Au Chloride Research Articles

Facile preparation of Au nanoparticles mediated by Foeniculum Vulgare aqueous extract and investigation of the anti-human breast carcinoma effects

This experiment evaluated antioxidant, anti-human breast cancer activities, and cytotoxicity effects of green synthesis of Au nanoparticles (AuNPs) containing Foeniculum Vulgare aqueous extract. Mixing Foeniculum Vulgare aqueous with Au chloride solution produced Au nanoparticles. The characteristics of Au nanoparticles determined using Fourier Transformed Infrared Spectroscopy (FT‐IR), Transmission Electron Microscopy (TEM), UV–Visible Spectroscopy (UV–Vis), and Field Emission Scanning Electron Microscopy (FE‐SEM). To check the cytotoxicity and anti-breast cancer effects of Au chloride, Foeniculum Vulgare aqueous extract, and AuNPs on common breast cancer cell lines i.e., ZR-75-30, T47D, and HCC1187 was used MTT assay. AuNPs showed no cytotoxicity and the most effective anti-breast cancer features compared to other items that were tested. They had no cytotoxic effects on normal cell line (HUVEC) and had very low cell viability, high anti-breast cancer activities dose-dependently against ZR-75-30, T47D, and HCC1187 cell lines. In the presence of butylated hydroxytoluene as the positive control, the DPPH test was used to evaluate the antioxidant features of Au chloride, Foeniculum Vulgare aqueous extract, and Au nanoparticles. AuNPs showed the best antioxidant properties compared to other items that were tested. Perhaps remarkable anti-human breast cancer activities of Au nanoparticles synthesized by Foeniculum Vulgare aqueous extract due to its antioxidant properties. After clinical trial and confirmation of results, this formulation can be used as an effective drug to treat breast cancer.

Anti-human ovarian cancer, cytotoxicity, and antioxidant effects of Nigella Sativa green-formulated Au nanoparticles: Describing a new chemotherapeutic supplement

IntroductionThe recent research showed that the Gold nanoparticles (GNPs) formulated with Nigella Sativa aqueous extract having potent antioxidant and anti-human ovarian cancer activities in vitro condition.Material and methodsFor determinate the properties of the GNPs that were produced from the reaction between gold chloride solution with aqueous Nigella Sativa extract, we used UV–Visible Spectroscopy (UV-Vis), Field Emission Scanning Electron Microscopy (FE‐SEM), Fourier Transformed Infrared Spectroscopy (FT‐IR), and Transmission Electron Microscopy (TEM). For evaluating anti-ovarian cancer and cytotoxicity effects of GNPs, Au chloride, and Nigella Sativa aqueous extract, we used MTT assay.ResultsThe result of this test showed that GNPs have no cytotoxicity on normal cell line (HUVEC) and have potent anti-ovarian cancer features dose-dependently against PA-1, SK-OV-3, and SW-626 cell lines. The IC50 of GNPs were 249, 361, and 433 µg/mL against PA-1, SW-626, and SK-OV-3 cell lines, respectively. For evaluating the antioxidant features of GNPs, Au chloride, and Nigella Sativa aqueous extract, we used the DPPH test, in this test butylated hydroxytoluene was a positive control, the results of this test showed that the GNPs have an effective antioxidant feature. In the antioxidant test, the IC50 of GNPs and BHT were 144 and 201 µg/mL, respectively.ConclusionsProbably, potent anti-human ovarian cancer activities of GNPs formulated with Nigella Sativa aqueous seed extract because of antioxidant properties. After evaluating the effectiveness of this formulation in clinical trial researches, it can be a good alternative to chemotherapy drugs.

Are Vapor-Like Fluids Viable Ore Fluids for Cu-Au-Mo Porphyry Ore Formation?

