Fabrication of gold nanoparticle/multi walled carbon nanotube hybrids by in situ reaction in water using poly(acryloyl beta-alanine)

Fabrication of a hybrid consists of gold nanoparticles and multi walled carbon nanotubes (MWCNTs) with the help of poly (amino acid) was investigated. Poly(acryloyl beta-alanine) was synthesized by precipitation polymerization in tetrahydrofuran. The polymers were used to form hybrids with MWCNTs in aqueous media. Subsequently, the polymer functionalized MWCNTs were fabricated by in situ formed gold nanoparticles. The fabrication by gold nanoparticles was confirmed by transmission electron microscopic analyses. The fabrication was attempted with different concentrations of lithium auric chloride solutions in the range of 0.1-1.2 mM in water. The lower concentration of the gold precursor solution resulted in the formation and attachment of gold nanoparticles without aggregation while the higher concentration above 1.0 mM led to the aggregation of gold nanoparticles. The gold nanoparticles were observed only on the surface of MWCNTs and none was in the bulk aqueous phase.     

Scanning AES and XPS analysis of a thin Au emissivity barrier on Ni alloy

Scanning Auger electron spectroscopy and x-ray photoelectron spectroscopy were used to analyze discolored gold plating on nickel alloys. Gold plated nickel alloy sheets have been used as a thermal shield inside nacelle housings for various jet engines. The thin gold film is applied to serve as a low emissivity coating to reflect thermal radiation. Inconel 625 sheet was gold plated and exposed to 590°C in air for 924 hours to achieve an appropriate service use reference point. The visual appearance of the gold thin-film surface had noticeably dulled after this prolonged exposure. In some cases, several dark spots a few microns in size also appeared on the dulled gold surface. Our hypothesis was that nickel or some alloy constituent had diffused through the gold film and changed the color of the gold surface. X-ray photoelectron spectroscopy and Auger electron spectroscopy were used to differentiate the composition of the gold plated Inconel samples prior to thermal exposure and after the prolonged exposure. Scanning Auger micrographs showed that the composition of the dulled gold surface had changed due to the diffusion of nickel from the substrate alloy through the gold thin film. Nickel was absent at the surface of the unexposed samples while significant nickel concentrations were detected on the discolored gold surface and with the highest nickel levels detected in the dark spots on the gold surfaces. Auger depth profiles made on the exposed gold film verified that a discrete gold layer remained on top of the Inconel with a broad Ni-Cr-Au zone beneath this gold layer.     

纳米金的制备及在化妆品中的应用初探

采用柠檬酸钠还原氯金酸制备纳米金,利用X射线荧光能谱和透射电子显微镜对产品进行了表征,通过纳米金溶胶及溶胶中含有的柠檬酸钠和保护剂PVP对Hela细胞、CHO细胞的MTT试验,研究了纳米金溶胶及纳米金颗粒对细胞的毒性,结果表明,纳米金溶胶和纳米金颗粒对这两种细胞均没有产生毒性。将纳米金加入到化妆品基础配方中制备得到了稳定的乳状液,为纳米金用于高级化妆品可行性提供部分实验依据。     

金在直接正性乳剂中的作用

直接正性乳剂预灰化时，金有重要作用。本文使用在灰化结束后加入卤化银溶剂的方法研究金在灰化过程中的作用，并交替应用金浴（Ａｕ＾＋）增强灰雾中心，再用氰化钠浴（ＣＮ＾－）选择性地除去灰雾中心的金，研究金与灰雾中心的作用。实验表明，在灰化过程中加入金可以影响灰雾中心大小分布；当乳剂层内还原剂量大时，沉积反应是主要反应；而当乳剂层内还原剂量少时，置换反应是主要反应。直接正性乳剂还原灰化时，Ａｕ＾＋被还原而     

Synthesis and characterization of gold cubic nanoshells using water-soluble GeO₂templates

