Separated Au Research Articles

Role of Gold Pre-deposition Layer on the Growth of Magnesium Oxide Nanorods

This paper investigates the role of Au pre-deposited layer in the growth of MgO structures by chemical vapor deposition (CVD) technique. Pre-deposition layer in the form of Au thin film of different thicknesses, and size selected Au nanoparticles have been used for this purpose. The diameter of the MgO rods is found to be related to the thickness of the pre-deposited layer. When Au thin films are used, diameter of the nanorods is observed to be larger than the size of Au particles formed after annealing the pre-deposited film. It has also been demonstrated that the diameter of MgO nanorods can be controlled by using size-selected and well separated Au nanoparticles on the Si substrate.

Development of the MOSFET Type Enzyme Biosensor Using GOx and ChOx

As the population ages, the management of health is one of the important problems. Before now, we developed the glucose sensor for using at Health Monitoring System (HMS). The whole blood contains the manifold health index markers, and it is very important to measure them. Glucose sensor specifically detects the glucose of the blood, and it monitors the glucose concentration. Our glucose sensor had ‘separated Au electrode’ which immobilized glucose oxidase (GOx). By utilizing this style, it becomes possible that the sensor part is easily miniaturized. In our previous work, GOx was immobilized onto electrode by using of SAMs (Self-Assembled Monolayor) method, and the sensor using this working electrode detected the glucose concentration of glucose aqueous solution. In this paper, glucose sensor which immobilized GOx using the cross-link method was produced. And we carried out operation confirmation of produced glucose sensor using diluted human serum and whole blood. In addition, the cholesterol sensor which immobilized cholesterol oxidase (ChOx) onto separated Au electrode by cross-link method was produced. The immobilization of the ChOx was evaluated from the spectra of ESCA (Electron Spectroscopy for Chemical Analysis), and the performance as a sensor was evaluated.

Developing depleted uranium and gold cocktail hohlraums for the National Ignition Facility

Fusion ignition experiments are planned to begin at the National Ignition Facility (NIF) [J. A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Technol. 26, 755 (1994)] using the indirect drive configuration [J. D. Lindl, P. Amendt, R. L. Berger, S. G. Glendinning, S. H. Glenzer, S. W. Haan, R. L, Kauffman, O. L. Landen, and L. J. Suter, Phys. Plasmas 11, 339 (2004)]. Although the x-ray drive in this configuration is highly symmetric, energy is lost in the conversion process due to x-ray penetration into the hohlraum wall. To mitigate this loss, depleted uranium is incorporated into the traditional gold hohlraum to increase the efficiency of the laser to x-ray energy conversion by making the wall more opaque to the x rays [H. Nishumura, T. Endo, H. Shiraga, U. Kato, and S. Nakai, Appl. Phys. Lett. 62, 1344 (1993)]. Multilayered depleted uranium (DU) and gold hohlraums are deposited by sputtering by alternately rotating a hohlraum mold in front of separate DU and Au sources to build up multilayers to the desired wall thickness. This mold is removed to leave a freestanding hohlraum half; two halves are used to assemble the complete NIF hohlraum to the design specifications. In practice, exposed DU oxidizes in air and other chemicals necessary to hohlraum production, so research has focused on developing a fabrication process that protects the U from damaging environments. This paper reports on the most current depleted uranium and gold cocktail hohlraum fabrication techniques, including characterization by Auger electron spectroscopy, which is used to verify sample composition and the amount of oxygen uptake over time.

The influence of roughness on some magnetic properties of layered structures of Fe, Co separated Cu or Au

AbstractThe system of two magnetic (M) layers divided by nonmagnetic (N) spacer is considered. Roughness in interface region is introduced employing model proposed by Bruno and Chappert. Presence of roughness leads to modification of interface exchange parameter and interface anisotropy in comparison to samples with ideal interface. The magnetisation distribution and Curie temperature has been calculated using Green function formalism for systems consisting of Fe or Co standing for M and Cu or Au standing for N, respectively. Parameters corresponding to GaAs have been taken into account to characterize the substrate. The results obtained show decreasing of Curie temperature and shift of magnetisation curve with increasing of roughness parameter. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Development of stable, non-cyanide solutions for electroplating Au-Sn alloy films

Au-Sn alloys, with a range of compositions, can be successfully pulse plated onto blank wafers and patterned wafers using a slightly acidic, chloride based solution. However, the plating solution has limited stability (about two to three days), after which deposit compositions are not controllable. The aim of this work was to develop a more stable Au-Sn electroplating solution. An alternative, to a single Au-Sn electroplating solution, is to prepare separate Au and Sn solutions and then mix them as needed to generate the Au-Sn solution. Using this approach, Au and Sn solutions were produced, which were stable for at least 12 months. The stable Au solution consisted of KAuCl4, ammonium citrate, and sodium sulfite; the stable Sn solution consisted of SnCl2 • 2H2O and ammonium citrate. Ascorbic acid is an important bridge component between the 2 solutions. Electroplating results showed that deposit composition, morphology and plating rate from the newly developed mixture were very similar to those obtained from the conventional Au-Sn solution.

