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Sample records for element gold silver

  1. 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.

  2. 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.

  3. The determination of the content of gold and silver in geological samples

    Directory of Open Access Journals (Sweden)

    B. NESIC

    2001-01-01

    Full Text Available A method has been elaborated for the determination of the content of gold and silver in geological samples by atomic absorption spectrophotometry (AAS in combination with the fire assay method. The weight of sample used for analysis was 10 g. Sulphur present as sulphide, which is an undesirable element in smelting, was removed by the addition of iron to the charge. The sample was smelted with fluxes and lead oxide to replace the silver and gold by lead and to transfer non-precious elements to slag. Lead was separated from precious metals by cupellation. The separated silver and gold alloy was dissolved with aqua regia with addition of hydrochloric acid in excess. Silver and gold were determined from the same solution. For determination of the silver content, the AAS method with an air-acetylene flame was used. Gold was determined in a graphite furnace with the addition of a matrix modifier in an argon current, at an atomization temperature of t = 2200°C. The lower determination limit for silver was 0.05 g/t and for gold 0.005 g/t. The results of the analysis for silver and gold obtained with the proposed method showed good agreement with the results of the analysis of the same samples with the fire assay method.

  4. Alternative Plasmonic Materials: Beyond Gold and Silver

    DEFF Research Database (Denmark)

    Naik, Gururaj V.; Shalaev, Vladimir M.; Boltasseva, Alexandra

    2013-01-01

    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...... conducting oxides, perovskite oxides, metal nitrides, silicides, germanides, and 2D materials such as graphene. This review provides a summary of the recent developments in the search for better plasmonic materials and an outlook of further research directions....

  5. Bioprospective of Sorbus aucuparia leaf extract in development of silver and gold nanocolloids.

    Science.gov (United States)

    Dubey, Shashi Prabha; Lahtinen, Manu; Särkkä, Heikki; Sillanpää, Mika

    2010-10-01

    At the present time the bioprospective field is a dynamic area of research. The rapid biosynthesis of silver and gold nanoparticles without using toxic chemicals is reported here. Sorbus aucuparia is omnipresent in Europe. The aqueous leaves extract of the plant were used as reducing agent for the synthesis of silver and gold nanoparticles from their salt solutions. The synthesized nanoparticles were spherical, triangular and hexagonal in shape with an average size of 16 and 18nm for silver and gold, respectively. Different extract quantities, metal concentrations, temperatures and contact times were investigated to find their effect on nanoparticles synthesis. The resulting silver and gold nanoparticles were characterized by transmission electron microscopy (TEM), UV-vis spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR). The concentration of residual silver and gold ions was measured by Inductively Coupled Plasma (ICP) spectroscopy. Silver and gold nanoparticle suspensions gave maximum UV-vis absorbance at 446 and 560nm, respectively. The XRD data illustrated characteristic diffraction patterns of the elemental silver and gold phases and the average size of the crystallites were estimated from the peak profiles by Scherrer method. FTIR spectra of the leaf extract before and after the development of nanoparticles were determined to allow identification of possible functional groups responsible for the conversion of metal ions to metal nanoparticles.

  6. Evolution, dissolution and reversible generation of gold and silver ...

    Indian Academy of Sciences (India)

    Unknown

    In this brief communication, we have highlighted for the first time the in situ preparation, dissolution and reversible generation of gold and silver nanoparticles from their cyano complexes by the UV-light. Here we have exhibited the preparation of gold and silver nanoparticles by UV- photoactivation method and then their ...

  7. Characterization and antimicrobial application of biosynthesized gold and silver nanoparticles by using Microbacterium resistens.

    Science.gov (United States)

    Wang, Chao; Singh, Priyanka; Kim, Yeon Ju; Mathiyalagan, Ramya; Myagmarjav, Davaajargal; Wang, Dandan; Jin, Chi-Gyu; Yang, Deok Chun

    2016-11-01

    Various microorganisms were found to be cable of synthesizing gold and silver nanoparticles when gold and silver salts were supplied in the reaction system. The main objective of this study was to evaluate the extracellular synthesis of gold and silver nanoparticles by the type strain Microbacterium resistens(T) [KACC14505]. The biosynthesized gold and silver nanoparticles were characterized by ultraviolet-visible spectroscopy (UV-Vis), field emission transmission electron micrograph (FE-TEM), energy dispersive X-ray spectroscopy (EDX), elemental mapping, and dynamic light scattering (DLS). Moreover, the nanoparticles were evaluated for antimicrobial potential against various pathogenic microorganisms such as Vibrio parahaemolyticus [ATCC 33844], Salmonella enterica [ATCC 13076], Staphylococcus aureus [ATCC 6538], Bacillus anthracis [NCTC 10340], Bacillus cereus [ATCC 14579], Escherichia coli [ATCC 10798], and Candida albicans [KACC 30062]. The silver nanoparticles were found as a potent antimicrobial agent whereas gold nanoparticles not showed any ability. Therefore, the current study describes the simple, green, and extracellular synthesis of gold and silver nanoparticles by the type strain Microbacterium resistens(T) [KACC14505].

  8. Recovery of Silver and Gold from Copper Anode Slimes

    Science.gov (United States)

    Chen, Ailiang; Peng, Zhiwei; Hwang, Jiann-Yang; Ma, Yutian; Liu, Xuheng; Chen, Xingyu

    2015-02-01

    Copper anode slimes, produced from copper electrolytic refining, are important industrial by-products containing several valuable metals, particularly silver and gold. This article provides a comprehensive overview of the development of the extraction processes for recovering silver and gold from conventional copper anode slimes. Existing processes, namely pyrometallurgical processes, hydrometallurgical processes, and hybrid processes involving the combination of pyrometallurgical and hydrometallurgical technologies, are discussed based in part on a review of the form and characteristics of silver and gold in copper anode slimes. The recovery of silver and gold in pyrometallurgical processes is influenced in part by the slag and matte/metal chemistry and related characteristics, whereas the extraction of these metals in hydrometallurgical processes depends on the leaching reagents used to break the structure of the silver- and gold-bearing phases, such as selenides. By taking advantage of both pyrometallurgical and hydrometallurgical techniques, high extraction yields of silver and gold can be obtained using such combined approaches that appear promising for efficient extraction of silver and gold from copper anode slimes.

  9. Biosynthesis of Silver and Gold Crystals Using Grapefruit Extract

    Directory of Open Access Journals (Sweden)

    Chen Long

    2016-01-01

    crystals is discussed, indicating that the soluble biomolecules such as protein(s and vitamin C in grapefruit extract may play a crucial role in defining the morphology and/or crystal phase of silver and gold crystals.

  10. Special Issue: Coinage Metal (Copper, Silver, and Gold Catalysis

    Directory of Open Access Journals (Sweden)

    Sónia Alexandra Correia Carabineiro

    2016-06-01

    Full Text Available The subject of catalysis by coinage metals (copper, silver, and gold comes up increasingly day-by-day. This Special Issue aims to cover the numerous aspects of the use of these metals as catalysts for several reactions. It deals with synthesis and characterization of copper, silver and gold based catalysis, their characterization and use, both for heterogeneous and homogeneous catalysis, and some of their potential applications.

  11. Special Issue: Coinage Metal (Copper, Silver, and Gold) Catalysis

    OpenAIRE

    Sónia Alexandra Correia Carabineiro

    2016-01-01

    The subject of catalysis by coinage metals (copper, silver, and gold) comes up increasingly day-by-day. This Special Issue aims to cover the numerous aspects of the use of these metals as catalysts for several reactions. It deals with synthesis and characterization of copper, silver and gold based catalysis, their characterization and use, both for heterogeneous and homogeneous catalysis, and some of their potential applications.

  12. Special Issue: Coinage Metal (Copper, Silver, and Gold) Catalysis.

    Science.gov (United States)

    Carabineiro, Sónia Alexandra Correia

    2016-06-08

    The subject of catalysis by coinage metals (copper, silver, and gold) comes up increasingly day-by-day. This Special Issue aims to cover the numerous aspects of the use of these metals as catalysts for several reactions. It deals with synthesis and characterization of copper, silver and gold based catalysis, their characterization and use, both for heterogeneous and homogeneous catalysis, and some of their potential applications.

  13. Biosynthesis and Application of Silver and Gold Nanoparticles

    OpenAIRE

    Sadowski, Zygmunt

    2010-01-01

    A green chemistry synthetic route has been used for both silver and gold nanoparticles synthesis. The reaction occurred at ambient temperature. Among the nanoparticles biological organism, some microorganisms such as bacteria, fungi, and yeast have been exploited for nanoparticles synthesis. Several plant biomass or plant extracts have been successfully used for extracellular biosynthesis of silver and gold nanoparticles. Analytical techniques, such as ultraviolet-visible spectroscopy (UV-vis...

  14. A strategic approach for rapid synthesis of gold and silver nanoparticles by Panax ginseng leaves.

    Science.gov (United States)

    Singh, Priyanka; Kim, Yeon Ju; Yang, Deok Chun

    2016-12-01

    The study highlights the synthesis of gold nanoparticles and silver nanoparticles by fresh leaves of Panax ginseng, an herbal medicinal plant. The reduction of auric chloride and silver nitrate led to the formation of gold and silver nanoparticles within 3 and 45 min, at 80°C, respectively. The developed methodology was rapid, facile, ecofriendly and the utmost significant is quite economical, which did not require subsequent processing for reduction or stabilization of nanoparticles. The nanoparticles were further characterized by Ultraviolet-visible spectroscopy (UV-vis) which showed the relevant peak for gold and silver nanoparticles at 578 and 420 nm, correspondingly. Field-emission transmission electron microscopy (FE-TEM) displayed the spherical shape of monodispersed nanoparticles. FE-TEM revealed that the gold nanoparticles were 10-20 nm and silver nanoparticles were 5-15 nm. The energy dispersive X-ray (EDX) and elemental mapping results indicated the maximum distribution of gold and silver elements in the respective nanoproducts, which further corresponds the purity. Further, the X-ray diffraction (XRD) results confirm the crystalline nature of synthesized nanoparticles. The biosynthesized AgNPs served as an efficient antimicrobial agent at 3 μg concentration against many pathogenic strains for instance, Escherichia coli, Salmonella enterica, Vibrio parahaemolyticus, Staphylococcus aureus, Bacillus anthracis and Bacillus cereus. In addition, AgNPs showed complete inhibition of biofilm formation by S. aureus and Pseudomonas aeruginosa at 4 μg/ml concentration. Moreover, the AuNPs and AgNPs found as a potent anticoagulant agent. Thus, the study claims the rapid synthesis of gold and silver nanoparticles by fresh P. ginseng leaf extract and its biological applications.

  15. Bismuth-silver mineralization in the Sergozerskoe gold occurrence

    Directory of Open Access Journals (Sweden)

    Kalinin A. A.

    2017-03-01

    Full Text Available Bismuth-silver mineralization attendant to gold mineralization in the Sergozerskoe gold occurrence has been studied in detail. Bi-Ag mineralization is connected with diorite porphyry dykes, which cut volcanic-sedimentary Lopian complexes of the Strel'ninsky greenstone belt – hornblendite and actinolite-chlorite amphibolites, biotite and bi-micaceous gneisses. Distribution of Bi-Ag mineralization similar to gold mineralization is controlled by 80 m thick zone of silicification. Bi minerals are found in brecciated diorite porphyry. Bismuth-silver mineralization includes native metals (bismuth, electrum, silver, tellurides (hedleyite, hessite, selenides (ikunolite, sulfides and sulfosalts of Bi and Ag (matildite, lillianite, eckerite, jalpaite, prustite, acanthite, a few undiagnosed minerals. All Bi and Ag minerals associate with galena. Composition of mineralization evolved from early to late stages of development, depending on intensity of rock alteration. The earliest Bi-Ag minerals were native bismuth and hedleyite formed dissemination in galena, and electrum with 30-45 mass.% Au. Later native bismuth was partly substituted by silver and bismuth sulfosalts and bismuth sulfides. The latest minerals were low-temperature silver sulfides eckerite, jalpaite, and acanthite, which were noted only in the most intensively altered rocks. As soon as the process of formation of Bi-Ag mineralization is the same as formation of gold, findings of bismuth-silver mineralization can serve as a positive exploration sign for gold in the region.

  16. Gold and silver/Si nanocomposite layers

    Energy Technology Data Exchange (ETDEWEB)

    Kleps, Irina [National Institute for Research and Development in Microtechnologies (IMT-Bucharest), P.O. Box 38-160, Bucharest (Romania)], E-mail: irinak@imt.ro; Danila, Mihai; Angelescu, Anca; Miu, Mihaela; Simion, Monica; Ignat, Teodora; Bragaru, Adina [National Institute for Research and Development in Microtechnologies (IMT-Bucharest), P.O. Box 38-160, Bucharest (Romania); Dumitru, Lucia; Teodosiu, Gabriela [Institute of Biology, 296 Splaiul Independentei, P.O. Box 56-53, Bucharest, 060031 (Romania)], E-mail: biologie@ibiol.ro

    2007-09-15

    Ag and Au nanolayers were realised by physical and chemical deposition methods on porous silicon (PS) nanostructured surfaces for biomedical applications: support for living cells, biodegradable material for the slow release of drugs/minerals, and as a bioactive material for scaffolds. Au nanoparticles on nanocrystalline Si are widely used in increasing substrate biocompatibility properties. It has an electrochemical potential of + 0.332 mV and surface energy around 25 erg/cm{sup 2}, close to those of living tissues. The Au nanocrystallites orientation on nanocrystalline Si substrates is also of great interest for application in biochemistry; the Au (111)/nc-Si surface has a higher density of atoms compared with Au (100); this favours the attachment of a higher number of atoms and bio-molecules on the gold surface. Ag nanoparticles on nanocrystalline Si are important for the latter's anti-microbial properties. In minute concentrations, Ag is highly toxic to germs while relatively non-toxic to human cells. Microbes are unlikely to develop a resistance against silver, as they do against conventional and highly targeted antibiotics. The Au and Ag nanoparticles/silicon nanocomposite layers as-deposited and thermally treated were investigated by optical microscopy, X-ray diffraction, and biological tests using eukaryotic and prokaryotic cell cultures. The experimental results sustain the use of Au/Si and Ag/Si or combined Ag/Au/Si nanocomposite structures as biocompatible and anti-microbial matrix.

  17. Alternative plasmonic materials: beyond gold and silver.

    Science.gov (United States)

    Naik, Gururaj V; Shalaev, Vladimir M; Boltasseva, Alexandra

    2013-06-25

    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 in plasmonics and metamaterials lacks good material building blocks in order to realize useful devices. Such devices suffer from many drawbacks arising from the undesirable properties of their material building blocks, especially metals. There are many materials, other than conventional metallic components 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 conducting oxides, perovskite oxides, metal nitrides, silicides, germanides, and 2D materials such as graphene. This review provides a summary of the recent developments in the search for better plasmonic materials and an outlook of further research directions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Extracellular synthesis of silver and gold nanoparticles by Sporosarcina koreensis DC4 and their biological applications.

    Science.gov (United States)

    Singh, Priyanka; Singh, Hina; Kim, Yeon Ju; Mathiyalagan, Ramya; Wang, Chao; Yang, Deok Chun

    2016-05-01

    The present study highlights the microbial synthesis of silver and gold nanoparticles by Sporosarcina koreensis DC4 strain, in an efficient way. The synthesized nanoparticles were characterized by ultraviolet-visible spectrophotometry, which displayed maximum absorbance at 424nm and 531nm for silver and gold nanoparticles, respectively. The spherical shape of nanoparticles was characterized by field emission transmission electron microscopy. The energy dispersive X-ray spectroscopy and elemental mapping were displayed the purity and maximum elemental distribution of silver and gold elements in the respective nanoproducts. The X-ray diffraction spectroscopy results demonstrate the crystalline nature of synthesized nanoparticles. The particle size analysis demonstrate the nanoparticles distribution with respect to intensity, volume and number of nanoparticles. For biological applications, the silver nanoparticles have been explored in terms of MIC and MBC against pathogenic microorganisms such as Vibrio parahaemolyticus, Escherichia coli, Salmonella enterica, Bacillus anthracis, Bacillus cereus and Staphylococcus aureus. Moreover, the silver nanoparticles in combination with commercial antibiotics, such as vancomycin, rifampicin, oleandomycin, penicillin G, novobiocin, and lincomycin have been explored for the enhancement of antibacterial activity and the obtained results showed that 3μg concentration of silver nanoparticles sufficiently enhance the antimicrobial efficacy of commercial antibiotics against pathogenic microorganism. Furthermore, the silver nanoparticles potential has been reconnoitered for the biofilm inhibition by S. aureus, Pseudomonas aeruginosa and E. coli and the results revealed sufficient activity at 6μg concentration. In addition, gold nanoparticles have been applied for catalytic activity, for the reduction of 4-nitrophenol to 4-aminophenol using sodium borohydride and positive results were attained. Copyright © 2016 Elsevier Inc. All

  19. Assisted laser ablation: silver/gold nanostructures coated with silica

    Science.gov (United States)

    González-Castillo, J. R.; Rodríguez-González, Eugenio; Jiménez-Villar, Ernesto; Cesar, Carlos Lenz; Andrade-Arvizu, Jacob Antonio

    2017-11-01

    The synthesis processes of metallic nanoparticles have seen a growing interest in recent years, mainly by the potential applications of the phenomenon of localized surface plasmon resonance associated with metallic nanoparticles. This paper shows a fast method to synthesize silver, gold and silver/gold alloy nanoparticles coated with a porous silica shell by the assisted laser ablation method in three steps. The method involves a redox chemical reaction where the reducing agent is supplied in nanometric form by laser ablation. In the first step, a silicon target immersed in water is ablated for several minutes. Later, AgNO3 and HAuCl4 aliquots are added to the solution. The redox reaction between the silver and gold ions and products resulting from ablation process can produce silver, gold or silver/gold alloy nanoparticles coated with a porous silica shell. The influence of the laser pulse energy, ablation time, Ag+ and Au3+ concentration, as well as the Ag+/Au3+ ratio, on optical and structural properties of the nanostructures was investigated. This work represents a step forward in the study of reaction mechanisms that take place during the synthesis of nanoscale materials by the assisted laser ablation technique.

  20. Assisted laser ablation: silver/gold nanostructures coated with silica

    Science.gov (United States)

    González-Castillo, J. R.; Rodríguez-González, Eugenio; Jiménez-Villar, Ernesto; Cesar, Carlos Lenz; Andrade-Arvizu, Jacob Antonio

    2017-09-01

    The synthesis processes of metallic nanoparticles have seen a growing interest in recent years, mainly by the potential applications of the phenomenon of localized surface plasmon resonance associated with metallic nanoparticles. This paper shows a fast method to synthesize silver, gold and silver/gold alloy nanoparticles coated with a porous silica shell by the assisted laser ablation method in three steps. The method involves a redox chemical reaction where the reducing agent is supplied in nanometric form by laser ablation. In the first step, a silicon target immersed in water is ablated for several minutes. Later, AgNO3 and HAuCl4 aliquots are added to the solution. The redox reaction between the silver and gold ions and products resulting from ablation process can produce silver, gold or silver/gold alloy nanoparticles coated with a porous silica shell. The influence of the laser pulse energy, ablation time, Ag+ and Au3+ concentration, as well as the Ag+/Au3+ ratio, on optical and structural properties of the nanostructures was investigated. This work represents a step forward in the study of reaction mechanisms that take place during the synthesis of nanoscale materials by the assisted laser ablation technique.

  1. Reusable magnetic nanobiocatalyst for synthesis of silver and gold nanoparticles.

    Science.gov (United States)

    Mazumder, Jahirul Ahmed; Ahmad, Razi; Sardar, Meryam

    2016-12-01

    In the present work, we describe a simple procedure for the biosynthesis of nanosilver and gold by the reduction of silver nitrate and auric chloride respectively using a nanobiocatalyst. The nanobiocatalyst was prepared by covalent coupling of alpha amylase on (3-aminopropyl)triethoxysilane (APTES) modified iron oxide magnetic nanoparticles. The nanobiocatalyst retains 77% of its activity as compared to free alpha amylase. The nanobiocatalyst can be used up to three consecutive cycles for the synthesis of nano silver and gold. The biosynthesized nanoparticles after each cycle were characterized by UV-vis spectrophotometer, Dynamic Light Spectroscopy (DLS), Transmission Electron Microscope (TEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Silver and gold nanoparticles of same morphology and dimensions were formed in each cycle. The procedure for synthesis of nanoparticles using an immobilized enzyme is eco-friendly and can be used repeatedly. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Biogenic synthesis of gold and silver nanoparticles by seed plants.

    Science.gov (United States)

    Iyer, R Indira; Panda, Tapobrata

    2014-02-01

    Nanoparticles have an enormous range of biomedical and environmental applications and can be used for development of various nanodevices for diagnostics and drug delivery. Biogenic production of nanoparticles, that is of silver and gold, by seed plants, especially flowering plants, has evoked considerable interest in the last decade. Different organs of plants as well as callus cultures have been used for the production of these metal nanoparticles. It is possible to regulate the geometry of the nanoparticles by modifying the experimental parameters. In many cases the phytosynthesized gold and silver nanoparticles have been demonstrated to be potentially useful for treatment of various diseases. The production of gold and silver nanoparticles by diverse species of seed plants and their biological activity are discussed in this article.

  3. Biosynthesis of silver and gold nanoparticles using Brevibacterium casei.

    Science.gov (United States)

    Kalishwaralal, Kalimuthu; Deepak, Venkataraman; Ram Kumar Pandian, SureshBabu; Kottaisamy, Muniasamy; BarathmaniKanth, Selvaraj; Kartikeyan, Bose; Gurunathan, Sangiliyandi

    2010-06-01

    The present study demonstrates an unprecedented green process for the production of spherical-shaped Au and Ag nanoparticles synthesized and stabilized using a bacterium, Brevibacterium casei. Aqueous solutions of chloroaurate ions for Au and Ag(+) ions for silver were treated with B. casei biomass for the formation of Au nanoparticles (AuNP) and Ag nanoparticles (AgNP). The nanometallic dispersions were characterized by surface plasmon absorbance measuring at 420 and 540 nm for Ag and Au nanoparticles, respectively. Transmission electron microscopy showed the formation of nanoparticles in the range of 10-50 nm (silver), and 10-50 nm (gold). XRD analysis of the silver and gold nanoparticles confirmed the formation of metallic silver and gold. Further analysis carried out by Fourier Transform Infrared Spectroscopy (FTIR), provides evidence for the presence of proteins as possible biomolecules responsible for the reduction and capping agent which helps in increasing the stability of the synthesized silver and gold nanoparticles. The biological activities of the synthesized particles were confirmed based on their stable anti-coagulant effects. The use of bacterium for nanoparticles synthesis offers the benefits of ecofriendliness and amenability for large-scale production. Copyright 2010 Elsevier B.V. All rights reserved.

  4. Investigating the Relationship between Gold and Silver Prices

    OpenAIRE

    Escribano, Álvaro; C.w.j. Granger

    1998-01-01

    This paper analyses the long-run relationship between gold and silver prices. The three main questions addressed are: the influence of a large bubble from 1979:9 to 1980:3 on the cointegration relationship, the extent to which by including error-correction terms in a non-linear way we can beat the random walk model out-of-sample, and the existence of a strong simultaneous relationship between the rates of return of gold and silver. Different efficient single-equation estimation techniques are...

  5. Silver and gold nanocluster catalyzed reduction of methylene blue ...

    Indian Academy of Sciences (India)

    Unknown

    nanoparticles in micellar medium. The arsine has been generated in situ from sodium arsenate ... trolled use of arsenic containing pesticides, paints and pigments etc. Keeping an eye on this grave situation of ... levels using micelle catalyzed reaction (Pal et al 1998). The participation of silver or gold nanoparticle as catalyst.

  6. Comparative study of synthesized silver and gold nanoparticles ...

    Indian Academy of Sciences (India)

    Abstract. Nanotechnology is an emerging field in science and technology, which can be applied to synthesize new materials at the nanoscale level. The present investigation aimed at comparing the synthesis, characterization and in vitro anticancer efficacy of synthesized silver and gold nanoparticles using leaves extract of ...

  7. PMAA`s Silver/Gold National Certification Program - update

    Energy Technology Data Exchange (ETDEWEB)

    Boltz, R. [Vincent R. Boltz, Inc., Lebanon, PA (United States)

    1996-07-01

    The Petroleum Marketers Association of America`s (PMAA) Silver/Gold National Certification Program is discussed. The oil heat technician certification is a process whose time has come. The information age has put us in an era of improved technology as well as improved equipment. The advantages of the oil heat certification program for oil heat dealers, technicians, and customers are listed.

  8. Comparative study of synthesized silver and gold nanoparticles ...

    Indian Academy of Sciences (India)

    Nanotechnology is an emerging field in science and technology, which can be applied to synthesize new materials at the nanoscale level. The present investigation aimed at comparing the synthesis, characterization andin vitro anticancer efficacy of synthesized silver and gold nanoparticles using leaves extract of Bauhinia ...

  9. Electroplating Gold-Silver Alloys for Spherical Capsules for NIF Double-Shell Targets

    Energy Technology Data Exchange (ETDEWEB)

    Bhandarkar, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Horwood, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bunn, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Stadermann, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-08-17

    For Inertial Confinement Fusion (ICF) implosions, a design based on gradients of high and mid Z materials could potentially be more robust than single element capsule systems. To that end, gold and silver alloys were electroplated on 2.0 mm diameter surrogate brass spheres using a new flow–based pulsed plating method specifically designed to minimize surface roughness without reducing plating rates. The coatings were analyzed by scanning electron microscope (SEM) and white light interferometry for surface topography, and by energy dispersive x-ray spectroscopy (EDX) to determine near-surface gold and silver compositions. The alloy range attainable was 15 to 85 weight percent gold using 1:1 and 1:3 silver to gold ratio plating baths at applied potentials of -0.7 volts to -1.8 volts. This range was bounded by the open circuit potential of the system and hydrogen evolution, and in theory could be extended by using ionic liquids or aprotic solutions. Preliminary gradient trials proved constant composition alloy data could be translated to smooth gradient plating, albeit at higher gold compositions.

  10. Synthesis of gold nanoparticles and silver nanoparticles via green technology

    Science.gov (United States)

    Ahmed, Zulfiqaar; Balu, S. S.

    2012-11-01

    The proposed work describes the comparison of various methods of green synthesis for preparation of Gold and Silver nanoparticles. Pure extracts of Lemon (Citrus limon) and Tomato (Solanum lycopersicum) were mixed with aqueous solution of auric tetrachloride and silver nitrate. The resultant solutions were treated with four common techniques to assist in the reduction namely photo catalytic, thermal, microwave assisted reduction and solvo - thermal reduction. UV - Visible Spectroscopy results and STM images of the final solutions confirmed the formation of stable metallic nanoparticles. A preliminary account of the green synthesis work is presented here.

  11. Leaching of gold, silver and accompanying metals from circuit boards (PCBs waste

    Directory of Open Access Journals (Sweden)

    Jana Ficeriová

    2011-12-01

    Full Text Available Au-Ag noble metal wastes represent a wide range of waste types and forms, with various accompanying metallic elements.The presented leaching strategy for Au-Ag contained in circuit boards (PCBs aims at gaining gold and silver in the metallic form.Application of the proposed ammonium thiosulphate leaching process for the treatment of the above mentioned Au-Ag containing wastesrepresents a practical, economic and at the same time an ecological solution. The ammonium thiosulphate based leaching of gold and silverfrom PCBs waste, using crushing as a pretreatment, was investigated. It was possible to achieve 98 % gold and 93 % silver recovery within48 hours of ammonium thiosulphate leaching. This type of leaching is a better leaching procedure for recovery of gold and silver from PCBwaste than the classical toxic cyanide leaching. 84 % Cu, 82 % Fe, 77 % Al, 76 % Zn, 70 % Ni, 90 % Pd, 88 % Pb and 83 % Sn recovery ofthe accompanying metals was achieved, using sulphuric acid with hydrogen peroxide, sodium chloride and aqua regia. A four steps leachingprocess gave a very satisfactory yield and a more rapid kinetics for all observed metals solubilization than other technologies.

  12. Silver and gold enhancement methods for lateral flow immunoassays.

    Science.gov (United States)

    Rodríguez, Myriam Oliveira; Covián, Lucía Blanco; García, Agustín Costa; Blanco-López, Maria Carmen

    2016-01-01

    Sensitivity is the main concern at the development of rapid test by lateral flow immunoassays. On the other hand, low limits of detection are often required at medical diagnostics and other field of analysis. To overcome this drawback, several enhancement protocols have been described. In this paper, we have selected different silver enhancement methods and one dual gold conjugation, and we critically compared the amplification produced when applied to a gold-nanoparticle based lateral flow immunoassay for the detection of prostate specific antigen (PSA). The highest amplification was obtained by using an immersion method based on a solution of silver nitrate and hydroquinone/citrate buffer in proportion 1:1. Under these conditions, the system is capable of detecting PSA within 20 min at levels as low as 0.1 ng/mL, with a 3-fold sensitivity improvement. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Gold and silver nanoparticles from Trianthema decandra: synthesis, characterization, and antimicrobial properties

    Science.gov (United States)

    Geethalakshmi, R; Sarada, DVL

    2012-01-01

    Background There is an increasing commercial demand for nanoparticles due to their wide applicability in various markets, including medicine, catalysis, electronics, chemistry, and energy. In this report, a simple and ecofriendly chemical reaction for the synthesis of gold and silver nanoparticles from Trianthema decandra (Aizoaceae) has been developed. Methods and results On treatment of aqueous solutions containing chloroauric acid or silver nitrate with root extract of T. decandra, stable gold or silver nanoparticles were rapidly formed. The kinetics of reduction of gold and silver ions during the reaction was analyzed by ultraviolet-visible spectroscopy. Field emission-scanning electron microscopy showed formation of gold nanoparticles in various shapes, including spherical, cubical, triangular, and hexagonal, while silver nanoparticles were spherical. The size of the gold nanoparticles was 33–65 nm and that of the silver nanoparticles was 36–74 nm. Energy dispersive x-ray and Fourier transform infrared spectroscopy confirmed the presence of metallic gold and metallic silver in the respective nanoparticles. The antimicrobial properties of the synthesized nanoparticles were analyzed using the Kirby-Bauer method. The results show varied susceptibility of microorganisms to the gold and silver nanoparticles. Conclusion It is believed that phytochemicals present in T. decandra extract reduce the silver and gold ions into metallic nanoparticles. This strategy reduces the cost of production and the environmental impact. The silver and gold nanoparticles formed showed strong activity against all microorganisms tested. PMID:23091381

  14. Gold and silver nanoparticles from Trianthema decandra: synthesis, characterization, and antimicrobial properties.

    Science.gov (United States)

    Geethalakshmi, R; Sarada, D V L

    2012-01-01

    There is an increasing commercial demand for nanoparticles due to their wide applicability in various markets, including medicine, catalysis, electronics, chemistry, and energy. In this report, a simple and ecofriendly chemical reaction for the synthesis of gold and silver nanoparticles from Trianthema decandra (Aizoaceae) has been developed. On treatment of aqueous solutions containing chloroauric acid or silver nitrate with root extract of T. decandra, stable gold or silver nanoparticles were rapidly formed. The kinetics of reduction of gold and silver ions during the reaction was analyzed by ultraviolet-visible spectroscopy. Field emission-scanning electron microscopy showed formation of gold nanoparticles in various shapes, including spherical, cubical, triangular, and hexagonal, while silver nanoparticles were spherical. The size of the gold nanoparticles was 33-65 nm and that of the silver nanoparticles was 36-74 nm. Energy dispersive x-ray and Fourier transform infrared spectroscopy confirmed the presence of metallic gold and metallic silver in the respective nanoparticles. The antimicrobial properties of the synthesized nanoparticles were analyzed using the Kirby-Bauer method. The results show varied susceptibility of microorganisms to the gold and silver nanoparticles. It is believed that phytochemicals present in T. decandra extract reduce the silver and gold ions into metallic nanoparticles. This strategy reduces the cost of production and the environmental impact. The silver and gold nanoparticles formed showed strong activity against all microorganisms tested.

  15. Silver and Gold Nanoparticles Alter Cathepsin Activity In vitro

    Science.gov (United States)

    Speshock, Janice L.; Braydich-Stolle, Laura K.; Szymanski, Eric R.; Hussain, Saber M.

    2011-12-01

    Nanomaterials are being incorporated into many biological applications for use as therapeutics, sensors, or labels. Silver nanomaterials are being utilized for biological implants and wound dressings as an antiviral material, whereas gold nanomaterials are being used as biological labels or sensors due to their surface properties and biocompatibility. Cytotoxicity data of these materials are becoming more prevalent; however, little research has been performed to understand how the introduction of these materials into cells affects cellular processes. Here, we demonstrate the impact that silver and gold nanoparticles have on cathepsin activity in vitro. Cathepsins are important cellular proteases that are imperative for proper immune system function. We have selected to examine gold and silver nanoparticles due to the increased use of these materials in biological applications. This manuscript depicts how both of these types of nanomaterials affect cathepsin activity, which could impact the host's immune system and its ability to respond to pathogens. Cathepsin B activity decreases in a dose-dependent manner with all nanoparticles tested. Alternatively, the impact of nanoparticles on cathepsin L activity depends greatly on the type and size of the material.

  16. Synthesis of large uniform gold and core-shell gold-silver nanoparticles: Effect of temperature control

    Science.gov (United States)

    Tiunov, I. A.; Gorbachevskyy, M. V.; Kopitsyn, D. S.; Kotelev, M. S.; Ivanov, E. V.; Vinokurov, V. A.; Novikov, A. A.

    2016-01-01

    The temperatures of nucleation and growth for gold and silver nanoparticles are quite close to each other in citrate-based seeded-growth synthesis. Hence, thorough temperature control during the synthesis of gold and gold-silver core-shell nanoparticles is expected to improve the yield of uniform non-aggregated nanoparticles suitable for selective contrasting of surface defects. Gold and gold-silver core-shell nanoparticles of size ranging from 20 to 160 nm were synthesized using various means of temperature control. The synthesized nanoparticles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and UV-Vis spectroscopy. Model nanocracks were milled on pipeline steel specimen by focused ion beam (FIB). It was found that to produce large uniform core-shell nanoparticles, thorough temperature control is required during formation of the gold seeds and the silver shell. Moreover, the synthesized nanoparticles were used for selective contrasting of defects on metal surface.

  17. Green Synthesis of Gold and Silver Nanoparticles Using Averrhoa bilimbi Fruit Extract

    OpenAIRE

    Rimal Isaac, R. S.; Sakthivel, G.; Ch. Murthy

    2013-01-01

    We report on rapid one-step green synthesis of gold and silver nanoparticles using fruit extract of Averrhoa bilimbi Linn. UV-Vis absorption spectroscopy was used to monitor the quantitative formation of gold and silver nanoparticles. The characteristics of the obtained gold and silver nanoparticles were studied using UV-Vis absorption spectroscopy (UV/Vis), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Energy-dispersive spectroscopy (EDX). UV/Vis spe...

  18. RECOVERY OF GOLD (Au) AND SILVER (Ag) METALS IN THE ELECTRONIC WASTE THROUGH MULTILEVEL PRECIPITATION PROCESS

    OpenAIRE

    Siti Marwati; Regina Tutik Padmaningrum; Sunarto Sunarto

    2016-01-01

    This research aims to determine the percent recovery of gold (Au) and silver (Ag) in the electronic waste such as CD-RW and determine the purity of gold and silver metals in the electronic waste such as CD-RW that through multilevel precipitation process. The first step was the optimization of the concentration of thiourea and time dissolution of gold and silver in the sample. The concentration of thiourea and the time dissolution optimum obtained from conentration of gold and silver maximum....

  19. Quantum plasmonics: longitudinal quantum plasmons in copper, gold, and silver

    Science.gov (United States)

    Moaied, M.; Palomba, S.; Ostrikov, K.

    2017-10-01

    The propagation of plasmonic waves in various metallic quantum nanostructures has received considerable attention for its applications in technology. The quantum plasmonic properties of metallic nanostructures in the quantum size regime have been difficult to describe using an appropriate model. Here nonlocal quantum plasmons are investigated in the most important metals of copper, gold, and silver. The dispersion properties of these metals and the propagation of longitudinal quantum plasmons in the high photon energy regime are studied using a new model of nonlocal quantum dielectric permittivity. The epsilon-near-zero properties are investigated and the spectrum and the damping rate of the longitudinal quantum plasmons are obtained in these metals. The quantum plasmons’ wave function is shown for both the classical and quantum limits. It is shown that silver is the most appropriate for quantum metallic structures in the development of next-generation quantum optical and sensing technologies, due to its low intrinsic loss.

  20. Gold and silver nanoparticles for biomolecule immobilization and enzymatic catalysis

    Science.gov (United States)

    Petkova, Galina A.; Záruba, Кamil; Žvátora, Pavel; Král, Vladimír

    2012-06-01

    In this work, a simple method for alcohol synthesis with high enantiomeric purity was proposed. For this, colloidal gold and silver surface modifications with 3-mercaptopropanoic acid and cysteamine were used to generate carboxyl and amine functionalized gold and silver nanoparticles of 15 and 45 nm, respectively. Alcohol dehydrogenase from Thermoanaerobium brockii (TbADH) and its cofactor (NADPH) were physical and covalent (through direct adsorption and using cross-linker) immobilized on nanoparticles' surface. In contrast to the physical and covalent immobilizations that led to a loss of 90% of the initial enzyme activity and 98% immobilization, the use of a cross-linker in immobilization process promoted a loss to 30% of the initial enzyme activity and >92% immobilization. The yield of NADPH immobilization was about 80%. The best results in terms of activity were obtained with Ag-citr nanoparticle functionalized with carboxyl groups (Ag-COOH), Au-COOH(CTAB), and Au-citr functionalized with amine groups and stabilized with CTAB (Au-NH2(CTAB)) nanoparticles treated with 0.7% and 1.0% glutaraldehyde. Enzyme conformation upon immobilization was studied using fluorescence and circular dichroism spectroscopies. Shift in ellipticity at 222 nm with about 4 to 7 nm and significant decreasing in fluorescence emission for all bioconjugates were observed by binding of TbADH to silver/gold nanoparticles. Emission redshifting of 5 nm only for Ag-COOH-TbADH bioconjugate demonstrated change in the microenvironment of TbADH. Enzyme immobilization on glutaraldehyde-treated Au-NH2(CTAB) nanoparticles promotes an additional stabilization preserving about 50% of enzyme activity after 15 days storage. Nanoparticles attached-TbADH-NADPH systems were used for enantioselective ( ee > 99%) synthesis of ( S)-7-hydroxy-2-tetralol.

  1. Antibacterial nanocarriers of resveratrol with gold and silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sohyun [College of Pharmacy, Inje University, 197 Inje-ro Gimhae, Gyeongnam 621-749 (Korea, Republic of); Cha, Song-Hyun [National Creative Research Initiatives (NCRI) Center for Isogeometric Optimal Design, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Cho, Inyoung [School of Civil, Environmental and Architecture Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 136-701 (Korea, Republic of); Park, Soomin [National Creative Research Initiatives (NCRI) Center for Isogeometric Optimal Design, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Park, Yohan [College of Pharmacy, Inje University, 197 Inje-ro Gimhae, Gyeongnam 621-749 (Korea, Republic of); Cho, Seonho [National Creative Research Initiatives (NCRI) Center for Isogeometric Optimal Design, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Park, Youmie, E-mail: youmiep@inje.ac.kr [College of Pharmacy, Inje University, 197 Inje-ro Gimhae, Gyeongnam 621-749 (Korea, Republic of); National Creative Research Initiatives (NCRI) Center for Isogeometric Optimal Design, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744 (Korea, Republic of)

    2016-01-01

    This study focused on the preparation of resveratrol nanocarrier systems and the evaluation of their in vitro antibacterial activities. Gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) for resveratrol nanocarrier systems were synthesized using green synthetic routes. During the synthesis steps, resveratrol was utilized as a reducing agent to chemically reduce gold and silver ions to AuNPs and AgNPs. This system provides green and eco-friendly synthesis routes that do not involve additional chemical reducing agents. Resveratrol nanocarriers with AuNPs (Res-AuNPs) and AgNPs (Res-AgNPs) were observed to be spherical and to exhibit characteristic surface plasmon resonance at 547 nm and at 412–417 nm, respectively. The mean size of the nanoparticles ranged from 8.32 to 21.84 nm, as determined by high-resolution transmission electron microscopy. The face-centered cubic structure of the Res-AuNPs was confirmed by high-resolution X-ray diffraction. Fourier-transform infrared spectra indicated that the hydroxyl groups and C=C in the aromatic ring of resveratrol were involved in the reduction reaction. Res-AuNPs retained excellent colloidal stability during ultracentrifugation and re-dispersion, suggesting that resveratrol also played a role as a capping agent. Zeta potentials of Res-AuNPs and Res-AgNPs were in the range of − 20.58 to − 48.54 mV. Generally, against Gram-positive and Gram-negative bacteria, the Res-AuNPs and Res-AgNPs exhibited greater antibacterial activity compared to that of resveratrol alone. Among the tested strains, the highest antibacterial activity of the Res-AuNPs was observed against Streptococcus pneumoniae. The addition of sodium dodecyl sulfate during the synthesis of Res-AgNPs slightly increased their antibacterial activity. These results suggest that the newly developed resveratrol nanocarrier systems with metallic nanoparticles show potential for application as nano-antibacterial agents with enhanced activities. - Highlights

  2. The Controversial Orientation of Adenine on Gold and Silver.

    Science.gov (United States)

    Harroun, Scott G

    2018-01-22

    In which orientation does adenine adsorb on gold and silver surfaces? This question has been a matter of debate for over 30 years. Since the dawn of surface-enhanced Raman spectroscopy (SERS), it and other techniques such as tip-enhanced Raman spectroscopy (TERS), surface-enhanced infrared absorption spectroscopy (SEIRAS), scanning tunneling microscopy (STM), density functional theory (DFT) simulations, and more, have been used in numerous attempts to answer this seemingly straightforward yet important question. Herein, the timeline and recent advances on this topic are explored, and the frequently contradictory findings are put into context and discussed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. High pressure melting curves of silver, gold and copper

    Directory of Open Access Journals (Sweden)

    Ho Khac Hieu

    2013-11-01

    Full Text Available In this work, based on the Lindemann's formula of melting and the pressure-dependent Grüneisen parameter, we have investigated the pressure effect on melting temperature of silver, gold and copper metals. The analytical expression of melting temperature as a function of volume compression has been derived. Our results are compared with available experimental data as well as with previous theoretical studies and the good and reasonable agreements are found. We also proposed the potential of this approach on predicting melting of copper at very high pressure.

  4. High pressure melting curves of silver, gold and copper

    Energy Technology Data Exchange (ETDEWEB)

    Hieu, Ho Khac, E-mail: hieuhk@duytan.edu.vn [Research and Development Center for Science and Technology, Duy Tan University, K7/25 Quang Trung, Danang (Viet Nam); Ha, Nguyen Ngoc [VNU-Hanoi University of Science, 334 Nguyen Trai, Hanoi (Viet Nam)

    2013-11-15

    In this work, based on the Lindemann's formula of melting and the pressure-dependent Grüneisen parameter, we have investigated the pressure effect on melting temperature of silver, gold and copper metals. The analytical expression of melting temperature as a function of volume compression has been derived. Our results are compared with available experimental data as well as with previous theoretical studies and the good and reasonable agreements are found. We also proposed the potential of this approach on predicting melting of copper at very high pressure.

  5. Synthesis of gold and silver nanoparticles using leaf extract of Perilla frutescens--a biogenic approach.

    Science.gov (United States)

    Basavegowda, Nagaraj; Lee, Yong Rok

    2014-06-01

    The present investigation demonstrates a rapid biogenic approach for the synthesis of gold and silver nanoparticles using biologically active and medicinal important Perilla frutescens leaf extract as a reducing and stabilizing agent under ambient conditions. Gold and silver nanoparticles were first synthesized from Perilla frutescens leaf extract which was used as a vegetable and in traditional medicines for a long time in Korea, Japan, and China. The nanoparticles obtained were characterized by UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Surface plasmon resonance spectra of gold and silver nanoparticles were obtained at 540 and 430 nm and triangular and spherical shape respectively. TEM studies showed that the particle sizes of gold and silver nanoparticles ranges -50 nm and -40 nm respectively. X-ray diffraction studies confirm that the biosynthesized nanoparticles were crystalline gold and silver. Fourier transform infra-red spectroscopy revealed that biomolecules were involved in the synthesis and capping of the nanoparticles produced. XRD and EDX confirmed the formation of gold and silver nanoparticles. This is a simple, efficient and rapid method to synthesize gold and silver nanoparticles at room temperature without use of toxic chemicals. Obtained gold and silver nanoparticles can be used in various biomedical and biotechnological applications.

  6. Laser ablation of silver and gold in liquid ammonia

    Science.gov (United States)

    Šmejkal, Petr; Pfleger, Jiří; Vlčková, Blanka

    2010-10-01

    Laser ablation of a silver (Ag) and/or gold (Au) target was performed in liquid ammonia (l-NH3) at 233 K using nanosecond laser pulses of 1064, 532 and 355 nm wavelengths. An “in situ” monitoring of the ablation process by UV/vis/NIR spectroscopy has shown the evolution of the surface plasmon extinction band of silver or gold nanoparticles and thus confirmed their formation. While sols of Au nanoparticles in l-NH3 are quite stable in air, those of Ag nanoparticles undergo oxidation to Ag(I) complexes with NH3 ligands. On the other hand, formation of solvated electrons, namely of the (e-)NH3 solvates, has not been unequivocally confirmed under the conditions of our laser ablation/nanoparticle fragmentation experiment, since only very weak vis/NIR spectral features of these solvates were observed with a low reproducibility. Reference experiments have shown that the well-known chemical production of these solvates is hindered by the presence of Ag and Au plates. Ag and Au targets can thus possibly act as electron scavengers in our ablation experiments.

  7. Thiourea leaching gold and silver from the printed circuit boards of waste mobile phones.

    Science.gov (United States)

    Jing-ying, Li; Xiu-li, Xu; Wen-quan, Liu

    2012-06-01

    The present communication deals with the leaching of gold and silver from the printed circuit boards (PCBs) of waste mobile phones using an effective and less hazardous system, i.e., a thiourea leaching process as an alternative to the conventional and toxic cyanide leaching of gold. The influence of particle size, thiourea and Fe(3+) concentrations and temperature on the leaching of gold and silver from waste mobile phones was investigated. Gold extraction was found to be enhanced in a PCBs particle size of 100 mesh with the solutions containing 24 g/L thiourea and Fe(3+) concentration of 0.6% under the room temperature. In this case, about 90% of gold and 50% of silver were leached by the reaction of 2h. The obtained data will be useful for the development of processes for the recycling of gold and silver from the PCBs of waste mobile phones. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Adiantum philippense L. Frond Assisted Rapid Green Synthesis of Gold and Silver Nanoparticles

    Directory of Open Access Journals (Sweden)

    Duhita G. Sant

    2013-01-01

    Full Text Available Development of an ecofriendly, reliable, and rapid process for synthesis of nanoparticles using biological system is an important bulge in nanotechnology. Antioxidant potential and medicinal value of Adiantum philippense L. fascinated us to utilize it for biosynthesis of gold and silver nanoparticles (AuNPs and AgNPs. The current paper reports utility of aqueous extract of A. philippense L. fronds for the green synthesis of AuNPs and AgNPs. Effect of various parameters on synthesis of nanoparticles was monitored by UV-Vis spectrometry. Optimum conditions for AuNPs synthesis were 1 : 1 proportion of original extract at pH 11 and 5 mM tetrachloroauric acid, whereas optimum conditions for AgNPs synthesis were 1 : 1 proportion of original extract at pH 12 and 9 mM silver nitrate. Characterization of nanoparticles was done by TEM, SAED, XRD, EDS, FTIR, and DLS analyses. The results revealed that AuNPs and AgNPs were anisotropic. Monocrystalline AuNPs and polycrystalline AgNPs measured 10 to 18 nm in size. EDS and XRD analyses confirmed the presence of elemental gold and silver. FTIR analysis revealed a possible binding of extract to AuNPs through –NH2 group and to AgNPs through C=C group. These nanoparticles stabilized by a biological capping agent could further be utilized for biomedical applications.

  9. Plectranthus amboinicus-mediated silver, gold, and silver-gold nanoparticles: phyto-synthetic, catalytic, and antibacterial studies

    Science.gov (United States)

    Purusottam Reddy, B.; Mallikarjuna, K.; Narasimha, G.; Park, Si-Hyun

    2017-08-01

    Bio-based green nanotechnology aims to characterize compounds from natural sources and establish efficient routes for the preparation of nontoxic materials that have applicability in biodegradable and biocompatible devices. The present study has investigated the use of Plectranthus amboinicus leaf extracts as reducing and capping materials for the green fabrication of silver, gold, and silver-gold (Ag, Au, and Ag/Au) metal and bimetallic nanoparticles. The catalytic behavior of these phyto-inspired nanoparticles was then assessed in terms of the reduction of 4-nitrophenol. Transmission electron microscopy was used to investigate the shape, morphology, distribution, and diameter of the phytomolecules capped with Ag, Au, and Ag/Au metal nanoparticles. The nature of the crystallinity of the nanoparticles was studied by small area electron diffraction (SAED) and x-ray diffraction analysis (XRD), and Fourier transform infrared (FTIR) spectroscopy was used to study the reduction and stabilizing involvement of the phyto-organic moieties in aqueous medium. The phyto-inspired Ag and Ag/Au nanoparticles demonstrated good antibacterial properties toward Gram-negative Escherichia coli and Pseudomonas spp. and Gram-positive Bacillus spp. and Staphylococcus spp. microorganisms using the well diffusion method. Notably, the Ag nanoparticles were shown to possess effective antibacterial properties.

  10. Triazene UV-triggered photogeneration of silver/gold nanoparticles in block copolymer templates

    Energy Technology Data Exchange (ETDEWEB)

    Melinte, Violeta; Chibac, Andreea; Buruiana, Tinca; Hitruc, Gabriela; Buruiana, Emil C., E-mail: emilbur@icmpp.ro [Petru Poni Institute of Macromolecular Chemistry, Polyaddition and Photochemistry Department (Romania)

    2015-10-15

    This article describes an attractive way to in situ create noble metal nanoparticles in block copolymer matrixes through the UV-triggered photodecomposition of the photolabile triazene units without the use of any conventional reducing agent. The poly(isodecyl methacrylate-co-triazene urethane methacrylate) random copolymer containing pendent photocleavable triazene junctions (COP-1) was synthesized under RAFT conditions and subsequently employed as macroinitiator to obtain a block copolymer, namely poly(isodecyl methacrylate-co-triazene urethane methacrylate)-block-poly(acrylic acid) (COP-2). The photogeneration of silver/gold metal nanoparticles (NPs) from noble metal precursors (1 wt% AgNO{sub 3} or AuBr{sub 3} metal salts) induced through the UV decomposition of triazene units with the formation of some radical active species was monitored in solution and thin films. The in situ growth of Ag/Au nanostructures into polymer matrixes for which the light is a key element has been confirmed by UV spectroscopy and TEM analysis. The TEM images allowed the visualization of the silver NPs (sizes of 4–16 nm in COP-1 and of 2–6 nm in COP-2) as well as of the gold NPs (sizes between 10 and 20 nm in COP-1 and from 15 to 25 nm in COP-2), which are mainly spherical in shape, even though there is some triangular or hexagonal gold nanoparticles.

  11. Optimization of Sensitivity and Stability of Gold/Silver bi-Layer Thin Films Used in Surface Plasmon Resonance Chips

    Directory of Open Access Journals (Sweden)

    M. Ghorbanpour

    2013-09-01

    Full Text Available The aim of this study is experimental assay of sensitivity and stability of a bimetallic silver/gold SPR sensor chip. This chip utilizes the sensitivity of the silver and the stability of the gold. Moreover, the Silver layer (instead of usual Cr or Ti layer was used as an adhesive intermediate layer between the Gold layer and the glass substrate. The optimization of the Gold/Silver thickness using SPR analysis and physical and chemical stability tests showed that the 20/30 gold/silver composite resulting in a better precision and more stable SPR sensing chip.

  12. Size Selective Green Synthesis of Silver and Gold Nanoparticles: Enhanced Antibacterial Efficacy of Resveratrol Capped Silver Sol.

    Science.gov (United States)

    Shukla, Shashi P; Roy, Mainak; Mukherjee, Poulomi; Das, Laboni; Neogy, Suman; Srivastava, Dinesh; Adhikari, Soumyakanti

    2016-03-01

    In view of potential biomedical application of the noble metal nanoparticles, we report a size controlled yet simple and green synthesis of resveratrol stabilized silver and gold nanoparticles having low polydispersity of size. Here, resveratrol plays two simultaneous roles, reducing the metal ions and providing efficient capping of the small nanoparticles. This gives rise to specific size of silver and gold nanoparticles at specific ratios of metal to resveratrol. The particles have been characterized by XRD and transmission electron microscopy. The nanoparticle sols are stable for months. The UV Visible absorption spectra of the silver sol show the plasmon peak of spherical nanoparticles, presence of which is further reflected in the TEM images. Size of the silver particles obtained is in between 11 to 21 nm depending on the ratio of resveratrol to metal ion used. Resveratrol capped silver nanoparticles exhibit high antibacterial activity against Gram negative wild type E coli BW (25113). The minimum inhibitory concentration (MIC) of nano-silver against the bacterium has been estimated to be 6.48 μg/ml, which is significantly lower than that reported in some earlier as well as recent publications. Reaction of gold ions with resveratrol, on the other hand, produces gold nanoparticles of sizes varying from 7 to 29 nm at different ratios of resveratrol to the metal ions. Particles with higher size and aspect ratio are formed at lower concentration of the capping agent whereas particles with very small size and pseudo-spherical morphology are formed at higher capping concentration. Difference in the formation kinetics of silver and gold nanoparticles has been attributed to the different growth mechanisms in the two cases. Possible modes of anchorage of resveratrol to silver nanoparticles have been investigated using surface enhanced resonance Raman spectroscopy (SERS) which shows that the silver nanoparticles are capped by resveratrol molecule primarily through O

  13. Memecylon edule leaf extract mediated green synthesis of silver and gold nanoparticles

    Science.gov (United States)

    Elavazhagan, Tamizhamudu; Arunachalam, Kantha D

    2011-01-01

    We used an aqueous leaf extract of Memecylon edule (Melastomataceae) to synthesize silver and gold nanoparticles. To our knowledge, this is the first report where M. edule leaf broth was found to be a suitable plant source for the green synthesis of silver and gold nanoparticles. On treatment of aqueous solutions of silver nitrate and chloroauric acid with M. edule leaf extract, stable silver and gold nanoparticles were rapidly formed. The gold nanoparticles were characterized by UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDAX) and Fourier transform infra-red spectroscopy (FTIR). The kinetics of reduction of aqueous silver and gold ions during reaction with the M. edule leaf broth were easily analyzed by UV-visible spectroscopy. SEM analysis showed that aqueous gold ions, when exposed to M. edule leaf broth, were reduced and resulted in the biosynthesis of gold nanoparticles in the size range 20–50 nm. TEM analysis of gold nanoparticles showed formation of triangular, circular, and hexagonal shapes in the size range 10–45 nm. The resulting silver nanoparticles were predominantly square with uniform size range 50–90 nm. EDAX results confirmed the presence of triangular nanoparticles in the adsorption peak of 2.30 keV. Further FTIR analysis was also done to identify the functional groups in silver and gold nanoparticles. The characterized nanoparticles of M. edule have potential for various medical and industrial applications. Saponin presence in aqueous extract of M. edule is responsible for the mass production of silver and gold nanoparticles. PMID:21753878

  14. Gold and silver nanoparticles based superquenching of fluorescence: A review

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Debanjana; Chattopadhyay, Nitin, E-mail: nitin.chattopadhyay@yahoo.com

    2015-04-15

    The short review highlights the recent advances on the gold and silver nanoparticles induced efficient quenching of fluorescence from various fluorophores looking at their promising use as optical rulers and chemo-/bio- sensors. The fluorescence quenching often leads to the increase in the Stern–Volmer constant (K{sub SV}~10{sup 7}–10{sup 10} mol{sup −1} dm{sup 3}) several orders of magnitude higher than the values observed for the normal photochemical quenching processes (~10{sup 2} mol{sup −1} dm{sup 3}). This amplified quenching has been termed as “super-quenching” or “hyper-quenching”. Energy transfer (ET) is established from the donor to the metal nanoparticles rationalizing these fast quenching processes. Considering the distance dependence of the ET process, Förster resonance energy transfer (FRET) and nanometal surface energy transfer (NSET) are ascribed to take place. These sensitive distance dependent phenomena serve as the spectroscopic ruler to measure the intra- or intermolecular distances between the interacting partners. In this account focus has been laid on the size dependent energy transfer and super- and hyper- quenching of the fluorescence of the donor moieties by the nanometals and their probable applications in sensing. Rationalization has been made for the nanoparticle induced huge enhancement in the quenching efficiency. The impact of this review lies in the possible application of these amplified quenching processes in designing high sensitive chemical and biological sensors. - Highlights: • Super efficient quenching of fluorescence of probes by gold and silver nanoparticles is highlighted. • The amplified fluorescence quenching of dyes and polymers is rationalized. • Energy transfer is assigned to be responsible for the efficient quenching process. • Amplified quenching has its potential use in designing sensitive chemical/biological sensors.

  15. Toxicity of silver and gold nanoparticles on marine microalgae.

    Science.gov (United States)

    Moreno-Garrido, Ignacio; Pérez, Sara; Blasco, Julián

    2015-10-01

    The increased use of nanomaterials in several novel industrial applications during the last decade has led to a rise in concerns about the potential toxic effects of released engineered nanoparticles (NPs) into the environment, as their potential toxicity to aquatic organisms is just beginning to be recognised. Toxicity of metallic nanoparticles to aquatic organisms, including microalgae, seems to be related to their physical and chemical properties, as well as their behaviour in the aquatic media where processes of dissolution, aggregation and agglomeration can occur. Although the production of these particles has increased considerably in recent years, data on their toxicity on microalgae, especially those belonging to marine or estuarine environments remain scarce and scattered. The literature shows a wide variation of results on toxicity, mainly due to the different methodology used in bioassays involving microalgae. These can range for up to EC50 data, in the case of AgNPs, representing five orders of magnitude. The importance of initial cellular density is also addressed in the text, as well as the need for keeping test conditions as close as possible to environmental conditions, in order to increase their environmental relevance. This review focuses on the fate and toxicity of silver, gold, and gold-silver alloy nanoparticles on microalgae, as key organisms in aquatic ecosystems. It is prompted by their increased production and use, and taking into account that oceans and estuaries are the final sink for those NPs. The design of bioassays and further research in the field of microalgae nanoecotoxicology is discussed, with a brief survey on newly developed technology of green (algae mediated) production of Ag, Au and Ag-Au bimetallic NPs, as well as some final considerations about future research on this field. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Biosynthesis, structural characterization and antimicrobial activity of gold and silver nanoparticles.

    Science.gov (United States)

    Ahmad, Tokeer; Wani, Irshad A; Manzoor, Nikhat; Ahmed, Jahangeer; Asiri, Abdullah M

    2013-07-01

    An eco friendly simple biosynthetic route was used for the preparation of monodisperse and highly crystalline gold and silver nanoparticles using cell free extract of fungus, Candida albicans. Transmission electron microscopic studies show the formation of gold and silver nanocrystals of average size of 5 nm and 30 nm with the specific surface areas of 18.9 m(2)/g and 184.4 m(2)/g respectively. The interaction of gold and silver nanoparticles with proteins has been formulated by FT-IR spectroscopy and thermal gravimetric analysis. The formation of gold and silver nanoparticles was also confirmed by the appearance of a surface plasmon band at 540 nm and 450 nm respectively. The antimicrobial activity of the synthesized gold and silver nanoparticles was investigated against both Staphylococcus aureus and Escherichia coli. The results suggest that these nanoparticles can be used as effective growth inhibitors against the test microorganisms. Greater bactericidal activity was observed for silver nanoparticles. The E. coli, a gram negative bacterium was found to be more susceptible to gold and silver nanoparticles than the S. aureus, a gram positive bacterium. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. The development of a green approach for the biosynthesis of silver and gold nanoparticles by using Panax ginseng root extract, and their biological applications.

    Science.gov (United States)

    Singh, Priyanka; Kim, Yeon Ju; Wang, Chao; Mathiyalagan, Ramya; Yang, Deok Chun

    2016-06-01

    The biosynthesis of nanoparticles has received attention because of the development of economic and environmentally friendly technology for the synthesis of nanoparticles. The study develops a convenient method for the green synthesis of silver and gold nanoparticles by utilizing fresh root extract of the four-year old Panax ginseng plant, and evaluated the antimicrobial applications of silver nanoparticles against pathogenic microorganisms. P. ginseng is a well-known herbal medicinal plant, and its active ingredients are mainly ginsenosides. The fresh root of the 4 year old P. ginseng plant has been explored for the synthesis of silver and gold nanoparticles without the use of any additional reducing and capping agents. The reduction of silver nitrate led to the formation of silver nanoparticles within 2 h of reaction at 80°C. The gold nanoparticles were also successfully synthesized by the reduction of auric acid at 80°C, within 5 min of reaction. The biosynthesized gold and silver nanoparticles were characterized by techniques using various instruments, viz. ultraviolet-visible spectroscopy (UV-Vis spectroscopy), field emission transmission electron microscopy (FE-TEM), energy dispersive X-ray analysis (EDX), elemental mapping, and X-ray diffraction (XRD). In addition, the silver nanoparticles have shown antimicrobial potential against Bacillus anthracis, Vibrio parahaemolyticus, Staphylococcus aureus, Escherichia coli, and Bacillus cereus.

  18. EPITHERMAL GOLD-SILVER MINERALIZATION RELATED TO VOLCANIC SUBSIDENCE IN THE CUSTER GRABEN, CUSTER COUNTY, IDAHO.

    Science.gov (United States)

    Johnson, Kathleen M.; McIntyre, David H.

    1984-01-01

    The Custer graben is a 13 by 32 km northeast-trending volcano-tectonic graben in the Challis volcanic field of central Idaho. Andesites, rhyolites, and associated pyroclastic rocks host vein and disseminated gold-silver deposits that are localized along discrete northeast- and northwest-trending fracture zones. Ore minerals in vein deposits are electrum, native gold and silver, chalcopyrite, and various sulfosalts in a gangue of pyrite and fine-grained quartz. At the Sunbeam Mine, near the center of the graben, vein and disseminated gold-silver mineralization occurred in hydrothermally altered rhyolite and pyroclastic rocks. The host rock has been pervasively silicified, and the feldspars altered to clay minerals. Analyses of surface and drill-core samples show that altered rocks are variably enriched in gold, silver, molybdenum, arsenic, zirconium, and selenium. Intense silicification is shown by SiO//2 values at high as 93%.

  19. Surface Plasmons and Surface Enhanced Raman Spectra of Aggregated and Alloyed Gold-Silver Nanoparticles

    Directory of Open Access Journals (Sweden)

    Y. Fleger

    2009-01-01

    Full Text Available Effects of size, morphology, and composition of gold and silver nanoparticles on surface plasmon resonance (SPR and surface enhanced Raman spectroscopy (SERS are studied with the purpose of optimizing SERS substrates. Various gold and silver films made by evaporation and subsequent annealing give different morphologies and compositions of nanoparticles and thus different position of the SPR peak. SERS measurements of 4-mercaptobenzoic acid obtained from these films reveal that the proximity of the SPR peak to the exciting laser wavelength is not the only factor leading to the highest Raman enhancement. Silver nanoparticles evaporated on top of larger gold nanoparticles show higher SERS than gold-silver alloyed nanoparticles, in spite of the fact that the SPR peak of alloyed nanoparticles is narrower and closer to the excitation wavelength. The highest Raman enhancement was obtained for substrates with a two-peak particle size distribution for excitation wavelengths close to the SPR.

  20. Substrate decomposition in galvanic displacement reaction: Contrast between gold and silver nanoparticle formation

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Tapas; Satpati, Biswarup, E-mail: biswarup.satpati@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700 064 (India); Kabiraj, D. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110067 (India)

    2015-06-24

    We have investigated substrate decomposition during formation of silver and gold nanoparticles in galvanic displacement reaction on germanium surfaces. Silver and gold nanoparticles were synthesized by electroless deposition on sputter coated germanium thin film (∼ 200 nm) grown initially on silicon substrate. The nanoparticles formation and the substrate corrosion were studied using scanning transmission electron microscopy (STEM) and the energy dispersive X-ray (EDX) spectroscopy.

  1. On the directional accuracy of survey forecasts: the case of gold and silver

    DEFF Research Database (Denmark)

    Fritsche, U.; Pierdzioch, C.; Rulke, J. C.

    2013-01-01

    We use a nonparametric market-timing test to study the directional accuracy of survey forecasts of the prices of gold and silver. We find that forecasters have market-timing ability with respect to the direction of change of the price of silver at various forecast horizons. In contrast, forecaste...

  2. Fabrication of gold and silver nanoparticles with pulsed laser ablation under pressurized CO2

    Science.gov (United States)

    Machmudah, Siti; Wahyudiono; Takada, Noriharu; Kanda, Hideki; Sasaki, Koichi; Goto, Motonobu

    2013-12-01

    Pulsed laser ablation (PLA) has become a promising method for the synthesis of nanoclusters for photonics, electronics and medicine. In this work PLA in pressurized CO2 has been applied for fabrication of gold and silver nanoparticles. Laser ablation was performed with an excitation wavelength of 532 nm under various pressures (0.1-20 MPa), temperatures (40-80 °C) of CO2 medium and ablation times (1500-9000 s). On the basis of the experimental result, it follows that structures of gold (Au) and silver (Ag) nanoparticles were significantly affected by the changes in CO2 density. The structures of gold and silver nanoparticles also changed with an increase of ablation time. From a field-emission scanning electron microscopy (FE-SEM) image of the fabricated gold nano-structured particles on silicon wafer, it was seen that a network structure of smaller gold particles was fabricated. A similar morphology of particles fabricated from silver plate was observed. Silver particles contain nanoparticles with large-varied diameter ranging from 5 nm to 1.2 μm. The mechanism of nanoparticles fabrication could be observed as follows. Bigger gold/silver particles melted during the ablation process and then ejected smaller spherical nanoparticles, which formed nanoclusters attached on the molten particles.

  3. Electromigration in gold and silver nanostructures; Elektromigration in Gold und Silber Nanostrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Stahlmecke, Burkhard

    2008-01-15

    Electromigration is the current induced mass transport in metallic wires. It is the main reason for electrical breakdown in integrated circuits and has been studied for more than 50 years. In this thesis, the electromigration behavior in polycrystalline gold as well as in self-organized single crystalline silver wires are studied. To study the electromigration behavior in detail, in-situ investigations of the wires are performed in a scanning electron microscope, for which a new test rig was successfully installed. During electromigration, the development of voids on the cathode and hillocks on the anode side of the wire are observed. This behavior is studied in detail in this thesis. Electrical breakdown in the gold wires takes place due to the presence of slit-like voids perpendicular to the current direction. The void area grows linearly during the course of the experiments, and the electrical breakdown takes place when the total void area reaches a value of 2 % to 4 % of the total wire area. The influence of single voids on the electrical resistance during high current stressing is determined. The dependence of the electromigration behavior on the width and height as well as on the crystallinity and temperature of the gold wires is studied in detail. For high resolution imaging of the wires during the experiments, a special layout with arbitrary kinks is used. The dependence of electromigration effects on current density and on the influence of the measurement setup itself are also discussed in this thesis. When reversing the current direction, a reversible electromigration behavior is observed. Also, the lifetime of the wires grows considerably. According to the resistance data, a remarkable stabilization of the polycrystalline wires is observed during this experiments. Furthermore, it is possible to define an alternative sheet length according to the position of voids and hillocks in the wires. This leads also to the determination of the critical product for

  4. Antibacterial nanocarriers of resveratrol with gold and silver nanoparticles.

    Science.gov (United States)

    Park, Sohyun; Cha, Song-Hyun; Cho, Inyoung; Park, Soomin; Park, Yohan; Cho, Seonho; Park, Youmie

    2016-01-01

    This study focused on the preparation of resveratrol nanocarrier systems and the evaluation of their in vitro antibacterial activities. Gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) for resveratrol nanocarrier systems were synthesized using green synthetic routes. During the synthesis steps, resveratrol was utilized as a reducing agent to chemically reduce gold and silver ions to AuNPs and AgNPs. This system provides green and eco-friendly synthesis routes that do not involve additional chemical reducing agents. Resveratrol nanocarriers with AuNPs (Res-AuNPs) and AgNPs (Res-AgNPs) were observed to be spherical and to exhibit characteristic surface plasmon resonance at 547 nm and at 412-417 nm, respectively. The mean size of the nanoparticles ranged from 8.32 to 21.84 nm, as determined by high-resolution transmission electron microscopy. The face-centered cubic structure of the Res-AuNPs was confirmed by high-resolution X-ray diffraction. Fourier-transform infrared spectra indicated that the hydroxyl groups and C=C in the aromatic ring of resveratrol were involved in the reduction reaction. Res-AuNPs retained excellent colloidal stability during ultracentrifugation and re-dispersion, suggesting that resveratrol also played a role as a capping agent. Zeta potentials of Res-AuNPs and Res-AgNPs were in the range of -20.58 to -48.54 mV. Generally, against Gram-positive and Gram-negative bacteria, the Res-AuNPs and Res-AgNPs exhibited greater antibacterial activity compared to that of resveratrol alone. Among the tested strains, the highest antibacterial activity of the Res-AuNPs was observed against Streptococcus pneumoniae. The addition of sodium dodecyl sulfate during the synthesis of Res-AgNPs slightly increased their antibacterial activity. These results suggest that the newly developed resveratrol nanocarrier systems with metallic nanoparticles show potential for application as nano-antibacterial agents with enhanced activities. Copyright © 2015

  5. The Hydrothermal Chemistry of Gold, Arsenic, Antimony, Mercury and Silver

    Energy Technology Data Exchange (ETDEWEB)

    Bessinger, Brad; Apps, John A.

    2003-03-23

    A comprehensive thermodynamic database based on the Helgeson-Kirkham-Flowers (HKF) equation of state was developed for metal complexes in hydrothermal systems. Because this equation of state has been shown to accurately predict standard partial molal thermodynamic properties of aqueous species at elevated temperatures and pressures, this study provides the necessary foundation for future exploration into transport and depositional processes in polymetallic ore deposits. The HKF equation of state parameters for gold, arsenic, antimony, mercury, and silver sulfide and hydroxide complexes were derived from experimental equilibrium constants using nonlinear regression calculations. In order to ensure that the resulting parameters were internally consistent, those experiments utilizing incompatible thermodynamic data were re-speciated prior to regression. Because new experimental studies were used to revise the HKF parameters for H2S0 and HS-1, those metal complexes for which HKF parameters had been previously derived were also updated. It was found that predicted thermodynamic properties of metal complexes are consistent with linear correlations between standard partial molal thermodynamic properties. This result allowed assessment of several complexes for which experimental data necessary to perform regression calculations was limited. Oxygen fugacity-temperature diagrams were calculated to illustrate how thermodynamic data improves our understanding of depositional processes. Predicted thermodynamic properties were used to investigate metal transport in Carlin-type gold deposits. Assuming a linear relationship between temperature and pressure, metals are predicted to predominantly be transported as sulfide complexes at a total aqueous sulfur concentration of 0.05 m. Also, the presence of arsenic and antimony mineral phases in the deposits are shown to restrict mineralization within a limited range of chemical conditions. Finally, at a lesser aqueous sulfur

  6. Enhancement of antibiotic effect via gold:silver-alloy nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Moreira dos Santos, Margarida, E-mail: margarida.santos@fct.unl.pt; Queiroz, Margarida Joao; Baptista, Pedro V. [Universidade Nova de Lisboa, CIGMH, Departamento Ciencias da Vida, Faculdade de Ciencias e Tecnologia (Portugal)

    2012-05-15

    A strategy for the development of novel antimicrobials is to combine the stability and pleiotropic effects of inorganic compounds with the specificity and efficiency of organic compounds, such as antibiotics. Here we report on the use of gold:silver-alloy (Au:Ag-alloy) nanoparticles, obtained via a single-step citrate co-reduction method, combined to conventional antibiotics to enhance their antimicrobial effect on bacteria. Addition of the alloy nanoparticles considerably decreased the dose of antibiotic necessary to show antimicrobial effect, both for bacterial cells growing in rich medium in suspension and for bacterial cells resting in a physiological buffer on a humid cellulose surface. The observed effect was more pronounced than the sum of the individual effects of the nanoparticles and antibiotic. We demonstrate the enhancement effect of Au:Ag-alloy nanoparticles with a size distribution of 32.5 {+-} 7.5 nm mean diameter on the antimicrobial effect of (i) kanamycin on Escherichia coli (Gram-negative bacterium), and (ii) a {beta}-lactam antibiotic on both a sensitive and resistant strain of Staphylococcus aureus (Gram-positive bacterium). Together, these results may pave the way for the combined use of nanoparticle-antibiotic conjugates towards decreasing antibiotic resistance currently observed for certain bacteria and conventional antibiotics.

  7. Enhancement of antibiotic effect via gold:silver-alloy nanoparticles

    Science.gov (United States)

    dos Santos, Margarida Moreira; Queiroz, Margarida João; Baptista, Pedro V.

    2012-05-01

    A strategy for the development of novel antimicrobials is to combine the stability and pleiotropic effects of inorganic compounds with the specificity and efficiency of organic compounds, such as antibiotics. Here we report on the use of gold:silver-alloy (Au:Ag-alloy) nanoparticles, obtained via a single-step citrate co-reduction method, combined to conventional antibiotics to enhance their antimicrobial effect on bacteria. Addition of the alloy nanoparticles considerably decreased the dose of antibiotic necessary to show antimicrobial effect, both for bacterial cells growing in rich medium in suspension and for bacterial cells resting in a physiological buffer on a humid cellulose surface. The observed effect was more pronounced than the sum of the individual effects of the nanoparticles and antibiotic. We demonstrate the enhancement effect of Au:Ag-alloy nanoparticles with a size distribution of 32.5 ± 7.5 nm mean diameter on the antimicrobial effect of (i) kanamycin on Escherichia coli (Gram-negative bacterium), and (ii) a β-lactam antibiotic on both a sensitive and resistant strain of Staphylococcus aureus (Gram-positive bacterium). Together, these results may pave the way for the combined use of nanoparticle-antibiotic conjugates towards decreasing antibiotic resistance currently observed for certain bacteria and conventional antibiotics.

  8. Directed organization of gold nanoclusters on silver nanowires: A step forward in heterostructure assembly

    Science.gov (United States)

    Sharma, Jadab; Vivek, J. P.; Vijayamohanan, Kunjukrishna P.; Singh, Poonam; Dharmadhikari, C. V.

    2006-05-01

    We investigate the directed assembly of tridecylamine protected gold nanoclusters of 4-5nm size on functionalized silver nanowires of 55-60nm diameter and the electron transfer behavior of this integrated structure using transmission electron microscopy, non-contact atomic force microscopy, and scanning tunneling microscopy/spectroscopy. Linear I-V for bare silver nanowire suggests metallic behavior but high tunnel resistance indicates presence of insulating layer on the surface. Identical I-Vs obtained for isolated gold nanoparticle and heterostructure suggests that electron transport across nanowires in the latter is governed by gold nanoparticles in contrast to expected ballistic or diffusive transport along their length.

  9. 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.

  10. Chrysopogon zizanioides aqueous extract mediated synthesis, characterization of crystalline silver and gold nanoparticles for biomedical applications.