Abstract Ore formation in porphyry Cu-Au-(Mo) systems involves the exsolution of metal-bearing fluids from magmas and the transport of the metals in magmatic-hydrothermal plumes that are subject to pressure fluctuations. Deposition of ore minerals occurs as a result of cooling and decompression of the hydrothermal fluids in partly overlapping ore shells. In this study, we address the role of vapor-like fluids in porphyry ore formation through numerical simulations of metal transport using the Gibbs energy minimization software, GEM-Selektor. The thermodynamic properties of the hydrated gaseous metallic species necessary for modeling metal solubility in fluids of moderate density (100–300 kg/m3) were derived from the results of experiments that investigated the solubility of metals in aqueous HCl- and H2S-bearing vapors. Metal transport and precipitation were simulated numerically as a function of temperature, pressure, and fluid composition (S, Cl, and redox). The simulated metal concentrations and ratios are compared to those observed in vapor-like and intermediate-density fluid inclusions from porphyry ore deposits, as well as gas condensates from active volcanoes. The thermodynamically predicted solubility of Cu, Au, Ag, and Mo decreases during isothermal decompression. At elevated pressure, the simulated metal solubility is similar to the metal content measured in vapor-like and intermediate-density fluid inclusions from porphyry deposits (at ~200–1,800 bar). At ambient pressure, the metal solubility approaches the metal content measured in gas condensates from active volcanoes (at ~1 bar), which is several orders of magnitude lower than that in the high-pressure environment. During isochoric cooling, the simulated solubility of Cu, Ag, and Mo decreases, whereas that of Au reaches a maximum between 35 ppb and 2.6 ppm depending on fluid density and composition. Similar observations are made from a compilation of vapor-like and intermediate-density fluid inclusion data showing that Cu, Ag, and Mo contents decrease with decreasing pressure and temperature. Increasing the Cl concentration of the simulated fluid promotes the solubility of Cu, Ag, and Au chloride species. Molybdenum solubility is highest under oxidizing conditions and low S content, and gold solubility is elevated at intermediate redox conditions and elevated S content. The S content of the vapor-like fluid strongly affects metal ratios. Thus, there is a decrease in the Cu/Au ratio as the S content increases from 0.1 to 1 wt %, whereas the opposite is the case for the Mo/Ag ratio; at S contents of >1 wt %, the Mo/Ag ratio also decreases. In summary, thermodynamic calculations based on experiments involving gaseous metallic species predict that vapor-like fluids may transport and efficiently precipitate metals in concentrations sufficient to form porphyry ore deposits. Finally, the fluid composition and pressure-temperature evolution paths of vapor-like and intermediate-density fluids have a strong effect on metal solubility in porphyry systems and potentially exert an important control on their metal ratios and zoning.

Modeling the Process of Au Sorption by Natural Sorbents in the Conditions of the Dispersion Train of a Sulfide Tailings

The experimental study is aimed at elucidation the laws of Au sorption/deposition by various natural sorbents in an acidic environment (pH=2). The experiments simulated the conditions of the dispersion train of the Ursk tailings (Kemerovo region, Russia), where active concentration of Au by natural organic matter in an acidic environment is observed. It was found that the degree of extraction of gold from a sulfate solution is generally higher than from chloride solution. This may indicate higher thermodynamic stability of Au chloride complexes in an acidic environment than sulfate ones. Higher deposition rates of gold are observed in solutions with a predominant content of sulfate ions. According to the degree of deposition of Au, a series was established (from larger to smaller): a mixture of clay minerals (smectite + palygorskite + muscovite) > humic acids > kaolinite

High Aspect Ratio Gold Nanorods Grown with Platinum Seeds

Using Au chloride as precursor, Pt nanocrystals as seeds, ascorbic acid as a reducer, and CTAB as surfactant and complexing agent, extremely long Au nanorods have been grown. The influence of different parameters such as the composition of the seeds, the amount of Pt, or the type of Pt present in solution has been analyzed. These large Au NRs have been exhaustively characterized by (S)TEM, SEM and optical microscopy as well as UV–vis spectroscopy and their morphology correlated with the growth mechanism.

Gold(I) Complexes with “Normal” 1,2,3-Triazolylidene Ligands: Synthesis and Catalytic Properties

1,2,3-Triazolylidenes as versatile, strong donor ligands have currently experienced a boost in complex synthesis as well as catalytic applications. Although many examples of “abnormal” 1,2,3-triazolylidenes have been described, their “normal” congeners have been barely examined to date (for abnormal carbenes the resonance structures of the carbenes cannot be drawn without adding additional charges, but this is possible for normal carbenes). Furthermore, no instance of utilization of this new ligand class in homogeneous catalysis can be found. Therefore, this work presents a variety of potential precatalysts descending from “normal” 1,2,3-triazolylidene Au chloride complexes. Synthesis and thorough characterization of the new compounds are presented, together with special ligand features such as buried volume and suspected anagostic interactions. The activity of the isolated precatalysts is examined in the intramolecular hydroamination of alkynes and compared with that of a popular imidazolylidene system. ...

