F.; Novakovic, R.; Leinenbach, C.

2013-06-01

Au-Ge-based alloys are potential substitutes for Pb-rich solders currently used for high-temperature applications. In the present work, the wetting behavior of two Au-Ge-X (X = Sb, Sn) ternary alloys, i.e., Au-15Ge-17Sb and Au-13.7 Ge-15.3Sn (at.%), in contact with Cu and Ni substrates has been investigated. Au-13.7Ge-15.3Sn alloy showed complete wetting on both Cu and Ni substrates. Total spreading of Au-15Ge-17Sb alloy on Cu was also observed, while the final contact angle of this alloy on Ni was about 29°. Pronounced dissolution of Cu substrates into the solder alloys investigated was detected, while the formation of Ni-Ge intermetallic compounds at the interface of both solder/Ni systems suppressed the dissolution of Ni into the solder.

Alloying of Yb-Cu and Yb-Ag utilizing liquid ammonia metal solutions of ytterbium

International Nuclear Information System (INIS)

Imamura, H.; Yoshimura, T.; Sakata, Y.

2003-01-01

In the course of the studies on preparation of novel compounds using the dissolution of Eu or Yb metals in liquid ammonia, the formation of Yb-Cu and Yb-Ag intermetallic films has been found. When Cu or Ag metal powders were placed in a reactor containing a solution of Yb metal in liquid ammonia, the dissolved Yb readily react with the Cu or Ag metal particles to form surface alloy compounds. X-ray diffraction of Yb-Cu showed that upon thermal treatment above 673 K, the Yb metal deposited on the Cu particles reacted together to be transformed into the YbCu 6.5 intermetallic compound. A characteristic endothermic peak at 749 K, due to alloying of Yb-Cu, was observed by the differential scanning calorimeter measurements. By use of the high reactivity of liquid ammonia metal solutions of ytterbium, it was found that the ytterbium intermetallic films were readily formed under mild conditions. Yb-Cu and Yb-Ag exhibited enhanced catalytic activity for the hydrogenation of ethene as a result of alloying

Tuning the shell thickness-dependent plasmonic absorption of Ag coated Au nanocubes: The effect of synthesis temperature

Energy Technology Data Exchange (ETDEWEB)

Zhu, Jian, E-mail: jianzhusummer@163.com; Zhang, Fan; Chen, Bei-Bei; Li, Jian-Jun; Zhao, Jun-Wu, E-mail: nanoptzhao@163.com

2015-09-15

Graphical abstract: Ag coating leads to great enhancement of SPR absorbance of Au nanocubes, and the Ag coating-dependent non-monotonous SPR shift is greater at lower temperature. - Highlights: • Au nanocubes with more uniform shape can be obtained at lower growth temperature. • Ag coating leads to great enhancement of SPR absorption intensity. • The Ag coating dependent non-monotonous SPR shift is greater at lower temperature. - Abstract: The temperature dependent synthesis and plasmonic optical properties of Ag coated Au nanocubes have been investigated experimentally. It has been found that the Au nanocubes with more uniform morphology and higher yield could be obtained by decreasing the growth temperature. Because of the non-spherical symmetry of the particles shape and the plasmon coupling between Au–Ag interface and outer Ag surface, four absorption peaks at most have been observed. As the Ag coating thickness is increased, the absorbance intensity of these plasmon peaks gets intense greatly, and the absorption peak at longest wavelength blue shifts firstly and then red shifts. The non-monotonous plasmonic shift has been attributed to the competition between the increase of Ag composition and the enlargement of the particle size. What's more, the wavelength region of both blue shift and red shift could also be enhanced by decreasing the temperature.

Tuning the shell thickness-dependent plasmonic absorption of Ag coated Au nanocubes: The effect of synthesis temperature

International Nuclear Information System (INIS)

Zhu, Jian; Zhang, Fan; Chen, Bei-Bei; Li, Jian-Jun; Zhao, Jun-Wu

2015-01-01

Graphical abstract: Ag coating leads to great enhancement of SPR absorbance of Au nanocubes, and the Ag coating-dependent non-monotonous SPR shift is greater at lower temperature. - Highlights: • Au nanocubes with more uniform shape can be obtained at lower growth temperature. • Ag coating leads to great enhancement of SPR absorption intensity. • The Ag coating dependent non-monotonous SPR shift is greater at lower temperature. - Abstract: The temperature dependent synthesis and plasmonic optical properties of Ag coated Au nanocubes have been investigated experimentally. It has been found that the Au nanocubes with more uniform morphology and higher yield could be obtained by decreasing the growth temperature. Because of the non-spherical symmetry of the particles shape and the plasmon coupling between Au–Ag interface and outer Ag surface, four absorption peaks at most have been observed. As the Ag coating thickness is increased, the absorbance intensity of these plasmon peaks gets intense greatly, and the absorption peak at longest wavelength blue shifts firstly and then red shifts. The non-monotonous plasmonic shift has been attributed to the competition between the increase of Ag composition and the enlargement of the particle size. What's more, the wavelength region of both blue shift and red shift could also be enhanced by decreasing the temperature

Relationship between Microstructure and Properties of Cu-Cr-Ag-(Ce) Alloy Using Microscopic Investigation.

Science.gov (United States)

Chen, Huiming; Yuan, Dawei; Wu, Shanjiang; Wang, Hang; Xie, Weibin; Yang, Bin

2017-01-01

Microstructure, precipitation hardening response, and mechanical and physical properties of Cu-Cr-Ag alloy and Cu-Cr-Ag-Ce alloy have been investigated using transmission electron microscopy, scanning electron microscope, optical microscope, electrical conductivity analysis, and tensile test. The influence of element Ce on the matrix refinement, impurity removal, and precipitation in the Cu-Cr-Ag alloys has been analyzed. The experimental results show that the strength and electrical conductivity of Ce containing alloys are greater than those of Ce-free alloys after each processing step. Improvement of strength and electrical conductivity of the Cu-Cr-Ag alloy by adding Ce element is attributed to removing oxygen and sulfur from as-cast alloy.

Cellular Energy Allocation to Assess the Impact of Nanomaterials on Soil Invertebrates (Enchytraeids: The Effect of Cu and Ag

Directory of Open Access Journals (Sweden)

Susana I. L. Gomes

2015-06-01

Full Text Available The effects of several copper (Cu and silver (Ag nanomaterials were assessed using the cellular energy allocation (CEA, a methodology used to evaluate the energetic status and which relates with organisms’ overall condition and response to toxic stress. Enchytraeus crypticus (Oligochatea, was exposed to the reproduction effect concentrations EC20/50 of several Cu and Ag materials (CuNO3, Cu-Field, Cu-Nwires and Cu-NPs; AgNO3, Ag NM300K, Ag-NPs Non-coated and Ag-NPs PVP-coated for 7 days (0-3-7d. The parameters measured were the total energy reserves available (protein, carbohydrate and lipid budgets and the energy consumption (Ec integrated to obtain the CEA. Results showed that these parameters allowed a clear discrimination between Cu and Ag, but less clearly within each of the various materials. For Cu there was an increase in Ec and protein budget, while for Ag a decrease was observed. The results corroborate known mechanisms, e.g., with Cu causing an increase in metabolic rate whereas Ag induces mitochondrial damage. The various Cu forms seem to activate different mechanisms with size and shape (e.g., Cu-NPs versus Cu-Nwires, causing clearly different effects. For Ag, results are in line with a slower oxidation rate of Ag-NMs in comparison with Ag-salt and hence delayed effects.

Enhancement of Au-Ag-Te contents in tellurium-bearing ore minerals via bioleaching

Science.gov (United States)

Choi, Nag-Choul; Cho, Kang Hee; Kim, Bong Ju; Lee, Soonjae; Park, Cheon Young

2018-03-01

The purpose of this study was to enhance the content of valuable metals, such as Au, Ag, and Te, in tellurium-bearing minerals via bioleaching. The ore samples composed of invisible Au and Au paragenesis minerals (such as pyrite, chalcopyrite, sphalerite and galena) in combination with tellurium-bearing minerals (hessite, sylvanite and Tellurobismuthite) were studied. Indigenous microbes from mine drainage were isolated and identified as Acidithiobacillus ferrooxidans, which were used in bioleaching after adaption to copper. The effect of the microbial adaption on the bioleaching performance was then compared with the results produced by the non-adaptive process. The microbial adaption enhanced the Au-Ag-Te contents in biological leaching of tellurium-bearing ore minerals. This suggests that bioleaching with adapted microbes can be used both as a pretreatment and in the main recovery processes of valuable metals.

Au@Ag Core-Shell Nanocubes with Finely Tuned and Well-Controlled Sizes, Shell Thicknesses, and Optical Properties

OpenAIRE

Ma, Yanyun; Li, Weiyang; Cho, Eun Chul; Li, Zhiyuan; Yu, Taekyung; Zeng, Jie; Xie, Zhaoxiong; Xia, Younan

2010-01-01

This paper describes a facile method for generating Au@Ag core-shell nanocubes with edge lengths controllable in the range of 13.4 to 50 nm. The synthesis involved the use of single-crystal, spherical Au nanocrystals of 11 nm in size as the seeds in an aqueous system, with ascorbic acid serving as the reductant and cetyltrimethylammonium chloride (CTAC) as the capping agent. The thickness of the Ag shells could be finely tuned from 1.2 to 20 nm by varying the ratio of AgNO3 precursor to Au se...

Onset of Intense Surface Enhanced Raman Scattering and Aggregation in the Au@Ag System

Directory of Open Access Journals (Sweden)

Priya Bhatia

2015-01-01

Full Text Available Gold core/silver shell (Au@Ag nanoparticles of ~37 ± 5 nm diameter generate intense SERS (λEX=785 nm responses in solution when they interact with the SERS labels rhodamine 6G (R6G, 4-mercaptopyridine (MPY, and 4-mercaptobenzoic acid (MBA. Herein the relationship between SERS intensity, aggregation, and adsorption phenomenon isobserved by titrating Au@Ag with the above labels. As the labels adsorb to the Au@Ag, they drive aggregation as evidenced by the creation of NIR extinction peaks, and the magnitude of this NIR extinction (measured at 830 nm correlates very closely to magnitude of the intense SERS signals. The label MBA is an exception since it does not trigger aggregation nor does it result in intense SERS; rather intense SERS is recovered only after MBA coated Au@Ag is aggregated with KCl. An “inner filter” model is introduced and applied to compensate for solution extinction when the exciting laser radiation is significantly attenuated. This model permits a summary of the SERS responses in the form of plots of SERS intensity versus the aggregate absorption at 830 nm, which shows the excellent correlation between intense SERS and LSPR bands extinction.

ECAE-processed Cu-Nb and Cu-Ag nanocomposite wires for pulse magnet applications

International Nuclear Information System (INIS)

Edgecumbe Summers, T.S.; Walsh, R.P.; Pernambuco-Wise, P.

1997-01-01

Cu-Nb and Cu-Ag nanocomposites have recently become of interest to pulse magnet designers because of their unusual combination of high strength with reasonable conductivity. In the as-cast condition, these conductors consist of two phases, one of almost pure Nb (or Ag) and the other almost pure Cu. When these castings are cold worked as in a wire-drawing operation for example, the two phases are drawn into very fine filaments which produce considerable strengthening without an unacceptable decrease in conductivity. Unfortunately, any increase in strength with operations such as wire drawing is accompanied by a reduction in the cross section of the billet, and thus far, no wires with strengths on the order of 1.5 GPa or more have been produced with cross sections large enough to be useful in magnet applications. Equal Channel Angular Extrusion (ECAE) is an innovative technique which allows for the refinement of the as-cast ingot structure without a reduction in the cross sectional dimensions. Samples processed by the ECAE technique prior to wire drawing should be stronger at a given wire diameter than those processed by wire drawing alone. The tensile properties of wire-drawn Cu-18%Nb and Cu-25%Ag both with and without prior ECAE processing were tested and compared at both room temperature and 77K. All samples were found to have resistivities consistent with their strengths, and the strengths of the ECAE-processed wires were significantly higher than their as-cast and drawn counterparts. Therefore, with ECAE processing prior to wire drawing, it appears to be possible to make high-strength conductors with adequately large cross sections for pulse magnets

Antimicrobial activity and biocompatibility of Ag{sup +}- and Cu{sup 2+}-doped biphasic hydroxyapatite/α-tricalcium phosphate obtained from hydrothermally synthesized Ag{sup +}- and Cu{sup 2+}-doped hydroxyapatite

Energy Technology Data Exchange (ETDEWEB)

Radovanović, Željko, E-mail: zradovanovic@tmf.bg.ac.rs [Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade (Serbia); Jokić, Bojan; Veljović, Djordje; Dimitrijević, Suzana [Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade (Serbia); Kojić, Vesna [Oncology Institute of Vojvodina, Institutski put 4, 21204 Sremska Kamenica (Serbia); Petrović, Rada; Janaćković, Djordje [Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade (Serbia)

2014-07-01

Hydroxyapatite (HAp) powders doped with Ag{sup +} or Cu{sup 2+} were synthesized by a hydrothermal method in order to obtain biomaterial with an antimicrobial effect. The synthesis was performed with two contents of dopant (Ag{sup +} or Cu{sup 2+}) by considering both the antimicrobial activities and biocompatibility of the powders. The doped HAp was annealed at 1200 °C for 2 h with the intention of investigating the influence of doping with Ag{sup +} and Cu{sup 2+} on the creation of the biphasic HAp/α-tricalcium phosphate (HAp/α-TCP) and determining the antimicrobial activity and biocompatibility of the obtained biphasic powders. Analyses of all powders, undoped and doped HAp and HAp/α-TCP, were performed by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic absorption spectroscopy (AAS) and energy-dispersive X-ray spectroscopy (EDS). The in vitro antibacterial activities of the powders were evaluated against: Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. All powders showed good antimicrobial activity but generally the powders of doped HAp/α-TCP had more uniform results against all pathogenic microorganisms than the powders of doped HAp. In vitro biocompatibility tests, MTT and DET, were used to evaluate the biocompatibility of Ag{sup +}- and Cu{sup 2+}-doped HAp/α-TCP with MRC-5 human fibroblast cells. These tests confirmed that powders do not have a cytotoxic effect. The HAp/α-TCP powders doped with the lower content of Ag{sup +} and Cu{sup 2+} showed especially good biocompatibility. Antimicrobial and biocompatibility tests recommend the Ag{sup +}- and Cu{sup 2+}-doped HAp/α-TCP as promising material for use in reconstructive surgery of bone.

Photocatalytic performances and activities of Ag-doped CuFe{sub 2}O{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Zhu, Zhengru, E-mail: zhengruzhu@gmail.com [Research Center of Hydrology and Water Source, School of Urban and Environment, Liaoning Normal University, Dalian, 116029 (China); State Key Laboratory of Fine Chemical, Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024 (China); Li, Xinyong; Zhao, Qidong [State Key Laboratory of Fine Chemical, Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024 (China); Li, Yonghua; Sun, Caizhi; Cao, Yongqiang [Research Center of Hydrology and Water Source, School of Urban and Environment, Liaoning Normal University, Dalian, 116029 (China)

2013-08-01

Graphical abstract: - Highlights: • CuFe{sub 2}O{sub 4} nanocrystals were synthesized by a co-precipitation method. • Ag/CuFe{sub 2}O{sub 4} catalyst was prepared by the wetness impregnation strategy. • The structural properties of Ag/CuFe{sub 2}O{sub 4} were investigated by XRD, TEM, DRS, and XPS techniques. • Ag/CuFe{sub 2}O{sub 4} has higher photocatalytic activity. - Abstract: In this work, CuFe{sub 2}O{sub 4} nanoparticles were synthesized by a chemical co-precipitation route. The Ag/CuFe{sub 2}O{sub 4} catalyst was prepared based on the CuFe{sub 2}O{sub 4} nanoparticles by the incipient wetness impregnation strategy, which showed excellent photoelectric property and catalytic activity. The structural properties of these samples were systematically investigated by X-ray powder diffraction (XRD), transmission electronic microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) techniques. The photo-induced charge separation in the samples was demonstrated by surface photovoltage (SPV) measurement. The photocatalytic degradation of 4-CP by the Ag/CuFe{sub 2}O{sub 4} and CuFe{sub 2}O{sub 4} samples were comparatively studied under xenon lamp irradiation. The results indicate that the Ag/CuFe{sub 2}O{sub 4} sample exhibited the higher efficiency for the degradation of 4-CP.

Intermixing, band alignment and charge transport in AgIn5S8/CuI heterojunctions

International Nuclear Information System (INIS)

Konovalov, I.; Makhova, L.; Hesse, R.; Szargan, R.

2005-01-01

Possibilities of creating photovoltaic devices using CuI/AgIn 5 S 8 heterojunctions are considered. Among other properties, preferential formation of polar (111) surfaces makes n-type AgIn 5 S 8 an attractive candidate for absorber layers of top cells in 4-terminal tandem structures. Cu-Ag exchange at the interface with p-type CuI was observed. This intermixing results in an additional component of Ag 3d5 photoelectron line after deposition of CuI, in the Cu (but not I) contamination of the surface after a chemical removal of CuI, and in a photoelectric sensitivity of the junction at energies below the band gaps. Valence band offsets of 0.4 and 0.5 eV (cliff) were found at interfaces with thin film and bulk AgIn 5 S 8 , supporting a conduction mechanism through interface recombination. Pinning conflict at the interface between materials with contradictory doping limitations is likely to promote the intermixing

Enhanced photocatalytic performance of sandwiched ZnO@Ag@Cu2O nanorod films: the distinct role of Ag NPs in the visible light and UV region

International Nuclear Information System (INIS)

Ren, Shoutian; Wang, Yingying; Wang, Benyang; Wang, Qiang; Zhao, Guoliang

2015-01-01

Sandwiched ZnO@Ag@Cu 2 O nanorod films were synthesized by successive electrodeposition, magnetron sputtering and the second electrodeposition. The as-synthesized composites were characterized by x-ray diffraction patterns, field emission scanning electron microscopy, low- and high-resolution transmission electron microscopy and a UV–vis spectrophotometer. Their photocatalytic performance was estimated by the degradation of a methyl orange solution under UV or visible-light irradiation, respectively. In the visible region, due to localized surface plasmon resonance absorption of Ag NPs, ZnO@Ag@Cu 2 O showed a significantly enhanced photocatalytic performance. The enhancement factor of Ag NPs on the catalytic performance of ZnO@Ag@Cu 2 O was estimated as a function of the Cu 2 O deposition time, and the corresponding enhancement mechanism was also evaluated by the monochromatic photocatalytic experiment and discrete dipole approximation simulation. In the UV region, due to the formation of a Schottky junction (e.g. Ag/ZnO, Ag/Cu 2 O), a limited enhanced photocatalytic performance was also realized for ZnO@Ag@Cu 2 O photocatalysts. (paper)

Properties and Microstructures of Sn-Ag-Cu-X Lead-Free Solder Joints in Electronic Packaging

Directory of Open Access Journals (Sweden)

Lei Sun

2015-01-01

Full Text Available SnAgCu solder alloys were considered as one of the most popular lead-free solders because of its good reliability and mechanical properties. However, there are also many problems that need to be solved for the SnAgCu solders, such as high melting point and poor wettability. In order to overcome these shortcomings, and further enhance the properties of SnAgCu solders, many researchers choose to add a series of alloying elements (In, Ti, Fe, Zn, Bi, Ni, Sb, Ga, Al, and rare earth and nanoparticles to the SnAgCu solders. In this paper, the work of SnAgCu lead-free solders containing alloying elements and nanoparticles was reviewed, and the effects of alloying elements and nanoparticles on the melting temperature, wettability, mechanical properties, hardness properties, microstructures, intermetallic compounds, and whiskers were discussed.

Synthesis of Au@Ag core-shell nanocubes containing varying shaped cores and their localized surface plasmon resonances.

Science.gov (United States)

Gong, Jianxiao; Zhou, Fei; Li, Zhiyuan; Tang, Zhiyong

2012-06-19

We have synthesized Au@Ag core-shell nanocubes containing Au cores with varying shapes and sizes through modified seed-mediated methods. Bromide ions are found to be crucial in the epitaxial growth of Ag atoms onto Au cores and in the formation of the shell's cubic shape. The Au@Ag core-shell nanocubes exhibit very abundant and distinct localized surface plasmon resonance (LSPR) properties, which are core-shape and size-dependent. With the help of theoretical calculation, the physical origin and the resonance mode profile of each LSPR peak are identified and studied. The core-shell nanocrystals with varying shaped cores offer a new rich category for LSPR control through the plasmonic coupling effect between core and shell materials.

Application of Direct Current Atmospheric Pressure Glow Microdischarge Generated in Contact with a Flowing Liquid Solution for Synthesis of Au-Ag Core-Shell Nanoparticles.

Science.gov (United States)

Dzimitrowicz, Anna; Jamroz, Piotr; Nyk, Marcin; Pohl, Pawel

2016-04-06

A direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between an Ar nozzle microjet and a flowing liquid was applied to produce Au-Ag core-shell nanoparticles (Au@AgCSNPs) in a continuous flow system. Firstly, operating dc-μAPGD with the flowing solution of the Au(III) ions as the cathode, the Au nanoparticles (AuNPs) core was produced. Next, to produce the core-shell nanostructures, the collected AuNPs solution was immediately mixed with an AgNO₃ solution and passed through the system with the reversed polarity to fabricate the Ag nanoshell on the AuNPs core. The formation of Au@AgCSNPs was confirmed using ultraviolet-visible (UV-Vis) absorbance spectrophotometry, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Three localized surface plasmon resonance absorption bands with wavelengths centered at 372, 546, and 675 nm were observed in the UV-Vis spectrum of Au@AgCSNPs, confirming the reduction of both the Au(III) and Ag(I) ions. The right configuration of metals in Au@AgCSNPs was evidenced by TEM. The Au core diameter was 10.2 ± 2.0 nm, while the thickness of the Ag nanoshell was 5.8 ± 1.8 nm. The elemental composition of the bimetallic nanoparticles was also confirmed by EDS. It is possible to obtain 90 mL of a solution containing Au@AgCSNPs per hour using the applied microdischarge system.

Cross-sections of 197Au(n,α)198Au and 63Cu(n,α)64Cu induced by 252Cf neutrons

International Nuclear Information System (INIS)

Mandal, Ranjita; Sengupta, D.; Roy, Malobika; Naik, Mamta; Bhoraskar, V.N.

2014-01-01

Analytical work, employing nuclear techniques, is normally carried out through (n,α) reaction because of the availability of neutrons either from reactors or laboratory sources such as Sb-Be, Am-Be, Ra-Be, Po-Be, 252 Cf, etc. The laboratory neutron sources are though portable and adaptable to a particular experimental arrangement, suffer from the disadvantage of slow neutron yield (except 252 Cf). In this set up since the neutrons available are monoenergetic, it was thought appropriate to initiate a program to measure cross-sections of a few nuclear reactions which have practical applications. Earlier studies on cross-section measurement of the reaction 197 Au(n,α) 198 Au and 63 Cu(n,α) 64 Cu has been carried out using different sources, monitors and techniques

Transparent Conducting Film Fabricated by Metal Mesh Method with Ag and Cu@Ag Mixture Nanoparticle Pastes

Directory of Open Access Journals (Sweden)

Hyun Min Nam

2017-05-01

Full Text Available Transparent conducting electrode film is highly desirable for application in touch screen panels (TSPs, flexible and wearable displays, sensors, and actuators. A sputtered film of indium tin oxide (ITO shows high transmittance (90% at low sheet resistance (50 Ω/cm2. However, ITO films lack mechanical flexibility, especially under bending stress, and have limitation in application to large-area TSPs (over 15 inches due to the trade-off in high transmittance and low sheet resistance properties. One promising solution is to use metal mesh-type transparent conducting film, especially for touch panel application. In this work, we investigated such inter-related issues as UV imprinting process to make a trench layer pattern, the synthesis of core-shell-type Ag and Cu@Ag composite nanoparticles and their paste formulation, the filling of Ag and Cu@Ag mixture nanoparticle paste to the trench layer, and touch panel fabrication processes.

Characterizing the economic value of an epithermal Au-Ag ore with Laser Induced Breakdown Spectroscopy (LIBS)

NARCIS (Netherlands)

Dalm, M.; Buxton, M.W.N.

2016-01-01

LIBS was applied to 19 Au-Ag ore samples to investigate if this technique can be used to distinguish between economic and sub-economic ore either by direct detection of these elements or by using other elements as indicators. However, the Au and Ag grades of the samples are below the detection limit

Amorphous Cu-Ag films with high stability

International Nuclear Information System (INIS)

Reda, I.M.; Hafner, J.; Pongratz, P.; Wagendristel, A.; Bangert, H.; Bhat, P.K.

