Reaction mechanism for target-like products from197Au target bombarded with12C ions of energies above 100 MeV/u

Target-like products, that is,^191–200Au,^185–200Pt, and^183–195Ir, from¹⁹⁷Au target bombarded with¹²C ions at the energies of 180, 230, and 400 MeV/u were measured by using off-line gamma-ray spectrometry combined with chemical separation procedures. Spallation systematics by Rudstam reproduces well the measured cross sections for formation of platinum and iridium isotopes. It was found that the cross sections of gold nuclides increase with increase of the incident energy in the range studied and they are enhanced if compared with the reported proton-induced reaction of gold at a similar incident energy. It is suggested that the electromagnetic dissociation process plays a role for production of such gold nuclides.     

Determination of noble metals by resonance neutron activation technique

Rhodium, palladium, platinum and iridium have been determined in silver matrix by nondestructive activation analysis upon activation with cadmium- and silver-filtered resonance neutrons. Experiments with different types of filter combinations are reported. The sensitivity of the method is 5·10⁻³% for rhodium, 5·10⁻³% for palladium, 3·10⁻²% for platinum and 5·10⁻³% for iridium.     

Spectrographic determination of gold and platinum metals in geological and other materials by fire-assay preconcentration

A method is described for the determination of gold, platinum, palladium, rhodium and iridium at microgram levels in geological and other materials by a combination of fire-assay preconcentration and emission spectrography. The noble metals are collected into 4-mg silver or platinum prills by a normal fire-assay technique. These prills are arced between graphite electrodes at 12 A d.c. No buffer is required to prevent ejection of the prill. Gold, platinum and palladium are determined in the silver prills and gold, palladium, rhodium and iridium in the platinum prills. Low, but reproducible, results are found for iridium. At the 0.08 ppm level an overall coefficient of variation of 11% is found. This technique is simple and rapid for the determination of the precious metals.     

State of Platinum Group Metals and Gold in Mineral Acid Solutions and the Catalytic Activity of These Metals in the Oxidation of N-Methyldiphenylamine-4-Sulfonic Acid

The state of rhodium, iridium, platinum, and gold in HCl, HClO₄, H₂SO₄, and HNO₃ solutions was studied by capillary electrophoresis. The electrophoresis was performed in an acidic phosphate buffer solution using an unmodified fused-silica capillary. It was found that the catalytic activity of the metals in the reaction of N-methyldiphenylamine-4-sulfonic acid oxidation with periodates in weakly acidic solutions depends on the analyte speciation. It was found that rhodium and iridium cations formed upon the treatment of a sample with concentrated perchloric acid catalyze the above reaction; this is favorable for the selective determination of these cations in the presence of platinum and gold.     

The simultaneous determination of osmium,ruthenium, iridium and gold in platinum by neutron activation analysis

Osmium, ruthenium, iridiuim and gold can be determined simultaneously in 100-mg platinum samples after irradiation for 11 days at a thermal neutron flux of 4'1011 n.cm^-2.sec^-1. An addition method of analysis is used; samples are dissolved in small sealed silica tubes before activation. After irradiation, Os and Ru are distilled from sulfuric acid-sodium bromate, Ru being determined by counting the 498-keV peak of ¹⁰³Ru; Os is determined after a second distillation. Gold is extracted with ethyl acetate from the residue of the first distillation; the ratio ¹⁹⁸Au/¹⁹⁹Au is a direct measure for the gold content, with appropriate correction for the second-order reaction ¹⁹⁶Pt(n,γ)¹⁹⁷Pt→¹⁹⁷Au(n,γ)¹⁹⁸Au. Ir is determined in the residual aqueous phase using the 317-keV peak of ¹⁹²Ir; a correction for the platinum activity (¹⁹¹Pt) is made. The lower limit of determination is ca. 0.5 p.p.m. for ruthenium, ca. 0.2 p.p.m. for osmium, ca. O.1 p.p.m. for gold and ca. O.1 p.p.m. for iridium. After a separation of Pt from Ir, the sensitivity for Ir can easily be improved to < 10 p.p.b.     

A critical review of titrimetric methods for determination of the noble metals-II

Titrimetric methods for palladium, platinum, rhodium, iridium, ruthenium and gold are critically reviewed to the end of 1964. Previous reviews covered the literature to the end of 1957 for the five platinum metals and to mid-1960 for gold.     

