Effect of the oxidation state of gold on the complete oxidation of isobutane on Au/CeO2 catalysts

Catalysts of highly dispersed gold supported on ceria were prepared by deposition precipitation method. Au is dispersed as Au⁰, Au⁺ and Au³⁺ species on ceria. The content of Au⁺ and Au³⁺ was highest on catalyst prepared on uncalcined ceria, which possess least ordered surface. It is inferred that oxygen vacancy on disordered ceria surface is essential for the preparation of highly dispersed gold catalysts and in stabilizing monolayer surface Au⁺ clusters while cationic vacancies are sites for substitutional Au³⁺. Au/CeO₂ catalysts showed low-temperature isobutane oxidation activity with maximum conversion at 150–180°C. Ex-situ XPS results demonstrated that the low temperature isobutane oxidation activity was closely related to the content of Au⁺ which we interpreted as surface gold oxide formed under reaction conditions. Isobutane oxidation activity associated with ceria at temperature above 300°C was enhanced by substitutional Au³⁺.     

Novel plating solution for electroless deposition of gold film onto glass surface

In this paper, a simple and environmentally friendly electroless plating solution of chloroauric acid (HAuCl₄) and hydrogen peroxide (H₂O₂) for depositing gold film onto (3-aminopropyl)-trimethoxysilane (APTMS) -coated glass surface has been developed. APTMS as an adhesive reagent was used to attach the gold nanoparticles (AuNPs) onto the glass substrate. These AuNPs could be regarded as the preferential nucleation or catalytic sites for gold electroless reduction, which accelerated the reduction of Au³⁺ on the glass surface and effectively prevented the formation of gold metal in the bulk solution. During the gold plating process, H₂O₂ as the reducing agent was thermodynamically capable of reducing Au³⁺ ions from the HAuCl₄ precursor to gold atoms, which deposited onto the glass surface and finally formed the continuous gold film. The resulting gold film was characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and atomic force microscope (AFM), respectively.     

利奈唑胺、去甲万古霉素等抗菌药物对耐甲氧西林金黄色葡萄球菌的抗菌活性

目的:研究北京市三家医院耐甲氧西林金黄色葡萄球菌(MRSA) 耐药现状, 评价利奈唑胺、去甲万古霉素等药物的抗菌活性。方法:收集解放军总医院、北京医院、北京协和医院三家医院分离的非重复MRSA 111 株, 头孢西丁纸片法确认MRSA, 采用琼脂稀释法测定抗菌药物的最低抑菌浓度(MIC) 。结果:111 株MRSA, 对β-内酰胺类的耐药率为100%, 对红霉素的耐药率为92.8%, 对氨基糖苷类(奈替米星、庆大霉素) 的耐药率为99.1%, 对氟喹酮类(加替沙星、莫西沙星、左氧氟沙星) 的耐药率为91.9% ～99.1%, 对氯霉素的耐药率为3.6%, 对去甲万古霉素、利奈唑胺全部敏感, 对去甲万古霉素MIC₅₀ 和MIC₉₀ 分别为0.5和1 μg/mL, 对利奈唑胺的MIC₅₀ 和MIC₉₀ 均为2 μg/mL 。结论:北京三家医院分离的MRSA 对本研究的大多数抗菌药物均耐药, 去甲万古霉素和利奈唑胺对于MRSA 有很高的抗菌活性。     

Nanogoldpharmaceutics (i) The use of colloidal gold to treat experimentally-induced arthritis in rat models; (ii) Characterization of the gold in Swarna bhasma, a microparticulate used in traditional Indian medicine

Nanosized gold particles (27 +/− 3 nm) have been proven to be effective in ameliorating the symptoms of mycobacterial-, collagen- and pristane-induced arthritis in rat models. This contrasts with the drug sodium aurothiomalate that was only effective against mycobacterial-induced arthritis but not to the same extent as Au⁰. Gold in the traditional Indian Ayurvedic medicine,Swarna bhasma (gold ash), has been characterized as globular particles of gold with an average size of 56–57 nm.     

