Growth of carbon nanotubes on a gold (111) surface using two-dimensional iron oxide nano-particle catalysts derived from iron storage protein

We report here the preparation of two-dimensional iron oxide nano-particles from the iron storage protein ferritin immobilized on a gold surface. This paper also reports the novel finding of the lattice-oriented like growth of carbon nanotubes on a gold (111) surface using the obtained two-dimensional iron oxide nano-particles on the gold surface as a catalyst.     

Separation and determination of gold from iron rich matrices by an off/on-line preconcentration system coupled to ICP-AES

A preconcentration/separation method has been developed for the off/on-line determination by ICP-AES of gold in complex matrices, containing iron and manganese which cause severe spectral interferences on the two most sensitive Au-lines. The available automated preconcentration apparatus was modified using as absorbent the highly selective, for precious metals, chelating anion exchanger SRAFION NMRR. From the elution of this resin with 5% thiourea a nearly quantitative recovery of gold and its separation from iron, existing in percent range in the matrix, and from manganese was obtained. The validity of the developed method was tested by the determination of gold in standard reference materials from BCR, such as sewage sludge of domestic and mainly industrial origin and in a calcareous loam soil. The preconcentration procedure was synchronized with the ICP operating parameters in order to get an optimised on-line coupling of these two systems. The described process has been successfully applied to the determination of low gold contents in dissolved iron rich sediments using for the gold prospection.     

Iron oxide coated gold nanorods: synthesis, characterization, and magnetic manipulation

We report a simple process to generate iron oxide coated gold nanorods. Gold nanorods, synthesized by our three-step seed mediated protocol, were coated with a layer of polymer, poly(sodium 4-styrenesulfonate). The negatively charged polymer on the nanorod surface electrostatically attracted a mixture of aqueous iron(II) and iron(III) ions. Base-mediated coprecipitation of iron salts was used to form uniform coatings of iron oxide nanoparticles onto the surface of gold nanorods. The magnetic properties were studied using a superconducting quantum interference device (SQUID) magnetometer, which indicated superparamagnetic behavior of the composites. These iron oxide coated gold nanorods were studied for macroscopic magnetic manipulation and were found to be weakly magnetic. For comparison, premade iron oxide nanoparticles, attached to gold nanorods by electrostatic interactions, were also studied. Although control over uniform coating of the nanorods was difficult to achieve, magnetic manipulation was improved in the latter case. The products of both synthetic methods were monitored by UV-vis spectroscopy, zeta potential measurements, and transmission electron microscopy. X-ray photoelectron spectroscopy was used to determine the oxidation state of iron in the gold nanorod-iron oxide composites, which is consistent with Fe2O3 rather than Fe3O4. The simple method of iron oxide coating is general and applicable to different nanoparticles, and it enables magnetic field-assisted ordering of assemblies of nanoparticles for different applications.     

Flame atomic absorption spectrometry of silver and gold in copper intermediates

The effect of hydrochloric acid and salts from the sample on the solubility of methyl isobutyl ketone (MIBK) in aqueous phase and the effect of hydrochloric acid concentration on the MIBK extraction of iron(III) and gold(III) were studied. As a result, an improved method by flame atomic absorption sepctrometry for determination of silver and gold in copper intermediates was developed, employing a more efficient removal of iron and special standards depending upon the concentration of salts introduced by different samples.     

Application of the graphite furnace to the determination of trace iron in gold and silver

Atomic-absorption analysis using a graphite furnace is a powerful technique for the determination of nanogram amounts of iron. It can be applied to the determination of traces of iron in gold and silver. These metals may be removed from solution by reduction to metallic gold and precipitation as silver chloride respectively. Iron is not co-precipitated. The iron content can be determined in 50-100 mg of the noble metals with an error of about 7% (or 0.1 ppm).     

Determination of gold in copper-bearing sulphide ores and metallurgical flotation products by atomic-absorption spectrometry

A method is described which is specific for the determination of gold in sulphide copper ores and concentrates. Direct decomposition with aqua regia was found to be incomplete. A carefully controlled roasting stage followed by treatment with hydrochloric acid and then aqua regia was effective for dissolving all the gold. The gold is extracted into 4-methylpentan-2-one (methyli-sobutylketone) then aspirated into a very lean air—acetylene flame and the gold determined by atomic-absorption spectrometry. No interferences were observed from large concentrations of copper, iron or nickel.     

