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Sample records for silver oxide phases

  1. Effect of silver on the phase transition and wettability of titanium oxide films

    Mosquera, Adolfo A.; Albella, Jose M.; Navarro, Violeta; Bhattacharyya, Debabrata; Endrino, Jose L.

    2016-01-01

    The effect of silver on the phase transition and microstructure of titanium oxide films grown by pulsed cathodic arc had been investigated by XRD, SEM and Raman spectroscopy. Following successive thermal annealing up to 1000 °C, microstructural analysis of annealed Ag-TiO2 films reveals that the incorporation of Ag nanoparticles strongly affects the transition temperature from the initial metastable amorphous phase to anatase and stable rutile phase. An increase of silver content into TiO2 matrix inhibits the amorphous to anatase phase transition, raising its temperature boundary and, simultaneously reduces the transition temperature to promote rutile structure at lower value of 600 °C. The results are interpreted in terms of the steric effects produced by agglomeration of Ag atoms into larger clusters following annealing which hinders diffusion of Ti and O ions for anatase formation and constrains the volume available for the anatase lattice, thus disrupting its structure to form rutile phase. The effect of silver on the optical and wetting properties of TiO2 was evaluated to demonstrate its improved photocatalytic performance. PMID:27571937

  2. Graphene oxide decorated with silver nanoparticles as a coating on a stainless-steel fiber for solid-phase microextraction.

    Wang, Licheng; Hou, Xiudan; Li, Jubai; Liu, Shujuan; Guo, Yong

    2015-07-01

    A novel graphene oxide decorated with silver nanoparticles coating on a stainless-steel fiber for solid-phase microextraction was prepared. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the coating surface and showed that silver nanoparticles were dispersed on the wrinkled graphene oxide surface. Coupled to gas chromatography with flame ionization detection, the extraction abilities of the fiber for polycyclic aromatic hydrocarbons were examined in the headspace solid-phase microextraction mode. The extraction parameters including adsorption time, adsorption temperature, salt concentration, desorption time and desorption temperature were investigated. Under the optimized condition, wide linearity with low limits of detection from 2 to 10 ng/L was obtained. The relative standard deviations for single-fiber repeatability and fiber-to-fiber reproducibility were less than 10.6 and 17.5%, respectively. The enrichment factors were from 1712.5 to 4503.7, showing the fiber has good extraction abilities. Moreover, the fiber exhibited a good stability and could be reused for more than 120 times. The established method was also applied for determination of polycyclic aromatic hydrocarbons in two real water samples and the recoveries of analytes ranged from 84.4-116.3% with relative standard deviations less than 16.2%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Selective liquid-phase oxidation of alcohols catalyzed by a silver-based catalyst promoted by the presence of ceria

    Beier, Matthias Josef; Hansen, Thomas Willum; Grunwaldt, Jan-Dierk

    2009-01-01

    simultaneously. When a high catalytic conversion (>30% over 2 h) was found the number of catalyst components was reduced in the following tests. Thereby, a collaborative effect between a physical mixture of ceria nanoparticles and silver-impregnated silica (10 wt.% Ag–SiO2) was found. The catalytic activity...... by in situ XAS experiments. Oxygen species incorporated in the silver lattice appear to be important for the catalytic oxidation of the alcohol for which a preliminary mechanism is presented. The application of the catalyst was extended to the oxidation of a wide range of primary and secondary alcohols....... Compared to palladium and gold catalysts, the new silver catalyst performed similarly or even superior in the presence of CeO2. In addition, the presence of ceria increased the catalytic activity of all investigated catalysts....

  4. Colloidosome-based synthesis of a multifunctional nanostructure of silver and hollow iron oxide nanoparticles

    Pan, Yue; Gao, Jinhao; Zhang, Bei; Zhang, Xixiang; Xu, Bing

    2010-01-01

    nitrate, and iron oxide exposed to the aqueous phase catalyzes the reduction of silver ions to afford a heterodimer of silver and hollow iron oxide nanoparticles. Transmission electron microscopy, selected area electron diffraction, energy-dispersive X

  5. Mixed phase titania nanocomposite codoped with metallic silver and vanadium oxide: New efficient photocatalyst for dye degradation

    Yang Xia [School of Urban and Environmental Sciences, Northeast Normal University, Changchun 130024 (China); School of Chemistry, Northeast Normal University, Changchun 130024 (China); Ma Fengyan; Li Kexin; Guo Yingna; Hu Jianglei; Li Wei [School of Chemistry, Northeast Normal University, Changchun 130024 (China); Huo Mingxin [School of Urban and Environmental Sciences, Northeast Normal University, Changchun 130024 (China); Guo Yihang, E-mail: guoyh@nenu.edu.cn [School of Chemistry, Northeast Normal University, Changchun 130024 (China)

    2010-03-15

    Titania nanocomposite codoped with metallic silver and vanadium oxide was prepared by a one-step sol-gel-solvothermal method in the presence of a triblock copolymer surfactant (P123). The resulting Ag/V-TiO{sub 2} three-component junction system exhibited an anatase/rutile (weight ratio of 73.8:26.2) mixed phase structure, narrower band gap (2.25 eV), and extremely small particle sizes (ca. 12 nm) with metallic Ag particles well distributed on the surface of the composite. The Ag/V-TiO{sub 2} nanocomposite was used as the visible- and UV-light-driven photocatalyst to degrade dyes rhodamine B (RB) and coomassie brilliant blue G-250 (CBB) in an aqueous solution. At 1.8% Ag and 4.9% V doping, the Ag/V-TiO{sub 2} system exhibited the highest visible- as well as UV-light photocatalytic activity; additionally, the activity of the three-component system exceeded that of Degussa P25, pure TiO{sub 2}, single-doped TiO{sub 2} system (Ag/TiO{sub 2} or V-TiO{sub 2}) as well as P123-free-Ag/V-TiO{sub 2} codoped system. The reasons for this enhanced photocatalytic activity were revealed.

  6. Antimicrobial effects of zinc oxide nanoparticles modified with silver

    Lopes, Rayssa Souza; Arantes, Tatiane Moraes

    2016-01-01

    Full text: With the emergence of resistant microbial organisms to multiple antibiotics, different shapes of silver nanoparticles are among the most promising antimicrobial agents that have been developed from nanotechnology. Besides the silver nanoparticles oxide nanoparticles such as zinc oxide (ZnO) is gaining prominence due to its bactericidal properties. [1-3]. Thus, this study aims to develop biomaterials from zinc oxide nanoparticles modified with silver with antimicrobial properties. The ZnO nanoparticles were synthesized by hydrothermal processing by alkaline hydrolysis zinc acetate. Colloidal dispersions of silver nanoparticles were synthesized by the Turkevich method using sodium citrate to reduce silver nitrate at high pH and at 90 °C in the presence of zinc oxide nanoparticles. Both nanoparticles were characterized by X-ray diffraction (XRD), FTIR and Raman spectroscopy and scanning electron microscopy (SEM). The XRD and Raman spectra showed crystalline ZnO colloidal nanoparticles were obtained in the hexagonal phase. XRD measure showed cubic silver diffraction peaks cubic phase confirmed the presence of the silver nanoparticles decorated zinc oxide nanoparticles. SEM images showed ZnO nanoparticles presented a nanorod shapes with length around 80 nm decorated with spherical silver nanoparticles about 20 nm in diameter The results showed that crystalline zinc oxide colloidal nanoparticles with rod-like morphology and uniform decorated with silver spherical nanoparticles size were obtained by hydrothermal synthesis. Results of antibacterial tests indicate that the ZnO/Ag nanoparticles have antibacterial properties against both Staphylococcus aureus and Escherichia coli. The results demonstrated that the ZnO/Ag nanoparticles have potential use as biomaterials in medical/odontological applications. (author)