    Science.gov (United States)

    Arunachalam, Kantha D; Annamalai, Sathesh Kumar

    2013-01-01

    The exploitation of various plant materials for the biosynthesis of nanoparticles is considered a green technology as it does not involve any harmful chemicals. The aim of this study was to develop a simple biological method for the synthesis of silver and gold nanoparticles using Chrysopogon zizanioides. To exploit various plant materials for the biosynthesis of nanoparticles was considered a green technology. An aqueous leaf extract of C. zizanioides was used to synthesize silver and gold nanoparticles by the bioreduction of silver nitrate (AgNO3) and chloroauric acid (HAuCl4) respectively. Water-soluble organics present in the plant materials were mainly responsible for reducing silver or gold ions to nanosized Ag or Au particles. The synthesized silver and gold nanoparticles were characterized by ultraviolet (UV)-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analysis. The kinetics decline reactions of aqueous silver/gold ion with the C. zizanioides crude extract were determined by UV-visible spectroscopy. SEM analysis showed that aqueous gold ions, when exposed to the extract were reduced and resulted in the biosynthesis of gold nanoparticles in the size range 20-50 nm. This eco-friendly approach for the synthesis of nanoparticles is simple, can be scaled up for large-scale production with powerful bioactivity as demonstrated by the synthesized silver nanoparticles. The synthesized nanoparticles can have clinical use as antibacterial, antioxidant, as well as cytotoxic agents and can be used for biomedical applications.

  11. Chrysopogon zizanioides aqueous extract mediated synthesis, characterization of crystalline silver and gold nanoparticles for biomedical applications

    Science.gov (United States)

    Arunachalam, Kantha D; Annamalai, Sathesh Kumar

    2013-01-01

    The exploitation of various plant materials for the biosynthesis of nanoparticles is considered a green technology as it does not involve any harmful chemicals. The aim of this study was to develop a simple biological method for the synthesis of silver and gold nanoparticles using Chrysopogon zizanioides. To exploit various plant materials for the biosynthesis of nanoparticles was considered a green technology. An aqueous leaf extract of C. zizanioides was used to synthesize silver and gold nanoparticles by the bioreduction of silver nitrate (AgNO3) and chloroauric acid (HAuCl4) respectively. Water-soluble organics present in the plant materials were mainly responsible for reducing silver or gold ions to nanosized Ag or Au particles. The synthesized silver and gold nanoparticles were characterized by ultraviolet (UV)-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analysis. The kinetics decline reactions of aqueous silver/gold ion with the C. zizanioides crude extract were determined by UV-visible spectroscopy. SEM analysis showed that aqueous gold ions, when exposed to the extract were reduced and resulted in the biosynthesis of gold nanoparticles in the size range 20–50 nm. This eco-friendly approach for the synthesis of nanoparticles is simple, can be scaled up for large-scale production with powerful bioactivity as demonstrated by the synthesized silver nanoparticles. The synthesized nanoparticles can have clinical use as antibacterial, antioxidant, as well as cytotoxic agents and can be used for biomedical applications. PMID:23861583

  12. Interference of Steroidogenesis by Gold Nanorod Core/Silver Shell Nanostructures: Implications for Reproductive Toxicity of Silver Nanomaterials.

    Science.gov (United States)

    Jiang, Xiumei; Wang, Liming; Ji, Yinglu; Tang, Jinglong; Tian, Xin; Cao, Mingjing; Li, Jingxuan; Bi, Shuying; Wu, Xiaochun; Chen, Chunying; Yin, Jun-Jie

    2017-03-01

    As a widely used nanomaterial in daily life, silver nanomaterials may cause great concern to female reproductive system as they are found to penetrate the blood-placental barrier and gain access to the ovary. However, it is largely unknown about how silver nanomaterials influence ovarian physiology and functions such as hormone production. This study performs in vitro toxicology study of silver nanomaterials, focusing especially on cytotoxicity and steroidogenesis and explores their underlying mechanisms. This study exposes primary rat granulosa cells to gold nanorod core/silver shell nanostructures (Au@Ag NRs), and compares outcomes with cells exposed to gold nanorods. The Au@Ag NRs generate more reactive oxygen species and reduce mitochondrial membrane potential and less production of adenosine triphosphate. Au@Ag NRs promote steroidogenesis, including progesterone and estradiol, in a time- and dose-dependent manner. Chemical reactivity and transformation of Au@Ag NRs are then studied by electron spin resonance spectroscopy and X-ray absorption near edge structure, which analyze the generation of free radical and intracellular silver species. Results suggest that both particle-specific activity and intracellular silver ion release of Au@Ag NR contribute to the toxic response of granulosa cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. The Use of Gold Dinar and Silver Dirham in Moslem Countries in the Contemporary Era

    Directory of Open Access Journals (Sweden)

    Muchammad Ichsan

    2017-08-01

    Full Text Available The dominance of the US dollar and other developed countries currencies, as well as the fact that their currencies have fallen behind, have urged groups of Moslems in some countries to call for the use of gold dinar and silver dirham as a medium of exchange. This paper aims at examining the need, application, and law on the use of gold dinar and silver dirham from the Islamic perspective. To reach the goal set at this moment, a descriptive method is employed in the writing while an analytical method is used to scrutinize the relevant problems. This study finds that in the current situation Moslems need to use gold dinar and silver dirham for their financial contracts. The use of gold dinar and silver dirham is applicable in this modern era although there are some obstacles and problems. Lastly, the use of gold dinar and silver dirham as a medium of exchange is allowed from the Islamic perspective based on some propositions.

  14. ARTICLE Adsorption Behaviors of 4-Mercaptobenzoic Acid on Silver and Gold Films

    Science.gov (United States)

    Ma, Wen-qiang; Fang, Yan; Hao, Gang-ling; Wang, Wei-guo

    2010-12-01

    The adsorption behaviors of 4-mercaptobenzoic acid on silver and gold nanoparticles were studied by surface-enhanced Raman scattering (SERS) and density functional theory. The silver and gold films by electrodeposition have the same excellent characteristics as SERS-active substrates. At the same, the SERS spectra indicate that 4-mercaptobenzoic acid molecules are adsorbed on the surfaces of gold nanoparticles through the S atom, and that the carboxyl group is far away from surface of gold nanoparticles, and that there is a certain angle between the plane of benzene ring and gold film. However, 4-mercaptobenzoic acid molecules are adsorbed on the surfaces of silver nanoparticles through the carboxyl group, and the S atom is far away from surface of silver nanoparticles, and there is also a certain angle between the plane of benzene ring and the surface of silver nanoparticles. Here it is demonstrated the calculated Raman frequencies are in good agreement with experimental values, and the calculated Raman frequencies are also helpful to infer the adsorption behaviors of 4-mercaptobenzoic acid molecules.

  15. Synthesis of gold and silver nanoparticles usingMukia maderaspatnaplant extract and its anticancer activity.

    Science.gov (United States)

    Devi, Guruviah Karthiga; Sathishkumar, Kannaiyan

    2017-03-01

    The present investigation reveals the in vitro cytotoxic effect of the biosynthesised metal nanoparticles on the MCF 7 breast cancer cell lines. The gold and silver nanoparticles were synthesised through an environmentally admissible route using the Mukia Maderaspatna plant extract. Initially, the biomolecules present in the plant extract were analysed using phytochemical analysis. Further, these biomolecules reduce the metal ion solution resulting from the formation of metal nanoparticles. The reaction parameters were optimised to control the size of nanoparticles which were confirmed by UV visible spectroscopy. Various instrumental techniques such as Fourier transform-infrared spectroscopy, high resolution transmission electron microscopy, energy dispersive X-ray and scanning electron microscopy were employed to characterise the synthesised gold and silver nanoparticles. The synthesised gold and silver nanoparticles were found to be 20-50 nm and were of different shapes including spherical, triangle and hexagonal. MTT and dual staining assays were carried out with different concentrations (1, 10, 25, 50 and 100 µg/ml) of gold and silver nanoparticles. The results show that the nanoparticles exhibited significant cytotoxic effects with IC 50 value of 44.8 µg/g for gold nanoparticles and 51.3 µg/g for silver nanoparticles. The observations in this study show that this can be developed as a promising nanomaterial in pharmaceutical and healthcare sector.

  16. Interactions of organodithiols with gold and silver nanoparticles in water

    Science.gov (United States)

    Gadogbe, Manuel

    Organodithiols including para-aryl dithiols (PADTs, HS-(C6H 4)n-SH, n = 1, 2 and 3) and alpha, omega-alkanedithiols (ADTs, HS-(CH2)n-SH, n = 2, 4, ...) with two distal thiols have been used extensively in molecular electronics, surface-enhanced Raman spectroscopy (SERS), and quantum electron tunneling between two gold or silver nanoparticles (AuNPs and AgNPs). The popular belief is that these dithiols cross-link noble metal nanoparticles (NPs) as monolayer dithiolate spacers. Reported is the finding that PADTs predominantly exist as monothiolate forms on AuNPs or AgNPs. No PADT-induced NP cross-linking was observed regardless of NP/PADT concentration ratios. 1,4-benzenedimethanethiol (HS-CH2-(C 6H4)-CH2-SH) and ADT can be completely deprotonated, forming dithiolates on AuNPs and AgNPs, while only one PADT thiol can be deprotonated even when PADTs are treated with concentrated NaOH or AgNO3. AuNP localized surface plasmon resonance (LSPR) measurement provides conclusive evidence that ADT in AuNP junctions primarily consisted of dithiolate monomers in which the two sulfides are either attached to the same AuNP, or cross-link two adjacent AuNPs as single-molecular spacers. However, ADT molecules most likely in the area surrounding the AuNP junction are monothiolate with their distal thiols either remaining intact or forming disulfide cross-links with neighboring adsorbed ADTs. The possibility for ADT to cross-link two AgNPs as single molecular linker is excluded on the basis of TEM measurements that showed ADT-induced AgNP disintegration. This work highlights the difference between organothiol interactions with AgNPs and AuNPs and should be of broad importance for plasmonic NP research given the popularity of PADTs in molecular electronics and SERS applications.

  17. Biofabrication of gold and silver nanoparticles for pharmaceutical applications

    Directory of Open Access Journals (Sweden)

    Hamed Barabadi

    2016-02-01

    Full Text Available Biofabrication by using fungi is an exciting recent interest to develop an eco-friendly production of metallic nanoparticles (NPs for pharmaceutical applications. This study aimed to synthesize and characterize gold (Au and silver (Ag NPs by using Penicillium simplisimum. The fungus was grown in fluid czapek dox broth on shaker at 28 ºC and 200 rpm for ten days. Then the supernatant was separated from the mycelia to convert HAuCl4 and AgNO3 solution into Au and Ag NPs separately. After 24 hours, synthesized Au and Ag NPs were characterized by using UV-Visible Spectroscopy as well as Photon Correlation spectroscopy (PCS involves Polydispersity Index (PDI and zeta potential. The UV-Visible Spectroscopy analysis revealed a plasmon bond peak around 533 nm and 400 nm suggesting formation of Au and Ag NPs, respectively. Furthermore, the PCS analysis showed an average diameter of 68 nm and 76 nm with PDI value of 0.2 and 0.23 for Au and Ag NPs, successively, which demonstrated that the nanoparticles formed with fairly well-defined dimensions and good monodispersity. Besides, a negative zeta potential were found for nanoparticles indicating their stability in the solution. The current approach suggests that the rapid synthesis of nanoparticles would be suitable for developing a green process for mass scale production. Besides, we believe that development of eco-friendly process for the formulation of metallic NPs is an important step in the field of application of nanotechnology and its optimization may make it a potential procedure for industrial production of NPs.

  18. Influence of gold, silver and gold–silver alloy nanoparticles on germ cell function and embryo development

    Directory of Open Access Journals (Sweden)

    Ulrike Taylor

    2015-03-01

    Full Text Available The use of engineered nanoparticles has risen exponentially over the last decade. Applications are manifold and include utilisation in industrial goods as well as medical and consumer products. Gold and silver nanoparticles play an important role in the current increase of nanoparticle usage. However, our understanding concerning possible side effects of this increased exposure to particles, which are frequently in the same size regime as medium sized biomolecules and accessorily possess highly active surfaces, is still incomplete. That particularly applies to reproductive aspects, were defects can be passed onto following generations. This review gives a brief overview of the most recent findings concerning reprotoxicological effects. The here presented data elucidate how composition, size and surface modification of nanoparticles influence viablility and functionality of reproduction relevant cells derived from various animal models. While in vitro cultured embryos displayed no toxic effects after the microinjection of gold and silver nanoparticles, sperm fertility parameters deteriorated after co-incubation with ligand free gold nanoparticles. However, the effect could be alleviated by bio-coating the nanoparticles, which even applies to silver and silver-rich alloy nanoparticles. The most sensitive test system appeared to be in vitro oocyte maturation showing a dose-dependent response towards protein (BSA coated gold–silver alloy and silver nanoparticles leading up to complete arrest of maturation. Recent biodistribution studies confirmed that nanoparticles gain access to the ovaries and also penetrate the blood–testis and placental barrier. Thus, the design of nanoparticles with increased biosafety is highly relevant for biomedical applications.

  19. Roasting of refractory gold and silver concentrate; Tostacion de un concentrado refractario de oro y plata

    Energy Technology Data Exchange (ETDEWEB)

    Coraonado, J. H.; Encinas, M. A.; Leyva, M. A.; Valenzuela, J. L.; Valenzuela, A.; Munive, G. T.

    2012-11-01

    In processing of precious metal ores with high pyrite content, refractory concentrates are obtained, which are difficult to process. A refractory gold and silver concentrate was leached with sodium cyanide. Results show low extraction percentages, being 34 % of gold and 40 % of silver. A roasting method to oxidize the concentrate was used, making it more susceptible to cyanidation, hence a more efficient way to extract precious metals. The variables include roasting temperature and roasting and cyanidation time. In addition, the hot calcine was added to the leaching solution at room temperature to analyze the effect on particle size and recovery. The best results, although not entirely satisfactory (50 % of gold and 61 % of silver) were obtained by roasting the concentrate for 4 h at 600 degree centigrade, followed by cyanidation for 20 h. The lime consumption to raise the pH to about 11.3 was increased markedly to 25 kg/m{sup 3}. (Author) 11 refs.

  20. 40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

    Science.gov (United States)

    2010-07-01

    ... any combination of these ores; (3) Mines and mills that use dump, heap, in-situ leach, or vat-leach... copper, lead, zinc, gold, silver, and molybdenum ores subcategory. 440.100 Section 440.100 Protection of... DRESSING POINT SOURCE CATEGORY Copper, Lead, Zinc, Gold, Silver, and Molybdenum Ores Subcategory § 440.100...

  1. Facially amphiphilic thiol capped gold and silver nanoparticles

    Indian Academy of Sciences (India)

    Wintec

    Generally, gold nanoparticles are easily produced in a liquid ('liquid chemical methods') by the reduction of chloroauric acid (HAuCl4), although more advanced and precise methods exist. As the neutral gold atoms form, the solution becomes su- persaturated, and gold gradually starts to precipitate in the form of ...

  2. Synthesis, characterization and in vitro effects of 7 nm alloyed silver-gold nanoparticles.

    Science.gov (United States)

    Ristig, Simon; Chernousova, Svitlana; Meyer-Zaika, Wolfgang; Epple, Matthias

    2015-01-01

    Alloyed silver-gold nanoparticles were prepared in nine different metal compositions with silver/gold molar ratios of ranging from 90:10 to 10:90. The one-pot synthesis in aqueous medium can easily be modified to gain control over the final particle diameter and the stabilizing agents. The purification of the particles to remove synthesis by-products (which is an important factor for subsequent in vitro experiments) was carried out by multiple ultracentrifugation steps. Characterization by transmission electron microscopy (TEM), differential centrifugal sedimentation (DCS), dynamic light scattering (DLS), UV-vis spectroscopy and atomic absorption spectroscopy (AAS) showed spherical, monodisperse, colloidally stable silver-gold nanoparticles of ≈7 nm diameter with measured molar metal compositions very close to the theoretical values. The examination of the nanoparticle cytotoxicity towards HeLa cells and human mesenchymal stem cells (hMSCs) showed that the toxicity is not proportional to the silver content. Nanoparticles with a silver/gold molar composition of 80:20 showed the highest toxicity.

  3. Biosynthesis and Characterization of Gold and Silver Nanoparticles Using Milk Thistle (Silybum marianum Seed Extract

    Directory of Open Access Journals (Sweden)

    R. Gopalakrishnan

    2014-01-01

    Full Text Available Biogenic synthesis of gold and silver nanoparticles from aqueous solutions using milk thistle (Silybum marianum seed extract as reducing and stabilizing agent has been reported. Formation and stabilization of nanoparticles were monitored using surface plasmon resonance (SPR bands of UV-Vis spectroscopy. Morphology of gold and silver nanoparticles was investigated using X-ray diffraction, high-resolution transmission electron microscopy with selected area electron diffraction analysis, and dynamic light scattering. Fourier transform-infrared spectroscopy was employed to identify the possible biomolecules responsible for the reduction and stabilization of nanoparticles.

  4. INDICATION OF GOLD AND SILVER OCCURRENCE AT SAMPIT BAY, KOTA WARINGIN TIMUR DISTRICT, CENTRAL KALIMANTAN PROVINCE

    Directory of Open Access Journals (Sweden)

    I Wayan Lugra

    2017-07-01

    Full Text Available The study area is fluviatile deposit which consists of yellow to light gray loose sand, iron oxide, and kaoline spreading from the land shallowing to sea direction. Concentration grade for determining of gold and silver content used a total analysis of the hot mixture HF-HNO3-HClO4 with measurements "Atomic Absorption Spectrofotometry".(AAS. Highest concentration of gold and silver found at sample GCTS-31 that gold 0.096 ppm and silver 2.284 ppm, in muddy sand type sediment, at 3.1 meters depth and arround 1,250 meter length from coast line. While the lowest concentration of the gold was 0.025 ppm found at sample GBTS 14 in very fine sand type sediment located at 1.07 meter depth and approximately 320 meters length from coast line. The lowest concentration of the silver was founded at sample GBTS 25 that is 0.860 ppm in sandy mud sediment type located at 2.49 meters depth and approximately 3,000 meters length from the coast line. The gold placer is may derived from weathering of Pambuang Formation which spreads in the west and north of Sampit Bay, and transported by Mentaya River and longshore current system.

  5. Ultrastructural localization of carbohydrates on thin sections of Staphylococcus aureus with silver methenamine and wheat germ agglutinin-gold complex.

    OpenAIRE

    Morioka, H; Tachibana, M; Suganuma, A

    1987-01-01

    Postembedding staining of intracellular carbohydrates on thin sections of Staphylococcus aureus was studied by the silver methenamine and the wheat germ agglutinin-gold techniques. Staining of silver grains was observed on both the cell wall and the cross wall. The staining was interpreted to be due to teichoic acid. Labeling by wheat germ agglutinin-gold particles was observed on both the cell wall and the cross wall, and the staining pattern resembled that of silver methenamine staining. Th...

  6. First discovery of high-mercury silver in ores of the Rogovik gold-silver deposit (Northeastern Russia)

    Science.gov (United States)

    Makshakov, A. S.; Kravtsova, R. G.; Goryachev, N. A.; Pal'yanova, G. A.; Pavlova, L. A.

    2017-09-01

    New data on mercurial mineralization are presented, and a detailed characteristic is given for the first discovery of mercurous silver in ores of the Rogovik gold-silver deposit (the Omsukchan trough, Northeastern Russia). It was found that native silver in the examined ores occurs as finely-dispersed inclusions in quartz filling microcracks and interstitions. It also occurs in associations with kustelite, Ag sulfosalts and selenides, selenitic acanthite, and argyrodite. The mercury admixture varies from "not detected" in the central parts of grains to 0.22-1.70 wt % along the edges, or, in independent grains, to the appearance of Ag amalgams containing 10.20-24.61 wt % of Hg. The xenomorph form of grains of 50 μm or less in size prevails. It is assumed that the appearance of mercurial mineralization is caused by the superposition of products of the young Hg-bearing Dogda-Erikit belt upon the more ancient Ag-bearing Omsukchan trough.

  7. The extra cellular synthesis of gold and silver nanoparticles and their free radical scavenging and antibacterial properties.

    Science.gov (United States)

    Ramamurthy, C H; Padma, M; samadanam, I Daisy mariya; Mareeswaran, R; Suyavaran, A; Kumar, M Suresh; Premkumar, K; Thirunavukkarasu, C

    2013-02-01

    The bio reduction of chloro auric acid (HAuCl(4)) and silver nitrate (AgNO(3)) is achieved extracellularly by using the aqueous extract of Solanum torvum (S. torvum) fruit. The nanoparticle formation was screened by UV-visible spectroscopy through color conversion due to surface plasma resonance bands at 560 nm and 430 nm for gold and silver nanoparticles respectively. The spherical shapes with smooth surface of gold and silver nanoparticles were analyzed through scanning electron microscope and its presence was confirmed by energy dispersive X-ray spectroscopy (SEM/EDX). The functional groups in the gold and silver salts and the bio interactive functional groups present in the S. torvum extract were characterized by employing Fourier transform infra-red spectroscopy (FTIR). The biomedical properties of gold and silver nanoparticles were premeditated as free radical scavenging activity and antibacterial static agents. Gold and silver nanoparticles serve as strong hydroxyl, superoxide, nitric oxide and DPPH radical scavengers in contrast to their corresponding metal oxides. The radical quenching properties of gold and silver nanoparticles were found to correlate with in vitro DNA protective effect. The silver nanoparticles show strong zone of inhibition against Escherichia coli, Pseudomonas and Bacillus whereas, gold nanoparticles exhibit fair zone of inhibition. To our knowledge this is the first report that S. torvum extract can reduce metal acids to nano materials. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Attenuation, scattering, and depolarization of light by gold nanorods with silver shells

    Science.gov (United States)

    Khlebtsov, B. N.; Khanadeev, V. A.; Khlebtsov, N. G.

    2010-01-01

    Gold nanoparticles with silver nanoshells are obtained by synthesizing gold nanorods in a growing solution containing cetyltrimethylammonium bromide, subsequent separation in a concentration gradient of glycerol, and reduction of silver nitrate by ascorbic acid under alkaline conditions in the presence of polyvinylpyrrolidone. The formation of silver nanoshells was monitored by the shift of plasmon resonances of extinction and differential light scattering, by the appearance of characteristics peaks of silver in the energy dispersive X-ray (EDX) spectra of samples, by the data of transmission electron microscopy, and by visual changes in the color of colloids. The spectrum of the intensity ratio of the co- and cross-polarized compo- nents of light scattered by gold-silver nanorods is measured for the first time, and it is observed that the maximum is shifted by 80-100 nm compared to previously published spectra of gold nanorods (Khlebtsov et al., J. Phys. Chem. C 112, 12760 (2008)). The extinction and light scattering spectra are calculated by the method of separation of variables using the model of a confocal two-layer spheroid and these calculations are found to agree with spectral measurements. A method for determining the thickness of a silver nanolayer by the spectral shift of an extinction longitudinal resonance is described. The obtained data of optical spectroscopy and transmission electron microscopy and estimations of the mass of the deposited metal show that the aver-age thickness of the silver layer varies from 0.12 to 4 nm as the Ag/Au ratio changes from 2/80 to 90/80 μg/μg.

  9. Ecofriendly synthesis of silver and gold nanoparticles by Euphrasia officinalis leaf extract and its biomedical applications.

    Science.gov (United States)

    Singh, Hina; Du, Juan; Singh, Priyanka; Yi, Tae Hoo

    2017-08-08

    Biogenic synthesis of silver (AgNPs) and gold nanoparticles (AuNPs) using aqueous extract of Euphrasia officinalis has been reported. Stable AgNPs and AuNPs were formed on adding aqueous solutions of silver nitrate and chloroauric acid with E. officinalis leaf extract, in 19 min and 2 min, respectively. The synthesis method used in present study was simple, reliable, rapid, cost effective and ecofriendly. The synthesized nanoparticles were characterized with field emission transmission electron microscopy (FE-TEM), elemental mapping, selected area diffraction pattern (SAED), energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), particle size distribution, zeta potential and Fourier-transform infrared spectroscopy (FTIR). The UV-Vis spectrum confirmed the synthesis of nanoparticles as the absorption band was observed at 450 nm for AgNPs and at 558 nm for AuNPs. The TEM images revealed quasi-spherical shape of AgNPs and AuNPs. The size of nanoparticles was determined to be 40.37 ± 1.8 nm for AgNPs and 49.72 ± 1.2 nm for AuNPs. The zeta potential value demonstrated the negative surface charge and stable nature of nanoparticles. Crystalline nature of the nanoparticles in the face-centred cubic (fcc) structure was confirmed by the peaks in the XRD pattern and SAED pattern. FTIR results showed the functional groups involved in reduction of silver and gold ions to metal nanoparticles. For biomedical application, the nanoparticles have been explored for anticancer, antibacterial and biofilm inhibition activities. It was observed that AgNPs exert anticancer activity against human lung cancer (A549) and human cervical cancer (HeLa) cell lines. On the other hand, AuNPs were able to inhibit only human cervical cancer cells. Furthermore, the AgNPs were active against clinically isolated human pathogens like Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Vibrio parahaemolyticus. Additionally, AgNPs also showed biofilm

  10. New riches in carbaporphyrin chemistry: silver and gold organometallic complexes of benzocarbaporphyrins.

    Science.gov (United States)

    Lash, Timothy D; Colby, Denise A; Szczepura, Lisa F

    2004-08-23

    The NH-N-NH-N core of the porphyrin system represents one of the best studied and most versatile platforms for coordination chemistry. However, the replacement of one or more of the interior nitrogens with carbon atoms would be expected to diminish the ability of these systems to form metallo derivatives considerably. Despite this expectation, carbaporphyrinoid systems have been shown to form stable organometallic derivatives. Although azuliporphyrins and benziporphyrins act as dianionic ligands, benzocarbaporphyrins are trianionic ligands. Treatment of five different meso unsubstituted benzocarbaporphyrins and two different meso tetraarylbenzocarbaporphyrins with excess silver(I) acetate afforded 65-97% yields of the corresponding silver(III) organometallic derivatives. The insertion of silver metal was confirmed by mass spectrometry and X-ray crystallography. The UV-vis spectra showed a strong Soret band at wavelengths between 437 and 451 nm, together with a series of Q-type bands at longer wavelengths. The new metallo carbaporphyrins demonstrate the presence of a strong diatropic ring current in their proton NMR spectra, and carbon-13 NMR spectroscopy indicates that the derivatives retain a plane of symmetry. The reaction of meso tetraaryl carbaporphyrins with gold(III) acetate afforded the related gold(III) complexes, and these also showed strongly porphyrin-like aromatic characteristics. The UV-vis spectra for the gold complexes again showed a strong Soret band between 437-439 nm, but a secondary band near 400 nm is somewhat intensified for the gold species compared to the spectra for the related silver(III) meso tetrasubstituted carbaporphyrins. The ring currents observed for the gold(III) complexes by proton NMR spectroscopy were comparable to those of the silver(III) derivatives, implying that both series have similar macrocyclic conformations. Cyclic voltammetry was performed on two different carbaporphyrins, their silver(III) derivatives, and a gold

  11. Combined DFT/FTIR structural studies of monodispersed PVP/Gold and silver nano particles

    Energy Technology Data Exchange (ETDEWEB)

    Abdelghany, A.M., E-mail: a.m_abdelghany@yahoo.com [Spectroscopy Department, Physics Division, National Research Center, Dokki, 12311, Cairo (Egypt); Mekhail, M.Sh.; Abdelrazek, E.M.; Aboud, M.M. [Physics Department, Faculty of Science, Mansoura University, 35516, Mansoura (Egypt)

    2015-10-15

    Nano-particles of two Nobel metals, namely, (silver and gold) were prepared and used as a dopant in polyvinyl pyrrolidone (PVP) polymeric matrix by the simple casting technique. Prepared samples examined theoretically using density functional theory (DFT) and experimentally with Fourier transform infrared (FTIR) and (UV/Vis) spectroscopy. DFT calculations and FTIR experimental results shows the persistence of the characteristic bands of polymeric network in their positions while pyrrolidinone adsorbed both silver and gold colloid surfaces preferably via the non-bonding electrons of the carbonyl group. UV/Vis experimental data was employed to calculate the optical energy gap of pristine and doped samples. Optical band gap and particle size were calculated and is in agreement with the results obtained from TEM data. Transmission electron microscopy shows that the prepared silver and gold nanoparticles were mono dispersed within the polymeric matrix. - Highlights: • Nano-particles of two Nobel metals, namely, (silver and gold) were prepared. • Polyvinyl pyrrolidone polymeric matrix doped with nobel metal were prepared via casting technique. • Prepared samples investigated via combined (DFT) and (FTIR). • Transmission electron microscopy shows monodispersed nanoparticles.

  12. Synthesis and Antitumour Activity of Gold(I) and Silver(I) Complexes ...

    African Journals Online (AJOL)

    NICO

    action of anticancer activity. KEYWORDS. Gold(I), silver(I), hydrazine, diphosphine, antitumour, anticancer, mitochondrial membrane potential. 1. Introduction. The use of inorganic compounds as cancer treatment became well established with the FDA approval of cisplatin in 1978.1. Cisplatin, carboplatin and oxaliplatin are ...

  13. Assessment of gold and silver in assorted mobile phone printed circuit boards (PCBs): Original article.

    Science.gov (United States)

    Vats, M C; Singh, S K

    2015-11-01

    Demand for gold and silver has been escalating with increasing usage of electronic equipment globally. Around 267.3 MT of gold and 7275 MT of silver are being consumed annually for manufacturing mobile phones, laptops and other electronic equipment. However, only 15% is recuperated from these equipment; the remainder lies in the storage yards or landfills. The waste comprise glass, plastics, wires, batteries, PCBs, metal casing, etc. The PCB is composed of precious metals, which creates immense purpose for recycling and recovery. This paper characterises and assesses the recoverable metallic fraction of gold and silver from PCBs of mobile phones. The methodology is based on dismantling of the mobile handset and subjecting the PCBs to roasting and acid digestion. The digested samples were analysed by atomic absorption spectroscopy and the content of gold and silver in the PCBs was to be found in the range of 0.009-0.017% and 0.25-0.79% by weight respectively. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Murraya Koenigii leaf-assisted rapid green synthesis of silver and gold nanoparticles

    Science.gov (United States)

    Philip, Daizy; Unni, C.; Aromal, S. Aswathy; Vidhu, V. K.

    2011-02-01

    A facile bottom-up 'green' and rapid synthetic route using Murraya Koenigii leaf extract as reducing and stabilizing agent produced silver nanoparticles at ambient conditions and gold nanoparticles at 373 K. The nanoparticles were characterized using UV-vis, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. This method allows the synthesis of well-dispersed silver and gold nanoparticles having size ˜10 nm and ˜20 nm, respectively. Silver nanoparticles with size ˜10 nm having symmetric SPR band centered at 411 nm is obtained within 5 min of addition of the extract to the solution of AgNO 3 at room temperature. Nearly spherical gold nanoparticles having size ˜20 nm with SPR at 532 nm is obtained on adding the leaf extract to the boiling solution of HAuCl 4. Crystallinity of the nanoparticles is confirmed from the high-resolution TEM images, selected area electron diffraction (SAED) and XRD patterns. From the FTIR spectra it is found that the biomolecules responsible for capping are different in gold and silver nanoparticles. A comparison of the present work with the author's earlier reports on biosynthesis is also included.

  15. Comparative study of formation and stabilization of Gold and Silver Clusters and Nanoparticles in Mordenites

    NARCIS (Netherlands)

    Bogdanchikova, N.; Tuzovskaya, I.; Pestryakov, A.; Susarrey Arce, A.

    2011-01-01

    Supporting silver and gold on mordenites by ion-exchange method with further reduction with H2 leads to formation of neutral and charged metal clusters inside zeolite channels as well as metal nanoparticles on external surface of mordenite. A portion of the cluster states of the metals and stability

  16. Alternative Plasmonic Materials: Alternative Plasmonic Materials: Beyond Gold and Silver (Adv. Mater. 24/2013)

    DEFF Research Database (Denmark)

    Naik, Gururaj V.; Shalaev, Vladimir M.; Boltasseva, Alexandra

    2013-01-01

    Beyond Silver and Gold: Better material buildingblocks are essential in transforming the novel ideas of plasmonics and metamaterials into technologies of the future, as reviewed by Alexandra Boltasseva and co-workers on page 3264. Devices built from tailored materials offer improved performance a...

  17. Take-Home Nanochemistry: Fabrication of a Gold- or Silver-Containing Window Cling

    Science.gov (United States)

    Campbell, Dean J.; Villarreal, Richard B.; Fitzjarrald, Tamara J.

    2012-01-01

    The purpose of this laboratory experiment is to introduce aspects of materials chemistry, such as polymers and nanoparticle synthesis and properties, to students by their fabrication of a take-home polydimethylsiloxane window cling containing gold or silver nanoparticles. This lab covers small portions of three successive laboratory periods and is…

  18. [The enrichment characteristic and mechanism of gold-silver minerals in submarine hydrothermal sulfides from the ultra-slow-spreading SWIR].

    Science.gov (United States)

    Wang, Yan; Sun, Xiao-ming; Wu, Zhong-wei; Deng, Xi-guang; Dai, Ying-zhi; Lin, Zhi-yong

    2014-12-01

    In the present study, content and occurrence of Au, Ag in three submarine hydrothermal sulfide samples from the ultra-slow-spreading Southwest Indian Ridge (SWIR) were studied by using inductively coupled plasma-atomic emission spectrometry (ICP-AES), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results of ICP-AES show that all of the samples have signs of Au-Ag enrichment. By SEM/EDS, we discovered a mass of gold-silver minerals in the samples. In S27-4, gold occurs as irregular-shaped native gold and electrum grains in sulfides or between crystal particles. However, we discovered lots of Au-independent silver minerals except parts of electrum in S35-22. EDS results of silver minerals indicate that silver minerals closely related with halogen element, inferring that silver minerals may be silver halides. Electrum in S35-22 can be absorbed at the surface or crystal edge of pyrite besides occurring in or between sulfides as S27-4, supposed to be related to surface defect in pyrite. Electrum is the only Au-Ag mineral discovered in S35-17. These electrum gains occur as inclusion gold, absorbed gold or fissure gold. In addition, there are different Au-Ag mole ratios of electrum in three samples, indicating distinct hydrothermal conditions. In the base of research before, we consider that AgCl2(-) is the dominant complex of silver in ore-forming fluid of S27-4, however, gold is transported as AuCl2(-) transforming to AuHS(0), indicating that hydrothermal fluids decreased from high-moderate to moderate-low temperature and conductive cooling played an important role in this process. Similar enrichment mechanism happened in S35-22, but silver halides discovered in S35-22 suggest a higher temperature and chloride in the early stage. However, The enrichment of electrums in black smoke sample (S35-17) relates to mixing of hydrothermal fluids and seawater.

  19. Trace elements contamination of soils around gold mine tailings ...

    African Journals Online (AJOL)

    ISHIOMA

    Improved tailings management strategies, among other factors, might have influenced the reduced level of trace elements .... Levels of As, Cu, Pb and Zn in soils around active and decommissioned gold mine tailings dams at Obuasi, Ghana (mg/kg). Trace element ..... USEPA, Office of Solid Waste, Special. Waste Branch ...

  20. Scaling of the Surface Plasmon Resonance in Gold and Silver Dimers Probed by EELS

    DEFF Research Database (Denmark)

    Kadkhodazadeh, Shima; de Lasson, Jakob Rosenkrantz; Beleggia, Marco

    2014-01-01

    . Instead, within the range 0.1R determined for both gold and silver dimers. Despite this common power dependence, consistently larger SPR wavelength shifts are registered for silver for a given change in d, implying......The dependence of surface plasmon coupling on the distance between two nanoparticles (dimer) is the basis of nanometrology tools such as plasmon rulers. Application of these nanometric rulers requires an accurate description of the scaling of the surface plasmon resonance (SPR) wavelength...... with distance. Here, we have applied electron energy-loss spectroscopy (EELS) and scanning transmission electron microscopy (STEM) imaging to investigate the relationship between the SPR wavelength of gold and silver nanosphere dimers (radius R) and interparticle distance (d) in the range 0.1R

  1. Synthesis and characterization of Gold and Silver nano-particles using different leaf extracts namely Catharanthus roseus, Datura metel and Azadirachta indica and Estimation of antimicrobial activity of silver nano-particles using disc diffusion method

    OpenAIRE

    Sarbjeet Singh Gujral

    2014-01-01

    Objective: synthesis of gold and silver nano-particles using leaf extracts of Catharanthus roseus, Datura metel and Azadirachta indica and Estimation of antimicrobial activity of silver nano-particles using disc diffusion method. Method: Green approach has been utilized for the synthesis of gold and silver nano-particles. Different aqueous plant extracts has been prepared which was then utilized for the biosynthesis of gold and silver nano-particles. Estimation for the synthesis of nano-parti...

  2. Multi-technique characterization of gold electroplating on silver substrates for cultural heritage applications

    Science.gov (United States)

    Ortega-Feliu, I.; Ager, F. J.; Roldán, C.; Ferretti, M.; Juanes, D.; Scrivano, S.; Respaldiza, M. A.; Ferrazza, L.; Traver, I.; Grilli, M. L.

    2017-09-01

    This work presents a detailed study of a series of silver plates gilded via electroplating techniques in which the characteristics of the coating gold layers are investigated as a function of the electroplating variables (voltage, time, anode surface and temperature). Some reference samples were coated by radio frequency sputtering in order to compare gold layer homogeneity and effective density. Surface analysis was performed by means of atomic and nuclear techniques (SEM-EDX, EDXRF, PIXE and RBS) to obtain information about thickness, homogeneity, effective density, profile concentration of the gold layers and Au-Ag diffusion profiles. The gold layer thickness obtained by PIXE and EDXRF is consistent with the thickness obtained by means of RBS depth profiling. Electroplated gold mass thickness increases with electroplating time, anode area and voltage. However, electrodeposited samples present rough interfaces and gold layer effective densities lower than the nominal density of Au (19.3 g/cm3), whereas sputtering produces uniform layers with nominal density. These analyses provide valuable information to historians and curators and can help the restoration process of gold-plated silver objects.

  3. The optical, photothermal, and facile surface chemical properties of gold and silver nanoparticles in biodiagnostics, therapy, and drug delivery

    Science.gov (United States)

    Austin, Lauren A.; Mackey, Megan A.; Dreaden, Erik C.

    2014-01-01

    Nanotechnology is a rapidly growing area of research in part due to its integration into many biomedical applications. Within nanotechnology, gold and silver nanostructures are some of the most heavily utilized nanomaterial due to their unique optical, photothermal, and facile surface chemical properties. In this review, common colloid synthesis methods and biofunctionalization strategies of gold and silver nanostructures are highlighted. Their unique properties are also discussed in terms of their use in biodiagnostic, imaging, therapeutic, and drug delivery applications. Furthermore, relevant clinical applications utilizing gold and silver nanostructures are also presented. We also provide a table with reviews covering related topics. PMID:24894431

  4. Facially amphiphilic thiol capped gold and silver nanoparticles

    Indian Academy of Sciences (India)

    Abstract. A series of bile acid-derived facially amphiphilic thiols have been used to cap sliver and gold nanoparticles. The self-assembling properties of these steroid-capped nanoparticles have been investigated and reported in this article.

  5. Training text chunkers on a silver standard corpus: can silver replace gold?

    Science.gov (United States)

    2012-01-01

    Background To train chunkers in recognizing noun phrases and verb phrases in biomedical text, an annotated corpus is required. The creation of gold standard corpora (GSCs), however, is expensive and time-consuming. GSCs therefore tend to be small and to focus on specific subdomains, which limits their usefulness. We investigated the use of a silver standard corpus (SSC) that is automatically generated by combining the outputs of multiple chunking systems. We explored two use scenarios: one in which chunkers are trained on an SSC in a new domain for which a GSC is not available, and one in which chunkers are trained on an available, although small GSC but supplemented with an SSC. Results We have tested the two scenarios using three chunkers, Lingpipe, OpenNLP, and Yamcha, and two different corpora, GENIA and PennBioIE. For the first scenario, we showed that the systems trained for noun-phrase recognition on the SSC in one domain performed 2.7-3.1 percentage points better in terms of F-score than the systems trained on the GSC in another domain, and only 0.2-0.8 percentage points less than when they were trained on a GSC in the same domain as the SSC. When the outputs of the chunkers were combined, the combined system showed little improvement when using the SSC. For the second scenario, the systems trained on a GSC supplemented with an SSC performed considerably better than systems that were trained on the GSC alone, especially when the GSC was small. For example, training the chunkers on a GSC consisting of only 10 abstracts but supplemented with an SSC yielded similar performance as training them on a GSC of 100-250 abstracts. The combined system even performed better than any of the individual chunkers trained on a GSC of 500 abstracts. Conclusions We conclude that an SSC can be a viable alternative for or a supplement to a GSC when training chunkers in a biomedical domain. A combined system only shows improvement if the SSC is used to supplement a GSC. Whether

  6. Training text chunkers on a silver standard corpus: can silver replace gold?

    Directory of Open Access Journals (Sweden)

    Kang Ning

    2012-01-01

    Full Text Available Abstract Background To train chunkers in recognizing noun phrases and verb phrases in biomedical text, an annotated corpus is required. The creation of gold standard corpora (GSCs, however, is expensive and time-consuming. GSCs therefore tend to be small and to focus on specific subdomains, which limits their usefulness. We investigated the use of a silver standard corpus (SSC that is automatically generated by combining the outputs of multiple chunking systems. We explored two use scenarios: one in which chunkers are trained on an SSC in a new domain for which a GSC is not available, and one in which chunkers are trained on an available, although small GSC but supplemented with an SSC. Results We have tested the two scenarios using three chunkers, Lingpipe, OpenNLP, and Yamcha, and two different corpora, GENIA and PennBioIE. For the first scenario, we showed that the systems trained for noun-phrase recognition on the SSC in one domain performed 2.7-3.1 percentage points better in terms of F-score than the systems trained on the GSC in another domain, and only 0.2-0.8 percentage points less than when they were trained on a GSC in the same domain as the SSC. When the outputs of the chunkers were combined, the combined system showed little improvement when using the SSC. For the second scenario, the systems trained on a GSC supplemented with an SSC performed considerably better than systems that were trained on the GSC alone, especially when the GSC was small. For example, training the chunkers on a GSC consisting of only 10 abstracts but supplemented with an SSC yielded similar performance as training them on a GSC of 100-250 abstracts. The combined system even performed better than any of the individual chunkers trained on a GSC of 500 abstracts. Conclusions We conclude that an SSC can be a viable alternative for or a supplement to a GSC when training chunkers in a biomedical domain. A combined system only shows improvement if the SSC is used to

  7. Optical properties and electrochemical dealloying of Gold-Silver alloy nanoparticles immobilized on composite thin-film electrodes

    Science.gov (United States)

    Starr, Christopher A.

    Gold-silver alloy nanoparticles (NPs) capped with adenosine 5'-triphosphate were synthesized by borohydride reduction of dilute aqueous metal precursors. High-resolution transmission electron microscopy showed the as-synthesized particles to be spherical with average diameters ~4 nm. Optical properties were measured by UV-Visible spectroscopy (UV-Vis), and the formation of alloy NPs was verified across all gold:silver ratios by a linear shift in the plasmon band maxima against alloy composition. The molar absorptivities of the NPs decreased non-linearly with increasing gold content from 2.0 x 108 M-1 cm-1 (lambdamax = 404 nm) for pure silver to 4.1 x 107 M-1 cm -1 (lambdamax = 511 nm) for pure gold. The NPs were immobilized onto transparent indium-tin oxide composite electrodes using layer-by-layer (LbL) deposition with poly(diallyldimethylammonium) acting as a cationic binder. The UV-Vis absorbance of the LbL film was used to calculate the surface coverage of alloy NPs on the electrode. Typical preparations had average NP surface coverages of 2.8 x 10-13 mol NPs/cm2 (~5% of cubic closest packing) with saturated films reaching ~20% of ccp for single-layer preparations (1.0 ~ 10-12 mol NPs/cm2). X-ray photoelectron spectroscopy confirmed the presence of alloy NPs in the LbL film and showed silver enrichment of the NP surfaces by ~9%. Irreversible oxidative dissolution (dealloying) of the less noble silver atoms from the NPs on LbL electrodes was performed by cyclic voltammetry (CV) in sulfuric acid. Alloy NPs with higher gold content required larger overpotentials for silver dealloying. Dealloying of the more-noble gold atoms from the alloy NPs was also achieved by CV in sodium chloride. The silver was oxidized first to cohesive silver chloride, and then gold dealloyed to soluble HAuCl 4- at higher potentials. Silver oxidation was inhibited during the first oxidative scan, but subsequent cycles showed typical, reversible silver-to-silver chloride voltammetry. The

  8. Geology of the Barite Hill gold-silver deposit in the southern Carolina slate belt

    Science.gov (United States)

    Clark, S.H.B.; Gray, K.J.; Back, J.M.

    1999-01-01

    Barite Hill is a stratiform gold-silver deposit associated with base metal sulfides and barite in greenschist facies rocks. The deposit, southernmost of four recently mined gold deposits in the Carolina slate belt, is located in the Lincolnton-McCormick district of Georgia and South Carolina, which includes several known gold-silver and base metal deposits in a Kuroko-type geological setting along with deposits of kyanite and manganese. Approximately 1,835,000 g of gold was produced mainly from oxidized ores in the Main and Rainsford pits from 1990 until their closing in 1994. Ore is hosted by sericitically altered felsic metavolcanic and metasedimentary rocks of the Late Proterozoic Persimmon Fork Formation. The deposit is stratigraphically below an overturned contact between upper and lower pyroclastic units, which overlie the Lincolnton metarhyolite, an intrusive unit. Gold-silver-rich zones in the Main pit are partly coincident with lenses of siliceous barite rock, but not confined to them, and occur more commonly in pyrite-quartz-altered fragmental rock. The Main pit ore is stratigraphically overlain by a zone of base metal and barite enrichment, which is, in turn, overlain by a talc-tremolite alteration zone locally. Siliceous barite zones are absent in the Rainsford pit, and gold-silver minerals are associated with silicified rocks and chert. The Barite Hill deposit is interpreted to be the result of Kuroko-type, volcanogenic, base metal sulfide mineralization, followed by gold-silver mineralization under epithermal conditions with the following stages of evolution: (1) massive sulfides, barite, and fine-grained siliceous exhalites were deposited during Late Proterozoic to Cambrian submarine volcanism, which was related to plate convergence and subduction in a microcontinental or island-arc setting distant from the North American continental plate; (2) Au-Ag-Te and base and precious metal Te-Se-Bi minerals were deposited either during waning stages of

  9. Gold-silver-tellurium mineral assemblages in different ore styles of the Southern Urals VHMS deposits

    Science.gov (United States)

    Maslennikov, V. V.; Zaykov, V. V.; Maslennikova, S. P.; Tesalina, S. G.; Herrington, R. J.; Buschmann, B.; Becker, K.; Petersen, S.; Orgeval, J. J.; Leistel, M.

    2003-04-01

    VMS deposits of the South Urals generally show a continuum in degradation and reworking ranging from pristine steep-sided hydrothermal sulphide mounds to deposits dominated by layered strata of clastic sulphides. Four different deposits with varying degrees of degradation in order of increased reworking: (Yaman-Kasy longrightarrow Molodezhnoe longrightarrow Alexandrinskoe longrightarrow Balta-Tau) have been ranged. The influence of sulphide mound destruction and of sea-floor alteration on mineral assemblages was investigated In the pristine Yaman-Kasy sulphide mound gold and silver occur as altaite+tellurium+hessite-stuetzite+sylvanite and later galena+native gold+pyrite assemblages in chalcopyrite+isocubanite-rich linings of former chimney conduits. Chalcopyrite-dominated conduit fragments in clastic ore facies contain native tellurium+gold intergrowths. In the weakly reworked Molodezhnoe deposit gold-silver assemblages only occur in sea-floor altered clastic sulphides on the slope of massive sulphide mounds in bornite- and tennantite-rich ores in association with Cu-Ag sulfides such as jalpaite, mckinstryite, and stromeyerite and rare Au-Ag-tellurides (petzite). The Alexandrinskoe deposit is dominated by clastic ores and here native gold and rare hessite occur together with galena in tennantite-sphalerite-dominated veins of the footwall as well as in drusy sphalerite forming conduits of vent chimneys. An assemblage of electrum+galena+tennantite was observed in secondary chalcopyrite in the outer walls of chimneys. Native gold+stromeyerite are common in bornite-rich clastic sulphides while an assemblage of Ag-sulphosalts+electrum is common in barite-rich ores. In the reworked Balta-Tau deposit Ag-sulphosalts+electrum-kustelite occur often together with tennantite+galena+barite banded ores. Gold-silver-telluride mineralisation in these VMS deposits changes with degree of reworking from Au-tellurides, and native gold+galena+pyrite in pristine sulphide mounds to

  10. Platinum group elements and gold in ferromanganese crusts from ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 116; Issue 1. Platinum group elements and gold in ferromanganese crusts from Afanasiy–Nikitin seamount, equatorial Indian Ocean: Sources and fractionation. V K Banakar J R Hein R P Rajani A R Chodankar. Volume 116 Issue 1 February 2007 pp 3-13 ...

  11. Trace elements contamination of soils around gold mine tailings ...

    African Journals Online (AJOL)

    This study investigated the issue of tailings dams as a potential source of trace elements contamination in soils at the Obuasi gold mine in Ghana. Soil samples taken from depths of up to 12 cm and within a radius of 400 m from the tailings dams (active and recommissioned), were analysed for As, Cu, Pb and. Zn using ...

  12. Size measurement of gold and silver nanostructures based on their extinction spectrum: limitations and extensions

    Directory of Open Access Journals (Sweden)

    A A Ashkarran

    2013-09-01

    Full Text Available  This paper reports on physical principles and the relations between extinction cross section and geometrical properties of silver and gold nanostructures. We introduce some simple relations for determining geometrical properties of silver and gold nanospheres based on the situation of their plasmonic peak. We also applied, investigated and compared the accuracy of these relations using other published works in order to make clear the effects of shape, size distribution and refractive index of particles’ embedding medium. Finally, we extended the equations to non-spherical particles and investigated their accuracy. We found that modified forms of the equations may lead to more exact results for non-spherical metal particles, but for better results, modified equations should depend on shape and size distribution of particles. It seems that these equations are not applicable to particles with corners sharper than cubes' corners i.e. nanostructures with spatial angles less than π/2 sr.

  13. An ultrasensitive, non-enzymatic glucose assay via gold nanorod-assisted generation of silver nanoparticles

    Science.gov (United States)

    Xianyu, Yunlei; Sun, Jiashu; Li, Yixuan; Tian, Yue; Wang, Zhuo; Jiang, Xingyu

    2013-06-01

    This report demonstrates a colorimetric, non-enzymatic glucose assay with a low detection limit of 0.07 μM based on negatively charged gold nanorod-enhanced redox reaction. This glucose assay could generate silver nanoparticles as the readout that can be visualized by the naked eye, and only 4 femtomoles of nanorods are needed for glucose determination in one human plasma sample.This report demonstrates a colorimetric, non-enzymatic glucose assay with a low detection limit of 0.07 μM based on negatively charged gold nanorod-enhanced redox reaction. This glucose assay could generate silver nanoparticles as the readout that can be visualized by the naked eye, and only 4 femtomoles of nanorods are needed for glucose determination in one human plasma sample. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01697h

  14. In vitro antioxidant, antimicrobial, cytotoxic potential of gold and silver nanoparticles prepared using Embelia ribes.

    Science.gov (United States)

    Dhayalan, Manikandan; Denison, Michael Immanuel Jesse; L, Anitha Jegadeeshwari; Krishnan, Kathiravan; N, Nagendra Gandhi

    2017-02-01

    In recent years, the green synthesis of gold (GNPs) and silver (SNPs) nanoparticles has gained great interest among chemists and researchers. The present study reports an eco-friendly, cost-effective, rapid and easy method for the synthesis of gold and silver nanoparticles using the seed extract of Embelia ribes (SEEr) as capping and reducing agent. The synthesised GNPs and SNPs were characterised using the following techniques: UV-vis spectroscopy, DLS, HR-TEM, FT-IR and XRD. The free radical scavenging potential of GNPs and SNPs was measured by DPPH assay and Phosphomolybdenum assay. Further, the antimicrobial activity against two micro-organisms were tested using disc diffusion method and cytotoxicity of GNPs and SNPs was determined against MCF-7 cell lines at different concentrations by MTT assay. Both the GNPs and SNPs prepared from E. ribes comparatively showed promising results thereby proving their clinical importance.

  15. Microchemical investigation of Greek and Roman silver and gold plated coins: coating techniques and corrosion mechanisms

    Science.gov (United States)

    Ingo, G. M.; Balbi, S.; de Caro, T.; Fragalà, I.; Riccucci, C.; Bultrini, G.

    2006-06-01

    Within the framework of a project financially supported by the European Commission (contract Nr. 509126, acronym PROMET) the metallurgical techniques used by Romans and Greeks for coating the copper core of coins with a thin or thick layer of gold or silver are studied by means of the combined use of scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS) and optical microscopy (OM) techniques. This approach is utilised to gain further insight into the micro-chemical structure of the external regions of the coins as well as into the bulk metallurgical features. The results indicate that several methods were used by the Greek and Roman craftsmen including the mechanical application of a thin malleable gold or silver foils to be welded via thermal treatment. The analytical approach is also used for investigating the corrosion products grown on the coins during the long-term burial and for identifying degradation mechanisms.

  16. Surface Enhanced Raman Scattering (SERS Studies of Gold and Silver Nanoparticles Prepared by Laser Ablation

    Directory of Open Access Journals (Sweden)

    Samuel P. Hernandez-Rivera

    2013-03-01

    Full Text Available Gold and silver nanoparticles (NPs were prepared in water, acetonitrile and isopropanol by laser ablation methodologies. The average characteristic (longer size of the NPs obtained ranged from 3 to 70 nm. 4-Aminobenzebethiol (4-ABT was chosen as the surface enhanced Raman scattering (SERS probe molecule to determine the optimum irradiation time and the pH of aqueous synthesis of the laser ablation-based synthesis of metallic NPs. The synthesized NPs were used to evaluate their capacity as substrates for developing more analytical applications based on SERS measurements. A highly energetic material, TNT, was used as the target compound in the SERS experiments. The Raman spectra were measured with a Raman microspectrometer. The results demonstrate that gold and silver NP substrates fabricated by the methods developed show promising results for SERS-based studies and could lead to the development of micro sensors.

  17. All that glitters is not gold: silver leaf gilding, another means to an end

    Directory of Open Access Journals (Sweden)

    Tiago Dias

    2015-01-01

    Full Text Available Complementing carved wood altarpieces and sculptures, the use of metallic leaves became paradigmatic of Portuguese religious ambiences during the 17th and 18th centuries. Although gold has always been favoured, alternative techniques to attain the desired golden lustre were developed simultaneously, mainly with the use of white metallic leaves covered with coloured glazes. Written historic references, present in various technical art texts, indicate that these imitation gildings have been a long time practice. Seldom mentioned, the silvering part of the process is generically described as identical to gilding, while much more attention is given to the golden glazes to be applied over the silvered surface, allowing for their material and technical evolution to be followed. Based on a survey of these historical references, an outline on these developments and the associated terminology is made, keeping in mind that the silver leaf's white glitter also shone on its own right.

  18. Chrysopogon zizanioides aqueous extract mediated synthesis characterization of crystalline silver and gold nanoparticles for biomedical applications

    OpenAIRE

    Arunachalam KD; Annamalai SK

    2013-01-01

    Kantha D Arunachalam, Sathesh Kumar Annamalai Center for Environmental Nuclear Research, Directorate of Research, SRM University, Chennai, Tamil Nadu, India Abstract: The exploitation of various plant materials for the biosynthesis of nanoparticles is considered a green technology as it does not involve any harmful chemicals. The aim of this study was to develop a simple biological method for the synthesis of silver and gold nanoparticles using Chrysopogon zizanioides. To exploit various pla...

  19. Distribution of copper, silver and gold during thermal treatment with brominated flame retardants

    Energy Technology Data Exchange (ETDEWEB)

    Oleszek, Sylwia, E-mail: sylwia_oleszek@yahoo.com [Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 1,1 Katahira, 2-Chome, Sendai 980-8577 (Japan); Institute of Environmental Engineering of the Polish Academy of Sciences, 34 M. Sklodowska-Curie St., 41-819 Zabrze (Poland); Grabda, Mariusz, E-mail: mariusz@mail.tagen.tohoku.ac.jp [Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 1,1 Katahira, 2-Chome, Sendai 980-8577 (Japan); Institute of Environmental Engineering of the Polish Academy of Sciences, 34 M. Sklodowska-Curie St., 41-819 Zabrze (Poland); Shibata, Etsuro, E-mail: etsuro@tagen.tohoku.ac.jp [Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 1,1 Katahira, 2-Chome, Sendai 980-8577 (Japan); Nakamura, Takashi, E-mail: ntakashi@tagen.tohoku.ac.jp [Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 1,1 Katahira, 2-Chome, Sendai 980-8577 (Japan)

    2013-09-15

    Highlights: • Copper, silver and gold during thermal treatment with brominated flame retardants. • Distribution of copper, silver and gold during thermal processing. • Thermodynamic considerations of the bromination reactions. - Abstract: The growing consumption of electric and electronic equipment results in creating an increasing amount of electronic waste. The most economically and environmentally advantageous methods for the treatment and recycling of waste electric and electronic equipment (WEEE) are the thermal techniques such as direct combustion, co-combustion with plastic wastes, pyrolysis and gasification. Nowadays, this kind of waste is mainly thermally treated in incinerators (e.g. rotary kilns) to decompose the plastics present, and to concentrate metals in bottom ash. The concentrated metals (e.g. copper, precious metals) can be supplied as a secondary raw material to metal smelters, while the pyrolysis of plastics allows the recovery of fuel gases, volatilising agents and, eventually, energy. Indeed, WEEE, such as a printed circuit boards (PCBs) usually contains brominated flame retardants (BFRs). From these materials, hydrobromic acid (HBr) is formed as a product of their thermal decomposition. In the present work, the bromination was studied of copper, silver and gold by HBr, originating from BFRs, such as Tetrabromobisphenol A (TBBPA) and Tetrabromobisphenol A-Tetrabromobisophenol A diglycidyl ether (TTDE) polymer; possible volatilization of the bromides formed was monitored using a thermo-gravimetric analyzer (TGA) and a laboratory-scale furnace for treating samples of metals and BFRs under an inert atmosphere and at a wide range of temperatures. The results obtained indicate that up to about 50% of copper and silver can evolve from sample residues in the form of volatile CuBr and AgBr above 600 and 1000 °C, respectively. The reactions occur in the molten resin phase simultaneously with the decomposition of the brominated resin. Gold is

  20. Photocatalytic degradation of methyl orange by gold silver nano-core/silica nano-shell

    Science.gov (United States)

    Badr, Y.; Mahmoud, M. A.

    2007-03-01

    The silica nanoparticles (SiO2 NPs), silver (Ag) NPs and gold (Au) NPs coated with SiO2 NPs (core shell) were prepared. The sizes and morphology of the particles were indicated. The three prepared NPs were used for photocatalytic degradation of methyl orange (MO) dye by xenon lamp. Rate of photocatalytic degradation reaction constant and lifetime were calculated for each catalyst. Moreover, the mechanism of the photocatalytic reaction was studied.

  1. Gold and silver nanoparticles from Trianthema decandra: synthesis, characterization, and antimicrobial properties

    OpenAIRE

    Geethalakshmi R; Sarada DV

    2012-01-01

    R Geethalakshmi, DVL SaradaDepartment of Biotechnology, School of Bioengineering, Sri Ramaswamy Memorial University, Kattankulathur, Tamil Nadu, IndiaBackground: There is an increasing commercial demand for nanoparticles due to their wide applicability in various markets, including medicine, catalysis, electronics, chemistry, and energy. In this report, a simple and ecofriendly chemical reaction for the synthesis of gold and silver nanoparticles from Trianthema decandra (Aizoaceae) has been d...

  2. Electron microscopy and EXAFS studies on oxide-supported gold-silver nanoparticles prepared by flame spray pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Hannemann, Stefan [Institute of Chemical and Bioengineering, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zurich (Switzerland); Grunwaldt, Jan-Dierk [Institute of Chemical and Bioengineering, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zurich (Switzerland)]. E-mail: grunwaldt@chem.ethz.ch; Krumeich, Frank [Laboratory of Inorganic Chemistry, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zurich (Switzerland); Kappen, Peter [Department of Physics, La Trobe University, Victoria 3086 (Australia); Baiker, Alfons [Institute of Chemical and Bioengineering, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zurich (Switzerland)

    2006-09-15

    Gold and gold-silver nanoparticles prepared by flame spray pyrolysis (FSP) were characterized by electron microscopy, in situ X-ray absorption spectroscopy (XANES and EXAFS), X-ray diffraction (XRD) and their catalytic activity in CO oxidation. Within this one-step flame-synthesis procedure, precursor solutions of dimethyl gold(III) acetylacetonate and silver(I) benzoate together with the corresponding precursor of the silica, iron oxide or titania support, were sprayed and combusted. In order to prepare small metal particles, a low noble metal loading was required. A loading of 0.1-1 wt.% of Au and Ag resulted in 1-6 nm particles. The size of the noble metal particles increased with higher loadings of gold and particularly silver. Both scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDXS) and X-ray absorption spectroscopy (XAS) studies proved the formation of mixed Au-Ag particles. In case of 1% Au-1% Ag/SiO{sub 2}, TEM combined with electron spectroscopic imaging (ESI) using an imaging filter could be used in addition to prove the presence of silver and gold in the same noble metal particle. CO oxidation in the presence of hydrogen was chosen as a test reaction sensitive to small gold particles. Both the influence of the particle size and the alloying of gold and silver were reflected in the CO oxidation activity.

  3. Equilibria of Gold and Silver between Molten Copper and FeOx-SiO2-Al2O3 Slag in WEEE Smelting at 1300 °C

    Science.gov (United States)

    Avarmaa, Katri; O'Brien, Hugh; Taskinen, Pekka

    Waste Electrical and Electronic Equipment (WEEE) offers a significant resource for precious metals such as gold and silver. To maximize precious metal recoveries and sustainable use their behavior during WEEE smelting with copper as the collector metal needs to be characterized. This study experimentally determines the distributions of gold and silver between metallic copper and FeOx-SiO2-Al2O3 slag (LCu/s[Me] = [Me]Copper/[Me]Slag) in alumina-saturation over the oxygen potential range of 10-5-10-10 atm at 1300 °C. The experiments were conducted employing equilibration / quenching followed by major element analysis by Electron Probe Micro-Analysis (EPMA) and trace element analysis by Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) techniques. Our results show silver distribution increased exponentially from 30 to 1000 as a function of decreasing oxygen partial pressure. Gold distribution was 105 at pO2 = 10-5 atm and >106 at pO2 = 10-6-10-10 atm.

  4. Mycosynthesis of silver and gold nanoparticles: Optimization, characterization and antimicrobial activity against human pathogens.

    Science.gov (United States)

    Balakumaran, M D; Ramachandran, R; Balashanmugam, P; Mukeshkumar, D J; Kalaichelvan, P T

    2016-01-01

    This study was aimed to isolate soil fungi from Kolli and Yercaud Hills, South India with the ultimate objective of producing antimicrobial nanoparticles. Among 65 fungi tested, the isolate, Bios PTK 6 extracellularly synthesized both silver and gold nanoparticles with good monodispersity. Under optimized reaction conditions, the strain Bios PTK 6 identified as Aspergillus terreus has produced extremely stable nanoparticles within 12h. These nanoparticles were characterized by UV-vis. spectrophotometer, HR-TEM, FTIR, XRD, EDX, SAED, ICP-AES and Zetasizer analyses. A. terreus synthesized 8-20 nm sized, spherical shaped silver nanoparticles whereas gold nanoparticles showed many interesting morphologies with a size of 10-50 nm. The presence and binding of proteins with nanoparticles was confirmed by FTIR study. Interestingly, the myco derived silver nanoparticles exhibited superior antimicrobial activity than the standard antibiotic, streptomycin except against Staphylococcus aureus and Bacillus subtilis. The leakage of intracellular components such as protein and nucleic acid demonstrated that silver nanoparticles damage the bacterial cells by formation of pores, which affects membrane permeability and finally leads to cell death. Further, presence of nanoparticles in the bacterial membrane and the breakage of cell wall were also observed using SEM. Thus, the obtained results clearly reveal that these antimicrobial nanoparticles could be explored as promising candidates for a variety of biomedical and pharmaceutical applications. Copyright © 2015 Elsevier GmbH. All rights reserved.

  5. Enhanced Antimicrobial and Anticancer Activity of Silver and Gold Nanoparticles Synthesised Using Sargassum incisifolium Aqueous Extracts

    Directory of Open Access Journals (Sweden)

    Mokone Mmola

    2016-12-01

    Full Text Available A detailed, methodical approach was used to synthesise silver and gold nanoparticles using two differently prepared aqueous extracts of the brown algae Sargassum incisifolium. The efficiency of the extracts in producing nanoparticles were compared to commercially available brown algal fucoidans, a major constituent of brown algal aqueous extracts. The nanoparticles were characterised using TEM, XRD and UV/Vis spectroscopy and zeta potential measurements. The rate of nanoparticle formation was assessed using UV/Vis spectroscopy and related to the size, shape and morphology of the nanoparticles as revealed by TEM. The antioxidant, reducing power and total polyphenolic contents of the aqueous extracts and fucoidans were determined, revealing that the aqueous extracts with the highest contents produced smaller, spherical, more monodisperse nanoparticles at a faster rate. The nanoparticles were assessed against two gram-negative bacteria, two gram-positive bacteria and one yeast strain. In contrast to the literature, the silver nanoparticles produced using the aqueous extracts were particularly toxic to Gram-negative bacteria, while the gold nanoparticles lacked activity. The cytotoxic activity of the nanoparticles was also evaluated against cancerous (HT-29, MCF-7 and non-cancerous (MCF-12a cell lines. The silver nanoparticles displayed selectivity, since the MCF-12a cell line was found to be resistant to the nanoparticles, while the cancerous HT-29 cell line was found to be sensitive (10% viability. The gold nanoparticles displayed negligible toxicity.

  6. Diffractive optical element embedded in silver-doped nanocomposite glass.

    Science.gov (United States)

    Fleming, Lauren A H; Wackerow, Stefan; Hourd, Andrew C; Gillespie, W Allan; Seifert, Gerhard; Abdolvand, Amin

    2012-09-24

    A diffractive optical element is fabricated with relative ease in a glass containing spherical silver nanoparticles 30 to 40 nm in diameter and embedded in a surface layer of thickness ~10 μm. The nanocomposite was sandwiched between a mesh metallic electrode with a lattice constant 2 μm, facing the nanoparticle containing layer and acting as an anode, and a flat metal electrode as cathode. Applying moderate direct current electric potentials of 0.4 kV and 0.6 kV at an elevated temperature of 200 °C for 30 minutes across the nanocomposites led to the formation of a periodic array of embedded structures of metallic nanoparticles. The current-time dynamics of the structuring processes, optical analyses of the structured nanocomposites and diffraction pattern of one such fabricated element are presented.

  7. Critical elements in Carlin, epithermal, and orogenic gold deposits

    Science.gov (United States)

    Goldfarb, Richard J.; Hofstra, Albert H.; Simmons, Stuart F.

    2016-01-01

    Carlin, epithermal, and orogenic gold deposits, today mined almost exclusively for their gold content, have similar suites of anomalous trace elements that reflect similar low-salinity ore fluids and thermal conditions of metal transport and deposition. Many of these trace elements are commonly referred to as critical or near-critical elements or metals and have been locally recovered, although typically in small amounts, by historic mining activities. These elements include As, Bi, Hg, In, Sb, Se, Te, Tl, and W. Most of these elements are now solely recovered as by-products from the milling of large-tonnage, base metal-rich ore deposits, such as porphyry and volcanogenic massive sulfide deposits.A combination of dominance of the world market by a single country for a single commodity and a growing demand for many of the critical to near-critical elements could lead to future recovery of such elements from select epithermal, orogenic, or Carlin-type gold deposits. Antimony continues to be recovered from some orogenic gold deposits and tellurium could potentially be a primary commodity from some such deposits. Tellurium and indium in sphalerite-rich ores have been recovered in the past and could be future commodities recovered from epithermal ores. Carlin-type gold deposits in Nevada are enriched in and may be a future source for As, Hg, Sb, and/or Tl. Some of the Devonian carbonaceous host rocks in the Carlin districts are sufficiently enriched in many trace elements, including Hg, Se, and V, such that they also could become resources. Thallium may be locally enriched to economic levels in Carlin-type deposits and it has been produced from Carlin-like deposits elsewhere in the world (e.g., Alsar, southern Macedonia; Lanmuchang, Guizhou province, China). Mercury continues to be recovered from shallow-level epithermal deposits, as well as a by-product of many Carlin-type deposits where refractory ore is roasted to oxidize carbon and pyrite, and mercury is then

  8. Quantification of gold and silver in minerals by laser-induced breakdown spectroscopy

    Science.gov (United States)

    Díaz, Daniel; Hahn, David W.; Molina, Alejandro

    2017-10-01

    The performance of laser-induced breakdown spectroscopy (LIBS) to identify and quantify gold and silver in ore samples was evaluated. Ores from a gold-producing mine and samples artificially doped with Au and Ag solutions to previously defined concentrations (surrogates) were prepared as 50-mm pellets prior to LIBS analysis. Silver detection and intensity measurement was straightforward for concentrations from 0.4 to 43 μg/g and from 1.1 to 375 μg/g in ore and surrogate samples, respectively. Au emission lines were not found after ensemble average or accumulation of 100-single shot LIBS spectra of ore samples containing up to 9.5 μg/g Au. However, the Au signal was present in the spectra of surrogate samples, for which a detection limit of about 0.8 μg/g was determined. When the number of sampling shots in ore samples increased, various single shot spectra registered Au emission lines. The number of spectra containing Au emission lines increased with the number of single shots. Those results, as well as scanning electron microscopy analysis of ore samples, suggest that the discrete analyte distribution as well as the inherent discrete characteristics associated to LIBS made the presence of gold in the LIBS spark an unlikely occurrence. The particle sampling rates (the percentage of laser pulses expected to sample at least one particle) were estimated for gold concentrations of 1.1 and 10.0 μg/g as 0.04% and 0.32%, respectively. A Monte Carlo simulation indicated that > 100 gold-containing particles should be sampled to accurately represent the discrete character of gold in the ore. Sampling 100 such particles requires > 105 laser pulses over a single pellet. Despite the fact that this rather large number of shots makes difficult to conduct conditional analysis on pellets, for some samples that withstood 5000 shots, gold quantification in ores was successfully achieved at concentrations as low as 1 μg/g. Results are encouraging and illustrate the applicability

  9. Eight-Electron Silver and Mixed Gold/Silver Nanoclusters Stabilized by Selenium Donor Ligands.

    Science.gov (United States)

    Chang, Wan-Ting; Lee, Po-Yi; Liao, Jian-Hong; Chakrahari, Kiran Kumarvarma; Kahlal, Samia; Liu, Yu-Chiao; Chiang, Ming-Hsi; Saillard, Jean-Yves; Liu, C W

    2017-08-14

    The first atomically and structurally precise silver-nanoclusters stabilized by Se-donor ligands, [Ag 20 {Se 2 P(O i Pr) 2 } 12 ] (3) and [Ag 21 {Se 2 P(OEt) 2 } 12 ] + (4), were isolated by ligand replacement reaction of [Ag 20 {S 2 P(O i Pr) 2 } 12 ] (1) and [Ag 21 {S 2 P(O i Pr) 2 } 12 ] + (2), respectively. Furthermore, doping reactions of 4 with Au(PPh 3 )Cl resulted in the formation of [AuAg 20 {Se 2 P(OEt) 2 } 12 ] + (5). Structures of 3, 4, and 5 were determined by single-crystal X-ray diffraction. The anatomy of cluster 3 with an Ag 20 core having C 3 symmetry is very similar to that of its dithiophosphate analogue 1. Clusters 4 and 5 exhibit an Ag 21 and Au@Ag 20 core of O h symmetry composed of eight silver capping atoms in a cubic arrangement and encapsulating an Ag 13 and Au@Ag 12 centered icosahedron, respectively. Both ligand exchange and heteroatom doping result in significant changes in optical and emissive properties for chalcogen-passivated silver nanoparticles, which have been theoretically confirmed as 8-electron superatoms. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Determination of trace elements in refined gold samples by inductively coupled plasma atomic emission spectrometry

    Directory of Open Access Journals (Sweden)

    Steharnik Mirjana

    2013-01-01

    Full Text Available This paper presents a method for determination the trace contents of silver, copper, iron, palladium, zinc and platinum in refined gold samples. Simultaneous inductively coupled plasma atomic emission spectrometer with radial torch position and cross flow nebulizer was used for determination. In order to compare the different calibration strategies, two sets of calibration standards were prepared. The first set was based on matrix matched calibration standards and the second was prepared without the addition of matrix material. Detection limits for matrix matching calibrations were higher for some elements than those without matrix matching. In addition, the internal standardization method was applied and experiments indicated that indium was the best option as internal standard. The obtained results for gold sample by matrix matching and matrix free calibrations were compared with the obtained results by standard addition method. The accuracy of the methods was tested performing recovery test. Recoveries for spiked sample were in the range of 90-115 %. The accuracy of the methods was also tested by analysis of certified reference material of high pure goldAuGHP1. The best results were achieved by matrix free calibration and standard addition method using indium as internal standard at wavelength of 230 nm. [Projekat Ministarstva nauke Republike Srbije, br. 34024: Development of Technologies for Recycling of Precious, Rare and Associated Metals from Solid Waste in Serbia to High Purity Products

  11. Modulatory Effect of Citrate Reduced Gold and Biosynthesized Silver Nanoparticles on α-Amylase Activity

    Directory of Open Access Journals (Sweden)

    Kantrao Saware

    2015-01-01

    Full Text Available Amylase is one of the important digestive enzymes involved in hydrolysis of starch. In this paper, we describe a novel approach to study the interaction of amylase enzyme with gold nanoparticles (AuNPs and silver nanoparticles (AgNPs and checked its catalytic function. AuNPs are synthesized using citrate reduction method and AgNPs were synthesized using biological route employing Ficus benghalensis and Ficus religiosa leaf extract as a reducing and stabilizing agent to reduce silver nitrate to silver atoms. A modulatory effect of nanoparticles on amylase activity was observed. Gold nanoparticles are excellent biocompatible surfaces for the immobilization of enzymes. Immobilized amylase showed 1- to 2-fold increase of activity compared to free enzyme. The biocatalytic activity of amylase in the bioconjugate was marginally enhanced relative to the free enzyme in solution. The bioconjugate material also showed significantly enhanced pH and temperature stability. The results indicate that the present study paves way for the modulator degradation of starch by the enzyme with AuNPs and biogenic AgNPs, which is a promising application in the medical and food industry.

  12. Sediment Distribution related to Gold and Silver Placer Deposits in Offshore of Sambas Besar Estuary, Sambas Regency, West Kalimantan

    Directory of Open Access Journals (Sweden)

    Ediar Usman

    2014-06-01

    Full Text Available DOI: 10.17014/ijog.v6i1.113Result of grain size analysis of the sea floor sediments from the study area indicates four sediment types, those are silt, sandy silt, silty sand, and sand. The silt unit has the widest distribution that is around 127.2 km2, sandy silt 12.65 km2, sand 1.176 km2, and silty sand 0.44 km2. Result of gold and silver content analysis from some selected samples indicates that the highest gold and silver amount are at PMK-08 location in northern part of the study area with gold content of 0.21 ppm and silver 13.36 ppm; both are silt sediment types. The highest gold and silver content occur within medium - coarse sediments containing subrounded grains of quartz and pyrite, at northern part of the study area. The presence of silver and gold is suggested to be controlled by a north-south longshore current pattern. The source of sediments from Sambas Besar River follows the longshore current, e.g. in northern estuary from south to north, and at southern estuary from north to south direction.