Extraction of iridium with tetraphenylarsonium chloride and its flotation—spectrophotometric determination with rhodamine 6g

A sensitive flotation—spectrophotometric method, based on the ion-associate formed by the anionic chloride and chlorostannate(II) complex of iridium with the basic dye rhodamine 6G (R6G) is described. A sparingly soluble compound precipitates when the aqueous phase is shaken with di-isopropyl ether. The separated and washed compound is then dissolved in acetone. The molar absorptivity is 3.6 × 10⁵ l mol^-1 cm^-1 at 530 nm. Beer's law is obeyed. The component ratios in the isolated compound were determined, and the formula [(R6G⁺)₃IrCl₂(SnCl₃)^3-₄] · [(R6G⁺)(SnCl^-₃)] is proposed for the adduct. The effects of other noble metals were examined. The interferences of rhodium and platinum with the determination of iridium in the proposed method can be greatly decreased by a preliminary extractive separation of iridium into chloroform as a tetraphenylarsonium hexachloroiridate(IV) complex. Optimum conditions for the iridium extraction are reported.     

Limit of detection for the determination of Pt in biological material by RNAA using electrolytic separation of gold

Neutron activation analysis based on the¹⁹⁹Au indicator for platinum requires the separation of gold at high radiochemical purity. The limit of detection is strongly affected by the presence of gold; with a gold content of 50 pg/g, irradiating for 5 days at 5·10¹³ n/cm²s is needed to achieve a limit of detection of approximately 30 pg/g. In this case the nuclear interference from gold will exceed the level of platinum by several orders of magnitude and has to be determined with exceedingly high precision. Preliminary results for SRM 1577 Bovine Liver with 95% yield gave consistent results for Au, but Pt could not be detected.     

Bestimmung von Palladium,Iridium und Platin in Silikatgesteinen durch Neutronenaktivierungsanalyse und chemische Abtrennung mit N,N′-Dibenzyl-Dithiooxamid

Palladium, iridium and platinum are determined by neutron activation and chemical separation via¹⁰⁹Pd,¹⁹²Ir and¹⁹⁷Pt. Palladium(II) reacts immediately with N, N-Dibenzyldithiooxamide, Pt(IV) after addition of SnCl₂ and Ir only upon heating in the presence of I. Palladium and platinum are separated together and measured simultaneously on a Ge-X-ray-detector. The chemical yields are determined by spectrophotometry of the extracted complexes. For samples of 0.2g the detection limits amount to 0.02 ppb Pd, 0.5 ppb Pt and 0.002 ppb Ir.     

Determination of platinum and iridium in reforming catalysts by second derivative and absorptiometric spectrophotometry

Summary Investigations on the spectrophotometric determination of platinum as a complex formed by tin(II)chloride in hydrochloric acid are reported. The determination of platinum was found to be interfered with by iridium, because it also forms a complex with tin(II) chloride. The features of the derivative absorption spectrophotometry for the quantitative determination of platinum and iridium was also studied. The analytical application of the method for the determination of platinum and iridium in catalysts was investigated.     

Spectrophotometric determination of noble metals with tin(II) in bromide solutions

In presence of tin(II) bromide, noble metals give coloured products which are suitable for spcctrophotometric determinations. The colours are red (platinum), yellow-orange (rhodium), yellow-brown (palladium), yellow (iridium) and violet (gold) They are extracted, except for gold, with isoamyl alcohol Platinum, rhodium and palladium can be separated from irdium, and rhodium and platinum from palladium. Rhodium and platinum can be determined simultaneously.     

Determination of platinum and gold in biological materials by neutron activation analysis

A procedure for platinum and gold determination utilizing, neutron activation combined with radiochemical separation, has been developed. The reaction¹⁹⁸Pt (n, )¹⁹⁹ is used for Pt determination. Four procedures for gold separation are examined: (1) adsorption on untreated polyurethane foam (UPF). (2) extraction with dibutyl sulphide. (3) reduction of gold to elementary state in conc. H₂SO₄, and extraction of gold as diethyldithiocarbamate complex. The extraction with Cu(DDC)₂ is chosen as the most suitable process and applied to platinum and gold determinations in Bowen's Kale and mice organs, previously treated with Biocisplatinum^® specimens.     

Structural diversity in the coordination of 1,4‐dihydro‐1,4‐diarsinine as a cyclic ditopic organoarsenic ligand to metal ions

A number of different complexation structures of cis‐1,4‐dihydro‐1,4‐dimethyl‐2,3,5,6‐tetrakis(t‐butoxycarbonyl)‐1,4‐diarsinine (cis‐DHDAtBu) with gold(I) and iridium(III) were synthesized and characterized by ¹H, ¹³C NMR spectra, X‐ray crystallography, and elemental analysis. Mono‐ and di‐nuclear gold(I) chloride complexes with cis‐DHDAtBu were obtained by simple addition of gold(I) chloride to cis‐DHDAtBu. A hetero‐trinuclear gold‐platinum‐gold complex (PtAu₂Cl₄(cis‐DHDAtBu)₂) was obtained by complexation of a mononuclear platinum(II) complex (trans‐PtCl₂(cis‐DHDAtBu)₂), which was obtained by complexation of cis‐DHDAtBu with a half‐equimolar amount of PtCl₂(PhCN)₂, with a twice‐equimolar amount of gold(I) chloride. An iridium(III) complex with cis‐DHDAtBu (IrCl₃(cis‐DHDAtBu)₂) was prepared from hydrated iridium(III) chloride and cis‐DHDAtBu. The complex comprises a five‐membered chelate cis‐DHDAtBu and an usual monodentate cis‐DHDAtBu. The interior angles at around the arsenic and the As–C—C bond angles were significantly varied from 113.4° to 129.4° in the present crystal. These observations suggest that the flexibility of the bond angles at around the arsenic center is inherent property in the present organoarsenic compounds. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 23:16–26, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20747     