1982-06-01

Films produced by quenching Cu-Ag vapour onto cooled substrates at liquid nitrogen temperature have been investigated using electron microscopy, electron diffraction and electrical resistivity measurements. In the composition range from 30 to 70 at% Cu the as quenched films are amorphous, and within the range of 35 to 63 at% Cu the amorphous phase is stable above room temperature with a maximum crystallization temperature Tsub(c)=381 K at 47.5 at% Cu. Crystallization results in the formation of a supersaturated fcc solid solution which decomposes in a second crystallization step. The effect of deposition rate, film thickness, temperature and surface of the substrate, and most importantly of the composition on the transition temperatures has been investigated. A comparative study of the formation of amorphous phases in a wide variety of Cu-based alloys is presented. (author)

First-principles study of Cu adsorption on vacancy-defected/Au-doped graphene

Science.gov (United States)

Liu, Yang; An, Libao; Gong, Liang

2018-04-01

To enhance the interaction between Cu and graphene in graphene reinforced Cu matrix composites, the first principles calculation was carried out to study the adsorption of Cu atoms on graphene. P-type doping and n-type doping were formed, respectively, on vacancy-defected and Au-doped graphene based on band structure analysis, and this was verified by subsequent investigation on density of states. A computation on charge transfer confirmed that p-type doping could promote the electron transport between Cu and graphene, while n-type doping would prevent it. In addition, adsorption energy and Mulliken population analysis revealed that both vacancy defects and Au doping could improve the stability of the Cu-graphene system. The research conducted in this paper provides useful guidance for the preparation of Cu/graphene composites.

Group 1B organometallic chemistry XXIX. Synthetic and structural aspects of polynuclear arylcopperlithium compounds Ar4Cu2Li2 ('arylcuprates') and interaggregate exchange phenomena in Ar4Cu4/Ar4Li4/Ar4Cu2Li2 systems

NARCIS (Netherlands)

Koten, G. van; Noltes, J.G.

1979-01-01

The thermally stable arylmetal-IB-lithium compounds (2-Me{2}NCHZC{6}H{4}){4}M{2}Li{2} (M = Cu, Ag or Au; Z = H or Me) and (2-Me{2}NC{6}H{4}){4}M{2}Li{2} have been prepared by a 21 molar reaction of the aryllithium compounds with the corresponding metal-IB halide (Cu or Ag) or metal-lB halide

Interdiffusion and grain-boundary migration in Au-Cu bilayers during ion-irradiation

International Nuclear Information System (INIS)

Alexander, D.E.; Rehn, L.E.; Baldo, P.M.

1991-11-01

Ion irradiation and annealing experiments have been conducted on Au/Cu bilayer films to evaluate the effect of irradiation on diffusion-induced grain boundary migration (DIGM). The Au films were prepared with a large-grained microstructure with grain boundaries perpendicular to the film surface and extending through the film thickness. Irradiations were conducted with 1.5 MeV Kr at 228 degree C. Rutherford backscattering spectrometry of the samples revealed that interdiffusion was substantially enhanced in the irradiated area relative to the unirradiated area. Both irradiated and annealed-only areas were characterized by a nearly uniform composition of 14 at.% and 7 at.% Cu respectively through the entire thickness of the underlying Au film. Small probe X-ray energy dispersive spectroscopy showed significant lateral compositional homogeneities in both irradiated and annealed areas. These two results are consistent with previous observations of DIGM in the Au/Cu system, suggesting that this previously unexamined mechanism contributes to ion beam mixing

Investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al alloy with Ag and Mn additions

International Nuclear Information System (INIS)

Silva, R.A.G.; Paganotti, A.; Gama, S.; Adorno, A.T.; Carvalho, T.M.; Santos, C.M.A.

2013-01-01

The investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al, Cu-11%Al-3%Ag, Cu-11%Al-10%Mn and Cu-11%Al-10%Mn-3%Ag alloys was made using microhardness measurements, differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, energy dispersion X-ray spectroscopy and magnetic moment change with applied field measurement. The results indicated that the Mn addition changes the phase stability range, the microhardness values and makes undetectable the eutectoid reaction in annealed Cu-11%Al and Cu-11%Al-3%Ag alloys while the presence of Ag does not modify the phase transformation sequence neither microhardness values of the annealed Cu-11%Al and Cu-11%Al-10%Mn alloys, but it increases the magnetic moment of this latter at about 2.7 times and decreases the rates of eutectoid and peritectoid reactions of the former. - Highlights: ► The microstructure of Cu-Al alloy is modified in the Ag presence. ► (α + γ) phase is stabilized down to room temperature when Ag is added to Cu-Al alloy. ► Ag-rich phase modifies the magnetic characteristics of Cu–Al–Mn alloy.

Focused-ion-beam-fabricated Au nanorods coupled with Ag nanoparticles used as surface-enhanced Raman scattering-active substrate for analyzing trace melamine constituents in solution

International Nuclear Information System (INIS)

Sivashanmugan, Kundan; Liao, Jiunn-Der; Liu, Bernard Haochih; Yao, Chih-Kai

2013-01-01

Graphical abstract: -- Highlights: •Well-ordered Au-nanorod array with a controlled tip ring diameter (Au N Rs d ) is made by focused ion beam. •Au N Rs d coupled with Ag nanoparticles (Ag NPs/Au N Rs d ) is competent to sense target molecules in a solution. •Ag NPs/Au N Rs d SERS active substrate can detect a single molecule of crystal violet. •Ag NPs/Au N Rs d as a SERS-active substrate can distinguish melamine contaminants at low concentrations (e.g., 10 −12 M). -- Abstract: A well-ordered Au-nanorod array with a controlled tip ring diameter (Au N Rs d ) was fabricated using the focused ion beam method. Au N Rs d was then coupled with Ag nanoparticles (Ag NPs) to bridge the gaps among Au nanorods. The effect of surface-enhanced Raman scattering (SERS) on Au N Rs d and Ag NPs/Au N Rs d was particularly verified using crystal violet (CV) as the molecular probe. Raman intensity obtained from a characteristic peak of CV on Au N Rs d was estimated by an enhancement factor of ≈10 7 in magnitude, which increased ≈10 12 in magnitude for that on Ag NPs/Au N Rs d . A highly SERS-active Ag NPs/Au N Rs d was furthermore applied for the detection of melamine (MEL) at very low concentrations. Raman-active peaks of MEL (10 −3 to 10 −12 M) in water or milk solution upon Au N Rs d or Ag NPs/Au N Rs d were well distinguished. The peaks at 680 and 702 cm −1 for MEL molecules were found suitable to be used as the index for sensing low-concentration MEL in a varied solution, while that at 1051 cm −1 was practical to interpret MEL molecules in water or milk solution bonded with Au (i.e., Au N Rs d ) or Ag (i.e., Ag NPs/Au N Rs d ) surface. At the interface of Ag NPs/Au N Rs d and MEL molecules in milk solution, a laser-induced electromagnetic field or hotspot effect was produced and competent to sense low-concentration MEL molecules interacting with Ag and Au surfaces. Accordingly, Ag NPs/Au N Rs d is very promising to be used as a fast and sensitive tool for

A new dental powder from nanocrystalline melt-spun Ag-Sn-Cu alloy ribbons

International Nuclear Information System (INIS)

Do-Minh, N.; Le-Thi, C.; Nguyen-Anh, S.

2003-01-01

A new non-gamma-two dental powder has been developed from nanocrystalline melt-spun Ag-Sn-Cu alloy ribbons. The amalgam made from this powder exhibits excellent properties for dental filling. The nanocrystalline microstructure was found for the first time in as-spun and heat treated Ag(27-28)Sn(9-32) Cu alloy ribbons, using X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy. As-spun ribbons exhibited a multi-phase microstructure with preferred existence of β (Ag 4 Sn) phase formed during rapid solidification (RS) due to supersaturating of copper (Cu) atoms and homogenous nanostructure with subgrain size of about (40-50) nm, which seems to be developed during RS process and can be caused by eutectic reaction of the Ag 3 Sn/Ag 4 Sn-Cu 3 Sn system. In heat treated ribbons the clustering of Cu atoms was always favored and stable in an ageing temperature and time interval determined by Cu content. The heat treatment led to essential changes of subgrain morphology, resulted in the appearance of large-angle boundaries with fine Cu 3 Sn precipitates and forming typical recrystallization twins. Such a microstructure variation in melt-spun ribbons could eventually yield enhanced technological, clinical and physical properties of the dental products, controlled by the ADA Specification N deg 1 and reported before. Thus, using the rapid solidification technique a new non-gamma-two dental material of high quality, nanocrystalline ribbon powder, can be produced. Copyright (2003) AD-TECH - International Foundation for the Advancement of Technology Ltd

Flexible nonvolatile memory devices based on Au/PMMA nanocomposites deposited on PEDOT:PSS/Ag nanowire hybrid electrodes

International Nuclear Information System (INIS)

Sung, Sihyun; Kim, Tae Whan

2017-01-01

Highlights: • Flexible nonvolatile memory (NVM) devices fabricated utilizing Au nanoparticles (AuNPs) embedded in a PMMA layer were fabricated. • The insertion of the PEDOT:PSS layer enhanced the surface uniformity of the AgNW bottom electrode, resulting in improved device performances. • Current-voltage curves for the Al/PMMA:AuNP/PEDOT:PSS/AgNW/PET devices showed clockwise current hysteresis behaviors. • ON/OFF ratio of 1 × 10 3 was maintained for retention times longer than 1 × 10 4 s. • Memory characteristics of the NVM devices before and after bending were similar. - Abstract: Flexible nonvolatile memory (NVM) devices fabricated utilizing Au nanoparticles (AuNPs) embedded in a poly(methylmethacrylate) (PMMA) layer were fabricated on a silver nanowire (AgNW) or a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/AgNW coated on poly(ethylene terephthalate) (PET) substrates. The transmittance and the sheet resistance of the PEDOT:PSS/AgNW hybrid layer were approximately 89% and 50 Ω/sq, respectively, which were comparable to the values for commercial indium-tin-oxide (ITO) electrodes. Current-voltage curves for the Al/PMMA:AuNP/PEDOT:PSS/AgNW/PET devices at 300 K showed clockwise current hysteresis behaviors due to the existence of the AuNPs. The endurance number of ON/OFF switching for the NVM devices was above 30 cycles. An ON/OFF ratio of 1 × 10 3 was maintained for retention times longer than 1 × 10 4 s. The maximum memory margins of the NVM devices before and after bending were approximately 3.4 × 10 3 and 1.4 × 10 3 , respectively. The retention times of the devices before and after bending remained same 1 × 10 4 s. The memory margin and the stability of flexible NVMs fabricated on AgNW electrodes were enhanced due to the embedded PEDOT:PSS buffer layer.

Flexible nonvolatile memory devices based on Au/PMMA nanocomposites deposited on PEDOT:PSS/Ag nanowire hybrid electrodes

Energy Technology Data Exchange (ETDEWEB)

Sung, Sihyun; Kim, Tae Whan, E-mail: twk@hanyang.ac.kr

2017-07-31

Highlights: • Flexible nonvolatile memory (NVM) devices fabricated utilizing Au nanoparticles (AuNPs) embedded in a PMMA layer were fabricated. • The insertion of the PEDOT:PSS layer enhanced the surface uniformity of the AgNW bottom electrode, resulting in improved device performances. • Current-voltage curves for the Al/PMMA:AuNP/PEDOT:PSS/AgNW/PET devices showed clockwise current hysteresis behaviors. • ON/OFF ratio of 1 × 10{sup 3} was maintained for retention times longer than 1 × 10{sup 4} s. • Memory characteristics of the NVM devices before and after bending were similar. - Abstract: Flexible nonvolatile memory (NVM) devices fabricated utilizing Au nanoparticles (AuNPs) embedded in a poly(methylmethacrylate) (PMMA) layer were fabricated on a silver nanowire (AgNW) or a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/AgNW coated on poly(ethylene terephthalate) (PET) substrates. The transmittance and the sheet resistance of the PEDOT:PSS/AgNW hybrid layer were approximately 89% and 50 Ω/sq, respectively, which were comparable to the values for commercial indium-tin-oxide (ITO) electrodes. Current-voltage curves for the Al/PMMA:AuNP/PEDOT:PSS/AgNW/PET devices at 300 K showed clockwise current hysteresis behaviors due to the existence of the AuNPs. The endurance number of ON/OFF switching for the NVM devices was above 30 cycles. An ON/OFF ratio of 1 × 10{sup 3} was maintained for retention times longer than 1 × 10{sup 4} s. The maximum memory margins of the NVM devices before and after bending were approximately 3.4 × 10{sup 3} and 1.4 × 10{sup 3}, respectively. The retention times of the devices before and after bending remained same 1 × 10{sup 4} s. The memory margin and the stability of flexible NVMs fabricated on AgNW electrodes were enhanced due to the embedded PEDOT:PSS buffer layer.

Enhancement in electrical conductivity of pastes containing submicron Ag-coated Cu filler with palmitic acid surface modification

Science.gov (United States)

Choi, Eun Byeol; Lee, Jong-Hyun

2017-09-01

The fabrication and applied use of submicron Ag-coated Cu (Cu@Ag) particles as a filler material for epoxy-based conductive pastes having the advantages of a lower material cost and antioxidation behavior were studied. Submicron Cu@Ag particles were successfully prepared and surface-modified using palmitic acid. Diffuse reflectance infrared Fourier transform spectroscopy and thermogravimetric differential scanning calorimetry results indicated the formation of an organic layer by the chemical interaction between the Cu@Ag surface and palmitic acid and the survival of the organic layer after treatment at 160 °C for 3 h in air. The printed pastes containing both commercial micron Cu@Ag flakes and the fabricated submicron Cu@Ag particles showed a greatly reduced electrical resistivity (4.68 × 10-4 Ω cm) after surface modification compared to an initial value of 1.85 × 10-3 Ω cm when cured.

Adsorption Behavior of TBPS in the Process of Cu Electrodeposition on an Au Film.

Science.gov (United States)

Chen, Liang-Huei; Liu, Yung-Fang; Krug, Klaus; Lee, Yuh-Lang

2018-05-15

The adsorption behavior of an Cu electroplating additive, 3,3 thiobis-(1-propanesulfonic acid sodium salt) (TBPS) in a process of Cu deposition onto a single crystalline Au(111) surface is studied by an in-situ Surface-Enhanced Infrared Absorption Spectroscopy (SEIRAS). The SEIRAS spectra of the TBPS adlayer on a Cu film is investigated first and compared to that on an Au film. These results are utilized to evaluate the characteristics of TBPS adlayer on the electrode surface during the Cu deposition and stripping processes. The results show that the SEIRAS spectra of TBPS adsorbed on the Cu film resembles closely to that on the Au film, and the most pronounced peaks are symmetric S-O (ss-SO) and asymmetric S-O (as-SO) stretching modes. However, the as-SO band is sharper with a higher intensity on the Cu film. Since the ss-SO and as-SO peaks correspond to the molecular with upright and lie-down orientations, respectively, it implies that the TBPS molecules have higher ratio of lie-down orientation on the Cu film. In the Cu electrodeposition process, the cyclic voltammetry (CV) result shows that the presence of the TBPS in the HClO 4 solution can decrease the inhibition effect of HClO 4 to the Cu deposition. For the spectra measured at various potential during cathodic and anodic sweeping, an obvious change of the spectra occurs at ca. 0.6 V, the initiation of Cu underpotential deposition (Cu-UPD). For potentials higher and lower than 0.6 V, the spectra are similar, respectively, to those measured for the Au and Cu films. This result indicates that the TBPS molecules originally adsorbing on the Au film transfer to the surface of deposited Cu layer. This inference is also confirmed by the variation in wavenumber and peak intensity of ss-SO and as-SO peaks during the potential sweeping.

Characterization of Binary Ag-Cu Ion Mixtures in Zeolites: Their Reduction Products and Stability to Air Oxidation

International Nuclear Information System (INIS)

Fiddy, Steven; Petranovskii, Vitalii; Ogden, Steve; Iznaga, Inocente Rodriguez

2007-01-01

A series of Ag+-Cu2+ binary mixtures with different Ag/Cu ratios were supported on mordenite with different Si/Al ratios and were subsequently reduced under hydrogen in the temperature range 323K - 473K. Ag and Cu K-edge X-ray Absorption Spectroscopy (XAS) was conducted on these systems in-situ to monitor the reduction species formed and the kinetics of their reduction. In-situ XANES clearly demonstrates that the formation of silver particles is severely impeded by the addition of copper and that the copper is converted from Cu(II) to Cu(I) during reduction and completely reverts back to Cu(II) during cooling. There are no indications at any stage of the formation of bimetallic Ag-Cu clusters. Interestingly, the Ag/Cu ratio appears to have no influence of the reduction kinetics and reduction products formed with only the highest Si/Al ratio (MR = 128) investigated during this study having an influence on the reduction and stability to air oxidation

c-T phase diagram and Landau free energies of (AgAu)55 nanoalloy via neural-network molecular dynamic simulations.

Science.gov (United States)

Chiriki, Siva; Jindal, Shweta; Bulusu, Satya S

2017-10-21

For understanding the structure, dynamics, and thermal stability of (AgAu) 55 nanoalloys, knowledge of the composition-temperature (c-T) phase diagram is essential due to the explicit dependence of properties on composition and temperature. Experimentally, generating the phase diagrams is very challenging, and therefore theoretical insight is necessary. We use an artificial neural network potential for (AgAu) 55 nanoalloys. Predicted global minimum structures for pure gold and gold rich compositions are lower in energy compared to previous reports by density functional theory. The present work based on c-T phase diagram, surface area, surface charge, probability of isomers, and Landau free energies supports the enhancement of catalytic property of Ag-Au nanoalloys by incorporation of Ag up to 24% by composition in Au nanoparticles as found experimentally. The phase diagram shows that there is a coexistence temperature range of 70 K for Ag 28 Au 27 compared to all other compositions. We propose the power spectrum coefficients derived from spherical harmonics as an order parameter to calculate Landau free energies.

Self-assembled monolayers of bimetallic Au/Ag nanospheres with superior surface-enhanced Raman scattering activity for ultra-sensitive triphenylmethane dyes detection.

Science.gov (United States)

Tian, Yue; Zhang, Hua; Xu, Linlin; Chen, Ming; Chen, Feng

2018-02-15

The bimetallic Au/Ag self-assembled monolayers (SAMs) were constructed by using mono-dispersed Au/Ag nanospheres (Ag: 4.07%-34.53%) via evaporation-based assembly strategy. The composition-dependent surface-enhanced Raman scattering (SERS) spectroscopy revealed that the Au/Ag (Ag: 16.83%) SAMs provide maximized activity for triphenylmethane dyes detection. With the inter-metallic synergy, the optimized SAMs enable the Raman intensity of crystal violet molecules to be about 223 times higher than that of monometallic Au SAMs. Moreover, the SERS signals with excellent uniformity (<5% variation) are sensitive down to 10 -13   M concentrations because of the optimal matching between bimetallic plasmon resonance and the incident laser wavelength.

Ag-Cu nanoalloyed film as a high-performance cathode electrocatalytic material for zinc-air battery

OpenAIRE

Lei, Yimin; Chen, Fuyi; Jin, Yachao; Liu, Zongwen

2015-01-01

A novel Ag50Cu50 film electrocatalyst for oxygen reduction reaction (ORR) was prepared by pulsed laser deposition (PLD) method. The electrocatalyst actually is Ag-Cu alloyed nanoparticles embedded in amorphous Cu film, based on transmission electron microscopy (TEM) characterization. The rotating disk electrode (RDE) measurements provide evidence that the ORR proceed via a four-electron pathway on the electrocatalysts in alkaline solution. And it is much more efficient than pure Ag catalyst. ...

Preparation of Au and Ag nanoparticles using Artemisia annua and their in vitro antibacterial and tyrosinase inhibitory activities

Energy Technology Data Exchange (ETDEWEB)

Basavegowda, Nagaraj; Idhayadhulla, Akber; Lee, Yong Rok, E-mail: yrlee@yu.ac.kr

2014-10-01

This work describes a plant-mediated approach to the preparation of metal nanoparticles using leaf extract of Artemisia annua (A. annua), an ethno-medicinal plant widely found in Asia, which was used as reducing and stabilizing agent. A. annua is used in traditional Chinese medicine to alleviate fever. Au and Ag nanoparticles were prepared using a one-step aqueous method at room temperature without any toxic chemicals. The formation of Au and Ag nanoparticles was monitored by UV–vis spectroscopy. Synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). TEM analysis of Au nanoparticles showed that they had triangular and spherical shapes with sizes ranging from 15 to 40 nm. The silver nanoparticles were predominantly spherical and uniformly sized (30–50 nm). The Au and Ag nanoparticles produced showed significant tyrosinase inhibitory and antibacterial effects. These results suggest that the synthesized nanoparticles provide good alternatives in varied medical and industrial applications. - Highlights: • Au and Ag nanoparticles were synthesized using Artemisia annua leaf aqueous extract. • Nanoparticles were characterized by UV–vis spectroscopy, FT-IR, TEM, EDX, XRD, and TGA. • Au and Ag nanoparticles were of size 25 and 30 nm respectively, in spherical forms. • Nanoparticles showed significant tyrosinase inhibitory and antibacterial activities.

Preparation of Au and Ag nanoparticles using Artemisia annua and their in vitro antibacterial and tyrosinase inhibitory activities

International Nuclear Information System (INIS)

Basavegowda, Nagaraj; Idhayadhulla, Akber; Lee, Yong Rok

2014-01-01

This work describes a plant-mediated approach to the preparation of metal nanoparticles using leaf extract of Artemisia annua (A. annua), an ethno-medicinal plant widely found in Asia, which was used as reducing and stabilizing agent. A. annua is used in traditional Chinese medicine to alleviate fever. Au and Ag nanoparticles were prepared using a one-step aqueous method at room temperature without any toxic chemicals. The formation of Au and Ag nanoparticles was monitored by UV–vis spectroscopy. Synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). TEM analysis of Au nanoparticles showed that they had triangular and spherical shapes with sizes ranging from 15 to 40 nm. The silver nanoparticles were predominantly spherical and uniformly sized (30–50 nm). The Au and Ag nanoparticles produced showed significant tyrosinase inhibitory and antibacterial effects. These results suggest that the synthesized nanoparticles provide good alternatives in varied medical and industrial applications. - Highlights: • Au and Ag nanoparticles were synthesized using Artemisia annua leaf aqueous extract. • Nanoparticles were characterized by UV–vis spectroscopy, FT-IR, TEM, EDX, XRD, and TGA. • Au and Ag nanoparticles were of size 25 and 30 nm respectively, in spherical forms. • Nanoparticles showed significant tyrosinase inhibitory and antibacterial activities

Focused-ion-beam-fabricated Au nanorods coupled with Ag nanoparticles used as surface-enhanced Raman scattering-active substrate for analyzing trace melamine constituents in solution

Energy Technology Data Exchange (ETDEWEB)

Sivashanmugan, Kundan [Department of Materials Science and Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Liao, Jiunn-Der, E-mail: jdliao@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Liu, Bernard Haochih; Yao, Chih-Kai [Department of Materials Science and Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China)

2013-10-24

Graphical abstract: -- Highlights: •Well-ordered Au-nanorod array with a controlled tip ring diameter (Au{sub N}Rs{sub d}) is made by focused ion beam. •Au{sub N}Rs{sub d} coupled with Ag nanoparticles (Ag NPs/Au{sub N}Rs{sub d}) is competent to sense target molecules in a solution. •Ag NPs/Au{sub N}Rs{sub d} SERS active substrate can detect a single molecule of crystal violet. •Ag NPs/Au{sub N}Rs{sub d} as a SERS-active substrate can distinguish melamine contaminants at low concentrations (e.g., 10{sup −12} M). -- Abstract: A well-ordered Au-nanorod array with a controlled tip ring diameter (Au{sub N}Rs{sub d}) was fabricated using the focused ion beam method. Au{sub N}Rs{sub d} was then coupled with Ag nanoparticles (Ag NPs) to bridge the gaps among Au nanorods. The effect of surface-enhanced Raman scattering (SERS) on Au{sub N}Rs{sub d} and Ag NPs/Au{sub N}Rs{sub d} was particularly verified using crystal violet (CV) as the molecular probe. Raman intensity obtained from a characteristic peak of CV on Au{sub N}Rs{sub d} was estimated by an enhancement factor of ≈10{sup 7} in magnitude, which increased ≈10{sup 12} in magnitude for that on Ag NPs/Au{sub N}Rs{sub d}. A highly SERS-active Ag NPs/Au{sub N}Rs{sub d} was furthermore applied for the detection of melamine (MEL) at very low concentrations. Raman-active peaks of MEL (10{sup −3} to 10{sup −12} M) in water or milk solution upon Au{sub N}Rs{sub d} or Ag NPs/Au{sub N}Rs{sub d} were well distinguished. The peaks at 680 and 702 cm{sup −1} for MEL molecules were found suitable to be used as the index for sensing low-concentration MEL in a varied solution, while that at 1051 cm{sup −1} was practical to interpret MEL molecules in water or milk solution bonded with Au (i.e., Au{sub N}Rs{sub d}) or Ag (i.e., Ag NPs/Au{sub N}Rs{sub d}) surface. At the interface of Ag NPs/Au{sub N}Rs{sub d} and MEL molecules in milk solution, a laser-induced electromagnetic field or hotspot effect was produced and

Synthesis of unidirectional structures of SiO2-Ag using Au nanoparticles as nucleation centers

International Nuclear Information System (INIS)

Villa S, G.; Mendoza A, D.; Gutierrez W, C.; Perez H, R.