  13. One-step green synthesis and characterization of leaf extract-mediated biocompatible silver and gold nanoparticles from Memecylon umbellatum

    Science.gov (United States)

    Arunachalam, Kantha D; Annamalai, Sathesh Kumar; Hari, Shanmugasundaram

    2013-01-01

    In this experiment, green-synthesized silver and gold nanoparticles were produced rapidly by treating silver and gold ions with an extract of Memecylon umbellatum leaf. The reaction process was simple and easy to handle, and was monitored using ultraviolet-visible spectroscopy. The effect of the phytochemicals present in M. umbellatum, including saponins, phenolic compounds, phytosterols, and quinones, on formation of stable silver and gold nanoparticles was investigated by Fourier-transform infrared spectroscopy. The morphology and crystalline phase of the nanoparticles were determined by transmission electron microscopy and energy-dispersive x-ray spectroscopy. The results indicate that the saponins, phytosterols, and phenolic compounds present in the plant extract play a major role in formation of silver and gold nanoparticles in their respective ions in solution. The characteristics of the nanoparticles formed suggest application of silver and gold nanoparticles as chemical sensors in the future. Given the simple and eco-friendly approach for synthesis, these nanoparticles could easily be commercialized for large-scale production. PMID:23569372

  14. One-step green synthesis and characterization of leaf extract-mediated biocompatible silver and gold nanoparticles from Memecylon umbellatum.

    Science.gov (United States)

    Arunachalam, Kantha D; Annamalai, Sathesh Kumar; Hari, Shanmugasundaram

    2013-01-01

    In this experiment, green-synthesized silver and gold nanoparticles were produced rapidly by treating silver and gold ions with an extract of Memecylon umbellatum leaf. The reaction process was simple and easy to handle, and was monitored using ultraviolet-visible spectroscopy. The effect of the phytochemicals present in M. umbellatum, including saponins, phenolic compounds, phytosterols, and quinones, on formation of stable silver and gold nanoparticles was investigated by Fourier-transform infrared spectroscopy. The morphology and crystalline phase of the nanoparticles were determined by transmission electron microscopy and energy-dispersive x-ray spectroscopy. The results indicate that the saponins, phytosterols, and phenolic compounds present in the plant extract play a major role in formation of silver and gold nanoparticles in their respective ions in solution. The characteristics of the nanoparticles formed suggest application of silver and gold nanoparticles as chemical sensors in the future. Given the simple and eco-friendly approach for synthesis, these nanoparticles could easily be commercialized for large-scale production.

  15. Schiff Base modified on CPE electrode and PCB gold electrode for selective determination of silver ion

    Science.gov (United States)

    Leepheng, Piyawan; Suramitr, Songwut; Phromyothin, Darinee

    2017-09-01

    The schiff base was synthesized by 2,5-thiophenedicarboxaldehyde and 1,2,4-thiadiazole-3,5-diamine with condensation method. There was modified on carbon paste electrode (CPE) and Printed circuit board (PCB) gold electrode for determination silver ion. The schiff base modified electrodes was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The electrochemical study was reported by cyclic voltammetry method and impedance spectroscopy using modified electrode as working electrode, platinum wire and Ag/AgCl as counter electrode and reference electrode, respectively. The modified electrodes have suitable detection for Ag+. The determination of silver ions using the modified electrodes depended linearly on Ag+ concentration in the range 1×10-10 M to 1×10-7 M, with cyclic voltammetry sensitivity were 2.51×108 μAM-1 and 1.88×108 μAM-1 for PCB gold electrode and CPE electrode, respectively, limits of detection were 5.33×10-9 M and 1.99×10-8 M for PCB gold electrode and CPE electrode, respectively. The modified electrodes have high accuracy, inexpensive and can applied to detection Ag+ in real samples.

  16. Simulations of quantum transport in nanoscale systems: application to atomic gold and silver wires

    DEFF Research Database (Denmark)

    Mozos, J.L.; Ordejon, P.; Brandbyge, Mads

    2002-01-01

    's function techniques are used to calculate the quantum conductance. Here we apply the method to the study of the electronic transport in wires of gold and silver with atomic thickness. We show the results of our calculations, and compare with some of the abundant experimental data on these systems.......We present a first-principles method for studying the electronic transport through nanoscale atomic systems under non-equilibrium conditions. The method is based on density functional theory, and allows the calculation of the response of the system to an applied finite potential difference...

  17. Structures of gold(i) and silver(i) thiolate complexes of medicinal interest: a review and recent results.

    Science.gov (United States)

    Howard-Lock, H E

    1999-01-01

    We review the crystal structures, electrospray ionization mass spectra (ESI-MS) data and chiral HPLC data for the racemic and optically pure mononuclear AuL2 complexes, and for racemic [AuLI]n and optically pure [AgLII]n polymers (LI = thiomalate, LII = D-penicillamine). We postulate an equilibrium between polymeric, mononuclear and free ligand species for [AuLII]n (gold sodium thiomalate or GST). The ESI-MS results clearly show a tetrameric principal species in the 1:1 gold polymers, [AuLI]n. For the 1:1 silver: D-penicillamine complex, [AgLII]n, a non-molecular crystal of double helical structure, the ESI-MS results show multi-ligand-silver species, including tetramers, pentamers and hexamers. Other, relevant gold, silver and copper complexes are compared.

  18. Silver electrodeposition catalyzed by colloidal gold on carbon paste electrode: application to biotin-streptavidin interaction monitoring.

    Science.gov (United States)

    González-García, M B; Costa-García, A

    2000-01-01

    A new electrochemical method to monitor biotin-streptavidin interaction on carbon paste electrode, based on silver electrodeposition catalyzed by colloidal gold, was investigated. Silver reduction potential changed when colloidal gold was attached to an electrode surface through the biotin-streptavidin interaction. Thus, the direct reduction of silver ions on the electrode surface could be avoided and therefore, they were only reduced to metallic silver on the colloidal gold particle surface, forming a shell around these particles. When an anodic scan was performed, this shell of silver was oxidized and an oxidation process at + 0.08 V was recorded in NH3 1.0 M. Biotinylated albumin was adsorbed on the pretreated electrode surface. This modified electrode was immersed in colloidal gold-streptavidin labeled solutions. The carbon paste electrode was then activated in adequate medium (NaOH 0.1 M and H2SO4 0.1 M) to remove proteins from the electrode surface while colloidal gold particles remained adsorbed on it. Then, a silver electrodeposition at -0.18 V for 2 min and anodic stripping voltammetry were carried out in NH3 1.0 M containing 2.0 x 10(-5) M of silver lactate. An electrode surface preparation was carried out to obtain a good reproducibility of the analytical signal (5.3%), using a new electrode for each experiment. In addition, a sequential competitive assay was carried out to determine streptavidin. A linear relationship between peak current and logarithm of streptavidin concentration from 2.25 x 10(-15) to 2.24 x 10(-12) M and a limit of detection of 2.0 x 10(15) M were obtained.

  19. Femtosecond Laser-Induced Formation of Gold-Rich Nanoalloys from the Aqueous Mixture of Gold-Silver Ions

    Directory of Open Access Journals (Sweden)

    Yuliati Herbani

    2010-01-01

    Full Text Available The synthesis of gold-silver (AuAg nanoalloys of various compositions has been performed by direct irradiation of highly intense femtosecond laser pulse in the presence of polyvinylpyrrolidone (PVP. The mixture of Au and Ag ions of low concentration was simply introduced into a glass vial and subjected to femtosecond laser pulses for several minutes. The AuAg nanoalloys of 2-3 nm with reasonably narrow size distribution were formed, and the position of the surface plasmon resonance (SPR increased monotonically with an increase in the gold molar fraction in the ion solutions. The high resolution transmission electron microscope (HRTEM images exhibited the absence of core-shell structures, and the energy dispersive X-ray spectroscopy (EDX analysis confirmed that the particles were Au-rich alloys even for the samples with large fraction of Ag+ ions fed in the solution mixture. The formation mechanism of the alloy nanoparticles in the high intensity optical field was also discussed.

  20. The optically detected coherent lattice oscillations in silver and gold monolayer periodic nanoprism arrays: the effect of interparticle coupling.

    Science.gov (United States)

    Huang, Wenyu; Qian, Wei; El-Sayed, Mostafa A

    2005-10-13

    Using femtosecond transient spectroscopy, we studied the optically detected laser-induced coherent phonon oscillation of monolayers of periodic arrays of prismatic-shaped silver and gold nanoparticles, assembled by using the technique of nanosphere lithography. In this method, the same size of polystyrene sphere and the same vacuum conditions are used. Under these circumstances, the gold nanoprisms formed are found to have sharper tips than the corresponding silver nanoprisms. For both gold and silver nanoparticles, the surface plasmon absorption maximum is found to depend linearly on size. The coherent lattice oscillation periods are also found to depend linearly on size. However, although the observed dependence for the silver nanoparticle is found to follow the calculated dependence of a single particle on size (based on a one-dimensional standing wave model), the gold nanoparticle deviates from this model, and the deviation is found to increase with the size of the nanoparticles. This deviation can be explained by considering interparticle coupling. A simple interparticle lattice oscillating dipolar coupling model of the dimer is found to qualitatively account for both the sign and the size dependence of the deviation. The absence of this deviation in the silver nanoparticle arrays is blamed on the weak interparticle coupling due to their rounded tips and the possibility of oxidation of their surfaces.

  1. Injection of ligand-free gold and silver nanoparticles into murine embryos does not impact pre-implantation development

    Directory of Open Access Journals (Sweden)

    Ulrike Taylor

    2014-05-01

    Full Text Available Intended exposure to gold and silver nanoparticles has increased exponentially over the last decade and will continue to rise due to their use in biomedical applications. In particular, reprotoxicological aspects of these particles still need to be addressed so that the potential impacts of this development on human health can be reliably estimated. Therefore, in this study the toxicity of gold and silver nanoparticles on mammalian preimplantation development was assessed by injecting nanoparticles into one blastomere of murine 2 cell-embryos, while the sister blastomere served as an internal control. After treatment, embryos were cultured and embryo development up to the blastocyst stage was assessed. Development rates did not differ between microinjected and control groups (gold nanoparticles: 67.3%, silver nanoparticles: 61.5%, sham: 66.2%, handling control: 79.4%. Real-time PCR analysis of six developmentally important genes (BAX, BCL2L2, TP53, OCT4, NANOG, DNMT3A did not reveal an influence on gene expression in blastocysts. Contrary to silver nanoparticles, exposure to comparable Ag+-ion concentrations resulted in an immediate arrest of embryo development. In conclusion, the results do not indicate any detrimental effect of colloidal gold or silver nanoparticles on the development of murine embryos.

  2. Toxicological risk assessment of elemental gold following oral exposure to sheets and nanoparticles – A review

    DEFF Research Database (Denmark)

    Hadrup, Niels; Sharma, Anoop Kumar; Poulsen, Morten

    2015-01-01

    of gold ions from its surface. Elemental gold, or the released ions, is, to some extent, absorbed in the gastrointestinal tract. Gold is distributed to organs such as the liver, heart, kidneys and lungs. The main excretion route of absorbed gold is through urine. Data on the oral toxicity of elemental...... gold is limited. The acute toxicity of elemental gold seems to be low, as rats were unaffected by a single dose of 2000mg nanoparticles/kg of body weight. Information on repeated dose toxicity is very limited. Skin rashes have been reported in humans following the ingestion of liquors containing gold...... melanogaster; however, genotoxicity studies in mammals are lacking. Overall, based on the literature and taking low human exposure into account, elemental gold via the oral route is not considered to pose a health concern to humans in general....

  3. Green synthesis, characterization of gold and silver nanoparticles and their potential application for cancer therapeutics

    Energy Technology Data Exchange (ETDEWEB)

    Patra, Sujata; Mukherjee, Sudip; Barui, Ayan Kumar; Ganguly, Anirban [Biomaterials Group, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007, Telangana State (India); Sreedhar, Bojja [Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007, Telangana State (India); Patra, Chitta Ranjan, E-mail: crpatra@iict.res.in [Biomaterials Group, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007, Telangana State (India)

    2015-08-01

    In the present article, we demonstrate the delivery of anti-cancer drug to the cancer cells using biosynthesized gold and silver nanoparticles (b-AuNP & b-AgNP). The nanoparticles synthesized by using Butea monosperma (BM) leaf extract are thoroughly characterized by various analytical techniques. Both b-AuNP and b-AgNP are stable in biological buffers and biocompatible towards normal endothelial cells (HUVEC, ECV-304) as well as cancer cell lines (B16F10, MCF-7, HNGC2 & A549). Administration of nanoparticle based drug delivery systems (DDSs) using doxorubicin (DOX) [b-Au-500-DOX and b-Ag-750-DOX] shows significant inhibition of cancer cell proliferation (B16F10, MCF-7) compared to pristine drug. Therefore, we strongly believe that biosynthesized nanoparticles will be useful for the development of cancer therapy using nanomedicine approach in near future. - Highlights: • Biosynthesis of gold and silver nanoparticles using plant leaf extract • The approach is clean, efficient, eco-friendly & economically safe. • Biosynthesized nanoparticles are biocompatible towards normal and cancer cells. • Design and development of biosynthesized nanoparticle based drug delivery systems • Biosynthesized nanoparticles could be useful for cancer and other diseases.

  4. Biosynthesis of gold and silver nanoparticles using a novel marine strain of Stenotrophomonas.

    Science.gov (United States)

    Malhotra, Ankit; Dolma, Kunzes; Kaur, Navjot; Rathore, Y S; Ashish; Mayilraj, S; Choudhury, Anirban Roy

    2013-08-01

    The present study aims at exploiting marine microbial diversity for biosynthesis of metal nanoparticles and also investigates role of microbial proteins in the process of bio-mineralization of gold and silver. This is the first report for concurrent production of gold and silver nanoparticles (AuNPs and AgNPs) by extracellular secretion of a novel strain of Stenotrophomonas, isolated from Indian marine origin. This novel strain has faster rate kinetics for AgNPs synthesis than any other organism reported earlier. The nanoparticles were further characterized using UV-vis spectrophotometer, TEM, DLS and EDAX confirming their size ranging from 10-50 nm and 40-60 nm in dimensions for AuNPs and AgNPs, respectively. TEM analysis indicated formation of multi-shaped nanoparticles with heterogeneous size distribution in both the cases. Finally, the SDS-PAGE analysis of extracellular media supernatant suggested a potential involvement of certain low molecular weight secretory proteins in AuNPs and AgNPs biosynthesis. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. Laser-induced damage thresholds of gold, silver and their alloys in air and water

    Science.gov (United States)

    Starinskiy, Sergey V.; Shukhov, Yuri G.; Bulgakov, Alexander V.

    2017-02-01

    The nanosecond-laser-induced damage thresholds of gold, silver and gold-silver alloys of various compositions in air and water have been measured for single-shot irradiation conditions. The experimental results are analyzed theoretically by solving the heat flow equation for the samples irradiated in air and in water taking into account vapor nucleation at the solid-water interface. The damage thresholds of Au-Ag alloys are systematically lower than those for pure metals, both in air and water that is explained by lower thermal conductivities of the alloys. The thresholds measured in air agree well with the calculated melting thresholds for all samples. The damage thresholds in water are found to be considerably higher, by a factor of ∼1.5, than the corresponding thresholds in air. This cannot be explained, in the framework of the used model, neither by the conductive heat transfer to water nor by the vapor pressure effect. Possible reasons for the high damage thresholds in water such as scattering of the incident laser light by the vapor-liquid interface and the critical opalescence in the superheated water are suggested. Optical pump-probe measurements have been performed to study the reflectance dynamics of the surface irradiated in air and water. Comparison of the transient reflectance signal with the calculated nucleation dynamics provides evidence that the both suggested scattering mechanisms are likely to occur during metal ablation in water.

  6. Facile one-pot synthesis of gold and silver nanocatalysts using edible coconut oil

    Science.gov (United States)

    Meena Kumari, M.; Philip, Daizy

    2013-07-01

    The use of edible oil for the synthesis of metal nanoparticles by wet chemical method is reported for the first time. The paper presents an environmentally benign bottom up approach for the synthesis of gold and silver nanoparticles using edible coconut oil at 373 K. The formation of silver nanoparticles is signaled by the brownish yellow color and that of gold nanoparticles by the purple color. Fine control over the nanoparticle size and shape from triangular to nearly spherical is achieved by varying the quantity of coconut oil. The nanoparticles have been characterized by UV-Visible, Transmission Electron Microscopy and X-ray Diffraction. The chemical interaction of capping agents with metal nanoparticles is manifested using Fourier Transform Infrared Spectroscopy. The stable and crystalline nanoparticles obtained using this simple method show remarkable size-dependent catalytic activity in the reduction of the cationic dye methylene blue (MB) to leuco methylene blue (LMB). The first order rate constants calculated uphold the size dependent catalytic activity of the synthesized nanoparticles.

  7. Gold and silver health plans: accommodating demand heterogeneity in managed competition.

    Science.gov (United States)

    Glazer, Jacob; McGuire, Thomas G

    2011-09-01

    New regulation of health insurance markets creates multiple levels of health plans, with designations like "Gold" and "Silver." The underlying rationale for the heavy-metal approach to insurance regulation is that heterogeneity in demand for health care is not only due to health status (sick demand more than the healthy) but also to other, "taste" related factors (rich demand more than the poor). This paper models managed competition with demand heterogeneity to consider plan payment and enrollee premium policies in relation to efficiency (net consumer benefit) and fairness (the European concept of "solidarity"). Specifically, this paper studies how to implement a "Silver" and "Gold" health plan efficiently and fairly in a managed competition context. We show that there are sharp tradeoffs between efficiency and fairness. When health plans cannot or may not (because of regulation) base premiums on any factors affecting demand, enrollees do not choose the efficient plan. When taste (e.g., income) can be used as a basis of payment, a simple tax can achieve both efficiency and fairness. When only health status (and not taste) can be used as a basis of payment, health status-based taxes and subsidies are required and efficiency can only be achieved with a modified version of fairness we refer to as "weak solidarity." An overriding conclusion is that the regulation of premiums for both the basic and the higher level plans is necessary for efficiency. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. Gold/silver core-shell 20 nm nanoparticles extracted from citrate solution examined by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Engelhard, Mark H.; Smith, Jordan N.; Baer, Donald R.

    2016-06-01

    Silver nanoparticles of many types are widely used in consumer and medical products. The surface chemistry of particles and the coatings that form during synthesis or use in many types of media can significantly impact the behaviors of particles including dissolution, transformation and biological or environmental impact. Consequently it is useful to be able to extract information about the thickness of surface coatings and other attributes of nanoparticles produced in a variety of ways. It has been demonstrated that X-ray Photoelectron Spectroscopy (XPS) can be reliably used to determine the thickness of organic and other nanoparticles coatings and shells. However, care is required to produce reliable and consistent information. Here we report the XPS spectra from gold/silver core-shell nanoparticles of nominal size 20 nm removed from a citrate saturated solution after one and two washing cycles. The Simulation of Electron Spectra for Surface Analysis (SESSA) program had been used to model peak amplitudes to obtain information on citrate coatings that remain after washing and demonstrate the presence of the gold core. This data is provided so that others can compare use of SESSA or other modeling approaches to quantify the nature of coatings to those already published and to explore the impacts particle non-uniformities on XPS signals from core-shell nanoparticles.

  9. Platycodon saponins from Platycodi Radix (Platycodon grandiflorum) for the Green Synthesis of Gold and Silver Nanoparticles.

    Science.gov (United States)

    Choi, Yoonho; Kang, Sehyeon; Cha, Song-Hyun; Kim, Hyun-Seok; Song, Kwangho; Lee, You Jeong; Kim, Kyeongsoon; Kim, Yeong Shik; Cho, Seonho; Park, Youmie

    2018-01-17

    A green synthesis of gold and silver nanoparticles is described in the present report using platycodon saponins from Platycodi Radix (Platycodon grandiflorum) as reducing agents. Platycodin D (PD), a major triterpenoidal platycodon saponin, was enriched by an enzymatic transformation of an aqueous extract of Platycodi Radix. This PD-enriched fraction was utilized for processing reduction reactions of gold and silver salts to synthesize gold nanoparticles (PD-AuNPs) and silver nanoparticles (PD-AgNPs), respectively. No other chemicals were introduced during the reduction reactions, providing an entirely green, eco-friendly, and sustainable method. UV-visible spectra showed the surface plasmon resonance bands of PD-AuNPs at 536 nm and PD-AgNPs at 427 nm. Spherically shaped nanoparticles were observed from high-resolution transmission electron microscopy with average diameters of 14.94 ± 2.14 nm for PD-AuNPs and 18.40 ± 3.20 nm for PD-AgNPs. Minor triangular and other polygonal shapes were also observed for PD-AuNPs along with spherical ones. Atomic force microscopy (AFM) images also demonstrated that both nanoparticles were mostly spherical in shape. Curvature-dependent evolution was employed to enhance the AFM images and precisely measure the sizes of the nanoparticles. The sizes were measured as 19.14 nm for PD-AuNPs and 29.93 nm for PD-AgNPs from the enhanced AFM images. Face-centered cubic structures for both nanoparticles were confirmed by strong diffraction patterns from high-resolution X-ray diffraction analyses. Fourier transform infrared spectra revealed the contribution of -OH, aromatic C=C, C-O, and C-H functional groups to the synthesis. Furthermore, the catalytic activity of PD-AuNPs was assessed with a reduction reaction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride. The catalytic activity results suggest the potential application of these gold nanoparticles as catalysts in the future. The green strategy

  10. Platycodon saponins from Platycodi Radix ( Platycodon grandiflorum) for the Green Synthesis of Gold and Silver Nanoparticles

    Science.gov (United States)

    Choi, Yoonho; Kang, Sehyeon; Cha, Song-Hyun; Kim, Hyun-Seok; Song, Kwangho; Lee, You Jeong; Kim, Kyeongsoon; Kim, Yeong Shik; Cho, Seonho; Park, Youmie

    2018-01-01

    A green synthesis of gold and silver nanoparticles is described in the present report using platycodon saponins from Platycodi Radix ( Platycodon grandiflorum) as reducing agents. Platycodin D (PD), a major triterpenoidal platycodon saponin, was enriched by an enzymatic transformation of an aqueous extract of Platycodi Radix. This PD-enriched fraction was utilized for processing reduction reactions of gold and silver salts to synthesize gold nanoparticles (PD-AuNPs) and silver nanoparticles (PD-AgNPs), respectively. No other chemicals were introduced during the reduction reactions, providing an entirely green, eco-friendly, and sustainable method. UV-visible spectra showed the surface plasmon resonance bands of PD-AuNPs at 536 nm and PD-AgNPs at 427 nm. Spherically shaped nanoparticles were observed from high-resolution transmission electron microscopy with average diameters of 14.94 ± 2.14 nm for PD-AuNPs and 18.40 ± 3.20 nm for PD-AgNPs. Minor triangular and other polygonal shapes were also observed for PD-AuNPs along with spherical ones. Atomic force microscopy (AFM) images also demonstrated that both nanoparticles were mostly spherical in shape. Curvature-dependent evolution was employed to enhance the AFM images and precisely measure the sizes of the nanoparticles. The sizes were measured as 19.14 nm for PD-AuNPs and 29.93 nm for PD-AgNPs from the enhanced AFM images. Face-centered cubic structures for both nanoparticles were confirmed by strong diffraction patterns from high-resolution X-ray diffraction analyses. Fourier transform infrared spectra revealed the contribution of -OH, aromatic C=C, C-O, and C-H functional groups to the synthesis. Furthermore, the catalytic activity of PD-AuNPs was assessed with a reduction reaction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride. The catalytic activity results suggest the potential application of these gold nanoparticles as catalysts in the future. The green strategy reported in this

  11. Wet chemical synthesis of gold nanoparticles using silver seeds: a shape control from nanorods to hollow spherical nanoparticles

    Science.gov (United States)

    Xu, Zhi-Chuan; Shen, Cheng-Min; Xiao, Cong-Wen; Yang, Tian-Zhong; Zhang, Huai-Ruo; Li, Jian-Qi; Li, Hu-Lin; Gao, Hong-Jun

    2007-03-01

    A seed-mediated method was employed here for CTAB-assisted gold nanoparticle growth. 3-4 nm silver aqueous colloid was stabilized by sodium citrate and used as seed solution to initial gold particle growth. The concentration of seed solution was calculated based on its relationship with silver atom concentration and seed particle statistical mean volume. It was found that there is a maximum seed concentration of 8.57 × 10-12 M (~25 µl 0.343 × 10-8 M seed solution added) in 10 ml 2.5 × 10-4 M HAuCl4 growth solution for growth of rodlike particles. Below this seed amount, the aspect ratio of nanorods could be controlled by varying the silver seed amount, i.e. nanorods with aspect ratio ~18.9 were obtained when the seed concentration in the growth solution was 0.343 × 10-12 M by adding 1 µl 0.343 × 10-8 M silver seed solution and nanorods with aspect ratio ~9.69 were obtained when the seed concentration in the growth solution was 1.715 × 10-12 M by adding 5 µl 0.343 × 10-8 M silver seed solution. As the seed concentration in the growth solution was more than 8.58 × 10-12 M (25 µl 0.343 × 10-8 M silver seed solution was added), there were no rodlike particles formed but spherical ones instead. These spheres were further studied by TEM and found to all be hollow structures. It was suggested that there were probably two different nucleation processes for growth of nanorods and spheres. For hollow spheres, the reaction between Ag seeds and Au ions formed hollow structures based on the Ag particle template effect. Then further growth of Au on these hollow structures produced hollow gold nanospheres. For nanorods, due to the very low concentration of silver seed (molar ratio of Ag seed: Au = 3.426 × 10-8), the growth process here probably was started by silver-induced Au nucleation, in which reduction of gold ions by silver resulted in small gold clusters. These gold clusters further grew up into nanoparticles and nanorods in the presence of CTAB.

  12. Advanced mercury removal from gold leachate solutions prior to gold and silver extraction: a field study from an active gold mine in Peru.

    Science.gov (United States)

    Matlock, Matthew M; Howerton, Brock S; Van Aelstyn, Mike A; Nordstrom, Fredrik L; Atwood, David A

    2002-04-01

    Mercury contamination in the Gold-Cyanide Process (GCP) is a serious health and environmental problem. Following the heap leaching of gold and silver ores with NaCN solutions, portions of the mercury-cyano complexes often adhere to the activated carbon (AC) used to extract the gold. During the electrowinning and retorting steps, mercury can be (and often is) emitted to the air as a vapor. This poses a severe health hazard to plant workers and the local environment. Additional concerns relate to the safety of workers when handling the mercury-laden AC. Currently, mercury treatment from the heap leach solution is nonexistent. This is due to the fact that chelating ligands which can effectively work under the adverse pH conditions (as present in the heap leachate solutions) do not exist. In an effort to economically and effectively treat the leachate solution prior to passing over the AC, a dipotassium salt of 1,3-benzenediamidoethanethiol (BDET2-) has been developed to irreversibly bind and precipitate the mercury. The ligand has proven to be highly effective by selectively reducing mercury levels from average initial concentrations of 34.5 ppm (parts per million) to 0.014 ppm within 10 min and to 0.008 ppm within 15 min. X-ray powder diffraction (XRD), proton nuclear magnetic resonance (1H NMR), Raman, and infrared (IR) spectroscopy demonstrate the formation of a mercury-ligand compound, which remains insoluble over pH ranges of 0.0-14.0. Leachate samples from an active gold mine in Peru have been analyzed using cold vapor atomic fluorescence (CVAF) and inductively coupled plasma optical emission spectroscopy (ICP-OES) for metal concentrations before and after treatment with the BDET2- ligand.

  13. Influence of photon beam energy on the dose enhancement factor caused by gold and silver nanoparticles: An experimental approach

    Energy Technology Data Exchange (ETDEWEB)

    Guidelli, Eder José, E-mail: ederguidelli@pg.ffclrp.usp.br; Baffa, Oswaldo [Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, 14040-901 Ribeirão Preto, SP (Brazil)

    2014-03-15

    Purpose: Noble metal nanoparticles have found several medical applications in the areas of radiation detection; x-ray contrast agents and cancer radiation therapy. Based on computational methods, many papers have reported the nanoparticle effect on the dose deposition in the surrounding medium. Here the authors report experimental results on how silver and gold nanoparticles affect the dose deposition in alanine dosimeters containing several concentrations of silver and gold nanoparticles, for five different beam energies, using electron spin resonance spectroscopy (ESR). Methods: The authors produced alanine dosimeters containing several mass percentage of silver and gold nanoparticles. Nanoparticle sizes were measured by dynamic light scattering and by transmission electron microscopy. The authors determined the dose enhancement factor (DEF) theoretically, using a widely accepted method, and experimentally, using ESR spectroscopy. Results: The DEF is governed by nanoparticle concentration, size, and position in the alanine matrix. Samples containing gold nanoparticles afford a DEF higher than 1.0, because gold nanoparticle size is homogeneous for all gold concentrations utilized. For samples containing silver particles, the silver mass percentage governs the nanoparticles size, which, in turns, modifies nanoparticle position in the alanine dosimeters. In this sense, DEF decreases for dosimeters containing large and segregated particles. The influence of nanoparticle size-position is more noticeable for dosimeters irradiated with higher beam energies, and dosimeters containing large and segregated particles become less sensitive than pure alanine (DEF < 1). Conclusions: ESR dosimetry gives the DEF in a medium containing metal nanoparticles, although particle concentration, size, and position are closely related in the system. Because this is also the case as in many real systems of materials containing inorganic nanoparticles, ESR is a valuable tool for

  14. Orange pectin mediated growth and stability of aqueous gold and silver nanocolloids

    Energy Technology Data Exchange (ETDEWEB)

    Nigoghossian, Karina; Santos, Molíria V. dos; Barud, Hernane S.; Silva, Robson R. da [Institute of Chemistry, São Paulo State University – UNESP, 14801-970 Araraquara, SP (Brazil); Rocha, Lucas A. [Departamento de Quimica, Universidade de Franca, Franca, SP (Brazil); Caiut, José M.A. [Departamento de Química, FFCLRP, USP, Ribeirão Preto, SP (Brazil); Assunção, Rosana M.N. de [Faculdade de Ciências Integradas do Pontal, Universidade Federal de Uberlândia, 38302-000 Ituiutaba, MG (Brazil); Spanhel, Lubomir [CEITEC-Central European Institute of Technology, Masaryk University Brno (Czech Republic); Institute of Chemical Sciences, University of Rennes 1, Campus Beaulieu, 35 042 Rennes (France); Poulain, Marcel [Institute of Chemical Sciences, University of Rennes 1, Campus Beaulieu, 35 042 Rennes (France); Messaddeq, Younes [Institute of Chemistry, São Paulo State University – UNESP, 14801-970 Araraquara, SP (Brazil); Ribeiro, Sidney J.L., E-mail: sidney@iq.unesp.br [Institute of Chemistry, São Paulo State University – UNESP, 14801-970 Araraquara, SP (Brazil)

    2015-06-30

    Graphical abstract: - Highlights: • Pectin from orange was used as stabilizer of Ag, Au and Ag–Au nanoparticles. • Sodium citrate, oxalic acid or pectin were used as reducing agents. • Colloids spanning all visible region were obtained depending on Ag/Au-ratio and pH. • Pectin is a highly efficient stabilizer of nanocolloidal solutions for years. - Abstract: The role of orange based pectin in the nucleation and growth of silver and gold nanoparticles is addressed. Pectin is a complex polysaccharide found in fruits such as oranges, lemons, passion fruits or apples. It displays smooth and hairy chain regions containing hydroxyl-, ester-, carboxylate- and eventually amine groups that can act as surface ligands interacting under various pH conditions more or less efficiently with growing nanometals. Here, a high methoxy pectin (>50% esterified) was used as a stabilizer/reducing agent in the preparation of gold, silver and silver–gold nanoparticles. Commercial pectin (CP) and pectin extracted from orange bagasse (OP) were used. Optionally, trisodium citrate or oxalic acid we used to reduce AgNO{sub 3} and HAuCl{sub 4} in aqueous environment. Characterization methods included UV–vis absorption spectroscopy, transmission electron microscopy, electron diffraction and energy-dispersive X-ray spectroscopy. The results show that under different pH conditions, pectin and reducing agents allow producing various nanostructures shapes (triangles, spheres, rods, octahedrons and decahedrons) often with high polydispersity and sizes ranging between 5 nm and 30 nm. In addition, depending on Ag/Au-ratio and pH, the surface plasmon bands can be continuously shifted between 410 nm and 600 nm. Finally, pectin seems to be a highly efficient stabilizer of the colloidal systems that show a remarkable stability and unchanged optical spectral response even after five years.

  15. Morphology of embryonic liver under the influence of silver and gold citrates on a background of lead intoxication

    Directory of Open Access Journals (Sweden)

    Harets V.I.

    2016-05-01

    Full Text Available Morphological state of embryonic liver under the influence of silver and gold citrates on a background of lead intoxication was studied. We found that values of the hepatofetal index in the groups Pb+Ag and Pb+Au had significant differences as compared to the group exposed to lead intoxication, but did not differ significantly from the control group and made up 0,086±0,001 and 0,083±0,001, respectively. Value of the relative area of blood vessels in groups Pb+Ag and Pb+Au was 13.08±0.53% and 16.83±0.53%, respectively, which had no significant difference as compared to control group, but differed from the value of lead intoxication group. Under the influence of silver citrate on a background of lead intoxication the relative area of hematopoietic cells was 52,5±0,95%; this indicates to modification action of silver on haematopoiesis. Thus, injection of silver and gold citrates prevents negative effect of lead on morphometric parameters of embryonic liver, relative area of blood vessels and hematopoietic cells. Experiment results showed protective effect of silver and gold citrates on a background of lead intoxication during hepatogenesis.

  16. Green synthesis of silver, gold and silver/gold bimetallic nanoparticles using the Gloriosa superba leaf extract and their antibacterial and antibiofilm activities.

    Science.gov (United States)

    Gopinath, Kasi; Kumaraguru, Shanmugasundaram; Bhakyaraj, Kasi; Mohan, Subramanian; Venkatesh, Kunga Sukumaran; Esakkirajan, Masanam; Kaleeswarran, Periyannan; Alharbi, Naiyf S; Kadaikunnan, Shine; Govindarajan, Marimuthu; Benelli, Giovanni; Arumugam, Ayyakannu

    2016-12-01

    The green fabrication of metal nanoparticles using botanical extracts is gaining increasing research attention in nanotechnology, since it does not require high energy inputs or the production of highly toxic chemical byproducts. Here, silver (Ag), gold (Au) and their bimetallic (Ag/Au) nanoparticles (NPs) were green synthesized using the Gloriosa superba aqueous leaf extract. Metal NPs were studied by spectroscopic (UV-visible spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, XRD and EDX) and microscopic (AFM and TEM) analysis. AFM and TEM showed that Ag and Au NPs had triangular and spherical morphologies, with an average size of 20 nm. Bimetallic Ag/Au NPs showed spherical shapes with an average size of 10 nm. Ag and Ag/Au bimetallic NPs showed high antibacterial and antibiofilm activities towards Gram-positive and Gram-negative bacteria. Overall, the proposed synthesis route of Ag, Au and Ag/Au bimetallic NPs can be exploited by the pharmaceutical industry to develop drugs effective in the fight against microbic infections. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. A microcantilever-based silver ion sensor using DNA-functionalized gold nanoparticles as a mass amplifier

    Science.gov (United States)

    You, Juneseok; Song, Yeongjin; Park, Chanho; Jang, Kuewhan; Na, Sungsoo

    2017-06-01

    Silver ions have been used to sterilize many products, however, it has recently been demonstrated that silver ions can be toxic. This toxicity has been studied over many years with the lethal concentration at 10 μM. Silver ions can accumulate through the food chain, causing serious health problems in many species. Hence, there is a need for a commercially available silver ion sensor, with high detection sensitivity. In this work, we develop an ultra-sensitive silver ion sensor platform, using cytosine based DNA and gold nanoparticles as the mass amplifier. We achieve a lower detection limit for silver ions of 10 pM; this detection limit is one million times lower than the toxic concentration. Using our sensor platform we examine highly selective characteristics of other typical ions in water from natural sources. Furthermore, our sensor platform is able to detect silver ions in a real practical sample of commercially available drinking water. Our sensor platform, which we have termed a ‘MAIS’ (mass amplifier ion sensor), with a simple detection procedure, high sensitivity, selectivity and real practical applicability has shown potential as an early toxicity assessment of silver ions in the environment.

  18. Soil-pore water distribution of silver and gold engineered nanoparticles in undisturbed soils under unsaturated conditions

    NARCIS (Netherlands)

    Tavares, D.S.; Rodrigues, S.M.; Cruz, N.; Carvalho, C.; Teixeira, T.; Carvalho, L.; Duarte, A.C.; Trindade, T.; Pereira, E.; Römkens, P.F.A.M.

    2015-01-01

    Release of engineered nanoparticles (ENPs) to soil is well documented but little is known on the subsequent soil-pore water distribution of ENPs once present in soil. In this study, the availability and mobility of silver (Ag) and gold (Au) ENPs added to agricultural soils were assessed in two

  19. A review on approaches to bio distribution studies about gold and silver engineered nanoparticles by inductively coupled plasma mass spectrometry

    NARCIS (Netherlands)

    Krystek, P.W.

    2012-01-01

    This paper gives a general overview about bio distribution studies which are especially related to engineered nanoparticles (NPs) made of gold and silver. The analysis of biological materials from bio distribution studies plays a significant role in the application of atomic spectrometry to study

  20. Tris(2-AminoethylAmine-Functionalized Fe3O4 Magnetic Nanoparticles as a Selective Sorbent for Separation of Silver and Gold Ions in Different pHs

    Directory of Open Access Journals (Sweden)

    Hamid Reza Lotfi Zadeh Zhad

    2013-01-01

    Full Text Available The usage of tris(2-aminoethylamine-functionalized Fe3O4 nanoparticles as a novel magnetic sorbent for rapid extraction, preconcentration, and determination of trace amounts of silver and gold ions was investigated. The optimum conditions for sample pH, eluent parameters (type, concentration and volume were obtained. The effect of various cationic interferences on the adsorption of silver and gold was evaluated. The analytical efficiency values of both silver and gold ions were higher than 98.0% in the optimum conditions. The limits of detection (LOD were less than 0.8 and 0.5 ng mL−1 for silver and gold, respectively. The linear ranges for silver and gold were 1.5–1000 ng mL−1 and 1.0–1000 ng mL−1 respectively. The maximum capacity of the modified magnetic nanoparticles was more than 97.3 mg g−1 and 167 mg g−1 for silver, and gold ions, respectively. The presented method was used to determine silver and gold ions in real samples. Finally, the method accuracy was confirmed by standard reference materials.

  1. Carotenoid stabilized gold and silver nanoparticles derived from the Actinomycete Gordonia amicalis HS-11 as effective free radical scavengers.

    Science.gov (United States)

    Sowani, Harshada; Mohite, Pallavi; Damale, Shailesh; Kulkarni, Mohan; Zinjarde, Smita

    2016-12-01

    The Actinomycete Gordonia amicalis HS-11 produced orange pigments when cultivated on n-hexadecane as the sole carbon source. When cells of this pigmented bacterium were incubated with 1mM chloroauric acid (HAuCl4) or silver nitrate (AgNO3), pH 9.0, at 25°C, gold and silver nanoparticles, respectively, were obtained in a cell associated manner. It was hypothesized that the pigments present in the cells may be mediating metal reduction reactions. After solvent extraction and High Performance Liquid Chromatography, two major pigments displaying UV-vis spectra characteristic of carotenoids were isolated. These were identified on the basis of Atmospheric Pressure Chemical Ionization Mass Spectrometry (APCI-MS) in the positive mode as 1'-OH-4-keto-γ-carotene (Carotenoid K) and 1'-OH-γ-carotene (Carotenoid B). The hydroxyl groups present in the carotenoids were eliminated under alkaline conditions and provided the reducing equivalents necessary for synthesizing nanoparticles. Cell associated and carotenoid stabilized nanoparticles were characterized by different analytical techniques. In vitro free radical scavenging activities of cells (control, gold and silver nanoparticle loaded), purified carotenoids and carotenoid stabilized gold and silver nanoparticles were evaluated. Silver nanoparticle loaded cells and carotenoid stabilized silver nanoparticles exhibited improved nitric oxide (NO) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activities compared to their control and gold counterparts. This paper thus reports cell associated nanoparticle synthesis by G. amicalis, describes for the first time the role of carotenoid pigments in metal reduction processes and demonstrates enhanced free radical scavenging activities of the carotenoid stabilized nanoparticles. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Magmatism and Epithermal Gold-Silver Deposits of the Southern Ancestral Cascade Arc, Western Nevada and Eastern California

    Science.gov (United States)

    John, David A.; du Bray, Edward A.; Henry, Christopher D.; Vikre, Peter

    2015-01-01

    hornblende, biotite, and pyroxene phenocrysts. Seven epithermal gold-silver deposits with >1 Moz gold production, several large elemental sulfur deposits, and many large areas (10s to >100 km2) of hydrothermally altered rocks are present in the southern ancestral arc, especially south of latitude 40°N. These deposits are principally hosted by intermediate to silicic lava dome complexes; only a few deposits are associated with mafic- to intermediate-composition stratovolcanoes. Large deposits are most abundant and well developed in volcanic fields whose evolution spanned millions of years. Most deposits are hundreds of thousands to several million years younger than their host rocks, although some quartz-alunite deposits are essentially coeval with their host rocks. Variable composition and thickness of crustal basement is the primary control on mineralization along the length of the southern ancestral arc; most deposits and large alteration zones are localized in basement rock terranes with a strong continental affinity, either along the edge of the North American craton (Goldfield, Tonopah) or in an accreted terrane with continental affinities (Walker Lake terrane; Aurora, Bodie, Comstock Lode, Paradise Peak). Epithermal deposits and quartz-alunite alteration zones are scarce to absent in the northern part of the ancestral arc above an accreted island arc (Black Rock terrane) or unknown basement rocks (Modoc Plateau). Walker Lane structures and areas that underwent large magnitude extension during the Late Cenozoic (areas with Oligocene-early Miocene volcanic rocks dipping >40°) do not provide regional control on mineralization. Instead, these features may have served as local-scale conduits for mineralizing fluids.

  3. Circulating tumor cell identification by functionalized silver-gold nanorods with multicolor, super-enhanced SERS and photothermal resonances

    Science.gov (United States)

    Nima, Zeid A.; Mahmood, Meena; Xu, Yang; Mustafa, Thikra; Watanabe, Fumiya; Nedosekin, Dmitry A.; Juratli, Mazen A.; Fahmi, Tariq; Galanzha, Ekaterina I.; Nolan, John P.; Basnakian, Alexei G.; Zharov, Vladimir P.; Biris, Alexandru S.

    2014-05-01

    Nanotechnology has been extensively explored for cancer diagnostics. However, the specificity of current methods to identify simultaneously several cancer biomarkers is limited due to color overlapping of bio-conjugated nanoparticles. Here, we present a technique to increase both the molecular and spectral specificity of cancer diagnosis by using tunable silver-gold nanorods with narrow surface-enhanced Raman scattering (SERS) and high photothermal contrast. The silver-gold nanorods were functionalized with four Raman-active molecules and four antibodies specific to breast cancer markers and with leukocyte-specific CD45 marker. More than two orders of magnitude of SERS signal enhancement was observed from these hybrid nanosystems compared to conventional gold nanorods. Using an antibody rainbow cocktail, we demonstrated highly specific detection of single breast cancer cells in unprocessed human blood. By integrating multiplex targeting, multicolor coding, and multimodal detection, our approach has the potential to improve multispectral imaging of individual tumor cells in complex biological environments.

  4. Unstable reshaping of gold nanorods prepared by a wet chemical method in the presence of silver nitrate.

    Science.gov (United States)

    Iqbal, Muhammad; Tae, Giyoong

    2006-11-01

    We characterized the stability of the gold nanorods synthesized by means of a seed mediated growth approach in the presence of AgNO3, which consists of synthesis of small diameter seed particles (approximately 4 nm) and subsequent growth of these nanoparticles into nanorods by addition to gold salt solution containing cetyltrimethylammonium bromide (CTAB) in the presence of ascorbic acid. The presence of silver nitrate significantly enhanced the nanorod synthesis as previously reported. However, the synthesized nanorods were unstable and reshaped in aqueous environment; the continuous blue-shift of the 2nd plasmon bands was monitored and the changes in the nanorod morphologies were also observed by electron microscopy with increasing storage time. This reshaping was observed at wide CTAB concentration range regardless of the removal of the unreacted gold or silver ions.

  5. Silver, gold and the corresponding core shell nanoparticles: synthesis and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Douglas, Fraser; Yanez, Ramon; Ros, Josep [Universitat Autonoma de Barcelona, Unitat de Quimica Inorganica, Departament de Quimica (Spain); Marin, Sergio; Escosura-Muniz, Alfredo de la [Institut Catala de Nanotecnologia, Nanobioelectronics and Biosensors Group (Spain); Alegret, Salvador [Universitat Autonoma de Barcelona, Group of Sensors and Biosensors, Departament de Quimica (Spain); Merkoci, Arben, E-mail: arben.merkoci.icn@uab.e [Institut Catala de Nanotecnologia, Nanobioelectronics and Biosensors Group (Spain)

    2008-12-15

    Simple strategies for producing silver and gold nanoparticles (AgNP and AuNP) along with the corresponding core shell nanoparticles (Au-Ag and Ag-Au) by reduction of the metal salts AgBF{sub 4} and HAuCl{sub 4} by NaBH{sub 4} in water will be presented. The morphologies of the obtained nanoparticles are determined by the order of addition of reactants. The obtained NPs, with sizes in the range 3-40 nm, are characterized by transmission electronic microscopy (TEM) and UV-Vis absorption spectroscopy, so as to evaluate their qualities. Moreover, a direct electrochemical detection protocol based on a cyclic voltammetry in water solution that involves the use of glassy carbon electrode is also applied to characterize the prepared NPs. The developed NPs and the related electroanalytical method seem to be with interest for future sensing and biosensing applications including DNA sensors and immunosensors.

  6. SERS enhancements via periodic arrays of gold nanoparticles on silver film structures.

    Science.gov (United States)

    Montgomery, Jason M; Imre, Alexandra; Welp, Ulrich; Vlasko-Vlasov, Vitalii; Gray, Stephen K

    2009-05-11

    We discuss surface enhanced Raman spectroscopy (SERS) structures aimed at providing robust and reproducible enhancements. The structures involve periodic arrays of gold nanospheres near silver film structures that may also be patterned. They enable one to excite Bloch wave surface plasmon polaritons (SPPs) that can also couple to local surface plasmons (LSPs) of the nanospheres, leading to the possibility of multiplicative enhancements. If the magnitude of the average electric field, /E/, between the particles is enhanced by g such that /E/ = g/E(0)/, /E(0)/ being the incident field, realistic finite-difference time-domain simulations show that under favorable circumstances g approximately equal 0.6 g(SPP) g(LSP), where g(SPP) and g(LSP) are enhancement factors associated with the individual components. SERS enhancements for the structures can be as high as O(g(4)) = 10(8).

  7. Colorimetric detection of glucose based on gold nanoparticles coupled with silver nanoparticles

    Science.gov (United States)

    Gao, Yan; Wu, Yiting; Di, Junwei

    2017-02-01

    We have coupled gold nanoparticles (AuNPs) with silver nanoparticles (AgNPs) to assemble a plasmonic sensing platform for colorimetric detection of glucose. In this system, small AuNPs ( 4 nm) can act as glucose oxidase (GOD) mimic enzyme to catalytically oxidize glucose in the presence of oxygen, producing hydrogen peroxide, which dissolves AgNPs to lead the color changes. Glucose can be detected not only by naked eyes (from yellow to red) but also by spectrophotometer in the concentration range of 5-70 μM, with detection limit of 3 μM. More importantly, we found that L-cysteine added in the system can markedly improve the selectivity for the detection of glucose. The proposed method was used to application for the detection of glucose in human serum with satisfactory results. This system is simple and low cost without using any enzymes and organic chromogenic agents.

  8. Green synthesis, characterization of gold and silver nanoparticles and their potential application for cancer therapeutics.

    Science.gov (United States)

    Patra, Sujata; Mukherjee, Sudip; Barui, Ayan Kumar; Ganguly, Anirban; Sreedhar, Bojja; Patra, Chitta Ranjan

    2015-08-01

    In the present article, we demonstrate the delivery of anti-cancer drug to the cancer cells using biosynthesized gold and silver nanoparticles (b-AuNP & b-AgNP). The nanoparticles synthesized by using Butea monosperma (BM) leaf extract are thoroughly characterized by various analytical techniques. Both b-AuNP and b-AgNP are stable in biological buffers and biocompatible towards normal endothelial cells (HUVEC, ECV-304) as well as cancer cell lines (B16F10, MCF-7, HNGC2 & A549). Administration of nanoparticle based drug delivery systems (DDSs) using doxorubicin (DOX) [b-Au-500-DOX and b-Ag-750-DOX] shows significant inhibition of cancer cell proliferation (B16F10, MCF-7) compared to pristine drug. Therefore, we strongly believe that biosynthesized nanoparticles will be useful for the development of cancer therapy using nanomedicine approach in near future. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Separating excess surfactant from silver and gold nanoparticles in micellar concentrates by means of nonaqueous electrophoresis

    Science.gov (United States)

    Bulavchenko, A. I.; Demidova, M. G.; Popovetskiy, P. S.; Podlipskaya, T. Yu.; Plyusnin, P. E.

    2017-08-01

    It is shown by physicochemical means (IR Fourier spectroscopy, CHN-analysis with preliminary sorption of surfactant on SiO2) that the content of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in an electrophoretic concentrate remains unchanged during the electrophoretic concentration of silver and gold nanoparticles. Diluting the concentrate and carrying out the second stage of electrophoresis reduces the concentration of surfactant from 0.25 to 0.015 M while maintaining the mass concentration of nanoparticles. Nanoparticles in organosols before and after electrophoresis are characterized by means of photon correlation spectroscopy, phase analysis light scattering, and spectrophotometry. Conducting films on glass substrates are obtained from concentrates with a different contents of surfactant via water-alcohol treatment and thermolysis.

  10. Double surface plasmon enhanced organic light-emitting diodes by gold nanoparticles and silver nanoclusters

    Science.gov (United States)

    Gao, Chia-Yuan; Chen, Ying-Chung; Chen, Kan-Lin; Huang, Chien-Jung

    2015-12-01

    The influence of gold nanoparticles (GNPs) and silver nanoclusters (SNCs) on the performance of organic light-emitting diodes is investigated in this study. The GNPs are doped into (poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate)) (PEDOT: PSS) and the SNCs are introduced between the electron-injection layer and cathode alumina. The power efficiency of the device, at the maximum luminance, with double surface plasmon resonance and buffer layer is about 2.15 times higher than that of the device without GNPs and SNCs because the absorption peaks of GNPs and SNCs are as good as the photoluminescence peak of the emission layer, resulting in strong surface plasmon resonance effect in the device. In addition, the buffer layer is inserted between PEDOT: PSS and the emitting layer in order to avoid that the nonradiative decay process of exciton is generated.

  11. A novel PLED architecture containing biologically synthesized gold nanoparticles and ultra thin silver layer

    Science.gov (United States)

    Pıravadılı Mucur, Selin; Tekin, Emine; San, Sait Eren; Duygulu, Özgür; Öztürk, Hasan Ümit; Utkan, Güldem; Denizci, Aziz Akın

    2015-09-01

    The influences of biologically synthesized gold nanoparticles (bio-GNPs) and ultra thin silver layer (UTSL) on the polymer light emitting diodes (PLEDs) are investigated for the first time. The performance of the fabricated PLEDs is enhanced by embedding of bio-GNPs into the hole transport layer (HTL). Furthermore, the tailored device architecture containing UTSL increases the electron transport through lightning rod effect. Bio-GNPs are successfully produced as spherical shape with size of circa 10.4 nm. Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene (MEH-PPV) and [poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate); (PEDOT:PSS)/bio-GNPs blends are used as an active layer and HTL, respectively. Novel PLEDs fabricated with 0.125 wt% bio-GNPs/PEDOT:PSS and 0.5 nm UTSL exhibit nearly 2.5-fold enhancement in the device efficiency.

  12. Gold-silver-alloy nanoprobes for one-pot multiplex DNA detection

    Energy Technology Data Exchange (ETDEWEB)

    Doria, G; Larguinho, M; Dias, J T; Baptista, P V [Centro de Investigacao em Genetica Molecular Humana (CIGMH), Departamento de Ciencias da Vida, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Pereira, E [Rede de Quimica e Tecnologia (REQUIMTE), Departamento de Quimica, Faculdade de Ciencias, Universidade do Porto, 4169-007 Porto (Portugal); Franco, R, E-mail: pmvb@fct.unl.pt [Rede de Quimica e Tecnologia (REQUIMTE), Departamento de Quimica, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)

    2010-06-25

    A specific colorimetric DNA detection method based on oligonucleotide functionalized gold-silver-alloy nanoparticles (AuAg-alloy-nanoprobes) is presented. The AuAg-alloy-nanoprobes were then used for the specific detection of a DNA sequence from TP53-a gene involved in cancer development. The AuAg-alloy-nanoprobes were then used in combination with Au-nanoprobes for a one-pot dual-colour detection strategy that allowed for the simultaneous differential detection of two distinct target sequences. This system poses an unprecedented opportunity to explore the combined use of metal nanoparticles with different composition towards the development of a multiplex one-pot colorimetric assay for DNA detection.

  13. Distribution of copper, silver and gold during thermal treatment with brominated flame retardants.

    Science.gov (United States)

    Oleszek, Sylwia; Grabda, Mariusz; Shibata, Etsuro; Nakamura, Takashi

    2013-09-01

    The growing consumption of electric and electronic equipment results in creating an increasing amount of electronic waste. The most economically and environmentally advantageous methods for the treatment and recycling of waste electric and electronic equipment (WEEE) are the thermal techniques such as direct combustion, co-combustion with plastic wastes, pyrolysis and gasification. Nowadays, this kind of waste is mainly thermally treated in incinerators (e.g. rotary kilns) to decompose the plastics present, and to concentrate metals in bottom ash. The concentrated metals (e.g. copper, precious metals) can be supplied as a secondary raw material to metal smelters, while the pyrolysis of plastics allows the recovery of fuel gases, volatilising agents and, eventually, energy. Indeed, WEEE, such as a printed circuit boards (PCBs) usually contains brominated flame retardants (BFRs). From these materials, hydrobromic acid (HBr) is formed as a product of their thermal decomposition. In the present work, the bromination was studied of copper, silver and gold by HBr, originating from BFRs, such as Tetrabromobisphenol A (TBBPA) and Tetrabromobisphenol A-Tetrabromobisophenol A diglycidyl ether (TTDE) polymer; possible volatilization of the bromides formed was monitored using a thermo-gravimetric analyzer (TGA) and a laboratory-scale furnace for treating samples of metals and BFRs under an inert atmosphere and at a wide range of temperatures. The results obtained indicate that up to about 50% of copper and silver can evolve from sample residues in the form of volatile CuBr and AgBr above 600 and 1000°C, respectively. The reactions occur in the molten resin phase simultaneously with the decomposition of the brominated resin. Gold is resistant to HBr and remains unchanged in the residue. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. Green synthesis of multifunctional silver and gold nanoparticles from the oriental herbal adaptogen: Siberian ginseng.

    Science.gov (United States)

    Abbai, Ragavendran; Mathiyalagan, Ramya; Markus, Josua; Kim, Yeon-Ju; Wang, Chao; Singh, Priyanka; Ahn, Sungeun; Farh, Mohamed El-Agamy; Yang, Deok Chun

    2016-01-01

    Pharmacologically active stem of the oriental herbal adaptogen, Siberian ginseng, was employed for the ecofriendly synthesis of Siberian ginseng silver nanoparticles (Sg-AgNPs) and Siberian ginseng gold nanoparticles (Sg-AuNPs). First, for metabolic characterization of the sample, liquid chromatography-tandem mass spectrometry analysis (indicated the presence of eleutherosides A and E), total phenol content, and total reducing sugar were analyzed. Second, the water extract of the sample mediated the biological synthesis of both Sg-AgNPs and Sg-AuNPs that were crystalline face-centered cubical structures with a Z-average hydrodynamic diameter of 126 and 189 nm, respectively. Moreover, Fourier transform infrared analysis indicated that proteins and aromatic hydrocarbons play a key role in the formation and stabilization of Sg-AgNPs, whereas phenolic compounds accounted for the synthesis and stability of Sg-AuNPs. 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide (MTT) assay determined that Sg-AgNPs conferred strong cytotoxicity against MCF7 (human breast cancer cell line) and was only slightly toxic to HaCaT (human keratinocyte cell line) at 10 µg⋅mL(-1). However, Sg-AuNPs did not display cytotoxic effects against both of the cell lines. The disc diffusion assay indicated a dose-dependent increase in the zone of inhibition of Staphylococcus aureus (ATCC 6538), Bacillus anthracis (NCTC 10340), Vibrio parahaemolyticus (ATCC 33844), and Escherichia coli (BL21) treated with Sg-AgNPs, whereas Sg-AuNPs did not show inhibitory activity. In addition, the 2,2-diphenyl-1-picrylhydrazyl assay demonstrated that both Sg-AgNPs and Sg-AuNPs possess strong antioxidant activity. To the best of our knowledge, this is the first report unraveling the potential of Eleutherococcus senticosus for silver and gold nanoparticle synthesis along with its biological applications, which in turn would promote widespread usage of the endemic Siberian ginseng.

  15. Synthesis of gold and silver nanoparticle S-ovalbumin protein conjugates by in situ conjugation process

    Science.gov (United States)

    Joshi, Deepti; Soni, R. K.

    2015-05-01

    Pure gold and silver nanoparticle (NP) generation and their conjugation with protein S-ovalbumin using in situ conjugation process have been reported. The in situ conjugation involves nanosecond pulse laser ablation of pure metal target in the protein S-ovalbumin solution. Transmission electron microscopy (TEM) and UV-Visible absorption results show decrease in mean NP size along with narrow particle size distribution on ablation in S-ovalbumin solution as compared to ablation in water for both Au and Ag NPs. Also, the NP size reduction was found to be dependent on the concentration of S-ovalbumin. For AuNPs, spherical NPs of mean size 4 nm with particle size distribution 2-6 nm were obtained at 300 nM S-ovalbumin concentration. Further, it has been observed that the resultant in situ-conjugated colloid gold and silver NP solutions were quite stable even in the presence of NaCl at physiological salt concentration (0.15 M). On post-laser irradiation (532 nm, 15 mJ) for 20 min, 9 nm red shift in surface plasmon resonance peak (SPR), along with increased broadening towards longer wavelength, was observed in the AuNPs-S-ovalbumin sample. Further increase in the time of irradiation showed shift in AuNPs-S-ovalbumin SPR towards lower wavelength. On laser irradiation (532 nm, 15 mJ) for 20 min, no significant change was observed in the line shape of the plasmon absorption band of the AgNPs-S-ovalbumin conjugate. FTIR spectra revealed that S-ovalbumin peptide backbone and secondary structure remain unchanged on laser irradiation during in situ conjugation process. Thus, integrity of S-ovalbumin does not get affected, and no degradation of S-ovalbumin takes place on laser-induced in situ conjugation. Raman results confirm that both Au and Ag NPs interact with S-ovalbumin via thiol-bearing cysteine residues of the disulfide bond.

  16. Antibacterial Efficacy of Gold and Silver Nanoparticles Functionalized with the Ubiquicidin (29–41 Antimicrobial Peptide

    Directory of Open Access Journals (Sweden)

    Enrique Morales-Avila

    2017-01-01

    Full Text Available Recent studies have demonstrated that drug antimicrobial activity is enhanced when metallic nanoparticles are used as an inorganic support, obtaining synergic effects against microorganisms. The cationic antimicrobial peptide ubiquicidin 29–41 (UBI has demonstrated high affinity and sensitivity towards fungal and bacterial infections. The aim of this research was to prepare and evaluate the antimicrobial efficacy of engineered multivalent nanoparticle systems based on silver or gold nanoparticles functionalized with UBI. Spectroscopy techniques demonstrated that NPs were functionalized with UBI mainly through interactions with the -NH2 groups. A significant increase in the antibacterial activity against Escherichia coli and Pseudomonas aeruginosa was obtained with the conjugate AgNP-UBI with regard to that of AgNP. No inhibition of bacterial growth was observed with AuNP and AuNP-UBI using a nanoparticle concentration of up to 182 μg mL−1. Nonetheless, silver nanoparticles conjugated to the UBI antimicrobial peptide may provide an alternative therapy for topical infections.

  17. Geology of epithermal silver-gold bulk-mining targets, bodie district, Mono County, California

    Science.gov (United States)

    Hollister, V.F.; Silberman, M.L.

    1995-01-01

    The Bodie mining district in Mono County, California, is zoned with a core polymetallic-quartz vein system and silver- and gold-bearing quartz-adularia veins north and south of the core. The veins formed as a result of repeated normal faulting during doming shortly after extrusion of felsic flows and tuffs, and the magmatic-hydrothermal event seems to span at least 2 Ma. Epithermal mineralization accompanied repeated movement of the normal faults, resulting in vein development in the planes of the faults. The veins occur in a very large area of argillic alteration. Individual mineralized structures commonly formed new fracture planes during separate fault movements, with resulting broad zones of veinlets growing in the walls of the major vein-faults. The veinlet swarms have been found to constitute a target estimated at 75,000,000 tons, averaging 0.037 ounce gold per ton. The target is amenable to bulkmining exploitation. The epithermal mineralogy is simple, with electrum being the most important precious metal mineral. The host veins are typical low-sulfide banded epithermal quartz and adularia structures that filled voids created by the faulting. Historical data show that beneficiation of the simple vein mineralogy is very efficient. ?? 1995 Oxford University Press.

  18. 3, 4-dihydroxy-L-phenylalanine-derived melanin from Yarrowia lipolytica mediates the synthesis of silver and gold nanostructures.

    Science.gov (United States)

    Apte, Mugdha; Girme, Gauri; Bankar, Ashok; Ravikumar, Ameeta; Zinjarde, Smita

    2013-01-30

    Nanobiotechnology applies the capabilities of biological systems in generating a variety of nano-sized structures. Plants, algae, fungi and bacteria are some systems mediating such reactions. In fungi, the synthesis of melanin is an important strategy for cell-survival under metal-stressed conditions. Yarrowia lipolytica, the biotechnologically significant yeast also produces melanin that sequesters heavy metal ions. The content of this cell-associated melanin is often low and precursors such as L-tyrosine or 3, 4-dihydroxy-L-phenylalanine (L-DOPA) can enhance its production. The induced melanin has not been exploited for the synthesis of nanostructures. In this investigation, we have employed L-DOPA-melanin for the facile synthesis of silver and gold nanostructures. The former have been used for the development of anti-fungal paints. Yarrowia lipolytica NCIM 3590 cells were incubated with L-DOPA for 18 h and the resultant dark pigment was subjected to physical and chemical analysis. This biopolymer was used as a reducing and stabilizing agent for the synthesis of silver and gold nanostructures. These nanoparticles were characterized by UV-Visible spectra, X-ray diffraction (XRD) studies, and electron microscopy. Silver nanoparticles were evaluated for anti-fungal activity. The pigment isolated from Y. lipolytica was identified as melanin. The induced pigment reduced silver nitrate and chloroauric acid to silver and gold nanostructures, respectively. The silver nanoparticles were smaller in size (7 nm) and displayed excellent anti-fungal properties towards an Aspergillus sp. isolated from a wall surface. An application of these nanoparticles as effective paint-additives has been demonstrated. The yeast mediated enhanced production of the metal-ion-reducing pigment, melanin. A simple and rapid method for the extracellular synthesis of nanoparticles with paint-additive-application was developed.

  19. Single particle ICP-MS characterization of titanium dioxide, silver, and gold nanoparticles during drinking water treatment.

    Science.gov (United States)

    Donovan, Ariel R; Adams, Craig D; Ma, Yinfa; Stephan, Chady; Eichholz, Todd; Shi, Honglan

    2016-02-01

    One of the most direct means for human exposure to nanoparticles (NPs) released into the environment is drinking water. Therefore, it is critical to understand the occurrence and fate of NPs in drinking water systems. The objectives of this study were to develop rapid and reliable analytical methods and apply them to investigate the fate and transportation of NPs during drinking water treatments. Rapid single particle ICP-MS (SP-ICP-MS) methods were developed to characterize and quantify titanium-containing, titanium dioxide, silver, and gold NP concentration, size, size distribution, and dissolved metal element concentration in surface water and treated drinking water. The effectiveness of conventional drinking water treatments (including lime softening, alum coagulation, filtration, and disinfection) to remove NPs from surface water was evaluated using six-gang stirrer jar test simulations. The selected NPs were nearly completely (97 ± 3%) removed after lime softening and alum coagulation/activated carbon adsorption treatments. Additionally, source and drinking waters from three large drinking water treatment facilities utilizing similar treatments with the simulation test were collected and analyzed by the SP-ICP-MS methods. Ti-containing particles and dissolved Ti were present in the river water samples, but Ag and Au were not present. Treatments used at each drinking water treatment facility effectively removed over 93% of the Ti-containing particles and dissolved Ti from the source water. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Effect of gold and silver nanoparticles on the morpho-functional state of the epididymis and prostate gland in rats

    Directory of Open Access Journals (Sweden)

    V. Y. Kalynovskyi

    2016-09-01

    Full Text Available Metals are widely used in modern medicine: iron, copper, zinc, vanadium, titanium – all of them are vital for treatment of different diseases. Recently a new field of medical technology has emerged, which focuses on the biomedical application of metallic nanoparticles, with a particular interest in a gold and silver-based materials. These structures are already used for photothermal anticancer therapy, drug delivery, bioimaging, radiosensitizers and as drugs themselves. Despite the wide usage of nanoparticles, we still don’t know much about the toxicity of nanomaterials. Nanotoxicological studies are mainly carried out in vitro, but in vivo effects are still elusive. Hence, we focused on the reproductive toxicity of gold and silver nanosized particles. Spherical 10–15 nm gold and silver nanoparticles were synthesized through the reduction of sodium tetrachloroaurate (III and silver nitrate respectively with ascorbic acid in the presence of sodium polyphosphate as a coating and stabilizing agent. Next, these particles were administered intraperitoneally to the young and adult animals (1- and 6-months old respectively at 1 mg/kg dose for 10 days. As quantitative markers of functional activity, we used the diameter of epididymal tubules, height and the nuclear cross-section of epididymal epitheliocytes and relative volume of the prostatic epithelium. We showed that intraperitoneal administrations of nanogold to young animals caused no significant histological changes, although we found a decrease in the nuclear cross-sectional area of epididymal epitheliocytes. At the same time, nanogold caused more morphometric changes in adult animals. Similar results were obtained from the nanosilver groups. Silver nanoparticles caused an observable decrease of sperm quantity in the lumen of epididymal tubules with a simultaneous increase in the number of extraepididymal cells in young animals. Morphometric parameters of the epididymis and prostate also

  1. Biomolecular adsorption at aqueous silver interfaces: first-principles calculations, polarizable force-field simulations, and comparisons with gold.

    Science.gov (United States)

    Hughes, Zak E; Wright, Louise B; Walsh, Tiffany R

    2013-10-29

    The molecular simulation of biomolecules adsorbed at noble metal interfaces can assist in the development of bionanotechnology applications. In line with advances in polarizable force fields for adsorption at aqueous gold interfaces, there is scope for developing a similar force field for silver. One way to accomplish this is via the generation of in vacuo adsorption energies calculated using first-principles approaches for a wide range of different but biologically relevant small molecules, including water. Here, we present such first-principles data for a comprehensive range of bio-organic molecules obtained from plane-wave density functional theory calculations using the vdW-DF functional. As reported previously for the gold force field, GolP-CHARMM (Wright, L. B.; Rodger, P. M.; Corni, S.; Walsh, T. R. GolP-CHARMM: first-principles based force-fields for the interaction of proteins with Au(111) and Au(100). J. Chem. Theory Comput. 2013, 9, 1616-1630), we have used these data to construct a a new force field, AgP-CHARMM, suitable for the simulation of biomolecules at the aqueous Ag(111) and Ag(100) interfaces. This force field is derived to be consistent with GolP-CHARMM such that adsorption on Ag and Au can be compared on an equal footing. Our force fields are used to evaluate the water overlayer stability on both silver and gold, finding good agreement with known behaviors. We also calculate and compare the structuring (spatial and orientational) of liquid water adsorbed at both silver and gold. Finally, we report the adsorption free energy of a range of amino acids at both the Au(111) and Ag(111) aqueous interfaces, calculated using metadynamics. Stronger adsorption on gold was noted in most cases, with the exception being the carboxylate group present in aspartic acid. Our findings also indicate differences in the binding free energy profile between silver and gold for some amino acids, notably for His and Arg. Our analysis suggests that the relatively

  2. Eco-friendly synthesis of silver and gold nanoparticles with enhanced bactericidal activity and study of silver catalyzed reduction of 4-nitrophenol

    Science.gov (United States)

    Naraginti, Saraschandra; Sivakumar, A.

    2014-07-01

    The present study reports a simple and robust method for synthesis of silver and gold nanoparticles using Coleus forskohlii root extract as reducing and stabilizing agent. Stable silver nanoparticles (AgNPs) and gold nanopoarticles (AuNPs) were formed on treatment of an aqueous silver nitrate (AgNO3) and chloroauric acid (HAuCl4) solutions with the root extract. The nanoparticles obtained were characterized by UV-Visible spectroscopy, Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). UV-Vis and TEM analysis indicate that with higher quantities of root extract, the interaction is enhanced leading to size reduction of spherical metal nanoparticles. XRD confirms face-centered cubic phase and the diffraction peaks can be attributed to (1 1 1), (2 0 0), (2 2 2) and (3 1 1) planes for these nanoparticles. These synthesized Ag and Au nanoparticles were found to exhibit excellent bactericidal activity against clinically isolated selected pathogens such as Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus). The synthesized AgNPs were also found to function as an efficient green catalyst in the reduction of anthropogenic pollutant 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride, which was apparent from the periodical color change from bright yellow to colorless, after the addition of AgNPs.

  3. Eco-friendly synthesis of silver and gold nanoparticles with enhanced bactericidal activity and study of silver catalyzed reduction of 4-nitrophenol.

    Science.gov (United States)

    Naraginti, Saraschandra; Sivakumar, A

    2014-07-15

    The present study reports a simple and robust method for synthesis of silver and gold nanoparticles using Coleus forskohlii root extract as reducing and stabilizing agent. Stable silver nanoparticles (AgNPs) and gold nanopoarticles (AuNPs) were formed on treatment of an aqueous silver nitrate (AgNO3) and chloroauric acid (HAuCl4) solutions with the root extract. The nanoparticles obtained were characterized by UV-Visible spectroscopy, Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). UV-Vis and TEM analysis indicate that with higher quantities of root extract, the interaction is enhanced leading to size reduction of spherical metal nanoparticles. XRD confirms face-centered cubic phase and the diffraction peaks can be attributed to (111), (200), (222) and (311) planes for these nanoparticles. These synthesized Ag and Au nanoparticles were found to exhibit excellent bactericidal activity against clinically isolated selected pathogens such as Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus). The synthesized AgNPs were also found to function as an efficient green catalyst in the reduction of anthropogenic pollutant 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride, which was apparent from the periodical color change from bright yellow to colorless, after the addition of AgNPs. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Evaluation of gold and silver leaching from printed circuit board of cellphones.

    Science.gov (United States)

    Petter, P M H; Veit, H M; Bernardes, A M

    2014-02-01

    Electronic waste has been increasing proportionally with the technology. So, nowadays, it is necessary to consider the useful life, recycling, and final disposal of these equipment. Metals, such as Au, Ag, Cu, Sn and Ni can be found in the printed circuit boards (PCB). According to this, the aims of this work is to characterize the PCBs of mobile phones with aqua regia; obtaining "reference" values of leaching, to gold and silver, with cyanide and nitric acid, respectively; and study the process of leaching of these metals in alternative leaching with sodium thiosulfate and ammonium thiosulfate. The metals were characterized by digesting the sample with aqua regia for 1 and 2h at 60°C and 80°C. The leaching of Au with a commercial reagent (cyanide) and the Ag with HNO3were made. The leaching of Au and Ag with alternative reagents: Na2S2O3, and (NH4)2S2O3 in 0.1M concentration with the addition of CuSO4, NH4OH, and H2O2, was also studied. The results show that the digestion with aqua regia was efficient to characterize the metals present in the PCBs of mobile phones. However, the best method to solubilize silver was by digesting the sample with nitric acid. The leaching process using sodium thiosulfate was more efficient when an additional concentration of 0.015 and 0.030 M of the CuSO4 was added. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. Synthesis of gold and silver nanoparticle S-ovalbumin protein conjugates by in situ conjugation process

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Deepti, E-mail: deeptimishrajoshi@gmail.com; Soni, R. K. [Indian Institute of Technology Delhi, Physics Department (India)

    2015-05-15

    Pure gold and silver nanoparticle (NP) generation and their conjugation with protein S-ovalbumin using in situ conjugation process have been reported. The in situ conjugation involves nanosecond pulse laser ablation of pure metal target in the protein S-ovalbumin solution. Transmission electron microscopy (TEM) and UV–Visible absorption results show decrease in mean NP size along with narrow particle size distribution on ablation in S-ovalbumin solution as compared to ablation in water for both Au and Ag NPs. Also, the NP size reduction was found to be dependent on the concentration of S-ovalbumin. For AuNPs, spherical NPs of mean size 4 nm with particle size distribution 2–6 nm were obtained at 300 nM S-ovalbumin concentration. Further, it has been observed that the resultant in situ-conjugated colloid gold and silver NP solutions were quite stable even in the presence of NaCl at physiological salt concentration (0.15 M). On post-laser irradiation (532 nm, 15 mJ) for 20 min, 9 nm red shift in surface plasmon resonance peak (SPR), along with increased broadening towards longer wavelength, was observed in the AuNPs–S-ovalbumin sample. Further increase in the time of irradiation showed shift in AuNPs–S-ovalbumin SPR towards lower wavelength. On laser irradiation (532 nm, 15 mJ) for 20 min, no significant change was observed in the line shape of the plasmon absorption band of the AgNPs–S-ovalbumin conjugate. FTIR spectra revealed that S-ovalbumin peptide backbone and secondary structure remain unchanged on laser irradiation during in situ conjugation process. Thus, integrity of S-ovalbumin does not get affected, and no degradation of S-ovalbumin takes place on laser-induced in situ conjugation. Raman results confirm that both Au and Ag NPs interact with S-ovalbumin via thiol-bearing cysteine residues of the disulfide bond.

  6. Green synthesis of multifunctional silver and gold nanoparticles from the oriental herbal adaptogen: Siberian ginseng

    Science.gov (United States)

    Abbai, Ragavendran; Mathiyalagan, Ramya; Markus, Josua; Kim, Yeon-Ju; Wang, Chao; Singh, Priyanka; Ahn, Sungeun; Farh, Mohamed El-Agamy; Yang, Deok Chun

    2016-01-01

    Pharmacologically active stem of the oriental herbal adaptogen, Siberian ginseng, was employed for the ecofriendly synthesis of Siberian ginseng silver nanoparticles (Sg-AgNPs) and Siberian ginseng gold nanoparticles (Sg-AuNPs). First, for metabolic characterization of the sample, liquid chromatography-tandem mass spectrometry analysis (indicated the presence of eleutherosides A and E), total phenol content, and total reducing sugar were analyzed. Second, the water extract of the sample mediated the biological synthesis of both Sg-AgNPs and Sg-AuNPs that were crystalline face-centered cubical structures with a Z-average hydrodynamic diameter of 126 and 189 nm, respectively. Moreover, Fourier transform infrared analysis indicated that proteins and aromatic hydrocarbons play a key role in the formation and stabilization of Sg-AgNPs, whereas phenolic compounds accounted for the synthesis and stability of Sg-AuNPs. 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide (MTT) assay determined that Sg-AgNPs conferred strong cytotoxicity against MCF7 (human breast cancer cell line) and was only slightly toxic to HaCaT (human keratinocyte cell line) at 10 µg⋅mL−1. However, Sg-AuNPs did not display cytotoxic effects against both of the cell lines. The disc diffusion assay indicated a dose-dependent increase in the zone of inhibition of Staphylococcus aureus (ATCC 6538), Bacillus anthracis (NCTC 10340), Vibrio parahaemolyticus (ATCC 33844), and Escherichia coli (BL21) treated with Sg-AgNPs, whereas Sg-AuNPs did not show inhibitory activity. In addition, the 2,2-diphenyl-1-picrylhydrazyl assay demonstrated that both Sg-AgNPs and Sg-AuNPs possess strong antioxidant activity. To the best of our knowledge, this is the first report unraveling the potential of Eleutherococcus senticosus for silver and gold nanoparticle synthesis along with its biological applications, which in turn would promote widespread usage of the endemic Siberian ginseng. PMID:27468232

  7. Synthesis of Gold Nanoparticle-Embedded Silver Cubic Mesh Nanostructures Using AgCl Nanocubes for Plasmonic Photocatalysis.