Size-tunable GeO? nanocubes were initially prepared by a modified sono-assisted reverse micelle method and then functionalized with an amino-terminated silanizing agent. Subsequently, gold decorated GeO? nanocomposites were prepared at pH ≈ 7 and 80?°C. It was found that well-dispersed gold nanoparticles on GeO? nanocubes could be obtained only if gold salt is abundant to favor simultaneous, homogeneous nucleation of gold particles. Additional gold ions were reduced onto these attached 'seed' particles accompanied by synchronous dissolution of water-soluble GeO? cores, resulting in gold hollow cubic shells. The GeO? nanocubes and Au/GeO? nanocomposites as well as gold hollow cubic shells were characterized by transmission electron microscopy, scanning electron microscopy, x-ray diffraction and UV-visible spectroscopy. In particular, gold hollow cubic shells feature a plasmon resonance peak at above 900 nm, which renders it quite promising in biochemical applications.     

The effect of cysteine on electrodeposition of gold nanoparticle

The most applications of gold nanoparticles are in the photo-electronical accessories and bio-chemical sensors. Chloride solution with cysteine additive was used as electrolyte in gold nanoparticles electrodeposition. The nucleation and growing mechanism were studied by electrochemical techniques such as cyclic voltammetry and chronoamperometry, in order to obtain a suitable nano structure. The deposition mechanism was determined as instantaneous nucleation and the dimension of particles was controlled in nanometric particle size range. Atomic Force Microscope was used to evaluate the effect of cysteine on the morphology and topography of gold nanoparticles. Finally the catalytic property of gold nanoparticle electrodeposited was studied in KOH solution, where oxygen reduction on the gold nanoparticle surface was eight times greater than that on the conventional gold deposits.     

仿玫瑰金电镀——BH-代金盐工艺研究

介绍了一种仿玫瑰金电镀工艺，并讨论了溶液组成、工艺操作条件对镀色泽的影响，同时还介绍了使用BH－代金盐的优点。结果表明，工艺工作范围宽、镀液稳定，维护简单，成本低廉。     

Light emission of gold nanoparticles induced by the reaction of bis(2,4,6-trichlorophenyl) oxalate and hydrogen peroxide

Light emission at approximately 415 nm was observed for gold particles with diameters of 2.6-6.0 nm dispersed in a solution containing bis(2,4,6-trichlorophenyl) oxalate and hydrogen peroxide. It was found that the light intensity was independent of the protecting reagents of the gold nanoparticles with similar size, the light intensity with gold nanoparticles of 5.0 and 6.0 nm in diameter was stronger than that with gold nanoparticles of 2.6 and 2.8 nm in diameter, and the light intensity increased linearly with the concentration of the gold nanoparticles using 6.0-nm gold nanoparticles. The gold nanoparticles were identified as emitting species, and the quantum yield was determined to be (2.8 +/- 0.3) x 10(-5) using 6.0-nm gold nanoparticles. The light emission is suggested to involve a sequence of steps: the oxidation reaction of bis(2,4,6-trichlorophenyl) oxalate with hydrogen peroxide yielding an energy-rich intermediate 1,2-dioxetanedione, the energy transfer from this intermediate to gold nanoparticles, and the radiative relaxation of the as-formed exited-state gold nanoparticles. The observed luminescence is expected to find applications in the field of bioanalysis owing to the excellent biocompatibility and relatively high stability of gold nanoparticles.     

Electrostatically stabilised nanoparticles: self-organization and electron-beam patterning

The self-organisation of citrate- and magnesium oleate-stabilised gold nanoparticles on SiO2/Si substrates was investigated. In drop deposition, nucleation of citrate-stabilised gold nanoparticles was observed at the rim of the droplet, symmetric or multibranched dendroid gold structures were found in the area between the rim and the central part of the droplet, depending on the drying temperature. Homogeneous submonolayer nanoparticle coverage was obtained by immersion of amineterminated SiO2/Si surfaces into a citrate-stabilised colloidal gold acidic solution. Drop deposition of magnesium oleate-stabilised gold nanoparticles onto the SiO2/Si surfaces resulted in the formation of uniformly close-packed nanoparticle arrays. Under electron beam irradiation, no apparent changes were found for monolayer films of citrate-stabilized particles, but sintering of the nanoparticles was observed in multilayer films. In contrast, coalescence of magnesium oleate-stabilised gold nanoparticle occurred in monolayer films after electron irradiation.     