Deep aromatics hydrogenation in the presence of DBT over Au–Pd/γ-alumina catalysts

Alumina-supported Pd, Au and Au–Pd catalysts were investigated for the simultaneous hydrogenation (HYD) of naphthalene (NP) and toluene (T) in the presence of dibenzothiophene (DBT). The nature of supported Au, its resistance against S-poisoning when applied along with Pd in the hydrogenation of aromatics was studied. Additionally, the effect of two kinds of γ-alumina (A(N) and A(S)) with different textural properties on the structure and performance of the catalysts was evaluated. Irrespectively of the support used, all the catalysts showed resistance to S-poisoning and their activity followed an order of NP > T > DBT. For hydrogenation of naphthalene, the specific reaction rates normalized to Pd loading follows trend: Au–Pd/ A ( N ) ≫ Au – Pd /A(S) > Pd(A(N) > Pd/A(S). The higher activity in the hydrogenation of naphthalene of the separate Au 0 and Pd 0 phases on a type-N alumina support with respect to those supported on a type-S alumina was related to a more homogeneous dispersion of Pd 0 and Au 0 crystallites and a lower extent of coke formation. Under an excess of hydrogen, the monometallic gold catalysts did not show any activity in the HYD of toluene. However, the Au catalysts showed over-hydrogenation of NP to decalin, in contrast with the performance of the Pd and Au–Pd samples. This behaviour can be exploited to avoid the over-hydrogenation of naphthalene by using the bimetallic Au–Pd formulation.

Effect of Glass Substrates on the Formation of Gold-Silver Colloids in Nanocomposite Thin Films

A sol-gel route to synthesize nanocomposite thin films containing phase separated metal colloids of gold (Au) and silver (Ag) was developed. Ag—Au colloids were prepared in silica films using dip coating technique. The annealing of the samples in air results in the formation of phase separated Ag and Au colloids in SiO2 thin films, showing the surface plasmon peaks at 410 nm and 528 nm. For the synthesis of phase separated Ag and Au colloids on float glass substrates, formation of the silver colloids was found strongly dependent on the surface of the float glass. On the tin rich surface formation of both gold and silver colloids took place, whereas, on the tin poor surface the formation of only gold colloids was observed. The surface dependence of the formation of silver colloids was attributed to the presence of tin as Sn2+ state on the glass surface, which oxidizes into Sn4+ during heat treatment, reducing Ag+ into silver colloids.

Effect of glass substrates on the formation of gold-silver colloids in nanocomposite thin films

A sol-gel route to synthesize nanocomposite thin films containing phase separated metal colloids of gold (Au) and silver (Ag) was developed. Ag—Au colloids were prepared in silica films using dip coating technique. The annealing of the samples in air results in the formation of phase separated Ag and Au colloids in SiO2 thin films, showing the surface plasmon peaks at 410 nm and 528 nm. For the synthesis of phase separated Ag and Au colloids on float glass substrates, formation of the silver colloids was found strongly dependent on the surface of the float glass. On the tin rich surface formation of both gold and silver colloids took place, whereas, on the tin poor surface the formation of only gold colloids was observed. The surface dependence of the formation of silver colloids was attributed to the presence of tin as Sn2+ state on the glass surface, which oxidizes into Sn4+ during heat treatment, reducing Ag+ into silver colloids.

Adsorption of AUCL4- by Kaolinites: Effect of pH, Temperature and Kaolinite Crystallinity

AbstractAdsorption of the AuCl4− complex by kaolinites of different crystallinities (Kao-1 and Kao-2) from 100 mL of AuCl3·HCl·4H2O solutions containing 10,000, 500 and 50 µg/L Au and 1 g of kaolinite was measured at pH 3 to 9 at ambient temperature and 120°C. Adsorption from the 50, 500 and 10,000 µg Au/L solutions ranged from 64 to 100% at ambient temperature and from 68 to 100% at 120°C for both kaolinites. Adsorption was pH dependent with a maximum at pH <5 and a minimum at neutral and alkaline pHs. Up to 1 mg Au/g kaolinite was adsorbed by the kaolinites at both ambient temperature and 120°C. In a separate Au adsorption experiment using 100 mL of 4000 µg Au/L solutions and 0.02 to 1.0 g of Kao-1, up to 8.55 mg Au/ g of kaolinite was adsorbed. The pH dependence of Au adsorption suggests that surface complexation of Au to alumina sites at the edges of kaolinite particles might be involved. Protonation of kaolinite surface sites might facilitate adsorption of the anionic Au complex. Both kaolinites adsorbed ~100% of added Au at low pH values, but the less crystalline kaolinite (Kao-2) adsorbed more Au at high pH. Greater Au adsorption would be expected for the less crystalline Kao-2 sample if adsorption occurred at the edges of kaolinite particles.