    Science.gov (United States)

    Joo, Jang Ho; Kim, Byung-Ho; Lee, Jae-Seung

    2017-11-01

    A novel room-temperature aqueous synthesis for gold nanoparticle-embedded silver cubic mesh nanostructures using AgCl templates via a template-assisted coreduction method is developed. The cubic AgCl templates are coreduced in the presence of AuCl4- and Ag+ , resulting in the reduction of AuCl4- into gold nanoparticles on the outer region of AgCl templates, followed by the reduction of AgCl and Ag+ into silver cubic mesh nanostructures. Removal of the template clearly demonstrates the delicately designed silver mesh nanostructures embedded with gold nanoparticles. The synthetic mechanism, structural properties, and surface functionalization are spectroscopically investigated. The plasmonic photocatalysis of the cubic mesh nanostructures for the degradation of organic pollutants and removal of highly toxic metal ions is investigated; the photocatalytic activity of the cubic mesh nanostructures is superior to those of conventional TiO2 catalysts and they are catalytically functional even in natural water, owing to their high surface area and excellent chemical stability. The synthetic development presented in this study can be exploited for the highly elaborate, yet, facile design of nanomaterials with outstanding properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Synthesis of gold and silver nanoparticles by electron irradiation at 5-15 keV energy

    Energy Technology Data Exchange (ETDEWEB)

    Mahapatra, S K; Bogle, K A; Dhole, S D; Bhoraskar, V N [Microtron Accelerator Laboratory, Department of Physics, University of Pune, Pune-411007 (India)

    2007-04-04

    Thin coatings ({approx}10 {mu}m) made from a mixture of polyvinyl alcohol (PVA) and HAuCl{sub 4} or PVA and AgNO{sub 3} on quartz plates were irradiated with 5-15 keV electrons, at room temperature. The electron energy was varied from coating to coating in the range of 5-15 keV, but electron fluence was kept constant at {approx}10{sup 15} e cm{sup -2}. Samples were characterized by the UV-vis, XRD, SEM and TEM techniques. The plasmon absorption peaks at {approx}511 and {approx}442 nm confirmed the formation of gold and silver nanoparticles in the respective electron-irradiated coatings. The XRD, SEM and TEM measurements reveal that the average size of the particles could be tailored in the range of 130-50 nm for gold and from 150-40 nm for silver by varying the electron energy in the range of 5-15 keV. These particles of gold and silver embedded in the polymer could also be separated by dissolving the coatings in distilled water.

  9. Comparative in vivo assessment of the subacute toxicity of gold and silver nanoparticles

    Science.gov (United States)

    Rathore, Mansee; Mohanty, Ipseeta Ray; Maheswari, Ujjwala; Dayal, Navami; Suman, Rajesh; Joshi, D. S.

    2014-04-01

    In spite of the projected therapeutic potentials of gold nanoparticles (GNP) and silver nanoparticles (SNP), very limited data are available on the interaction of nanoparticles with the biological systems. The present investigation was designed to evaluate as well as compare the subacute toxicity of GNP and SNP. Stable suspensions of GNP and SNP with mean particle diameter 10 and 25 nm, respectively, were prepared. Wistar rats were orally fed SNP (3 mg/kg) or GNP (20 μg/kg), once a day for 21 days. Biochemical indices (creatinine phosphokinase-MB, urea, blood urea nitrogen, aspartate transaminase, alkaline alanine transferase) and histopathological features of the liver, heart, brain, lungs, and kidney were evaluated for signs of toxicity. A significant decline in hepatic and renal function in the GNP treated group was observed as compared to SNP. GNP was found to be relatively more toxic on the lungs and SNP on the myocardial tissue as compared to SNP and GNP treatments, respectively. Interestingly, neither SNP nor GNP adversely affected the basal architecture of the brain as compared to sham. The present study demonstrated that GNP was significantly more noxious on the liver and kidney as compared with SNP.

  10. Qualitative assessment of silver and gold nanoparticle synthesis in various plants: a photobiological approach

    Science.gov (United States)

    Rajasekharreddy, Pala; Usha Rani, Pathipati; Sreedhar, Bojja

    2010-06-01

    The development of rapid and ecofriendly processes for the synthesis of silver (Ag) and gold (Au) nanoparticles is of great importance in the field of nanotechnology. In this study, the extracellular production of Ag and Au nanoparticles was carried out from the leaves of the plants, Tridax procumbens L. (Coat buttons), Jatropa curcas L. (Barbados nut), Calotropis gigantea L. (Calotropis), Solanum melongena L. (Eggplant), Datura metel L. (Datura), Carica papaya L. (Papaya) and Citrus aurantium L. (Bitter orange) by the sunlight exposure method. Qualitative comparisons of the synthesized nanoparticles between the plants were measured. Among these T. procumbens, J. curcas and C. gigantea plants synthesized <20 nm sized and spherical-shaped Ag particles, whereas C. papaya, D. metel and S. melongena produced <20 nm sized monodispersed Au particles. The amount of nanoparticles synthesized and its qualitative characterization was done by UV-vis spectroscopy and transmission electron microscopy (TEM), respectively. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used for structural confirmation. Further analysis carried out by fourier transform infrared spectroscopy (FTIR), provided evidence for the presence of amino groups, which increased the stability of the synthesized nanoparticles.

  11. Qualitative assessment of silver and gold nanoparticle synthesis in various plants: a photobiological approach

    Energy Technology Data Exchange (ETDEWEB)

    Rajasekharreddy, Pala; Usha Rani, Pathipati, E-mail: purani@iict.res.i [Indian Institute of Chemical Technology, Biology and Biotechnology Division (India); Sreedhar, Bojja [Indian Institute of Chemical Technology, Inorganic and Physical Chemistry Laboratory (India)

    2010-06-15

    The development of rapid and ecofriendly processes for the synthesis of silver (Ag) and gold (Au) nanoparticles is of great importance in the field of nanotechnology. In this study, the extracellular production of Ag and Au nanoparticles was carried out from the leaves of the plants, Tridax procumbens L. (Coat buttons), Jatropa curcas L. (Barbados nut), Calotropis gigantea L. (Calotropis), Solanum melongena L. (Eggplant), Datura metel L. (Datura), Carica papaya L. (Papaya) and Citrus aurantium L. (Bitter orange) by the sunlight exposure method. Qualitative comparisons of the synthesized nanoparticles between the plants were measured. Among these T. procumbens, J. curcas and C. gigantea plants synthesized <20 nm sized and spherical-shaped Ag particles, whereas C. papaya, D. metel and S. melongena produced <20 nm sized monodispersed Au particles. The amount of nanoparticles synthesized and its qualitative characterization was done by UV-vis spectroscopy and transmission electron microscopy (TEM), respectively. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used for structural confirmation. Further analysis carried out by fourier transform infrared spectroscopy (FTIR), provided evidence for the presence of amino groups, which increased the stability of the synthesized nanoparticles.

  12. Silver and gold nanoparticle coated membranes applied to protein dot blots

    Science.gov (United States)

    Xie, F.; Drozdowicz-Tomsia, K.; Shtoyko, T.; Goldys, E. M.

    2011-02-01

    Detection and identification of low abundance biomarker proteins is frequently based on various types of membrane-based devices. Lowering of the protein detection limits is vital in commercial applications such as lateral flow assays and in Western blots widely used in proteomics. These currently suffer from insufficient detection sensitivity and low retention for small 2-5 kDa proteins. In this study, we report the deposition of two types of metal nanoparticles: gold colloids (50-95 nm diameter) and silver fractals onto a range of commonly used types of membranes including polyvinylidene fluoride (PVDF). Due to strong affinity of proteins to noble metals, such modified membranes have the potential to effectively capture trace proteins preventing their loss. The membranes modified by metal particles were characterized optically and by SEM. The membrane performance in protein dot blots was evaluated using the protein—fluorophore conjugates Deep Purple-bovine serum albumin and fluorescein—human serum albumin. We found that the metal nanoparticles increase light extinction by metals, which is balanced by increased fluorescence, so that the effective fluorescence signal is unchanged. This feature combined with the capture of proteins by the nanoparticles embedded in the membrane increases the detection limit of membrane assays.

  13. Plasmonic Modes and Optical Properties of Gold and Silver Ellipsoidal Nanoparticles by the Discrete Dipole Approximation

    Directory of Open Access Journals (Sweden)

    Mohammed Alsawafta

    2012-01-01

    Full Text Available The discrete dipole approximation (DDA is used to model the absorption efficiency of isolated gold (Au and silver (Ag ellipsoidal nanoparticles. The characteristics of the plasmonic bands of those nanostructures depend strongly on the size and orientation of the particles in both the lab and target frames. At specific rotation and incident angles, the desired plasmonic mode can be excited. The result of the simulation shows the possibility of excitation of three plasmonic modes—one longitudinal mode (LM and two transverse modes (TM—corresponding to the redistribution of the polarization charges along each principal axis. At oblique incidence of the incoming light, both the Au LM and a hybrid Au TM are observed whereas three more distinct plasmonic modes can be found in the case of the Ag particle. The effect of length distribution on the characteristics of the plasmonic bands is also examined for the three principal axes. The band position of the plasmonic bands associated with the electronic oscillation along each principal axis is found to vary linearly with the axis length. The linear variation of the band position of the LM is steeper as compared with the one found for the other modes.

  14. Silver nanoparticles decorated nanoporous gold for surface-enhanced Raman scattering

    Science.gov (United States)

    Yang, Min; Zhang, Ling; Chen, Bin; Wang, Zheng; Chen, Chao; Zeng, Heping

    2017-02-01

    Raman spectra are considered as signatures of matter and have been widely used to identify several classes of materials. The development of mobile spectrometers further extends applications of Raman spectroscopy, and both indoor/outdoor and in vivo/in vitro measurements have been evaluated on site. However, the finite detection level restricts its application in high density matters. Here we report a facile silver nanoparticle decorated nanoporous gold (NanoAg@NPG) substrate, which can provide high enhancement of the Raman signal from nearby molecules by 785 nm photoexcitation. This enhancement is attributed to the abundant Raman-active nanogaps constructed by adjacent nanoparticles and also by the NPG ligaments and adhered nanoparticles. This NanoAg@NPG substrate shows great potential as a reproducible and quantifiable near infrared surface-enhanced Raman scattering probe for various targets, since it performs well in the so-called biological window which can avoid autofluorescence and absorption either from targets or surroundings in the visible optical region.

  15. Plasmon-mediated binding forces on gold or silver homodimer and heterodimer

    Science.gov (United States)

    Liaw, Jiunn-Woei; Kuo, Ting-Yu; Kuo, Mao-Kuen

    2016-02-01

    This study theoretically investigates plasmon-mediated optical binding forces, which are exerted on metal homo or heterodimers, induced by the normal illumination of a linearly polarized plane wave or Gaussian beam. Using the multiple multipole method, we analyzed the optical force in terms of Maxwell's stress tensor for various interparticle distance at some specific wavelengths. Numerical results show that for a given wavelength there are several stable equilibrium distances between two nanoparticles (NPs) of a homodimer, which are slightly shorter than some integer multiples of the wavelength in medium, such that metal dimer acts as bonded together. At these specific interparticle distances, the optical force between dimer is null and serves a restoring force, which is repulsive and attractive, respectively, as the two NPs are moving closer to and away from each other. The spring constant of the restoring force at the first stable equilibrium is always the largest, indicating that the first stable equilibrium distance is the most stable one. Moreover, the central line (orientation) of a dimer tends to be perpendicular to the polarization of light. For the cases of heterodimers, the phenomenon of stable equilibrium interparticle distance still exists, except there is an extra net photophoretic force drifting the heterodimer as one. Moreover, gradient force provided by a Gaussian beam may reduce the stability of these equilibriums, so larger NPs are preferred to stabilize a dimer under illumination of Gaussian beam. The finding may pave the way for using optical manipulation on the gold or silver colloidal self-assembly.

  16. Coalescence of functional gold and monodisperse silver nanoparticles mediated by black Panax ginseng Meyer root extract.

    Science.gov (United States)

    Wang, Dandan; Markus, Josua; Kim, Yeon-Ju; Wang, Chao; Jiménez Pérez, Zuly Elizabeth; Ahn, Sungeun; Aceituno, Verónica Castro; Mathiyalagan, Ramya; Yang, Deok Chun

    A rapid biological synthesis of multifunctional gold nanoparticle (AuNp) and monodisperse silver nanoparticle (AgNp) was achieved by an aqueous extract of black Panax ginseng Meyer root. The physicochemical transformation into black ginseng (BG) greatly enhanced the pharmacological activities of white ginseng and its minor ginsenoside content. The optimal temperature conditions and kinetics of bioreduction were investigated. Formation of BG-AuNps and BG-AgNps was verified by ultraviolet-visible spectrophotometry at 548 and 412 nm, respectively. The biosynthesized BG-AgNps were spherical and monodisperse with narrow distribution, while BG-AuNps were icosahedral-shaped and moderately polydisperse. Synthesized nanoparticles exhibited long-term stability in buffers of pH 7.0-8.0 and biological media (5% bovine serum albumin) at an ambient temperature and at 37°C. BG-AgNps showed effective antibacterial activity against Escherichia coli and Staphylococcus aureus. BG-AuNps and BG-AgNps demonstrated increased scavenging activity against 2,2-diphenyl-1-picrylhydrazyl free radicals. In addition, BG-AuNps and BG-AgNps were nontoxic to HaCaT and MCF-7 cells; the latter showed no cytotoxicity at concentrations lower than 10 µg/mL. At higher concentrations, BG-AgNps exhibited apparent apoptotic activity in MCF-7 breast cancer cell line through reactive oxygen species generation and nuclear fragmentation.

  17. A plasmonic colorimetric strategy for biosensing through enzyme guided growth of silver nanoparticles on gold nanostars.

    Science.gov (United States)

    Guo, Yuehua; Wu, Jie; Li, Jie; Ju, Huangxian

    2016-04-15

    A plasmonic colorimetric strategy was designed for sensitive detection of biomolecules through enzyme guided silver nanoparticles (AgNPs) growth on gold nanostars (AuNS). The growth of AgNPs on AuNS led to a substantial blue shift of the localized surface plasmon resonance (LSPR) peak and the color change of AuNS from blue to dark blue, purple and ultimately orange. Both the LSPR blueshift wavelength and the color of detection solution containing AuNS, Ag(+) and ascorbic acid 2-phosphate (AAP) depend on the amount of enzyme that catalyzed the dephosphorylation of AAP to reduce Ag(+) on AuNS surface. Thus this strategy could be used for LSPR and naked-eye detections of both the enzyme such as alkaline phosphatase (ALP) and other biomolecules involved in biorecognition events using ALP as a tag. The LSPR detection method for ALP showed a linear range from 1.0 pM to 25 nM with a detection limit of 0.5 pM. Using DNA as a mode target molecule, this technique showed a detection range from 10 fM to 50 pM DNA with a detection limit of 2.6 fM through the convenient combination with hybridization chain reaction amplification. The proposed plasmonic colorimetric strategy could be extended as a general analytical platform for design of immunosensors and aptasensors with ALP as a label. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Green synthesis of silver and gold nanoparticles using Rosa damascena and its primary application in electrochemistry

    Science.gov (United States)

    Ghoreishi, Sayed M.; Behpour, Mohsen; Khayatkashani, Maryam

    2011-10-01

    Biosynthesis and characterizations of nanoparticles have become an important branch of nanotechnology. In this paper, green synthesis of gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) using the flower extract of Rosa damascena as a reducing and stabilizing agent, has been discussed. This approach is simple, cost-effective and stable for a long time, reproducible at room temperature and in an eco-friendly manner to obtain a self-assembly of AuNPs and AgNPs. The resulting nanoparticles are characterized using UV-vis, TEM, XRD and FT-IR spectroscopic techniques. A modified glassy carbon electrode using AuNPs (AuNPs/GCE) was investigated by means of cyclic voltammetry in a solution of 0.1 M KCl and 5.0×10 -3 M [Fe(CN) 6] 3-/4-. The results show that electronic transmission rate between the modified electrode and [Fe(CN) 6] 3-/4- increased.

  19. Genetic environment of germanium-bearing gold-silver vein ores from the Wolyu mine, Republic of Korea

    Science.gov (United States)

    Yun, Seong-Taek; So, Chil-Sup; Choi, Sang-Hoon; Shelton, Kevin L.; Koo, Ja-Hak

    1993-04-01

    The Wolyu mine is one of the largest vein-type gold-silver-bearing epithermal systems in the Youngdong district and is the first gold-silver deposit in Korea found to contain significant germanium, in the form of argyrodite (Ag8GeS6). Mineralized veins (78.9 ± 1.2 Ma) crosscutting Late Cretaceous hostrock tuff and quartz porphyry (81.5 ± 1.8 Ma) consist of three stages of quartz and carbonates, the first of which contains pyrite, basemetal sulfides and Au-Ag-minerals. Stage I Au-Ag-Ge-mineralized veins show a systematic variation of mineral assemblage with time: (1) quartz + pyrite; (2) quartz + pyrite + sphalerite + electrum + argentite; (3) carbonate + quartz + sphalerite + electrum + argentite; (4) carbonate + native silver + argentite + Ag-sulfosalts + argyrodite + sphalerite. Calculated values of temperature and sulfur activity are: assemblage (1), 360-280°C and 10-7-10-10; (2), 280-210°C and 10-10-10-14; (3), 210-180°C and 10-14-10-16; (4), 180-155°C and 10-17-10-18. These data, the frequent association of gold with sulfides, and the abundance of pyrite in alteration zones indicate that decreasing sulfur activity and cooling were important in triggering gold deposition. Hydrogen and oxygen isotope compositions of ore fluids display a systematic variation with increasing time. Within the main Ag-Au-Ge mineralization, δD and δ 18O values decrease with the transition from quartz to carbonate deposition (from -78 and -2.8% to -90 and -8.7%., respectively), indicating increasing involvement (mixing) of less evolved meteoric water which resulted in progressive cooling and dilution of ore fluids in the shallow (≈ 370 600 m) Wolyu epithermal system.

  20. Geochemistry, geochronology, mineralogy, and geology suggest sources of and controls on mineral systems in the southern Toquima Range, Nye County, Nevada; with geochemistry maps of gold, silver, mercury, arsenic, antimony, zinc, copper, lead, molybdenum, bismuth, iron, titanium, vanadium, cobalt, beryllium, boron, fluorine, and sulfur; and with a section on lead associations, mineralogy and paragenesis, and isotopes

    Science.gov (United States)

    Shawe, Daniel R.; Hoffman, James D.; Doe, Bruce R.; Foord, Eugene E.; Stein, Holly J.; Ayuso, Robert A.

    2003-01-01

    Geochemistry maps showing the distribution and abundance of 18 elements in about 1,400 rock samples, both mineralized and unmineralized, from the southern Toquima Range, Nev., indicate major structural and lithologic controls on mineralization, and suggest sources of the elements. Radiometric age data, lead mineralogy and paragenesis data, and lead-isotope data supplement the geochemical and geologic data, providing further insight into timing, sources, and controls on mineralization. Major zones of mineralization are centered on structural margins of calderas and principal northwest-striking fault zones, as at Round Mountain, Manhattan, and Jefferson mining districts, and on intersections of low-angle and steep structures, as at Belmont mining district. Paleozoic sedimentary rocks, mostly limestones (at Manhattan, Jefferson, and Belmont districts), and porous Oligocene ash-flow tuffs (at Round Mountain district) host the major deposits, although all rock types have been mineralized as evidenced by numerous prospects throughout the area. Principal mineral systems are gold-silver at Round Mountain where about 7 million ounces of gold and more than 4 million ounces of silver has been produced; gold at Gold Hill in the west part of the Manhattan district where about a half million ounces of gold has been produced; gold-mercury-arsenic-antimony in the east (White Caps) part of the Manhattan district where a few hundred thousand ounces of gold has been produced; and silver-lead-antimony at Belmont where more than 150,000 ounces of silver has been produced. Lesser amounts of gold and silver have been produced from the Jefferson district and from scattered mines elsewhere in the southern Toquima Range. A small amount of tungsten was produced from mines in the granite of the Round Mountain pluton exposed east of Round Mountain, and small amounts of arsenic, antimony, and mercury have been produced elsewhere in the southern Toquima Range. All elements show unique

  1. SENSING OF PROSTATE SPESIFIC ANTIGEN BY DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMMETRY OF GOLD NANOPARTICLE - SILVER ENHANCED LABELS

    Directory of Open Access Journals (Sweden)

    Rika Endara Safitri

    2016-09-01

    Full Text Available A sensitive prostate specific antigen (PSA detection method based on peptide cleavage and silver enhancement of gold nanoparticle (AuNP has been developed. PSA is serine protease produced by both normal prostate glandular cells and prostate cancer cells. PSA widely used as a biomarker for prostate cancer (PCa. The activity of PSA was detected by following mechanism: first, some immobilized peptide on the bottom of wellplate was undergo cleaving process via biotin-avidin interaction, leaving short peptide (without thiol group that could not form a link with gold nanoparticle. Meanwhile, the remaining peptide which not undergo such process could self-assemble with AuNPs, followed by autocatalytic reduction with silver enhancement solutions to silver metal (Ag. The Ag content on AuNPs was determined by differential pulse anodic stripping voltammetry, after axidation of Ag metal to Ag+ ions, using screen printed carbon electrode. The measurement conditions and immunoassay components had been optimized in this study. The detection of PSA was successfully carried out by this method with limit detection value of 152.204 ng/mL, but further development is necessary to improve the limit detection value.

  2. Observation of exchanging role of gold and silver nanoparticles in bimetallic thin film upon annealing above the glass transition temperature

    Science.gov (United States)

    Htet Kyaw, Htet; Tay Zar Myint, Myo; Hamood Al-Harthi, Salim; Maekawa, Toru; Yanagisawa, Keiichi; Sellai, Azzouz; Dutta, Joydeep

    2017-08-01

    The exchange role of gold (Au) and silver (Ag) in bimetallic films co-evaporated onto soda-lime glass substrates with Au-Ag volume ratios of 1:2, 1:1 and 2:1 have been demonstrated. Annealing of the films above the glass transition temperature in air led to non-alloying nature of the films, silver neutrals (Ag0) and gold nanoparticles (AuNPs) on the surface, along with silver nanoparticles (AgNPs) inside the glass matrix. Moreover, the size distribution and interparticle spacing of the AuNPs on the surface were governed by the Ag content in the deposited film. In contrast, the content of Au in the film played an opposite role leading to the migration of Ag ions (i.e. Ag0 being transformed to Ag ions after annealing in oxygen ambient) to form AgNPs inside the glass matrix. The higher the Au content in the film is, the more likely Ag0 to stay on the surface and impacts on the size distribution of AuNPs and consequently on the refractive index sensitivity measurements. Experimental realisation of this fact was reflected from the best performance for localized surface plasmon resonance (LSPR) sensitivity test achieved with Au-Ag ratio of 1:2. The Au/Ag/glass bimetallic dynamic results of this study can be pertinent to sensor applications integrated with optical devices.

  3. Gold silver alloy nanoparticles (GSAN): an imaging probe for breast cancer screening with dual-energy mammography or computed tomography

    Science.gov (United States)

    Naha, Pratap C.; Lau, Kristen C.; Hsu, Jessica C.; Hajfathalian, Maryam; Mian, Shaameen; Chhour, Peter; Uppuluri, Lahari; McDonald, Elizabeth S.; Maidment, Andrew D. A.; Cormode, David P.

    2016-07-01

    Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various analytical methods. DEM and computed tomography (CT) phantom imaging showed that GSAN produced robust contrast that was comparable to silver alone. Cell viability, reactive oxygen species generation and DNA damage results revealed that the formulations with 30% or higher gold content are cytocompatible to Hep G2 and J774A.1 cells. In vivo imaging was performed in mice with and without breast tumors. The results showed that GSAN produce strong DEM and CT contrast and accumulated in tumors. Furthermore, both in vivo imaging and ex vivo analysis indicated the excretion of GSAN via both urine and feces. In summary, GSAN produce strong DEM and CT contrast, and has potential for both blood pool imaging and for breast cancer screening.Earlier detection of breast cancer reduces mortality from this disease. As a result, the development of better screening techniques is a topic of intense interest. Contrast-enhanced dual-energy mammography (DEM) is a novel technique that has improved sensitivity for cancer detection. However, the development of contrast agents for this technique is in its infancy. We herein report gold-silver alloy nanoparticles (GSAN) that have potent DEM contrast properties and improved biocompatibility. GSAN formulations containing a range of gold : silver ratios and capped with m-PEG were synthesized and characterized using various

  4. A comparison of gold versus silver electrode contacts for high-resolution gastric electrical mapping using flexible printed circuit board arrays.

    Science.gov (United States)

    O'Grady, G; Paskaranandavadivel, N; Angeli, T R; Du, P; Windsor, J A; Cheng, L K; Pullan, A J

    2011-03-01

    Stomach contractions are initiated and coordinated by electrical events termed slow waves, and slow wave abnormalities contribute to gastric motility disorders. Recently, flexible printed circuit board (PCB) multi-electrode arrays were introduced, facilitating high-resolution mapping of slow wave activity in humans. However PCBs with gold contacts have shown a moderately inferior signal quality to previous custom-built silver-wire platforms, potentially limiting analyses. This study determined if using silver instead of gold contacts improved flexible PCB performance. In a salt-bath test, modestly higher stimulus amplitudes were recorded from silver PCBs (mean 312, s.d. 89 µV) than those from gold (mean 281, s.d. 85 µV) (p < 0.001); however, the signal-to-noise ratio (SNR) was similar (p = 0.26). In eight in vivo experimental studies, involving gastric serosal recordings from five pigs, no silver versus gold differences were found in terms of slow wave amplitudes (mean 677 versus 682 µV; p = 0.91), SNR (mean 8.8 versus 8.8 dB; p = 0.94) or baseline drift (NRMS; mean 12.0 versus 12.1; p = 0.97). Under the prescribed conditions, flexible PCBs with silver or gold contacts provide comparable results in vivo, and contact material difference does not explain the performance difference between current-generation slow wave mapping platforms. Alternative explanations for this difference and the implications for electrode design are discussed.

  5. Interaction of gold and silver nanoparticles with human plasma: Analysis of protein corona reveals specific binding patterns.

    Science.gov (United States)

    Lai, Wenjia; Wang, Qingsong; Li, Lumeng; Hu, Zhiyuan; Chen, Jiankui; Fang, Qiaojun

    2017-04-01

    Determining how nanomaterials interact with plasma will assist in understanding their effects on the biological system. This work presents a systematic study of the protein corona formed from human plasma on 20nm silver and gold nanoparticles with three different surface modifications, including positive and negative surface charges. The results show that all nanoparticles, even those with positive surface modifications, acquire negative charges after interacting with plasma. Approximately 300 proteins are identified on the coronas, while 99 are commonly found on each nanomaterial. The 20 most abundant proteins account for over 80% of the total proteins abundance. Remarkably, the surface charge and core of the nanoparticles, as well as the isoelectric point of the plasma proteins, are found to play significant roles in determining the nanoparticle coronas. Albumin and globulins are present at levels of less than 2% on these nanoparticle coronas. Fibrinogen, which presents in the plasma but not in the serum, preferably binds to negatively charged gold nanoparticles. These observations demonstrate the specific plasma protein binding pattern of silver and gold nanoparticles, as well as the importance of the surface charge and core in determining the protein corona compositions. The potential downstream biological impacts of the corona proteins were also investigated. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Radiotracer study of the adsorption of organic compounds on gold. adsorption of chloroacetic and phenylacetic acid, and the effects of cadmium, copper, and silver adatoms on it

    Energy Technology Data Exchange (ETDEWEB)

    Horani, G.; Andreev, V.N.; Vazarinov, V.E.

    1986-04-01

    This paper studies the adsorption of monochloroacetic and phenylacetic acid (MA and PA, respectively) by the radiotracer technique on gold-plated gold electrodes in acidic solutions. The authors also study the effect of cadmium, copper, and silver adatoms on these processes. The adsorption of MA was measured as a function of potential of the electrode. Data from these measurements are presented. Data show that cadmium, copper, and silver ions present in the solution have no effect on the adsorption of PA at potentials where they are not adsorbed on the gold surface. It is confirmed that the radiotracer technique will be as effective in adsorption studies on the gold-plated gold electrode as it was in the case of the platinized platinum electrode.

  7. Biosynthesis of gold and silver nanoparticles by natural precursor clove and their functionalization with amine group

    Science.gov (United States)

    Singh, Ashwani Kumar; Talat, Mahe; Singh, D. P.; Srivastava, O. N.

    2010-06-01

    We report a simple and cost effective way for synthesis of metallic nanoparticles (Au and Ag) using natural precursor clove. Au and Ag nanoparticles have been synthesized by reducing the aqueous solution of AuCl4 and AgNO3 with clove extract. One interesting aspect here is that reduction time is quite small (few minutes instead of hours as compared to other natural precursors). We synthesized gold and silver nanoparticles of different shape and size by varying the ratio of AuCl4 and AgNO3 with respect to clove extract, where the dominant component is eugenol. The evolution of Au and Ag nanoparticles from the reduction of different ratios of AuCl4 and AgNO3 with optimised concentration of the clove extract has been evaluated through monitoring of surface plasmon behaviour as a function of time. The reduction of AuCl4 and AgNO3 by eugenol is because of the inductive effect of methoxy and allyl groups which are present at ortho and para positions of proton releasing -OH group as two electrons are released from one molecule of eugenol. This is followed by the formation of resonating structure of the anionic form of eugenol. The presence of methoxy and allyl groups has been confirmed by FTIR. To the best of our knowledge, use of clove as reducing agent, the consequent very short time (minutes instead of hours and without any scavenger) and the elucidation of mechanism of reduction based on FTIR analysis has not been attempted earlier.

  8. Comparative catalytic activity of PET track-etched membranes with embedded silver and gold nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Mashentseva, Anastassiya, E-mail: mashentseva.a@gmail.com [Institute of Nuclear Physics, Ibragimov St. 1, 050032 Almaty (Kazakhstan); The L.N. Gumilyov Eurasian National University, Satpayev Str., 2, 010008 Astana (Kazakhstan); Borgekov, Daryn [Institute of Nuclear Physics, Ibragimov St. 1, 050032 Almaty (Kazakhstan); The L.N. Gumilyov Eurasian National University, Satpayev Str., 2, 010008 Astana (Kazakhstan); Kislitsin, Sergey [Institute of Nuclear Physics, Ibragimov St. 1, 050032 Almaty (Kazakhstan); Zdorovets, Maxim [Institute of Nuclear Physics, Ibragimov St. 1, 050032 Almaty (Kazakhstan); The L.N. Gumilyov Eurasian National University, Satpayev Str., 2, 010008 Astana (Kazakhstan); Migunova, Anastassiya [Institute of Nuclear Physics, Ibragimov St. 1, 050032 Almaty (Kazakhstan)

    2015-12-15

    Irradiated by heavy ions nanoporous polyethylene terephthalate track-etched membranes (PET TeMs) after {sup +15}Kr{sup 84} ions bombardment (1.75 MeV/nucl with the ion fluency of 1 × 10{sup 9} cm{sup −2}) and sequential etching was applied in this research as a template for development of composites with catalytically enriched properties. A highly ordered silver and gold nanotubes arrays were embedded in 100 nm pores of PET TeMs via electroless deposition technique at 4 °C during 1 h. All “as-prepared” composites were examined for catalytic activity using reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride as a common reaction to test metallic nanostructures catalysts. The effect of temperature on the catalytic activity was investigated in range of 292–313 K and activation energy were calculated. K{sub app} of Ag/PET composites linearly increase with an increase of the temperature thus normal Arrhenius behavior have been seen and the activation energy was calculated to be 42.13 kJ/mol. Au/PET composites exhibit not only more powerful catalytic activity but also non-linear dependence of rate constant from temperature. K{sub app} increased with increasing temperature throughout the 292–308 K temperature range; the reaction had an activation energy 65.32 kJ/mol. In range 311–313 K rate constant dramatically decreased and the apparent activation energy at this temperature rang was −91.44 kJ/mol due some structural changes, i.e. agglomeration of Au nanoparticles on the surface of composite.

  9. Biosynthesis of gold and silver nanoparticles by natural precursor clove and their functionalization with amine group

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ashwani Kumar; Talat, Mahe [Banaras Hindu University, Nanoscience and Nanotechnology Unit, Department of Physics (India); Singh, D. P. [Southern Illinois University Carbondale, Department of Physics (United States); Srivastava, O. N., E-mail: hepons@yahoo.co [Banaras Hindu University, Nanoscience and Nanotechnology Unit, Department of Physics (India)

    2010-06-15

    We report a simple and cost effective way for synthesis of metallic nanoparticles (Au and Ag) using natural precursor clove. Au and Ag nanoparticles have been synthesized by reducing the aqueous solution of AuCl{sub 4} and AgNO{sub 3} with clove extract. One interesting aspect here is that reduction time is quite small (few minutes instead of hours as compared to other natural precursors). We synthesized gold and silver nanoparticles of different shape and size by varying the ratio of AuCl{sub 4} and AgNO{sub 3} with respect to clove extract, where the dominant component is eugenol. The evolution of Au and Ag nanoparticles from the reduction of different ratios of AuCl{sub 4} and AgNO{sub 3} with optimised concentration of the clove extract has been evaluated through monitoring of surface plasmon behaviour as a function of time. The reduction of AuCl{sub 4} and AgNO{sub 3} by eugenol is because of the inductive effect of methoxy and allyl groups which are present at ortho and para positions of proton releasing -OH group as two electrons are released from one molecule of eugenol. This is followed by the formation of resonating structure of the anionic form of eugenol. The presence of methoxy and allyl groups has been confirmed by FTIR. To the best of our knowledge, use of clove as reducing agent, the consequent very short time (minutes instead of hours and without any scavenger) and the elucidation of mechanism of reduction based on FTIR analysis has not been attempted earlier.

  10. Green synthesis of silver and gold nanoparticles from Gymnema sylvestre leaf extract: study of antioxidant and anticancer activities

    Energy Technology Data Exchange (ETDEWEB)

    Nakkala, Jayachandra Reddy; Mata, Rani; Bhagat, Ekta; Sadras, Sudha Rani, E-mail: dr.ssrlab@gmail.com, E-mail: sadrassudha@gmail.com [Pondicherry University, Department of Biochemistry and Molecular Biology, School of Life Sciences (India)

    2015-03-15

    The present study reports the biological synthesis of silver and gold nanoparticles from Gymnema sylvestre leaf extract and their in vitro free radical scavenging efficacy as well as antiproliferative effect in Hep2 cells. The formation of silver (GYAgNPs) and gold nanoparticles (GYAuNPs) was confirmed by UV–visible spectroscopy. The average size of synthesized GYAgNPs and GYAuNPs was found to be 33 and 26 nm, respectively, by DLS particle size analyzer. TEM analysis indicated spherical shape of GYAgNPs and GYAuNPs and in EDX analysis they produced strong signal for silver and gold, respectively. Both GYAgNPs and GYAuNPs exhibited strong in vitro free radical quenching ability and their activity was comparable to that of GYLE. The cytotoxic effect of GYAgNPs and GYAuNPs in Hep2 cells was examined by MTT assay in which GYAgNPs displayed an IC{sub 50} value of 121 µg ml{sup −1}, while GYAuNPs produced up to 38 % of inhibition at the maximum concentration of 250 µg ml{sup −1} used in this study. Distinct morphological changes were observed in Hep2 cells following treatment with GYAgNPs and GYAuNPs at 24 h, and orange-colored apoptotic bodies were located by acridine orange and ethidium bromide double-staining technique. Also, there was increase in the levels of reactive oxygen species in treated cells as indicated by 2′,7′-dichlorofluorescin diacetate staining. Further, nuclear changes like chromatin condensation/fragmentation were also observed by propidium iodide and 4′,6-diamidino-2-phenylindole dilactate staining methods. These findings support that the antiproliferative effects of GYAgNPs and GYAuNPs in Hep2 cells are mediated through induction of apoptosis.

  11. Green synthesis of silver and gold nanoparticles from Gymnema sylvestre leaf extract: study of antioxidant and anticancer activities

    Science.gov (United States)

    Nakkala, Jayachandra Reddy; Mata, Rani; Bhagat, Ekta; Sadras, Sudha Rani

    2015-03-01

    The present study reports the biological synthesis of silver and gold nanoparticles from Gymnema sylvestre leaf extract and their in vitro free radical scavenging efficacy as well as antiproliferative effect in Hep2 cells. The formation of silver (GYAgNPs) and gold nanoparticles (GYAuNPs) was confirmed by UV-visible spectroscopy. The average size of synthesized GYAgNPs and GYAuNPs was found to be 33 and 26 nm, respectively, by DLS particle size analyzer. TEM analysis indicated spherical shape of GYAgNPs and GYAuNPs and in EDX analysis they produced strong signal for silver and gold, respectively. Both GYAgNPs and GYAuNPs exhibited strong in vitro free radical quenching ability and their activity was comparable to that of GYLE. The cytotoxic effect of GYAgNPs and GYAuNPs in Hep2 cells was examined by MTT assay in which GYAgNPs displayed an IC50 value of 121 µg ml-1, while GYAuNPs produced up to 38 % of inhibition at the maximum concentration of 250 µg ml-1 used in this study. Distinct morphological changes were observed in Hep2 cells following treatment with GYAgNPs and GYAuNPs at 24 h, and orange-colored apoptotic bodies were located by acridine orange and ethidium bromide double-staining technique. Also, there was increase in the levels of reactive oxygen species in treated cells as indicated by 2',7'-dichlorofluorescin diacetate staining. Further, nuclear changes like chromatin condensation/fragmentation were also observed by propidium iodide and 4',6-diamidino-2-phenylindole dilactate staining methods. These findings support that the antiproliferative effects of GYAgNPs and GYAuNPs in Hep2 cells are mediated through induction of apoptosis.

  12. Comparison of 20 nm silver nanoparticles synthesized with and without a gold core: Structure, dissolution in cell culture media, and biological impact on macrophages

    Science.gov (United States)

    Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H.; Baer, Donald R.; Smith, Jordan N.; Liu, Chongxuan; Kodali, Vamsi; Thrall, Brian D.; Chen, Shu; Porter, Alexandra E.; Ryan, Mary P.

    2015-01-01

    Widespread use of silver nanoparticles raises questions of environmental and biological impact. Many synthesis approaches are used to produce pure silver and silver-shell gold-core particles optimized for specific applications. Since both nanoparticles and silver dissolved from the particles may impact the biological response, it is important to understand the physicochemical characteristics along with the biological impact of nanoparticles produced by different processes. The authors have examined the structure, dissolution, and impact of particle exposure to macrophage cells of two 20 nm silver particles synthesized in different ways, which have different internal structures. The structures were examined by electron microscopy and dissolution measured in Rosewell Park Memorial Institute media with 10% fetal bovine serum. Cytotoxicity and oxidative stress were used to measure biological impact on RAW 264.7 macrophage cells. The particles were polycrystalline, but 20 nm particles grown on gold seed particles had smaller crystallite size with many high-energy grain boundaries and defects, and an apparent higher solubility than 20 nm pure silver particles. Greater oxidative stress and cytotoxicity were observed for 20 nm particles containing the Au core than for 20 nm pure silver particles. A simple dissolution model described the time variation of particle size and dissolved silver for particle loadings larger than 9 μg/ml for the 24-h period characteristic of many in-vitro studies. PMID:26178265

  13. Comparison of 20 nm silver nanoparticles synthesized with and without a gold core: Structure, dissolution in cell culture media, and biological impact on macrophages.

    Science.gov (United States)

    Munusamy, Prabhakaran; Wang, Chongmin; Engelhard, Mark H; Baer, Donald R; Smith, Jordan N; Liu, Chongxuan; Kodali, Vamsi; Thrall, Brian D; Chen, Shu; Porter, Alexandra E; Ryan, Mary P

    2015-09-15

    Widespread use of silver nanoparticles raises questions of environmental and biological impact. Many synthesis approaches are used to produce pure silver and silver-shell gold-core particles optimized for specific applications. Since both nanoparticles and silver dissolved from the particles may impact the biological response, it is important to understand the physicochemical characteristics along with the biological impact of nanoparticles produced by different processes. The authors have examined the structure, dissolution, and impact of particle exposure to macrophage cells of two 20 nm silver particles synthesized in different ways, which have different internal structures. The structures were examined by electron microscopy and dissolution measured in Rosewell Park Memorial Institute media with 10% fetal bovine serum. Cytotoxicity and oxidative stress were used to measure biological impact on RAW 264.7 macrophage cells. The particles were polycrystalline, but 20 nm particles grown on gold seed particles had smaller crystallite size with many high-energy grain boundaries and defects, and an apparent higher solubility than 20 nm pure silver particles. Greater oxidative stress and cytotoxicity were observed for 20 nm particles containing the Au core than for 20 nm pure silver particles. A simple dissolution model described the time variation of particle size and dissolved silver for particle loadings larger than 9 μg/ml for the 24-h period characteristic of many in-vitro studies.

  14. Antibacterial Study of Silver, Copper, Gold, and Titanium Dioxide Nanoparticles Prepared by DC and RF Magnetron Sputtering

    OpenAIRE

    Mohammed K. Khalaf; Husham K.Oudah; Amal A. Halob; Sabri J. Mohammed; Mohammed J. Dathan

    2017-01-01

    In this work, the antibacterial activity of nanomaterial’s copper, silver, gold and titanium dioxide sportily was investigated on both gram positive and negative bacteria. Nanoparticles of Cu, Ag, Au and TiO2 films were grown on glass substrates by dc and RF magnetron sputtering techniques. Nanoparticles films deposition were carried out at optimized argon pressure of 5.5×10-2mbar, sputtering plasma power of 30 Watt for Cu, Ag and Au samples and pressure of 1×10-3 mbar, plasma sputtering powe...

  15. Asymmetric dumbbell-shaped silver nanoparticles and spherical gold nanoparticles green-synthesized by mangosteen (Garcinia mangostana) pericarp waste extracts.

    Science.gov (United States)

    Park, Ji Su; Ahn, Eun-Young; Park, Youmie

    2017-01-01

    Mangosteen ( Garcinia mangostana ) pericarp waste extract was used to synthesize gold and silver nanoparticles by a green strategy. The extract was both a reducing and stabilizing agent during synthesis. Phytochemical screening of the extract was conducted to obtain information regarding the presence/absence of primary and secondary metabolites in the extract. The in vitro antioxidant activity results demonstrated that the extract had excellent antioxidant activity, which was comparable to a standard (butylated hydroxy toluene). Spherical gold nanoparticles (gold nanoparticles green synthesized by mangosteen pericarp extract [GM-AuNPs]) with an average size of 15.37±3.99 to 44.20±16.99 nm were observed in high-resolution transmission electron microscopy (HR-TEM) images. Most interestingly, the silver nanoparticles (silver nanoparticles green synthesized by mangosteen pericarp extract [GM-AgNPs]) had asymmetric nanodumbbell shapes where one tail grew from a spherical head. The average head size was measured to be 13.65±5.07 to 31.08±3.99 nm from HR-TEM images. The hydrodynamic size of both nanoparticles tended to increase with increasing extract concentration. Large negative zeta potentials (-18.92 to -34.77 mV) suggested that each nanoparticle solution possessed excellent colloidal stability. The reaction yields were 99.7% for GM-AuNPs and 82.8% for GM-AgNPs, which were assessed by inductively coupled plasma optical emission spectroscopy. A high-resolution X-ray diffraction pattern confirmed the face-centered cubic structure of both nanoparticles. Based on phytochemical screening and Fourier transform infrared spectra, the hydroxyl functional groups of carbohydrates, flavonoids, glycosides, and phenolic compounds were most likely involved in a reduction reaction of gold or silver salts to their corresponding nanoparticles. The in vitro cytotoxicity (based on a water-soluble tetrazolium assay) demonstrated that GM-AgNPs were toxic to both A549 (a human lung

  16. Simultaneous determination of coinage metals, copper, silver and gold in tissues using electrospray ionization tandem mass spectrometry

    OpenAIRE

    Minakata, Kayoko; Yamagishi, Itaru; Nozawa, Hideki; Gonmori, Kunio; Hasegawa, Koutaro; Suzuki, Masako; Horio, Fumihiko; Watanabe, Kanako; Suzuki, Osamu

    2012-01-01

    A rapid and sensitive mass spectrometric method was developed for the simultaneous determination of coinage metals such as copper (Cu), silver (Ag) and gold (Au). The metals in a wet ashed tissue solution were complexed with diethyldithiocarbamate (DDC; C4H10NCS2) and were extracted together with isoamyl alcohol. After the acidification of the extract with oxalic acid, metals were quantified using their product ions, Cu(DDCH)+, Ag(DDCH) + and Au(DDCH)+ that derived from the precursor ions Cu(...

  17. The substrate effect in electron energy-loss spectroscopy of localized surface plasmons in gold and silver nanoparticles

    DEFF Research Database (Denmark)

    Kadkhodazadeh, Shima; Christensen, Thomas; Beleggia, Marco

    2017-01-01

    , as in optical measurements, the substrate material can modify the acquired signal. Here, we have investigated how the EELS signal recorded from supported silver and gold spheroidal nanoparticles at different electron beam impact parameter positions is affected by the choice of a dielectric substrate material......Electron energy-loss spectroscopy (EELS) has become increasingly popular for detailed characterization of plasmonic nanostructures, owing to the unparalleled spatial resolution of this technique. The typical setup in EELS requires nanoparticles to be supported on thin substrates. However...

  18. Green synthesis of gold and silver nanoparticles using gallic acid: catalytic activity and conversion yield toward the 4-nitrophenol reduction reaction

    Science.gov (United States)

    Park, Jisu; Cha, Song-Hyun; Cho, Seonho; Park, Youmie

    2016-06-01

    In the present report, gallic acid was used as both a reducing and stabilizing agent to synthesize gold and silver nanoparticles. The synthesized gold and silver nanoparticles exhibited characteristic surface plasmon resonance bands at 536 and 392 nm, respectively. Nanoparticles that were approximately spherical in shape were observed in high-resolution transmission electron microscopy and atomic force microscopy images. The hydrodynamic radius was determined to be 54.4 nm for gold nanoparticles and 33.7 nm for silver nanoparticles in aqueous medium. X-ray diffraction analyses confirmed that the synthesized nanoparticles possessed a face-centered cubic structure. FT-IR spectra demonstrated that the carboxylic acid functional groups of gallic acid contributed to the electrostatic binding onto the surface of the nanoparticles. Zeta potential values of -41.98 mV for the gold nanoparticles and -53.47 mV for the silver nanoparticles indicated that the synthesized nanoparticles possess excellent stability. On-the-shelf stability for 4 weeks also confirmed that the synthesized nanoparticles were quite stable without significant changes in their UV-visible spectra. The synthesized nanoparticles exhibited catalytic activity toward the reduction reaction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride. The rate constant of the silver nanoparticles was higher than that of the gold nanoparticles in the catalytic reaction. Furthermore, the conversion yield (%) of 4-nitrophenol to 4-aminophenol was determined using reversed-phase high-performance liquid chromatography with UV detection at 254 nm. The silver nanoparticles exhibited an excellent conversion yield (96.7-99.9 %), suggesting that the synthesized silver nanoparticles are highly efficient catalysts for the 4-nitrophenol reduction reaction.

  19. Fabrication of dense two-dimensional assemblies over vast areas comprising gold(core)-silver(shell) nanoparticles and their surface-enhanced Raman scattering properties.

    Science.gov (United States)

    Sugawa, Kosuke; Tanoue, Yoshimasa; Ube, Takuji; Yanagida, Sayaka; Yamamuro, Takahiro; Kusaka, Yasuyuki; Ushijima, Hirobumi; Akiyama, Tsuyoshi

    2014-01-01

    Fabrication of dense two-dimensional assemblies consisting of gold(core)-silver(shell) nanoparticles and the resulting peculiar surface-enhanced Raman scattering (SERS) activity are reported. The assemblies were prepared via assembly at air-toluene interfaces by drop-casting toluene solutions containing the nanoparticles protected with octadecylamine molecules onto glass plates. This simple process, which does not require special apparatus or significant fabrication time, leads to uniform assemblies over vast areas (~34 cm(2)). In the SERS measurements, the high spatial reproducibility of the SERS signals from p-aminothiophenol adsorbed on the assemblies over vast areas demonstrates that this method is useful for the quantitative investigation of SERS mechanisms. Under 532 nm laser excitation, the difference in the enhancement factors of the SERS signals at the a1 mode between assemblies consisting of gold, silver, and core-shell nanoparticles can be explained by the degree of overlap of the excitation wavelength with their plasmon coupling modes. In contrast, under 785 nm excitation, even though the plasmon band of the core-shell nanoparticle assemblies does not significantly overlap with the excitation wavelength as compared with that of gold nanoparticle assemblies, the enhancement factor from the core-shell nanoparticle assemblies was stronger than those from the gold nanoparticle assemblies. Therefore, we have demonstrated that the gold(core)-silver(shell) nanoparticle assemblies are excellent SERS active materials, which have strong electromagnetic mechanism (EM) as well as chemical mechanism (CM) effects due to the silver shells.

  20. Novel Gold(I) and Silver(I) Complexes of Phosphorus-1,1,-dithiolates and Molecular Structure of [O,O'-(Bornyl)2PS2]H3NC(CH3)3.

    Science.gov (United States)

    Solak, Samet; Aydemir, Cemal; Karakus, Mehmet; Lönnecke, Peter

    2013-05-20

    The novel chiral phosphorus-1,1-dithiolates [4-CH3OC6H4P(S)(OR)S]-[H3NC(CH3)3]+ were synthesized by the reaction of [RPS2)]2 (R = 4-MeOC6H4) or P2S5 and the respective alcohol ROH (R = myrtanyl, 2-naphthylethyl, myrtenyl, borneol) in toluene. The reaction of phosphorus-1,1-dithiolates 1-4 and Au(tht)Cl, AuClPPh3 or AgNO3 and PPh3 gave rise to gold(I)- and silver(I)-complexes in THF. All compounds have been characterised by elemental analyses, IR, NMR (1H-, 13C- and 31P-) spectroscopy as well as MS measurements. Optical rotation values confirmed the chirality of the compounds. The Compound 4 has been characterized structurally by X-ray crystallography. Phosphorus-1,1,-dithiolate compounds were formed as liquids and were treated with suitable amine in order to convert them to their salts 1-4 . They have been successfully characterized spectroscopically (IR, 1H, 13C, 31P NMR) as well as mass spectra. The compound 4 has been also structurally by X-ray crystallography. The compound 4 crystallizes in the orthorhombic space group P2(1)2(1)2(1) with Z = 4. Compounds containing phosphorus and sulfur donor atoms are excellent ligands due to offering many metal complexes especially group 11-12 metals. The synthesis of gold(I) and silver(I) complexes with chiral phosphorus-1,1,-dithiolate and triphenylphosphine have been described and investigated. In the present work, we report the synthesis, charactreization of the chiral phosphorus-1,1-dithiolate ligands and preparing the gold(I) and silver(I) phosphorus-1,1-dithiolate or S-donor with phosphine complexes. The molecular structure of the Compound 4 was determined by X-ray diffraction. Due to an easy synthesis method of phosphorus-1,1-dithiolate compounds and a good complexion reagent, it is possible the improvement of the collecting metallic gold or silver from the minerals. When the more ionic salt of phosphorus-1,1-dithiolate compounds were prepared in this way, the water can be used as a cheap solvent. As a

  1. High-temperature tribological characteristics of silver and gold coatings on ceramics prepared by ion-beam-assisted deposition

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, A.; Erck, R.A.; Fenske, G.R.; Nichols, F.A.

    1992-04-01

    An ion-beam-assisted deposition (IBAD) system was used to deposit silver and gold coatings on polycrystalline {alpha}-alumina (Al{sub 2}O{sub 3}) substrates for tribological studies at temperatures to 400{degrees}C. The wear tests were performed with an oscillating ball-on-flat type of test apparatus as a partial simulation of ring/liner motion and contact geometry in actual engine systems. The test results showed that without a surface coating, both the wear rates and the friction coefficients of Al{sub 2}O{sub 3}/Al{sub 2}O{sub 3} test pairs were quite high, and increased substantially with temperature. In contract, the wear of flats coated with silver and gold was at unmeasurable levels, even after sliding tests of 110,000 passes. The wear of balls (uncoated) sliding against the Ag- and Au-coated flats was reduced by factors of 45 to more than 500 depending on coating type and ambient temperature. The friction coefficients of pairs with an IBAD-Ag or Au coating were in the range of 0.32--0.5.

  2. A novel nonenzymatic hydrogen peroxide sensor based on multi-wall carbon nanotube/silver nanoparticle nanohybrids modified gold electrode.

    Science.gov (United States)

    Zhao, Wei; Wang, Huicai; Qin, Xia; Wang, Xinsheng; Zhao, Zixia; Miao, Zhiying; Chen, Lili; Shan, Miaomiao; Fang, Yuxin; Chen, Qiang

    2009-12-15

    A novel strategy to fabricate hydrogen peroxide (H(2)O(2)) sensor was developed based on multi-wall carbon nanotube/silver nanoparticle nanohybrids (MWCNT/Ag nanohybrids) modified gold electrode. The process to synthesize MWCNT/Ag nanohybrids was facile and efficient. In the presence of carboxyl groups functionalized multi-wall carbon nanotubes (MWCNTs), silver nanoparticles (Ag NPs) were in situ generated from AgNO(3) aqueous solution and readily attached to the MWCNTs convex surfaces at room temperature, without any additional reducing reagent or irradiation treatment. The formation of MWCNT/Ag nanohybrids product was observed by transmission electron microscope (TEM), and the electrochemical properties of MWCNT/Ag nanohybrids modified gold electrode were characterized by electrochemical measurements. The results showed that this sensor had a favorable catalytic ability for the reduction of H(2)O(2). The resulted sensor could detect H(2)O(2) in a linear range of 0.05-17 mM with a detection limit of 5x10(-7)M at a signal-to-noise ratio of 3. The sensitivity was calculated as 1.42 microA/mM at a potential of -0.2 V. Additionally, it exhibited good reproducibility, long-term stability and negligible interference of ascorbic acid (AA), uric acid (UA), and acetaminophen (AP).

  3. Paederia foetida Linn. promoted biogenic gold and silver nanoparticles: Synthesis, characterization, photocatalytic and in vitro efficacy against clinically isolated pathogens.

    Science.gov (United States)

    Bhuyan, Bishal; Paul, Arijita; Paul, Bappi; Dhar, Siddhartha Sankar; Dutta, Pranab

    2017-08-01

    Development of newer improved therapeutic agents with efficient antimicrobial activities continues to draw attention of researchers till date. Moreover, abatement of polluting dyes released from industry with enhanced efficiency is currently being considered as challenging task for people working on material sciences. In the present study, we report a facile biogenic synthesis of gold and silver nanoparticles (NPs) in which aqueous extracts of Paederia foetida Linn. was used as reducing as well as stabilizing agent. The biosynthesized Au and Ag NPs were characterized by UV-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The photocatalytic activity of these nanoparticles were tested against Rhodamine B (RhB). The antimicrobial activity of these biosynthesized NPs were investigated against four human pathogens viz. B. cereus, E. coli, S. aureus and A. niger. Biogenic silver nanoparticles presented a strong antimicrobial activity against B. cereus (26.13) followed by E. coli (26.02), S. aureus (25.43) and A. niger (22.69). Ag NPs owing to their small size (5-25nm) could have easily penetrate into the cell membrane, disturb the metabolism, cause irretrievable damage finally leading to the microbial cell death. Interestingly biogenic gold nanoparticles didn't show any antimicrobial activity. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Phyto-crystallization of silver and gold by Erigeron annuus (L. Pers flower extract and catalytic potential of synthesized and commercial nano silver immobilized on sodium alginate hydrogel

    Directory of Open Access Journals (Sweden)

    Palanivel Velmurugan

    2016-05-01

    Full Text Available A green, eco-friendly approach for the synthesis of silver and gold nanoparticles (AgNPs and AuNPs using Erigeron annuus (L. pers flower extract as both the reducing and capping agent is reported for the first time. Optimal nanoparticle production was achieved by adjusting various parameters including pH, extract concentration, metal ion concentration, and time. Initial verification of AgNP and AuNP production was done by visual observation and measuring surface plasmon spectra at 434 and 537 nm, respectively. The synthesized AgNPs and AuNPs were characterized by high resolution-transmission electron microscopy (HR-TEM, X-ray diffraction (XRD, energy dispersive spectrophotometry (EDS, Fourier transform infrared spectroscopy (FTIR and zeta potential. The catalytic potential of E. annuus flower extract, silver ions, synthesized AgNPs, commercial grade AgNPs, and a mixture of flower extract and AgNPs immobilized on sodium alginate hydrogel beads (Na/Al HB was analyzed. The ability of these immobilized materials to degrade methylene blue was investigated. Commercial grade AgNPs immobilized with Na/Al HB 1.5 g/20 mL were observed to have good catalytic activity followed by a mixture of synthesized AgNPs immobilized with Na/Al HB and E. annuus flower extract immobilized with Na/Al HB at 1.5 g/20 mL.

  5. The synthesis of four-layer gold-silver-polymer-silver core-shell nanomushroom with inbuilt Raman molecule for surface-enhanced Raman scattering

    Science.gov (United States)

    Jiang, Tao; Wang, Xiaolong; Zhou, Jun

    2017-12-01

    A facial two-step reduction method was proposed to synthesize four-layer gold-silver-polymer-silver (Au@Ag@PSPAA@Ag) core-shell nanomushrooms (NMs) with inbuilt Raman molecule. The surface-enhanced Raman scattering (SERS) intensity of 4MBA adhered on the surface of Au core gradually increased with the modification of middle Ag shell and then Ag mushroom cap due to the formation of two kinds of ultra-small interior nanogap. Compared with the initial Au nanoparticles, the SERS enhancement ratio of the Au@Ag@PSPAA@Ag NMs approached to nearly 40. The novel core-shell NMs also exhibited homogeneous SERS signals for only one sample and reproducible signals for 10 different samples, certified by the low relative standard deviation values of less than 10% and 15% for the character peaks of 4-mercaptobenzoic acid, respectively. Such a novel four-layer core-shell nanostructure with reliable SERS performance has great potential application in quantitative SERS-based immunoassay.

  6. Dissolution of Gold and Silver with Ammonium Thiosulfate from Mangano-Argentiferous Ores Treated in Acid-Reductive Conditions

    Science.gov (United States)

    Tiburcio Munive, G.; Encinas Romero, M. A.; Vazquez, V. M.; Valenzuela García, J. L.; Valenzuela Soto, A.; Coronado Lopez, J. H.

    2017-10-01

    A novel process was studied to extract economic metals from refractory ores that are difficult to leach with cyanide and ammonium thiosulfate, such as the well-known mangano argentiferous minerals, which are minerals of manganese, iron, and silver. The mineral under consideration originates from the tailings of the Monte del Favor, Hostotipaquillo Jalisco, Mexico. The sample was characterized by x-ray diffractometry, atomic absorption spectroscopy, scanning electron microscopy, and microanalysis by energy-dispersive x-ray spectroscopy. First, the material was passed through a 100-mesh screen, and then it was subjected to reductive leaching by varying the liquid-solid ( L/ S) ratio from 2:1 to 10:1 (observations were carried out at a ratio of 5:1, which yielded higher extraction of manganese). With H2SO4 and Na2SO3 as the reducing agents, manganese extraction of up to 96.05% was achieved during the first 3 h with a mineral head of manganese 3.58%, acid consumption of 90.74 g/L, and sulfite consumption of 25.8 g/L. The mineral was then filtered and proceeded to neutralize the acidity, reaching a pH of 8 with calcium hydroxide. Then, the material was subjected to a new leaching of gold and silver values with ammonium thiosulfate. The L/ S ratio was varied (1:1, 2:1, 3:1, 4:1), and the contact time and the concentration of ammonium thiosulfate was investigated, while controlling the pH using Ca(OH)2 and NH4Cl. An L/ S ratio of 2:1 showed the best extraction of silver (97.06%) and gold (86.66%), and the thiosulfate consumption was 10.36 g/L. The mineral head of gold and silver was 0.30 g/ton and 310 g/ton, respectively. The pH was maintained between 9.8 and 8.4, such that ammonium thiosulfate stabilized with lime, and ammonium chloride did not suffer any decomposition.

  7. Eco-friendly microwave-assisted green and rapid synthesis of well-stabilized gold and core-shell silver-gold nanoparticles.

    Science.gov (United States)

    El-Naggar, Mehrez E; Shaheen, Tharwat I; Fouda, Moustafa M G; Hebeish, Ali A

    2016-01-20

    Herein, we present a new approach for the synthesis of gold nanoparticles (AuNPs) individually and as bimetallic core-shell nanoparticles (AgNPs-AuNPs). The novelty of the approach is further maximized by using curdlan (CRD) biopolymer to perform the dual role of reducing and capping agents and microwave-aided technology for affecting the said nanoparticles with varying concentrations in addition to those affected by precursor concentrations. Thus, for preparation of AuNPs, curdlan was solubilized in alkali solution followed by an addition of tetrachloroauric acid (HAuCl4). The curdlan solution containing HAuCl4 was then subjected to microwave radiation for up to 10 min. The optimum conditions obtained with the synthesis of AuNPs were employed for preparation of core-shell silver-gold nanoparticles by replacing definite portion of HAuCl4 with an equivalent portion of silver nitrate (AgNO3). The portion of AgNO3 was added initially and allowed to be reduced by virtue of the dual role of curdlan under microwave radiation. The corresponding portion of HAuCl4 was then added and allowed to complete the reaction. Characterization of AuNPs and AgNPs-AuNPs core-shell were made using UV-vis spectra, TEM, FTIR, XRD, zeta potential, and AFM analysis. Accordingly, strong peaks of the colloidal particles show surface plasmon resonance (SPR) at maximum wavelength of 540 nm, proving the formation of well-stabilized gold nanoparticles. TEM investigations reveal that the major size of AuNPs formed at different Au(+3)concentration lie below 20 nm with narrow size distribution. Whilst, the SPR bands of AgNPs-AuNPs core-shell differ than those obtained from original AgNPs (420 nm) and AuNPs (540 nm). Such shifting due to SPR of Au nanoshell deposited onto AgNPs core was significantly affected by the variation of bimetallic ratios applied. TEM micrographs show variation in contrast between dark silver core and the lighter gold shell. Increasing the ratio of silver ions leads to

  8. Rapid green synthesis of silver and gold nanoparticles using Dendropanax morbifera leaf extract and their anticancer activities.

    Science.gov (United States)

    Wang, Chao; Mathiyalagan, Ramya; Kim, Yeon Ju; Castro-Aceituno, Veronica; Singh, Priyanka; Ahn, Sungeun; Wang, Dandan; Yang, Deok Chun

    2016-01-01

    Dendropanax morbifera Léveille is an oriental medicinal plant that is traditionally used in folk medicine and grows in a specific region of South Korea. We aimed to enhance the utilization of D. morbifera medicinal plants for synthesis of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs). D. morbifera leaf extract acted as both a reducing and a stabilizing agent that rapidly synthesized Dendropanax AgNPs (D-AgNPs) and Dendropanax AuNPs (D-AuNPs). The D-AgNPs and D-AuNPs were characterized by ultraviolet-visible spectroscopy, energy dispersive X-ray analysis, elemental mapping, field emission transmission electron microscopy, X-ray diffraction, and dynamic light scattering. The characterizations revealed that the D-AgNPs and D-AuNPs were in polygon and hexagon shapes with average sizes of 100-150 nm and 10-20 nm, respectively. The important outcomes were the synthesis of AgNPs and AuNPs within 1 hour and 3 minutes, respectively, avoiding the subsequent processing for removal of any toxic components or for stabilizing the nanoparticles. Additionally, D-AgNPs and D-AuNPs were examined for cytotoxicity in a human keratinocyte cell line and in A549 human lung cancer cell line. The results indicated that D-AgNPs exhibited less cytotoxicity in the human keratinocyte cell line at 100 µg/mL after 48 hours. On the other hand, D-AgNPs showed potent cytotoxicity in the lung cancer cells at the same concentration after 48 hours, whereas D-AuNPs did not exhibit cytotoxicity in both cell lines at the same concentration. However, both D-AgNPs and D-AuNPs at 50 µg/mL enhanced the cytotoxicity of ginsenoside compound K at 25 µM after 48 hours of treatment compared with CK alone. We believe that this rapid green synthesis of D-AgNPs and D-AuNPs is a valuable addition to the applications of D. morbifera medicinal plant. D-AuNPs can be used as carriers for drug delivery and in cancer therapy due to their lack of normal cell cytotoxicity.

  9. Structural development of gold and silver nanoparticles within hexagonally ordered spherical micellar diblock copolymer thin films

    Science.gov (United States)

    Chen, Chia-Min; Huang, Yi-Jiun; Wei, Kung-Hwa

    2014-05-01

    The spatial arrangement of metal nanoparticle (NP) arrays in block copolymers has many potential applications in OFET-type memory devices. In this study, we adopted a trapping approach in which we used a monolayer thin film of polystyrene-block-poly(4-vinylpyridine) (PS56k-b-P4VP8k)--a highly asymmetric diblock copolymer having a spherical micelle morphology--to incorporate various amounts of one-phase-synthesized dodecanethiol-passivated silver (DT-Ag) NPs and a fixed amount of ligand-exchanged pyridine-coated gold (Py-Au) NPs into the polystyrene (PS) and poly(4-vinylpyridine) (P4VP) blocks, respectively. We characterized the packing of these metal NPs in the two blocks of the nanostructured diblock copolymer using reciprocal-space synchrotron grazing incidence small-angle X-ray scattering (GISAXS) as well as atomic force microscopy (AFM) and transmission electron microscopy (TEM) in the real space. The packing of the Ag NPs in the PS block was dependent on their content, which we tuned by varying the concentrations in the composite solution at a constant rate of spin-coating. The two-dimensional hierarchical arrangement of Ag and Au NPs within the BCP thin films was enhanced after addition of the Py-Au NPs into the P4VP block and after spin-coating a thinner film from a low concentration solution (0.1 wt%), due to the DT-Ag NPs accumulating around the Py-Au/P4VP cores; this two-dimensional hierarchical arrangement decreased at a critical DT-Ag NP weight ratio (c) of 0.8 when incorporating the Py-Au NPs into the P4VP domains through spin-coating at higher solution concentration (0.5 wt%), where the DT-Ag NPs realigned by rotating 20° along the z axis in the real space, due to oversaturation of the DT-Ag NPs within the PS domains.The spatial arrangement of metal nanoparticle (NP) arrays in block copolymers has many potential applications in OFET-type memory devices. In this study, we adopted a trapping approach in which we used a monolayer thin film of

  10. Chemical vs. Sonochemical Synthesis and Characterization of Silver, Gold, and Hybrid Nanoparticles

    Science.gov (United States)

    2011-09-01

    best suit silver (Ag) nanoparticles. Previous research indicated that bismuth silver sulfate (AgBiS2) was synthesized through the sonochemical (4...AgNO3, 2 mL of 20-mM potassium hydroxide , 83 mL of 18.3-MΩ filtered distilled water, and 5 mL of 0.2M poly(vinylpyrrolidone) (PVP). This polymer

  11. THE CYANIDE LEACH TECHNOLOGY IN GOLD AND SILVER MINING HARMFUL EFFECTS AND SUGGESTIONS FOR REMEDYING

    Directory of Open Access Journals (Sweden)

    Judit PETRES

    2013-11-01

    Full Text Available The region named Roşia Montană became famous due to its rich mineral resources. The most precious treasure which has been found is the gold. A state-run gold mine functioned for many years and the continuous pollution due to the gold extraction became very dangerous. All these cyanide-containing waste are hazardous to wildlife, natural resources and human health if not properly managed. The consequences of cyanide hazards may be devastating, sometimes killing everything for several miles downstream. It has not yet been found a way of both taking advantages of the economic benefits of gold and maintaining a liveable habitat.

  12. Gold-metallic textile and gold-silver lace in women’s headwear of the XVIII century: results of research in the archaeological textile from Nizhniy Novgorod

    Directory of Open Access Journals (Sweden)

    Orfinskaya Olga V.

    2015-09-01

    Full Text Available The article deals with research results of women’s headwear, which was discovered during archaeological excavations the necropolis at Verhneposadskaya St. Nicholas Church in Nizhny Novgorod. The structure of the textile and lace, the headwear cutting, the location of lace, and the time of its creation have been determined in the course of study. Most attention has been given to the gold-metallic threads. Technological classification of goldmetallic archaeological threads from different historical periods is considered in the article. The headwear was made of gold brocade of tinsel thread. It can be attributed to the mid or low value for the price. At the same time the good quality threads were used in the silver lace. According to the analysis of types and kinds of women’s headgear in Western fashion the time of creation a cap under study is determined as the middle or second half of the XVIII century. Dating is supported by results of the lace research. It is a typical XVIII century fan-shaped agramant named «vilyushka». Overall research results became a possible reconstruction of headdress. It is a small cap decorated with metallic lace along a bottom edge and the axis of symmetry of the forehead to the nape of the neck.

  13. The role of nuclear microprobes in the study of technology, provenance and corrosion of cultural heritage: The case of gold and silver items

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, M.F., E-mail: maria.guerra@culture.gouv.fr [Centre de Recherche et de Restauration des Musées de France and UMR 8220 CNRS, Palais du Louvre – 14, Quai François Mitterrand, 75001 Paris (France); Tissot, I., E-mail: isabel.tissot@archeofactu.pt [Archeofactu, Rua do Cerrado das Oliveiras n°14, 2°Dto., 2610-035 Alfragide (Portugal)

    2013-07-01

    This work gives an overview of the main questions raised by gold and silver items kept in museum collections and of the role of nuclear microprobes in their study and conservation. The different approached questions are illustrated by examples; analytical data is given and discussed; and the advantages of IBA are considered: spatial resolution, penetration depth, limits of detection, mapping, etc.

  14. Ultrastructural localisation of intramuscular expression of BDNF mRNA by silver-gold intensified non-radioactive in situ hybridisation

    NARCIS (Netherlands)

    Liem, RSB; Brouwer, N; Copray, JCVM

    2001-01-01

    A non-radioactive in situ hybridisation method is described for the detection of low intramuscular levels of brain-derived neurotrophic factor (BDNF) mRNA at the electron microscope level. Application of high-grade silver-gold intensification of the diaminobenzidine end product of in situ

  15. Acalypha indica Linn: Biogenic synthesis of silver and gold nanoparticles and their cytotoxic effects against MDA-MB-231, human breast cancer cells

    Directory of Open Access Journals (Sweden)

    C. Krishnaraj

    2014-12-01

    Full Text Available This study reports the in vitro cytotoxic effect of biologically synthesized silver and gold nanoparticles against MDA-MB-231, human breast cancer cells. Formation of silver and gold nanoparticles was observed within 30 min and the various characterization techniques such as UV–vis spectrophotometer, FE-SEM, TEM and XRD studies were confirmed the synthesis of nanoparticles. Further, MTT, acridine orange and ethidium bromide (AO/EB dual staining, caspase-3 and DNA fragmentation assays were carried out using various concentrations of silver and gold nanoparticles ranging from 1 to 100 μg/ml. At 100 μg/ml concentration, the plant extract derived nanoparticles exhibited significant cytotoxic effects and the apoptotic features were confirmed through caspase-3 activation and DNA fragmentation assays. Thus, the results of the present study indicate that biologically synthesized silver and gold nanoparticles might be used to treat breast cancer; however, it necessitates clinical studies to ascertain their potential as anticancer agents.

  16. Spectrophotometric evaluation of surface morphology dependent catalytic activity of biosynthesized silver and gold nanoparticles using UV–vis spectra: A comparative kinetic study

    Energy Technology Data Exchange (ETDEWEB)

    Ankamwar, Balaprasad, E-mail: bankamwar@yahoo.com [Bio-inspired Materials Research Laboratory, Department of Chemistry, Savitribai Phule Pune University, Ganeshkhind, Pune 411007 (India); Kamble, Vaishali; Sur, Ujjal Kumar [Bio-inspired Materials Research Laboratory, Department of Chemistry, Savitribai Phule Pune University, Ganeshkhind, Pune 411007 (India); Santra, Chittaranjan [Department of Chemistry, Netaji Nagar Day College, Regent Park, Kolkata 700092 (India)

    2016-03-15

    Graphical abstract: - Highlights: • The biosynthesized silver nanoparticles were stable for 6 months and used as effective SERS active substrate. • They are effective catalyst in the chemical reduction of 4-nitrophenol to 4-aminophenol. • Comparative catalytic efficiency of both silver and gold nanoparticles was studied spectrophotometrically. • Our results demonstrate surface morphology dependent catalytic activity of both nanoparticles. - Abstract: The development of eco-friendly and cost-effective synthetic protocol for the preparation of nanomaterials, especially metal nanoparticles is an emerging area of research in nanotechnology. These metal nanoparticles, especially silver can play a crucial role in various catalytic reactions. The biosynthesized silver nanoparticles described here was very stable up to 6 months and can be further exploited as an effective catalyst in the chemical reduction of 4-nitrophenol to 4-aminophenol. The silver nanoparticles were utilized as an efficient surface-enhanced Raman scattering (SERS) active substrate using Rhodamine 6G as Raman probe molecule. We have also carried out systematic comparative studies on the catalytic efficiency of both silver and gold nanoparticles using UV–vis spectra to monitor the above reaction spectrophotometrically. We find that the reaction follows pseudo-first order kinetics and the catalytic activity can be explained by a simple model based on Langmuir–Hinshelwood mechanism for heterogeneous catalysis. We also find that silver nanoparticles are more efficient as a catalyst compare to gold nanoparticles in the reduction of 4-nitrophenol to 4-aminophenol, which can be explained by the morphology of the nanoparticles as determined by transmission electron microscopy.

  17. Thermodynamic properties of gold-rare earth elements

    Science.gov (United States)

    Otmani, Samira; Tamim, Rkia; Moustaine, Driss; Mahdouk, Kamal

    2017-04-01

    This work presents the results of the thermodynamic optimizations of several Au-RE (RE = Ce, Nd, Sm, Eu, Gd, Tb, Dy and Yb) binary phase diagrams using the CALPHAD approach [D. Moustaine, K. Mahdouk, J. Alloys Comp. 683, 599 (2016); 673, 115 (2016); S. Otmani, K. Mahdouk, J. Alloys Comp. 670, 369 (2016); 648, 581 (2015)]. We compare and discuss, in this study, the alloying behavior as well as the evolution of multiple thermodynamic data relative to the Au-RE phases versus the atomic number of the RE element.