2008-01-01

This paper reports a method to synthesize Ag unidirectional structures covered with SiO 2 by sol-gel technique using Au nanoparticles as nucleation centers of the unidirectional structures. In the first phase unidirectional structures of SiO 2 -Ag CI are obtained by sol-gel, using TEOS as a precursor of metallic structures (Ag) and the incorporation of Au nanoparticles as nucleation centers for growth of unidirectional structures. In the second stage, one-way systems are subjected to thermal treatment in H 2 atmosphere for obtain AG 0 particles through mechanisms that diffusion and coalescence of silver to form structures that have a thin cover of SiO 2 . Analysis by scanning electron microscopy, transmission and atomic force microscopy allowed to determine the chemical composition and microstructural properties of unidirectional systems SiO 2 -Ag. (Author)

Impact of ambient environment on the electronic structure of CuPc/Au sample

Science.gov (United States)

Sinha, Sumona; Mukherjee, M.

2018-02-01

The performances of organic devices are crucially connected with their stability in the ambient environment. The impact of 24 h. Ambient environment exposure to the electronic structures of about 12 nm thick CuPc thin film on clean Au substrate have been studied employing UV photoemission spectroscopy technique. X-ray photoemission spectroscopy (XPS) was used to find out the origin of the change of the electronic structures in the sample with the exposure. The XPS study suggests that the oxidation occurs at the CuPc thin film. Due to the adsorption of oxygen in the CuPc film from the ambient air, charge carriers are formed within the CuPc film. Moreover, the XPS results imply that the CuPc film is sufficiently thinner for diffusing oxygen molecules through it and gets physically absorbed on Au substrate during the ambient exposure. Consequently, the hole injection barrier height of pristine CuPc film, grown on Au substrate, is reduced by about 0.50 eV and work-function of the pristine CuPc sample is enhanced by around 0.25 eV in the exposure. The findings will help to understand the mechanism that governs the degradation of performance of CuPc based devices in ambient environment.

Controlled preparation of M(Ag, Au)/TiO2 through sulfydryl-assisted method for enhanced photocatalysis

Science.gov (United States)

Xia, Hongbo; Wu, Suli; Bi, Jiajie; Zhang, Shufen

2017-11-01

Here a simple and effective method was explored to fabricate M/TiO2 (M = Ag, Au) composites, which required neither pre-treatment of TiO2 nor any additives as reducing agent. Using amorphous TiO2 spheres functionalized with SH groups as starting materials, the noble metallic ions (Ag, Au) can be adsorbed by TiO2 due to their special affinity with SH groups, which is beneficial to the uniform dispersion of metallic ions on the surface of TiO2. Then the adsorbed ions were reduced to form noble metal nanoparticles by heating process (95 °C) directly without additive as reduction agent. Meanwhile, the amorphous TiO2 was transformed into anatase phase during the heating process. Thus, the transformation of TiO2 along with the reduction of noble metallic ions (Ag, Au) was simultaneously carried out by heating. The XRD patterns proved the formation of anatase TiO2 after heating. The characterizations of XPS and TEM proved the formation of Ag and Au nanoparticles on the surface of TiO2. The element mapping indicated that Ag nanoparticles are dispersed uniformly on the surface of TiO2. The photocatalytic activity of the composites has been investigated by the degradation of methyl orange under visible light irradiation. The results showed that when Ag/TiO2 (2.8 wt%) was used as photocatalyst, about 98% of the MO molecules were degraded in 70 min.

Biogenic synthesis of Ag-Au-In decorated on rGO nanosheet and its antioxidant and biological activities

Science.gov (United States)

Hazarika, Moushumi; Sonowal, Shashanka; Saikia, Indranirekha; Boruah, Purna K.; Das, Manash R.; Tamuly, Chandan

2017-09-01

Au-Ag-In-rGO nanocomposite was synthesized using fruit extract of Zanthoxylum rhetsa which is an eco-friendly, simple and green method. It was characterized by UV-visible, FT-IR, XRD, XPS, EDX, TEM technique. The antioxidant capacity of the nanocomposite was evaluated in presence of AgNO3, HAuCl4 and InCl3 solution respectively at 25 °C. The results showed significant antioxidant activity in presence of 1  ×  10-5 mM AgNO3 solution. The antibacterial activity of Au-Ag-In-rGO nanoparticles was carried out against the gram  -ve bacteria Pseudomonas aeruginosa, Escherichia coli and gram  +ve bacteria Staphylococcus aureus and Bacillus cereus. The bacterial growth kinetics was studied. The bacterial strain E. coli and S. aureus showed complete inhibition at concentration 100 µg ml-1. The activity is more effective in case of Au-Ag-In-rGO compared to GO.

CuO and Ag2O effect on electrical properties of barium vanadate glasses

International Nuclear Information System (INIS)

Bogomolova, L.D.; Glasova, M.N.; Kalygina, V.M.; Spasibkina, S.N.; Khorikov, A.A.

1987-01-01

Effect of CuO on barium vanadate glass (BVG) conductivity on direct and alternating currents in the frequency range (10 2 -10 4 )Hz has been studied. Effect of Ag 2 O has been also studied for comparison, as Ag and Cu have idendical structure of external electron shells (d 10 , S 1 ). CuO introduction to binary barium vanadate glasses as a modificator results in the conductivity improvement on direct and alternating currents conditioned with reducing activation energy of small radius polaron jump, apparently, owing to exchange (ferromagnetic) interaction between V(IV) and Cu(II). Jump activation energy in barium vanadate glasses with Ag 2 O increases and conductivity drops due to the distance increase between vanadium atoms

Galvanic replacement-free deposition of Au on Ag for core-shell nanocubes with enhanced chemical stability and SERS activity.

Science.gov (United States)

Yang, Yin; Liu, Jingyue; Fu, Zheng-Wen; Qin, Dong

2014-06-11

We report a robust synthesis of Ag@Au core-shell nanocubes by directly depositing Au atoms on the surfaces of Ag nanocubes as conformal, ultrathin shells. Our success relies on the introduction of a strong reducing agent to compete with and thereby block the galvanic replacement between Ag and HAuCl4. An ultrathin Au shell of 0.6 nm thick was able to protect the Ag in the core in an oxidative environment. Significantly, the core-shell nanocubes exhibited surface plasmonic properties essentially identical to those of the original Ag nanocubes, while the SERS activity showed a 5.4-fold further enhancement owing to an improvement in chemical enhancement. The combination of excellent SERS activity and chemical stability may enable a variety of new applications.

CrCuAgN PVD nanocomposite coatings: Effects of annealing on coating morphology and nanostructure

Energy Technology Data Exchange (ETDEWEB)

Liu, Xingguang, E-mail: xingguangliu1@gmail.com [Department of Materials Science and Engineering, Sir Robert Hadfield Building, The University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom); Iamvasant, Chanon, E-mail: ciamvasant1@sheffield.ac.uk [Department of Materials Science and Engineering, Sir Robert Hadfield Building, The University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom); Liu, Chang, E-mail: chang.liu@sheffield.ac.uk [Department of Materials Science and Engineering, Sir Robert Hadfield Building, The University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom); Matthews, Allan, E-mail: allan.matthews@manchester.ac.uk [Pariser Building - B24 ICAM, School of Materials, The University of Manchester, Manchester, M13 9PL (United Kingdom); Leyland, Adrian, E-mail: a.leyland@sheffield.ac.uk [Department of Materials Science and Engineering, Sir Robert Hadfield Building, The University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom)

2017-01-15

Highlights: • Coatings with nitrogen content up to 16 at.% exhibit a metallic Cr solid solution, even after post-coat annealing at 300 °C and 500 °C. • At higher N/Cr atomic ratios (approaching Cr{sub 2}N stoichiometry), chromium was still inclined to exist in solid solution with nitrogen, rather than as a ceramic nitride phase, even after annealing at 500 °C. • Transportation of Cu and Ag to the surface depends on annealing temperature, annealing duration, nitrogen concentration and ‘global’ Cu + Ag concentration. • Incorporation of copper appears to be a powerful strategy to enhance Ag mobility at low concentration (∼3 at.% Ag in this study) under moderately high service temperature. • A significant decrease in friction coefficient was obtained at room temperature after annealing, or during sliding wear testing at elevated temperature. - Abstract: CrCuAgN PVD nanocomposite coatings were produced using pulsed DC unbalanced magnetron sputtering. This investigation focuses on the effects of post-coat annealing on the surface morphology, phase composition and nanostructure of such coatings. In coatings with nitrogen contents up to 16 at.%, chromium exists as metallic Cr with N in supersaturated solid solution, even after 300 °C and 500 °C post-coat annealing. Annealing at 300 °C did not obviously change the phase composition of both nitrogen-free and nitrogen-containing coatings; however, 500 °C annealing resulted in significant transformation of the nitrogen-containing coatings. The formation of Ag aggregates relates to the (Cu + Ag)/Cr atomic ratio (threshold around 0.2), whereas the formation of Cu aggregates relates to the (Cu + Ag + N)/Cr atomic ratio (threshold around 0.5). The primary annealing-induced changes were reduced solubility of Cu, Ag and N in Cr, and the composition altering from a mixed ultra-fine nanocrystalline and partly amorphous phase constitution to a coarser, but still largely nanocrystalline structure. It was also

Centrality and collision system dependence of antiproton production from p+A to Au+Au collisions at AGS energies

International Nuclear Information System (INIS)

Sako, H.; Ahle, L.; Akiba, Y.

1997-12-01

Antiproton production in heavy ion collisions reflects subtle interplay between initial production and absorption by nucleons. Because the AGS energies (10--20 A·GeV/c) are close to the antiproton production threshold, antiproton may be sensitive to cooperative processes such as QGP and hadronic multi-step processes. On the other hand, antiproton has been proposed as a probe of baryon density due to large N anti N annihilation cross sections. Cascade models predict the maximum baryon density reaches about 10 times the normal nucleus density in central Au+Au collisions, where the strong antiproton absorption is expected. In this paper, the authors show systematic studies of antiproton production from p+A to Au+Au collisions

Thermal Analysis of the Sn-Ag-Cu-In Solder Alloy

DEFF Research Database (Denmark)

Sopousek, J.; Palcut, Marián; Hodúlová, Erika

2010-01-01

The tin-based alloy Sn-1.5Ag-0.7Cu-9.5In (composition in wt.%) is a potential candidate for lead-free soldering at temperatures close to 200°C due to the significant amount of indium. Samples of Sn-1.5Ag-0.7Cu-9.5In were prepared by controlled melting of the pure elements, followed by quenching...... to room temperature. The samples were analyzed by scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDS) and electron backscatter diffraction. The solidified melt consisted of four different phases. Solidification behavior was monitored by heat-flux differential scanning calorimetry...

A DFT-based genetic algorithm search for AuCu nanoalloy electrocatalysts for CO2 reduction

DEFF Research Database (Denmark)

Lysgaard, Steen; Mýrdal, Jón Steinar Garðarsson; Hansen, Heine Anton

2015-01-01

Using a DFT-based genetic algorithm (GA) approach, we have determined the most stable structure and stoichiometry of a 309-atom icosahedral AuCu nanoalloy, for potential use as an electrocatalyst for CO2 reduction. The identified core–shell nano-particle consists of a copper core interspersed....... This shows that the mixed Cu135@Au174 core–shell nanoalloy has a similar adsorption energy, for the most favorable site, as a pure gold nano-particle. Cu, however, has the effect of stabilizing the icosahedral structure because Au particles are easily distorted when adding adsorbates....... that it is possible to use the LCAO mode to obtain a realistic estimate of the molecular chemisorption energy for systems where the computation in normal grid mode is not computationally feasible. These corrections are employed when calculating adsorption energies on the Cu, Au and most stable mixed particles...

Order-disorder phase transitions in Au-Cu nanocubes: from nano-thermodynamics to synthesis.

Science.gov (United States)

Mendoza-Cruz, R; Bazán-Diaz, L; Velázquez-Salazar, J J; Samaniego-Benitez, J E; Ascencio-Aguirre, F M; Herrera-Becerra, R; José-Yacamán, M; Guisbiers, G

2017-07-13

Catalysts have been widely used in industries and can be optimized by tuning the composition and chemical ordering of the elements involved in the nano-alloy. Among bi-metallic alloys, the Au-Cu system is of particular interest because it exhibits ordered phases at low temperatures. Nevertheless, the temperature at which these ordered structures are formed is totally unknown at the nanoscale. Consequently, to speed up the development of these catalysts, this paper theoretically predicts the structural phase transitions between ordered and disordered phases for the Au-Cu system by using nano-thermodynamics. Following the predictions, the suggested annealing temperatures have been carefully chosen and consequently, Au-Cu ordered nanocubes have been successfully synthesized through a solventless protocol. The results are fully supported by electron microscopy observations.

Evidence of significant covalent bonding in Au(CN)(2)(-).

Science.gov (United States)

Wang, Xue-Bin; Wang, Yi-Lei; Yang, Jie; Xing, Xiao-Peng; Li, Jun; Wang, Lai-Sheng

2009-11-18

The Au(CN)(2)(-) ion is the most stable Au compound known for centuries, yet a detailed understanding of its chemical bonding is still lacking. Here we report direct experimental evidence of significant covalent bonding character in the Au-C bonds in Au(CN)(2)(-) using photoelectron spectroscopy and comparisons with its lighter congeners, Ag(CN)(2)(-) and Cu(CN)(2)(-). Vibrational progressions in the Au-C stretching mode were observed for all detachment transitions for Au(CN)(2)(-), in contrast to the atomic-like transitions for Cu(CN)(2)(-), revealing the Au-C covalent bonding character. In addition, rich electronic structural information was obtained for Au(CN)(2)(-) by employing 118 nm detachment photons. Density functional theory and high-level ab initio calculations were carried out to understand the photoelectron spectra and obtain insight into the nature of the chemical bonding in the M(CN)(2)(-) complexes. Significant covalent character in the Au-C bonding due to the strong relativistic effects was revealed in Au(CN)(2)(-), consistent with its high stability.

Surface structure of AU3Cu(001)

DEFF Research Database (Denmark)

Eckstein, G.A.; Maupai, S.; Dakkouri, A.S.

1999-01-01

The surface morphology, composition, and structure of Au3Cu(001) as determined by scanning tunneling microscopy and surface x-ray diffraction are presented. Atomic resolution STM images reveal distinctive geometric features. The analysis of the surface x-ray diffraction data provides clear evidence...... for the surface structure. [S0163-1829(99)04535-X]....

Synthesis of Ag and Au nanoparticles embedded in carbon film: Optical, crystalline and topography analysis

Science.gov (United States)

Gholamali, Hediyeh; Shafiekhani, Azizollah; Darabi, Elham; Elahi, Seyed Mohammad

2018-03-01

Atomic force microscopy (AFM) images give valuable information about surface roughness of thin films based on the results of power spectral density (PSD) through the fast Fourier transform (FFT) algorithms. In the present work, AFM data are studied for silver and gold nanoparticles (Ag NPs a-C: H and Au NPs a-C: H) embedded in amorphous hydrogenated carbon films and co-deposited on glass substrate via of RF-Sputtering and RF-Plasma Enhanced Chemical Vapor Deposition methods. Here, the working gas is acetylene and the targets are Ag and Au. While time and power are constant, the only variable parameter in this study is initial pressure. In addition, the crystalline structure of Ag NPs a-C: H and Au NPs a-C: H are studied using X-ray diffraction (XRD). UV-visible spectrophotometry will also investigate optical properties and localized surface plasmon resonance (LSPR) of samples.

Au-Cu core-shell nanocube-catalyzed click reactions for efficient synthesis of diverse triazoles.

Science.gov (United States)

Madasu, Mahesh; Hsia, Chi-Fu; Huang, Michael H

2017-06-01

Au-Cu core-shell nanocubes and octahedra synthesized in aqueous solution were employed to catalyze a 1,3-dipolar cycloaddition reaction between phenylacetylene and benzyl azide in water at 50 °C for 3 h. Interestingly, the nanocubes were far more efficient in catalyzing this reaction, giving 91% yield of a regioselective 1,4-triazole product, while octahedra only recorded 46% yield. The Au-Cu nanocubes were subsequently employed to catalyze the click reaction between benzyl azide and a broad range of aromatic and aliphatic alkynes. The product yields ranged from 78 to 99%. Clearly the Au-Cu cubes exposing {100} surfaces are an excellent and green catalyst for click reactions.

Comparative Compton scattering studies in Cu2O and Ag2O

International Nuclear Information System (INIS)

Bandyopadhyay, S.; Chatterjee, A.K.; Saha, S.K.; Chatterjee, A.

1994-01-01

Compton scattering studies in polycrystalline Cu 2 O and Ag 2 O with 59.54 keV γ radiation are reported. A comparison has been made between the valance Compton profiles of these two components scaled to lattice momentum by normalizing them to equal electron density for outer valence electrons, and this comparison shows some differences between the bonding characters of Cu 2 O and Ag 2 O. (author)

Core–shell Au/Ag nanoparticles embedded in silicate sol–gel ...

Indian Academy of Sciences (India)

Administrator

Dedicated to the memory of the late Professor S K Rangarajan. *For correspondence. Core–shell Au/Ag nanoparticles embedded in silicate sol–gel network for sensor .... An immediate colour change was observed for the mixed solution, indicating the dis- persion of metal nanoparticles in the MTMOS sol– gel matrix.

Preparation and characterization of sub-20 nm Cu{sub X}@Ag{sub 1} core-shell nanoparticles by changing concentration of silver precursor

Energy Technology Data Exchange (ETDEWEB)

Chee, Sang-Soo; Lee, Jong-Hyun, E-mail: pljh@snut.ac.kr

2017-01-01

Ultrafine Ag-coated Cu (Cu@Ag) nanoparticles (NPs) less than 20 nm in diameter were prepared. After synthesizing ultrafine Cu NPs using a solvothermal method to serve as the core particles, Cu@Ag NPs were fabricated with different initial Ag precursor concentrations, resulting in different thicknesses, densities, and uniformities of Ag shells. The average thickness and density of the Ag shell increased with increasing initial Ag precursor concentration in a Cu:Ag atomic ratio from 6:1 to 1:1. However, excessive Ag precursor concentrations induced homogeneous nucleation and growth of surplus fine pure NPs. Ag dewetting behavior and Cu oxidation in the Cu{sub 4}@Ag{sub 1} NPs were observed, they occurred during heating at 200 and 250 °C, respectively. The electrical resistivities of sintered Cu{sub 4}@Ag{sub 1} films decreased with increasing temperature from 200 to 240 °C. The resistivity after washing the OA and sintering for 60 min at 240 °C in air was measured to be 4.96 × 10{sup −3} Ω cm. The film was sintered in nitrogen using the ink containing non-washed Cu{sub 4}@Ag{sub 1} NPs indicated the lower resistivity of 2.70 × 10{sup −3} Ω cm owing to the non-oxidation atmosphere, although the chemically capped oleylamine in the core-shell NPs hindered the sintering behavior. - Highlights: • Ultrafine Ag-coated Cu nanoparticles less than 20 nm in diameter were fabricated. • Different Ag precursor concentrations influenced thickness and density of Ag shell. • Excessive Ag precursor concentrations induced formation of surplus fine pure NPs. • Ag dewetting behavior and Cu oxidation in Cu{sub 4}@Ag{sub 1} nanoparticles were observed. • Electrical resistivities of sintered Cu{sub 4}@Ag{sub 1} films were 2.70–4.96 × 10{sup −3} Ω cm.

Typomorphic Characteristics of Molybdenite from the Bystrinsky Cu-Au Porphyry-Skarn Deposit, Eastern Transbaikal Region, Russia

Science.gov (United States)

Kovalenker, V. A.; Trubkin, N. V.; Abramova, V. D.; Plotinskaya, O. Yu.; Kiseleva, G. D.; Borisovskii, S. E.; Yazykova, Yu. I.

2018-01-01

The paper presents pioneering data on the composition, texture, and crystal structure of molybdenite from various types of molybdenum mineralization at the Bystrinsky Cu-Au-Fe porphyry-skarn deposit in the eastern Transbaikal region, Russia. The data were obtained using electron microprobe analysis (EMPA), laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), and high-resolution transmission electron microscopy (HRTEM). Molybdenite found at the deposit in skarn, sulfide-poor quartz veins, and quartz-feldspar alteration markedly differs in the concentrations of trace elements determined by their species in the mineral, as well as in its structural features. Molybdenite-2H from skarn associated with phyllosilicates occurs as ultrafine crystals with uniform shape and texture; no dislocations or inclusions were found but amorphous silica was. The molybdenite composition is highly contrasting in the content and distribution of both structure-related (Re, W, and Se) and other (Mn, Co, Ni, Cu, Zn, As, Ag, Cd, Sb, Te, Ag, Pd, Au, Hg, Pb, and Bi) metals. In the sulfide-poor quartz veins, highly structurally heterogeneous (2H + 3R) molybdenite microcrystals with abundant defects (dislocations and volumetrically distributed inclusions) are associated with illite, goethite, and barite. Some single crystals are unique three-phase (2H + 3R polytypes + amorphous MoS2). The mineral has a low concentration of all trace elements, which are uniformly distributed. However, individual domains with uniquely high Pd, Te, Ni, Hg, and W concentrations caused by mineral inclusions are found in some grains. Molybdenite from quartz-feldspar alteration is characterized by low concentrations of all trace elements except for Re and Se, which enrich some domains of the grains. Our data indicate that the compositional and structural heterogeneity of molybdenite from the Bystrinsky deposit are its crucial features, which obviously correlate with the types of Mo mineralization.

Cu-Ag core–shell nanoparticles with enhanced oxidation stability for printed electronics

International Nuclear Information System (INIS)

Lee, Changsoo; Kim, Na Rae; Koo, Jahyun; Lee, Yung Jong; Lee, Hyuck Mo

2015-01-01

In this work, we synthesized uniform Cu–Ag core–shell nanoparticles using a facile two-step process that consists of thermal decomposition and galvanic displacement methods. The core–shell structure of these nanoparticles was confirmed through characterization using transmission electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Furthermore, we investigated the oxidation stability of the Cu–Ag core–shell nanoparticles in detail. Both qualitative and quantitative x-ray photoelectron spectroscopy analyses confirm that the Cu–Ag core–shell nanoparticles have considerably higher oxidation stability than Cu nanoparticles. Finally, we formulated a conductive ink using the synthesized nanoparticles and coated it onto glass substrates. Following the sintering process, we compared the resistivity of the Cu–Ag core–shell nanoparticles with that of the Cu nanoparticles. The results of this study clearly show that the Cu–Ag core–shell nanoparticles can potentially be used as an alternative to Ag nanoparticles because of their superior oxidation stability and electrical properties. (paper)

Effect of Intermetallic on Electromigration and Atomic Diffusion in Cu/SnAg3.0Cu0.5/Cu Joints: Experimental and First-Principles Study

Science.gov (United States)

Zhou, Wei; Liu, Lijuan; Li, Baoling; Wu, Ping

2009-06-01

Electromigration phenomena in a one-dimensional Cu/SnAg3.0Cu0.5/Cu joint were investigated with current stressing. The special effect of intermetallic compound (IMC) layers on the formation of serious electromigration damage induced by nonuniform current density distribution was discussed based on experimental results. Meanwhile, hillocks were observed both at the anode and near the cathode of the joint, and they were described as the result of diffusion of atoms and compressive stress released along grain boundaries to the relatively free surface. Moreover, the diffusion behavior of Cu at the cathode was analyzed with the electromigration equation, and the stability of Ag atoms in the solder during electromigration was evaluated with a first-principles method.

Fabrication of Au/graphene oxide/Ag sandwich structure thin film and its tunable energetics and tailorable optical properties

Directory of Open Access Journals (Sweden)

Ruijin Hong

2017-01-01

Full Text Available Au/graphene oxide/Ag sandwich structure thin film was fabricated. The effects of graphene oxide (GO and bimetal on the structure and optical properties of metal silver films were investigated by X-ray diffraction (XRD, optical absorption, and Raman intensity measurements, respectively. Compared to silver thin film, Au/graphene oxide/Ag sandwich structure composite thin films were observed with wider optical absorption peak and enhanced absorption intensity. The Raman signal for Rhodamine B molecules based on the Au/graphene oxide/Ag sandwich nanostructure substrate were obviously enhanced due to the bimetal layer and GO layer with tunable absorption intensity and fluorescence quenching effects.

Synthesis and characterization of Pd@M(x)Cu(1-x) (M = Au, Pd, and Pt) nanocages with porous walls and a yolk-shell structure through galvanic replacement reactions.