Surface enhanced fluorescence of Rh6G with gold nanohole arrays

Five gold nanohole arrays with distinct aperture size were fabricated by magnetron sputtering technique. Fluorescence enhancements of Rh6G fluorophore in the close vicinity of gold nanohole arrays were observed. Up to 40 times increase of fluorescence intensity was obtained from gold nanohole arrays as compared with a smooth gold surface control sample. A double-peak curve was presented in the excitation spectrum of enhanced fluorescence emission when the excitation wavelength was scanning from 300 nm to 550 nm. It was found that smaller aperture size and proper excitation wavelength matching with the surface plasmon resonances condition were favorable for a better fluorescence enhancement.     

化学镀镍金在印制电路板制造中的应用

本文简单介绍了印制板化学镀镍金工艺 ,对化学镀镍金的工艺流程、可焊性控制和化学镀镍金与其他表面镀镍金工艺的区别进行了较为详细的论述     

MOS capacitor for simple thiol based biosensor applications

Thiols attached to thin gold films provide the platform for many biosensors to detect DNA. Attachment of thiol to gold can cause stress in gold especially if the layer is thin, inducing a change in the work function of gold. We report here a simple method to estimate this effect of attaching thiol to gold by monitoring the flat-band voltage of a metal-oxide-semiconductor (MOS) capacitor with gold as the metal. Capacitance-voltage (CV) characteristics were measured on gold gated MOS before and after attaching thiol to gold. A negative shift in the CV was seen for 1-octadecanethiol, while the shift was positive for 4-flurothipohenol. The MOS capacitor showed an increased change in the work function for increasing duration of immersion of the sample in the thiol solution saturating at longer times. Effect of attaching DNA molecules to the thiol on the CV characteristic was also investigated.     

Biosynthesis of Au nanoparticles using cumin seed powder extract

Cumin seed was investigated for synthesis of gold nanoparticles. Polydispersed particles were obtained at pH 3 and 30 degrees C, and the effect of temperature and pH on synthesis of gold nanoparticles was analyzed. TEM images showed that amount of platelets formed were predominant at lower temperature where as more number of monodispersed spherical particle of size 1-10 nm were perceived at high temperatures. The gold nanoparticles particles formed at higher pH were stable, uniform and spherical in shape. XPS analysis showed the presence of pure gold nanoparticles.     

Deposition of the fractal-like gold particles onto electrospun polymethylmethacrylate fibrous mats and their application in surface-enhanced Raman scattering

The ultrafine polymethylmethacrylate fibers containing gold nanoparticles have been prepared by using the electrospinning technique. Then the continuously coarse gold films formed by fractal-like thorny gold particles were deposited on the organic eletrospun fiber surface by an electroless process. The morphology of coarse gold films was characterized by scanning electron and transmission electron microscopy. The results revealed that the morphology of the gold particles was affected not only by the amount of gold seeds embedded in the organic fibers but also by the amount of gold deposited on the fiber's surfaces. The surface-enhanced Raman scattering (SERS) effect of the fibrous mats coated with gold films was evaluated by using Rhodamine B as an adsorbate. The results indicated that this kind of fibrous mat exhibited high and reproducible SERS activity and could be developed as highly sensitive SERS substrate.     

Gold Sensitization Experiments

The paper describes the sensitization of a neutral iodobromide gelatin emulsion by gold thiocyanate. The variables studied were grain size, the stage of emulsion preparation at which the gold additions were made and the amount of gold added. The greatest increase in sensitivity was obtained by adding the gold thiocyanate solution immediately before the second ripening (digestion). The increase was inversely proportional to the grain size. At the same time the gradation was also increased. In two cases the gold solution was added before washing of the emulsions, very little sensitizing was observed, and the gradation tended to fall. The results confirm that a certain relation exists between the increase in sensitivity due to gold thiocyanate and the grain size (or the grain surface).     

