WorldWideScience

Sample records for responsive hollow-type gold

  1. Diagnosis and therapy of macrophage cells using dextran-coated near-infrared responsive hollow-type gold nanoparticles

    Science.gov (United States)

    Taik Lim, Yong; Cho, Mi Young; Sil Choi, Bang; Noh, Young-Woock; Chung, Bong Hyun

    2008-09-01

    We describe the development of hollow-type gold nanoparticles (NPs) for the photonic-based imaging and therapy of macrophage cells. The strong light-absorption and light-scattering properties of gold NPs render them to be useful as molecular imaging agents as well as therapeutic moieties. By controlling the geometry of the gold NPs, the optical resonance peak was shifted to around the near-infrared (NIR) region, where light transmission through biological tissue is known to be fairly high. Hollow-type gold NPs modified with dextran were phagocytosed by macrophage cells. Using dark-field microscopy, it was possible to image macrophage cells targeted with NPs. After NIR irradiation, macrophages labeled with NPs were selectively destroyed by the photothermal effect. FACS analysis revealed that the photothermal effect caused principally late apoptosis-related cell death or secondary necrosis. The experimental results showed that hollow-type gold NPs conjugated with dextran could be used not only as optical imaging contrast agents but also as a component of a novel anti-macrophage therapeutic strategy.

  2. Gold Nanospheres Dispersed Light Responsive Epoxy Vitrimers

    Directory of Open Access Journals (Sweden)

    Zhenhua Wang

    2018-01-01

    Full Text Available Vitrimers represent a new class of smart materials. They are covalently crosslinked like thermosets, yet they can be reprocessed like thermoplastics. The underlying mechanism is the rapid exchange reactions which form new bonds while breaking the old ones. So far, heating is the most widely used stimulus to activate the exchange reaction. Compared to heating, light not only is much more convenient to achieve remote and regional control, but can also offer fast healing. Gold nanospheres are excellent photothermal agents, but they are difficult to disperse into vitrimers as they easily aggregate. In this paper, we use polydopamine to prepare gold nanospheres. The resultant polydopamine-coated gold nanospheres (GNS can be well dispersed into epoxy vitrimers, endowing epoxy vitrimers with light responsivity. The composites can be reshaped permanently and temporarily with light at different intensity. Efficient surface patterning and healing are also demonstrated.

  3. Responsive Block Copolymer and Gold Nanoparticle Hybrid Nanotubes.

    Science.gov (United States)

    Chang, Sehoon; Singamaneni, Srikanth; Young, Seth; Tsukruk, Vladimir

    2009-03-01

    We demonstrate the facile fabrication of responsive polymer and metal nanoparticle composite nanotube structures. The nanotubes are comprised of responsive block copolymer, polystyrene-block-poly (2-vinylpyridine) (PS-b-P2VP), and gold nanoparticles. PS-b-P2VP nanotubes were fabricated using porous alumina template and in situ reduction of the gold nanoparticles in P2VP domains. Owing to the pH sensitive nature of P2VP (anionic polymer with a pKa of 3.8), the nanotubes exhibit a dramatic change in topology in response to the changes in the external pH. Furthermore, the gold nanoparticles in the responsive block exhibit a reversible aggregation, causing a reversible change in optical properties such as absorption.

  4. CORPORATE SOCIAL RESPONSIBILITY. EXAMPLE ROSIA MONTANA GOLD CORPORATION

    OpenAIRE

    Vasile Burja; Silvia – Stefania Mihalache

    2010-01-01

    Corporate Social Responsibility, a concept without a world accepted definition is starting to beused in Romania as well. This is the reason why in the present article we try to make a theoreticaldescription of the present concept and to exemplify it by presenting the responsible activities of acorporation in Romania, Rosia Montana Gold Corporation.

  5. Melting experiment on concrete waste using a hollow type plasma torch mounted on furnace

    International Nuclear Information System (INIS)

    Moon, Y. P.; Kim, T. W.; Kim, H. S.; Shin, S. U.; Lee, M. C.

    2000-01-01

    A furnace coupled with a hollow type plasma torch was manufactured and installed in order to develop a volume reduction technology for non-combustible radioactive waste using plasma. A melting test with 10kg of concrete waste was carried out for the evaluation of melting characteristics in the non-transferred operation mode for 20 minutes with the melter. Feeded concrete was completely melted. However, the molten bath was not easily discharged because of its high viscosity. It was found that some molten slag spat from the molten bath was coated on the surface of torch which was mounted vertically inside furnace

  6. Investigating the toxicity, uptake, nanoparticle formation and genetic response of plants to gold.

    Directory of Open Access Journals (Sweden)

    Andrew F Taylor

    Full Text Available We have studied the physiological and genetic responses of Arabidopsis thaliana L. (Arabidopsis to gold. The root lengths of Arabidopsis seedlings grown on nutrient agar plates containing 100 mg/L gold were reduced by 75%. Oxidized gold was subsequently found in roots and shoots of these plants, but gold nanoparticles (reduced gold were only observed in the root tissues. We used a microarray-based study to monitor the expression of candidate genes involved in metal uptake and transport in Arabidopsis upon gold exposure. There was up-regulation of genes involved in plant stress response such as glutathione transferases, cytochromes P450, glucosyl transferases and peroxidases. In parallel, our data show the significant down-regulation of a discreet number of genes encoding proteins involved in the transport of copper, cadmium, iron and nickel ions, along with aquaporins, which bind to gold. We used Medicago sativa L. (alfalfa to study nanoparticle uptake from hydroponic culture using ionic gold as a non-nanoparticle control and concluded that nanoparticles between 5 and 100 nm in diameter are not directly accumulated by plants. Gold nanoparticles were only observed in plants exposed to ionic gold in solution. Together, we believe our results imply that gold is taken up by the plant predominantly as an ionic form, and that plants respond to gold exposure by up-regulating genes for plant stress and down-regulating specific metal transporters to reduce gold uptake.

  7. Investigating the Toxicity, Uptake, Nanoparticle Formation and Genetic Response of Plants to Gold

    Science.gov (United States)

    Taylor, Andrew F.; Rylott, Elizabeth L.; Anderson, Christopher W. N.; Bruce, Neil C.

    2014-01-01

    We have studied the physiological and genetic responses of Arabidopsis thaliana L. (Arabidopsis) to gold. The root lengths of Arabidopsis seedlings grown on nutrient agar plates containing 100 mg/L gold were reduced by 75%. Oxidized gold was subsequently found in roots and shoots of these plants, but gold nanoparticles (reduced gold) were only observed in the root tissues. We used a microarray-based study to monitor the expression of candidate genes involved in metal uptake and transport in Arabidopsis upon gold exposure. There was up-regulation of genes involved in plant stress response such as glutathione transferases, cytochromes P450, glucosyl transferases and peroxidases. In parallel, our data show the significant down-regulation of a discreet number of genes encoding proteins involved in the transport of copper, cadmium, iron and nickel ions, along with aquaporins, which bind to gold. We used Medicago sativa L. (alfalfa) to study nanoparticle uptake from hydroponic culture using ionic gold as a non-nanoparticle control and concluded that nanoparticles between 5 and 100 nm in diameter are not directly accumulated by plants. Gold nanoparticles were only observed in plants exposed to ionic gold in solution. Together, we believe our results imply that gold is taken up by the plant predominantly as an ionic form, and that plants respond to gold exposure by up-regulating genes for plant stress and down-regulating specific metal transporters to reduce gold uptake. PMID:24736522

  8. Gold ions bio-released from metallic gold particles reduce inflammation and apoptosis and increase the regenerative responses in focal brain injury

    DEFF Research Database (Denmark)

    Larsen, Agnete; Kolind, Kristian; Pedersen, Dan Sonne

    2008-01-01

    neural stem cell response. We conclude that bio-liberated gold ions possess pronounced anti-inflammatory and neuron-protective capacities in the brain and suggest that metallic gold has clinical potentials. Intra-cerebral application of metallic gold as a pharmaceutical source of gold ions represents......Traumatic brain injury results in loss of neurons caused as much by the resulting neuroinflammation as by the injury. Gold salts are known to be immunosuppressive, but their use are limited by nephrotoxicity. However, as we have proven that implants of pure metallic gold release gold ions which do...... not spread in the body, but are taken up by cells near the implant, we hypothesize that metallic gold could reduce local neuroinflammation in a safe way. Bio-liberation, or dissolucytosis, of gold ions from metallic gold surfaces requires the presence of disolycytes i.e. macrophages and the process...

  9. Ultrafast Non-thermal Response of Plasmonic Resonance in Gold Nanoantennas

    Science.gov (United States)

    Soavi, Giancarlo; Valle, Giuseppe Della; Biagioni, Paolo; Cattoni, Andrea; Longhi, Stefano; Cerullo, Giulio; Brida, Daniele

    Ultrafast thermalization of electrons in metal nanostructures is studied by means of pump-probe spectroscopy. We track in real-time the plasmon resonance evolution, providing a tool for understanding and controlling gold nanoantennas non-linear optical response.

  10. Effects of Gold Nanoparticles on the Response of Phenol Biosensor Containing Photocurable Membrane with Tyrosinase

    Directory of Open Access Journals (Sweden)

    Ahmad Musa

    2008-10-01

    Full Text Available The role of incorporation of gold nanoparticles (50-130 nm in diameter into a series of photocurable methacrylic-acrylic based biosensor membranes containing tyrosinase on the response for phenol detection was investigated. Membranes with different hydrophilicities were prepared from 2-hydroxyethyl methacrylate and n-butyl acrylate via direct photocuring. A range of gold nanoparticles concentrations from 0.01 to 0.5 % (w/w was incorporated into these membranes during the photocuring process. The addition of gold nanoparticles to the biosensor membrane led to improvement in the response time by a reduction of approximately 5 folds to give response times of 5-10 s. The linear response range of the phenol biosensor was also extended from 24 to 90 mM of phenol. The hydrophilicities of the membrane matrices demonstrated strong influence on the biosensor response and appeared to control the effect of the gold nanoparticles. For less hydrophilic methacrylic-acrylic membranes, the addition of gold nanoparticles led to a poorer sensitivity and detection limit of the biosensor towards phenol. Therefore, for the application of gold nanoparticles in the enhancement of a phenol biosensor response, the nanoparticles should be immobilized in a hydrophilic matrix rather than a hydrophobic material.

  11. Effect of gold photocathode contamination on a flat spectral response X-ray diode

    Science.gov (United States)

    Wang, Kun-lun; Zhang, Si-qun; Zhou, Shao-tong; Huang, Xian-bin; Ren, Xiao-dong; Dan, Jia-kun; Xu, Qiang

    2018-03-01

    A detector with an approximately flat spectral response is important for diagnosing intense thermal X-ray flux. A flat-spectral-response X-ray diode (FSR-XRD) utilizes a gold photocathode X-ray diode and a specially configured gold filter to give rise to a nearly flat spectral response in the photon energy range of 100-4000 eV. It has been observed that the spectral responses of several FSR-XRDs changed after a few shots of z-pinch experiments on the Primary Test Stand facility. This paper presents an analysis of the changes by fitting the spectral responses of the gold photocathodes using a model with a free parameter which characterizes the thickness of the contamination. The spectral responses of FSR-XRDs were calibrated with synchrotron radiation, and several cleaning methods were tested with the calibration. Considering the results of model and cleaning, it may be anticipated that contamination was the major reason of the response changing. Contamination worsened the flatness of the spectral response of the FSR-XRD and decreased the averaged response, hence it is important to avoid contamination. Current results indicate a requirement of further study of the contamination.

  12. Monolayers of gold nanostars with two Near-IR LSPR capable of additive photothermal response

    KAUST Repository

    Pallavicini, Piersandro; Basile, Simone; Chirico, Giuseppe; Dacarro, Giacomo; D'Alfonso, Laura; Donà , Alice; Patrini, Maddalena; Falqui, Andrea; Sironi, Laura; Taglietti, Angelo

    2015-01-01

    Monolayers of photothermally responsive gold nanostars on PEI-coated surfaces display two Localized Surface Plasmon Resonances (LSPR) in the near-IR region that can be laser-irradiated either separately, obtaining two different T jumps, or simultaneously, obtaining a T jump equal to the sum of what obtained with separate irradiations

  13. Monolayers of gold nanostars with two Near-IR LSPR capable of additive photothermal response

    KAUST Repository

    Pallavicini, Piersandro

    2015-07-06

    Monolayers of photothermally responsive gold nanostars on PEI-coated surfaces display two Localized Surface Plasmon Resonances (LSPR) in the near-IR region that can be laser-irradiated either separately, obtaining two different T jumps, or simultaneously, obtaining a T jump equal to the sum of what obtained with separate irradiations

  14. Calibrating the photo-thermal response of magneto-fluorescent gold nanoshells.

    Science.gov (United States)

    Biswal, Nrusingh C; Ayala-Orzoco, Ciceron; Halas, Naomi J; Joshi, Amit

    2011-01-01

    We report the photothermal response and Near Infrared (NIR) imaging sensitivities of magneto-fluorescent silica core gold nanocomplexes designed for molecular image guided thermal therapy of cancer. Approximately 160 nm Silica core gold nanoshells were designed to provide NIR fluorescent and Magnetic Resonance (MR) contrast by incorporating FDA approved dye indocyanine green (ICG) and iron-oxide within an outer silica epilayer. The imaging and therapeutic sensitivity, and the stability of fluorescence contrast for 12 microliters of suspension (containing approximately 7.9 × 10(8) or 1.3 femtoMole nanoshells) buried at depths of 2-8 mm in tissue mimicking scattering media is reported.

  15. Biological response of HeLa cells to gold nanoparticles coated with organic molecules.

    Science.gov (United States)

    Cardoso Avila, P E; Rangel Mendoza, A; Pichardo Molina, J L; Flores Villavicencio, L L; Castruita Dominguez, J P; Chilakapati, M K; Sabanero Lopez, M

    2017-08-01

    In this work, gold nanospheres functionalized with low weight organic molecules (4-aminothiphenol and cysteamine) were synthesized in a one-step method for their in vitro cytotoxic evaluation on HeLa cells. To enhance the biocompatibility of the cysteamine-capped GNPs, BSA was used due to its broad PH stability and high binding affinity to gold nanoparticles. Besides, the widely reported silica coated gold nanorods were tested here to contrast their toxic response against our nanoparticles coated with organic molecules. Our results shown, the viability measured at 1.9×10 -5 M did not show significant differences against negative controls for all the samples; however, the metabolic activity of HeLa cells dropped when they were exposed to silica gold nanorods in the range of concentrations from 2.9×10 -7 M to 3.0×10 -4 M, while in the cases of gold nanospheres, we found that only at concentrations below 1.9×10 -5 M metabolic activity was normal. Our preliminary results did not indicate any perceivable harmful toxicity to cell membrane, cytoskeleton or nucleus due to our nanospheres at 1.9×10 -5 M. Additional test should be conducted in order to ensure a safe use of them for biological applications, and to determine the extent of possible damage. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. High-yield synthesis and optical response of gold nanostars

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pandian Senthil [Departamento de Quimica Fisica and Unidad Asociada CSIC-Universidade de Vigo, 36310 Vigo (Spain); Pastoriza-Santos, Isabel [Departamento de Quimica Fisica and Unidad Asociada CSIC-Universidade de Vigo, 36310 Vigo (Spain); RodrIguez-Gonzalez, Benito [Departamento de Quimica Fisica and Unidad Asociada CSIC-Universidade de Vigo, 36310 Vigo (Spain); Abajo, F Javier GarcIa de [Instituto de Optica-CSIC, Serrano 121, 28006 Madrid (Spain); Liz-Marzan, Luis M [Departamento de Quimica Fisica and Unidad Asociada CSIC-Universidade de Vigo, 36310 Vigo (Spain)

    2008-01-09

    Multipod Au nanoparticles (nanostars) with single crystalline tips were synthesized in extremely high yield through the reduction of HAuCl{sub 4} in a concentrated solution of poly(vinylpyrrolidone) (PVP) in N,N-dimethylformamide (DMF), in the presence of preformed Au nanoparticle seeds, but with no need for external energy sources. Nanostar dispersions display a well-defined optical response, which was found (through theoretical modeling) to comprise a main mode confined within the tips and a secondary mode confined in the central body. Calculations of the surface enhanced Raman scattering (SERS) response additionally show that this morphology will be relevant for sensing applications.

  17. High-yield synthesis and optical response of gold nanostars

    Science.gov (United States)

    Senthil Kumar, Pandian; Pastoriza-Santos, Isabel; Rodríguez-González, Benito; García de Abajo, F. Javier; Liz-Marzán, Luis M.

    2008-01-01

    Multipod Au nanoparticles (nanostars) with single crystalline tips were synthesized in extremely high yield through the reduction of HAuCl4 in a concentrated solution of poly(vinylpyrrolidone) (PVP) in N,N-dimethylformamide (DMF), in the presence of preformed Au nanoparticle seeds, but with no need for external energy sources. Nanostar dispersions display a well-defined optical response, which was found (through theoretical modeling) to comprise a main mode confined within the tips and a secondary mode confined in the central body. Calculations of the surface enhanced Raman scattering (SERS) response additionally show that this morphology will be relevant for sensing applications.

  18. High-yield synthesis and optical response of gold nanostars

    International Nuclear Information System (INIS)

    Kumar, Pandian Senthil; Pastoriza-Santos, Isabel; RodrIguez-Gonzalez, Benito; Abajo, F Javier GarcIa de; Liz-Marzan, Luis M

    2008-01-01

    Multipod Au nanoparticles (nanostars) with single crystalline tips were synthesized in extremely high yield through the reduction of HAuCl 4 in a concentrated solution of poly(vinylpyrrolidone) (PVP) in N,N-dimethylformamide (DMF), in the presence of preformed Au nanoparticle seeds, but with no need for external energy sources. Nanostar dispersions display a well-defined optical response, which was found (through theoretical modeling) to comprise a main mode confined within the tips and a secondary mode confined in the central body. Calculations of the surface enhanced Raman scattering (SERS) response additionally show that this morphology will be relevant for sensing applications

  19. Temperature and anion responsive self-assembly of ionic liquid block copolymers coating gold nanoparticles

    Science.gov (United States)

    Li, Junbo; Zhao, Jianlong; Wu, Wenlan; Liang, Ju; Guo, Jinwu; Zhou, Huiyun; Liang, Lijuan

    2016-06-01

    In this paper, double hydrophilic ionic liquid block copolymers (ILBCs), poly poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)]- block-(N-isopropylacrylamide) (PMMPImB- b-PNIPAAm) was first synthesized by reversible additionfragmentation chain transfer (RAFT) and then attached on the surface of gold nanoparticles (Au NPs) via a strong gold-sulfur bonding for preparing hybrid nanoparticles (PMMPImB- b-PNIPAAm-@-Au NPs). The hybrid NPs had a three layers micelle-like structure, including a gold core, thermo-responsive inner shell and anion responsive outer corona. The self-assembling behavior of thermal- and anion-response from shell and corona were respectively investigated by change of temperature and addition of (CF3SO2)2N-. The results showed the hybrid NPs retained a stable dispersion beyond the lower critical solution temperature (LCST) because of the space or electrostatic protecting by outer PMMPImB. However, with increasing concentration of (CF3SO2)2N-, the micellization of self-assembling PMMPImB- b-PNIPAAm-@-Au NPs was induced to form micellar structure containing the core with hydrophobic PMMPImB-(CF3SO2)2N- surrounded by composite shell of Au NPs-PNIPAAm via the anionresponsive properties of ILBCs. These results indicated that the block copolymers protected plasmonic nanoparticles remain self-assembling properties of block copolymers when phase transition from outer corona polymer.

  20. Characterization of the cellular response triggered by gold nanoparticle-mediated laser manipulation.

    Science.gov (United States)

    Kalies, Stefan; Keil, Sebastian; Sender, Sina; Hammer, Susanne C; Antonopoulos, Georgios C; Schomaker, Markus; Ripken, Tammo; Murua Escobar, Hugo; Meyer, Heiko; Heinemann, Dag

    2015-11-01

    Laser-based transfection techniques have proven high applicability in several cell biologic applications. The delivery of different molecules using these techniques has been extensively investigated. In particular, new high-throughput approaches such as gold nanoparticle–mediated laser transfection allow efficient delivery of antisense molecules or proteins into cells preserving high cell viabilities. However, the cellular response to the perforation procedure is not well understood. We herein analyzed the perforation kinetics of single cells during resonant gold nanoparticle–mediated laser manipulation with an 850-ps laser system at a wavelength of 532 nm. Inflow velocity of propidium iodide into manipulated cells reached a maximum within a few seconds. Experiments based on the inflow of FM4-64 indicated that the membrane remains permeable for a few minutes for small molecules. To further characterize the cellular response postmanipulation, we analyzed levels of oxidative heat or general stress. Although we observed an increased formation of reactive oxygen species by an increase of dichlorofluorescein fluorescence, heat shock protein 70 was not upregulated in laser-treated cells. Additionally, no evidence of stress granule formation was visible by immunofluorescence staining. The data provided in this study help to identify the cellular reactions to gold nanoparticle–mediated laser manipulation.

  1. Gold nanoparticle-mediated laser stimulation induces a complex stress response in neuronal cells.

    Science.gov (United States)

    Johannsmeier, Sonja; Heeger, Patrick; Terakawa, Mitsuhiro; Kalies, Stefan; Heisterkamp, Alexander; Ripken, Tammo; Heinemann, Dag

    2018-04-25

    Stimulation of neuronal cells generally resorts to electric signals. Recent advances in laser-based stimulation methods could present an alternative with superior spatiotemporal resolution. The avoidance of electronic crosstalk makes these methods attractive for in vivo therapeutic application. In particular, nano-mediators, such as gold nanoparticles, can be used to transfer the energy from a laser pulse to the cell membrane and subsequently activate excitable cells. Although the underlying mechanisms of neuronal activation have been widely unraveled, the overall effect on the targeted cell is not understood. Little is known about the physiological and pathophysiological impact of a laser pulse targeted onto nanoabsorbers on the cell membrane. Here, we analyzed the reaction of the neuronal murine cell line Neuro-2A and murine primary cortical neurons to gold nanoparticle mediated laser stimulation. Our study reveals a severe, complex and cell-type independent stress response after laser irradiation, emphasizing the need for a thorough assessment of this approach's efficacy and safety.

  2. Synthesis and controlled self-assembly of UV-responsive gold nanoparticles in block copolymer templates.

    Science.gov (United States)

    Song, Dong-Po; Wang, Xinyu; Lin, Ying; Watkins, James J

    2014-11-06

    We demonstrate the facile synthesis of gold nanoparticles (GNPs) functionalized by UV-responsive block copolymer ligands, poly(styrene)-b-poly(o-nitrobenzene acrylate)-SH (PS-b-PNBA-SH), followed by their targeted distribution within a lamellae-forming poly(styrene)-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer. The multilayer, micelle-like structure of the GNPs consists of a gold core, an inner PNBA layer, and an outer PS layer. The UV-sensitive PNBA segment can be deprotected into a layer containing poly(acrylic acid) (PAA) when exposed to UV light at 365 nm, which enables the simple and precise tuning of GNP surface properties from hydrophobic to amphiphilic. The GNPs bearing ligands of different chemical compositions were successfully and selectively incorporated into the PS-b-P2VP block copolymer, and UV light showed a profound influence on the spatial distributions of GNPs. Prior to UV exposure, GNPs partition along the interfaces of PS and P2VP domains, while the UV-treated GNPs are incorporated into P2VP domains as a result of hydrogen bond interactions between PAA on the gold surface and P2VP domains. This provides an easy way of controlling the arrangement of nanoparticles in polymer matrices by tailoring the nanoparticle surface using UV light.

  3. Third-order nonlinear optical response of colloidal gold nanoparticles prepared by sputtering deposition

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Hemerson P. S.; Alencar, Márcio A. R. C.; Hickmann, Jandir M. [Optics and Materials Group–OPTMA, Universidade Federal de Alagoas, CAIXA POSTAL 2051, 57061-970 Maceió (Brazil); Wender, Heberton [Brazilian Synchrotron National Laboratory (LNLS), CNPEM, Rua Giuseppe Máximo Scolfaro 10.000, 13083-970 Campinas (Brazil); Department of Physics, Universidade Federal do Mato Grosso do Sul, 79070-900, Campo Grande (Brazil); Teixeira, Sergio R. [Institute of Physics, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre (Brazil); Dupont, Jairton [Laboratory of Molecular Catalysis, Institute of Chemistry, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre (Brazil)

    2013-11-14

    The nonlinear optical responses of gold nanoparticles dispersed in castor oil produced by sputtering deposition were investigated, using the thermally managed Z-scan technique. Particles with spherical shape and 2.6 nm of average diameter were obtained and characterized by transmission electron microscopy and small angle X-ray scattering. This colloid was highly stable, without the presence of chemical impurities, neither stabilizers. It was observed that this system presents a large refractive third-order nonlinear response and a negligible nonlinear absorption. Moreover, the evaluation of the all-optical switching figures of merit demonstrated that the colloidal nanoparticles prepared by sputtering deposition have a good potential for the development of ultrafast photonic devices.

  4. Sealing-free fast-response paraffin/nanoporous gold hybrid actuator

    Science.gov (United States)

    Ye, Xing-Long; Jin, Hai-Jun

    2017-09-01

    Paraffin-based actuators can deliver large actuation strokes and high actuation stress, but often suffer from a low response rate and leaking problems. Here, we report a new paraffin/metal hybrid actuator, which was fabricated by infiltrating nanoporous gold with paraffin. It exhibits a fast actuation rate owing to the high thermal conductivity of the inter-connected metal phase, and requires no external sealing because liquid paraffin can be well confined in nanoscale channels, due to the large capillarity. We found that in this hybrid actuator, the stress generated by actuation is negligibly small when the characteristic size of the nanoporous gold (L) is above ˜70 nm, and increases dramatically with a decreasing size when L paraffin wax—the paraffin in smaller pores can sustain larger tensile stress, and thus the contraction of paraffin during cooling can be translated into larger compression stress and strain energy in a metal framework, leading to a larger actuation stress and energy. We also demonstrate that complex actuation motions can be achieved by incorporating hierarchical-structured nanoporous metal with paraffin.

  5. Stimulus-Responsive Plasmonic Chiral Signals of Gold Nanorods Organized on DNA Origami.

    Science.gov (United States)

    Jiang, Qiao; Liu, Qing; Shi, Yuefeng; Wang, Zhen-Gang; Zhan, Pengfei; Liu, Jianbing; Liu, Chao; Wang, Hui; Shi, Xinghua; Zhang, Li; Sun, Jiashu; Ding, Baoquan; Liu, Minghua

    2017-11-08

    In response to environmental variations, living cells need to arrange the conformational changes of macromolecules to achieve the specific biofunctions. Inspired by natural molecular machines, artificial macromolecular assemblies with controllable nanostructures and environmentally responsive functions can be designed. By assembling macromolecular nanostructures with noble metal nanoparticles, environmental information could be significantly amplified and modulated. However, manufacturing dynamic plasmonic nanostructures that are efficiently responsive to different stimuli is still a challenging task. Here we demonstrate a stimulus-responsive plasmonic nanosystem based on DNA origami-organized gold nanorods (GNRs). L-shaped GNR dimers were assembled on rhombus-shaped DNA origami templates. The geometry and chiral signals of the GNR nanoarchitectures respond to multiple stimuli, including glutathione reduction, restriction enzyme action, pH change, or photoirradiation. While the glutathione reduction or restriction enzyme caused irreversible changes in the plasmonic circular dichroism (CD) signals, both pH and light irradiation triggered reversible changes in the plasmonic CD. Our system transduces external stimuli into conformational changes and circular dichroism responses in near-infrared (NIR) wavelengths. By this approach, programmable optical reporters for essential biological signals can be fabricated.

  6. Colorimetric detection with aptamer–gold nanoparticle conjugates: effect of aptamer length on response

    International Nuclear Information System (INIS)

    Chávez, Jorge L.; MacCuspie, Robert I.; Stone, Morley O.; Kelley-Loughnane, Nancy

    2012-01-01

    A riboflavin binding aptamer (RBA) was used in combination with gold nanoparticles (AuNPs) to detect riboflavin in vitro. The RBA–AuNP conjugates (RBA–AuNPs) responded colorimetrically to the presence of riboflavin and this response could be followed by the naked eye. This system was used as a model to study how modifications on the aptamer sequence affect the RBA–AuNPs’ stability and their response to their target. To mimic primers and other sequence modifications typically used in aptamer work, the RBA was extended by adding extra bases to its 5′ end. These extra bases were designed to avoid interactions with the RBA binding site. The response of these RBA–AuNPs was evaluated and compared. Dynamic light scattering and UV-aggregation kinetics studies showed that the length of the aptamer significantly affected the RBA–AuNPs’ stability and, as a consequence, the magnitude of the detection response to riboflavin. The addition of thymine nucleotides instead of random tails to the RBA showed that the effects observed were not specific to the sequence used. This study shows that modifications of the aptamer sequence provide a means to improve the stability of aptamer–AuNPs conjugates and their sensing response.

  7. Colorimetric detection with aptamer-gold nanoparticle conjugates: effect of aptamer length on response

    Energy Technology Data Exchange (ETDEWEB)

    Chavez, Jorge L. [Wright-Patterson Air Force Base, 711th Human Performance Wing, Human Effectiveness Directorate, Air Force Research Laboratory (United States); MacCuspie, Robert I. [National Institute of Standards and Technology, Ceramics Division (United States); Stone, Morley O.; Kelley-Loughnane, Nancy, E-mail: Nancy.Kelley-Loughnane@wpafb.af.mil [Wright-Patterson Air Force Base, 711th Human Performance Wing, Human Effectiveness Directorate, Air Force Research Laboratory (United States)

    2012-10-15

    A riboflavin binding aptamer (RBA) was used in combination with gold nanoparticles (AuNPs) to detect riboflavin in vitro. The RBA-AuNP conjugates (RBA-AuNPs) responded colorimetrically to the presence of riboflavin and this response could be followed by the naked eye. This system was used as a model to study how modifications on the aptamer sequence affect the RBA-AuNPs' stability and their response to their target. To mimic primers and other sequence modifications typically used in aptamer work, the RBA was extended by adding extra bases to its 5 Prime end. These extra bases were designed to avoid interactions with the RBA binding site. The response of these RBA-AuNPs was evaluated and compared. Dynamic light scattering and UV-aggregation kinetics studies showed that the length of the aptamer significantly affected the RBA-AuNPs' stability and, as a consequence, the magnitude of the detection response to riboflavin. The addition of thymine nucleotides instead of random tails to the RBA showed that the effects observed were not specific to the sequence used. This study shows that modifications of the aptamer sequence provide a means to improve the stability of aptamer-AuNPs conjugates and their sensing response.

  8. Zumba Gold®: Are The Physiological Responses Sufficient to Improve Fitness in Middle-Age to Older Adults?

    Directory of Open Access Journals (Sweden)

    Lance C. Dalleck, Katie A. Roos, Bryant R. Byrd, Ryan M. Weatherwax

    2015-09-01

    Full Text Available Zumba® is currently one the most popular group-based exercise classes in the world with an estimated 12 million people of all shapes and sizes participating in Zumba classes on a weekly basis (Luettgen et al., 2012. Previous research by Luettgen and colleagues (2012 has found Zumba to be a highly effective workout for young women of various fitness levels. It was reported that participation in a single Zumba exercise class burned on average 360 calories and elicited a heart rate response equivalent to 80% of maximal heart rate (Luettgen et al., 2012. Zumba Gold® is a modified form of Zumba that was designed to meet the anatomical, physiological, and psychological needs of seniors. However, to our knowledge there is no research examining the physiological responses to Zumba Gold in the older-adult population. Understanding the cardiovascular and metabolic responses to exercise is essential for designing safe and effective physical activity and rehabilitation programs. For example, it would be beneficial to understand the metabolic equivalent (MET value associated with a Zumba Gold exercise class. A MET value would allow the quantification of Zumba Gold exercise intensity as low, moderate, or vigorous in nature, and hence, aid in establishing a safe and effective target workload. The lack of research concerning the physiological responses to Zumba Gold in middle-aged and older adult populations coupled with its increasing popularity prompted the present study. Therefore, the purpose of this study was (a to assess the cardiovascular and metabolic responses to Zumba Gold and (b to determine if Zumba Gold meets current guidelines for improving and maintaining cardiorespiratory fitness. Sixteen men and women participated in this study. All descriptive characteristics of the participants are presented in Table 1. This study was approved by the Human Research Committee at Western State Colorado University. Prior to participation, each participant

  9. Optoacoustic response of gold nanorods in soft phantoms using high-power diode laser assemblies at 870 and 905 nm.

    Science.gov (United States)

    Leggio, L; Gawali, S; Gallego, D; Rodríguez, S; Sánchez, M; Carpintero, G; Lamela, H

    2017-03-01

    In the present paper we show the optoacoustic (OA) response of two solutions of gold nanorods dispersed in distilled water (0.8 mg/ml) and hosted in tissue-like phantoms by using small arrays of HPDLs at 870 and 905 nm as excitation sources. The HPDLs are coupled to a 7-to-1 optical fiber bundle with output diameter of 675 μm. Each solution of gold nanorods exhibits an absorption peak close to the operating wavelength, i.e. ~860 nm and ~900 nm, respectively, to optimize the generation of OA signals. The phantoms are made of agar, intralipid and hemoglobin to simulate a soft biological tissue with reduced properties of scattering. Three 3-mm diameter tubes done in the phantoms at different depths (0.9 cm, 1.8 cm, and 2.7 cm) have been filled with gold nanorods. In this way, OA signals with appreciable SNR are generated at different depths in the phantoms. The high OA response exhibited by gold nanorods suggests their application in OA spectroscopy as exogenous contrast agents to detect and monitor emerging diseases like metastasis and arteriosclerotic plaques.

  10. The Effect of Multilayer Gold Nanoparticles on the Electrochemical Response of Ammonium Ion Biosensor Based on Alanine Dehydrogenase Enzyme

    Directory of Open Access Journals (Sweden)

    Tan Ling Ling

    2011-01-01

    Full Text Available The use of multilayer of gold nanoparticles (AuNPs attached on gold electrode surface via thiol chemistry to fabricate an ammonium (NH4+ ion biosensor based on alanine dehydrogenase (AlaDH was investigated. The approach of the study was based on construction of biosensor by direct deposition of AuNPs and 1,8-octanedithiol (C8-DT onto the gold electrode surface. For the immobilisation of enzyme, 2-mercaptoethanol (2BME was first covalently attached to AlaDH via esther bonding and then followed by chemically attached the 2BME-modified AlaDH (2BME-AlaDH moiety onto the AuNPs electrode via the exposed thiol group of 2BME. The resulting biosensor response was examined by means of amperometry for the quantification of NH4+ ion. In the absence of enzyme attachment, the use of three layers of AuNPs was found to improve the electrochemistry of the gold electrode when compared with no AuNPs was coated. However, when more than three layers of AuNPs were coated, the electrode response deteriorated due to excessive deposition of C8-DT. When AlaDH was incoporated into the AuNPs modified electrode, a linear response to NH4+ ion over the concentration range of 0.1–0.5 mM with a detection limit of 0.01 mM was obtained. In the absence of AuNPs, the NH4+ ion biosensor did not exhibit any good linear response range although the current response was observed to be higher. This work demonstrated that the incorporation of AuNPs could lead to the detection of higher NH4+ ion concentration without the need of dilution for high NH4+ ion concentration samples with a rapid response time of <1 min.

  11. Genome Wide Transcriptome Analysis reveals ABA mediated response in Arabidopsis during Gold (AuCl4- treatment

    Directory of Open Access Journals (Sweden)

    Devesh eShukla

    2014-11-01

    Full Text Available The unique physico-chemical properties of gold nanoparticles (AuNPs find manifold applications in diagnostics, medicine and catalysis. Chemical synthesis produces reactive AuNPs and generates hazardous by-products. Alternatively, plants can be utilized to produce AuNPs in an eco-friendly manner. To better control the biosynthesis of AuNPs, we need to first understand the detailed molecular response induced by AuCl4- In this study, we carried out global transcriptome analysis in root tissue of Arabidopsis grown for 12- hours in presence of gold solution (HAuCl4 using the novel unbiased Affymetrix exon array. Transcriptomics analysis revealed differential regulation of a total of 704 genes and 4900 exons. Of these, 492 and 212 genes were up- and downregulated, respectively. The validation of the expressed key genes, such as glutathione-S-transferases, auxin responsive genes, cytochrome P450 82C2, methyl transferases, transducin (G protein beta subunit, ERF transcription factor, ABC, and MATE transporters, was carried out through quantitative RT-PCR. These key genes demonstrated specific induction under AuCl4- treatment relative to other heavy metals, suggesting a unique plant-gold interaction. GO enrichment analysis reveals the upregulation of processes like oxidative stress, glutathione binding, metal binding, transport, and plant hormonal responses. Changes predicted in biochemical pathways indicated major modulation in glutathione mediated detoxification, flavones and derivatives, and plant hormone biosynthesis. Motif search analysis identified a highly significant enriched motif, ACGT, which is an abscisic acid responsive core element (ABRE, suggesting the possibility of ABA- mediated signaling. Identification of abscisic acid response element (ABRE points to the operation of a predominant signaling mechanism in response to AuCl4- exposure. Overall, this study presents a useful picture of plant-gold interaction with an identification of

  12. Designing Hybrids of Graphene Oxide and Gold Nanoparticles for Nonlinear Optical Response

    Science.gov (United States)

    Yadav, Rajesh Kumar; Aneesh, J.; Sharma, Rituraj; Abhiramnath, P.; Maji, Tuhin Kumar; Omar, Ganesh Ji; Mishra, A. K.; Karmakar, Debjani; Adarsh, K. V.

    2018-04-01

    Nonlinear optical absorption of light by materials is weak due to its perturbative nature, although a strong nonlinear response is of crucial importance to applications in optical limiting and switching. Here we demonstrate experimentally and theoretically an extremely efficient scheme of excited-state absorption by charge transfer between donor and acceptor materials as a method to enhance the nonlinear absorption by orders of magnitude. With this idea, we demonstrate a strong excited-state absorption (ESA) in reduced graphene oxide that otherwise shows an increased transparency at high fluence and enhancement of ESA by one order of magnitude in graphene oxide by attaching gold nanoparticles (Au NP) in the tandem configuration that acts as an efficient charge-transfer pair when excited at the plasmonic wavelength. To explain the unprecedented enhancement, we develop a five-level rate-equation model based on the charge transfer between the two materials and numerically simulate the results. To understand the correlation of interfacial charge transfer with the concentration and type of the functional ligands attached to the graphene oxide sheet, we investigate the Au-NP—graphene oxide interface with various possible ligand configurations from first-principles calculations. By using the strong ESA of our hybrid materials, we fabricate liquid cell-based high-performance optical limiters with important device parameters better than that of the benchmark optical limiters.

  13. Biocompatibility and favorable response of mesenchymal stem cells on fibronectin-gold nanocomposites.

    Directory of Open Access Journals (Sweden)

    Huey-Shan Hung

    Full Text Available A simple surface modification method, comprising of a thin coating with gold nanoparticles (AuNPs and fibronectin (FN, was developed to improve the biocompatibility required for cardiovascular devices. The nanocomposites from FN and AuNPs (FN-Au were characterized by the atomic force microscopy (AFM, UV-Vis spectrophotometry (UV-Vis, and Fourier transform infrared spectroscopy (FTIR. The biocompatibility of the nanocomposites was evaluated by the response of monocytes and platelets to the material surface in vitro. FN-Au coated surfaces demonstrated low monocyte activation and platelet activation. The behavior of human umbilical cord-derived mesenchymal stem cells (MSCs on FN-Au was further investigated. MSCs on FN-Au nanocomposites particularly that containing 43.5 ppm of AuNPs (FN-Au 43.5 ppm showed cell proliferation, low ROS generation, as well as increases in the protein expression levels of matrix metalloproteinase-9 (MMP-9 and endothelial nitric oxide synthase (eNOS, which may account for the enhanced MSC migration on the nanocomposites. These results suggest that the FN-Au nanocomposite thin film coating may serve as a potential and simple solution for the surface modification of blood-contacting devices such as vascular grafts.

  14. Evaluation of Radiation Response and Gold Nanoparticle Enhancement in Drug-Resistant Pancreatic Cancer Cells

    Science.gov (United States)

    Abourabia, Assya

    literature, we hypothesize that oxaliplatin-resistant pancreatic cancer cells, PANC-1/OR, are much more resistant to radiation exposure than their drug-sensitive analogues, PANC-1 cells. We think that the acquisition of chemoresistance entails mechanisms that also impart some loss of radiation sensitivity in PANC-1/OR cells. Responsiveness of pancreatic cancer cells to the radiation was measured by clonogenic survival. The results presented in this thesis show that drug-resistant PANC- 1/OR cells survive high doses of radiation exposure better than PANC-1 cells. Moreover, the presence of gold nanoparticles decreases cell survival when combined with the X-ray radiation. In conclusion, the combination of GNP and X-rays radiation produces a slight radiosensitizing effect for pancreatic cancer cells, PANC-1, and their chemoresistance variant, and we can speculate that this is a good mean of achieving additive cytotoxic effects on pancreatic cells.

  15. Numerical estimation of stability and improvement for coolant passage design in Hollow type CICC; Hollow gata CICC no reikyaku ryuro kaizen to anteisei no suchiteki kento

    Energy Technology Data Exchange (ETDEWEB)

    Miyauchi, M. [Yamagata Univ., Yamagata (Japan); Yoshiki, H. [The Univ. of Tokyo, Tokyo (Japan)

    1999-06-07

    The Hollow type CICC has a central channel (Hole) and is separated from surrounding bundle by a spiral tape with a gap, heat of a strand can effectively be convected to the Hole zone. However, even strong convection currents are induced in two ends of a thermal generating zone, but the heat is accumulated in the central part, and stability margin drops while relatively a long time heat has input for about 100 msec. In this study, the helium deposit inside the heating zone is reduced by a little design changing of the spiral tape that separates the bundle and the hole and efforts of improving stability of low energy density against heating are attempted. The instability caused by low energy and a long time heat invasion of the CICC appears also in simulation of Zanino at el. using a MITHRANDIR code. At this time, a method for calculating overflow of helium flowing to the bundle/Hole taking references of a branch current model and a joint flow model that are used in engine simulations is developed. (NEDO)

  16. Nonlinear optical response of a gold surface in the visible range: A study by two-color sum-frequency generation spectroscopy. I. Experimental determination.

    Science.gov (United States)

    Dalstein, L; Revel, A; Humbert, C; Busson, B

    2018-04-07

    We experimentally determine the effective nonlinear second-order susceptibility of gold over the visible spectral range. To reach that goal, we probe by vibrational two-color sum-frequency generation spectroscopy the methyl stretching region of a dodecanethiol self-assembled monolayer adsorbed on a gold film. The sum-frequency generation spectra show a remarkable shape reversal when the visible probe wavelength is tuned from 435 to 705 nm. After correcting from Fresnel effects, the methyl stretching vibrations serve as an internal reference, allowing to extract the dispersion of the absolute phase and relative amplitude of the effective nonlinear optical response of gold in the visible range.

  17. Reorientation response of magnetic microspheres attached to gold electrodes under an applied magnetic field

    International Nuclear Information System (INIS)

    De Los Santos Valladares, L.; Reeve, R.M.; Mitrelias, T.; Langford, R.M.; Barnes, C.H.W.; Bustamante Dominguez, A.; Aguiar, J. Albino; Majima, Y.

    2013-01-01

    In this work, we report the mechanical reorientation of thiolated ferromagnetic microspheres bridging a pair of gold electrodes under an external magnetic field. When an external magnetic field (7 kG) is applied during the measurement of the current-voltage characteristics of a carboxyl ferromagnetic microsphere (4 μm diameter) attached to two gold electrodes by self-assembled monolayers (SAMs) of octane dithiol (C 8 H 18 S 2 ), the current signal is distorted. Rather than due to magnetoresistance, this effect is caused by a mechanical reorientation of the ferromagnetic sphere, which alters the number of SAMs between the sphere and the electrodes and therefore affects conduction. To study the physical reorientation of the ferromagnetic particles, we measure their hysteresis loops while suspended in a liquid solution. (author)

  18. Reorientation response of magnetic microspheres attached to gold electrodes under an applied magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    De Los Santos Valladares, L.; Reeve, R.M.; Mitrelias, T.; Langford, R.M.; Barnes, C.H.W., E-mail: luis_d_v@hotmail.com [Cavendish Laboratory, Department of Physics, University of Cambridge Materials and Structures Laboratory (United Kingdom); Bustamante Dominguez, A. [Laboratorio de Ceramicos y Nanomateriales, Facultad de Ciencias Fisicas, Universidad Nacional Mayor de San Marcos, Lima (Peru); Aguiar, J. Albino [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Fisica; Azuma, Y. [Materials and Structures Laboratory, Tokyo Institute of Technology, Midori-ku, Yokohama (Japan); Majima, Y. [CREST, Japan Science and Technology Agency (JST), Midori-ku, Yokohama (Japan)

    2013-08-15

    In this work, we report the mechanical reorientation of thiolated ferromagnetic microspheres bridging a pair of gold electrodes under an external magnetic field. When an external magnetic field (7 kG) is applied during the measurement of the current-voltage characteristics of a carboxyl ferromagnetic microsphere (4 μm diameter) attached to two gold electrodes by self-assembled monolayers (SAMs) of octane dithiol (C{sub 8}H{sub 18}S{sub 2}), the current signal is distorted. Rather than due to magnetoresistance, this effect is caused by a mechanical reorientation of the ferromagnetic sphere, which alters the number of SAMs between the sphere and the electrodes and therefore affects conduction. To study the physical reorientation of the ferromagnetic particles, we measure their hysteresis loops while suspended in a liquid solution. (author)

  19. Room temperature synthesis of an optically and thermally responsive hybrid PNIPAM-gold nanoparticle

    International Nuclear Information System (INIS)

    Morones, J. Ruben; Frey, Wolfgang

    2010-01-01

    Composites of metal nanoparticles and environmentally sensitive polymers are useful as nanoactuators that can be triggered externally using light of a particular wavelength. We demonstrate a synthesis route that is easier than grafting techniques and allows for the in situ formation of individual gold nanoparticles encapsulated by an environmentally sensitive polymer, while also providing a strong interaction between the polymer and the metal particle. We present a one-pot, room-temperature synthesis route for gold metal nanoparticles that uses poly-N-isopropyl acrylamide as the capping and stabilizing agent and ascorbic acid as the reducing agent and achieves size control similar to the most common citric acid synthesis. We show that the composite can be precipitated reversibly by temperature or light using the non-radiative decay and conversion to heat of the surface plasmon resonance of the metal nanoparticle. The precipitation is induced by the collapse of the polymer cocoon surrounding each gold nanoparticle, as can be seen by surface plasmon spectroscopy. The experiments agree with theoretical models for the heat generation in a colloidal suspension that support fast switching with low laser power densities. The synthesized composite is a simple nanosized opto-thermal switch.

  20. Delivery of vincristine sulfate-conjugated gold nanoparticles using liposomes: a light-responsive nanocarrier with enhanced antitumor efficiency

    Directory of Open Access Journals (Sweden)

    Liu Y

    2015-04-01

    Full Text Available Ying Liu,1,* Man He,1,* Mengmeng Niu,1 Yiqing Zhao,1 Yuanzhang Zhu,1 Zhenhua Li,2 Nianping Feng1 1Department of Pharmaceutical Sciences, School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai, People’s Republic of China; 2Cedars-Sinai Medical Center, Los Angeles, CA, USA *These authors contributed equally to this work Abstract: Rapid drug release at the specific site of action is still a challenge for antitumor therapy. Development of stimuli-responsive hybrid nanocarriers provides a promising strategy to enhance therapeutic effects by combining the unique features of each component. The present study explored the use of drug–gold nanoparticle conjugates incorporated into liposomes to enhance antitumor efficiency. A model drug, vincristine sulfate, was physically conjugated with gold nanoparticles and verified by UV-visible and fourier transform infrared spectroscopy, and differential scanning calorimetry. The conjugates were incorporated into liposomes by film dispersion to yield nanoparticles (113.4 nm with light-responsive release properties, as shown by in vitro release studies. Intracellular uptake and distribution was studied in HeLa cells using transmission electron microscopy and confocal laser scanning microscopy. This demonstrated liposome internalization and localization in endosomal–lysosomal vesicles. Fluorescence intensity increased in cells exposed to UV light, indicating that this stimulated intracellular drug release; this finding was confirmed by quantitative analyses using flow cytometry. Antitumor efficacy was evaluated in HeLa cells, both in culture and in implants in vivo in nude mice. HeLa cell viability assays showed that light exposure enhanced liposome cytotoxicity and induction of apoptosis. Furthermore, treatment with the prepared liposomes coupled with UV light exposure produced greater antitumor effects in nude mice and reduced side effects, as compared with free vincristine sulfate

  1. Anti-fouling response of gold-carbon nanotubes composite for enhanced ethanol electrooxidation

    Science.gov (United States)

    Sai Siddhardha, R. S.; Anupam Kumar, Manne; Lakshminarayanan, V.; Ramamurthy, Sai Sathish

    2014-12-01

    We report the synthesis of gold carbon nanotubes composite through a one-pot surfactant free approach and its utility for ethanol electrooxidation reaction (EOR). The method involves the application of laser ablation for nanoparticle synthesis and simultaneous assembly of these on carbon nanotubes. The catalyst has been characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX) and UV-vis spectroscopic techniques. A systematic study of gold carbon nanotubes modified carbon paste electrode for EOR has been pursued. The kinetic study revealed the excellent stability of the modified electrode even after 200 cycles of EOR and with an Arrhenius energy as low as ∼28 kJ mol-1. Tafel slopes that are the measure of electrode activity have been monitored as a function of temperature of the electrolyte. The results indicate that despite an increase in the reaction rate with temperature, the electrode surface has not been significantly passivated by carbonaceous species produced at high temperatures.

  2. Cyclic voltammetric response of nicotinic acid and nicotinamide on a polycrystalline gold electrode

    International Nuclear Information System (INIS)

    Wang Xiaoxia; Yang Nianjun; Wan Qijin

    2006-01-01

    The oxidation of nicotinic acid and nicotinamide on a polycrystalline gold electrode occurred at almost same potentials but their reduction did at different peak potentials. The redox reaction mechanisms of nicotinic acid and nicotinamide were rationalized by the formation/disappearance of the new nitrogen-oxygen bonds in the pyridine rings by means of cyclic voltammetry and bulk electrolysis. The anodic currents of nicotinic acid and nicotinamide were controlled by diffusion, while the cathodic ones by adsorption. The difference in the cathodic peak potentials of nicotinic acid and nicotinamide on the polycrystalline gold electrode is attributed to the effect of the electron densities of remote substituents on the pyridine rings. The cathodic peak currents at about 0.20 V were linear with their concentrations in the range of 2.4 mM to 2.7 μM and 2.4 mM to 3.3 μM with detection limits of 0.27 and 0.33 μM for nicotinic acid and nicotinamide, respectively. Voltammetry was then adopted for the selective monitoring the content of nicotinic acid and nicotinamide in pharmaceuticals

  3. Growth of silver-coated gold nanoshells with enhanced linear and nonlinear optical responses

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ya-Fang; Wang, Jia-Hong; Ma, Liang; Nan, Fan; Cheng, Zi-Qiang; Zhou, Li, E-mail: zhouli@whu.edu.cn; Wang, Qu-Quan, E-mail: qqwang@whu.edu.cn [Wuhan University, Department of Physics, Key Laboratory of Artificial Miro- and Nano-structures of the Ministry of Education, and School of Physics and Technology (China)

    2015-03-15

    Silver-coated gold nanoshells with 1,4-BDT molecules as the spacer (Ag/BDT/Au) were synthesized on the surface of SiO{sub 2} nanospheres. The surface plasmon resonance of Au/SiO{sub 2} and Ag/BDT/Au/SiO{sub 2} nanoparticles with single and double shells were tuned by adjusting the thickness of Au and Ag nanoshells. The enhanced local field in the gap of Au and Ag shells is demonstrated by measuring Raman scattering and nonlinear refraction. The results show that the Raman intensity is enhanced by 17 times and the nonlinear refractive index is enhanced by 30 % due to the growth of Ag shells.

  4. Ionic liquid functionalized synthesis of gold nanoparticles in response to Elaise Guineensis (oil palm) leaves amount

    Science.gov (United States)

    Irfan, Muhammad; Ahmad, Tausif; Moniruzzaman, Muhammad; Abdullah, Bawadi

    2018-05-01

    A modified bio-synthesis method was developed to synthesize gold nanoparticles (AuNPs) using Elaeis Guineensis (oil palm) leaves (OPL) extract prepared in aqueous solution of IL, [EMIM][OAc]. The strong interaction and capping ability of IL at surface of AuNPs was examined through XPS analysis. The effect of OPL powder to liquid (P/L) ratio on absorbance, maximum wavelength (λmax) and size variation of AuNPs was observed through UV-vis. TEM analysis indicated predominantly spherical shape AuNPs with mean diameter of 15.76 nm. This study exhibits a rapid, cheap and efficient method to achieve stable AuNPs using bio-waste material.

  5. Surfactant-Modified Ultrafine Gold Nanoparticles with Magnetic Responsiveness for Reversible Convergence and Release of Biomacromolecules.

    Science.gov (United States)

    Xu, Lu; Dong, Shuli; Hao, Jingcheng; Cui, Jiwei; Hoffmann, Heinz

    2017-03-28

    It is difficult to synthesize magnetic gold nanoparticles (AuNPs) with ultrafine sizes (coating AuNPs using magnetic particles, compounds, or ions. Here, magnetic cationic surfactants C 16 H 33 N + (CH 3 ) 3 [CeCl 3 Br] - (CTACe) and C 16 H 33 N + (CH 3 ) 3 [GdCl 3 Br] - (CTAGd) are prepared by a one-step coordination reaction, i.e., C 16 H 33 N + (CH 3 ) 3 Br - (CTABr) + CeCl 3 or GdCl 3 → CTACe or CTAGd. A simple strategy for fabricate ultrafine (gold nanoparticles (AuNPs) via surface modification with weak oxidizing paramagnetic cationic surfactants, CTACe or CTAGd, is developed. The resulting AuNPs can highly concentrate the charges of cationic surfactants on their surfaces, thereby presenting strong electrostatic interaction with negatively charged biomacromolecules, DNA, and proteins. As a consequence, they can converge DNA and proteins over 90% at a lower dosage than magnetic surfactants or existing magnetic AuNPs. The surface modification with these cationic surfactants endows AuNPs with strong magnetism, which allows them to magnetize and migrate the attached biomacromolecules with a much higher efficiency. The native conformation of DNA and proteins can be protected during the migration. Besides, the captured DNA and proteins could be released after adding sufficient inorganic salts such as at c NaBr = 50 mmol·L -1 . Our results could offer new guidance for a diverse range of systems including gene delivery, DNA transfection, and protein delivery and separation.

  6. Assembling gold nanorods on a poly-cysteine modified glassy carbon electrode strongly enhance the electrochemical response to tetrabromobisphenol A

    International Nuclear Information System (INIS)

    Wang, Yanying; Liu, Guishen; Hou, Xiaodong; Huang, Yina; Li, Chunya; Wu, Kangbing

    2016-01-01

    Cysteine (Cys) was electrochemically deposited on a glassy carbon electrode (GCE) by cyclic voltammetry. The poly-Cys modified electrode was placed in a solution of gold nanorods (GNRs) to induced self-assembly of the GNRs. The GNRs/poly-Cys/GCEs were characterized by scanning electron microscopy and electrochemical impedance spectroscopy. A voltammetric study on tetrabromobisphenol A (TBBPA) with this GCE showed the current response to be enhanced by a factor of 11 compared to a non-modified GCE. Based on these findings, a square wave voltammetric assay was worked out. Under optimized conditions, a linear relationship between the oxidation peak current and TBBPA is found for the 10 nM to 10 μM concentration range. The detection limit is 3.2 nM (at an S/N ratio of 3). The electrode was successfully applied to the determination of TBBPA in spiked tap water and lake water samples. (author)

  7. Identification of Response Options to Artisanal and Small-Scale Gold Mining (ASGM in Ghana via the Delphi Process

    Directory of Open Access Journals (Sweden)

    Avik Basu

    2015-09-01

    Full Text Available The Delphi technique is a means of facilitating discussion among experts in order to develop consensus, and can be used for policy formulation. This article describes a modified Delphi approach in which 27 multi-disciplinary academics and 22 stakeholders from Ghana and North America were polled about ways to address negative effects of small-scale gold mining (ASGM in Ghana. In early 2014, the academics, working in disciplinary groups, synthesized 17 response options based on data aggregated during an Integrated Assessment of ASGM in Ghana. The researchers participated in two rounds of Delphi polling in March and April 2014, during which 17 options were condensed into 12. Response options were rated via a 4-point Likert scale in terms of benefit (economic, environmental, and benefit to people and feasibility (economic, social/cultural, political, and implementation. The six highest-scoring options populated a third Delphi poll, which 22 stakeholders from diverse sectors completed in April 2015. The academics and stakeholders also prioritized the response options using ranking exercises. The technique successfully gauged expert opinion on ASGM, and helped identify potential responses, policies and solutions for the sector. This is timely given that improvement to the ASGM sector is an important component within the UN Minamata Convention.

  8. Identification of Response Options to Artisanal and Small-Scale Gold Mining (ASGM) in Ghana via the Delphi Process.

    Science.gov (United States)

    Basu, Avik; Phipps, Sean; Long, Rachel; Essegbey, George; Basu, Niladri

    2015-09-10

    The Delphi technique is a means of facilitating discussion among experts in order to develop consensus, and can be used for policy formulation. This article describes a modified Delphi approach in which 27 multi-disciplinary academics and 22 stakeholders from Ghana and North America were polled about ways to address negative effects of small-scale gold mining (ASGM) in Ghana. In early 2014, the academics, working in disciplinary groups, synthesized 17 response options based on data aggregated during an Integrated Assessment of ASGM in Ghana. The researchers participated in two rounds of Delphi polling in March and April 2014, during which 17 options were condensed into 12. Response options were rated via a 4-point Likert scale in terms of benefit (economic, environmental, and benefit to people) and feasibility (economic, social/cultural, political, and implementation). The six highest-scoring options populated a third Delphi poll, which 22 stakeholders from diverse sectors completed in April 2015. The academics and stakeholders also prioritized the response options using ranking exercises. The technique successfully gauged expert opinion on ASGM, and helped identify potential responses, policies and solutions for the sector. This is timely given that improvement to the ASGM sector is an important component within the UN Minamata Convention.

  9. Identification of Response Options to Artisanal and Small-Scale Gold Mining (ASGM) in Ghana via the Delphi Process

    Science.gov (United States)

    Basu, Avik; Phipps, Sean; Long, Rachel; Essegbey, George; Basu, Niladri

    2015-01-01

    The Delphi technique is a means of facilitating discussion among experts in order to develop consensus, and can be used for policy formulation. This article describes a modified Delphi approach in which 27 multi-disciplinary academics and 22 stakeholders from Ghana and North America were polled about ways to address negative effects of small-scale gold mining (ASGM) in Ghana. In early 2014, the academics, working in disciplinary groups, synthesized 17 response options based on data aggregated during an Integrated Assessment of ASGM in Ghana. The researchers participated in two rounds of Delphi polling in March and April 2014, during which 17 options were condensed into 12. Response options were rated via a 4-point Likert scale in terms of benefit (economic, environmental, and benefit to people) and feasibility (economic, social/cultural, political, and implementation). The six highest-scoring options populated a third Delphi poll, which 22 stakeholders from diverse sectors completed in April 2015. The academics and stakeholders also prioritized the response options using ranking exercises. The technique successfully gauged expert opinion on ASGM, and helped identify potential responses, policies and solutions for the sector. This is timely given that improvement to the ASGM sector is an important component within the UN Minamata Convention. PMID:26378557

  10. Pancreatic Response to Gold Nanoparticles Includes Decrease of Oxidative Stress and Inflammation In Autistic Diabetic Model

    Directory of Open Access Journals (Sweden)

    Manar E. Selim

    2015-01-01

    Full Text Available Background: Gold nanoparticles (AuNPs have a wide range of applications in various fields. This study provides an understanding of the modulatory effects of AuNPs on an antioxidant system in male Wistar diabetic rats with autism spectrum disorder (ASD. Normal littermates fed by control mothers were injected with citrate buffer alone and served as normal, untreated controls controlin this study. Diabetes mellitus (DM was induced by administering a single intraperitoneal injection of streptozotocin (STZ (100 mg/kg to the pups of (ND diabetic group, which had been fasted overnight. Autistic pups from mothers that had received a single intraperitoneal injection of 600 mg/kg sodium valproate on day 12.5 after conception were randomly divided into 2 groups (n 2 7/group as follow; administering single intraperitoneal injection of streptozotocin (STZ ( (100 mg/kg to the overnight fasted autistic pups of (AD autistic diabetic group. The treatment was started on the 5th day after STZ injection with the same dose as in group II and it was considered as 1st day of treatment with gold nanoparticles for 7 days to each rat of (group IV treated autistic diabetic group(TAD at a dosage of 2.5 mg/kg. b. wt. Results: At this dose of administration AuNPs, the activities of hepatic superoxide dismutase (SOD, glutathione peroxidase (GPx, and catalase were greater in group TAD compared with the control group (P 0.05 in the liver of autistic diabetic AuNPs -supplemented rats, whereas reduced glutathione was markedly higher than in control rats, especially after administration of AuNPs. Moreover, the kidney functions in addition to the fat profile scoring supported the protective potential of that dose of AuNPs. The beta cells revealed euchromatic nuclei with no evidence of separation of nuclear membrane. Conclusions: Our results showed that AuNPs improved many of the oxidative stress parameters (SOD, GPx and, CAT, plasma antioxidant capacity (ORAC and lipid profile

  11. Size-dependent multispectral photoacoustic response of solid and hollow gold nanoparticles

    International Nuclear Information System (INIS)

    Gutrath, Benjamin S; Buchkremer, Anne; Timper, Jan; Leifert, Annika; Simon, Ulrich; Beckmann, Martin F; Schmitz, Georg; Eckert, Thomas; Richtering, Walter

    2012-01-01

    Photoacoustic (PA) imaging attracts a great deal of attention as an innovative modality for longitudinal, non-invasive, functional and molecular imaging in oncology. Gold nanoparticles (AuNPs) are identified as superior, NIR-absorbing PA contrast agents for biomedical applications. Until now, no systematic comparison of the optical extinction and PA efficiency of water-soluble AuNPs of various geometries and small sizes has been performed. Here spherical AuNPs with core diameters of 1.0, 1.4 and 11.2 nm, nanorods with longitudinal/transversal elongation of 38/9 and 44/12 nm and hollow nanospheres with outer/inner diameters of 33/19, 57/30, 68/45 and 85/56 nm were synthesized. The diode laser set-up with excitations at 650, 808, 850 and 905 nm allowed us to correlate the molar PA signal intensity with the molar extinction of the respective AuNPs. Deviations were explained by differences in heat transfer from the particle to the medium and, for larger particles, by the scattering of light. The molar PA intensity of 1.0 nm AuNPs was comparable to the commonly used organic dye methylene blue, and rapidly increased with the lateral size of AuNPs. (paper)

  12. Angular plasmon response of gold nanoparticles arrays: approaching the Rayleigh limit

    Directory of Open Access Journals (Sweden)

    Marae-Djouda Joseph

    2016-07-01

    Full Text Available The regular arrangement of metal nanoparticles influences their plasmonic behavior. It has been previously demonstrated that the coupling between diffracted waves and plasmon modes can give rise to extremely narrow plasmon resonances. This is the case when the single-particle localized surface plasmon resonance (λLSP is very close in value to the Rayleigh anomaly wavelength (λRA of the nanoparticles array. In this paper, we performed angle-resolved extinction measurements on a 2D array of gold nano-cylinders designed to fulfil the condition λRA<λLSP. Varying the angle of excitation offers a unique possibility to finely modify the value of λRA, thus gradually approaching the condition of coupling between diffracted waves and plasmon modes. The experimental observation of a collective dipolar resonance has been interpreted by exploiting a simplified model based on the coupling of evanescent diffracted waves with plasmon modes. Among other plasmon modes, the measurement technique has also evidenced and allowed the study of a vertical plasmon mode, only visible in TM polarization at off-normal excitation incidence. The results of numerical simulations, based on the periodic Green’s tensor formalism, match well with the experimental transmission spectra and show fine details that could go unnoticed by considering only experimental data.

  13. Influence of PEG coating on optical and thermal response of gold nanoshperes and nanorods

    Science.gov (United States)

    Chen, Qin; Ren, Yatao; Qi, Hong; Ruan, Liming

    2018-06-01

    PEGylation is widely applied as a surface modification method for nanoparticles in biomedical applications to improve their biological properties, including biocompatibility and immunogenicity. In most of its biomedical applications, nanoparticles are served as optical or thermal contrast agents. Therefore, the impact of poly (ethylene glycol) (PEG) coating thickness on the optical and thermal properties of nanoparticles needs to be further investigated. In the present work, we studied two kinds of commonly used nanoparticles, including nanosphere and nanorod. The temperature and electric fields are obtained for nanoparticles with different PEG coating thicknesses. It is found that the change of PEG coating thickness on gold nanospheres only has impact on the absolute value of maximum absorption and scattering efficiencies, which barely influences the LSPR wavelength λmax and other optical and thermal characteristics. In contrast, for nanorod, the maximum efficiencies are barely influenced by the variation of PEG coating thickness. On the other hand, the localized surface plasmon resonance wavelength has an evident red shift with the increasing of PEG coating thickness. The maximum absorption efficiency is a way to evaluate the energy dissipation rate, which decides the scale of the heat source induced by nanoparticles. These findings are crucial for the accurate prediction of optical and thermal properties of nanoparticles in biomedical application. The present work also presents a possible way to manipulate the optical and thermal behaviors of nanoparticles in the application of biomedicine without changing the morphology of nanoparticles.