Science.gov (United States)

Xie, Shuifen; Jin, Mingshang; Tao, Jing; Wang, Yucai; Xie, Zhaoxiong; Zhu, Yimei; Xia, Younan

2012-11-19

This paper describes the synthesis of Pd@M(x)Cu(1-x) (M = Au, Pd, and Pt) nanocages with a yolk-shell structure through galvanic replacement reactions that involve Pd@Cu core-shell nanocubes as sacrificial templates and ethylene glycol as the solvent. Compared with the most commonly used templates based on Ag, Cu offers a much lower reduction potential (0.34 versus 0.80 V), making the galvanic reaction more easily to conduct, even at room temperature. Our structural and compositional characterizations indicated that the products were hollow inside, and each one of them contained porous M-Cu alloy walls and a Pd cube in the interior. For the Pd@Au(x)Cu(1-x) yolk-shell nanocages, they displayed broad extinction peaks extending from the visible to the near-IR region. Our mechanistic study revealed that the dissolution of the Cu shell preferred to start from the slightly truncated corners and then progressed toward the interior, because the Cu {100} side faces were protected by a surface capping layer of hexadecylamine. This galvanic approach can also be extended to generating other hollow metal nanostructures by using different combinations of Cu nanostructures and salt precursors. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tem Observation Of Precipitate Structures In Al-Zn-Mg Alloys With Additions Of Cu/Ag

Directory of Open Access Journals (Sweden)

Watanabe K.

2015-06-01

Full Text Available Al-Zn-Mg alloy has been known as one of the aluminum alloys with the good age-hardening ability and the high strength among commercial aluminum alloys. The mechanical property of the limited ductility, however, is required to further improvement. In this work, three alloys, which were added Cu or Ag into the Al-Zn-Mg alloy, were prepared to compare the effect of the additional elements on the aging behavior. The content of Ag and Cu were 0.2at.% and the same as, respectively. Ag or Cu added alloy showed higher maximum hardness than base alloy. The particle shape and rod shape precipitates were observed in all alloys peak-aged at 423K. According to addition of Ag or Cu, the number density of the precipitates increased higher than that of base alloy.

Microstructures and Properties of 40Cu/Ag(Invar) Composites Fabricated by Powder Metallurgy and Subsequent Thermo-Mechanical Treatment

Science.gov (United States)

Zhang, Xin; Huang, Yingqiu; Liu, Xiangyu; Yang, Lei; Shi, Changdong; Wu, Yucheng; Tang, Wenming

2018-03-01

Composites of 40Cu/Ag(Invar) were prepared via pressureless sintering and subsequent thermo-mechanical treatment from raw materials of electroless Ag-plated Invar alloy powder and electrolytic Cu powder. Microstructures and properties of the prepared composites were studied to evaluate the effect of the Ag layer on blocking Cu/Invar interfacial diffusion in the composites. The electroless-plated Ag layer was dense, uniform, continuous, and bonded tightly with the Invar alloy substrate. During sintering of the composites, the Ag layer effectively prevented Cu/Invar interfacial diffusion. During cold-rolling, the Ag layer was deformed uniformly with the Invar alloy particles. The composites exhibited bi-continuous network structure and considerably improved properties. After sintering at 775 °C and subsequent thermo-mechanical treatment, the 40Cu/Ag(Invar) composites showed satisfactory comprehensive properties: relative density of 99.0 pct, hardness of HV 253, thermal conductivity of 55.7 W/(m K), and coefficient of thermal expansion of 11.2 × 10-6/K.

Properties and Microstructures of Sn-Ag-Cu-X Lead-Free Solder Joints in Electronic Packaging

OpenAIRE

Sun, Lei; Zhang, Liang

2015-01-01

SnAgCu solder alloys were considered as one of the most popular lead-free solders because of its good reliability and mechanical properties. However, there are also many problems that need to be solved for the SnAgCu solders, such as high melting point and poor wettability. In order to overcome these shortcomings, and further enhance the properties of SnAgCu solders, many researchers choose to add a series of alloying elements (In, Ti, Fe, Zn, Bi, Ni, Sb, Ga, Al, and rare earth) and nanoparti...

Kinetics of intermetallic phase formation at the interface of Sn-Ag-Cu-X (X = Bi, In) solders with Cu substrate

International Nuclear Information System (INIS)

Hodulova, Erika; Palcut, Marian; Lechovic, Emil; Simekova, Beata; Ulrich, Koloman

2011-01-01

Highlights: → In substitutes Sn in intermetallic compounds formed at the Cu-solder interface. → Bi and In decrease the parabolic rate constant of Cu 3 Sn layer growth. → In increases the parabolic rate constant of Cu 6 Sn 5 layer growth. → High In concentrations should be avoided since they may lead to a pre-mature solder joint degradation. - Abstract: The effects of Bi and In additions on intermetallic phase formation in lead-free solder joints of Sn-3.7Ag-0.7Cu; Sn-1.0Ag-0.5Cu-1.0Bi and Sn-1.5Ag-0.7Cu-9.5In (composition given in weight %) with copper substrate are studied. Soldering of copper plate was conducted at 250 deg. C for 5 s. The joints were subsequently aged at temperatures of 130-170 deg. C for 2-16 days in a convection oven. The aged interfaces were analyzed by optical microscopy and energy dispersive X-ray spectroscopy (EDX) microanalysis. Two intermetallic layers are observed at the interface - Cu 3 Sn and Cu 6 Sn 5 . Cu 6 Sn 5 is formed during soldering. Cu 3 Sn is formed during solid state ageing. Bi and In decrease the growth rate of Cu 3 Sn since they appear to inhibit tin diffusion through the grain boundaries. Furthermore, indium was found to produce a new phase - Cu 6 (Sn,In) 5 instead of Cu 6 Sn 5 , with a higher rate constant. The mechanism of the Cu 6 (Sn,In) 5 layer growth is discussed and the conclusions for the optimal solder chemical composition are presented.

Room temperature nanojoining of Cu-Ag core-shell nanoparticles and nanowires

International Nuclear Information System (INIS)

Wang, Jiaqi; Shin, Seungha

2017-01-01

Room temperature (T room , 300 K) nanojoining of Ag has been widely employed in fabrication of microelectronic applications where the shapes and structures of microelectronic components must be maintained. In this research, the joining processes of pure Ag nanoparticles (NPs), Cu-Ag core-shell NPs, and nanowires (NWs) are studied using molecular dynamics simulations at T room . The evolution of densification, potential energy, and structural deformation during joining process are analyzed to identify joining mechanisms. Depending on geometry, different joining mechanisms including crystallization-amorphization, reorientation, Shockley partial dislocation are determined. A three-stage joining scenario is observed in both joining process of NPs and NWs. Besides, the Cu core does not participate in all joining processes, however, it enhances the mobility of Ag shell atoms, contributing to a higher densification and bonding strength at T room , compared with pure Ag nanomaterials. The tensile test shows that the nanojoint bears higher rupture strength than the core-shell NW itself. This study deepens understanding in the underlying joining mechanisms and thus nanojoint with desirable thermal, electrical, and mechanical properties could be potentially achieved.

SERS study of surface plasmon resonance induced carrier movement in Au@Cu2O core-shell nanoparticles

Science.gov (United States)

Chen, Lei; Zhang, Fan; Deng, Xin-Yu; Xue, Xiangxin; Wang, Li; Sun, Yantao; Feng, Jing-Dong; Zhang, Yongjun; Wang, Yaxin; Jung, Young Mee

2018-01-01

A plasmon induced carrier movement enhanced mechanism of surface-enhanced Raman scattering (SERS) was investigated using a charge-transfer (CT) enhancement mechanism. Here, we designed a strategy to study SERS in Au@Cu2O nanoshell nanoparticles with different shell thicknesses. Among the plasmonically coupled nanostructures, Au spheres with Cu2O shells have been of special interest due to their ultrastrong electromagnetic fields and controllable carrier transfer properties, which are useful for SERS. Au@Cu2O nanoshell nanoparticles (NPs) with shell thicknesses of 48-56 nm are synthesized that exhibit high SERS activity. This high activity originates from plasmonic-induced carrier transfer from Au@Cu2O to 4-mercaptobenzoic acid (MBA). The CT transition from the valence band (VB) of Cu2O to the second excited π-π* transition of MBA, and is of b2 electronic symmetry, which was enhanced significantly. The Herzberg-Teller selection rules were employed to predict the observed enhanced b2 symmetry modes. The system constructed in this study combines the long-range electromagnetic effect of Au NPs, localized surface plasmon resonance (LSPR) of the Au@Cu2O nanoshell, and the CT contribution to assist in understanding the SERS mechanism based on LSPR-induced carrier movement in metal/semiconductor nanocomposites.

Synthesis of polymer-stabilized monometallic Cu and bimetallic Cu/Ag nanoparticles and their surface-enhanced Raman scattering properties

Science.gov (United States)

Zhang, Danhui; Liu, Xiaoheng

2013-03-01

The present study demonstrates a facile process for the production of spherical-shaped Cu and Ag nanoparticles synthesized and stabilized by hydrazine and gelatin, respectively. Advantages of the synthetic method include its production of water dispersible copper and copper/silver nanoparticles at room temperature under no inert atmosphere. The resulting nanoparticles (copper or copper/silver) are investigated by X-ray diffraction (XRD), UV-vis spectroscopy, and transmission electron microscopy (TEM). The nanometallic dispersions were characterized by surface plasmon absorbance measuring at 420 and 572 nm for Ag and Cu nanoparticles, respectively. Transmission electron microscopy showed the formation of nanoparticles in the range of ˜10 nm (silver), and ˜30 nm (copper). The results also demonstrate that the reducing order of Cu2+/Ag+ is important for the formation of the bimetallic nanoparticles. The surface-enhanced Raman scattering effects of copper and copper/silver nanoparticles were also displayed. It was found that the enhancement ability of copper/silver nanoparticles was little higher than the copper nanoparticles.

Charge-state distribution in close collisions of 3 MeV C2+ ions with Ag and Au atoms

NARCIS (Netherlands)

Boerma, D.O; Arnoldbik, W.M.; Kabachnik, N.M.; Khodyrev, V.A.

The charge-state distributions of 3 MeV carbon ions scattered over angles of 40 degrees and 60 degrees from sub-monolayers of Ag and Au atoms evaporated on a substrate and from thick layers of Ag and Au have been measured. A close similarity of the charge distributions in all cases is interpreted as

Atom probe tomography simulations and density functional theory calculations of bonding energies in Cu3Au

KAUST Repository

Boll, Torben; Zhu, Zhiyong; Al-Kassab, Talaat; Schwingenschlö gl, Udo

2012-01-01

In this article the Cu-Au binding energy in Cu3Au is determined by comparing experimental atom probe tomography (APT) results to simulations. The resulting bonding energy is supported by density functional theory calculations. The APT simulations

On the ternary Ag – Cu – Ga system: Electromotive force measurement and thermodynamic modeling

International Nuclear Information System (INIS)

Gierlotka, Wojciech; Jendrzejczyk-Handzlik, Dominika; Fitzner, Krzysztof; Handzlik, Piotr

2015-01-01

The ternary silver–copper–gallium system found application as a solder material in jewel crafting and electronics, thus a phase diagram of this system seems to be important tool, which is necessary for a proper application of different alloys. The activity of gallium in liquid phase was determined by electromotive measurement technique and after that the equilibrium diagram of Ag – Cu – Ga was modeled based on available experimental data using Calphad approach. A set of Gibbs energies was found and used for calculation a phase diagram and thermodynamic properties of liquid phase. The experimental data was reproduced well by calculation. - Highlights: • For the first time activity of Ga in liquid Ag – Cu – Ga alloys was measured. • For the first time the ternary Ag – Cu – Ga system was thermodynamically modeled. • Modeled Ag – Cu – Ga system reproduces experimental data well

Ag-Cu nanoalloyed film as a high-performance cathode electrocatalytic material for zinc-air battery

Science.gov (United States)

Lei, Yimin; Chen, Fuyi; Jin, Yachao; Liu, Zongwen

2015-04-01

A novel Ag50Cu50 film electrocatalyst for oxygen reduction reaction (ORR) was prepared by pulsed laser deposition (PLD) method. The electrocatalyst actually is Ag-Cu alloyed nanoparticles embedded in amorphous Cu film, based on transmission electron microscopy (TEM) characterization. The rotating disk electrode (RDE) measurements provide evidence that the ORR proceed via a four-electron pathway on the electrocatalysts in alkaline solution. And it is much more efficient than pure Ag catalyst. The catalytic layer has maximum power density of 67 mW cm-2 and an acceptable cell voltage at 0.863 V when current densities increased up to 100 mA cm-2 in the Ag50Cu50-based primary zinc-air battery. The resulting rechargeable zinc-air battery exhibits low charge-discharge voltage polarization of 1.1 V at 20 mAcm-2 and high durability over 100 cycles in natural air.

Localized surface plasmon resonance properties of symmetry-broken Au-ITO-Ag multilayered nanoshells

Science.gov (United States)

Lv, Jingwei; Mu, Haiwei; Lu, Xili; Liu, Qiang; Liu, Chao; Sun, Tao; Chu, Paul K.

2018-06-01

The plasmonic properties of symmetry-broken Au-ITO-Ag multilayered nanoshells by shell cutting are studied by the finite element method. The influence of the polarization of incident light and geometrical parameters on the plasmon resonances of the multilayered nanoshells are investigated. The polarization-dependent multiple plasmon resonances appear from the multilayered nanoshells due to symmetry breaking. In nanostructures with a broken symmetry, the localized surface plasmon resonance modes are enhanced resulting in higher order resonances. According to the plasmon hybridization theory, these resonance modes and greater spectral tunability derive from the interactions of an admixture of both primitive and multipolar modes between the inner Au core and outer Ag shell. By changing the radius of the Au core, the extinction resonance modes of the multilayered nanoshells can be easily tuned to the near-infrared region. To elucidate the symmetry-broken effects of multilayered nanoshells, we link the geometrical asymmetry to the asymmetrical distributions of surface charges and demonstrate dipolar and higher order plasmon modes with large associated field enhancements at the edge of the Ag rim. The spectral tunability of the multiple resonance modes from visible to near-infrared is investigated and the unique properties are attractive to applications including angularly selective filtering to biosensing.

Effect of polyvinyl alcohol (PVA) on Ag-Cu nanopaste performance

Science.gov (United States)

Noordin, Norasiah Mohammad; Razak, Khairunisak Abd; Cheong, Kuan Yew

2017-07-01

Electronic devices used for extreme high temperature continue to be in demand, for instance in aviation, aerospace and automotive industry. The reliability of these devices strongly depends on electronic packaging. Die attach materials is vital in electronic packaging as it provides an interface in between a die and a substrate, and its quality will determine the performance of the devices. Nanopaste is one of categories classified in the die attach systems. It is a mixture of nano sized metal particles and organic additives (binder, surfactant, solvent). In this study, Ag and Cu nanoparticles was mixed into an organic binder system, polyvinyl alcohol (PVA) serves as binder and ethylene glycol functions as surfactant while deionized water used to dissolve PVA. The mixture was inserted in vacuum oven at 70°C and then proceeds for sintering in horizontal tube furnace with various sintering temperature, a dwell time of 30 min and ramp rate of 5°C/min. The samples were then characterized using field emission scanning electron microscope (FE-SEM) to examine the morphology, X-ray diffraction (XRD) for phase identification, Four Point Probe to measure sheet resistance, and thermogravimetric and differential scanning calorimetry analysis (TGA/DSC) to study the thermal response with respect to temperature. These parameter were studied, the effect of PVA amount (0.10, 0.15, 0.20, 0.30, 0.40, 0.50 g) in Ag-Cu nanopaste formulation was visual inspected, the variation of drying time (20, 30, 40, 60, 80, 100, 120 min) in vacuum oven and sintering temperature (280, 300, 320, 340, 360, 380, 400°C) was recorded. The optimum condition for producing Ag-Cu nanopaste is by using 0.15 g of PVA in the Ag-Cu formulation, 30 min drying time and 340°C sintering temperature.

Planar potentiometric sensors based on Au and Ag microelectrodes and conducting polymers for flow-cell analysis

International Nuclear Information System (INIS)

ToczyIowska, Renata; Pokrop, RafaI; Dybko, Artur; Wroblewski, Wojciech

2005-01-01

Back-side contact Au and Ag microelectrodes were used as transducers to construct planar all-solid-state electrodes suitable for flow-through analysis. The microsensors were based on plasticized PVC potassium-selective membranes containing ion-electron conducting polymer-polypyrrole doped with di(2-ethylhexyl) sulfosuccinate. The proposed technique allowed simple construction of microsensors in one step, by membrane solution casting directly on the surface of the planar metallic transducers. The performance of the microsensors based on Au and Ag transducers were determined and compared with planar sensors based on internal electrolyte immobilized in polyHEMA. The addition of the polypyrrole to the membrane composition did not influence on the selectivity, reproducibility and long-term stability of the microsensors but improved their standard potential stability in time in comparison with coated-wire type sensors. Moreover, all-solid-state microsensors based on Au transducers exhibited better signal stability than Ag based sensors

Near-side azimuthal and pseudorapidity correlations using neutral strange baryons and mesons in d +Au , Cu + Cu, and Au + Au collisions at √{sN N}=200 GeV

Science.gov (United States)

Abelev, B.; Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Barnby, L. S.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bombara, M.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chatterjee, A.; Chattopadhyay, S.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; di Ruzza, B.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Eppley, G.; Esha, R.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Gaillard, L.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Hamad, A. I.; Hamed, A.; Haque, R.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, T.; Huang, B.; Huang, X.; Huang, H. Z.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Jentsch, A.; Jia, J.; Jiang, K.; Jones, P. G.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z. H.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Koetke, D. D.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kumar, L.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, C.; Li, Y.; Li, W.; Li, X.; Li, X.; Lin, T.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, S.; Luo, X.; Ma, L.; Ma, R.; Ma, G. L.; Ma, Y. G.; Magdy, N.; Majka, R.; Manion, A.; Margetis, S.; Markert, C.; Matis, H. S.; McDonald, D.; McKinzie, S.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nattrass, C.; Nasim, Md.; Nayak, T. K.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, B.; Sharma, A.; Sharma, M. K.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stepanov, M.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, Z.; Sun, X. M.; Surrow, B.; Svirida, D. N.; Tang, Z.; Tang, A. H.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Varma, R.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, H.; Wang, Y.; Wang, G.; Wang, Y.; Wang, J. S.; Wang, F.; Webb, G.; Webb, J. C.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xin, K.; Xu, Y. F.; Xu, Q. H.; Xu, N.; Xu, J.; Xu, H.; Xu, Z.; Yang, Y.; Yang, Q.; Yang, S.; Yang, Y.; Yang, Y.; Yang, C.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, S.; Zhang, X. P.; Zhang, Y.; Zhang, S.; Zhang, J. B.; Zhang, J.; Zhang, J.; Zhang, Z.; Zhao, J.; Zhong, C.; Zhou, L.; Zhu, X.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

2016-07-01

We present measurements of the near side of triggered di-hadron correlations using neutral strange baryons (Λ ,Λ ¯) and mesons (KS0) at intermediate transverse momentum (3 < pT <6 GeV /c ) to look for possible flavor and baryon-meson dependence. This study is performed in d +Au , Cu+Cu, and Au+Au collisions at √{sN N}=200 GeV measured by the STAR experiment at RHIC. The near-side di-hadron correlation contains two structures, a peak which is narrow in azimuth and pseudorapidity consistent with correlations from jet fragmentation, and a correlation in azimuth which is broad in pseudorapidity. The particle composition of the jet-like correlation is determined using identified associated particles. The dependence of the conditional yield of the jet-like correlation on the trigger particle momentum, associated particle momentum, and centrality for correlations with unidentified trigger particles are presented. The neutral strange particle composition in jet-like correlations with unidentified charged particle triggers is not well described by PYTHIA. However, the yield of unidentified particles in jet-like correlations with neutral strange particle triggers is described reasonably well by the same model.

The effect of silver (Ag) addition to mechanical and electrical properties of copper alloy (Cu) casting product

Science.gov (United States)

Felicia, Dian M.; Rochiem, R.; Laia, Standley M.

2018-04-01

Copper have good mechanical properties and good electrical conductivities. Therefore, copper usually used as electrical components. Silver have better electrical conductivities than copper. Female contact resistor is one of the electrical component used in circuit breaker. This study aims to analyze the effect of silver addition to hardness, strength, and electric conductivity properties of copper alloy. This study uses variation of 0; 0.035; 0.07; 0.1 wt. % Ag (silver) addition to determine the effect on mechanical properties and electrical properties of copper alloy through sand casting process. Modelling of thermal analysis and structural analysis was calculated to find the best design for the sand casting experiments. The result of Cu-Ag alloy as cast will be characterized by OES test, metallography test, Brinell hardness test, tensile test, and LCR meter test. The result of this study showed that the addition of silver increase mechanical properties of Cu-Ag. The maximum hardness value of this alloy is 83.1 HRB which is Cu-0.01 Ag and the lowest is 52.26 HRB which is pure Cu. The maximum strength value is 153.2 MPa which is Cu-0.07 Ag and the lowest is 94.6 MPa which is pure Cu. Silver addition decrease electrical properties of this alloy. The highest electric conductivity is 438.98 S/m which is pure Cu and the lowest is 52.61 S.m which is Cu-0.1 Ag.

Participant and spectator scaling of spectator fragments in Au + Au and Cu + Cu collisions at √{sN N}=19.6 and 22.4 GeV

Science.gov (United States)

Alver, B.; Back, B. B.; Baker, M. D.; Ballintijn, M.; Barton, D. S.; Betts, R. R.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Chai, Z.; Chetluru, V.; Decowski, M. P.; García, E.; Gburek, T.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Harnarine, I.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Hołyński, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Li, W.; Lin, W. T.; Loizides, C.; Manly, S.; McLeod, D.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Richardson, E.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Sedykh, I.; Skulski, W.; Smith, C. E.; Stankiewicz, M. A.; Steinberg, P.; Stephans, G. S. F.; Sukhanov, A.; Szostak, A.; Tang, J.-L.; Tonjes, M. B.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Vaurynovich, S. S.; Verdier, R.; Veres, G. I.; Walters, P.; Wenger, E.; Willhelm, D.; Wolfs, F. L. H.; Wosiek, B.; Woźniak, K.; Wuosmaa, A. H.; Wyngaardt, S.; Wysłouch, B.; Phobos Collaboration

2016-08-01

Spectator fragments resulting from relativistic heavy ion collisions, consisting of single protons and neutrons along with groups of stable nuclear fragments up to nitrogen (Z =7 ), are measured in PHOBOS. These fragments are observed in Au+Au (√{sNN}=19.6 GeV ) and Cu+Cu (22.4 GeV) collisions at high pseudorapidity (η ). The dominant multiply-charged fragment is the tightly bound helium (α ), with lithium, beryllium, and boron all clearly seen as a function of collision centrality and pseudorapidity. We observe that in Cu+Cu collisions, it becomes much more favorable for the α fragments to be released than lithium. The yields of fragments approximately scale with the number of spectator nucleons, independent of the colliding ion. The shapes of the pseudorapidity distributions of fragments indicate that the average deflection of the fragments away from the beam direction increases for more central collisions. A detailed comparison of the shapes for α and lithium fragments indicates that the centrality dependence of the deflections favors a scaling with the number of participants in the collision.

Magma Fertility is the First-Order Factor for the Formation of Porphyry Cu±Au Deposits

Science.gov (United States)

Park, J. W.; Campbell, I. H.; Malaviarachchi, S. P. K.; Cocker, H.; Nakamura, E.; Kay, S. M.

2017-12-01

Magma fertility, the metal abundance in magma, has been considered to be one of the key factors for the formation of porphyry Cu±Au deposits. In this study we provide clear evidence to support the hypothesis that the platinum group element (PGE) can be used to distinguish barren from ore-bearing Cu±Au felsic suites. We determined the PGE contents of three barren volcanic and subvolcanic suites from Argentina and Japan, and compare the results with two porphyry Cu-bearing subvolcanic suites from Chile and two porphyry Cu-Au-bearing suites from Australia. The barren suites are significantly depleted in PGE abundances by the time of fluid exsolution, which is attributed to early sulfide saturation at mid to lower crust depths or assimilation of chalcophile element-poor crustal materials. Barren magma, produced by melting continental crust, may have been initially deficient in chalcophile elements. In contrast, the Cu±Au ore-bearing suites contain at least an order of magnitude higher PGE contents than those of the barren suites by the time of fluid saturation. They are characterized by late sulfide saturation in a shallow magma chamber, which allows the chalcophile elements to concentrate in the fractionating magma from which they are sequestered by ore-forming fluids. We suggest the Pd/MgO and Pd/Pt ratios of igneous rocks can be used as magma fertility indicators, and to distinguish between barren, porphyry Cu and porphyry Cu-Au magmatic systems.

Electronic structure of clean and Ag-covered single-crystalline Bi2Sr2CuO6

International Nuclear Information System (INIS)

Lindberg, P.A.P.; Shen, Z.; Wells, B.O.; Mitzi, D.B.; Lindau, I.; Spicer, W.E.; Kapitulnik, A.