An X-ray Absorption Fine Structure study of Au adsorbed onto the non-metabolizing cells of two soil bacterial species

Gram-positive and Gram-negative bacterial cells can remove Au from Au(III)–chloride solutions, and the extent of removal is strongly pH dependent. In order to determine the removal mechanisms, X-ray Absorption Fine Structure (XAFS) spectroscopy experiments were conducted on non-metabolizing biomass of Bacillus subtilis and Pseudomonas putida with fixed Au(III) concentrations over a range of bacterial concentrations and pH values. X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) data on both bacterial species indicate that more than 90% of the Au atoms on the bacterial cell walls were reduced to Au(I). In contrast to what has been observed for Au(III) interaction with metabolizing bacterial cells, no Au(0) or Au–Au nearest neighbors were observed in our experimental systems. All of the removed Au was present as adsorbed bacterial surface complexes. For both species, the XAFS data suggest that although Au–chloride–hydroxide aqueous complexes dominate the speciation of Au in solution, Au on the bacterial cell wall is characterized predominantly by binding of Au atoms to sulfhydryl functional groups and amine and/or carboxyl functional groups, and the relative importance of the sulfhydryl groups increases with increasing pH and with decreasing Au loading. The XAFS data for both microorganism species suggest that adsorption is the first step in the formation of Au nanoparticles by bacteria, and the results enhance our ability to account for the behavior of Au in bacteria-bearing geologic systems.

Novel dehydration of carbohydrates to 5-hydroxymethylfurfural catalyzed by Ir and Au chlorides in ionic liquids

Catalytic dehydration of carbohydrates into 5-hydroxymethylfurfural (5-HMF) has been studied in the presence of ionic liquids, i.e., 1-butyl-3-methyl imidazolium chloride ([BMIM]Cl) and triethylamine sulphate ([Et 3NH][HSO 4]) using metal salts as catalysts. Novel metal chlorides IrCl 3 and AuCl 3·HCl as catalysts in ionic liquid showed remarkable activity and selectivity to 5-HMF for the reaction of fructose dehydration. The reaction conditions of fructose dehydration were optimized as follows: reaction temperature 120 °C, reaction time 30 min, IrCl 3 content 7% (mol% based on fructose) in [BMIM]Cl, at which the conversion of fructose and the yield of 5-HMF reached 97.7% and 89.0%, respectively. By simply assuming the fructose simultaneously converts to 5-HMF and other by-products by the first-order reaction kinetics, the energies of activation are estimated to be 165 kJ/mol for the formation of 5-HMF and 124 kJ/mol for the formation of other by-products from 80 to 100 °C, respectively. The existence of water in the media more than 0.5% (v/v) would significantly slow down the dehydration rate of fructose, while it seemed not necessary to further remove water during the reaction when the water was less than 0.5%. Compared with the dehydration of fructose, the dehydration of other carbohydrates such as glucose, sucrose and maltose was rather difficult.

The Preparation of Highly Dispersed Au/Al2O3 by Aqueous Impregnation

In this work, we report an impregnation method for preparing Au supported on alumina from HAuCl4. In the literature, impregnation under acidic conditions has been found to lead to poor dispersions of Au and the resulting catalysts are not as active as those prepared by deposition-precipitation. To overcome these problems, we have developed a two-step procedure: in the first step, the acidified Au solution is contacted with alumina to adsorb the Au chloride on the alumina. After washing off the excess Au precursor, we treat the solid with a strong base to convert the chloride to an absorbed hydroxide. Drying and calcination at 400 °C yields a catalyst with Au particles having a number average diameter of 2.4 nm. The reactivity for CO oxidation at room temperature is comparable to catalysts prepared by deposition-precipitation. These catalysts are stable to hydrothermal sintering, with average particle size around 4 nm after sintering in 10 mol% H2O at 600 °C for 100 h. This work shows that stable Au/Al2O3 catalysts having a high reactivity for CO oxidation can be prepared by impregnation under acidic conditions.