  14. Near-Infrared Light Responsive Folate Targeted Gold Nanorods for Combined Photothermal-Chemotherapy of Osteosarcoma.

    Science.gov (United States)

    Li Volsi, Anna; Scialabba, Cinzia; Vetri, Valeria; Cavallaro, Gennara; Licciardi, Mariano; Giammona, Gaetano

    2017-04-26

    Folate-targeted gold nanorods (GNRs) are proposed as selective theranostic agents for osteosarcoma treatment. An amphiphilic polysaccharide based graft-copolymer (INU-LA-PEG-FA) and an amino derivative of the α,β-poly(N-2-hydroxyethyl)-d,l-aspartamide functionalized with folic acid (PHEA-EDA-FA), have been synthesized to act as coating agents for GNRs. The obtained polymer-coated GNRs were characterized in terms of size, shape, zeta potential, chemical composition, and aqueous stability. They protected the anticancer drug nutlin-3 and were able to deliver it efficiently in different physiological media. The ability of the proposed systems to selectively kill tumor cells was tested on U2OS cancer cells expressing high levels of FRs and compared with human bronchial epithelial cells (16HBE) and human dermal fibroblasts (HDFa). The property of the nanosystems of efficiently controlling drug release upon NIR laser irradiation and of acting as an excellent hyperthermia agent as well as Two Photon Luminescence imaging contrast agents was demonstrated. The proposed folate-targeted GNRs have also been tested in terms of chemoterapeutic and thermoablation efficacy on tridimensional (3-D) osteosarcoma models.

  15. "Smart" gold nanoparticles for photoacoustic imaging: an imaging contrast agent responsive to the cancer microenvironment and signal amplification via pH-induced aggregation.

    Science.gov (United States)

    Song, Jaejung; Kim, Jeesu; Hwang, Sekyu; Jeon, Mansik; Jeong, Sanghwa; Kim, Chulhong; Kim, Sungjee

    2016-07-07

    'Smart' gold nanoparticles can respond to mild acidic environments, rapidly form aggregates, and shift the absorption to red and near-infrared. They were used as a photoacoustic imaging agent responsive to the cancer microenvironment, and have demonstrated the cancer-specific accumulation at the cellular level and an amplified signal which is twice higher than the control in vivo.

  16. IMPACT OF POLYCYCLIC AROMATIC HYDROCARBONS OF THE ELECTROCHEMICAL RESPONSES OF A FERRICYNIDE PROBE AT TEMPLATE-MODIFIED SELF ASSEMBLED MONOLAYERS ON GOLD ELECTRODES

    Science.gov (United States)

    The impact of pyrene on the electrochemical response of the ferricyanide probe using Self Assembled Monolayer (SAM)-modified gold electrodes was investigated using Cyclic Voltammetry (CV) and Square Wave Voltammetry (SWV). These results suggest the feasibility of using SAMs, par...

  17. Gold prices

    OpenAIRE

    Joseph G. Haubrich

    1998-01-01

    The price of gold commands attention because it serves as an indicator of general price stability or inflation. But gold is also a commodity, used in jewelry and by industry, so demand and supply affect its pricing and need to be considered when gold is a factor in monetary policy decisions.

  18. Comparing Seismic And Magnetic Responses To Copper Gold Deposits Under Different Cover Sequences

    Directory of Open Access Journals (Sweden)

    Okan Evans Onojasun

    2015-08-01

    Full Text Available Appropriate application of geophysical techniques is required to effectively explore through the cover sequences that will allow the discovery of deep seated orebodies within the 1-3km depth range. Whilst potential field methods that are traditionally used for Cu-Au exploration seems effective they lack the expected resolution required to detect deeper mineral deposits under 500 m cover. Seismic reflection techniques offers a distinct advantage over all other geophysical techniques because of its ability to penetrate deeper into the subsurface without losing its resolution. We present in this report modelling results from magnetic and seismic responses to Cu-Au deposits when located within 100-1000m depth range. In the case of magnetic modelling we apply upward continuation filters which calculate the potential field that would have been recorded at 100m 250m 500m and 1000 m levels by filtering away shallow anomalies from the initial data. For seismic modelling simple but realistic geological model with varying cover thicknesses 100m 250m 500m and 1000m were created and then populate these models with petrophysical data. Simulated synthetic seismic responses from the models was processed using basic processing flows to obtained depth migrated images. Results show that for shower depths 0-100m good correlation exist between the magnetic and the seismic responses. From 100-250m depth cover though we can still see some magnetic anomalies within the target zone its effectiveness decreases with depths whereas seismic responses was maintain within the depth range. From 500m to 1000m magnetic response becomes spear or fuzzy as much useful information is practically missed out. Similarly high resolution power of seismic was ably demonstrated as the depth of even 2km did not degrade its resolution. Thus both magnetic and seismic methods are very useful for shallow investigation but at greater depth seismic method appears to be a more valid exploration

  19. Citrate-capped gold nanoparticle electrophoretic heat production in response to a time-varying radiofrequency electric-field.

    Science.gov (United States)

    Corr, Stuart J; Raoof, Mustafa; Mackeyev, Yuri; Phounsavath, Sophia; Cheney, Matthew A; Cisneros, Brandon T; Shur, Michael; Gozin, Michael; McNally, Patrick J; Wilson, Lon J; Curley, Steven A

    2012-11-15

    The evaluation of heat production from gold nanoparticles (AuNPs) irradiated with radiofrequency (RF) energy has been problematic due to Joule heating of their background ionic buffer suspensions. Insights into the physical heating mechanism of nanomaterials under RF excitations must be obtained if they are to have applications in fields such as nanoparticle-targeted hyperthermia for cancer therapy. By developing a purification protocol which allows for highly-stable and concentrated solutions of citrate-capped AuNPs to be suspended in high-resistivity water, we show herein, for the first time, that heat production is only evident for AuNPs of diameters ≤ 10 nm, indicating a unique size-dependent heating behavior not previously observed. Heat production has also shown to be linearly dependent on both AuNP concentration and total surface area, and severely attenuated upon AuNP aggregation. These relationships have been further validated using permittivity analysis across a frequency range of 10 MHz to 3 GHz, as well as static conductivity measurements. Theoretical evaluations suggest that the heating mechanism can be modeled by the electrophoretic oscillation of charged AuNPs across finite length scales in response to a time-varying electric field. It is anticipated these results will assist future development of nanoparticle-assisted heat production by RF fields for applications such as targeted cancer hyperthermia.

  20. Surface excess elasticity of gold: Ab initio coefficients and impact on the effective elastic response of nanowires

    International Nuclear Information System (INIS)

    Elsner, B.A.M.; Müller, S.; Bargmann, S.; Weissmüller, J.

    2017-01-01

    Predicting the influence of the surface on the effective elastic properties of nanoscale structures and nanomaterials remains a challenge, which we here address on both levels, continuum and atomic. Density Functional Theory (DFT) computation at the atomic level yields the first reliable surface excess elastic parameters for the (111) and (001) surfaces of gold. At the continuum level, we derive closed-form expressions for the effective elastic behavior that can be combined with the DFT-derived excess elastic parameters to obtain the effective axial, torsion, and bending stiffness of circular nanowires with surface excess elasticity. The two approaches use different reference frames, and we emphasize the need for consistent stress definitions and for conversion between the separate stress measures when transferring results between the approaches. We present excess elastic parameters separately for Cauchy and 2 nd Piola-Kirchhoff stresses, demonstrating that the conversion substantially modifies their numerical value and may even invert their sign. The results afford an assessment of the contribution of the surface excess elastic parameters to the effective elastic response of nanoscale beams or wires. This assessment sheds doubt on earlier suggestions relating experimental observations of an effective stiffening or softening at small size to the excess elasticity of clean surfaces.

  1. Dual stimuli-sensitive dendrimers: Photothermogenic gold nanoparticle-loaded thermo-responsive elastin-mimetic dendrimers.

    Science.gov (United States)

    Fukushima, Daichi; Sk, Ugir Hossain; Sakamoto, Yasuhiro; Nakase, Ikuhiko; Kojima, Chie

    2015-08-01

    Dendrimers are synthetic macromolecules with unique structures that can work as nanoplatforms for both photothermogenic gold nanoparticles (AuNPs) and thermosensitive elastin-like peptides (ELPs) with valine-proline-glycine-valine-glycine (VPGVG) repeats. In this study, photothermogenic AuNPs were loaded into thermo-responsive elastin-mimetic dendrimers (dendrimers conjugating ELPs at their periphery) to produce dual stimuli-sensitive nanoparticles. Polyamidoamine G4 dendrimers were modified with acetylated VPGVG and (VPGVG)2, and the resulting materials were named ELP1-den and ELP2-den, respectively. The AuNPs were prepared by the reduction of Au ions using a dendrimer-nanotemplated method. The AuNP-loaded elastin-mimetic dendrimers exhibited photothermal properties. ELP1-den and ELP2-den showed similar temperature-dependent changes in their conformations. Phase transitions were observed at around 55°C and 35°C for the AuNP-loaded ELP1-den and AuNP-loaded ELP2-den, respectively, but not for the corresponding PEGylated dendrimer. In contrast to the AuNP-loaded PEGylated dendrimer, AuNP-loaded ELP2-den readily associated with cells and induced efficient photocytotoxicity at 37°C. The cell association and the photocytotoxicity properties of AuNP-loaded ELP2-den could be controlled by temperature. These results therefore suggest that dual stimuli-sensitive dendrimer nanoparticles of this type could be used for photothermal therapy. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Use of QuantiFERON®-TB Gold in-tube culture supernatants for measurement of antibody responses.

    Directory of Open Access Journals (Sweden)

    Simon G Kimuda

    Full Text Available QuantiFERON®-TB Gold in-tube (QFT-GIT supernatants may be important samples for use in assessment of anti-tuberculosis (TB antibodies when only limited volumes of blood can be collected and when a combination of antibody and cytokine measurements are required. These analytes, when used together, may also have the potential to differentiate active pulmonary TB (APTB from latent TB infection (LTBI. However, few studies have explored the use of QFT-GIT supernatants for investigations of antibody responses. This study determined the correlation and agreement between anti-CFP-10 and anti-ESAT-6 antibody concentrations in QFT-GIT nil supernatant and serum pairs from 68 TB household contacts. We also explored the ability of Mycobacterium tuberculosis (M.tb specific antibodies, or ratios of antibody to interferon gamma (IFN-γ in QFT-GIT supernatants, to differentiate 97 APTB cases from 58 individuals with LTBI. Sputum smear microscopy was used to define APTB, whereas the QFT-GIT and tuberculin skin test were used to define LTBI. There were strong and statistically significant correlations between anti-CFP-10 and anti-ESAT-6 antibodies in unstimulated QFT-GIT supernatants and sera (r = 0.89; p<0.0001 for both, and no significant differences in antibody concentration between them. Anti-CFP-10 & anti-ESAT-6 antibodies differentiated APTB from LTBI with sensitivities of 88.7% & 71.1% and specificities of 41.4% & 51.7% respectively. Anti-CFP-10 antibody/M.tb specific IFN-γ and anti-ESAT-6 antibody/M.tb specific IFN-γ ratios had sensitivities of 48.5% & 54.6% and specificities of 89.7% and 75.9% respectively. We conclude that QFT-GIT nil supernatants may be used in the place of sera when measuring antibody responses, reducing blood volumes needed for such investigations. Antibodies in QFT-GIT nil supernatants on their own discriminate APTB from LTBI with high sensitivity but have poor specificity, whereas the reverse is true when antibodies are used in

  3. Gold Returns

    OpenAIRE

    Robert J. Barro; Sanjay P. Misra

    2013-01-01

    From 1836 to 2011, the average real rate of price change for gold in the United States is 1.1% per year and the standard deviation is 13.1%, implying a one-standard-deviation confidence band for the mean of (0.1%, 2.1%). The covariances of gold's real rate of price change with consumption and GDP growth rates are small and statistically insignificantly different from zero. These negligible covariances suggest that gold's expected real rate of return--which includes an unobserved dividend yiel...

  4. The mode of occurrence of gold and silver in the Dominian Reef and their response to cyanidation after pressure leading

    International Nuclear Information System (INIS)

    Glatthaar, C.W.; Feather, C.E.

    1985-01-01

    Gold and silver in the Upper Reef of the Dominion Group in the Afrikander Lease area occur in several minerals. Native gold, electrum, and amalgam are the main gold bearers, whereas silver, in addition to being present in the above alloys, is also represented by native silver, in mercurian silver (arquerite), acanthite, stromeyerite, and a bismuth-silver sulphide (schaba-chite or pavionite), and in solid solution in galena. Only minute quantities of these silver-bearing minerals were found, and attempts to evaluate their relative abundances in the ore proved to be difficult. It was possible, however, by use of an electron microprobe, to quantify the silver contents in electrum, amalgam, mercurian silver, and galena. Mass-balance studies based on the calculated galena content suggest that about half of the total silver is associated with galena in solid solution. In practice, the uranium present in the conglomerates of the Dominion Group is extracted first. Because of the refractory nature of the uranium-bearing minerals, a leach at high temperature and high pressure is recommended. While this pressure leach is beneficial to the subsequent cyanidation of gold, a large proportion of the silver present is rendered refractory. The poor recoveries of silver are believed to be due close association of silver and galena. It is believed that silver is released during the dissolution of galena, acanthite, other silver sulphides, and native silver, and subsequently precipitated either as an insoluble complex silver-iron sulphate (argentojarosite) or in solid solution in jarosite (potassium-iron sulphate). Neither compound is amenable to cyanidation. A mixture of plumbojarosite (lead-iron sulphate) and jarosite were seen to form protective coatings on galena particles, and may occlude other silver-bearing minerals in the same manner. In contrast, finely divided gold particles are liberated from pyrite and other minerals during pressure leaching and become readily available to

  5. Gold monetization and gold discipline

    OpenAIRE

    Robert P. Flood; Peter M. Garber

    1981-01-01

    The paper is a study of the price level and relative price effects of a policy to monetize gold and fix its price at a given future time and at the then prevailing nominal price. Price movements are analyzed both during the transition to the gold standard and during the post-monetization period. The paper also explores the adjustments to fiat money which are necessary to ensure that this type of gold monetization is non-inflationary. Finally, some conditions which produce a run on the governm...

  6. Gold Museum

    OpenAIRE

    Efraín Sánchez Cabra

    2003-01-01

    On 22 december 1939, the Banco de la República, the Central Bank of Colombia, purchased a 23.5 centimetres high pre-Columbian gold arte fact weighing 777·7 grams that was to become the Gold M useum's foundation stone. Described as a Quimbaya poporo, it is a masterpiece of pre-Hispanic goldwork, an object of beauty whose brightly burnished body and neck, crowned with four sphere-like or naments, rest on an exquisite cast metal tiligree base and which seems to ftoat in a space of its own. The b...

  7. Green Gold

    International Nuclear Information System (INIS)

    Salamandra Martinez, Carlos

    2004-01-01

    The main purpose of this work is to offer a general panoramic of the processes or experiences pilot that are carried out in the Project Green Gold, as strategy of environmental sustainability and organizational invigoration in Choco, especially in the 12 communities of the municipalities of Tado and Condoto. It is also sought to offer a minimum of information on the techniques of handmade production and to show the possibilities to carry out in a rational way the use and use of the natural resources. The Project Green Gold is carried out by the Corporation Green Gold (COV) and co-financed with resources of international and national character, the intervention of the financial resources it achievement mainly for the use of clean processes in the extraction stages and metals benefit. The project is centered primarily in the absence of use of products or toxic substances as the mercury, fair trade, organizational invigoration, execution of 11 approaches and certification of the metals Gold and Platinum. The COV, it has come executing the proposal from the year 2001 with the premise of contributing to the balance between the rational exploitation of the natural resources and the conservation of the environment in the Choco. In the project they are used technical handmade characteristic of the region framed inside the mining activity and production activities are diversified in the productive family units. Those producing with the support of entities of juridical character, specify the necessary game rules for the extraction and products commercialization

  8. Protein-coated pH-responsive gold nanoparticles: Microwave-assisted synthesis and surface charge-dependent anticancer activity

    Directory of Open Access Journals (Sweden)

    Dickson Joseph

    2014-09-01

    Full Text Available The biocompatibility and ease of functionalization of gold nanoparticles underlie significant potential in biotechnology and biomedicine. Eight different proteins were examined in the preparation of gold nanoparticles (AuNPs in aqueous medium under microwave irradiation. Six of the proteins resulted in the formation of AuNPs. The intrinsic pH of the proteins played an important role in AuNPs with strong surface plasmon bands. The hydrodynamic size of the nanoparticles was larger than the values observed by TEM and ImageJ. The formation of a protein layer on the AuNPs accounts for this difference. The AuNPs exhibited sensitivity towards varying pH conditions, which was confirmed by determining the difference in the isoelectric points studied by using pH-dependent zeta potential titration. Cytotoxicity studies revealed anticancerous effects of the AuNPs at a certain micromolar concentration by constraining the growth of cancer cells with different efficacies due to the use of different proteins as capping agents. The positively charged AuNPs are internalized by the cells to a greater level than the negatively charged AuNPs. These AuNPs synthesized with protein coating holds promise as anticancer agents and would help in providing a new paradigm in area of nanoparticles.

  9. [Biosynthesis of gold nanoparticles by Azospirillum brasilense].

    Science.gov (United States)

    Kupriashina, M A; Vetchinkina, E P; Burov, A M; Ponomareva, E G; Nikitina, V E

    2014-01-01

    Plant-associated nitrogen-fixing soil bacteria Azospirillum brasilense were shown to reduce the gold of chloroauric acid to elemental gold, resulting in formation of gold nanoparicles. Extracellular phenoloxidizing enzymes (laccases and Mn peroxidases) were shown to participate in reduction of Au+3 (HAuCl4) to Au(0). Transmission electron microscopy revealed accumulation of colloidal gold nanoparticles of diverse shape in the culture liquid of A. brasilense strains Sp245 and Sp7. The size of the electron-dense nanospheres was 5 to 50 nm, and the size of nanoprisms varied from 5 to 300 nm. The tentative mechanism responsible for formation of gold nanoparticles is discussed.

  10. Determination of gold in gold ores

    International Nuclear Information System (INIS)

    Keedy, C.R.; Parson, L.; Shen, J.

    1989-01-01

    The gold content of placer gold flakes and gold bearing ores was determined by instrumental and radiochemical neutron activation analysis, respectively. It was discovered that significant errors result in the instrumental method for gold flakes as small as 10 mg due to sample self-absorption of neutrons during irradiation. Reliable results were obtained for both ore samples and gold flakes by dissolving the samples in aqua regia prior to irradiation. (author) 7 refs.; 3 tabs

  11. Analysis on the Impact of the Fluctuation of the International Gold Prices on the Chinese Gold Stocks

    Directory of Open Access Journals (Sweden)

    Jiankang Jin

    2014-01-01

    Full Text Available Five gold stocks in Chinese Shanghai and Shenzhen A-share and Comex gold futures are chosen to form the sample, for the purpose of analysing the impact of the fluctuation of the international gold prices on the gold stocks in Chinese Shanghai and Shenzhen A-share. Using the methods of unit root test, Granger causality test, VAR model, and impulse response function, this paper has analysed the relationship between the price change of the international gold futures and the price fluctuation of gold stocks in Chinese Shanghai and Shenzhen comprehensively. The results suggest the fluctuation of the international gold futures has a strong influence on the domestic futures.

  12. Computational study of plasma-assisted photoacoustic response from gold nanoparticles irradiated by off-resonance ultrafast laser

    International Nuclear Information System (INIS)

    Hatef, Ali; Darvish, Behafarid; Sajjadi, Amir Yousef

    2017-01-01

    The gold nanoparticles (AuNPs) are capable of enhancing the incident laser field in the form of scattered near field for even an off-resonance irradiation where the incident laser wavelength is far away from the localized surface plasmon resonance (LSPR). If the intensity of the pulse laser is large enough, this capability can be employed to generate a highly localized free electron (plasma) in the vicinity of the particles. The generated plasma can absorb more energy during the pulse, and this energy deposition can be considered as an energy source for structural mechanics calculations in the surrounding media to generate a photoacoustic (PA) signal. To show this, in this paper, we model plasma-mediated PA pressure wave propagation from a 100-nm AuNPs and the surrounding media irradiated by an ultrashort pulse laser. In this model, the AuNP is immersed in water and the laser pulse width is ranging from 70 fs to 2 ps at the wavelength of 800 nm (off-resonance). Our results qualitatively show the substantial impact of the energy deposition in plasma on the PA signal through boosting the pressure amplitudes up to ∼1000 times compared to the conventional approach.

  13. Computational study of plasma-assisted photoacoustic response from gold nanoparticles irradiated by off-resonance ultrafast laser

    Energy Technology Data Exchange (ETDEWEB)

    Hatef, Ali, E-mail: alih@nipissingu.ca; Darvish, Behafarid [Nipissing University, Nipissing Computational Physics Laboratory (NCPL), Department of Computer Science and Mathematics (Canada); Sajjadi, Amir Yousef [Massachusetts General Hospital, Cutaneous Biology Research Center (United States)

    2017-02-15

    The gold nanoparticles (AuNPs) are capable of enhancing the incident laser field in the form of scattered near field for even an off-resonance irradiation where the incident laser wavelength is far away from the localized surface plasmon resonance (LSPR). If the intensity of the pulse laser is large enough, this capability can be employed to generate a highly localized free electron (plasma) in the vicinity of the particles. The generated plasma can absorb more energy during the pulse, and this energy deposition can be considered as an energy source for structural mechanics calculations in the surrounding media to generate a photoacoustic (PA) signal. To show this, in this paper, we model plasma-mediated PA pressure wave propagation from a 100-nm AuNPs and the surrounding media irradiated by an ultrashort pulse laser. In this model, the AuNP is immersed in water and the laser pulse width is ranging from 70 fs to 2 ps at the wavelength of 800 nm (off-resonance). Our results qualitatively show the substantial impact of the energy deposition in plasma on the PA signal through boosting the pressure amplitudes up to ∼1000 times compared to the conventional approach.

  14. Evaluation of immune responses in HIV infected patients with pleural tuberculosis by the QuantiFERON® TB-Gold interferon-gamma assay

    Directory of Open Access Journals (Sweden)

    Lekabe Jacob M

    2008-03-01

    Full Text Available Abstract Background Diagnosis of tuberculous (TB pleuritis is difficult and better diagnostic tools are needed. New blood based interferon-gamma (IFN-γ tests are promising, but sensitivity could be low in HIV positive patients. The IFN-γ tests have not yet been validated for use in pleural fluid, a compartment with higher level of immune activation than in blood. Methods The QuantiFERON TB®-Gold (QFT-TB test was analysed in blood and pleural fluid from 34 patients presenting with clinically suspected pleural TB. Clinical data, HIV status and CD4 cell counts were recorded. Adenosine deaminase activity (ADA analysis and TB culture were performed on pleural fluid. Results The patients were categorised as 'confirmed TB' (n = 12, 'probable TB' (n = 16 and 'non-TB' pleuritis (n = 6 based on TB culture results and clinical and biochemical criteria. The majority of the TB patients were HIV infected (82%. The QFT-TB in pleural fluid was positive in 27% and 56% of the 'confirmed TB' and 'probable TB' cases, respectively, whereas the corresponding sensitivities in blood were 58% and 83%. Indeterminate results in blood (25% were caused by low phytohemagglutinin (PHA = positive control IFN-γ responses, significantly lower in the TB patients as compared to the 'non-TB' cases (p = 0.02. Blood PHA responses correlated with CD4 cell count (r = 0.600, p = 0.028. In contrast, in pleural fluid indeterminate results (52% were caused by high Nil (negative control IFN-γ responses in both TB groups. Still, the Nil IFN-γ responses were lower than the TB antigen responses (p Conclusion The QFT-TB test in blood could contribute to the diagnosis of TB pleuritis in the HIV positive population. Still, the number of inconclusive results is too high to recommend the commercial QFT-TB test for routine use in pleural fluid in a TB/HIV endemic resource-limited setting.

  15. Insulin response in individual tissues of control and gold thioglucose-obese mice in vivo with [1-14C]2-deoxyglucose

    International Nuclear Information System (INIS)

    Cooney, G.J.; Astbury, L.D.; Williams, P.F.; Caterson, I.D.

    1987-01-01

    The dose-response characteristics of several glucose-utilizing tissues (brain, heart, white adipose tissue, brown adipose tissue, and quadriceps muscle) to a single injection of insulin have been compared in control mice and mice made obese with a single injection of gold thioglucose (GTG). Tissue content of [1- 14 C]2-deoxyglucose 6-phosphate and blood disappearance rate of [1- 14 C]2-deoxyglucose (2-DG) were measured at nine different insulin doses and used to calculate rates of 2-DG uptake and phosphorylation in tissues from control and obese mice. The insulin sensitivity of tissues reflected in the ED50 of insulin response varied widely, and brown adipose tissue was the most insulin-sensitive tissue studied. In GTG-obese mice, heart, quadriceps, and brown adipose tissue were insulin resistant (demonstrated by increased ED50), whereas in white adipose tissue, 2-DG phosphorylation was more sensitive to insulin. Brain 2-DG phosphorylation was insulin independent in control and obese animals. The largest decrease in insulin sensitivity in GTG-obese mice was observed in brown adipose tissue. The loss of diet-induced thermogenesis in brown adipose tissue as a result of the hypothalamic lesion in GTG-obese mice could be a major cause of insulin resistance in brown adipose tissue. Because brown adipose tissue can make a major contribution to whole-body glucose utilization, insulin resistance in this tissue may have a significant effect on whole-animal glucose homeostasis in GTG-obese mice

  16. Use of an Ethanol-Driven Pressure Cell to Measure Hydrostatic Pressure Response of Protein-Stabilized Gold Nanoclusters

    Science.gov (United States)

    2016-01-01

    ARL-TR-7577 ● JAN 2016 US Army Research Laboratory Use of an Ethanol-Driven Pressure Cell to Measure Hydrostatic Pressure ...ARL-TR-7577 ● JAN 2016 US Army Research Laboratory Use of an Ethanol-Driven Pressure Cell to Measure Hydrostatic Pressure Response of...DATES COVERED (From - To) May 2014–September 2014 4. TITLE AND SUBTITLE Use of an Ethanol-Driven Pressure Cell to Measure Hydrostatic Pressure

  17. Stimuli-Responsive Polyelectrolyte Brushes As a Matrix for the Attachment of Gold Nanoparticles: The Effect of Brush Thickness on Particle Distribution

    Directory of Open Access Journals (Sweden)

    Stephanie Christau

    2014-06-01

    Full Text Available The effect of brush thickness on the loading of gold nanoparticles (AuNPs within stimuli-responsive poly-(N,N-(dimethylamino ethyl methacrylate (PDMAEMA polyelectrolyte brushes is reported. Atom transfer radical polymerization (ATRP was used to grow polymer brushes via a “grafting from” approach. The brush thickness was tuned by varying the polymerization time. Using a new type of sealed reactor, thick brushes were synthesized. A systematic study was performed by varying a single parameter (brush thickness, while keeping all other parameters constant. AuNPs of 13 nm in diameter were attached by incubation. X-ray reflectivity, electron scanning microscopy and ellipsometry were used to study the particle loading, particle distribution and interpenetration of the particles within the brush matrix. A model for the structure of the brush/particle hybrids was derived. The particle number densities of attached AuNPs depend on the brush thickness, as do the optical properties of the hybrids. An increasing particle number density was found for increasing brush thickness, due to an increased surface roughness.

  18. Electro-optically responsive composites of gold nanospheres in 5CB liquid crystal under direct current and alternating current joint action

    International Nuclear Information System (INIS)

    Hadjichristov, Georgi B.; Marinov, Yordan G.; Petrov, Alexander G.; Bruno, Emanuela; Marino, Lucia; Scaramuzza, Nicola

    2014-01-01

    Direct current (DC) electro-optical (EO) control of transmitted laser beam intensity based on EO controlled coherent light scattering and diffraction by stationary longitudinal texture pattern (LTP) is achieved in planar-oriented cells with a composite mixture of polymer-coated gold spherical nanoparticles (Au-NPs) with a mean diameter of about 12 nm and the room-temperature nematic pentylcyanobiphenyl (5CB). At relatively low DC voltage of about 5 V, the effective scattering/diffraction by Au-NPs/5CB composites leads to a spatial spreading of transmitted coherent light from a low-power continuous wave laser beam, resulting in a drastic reduction of its local intensity. The effect is polarization dependent and is strongest when the polarization of the input laser beam is along the LTP. The EO response of Au-NPs/5CB mixtures is studied under DC and alternating current (AC) joint action with the aim of the potential use of these composite materials as EO controlled diffusers. The specific V-shaped sharp dip in the DC voltage-dependent coherent light transmittance of Au-NPs/5CB planar films, as well as the possibility for erasing the scattering/diffractive LTP in the films by joint low AC voltage, can be useful for EO applications in the field of process control and for detection of weak dynamic electric fields

  19. Electro-optically responsive composites of gold nanospheres in 5CB liquid crystal under direct current and alternating current joint action

    Energy Technology Data Exchange (ETDEWEB)

    Hadjichristov, Georgi B.; Marinov, Yordan G.; Petrov, Alexander G. [Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia 1784 (Bulgaria); Bruno, Emanuela [Dipartimento di Fisica, Università della Calabria, Via Pietro Bucci, Cubo 31C, 87036 Rende (CS) (Italy); Marino, Lucia, E-mail: lucia.marino@fis.unical.it [CNR-IPCF UoS di Cosenza, Licryl Laboratory, and Centro di Eccellenza CEMIF.CAL, Università della Calabria, 87036 Rende (CS) (Italy); Scaramuzza, Nicola [Dipartimento di Fisica, Università della Calabria, Via Pietro Bucci, Cubo 31C, 87036 Rende (CS) (Italy); CNR-IPCF UoS di Cosenza, Licryl Laboratory, and Centro di Eccellenza CEMIF.CAL, Università della Calabria, 87036 Rende (CS) (Italy)

    2014-02-28

    Direct current (DC) electro-optical (EO) control of transmitted laser beam intensity based on EO controlled coherent light scattering and diffraction by stationary longitudinal texture pattern (LTP) is achieved in planar-oriented cells with a composite mixture of polymer-coated gold spherical nanoparticles (Au-NPs) with a mean diameter of about 12 nm and the room-temperature nematic pentylcyanobiphenyl (5CB). At relatively low DC voltage of about 5 V, the effective scattering/diffraction by Au-NPs/5CB composites leads to a spatial spreading of transmitted coherent light from a low-power continuous wave laser beam, resulting in a drastic reduction of its local intensity. The effect is polarization dependent and is strongest when the polarization of the input laser beam is along the LTP. The EO response of Au-NPs/5CB mixtures is studied under DC and alternating current (AC) joint action with the aim of the potential use of these composite materials as EO controlled diffusers. The specific V-shaped sharp dip in the DC voltage-dependent coherent light transmittance of Au-NPs/5CB planar films, as well as the possibility for erasing the scattering/diffractive LTP in the films by joint low AC voltage, can be useful for EO applications in the field of process control and for detection of weak dynamic electric fields.

  20. Assessment of gold nanoparticles as a size-dependent vaccine carrier for enhancing the antibody response against synthetic foot-and-mouth disease virus peptide

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yu-Shiun [Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, EE137, Hsinchu 300, Taiwan (China); Hung, Yao-Ching [Department of Obstetrics and Gynecology, School of Medicine, China Medical University and Hospital, 91 Hsueh-Shih Road, Taichung 40402, Taiwan (China); Lin, Wei-Hsu [Institute of Nanotechnology, National Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan (China); Huang, Guewha Steven, E-mail: gstevehuang@mail.nctu.edu.tw [Department of Materials Science and Engineering, Institute of Nanotechnology, National Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan, Republic of China (China)

    2010-05-14

    To assess the ability of gold nanoparticles (GNPs) to act as a size-dependent carrier, a synthetic peptide resembling foot-and-mouth disease virus (FMDV) protein was conjugated to GNPs ranging from 2 to 50 nm in diameter (2, 5, 8, 12, 17, 37, and 50 nm). An extra cysteine was added to the C-terminus of the FMDV peptide (pFMDV) to ensure maximal conjugation to the GNPs, which have a high affinity for sulfhydryl groups. The resultant pFMDV-GNP conjugates were then injected into BALB/c mice. Immunization with pFMDV-keyhole limpet hemocyanin (pFMDV-KLH) conjugate was also performed as a control. Blood was obtained from the mice after 4, 6, 8, and 10 weeks and antibody titers against both pFMDV and the carriers were measured. For the pFMDV-GNP immunization, specific antibodies against the synthetic peptide were detected in the sera of mice injected with 2, 5, 8, 12, and 17 nm pFMDV-GNP conjugates. Maximal antibody binding was noted for GNPs of diameter 8-17 nm. The pFMDV-GNPs induced a three-fold increase in the antibody response compared to the response to pFMDV-KLH. However, sera from either immunized mouse group did not exhibit an antibody response to GNPs, while the sera from pFMDV-KLH-immunized mice presented high levels of binding activity against KLH. Additionally, the uptake of pFMDV-GNP in the spleen was examined by inductively coupled plasma mass spectroscopy (ICP-MS) and transmission electron microscopy (TEM). The quantity of GNPs that accumulated in the spleen correlated to the magnitude of the immune response induced by pFMDV-GNP. In conclusion, we demonstrated the size-dependent immunogenic properties of pFMDV-GNP conjugates. Furthermore, we established that GNPs ranging from 8 to 17 nm in diameter may be ideal for eliciting a focused antibody response against a synthetic pFMDV peptide.

  1. Assessment of gold nanoparticles as a size-dependent vaccine carrier for enhancing the antibody response against synthetic foot-and-mouth disease virus peptide

    Science.gov (United States)

    Chen, Yu-Shiun; Hung, Yao-Ching; Lin, Wei-Hsu; Huang, Guewha Steven

    2010-05-01

    To assess the ability of gold nanoparticles (GNPs) to act as a size-dependent carrier, a synthetic peptide resembling foot-and-mouth disease virus (FMDV) protein was conjugated to GNPs ranging from 2 to 50 nm in diameter (2, 5, 8, 12, 17, 37, and 50 nm). An extra cysteine was added to the C-terminus of the FMDV peptide (pFMDV) to ensure maximal conjugation to the GNPs, which have a high affinity for sulfhydryl groups. The resultant pFMDV-GNP conjugates were then injected into BALB/c mice. Immunization with pFMDV-keyhole limpet hemocyanin (pFMDV-KLH) conjugate was also performed as a control. Blood was obtained from the mice after 4, 6, 8, and 10 weeks and antibody titers against both pFMDV and the carriers were measured. For the pFMDV-GNP immunization, specific antibodies against the synthetic peptide were detected in the sera of mice injected with 2, 5, 8, 12, and 17 nm pFMDV-GNP conjugates. Maximal antibody binding was noted for GNPs of diameter 8-17 nm. The pFMDV-GNPs induced a three-fold increase in the antibody response compared to the response to pFMDV-KLH. However, sera from either immunized mouse group did not exhibit an antibody response to GNPs, while the sera from pFMDV-KLH-immunized mice presented high levels of binding activity against KLH. Additionally, the uptake of pFMDV-GNP in the spleen was examined by inductively coupled plasma mass spectroscopy (ICP-MS) and transmission electron microscopy (TEM). The quantity of GNPs that accumulated in the spleen correlated to the magnitude of the immune response induced by pFMDV-GNP. In conclusion, we demonstrated the size-dependent immunogenic properties of pFMDV-GNP conjugates. Furthermore, we established that GNPs ranging from 8 to 17 nm in diameter may be ideal for eliciting a focused antibody response against a synthetic pFMDV peptide.

  2. Assessment of gold nanoparticles as a size-dependent vaccine carrier for enhancing the antibody response against synthetic foot-and-mouth disease virus peptide

    International Nuclear Information System (INIS)

    Chen, Yu-Shiun; Hung, Yao-Ching; Lin, Wei-Hsu; Huang, Guewha Steven

    2010-01-01

    To assess the ability of gold nanoparticles (GNPs) to act as a size-dependent carrier, a synthetic peptide resembling foot-and-mouth disease virus (FMDV) protein was conjugated to GNPs ranging from 2 to 50 nm in diameter (2, 5, 8, 12, 17, 37, and 50 nm). An extra cysteine was added to the C-terminus of the FMDV peptide (pFMDV) to ensure maximal conjugation to the GNPs, which have a high affinity for sulfhydryl groups. The resultant pFMDV-GNP conjugates were then injected into BALB/c mice. Immunization with pFMDV-keyhole limpet hemocyanin (pFMDV-KLH) conjugate was also performed as a control. Blood was obtained from the mice after 4, 6, 8, and 10 weeks and antibody titers against both pFMDV and the carriers were measured. For the pFMDV-GNP immunization, specific antibodies against the synthetic peptide were detected in the sera of mice injected with 2, 5, 8, 12, and 17 nm pFMDV-GNP conjugates. Maximal antibody binding was noted for GNPs of diameter 8-17 nm. The pFMDV-GNPs induced a three-fold increase in the antibody response compared to the response to pFMDV-KLH. However, sera from either immunized mouse group did not exhibit an antibody response to GNPs, while the sera from pFMDV-KLH-immunized mice presented high levels of binding activity against KLH. Additionally, the uptake of pFMDV-GNP in the spleen was examined by inductively coupled plasma mass spectroscopy (ICP-MS) and transmission electron microscopy (TEM). The quantity of GNPs that accumulated in the spleen correlated to the magnitude of the immune response induced by pFMDV-GNP. In conclusion, we demonstrated the size-dependent immunogenic properties of pFMDV-GNP conjugates. Furthermore, we established that GNPs ranging from 8 to 17 nm in diameter may be ideal for eliciting a focused antibody response against a synthetic pFMDV peptide.

  3. A dual pH/thermal responsive nanocarrier for combined chemo-thermotherapy based on a copper-doxorubicin complex and gold nanorods

    Science.gov (United States)

    Lei, Mingzhu; Ma, Man; Pang, Xiaojuan; Tan, Fengping; Li, Nan

    2015-09-01

    The development of treatment protocols that results in a complete response to chemotherapy has been hampered by low efficacy and systemic toxicity. Here, we created a pH sensitive copper-doxorubicin complex within the core of temperature-sensitive liposomes to maintain the stability during blood circulation and trigger Dox release in the tumor site. Synergistically, we also rationally applied gold nanorods (AuNRs) coupled with near-infrared (NIR) field strength to produce a precise and localized temperature, which not only remotely controlled the drug release but also directly destroyed the tumor, to enhance the therapeutic efficacy. As expected, the in vitro release studies showed that the drug release from CuDox-TSLs (Copper ion mediated Doxorubicin loading-Temperature Sensitive Liposomes) was both pH-dependent and temperature-dependent. Furthermore, MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) assays showed that CuDox-TSLs combined with AuNRs exhibited a closer antiproliferative activity to free Dox in MCF-7 cells. The efficient intracellular Dox release from CuDox-TSLs toward the tumor cells further confirmed the anti-tumor effect. Moreover, the in vivo imaging and biodistribution studies revealed that CuDox-TSLs combined with AuNRs could actively target the tumor site. In addition, the therapeutic studies in MCF-7 nude mice exhibited CuDox-TSLs plus AuNRs in combination with NIR irradiation inhibited tumor growth to a great extent and possessed much lower side effects, which were further confirmed by systemic histological analyses. All detailed evidence suggested a considerable potential of CuDox-TSLs combined with AuNRs for treatment of metastatic cancer.The development of treatment protocols that results in a complete response to chemotherapy has been hampered by low efficacy and systemic toxicity. Here, we created a pH sensitive copper-doxorubicin complex within the core of temperature-sensitive liposomes to maintain the stability

  4. 'Outbreak Gold Standard' selection to provide optimized threshold for infectious diseases early-alert based on China Infectious Disease Automated-alert and Response System.

    Science.gov (United States)

    Wang, Rui-Ping; Jiang, Yong-Gen; Zhao, Gen-Ming; Guo, Xiao-Qin; Michael, Engelgau

    2017-12-01

    The China Infectious Disease Automated-alert and Response System (CIDARS) was successfully implemented and became operational nationwide in 2008. The CIDARS plays an important role in and has been integrated into the routine outbreak monitoring efforts of the Center for Disease Control (CDC) at all levels in China. In the CIDARS, thresholds are determined using the "Mean+2SD‟ in the early stage which have limitations. This study compared the performance of optimized thresholds defined using the "Mean +2SD‟ method to the performance of 5 novel algorithms to select optimal "Outbreak Gold Standard (OGS)‟ and corresponding thresholds for outbreak detection. Data for infectious disease were organized by calendar week and year. The "Mean+2SD‟, C1, C2, moving average (MA), seasonal model (SM), and cumulative sum (CUSUM) algorithms were applied. Outbreak signals for the predicted value (Px) were calculated using a percentile-based moving window. When the outbreak signals generated by an algorithm were in line with a Px generated outbreak signal for each week, this Px was then defined as the optimized threshold for that algorithm. In this study, six infectious diseases were selected and classified into TYPE A (chickenpox and mumps), TYPE B (influenza and rubella) and TYPE C [hand foot and mouth disease (HFMD) and scarlet fever]. Optimized thresholds for chickenpox (P 55 ), mumps (P 50 ), influenza (P 40 , P 55 , and P 75 ), rubella (P 45 and P 75 ), HFMD (P 65 and P 70 ), and scarlet fever (P 75 and P 80 ) were identified. The C1, C2, CUSUM, SM, and MA algorithms were appropriate for TYPE A. All 6 algorithms were appropriate for TYPE B. C1 and CUSUM algorithms were appropriate for TYPE C. It is critical to incorporate more flexible algorithms as OGS into the CIDRAS and to identify the proper OGS and corresponding recommended optimized threshold by different infectious disease types.

  5. Evaluation of oxidative response and tissular damage in rat lungs exposed to silica-coated gold nanoparticles under static magnetic fields

    Directory of Open Access Journals (Sweden)

    Ferchichi S

    2016-06-01

    Full Text Available Soumaya Ferchichi,1 Hamdi Trabelsi,1 Inès Azzouz,1 Amel Hanini,2 Ahmed Rejeb,3 Olfa Tebourbi,1 Mohsen Sakly,1 Hafedh Abdelmelek1 1Laboratory of Integrative Physiology, Faculty Of Sciences of Bizerte, 2Laboratory of Vascular Pathology, Carthage University, Carthage 3Laboratory of Pathological Anatomy, National School of Veterinary Medicine of Sidi Thabet, Manouba Univeristy, Manouba, Tunisia Abstract: The purpose of our study was the evaluation of toxicological effects of silica-coated gold nanoparticles (GNPs and static magnetic fields (SMFs; 128 mT exposure in rat lungs. Animals received a single injection of GNPs (1,100 µg/kg, 100 nm, intraperitoneally and were exposed to SMFs, over 14 days (1 h/day. Results showed that GNPs treatment induced a hyperplasia of bronchus-associated lymphoid tissue. Fluorescence microscopy images showed that red fluorescence signal was detected in rat lungs after 2 weeks from the single injection of GNPs. Oxidative response study showed that GNPs exposure increased malondialdehyde level and decreased CuZn-superoxide dismutase, catalase, and glutathione peroxidase activities in rat lungs. Furthermore, the histopathological study showed that combined effects of GNPs and SMFs led to more tissular damages in rat lungs in comparison with GNPs-treated rats. Interestingly, intensity of red fluorescence signal was enhanced after exposure to SMFs indicating a higher accumulation of GNPs in rat lungs under magnetic environment. Moreover, rats coexposed to GNPs and SMFs showed an increased malondialdehyde level, a fall of CuZn-superoxide dismutase, catalase, and glutathione peroxidase activities in comparison with GNPs-treated group. Hence, SMFs exposure increased the accumulation of GNPs in rat lungs and led to more toxic effects of these nanocomplexes. Keywords: malondialdehyde, catalase, superoxide dismutase, glutathione peroxidase, bronchus-associated lymphoid tissue, nanotoxicity, histopathological study

  6. Frontiers in Gold Chemistry

    OpenAIRE

    Ahmed A. Mohamed

    2015-01-01

    Basic chemistry of gold tells us that it can bond to sulfur, phosphorous, nitrogen, and oxygen donor ligands. The Frontiers in Gold Chemistry Special Issue covers gold complexes bonded to the different donors and their fascinating applications. This issue covers both basic chemistry studies of gold complexes and their contemporary applications in medicine, materials chemistry, and optical sensors. There is a strong belief that aurophilicity plays a major role in the unending applications of g...

  7. Gold in plants

    International Nuclear Information System (INIS)

    Girling, C.A.; Peterson, P.J.

    1980-01-01

    Many plants have the ability to take up gold from the soil and to accumulate it in their tisssue. Advances have been made in understanding these processes to the point where their exploitation in the field of prospecting for gold appears practically feasible. Neutron activation analysis is used for the determination of the small quantities of gold in plants

  8. Optical redox ratio using endogenous fluorescence to assess the metabolic changes associated with treatment response of bioconjugated gold nanoparticles in streptozotocin-induced diabetic rats

    Science.gov (United States)

    Adavallan, K.; Gurushankar, K.; Nazeer, Shaiju S.; Gohulkumar, M.; Jayasree, Ramapurath S.; Krishnakumar, N.

    2017-06-01

    Fluorescence spectroscopic techniques have the potential to assess the metabolic changes during disease development and evaluation of treatment response in a non-invasive and label-free manner. The present study aims to evaluate the effect of mulberry-mediated gold nanoparticles (MAuNPs) in comparison with mulberry leaf extract alone (MLE) for monitoring endogenous fluorophores and to quantify the metabolic changes associated with mitochondrial redox states during streptozotocin-induced diabetic liver tissues using fluorescence spectroscopy. Two mitochondrial metabolic coenzymes, reduced nicotinamide dinucleotide (NADH) and oxidized flavin adenine dinucleotide (FAD) are autofluorescent and are important optical biomarkers to estimate the redox state of a cell. Significant differences in the autofluorescence spectral signatures between the control and the experimental diabetic animals have been noticed under the excitation wavelength at 320 nm with emission ranging from 350-550 nm. A direct correlation between the progression of diabetes and the levels of collagen and optical redox ratio was observed. The results revealed that a significant increase in the emission of collagen in diabetic liver tissues as compared with the control liver tissues. Moreover, there was a significant decrease in the optical redox ratio (FAD/(FAD  +  NADH)) observed in diabetic control liver tissues, which indicates an increased oxidative stress compared to the liver tissues of control rats. Further, the extent of increased oxidative stress was confirmed by the reduced levels of reduced glutathione (GSH) in diabetic liver tissues. On a comparative basis, treatment with MAuNPs was found to be more effective than MLE for reducing the progression of diabetes and improving the optical redox ratio to a near normal range in streptozotocin-induced diabetic liver tissues. Furthermore, principal component analysis followed by linear discriminant analysis (PC-LDA) has been used to

  9. Gold-Mining

    DEFF Research Database (Denmark)

    Raaballe, J.; Grundy, B.D.

    2002-01-01

      Based on standard option pricing arguments and assumptions (including no convenience yield and sustainable property rights), we will not observe operating gold mines. We find that asymmetric information on the reserves in the gold mine is a necessary and sufficient condition for the existence...... of operating gold mines. Asymmetric information on the reserves in the mine implies that, at a high enough price of gold, the manager of high type finds the extraction value of the company to be higher than the current market value of the non-operating gold mine. Due to this under valuation the maxim of market...

  10. Manipulation of the Geometry and Modulation of the Optical Response of Surfactant-Free Gold Nanostars: A Systematic Bottom-Up Synthesis.

    Science.gov (United States)

    De Silva Indrasekara, Agampodi S; Johnson, Sean F; Odion, Ren A; Vo-Dinh, Tuan

    2018-02-28

    Among plasmonic nanoparticles, surfactant-free branched gold nanoparticles have exhibited exceptional properties as a nanoplatform for a wide variety of applications ranging from surface-enhanced Raman scattering sensing and imaging applications to photothermal treatment and photoimmunotherapy for cancer treatments. The effectiveness and reliability of branched gold nanoparticles in biomedical applications strongly rely on the consistency and reproducibility of physical, chemical, optical, and therapeutic properties of nanoparticles, which are mainly governed by their morphological features. Herein, we present an optimized bottom-up synthesis that improves the reproducibility and homogeneity of the gold-branched nanoparticles with desired morphological features and optical properties. We identified that the order of reagent addition is crucial for improved homogeneity of the branched nature of nanoparticles that enable a high batch-to-batch reproducibility and reliability. In addition, a different combination of the synthesis parameters, in particular, additive halides and concentration ratios of reactive Au to Ag and Au to Au seeds, which yield branched nanoparticle of similar localized surface plasmon resonances but with distinguishable changes in the dimensions of the branches, was realized. Overall, our study introduces the design parameters for the purpose-tailored manufacturing of surfactant-free gold nanostars in a reliable manner.

  11. Electrocatalytic glucose oxidation at gold and gold-carbon nanoparticulate film prepared from oppositely charged nanoparticles

    International Nuclear Information System (INIS)

    Karczmarczyk, Aleksandra; Celebanska, Anna; Nogala, Wojciech; Sashuk, Volodymyr; Chernyaeva, Olga; Opallo, Marcin

    2014-01-01

    Graphical abstract: - Highlights: • Gold nanoparticulate film electrodes were prepared by layer-by-layer method from oppositely charged nanoparticles. • Positively charged nanoparticles play dominant role in glucose oxidation in alkaline solution. • Gold and gold-carbon nanoparticulate film electrodes exhibit similar glucose oxidation current and onset potential. - Abstract: Electrocatalytic oxidation of glucose was studied at nanoparticulate gold and gold-carbon film electrodes. These electrodes were prepared by a layer-by-layer method without application of any linker molecules. Gold nanoparticles were stabilized by undecane thiols functionalized by trimethyl ammonium or carboxylate groups, whereas the carbon nanoparticles were covered by phenylsulfonate functionalities. The gold nanoparticulate electrodes were characterized by UV-vis and XPS spectroscopy, atomic force microscopy and voltammetry, before and after heat-treatment. Heat-treatment facilitates the aggregation of the nanoparticles and affects the structure of the film. The comparison of the results obtained with film electrodes prepared from gold nanoparticles with the same charge and with gold-carbon nanoparticulate electrodes, proved that positively charged nanoparticles are responsible for the high electrocatalytic activity, whereas negatively charged ones act rather as a linker of the film

  12. Carbonate hosted gold deposit in Tasmania, Australia

    International Nuclear Information System (INIS)

    Abadi, M.H.

    1999-01-01

    Full text: This study uses elemental and isotopic composition of carbonates associated with gold from Henty and Beaconsfield in Tasmania, Australia, to illustrate source of gold-bearing fluids, salinity, temperature and dissolution and reprecipitation of carbonate. The Beaconsfield and Henty gold mines are located in northern and western Tasmania respectively. Gold mineralisation in Beaconsfield occurs within the quartz-carbonate Tasmania Reef (Lower to Middle Palaeozoic sequence, Hills, 1998). The Henty gold mine is located at the base of the Cambrian Tyndall Group (volcano-sedimentary succession, White and McPhie, 1996) close to Henty Fault. Gold in carbonate samples from Henty ranges from 7.7 to 9360 ppm and in Beaconsfield ranges from 0.01 to 434 ppm. The amount of carbonate in samples from Henty and Beaconsfield gold mines varies from approximately 24 to 99.8%. Bivariate plot of Ca relative to total amounts of Mg, Fe and Mn illustrates that the major carbonate minerals at Beaconsfield and Henty gold mines are magnesian ankerite and calcite. The difference in carbonate mineralogy, at Henty and Beaconsfield gold mines, is attributed to the composition of fluids responsible for carbonate alteration. Gold and magnesium in Beaconsfield ankerite are derived from the leaching of Cambrian ultramafic rocks during the Devonian by the passage of meteoric fluids through tectonically affected Ordovician carbonates (Rao and Adabi, 1999). The total concentration of Fe and Mn are low (0.5 to 2%) in Henty and high (1 to 17.5%) in Beaconsfield ankerite, possibly due to oxidising conditions at Henty and reducing conditions at Beaconsfield gold mines during gold mineralisation. Variation of Sr values between Beaconsfield ankerite and Henty calcite is related to dissolution of limestone that increase Sr concentrations in gold mineralising fluids. Na values in both Beaconsfield (20 to 1100 ppm) and Henty carbonates (25 to 1650 ppm) suggest low salinity fluids responsible for gold

  13. Gold and uranium extraction

    International Nuclear Information System (INIS)

    James, G.S.; Davidson, R.J.

    1977-01-01

    A process for extracting gold and uranium from an ore containing them both comprising the steps of pulping the finely comminuted ore with a suitable cyanide solution at an alkaline pH, acidifying the pulp for uranium dissolution, adding carbon activated for gold recovery to the pulp at a suitable stage, separating the loaded activated carbon from the pulp, and recovering gold from the activated carbon and uranium from solution

  14. Gold mineralogy and extraction

    Energy Technology Data Exchange (ETDEWEB)

    Cashion, J.D.; Brown, L.J. [Monash University, Physics Department (Australia)

    1998-12-15

    Several examples are examined in which Moessbauer spectroscopic analysis of gold mineral samples, treated concentrates and extracted species has provided information not obtainable by competing techniques. Descriptions are given of current work on bacterial oxidation of pyritic ores and on the adsorbed species from gold extracted from cyanide and chloride solutions onto activated carbon and polyurethane foams. The potential benefits for the gold mining industry from Moessbauer studies and some limitations on the use of the technique are also discussed.

  15. Gold mineralogy and extraction

    International Nuclear Information System (INIS)

    Cashion, J.D.; Brown, L.J.

    1998-01-01

    Several examples are examined in which Moessbauer spectroscopic analysis of gold mineral samples, treated concentrates and extracted species has provided information not obtainable by competing techniques. Descriptions are given of current work on bacterial oxidation of pyritic ores and on the adsorbed species from gold extracted from cyanide and chloride solutions onto activated carbon and polyurethane foams. The potential benefits for the gold mining industry from Moessbauer studies and some limitations on the use of the technique are also discussed

  16. Synthesis of PEGylated gold nanostars and bipyramids for intracellular uptake

    International Nuclear Information System (INIS)

    Navarro, Julien R G; Lerouge, Frédéric; Chaput, Frédéric; Micouin, Guillaume; Gabudean, Ana-Maria; Baldeck, Patrice L; Kamada, Kenji; Parola, Stephane; Manchon, Delphine; Mosset, Alexis; Cottancin, Emmanuel; Blanchard, Nicholas P; Marotte, Sophie; Leverrier, Yann; Marvel, Jacqueline

    2012-01-01

    A great number of works have focused their research on the synthesis, design and optical properties of gold nanoparticles for potential biological applications (bioimaging, biosensing). For this kind of application, sharp gold nanostructures appear to exhibit the more interesting features since their surface plasmon bands are very sensitive to the surrounding medium. In this paper, a complete study of PEGylated gold nanostars and PEGylated bipyramidal-like nanostructures is presented. The nanoparticles are prepared in high yield and their surfaces are covered with a biocompatible polymer. The photophysical properties of gold bipyramids and nanostars, in suspension, are correlated with the optical response of single and isolated objects. The resulting spectra of isolated gold nanoparticles are subsequently correlated to their geometrical structure by transmission electron microscopy. Finally, the PEGylated gold nanoparticles were incubated with melanoma B16-F10 cells. Dark-field microscopy showed that the biocompatible gold nanoparticles were easily internalized and most of them localized within the cells. (paper)

  17. Is the largest aqueous gold cluster a superatom complex? Electronic structure & optical response of the structurally determined Au146(p-MBA)57.

    Science.gov (United States)

    López-Lozano, Xóchitl; Plascencia-Villa, G; Calero, G; Whetten, R L; Weissker, Hans-Christian

    2017-12-07

    The new water-soluble gold cluster Au 146 (p-MBA) 57 , the structure of which has been recently determined at sub-atomic resolution by Vergara et al., is the largest aqueous gold cluster ever structurally determined and likewise the smallest cluster with a stacking fault. The core presents a twinned truncated octahedron, while additional peripheral gold atoms follow a C 2 rotational symmetry. According to the usual counting rules of the superatom complex (SAC) model, the compound attains a number of 92 SAC electrons if the overall net charge is 3- (three additional electrons). As this is the number of electrons required for a major shell closing, the question arises of whether Au 146 (p-MBA) 57 should be regarded as a superatom complex. Starting from the experimental coordinates we have analyzed the structure using density-functional theory. The optimized (relaxed) structure retains all the connectivity of the experimental coordinates, while removing much of its irregularities in interatomic distances, thereby enhancing the C 2 -symmetry feature. On analyzing the angular-momentum-projected states, we show that, despite a small gap, the electronic structure does not exhibit SAC model character. In addition, optical absorption spectra are found to be relatively smooth compared to the example of the Au 144 (SR) 60 cluster. The Au 146 (SR) 57 does not derive its stability from SAC character; it cannot be considered as a superatom complex.

  18. Effects of gold coating on experimental implant fixation

    DEFF Research Database (Denmark)

    Zainali, Kasra; Danscher, Gorm; Jakobsen, Thomas

    2009-01-01

    Insertions of orthopedic implants are traumatic procedures that trigger an inflammatory response. Macrophages have been shown to liberate gold ions from metallic gold. Gold ions are known to act in an antiinflammatory manner by inhibiting cellular NF-kappa B-DNA binding and suppressing I-kappa B......-kinase activation. The present study investigated whether gilding implant Surfaces augmented early implant osseointegration and implant fixation by its modulatory effect on the local inflammatory response. Ion release was traced by autometallographic silver enhancement. Gold-coated cylindrical porous coated Ti6Al4V...

  19. BROOKHAVEN: High energy gold

    International Nuclear Information System (INIS)

    Bleser, Ed

    1992-01-01

    On April 24, Brookhaven's Alternating Gradient Synchrotron (AGS) started to deliver gold ions at 11.4 GeV per nucleon (2,000 GeV per ion) to experimenters who were delighted not only to receive the world's highest energy gold beam but also to receive it on schedule

  20. Biological responses of T cells encapsulated with polyelectrolyte-coated gold nanorods and their cellular activities in a co-culture system

    Science.gov (United States)

    Wattanakull, Porntida; Killingsworth, Murray C.; Pissuwan, Dakrong

    2017-11-01

    Currently, human T cell therapy is of considerable scientific interest. In addition, cell encapsulation has become an attractive approach in biomedical applications. Here, we propose an innovative technique of single-cell encapsulation of human T cells using polyelectrolytes combined with gold nanorods. We have demonstrated encapsulation of human Jurkat T cells with poly(sodium 4-styrenesulfonate) (PSS)-coated gold nanorods (PSS-GNRs). Other forms of encapsulation, using polyelectrolytes without GNRs, were also performed. After Jurkat T cells were encapsulated with poly(allylamine hydrochloride) (PAH) and/or PSS-GNRs or PSS, most cells survived and could proliferate. Jurkat T cells encapsulated with a double layer of PSS-GNR/PAH (PSS-GNR/PAH@Jurkat) showed the highest rate of cell proliferation when compared to 24-h encapsulated cells. With the exception of IL-6, no significant induction of inflammatory cytokines (IL-2, IL-1β, and TNF-α) was observed. Interestingly, when encapsulated cells were co-cultured with THP-1 macrophages, co-cultures exhibited TNF-α production enhancement. However, the co-culture of THP-1 macrophage and PSS-GNR/PAH@Jurkat or PSS/PAH@Jurkat did not enhance TNF-α production. No significant inductions of IL-2, IL-1β, and IL-6 were detected. These data provide promising results, demonstrating the potential use of encapsulated PSS-GNR/PAH@Jurkat to provide a more inert T cell population for immunotherapy application and other biomedical applications.

  1. Medicinal gold compounds

    International Nuclear Information System (INIS)

    Parish, R.V.; Cottrill, S.M.

    1987-01-01

    A major use of gold compounds in the pharmaceutical industry is for anti-arthritic agents. The disease itself is not understood and little is known about the way in which the drugs act, but detailed pictures of the distribution of gold in the body are available, and some of the relevant biochemistry is beginning to emerge. The purpose of this article is to give a survey of the types of compounds presently employed in medicine, of the distribution of gold in the body which results from their use, and of some relevant chemistry. Emphasis is placed on results obtained in the last few years

  2. Combination of Gold Nanoparticle-Conjugated Tumor Necrosis Factor-α and Radiation Therapy Results in a Synergistic Antitumor Response in Murine Carcinoma Models.

    Science.gov (United States)

    Koonce, Nathan A; Quick, Charles M; Hardee, Matthew E; Jamshidi-Parsian, Azemat; Dent, Judith A; Paciotti, Giulio F; Nedosekin, Dmitry; Dings, Ruud P M; Griffin, Robert J

    2015-11-01

    Although remarkable preclinical antitumor effects have been shown for tumor necrosis factor-α (TNF) alone and combined with radiation, its clinical use has been hindered by systemic dose-limiting toxicities. We investigated the physiological and antitumor effects of radiation therapy combined with the novel nanomedicine CYT-6091, a 27-nm average-diameter polyethylene glycol-TNF-coated gold nanoparticle, which recently passed through phase 1 trials. The physiologic and antitumor effects of single and fractionated radiation combined with CYT-6091 were studied in the murine 4T1 breast carcinoma and SCCVII head and neck tumor squamous cell carcinoma models. In the 4T1 murine breast tumor model, we observed a significant reduction in the tumor interstitial fluid pressure (IFP) 24 hours after CYT-6091 alone and combined with a radiation dose of 12 Gy (P.05 vs control) despite extensive vascular damage observed. The IFP reduction in the 4T1 model was also associated with marked vascular damage and extravasation of red blood cells into the tumor interstitium. A sustained reduction in tumor cell density was observed in the combined therapy group compared with all other groups (P<.05). Finally, we observed a more than twofold delay in tumor growth when CYT-6091 was combined with a single 20-Gy radiation dose-notably, irrespective of the treatment sequence. Moreover, when hypofractionated radiation (12 Gy × 3) was applied with CYT-6091 treatment, a more than five-fold growth delay was observed in the combined treatment group of both tumor models and determined to be synergistic. Our results have demonstrated that TNF-labeled gold nanoparticles combined with single or fractionated high-dose radiation therapy is effective in reducing IFP and tumor growth and shows promise for clinical translation. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. The Gold Standard Programme

    DEFF Research Database (Denmark)

    Neumann, Tim; Rasmussen, Mette; Ghith, Nermin

    2013-01-01

    To evaluate the real-life effect of an evidence-based Gold Standard Programme (GSP) for smoking cessation interventions in disadvantaged patients and to identify modifiable factors that consistently produce the highest abstinence rates.......To evaluate the real-life effect of an evidence-based Gold Standard Programme (GSP) for smoking cessation interventions in disadvantaged patients and to identify modifiable factors that consistently produce the highest abstinence rates....

  4. Gold nanoprobes for theranostics

    Science.gov (United States)

    Panchapakesan, Balaji; Book-Newell, Brittany; Sethu, Palaniappan; Rao, Madhusudhana; Irudayaraj, Joseph

    2011-01-01

    Gold nanoprobes have become attractive diagnostic and therapeutic agents in medicine and life sciences research owing to their reproducible synthesis with atomic level precision, unique physical and chemical properties, versatility of their morphologies, flexibility in functionalization, ease of targeting, efficiency in drug delivery and opportunities for multimodal therapy. This review highlights some of the recent advances and the potential for gold nanoprobes in theranostics. PMID:22122586

  5. Facts and Fantasies about Gold

    OpenAIRE

    Klement, Joachim

    2015-01-01

    Due to the increasing popularity of gold as an investment the demand for effective risk management techniques for gold investments has increased as well. In this paper we analyze several drivers of the price of gold that have been proposed in the past. Our analysis indicates that short-term volatility of the price of gold remains rather unpredictable with many of the explanations like the fund flows in physical gold ETF either unreliable or unstable over time. Our analysis suggests that there...

  6. Enhanced performance of VOx-based bolometer using patterned gold black absorber

    Science.gov (United States)

    Smith, Evan M.; Panjwani, Deep; Ginn, James; Warren, Andrew; Long, Christopher; Figuieredo, Pedro; Smith, Christian; Perlstein, Joshua; Walter, Nick; Hirschmugl, Carol; Peale, Robert E.; Shelton, David J.

    2015-06-01

    Patterned highly absorbing gold black film has been selectively deposited on the active surfaces of a vanadium-oxide-based infrared bolometer array. Patterning by metal lift-off relies on protection of the fragile gold black with an evaporated oxide, which preserves gold black's near unity absorption. This patterned gold black also survives the dry-etch removal of the sacrificial polyimide used to fabricate the air-bridge bolometers. Infrared responsivity is substantially improved by the gold black coating without significantly increasing noise. The increase in the time constant caused by the additional mass of gold black is a modest 14%.

  7. Biosynthesis of gold nanoparticles using diatoms-silica-gold and EPS-gold bionanocomposite formation

    OpenAIRE

    Schröfel, Adam; Kratošová, Gabriela; Bohunická, Markéta; Dobročka, Edmund; Vávra, Ivo

    2011-01-01

    Novel synthesis of gold nanoparticles, EPS-gold, and silica-gold bionanocomposites by biologically driven processes employing two diatom strains (Navicula atomus, Diadesmis gallica) is described. Transmission electron microscopy (TEM) and electron diffraction analysis (SAED) revealed a presence of gold nanoparticles in the experimental solutions of the diatom culture mixed with tetrachloroaureate. Nature of the gold nanoparticles was confirmed by X-ray diffraction studies. Scanning electron m...