粗糙铁电极在盐水中的二维拉曼成像(英文)

本文利用具有表面增强活性的铁电极 ,对其在盐水中的点蚀过程进行现场拉曼光谱研究 .利用四氧化三铁的特征峰 ,对发生点蚀的铁电极表面进行拉曼成像 ,发现拉曼成像和普通显微镜下所观测到的图象有着显著的不同 ,点蚀抗内存在多种腐蚀产物 ,且其分布也不均匀 ,体现了拉曼成像技术具有化学的敏感性的独特优势 .     

Reversible Modulation of Surface Plasmons in Gold Nanoparticles Enabled by Surface Redox Chemistry

Switchable surface redox chemistry is demonstrated in gold@iron/iron oxide core–shell nanoparticles with ambient oxidation and plasmon‐mediated reduction to modulate the oxidation state of shell layers. The iron shell can be oxidized to iron oxide through ambient oxidation, leading to an enhancement and red‐shift of the gold surface plasmon resonance (SPR). This enhanced gold SPR can drive reduction of the iron oxide shell under broadband illumination to reversibly blue‐shift and significantly dampen gold SPR absorption. The observed phenomena provide a unique mechanism for controlling the plasmonic properties and surface chemistry of small metal nanoparticles.     

Electrochemically Induced Uptake and Release of Iron by Recombinant Horse H‐Chain Ferritin Covalently Immobilized on 6‐Mercaptohexanoic Acid Modified Gold Electrodes

Ferritin composed entirely of the H‐chain subunit (rHF) was studied to determine whether electrochemical potential alone could induce rHF to take up or release iron. Horse rHF was expressed in E. coli, purified, and covalently immobilized on a self‐assembled monolayer of 6‐mercaptohexanoic acid on gold electrodes. Cyclic voltammetry was used to show that iron was released from rHF following electrochemical reduction, and iron uptake was induced by applying an oxidizing potential to rHF in the presence of ferrous ion.     

An investigation into the use of platinum ware for silicate analysis

The amount of platinum dissolved from platinum apparatus used for dissolving silicate materials to obtain solutions for analysis has been determined. The study included apparatus made from an alloy containing 95 % platinum and 5 % gold. The affinity of iron and platinum was investigated, together with the problem of removing iron from platinum after the latter has been contaminated during fusions. The behaviour of platinum in a classical scheme for the analysis of silicate materials was investigated and the distribution of the platinum in various precipitates established. Platinum has been found to interfere in commonly used methods for the determination of silica, aluminium, iron, titanium, calcium and magnesium.     

Distinct reaction pathways for some classical and nonclassical transition metal dihydrides

Chlorophosphine gold(I) compounds [Au(PR₃)Cl] (R = Et, Ph) have been used as reagents for distinguishing classical from nonclassical structures in a family of dihydrides or dihydrogen complexes of iron, cobalt, rhodium and iridium stabilized by the tripodal polyphosphine PP₃ [PP₃ = P(CH₂CH₂PPh₂)₃]. Novel mixed transition-metal gold hydrides, including the first iron—gold species, are described.     

Photometric and spectrochemical determination of gold in iron pyrites, copper and lead concentrates

A photometric and a spectrochemical method have been developed for determining gold in iron pyrites, copper and lead concentrates. In both, the sample is dissolved and gold is extracted from 1M hydrochloric add solution with a mixture of ethyl methyl ketone and chloroform (1:1). Gold was determined photometrically with N,N'-tetramethyl-o-tolidine. Conditions have been found for satisfactorily sensitive and reproducible spectral determination of gold. For this purpose the effect of various collectors and buffers on the evaporation curves of gold has been studied, as well as excitation conditions, form of the electrodes, optimum slit-width, and photographic variables. The sensitivity and precision of both methods have been evaluated.     

Anodic Stripping Voltammetric Determination of Iron(II) at a Carbon Paste Electrode Modified with Dithiodianiline (DTDA) and Gold Nanoparticles (GNP)

A differential pulse anodic stripping voltammetric procedure was developed for the determination of trace amounts of iron(II) in the presence of iron(III) at a carbon paste electrode (CPE) modified with dithiodianiline and gold nanoparticle. At the pH working of 3.0, a wide concentration range from 0.1 nM to 100 nM was observed with the detection limit of 0.05 nM. The relative standard deviation for a solution containing 50 nM of iron(II) was found to be 3.11 % (n=9). Possible interferences from the coexisting ions were also investigated. The validity of the method and applicability of the sensor were successfully tested by determining of iron(II) in lentil, wheat seed and barley seed samples.     

