Gold Bulletin最新文献

The purpose of this study was to evaluate the possible synergistic effect of gold nano-therapy (Au-NPs) on Y79 cells treated with ultrasonic hyperthermia. The cells in the presence and absence of gold nanoparticles were subjected to ultrasonic irradiation (3?MHz, 1?W/cm², 40% pulse mode). Gold nanoparticles with an average diameter of 60?nm were synthesized. The cell viability of the Y79 cells was evaluated 48?h after performing 0.5–11?min hyperthermia with and without Au-NPs using the MTT assay. There was no cytotoxicity with 1.7?μg/mL Au-NP concentration. Moreover, the results revealed a significant difference in the cell viability between the control group and the groups with a hyperthermia period of more than 4?min. The results indicated that with increasing the concentration of Au-NPs (1.75, 3.5, 7, 14, 28 and 56?μg/mL), the cytotoxicity increased. The Y79 cell viability of 50% was caused for 9?min hyperthermia time alone and 4.5?min hyperthermia time in the presence of gold nanoparticles. The cell viability of the Y79 cells for a 0.5 to 11?min hyperthermia time, compared with the control group, was 93 to 27% and 95 to 32% with and without Au-NPs, respectively. It is concluded that the cells are more sensitive to hyperthermia induced by ultrasound irradiation in the presence of Au-NPs.

In the present work, sulfur-doped carbon nanotubes (SCNTs) have been prepared using chemical vapor deposition method and various cobalt-containing catalysts. In this line, simple and silica-supported cobalt nanoparticles (Co and Co/SiO₂) and 5 cobalt spinels (MCo₂O₄, M?=?Ni, Cu, Mn, Fe, Cr, and Mg) were used as the growth catalysts and four different temperatures (600, 650, 700, and 750?°C) were used to obtain the optimized condition for the preparation of SCNTs. Among the employed catalysts, Co/SiO₂ at 600?°C showed the higher abilities for the preparation of desired SCNTs. All products were characterized using FESEM, EDS, XRD, Raman, static contact angle, TGA, and DTA analyzes. The electrochemical behaviors of the two best products (SCNTs-Co/SiO₂ and SCNTs-Co) in hydrogen evolution reaction (HER) were examined, which confirmed the higher ability of SCNTs-Co/SiO₂. This best product was decorated with 2, 5, and 10% of gold nanoparticles to examine the effect of gold decoration of the properties and electrochemical abilities of the product. All decorated products exposure the higher electrochemical potencies versus the simple SCNTs and among the decorated products, 10% Au-SCNT was the most appropriate product for this purpose with small differences with the other ones.

Gold, used for jewelry and ornaments at times, is now considered a safe metal for investment. In addition to buying and selling gold physically, some markets offer electronic trade in gold. Trade volume is on surge in these bullion markets with each passing day. Daily opening and closing gold prices are used for analysis for 7740?days. Data series of daily return on investment in gold is split into two data series; first when the price goes up and second when the price goes down, at the day’s end. Statistical properties of three data series are analyzed and probabilities to earn profits are calculated during any day regardless of what types of decisions are going to be made that day. Probabilities of daily return, for both long and short positions, are presented in the form of tables. The expected daily profit of a trader with associated probability is explained in an illustrative example.

Gold nanoparticle thin films were deposited on copper substrate using electrophoretic deposition (EPD) method. At first, gold nanoparticles were synthesized, using pulsed laser ablation method of a high-purity gold target in distilled water. Ablation was carried out, employing the fundamental wavelength of a Q-switched Nd:YAG laser at 1064?nm and pulse width of 7?ns. Suspension of gold nanoparticle was used as the electrolyte of EPD, in which two copper electrodes with 7?mm gap were immersed. Five samples of gold nanoparticle thin films were prepared at different deposition times and applied voltages. Nanoparticles and thin films were characterized by different diagnostics such as X-ray diffraction pattern, atomic force microscopy (AFM), and scanning electron microscopy (SEM) images as well as optical spectroscopy. XRD pattern determined crystalline structure of gold thin films. SEM image showed the effect of deposition time and applied voltage on the morphology of deposited films. AFM results demonstrated the variations in roughness, thickness, and surface quality due to changes in applied voltage and deposition time. Also, the optical properties of thin films were studied by UV-vis reflection spectroscopy.

Globally, continuous R & D efforts are being made to recuperate precious metals from wastes in order to conserve the natural resources as well as minimize environmental pollution. Keeping in view of the above, a process has been developed to recover gold from industrial effluent using hydrometallurgical route. Initially, the effluent was pre-treated using precipitation and solvent extraction techniques to remove impurities, i.e., iron and copper as value added products. Iron was removed up to 99.99% at pH ~?3.5. Further, copper was extracted using 10% LIX 84IC maintaining phase ratio 1/1 in mixing time of 15?min and equilibrium (eq.). pH?2.2. Selective adsorption of gold was carried out using ionenaustauscher-II and resulted in 99% gold adsorption between pH?7 and 8 in contact time of 30?min. Experimental results obtained for the adsorption of gold was found to follow second order reaction and fitted well with the Freundlich isotherm. Gold from the loaded resin was eluted using a mixture of hydrochloric acid and thiourea. From the pure gold solution, metal could be produced using cementation/charcoal adsorption followed by heat treatment, respectively.