  7. Antimicrobial effects of zinc oxide nanoparticles modified with silver

    Lopes, Rayssa Souza; Arantes, Tatiane Moraes, E-mail: rayssasouza.net@gmail.com [Universidade Federal de Goias (UFG), Goiania (Brazil)

    2016-07-01

    Full text: With the emergence of resistant microbial organisms to multiple antibiotics, different shapes of silver nanoparticles are among the most promising antimicrobial agents that have been developed from nanotechnology. Besides the silver nanoparticles oxide nanoparticles such as zinc oxide (ZnO) is gaining prominence due to its bactericidal properties. [1-3]. Thus, this study aims to develop biomaterials from zinc oxide nanoparticles modified with silver with antimicrobial properties. The ZnO nanoparticles were synthesized by hydrothermal processing by alkaline hydrolysis zinc acetate. Colloidal dispersions of silver nanoparticles were synthesized by the Turkevich method using sodium citrate to reduce silver nitrate at high pH and at 90 °C in the presence of zinc oxide nanoparticles. Both nanoparticles were characterized by X-ray diffraction (XRD), FTIR and Raman spectroscopy and scanning electron microscopy (SEM). The XRD and Raman spectra showed crystalline ZnO colloidal nanoparticles were obtained in the hexagonal phase. XRD measure showed cubic silver diffraction peaks cubic phase confirmed the presence of the silver nanoparticles decorated zinc oxide nanoparticles. SEM images showed ZnO nanoparticles presented a nanorod shapes with length around 80 nm decorated with spherical silver nanoparticles about 20 nm in diameter The results showed that crystalline zinc oxide colloidal nanoparticles with rod-like morphology and uniform decorated with silver spherical nanoparticles size were obtained by hydrothermal synthesis. Results of antibacterial tests indicate that the ZnO/Ag nanoparticles have antibacterial properties against both Staphylococcus aureus and Escherichia coli. The results demonstrated that the ZnO/Ag nanoparticles have potential use as biomaterials in medical/odontological applications. (author)

  8. Silver manganese oxide electrodes for lithium batteries

    Thackeray, Michael M.; Vaughey, John T.; Dees, Dennis W.

    2006-05-09

    This invention relates to electrodes for non-aqueous lithium cells and batteries with silver manganese oxide positive electrodes, denoted AgxMnOy, in which x and y are such that the manganese ions in the charged or partially charged electrodes cells have an average oxidation state greater than 3.5. The silver manganese oxide electrodes optionally contain silver powder and/or silver foil to assist in current collection at the electrodes and to improve the power capability of the cells or batteries. The invention relates also to a method for preparing AgxMnOy electrodes by decomposition of a permanganate salt, such as AgMnO4, or by the decomposition of KMnO4 or LiMnO4 in the presence of a silver salt.

  9. Silver Biocide Analysis & Control Device, Phase II

    National Aeronautics and Space Administration — Rapid, accurate measurement and process control of silver ion biocide concentrations in future space missions is needed. The purpose of the Phase II program is to...

  10. Silver Nanoparticles-graphene Oxide Nanocomposite for Antibacterial Purpose

    Chook, S.W.; Chia, C.H.; Sarani Zakaria; Mohd Khan Ayob; Chee, K.L.; Neoh, H.M.; Huang, N.M.

    2011-01-01

    Graphene oxide (GO) sheets, a single layer of carbon atoms which can be served as substrates for fabricating metallic nanoparticles-GO nano composites, have been used in this study The nanocomposite of silver nanoparticles and graphene oxide were produced via in-situ synthesis and with the aid of chitosan to investigate the formation of silver nanoparticles on the graphene oxide sheets. XRD and UV-Vis studies confirmed the formation of silver nanoparticles on GO sheets, while TEM and FESEM images presented the loading of silver nanoparticles on the GO sheets. The degree of loading and distribution of the silver nanoparticles on the graphene oxide were depended on the procedure during the formation of silver nanoparticles. The nano composites can be potentially used in food packaging and biomedical applications. (author)

  11. Visualizing the mobility of silver during catalytic soot oxidation

    Gardini, Diego; Christensen, Jakob M.; Damsgaard, Christian Danvad

    2016-01-01

    The catalytic activity and mobility of silver nanoparticles used as catalysts in temperature programmed oxidation of soot:silver (1:5 wt:wt) mixtures have been investigated by means of flow reactor experiments and in situ environmental transmission electron microscopy (ETEM). The carbon oxidation...

  12. Colloidosome-based synthesis of a multifunctional nanostructure of silver and hollow iron oxide nanoparticles

    Pan, Yue

    2010-03-16

    Nanoparticles that self-assemble on a liquid-liquid interface serve as the building block for making heterodimeric nanostructures. Specifically, hollow iron oxide nanoparticles within hexane form colloidosomes in the aqueous solution of silver nitrate, and iron oxide exposed to the aqueous phase catalyzes the reduction of silver ions to afford a heterodimer of silver and hollow iron oxide nanoparticles. Transmission electron microscopy, selected area electron diffraction, energy-dispersive X-ray spectrometry, X-ray diffraction, UV-vis spectroscopy, and SQUID were used to characterize the heterodimers. Interestingly, the formation of silver nanoparticles helps the removal of spinglass layer on the hollow iron oxide nanoparticles. This work demonstrates a powerful yet convenient strategy for producing sophisticated, multifunctional nanostructures. © 2010 American Chemical Society.

  13. Electrocontact material based on silver dispersion-strengthened by nickel, titanium, and zinc oxides

    Zeer, G. M.; Zelenkova, E. G.; Belousov, O. V.; Beletskii, V. V.; Nikolaev, S. V.; Ledyaeva, O. N.

    2017-09-01

    Samples of a composite electrocontact material based on silver strengthened by the dispersed phases of zinc and titanium oxides have been investigated by the electron microscopy and energy dispersive X-ray spectroscopy. A uniform distribution of the oxide phases containing 2 wt % zinc oxide in the initial charge has been revealed. The increase in the amount of zinc oxide leads to an increase of the size of the oxide phases. It has been shown that at the zinc oxide content of 2 wt %, the minimum wear is observed in the process of electroerosion tests; at 3 wt %, an overheating and welding of the contacts are observed.

  14. Determination of colloidal and dissolved silver in water samples using colorimetric solid-phase extraction.

    Hill, April A; Lipert, Robert J; Porter, Marc D

    2010-03-15

    The increase in bacterial resistance to antibiotics has led to resurgence in the use of silver as a biocidal agent in applications ranging from washing machine additives to the drinking water treatment system on the International Space Station (ISS). However, growing concerns about the possible toxicity of colloidal silver to bacteria, aquatic organisms and humans have led to recently issued regulations by the US EPA and FDA regarding the usage of silver. As part of an ongoing project, we have developed a rapid, simple method for determining total silver, both ionic (silver(I)) and colloidal, in 0.1-1mg/L aqueous samples, which spans the ISS potable water target of 0.3-0.5mg/L (total silver) and meets the US EPA limit of 0.1mg/L in drinking water. The method is based on colorimetric solid-phase extraction (C-SPE) and involves the extraction of silver(I) from water samples by passage through a solid-phase membrane impregnated with the colorimetric reagent DMABR (5-[4-(dimethylamino)benzylidene]rhodanine). Silver(I) exhaustively reacts with impregnated DMABR to form a colored compound, which is quantified using a handheld diffuse reflectance spectrophotometer. Total silver is determined by first passing the sample through a cartridge containing Oxone, which exhaustively oxidizes colloidal silver to dissolved silver(I). The method, which takes less than 2 min to complete and requires only approximately 1 mL of sample, has been validated through a series of tests, including a comparison with the ICP-MS analysis of a water sample from ISS that contained both silver(I) and colloidal silver. Potential earth-bound applications are also briefly discussed. Copyright (c) 2009 Elsevier B.V. All rights reserved.