1989-01-01

Photoemission studies of single-crystalline samples of Bi 2 Sr 2 CuO 6 show clear resemblance to the corresponding data for single crystals of Bi 2 Sr 2 CaCu 2 O 8 . In particular, a sharp Fermi-level cutoff, giving evidence of metallic conductivity at room temperature, as well as single-component O 1s emission and Cu 2p satellites with a strength amounting to about 50% of that of the main Cu 2p line, are observed. An analysis of the relative core-level photoemission intensities shows that the preferential cleavage plane of single-crystalline Bi 2 Sr 2 CuO 6 is between adjacent Bi-O layers. Deposition of Ag adatoms causes only weak reaction with the Bi and O ions of the Bi 2 Sr 2 CuO 6 substrate, while the Cu states rapidly react with the Ag adatoms, as monitored by a continuous reduction of the Cu 2p satellite intensity as the Ag overlayer becomes thicker

Magnetic and thermodynamic properties of GdCu4Au

International Nuclear Information System (INIS)

Bashir, Aiman K; Tchokonté, Moise B Tchoula; Britz, Douglas; Sondezi, B M; Strydom, André M

2015-01-01

The results of magnetic susceptibility, χ(T), magnetization, σ(μ 0 H), and specific heat, C P (T), for GdCu 4 Au are presented. The room temperature powder X-ray diffraction studies indicate a cubic MgCu 4 Sn – type crystal structure with space group F4-bar 3m (No.216). The low field dc χ(T) data shows an antiferromagnetic – like (AFM) anomaly associated with a Néel temperature T N = 10.8 K for GdCu 4 Au. In the paramagnetic region above T N , χ(T) data follows the Curies – Weiss law with an effective magnetic moment μ eff = 7.444(1) μ B and paramagnetic Weiss temperature θ P = -15.01(2) K. The experimental value of is close to the calculated value of 7.94 μ B expected for the free Gd 3+ -ion. The field-cooled (FC) and zero-field-cooled (ZFC) χ(T) data provide evidence for the formation of spin-glass state with a freezing temperature T f = 15 K. σ(μ 0 H) measured in the ordering region (below TN) shows that GdCu 4 Au undergoes metamagnetic transition above 0.7 T, characterized by a slight upward curvature above this field. Measurement of σ(μ 0 H) in the paramagnetic regions show a linear behaviour up to 0.7 T and a downward curvature at high fields. C P (T) data shows an AFM – like phase transition at T N = 10.4 K close to the phase transition observed in χ(T) results. The 4f-electron entropy reaches the value of Rln2 close to T N at 9.02 K and reaches the value of Rln(2J + 1) at T = 180 K

Diffusion of Ag, Au and Cs implants in MAX phase Ti3SiC2

Energy Technology Data Exchange (ETDEWEB)

Jiang, Weilin; Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R.; Zhang, Chonghong; Gou, Jie

2015-05-16

MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti3SiC2/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including x-ray diffraction, electron backscatter diffraction, energy dispersive x-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti3SiC2 within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti3SiC2 was also observed. Cs out-diffusion and release from Ti3SiC2 occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

Temperature dependence of residual electrical resistivity of Cu-Au in pseudopotential approximation

International Nuclear Information System (INIS)

Khwaja, F.A.; Ahmed, I.; Shaukat, A.

1986-08-01

The problem of temperature dependence of residual electrical resistivity of Cu-Au system is re-examined in the light of static distortion and thermal vibration of the lattice along with the short-range-order of atoms above critical temperature. The extended version of Ziman's formula for resistivity obtained yields a unified version for the calculation of resistivity in pseudopotential approximation. The temperature dependence of the quantity Δρ/ρ in this framework for Cu-Au system is found to be in better agreement with the experimental data as compared to previous calculation. (author)

Anomalous property of Ag(BO2)2 hyperhalogen: does spin-orbit coupling matter?

Science.gov (United States)

Chen, Hui; Kong, Xiang-Yu; Zheng, Weijun; Yao, Jiannian; Kandalam, Anil K; Jena, Puru

2013-10-07

Hyperhalogens were recently identified as a new class of highly electronagative species which are composed of metals and superhalogens. In this work, high-level theoretical calculations and photoelectron spectroscopy experiments are systematically conducted to investigate a series of coinage-metal-containing hyperhalogen anions, Cu(BO(2))(2)(-), Ag(BO(2))(2)(-), and Au(BO(2))(2)(-). The vertical electron detachment energy (VDE) of Ag(BO(2))(2)(-) is anomalously higher than those of Au(BO(2))(2)(-) and Cu(BO(2))(2)(-). In quantitative agreement with the experiment, high-level ab initio calculations reveal that spin-orbit coupling (SOC) lowers the VDE of Au(BO(2))(2)(-) significantly. The sizable magnitude of about 0.5 eV of SOC effect on the VDE of Au(BO(2))(2)(-) demonstrates that SOC plays an important role in the electronic structure of gold hyperhalogens. This study represents a new paradigm for relativistic electronic structure calculations for the one-electron-removal process of ionic Au(I)L(2) complexes, which is characterized by a substantial SOC effect. Copyright © 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct flow in 10.8 GeV/nucleon Au+Au collisions measured in experiment E917 at the AGS

International Nuclear Information System (INIS)

Back, B. B.; Betts, R. R.; Britt, H. C.; Chang, J.; Chang, W. C.; Gillitzer, A.; Henning, W. F.; Hofman, D. J.; Nanal, V.; Wuosmaa, A. H.

1999-01-01

Analysis of directed flow observable for protons and pions from Au+Au collisions at 10.8 GeV/nucleon from experiment E917 at the AGS is presented. Using a Fourier series expansion, the first Fourier component, ν 1 ,was extracted as a function of rapidity for mid-central collisions (17-24%). Clear evidence for positive directed flow is found in the proton data, and a weak, possibly negative directed flow signal is observed for π + and π -

Short-range ferromagnetism in alloy ribbons of Fe-Cr-Si-Nb-(Ag, Cu)

Energy Technology Data Exchange (ETDEWEB)

THANH, P. Q.; HOA, N. Q.; CHAU, N. [Vietnam National University, Hanoi (Viet Nam); HUU, C. X. [Danang University of Technology, Danang (Viet Nam); NGO, D. T. [Technical University of Denmark, Kgs. Lyngby (Denmark); PHAN, T. L. [Chungbuk National University, Cheongju (Korea, Republic of)

2014-04-15

We have studied the magnetic properties of two amorphous alloy ribbons Fe{sub 72}Cr{sub 6}Si{sub 4}Nb{sub 5}B{sub 12}Ag{sub 1} (FCSNB-Ag) and Fe{sub 72}Cr{sub 6}Si{sub 4}Nb{sub 5}B{sub 12}Cu{sub 1} (FCSNB-Cu), prepared by using a melt-spinning technique. Magnetization (M) measurements for various temperatures (T) and magnetic fields (H) indicate that ferromagnetic-paramagnetic (FM-PM) phase transitions take place in FCSNB-Ag and FCSNB-Cu at Curie temperatures (T{sub C} ) of about 308.3 K and 322.5 K, respectively. Analyses of M - H data at different temperatures in the vicinity of the FM-PM phase transition based on the modified Arrott plot method and scaling hypothesis yielded the exponent values of β = 0.369 ± 0.005, γ = 1.359 ± 0.005 and δ = 4.7 ± 0.1 for FCSNB-Ag, and β = 0.376 ± 0.002, γ = 1.315 ± 0.006 and δ = 4.5 ± 0.1 for FCSNB-Cu. Compared with the values from theoretical models, these values are close to those expected for the 3D Heisenberg model, demonstrating the existence of short-range FM order in the amorphous alloy ribbons.

40Ar-39Ar dating of Archean iron oxide Cu-Au and Paleoproterozoic granite-related Cu-Au deposits in the Carajás Mineral Province, Brazil: implications for genetic models

Science.gov (United States)

Pollard, Peter J.; Taylor, Roger G.; Peters, Lisa; Matos, Fernando; Freitas, Cantidiano; Saboia, Lineu; Huhn, Sergio

2018-05-01

40Ar-39Ar dating of biotite from IOCG and granite-related Cu-Au deposits in the Carajás Mineral Province provides evidence for the timing of mineralization and constraints on genetic models of ore formation. Ages of biotite from greisen and quartz-rich vein and breccia deposits, Alvo 118—1885 ± 4 Ma, Breves—1886 ± 5 Ma, Estrela—1896 ± 7 Ma, and Gameleira—1908 ± 7 Ma, demonstrate the close temporal relationship between Cu-Au mineralization and subjacent A-type granites. Mineralization is hosted within granite cupolas (Breves) or in vein/breccia systems emanating from the cupolas (Estrela and Gameleira), consistent with a genetic relationship of mineralization to the B-Li-F-rich granites. Plateau and minimum ages of biotite from IOCG deposits, including Igarapé Bahia, Cristalino, Corta Goela, and GT34, range from 2537 ± 6 Ma to 2193 ± 4 Ma. The 40Ar-39Ar age of biotite from Igarapé Bahia (2537 ± 6 Ma) is similar to a previous SHRIMP 207Pb-206Pb age for monazite of 2575 ± 12 Ma when the uncertainties in the respective analyses and standards are taken into account. The age spectrum for biotite from Cristalino shows increasing ages for successive steps, consistent with post-crystallization Ar loss, and the age of 2388 ± 5 Ma for the last three steps is considered a minimum age for Cu-Au mineralization. The age of biotite from the GT34 prospect (2512 ± 7 Ma) coincides with a previously identified period of basement reactivation and may indicate the formation of Cu-Au mineralization at this time or resetting of biotite from an older mineralization event at this time. At Corta Goela, within the Canaã Shear Zone, the biotite age of 2193 ± 4 Ma lies between the ages of IOCG (2.57-2.76 Ga) and granite-related Cu-Au ( 1.88 Ga) deposits elsewhere in the Carajás district but is similar to previously reported 40Ar-39Ar ages for amphibole from Sossego, possibly indicating that mineralization at both Sossego and Corta Goela was affected by a thermal event at

Room temperature nanojoining of Cu-Ag core-shell nanoparticles and nanowires

Energy Technology Data Exchange (ETDEWEB)

Wang, Jiaqi; Shin, Seungha, E-mail: sshin@utk.edu [The University of Tennessee, Department of Mechanical, Aerospace and Biomedical Engineering (United States)

2017-02-15

Room temperature (T{sub room}, 300 K) nanojoining of Ag has been widely employed in fabrication of microelectronic applications where the shapes and structures of microelectronic components must be maintained. In this research, the joining processes of pure Ag nanoparticles (NPs), Cu-Ag core-shell NPs, and nanowires (NWs) are studied using molecular dynamics simulations at T{sub room}. The evolution of densification, potential energy, and structural deformation during joining process are analyzed to identify joining mechanisms. Depending on geometry, different joining mechanisms including crystallization-amorphization, reorientation, Shockley partial dislocation are determined. A three-stage joining scenario is observed in both joining process of NPs and NWs. Besides, the Cu core does not participate in all joining processes, however, it enhances the mobility of Ag shell atoms, contributing to a higher densification and bonding strength at T{sub room}, compared with pure Ag nanomaterials. The tensile test shows that the nanojoint bears higher rupture strength than the core-shell NW itself. This study deepens understanding in the underlying joining mechanisms and thus nanojoint with desirable thermal, electrical, and mechanical properties could be potentially achieved.

Novel multifunctional graphene sheets with encased Au/Ag nanoparticles for advanced electrochemical analysis of organic compounds.

Science.gov (United States)

Pruneanu, Stela; Biris, Alexandru R; Pogacean, Florina; Lazar, Diana Mihaela; Ardelean, Stefania; Watanabe, Fumyia; Dervishi, Enkeleda; Biris, Alexandru S

2012-11-12

This work is the first presentation of the synthesis of few-layer graphene decorated with gold and silver nanoparticles (Gr-Au-Ag) by chemical vapor deposition over a catalytic system formed of bimetallic Au-Ag nanoclusters supported on MgO and with methane used as the source of carbon. The sheetlike morphology of the graphene nanostructures, with mean sizes in the range of hundreds of nanometers, was observed by high-resolution electron microscopy. The distinctive feature found in all the samples was the regular rectangular or square shapes. This multi-component organic-inorganic nanomaterial was used to modify a platinum substrate and subsequently employed for the detection of carbamazepine, an anti-convulsion drug. UV/Vis spectroscopy revealed that a strong hypochromism occurred over time, after mixing solutions of graphene-Au-Ag with carbamazepine. This can be attributed to π-π stacking between the aromatic groups of the two compounds. Linear sweep voltammetry (LCV) provided evidence that the modified platinum substrate presented a significant electrocatalytic reaction toward the oxidation of carbamazepine. The intensity of the current was found to increase by up to 2.5 times, and the oxidation potential shifted from +1.5 to +1.35 V(Ag/AgCl) in comparison with the unmodified electrode. Electrochemical impedance spectroscopy (EIS) was further used to thoroughly assess the activity of the platinum electrode that was modified by the deposition of the Gr-Au-Ag composites in the presence of various concentrations of carbamazepine. The experimental EIS records were used for the generation of an equivalent electrical circuit, based on the charge-transfer resistance (R(ct)), Warburg impedance (Z(D)), solution resistance (R(s)), and a constant phase element (CPE) that characterizes the non-ideal interface capacitive responses. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of Agcore/Aushell bimetallic nanoparticles from physical mixtures of Au clusters and Ag ions under dark conditions and their catalytic activity for aerobic glucose oxidation

International Nuclear Information System (INIS)

Zhang, Haijun; Toshima, Naoki; Takasaki, Kanako; Okumura, Mitsutaka

2014-01-01

Graphical abstract: The synthesis, characterization and catalytic activities for glucose oxidation of AgAu bimetallic nanoparticles (BNPs) with size of less than 2 nm are reported. The catalytic activity of Ag 10 Au 90 BNPs was about two times higher than that of Au NPs, even the BNPs have a larger particle size than that of Au NPs. -- Highlights: • Ag core /Au shell BNPs with size of less than 2.0 nm were prepared. • No any reducing reagents and lights were used for the preparation of the BNPs. • The catalytic activity of the BNPs is about two times higher than that of Au NPs. -- Abstract: AgAu bimetallic nanoparticles (BNPs), one of the most extensively studied bimetallic systems in the literatures, could have various structures and compositions depending on their preparation conditions. In the present work, catalytically highly active PVP-protected Ag core /Au shell BNPs of about 2.5 nm in diameter were fabricated from physical mixtures of aqueous dispersions of Au nanoparticles and Ag + ions under dark conditions without using any reducing agents. The prepared Ag core /Au shell BNP colloidal catalysts, which possessed a high activity for aerobic glucose oxidation, were characterized by Ultraviolet–visible spectrophotometry (UV–Vis), Inductive coupled plasma emission spectrometer (ICP), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Energy disperse spectroscopy (EDS) in High-resolution scanning transmission electron microscopy (HR-STEM). The highest activity (11,360 mol-glucose h −1 mol-metal −1 ) was observed for the BNPs with the Ag/Au atomic ratio of 1/9, the TOF value of which is about two times higher than that of Au nanoparticles with the particle size of 1.3 nm. The enhanced catalytic activity of the prepared Ag core /Au shell BNPs compared to Au NPs can be ascribed to the presence of negatively charged Au atoms resulted from electron donations from neighboring Ag atoms and PVP due to electronic charge

Carbon dot-Au(i)Ag(0) assembly for the construction of an artificial light harvesting system.

Science.gov (United States)

Jana, Jayasmita; Aditya, Teresa; Pal, Tarasankar

2018-03-06

Artificial light harvesting systems (LHS) with inorganic counterparts are considered to be robust as well as mechanistically simple, where the system follows the donor-acceptor principle with an unchanged structural pattern. Plasmonic gold or silver nanoparticles are mostly chosen as inorganic counterparts to design artificial LHS. To capitalize on its electron accepting capability, Au(i) has been considered in this work for the synergistic stabilization of a system with intriguingly fluorescing silver(0) clusters produced in situ. Thus a stable fluorescent Au(i)Ag(0) assembly is generated with electron accepting capabilities. On the other hand, carbon dots have evolved as new fluorescent probes due to their unique physicochemical properties. Utilizing the simple electronic behavior of carbon dots, an electronic interaction between the fluorescent Au(i)Ag(0) and a carbon dot has been investigated for the construction of a new artificial light harvesting system. This coinage metal assembly allows surface energy transfer where it acts as an acceptor, while the carbon dot behaves as a good donor. The energy transfer efficiency has been calculated experimentally to be significant (81.3%) and the Au(i)Ag(0)-carbon dot assembly paves the way for efficient artificial LHS.

The Ag-Al-Cu system

Energy Technology Data Exchange (ETDEWEB)

Witusiewicz, V.T. [ACCESS e. V., Intzestr. 5, D-52072 Aachen (Germany)]. E-mail: victor@access.rwth-aachen.de; Hecht, U. [ACCESS e. V., Intzestr. 5, D-52072 Aachen (Germany); Fries, S.G. [ACCESS e. V., Intzestr. 5, D-52072 Aachen (Germany); Rex, S. [ACCESS e. V., Intzestr. 5, D-52072 Aachen (Germany)

2005-01-25

The thermodynamic description of the Ag-Al-Cu system is obtained by modelling the Gibbs energy of all individual phases in the system using the CALPHAD approach. The model parameters have been evaluated, by means of a computer optimisation technique, based on the descriptions of the constituent binaries proposed in the first part of the work and relevant experimental information for ternary alloys both from literature and own experimental measurements. Several vertical and isothermal sections, the liquidus surface and some thermodynamic properties are calculated using the evaluated parameters. A good agreement between the calculations and the experimental data is achieved.

A novel surface plasmon resonance biosensor based on the PDA-AgNPs-PDA-Au film sensing platform for horse IgG detection

Science.gov (United States)

Wang, Ning; Zhang, Di; Deng, Xinyu; Sun, Ying; Wang, Xinghua; Ma, Pinyi; Song, Daqian

2018-02-01

Herein we report a novel polydopamine-silver nanoparticle-polydopamine-gold (PDA-AgNPs-PDA-Au) film based surface plasmon resonance (SPR) biosensor for horse IgG detection. The PDA-AgNPs-PDA-Au film sensing platform was built on Au-film via layer-by-layer self-assembly. Ag ion was reduced in situ to AgNPs in presence of PDA. The top PDA layer can prevent AgNPs from being oxidized and connect with antibody via Schiff alkali reaction directly. The morphology and thickness of the modified gold film were characterized using scanning electron microscope and Talystep. Experimental results show that the PDA-AgNPs-PDA-Au film sensing platform is stable, regenerative and sensitive for horse IgG detection. The detection limit of horse IgG obtained with the present biosensor is 0.625 μg mL- 1, which is 2-fold and 4-fold lower than that obtained with biosensor based on PDA modified Au film and conventional biosensor based on MPA, respectively. Furthermore, when challenged to real serum samples, our sensor exhibited excellent specificity to horse IgG, suggesting its potential for industrial application.

Strong enhancement of the electrochemiluminescence of luminol by AuAg and PtAg alloy nanoclusters, and its sensitization by phenolic artificial oestrogens

International Nuclear Information System (INIS)

Wang, Ke; Tu, Yifeng; Wei, Xiuhua

2014-01-01

This paper reports on the synthesis of AuAg and PtAg alloy nanoclusters (NCs) and their enhancement effect on the electrochemiluminescence (ECL) of luminol. The conditions of synthesis were optimized, and the structure and properties of the NCs were characterized by X-ray diffraction, transmission electron microscopy, electrochemistry, and optical spectroscopy. The NCs are found to intensify (by up to 20 times) the ECL of luminol in solution of pH 8.5. This finding can largely extend the useful pH range of the ECL of luminol. The enhanced ECL is strongly affected by oxygen and hydrogen peroxide, and the mechanism of enhancement is attributed to the accelerated production of reactive oxygen species. The enhanced ECL is also affected by phenolic artificial estrogens, and this was used for their determination with detection limits as low as 700 pg L −1 (with AuAg) and 1.6 ng L −1 (with PtAg). The method was applied to the determination of such estrogens in egg samples using diethylstilbestrol as a reference substance. (author)

Sensitive and selective detection of Hg2+ and Cu2+ ions by fluorescent Ag nanoclusters synthesized via a hydrothermal method

Science.gov (United States)

Liu, Jing; Ren, Xiangling; Meng, Xianwei; Fang, Zheng; Tang, Fangqiong

2013-09-01

An easily prepared fluorescent Ag nanoclusters (Ag NCs) probe for the sensitive and selective detection of Hg2+ and Cu2+ ions was developed here. The Ag NCs were synthesized by using polymethacrylic acid sodium salt as a template via a convenient hydrothermal process. The as-prepared fluorescent Ag NCs were monodispersed, uniform and less than 2 nm in diameter, and can be quenched in the presence of mercury (Hg2+) or copper (Cu2+) ions. Excellent linear relationships existed between the quenching degree of the Ag NCs and the concentrations of Hg2+ or Cu2+ ions in the range of 10 nM to 20 μM or 10 nM to 30 μM, respectively. By using ethylenediaminetetraacetate (EDTA) as the masking agent of Cu2+, Hg2+ was exclusively detected in coexistence with Cu2+ with high sensitivity (LOD = 10 nM), which also provided a reusable detection method for Cu2+. Furthermore, the different quenching phenomena caused by the two metals ions such as changes in visible colour, shifts of UV absorbance peaks and changes in size of Ag NCs make it easy to distinguish between them. Therefore the easily synthesized fluorescent Ag NCs may have great potential as Hg2+ and Cu2+ ions sensors.An easily prepared fluorescent Ag nanoclusters (Ag NCs) probe for the sensitive and selective detection of Hg2+ and Cu2+ ions was developed here. The Ag NCs were synthesized by using polymethacrylic acid sodium salt as a template via a convenient hydrothermal process. The as-prepared fluorescent Ag NCs were monodispersed, uniform and less than 2 nm in diameter, and can be quenched in the presence of mercury (Hg2+) or copper (Cu2+) ions. Excellent linear relationships existed between the quenching degree of the Ag NCs and the concentrations of Hg2+ or Cu2+ ions in the range of 10 nM to 20 μM or 10 nM to 30 μM, respectively. By using ethylenediaminetetraacetate (EDTA) as the masking agent of Cu2+, Hg2+ was exclusively detected in coexistence with Cu2+ with high sensitivity (LOD = 10 nM), which also provided a

The effect of intermetallic compound morphology on Cu diffusion in Sn-Ag and Sn-Pb solder bump on the Ni/Cu Under-bump metallization

Science.gov (United States)

Jang, Guh-Yaw; Duh, Jenq-Gong

2005-01-01

The eutectic Sn-Ag solder alloy is one of the candidates for the Pb-free solder, and Sn-Pb solder alloys are still widely used in today’s electronic packages. In this tudy, the interfacial reaction in the eutectic Sn-Ag and Sn-Pb solder joints was investigated with an assembly of a solder/Ni/Cu/Ti/Si3N4/Si multilayer structures. In the Sn-3.5Ag solder joints reflowed at 260°C, only the (Ni1-x,Cux)3Sn4 intermetallic compound (IMC) formed at the solder/Ni interface. For the Sn-37Pb solder reflowed at 225°C for one to ten cycles, only the (Ni1-x,Cux)3Sn4 IMC formed between the solder and the Ni/Cu under-bump metallization (UBM). Nevertheless, the (Cu1-y,Niy)6Sn5 IMC was observed in joints reflowed at 245°C after five cycles and at 265°C after three cycles. With the aid of microstructure evolution, quantitative analysis, and elemental distribution between the solder and Ni/Cu UBM, it was revealed that Cu content in the solder near the solder/IMC interface played an important role in the formation of the (Cu1-y,Niy)6Sn5 IMC. In addition, the diffusion behavior of Cu in eutectic Sn-Ag and Sn-Pb solders with the Ni/Cu UBM were probed and discussed. The atomic flux of Cu diffused through Ni was evaluated by detailed quantitative analysis in an electron probe microanalyzer (EPMA). During reflow, the atomic flux of Cu was on the order of 1016-1017 atoms/cm2sec in both the eutectic Sn-Ag and Sn-Pb systems.

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

Science.gov (United States)

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

Developing an aqueous approach for synthesizing Au and M@Au (M = Pd, CuPt) hybrid nanostars with plasmonic properties

OpenAIRE

Du, Jingshan; Yu, Junjie; Xiong, Yalin; Lin, Zhuoqing; Zhang, Hui; Yang, Deren

2014-01-01

Anisotropic Au nanoparticles show unique localized surface plasmon resonance (LSPR) properties, which make it attractive in optical, sensing, and biomedical applications. In this contribution, we report a general and facile strategy towards aqueous synthesis of Au and M@Au (M = Pd, CuPt) hybrid nanostars by reducing HAuCl4 with ethanolamine in the presence of cetyltrimethylammonium bromide (CTAB). According to electron microscopic observation and spectral monitoring, we found that the layered...