  8. Combination of Gold Nanoparticle-Conjugated Tumor Necrosis Factor-α and Radiation Therapy Results in a Synergistic Antitumor Response in Murine Carcinoma Models

    Energy Technology Data Exchange (ETDEWEB)

    Koonce, Nathan A. [Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, Arkansas (United States); Quick, Charles M. [Department of Pathology, University of Arkansas for Medical Sciences, Little Rock, Arkansas (United States); Hardee, Matthew E.; Jamshidi-Parsian, Azemat; Dent, Judith A. [Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, Arkansas (United States); Paciotti, Giulio F. [CytImmune Sciences, Rockville, Maryland (United States); Nedosekin, Dmitry [Department of Otolaryngology, University of Arkansas for Medical Sciences, Little Rock, Arkansas (United States); Dings, Ruud P.M. [Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, Arkansas (United States); Griffin, Robert J., E-mail: RJGriffin@uams.edu [Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, Arkansas (United States)

    2015-11-01

    Purpose: Although remarkable preclinical antitumor effects have been shown for tumor necrosis factor-α (TNF) alone and combined with radiation, its clinical use has been hindered by systemic dose-limiting toxicities. We investigated the physiological and antitumor effects of radiation therapy combined with the novel nanomedicine CYT-6091, a 27-nm average-diameter polyethylene glycol-TNF-coated gold nanoparticle, which recently passed through phase 1 trials. Methods and Materials: The physiologic and antitumor effects of single and fractionated radiation combined with CYT-6091 were studied in the murine 4T1 breast carcinoma and SCCVII head and neck tumor squamous cell carcinoma models. Results: In the 4T1 murine breast tumor model, we observed a significant reduction in the tumor interstitial fluid pressure (IFP) 24 hours after CYT-6091 alone and combined with a radiation dose of 12 Gy (P<.05 vs control). In contrast, radiation alone (12 Gy) had a negligible effect on the IFP. In the SCCVII head and neck tumor model, the baseline IFP was not markedly elevated, and little additional change occurred in the IFP after single-dose radiation or combined therapy (P>.05 vs control) despite extensive vascular damage observed. The IFP reduction in the 4T1 model was also associated with marked vascular damage and extravasation of red blood cells into the tumor interstitium. A sustained reduction in tumor cell density was observed in the combined therapy group compared with all other groups (P<.05). Finally, we observed a more than twofold delay in tumor growth when CYT-6091 was combined with a single 20-Gy radiation dose—notably, irrespective of the treatment sequence. Moreover, when hypofractionated radiation (12 Gy × 3) was applied with CYT-6091 treatment, a more than five-fold growth delay was observed in the combined treatment group of both tumor models and determined to be synergistic. Conclusions: Our results have demonstrated that TNF-labeled gold

  9. Geobiological Cycling of Gold: From Fundamental Process Understanding to Exploration Solutions

    Directory of Open Access Journals (Sweden)

    Frank Reith

    2013-11-01

    Full Text Available Microbial communities mediating gold cycling occur on gold grains from (sub-tropical, (semi-arid, temperate and subarctic environments. The majority of identified species comprising these biofilms are β-Proteobacteria. Some bacteria, e.g., Cupriavidus metallidurans, Delftia acidovorans and Salmonella typhimurium, have developed biochemical responses to deal with highly toxic gold complexes. These include gold specific sensing and efflux, co-utilization of resistance mechanisms for other metals, and excretion of gold-complex-reducing siderophores that ultimately catalyze the biomineralization of nano-particulate, spheroidal and/or bacteriomorphic gold. In turn, the toxicity of gold complexes fosters the development of specialized biofilms on gold grains, and hence the cycling of gold in surface environments. This was not reported on isoferroplatinum grains under most near-surface environments, due to the lower toxicity of mobile platinum complexes. The discovery of gold-specific microbial responses can now drive the development of geobiological exploration tools, e.g., gold bioindicators and biosensors. Bioindicators employ genetic markers from soils and groundwaters to provide information about gold mineralization processes, while biosensors will allow in-field analyses of gold concentrations in complex sampling media.

  10. Cytosine-assisted synthesis of gold nanochains and gold nanoflowers for the construction of a microperoxidase-11 based amperometric biosensor for hydrogen peroxide

    International Nuclear Information System (INIS)

    Zhang, Qian-Li; Zhou, Dan-Ling; Wang, Ai-Jun; Qin, Su-Fang; Feng, Jiu-Ju; Li, Yong-Fang

    2014-01-01

    A simple method was developed for synthesis of network-like gold nanochains and gold nanoflowers in the presence of cytosine by reduction of tetrachloroauric acid with sodium borohydride and ascorbic acid, respectively. The resulting gold nanocrystals were coated with microperoxidase-11 via electrostatic interactions. Electrodes modified with protein-coated gold nanochains or nanoflowers display well-defined and quasi reversible redox peaks and enhanced high electrocatalytic activity toward the reduction of H 2 O 2 that is due to direct electron transfer to the protein. The effects were exploited for the amperometric detection of H 2 O 2 with a linear response from 0.5 μM to 0.13 mM (for the gold nanochains) and from 1.0 μM to 0.11 mM (for the gold nanoflowers), respectively. The sensor shows lower detection limit and faster response time than sensors based on the use of spherical gold nanoparticles. (author)

  11. GOLD IS EARNED FROM THE PRODUCTION OF THAI GOLD LEAF

    Directory of Open Access Journals (Sweden)

    Dirk Bax

    2010-06-01

    Full Text Available Thai people like to cover sacred objects or things dear to them with gold leaf.. Statues of Buddha are sometimes covered with so many layers of gold leaf that they become formless figures, that can hardly be recognized. Portraits of beloved ancestors, statues of elephants and grave tombs are often covered with gold leaf. If one considers the number of Thai people and the popularity of the habit, the amount of gold involved could be considerable.

  12. Fluorescence resonance energy transfer between NaYF{sub 4}:Yb,Tm upconversion nanoparticles and gold nanorods: Near-infrared responsive biosensor for streptavidin

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shuang; Wang, Jing; Xu, Wen; Chen, Boting; Yu, Wei; Xu, Lin; Song, Hongwei, E-mail: songhw@jlu.edu.cn

    2014-03-15

    We represent a fluorescence resonance energy transfer (FRET) system using upconversion nanoparticles (UCNPs) and the gold nanorods (GNRs) as the energy donor–acceptor pair for directly determining streptavidin in near-infrared (NIR) region. NaYF{sub 4}:Yb,Tm UCNPs, which had a strong emission at 800 nm under 980-nm excitation, were adopted as the energy donor. The GNRs, which demonstrated strong surface plasmon absorption around 800 nm, were chosen as acceptor to quench the 800 nm emissions of the UCNPs. There had the spectral overlap between the emission of the donor nanoparticles (UCNPs) and the absorption of the acceptor nanoparticles (GNRs). This UCNP-based FRET system was then used to determine the amount of streptavidin. In this system, NaYF{sub 4}:Yb,Tm UCNPs conjugated with biotin, while GNRs conjugated with streptavidin. When added GNRs into UCNPs, the streptavidin were preferred to bind with biotin and decreased spacing between the donor and acceptor NPs. Consequently, FRET occurred and a linear relationship between the luminescence quenching efficiency and the concentration of streptavidin was obtained. Owing to the aforementioned merits of UCNPs as an energy donor and the strong quenching ability of GNRs, satisfactory analytical performances have been acquired. -- Highlights: • NaYF4:Yb,Tm and GNRs are as NIR energy donor and quenching acceptor for FRET. • Linkage between biotin and streptavidin make the distance between the donors and the acceptors short enough for FRET. • The FRET system in this work was applicable for the detection of streptavidin. • The donor and acceptor NPs can be modified by proper molecules for other biological molecules detection.

  13. Fluorescence resonance energy transfer between NaYF4:Yb,Tm upconversion nanoparticles and gold nanorods: Near-infrared responsive biosensor for streptavidin

    International Nuclear Information System (INIS)

    Zhang, Shuang; Wang, Jing; Xu, Wen; Chen, Boting; Yu, Wei; Xu, Lin; Song, Hongwei

    2014-01-01

    We represent a fluorescence resonance energy transfer (FRET) system using upconversion nanoparticles (UCNPs) and the gold nanorods (GNRs) as the energy donor–acceptor pair for directly determining streptavidin in near-infrared (NIR) region. NaYF 4 :Yb,Tm UCNPs, which had a strong emission at 800 nm under 980-nm excitation, were adopted as the energy donor. The GNRs, which demonstrated strong surface plasmon absorption around 800 nm, were chosen as acceptor to quench the 800 nm emissions of the UCNPs. There had the spectral overlap between the emission of the donor nanoparticles (UCNPs) and the absorption of the acceptor nanoparticles (GNRs). This UCNP-based FRET system was then used to determine the amount of streptavidin. In this system, NaYF 4 :Yb,Tm UCNPs conjugated with biotin, while GNRs conjugated with streptavidin. When added GNRs into UCNPs, the streptavidin were preferred to bind with biotin and decreased spacing between the donor and acceptor NPs. Consequently, FRET occurred and a linear relationship between the luminescence quenching efficiency and the concentration of streptavidin was obtained. Owing to the aforementioned merits of UCNPs as an energy donor and the strong quenching ability of GNRs, satisfactory analytical performances have been acquired. -- Highlights: • NaYF4:Yb,Tm and GNRs are as NIR energy donor and quenching acceptor for FRET. • Linkage between biotin and streptavidin make the distance between the donors and the acceptors short enough for FRET. • The FRET system in this work was applicable for the detection of streptavidin. • The donor and acceptor NPs can be modified by proper molecules for other biological molecules detection

  14. Gold film with gold nitride - A conductor but harder than gold

    International Nuclear Information System (INIS)

    Siller, L.; Peltekis, N.; Krishnamurthy, S.; Chao, Y.; Bull, S.J.; Hunt, M.R.C.

    2005-01-01

    The formation of surface nitrides on gold films is a particularly attractive proposition, addressing the need to produce harder, but still conductive, gold coatings which reduce wear but avoid the pollution associated with conventional additives. Here we report production of large area gold nitride films on silicon substrates, using reactive ion sputtering and plasma etching, without the need for ultrahigh vacuum. Nanoindentation data show that gold nitride films have a hardness ∼50% greater than that of pure gold. These results are important for large-scale applications of gold nitride in coatings and electronics

  15. Activated carbons and gold

    International Nuclear Information System (INIS)

    McDougall, G.J.; Hancock, R.D.

    1980-01-01

    The literature on activated carbon is reviewed so as to provide a general background with respect to the effect of source material and activation procedure on carbon properties, the structure and chemical nature of the surface of the activated carbon, and the nature of absorption processes on carbon. The various theories on the absorption of gold and silver from cyanide solutions are then reviewed, followed by a discussion of processes for the recovery of gold and silver from cyanide solutions using activated carbon, including a comparison with zinc precipitation

  16. ['Gold standard', not 'golden standard'

    NARCIS (Netherlands)

    Claassen, J.A.H.R.

    2005-01-01

    In medical literature, both 'gold standard' and 'golden standard' are employed to describe a reference test used for comparison with a novel method. The term 'gold standard' in its current sense in medical research was coined by Rudd in 1979, in reference to the monetary gold standard. In the same

  17. Spectroscopic diagnostic of gold plasma

    International Nuclear Information System (INIS)

    Busquet, M.

    1986-01-01

    Results of a simulation of a gold-aluminium alloy target irradiated by laser are presented. FCI code has been used with a processing out of LTE of atomic physics of gold and of multigroup photonics. Emission and reabsorption of gold and aluminium lines are included [fr

  18. Spectroscopic diagnostic of gold plasma

    Energy Technology Data Exchange (ETDEWEB)

    Busquet, M.

    1986-06-01

    Results of a simulation of a gold-aluminium alloy target irradiated by laser are presented. FCI code has been used with a processing out of LTE of atomic physics of gold and of multigroup photonics. Emission and reabsorption of gold and aluminium lines are included.

  19. Terminalia chebula mediated green and rapid synthesis of gold nanoparticles

    Science.gov (United States)

    Mohan Kumar, Kesarla; Mandal, Badal Kumar; Sinha, Madhulika; Krishnakumar, Varadhan

    2012-02-01

    Biologically inspired experimental process in synthesising nanoparticles is of great interest in present scenario. Biosynthesis of nanoparticles is considered to be one of the best green techniques in synthesising metal nanoparticles. Here, an in situ green biogenic synthesis of gold nanoparticles using aqueous extracts of Terminalia chebula as reducing and stabilizing agent is reported. Gold nanoparticles were confirmed by surface plasmon resonance in the range of 535 nm using UV-visible spectrometry. TEM analysis revealed that the morphology of the particles thus formed contains anisotropic gold nanoparticles with size ranging from 6 to 60 nm. Hydrolysable tannins present in the extract of T. chebula are responsible for reductions and stabilization of gold nanoparticles. Antimicrobial activity of gold nanoparticles showed better activity towards gram positive S. aureus compared to gram negative E. coli using standard well diffusion method.

  20. Gold Nanoparticle Microwave Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Krantz, Kelsie E. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Christian, Jonathan H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Coopersmith, Kaitlin [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Washington, II, Aaron L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Murph, Simona H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-07-27

    At the nanometer scale, numerous compounds display different properties than those found in bulk material that can prove useful in areas such as medicinal chemistry. Gold nanoparticles, for example, display promise in newly developed hyperthermia therapies for cancer treatment. Currently, gold nanoparticle synthesis is performed via the hot injection technique which has large variability in final particle size and a longer reaction time. One underdeveloped area by which these particles could be produced is through microwave synthesis. To initiate heating, microwaves agitate polar molecules creating a vibration that gives off the heat energy needed. Previous studies have used microwaves for gold nanoparticle synthesis; however, polar solvents were used that partially absorbed incident microwaves, leading to partial thermal heating of the sample rather than taking full advantage of the microwave to solely heat the gold nanoparticle precursors in a non-polar solution. Through this project, microwaves were utilized as the sole heat source, and non-polar solvents were used to explore the effects of microwave heating only as pertains to the precursor material. Our findings show that the use of non-polar solvents allows for more rapid heating as compared to polar solvents, and a reduction in reaction time from 10 minutes to 1 minute; this maximizes the efficiency of the reaction, and allows for reproducibility in the size/shape of the fabricated nanoparticles.

  1. Bioassisted Phytomining of Gold

    Science.gov (United States)

    Maluckov, Biljana S.

    2015-05-01

    Bioassisted phytomining implies targeted use of microorganisms and plants for the selective recovery of the metal. Metals from undissolved compounds are dissolved by applying specially chosen microorganisms and therefore become available to the hyperaccumulating plants. In the article, the selective extraction method of base metals and the precious metal gold by using microorganisms and plants is discussed.

  2. Digging for Gold

    Science.gov (United States)

    Waters, John K.

    2012-01-01

    In the case of higher education, the hills are more like mountains of data that "we're accumulating at a ferocious rate," according to Gerry McCartney, CIO of Purdue University (Indiana). "Every higher education institution has this data, but it just sits there like gold in the ground," complains McCartney. Big Data and the new tools people are…

  3. GOLD PRESSURE VESSEL SEAL

    Science.gov (United States)

    Smith, A.E.

    1963-11-26

    An improved seal between the piston and die member of a piston-cylinder type pressure vessel is presented. A layer of gold, of sufficient thickness to provide an interference fit between the piston and die member, is plated on the contacting surface of at least one of the members. (AEC)

  4. Gold Nanoparticle Microwave Synthesis

    International Nuclear Information System (INIS)

    Krantz, Kelsie E.; Christian, Jonathan H.; Coopersmith, Kaitlin; Washington II, Aaron L.; Murph, Simona H.

    2016-01-01

    At the nanometer scale, numerous compounds display different properties than those found in bulk material that can prove useful in areas such as medicinal chemistry. Gold nanoparticles, for example, display promise in newly developed hyperthermia therapies for cancer treatment. Currently, gold nanoparticle synthesis is performed via the hot injection technique which has large variability in final particle size and a longer reaction time. One underdeveloped area by which these particles could be produced is through microwave synthesis. To initiate heating, microwaves agitate polar molecules creating a vibration that gives off the heat energy needed. Previous studies have used microwaves for gold nanoparticle synthesis; however, polar solvents were used that partially absorbed incident microwaves, leading to partial thermal heating of the sample rather than taking full advantage of the microwave to solely heat the gold nanoparticle precursors in a non-polar solution. Through this project, microwaves were utilized as the sole heat source, and non-polar solvents were used to explore the effects of microwave heating only as pertains to the precursor material. Our findings show that the use of non-polar solvents allows for more rapid heating as compared to polar solvents, and a reduction in reaction time from 10 minutes to 1 minute; this maximizes the efficiency of the reaction, and allows for reproducibility in the size/shape of the fabricated nanoparticles.

  5. Gold and gold working in Late Bronze Age Northern Greece

    Science.gov (United States)

    Vavelidis, M.; Andreou, S.

    2008-04-01

    Numerous objects of gold displaying an impressive variety of types and manufacturing techniques are known from the Late Bronze Age (LBA) contexts of Mycenaean Greece, but very little is known about the origin and processing of gold during the second millennium b.c. Ancient literature and recent research indicate that northern Greece is probably the richest gold-bearing region in Greece, and yet, very little evidence exists regarding the exploitation of its deposits and the production as well as use of gold in the area during prehistory. The unusual find of a group of small stone crucibles at the prehistoric settlement of Thessaloniki Toumba, one with visible traces of gold melting, proves local production and offers a rare opportunity to examine the process of on-site gold working. Furthermore, the comparison of the chemical composition of prehistoric artefacts from two settlements with those of gold deposits in their immediate areas supports the local extraction of gold and opens up the prospect for some of the Mycenaean gold to have originated in northern Greece. The scarcity of gold items in northern Greek LBA contexts may not represent the actual amount of gold produced and consumed, but could be a result of the local social attitudes towards the circulation and deposition of artefacts from precious metals.

  6. Moessbauerspectroscopy on Gold Ruby Glass

    International Nuclear Information System (INIS)

    Haslbeck, S.

    2005-01-01

    In this thesis, the chemical states of gold and the physical mechanisms of the growing process of the particles under the influence of additional ingredients like tin, lead, antimony and selenium before, during and after the colouring process are investigated by using the Moessbauer spectroscopy on 197 Au, 119 Sn and 121 Sb, optical spectroscopy and X-ray-diffraction. Gold in an unnealed, colourless state of the glasses consists of monovalent forming linear bonds to two neighbouring oxygen atoms. The Lamb-Moessbauer factor of these gold oxide bondings is observed as 0.095 at 4.2 K. The gold in it's oxide state transforms to gold particles with a diameter of 3 nm to 60 nm. The size of the gold particles is quite definable within the optical spectra and certain sizes are also discernable within the Moessbauer spectra. One component of the Moessbauer spectra is assigned to the surface layer of the gold particles. By comparing this surface component with the amount of the bulk metallic core, one can calculate the size of the gold particles. In the Moessbauer spectra of the colourless glass one also can find parts of bulk metallic gold. Investigations with X-ray diffraction show that these are gold particles with a diameter of 100 nm to 300 nm and therefore have no additional colouring effect within the visible spectrum. The Moessbauer spectra on gold of the remelt glasses are similar to those which have been measured on the initial colourless glasses

  7. For the love of gold

    International Nuclear Information System (INIS)

    Young, J.E.

    1993-01-01

    Gold is found in minute quantities and gold mining generates enormous amounts of waste materials and long history of environmental destruction: mercury in tailing, eroded land, and acid mine drainage are legacies of the past. The problem has become worse in recent years in North America, Australia, the Amazon basin, Philippines. This paper describes the economics of gold and the changes in the world economy which has precipitated the new gold rushes. Current technology uses a cyanide solution for leaching small amounts of gold from tons of waste, and mercury remains a toxic waste of gold mining. Both short and long term results of gold mining, on the environment and on indiginous populations are described

  8. Rushing for gold

    DEFF Research Database (Denmark)

    Jønsson, Jesper Bosse; Bryceson, Deborah Fahy

    2009-01-01

    African rural dwellers have faced depressed economic prospects for several decades. Now, in a number of mineral-rich countries, multiple discoveries of gold and precious stones have attracted large numbers of prospective small-scale miners. While their 'rush' to, and activities within, mining sit...... affluent than the others, suggesting that movement can be rewarding for those willing to 'try their luck' with the hard work and social networking demands of mining another site.......African rural dwellers have faced depressed economic prospects for several decades. Now, in a number of mineral-rich countries, multiple discoveries of gold and precious stones have attracted large numbers of prospective small-scale miners. While their 'rush' to, and activities within, mining sites...

  9. Gold' 82 - technical sessions

    International Nuclear Information System (INIS)

    Viewing, K.

    1983-01-01

    Sulphur-isotope studies had been applied by Dr. I. Lambert to a number of deposits in Western Australia and also to certain samples from Vubachickwe and other deposits in Zimbabwe. A study of the sulphur isotopes at the Dickenson Mine, revealed a wide spread of values in the mineralised zones. Metamorphic processes were likely to be significant in the concentration of gold. The iron formations at the Old Jardine Mine had been unfolded by Dr. W.S. Hallager and the pattern of sedimentation was unraveled. A gold-rich zone was separated by a barren gap from the other part of the mineralised zone. Research was also done on the effects of the metamorphic processes, and the ages of mineralisation

  10. Radioactive gold ring dermatitis

    International Nuclear Information System (INIS)

    Miller, R.A.; Aldrich, J.E.

    1990-01-01

    A superficial squamous cell carcinoma developed in a woman who wore a radioactive gold ring for more than 30 years. Only part of the ring was radioactive. Radiation dose measurements indicated that the dose to basal skin layer was 2.4 Gy (240 rad) per week. If it is assumed that the woman continually wore her wedding ring for 37 years since purchase, she would have received a maximum dose of approximately 4600 Gy

  11. Assessing the Equivalence of Paper, Mobile Phone, and Tablet Survey Responses at a Community Mental Health Center Using Equivalent Halves of a 'Gold-Standard' Depression Item Bank.

    Science.gov (United States)

    Brodey, Benjamin B; Gonzalez, Nicole L; Elkin, Kathryn Ann; Sasiela, W Jordan; Brodey, Inger S

    2017-09-06

    The computerized administration of self-report psychiatric diagnostic and outcomes assessments has risen in popularity. If results are similar enough across different administration modalities, then new administration technologies can be used interchangeably and the choice of technology can be based on other factors, such as convenience in the study design. An assessment based on item response theory (IRT), such as the Patient-Reported Outcomes Measurement Information System (PROMIS) depression item bank, offers new possibilities for assessing the effect of technology choice upon results. To create equivalent halves of the PROMIS depression item bank and to use these halves to compare survey responses and user satisfaction among administration modalities-paper, mobile phone, or tablet-with a community mental health care population. The 28 PROMIS depression items were divided into 2 halves based on content and simulations with an established PROMIS response data set. A total of 129 participants were recruited from an outpatient public sector mental health clinic based in Memphis. All participants took both nonoverlapping halves of the PROMIS IRT-based depression items (Part A and Part B): once using paper and pencil, and once using either a mobile phone or tablet. An 8-cell randomization was done on technology used, order of technologies used, and order of PROMIS Parts A and B. Both Parts A and B were administered as fixed-length assessments and both were scored using published PROMIS IRT parameters and algorithms. All 129 participants received either Part A or B via paper assessment. Participants were also administered the opposite assessment, 63 using a mobile phone and 66 using a tablet. There was no significant difference in item response scores for Part A versus B. All 3 of the technologies yielded essentially identical assessment results and equivalent satisfaction levels. Our findings show that the PROMIS depression assessment can be divided into 2 equivalent

  12. Immunological properties of gold nanoparticles.

    Science.gov (United States)

    Dykman, Lev A; Khlebtsov, Nikolai G

    2017-03-01

    In the past decade, gold nanoparticles have attracted strong interest from the nanobiotechnological community owing to the significant progress made in robust and easy-to-make synthesis technologies, in surface functionalization, and in promising biomedical applications. These include bioimaging, gene diagnostics, analytical sensing, photothermal treatment of tumors, and targeted delivery of various biomolecular and chemical cargos. For the last-named application, gold nanoparticles should be properly fabricated to deliver the cargo into the targeted cells through effective endocytosis. In this review, we discuss recent progress in understanding the selective penetration of gold nanoparticles into immune cells. The interaction of gold nanoparticles with immune cell receptors is discussed. As distinct from other published reviews, we present a summary of the immunological properties of gold nanoparticles. This review also summarizes what is known about the application of gold nanoparticles as an antigen carrier and adjuvant in immunization for the preparation of antibodies in vivo . For each of the above topics, the basic principles, recent advances, and current challenges are discussed. Thus, this review presents a detailed analysis of data on interaction of gold nanoparticles with immune cells. Emphasis is placed on the systematization of data over production of antibodies by using gold nanoparticles and adjuvant properties of gold nanoparticles. Specifically, we start our discussion with current data on interaction of various gold nanoparticles with immune cells. The next section describes existing technologies to improve production of antibodies in vivo by using gold nanoparticles conjugated with specific ligands. Finally, we describe what is known about adjuvant properties of bare gold or functionalized nanoparticles. In the Conclusion section, we present a short summary of reported data and some challenges and perspectives.

  13. Ligand-Enhanced Optical Response of Gold Nanomolecules and Its Fragment Projection Analysis: The Case of Au 30 (SR) 18

    Energy Technology Data Exchange (ETDEWEB)

    Sementa, Luca; Barcaro, Giovanni; Baseggio, Oscar; De Vetta, Martina; Dass, Amala; Apra, Edoardo; Stener, Mauro; Fortunelli, Alessandro

    2017-01-10

    Here we investigate via first-principles simulations the optical absorption spectra of three different Au30(SR)18 monolayer-protected clusters (MPC): Au30(StBu)18, which is known in the literature and whose crystal structure is available, and two species – Au30(SPh)18 and Au30(SPh-pNO2)18 – which have been designed by replacing the tert-butyl organic residues with aromatic ones so as to investigate the effects of ligand replacement on the optical response of Au nanomolecules. In analogy with previously studied but rather different Au23(SR)16- anionic species, a substantial ligand-enhancement of the absorption intensity in the optical region is obtained for the Au30(SPhpNO2)18 neutral MPC. This demonstrates that using conjugated aromatic ligands with properly chosen electron withdrawal substituents and exhibiting steric hindrance so as to also achieve charge decompression at the surface is a general approach to enhance MPC photo-absorption intensity in the optical region. Moreover, the ligand-enhancement phenomenon is subjected to a detailed analysis based on fragment projection of electronic excited states and on induced transition densities, leading to a better understanding of its physical origin, thus opening avenues to its more precise control and exploitation.

  14. The extractive metallurgy of gold

    Energy Technology Data Exchange (ETDEWEB)

    Kongolo, K.; Mwema, M.D. [University of Lubumbashi, Zaire, Gecamines Metallurgical Research Centre, Likasi, Zaire, c/o Gecamines Brussels (Belgium)

    1998-12-15

    Moessbauer spectroscopy has been successfully used in investigation of the gold compounds present in ores and the gold species which occur during the process metallurgy of this metal. This paper is a survey of the basic recovery methods and techniques used in extractive metallurgy of gold. Process fundamentals on mineral processing, ore leaching, zinc dust cementation, adsorption on activated carbon, electrowinning and refining are examined. The recovery of gold as a by-product of the copper industry is also described. Alternative processing methods are indicated in order to shed light on new interesting research topics where Moessbauer spectroscopy could be applied.

  15. The extractive metallurgy of gold

    Science.gov (United States)

    Kongolo, K.; Mwema, M. D.

    1998-12-01

    Mössbauer spectroscopy has been successfully used in investigation of the gold compounds present in ores and the gold species which occur during the process metallurgy of this metal. This paper is a survey of the basic recovery methods and techniques used in extractive metallurgy of gold. Process fundamentals on mineral processing, ore leaching, zinc dust cementation, adsorption on activated carbon, electrowinning and refining are examined. The recovery of gold as a by-product of the copper industry is also described. Alternative processing methods are indicated in order to shed light on new interesting research topics where Mössbauer spectroscopy could be applied.

  16. The extractive metallurgy of gold

    International Nuclear Information System (INIS)

    Kongolo, K.; Mwema, M.D.

    1998-01-01

    Moessbauer spectroscopy has been successfully used in investigation of the gold compounds present in ores and the gold species which occur during the process metallurgy of this metal. This paper is a survey of the basic recovery methods and techniques used in extractive metallurgy of gold. Process fundamentals on mineral processing, ore leaching, zinc dust cementation, adsorption on activated carbon, electrowinning and refining are examined. The recovery of gold as a by-product of the copper industry is also described. Alternative processing methods are indicated in order to shed light on new interesting research topics where Moessbauer spectroscopy could be applied

  17. Surface-stabilized gold nanocatalysts

    Science.gov (United States)

    Dai, Sheng [Knoxville, TN; Yan, Wenfu [Oak Ridge, TN

    2009-12-08

    A surface-stabilized gold nanocatalyst includes a solid support having stabilizing surfaces for supporting gold nanoparticles, and a plurality of gold nanoparticles having an average particle size of less than 8 nm disposed on the stabilizing surfaces. The surface-stabilized gold nanocatalyst provides enhanced stability, such as at high temperature under oxygen containing environments. In one embodiment, the solid support is a multi-layer support comprising at least a first layer having a second layer providing the stabilizing surfaces disposed thereon, the first and second layer being chemically distinct.

  18. 31 CFR 100.4 - Gold coin and gold certificates in general.

    Science.gov (United States)

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Gold coin and gold certificates in... EXCHANGE OF PAPER CURRENCY AND COIN In General § 100.4 Gold coin and gold certificates in general. Gold coins, and gold certificates of the type issued before January 30, 1934, are exchangeable, as provided...

  19. Determining gold content

    International Nuclear Information System (INIS)

    Clayton, C.G.; Wormald, M.R.

    1981-01-01

    A method for determining the gold content of a material, comprises irradiating a body of the material with neutrons and determining the intensity of γ-rays having an energy of 279 keV arising from the reaction 179 Au(nn') 179 Au → 279 keV. The apparatus has means for conveying the materials past an assembly, which has a neutron source, which does not produce neutrons having sufficient energy to excite fast neutron reactions in non-auriferous constituents. (author)

  20. Turning lead into gold

    DEFF Research Database (Denmark)

    Jensen, Steffen Moltrup Ernø

    For years the field of entrepreneurship has been blinded by the alchemical promise of turning lead into gold, of finding the ones most likely to become the next Branson, Zuckerberg or Gates. The promise has been created in the midst of political and scientific agendas where certain individuals...... is not to accumulate state or market wealth, but for entrepreneurial skills to become tools towards the liberation of the individual from oppressive systems of control – essentially to add public value rather than economic value. In this presentation I will sketch an anarchist perspective on entrepreneurship, looking...

  1. Determination of Gold from Gold Matrix of North Western Nigeria ...

    African Journals Online (AJOL)

    The research paper presents analytical results of Au, Mn and V concentrations of some Nigerian gold ores using two techniques: epithermal neutron activation analysis (ENAA) and proton induced X-ray emission (PIXE). Fourteen samples were collected from gold fields of North Western Nigeria, prepared separately to a ...

  2. Mercury use in small scale gold mining in Ghana: an assessment of its impact on miners

    International Nuclear Information System (INIS)

    Biagya, Robert Yakubu

    2002-12-01

    Small scale gold mining is responsible for about 5% of Ghana’s annual gold production. It is estimated that between 80,000 and 100,000 people are engaged in small scale gold mining either on part-time or permanent basis. Amalgamation is the preferred method used by small scale gold miners for extracting free gold from its ores. The rate at which mercury, an important input in this method, is discharged into the atmosphere and water bodies is alarming. This research describes the various mining and processing methods in small scale gold mining and the extent of mercury use and releases to the environment. It discusses mercury and its human and environmental effects. It defines the various forms of mercury, routes of exposure, toxic effects. The levels of exposure to mercury by all groups of small scale gold miners are determined, and the impacts on the miners and the environment are assessed. It concludes that: • Mercury is mainly released into the environment as a result of small scale gold mining through spillage of elemental mercury and evaporation of mercury from the amalgam and sponge gold when they are heated on open fire. • Mercury in environmental samples from small scale gold mining areas is well above standard limit values. • Mercury released into the environment through small scale gold mining impacts negatively on the miners themselves and the general environment. Finally, it recommends the need for the adoption of mercury emission reduction strategies for dealing with the mercury problem. (au)

  3. Tamper indicating gold nanocup plasmonic films

    Energy Technology Data Exchange (ETDEWEB)

    DeVetter, Brent M.; Bernacki, Bruce E.; Bennett, Wendy D.; Schemer-Kohrn, Alan; Alvine, Kyle J.

    2017-02-13

    The spectral signature of nanoplasmonic films are both robust and tailorable with optical responses ranging from the visible to the near-infrared. We present the development of flexible, elastomeric nanoplasmonic films consisting of periodic arrays of gold nanocups as tamper indicating films. Gold nanocups have polarization-sensitive optical properties that may be manufactured into films that offer unique advantages for tamper indication. These flexible films can be made quickly and at low-cost using commercially available monodisperse polystyrene nanospheres through self-assembly followed by plasma etching, metal deposition, and lift-off from a sacrificial substrate. Polarization- and angle-dependent optical spectroscopic measurements were performed to characterize the fabricated films. Using polarization-sensitive hyperspectral imaging, we demonstrate how these films can be applied to tamper indication and counterfeit resistance applications.

  4. Activation analysis in gold industry

    International Nuclear Information System (INIS)

    Kist, A. A.

    2003-01-01

    Nuclear techniques and methods were, are, and will be very important for many fields of science, agriculture, industry, etc. Among other examples one can remember role of the nuclear medicine (radiotherapy and radiodiagnostic methods) or semiconductors (communication, computing, information, etc.) which industrial production has been on initial stage based on activation analysis. One of very illustrative examples is application of nuclear methods in gold industry. This is given by favorable nuclear properties of gold. Uzbekistan is one of the main producers of gold. Open-cast mining and hydro metallurgic extraction (using leaching by cyanide and sorption by ion-exchange resin) is the mostly used technology. The typical gold ores are sulfide and contain elevated concentration of As and Sb. That needs special technology of gold extraction. Importance of gold for Uzbekistan economy is a reason why for many years there are carried out studies concerning to gold production. These studies include also nuclear methods and their results are successfully used in gold industry. The present paper gives a brief overview for period of 25 years. For many reasons most of these studies were not published before completely. Despite some results are obtained decades ago we decided to present the overview as an example how nuclear methods can cover requirements of the whole process. We are trying to sort these studies according to methods and applications

  5. Polyvinylpyrrolidone-coated gold nanoparticles inhibit endothelial cell viability, proliferation, and ERK1/2 phosphorylation and reduce the magnitude of endothelial-independent dilator responses in isolated aortic vessels

    Directory of Open Access Journals (Sweden)

    Mohamed T

    2017-12-01

    viability/proliferation. These inhibitory effects were lost after 48 hours’ exposure (except for the PVP-modified AuNPs. Furthermore, all AuNPs decreased acetylcholine (ACh-induced phosphorylation of ERK1/2, a key signaling protein of cell function. mPEG-modified AuNPs had lower cytostatic effects than PVP-modified AuNPs. Citrate-stabilized AuNPs did not alter endothelial-dependent vasodilation induced by ACh, but attenuated endothelial-independent responses induced by sodium nitroprusside. PVP-modified AuNPs attenuated ACh-induced dilation, whereas mPEG-modified AuNPs did not, though this was dose-related.Conclusion: We demonstrated that mPEG-modified AuNPs at a therapeutic dosage showed lower cytostatic effects and were less detrimental to vasodilator function than PVP-modified AuNPs, indicating greater potential as agents for diagnostic imaging and therapy. Keywords: nanoparticles, gold, vascular, vasodilation, artery, cell culture

  6. Stealing the Gold

    International Nuclear Information System (INIS)

    Whittington, S G

    2005-01-01

    Stealing the Gold presents a survey of some of the most exciting topics in condensed matter physics today, from the perspective of the pioneering work of Sam Edwards. Original articles from leaders in the field, including several Nobel laureates, highlight the historical development as well as new and emerging areas. This book would be of interest to graduate students and researchers in condensed matter physics, statistical physics and theoretical physics. Over the course of nearly half a century, Sam Edwards has led the field of condensed matter physics in new directions, ranging from the electronic and statistical properties of disordered materials to the mechanical properties of granular materials. Along the way he has provided seminal contributions to fluid mechanics, polymer science, surface science and statistical mechanics. This volume celebrates the immense scope of his influence by presenting a collection of original articles by recognized leaders in theoretical physics, including two Nobel laureates and a Fields medalist, which describe the genesis, evolution and future prospects of the various sub-fields of condensed matter theory, along with reprints of a selection of Edwards' seminal papers that helped give birth to the subject. Stealing the Gold, Edwards' favourite caricature of the relationship between theoretical physicists and nature, will be of singular interest to graduate students looking for an overview of some of the most exciting areas of theoretical physics, as well as to researchers in condensed matter physics looking for a comprehensive, broad and uniquely incisive snapshot of their subject at the dawn of the 21st century. (book review)

  7. The gold standard: gold nanoparticle libraries to understand the nano-bio interface.

    Science.gov (United States)

    Alkilany, Alaaldin M; Lohse, Samuel E; Murphy, Catherine J

    2013-03-19

    Since the late 1980s, researchers have prepared inorganic nanoparticles of many types--including elemental metals, metal oxides, metal sulfides, metal selenides, and metal tellurides--with excellent control over size and shape. Originally many researchers were primarily interested in exploring the quantum size effects predicted for such materials. Applications of inorganic nanomaterials initially centered on physics, optics, and engineering but have expanded to include biology. Many current nanomaterials can serve as biochemical sensors, contrast agents in cellular or tissue imaging, drug delivery vehicles, or even as therapeutics. In this Account we emphasize that the understanding of how nanomaterials will function in a biological system relies on the knowledge of the interface between biological systems and nanomaterials, the nano-bio interface. Gold nanoparticles can serve as excellent standards to understand more general features of the nano-bio interface because of its many advantages over other inorganic materials. The bulk material is chemically inert, and well-established synthetic methods allow researchers to control its size, shape, and surface chemistry. Gold's background concentration in biological systems is low, which makes it relatively easy to measure it at the part-per-billion level or lower in water. In addition, the large electron density of gold enables relatively simple electron microscopic experiments to localize it within thin sections of cells or tissue. Finally, gold's brilliant optical properties at the nanoscale are tunable with size, shape, and aggregation state and enable many of the promising chemical sensing, imaging, and therapeutic applications. Basic experiments with gold nanoparticles and cells include measuring the toxicity of the particles to cells in in vitro experiments. The species other than gold in the nanoparticle solution can be responsible for the apparent toxicity at a particular dose. Once the identity of the toxic

  8. Size control synthesis of starch capped-gold nanoparticles

    International Nuclear Information System (INIS)

    Tajammul Hussain, S.; Iqbal, M.; Mazhar, M.

    2009-01-01

    Metallic gold nanoparticles have been synthesized by the reduction of chloroaurate anions [AuCl 4 ] - solution with hydrazine in the aqueous starch and ethylene glycol solution at room temperature and at atmospheric pressure. The characterization of synthesized gold nanoparticles by UV-vis spectroscopy, high resolution transmission electron microscopy (HRTEM), electron diffraction analysis, X-ray diffraction (XRD), and X-rays photoelectron spectroscopy (XPS) indicate that average size of pure gold nanoparticles is 3.5 nm, they are spherical in shape and are pure metallic gold. The concentration effects of [AuCl 4 ] - anions, starch, ethylene glycol, and hydrazine, on particle size, were investigated, and the stabilization mechanism of Au nanoparticles by starch polymer molecules was also studied by FT-IR and thermogravimetric analysis (TGA). FT-IR and TGA analysis shows that hydroxyl groups of starch are responsible of capping and stabilizing gold nanoparticles. The UV-vis spectrum of these samples shows that there is blue shift in surface plasmon resonance peak with decrease in particle size due to the quantum confinement effect, a supporting evidence of formation of gold nanoparticles and this shift remains stable even after 3 months.

  9. Prehospital Emergencies in Illegal Gold Mining Sites in French Guiana.

    Science.gov (United States)

    Egmann, Gérald; Tattevin, Pierre; Palancade, Renaud; Nacher, Matthieu

    2018-03-01

    Illegal gold mining is flourishing in French Guiana, existing outside the law due to both the high cost of gold mining permits and the challenges of law enforcement within the Amazon forest. We report the characteristics of, and the medical responses to, medical emergencies in illegal gold mining sites. We performed a retrospective study of all medical emergencies reported from illegal gold mining sites to the centralized call office of SAMU 973 from 1998 through 2000 and from 2008 through 2010. According to the national health care system, any medical emergency within the territory is handled by the prehospital emergency medical service (SAMU 973), irrespective of the patients' legal status. Data were extracted from the SAMU 973 notebook registry (1998-2000) or the SAMU 973 computerized database (2008-2010) and werre collected using a standardized questionnaire. Of 71,932 calls for medical emergencies in French Guiana during the study periods, 340 (0.5%) originated from illegal gold mining sites. Of these, 196 (58%) led to medical evacuation by helicopter, whereas the overall rate of evacuation by helicopter after placing a call to SAMU 973 was only 4% (3020/71,932; PAmazon forest mostly include infectious diseases, followed by trauma, and often require medical evacuation by helicopter. Our study suggests that implementation of preventive medicine within gold mining sites, irrespective of their legal status, could be cost-effective and reduce morbidity. Copyright © 2017 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.

  10. Directed Assembly of Gold Nanoparticles

    DEFF Research Database (Denmark)

    Westerlund, Axel Rune Fredrik; Bjørnholm, Thomas

    2009-01-01

    As a complement to common "top-down" lithography techniques, "bottom-up" assembly techniques are emerging as promising tools to build nanoscale structures in a predictable way. Gold nanoparticles that are stable and relatively easy to synthesize are important building blocks in many such structures...... due to their useful optical and electronic properties. Programmed assembly of gold nanoparticles in one, two, and three dimensions is therefore of large interest. This review focuses on the progress from the last three years in the field of directed gold nanoparticle and nanorod assembly using...

  11. GOLD and the fixed ratio

    Directory of Open Access Journals (Sweden)

    Vestbo J

    2012-09-01

    Full Text Available Jørgen VestboUniversity of Manchester, Manchester, UKI read with interest the paper entitled "Diagnosis of airway obstruction in the elderly: contribution of the SARA study" by Sorino et al in a recent issue of this journal.1 Being involved in the Global Initiative for Obstructive Lung Diseases (GOLD, it is nice to see the interest sparked by the GOLD strategy document. However, in the paper by Sorino et al, there are a few misunderstandings around GOLD and the fixed ratio (forced expiratory volume in 1 second/forced volume vital capacity < 0.70 that need clarification.View original paper by Sorino and colleagues.

  12. Enhancement of gold recovery using bioleaching from gold concentrate

    Science.gov (United States)

    Choi, S. H.; Cho, K. H.; Kim, B. J.; Choi, N. C.; Park, C. Y.

    2012-04-01

    The gold in refractory ores is encapsulated as fine particles (sometimes at a molecular level) in the crystal structure of the sulfide (typically pyrite with or without arsenopyrite) matrix. This makes it impossible to extract a significant amount of refractory gold by cyanidation since the cyanide solution cannot penetrate the pyrite/arsenopyrite crystals and dissolve gold particles, even after fine grinding. To effectively extract gold from these ores, an oxidative pretreatment is necessary to break down the sulfide matrix. The most popular methods of pretreatment include nitric acid oxidation, roasting, pressure oxidation and biological oxidation by microorganisms. This study investigated the bioleaching efficiency of Au concentrate under batch experimental conditions (adaptation cycles and chemical composition adaptation) using the indigenous acidophilic bacteria collected from gold mine leachate in Sunsin gold mine, Korea. We conducted the batch experiments at two different chemical composition (CuSO4 and ZnSO4), two different adaptation cycles 1'st (3 weeks) and 2'nd (6 weeks). The results showed that the pH in the bacteria inoculating sample decreased than initial condition and Eh increased. In the chemical composition adaptation case, the leached accumulation content of Fe and Pb was exhibited in CuSO4 adaptation bacteria sample more than in ZnSO4 adaptation bacteria samples, possibly due to pre-adaptation effect on chalcopyrite (CuFeS2) in gold concentrate. And after 21 days on the CuSO4 adaptation cycles case, content of Fe and Pb was appeared at 1'st adaptation bacteria sample(Fe - 1.82 and Pb - 25.81 times per control sample) lower than at 2'nd adaptation bacteria sample(Fe - 2.87 and Pb - 62.05 times per control sample). This study indicates that adaptation chemical composition and adaptation cycles can play an important role in bioleaching of gold concentrate in eco-/economic metallurgy process.

  13. In harmony with gold and uranium

    International Nuclear Information System (INIS)

    Anon.

    1983-01-01

    A profile is given on Mr Clive Knobbs as managing director of Harmony gold mine. From March 1 1983 he succeeded as deputy chairman of the group's gold and uranium division, and became the Rand Mines representative on the Gold Producers Committee and the Executive Committee of the Chamber of Mines. The article also takes a look at gold and uranium mining in general

  14. 41 CFR 101-45.002 - Gold.

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 2 2010-07-01 2010-07-01 true Gold. 101-45.002 Section... PERSONAL PROPERTY § 101-45.002 Gold. (a) Gold will be sold in accordance with this section and part 102-38 of the Federal Management Regulation. (b) Sales of gold shall be processed to— (1) Use the sealed bid...

  15. Improved Adhesion of Gold Thin Films Evaporated on Polymer Resin: Applications for Sensing Surfaces and MEMS

    Directory of Open Access Journals (Sweden)

    Behrang Moazzez

    2013-05-01

    Full Text Available We present and analyze a method to improve the morphology and mechanical properties of gold thin films for use in optical sensors or other settings where good adhesion of gold to a substrate is of importance and where controlled topography/roughness is key. To improve the adhesion of thermally evaporated gold thin films, we introduce a gold deposition step on SU-8 photoresist prior to UV exposure but after the pre-bake step of SU-8 processing. Shrinkage and distribution of residual stresses, which occur during cross-linking of the SU-8 polymer layer in the post-exposure baking step, are responsible for the higher adhesion of the top gold film to the post-deposition cured SU-8 sublayer. The SU-8 underlayer can also be used to tune the resulting gold film morphology. Our promoter-free protocol is easily integrated with existing sensor microfabrication processes.

  16. Size fraction assaying of gold bearing rocks (for gold extraction) by ...

    African Journals Online (AJOL)

    A novel method has been developed for processing and extraction of gold from gold bearing rocks for use by small-scale gold miners in Ghana. The methodology involved crushing of gold bearing hard rocks to fine particles to form a composite sample and screening at a range of sizes. Gold distribution in the composite ...

  17. Two-photon luminescence microscopy of field enhancement at gold nanoparticles

    DEFF Research Database (Denmark)

    Beermann, Jonas; Bozhevolnyi, Sergey I.

    2005-01-01

    Using a reflection scanning optical microscope detecting two-photon luminescence (TPL) we have imaged square gold bumps positioned in a periodic array either on a smooth gold film or directly on a glass substrate. The second-harmonic (SH) and TPL response from these structures show both...

  18. Gold--a controversial sensitizer

    DEFF Research Database (Denmark)

    Bruze, M; Andersen, Klaus Ejner

    1999-01-01

    allergy to gold sodium thiosulfate were published at the beginning of the 1990s, the allergic nature of the reported positive patch test reactions to gold was questioned. The major argument for such questioning was the lack of demonstrable clinical relevance in most positive reactors. A major reason......Until recently, gold allergy was considered to be extremely rare. Gold has been used and worshipped for thousands of years without any obvious complaints of skin problems, either in those participating in mining and other ways of prospecting, or in those wearing jewellery. When studies on contact...... for the questioning may have been confusion in differentiating between contact allergy and allergic contact dermatitis. To arrive at a diagnosis of allergic contact dermatitis, 3 steps have, in principle, to be fulfilled: (i) establishment of contact allergy; (ii) demonstration of present exposure; (iii) assessment...

  19. Gold, currencies and market efficiency

    Science.gov (United States)

    Kristoufek, Ladislav; Vosvrda, Miloslav

    2016-05-01

    Gold and currency markets form a unique pair with specific interactions and dynamics. We focus on the efficiency ranking of gold markets with respect to the currency of purchase. By utilizing the Efficiency Index (EI) based on fractal dimension, approximate entropy and long-term memory on a wide portfolio of 142 gold price series for different currencies, we construct the efficiency ranking based on the extended EI methodology we provide. Rather unexpected results are uncovered as the gold prices in major currencies lay among the least efficient ones whereas very minor currencies are among the most efficient ones. We argue that such counterintuitive results can be partly attributed to a unique period of examination (2011-2014) characteristic by quantitative easing and rather unorthodox monetary policies together with the investigated illegal collusion of major foreign exchange market participants, as well as some other factors discussed in some detail.

  20. Optical trapping of gold aerosols

    DEFF Research Database (Denmark)

    Schmitt, Regina K.; Pedersen, Liselotte Jauffred; Taheri, S. M.

    2015-01-01

    Aerosol trapping has proven challenging and was only recently demonstrated.1 This was accomplished by utilizing an air chamber designed to have a minimum of turbulence and a laser beam with a minimum of aberration. Individual gold nano-particles with diameters between 80 nm and 200 nm were trapped...... in air using a 1064 nm laser. The positions visited by the trapped gold nano-particle were quantified using a quadrant photo diode placed in the back focal plane. The time traces were analyzed and the trapping stiffness characterizing gold aerosol trapping determined and compared to aerosol trapping...... of nanometer sized silica and polystyrene particles. Based on our analysis, we concluded that gold nano-particles trap more strongly in air than similarly sized polystyrene and silica particles. We found that, in a certain power range, the trapping strength of polystyrene particles is linearly decreasing...

  1. Biomass processing over gold catalysts

    CERN Document Server

    Simakova, Olga A; Murzin, Dmitry Yu

    2014-01-01

    The book describes the valorization of biomass-derived compounds over gold catalysts. Since biomass is a rich renewable feedstock for diverse platform molecules, including those currently derived from petroleum, the interest in various transformation routes has become intense. Catalytic conversion of biomass is one of the main approaches to improving the economic viability of biorefineries.  In addition, Gold catalysts were found to have outstanding activity and selectivity in many key reactions. This book collects information about transformations of the most promising and important compounds derived from cellulose, hemicelluloses, and woody biomass extractives. Since gold catalysts possess high stability under oxidative conditions, selective oxidation reactions were discussed more thoroughly than other critical reactions such as partial hydrogenation, acetalization, and isomerization. The influence of reaction conditions, the role of the catalyst, and the advantages and disadvantages of using gold are pre...

  2. Immunological properties of gold nanoparticles

    OpenAIRE

    Dykman, Lev A.; Khlebtsov, Nikolai G.

    2016-01-01

    In the past decade, gold nanoparticles have attracted strong interest from the nanobiotechnological community owing to the significant progress made in robust and easy-to-make synthesis technologies, in surface functionalization, and in promising biomedical applications. These include bioimaging, gene diagnostics, analytical sensing, photothermal treatment of tumors, and targeted delivery of various biomolecular and chemical cargos. For the last-named application, gold nanoparticles should be...

  3. Biosensors based on gold nanostructures

    OpenAIRE

    Vidotti,Marcio; Carvalhal,Rafaela F.; Mendes,Renata K.; Ferreira,Danielle C. M.; Kubota,Lauro T.

    2011-01-01

    The present review discusses the latest advances in biosensor technology achieved by the assembly of biomolecules associated with gold nanoparticles in analytical devices. This review is divided in sections according to the biomolecule employed in the biosensor development: (i) immunocompounds; (ii) DNA/RNA and functional DNA/RNA; and (iii) enzymes and Heme proteins. In order to facilitate the comprehension each section was subdivided according to the transduction mode. Gold nanoparticles bas...

  4. Characterisation of gold from Fiji

    OpenAIRE

    Naden, Jon; Henney, P.J.

    1995-01-01

    This is a study of the variation in chemistry and inclusion mineralogy of bedrock and placer gold from Fiji. It forms part of a large project, undertaking gold characterisation from a wide range of geological environments in Ecuador, Zimbabwe, Malaysia and Fiji. The work was carried out under the Overseas Development AdministratiodBritish Geological Survey Technology Development and Research programme (Project R5549) as part of the British Government’s provision of technical...

  5. Goldenphilicity: Luminescent gold compounds

    International Nuclear Information System (INIS)

    Sansores, L.E.

    2002-01-01

    In the solids and molecules different types of bonds are presented depending on the involved atoms, covalent bonds are common among elements of open shell, where more bond orbitals are filled than anti bond orbitals. It is expected that ionic bonds among closed shell atoms which have charges of opposite sign. Bonds type Van der Waals are presented among molecules which have a bipolar moment. It would not be expected bonds among zero charge species, or more generally with the same nominal charge and in any case the attractive forces would be very small. In fact it is expected that two metallic cations to be repelled each other. There recently is evidence that in organic or organometallic compounds could exist attractive interactions between two cations of the d 8 -d 10 -s 2 families. These bonds are weak but stronger than those of Van der Waals. They are compared with the hydrogen bonds. In this work it was reviewed some examples in which the goldenphilicity plays an important role in the luminescence that the gold complexes present. Examples of mono, bi and trinuclear and the structures that these organometallic compounds could take are examined. (Author)

  6. Pulse-voltammetric glucose detection at gold junction electrodes.

    Science.gov (United States)

    Rassaei, Liza; Marken, Frank

    2010-09-01

    A novel glucose sensing concept based on the localized change or "modulation" in pH within a symmetric gold-gold junction electrode is proposed. A paired gold-gold junction electrode (average gap size ca. 500 nm) is prepared by simultaneous bipotentiostatic electrodeposition of gold onto two closely spaced platinum disk electrodes. For glucose detection in neutral aqueous solution, the potential of the "pH-modulator" electrode is set to -1.5 V vs saturated calomel reference electrode (SCE) to locally increase the pH, and simultaneously, either cyclic voltammetry or square wave voltammetry experiments are conducted at the sensor electrode. A considerable improvement in the sensor electrode response is observed when a normal pulse voltammetry sequence is applied to the modulator electrode (to generate "hydroxide pulses") and the glucose sensor electrode is operated with fixed bias at +0.5 V vs SCE (to eliminate capacitive charging currents). Preliminary data suggest good linearity for the glucose response in the medically relevant 1-10 mM concentration range (corresponding to 0.18-1.8 g L(-1)). Future electroanalytical applications of multidimensional pulse voltammetry in junction electrodes are discussed.

  7. Positron emission tomography response criteria in solid tumours criteria for quantitative analysis of [18F]-fluorodeoxyglucose positron emission tomography with integrated computed tomography for treatment response assessment in metastasised solid tumours: All that glitters is not gold.

    Science.gov (United States)

    Willemsen, Annelieke E C A B; Vlenterie, Myrella; van Herpen, Carla M L; van Erp, Nielka P; van der Graaf, Winette T A; de Geus-Oei, Lioe-Fee; Oyen, Wim J G

    2016-03-01

    For solid tumours, quantitative analysis of [(18)F]-fluorodeoxyglucose positron emission tomography with integrated computed tomography potentially can have significant value in early response assessment and thereby discrimination between responders and non-responders at an early stage of treatment. Standardised strategies for this analysis have been proposed, and the positron emission tomography response criteria in solid tumours (PERCIST) criteria can be regarded as the current standard to perform quantitative analysis in a research setting, yet is not implemented in daily practice. However, several exceptions and limitations limit the feasibility of PERCIST criteria. In this article, we point out dilemmas that arise when applying proposed criteria like PERCIST on an expansive set of patients with metastasised solid tumours. Clinicians and scientists should be aware of these limitations to prevent that methodological issues impede successful introduction of research data into clinical practice. Therefore, to deliver on the high potential of quantitative imaging, consensus should be reached on a standardised, feasible and clinically useful analysis methodology. This methodology should be applicable in the majority of patients, tumour types and treatments. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Structure and bonding in gold compounds

    International Nuclear Information System (INIS)

    Parish, R.V.

    1988-01-01

    Recent developments in chemical applications of 197 Au Moessbauer spectroscopy are reviewed. For gold(I) and gold(III), systematic variations in isomer shift and quadrupole splitting are seen as the ligands are changed; the effects of change in coordination number of the gold atoms are also systematic. Data for gold(II) systems involving gold-gold bonds lie between those for corresponding gold(I) and gold(III) materials, showing a small increase in isomer shift and a larger increase in quadrupole splitting as the oxidation state decreases; these trends are explained in terms of the structures. Data for mixed-metal cluster compounds are much more sensitive to structural effects than in homonuclear clusters. Both sets of data show systematic changes with increase in the number of metal atoms to which the gold atom is bound. The connectivity also influences the recoil-free fraction. (orig.)

  9. Geometric effect on second harmonic generation from gold grating

    Science.gov (United States)

    Lu, Jiao; Ding, Baoyong; Huo, Yanyan; Ning, Tingyin

    2018-05-01

    We numerically investigate second harmonic generation from gold gratings of an ideal rectangular and ladder-shaped cross-section. The SHG efficiency from the gold gratings of the ladder-shaped cross-section is significantly enhanced compared with that from the ideal rectangular cross-section with a maximum enhancement factor of around two. The enhancement is ascribe to the nanostructure dependent local fundamental electric field, the nonlinear sources and thus the far field radiation. Our results have a practical meaning in the explanation of experimental SHG measurement, and the modulation of SHG response in the metallic nanostructure.

  10. Annealing relaxation of ultrasmall gold nanostructures

    Science.gov (United States)

    Chaban, Vitaly

    2015-01-01

    Except serving as an excellent gift on proper occasions, gold finds applications in life sciences, particularly in diagnostics and therapeutics. These applications were made possible by gold nanoparticles, which differ drastically from macroscopic gold. Versatile surface chemistry of gold nanoparticles allows coating with small molecules, polymers, biological recognition molecules. Theoretical investigation of nanoscale gold is not trivial, because of numerous metastable states in these systems. Unlike elsewhere, this work obtains equilibrium structures using annealing simulations within the recently introduced PM7-MD method. Geometries of the ultrasmall gold nanostructures with chalcogen coverage are described at finite temperature, for the first time.

  11. Phage based green chemistry for gold ion reduction and gold retrieval.

    Science.gov (United States)

    Setyawati, Magdiel I; Xie, Jianping; Leong, David T

    2014-01-22

    The gold mining industry has taken its toll on the environment, triggering the development of more environmentally benign processes to alleviate the waste load release. Here, we demonstrate the use of bacteriophages (phages) for biosorption and bioreduction of gold ions from aqueous solution, which potentially can be applied to remediate gold ions from gold mining waste effluent. Phage has shown a remarkably efficient sorption of gold ions with a maximum gold adsorption capacity of 571 mg gold/g dry weight phage. The product of this phage mediated process is gold nanocrystals with the size of 30-630 nm. Biosorption and bioreduction processes are mediated by the ionic and covalent interaction between gold ions and the reducing groups on the phage protein coat. The strategy offers a simple, ecofriendly and feasible option to recover of gold ions to form readily recoverable products of gold nanoparticles within 24 h.

  12. Development of a gold-nanostructured surface for amperometric genosensors

    Energy Technology Data Exchange (ETDEWEB)

    Zanardi, Chiara, E-mail: chiara.zanardi@unimore.it [Universita di Modena e Reggio Emilia, Dipartimento di Chimica (Italy); Baldoli, Clara, E-mail: clara.baldoli@istm.cnr.it [Istituto di Scienze e Tecnologie Molecolari del CNR (Italy); Licandro, Emanuela [Universita degli Studi di Milano, Dipartimento di Chimica Organica ed Industriale (Italy); Terzi, Fabio; Seeber, Renato [Universita di Modena e Reggio Emilia, Dipartimento di Chimica (Italy)

    2012-10-15

    A gold-nanostructured surface has been obtained by stable deposition of chemically synthesized gold nanoparticles (2.1-5.5 nm size range) on a gold substrate through a dithiol linker. The method proposed for the obtainment of the nanostructure is suitable for the further stable anchoring of a peptide nucleic acid oligomer through four amine groups of lysine terminal residues, leading to fairly reproducible systems. The geometric area of the nanostructured surface is compared with those of a smooth and of an electrochemically generated nanostructured surface by depositing a probe bearing an electrochemically active ferrocene residue. Despite the area of the two nanostructures being quite similar, the response toward a 2 nM target oligonucleotide sequence is particularly high when using the surface built up by nanoparticle deposition. This aspect indicates that morphologic details of the nanostructure play a key role in conditioning the performances of the genosensors.

  13. Development of a gold-nanostructured surface for amperometric genosensors

    International Nuclear Information System (INIS)

    Zanardi, Chiara; Baldoli, Clara; Licandro, Emanuela; Terzi, Fabio; Seeber, Renato

    2012-01-01

    A gold-nanostructured surface has been obtained by stable deposition of chemically synthesized gold nanoparticles (2.1–5.5 nm size range) on a gold substrate through a dithiol linker. The method proposed for the obtainment of the nanostructure is suitable for the further stable anchoring of a peptide nucleic acid oligomer through four amine groups of lysine terminal residues, leading to fairly reproducible systems. The geometric area of the nanostructured surface is compared with those of a smooth and of an electrochemically generated nanostructured surface by depositing a probe bearing an electrochemically active ferrocene residue. Despite the area of the two nanostructures being quite similar, the response toward a 2 nM target oligonucleotide sequence is particularly high when using the surface built up by nanoparticle deposition. This aspect indicates that morphologic details of the nanostructure play a key role in conditioning the performances of the genosensors.

  14. Gold nanoparticle trapping and delivery for therapeutic applications

    Directory of Open Access Journals (Sweden)

    Aziz MS

    2011-12-01

    Full Text Available MS Aziz1, Nathaporn Suwanpayak3,4, Muhammad Arif Jalil2, R Jomtarak4, T Saktioto2, Jalil Ali1, PP Yupapin41Institute of Advanced Photonics Science, 2Ibnu Sina Institute of Fundamental Science Studies, Nanotechnology Research Alliance, Universiti Teknologi Malaysia, Johor Bahru, Malaysia; 3King Mongkut's Institute of Technology Ladkrabang, Chump on Campus, Chumphon, 4Nanoscale Science and Engineering Research Alliance (N'SERA, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok, ThailandAbstract: A new optical trapping design to transport gold nanoparticles using a PANDA ring resonator system is proposed. Intense optical fields in the form of dark solitons controlled by Gaussian pulses are used to trap and transport nanoscopic volumes of matter to the desired destination via an optical waveguide. Theoretically, the gradient and scattering forces are responsible for this trapping phenomenon, where in practice such systems can be fabricated and a thin-film device formed on the specific artificial medical materials, for instance, an artificial bone. The dynamic behavior of the tweezers can be tuned by controlling the optical pulse input power and parameters of the ring resonator system. Different trap sizes can be generated to trap different gold nanoparticles sizes, which is useful for gold nanoparticle therapy. In this paper, we have shown the utility of gold nanoparticle trapping and delivery for therapy, which may be useful for cosmetic therapy and related applications.Keywords: gold nanoparticle trapping, particle trapping, therapy, transport

  15. Thermionic field emission in gold nitride Schottky nanodiodes

    Science.gov (United States)

    Spyropoulos-Antonakakis, N.; Sarantopoulou, E.; Kollia, Z.; Samardžija, Z.; Kobe, S.; Cefalas, A. C.

    2012-11-01

    We report on the thermionic field emission and charge transport properties of gold nitride nanodomains grown by pulsed laser deposition with a molecular fluorine laser at 157 nm. The nanodomains are sandwiched between the metallic tip of a conductive atomic force microscope and a thin gold layer forming thus a metal-semiconductor-metal junction. Although the limited existing data in the literature indicate that gold nitride was synthesized previously with low efficiency, poor stability, and metallic character; in this work, it is shown that gold nitride nanodomains exhibit semiconducting behavior and the metal-semiconductor-metal contact can be modeled with the back-to-back Schottky barrier model. From the experimental I-V curves, the main charge carrier transport process is found to be thermionic field emission via electron tunneling. The rectifying, near symmetric and asymmetric current response of nanocontacts is related to the effective contact area of the gold nitride nanodomains with the metals. A lower limit for the majority charge carriers concentration at the boundaries of nanodomains is also established using the full depletion approximation, as nanodomains with thickness as low as 6 nm were found to be conductive. Current rectification and charge memory effects are also observed in "quite small" conductive nanodomains (6-10 nm) due to stored charges. Indeed, charges near the surface are identified as inversion domains in the phase shift mapping performed with electrostatic force microscopy and are attributed to charge trapping at the boundaries of the nanodomains.

  16. Gold nanoparticles stabilized by chitosan

    International Nuclear Information System (INIS)

    Geraldes, Adriana N.; Oliveira, Maria Jose A.; Silva, Andressa A. da; Leal, Jessica; Batista, Jorge G.S.; Lugao, Ademar B.

    2015-01-01

    In our laboratory has been growing the interest in studying gold nanoparticles and for this reason, the aim of this work is report the first results of the effect of chitosan as stabilizer in gold nanoparticle formulation. AuNPs were synthesized by reducing hydrogen tetrachloroaurate (HAuCl 4 ) using NaBH 4 or gamma irradiation (25kGy) as reduction agent. The chitosan (3 mol L -1 ) was added at 0.5; 1.0 and 1.5 mL. The gold nanoparticles were characterized by UV-Vis absorption spectroscopy, X-ray diffraction (XRD) and Transmission electron microscopy (TEM). Their physical stability was determined using a UV-Vis spectrophotometer over one week during storage at room temperature. Absorption measurements indicated that the plasmon resonance wavelength appears at a wavelength around 530 nm. Has been observed that Chitosan in such quantities were not effective in stabilizing the AuNPs. (author)

  17. Light-induced reversible expansion of individual gold nanoplates

    Directory of Open Access Journals (Sweden)

    Jinsheng Lu

    2017-10-01

    Full Text Available Light-induced mechanical response of materials has been extensively investigated and widely utilized to convert light energy into mechanical energy directly. The metallic nanomaterials have excellent photothermal properties and show enormous potential in micromechanical actuators, etc. However, the photo-thermo-mechanical properties of individual metallic nanostructures have yet to be well investigated. Here, we experimentally demonstrate a way to realize light-induced reversible expansion of individual gold nanoplates on optical microfibers. The light-induced thermal expansion coefficient is obtained as 21.4 ± 4.6 ∼ 31.5 ± 4.2 μ·K-1 when the light-induced heating temperature of the gold nanoplates is 240 ∼ 490 °C. The photo-thermo-mechanical response time of the gold nanoplates is about 0.3 ± 0.1 s. This insight into the photo-thermo-mechanical properties of the gold nanoplates could deepen the understanding of the light-induced reversible expansion behavior in nanoscale and pave the way for applications based on this piezoelectric-like response, such as light-driven metallic micromotors.