Synthesis and antimicrobial activities of gold(I) sulfanylcarboxylates

Reaction of NaAuCl₄·H₂O and thiodiglycol (1:3 molar ratio) with 3-(aryl)-2-sulfanylpropenoic acids, H₂ xspa = [x:p = 3-phenyl-, f = 3-(2-furyl)-, t = 3-(2-thienyl)-, o-py = 3-(2-pyridyl)-, Clp = 3-(2-chlorophenyl)-, -o-mp = 3-(2-methoxyphenyl)-, -p-mp = 3-(4-methoxyphenyl)-, -o-hp = 3-(2-hydroxyphenyl)-, -p-hp = 3-(4-hydroxyphenyl)-, diBr-o-hp = 3-(3,5-dibromo-2-hydroxyphenyl)] and 2-cyclopentylidene-2-sulfanylacetic acid (H₂cpa) in a 1:1 metal/ligand molar ratio gave compounds of the type [Au(Hxspa)] or [Au(Hcpa)]. These compounds were reacted with diisopropylamine to afford [HQ][Au(xspa)] or [HQ][Au(cpa)] (HQ = diisopropylammonium) and with NaOH to afford Na[Au(xspa)]·H₂O and Na[Au(cpa)]·H₂O. All of the new compounds were isolated and characterised by IR and ¹H and ¹³C NMR spectroscopy. The antimicrobial activities of the complexes against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albicans, Pseudomonas aeruginosa and carbapenem-resistant P. aeruginosa were evaluated and compared to those of the equivalent silver(I) complexes. The comparison shows that the gold compounds generally show better activity than the silver analogues against S. aureus and B. subtilis, but low sensitivity against E. coli, P. aeruginosa and C. albicans, suggesting a different mode of antimicrobial action for equivalent silver and gold compounds.     

Gold complexes with

The reactions of methane with the gold complexes [Au(OH)]⁻, [Au(OCH₃)₄]⁻, [Au(O(CO)₂O₂]⁻ and [Au(O₂CH)₂]⁺, [Au^I(acac)], [Au^III(acac)₂]⁺ (acac-acetylacetonato) were studied using the DFT/PBE method with the SBK basis set. High activation barriers were obtained for the electrophilic substitution in [Au(OH)]⁻, [Au(OCH₃)⁴]⁻, [Au(O(CO)₂O)₂]-and [Au^III(acac)₂]⁺ complexes, which excludes the possibility that these reactions might proceed under mild conditions. The reactions of the [Au(HCO₂)₂]⁺ and [AuI(acac)] complexes with methane have rather low energy barriers and proceed through the formation of an intermediate complex. The alternative mechanism of methane oxidation with a gold complex in the presence of oxygen is simulated.     

Interatomic interaction in solid solutions of gold in copper

It is supposed that not only pairwise but also many-particle interaction exists between metal atoms in binary solid solutions. Therefore, the mixing energy in the solid solution V _i that is determined from the data on the parameters of short-range order in terms of the model of pairwise interaction has no direct physical sense and proves to be dependent on the concentration of the solute c:V _i = V _i (c). Only the pair potential h _i = V _i (0) for impurity atoms to approach each other in the lattice of solvent, which is determined by extrapolation of the V _i (c) dependence to zero concentration, is physically meaningful. The potential h _i can be used for the calculation of the Wagner interaction parameter and first-order enthalpy parameter. These considerations have been applied to solid solutions of gold in copper. For the Wagner parameter of interaction ε _Au ^Au and enthalpy parameter η _Au ^Au in copper-based alloys at 800 K, a satisfactory agreement of the theory and experiment has been obtained.     