Probing Interactions between AuNPs/AgNPs and Giant Unilamellar Vesicles (GUVs Using Hyperspectral Dark-field Microscopy

Directory of Open Access Journals (Sweden)

Anupama Bhat

2018-03-01

Full Text Available Noble metallic nanoparticles (NPs such as gold and silver nanoparticles (AuNPs and AgNPs have been shown to exhibit anti-tumor effect in anti-angiogenesis, photothermal and radio therapeutics. On the other hand, cell membranes are critical locales for specific targeting of cancerous cells. Therefore, NP-membrane interactions need be studied at molecular level to help better understand the underlying physicochemical mechanisms for future applications in cancer nanotechnology. Herein, we report our study on the interactions between citrate stabilized colloidal AuNPs/AgNPs (10 nm in size and giant unilamellar vesicles (GUVs using hyperspectral dark-field microscopy. GUVs are large model vesicle systems well established for the study of membrane dynamics. GUVs used in this study were prepared with dimyristoyl phosphatidylcholine (DMPC and doped with cholesterol at various molar concentrations. Both imaging and spectral results support that AuNPs and AgNPs interact very differently with GUVs, i.e., AuNPs tend to integrate in between the lipid bilayer and form a uniform golden-brown crust on vesicles, whereas AgNPs are bejeweled on the vesicle surface as isolated particles or clusters with much varied configurations. The more disruptive capability of AuNPs is hypothesized to be responsible for the formation of golden brown crusts in AuNP-GUV interaction. GUVs of 20 mol% CHOL:DMPC were found to be a most economical concentration for GUVs to achieve the best integrity and the least permeability, consistent with the finding from other phase studies of lipid mixture that the liquid-ordered domains have the largest area fraction of the entire membrane at around 20 mol% of cholesterol.

Superconducting Bi-Sr-Ca-Cu-O thin films from metallo-organic complexes

International Nuclear Information System (INIS)

Gruber, H.; Krautz, E.; Fritzer, H.P.; Popitsch, A.

1991-01-01

Thin films in the Bi-Sr-Ca-Cu-O system are produced by decomposition of organic precursor compounds containing different metallo-organic complexes. The superconducting phase identified is Bi 2 Sr 2 CaCu 2 O 8+x on (100)-MgO single crystal substrates, polycrystalline Au- and Ag-ribbons and Bi 2 Sr 2 Ca 2 Cu 3 O 10+x on Ag-ribbons. For the 2212-phase a zero resistance temperature of 79 K is found. The 2223-samples on Ag-ribbons show a broad transition at 110 K with a zero resistance at 85 K. SEM and EDX are used for the detection of the microstructure and composition of the prepared films. (orig.)

Highly sensitive colorimetric detection of glucose in a serum based on DNA-embeded Au@Ag core–shell nanoparticles

International Nuclear Information System (INIS)

Kang, Fei; Xu, Kun; Hou, Xiangshu

2015-01-01

Glucose is a key energy substance in diverse biology and closely related to the life activities of the organism. To develop a simple and sensitive method for glucose detection is extremely urgent but still remains a key challenge. Herein, we report a colorimetric glucose sensor in a homogeneous system based on DNA-embedded core–shell Au@Ag nanoparticles. In this assay, a glucose substrate was first catalytically oxidized by glucose oxidase to produce H 2 O 2 which would further oxidize and gradually etch the outer silver shell of Au@Ag nanoparticles. Afterwards, the solution color changed from yellow to red and the surface plasmon resonance (SPR) band of Au@Ag nanoparticles declined and red-shifted from 430 to 516 nm. Compared with previous silver-based glucose colorimetric detection strategies, the distinctive SPR band change is superior to the color variation, which is critical to the high sensitivity of this assay. Benefiting from the outstanding optical property, robust stability and well-dispersion of the core–shell Au@AgNPs hybrid, this colorimetric assay obtained a detection limit of glucose as low as 10 nM, which is at least a 10-fold improvement over other AgNPs-based procedures. Moreover, this optical biosensor was successfully employed to the determination of glucose in fetal bovine serum. (paper)

Effect of rare earth Ce on the fatigue life of SnAgCu solder joints in WLCSP device using FEM and experiments

International Nuclear Information System (INIS)

Zhang, Liang; Han, Ji-guang; Guo, Yong-huan; He, Cheng-wen

2014-01-01

With the addition of 0.03 wt% rare earth Ce, in our previous works, the properties of SnAgCu solder were enhanced obviously. Based on the Garofalo–Arrhenius creep constitutive model, finite element method was used to simulate the stress–strain response during thermal cycle loading, and combined with the fatigue life prediction models, the fatigue life of SnAgCu/SnAgCuCe solder joints was calculated respectively, which can demonstrate the effect of the rare earth Ce on the fatigue life of SnAgCu solder joints. The results indicated that the maximum stress–strain can be found on the top surface of the corner solder joint, and the warpage of the PCB substrate occurred during thermal cycle loading. The trends obtained from modeling results have a good agreement with the experimental data reported in the literature for WLCSP devices. In addition, the stress–strain of SnAgCuCe solder joints is lower than that of SnAgCu solder joints. The thermal fatigue lives of solder joints calculated based on the creep model and creep strain energy density model show that the fatigue life of SnAgCuCe solder joints is higher than the SnAgCu solder joints. The fatigue life of SnAgCuCe solder joints can be enhanced significantly with the addition of Ce, is 30.2% higher than that of SnAgCu solder joints, which can be attributed to the CeSn 3 particles formed resisting the motion of dislocation; moreover, the refinement of microstructure and the IMC sizes also contribute to the enhancement of fatigue life, which elucidates that SnAgCuCe solder can be utilized in electronic industry with high reliability replacing the SnAgCu solder

Tuning of Ag doped core−shell ZnO NWs/Cu2O grown by electrochemical deposition

International Nuclear Information System (INIS)

Makhlouf, Houssin; Messaoudi, Olfa; Souissi, Ahmed; Ben Assaker, Ibtissem; Oueslati, Mihrez; Bechelany, Mikhael; Chtourou, Radhouane

2015-01-01

ZnO nanowires (NWs)/Cu 2 O–Ag core–shell nanostructures (NSs) have been synthesized by electrochemical deposition method on ITO-coated glass substrates in order to improve the efficiency of the type-II transition of core–shell ZnO NWs/Cu 2 O–Ag NSs. The morphologies of the obtained NSs were studied by scanning electron microscopy confirming the presence of core–shell NSs. The crystalline proprieties were analyzed by x-ray diffraction and micro-Raman measurement: wurtzite ZnO and cuprit Cu 2 O phase were founded. The presence of Ag content in core–shell NS was detected by EDX. Optical measurement reveals an additional contribution δE at about 1.72 eV attributed to the type-II interfacial transition between the valance band of cuprit−Cu 2 O and the conduction band of W−ZnO. The effect of the Ag doping into the type-II transition was investigated. A red shift of the type-II transition was detected according to the Ag concentration. These materials could have potential applications in photocatalytic and photovoltaic fields. (paper)

Synthesis of Small Au-Ag Core-Shell Cubes, Cuboctahedra, and Octahedra with Size Tunability and Their Optical and Photothermal Properties.

Science.gov (United States)

Chiang, Chieh; Huang, Michael H

2015-12-02

Aqueous phase synthesis of small Au-Ag core-shell nanocubes, cuboctahedra, and octahedra is achieved through the deposition of Ag shells on small octahedral Au cores. These nanocrystals show efficient photothermal activity and can assemble into supercrystals. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of microstructure on corrosion behavior of Ag-30Cu-27Sn alloy in vitro media

International Nuclear Information System (INIS)

Salehisaki, Mehdi; Aryana, Maryam

2014-01-01

Highlights: • High cooling rates decrease the number of Ag intermetallic particles in Cu-rich phase. • Increasing cooling rate improves corrosion behavior of Ag-30Cu-27Sn dental alloy. • Cathode/anode ratio in Cu-rich phases determines the corrosion behavior of alloy. - Abstract: In the present work, three simple heat treatment cycles were used to study the effects of microstructure on electrochemical corrosion behavior of Ag-30Cu-27Sn dental alloy. The electrochemical impedance spectroscopy (EIS) measurements and potentiodynamic polarization tests were carried out to investigate the corrosion behavior of as-cast and heat treated samples in synthetic saliva solution. The presence of intermetallic compounds were studied by X-ray diffraction method (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray detector (EDAX). The microstructural observations and electrochemical corrosion results revealed that, increasing the cooling rate improves the corrosion behavior of under investigation samples. Improvement of the corrosion behavior is attributed to reducing the area of fine distributed Ag 3 Sn islands in the Cu-rich matrix which decrease the cathode/anode ratio of microgalvanic cells

Investigation of modulus hardening of various co-clusters in aged Al-Cu-Mg-Ag alloy by atom probe tomography

Energy Technology Data Exchange (ETDEWEB)

Bai, Song [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Liu, Zhiyi, E-mail: liuzhiyi@csu.edu.cn [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Ying, Puyou; Wang, Jian; Li, Junlin [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China)

2016-06-21

The modulus hardening capability of various co-clusters in a low Cu/Mg ratio Al-Cu-Mg-Ag alloy aged at 165 °C is investigated by quantitative atom probe tomography analysis. Prolonged aging from 5 min to 2 h leads to the simultaneous increase in the critical shear stress of both Mg-Ag and Cu-Mg co-clusters. Regardless of the higher shear modulus of Cu-Mg co-clusters, calculation results show that Mg-Ag co-clusters possess a greater modulus hardening capability than Cu-Mg co-clusters, suggesting its primary contribution to the rapid hardening at the early aging stage. As aging extends from 30 min to 2 h, the increment in the critical shear stress of Mg-Ag co-clusters is lower than that of Cu-Mg co-clusters due to the precipitation of high density Ω phase. In addition, the shear modulus of Mg-Ag co-clusters is generally independent on its size at each investigated condition.

Investigation of modulus hardening of various co-clusters in aged Al-Cu-Mg-Ag alloy by atom probe tomography

International Nuclear Information System (INIS)

Bai, Song; Liu, Zhiyi; Ying, Puyou; Wang, Jian; Li, Junlin

2016-01-01

The modulus hardening capability of various co-clusters in a low Cu/Mg ratio Al-Cu-Mg-Ag alloy aged at 165 °C is investigated by quantitative atom probe tomography analysis. Prolonged aging from 5 min to 2 h leads to the simultaneous increase in the critical shear stress of both Mg-Ag and Cu-Mg co-clusters. Regardless of the higher shear modulus of Cu-Mg co-clusters, calculation results show that Mg-Ag co-clusters possess a greater modulus hardening capability than Cu-Mg co-clusters, suggesting its primary contribution to the rapid hardening at the early aging stage. As aging extends from 30 min to 2 h, the increment in the critical shear stress of Mg-Ag co-clusters is lower than that of Cu-Mg co-clusters due to the precipitation of high density Ω phase. In addition, the shear modulus of Mg-Ag co-clusters is generally independent on its size at each investigated condition.

Dosimetric characteristics of Li2B4O7:Cu,Ag,P solid TL detectors

International Nuclear Information System (INIS)

Proki, M.

2002-01-01

The main dosimetric characteristics are presented of newly prepared tissue-equivalent, highly sensitive thermoluminescent detector, Li 2 B 4 O 7 :Cu,Ag,P in the form of sintered pellets, developed at the Institute of Nuclear Sciences, Vin a . As a result of an advancement in the preparation procedure by the sensitising of basic copper activated lithium borate TL material, significant improvement in the TL sensitivity of Li 2 B 4 O 7 :Cu,Ag,P was gained. The glow curve of Li 2 B 4 O 7 :Cu,Ag,P consists of well defined main dosimetric peak situated at about 185-190 deg. C with the TL sensitivity which is about four to five times higher than that of LiF:Mg,Ti (TLD-100). From the experimental results a very wide linear dose response range, up to 10 3 Gy is evident. Dosimetric characteristics make sintered solid Li 2 B 4 O 7 :Cu,Ag,P TL detectors very promising for different dosimetry applications particularly in medical dosimetry and also for individual monitoring. (author)

Effect of Ag micro-alloying on the microstructure and properties of Cu-14Fe in situ composite

International Nuclear Information System (INIS)

Liu, K.M.; Lu, D.P.; Zhou, H.T.; Atrens, A.; Zou, J.; Yang, Y.L.; Zeng, S.M.

2010-01-01

This paper studied Ag micro-alloying in the deformation-processed Cu-14Fe in situ composite, by a comparison of Cu-14Fe and Cu-14Fe-0.06Ag. Each alloy was prepared by casting and processed into an in situ composite by hot and cold working. The microstructures were documented using light microscopy and scanning electron microscopy (SEM). The mechanical properties were measured with a tensile-testing machine. The electrical conductivity was measured with a micro-ohmmeter. For both alloys, the as-cast microstructure consisted of a Cu matrix and Fe dendrites; after hot and cold working the microstructure consisted of a Cu matrix containing Fe fibres elongated in the working direction. The as-cast Ag-containing alloy contained finer Fe dendrites. The Ag-containing in situ composite had thinner Fe fibres, higher tensile strength, higher ductility, and higher conductivity. The cold worked Cu-14Fe-0.06Ag in situ composite with cumulative cold deformation strain η = 7.8 (where η = ln(A 0 /A) and A 0 and A are the original and final cross-section areas, respectively), achieved a tensile strength of 930 MPa and a conductivity of 56%IACS (International Annealed Copper Standard; 17.241 nΩ m is defined as 100%IACS). The Ag micro-alloyed in situ composite had a combination of properties comparable to that of a much more expensive alloy containing much more Ag. After 1 h heat treatment at 300 deg. C, the tensile strength was increased to 950 MPa and the conductivity was increased to 56.4%IACS.

Evaluation of the photophysicochemical properties and photodynamic therapy activity of nanoconjugates of zinc phthalocyanine linked to glutathione capped Au and Au3Ag1 nanoparticles

CSIR Research Space (South Africa)

Oluwole, DA

2018-03-01

Full Text Available , Charles Maphanga, Saturnin Ombinda-Lemboumba, Patience Mthunzi-Kufa, Tebello Nyokong ABSTRACT: We report on the synthesis of glutathione capped gold (AuNPs–GSH) and gold– silver (Au3Ag1NPs–GSH) nanoparticles and their covalent attachment to Zn...

Single crystal structures of the new vanadates CuMgVO{sub 4} and AgMgVO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Ben Yahia, Hamdi, E-mail: Hyahia@qf.org.qa [Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, PO Box 5825, Doha (Qatar); Shikano, Masahiro, E-mail: shikano.masahiro@aist.go.jp [Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Essehli, Rachid; Belharouak, Ilias [Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, PO Box 5825, Doha (Qatar)

2016-08-01

The new compounds CuMgVO{sub 4} and AgMgVO{sub 4} have been synthesized by a solid state reaction route. Their crystal structures were determined from single-crystal X-ray diffraction data. CuMgVO{sub 4} crystallizes with Na{sub 2}CrO{sub 4}-type structure with space group Cmcm, a = 5.6932 (10), b = 8.7055 (15), c = 6.2789 (10) Å, V = 311.20 (9) Å{sup 3}, and Z = 4, whereas AgMgVO{sub 4} crystallizes in the maricite-type structure with space group Pnma, a = 9.4286 (14), b = 6.7465 (10), c = 5.3360 (8) Å, V = 339.42 (9) Å{sup 3}, and Z = 4. Both structures of CuMgVO{sub 4}, and AgMgVO{sub 4} contain MgO{sub 4} chains made up of edge-sharing MgO{sub 6} octahedra. In CuMgVO{sub 4} the MgO{sub 4} chains are interconnected through CuVO{sub 4} double chains made up of VO{sub 4} and CuO{sub 4} tetrahedra sharing corners and edges, however in AgMgVO{sub 4} the chains are interlinked by the VO{sub 4} and AgO{sub 4} tetrahedra sharing only corners. - Highlights: • We have been able to grow CuMgVO{sub 4} and AgMgVO{sub 4} single crystals. • We solved their crystal structures using single crystal data. • We compared the crystal structures of CuMgVO{sub 4} and AgMgVO{sub 4}.

Coincidence Doppler broadening and 3DAP study of the pre-precipitation stage of an Al-Li-Cu-Mg-Ag alloy

International Nuclear Information System (INIS)

Honma, T.; Yanagita, S.; Hono, K.; Nagai, Y.; Hasegawa, M.

2004-01-01

Pre-precipitation solute clustering in Al-Li-Cu-Mg-Ag and Al-Cu-Mg-Ag alloys has been investigated by coincidence Doppler broadening (CDB) spectroscopy of positron annihilation and three-dimensional atom probe (3DAP) analysis. Although Ag-Mg co-clusters form in the Al-Cu-Mg-Ag alloy in the early stage of aging, no evidence for the co-cluster formation was obtained from the Li containing alloy using 3DAP. While CDB spectra indicated that vacancies are associated with Ag after aging for 15 s in the Al-Cu-Mg-Ag alloy, vacancy-Ag association is suppressed in the Li containing alloy. Based on the 3DAP and CDB results, the reasons for the completely different clustering behaviors observed in these two similar alloys are discussed

Determination of the compositions of the DIGM zone in nanocrystalline Ag/Au and Ag/Pd thin films by secondary neutral mass spectrometry

Directory of Open Access Journals (Sweden)

Gábor Y. Molnár

2016-03-01

Full Text Available Alloying by grain boundary diffusion-induced grain boundary migration is investigated by secondary neutral mass spectrometry depth profiling in Ag/Au and Ag/Pd nanocrystalline thin film systems. It is shown that the compositions in zones left behind the moving boundaries can be determined by this technique if the process takes place at low temperatures where solely the grain boundary transport is the contributing mechanism and the gain size is less than the half of the grain boundary migration distance. The results in Ag/Au system are in good accordance with the predictions given by the step mechanism of grain boundary migration, i.e., the saturation compositions are higher in the slower component (i.e., in Au or Pd. It is shown that the homogenization process stops after reaching the saturation values and further intermixing can take place only if fresh samples with initial compositions, according to the saturation values, are produced and heat treated at the same temperature. The reversal of the film sequence resulted in the reversal of the inequality of the compositions in the alloyed zones, which is in contrast to the above theoretical model, and explained by possible effects of the stress gradients developed by the diffusion processes itself.

Fast and facile preparation of CTAB based gels and their applications in Au and Ag nanoparticles synthesis

Energy Technology Data Exchange (ETDEWEB)

Upadhyay, Ravi Kant, E-mail: rkupadhyay85@gmail.com [Department of Chemistry, School of Natural Sciences, Shiv Nadar University, Gautam Budh Nagar, 201314 Uttar Pradesh (India); Soin, Navneet, E-mail: n.soin@bolton.ac.uk [Knowledge Centre for Materials Chemistry (KCMC), Institute for Materials Research and Innovation (IMRI), University of Bolton, Deane Road, Bolton BL3 5AB (United Kingdom); Saha, Susmita, E-mail: ssaha@bose.res.in [Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Barman, Anjan, E-mail: abarman@bose.res.in [Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Sinha Roy, Susanta, E-mail: susanta.roy@snu.edu.in [Department of Physics, School of Natural Sciences, Shiv Nadar University, Gautam Budh Nagar, 201314 Uttar Pradesh (India)

2015-04-15

We have demonstrated that the gel-like mesophase of Cetyltrimethylammonium bromide (CTAB) can be synthesized by judicial adjustment of water to surfactant molar ratio (W{sub 0}), without using any additional salts, gelating agents or co-surfactants. Gel formation was found to be highly dependent on the water to surfactant molar ratio (W{sub 0}), with the lowest value of W{sub 0} (41.5) resulting in rapid gel formation. Environmental scanning electron microscope (ESEM) analysis revealed that the gel was comprised of interconnected cylindrical structures. The presence of hydrogen bonding in the gel-like mesophase was confirmed by Fourier Transform Infrared spectroscopy (FTIR) analysis. Rheology measurements revealed that all the gel samples were highly viscoelastic in nature. Furthermore, Au and Ag containing CTAB gels were explored as precursors for the preparation of spherical Gold (Au) and Silver (Ag) nanoparticles using Sodium borohydride (NaBH{sub 4}) as reducing agent. The effects of NaBH{sub 4} concentration on the particle size and morphology of the Au and Ag nanoparticles have also been studied. - Highlights: • A facile synthesis of CTAB based gel-like mesophase is reported. • CTAB gels were obtained by adjusting water to surfactant molar ratio (W{sub 0}). • FTIR analysis revealed that hydrogen bonding plays a key role in gel formation. • Au, Ag nanoparticles were synthesized by using CTAB gel and NaBH{sub 4}.

Comment on ``(Au-Ag)144(SR)60 alloy nanomolecules'' by C. Kumara and A. Dass, Nanoscale, 2011, 3, 3064

Science.gov (United States)

Barcaro, Giovanni; Sementa, Luca; Fortunelli, Alessandro; Stener, Mauro

2015-04-01

A recent paper in this journal reported the synthesis and characterization via electrospray ionization mass spectroscopy and UV-vis spectroscopy of (Au-Ag)144(SR)60 alloy nanomolecules with different compositions, ranging from 1 : 0 to 1 : 0.75 Au : Ag ratios. The UV-vis spectra of such systems were found to exhibit absorption peaks at 310 nm, 425 nm and 560 nm, interpreted as reminiscent of the silver surface plasmon resonance band due to simple atomic replacement of Au by Ag atoms in a fixed structural framework. On the basis of a comparison of experimentally observed and theoretically simulated optical absorption spectra, we conclude that the experimental situation must be more complicated, and that further work is needed to achieve atomistic insight into these fascinating systems.

Effect of Cooling Rate on the Longitudinal Modulus of Cu3Sn Phase of Ag-Sn-Cu Amalgam Alloy (Part II

Directory of Open Access Journals (Sweden)

R. H. Rusli

2015-10-01

Full Text Available Effects of cooling rate (at the time of solidification on the elastic constants of Cu3Sn phase of Ag-Sn-Cu dental amalgam alloy were studied. In this study, three types of alloys were made, with the composition Cu-38-37 wt% Sn by means of casting, where each alloy was subjected to different cooling rate, such as cooling on the air (AC, air blown (AB, and quenched in the water (WQ. X-ray diffraction, metallography, and Scanning Electron Microscopy with Energy Dispersive Spectroscopy studies of three alloys indicated the existence of Cu3Sn phase. Determination of the modulus of elasticity of Cu3Sn (ε phase was carried out by the measurement of longitudinal and transversal waves velocity using ultrasonic technique. The result shows that Cu3Sn (ε phase on AC gives higher modulus of elasticity values than those of Cu3Sn (ε on AB and WQ. The high modulus of elasticity value will produce a strong Ag-Sn-Cu dental amalagam alloy.

The photovoltaic performance of Ag2S quantum dots-sensitized solar cells using plasmonic Au nanoparticles/TiO2 working electrodes

Science.gov (United States)

Badawi, Ali; Mostafa, Nasser Y.; Al-Hosiny, Najm M.; Merazga, Amar; Albaradi, Ateyyah M.; Abdel-Wahab, F.; Atta, A. A.

2018-06-01

The photovoltaic performance of silver sulfide (Ag2S) quantum dots-sensitized solar cells (QDSSCs) using different concentrations (0, 0.05, 0.1, 0.3 and 0.5 wt.%) of plasmonic Au nanoparticles (NPs)/titania (TiO2) electrodes has been investigated. Ag2S quantum dots (QDs) were adsorbed onto the Au NPs/titania electrodes using the successive ionic layer adsorption and reaction (SILAR) deposition technique. The morphological properties of the Au NPs and the prepared titania electrodes were characterized using transmission electron microscope (TEM) and scanning electron microscope (SEM), respectively. The energy-dispersive X-ray (EDX) spectra of the bare titania and Ag2S QDs-sensitized titania electrodes were recorded. The optical properties of the prepared Ag2S QDs-sensitized titania electrodes were measured using a UV-visible spectrophotometer. The estimated energy band gap of Ag2S QDs-sensitized titania electrodes is 1.96 eV. The photovoltaic performance of the assembled Ag2S QDSSCs was measured under 100 mW/cm2 solar illumination. The optimal photovoltaic parameters were obtained as follows: open circuit voltage Voc = 0.50 V, current density Jsc = 3.18 mA/cm2, fill factor (FF) = 0.35 and energy conversion efficiency η = 0.55% for 0.3 wt.% of Au NPs/titania electrode. These results are attributed to the enhancement in the absorption and decrease in the electron-hole pairs recombination rate. The open circuit voltage decay (OCVD) measurements of the assembled Ag2S QDSSCs were measured. The calculated electron lifetime (τ) in Ag2S QDSSCs with Au NPs/titania electrodes is at least one order of magnitude more than that with bare titania electrode. The cut-on-cut-off cycles of the solar illumination measurements show the rapid sensitivity and good reproducibility of the assembled Ag2S QDSSCs.