  18. Plasmonic Horizon in Gold Nanosponges.

    Science.gov (United States)

    Vidal, Cynthia; Sivun, Dmitry; Ziegler, Johannes; Wang, Dong; Schaaf, Peter; Hrelescu, Calin; Klar, Thomas A

    2018-02-14

    An electromagnetic wave impinging on a gold nanosponge coherently excites many electromagnetic hot-spots inside the nanosponge, yielding a polarization-dependent scattering spectrum. In contrast, a hole, recombining with an electron, can locally excite plasmonic hot-spots only within a horizon given by the lifetime of localized plasmons and the speed carrying the information that a plasmon has been created. This horizon is about 57 nm, decreasing with increasing size of the nanosponge. Consequently, photoluminescence from large gold nanosponges appears unpolarized.

  19. New Trends in Gold Catalysts

    Directory of Open Access Journals (Sweden)

    Leonarda F. Liotta

    2014-07-01

    Full Text Available Gold is an element that has fascinated mankind for millennia. The catalytic properties of gold have been a source of debate, due to its complete chemical inertness when in a bulk form, while it can oxidize CO at temperatures as low as ~200 K when in a nanocrystalline state, as discovered by Haruta in the late 1980s [1]. Since then, extensive activity in both applied and fundamental research on gold has been initiated. The importance of the catalysis by gold represents one of the fasted growing fields in science and is proven by the promising applications in several fields, such as green chemistry and environmental catalysis, in the synthesis of single-walled carbon nanotubes, as modifiers of Ni catalysts for methane steam and dry reforming reactions and in biological and electrochemistry applications. The range of reactions catalyzed by gold, as well as the suitability of different supports and the influence of the preparation conditions have been widely explored and optimized in applied research [2]. Gold catalysts appeared to be very different from the other noble metal-based catalysts, due to their marked dependence on the preparation method, which is crucial for the genesis of the catalytic activity. Several methods, including deposition-precipitation, chemical vapor deposition and cation adsorption, have been applied for the preparation of gold catalysts over reducible oxides, like TiO2. Among these methods, deposition-precipitation has been the most frequently employed method for Au loading, and it involves the use of tetrachloroauric (III acid as a precursor. On the other hand, the number of articles dealing with Au-loaded acidic supports is smaller than that on basic supports, possibly because the deposition of [AuCl4]− or [AuOHxCl4−x]− species on acidic supports is difficult, due to their very low point of zero charge. Despite this challenge, several groups have reported the use of acidic zeolites as supports for gold. Zeolites

  20. Gold nanorod vaccine for respiratory syncytial virus

    International Nuclear Information System (INIS)

    Stone, John W; Thornburg, Natalie J; Blum, David L; Kuhn, Sam J; Crowe Jr, James E; Wright, David W

    2013-01-01

    Respiratory syncytial virus (RSV) is a major cause of pneumonia and wheezing in infants and the elderly, but to date there is no licensed vaccine. We developed a gold nanorod construct that displayed the major protective antigen of the virus, the fusion protein (F). Nanorods conjugated to RSV F were formulated as a candidate vaccine preparation by covalent attachment of viral protein using a layer-by-layer approach. In vitro studies using ELISA, electron microscopy and circular dichroism revealed that conformation-dependent epitopes were maintained during conjugation, and transmission electron microscopy studies showed that a dispersed population of particles could be achieved. Human dendritic cells treated with the vaccine induced immune responses in primary human T cells. These results suggest that this vaccine approach may be a potent method for immunizing against viruses such as RSV with surface glycoproteins that are targets for the human immune response. (paper)

  1. A Novel Strategy for Synthesis of Gold Nanoparticle Self Assemblies

    NARCIS (Netherlands)

    Verma, Jyoti; Lal, Sumit; van Veen, Henk A.; van Noorden, Cornelis J. F.

    2014-01-01

    Gold nanoparticle self assemblies are one-dimensional structures of gold nanoparticles. Gold nanoparticle self assemblies exhibit unique physical properties and find applications in the development of biosensors. Methodologies currently available for lab-scale and commercial synthesis of gold

  2. Ligations of Gold Atoms with Iron Porphyrin

    DEFF Research Database (Denmark)

    Zhang, Ling; Kepp, Kasper Planeta; Ulstrup, Jens

    Gold is an exotic material with d-electrons deciding electronic mappings andconfigurations of adsorbed molecules. The specific interaction of Au atoms and S-, Ncappedmolecules make gold nanoparticles widely applied in the medicine transport andimmunoassay. Density functional theory demonstrates t...

  3. Metallic gold beads in hyaluronic acid

    DEFF Research Database (Denmark)

    Pedersen, Dan Sonne; Tran, Thao Phuong; Smidt, Kamille

    2013-01-01

    . In conclusion, our findings support that bio-liberation of gold from metallic gold surfaces have anti-inflammatory properties similar to classic gold compounds, warranting further studies into the pharmacological potential of this novel gold-treatment and the possible synergistic effects of hyaluronic acid....... by exploiting macrophage-induced liberation of gold ions (dissolucytosis) from gold surfaces. Injecting gold beads in hyaluronic acid (HA) as a vehicle into the cavities of the brain can delay clinical signs of disease progression in the MS model, experimental autoimmune encephalitis (EAE). This study...... investigates the anti-inflammatory properties of metallic gold/HA on the gene expression of tumor necrosis factor (Tnf-α), Interleukin (Il)-1β, Il-6, Il-10, Colony-stimulating factor (Csf)-v2, Metallothionein (Mt)-1/2, Bcl-2 associated X protein (Bax) and B cell lymphoma (Bcl)-2 in cultured J774 macrophages...

  4. The geology of the gold deposits of Prestea gold belt of Ghana ...

    African Journals Online (AJOL)

    This paper presents the geology of the gold deposits along the Prestea gold belt of Ghana to assist exploration work for new orebodies along the belt. Prestea district is the third largest gold producer in West Africa after Obuasi and Tarkwa districts (over 250 metric tonnes Au during the last century). The gold deposits are ...

  5. Gold Nanoparticle Mediated Phototherapy for Cancer

    International Nuclear Information System (INIS)

    Yao, C.; Zhang, L.; Wang, J.; He, Y.; Xin, J.; Wang, S.; Xu, H.; Zhang, Z.

    2016-01-01

    Gold nanoparticles exhibit very unique physiochemical and optical properties, which now are extensively studied in range of medical diagnostic and therapeutic applications. In particular, gold nanoparticles show promise in the advancement of cancer treatments. This review will provide insights into the four different cancer treatments such as photothermal therapy, gold nanoparticle-aided photodynamic therapy, gold nanoparticle-aided radiation therapy, and their use as drug carrier. We also discuss the mechanism of every method and the adverse effects and its limitations

  6. Use of Soybean Lecithin in Shape Controlled Synthesis of Gold Nanoparticles

    Science.gov (United States)

    Ayres, Benjamin Robert

    The work presented in this dissertation is a composite of experiments in the growth of gold nanoparticles with specific optical properties of interest. The goal is to synthesize these gold nanoparticles using soybean extract for not only shape control, but for propensity as a biocompatible delivery system. The optical properties of these nanoparticles has found great application in coloring glass during the Roman empire and, over the centuries, has grown into its own research field in applications of nanoparticulate materials. Many of the current functions include use in biological systems as biosensors and therapeutic applications, thus making biocompatibility a necessity. Current use of cetyltrimethylammonium bromide leads to rod-shaped gold nanoparticles, however, the stability of these gold nanoparticles does not endure for extended periods of time in aqueous media. In my research, two important components were found to be necessary for stable, anisotropic growth of gold nanoparticles. In the first experiments, it was found that bromide played a key role in shape control. Bromide exchange on the gold atoms led to specific packing of the growing crystals, allowing for two-dimensional growth of gold nanoparticles. It was also discerned that soybean lecithin contained ligands that blocked specific gold facets leading to prismatic gold nanoparticle growth. These gold nanoprisms give a near infrared plasmon absorption similar to that of rod-shaped gold nanoparticles. These gold nanoprisms are discovered to be extremely stable in aqueous media and remain soluble for extended periods of time, far longer than that of gold nanoparticles grown using cetyltrimethylammonium bromide. Since soy lecithin has a plethora of compounds present, it became necessary to discover which compound was responsible for the shape control of the gold nanoprisms in order to optimize the synthesis and allow for a maximum yield of the gold nanoprisms. Many of these components were identified

  7. Highly active thermally stable nanoporous gold catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Biener, Juergen; Wittstock, Arne; Biener, Monika M.; Bagge-Hansen, Michael; Baeumer, Marcus; Wichmann, Andre; Neuman, Bjoern

    2016-12-20

    In one embodiment, a system includes a nanoporous gold structure and a plurality of oxide particles deposited on the nanoporous gold structure; the oxide particles are characterized by a crystalline phase. In another embodiment, a method includes depositing oxide nanoparticles on a nanoporous gold support to form an active structure and functionalizing the deposited oxide nanoparticles.

  8. Gold and Silver Extraction from Leach Solutions

    OpenAIRE

    Bagdaulet K. Kenzhaliyev; Renata R. Iskhakova; Zamzagul D. Dosymbaeva; Esen N. Sulejmenov

    2014-01-01

    There has been carried out an investigation on the extraction of gold and silver from thiosulfate solutions: standard test and technological solutions of chemical and electrochemical leaching. The influence of related metals on the process of extracting gold from solution was studied. There has been conducted a comparative study of the IR spectra of solutions after the sorption of gold, silver and related metals.

  9. Cancer caused by radioactive gold rings

    International Nuclear Information System (INIS)

    Callary, E.M.

    1989-01-01

    Two recent cases of skin cancer caused by radioactive gold rings are described. The gold was contaminated with radon daughters from hollow goldseeds used to hold radon, back in the 1930s or possibly later. Other radioactive gold rings are probably being worn. The Canadian AECB offers free testing

  10. Targeting dendritic cells through gold nanoparticles: A review on the cellular uptake and subsequent immunological properties.

    Science.gov (United States)

    Ahmad, Suhana; Zamry, Anes Ateqah; Tan, Hern-Tze Tina; Wong, Kah Keng; Lim, JitKang; Mohamud, Rohimah

    2017-11-01

    Gold nanoparticles (NPs) have been proposed as a highly potential tool in immunotherapies due to its advantageous properties including customizable size and shapes, surface functionality and biocompatibility. Dendritic cells (DCs), the sentinels of immune response, have been of interest to be manipulated by using gold NPs for targeted delivery of immunotherapeutic agent. Researches done especially in human DCs showed a variation of gold NPs effects on cellular uptake and internalization, DC maturation and subsequent T cells priming as well as cytotoxicity. In this review, we describe the synthesis and physiochemical properties of gold NPs as well as the importance of gold NPs in immunotherapies through their actions on human DCs. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  11. Ultrafast vibrations of gold nanorings

    DEFF Research Database (Denmark)

    Kelf, T; Tanaka, Y; Matsuda, O

    2011-01-01

    We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We...

  12. Ultrafast vibrations of gold nanorings

    DEFF Research Database (Denmark)

    Kelf, T; Tanaka, Y; Matsuda, O

    2011-01-01

    We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We elucid...

  13. [History of gold--with danish contribution to tuberculosis and rheumatoid arthritis].

    Science.gov (United States)

    Norn, Svend; Permin, Henrik; Kruse, Poul R; Kruse, Edith

    2011-01-01

    Gold has a long history as a therapeutic agent, first as gold particles and colloidal gold, then as a soluble salt made by the alchemists, and potable gold was recommended almost as a panacea against different diseases. Gold compounds were introduced in the treatment of tuberculosis, based initially on the reputation of Robert Koch, who found gold cyanide effective against Mycobacterium tuberculosis in cultures. Although several investigations of gold salts showed no convincing effect in experimental tuberculosis in guinea pigs, the idea of using gold compounds as chemotherapy was furthermore encouraged from the work of Paul Ehrlich with arsenicals. The enthusiasm and the craving desperately for a remedy for tuberculosis forced Danish physicians, in the mid-1920s to treat tuberculosis with Sanocrysin (gold sodium thiosulfate). Professor Holger Møllgaard, in collaboration with the clinicians the professors Knud Secher and Knud Faber, was the theoretical promoter of the project. He recommended sanocrysin-antiserum therapy, since sanocrysin caused serious reactions in tuberculosis animals, possible by releasing toxins from tubercle bacilli "killed" by sanocrysin. However the enthusiastic response to sanocrysin in Europe declined along by controlled trials and reports on toxicity in the 1930s. The belief that rheumatoid arthritis was a form of tuberculosis caused a renaissance in chrysotherapy. In France Jacques Forestier obtained encouraging results in the treatment of rheumatoid arthritis with myochrysine and other gold salts, and he pointed out the disease modifying effect of chrysotherapy. In Denmark Knud Secher, who was the clinical initiator of Sanocrysin therapy in tuberculosis, now became the founder of chrysotherapy in rheumatoid arthritis. Although new potential agents are now taking over in the treatment of arthritis, it is still believed, that there is a place for the chrysotherapy. However a new future for gold, in the form of nanoparticles, appears on

  14. Probabilistic estimation of dune retreat on the Gold Coast, Australia

    Science.gov (United States)

    Palmsten, Margaret L.; Splinter, Kristen D.; Plant, Nathaniel G.; Stockdon, Hilary F.

    2014-01-01

    Sand dunes are an important natural buffer between storm impacts and development backing the beach on the Gold Coast of Queensland, Australia. The ability to forecast dune erosion at a prediction horizon of days to a week would allow efficient and timely response to dune erosion in this highly populated area. Towards this goal, we modified an existing probabilistic dune erosion model for use on the Gold Coast. The original model was trained using observations of dune response from Hurricane Ivan on Santa Rosa Island, Florida, USA (Plant and Stockdon 2012. Probabilistic prediction of barrier-island response to hurricanes, Journal of Geophysical Research, 117(F3), F03015). The model relates dune position change to pre-storm dune elevations, dune widths, and beach widths, along with storm surge and run-up using a Bayesian network. The Bayesian approach captures the uncertainty of inputs and predictions through the conditional probabilities between variables. Three versions of the barrier island response Bayesian network were tested for use on the Gold Coast. One network has the same structure as the original and was trained with the Santa Rosa Island data. The second network has a modified design and was trained using only pre- and post-storm data from 1988-2009 for the Gold Coast. The third version of the network has the same design as the second version of the network and was trained with the combined data from the Gold Coast and Santa Rosa Island. The two networks modified for use on the Gold Coast hindcast dune retreat with equal accuracy. Both networks explained 60% of the observed dune retreat variance, which is comparable to the skill observed by Plant and Stockdon (2012) in the initial Bayesian network application at Santa Rosa Island. The new networks improved predictions relative to application of the original network on the Gold Coast. Dune width was the most important morphologic variable in hindcasting dune retreat, while hydrodynamic variables, surge and

  15. Gas sensing with gold-decorated vertically aligned carbon nanotubes.

    Science.gov (United States)

    Mudimela, Prasantha R; Scardamaglia, Mattia; González-León, Oriol; Reckinger, Nicolas; Snyders, Rony; Llobet, Eduard; Bittencourt, Carla; Colomer, Jean-François

    2014-01-01

    Vertically aligned carbon nanotubes of different lengths (150, 300, 500 µm) synthesized by thermal chemical vapor deposition and decorated with gold nanoparticles were investigated as gas sensitive materials for detecting nitrogen dioxide (NO2) at room temperature. Gold nanoparticles of about 6 nm in diameter were sputtered on the top surface of the carbon nanotube forests to enhance the sensitivity to the pollutant gas. We showed that the sensing response to nitrogen dioxide depends on the nanotube length. The optimum was found to be 300 µm for getting the higher response. When the background humidity level was changed from dry to 50% relative humidity, an increase in the response to NO2 was observed for all the sensors, regardless of the nanotube length.

  16. Gas sensing with gold-decorated vertically aligned carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Prasantha R. Mudimela

    2014-06-01

    Full Text Available Vertically aligned carbon nanotubes of different lengths (150, 300, 500 µm synthesized by thermal chemical vapor deposition and decorated with gold nanoparticles were investigated as gas sensitive materials for detecting nitrogen dioxide (NO2 at room temperature. Gold nanoparticles of about 6 nm in diameter were sputtered on the top surface of the carbon nanotube forests to enhance the sensitivity to the pollutant gas. We showed that the sensing response to nitrogen dioxide depends on the nanotube length. The optimum was found to be 300 µm for getting the higher response. When the background humidity level was changed from dry to 50% relative humidity, an increase in the response to NO2 was observed for all the sensors, regardless of the nanotube length.

  17. Surface vertical deposition for gold nanoparticle film

    International Nuclear Information System (INIS)

    Diao, J J; Qiu, F S; Chen, G D; Reeves, M E

    2003-01-01

    In this rapid communication, we present the surface vertical deposition (SVD) method to synthesize the gold nanoparticle films. Under conditions where the surface of the gold nanoparticle suspension descends slowly by evaporation, the gold nanoparticles in the solid-liquid-gas junction of the suspension aggregate together on the substrate by the force of solid and liquid interface. When the surface properties of the substrate and colloidal nanoparticle suspension define for the SVD, the density of gold nanoparticles in the thin film made by SVD only depends on the descending velocity of the suspension surface and on the concentration of the gold nanoparticle suspension. (rapid communication)

  18. Gold and not so real gold in Medieval treatises

    Directory of Open Access Journals (Sweden)

    Srebrenka Bogovic-Zeskoski

    2015-01-01

    Full Text Available The aim of this study is to evidence diverse materials and processes used by artisans (and alchemists required to synthesize a visually viable replacement for gold. The emphasis of the research is upon the production of mosaic gold or porporina, a pigment that has survived into modern times, which was used as ink and as paint. Base metals, mostly tin, but also alloys were used both into foils coated with glazes and varnishes and as pigment. The research focuses upon recipes documented in treatises dating from Antiquity to the late Medieval period (ca. 1500 and an attempt is made to answer two questions. In the first place, why was there a need for a surrogate? Secondly, why are there so few tangible examples detected on surviving artifacts? In conclusion, an argument is offered pointing out that, although much can be learned by scientific examination of artifacts, textual analysis is equally important and necessary to unravel mysteries of ancient technologies

  19. Nanotoxicity of gold and gold-cobalt nanoalloy.

    Science.gov (United States)

    Girgis, E; Khalil, W K B; Emam, A N; Mohamed, M B; Rao, K V

    2012-05-21

    Nanotoxicology test of gold nanoparticles (Au NPs) and gold-cobalt (Au-Co) nanoalloy is an important step in their safety evaluation for biomedical applications. The Au and Au-Co NPs were prepared by reducing the metal ions using sodium borohydride (NaBH(4)) in the presence of polyvinyl pyrrolidone (PVP) as a capping material. The average size and shape of the nanoparticles (NPs) were characterized using high resolution transmission electron microscopy (HRTEM). Cobalt presence in the nanoalloy was confirmed by energy dispersive X-ray spectroscopy (EDX) analysis, and the magnetic properties of these particles were determined using a vibrating sample magnetometer (VSM). The Gold and gold-cobalt NPs of average size 15 ± 1.5 nm were administered orally to mice with a dose of 80, 160, and 320 mg/kg per body weight (bw) using gavages. Samples were collected after 7 and 14 days of the treatment. The results indicated that the Au-Co NPs were able to induce significant alteration in the tumor-initiating genes associated with an increase of micronuclei (MNs) formation and generation of DNA adduct (8-hydroxy-2-deoxyguanosine, 8-OHdG) as well as a reduction in the glutathione peroxidase activity. This action of Au-Co NPs was observed using 160 and 320 mg/kg bw at both time intervals. However, Au NPs had much lower effects than Au-Co NPs on alteration in the tumor-initiating genes, frequency of MNs, and generation of 8-OHdG as well as glutathione peroxidase activity except with the highest dose of Au NPs. This study suggests that the potential to cause in vivo genetic and antioxidant enzyme alterations due to the treatment by Au-Co nanoalloy may be attributed to the increase in oxidative stress in mice.

  20. The infrared transmission through gold films on ordered two-dimensional non-close-packed colloidal crystals

    International Nuclear Information System (INIS)

    Ju Jing; Zhou Yuqin; Dong Gangqiang

    2014-01-01

    We studied the infrared transmission properties of gold films on ordered two-dimensional non-close-packed polystyrene (PS) colloidal crystal. The gold films consist of gold half-shells on the PS spheres and gold film with 2D arrays of holes on the glass substrate. An extraordinary optical transmission phenomenon could be found in such a structure. Simulations with the finite-difference time-domain method were also employed to get the transmission spectra and electric field distribution. The transmission response of the samples can be adjusted by controlling the thickness of the gold films. Angle-resolved measurements were performed using polarized light to obtain more information about the surface plasmon polariton resonances of the gold films. As the angle changes, the transmission spectra change a lot. The transmission spectra of p-polarized light have quite different properties compared to those of s-polarized light. (semiconductor physics)

  1. Response

    Science.gov (United States)

    Higgins, Chris

    2012-01-01

    This article presents the author's response to the reviews of his book, "The Good Life of Teaching: An Ethics of Professional Practice." He begins by highlighting some of the main concerns of his book. He then offers a brief response, doing his best to address the main criticisms of his argument and noting where the four reviewers (Charlene…

  2. Innate stimulatory capacity of high molecular weight transition metals Au (gold) and Hg (mercury).

    Science.gov (United States)

    Rachmawati, Dessy; Alsalem, Inás W A; Bontkes, Hetty J; Verstege, Marleen I; Gibbs, Sue; von Blomberg, B M E; Scheper, Rik J; van Hoogstraten, Ingrid M W

    2015-03-01

    Nickel, cobalt and palladium ions can induce an innate immune response by triggering Toll-like receptor (TLR)-4 which is present on dendritic cells (DC). Here we studied mechanisms of action for DC immunotoxicity to gold and mercury. Next to gold (Na3Au (S2O3)2⋅2H2O) and mercury (HgCl2), nickel (NiCl2) was included as a positive control. MoDC activation was assessed by release of the pro-inflammatory mediator IL-8. Also PBMC were studied, and THP-1 cells were used as a substitution for DC for evaluation of cytokines and chemokines, as well as phenotypic, alterations in response to gold and mercury. Our results showed that both Na3Au (S2O3)2⋅2H2O and HgCl2 induce substantial release of IL-8, but not IL-6, CCL2 or IL-10, from MoDc, PBMC, or THP-1 cells. Also gold and, to a lesser extent mercury, caused modest dendritic cell maturation as detected by increased membrane expression of CD40 and CD80. Both metals thus show innate immune response capacities, although to a lower extent than reported earlier for NiCl2, CoCl2 and Na2 [PdCl4]. Importantly, the gold-induced response could be ascribed to TLR3 rather than TLR4 triggering, whereas the nature of the innate mercury response remains to be clarified. In conclusion both gold and mercury can induce innate immune responses, which for gold could be ascribed to TLR3 dependent signalling. These responses are likely to contribute to adaptive immune responses to these metals, as reflected by skin and mucosal allergies. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Distribution and composition of gold in porphyry gold systems: example from the Biely Vrch deposit, Slovakia

    Science.gov (United States)

    Koděra, Peter; Kozák, Jaroslav; Brčeková, Jana; Chovan, Martin; Lexa, Jaroslav; Jánošík, Michal; Biroň, Adrián; Uhlík, Peter; Bakos, František

    2018-03-01

    The Biely Vrch deposit in the Western Carpathians is assigned to the shallow, sulfide-poor porphyry gold deposit type and has an exceptionally low Cu/Au ratio. According to 3-D geochemical models, there is a limited spatial correlation between Au and Cu due to the primary introduction of gold by a salt melt and Cu by low-density vapor. Despite a rough spatial correlation of gold grades with quartz stockwork intensity, gold is hosted mostly by altered rock, exclusively in native form. Three main gold mineral assemblages were recognized here. In the deepest parts of the system, the K- and Ca-Na silicate gold assemblage is associated with minerals of high-temperature alteration (plagioclase, K-feldspar, actinolite), with gold grades and fineness depending on depth and potassium content of the host rock: K-silicate alteration hosts the lowest fineness gold ( 914), whereas Ca-Na silicate alteration has the highest ( 983). The intermediate argillic gold assemblage is the most widespread, with gold hosted mainly by chlorite, illite, smectite, and interstratified illite-chlorite-smectite minerals. The gold fineness is mostly variable (875-990) and inherited from the former gold mineral assemblages. The latest advanced argillic gold assemblage has its gold mostly in kaolinite. The extremely high fineness ( 994) results from gold remobilization by late-stage aqueous magmatic-hydrothermal fluids. Uncommon bonanza-grade appears where the earlier gold mineral assemblages were further enriched by this remobilized gold. Primary precipitation of gold occurred during ascent and cooling of salt melts at 450 to 309 °C, mostly during retrograde quartz solubility.

  4. Byzantine gold coins and jewellery

    International Nuclear Information System (INIS)

    Oddy, A.; La Niece, S.

    1986-01-01

    The article deals with the dating of Byzantine gold coinage. The results of such a study are of fundamental importance for the study of the economic history of the later Byzantine Empire and they are also of importance for the historian of technology when studying the composition of the contemporary Byzantine jewellery. Although Carbon-14 dating cannot be used as a method af dating, historians can still benefit from the analysis of the alloy of which the antiquity is made, as this is sometimes characteristic of the period in which it was used. A number of pieces of Byzantine jewellery has been analysed by x-ray fluorescence analysis, after first gently abrading a small area of the surface of the gold with the carborundum paper in an inconspicious position on the back or side of the object. A table is given on the results of this analysis

  5. Reverse Transfection Using Gold Nanoparticles

    Science.gov (United States)

    Yamada, Shigeru; Fujita, Satoshi; Uchimura, Eiichiro; Miyake, Masato; Miyake, Jun

    Reverse transfection from a solid surface has the potential to deliver genes into various types of cell and tissue more effectively than conventional methods of transfection. We present a method for reverse transfection using a gold colloid (GC) as a nanoscaffold by generating nanoclusters of the DNA/reagentcomplex on a glass surface, which could then be used for the regulation of the particle size of the complex and delivery of DNA into nuclei. With this method, we have found that the conjugation of gold nanoparticles (20 nm in particle size) to the pEGFP-N1/Jet-PEI complex resulted in an increase in the intensity of fluorescence of enhanced green fluorescent protein (EGFP) (based on the efficiency of transfection) from human mesenchymal stem cells (hMSCs), as compared with the control without GC. In this manner, we constructed a method for reverse transfection using GC to deliver genes into the cells effectively.

  6. CMS Industries awarded gold, crystal

    CERN Multimedia

    2006-01-01

    The CMS collaboration honoured 10 of its top suppliers in the seventh annual awards ceremony The representatives of the firms that recieved the CMS Gold and Crystal Awards stand with their awards after the ceremony. The seventh annual CMS Awards ceremony was held on Monday 13 March to recognize the industries that have made substantial contributions to the construction of the collaboration's detector. Nine international firms received Gold Awards, and General Tecnica of Italy received the prestigious Crystal Award. Representatives from the companies attended the ceremony during the plenary session of CMS week. 'The role of CERN, its machines and experiments, beyond particle physics is to push the development of equipment technologies related to high-energy physics,'said CMS Awards Coordinator Domenico Campi. 'All of these industries must go beyond the technologies that are currently available.' Without the involvement of good companies over the years, the construction of the CMS detector wouldn't be possible...

  7. Nanobubble trouble on gold surfaces

    DEFF Research Database (Denmark)

    Holmberg, Maria; Kuhle, A.; Garnaes, J.

    2003-01-01

    When analyzing surfaces related to biosensors with in situ atomic force microscopy (AFM), the existence of nanobubbles called for our attention. The bubbles seem to form spontaneously when gold surfaces are immersed in clean water and are probably a general phenomenon at water-solid interfaces....... Besides from giving rise to undesired effects in, for example, biosensors, nanobubbles can also cause artifacts in AFM imaging. We have observed nanobubbles on unmodified gold surfaces, immersed in clean water, using standard silicon AFM probes. Nanobubbles can be made to disappear from contact mode AFM...... images and then to reappear by changing the scanning force. By combining contact mode AFM imaging and local force measurements, the interaction between the nanobubbles and the probe can be analyzed and give information about the characteristics of nanobubbles. A model of the forces between the AFM probe...

  8. The frequencies of IFNγ+IL2+TNFα+ PPD-specific CD4+CD45RO+ T-cells correlate with the magnitude of the QuantiFERON® gold in-tube response in a prospective study of healthy indian adolescents.

    Science.gov (United States)

    Jenum, Synne; Grewal, Harleen M S; Hokey, David A; Kenneth, John; Vaz, Mario; Doherty, Timothy Mark; Jahnsen, Frode Lars

    2014-01-01

    QuantiFERON-TB Gold In-Tube (QFT) is an IFNγ-release assay used in the diagnosis of Mycobacterium tuberculosis (MTB) infection. The risk of TB progression increases with the magnitude of the MTB-specific IFNγ-response. QFT reversion, also associated with low Tuberculin Skin Test responses, may therefore represent a transient immune response with control of M. tuberculosis infection. However, studies at the single cell level have suggested that the quality (polyfunctionality) of the T-cell response is more important than the quantity of cytokines produced. To explore the quality and/or magnitude of mycobacteria-specific T-cell responses associated with QFT reversion and persistent QFT-positivity. Multi-color flowcytometry on prospectively collected peripheral blood mononuclear cells was applied to assess mycobacteria-specific T-cell responses in 42 QFT positive Indian adolescents of whom 21 became QFT negative (reverters) within one year. Ten QFT consistent negatives were also included as controls. There was no difference in the qualitative PPD-specific CD4+ T-cell response between QFT consistent positives and reverters. However, compared with QFT consistent positives, reverters displayed lower absolute frequencies of polyfunctional (IFNγ+IL2+TNFα+) CD4+ T-cells at baseline, which were further reduced to the point where they were not different to QFT negative controls one year later. Moreover, absolute frequencies of these cells correlated well with the magnitude of the QFT-response. Whereas specific polyfunctional CD4+ T-cells have been suggested to protect against TB progression, our data do not support that higher relative or absolute frequencies of PPD-specific polyfunctional CD4+ T-cells in peripheral blood can explain the reduced risk of TB progression observed in QFT reverters. On the contrary, absolute frequencies of these cells correlated with the QFT-response, suggesting that this readout reflects antigenic load.

  9. Stress corrosion cracking and dealloying of copper-gold alloy in iodine vapor

    International Nuclear Information System (INIS)

    Galvez, M.F.; Bianchi, G.L.; Galvele, J.R.

    1993-01-01

    The susceptibility to stress corrosion cracking of copper-gold alloy in iodine vapor was studied and the results were analyzed under the scope of the surface mobility stress corrosion cracking mechanism. The copper-gold alloy undergoes stress corrosion cracking in iodine. Copper iodide was responsible of that behavior. The copper-gold alloy shows two processes in parallel: stress corrosion cracking and dealloying. As was predicted by the surface mobility stress corrosion cracking mechanism, the increase in strain rate induces an increase in the crack propagation rate. (Author)

  10. Gold, currencies and market efficiency

    Czech Academy of Sciences Publication Activity Database

    Krištoufek, Ladislav; Vošvrda, Miloslav

    2016-01-01

    Roč. 449, č. 1 (2016), s. 27-34 ISSN 0378-4371 R&D Projects: GA ČR(CZ) GBP402/12/G097 Institutional support: RVO:67985556 Keywords : Efficient market hypothesis, * Gold * Currencies, * Fractal dimension * Entropy * Long-Term memory Subject RIV: AH - Economics Impact factor: 2.243, year: 2016 http://library.utia.cas.cz/separaty/2016/E/kristoufek-0455876.pdf

  11. Ground Optical Lightning Detector (GOLD)

    Science.gov (United States)

    Jackson, John, Jr.; Simmons, David

    A photometer developed to characterize lightning from the ground is discussed. The detector and the electronic signal processing and data storage systems are presented along with field data measured by the system. The discussion will include improvements that will be incorporated to enhance the measurement of lightning and the data storage capability to record for many days without human involvement. Finally, the calibration of the GOLD system is presented.

  12. Extinction Coefficient of Gold Nanostars

    OpenAIRE

    de Puig, Helena; Tam, Justina O.; Yen, Chun-Wan; Gehrke, Lee; Hamad-Schifferli, Kimberly

    2015-01-01

    Gold nanostars (NStars) are highly attractive for biological applications due to their surface chemistry, facile synthesis and optical properties. Here, we synthesize NStars in HEPES buffer at different HEPES/Au ratios, producing NStars of different sizes and shapes, and therefore varying optical properties. We measure the extinction coefficient of the synthesized NStars at their maximum surface plasmon resonances (SPR), which range from 5.7 × 108 to 26.8 × 108 M−1cm−1. Measured values correl...

  13. Biomolecular Assembly of Gold Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Micheel, Christine Marya [Univ. of California, Berkeley, CA (United States)

    2005-05-20

    Over the past ten years, methods have been developed to construct discrete nanostructures using nanocrystals and biomolecules. While these frequently consist of gold nanocrystals and DNA, semiconductor nanocrystals as well as antibodies and enzymes have also been used. One example of discrete nanostructures is dimers of gold nanocrystals linked together with complementary DNA. This type of nanostructure is also known as a nanocrystal molecule. Discrete nanostructures of this kind have a number of potential applications, from highly parallel self-assembly of electronics components and rapid read-out of DNA computations to biological imaging and a variety of bioassays. My research focused in three main areas. The first area, the refinement of electrophoresis as a purification and characterization method, included application of agarose gel electrophoresis to the purification of discrete gold nanocrystal/DNA conjugates and nanocrystal molecules, as well as development of a more detailed understanding of the hydrodynamic behavior of these materials in gels. The second area, the development of methods for quantitative analysis of transmission electron microscope data, used computer programs written to find pair correlations as well as higher order correlations. With these programs, it is possible to reliably locate and measure nanocrystal molecules in TEM images. The final area of research explored the use of DNA ligase in the formation of nanocrystal molecules. Synthesis of dimers of gold particles linked with a single strand of DNA possible through the use of DNA ligase opens the possibility for amplification of nanostructures in a manner similar to polymerase chain reaction. These three areas are discussed in the context of the work in the Alivisatos group, as well as the field as a whole.

  14. Gold Nanocages for Biomedical Applications**

    OpenAIRE

    Skrabalak, Sara E.; Chen, Jingyi; Au, Leslie; Lu, Xianmao; Li, Xingde; Xia, Younan

    2007-01-01

    Nanostructured materials provide a promising platform for early cancer detection and treatment. Here we highlight recent advances in the synthesis and use of Au nanocages for such biomedical applications. Gold nanocages represent a novel class of nanostructures, which can be prepared via a remarkably simple route based on the galvanic replacement reaction between Ag nanocubes and HAuCl4. The Au nanocages have a tunable surface plasmon resonance peak that extends into the near-infrared, where ...

  15. Jabiluka gold-uranium project

    International Nuclear Information System (INIS)

    1988-01-01

    The Jabiluka gold-uranium deposit, 230km east of Darwin in the Alligator Rivers Region of the Northern Territory, was discovered by Pancontinental Mining Limited in 1971. Jabiluka, with reserves in excess of 200,000 tonnes of contained U 3 O 8 in two deposits 500 metres apart, is the world's largest high grade uranium deposit and also contains nearly 12 tonnes of gold. It is proposed that only the larger deposit, Jabiluka II will be mined - by underground extraction methods, and that 275,000 tonnes of ore per year will be mined and processed to produce 1,500 tonnes of U 3 O 8 and up to 30,000 oz of gold. The revenue from the uranium sales is estimated to be of the order of A$100 million per year at A$30/lb. By the end of 1982 all necessary mining and environmental approvals had been obtained and significant marketing progress made. With the Australian Labor Party winning Commonwealth Government in the 1983 election, Pancontinental's permission to seek sales contracts was withdrawn and development of the Jabiluka deposit ceased. Jabiluka remains undeveloped - awaiting a change in Australian Government policy on uranium. figs., maps

  16. Analysis of gold and silver concentration on gold mining tailings by neutron activation analysis

    International Nuclear Information System (INIS)

    Sadikov, I.I.; Salimov, M.I.; Sadykova, Z.O.

    2014-01-01

    Full text: Instrumental neutron-activation analysis without radiochemical separation is one of most applicable and often used methods to analyze the concentration of gold, silver and other rare and noble metals in gold ores. This method is not suitable for analyzing low concentration of gold and silver in gold mining tailings due to rather high concentration of some elements. Samples are dissolved by boiling in a mixture of concentrated hydrochloric and nitric acids to extract gold and silver into the solution. Chemical yield of gold and silver after dissolution of the sample and further chromatographic separation is between 92 and 95 percent respectively

  17. Surface plasmon-enhanced molecular fluorescence induced by gold nanostructures

    International Nuclear Information System (INIS)

    Teng, Y.; Ueno, K.; Shi, X.; Aoyo, D.; Misawa, H.; Qiu, J.

    2012-01-01

    The authors report on surface plasmon-enhanced fluorescence of Eosin Y molecules induced by gold nanostructures. Al 2 O 3 films deposited by atomic layer deposition with sub-nanometer resolution were used as the spacer layer to control the distance between molecules and the gold surface. As the thickness of the Al 2 O 3 film increased, the fluorescence intensity first increased and then decreased. The highest enhancement factor is achieved with a 1 nm Al 2 O 3 film. However, the trend for the fluorescence lifetime is the opposite. It first decreased and then increased. The changes in the fluorescence quantum yield were also calculated. The yield shows a similar trend to the fluorescence intensity. The competition between the surface plasmon-induced increase in the radiative decay rate and the gold-induced fluorescence quenching is responsible for the observed phenomenon. In addition, this competition strongly depends on the thickness of the spacer layer between Eosin Y molecules and the gold surface. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Transient extracellular application of gold nanostars increases hippocampal neuronal activity.

    Science.gov (United States)

    Salinas, Kirstie; Kereselidze, Zurab; DeLuna, Frank; Peralta, Xomalin G; Santamaria, Fidel

    2014-08-20

    With the increased use of nanoparticles in biomedical applications there is a growing need to understand the effects that nanoparticles may have on cell function. Identifying these effects and understanding the mechanism through which nanoparticles interfere with the normal functioning of a cell is necessary for any therapeutic or diagnostic application. The aim of this study is to evaluate if gold nanoparticles can affect the normal function of neurons, namely their activity and coding properties. We synthesized star shaped gold nanoparticles of 180 nm average size. We applied the nanoparticles to acute mouse hippocampal slices while recording the action potentials from single neurons in the CA3 region. Our results show that CA3 hippocampal neurons increase their firing rate by 17% after the application of gold nanostars. The increase in excitability lasted for as much as 50 minutes after a transient 5 min application of the nanoparticles. Further analyses of the action potential shape and computational modeling suggest that nanoparticles block potassium channels responsible for the repolarization of the action potentials, thus allowing the cell to increase its firing rate. Our results show that gold nanoparticles can affect the coding properties of neurons by modifying their excitability.

  19. Plasmonic Gold Decorated MWCNT Nanocomposite for Localized Plasmon Resonance Sensing

    Science.gov (United States)

    Ozhikandathil, J.; Badilescu, S.; Packirisamy, M.

    2015-01-01

    The synergism of excellent properties of carbon nanotubes and gold nanoparticles is used in this work for bio-sensing of recombinant bovine growth hormones (rbST) by making Multi Wall Carbon Nanotubes (MWCNT) locally optically responsive by augmenting it optical properties through Localized Surface Plasmon Resonance (LSPR). To this purpose, locally gold nano particles decorated gold–MWCNT composite was synthesized from a suspension of MWCNT bundles and hydrogen chloroauric acid in an aqueous solution, activated ultrasonically and, then, drop-casted on a glass substrate. The slow drying of the drop produces a “coffee ring” pattern that is found to contain gold–MWCNT nanocomposites, accumulated mostly along the perimeter of the ring. The reaction is studied also at low-temperature, in the vacuum chamber of the Scanning Electron Microscope and is accounted for by the local melting processes that facilitate the contact between the bundle of tubes and the gold ions. Biosensing applications of the gold–MWCNT nanocomposite using their LSPR properties are demonstrated for the plasmonic detection of traces of bovine growth hormone. The sensitivity of the hybrid platform which is found to be 1 ng/ml is much better than that measuring with gold nanoparticles alone which is only 25 ng/ml. PMID:26282187

  20. Resistivity of thiol-modified gold thin films

    International Nuclear Information System (INIS)

    Correa-Puerta, Jonathan; Del Campo, Valeria; Henríquez, Ricardo; Häberle, Patricio

    2014-01-01

    In this work, we study the effect of thiol self assembled monolayers on the electrical resistivity of metallic thin films. The analysis is based on the Fuchs–Sondheimer–Lucas theory and on electrical transport measurements. We determined resistivity change due to dodecanethiol adsorption on gold thin films. For this purpose, we controlled the deposition and annealing temperatures of the films to change the surface topography and to diminish the effect of electron grain boundary scattering. Results show that the electrical response to the absorption of thiols strongly depends on the initial topography of the surface. - Highlights: • We study the effect of self assembled monolayers on the resistivity of thin films. • Fuchs–Sondheimer theory reproduces the resistivity increase due to thiol deposition. • We determined resistivity change due to dodecanethiol deposition on gold thin films. • The electrical response strongly depends on the substrate surface topography

  1. Resistivity of thiol-modified gold thin films

    Energy Technology Data Exchange (ETDEWEB)

    Correa-Puerta, Jonathan [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Av. Universidad 330, Curauma, Valparaíso (Chile); Del Campo, Valeria [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaiso 2390123 (Chile); Henríquez, Ricardo, E-mail: ricardo.henriquez@usm.cl [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaiso 2390123 (Chile); Häberle, Patricio [Departamento de Física, Universidad Técnica Federico Santa María, Av. España 1680, Valparaiso 2390123 (Chile)

    2014-11-03

    In this work, we study the effect of thiol self assembled monolayers on the electrical resistivity of metallic thin films. The analysis is based on the Fuchs–Sondheimer–Lucas theory and on electrical transport measurements. We determined resistivity change due to dodecanethiol adsorption on gold thin films. For this purpose, we controlled the deposition and annealing temperatures of the films to change the surface topography and to diminish the effect of electron grain boundary scattering. Results show that the electrical response to the absorption of thiols strongly depends on the initial topography of the surface. - Highlights: • We study the effect of self assembled monolayers on the resistivity of thin films. • Fuchs–Sondheimer theory reproduces the resistivity increase due to thiol deposition. • We determined resistivity change due to dodecanethiol deposition on gold thin films. • The electrical response strongly depends on the substrate surface topography.

  2. Recovery of carrier-free gold-195

    International Nuclear Information System (INIS)

    Iofa, B.Z.; Ivanova, N.A.

    1995-01-01

    It is known that gold(III) is readily extracted from nitric acid solutions with ethers. The authors have studied extraction of trace amounts of gold(III) from nitric acid solutions with diethyl and diisopropyl ethers in the presence of significant excess of Pt(IV). Distribution coefficients of gold(III) were measured radiometrically using carrier-free gold-195 or spectrophotometrically in the presence of platinum(IV). Very high coefficients of gold separation from platinum may be achieved. Preliminary experiments have shown that zinc-65 was not extracted with ethers from nitric acid solutions. As an extraction system, the authors have chosen the system 10 M HNO 3 -diisopropyl ether. After model experiments, the authors have performed recovery of carrier-free gold-195 from a real platinum target irradiated with protons in a cyclotron

  3. Linear Optical Properties of Gold Colloid

    Directory of Open Access Journals (Sweden)

    Jingmin XIA

    2015-11-01

    Full Text Available Gold colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The morphology, size of gold nanoparticles and the optical property of colloid were characterized by transmission electron microscope and UV-Vis spectrophotometer, respectively. It shows that the gold nanoparticles are in the shape of spheres with diameters less than 8 nm, and the surface plasmon resonance absorption peak is located at about 438 nm. As the volume fraction of gold particles increases, the intensity of absorption peak strengthens. The optical property of gold colloid was analyzed by Maxwell-Garnett (MG effective medium theory in the company of Drude dispersion model. The results show that the matrix dielectric constant is a main factor, which influences the optical property of gold colloid.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9558

  4. Physiological investigation of gold nanorods toward watermelon.

    Science.gov (United States)

    Wan, Yujie; Li, Junli; Ren, Hongxuan; Huang, Jin; Yuan, Hong

    2014-08-01

    The objective of the present study was to evaluate the phytotoxicity and oxidant stress of the gold nanorods toward watermelon, and hence give a quantitative risk assessment of both seeds and plants phase. The seed germination, the activity of antioxidant enzymes, and the contents of soluble protein and malondialdehyde (MDA) have been measured while the plant roots were observed by transmission electron microscopy (TEM). It was found that the gold nanorods significantly promoted the root elongation. Furthermore, the results on the enzymes activities of plant indicated that oxidative stress happened in the plant treated with gold nanorods. However, the gold nanorods resulted in the phytotoxicity toward plant especially at high concentration. The TEM images of the plant roots with and without the treatment of gold nanorods showed the significant different size of starch granules. In conclusion, significant physiological changes of plant occurred after treatment with the gold nanorods.

  5. Gold nanocages: from synthesis to theranostic applications.

    Science.gov (United States)

    Xia, Younan; Li, Weiyang; Cobley, Claire M; Chen, Jingyi; Xia, Xiaohu; Zhang, Qiang; Yang, Miaoxin; Cho, Eun Chul; Brown, Paige K

    2011-10-18

    some of the most recent advances in the use of Au nanocages for a broad range of theranostic applications. First, we describe their use as tracers for tracking by multiphoton luminescence. Gold nanocages can also serve as contrast agents for photoacoustic (PA) and mutimodal (PA/fluorescence) imaging. In addition, these nanostructures can be used as photothermal agents for the selective destruction of cancerous or diseased tissue. Finally, Au nanocages can serve as drug delivery vehicles for controlled and localized release in response to external stimuli such as NIR radiation or high-intensity focused ultrasound (HIFU).

  6. Gold and Silver Extraction from Leach Solutions

    Directory of Open Access Journals (Sweden)

    Bagdaulet K. Kenzhaliyev

    2014-03-01

    Full Text Available There has been carried out an investigation on the extraction of gold and silver from thiosulfate solutions: standard test and technological solutions of chemical and electrochemical leaching. The influence of related metals on the process of extracting gold from solution was studied. There has been conducted a comparative study of the IR spectra of solutions after the sorption of gold, silver and related metals.

  7. Geochemical indicators of gold ore fields

    International Nuclear Information System (INIS)

    Shcherbakov, Yu.G.

    1995-01-01

    The principles of selection of indicators for genetic reconstructions and prognostic valuations of gold mineralization of diverse morphological and geochemical types have been substantiated. The neutron-activation analysis with radiochemical separation and detection limit of 1-10 -8 %, instrumental neutron-activation analysis and atomic-absorption analysis are the main methods of determination of gold low contents in the rocks, as well as diverse elements, including transition, rare earth elements and tellurium, in gold. 50 refs.; 1 fig.; 3 tabs

  8. Glyco-gold nanoparticles: synthesis and applications

    OpenAIRE

    Compostella, Federica; Pitirollo, Olimpia; Silvestri, Alessandro; Polito, Laura

    2017-01-01

    Glyco-gold nanoparticles combine in a single entity the peculiar properties of gold nanoparticles with the biological activity of carbohydrates. The result is an exciting nanosystem, able to mimic the natural multivalent presentation of saccharide moieties and to exploit the peculiar optical properties of the metallic core. In this review, we present recent advances on glyco-gold nanoparticle applications in different biological fields, highlighting the key parameters which inspire the glyco ...

  9. Glyco-gold nanoparticles: synthesis and applications

    Directory of Open Access Journals (Sweden)

    Federica Compostella

    2017-05-01

    Full Text Available Glyco-gold nanoparticles combine in a single entity the peculiar properties of gold nanoparticles with the biological activity of carbohydrates. The result is an exciting nanosystem, able to mimic the natural multivalent presentation of saccharide moieties and to exploit the peculiar optical properties of the metallic core. In this review, we present recent advances on glyco-gold nanoparticle applications in different biological fields, highlighting the key parameters which inspire the glyco nanoparticle design.

  10. Coal gold agglomeration: an innovative approach to the recovery of gold in environmentally sensitive areas

    Energy Technology Data Exchange (ETDEWEB)

    Wall, N.C.; Hughes-Narborough, C.; Willey, G. [Davy (Stockton) Ltd., Stockton-on-Tees (United Kingdom)

    1994-11-01

    Coal Gold Agglomeration (CGA) was developed by BP Minerals and involves the selective recovery of oleophilic gold particles from an aqueous slurry into coal-oil agglomerates. These agglomerates are allowed to build up to a high gold loading and are then separated from the slurry. The loaded agglomerates are burned and the gold is finally recovered from the ash residue by dissolution and precipitation or by direct smelting. 6 figs.

  11. Gold nano-particles fixed on glass

    International Nuclear Information System (INIS)

    Worsch, Christian; Wisniewski, Wolfgang; Kracker, Michael; Rüssel, Christian

    2012-01-01

    Highlights: ► We produced wear resistant gold–ruby coatings on amorphous substrates. ► Thin sputtered gold layers were covered by or embedded in silica coatings. ► Annealing above T g of the substrate glass led to the formation of gold nano particles. ► A 1 1 1-texture of the gold particles is observed via XRD and EBSD. ► EBSD-patterns can be acquired from crystals covered by a thin layer of glass. - Abstract: A simple process for producing wear resistant gold nano-particle coatings on transparent substrates is proposed. Soda-lime-silica glasses were sputtered with gold and subsequently coated with SiO 2 using a combustion chemical vapor deposition technique. Some samples were first coated with silica, sputtered with gold and then coated with a second layer of silica. The samples were annealed for 20 min at either 550 or 600 °C. This resulted in the formation of round, well separated gold nano-particles with sizes from 15 to 200 nm. The color of the coated glass was equivalent to that of gold–ruby glasses. Silica/gold/silica coatings annealed at 600 °C for 20 min were strongly adherent and scratch resistant. X-ray diffraction and electron backscatter diffraction (EBSD) were used to describe the crystal orientations of the embedded particles. The gold particles are preferably oriented with their (1 1 1) planes perpendicular to the surface.

  12. CO oxidation on gold nanoparticles: Theoretical studies

    DEFF Research Database (Denmark)

    Remediakis, Ioannis; Lopez, Nuria; Nørskov, Jens Kehlet

    2005-01-01

    We present a summary of our theoretical results regarding CO oxidation on both oxide-supported and isolated gold nanoparticles. Using Density Functional Theory we have studied the adsorption of molecules and the oxidation reaction of CO on gold clusters. Low-coordinated sites on the gold...... nanoparticles can adsorb small inorganic molecules such as O2 and CO, and the presence of these sites is the key factor for the catalytic properties of supported gold nanoclusters. Other contributions, induced by the presence of the support, can provide parallel channels for the reaction and modulate the final...

  13. Gold Rushes and mineral property rights allocation

    DEFF Research Database (Denmark)

    Sinding, Knud

    , is to handle the other projects that are generated by the "gold rush" informational externalities created by the initial discovery. At the core of the problems of dealing with a gold rush situation is both the informational externality and an institutional framework which is not designed to deal with large...... influxes of prospectors competing for a very limited area. This paper charts significant gold rush events in the mineral industry in recent decades and uses preliminary data on the areas impacted by these gold rushes to argue that many mineral tenure systems should be modified in order to be better able...

  14. The GOLD Science Data Center - Algorithm Heritage, Data Product Descriptions and User Services

    Science.gov (United States)

    Lumpe, J. D.; Foroosh, H.; Eastes, R.; Krywonos, A.; Evans, J. S.; Burns, A. G.; Strickland, D. J.; Daniell, R. E.; England, S.; Solomon, S. C.; McClintock, W. E.; Anderson, D. N.

    2013-12-01

    The Global-scale Observations of the Limb and Disk (GOLD) instrument is an imaging spectrograph to be launched onboard a commercial communications satellite in 2017. From its vantage point in geosynchronous orbit GOLD will image the Earth in the far-ultraviolet from 132 to 162 nm. The instrument consists of two independent optical channels, allowing for simultaneous implementation of multiple measurement sequences with different temporal sampling and spectral resolution. In addition to continuously scanning the disk of the Earth, GOLD will also perform routine limb scan and stellar occultation measurements. These measurements will be used to retrieve a variety of data products characterizing the temperature and composition of the thermosphere-ionosphere, and their response to geomagnetic storms and solar forcing. Primary data products include: daytime neutral temperatures near 160 km altitude; daytime O/N2 column density ratios; nighttime peak electron density; thermospheric O2 density profiles (day and night); daytime exospheric neutral temperature on the limb; atmospheric tides from temperature perturbations; and the location and evolution of ionospheric bubbles. GOLD data will be processed at the Science Data Center (SDC) located at the University of Central Florida. The SDC will also serve as the primary gateway for distribution of GOLD data products to end-users. In this talk we summarize the heritage and theoretical basis of the GOLD retrieval algorithms and describe the full range of GOLD data products that will be available at the SDC, including estimates of data latency and quality.

  15. Conductometric gas sensors based on metal oxides modified with gold nanoparticles: a review

    International Nuclear Information System (INIS)

    Korotcenkov, Ghenadii; Cho, Beong K.; Brinzari, Vladimir

    2016-01-01

    This review (with 170 refs.) discusses approaches towards surface functionalizaton of metal oxides by gold nanoparticles, and the application of the resulting nanomaterials in resistive gas sensors. The articles is subdivided into sections on (a) methods for modification of metal oxides with gold nanoparticles; (b) the response of gold nanoparticle-modified metal oxide sensors to gaseous species, (c) a discussion of the limitations of such sensors, and (d) a discussion on future tasks and trends along with an outlook. It is shown that, in order to achieve significant improvements in sensor parameters, it is necessary to warrant a good control the size and density of gold nanoparticles on the surface of metal oxide crystallites, the state of gold in the cluster, and the properties of the metal oxide support. Current challenges include an improved reproducibility of sensor preparation, better long-term stabilities, and a better resistance to sintering and poisoning of gold clusters during operation. Additional research focused on better understanding the role of gold clusters and nanoparticles in gas-sensing effects is also required. (author)

  16. Causes and consequences of a tropical forest gold rush in the Guiana Shield, South America.

    Science.gov (United States)

    Hammond, David S; Gond, Valéry; de Thoisy, Benoit; Forget, Pierre-Michel; DeDijn, Bart P E

    2007-12-01

    Statistical and spatial analyses of both historical time series and remotely sensed data show a link between the spatial distribution and growth of gold production across the Guiana Shield in northeast Amazonia. Results indicate that an exponential rise in production across an expanding area is primarily a delayed response to the 1971-1978 market flotation of international gold prices. The subsequent 10-fold (2-fold) average nominal (real) price increase has provided a compelling economic incentive to mass exploitation of lower-grade gold deposits. The ground-based and remotely sensed distributions of mining activity are strongly attached to these deposits that dominate the region's gold geology. The presence of these gold-bearing formations in conservation and sustainable timber zones has sparked social conflict and environmental degradation across the region. Left unmanaged, more than a quarter-million square-kilometer area of tropical forest zoned for protection and sustainable management could ultimately be compromised by the price-driven boom in gold mining through poorly integrated resource use planning, lack of reclamation effort, and control of illegal operations. Serious public health issues propagated through the unregulated mining environment further erode the financial benefits achieved through gold extraction. This study demonstrates in part how international economic policies successfully stabilizing more conspicuous centers of the global economy can have unintended but profound environmental and social impacts on remote commodity frontiers.

  17. Land Use Change Driven by Gold Mining; Peruvian Amazon

    Science.gov (United States)

    Swenson, J. J.; Carter, C. E.; domec, J.; Delgado, C. I.

    2011-12-01

    Many factors such as poverty, ineffective institutions and environmental regulations may prevent developing countries from managing how natural resources are extracted to meet a strong market demand. Extraction for some resources has reached such proportions that evidence is measurable from space. We present recent evidence of the global demand for a single commodity and the ecosystem destruction resulting from commodity extraction, recorded by satellites for one of the most biodiverse areas of the world. We find that since 2003, recent mining deforestation in Madre de Dios, Peru is increasing nonlinearly alongside a constant annual rate of increase in international gold price (~18%/yr). We detect that the new pattern of mining deforestation (1915 ha/year, 2006-2009) is outpacing that of nearby settlement deforestation. We show that gold price is linked with exponential increases in Peruvian national mercury imports over time (R2 = 0.93, p = 0.04, 2003- 2009). Given the past rates of increase we predict that mercury imports may more than double for 2011 (~500 t/year). Virtually all of Peru's mercury imports are used in artisanal gold mining. Much of the mining increase is unregulated/ artisanal in nature, lacking environmental impact analysis or miner education. As a result, large quantities of mercury are being released into the atmosphere, sediments and waterways. Other developing countries endowed with gold deposits are likely experiencing similar environmental destruction in response to recent record high gold prices. The increasing availability of satellite imagery ought to evoke further studies linking economic variables with land use and cover changes on the ground.

  18. Nuclear excitation in muonic gold

    CERN Document Server

    Robert Tissot, B; Debrunner, P; Engfer, R; Link, R; Schellenberg, L; Schneuwly, H; Walter, H K

    1973-01-01

    Energies and intensities of muonic X-rays in gold were measured at the CERN muon channel with an experimental set-up as described by Backe et al. (1972). The 2p-1s and 3d-2p transitions could only be analysed taking into account beside the static quadrupole interaction a dynamical hyperfine interaction of the 2p states, which leads to an excitation of the first four nuclear levels. The dynamical hyperfine interaction was calculated using the core excitation model (de Shalit, (1961)). (0 refs).

  19. The Resonance Integral of Gold

    Energy Technology Data Exchange (ETDEWEB)

    Jirlow, K; Johansson, E

    1959-04-15

    The resonance activation integral of gold has been determined, by means of cadmium ratio measurements of thin foils in a neutron beam. Comparison was made with a 1/v detector, and the neutron spectra were measured with a chopper. The resonance integral, RI, is defined as {integral}{sub 0.5}{sup {infinity}}{sigma}{sub r}(E)dE/E, where {sigma}{sub r}(E) is the differenc between the total absorption cross section and the 1/v part. An experimental value of 1490 {+-} 40 barns has been obtained. RI has also been computed from resonance parameter data with the result 1529 {+-} 70 barns.

  20. Self-assembled lipoprotein based gold nanoparticles for detection and photothermal disaggregation of β-amyloid aggregates

    KAUST Repository

    Martins, P. A. T.; Alsaiari, Shahad K.; Julfakyan, Khachatur; Nie, Z.; Khashab, Niveen M.

    2017-01-01

    We present a reconstituted lipoprotein-based nanoparticle platform comprising a curcumin fluorescent motif and an NIR responsive gold core. This multifunctional nanosystem is successfully used for aggregation-dependent fluorescence detection and photothermal disassembly of insoluble amyloid aggregates.

  1. Self-assembled lipoprotein based gold nanoparticles for detection and photothermal disaggregation of β-amyloid aggregates

    KAUST Repository

    Martins, P. A. T.

    2017-01-10

    We present a reconstituted lipoprotein-based nanoparticle platform comprising a curcumin fluorescent motif and an NIR responsive gold core. This multifunctional nanosystem is successfully used for aggregation-dependent fluorescence detection and photothermal disassembly of insoluble amyloid aggregates.

  2. Geochemical methodology for gold prospect ion in Uruguay

    International Nuclear Information System (INIS)

    Spangenber, J.

    1987-01-01

    This work is about the history of gold prospection in Uruguay. In this study there are considered the geochemical aspects, the gold performance, the applicability to mining prospection and the gold prospection aluvionar

  3. An Effective Amperometric Biosensor Based on Gold Nanoelectrode Arrays

    Directory of Open Access Journals (Sweden)

    Zhu Yingchun

    2008-01-01

    Full Text Available Abstract A sensitive amperometric biosensor based on gold nanoelectrode array (NEA was investigated. The gold nanoelectrode array was fabricated by template-assisted electrodeposition on general electrodes, which shows an ordered well-defined 3D structure of nanowires. The sensitivity of the gold NEA to hydrogen peroxide is 37 times higher than that of the conventional electrode. The linear range of the platinum NEA toward H2O2is from 1 × 10−6to 1 × 10−2 M, covering four orders of magnitudes with detection limit of 1 × 10−7 M and a single noise ratio (S/N of four. The enzyme electrode exhibits an excellent response performance to glucose with linear range from 1 × 10−5to 1 × 10−2 M and a fast response time within 8 s. The Michaelis–Menten constantkm and the maximum current densityi maxof the enzyme electrode were 4.97 mM and 84.60 μA cm−2, respectively. This special nanoelectrode may find potential application in other biosensors based on amperometric signals.

  4. Gold emissivities for hydrocode applications

    Science.gov (United States)

    Bowen, C.; Wagon, F.; Galmiche, D.; Loiseau, P.; Dattolo, E.; Babonneau, D.

    2004-10-01

    The Radiom model [M. Busquet, Phys Fluids B 5, 4191 (1993)] is designed to provide a radiative-hydrodynamic code with non-local thermodynamic equilibrium (non-LTE) data efficiently by using LTE tables. Comparison with benchmark data [M. Klapisch and A. Bar-Shalom, J. Quant. Spectrosc. Radiat. Transf. 58, 687 (1997)] has shown Radiom to be inaccurate far from LTE and for heavy ions. In particular, the emissivity was found to be strongly underestimated. A recent algorithm, Gondor [C. Bowen and P. Kaiser, J. Quant. Spectrosc. Radiat. Transf. 81, 85 (2003)], was introduced to improve the gold non-LTE ionization and corresponding opacity. It relies on fitting the collisional ionization rate to reproduce benchmark data given by the Averroès superconfiguration code [O. Peyrusse, J. Phys. B 33, 4303 (2000)]. Gondor is extended here to gold emissivity calculations, with two simple modifications of the two-level atom line source function used by Radiom: (a) a larger collisional excitation rate and (b) the addition of a Planckian source term, fitted to spectrally integrated Averroès emissivity data. This approach improves the agreement between experiments and hydrodynamic simulations.

  5. Gold emissivities for hydrocode applications

    International Nuclear Information System (INIS)

    Bowen, C.; Wagon, F.; Galmiche, D.; Loiseau, P.; Dattolo, E.; Babonneau, D.

    2004-01-01

    The Radiom model [M. Busquet, Phys Fluids B 5, 4191 (1993)] is designed to provide a radiative-hydrodynamic code with non-local thermodynamic equilibrium (non-LTE) data efficiently by using LTE tables. Comparison with benchmark data [M. Klapisch and A. Bar-Shalom, J. Quant. Spectrosc. Radiat. Transf. 58, 687 (1997)] has shown Radiom to be inaccurate far from LTE and for heavy ions. In particular, the emissivity was found to be strongly underestimated. A recent algorithm, Gondor [C. Bowen and P. Kaiser, J. Quant. Spectrosc. Radiat. Transf. 81, 85 (2003)], was introduced to improve the gold non-LTE ionization and corresponding opacity. It relies on fitting the collisional ionization rate to reproduce benchmark data given by the Averroes superconfiguration code [O. Peyrusse, J. Phys. B 33, 4303 (2000)]. Gondor is extended here to gold emissivity calculations, with two simple modifications of the two-level atom line source function used by Radiom: (a) a larger collisional excitation rate and (b) the addition of a Planckian source term, fitted to spectrally integrated Averroes emissivity data. This approach improves the agreement between experiments and hydrodynamic simulations

  6. Extracellular biosynthesis of gold and silver nanoparticles using Krishna tulsi ( Ocimum sanctum) leaf

    Science.gov (United States)

    Philip, Daizy; Unni, C.

    2011-05-01

    Aqueous extract of Ocimum sanctum leaf is used as reducing agent for the environmentally friendly synthesis of gold and silver nanoparticles. The nanoparticles were characterized using UV-vis, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. These methods allow the synthesis of hexagonal gold nanoparticles having size ∼30 nm showing two surface plasmon resonance (SPR) bands by changing the relative concentration of HAuCl 4 and the extract. Broadening of SPR is observed at larger quantities of the extract possibly due to biosorption of gold ions. Silver nanoparticles with size in the range 10-20 nm having symmetric SPR band centered around 409 nm are obtained for the colloid synthesized at room temperature at a pH of 8. Crystallinity of the nanoparticles is confirmed from the XRD pattern. Biomolecules responsible for capping are different in gold and silver nanoparticles as evidenced by the FTIR spectra.

  7. Anthelmintic efficacy of gold nanoparticles derived from a phytopathogenic fungus, Nigrospora oryzae.

    Directory of Open Access Journals (Sweden)

    Pradip Kumar Kar

    Full Text Available Exploring a green chemistry approach, this study brings to the fore, the anthelmintic efficacy of gold nanoparticles, highlighting the plausible usage of myconanotechnology. Gold nanoparticles of ∼6 to ∼18 nm diameter were synthesized by treating the mycelia-free culture filtrate of the phytopathogenic fungus with gold chloride. Their size and morphology were confirmed by UV-Vis spectroscopy, DLS data, AFM and TEM images. The XRD studies reveal a crystalline nature of the nanoparticles, which are in cubic phase. The FTIR spectroscopic studies before and after the formation of nanoparticles show the presence of possible functional groups responsible for the bio-reduction and capping of the synthesized gold nanoparticles. The latter were tested as vermifugal agents against a model cestode Raillietina sp., an intestinal parasite of domestic fowl. Further, ultrastructural and biochemical parameters were used to corroborate the efficacy study.