  15. Lithium diffusion in silver vanadium oxide

    Takeuchi, E.S.; Thiebolt, W.C. III

    1989-01-01

    Lithium/silver vanadium oxide (SVO) batteries have been developed to power implantable devices. The voltage of Li/SVO cells decreases with discharge allowing state of charge assessment by accurate determination of the cells' open circuit voltage. The open circuit voltage recovery of Li/SVO cells was monitored during intermittent high rate discharge. It was found that the voltage does not recover at the same rate or magnitude at all depths of discharge. The authors describe lithium diffusion in SVO studied by low scan rate voltammetry where utilization of SVO at various scan rates was used to determine the diffusion rate of lithium. A pulse technique was also used where the rate of lithium diffusion was measured at various depths of discharge

  16. Rapid Fabrication of Silver Nanowires through Photoreduction of Silver Nitrate from an Anodic-Aluminum-Oxide Template

    Lin, Yu-Hsuan; Chen, Kun-Tso; Ho, Jeng-Rong

    2011-06-01

    A method for rapidly fabricating dense and high-aspect-ratio silver nanowires, with wire diameter of 200 nm and wire length more than 30 µm, is reported. The fabrication process simply involves filling the silver nitrate solution into the pores of an anodic-aluminum-oxide (AAO) membrane through capillary attraction and irradiating the dried template AAO membrane using a pulsed ArF excimer laser. Through varying the thickness and pore diameter of the employed AAO membrane, the primary dimensions of the targeted silver nanowires can be plainly specified; and, by amending the initial concentration of the silver nitrate solution and adjusting the laser operation parameters, laser fluence and number of laser pulses, the surface morphology and size of the resulting nanowires can be finely regulated. The wire formation mechanism is considered through two stages: the period of precipitation of silver particles from the dried silver nitrate film through the laser-induced photoreduction; and, the phase of clustering, merging and fusing of the reduced particles to form nanowires in the template pores by the thermal energy owing to photothermal effect. This approach is straightforward and takes the advantage that all the fabrication processes can be executed in an ambient environment and at room temperature. In addition, by the excellence in local processing that the laser possesses, this method is suitable for precisely growing nanowires.

  17. The sorption of silver by poorly crystallized manganese oxides

    Anderson, B.J.; Jenne, E.A.; Chao, T.T.

    1973-01-01

    The sorption of silver by poorly crystallized manganese oxides was studied using synthesized samples of three members of the manganous manganite (birnessite) group, of different chemical composition and crystallinity, and a poorly organized ??-MnO2. All four oxides sorbed significant quantities of silver. The manganous manganites showed the greatest sorption (up to 0.5 moles silver/mole MnOx at pH 7) while the ??-MnO2 showed the least (0.3 moles silver/ mole MnOx at pH 7). Sorption of silver was adequately described by the Langmuir equation over a considerable concentration range. The relationship failed at low pH values and high equilibrium silver concentrations. The sorption capacity showed a direct relationship with pH. However, the rate of increase of sorption capacity decreased at the higher pH values. Silver sorption maxima. were not directly related to surface area but appeared to vary with the amount of occluded sodium and potassium present in the manganese oxide. The important processes involved in the uptake of silver by the four poorly crystallized manganese oxides ara considered to be surface exchange for manganese, potassium and sodium as well as exchange for structural manganese, potassium and sodium. ?? 1973.

  18. Chitosan–silver oxide nanocomposite film: Preparation and ...

    (Yoshida et al 1999; Herrera et al 2001), ion exchange fibres. (Nonaka et al ... In this communication, we report the synthesis of .... The SEM pictures of chitosan, silver oxide and .... system for silver ions or as a contact-active material (Chan.

  19. One-step microwave-assisted colloidal synthesis of hybrid silver oxide/silver nanoparticles: characterization and catalytic study

    Prakoso, S. P.; Taufik, A.; Saleh, R.

    2017-04-01

    This study reports the characterization and catalytic activities of silver-oxide/silver nanoparticles (Ag2O/Ag NPs) synthesized by microwave-assisted colloidal method in the presence of anionic sodium dodecyl sulfate (SDS) surfactant. To promote different contents of silver in silver oxide, the volume ratio (VR) of ethylene glycol (EG) was varied (VR: 10% to 14%) in relation to the total volume of distilled water solvent. The plasmonic resonance of Ag2O/Ag NPs could be detected around a wavelength of 350 nm, and it is suggested that Ag2O/Ag NPs were successfully formed in the colloid solution following exposure to microwaves. Additionally, the growth rate for each crystal phase within Ag2O and Ag was influenced by an increase of EG as revealed by x-ray diffraction patterns. The morphology, average diameter, and uniformity of Ag2O/Ag NPs were studied simultaneously by transmission electron microscopy. Infrared absorption measurement of Ag2O/Ag NPs confirmed the existence of SDS surfactant as a protective agent. Based on the characterization data, Ag2O/Ag NPs synthesized using this technique exhibited good properties, with high-yield production of NPs. The photocatalytic experiments demonstrate the key role of the crystal phase of Ag2O/Ag NPs in photocatalytic efficiency.

  20. In situ Oxidation of Ultrathin Silver Films on Ni(111)

    Meyer, A.; Flege, I.; Senanayake, S.; Kaemena, B.; Rettew, R.; Alamgir, F.; Falta, J.

    2011-01-01

    Oxidation of silver films of one- and two-monolayer thicknesses on the Ni(111) surface was investigated by low-energy electron microscopy at temperatures of 500 and 600 K. Additionally, intensity-voltage curves were measured in situ during oxidation to reveal the local film structure on a nanometer scale. At both temperatures, we find that exposure to molecular oxygen leads to the destabilization of the Ag film with subsequent relocation of the silver atoms to small few-layer-thick silver patches and concurrent evolution of NiO(111) regions. Subsequent exposure of the oxidized surface to ethylene initiates the transformation of bilayer islands back into monolayer islands, demonstrating at least partial reversibility of the silver relocation process at 600 K.

  1. Antibacterial effects of electrospun chitosan/poly(ethylene oxide) nanofibrous membranes loaded with chlorhexidine and silver

    Song, J.; Remmers, S.J.; Shao, J.; Kolwijck, E.; Walboomers, X.F.; Jansen, J.A.; Leeuwenburgh, S.C.; Yang, F.

    2016-01-01

    To prevent percutaneous device associated infections (PDAIs), we prepared electrospun chitosan/poly(ethylene oxide) (PEO) nanofibrous membrane containing silver nanoparticles as an implantable delivery vehicle for the dual release of chlorhexidine and silver ions. We observed that the silver

  2. Oxidative Decarboxylation of Levulinic Acid by Silver(I/Persulfate

    Yan Gong

    2011-03-01

    Full Text Available The oxidative decarboxylation of levulinic acid (LA by silver(I/persulfate [Ag(I/S2O82−] has been investigated in this paper. The effects of buffer solution, initial pH value, time and temperature and dosages of Ag(I/S2O82− on the decarboxylation of LA were examined in batch experiments and a reaction scheme was proposed on basis of the reaction process. The experimental results showed that a solution of NaOH-KH2PO4 was comparatively suitable for the LA decarboxylation reaction by silver(I/persulfate. Under optimum conditions (temperature 160 °C, pH 5.0, and time 0.5 h, the rate of LA conversion in NaOH-KH2PO4 solutions with an initial concentration of 0.01 mol LA reached 70.2%, 2-butanone (methyl ethyl ketone was the single product in the gas phase and the resulted molar yield reached 44.2%.