Di-(2-ethylhexyl) dithiophosphoric acid surface protected gold nanoparticles: micellar synthesis, stabilization, isolation, and properties

Gold nanoparticles (AuNPs) were synthesized in the organic solution by means of the reduction of HAuCl₄ by hydrazine in reverse micelles of oxyethylated surfactant Triton N-42, with decane as the dispersion medium. To isolate the powder of particles, the micelles were destroyed with chloroform in the presence of di-(2-ethylhexyl) dithiophosphoric acid as a surface protecting agent. According to the results of several experiments, the yield is within the limits of 90–98%, calculated for gold. The obtained preparations are dark blue hydrophobic powders containing aggregated but not agglomerated gold nanoparticles, as well as microcrystals (∼0.08–0.2 μm) of NaCl. The powders get re-dispersed in weakly polar organic solvents with the formation of colloidal solutions. The shape of the nanoparticles is spherical. Their nuclei are gold single crystals with a narrow size distribution; their diameter (d _Au) is about two times as large as the diameter of the aqueous nucleus (d _c) of initial micelles: d _Au = 7.7 ± 1.4 nm (d _c = 3.6 nm) and 8.8 ± 1.5 nm (4.6 nm). The preparations were studied by means of dynamic light scattering, atomic force microscopy, transmission electron microscopy, UV–vis spectroscopy, IR spectroscopy, X-ray powder diffraction, and thermogravimetric and elemental analyses. In the case of the particles with d _Au = 8.8 nm, the product is a mixture of AuNPs and the salt with the molar ratio Au/NaCl ≈ 1:4.54, while the gross composition of AuNPs per one gold atom is estimated as Au(C₁₆H₃₄O₂PS₂Na∙2N₂H₄)_0.16 with the number of gold atoms in one particle ∼21,000.     

Gold anion catalysis of methane to methanol

The oxidation of CH₄ has been investigated in the presence and absence of the atomic Au⁻ ion catalyst. We have employed the first principles density functional theory (DFT) and dispersion-corrected DFT calculations for the transition state on the Au⁻ ion and analyzed the thermodynamics properties of the reactions as well. Our results demonstrate that atomic gold anions could be used to catalyze CH₄ into valuable industrial products without the emission of CO₂, thereby making gold extremely valuable. The fundamental mechanism involves breaking the C–H bond through the formation of the anionic Au⁻(CH₄) molecular complex permitting the oxidation of CH₄ to methanol at the temperature of 325 K which is below that of CO₂ emission. Potentially, this could significantly impact the quality of our environment.     

4种抗生素在兔髓核中的分布

目的 观察青霉素G、头孢唑林、妥布霉素和克林霉素在兔椎间盘髓核中的分布。方法 兔耳静脉注射4种抗生素,采用高效液相色谱法测定兔血清、正常椎间盘和感染后椎间盘在给药后0.5h和1h时的药物浓度(含量),并比较血清浓度与髓核含量之间的相关性。结果 比较髓核中药物含量与血清中药物浓度的比例,药物进入髓核分布比例青霉素G<头孢唑林<妥布霉素<克林霉素。感染后进入髓核的比例增加,除青霉素G外,其他药物髓核药物含量/血清药物浓度,感染组均大于正常组,并且妥布霉素和克林霉素明显增加(P<0.05)。药物在髓核中消除速度比在血清中慢。结论 血清的药物浓度与髓核含量无相关性;妥布霉素和克林霉素治疗椎间盘感染应为首选。     

Thermodynamic calculation of the critical potentials of the selective dissolution of Ag-Au and Cu-Au alloys

A thermodynamic approach to estimating the critical potential of the selective alloy dissolution E _c at a vacancy concentration N _v(s) in the superficial layer is considered. The N _v(s) dependence on the potential and the concentration of gold N _Au in the alloy is calculated. The E _c potential corresponds to the critical concentration of vacancies N _v(s) ≈ 10⁻², and the E _c value itself is determined chiefly by the zero-point potential of the alloy, which is a pronounced function of the surface enrichment in gold. The calculated E _c-N _Au functions for Ag-Au and Cu-Au alloys satisfactorily coincide with the experimental dependences. Original Russian Text ? A.E. Kutyrev, Yu.Ya. Andreev, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 2, pp. 152–159.     

The open circuit behaviour of ferric oxide deposited on gold

The open circuit behaviour of ferric oxide films on a gold substrate in NaCl solutions containing low concentrations of Fe²⁺ ions is reported. The film oxide is readily transformed to a lower oxidation state oxide with a Fe²⁺/total Fe ratio corresponding to that of magnetite. An interpretation of the reaction is proposed.     