  8. Paper Money but a Gold Debt. Italy in the Gold Standard

    OpenAIRE

    Giuseppe Tattara; or consequences)

    2002-01-01

    During the 52 years between the Unification of the Kingdom of Italy and World War 1, the lira was legally convertible into metal for a limited period of time. Although not formally committed to gold, the lira exchange towards the gold standard countries proved remarkably stable, \\223shadowing\\224 gold. It is widely claimed that being one of the successful members of the gold standard circle entailed a number of advantages. If the lira was closely linked to gold, suggesting that there was only...

  9. Metallic gold treatment reduces proliferation of inflammatory cells, increases expression of VEGF and FGF, and stimulates cell proliferation in the subventricular zone following experimental traumatic brain injury

    DEFF Research Database (Denmark)

    Pedersen, Mie Østergaard; Larsen, Agnete; Pedersen, Dan Sonne

    2009-01-01

    Traumatic brain injury represents a leading cause of morbidity in young individuals and there is an imperative need for neuroprotective treatments limiting the neurologic impairment following such injury. It has recently been demonstrated that bio-liberated gold ions liberated from small metallic...... gold implants reduce inflammation and neuronal apoptosis, while generating an increased neuronal stem cell response following focal brain damage. In this study mice were subjected to a unilateral traumatic cryo-lesion with concomitant injection of 25-45 microm gold particles near the lesion. Placebo...... increase in cell proliferation in both the ipsilateral and the contralateral subventricular zone was found in response to gold-treatment. In conclusion: we confirmed the previously demonstrated anti-inflammatory effect of bio-liberated gold ions, and further show that metallic gold increases growth factor...

  10. Fano resonances in heterogeneous dimers of silicon and gold nanospheres

    Science.gov (United States)

    Zhao, Qian; Yang, Zhong-Jian; He, Jun

    2018-06-01

    We theoretically investigate the optical properties of dimers consisting of a gold nanosphere and a silicon nanosphere. The absorption spectrum of the gold sphere in the dimer can be significantly altered and exhibits a pronounced Fano profile. Analytical Mie theory and numerical simulations show that the Fano profile is induced by constructive and destructive interference between the incident electric field and the electric field of the magnetic dipole mode of the silicon sphere in a narrow wavelength range. The effects of the silicon sphere size, distance between the two spheres, and excitation configuration on the optical responses of the dimers are studied. Our study reveals the coherent feature of the electric fields of magnetic dipole modes in dielectric nanostructures and the strong interactions of the coherent fields with other nanophotonic structures.

  11. Events affecting gold exploration in Venezuela since 1999

    Science.gov (United States)

    Wilburn, David R.

    2014-01-01

    The structure of the gold mining industry in Venezuela has changed significantly since 1999 as a result of Government policy changes and industry response to these changes. This report documents the policy decisions that have affected the mining industry, discusses the response of the industry on a site by site basis, and suggests possible effects of these changes on the global economy. For the short term, at least, it appears that these changes have made Venezuela a more difficult place to invest for U.S. and Canadian companies, while investment by Chinese entities has been encouraged.

  12. Spherical aggregates composed of gold nanoparticles

    International Nuclear Information System (INIS)

    Chen, C-C; Kuo, P-L; Cheng, Y-C

    2009-01-01

    Alkylated triethylenetetramine (C12E3) was synthesized and used as both a reductant in the preparation of gold nanoparticles by the reduction of HAuCl 4 and a stabilizer in the subsequent self-assembly of the gold nanoparticles. In acidic aqueous solution, spherical aggregates (with a diameter of about 202 ± 22 nm) of gold nanoparticles (with the mean diameter of ∼18.7 nm) were formed. The anion-induced ammonium adsorption of the alkylated amines on the gold nanoparticles was considered to provide the electrostatic repulsion and steric hindrance between the gold nanoparticles, which constituted the barrier that prevented the individual particles from coagulating. However, as the amino groups became deprotonated with increasing pH, the ammonium adsorption was weakened, and the amino groups were desorbed from the gold surface, resulting in discrete gold particles. The results indicate that the morphology of the reduced gold nanoparticles is controllable through pH-'tunable' aggregation under the mediation of the amino groups of alkylated amine to create spherical microstructures.

  13. Gold deposits of the southern Piedmont

    Science.gov (United States)

    Pardee, J.T.; Park, C.F.

    1948-01-01

    This report deals chiefly with the gold mines in the Southern Appalachian gold belt whose workings were accessible at the time of examination, but it also · summarizes available information concerning many mines that were not accessible. Most of the mines lie within a belt, 10 to 100 miles wide, that extends

  14. Nonlinear optical studies of single gold nanoparticles

    NARCIS (Netherlands)

    Dijk, Meindert Alexander van

    2007-01-01

    Gold nanoparticles are spherical clusters of gold atoms, with diameters typically between 1 and 100 nanometers. The applications of these particles are rather diverse, from optical labels for biological experiments to data carrier for optical data storage. The goal of my project was to develop new

  15. Ionization model for nickel-like gold

    International Nuclear Information System (INIS)

    Busquet, M.; Bruneau, J.

    1986-04-01

    Before we build an extensive population model for gold ionized 49 to 52 times, we have studied with a more simple model the effect of accounting for cascades (or dielectronic recombination) and Δn = 0 transitions. These transitions allow some understanding of typical feature of experimental gold spectra

  16. The Stability of Supported Gold Catalysts

    NARCIS (Netherlands)

    Masoud, Nazila

    2018-01-01

    Gold has supreme cultural and financial value and, in form of nanoparticles smaller than 10 nm, is a unique catalyst for different industrially relevant reactions. Intriguing properties of the gold catalysts have spurred demand in the chemical industry for Au catalysts, the application of which

  17. Goudafzettingen in Suriname (Gold deposits in Surinam)

    NARCIS (Netherlands)

    Brinck, J.W.

    1956-01-01

    THE GOLD DEPOSITS IN SURINAM AND THE DISTRIBUTION OF CONCESSIONS THROUGH THE COUNTRY The fieldwork on the occurrence of primary and secondary gold deposits in Surinam on which this thesis is based was carried out by order of the Welfare Fund Surinam (Welvaarts Fonds Suriname) during the periods

  18. Gold - Old Drug with New Potentials.

    Science.gov (United States)

    Faa, Gavino; Gerosa, Clara; Fanni, Daniela; Lachowicz, Joanna I; Nurchi, Valeria M

    2018-01-01

    Research into gold-based drugs for a range of human diseases has seen a revival in recent years. This article reviews the most important applications of gold products in different fields of human pathology. Au(I) and Au(III) compounds have been re-introduced in clinical practice for targeting the cellular components involved in the onset and progression of viral and parasitic diseases, rheumatoid arthritis and cancer. After some brief historical notes, this article takes into account the applications of gold compounds against Mycobacterium tuberculosis, and also in tuberculosis and in rheumatoid arthritis treatment. The use of gold containing drugs in the cure of cancer are then considered, with special emphasis to the use of nanoparticles and to the photo-thermal cancer therapy. The use of colloidal gold in diagnostics, introduced in the last decade is widely discussed. As a last point a survey on the adverse effects and on the toxicity of the various gold derivatives in use in medicine is presented. In this review, we described the surprisingly broad spectrum of possible uses of gold in diagnostics and in therapeutic approaches to multiple human diseases, ranging from degenerative to infectious diseases, and to cancer. In particular, gold nanoparticles appear as attractive elements in modern clinical medicine, combining high therapeutic properties, high selectivity in targeting cancer cells and low toxicity. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  19. Numerical simulations of nanostructured gold films

    DEFF Research Database (Denmark)

    Repän, Taavi; Frydendahl, Christian; Novikov, Sergey M.

    2017-01-01

    We present an approach to analyse near-field effects on nanostructured gold films by finite element simulations. The studied samples are formed by fabricating gold films near the percolation threshold and then applying laser damage. Resulting samples have complicated structures, which...

  20. Gold 100: proceedings of the international conference on gold. V. 2

    International Nuclear Information System (INIS)

    Fivaz, C.E.; King, R.P.

    1986-01-01

    The proceedings of Gold 100 have been published in three separate volumes. The first deals with the mining of gold, the second with the extractive metallurgy of gold, and the third with industrial uses of gold. In this second volume, the papers on extractive metallurgy presented at the Conference reflect most of the problems that are currently of significant technical interest to the industry. This volume is divided in six main parts covering plant design, carbon-in-pulp technology, refractory gold, new technology, grinding and concentration, and leaching. The part on new technology includes papers on x-ray fluorescence analyzers, Moessbauer spectroscopy and leaching processes for uranium, while the part on grinding and concentration includes papers on nuclear and radiotracer techniques for the recovery of gold as well as various flotation parameters in the flotation behaviour of gold and uranium

  1. Sandwiched gold/PNIPAm/gold microstructures for smart plasmonics application: towards the high detection limit and Raman quantitative measurements.

    Science.gov (United States)

    Elashnikov, R; Mares, D; Podzimek, T; Švorčík, V; Lyutakov, O

    2017-08-07

    A smart plasmonic sensor, comprising a layer of a stimuli-responsive polymer sandwiched between two gold layers, is reported. As a stimuli-responsive material, a monolayer of poly(N-isopropylacrylamide) (PNIPAm) crosslinked globules is used. A quasi-periodic structure of the top gold layer facilitates efficient excitation and serves as a support for plasmon excitation and propagation. The intermediate layer of PNIPAm efficiently entraps targeted molecules from solutions. The sensor structure was optimized for efficient light focusing in the "active" PNIPAm layer. The optimization was based on the time-resolved finite-element simulations, which take into account the thickness of gold layers, size of PNIPAm globules and Raman excitation wavelength (780 nm). The prepared structures were characterized using SEM, AFM, UV-Vis refractometry and goniometry. Additional AFM scans were performed in water at two temperatures corresponding to the collapsed and swollen PNIPAm states. The Raman measurements demonstrate a high detection limit and perfect reproducibility of the Raman scattering signal for the prepared sensor. In addition, the use of created SERS structures for the detection of relevant molecules in the medical, biological and safety fields was demonstrated.

  2. Gold analysis by the gamma absorption technique

    International Nuclear Information System (INIS)

    Kurtoglu, Arzu; Tugrul, A.B.

    2003-01-01

    Gold (Au) analyses are generally performed using destructive techniques. In this study, the Gamma Absorption Technique has been employed for gold analysis. A series of different gold alloys of known gold content were analysed and a calibration curve was obtained. This curve was then used for the analysis of unknown samples. Gold analyses can be made non-destructively, easily and quickly by the gamma absorption technique. The mass attenuation coefficients of the alloys were measured around the K-shell absorption edge of Au. Theoretical mass attenuation coefficient values were obtained using the WinXCom program and comparison of the experimental results with the theoretical values showed generally good and acceptable agreement

  3. Synthesis of camptothecin-loaded gold nanomaterials

    International Nuclear Information System (INIS)

    Xing Zhimin; Liu Zhiguo; Zu Yuangang; Fu Yujie; Zhao Chunjian; Zhao Xiuhua; Meng Ronghua; Tan Shengnan

    2010-01-01

    Camptothecin-loaded gold nanomaterials have been synthesized by the sodium borohydride reduction method under a strong basic condition. The obtained gold nanomaterials have been characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV-vis absorption spectroscopy. The camptothecin-loaded gold colloidal solution was very stable and can be stored for more than two months at room temperature without obvious changes. The color of the colloidal solution can change from wine red to purple and blue during the acidifying process. It was revealed that the release of camptothecin and the aggregation of gold nanoparticles can be controlled by tuning the solution pH. The present study implied that the gold nanomaterials can be used as the potential carrier for CPT delivery.

  4. Hydrofluorination of Alkynes Catalysed by Gold Bifluorides.

    Science.gov (United States)

    Nahra, Fady; Patrick, Scott R; Bello, Davide; Brill, Marcel; Obled, Alan; Cordes, David B; Slawin, Alexandra M Z; O'Hagan, David; Nolan, Steven P

    2015-01-01

    We report the synthesis of nine new N -heterocyclic carbene gold bifluoride complexes starting from the corresponding N -heterocyclic carbene gold hydroxides. A new methodology to access N,N' -bis(2,6-diisopropylphenyl)imidazol-2-ylidene gold(I) fluoride starting from N,N' -bis(2,6-diisopropylphenyl)imidazol-2-ylidene gold(I) hydroxide and readily available potassium bifluoride is also reported. These gold bifluorides were shown to be efficient catalysts in the hydrofluorination of symmetrical and unsymmetrical alkynes, thus affording fluorinated stilbene analogues and fluorovinyl thioethers in good to excellent yields with high stereo- and regioselectivity. The method is exploited further to access a fluorinated combretastatin analogue selectively in two steps starting from commercially available reagents.

  5. Synthesis of camptothecin-loaded gold nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Xing Zhimin [Key Laboratory of Forest Plant Ecology of Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Engineering Research Center of Forest Bio-preparation, Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Liu Zhiguo, E-mail: zguoliu@yahoo.com.cn [Key Laboratory of Forest Plant Ecology of Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Engineering Research Center of Forest Bio-preparation, Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Zu Yuangang, E-mail: nefunano@yahoo.com.cn [Key Laboratory of Forest Plant Ecology of Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Engineering Research Center of Forest Bio-preparation, Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Fu Yujie; Zhao Chunjian; Zhao Xiuhua; Meng Ronghua; Tan Shengnan [Key Laboratory of Forest Plant Ecology of Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Engineering Research Center of Forest Bio-preparation, Ministry of Education, Northeast Forestry University, Harbin 150040 (China)

    2010-04-01

    Camptothecin-loaded gold nanomaterials have been synthesized by the sodium borohydride reduction method under a strong basic condition. The obtained gold nanomaterials have been characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV-vis absorption spectroscopy. The camptothecin-loaded gold colloidal solution was very stable and can be stored for more than two months at room temperature without obvious changes. The color of the colloidal solution can change from wine red to purple and blue during the acidifying process. It was revealed that the release of camptothecin and the aggregation of gold nanoparticles can be controlled by tuning the solution pH. The present study implied that the gold nanomaterials can be used as the potential carrier for CPT delivery.

  6. Worth their weight in gold

    International Nuclear Information System (INIS)

    Van Ryssen, E.

    1986-01-01

    A radiotherapeutic method of treating tumours in, on and around the eye, developed and improved over more than a decade of research at the University of Cape Town's Medical School and at the city's Groote Schuur Hospital, has won worldwide recognition. A problem when irradiating eye tumours is that the rays can damage surrounding tissues. Professor Sealy's team overcome this problem by using tailor-made gold or stainless steel shields moulded indiridually to fit the curve of the eyeball of each patient. Depending on the location of the tumour, small radioactive seeds of iodine 125 are placed on the inner or outer curve of the shield in such a way that their rays are confined to the desired location. The number and position of the seeds is worked out to give the desired dose of radiation

  7. Gold nanoparticles: generation and characterization

    International Nuclear Information System (INIS)

    Dey, G.R.

    2013-07-01

    In this presentation we report the reduction of Au 3+ through chemical and free radical (e solv - ) reactions both in non-aqueous and aqueous media. In chemical reduction, the spectral nature in ascorbic acid (AA) and citric acid (CA) systems was different. The band intensity of gold nanoparticles was lower in AA system. While in free radical reaction, the yield of nanoparticles was pure i.e. free from excess reactants. Under the study 60-200 nm size nanoparticles were generated, which are inert to oxygen. Using pulse radiolysis technique, the initial rate for e solv - reaction with Au 3+ was determined to be 7.6 x 10 9 M -1 s -1 . (author)

  8. Extinction Coefficient of Gold Nanostars.

    Science.gov (United States)

    de Puig, Helena; Tam, Justina O; Yen, Chun-Wan; Gehrke, Lee; Hamad-Schifferli, Kimberly

    2015-07-30

    Gold nanostars (NStars) are highly attractive for biological applications due to their surface chemistry, facile synthesis and optical properties. Here, we synthesize NStars in HEPES buffer at different HEPES/Au ratios, producing NStars of different sizes and shapes, and therefore varying optical properties. We measure the extinction coefficient of the synthesized NStars at their maximum surface plasmon resonances (SPR), which range from 5.7 × 10 8 to 26.8 × 10 8 M -1 cm -1 . Measured values correlate with those obtained from theoretical models of the NStars using the discrete dipole approximation (DDA), which we use to simulate the extinction spectra of the nanostars. Finally, because NStars are typically used in biological applications, we conjugate DNA and antibodies to the NStars and calculate the footprint of the bound biomolecules.

  9. Intensification Behavior of Mercury Ions on Gold Cyanide Leaching

    Directory of Open Access Journals (Sweden)

    Qiang Zhong

    2018-01-01

    Full Text Available Cyanidation is the main method used to extract gold from gold raw materials; however, a serious problem with this method is the low leaching rate. In order to improve gold leaching, the intensification behavior of mercury ions on gold cyanide leaching, for two types of materials, sulphide gold concentrate and oxide gold ore, was investigated. The results showed that mercury ions, with only a 10−5 M dosage, could significantly intensify leaching and gold recovery. The dissolution behavior of gold plate was also intensified by 10−5 M mercury ions. Microstructure analysis showed that mercury ions intensified the cyanidation corrosion of the gold surface, resulting in a loose structure, where a large number of deep ravines and raised particles were evident across the whole gold surface. The loose structure added contact surface between the gold and cyanide, and accelerated gold dissolution. Moreover, mercury ions obstructed the formation of insoluble products, such as AuCN, Au(OHCN, and Au(OHx, that lead to a passivation membrane on the gold surface, reducing contact between the gold and cyanide. These effects, brought about by mercury ions, change the structure and product of the gold surface during gold cyanidation and promote gold leaching.

  10. Enrichment of Gold in Antimony Matte by Direct Smelting of Refractory Gold Concentrate

    Science.gov (United States)

    Yang, Tianzu; Xie, Boyi; Liu, Weifeng; Zhang, Duchao; Chen, Lin

    2018-04-01

    Conventional cyanidation technology achieves low gold recovery when used to process refractory gold concentrate. Based on the geochemical characteristics of gold deposit mineralization, a new method is proposed herein for gold enrichment in antimony matte by smelting of refractory gold concentrate. The effects of the FeO/SiO2 and CaO/SiO2 ratios, smelting temperature, and smelting time on the gold recovery were investigated in detail. The optimum conditions were determined to be FeO/SiO2 ratio of 1.2, CaO/SiO2 ratio of 0.4, smelting temperature of 1200°C, and smelting time of 45 min. The gold content in antimony matte and smelting slag was 96.68 and 1.13 g/t, respectively. The gold, antimony, and arsenic recovery was 97.72%, 26.89%, and 6.56%, respectively, with most of the antimony and arsenic volatilized into dust. Mineral liberation analyzer results showed that the antimony matte mainly consisted of FeS and FeO, with three phases, viz. FeAs, SbAs, and AuSb, embedded between them, indicating that gold was easily enriched with antimony and arsenic during smelting of refractory gold concentrate.

  11. Coal-gold agglomeration: an alternative separation process in gold recovery

    Energy Technology Data Exchange (ETDEWEB)

    Akcil, A.; Wu, X.Q.; Aksay, E.K. [Suleyman Demirel University, Isparta (Turkey). Dept. of Mining Engineering

    2009-07-01

    Considering the increasing environmental concerns and the potential for small gold deposits to be exploited in the future, the uses of environmentally friendly processes are essential. Recent developments point to the potential for greatly increased plant performance through a separation process that combines the cyanide and flotation processes. In addition, this kind of alternative treatment processes to the traditional gold recovery processes may reduce the environmental risks of present small-scale gold mining. Gold recovery processes that applied to different types of gold bearing ore deposits show that the type of deposits plays an important role for the selection of mineral processing technologies in the production of gold and other precious metals. In the last 25 years, different alternative processes have been investigated on gold deposits located in areas where environmental issues are a great concern. In 1988, gold particles were first recovered by successful pilot trial of coal-gold agglomeration (CGA) process in Australia. The current paper reviews the importance of CGA in the production of gold ore and identifies areas for further development work.

  12. Gold Leaching Characteristics and Intensification of a High S and As-Bearing Gold Concentrate

    Science.gov (United States)

    Yang, Yong-bin; Liu, Xiao-liang; Jiang, Tao; Li, Qian; Xu, Bin; Zhang, Yan

    Some high sulfur and arsenic-bearing gold concentrate has a gold leaching rate less than 80% by oxidation roasting-pickling-cyanidation process. The characteristics and intensification of gold leaching were studied systemically. By combining chemical composition and phase analysis, the low gold leaching rate was found to lie in the capsulation of gold by iron-containing phases including iron oxides, arsenopyrite and pyrite. 96.66% of gold in the industrial leaching residue was capsulated and 95.88% of the capsulated turned out to be in the iron-containing phases. The results of laboratory pickling-cyanidation experiments on the calcine and industrial leaching residue presented further demonstration for the fact that gold capsulated in the iron-containing phases was hard to be leached. However, the gold cyanide leaching rate of calcine could be raised over 95% by a reduction roasting-pickling pretreatment which played such a significant role in exposing the capsulated gold that gold leaching was intensified remarkably.

  13. Enrichment of Gold in Antimony Matte by Direct Smelting of Refractory Gold Concentrate

    Science.gov (United States)

    Yang, Tianzu; Xie, Boyi; Liu, Weifeng; Zhang, Duchao; Chen, Lin

    2018-06-01

    Conventional cyanidation technology achieves low gold recovery when used to process refractory gold concentrate. Based on the geochemical characteristics of gold deposit mineralization, a new method is proposed herein for gold enrichment in antimony matte by smelting of refractory gold concentrate. The effects of the FeO/SiO2 and CaO/SiO2 ratios, smelting temperature, and smelting time on the gold recovery were investigated in detail. The optimum conditions were determined to be FeO/SiO2 ratio of 1.2, CaO/SiO2 ratio of 0.4, smelting temperature of 1200°C, and smelting time of 45 min. The gold content in antimony matte and smelting slag was 96.68 and 1.13 g/t, respectively. The gold, antimony, and arsenic recovery was 97.72%, 26.89%, and 6.56%, respectively, with most of the antimony and arsenic volatilized into dust. Mineral liberation analyzer results showed that the antimony matte mainly consisted of FeS and FeO, with three phases, viz. FeAs, SbAs, and AuSb, embedded between them, indicating that gold was easily enriched with antimony and arsenic during smelting of refractory gold concentrate.

  14. The giant Jiaodong gold province: The key to a unified model for orogenic gold deposits?

    Directory of Open Access Journals (Sweden)

    David I. Groves

    2016-05-01

    Full Text Available Although the term orogenic gold deposit has been widely accepted for all gold-only lode-gold deposits, with the exception of Carlin-type deposits and rare intrusion-related gold systems, there has been continuing debate on their genesis. Early syngenetic models and hydrothermal models dominated by meteoric fluids are now clearly unacceptable. Magmatic-hydrothermal models fail to explain the genesis of orogenic gold deposits because of the lack of consistent spatially – associated granitic intrusions and inconsistent temporal relationships. The most plausible, and widely accepted, models involve metamorphic fluids, but the source of these fluids is hotly debated. Sources within deeper segments of the supracrustal successions hosting the deposits, the underlying continental crust, and subducted oceanic lithosphere and its overlying sediment wedge all have their proponents. The orogenic gold deposits of the giant Jiaodong gold province of China, in the delaminated North China Craton, contain ca. 120 Ma gold deposits in Precambrian crust that was metamorphosed over 2000 million years prior to gold mineralization. The only realistic source of fluid and gold is a subducted oceanic slab with its overlying sulfide-rich sedimentary package, or the associated mantle wedge. This could be viewed as an exception to a general metamorphic model where orogenic gold has been derived during greenschist- to amphibolite-facies metamorphism of supracrustal rocks: basaltic rocks in the Precambrian and sedimentary rocks in the Phanerozoic. Alternatively, if a holistic view is taken, Jiaodong can be considered the key orogenic gold province for a unified model in which gold is derived from late-orogenic metamorphic devolatilization of stalled subduction slabs and oceanic sediments throughout Earth history. The latter model satisfies all geological, geochronological, isotopic and geochemical constraints but the precise mechanisms of auriferous fluid release, like many

  15. Ultrafast nonlinear dynamics of thin gold films due to an intrinsic delayed nonlinearity

    Science.gov (United States)

    Bache, Morten; Lavrinenko, Andrei V.

    2017-09-01

    Using long-range surface plasmon polaritons light can propagate in metal nano-scale waveguides for ultracompact opto-electronic devices. Gold is an important material for plasmonic waveguides, but although its linear optical properties are fairly well understood, the nonlinear response is still under investigation. We consider the propagation of pulses in ultrathin gold strip waveguides, modeled by the nonlinear Schrödinger equation. The nonlinear response of gold is accounted for by the two-temperature model, revealing it as a delayed nonlinearity intrinsic in gold. The consequence is that the measured nonlinearities are strongly dependent on pulse duration. This issue has so far only been addressed phenomenologically, but we provide an accurate estimate of the quantitative connection as well as a phenomenological theory to understand the enhanced nonlinear response as the gold thickness is reduced. In comparison with previous works, the analytical model for the power-loss equation has been improved, and can be applied now to cases with a high laser peak power. We show new fits to experimental data from the literature and provide updated values for the real and imaginary parts of the nonlinear susceptibility of gold for various pulse durations and gold layer thicknesses. Our simulations show that the nonlinear loss is inhibiting efficient nonlinear interaction with low-power laser pulses. We therefore propose to design waveguides suitable for the mid-IR, where the ponderomotive instantaneous nonlinearity can dominate over the delayed hot-electron nonlinearity and provide a suitable plasmonics platform for efficient ultrafast nonlinear optics.

  16. Gold nanoparticles produced in a microalga

    International Nuclear Information System (INIS)

    Luangpipat, Tiyaporn; Beattie, Isabel R.; Chisti, Yusuf; Haverkamp, Richard G.

    2011-01-01

    An efficient biological route to production of gold nanoparticles which allows the nanoparticles to be easily recovered remains elusive. Live cells of the green microalga Chlorella vulgaris were incubated with a solution of gold chloride and harvested by centrifugation. Nanoparticles inside intact cells were identified by transmission electron microscopy and confirmed to be metallic gold by synchrotron based X-ray powder diffraction and X-ray absorption spectroscopy. These intracellular gold nanoparticles were 40–60 nm in diameter. At a concentration of 1.4% Au in the alga, a better than 97% recovery of the gold from solution was achieved. A maximum of 4.2% Au in the alga was obtained. Exposure of C. vulgaris to solutions containing dissolved salts of palladium, ruthenium, and rhodium also resulted in the production of the corresponding nanoparticles within the cells. These were surmised to be also metallic, but were produced at a much lower intracellular concentration than achieved with gold. Iridium was apparently toxic to the alga. No nanoparticles were observed using platinum solutions. C. vulgaris provides a possible route to large scale production of gold nanoparticles.

  17. NUCLEATION STUDIES OF GOLD ON CARBON ELECTRODES

    Directory of Open Access Journals (Sweden)

    S. SOBRI

    2008-04-01

    Full Text Available Interest has grown in developing non-toxic electrolytes for gold electrodeposition to replace the conventional cyanide-based bath for long term sustainability of gold electroplating. A solution containing thiosulphate and sulphite has been developed specially for microelectronics applications. However, at the end of the electrodeposition process, the spent electrolyte can contain a significant amount of gold in solution. This study has been initiated to investigate the feasibility of gold recovery from a spent thiosulphate-sulphite electrolyte. We have used flat-plate glassy carbon and graphite electrodes to study the mechanism of nucleation and crystal growth of gold deposition from the spent electrolyte. It was found that at the early stages of reduction process, the deposition of gold on glassy carbon exhibits an instantaneous nucleation of non-overlapping particles. At longer times, the particles begin to overlap and the deposition follows a classic progressive nucleation phenomenon. On the other hand, deposition of gold on graphite does not follow the classical nucleation phenomena.

  18. Nature vs. nurture: gold perpetuates "stemness".

    Science.gov (United States)

    Paul, Willi; Sharma, Chandra P; Deb, Kaushik Dilip

    2011-01-01

    Adult tissues contain quiescent reservoirs of multipotent somatic stem cells and pluripotent embryonic-like stem cells (ELSCs). Credited with regenerative properties gold is used across both -contemporary and -ancient medicines. Here, we show that gold exerted these effects by enhancing the pool of pluripotent ELSC while improving their stemness. We used hESCs as an in-vitro model to understand if gold could enhance self-renewal and pluripotency. Swarna-bhasma (SB), an ancient Indian gold microparticulate (41.1 nm), preparation, reduced spontaneous-differentiation, improved self-renewal, pluripotency and proliferation of hESCs. Colloidal gold-nanoparticles (GNP) (15.59 nm) were tested to confirm that the observations were attributable to nanoparticulate-gold. SB and GNP exposure: maintained -stemness, -karyotypic stability, enhanced pluripotency till day-12, increased average colony-sizes, and reduced the number of autonomously-derived differentiated FGFR1 positive fibroblast-niche-cells/colony. Particulate-gold induced upregulation of FGFR1 and IGF2 expression, and decrease in IGF1 secretion indicates IGF1/2 mediated support for enhanced pluripotency and self-renewal in hESCs.

  19. Urban artisanal gold shops and mercury emissions

    International Nuclear Information System (INIS)

    Cordy, P.; Veiga, M.; Carrasco, V.H.G.

    2008-01-01

    Artisanal miners in developing countries use mercury amalgamation processes to extract gold. The amalgams are then refined before being sold on to urban gold shops. The amalgams can often contain between 2 to 40 per cent mercury. Unburned amalgams are also often sold directly to gold shops. There are serious health risks for shop employees and nearby populations when the gold is melted and further purified. Studies have shown that mercury concentrations in the ambient air of gold shops often exceeds World Health Organization (WHO) limits by an order of magnitude or more. This study examined the practices and technologies used to refine gold in Latin America and Indonesia. The study compared and contrasted various refining methods and their resulting mercury emissions. Methods of reducing mercury emissions were also investigated, including a filtration system designed to capture 80 per cent of mercury emissions. Barriers to implementing mercury emissions reduction plans were also investigated. It was concluded that the design of urban gold shops must include condensers, fume hoods, and efficient mercury capture systems. 15 refs

  20. Cyto- and genotoxicity assessment of Gold nanoparticles obtained by laser ablation in A549 lung adenocarcinoma cells

    International Nuclear Information System (INIS)

    Bucchianico, Sebastiano Di; Migliore, Lucia; Marsili, Paolo; Vergari, Chiara; Giammanco, Francesco; Giorgetti, Emilia

    2015-01-01

    Gold nanoparticles have attracted enormous interest in biomedical applications, based on their unique optical properties. However, their toxicity on human tissues is still an open issue. Beyond the potential intrinsic toxicity of nanostructured gold, a non-negligible contribution of stabilizers or reaction by-products related to current wet chemical synthesis procedures can be expected. Aimed at isolating gold contribution from that of any other contaminant, we produced colloidal suspensions of Gold nanoparticles having average size <10 nm in deionized water or acetone by pulsed laser ablation, that permits preparation of uncoated and highly stable Gold nanoparticles in pure solvents. Subsequently, we investigated the role of surface chemistry, size, and dispersivity of synthesized Gold nanoparticles in exerting toxicity in a cell model system of deep respiratory tract, representing the main route of exposure to NPs, namely adenocarcinoma epithelial A549 cells. Gold nanoparticles prepared in water showed no particular signs of cytotoxicity, cytostasis, and/or genotoxicity as assessed by MTT colorimetric viability test and Cytokinesis-block micronucleus cytome assay up to concentrations of the order of 5 μg/mL. In contrast, Gold nanoparticles produced in pure acetone and then transferred into deionized water showed impaired cell viability, apoptosis responses, micronuclei, and dicentric chromosomes induction as well as nuclear budding, as a function of the amount of surface contaminants like amorphous carbon and enolate ions

  1. Cyto- and genotoxicity assessment of Gold nanoparticles obtained by laser ablation in A549 lung adenocarcinoma cells

    Energy Technology Data Exchange (ETDEWEB)

    Bucchianico, Sebastiano Di [Karolinska Institutet, Institute of Environmental Medicine (Sweden); Migliore, Lucia [University of Pisa, Department of Translational Research and New Technologies in Medicine and Surgery, Division of Medical Genetics (Italy); Marsili, Paolo [Institute of Complex Systems (ISC-CNR) (Italy); Vergari, Chiara [Plasma Diagnostics and Technologies s.r.l. (Italy); Giammanco, Francesco [University of Pisa, Department of Physics “E. Fermi” (Italy); Giorgetti, Emilia, E-mail: emilia.giorgetti@fi.isc.cnr.it [Institute of Complex Systems (ISC-CNR) (Italy)

    2015-05-15

    Gold nanoparticles have attracted enormous interest in biomedical applications, based on their unique optical properties. However, their toxicity on human tissues is still an open issue. Beyond the potential intrinsic toxicity of nanostructured gold, a non-negligible contribution of stabilizers or reaction by-products related to current wet chemical synthesis procedures can be expected. Aimed at isolating gold contribution from that of any other contaminant, we produced colloidal suspensions of Gold nanoparticles having average size <10 nm in deionized water or acetone by pulsed laser ablation, that permits preparation of uncoated and highly stable Gold nanoparticles in pure solvents. Subsequently, we investigated the role of surface chemistry, size, and dispersivity of synthesized Gold nanoparticles in exerting toxicity in a cell model system of deep respiratory tract, representing the main route of exposure to NPs, namely adenocarcinoma epithelial A549 cells. Gold nanoparticles prepared in water showed no particular signs of cytotoxicity, cytostasis, and/or genotoxicity as assessed by MTT colorimetric viability test and Cytokinesis-block micronucleus cytome assay up to concentrations of the order of 5 μg/mL. In contrast, Gold nanoparticles produced in pure acetone and then transferred into deionized water showed impaired cell viability, apoptosis responses, micronuclei, and dicentric chromosomes induction as well as nuclear budding, as a function of the amount of surface contaminants like amorphous carbon and enolate ions.

  2. Phytomining for Artisanal Gold Mine Tailings Management

    Directory of Open Access Journals (Sweden)

    Baiq Dewi Krisnayanti

    2016-08-01

    Full Text Available Mine tailings are generally disposed of by artisanal and small scale gold miners in poorly constructed containment areas and this leads to environmental risk. Gold phytomining could be a possible option for tailings management at artisanal and small-scale gold mining (ASGM locations where plants accumulate residual gold in their above ground biomass. The value of metal recovered from plants could offset some of the costs of environmental management. Getting gold into plants has been repeatedly demonstrated by many research groups; however, a simple working technology to get gold out of plants is less well described. A field experiment to assess the relevance of the technology to artisanal miners was conducted in Central Lombok, Indonesia between April and June 2015. Tobacco was planted in cyanidation tailings (1 mg/kg gold and grown for 2.5 months before the entire plot area was irrigated with NaCN to induce metal uptake. Biomass was then harvested (100 kg, air dried, and ashed by miners in equipment currently used to ash activated carbon at the end of a cyanide leach circuit. Borax and silver as a collector metal were added to the tobacco ash and smelted at high temperature to extract metals from the ash. The mass of the final bullion (39 g was greater than the mass of silver used as a collector (31 g, indicating recovery of metals from the biomass through the smelt process. The gold yield of this trial was low (1.2 mg/kg dry weight biomass concentration, indicating that considerable work must still be done to optimise valuable metal recovery by plants at the field scale. However, the described method to process the biomass was technically feasible, and represents a valid technique that artisanal and small-scale gold miners are willing to adopt if the economic case is good.

  3. Electrochemical Oxidation of Glycerol Using Gold Electrode

    International Nuclear Information System (INIS)

    Mohamed Rozali Othman; Amirah Ahmad

    2015-01-01

    Cyclic voltammetry, potential linear V and chronocuolometry methods were carried out to gain electrochemical behavior of glycerol at a gold electrode. Potassium hydroxide and sulfuric acid were chosen to be the electrolyte for the electro-oxidation of this organic compound. Besides gold plate electrode, gold composite electrode (Au-PVC) was also used as the working electrode. The Au-PVC composite electrode was characterized by Scanning Electron Microscopy (SEM) to determine its morphological aspects before and after used in electrochemical oxidation of glycerol. In alkaline solution, the adsorption of hydroxide species onto the surface of both gold plate and composite Au-PVC electrodes occurs at potential around 500 mV vs SCE. However, at gold plate electrode, there was a small, broad peak before the drastic escalation of current densities which indicates the charge transfer of the chemisorbed OH - anion. In acidic media, the gold oxide was formed after potential 1.0 V. From the cyclic voltammogram glycerol undergo oxidation twice in potassium hydroxide at gold plate and Au-PVC composite electrodes, while in sulfuric acid, oxidation reaction happened once for glycerol on the gold plate electrode. Overall, electrochemical oxidation of glycerol was more effective in alkaline media. Tafel graph which plotted from potential linear V method shows that Au-PVC composite electrode is better than gold plate electrode for the electro-oxidation of glycerol in alkaline solution. Electrochemical oxidation of glycerol products as analyzed by Gas Chromatography-Mass Spectrometry (GC-MS) produced several carboxylic acids and phenolic compounds. (author)

  4. Russian and Belorussian firms receive CMS Gold Awards

    CERN Multimedia

    Maximilien Brice

    2003-01-01

    On 7 March, CMS handed out its three latest Gold Awards in recognition of outstanding supplier performance. Photos 01,02: Prof. Felicitas Pauss, Deputy Chair of the CMS Collaboration Board, presents a CMS Gold Award to Professor Valery Novikov, Director-General of Myasishchev Design Bureau, Zhukovsky, Moscow Region, Russia. The Myasishchev company was responsible for the carbon fibre structures in which the fragile lead tungstate crystals of the electromagnetic calorimeter end-caps are to be embedded. These lightweight structures must support a weight of 22.9 tonnes in each end-cap! The company produced a very thin-walled modular structure that ensured the calorimeter performance would not be harmed, while remaining stable and strong. Photos 03,04: Prof. Felicitas Pauss, Deputy Chair of the CMS Collaboration Board, presents a CMS Gold Award to Professor Boris Gabaraev, General director of N.A. Dollezhal Research and Development Institute of Power Engineering (NIKIET), Moscow, Russia (a.k.a. ENTEK) for the de...

  5. Women, mercury and artisanal gold mining : Risk communication and mitigation

    Science.gov (United States)

    Hinton, J. J.; Veiga, M. M.; Beinhoff, C.

    2003-05-01

    Artisanal miners employ rudimentary techniques for minéral extraction and often operate under hazardous, labour intensive, highly disorganized and illegal conditions. Gold is the main mineral extracted by artisanal miners, and the ecological and human health impacts resulting from mercury (Hg) use in gold extraction warrant special consideration. More than 30% of world's 13 million artisanal miners are women and, as they are often perceived to be less suited for labour intensive mining methods, the majority of women work in the processing aspect of artisanal mining, including amalgamation with Hg. As women are also predominantly responsible for food preparation, they are in an excellent position to respond to health risks associated with consumption of Hg-contaminated foods in impacted areas. In addition to their influence on consumption habits, women in artisanal mining communities may be in a position to effect positive change with respect to the technologies employed. Thus, gender sensitive approaches are necessary to reduce exposure risks to women and their families, promote clean technologies and support the development of stronger, healthier artisanal mining communities. This paper describes the roles of women in artisanal gold mining, highlights their importance in reducing the Hg exposure in these communities, and provides insight into how risks from Hg pollution can effectively be communicated and mitigated.

  6. Single cell targeting using plasmon resonant gold-coated liposomes

    Science.gov (United States)

    Leung, Sarah J.; Romanowski, Marek

    2012-03-01

    We have developed an experimental system with the potential for the delivery and localized release of an encapsulated agent with high spatial and temporal resolution. We previously introduced liposome-supported plasmon resonant gold nanoshells; in this composite structure, the liposome allows for the encapsulation of substances, such as therapeutic agents, neurotransmitters, or growth factors, and the plasmon resonant structure facilitates the rapid release of encapsulated contents upon laser light illumination. More recently, we demonstrated that these gold-coated liposomes are capable of releasing their contents in a spectrally-controlled manner, where plasmon resonant nanoparticles only release content upon illumination with a wavelength of light matching their plasmon resonance band. We now show that this release mechanism can be used in a biological setting to deliver a peptide derivative of cholecystokinin to HEK293 cells overexpressing the CCK2 receptor. Using directed laser light, we may enable localized release from gold-coated liposomes to enable accurate perturbation of cellular functions in response to released compounds; this system may have possible applications in signaling pathways and drug discovery.

  7. A statistical analysis of mineral relationships in a Witwatersrand gold placer at Randfontein Estates

    International Nuclear Information System (INIS)

    Tucker, R.F.

    1983-01-01

    The Proterozoic 'Composite Reef' on the Randfontein Estates Gold Mine, is a proximal Witwatersrand braided-stream placer, in which pyrite, chromite, zircon, uraninite, and gold are the more common detrital minerals. They range in concentration from a few ppm to over 3 per cent. Optimum concentration of these minerals occurs on scour- and pebble-armoured surfaces, in conglomerate gravel bars, and in trough cross-bedded quartz-arenites. The distribution of gold is, however, complex and the relative proportions of the detrital minerals change from one depositional situation to another. The abundance of detrital and other related minerals was monitored geochemically and quantitatively indicates the prevalence of optimal placer concentration situations in preserved depositional subenvironments of the 'Composite Reef'. The relationships between 20 elements were determined by using an R-mode factor-analysis of the geochemical data. The elements load on to chalcophile, detrital oxide, hydrothermal and clay factors, suggesting the consanguinity of four subsets of elements. A multiple linear regression of gold against the other elements provides the framework for an improved prediction of gold where only very small or single samples are available. The method uses many elements in a single sample to achieve statistical reliability, as opposed to the geostatistical method where many samples of a single element are analysed. The regression equation demonstrates the geochemical validity of the geological-response model for optimum gold mineralization

  8. Identification of second harmonic optical effects from vaccine coated gold microparticles

    International Nuclear Information System (INIS)

    Jumah, N A; Ameer-Beg, S M; White, N S; Prasad, K V R; Bellhouse, B J

    2004-01-01

    This study investigates the optical effects observed from uncoated and protein vaccine coated gold microparticles while imaging with two-photon excitation in the Mie scattering regime. When observed with time correlated single photon counting fluorescence lifetime microscopy, the emission from the gold microparticles appeared as an intense instrument-limited temporal response. The intensity of the emission showed a second-order dependence on the laser power and frequency doubling of the emitted light was observed for fundamental light between 890 and 970 nm. The optical effect was attributed to two-photon induced second harmonic generation. The vaccine coated gold microparticles had a much weaker second harmonic signal than the uncoated gold microparticles. Chemical analysis of the surface of the gold microparticles revealed that the vaccine coating decreases the surface charge thereby diminishing the observed second harmonic signal. These optical properties can be exploited to identify both the location of the protein vaccine coating as well as the gold microparticles in vitro and potentially to investigate the vaccine delivery kinetics in vivo

  9. Synthesis of gold nanoparticles with graphene oxide.

    Science.gov (United States)

    Wang, Wenshuo; He, Dawei; Zhang, Xiqing; Duan, Jiahua; Wu, Hongpeng; Xu, Haiteng; Wang, Yongsheng

    2014-05-01

    Single sheets of functionalized graphene oxide are derived through chemical exfoliation of natural flake graphite. We present an effective synthetic method of graphene-gold nanoparticles hybrid nanocomposites. AFM (Atomic Force Microscope) was used to measure the thickness of the individual GO nanosheet. FTIR (Fourier transform infrared) spectroscopy was used to verify the attachment of oxygen functionalities on the surface of graphene oxide. TEM (Transmission Electron Microscope) data revealed the average diameters of the gold colloids and characterized the composite particles situation. Absorption spectroscopy showed that before and after synthesis the gold particle size did not change. Our studies indicate that the hybrid is potential substrates for catalysts and biosensors.

  10. Biosynthesis of Gold Nanoparticles Using Pseudomonas Aeruginosa

    International Nuclear Information System (INIS)

    Abd El-Aziz, M.; Badr, Y.; Mahmoud, M. A.

    2007-01-01

    Pseudomonas aeruginosa were used for extracellular biosynthesis of gold nanoparticles (Au NPs). Consequently, Au NPs were formed due to reduction of gold ion by bacterial cell supernatant of P. aeruginos ATCC 90271, P. aeruginos (2) and P. aeruginos (1). The UV-Vis. and fluorescence spectra of the bacterial as well as chemical prepared Au NPs were recorded. Transmission electron microscopy (TEM) micrograph showed the formation of well-dispersed gold nanoparticles in the range of 15-30 nm. The process of reduction being extracellular and may lead to the development of an easy bioprocess for synthesis of Au NPs

  11. The giant Kalgoorlie Gold Field revisited

    Directory of Open Access Journals (Sweden)

    Noreen Mary Vielreicher

    2016-05-01

    Direct timing constraints on gold mineralization indicate that Fimiston- and Mt Charlotte-style mineralization formed within a relative short period of time around 2.64 Ga, and, as such, support a model of progressive deformation of a rheologically heterogeneous rock package late in the structural history. Fluid characteristics, combined with the structural, metamorphic and absolute timing, support description of gold mineralization at the Golden Mile as orogenic and mesozonal, and this allows direct correlation with orogenic gold deposits worldwide, which classically formed during accretion along convergent margins throughout Earth history.

  12. Nondestructive analysis of the gold quarter liras

    International Nuclear Information System (INIS)

    Cakir, C.; Guerol, A.; Demir, L.; Sahin, Y.

    2009-01-01

    In this study, we have prepared seven Au-Cu standards in the concentration range of 18-24 (as carat) for nondestructive control of gold quarter liras. Some calibration curves for quantitative analysis of Au in the gold quarter liras that commercially present in Turkey have been plotted using these standard samples. The characteristic X-rays of Au and Cu emitted from these standard samples and the test sample with known composition are recorded by using a Ge(Li) detector. These calibration curves provide a nondestructive analysis of gold quarter liras with the uncertainties about 1.18%. (author)

  13. Refractory concentrate gold leaching: Cyanide vs. bromine

    Science.gov (United States)

    Dadgar, Ahmad

    1989-12-01

    Gold extraction, recovery and economics for two refractory concentrates were investigated using cyanide and bromine reagents. Gold extractions for cyanide leaching (24-48 hours) and bromine leaching (six hours) were the same and ranged from 94 to 96%. Gold recoveries from bromine pregnant solutions using carbon adsorption, ion exchange, solvent extraction, and zinc and aluminum precipitation methods were better than 99.9%. A preliminary economic analysis indicates that chemical costs for cyanidation and bromine process are 11.70 and 11.60 respectively, per tonne of calcine processed.

  14. Gold's monetary roll will be strengthened - Plumbridge

    International Nuclear Information System (INIS)

    Anon.

    1977-01-01

    Delivering his Presidential address at the Chamber's annual general meeting, Mr Plumbridge said the gold market would enter a new phase and listed seven reasons why gold's monetary role would be strengthened. There was a dramatic increase in the demand for gold jewellery. He also forecasted that South African uranium production would again attain its former peak annual production of about 6000t. There is an essential need for a sustained growth in nuclear power and the prospects for uranium mining industry remain encouraging

  15. Gold nanoparticles extraction from dielectric scattering background

    Science.gov (United States)

    Hong, Xin; Wang, Jingxin

    2014-11-01

    The unique advantages such as brightness, non-photobleaching, good bio-compatibility make gold nanoparticles desirable labels and play important roles in biotech and related research and applications. Distinguishing gold nanoparticles from other dielectric scattering particles is of more importance, especially in bio-tracing and imaging. The enhancement image results from the localized surface plasmon resonance associated with gold nanopartilces makes themselves distinguishable from other dielectric particles, based on which, we propose a dual-wavelength detection method by employing a high sensitive cross-polarization microscopy.

  16. Gold Photoluminescence: Wavelength and Polarization Engineering

    DEFF Research Database (Denmark)

    Andersen, Sebastian Kim Hjælm; Pors, Anders Lambertus; Bozhevolnyi, Sergey I.

    2015-01-01

    We demonstrate engineering of the spectral content and polarization of photoluminescence (PL) from arrayed gold nanoparticles atop a subwavelength-thin dielectric spacer and optically-thick gold film, a configuration that supports gap-surface plasmon resonances (GSPRs). Choice of shapes...... and dimensions of gold nanoparticles influences the GSPR wavelength and polarization characteristics, thereby allowing us to enhance and spectrally mold the plasmon-assisted PL while simultaneously controlling its polarization. In order to understand the underlying physics behind the plasmon-enhanced PL, we...

  17. Nuclear analyses of the Pietroasa gold hoard

    International Nuclear Information System (INIS)

    Cojocaru, V.; Besliu, C.

    1999-01-01

    By means of nuclear analyses the concentrations of Au, Ag, Cu, Ir, Os, Pt, Co and Hg were measured in the 12 artifacts of the gold hoard discovered in 1837 at Pietroasa, Buzau country in Romania. The concentrations of the first four elements were used to compare different stylistic groups assumed by historians. Comparisons with gold nuggets from the old Dacian territory and gold Roman imperial coins were also made. A good agreement was found with the oldest hypothesis which considers that the hoard is represented by three styles appropriated mainly by the Goths. (author)

  18. Coal-oil gold agglomeration assisted flotation to recover gold from refractory ore

    Science.gov (United States)

    Otsuki, A.; Yue, C.

    2017-07-01

    This study aimed to investigate the applicability of coal-oil gold agglomeration (CGA) assisted flotation to recover gold from a refractory ore. The ore with the grade of 2-5 g/t was tested with the CGA-flotation process in six different size fractions from 38 to 300 urn using different collector types and dosages. In addition, the flotation without CGA was performed under the same condition for comparison. The results showed that the higher gold grade and recovery were achieved by applying the CGA-flotation, compared with the flotation without CGA. More than 20-60 times grade increase from the head grade was obtained with CGA-flotation. The elemental analysis of gold and sulphur explained their relationship with gold recovery. The results well indicated the applicability of CGA to upgrade the refractory gold ore.

  19. Gold deposit styles and placer gold characterisation in northern and east-central Madagascar

    Science.gov (United States)

    Pitfield, Peter E. J; Styles, Michael T.; Taylor, Cliff D.; Key, Roger M.; Bauer,; Ralison, A

    2009-01-01

    Microchemical characterisation of bedrock and placer gold grains from six gold districts within the Archaean domains and intervening Neoproterozoic Anaboriana-Manampotsy belt of northern and east-central Madagascar show few opaque inclusions (e.g pyrrhotite, Bi tellurides) but wide range of Ag contents (40wt%). Some districts exhibit multiple source populations of grains. The ‘greenstone belt’ terranes have an orogenic gold signature locally with an intrusion-related to epithermal overprint. Proterozoic metasediments with felsic to ultramafic bodies yield dominantly intrusion-related gold. A high proportion of secondary gold (<0.5wt% Ag) is related to recycling of paleoplacers and erosion of post-Gondwana planation surfaces and indicates that some mesothermal gold systems were already partially to wholly removed by erosion by the PermoTriassic.

  20. Effects of dissolucytotic gold ions on recovering brain lesions.

    Science.gov (United States)

    Danscher, Gorm; Larsen, Agnete

    2010-04-01

    Recent experimental research has shown that metallic gold releases charged gold atoms when placed intracerebrally and that the liberated gold ions affect inflammation in the brain. The observations suggest that metallic gold can be used as a safe suppressor of inflammation in the central nervous system.

  1. Electroplating of gold using a sulfite-based electrolyte

    NARCIS (Netherlands)

    Smalbrugge, E.; Jacobs, B.; Falcone, S.; Geluk, E.J.; Karouta, F.; Leijtens, X.J.M.; Besten, den J.H.

    2000-01-01

    Electroplating of gold is often used in optoelectronic and microelectronic devices for air-bridges, heat-sinks or gold-bumps for flip-chip techniques. The gold-cyanide electrolytes, which are commonly used in gold-electroplating, are toxic and attack resist patterns causing cracks during the plating

  2. Modified gold surfaces by 6-(ferrocenyl)hexanethiol/dendrimer/gold nanoparticles as a platform for the mediated biosensing applications

    Energy Technology Data Exchange (ETDEWEB)

    Karadag, Murat; Geyik, Caner; Demirkol, Dilek Odaci [Ege University, Faculty of Science, Biochemistry Department, 35100 Bornova-Izmir (Turkey); Ertas, F. Nil [Ege University, Faculty of Science, Chemistry Department, 35100, Bornova-Izmir (Turkey); Timur, Suna, E-mail: suna.timur@ege.edu.tr [Ege University, Faculty of Science, Biochemistry Department, 35100 Bornova-Izmir (Turkey)

    2013-03-01

    An electrochemical biosensor mediated by using 6-(Ferrocenyl) hexanethiol (FcSH) was fabricated by construction of gold nanoparticles (AuNPs) on the surface of polyamidoamine dendrimer (PAMAM) modified gold electrode. Glucose oxidase (GOx) was used as a model enzyme and was immobilized onto the gold surface forming a self assembled monolayer via FcSH and cysteamine. Cyclic voltammetry and amperometry were used for the characterization of electrochemical response towards glucose substrate. Following the optimization of medium pH, enzyme loading, AuNP and FcSH amount, the linear range for the glucose was studied and found as 1.0 to 5.0 mM with the detection limit (LOD) of 0.6 mM according to S/N = 3. Finally, the proposed Au/AuNP/(FcSH + Cyst)/PAMAM/GOx biosensor was successfully applied for the glucose analysis in beverages, and the results were compared with those obtained by HPLC. Highlights: Black-Right-Pointing-Pointer Immobilized mediator in SAM layer and dendrimeric structure to expand surface area. Black-Right-Pointing-Pointer Au nanoparticles for enhanced electron transfer. Black-Right-Pointing-Pointer Satisfactory Limit of Detection with 0.6 mM.

  3. A study on gold detection in Wenyu gold mine with XRF techniques

    International Nuclear Information System (INIS)

    Liu Liuchun

    1988-01-01

    A portable X ray fluorescence analyzer was used for detecting fluorcescent X rays from the elements associated with gold ores. Fe, As and Ni were chosen to be the indicator elements to analyse rock samples in Wenyu gold mine. Optimum indicators were determined, and it had proved to be successful to detect gold indirectly by measuring the yields of characteristic X rays of the elements. The method provided also valuable information on geology mapping and deposits forming environment

  4. In-vitro Anticancer and Antioxidant Activity of Gold Nanoparticles Conjugate with Tabernaemontana divaricata flower SMs Against MCF -7 Breast Cancer Cells

    International Nuclear Information System (INIS)

    Preetam, Raj J. P.; Purushothaman, M; Khusro, Ameer; Panicker, Shirly George

    2016-01-01

    Biologically stabilized gold nanoparticles were synthesized from the flower aqueous extract of T. divaricata. The synthesized nanoparticles were characterized by UV-Vis spectrophotometer, Zeta sizer, FTIR and TEM analysis. T. divaricata reduced gold nanoparticles having particle size and potential of 106.532 nm and -10.2 mV, respectively, with a characteristic peak of 550 nm in UV-visible spectrophotometer. FTIR graph after comparison between the crude flower extract and gold nanoparticles showed three major shifts in the functional groups. The morphology and size of the gold nanoparticles were examined by HRTEM analysis, which showed that most of the nanoparticles were nearly spherical with size of 100 nm. The gold nanoparticles synthesized demonstrated potent anticancer activity against MCF-7 cell line. The findings conclude that the antioxidant molecule present in T. divaricata may be responsible for both reduction and capping of gold nanoparticles which possess potential applications in medicine and pharmaceutical fields

  5. In-vitro Anticancer and Antioxidant Activity of Gold Nanoparticles Conjugate with Tabernaemontana divaricata flower SMs Against MCF -7 Breast Cancer Cells

    Energy Technology Data Exchange (ETDEWEB)

    Preetam, Raj J. P.; Purushothaman, M; Khusro, Ameer; Panicker, Shirly George [PG Biotechnology, Tamil Nadu (India)

    2016-02-15

    Biologically stabilized gold nanoparticles were synthesized from the flower aqueous extract of T. divaricata. The synthesized nanoparticles were characterized by UV-Vis spectrophotometer, Zeta sizer, FTIR and TEM analysis. T. divaricata reduced gold nanoparticles having particle size and potential of 106.532 nm and -10.2 mV, respectively, with a characteristic peak of 550 nm in UV-visible spectrophotometer. FTIR graph after comparison between the crude flower extract and gold nanoparticles showed three major shifts in the functional groups. The morphology and size of the gold nanoparticles were examined by HRTEM analysis, which showed that most of the nanoparticles were nearly spherical with size of 100 nm. The gold nanoparticles synthesized demonstrated potent anticancer activity against MCF-7 cell line. The findings conclude that the antioxidant molecule present in T. divaricata may be responsible for both reduction and capping of gold nanoparticles which possess potential applications in medicine and pharmaceutical fields.

  6. Formation of gold nanorods and gold nanorod films for surface-enhanced Raman scattering spectroscopy

    International Nuclear Information System (INIS)

    Trotsyuk, L.L.; Kulakovich, O.S.; Shabunya-Klyachkovskaya, E.V.; Gaponenko, S.V.; Vashchenko, S.V.

    2016-01-01

    The formation of gold nanorods as well as thin films prepared via electrostatic deposition of gold nanorods has been investigated. The obtained gold nanorods films have been used as substrates for the surface-enhanced Raman scattering analysis of sulfur-free organic molecules mitoxantrone and malachite green as well as inorganic malachite microcrystals for the first time. The additional modification of films with L-cysteine allows one to significantly extend the use of gold nanorods for the surface-enhanced Raman scattering analysis. (authors)

  7. EOP Gold Coral (Gerardia sp.) Growth Measurements

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Gold coral (Gerardia sp.) trees that were inspected years earlier on Pisces submersible dives were revisited and their change in size measured. The fishery for...

  8. Poly-thiosemicarbazide membrane for gold recovery

    KAUST Repository

    Villalobos, Luis Francisco; Yapici, Tahir; Peinemann, Klaus-Viktor

    2014-01-01

    A novel polymeric membrane adsorber with a high density of adsorption sites that can selectively capture Au(III) ions, is proposed as an efficient alternative to recover gold from dilute solutions. Poly-thiosemicarbazide (PTSC), a polymer

  9. Lamellar multilayer hexadecylaniline-modified gold nanoparticle ...

    Indian Academy of Sciences (India)

    standard Wilhelmy plate was used for surface pressure sensing. Multilayer ... carried out on a JEOL model 1200EX instrument operated at an accelerating voltage of ... the gold nanoparticles within domains (and reorganization of the domains ...

  10. A new route to gold nanoflowers

    Science.gov (United States)

    Liebig, Ferenc; Henning, Ricky; Sarhan, Radwan M.; Prietzel, Claudia; Bargheer, Matias; Koetz, Joachim

    2018-05-01

    Catanionic vesicles spontaneously formed by mixing the anionic surfactant bis(2-ethylhexyl) sulfosuccinate sodium salt with the cationic surfactant cetyltrimethylammonium bromide were used as a reducing medium to produce gold clusters, which are embedded and well-ordered into the template phase. The gold clusters can be used as seeds in the growth process that follows by adding ascorbic acid as a mild reducing component. When the ascorbic acid was added very slowly in an ice bath round-edged gold nanoflowers were produced. When the same experiments were performed at room temperature in the presence of Ag+ ions, sharp-edged nanoflowers could be synthesized. The mechanism of nanoparticle formation can be understood to be a non-diffusion-limited Ostwald ripening process of preordered gold nanoparticles embedded in catanionic vesicle fragments. Surface-enhanced Raman scattering experiments show an excellent enhancement factor of 1.7 · 105 for the nanoflowers deposited on a silicon wafer.

  11. Deep gold mine fracture zone behaviour

    CSIR Research Space (South Africa)

    Napier, JAL

    1998-12-01

    Full Text Available The investigation of the behaviour of the fracture zone surrounding deep level gold mine stopes is detailed in three main sections of this report. Section 2 outlines the ongoing study of fundamental fracture process and their numerical...

  12. Optical properties of spherical gold mesoparticles

    DEFF Research Database (Denmark)

    Evlyukhin, A. B.; Kuznetsov, A. I.; Novikov, S. M.

    2012-01-01

    Optical properties of spherical gold particles with diameters of 150-650 nm (mesoparticles) are studied by reflectance spectroscopy. Particles are fabricated by laser-induced transfer of metallic droplets onto metal and dielectric substrates. Contributions of higher multipoles (beyond...

  13. Adsorption-induced restructuring of gold nanochains

    DEFF Research Database (Denmark)

    Bahn, Sune Rastad; Lopez, Nuria; Nørskov, Jens Kehlet

    2002-01-01

    The chemical properties of single-atomic chains of gold atoms are investigated using density functional calculations. The nanochains are shown to be unusually chemically active with strong chemisorption of oxygen atoms and carbon monoxide. The chemisorption energies vary significantly with the st......The chemical properties of single-atomic chains of gold atoms are investigated using density functional calculations. The nanochains are shown to be unusually chemically active with strong chemisorption of oxygen atoms and carbon monoxide. The chemisorption energies vary significantly...... with the strain/stress conditions for the chain. Oxygen atoms are found to energetically prefer to get incorporated into a chain forming a new type of gold-oxygen nanochain with a conductance of one quantum unit. We suggest that the long bond lengths observed in electron microscopy investigations of gold chains...

  14. Synthesis method of asymmetric gold particles.

    Science.gov (United States)

    Jun, Bong-Hyun; Murata, Michael; Hahm, Eunil; Lee, Luke P

    2017-06-07

    Asymmetric particles can exhibit unique properties. However, reported synthesis methods for asymmetric particles hinder their application because these methods have a limited scale and lack the ability to afford particles of varied shapes. Herein, we report a novel synthetic method which has the potential to produce large quantities of asymmetric particles. Asymmetric rose-shaped gold particles were fabricated as a proof of concept experiment. First, silica nanoparticles (NPs) were bound to a hydrophobic micro-sized polymer containing 2-chlorotritylchloride linkers (2-CTC resin). Then, half-planar gold particles with rose-shaped and polyhedral structures were prepared on the silica particles on the 2-CTC resin. Particle size was controlled by the concentration of the gold source. The asymmetric particles were easily cleaved from the resin without aggregation. We confirmed that gold was grown on the silica NPs. This facile method for synthesizing asymmetric particles has great potential for materials science.

  15. Biological synthesis and characterization of intracellular gold ...

    Indian Academy of Sciences (India)

    thods of reduction of metal ions using plants or microorganisms are often ... have several advantages over bacteria, they are often pre- ferred. ... in static condition for a period of 7 days. ... work was focused on the production of intracellular gold.

  16. Preparation, characterization, and nonlinear optical properties of hybridized graphene @ gold nanorods nanocomposites

    Science.gov (United States)

    Guo, Jia; Ning, Tingyin; Han, Yanshun; Sheng, Yingqiang; Li, Chonghui; Zhao, Xiaofei; Lu, Zhengyi; Man, Baoyuan; Jiao, Yang; Jiang, Shouzhen

    2018-03-01

    The methods of chemical vapor deposition (CVD) and seed-mediated growth were used to obtain graphene and gold nanorods (GNRs), respectively. We fabricate graphene @ gold nanorods (G@GNRs) nanocomposites by successively using dropping and transferring methods Through SEM, Raman spectra and TEM analysis, the number of graphene layers is 6-7. The diameter of gold nanorods (GNRs) is about 10 nm and the average aspect ratio is 6.5. In addition, we systematically investigate their nonlinear optical responses by using open-aperture Z-scan technique. In contrast with graphene and GNRs, the G@GNRs nanocomposites exhibit excellent nonlinear optical response with a modulation depth of about 51% and a saturable intensity of about 6.23 GW/cm2. The results suggest that the G@GNRs nanocomposites could potentially be used as an optical modulator in pulsed laser generation.

  17. Uranium extraction from gold-uranium ores

    Energy Technology Data Exchange (ETDEWEB)

    Laskorin, B.N.; Golynko, Z.Sh.

    1981-01-01

    The process of uranium extraction from gold-uranium ores in the South Africa is considered. Flowsheets of reprocessing gold-uranium conglomerates, pile processing and uranium extraction from the ores are presented. Continuous counter flow ion-exchange process of uranium extraction using strong-active or weak-active resins is noted to be the most perspective and economical one. The ion-exchange uranium separation with the succeeding extraction is also the perspective one.

  18. The Modern Monetary System and Gold

    Directory of Open Access Journals (Sweden)

    N N Rubtsov

    2013-12-01

    Full Text Available The article considers the nature of modern money, analyzes the mechanism of its creation, showing that it is basically generated by credit and the principle of partial bank reserve. The article draws comparative parallels between trade money based on gold and contemporary, credit money; the author quotes leading bankers and finance experts on the need for partial return to the principles of functioning of the gold standard as the most effective institute of regulating the monetary system in society.

  19. Optical Epitaxial Growth of Gold Nanoparticle Arrays.

    Science.gov (United States)

    Huang, Ningfeng; Martínez, Luis Javier; Jaquay, Eric; Nakano, Aiichiro; Povinelli, Michelle L

    2015-09-09

    We use an optical analogue of epitaxial growth to assemble gold nanoparticles into 2D arrays. Particles are attracted to a growth template via optical forces and interact through optical binding. Competition between effects determines the final particle arrangements. We use a Monte Carlo model to design a template that favors growth of hexagonal particle arrays. We experimentally demonstrate growth of a highly stable array of 50 gold particles with 200 nm diameter, spaced by 1.1 μm.

  20. Synthesis of radioactive gold nanoparticle in surfactant medium

    International Nuclear Information System (INIS)

    Swadesh Mandal

    2014-01-01

    The present study describes the synthesis of radioactive gold nanoparticle in surfactant medium. Proton irradiated stable 197 Au and radioactive 198 Au were simultaneously used for production of radioactive gold nanoparticle. Face centered cubic gold nanoparticles with size of 4-50 nm were found in proton irradiated gold foil. However, the size of nanoparticle varies with pH using both stable and radioactive gold. (author)

  1. Aquatic Fern (Azolla Sp.) Assisted Synthesis of Gold Nanoparticles

    Science.gov (United States)

    Jha, Anal K.; Prasad, K.