The separation of gold by selective extraction of HAuBr(4) using a poly(tetramethylene) ether glycol impregnated filter

The separation of gold(III) by selective extraction on an organic- impregnated filter (OIF) was studied. Gold was found to be rapidly extracted into the active polytetramethylene ether glycol (polyTHF) layer of the filter from strongly acidic solutions of HBr, as the HAuBr(4) complex. Quantitative extraction of gold from solution was obtained with flow rates up to 600 ml min(-1) through the 10.75 cm(2) OIF and at ng ml(-1) concentration levels. The extraction is shown to be dependent on the solution flow rate and HBr concentration as well as the filter pore size, thickness and porosity. Gold can be eluted from the filter by converting it into the AuBr(4)(-) complex using a KBr solution. The separation of gold is demonstrated from simple binary metal mixtures involving iron and cadmium, as well as from a more complicated matrix, gold ore solution.     

The properties of gold catalysts precursors adsorbed on the MCM-41 materials modified with Mn and Fe oxides

Silica mesoporous materials modified with manganese and iron were obtained by the hydrothermal method. Gold was introduced to pure and modified silica materials by the direct hydrothermal and impregnation methods. Nitrogen adsorption/desorption studies evidenced formation of the materials with large total surface area and mesoporous structure. Unmodified silica materials showed regular pore arrangement. The uniform porous structure was distorted in the iron or manganese containing samples. XRD, UV-Vis/DRS spectroscopy and temperature programmed reduction studies revealed changes of the nature of transition metal oxide and gold species on the different preparation stages. The oxide species after drying were strongly dispersed and partially incorporated to the silica framework. High temperature treatment led to the formation of extraframework Mn and Fe oxide species. Complex processes of gold deposition were observed during hydrothermal synthesis and impregnation of modified silica materials. The increase of the size of gold species was observed during calcination. The presence of transition metal oxides decreased sintering of gold crystallites.     

Polystyrenes impregnated with ethers-A polymeric reagent selective for gold

A polymeric reagent selective for gold was obtained by impregnating XAD-2 polymeric absorbant with ethylene diglycol dibutyl ether, a gold-selective liquid. The reagent showed a high selectivity for gold over the platinum group metals, nickel(II) and copper(II), but the selectivity relative to iron(III) was pH-dependent.     

Make conjugation simple: a facile approach to integrated nanostructures

We report a facile approach to the conjugation of protein-encapsulated gold fluorescent nanoclusters to the iron oxide nanoparticles through catechol reaction. This method eliminates the use of chemical linkers and can be readily extended to the conjugation of biological molecules and other nanomaterials onto nanoparticle surfaces. The key to the success was producing water-soluble iron oxide nanoparticles with active catechol groups. Further, advanced electron microscopy analysis of the integrated gold nanoclusters and iron oxide nanoparticles provided direct evidence of the presence of a single fluorescent nanocluster per protein template. Interestingly, the integrated nanoparticles exhibited enhanced fluorescent emission in biological media. These studies will provide significantly practical value in chemical conjugation, the development of multifunctional nanostructures, and exploration of multifunctional nanoparticles for biological applications.     

The determination of gold by atomic absorption spectrophotometry

Gold can be isolated from most other elements other than the platinum metals by the extraction of iron(II) 1,10-phenanthroline tetrabromoaurate in chloroform. After isolation gold can be determined in the organic solvent by atomic absorption spectroscopy or colorimetrically by decomposition of the complex and determination of the iron by bathophenanthroline.     

Kinetics and Mechanism of the Dissolution of Gold in Solutions of Thiocarbamide

The kinetics and mechanism of the dissolution of metallic gold in solutions of thiocarbamide in the presence of iron(III) were investigated. The dependence of the dissolution rate of gold on the pH of the solution and the ratio of the concentrations of iron(III) and thiocarbamide was determined, and the optimum conditions for the dissolution of gold were determined. The first-order rate constant for the dissolution of gold and the equilibrium constants for the formation of the complex cations Au[SC(NH₂)₂]⁺ ₂ and the formation of formamide disulfide S₂C₂(NH)₂(NH₂)₂ were calculated.