The determination of pd,pt, au,ag and ir in copper by neutron activation analysis

The determination of palladium, platinum and gold in copper metal by neutron activation analysis is described. The matrix activity was separated from the noble metals by cation-exchange adsorption. Gold was extracted; palladium and platinum were precipitated. The precipitates were counted with a low-energy photon detector. The gold results were checked by instrumental neutron activation analysis. Silver, iridium, selenium, antimony and arsenic were also determined simultaneously.     

Enhanced electrochemical evolution of oxygen by using nanoflowers made from a gold and iridium oxide composite

We report on the synthesis of a composite made from iridium oxide and gold that has a flower-like morphology. The ratio of iridium oxide to gold can be controlled by altering the concentrations of the metal precursors or the pH of the solution containing the reductant citrate. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and laser confocal micro-Raman spectroscopy were applied to characterize the structures of the nanoflowers, and a mechanism of their formation was deduced. The nanoflowers display an electrocatalytic activity in an oxygen evolution reaction (OER) that is significantly enhanced compared to bare iridium oxide nanoparticles. The highest turnover frequency for the OER of the new nanoflowers is 10.9?s^?1, which is almost one order of magnitude better than that of the respective nanoparticles. These attractive features are attributed to the high oxidation states of iridium in the nanoflowers which is caused by the transfer of electronic charge from metal oxides to gold, and also to the flower fractal structure which is thought to provide a much more accessible surface than suspensions of the respective nanoparticle.

Cation-exchange in thiourea-hydrochloric acid solutions

Ion-exchange distribution coefficients are reported for several transition and post-transition elements in solutions of hydrochloric acid (0.1-3.0M) and thiourea on AG50W resins. Some typical elution curves illustrate use of the systems with special reference to the separation of small amounts of gold, palladium, platinum, rhodium and iridium from large amounts of numerous base metals by using 1.5M hydrochloric acid-0.1M thiourea as eluent. Also illustrated is the use of a bromine-containing solution to strip thiourea complexes from a cation-exchange column.     

Gold(III) Alkyne Complexes: Bonding and Reaction Pathways

The synthesis and characterization of hitherto hypothetical Au^III π‐alkyne complexes is reported. Bonding and stability depend strongly on the trans effect and steric factors. Bonding characteristics shed light on the reasons for the very different stabilities between the classical alkyne complexes of Pt^II and their drastically more reactive Au^III congeners. Lack of back‐bonding facilitates alkyne slippage, which is energetically less costly for gold than for platinum and explains the propensity of gold to facilitate C−C bond formation. Cycloaddition followed by aryl migration and reductive deprotonation is presented as a new reaction sequence in gold chemistry.     

1H bridging and terminal hydride T1 values. Comments on classical vs non-classical hydride identification using T1 criteria

Hydride ¹H T₁ values are reported for a selected series of ruthenium, iridium and platinum complexes. These T₁ values range from 6.9 to 0.05 s with the shortest value, 0.05 s, assigned to a complex containing both hydride and coordinated molecular hydrogen, i.e. “M(H₂)”. There are nuclear Overhauser enhancements arising both from protons on coordinated ligands and other hydride ligands. It is suggested that the molecular weight of the complex and the measurement conditions can be important factors for T₁.     

Formation of stacking defects at surfaces: From atomistic simulations to density functional theory calculations

We have performed electronic structure calculations to study the evolution of the stacking fault energy at (111) surfaces of metals. We first apply an sp–d tight-binding model and then increase the accuracy on the electronic structure by using density functional theory (DFT) calculations. We show in this way the relative importance of sp–d hybridization both in the formation of defects at the surface of metals and in reconstruction phenomena as a function of band filling especially at the end of transition metal series. Comparing our results with atomistic simulations it is concluded that although atomistic calculations are powerful tools to investigate relaxation mechanisms at surfaces, a higher degree of accuracy on electronic structure is necessary to quantify the energy of some defects at surfaces like stacking faults. In particular long range interactions associated to less localized sp electrons are playing a rather important role in reconstruction phenomena for metals like platinum and gold. These results are backed up by DFT calculations applied to iridium, platinum and gold (111) surfaces.