Search results for " gold"
showing 10 items of 278 documents
Ascorbic Acid determination using linear sweep voltammetry on flexible electrode modified with gold nanoparticles and reduced graphene oxide
2020
Indium tin oxide (ITO) coated on flexible polyethylene terephthalate (PET) substrate electrode was modified with reduced graphene oxide and gold nanoparticles by simple co-electrodeposition performed at -0.8 V vs SCE for 200 s. All samples were characterized by electron scan microscopy. The as prepared electrode was used as electrochemical sensor to selective detection of ascorbic acid using linear sweep voltammetry. Excellent results were obtained in a linear range from 20 to 150 µM of ascorbic acid with a limit of detection of about 3.1 µM (S/N=3.3). The sensors have a reproducibility of about 5.5% and also show high selectivity towards different interferents such as chlorine, calcium, ma…
Structure of the Metal–Support Interface and Oxidation State of Gold Nanoparticles Supported on Ceria
2012
An Au/CeO2 model catalyst was prepared by deposition–precipitation, with the aim of obtaining a sample suitable for a detailed X-ray absorption fine structure (XAFS) analysis of the gold–ceria interface structure. The results demonstrate the existence of a large interface between the gold particle and the support oxide, characterized by well-defined Au–O and Au–Ce interactions extending up to ∼6.4 A. The complex interface structure is retained after CO treatment up to 250 °C and subsequent reoxidation at 400 °C. The analysis of the XANES spectra, and the Au–O distance of 2.21 A, longer than Au–O bond lengths previously reported for Au/ceria catalysts, suggest a low oxidation state for the g…
A novel method of nanocrystal fabrication based on laser ablation in liquid environment
2008
Abstract Metal nanoparticles can be prepared by a novel technique that consists of the laser ablation of a solid target immersed in a water solution of a metal salt. Silicon was chosen as the most adequate target to synthesize silver and gold nanoparticles from a water solution of either AgNO3 or HAuCl4. The influence of both the silver nitrate concentrations and the irradiation time of the Si target on the optical properties of the Au and Ag nanoparticles have been investigated. The crystalline nature of the metal nanoparticles has been determined by X-ray diffraction (XRD). Average size and particle size distribution have been measured by means of TEM. The absorbance spectra show the char…
Mechanical Coupling in Gold Nanoparticles Supermolecules Revealed by Plasmon-Enhanced Ultralow Frequency Raman Spectroscopy
2016
International audience; Acoustic vibrations of assemblies of gold nanoparticles were investigated using ultralow frequency micro-Raman scattering and finite element simulations. When exciting the assemblies resonantly with the surface plasmon resonance of electromagnetically coupled nano-particles, Raman spectra present an ultralow frequency band whose frequency lies below the lowest Raman active Lamb mode of single nanoparticles that was observed. This feature was ascribed to a Raman vibration mode of gold nanoparticle " supermolecules " , that is, nanoparticles mechanically coupled by surrounding polymer molecules. Its measured frequency is inversely proportional to the nanoparticle diame…
One pot microwave assisted synthesis of bisphosphonate alkene capped gold nanoparticles
2014
International audience; A new synthetic pathway for the direct synthesis of water soluble gold nanoparticles (GNPs) already possessing terminal alkene functional groups was developed. This is achieved by using synthesized (1-hydroxy-1-phosphonopent-4-enyl)phosphonic acid (HMBPene), presenting advantages of the well known bisphosphonate coating applied to colloidal gold instead of metal oxides. The proposed protocol allowed an accurate control of the particle size in the 13–20 nm diameter range with a high spherical uniformity, which is a crucial point for these colloids' properties. We have shown that it is possible to synthesize a functionalized nanoplatform in a one-pot one-phase process …
Structure and the metal-support interaction of the Au/Mn oxide catalysts
2010
Gold catalysts with loading 1 and 10 wt % were-prepared by deposition precipitation method with urea over mesoporous manganese oxide, obtained through a surfactant-assisted procedure by using cetyltrimethylammonium bromide (CTAB), followed by treatment with sulphuric acid. For comparison, Au(10 wt %) was also deposited over commercial CeO2 and SiO2 supports. The materials were characterized by XRD and EXAFS at the Mn K and Au L-III edges and XPS. Moreover, the analyses were performed on the samples treated under 1%CO/He, at 250 degrees C for 90 min. The structural and surface results of the as prepared manganese oxide confirmed the formation of gamma-MnO2 along with some amorphous Mn3O4 upo…
Gold Nanoparticles on 3D-Printed Filters : From Waste to Catalysts
2019
Three-dimensionally printed solid but highly porous polyamide-12 (PA12) plate-like filters were used as selective adsorbents for capturing tetrachloroaurate from acidic solutions and leachates to prepare PA12–Au composite catalysts. The polyamide-adsorbed tetrachloroaurate can be readily reduced to gold nanoparticles by using sodium borohydride, ascorbic acid, hydrogen peroxide, UV light, or by heating. All reduction methods led to polyamide-anchored nanoparticles with an even size distribution and high dispersion. The particle sizes were somewhat dependent on the reduction method, but the average diameters were typically about 20 nm. Particle sizes were determined by using a combination of…
Gold recycling at laboratory scale: from nanowaste to nanospheres
2019
The market for products based on nanotechnology, and with it the use of nanomaterials and the generation of nanowaste, increases day by day. Among the vast variety of nanomaterials available, gold nanoparticles (AuNPs) are among the most studied and applied in commercial products. This current situation requires both the development of recovery methods to reduce the amount of nanowaste produced, and new synthetic methods that allow the reuse of recovered gold for new nanomaterial production, keeping in mind both economical and ecological considerations. In this work, a methodology to recover gold from aqueous laboratory nanowaste and transform it into an aqueous HAuCl4 solution was develope…
Mammalian cell growth on gold nanoparticle-decorated substrates is influenced by the nanoparticle coating
2014
In this work, we study epithelial cell growth on substrates decorated with gold nanorods that are functionalized either with a positively charged cytotoxic surfactant or with a biocompatible polymer exhibiting one of two different end groups, resulting in a neutral or negative surface charge of the particle. Upon observation of cell growth for three days by live cell imaging using optical dark field microscopy, it was found that all particles supported cell adhesion while no directed cell migration and no significant particle internalization occurred. Concerning cell adhesion and spreading as compared to cell growth on bare substrates after 3 days of incubation, a reduction by 45% and 95%, …
Mechanical properties of MDCK II cells exposed to gold nanorods
2015
Background: The impact of gold nanoparticles on cell viability has been extensively studied in the past. Size, shape and surface functionalization including opsonization of gold particles ranging from a few nanometers to hundreds of nanometers are among the most crucial parameters that have been focussed on. Cytoxicity of nanomaterial has been assessed by common cytotoxicity assays targeting enzymatic activity such as LDH, MTT and ECIS. So far, however, less attention has been paid to the mechanical parameters of cells exposed to gold particles, which is an important reporter on the cellular response to external stimuli.Results: Mechanical properties of confluent MDCK II cells exposed to go…