  18. Determination of silver, gold, zinc and copper in mineral samples by various techniques of instrumental neutron activation analysis; Determinacion de plata, oro, zinc y cobre en muestras minerales mediante diversas tecnicas de analisis por activacion de neutrones instrumental

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez R, N. I.; Rios M, C.; Pinedo V, J. L. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico); Yoho, M.; Landsberger, S., E-mail: neisla126@hotmail.com [University of Texas at Austin, Nuclear Engineering Teaching Laboratory, Austin 78712, Texas (United States)

    2015-09-15

    Using the method of instrumental neutron activation analysis, mineral exploration samples were analyzed in order to determine the concentrations of silver, gold, zinc and copper; these minerals being the main products of benefit of Tizapa and Cozamin mines. Samples were subjected to various techniques, where the type of radiation and counting methods were chosen based on the specific isotopic characteristics of each element. For calibration and determination of concentrations the comparator method was used, certified standards were subjected to the same conditions of irradiation and measurement that the prospecting samples. The irradiations were performed at the research reactor TRIGA Mark II of the University of Texas at Austin. The silver concentrations were determined by Cyclical Epithermal Neutron Activation Analysis. This method in combination with the transfer pneumatic system allowed a good analytical precision and accuracy in prospecting for silver, from photo peak measurement 657.7 keV of short half-life radionuclide {sup 110}Ag. For the determination of gold and zinc, Epithermal Neutron Activation Analysis was used, the photo peaks analyzed corresponded to the energies 411.8 keV of radionuclide {sup 199}Au and 438.6 keV of metastable radionuclide {sup 69m}Zn. On the other hand, copper quantification was based on the photo peak analysis of 1039.2 keV produced by the short half-life radionuclide {sup 66}Cu, by Thermal Neutron Activation Analysis. The photo peaks measurement corresponding to gold, zinc and copper was performed using a Compton suppression system, which allowed an improvement in the signal to noise relationship, so that better detection limits and low uncertainties associated with the results were obtained. Comparing elemental concentrations the highest values in silver, zinc and copper was for samples of mine Tizapa. Regarding gold values were found in the same range for both mines. To evaluate the precision and accuracy of the methods used

  19. Strontium isotope ratio in metasomatites of gold-silver formation deposits in connection with the problem of ore matter sources

    Energy Technology Data Exchange (ETDEWEB)

    Gundobin, G.M.; Nikolaev, V.M.; Pakhol' chenko, Yu.A.; Plyusnin, G.S.; Posokhov, V.F.; Sandimirova, G.P. (AN SSSR, Irkutsk. Inst. Geokhimii)

    1983-01-01

    Strontium isotope ratio (/sup 87/Sr//sup 86/Sr) in metasomatites of gold-silver formation deposits in Verkhojansk complex has been studied. Strontium isotope ratio is analyzed using mass-spectrometric method, analysis for K and Rb is carried out using the method of flame photometry, for using X-ray spectral and quantitative spectral methods. Linear dependence between the value /sup 87/Sr//sup 86/Sr and K content in metasomatites is established. The dependence reflects the main tendency of /sup 87/Sr//sup 86/Sr ratio evolution consisting in its regular decrease during ore development process. It is shown that mineralization is not connected with specific magmatic rocks of the region. Connection between them is indirect and is caused by functionation of deep mantle hearth.

  20. The substrate effect in electron energy-loss spectroscopy of localized surface plasmons in gold and silver nanoparticles

    DEFF Research Database (Denmark)

    Kadkhodazadeh, Shima; Christensen, Thomas; Beleggia, Marco

    2017-01-01

    Electron energy-loss spectroscopy (EELS) has become increasingly popular for detailed characterization of plasmonic nanostructures, owing to the unparalleled spatial resolution of this technique. The typical setup in EELS requires nanoparticles to be supported on thin substrates. However, as in o......Electron energy-loss spectroscopy (EELS) has become increasingly popular for detailed characterization of plasmonic nanostructures, owing to the unparalleled spatial resolution of this technique. The typical setup in EELS requires nanoparticles to be supported on thin substrates. However......, as in optical measurements, the substrate material can modify the acquired signal. Here, we have investigated how the EELS signal recorded from supported silver and gold spheroidal nanoparticles at different electron beam impact parameter positions is affected by the choice of a dielectric substrate material...

  1. Stability of contamination-free gold and silver nanoparticles produced by nanosecond laser ablation of solid targets in water

    Energy Technology Data Exchange (ETDEWEB)

    Nikov, R.G., E-mail: rosen_nikov@abv.bg [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Nikolov, A.S.; Nedyalkov, N.N. [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Dimitrov, I.G. [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Institute of Experimental Pathology and Parasitology, Bulgarian Academy of Sciences, G. Bonchev Street, bl. 25, Sofia 1113 (Bulgaria); Atanasov, P.A. [Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784 (Bulgaria); Alexandrov, M.T. [Institute of Experimental Pathology and Parasitology, Bulgarian Academy of Sciences, G. Bonchev Street, bl. 25, Sofia 1113 (Bulgaria)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Au and Ag colloids were prepared by nanosecond laser ablation of solids in water. Black-Right-Pointing-Pointer The alteration of the produced colloids during one month was investigated. Black-Right-Pointing-Pointer Optical transmission spectra of the samples were measured from 350 to 800 nm. Black-Right-Pointing-Pointer TEM measurements were made of as-prepared colloids and on the 30-th day. Black-Right-Pointing-Pointer Zeta potential measurements were performed of as-prepared samples. - Abstract: Preparation of noble metal nanoparticle (NPs) colloids using pulsed laser ablation in water has an inherent advantage compared to the different chemical methods used, especially when biological applications of the colloids are considered. The fabrication method is simple and the NPs prepared in this way are contamination free. The method of laser ablation of a solid target in water is applied in the present work in order to obtain gold and silver NP colloids. The experiment was preformed by using the fundamental wavelength (1064 nm) of a Nd:YAG laser system. The target immersed in double distilled water was irradiated for 20 min by laser pulses with duration of 15 ns and repetition rate of 10 Hz. The sedimentation and aggregation of NPs in the colloids, stored at constant temperature, as a function of the time after preparation were investigated. The analyses are based on optical transmission spectroscopy in UV and vis regions. The change of the plasmon resonance wavelength as a function of time was studied. Zeta potential measurement was also utilized to measure the charge of the NPs in the colloids. The size distribution of the NPs and its change in time was determined by transmission electron microscopy (TEM). On the basis of the results obtained, the optimal conditions of post fabrication manipulation with gold and silver colloids are defined in view of producing stable NPs with a narrow size distribution.

  2. Sensing colorimetric approaches based on gold and silver nanoparticles aggregation: Chemical creativity behind the assay. A review

    Energy Technology Data Exchange (ETDEWEB)

    Vilela, Diana; Gonzalez, Maria Cristina [Departamento de Quimica Analitica e Ingenieria Quimica, Facultad de Quimica, Edificio Polivalente, Universidad de Alcala, Ctra. Madrid-Barcelona km 33,600, 28871 Alcala de Henares, Madrid (Spain); Escarpa, Alberto, E-mail: alberto.escarpa@uah.es [Departamento de Quimica Analitica e Ingenieria Quimica, Facultad de Quimica, Edificio Polivalente, Universidad de Alcala, Ctra. Madrid-Barcelona km 33,600, 28871 Alcala de Henares, Madrid (Spain)

    2012-11-02

    Highlights: Black-Right-Pointing-Pointer Visual detection based gold and silver nanoparticles aggregation. Black-Right-Pointing-Pointer Functionalized and non-functionalized nanoparticles. Black-Right-Pointing-Pointer High selectivity and sensitivity. Black-Right-Pointing-Pointer No complex instrumentation is required/chemical creativity for analyte detection. - Abstract: Localized surface plasmon resonance (LSPR) is one of the most remarkable features of gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs). Due to these inherent optical properties, colloidal solutions of Au and Ag NPs have high extinction coefficients and different colour in the visible region of the spectrum when they are well-spaced in comparison with when they are aggregated. Therefore, a well-designed chemical interaction between the analyte and NPs surroundings leads to a change of colour (red to blue for Au NPs and yellow to brown for Ag NPs from well-spaced to aggregated ones, respectively) allowing the visual detection of the target analyte. These approaches have exhibited an excellent analytical performance with high sensitivities due to the strong LSPR and excellent selectivity strategically driven by the interaction analyte-NPs surroundings involving mainly electrostatic and hydrogen bond interactions as well as donor-acceptor chemical reactions, among others. In addition, this kind of colorimetric assays has received considerable attention in the analytical field because of their simplicity and low cost since they do not require any expensive or complex instrumentation. As a consequence of this, detection of molecules with a high significance in the bio-medical, clinical, food safety and environmental fields including DNA, proteins and a wide spectrum of organic molecules as well as inorganic ions have been impressively reported in the most relevant literature using these assays. This timely review offers a rational vision of the main achievements yielded in the relevant

  3. Lithographically patterned electrodeposition of gold, silver, and nickel nanoring arrays with widely tunable near-infrared plasmonic resonances.

    Science.gov (United States)

    Halpern, Aaron R; Corn, Robert M

    2013-02-26

    A novel low-cost nanoring array fabrication method that combines the process of lithographically patterned nanoscale electrodeposition (LPNE) with colloidal lithography is described. Nanoring array fabrication was accomplished in three steps: (i) a thin (70 nm) sacrificial nickel or silver film was first vapor-deposited onto a plasma-etched packed colloidal monolayer; (ii) the polymer colloids were removed from the surface, a thin film of positive photoresist was applied, and a backside exposure of the photoresist was used to create a nanohole electrode array; (iii) this array of nanoscale cylindrical electrodes was then used for the electrodeposition of gold, silver, or nickel nanorings. Removal of the photoresist and sacrificial metal film yielded a nanoring array in which all of the nanoring dimensions were set independently: the inter-ring spacing was fixed by the colloidal radius, the radius of the nanorings was controlled by the plasma etching process, and the width of the nanorings was controlled by the electrodeposition process. A combination of scanning electron microscopy (SEM) measurements and Fourier transform near-infrared (FT-NIR) absorption spectroscopy were used to characterize the nanoring arrays. Nanoring arrays with radii from 200 to 400 nm exhibited a single strong NIR plasmonic resonance with an absorption maximum wavelength that varied linearly from 1.25 to 3.33 μm as predicted by a simple standing wave model linear antenna theory. This simple yet versatile nanoring array fabrication method was also used to electrodeposit concentric double gold nanoring arrays that exhibited multiple NIR plasmonic resonances.

  4. Shell thickness-dependent antibacterial activity and biocompatibility of gold@silver core–shell nanoparticles

    Science.gov (United States)

    Antimicrobial activity of silver is highly effective and broad-spectrum; however, poor long-term antibacterial efficiency and cytotoxicity toward mammalian cells have restricted their applications. Here, we fabricated Au@Ag NPs with tailored shell thickness, and investigated their antibacterial acti...

  5. Swift heavy ion irradiation of MgB{sub 2} thin films: a comparison between gold and silver ion irradiations

    Energy Technology Data Exchange (ETDEWEB)

    Narayan, Himanshu [Superconductivity Division, National Physical Laboratory, Dr K S Krishnan Marg, New Delhi 110012 (India); Bhatt, Ravindra K [Department of Physics, G B Pant University of Agriculture and Technology, Pantnagar 263145 (India); Agrawal, H M [Department of Physics, G B Pant University of Agriculture and Technology, Pantnagar 263145 (India); Kushwaha, R P S [Department of Physics, G B Pant University of Agriculture and Technology, Pantnagar 263145 (India); Kishan, H [Superconductivity Division, National Physical Laboratory, Dr K S Krishnan Marg, New Delhi 110012 (India)

    2007-04-04

    The effect of 200 MeV Au ion irradiation on the temperature and field dependence of the critical current density, J{sub c}, of MgB{sub 2} thin films on sapphire substrates is reported. The results have been presented in comparison with those obtained after 200 MeV Ag ion irradiation of a similar film. After irradiation, the critical temperature T{sub c} decreased for all samples except for the one with a higher dose of gold ions, where it increased marginally. This observation was also confirmed from measurements of magnetization as a function of temperature with a constant applied field of 10{sup -2} T. The critical current density, J{sub c}, was estimated from the widths of magnetization loops using Bean's critical state model. It has been found that J{sub c} increases after irradiation, the enhancement being more pronounced for the Au ion irradiation. The higher enhancement of J{sub c} by Au ion irradiation may be attributed to higher flux-pinning efficiency of the irradiated samples. It has been concluded that, although the flux-line shear (FLS) model satisfactorily explains the silver ion irradiation induced enhancement of J{sub c}, some other mechanisms also seem to play a role in the J{sub c} enhancement by gold ion irradiation.

  6. Development of silver/gold nanocages onto indium tin oxide glass as a reagentless plasmonic mercury sensor

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Daodan; Hu, Tingting; Chen, Na [The Key Lab of Health Chemistry and Molecular Diagnosis of Suzhou, College of Chemistry, Chemical Engineering and Material Science, Soochow University, Suzhou 215123 (China); Zhang, Wei, E-mail: zhangwei@cigit.ac.cn [Key Laboratory of Multi-scale Manufacturing Technology, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714 (China); Di, Junwei, E-mail: djw@suda.edu.cn [The Key Lab of Health Chemistry and Molecular Diagnosis of Suzhou, College of Chemistry, Chemical Engineering and Material Science, Soochow University, Suzhou 215123 (China)

    2014-05-01

    Highlights: • A reagentless, sensitive and selective optical sensor for detection of Hg(II) was developed. • Silver–gold nanocages were prepared on the transparent indium tin oxide coated glass surface. • The nanomaterials could act as optical sensing probe as well as reducing agent. • The plasmonic sensor could be used to detect mercury ions in field analysis. Abstract: We demonstrate the utilization of silver/gold nanocages (Ag/Au NCs) deposited onto transparent indium tin oxide (ITO) film glass as the basis of a reagentless, simple and inexpensive mercury probe. The localized surface plasmon resonance (LSPR) peak wavelength was located at ~800 nm. By utilizing the redox reaction between Hg²⁺ ions and Ag atoms that existed in Ag/Au NCs, the LSPR peak of Ag/Au NCs was blue-shifted. Thus, we develop an optical sensing probe for the detection of Hg²⁺ ions. The LSPR peak changes were lineally proportional to the concentration of Hg²⁺ ions over the range from 10 ppb to 0.5 ppm. The detection limit was ~5 ppb. This plasmonic probe shows good selectivity and high sensitivity. The proposed optical probe is successfully applied to the sensing of Hg²⁺ in real samples.

  7. Trace element mapping of pyrite from Archean gold deposits - A comparison between PIXE and EPMA

    Science.gov (United States)

    Agangi, A.; Przybyłowicz, W.; Hofmann, A.

    2015-04-01

    Chemical zoning of pyrites can record the evolution of mineralising fluids at widely varying P-T conditions ranging from diagenesis to medium-grade metamorphism. If preserved, zoning can reveal growth textures, brecciation and veining, resorption and recrystallisation events, thus shedding light on the processes that contributed to ore formation. Chemical zoning of sulfides is invisible in optical microscopy, but can be studied by chemical etching, high-contrast back-scattering electron images, and elemental imaging. In this study we compared micro-PIXE and WDS-EPMA elemental maps on the chemically zoned pyrites in mineralised vein-bearing samples from the Sheba and Fairview gold mines in the Barberton Greenstone Belt, South Africa. Elemental images show complex distribution of trace elements, suggesting multiple events of pyrite crystallisation and gold deposition. EPMA maps show fine-scale variations reflecting growth and recrystallisation textures marked, in particular, by variations of As, Ni, and Co. In PIXE maps, gold occurs both as finely-distributed and discrete inclusions, suggesting incorporation in the pyrite structure as solid solution, and deposition as electrum inclusions, respectively. Micro-PIXE and EPMA provide complementary information, forming together a powerful tool to obtain information on chemical zoning of pyrites in ore deposits.

  8. Trace element analysis of Alexander the Great's silver tetradrachms minted in Macedonia

    Science.gov (United States)

    Kallithrakas-Kontos, N.; Katsanos, A. A.; Touratsoglou, J.

    2000-11-01

    The coinage of Alexander the Great presents a special interest because of its international character in the frame of the ancient times. At least 31 mints (from Aigai to Babylon and from Pella to Alexandreia) operated in the vast state, which was created by Alexander in just over 10 years (334-323 BC). Impressive quantities of tetradrachms were consequently minted for the economic affairs of an expanding state. The mints continued to be active and after the premature death of the Macedonian king, producing among others and tetradrachms in his name. The elemental chemical composition of silver tetradrachms minted in Amphipolis as well as in other Macedonian Greek cities was analysed by energy dispersive X-ray fluorescence (EDXRF), and 12 elements were determined. The problem of the patina (silver corrosion layer) effects on the results was examined by analysis before and after the corrosion product removal. From the results of the chemical composition, a similar numismatic policy is deduced for all the analysed coin as well as metal provenance indications for some of the coins.

  9. Adhesive performance of silver-palladium-copper-gold alloy and component metals bonded with organic sulfur-based priming agents and a tri-n-butylborane initiated luting material.

    Science.gov (United States)

    Yamashita, Miyuki; Koizumi, Hiroyasu; Ishii, Takaya; Nakayama, Daisuke; Oba, Yusuke; Matsumura, Hideo

    2013-01-01

    The purpose of the current study was to evaluate the effect of thione-based metal priming agents on the adhesive behavior of a Ag-Pd-Cu-Au alloy and component metals bonded with an acrylic resin. Disk specimens (10 mm in diameter by 3 mm thick) were prepared from a silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy (Castwell M.C.12), high-purity silver, palladium, copper and gold. Four single-liquid priming agents containing organic sulfur compound (Alloy Primer, Metaltite, M.L. Primer and V-Primer) and three acidic priming agents (All Bond II Primer B, Estenia Opaque Primer and Super-Bond Liquid) were assessed. The metal specimens were flat-ground with abrasive papers, primed with one of the agents and bonded with a tri-n-butylborane initiated resin. The shear bond strengths were determined both before and after repeated thermocycling (5°C and 55°C, 1 min each, 20,000 cycles). The results were statistically analyzed with a non-parametric procedure (p = 0.05 level). The post-thermocycling bond strengths in MPa (median; n = 11) associated with the Alloy Primer, Metaltite, M.L. Primer and V-Primer materials were, respectively, 20.8, 22.8, 17.8 and 18.4 for the Ag-Pd-Cu-Au alloy; 19.6, 21.9, 14.4 and 20.1 for silver; 5.4, 4.5, 12.8 and 5.3 for palladium; 17.1, 19.2, 0.7 and 6.6 for copper; and 18.5, 17.7, 22.8 and 15.4 for gold. It can be concluded that the use of the four priming agents, which are based on organic sulfur compounds, effectively enhanced bonding to the Ag-Pd-Cu-Au alloy and the component metals, although the bonding performance varied among the priming agents and metal elements. The priming agents appeared to have more of an effect on the alloy, silver and gold than on the palladium and copper.

  10. Effect of Gold on the Microstructural Evolution and Integrity of a Sintered Silver Joint

    Science.gov (United States)

    Muralidharan, Govindarajan; Leonard, Donovan N.; Meyer, Harry M.

    2017-07-01

    There is a need for next-generation, high-performance power electronic packages and systems employing wide-bandgap devices to operate at high temperatures in automotive and electric grid applications. Sintered silver joints are currently being evaluated as an alternative to Pb-free solder joints. Of particular interest is the development of joints based on silver paste consisting of nano- or micron-scale particles that can be processed without application of external pressure. The microstructural evolution at the interface of a pressureless-sintered silver joint formed between a SiC die with Ti/Ni/Au metallization and an active metal brazed (AMB) substrate with Ag metallization at 250°C has been evaluated using scanning electron microscopy (SEM), x-ray microanalysis, and x-ray photoelectron spectroscopy (XPS). Results from focused ion beam (FIB) cross-sections show that, during sintering, pores in the sintered region near to the Au layer tend to be narrow and elongated with long axis oriented parallel to the interface. Further densification results in formation of many small, relatively equiaxed pores aligned parallel to the interface, creating a path for easy crack propagation. X-ray microanalysis results confirm interdiffusion between Au and Ag and that a region with poor mechanical strength is formed at the edge of this region of interdiffusion.

  11. Comparison of Some Mechanical and Physical Methods for Measurement of Residual Stresses in Brush-Plated Nickel Hardened Gold and Silver Coatings

    Directory of Open Access Journals (Sweden)

    Harri LILLE

    2016-05-01

    Full Text Available Hard gold and silver are applied in coating owing to their high hardness, good wear and corrosion resistance for engineering application (e.g. on generators slip rings, sliding contacts and small machine parts and are typically plated on copper (mostly, brass and bronze. The studied nickel-hardened gold and silver coatings were brush plated on open thin-walled copper ring substrates. Residual stresses in the coatings were calculated from the curvature changes of the substrates. Biaxial intrinsic residual stresses were also determined by nanoindentation testing and by the X-ray technique. The values of the residual stresses represented tensile stresses and when determined by the techniques used they were comparable within a maximum limit of measurement uncertainty. These stresses relax; the dependence of relaxation time was approximated by a linear-fractional function.DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7439

  12. Synthesis and catalytic applications of 1,2,3-triazolylidene gold(i) complexes in silver-free oxazoline syntheses and C-H bond activation.

    Science.gov (United States)

    Pretorius, René; Fructos, Manuel R; Müller-Bunz, Helge; Gossage, Robert A; Pérez, Pedro J; Albrecht, Martin

    2016-10-07

    A series of novel 1,2,3-triazolylidene gold(i) chloride complexes have been synthesised and fully characterised. Silver-free methodologies for chloride ion abstraction of these complexes were evaluated for their potential as Au-based catalyst precursors. Using simple potassium salts or MeOTf as chloride scavengers produced metal complexes that catalyse both the regioselective synthesis of oxazolines and the C-H activation of benzene or styrene for carbene transfer from ethyl diazoacetate. These results indicate that Ag-free activation of 1,2,3-triazolylidene gold(i) chloride complexes is feasible for the generation of catalytically active Au triazolylidene species. However, silver-mediated activation imparts substantially higher catalytic activity in oxazoline synthesis.

  13. In-vitro free radical scavenging activity of biosynthesized gold and silver nanoparticles using Prunus armeniaca (apricot) fruit extract

    Science.gov (United States)

    Dauthal, Preeti; Mukhopadhyay, Mausumi

    2013-01-01

    In-vitro free radical scavenging activity of biosynthesized gold (Au-NPs) and silver (Ag-NPs) nanoparticles was investigated in the present study. Natural precursor Prunus armeniaca (apricot) fruit extract was used as a reducing agent for the nanoparticle synthesis. The free radical scavenging activity of the nanoparticles were observed by modified 1,1'-diphynyl-2-picrylhydrazyl, DPPH and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid), ABTS assay. The synthesized nanoparticles were characterized by UV-Visible spectroscopy, dynamic light scattering, transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectroscopy, and fourier transform infrared spectroscopy (FTIR). Appearance of optical absorption peak at 537 nm (2.20 keV) and 435 nm (3 keV) within 0.08 and 0.5 h of reaction time was confirmed the presence of metallic Au and Ag nanoclusters, respectively. Nearly spherical nanoparticles with majority of particle below 20 nm (TEM) for both Au-NPs and Ag-NPs were synthesized. XRD pattern confirmed the existence of pure nanocrystalline Au-NPs while few additional peaks in the vicinity of fcc silver-speculated crystallization of metalloproteins of fruit extract on the surface of the Ag-NPs and vice versa. FTIR spectra was supported the role of amino acids of protein/enzymes of fruit extract for synthesis and stabilization of nanoparticles. Dose-dependent scavenging activity was observed for Au-NPs and Ag-NPs in both DPPH and ABTS in-vitro assay. 50 % scavenging activity for DPPH were 11.27 and 16.18 mg and for ABTS 3.40 and 7.12 mg with Au-NPs and Ag-NPs, respectively.

  14. Green synthesis and characterization of gold and silver nanoparticles using Mussaenda glabrata leaf extract and their environmental applications to dye degradation.

    Science.gov (United States)

    Francis, Sijo; Joseph, Siby; Koshy, Ebey P; Mathew, Beena

    2017-07-01

    Plant-derived nanomaterials opened a green approach in solving the current environment issues. Present study focused on rapid microwave-assisted synthesis and applications of gold and silver nanoparticles mediated by aqueous leaf extract of Mussaenda glabrata. The synthesized nanoparticles were characterized by UV-vis, FT-IR, powder XRD, energy-dispersive X-ray spectroscopy (EDX), transmission electron (TEM), and atomic force microscopic techniques (AFM). FCC crystal structure of both nanoparticles was confirmed by peaks corresponding to (111), (200), (220), and (311) planes in XRD spectra and bright circular spots in SAED pattern. IC50 values shown by gold and silver nanoparticles (44.1 ± 0.82 and 57.92 ± 1.33 μg/mL) reflected their high free radical scavenging potential. The synthesized gold and silver nanoparticles revealed their potency to inhibit pathogenic microorganisms Bacillus pumilus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Aspergillus niger, and Penicillium chrysogenum. Anthropogenic pollutants rhodamine B and methyl orange were effectively degraded from aquatic environment and waste water sewages of dye industries using the prepared nanocatalysts. The catalytic capacities of the synthesized nanoparticles were also exploited in the reduction of 4-nitrophenol. Graphical abstract.

  15. Employment of gold-coated silver nanowires as transparent conductive electrode for organic light emitting diodes

    Science.gov (United States)

    Kim, Sunho; Kim, Bongsung; Im, Inseob; Kim, Dongjae; Lee, Haeseong; Nam, Jaewook; Chung, Ho Kyoon; Lee, Hoo-Jeong; Cho, Sung Min

    2017-08-01

    This study proposes a simple method of Au coating on silver nanowires (Ag NWs) transparent conductive films as the anode of organic light emitting diodes (OLED) to increase the work function of the film and thus enhance hole transport. We carefully engineer the process conditions (pretreatment, solution concentrations, and coating number) of the coating using a diluted HAuCl4 solution on the Ag NWs film to minimize etching damage on Ag NWs accompanying the galvanic replacement reaction. Ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy show work function increase of Ag NWs upon Au coating. OLED devices based on Au-coated Ag NWs show a lower turn-on voltage and higher luminance, compared with pristine Ag NWs device. Although the Ag NWs device displays poor efficiencies in the low luminance range due to a high leakage, some of the Au-coated Ag NWs devices showed efficiencies higher than those of the ITO device in a high luminance.

  16. Gold Doping of Silver Nanoclusters: A 26-Fold Enhancement in the Luminescence Quantum Yield

    KAUST Repository

    Soldan, Giada

    2016-04-10

    A high quantum yield (QY) of photoluminescence (PL) in nanomaterials is necessary for a wide range of applications. Unfortunately, the weak PL and moderate stability of atomically precise silver nanoclusters (NCs) suppress their utility. Herein, we accomplished a ≥26-fold PL QY enhancement of the Ag29(BDT)12(TPP)4 cluster (BDT: 1,3-benzenedithiol; TPP: triphenylphosphine) by doping with a discrete number of Au atoms, producing Ag29-xAux(BDT)12(TPP)4, x=1-5. The Au-doped clusters exhibit an enhanced stability and an intense red emission around 660nm. Single-crystal XRD, mass spectrometry, optical, and NMR spectroscopy shed light on the PL enhancement mechanism and the probable locations of the Au dopants within the cluster.

  17. Tryptophan-Assisted Synthesis Reduces Bimetallic Gold/Silver Nanoparticle Cytotoxicity and Improves Biological Activity

    Directory of Open Access Journals (Sweden)

    Igor O. Shmarakov

    2014-10-01

    Full Text Available Aiming to reduce the potential in vivo hepato-and nephrotoxicity of Ag/Au bimetallic nanoparticles (NPs stabilized by sodium dodecyl sulphate (SDS, an approach involving a simultaneous reduction of silver nitrate and tetrachlorauratic acid using tryptophan (Trp as a reducing/stabilizing agent was applied during NP synthesis. The obtained Ag/Au/Trp NPs (5–15 nm sized were able to form stable aggregates with an average size of 370–450 nm and were potentially less toxic than Ag/Au/SDS in relation to a mouse model system based on clinical biochemical parameters and oxidative damage product estimation. Ag/Au/Trp NPs were shown to exhibit anticancer activity in relation to a Lewis lung carcinoma model. The data generated from the present study support the fact that the use of tryptophan in NP synthesis is effective in attenuating the potential hepatotoxicity and nephrotoxicity of NPs during their in vivo application.

  18. Study of adsorption of organic compounds on gold with radioactive tracers - adsorption of chloroacetic and phenylacetic acids and effect on it of cadmium, copper and silver adsorbed atoms

    Energy Technology Data Exchange (ETDEWEB)

    Khorani, G.; Andreev, V.N.; Kazarinov, V.E.

    1985-10-01

    Compared with platinum, gold is less active as a catalyst and the adsorption of organic compounds on its surface my therefore be less subject to destructive changes. This opens up the possibility of conducting new reactions of organic synthesis on its surface. Results of a study of the adsorption of monochloroacetic and phenylacetic acids on a gilded fold electrode in acid medium employing radioactive HCl and the effects of copper, cadmium and silver adsorbed atoms are reported. The results show that at E > 0.7v the presence of copper ions has no effect on the adsorption of organic compounds on the gold electrode. At E approx. = 0.7v, adsorption increases. Cadmium, copper and silver present in solution have no effect on the adsorption of phenylacetic acid at those potentials where these ions are not adsorbed on a gold surface, although they do suppress phenylacetic acid adsorption at potentials where they are adsorbed. The results confirm that the radioactive tracer method is just as effective for studying gilded gold electrodes as it was for platinized platinum. 19 references, 4 figures.

  19. Antibiofilm properties of silver and gold incorporated PU, PCLm, PC and PMMA nanocomposites under two shear conditions.

    Science.gov (United States)

    Sawant, Shilpa N; Selvaraj, Veerapandian; Prabhawathi, Veluchamy; Doble, Mukesh

    2013-01-01

    Silver and gold nanoparticles (of average size ∼20-27 nm) were incorporated in PU (Polyurethane), PCLm (Polycaprolactam), PC (polycarbonate) and PMMA (Polymethylmethaacrylate) by swelling and casting methods under ambient conditions. In the latter method the nanoparticle would be present not only on the surface, but also inside the polymer. These nanoparticles were prepared initially by using a cosolvent, THF. PU and PCLm were dissolved and swollen with THF. PC and PMMA were dissolved in CHCl₃ and here the cosolvent, THF, acted as an intermediate between water and CHCl₃. FTIR indicated that the interaction between the polymer and the nanoparticle was through the functional group in the polymer. The formation of E.coli biofilm on these nanocomposites under low (in a Drip flow biofilm reactor) and high shear (in a Shaker) conditions indicated that the biofilm growth was higher (twice) in the former than in the latter (ratio of shear force = 15). A positive correlation between the contact angle (of the virgin surface) and the number of colonies, carbohydrate and protein attached on it were observed. Ag nanocomposites exhibited better antibiofilm properties than Au. Bacterial attachment was highest on PC and least on PU nanocomposite. Casting method appeared to be better than swelling method in reducing the attachment (by a factor of 2). Composites reduced growth of organisms by six orders of magnitude, and protein and carbohydrate by 2-5 times. This study indicates that these nanocomposites may be suitable for implant applications.

  20. Synthesis and characterisation of cross-linked chitosan composites functionalised with silver and gold nanoparticles for antimicrobial applications.

    Science.gov (United States)

    Ryan, Catherine; Alcock, Emma; Buttimer, Finbarr; Schmidt, Michael; Clarke, David; Pemble, Martyn; Bardosova, Maria

    2017-01-01

    We present a study of a range of cross-linked chitosan composites with potential antimicrobial applications. They were formed by cross-linking chitosan and siloxane networks and by introducing silver and gold nanoparticles (NPs). The aim was to investigate whether adding the metal NPs to the chitosan-siloxane composite would lead to a material with enhanced antimicrobial ability as compared to chitosan itself. The composites were synthesised in hydrogel form with the metal NPs embedded in the cross-linked chitosan network. Spectroscopic and microscopic techniques were employed to investigate the structural properties of the composite and the tensile strength of the structures was measured. It was found that the addition of metal NPs did not influence the mechanical strength of the composite. A crystal violet attachment assay results displayed a significant reduction in the attachment of E. coli to the cross-linked chitosan surfaces. Release profile tests suggest that the metal NPs do not contribute to the overall antimicrobial activity under neutral conditions. The contribution to the mechanical and antimicrobial properties from cross-linking with siloxane is significant, giving rise to a versatile, durable, antimicrobial material suitable for thin film formation, wound dressings or the coating of various surfaces where robustness and antimicrobial control are required.

  1. Cytotoxicity and inflammation in human alveolar epithelial cells following exposure to occupational levels of gold and silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Bachand, George D., E-mail: gdbacha@sandia.gov [Sandia National Laboratories, Center for Integrated Nanotechnologies (United States); Allen, Amy [Sandia National Laboratories, Department of Analytical Science (United States); Bachand, Marlene [Sandia National Laboratories, Department of Nanobiology (United States); Achyuthan, Komandoor E. [Sandia National Laboratories, Department of Biosensors and Nanomaterials (United States); Seagrave, Jean Clare [Lovelace Respiratory Research Institute, Applied Life Science and Toxicology Division (United States); Brozik, Susan M. [Sandia National Laboratories, Department of Biosensors and Nanomaterials (United States)

    2012-10-15

    While inhalation represents one of the most likely routes of exposure, the toxicity and response of nanoparticles at concentrations expected from such an exposure are not well understood. Here we characterized the in vitro response of human A549 adenocarcinomic alveolar epithelial cells following exposure to gold (AuNP) and silver (AgNP) nanoparticles at levels approximating an occupational exposure. Changes in neither oxidative stress nor cytotoxicity were significantly affected by exposure to AgNPs and AuNPs, regardless of NP type (Ag vs. Au), concentration, surface ligand (citrate or tannic acid), or size. An inflammatory response was, however, observed in response to 20 nm AgNPs and 20 nm AuNPs, where significant differences in the release of interleukin (IL)-8 but not IL-6 were observed. Additional data demonstrated that increased IL-8 secretion was strongly dependent on both nanoparticle size and concentration. Overall these data suggest that, while not acutely toxic, occupational exposure to AuNPs and AgNPs may trigger a significant inflammatory response in alveolar epithelium. Moreover, the differential responses in IL-8 and IL-6 secretion suggest that NPs may induce a response pathway that is distinct from those commonly elicited by allergens and pathogens.

  2. Highly sensitive visual detection of copper (II) using water-soluble azide-functionalized gold nanoparticles and silver enhancement.

    Science.gov (United States)

    Zhang, Zhen; Li, Wenqing; Zhao, Qiuling; Cheng, Ming; Xu, Li; Fang, Xiaohong

    2014-09-15

    A high-sensitive method for the visual detection of copper ions in aqueous solution is developed. The method is based on copper ion-catalyzed 'click' reaction between the water-soluble azide-functionalized gold nanoparticles (AuNPs) and alkyne-modified glass slide. The PEG linker was employed as a stabilizing component along with the terminal azide group to keep the AuNPs stably dispersed in water without the assistance of any organic solvent. In the presence of copper ions, the AuNPs are 'clicked' on the slide, and the darkness of the AuNPs in the sample spot is promoted by silver enhancement process. Only a tiny amount of sample (10 μl) is needed with the detectable concentration down to 62 pM by the commonly used flatbed scanner, which is 2-3 orders of magnitude lower than those in previous reports. The selectivity relative to other potentially interfering ions and the applicability in real samples, human serum and tap water, have also been evaluated. Our method has a good potential in point-of-use applications and environment surveys. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Antibiofilm properties of silver and gold incorporated PU, PCLm, PC and PMMA nanocomposites under two shear conditions.

    Directory of Open Access Journals (Sweden)

    Shilpa N Sawant

    Full Text Available Silver and gold nanoparticles (of average size ∼20-27 nm were incorporated in PU (Polyurethane, PCLm (Polycaprolactam, PC (polycarbonate and PMMA (Polymethylmethaacrylate by swelling and casting methods under ambient conditions. In the latter method the nanoparticle would be present not only on the surface, but also inside the polymer. These nanoparticles were prepared initially by using a cosolvent, THF. PU and PCLm were dissolved and swollen with THF. PC and PMMA were dissolved in CHCl₃ and here the cosolvent, THF, acted as an intermediate between water and CHCl₃. FTIR indicated that the interaction between the polymer and the nanoparticle was through the functional group in the polymer. The formation of E.coli biofilm on these nanocomposites under low (in a Drip flow biofilm reactor and high shear (in a Shaker conditions indicated that the biofilm growth was higher (twice in the former than in the latter (ratio of shear force = 15. A positive correlation between the contact angle (of the virgin surface and the number of colonies, carbohydrate and protein attached on it were observed. Ag nanocomposites exhibited better antibiofilm properties than Au. Bacterial attachment was highest on PC and least on PU nanocomposite. Casting method appeared to be better than swelling method in reducing the attachment (by a factor of 2. Composites reduced growth of organisms by six orders of magnitude, and protein and carbohydrate by 2-5 times. This study indicates that these nanocomposites may be suitable for implant applications.

  4. Biosynthesis of silver and gold nanoparticles using Trichoderma atroviride for the biological control of Phomopsis canker disease in tea plants.

    Science.gov (United States)

    Ponmurugan, Ponnusamy

    2017-04-01

    The biological way of metallic nanoparticles production using ecofriendly biocontrol agents are largely used to control many plant pathogenic microorganisms in agriculture. Hence, an attempt was made to evaluate the potential of suppressive activity of nanoparticles produced by an indigenous isolate, Trichoderma atroviride against a tea pathogenic fungus namely Phomopsis theae. The presence of biosynthesised nanoparticles was primarily confirmed through ultraviolet-visible spectroscopy analysis and was characterised using X-ray diffraction and scanning electron microscopy-energy dispersive X-ray analysis to delineate the size, shape and nature of particles. Further, Fourier transform infrared analysis revealed the functional biomolecules responsible for capping and stabilisation of nanoparticles. In addition, culture filtrate containing nanoparticles was subjected to invitro antifungal studies which revealed a considerable suppression on the growth of P. theae. The biosynthesised nanoparticles were found to be active even after 3 months which established and confirmed the stability. Finally, field experiments conducted with soil application and wound dressing of nanoparticles exhibited a significant reduction in canker size when plants treated with gold followed by silver nanoparticles. Similarly, improvement in leaf yield was noted in response to these treatments. The above study confirmed the efficacy of metallic nanoparticles in management of stem disease in tea plantation.

  5. Synthesis and characterization of silver and gold nanoparticles using aqueous extract of seaweed, Turbinaria conoides, and their antimicrofouling activity.

    Science.gov (United States)

    Vijayan, Sri Ramkumar; Santhiyagu, Prakash; Singamuthu, Muthukkumarasamy; Kumari Ahila, Natarajan; Jayaraman, Ravindran; Ethiraj, Kannapiran

    2014-01-01

    Silver and gold nanoparticles were synthesized using an aqueous extract of the seaweed Turbinaria conoides and their antibiofilm activity against marine biofilm forming bacteria is reported here. The UV-Vis spectra showed the characteristics SPR absorption band for Ag NPs at 421 and for Au NPs at 538 nm. Further, the synthesized nanoparticles were characterized using FT-IR, XRD, FESEM, EDX, and HRTEM analysis. Spherical and triangular nanostructures of the Ag and Au nanoparticles were observed between the size ranges of 2-17 nm and 2-19 nm, respectively. The synthesized Ag NPs are efficient in controlling the bacterial biofilm formation; however, Au NPs did not show any remarkable antibiofilm activity. The maximum zone of inhibition was recorded against E. coli (17.6 ± 0.42 mm), followed by Salmonella sp., S. liquefaciens, and A. hydrophila. The macrotube dilution method inferred the MIC (20-40 µL mL(-1)) and MBC (40-60 µL mL(-1)) of Ag NPs. The CLSM images clearly showed the weak adherence and disintegrating biofilm formation of marine biofilm bacterial strains treated with Ag NPs. The Artemia cytotoxicity assay recorded the LC50 value of 88.914 ± 5.04 µL mL(-1). Thus the present study proved the efficiency of Ag NPs as a potent antimicrofouling agent and became the future perspective for the possible usage in the biofouling related issues in the aquaculture installations and other marine systems.

  6. SERS Characterization of the Indocyanine-Type Dye IR-820 on Gold and Silver Nanoparticles in the Near Infrared

    Directory of Open Access Journals (Sweden)

    Tatiana B. V. Neves

    2015-01-01

    Full Text Available The Raman spectrum of the indocyanine-type dye IR-820 has been assigned for both solid and solution. SERS spectra of IR-820 on both silver and gold nanoparticles suspensions excited at 1064 nm were obtained. AgNPs allowed the detection of the dye through SERS down to 0.1 micromoles per liter; for the AuNPs the lowest concentration of the dye detectable was 10 micromoles per liter. Changes in the SERS relative intensities compared to the Raman spectrum in solution are subtle, mostly due to the preresonance effect of the dye. However, a perpendicular orientation relative to the metallic surface was inferred for the dye on both AgNPs and AuNPs. The easily distinguishable SERS spectra of the dye excited at 1064 nm, together with the high biological compatibility of cyanine dyes, are both indicative that IR-820 could be used as a high-performance probe molecule for SERS.

  7. Gold-silver mining districts, alteration zones, and paleolandforms in the Miocene Bodie Hills Volcanic Field, California and Nevada

    Science.gov (United States)

    Vikre, Peter G.; John, David A.; du Bray, Edward A.; Fleck, Robert J.

    2015-09-25

    The Bodie Hills is a ~40 by ~30 kilometer volcanic field that straddles the California-Nevada state boundary between Mono Lake and the East Walker River. Three precious metal mining districts and nine alteration zones are delineated in Tertiary-Quaternary volcanic and Mesozoic granitic and metamorphic rocks that comprise the volcanic field. Cumulative production from the mining districts, Bodie, Aurora, and Masonic, is 3.4 million ounces of gold and 28 million ounces of silver. Small amounts of mercury were produced from the Potato Peak, Paramount-Bald Peak, and Cinnabar Canyon-US 395 alteration zones; a native sulfur resource in the Cinnabar Canyon-US 395 alteration zone has been identified by drilling. There are no known mineral resources in the other six alteration zones, Red Wash-East Walker River, East Brawley Peak, Sawtooth Ridge, Aurora Canyon, Four Corners, and Spring Peak. The mining districts and alteration zones formed between 13.4 and 8.1 Ma in predominantly ~15–9 Ma volcanic rocks of the Bodie Hills volcanic field. Ages of hydrothermal minerals in the districts and zones are the same as, or somewhat younger than, the ages of volcanic host rocks.

  8. Eco-friendly approach for nanoparticles synthesis and mechanism behind antibacterial activity of silver and anticancer activity of gold nanoparticles.

    Science.gov (United States)

    Patil, Maheshkumar Prakash; Kim, Gun-Do

    2017-01-01

    This review covers general information about the eco-friendly process for the synthesis of silver nanoparticles (AgNP) and gold nanoparticles (AuNP) and focuses on mechanism of the antibacterial activity of AgNPs and the anticancer activity of AuNPs. Biomolecules in the plant extract are involved in reduction of metal ions to nanoparticle in a one-step and eco-friendly synthesis process. Natural plant extracts contain wide range of metabolites including carbohydrates, alkaloids, terpenoids, phenolic compounds, and enzymes. A variety of plant species and plant parts have been successfully extracted and utilized for AgNP and AuNP syntheses. Green-synthesized nanoparticles eliminate the need for a stabilizing and capping agent and show shape and size-dependent biological activities. Here, we describe some of the plant extracts involved in nanoparticle synthesis, characterization methods, and biological applications. Nanoparticles are important in the field of pharmaceuticals for their strong antibacterial and anticancer activity. Considering the importance and uniqueness of this concept, the synthesis, characterization, and application of AgNPs and AuNPs are discussed in this review.

  9. A comparative study of the reduction of silver and gold salts in water by a cathodic microplasma electrode

    Science.gov (United States)

    De Vos, Caroline; Baneton, Joffrey; Witzke, Megan; Dille, Jean; Godet, Stéphane; Gordon, Michael J.; Mohan Sankaran, R.; Reniers, François

    2017-03-01

    A comparative study of the reduction of aqueous silver (Ag) and gold (Au) salts to colloidal Ag and Au nanoparticles, respectively, by a gaseous, cathodic, atmospheric-pressure microplasma electrode is presented. The resulting nanoparticles (NPs) were characterized by ultraviolet-visible (UV-vis) absorption spectroscopy and transmission electron microscopy (TEM), and the aqueous solution composition before and after experiments was determined by ionic conductivity, electrochemical potential, and/or UV-vis absorption measurements. TEM showed that Ag and Au NPs were spherical and non-agglomerated when synthesized in the presence of a stabilizer, polyvinyl alcohol. The charge injected by the plasma was correlated to the maximum intensity in the absorbance spectra which in turn depends on the nanoparticle concentration. Separately, the charge injected was correlated to the metal cation concentration. Ag and Au reduction rates were found to be directly proportional to the charge injected, independent of plasma current and process time. Differences in the mechanism for Ag and Au reduction were also observed, and solution species generated by the plasma and their role in the reduction process (e.g. H2O2, electrons) is discussed.

  10. Targeting nano drug delivery to cancer cells using tunable, multi-layer, silver-decorated gold nanorods.

    Science.gov (United States)

    Nima, Zeid A; Alwbari, Ahmed M; Dantuluri, Vijayalakshmi; Hamzah, Rabab N; Sra, Natasha; Motwani, Pooja; Arnaoutakis, Konstantinos; Levy, Rebecca A; Bohliqa, Amani F; Nedosekin, Dmitry; Zharov, Vladimir P; Makhoul, Issam; Biris, Alexandru S

    2017-12-01

    Multifunctional nanoparticles have high potential as targeting delivery vehicles for cancer chemotherapy. In this study, silver-decorated gold nanorods (AuNR\\Ag) have been successfully used to deliver specific, targeted chemotherapy against breast cancer (MCF7) and prostate carcinoma (PC3) cell lines. Doxorubicin, a commonly used chemotherapy, and anti-Epithelial cell adhesion molecule (anti-EpCAM) antibodies were covalently bonded to thiolated polyethylene glycol-coated AuNR\\Ag, and the resultant system was used to deliver the drugs to cancer cells in vitro. Furthermore, these nanoparticles have a unique spectral signature by surface enhanced Raman spectroscopy (SERS), which enables reliable detection and monitoring of the distribution of these chemotherapy constructs inside cells. The development of interest in a plasmonic nano drugs system with unique spectroscopic signatures could result in a clinical approach to the precise targeting and visualization of cells and solid tumors while delivering molecules for the enhanced treatment of cancerous tumors. Copyright © 2017 John Wiley & Sons, Ltd.

  11. Chiral gold(I vs chiral silver complexes as catalysts for the enantioselective synthesis of the second generation GSK-hepatitis C virus inhibitor

    Directory of Open Access Journals (Sweden)

    María Martín-Rodríguez

    2011-07-01

    Full Text Available The synthesis of a GSK 2nd generation inhibitor of the hepatitis C virus, by enantioselective 1,3-dipolar cycloaddition between a leucine derived iminoester and tert-butyl acrylate, was studied. The comparison between silver(I and gold(I catalysts in this reaction was established by working with chiral phosphoramidites or with chiral BINAP. The best reaction conditions were used for the total synthesis of the hepatitis C virus inhibitor by a four step procedure affording this product in 99% ee and in 63% overall yield. The origin of the enantioselectivity of the chiral gold(I catalyst was justified according to DFT calculations, the stabilizing coulombic interaction between the nitrogen atom of the thiazole moiety and one of the gold atoms being crucial.

  12. Self-assembly of gold nanoparticles to silver microspheres as highly efficient 3D SERS substrates

    Science.gov (United States)

    Chen, Shouhui; Huang, Peng; Wang, Zhihua; Wang, Zhe; Swierczewska, Magdalena; Niu, Gang; Cui, Daxiang; Chen, Xiaoyuan

    2013-04-01

    Herein we report a simple, one-pot, surfactant-free synthesis of 3D Ag microspheres (AgMSs) in aqueous phase at room temperature. The 3D AgMSs act as supports to fix the gold nanoparticles (GNPs) in 3D space via the interaction between the carboxyl groups of GNPs and the Ag atoms of AgMSs. The ensemble of AgMSs@GNPs with high surface-enhanced Raman scattering (SERS) activity and sensitivity can be an ideal 3D substrate choice for practical SERS detection applications. The simple self-assembly strategy may be extended to other metallic materials with great potentials in SERS, catalysis, and photoelectronic devices.

  13. Novel fabrication and catalytic application of poly(ethylenimine)-stabilized gold-silver alloy nanoparticles

    Science.gov (United States)

    Shin, Kuan Soo; Kim, Ji Hoon; Kim, In Hyun; Kim, Kwan

    2012-03-01

    Novel synthesis of amine-stabilized Au-Ag alloy nanoparticles with controlled composition has been devised using poly(ethylenimine) (PEI) as a reducing and a stabilizing agent simultaneously. The composition of Au-Ag alloy nanoparticles was readily controlled by varying the initial relative amount of HAuCl4 and AgNO3. Due to the presence of abundant amine functional groups in PEI, which could act as the dissolving ligand for AgCl, the precipitation problem of Ag+ in the presence of Cl- from the gold salt was avoided. On this basis, the relatively high concentrations of HAuCl4 and AgNO3 salts were used for the fabrication of Au-Ag alloy nanoparticles. The PEI thus plays triple roles in this study that include the co-reducing agents for HAuCl4 and AgNO3, the stabilizing agents for Au-Ag alloy nanoparticles, and even the dissolving agents for AgCl. As a novel material for use in catalysis, the Au-Ag alloy nanoparticles including pure Au and Ag samples were exploited as catalysts for the reduction of 4-nitrophenol in the presence of NaBH4. As the Au content was increased in the Au-Ag alloy nanoparticles, the rate constant of the reduction was exponentially increased from pure Ag to pure Au.

  14. Novel fabrication and catalytic application of poly(ethylenimine)-stabilized gold-silver alloy nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Kuan Soo, E-mail: kshin@ssu.ac.kr; Kim, Ji Hoon; Kim, In Hyun [Soongsil University, Department of Chemistry (Korea, Republic of); Kim, Kwan, E-mail: kwankim@snu.ac.kr [Seoul National University, Department of Chemistry (Korea, Republic of)

    2012-03-15

    Novel synthesis of amine-stabilized Au-Ag alloy nanoparticles with controlled composition has been devised using poly(ethylenimine) (PEI) as a reducing and a stabilizing agent simultaneously. The composition of Au-Ag alloy nanoparticles was readily controlled by varying the initial relative amount of HAuCl{sub 4} and AgNO{sub 3}. Due to the presence of abundant amine functional groups in PEI, which could act as the dissolving ligand for AgCl, the precipitation problem of Ag{sup +} in the presence of Cl{sup -} from the gold salt was avoided. On this basis, the relatively high concentrations of HAuCl{sub 4} and AgNO{sub 3} salts were used for the fabrication of Au-Ag alloy nanoparticles. The PEI thus plays triple roles in this study that include the co-reducing agents for HAuCl{sub 4} and AgNO{sub 3}, the stabilizing agents for Au-Ag alloy nanoparticles, and even the dissolving agents for AgCl. As a novel material for use in catalysis, the Au-Ag alloy nanoparticles including pure Au and Ag samples were exploited as catalysts for the reduction of 4-nitrophenol in the presence of NaBH{sub 4}. As the Au content was increased in the Au-Ag alloy nanoparticles, the rate constant of the reduction was exponentially increased from pure Ag to pure Au.

  15. Altering the dewetting characteristics of ultrathin gold and silver films using a sacrificial antimony layer.

    Science.gov (United States)

    Farzinpour, P; Sundar, A; Gilroy, K D; Eskin, Z E; Hughes, R A; Neretina, S

    2012-12-14

    Solid state dewetting of ultrathin films is the most straightforward means of fabricating substrate-supported noble metal nanostructures. This assembly process is, however, quite inflexible, yielding either densely packed smaller structures or widely spaced larger structures. Here, we demonstrate the utility of introducing a sacrificial antimony layer between the substrate and noble metal overlayer. We observe an agglomeration process which is radically altered by the concurrent sublimation of antimony. In stark contrast with conventional dewetting, where the thickness of the deposited metal film determines the characteristic length scales of the assembly process, it is the thickness of the sacrificial antimony layer which dictates both the nanoparticle size and interparticle spacing. The result is a far more flexible self-assembly process where the nanoparticle size and areal density can be varied widely. Demonstrations show nanoparticle areal densities which are varied over four orders of magnitude assembled from the identical gold layer thickness, where the accompanying changes to nanostructure size see a systematic shift in the wavelength of the localized surface plasmon resonance. As a pliable self-assembly process, it offers the opportunity to tailor the properties of an ensemble of nanostructures to meet the needs of specific applications.

  16. Formation conditions of high-grade gold-silver ore of epithermal Tikhoe deposit, Russian Northeast

    Science.gov (United States)

    Volkov, A. V.; Kolova, E. E.; Savva, N. E.; Sidorov, A. A.; Prokof'ev, V. Yu.; Ali, A. A.

    2016-09-01

    The Tikhoe epithermal deposit is located in the Okhotsk-Chukotka volcanic belt (OChVB) 250 km northeast of Magadan. Like other deposits belonging to the Ivan'insky volcanic-plutonic depression (VTD), the Tikhoe deposit is characterized by high-grade Au-Ag ore with an average Au grade of 23.13 gpt Au and Au/Ag ratio varying from 1: 1 to 1: 10. The detailed explored Tikhoe-1 orebody is accompanied by a thick (20 m) aureole of argillic alteration. Pyrite is predominant among ore minerals; galena, arsenopyrite, sphalerite, Ag sulfosalts, fahlore, electrum, and küstelite are less abundant. The ore is characterized by abundant Sebearing minerals. Cu-As geochemical specialization is noted for silver minerals. Elevated Se and Fe molar fractions of the main ore minerals are caused by their formation in the near-surface argillic alteration zone. The veins and veinlets of the Tikhoe-1 ore zone formed stepwise at a temperature of 230 to 105°C from Nachloride solution enriched in Mg and Ca cations with increasing salinity. The parameters of the ore-forming fluid correspond to those of epithermal low-sulfidation deposits and assume the formation of high-grade ore under a screening unit of volcanic rocks. In general, the composition of the ore-forming fluid fits the mineralogy and geochemistry of ore at this deposit. The similarity of the ore composition and parameters of the ore-forming fluid between the Tikhoe and Julietta deposits is noteworthy. Meanwhile, differences are mainly related to the lower temperature and fluid salinity at the Julietta deposit with respect to the Tikhoe deposit. The fluid at the Julietta deposit is depleted in most components compared with that at the Tikhoe deposit except for Sb, Cd, and Ag. The results testify to a different erosion level at the deposits as derivatives of the same ore-forming system. The large scale of the latter allows us to predict the discovery of new high-grade objects, including hidden mineralization, which is not exposed at

  17. Christmas-tree Derived Amplification Immuno-strategy for Sensitive Visual Detection of Vibrio parahaemolyticus Based on Gold Label Silver Stain Technology.

    Science.gov (United States)

    Song, Xinxin; Wu, Yanjie; Wu, Lin; Hu, Yufang; Li, Wenrou; Guo, Zhiyong; Su, Xiurong; Jiang, Xiaohua

    2017-01-01

    A developed Christmas-tree derived immunosensor based on a gold label silver stain (GLSS) technique was fabricated for a highly sensitive analysis of Vibrio parahaemolyticu (VP). In this strategy, captured VP antibody (cAb) was immobilized on a solid substrate; then, the VPs were sequentially tagged with a signal probe by incubating the assay with a detection VP antibody (dAb) conjugated gold nanoparticles (AuNPs)-labeled graphite-like carbon nitride (g-C3N4). Finally, the attached signal probe could harvest a visible signal by the silver meal deposition, and then followed by homebrew Matlab 6.0 as a grey value acquisition. In addition, the overall design of the biosensor was established in abundant AuNPs and g-C3N4 with a two-dimensional structure, affording a bulb-decorated Christmas-tree model. Moreover, with the optimized conditions, the detection limit of the as-proposed biosensor is as low as 102 CFU (Colony-Forming Units) mL-1, exhibiting an increase of two orders of magnitude compared with the traditional immune-gold method. Additionally, the developed visible immunosensor was also successfully applied to the analysis of complicated samples.

  18. Mechanism of adsorption of single and double stranded DNA on gold and silver nanoparticles: Investigating some important parameters in bio-sensing applications.

    Science.gov (United States)

    Farkhari, Nahid; Abbasian, Sara; Moshaii, Ahmad; Nikkhah, Maryam

    2016-12-01

    The mechanism of adsorption of single and double stranded DNAs on colloidal gold and silver nanoparticles has been studied by measuring the resistance of the nanoparticles, surrounded by various oligonucleotides, against salt induced aggregation. It is shown that both single and double stranded DNAs can be adsorbed on the metal nanoparticles and the adsorption strength is determined by the interaction between various bases of DNA and the nanoparticles. By changing the salt concentration, the difference between adsorption of various DNA strands on the nanoparticles can be specified. The results indicate that a key parameter in success of a sensing assay of DNA hybridization is the salt concentration which should be greater than a minimum threshold depending on the nanoparticles characteristics. We have also investigated the interaction mechanism between various DNA bases with the metal nanoparticles. For both gold and silver nanoparticles, adenine has the highest and thymine has the lowest attachment to the nanoparticles. From surface enhanced Raman spectroscopy (SERS) data of various bases in the presence of gold nanoparticles, the probable interaction points in the bases with the nanoparticles have been determined, which are mainly the nitrogen sites of these oligonucleotides. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Plasmonically Enhanced Photocatalytic Hydrogen Production from Water: The Critical Role of Tunable Surface Plasmon Resonance from Gold-Silver Nanoshells.

    Science.gov (United States)

    Li, Chien-Hung; Li, Min-Chih; Liu, Si-Ping; Jamison, Andrew C; Lee, Dahye; Lee, T Randall; Lee, Tai-Chou

    2016-04-13

    Gold-silver nanoshells (GS-NSs) having a tunable surface plasmon resonance (SPR) were employed to facilitate charge separation of photoexcited carriers in the photocalytic production of hydrogen from water. Zinc indium sulfide (ZnIn2S4; ZIS), a visible-light-active photocatalyst, where the band gap varies with the [Zn]/[In] ratio, was used as a model ZIS system (E(g) = 2.25 eV) to investigate the mechanisms of plasmonic enhancement associated with the nanoshells. Three types of GS-NS cores with intense absorptions centered roughly at 500, 700, and 900 nm were used as seeds for preparing GS-NS@ZIS core-shell structures via a microwave-assisted hydrothermal reaction, yielding core-shell particles with composite diameters of ∼200 nm. Notably, an interlayer of dielectric silica (SiO2) between the GS-NSs and the ZIS photocatalyst provided another parameter to enhance the production of hydrogen and to distinguish the charge-transfer mechanisms. In particular, the direct transfer of hot electrons from the GS-NSs to the ZIS photocatalyst was blocked by this layer. Of the 10 particle samples examined in this study, the greatest hydrogen gas evolution rate was observed for GS-NSs having a SiO2 interlayer thickness of ∼17 nm and an SPR absorption centered at ∼700 nm, yielding a rate 2.6 times higher than that of the ZIS without GS-NSs. The apparent quantum efficiencies for these core-shell particles were recorded and compared to the absorption spectra. Analyses of the charge-transfer mechanisms were evaluated and are discussed based on the experimental findings.

  20. Biosynthesis, Characterization, and Bioactivities Evaluation of Silver and Gold Nanoparticles Mediated by the Roots of Chinese Herbal Angelica pubescens Maxim.

    Science.gov (United States)

    Markus, Josua; Wang, Dandan; Kim, Yeon-Ju; Ahn, Sungeun; Mathiyalagan, Ramya; Wang, Chao; Yang, Deok Chun

    2017-12-01

    A facile synthesis and biological applications of silver (DH-AgNps) and gold nanoparticles (DH-AuNps) mediated by the aqueous extract of Angelicae Pubescentis Radix (Du Huo) are explored. Du Huo is a medicinal root belonging to Angelica pubescens Maxim which possesses anti-inflammatory, analgesic, and antioxidant properties. The absorption spectra of nanoparticles in varying root extract and metal ion concentration, pH, reaction temperatures, and time were recorded by ultraviolet-visible (UV-Vis) spectroscopy. The presence of DH-AgNps and DH-AuNps was confirmed from the surface plasmon resonance intensified at ~414 and ~540 nm, respectively. Field emission transmission electron micrograph (FE-TEM) analysis revealed the formation of quasi-spherical DH-AgNps and spherical icosahedral DH-AuNps. These novel DH-AgNps and DH-AuNps maintained an average crystallite size of 12.48 and 7.44 nm, respectively. The biosynthesized DH-AgNps and DH-AuNps exhibited antioxidant activity against 2,2-diphenyl-1-picrylhydrzyl (DPPH) radicals and the former exhibited antimicrobial activity against clinical pathogens including Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enterica. The expected presence of flavonoids, sesquiterpenes, and phenols on the nanoparticle surface were conjectured to grant protection against aggregation and free radical scavenging activity. DH-AgNps and DH-AuNps were further investigated for their cytotoxic properties in RAW264.7 macrophages for their potential application as drug carriers to sites of inflammation. In conclusion, this green synthesis is favorable for the advancement of plant mediated nano-carriers in drug delivery systems, cancer diagnostic, and medical imaging. Schematic diagram of biosynthesis of DH-AgNps and DH-AuNps and evaluation of their bioactivities.

  1. Cytotoxicity and terminal differentiation of human oral keratinocyte by indium ions from a silver-palladium-gold-indium dental alloy.

    Science.gov (United States)

    Lee, Jung-Hwan; Seo, Sang-Hee; Lee, Sang-Bae; Om, Ji-Yeon; Kim, Kwang-Mahn; Kim, Kyoung-Nam

    2015-02-01

    Dental alloys containing indium (In) have been used in dental restoration for two decades; however, no study has investigated the biological effects of In ions, which may be released in the oral cavity, on human oral keratinocytes. The objective of the present study was to investigate the biological effects of In ions on human oral keratinocyte after confirming their release from a silver-palladium-gold-indium (Ag-Pd-Au-In) dental alloy. As a corrosion assay, a static immersion tests were performed by detecting the released ions in the corrosion solution from the Ag-Pd-Au-In dental alloy using inductively coupled plasma atomic emission spectroscopy. The cytotoxicity and biological effects of In ions were then studied with In compounds in three human oral keratinocyte cell lines: immortalized human oral keratinocyte (IHOK), HSC-2, and SCC-15. Higher concentrations of In and Cu ions were detected in Ag-Pd-Au-In (P<0.05) than in Ag-Pd-Au, and AgCl deposition occurred on the surface of Ag-Pd-Au-In after a 7-day corrosion test due to its low corrosion resistance. At high concentrations, In ions induced cytotoxicity; however, at low concentrations (∼0.8In(3+)mM), terminal differentiation was observed in human oral keratinocytes. Intracellular ROS was revealed to be a key component of In-induced terminal differentiation. In ions were released from dental alloys containing In, and high concentrations of In ions resulted in cytotoxicity, whereas low concentrations induced the terminal differentiation of human oral keratinocytes via increased intracellular ROS. Therefore, dental alloys containing In must be biologically evaluated for their safe use. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. ASSESSMENT OF THE CHEMICAL POLLUTION OF THE SOIL, GROUND AND BOTTOM SEDIMENTS AT KLEN GOLD AND SILVER DEPOSIT

    Directory of Open Access Journals (Sweden)

    Bryukhan' Fedor Fedorovich

    2012-10-01

    Full Text Available Currently, prospecting and design-related works are performed prior to the upcoming launch of mining operations at Klen gold and silver deposit in Chukot Autonomous District. The anthropogenic impact of the geological exploration in this intact territory has been produced since 1984. A considerable amount of borehole drilling, prospecting, road building, and temporary housing development has been performed. The engineering research, including ecological surveys, has been completed to assess the ecological impact of upcoming exploratory and mining operations at the deposit. Assessment of the geochemical condition of the landscape constituents, including the soil, ground and bottom sediments is of special importance in terms of their engineering protection and rational management of the natural environment. The above assessments were based on the field sampling made by «Sibgeoconsulting», CJSC (Krasnoyarsk and the laboratory research made by accredited laboratories of Federal State Unitary Geological Enterprise «Urangeolograzvedka» (Irkutsk and «Krasnoyarskgeologiya» (Krasnoyarsk. The analysis of the chemical pollution of soils, ground and bottom sediments is based on the examination of 30 samples. Peculiarities of the chemical composition of samples extracted at the deposit were identified. It has been discovered that pH values of the soil vary from 5.1 to 7.3. The concentration of metal in bottom sediments exceeds its concentration in the soil by far. Almost all irregular features of the sample water in the whole territory of the deposit are caused by the anthropogenic impact. In general, the metal content in soils, ground and bottom sediments within the territory of the deposit is slightly different from the regular clarke.

  3. Biosynthesis, Characterization, and Bioactivities Evaluation of Silver and Gold Nanoparticles Mediated by the Roots of Chinese Herbal Angelica pubescens Maxim

    Science.gov (United States)

    Markus, Josua; Wang, Dandan; Kim, Yeon-Ju; Ahn, Sungeun; Mathiyalagan, Ramya; Wang, Chao; Yang, Deok Chun

    2017-01-01

    A facile synthesis and biological applications of silver (DH-AgNps) and gold nanoparticles (DH-AuNps) mediated by the aqueous extract of Angelicae Pubescentis Radix (Du Huo) are explored. Du Huo is a medicinal root belonging to Angelica pubescens Maxim which possesses anti-inflammatory, analgesic, and antioxidant properties. The absorption spectra of nanoparticles in varying root extract and metal ion concentration, pH, reaction temperatures, and time were recorded by ultraviolet-visible (UV-Vis) spectroscopy. The presence of DH-AgNps and DH-AuNps was confirmed from the surface plasmon resonance intensified at 414 and 540 nm, respectively. Field emission transmission electron micrograph (FE-TEM) analysis revealed the formation of quasi-spherical DH-AgNps and spherical icosahedral DH-AuNps. These novel DH-AgNps and DH-AuNps maintained an average crystallite size of 12.48 and 7.44 nm, respectively. The biosynthesized DH-AgNps and DH-AuNps exhibited antioxidant activity against 2,2-diphenyl-1-picrylhydrzyl (DPPH) radicals and the former exhibited antimicrobial activity against clinical pathogens including Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enterica. The expected presence of flavonoids, sesquiterpenes, and phenols on the nanoparticle surface were conjectured to grant protection against aggregation and free radical scavenging activity. DH-AgNps and DH-AuNps were further investigated for their cytotoxic properties in RAW264.7 macrophages for their potential application as drug carriers to sites of inflammation. In conclusion, this green synthesis is favorable for the advancement of plant mediated nano-carriers in drug delivery systems, cancer diagnostic, and medical imaging.

  4. Synthesis and Characterization of Silver and Gold Nanoparticles Using Aqueous Extract of Seaweed, Turbinaria conoides, and Their Antimicrofouling Activity

    Directory of Open Access Journals (Sweden)

    Sri Ramkumar Vijayan

    2014-01-01

    Full Text Available Silver and gold nanoparticles were synthesized using an aqueous extract of the seaweed Turbinaria conoides and their antibiofilm activity against marine biofilm forming bacteria is reported here. The UV-Vis spectra showed the characteristics SPR absorption band for Ag NPs at 421 and for Au NPs at 538 nm. Further, the synthesized nanoparticles were characterized using FT-IR, XRD, FESEM, EDX, and HRTEM analysis. Spherical and triangular nanostructures of the Ag and Au nanoparticles were observed between the size ranges of 2–17 nm and 2–19 nm, respectively. The synthesized Ag NPs are efficient in controlling the bacterial biofilm formation; however, Au NPs did not show any remarkable antibiofilm activity. The maximum zone of inhibition was recorded against E. coli (17.6±0.42 mm, followed by Salmonella sp., S. liquefaciens, and A. hydrophila. The macrotube dilution method inferred the MIC (20–40 µL mL−1 and MBC (40–60 µL mL−1 of Ag NPs. The CLSM images clearly showed the weak adherence and disintegrating biofilm formation of marine biofilm bacterial strains treated with Ag NPs. The Artemia cytotoxicity assay recorded the LC50 value of 88.914±5.04 µL mL−1. Thus the present study proved the efficiency of Ag NPs as a potent antimicrofouling agent and became the future perspective for the possible usage in the biofouling related issues in the aquaculture installations and other marine systems.

  5. Maps showing mineral resource assessment for skarn deposits of gold, silver, copper, tungsten, and iron in the Butte 1 degree by 2 degrees Quadrangle, Montana

    Science.gov (United States)

    Elliott, J.E.; Wallace, C.A.; Lee, G.K.; Antweiler, J.C.; Lidke, D.J.; Rowan, L.C.; Hanna, W.F.; Trautwein, C.M.; Dwyer, J.L.; Moll, S.H.

    1992-01-01

    The purpose of this report is to assess the potential for undiscovered skarn deposits of gold, silver, copper, tungsten, and iron in the Butte 1 °X2° quadrangle. Other deposit types have been assessed and reports for each of the following have been prepared: Vein and replacement deposits of gold, silver, copper, lead, zinc, ·manganese, and tungsten; porphyry-stockwork deposits of copper, molybdenum, and tungsten; stockwork-disseminated deposits of gold and silver; placer deposits of gold; and miscellaneous deposit types including strata-bound deposits of copper and silver in rocks of the Middle Proterozoic Belt Supergroup, phosphate deposits in the Permian Phosporia Formation, and deposits of barite and fluorite. The Butte quadrangle, in west-central Montana, is one of the most mineralized and productive mining regions in the U.S. Its mining districts, including the world famous Butte or Summit Valley district, have produced a variety of metallic and nonmetallic mineral commodities valued at more than $6.4 billion (at the time of production). Because of its importance as a mineral producing region, the Butte quadrangle was selected for study by the U.S. Geological Survey under the Conterminous United States Mineral Assessment Program (CUSMAP). Under this program, new data on geology, geochemistry, geophysics, geochronology, mineral resources, and remote sensing were collected and synthesized. The field and laboratory studies were supported, in part, by funding from the Geologic Framework and Synthesis Program and the Wilderness Program. The methods used in resource assessment include a compilation of all data into data sets, the development of an occurrence model for skarn deposits in the quadrangle, and the analysis of data using techniques provided by a Geographic Information System (GIS). This map is one of a number of reports and maps on the Butte 1 °X2° quadrangle. Other publications resulting from this study include U.S. Geological Survey (USGS

  6. Pyrite deformation and connections to gold mobility: insight from micro-structural analysis and trace element mapping

    Science.gov (United States)

    Dubosq, Renelle; Rogowitz, Anna; Lawley, Christopher; Schneider, David; Jackson, Simon

    2017-04-01

    Pyrite is an important and ubiquitous gold-bearing phase in many orogenic gold deposits making the study of its deformation behaviour under metamorphic conditions crucial to the understanding of gold (re)mobilization. However, pyrite deformation mechanisms and their influence on the retention or release of trace elements during deformation and metamorphism remain poorly understood. We propose a syn- to post-peak metamorphic and deformation driven gold upgrading model where gold is remobilized through deformation-induced diffusion pathways in the form of substructures in pyrite. The middle amphibolite facies assemblage (actinolite-biotite-plagioclase-almandine) of the Detour Lake deposit (Canada) makes it an ideal study area due to maximum temperatures reaching 550°C, exceeding the conditions for plastic deformation in pyrite (450°C). The world-class Detour Lake deposit, containing 16.4 Moz of Au at 1 g/t, is a Neoarchean orogenic gold ore body located in the northern Abitibi district within the Superior Province. The mine is situated along the high strain, sub-vertical ductile-brittle Sunday Lake Deformation Zone (SLDZ) parallel to the broadly E-W trending Abitibi greenstone belt. Herein we combine orientation contrast (OC) forescatter imaging, electron backscatter diffraction (EBSD) and 2D laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) trace element pyrite mapping to evaluate the influence of pyrite brittle and plastic deformation on the release of trace elements during syn-metamorphic gold remobilization. Local misorientation patterns in pyrite exhibit parallel bands that can be described by continuous rotation around one of the axes, whereas higher strain areas reveal more heterogeneous misorientation patterns and the development of low-angle grain boundaries with late fractures indicative of dislocation creep and strain hardening. These late fractures are an important micro-structural setting for gold and clusters of precious

  7. Study of the Reaction Rate of Gold Nanotube Synthesis from Sacrificial Silver Nanorods through the Galvanic Replacement Method

    OpenAIRE

    Sunil Kwon; Hyunbae Dong; Sang-Yup Lee

    2010-01-01

    An investigation was carried out about the gold nanotube synthesis via a galvanic replacement reaction. The progress of the gold nanotube synthesis was investigated using electron microscopy and UV-Vis spectroscopy. In addition, the reaction rates of gold nanotube formation in the early stage of the reaction were studied. The chlorine ion concentration linearly increased with the gold precursor concentration but deviated from the stoichiometric amounts. This deviation was probably due to AgCl...

  8. Electrum, the Gold-Silver Alloy, from the Bulk Scale to the Nanoscale: Synthesis, Properties, and Segregation Rules.

    Science.gov (United States)

    Guisbiers, Grégory; Mendoza-Cruz, Rubén; Bazán-Díaz, Lourdes; Velázquez-Salazar, J Jesús; Mendoza-Perez, Rafael; Robledo-Torres, José Antonio; Rodriguez-Lopez, José-Luis; Montejano-Carrizales, Juan Martín; Whetten, Robert L; José-Yacamán, Miguel

    2016-01-26

    The alloy Au-Ag system is an important noble bimetallic phase, both historically (as "Electrum") and now especially in nanotechnology, as it is applied in catalysis and nanomedicine. To comprehend the structural characteristics and the thermodynamic stability of this alloy, a knowledge of its phase diagram is required that considers explicitly its size and shape (morphology) dependence. However, as the experimental determination remains quite challenging at the nanoscale, theoretical guidance can provide significant advantages. Using a regular solution model within a nanothermodynamic approach to evaluate the size effect on all the parameters (melting temperature, melting enthalpy, and interaction parameters in both phases), the nanophase diagram is predicted. Besides an overall shift downward, there is a "tilting" effect on the solidus-liquidus curves for some particular shapes exposing the (100) and (110) facets (cube, rhombic dodecahedron, and cuboctahedron). The segregation calculation reveals the preferential presence of silver at the surface for all the polyhedral shapes considered, in excellent agreement with the latest transmission electron microscopy observations and energy dispersive spectroscopy analysis. By reviewing the nature of the surface segregated element of different bimetallic nanoalloys, two surface segregation rules, based on the melting temperatures and surface energies, are deduced. Finally, the optical properties of Au-Ag nanoparticles, calculated within the discrete dipole approximation, show the control that can be achieved in the tuning of the local surface plasmon resonance, depending of the alloy content, the chemical ordering, the morphology, the size of the nanoparticle, and the nature of the surrounding environment.

  9. Multiple signal amplified electrochemiluminescent immunoassay for brombuterol detection using gold nanoparticles and polyamidoamine dendrimers-silver nanoribbon

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Tiantian; Hu, Liuyi; Zhao, Kang; Deng, Anping, E-mail: denganping@suda.edu.cn; Li, Jianguo, E-mail: lijgsd@suda.edu.cn

    2016-11-16

    Electrochemiluminescent (ECL) immunosensor with multiple signal amplification was designed based on gold nanoparticles (AuNPs), polyamidoamine dendrimers (PAMAM) and silver-cysteine hybrid nanoribbon (SNR). Low toxic L-cysteine capped CdSe QDs was chosen as the ECL signal probe. To verify the proposed ultrasensitive ECL immunosensor for β-adrenergic agonists (β-AA), we detected Brombuterol (Brom) as a proof-of-principle analyte. Therein, AuNPs as the substrate can simplify the experiment process, accelerate the electron transfer rate, and carry more coating antigen (Ag-OVA) to enlarge ECL signal. On one hand, SNR on the surface of electrode can avoid the aggregation of AuNPs, and SNR-PAMAM-AuNPs also can be acted as a good accelerator for electron transfer. On the other hand, PAMAM (16 -NH{sub 2}) functionalized SNR (SNR-PAMAM) with numerous amino groups could be employed to bond abundant actived QDs to further amplify ECL signal. The new immunosensor can offer a simple, reliable, rapid, and selective detection for Brom, which have a dynamic range of 0.005–700 ng mL{sup −1} with a low detection limit at 1.5 pg mL{sup −1}. The proposed biosensor will extend the application of nanomaterials in ECL immunoassays and open a new road for the detection of Brom and other β-AA in the future. - Highlights: • A multiple signal amplification ECL immunosensor of eco-friendly CdSe QDs for brombuterol determination was developed. • Besides substrates, AuNPs and PAMAM-SNR were creatively used to accelerate the electron transport between electrode and QDs. • SNR-PAMAM with numerous amino groups also could be employed to bond abundant actived QDs to amplify ECL signal. • Competitive immunoassay was performed with ECL to detect small molecules of brombuterol. • It provided a method for detecting Brom and enlarged the usage of QDs, AuNPs and SNR-PAMAM in ECL biosensing.