    2016-02-01

    Aquatic pteridophyte (Azolla sp.) was taken to assess its potential to synthesize the metal (Au) nanoparticles. The synthesized particles were characterized using X-ray, UV-visible, scanning and transmission electron microscopy analyses. Nanoparticles almost spherical in shape having the sizes of 5-17nm are found. UV-visible study revealed the surface plasmon resonance at 538nm. Responsible phytochemicals for the transformation were principally phenolics, tannins, anthraquinone glycosides and sugars present abundantly in the plant thereby bestowing it adaptive prodigality. Also, the use of Azolla sp. for the synthesis of gold nanoparticles offers the benefit of eco-friendliness.

  2. Study on Sumbawa gold recovery using centrifuge

    Science.gov (United States)

    Ferdana, A. D.; Petrus, H. T. B. M.; Bendiyasa, I. M.; Prijambada, I. D.; Hamada, F.; Sachiko, T.

    2018-01-01

    The Artisanal Small Gold Mining in Sumbawa has been processing gold with mercury (Hg), which poses a serious threat to the mining and global environment. One method of gold processing that does not use mercury is by gravity method. Before processing the ore first performed an analysis of Mineragraphy and analysis of compound with XRD. Mineragraphy results show that gold is associated with chalcopyrite and covelite and is a single particle (native) on size 58.8 μm, 117 μm up to 294 μm. characterization with XRD shows that the Sumbawa Gold Ore is composed of quartz, pyrite, pyroxene, and sericite compounds. Sentrifugation is one of separation equipment of gravity method to increase concentrate based on difference of specific gravity. The optimum concentration result is influenced by several variables, such as water flow rate and particle size. In this present research, the range of flow rate is 5 lpm and 10 lpm, the particle size - 100 + 200 mesh and -200 +300 mesh. Gold concentration in concentrate is measured by EDX. The result shows that the optimum condition is obtained at a separation with flow rate 5 lpm and a particle size of -100 + 200 mesh.

  3. Gold Nanocages for Biomedical Applications**

    Science.gov (United States)

    Skrabalak, Sara E.; Chen, Jingyi; Au, Leslie; Lu, Xianmao; Li, Xingde; Xia, Younan

    2008-01-01

    Nanostructured materials provide a promising platform for early cancer detection and treatment. Here we highlight recent advances in the synthesis and use of Au nanocages for such biomedical applications. Gold nanocages represent a novel class of nanostructures, which can be prepared via a remarkably simple route based on the galvanic replacement reaction between Ag nanocubes and HAuCl4. The Au nanocages have a tunable surface plasmon resonance peak that extends into the near-infrared, where the optical attenuation caused by blood and soft tissue is essentially negligible. They are also biocompatible and present a well-established surface for easy functionalization. We have tailored the scattering and absorption cross-sections of Au nanocages for use in optical coherence tomography and photothermal treatment, respectively. Our preliminary studies show greatly improved spectroscopic image contrast for tissue phantoms containing Au nanocages. Our most recent results also demonstrate the photothermal destruction of breast cancer cells in vitro by using immuno-targeted Au nanocages as an effective photo-thermal transducer. These experiments suggest that Au nanocages may be a new class of nanometer-sized agents for cancer diagnosis and therapy. PMID:18648528

  4. Gold Nanocages for Biomedical Applications.

    Science.gov (United States)

    Skrabalak, Sara E; Chen, Jingyi; Au, Leslie; Lu, Xianmao; Li, Xingde; Xia, Younan

    2007-10-17

    Nanostructured materials provide a promising platform for early cancer detection and treatment. Here we highlight recent advances in the synthesis and use of Au nanocages for such biomedical applications. Gold nanocages represent a novel class of nanostructures, which can be prepared via a remarkably simple route based on the galvanic replacement reaction between Ag nanocubes and HAuCl(4). The Au nanocages have a tunable surface plasmon resonance peak that extends into the near-infrared, where the optical attenuation caused by blood and soft tissue is essentially negligible. They are also biocompatible and present a well-established surface for easy functionalization. We have tailored the scattering and absorption cross-sections of Au nanocages for use in optical coherence tomography and photothermal treatment, respectively. Our preliminary studies show greatly improved spectroscopic image contrast for tissue phantoms containing Au nanocages. Our most recent results also demonstrate the photothermal destruction of breast cancer cells in vitro by using immuno-targeted Au nanocages as an effective photo-thermal transducer. These experiments suggest that Au nanocages may be a new class of nanometer-sized agents for cancer diagnosis and therapy.

  5. The Kolar Gold Field experiment

    International Nuclear Information System (INIS)

    Sreekantan, B.V.

    1982-01-01

    Meson theory was propounded to explain the nuclear force which holds neutrons and protons inside the nucleus. Subsequently, quark theory was put forward to bring some order into an enormously large number of fundamental particles discovered in the hadron family. These two theories are briefly explained. The gravitational force, the electromagnetic force, the weak nuclear force and the strong nuclear force are the basic forces which determine the behaviour of fundamental particles when they are in close proximity. If the last three of the above-mentioned four forces are one or just different aspects of a single force, quarks and leptons can be mingled in the same theoretical framework indicating the non-conservation of baryon number and the spontaneous decay of the proton into leptons. In order to test the last possibility i.e. proton decay, an experiment has been set up in the Kolar Gold Field at a depth of 2300 metres in India. 1650 gas proportional counters are sandwiched between iron plates. The total amount of iron in the form of iron plates and walls of the counters is 140 tons. In this experiment, nuclei of iron are serving as the source of protons and neutrons and the depth eliminates the background events which mimic proton decay. The amount of iron used in the experiment i.e. 140 tons is more than enough to obtain evidence of 10 proton decay events in a year, assuming that the lifetime of proton is 10 30 years or below. (M.G.B.)

  6. Curcumin: the Indian solid gold.

    Science.gov (United States)

    Aggarwal, Bharat B; Sundaram, Chitra; Malani, Nikita; Ichikawa, Haruyo

    2007-01-01

    Turmeric, derived from the plant Curcuma longa, is a gold-colored spice commonly used in the Indian subcontinent, not only for health care but also for the preservation of food and as a yellow dye for textiles. Curcumin, which gives the yellow color to turmeric, was first isolated almost two centuries ago, and its structure as diferuloylmethane was determined in 1910. Since the time of Ayurveda (1900 Bc) numerous therapeutic activities have been assigned to turmeric for a wide variety of diseases and conditions, including those of the skin, pulmonary, and gastrointestinal systems, aches, pains, wounds, sprains, and liver disorders. Extensive research within the last half century has proven that most of these activities, once associated with turmeric, are due to curcumin. Curcumin has been shown to exhibit antioxidant, anti-inflammatory, antiviral, antibacterial, antifungal, and anticancer activities and thus has a potential against various malignant diseases, diabetes, allergies, arthritis, Alzheimer's disease, and other chronic illnesses. These effects are mediated through the regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other enzymes. Curcumin exhibits activities similar to recently discovered tumor necrosis factor blockers (e.g., HUMIRA, REMICADE, and ENBREL), a vascular endothelial cell growth factor blocker (e.g., AVASTIN), human epidermal growth factor receptor blockers (e.g., ERBITUX, ERLOTINIB, and GEFTINIB), and a HER2 blocker (e.g., HERCEPTIN). Considering the recent scientific bandwagon that multitargeted therapy is better than monotargeted therapy for most diseases, curcumin can be considered an ideal "Spice for Life".

  7. Layer-by-layer self-assembled nanostructured phthalocyaninatoiron(II)/SWCNT-poly(m-aminobenzenesulfonic acid) hybrid system on gold surface: Electron transfer dynamics and amplification of H{sub 2}O{sub 2} response

    Energy Technology Data Exchange (ETDEWEB)

    Pillay, Jeseelan [Molecular and Nanomaterials Electrochemistry laboratory, Department of Chemistry, University of Pretoria, Pretoria 0002 (South Africa); Ozoemena, Kenneth I. [Molecular and Nanomaterials Electrochemistry laboratory, Department of Chemistry, University of Pretoria, Pretoria 0002 (South Africa)], E-mail: kenneth.ozoemena@up.ac.za

    2009-09-01

    The fabrication of nanostructured platform of poly(m-aminobenzenesulfonic acid) functionalised single-walled carbon nanotubes (SWCNTs-PABS)-iron(II)phthalocyanine nanoparticles (nanoFePc) using layer-by-layer(LBL) self-assembly strategy is described. The substrate build-up, via strong electrostatic interaction, was monitored using atomic force microscopy (AFM) and electrochemical measurements. As the number of bilayers is increased, the electron transfer kinetics of the ferricyaninde/ferrocyanide redox probe is decreased, while the electrochemical reduction of H{sub 2}O{sub 2} at a constant concentration is amplified. The amplification of the electrochemical response to H{sub 2}O{sub 2} detection suggests that this type of electrode could provide an important nano-architectural sensing platform for the development of a sensor.

  8. Subchronic inhalation toxicity of gold nanoparticles

    Directory of Open Access Journals (Sweden)

    Chung Yong

    2011-05-01

    Full Text Available Abstract Background Gold nanoparticles are widely used in consumer products, including cosmetics, food packaging, beverages, toothpaste, automobiles, and lubricants. With this increase in consumer products containing gold nanoparticles, the potential for worker exposure to gold nanoparticles will also increase. Only a few studies have produced data on the in vivo toxicology of gold nanoparticles, meaning that the absorption, distribution, metabolism, and excretion (ADME of gold nanoparticles remain unclear. Results The toxicity of gold nanoparticles was studied in Sprague Dawley rats by inhalation. Seven-week-old rats, weighing approximately 200 g (males and 145 g (females, were divided into 4 groups (10 rats in each group: fresh-air control, low-dose (2.36 × 104 particle/cm3, 0.04 μg/m3, middle-dose (2.36 × 105 particle/cm3, 0.38 μg/m3, and high-dose (1.85 × 106 particle/cm3, 20.02 μg/m3. The animals were exposed to gold nanoparticles (average diameter 4-5 nm for 6 hours/day, 5 days/week, for 90-days in a whole-body inhalation chamber. In addition to mortality and clinical observations, body weight, food consumption, and lung function were recorded weekly. At the end of the study, the rats were subjected to a full necropsy, blood samples were collected for hematology and clinical chemistry tests, and organ weights were measured. Cellular differential counts and cytotoxicity measurements, such as albumin, lactate dehydrogenase (LDH, and total protein were also monitored in a cellular bronchoalveolar lavage (BAL fluid. Among lung function test measurements, tidal volume and minute volume showed a tendency to decrease comparing control and dose groups during the 90-days of exposure. Although no statistically significant differences were found in cellular differential counts, histopathologic examination showed minimal alveoli, an inflammatory infiltrate with a mixed cell type, and increased macrophages in the high-dose rats. Tissue

  9. Gold Nanoparticles Obtained by Bio-precipitation from Gold(III) Solutions

    International Nuclear Information System (INIS)

    Gardea-Torresdey, J.L.; Tiemann, K.J.; Gamez, G.; Dokken, K.; Tehuacanero, S.; Jose-Yacaman, M.

    1999-01-01

    The use of metal nanoparticles has shown to be very important in recent industrial applications. Currently gold nanoparticles are being produced by physical methods such as evaporation. Biological processes may be an alternative to physical methods for the production of gold nanoparticles. Alfalfa biomass has shown to be effective at passively binding and reducing gold from solutions containing gold(III) ions and resulting in the formation of gold(0) nanoparticles. High resolution microscopy has shown that five different types of gold particles are present after reaction with gold(III) ions with alfalfa biomass. These particles include: fcc tetrahedral, hexagonal platelet, icosahedral multiple twinned, decahedral multiple twinned, and irregular shaped particles. Further analysis on the frequency of distribution has shown that icosahedral and irregular particles are more frequently formed. In addition, the larger particles observed may be formed through the coalescence of smaller particles. Through modification of the chemical parameters, more uniform particle size distribution may be obtained by the alfalfa bio-reduction of gold(III) from solution

  10. Gold and gold-copper nanoparticles in 2-propanol: A radiation chemical study

    International Nuclear Information System (INIS)

    Dey, G.R.

    2011-01-01

    The studies on the reduction of Au 3+ to gold nanoparticles in presence and absence of Cu 2+ under deoxygenated conditions in 2-propanol by radiolytic method have been carried out. On γ-radiolysis, preliminary yellow colored solution of Au 3+ changed to purple color owing to gold nanoparticles formation, which exhibits an absorption peak at around 540 nm. In the presence of Cu 2+ , absorption of gold-copper nanoparticles, which was also produced during γ-radiolysis, was red shifted in contrast to the system containing no Cu 2+ . Under DLS studies the sizes of gold nanoparticles in the absence and the presence of Cu 2+ were found to be larger (>400 nm). However, in presence of polyethylene glycol, a stabilizer the nanoparticle sizes became smaller, sizes measured for gold and gold-copper nanoparticles are 40 and 140 nm, respectively. Moreover, the change in UV-vis spectra in the Cu 2+ and Au 3+ mixed system highlights the formation of gold-copper nanoparticles in core-shell type arrangement. - Highlights: → Present radiation chemical study highlights high reactivity of Au ·2+ with Cu 2+ . → Absorption of gold-copper nanoparticles is blue shifted as compared to copper nanoparticles. → Change in UV-vis spectra with dose emphasizes core-shell type arrangement of Au-Cu nanoparticles.

  11. Knowledge-driven GIS modeling technique for gold exploration, Bulghah gold mine area, Saudi Arabia

    Directory of Open Access Journals (Sweden)

    Ahmed A. Madani

    2011-12-01

    Full Text Available This research aims to generate a favorability map for gold exploration at the Bulghah gold mine area using integration of geo-datasets within a GIS environment. Spatial data analyses and integration of different geo-datasets are carried out based on knowledge-driven and weighting technique. The integration process involves the weighting and scoring of different layers affecting the gold mineralization at the study area using the index overlay method within PCI Geomatica environment. Generation of the binary predictor maps for lithology, lineaments, faults and favorable contacts precede the construction of the favorability map. About 100 m buffer zones are generated for favorable contacts, lineaments and major faults layers. Internal weighting is assigned to each layer based on favorability for gold mineralization. The scores for lithology, major faults, lineaments and favorable contacts layers in the constructed favorability map are 50%, 25%, 10% and 15%, respectively. Final favorability map for the Bulghah gold mine area shows the recording of two new sites for gold mineralization located at the northern and southern extensions of tonalite–diorite intrusions. The northern new site is now exploited for gold from the Bulghah North mine. The southern new site is narrow and small; its rocks resemble those of the Bulghah gold mine.

  12. Genesis of uranium-gold pyritic conglomerates

    International Nuclear Information System (INIS)

    Myers, W.B.

    1981-01-01

    The ancient pyritic ore conglomerates have a common origin best exemplified by the Witwatersrand deposits. All contain detrital pyrite and uraninite, which are unstable in modern oxygenated environments and were deposited in a reducing atmosphere. The Rand reefs are not similar to modern gold placers. Placers result from the near incapacity of streams and currents to transport coarse gold. Placers as rich as Rand reef occur only in narrow paystreaks within 15 kilometers of a coarse-gold source. The board dispersion of gold in the reefs is due to solution transport of metal complexed as aurous sulfide, leached anoxygenically from crustal rocks, probably from sea-floor basalt, and precipitated by a slow reaction driven by the radioactive decay of detrital uraninite. Radiolysis of water on shallow marine unconformities resulted in diffusion of hydrogen to the atmosphere and a slight excess of hydroxyl free radical in the reef environment. The mild oxidizing tendency slowly dissolved uranium, precipitated gold, and oxygenated thucholite. These actions define a maturing process. A uraninite placer accumulating on an unconformity becomes progressively converted to a gold reef with little residual uraninite. The most mature reefs tend to grade toward the thucholite-seam type, very thin but exceedingly rich in gold. A combination of chemical attack and physical reworking accounts for the general thinness of mature reefs. Pyrite, like uraninite, decreases in abundance with increasing maturity; buffering by pyrite moderated the oxidative depletion of uranium. Where pyrite was scanty or absent, uraninite was completely dissolved by the effects of radiolysis and no ore formed

  13. Ultrafast nonlinear dynamics of thin gold films due to an intrinsic delayed nonlinearity

    DEFF Research Database (Denmark)

    Bache, Morten; Lavrinenko, Andrei

    2017-01-01

    Using long-range surface plasmon polaritons light can propagate in metal nano-scale waveguides for ultracompact opto-electronic devices. Gold is an important material for plasmonic waveguides, but although its linear optical properties are fairly well understood, the nonlinear response is still...

  14. Environmental Remediation to Address Childhood Lead Poisoning Epidemic due to Artisanal Gold Mining in Zamfara, Nigeria

    OpenAIRE

    Tirima, Simba; Bartrem, Casey; von Lindern, Ian; von Braun, Margrit; Lind, Douglas; Anka, Shehu Mohammed; Abdullahi, Aishat

    2016-01-01

    Background: From 2010 through 2013, integrated health and environmental responses addressed an unprecedented epidemic lead poisoning in Zamfara State, northern Nigeria. Artisanal gold mining caused widespread contamination resulting in the deaths of > 400 children. Socioeconomic, logistic, and security challenges required remediation and medical protocols within the context of local resources, labor practices, and cultural traditions. Objectives: Our aim was to implement emergency environ...

  15. Effects of gold and silver backings on the dose rate around an 125I seed

    International Nuclear Information System (INIS)

    Cygler, J.; Szanto, J.; Soubra, M.; Rogers, D.W.

    1990-01-01

    Measurements of the effect of either gold or silver backing on the dose rate around an 125I seed were performed using a Therados RFA7 dosimetry system and a small diode detector which was 2.5 mm in diameter and 0.06 mm thick. It was found that the presence of the gold or silver backing modifies the diode response on the side of the 125I seed away from the backing. The effect depends on the backing material and the distance from the seed. There is a small increase close to the gold backing but a decrease further away. This decrease at distances greater than 10 mm from the seed is uniformly 10%, the same as found when the seed is backed by air. There is an increase of up to 25% observed with silver backing the seed and this increase remains significant more than 30 mm from the seed. When the response increases, the results are hard to interpret quantitatively because of variations in the diode response per unit dose with photon energy and extreme sensitivity to geometric changes. Nonetheless, except for the increase at close distances with the gold, the results are in agreement with EGS4 Monte Carlo photon transport simulations which are for a simplified geometry and account for x-ray fluorescence from the K-shell. Furthermore, the increase in the gold-backed case is qualitatively explained by Williamson's Monte Carlo calculations which take into account the L-shell fluorescent x-rays from gold

  16. Beneficiation of the gold bearing ore by gravity and flotation

    Science.gov (United States)

    Gül, Alim; Kangal, Olgaç; Sirkeci, Ayhan A.; Önal, Güven

    2012-02-01

    Gold concentration usually consists of gravity separation, flotation, cyanidation, or the combination of these processes. The choice among these processes depends on the mineralogical characterization and gold content of the ore. Recently, the recovery of gold using gravity methods has gained attention because of low cost and environmentally friendly operations. In this study, gold pre-concentrates were produced by the stepwise gravity separation and flotation techniques. The Knelson concentrator and conventional flotation were employed for the recovery of gold. Gold bearing ore samples were taken from Gümüşhane Region, northern east part of Turkey. As a result of stepwise Knelson concentration experiments, a gold concentrate assaying around 620 g/t is produced with 41.4wt% recovery. On the other hand, a gold concentrate about 82 g/t is obtained with 89.9wt% recovery from a gold ore assaying 6 g/t Au by direct flotation.

  17. Gold leaf counter electrodes for dye-sensitized solar cells

    Science.gov (United States)

    Shimada, Kazuhiro; Toyoda, Takeshi

    2018-03-01

    In this study, a gold leaf 100 nm thin film is used as the counter electrode in dye-sensitized solar cells. The traditional method of hammering gold foil to obtain a thin gold leaf, which requires only small amounts of gold, was employed. The gold leaf was then attached to the substrate using an adhesive to produce the gold electrode. The proposed approach for fabricating counter electrodes is demonstrated to be facile and cost-effective, as opposed to existing techniques. Compared with electrodes prepared with gold foil and sputtered gold, the gold leaf counter electrode demonstrates higher catalytic activity with a cobalt-complex electrolyte and higher cell efficiency. The origin of the improved performance was investigated by surface morphology examination (scanning electron microscopy), various electrochemical analyses (cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy), and crystalline analysis (X-ray diffractometry).

  18. Moessbauer study of the chemical state of gold in gold ores

    International Nuclear Information System (INIS)

    Wagner, F.E.; Marion, P.H.; Regnard, J.-R.

    1986-01-01

    Information on the chemical state of gold in gold ores has been obtained by 197 Au Moessbauer spectroscopy in cases where the state of this element cannot be determined by such standard methods as optical or electron microscopy. Ore concentrates consisting mainly of pyrite or arsenopyrite and roasted ore and matte samples were studied. The results yielded directly the respective amounts of metallic and chemically bound gold. Unless the gold is metallic, its chemical state in the ores turns out to be different from that in the minerals studied so far as reference materials. The chemical processes taking place during various treatments of the ores, such as roasting or leaching, can also be followed by Moessbauer spectroscopy. It is hoped that Moessbauer spectroscopy will eventually facilitate the development of more efficient methods of gold extraction

  19. Oxidation state of gold and arsenic in gold-bearing arsenian pyrite

    Energy Technology Data Exchange (ETDEWEB)

    Simon, G.; Huang, H.; Penner-Hahn, J.E.; Kesler, S.E.; Kao, L.S. [Univ. of Michigan, Ann Arbor, MI (United States)

    1999-07-01

    XANES measurements on gold-bearing arsenian pyrite from the Twin Creeks Carlin-type gold deposits show that gold is present as both Au{sup 0} and Au{sup 1+} and arsenic is present as As{sup 1{minus}}. Au{sup 0} is attributed to sub-micrometer size inclusions of free gold, whereas Au{sup 1+} is attributed to gold in the lattice of the arsenian pyrite. STEM observations suggest that As{sup 1{minus}} is probably concentrated in angstrom-scale, randomly distributed layers with a marcasite or arsenopyrite structure. Ionic gold (Au{sup 1+}) could be concentrated in these layers as well, and is present in both twofold- and fourfold-coordinated forms, with fourfold-coordinated Au{sup 1+} more abundant. Twofold-coordinated Au{sup 1+} is similar to gold in Au{sub 2}S in which it is linearly coordinated to two sulfur atoms. The nature of fourfold-coordinated Au{sup 1+} is not well understood, although it might be present as an Au-As-S compound where gold is bonded in fourfold coordination to sulfur and arsenic atoms, or in vacancy positions on a cation site in the arsenian pyrite. Au{sup 1+} was probably incorporated into arsenian pyrite by adsorption onto pyrite surfaces during crystal growth. The most likely compound in the case of twofold-coordinated Au{sup 1+} was probably a tri-atomic surface complex such as S{sub pyrite}-Au{sup 1+}-S{sub bi-sulfide}H or Au{sup 1+}-S-Au{sup 1+}. The correlation between gold and arsenic might be related to the role of arsenic in enhancing the adsorption of gold complexes of this type on pyrite surfaces, possibly through semiconductor effects.

  20. Silver, gold, and alloyed silver-gold nanoparticles: characterization and comparative cell-biologic action

    Energy Technology Data Exchange (ETDEWEB)

    Mahl, Dirk; Diendorf, Joerg; Ristig, Simon [University of Duisburg-Essen, Department of Inorganic Chemistry, Center for Nanointegration Duisburg-Essen (CeNIDE) (Germany); Greulich, Christina [Ruhr-University of Bochum, Bergmannsheil University Hospital/Surgical Research (Germany); Li Zian; Farle, Michael [University of Duisburg-Essen, Faculty of Physics, Center for Nanointegration Duisburg-Essen (CeNIDE) (Germany); Koeller, Manfred [Ruhr-University of Bochum, Bergmannsheil University Hospital/Surgical Research (Germany); Epple, Matthias, E-mail: matthias.epple@uni-due.de [University of Duisburg-Essen, Department of Inorganic Chemistry, Center for Nanointegration Duisburg-Essen (CeNIDE) (Germany)

    2012-10-15

    Silver, gold, and silver-gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly(N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15-25 nm), gold (5-6 nm), and silver-gold (50:50; 10-12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver-gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver-gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver-gold nanoparticles in the concentration range of 5-20 {mu}g mL{sup -1} induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

  1. Silver, gold, and alloyed silver-gold nanoparticles: characterization and comparative cell-biologic action

    Science.gov (United States)

    Mahl, Dirk; Diendorf, Jörg; Ristig, Simon; Greulich, Christina; Li, Zi-An; Farle, Michael; Köller, Manfred; Epple, Matthias

    2012-10-01

    Silver, gold, and silver-gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly( N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15-25 nm), gold (5-6 nm), and silver-gold (50:50; 10-12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver-gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver-gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver-gold nanoparticles in the concentration range of 5-20 μg mL-1 induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

  2. Silver, gold, and alloyed silver–gold nanoparticles: characterization and comparative cell-biologic action

    International Nuclear Information System (INIS)

    Mahl, Dirk; Diendorf, Jörg; Ristig, Simon; Greulich, Christina; Li Zian; Farle, Michael; Köller, Manfred; Epple, Matthias

    2012-01-01

    Silver, gold, and silver–gold-alloy nanoparticles were prepared by citrate reduction modified by the addition of tannin during the synthesis, leading to a reduction in particle size by a factor of three. Nanoparticles can be prepared by this easy water-based synthesis and subsequently functionalized by the addition of either tris(3-sulfonatophenyl)phosphine or poly(N-vinylpyrrolidone). The resulting nanoparticles of silver (diameter 15–25 nm), gold (5–6 nm), and silver–gold (50:50; 10–12 nm) were easily dispersable in water and also in cell culture media (RPMI + 10 % fetal calf serum), as shown by nanoparticle tracking analysis and differential centrifugal sedimentation. High-resolution transmission electron microscopy showed a polycrystalline nature of all nanoparticles. EDX on single silver–gold nanoparticles indicated that the concentration of gold is higher inside a nanoparticle. The biologic action of the nanoparticles toward human mesenchymal stem cells (hMSC) was different: Silver nanoparticles showed a significant concentration-dependent influence on the viability of hMSC. Gold nanoparticles showed only a small effect on the viability of hMSC after 7 days. Surprisingly, silver–gold nanoparticles had no significant influence on the viability of hMSC despite the silver content. Silver nanoparticles and silver–gold nanoparticles in the concentration range of 5–20 μg mL −1 induced the activation of hMSC as indicated by the release of IL-8. In contrast, gold nanoparticles led to a reduction of the release of IL-6 and IL-8.

  3. Reducing HAuCl4 by the C60 dianion: C60-directed self-assembly of gold nanoparticles into novel fullerene bound gold nanoassemblies

    International Nuclear Information System (INIS)

    Liu Wei; Gao Xiang

    2008-01-01

    The C 60 dianion is used to reduce tetrachloroauric acid (HAuCl 4 ) for the first time; three-dimensional C 60 bound gold (Au-C 60 ) nanoclusters are obtained from C 60 -directed self-assembly of gold nanoparticles due to the strong affinities of Au-C 60 and C 60 -C 60 . The process was monitored in situ by UV-vis-NIR spectroscopy. The resulting Au-C 60 nanoclusters were characterized using transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive spectroscopy (EDS), x-ray powder diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and FT-IR and Raman spectroscopies. TEM demonstrates the formation of 3D nanonetwork aggregates, which are composed of discrete gold nanocores covered with a C 60 monolayer. The SAED and XRD patterns indicate that the gold nanocores inside the capped C 60 molecules belong to the face-centred cubic crystal structure, while the C 60 molecules are amorphous. The EDS and XPS measurements validate that the Au-C 60 nanoclusters contain only Au and C elements and Au 3+ is reduced to Au 0 . FT-IR spectroscopy shows the chemiadsorption of C 60 to the gold nanocores, while Raman spectroscopy demonstrates the electron transfer from the gold nanocores to the chemiadsorbed C 60 molecules. Au-C 60 nanoclusters embedded in tetraoctyl-n-ammonium bromide (TOAB) on glassy carbon electrodes (GCEs) have been fabricated and have shown stable and well-defined electrochemical responses in aqueous solution

  4. International SUSMIN-project aims at sustainable gold mining in EU

    Science.gov (United States)

    Backnäs, Soile; Neitola, Raisa; Turunen, Kaisa; Lima, Alexandre; Fiúza, António; Szlachta, Malgorzata; Wójtowicz, Patryk; Maftei, Raluca; Munteanu, Marian; Alakangas, Lena; Baciu, Calin; Fernández, Dámaris

    2015-04-01

    Although the gold demand has been constantly increasing in past years, the commodity findings have been decreasing and the extraction of gold has complicated due to increasing complexity and decreasing grade of the ores. Additionally, even gold mining could increase economical development, it has also challenges in eco-efficiency and extraction methods (e.g. cyanide). Thus, the novel energy and resource-efficient methods and technologies for mineral processing should be developed to concentrate selectively different gold bearing minerals. Furthermore, technologies for efficient treatment of mine waters, sustainable management of wastes, and methods to diminish environmental and social impacts of mining are needed. These problems will be addressed by the three year long project SUSMIN. The SUSMIN-project identifies and evaluates environmental impacts and economical challenges of gold mining within EU. The objective of the project is to increase the transnational cooperation and to support environmentally, socially and economically sustainable viable gold production. The focus is to develop and test geophysical techniques for gold exploration, eco-efficient ore beneficiation methods and alternatives for cyanide leaching. Additionally, the research will improve treatment methods for mine waters by the development and testing of advanced adsorbents. The research on socio-economic issues pursues to develop tools for enhancing the mechanisms of the corporate social responsibility as well as community engagement and management of the relations with the stakeholders. Moreover, with the environmental risk assessment and better knowledge of the geochemistry and long-term transformation of the contaminants in mining wastes and mine waters, the mining companies are able to predict and prevent the impacts to the surrounding environment, resulting in an improved environmental management solution. The SUSMIN consortium led by Geological Survey of Finland (GTK) includes seven

  5. Simple Synthesis and Enhanced Performance of Graphene Oxide-Gold Composites

    Directory of Open Access Journals (Sweden)

    Min Song

    2012-01-01

    Full Text Available Graphene oxide-gold composites were prepared by one-step reaction in aqueous solution, where the gold nanoparticles were deposited on the graphene oxide during their synthesis process. Transmission electron morphology, X-ray diffraction, Roman spectra, and UV-Vis absorption spectra were used to characterize the obtained composites. Furthermore, based on the BET analysis results, it was found that the surface area of the composite film was obviously enhanced compared with the synthesized graphene oxide. Electrochemical measurements indicated that the modification of the composites on electrode could efficiently enhance the voltammetric response, suggesting the potential application for making electrochemical sensors.

  6. Permanent magnetism in phosphine- and chlorine-capped gold: from clusters to nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Munoz-Marquez, Miguel A., E-mail: miguel.angel@icmse.csic.es; Guerrero, Estefania; Fernandez, Asuncion [Instituto de Ciencia de Materiales de Sevilla (CSIC-US) (Spain); Crespo, Patricia; Hernando, Antonio [Instituto de Magnetismo Aplicado (UCM-ADIF-CSIC) (Spain); Lucena, Raquel; Conesa, Jose C. [Instituto de Catalisis y Petroleoquimica (CSIC) (Spain)

    2010-05-15

    Magnetometry results have shown that gold NPs ({approx}2 nm in size) protected with phosphine and chlorine ligands exhibit permanent magnetism. When the NPs size decreases down to the subnanometric size range, e.g. undecagold atom clusters, the permanent magnetism disappears. The near edge structure of the X-ray absorption spectroscopy data points out that charge transfer between gold and the capping system occurs in both cases. These results strongly suggest that nearly metallic Au bonds are also required for the induction of a magnetic response. Electron paramagnetic resonance observations indicate that the contribution to magnetism from eventual iron impurities can be disregarded.

  7. Anomalous complete opaqueness in a sparse array of gold nanoparticle chains

    International Nuclear Information System (INIS)

    Bai Benfeng; Li Xiaowei; Vartiainen, Ismo; Lehmuskero, Anni; Turunen, Jari; Kuittinen, Markku; Vahimaa, Pasi; Kang Guoguo

    2011-01-01

    We report on an anomalous polarization-switching extinction effect in a sparse array of gold nanoparticle chains: under normal incidence of light, the array is almost transparent for one polarization; whereas it is fully opaque (with nearly zero transmittance) for the orthogonal polarization within a narrow band, even though the nanoparticles cover only a tiny fraction (say, 3.5%) of the transparent substrate surface. We reveal that the strong polarization-dependent short-range dipolar coupling and long-range radiative coupling of gold nanoparticles in this highly asymmetric array is responsible for this extraordinary effect.

  8. Authentication of gold products by nuclear methods

    International Nuclear Information System (INIS)

    De Jesus, A.S.M.

    1985-01-01

    The falsification of valuable gold items is a threat to the authenticity of gold products. To solve this, there is a continuous search for reliable, practicle and cost-effective means of identifying forgeries. Because nuclear techniques as applied to elemental analysis have a high degree of specificity, are non-destructive and permit the availability of results within a relatively short time, a few of these techniques were investigated and reviewed in the article. Work on some promising methods in the author's laboratory is also discussed. Constraints such as those imposed by the time taken by the measurement, negligible residual activity within a relatively short time were also considered. The techniques that were investigated include: the transmission of electromagnetic radiation through a medium; scattering of electromagnetic radiation; x-ray fluorescence analysis; neutron activation analysis; activation by the inelastic scattering of gamma radiation; activation by the inelastic scattering of fast neutrons; absorption and scattering of fast neutrons; self-attenuation of gamma radiation. The shape of the object being investigated, should also be considered. It is concluded that a system based on the inelastic scattering of neutrons emitted by a 241 Am/Be source (halflife = 433 years) is practical and capable of authenticating gold and gold alloy coins such as Krugerrands. The feasibility study on the assaying of gold jewelry by means of nuclear methods also showed it to be impractical

  9. Gold nanoparticle-based electrochemical biosensors

    Energy Technology Data Exchange (ETDEWEB)

    Pingarron, Jose M.; Yanez-Sedeno, Paloma; Gonzalez-Cortes, Araceli [Department of Analytical Chemistry, Faculty of Chemistry, University Complutense of Madrid, 28040 Madrid (Spain)

    2008-08-01

    The unique properties of gold nanoparticles to provide a suitable microenvironment for biomolecules immobilization retaining their biological activity, and to facilitate electron transfer between the immobilized proteins and electrode surfaces, have led to an intensive use of this nanomaterial for the construction of electrochemical biosensors with enhanced analytical performance with respect to other biosensor designs. Recent advances in this field are reviewed in this article. The advantageous operational characteristics of the biosensing devices designed making use of gold nanoparticles are highlighted with respect to non-nanostructured biosensors and some illustrative examples are commented. Electrochemical enzyme biosensors including those using hybrid materials with carbon nanotubes and polymers, sol-gel matrices, and layer-by-layer architectures are considered. Moreover, electrochemical immunosensors in which gold nanoparticles play a crucial role in the electrode transduction enhancement of the affinity reaction as well as in the efficiency of immunoreagents immobilization in a stable mode are reviewed. Similarly, recent advances in the development of DNA biosensors using gold nanoparticles to improve DNA immobilization on electrode surfaces and as suitable labels to improve detection of hybridization events are considered. Finally, other biosensors designed with gold nanoparticles oriented to electrically contact redox enzymes to electrodes by a reconstitution process and to the study of direct electron transfer between redox proteins and electrode surfaces have also been treated. (author)

  10. Gold Nanoparticle Labels Amplify Ellipsometric Signals

    Science.gov (United States)

    Venkatasubbarao, Srivatsa

    2008-01-01

    The ellipsometric method reported in the immediately preceding article was developed in conjunction with a method of using gold nanoparticles as labels on biomolecules that one seeks to detect. The purpose of the labeling is to exploit the optical properties of the gold nanoparticles in order to amplify the measurable ellipsometric effects and thereby to enable ultrasensitive detection of the labeled biomolecules without need to develop more-complex ellipsometric instrumentation. The colorimetric, polarization, light-scattering, and other optical properties of nanoparticles depend on their sizes and shapes. In the present method, these size-and-shape-dependent properties are used to magnify the polarization of scattered light and the diattenuation and retardance of signals derived from ellipsometry. The size-and-shape-dependent optical properties of the nanoparticles make it possible to interrogate the nanoparticles by use of light of various wavelengths, as appropriate, to optimally detect particles of a specific type at high sensitivity. Hence, by incorporating gold nanoparticles bound to biomolecules as primary or secondary labels, the performance of ellipsometry as a means of detecting the biomolecules can be improved. The use of gold nanoparticles as labels in ellipsometry has been found to afford sensitivity that equals or exceeds the sensitivity achieved by use of fluorescence-based methods. Potential applications for ellipsometric detection of gold nanoparticle-labeled biomolecules include monitoring molecules of interest in biological samples, in-vitro diagnostics, process monitoring, general environmental monitoring, and detection of biohazards.

  11. Gold nanoparticle-based electrochemical biosensors

    International Nuclear Information System (INIS)

    Pingarron, Jose M.; Yanez-Sedeno, Paloma; Gonzalez-Cortes, Araceli

    2008-01-01

    The unique properties of gold nanoparticles to provide a suitable microenvironment for biomolecules immobilization retaining their biological activity, and to facilitate electron transfer between the immobilized proteins and electrode surfaces, have led to an intensive use of this nanomaterial for the construction of electrochemical biosensors with enhanced analytical performance with respect to other biosensor designs. Recent advances in this field are reviewed in this article. The advantageous operational characteristics of the biosensing devices designed making use of gold nanoparticles are highlighted with respect to non-nanostructured biosensors and some illustrative examples are commented. Electrochemical enzyme biosensors including those using hybrid materials with carbon nanotubes and polymers, sol-gel matrices, and layer-by-layer architectures are considered. Moreover, electrochemical immunosensors in which gold nanoparticles play a crucial role in the electrode transduction enhancement of the affinity reaction as well as in the efficiency of immunoreagents immobilization in a stable mode are reviewed. Similarly, recent advances in the development of DNA biosensors using gold nanoparticles to improve DNA immobilization on electrode surfaces and as suitable labels to improve detection of hybridization events are considered. Finally, other biosensors designed with gold nanoparticles oriented to electrically contact redox enzymes to electrodes by a reconstitution process and to the study of direct electron transfer between redox proteins and electrode surfaces have also been treated

  12. Gold prices: Analyzing its cyclical behavior

    Directory of Open Access Journals (Sweden)

    Martha Gutiérrez

    2013-07-01

    Full Text Available Gold is a commodity that is seen as a safe haven when a financial crisis strikes, but when stock markets are prosperous, these are more attractive investment alternatives, and so the gold cycle goes on and on. The DJIA/GF (Dow Jones Industrial Average and Gold Fix ratio is chosen to establish the evolution of gold prices in relation to the NYSE. This paper has two goals: to prove that the DJIA/GF ratio is strongly cyclical by using Fourier analysis and to set a predictive neural networks model to forecast the behavior of this ratio during 2011-2020. To this end, business cycle events like the Great Depression along with the 1970s crisis, and the 1950s boom along with the world economic recovery of the 1990s are contrasted in light of the mentioned ratio. Gold prices are found to evolve cyclically with a dominant period of 37 years and are mainly affected by energy prices, financial markets and macroeconomic indicators.

  13. The Complete Reconfiguration of Dendritic Gold

    Science.gov (United States)

    Paneru, Govind; Flanders, Bret

    2014-03-01

    Reconfigurability-by-design is an important strategy in modern materials science, as materials with this capability could potentially be used to confer hydrophobic, lipophobic, or anti-corrosive character to substrates in a regenerative manner. The present work extends the directed electrochemical nanowire assembly (DENA) methodology, which is a technique that employs alternating voltages to grow single crystalline metallic nanowires and nano-dendrites from simple salt solutions, to enable the complete dissolution of macroscopic arrays of metallic dendrites following their growth. Our main finding is that structural reconfiguration of dendritic gold is induced by changes in the MHz-level frequencies of voltages that are applied to the dendrites. Cyclic voltammetry and micro-Raman spectroscopy have been used to show that dendritic gold grows and dissolves by the same chemical mechanisms as bulk gold. Hence, the redox chemistry that occurs at the crystal-solution interface is no different than the established electrochemistry of gold. What differs in this process and allows for reconfiguration to occur is the diffusive behavior of the gold chloride molecules in the solution adjacent to the interface. We will present a simple model that captures the physics of this behavior.

  14. Radiofrequency Heating Pathways for Gold Nanoparticles

    Science.gov (United States)

    Collins, C. B.; McCoy, R. S.; Ackerson, B. J.; Collins, G. J.

    2015-01-01

    This feature article reviews the thermal dissipation of nanoscopic gold under radiofrequency (RF) irradiation. It also presents previously unpublished data addressing obscure aspects of this phenomenon. While applications in biology motivated initial investigation of RF heating of gold nanoparticles, recent controversy concerning whether thermal effects can be attributed to nanoscopic gold highlight the need to understand the involved mechanism or mechanisms of heating. Both the nature of the particle and the nature of the RF field influence heating. Aspects of nanoparticle chemistry and physics, including the hydrodynamic diameter of the particle, the oxidation state and related magnetism of the core, and the chemical nature of the ligand shell may all strongly influence to what extent a nanoparticle heats in an RF field. Aspects of RF include: power, frequency and antenna designs that emphasize relative strength of magnetic or electric fields, and also influence the extent to which a gold nanoparticle heats in RF. These nanoparticle and RF properties are analysed in the context of three heating mechanisms proposed to explain gold nanoparticle heating in an RF field. This article also makes a critical analysis of the existing literature in the context of the nanoparticle preparations, RF structure, and suggested mechanisms in previously reported experiments. PMID:24962620

  15. Simple fabrication of gold nanobelts and patterns.

    Directory of Open Access Journals (Sweden)

    Renyun Zhang

    Full Text Available Gold nanobelts are of interest in several areas; however, there are only few methods available to produce these belts. We report here on a simple evaporation induced self-assembly (EISA method to produce porous gold nanobelts with dimensions that scale across nanometer (thickness ∼80 nm and micrometer (width ∼20 µm, to decimeter (length ∼0.15 m. The gold nanobelts are well packed on the beaker wall and can be easily made to float on the surface of the solution for depositing onto other substrates. Microscopy showed that gold nanobelts had a different structure on the two sides of the belt; the density of gold nanowires on one side was greater than on the other side. Electrical measurements showed that these nanobelts were sensitive to compressive or tensile forces, indicating a potential use as a strain sensor. The patterned nanobelts were further used as a template to grow ZnO nanowires for potential use in applications such as piezo-electronics.

  16. Environmental stewardship for gold mining in tropical regions

    Directory of Open Access Journals (Sweden)

    A Isahak

    2013-10-01

    Full Text Available Mining has gained strong popularity in recent years due to the increase in global demand for metals and other industrial raw material derived from the ground. However, information and good governance regarding activities related to mining is still very much lacking especially in underdeveloped and developing countries in the tropics. In Malaysia, the importance of environmental stewardship in mining is a new phenomenon. The new National Mineral Policy 2 calls for compliance with existing standards and guidelines, stresses on progressive and post mining rehabilitation as well as promotes the gathering and dissemination of information, best mining practices, public disclosure and corporate social responsibility. Our preliminary studies however have shown that its implementation may have been hampered by inadequate legal and administrative structures, lack of freedom of information, physical inaccessibility, lack of information and public participation. In this presentation, the above issues and measures to reduce the impact of mining, particularly that of gold on the environment with a special focus on Malaysia is discussed. These measures include alternative gold extraction methods, appropriate tailing dam construction and management, health risk assessment and risk management, compliance with the Cyanide Code and liberalization of access to information, facilitation of access to justice, the strengthening of legal and administrative structures as well as corporate accountability to the public as part of corporate social responsibility.

  17. In vitro toxicity studies of polymer-coated gold nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Rayavarapu, Raja G; Petersen, Wilma; Manohar, Srirang; Van Leeuwen, Ton G [Biomedical Photonic Imaging Group, MIRA Institute for Biomedical Technology and Technical Medicine, Faculty of Science and Technology, University of Twente, PO Box 217, 7500AE Enschede (Netherlands); Hartsuiker, Liesbeth; Otto, Cees [Medical Cell Biophysics, MIRA Institute for Biomedical Technology and Technical Medicine, Faculty of Science and Technology, University of Twente, PO Box 217, 7500AE Enschede (Netherlands); Chin, Patrick; Van Leeuwen, Fijs W B [Division of Diagnostic Oncology, Netherlands Cancer Institute, 1066 CX Amsterdam (Netherlands); Janssen, Hans, E-mail: S.Manohar@utwente.nl [Division of Cell Biology, The Netherlands Cancer Institute, 1066 CX Amsterdam (Netherlands)

    2010-04-09

    We evaluated cellular responses to polymer-treated gold nanorods, which were synthesized using the standard wet-chemistry method that utilizes hexadecyltrimethylammonium bromide (CTAB). The nanorod dispersions were coated with either polystyrene sulfonate (PSS) or polyethylene glycol (PEG). Two sizes of nanorods were tested, with optical responses peaking at 628 and 773 nm. The cells were from mammary adenocarcinoma (SKBR3), Chinese Hamster Ovary (CHO), mouse myoblast (C2C12) and Human Leukemia (HL60) cell lines. Their mitochondrial function following exposure to the nanorods were assessed using the MTS assay. We found PEGylated particles to have superior biocompatibility compared with PSS-coated nanorods, which showed substantial cytotoxicity. Electron microscopy showed no cellular uptake of PEGylated particles compared with their PSS counterparts. PEGylated gold nanorods also exhibited better dispersion stability in the presence of cell growth medium; PSS-coated rods tended to flocculate or cluster. In the case of the PSS particles, toxicity correlated with surface area across the two sizes of nanorods studied.

  18. Direct Electrochemistry of Horseradish Peroxidase-Gold Nanoparticles Conjugate

    Directory of Open Access Journals (Sweden)

    Chanchal K. Mitra

    2009-02-01

    Full Text Available We have studied the direct electrochemistry of horseradish peroxidase (HRP coupled to gold nanoparticles (AuNP using electrochemical techniques, which provide some insight in the application of biosensors as tools for diagnostics because HRP is widely used in clinical diagnostics kits. AuNP capped with (i glutathione and (ii lipoic acid was covalently linked to HRP. The immobilized HRP/AuNP conjugate showed characteristic redox peaks at a gold electrode. It displayed good electrocatalytic response to the reduction of H2O2, with good sensitivity and without any electron mediator. The covalent linking of HRP and AuNP did not affect the activity of the enzyme significantly. The response of the electrode towards the different concentrations of H2O2 showed the characteristics of Michaelis Menten enzyme kinetics with an optimum pH between 7.0 to 8.0. The preparation of the sensor involves single layer of enzyme, which can be carried out efficiently and is also highly reproducible when compared to other systems involving the layer-by-layer assembly, adsorption or encapsulation of the enzyme. The immobilized AuNP-HRP can be used for immunosensor applications

  19. Precipitation of lamellar gold nanocrystals in molten polymers

    International Nuclear Information System (INIS)

    Palomba, M.; Carotenuto, G.

    2016-01-01

    Non-aggregated lamellar gold crystals with regular shape (triangles, squares, pentagons, etc.) have been produced by thermal decomposition of gold chloride (AuCl) molecules in molten amorphous polymers (polystyrene and poly(methyl methacrylate)). Such covalent inorganic gold salt is high soluble into non-polar polymers and it thermally decomposes at temperatures compatible with the polymer thermal stability, producing gold atoms and chlorine radicals. At the end of the gold precipitation process, the polymer matrix resulted chemically modified because of the partial cross-linking process due to the gold atom formation reaction.

  20. Gold grade variation and particle microchemistry in exploration pits of the Batouri gold district, SE Cameroon

    Science.gov (United States)

    Vishiti, A.; Suh, C. E.; Lehmann, B.; Egbe, J. A.; Shemang, E. M.

    2015-11-01

    The Batouri area hosts lode-gold mineralization under several-m-thick lateritic cover. Pitting to bed rock on a geochemical Au anomaly defined from previous reconnaissance soil sampling identified five horizons ranging from saprock at the base to laterite at the top. Analysis of bulk samples from each horizon by fire assay shows that most of the horizons are barren although 119 ppb and 48 ppb Au values were obtained from one laterite horizon and one saprolite horizon, respectively, from two separate pits. All the horizons were panned and particulate gold was also recovered only from these two horizons. The gold grains from both horizons are morphologically and compositionally indistinguishable with rare quartz, pyrite and galena inclusions. The grains have irregular, sub-rounded, bean to elongated shapes and they show a remarkable core-rim zonation. Electron microprobe analysis of the grains recorded high gold content in the rims (86.3-100 wt%) and along fissures within the grains (95.1-100 wt%). The cores are relatively Ag rich (11.8-14 wt% Ag) while the rims (0.63-13.7 wt% Ag, most of the values fall within the lower limit of this range) and fissures (0.03-5.02 wt% Ag) are poor in Ag. The low Ag concentration in the rims and along fissures is attributed to preferential leaching of Ag; a process recognized in gold grains and platiniferous alloys from alluvia. The core composition of the grains is similar to that of primary gold composition in the bedrock. These results show that gold in the soil is relic particulate gold derived from the primary source with no evidence of secondary gold precipitation in the weathering cycle. In all the pits no horizon was systematically enriched in gold suggesting there has been no chemical remobilization of gold in this environment. Rather the dispersion of gold here is in the particulate form. Therefore combining particulate gold features with assay data is relevant to exploration in such tropical environments.

  1. Geomicrobial Optical Logging Detectors (GOLD)

    Science.gov (United States)

    Bramall, N. E.; Stoker, C. R.; Price, P. B.; Coates, J. D.; Allamandola, L. J.; Mattioda, A. L.

    2008-12-01

    to in situ processes. 4) Temperature and Oxygen Sensors: The ambient temperature will be recorded as well as the presence of oxygen. Oxygen presence can be measured using a fluorescence quenching fiber optic probe to avoid interference from other gases. We forsee that this technology will enable experiments including studies of gene transfer, microbial habitat, in situ stratigraphy and hydrological processes. In addition, though designed to scan borehole walls, GOLD could be used to scan core samples as they are recovered for rapid quantification and analysis in order to discover samples of particular interest that could then be prioritized for more in-depth, traditional analysis.

  2. Robust gold nanoparticles stabilized by trithiol for application in chemiresistive sensors

    Energy Technology Data Exchange (ETDEWEB)

    Garg, Niti; Mohanty, Ashok; Jin, Rongchao [Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Lazarus, Nathan; Santhanam, Suresh; Fedder, Gary K [Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Schultz, Lawrence; Weiss, Lee [Robotics Institute, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Rozzi, Tony R; Snyder, Jay L, E-mail: zpx5@cdc.gov, E-mail: fedder@ece.cmu.edu, E-mail: rongchao@andrew.cmu.edu [National Institute for Occupational Safety and Health (NIOSH), Pittsburgh, PA 15236 (United States)

    2010-10-08

    The use of gold nanoparticles coated with an organic monolayer of thiol for application in chemiresistive sensors was initiated in the late 1990s; since then, such types of sensors have been widely pursued due to their high sensitivities and reversible responses to volatile organic compounds (VOCs). However, a major issue for chemical sensors based on thiol-capped gold nanoparticles is their poor long-term stability as a result of slow degradation of the monothiol-to-gold bonds. We have devised a strategy to overcome this limitation by synthesizing a more robust system using Au nanoparticles capped by trithiol ligands. Compared to its monothiol counterpart, the new system is significantly more stable and also shows improved sensitivity towards different types of polar or non-polar VOCs. Thus, the trithiol-Au nanosensor shows great promise for use in real world applications.

  3. Robust gold nanoparticles stabilized by trithiol for application in chemiresistive sensors

    International Nuclear Information System (INIS)

    Garg, Niti; Mohanty, Ashok; Jin, Rongchao; Lazarus, Nathan; Santhanam, Suresh; Fedder, Gary K; Schultz, Lawrence; Weiss, Lee; Rozzi, Tony R; Snyder, Jay L

    2010-01-01

    The use of gold nanoparticles coated with an organic monolayer of thiol for application in chemiresistive sensors was initiated in the late 1990s; since then, such types of sensors have been widely pursued due to their high sensitivities and reversible responses to volatile organic compounds (VOCs). However, a major issue for chemical sensors based on thiol-capped gold nanoparticles is their poor long-term stability as a result of slow degradation of the monothiol-to-gold bonds. We have devised a strategy to overcome this limitation by synthesizing a more robust system using Au nanoparticles capped by trithiol ligands. Compared to its monothiol counterpart, the new system is significantly more stable and also shows improved sensitivity towards different types of polar or non-polar VOCs. Thus, the trithiol-Au nanosensor shows great promise for use in real world applications.

  4. Biosynthesis of silver and gold nanoparticles by novel sundried Cinnamomum camphora leaf

    International Nuclear Information System (INIS)

    Huang Jiale; Li Qingbiao; Sun Daohua; Lu Yinghua; Su Yuanbo; Yang Xin; Wang Huixuan; Wang Yuanpeng; Shao Wenyao; He Ning; Hong Jinqing; Chen Cuixue

    2007-01-01

    The synthesis of nanocrystals is in the limelight in modern nanotechnology. Biosynthesis of nanoparticles by plant extracts is currently under exploitation. Not only could silver nanoparticles ranging from 55 to 80 nm in size be fabricated, but also triangular or spherical shaped gold nanoparticles could be easily modulated by reacting the novel sundried biomass of Cinnamomum camphora leaf with aqueous silver or gold precursors at ambient temperature. The marked difference of shape control between gold and silver nanoparticles was attributed to the comparative advantage of protective biomolecules and reductive biomolecules. The polyol components and the water-soluble heterocyclic components were mainly responsible for the reduction of silver ions or chloroaurate ions and the stabilization of the nanoparticles, respectively. The sundried leaf in this work was very suitable for simple synthesis of nanoparticles

  5. Amorphous Carbon Gold Nanocomposite Thin Films: Structural and Spectro-ellipsometric Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Montiel-Gonzalez, Z., E-mail: zeuzmontiel@hotmail.com [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito exterior s/n, Ciudad Universitaria, Coyoacan 04510, Mexico D.F (Mexico); Rodil, S.E.; Muhl, S. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito exterior s/n, Ciudad Universitaria, Coyoacan 04510, Mexico D.F (Mexico); Mendoza-Galvan, A. [Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, Unidad Queretaro, 76010 Queretaro, Queretaro (Mexico); Rodriguez-Fernandez, L. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Circuito de la Investigacion Cientifica, Ciudad Universitaria, 04510, Mexico D.F (Mexico)

    2011-07-01

    Spectroscopic Ellipsometry was used to determine the optical and structural properties of amorphous carbon:gold nanocomposite thin films deposited by dc magnetron co-sputtering at different deposition power. The incorporation of gold as small particles distributed in the amorphous carbon matrix was confirmed by X-ray Diffraction, Rutherford Backscattering measurements and High Resolution Transmission Electron Microscopy. Based on these results, an optical model for the films was developed using the Maxwell-Garnett effective medium with the Drude-Lorentz model representing the optical response of gold and the Tauc-Lorentz model for the amorphous carbon. The gold volume fraction and particle size obtained from the fitting processes were comparable to those from the physical characterization. The analysis of the ellipsometric spectra for all the samples showed strong changes in the optical properties of the carbon films as a consequence of the gold incorporation. These changes were correlated to the structural modification observed by Raman Spectroscopy, which indicated a clustering of the sp{sup 2} phase with a subsequent decrease in the optical gap. Finally, measurements of Reflection and Transmission Spectroscopy were carried out and Transmission Electron Microscopy images were obtained in order to support the ellipsometric model results.

  6. Tuning Surface Chemistry of Polyetheretherketone by Gold Coating and Plasma Treatment

    Science.gov (United States)

    Novotná, Zdeňka; Rimpelová, Silvie; Juřík, Petr; Veselý, Martin; Kolská, Zdeňka; Hubáček, Tomáš; Borovec, Jakub; Švorčík, Václav

    2017-06-01

    Polyetheretherketone (PEEK) has good chemical and biomechanical properties that are excellent for biomedical applications. However, PEEK exhibits hydrophobic and other surface characteristics which cause limited cell adhesion. We have investigated the potential of Ar plasma treatment for the formation of a nanostructured PEEK surface in order to enhance cell adhesion. The specific aim of this study was to reveal the effect of the interface of plasma-treated and gold-coated PEEK matrices on adhesion and spreading of mouse embryonic fibroblasts. The surface characteristics (polarity, surface chemistry, and structure) before and after treatment were evaluated by various experimental techniques (gravimetry, goniometry, X-ray photoelectron spectroscopy (XPS), and electrokinetic analysis). Further, atomic force microscopy (AFM) was employed to examine PEEK surface morphology and roughness. The biological response of cells towards nanostructured PEEK was evaluated in terms of cell adhesion, spreading, and proliferation. Detailed cell morphology was evaluated by scanning electron microscopy (SEM). Compared to plasma treatment, gold coating improved PEEK wettability. The XPS method showed a decrease in the carbon concentration with increasing time of plasma treatment. Cell adhesion determined on the interface between plasma-treated and gold-coated PEEK matrices was directly proportional to the thickness of a gold layer on a sample. Our results suggest that plasma treatment in a combination with gold coating could be used in biomedical applications requiring enhanced cell adhesion.

  7. Surface enhanced imaging and IR spectroscopy of the biological cells on the nanostructured gold film

    Directory of Open Access Journals (Sweden)

    G.I. Dovbeshko

    2017-07-01

    Full Text Available New approach for optical imaging, structural study and cell cultivation based on the effect of the enhancement of optical signals from biomolecules and biological cells near nanostructured rough gold surface is proposed. The surface enhanced IR absorption (SEIRA spectroscopy and confocal microscopy experiments were made using the culture of SPEV (porcine embryonic kidney epithelium transplantable line and fibroblast cells, cultivated and/or adsorbed on the gold substrate. The SEIRA spectra registered from monolayer of the SPEV cells cultivated on the rough gold showed a low frequency shift of about 2 to 7 cm 1 for the most characteristic IR vibrations, compared with those adsorbed from suspension on the same substrate. An enhancement factor of 15…30 was obtained for different molecular vibrations. The confocal microscopy contrast images of the SPEV cells on rough gold substrate were obtained in laser fluorescence mode. This approach opens new possibilities for visualization of the living cells in vivo without staining. The fluorescence of the rough gold surfaces and effects responsible for our findings have been discussed.

  8. Lime in gold and uranium mining

    International Nuclear Information System (INIS)

    Van Staden, C.M.

    1979-01-01

    In this article the author discusses the role of lime in gold and uranium extraction and looks more closely at the industry's efforts to improve the environment by vegetation of sand dumps and slimes dams. He then comes to the conclusion that lime has been and still is the most effective, practical and cheapest chemical that can be used in the South African gold and uranium mining industry to settle pulps, protect cyanide solutions, aid the vegetation of dumps and neutralise acidic waters and residues. The gold and uranium industry is very pollution concious, and in South Africa the importance of the role that lime plays in combating air and water pollution cannot be over emphasised

  9. Cancer nanotechnology: emerging role of gold nanoconjugates.

    Science.gov (United States)

    Kudgus, Rachel A; Bhattacharya, Resham; Mukherjee, Priyabrata

    2011-12-01

    Over the last few decades, the study of nanotechnology has grown exponentially. Nanotechnology bridges science, engineering and technology; it continues to expand in definition as well as practice. One sub-set of nanotechnology is bionanotechnology, this will be the focus of this review. Currently, bionanotechnology is being studied and exploited for utility within medicinal imaging, diagnosis and therapy in regard to cancer. Cancer is a world-wide health problem and the implication rate as well as the death rate increase year to year. However promising work is being done with gold nanoparticles for detection, diagnosis and targeted drug delivery therapy. Gold nanoparticles can be synthesized in various shapes and sizes, which directly correlates to the color; they can also be manipulated to carry various antibody, protein, plasmid, DNA or small molecule drug. Herein we summarize some of the very influential research being done in the field of Cancer Nanotechnology with an emphasis on gold nanoparticles.

  10. Optical constant of thin gold films

    DEFF Research Database (Denmark)

    Yakubovsky, D. I.; Fedyanin, D. Yu; Arsenin, A. V.

    2017-01-01

    The performance of metal-based devices is limited by ohmic losses in the metal, which are determined by electron scattering. The structural properties of gold thin films also play an important role in the film quality, which may affect its' optical properties and the overall capability...... and spectroscopic ellipsometry, the structural morphology and optical properties of polycrystalline gold thin films (fabricated by e-beam deposition at a low sputtering rate smooth gold) in the thickness range of 20 - 200 nm. By extracting the real and imaginary dielectric function and the Drude parameter...... of the device. At the same time, metal films of different thicknesses are needed for different applications and, since these films are polycrystalline, their internal properties and surface roughness can greatly vary from one thickness to another. In this work, we study, using atomic force microscopy...

  11. Microbially Induced Precipitation of Gold(0) Nanoparticles.

    Science.gov (United States)

    Roh, Yu; Kang, Serku; Park, Bitna; Kim, Yumi

    2015-01-01

    The objectives of this study were to synthesize gold nanoparticles by biomineralization using metal-reducing bacteria and to characterize their mineralogical properties. The metal-reducing bacteria were able to reduce Au(III) to Au(0) with organic fatty acids as electron donors, as indicated by the color change of the culture solution from colorless gold ions to black precipitates at 25 degrees C. XRD, SEM- and TEM-EDS analyses of the precipitates showed that Au(0) was precipitated and formed at either the cell membrane or extracellularly. The Au(0) nanoparticles were about 200 nm in size and ball-shaped. Biomineralization for elemental Au(0) nanoparticle synthesis may be useful for the recovery of natural gold in natural environments.

  12. Preparation of radioactive colloidal gold 198Au

    International Nuclear Information System (INIS)

    Cammarosano, S.A.

    1979-01-01

    The preparation with simple equipment of radioactive colloidal gold of particle size about approximately 300 A from seed colloid stabilized by gelatine is described. Some physico-chemical parameters which can affect the process of formation of these colloidal particles are analysed; particle size has been meassured with an electron microscope. The colloid stability has been studied as a function of dilution, age and pH. Nucleation and growth of radioactive colloidal gold have been studied using spectrophotometry. Absorption spectra of the two ones are presented and compared. Quality control of the production process is verified through measurement of parameters, such as radioactive and radiochemical purity and biological distribution in laboratorial animals. This distribution was evalusted for rats injected endovenously with the gold colloidal solution.(Author) [pt

  13. Free gold recovery by coal-oil agglomeration

    Energy Technology Data Exchange (ETDEWEB)

    Kotze, W.; Petersen, F.W. [Cape Technikon Cape Town (South Africa). Dept. of Chemical Engineering

    2000-02-01

    The gold mining industry has mainly relied upon the use of highly polluting chemicals, such as mercury and cyanide to recover gold from its ores. The Coal Gold Agglomeration (CGA) process was developed some years ago and has the advantage in that gold is recovered by a procedure which has little or no negative impact on the environment. A gold ore containing liberated gold particles is contacted with coal-oil agglomerates, whereby the gold is recovered into the coal/oil phase. Laboratory scale batch tests were performed on an artificial mixture gold slurry and gold recoveries of up to 85% were found under optimized conditions. By recycling the coal/oil phase, it was found that the gold loading onto the agglomerates was increased. Tests performed on an industrial ore yielded slightly lower gold recoveries, and X-ray Diffraction (XRD) analysis on the coal/oil phase showed that minerals other than gold were recovered into this phase. A comparative study was conducted whereby the CGA process was compared to mercury amalgamation. Gold recoveries obtained through amalgamation were 15% lower than by the agglomeration process, which indicates that this process can be considered favourably as an alternative to amalgamation. 16 refs., 2 figs., 6 tabs.

  14. Size fraction assaying of gold bearing rocks (for gold extraction) by instrumental neutron activation analysis

    International Nuclear Information System (INIS)

    Ahmed, K.; Dampare, S.B.; Addo, M.A.; Osae, S.; Adotey, D.K.; Adomako, D.

    2005-01-01

    A novel method has been developed for processing and extraction of gold from gold bearing rocks for use by small-scale gold miners in Ghana. The methodology involved crushing of gold bearing hard rocks to fine particles to form a composite sample and screening at a range of sizes. Gold distribution in the composite sample was determined as a function of particle size by using Instrumental Neutron Activation Analysis. The concentrations of gold for the corresponding particle sizes were 16.4 ± 0.17mg/kg for sizes <63μm; 161± 0.75 mg/kg for 63 - 125 μm, 0.53 + 0.03 mg/kg for 125 - 250 μm, 4.66± 0.07 mg/kg for 250 - 355 μm, 1.55 ± 0.06 for 355 - 425 μm, 0.80 ± 0.008 mg/kg for 425 -1000 μm, and 1.27 + 0.05 mg/kg for 1000-2000 μm. The average gold content in a 7.127 kg composite sample based on particle size found to be 3.08 mg/kg. (au)

  15. Major Brazilian gold deposits - 1982 to 1999

    Science.gov (United States)

    Thorman, Charles H.; DeWitt, Ed; Maron, Marcos A.; Ladeira, Eduardo A.

    2001-07-01

    Brazil has been a major but intermittent producer of gold since its discovery in 1500. Brazil led the world in gold production during the 18th and early 19th centuries. From the late 19th century to the late 20th century, total mining company and garimpeiro production was small and relatively constant at about 5 to 8 t/year. The discovery of alluvial deposits in the Amazon by garimpeiros in the 1970s and the opening of eight mines by mining companies from 1983 to 1990 fueled a major boom in Brazil's gold production, exceeding 100 t/year in 1988 and 1989. However, garimpeiro alluvial production decreased rapidly in the 1990s, to about 10 t/year by 1999. Company production increased about tenfold from about 4 t/year in 1982 to 40 t in 1992. Production from 1992 to the present remained relatively stable, even though several mines were closed or were in the process of closing and no new major mines were put into production during that period. Based on their production history from 1982-1999, 17 gold mines are ranked as major (>20 t) and minor (3-8 t) mines. From 1982-1999, deposits hosted in Archean rocks produced 66% of the gold in Brazil, whereas deposits in Paleoproterozoic and Neoproterozoic rocks accounted for 19% and 15%, respectively. Deposits in metamorphosed sedimentary rocks, especially carbonate-rich rocks and carbonate iron-formation, yielded the great bulk of the gold. Deposits in igneous rocks were of much less importance. The Archean and Paleoproterozoic terranes of Brazil largely lack base-metal-rich volcanogenic massive sulfide deposits, porphyry deposits, and polymetallic veins and sedimentary exhalative deposits. An exception to this is in the Carajás Mineral Province.