  3. Synthesis and Oxidation of Silver Nano-particles

    2011-01-01

    solution (20%wt propyl alcohol, 5%wt hydrochloric acid and 5%wt stannous chloride in water). Scheme 1b and c illustrate the sensitization and silver... Synthesis and Oxidation of Silver Nano-particles Hua Qi*, D. A. Alexson, O.J. Glembocki and S. M. Prokes* Electronics Science and Technology...energy dispersive x-ray (EDX) techniques. The results Quantum Dots and Nanostructures: Synthesis , Characterization, and Modeling VIII, edited by Kurt

  4. Characteristics of MOX dissolution with silver mediated electrolytic oxidation method

    Umeda, Miki; Nakazaki, Masato; Kida, Takashi; Sato, Kenji; Kato, Tadahito; Kihara, Takehiro; Sugikawa, Susumu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2003-03-01

    MOX dissolution with silver mediated electrolytic oxidation method is to be applied to the preparation of plutonium nitrate solution to be used for criticality safety experiments at Nuclear Fuel Cycle Safety Engineering Research Facility (NUCEF). Silver mediated electrolytic oxidation method uses the strong oxidisation ability of Ag(II) ion. This method is though to be effective for the dissolution of MOX, which is difficult to be dissolved with nitric acid. In this paper, the results of experiments on dissolution with 100 g of MOX are described. It was confirmed from the results that the MOX powder to be used at NUCEF was completely dissolved by silver mediated electrolytic oxidation method and that Pu(VI) ion in the obtained solution was reduced to tetravalent by means of NO{sub 2} purging. (author)

  5. Electrodeposition of silver nanoparticle arrays on transparent conductive oxides

    Zhang, Dezhong; Tang, Yang; Jiang, Fuguo; Han, Zhihua; Chen, Jie

    2016-01-01

    Highlights: • The sliver nanoparticles' size and the distance between nanoparticles are tunable. - Abstract: In this paper, we present a facile method for the preparation of silver nanoparticles on aluminum-doped zinc oxide (AZO) via electrodeposition techniques at room temperature. The morphology and structure of silver nanoparticles are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. Due to localized surface plasmon resonances, as-prepared silver nanoparticles on AZO glass exhibited different reflectivity in contrast with bare AZO glass. The weighted reflection of AZO substrate increased from 10.2% to 12.8%. The high reflection property of silver nanoparticle arrays on AZO substrate might be applicable for thin film solar cells and other optoelectronics applications.

  6. Electrodeposition of silver nanoparticle arrays on transparent conductive oxides

    Zhang, Dezhong; Tang, Yang, E-mail: tangyang@nicenergy.com; Jiang, Fuguo; Han, Zhihua; Chen, Jie

    2016-04-30

    Highlights: • The sliver nanoparticles' size and the distance between nanoparticles are tunable. - Abstract: In this paper, we present a facile method for the preparation of silver nanoparticles on aluminum-doped zinc oxide (AZO) via electrodeposition techniques at room temperature. The morphology and structure of silver nanoparticles are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. Due to localized surface plasmon resonances, as-prepared silver nanoparticles on AZO glass exhibited different reflectivity in contrast with bare AZO glass. The weighted reflection of AZO substrate increased from 10.2% to 12.8%. The high reflection property of silver nanoparticle arrays on AZO substrate might be applicable for thin film solar cells and other optoelectronics applications.

  7. Investigation of interaction between silver oxide electrode and separator hydrated cellulose film in silver-cadmium accumulators

    Molotkova, E.N.; Yarochkina, E.N.

    1975-01-01

    Oxidation-reduction interaction of the oxysilver electrode with hydrocellulose film during storing charged silver-cadmium accumulators. It was demonstrated that accumulator electric characteristics durinq storing are linearly depending on the capacity of this hydrocellulose film to interact with silver oxide: the more silver is absorbed by film the quicker is the decreasing of the electromotive force and capacity of the accumulators. Preservation of the silver electrode capacity in the silver-cadmium accumulators is determined first of all by hydrocellulose separation film properties and especially by film layer adjacent to positive electrode. The more inert film layer is, regarding to silver oxide in the electrolite, the slower is dissolution of the electrode and also decompousing speed of AgO, the longer is the accumulator preservation time

  8. Simplified kinetic models of methanol oxidation on silver

    Andreasen, A.; Lynggaard, H.; Stegelmann, C.

    2005-01-01

    Recently the authors developed a microkinetic model of methanol oxidation on silver [A. Andreasen, H. Lynggaard, C. Stegelmann, P. Stoltze, Surf. Sci. 544 (2003) 5-23]. The model successfully explains both surface science experiments and kinetic experiments at industrial conditions applying...

  9. Processing, characterization, and bactericidal activity of undoped and silver-doped vanadium oxides

    Tousley, M.E.; Wren, A.W.; Towler, M.R. [Inamori School of Engineering, Alfred University, Alfred, NY 14803 (United States); Mellott, N.P., E-mail: mellott@alfred.edu [Inamori School of Engineering, Alfred University, Alfred, NY 14803 (United States)

    2012-12-14

    Vanadium oxide (V) and silver-doped vanadium oxide (Ag-V) powders were prepared via sol-gel processing. Structural evolution and bactericidal activity was examined as a function of temperature ranging from 250, 350, 450 and 550 Degree-Sign C. Powders were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Raman spectroscopy. Results from all techniques showed vanadium pentoxide (V{sub 2}O{sub 5}) is the predominant phase regardless of heat treatment temperature or the addition of silver (Ag). XRD analysis suggests Ag is present as AgCl in samples heat treated to 250, 350, and 450 Degree-Sign C and as AgV{sub 6}O{sub 15} at 550 Degree-Sign C. Bactericidal activity was evaluated against Escherichia coli using the agar disk diffusion method considering both Ag-V and undoped, V powders. While the addition of Ag significantly increased bactericidal properties, the specific Ag valency, or crystal structure and morphology formed at higher temperatures, had little effect on functionality. -- Highlights: Black-Right-Pointing-Pointer Vanadium and silver-doped vanadium oxide powders were prepared via sol-gel. Black-Right-Pointing-Pointer Powders were characterized using advanced, complementary structural techniques. Black-Right-Pointing-Pointer Bactericidal activity was evaluated against E. coli. Black-Right-Pointing-Pointer Both vanadium and silver doped vanadium oxide show bactericidal activity.

  10. Electrochemical Oxidation of Silver and Copper in Aqueous Basic Media and in Fused Hydroxide Electrolytes

    Tejada-Rosales, E. M.

    2004-04-01

    Full Text Available The anodic oxidations of copper and silver electrodes in basic media are reported. Experiments were conducted both in aqueous NaOH solutions and in a flux of molten NaOH/KOH eutectic. The oxidation processes were studied by means of cyclic voltammetry and chronoamperometries and the phases obtained were systematically characterized by x-ray diffraction. The ranges of stability of each phase in the different media studied are reported. In addition to known oxides of copper or silver, a new silver oxide was isolated.

    En este trabajo se describe la oxidación anódico de electrodos de plata y de cobre en medios básicos. Se han utilizado tanto medios acuosos como hidróxidos fundidos (eutéctico NaOH/KOH. Los procesos de oxidación se han estudiado mediante voltametría cíclica y cronoamperometría, y las fases resultantes han sido caracterizadas por difracción de Rayos X. Los rangos de estabilidad encontrados para cada uno dependen del medio utilizado. Además de óxidos conocidos de cobre y de plata, se ha aislado un nuevo óxido de plata.

  11. 2D phase field modeling of sintering of silver nanoparticles

    Chockalingam, K.; Kouznetsova, V.; van der Sluis, O.; Geers, M.G.D.