  10. Source of boron in the Palokas gold deposit, northern Finland: evidence from boron isotopes and major element composition of tourmaline

    Science.gov (United States)

    Ranta, Jukka-Pekka; Hanski, Eero; Cook, Nick; Lahaye, Yann

    2017-06-01

    The recently discovered Palokas gold deposit is part of the larger Rompas-Rajapalot gold-mineralized system located in the Paleoproterozoic Peräpohja Belt, northern Finland. Tourmaline is an important gangue mineral in the Palokas gold mineralization. It occurs as tourmalinite veins and as tourmaline crystals in sulfide-rich metasomatized gold-bearing rocks. In order to understand the origin of tourmaline in the gold-mineralized rocks, we have investigated the major element chemistry and boron isotope composition of tourmaline from three areas: (1) the Palokas gold mineralization, (2) a pegmatitic tourmaline granite, and (3) the evaporitic Petäjäskoski Formation. Based on textural evidence, tourmaline in gold mineralization is divided into two different types. Type 1 is located within the host rock and is cut by rock-forming anthophyllite crystals. Type 2 occurs in late veins and/or breccia zones consisting of approximately 80% tourmaline and 20% sulfides, commonly adjacent to quartz veins. All the studied tourmaline samples belong to the alkali-group tourmaline and can be classified as dravite and schorl. The δ11B values of the three localities lie in the same range, from 0 to -4‰. Tourmaline from the Au mineralization and from the Petäjäskoski Formation has similar compositional trends. Mg is the major substituent for Al; inferred low Fe3+/Fe2+ ratios and Na values (age of molybdenite related to the tourmaline-sulfide-quartz veins, we propose that the tourmaline-forming process is a result of a single magmatic-hydrothermal event related to the extensive granite magmatism at around 1.79-1.77 Ga. Tourmaline was crystallized throughout the hydrothermal process, which resulted in the paragenetic variation between type 1 and type 2. The close association of tourmaline and gold suggests that the gold precipitated from the same boron-rich source as tourmaline.

  11. Fabrication and characterization of homogeneous surface-enhanced Raman scattering substrates by single pulse UV-laser treatment of gold and silver films.

    Science.gov (United States)

    Christou, Konstantin; Knorr, Inga; Ihlemann, Jürgen; Wackerbarth, Hainer; Beushausen, Volker

    2010-12-07

    The fabrication of SERS-active substrates, which offer high enhancement factors as well as spatially homogeneous distribution of the enhancement, plays an important role in the expansion of surface-enhanced Raman scattering (SERS) spectroscopy to a powerful, quantitative, and noninvasive measurement technique for analytical applications. In this paper, a novel method for the fabrication of SERS-active substrates by laser treatment of 20, 40, and 60 nm thick gold and of 40 nm thick silver films supported on quartz glass is presented. Single 308 nm UV-laser pulses were applied to melt the thin gold and silver films. During the cooling process of the noble metal, particles were formed. The particle size and density were imaged by atomic force microscopy. By varying the fluence, the size of the particles can be controlled. The enhancement factors of the nanostructures were determined by recording self-assembled monolayers of benzenethiol. The intensity of the SERS signal from benzenethiol is correlated to the mean particle size and thus to the fluence. Enhancement factors up to 10(6) with a high reproducibility were reached. Finally we have analyzed the temperature dependence of the SERS effect by recording the intensity of benzenethiol vibrations from 300 to 120 K. The temperature dependence of the SERS effect is discussed with regard to the metal properties.

  12. A review on the biosynthesis of metallic nanoparticles (gold and silver) using bio-components of microalgae: Formation mechanism and applications.

    Science.gov (United States)

    Shankar, P Dheeban; Shobana, Sutha; Karuppusamy, Indira; Pugazhendhi, Arivalagan; Ramkumar, Vijayan Sri; Arvindnarayan, Sundaram; Kumar, Gopalakrishnan

    2016-12-01

    The synthesis of nanoparticles (NP) using algae has been underexploited and even unexplored. In recent times, there are few reports on the synthesis of NP using algae, which are being used as a bio-factory for the synthesis. Moreover, the algae are a renewable source, so that it could be effectively explored in the green synthesis of NP. Hence, this review reports on the biosynthesis of NP especially gold and silver NP using algae. The most widely reported NP from algae are silver and gold than any other metallic NP, which might be due to their enormous biomedical field applications. The NP synthesized by this method is mainly in spherical shape; the reports are revealing the fact that the cell free extracts are highly exploited for the synthesis than the biomass, which is associated with the problem of recovering the particles. Besides, mechanism involving in the reduction and stabilization is well demonstrated to deepen the knowledge towards enhancement possibilities for the synthesis and applications. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Phytoextraction of trace elements by water hyacinth in contaminated area of gold mine tailing.

    Science.gov (United States)

    Romanova, Tamara E; Shuvaeva, Olga V; Belchenko, Ludmila A

    2016-01-01

    The ability of water hyacinth (Eichhornia crassipes) to uptake Ag, Ba, Cd, Mo, and Pb from waters in gold mine tailing area was studied. All experiments were carried out in the field conditions without using of model system. Bioconcentration (BCF) and translocation factors (TF) as well as elements accumulation by plant in different points of tailings-impacted area were evaluated. It has been shown that water hyacinth demonstrates high ability to accumulate Mo, Pb, and Ba with BCF values 24,360 ± 3600, 18,800 ± 2800 and 10,040 ± 1400, respectively and is efficient in translocation of Mo and Cd. The general trend of the plant accumulation ability in relation to the studied elements corresponds to their concentration in the medium. As the distance from tailings increases, concentration of Ag, Ba and Pb in plant decreases more clearly than that of Cd, while the amount of Mo accumulated by plant doesn't drop significantly in accordance with its concentration in water. Under the conditions of the confluence of river Ur and drainage stream Ba and Ag can be considered as potential candidates for phytomining.

  14. Geochemical distribution of trace element concentrations in the vicinity of Boroo gold mine, Selenge Province, Mongolia.

    Science.gov (United States)

    Inam, Edu; Khantotong, Supawan; Kim, Kyoung-Woong; Tumendemberel, Bulgan; Erdenetsetseg, Sugar; Puntsag, Tamir

    2011-01-01

    The environmental impacts of Boroo gold mine project in Mongolia was evaluated by chemical characterization of trace element concentrations in water, soils and tailing dam sediment samples. The results showed that concentrations of B, Cd, Ni and Se in the water samples were within the accepted levels of the Mongolia water quality standard (MNS4586: 1998). However, the concentrations of Al, As, Cu, Mn, Fe, Pb, U and Zn were higher than the maximum allowable concentration especially in the monitoring and heap leach wells. The average concentrations of As, Cd, Cu, Ni, Pb and Zn in the tailing dam sediment were 4419, 58.5, 56.0, 4.8, 20.6 and 25.7 mg/kg, respectively. Generally, arsenic and heavy metals in the soil samples were within the acceptable concentrations of the soil standard of Mongolia (MNS 5850: 2008). The chemical characterization of As solid phase in tailing dam sediment showed that the majority of As were found in the residual fraction comprising about 74% of total As. Assessing the potential risk to humans, simple bioavailability extraction test was used to estimate bioavailability of arsenic and heavy metals, and the concentrations extracted from tailing dam sediment were; 288.2 mg/kg As, 7.2 mg/kg Cd, 41.1 mg/kg Cu, 13.5 mg/kg Pb, 4.7 mg/kg Ni and 23.5 mg/kg Zn, respectively. From these results, the Boroo gold mine project has presently not significantly impacted the environment, but there is a high probability that it may act as a source of future contamination.

  15. Investigation of Gold and Silver Nanoparticles as Acid-base pH Indicators and Their Transition pH Ranges

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Byoung Gue; Jo, Ji Hee; Yu, Jin Won; Lim, Jong Kuk [Chosun University, Gwangju (Korea, Republic of)

    2014-09-15

    Monitoring of pH, especially under highly alkaline conditions, is necessary in various processes in the industrial, biotechnological, agricultural, and environmental fields. However, few pH indicators that can function at highly alkaline levels are available, and most of which are organic-based pH indicators. Several years ago, it was reported that gold nanoparticles prepared using trisodium citrate dihydrate were rapidly aggregated at pH values higher than ⁓ 12.7. A shift of surface plasmon resonance for such aggregated gold nanoparticles can be applied to pH indicators, allowing for the substitution of traditional organic-based pH indicators. The most important characteristic of pH indicators is the transition pH range. Herein, gold and silver nanoparticles are prepared using different reducing agents, and their transition pH ranges are examined. The results showed that all nanoparticles prepared in this study exhibit similar transition pH ranges spanning 11.9 - 13.0, regardless of the nanoparticle material, reducing agents, and concentration.

  16. Characterization and risk of exposure to elements from artisanal gold mining operations in the Bolivian Andes.

    Science.gov (United States)

    Pavilonis, Brian; Grassman, Jean; Johnson, Glen; Diaz, Yilmael; Caravanos, Jack

    2017-04-01

    Artisanal and small-scale gold mining (ASGM) offers low-skilled workers an opportunity to elevate themselves out of poverty. However, this industry operates with little to no pollution controls and the cost to the environment and human health can be large. The objectives of this study were to measure levels of arsenic (As), manganese (Mn), cobalt (Co), lead (Pb), and mercury (Hg) in the environment and characterize health risks to miners and residents in an area with active ASGM operations. An exposure assessment was conducted at two different mining sites and a nearby village in the Bolivian Anders. The resulting measurements were then used to quantify cancerous and noncancerous health risks to children and adults working at and living near ASGM areas. Soil concentrations of As were well above background levels and showed great variations between the village and mining area. Mercury vapor levels at the two mining sites were approximately 30 times larger than the EPA reference concentration. The risk of developing non-cancerous health effects were primarily due to exposure to As and Hg. The probability of individuals developing cancer was considerably increased with adult miners having a probability of 1.3 out of 100. Cancer potential was driven by exposure to As, with de minimus cancer risk from all other elements. Based on the environmental characterization of elements in soils and Hg vapors, the risk of developing cancerous and non-cancerous health outcomes were above a level of concern based on EPA risk assessment guidance. Personal protective equipment was not worn by workers and Hg amalgam is commonly heated in workers' homes. Better education of the risks of ASGM is needed as well as simple controls to reduce exposure. Published by Elsevier Inc.

  17. Specific composition of native silver from the Rogovik Au–Ag deposit, Northeastern Russia

    Science.gov (United States)

    Kravtsova, R. G.; Tauson, V. L.; Palyanova, G. A.; Makshakov, A. S.; Pavlova, L. A.

    2017-09-01

    The first data on native silver from the Rogovik Au-Ag deposit in northeastern Russia are presented. The deposit is situated in central part of the Okhotsk-Chukchi Volcanic Belt (OCVB) in the territory of the Omsukchan Trough, unique in its silver resources. Native silver in the studied ore makes up finely dispersed inclusions no larger than 50 μm in size, which are hosted in quartz; fills microfractures and interstices in association with küstelite, electrum, acanthite, silver sulfosalts and selenides, argyrodite, and pyrite. It has been shown that the chemical composition of native silver, along with its typomorphic features, is a stable indication of the various stages of deposit formation and types of mineralization: gold-silver (Au-Ag), silver-base metal (Ag-Pb), and gold-silver-base metal (Au-Ag-Pb). The specificity of native silver is expressed in the amount of trace elements and their concentrations. In Au-Ag ore, the following trace elements have been established in native silver (wt %): up to 2.72 S, up to 1.86 Au, up to 1.70 Hg, up to 1.75 Sb, and up to 1.01 Se. Native silver in Ag-Pb ore is characterized by the absence of Au, high Hg concentrations (up to 12.62 wt %), and an increase in Sb, Se, and S contents; the appearance of Te, Cu, Zn, and Fe is notable. All previously established trace elements—Hg, Au, Sb, Se, Te, Cu, Zn, Fe, and S—are contained in native silver of Au-Ag-Pb ore. In addition, Pb appears, and silver and gold amalgams are widespread, as well as up to 24.61 wt % Hg and 11.02 wt % Au. Comparison of trace element concentrations in native silver at the Rogovik deposit with the literature data, based on their solubility in solid silver, shows that the content of chalcogenides (S, Se, Te) exceeds saturated concentrations. Possible mechanisms by which elevated concentrations of these elements are achieved in native silver are discussed. It is suggested that the appearance of silver amalgams, which is unusual for Au-Ag mineralization

  18. Prospectivity analysis of gold and iron oxide copper-gold-(silver mineralizations from the Faina Greenstone Belt, Brazil, using multiple data sets

    Directory of Open Access Journals (Sweden)

    Daniela Schievano de Campos

    Full Text Available ABSTRACT: The Faina Greenstone Belt is located in the southern sector of the Goiás Archean Block and has been investigated since the 18th century because of its gold deposits. Recent studies have revealed the polymetallic potential of the belt, which is indicated by anomalous levels of Ag, Cu, Fe and Co in addition to Mn, Ba, Li, Ni, Cr and Zn. This study was developed based on a detailed analysis of two selected target sites, Cascavel and Tinteiro, and multiple data sets, such as airborne geophysics, geochemistry and geological information. These datasets were used to create a final prospectivity map using the fuzzy logic technique. The gold mineralization of Cascavel target is inserted in an orogenic system and occurs in two overlapping quartz veins systems, called Mestre-Cascavel and Cuca, embedded in quartzite with an average thickness 50 cm and guidance N45º-60ºW/25ºSW with free coarse gold in grains 2-3 mm to 3 cm. The prospectivity map created for this prospect generated four first-order favorable areas for mineralization and new medium-favorability foci. The Tinteiro area, derived from studies conducted by Orinoco do Brasil Mineração Ltda., shows polymetallic mineralization associated with an iron oxide-copper-gold ore deposit (IOCG system posterior to Cascavel target mineralization. Its prospectivity map generated 19 new target sites with the potential for Au, Cu and Ag mineralization, suggesting new directions for future prospecting programs.

  19. Biomedical and Catalytic Applications of Gold and Silver-Gold Alloy Nanoparticles Biosynthesized Using Cell-Free Extract of Bacillus Safensis LAU 13: Antifungal, Dye Degradation, Anti-Coagulant and Thrombolytic Activities.

    Science.gov (United States)

    Ojo, Sunday A; Lateef, Agbaje; Azeez, Musibau A; Oladejo, Suliat M; Akinwale, Abiola S; Asafa, Tesleem B; Yekeen, Taofeek A; Akinboro, Akeem; Oladipo, Iyabo C; Gueguim-Kana, Evariste B; Beukes, Lorika S

    2016-07-01

    This study investigated the green biosynthesis of gold (Au) and silver-gold alloy (Ag-Au) nanoparticles using cell-free extract of Bacillus safensis LAU 13 strain (GenBank accession No: KJ461434). The biosynthesized AuNPs and Ag-AuNPs were characterized using UV-Vis spectroscopy, Fourier-transform infrared spectroscopy, and transmission electron microscopy. Evaluation of the antifungal activities, degradation of malachite green, anti-coagulation of blood, and thrombolysis of human blood clot by the biosynthesized nanoparticles were investigated. The AuNPs and Ag-AuNPs had maximum absorbance at 561 and 545 nm, respectively. The FTIR peaks at 3318, 2378, 2114, 1998, 1636, 1287, 446, 421 cm-1 for AuNPs; and 3310, 2345, 2203, 2033, 1636, 1273, 502, 453, 424 cm-1 for Ag-AuNPs indicated that proteins were the capping and stabilization molecules in the biosynthesized nanoparticles. The particles were fairly spherical in shape with size of 10-45 nm for AuNPs and 13-80 nm for Ag-AuNPs. Moreover, energy dispersive X-ray analysis of AuNPs revealed gold as the most prominent metal in the AuNPs solution, while silver and gold were the most prominent in the case of Ag-AuNPs. Selected area electron diffraction showed the biosynthesized nanoparticles as crystal structures with ring shape pattern. AuNPs and Ag-AuNPs displayed growth inhibitions of 66.67-90.78% against strains of Aspergillus fumigatus and A. niger at concentration of 200 μg/ml , and remarkable degradation (> 90%) of malachite green after 48 h. Furthermore, the nanoparticles prevented coagulation of blood, and also completely dissolved blood clots, indicating the biomedical potential of AuNPs and Ag-AuNPs in the management of blood coagulation disorders. This is the first report of the synthesis of AuNPs and Ag-AuNPs using a strain of B. safensis for biomedical and catalytic applications.

  20. Agro-Industrial Wastes for Production of Biosurfactant by Bacillus subtilis ANR 88 and Its Application in Synthesis of Silver and Gold Nanoparticles

    Directory of Open Access Journals (Sweden)

    Ashwini N. Rane

    2017-03-01

    Full Text Available Biosurfactants, surface-active amphiphilic compounds, despite having a wide range of applications, have a high cost of production, which severely restricts their use. For cheaper production of biosurfactant, we investigated the potential of the indigenously isolated biosurfactant producing organism, Bacillus subtilis ANR 88, to grow on different cheap carbon sources (molasses, whey, and extracts of potato peels, orange peels, banana peels, and bagasse. We found that, B. subtilis ANR 88 used significant amounts of total sugar to produce cell biomass and biosurfactant. The biosurfactant production in minimal medium containing glucose as sole source of carbon was 0.207 g/l and the same with molasses as carbon source was 0.241 g/l. With whey as carbon source, isolate failed to produce biosurfactant. Amongst the extracts of the agro-wastes, the extracts of bagasse and orange peels gave 0.127 and 0.089 g/l of biosurfactant respectively. One-variable-at-a-time (OVAT studies carried out to optimize the production of biosurfactant by B. subtilis ANR 88 resulted into maximum biosurfactant yield of 0.513 g/l in medium: molasses 4%, ammonium ferric citrate 0.25%, pH 7. Plackett–Burman design based statistical method for optimization increased the production of biosurfactant to 0.746 g/l, which is 3.6-fold of that produced on glucose. The biosurfactant produced by B. subtilis ANR 88 was analyzed by Fourier Transform Infrared Spectroscopy (FT-IR; it showed that the biosurfactant contained alkyl as well as peptide groups. The biosurfactant of B. subtilis ANR 88 was found effective in the synthesis of silver as well as gold nanoparticles in the total absence of conventional chemical reducing agents. Interestingly, nanoparticles produced were almost uniform in their size and shapes i.e., spherical silver (4–18 nm and hexagonal gold nanoparticles (40–60 nm, as evident in TEM images.

  1. Synthesis of silver and gold nanoparticles using Jasminum nervosum leaf extract and its larvicidal activity against filarial and arboviral vector Culex quinquefasciatus Say (Diptera: Culicidae).

    Science.gov (United States)

    Lallawmawma, H; Sathishkumar, Gnanasekar; Sarathbabu, Subburayan; Ghatak, Souvik; Sivaramakrishnan, Sivaperumal; Gurusubramanian, Guruswami; Kumar, Nachimuthu Senthil

    2015-11-01

    Silver and gold nanoparticles of Jasminum nervosum L. had unique optical properties such as broad absorbance band in the visible region of the electromagnetic spectrum. Characterization of the nanoparticles using UV spectrophotometer, Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy confirmed that the particles were silver (AgNPs) and gold (AuNPs) ranging between 4-22 and 2-20 nm with an average particles size of 9.4 and 10 nm, respectively. AgNPs and AuNPs of J. nervosum had high larvicidal activity on the filarial and arboviral vector, Culex quinquefasciatus, than the leaf aqueous extract. Observed lethal concentrations (LC50 and LC95) against the third instar larvae were 57.40 and 144.36 μg/ml for AgNPs and 82.62 and 254.68 μg/ml for AuNPs after 24 h treatment, respectively. The lethal time to kill 50% of C. quinquefasciatus larvae were 2.24 and 4.51 h at 150 μg/ml of AgNPs and AuNPs, respectively, while in the case of aqueous leaf extract of J. nervosum it was 9.44 h at 500 μg/ml (F 2,14 = 397.51, P < 0.0001). The principal component analysis plot presented differential clustering of the aqueous leaf extract, AgNP and AuNPs in relation to lethal dose and lethal time. It is concluded from the present findings that the biosynthesised AgNPs and AuNPs using leaf aqueous extract of J. nervosum could be an environmentally safer nanobiopesticide, and provided potential larvicidal effect on C. quinquefasciatus larvae which could be used for prevention of several dreadful diseases.

  2. Production of porous filter elements from PEUAPM nanocomposites and silver nanoparticles; Producao de elementos filtrantes porosos a partir de nanocompositos de PEUAPM e nanoparticulas de prata

    Energy Technology Data Exchange (ETDEWEB)

    Bizzo, M.A.; Hui, W.S., E-mail: mbizzo@usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Escola Politecnica. Departamento de Engenharia Metalurgica e de Materiais

    2014-07-01

    The production of filter elements for water based in polymers is widespread in the market, but has an undesirable characteristic: they are not efficient and able to retain or eliminate microorganisms at all times. This paper proposes to produce nanocomposite filters with biocidal properties composed of ultra-high molecular weight polyethylene(UHMWPE) and silver nanoparticles, the UHMWPE is responsible for the uniform porous structure of the filters and the silver nanoparticles incorporated on the polymer are responsible for the biocide action. Particulate polymer that presents a different particle size curve was used for sintering the filters. Samples of filter elements obtained in this work were characterized by the techniques of X-ray diffraction, scanning electron microscopy and EDS microanalysis. The results indicated a porosity of approximately 49% in the filter, and the formation of the nanocomposite. key-words: nanocomposites, silver, UHMWPE, filter elements. (author)

  3. Site-Selective Controlled Dealloying Process of Gold-Silver Nanowire Array: a Simple Approach towards Long-Term Stability and Sensitivity Improvement of SERS Substrate

    Science.gov (United States)

    Wiriyakun, Natta; Pankhlueab, Karuna; Boonrungsiman, Suwimon; Laocharoensuk, Rawiwan

    2016-12-01

    Limitations of achieving highly sensitive and stable surface-enhanced Raman scattering (SERS) substrate greatly concern the suitable method for fabrication of large-area plasmonic nanostructures. Herein we report a simple approach using template-based synthesis to create a highly ordered two-dimensional array of gold-silver alloy nanowires, followed by the controlled dealloying process. This particular step of mild acid etching (15%v/v nitric acid for 5 min) allowed the formation of Raman hot spots on the nanowire tips while maintaining the integrity of highly active alloy composition and rigid nanowire array structure. Full consideration of SERS substrate performance was accomplished using 4-mercaptobenzoic acid (4-MBA) as a probe molecule. Exceedingly higher SERS signal (150-fold) can be achieved with respect to typical gold film substrate. Moreover, an excellent stability of SERS substrate was also determined for over 3 months storage time. In contrast to the previous studies which stability improvement was accomplished at a cost of sensitivity reduction, the simultaneous improvement of sensitivity and stability makes the controlled dealloying process an excellent choice of SERS substrate fabrication. In addition, uniformity and reproducibility studies indicated satisfactory results with the acceptable values of relative standard deviation.

  4. Aggregation-induced emission from gold nanoclusters for use as a luminescence-enhanced nanosensor to detect trace amounts of silver ions.

    Science.gov (United States)

    Li, Bingzhi; Wang, Xi; Shen, Xin; Zhu, Wanying; Xu, Lei; Zhou, Xuemin

    2016-04-01

    Several research have reported that silver ions (Ag(+)) could enhance the photoluminescence of some kinds of gold nanoclusters (AuNCs), and redox reaction involved mechanisms were recognized as the main reason to cause such phenomenon. However, in this work, we found that Ag(+) could enhance the luminescence of aggregation-induced emission gold nanoclusters (AIE-AuNCs) without valence state change. Upon addition of Ag(+), the luminescence of AIE-AuNCs enhanced instantly by 7.2 times with a red-shift of emission peak and a complete restoration of luminescence features was observed when Ag(+) was removed. A cost-effective, rapid-response, highly sensitive and selective method to detect trace amount of Ag(+) has thereby been established using AIE-AuNCs as a nanosensor. This analytical method exhibited a linear range of 0.5nM-20μM with a limit of detection of 0.2nM and it showed great promise for Ag(+) monitoring in environmental water. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Gold-Silver mineralization in porphyry-epithermal systems of the Baimka trend, western Chukchi Peninsula, Russia

    Science.gov (United States)

    Nikolaev, Yu. N.; Baksheev, I. A.; Prokofiev, V. Yu.; Nagornaya, E. V.; Marushchenko, L. I.; Sidorina, Yu. N.; Chitalin, A. F.; Kal'ko, I. A.

    2016-07-01

    Mineralogical, fluid inclusion, and geochemical studies of precious metal mineralization within the Baimka trend in the western Chukchi Peninsula have been preformed. Porphyry copper-molybdenum-gold deposits and prospects of the Baimka trend are spatially related to monzonitic rocks of the Early Cretaceous Egdygkych Complex. Four types of precious metal-bearing assemblages have been identified: (1) chalcopyrite + bornite + quartz with high-fineness native gold enclosed in bornite, (2) low-Mn dolomite + quartz + sulfide (chalcopyrite, sphalerite, galena, tennantite-tetrahedrite) ± tourmaline with low-fineness native gold and hessite, (3) rhodochrosite + high-Mn dolomite + quartz + sulfide (chalcopyrite, sphalerite, galena, tennantite- tetrahedrite) with low-fineness native gold, electrum, acanthite, Ag and Au-Ag tellurides, and Ag sulfosalts, and (4) calcite + quartz + sulfide (chalcopyrite, sphalerite, galena) with low-fineness native gold, Ag sulfides and selenides, and Ag-bearing sulfosalts. Study of fluid inclusions from quartz, sphalerite, and fluorite have revealed that hydrothermal ores within the Baimka trend precipitated from fluids with strongly variable salinity at temperatures and pressures ranging from 594 to 104°C and from 1200 to 170 bar, respectively. An indicator of vertical AgPbZn/CuBiMo geochemical zoning is proposed. The value range of this indicator makes it possible to estimate the erosion level of the porphyry-epithermal system. The erosion level of the Baimka deposits and prospects deepens in the following order: Vesenny deposit → Pryamoi prospect → Nakhodka prospect → Peschanka deposit → III Vesenny prospect.

  6. Formation and emission of gold and silver carbide cluster ions in a single C60- surface impact at keV energies: experiment and calculations.

    Science.gov (United States)

    Cohen, Y; Bernshtein, V; Armon, E; Bekkerman, A; Kolodney, E

    2011-03-28

    Impact of fullerene ions (C(60)(-)) on a metallic surface at keV kinetic energies and under single collision conditions is used as an efficient way for generating gas phase carbide cluster ions of gold and silver, which were rarely explored before. Positively and negatively charged cluster ions, Au(n)C(m)(+) (n = 1-5, 1 ≤ m ≤ 12), Ag(n)C(m)(+) (n = 1-7, 1 ≤ m ≤ 7), Au(n)C(m)(-) (n = 1-5, 1 ≤ m ≤ 10), and Ag(n)C(m)(-) (n = 1-3, 1 ≤ m ≤ 6), were observed. The Au(3)C(2)(+) and Ag(3)C(2)(+) clusters are the most abundant cations in the corresponding mass spectra. Pronounced odd/even intensity alternations were observed for nearly all Au(n)C(m)(+/-) and Ag(n)C(m)(+/-) series. The time dependence of signal intensity for selected positive ions was measured over a broad range of C(60)(-) impact energies and fluxes. A few orders of magnitude immediate signal jump instantaneous with the C(60)(-) ion beam opening was observed, followed by a nearly constant plateau. It is concluded that the overall process of the fullerene collision and formation∕ejection of the carbidic species can be described as a single impact event where the shattering of the incoming C(60)(-) ion into small C(m) fragments occurs nearly instantaneously with the (multiple) pickup of metal atoms and resulting emission of the carbide clusters. Density functional theory calculations showed that the most stable configuration of the Au(n)C(m)(+) (n = 1, 2) clusters is a linear carbon chain with one or two terminal gold atoms correspondingly (except for a bent configuration of Au(2)C(+)). The calculated AuC(m) adiabatic ionization energies showed parity alternations in agreement with the measured intensity alternations of the corresponding ions. The Au(3)C(2)(+) ion possesses a basic Au(2)C(2) acetylide structure with a π-coordinated third gold atom, forming a π-complex structure of the type [Au(π-Au(2)C(2))](+). The calculation shows meaningful contributions of direct gold-gold bonding to

  7. Geophagy practices and the content of chemical elements in the soil eaten by pregnant women in artisanal and small scale gold mining communities in Tanzania

    National Research Council Canada - National Science Library

    Nyanza, Elias C; Joseph, Mary; Premji, Shahirose S; Thomas, Deborah Sk; Mannion, Cynthia

    2014-01-01

    ...). The present study examined geophagy practices of pregnant women in a gold mining area of Geita District in northwestern Tanzania, and also examined the potential for exposure to chemical elements...

  8. Structures of Gold(I) and Silver(I) Thiolate Complexes of Medicinal Interest: A Review and Recent Results

    OpenAIRE

    Howard-Lock, Helen E.

    1999-01-01

    We review the crystal structures, electrospray ionization mass spectra (ESI-MS) data and chiral HPLC data for the racemic and optically pure mononuclear AuL2 complexes, and for racemic [AuLI]n and optically pure [AgLII]n polymers (LI = thiomalate, LII = D-penicillamine). We postulate an equilibrium between polymeric, mononuclear and free ligand species for [AuLII]n (gold sodium thiomalate or GST). The ESI-MS results clearly show a tetrameric principal species in the 1:1 gold polymers, [AuLI]n...

  9. Oxygen isotope exchange with quartz during pyrolysis of silver sulfate and silver nitrate.

    Science.gov (United States)

    Schauer, Andrew J; Kunasek, Shelley A; Sofen, Eric D; Erbland, Joseph; Savarino, Joel; Johnson, Ben W; Amos, Helen M; Shaheen, Robina; Abaunza, Mariana; Jackson, Terri L; Thiemens, Mark H; Alexander, Becky

    2012-09-30

    Triple oxygen isotopes of sulfate and nitrate are useful metrics for the chemistry of their formation. Existing measurement methods, however, do not account for oxygen atom exchange with quartz during the thermal decomposition of sulfate. We present evidence for oxygen atom exchange, a simple modification to prevent exchange, and a correction for previous measurements. Silver sulfates and silver nitrates with excess (17)O were thermally decomposed in quartz and gold (for sulfate) and quartz and silver (for nitrate) sample containers to O(2) and byproducts in a modified Temperature Conversion/Elemental Analyzer (TC/EA). Helium carries O(2) through purification for isotope-ratio analysis of the three isotopes of oxygen in a Finnigan MAT253 isotope ratio mass spectrometer. The Δ(17)O results show clear oxygen atom exchange from non-zero (17)O-excess reference materials to zero (17)O-excess quartz cup sample containers. Quartz sample containers lower the Δ(17)O values of designer sulfate reference materials and USGS35 nitrate by 15% relative to gold or silver sample containers for quantities of 2-10 µmol O(2). Previous Δ(17)O measurements of sulfate that rely on pyrolysis in a quartz cup have been affected by oxygen exchange. These previous results can be corrected using a simple linear equation (Δ(17)O(gold) = Δ(17)O(quartz) * 1.14 + 0.06). Future pyrolysis of silver sulfate should be conducted in gold capsules or corrected to data obtained from gold capsules to avoid obtaining oxygen isotope exchange-affected data. Copyright © 2012 John Wiley & Sons, Ltd.

  10. Silver and gold nanoparticles exposure to in vitro cultured retina--studies on nanoparticle internalization, apoptosis, oxidative stress, glial- and microglial activity.

    Directory of Open Access Journals (Sweden)

    Erika Söderstjerna

    Full Text Available The complex network of neuronal cells in the retina makes it a potential target of neuronal toxicity--a risk factor for visual loss. With growing use of nanoparticles (NPs in commercial and medical applications, including ophthalmology, there is a need for reliable models for early prediction of NP toxicity in the eye and retina. Metal NPs, such as gold and silver, gain much of attention in the ophthalmology community due to their potential to cross the barriers of the eye. Here, NP uptake and signs of toxicity were investigated after exposure to 20 and 80 nm Ag- and AuNPs, using an in vitro tissue culture model of the mouse retina. The model offers long-term preservation of retinal cell types, numbers and morphology and is a controlled system for delivery of NPs, using serum-free defined culture medium. AgNO3-treatment was used as control for toxicity caused by silver ions. These end-points were studied; gross morphological organization, glial activity, microglial activity, level of apoptosis and oxidative stress, which are all well described as signs of insult to neural tissue. TEM analysis demonstrated cellular- and nuclear uptake of all NP types in all neuronal layers of the retina. Htx-eosin staining showed morphological disruption of the normal complex layered retinal structure, vacuole formation and pyknotic cells after exposure to all Ag- and AuNPs. Significantly higher numbers of apoptotic cells as well as an increased number of oxidative stressed cells demonstrated NP-related neuronal toxicity. NPs also caused increased glial staining and microglial cell activation, typical hallmarks of neural tissue insult. This study demonstrates that low concentrations of 20 and 80 nm sized Ag- and AuNPs have adverse effects on the retina, using an organotypic retina culture model. Our results motivate careful assessment of candidate NP, metallic or-non-metallic, to be used in neural systems for therapeutic approaches.

  11. Silver and gold nanoparticles exposure to in vitro cultured retina--studies on nanoparticle internalization, apoptosis, oxidative stress, glial- and microglial activity.

    Science.gov (United States)

    Söderstjerna, Erika; Bauer, Patrik; Cedervall, Tommy; Abdshill, Hodan; Johansson, Fredrik; Johansson, Ulrica Englund

    2014-01-01

    The complex network of neuronal cells in the retina makes it a potential target of neuronal toxicity--a risk factor for visual loss. With growing use of nanoparticles (NPs) in commercial and medical applications, including ophthalmology, there is a need for reliable models for early prediction of NP toxicity in the eye and retina. Metal NPs, such as gold and silver, gain much of attention in the ophthalmology community due to their potential to cross the barriers of the eye. Here, NP uptake and signs of toxicity were investigated after exposure to 20 and 80 nm Ag- and AuNPs, using an in vitro tissue culture model of the mouse retina. The model offers long-term preservation of retinal cell types, numbers and morphology and is a controlled system for delivery of NPs, using serum-free defined culture medium. AgNO3-treatment was used as control for toxicity caused by silver ions. These end-points were studied; gross morphological organization, glial activity, microglial activity, level of apoptosis and oxidative stress, which are all well described as signs of insult to neural tissue. TEM analysis demonstrated cellular- and nuclear uptake of all NP types in all neuronal layers of the retina. Htx-eosin staining showed morphological disruption of the normal complex layered retinal structure, vacuole formation and pyknotic cells after exposure to all Ag- and AuNPs. Significantly higher numbers of apoptotic cells as well as an increased number of oxidative stressed cells demonstrated NP-related neuronal toxicity. NPs also caused increased glial staining and microglial cell activation, typical hallmarks of neural tissue insult. This study demonstrates that low concentrations of 20 and 80 nm sized Ag- and AuNPs have adverse effects on the retina, using an organotypic retina culture model. Our results motivate careful assessment of candidate NP, metallic or-non-metallic, to be used in neural systems for therapeutic approaches.

  12. Oxidative stress and repetitive element methylation changes in artisanal gold miners occupationally exposed to mercury

    Directory of Open Access Journals (Sweden)

    Diana M. Narváez

    2017-09-01

    Full Text Available Mercury (Hg exposure is a public health concern due to its persistence in the environment and its high toxicity. Such toxicity has been associated with the generation of oxidative stress in occupationally exposed subjects, such as artisanal gold miners. In this study, we characterize occupational exposure to Hg by measuring blood, urine and hair levels, and investigate oxidative stress and DNA methylation associated with gold mining. To do this, samples from 53 miners and 36 controls were assessed. We show higher levels of oxidative stress marker 8-OHdG in the miners. Differences in LINE1 and Alu(Yb8 DNA methylation between gold miners and control group are present in peripheral blood leukocytes. LINE1 methylation is positively correlated with 8-OHdG levels, while XRCC1 and LINE1 methylation are positively correlated with Hg levels. These results suggest an effect of Hg on oxidative stress and DNA methylation in gold miners that may have an impact on miners’ health.

  13. Applying the silver-tube introduction method for thermal conversion elemental analyses and a new δ2H value for NBS 22 oil

    Science.gov (United States)

    Coplen, Tyler B.; Qi, Haiping

    2010-01-01

    The δ2HVSMOW–SLAP value of total hydrogen of the international measurement standard NBS 22 oil was determined by a new method of sealing water in silver tubes for use in a thermal conversion elemental analysis (TC/EA) reduction unit. The isotopic fractionation of water due to evaporation is virtually non-existent in this silver-tube method. A new value for the δ2HVSMOW–SLAP of NBS 22 oil, calibrated with isotopic reference waters, was determined to be −116.9 ± 0.8‰ (1σ and n = 31).

  14. Trace elements in pyrite from the Petropavlovsk gold-porphyry deposit (Polar Urals): Results of LA-ICP-MS analysis

    Science.gov (United States)

    Vikentiev, I. V.; Abramova, V. D.; Ivanova, Yu. N.; Tyukova, E. E.; Kovalchuk, E. V.; Bortnikov, N. S.

    2016-09-01

    The first study of the pyrite composition from gold deposit in the Urals by the LA-ICP-MS method has been carried out. In the pyrite high contents of Au (up to 49 ppm), Ag (105 ppm), and other micronutrients (As (417 ppm), Ag (105 ppm), Co (2825 ppm), Ni (75 ppm), Cu (1442 ppm), and Zn (19 ppm)) were detected. Furthermore, an increase in the concentrations of trace elements from early to later generations of pyrite (from Py-1 to Py-3) Au, Ag, Te, Sn, Te, and Bi and depletion of Co, As, and Ni have been revealed. Gold is mainly concentrated in the pyrite of the second generation (Py-2) and occurs mostly as an "invisible" form with prevalence of nano-sized particles of native Au, similar in composition to electrum AuAg, as well as Au- and Au-Ag tellurides. The presence in the pyrite of admixtures of Cu, Co, Ni, Pb, As, and Te, possibly favors the entrance of Au into it (up to 5-50 ppm), while in common pyrite, poor in the mentioned impurities, the gold content is <1 ppm.

  15. Geologic setting and genesis of the Mule Canyon low-sulfidation epithermal gold-silver deposit, north-central Nevada

    Science.gov (United States)

    John, D.A.; Hofstra, A.H.; Fleck, R.J.; Brummer, J.E.; Saderholm, E.C.

    2003-01-01

    /or marcasite veins. Ore minerals consist mostly of electrum and Ag sulfide and selenide minerals, with minor to major amounts of pyrite, marcasite, and arsenopyrite, and local stibnite. Both types of ores have similar geochemical signatures, characterized by high Au, Ag, As, Sb, and Se contents, locally high Hg, Mo, Tl, and W contents, and low Cu, Pb, and Zn contents. Stable isotope data indicate that ore fluids consisted dominantly of meteoric water that evolved by deep circulation through Paleozoic sedimentary rocks at low water/rock ratios (about 1) and high temperatures (>200??C). Calculated isotopic compositions of ore fluids are ??18OH2O = -3 to -7 per mil, ??DH2O = -107 to -124 per mil, ??13CCO2 = 0 to -6 per mil, and ??34SH2S = -3 to +8 per mil. The ore fluids obtained much of their H2S and CO2 and probably scavenged ore metals and trace elements from the Paleozoic sedimentary rocks. Some H2S and CO2 may have been derived from degassing Miocene magmas. Mule Canyon formed at shallow depths, probably about 100 m below the paleosurface. Ore fluids were dilute, nearly neutral in pH, reduced, H2S-rich, and CO2-bearing. Peak temperatures in ore zones reached 230?? to 265??C at nearly lithostatic pressures when some crystalline quartz ?? adularia precipitated, but most ore formed at temperatures <200??C at near hydrostatic pressures and was accompanied by precipitation of opaline and chalcedonic silica ?? adularia ?? calcite and dolomite. Deposition of gold in As-rich overgrowths on pyrite and/or marcasite in disseminated ores occurred owing to decreasing H2S in the ore fluids resulting from sulfidation reactions. Later electrum and Ag selenide precipitation in open spaces occurred owing to boiling, loss of H2S to the vapor phase, and cooling. Mule Canyon is similar to most other low-sulfidation Au-Ag deposits associated with Miocene tholeiitic bimodal basalt-rhyolite magmatism in the Great Basin, such as Sleeper, Midas, and Buckhorn. Major differences at Mule Canyon are

  16. Residence of silver in mineral deposits of the Thunder Mountain caldera complex, Central Idaho, U.S.A.

    Science.gov (United States)

    Leonard, B.F.; Christian, R.P.

    1987-01-01

    Silver is an accessory element in gold, antimony, and tungsten deposits of the caldera complex. Most of the deposits are economically of low grade and genetically of xenothermal or epithermal character. Their gold- and silver-bearing minerals are usually disseminated, fine grained, and difficult to study. Sparsely disseminated pyrite and arsenoprite are common associates. Identified silver minerals are: native silver and electrum; the sulfides acanthite, argentite (the latter always inverted to acanthite), and members of the Silberkies group; the sulfosalts matildite, miargyrite, pyrargyrite, argentian tetrahedrite, and unnamed Ag-Sb-S and Ag-Fe-Sb-S minerals; the telluride hessite and the selenide naumannite; halides of the cerargyrite group; and the antimonate stetefeldtite. Suspected silver minerals include the sulfide uytenbogaardtite and the sulfosalts andorite, diaphorite, and polybasite. Electrum, acanthite, and argentian tetrahedrite are common, though nowhere abundant. The other silver minerals are rare. Silver is present as a minor element in the structure of some varieties of other minerals. These include arsenopyrite, chalcopyrite, chalcostibite, covelline, digenite, galena, sphalerite, and stibnite. The search for adventitious Ag in most of these minerals has been cursory. The results merely indicate that elemental silver is not confined to discrete silver minerals and is, therefore, an additional complication for the recovery of silver-bearing material from some deposits. Silver occurs cryptically in some plants of the region. At Red Mountain, for example, the ashed sapwood of Douglas-fir (Pseudotsuga menziesii) contains 2 to 300 ppm Ag. Silver in the ashed wood is roughly 100 times as abundant as it is in soil. The phenomenon, useful in biogeochemical exploration, deserves the attention of mineralogists. ?? 1987 Springer-Verlag.

  17. Antibody Conjugated, Raman Tagged Hollow Gold-Silver Nanospheres for Specific Targeting and Multimodal Dark-Field/SERS/Two Photon-FLIM Imaging of CD19(+) B Lymphoblasts.

    Science.gov (United States)

    Nagy-Simon, Timea; Tatar, Andra-Sorina; Craciun, Ana-Maria; Vulpoi, Adriana; Jurj, Maria-Ancuta; Florea, Adrian; Tomuleasa, Ciprian; Berindan-Neagoe, Ioana; Astilean, Simion; Boca, Sanda

    2017-06-28

    In this Research Article, we propose a new class of contrast agents for the detection and multimodal imaging of CD19(+) cancer lymphoblasts. The agents are based on NIR responsive hollow gold-silver nanospheres conjugated with antiCD19 monoclonal antibodies and marked with Nile Blue (NB) SERS active molecules (HNS-NB-PEG-antiCD19). Proof of concept experiments on specificity of the complex for the investigated cells was achieved by transmission electron microscopy (TEM). The microspectroscopic investigations via dark field (DF), surface-enhanced Raman spectroscopy (SERS), and two-photon excited fluorescence lifetime imaging microscopy (TPE-FLIM) corroborate with TEM and demonstrate successful and preferential internalization of the antibody-nanocomplex. The combination of the microspectroscopic techniques enables contrast and sensitivity that competes with more invasive and time demanding cell imaging modalities, while depth sectioning images provide real time localization of the nanoparticles in the whole cytoplasm at the entire depth of the cells. Our findings prove that HNS-NB-PEG-antiCD19 represent a promising type of new contrast agents with great possibility of being detected by multiple, non invasive, rapid and accessible microspectroscopic techniques and real applicability for specific targeting of CD19(+) cancer cells. Such versatile nanocomplexes combine in one single platform the detection and imaging of cancer lymphoblasts by DF, SERS, and TPE-FLIM microspectroscopy.

  18. Agro-industrial waste-mediated synthesis and characterization of gold and silver nanoparticles and their catalytic activity for 4-nitroaniline hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Dauthal, Preeti; Mukhopadhyay, Mausumi [S.V. National Institute of Technology, Surat (India)

    2015-05-15

    The biosynthesis of gold (Au-NPs) and silver nanoparticles (Ag-NPs) using agro-industrial waste Citrus aurantifolia peel extract as a bio-reducing agent is reported. Catalytic activity of nanoparticles (NPs) was evaluated for hydrogenation of anthropogenic pollutant 4-nitroaniline (4-NA). Both synthesized NPs were nearly spherical and distributed in size range of 6-46 and 10-32 nm for Au-NPs and Ag-NPs, respectively. XRD analysis revealed face centered cubic (fcc) structure of both NPs. ζ potential value obtained from colloidal solution of Au-NPs and Ag-NPs was −28.0 and −26.1mV, respectively, indicating the stability of the NPs in colloidal solution. FTIR spectra supported the role of citric and ascorbic acids of peel extract for biosynthesis and stabilization of NPs. The biosynthesized NPs exhibited excellent catalytic activity for hydrogenation of 4-NA in the presence of NaBH{sub 4}.

  19. Bioleaching of Gold and Silver from Waste Printed Circuit Boards by Pseudomonas balearica SAE1 Isolated from an e-Waste Recycling Facility.

    Science.gov (United States)

    Kumar, Anil; Saini, Harvinder Singh; Kumar, Sudhir

    2018-02-01

    Indigenous bacterial strain Pseudomonas balearica SAE1, tolerant to e-waste toxicity was isolated from an e-waste recycling facility Exigo Recycling Pvt. Ltd., India. Toxicity tolerance of bacterial strain was analyzed using crushed (particle size ≤150 µm) waste computer printed circuit boards (PCBs)/liter (L) of culture medium. The EC 50 value for SAE1 was 325.7 g/L of the e-waste pulp density. Two-step bioleaching was then applied to achieve the dissolution of gold (Au) and silver (Ag) from the e-waste. To maximize precious metal dissolution, factors including pulp density, glycine concentration, pH level, and temperature were optimized. The optimization resulted in 68.5 and 33.8% of Au and Ag dissolution, respectively, at a pH of 9.0, a pulp density of 10 g/L, a temperature of 30 °C, and a glycine concentration of 5 g/L. This is the first study of Au and Ag bioleaching using indigenous e-waste bacteria and its analysis to determine e-waste toxicity tolerance.

  20. Phototodynamic activity of zinc monocarboxyphenoxy phthalocyane (ZnMCPPc) conjugated to gold silver (AuAg) nanoparticles in melanoma cancer cells

    Science.gov (United States)

    Manoto, Sello L.; Oluwole, David O.; Malabi, Rudzani; Maphanga, Charles; Ombinda-Lemboumba, Saturnin; Nyokong, Tebello; Mthunzi-Kufa, Patience

    2017-02-01

    Photodynamic therapy (PDT) is a minimally invasive therapeutic modality for the treatment of neoplastic and non-neoplastic diseases. In PDT of cancer, irradiation with light of a specific wavelength leads to activation of a photosensitizer which results in generation of reactive oxygen species (ROS) which induces cell death. Many phthalocyanine photosensitizers are hydrophobic and insoluble in water, which limits their therapeutic efficiency. Consequently, advanced delivery systems and strategies are needed to improve the effectiveness of these photosensitizers. Nanoparticles have shown promising results in increasing aqueous solubility, bioavailability, stability and delivery of photosensitizers to their target. This study investigated the photodynamic activity of zinc monocarboxyphenoxy phthalocyanine (ZnMCPPc) conjugated to gold silver (AuAg) nanoparticles in melanoma cancer cells. The photodynamic activity of ZnMCPPc conjugated to AuAg nanoparticles were evaluated using cellular morphology, viability, proliferation and cytotoxicity. Untreated cells showed no changes in cellular morphology, proliferation and cytotoxicity. However, photoactivated ZnMCPPc conjugated to AuAg nanoparticles showed changes in cell morphology and a dose dependent decrease in cellular viability, proliferation and an increase in cell membrane damage. The ZnMCPPc conjugated to AuAg nanoparticles used in this study was highly effective in inducing cell death of melanoma cancer cells.

  1. Broadband optical absorption enhancement of N719 dye in ethanol by gold-silver alloy nanoparticles fabricated under laser ablation technique

    Science.gov (United States)

    Al-Azawi, Mohammed A.; Bidin, Noriah; Abbas, Khaldoon N.; Bououdina, Mohamed; Azzez, Shrook A.

    2016-04-01

    The formation of gold-silver alloy nanoparticles (Au-Ag alloy NPs) by a two-step process with a pulsed Nd:YAG laser without any additives is presented. Mixtures of Au and Ag colloidal suspensions were separately obtained by 1064-nm laser ablation of metallic targets immersed in ethanol. Subsequently, the as-mixed colloidal suspensions were reirradiated by laser-induced heating at the second-harmonic generation (532 nm) for different irradiation periods of time. The absorption spectra and morphology of the colloidal alloys were studied as a function of exposure time to laser irradiation. Transmission electron microscopy revealed the formation of monodispersed spherical nanoparticles with a homogeneous size distribution in all the synthesized samples. UV-vis and photoluminescence spectroscopy measurements were also employed to characterize the changes in the light absorption and emission of N719 dye solution with different concentrations of Au-Ag colloidal alloys, respectively. The localized surface plasmon resonance (LSPR) of Au-Ag alloy NPs enhanced the absorption and fluorescence peak of the dye solution. The mixture of dye molecules with a higher concentration of alloy NPs exhibited an additional coupling of dipole moments with the LSPR, thereby contributing to the improvement of the optical properties of the mixture.

  2. Fabrication of novel compound SERS substrates composed of silver nanoparticles and porous gold nanoclusters: A study on enrichment detection of urea

    Science.gov (United States)

    Li, Yali; Li, Qianwen; Sun, Chengbin; Jin, Sila; Park, Yeonju; Zhou, Tieli; Wang, Xu; Zhao, Bing; Ruan, Weidong; Jung, Young Mee

    2018-01-01

    A new type of surface-enhanced Raman scattering (SERS) substrate was fabricated through the layer-by-layer self-assembly of silver nanoparticles (AgNPs, av. 45 nm in diameter) and porous gold nanoclusters/nanoparticles (AuNPs, av. 143 nm in diameter). The development of the porosity of the AuNPs was investigated, and successful SERS applications of the porous AuNPs were also examined. As compared with AgNP films, the enhancement factor of Ag-Au compound substrates is increased 6 times at the concentration of 10-6 M. This additional enhancement contributes to the trace-amount-detection of target molecules enormously. The contribution is generated through the increase of the usable surface area arising from the nanoscale pores distributed three-dimensionally in the porous AuNPs, which enrich the adsorption sites and hot spots for the adsorption of probe molecules, making the developed nanofilms highly sensitive SERS substrates. The substrates were used for the detection of a physiological metabolite of urea molecules. The results reached to a very low concentration of 1 mM and exhibited good quantitative character over the physiological concentration range (1 ∼ 20 mM) under mimicking biophysical conditions. These results show that the prepared substrate has great potential in the ultrasensitive SERS-based detection and in SERS-based biosensors.

  3. Interaction of glucose-derived carbon quantum dots with silver and gold nanoparticles and its application for the fluorescence detection of 6-thioguanine.

    Science.gov (United States)

    Amjadi, Mohammad; Shokri, Roghayeh; Hallaj, Tooba

    2017-05-01

    The interaction of glucose-derived carbon quantum dots (CQDs) with silver (Ag) and gold (Au) nanoparticles (NPs) was explored by fluorescence spectroscopy. Both metal NPs cause an efficient quenching of CQD fluorescence, which is likely due to the energy transfer process between CQDs as donors and metal NPs as acceptors. The Stern-Volmer plots were evaluated and corresponding quenching constants were found to be 1.9 × 10(10) and 2.2 × 10(8) M(-1) for AgNPs and AuNPs, respectively. The analytical applicability of these systems was demonstrated for turn-on fluorescence detection of the anti-cancer drug, 6-thioguanine. Because the CQD-AgNP system had much higher sensitivity than the CQD-AuNP system, we used it as a selective fluorescence probe in a turn-on assay of 6-thioguanine. Under optimum conditions, the calibration graph was linear from 0.03 to 1.0 μM with a detection limit of 0.01 μM. The developed method was applied to the analysis of human plasma samples with satisfactory results. Copyright © 2016 John Wiley & Sons, Ltd.

  4. Capture of elemental and organic iodine from dilute gas streams by silver-exchanged mordenite

    Energy Technology Data Exchange (ETDEWEB)

    Bruffey, S.H.; Jubin, R.T.; Jordan, J.A. [Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831 (United States)

    2016-07-01

    The treatment of off-gas streams arising from reprocessing of used nuclear fuel (UNF) is an area of active study by the U.S. Department of Energy. Such off-gas streams contain volatile fission products, including long-lived {sup 129}I. Although {sup 129}I is released into the off-gas at multiple points within the chemical reprocessing flowsheet, previous research has focused on removal from the dissolver off-gas stream (DOG). The DOG is expected to contain up to 98% of iodine in UNF at ppm levels within the stream. Other off-gas streams will also contain iodine but at substantially lower concentrations. Recent work has shown that compliance with U.S. regulations will likely require capture of iodine from these dilute streams in addition to capture from DOG. In particular, the vessel off-gas (VOG) stream is expected to contain 1-3% of the total iodine inventory at ppb concentrations. A review of literature also indicates that the speciation of iodine in the VOG stream will differ from that of the DOG, with the DOG containing primarily I{sub 2} and the VOG containing a mixture of I{sub 2} and organic iodine species. Silver-exchanged mordenite (AgZ) has been identified for use in the removal of iodine from off-gas streams. It is an effective capture material for I{sub 2} at the concentrations expected in the DOG, but little is known about its performance in gas streams that may contain both I{sub 2} and organic iodides at very dilute concentrations. The experiments to be described were designed to separately characterize the adsorption of I{sub 2} and methyl iodide on AgZ through extended duration testing. Simulated vessel off-gases containing low levels of either I{sub 2} or methyl iodide were contacted with AgZ sorbent beds for up to four months. Through the use of sorbent beds in series and varied sampling times, key parameters such as adsorption rate, decontamination factor, and performance over time could be determined for the capture of each species by AgZ. This

  5. Detection of mercury ions using silver telluride nanoparticles as a substrate and recognition element through surface-enhanced Raman scattering

    Directory of Open Access Journals (Sweden)

    Chia-Wei eWang

    2013-10-01

    Full Text Available In this paper we unveil a new sensing strategy for sensitive and selective detection of Hg2+ through surface-enhanced Raman scattering (SERS using Ag2Te nanoparticles (NPs as a substrate and recognition element and rhodamine 6G (R6G as a reporter. Ag2Te NPs prepared from tellurium dioxide and silver nitrate and hydrazine in aqueous solution containing sodium dodecyl sulfate at 90ºC with an average size of 26.8 ± 4.1 nm (100 counts have strong SERS activity. The Ag2Te substrate provides strong SERS signals of R6G with an enhancement factor of 3.6 × 105 at 1360 cm-1, which is comparable to Ag NPs. After interaction of Ag2Te NPs with Hg2+, some HgTe NPs are formed, leading to decreases in the SERS signal of R6G, mainly because HgTe NPs relative to Ag2Te NPs have weaker SERS activity. Under optimum conditions, this SERS approach using Ag2Te as substrates is selective for the detection of Hg2+, with a limit of detection of 3 nM and linearity over 10-150 nM. The practicality of this approach has been validated for the determination of the concentrations of spiked Hg2+ in a pond water sample.

  6. EDXRF study of Indian punch-marked silver coins

    Science.gov (United States)

    Vijayan, V.; Rautray, T. R.; Basa, D. K.

    2004-09-01

    Coins are important archaeological objects that can provide valuable information regarding coin minting methodology and provenance as well as politics and economics of the time. Punch-marked coins are the oldest known numismatics used in ancient India. 23 Indian punch-marked silver coins were analysed, for the first time, by using multi-elemental non-destructive energy dispersive X-ray fluorescence (EDXRF) technique. Our study reveals that silver, copper, iron, gold and lead are the significant constituents of the Indian punch marked silver coins, with minor/trace of elements like Ti, Cr, Co, Ni, As and Y also seems to indicate the fragmentation as well as the impoverishment of the power for the regimes that had produced the studied coins.

  7. Palaeozoic Magmatism Associated with Gold-Antimony-Tin-Tungsten-Lead-Zinc and Silver Mineralization in the Neighbouring of Porto, Northern Portugal

    Science.gov (United States)

    Couto, Helena; Roger, Guy

    2017-12-01

    In the studied area there are evidences of Palaeozoic magmatism along the stratigraphic succession from Cambrian to Carboniferous. Igneous, volcanic and sub-volcanic rocks occur along and around a significant Variscan structure, the Valongo Anticline, an asymmetrical antiform anticline, trending NW-SE, located in Central Iberian Zone in the neighbourhood of Porto (Northern Portugal). Mineralizations of gold-antimony-tin-tungsten-lead-zinc and silver occur in the area. Magmatism related to acid and basic subvolcanic and volcanic rocks occurs interbedded in Montalto Formation metasediments (conglomerates, quartzite, wakes and slates) of Cambrian age. In the transition Cambrian-Ordovician (Tremadocian?) underlying the Lower Ordovician massive quartzite of Santa Justa Formation (Floian age), volcanic rocks show bimodal composition and occur interbedded in a lithologic association mainly composed of conglomerate and quartzite with minor slate and wake intercalations. The acid volcanism consists of interbedded volcanoclastic rocks of rhyolitic affinities and black and green cherts in thick layers represent the basic volcanism. To the top of this basal Early Ordovician volcano-sedimentary succession, overlaying Floian massive quartzites, a succession of interbedded quartzite’s, wackes and slates, enriched in ironstones in the normal limb, and bearing prints of volcanic origin occur. Sub-concordant quartz veins (exhalative-origin) interbedded in the ironstones were interpreted as volcanic layers recrystallized during the circulation of hydrothermal mineralizing fluids. The presence of igneous rocks in Palaeozoic Carboniferous metasediments around Porto is known since middle of nineteen century. Granodioritic porphyry intrusion occurs interbedded in carboniferous metasediments. Metasedimentary country rocks are surrounded by pre- to post-orogenic Variscan granites with no direct spatial relationship with mineralization but hidden granitic apexes suggest an indirect

  8. Amperometric determination of total phenolic content in wine by laccase immobilized onto silver nanoparticles/zinc oxide nanoparticles modified gold electrode.

    Science.gov (United States)

    Chawla, Sheetal; Rawal, Rachna; Kumar, Dheeraj; Pundir, Chandra Shekhar

    2012-11-01

    A method is described for construction of a highly sensitive amperometric biosensor for measurement of total phenolic compounds in wine by immobilizing laccase covalently onto nanocomposite of silver nanoparticles (AgNPs)/zinc oxide nanoparticles (ZnONPs) electrochemically deposited onto gold (Au) electrode. Scanning electron microscopy, X-ray diffraction, and electrochemical impedance spectroscopy were applied for characterization of the surface morphology of the modified electrode, and cyclic voltammetry was used to investigate the electrochemical properties of the proposed electrode toward the oxidation of guaiacol. The linearity between the oxidation current and the guaiacol concentration was obtained in a range of 0.1 to 500μM with a detection limit of 0.05μM (signal-to-noise ratio (S/N)=3) and sensitivity of 0.71μAμM(-1)cm(-2). The electrode showed increased oxidation and reduced reduction current with the deposition of AgNPs/ZnONPs on it. R(CT) values of ZnONPs/Au, AgNPs/ZnONPs/Au, and laccase/AgNPs/ZnONPs/Au electrode were 220, 175, and 380Ω, respectively. The biosensor showed an optimal response within 8s at pH 6.0 (0.1M acetate buffer) and 35°C when operated at 0.22V against Ag/AgCl. Analytical recovery of added guaiacol was 98%. The method showed a good correlation (r=0.99) with the standard spectrophotometric method, with the regression equation being y=1.0053x-3.5541. The biosensor lost 25% of its initial activity after 200 uses over 5months. Copyright © 2012 Elsevier Inc. All rights reserved.

  9. Carbohydrate-directed synthesis of silver and gold nanoparticles: effect of the structure of carbohydrates and reducing agents on the size and morphology of the composites.

    Science.gov (United States)

    Shervani, Zameer; Yamamoto, Yasushi

    2011-04-01

    A monosaccharide (β-D-glucose) and polysaccharide (soluble starch) were used as structure directing and subsequently stabilizing agents for the synthesis of spherical nanoparticles (NPs) and nanowires of silver and gold. Homogeneous monodispersed Ag(0) nanoparticles (Ag NPs) of 15 nm diameter were obtained when 10(-4)M AgNO(3) precursor salt was reduced in starch (1 wt%)-water gel by 1 wt% β-D-glucose. For a second preparation the effect of reducing agents on the synthesis of Au(0) metallic nanoparticles (Au NPs) of 2 × 10(-4)M concentration prepared in a β-D-glucose (0.03 M)-water dispersion was studied first in detail. Different equivalent amounts of NaBH(4) and a number of pH values were evaluated for the reduction of the Au salt HAuCl(4)·3H(2)O to obtain Au NPs. The type and the amount of reducing agent, as well as the pH of the solution was shown to affect the size and morphology of the NPs. NaBH(4) (4 equiv) produced the smallest (5.3 nm (σ 0.7)) metallic particles compared to larger particles (10.0 nm (σ 1.4)) when the salt was reduced by 1 equiv of NaBH(4). Addition of excess NaBH(4) caused the NPs to settle out as a precipitate forming a mesh or wire structure rather than monodispersed particles. Low pH (pH 6) resulted in incomplete reduction, while at pH 8 the salt was completely reduced. When the salt was reduced by NaOH at pH 8, the particles were larger (14.2 nm) and less homogeneous (σ 2.8) compared to those from NaBH(4) reduction. Copyright © 2011 Elsevier Ltd. All rights reserved.

  10. Structural, photoluminescence, and theoretical DFT studies of gold(I) and silver(I) metallacycle dinuclear complexes of 1-methylbenzimidazolediphenyl phosphine (MBDP) ligand

    Science.gov (United States)

    Jenkins, Darkus E.; Assefa, Zerihun

    2017-04-01

    The synthesis and structural characterization of the bridging ligand, 1-methyl benzimidazole diphenylphosphine (MBDP) and its coordination with Au(I) and Ag(I) metal ions is reported. Two ligands coordinate to the metal ions in head to tail fashion forming a metallacycle coordination consisting of strong M-M bonding interaction with Ausbnd Au = 2.808 and Agsbnd Ag = 3.017 Å. Linear coordination is observed for the gold, while the silver shows distorted tetrahedral arrangement. X-ray crystal data of [(MBDP)2Au2](CH3CN)(BF4)2 (2) crystallizes in the monoclinic system with the space group of P21/n with cell constants of a = 8.9993 (8) Å, b = 19.6166 (18) Å, c = 13.4484 (12) Å, β = 100.966 (2)°, R = 0.026, and Rw = 0.064. The structure of [(MBDP)2(CH3CN)4Ag2](BF4)2, (3) crystallizes in the P (-)1 space group and the unit cell is a = 10.5423 (10) Å, b = 10.7638 (10) Å, c = 12.3530 (12) Å; α = 88.592 (3)°, β = 73.097 (3)°, γ = 84.422 (3)°, V = 1334.8 (2) Å3 with Z = 1, R = 0.034 and Rw = 0.093. The coordinating ligand as well as both dinuclear compounds reported here are luminescent in the near UV region. As supported by the DFT theoretical work, the emission is suggested to be primarily ligand based π- π* transition.

  11. Bio-reduction of elemental sulfur to increase the gold recovery from enargite

    NARCIS (Netherlands)

    Hol, A.; Weijden, van der R.D.; Weert, van G.; Kondos, P.; Buisman, C.J.N.

    2012-01-01

    The mineral enargite can be of interest to the mining industry as a copper and precious metal source. The mineral has a refractory character towards oxidation, which is attributed to the formation of elemental sulfur that seals off the mineral surface. In this study it was investigated whether

  12. 75 FR 37406 - Order Exempting the Trading and Clearing of Certain Products Related to ETFS Physical Swiss Gold...

    Science.gov (United States)

    2010-06-29

    ... COMMISSION Order Exempting the Trading and Clearing of Certain Products Related to ETFS Physical Swiss Gold... Physical Swiss Gold Shares (``Gold Products'') and ETFS Physical Silver Shares (``Silver Products'') (collectively, ``Gold and Silver Products''), which would be traded on national securities exchanges (as to...

  13. Mineral commodity profiles: Silver

    Science.gov (United States)

    Butterman, W.C.; Hilliard, Henry E.

    2005-01-01

    Overview -- Silver is one of the eight precious, or noble, metals; the others are gold and the six platinum-group metals (PGM). World mine production in 2001 was 18,700 metric tons (t) and came from mines in 60 countries; the 10 leading producing countries accounted for 86 percent of the total. The largest producer was Mexico, followed by Peru, Australia, and the United States. About 25 percent of the silver mined in the world in 2001 came from silver ores; 15 percent, from gold ores and the remaining 60 percent, from copper, lead, and zinc ores. In the United States, 14 percent of the silver mined in 2001 came from silver ores; 39 percent, from gold ores; 10 percent, from copper and copper-molybdenum ores; and 37 percent, from lead, zinc, and lead-zinc ores. The precious metal ores (gold and silver) came from 30 lode mines and 10 placer mines; the base-metal ores (copper, lead, molybdenum, and zinc) came from 24 lode mines. Placer mines yielded less than 1 percent of the national silver production. Silver was mined in 12 States, of which Nevada was by far the largest producer; it accounted for nearly one-third of the national total. The production of silver at domestic mines generated employment for about 1,100 mine and mill workers. The value of mined domestic silver was estimated to be $290 million. Of the nearly 27,000 t of world silver that was fabricated in 2001, about one-third went into jewelry and silverware, one-fourth into the light-sensitive compounds used in photography, and nearly all the remainder went for industrial uses, of which there were 7 substantial uses and many other small-volume uses. By comparison, 85 percent of the silver used in the United States went to photography and industrial uses, 8 percent to jewelry and silverware, and 7 percent to coins and medals. The United States was the largest consumer of silver followed by India, Japan, and Italy; the 13 largest consuming countries accounted for nearly 90 percent of the world total. In the

  14. Rapid efficient synthesis and characterization of silver, gold, and bimetallic nanoparticles from the medicinal plant Plumbago zeylanica and their application in biofilm control.

    Science.gov (United States)

    Salunke, Gayatri R; Ghosh, Sougata; Santosh Kumar, R J; Khade, Samiksha; Vashisth, Priya; Kale, Trupti; Chopade, Snehal; Pruthi, Vikas; Kundu, Gopal; Bellare, Jayesh R; Chopade, Balu A

    2014-01-01

    Nanoparticles (NPs) have gained significance in medical fields due to their high surface-area-to-volume ratio. In this study, we synthesized NPs from a medicinally important plant - Plumbago zeylanica. Aqueous root extract of P. zeylanica (PZRE) was analyzed for the presence of flavonoids, sugars, and organic acids using high-performance thin-layer chromatography (HPTLC), gas chromatography-time of flight-mass spectrometry (GC-TOF-MS), and biochemical methods. The silver NPs (AgNPs), gold NPs (AuNPs), and bimetallic NPs (AgAuNPs) were synthesized from root extract and characterized using ultraviolet-visible spectra, X-ray diffraction (XRD), energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The effects of these NPs on Acinetobacter baumannii, Staphylococcus aureus, and Escherichia coli biofilms were studied using quantitative biofilm inhibition and disruption assays, as well as using fluorescence, scanning electron microscopy, and atomic force microscopy. PZRE showed the presence of phenolics, such as plumbagin, and flavonoids, in addition to citric acid, sucrose, glucose, fructose, and starch, using HPTLC, GC-TOF-MS, and quantitative analysis. Bioreduction of silver nitrate (AgNO₃) and chloroauric acid (HAuCl₄) were confirmed at absorbances of 440 nm (AgNPs), 570 nm (AuNPs), and 540 nm (AgAuNPs), respectively. The maximum rate of synthesis at 50°C was achieved with 5 mM AgNO₃ within 4.5 hours for AgNPs; and with 0.7 mM HAuCl4 within 5 hours for AuNPs. The synthesis of AgAuNPs, which completed within 90 minutes with 0.7 mM AgNO₃ and HAuCl₄, was found to be the fastest. Fourier-transform infrared spectroscopy confirmed bioreduction, while EDS and XRD patterns confirmed purity and the crystalline nature of the NPs, respectively. TEM micrographs and DLS showed about 60 nm monodispersed Ag nanospheres, 20-30 nm Au nanospheres adhering to form Au nanotriangles, and about 90 nm hexagonal blunt

  15. Ultrastable silver nanoparticles.

    Science.gov (United States)

    Desireddy, Anil; Conn, Brian E; Guo, Jingshu; Yoon, Bokwon; Barnett, Robert N; Monahan, Bradley M; Kirschbaum, Kristin; Griffith, Wendell P; Whetten, Robert L; Landman, Uzi; Bigioni, Terry P

    2013-09-19

    Noble-metal nanoparticles have had a substantial impact across a diverse range of fields, including catalysis, sensing, photochemistry, optoelectronics, energy conversion and medicine. Although silver has very desirable physical properties, good relative abundance and low cost, gold nanoparticles have been widely favoured owing to their proved stability and ease of use. Unlike gold, silver is notorious for its susceptibility to oxidation (tarnishing), which has limited the development of important silver-based nanomaterials. Despite two decades of synthetic efforts, silver nanoparticles that are inert or have long-term stability remain unrealized. Here we report a simple synthetic protocol for producing ultrastable silver nanoparticles, yielding a single-sized molecular product in very large quantities with quantitative yield and without the need for size sorting. The stability, purity and yield are substantially better than those for other metal nanoparticles, including gold, owing to an effective stabilization mechanism. The particular size and stoichiometry of the product were found to be insensitive to variations in synthesis parameters. The chemical stability and structural, electronic and optical properties can be understood using first-principles electronic structure theory based on an experimental single-crystal X-ray structure. Although several structures have been determined for protected gold nanoclusters, none has been reported so far for silver nanoparticles. The total structure of a thiolate-protected silver nanocluster reported here uncovers the unique structure of the silver thiolate protecting layer, consisting of Ag2S5 capping structures. The outstanding stability of the nanoparticle is attributed to a closed-shell 18-electron configuration with a large energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, an ultrastable 32-silver-atom excavated-dodecahedral core consisting of a hollow 12-silver

  16. Silver and gold nanoparticle separation using asymmetrical flow-field flow fractionation: Influence of run conditions and of particle and membrane charges.

    Science.gov (United States)

    Meisterjahn, Boris; Wagner, Stephan; von der Kammer, Frank; Hennecke, Dieter; Hofmann, Thilo

    2016-04-01

    Flow-Field Flow Fractionation (Flow-FFF), coupled with online detection systems is one of the most promising tools available for the separation and quantification of engineered nanoparticles (ENPs) in complex matrices. To correctly relate the retention of nanoparticles in the Flow-FFF-channel to the particle size, ideal separation conditions must be met. This requires optimization of the parameters that influence the separation behavior. The aim of this study was therefore to systematically investigate and evaluate the influence of parameters such as the carrier liquid, the cross flow, and the membrane material, on the separation behavior of two metallic ENPs. For this purpose the retention, recovery, and separation efficiency of sterically stabilized silver nanoparticles (AgNPs) and electrostatically stabilized gold nanoparticles (AuNPs), which represent two materials widely used in investigations on environmental fate and ecotoxicology, were investigated against a parameter matrix of three different cross-flow densities, four representative carrier solutions, and two membrane materials. The use of a complex mixture of buffers, ionic and non-ionic surfactants (FL-70 solution) together with a medium cross-flow density provided an acceptable compromise in peak quality and recovery for both types of ENPs. However, these separation conditions do not represent a perfect match for both particle types at the same time (maximized recovery at maximized retention). It could be shown that the behavior of particles within Flow-FFF channels cannot be predicted or explained purely in terms of electrostatic interactions. Particles were irreversibly lost under conditions where the measured zeta potentials suggested that there should have been sufficient electrostatic repulsion to ensure stabilization of the particles in the Flow-FFF channel resulting in good recoveries. The wide variations that we observed in ENP behavior under different conditions, together with the different

  17. Evidence for de-sulfidation to form native electrum in the Fire Creek epithermal gold-silver deposit, north-central Nevada

    Science.gov (United States)

    Perez, J.; Day, J. M.; Cook, G. W.

    2012-12-01

    The Fire Creek property is a newly developed and previously unstudied epithermal Au-Ag deposit located in the Northern Shoshone range of north central Nevada. The mineralization occurs within and above en echelon N-NW trending basaltic dykes that are hosted within a co-genetic and bimodal suite of mid-Miocene basalts and andesites formed in association with the Yellowstone hotspot-track. Previous studies of Au-Ag mineralization in the Great Basin have focused primarily on extensively mined and/or low-grade deposits. Therefore, the ability for unrestricted sampling of a major Au-Ag deposit early in its exploration and development represents an opportunity for refined understanding of epithermal ore genesis processes. New petrology reveals at least two distinct pulses of mineralization that in relative order of timing are: 1) S-rich veins which are associated with initial host-rock alteration; 2) quartz- and/or calcite-rich veins which vary from fine-grained to lath-like quartz crystals with large calcite crystals in vein centers. Native electrum occurs only within the second phase of mineralization and typically occurs within quartz and adjacent to cross-cut first-phase S-rich veins. In places the electrum appears to replace or form overgrowths around existing sulfide phases. High levels of gold and silver are found in both the first (0.8 g Au/tonne) and second-phase pulses (37 g Au/tonne). Fire Creek shares many similarities with its northern neighbor, the Mule Canyon Au-Ag deposit, with high Fe sulfide contents for some of the ores, altered wall-rocks and the presence of narrow and discontinuous gold-bearing siliceous veins. Like Fire Creek, Mule Canyon possesses two distinct mineralizing phases, a sulfide rich and a late stage calcite/silica assemblage. The first pulse appears to be identical in both locations with a variation of disseminated to euhedral iron-sulfides and associated intense alteration of host rock. However, Fire Creek differs from Mule Canyon in

  18. Rapid and simultaneous detection of human hepatitis B virus and hepatitis C virus antibodies based on a protein chip assay using nano-gold immunological amplification and silver staining method

    Directory of Open Access Journals (Sweden)

    Wan Zhixiang

    2005-07-01

    Full Text Available Abstract Background Viral hepatitis due to hepatitis B virus and hepatitis C virus are major public health problems all over the world. Traditional detection methods including polymerase chain reaction (PCR-based assays and enzyme-linked immunosorbent assays (ELISA are expensive and time-consuming. In our assay, a protein chip assay using Nano-gold Immunological Amplification and Silver Staining (NIASS method was applied to detect HBV and HCV antibodies rapidly and simultaneously. Methods Chemically modified glass slides were used as solid supports (named chip, on which several antigens, including HBsAg, HBeAg, HBcAg and HCVAg (a mixture of NS3, NS5 and core antigens were immobilized respectively. Colloidal nano-gold labelled staphylococcal protein A (SPA was used as an indicator and immunogold silver staining enhancement technique was applied to amplify the detection signals, producing black image on array spots, which were visible with naked eyes. To determine the detection limit of the protein chip assay, a set of model arrays in which human IgG was spotted were structured and the model arrays were incubated with different concentrations of anti-IgG. A total of 305 serum samples previously characterized with commercial ELISA were divided into 4 groups and tested in this assay. Results We prepared mono-dispersed, spherical nano-gold particles with an average diameter of 15 ± 2 nm. Colloidal nano-gold-SPA particles observed by TEM were well-distributed, maintaining uniform and stable. The optimum silver enhancement time ranged from 8 to 12 minutes. In our assay, the protein chips could detect serum antibodies against HBsAg, HBeAg, HBcAg and HCVAg with the absence of the cross reaction. In the model arrays, the anti-IgG as low as 3 ng/ml could be detected. The data for comparing the protein chip assay with ELISA indicated that no distinct difference (P > 0.05 existed between the results determined by our assay and ELISA respectively. Conclusion

  19. The geomicrobiology of gold.

    Science.gov (United States)

    Reith, Frank; Lengke, Maggy F; Falconer, Donna; Craw, David; Southam, Gordon

    2007-11-01

    Microorganisms capable of actively solubilizing and precipitating gold appear to play a larger role in the biogeochemical cycling of gold than previously believed. Recent research suggests that bacteria and archaea are involved in every step of the biogeochemical cycle of gold, from the formation of primary mineralization in hydrothermal and deep subsurface systems to its solubilization, dispersion and re-concentration as secondary gold under surface conditions. Enzymatically catalysed precipitation of gold has been observed in thermophilic and hyperthermophilic bacteria and archaea (for example, Thermotoga maritime, Pyrobaculum islandicum), and their activity led to the formation of gold- and silver-bearing sinters in New Zealand's hot spring systems. Sulphate-reducing bacteria (SRB), for example, Desulfovibrio sp., may be involved in the formation of gold-bearing sulphide minerals in deep subsurface environments; over geological timescales this may contribute to the formation of economic deposits. Iron- and sulphur-oxidizing bacteria (for example, Acidothiobacillus ferrooxidans, A. thiooxidans) are known to breakdown gold-hosting sulphide minerals in zones of primary mineralization, and release associated gold in the process. These and other bacteria (for example, actinobacteria) produce thiosulphate, which is known to oxidize gold and form stable, transportable complexes. Other microbial processes, for example, excretion of amino acids and cyanide, may control gold solubilization in auriferous top- and rhizosphere soils. A number of bacteria and archaea are capable of actively catalysing the precipitation of toxic gold(I/III) complexes. Reductive precipitation of these complexes may improve survival rates of bacterial populations that are capable of (1) detoxifying the immediate cell environment by detecting, excreting and reducing gold complexes, possibly using P-type ATPase efflux pumps as well as membrane vesicles (for example, Salmonella enterica

  20. Probing the Adsorption Behavior of 4,5-Diazafluoren-9-one and Its Schiff Base Derivatives on SIlver and Gold Nanosurfaces Using Raman Spectroscopy, Density Functional Theory and Potential Energy Distribution Calculations

    Science.gov (United States)

    McCoy, Rhonda Patrice

    4,5-Diazafluoren-9-one (DAFO) is an aromatic ketone synthesized by oxidizing 1,10-phenanthroline with potassium permanganate. In this present study, the Raman spectra of DAFO in the solid and solution states were recorded in the 100-2000 cm-1 spectral region using 1064, 633, 532, and 514 nm excitation sources. A normal mode analysis of DAFO was performed using density functional theory; the BLYP and B3LYP functionals, each with the 6-31G(d) and 6-311(d) basis sets were employed. The fundamental modes on the Raman spectrum of DAFO were assigned with the appropriate symmetry element using the BLYP functional and 6-31G(d) basis set. The vibrational modes were described and quantified by potential energy distribution calculations. The Raman frequencies for the solid and solution spectra were compared; the observed frequency shifts are attributed to hydrogen bonding or dipole-dipole interactions occurring between the solvent and DAFO ligand. To further assess solute-solvent interactions the UV-vis spectra of DAFO was obtained in hydrogen bonding, polar aprotic, and non-polar solvents. The fine structure of the band observed at lambda max becomes more resolved as solvent polarity decreases, therefore confirming solute-solvent interactions in polar solvents. A silver complex of DAFO was synthesized with the intent of understanding how coordination affected the Raman frequencies. The bands assigned to pyridine ring bending, nu(C=N), and nu(C=O) were shifted because of coordination. These shifts have been attributed to the molecule being perturbed because of coordination. Therefore, the Ag-DAFO complex was analyzed by X-Ray diffraction and the molecular geometries of the free and coordinated ligand were compared. The resolved crystalline structure revealed the silver ion coordinated DAFO using the lone pairs of electrons from the nitrogens in the pyridine ring. Analysis of the molecular geometry revealed the C=O bond increases in double bond character and the C5-C14 bond

  1. Comparisons in the behavior of stable copper(II), silver(II), and gold(II) complexes in the gas phase: are there implications for condensed-phase chemistry?