Synthesis and applications of poly(acryl p-aminobenzenesulfonamideamidine- p-aminobenzenesulfonylamide) chelating fiber for pre-concentrating and separating trace Bi(III), Hg(III), Au(III) and Pd(IV) from solution samples.

Poly(acryl p-aminobenzenesulfonamideamidine- p-aminobenzenesulfonylamide) chelating fiber containing "S", "N", and "O" elements was synthesized from polyacrylonitrile fiber and p-aminobenzene sulfonamide and used to enrich and separate trace Bi(III), Hg(III), Au(III), and Pd(IV) ions from wastewater and ore sample solution. The enrichment acidity, flow rate, elution conditions, reuse, interference ions, saturated adsorption capacity, constant of adsorption rate, analytical accuracy, and actual samples on chelating fiber were investigated by means of inductively coupled plasma optical emission spectrometry (ICP-OES) with satisfactory results. Solutions of 100 ng mL(-1) of Bi(III), Hg(III), Au(III), and Pd(IV) ions can be enriched quantitatively by this chelating fiber at a rate of 1.0 mL min(-1) at pH 4 and desorbed quantitatively with 20 mL of 0.25 M HCl and 2% CS(NH(2))(2) solution at 50 degrees C (with recovery >/=97%). When the chelating fiber was reused for 20 times, the recoveries of the analyzed ions enriched by the fiber were still over 95% (except for Hg(III)). One thousand-fold excesses of Mn(2+), Ca(2+), Zn(2+), Mg(2+), Fe(3+), Cu(2+), Ni(2+), Al(3+), and Ba(2+) ions and thousands-fold excesses of Na(+ )and K(+) cause little interference in the pre-concentration and determination of the analyzed ions. The saturated adsorption capacity of Bi(III), Hg(III), Au(III), and Pd(IV) was 4.850 x 10(-4), 3.235 x 10(-4), 2.807 x 10(-4), and 3.386 x 10(-4) mol g(-1), respectively. The constants of adsorption rate were 0.409 min(-1) for Bi, 0.122 min(-1) for Hg, 0.039 min(-1) for Au, and 0.080 min(-1 )for Pd. The relative standard deviations (RSDs) for the enrichment and determination of 10 ng mL(-1) Bi(III), Hg(III), Au(III), and Pd(IV) were lower than 2.3%. The results obtained for these ions in actual samples by this method were basically in agreement with the given values with average errors of less than 1.0%. FT-IR spectra shows that the existence of -SO(2)-Ar, -H(2)N-Ar, O=C-NH-, HN=C-NH-, and -HN-SO(2) functional groups are verified in the chelating fiber. From the FT-IR spectroscopy, we can see that Hg(III), Au(III), and Pd(IV) are mainly combined with nitrogen and sulfur (or oxygen), and Bi(III) is mainly combined with nitrogen (or oxygen) of the groups to form a chelating complex.

Properties and application of poly(acrylphenylamidrazone‐phenylhydrazide) chelating fiber for enrichment–separation of trace gold and ruthenium from solution samples

AbstractAn ICP‐OES method using a new poly(acrylphenylamidrazone‐phenylhydrazide) chelating fiber to enrich and separate trace Au(III) and Ru(III) ions from solution samples is established. The results show that 50–500 ng/mL of Au or Ru ions can be enriched quantitatively by 0.1 g of the fiber at pH 4, with recoveries > 96%. The ions can be desorbed quantitatively with 10 mL of 4 M HCl and 3.0% CS(NH2)2 solution from the fiber column, with recoveries > 97%, and 200–1000‐fold excesses of Cu(II), Zn(II), Ca(II), Mg(II), Mn(II), Cr(III), Fe(III), Ba(II), and Al(III) caused little interference in the determination of these ions by ICP–OES. The chelating fiber can be reused eight times, and the recoveries are all > 95%. The relative standard deviations for enrichment and determination of 50 ng/mL of Au and Ru are in the range 1.8–1.9% (1.9% for Au and 1.8% for Ru). The recoveries of trace Au and Ru ions added to real waste water and alloy samples are 96–98%. The concentration of each ion found in the alloy samples was in good agreement with that provided by the plant. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2656–2660, 2001