    2016-01-01

    The sintering mechanism of silver nanoparticles is modelled by incorporating surface, volume and grain boundary diffusion in a phase field model. A direction-dependent tensorial mobility formulation is adopted, capturing the fact that diffusion mainly occurs along the directions tangential to the

  12. Phase stability of silver particles embedded calcium phosphate ...

    Abstract. In this paper, we report the compositional variation-dependent phase stability of hydroxyapatite ... material along with other calcium phosphate bioceramics.3–5 ... Model U-3310). ... recorded using a Field Emissio scanning electron microscope .... the colour change of the silver-doped samples only after sin-.

  13. Ag2CuMnO4: A new silver copper oxide with delafossite structure

    Munoz-Rojas, David; Subias, Gloria; Oro-Sole, Judith; Fraxedas, Jordi; Martinez, Benjamin; Casas-Cabanas, Montse; Canales-Vazquez, Jesus; Gonzalez-Calbet, Jose; Garcia-Gonzalez, Ester; Walton, Richard I.; Casan-Pastor, Nieves

    2006-01-01

    The use of hydrothermal methods has allowed the synthesis of a new silver copper mixed oxide, Ag 2 CuMnO 4 , the first example of a quaternary oxide containing both elements. It crystallizes with the delafossite 3R structure, thus being the first delafossite to contain both Ag and Cu. Synthesis conditions affect the final particle size (30-500nm). Powder X-ray diffraction Rietveld refinement indicates a trigonal structure (R3-bar m) and cell parameters a=2.99991A and c=18.428A, where Cu and Mn are disordered within the octahedral B positions in the plane and linearly coordinated Ag occupies de A position between layers. X-ray absorption near edge spectroscopy (XANES) for copper and manganese, and XPS for silver evidence +2, +4, and +1 oxidation states. The microstructure consists of layered particles that may form large twins showing 5nm nanodomains. Finally, magnetic measurements reveal the existence of ferromagnetic coupling yielding in-plane moments that align antiferromagnetically at lower temperatures. The singularity of the new phase resides on the fact that is an example of a bidimensional arrangement of silver and copper in an oxide that also shows clear bidimensionality in its physical properties. That is of special relevance to the field of high T c superconducting oxides, while the ferromagnetic coupling in a bidimensional system deserves itself special attention

  14. The oxidative dehydrogenation of methanol to formaldehyde over silver catalysts in relation to the oxygen-silver interaction

    Lefferts, Leonardus; van Ommen, J.G.; Ross, J.R.H.

    1986-01-01

    The properties of silver in the oxidative dehydrogenation of methanol were studied in a flow reactor under near industrial conditions. The influences of temperature, concentration of both reactants, gas velocity, space velocity, the form of the silver catalyst and surface composition of the catalyst

  15. Catalytic oxidation of butyl acetate over silver-loaded zeolites

    Wong, Cheng Teng; Abdullah, Ahmad Zuhairi; Bhatia, Subhash

    2008-01-01

    The performance of silver-loaded zeolite (HY and HZSM-5) catalysts in the oxidation of butyl acetate as a model volatile organic compound (VOC) was studied. The objective was to find a catalyst with superior activity, selectivity towards deep oxidation product and stability. The catalyst activity was measured under excess oxygen condition in a packed bed reactor operated at gas hourly space velocity (GHSV) = 15,000-32,000 h -1 , reaction temperature between 150 and 500 deg. C and butyl acetate inlet concentration of 1000-4000 ppm. Both AgY and AgZSM-5 catalysts exhibited high activity in the oxidation of butyl acetate. Despite lower silver content, AgY showed better activity, attributed to better metal dispersion, surface characteristics and acidity, and its pore system. Total conversion of butyl acetate was achieved at above 400 deg. C. The oxidation of butyl acetate followed a simple power law model. The reaction orders, n and m were evaluated under differential mode by varying the VOC partial pressure between 0.004 and 0.018 atm and partial pressure of oxygen between 0.05 and 0.20 atm. The reaction rate was independent of oxygen concentration and single order with respect to VOC concentration. The activation energies were 19.78 kJ/mol for AgY and 32.26 kJ/mol for AgZSM-5, respectively

  16. The growth and tensile deformation behavior of the silver solid solution phase with zinc

    Wu, Jiaqi; Lee, Chin C.

    2016-01-01

    The growth of homogeneous silver solid solution phase with zinc are conducted at two different compositions. X-ray diffraction (XRD) and Scanning electron microscope/Energy dispersive X-ray spectroscopy (SEM/EDX) are carried out for phase identification and chemical composition verification. The mechanical properties of silver solid solution phase with zinc are evaluated by tensile test. The engineering and true stress vs. strain curves are presented and analyzed, with those of pure silver in comparison. According to the experimental results, silver solid solution phase with zinc at both compositions show tempered yield strength, high tensile strength and large uniform strain compared to those of pure silver. Fractography further confirmed the superior ductility of silver solid solution phase with zinc at both compositions. Our preliminary but encouraging results may pave the way for the silver based alloys to be applied in industries such as electronic packaging and structure engineering.

  17. A microkinetic model of the methanol oxidation over silver

    Andreasen, A.; Lynggaard, H.; Stegelmann, C.

    2003-01-01

    A simple microkinetic model for the oxidation of methanol on silver based on surface science studies at UHV and low temperatures has been formulated. The reaction mechanism is a simple Langmuir-Hinshelwood mechanism, with one type of active oxygen and one route to formaldehyde and carbon dioxide......, respectively. The model explains observed reaction orders, selectivity, apparent activation enthalpies and the choice of industrial reaction conditions. More interesting the model disproves the notion that the mechanism deduced from surface science in UHV cannot be responsible for formaldehyde synthesis...

  18. Smart methanol sensor based on silver oxide-doped zinc oxide nanoparticles deposited on microchips

    Rahman, Mohammed M.; Khan, Sher Bahadar; Asiri, Abdullah M.

    2014-01-01

    We have prepared calcined silver oxide-doped zinc oxide nanoparticles (NPs) by a hydrothermal method using reducing agents in alkaline medium. The doped NPs were characterized by UV/vis, FTIR, and X-ray photoelectron spectroscopy, and by X-ray powder diffraction and field-emission scanning electron microscopy. The NPs were deposited on microchips to result in a sensor that has a fast response to methanol in the liquid phase. Features include high sensitivity, low-sample volume, reliability, reproducibility, ease of integration, long-term stability, and enhanced electrochemical responses. The calibration plot is linear (r 2  = 0.9981) over the 0.25 mmolL −1 to 0.25 molL −1 methanol concentration range. The sensitivity is ∼7.917 μA cm −2 mmolL −2 , and the detection limit is 71.0 ± 0.5 μmolL −1 at a signal-to-noise-ratio of 3. (author)

  19. The Silver Oxide-Zinc Alkaline Primary Cell. Part 2. Effects of Various Types of Negative Electrodes on Cell Characteristics

    Shepherd, C. M

    1951-01-01

    ... (generally a potassium hydroxide solution). During discharge, the silver peroxide in the positive electrode is reduced to metallic silver and the metallic zinc in the negative electrode is oxidized either to zinc oxide or to a complex zincate ion...

  20. Chemical phase analysis of seed mediated synthesized anisotropic silver nanoparticles

    Bharti, Amardeep; Goyal, Navdeep; Singh, Suman; Singla, M. L.