    Science.gov (United States)

    Walker, N R; Wright, R R; Barran, P E; Murrell, J N; Stace, A J

    2001-05-09

    Experiments conducted in the gas phase have led to the formation of a series of stable gold(II) complexes with nitrogen- and oxygen-containing ligands. Such complexes are very rare in condensed-phase chemistry. However, there is also a significant group of potential ligands, for example, H2O and NH3, for which stable complexes could not be formed. There are strong similarities between these observations and earlier results presented for silver(II), but both metal ions behave markedly different from copper(II). As a group the majority of successful gold(II) ligands are characterized by being good sigma donor-pi acceptor molecules; however, it is also possible to understand the ability of individual ligands to stabilize the metal ion in terms of a simple electrostatic model. Application of the latter reveals a semiquantitative trend between the physical properties of a ligand, e.g. ionization energy, dipole moment, and polarizability, and the ligand's ability to stabilize either Cu(II), Ag(II), or Au(II). The model successfully accounts for the preference of Cu(II) for aqueous chemistry, in comparison to the complete absence of such behavior on the part of Ag(II) and Au(II). Ligands from recent examples of stable condensed-phase gold(II) complexes appear to meet at least one of the criteria identified from the model.

  2. Synthesizing A Phase Changing Bistable Electroactive Polymer And Silver Nanoparticles Coated Fabric As A Resistive Heating Element

    Science.gov (United States)

    Ren, Zhi

    that decreases to several MPa at above 70°C after a rigid-to-rubbery transition via glass transition. The rubbery BSEP possesses a stable storage modulus regardless of temperature fluctuations, which is beneficial to stable electrical actuation performances under an electric field. The bimodal structure creates a framework involving both long chain crosslinkers and small molecular crosslinkers. Due to the limited chain extensibility of this bimodal framework, the rubbery BSEP can self-stiffen at modest strains to suppress electromechanical instability, which is responsible for the premature electrical breakdown of the previous BSEP materials in their rubbery states. A BSEP actuator with a braille dot size exhibits steadily increased actuation height with increasing electric field at 70 °C. A stable actuation with a cycle lifetime of over 2000 cycles at a raised dot height of 0.4 mm was demonstrated. A fabrication process for a page-size braille paper using the BSEP has been developed. A selective heating strategy has been investigated based on a 2-cell device to provide a selective actuation strategy of BSEP braille dots. Wearable thermal management strategy has presented itself recently as a new challenge to offer an optimal thermal experience for the occupant as well as to reduce building energy usage for heating, ventilation and air conditioning (HVAC). Joule heating based on silver nanoparticles (AgNPs) coated non-woven fabric can provide a wearable localized heating element.A sheet resistance of bonding between oxygen groups on the fabrics' surface and AgNPs. As a result, the bonding between the AgNPs layer and the polyester fabrics is strong enough to resist sonication damage. The resistance only increased slightly after an 80minutes of sonication and therefore the AgNPs-polyester fabrics composite are regarded as washable. The AgNPs coated polyester fabrics was employed as a heating element. A voltage as low as 1volt is adequate to heat up the Ag

  3. Finite element analysis to compare stress distribution of gold alloy, lithium-disilicate reinforced glass ceramic and zirconia based fixed partial denture.

    Science.gov (United States)

    Zheng, Zhiqiang; Lin, Jie; Shinya, Akikazu; Matinlinna, Jukka P; Botelho, Michael G; Shinya, Akiyoshi

    2012-11-01

    Clinical data indicate that veneer chipping of zirconia core is more likely than with ceramic-fused-to-metal structures. The purposes of this simulation study were to: (a) use two-dimensional finite element modeling to simulate stresses at the interface of three-unit posterior fixed partial dentures (FPDs) made with three different core materials; and (b) to investigate the influence of three different veneer thicknesses on the stress distribution within the veneer-core complex. A mesio-distal cross-section of a three-unit FPD was digitized and used to create two-dimensional models of the teeth, supporting bone, different core materials (gold alloy, zirconia and lithia-disilicate reinforced glass ceramic), and different pontic preparation configurations (occlusal veneer thickness 1.0, 1.5, and 2.0 mm). A simulated 100 N vertical occlusal load was applied to the standardized pontic element. Compression stress and tensile stress values were calculated by finite element analysis along the veneer-core interface and compared. The veneer-core interfacial stress of zirconia-based FPD is greater than that of gold alloy and lithium-disilicate reinforced glass ceramic core. The veneer-core interface stress value decreased with increasing occlusal veneer thickness. Finite element modeling revealed differences in tensile and compressive stresses between different pontic preparation configurations and core materials. In general, gold alloy and lithium-disilicate reinforced glass ceramic core provided more even stress distribution at the connector and pontic of fixed partial denture than a zirconia framework. © 2012 Wiley Publishing Asia Pty Ltd.

  4. Silver enhancement of nanogold and undecagold

    Energy Technology Data Exchange (ETDEWEB)

    Hainfield, J.F.; Furuya, F.R.

    1995-07-01

    A recent advance in immunogold technology has been the use of molecular gold instead of colloidal gold. A number of advantages are realized by this approach, such as stable covalent, site-specific attachment, small probe size and absence of aggregates for improved penetration. Silver enhancement has led to improved and unique results for electron and light microscopy, as well as their use with blots and gels. Most previous work with immunogold silver staining has been done with colloidal gold particles. More recently, large gold compounds (``clusters``) having a definite number of gold atoms and defined organic shell, have been used, frequently with improved results. These gold dusters, large compared to simple compounds, are, however, at the small end of the colloidal gold scale in size; undecagold is 0.8 nm and Nanogold is 1.4 nm. They may be used in practically all applications where colloidal gold is used (Light and electron microscopy, dot blots, etc.) and in some unique applications, where at least the larger colloidal golds don`t work, such as running gold labeled proteins on gels (which are later detected by silver enhancement). The main differences between gold clusters and colloidal golds are the small size of the dusters and their covalent attachment to antibodies or other molecules.

  5. ``Gold corrosion'': red stains on a gold Austrian Ducat

    Science.gov (United States)

    Gusmano, G.; Montanari, R.; Kaciulis, S.; Montesperelli, G.; Denk, R.

    Stains of different colours have been observed on historic and modern gold coins in several countries. An Austrian Ducat at the Kunsthistorisches Museum in Vienna has developed some red spots on its surface over the years. The same defects have also been observed in modern coins of higher gold purity. The spots have been examined by OM, SEM, EDS, XPS and AES. Optical microscopy showed that ``red'' defects exhibit in fact a nuance of colours. The surface analysis put in evidence the presence in the stains, in addition to gold, of silver and sulphur. The values of the modified Auger parameter α' of silver correspond to those of Ag2S; thus, it can be assumed that the stains are composed of silver sulphide (Ag2S). It was not possible to determine whether the presence of silver on the surface is due to segregation towards the surface or to external particles of silver embedded in the matrix. Depth profiling performed on modern coins suffering from the same problem allowed us to demonstrate that the nuance of colours is due to the inhomogeneous thickness of the spots. Moreover, it was demonstrated that spots are formed by two layers: an outer layer of silver sulphide and an inner layer of silver.

  6. Development of filter element from nanocomposites of ultra high molar mass polyethylene having silver nanoparticles; Desenvolvimento de elemento filtrante a partir de nanocompositos de polietileno de ultra-alta massa molar contendo nanoparticulas de prata

    Energy Technology Data Exchange (ETDEWEB)

    Bizzo, Maurizio A.; Wang, S. Hui, E-mail: mbizzo@usp.br [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Escola Politecnica de Engenharia Metalurgica e de Materiais

    2015-07-01

    The production of polymer based filter elements for water is widespread in the market but has an undesirable characteristic, they are not always efficient and capable of retaining or eliminating microorganisms. This paper proposes the production of filters with biocidal activity, comprised by nanocomposites of ultra-high molar mass polyethylene (UHMMPE) containing silver nanoparticles. The polymer is responsible for the uniform porous structure of the filter element and the Ag nanoparticles for its biocidal action. The filter elements were produced from two kinds of UHMMPE particles with different particle size distributions, one in the range of 150 to 200μm and the other of 300 to 400μm. Samples were collected from the obtained filter elements and characterized by X-ray diffractometry, scanning electron microscopy and microanalysis. The results indicated the formation of nanocomposite containing silver nanoparticles. (author)

  7. Autometallography: tissue metals demonstrated by a silver enhancement kit

    DEFF Research Database (Denmark)

    Danscher, G; Nørgaard, J O; Baatrup, E

    1987-01-01

    In biological tissue, minute accumulations of gold, silver, mercury and zinc can be visualized by a technique whereby metallic silver is precipitated on tiny accumulations of the two noble metals, or on selenites or sulphides of all four metals. In the present study a silver enhancement kit, prim...... methods and for demonstration of gold, silver, and mercury in tissues from animals intravitally exposed to these metals. It can also be used for counterstaining silver treated osmium fixed tissues embedded in plastic. Udgivelsesdato: 1987-null...

  8. Proof of concept for a passive sampler for monitoring of gaseous elemental mercury in artisanal gold mining.

    Science.gov (United States)

    de Barros Santos, Elias; Moher, Paleah; Ferlin, Stacy; Fostier, Anne Hélène; Mazali, Italo Odone; Telmer, Kevin; Brolo, Alexandre Guimarães

    2017-11-28

    Mercury emissions from artisanal gold mining operations occurring in roughly 80 developing countries are a major workplace health hazard for millions of people as well as the largest contributor to global mercury pollution. There are no portable, cheap, and rapid methods able to inform workers or health practitioners of mercury exposure on site in remote locations. In this work, a proof of concept for a miniaturized mercury sampler, prepared by the direct reduction of gold into the porous nanostructures of Vycor glass (PVG), is introduced. Mercury retention on the PVG/Au sampler induces significant color changes, due to the formation of Au-Hg amalgam that affects the surface plasmon resonance characteristics of the material. The color change can potentially be quantified by the analysis of pictures obtained with a cell phone camera rapidly and onsite. Laboratory experiments showed the viability of using PVG/Au as passive sampler for monitoring of Hg°. PVG/Au samplers were then deployed in an artisanal and small-scale gold mining (ASGM) operations in Burkina Faso and it was able to indicate personal mercury exposures. The amount of mercury quantified in the samplers for all miners was higher than the current personal exposure limit set by the US Occupational Safety & Health Administration (OSHA).

  9. Carbon-oxygen isotopes and rare earth elements as an exploration vector for Carlin-type gold deposits: A case study of the Shuiyindong gold deposit, Guizhou Province, SW China

    Science.gov (United States)

    Tan, Qin-Ping; Xia, Yong; Wang, Xueqiu; Xie, Zhuo-Jun; Wei, Dong-Tian

    2017-10-01

    The Shuiyindong gold deposit is a deeply concealed strata-bound Carlin-type deposit in southwestern Guizhou Province, China. The deposit lies on the eastern limb of the Huijiabao anticline with ores mainly along the anticline axis and hosted in bioclastic limestone, containing calcite veins, of the Permian Longtan Formation units. In this study, we measured carbon and oxygen isotopic ratios and rare earth element (REE) concentrations of the host rocks and calcite veins along a profile across the Shuiyindong deposit. Orebodies in the upper unit of the Longtan Formation have higher δ18O values (20.6-22.4‰) and lower δ13C values (-3.7 to -0.5‰) than the country rocks (δ18O: 18.8-21.4‰; δ13C: -0.7 to 0.8‰). However, there are no obvious trends of δ18O and δ13C values from the country rocks to the orebodies in the middle unit of the Longtan Formation. The spatial distribution of the calcite veins displays distinct halos of δ13C and δ18O values and REE concentrations. Calcite veins along the anticlinal axis and major reverse fault are enriched in Middle REE (Sm, Eu, Gd, and Tb) and 18O and depleted in 13C. Surficial veining calcite-filled fractures/faults that connect to deep concealed strata-bound gold mineralization systems can be vectors toward deep ores in southwestern Guizhou Province, China.

  10. The platinum group elements and gold: analysis by radiochemical and instrumental neutron activation analysis and relevance to geological exploration and related problems

    Energy Technology Data Exchange (ETDEWEB)

    Reeves, S.; Plimer, I. R. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1996-12-31

    This paper presents an overview of research conducted with the support of the Australian Institute of Nuclear Science and Engineering, at the University of Melbourne, School of Earth Sciences, Radiochemical Neutron Activation Laboratory. The primary objective of this research is to realize the high potential of the platinum group elements (PGE) and gold to the solution of petrogenetic problems, the study of magma generation and magmatic processes in mafic/ultramafic rock suites, as tracers in hydrothermal ore formation. The PGEs (Os, Ru, Ir, Pt, Pd and Rh) are among the least abundant of all elements on earth with unique properties such as high melting points, high electrical and thermal conductivity, high density, strength and toughness as alloys. They exhibit both siderophile and chalcophile characteristics and are valuable tools in providing information about magmatic processes, in particular S-saturation, as well as crystal fractionation trends. Two distinct groups of PGEs are discerned; the IPGEs (Ru, Os, Ir) and the PPGEs (Pt, Pd, Rh, Au) on the basis of their behaviour during fractionation processes. Using chondrite normalized PGE patterns it is possible to distinguish between sulphides that segregated from primitive magmas, such as komatiites, and sulphides which segregated from more fractionated magmas, such as tholeiites. It is critical to the understanding of these processes to be able to analyse key elements, such as the PGE and gold, in the parts per billion to parts per trillion range. Platinum group elements and Au were determined by radiochemical neutron activation analysis using a modified NiS fire-assay preconcentration technique, adapted from procedures first used by Robert, R.V. D. and van Wyk, E. (1975) . Detection limits are generally 0.005-0.01 ppb (Au and Ir), 0.1-0.2 ppb (Pd and Pt), and 0.1-0.5 ppb for Ru. 9 refs.

  11. Mineralogy, mineral chemistry, and paragenesis of gold, silver, and base-metal ores of the North Amethyst vein system, San Juan Mountains, Mineral County, Colorado

    Science.gov (United States)

    Foley, Nora K.; Caddey, Stanton W.; Byington, Craig B.; Vardiman, David M.

    1993-01-01

    Gold-rich adularia-sericite-type mineralization occurs near the southern margin of the San Luis caldera, at the intersection of the Equity fault and the northern extension of the Amethyst fault system. Mineralized rock is confined primarily to steeply dipping structures in silicified rhyolite and dacite. Intense sericitic alteration occurs at higher levels in the vein system, and wall rock adjacent to some veins is bleached. The ores are multiply brecciated, and vein filling locally shows sedimentary textures.

  12. A gold nanohole array based surface-enhanced Raman scattering biosensor for detection of silver(i) and mercury(ii) in human saliva

    Science.gov (United States)

    Zheng, Peng; Li, Ming; Jurevic, Richard; Cushing, Scott K.; Liu, Yuxin; Wu, Nianqiang

    2015-06-01

    A surface-enhanced Raman scattering (SERS) biosensor has been developed by incorporating a gold nanohole array with a SERS probe (a gold nanostar@Raman-reporter@silica sandwich structure) into a single detection platform via DNA hybridization, which circumvents the nanoparticle aggregation and the inefficient Raman scattering issues. Strong plasmonic coupling between the Au nanostar and the Au nanohole array results in a large enhancement of the electromagnetic field, leading to amplification of the SERS signal. The SERS sensor has been used to detect Ag(i) and Hg(ii) ions in human saliva because both the metal ions could be released from dental amalgam fillings. The developed SERS sensor can be adapted as a general detection platform for non-invasive measurements of a wide range of analytes such as metal ions, small molecules, DNA and proteins in body fluids.A surface-enhanced Raman scattering (SERS) biosensor has been developed by incorporating a gold nanohole array with a SERS probe (a gold nanostar@Raman-reporter@silica sandwich structure) into a single detection platform via DNA hybridization, which circumvents the nanoparticle aggregation and the inefficient Raman scattering issues. Strong plasmonic coupling between the Au nanostar and the Au nanohole array results in a large enhancement of the electromagnetic field, leading to amplification of the SERS signal. The SERS sensor has been used to detect Ag(i) and Hg(ii) ions in human saliva because both the metal ions could be released from dental amalgam fillings. The developed SERS sensor can be adapted as a general detection platform for non-invasive measurements of a wide range of analytes such as metal ions, small molecules, DNA and proteins in body fluids. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02142a

  13. Radio Frequency Controlled Stimulation of Intracellular Gold or Silver Nanoparticle Conjugates for Use as Potential Sensors or Modulators of Biological Function

    Science.gov (United States)

    2010-09-01

    2008) Label-Free Colorimetric Detection of Lead Ions with a Nanomolar Detection Limit and Tunable Dynamic Range by using Gold Nanoparticles and...collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources ...it also correlates to a visible color change in the NP solution, providing a colorimetric response which is recordable by any spectroscopic equipment

  14. Ginseng-berry-mediated gold and silver nanoparticle synthesis and evaluation of their in vitro antioxidant, antimicrobial, and cytotoxicity effects on human dermal fibroblast and murine melanoma skin cell lines.

    Science.gov (United States)

    Jiménez Pérez, Zuly Elizabeth; Mathiyalagan, Ramya; Markus, Josua; Kim, Yeon-Ju; Kang, Hyun Mi; Abbai, Ragavendran; Seo, Kwang Hoon; Wang, Dandan; Soshnikova, Veronika; Yang, Deok Chun

    2017-01-01

    There has been a growing interest in the design of environmentally affable and biocompatible nanoparticles among scientists to find novel and safe biomaterials. Panax ginseng Meyer berries have unique phytochemical profile and exhibit beneficial pharmacological activities such as antihyperglycemic, antiobesity, antiaging, and antioxidant properties. A comprehensive study of the biologically active compounds in ginseng berry extract (GBE) and the ability of ginseng berry (GB) as novel material for the biosynthesis of gold nanoparticles (GBAuNPs) and silver nanoparticles (GBAgNPs) was conducted. In addition, the effects of GBAuNPs and GBAgNPs on skin cell lines for further potential biological applications are highlighted. GBAuNPs and GBAgNPs were synthesized using aqueous GBE as a reducing and capping agent. The synthesized nanoparticles were characterized for their size, morphology, and crystallinity. The nanoparticles were evaluated for antioxidant, anti-tyrosinase, antibacterial, and cytotoxicity activities and for morphological changes in human dermal fibroblast and murine melanoma skin cell lines. The phytochemicals contained in GBE effectively reduced and capped gold and silver ions to form GBAuNPs and GBAgNPs. The optimal synthesis conditions (ie, temperature and v/v % of GBE) and kinetics were investigated. Polysaccharides and phenolic compounds present in GBE were suggested to be responsible for stabilization and functionalization of nanoparticles. GBAuNPs and GBAgNPs showed increased scavenging activity against 2,2-diphenyl-1-picrylhydrazyl free radicals compared to GBE. GBAuNPs and GBAgNPs effectively inhibited mushroom tyrosinase, while GBAgNPs showed antibacterial activity against Escherichia coli and Staphylococcus aureus. In addition, GBAuNPs were nontoxic to human dermal fibroblast and murine melanoma cell lines, and GBAgNPs showed cytotoxic effect on murine melanoma cell lines. The current results evidently suggest that GBAgNPs can act as potential

  15. Reactions of anionic porphyrin with group 11 elements: a spectrophotometric and electrospray ionization mass spectrometry study.

    Science.gov (United States)

    Giovannetti, Rita; Bartocci, Vito; Pucciarelli, Filippo; Ricciutelli, Massimo

    2004-07-08

    The reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) with the elements of 11 group have been studied. CPI is an anionic porphyrin that slowly reacts with copper ion to form Cu(II)CPI and with silver ions to form Ag(II)CPI, Ag(III)CPI complexes and colloidal silver. Gold ions do not form complexes with CPI, but, in the main, colloidal gold and some CPI-N-oxide. The kinetics of the reactions with copper and silver were spectrophotometerically studied and the rate constants were calculated. The identification and characterization of this water-soluble anionic porphyrin and its metal complexes have been performed by electrospray mass spectrometry (ESI-MS) that proved to be an excellent method for these determinations. The multiple charged parent ions for metal free ligand and their metal complexes were identified.

  16. X-Ray Fluorescence Analysis of XII–XIV Century Italian Gold Coins

    Directory of Open Access Journals (Sweden)

    Monica Baldassarri

    2014-01-01

    Full Text Available An extensive analytical study has been performed on a large number of gold coins (Norman-Swabian Augustale and Tarì, Grosso of Lucca, Florin of Florence minted in Italy from the end of XII century to XIV century. The X-ray fluorescence (XRF technique was used for verifying the composition of the coins. XRF is a nondestructive technique particularly suited for in situ quantitative analysis of gold and minor elements in the precious alloy. The Florins turned out to have a gold content very close to 24 carats (pure gold although in a couple of cases we observed relatively high concentrations of iron (around 2% or lead (around 1%. The Grosso of Lucca has a similar composition, with a measured gold content around 97% due to a higher silver percentage (about 2%, with respect to the average Florin. The Augustali analyzed showed, on average, a gold content around 89%. The average gold content of the Tarì analysed is around 72%, with a relatively large variability. The analysis revealed the use of native gold for the coinage of the Florins, excluding the possibility of recycling gold coming from other sources. On the other hand, the variability observed in the compositions of the Tarì and Augustali could suggest the reuse of Islamic and North African gold. The study could shed some light on the sudden diffusion of gold coins in Italy around the first half of XIII century, allowing hypotheses on the provenience of the gold used for a coinage that dominated the economic trades from then on.

  17. Mineralization and trace element distribution in pyrite using EMPA in exploration drill holes from Cheshmeh Zard gold district, Khorasan Razavi Province, Iran

    Directory of Open Access Journals (Sweden)

    Zahra Alaminia

    2015-10-01

    Full Text Available Introduction Pyrite is the most abundant sulfide mineral in low sulfidation ore deposits. Experimental studies have shown that low-temperature ( 200°C from hydrothermal or metamorphic fluids (Butler and Rickard, 2000. Framboidal pyrite mostly occurs in sedimentary environments, though it could also form during metamorphism and hydrothermal alteration (Scott et al., 2009. The pyrite formed tends to be enriched in various trace elements such as Au and As. For this study we have combined the geology, alteration, mineralization with recent studies of the description of the deposit from core logging and underground mapping and geochemistry in the CheshmehZard gold district and also investigated the compositional variation and textural differences between pyrite types. This study is based on the results of our alteration and mineralization mapping and detailed logging of 1937.8 m of drill core. Materials and Methods Geology, hydrothermal alteration and mineralization were examined in drill holes along several cross sections. Host-rock alteration minerals and veins were determined for 11 samples using standard X-ray diffraction (XRD and X-ray fluorescence spectrometry (XRF techniques. Polished sections were studied by reflected light microscopy and backscattered electron images (BSE. In this study, the trace-element composition of pyrite samples from the Au-III vein system was obtained using electron microprobe analyzer (EMPA data. All analyseswere carried out at the department of Materials Engineering and Physics of the University of Salzburg in Austria. The EMPA measurements and BSE imaging were made using a JXA-8600 electron microprobe. Spot analyses of 30 pyrite grains from CheshmehZard are given in Table 1. Results The study area is located in the north of Khorasan Razavi Province 45 km to the south of Neyshabour. The area near CheshmehZard could become important as a site of economically significant gold mineralization. Six gold-bearing vein

  18. Redistribution of elements between wastes and organic-bearing material in the dispersion train of gold-bearing sulfide tailings: Part I. Geochemistry and mineralogy.

    Science.gov (United States)

    Saryg-Ool, B Yu; Myagkaya, I N; Kirichenko, I S; Gustaytis, M A; Shuvaeva, O V; Zhmodik, S M; Lazareva, E V

    2017-03-01

    Migration and redistribution of elements during prolonged interaction of cyanide wastes with the underlying natural organic-bearing material have been studied in two ~40cm deep cores that sample primary ores and their weathering profile (wastes I and II, respectively) in the dispersion train of gold-bearing sulfide tailings in Siberia. Analytical results of SR-XRF, whole-rock XRF, AAS, CHNS, and SEM measurements of core samples show high K, Sr, Ti, and Fe enrichments and correlation of P2O5 and Mn with LOI and Corg. Organic material interlayered or mixed with the wastes accumulates Cu, Zn, Se, Cd, Ag, Au, and Hg. The peat that contacts wastes II bears up to 3wt.% Zn, 1000g/t Se, 100g/t Cd, and 8000g/t Hg. New phases of Zn and Hg sulfides and Hg selenides occur as abundant sheaths over bacterial cells suggesting microbial mediation in sorption of elements. Organic-bearing material in the cores contains 10-30g/t Au in 2-5cm thick intervals, both within and outside the intervals rich in sulfides and selenides. Most of gold is invisible but reaches 345g/t and forms 50nm to 1.5μm Au0 particles in a thin 2-3cm interval of organic remnants mixed with wastes I. Vertical and lateral infiltration of AMD waters in peat and oxidative dissolution of wastes within the dispersion train of the Ursk tailings lead to redistribution of elements and their accumulation by combined physical (material's permeability, direction AMD), chemical (complexing, sorption by organic matter and Fe(III) hydroxides) and biochemical (metabolism of sulfate-reducing bacteria) processes. The accumulated elements form secondary sulfates, and Hg and Zn selenides. The results provide insights into accumulation of elements in the early history of coal and black shale deposits and have implications for remediation of polluted areas and for secondary enrichment technologies. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Green preparation and spectroscopic characterization of plasmonic silver nanoparticles using fruits as reducing agents

    DEFF Research Database (Denmark)

    Hyllested, Jes Ærøe; Espina Palanco, Marta; Hagen, Nicolai

    2015-01-01

    Chemicals typically available in plants have the capability to reduce silver and gold salts and to create silver and gold nanoparticles. We report the preparation of silver nanoparticles with sizes between 10 and 300 nm from silver nitrate using fruit extract collected from pineapples and oranges...... as reducing agents. The evolvement of a characteristic surface plasmon extinction spectrum in the range of 420 nm to 480 nm indicates the formation of silver nanoparticles after mixing silver nitrate solution and fruit extract. Shifts in plasmon peaks over time indicate the growth of nanoparticles. Electron...... absorption correlates with the decrease of absorption band in the UV. This confirms the evolution of silver nanoparticles from silver clusters. The presence of various silver clusters on the surface of the “green” plasmonic silver nanoparticles is also supported by a strong multi-color luminesce signal...

  20. Detection of Glucose with Atomic Absorption Spectroscopy by Using Oligonucleotide Functionalized Gold Nanoparticle.

    Science.gov (United States)

    Zhang, Hong; Yan, Honglian; Ling, Liansheng

    2016-06-01

    A novel method for the detection of glucose was established with atomic absorption spectroscopy by using the label of gold nanoparticle (AuNP). Silver-coated glass assembled with oligonucleotide 5'-SH-T12-AGA CAA GAG AGG-3' (Oligo 1) was acted as separation probe, oligonucleotide 5'-CAA CAG AGA ACG-T12-SH-3' modified gold nanoparticle (AuNP-Oligo 2) was acted as signal-reporting probe. Oligonucleotide 5'-CGT TCT CTG TTG CCT CTC TTG TCT-3' (Oligo 3) could hybridize with Oligo 1 on the surface of silver-coated glass and AuNP-Oligo 2, and free AuNP-Oligo 2 could be removed by rinsing with buffer. Hence the concentration of Oligo 3 was transformed into the concentration of gold element. In addition, Oligo 3 could be cleaved into DNA fragments by glucose, glucose oxidase and Fe(2+)-EDTA through Fenton reaction. Thereby the concentration of glucose could be transformed to the absorbance of gold element. Under the optimum conditions, the integrated absorbance decreased proportionally to the concentration of glucose over the range from 50.0 μM to 1.0 mM with a detection limit of 40.0 μM. Moreover, satisfactory result was obtained when the assay was used to determinate glucose in human serum.

  1. Effects of Ar or O2 Gas Bubbling for Shape, Size, and Composition Changes in Silver-Gold Alloy Nanoparticles Prepared from Galvanic Replacement Reaction

    Directory of Open Access Journals (Sweden)

    Md. Jahangir Alam

    2013-01-01

    Full Text Available The galvanic replacement reaction between silver nanostructures and AuCl4- solution has recently been demonstrated as a versatile method for generating metal nanostructures with hollow interiors. Here we describe the results of a systematic study detailing the morphological, structural, compositional, and spectral changes involved in such a heterogeneous reaction on the nanoscale. Effects of Ar or O2 gas bubbling for the formation of Ag-Au alloy nanoparticles by the galvanic replacement between spherical Ag nanoparticles and AuCl4- especially were studied in ethylene glycol (EG at 150°C. The shape, size, and composition changes occur rapidly under O2 bubbling in comparison with those under Ar bubbling. The major product after 60 min heating under Ar gas bubbling was perforated Ag-Au alloy particles formed by the replacement reaction and the minor product was ribbon-type particles produced from splitting off some perforated particles. On the other hand, the major product after 60 min heating under O2 gas bubbling was ribbon-type particles. In addition, small spherical Ag particles are produced. They are formed through rereduction of Ag+ ions released from the replacement reaction and oxidative etching of Ag nanoparticles by O2/Cl− in EG.

  2. Application of Gold Nanoparticles to Paint Colorants

    Science.gov (United States)

    Ishibashi, Hideo

    Metal nanoparticles possess unique properties that they do not exhibit in their bulk states. One of these properties is the color due to surface plasmon resonance. Gold nanoparticles appear red. This color has been utilized in glass for a long long time. In recent years, highly concentrated pastes of gold and silver nanoparticles have been successfully produced by using a special type of protective polymer and a mild reductant. The paste of gold nanoparticles can be used for paint and other materials as red colorants. In this article,application examples of gold nanoparticles as colorant are introduced. Recently, methods for producing bimetal nanoparticles such as gold/silver and gold/copper have been developed. These nanoparticles allow colors from yellow to green to be created. These methods and colors they produce are also described in this article.

  3. Plasmonic black gold by adiabatic nanofocusing and absorption of light in ultra-sharp convex grooves

    National Research Council Canada - National Science Library

    Søndergaard, Thomas; Novikov, Sergey M; Holmgaard, Tobias; Eriksen, René L; Beermann, Jonas; Han, Zhanghua; Pedersen, Kjeld; Bozhevolnyi, Sergey I

    2012-01-01

    Excitation of localized and delocalized surface plasmon resonances can be used for turning excellent reflectors of visible light, such as gold and silver, into efficient absorbers, whose wavelength...

  4. Platinum group elements and gold in ferromanganese crusts from Afanasiy-Nikitin seamount, equatorial Indian Ocean: Sources and fractionation

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Hein, J.R.; Rajani, R.P.; Chodankar, A.R.

    of correlation of those ratios with Co, Ce, and Ce/Co, indicate that the ANS Fe–Mn crusts are distinct from Pacific seamount Fe–Mn crusts, and reflect region-specific chemical characteristics. The platinum group elements (PGE: Ir, Ru, Rh, Pt, and Pd) and Au...

  5. Nanomineralogy and nanogeochemistry of ores from gold deposits of Uzbekistan

    Science.gov (United States)

    Koneev, R. I.; Khalmatov, R. A.; Mun, Yu. S.

    2010-12-01

    Gold deposits of Uzbekistan are localized in the Kyzylkum, Nurata, and Kurama ore districts of the Kyzylkum-Kurama metallogenic belt. They comprise a consecutive series of deposit types corresponding to the series of geochemical associations: (Au-W)—(Au-As)—(Au-Te)—(Au-Ag)—(Au-Sb)—(Au-Hg), which are arranged as a system of zones in orebodies, deposits, ore fields, and ore districts. The distribution of chemical elements characterized by average global concentrations in the crust within the ppm-ppb (10-6-10-9 t) range was studied in ores of gold deposits using an ICP MS Elan DRC II device. Mineral nanoassemblages with a grain size of 10-6 to 10-9 m were examined with a Jeol YXA 8800R Superprobe. The Au-W, Au-As, and Au-Te associations with Bi tellurides and maldonite in ore dominate at hypo- and meso-abyssal gold deposits of the Kyzylkum district (Muruntau, Myutenbay). The contribution of the Au-Sb association with Pb, Ag, and Fe sulfoantimonites and aurostibite increases at the Daughyztau, Kokpatas, and Amantaitau gold deposits. The Au-As, Au-Te, and Au-Sb associations with Bi tellurides, maldonite, sulfoantimonites, and aurostibite dominate at the mesoabyssal gold deposits of the Nurata district (Charmitan, Guzhumsay). The Au-Te and Au-Ag associations with Au, Ag, Pb, Sb, Bi, and Hg tellurides and Bi selenides dominate at the hypabyssal gold deposits of the Kurama district (Kochbulak, Kayragach). The gold-silver deposits of the Kyzylkum district (Kosmanachi, Vysokovol'tnoe) and the Kurama district (Kyzylalmasay, Arabulak) are close in composition. They are characterized by development of intermetallides, sulfides, sulfosalts, and selenides of Au-Ag and occasionally Au-Sb associations. Fineness of gold decreases from early to late geochemical associations, whereas the size of gold grains increases in the same direction from nanogold to visible gold. The studies at the micro- and nanolevel make it possible to establish the attributes of specific gold

  6. Controlled Aspect Ratios of Gold Nanorods in Reduction-Limited Conditions

    Directory of Open Access Journals (Sweden)

    Jong-Yeob Kim

    2011-01-01

    Full Text Available Aspect ratios of gold nanorods have been finely modified in reduction-limited conditions via two electrochemical ways: by changing the amount of a growth solution containing small gold clusters in the presence of already prepared gold nanorods as seeds or by changing electrolysis time in the presence or absence of a silver plate. While the atomic molar ratio of gold in the growth solution to gold in the seed solution is critical in the former method, the relative molar ratio of gold ions to silver ions in the electrolytic solution is important in the latter way for the control of the aspect ratios of gold nanorods. The aspect ratios of gold nanorods decrease with an increase of electrolysis time in the absence of a silver plate, but they increase with an increase of electrolysis time in the presence of a silver plate.

  7. Silver Nanoparticles

    Science.gov (United States)

    Khaydarov, R. R.; Khaydarov, R. A.; Estrin, Y.; Evgrafova, S.; Scheper, T.; Endres, C.; Cho, S. Y.

    The bactericidal effect of silver nanoparticles obtained by a novel electrochemical method on Escherichia coli, Staphylococcus aureus, Aspergillus niger and Penicillium phoeniceum cultures has been studied. The tests conducted have demonstrated that synthesized silver nanoparticles — when added to water paints or cotton fabrics — show a pronounced antibacterial/antifungal effect. It was shown that smaller silver nanoparticles have a greater antibacterial/antifungal efficacy. The paper also provides a review of scientific literature with regard to recent developments in the field of toxicity of silver nanoparticles and its effect on environment and human health.

  8. Trace element distribution, with a focus on gold, in copper-rich and zinc-rich sulfide chimneys from Brothers submarine volcano, Kermadec arc

    Science.gov (United States)

    Berkenbosch, H. A.; de Ronde, C. E.; McNeill, A.; Goemann, K.; Gemmell, J. B.

    2012-12-01

    . These tellurides are the first gold-bearing phase to be identified in these chimneys, and the Bi-Au association suggests that gold-enrichment up to 91 ppm is due to scavenging by liquid bismuth. To better understand the mineral associations and zonation of these and other trace elements within the chimney walls, we have undertaken element mapping on the four different chimneys types with both X-Ray fluorescence microscopy using synchrotron radiation and with Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). For example, in a chalcopyrite-rich chimney, visibly laminated chalcopyrite in the interior contains bands with a magmatic suite of elements including Co, Mo, Ag, Te, Au, and Bi. In comparison in a sphalerite-chalcopyrite-rich chimney, Au is again associated with minor Cu, although not with Bi and Te indicating alternative methods of gold transport and deposition are dominant. Element mapping allows us to better understand the physico-chemical gradients within chimney walls, as well as metal sources and transportation, and depositional processes.

  9. The mineralogy and mineral associations of platinum group elements and gold in the Platreef at Zwartfontein, Akanani Project, Northern Bushveld Complex, South Africa

    Science.gov (United States)

    van der Merwe, Frits; Viljoen, Fanus; Knoper, Mike

    2012-09-01

    The mineralogy of the platinum-group elements (PGE), and gold, in the Platreef of the Bushveld Complex, was investigated using an FEI Mineral Liberation Analyser. Polished sections were prepared from 171 samples collected from two boreholes, for the in-situ examination of platinum group minerals (PGM). PGM and gold minerals encountered include maslovite (PtBiTe, 32 area% of total PGM), kotulskite (Pd(BiTe), 17 %), isoferroplatinum (Pt3Fe, 15 %), sperrylite (PtAs2, 11 %), cooperite (PtS, 5 %), moncheite (PtTe2; 5 %), electrum (AuAg; 5 %), michenerite (PdBiTe; 3 %), Pd alloys (Pd, Sb, Sn; 3 %), hollingworthite ((Rh,Pt)AsS; 2 %), as well as minor (all <1 area% of total PGM) merenskyite (PdBiTe2), laurite (RuS2), rustenburgite (Pt0.4Pd0.4Sn0.2), froodite (PdBi2), atokite (Pd0.5Pt0.3Sn0.2), stumpflite (PtSb), plumbopalladinite (Pd3Pb2), and zvyagintsevite (Pd3Pb). An observed association of all PGM with base metal sulfides (BMS), and a pronounced association of PGE tellurides, arsenides and Pd&Pt alloys with secondary silicates, is consistent with the remobilisation and recrystallisation of some of the PGM's during hydrothermal alteration and serpentinisation subsequent to their initial (primary) crystallisation from BMS (e.g. Godel et al. J Petrol 48:1569-1604, 2007; Hutchinson and McDonald Appl Earth Sci (Trans Inst Min Metall B) 114:B208-224, 2008).

  10. Size-dependent characterisation of historical gold mine wastes to examine human pathways of exposure to arsenic and other potentially toxic elements.

    Science.gov (United States)

    Martin, Rachael; Dowling, Kim; Pearce, Dora C; Florentine, Singarayer; Bennett, John W; Stopic, Attila

    2016-10-01

    Abandoned historical gold mining wastes often exist as geographically extensive, unremediated, and poorly contained deposits that contain elevated levels of As and other potentially toxic elements (PTEs). One of the key variables governing human exposure to PTEs in mine waste is particle size. By applying a size-resolved approach to mine waste characterisation, this study reports on the proportions of mine waste relevant to human exposure and mobility, as well as their corresponding PTE concentrations, in four distinct historical mine wastes from the gold province in Central Victoria, Australia. To the best of our knowledge, such a detailed investigation and comparison of historical mining wastes has not been conducted in this mining-affected region. Mass distribution analysis revealed notable proportions of waste material in the readily ingestible size fraction (≤250 µm; 36.1-75.6 %) and the dust size fraction (≤100 µm; 5.9-45.6 %), suggesting a high potential for human exposure and dust mobilisation. Common to all mine waste types were statistically significant inverse trends between particle size and levels of As and Zn. Enrichment of As in the finest investigated size fraction (≤53 µm) is of particular concern as these particles are highly susceptible to long-distance atmospheric transport. Human populations that reside in the prevailing wind direction from a mine waste deposit may be at risk of As exposure via inhalation and/or ingestion pathways. Enrichment of PTEs in the finer size fractions indicates that human health risk assessments based on bulk contaminant concentrations may underestimate potential exposure intensities.

  11. Comparison of 3D Adaptive Remeshing Strategies for Finite Element Simulations of Electromagnetic Heating of Gold Nanoparticles

    Directory of Open Access Journals (Sweden)

    Fadhil Mezghani

    2015-01-01

    Full Text Available The optical properties of metallic nanoparticles are well known, but the study of their thermal behavior is in its infancy. However the local heating of surrounding medium, induced by illuminated nanostructures, opens the way to new sensors and devices. Consequently the accurate calculation of the electromagnetically induced heating of nanostructures is of interest. The proposed multiphysics problem cannot be directly solved with the classical refinement method of Comsol Multiphysics and a 3D adaptive remeshing process based on an a posteriori error estimator is used. In this paper the efficiency of three remeshing strategies for solving the multiphysics problem is compared. The first strategy uses independent remeshing for each physical quantity to reach a given accuracy. The second strategy only controls the accuracy on temperature. The third strategy uses a linear combination of the two normalized targets (the electric field intensity and the temperature. The analysis of the performance of each strategy is based on the convergence of the remeshing process in terms of number of elements. The efficiency of each strategy is also characterized by the number of computation iterations, the number of elements, the CPU time, and the RAM required to achieve a given target accuracy.

  12. Rapid Evolution of Silver Nanoparticle Resistance in Escherichia coli

    Directory of Open Access Journals (Sweden)

    Joseph L. Graves

    2015-02-01

    Full Text Available The recent exponential increase in the use of engineered nanoparticles (eNPs means both greater intentional and unintentional exposure of eNPs to microbes. Intentional use includes the use of eNPs as biocides. Unintentional exposure results from the fact that eNPs are included in a variety of commercial products (paints, sunscreens, cosmetics. Many of these eNPs are composed of heavy metals or metal oxides such as silver, gold, zinc, titanium dioxide, and zinc oxide. It is thought that since metallic/metallic oxide NPs impact so many aspects of bacterial physiology that it will difficult for bacteria to evolve resistance to them. This study utilized laboratory experimental evolution to evolve silver nanoparticle (AgNP resistance in the bacterium Escherichia coli (K12 MG1655, a bacterium that did not harbor any silver resistance elements. After 225 generations of exposure to the AgNP environment, the treatment populations demonstrated greater fitness versus control strains as measured by optical density (OD and colony forming units (CFU in the presence of varying concentrations of 10nm citrate-coated silver nanoparticles (AgNP or silver nitrate (AgNO3. Genomic analysis shows that changes associated with AgNP resistance were already accumulating within the treatment populations by generation 100, and by generation 200 three mutations had swept to high frequency in the AgNP resistance stocks. This study indicates that despite previous claims to the contrary bacteria can easily evolve resistance to AgNPs, and this occurs by relatively simple genomic changes. These results indicate that care should be taken with regards to the use of eNPs as biocides as well as with regards to unintentional exposure of microbial communities to eNPs in waste products.

  13. Rapid evolution of silver nanoparticle resistance in Escherichia coli.

    Science.gov (United States)

    Graves, Joseph L; Tajkarimi, Mehrdad; Cunningham, Quincy; Campbell, Adero; Nonga, Herve; Harrison, Scott H; Barrick, Jeffrey E

    2015-01-01

    The recent exponential increase in the use of engineered nanoparticles (eNPs) means both greater intentional and unintentional exposure of eNPs to microbes. Intentional use includes the use of eNPs as biocides. Unintentional exposure results from the fact that eNPs are included in a variety of commercial products (paints, sunscreens, cosmetics). Many of these eNPs are composed of heavy metals or metal oxides such as silver, gold, zinc, titanium dioxide, and zinc oxide. It is thought that since metallic/metallic oxide NPs impact so many aspects of bacterial physiology that it will difficult for bacteria to evolve resistance to them. This study utilized laboratory experimental evolution to evolve silver nanoparticle (AgNP) resistance in the bacterium Escherichia coli (K-12 MG1655), a bacterium that does not harbor any known silver resistance elements. After 225 generations of exposure to the AgNP environment, the treatment populations demonstrated greater fitness vs. control strains as measured by optical density (OD) and colony forming units (CFU) in the presence of varying concentrations of 10 nm citrate-coated silver nanoparticles (AgNP) or silver nitrate (AgNO3). Genomic analysis shows that changes associated with AgNP resistance were already accumulating within the treatment populations by generation 100, and by generation 200 three mutations had swept to high frequency in the AgNP resistance stocks. This study indicates that despite previous claims to the contrary bacteria can easily evolve resistance to AgNPs, and this occurs by relatively simple genomic changes. These results indicate that care should be taken with regards to the use of eNPs as biocides as well as with regards to unintentional exposure of microbial communities to eNPs in waste products.

  14. Use of UV-vis-NIR spectroscopy to monitor label-free interaction between molecular recognition elements and erythropoietin on a gold-coated polycarbonate platform.

    Science.gov (United States)

    Citartan, Marimuthu; Gopinath, Subash C B; Tominaga, Junji; Chen, Yeng; Tang, Thean-Hock

    2014-08-01

    Label-free-based detection is pivotal for real-time monitoring of biomolecular interactions and to eliminate the need for labeling with tags that can occupy important binding sites of biomolecules. One simplest form of label-free-based detection is ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy, which measure changes in reflectivity as a means to monitor immobilization and interaction of biomolecules with their corresponding partners. In biosensor development, the platform used for the biomolecular interaction should be suitable for different molecular recognition elements. In this study, gold (Au)-coated polycarbonate was used as a platform and as a proof-of-concept, erythropoietin (EPO), a doping substance widely abused by the athletes was used as the target. The interaction of EPO with its corresponding molecular recognition elements (anti-EPO monoclonal antibody and anti-EPO DNA aptamer) is monitored by UV-vis-NIR spectroscopy. Prior to this, to show that UV-vis-NIR spectroscopy is a suitable method for measuring biomolecular interaction, the interaction between biotin and streptavidin was demonstrated via this strategy and reflectivity of this interaction decreased by 25%. Subsequent to this, interaction of the EPO with anti-EPO monoclonal antibody and anti-EPO DNA aptamer resulted in the decrease of reflectivity by 5% and 10%, respectively. The results indicated that Au-coated polycarbonate could be an ideal biosensor platform for monitoring biomolecular interactions using UV-vis-NIR spectroscopy. A smaller version of the Au-coated polycarbonate substrates can be derived from the recent set-up, to be applied towards detecting EPO abuse among atheletes. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Platinum-group element and Re-Os geochemistry of lamprophyres in the Zhenyuan gold deposit, Yunnan Province, China: Implications for petrogenesis and mantle evolution

    Science.gov (United States)

    Gan, Ting; Huang, Zhilong

    2017-06-01

    Cenozoic lamprophyres are widespread along the Ailaoshan suture, SW Yunnan, SW China, where there are also many important gold deposits, especially the Zhenyuan deposit. We have carried out a geochemical investigation of the Zhenyuan lamprophyres in terms of major and trace elements, platinum-group elements (PGE), and Os isotopes. The Zhenyuan lamprophyres can be classified into groups with high or low Os concentrations. The 187Os/188Os ratios, corrected for in situ growth, are highly variable in both types of lamprophyre, ranging from mantle values up to 1.13. The highly radiogenic Os isotopic signatures are interpreted as being due to long-term accumulation of elevated Re/Os in the lithospheric mantle, as a result of subduction-related metasomatism. The highly variable 187Os/188Os ratios of the low-Os lamprophyres might also have resulted from metasomatism of a deeply derived carbonate melt, which did not elevate Os concentrations significantly. The Zhenyuan lamprophyres feature low PGE contents and can be classified into two groups: A and B, based on their primitive-mantle-normalized PGE patterns. Group A is characterized by strongly negative Ru anomalies, while Group B is characterized by slightly negative Ru anomalies and low total PGE contents. The PGE characteristics may be explained by a two-stage model of magma evolution. Very high Cu/Pd and low Pt/Y ratios indicate the first stage involved sulfur saturation and sulfide removal, producing variable total-PGE concentrations, especially in Group B. The second stage involved S-undersaturation and the early crystallization of silicate minerals (e.g., olivine) along with laurite and/or Ru-Ir-Os alloy, fractionating PGEs and producing marked negative Eu anomalies.

  16. A Hoard of Silver Currency from Achaemenid Babylon

    DEFF Research Database (Denmark)

    Reade, Julian

    1986-01-01

    Analytical appendix by M.J. Hughes and M.R. Cowell of some 25 silver items, both sheets and coins, from the hoard, includes analysis by x-ray fluorescence and atomic absorption spectroscopy. All items are of fairly good silver, with one or two parts of copper, and substantial traces of gold and a...

  17. Boiling and vertical mineralization zoning: a case study from the Apacheta low-sulfidation epithermal gold-silver deposit, southern Peru

    Science.gov (United States)

    André-Mayer, Anne-Sylvie; Leroy, Jacques; Bailly, Laurent; Chauvet, Alain; Marcoux, Eric; Grancea, Luminita; Llosa, Fernando; Rosas, Juan

    2002-06-01

    The Au-Ag (±Pb-Zn) Apacheta deposit is located in the Shila district, 600 km southeast of Lima in the Cordillera Occidental of Arequipa Province, southern Peru. The vein mineralization is found in Early to Middle Miocene calc-alkaline lava flows and volcanic breccias. Both gangue and sulfide mineralization express a typical low-sulfidation system; assay data show element zoning with base metals enriched at depth and higher concentrations of precious metals in the upper part of the veins. Three main deposition stages are observed: (1) early pyrite and base-metal sulfides with minor electrum 1 and acanthite; (2) brecciation of this mineral assemblage and cross-cutting veinlets with subhedral quartz crystals, Mn-bearing calcite and rhombic adularia crystals; and finally (3) veinlets and geodal filling of an assemblage of tennantite/tetrahedrite + colorless sphalerite 2 + galena + chalcopyrite + electrum 2. Fluid inclusions in the mineralized veins display two distinct types: aqueous-carbonic liquid-rich Lw-c inclusions, and aqueous-carbonic vapor-rich Vw-c inclusions. Microthermometric data indicate that the ore minerals were deposited between 300 and 225 °C from relatively dilute hydrothermal fluids (0.6-3.4 wt% NaCl). The physical and chemical characteristics of the hydrothermal fluids show a vertical evolution, with in particular a drop in temperature and a loss of H2S. The presence of adularia and platy calcite and of co-existing liquid-rich and vapor-rich inclusions in the ore-stage indicates a boiling event. Strong H2S enrichment in the Vw-c inclusions observed at -200 m, the abundance of platy calcite, and the occurrence of hydrothermal breccia at this level may indicate a zone of intense boiling. The vertical element zoning observed in the Apacheta deposit thus seems to be directly related to the vertical evolution of hydrothermal-fluid characteristics. Precious-metal deposition mainly occurred above the 200-m level below the present-day surface, in response

  18. Detection of gold particles in the neck skin after lightning stroke with evaporation of an ornamental chain.

    Science.gov (United States)

    Jonas, Ludwig; Fulda, Gerhard; Nizze, Horst; Zimmermann, Regina; Gross, Gerd; Zack, Fred; Kröning, Geofred; Holzhüter, Gerd; Haas, H J

    2002-01-01

    A German couple was struck by lightning. Both patients survived this event. Whereas the husband was unconscious for only a few minutes, his wife fell into coma for 24 h. The lightning stroke entered the body of the woman behind the left ear and left it at the left shoe. The stroke caused a partial evaporation of a gold ornamental chain on the neck, resulting in a tattoo of the neck skin. A biopsy of the skin 6 months after the event showed the accumulation of gold particles of different size in the dermis down to the subcutaneous fatty tissue. In semithin sections, histiocytes, multinucleated foreign giant cells, and fibroblasts were visible with uptaken metallic particles. In transmission electron microscopy, gold globules of up to 30 microm in diameter were visible outside the cells in the collageneous matrix of the connective tissue besides smaller metallic particles up to 5 nm inside lysosomes and residual bodies of phagocytic cells. Four different kinds of gold particles could be differentiated: globules, granular irregular particles, tubules, and tanglelike tracks. In scanning electron microscopy, gold particles were demonstrated by backscatter detection in the connective tissue of subcutis, where the EDX elemental analysis showed strong signals of aurum (Au), copper (Cu), and argentum (Ag). The detected metals were quantified by AAS as 70% gold, 21% silver, and 9% copper, which demonstrates the composition of gold alloy of the neck chain of the patient. Tanglelike tracks and elongated gold deposits represent crystals of gold salts, as detected by electron diffraction and polarization microscopy. Attempts to remove the gold particles from the skin to remove the tattoo should not be undertaken because the gold is deep and widespread.

  19. Orthodontic silver brazing alloys.

    Science.gov (United States)

    Brockhurst, P J; Pham, H L

    1989-10-01

    Orthodontic silver brazing alloys suffer from the presence of cadmium, excessive flow temperatures, and crevice corrosion on stainless steel. Seven alloys were examined. Two alloys contained cadmium. The lowest flow temperature observed was 629 degrees C for a cadmium alloy and 651 degrees C for two cadmium free alloys. Three alloys had corrosion resistance superior to the other solders. Addition of low melting temperature elements gallium and indium reduced flow temperature in some cases but produced brittleness in the brazing alloy.

  20. Controlled synthesis of pentagonal gold nanotubes at room temperature

    Science.gov (United States)

    Bi, Yingpu; Lu, Gongxuan

    2008-07-01

    Large quantities of pentagonal gold nanotubes have been synthesized by reducing chloroauric acid with silver nanowires in an aqueous solution of hexadecyltrimethylammonium bromide (CTAB) at room temperature. These gold nanotubes possess perfect structures, smooth surfaces, highly crystalline walls, and similar cross-sections to that of the silver template. In this process, the CTAB participation was found to be crucial for shape-controlled synthesis of pentagonal gold nanotubes. In the absence of CTAB, loose and hollow gold structures were routinely generated, while bundled gold nanotubes with rough surfaces were obtained by replacing the CTAB with poly(vinyl pyrrolidone) (PVP). The possible formation mechanism of pentagonal gold nanotubes has also been discussed on the basis of various growth stages studied by field-emission scanning electron microscopy (FE-SEM) images. In addition, the catalytic properties of these hollow nanostructures for hydrogen generation reaction from HCHO solution have also been investigated. They showed higher activity than that of spherical gold nanoparticles.

  1. ELECTRO-GRAVIMETRIC RECOVERY OF SILVER FROM ...

    African Journals Online (AJOL)

    with gold and other metals. Generally, silver is associated with sulfides of Fe, As, Cu as well compounds of antimony and selenium [7]. Cyanide leaching, activated carbon and thiourea methods have been applied for effective leaching, adsorption and desorption of precious metals. In this regard an electrolytic cell holding.

  2. Contributions to the gold metallogeny of northern Nevada

    Science.gov (United States)

    Tosdal, Richard M.

    1998-01-01

    Nevada is one of the Earth's premier gold producing regions, accounting for approximately 64 percent of the U.S and nine percent of the world total. The impact of these mines on nearby local economies and on our national balance of payments is profound, and will continue well into the next century. Of principal importance in this region are giant sedimentary-rock-hosted (Carlin-type) deposits. These are some of the world's largest deposits, but yet are poorly understood. Other sedimentary-rock hosted deposits in the region, the distal-disseminated Ag-Au type, are genetically related to shallow plutonic complexes. Hot-spring gold-silver systems associated with Tertiary volcanic rocks represent a third type of precious metal deposit in northern Nevada. These deposits, despite being generally smaller than sedimentary-rock-hosted gold deposits, are also important gold-silver resources. Aspects about the geologic and metallogenic setting of gold-silver deposits in northern Nevada are addressed in the twenty-two chapters that compose this volume. The volume is organized along four themes: (1) crustal structure; (2) Carlin-type deposits; (3) pluton-related gold-silver deposits near Battle Mountain; and (4) hot-spring gold-silver deposits. This Open-File Report, the result of ongoing geologic and mineral-resource investigations, provides a basis for mineral exploration, for land-use planning decisions, and for environmental questions in northern Nevada.

  3. Portrait of Evan Parker (Silver and Gold)

    OpenAIRE

    Henderson, Neil

    2009-01-01

    This film explores the musical technique of Evan Parker and the effect it has on his soprano saxophone. The camera is placed below the instrument so it can catch the light entering the instrument as it is played. There is a direct correlation between what we see and what we hear, each light has its counterpart in sound.

  4. Unexpected interactions between gold and N-morpholino-sulfonates

    DEFF Research Database (Denmark)

    Nielsen, Frederick Stappen; Engelbrekt, Christian; Elliot, Samuel Gilbert

    Nanoporous gold (NPG) has a high surface area and excellent conductivity. It is an ideal supporting material for the electrocatalysis, e.g. in fuel cell applications. NPG is traditionally produced by etching a gold/silver alloy. This method has significant drawbacks, such as the introduction of s...

  5. Gold particle formation via photoenhanced deposition on lithium niobate

    Energy Technology Data Exchange (ETDEWEB)

    Zaniewski, A.M., E-mail: azaniews@asu.edu; Meeks, V.; Nemanich, R.J.

    2017-05-31

    Highlights: • Gold chloride is reduced into solid gold nanoparticles at the surface of a polarized semiconductor. • Reduction processes are driven by ultraviolet light. • Gold nanoparticle and silver nanoparticle deposition patterns are compared. - Abstract: In this work, we report on a technique to reduce gold chloride into sub-micron particles and nanoparticles. We use photoelectron transfer from periodically polarized lithium niobate (PPLN) illuminated with above band gap light to drive the surface reactions required for the reduction and particle formation. The particle sizes and distributions on the PPLN surface are sensitive to the solution concentration, with inhibited nucleation and large particles (>150 nm) for both low (2E−8M to 9E−7M) and high (1E−5M to 1E−3M) concentrations of gold chloride. At midrange values of the concentration, nucleation is more frequent, resulting in smaller sized particles (<150 nm). We compare the deposition process to that for silver, which has been previously studied. We find that the reduction of gold chloride into nanoparticles is inhibited compared to silver ion reduction, due to the multi-step reaction required for gold particle formation. This also has consequences for the resulting deposition patterns: while silver deposits into nanowires along boundaries between areas with opposite signed polarizations, such patterning of the deposition is not observed for gold, for a wide range of concentrations studied (2E−8 to 1E−3M).

  6. Synthesis of porous gold nanoshells by controlled transmetallation reaction

    Energy Technology Data Exchange (ETDEWEB)

    Pattabi, Manjunatha, E-mail: manjupattabi@yahoo.com; M, Krishnaprabha [Department of Materials Science, Mangalore University, Mangalagangothri-574199 (India)

    2015-06-24

    Aqueous synthesis of porous gold nanoshells in one step is carried out through controlled transmetallation (TM) reaction using a naturally available egg shell membrane (ESM) as a barrier between the sacrificial silver particles (AgNPs) and the gold precursor solution (HAuCl{sub 4}). The formation of porous gold nanoshells via TM reaction is inferred from UV-Vis spectroscopy and the scanning electron microscopic (SEM) studies.

  7. μ3-Oxido-tris{dichlorido[1,3-bis(1,3,5-trimethylphenylimidazol-2-ylidene]gold(III} bis(trifluoromethanesulfonylimide–[bis(trifluoromethanesulfonylimide]silver(I (1/2

    Directory of Open Access Journals (Sweden)

    Marek Pažický

    2010-07-01

    Full Text Available The unusual trinuclear AuIII oxide title complex, [Au3Cl6O(C21H24N23](C2F6NO4S2·2[Ag(C2F6NO4S2], is the side product of the reaction of [1,3-bis(1,3,5-trimethylphenylimidazol-2-ylidene]dichloridophenylgold(III with silver bis(trifluoromethanesulfonylimide in the presence of traces of water. In contrast to corresponding AuI complexes, the core structure of the title compound is planar. Two silver(I bis(trifluoromethanesulfonylimide units are loosely bound to the complex cation. Here the silver atoms, disordered over two positions in a 0.870 (2:0.130 (2 ratio, interact either with the lone pairs of three chlorine ligands or two chlorine ligands and one edge of the mesityl π-system. The crystal under investigation was a partial racemic twin.

  8. Russell-Silver syndrome

    Science.gov (United States)

    Silver-Russell syndrome; Silver syndrome; RSS; Russell-Silver syndrome ... One in 10 children with this syndrome has a problem involving chromosome 7. In other people with the syndrome, it may affect chromosome 11. Most of the time, it ...

  9. Gold nephropathy.

    Science.gov (United States)

    Antonovych, T T

    1981-01-01

    The early use of gold in medicine and dentistry dates back to the ancient Chinese and Egyptians. The discovery in 1890 that gold salts were toxic in vitro to tubercle bacilli led to the extensive treatment of tuberculosis with gold salts in the first three decades of this century. Eventually, gold therapy was extended to arthritis and lupus erythematosus, because of the belief that these diseases were forms of tuberculosis. Because of its beneficial effect particularly on active rheumatoid arthritis, chrysotherapy has remained one of the most widely used treatments of rheumatoid arthritis for the past half century. Toxicity of gold salts includes hypersensitivity reaction of skin and mucous membranes, bone marrow depression, and nephrotoxicity. The nephrotoxic clinical manifestations are renal insufficiency, proteinuria and hematuria, and the nephrotic syndrome. The pathologic changes are tubular degeneration, acute tubular necrosis or immune complex glomerulonephritis. The justification that any of these possible changes are the result of gold therapy rests clinically upon the time relationship of gold therapy and the renal symptoms, and pathologically upon the presence of gold inclusions (aurosomes) in proximal tubular epithelial cells. Aurosomes can at times be visualized by light microscopy, are usually seen by electron microscopy, and can be identified by microprobe analysis. Their pathology will be illustrated and pathogenic mechanisms discussed.

  10. Separation of silver ions and starch modified silver nanoparticles using high performance liquid chromatography with ultraviolet and inductively coupled mass spectrometric detection

    Science.gov (United States)

    Hanley, Traci A.; Saadawi, Ryan; Zhang, Peng; Caruso, Joseph A.; Landero-Figueroa, Julio

    2014-10-01

    The production of commercially available products marketed to contain silver nanoparticles is rapidly increasing. Species-specific toxicity is a phenomenon associated with many elements, including silver, making it imperative to develop a method to identify and quantify the various forms of silver (namely, silver ions vs. silver nanoparticles) possibly present in these products. In this study a method was developed using high performance liquid chromatography (HPLC) with ultraviolet (UV-VIS) and inductively coupled mass spectrometric (ICP-MS) detection to separate starch stabilized silver nanoparticles (AgNPs) and silver ions (Ag+) by cation exchange chromatography with 0.5 M nitric acid mobile phase. The silver nanoparticles and ions were baseline resolved with an ICP-MS response linear over four orders of magnitude, 0.04 mg kg- 1 detection limit, and 90% chromatographic recovery for silver solutions containing ions and starch stabilized silver nanoparticles smaller than 100 nm.

  11. Regional framework and geology of iron oxide-apatite-rare earth element and iron oxide-copper-gold deposits of the Mesoproterozoic St. Francois Mountains Terrane, southeast Missouri

    Science.gov (United States)

    Day, Warren C.; Slack, John F.; Ayuso, Robert A.; Seeger, Cheryl M.

    2016-01-01

    This paper provides an overview on the genesis of Mesoproterozoic igneous rocks and associated iron oxide ± apatite (IOA) ± rare earth element, iron oxide-copper-gold (IOCG), and iron-rich sedimentary deposits in the St. Francois Mountains terrane of southeast Missouri, USA. The St. Francois Mountains terrane lies along the southeastern margin of Laurentia as part of the eastern granite-rhyolite province. The province formed during two major pulses of igneous activity: (1) an older early Mesoproterozoic (ca. 1.50–1.44 Ga) episode of volcanism and granite plutonism, and (2) a younger middle Mesoproterozoic (ca. 1.33–1.30 Ga) episode of bimodal gabbro and granite plutonism. The volcanic rocks are predominantly high-silica rhyolite pyroclastic flows, volcanogenic breccias, and associated volcanogenic sediments with lesser amounts of basaltic to andesitic volcanic and associated subvolcanic intrusive rocks. The iron oxide deposits are all hosted in the early Mesoproterozoic volcanic and volcaniclastic sequences. Previous studies have characterized the St. Francois Mountains terrane as a classic, A-type within-plate granitic terrane. However, our new whole-rock geochemical data indicate that the felsic volcanic rocks are effusive derivatives from multicomponent source types, having compositional similarities to A-type within-plate granites as well as to S- and I-type granites generated in an arc setting. In addition, the volcanic-hosted IOA and IOCG deposits occur within bimodal volcanic sequences, some of which have volcanic arc geochemical affinities, suggesting an extensional tectonic setting during volcanism prior to emplacement of the ore-forming systems.The Missouri iron orebodies are magmatic-related hydrothermal deposits that, when considered in aggregate, display a vertical zonation from high-temperature, magmatic ± hydrothermal IOA deposits emplaced at moderate depths (~1–2 km), to magnetite-dominant IOA veins and IOCG deposits emplaced at shallow

  12. Implementation of a multisource model for gold nanoparticle-mediated plasmonic heating with near-infrared laser by the finite element method.

    Science.gov (United States)

    Reynoso, Francisco J; Lee, Chae-Deok; Cheong, Seong-Kyun; Cho, Sang Hyun

    2013-07-01

    The use of optically tunable gold nanoparticles (GNPs) in conjunction with near-infrared (NIR) laser has emerged as an attractive option for laser-induced thermal therapy (LITT), as it capitalizes on plasmonic heating of GNPs tuned to absorb light strongly in the NIR region. Previously, the authors developed a multisource model to predict the temperature change in a GNP-laden tissue-like medium illuminated by NIR laser and implemented it by a linear superposition (LS) method combining analytic and finite element method (FEM) solutions. While it is intuitive and straightforward, the LS approach might be somewhat cumbersome to implement for realistic LITT cases because it requires separate calculations of the temperature change due to individual GNP heat sources and the laser heat source. Therefore, the current investigation aimed to develop a simpler yet mathematically more elegant and computationally more efficient method solely based on FEM to implement the authors' multisource model. A multisource FEM model was developed to calculate the full spatiotemporal temperature distribution due to all heat sources (i.e., individual GNPs and the laser heat source) by solving the heat diffusion equation with multiple heat sources using FEM. This model was tested for its validity using two computational phantoms, a two-layer GNP-laden cylindrical phantom and a breast phantom with a GNP-laden microcavity. For comparison, the results for the two phantom cases were also obtained from the LS method. For the two-layer phantom case, the FEM approach resulted in a maximum temperature increase of 16.4 °C at a depth of 1.35 cm, 2.5 mm below the interface between the two layers, while the LS method produced a maximum temperature increase of 16.7 °C at a depth of 1.3 cm, 2 mm below the interface between the two layers. A comparison of the depth versus temperature changes obtained from the two approaches showed reasonably good agreement within 6%. In the breast phantom case, the LS

  13. Ore-microscopic and geochemical characteristics of gold-tellurides-sulfide mineralization in the Macassa Gold Mine, Abitibi Belt, Canada

    Science.gov (United States)

    Tesfaye, G.

    1992-01-01

    The Macassa Gold Mine is the only operational mine (Lac-Minerals Ltd., Macassa Division) of seven original gold producers in the Kirkland Lake camp of northern Ontario, Canada. The gold deposit is in Archaean volcanic and sedimentary rocks which have been intruded by a composite syenite stock. The mineralization has taken place in two stages. The first stage is not gold bearing but involves pyritization and concomitant development of titanium phase minerals (leucoxene, rutile) and hematite. It is mainly associated with carbonatization, silicification and hematitization marked by Ba, Sr and Rb enrichment. In contrast to this, the quartz vein-type mineralization is associated mainly with later silicification and enrichment with tellurium, lead, silver, gold and copper. It is relatively depleted in Sr, Ba and Rb. The ore mineralogical assemblages in the second stage include pyrite, chalcopyrite, petzite, altaite and native gold. Geochemical and petrographic evidence indicate that the reddened wall rocks (hematitized) and reddened fragments are neither related with nor contain any gold. Therefore, hematitization and the presence of barium, in this case in K-feldspars, could not be considered as the sole evidence to suggest a magmatic oxidizing fluid model for the genesis of Macassa gold deposit. Regarding the metals transport, tellurides and thiocomplexes are considered as the important carriers of gold and silver. Hence, fugacity of tellurium and sulphur controlled the precipitation of gold in the Macassa gold deposit.

  14. Controllable synthesis and SERS characteristics of hollow sea-urchin gold nanoparticles.

    Science.gov (United States)

    Li, Junpeng; Zhou, Jun; Jiang, Tao; Wang, Binbing; Gu, Min; Petti, Lucia; Mormile, Pasquale

    2014-12-14

    Hollow sea-urchin gold nanoparticles (HSU-GNPs) were successfully prepared through a novel one-step galvanic replacement strategy, and their corresponding optical properties was studied in detail. During the synthesis process, the sizes of the interior hollows of the HSU-GNPs could be changed by adjusting the amount of silver nitrate added into hydrogen tetrachloroaurate trihydrate solution. The absorption spectra of the HSU-GNPs showed that the localized surface plasmon resonance (LSPR) peaks were red-shifted with increasing size of the interior hollows in the HSU-GNPs. When the added amount of silver nitrate was up to 6 μl, the LSPR peak of the synthesized HSU-GNP reached 726 nm as a maximum red-shift. Furthermore, the absorption spectra of the HSU-GNPs with different morphologies were theoretically simulated by the finite element method, which was consistent with the experimental results and explained the origin of the red-shift of the LSPR peaks. In addition, the surface-enhanced Raman scattering (SERS) of the sea urchin gold nanoparticles were also investigated using 4-mercaptobenzoic acid as a Raman reporter molecule. Both the experimental and calculated results showed that the HSU-GNPs had stronger SERS enhancement than the solid sea-urchin gold nanoparticles. In particular, the HSU-GNPs prepared by adding 6 μl silver nitrate exhibited a maximum SERS enhancement factor, EF = 1.1 × 10(9), due to the LSPR peak at 726 nm which is near to the excitation wavelength, 785 nm. This feature is significant for designing a biosensor with a super-high sensitivity based on the morphology of the HSU-GNPs.

  15. Silver Selenide Thermodynamics for Copper Anode Slime Refining

    Science.gov (United States)

    Feng, Dawei; Taskinen, Pekka

    Copper anode slimes are a by-product of the electrolytic refining of anode copper, which contains significant amounts of silver, selenium, copper, and gold. Slimes are usually smelted to recover silver and gold. The thermodynamics of the smelting of such selenium-rich materials have received only little attention. In this work, the numerical values on the standard thermodynamic functions of Ag2Se (Naumannite) were determined by the electromotive force (EMF) method in a solid-state galvanic cell with superionic conductor RbAg4I5 as the solid electrolyte. Ag2Se was synthesized from pure elements in evacuated quartz glass ampoules and examined to be homogenous by SEM and EDS. According to the experimental data on the EMF versus temperature, the analytical equations were obtained for the polymorphic forms of Ag2Se. The temperature of phase transformation from α-Ag2Se to β-Ag2Se is determined experimentally to be 407.7 K by interpolation of the EMF vs. T data, and the enthalpy of phase transformation is 6.06 kJ•mol-1. The Gibbs energy of formation for Ag2Se is given by Δ {\\overline G _{α - A{g_2}Se}},J = - ( {40869.14 ± 0.58129} ) - ( {27.94759 ± 1.53034} ) \\cdot T,( {350 < T/K < 408} ), Δ {\\overline G _{β - A{g_2}Se}},J = - ( {35062.17 ± 0.09895} ) - ( {42.17847 ± 0.21827} ) \\cdot T,( {408 < T/K < 500} ).

  16. [Ag25(SR)18]¯: The ‘Golden’ Silver Nanoparticle

    KAUST Repository

    Joshi, Chakra Prasad

    2015-08-31

    Silver nanoparticles with an atomically precise molecular formula [Ag25(SR)18]¯ (‒SR: thiolate) are synthesized and their single-crystal structure is determined. This synthesized nanocluster is the only silver nanoparticle that has a virtually identical analogue in gold, i.e., [Au25(SR)18]¯, in terms of number of metal atoms, ligand count, super-atom electronic configuration, and atomic arrangement. Furthermore, both [Ag25(SR)18]¯ and its gold analogue share a number of features in their optical absorption spectra. This unprecedented molecular synthesis in silver to mimic gold offers the first model nanoparticle platform to investigate the centuries-old problem of understanding the fundamental differences between silver and gold in terms of nobility, catalytic activity, and optical property.

  17. Biosynthesis of silver nanoparticles

    African Journals Online (AJOL)

    SIMBU

    2013-05-22

    May 22, 2013 ... exposure to silver can cause agyrosis and argyria also; it is toxic to mammalian cells (Gong et al., 2007). The current investigation supports that use of silver ion or metallic silver as well as, silver nanoparticles can be exploited in medicine for burn treatment, dental materials, coating stainless steel materials, ...

  18. 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.