Accelerating the decarbonization of carbonaceous gold ore by suspension oxidation roasting towards the improvement of gold leaching efficiency

Eliminating the gold preg-robbing effect of carbonaceous matter in carbonaceous gold ores is crucial for gold leaching. In this study, suspension oxidation roasting was proposed to accelerate the decarbonization of carbonaceous gold ore. The characteristics of oxidation reaction process and gas release were analyzed by TG-DTA-FTIR. The phase transformation and microstructure evolution of samples during roasting were analyzed by XRD, SEM and BET. The results show that the gold preg-robbing effect was eliminated after the gasification of carbonaceous matter, and the CaO generated by decomposition of carbonates can effectively capture the SO₂. After roasting for 75 min at 650 °C in a 20% O₂ atmosphere, the total carbon removal rate reached 99.42%, the distribution of exposed gold increased from 28.85% to 77.10% and the gold leaching efficiency increased from 4.55% to 84.83%. In addition, about 70% sulfur was mainly fixed in the roasted products in the form of sulfate. Therefore, the suspension oxidation roasting process is an efficient and clean pretreatment method for carbonaceous gold ores.     

The effects of a glow discharge on the nucleation characteristics of gold on polymer substrates

Small amounts of gold were deposited onto organic substrates of stearic acid and polyethylene. Some nucleation characteristics of the gold were studied using transmission electron microscopy and were compared with the nucleation characteristics observed on the more conventional carbon substrates. It was shown that, by exposing the organic substrates to a glow discharge in air, their surface structure was changed by the removal of hydrogen by plasma etching. This produced a surface layer composed mainly of carbon or of carbon and oxygen and it was demonstrated that the subsequent nucleation behaviour of gold on these exposed surfaces was very similar to that of gold on pure carbon films.     

Effect of synthetic temperature on the dispersion stability of gold nanocolloid produced via electrical explosion of wire

In this study, gold nanocolloid was produced via the electrical explosion of wire in water, for the purpose of medical treatment. Thus, the use of other additives was avoided to stabilize the gold nanocolloid. The temperature of the water that was to be used for explosion was changed, and its effect on the stability of the gold nanocolloid was investigated. The synthetic temperature was varied from ice temperature to 80 degrees C. The morphology and particle size were studied using a transmission electron microscope. The UV-Vis spectra confirmed the formation of gold nanoparticles in the water. The stability of the gold nanocolloid was estimated using the zeta-potential and Turbiscan methods. The results showed that the synthetic temperature affected the stability of the gold nanocolloid. The TEM images of the gold nanoparticles prepared at low temperatures (0 and 20 degrees C) have several big particles. But, when the synthetic temperature was increased to 80 degrees C, most of the nanoparticles formed a spherical shape, without neck connection. Better stability was obtained in the gold nanocolloid sample prepared at a higher temperature. The gold nanocolloid that was synthesized at 80 degrees C was stable for more than three months, with small sedimentation.     

Photochemical synthesis of gold nanoparticles via controlled nucleation using a bioactive molecule

Synthesis of gold nanoparticles had been achieved using dopamine hydrochloride (dhc), an important bioactive molecule in a photochemical way. Solutions containing sodium dodecyl sulfate (SDS), HAuCl₄ and dhc were photoirradiated to form gold nanoparticles. Gold nanoparticles in different size range was obtained by varying the concentration of dhc. The growth of different-sized gold with time was monitored. The particles were characterized by absorption spectra and TEM analysis. The procedure involved a new technique for gold nanoparticle preparation and was simple, reproducible and required single step.     

Nanoporous gold prism microassembly through a self-organizing route

We report a simple and spontaneous synthesis of a nanoporous gold prism microassembly with highly dense skins, which is achieved just by immersing nanoporous gold into concentrated hydrochloric acid. The ligament size was coarsened to several hundred nanometers, but the crystal face orientation was still preserved. The same trends were seen in the case of coarsening by annealing; however, the morphology of the nanoporous gold prism microassembly was significantly different from the annealed nanoporous gold.