    2015-01-01

    Noble-metal nanoparticles are of great interest because of its broad applications almost in every stream (i.e. biology, chemistry and engineering) due to their unique size/shape dependant properties. In this paper, chemical phase of seed mediated synthesized anisotropic silver nanoparticle (AgNPs) has been investigated via fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). These nanaoparticles were synthesized by seed-growth method controlled by urea and dextrose results to highly stable 12-20 nm particle size revealed by zeta potential and transmission electron microscopy (TEM)

  1. Deposition and Characterization of Silver Oxide from Solution of Silver, Cassava and Sugarcane Juice Effects

    Uche E. Ekpunobi

    2013-06-01

    Full Text Available Silver oxide was deposited on metallic substrates (zinc and lead from silver solution with different additives at a pH of 5, dc current of 0.2A, 4V for 20seconds at 25°C. The additives were cassava solution and sugarcane juice. The metallic substrates served as cathode while a copper electrode serves as the anode. Compositions of the electrolytes were 50ml AgNO3, 50ml AgNO3 and 50ml of cassava solution or 50ml of sugarcane juice. Structural and textural characterizations were carried out on the deposits. The result showed that deposition using zinc substrate gave a better result than that of lead in that the deposits were pure without impurities. Using cassava solution as additive, a pure Ag2O3 deposit was obtained while sugarcane juice gave a pure intergrowth of Ag2O3 and Ag3O4 deposits both on zinc substrates.

  2. Nanostructured high valence silver oxide produced by pulsed laser deposition

    Dellasega, D.; Facibeni, A.; Di Fonzo, F.; Russo, V.; Conti, C.; Ducati, C.; Casari, C.S.; Li Bassi, A.; Bottani, C.E.

    2009-01-01

    Among silver oxides, Ag 4 O 4 , i.e. high valence Ag(I)Ag(III) oxide, is interesting for applications in high energy batteries and for the development of antimicrobial coatings. We here show that ns UV pulsed laser deposition (PLD) in an oxygen containing atmosphere allows the synthesis of pure Ag 4 O 4 nanocrystalline thin films, permitting at the same time to control the morphology of the material at the sub-micrometer scale. Ag 4 O 4 films with a crystalline domain size of the order of tens of nm can be deposited provided the deposition pressure is above a threshold (roughly 4 Pa pure O 2 or 20 Pa synthetic air). The formation of this particular high valence silver oxide is explained in terms of the reactions occurring during the expansion of the ablated species in the reactive atmosphere. In particular, expansion of the PLD plasma plume is accompanied by formation of low stability Ag-O dimers and atomic oxygen, providing reactive species at the substrate where the film grows. Evidence of reactive collisions in the expanding ablation plume is obtained by analysis of the plume visible shape in inert and reactive atmospheres. In addition, we show how the dimensionless deposition parameter L, relating the target-to-substrate distance to the ablation plume maximum expansion length, can be used to classify different growth regimes. It is thus possible to vary the stoichiometry and the morphology of the films, from compact and columnar to foam-like, by controlling both the gas pressure and the target-to-substrate distance

  3. Silver nanowires-templated metal oxide for broadband Schottky photodetector

    Patel, Malkeshkumar; Kim, Hong-Sik; Kim, Joondong, E-mail: joonkim@inu.ac.kr [Photoelectric and Energy Device Application Lab (PEDAL) and Department of Electrical Engineering, Incheon National University, 119 Academy Rd. Yeonsu, Incheon 406772 (Korea, Republic of); Park, Hyeong-Ho [Applied Device and Material Lab., Device Technology Division, Korea Advanced Nano Fab Center (KANC), Suwon 443270 (Korea, Republic of)

    2016-04-04

    Silver nanowires (AgNWs)-templated transparent metal oxide layer was applied for Si Schottky junction device, which remarked the record fastest photoresponse of 3.4 μs. Self-operating AgNWs-templated Schottky photodetector showed broad wavelength photodetection with high responsivity (42.4 A W{sup −1}) and detectivity (2.75 × 10{sup 15} Jones). AgNWs-templated indium-tin-oxide (ITO) showed band-to-band excitation due to the internal photoemission, resulting in significant carrier collection performances. Functional metal oxide layer was formed by AgNWs-templated from ITO structure. The grown ITO above AgNWs has a cylindrical shape and acts as a thermal protector of AgNWs for high temperature environment without any deformation. We developed thermal stable AgNWs-templated transparent oxide devices and demonstrated the working mechanism of AgNWs-templated Schottky devices. We may propose the high potential of hybrid transparent layer design for various photoelectric applications, including solar cells.

  4. Phase equilibrium of the system Ag-Fe-Nd, and Nd extraction from magnet scraps using molten silver

    Takeda, O.; Okabe, T.H.; Umetsu, Y.

    2004-01-01

    To develop a new recycling process, we examined the direct extraction of neodymium (Nd) metal from Nd-Fe-B magnet scraps using molten silver (Ag) as an extraction medium. Prior to the extraction experiment, the phase equilibrium of the system Ag-Fe-Nd was investigated to estimate the theoretical extraction limit. It was observed that the Fe/Nd 2 Fe 17 mixture equilibrates with the molten Ag-Nd alloy containing 50-52 mol% Nd (57-59 mass% Nd) at 1363 K. The experimental results were in good agreement with the thermodynamic calculation based on literature values. By reacting Nd-Fe-B magnet scraps with molten silver at 1273 K, more than 90% of the neodymium in the scrap was extracted, and an Ag-Nd alloy containing 40-50 mass% Nd was obtained. The neodymium in the Ag-Nd alloy was separated from silver as Nd 2 O 3 by oxidizing the obtained alloy in air. Although the wettability of Nd 2 O 3 with molten silver caused some difficulties in the separation of neodymium from silver, molten silver is shown to be an effective medium for neodymium extraction from magnet scrap

  5. High Density Silver Nanowire Arrays using Self-ordered Anodic Aluminum Oxide (AAO) Membrane

    Han, Young-Hwan

    2008-01-01

    High density silver nanowire arrays were synthesized through the self-ordered Anodic Aluminum Oxide (AAO) template. The pore size in the AAO membrane was confirmed by processing the widening porosity with a honeycomb structure with cross sections of 20nm, 50nm, and 100nm, by SEM. Pore numbers by unit area were consistent; only pore size changed. The synthesized silver nanowire, which was crystallized, was dense in the cross sections of the amorphous AAO membrane. The synthesized silver nanowi...

  6. Coaxial silver nanowire network core molybdenum oxide shell supercapacitor electrodes

    Yuksel, Recep; Coskun, Sahin; Unalan, Husnu Emrah

    2016-01-01

    We present a new hybrid material composed of molybdenum (IV) oxide (MoO 2 ) shell on highly conducting silver nanowire (Ag NW) core in the network form for the realization of coaxial Ag NW/MoO 2 nanocomposite supercapacitor electrodes. Ag NWs were simply spray coated onto glass substrates to form conductive networks and conformal MoO 2 layer was electrodeposited onto the Ag NW network to create binder-free coaxial supercapacitor electrodes. Combination of Ag NWs and pseudocapacitive MoO 2 generated an enhanced electrochemical energy storage capacity and a specific capacitance of 500.7 F/g was obtained at a current density of 0.25 A/g. Fabricated supercapacitor electrodes showed excellent capacity retention after 5000 cycles. The methods and the design investigated herein open a wide range of opportunities for nanowire based coaxial supercapacitors.

  7. High rate capability of lithium/silver vanadium oxide cells

    Takeuchi, E.S.; Zelinsky, M.A.; Keister, P.