  19. Green preparation and spectroscopic characterization of plasmonic silver nanoparticles using fruits as reducing agents

    Directory of Open Access Journals (Sweden)

    Jes Ærøe Hyllested

    2015-01-01

    Full Text Available Chemicals typically available in plants have the capability to reduce silver and gold salts and to create silver and gold nanoparticles. We report the preparation of silver nanoparticles with sizes between 10 and 300 nm from silver nitrate using fruit extract collected from pineapples and oranges as reducing agents. The evolvement of a characteristic surface plasmon extinction spectrum in the range of 420 nm to 480 nm indicates the formation of silver nanoparticles after mixing silver nitrate solution and fruit extract. Shifts in plasmon peaks over time indicate the growth of nanoparticles. Electron microscopy shows that the shapes of the nanoparticles are different depending on the fruit used for preparation. The green preparation process can result in individual nanoparticles with a very poor tendency to form aggregates with narrow gaps even when aggregation is forced by the addition of NaCl. This explains only modest enhancement factors for near-infrared-excited surface enhanced Raman scattering. In addition to the surface plasmon band, UV–visible absorption spectra show features in the UV range which indicates also the presence of small silver clusters, such as Ag42+. The increase of the plasmon absorption correlates with the decrease of absorption band in the UV. This confirms the evolution of silver nanoparticles from silver clusters. The presence of various silver clusters on the surface of the “green” plasmonic silver nanoparticles is also supported by a strong multicolor luminesce signal emitted by the plasmonic particles during 473 nm excitation.

  20. Biosynthesis of nanoparticles of metals and metalloids by basidiomycetes. Preparation of gold nanoparticles by using purified fungal phenol oxidases.

    Science.gov (United States)

    Vetchinkina, Elena P; Loshchinina, Ekaterina A; Vodolazov, Ilya R; Kursky, Viktor F; Dykman, Lev A; Nikitina, Valentina E

    2017-02-01

    The work shows the ability of cultured Basidiomycetes of different taxonomic groups-Lentinus edodes, Pleurotus ostreatus, Ganoderma lucidum, and Grifola frondosa-to recover gold, silver, selenium, and silicon, to elemental state with nanoparticles formation. It examines the effect of these metal and metalloid compounds on the parameters of growth and accumulation of biomass; the optimal cultivation conditions and concentrations of the studied ion-containing compounds for recovery of nanoparticles have been identified. Using the techniques of transmission electron microscopy, dynamic light scattering, X-ray fluorescence and X-ray phase analysis, the degrees of oxidation of the bioreduced elements, the ζ-potential of colloidal solutions uniformity, size, shape, and location of the nanoparticles in the culture fluid, as well as on the surface and the inside of filamentous hyphae have been determined. The study has found the part played by homogeneous chromatographically pure fungal phenol-oxidizing enzymes (laccases, tyrosinases, and Mn-peroxidases) in the recovery mechanism with formation of electrostatically stabilized colloidal solutions. A hypothetical mechanism of gold(III) reduction from HAuCl4 to gold(0) by phenol oxidases with gold nanoparticles formation of different shapes and sizes has been introduced.

  1. Nanostructured Antibacterial Silver Deposited on Polypropylene Nonwovens

    Science.gov (United States)

    Hong-Bo, Wang; Jin-Yan, Wang; Qu-Fu, Wei; Jian-Han, Hong; Xiao-Yan, Zhao

    Nanostructured silver films were deposited on polypropylene (PP) nonwovens by RF magnetron sputter coating to obtain the antibacterial properties. Shake flask test was used to evaluate the antibacterial properties of the materials. Atomic force microscope (AFM) was utilized to observe the surface morphology. Energy-dispersive X-ray (EDX) was also employed to analyze the surface elemental compositions. The antibacterial results indicated that the prolonged deposition time led to a significant improvement in antibacterial effect, and sputtering power and argon pressure did not show obvious effect on antibacterial performance. It is believed that the total amount of silver ions released from the silver coating was increased as the deposition time increased. AFM images and quantitative analysis of EDX, respectively revealed that increase in deposition time led to the increased coverage of silver film and the increased silver weight percentage per unit surface, which provided evidences for the increased release rate of silver ions from the coating. Moreover, it was found that the optimum silver coating thickness was about 3 nm, taking antibacterial effect and cost of production into account.

  2. Functionalization of biosynthesized gold nanoparticle from aqueous ...

    African Journals Online (AJOL)

    The absorption peak of the biosynthesized Gold nanoparticle was found to be 545.5 nm and Zetasizer analysis showed that the average particle size was 28.5 nm with morphological structure of spherical and triangular shapes using SEM and TEM. EDAX confirmed the presence of element gold, carbon, oxygen and copper.

  3. The facet selectivity of inorganic ions on silver nanocrystals in etching reactions

    Energy Technology Data Exchange (ETDEWEB)

    Xu Shuping; Tang Bin; Zheng Xianliang; Zhou Ji; An Jing; Ning Xiaohua; Xu Weiqing, E-mail: xuwq@jlu.edu.cn [State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012 (China)

    2009-10-14

    The facet selectivity of the halide ions and chlorauric acid for several shaped silver nanocrystals is presented in this paper. Two inorganic ions show different representations when they are used for etching silver nanocrystals in the self-sacrificial template reaction. The morphological changes of the silver nanocrystals indicate that the halide ions prefer to etch the (110) facets of silver nanocrystals, while in the chlorauric acid etching reaction, gold first modifies the (110) facets and then lets chlorauric acid etch the (111) facets instead. The selective facet etching on individual nanoparticles in the solution phase has crucial significance in the control-synthesis of nanocrystals and the facet asymmetric reaction.

  4. Defining rules for the shape evolution of gold nanoparticles.

    Science.gov (United States)

    Langille, Mark R; Personick, Michelle L; Zhang, Jian; Mirkin, Chad A

    2012-09-05

    The roles of silver ions and halides (chloride, bromide, and iodide) in the seed-mediated synthesis of gold nanostructures have been investigated, and their influence on the growth of 10 classes of nanoparticles that differ in shape has been determined. We systematically studied the effects that each chemical component has on the particle shape, on the rate of particle formation, and on the chemical composition of the particle surface. We demonstrate that halides can be used to (1) adjust the reduction potential of the gold ion species in solution and (2) passivate the gold nanoparticle surface, both of which control the reaction kinetics and thus enable the selective synthesis of a series of different particle shapes. We also show that silver ions can be used as an underpotential deposition agent to access a different set of particle shapes by controlling growth of the resulting gold nanoparticles through surface passivation (more so than kinetic effects). Importantly, we show that the density of silver coverage can be controlled by the amount and type of halide present in solution. This behavior arises from the decreasing stability of the underpotentially deposited silver layer in the presence of larger halides due to the relative strengths of the Ag(+)/Ag(0)-halide and Au(+)/Au(0)-halide interactions, as well as the passivation effects of the halides on the gold particle surface. We summarize this work by proposing a set of design considerations for controlling the growth and final shape of gold nanoparticles prepared by seed-mediated syntheses through the judicious use of halides and silver ions.

  5. Optimization of silver-dielectric-silver nanoshell for sensing applications

    Energy Technology Data Exchange (ETDEWEB)

    Shirzaditabar, Farzad; Saliminasab, Maryam [Department of Physics, Razi University, Kermanshah 67144-15111 (Iran, Islamic Republic of)

    2013-08-15

    In this paper, resonance light scattering (RLS) properties of a silver-dielectric-silver nanoshell, based on quasi-static approach and plasmon hybridization theory, are investigated. Scattering spectrum of silver-dielectric-silver nanoshell has two intense and clearly separated RLS peaks and provides a potential for biosensing based on surface plasmon resonance and surface-enhanced Raman scattering. The two RLS peaks in silver-dielectric-silver nanoshell are optimized by tuning the geometrical dimensions. In addition, the optimal geometry is discussed to obtain the high sensitivity of silver-dielectric-silver nanoshell. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness increases the sensitivity of silver-dielectric-silver nanoshell.

  6. Invisible gold and arsenic in pyrite from the high-grade Hishikari gold deposit, Japan

    Science.gov (United States)

    Morishita, Y.; Shimada, N.; Shimada, K.

    2008-12-01

    Gold occurs as both electrum (a natural alloy of gold and silver) and invisible gold in arsenian pyrite in the Hishikari epithermal gold deposit in Japan. Microanalyses of arsenian pyrite from the deposit using secondary ion mass spectrometry (SIMS) and electron probe microanalysis (EPMA) revealed that Au concentrations (0.1-2600 ppm) are positively correlated with As concentrations (0.0-6.1%). A small (3 μm) area of pyrite was analyzed because the sample textures were fine and complicated. The Au/As ratio is high in the Sanjin ore zone, which has very high-grade veins, while the ratio is low in the Yamada ore zone, which has average-grade veins.

  7. Compositional study of Parthian silver coins using PIXE technique

    Science.gov (United States)

    Hajivaliei, M.; Khademi Nadooshan, F.

    2012-10-01

    The study of the elemental composition of silver coins minted in the Ecbatana mint houses during the Parthian period can help to elucidate key questions such as provenance of the silver metal and the socio-economic situation of that period. Commercial activity and population growth increased the demand for silver, forcing the Parthian to look for new sources of this metal. The aim of this work is to study the chemical composition of some Parthian coins to find any relation between the mines used for extraction of silver and the actual silver coins minted at that time. Using PIXE technique, the metallic elements Ti, Fe, Cu, Zn, Ag, Au, and Pb were observed. The results show that Parthian's kings used almost two types of mines for their coins.

  8. Real Silver and Its Investment and Business Options

    Directory of Open Access Journals (Sweden)

    Novotný Josef

    2016-06-01

    Full Text Available The article deals with investment and business opportunities offered by silver. Silver is the metal used in industry and for investing at financial markets. The main problem related to this real commodity is the issue of “the undervaluation” of its investment options, if compared to gold. If considering silver as the investment option, its investment potential is significantly enhanced by its industrial usage. The aim of this paper is to highlight business and investment opportunities for both professionals and non professional investors at the commodity markets. The price growth of this investment and industrial metal can generate profits for the investors. And on the other hand, industries which cannot do without silver in their production may efficiently utilize the knowledge of setting up its price at the markets.

  9. In vitro element release and biological aspects of base?metal alloys for metal-ceramic applications

    OpenAIRE

    Holm, Charlotta; Morisbak, Else; Kalfoss, Torill; Dahl, Jon E.

    2015-01-01

    Abstract Objective: The aims of this study were to investigate the release of element from, and the biological response in vitro to, cobalt?chromium alloys and other base?metal alloys used for the fabrication of metal-ceramic restorations. Material and methods: Eighteen different alloys were investigated. Nine cobalt?chromium alloys, three nickel?chromium alloys, two cobalt?chromium?iron alloys, one palladium?silver alloy, one high-noble gold alloy, titanium grade II and one type III copper?a...

  10. Going for Gold : An Analysis of Morningstar Analyst Ratings

    NARCIS (Netherlands)

    W.J. Armstrong (Will); E. Genc (Egemen); M.J.C.M. Verbeek (Marno)

    2014-01-01

    textabstractIn September 2011 Morningstar launched its qualitative forward-looking analyst ratings to supplement its widely followed backward-looking star ratings. This new system is designed to convey information about a mutual fund’s future performance using a five-tier scale: Gold, Silver,

  11. Arsenic, antimony, gold, and mercury levels in the soft tissues of intertidal and terrestrial molluscs and trace element composition of their shells.

    Science.gov (United States)

    Ndiokwere, C L

    1983-03-01

    The concentration levels of As, Au, Hg, and Sb in the fleshy tissues of the giant African land snails (Archachatina Marginata) and periwinkles (Littorina littorea) have been measured by neutron activation analysis (NAA). Post-irradiation separation of 76As, 198Au, 197Hg, and 122Sb as bromides after wet-ashing the samples in a concentrated H2SO4-HBr medium was employed. The concentration ranges of 0.015 approximately 2.48, 0.037 approximately 0.091, 0.018 approximately 0.072, and less than 0.01 approximately 0.25 microgram/g wet weight were determined for As, Au, Hg, and Sb, respectively. The periwinkles showed higher concentrations of As, Au, and Hg than the snails. The concentrations of 16 elements, Al, Br, Ca, Cl, Co, Eu, Fe, K, La, Mn, S, Sc, Si, Sm, Sr, and Zn also have been determined in the calcareous shells of these molluscs.

  12. Reactivity and Catalytic Activity of Hydrogen Atom Chemisorbed Silver Clusters.

    Science.gov (United States)

    Manzoor, Dar; Pal, Sourav

    2015-06-18

    Metal clusters of silver have attracted recent interest of researchers as a result of their potential in different catalytic applications and low cost. However, due to the completely filled d orbital and very high first ionization potential of the silver atom, the silver-based catalysts interact very weakly with the reacting molecules. In the current work, density functional theory calculations were carried out to investigate the effect of hydrogen atom chemisorption on the reactivity and catalytic properties of inert silver clusters. Our results affirm that the hydrogen atom chemisorption leads to enhancement in the binding energy of the adsorbed O2 molecule on the inert silver clusters. The increase in the binding energy is also characterized by the decrease in the Ag-O and increase in the O-O bond lengths in the case of the AgnH silver clusters. Pertinent to the increase in the O-O bond length, a significant red shift in the O-O stretching frequency is also noted in the case of the AgnH silver clusters. Moreover, the hydrogen atom chemisorbed silver clusters show low reaction barriers and high heat of formation of the final products for the environmentally important CO oxidation reaction as compared to the parent catalytically inactive clusters. The obtained results were compared with those of the corresponding gold and hydrogen atom chemisorbed gold clusters obtained at the same level of theory. It is expected the current computational study will provide key insights for future advances in the design of efficient nanosilver-based catalysts through the adsorption of a small atom or a ligand.

  13. Biosynthesis of PVA encapsulated silver nanoparticles

    Directory of Open Access Journals (Sweden)

    Sharmila Chandran

    2016-10-01

    Full Text Available Green synthesis of metal nanoparticles is an important technique in the methods of eco-friendly nanoparticle production. The synthesis of silver nanoparticles was accomplished using Ocimum sanctum leaf extract at room temperature. These particles were then encapsulated with polyvinyl alcohol (PVA polymer matrix. The presence of silver was confirmed by different characterization techniques such as UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR and X-Ray Diffraction (XRD. Scanning electron microscopic (SEM images of the synthesized powder shows spherical shaped silver nanoparticles embedded in sponge-like polymer matrix. The energy dispersive X-ray analysis confirms the presence of elemental silver along with iron signal. Energy dispersive signal corresponding to elemental iron has been attributed to O. sanctum plant. The silver nanoparticles in PVA matrix thus obtained shows high antibacterial activity against gram positive Staphylococcus aureus (S. aureus and gram negative Escherichia coli (E. coli water borne bacteria. The inhibition zone against S. aureus and E. coli were also calculated.

  14. Effects of gold coating on experimental implant fixation

    Science.gov (United States)

    Zainali, Kasra; Danscher, Gorm; Jakobsen, Thomas; Jakobsen, Stig S.; Baas, Jørgen; Møller, Per; Bechtold, Joan E.; Soballe, Kjeld

    2013-01-01

    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-κB–DNA binding and suppressing I-κ 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 implants were inserted press-fit in the proximal part of tibiae in nine canines and control implants without gold inserted contralateral. Observation time was 4 weeks. Biomechanical push-out tests showed that implants with gold coating had ~50% decrease in mechanical strength and stiffness. Histomorphometrical analyses showed gold-coated implants had a decrease in overall total bone-to-implant contact of 35%. Autometallographic analysis revealed few cells loaded with gold close to the gilded implant surface. The findings demonstrate that gilding of implants negatively affects mechanical strength and osseointegration because of a significant effect of the released gold ions on the local inflammatory process around the implant. The possibility that a partial metallic gold coating could prolong the period of satisfactory mechanical strength, however, cannot be excluded. PMID:18335533

  15. Mineralogical, fluid inclusion, and stable isotope constraints on mechanisms of ore deposition at the Samgwang mine (Republic of Korea)—a mesothermal, vein-hosted gold-silver deposit

    Science.gov (United States)

    Yoo, Bong Chul; Lee, Hyun Koo; White, Noel C.

    2010-02-01

    The Samgwang mine is located in the Cheongyang gold district (Cheonan Metallogenic Province) of the Republic of Korea. It consists of eight massive, gold-bearing quartz veins that filled NE- and NW-striking fractures along fault zones in Precambrian granitic gneiss of the Gyeonggi massif. Their mineralogy and paragenesis allow two separate vein-forming episodes to be recognized, temporally separated by a major faulting event. The ore minerals occur in quartz and calcite of stage I, associated with fracturing and healing of veins. Hydrothermal wall-rock alteration minerals of stage I include Fe-rich chlorite (Fe/(Fe+Mg) ratios 0.74-0.81), muscovite, illite, K-feldspar, and minor arsenopyrite, pyrite, and carbonates. Sulfide minerals deposited along with electrum during this stage include arsenopyrite, pyrite, pyrrhotite, sphalerite, marcasite, chalcopyrite, galena, argentite, pyrargyrite, and argentian tetrahedrite. Only calcite was deposited during stage II. Fluid inclusions in quartz contain three main types of C-O-H fluids: CO2-rich, CO2-H2O, and aqueous inclusions. Quartz veins related to early sulfides in stage I were deposited from H2O-NaCl-CO2 fluids (1,500-5,000 bar, average 3,200) with T htotal values of 200°C to 383°C and salinities less than about 7 wt.% NaCl equiv. Late sulfide deposition was related to H2O-NaCl fluids (140-1,300 bar, average 700) with T htotal values of 110°C to 385°C and salinities less than about 11 wt.% NaCl equiv. These fluids either evolved through immiscibility of H2O-NaCl-CO2 fluids as a result of a decrease in fluid pressure, or through mixing with deeply circulated meteoric waters as a result of uplift or unloading during mineralization, or both. Measured and calculated sulfur isotope compositions (δ34SH2S = 1.5 to 4.8‰) of hydrothermal fluids from the stage I quartz veins indicate that ore sulfur was derived mainly from a magmatic source. The calculated and measured oxygen and hydrogen isotope compositions (δ18OH2O

  16. Determination of the platinum - Group elements (PGE) and gold (Au) in manganese nodule reference samples by nickel sulfide fire-assay and Te coprecipitation with ICP-MS

    Science.gov (United States)

    Balaram, V.; Mathur, R.; Banakar, V.K.; Hein, J.R.; Rao, C.R.M.; Gnaneswara, Rao T.; Dasaram, B.

    2006-01-01

    Platinum group elements (PGE) and Au data in polymetallic oceanic ferromanganese nodule reference samples and crust samples obtained by inductively coupled plasma mass spectrometry (ICP-MS), after separation and pre-concentration by nickel sulfide fire-assay and Te coprecipitation, are presented. By optimizing several critical parameters such as flux composition, matrix matching calibration, etc., best experimental conditions were established to develop a method suitable for routine analysis of manganese nodule samples for PGE and Au. Calibrations were performed using international PGE reference materials, WMG-1 and WMS-1. This improved procedure offers extremely low detection limits in the range of 0.004 to 0.016 ng/g. The results obtained in this study for the reference materials compare well with previously published data wherever available. New PGE data arc also provided on some international manganese nodule reference materials. The analytical methodology described here can be used for the routine analysis of manganese nodule and crust samples in marine geochemical studies.

  17. Arsenic, antimony, gold, and mercury levels in the soft tissues of intertidal and terrestrial molluscs and trace element composition of their shells

    Energy Technology Data Exchange (ETDEWEB)

    Ndiokwere, C.L.

    1983-03-01

    The concentration levels of As, Au, Hg, and Sb in the fleshy tissues of the giant African land snails (Archachatina Marginata) and periwinkles (Littorina littorea) have been measured by neutron activation analysis (NAA). Post-irradiation separation of 76As, 198Au, 197Hg, and 122Sb as bromides after wet-ashing the samples in a concentrated H/sub 2/SO/sub 4/-HBr medium was employed. The concentration ranges of 0.015 approximately 2.48, 0.037 approximately 0.091, 0.018 approximately 0.072, and less than 0.01 approximately 0.25 microgram/g wet weight were determined for As, Au, Hg, and Sb, respectively. The periwinkles showed higher concentrations of As, Au, and Hg than the snails. The concentrations of 16 elements, Al, Br, Ca, Cl, Co, Eu, Fe, K, La, Mn, S, Sc, Si, Sm, Sr, and Zn also have been determined in the calcareous shells of these molluscs.

  18. Gold particle formation via photoenhanced deposition on lithium niobate

    Science.gov (United States)

    Zaniewski, A. M.; Meeks, V.; Nemanich, R. J.

    2017-05-01

    In this work, we report on a technique to reduce gold chloride into sub-micron particles and nanoparticles. We use photoelectron transfer from periodically polarized lithium niobate (PPLN) illuminated with above band gap light to drive the surface reactions required for the reduction and particle formation. The particle sizes and distributions on the PPLN surface are sensitive to the solution concentration, with inhibited nucleation and large particles (>150 nm) for both low (2E-8M to 9E-7M) and high (1E-5M to 1E-3M) concentrations of gold chloride. At midrange values of the concentration, nucleation is more frequent, resulting in smaller sized particles (<150 nm). We compare the deposition process to that for silver, which has been previously studied. We find that the reduction of gold chloride into nanoparticles is inhibited compared to silver ion reduction, due to the multi-step reaction required for gold particle formation. This also has consequences for the resulting deposition patterns: while silver deposits into nanowires along boundaries between areas with opposite signed polarizations, such patterning of the deposition is not observed for gold, for a wide range of concentrations studied (2E-8 to 1E-3M).

  19. Gold nanoparticles as intermediate ligands for polymer monolithic capillary microextraction of trace rare earth elements followed by inductively coupled plasma mass spectrometry detection

    Science.gov (United States)

    Cai, Yabing; Chen, Beibei; He, Man; Liu, Xiaolan; Bin, Hu

    2017-01-01

    In this work, a novel method of Au nanoparticles (NPs) modified polymer monolithic capillary microextraction (CME) on-line coupling with inductively coupled plasma-mass spectrometry (ICP-MS) was developed for the determination of trace rare earth elements (REEs) in environmental and biological samples. The poly(glycidyl methacrylate-ethylene dimethacrylate) monolithic capillary was prepared, functionalized with thiol ligands for the attaching of Au NPs, and then modified with mercaptosuccinic acid to provide massive carboxyl groups which have high affinity to REEs. With the modification of Au NPs, the adsorption capacity of the monolith towards target REEs has been improved by 3 to 6.5 times. Under the optimized conditions, the limits of detection of the developed method for REEs were in the range of 0.16 (Tb)-0.85 (Gd) ng L- 1. The enrichment factor was 25-fold with the sample throughput of 10 h- 1. And the relative standard deviations were between 2.7 (Lu) and 9.8% (Dy) (c = 10 ng L- 1, n = 9). The accuracy of the method was validated by the analysis of a standard stock solution of GSB04-1789-2004 and a Certified Reference Material of GBW07301a stream sediment. The proposed method was applied for the analysis of trace REEs in seawater samples as well as human whole blood with good recoveries. The prepared monolith is featured with strong anti-interference ability, superior adsorption capacity as well as long lifespan, and the developed monolithic CME-ICP-MS is sensitive, simple and rapid for the analysis of trace/ultra-trace REEs in environmental and biological samples with complex matrix.

  20. Trace elements in bed sediments and aquatic invertebrates from three streams in Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence, S. [Geological Survey, Carson City, NV (United States). Water Resources Div.

    1995-12-31

    In September 1992, the US Geological Survey, as part of the National Water Quality Assessment Program, collected crayfish (Pacifastacus Ieniusculus and Procambarus clarkii), asiatic clam (Corbicula fluminea), caddis-fly larvae (Hydropsyche spp.) and bed-sediment samples from the Truckee and Carson Rivers, and Las Vegas Wash in Nevada and analyzed them for selected trace elements. This report describes and compares the concentrations of arsenic, copper, manganese, mercury, silver, and zinc in those samples. In the Truckee and Carson Rivers, concentrations of the six trace elements in aquatic invertebrate samples are similar to concentrations measured in bed sediments. In the Truckee River, concentrations of these elements in crayfish and bed-sediment samples were highest in the Reno-Sparks urban area. In the Carson River, arsenic and copper are highest in bed-sediment samples upstream of Carson City due to geothermal springs and acid-mine drainage from an abandoned sulfur mine; concentrations of manganese, mercury, silver, and zinc were highest in bed-sediment samples collected downstream of the Carson City urban area due to historic gold and silver mining, and urban runoff. The highest mercury concentration in crayfish tissue, 48 {micro}g/g dry weight, was measured in a sample from the lower Carson River. In Las Vegas Wash, bed-sediment concentrations were lower than those in the Truckee and Carson Rivers; but, trace-element concentrations in crayfish tissue tended to be higher than those in bed sediment. Samples collected during this study show that trace elements are enriched in the bed sediments of all three rivers and are bioavailable. Trace-element concentrations among samples of crayfish, asiatic clam, and caddis-fly larvae showed little similarity.

  1. Glass, gold, and gold-glasses

    National Research Council Canada - National Science Library

    Whitehouse, David

    1996-01-01

      Gold-glasses, objects with gold foil ornament sandwiched between two fused layers of glass, were the first category of Roman glass to attract the attention of collectors and antiquarians in the 17th century...

  2. Characterizations of silver alloys used in modern Mexican coins

    Energy Technology Data Exchange (ETDEWEB)

    Mendoza-Lopez, M.L. [Instituto Tecnologico de Queretaro, Avenida Tecnologico S/N, Queretaro, Qro, C.P. 76000 (Mexico); Centro de Fisica Aplicada y Tecnologia Avanzada, Departamento de Nanotecnologia, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Apdo. Postal 1-1010, Queretaro Qro. C.P. 76230 (Mexico); Perez-Bueno, J.J. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Parque Tecnologico Queretaro-Sanfandila, Pedro Escobedo, Qro., C.P. 760703 (Mexico); Rodriguez-Garcia, M.E., E-mail: marioga@fata.unam.mx [Departamento de Posgrado e Investigacion, Facultad de Ingenieria, Centro Universitario S/N, Queretaro, Qro (Mexico)

    2009-09-15

    This paper presents a complete methodology for the characterization of silver alloys used in modern coin production. Mexican coins with a nominal silver concentration from 10% to 99.99% were used in this study. Calibrated Glow Discharge Optical Emission Spectrometers were used to determine the chemical composition of the alloys as a function of the depth, while inductively coupled plasma was used to determine the total element composition in bulk. Scanning Electron Microscope was used to study the phase distributions in the different silver coins. According to Glow Discharge Optical Emission Spectrometers and inductively coupled plasma, the silver content found in the studied samples was consistently greater than that of the nominal silver content reported by the Mexican mint. This may lead to a review of the new methods of analysis used nowadays in contemporary coin minting. This result is very important because silver is increasing in value as metal and, considering the volume of production of silver coins, this may increase further as a consequence of a growing popular confidence in silver currency. In the case of silver studies, an advantage of the absence of silver detector in the Glow Discharge Optical Emission Spectrometers system is that it allows for the recalibration to have a better range of detection of other metals present in the alloys. A calibration curve using the copper content obtained by inductively coupled plasma (bulk) and Glow Discharge Optical Emission Spectrometers (depth profile) was performed. The relevance of control in modern silver coin minting was clarified, especially in minimizing the discrepancy between the nominal and the core fineness. The physical and chemical properties of the alloys studied are defined, revealing important variations in silver and copper contents. A new methodology and metrology for the control of coinage are suggested.

  3. Photochemical Synthesis of Silver Nanodecahedrons and Related Nanostructures for Plasmonic Field Enhancement Applications

    Science.gov (United States)

    Lu, Haifei

    Noble-metal nanocrystals have received considerable attention in recent years for their size and shape dependent localized surface Plasmon resonances (LSPR). Various applications based on colloidal nanoparticles, such as surface enhanced Raman scattering (SERS), surface enhanced fluorescence (SEF), plasmonic sensing, photothermal therapy etc., have been broadly explored in the field of biomedicine, because of their extremely large optical scattering and absorption cross sections, as well as giant electric field enhancement on their surface. However, despite its high chemical stability, gold exhibits quite large losses and electric field enhancement is comparatively weaker than silver. Silver nanoparticles synthesized by the traditional technique only cover an LSPR ranged from 420~500 nm. On the other hand, the range of 500~660 nm, which is covered by several easily available commercial laser lines, very limited colloidal silver nanostructures with controllable size and shape have been reported, and realization of tuning the resonance to longer wavelengths is very important for the practical applications. In this thesis, a systematic study on photochemical synthesis of silver nanodecahedrons (NDs) and related nanostructures, and their plasmonic field enhancements are presented. First, the roles of chemicals and the light source during the formation of silver nanoparticles have been studied. We have also developed a preparation route for the production size-controlled silver nanodecahedrons (LSPR range 420 ~ 660 nm) in high purity. Indeed our experiments indicate that both the chemicals and the light sources can affect the shape and purity of final products. Adjusting the molar ratio between sodium citrate and silver nitrate can help to control the crystal structure following rapid reduction from sodium borohydride. Light from a blue LED (465 nm) can efficiently transform the polyvinylpyrrolidone stabilized small silver nanoparticles into silver NDs through photo

  4. Electrochemical investigation of 18k gold in acidic electrolyte

    Directory of Open Access Journals (Sweden)

    Grekulović Vesna J.

    2009-01-01

    Full Text Available The results of an attempt in using cyclic voltammetry for characterization of gold, silver, copper and 18-k gold alloys by their anodic behavior in 1 mol/dm3 H2SO4 are presented in this paper. Gold alloys containing 75 mass% Au are named as 18-k gold, but it is usually three component alloy containing 75 mass% Au, 12.5 mass% Ag and 12.5 mass% Cu as the main components. Investigated alloys were obtained by melting powders of pure metals mixed in corresponding ratio, casting, cooling in air, rolling and drawing in the wire shape. To achieve the required mechanical properties, the alloys had heat-treated three times. Each alloy exhibits characteristic current peaks on voltammogram that can be used to recognize the kind of present alloying metal in gold. Also, the content of the alloying metal can be roughly estimated from the peak value of current densities.

  5. Effects of gold coating on experimental implant fixation

    DEFF Research Database (Denmark)

    Zainali, Kasra; Danscher, Gorm; Jakobsen, Thomas

    2009-01-01

    -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...... implants Were inserted press-fit in the proximal part of tibiae in nine canines and control implants without gold inserted contralateral. Observation time was 4 weeks. Biomechanical push-out tests showed that implant,,, with gold coating had decrease in mechanical strength and stiffness....... Histomorphometrical analyses showed gold-coated implants had a decrease in overall total bone-to-implant contact of 35%. Autometallographic analysis revealed few cells loaded with gold close to the gilded implant surface. The findings demonstrate that gilding of implants negatively, affects mechanical strength...

  6. Contrasting Surficial Composition of Native Gold from Two Different Types of Gold Ore Deposits

    Directory of Open Access Journals (Sweden)

    Vladimir L. Tauson

    2017-08-01

    Full Text Available Native gold grains sampled at two different gold ore deposits in Eastern Russia have been studied by the techniques of electron spectroscopy (X-ray photoelectron spectroscopy (XPS and Auger electron spectroscopy (AES, electron microprobe analysis (EMPA, and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDX. The high-fineness gold of the deposit hosted by relatively high temperature gold-quartz-sulfide mesothermal ore formation contains no oxidized Au constituents on grain surfaces, whereas the less fine gold of the epithermal Au-Ag deposit contains gold oxidized to the Au (I state, or higher, in half of the cases. At this deposit the surface of native Au consists of a thin layer (~15 nm with elevated Ag and S contents and an underlying SiO2–containing layer ~30–60 nm thick. Such a composite coating can perform a protective function and prevent the gold-silver sulfides in surficial parts of AuAg grains from oxidation. The sulfur-enriched marginal parts of native gold particles do not always correlate with the stoichiometry of well-known binary AuAg-sulfides and have a variable composition. This may be due to the existence of solid solutions, Ag2−xAuxS, if there is enough S or S adsorption-stabilized cluster agglomerates, AgnAumS, under sulfur deficit. The effect of the formation of nano-scale surficial zonality on the surface of native gold is quite common in nature and applicable to geological exploration and technology of gold-ore processing. It can facilitate establishing the geochemical environment and genetic type of Au mineralization.

  7. Probing the effect of charge transfer enhancement in off resonance mode SERS via conjugation of the probe dye between silver nanoparticles and metal substrates.

    Science.gov (United States)

    Selvakannan, Pr; Ramanathan, Rajesh; Plowman, Blake J; Sabri, Ylias M; Daima, Hemant K; O'Mullane, Anthony P; Bansal, Vipul; Bhargava, Suresh K

    2013-08-21

    The charge transfer-mediated surface enhanced Raman scattering (SERS) of crystal violet (CV) molecules that were chemically conjugated between partially polarized silver nanoparticles and optically smooth gold and silver substrates has been studied under off-resonant conditions. Tyrosine molecules were used as a reducing agent to convert silver ions into silver nanoparticles where oxidised tyrosine caps the silver nanoparticle surface with its semiquinone group. This binding through the quinone group facilitates charge transfer and results in partially oxidised silver. This establishes a chemical link between the silver nanoparticles and the CV molecules, where the positively charged central carbon of CV molecules can bind to the terminal carboxylate anion of the oxidised tyrosine molecules. After drop casting Ag nanoparticles bound with CV molecules it was found that the free terminal amine groups tend to bind with the underlying substrates. Significantly, only those CV molecules that were chemically conjugated between the partially polarised silver nanoparticles and the underlying gold or silver substrates were found to show SERS under off-resonant conditions. The importance of partial charge transfer at the nanoparticle/capping agent interface and the resultant conjugation of CV molecules to off resonant SERS effects was confirmed by using gold nanoparticles prepared in a similar manner. In this case the capping agent binds to the nanoparticle through the amine group which does not facilitate charge transfer from the gold nanoparticle and under these conditions SERS enhancement in the sandwich configuration was not observed.

  8. PIXE analysis of medieval silver coins

    Energy Technology Data Exchange (ETDEWEB)

    Abdelouahed, H. Ben, E-mail: habdelou@cern.ch [Centre National des Sciences et Technologies Nucleaires (CNSTN), Pole technologique, 2020 Sidi Thabet, Tunis (Tunisia); Gharbi, F. [Centre National des Sciences et Technologies Nucleaires (CNSTN), Pole technologique, 2020 Sidi Thabet, Tunis (Tunisia); Roumie, M. [IBA Laboratory, Lebanese Atomic Energy Commission, National Council for Scientific Research, 11-8281, Beirut (Lebanon); Baccouche, S. [Centre National des Sciences et Technologies Nucleaires (CNSTN), Pole technologique, 2020 Sidi Thabet, Tunis (Tunisia); Romdhane, K. Ben [Faculte des lettres et des sciences humaines, Universite de Tunis (Tunisia); Nsouli, B. [IBA Laboratory, Lebanese Atomic Energy Commission, National Council for Scientific Research, 11-8281, Beirut (Lebanon); Trabelsi, A. [Centre National des Sciences et Technologies Nucleaires (CNSTN), Pole technologique, 2020 Sidi Thabet, Tunis (Tunisia)

    2010-01-15

    We applied the proton-induced X-ray emission (PIXE) analytical technique to twenty-eight medieval silver coins, selected from the Tunisian treasury. The purpose is to study the fineness evolution from the beginning of the 7th to the 15th centuries AD. Each silver coin was cleaned with a diluted acid solution and then exposed to a 3 MeV proton beam from a 1.7 MV tandem accelerator. To allow the simultaneous detection of light and heavy elements, a funny aluminum filter was positioned in front of the Si(Li) detector entrance which is placed at 135{sup o} to the beam direction. The elements Cu, Pb, and Au were observed in the studied coins along with the major component silver. The concentration of Ag, presumably the main constituent of the coins, varies from 55% to 99%. This significant variation in the concentration of the major constituent reveals the economical difficulties encountered by each dynasty. It could be also attributed to differences in the composition of the silver mines used to strike the coins in different locations. That fineness evolution also reflects the poor quality of the control practices during this medieval period. In order to verify the ability of PIXE analytical method to distinguish between apparently similar coins, we applied hierarchical cluster analysis to our results to classify them into different subgroups of similar elemental composition.

  9. The silver ions contribution into the cytotoxic activity of silver and silver halides nanoparticles

    Science.gov (United States)

    Klimov, A. I.; Zherebin, P. M.; Gusev, A. A.; Kudrinskiy, A. A.; Krutyakov, Y. A.

    2015-11-01

    The biocidal action of silver nanoparticles capped with sodium citrate and silver halides nanoparticles capped with non-ionic surfactant polyoxyethylene(20)sorbitan monooleate (Tween 80®) against yeast cells Saccharomyces cerevisiae was compared to the effect produced by silver nitrate and studied through the measurement of cell loss and kinetics of K+ efflux from the cells. The cytotoxicity of the obtained colloids was strongly correlated with silver ion content in the dispersions. The results clearly indicated that silver and silver halides nanoparticles destroyed yeast cells through the intermediate producing of silver ions either by dissolving of salts or by oxidation of silver.

  10. Biosynthesis of silver nanoparticles using leaves of Stevia rebaudiana

    Energy Technology Data Exchange (ETDEWEB)

    Yilmaz, M. [Department of Metallurgy and Materials Engineering, Faculty of Engineering, Bartin University, Bartin (Turkey); Turkdemir, H. [Department of Chemistry, Faculty of Arts and Sciences, Uludag University, 16059 Goeruekle, Bursa (Turkey); Kilic, M. Akif [Department of Biology, Faculty of Science, Akdeniz University, Campus 07058, Antalya (Turkey); Bayram, E. [Department of Chemistry, Faculty of Science, Akdeniz University, Campus 07058, Antalya (Turkey); Cicek, A. [Department of Physics, Faculty of Arts and Sciences, Mehmet Akif Ersoy University, 15100 Burdur (Turkey); Department of Physics, Faculty of Science, Akdeniz University, Campus 07058, Antalya (Turkey); Mete, A. [Department of Chemistry, Faculty of Arts and Sciences, Inonu University, Malatya (Turkey); Ulug, B., E-mail: bulug@akdeniz.edu.tr [Department of Physics, Faculty of Science, Akdeniz University, Campus 07058, Antalya (Turkey)

    2011-11-01

    Highlights: {yields} Green synthesis of silver nanoparticles using leaves of Stevia Rebaudiana. {yields} Spherical and polydispersed nanoparticles with diameters below 50 nm. {yields} Interplay of nanoparticle formation and aggregation over time. {yields} Capping reagents similar to those in gold synthesis via the same biomass. {yields} Ketones to play active roles in the reduction of silver ions. - Abstract: The synthesis of silver nanoparticles employing a shadow-dried Stevia rebaudiana leaf extract in AgNO{sub 3} solution is reported. Transmission electron microscopy and X-ray diffraction inspections indicate that nanoparticles are spherical and polydispersed with diameters ranging between 2 and 50 nm with a maximum at 15 nm. Ultraviolet-visible spectra recorded against the reaction time confirms the reduction of silver nanoparticles indicating that the formation and the aggregation of nanoparticles take place shortly after the mixing, as they persist concurrently with characteristic times of 48.5 min and 454.5 min, respectively. Aggregation is found to be the dominant mechanism after the first 73 min. Proton nuclear magnetic resonance spectrum of the silver nanoparticles reveals the existence of aliphatic, alcoholic and olefinic CH{sub 2} and CH{sub 3} groups, as well as some aromatic compounds but no sign of aldehydes or carboxylic acids. Infrared absorption of the silver nanoparticles suggests that the capping reagents of silver and gold nanoparticles reduced in plant extracts/broths are of the same chemical composition of different ratios. Ketones are shown to play a somehow active role for the formation of nanoparticles in plant extracts/broths.

  11. Specific biomolecule corona is associated with ring-shaped organization of silver nanoparticles in cells

    Science.gov (United States)

    Drescher, Daniela; Guttmann, Peter; Büchner, Tina; Werner, Stephan; Laube, Gregor; Hornemann, Andrea; Tarek, Basel; Schneider, Gerd; Kneipp, Janina

    2013-09-01

    We correlate the localization of silver nanoparticles inside cells with respect to the cellular architecture with the molecular information in the vicinity of the particle surface by combining nanoscale 3D cryo-soft X-ray tomography (cryo-SXT) with surface-enhanced Raman scattering (SERS). The interaction of the silver nanoparticle surface with small molecules and biopolymers was monitored by SERS in vitro over time in living cells. The spectra indicate a stable, time-independent surface composition of silver nanoparticles, despite the changing environment in the endosomal structure. Cryo-SXT reveals a characteristic ring-shaped organization of the silver nanoparticles in endosomes of different cell types. The ring-like structures inside the endosomes suggest a strong association among silver particles and with membrane structures. The comparison of the data with those obtained with gold nanoparticles suggests that the interactions between the nanoparticles and with the endosomal component are influenced by the molecular composition of the corona.We correlate the localization of silver nanoparticles inside cells with respect to the cellular architecture with the molecular information in the vicinity of the particle surface by combining nanoscale 3D cryo-soft X-ray tomography (cryo-SXT) with surface-enhanced Raman scattering (SERS). The interaction of the silver nanoparticle surface with small molecules and biopolymers was monitored by SERS in vitro over time in living cells. The spectra indicate a stable, time-independent surface composition of silver nanoparticles, despite the changing environment in the endosomal structure. Cryo-SXT reveals a characteristic ring-shaped organization of the silver nanoparticles in endosomes of different cell types. The ring-like structures inside the endosomes suggest a strong association among silver particles and with membrane structures. The comparison of the data with those obtained with gold nanoparticles suggests that the

  12. Copper and silver halates

    CERN Document Server

    Woolley, EM; Salomon, M

    2013-01-01

    Copper and Silver Halates is the third in a series of four volumes on inorganic metal halates. This volume presents critical evaluations and compilations for halate solubilities of the Group II metals. The solubility data included in this volume are those for the five compounds, copper chlorate and iodate, and silver chlorate, bromate and iodate.

  13. 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.

  14. Silver delafossite oxides.

    Science.gov (United States)

    Sheets, William C; Stampler, Evan S; Bertoni, Mariana I; Sasaki, Makoto; Marks, Tobin J; Mason, Thomas O; Poeppelmeier, Kenneth R

    2008-04-07

    A single-step, low-temperature (<210 degrees C) and -pressure (<20 atm) hydrothermal method has been developed to synthesize a series of silver delafossites, AgBO2 (B = Al, Ga, Sc, and In). Experimental and computational studies were performed to understand the optical and electric properties of these silver delafossites, including the first in-depth study of AgAlO2 and AgScO2. Their properties were examined as a function of the trivalent cation radius and compared to those of copper delafossites to elucidate the role of both the A- and B-site cations. While optical band gaps for silver delafossites were larger and visible light absorption was lower than values previously reported for polycrystalline powder samples of copper delafossites, the conductivities of silver delafossites are similar or lower. Electronic structure calculations indicate that these properties are due to the scarcity of silver 4d states just below the valence band maximum.

  15. A halogen-free synthesis of gold nanoparticles using gold(III) oxide

    Science.gov (United States)

    Sashuk, Volodymyr; Rogaczewski, Konrad

    2016-09-01

    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.

  16. Biosynthesis, characterization, and antimicrobial applications of silver nanoparticles.

    Science.gov (United States)

    Singh, Priyanka; Kim, Yeon Ju; Singh, Hina; Wang, Chao; Hwang, Kyu Hyon; Farh, Mohamed El-Agamy; Yang, Deok Chun

    2015-01-01

    In the present study, the strain Brevibacterium frigoritolerans DC2 was explored for the efficient and extracellular synthesis of silver nanoparticles. These biosynthesized silver nanoparticles were characterized by ultraviolet-visible spectrophotometry, which detected the formation of silver nanoparticles in the reaction mixture and showed a maximum absorbance at 420 nm. In addition, field emission transmission electron microscopy revealed the spherical shape of the nanoparticles. The dynamic light scattering results indicated the average particle size of the product was 97 nm with a 0.191 polydispersity index. Furthermore, the product was analyzed by energy dispersive X-ray spectroscopy, X-ray diffraction, and elemental mapping, which displayed the presence of elemental silver in the product. Moreover, on a medical platform, the product was checked against pathogenic microorganisms including Vibrio parahaemolyticus, Salmonella enterica, Bacillus anthracis, Bacillus cereus, Escherichia coli, and Candida albicans. The nanoparticles demonstrated antimicrobial activity against all of these pathogenic microorganisms. Additionally, the silver nanoparticles were evaluated for their combined effects with the commercial antibiotics lincomycin, oleandomycin, vancomycin, novobiocin, penicillin G, and rifampicin against these pathogenic microorganisms. These results indicated that the combination of antibiotics with biosynthesized silver nanoparticles enhanced the antimicrobial effects of antibiotics. Therefore, the current study is a demonstration of an efficient biological synthesis of silver nanoparticles by B. frigoritolerans DC2 and its effect on the enhancement of the antimicrobial efficacy of well-known commercial antibiotics.

  17. Pseudomonas deceptionensis DC5-mediated synthesis of extracellular silver nanoparticles.

    Science.gov (United States)

    Jo, Jae H; Singh, Priyanka; Kim, Yeon J; Wang, Chao; Mathiyalagan, Ramya; Jin, Chi-Gyu; Yang, Deok C

    2016-09-01

    The biological synthesis of metal nanoparticles is of great interest in the field of nanotechnology. The present work highlights the extracellular biological synthesis of silver nanoparticles using Pseudomonas deceptionensis DC5. The particles were synthesized in the culture supernatant within 48 h of incubation. Extracellular synthesis of silver nanoparticles in the culture supernatant was confirmed by ultraviolet-visible spectroscopy, which showed the absorption peak at 428 nm, and also under field emission transmission electron microscopy which displayed the spherical shape. In addition, the particles were characterized by X-ray diffraction spectroscopy, which corresponds to the crystalline nature of nanoparticles, and energy-dispersive X-ray analysis which exhibited the intense peak at 3 keV, resembling the silver nanoparticles. Further, the synthesized nanoparticles were examined by elemental mapping which displayed the dominance of the silver element in the synthesized product, and dynamic light scattering which showed the distribution of silver nanoparticles with respect to intensity, volume, and number of particles. Moreover, the silver nanoparticles have been found to be quite active in antimicrobial activity and biofilm inhibition activity against pathogenic microorganisms. Thus, the present work emphasized the prospect of using the P. deceptionensis DC5 to achieve the extracellular synthesis of silver nanoparticles in a facile and environmental manner.

  18. Biosynthesis, characterization, and antimicrobial applications of silver nanoparticles

    Science.gov (United States)

    Singh, Priyanka; Kim, Yeon Ju; Singh, Hina; Wang, Chao; Hwang, Kyu Hyon; Farh, Mohamed El-Agamy; Yang, Deok Chun

    2015-01-01

    In the present study, the strain Brevibacterium frigoritolerans DC2 was explored for the efficient and extracellular synthesis of silver nanoparticles. These biosynthesized silver nanoparticles were characterized by ultraviolet-visible spectrophotometry, which detected the formation of silver nanoparticles in the reaction mixture and showed a maximum absorbance at 420 nm. In addition, field emission transmission electron microscopy revealed the spherical shape of the nanoparticles. The dynamic light scattering results indicated the average particle size of the product was 97 nm with a 0.191 polydispersity index. Furthermore, the product was analyzed by energy dispersive X-ray spectroscopy, X-ray diffraction, and elemental mapping, which displayed the presence of elemental silver in the product. Moreover, on a medical platform, the product was checked against pathogenic microorganisms including Vibrio parahaemolyticus, Salmonella enterica, Bacillus anthracis, Bacillus cereus, Escherichia coli, and Candida albicans. The nanoparticles demonstrated antimicrobial activity against all of these pathogenic microorganisms. Additionally, the silver nanoparticles were evaluated for their combined effects with the commercial antibiotics lincomycin, oleandomycin, vancomycin, novobiocin, penicillin G, and rifampicin against these pathogenic microorganisms. These results indicated that the combination of antibiotics with biosynthesized silver nanoparticles enhanced the antimicrobial effects of antibiotics. Therefore, the current study is a demonstration of an efficient biological synthesis of silver nanoparticles by B. frigoritolerans DC2 and its effect on the enhancement of the antmicrobial efficacy of well-known commercial antibiotics. PMID:25848272

  19. SERS Properties of Different Sized and Shaped Gold Nanoparticles Biosynthesized under Different Environmental Conditions by Neurospora crassa Extract

    Science.gov (United States)

    Quester, Katrin; Avalos-Borja, Miguel; Vilchis-Nestor, Alfredo Rafael; Camacho-López, Marco Antonio; Castro-Longoria, Ernestina

    2013-01-01

    Surface-enhanced Raman scattering (SERS) is a surface-sensitive technique that enhances Raman scattering by molecules adsorbed on rough metal surfaces. It is known that metal nanoparticles, especially gold and silver nanoparticles, exhibit great SERS properties, which make them very attractive for the development of biosensors and biocatalysts. On the other hand, the development of ecofriendly methods for the synthesis of metallic nanostructures has become the focus of research in several countries, and many microorganisms and plants have already been used to biosynthesize metallic nanostructures. However, the majority of these are pathogenic to plants or humans. Here, we report gold nanoparticles with good SERS properties, biosynthesized by Neurospora crassa extract under different environmental conditions, increasing Raman signals up to 40 times using methylene blue as a target molecule. Incubation of tetrachloroauric acid solution with the fungal extract at 60°C and a pH value of a) 3, b) 5.5, and c) 10 resulted in the formation of gold nanoparticles of a) different shapes like triangles, hexagons, pentagons etc. in a broad size range of about 10-200 nm, b) mostly quasi-spheres with some different shapes in a main size range of 6-23 nm, and c) only quasi-spheres of 3-12 nm. Analyses included TEM, HRTEM, and EDS in order to corroborate the shape and the elemental character of the gold nanoparticles, respectively. The results presented here show that these ‘green’ synthesized gold nanoparticles might have potential applicability in the field of biological sensing. PMID:24130891

  20. 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 then was ca...... then was captured using scanning transmission electron microscopy (STEM) and the obtained dark field images are used to set up COMSOL simulations corresponding to actual structures....

  1. Rajkonkoski gold-telluride ore occurrence: A new high prospective type of complex noble metal mineralization in the Karelian Proterozoic

    Science.gov (United States)

    Ivashchenko, V. I.; Sundblad, K.; Toritsin, A. N.; Golubev, A. I.; Lavrov, O. B.

    2008-11-01

    The Rajkonkoski ore occurrence is located within the region of the Karelian craton (AR2) and the Svecofennian folded belt (PR1) conjugation. It is presented by quartz-carbonate veins in metadoleriles and a zone of brecciation, crumple, and silification of carbonaceous shales within the volcanites of the Soanlakhtinsky suite (PR1). Ore mineralization in black shales and quartz veins has features of genetic similarity presenting different levels of the ore system controlled by different range strike-slip fault dislocations. At the Rajkonkoski ore occurrence, 41 ore minerals have been identified: 12 tellurides (native tellurium, hedleyite, pilsenite, tsumoite, tellurobismuthite, hessite, stuetzite, radclidzhite, joseite-B, altaite, volynskite, petzite); 4 bismuth-tellurides of the following compositions Bi3Te, Bi3Te2, BiTe4, PbBiTe; 3 selenides (clausthalite, tellurolaitakarite, native selenium); and 12 native metals (gold, silver, electrum, copper, iron, lead, tin, bismuth, osmiridium). The contents of the main ore minerals in places exceed 10%, and the concentrations of elements reach as follows: Cu and Pb, 5%; Zn, Bi, 1%; Se, 219 ppm; Te, 171 ppm; Sb, 3 ppm; As, 5 ppm; Ag, >0.1%; Au, 35.28 ppm. Ore mineralization is formed during the temperature interval from 550°C up to 300°C) complete miscibilities galenite-clausthalite and galenite-altaite are observed. In aggregate with a wide temperature interval (>400°C) of ore process evolution and mineral specia variety of telluride and native metal mineralizations, the original “torsion” of different temperature mineralizations makes it possible to determine the affiliation of the Rajkonkoski ore occurrence to the xenothermal type deposits or epithermal “alkaline,” gold-telluride A-type characterized by a close connection with magmatism of increased alkalinity and the original geochemical (Te-V-F) and mineral (tellurides of gold, silver and other metals, fluorite, roscoelite, vanadium-containing sulfides

  2. Synthesis and NIR optical properties of hollow gold nanospheres with LSPR greater than one micrometer

    Science.gov (United States)

    Xie, Hai-Nan; Larmour, Iain A.; Chen, Yi-Chieh; Wark, Alastair W.; Tileli, Vasiliki; McComb, David W.; Faulds, Karen; Graham, Duncan

    2012-12-01

    Optical analysis in the near infrared region is of significant biological importance due to better tissue penetration and reduced autofluorescence. In this work, an improved synthesis of hollow gold nanospheres (HGNs), which provides a tunable localized surface plasmon resonance (LSPR) from 610 nm up to 1320 nm, is demonstrated. The scattering properties of these nanoparticles are shown using surface enhanced Raman scattering (SERS) at 1064 nm excitation wavelength and are compared to citrate reduced gold and silver nanoparticles of similar physical sizes and surface properties. After the addition of salts, a strong signal was observed from hollow gold with a LSPR of 650 nm and a weaker, yet observable, signal from HGNs with a LSPR of 775 nm. However, no obvious signals were observed in the case of standard citrate reduced gold, silver or HGNs with a LSPR of 1080 nm. The absorption properties of HGNs were investigated by monitoring their photothermal activity. In this case, different nanoparticle suspensions including citrate reduced gold, silver, and HGNs were illuminated by a continuous laser at 785 nm excitation wavelength and the absorption efficiency of HGNs with a LSPR of 775 nm was calculated to be 0.81% which is more than 5 times higher than the absorption efficiency of citrate reduced gold nanoparticles under similar conditions.Optical analysis in the near infrared region is of significant biological importance due to better tissue penetration and reduced autofluorescence. In this work, an improved synthesis of hollow gold nanospheres (HGNs), which provides a tunable localized surface plasmon resonance (LSPR) from 610 nm up to 1320 nm, is demonstrated. The scattering properties of these nanoparticles are shown using surface enhanced Raman scattering (SERS) at 1064 nm excitation wavelength and are compared to citrate reduced gold and silver nanoparticles of similar physical sizes and surface properties. After the addition of salts, a strong signal was

  3. Silver based SERS substrates fabricated from block copolymer thin film

    Science.gov (United States)

    Zhang, Xin; Lee, Wonjoo; Lee, Seung Yong; Gao, Zhenghan; Rabin, Oded; Briber, R. M.

    2013-03-01

    Poly (styrene-block-4-vinyl pyridine) (PS-b-P4VP, Mw = 47-b-10 kDa, PDI =1.10) thin films were used to form large-scale long range ordered self-assembled hexagonal patterns of vertically P4VP oriented cylinders in a PS matrix on Si substrates. The P4VP cylindrical domains were crosslinked and quaternized using 1,4-dibromobutane. Negatively charged 15nm gold nanoparticles were attached to the quaternized P4VP domains through Coulombic interactions. Silver was then grown on the gold seeds to create nanometer scale gaps between the nanoparticles. The gap between the nanoparticles was fine tuned by controlling the silver growth time. The substrates showed large enhancement factors in the Raman scattering signal for a broad range of incident wavelengths. Present address: LG Chem Ltd, Information Technology & Electronic Materials R&D, Yuseong-gu Daejeon, South Korea

  4. Lysozyme Catalyzes the Formation of Antimicrobial Silver Nanoparticles (POSTPRINT)

    Science.gov (United States)

    2009-04-01

    in reactive oxygen species was observed at 25 g mL1, well as some evidence of DNA damage , although lower concentrations of silver nano- particles...acquired heavy metal and multiple antibiotic resistance through the se- lective enrichment of mobile genetic elements in the oral and intestinal ...microflora of primates with mercury- and silver-containing dental amalgam fillings.43,44 The plasmid pMG101, originally isolated from a Salmonella

  5. 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.

  6. 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.

  7. The effect of biologically and chemically synthesized silver nanoparticles (AgNPs) on biofilm formation

    Science.gov (United States)

    Chojniak, Joanna; Biedroń, Izabela; Mendrek, Barbara; Płaza, Grażyna

    2017-11-01

    Bionanotechnology has emerged up as integration between biotechnology and nanotechnology for developing biosynthetic and environmental-friendly technology for synthesis of nanomaterials. Different types of nanomaterials like copper, zinc, titanium, magnesium, gold, and silver have applied in the various industries but silver nanoparticles have proved to be most effective against bacteria, viruses and eukaryotic microorganisms. The antimicrobial property of silver nanoparticles are widely known. Due to strong antibacterial property silver nanoparticles are used, e.g. in clothing, food industry, sunscreens, cosmetics and many household and environmental appliances. The aim of the study was to compare the effect of silver nanoparticles (AgNPs) synthesized biologically and chemically on the biofilm formation. The biofilm was formed by the bacteria isolated from the water supply network. The commonly used crystal violet assay (CV) was applied for biofilm analysis. In this study effect of biologically synthesized Ag-NPs on the biofilm formation was evaluated.

  8. Silver from Ur of Ancient Mesopotamia.

    Science.gov (United States)

    Mellichamp, J W; Levey, M

    1963-10-04

    Silver jewelry from the Royal Tombs of Ur, about 2500 B.C., compares favorably in purity with present-day sterling, and it also met specifications recorded in cuneiform literatutre of a later period for similar objects. The original chemical composition has been greatly modified by corrosion, calcification, and chlorination. The source and diffusion of various elements detected were traced to study the original composition.

  9. Fano resonances in planar silver nanosphere clusters

    Energy Technology Data Exchange (ETDEWEB)

    Bao, Kui; Nordlander, Peter [Rice Quantum Institute, Laboratory for Nanophotonics, Houston (United States); Rice University, Department of Physics, Houston, TX (United States); Mirin, Nikolay A. [Rice Quantum Institute, Laboratory for Nanophotonics, Houston (United States); Rice University, Department of Chemistry, Houston, TX (United States)

    2010-08-15

    The plasmonic properties of silver nanosphere clusters are investigated using the finite element and the plasmon hybridization methods. The nanoparticle clusters are found to exhibit multiple plasmon resonances with large induced electromagnetic field enhancements. For symmetric clusters, we show how group theory can be used to identify the microscopic nature of the plasmon resonances. For larger clusters, we show that narrow Fano resonances are frequently present in their optical spectra. (orig.)

  10. 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

  11. Speciation Matters: Bioavailability of Silver and Silver Sulfide Nanoparticles to Alfalfa (Medicago sativa).

    Science.gov (United States)

    Stegemeier, John P; Schwab, Fabienne; Colman, Benjamin P; Webb, Samuel M; Newville, Matthew; Lanzirotti, Antonio; Winkler, Christopher; Wiesner, Mark R; Lowry, Gregory V

    2015-07-21

    Terrestrial crops are directly exposed to silver nanoparticles (Ag-NPs) and their environmentally transformed analog silver sulfide nanoparticles (Ag2S-NPs) when wastewater treatment biosolids are applied as fertilizer to agricultural soils. This leads to a need to understand their bioavailability to plants. In the present study, the mechanisms of uptake and distribution of silver in alfalfa (Medicago sativa) were quantified and visualized upon hydroponic exposure to Ag-NPs, Ag2S-NPs, and AgNO3 at 3 mg total Ag/L. Total silver uptake was measured in dried roots and shoots, and the spatial distribution of elements was investigated using transmission electron microscopy (TEM) and synchrotron-based X-ray imaging techniques. Despite large differences in release of Ag(+) ions from the particles, Ag-NPs, Ag2S-NPs, and Ag(+) became associated with plant roots to a similar degree, and exhibited similarly limited (<1%) amounts of translocation of silver into the shoot system. X-ray fluorescence (XRF) mapping revealed differences in the distribution of Ag into roots for each treatment. Silver nanoparticles mainly accumulated in the (columella) border cells and elongation zone, whereas Ag(+) accumulated more uniformly throughout the root. In contrast, Ag2S-NPs remained largely adhered to the root exterior, and the presence of cytoplasmic nano-SixOy aggregates was observed. Exclusively in roots exposed to particulate silver, NPs smaller than the originally dosed NPs were identified by TEM in the cell walls. The apparent accumulation of Ag in the root apoplast determined by XRF, and the presence of small NPs in root cell walls suggests uptake of partially dissolved NPs and translocation along the apoplast.

  12. Hydroquinone Based Synthesis of Gold Nanorods.

    Science.gov (United States)

    Picciolini, Silvia; Mehn, Dora; Ojea-Jiménez, Isaac; Gramatica, Furio; Morasso, Carlo

    2016-08-10

    Gold nanorods are an important kind of nanoparticles characterized by peculiar plasmonic properties. Despite their widespread use in nanotechnology, the synthetic methods for the preparation of gold nanorods are still not fully optimized. In this paper we describe a new, highly efficient, two-step protocol based on the use of hydroquinone as a mild reducing agent. Our approach allows the preparation of nanorods with a good control of size and aspect ratio (AR) simply by varying the amount of hexadecyl trimethylammonium bromide (CTAB) and silver ions (Ag(+)) present in the "growth solution". By using this method, it is possible to markedly reduce the amount of CTAB, an expensive and cytotoxic reagent, necessary to obtain the elongated shape. Gold nanorods with an aspect ratio of about 3 can be obtained in the presence of just 50 mM of CTAB (versus 100 mM used in the standard protocol based on the use of ascorbic acid), while shorter gold nanorods are obtained using a concentration as low as 10 mM.

  13. Gold nanoparticles prepared using cape aloe active components.

    Science.gov (United States)

    Krpetić, Zeljka; Scarì, Giorgio; Caneva, Enrico; Speranza, Giovanna; Porta, Francesca

    2009-07-07

    A novel use of two components of Cape aloe, aloin A and aloesin, acting as stabilizers in the preparation of gold and silver nanoparticles, is reported. Stable water-soluble particles of different size and shape are prepared by varying the reaction conditions, temperature, reaction time, and reducing agents. Characterization of the obtained particles is performed using UV-visible, attenuated total reflection Fourier transform infrared (ATR-FTIR), and 1H NMR spectroscopies and transmission electron microscopy (TEM). The efficient cellular uptake of 50 nm sized aloin A and aloesin stabilized gold particles into macrophages and HeLa cells was investigated, proposing these particles as nanovehicles.

  14. Fluorescent Thiol-Derivatized Gold Clusters Embedded in Polymers

    Directory of Open Access Journals (Sweden)

    G. Carotenuto

    2013-01-01

    Full Text Available Owing to aurophilic interactions, linear and/or planar Au(I-thiolate molecules spontaneously aggregate, leading to molecular gold clusters passivated by a thiolate monolayer coating. Differently from the thiolate precursors, such cluster compounds show very intensive visible fluorescence characteristics that can be tuned by alloying the gold clusters with silver atoms or by conjugating the electronic structure of the metallic core with unsaturated electronic structures in the organic ligand through the sulphur atom. Here, the photoluminescence features of some examples of these systems are shortly described.

  15. Skin contact with gold and gold alloys.

    Science.gov (United States)

    Rapson, W S

    1985-08-01

    3 types of reaction to gold merit discussion. First, there is the effect known as black dermographism, in which stroking with certain metals immediately produces well-defined black lines on the skin. Some gold alloys are amongst such metals. The evidence indicates that the effect is the result of impregnation of the skin with black metallic particles generated by mechanical abrasion of the metal by contaminants of the skin. There is no positive and unequivocal evidence of the ability of metals to mark uncontaminated skin so rapidly that it is possible to write upon it. Secondly there are the 2 related phenomena of the wear of gold jewelry, and the susceptibility to certain individuals to blackening of the skin where it is in contact with such jewelry. The occurrence of smudge, as it is often called, is not very common, but is brought to the attention of most jewelers from time to time. In extreme cases it may make it embarrassing for the person concerned to wear metallic jewelry. It would appear as if gold smudge also results mainly from mechanical abrasion of jewelry, though this may be aided and/or supplemented in some instances by corrosion of gold or gold alloy induced by certain components of the sweat. Finally, there is the question of true allergic responses to contact of the skin with gold and its alloys. Judging from the very few cases which have been recorded, such responses are extremely rare. Some recent observations on the reactions of metallic gold with amino acids and of reaction to contact of the skin with gold on the part of rheumatoid arthritis patients undergoing gold therapy, are, however, relevant in this connection.

  16. A halogen-free synthesis of gold nanoparticles using gold(III) oxide

    Energy Technology Data Exchange (ETDEWEB)

    Sashuk, Volodymyr, E-mail: vsashuk@ichf.edu.pl; Rogaczewski, Konrad [Polish Academy of Sciences, Institute of Physical Chemistry (Poland)

    2016-09-15

    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.

  17. Controlling the morphology of multi-branched gold nanoparticles

    Science.gov (United States)

    Ahmed, Waqqar; Kooij, E. Stefan; van Silfhout, Arend; Poelsema, Bene

    2010-03-01

    We demonstrate a simple and versatile way to achieve high yield synthesis of shape- and size-controlled multi-branched gold nanoparticles (MBNPs). Control over the shape of the MBNPs was achieved by varying the ratio of gold to the mild reducing agent ascorbic acid, using a seed-mediated growth approach. Higher ascorbate concentrations resulted in the smoothing of branches, leading to the yield of relatively more isotropic particles. Furthermore, we found that using much higher silver concentrations in the growth solution resulted in the formation of rod-shaped micro-features together with MBNPs; we postulate them to be cetyltrimethyl ammonium silver bromide crystals. The as-prepared MBNPs show interesting tunable optical properties that are strongly influenced by the particle shape. The results are discussed in terms of plasmon coupling between the core and branches of the MBNPs.

  18. Biodistribution of gold nanoparticles in mouse lung following intratracheal instillation

    Directory of Open Access Journals (Sweden)

    Vogel Ulla

    2009-11-01

    Full Text Available Abstract Background The fate of gold nanoparticles, 2, 40 and 100 nm, administered intratracheally to adult female mice was examined. The nanoparticles were traced by autometallography (AMG at both ultrastructural and light microscopic levels. Also, the gold content was quantified by inductively coupled plasma mass spectrometry (ICP-MS and neutron activation analysis (NAA. The liver is the major site of deposition of circulating gold nanoparticles. Therefore the degree of translocation was determined by the hepatic deposition of gold. Mice were instilled with 5 intratracheal doses of gold nanoparticles distributed over a period of 3 weeks and were killed 24 h after the last dose. One group of mice were given a single intratracheal dose and were killed after 1 h. Results The instilled nanoparticles were found in lung macrophages already 1 h after a single instillation. In mice instilled treated repeatedly during 3 weeks, the load was substantial. Ultrastructurally, AMG silver enhanced gold nanoparticles were found in lysosome-/endosome-like organelles of the macrophages and analysis with AMG, ICP-MS and NAA of the liver revealed an almost total lack of translocation of nanoparticles. In mice given repeated instillations of 2 nm gold nanoparticles, 1.4‰ (by ICP-MS to 1.9‰ (by NAA of the instilled gold was detected in the liver. With the 40 nm gold, no gold was detected in the liver (detection level 2 ng, 0.1‰ except for one mouse in which 3‰ of the instilled gold was found in the liver. No gold was detected in any liver of mice instilled with 100 nm gold (detection level 2 ng, 0.1‰ except in a single animal with 0.39‰ of the dose in the liver. Conclusion We found that that: (1 inert gold nanoparticles, administered intratracheally are phagocytosed by lung macrophages; (2 only a tiny fraction of the gold particles is translocated into systemic circulation. (3 The translocation rate was greatest with the 2 nm gold particles.

  19. Gold and its relationship to neurological/glandular conditions.

    Science.gov (United States)

    Richards, Douglas G; McMillin, David L; Mein, Eric A; Nelson, Carl D

    2002-01-01

    Despite increasing sales of gold supplements, and claims of benefits for neurological and glandular conditions, gold has received little attention in modern medical literature except as a drug for rheumatoid arthritis. Historically, however, gold had a reputation as a "nervine," a therapy for nervous disorders. A review of the historical literature shows gold in use during the 19th century for conditions including depression, epilepsy, migraine, and glandular problems such as amenorrhea and impotence. The most notable use of gold was in a treatment for alcoholism developed by Keeley (1897). In the modern medical literature, gold-containing medicines for rheumatoid arthritis are known to have occasional neurotoxic adverse effects. There are also a few studies suggesting a role for gold as a naturally occurring trace element in the reproductive glands. One small recent study demonstrated a possible positive effect of gold on cognitive ability. There is a need for more experimental and clinical research of the neuropharmacology and neurochemistry of gold, and for the exploration of gold's possible role as a trace element.

  20. Silver-hafnium braze alloy

    Science.gov (United States)

    Stephens, Jr., John J.; Hosking, F. Michael; Yost, Frederick G.

    2003-12-16

    A binary allow braze composition has been prepared and used in a bonded article of ceramic-ceramic and ceramic-metal materials. The braze composition comprises greater than approximately 95 wt % silver, greater than approximately 2 wt % hafnium and less than approximately 4.1 wt % hafnium, and less than approximately 0.2 wt % trace elements. The binary braze alloy is used to join a ceramic material to another ceramic material or a ceramic material, such as alumina, quartz, aluminum nitride, silicon nitride, silicon carbide, and mullite, to a metal material, such as iron-based metals, cobalt-based metals, nickel-based metals, molybdenum-based metals, tungsten-based metals, niobium-based metals, and tantalum-based metals. A hermetic bonded article is obtained with a strength greater than 10,000 psi.

  1. Tuning Properties in Silver Clusters

    KAUST Repository

    Joshi, Chakra Prasad

    2015-07-09

    The properties of Ag nanoclusters are not as well understood as those of their more precious Au cousins. However, a recent surge in the exploration of strategies to tune the physicochemical characteristics of Ag clusters addresses this imbalance, leading to new insights into their optical, luminescence, crystal habit, metal-core, ligand-shell and environmental properties. In this Perspective, we provide an overview of the latest strategies along with a brief introduction of the theoretical framework necessary to understand the properties of silver nanoclusters and the basis for their tuning. The advances in cluster research and the future prospects presented in this Perspective will eventually guide the next large systematic study of nanoclusters, resulting in a single collection of data similar to the periodic table of elements.

  2. Gold in the past, today and future

    Directory of Open Access Journals (Sweden)

    R. Rudolf

    2012-04-01

    Full Text Available This paper deals with gold, which is described as a chemical element. Special attention is paid to its physical-chemical properties and, furthermore, where or in what form it can be found in nature. We discuss the role it has played through history and we inform how gold has been developed to the level it has reached today’s value. Still more, when gold is broken into nanoparticles, this form could be highly useful for a wide range of processes, including general nanotechnology, electronics manufacturing and the synthesizing of different functional materials. It is important that we know that gold is also used in industry in many engineering applications (contacts in micro-electronics and medicine (dental alloys, implants.

  3. Leaching of Silver from Silver-Impregnated Food Storage Containers

    Science.gov (United States)

    Hauri, James F.; Niece, Brian K.

    2011-01-01

    The use of silver in commercial products has proliferated in recent years owing to its antibacterial properties. Food containers impregnated with micro-sized silver promise long food life, but there is some concern because silver can leach out of the plastic and into the stored food. This laboratory experiment gives students the opportunity to…

  4. Genetics Home Reference: Silver syndrome

    Science.gov (United States)

    ... movement and sensations. Silver syndrome is a complex hereditary spastic paraplegia. The first sign of Silver syndrome is usually ... links) GeneReview: BSCL2-Related Neurologic Disorders/Seipinopathy GeneReview: Hereditary ... Paraplegia Foundation, Inc.: Treatments and Therapies ...

  5. Geochemistry of Gold Deposits in Anka Schist Belt, Northwestern ...

    African Journals Online (AJOL)

    Gold quartz veins have been identified associated with the rock formations of the Anka Schist Belt forming eight gold deposits that include Kuba I, Kuba II, Doka, Dumi I, Dumi II, Zurzurfa I, Zurzurfa II, Jameson and Kwali. The present study involves the use of major and trace elements to characterize some of the features that ...

  6. Geochemistry of Gold Deposits in Anka Schist Belt, Northwestern ...

    African Journals Online (AJOL)

    HP USER

    ABSTRACT. Gold quartz veins have been identified associated with the rock formations of the Anka Schist Belt forming eight gold deposits that include Kuba I, Kuba II, Doka, Dumi I, Dumi II, Zurzurfa I, Zurzurfa II, Jameson and Kwali. The present study involves the use of major and trace elements to characterize some of the.

  7. A visible light-induced photocatalytic silver enhancement reaction for gravimetric biosensors

    Science.gov (United States)

    Ko, Wooree; Yim, Changyong; Jung, Namchul; Joo, Jinmyoung; Jeon, Sangmin; Seo, Hyejung; Lee, Soo Suk; Park, Jae Chan

    2011-10-01

    We have developed a novel microgravimetric immunosensor using a WO3 nanoparticle-modified immunoassay and a silver enhancement reaction. When the nanoparticles in silver ion solution (i.e. AgNO3) are exposed to visible light, the silver ions are photocatalytically reduced and form a metallic silver coating on the nanoparticles. This silver coating consequently induces changes in the mass and light absorption spectrum. Although photocatalytic reduction reactions can be achieved using ultraviolet (UV) light and TiO2 nanoparticles as described in our previous publication (Seo et al 2010 Nanotechnology 21 505502), the use of UV light in biosensing applications has drawbacks in that UV light can damage proteins. In addition, conventional quartz crystal substrates must be passivated to prevent undesirable silver ion reduction on their gold-coated sensing surfaces. We addressed these problems by adopting a visible light-induced photocatalytic silver enhancement method using WO3 nanoparticles and lateral field excited (LFE) quartz crystals. As a proof-of-concept demonstration of the technique, streptavidin was adsorbed onto an LFE quartz crystal, and its mass was enhanced with biotinylated WO3 nanoparticles, this being followed by a photocatalytic silver enhancement reaction. The mass change due to the enhancement was found to be > 30 times greater than the mass change obtained with the streptavidin alone.

  8. A visible light-induced photocatalytic silver enhancement reaction for gravimetric biosensors

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Wooree; Yim, Changyong; Jung, Namchul; Joo, Jinmyoung; Jeon, Sangmin [Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang (Korea, Republic of); Seo, Hyejung; Lee, Soo Suk; Park, Jae Chan, E-mail: jeons@postech.ac.kr [Samsung Advanced Institute of Technology (SAIT), Suwon (Korea, Republic of)

    2011-10-07

    We have developed a novel microgravimetric immunosensor using a WO{sub 3} nanoparticle-modified immunoassay and a silver enhancement reaction. When the nanoparticles in silver ion solution (i.e. AgNO{sub 3}) are exposed to visible light, the silver ions are photocatalytically reduced and form a metallic silver coating on the nanoparticles. This silver coating consequently induces changes in the mass and light absorption spectrum. Although photocatalytic reduction reactions can be achieved using ultraviolet (UV) light and TiO{sub 2} nanoparticles as described in our previous publication (Seo et al 2010 Nanotechnology 21 505502), the use of UV light in biosensing applications has drawbacks in that UV light can damage proteins. In addition, conventional quartz crystal substrates must be passivated to prevent undesirable silver ion reduction on their gold-coated sensing surfaces. We addressed these problems by adopting a visible light-induced photocatalytic silver enhancement method using WO{sub 3} nanoparticles and lateral field excited (LFE) quartz crystals. As a proof-of-concept demonstration of the technique, streptavidin was adsorbed onto an LFE quartz crystal, and its mass was enhanced with biotinylated WO{sub 3} nanoparticles, this being followed by a photocatalytic silver enhancement reaction. The mass change due to the enhancement was found to be > 30 times greater than the mass change obtained with the streptavidin alone.

  9. Determination of gold in geologic materials by solvent extraction and atomic-absorption spectrometry

    Science.gov (United States)

    Huffman, Claude; Mensik, J.D.; Riley, L.B.

    1967-01-01

    The two methods presented for the determination of traces of gold in geologic materials are the cyanide atomic-absorption method and the fire-assay atomic-absorption method. In the cyanide method gold is leached with a sodium-cyanide solution. The monovalent gold is then oxidized to the trivalent state and concentrated by extracting into methyl isobutyl ketone prior to estimation by atomic absorption. In the fire-assay atomic-absorption method, the gold-silver bead obtained from fire assay is dissolved in nitric and hydrochloric acids. Gold is then concentrated by extracting into methyl isobutyl ketone prior to determination by atomic absorption. By either method concentrations as low as 50 parts per billion of gold can be determined in a 15-gram sample.

  10. Increased sensitivity of lateral flow immunoassay for ochratoxin A through silver enhancement.

    Science.gov (United States)

    Anfossi, L; Di Nardo, F; Giovannoli, C; Passini, C; Baggiani, C

    2013-12-01

    Silver nucleation on gold has been exploited for signal amplification and has found application in several qualitative and quantitative bio-sensing techniques, thanks to the simplicity of the method and the high sensitivity achieved. Very recen