Cooling thermal parameters and microstructure features of directionally solidified ternary Sn–Bi–(Cu,Ag) solder alloys

Energy Technology Data Exchange (ETDEWEB)

Silva, Bismarck L., E-mail: bismarck_luiz@yahoo.com.br [Department of Materials Engineering, Federal University of São Carlos, UFSCar, 13565-905 São Carlos, SP (Brazil); Garcia, Amauri [Department of Manufacturing and Materials Engineering, University of Campinas, UNICAMP, 13083-860 Campinas, SP (Brazil); Spinelli, José E. [Department of Materials Engineering, Federal University of São Carlos, UFSCar, 13565-905 São Carlos, SP (Brazil)

2016-04-15

Low temperature soldering technology encompasses Sn–Bi based alloys as reference materials for joints since such alloys may be molten at temperatures less than 180 °C. Despite the relatively high strength of these alloys, segregation problems and low ductility are recognized as potential disadvantages. Thus, for low-temperature applications, Bi–Sn eutectic or near-eutectic compositions with or without additions of alloying elements are considered interesting possibilities. In this context, additions of third elements such as Cu and Ag may be an alternative in order to reach sounder solder joints. The length scale of the phases and their proportions are known to be the most important factors affecting the final wear, mechanical and corrosions properties of ternary Sn–Bi–(Cu,Ag) alloys. In spite of this promising outlook, studies emphasizing interrelations of microstructure features and solidification thermal parameters regarding these multicomponent alloys are rare in the literature. In the present investigation Sn–Bi–(Cu,Ag) alloys were directionally solidified (DS) under transient heat flow conditions. A complete characterization is performed including experimental cooling thermal parameters, segregation (XRF), optical and scanning electron microscopies, X-ray diffraction (XRD) and length scale of the microstructural phases. Experimental growth laws relating dendritic spacings to solidification thermal parameters have been proposed with emphasis on the effects of Ag and Cu. The theoretical predictions of the Rappaz-Boettinger model are shown to be slightly above the experimental scatter of secondary dendritic arm spacings for both ternary Sn–Bi–Cu and Sn–Bi–Ag alloys examined. - Highlights: • Dendritic growth prevailed for the ternary Sn–Bi–Cu and Sn–Bi–Ag solder alloys. • Bi precipitates within Sn-rich dendrites were shown to be unevenly distributed. • Morphology and preferential region for the Ag{sub 3}Sn growth depend on Ag

Label-free sensitive luminescence biosensor for immunoglobulin G based on Ag6Au6 ethisterone cluster-estrogen receptor α aggregation and graphene.

Science.gov (United States)

Chen, Nannan; Guo, Wenjing; Lin, Zhixiang; Wei, Qiaohua; Chen, Guonan

2018-08-01

A specific and label-free "on-off-on" luminescence biosensor based on a novel heterometallic cluster [Ag 6 Au 6 (ethisterone) 12 ]-estrogen receptor α (Ag 6 Au 6 Eth-ERα) aggregation utilizing graphene oxide (GO) as a quencher to lead a small background signal was firstly constructed to detect immunoglobulin G (IgG) with a simple process and high selectivity. The efficient photoluminescent (PL) Ag 6 Au 6 Eth-ERα aggregation is strongly quenched by GO. In the presence of IgG, the PL of this system will be restored, and perceivable by human eyes under UV lamp excitation (365 nm). The quenching mechanism of GO on Ag 6 Au 6 Eth-ERα and enhancement mechanism of IgG on Ag 6 Au 6 Eth-ERα-GO were investigated in detail. Under the optimum conditions, the biosensor for high sensitive IgG detection expressed a wider linear range of 0.0078-10 ng/mL and a lower detection limit of 0.65 pg/mL with good stability and repeatability, which provided a new approach for label-free IgG detection. Copyright © 2018 Elsevier B.V. All rights reserved.

Highly efficient and porous TiO{sub 2}-coated Ag@Fe{sub 3}O{sub 4}@C-Au microspheres for degradation of organic pollutants

Energy Technology Data Exchange (ETDEWEB)

Shen, Mao, E-mail: shenmao19820808@163.com; Chen, Suqing, E-mail: 465060605@qq.com; Jia, Wenping, E-mail: tzcjwp@tzc.edu.cn [Taizhou University, College of Pharmaceutical and Chemical Engineering (China); Fan, Guodong, E-mail: fangd@sust.edu.cn [Shan xi University of Science and Technology, Key Laboratory of Auxiliary Chemistry and Technology for Chemical Industry, Ministry of Education (China); Jin, Yanxian, E-mail: shirleyj@tzc.edu.cn; Liang, Huading, E-mail: shanjian8208@163.com [Taizhou University, College of Pharmaceutical and Chemical Engineering (China)

2016-12-15

In this paper, we reported a novel hierarchical porous Ag@Fe{sub 3}O{sub 4}@C-Au@TiO{sub 2} core@shell microspheres with a highly photocatalytic activity and magnetically separable properties. The synthesis method is included of a Fe{sub 3}O{sub 4} magnetic embedded Ag core (Ag@Fe{sub 3}O{sub 4}), an interlayer of carbon modified by PEI to form sufficient amounts of amine functional groups (Ag@Fe{sub 3}O{sub 4}@C-PEI), the grafting of Au nanoparticles on the surface of Ag@Fe{sub 3}O{sub 4}@C-PEI (Ag@Fe{sub 3}O{sub 4}@C-Au), and an ordered porous TiO{sub 2} structured shell. As an example of the applications, the photocatalytic activities of the samples were investigated by the reduction of Rhodamine B (RhB) under visible-light irradiation. The results show that the porous Ag@Fe{sub 3}O{sub 4}@C-Au@TiO{sub 2} core@shell microspheres display higher adsorption and photocatalytic activities compared to the pure porous TiO{sub 2} and Ag@Fe{sub 3}O{sub 4}@C@TiO{sub 2} microspheres, which are attributed to the local surface plasmon resonance (LSPR) by the Ag and Au nanoparticles and the high specific surface area.

Hydrazine reduction of metal ions to porous submicro-structures of Ag, Pd, Cu, Ni, and Bi

Energy Technology Data Exchange (ETDEWEB)

Wang Yue; Shi Yongfang; Chen Yubiao [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Wu Liming, E-mail: liming_wu@fjirsm.ac.cn [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

2012-07-15

Porous submicro-structures of Ag, Pd, Cu, Ni, and Bi with high surface area have been prepared by the reduction of hydrazine in glycerol-ethanol solution at room temperature or 120-180 Degree-Sign C. Phase purity, morphology, and specific surface area have been characterized. The reactions probably undergo three different mechanisms: simple reduction for Ag and Pd, coordination-then-reduction for Cu and Ni, and hydrolysis-then-reduction for Bi. The reductant hydrazine also plays an important role to the formation of the porous submicro-structure. The reaction temperature influences the size of the constituent particles and the overall architecture of the submicro-structure so as to influence the surface area value. The as-prepared porous metals have shown the second largest surface area ever reported, which are smaller than those made by the reduction of NaBH{sub 4}, but larger than those made by hard or soft template methods. - Graphical abstract: Porous submicro-structures of Ag, Pd, Cu, Ni, and Bi with high surface area have been prepared by the reduction of hydrazine in the glycerol-ethanol solution at room temperature or 120-180 Degree-Sign C. The reactions undergo different mechanisms: simple reduction for Ag and Pd, coordination-then-reduction for Cu and Ni, and hydrolysis-then-reduction for Bi. Highlights: Black-Right-Pointing-Pointer Syntheses of porous Ag, Pd, Cu, Ni, and Bi with high surface area. Black-Right-Pointing-Pointer Ag and Pd undergo simple reduction. Black-Right-Pointing-Pointer Cu and Ni undergo coordination-then-reduction. Black-Right-Pointing-Pointer Bi undergoes hydrolysis-then-reduction. Black-Right-Pointing-Pointer The as-prepared metals have shown the second largest surface area ever reported.

Molecular dynamics simulation of joining process of Ag-Au nanowires and mechanical properties of the hybrid nanojoint

Directory of Open Access Journals (Sweden)

Su Ding

2015-05-01

Full Text Available The nanojoining process of Ag-Au hybrid nanowires at 800K was comprehensively studied by virtue of molecular dynamics (MD simulation. Three kinds of configurations including end-to-end, T-like and X-like were built in the simulation aiming to understand the nanojoining mechanism. The detailed dynamic evolution of atoms, crystal structure transformation and defects development during the nanojoining processes were performed. The results indicate that there are two stages in the nanojoining process of Ag-Au nanowires which are atom diffusion and new bonds formation. Temperature is a key parameter affecting both stages ascribed to the energy supply and the optimum temperature for Ag-Au nanojoint with diameter of 4.08 nm has been discussed. The mechanical properties of the nanojoint were examined with simulation of tensile test on the end-to-end joint. It was revealed that the nanojoint was strong enough to resist fracture at the joining area.

In Situ Synthesis of Ag@Cu2O-rGO Architecture for Strong Light-Matter Interactions

Directory of Open Access Journals (Sweden)

Shuang Guo

2018-06-01

Full Text Available Emerging opportunities based on two-dimensional (2D layered structures can utilize a variety of complex geometric architectures. Herein, we report the synthesis and properties of a 2D+0D unique ternary platform-core-shell nanostructure, termed Ag@Cu2O-rGO, where the reduced graphene oxide (rGO 2D acting as a platform is uniformly decorated by Ag@Cu2O core-shell nanoparticles. Cu2O nanoparticles occupy the defect positions on the surface of the rGO platform and restore the conjugation of the rGO structure, which contributes to the significant decrease of the ID/IG intensity ratio. The rGO platform can not only bridge the isolated nanoparticles together but also can quickly transfer the free electrons arising from the Ag core to the Cu2O shell to improve the utilization efficiency of photogenerated electrons, as is verified by high efficient photocatalytic activity of Methyl Orange (MO. The multi-interface coupling of the Ag@Cu2O-rGO platform-core-shell nanostructure leads to the decrease of the bandgap with an increase of the Cu2O shell thickness, which broadens the absorption range of the visible light spectrum.

Growth and morphological analysis of segmented AuAg alloy nanowires created by pulsed electrodeposition in ion-track etched membranes

Directory of Open Access Journals (Sweden)

Ina Schubert

2015-06-01

Full Text Available Background: Multicomponent heterostructure nanowires and nanogaps are of great interest for applications in sensorics. Pulsed electrodeposition in ion-track etched polymer templates is a suitable method to synthesise segmented nanowires with segments consisting of two different types of materials. For a well-controlled synthesis process, detailed analysis of the deposition parameters and the size-distribution of the segmented wires is crucial.Results: The fabrication of electrodeposited AuAg alloy nanowires and segmented Au-rich/Ag-rich/Au-rich nanowires with controlled composition and segment length in ion-track etched polymer templates was developed. Detailed analysis by cyclic voltammetry in ion-track membranes, energy-dispersive X-ray spectroscopy and scanning electron microscopy was performed to determine the dependency between the chosen potential and the segment composition. Additionally, we have dissolved the middle Ag-rich segments in order to create small nanogaps with controlled gap sizes. Annealing of the created structures allows us to influence their morphology.Conclusion: AuAg alloy nanowires, segmented wires and nanogaps with controlled composition and size can be synthesised by electrodeposition in membranes, and are ideal model systems for investigation of surface plasmons.

Microstructure and mechanical properties of Al-Cu-Mg-Mn-Zr alloy with trace amounts of Ag

International Nuclear Information System (INIS)

Liu Xiaoyan; Pan Qinglin; Lu Congge; He Yunbin; Li Wenbin; Liang Wenjie

2009-01-01

The microstructure and mechanical properties of Al-Cu-Mg-(Ag)-Mn-Zr alloys were studied by means of tensile testing, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that small additions of Ag to Al-Cu-Mg-Mn-Zr alloy can accelerate the hardening effect of the aged alloy and reduce the time to peak-aged. The mechanical properties can be improved both at room temperature and at elevated temperatures, which is attributed to the fine and uniform plate-like Ω precipitates. Meanwhile the ductility of the studied alloys remains at relatively high level. The major strengthening phases of the Ag-free alloy are θ' and less S', while that of Al-Cu-Mg-Mn-Zr alloy containing trace amounts of Ag are Ω and less θ'.

Fabrication of Au/graphene oxide/Ag sandwich structure thin film and its tunable energetics and tailorable optical properties

OpenAIRE

Ruijin Hong; Jialin Ji; Chunxian Tao; Daohua Zhang; Dawei Zhang

2017-01-01

Au/graphene oxide/Ag sandwich structure thin film was fabricated. The effects of graphene oxide (GO) and bimetal on the structure and optical properties of metal silver films were investigated by X-ray diffraction (XRD), optical absorption, and Raman intensity measurements, respectively. Compared to silver thin film, Au/graphene oxide/Ag sandwich structure composite thin films were observed with wider optical absorption peak and enhanced absorption intensity. The Raman signal for Rhodamine B ...

Rational design of organic superconductors through the use of the large, discrete molecular anions M(CF3)4-(M = Cu, Ag, Au) and SO3CF2CH2SF5-

International Nuclear Information System (INIS)

Schlueter, J.A.; Geiser, U.; Williams, J.M.

1996-01-01

A new approach to synthesis of organic superconductors has recently been pioneered which involves the use of large discrete molecular anions as the charge-compensating entities in these charge transfer salts. The organic electron-donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) has been electrocrystallized with the novel organometallic M(CF 3 ) 4 - (M=Cu, Ag, Au) anions in a variety of 1,1,2-trihaloethane solvents. Over 20 organic superconductors have been synthesized which can be described by (ET) 2 M(CF 3 ) 4 (1,1,2- trihaloethane). These solvated salts are shown to have highly anisotropic physical properties which can be tuned via modifications of each of their three molecular components: ET electron donor molecule, M(CF 3 ) 4 - anion, and neutral 1,1,2- trihaloethane solvent molecule. Superconductivity has also been observed in an ET salt containing the discrete SF 5 CH 2 CF 2 SO 3 - anion with onset temperature near 5.2 K

Electrodeposition of Au/Ag bimetallic dendrites assisted by Faradaic AC-electroosmosis flow

Energy Technology Data Exchange (ETDEWEB)

Ji, Jianlong; Li, Pengwei; Sang, Shengbo, E-mail: sbsang@tyut.edu.cn; Zhang, Wendong, E-mail: wdzhang@tyut.edu.cn; Li, Gang; Hu, Jie [Micro and Nano-system Research Centre, College of Information Engineering, Taiyuan University of Technology, 030024, Taiyuan (China); Zhou, Zhaoying, E-mail: zhouzy@mail.tsinghua.edu.cn; Yang, Xing; Dong, Hualai [MEMS Laboratory, Department of Precision Instruments, Tsinghua University, 100084, Beijing (China)

2014-03-15

Au/Ag bimetallic dendrites were synthesized successfully from the corresponding aqueous solution via the AC electrodeposition method. Both of the morphologies and compositions could be tuned by the electrolyte concentration and AC frequency. The prepared bimetallic dendrites were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and UV–vis spectroscopy. The underlying dendrite growth mechanism was then proposed in the context of the Directed Electrochemical Nanowires Assembly (DENA) models. Owing to the unscreened voltage dropping in the electrolyte bulk, electromigration dominates the species flux process, and cations tend to accumulate in areas with strong electric field intensity, such as electrode edges. Moreover, Faradaic AC-electro-osmosis (ACEO) flow could increase the effective diffusion layer thickness in these areas during the electrochemical reaction, and leads to dendrite growth. Further Micro-Raman observations illustrated that the Au/Ag bimetallic dendrites exhibited pronounced surface-enhanced Raman scattering (SERS) activity, using 4-mercaptopyridine (4-MP) as model molecules.

Electrodeposition of Au/Ag bimetallic dendrites assisted by Faradaic AC-electroosmosis flow

Directory of Open Access Journals (Sweden)

Jianlong Ji

2014-03-01

Full Text Available Au/Ag bimetallic dendrites were synthesized successfully from the corresponding aqueous solution via the AC electrodeposition method. Both of the morphologies and compositions could be tuned by the electrolyte concentration and AC frequency. The prepared bimetallic dendrites were characterized by scanning electron microscopy (SEM, energy dispersive X-ray spectrometer (EDS, transmission electron microscopy (TEM and UV–vis spectroscopy. The underlying dendrite growth mechanism was then proposed in the context of the Directed Electrochemical Nanowires Assembly (DENA models. Owing to the unscreened voltage dropping in the electrolyte bulk, electromigration dominates the species flux process, and cations tend to accumulate in areas with strong electric field intensity, such as electrode edges. Moreover, Faradaic AC-electro-osmosis (ACEO flow could increase the effective diffusion layer thickness in these areas during the electrochemical reaction, and leads to dendrite growth. Further Micro-Raman observations illustrated that the Au/Ag bimetallic dendrites exhibited pronounced surface-enhanced Raman scattering (SERS activity, using 4-mercaptopyridine (4-MP as model molecules.

Partially and fully de-alloyed glassy ribbons based on Au: Application in methanol electro-oxidation studies

Energy Technology Data Exchange (ETDEWEB)

Paschalidou, Eirini Maria, E-mail: epaschal@unito.it [Dipartimento di Chimica e Centro Interdipartimentale NIS (Nanostructured Surfaces and Interfaces), Università di Torino, Via Pietro Giuria 7, 10125, Torino (Italy); Scaglione, Federico [Dipartimento di Chimica e Centro Interdipartimentale NIS (Nanostructured Surfaces and Interfaces), Università di Torino, Via Pietro Giuria 7, 10125, Torino (Italy); Gebert, Annett; Oswald, Steffen [Leibniz Institut für Festkörper- und Werkstoffforschung IFW, Helmholtzstraße 20, 01069, Dresden (Germany); Rizzi, Paola; Battezzati, Livio [Dipartimento di Chimica e Centro Interdipartimentale NIS (Nanostructured Surfaces and Interfaces), Università di Torino, Via Pietro Giuria 7, 10125, Torino (Italy)

2016-05-15

In this work, electrochemical de-alloying of an amorphous alloy, Au{sub 40}Cu{sub 28}Ag{sub 7}Pd{sub 5}Si{sub 20}, cast in ribbon form by melt spinning, has been performed, obtaining self standing nanoporous materials suitable for use as electrodes for electrocatalytic applications. The de-alloying encompasses removal of less noble elements and the crystallization of Au, resulting in interconnected ligaments whose size and morphology are described as a function of time. Depending on de-alloying time, the crystals may contain residual amounts of Cu, Ag and Pd, as shown by Auger Electron Spectroscopy (AES), Energy Dispersive Spectroscopy (EDS) and Cyclic Voltammetry (CV) in a basic solution. Current density peaks in the 0.16–0.28 V range (vs Ag/AgCl) indicate that the porous ribbons are active for the electro-oxidation of methanol. The partially de-alloyed samples, which still partially contain the amorphous phase because of the shorter etching times, have finer ligaments and display peaks at lower potential. However, the current density decreases rapidly during repeated potential scans. This is attributed to the obstruction of Au sites, mainly by the Cu oxides formed during the scans. The fully de-alloyed ribbons display current peaks at about 0.20 V and remain active for hundreds of scans at more than 60% of the initial current density. They can be fully re-activated to achieve the same performance levels after a brief immersion in nitric acid. The good activity is due to trapped Ag and Pd atoms in combination with ligament morphology. - Graphical abstract: Fine ligaments and pores made by de-alloying a glassy ribbon of a Au-based alloy, homogeneously produced across the thickness (25 μm) for studying methanol's electro-oxidation behavior. - Highlights: • Size and composition of nanoporous layers tailored in de-alloying Au-based glassy ribbons. • From amorphous precursor fine crystals occur in ligaments with residual Pd and Ag. • Fully de

Efficient CH3NH3PbI3 perovskite/fullerene planar heterojunction hybrid solar cells with oxidized Ni/Au/Cu transparent electrode

Science.gov (United States)

Lai, Wei-Chih; Lin, Kun-Wei; Guo, Tzung-Fang; Chen, Peter; Liao, Yuan-Yu

2018-02-01

We demonstrated the performance of inverted CH3NH3PbI3 perovskite-based solar cells (SCs) with a thermally oxidized nickel/gold/copper (Ni/Au/Cu) trilayer transparent electrode. Oxidized Ni/Au/Cu is a high transparent layer and has less resistance than the oxidized Ni/Au layer. Like the oxidized Ni/Au layer, oxidized Ni and Cu in oxidized Ni/Au/Cu could perform as a hole transport layer of the perovskite-based SCs. It leads to improved perovskite SC performance on an open circuit voltage of 1.01 V, a short circuit current density of 14.36 mA/cm2, a fill factor of 76.7%, and a power conversion efficiency (η%) of 11.1%. The η% of perovskite SCs with oxidized Ni (10 nm)/Au (6 nm)/Cu (1 nm) improved by approximately 10% compared with that of perovskite SCs with oxidized Ni/Au.

Tin-phthalocyanine adsorption and diffusion on Cu and Au (111) surfaces: A density functional theory study

Science.gov (United States)

Qin, Dan; Ge, Xu-Jin; Lü, Jing-Tao

2018-05-01

Through density functional theory based calculations, we study the adsorption and diffusion of tin phthalocyanine (SnPc) molecule on Au(111) and Cu(111) surfaces. SnPc has two conformers with Sn pointing to the vacuum (Sn-up) and substrate (Sn-down), respectively. The binding energies of the two conformers with different adsorption sites on the two surfaces, including top, bridge, fcc, hcp, are calculated and compared. It is found that the SnPc molecule binds stronger on Cu(111) surface, with binding energy about 1 eV larger than that on Au(111). Only the bridge and top adsorption sites are stable on Cu(111), while all the four adsorption sites are stable on Au(111), with small diffusion barriers between them. Moreover, the flipping barrier from Sn-up to Sn-down conformer is of the same magnitude on the two metal surfaces. These results are consistent with a recent experiment [Zhang, et al., Angew. Chem., 56, 11769 (2017)], which shows that conformation change from Sn-up to Sn-down on Cu(111) surface can be induced by a C60-functionalized STM tip, while similar change is difficult to realize on Au(111), due to smaller diffusion barrier on Au(111).

X-ray and magnetic studies on intermetallic phases of the type CaCu5 using noble metals and strontium

International Nuclear Information System (INIS)

Heumann, T.; Birnschein, R.R.

1976-01-01

The intermetallic phases SrAu 5 , SrAg 5 and SrPd 5 and their binary part systems with the specific noble metals as well as the pseudobinary series SrAu 5 -SrPd 5 and SrAg 5 -SrPd 5 are dealt with within the framework of this lecture. The noble metals gold, silver and palladium form AB 5 phases with strontium which cristallize in CaCu 5 structure. The atomic susceptibilities of the part systems Ag-SrAg 5 and Au-SrAu 5 as a function of the Sr concentration, of the part system Pd-SrPd 5 as a function of the temperature and the Sr concentration, of Au-Pd as a function of the Pd concentration, of the series SrAu 5 -SrPd 5 as a function of the SrPd 5 concentration, of the series SrAg 5 -SrPd 5 as function of the SrPd 5 concentration, the electrical resistance of Ag-SrAg 5 and Au-SrAu 5 as function of the Sr concentration, the lattice constants of the series SrAu 5 -SrPd 5 as a function of the SrPd 5 concentration, as well as the number of effective magnetones in the system Au-Pd as a function of the Pd concentration, were measured and evaluated. (orig./LH) [de

Molecular dynamics simulation of Cu/Au thin films under temperature gradient

International Nuclear Information System (INIS)

Li, Qibin; Peng, Xianghe; Peng, Tiefeng; Tang, Qizhong; Zhang, Xiaomin; Huang, Cheng

2015-01-01

Graphical abstract: Heat transportation in the thin films. - Highlights: • The coherent lattice interface is found at thin films after annealing. • The vacancies are observed clearly in the deposit thin films. • The defect and component will influence the energy transportation in the coatings. • The vacancies and lattice mismatch can enlarge the mobility of atoms. • The phonon transportation in thin films has no apparent rule. - Abstract: Three modulation period thin films, 1.8 nm Cu/3.6 nm Au, 2.7 nm Cu/2.7 nm Au and 3.6 nm Cu/1.8 nm Au, are obtained from deposition method and ideal modeling based on lattice constant, to examine their structures and thermophysical characteristics under temperature gradient. The coherent lattice interface is found both at deposit and ideal thin films after annealing. Also, the vacancies are observed clearly in the deposit thin films. The defect and component of thin films will influence the energy transportation in the coatings. The vacancies and lattice mismatch can enlarge the mobility of atoms and result in the failure of coating under the thermal stress. The power spectrum of atoms’ movement has no apparent rule for phonon transportation in thin films. The results are helpful to reveal the micro-mechanism and provide reasonable basis for the failure of metallic coatings.

Molecular dynamics simulation of Cu/Au thin films under temperature gradient

Energy Technology Data Exchange (ETDEWEB)

Li, Qibin, E-mail: qibinli@cqu.edu.cn [College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030 (China); Chongqing Key Laboratory of Heterogeneous Material Mechanics, Chongqing University, Chongqing 400030 (China); Peng, Xianghe [College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030 (China); Peng, Tiefeng, E-mail: pengtiefeng@cqu.edu.cn [State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030 (China); Tang, Qizhong [College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); Zhang, Xiaomin [College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); Chongqing Key Laboratory of Heterogeneous Material Mechanics, Chongqing University, Chongqing 400030 (China); Huang, Cheng [College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China)

2015-12-01

Graphical abstract: Heat transportation in the thin films. - Highlights: • The coherent lattice interface is found at thin films after annealing. • The vacancies are observed clearly in the deposit thin films. • The defect and component will influence the energy transportation in the coatings. • The vacancies and lattice mismatch can enlarge the mobility of atoms. • The phonon transportation in thin films has no apparent rule. - Abstract: Three modulation period thin films, 1.8 nm Cu/3.6 nm Au, 2.7 nm Cu/2.7 nm Au and 3.6 nm Cu/1.8 nm Au, are obtained from deposition method and ideal modeling based on lattice constant, to examine their structures and thermophysical characteristics under temperature gradient. The coherent lattice interface is found both at deposit and ideal thin films after annealing. Also, the vacancies are observed clearly in the deposit thin films. The defect and component of thin films will influence the energy transportation in the coatings. The vacancies and lattice mismatch can enlarge the mobility of atoms and result in the failure of coating under the thermal stress. The power spectrum of atoms’ movement has no apparent rule for phonon transportation in thin films. The results are helpful to reveal the micro-mechanism and provide reasonable basis for the failure of metallic coatings.