    1986-01-01

    High rate characteristics of the lithium/silver vanadium oxide system were investigated in test cells providing four different limiting surface areas. The cells were tested by constant current and constant resistance discharge with current densities ranging from 0.04 to 6.4 mA/cm/sup 2/. The maximum current density under constant resistance and constant current discharges which would deliver 50% of theoretical capacity was determined. The ability of the cells to deliver high current pulses was evaluated by application of 10 second pulses with current densities ranging from 3 to 30 mA/cm/sup 2/. The voltage delay characteristics of the cells were determined after 1 to 3 months of storage at open circuit voltage or under low level background currents. The volumetric and gravimetric energy density of the SVO system is compared to other cathode materials

  8. Use of carbon paste electrodes for the voltammetric detection of silver leached from the oxidative dissolution of silver nanoparticles

    Mullaugh, Katherine M.; Pearce, Olivia M.

    2017-04-01

    The widespread use of silver nanoparticles (Ag NPs) in consumer goods has raised concerns about the release of silver in environmental waters. Of particular concern is the oxidative dissolution of Ag NPs to release Ag+ ions, which are highly toxic to many aquatic organisms. Here, we have investigated the application of differential pulse stripping voltammetry (DPSV) with carbon paste electrodes (CPEs) in monitoring the oxidation of Ag NPs. Using a commercially available, unmodified carbon paste and 60-s deposition times, a detection limit of 3 nM Ag+ could be achieved. We demonstrate its selectivity for free Ag+ ions over Ag nanoparticles, allowing for analysis of the oxidation of Ag NPs without the need for separation of ions and nanoparticles prior to analysis. We applied this approach to investigate the effect of pH in the oxidative dissolution of Ag NPs, demonstrating the usefulness of CPEs in studies of this type.

  9. Use of carbon paste electrodes for the voltammetric detection of silver leached from the oxidative dissolution of silver nanoparticles

    Mullaugh, Katherine M.; Pearce, Olivia M.

    2017-01-01

    The widespread use of silver nanoparticles (Ag NPs) in consumer goods has raised concerns about the release of silver in environmental waters. Of particular concern is the oxidative dissolution of Ag NPs to release Ag"+ ions, which are highly toxic to many aquatic organisms. Here, we have investigated the application of differential pulse stripping voltammetry (DPSV) with carbon paste electrodes (CPEs) in monitoring the oxidation of Ag NPs. Using a commercially available, unmodified carbon paste and 60-s deposition times, a detection limit of 3 nM Ag"+ could be achieved. We demonstrate its selectivity for free Ag"+ ions over Ag nanoparticles, allowing for analysis of the oxidation of Ag NPs without the need for separation of ions and nanoparticles prior to analysis. We applied this approach to investigate the effect of pH in the oxidative dissolution of Ag NPs, demonstrating the usefulness of CPEs in studies of this type.

  10. Use of carbon paste electrodes for the voltammetric detection of silver leached from the oxidative dissolution of silver nanoparticles

    Mullaugh, Katherine M., E-mail: mullaughkm@cofc.edu; Pearce, Olivia M. [College of Charleston, Department of Chemistry & Biochemistry (United States)

    2017-04-15

    The widespread use of silver nanoparticles (Ag NPs) in consumer goods has raised concerns about the release of silver in environmental waters. Of particular concern is the oxidative dissolution of Ag NPs to release Ag{sup +} ions, which are highly toxic to many aquatic organisms. Here, we have investigated the application of differential pulse stripping voltammetry (DPSV) with carbon paste electrodes (CPEs) in monitoring the oxidation of Ag NPs. Using a commercially available, unmodified carbon paste and 60-s deposition times, a detection limit of 3 nM Ag{sup +} could be achieved. We demonstrate its selectivity for free Ag{sup +} ions over Ag nanoparticles, allowing for analysis of the oxidation of Ag NPs without the need for separation of ions and nanoparticles prior to analysis. We applied this approach to investigate the effect of pH in the oxidative dissolution of Ag NPs, demonstrating the usefulness of CPEs in studies of this type.

  11. Randomized controlled trial on collagen/oxidized regenerated cellulose/silver treatment

    Gottrup, Finn; Cullen, Breda Mary; Karlsmark, Tonny

    2013-01-01

    Collagen/oxidized regenerated cellulose (ORC)/silver therapy has been designed to facilitate wound healing by normalizing the microenvironment and correcting biochemical imbalances in chronic wounds. The aim of this study was to compare collagen/ORC/silver therapy to control (standard treatment)....

  12. Enhanced sensitivity of surface plasmon resonance phase-interrogation biosensor by using oblique deposited silver nanorods.

    Chung, Hung-Yi; Chen, Chih-Chia; Wu, Pin Chieh; Tseng, Ming Lun; Lin, Wen-Chi; Chen, Chih-Wei; Chiang, Hai-Pang

    2014-01-01

    Sensitivity of surface plasmon resonance phase-interrogation biosensor is demonstrated to be enhanced by oblique deposited silver nanorods. Silver nanorods are thermally deposited on silver nanothin film by oblique angle deposition (OAD). The length of the nanorods can be tuned by controlling the deposition parameters of thermal deposition. By measuring the phase difference between the p and s waves of surface plasmon resonance heterodyne interferometer with different wavelength of incident light, we have demonstrated that maximum sensitivity of glucose detection down to 7.1 × 10(-8) refractive index units could be achieved with optimal deposition parameters of silver nanorods.

  13. Highly sensitive methanol chemical sensor based on undoped silver oxide nanoparticles prepared by a solution method

    Rahman, M.M.; Khan, S.B.; Asiri, A.M.; Jamal, A.; Faisal, M.

    2012-01-01

    We have prepared silver oxide nanoparticles (NPs) by a simple solution method using reducing agents in alkaline medium. The resulting NPs were characterized by UV-vis and FT-IR spectroscopy, X-ray powder diffraction, and field-emission scanning electron microscopy. They were deposited on a glassy carbon electrode to give a sensor with a fast response towards methanol in liquid phase. The sensor also displays good sensitivity and long-term stability, and enhanced electrochemical response. The calibration plot is linear (r 2 = 0.8294) over the 0.12 mM to 0.12 M methanol concentration range. The sensitivity is ∼ 2.65 μAcm -2 mM -1 , and the detection limit is 36.0 μM (at a SNR of 3). We also discuss possible future prospective uses of this metal oxide semiconductor nanomaterial in terms of chemical sensing. (author)

  14. Silver nanoparticles anchored reduced graphene oxide for enhanced electrocatalytic activity towards methanol oxidation

    Kumar, Sanjeev; Mahajan, Mani; Singh, Rajinder; Mahajan, Aman

    2018-02-01

    In this report, silver nanoparticles (Ag NPs) anchored reduced graphene oxide (rGO) sheets (rGO/Ag) nanohybrid has been explored as anode material in direct methanol fuel cells (DMFCs). The synthesized rGO/Ag nanohybrid is characterized by XRD, XPS, FTIR spectroscopy and HRTEM techniques. Cyclic voltammograms demonstrate that the rGO/Ag nanohybrid exhibits higher electrocatalytic activity in comparison to rGO sheets for methanol oxidation reaction (MOR). This enhancement is attributed to the synergetic effect produced by the presence of more active sites provided by Ag NPs anchored on a conducting network of large surface area rGO sheets.

  15. Communication: CO oxidation by silver and gold cluster cations: Identification of different active oxygen species

    Popolan, Denisia M.; Bernhardt, Thorsten M.

    2011-01-01

    The oxidation of carbon monoxide with nitrous oxide on mass-selected Au 3 + and Ag 3 + clusters has been investigated under multicollision conditions in an octopole ion trap experiment. The comparative study reveals that for both gold and silver cations carbon dioxide is formed on the clusters. However, whereas in the case of Au 3 + the cluster itself acts as reactive species that facilitates the formation of CO 2 from N 2 O and CO, for silver the oxidized clusters Ag 3 O x + (n= 1-3) are identified as active in the CO oxidation reaction. Thus, in the case of the silver cluster cations N 2 O is dissociated and one oxygen atom is suggested to directly react with CO, whereas a second kind of oxygen strongly bound to silver is acting as a substrate for the reaction.