Kinetics and mechanism of the gold corrosion dissolution in hypochlorite solutions

Kinetics and mechanism of the gold metal dissolution by means of corrosion in chloride-hypochlorite solutions are studied. The dependences of the dissolution rate on the solution pH, sodium hypochlorite concentration, and temperature are determined. Conditions of the gold passivation surface during its corrosion in the studied solutions are discussed. The first-order rate constants of the gold dissolution (k_i = 0.079–0.4030 s^–1) at temperatures from 277 to 304 K and others are calculated. The equilibrium constants of the dissolution reactions in acid and alkaline chloride-hypochlorite solutions are different: 1.2 × 10⁶ and 2.39 × 10², respectively. The activation energy calculated from the temperature dependence of the rate constants (53.43 kJ/mol) evidences a kinetic control of the gold dissolution. Quantitative data on the composition of surface adsorption films, formed by oxidation gold dissolution products, are obtained using the Auger spectroscopyTranslated from Zashchita Metallov, Vol. 41, No. 1, 2005, pp. 26–33.Original Russian Text Copyright © 2005 by Kozin, Prokopenko, Bogdanova.     

New In–Pd mechanical loss peak in ternary gold alloys

A point defect relaxation peak has been observed in a ternary 18-carat gold alloy with the composition Au_62.5Pd_32.5In₅. It shows a Curie–Weiss dependence on the temperature, as is commonly observed for a Zener peak. However, the peak is absent in the binary alloys AuPd and AuIn and therefore it is a new type of relaxation that is due to In–Pd pairs. The relaxation strength shows a linear dependence on the indium concentration. We have developed a model of elastic dipoles containing one palladium and one indium atom in a gold matrix. The model is based on the reorientation under stress of InPd dipoles in a gold matrix and takes into account the atom ordering. The model accounts for a linear dependence of the relaxation strength on the indium concentration in a dilute alloy and is also valid for more concentrated alloys.     

Co-intensification of cyanide leaching gold by mercury ions and oxidant

The effects of mercury ions on gold cyanidation were studied. The results show that under low cyanide concentration, gold cyanide process is controlled by CN^? transfer, while at higher cyanide concentration, there forms passivation on gold surface. Therefore, chemical oxidation of gold in cyanide solution of higher concentration is controlled by surface reaction. Small quantity of additions of mercury ions bring about great increases in anodic gold dissolution rate, decreases the passivation and reduces the equilibrium activated energy. In addition, they also markedly change the effect pattern of cyanide concentration. Mercury ions show positive effects on cathodic reduction of oxygen and raise the rate of electrochemical step of the cathodic reduction of oxygen. Addition of a certain amount of hydrogen peroxide is confirmed to be an effective way for intensification of cathodic process on gold electrode. Active potential range and current peak on anodic dissolution are enlarged when being co-intensified with Hg²⁺ and hydrogen peroxide. Co-intensifying effect may be obtained and gold leaching rate is considerably increased on cyanide leaching of gold from gold concentrates.     

Design of luminescent sulfur-containing polynuclear gold(I) complexes for advanced nanomaterials and chemosensors

A series of high-nuclearity gold(I) sulfido complexes with bridging diphosphine ligands have been synthesized and isolated, with the general formulae of [Au₁₀(μ-P^P)₄(μ₃-S)₄]X₂ and [Au₁₂(μ-P^P)₄(μ₃-S)₄]X₄ (P^P = diphosphine; X = PF₆ or ClO₄). Intense green and orange emissions were observed upon excitation at λ > 350 nm both in the solid state and in solutions. The green emission has been attributed to originate from excited states derived from the metal-perturbed intraligand (IL) transition while the orange emission arises from the ligand-to-metal-metal bond charge-transfer (LMMCT; S(Au...Au) states. The switching on and off of the LMMCT emission in a series of dinuclear gold(I) thiolate complexes with crown ether pendants induced by ion-binding has been demonstrated, and this provides a new strategy for the design of luminescence signalling and chemosensing devices in optoelectronics and sensor technology.     