Induced Rashba splitting of electronic states in monolayers of Au, Cu on a W(110) substrate

International Nuclear Information System (INIS)

Shikin, A M; Rybkina, A A; Rybkin, A G; Marchenko, D; Korshunov, A S; Kudasov, Yu B; Frolova, N V; Sánchez-Barriga, J; Varykhalov, A; Rader, O

2013-01-01

The paper sums up a theoretical and experimental investigation of the influence of the spin–orbit coupling in W(110) on the spin structure of electronic states in deposited Au and Cu monolayers. Angle-resolved photoemission spectroscopy reveals that in the case of monolayers of Au and Cu spin–orbit split bands are formed in a surface-projected gap of W(110). Spin resolution shows that these states are spin polarized and that, therefore, the spin–orbit splitting is of Rashba type. The states evolve from hybridization of W 5d, 6p-derived states with the s, p states of the deposited metal. Interaction with Au and Cu shifts the original W 5d-derived states from the edges toward the center of the surface-projected gap. The size of the spin–orbit splitting of the formed states does not correlate with the atomic number of the deposited metal and is even higher for Cu than for Au. These states can be described as W-derived surface resonances modified by hybridization with the p, d states of the adsorbed metal. Our electronic structure calculations performed in the framework of the density functional theory correlate well with the experiment and demonstrate the crucial role of the W top layer for the spin–orbit splitting. It is shown that the contributions of the spin–orbit interaction from W and Au act in opposite directions which leads to a decrease of the resulting spin–orbit splitting in the Au monolayer on W(110). For the Cu monolayer with lower spin–orbit interaction the resulting spin splitting is higher and mainly determined by the W. (paper)

Structural and spectroscopic properties of MITh2(PO4)32 (M = Cu+, Ag+, Na+, K+)

International Nuclear Information System (INIS)

Arsalane, S.; Ziyad, M.

1996-01-01

Phosphates of general formulae M I Th 2 (PO 4 ) 3 where M = Cu + and Ag + were synthesized using sol-gel type methods and Cu + /Ag + ion exchange. Their structures were investigated by X-ray diffraction, FTIR, and 31 P MAS NMR spectroscopies. AgTh 2 (PO 4 ) 3 and NaTh 2 (PO 4 ) 3 were found to be isostructural. Their 31 P NMR spectra exhibit three resonances agreeing with the noncentrosymmetric space group Cc to which they belong. On the other hand, CuTh 2 (PO 4 ) 3 does not show a real crystallographic resemblance with the other M I Th 2 (PO 4 ) 3 phosphates of this family. Its 31 P NMR spectrum is similar to that of KTh 2 (PO 4 ) 3 and exhibits two sharp resonances in good agreement with the C2/c space group. Nevertheless, the [PO 4 ] groups in this phosphate are highly distorted because of the linear coordination of the Cu + copper ions

A Study of the Influence of Percentage of Copper on the Structural and Optical Properties of Au-Cu Nanoparticle

Directory of Open Access Journals (Sweden)

Parivash Mashayekhi Shams

2016-07-01

Full Text Available Here we present our experimental results in synthesizing Au-Cu nano-particles with tunable localized surface plasmon resonance frequency through wet-chemical at temperature room. The reaction is performed in the presence of ascorbic acid as a reducing agent and polyvinyl pyrrolidone as capping agent via four different procedures: (1 mixture of 90% HAuCl4 and 10% CuSO4.5H2O precursors, (2 mixture of 75% HAuCl4 and 25% CuSO4.5H2O precursors, (3 mixture of 50% HAuCl4 and 50% CuSO4.5H2O precursors (4 mixture of 25% HAuCl4 and 75% CuSO4.5H2O precursors. Effect of different percentages of Cu on Au nanoparticles has been analyzed using X-ray diffraction (XRD, scanning electron microscopy (SEM with EDAX analysis, DRS UV-Vis, and Fourier transform IR spectra (FTIR analysis. X-ray diffraction (XRD analysis revealed that the nanoparticles are of cubic structure without an impure phase. The successful doping of the Cu into the Au host was evident by XRD line shiftings. The increasing percentage of copper leads to the decreasing grain size. With the increase of Cu2+ to Au3+ ratio in the Cu2+/Au3+ mixed solution (> 50% Cu, XRD lines show no shifting. The average crystal sizes of the particles at room temperature were less than 9.9 nm. The surface plasmon resonance peak shifts from 380 to 340 nm, party due to the change in particle size. SEM images show a spherical shape and the size of nanoparticles becomes smaller with increasing the percentage of copper. Moreover, in the molar ratio of Cu2+/Au3+ = 75/25 (>50% Cu, mixture of spherical and trigonal nanoparticles were prepared. Fourier transform infrared spectroscopy (FT-IR showed the coordination and conjugation nanoparticles with N and O atoms of C-N and C=O bonds.

Rapidity densities and their fluctuations in central 200 A GeV 32S interactions with Au and Ag, Br nuclei

International Nuclear Information System (INIS)

Adamovich, M.I.; Alexandrov, Y.A.; Chernyavsky, M.M.; Gerassimov, S.G.; Kharlamov, S.P.; Larionova, V.G.; Orlova, G.I.; Peresadko, N.G.; Salmanova, N.A.; Tretyakova, M.I.; Andreeva, N.P.; Anson, Z.V.; Ameeva, Z.V.; Bubnov, V.I.; Chasnicov, I.Y.; Eremenko, L.E.; Eligbaeva, G.Z.; Gaitinov, A.S.; Kalyachkina, G.S.; Kanygina, E.K.; Shakhova, T.I.; Azimov, S.A.; Chernova, L.P.; Gadzhieva, S.I.; Gulamov, K.G.; Kadyrov, F.G.; Lukicheva, N.S.; Navotny, V.S.; Svechnikova, L.N.; Bhasin, A.; Kachroo, S.; Kaul, G.L.; Mangotra, L.K.; Rao, N.K.; Burnett, T.H.; Grote, J.; Koss, T.; Lord, J.; Skelding, D.; Strausz, S.; Wilkes, R.J.; Cai, X.; Liu, L.S.; Maslennikova, N.V.; Qian, W.Y.; Wang, H.Q.; Zhou, D.C.; Zhou, J.C.; Dressel, B.; Ganssauge, E.R.; Hackel, S.; Kallies, H.; Mueller, C.; Rhee, J.T.; Schultz, W.; Garpman, S.; Otterlund, I.; Persson, S.; Soderstrom, K.; Stenlund, E.; Judek, B.; Storey, R.S.; Xu, G.F.; Zheng, P.Y.; Zhang, D.H.

1989-01-01

The pseudo-rapidity density distributions of shower particles (n s ) are measured in central inelastic S+Au and S+Ag, Br interactions. The extracted maximum energy densities, while being higher for Au than for Ag,Br interactions, were found to be similar to those obtained for oxygen emulsion interactions. The correlation between rapidity density and shower particle multiplicity shows a small deviation from the Lund Model Fritiof for the highest energy densities in S+Au interactions, whereas the bulk of the data yields satisfactory agreement. (orig.)

Moessbauer and transport studies of amorphous and icosahedral Zr-Ni-Cu-Ag-Al alloys

International Nuclear Information System (INIS)

Stadnik, Z.M.; Rapp, O.; Srinivas, V.; Saida, J.; Inoue, A.

2002-01-01

The alloy Zr 65 Al 7.5 Ni 10 Cu 7.3 Fe 0.2 Ag 10 in the amorphous and icosahedral states, and the bulk amorphous alloy Zr 65 Al 7.5 Ni 10 Cu 7.5 Ag 10 , have been studied with 57 Fe Moessbauer spectroscopy, electrical resistance and magnetoresistance techniques. The average quadrupole splitting in both alloys decreases with temperature as T 3/2 . The average quadrupole splitting in the icosahedral alloy is the largest ever reported for a metallic system. The lattice vibrations of the Fe atoms in the amorphous and icosahedral alloys are well described by a simple Debye model, with the characteristic Moessbauer temperatures of 379(29) and 439(28) K, respectively. Amorphous alloys Zr 65 Al 7. )5Ni 10 Cu 7.5 Ag 10 and Zr 65 Al 7.5 Ni 10 Cu 7.3 Fe 0.2 Ag 10 have been found to be superconducting with the transition temperature, T c , of about 1.7 K. The magnitude of Tc and the critical field slope at Tc are in agreement with previous work on Zr-based amorphous superconductors, while the low-temperature normal state resistivity is larger than typical results for binary and ternary Zr-based alloys. The resistivity of icosahedral Zr 65 Al 7.5 Ni 10 Cu 7.3 Fe 0.2 Ag 10 is larger than that for the amorphous ribbon of the same composition, as inferred both from direct measurements on the ribbons and from the observed magnetoresistance. However the icosahedral sample is non-superconducting in the measurement range down to 1.5 K. The results for the resistivity and the superconducting T c both suggest a stronger electronic disorder in the icosahedral phase than in the amorphous phase. (author)

Self-catalytic stabilized Ag-Cu nanoparticles with tailored SERS response for plasmonic photocatalysis

Science.gov (United States)

He, Lili; Liu, Changqing; Tang, Jia; Zhou, Youchen; Yang, Hui; Liu, Ruiyu; Hu, Jiugang

2018-03-01

In-situ SERS monitoring of direct plasmon-driven photocatalysis was achieved using relatively earth-abundant Cu NPs following their decoration with tiny amounts of silver, which promoted excellent SERS and high catalytic activity. The SERS and catalytic performance of the Ag-Cu NPs can be tuned by changing their composition. In particular, it was found that the surface oxidation state of copper could be switched to its metallic state via self-plasmon catalysis under laser irradiation, highlighting the potential of air-unstable copper NPs as stable plasmonic catalysts. These dual functional Ag-Cu NPs were used for SERS real-time monitoring of plasmon-driven photocatalysis reactions involving the degradation of Rhodamine 6G and the dimerization of 4-nitrothiophenol. The corresponding catalytic reaction mechanisms were discussed.

Disruption, segregation, and passivation for Pd and noble-metal overlayers on YBa2Cu3O/sub 6.9/

International Nuclear Information System (INIS)

Wagener, T.J.; Gao, Y.; Vitomirov, I.M.; Aldao, C.M.; Joyce, J.J.; Capasso, C.; Weaver, J.H.; Capone II, D.W.

1988-01-01

We have investigated interfaces formed when Pd and the noble metals Cu, Ag, and Au are deposited onto polycrystalline samples of YBa 2 Cu 3 O/sub 6.9/ fractured in ultrahigh vacuum. Synchrotron-radiation photoemission results show that Cu and Pd overlayers leach oxygen from the underlying YBa 2 Cu 3 O/sub 6.9/ substrate, disrupt the superconductor, and destroy electronic states near the Fermi level. Interface reactions become kinetically limited at room temperature after the deposition of ∼4 A of Cu or Pd, significantly sooner than for the reactive metals Fe, Al, Ti, and In. The presence of Ba near the surface after the deposition of more than 100 A of Cu and Pd reflects substrate disruption and subsequent surface segregation. In contrast, overlayers of Ag and Au do not disrupt the superconductor substrate, no segregation is observed, but the overlayers are nonuniform and the quality of passivation is in question for coverages <100 A

Size and alloying induced shift in core and valence bands of Pd-Ag and Pd-Cu nanoparticles

International Nuclear Information System (INIS)

Sengar, Saurabh K.; Mehta, B. R.; Govind

2014-01-01

In this report, X-ray photoelectron spectroscopy studies have been carried out on Pd, Ag, Cu, Pd-Ag, and Pd-Cu nanoparticles having identical sizes corresponding to mobility equivalent diameters of 60, 40, and 20 nm. The nanoparticles were prepared by the gas phase synthesis method. The effect of size on valence and core levels in metal and alloy nanoparticles has been studied by comparing the values to those with the 60 nm nanoparticles. The effect of alloying has been investigated by comparing the valence and core level binding energies of Pd-Cu and Pd-Ag alloy nanoparticles with the corresponding values for Pd, Ag, and Cu nanoparticles of identical sizes. These effects have been explained in terms of size induced lattice contractions, alloying induced charge transfer, and hybridization effects. The observation of alloying and size induced binding energy shifts in bimetallic nanoparticles is important from the point of view of hydrogen reactivity

System size and energy dependence of jet-induced hadron pair correlation shapes in Cu+Cu and Au+Au collisions at square root sNN=200 and 62.4 GeV.

Science.gov (United States)

Adare, A; Adler, S S; Afanasiev, S; Aidala, C; Ajitanand, N N; Akiba, Y; Al-Bataineh, H; Alexander, J; Al-Jamel, A; Aoki, K; Aphecetche, L; Armendariz, R; Aronson, S H; Asai, J; Atomssa, E T; Averbeck, R; Awes, T C; Azmoun, B; Babintsev, V; Baksay, G; Baksay, L; Baldisseri, A; Barish, K N; Barnes, P D; Bassalleck, B; Bathe, S; Batsouli, S; Baublis, V; Bauer, F; Bazilevsky, A; Belikov, S; Bennett, R; Berdnikov, Y; Bickley, A A; Bjorndal, M T; Boissevain, J G; Borel, H; Boyle, K; Brooks, M L; Brown, D S; Bruner, N; Bucher, D; Buesching, H; Bumazhnov, V; Bunce, G; Burward-Hoy, J M; Butsyk, S; Camard, X; Campbell, S; Chai, J-S; Chand, P; Chang, B S; Chang, W C; Charvet, J-L; Chernichenko, S; Chiba, J; Chi, C Y; Chiu, M; Choi, I J; Choudhury, R K; Chujo, T; Chung, P; Churyn, A; Cianciolo, V; Cleven, C R; Cobigo, Y; Cole, B A; Comets, M P; Constantin, P; Csanád, M; Csörgo, T; Cussonneau, J P; Dahms, T; Das, K; David, G; Deák, F; Deaton, M B; Dehmelt, K; Delagrange, H; Denisov, A; d'Enterria, D; Deshpande, A; Desmond, E J; Devismes, A; Dietzsch, O; Dion, A; Donadelli, M; Drachenberg, J L; Drapier, O; Drees, A; Dubey, A K; Durum, A; Dutta, D; Dzhordzhadze, V; Efremenko, Y V; Egdemir, J; Ellinghaus, F; Emam, W S; Enokizono, A; En'yo, H; Espagnon, B; Esumi, S; Eyser, K O; Fields, D E; Finck, C; Finger, M; Finger, M; Fleuret, F; Fokin, S L; Forestier, B; Fox, B D; Fraenkel, Z; Frantz, J E; Franz, A; Frawley, A D; Fujiwara, K; Fukao, Y; Fung, S-Y; Fusayasu, T; Gadrat, S; Garishvili, I; Gastineau, F; Germain, M; Glenn, A; Gong, H; Gonin, M; Gosset, J; Goto, Y; Granier de Cassagnac, R; Grau, N; Greene, S V; Grosse Perdekamp, M; Gunji, T; Gustafsson, H-A; Hachiya, T; Hadj Henni, A; Haegemann, C; Haggerty, J S; Hagiwara, M N; Hamagaki, H; Han, R; Hansen, A G; Harada, H; Hartouni, E P; Haruna, K; Harvey, M; Haslum, E; Hasuko, K; Hayano, R; Heffner, M; Hemmick, T K; Hester, T; Heuser, J M; He, X; Hidas, P; Hiejima, H; Hill, J C; Hobbs, R; Hohlmann, M; Holmes, M; Holzmann, W; Homma, K; Hong, B; Hoover, A; Horaguchi, T; Hornback, D; Hur, M G; Ichihara, T; Ikonnikov, V V; Imai, K; Inaba, M; Inoue, Y; Inuzuka, M; Isenhower, D; Isenhower, L; Ishihara, M; Isobe, T; Issah, M; Isupov, A; Jacak, B V; Jia, J; Jin, J; Jinnouchi, O; Johnson, B M; Johnson, S C; Joo, K S; Jouan, D; Kajihara, F; Kametani, S; Kamihara, N; Kamin, J; Kaneta, M; Kang, J H; Kanou, H; Katou, K; Kawabata, T; Kawagishi, T; Kawall, D; Kazantsev, A V; Kelly, S; Khachaturov, B; Khanzadeev, A; Kikuchi, J; Kim, D H; Kim, D J; Kim, E; Kim, G-B; Kim, H J; Kim, Y-S; Kinney, E; Kiss, A; Kistenev, E; Kiyomichi, A; Klay, J; Klein-Boesing, C; Kobayashi, H; Kochenda, L; Kochetkov, V; Kohara, R; Komkov, B; Konno, M; Kotchetkov, D; Kozlov, A; Král, A; Kravitz, A; Kroon, P J; Kubart, J; Kuberg, C H; Kunde, G J; Kurihara, N; Kurita, K; Kweon, M J; Kwon, Y; Kyle, G S; Lacey, R; Lai, Y-S; Lajoie, J G; Lebedev, A; Le Bornec, Y; Leckey, S; Lee, D M; Lee, M K; Lee, T; Leitch, M J; Leite, M A L; Lenzi, B; Lim, H; Liska, T; Litvinenko, A; Liu, M X; Li, X; Li, X H; Love, B; Lynch, D; Maguire, C F; Makdisi, Y I; Malakhov, A; Malik, M D; Manko, V I; Mao, Y; Martinez, G; Masek, L; Masui, H; Matathias, F; Matsumoto, T; McCain, M C; McCumber, M; McGaughey, P L; Miake, Y; Mikes, P; Miki, K; Miller, T E; Milov, A; Mioduszewski, S; Mishra, G C; Mishra, M; Mitchell, J T; Mitrovski, M; Mohanty, A K; Morreale, A; Morrison, D P; Moss, J M; Moukhanova, T V; Mukhopadhyay, D; Muniruzzaman, M; Murata, J; Nagamiya, S; Nagata, Y; Nagle, J L; Naglis, M; Nakagawa, I; Nakamiya, Y; Nakamura, T; Nakano, K; Newby, J; Nguyen, M; Norman, B E; Nyanin, A S; Nystrand, J; O'Brien, E; Oda, S X; Ogilvie, C A; Ohnishi, H; Ojha, I D; Okada, H; Okada, K; Oka, M; Omiwade, O O; Oskarsson, A; Otterlund, I; Ouchida, M; Oyama, K; Ozawa, K; Pak, R; Pal, D; Palounek, A P T; Pantuev, V; Papavassiliou, V; Park, J; Park, W J; Pate, S F; Pei, H; Penev, V; Peng, J-C; Pereira, H; Peresedov, V; Peressounko, D Yu; Pierson, A; Pinkenburg, C; Pisani, R P; Purschke, M L; Purwar, A K; Qualls, J M; Qu, H; Rak, J; Rakotozafindrabe, A; Ravinovich, I; Read, K F; Rembeczki, S; Reuter, M; Reygers, K; Riabov, V; Riabov, Y; Roche, G; Romana, A; Rosati, M; Rosendahl, S S E; Rosnet, P; Rukoyatkin, P; Rykov, V L; Ryu, S S; Sahlmueller, B; Saito, N; Sakaguchi, T; Sakai, S; Sakata, H; Samsonov, V; Sanfratello, L; Santo, R; Sato, H D; Sato, S; Sawada, S; Schutz, Y; Seele, J; Seidl, R; Semenov, V; Seto, R; Sharma, D; Shea, T K; Shein, I; Shevel, A; Shibata, T-A; Shigaki, K; Shimomura, M; Shohjoh, T; Shoji, K; Sickles, A; Silva, C L; Silvermyr, D; Silvestre, C; Sim, K S; Singh, C P; Singh, V; Skutnik, S; Slunecka, M; Smith, W C; Soldatov, A; Soltz, R A; Sondheim, W E; Sorensen, S P; Sourikova, I V; Staley, F; Stankus, P W; Stenlund, E; Stepanov, M; Ster, A; Stoll, S P; Sugitate, T; Suire, C; Sullivan, J P; Sziklai, J; Tabaru, T; Takagi, S; Takagui, E M; Taketani, A; Tanaka, K H; Tanaka, Y; Tanida, K; Tannenbaum, M J; Taranenko, A; Tarján, P; Thomas, T L; Togawa, M; Toia, A; Tojo, J; Tomásek, L; Torii, H; Towell, R S; Tram, V-N; Tserruya, I; Tsuchimoto, Y; Tuli, S K; Tydesjö, H; Tyurin, N; Uam, T J; Vale, C; Valle, H; vanHecke, H W; Velkovska, J; Velkovsky, M; Vertesi, R; Veszprémi, V; Vinogradov, A A; Virius, M; Volkov, M A; Vrba, V; Vznuzdaev, E; Wagner, M; Walker, D; Wang, X R; Watanabe, Y; Wessels, J; White, S N; Willis, N; Winter, D; Wohn, F K; Woody, C L; Wysocki, M; Xie, W; Yamaguchi, Y L; Yanovich, A; Yasin, Z; Ying, J; Yokkaichi, S; Young, G R; Younus, I; Yushmanov, I E; Zajc, W A; Zaudtke, O; Zhang, C; Zhou, S; Zimányi, J; Zolin, L; Zong, X

2007-06-08

We present azimuthal angle correlations of intermediate transverse momentum (1-4 GeV/c) hadrons from dijets in Cu+Cu and Au+Au collisions at square root sNN=62.4 and 200 GeV. The away-side dijet induced azimuthal correlation is broadened, non-Gaussian, and peaked away from Delta phi=pi in central and semicentral collisions in all the systems. The broadening and peak location are found to depend upon the number of participants in the collision, but not on the collision energy or beam nuclei. These results are consistent with sound or shock wave models, but pose challenges to Cherenkov gluon radiation models.

Silica-covered star-shaped Au-Ag nanoparticles as new electromagnetic nanoresonators for Raman characterisation of surfaces

Science.gov (United States)

Krajczewski, Jan; Kołątaj, Karol; Pietrasik, Sylwia; Kudelski, Andrzej

2018-03-01

One of the tools used for determining the composition of surfaces of various materials is shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). SHINERS is a modification of "standard" surface-enhanced Raman spectroscopy (SERS), in which, before Raman spectra are recorded, the surfaces analysed are covered with a layer of plasmonic nanoparticles protected by a very thin layer of a transparent dielectric. The plasmonic cores of the core-shell nanoparticles used in SHINERS measurements generate a local enhancement of the electric field of the incident electromagnetic radiation, whereas the transparent coatings prevent the metal cores from coming into direct contact with the material being analysed. In this contribution, we propose a new type of SHINERS nanoresonators that contain spiky, star-shaped metal cores (produced from a gold/silver alloy). These spiky, star-shaped Au-Ag nanoparticles have been covered by a layer of silica. The small radii of the ends of the tips of the spikes of these plasmonic nanostructures make it possible to generate a very large enhancement of the electromagnetic field there, with the result that such SHINERS nanoresonators are significantly more efficient than the standard semi-spherical nanostructures. The Au-Ag alloy nanoparticles were synthesised by the reduction of a solution containing silver nitrate and chloroauric acid by ascorbic acid. The final geometry of the nanostructures thus formed was controlled by changing the ratio between the concentrations of AuCl4- and Ag+ ions. The shape of the synthesised star-shaped Au-Ag nanoparticles does not change significantly during the two standard procedures for depositing a layer of silica (by the decomposition of sodium silicate or the decomposition of tetraethyl orthosilicate).

Phase transformation and morphology of the intermetallic compounds formed at the Sn-9Zn-3.5Ag/Cu interface in aging

International Nuclear Information System (INIS)

Hon, M.-H.; Chang, T.-C.; Wang, M.-C.

2008-01-01

The morphology and phase transformation of the intermetallic compounds (IMCs) formed at the Sn-9Zn-3.5Ag/Cu interface in a solid-state reaction have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The monoclinic η'-Cu 6 Sn 5 transforms to the hexagonal η-Cu 6 Sn 5 and the orthorhombic Cu 5 Zn 8 transforms to the body-centered cubic (bcc) γ-Cu 5 Zn 8 as aged at 180 deg. C. The scallop-shaped Cu 6 Sn 5 layer is retained after aging at 180 deg. C for 1000 h. In the solid-state reaction, Ag is repelled from η'-Cu 6 Sn 5 and reacts with Sn to form Ag 3 Sn, and the Cu 5 Zn 8 layer decomposes. Kirkendall voids are not observed at the Sn-9Zn-3.5Ag/Cu interface even after aging at 180 deg. C for 1000 h