Adsorption of Au(I, III) complexes on Fe, Mn oxides and humic acid

The adsorption of AuCl 4 −, AuCl 2 − and Au(S 2O 3) 2 3− at low Au concentrations relevant to most supergene waters on geothite, birnessite and soil humic acid was investigated at pH 4, pH 2–11.6, in 0.01 and 0.1 M NaNO 3 solutions. At pH 4 and two electrolyte strengths, the adsorption isotherms for the two Au chloride complexes are well described by the Freundlich equation. The Freundlich parameter 1/ n reflects the heterogeneity of the birnessite surface and the nonlinearity of Au adsorption isotherm. The adsorption of Au(S 2O 3) 2 3− is significantly greater than that of AuCl 4 − on birnessite, but the adsorption of Au(S 2O 3) 2 3− is significantly smaller for geothite and humic acid. The adsorption of AuCl 4 − on birnessite and geothite is depressed by increasing electrolyte strength. As birnessite could only adsorb gold anions specifically and goethite could adsorb gold anions by anionic exchange and specific adsorption, the adsorption on goethite is more sensitive to the electrolyte strength. Under these experimental conditions, the Au surface coverage on birnessite is 0.68–0.85% for AuCl 4 − and 1.06–1.10% for Au(S 2O 3) 2 3−, and for goethite is approximately 2.33–6.02% for AuCl 4 − and 0.6–1.05% for Au(S 2O 3) 2 3−. For the pH ranges from 2 to 11.6 and with 0.1 M NaNO 3 as the background electrolyte, Au adsorption decreases with increasing solution pH, which is consistent with the adsorption regularity for anion adsorption on a variable charge surface. For the three surfaces, true solid–liquid distribution coefficients for the Au complexes at these low concentrations that are relevant to most supergene water are significantly negatively correlated with solution pH with the correlation coefficient ranging from −0.941 to −0.996. According to the Kurbatov plot and surface hydroxyl density, the conditional equilibrium constants (log K part) can be estimated. For the three surfaces, values of log K part for adsorption of AuCl 4 − are in the order: birnessite>goethite>humic acid; but for adsorption of AuCl 2 − are goethite>birnessite>humic acid. The effect of the dissolved humic acid on data could be corrected by using a three-phase partition model that accounts for the complexation of the solute by dissolved organic matter in the liquid phase. For low pH (pH<3) solutions, the sorption of AuCl 4 − on humic acid may be related to reduction of Au(III) by the humic acid. However, adsorption of AuCl 4 − and AuCl 2 − on humic acid is similar to that for birnessite and geothite for the higher pH solutions. Hence, birnessite, geothite, and humic acid preferentially adsorb chloro and chloro-hydroxo Au complexes produced from hydrolysis of AuCl 4 − and AuCl 2 − hydrolysis. Gold anion surface complexation and Au speciation in solution lead to the decrease in adsorption of Au complexes with increasing solution pH. As birnessite has very strong oxidation and adsorption abilities for monovalent Au complexes such as Au(S 2O 3) 2 3−, it may play an important role in the deposition and accumulation of the dissolved gold in the supergene environment. Whether and how Au(III) complexes could be transformed to Au(I) complexes or Au ∘ is controversial and needs further investigation.

Fluid inclusion studies of gold-bearing quartz veins from the Yirisen deposit, Sula Mountains greenstone belt, Masumbiri, Sierra Leone

The auriferous veins at Yirisen, Masumbiri, Sierra Leone, occurring mainly in the form of sericitic quartz-sulphide lodes and stringers, are hosted in metamorphosed volcano-sedimentary assemblages invaded by at least two generations of granitic intrusions. Detailed microthermometric studies of fluid inclusions from the veins coupled with laser Raman spectroscopic analysis show that the inclusions contain aqueous fluids of variable salinity (5 to 60 wt.% NaCl equivalent) and dense carbonic fluids (pure CO 2: 1.08> d>0.88 g/cm 3). Optical observations and analysis on opened inclusions by scanning electron microscopy (SEM) reveal that some of the aqueous inclusions contain a number of daughter minerals: halite, sylvite, Ca-, Fe-, Mg- and possibly Li-bearing chlorides, and anhydrite; nahcolite occurs also in some of the CO 2 inclusions. The SEM runs also detected a small amount of electrum, suggesting that silver might be a bi-product of the mineralisation. The aqueous and carbonic fluids remained immiscible throughout the formation and evolution of the hydrothermal veins. A few mixed (H 2O+CO 2) inclusions apparently resulted from accidental trapping of both fluids in the same cavity. The wide range of salinities observed in the aqueous inclusions is attributed to the mixing of relatively hot, low-salinity aqueous fluids and colder, high-salinity brines. The CO 2-rich and low-salinity H 2O inclusions are considered to be derived from the metamorphic decarbonation/dehydration of the greenstone pile whilst the high-salinity brines are believed to be basinal in origin. Pressure–temperature ( P– T) conditions of entrapment, inferred from the intersection of representative isochores of the immiscible fluids, indicate that the formation of the veins started at T=400°C and P about 4 kbar, in the presence of the high-density CO 2 and low-salinity H 2O fluids. At about 200°C, pressure fluctuations (incremental opening of the vein) correspond to the trapping of the lower-density CO 2 inclusions and high-salinity brines. It is proposed that the decarbonation/dehydration processes (possibly aided by later magmatic processes) expelled and mobilised the gold from the greenstone pile and concentrated it in the CO 2-bearing hydrothermal fluid in the form of Au–chloride complexes. High thermal gradients are believed to have caused the upward migration of this fluid from the bottom of the greenstone pile through structurally controlled conduits. We contend that phase separation of the H 2O–CO 2 metamorphic fluid, aided possibly by some wall–rock alteration, most probably triggered a decrease in ligand activity and thus, precipitation of the gold into lodes. Percolation of the basinal brines is thought to have remobilised some of the gold together with some silver.