  16. Major brazilian gold deposits - 1982 to 1999

    Science.gov (United States)

    Thorman, C.H.; Dewitt, E.; Maron, M.A.; Ladeira, E.A.

    2001-01-01

    Brazil has been a major but intermittent producer of gold since its discovery in 1500. Brazil led the world in gold production during the 18th and early 19th centuries. From the late 19th century to the late 20th century, total mining company and garimpeiro production was small and relatively constant at about 5 to 8 t/year. The discovery of alluvial deposits in the Amazon by garimpeiros in the 1970s and the opening of eight mines by mining companies from 1983 to 1990 fueled a major boom in Brazil's gold production, exceeding 100 t/year in 1988 and 1989. However, garimpeiro alluvial production decreased 'rapidly in the 1990s, to about 10 t/year by 1999. Company production increased about tenfold from about 4 t/year in 1982 to 40 t in 1992. Production from 1992 to the present remained relatively stable, even though several mines were closed or were in the process of closing and no new major mines were put into production during that period. Based on their production history from 1982-1999, 17 gold mines are ranked as major (> 20 t) and minor (3-8 t) mines. From 1982-1999, deposits hosted in Archean rocks produced 66% of the gold in Brazil, whereas deposits in Paleoproterozoic and Neoproterozoic rocks accounted for 19% and 15%, respectively. Deposits in metamorphosed sedimentary rocks, especially carbonate-rich rocks and carbonate iron-formation, yielded the great bulk of the gold. Deposits in igneous rocks were of much less importance. The Archean and Paleoproterozoic terranes of Brazil largely lack base-metal-rich volcanogenic massive sulfide deposits, porphyry deposits, and polymetallic veins and sedimentary exhalative deposits. An exception to this is in the Caraja??s Mineral Province.

  17. Gold nanowires and the effect of impurities

    Directory of Open Access Journals (Sweden)

    Novaes Frederico

    2006-01-01

    Full Text Available AbstractMetal nanowires and in particular gold nanowires have received a great deal of attention in the past few years. Experiments on gold nanowires have prompted theory and simulation to help answer questions posed by these studies. Here we present results of computer simulations for the formation, evolution and breaking of very thin Au nanowires. We also discuss the influence of contaminants, such as atoms and small molecules, and their effect on the structural and mechanical properties of these nanowires.

  18. Aneurysm, arachnoiditis and intrathecal Au (gold)

    International Nuclear Information System (INIS)

    Pence, D.M.; Kim, T.H.; Levitt, S.H.

    1990-01-01

    This report is a 20-year follow-up of 14 patients treated with external beam craniospinal irradiation and intrathecal gold (10-45 mCi) for medulloblastoma. Six of the patients died within 2 years of treatment from persistent disease. No patients are alive without complications. Six of eight surviving patients developed arachnoiditis and cauda equina syndrome within 5 to 10 years of treatment. Seven of eight survivors developed aneurysms and/or cerebrovascular accidents 9 to 20 years after treatment. Four of the cerebrovascular events were fatal. Intrathecal gold pools in the basal cisterns and cauda equina delivering an extremely inhomogeneous dose throughout the neuroaxis. Its use is discouraged

  19. Nuclear shape transition in light gold isotopes

    International Nuclear Information System (INIS)

    Wallmeroth, K.; Bollen, G.; Dohn, A.; Egelhof, P.; Kroenert, U.; Heyde, K.; Coster, C. de; Wood, J.L.; Kluge, H.J.; European Organization for Nuclear Research, Geneva; European Organization for Nuclear Research, Geneva

    1989-01-01

    The hyperfine structure and isotope shifts of short-lived gold isotopes with 185≤A≤190 and the 11/2 - isomer of 189 Au have been investigated by application of on-line resonance ionization mass spectroscopy. A detection efficiency of ε=10 -8 for gold atoms was observed at a background of about one event per 1000 laser shots. The deduced charge radii show a drastic change between A=187 and A=186 which is interpreted as an onset of strong deformation (β 2 ≅ 0.25) in 186 Au and 185 Au due to the influence of the π1h 9/2 intruder orbital. (orig.)

  20. Gold nanoparticle-pentacene memory-transistors

    OpenAIRE

    Novembre , Christophe; Guerin , David; Lmimouni , Kamal; Gamrat , Christian; Vuillaume , Dominique

    2008-01-01

    We demonstrate an organic memory-transistor device based on a pentacene-gold nanoparticles active layer. Gold (Au) nanoparticles are immobilized on the gate dielectric (silicon dioxide) of a pentacene transistor by an amino-terminated self-assembled monolayer. Under the application of writing and erasing pulses on the gate, large threshold voltage shift (22 V) and on/off drain current ratio of ~3E4 are obtained. The hole field-effect mobility of the transistor is similar in the on and off sta...

  1. Gold Nanoparticles and Their Alternatives for Radiation Therapy Enhancement

    Directory of Open Access Journals (Sweden)

    Daniel R. Cooper

    2014-10-01

    Full Text Available Radiation therapy is one of the most commonly used treatments for cancer. The dose of delivered ionizing radiation can be amplified by the presence of high-Z materials via an enhancement of the photoelectric effect; the most widely studied material is gold (atomic number 79. However, a large amount is needed to obtain a significant dose enhancement, presenting a challenge for delivery. In order to make this technique of broader applicability, the gold must be targeted, or alternative formulations developed that do not rely solely on the photoelectric effect. One possible approach is to excite scintillating nanoparticles with ionizing radiation, and then exploit energy transfer between these particles and attached dyes in a manner analogous to photodynamic therapy. Doped rare-earth halides and semiconductor quantum dots have been investigated for this purpose. However, although the spectrum of emitted light after radiation excitation is usually similar to that seen with light excitation, the yield is not. Measurement of scintillation yields is challenging, and in many cases has been done only for bulk materials, with little understanding of how the principles translate to the nanoscale. Another alternative is to use local heating using gold or iron, followed by application of ionizing radiation. Hyperthermia pre-sensitizes the tumors, leading to an improved response. Another approach is to use chemotherapeutic drugs that can radiosensitize tumors. Drugs may be attached to high-Z nanoparticles or encapsulated. This article discusses each of these techniques, giving an overview of the current state of nanoparticle-assisted radiation therapy and future directions.

  2. Production of gold nanoparticles by Streptomyces djakartensis isolate B-5

    Directory of Open Access Journals (Sweden)

    Sara Biglari

    2014-09-01

    Full Text Available  Objective(s: Biosynthesis of gold nanoparticles (NGPs is environmentally safer than chemical and physical procedures. This method requires no use of toxic solvents and synthesis of dangerous products and is environmentally safe. In this study, we report the biosynthesis of NGPs using Streptomyces djakartensis isolate B-5. Materials and Methods: NGPs were biosynthesized by reducing aqueous gold chloride solution via a Streptomyces isolate without the need for any additive for protecting nanoparticles from aggregation. We characterized the responsible Streptomycete; its genome DNA was isolated, purified and 16S rRNA was amplified by PCR. The amplified isolate was sequenced; using the BLAST search tool from NCBI, the microorganism was identified to species level. Results: Treating chloroauric acid solutions with this bacterium resulted in reduction of gold ions and formation of stable NGPs. TEM and SEM electro micrographs of NGPs indicated size range from 2- 25 nm with average of 9.09 nm produced intracellular by the bacterium. SEM electro micrographs revealed morphology of spores and mycelia. The amplified PCR fragment of 16S rRNA gene was cloned and sequenced from both sides; it consisted of 741 nucleotides. According to NCBI GenBank, the bacterium had 97.1% homology with Streptomyces djakartensis strain RT-49. The GenBank accession number for partial 16S rRNA gene was recorded as JX162550. Conclusion: Optimized application of such findings may create applications of Streptomycetes for use as bio-factories in eco-friendly production of NGPs to serve in demanding industries and related biomedical areas. Research in this area should also focus on the unlocking the full mechanism of NGPs biosynthesis by Streptomycetes.

  3. Hand-arm vibration syndrome in South African gold miners.

    Science.gov (United States)

    Nyantumbu, Busi; Barber, Chris M; Ross, Mary; Curran, Andrew D; Fishwick, David; Dias, Belinda; Kgalamono, Spo; Phillips, James I

    2007-01-01

    Hand-arm vibration syndrome (HAVS) is associated with the use of hand-held vibrating tools. Affected workers may experience symptoms of tingling, numbness, loss of grip strength and pain. Loss of dexterity may impair everyday activities, and potentially increase the risk of occupational accidents. Although high vibration levels (up to 31 m/s(2)) have been measured in association with rock drills, HAVS has not been scientifically evaluated in the South African mining industry. The aim of this study was to determine the prevalence and severity of HAVS in South African gold miners, and to identify the tools responsible. A cross-sectional study was conducted in a single South African gold-mine. Participants were randomly selected from mineworkers returning from annual leave, comprising 156 subjects with occupational exposure to vibration, and 140 workers with no exposure. Miners who consented to participate underwent a clinical HAVS assessment following the UK Health and Safety Laboratory protocol. The prevalence of HAVS in vibration-exposed gold miners was 15%, with a mean latent period of 5.6 years. Among the non-exposed comparison group, 5% had signs and symptoms indistinguishable from HAVS. This difference was statistically significant (P < 0.05). All the cases of HAVS gave a history of exposure to rock drills. The study has diagnosed the first cases of HAVS in the South African mining industry. The prevalence of HAVS was lower than expected, and possible explanations for this may include a survivor population, and lack of vascular symptom reporting due to warm-ambient temperatures.

  4. Modelling spatial anisotropy of gold concentration data using GIS ...

    Indian Academy of Sciences (India)

    Linear trends of anomalously high gold values in the Florida Canyon gold deposit, Nevada have been identified using a ... starting at 3500 ft above mean sea level (msl). Relatively high ..... by slower rise in semivariances for longer distance.

  5. Plasmonic properties of gold-coated nanoporous anodic alumina ...

    Indian Academy of Sciences (India)

    gold-coated NAA is strongly quenched due to the strong plasmonic coupling. Keywords. Plasmon ... When coated by a thin film of gold, these templates can support surface plasmon resonance. ... 2.2 Equipment for characterization. Surface ...

  6. Hydrothermal Gold Mineralization and Structural Controls near May ...

    African Journals Online (AJOL)

    Mickiale

    controlled gold mineralized zones of gold near Workamba. .... consists of rounded to sub-rounded clasts of blue quartz eyes and varies in size from ... Based on the field observation, petrographic study and their cross cutting relationships; four.

  7. New progress of the study on uranium-gold association

    International Nuclear Information System (INIS)

    Feng Mingyue; Sun Zhifu

    1992-01-01

    Through the study on heavy minerals from the uraniferous granite-pegmatite it is found that nature gold is associated with uraninite, which provides the new information for the study on uranium-gold association and its metallogenesis

  8. New progress of the study on uranium-gold association

    Energy Technology Data Exchange (ETDEWEB)

    Mingyue, Feng; Zhifu, Sun [Beijing Research Inst. of Uranium Geology (China)

    1992-07-01

    Through the study on heavy minerals from the uraniferous granite-pegmatite it is found that nature gold is associated with uraninite, which provides the new information for the study on uranium-gold association and its metallogenesis.

  9. Determination of gold coating thickness measurement by using EDXRF

    International Nuclear Information System (INIS)

    Meor Yusoff Meor Sulaian; Masliana Muslimin; Fadlullah Jili Fursani

    2005-01-01

    The paper relates a study on the development of an analysis procedure for measuring the gold coating thickness using EDXRF technique. Gold coating thickness was measured by relating the counts under the Au L? peak its thickness value. In order to get a reasonably accurate result, a calibration graph was plotted using five gold-coated reference standards of different thickness. The calibration graph shows a straight line for thin coating measurement until 0.9 μm. Beyond this the relationship was not linear and this may be resulted from the self-absorption effect. Quantitative analysis was also performed on two different samples of gold coated jewelry and a phone connector. Result from the phone connector analysis seems to agree with the manufacturer gold coating value. From the analysis of gold-coated jewelry it had been able to differentiate the two articles as gold wash and gold electroplated. (Author)

  10. Phonon assisted thermophoretic motion of gold nanoparticles inside carbon nanotubes

    DEFF Research Database (Denmark)

    Schoen, Philipp A.E.; Walther, Jens Honore; Poulikakos, Dimos

    2007-01-01

    The authors investigate the thermally driven mass transport of gold nanoparticles confined inside carbon nanotubes using molecular dynamics simulations. The observed thermophoretic motion of the gold nanoparticles correlates with the phonon dispersion exhibited by a standard carbon nanotube and...

  11. Metallogenic epoch of the Jiapigou gold belt, Jilin Province, China

    Indian Academy of Sciences (India)

    Metallogenic epoch of the Jiapigou gold belt, Jilin Province, China: ... The Jiapigou gold belt is located on the northern margin of the North China Craton, and is one of the ... 29, Xueyuan Road, Beijing 100083, People's Republic of China.

  12. Albumin-gold-glutathione is a probable auranofin metabolite

    International Nuclear Information System (INIS)

    Shaw, C.F. III; Coffer, M.; Isab, A.A.

    1989-01-01

    The newly licensed gold drug, auranofin ((2,3,4,6-tetra-O-acetyl-β-1-D-gluco-pyranosato-S-)triethylphoshine-gold(I)) crosses cell membranes and enters cells which are inaccessible to parenteral gold drugs. In vivo, the triethylphosphine ligand and gold of auranofin, but not the thio-sugar moiety, accumulate in and subsequently efflux from red blood cells (RBCs). Extracellular albumin increases in the extent of gold efflux and acts as a gold binding site. The rate of efflux is first-order in RBC gold concentration. Studies using RBCs in which labelled [ 14 C]-glutathione is generated in situ incorporation of [ 14 C]- glycine demonstrate that glutathione also effluxes from the RBCs and forms a gold-glutathione-albumin complex. This may be the immunopharmacologically active complex

  13. Surface-enhanced Raman scattering on gold nanotrenches and nanoholes

    KAUST Repository

    Yue, Weisheng; Yang, Yang; Wang, Zhihong; Chen, Longqing; Wong, Ka Chun; Syed, Ahad A.; Chen, Zong; Wang, Xianbin

    2012-01-01

    Dependent effects on edge-to-edge distance and incidence polarization in surface-enhanced Raman Scattering (SERS) were studied in detection of 4-mercaptopyridine (4-MPy) molecules absorbed on gold nanotrenches and nanoholes. The gold nanostructures

  14. A Preliminary Study on Detecting Fake Gold Bars Using Prompt Gamma Activation Analysis: Simulation of Neutron Transmission in Gold Bar

    International Nuclear Information System (INIS)

    Lee, K. M.; Sun, G. M.

    2016-01-01

    The purpose of this study is to develop fake gold bar detecting method by using Prompt-gamma activation analysis (PGAA) facility at the Korea Atomic Energy Research Institute (KAERI). PGAA is an established nuclear analytical technique for non-destructive determination of elemental and isotopic compositions. For a preliminary study on detecting fake gold bar, Monte Carlo simulation of neutron transmission in gold bar was conducted and the possibility for detecting fake gold bar was confirmed. Under the gold bullion standard, it guaranteed the government would redeem any amount of currency for its value in gold. After the gold bullion standard ended, gold bars have been the target for investment as ever. But it is well known that fake gold bar exist in the gold market. This cannot be identified easily without performing a testing as it has the same appearance as the pure gold bar. In order to avoid the trading of fake gold bar in the market, they should be monitored thoroughly. Although the transmissivity of cold neutrons are low comparing that of thermal neutrons, the slower neutrons are more apt to be absorbed in a target, and can increase the prompt gamma emission rate. Also the flux of both thermal and cold neutron beam is high enough to activate thick target. If the neutron beam is irradiated on the front and the reverse side of gold bar, all insides of it can be detected

  15. A Preliminary Study on Detecting Fake Gold Bars Using Prompt Gamma Activation Analysis: Simulation of Neutron Transmission in Gold Bar

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K. M.; Sun, G. M. [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    The purpose of this study is to develop fake gold bar detecting method by using Prompt-gamma activation analysis (PGAA) facility at the Korea Atomic Energy Research Institute (KAERI). PGAA is an established nuclear analytical technique for non-destructive determination of elemental and isotopic compositions. For a preliminary study on detecting fake gold bar, Monte Carlo simulation of neutron transmission in gold bar was conducted and the possibility for detecting fake gold bar was confirmed. Under the gold bullion standard, it guaranteed the government would redeem any amount of currency for its value in gold. After the gold bullion standard ended, gold bars have been the target for investment as ever. But it is well known that fake gold bar exist in the gold market. This cannot be identified easily without performing a testing as it has the same appearance as the pure gold bar. In order to avoid the trading of fake gold bar in the market, they should be monitored thoroughly. Although the transmissivity of cold neutrons are low comparing that of thermal neutrons, the slower neutrons are more apt to be absorbed in a target, and can increase the prompt gamma emission rate. Also the flux of both thermal and cold neutron beam is high enough to activate thick target. If the neutron beam is irradiated on the front and the reverse side of gold bar, all insides of it can be detected.

  16. Electrografting of N’,N’-dimethylphenothiazin-5-ium-3,7-diamine (Azure A) diazonium salt forming electrocatalytic organic films on gold or graphene oxide gold hybrid electrodes

    International Nuclear Information System (INIS)

    Gómez-Anquela, C.; Revenga-Parra, M.; Abad, J.M.; Marín, A. García; Pau, J.L.; Pariente, F.; Piqueras, J.; Lorenzo, E.

    2014-01-01

    Electroactive films containing redox active phenothiazine moieties are covalently bound onto gold and graphene oxide gold hybrid electrodes, using reductive redox grafting of N’,N’-dimethylphenothiazin-5-ium-3,7-diamine (Azure A) diazonium salt. The grafting procedure is based on continuous voltammetric potential sweep of solutions containing the phenothiazine diazonium salt previously generated in situ. Control of the film thickness, electroactivity and stability can easily be exerted through appropriate choice of the concentration and number of potential scans performed. Cyclic Voltammetry, Electrochemical Quartz Crystal Microbalance (EQCM) and Spectroscopic Ellipsometry are used to characterize the growth process as well as the viscoelastic properties of the resulting stable electrografted films. The electron transfer reactions through the films are mediated by the presence of the Azure A redox moieties, which show a quasi-reversible electrochemical response and exhibit a potent electrocatalytic effect toward the oxidation of NADH. This electrocatalytic model has been used to compare the properties of Azure A electrografted films generated on gold electrodes with those obtained on hybrid electrodes composed by graphene oxide modified gold electrodes

  17. Role of nanostructured gold surfaces on monocyte activation and Staphylococcus epidermidis biofilm formation

    Directory of Open Access Journals (Sweden)

    Svensson S

    2014-02-01

    Full Text Available Sara Svensson,1,2 Magnus Forsberg,1,2 Mats Hulander,1,2 Forugh Vazirisani,1,2 Anders Palmquist,1,2 Jukka Lausmaa,2,3 Peter Thomsen,1,2 Margarita Trobos1,21Department of Biomaterials, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; 2BIOMATCELL VINN Excellence Center of Biomaterials and Cell Therapy, Gothenburg, Sweden; 3SP Technical Research Institute of Sweden, Borås, SwedenAbstract: The role of material surface properties in the direct interaction with bacteria and the indirect route via host defense cells is not fully understood. Recently, it was suggested that nanostructured implant surfaces possess antimicrobial properties. In the current study, the adhesion and biofilm formation of Staphylococcus epidermidis and human monocyte adhesion and activation were studied separately and in coculture in different in vitro models using smooth gold and well-defined nanostructured gold surfaces. Two polystyrene surfaces were used as controls in the monocyte experiments. Fluorescent viability staining demonstrated a reduction in the viability of S. epidermidis close to the nanostructured gold surface, whereas the smooth gold correlated with more live biofilm. The results were supported by scanning electron microscopy observations, showing higher biofilm tower formations and more mature biofilms on smooth gold compared with nanostructured gold. Unstimulated monocytes on the different substrates demonstrated low activation, reduced gene expression of pro- and anti-inflammatory cytokines, and low cytokine secretion. In contrast, stimulation with opsonized zymosan or opsonized live S. epidermidis for 1 hour significantly increased the production of reactive oxygen species, the gene expression of tumor necrosis factor-α (TNF-α, interleukin-1β (IL-1β, IL-6, and IL-10, as well as the secretion of TNF-α, demonstrating the ability of the cells to elicit a response and actively phagocytose prey. In addition, cells cultured on the smooth

  18. Formation of gold nanoparticles by glycolipids of Lactobacillus casei

    OpenAIRE

    Kikuchi, Fumiya; Kato, Yugo; Furihata, Kazuo; Kogure, Toshihiro; Imura, Yuki; Yoshimura, Etsuro; Suzuki, Michio

    2016-01-01

    Gold nanoparticles have particular properties distinct from those of bulk gold crystals, and such nanoparticles are used in various applications in optics, catalysis, and drug delivery. Many reports on microbial synthesis of gold nanoparticles have appeared. However, the molecular details (reduction and dispersion) of such synthesis remain unclear. In the present study, we studied gold nanoparticle synthesis by Lactobacillus casei. A comparison of L. casei components before and after addition...

  19. Using mineralogy to optimize gold recovery by direct cyanidation

    Science.gov (United States)

    Venter, D.; Chryssoulis, S. L.; Mulpeter, T.

    2004-08-01

    The complete and accurate gold deportments of direct cyanide leach residues provide a clear picture of the occurrence of unrecovered gold and identify causes for poor extraction. Based on the independent measurement of each form and carrier of unleached gold, opportunities for recovery optimization can be assessed more accurately by providing meaningful targets and can help identify the means to achieve such targets. In ten of 14 leach plants surveyed, 23% of the unrecovered gold could be extracted without finer grinding.

  20. Natural gold composition studied by proton activation analysis (PAA)

    International Nuclear Information System (INIS)

    Cojocaru, V.; Badica, T.; Popescu, I.V.

    2003-01-01

    The minor and trace element concentration of natural gold is essential for provenance studies of gold archaeological artifacts. In this work proton activation analysis is used in order to find what elements can be put into evidence in natural gold. For that purpose some gold nuggets from Romania were used. It was found that PAA is a good supplemental method to neutron activation analysis. (authors)

  1. An ultrasensitive electrochemical biosensor for glucose using CdTe-CdS core-shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle

    International Nuclear Information System (INIS)

    Gu Zhiguo; Yang Shuping; Li Zaijun; Sun Xiulan; Wang Guangli; Fang Yinjun; Liu Junkang

    2011-01-01

    Graphical abstract: We first reported an ultrasensitive electrochemical biosensor for glucose using CdTe-CdS core-shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle. Since promising their electrocatalytic synergy towards glucose was achieved, the biosensor showed high sensitivity (5762.8 nA nM -1 cm -2 ), low detection limit (S/N = 3) (3 x 10 -12 M) and fast response time (0.045 s). - Abstract: The paper reported an ultrasensitive electrochemical biosensor for glucose which was based on CdTe-CdS core-shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle. Since efficient electron transfer between glucose oxidase and the electrode was achieved, the biosensor showed high sensitivity (5762.8 nA nM -1 cm -2 ), low detection limit (S/N = 3) (3 x 10 -12 M), fast response time (0.045 s), wide calibration range (from 1 x 10 -11 M to 1 x 10 -8 M) and good long-term stability (26 weeks). The apparent Michaelis-Menten constant of the glucose oxidase on the medium, 5.24 x 10 -6 mM, indicates excellent bioelectrocatalytic activity of the immobilized enzyme towards glucose oxidation. Moreover, the effects of omitting graphene-gold nanocomposite, CdTe-CdS core-shell quantum dot and gold nanoparticle were also investigated. The result showed sensitivity of the biosensor is 7.67-fold better if graphene-gold nanocomposite, CdTe-CdS core-shell quantum dot and gold nanoparticle are used. This could be ascribed to improvement of the conductivity between graphene nanosheets due to introduction of gold nanoparticles, ultrafast charge transfer from CdTe-CdS core-shell quantum dot to graphene nanosheets and gold nanoparticle due to unique electrochemical properties of the CdTe-CdS core-shell quantum dot and good biocompatibility of gold nanoparticle for glucose oxidase. The biosensor is of best sensitivity in all glucose biosensors based on graphene nanomaterials up to

  2. An ultrasensitive electrochemical biosensor for glucose using CdTe-CdS core-shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Gu Zhiguo; Yang Shuping [School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China); Li Zaijun, E-mail: zaijunli@263.net [School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China); Sun Xiulan [School of Food Science and Technology, Jiangnan University, Wuxi 214122 (China); Wang Guangli [School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China); Fang Yinjun [Zhejiang Zanyu Technology Co., Ltd., Hangzhou 310009 (China); Liu Junkang [School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China)

    2011-10-30

    Graphical abstract: We first reported an ultrasensitive electrochemical biosensor for glucose using CdTe-CdS core-shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle. Since promising their electrocatalytic synergy towards glucose was achieved, the biosensor showed high sensitivity (5762.8 nA nM{sup -1} cm{sup -2}), low detection limit (S/N = 3) (3 x 10{sup -12} M) and fast response time (0.045 s). - Abstract: The paper reported an ultrasensitive electrochemical biosensor for glucose which was based on CdTe-CdS core-shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle. Since efficient electron transfer between glucose oxidase and the electrode was achieved, the biosensor showed high sensitivity (5762.8 nA nM{sup -1} cm{sup -2}), low detection limit (S/N = 3) (3 x 10{sup -12} M), fast response time (0.045 s), wide calibration range (from 1 x 10{sup -11} M to 1 x 10{sup -8} M) and good long-term stability (26 weeks). The apparent Michaelis-Menten constant of the glucose oxidase on the medium, 5.24 x 10{sup -6} mM, indicates excellent bioelectrocatalytic activity of the immobilized enzyme towards glucose oxidation. Moreover, the effects of omitting graphene-gold nanocomposite, CdTe-CdS core-shell quantum dot and gold nanoparticle were also investigated. The result showed sensitivity of the biosensor is 7.67-fold better if graphene-gold nanocomposite, CdTe-CdS core-shell quantum dot and gold nanoparticle are used. This could be ascribed to improvement of the conductivity between graphene nanosheets due to introduction of gold nanoparticles, ultrafast charge transfer from CdTe-CdS core-shell quantum dot to graphene nanosheets and gold nanoparticle due to unique electrochemical properties of the CdTe-CdS core-shell quantum dot and good biocompatibility of gold nanoparticle for glucose oxidase. The biosensor is of best sensitivity in all glucose

  3. Gold-coated nanoparticles for use in biotechnology applications

    Science.gov (United States)

    Berning, Douglas E [Los Alamos, NM; Kraus, Jr., Robert H.; Atcher, Robert W [Los Alamos, NM; Schmidt, Jurgen G [Los Alamos, NM

    2009-07-07

    A process of preparing gold-coated magnetic nanoparticles is disclosed and includes forming a suspension of magnetic nanoparticles within a suitable liquid, adding an amount of a reducible gold compound and a reducing agent to the suspension, and, maintaining the suspension for time sufficient to form gold-coated magnetic nanoparticles.

  4. Protracted elimination of gold nanoparticles from mouse liver

    DEFF Research Database (Denmark)

    Sadauskas, Evaldas; Wallin, Håkan; Stoltenberg, Meredin

    2009-01-01

    The present study aims at revealing the fate of 40-nm gold nanoparticles after intravenous injections. The gold nanoparticles were traced histochemically with light and transmission electron microscopy using autometallographic (AMG) staining, and the gold content in the liver was determined with ...

  5. Quinone-Enriched Gold Nanoparticles in Bioelectrochemistry and Charge Storage

    DEFF Research Database (Denmark)

    Wagner, Michal; Qvortrup, Katrine; Tanner, David Ackland

    for merging gold nanoparticles with resultant anthraquinones include one-pot microwave assisted synthesis or after-mixing of separately prepared gold nanoparticles with selected compounds. The quinone-enriched gold nanoparticles can be transferred onto different electrode surfaces, thus enabling facile...

  6. Gold nanoparticles: preparation, functionalisation and applications in biochemistry and immunochemistry

    International Nuclear Information System (INIS)

    Dykman, Lev A; Bogatyrev, Vladimir A

    2007-01-01

    The review summarises data on the synthesis and functionalisation of gold nanoparticles and their applications in biological investigations. Particular attention is given to applications of colloidal gold in solid-phase assays, immunoassay and studies of biologically active compounds by vibrational spectroscopy. A special section deals with the use of gold nanoparticles as antigen carriers in immunisation.

  7. An experimental study on gold precipitation from leach solutions of ...

    African Journals Online (AJOL)

    This paper presents the results of the study dedicated to the determination of the optimum parameters for the electrolytic gold precipitation from thiourea leach solutions. The leaching was carried out using technogenic gold-bearing raw materials (gold-bearing sands) of the Far East of the Russian Federation. The study ...

  8. Crystal growth, structure and phase studies on gold halides

    NARCIS (Netherlands)

    Janssen, Eugenius Maria Wilhelmus Janssen

    1977-01-01

    Only very corrosive substances attack gold, the most noble metal. In this study the reactivity and the phase diagrams of gold with the halogens chlorine, bromine and iodine have been investigated. owing to the noble behaviour of gold, its halides are sensitive to heat; on heating they decompose into

  9. Preg-robbing of Gold by Carbonaceous Materials Encountered in ...

    African Journals Online (AJOL)

    Processing of gold from refractory ores containing carbonaceous materials (CM) poses challenges due to the ability of the CM to preg-rob dissolved gold. Depending on the type and maturity of CM encountered, preg-robbing of aurocyanide ion can lead to reduction in gold recovery ranging from a few percentages to more ...

  10. 76 FR 60355 - Gold Star Mother's and Family's Day, 2011

    Science.gov (United States)

    2011-09-28

    ... Gold Star Mother's and Family's Day, 2011 By the President of the United States of America A... grief their families carry we can never fully know. Gold Star mothers and families know the immeasurable... inspired by their strength and determination. Through heartbreaking loss, our Gold Star families continue...

  11. Increased cellular uptake of peptide-modified PEGylated gold nanoparticles.

    Science.gov (United States)

    He, Bo; Yang, Dan; Qin, Mengmeng; Zhang, Yuan; He, Bing; Dai, Wenbing; Wang, Xueqing; Zhang, Qiang; Zhang, Hua; Yin, Changcheng

    2017-12-09

    Gold nanoparticles are promising drug delivery vehicles for nucleic acids, small molecules, and proteins, allowing various modifications on the particle surface. However, the instability and low bioavailability of gold nanoparticles compromise their clinical application. Here, we functionalized gold nanoparticles with CPP fragments (CALNNPFVYLI, CALRRRRRRRR) through sulfhydryl PEG to increase their stability and bioavailability. The resulting gold nanoparticles were characterized with transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-visible spectrometry and X-ray photoelectron spectroscopy (XPS), and the stability in biological solutions was evaluated. Comparing to PEGylated gold nanoparticles, CPP (CALNNPFVYLI, CALRRRRRRRR)-modified gold nanoparticles showed 46 folds increase in cellular uptake in A549 and B16 cell lines, as evidenced by the inductively coupled plasma atomic emission spectroscopy (ICP-AES). The interactions between gold nanoparticles and liposomes indicated CPP-modified gold nanoparticles bind to cell membrane more effectively than PEGylated gold nanoparticles. Surface plasmon resonance (SPR) was used to measure interactions between nanoparticles and the membrane. TEM and uptake inhibitor experiments indicated that the cellular entry of gold nanoparticles was mediated by clathrin and macropinocytosis. Other energy independent endocytosis pathways were also identified. Our work revealed a new strategy to modify gold nanoparticles with CPP and illustrated the cellular uptake pathway of CPP-modified gold nanoparticles. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Benchmarking Density Functionals for Chemical Bonds of Gold

    DEFF Research Database (Denmark)

    Kepp, Kasper Planeta

    2017-01-01

    Gold plays a major role in nanochemistry, catalysis, and electrochemistry. Accordingly, hundreds of studies apply density functionals to study chemical bonding with gold, yet there is no systematic attempt to assess the accuracy of these methods applied to gold. This paper reports a benchmark aga...

  13. Plasmonic and Magnetically Responsive Gold ShellMagnetic Nanorod Hybrids

    Science.gov (United States)

    2017-10-10

    including bio -targeting/sensing,1,2 structural enhancement/health monitoring,3,4 and energy harvesting/storage.5,6 Typical approaches to achieve...Mirshahghassemi S, Ebner AD, Cai B, Lead JR, Application of high gradient magnetic separation for oil remediation using polymer-coated magnetic

  14. Domestic Terrorism, Official Response and the Politics of Black Gold ...

    African Journals Online (AJOL)

    Modern societies are embroiled with varied levels of conflict. The type and intensity of conflict is often historically determined and the causative factors are also closely tied to the social dynamics of the global community. Many factors tend to account for modern conflict. Apart from having political, economic, and ...

  15. Colloidal Gold--Collagen Protein Core--Shell Nanoconjugate: One-Step Biomimetic Synthesis, Layer-by-Layer Assembled Film, and Controlled Cell Growth.

    Science.gov (United States)

    Xing, Ruirui; Jiao, Tifeng; Yan, Linyin; Ma, Guanghui; Liu, Lei; Dai, Luru; Li, Junbai; Möhwald, Helmuth; Yan, Xuehai

    2015-11-11

    The biogenic synthesis of biomolecule-gold nanoconjugates is of key importance for a broad range of biomedical applications. In this work, a one-step, green, and condition-gentle strategy is presented to synthesize stable colloidal gold-collagen core-shell nanoconjugates in an aqueous solution at room temperature, without use of any reducing agents and stabilizing agents. It is discovered that electrostatic binding between gold ions and collagen proteins and concomitant in situ reduction by hydroxyproline residues are critically responsible for the formation of the core-shell nanoconjugates. The film formed by layer-by-layer assembly of such colloidal gold-collagen nanoconjugates can notably improve the mechanical properties and promote cell adhesion, growth, and differentiation. Thus, the colloidal gold-collagen nanoconjugates synthesized by such a straightforward and clean manner, analogous to a biomineralization pathway, provide new alternatives for developing biologically based hybrid biomaterials toward a range of therapeutic and diagnostic applications.

  16. Surface interactions between gold nanoparticles and biochar

    Science.gov (United States)

    Engineered nanomaterials are directly applied to agricultural soils as a part of pesticide/fertilize formulations and sludge/manure amendments. Yet, no prior reports are available on the extent and reversibility of gold nanoparticles (nAu) retention by soil components including charcoal black carbo...

  17. Bacterial leaching of pyritic gold ores

    International Nuclear Information System (INIS)

    Gagliardi, F.M.; Cashion, J.D.; Brown, J.; Jay, W.H.

    1998-01-01

    Full text: Pyritic ores (pyrite and arsenopyrite) containing gold concentrations in excess of 50g Au/t can be processed to recover the gold by the removal of the sulphur from the ore. This may be achieved by roasting (producing sulphur dioxide emissions), pressure oxidation (expensive and suitable for large high grade deposits), pressure leaching (still currently being developed) or bacterial oxidation. The bacterial oxidation process is a well known process in nature but has only recently come under investigation as a economically viable and relatively clean method of gold recovery from deep low grade sulphidic ores. Samples were obtained from the Wiluna Gold Mine in Western Australia consisting of the original ore, six successive bacterial reactors and the final products. Moessbauer experiments have been performed at room temperature, liquid nitrogen and liquid helium temperatures, and in applied magnetic fields. The main components of the iron phases which were present during the bacterial treatment were pyrite and arsenopyrite which were readily oxidised by the bacteria. Ferric sulfates and ferric arsenates were identified as by-products of the process with a small amount of the oxyhydroxide goethite. These results are in contrast to the similar study of the Fairview Mine in South Africa where principally Fe(II) species were observed

  18. Deposition kinetics of nanocolloidal gold particles

    NARCIS (Netherlands)

    Brouwer, E.A.M.; Kooij, Ernst S.; Hakbijl, Mark; Wormeester, Herbert; Poelsema, Bene

    2005-01-01

    The deposition kinetics of the irreversible adsorption of citrate-stabilized, nanocolloidal gold particles on Si/SiO2 surfaces, derivatized with (aminopropyl)triethoxysilane (APTES), is investigated in situ using single wavelength optical reflectometry. A well-defined flow of colloids towards the

  19. A nanoporous gold membrane for sensing applications

    Directory of Open Access Journals (Sweden)

    Swe Zin Oo

    2016-03-01

    Full Text Available Design and fabrication of three-dimensionally structured, gold membranes containing hexagonally close-packed microcavities with nanopores in the base, are described. Our aim is to create a nanoporous structure with localized enhancement of the fluorescence or Raman scattering at, and in the nanopore when excited with light of approximately 600 nm, with a view to provide sensitive detection of biomolecules. A range of geometries of the nanopore integrated into hexagonally close-packed assemblies of gold micro-cavities was first evaluated theoretically. The optimal size and shape of the nanopore in a single microcavity were then considered to provide the highest localized plasmon enhancement (of fluorescence or Raman scattering at the very center of the nanopore for a bioanalyte traversing through. The optimized design was established to be a 1200 nm diameter cavity of 600 nm depth with a 50 nm square nanopore with rounded corners in the base. A gold 3D-structured membrane containing these sized microcavities with the integrated nanopore was successfully fabricated and ‘proof of concept’ Raman scattering experiments are described. Keywords: Nanopore, Polymer sphere, Gold membrane, Plasmons, Sensing, SERS

  20. Photosynthetic light reactions at the gold interface

    NARCIS (Netherlands)

    Kamran, Muhammad

    2014-01-01

    In the project described in this thesis we studied a simple bio-electronic device for solar energy conversion by surface-assembly of photosynthetic pigment-protein complexes on a bare gold-electrode. Optical excitation of the photosynthetic pigments gives rise to charge separation in the so-called

  1. Substoichiometric neutron activation determination of gold

    International Nuclear Information System (INIS)

    Mitchell, J.W.; Riley, J.E. Jr.; Payne, V.

    1978-01-01

    A highly precise and selective method is described for the determination of traces of gold by substoichiometric extraction from hydrochloric acid with tri-n-octylphosphine sulfide in cyclohexane following thermal neutron activation. Fundamental aspects of the extraction system are discussed and results are reported for the determination of gold in an effluent from a recovery process containing a complexed species of gold and unknown amounts of cyanide, citrate, phosphate, potassium and sodium. Other constituents of the effluent stream include traces of the transition elements Co, Ni, Fe, Cu, Zn, Pb and Sn at concentrations less than 50 ppm. One hour was allowed for the Au 3+ carrier and the 198 Au complexed species in samples and standards to oxidize, exchange, and reach chemical equilibrium. Samples were then equilibrated by shaking with the organic phase for thirty min. The percentage extractions (%E) for the substoichiometric separation of gold from the effluent and from the corresponding comparison standards were monitored. The mean percentage extractions for the substoichiometric separations of carrier from the effluent, and its corresponding standard were 75.3 and 59.3, respectively. These data are estimated to be accurate within +-2.0%. (T.G.)

  2. Uranium and gold in Serra da Jacobina

    International Nuclear Information System (INIS)

    Lemos, J.C.

    1974-01-01

    The study in details of the conglomerates of Serra do Corrego Formation is presented. In the Canavieira Gold Mine we made the radiometric research of the work front, sistematic sampling and gamma-ray of drilled holes. Many ore products from the jig of Canavieira Mine were analysed to determine a representative uranium content

  3. Gold nanoparticles as nanosources of heat

    Science.gov (United States)

    Baffou, Guillaume

    2018-04-01

    Under illumination at their plasmonic resonance wavelength, gold nanoparticles can absorb incident light and turn into efficient nanosources of heat remotely controllable by light. This fundamental scheme is at the basis of an active field of research coined thermoplasmonics and encompasses numerous applications in physics, chemistry and biology at the micro and nano scales. Warning, no authors found for 2018Phot........48.

  4. Absorption Spectra of Gold Nanoparticle Suspensions

    Science.gov (United States)

    Anan'eva, M. V.; Nurmukhametov, D. R.; Zverev, A. S.; Nelyubina, N. V.; Zvekov, A. A.; Russakov, D. M.; Kalenskii, A. V.; Eremenko, A. N.

    2018-02-01

    Three gold nanoparticle suspensions are obtained, and mean radii in distributions - (6.1 ± 0.2), (11.9 ± 0.3), and (17.3 ± 0.7) nm - are determined by the transmission electron microscopy method. The optical absorption spectra of suspensions are obtained and studied. Calculation of spectral dependences of the absorption index of suspensions at values of the gold complex refractive index taken from the literature showed a significant deviation of experimental and calculated data in the region of 450-800 nm. Spectral dependences of the absorption of suspensions are simulated within the framework of the Mie-Drude theory taking into account the interband absorption in the form of an additional term in the imaginary part of the dielectric permittivity of the Gaussian type. It is shown that to quantify the spectral dependences in the region of the plasmon absorption band of nanoparticles, correction of the parameters of the interband absorption is necessary in addition to the increase of the relaxation parameter of the Drude theory. Spectral dependences of the dielectric permittivity of gold in nanodimensional state are refined from the solution of the inverse problem. The results of the present work are important for predicting the special features of operation of photonic devices and optical detonators based on gold nanoparticles.

  5. The golden age: gold nanoparticles for biomedicine†

    Science.gov (United States)

    Dreaden, Erik C.; Alkilany, Alaaldin M.; Huang, Xiaohua; Murphy, Catherine J.; El-Sayed, Mostafa A.

    2018-01-01

    Gold nanoparticles have been used in biomedical applications since their first colloidal syntheses more than three centuries ago. However, over the past two decades, their beautiful colors and unique electronic properties have also attracted tremendous attention due to their historical applications in art and ancient medicine and current applications in enhanced optoelectronics and photovoltaics. In spite of their modest alchemical beginnings, gold nanoparticles exhibit physical properties that are truly different from both small molecules and bulk materials, as well as from other nanoscale particles. Their unique combination of properties is just beginning to be fully realized in range of medical diagnostic and therapeutic applications. This critical review will provide insights into the design, synthesis, functionalization, and applications of these artificial molecules in biomedicine and discuss their tailored interactions with biological systems to achieve improved patient health. Further, we provide a survey of the rapidly expanding body of literature on this topic and argue that gold nanotechnology-enabled biomedicine is not simply an act of ‘gilding the (nanomedicinal) lily’, but that a new ‘Golden Age’ of biomedical nanotechnology is truly upon us. Moving forward, the most challenging nanoscience ahead of us will be to find new chemical and physical methods of functionalizing gold nanoparticles with compounds that can promote efficient binding, clearance, and biocompatibility and to assess their safety to other biological systems and their long-term term effects on human health and reproduction (472 references). PMID:22109657

  6. Gold(III)-Catalyzed Hydration of Phenylacetylene

    Science.gov (United States)

    Leslie, J. Michelle; Tzeel, Benjamin A.

    2016-01-01

    A guided inquiry-based experiment exploring the regioselectivity of the hydration of phenylacetylene is described. The experiment uses an acidic gold(III) catalyst in a benign methanol/water solvent system to introduce students to alkyne chemistry and key principles of green chemistry. The experiment can be easily completed in approximately 2 h,…

  7. High-energy band structure of gold

    DEFF Research Database (Denmark)

    Christensen, N. Egede

    1976-01-01

    The band structure of gold for energies far above the Fermi level has been calculated using the relativistic augmented-plane-wave method. The calculated f-band edge (Γ6-) lies 15.6 eV above the Fermi level is agreement with recent photoemission work. The band model is applied to interpret...

  8. Poly-thiosemicarbazide membrane for gold recovery

    KAUST Repository

    Villalobos, Luis Francisco

    2014-11-01

    A novel polymeric membrane adsorber with a high density of adsorption sites that can selectively capture Au(III) ions, is proposed as an efficient alternative to recover gold from dilute solutions. Poly-thiosemicarbazide (PTSC), a polymer that contains one chelate site per monomeric unit, was used to fabricate the membranes. This polymer can be easily processed into membranes by a phase inversion technique, resulting in an open and interconnected porous structure suitable for high flux liquid phase applications. This method overcomes the usual low capacities of membrane adsorbents by selecting a starting material that contains the adsorption sites within it, therefore avoiding the necessity to add an external agent into the membrane matrix. The resulting mechanically stable PTSC membranes can operate in a pressure driven permeation process, which eliminates the diffusion limitations commonly present in packed column adsorption processes. This process can selectively recover 97% of the gold present in a solution containing a 9-fold higher copper concentration, while operating at a flux as high as 1868 L/m2 h. The maximum gold uptake measured without sacrificing the mechanical stability of the membrane was 5.4 mmol Au/g. Furthermore the gold can be easily eluted from the membrane with a 0.1 M thiourea solution and the membrane can be reused for at least three cycles without any decrease in its performance. Finally, the ability of this membrane for recovering metals from real-life samples, like seawater and tap water, was tested with promising results.

  9. Opposition to gold mining at Bergama, Turkey

    NARCIS (Netherlands)

    M. Arsel (Murat)

    2012-01-01

    textabstractIntroduction For much of the 1990s, the tourist town of Bergama was the epicentre of Turkey's most effective and visible environmental social movement against a multinational mining corporation aiming to establish the first modern gold mine in the country. Bringing

  10. Biological synthesis and characterization of intracellular gold ...

    Indian Academy of Sciences (India)

    In the present study, Aspergillus fumigatus was used for the intracellular synthesis of gold nanoparticles. Stable nanoparticles were produced when an aqueous solution of chloroauric acid (HAuCl4) was reduced by A. fumigatus biomass as the reducing agent. Production of nanoparticles was confirmed by the colour ...

  11. Benchmarking Exercises To Validate The Updated ELLWF GoldSim Slit Trench Model

    International Nuclear Information System (INIS)

    Taylor, G. A.; Hiergesell, R. A.

    2013-01-01

    The Savannah River National Laboratory (SRNL) results of the 2008 Performance Assessment (PA) (WSRC, 2008) sensitivity/uncertainty analyses conducted for the trenches located in the EArea LowLevel Waste Facility (ELLWF) were subject to review by the United States Department of Energy (U.S. DOE) Low-Level Waste Disposal Facility Federal Review Group (LFRG) (LFRG, 2008). LFRG comments were generally approving of the use of probabilistic modeling in GoldSim to support the quantitative sensitivity analysis. A recommendation was made, however, that the probabilistic models be revised and updated to bolster their defensibility. SRS committed to addressing those comments and, in response, contracted with Neptune and Company to rewrite the three GoldSim models. The initial portion of this work, development of Slit Trench (ST), Engineered Trench (ET) and Components-in-Grout (CIG) trench GoldSim models, has been completed. The work described in this report utilizes these revised models to test and evaluate the results against the 2008 PORFLOW model results. This was accomplished by first performing a rigorous code-to-code comparison of the PORFLOW and GoldSim codes and then performing a deterministic comparison of the two-dimensional (2D) unsaturated zone and three-dimensional (3D) saturated zone PORFLOW Slit Trench models against results from the one-dimensional (1D) GoldSim Slit Trench model. The results of the code-to-code comparison indicate that when the mechanisms of radioactive decay, partitioning of contaminants between solid and fluid, implementation of specific boundary conditions and the imposition of solubility controls were all tested using identical flow fields, that GoldSim and PORFLOW produce nearly identical results. It is also noted that GoldSim has an advantage over PORFLOW in that it simulates all radionuclides simultaneously - thus avoiding a potential problem as demonstrated in the Case Study (see Section 2.6). Hence, it was concluded that the follow

  12. Benchmarking Exercises To Validate The Updated ELLWF GoldSim Slit Trench Model

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, G. A.; Hiergesell, R. A.

    2013-11-12

    The Savannah River National Laboratory (SRNL) results of the 2008 Performance Assessment (PA) (WSRC, 2008) sensitivity/uncertainty analyses conducted for the trenches located in the EArea LowLevel Waste Facility (ELLWF) were subject to review by the United States Department of Energy (U.S. DOE) Low-Level Waste Disposal Facility Federal Review Group (LFRG) (LFRG, 2008). LFRG comments were generally approving of the use of probabilistic modeling in GoldSim to support the quantitative sensitivity analysis. A recommendation was made, however, that the probabilistic models be revised and updated to bolster their defensibility. SRS committed to addressing those comments and, in response, contracted with Neptune and Company to rewrite the three GoldSim models. The initial portion of this work, development of Slit Trench (ST), Engineered Trench (ET) and Components-in-Grout (CIG) trench GoldSim models, has been completed. The work described in this report utilizes these revised models to test and evaluate the results against the 2008 PORFLOW model results. This was accomplished by first performing a rigorous code-to-code comparison of the PORFLOW and GoldSim codes and then performing a deterministic comparison of the two-dimensional (2D) unsaturated zone and three-dimensional (3D) saturated zone PORFLOW Slit Trench models against results from the one-dimensional (1D) GoldSim Slit Trench model. The results of the code-to-code comparison indicate that when the mechanisms of radioactive decay, partitioning of contaminants between solid and fluid, implementation of specific boundary conditions and the imposition of solubility controls were all tested using identical flow fields, that GoldSim and PORFLOW produce nearly identical results. It is also noted that GoldSim has an advantage over PORFLOW in that it simulates all radionuclides simultaneously - thus avoiding a potential problem as demonstrated in the Case Study (see Section 2.6). Hence, it was concluded that the follow

  13. Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods.

    Science.gov (United States)

    Chakraborty, Amrita; Fernandez, Ann Candice; Som, Anirban; Mondal, Biswajit; Natarajan, Ganapati; Paramasivam, Ganesan; Lahtinen, Tanja; Häkkinen, Hannu; Nonappa, Nonappa; Pradeep, Thalappil

    2018-04-01

    We present the self-assembled structures of atomically precise, ligand-protected noble metal nanoclusters leading to encapsulation of plasmonic gold nanorods (GNRs). Unlike highly sophisticated DNA nanotechnology, our approach demonstrates a strategically simple hydrogen bonding-directed self-assembly of nanoclusters leading to octahedral nanocrystals encapsulating GNRs. Specifically, we use the p-mercaptobenzoic acid (pMBA) protected atomically precise nanocluster, Na4[Ag44(pMBA)30] and pMBA functionalized GNRs. High resolution transmission and scanning transmission electron tomographic reconstructions suggest that the geometry of the GNR surface is responsible for directing the assembly of silver nanoclusters via H-bonding leading to octahedral symmetry. Further, use of water dispersible gold nanoclusters, Au~250(pMBA)n and Au102(pMBA)44 also formed layered shells encapsulating GNRs. Such cluster assemblies on colloidal particles present a new category of precision hybrids with diverse possibilities. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Dielectrophoresis of gold nanoparticles conjugated to DNA origami structures

    Directory of Open Access Journals (Sweden)

    Anja Henning-Knechtel

    2016-07-01

    Full Text Available DNA nanostructures are promising construction materials to bridge the gap between self-assembly of functional molecules and conventional top-down fabrication methods in nanotechnology. Their positioning onto specific locations of a microstructured substrate is an important task towards this aim. Here we study manipulation and positioning of pristine and of gold nanoparticle-conjugated tubular DNA origami structures using ac dielectrophoresis. The dielectrophoretic behavior was investigated employing fluorescence microscopy. For the pristine origami, a significant dielectrophoretic response was found to take place in the megahertz range, whereas, due to the higher polarizability of the metallic nanoparticles, the nanoparticle/DNA hybrid structures required a lower electrical field strength and frequency for a comparable trapping at the edges of the electrode structure. The nanoparticle conjugation additionally resulted in a remarkable alteration of the DNA structure arrangement. The growth of linear, chain-like structures in between electrodes at applied frequencies in the megahertz range was observed. The long-range chain formation is caused by a local, gold nanoparticle-induced field concentration along the DNA nanostructures, which in turn, creates dielectrophoretic forces that enable the observed self-alignment of the hybrid structures.

  15. Gold Nanoparticles in Photonic Crystals Applications: A Review.

    Science.gov (United States)

    Venditti, Iole

    2017-01-24

    This review concerns the recently emerged class of composite colloidal photonic crystals (PCs), in which gold nanoparticles (AuNPs) are included in the photonic structure. The use of composites allows achieving a strong modification of the optical properties of photonic crystals by involving the light scattering with electronic excitations of the gold component (surface plasmon resonance, SPR) realizing a combination of absorption bands with the diffraction resonances occurring in the body of the photonic crystals. Considering different preparations of composite plasmonic-photonic crystals, based on 3D-PCs in presence of AuNPs, different resonance phenomena determine the optical response of hybrid crystals leading to a broadly tunable functionality of these crystals. Several chemical methods for fabrication of opals and inverse opals are presented together with preparations of composites plasmonic-photonic crystals: the influence of SPR on the optical properties of PCs is also discussed. Main applications of this new class of composite materials are illustrated with the aim to offer the reader an overview of the recent advances in this field.

  16. Gold Nanoparticles in Photonic Crystals Applications: A Review

    Directory of Open Access Journals (Sweden)

    Iole Venditti

    2017-01-01

    Full Text Available This review concerns the recently emerged class of composite colloidal photonic crystals (PCs, in which gold nanoparticles (AuNPs are included in the photonic structure. The use of composites allows achieving a strong modification of the optical properties of photonic crystals by involving the light scattering with electronic excitations of the gold component (surface plasmon resonance, SPR realizing a combination of absorption bands with the diffraction resonances occurring in the body of the photonic crystals. Considering different preparations of composite plasmonic-photonic crystals, based on 3D-PCs in presence of AuNPs, different resonance phenomena determine the optical response of hybrid crystals leading to a broadly tunable functionality of these crystals. Several chemical methods for fabrication of opals and inverse opals are presented together with preparations of composites plasmonic-photonic crystals: the influence of SPR on the optical properties of PCs is also discussed. Main applications of this new class of composite materials are illustrated with the aim to offer the reader an overview of the recent advances in this field.

  17. Gold nanoparticles enlighten the future of cancer theranostics

    Directory of Open Access Journals (Sweden)

    Guo J

    2017-08-01

    Full Text Available Jianfeng Guo,1 Kamil Rahme,2–4 Yan He,1 Lin-Lin Li,5 Justin D Holmes,3,4 Caitriona M O’Driscoll6 1School of Pharmaceutical Sciences, Jilin University, Changchun, China; 2Department of Sciences, Faculty of Natural and Applied Science, Notre Dame University (Louaize, Zouk Mosbeh, Lebanon; 3Department of Chemistry, Tyndall National Institute, University College Cork, Cork, 4AMBER@CRANN, Trinity College Dublin, Dublin, Ireland; 5The First Hospital of Jilin University, Changchun, China; 6Pharmacodelivery Group, School of Pharmacy, University College Cork, Cork, Ireland Abstract: Development of multifunctional nanomaterials, one of the most interesting and advanced research areas in the field of nanotechnology, is anticipated to revolutionize cancer diagnosis and treatment. Gold nanoparticles (AuNPs are now being widely utilized in bioimaging and phototherapy due to their tunable and highly sensitive optical and electronic properties (the surface plasmon resonance. As a new concept, termed “theranostics,” multifunctional AuNPs may contain diagnostic and therapeutic functions that can be integrated into one system, thereby simultaneously facilitating diagnosis and therapy and monitoring therapeutic responses. In this review, the important properties of AuNPs relevant to diagnostic and phototherapeutic applications such as structure, shape, optics, and surface chemistry are described. Barriers for translational development of theranostic AuNPs and recent advances in the application of AuNPs for cancer diagnosis, photothermal, and photodynamic therapy are discussed. Keywords: multifunctional gold nanoparticles, cancer bioimaging, cancer photothermal and photodynamic therapy

  18. Gold Nanoparticles Assembly on Silicon and Gold Surfaces: Mechanism, Stability and Efficiency in Diclofenac Biosensing

    OpenAIRE

    Ben Haddada , Maroua; Hübner , Maria; Casale , Sandra; Knopp , Dietmar; Niessner , Reinhard; Salmain , Michele; Boujday , Souhir

    2016-01-01

    International audience; We investigated the assembly of Gold nanoparticles (AuNPs) on Gold and Silicon sensors with two final objectives: (i) understanding the factors governing the interaction and (ii) building up a nanostructured piezoelectric immunosensor for diclofenac, a small-sized pharmaceutical pollutant. Different surface chemistries were devised to achieve AuNPs assembly on planar substrates. These surface chemistries included amines to immobilize AuNPs via electrostatic interaction...

  19. Direct formation of gold nanorods on surfaces using polymer-immobilised gold seeds

    Directory of Open Access Journals (Sweden)

    Majid K. Abyaneh

    2016-06-01

    Full Text Available Herein, we present the formation of gold nanorods (GNRs on novel gold–poly(methyl methacrylate (Au–PMMA nanocomposite substrates with unprecedented growth control through the polymer molecular weight (Mw and gold-salt-to-polymer weight ratio. For the first time, GNRs have been produced by seed-mediated direct growth on surfaces that were pre-coated with polymer-immobilised gold seeds. A Au–PMMA nanocomposite formed by UV photoreduction has been used as the gold seed. The influence of polymer Mw and gold concentration on the formation of GNRs has been investigated and discussed. The polymer nanocomposite formed with a lower Mw PMMA and 20 wt % gold salt provides a suitable medium for growing well-dispersed GNRs. In this sample, the average dimension of produced GNRs is 200 nm in length with aspect ratios up to 10 and a distribution of GNRs to nanoparticles of nearly 22%. Suitable characterization techniques such as AFM and SEM have been used to support concept of the proposed growth method.

  20. Occurrences of dendritic gold at the McLaughlin Mine hot-spring gold deposit

    Science.gov (United States)

    Sherlock, R. L.; Lehrman, N. J.

    1995-06-01

    Two styles of gold dendrites are variably developed at the McLaughlin Mine. The most abundant occurrence is hosted by amber-coloured hydrocarbon-rich opal. Silica likely precipitated from a boiling hydrothermal fluid and complexed with immiscible hydrocarbons forming an amorphous hydrocarbon-silica phase. This phase likely scavenged particulate gold by electrostatic attraction to the hydrocarbon-silica phase. The dendritic nature of the gold is secondary and is the result of dewatering of the amorphous hydrocarbon-silica phase and crystallization of gold into syneresis fractures. The second style of dendritic gold is hosted within vein swarms that focused large volumes of fluid flow. The dendrites occur along with hydrocarbon-rich silica at the upper contact of the vein margins which isolated the dendrites allowing sufficient time for them to grow. In a manner similar to the amber-coloured opal, the dendrites may have formed by scavenging particulate gold by electrostatic attraction to the hydrocarbon-silica phase.

  1. Analysis of gold(I/III)-complexes by HPLC-ICP-MS demonstrates gold(III) stability in surface waters.

    Science.gov (United States)

    Ta, Christine; Reith, Frank; Brugger, Joël; Pring, Allan; Lenehan, Claire E

    2014-05-20

    Understanding the form in which gold is transported in surface- and groundwaters underpins our understanding of gold dispersion and (bio)geochemical cycling. Yet, to date, there are no direct techniques capable of identifying the oxidation state and complexation of gold in natural waters. We present a reversed phase ion-pairing HPLC-ICP-MS method for the separation and determination of aqueous gold(III)-chloro-hydroxyl, gold(III)-bromo-hydroxyl, gold(I)-thiosulfate, and gold(I)-cyanide complexes. Detection limits for the gold species range from 0.05 to 0.30 μg L(-1). The [Au(CN)2](-) gold cyanide complex was detected in five of six waters from tailings and adjacent monitoring bores of working gold mines. Contrary to thermodynamic predictions, evidence was obtained for the existence of Au(III)-complexes in circumneutral, hypersaline waters of a natural lake overlying a gold deposit in Western Australia. This first direct evidence for the existence and stability of Au(III)-complexes in natural surface waters suggests that Au(III)-complexes may be important for the transport and biogeochemical cycling of gold in surface environments. Overall, these results show that near-μg L(-1) enrichments of Au in environmental waters result from metastable ligands (e.g., CN(-)) as well as kinetically controlled redox processes leading to the stability of highly soluble Au(III)-complexes.

  2. Mercury Detection with Gold Nanoparticles: Investigating Fundamental Phenomena and Expanding Applications

    Science.gov (United States)

    Crosby, Jeffrey Scott

    Mercury is a pollutant of grave concern with well documented neurological and developmental health impacts. Better sensing methodology would improve detection and control of mercury and thus reduce its health burden. Gold nanoparticles provide a sensing medium with potential advantages in sensitivity, selectivity, robustness, and cost over established techniques. Mercury readily adsorbs onto the surface of the gold changing the localized surface plasmon resonance which is measured as a shift in the peak optical absorbance wavelength. This shift is dependent on the mercury concentration and predictable with classical electromagnetism. This work investigates some of the fundamental relationships driving sensor response. The effects of mass transfer and surface kinetics on mercury/gold nanoparticle adsorption are determined with analytical models and experimental results based on impinging flow geometry. To decouple mass transfer and surface kinetics adsorption, electrical analogy models are constructed and fit to the experimental data. The models can account for variations in flow conditions and surface coatings on the nanoparticles. These models are generalizable to other systems. Results from these fundamental investigations are used to improve and extend sensor performance. The time response or collection efficiency is optimized depending on system requirements. Using the knowledge gained, the applicability of gold nanoparticle mercury sensors is extended to a fiber optic based system and aqueous detection. Nanorods deposited on the surface of a fiber optic cable have a linear response with concentration and are able to detect mercury down to 1.0 mug/m3. The modification of an established oxidation/reduction scheme for use with the sensor allows for the detection of ionic and organic mercury from water samples which ordinarily would not be reactive with gold nanoparticles. The aqueous sensor was able to detect mercury below the EPA's drinking water limit.

  3. Selective detection and recovery of gold at tannin-immobilized non-conducting electrode

    Energy Technology Data Exchange (ETDEWEB)

    Banu, Khaleda, E-mail: kbanu@ucla.edu [Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095 (United States); Venture Business Laboratory, Center for Advanced Science and Innovation, Osaka University, Suita, Osaka 565-0871 (Japan); Shimura, Takayoshi [Venture Business Laboratory, Center for Advanced Science and Innovation, Osaka University, Suita, Osaka 565-0871 (Japan); Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University (Japan); Sadeghi, Saman, E-mail: samsadeghi@mednet.ucla.edu [Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095 (United States)

    2015-01-01

    Highlights: • Selective detection of gold at non-conducting (NC) polymer modified electrode. • Mimosa tannin oxidized on glassy carbon electrode surface as NC polymeric film. • Permselective diffusion and mediated electron transfer at NC electrode surface. • Chemical recovery of gold is due to the reducing ability of the NC polymeric film. • Adsorption capacity of Au(III) on carbon fiber was 29 ± 1.45 mg g{sup −1} at 60 °C. - Abstract: A tannin-immobilized glassy carbon electrode (TIGC) was prepared via electrochemical oxidation of the naturally occurring polyphenolic mimosa tannin, which generated a non-conducting polymeric film (NCPF) on the electrode surface. The fouling of the electrode surface by the electropolymerized film was evaluated by monitoring the electrode response of ferricyanide ions as a redox marker. The NCPF was permselective to HAuCl{sub 4}, and the electrochemical reduction of HAuCl{sub 4} to metallic gold at the TIGC electrode was evaluated by recording the reduction current during cyclic voltammetry measurement. In the mixed electrolyte containing HAuCl{sub 4} along with FeCl{sub 3} and/or CuCl{sub 2}, the NCPF remained selective toward the electrochemical reduction of HAuCl{sub 4} into the metallic state. The chemical reduction of HAuCl{sub 4} into metallic gold was also observed when the NCPF was inserted into an acidic gold solution overnight. The adsorption capacity of Au(III) on tannin-immobilized carbon fiber was 29 ± 1.45 mg g{sup −1} at 60 °C. In the presence of excess Cu(II) and Fe(III), tannin-immobilized NCPF proved to be an excellent candidate for the selective detection and recovery of gold through both electrochemical and chemical processes.