The transport of gold(III) across a supported liquid membrane containing the ionic liquid Cyphos IL102 (trihexyl(tetradecyl)phosphonium bromide) in Solvesso 100 has been investigated. The investigation was carried out under various experimental variables affecting to the transport process: stirring speed in the aqueous feed solution, HCl and gold(III) concentrations in this same phase, and carrier concentration in the membrane phase. The transport of gold(III) was compared against the transport of Fe(III), Cu(II), and Ni(II) from aqueous solutions containing the four elements, whereas the performance of Cyphos IL102 was compared, with respect to the gold transport, against other potential carriers for gold(III) from this acidic medium. Gold can be recovered in the strip solution as zero valent gold nanoparticles.

In this study, gold nanoparticles were supported at graphene derivatives (AuNPs@GDs) from chloroauric acid and graphene oxide (GO) by using sodium citrate, L-ascorbic acid, and 4-(2-hydroxyethyl)-1-piperazineethane-sulfonic acid (HEPES) as green reductants to evaluate the catalytic activity in the 4-nitrophenol (4-NP) reduction system. Among the three reductants, HEPES which derived AuNP@GD (3) exhibited up to 8.44-fold higher catalytic activity compared with sodium citrate and L-ascorbic acid. To evaluate the influence of mass ratio between Au and GO on the catalytic activity, we controlled adding amounts of chloroauric acid while the other conditions using HEPES were fixed. Notably, decreasing the mass ratio of Au/GO from 0.59 to 0.10 increased the rate constant in the range of 7.6?×?10^?3 to 16.1?×?10^?3/s. However, when the turnover frequency (TOF) was considered, the maximum value was obtained when Au/GO was 0.39. It can be concluded that AuNPs@GD (4) synthesized using HEPES significantly improved the catalytic activity in both rate constant (10.4?×?10^?3/s) and TOF (8.08?×?10^?5?mol/g·s) in 4-NP reduction. These results suggest that the type of reductants used to synthesize AuNPs@GDs is a significant factor on the catalytic activity and that GO can help increase the catalytic activity, but has an effective ratio with Au.

In this study, we report on the influence of support and gas atmosphere on the thermal stability of Au nanoparticles on oxidic supports. All samples were prepared with a modified impregnation method and have initial Au particle sizes in the range of 3–4?nm. We observed that in air, Au nanoparticles on SiO₂ and Al₂O₃ are thermally much more stable than Au nanoparticles on TiO₂. For instance, upon treatment up to 700?°C, on SiO₂, Au particles grew from 4 to 6?nm while on TiO₂ from 3 to 13?nm. For Au nanoparticles on TiO₂, growth is accelerated by oxidizing atmospheres and the presence of water and/or chloride. On non-reducible supports and in non-oxidizing atmosphere, the supported Au nanoparticles were remarkably stable. The insight into the growth of oxide-supported Au nanoparticles in reactive atmosphere offers an additional tool for a rational choice of a support for high-temperature gas-phase reactions involving gold nanocatalysts.

Gold nanostructures (AuNP) are important as strong platforms for targeted therapeutic and diagnostic applications. Tireless effort has been devoted nowadays to explore the multifunctionality of AuNP in multicomponent biostructures. Herein, we report the fabrication of horseradish peroxidase enzyme (HRP)-AuNP/ZnAlLDH heterostructure by the facile synthesis of AuNP on the biocompatible matrices of layered double hydroxides (LDH) followed by the immobilization of the enzyme on AuNP/LDH assemblies. During this process, ZnAlLDH have a dual function of exploring its structural “memory effect” for the synthesis of nanogold and acting as a support for the enzyme immobilization. X-ray diffraction (XRD), UV-Vis spectrometry, transmission electronic microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and infrared (FTIR) spectroscopy have been used to characterize the structural, chemical composition, optical, and morphology of the novel materials. We present here the release of AuNP from HRP-AuNP/ZnAlLDH by using as controlled variables HRP:LDHs ratio and the pH of the solution. Results show that AuNP established close interactions with HRP and formed an HRP-AuNP bioconjugate. Results reveal that HRP suffers a significant loss of the activity in the presence of nanoparticles of gold, such that, AuNP act to inhibit the activity of the enzyme. AuNP behavior in enzyme-bio-heterostructures should be inspiring for future applications of AuNP in nanomedicine.

Metallic gold is not completely inert towards biological tissues and cells. Cytotoxicity and immunotoxicity are concerns in various gold applications. This study shows that treating the surface of gold with OH^? radicals renders the gold surface non-cytotoxic, as well as prevents any biocorrosion of gold implants by an immune reaction. The detoxification is discussed as resulting from the selective dissolution of active gold atoms from the surface.