The adsorption of gold to galena surfaces: Calculation of adsorption/reduction energies, reaction mechanisms, XPS spectra, and STM images

In order to evaluate the thermodynamics and reaction mechanisms of the adsorption and reduction of gold on galena surfaces, reaction energies were calculated for the adsorption of AuCl 4 − from solution and for the stepwise reduction of gold from Au(III) to Au(0) by using an ab initio cluster approach. The adsorption of gold chloride onto galena and the reduction from Au(III) to Au(0) were found to be slightly exothermic, but only if hydration energies are included. All adsorbate structures with intermediate oxidation states occupy local energy minima, that is, they are potentially metastable. Even though gold is in the formal oxidation state Au(III) in galena-AuCl 3, the main electron transfer from the galena surface to the gold atom has already taken place by withdrawing about 0.1 unit charges from all sulfur atoms in the cluster. This mechanism explains the unique affinity of gold to semiconducting sulfide surfaces. Au(0) is stabilized by the formation of gold dimers and islands due to the formation of gold-gold metal bonds. The formation of gold islands is enhanced by the low activation energy for Au(0) diffusion along the S S diagonal. We calculated this activation energy for diffusion to be less than four times the thermal energy if Au(0) travels along the S S path by being in contact with the delocalized S 3p valence band density. Therefore, almost one percent of all Au(0) atoms can hop from one sulfur atom to the next at any time. A reaction path involving six-membered polysulfide rings was found to be much more exothermic than reduction of gold chloride by galena alone. However, at the initial stage of gold reduction, reaction rates and the importance of a reaction path involving polysulfides may be limited by the availability of Pb-polysulfide or elemental sulfur. XPS spectra were calculated for the adsorbed gold, Au chlorides, and Au polysulfides. All these species cause similar peak chemical shifts of the S(2p 3/2) and S(2s) XPS peaks. Therefore, it is likely that experimentally obtained and fitted XPS peaks contain varying contribution of different oxidation states and gold ligands. Calculated XPS spectra also show how the charge density distribution of adsorbate structures influences the electronic structure of the underlying substrate. STS spectra were calculated in order to develop a tool that can help to identify which adsorbate structure is present at the surface and to study the local electronic structure of such sites. The most significant difference is the change of the local band gap which decreases from ≈ eV for galena-Au(III)Cl 3 and about 0.5 eV for galena-Au(I)Cl to a metal-like local environment with no bandgap for elemental gold in galena-Au and galena-Au 2 (the bulk bandgap of fresh galena is ≈0.4 eV). The calculated STS spectrum of galena-Au 2 was found to be very similar to STS spectra near the rim of the gold island.

ChemInform Abstract: Transition‐Metal Silyl Complexes. Part 26. Gold(I) Silyl Complexes.

AbstractComplexes of the type (III), (V), and (VI) are prepared from the corresponding Au chloride complexes and silyl lithium compounds as demonstrated in the scheme.

Gold uptake by perennial ryegrass: The influence of humates on the cycling of gold in soils

An experiment in which perennial ryegrass (Lolium perenne L.) was grown in solution cultures containing various forms of radioactive gold (198Au) is described. Uptake of labelled Au from solutions containing either Au chloride or various Au-humic acid (HA) complexes is compared. In each case concentrations of Au in the plant roots were several fold higher than in the plant shoots. However, the Au concentration in roots from some of the Au-HA preparations was only about 5% of that from the Au-HA solutions. High voltage electrophoresis studies indicate the presence of several Au-HA complexes in the solution cultures. The relevance of these findings to the cycling of Au within soils is discussed.