Integrated membrane process for gold recovery from hydrometallurgical solutions

AbstractThis work reports the nondispersive solvent extraction (NDSX) of gold cyanide from aqueous alkaline cyanide media with LIX79 and stripping of gold from the organic complex simultaneousty using two microporous hydrophobic polypropylene hollow‐fiber contactors for extraction and stripping, respectively. Extraction was studied under different hydrodynamic conditions and mass‐transfer correlations for shell and tube sides. The mass‐transfer process was compared with experimental results. The HFNDSX was operated with 12–18% LIX 79 in n‐heptane by contacting alkaline cyanide feed containing gold through the tube side and organic extractant through the shell side, which was recirculated between extraction and stripping hollow‐fiber modules through the shell side countercurrently. In the second HF contactor, the stripping solution, 1M NaOH flowed through the tube side countercurrently. Modeling of the system identified rate‐controlling steps under different experimental conditions. The interfacial chemical reaction rate at the dominant surface, and mass‐transfer resistance caused by this reaction controlled the entire extraction process. Several experiments with synthetic solutions of different compositions of gold hydrometallurgical solutions established optimum conditions to achieve a clean separation of Au(I). It was possible to separate Au(I) in the presence of other metal cyanide salts, such us Fe(II), Cu(II), Ni(II), Ag(I), and Zn(II) (NaCN = 1,000–5,000 ppm), which was concentrated in the stripping phase containing NaOH.

Formation of Au and AuSi x-Pyramids in Separation by Implanted Oxygen Wafers with Si Pillars in SiO2 Layer

Formation of Au and AuSi x-Pyramids in Separation by Implanted Oxygen Wafers with Si Pillars in SiO2 Layer

Synthesis and efficiency of poly(acrylamidrazonehydrazide) chelating fiber for preconcentrating and separating trace gold and palladium from solution

A new poly(acrylamidrazone-hydrazide) chelating fiber has been synthesized using polyacrylonitrile fiber as a starting material. An ICP-OES method for applying the fiber to preconcentrate and separate trace Au(III) and Pd(IV) ions in solution has been established. The experiments show that 8 ng/ml Au(III) and 6 ng/ml Pd(IV) in 1000 ml of solution can be enriched quantitatively by the fiber column at a flow rate of 12 ml/min at pH 2. These ions can be desorbed quantitatively with 10 ml of 2.5% CS(NH2)2 + 6% H2SO4 containing 0.2% Fe(II) from the column at an elution rate of 6 ml/min. A fiber treated with 12M HCl or 15M HNO3 can be re-used 10 times with above 95% recoveries of Au(III) and Pd(IV), and 120–800-fold excesses of Cu(II), Mn(II), Fe(III), Al(III), Ni(II), Mg(II) and Ca(II) ions cause little interference. The RSDs are 2.0% for 8 ng/ml Au and 3.5% for 6 ng/ml Pd. The recovery of added standard in a solution sample from a metal smelter is 96.2% for Au and 100% for Pd, and the content of each ion in the sample determined by the method is in agreement with the analysed value from the smelter laboratory.

Beseitigung des Matrixeffekts bei der Analyse von Edelmetallspuren mit induktiv gekoppeltem Plasma

Spectral interferences associated with the determination of trace contents of Au, Ag, Pt and Pd in samples with complex matrices (hydrometallurgical solutions, metallurgical products and ore processing products) were investigated. It was found that it is necessary to separate Au, Pt and Pd from the matrix elements. The results obtained with various methods for separation and pre-concentration of these elements showed that in the case of hydrometallurgical solutions adsorption on activated carbon satisfies the requirements of analytical control. For the determination of these elements in ore processing products it is necessary to use additional extraction for their preconcentration. The most suitable organic solution found for the extraction of Au, Pt and Pd and their determination with ICP is isoamyl alcohol.

The growth of AuGa2 thin films on GaAs(001) to form chemically unreactive interfaces

Thin AuGa2 films were grown by codeposition from separate Au and Ga evaporation sources on clean GaAs(001) substrates in ultrahigh vacuum, and were studied by Auger electron spectroscopy, electron energy-loss spectroscopy, low-energy electron diffraction, scanning electron microscopy, and x-ray diffractometry. The morphology and crystallinity of the AuGa2 were highly dependent upon the film deposition and annealing history. Films grown on room-temperature substrates were continuous, specular, and polycrystalline, but the dominant orientation was with the (001) planes of the crystallites parallel to the substrate surface. Annealing to temperatures between 300°and 480°C caused the film to break up and coalesce into rectangular crystallites, which were all oriented with (001) parallel to the surface. An anneal to 500°C, which is above the AuGa2 melting point, resulted in the formation of irregular polycrystalline islands of AuGa2 on the GaAs(001) substrate. No interface roughening or chemical reactions between the film and substrate or interface were observed for even the highest-temperature anneals.