Preparation of a functional nanofibrous polymer membrane incorporated with poly(2-aminothio phenol) stabilized gold nanoparticles

Functional nanofibrous polymer membranes were prepared by incorporating poly(2-aminothio phenol) (P2AT) stabilized Au NPs onto electrospun polyvinylidene fluoride (PVdF) nanofibers (designated as P2AT-Au NPs@PVdF-NFM). The preparation of P2AT-Au NPs@PVdF-NFM involves two steps: loading of 2AT (monomer) into electrospun PVdF nanofibrous membrane and polymerization of 2AT by gold chloride. P2AT and Au NPs were simultaneously formed into the electrospun PVdF-NFM. Transmission electron microscope image of P2AT-Au NPs@PVdF-NFM informs the presence of Au NPs (with sizes ~10 nm) onto PVdF-NFM.     

Characterization of Cr（Ⅵ） resistance and reduction by Pseudomonas aeruginosa

The experiments were conducted to evaluate the Cr(VI) resistance and reduction by Pseudomonas aeruginosa. After this bacterium tolerated 40 mg/L Cr(VI), the growth of cells was observed. The bacterial growth was obviously lower than the controls over 24 h and the binary cell fission was observed in cell morphology by scanning electron microscope. P.aeruginosa was found to be able to reduce Cr(VI) although Cr(VI) had toxic effects on the cells. The results demonstrate that Cr(VI) is reduced from 40 mg/L to about 18 mg /L in 72 h. The value of pH drops from 7.02 to around 5.65 after 72 h. A significant increase in the value of redox potential occurs during Cr(VI) reduction and Cr(VI) reduction can be observed over a range of redox potential from +3 mV to +91 mV. Both of SO₄²⁻ and NO₃⁻ have no effect on Cr(VI) reduction. The presence of Zn²⁺ has a notable inhibitory effect on Cr(VI) reduction while Cu²⁺ substantially stimulates Cr(VI) reduction. In the presence of Zn²⁺, Cr(VI) decreases from 40 mg/L to only 26–27 mg/L, whereas Cr(VI) drops to 1–2 mg/L after 48 h in the presence of Cu²⁺.     

Kinetics of phase transformations in the surface layer of a binary alloy at the selective dissolution: III. Cu-Au | Cu<Superscript>2+</Superscript> system

Conditions of the phase transformation of gold on the surface of Cu-Au alloys selectively dissolved in an acidic sulfate solution at the overcritical anodic polarization are experimentally found. Kinetic regularities of the formation of an individual Au⁰ gold phase on the alloy surface depending on the alloy composition, anodic potential, and the presence of organic surfactants in the solutions are determined.     

Tin-modified gold-based bulk metallic glasses

Tin was selected as a modifying element in low-gold-content (50 at.%) bulk metallic glasses (BMGs) aiming at developing alloys with cost-effective performance. New gold-based Au–Sn–Cu–Si alloys were fabricated by injection-casting into a copper mold. The as-cast BMG Au₅₀Sn₆Cu₂₆Si₁₈ with 18.6-karat gold and a diameter of 1 mm possessed a lower glass transition temperature (T _g) of 82°C (355 K), a lower liquid temperature of 330°C (603 K), and a super-cooled liquid region of 31°C. The viscosity range of this BMG Au₅₀Sn₆Cu₂₆Si₁₈ was from 10⁸ to 10⁹ Pa s measured at a low applied stress of 13 kPa. To compare the viscosity with different applied stresses, its viscosity clearly increased with applied stress below T _g but not so obvious above T _g. The low viscosity of this BMG Au₅₀Sn₆Cu₂₆Si₁₈ at around 102°C, which is very close to the boiling temperature of water (100°C), rendered easy thermal–mechanical deformation in a boiling water-bath by hand-pressing and tweezers-bending. Such a deformation capability in boiling water is beneficial to the further applications in various fields.