  4. Selective detection and recovery of gold at tannin-immobilized non-conducting electrode

    International Nuclear Information System (INIS)

    Banu, Khaleda; Shimura, Takayoshi; Sadeghi, Saman

    2015-01-01

    Highlights: • Selective detection of gold at non-conducting (NC) polymer modified electrode. • Mimosa tannin oxidized on glassy carbon electrode surface as NC polymeric film. • Permselective diffusion and mediated electron transfer at NC electrode surface. • Chemical recovery of gold is due to the reducing ability of the NC polymeric film. • Adsorption capacity of Au(III) on carbon fiber was 29 ± 1.45 mg g −1 at 60 °C. - Abstract: A tannin-immobilized glassy carbon electrode (TIGC) was prepared via electrochemical oxidation of the naturally occurring polyphenolic mimosa tannin, which generated a non-conducting polymeric film (NCPF) on the electrode surface. The fouling of the electrode surface by the electropolymerized film was evaluated by monitoring the electrode response of ferricyanide ions as a redox marker. The NCPF was permselective to HAuCl 4 , and the electrochemical reduction of HAuCl 4 to metallic gold at the TIGC electrode was evaluated by recording the reduction current during cyclic voltammetry measurement. In the mixed electrolyte containing HAuCl 4 along with FeCl 3 and/or CuCl 2 , the NCPF remained selective toward the electrochemical reduction of HAuCl 4 into the metallic state. The chemical reduction of HAuCl 4 into metallic gold was also observed when the NCPF was inserted into an acidic gold solution overnight. The adsorption capacity of Au(III) on tannin-immobilized carbon fiber was 29 ± 1.45 mg g −1 at 60 °C. In the presence of excess Cu(II) and Fe(III), tannin-immobilized NCPF proved to be an excellent candidate for the selective detection and recovery of gold through both electrochemical and chemical processes

  5. Geochemical Characteristics of Metamorphic Rock-Hosted Gold Deposit At Onzon-Kanbani Area, Central Myanmar

    Directory of Open Access Journals (Sweden)

    Aung Tay Zar

    2017-09-01

    Full Text Available Gold and associated base metal mineralization of Onzon-Kabani area located in the western border of generally N-S trending Mogoke Metamorphic Belt where well-known Sagaing fault is served as a western boundary of this area. In this research area, many artisanal and small-scale gold mines were noted in last three decades. Gold mineralization is hosted in marble and gneiss unit of research area but most common in marble unit. Variety of igneous intrusions are also observed in research area. Mineralizations are observed as fissure filling veins as well as lesser amount of disseminated nature in marble unit. Mineralogically, gold are associated with other base metal such as pyrite, galena, sphalerite, chalcopyrite, marcasite and arsenopyrite. Hydrothermal alteration halos are developed in peripheral of hydrothermal conduits or mineralization veins from proximal to distal such as 1 silicic, 2 sericite-illite, and 3 propylitic alteration.  Most of hydrothermal minerals from each altered zones showed that near neutral condition of pH (e.g. adularia, calcite, illite, sericite and chlorite. Alternatively, hydrothermal alteration zones that show with ore minerals such as native gold, electrum, sphalerite, galena, chalcopyrite, arsenopyrite and marcasite which mostly observed in silicic alteration zone. Typical boiling characters of vein textures and fluid inclusion petrography are observed in hydrothermal system of research area. Boiling, cooling and mixing are possiblily responsible for gold deposition in hydrothermal system. In this paper, authors are documented to clarify the type of mineralization based on hydrothermal alterations, ore and gangue mineral assemblages and fluid inclusion study. All of these data can describe and play an important role for both with respect to understanding deposit genesis and in mineral exploration.

  6. Low-cost mercury (II) ion sensor by biosynthesized gold nanoparticles (AuNPs)

    Science.gov (United States)

    Guerrero, Jet G.; Candano, Gabrielle Jackie; Mendoza, Aileen Nicole; Paderanga, Marciella; Cardino, Krenz John; Locsin, Alessandro; Bibon, Cherilou

    2017-11-01

    Biosynthesis of gold nanoparticles has attracted the curiosity of scientists over the past few decades. Nanoparticles have been proven to exhibit enhanced properties and offer a variety of applications in different fields of study. Utilizing nanoparticles instead of bulky equipment and noxious chemicals has become more convenient; reagents needed for synthesis have been proven to be benign (mostly aqueous solutions) and are cost-effective. In this study, gold nanoparticles were biosynthesized using guyabano (Annonamuricata) peel samples as the source of reducing agents. The optimum concentration ratio of gold chloride to guyabano extract was determined to be 1:7. Characterization studies were accomplished using UV Vis Spectroscopy, Fourier Transform Electron Microscopy (FTIR) and Scanning Electron Microscopy (SEM). Spectroscopic maximum absorbance was found to be at 532 nm thereby confirming the presence of gold nanoparticles. Hydroxyl (O-H stretching), carbonyl (C=O stretching), and amide (N-H stretching) functional groups shown in the FTIR spectra are present on possible reducing agents such as phenols, alkaloids, and saponins found in the plant extract. SEM images revealed spherical shaped nanoparticles with mean diameter of 23.18 nm. It was observed that the bio-synthesized AuNPs were selective to mercury ions through uniform color change from wine red to yellow. A novel smartphone-based mercury (II) ions assay was developed using the gold nanoparticles. A calibration curve correlated the analytical response (Red intensity) to the concentrations of Hg 2+ ions. Around 94% of the variations in the intensity is accounted for by the variations in the concentration of mercury (II) ions suggesting a good linear relationship between the two variables. A relative standard deviation (RSD) of less than 1% was achieved at all individual points. The metal sensor displayed a sensitivity of 0.039 R.I./ppm with an LOD of 93.79 ppm. Thus, the bio-fabricated gold nanoparticles

  7. Induction of Localized Hyperthermia by Millisecond Laser Pulses in the Presence of Gold-Gold Sulphide Nanoparticles in a Phantom

    Directory of Open Access Journals (Sweden)

    Zahra Shahamat

    2015-05-01

    Full Text Available Introduction Application of near-infrared absorbing nanostructures can induce hyperthermia, in addition to providing more efficient  photothermal effects. Gold-gold sulfide (GGS is considered as one of these nanostructures. This study was performed on a tissue-equivalent optical-thermal phantom to determine the temperature profile in the presence and absence of GGS and millisecond pulses of a near-infrared laser. Moreover, the feasibility of hyperthermia induction was investigated in a simulated tumor. Materials and Methods A tumor with its surrounding tissues was simulated in a phantom made of Agarose and Intralipid. The tumor was irradiated by 30 laser pulses with durations of 30, 100, and 400 ms and fluences of 40 and 60 J/cm2. Temperature variations in the phantom with and without GGS were recorded, using fast-response sensors of a digital thermometer, placed at different distances from the central axis at three depths. The temperature rise was recorded by varying duration and fluence of the laser pulses. Results The rise in temperature was recorded by increasing laser fluence and number of pulses for three durations. The temperature profile was obtained at each depth. The presence of GGS resulted in a significant increase in temperature in all cases (P

  8. Ultrasensitive electrochemiluminescent immunoassay for morphine using a gold electrode modified with CdS quantum dots, polyamidoamine, and gold nanoparticles

    International Nuclear Information System (INIS)

    Fei, Wenjuan; Chen, Feifei; Sun, Li; Li, Qianhua; Wu, Ying; Yang, Jianping

    2014-01-01

    We report on a novel electrochemiluminescent (ECL) immunoassay for the ultrasensitive determination of morphine by making use of a gold electrode which was modified with a nanocomposite film containing self-assembled polyamidoamine (PAMAM) CdS quantum dots and electrodeposited gold nanoparticles (Au-NPs). The highly uniform and well-dispersed quantum dots were capped with PAMAM dendrimers. Due to the synergistic effect of the modified quantum dots and the electrodeposited Au-NPs, the ECL response is dramatically enhanced. Under optimal experimental conditions, the immunoreaction between morphine and anti-morphine antibody resulted in a decrease of the ECL signal because of steric hindrance. The calibration plot is linear in the morphine concentration range from 0.2 to 180 ng•mL −1 , with a detection limit as low as 67 pg•mL −1 . The sensor was successfully applied to the determination of morphine in blood plasma. This kind of assay is expected to pave new avenues in label-free drug assays. (author)

  9. Morphology dependent electrical transport behavior in gold nanostructures

    International Nuclear Information System (INIS)

    Alkhatib, A.; Souier, T.; Chiesa, M.

    2011-01-01

    The mechanism of electron transport in ultra-thin gold films is investigated and its dependence on the gold islands size is reported. For gold films of thickness below 38 nm, the electrical transport occurs by tunneling within electrically discontinuous islands of gold. Simmons model for metal-insulator-metal junction describes the non-ohmic experimental current-voltage curves obtained by means of conductive atomic force microscopy. Field emission is the predominant transport for thicknesses below 23 nm while direct tunneling occurs in thicker films. The transition between the two regimes is controlled by the gold islands size and their inter-distance.

  10. The activation analysis of gold in small refractory pebbles

    International Nuclear Information System (INIS)

    Bibby, D.M.; Chaix, R.P.

    1975-08-01

    The gold content of a suite of small pebbles, residual to the milling and leach of a gold bearing ore, has been investigated by means of neutron activation analysis (NAA). An NAA technique presenting a sensitivity of 0.02μgm gold, was used as being appropriate to the samples under investigation. An alternative NAA technique developed with the same sample suite showed a sensitivity of the order of 10 -4 to 10 -5 μgm gold. The NAA techniques developed, are appropriate to the determination of gold in small samples of ore not normally amenable to milling and/or dissolution

  11. An eco-friendly method of synthesizing gold nanoparticles using an otherwise worthless weed pistia (Pistia stratiotes L.).

    Science.gov (United States)

    Anuradha, J; Abbasi, Tasneem; Abbasi, S A

    2015-09-01

    A biomimetic method of gold nanoparticles synthesis utilizing the highly invasive aquatic weed pistia (Pistia stratiotes) is presented. In an attempt to utilize the entire plant, the efficacy of the extracts of all its parts - aerial and submerged - was explored with different proportions of gold (III) solution in generating gold nanoparticles (GNPs). The progress of the synthesis, which occurred at ambient temperature and pressure and commenced soon after mixing the pistia extracts and gold (III) solutions, was tracked using UV-visible spectrophotometry. The electron micrographs of the synthesized GNPs revealed that, depending on the metal-extract concentrations used in the synthesis, GNPs of either monodispersed spherical shape were formed or there was anisotropy resulting in a mixture of triangular, hexagonal, pentagonal, and truncated triangular shaped GNPs. This phenomenon was witnessed with the extracts of aerial parts as well as submerged parts of pistia. The presence of gold atoms in the nanoparticles was confirmed from the EDAX and X-ray diffraction studies. The FT-IR spectral study indicated that the primary and secondary amines associated with the polypeptide biomolecules could have been responsible for the reduction of the gold (III) ions to GNPs and their subsequent stabilization.

  12. Cyto- and genotoxicity assessment of Gold nanoparticles obtained by laser ablation in A549 lung adenocarcinoma cells

    Science.gov (United States)

    Di Bucchianico, Sebastiano; Migliore, Lucia; Marsili, Paolo; Vergari, Chiara; Giammanco, Francesco; Giorgetti, Emilia

    2015-05-01

    Gold nanoparticles have attracted enormous interest in biomedical applications, based on their unique optical properties. However, their toxicity on human tissues is still an open issue. Beyond the potential intrinsic toxicity of nanostructured gold, a non-negligible contribution of stabilizers or reaction by-products related to current wet chemical synthesis procedures can be expected. Aimed at isolating gold contribution from that of any other contaminant, we produced colloidal suspensions of Gold nanoparticles having average size exposure to NPs, namely adenocarcinoma epithelial A549 cells. Gold nanoparticles prepared in water showed no particular signs of cytotoxicity, cytostasis, and/or genotoxicity as assessed by MTT colorimetric viability test and Cytokinesis-block micronucleus cytome assay up to concentrations of the order of 5 μg/mL. In contrast, Gold nanoparticles produced in pure acetone and then transferred into deionized water showed impaired cell viability, apoptosis responses, micronuclei, and dicentric chromosomes induction as well as nuclear budding, as a function of the amount of surface contaminants like amorphous carbon and enolate ions.

  13. The in vitro formation of placer gold by bacteria

    Science.gov (United States)

    Southam, Gordon; Beveridge, Terrance J.

    1994-10-01

    A laboratory simulation was developed to provide mechanistic information about placer (nugget) gold development in the natural environment. To initiate the simulation, ionic gold was immobilized to a high capacity by Bacillus subtilis 168 (116.2 μg/mg dry weight bacteria) as fine-grained intracellular colloids (5-50 nm). During the low-temperature diagenesis experiment (60°C), the release of organics due to bacterial autolysis coincided with the in vitro formation of hexagonal-octahedral gold crystals (20 μm). This octahedral gold was observed to aggregate, forming fine-grained placer gold (50 μm). In addition to achieving a fundamental understanding into secondary gold deposition, a significant economic benefit could be realized by employing this environmentally safe procedure to concentrate widely dispersed gold in placer deposits to facilitate mining by conventional methodologies.

  14. Use of coal-oil agglomerates for particulate gold recovery

    Energy Technology Data Exchange (ETDEWEB)

    Calvez, J.P.S.; Kim, M.J.; Wong, P.L.M.; Tran, T. [University of New South Wales, Sydney, NSW (Australia). School of Chemical Engineering and Industrial Chemistry

    1998-09-01

    The underlying principles by which gold is recovered by coal-oil agglomerates was investigated. The effects of various parameters such as oil:coal ratios, agglomerate:ore ratios, pH and coal particle size on gold recovery were evaluated using synthetic gold bearing samples, bituminous coal, and diesel oil and kerosene. The effects of sulfides on gold recovery and the depth of gold particle penetration within the agglomerates were also investigated. Results showed that gold recovery was increased by increasing agglomerate:ore ratio, decreasing oil:coal ratio and decreasing coal particle size. There was no significant difference in gold recoveries at pH range of 4-12 and at up to 5% sulfides in the feed.

  15. The use of gold nanoparticles to enhance radiotherapy in mice

    International Nuclear Information System (INIS)

    Hainfeld, James F; Slatkin, Daniel N; Smilowitz, Henry M

    2004-01-01

    Mice bearing subcutaneous EMT-6 mammary carcinomas received a single intravenous injection of 1.9 nm diameter gold particles (up to 2.7 g Au/kg body weight), which elevated concentrations of gold to 7 mg Au/g in tumours. Tumour-to-normal-tissue gold concentration ratios remained ∼8:1 during several minutes of 250 kVp x-ray therapy. One-year survival was 86% versus 20% with x-rays alone and 0% with gold alone. The increase in tumours safely ablated was dependent on the amount of gold injected. The gold nanoparticles were apparently non-toxic to mice and were largely cleared from the body through the kidneys. This novel use of small gold nanoparticles permitted achievement of the high metal content in tumours necessary for significant high-Z radioenhancement. (note)

  16. Preparation of gold nanoparticles by arc discharge in water

    International Nuclear Information System (INIS)

    Lung, Jen-Kuang; Huang, Jen-Chuen; Tien, Der-Chi; Liao, Chih-Yu; Tseng, Kuo-Hsiung; Tsung, Tsing-Tshin; Kao, Wen-Shiow; Tsai, Teh-Hua; Jwo, Ching-Song; Lin, Hong-Ming; Stobinski, Leszek

    2007-01-01

    Gold nanoparticles have been attracting attention due to their extensive application in chemistry, physics, material science, electronics, catalysis and bionanotechnology. Synthesis of gold nanoparticles often involves toxic and expensive physical-chemistry methods. Preparation of gold nanoparticles by arc discharge in water is proposed for the first time. Fabrication of gold nanostructures in deionized water has been successfully established. The evidence of gold particles' light absorbance reveals a unique surface plasmon resonance for Au nanoparticles suspended in deionized water. Gold nanostructures uniformly dispersed in water, their UV-Vis absorption and crystalline size are shown. Our experimental results demonstrate that fabrication of gold nanoparticles by arc discharge in water is an alternative, cheap, effective and environmentally friendly method

  17. Physicochemical Properties of Gold Nanostructures Deposited on Glass

    Directory of Open Access Journals (Sweden)

    Zdenka Novotna

    2014-01-01

    Full Text Available Properties of gold films sputtered onto borosilicate glass substrate were studied. UV-Vis absorption spectra were used to investigate optical parameters. XRD analysis provided information about the gold crystalline nanostructure, the texture, and lattice parameter and biaxial tension was also determined by the XRD method. The surface morphology was examined by atomic force microscopy (AFM; chemical structure of sputtered gold nanostructures was examined by X-ray photoelectron spectroscopy (ARXPS. The gold crystallites are preferentially [111] oriented on the sputtered samples. Gold deposition leads to dramatic changes in the surface morphology in comparison to pristine glass substrate. Oxygen is not incorporated into the gold layer during gold deposition. Experimental data on lattice parameter were also confirmed by theoretical investigations of nanoclusters using tight-binding potentials.

  18. Gold nanoshell photomodification under a single-nanosecond laser pulse accompanied by color-shifting and bubble formation phenomena

    International Nuclear Information System (INIS)

    Akchurin, Garif; Khlebtsov, Boris; Akchurin, Georgy; Tuchin, Valery; Zharov, Vladimir; Khlebtsov, Nikolai

    2008-01-01

    Laser-nanoparticle interaction is crucial for biomedical applications of lasers and nanotechnology to the treatment of cancer or pathogenic microorganisms. We report on the first observation of laser-induced coloring of gold nanoshell solution after a one nanosecond pulse and an unprecedentedly low bubble formation (as the main mechanism of cancer cell killing) threshold at a laser fluence of about 4 mJ cm -2 , which is safe for normal tissue. Specifically, silica/gold nanoshell (140/15 nm) suspensions were irradiated with a single 4 ns (1064 nm) or 8 ns (900 nm) laser pulse at fluences ranging from 0.1 mJ cm -2 to 50 J cm -2 . Solution red coloring was observed by the naked eye confirmed by blue-shifting of the absorption spectrum maximum from the initial 900 nm for nanoshells to 530 nm for conventional colloidal gold nanospheres. TEM images revealed significant photomodification of nanoparticles including complete fragmentation of gold shells, changes in silica core structure, formation of small 20-30 nm isolated spherical gold nanoparticles, gold nanoshells with central holes, and large and small spherical gold particles attached to a silica core. The time-resolved monitoring of bubble formation phenomena with the photothermal (PT) thermolens technique demonstrated that after application of a single 8 ns pulse at fluences 5-10 mJ cm -2 and higher the next pulse did not produce any PT response, indicating a dramatic decrease in absorption because of gold shell modification. We also observed a dependence of the bubble expansion time on the laser energy with unusually very fast PT signal rising (∼3.5 ns scale at 0.2 J cm -2 ). Application of the observed phenomena to medical applications is discussed, including a simple visual color test for laser-nanoparticle interaction

  19. Measurement of the isotope effect of the diffusion of silver and gold in gold and of silver in silver-gold alloys

    International Nuclear Information System (INIS)

    Wolter, D.

    1974-01-01

    The silver isotopes Ag 105 and Agsup(110m) and the gold isotopes Au 195 and Au 199 were used for isotope effect measurements. The isotope effect of the gold self-diffusion was measured on four monocrystals samples at about 850 0 C, that of silver in gold monocrystals at five different temperatures between 731 0 C and 1050 0 C. Furthermore, the isotope effect for silver at 904 0 C was measured on seven silver-gold alloys of varying silver concentration. The correlation factor was determined from the measurements. (HPOE/LH) [de

  20. GOLD-BEARING MINERALIZED ZONES OF THE YUZHNOE ORE OCCURRENCE AND ITS COMPARISON WITH LODE GOLD DEPOSITS OF YENISEI RIDGE

    OpenAIRE

    MANSUROV R.KH.

    2016-01-01

    The relevance of the discussed issue is caused by the need to detect a new gold ore deposits within the Yenisei ridge to replenish the mineral resources of gold ore in Russia. The main aim of the study is to explore the features of geological structure and gold ore mineralized zones of ore occurrence Yuzhnoe in order to forecast gold ore bodies, and to substantiate the continuation of geological exploration. The prospecting is realized by the express method of prospecting of gold ore deposits...

  1. Metamorphic Rock-Hosted Orogenic Gold Deposit Type as a Source of Langkowala Placer Gold, Bombana, Southeast Sulawesi

    OpenAIRE

    Idrus, Arifudin; Nur, I; Warmada, I. W; Fadlin, Fadlin

    2011-01-01

    DOI: 10.17014/ijog.v6i1.114In 2008, placer gold was discovered in Langkowala area (Bombana Regency), Southeast Sulawesi, Indonesia, and more than 60,000 traditional gold miners in the early 2009 have been operating by digging vertical pits and panning active stream sediments. The grade of placer gold ranges from 50 to 140 g/t. Local geological framework indicates that the placer gold is not related to volcanic rock-related hydrothermal gold deposit, e.g. epithermal, skarn or porphyry. This pa...

  2. Coal-oil assisted flotation for the gold recovery

    Energy Technology Data Exchange (ETDEWEB)

    Sen, S.; Seyrankaya, A.; Cilingir, Y. [Dokuz Eylul University, Izmir (Turkey). Mining Engineering Department

    2005-09-01

    Using coal-oil agglomeration method for free or native gold recovery has been a research subject for many researchers over the years. In this study, a new approach 'coal-oil assisted gold flotation' was used to recover gold particles. The coal-oil-gold agglomeration process considers the preferential wetting of coal and gold particles. The method takes advantage of the greater hydrophobicity and oleophilicity of coal and gold compared to that the most gangue materials. Unlike the previous studies about coal-oil-gold agglomeration, this method uses a very small amount of coal and agglomerating agents. Some experiments were conducted on synthetic gold ore samples to reveal the reaction of the coal-oil assisted gold flotation process against the size and the number of gold particles in the feed. It was observed that there is no significant difference in process gold recoveries for feeds assaying different Au. Although there was a slight decrease for coarse gold particles, the process seems to be effective for the recovery of gold grains as coarse as 300 {mu} m. The decrease in the finest size ({lt} 53 {mu} m) is considered to be the decrease in the collision efficiency between the agglomerates and the finest gold particles. The effect of changing coal quantity for constant ore and oil amounts was also investigated. The experiments showed that the process gives very similar results for both artificial and natural ore samples; the best results have been obtained by using 30/1 coal-oil ratio.

  3. Red gold analysis by using gamma absorption tchnique

    International Nuclear Information System (INIS)

    Kurtoglu, A.; Tugrul, A.B.

    2001-01-01

    Gold is a valuable metal and also preferable materials for antique artefacts and some advanced technology products. It can be offered for the analysis of the gold as namely; neutron activation analysis, X-ray florescence technique, Auger spectroscopy, atomic absorption and wet chemistry. Some limitations exist in practice for these techniques, especially in the points of financial and applicability concepts. An advanced a practical technique is gamma absorption technique for the gold alloys. This technique is based on discontinuities in the absorption coefficient for gamma rays at corresponding to the electronic binding energies of the absorber. If irradiation is occurred at gamma absorption energy for gold, absorption rates of the red gold changes via the gold amounts in the alloy. Red gold is a basic and generally preferable alloy that has copper and silver additional of the gold in it. The gold amount defines as carat of the gold. Experimental studies were observed for four different carats of red gold; these are 8, 14, 18 and 22 carats. K-edge energy level of the gold is on 80 keV energy. So, Ba-133 radioisotope is preferred as the gamma source because of it has gamma energy peak in that energy. Experiments observed in the same geometry for all samples. NaI(Tl) detector and multichannel analyser were used for measurements. As a result of the experiments, the calibration curves could be drawn for red gold. For examine this curve, unknown samples are measured in experimental set and it can be determined the carat of it with the acceptability. So the red gold analysis can be observed non-destructively, easily and quickly by using the gamma absorption technique

  4. Antifungal activity of gold nanoparticles prepared by solvothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Tokeer, E-mail: tahmad3@jmi.ac.in [Nanochemistry Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025 (India); Wani, Irshad A.; Lone, Irfan H.; Ganguly, Aparna [Nanochemistry Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025 (India); Manzoor, Nikhat; Ahmad, Aijaz [Department of Biosciences, Jamia Millia Islamia, New Delhi 110025 (India); Ahmed, Jahangeer [Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Al-Shihri, Ayed S. [Department of Chemistry, Faculty of Science, King Khalid University, Abha 61413, P.O. Box 9004 (Saudi Arabia)

    2013-01-15

    Graphical abstract: Gold nanoparticles (7 and 15 nm) of very high surface area (329 and 269 m{sup 2}/g) have been successfully synthesized through solvothermal method by using tin chloride and sodium borohydride as reducing agents. As-prepared gold nanoparticles shows very excellent antifungal activity against Candida isolates and activity increases with decrease in the particle size. Display Omitted Highlights: ► Effect of reducing agents on the morphology of gold nanoparticles. ► Highly uniform and monodisperse gold nanoparticles (7 nm). ► Highest surface area of gold nanoparticles (329 m{sup 2/}g). ► Excellent antifungal activity of gold nanoparticles against Candida strains. -- Abstract: Gold nanoparticles have been successfully synthesized by solvothermal method using SnCl{sub 2} and NaBH{sub 4} as reducing agents. X-ray diffraction studies show highly crystalline and monophasic nature of the gold nanoparticles with face centred cubic structure. The transmission electron microscopic studies show the formation of nearly spherical gold nanoparticles of average size of 15 nm using SnCl{sub 2}, however, NaBH{sub 4} produced highly uniform, monodispersed and spherical gold nanoparticles of average grain size of 7 nm. A high surface area of 329 m{sup 2}/g for 7 nm and 269 m{sup 2}/g for 15 nm gold nanoparticles was observed. UV–vis studies assert the excitations over the visible region due to transverse and longitudinal surface plasmon modes. The gold nanoparticles exhibit excellent size dependant antifungal activity and greater biocidal action against Candida isolates for 7 nm sized gold nanoparticles restricting the transmembrane H{sup +} efflux of the Candida species than 15 nm sized gold nanoparticles.

  5. Antifungal activity of gold nanoparticles prepared by solvothermal method

    International Nuclear Information System (INIS)

    Ahmad, Tokeer; Wani, Irshad A.; Lone, Irfan H.; Ganguly, Aparna; Manzoor, Nikhat; Ahmad, Aijaz; Ahmed, Jahangeer; Al-Shihri, Ayed S.

    2013-01-01

    Graphical abstract: Gold nanoparticles (7 and 15 nm) of very high surface area (329 and 269 m 2 /g) have been successfully synthesized through solvothermal method by using tin chloride and sodium borohydride as reducing agents. As-prepared gold nanoparticles shows very excellent antifungal activity against Candida isolates and activity increases with decrease in the particle size. Display Omitted Highlights: ► Effect of reducing agents on the morphology of gold nanoparticles. ► Highly uniform and monodisperse gold nanoparticles (7 nm). ► Highest surface area of gold nanoparticles (329 m 2/ g). ► Excellent antifungal activity of gold nanoparticles against Candida strains. -- Abstract: Gold nanoparticles have been successfully synthesized by solvothermal method using SnCl 2 and NaBH 4 as reducing agents. X-ray diffraction studies show highly crystalline and monophasic nature of the gold nanoparticles with face centred cubic structure. The transmission electron microscopic studies show the formation of nearly spherical gold nanoparticles of average size of 15 nm using SnCl 2 , however, NaBH 4 produced highly uniform, monodispersed and spherical gold nanoparticles of average grain size of 7 nm. A high surface area of 329 m 2 /g for 7 nm and 269 m 2 /g for 15 nm gold nanoparticles was observed. UV–vis studies assert the excitations over the visible region due to transverse and longitudinal surface plasmon modes. The gold nanoparticles exhibit excellent size dependant antifungal activity and greater biocidal action against Candida isolates for 7 nm sized gold nanoparticles restricting the transmembrane H + efflux of the Candida species than 15 nm sized gold nanoparticles.

  6. Direct determination of thermodynamic activities of gold in the systems gold-palladium and gold-silver-palladium

    International Nuclear Information System (INIS)

    Hoehn, R.; Herzig, C.

    1986-01-01

    The thermodynamic activity of the gold component was directly measured in Au-Pd alloys in the concentration range between X Au =0.048 and 0.850 and in the temperature range 1070 and 1300 K. The ratio of the vapour pressures of pure gold and of the gold component of the alloys was determined - after effusion from a Knudsen twin cell and condensation on a collecting plate - by analysing the decay rate of the radioisotopes 195 Au and 198 Au in an intrinsic germanium well-type detector. The partial mixing enthalpy and the partial mixing entropy of Au were directly obtained from these results. By Gibbs-Duhem integration the integral mixing functions were deduced. Similar measurements were performed in several ternary Au-Ag-Pd alloys of fixed mole fraction X Ag /X Pd =1/9. A comparison of the directly measured partial free excess enthalpy of Au in these ternary alloys with data obtained by the approximate models of Kohler, Toop and Bonnier using data of the corresponding three binary systems yields satisfactory agreement. (orig.) [de

  7. Gold in the hills: patterns of placer gold accumulation under dynamic tectonic and climatic conditions

    Science.gov (United States)

    Roy, Sam; Upton, Phaedra; Craw, Dave

    2018-01-01

    Formation of placer accumulations in fluvial environments requires 103-106 or even greater times concentration of heavy minerals. For this to occur, regular sediment supply from erosion of adjacent topography is required, the river should remain within a single course for an extended period of time and the material must be reworked such that a high proportion of the sediment is removed while a high proportion of the heavy minerals remains. We use numerical modeling, constrained by observations of circum-Pacific placer gold deposits, to explore processes occurring in evolving river systems in dynamic tectonic environments. A fluvial erosion/transport model is used to determine the mobility of placer gold under variable uplift rate, storm intensity, and rock mass strength conditions. Gold concentration is calculated from hydraulic and bedload grain size conditions. Model results suggest that optimal gold concentration occurs in river channels that frequently approach a threshold between detachment-limited and transport-limited hydraulic conditions. Such a condition enables the accumulation of gold particles within the framework of a residual gravel lag. An increase in transport capacity, which can be triggered by faster uplift rates, more resistant bedrock, or higher intensity storm events, will strip all bedload from the channel. Conversely, a reduction in transport capacity, triggered by a reduction in uplift rate, bedrock resistance, or storm intensity, will lead to a greater accumulation of a majority of sediments and a net decrease in gold concentration. For our model parameter range, the optimal conditions for placer gold concentration are met by 103 times difference in strength between bedrock and fault, uplift rates between 1 and 5 mm a-1, and moderate storm intensities. Fault damage networks are shown to be a critical factor for high Au concentrations and should be a target for exploration.

  8. Synthesis and Evaluation of Nanostructured Gold-Iron Oxide Catalysts for the Oxidative Dehydrogenation of Cyclohexane

    Science.gov (United States)

    Wu, Peng

    Shape-controlled iron oxide and gold-iron oxide catalysts with a cubic inverse spinel structure were studied in this thesis for the oxidative dehydrogenation of cyclohexane. The structure of iron oxide and gold-iron oxide catalysts has no major impact on their oxidative dehydrogenation activity. However, the product selectivity is influenced. Both cyclohexene and benzene are formed on bare iron oxide nanoshapes, while benzene is the only dehydrogenation product in the presence of gold. The selectivity of benzene over CO2 depends strongly on the stability of the iron oxide support and the gold-support interaction. The highest benzene yield has been observed on gold-iron oxide octahedra. {111}-bound nanooctahedra are highly stable in reaction conditions at 300 °C, while {100}-bound nanocubes start to sinter above 250 °C. The highest benzene yield has been observed on gold-iron oxide nanooctahedra, which are likely to have gold atoms, and few-atom gold clusters strongly-bound on their surface. Cationic gold appears to be the active site for benzene formation. An all-organic method to prepare Au-FeOx nano-catalysts is needed due to the inconvenience of the half-organic, half-inorganic synthesis process discussed above. Several methods from the literature to prepare gold-iron oxide nanocomposites completely in organic solvents were reviewed and followed. FeOx Au synthesis procedures in literatures are initially designed for a Au content of over 70%. This approach was tried here to prepare composites with a much lower Au content (2-5 atom. %). Heat treatment is required to bond Au and FeOx NPs in the organic-phase syntheses. Au-FeOx-4 was obtained as a selective catalyst for the ODH of cyclohexane. A Audelta+ peak is observed in the UV-Vis spectrum of sample Au-FeOx-4. This different Au delta+ form may be cationic Au nano-clusters interacting with the FeOx support. It has been demonstrated that cationic gold is responsible for dehydrogenation behavior. Furthermore, the

  9. Near-field second-harmonic generation from gold nanoellipsoids

    Energy Technology Data Exchange (ETDEWEB)

    Celebrano, M; Zavelani-Rossi, M; Polli, D; Cerullo, G [Istituto di Fotonica e Nanotecnologie, CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Biagioni, P; Finazzi, M; Duo, L [LNESS - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Labardi, M; Allegrini, M [CNR-INFM, polyLab, Dipartimento di Fisica ' Enrico Fermi' , Universita di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy); Grand, J; Adam, P M; Royer, P [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de Technologie de Troyes, 12 rue Marie Curie, BP 2060 10010 Troyes cedex (France)

    2008-07-01

    Second-harmonic generation from single gold nanofabricated particles is experimentally investigated by a nonlinear scanning near-field optical microscope (SNOM). High peak power femtosecond polarized light pulses at the output of a hollow pyramid aperture allow for efficient second-harmonic imaging, with sub-100-nm spatial resolution and high contrast. The near-field nonlinear response is found to be directly related to both local surface plasmon resonances and particle morphology. The combined analysis of linear and second-harmonic SNOM images allows one to discriminate among near-field scattering, absorption and re-emission processes, which would not be possible with linear techniques alone. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Determination of gold of No. 501 uranium deposits and soil samples by cold leaching gold in dilute aqua regia and collection on activated charcoal

    International Nuclear Information System (INIS)

    Shen Maogen; Yao Liying.

    1989-01-01

    The gold determination method is described by cold leaching gold in dilute aqua regia and collection on activated charcoal and presents the results obtained in determining gold of uranium deposits and soil samples

  11. Plasmonic Switches and Sensors Based on PANI-Coated Gold Nanostructures

    Science.gov (United States)

    Jiang, Nina

    Gold nanostructures have been received intense and growing attention due to their unique properties associated with localized surface plasmon resonance (LSPR). The frequency and strength of the LSPR are highly dependent on the dielectric properties of the surrounding environment around gold nanostructures. Such dependence offers the essential basis for the achievement of plasmonic switching and sensing. While the plasmonic response of gold nanostructures is tuned by changing their dielectric environment, the external stimuli inducing the changes in the dielectric environment will be read out through the plasmonic response of gold nanostructures. As a consequence, plasmonic sensors and switches can be engineered by integrating active media that can respond to external stimuli with gold nanostructures. In this thesis research, I have achieved the coating of polyaniline (PANI) ' a conductive polymer, on gold nanostructures, and exploited the application of the core/shell nanostructures in plasmonic switching and sensing. Large modulation of the longitudinal plasmon resonance of single gold nanorods is achieved by coating PANI shell onto gold nanorods to produce colloidal plasmonic switches. The dielectric properties of PANI shell can be tuned by changing the proton-doping levels, which allows for the modulation of the plasmonic response of gold nanorods. The coated nanorods are sparsely housed in a simple microfluidic chamber. HCl and NaOH solutions are alternately pumped through the chamber for the realization of proton doping and dedoping. The plasmonic switching behavior is examined by monitoring the single-particle scattering spectra under the proton-doped and dedoped state of PANI. The coated nanorods exhibit a remarkable switching performance, with the modulation depth and scattering peak shift reaching 10 dB and 100 nm, respectively. Electrodynamic simulations are employed to confirm the plasmon switching behavior. I have further investigated the modulation of

  12. Analysis of the toxicity of gold nano particles on the immune system: effect on dendritic cell functions

    International Nuclear Information System (INIS)

    Villiers, Christian L.; Freitas, Heidi; Couderc, Rachel; Villiers, Marie-Bernadette; Marche, Patrice N.

    2010-01-01

    The effect of manufactured gold nanoparticles (NPs) on the immune system was analysed through their ability to perturb the functions of dendritic cells (DCs), a major actor of both innate and acquired immune responses. For this purpose, DCs were produced in culture from mouse bone marrow progenitors. The analysis of the viability of the cells after their incubation in the presence of gold NPs shows that these NPs are not cytotoxics even at high concentration. Furthermore, the phenotype of the DC is unchanged after the addition of NPs, indicating that there is no activation of the DC. However, the analysis of the cells at the intracellular level reveals important amounts of gold NPs amassing in endocytic compartments. Furthermore, the secretion of cytokines is significantly modified after such internalisation indicating a potential perturbation of the immune response.

  13. Highly sensitive electrochemical detection of methyl salicylate using electroactive gold nanoparticles.

    Science.gov (United States)

    Umasankar, Yogeswaran; Ramasamy, Ramaraja P

    2013-11-07

    Electrochemical sensing of methyl salicylate, a key plant volatile has been achieved using a gold nanoparticle (AuNP) modified screen printed carbon electrode (SPCE). The electrochemical response of planar gold electrodes, SPCE and AuNP-SPCE in alkaline electrolyte in the presence and absence of methyl salicylate were studied to understand the amperometric response of various electrochemical reactions. The reaction mechanism includes hydrolysis of methyl salicylate and the oxidation of negative species. The electrochemical responses were recorded using cyclic voltammetry and differential pulse voltammetry techniques, where the results showed characteristic signals for methyl salicylate oxidation. Among the examined electrodes, AuNP-SPCE possessed three fold better sensitivity than planar gold and 35 times better sensitivity than SPCE (at 0.5 V). The methyl salicylate sensing by AuNP-SPCE possessed 95% of its methyl salicylate response. The electroanalytical results of soybean extract showed that AuNP-SPCE can be employed for the determination of methyl salicylate in real samples.

  14. Assessment of the In Vivo Toxicity of Gold Nanoparticles

    Directory of Open Access Journals (Sweden)

    Liau Ian

    2009-01-01

    Full Text Available Abstract The environmental impact of nanoparticles is evident; however, their toxicity due to their nanosize is rarely discussed. Gold nanoparticles (GNPs may serve as a promising model to address the size-dependent biological response to nanoparticles because they show good biocompatibility and their size can be controlled with great precision during their chemical synthesis. Naked GNPs ranging from 3 to 100 nm were injected intraperitoneally into BALB/C mice at a dose of 8 mg/kg/week. GNPs of 3, 5, 50, and 100 nm did not show harmful effects; however, GNPs ranging from 8 to 37 nm induced severe sickness in mice. Mice injected with GNPs in this range showed fatigue, loss of appetite, change of fur color, and weight loss. Starting from day 14, mice in this group exhibited a camel-like back and crooked spine. The majority of mice in these groups died within 21 days. Injection of 5 and 3 nm GNPs, however, did not induce sickness or lethality in mice. Pathological examination of the major organs of the mice in the diseased groups indicated an increase of Kupffer cells in the liver, loss of structural integrity in the lungs, and diffusion of white pulp in the spleen. The pathological abnormality was associated with the presence of gold particles at the diseased sites, which were verified by ex vivo Coherent anti-Stoke Raman scattering microscopy. Modifying the surface of the GNPs by incorporating immunogenic peptides ameliorated their toxicity. This reduction in the toxicity is associated with an increase in the ability to induce antibody response. The toxicity of GNPs may be a fundamental determinant of the environmental toxicity of nanoparticles.

  15. Ordered arrays of nanoporous gold nanoparticles

    Directory of Open Access Journals (Sweden)

    Dong Wang

    2012-09-01

    Full Text Available A combination of a “top-down” approach (substrate-conformal imprint lithography and two “bottom-up” approaches (dewetting and dealloying enables fabrication of perfectly ordered 2-dimensional arrays of nanoporous gold nanoparticles. The dewetting of Au/Ag bilayers on the periodically prepatterned substrates leads to the interdiffusion of Au and Ag and the formation of an array of Au–Ag alloy nanoparticles. The array of alloy nanoparticles is transformed into an array of nanoporous gold nanoparticles by a following dealloying step. Large areas of this new type of material arrangement can be realized with this technique. In addition, this technique allows for the control of particle size, particle spacing, and ligament size (or pore size by varying the period of the structure, total metal layer thickness, and the thickness ratio of the as-deposited bilayers.

  16. Formation of Silver and Gold Dendrimer Nanocomposites

    International Nuclear Information System (INIS)

    Balogh, Lajos; Valluzzi, Regina; Laverdure, Kenneth S.; Gido, Samuel P.; Hagnauer, Gary L.; Tomalia, Donald A.

    1999-01-01

    Structural types of dendrimer nanocomposites have been studied and the respective formation mechanisms have been described, with illustration of nanocomposites formed from poly(amidoamine) PAMAM dendrimers and zerovalent metals, such as gold and silver. Structure of {(Au(0)) n- PAMAM} and {(Ag(0)) n- PAMAM} gold and silver dendrimer nanocomposites was found to be the function of the dendrimer structure and surface groups as well as the formation mechanism and the chemistry involved. Three different types of single nanocomposite architectures have been identified, such as internal ('I'), external ('E') and mixed ('M') type nanocomposites. Both the organic and inorganic phase could form nanosized pseudo-continuous phases while the other components are dispersed at the molecular or atomic level either in the interior or on the surface of the template/container. Single units of these nanocomposites may be used as building blocks in the synthesis of nanostructured materials

  17. Biological synthesis of triangular gold nanoprisms

    Science.gov (United States)

    Shankar, S. Shiv; Rai, Akhilesh; Ankamwar, Balaprasad; Singh, Amit; Ahmad, Absar; Sastry, Murali

    2004-07-01

    The optoelectronic and physicochemical properties of nanoscale matter are a strong function of particle size. Nanoparticle shape also contributes significantly to modulating their electronic properties. Several shapes ranging from rods to wires to plates to teardrop structures may be obtained by chemical methods; triangular nanoparticles have been synthesized by using a seeded growth process. Here, we report the discovery that the extract from the lemongrass plant, when reacted with aqueous chloroaurate ions, yields a high percentage of thin, flat, single-crystalline gold nanotriangles. The nanotriangles seem to grow by a process involving rapid reduction, assembly and room-temperature sintering of 'liquid-like' spherical gold nanoparticles. The anisotropy in nanoparticle shape results in large near-infrared absorption by the particles, and highly anisotropic electron transport in films of the nanotriangles.

  18. Synoviorthesis with radioactive gold in hemophiliacs

    International Nuclear Information System (INIS)

    Ahlberg, Aa.; Petterson, H.

    1979-01-01

    Twenty-seven patients with hemophilia treated with intra-articular injection of radioactive gold were followed up clinically and radiologically for 3 to 9 years after treatment. To assess the radiological changes, a new classification was designed, with a score describing the severity of the changes in a more accurate manner than the methods previously used. The treatment decreased the bleeding frequency and stopped the progress of the arthropathy if applied at an early stage when the arthropathy was still reversible. If the treatment was begun at a later stage, the arthropathy seemed to progress independently of the effect on the bleeding frequency. No negative effect of the radioactive gold was observed on the joint or the growing zone. (author)

  19. Gold-bearing hydrothermal veins in Chukotka

    Energy Technology Data Exchange (ETDEWEB)

    Davidenko, N.M.

    1980-01-01

    Indicators such as the correlation of mineralization to plutonic and vulcanic formations and various facies of metamorphism, the character of the structural-tectonic control of mineralization, characteristics of silica redistribution as well that of calcium, water, and other components in altering ore zones, the specificity of sygenetic fluid inclusions in minerals, morphology, the internal structure and other typomorphic indicators of native gold and its accessories are utilized in the working out of a genetic classification for compiling a complex of diagnostic indicators of post-magmatic mineralization on Chukotka at various depths. Those indicators, in addition to earlier known hydrothermal gold ore formations, can be used to identify still other types of mineralization, particularly pyrite group minerals.

  20. Reversible peptide oligomerization over nanoscale gold surfaces

    Directory of Open Access Journals (Sweden)

    Kazushige Yokoyama

    2015-11-01

    Full Text Available A selective oligomeric formation of amyloid beta 1-40 (Ab1-40 monomers over a nanogold colloidal surface was investigated. An unfolded Ab1-40 monomer is considered to construct a dimer or trimer based oligomeric form with its hydrophobic segment placing outward under an acidic condition. Under a basic condition, a conformation of Ab is expected to take a folded monomeric form with its hydrophilic segment folded inward, avoiding the networking with residual colloidal particles. The most probable oligomeric form constructed over a 20 nm gold colloidal surface within a 25 ℃ to 65 ℃ temperature range is a dimer based unit and that over 30 or 40 nm gold colloidal surface below 15 ℃ is concluded to be a trimer based unit. However, selective oligomerization was not successfully reproduced under the rest of the conditions. A dipole-induced dipole interaction must cause a flexible structural change between folded and unfolded forms.

  1. Poly-thiosemicarbazide Membrane for Gold Adsorption and In-situ Growth of Gold Nanoparticles

    KAUST Repository

    Parra, Luis F.

    2012-12-01

    In this work the synergy between a polymer containing chelate sites and gold ions was explored by the fabrication of a polymeric membrane with embedded gold nanoparticles inside its matrix and by developing a process to recover gold from acidic solutions. After realizing that the thiosemicarbazide groups present in the monomeric unit of poly-thiosemicarbazide (PTSC) formed strong complexes with Au ions, membrane technology was used to exploit this property to its maximum. The incorporation of metal nanoparticles into polymeric matrices with current technologies involves either expensive and complicated procedures or leads to poor results in terms of agglomeration, loading, dispersion, stability or efficient use of raw materials. The fabrication procedure described in this thesis solves these problems by fabricating a PTSC membrane containing 33.5 wt% in the form of 2.9 nm gold nanoparticles (AuNPs) by a three step simple and scalable procedure. It showed outstanding results in all of the areas mentioned above and demonstrated catalytic activity for the reduction of 4-Nitrophenol (4−NP) to 4-Aminophenol (4−AP). The current exponential demand of gold for electronics has encouraged the development of efficient processes to recycle it. Several adsorbents used to recover gold from acidic solutions can be found in the literature with outstanding maximum uptakes,yet, poor kinetics leading to an overall inefficient process. The method developed in this dissertation consisted in permeating the gold-containing solution through a PTSC membrane that will capture all the Au ions by forming a metal complex with them. Forcing the ions through the pores of the membrane eliminates the diffusion limitations and the adsorption will only depended on the fast complexation kinetics, resulting in a very efficient process. A flux as high as 1868 L/h m2 was enough to capture >90% of the precious metal present in a solution of 100 ppm Au. The maximum uptake achieved without sacrificing

  2. Microbial biosynthesis of nontoxic gold nanoparticles

    International Nuclear Information System (INIS)

    Roy, Swarup; Das, Tapan Kumar; Maiti, Guru Prasad; Basu, Utpal

    2016-01-01

    Graphical abstract: The manuscript deals with the fungus mediated optimized biologically synthesized GNPs using Aspergillus foetidus and characterization of biosynthesized GNPs using various physico-chemical methods. The fairly stable synthesized nanoparticles have size in the range of 10–40 nm. Cytotoxicity study of biosynthesized GNPs on Human lung cancer cell line A549 showed no significant toxicity of GNPs. - Highlights: • A novel biosynthesis process of GNPs using Aspergillus foetidus. • Biosynthesized GNPs are in the range of 10–40 nm as observed from TEM. • This process of synthesis is an optimized biosynthesis process of GNPs. • Biosynthesized GNPs are noncytotoxic against A549 cell line. - Abstract: We study the extracellular biosynthesis of gold nanoparticles (GNPs) using the fungal species Aspergillus foetidus. The formation of GNPs were initially monitored by visual observation and then characterized with the help of various characterization techniques. X-ray diffraction (XRD) results revealed distinctive formation of face centered cubic crystalline GNPs. From field emission scanning electron microscopy (FESEM) the morphology of the nanoparticles were found to be roughly spherical and within the size range of 30–50 nm. The spherical and polydispersed GNPs in the range of 10–40 nm were observed by transmission electron microscopy (TEM) analysis. It was established that alkaline pH, 1 mM gold salt concentration and 75 °C temperature were the respective optimum parameter for biosynthesis of GNPs. Cell cytotoxicity of GNP was compared with that of normal gold salt solution on A549 cell. The A549 cell growth in presence of GNPs was found to be comparatively less toxic than the gold ion.

  3. NA35: sulphur-gold collision

    CERN Multimedia

    1991-01-01

    In this image the real particles produced by the collision of a 6400 GeV sulphur ion with a gold target can be seen as they pass through a streamer chamber. Streamer chambers consist of a gas chamber through which a strong pulsed electric field is passed, creating sparks as a charged particle passes through it. The NA35 experiment, which was in operation in the 1980s, was part of CERN's ongoing heavy ion project.

  4. Radiotracer investigation in gold leaching tanks

    Energy Technology Data Exchange (ETDEWEB)

    Dagadu, C.P.K., E-mail: dagadukofi@yahoo.co.uk [Ghana Atomic Energy Commission, P.O. Box LG 80, Legon, Accra (Ghana); Akaho, E.H.K.; Danso, K.A. [Ghana Atomic Energy Commission, P.O. Box LG 80, Legon, Accra (Ghana); Stegowski, Z.; Furman, L. [Faculty of Physics and Applied Computer Science, AGH-UST, 30-059 Krakow (Poland)

    2012-01-15

    Measurement and analysis of residence time distribution (RTD) is a classical method to investigate performance of chemical reactors. In the present investigation, the radioactive tracer technique was used to measure the RTD of aqueous phase in a series of gold leaching tanks at the Damang gold processing plant in Ghana. The objective of the investigation was to measure the effective volume of each tank and validate the design data after recent process intensification or revamping of the plant. I-131 was used as a radioactive tracer and was instantaneously injected into the feed stream of the first tank and monitored at the outlet of different tanks. Both sampling and online measurement methods were used to monitor the tracer concentration. The results of measurements indicated that both the methods provided identical RTD curves. The mean residence time (MRT) and effective volume of each tank was estimated. The tanks-in-series model with exchange between active and stagnant volume was used and found suitable to describe the flow structure of aqueous phase in the tanks. The estimated effective volume of the tanks and high degree of mixing in tanks could validate the design data and confirmed the expectation of the plant engineer after intensification of the process. - Highlights: Black-Right-Pointing-Pointer I-131 radioactive tracer is suitable for tracing the aqueous phase in gold ore slurry. Black-Right-Pointing-Pointer Online data collection is more convenient method for tracer monitoring in industrial process systems. Black-Right-Pointing-Pointer The tanks-in-series model with exchange between active and stagnant zones is suitable to describe the flow behavior of leaching tanks. Black-Right-Pointing-Pointer The radiotracer RTD technique could be used to validate design data after process intensification in gold leaching tanks.

  5. Microbial biosynthesis of nontoxic gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Swarup, E-mail: swaruproy@klyuniv.ac.in [Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal (India); Das, Tapan Kumar [Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal (India); Maiti, Guru Prasad [Department of Molecular Biology and Biotechnology, University of Kalyani, Kalyani 741235, West Bengal (India); Department of Anesthesiology, Texas Tech University Health science Center, 3601 4th Street, Lubbock, TX 79430 (United States); Basu, Utpal [Department of Molecular Biology and Biotechnology, University of Kalyani, Kalyani 741235, West Bengal (India)

    2016-01-15

    Graphical abstract: The manuscript deals with the fungus mediated optimized biologically synthesized GNPs using Aspergillus foetidus and characterization of biosynthesized GNPs using various physico-chemical methods. The fairly stable synthesized nanoparticles have size in the range of 10–40 nm. Cytotoxicity study of biosynthesized GNPs on Human lung cancer cell line A549 showed no significant toxicity of GNPs. - Highlights: • A novel biosynthesis process of GNPs using Aspergillus foetidus. • Biosynthesized GNPs are in the range of 10–40 nm as observed from TEM. • This process of synthesis is an optimized biosynthesis process of GNPs. • Biosynthesized GNPs are noncytotoxic against A549 cell line. - Abstract: We study the extracellular biosynthesis of gold nanoparticles (GNPs) using the fungal species Aspergillus foetidus. The formation of GNPs were initially monitored by visual observation and then characterized with the help of various characterization techniques. X-ray diffraction (XRD) results revealed distinctive formation of face centered cubic crystalline GNPs. From field emission scanning electron microscopy (FESEM) the morphology of the nanoparticles were found to be roughly spherical and within the size range of 30–50 nm. The spherical and polydispersed GNPs in the range of 10–40 nm were observed by transmission electron microscopy (TEM) analysis. It was established that alkaline pH, 1 mM gold salt concentration and 75 °C temperature were the respective optimum parameter for biosynthesis of GNPs. Cell cytotoxicity of GNP was compared with that of normal gold salt solution on A549 cell. The A549 cell growth in presence of GNPs was found to be comparatively less toxic than the gold ion.

  6. Alternative Plasmonic Materials: Beyond Gold and Silver

    DEFF Research Database (Denmark)

    Naik, Gururaj V.; Shalaev, Vladimir M.; Boltasseva, Alexandra

    2013-01-01

    Materials research plays a vital role in transforming breakthrough scientific ideas into next‐generation technology. Similar to the way silicon revolutionized the microelectronics industry, the proper materials can greatly impact the field of plasmonics and metamaterials. Currently, research...... such as gold and silver, that exhibit metallic properties and provide advantages in device performance, design flexibility, fabrication, integration, and tunability. This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent...

  7. A perspective on gold mine capex

    International Nuclear Information System (INIS)

    Brown, M.F.

    1982-01-01

    Capital expenditure by South Africa's gold and uranium mines is expected to total R5 248 million over the period 1982/1987 - well in excess of the R4 076 million spent in the six years preceding 1982. However, once inflation is taken into account the conclusion is one of declining real capex. This is the view of M F Brown, Chief Economist of the Chamber of Mines of South Africa

  8. Nanotoxicity of gold and iron nanoparticles.

    Science.gov (United States)

    Maiti, Souvik

    2011-02-01

    The extensive use of potentially hazardous nanoparticles in industrial applications suggest that their biological effects need to be evaluated following clinical testing practices as applicable for any new pharmaceutical. It was rationalized that a non hypothesis-driven approach is best suited for discovering the biological effects of nanoparticles. Gold nanoparticles (approximately 18 nm), showed no drastic effect on gene expression in cells but iron nanoparticles showed perturbations in the expression of a set of functional genes.

  9. Radiotracer investigation in gold leaching tanks

    International Nuclear Information System (INIS)

    Dagadu, C.P.K.; Akaho, E.H.K.; Danso, K.A.; Stegowski, Z.; Furman, L.

    2012-01-01

    Measurement and analysis of residence time distribution (RTD) is a classical method to investigate performance of chemical reactors. In the present investigation, the radioactive tracer technique was used to measure the RTD of aqueous phase in a series of gold leaching tanks at the Damang gold processing plant in Ghana. The objective of the investigation was to measure the effective volume of each tank and validate the design data after recent process intensification or revamping of the plant. I-131 was used as a radioactive tracer and was instantaneously injected into the feed stream of the first tank and monitored at the outlet of different tanks. Both sampling and online measurement methods were used to monitor the tracer concentration. The results of measurements indicated that both the methods provided identical RTD curves. The mean residence time (MRT) and effective volume of each tank was estimated. The tanks-in-series model with exchange between active and stagnant volume was used and found suitable to describe the flow structure of aqueous phase in the tanks. The estimated effective volume of the tanks and high degree of mixing in tanks could validate the design data and confirmed the expectation of the plant engineer after intensification of the process. - Highlights: ► I-131 radioactive tracer is suitable for tracing the aqueous phase in gold ore slurry. ► Online data collection is more convenient method for tracer monitoring in industrial process systems. ► The tanks-in-series model with exchange between active and stagnant zones is suitable to describe the flow behavior of leaching tanks. ► The radiotracer RTD technique could be used to validate design data after process intensification in gold leaching tanks.

  10. Broadband Spectroscopy of Nanoporous-Gold Promoter

    Directory of Open Access Journals (Sweden)

    S. K. Nakatani

    2014-02-01

    Full Text Available The efficiency of UV photocatalysis on TiO2 particles was increased by mixing TiO2 particles with nanoporous gold (NPG with pore diameters of 10–40 nm. This means that NPG acts as a promoter in the photocatalytic reaction of TiO2. Broadband spectroscopic results from millimeter wave to ultra violet of NPG membrane are discussed to estimate plasmonic effect on the catalysis.

  11. Application of gold nanoparticles in separation sciences

    Czech Academy of Sciences Publication Activity Database

    Sýkora, D.; Kašička, Václav; Mikšík, Ivan; Řezanka, P.; Záruba, K.; Matějka, P.; Král, V.

    2010-01-01

    Roč. 33, č. 3 (2010), s. 372-387 ISSN 1615-9306 R&D Projects: GA ČR(CZ) GA203/09/0675; GA ČR(CZ) GA203/08/1428; GA MŠk(CZ) 1M0510 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z50110509 Keywords : gold nanoparticles * electrophoresis * chromatography Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 2.631, year: 2010

  12. Optical characteristics of jewellery gold alloys

    International Nuclear Information System (INIS)

    Wan Mahmood bin Mat Yunus; Zainal Abidin bin Talib; Maarof bin Moksin; Abdul Fatah bin Awang Mat

    1994-01-01

    Measurements of the reflection of various sample of gold alloys were made over the wavelength range 400-800 nm. Samples were measured using a single beam spectrophotometer at 45 deg. angle of incidence. In this measurement no attempt was made to obtain the optical constants of the samples. The results showed that there were significant differences between bulk and thick samples, with sufficient spectra difference between different composition of the alloys

  13. Diazonium-derived aryl films on gold nanoparticles: evidence for a carbon-gold covalent bond.

    Science.gov (United States)

    Laurentius, Lars; Stoyanov, Stanislav R; Gusarov, Sergey; Kovalenko, Andriy; Du, Rongbing; Lopinski, Gregory P; McDermott, Mark T

    2011-05-24

    Tailoring the surface chemistry of metallic nanoparticles is generally a key step for their use in a wide range of applications. There are few examples of organic films covalently bound to metal nanoparticles. We demonstrate here that aryl films are formed on gold nanoparticles from the spontaneous reduction of diazonium salts. The structure and the bonding of the film is probed with surface-enhanced Raman scattering (SERS). Extinction spectroscopy and SERS show that a nitrobenzene film forms on gold nanoparticles from the corresponding diazonium salt. Comparison of the SERS spectrum with spectra computed from density functional theory models reveals a band characteristic of a Au-C stretch. The observation of this stretch is direct evidence of a covalent bond. A similar band is observed in high-resolution electron energy loss spectra of nitrobenzene layers on planar gold. The bonding of these types of films through a covalent interaction on gold is consistent with their enhanced stability observed in other studies. These findings provide motivation for the use of diazonium-derived films on gold and other metals in applications where high stability and/or strong adsorbate-substrate coupling are required.

  14. A halogen-free synthesis of gold nanoparticles using gold(III) oxide

    International Nuclear Information System (INIS)

    Sashuk, Volodymyr; Rogaczewski, Konrad

    2016-01-01

    Gold nanoparticles are one of the most used nanomaterials. They are usually synthesized by the reduction of gold(III) chloride. However, the presence of halide ions in the reaction mixture is not always welcome. In some cases, these ions have detrimental influence on the morphology and structure of resulting nanoparticles. Here, we present a simple and halogen-free procedure to prepare gold nanoparticles by reduction of gold(III) oxide in neat oleylamine. The method provides the particles with an average size below 10 nm and dispersity of tens of percent. The process of nanoparticle formation was monitored using UV–Vis spectroscopy. The structure and chemical composition of the nanoparticles was determined by SEM, XPS and EDX. We also proposed the mechanism of reduction of gold(III) oxide based on MS, IR and NMR data. Importantly, the synthetic protocol is general and applicable for the preparation of other coinage metal nanoparticles from the corresponding metal oxides. For instance, we demonstrated that the absence of halogen enables efficient alloying of metals when preparing gold–silver bimetallic nanoparticles.

  15. Nanostructured gold microelectrodes for extracellular recording

    Energy Technology Data Exchange (ETDEWEB)

    Brueggemann, Dorothea; Wolfrum, Bernhard; Maybeck, Vanessa; Offenhaeusser, Andreas [CNI Center of Nanoelectronic Systems for Information Technology and Institute of Bio- and Nanosystems 2, Forschungszentrum Juelich (Germany)

    2010-07-01

    Electrophysiological activity of electrogenic cells is currently recorded with planar bioelectronic interfaces such as microelectrode arrays (MEAs). In this work, a novel concept of biocompatible nanostructured gold MEAs for extracellular signal recording is presented. MEAs were fabricated using clean room technologies, e.g. photolithography and metallization. Subsequently, they were modified with gold nanopillars of approximately 300 to 400 nm in height and 60 nm width. The nanostructuring process was carried out with a template-assisted approach using nanoporous aluminium oxide. Impedance spectroscopy of the resulting nanostructures showed higher capacitances compared to planar gold. This confirmed the expected increase of the surface area via nanostructuring. We used the nanostructured microelectrodes to record extracellular potentials from heart muscle cells (HL1), which were plated onto the chips. Good coupling between the HL1 cells and the nanostructured electrodes was observed. The resulting signal-to-noise ratio of nanopillar-MEAs was increased by a factor of 2 compared to planar MEAs. In future applications this nanopillar concept can be adopted for distinct interface materials and coupling to cellular and molecular sensing components.

  16. Improved synthesis of gold and silver nanoshells.

    Science.gov (United States)

    Brito-Silva, Antonio M; Sobral-Filho, Regivaldo G; Barbosa-Silva, Renato; de Araújo, Cid B; Galembeck, André; Brolo, Alexandre G

    2013-04-02

    Metallic nanoshells have been in evidence as multifunctional particles for optical and biomedical applications. Their surface plasmon resonance can be tuned over the electromagnetic spectrum by simply adjusting the shell thickness. Obtaining these particles, however, is a complex and time-consuming process, which involves the preparation and functionalization of silica nanoparticles, synthesis of very small metallic nanoparticles seeds, attachment of these seeds to the silica core, and, finally, growing of the shells in a solution commonly referred as K-gold. Here we present synthetic modifications that allow metallic nanoshells to be obtained in a faster and highly reproducible manner. The main improved steps include a procedure for quick preparation of 2.3 ± 0.5 nm gold particles and a faster approach to synthesize the silica cores. An investigation on the effect of the stirring speed on the shell growth showed that the optimal stirring speeds for gold and silver shells were 190 and 1500 rpm, respectively. In order to demonstrate the performance of the nanoshells fabricated by our method in a typical plasmonic application, a method to immobilize these particles on a glass slide was implemented. The immobilized nanoshells were used as substrates for the surface-enhanced Raman scattering from Nile Blue A.

  17. Ultrasensitive interdigitated capacitance immunosensor using gold nanoparticles

    Science.gov (United States)

    Alizadeh Zeinabad, Hojjat; Ghourchian, Hedayatollah; Falahati, Mojtaba; Fathipour, Morteza; Azizi, Marzieh; Boutorabi, Seyed Mehdi

    2018-06-01

    Immunosensors based on interdigitated electrodes (IDEs), have recently demonstrated significant improvements in the sensitivity of capacitance detection. Herein, a novel type of highly sensitive, compact and portable immunosensor based on a gold interdigital capacitor has been designed and developed for the rapid detection of hepatitis B surface antigen (HBsAg). To improve the efficiency of antibody immobilization and time-saving, a self-assembled monolayer (SAM) of 2-mercaptoethylamine film was coated on IDEs. Afterwards, carboxyl groups on primary antibodies were activated through 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and were immobilized on amino-terminated SAM for better control of the oriented immobilization of antibodies on gold IDEs. In addition, gold nanoparticles conjugated with a secondary antibody were used to enhance the sensitivity. Under optimal conditions, the immunosensor exhibited the sensitivity of 0.22 nF.pg ml–1, the linear range from 5 pg ml‑1 to 1 ng ml–1 and the detection limit of 1.34 pg ml‑1, at a signal-to-noise ratio of 3.

  18. All That Glitters Is Not Gold

    CERN Multimedia

    2001-01-01

    The surface treatment lab team. From left to right, J. Carosone, M. Malabaila, J-P. Malivert (front row), M. Thiebert, and A. Lasserre (back row). Apiece of stainless steel equipment, destined for the LHC, was delivered to building 102 last Friday morning. This past Monday the equipment emerged from the same building in the afternoon, looking very much the same as it did when it arrived... with one small difference. The equipment was no longer steel, but gold. This may sound like medieval alchemy, but not all is as it appears. In fact there is no sorcery involved, just lots of careful chemical engineering. No wizards either, but rather a talented team of individuals... the CERN surface treatment lab group. Copper, silver, and gold are all incredibly important to particle physics projects because of their ability to conduct electricity with very low resistance. Unfortunately, these metals are also expensive and cannot be used frequently in large quantities. So instead of building equipment out of gold, equi...

  19. Identification of Paracoccidioides brasiliensis by gold nanoprobes

    Science.gov (United States)

    Martins, Jaciara F. S.; Castilho, Maiara L.; Cardoso, Maria A. G.; Carreiro, Andrea P.; Martin, Airton A.; Raniero, Leandro

    2012-01-01

    Paracoccidioides brasiliensis (P. brasiliensis) is a thermal dimorphic fungus and causal agent of paracoccidioidomycosis. Epidemiological data shows that it is mainly concentrated in Central and South America countries, with most registered cases in Colombia, Brazil, and Venezuela. The histopathological similarity with others fungal infection makes the diagnosis of P. brasiliensis more complicated. Therefore, the aim of this work was to find a positive and negative test for P. brasiliensis using gold nanoprobes as a new tool for P. brasiliensis detection. Gold nanoparticles were synthesized by reduction of gold chloride with sodium citrate. The results of this procedure is a wine-red solution with a maximum absorption in the range of ~520-530nm. A specific P. brasiliensis sequence of oligonucleotide was bonded to the nanoparticles, which maintained the wine-red color. The color changes from red to blue for negative diagnostic and is unchanged for a positive test. The H-bond interaction of DNA with the complementary DNA keeps strands together and forms double helical structure, maintaining the colloid stability. However, for non-complimentary DNA sequence the nanoprobes merge into a cluster, changing the light absorption.

  20. Gold, nickel and copper mining and processing.

    Science.gov (United States)

    Lightfoot, Nancy E; Pacey, Michael A; Darling, Shelley

    2010-01-01

    Ore mining occurs in all Canadian provinces and territories except Prince Edward Island. Ores include bauxite, copper, gold, iron, lead and zinc. Workers in metal mining and processing are exposed, not only to the metal of interest, but also to various other substances prevalent in the industry, such as diesel emissions, oil mists, blasting agents, silica, radon, and arsenic. This chapter examines cancer risk related to the mining of gold, nickel and copper. The human carcinogenicity of nickel depends upon the species of nickel, its concentration and the route of exposure. Exposure to nickel or nickel compounds via routes other than inhalation has not been shown to increase cancer risk in humans. As such, cancer sites of concern include the lung, and the nasal sinus. Evidence comes from studies of nickel refinery and leaching, calcining, and sintering workers in the early half of the 20th century. There appears to be little or no detectable risk in most sectors of the nickel industry at current exposure levels. The general population risk from the extremely small concentrations detectable in ambient air are negligible. Nevertheless, animal carcinogenesis studies, studies of nickel carcinogenesis mechanisms, and epidemiological studies with quantitative exposure assessment of various nickel species would enhance our understanding of human health risks associated with nickel. Definitive conclusions linking cancer to exposures in gold and copper mining and processing are not possible at this time. The available results appear to demand additional study of a variety of potential occupational and non-occupational risk factors.