  16. Communication: CO oxidation by silver and gold cluster cations: Identification of different active oxygen species

    Popolan, Denisia M.; Bernhardt, Thorsten M.

    2011-03-01

    The oxidation of carbon monoxide with nitrous oxide on mass-selected Au3+ and Ag3+ clusters has been investigated under multicollision conditions in an octopole ion trap experiment. The comparative study reveals that for both gold and silver cations carbon dioxide is formed on the clusters. However, whereas in the case of Au3+ the cluster itself acts as reactive species that facilitates the formation of CO2 from N2O and CO, for silver the oxidized clusters Ag3Ox+ (n = 1-3) are identified as active in the CO oxidation reaction. Thus, in the case of the silver cluster cations N2O is dissociated and one oxygen atom is suggested to directly react with CO, whereas a second kind of oxygen strongly bound to silver is acting as a substrate for the reaction.

  17. Modified silver nanowire transparent electrodes with exceptional stability against oxidation

    Idier, J; Neri, W; Ly, I; Poulin, P; Backov, R; Labrugère, C

    2016-01-01

    We report an easy method to prepare thin, flexible and transparent electrodes that show enhanced inertness toward oxidation using modified silver nanowires (Ag NWs). Stabilization is achieved through the adsorption of triphenylphosphine (PPh 3 ) onto the Ag NW hybrid dispersions prior to their 2D organization as transparent electrodes on polyethylene terephtalate (PET) films. After 110 days in air (20 °C) under atmospheric conditions, the transmittance of the PET/Ag NW/PPh 3 based films is nearly unchanged, while the transmittance of the PET/Ag NW-based films decreases by about 5%. The sheet resistance increases for both materials as time elapses, but the rate of increase is more than four times slower for films stabilized by PPh 3 . The improved transmittance and conductivity results in a significantly enhanced stability for the figure of merit σ dc /σ op . This phenomenon is highlighted in highly oxidative nitric acid vapor. The tested stabilized films in such conditions exhibit a decrease to σ dc /σ op of only 38% after 75 min, whereas conventional materials exhibit a relative loss of 71%. In addition, by contrast to other classes of stabilizers, such as polymer or graphene-based encapsulants, PPh 3 does not alter the transparency or conductivity of the modified films. While the present films are made by membrane filtration, the stabilization method could be implemented directly in other liquid processes, including industrially scalable ones. (paper)

  18. Diclofenac and 2‐anilinophenylacetate degradation by combined activity of biogenic manganese oxides and silver

    Meerburg, Francis; Hennebel, Tom; Vanhaecke, Lynn; Verstraete, Willy; Boon, Nico

    2012-01-01

    Summary The occurrence of a range of recalcitrant organic micropollutants in our aquatic environment has led to the development of various tertiary wastewater treatment methods. In this study, biogenic manganese oxides (Bio‐MnOx), biogenic silver nanoparticles (Bio‐Ag0) and ionic silver were used for the oxidative removal of the frequently encountered drug diclofenac and its dechlorinated form, 2‐anilinophenylacetate (APA). Diclofenac was rapidly degraded during ongoing manganese oxidation by Pseudomonas putida MnB6. Furthermore, whereas preoxidized Bio‐MnOx, Bio‐Ag0 and Ag+ separately did not show any removal capacity for diclofenac, an enhanced removal occurred when Bio‐MnOx and silver species were combined. Similar results were obtained for APA. Finally, a slow removal of diclofenac but more rapid APA degradation was observed when silver was added to manganese‐free P. putida biomass. Combining these results, three mechanisms of diclofenac and APA removal could be distinguished: (i) a co‐metabolic removal during active Mn2+ oxidation by P. putida; (ii) a synergistic interaction between preoxidized Bio‐MnOx and silver species; and (iii) a (bio)chemical process by biomass enriched with silver catalysts. This paper demonstrates the use of P. putida for water treatment purposes and is the first report of the application of silver combined with biogenic manganese for the removal of organic water contaminants. PMID:22221449

  19. Antibacterial activity of nitric oxide releasing silver nanoparticles

    Seabra, Amedea B.; Manosalva, Nixson; de Araujo Lima, Bruna; Pelegrino, Milena T.; Brocchi, Marcelo; Rubilar, Olga; Duran, Nelson

    2017-06-01

    Silver nanoparticles (AgNPs) are well known potent antimicrobial agents. Similarly, the free radical nitric oxide (NO) has important antibacterial activity, and due to its instability, the combination of NO and nanomaterials has been applied in several biomedical applications. The aim of this work was to synthesize, characterize and evaluate the antibacterial activity of a new NO-releasing AgNPs. Herein, AgNPs were synthesized by the reduction of silver ions (Ag+) by catechin, a natural polyphenol and potent antioxidant agent, derived from green tea extract. Catechin acts as a reducing agent and as a capping molecule on the surface of AgNPs, minimizing particle agglomeration. The as-synthesized nanoparticles were characterized by different techniques. The results showed the formation of AgNPs with average hydrodynamic size of 44 nm, polydispersity index of 0.21, and zeta potential of -35.9 mV. X-ray diffraction and Fourier transform infrared spectroscopy revealed the presence of the AgNP core and cathecin as capping agent. The low molecular weight mercaptosuccinic acid (MSA), which contain free thiol group, was added on the surface of catechin-AgNPs, leading to the formation of MSA-catechin-AgNPs (the NO precursor nanoparticle). Free thiol groups of MSA-catechin-AgNPs were nitrosated leading to the formation of S-nitroso-mercaptosuccinic acid (S-nitroso-MSA), the NO donor. The amount of 342 ± 16 µmol of NO was released per gram of S-nitroso-MSA-catechin-AgNPs. The antibacterial activities of catechin-AgNPs, MSA-catechin-AgNPs, and S-nitroso-MSA-catechin-AgNPs were evaluated towards different resistant bacterial strains. The results demonstrated an enhanced antibacterial activity of the NO-releasing AgNP. For instance, the minimal inhibitory concentration values for Pseudomonas aeruginosa (ATCC 27853) incubated with AgNPs-catechin, AgNPs-catechin-MSA, and AgNPs-catechin-S-nitroso-MSA were found to be 62, 125 and 3 µg/mL, respectively. While in the case of

  20. Electrical and optical properties of reactive DC magnetron sputtered silver oxide thin films: role of oxygen

    Kumar Barik, Ullash; Srinivasan, S; Nagendra, C L; Subrahmanyam, A

    2003-04-01

    Silver oxide thin films have been prepared on soda lime glass substrates at room temperature (300 K) by reactive DC Magnetron sputtering technique using pure silver metal target; the oxygen flow rates have been varied in the range 0.00-2.01 sccm. The X-ray diffraction data on these films show a systematic change from metallic silver to silver (sub) oxides. The electrical resistivity increases with increasing oxygen flow. The films show a p-type behavior (by both Hall and Seebeck measurements) for the oxygen flow rates of 0.54, 1.09 and 1.43 sccm. The refractive index of the films (at 632.8 nm) decreases with increasing oxygen content and is in the range 1.167-1.145, whereas the p-type films show a higher refractive index (1.186-1.204). The work function of these silver oxide films has been measured by Kelvin Probe technique. The results, in specific, the p-type conductivity in the silver oxide films, have been explained on the basis of the theory of partial ionic charge proposed by Sanderson.

  1. Electrical and optical properties of reactive DC magnetron sputtered silver oxide thin films: role of oxygen

    Kumar Barik, Ullash; Srinivasan, S.; Nagendra, C.L.; Subrahmanyam, A.

    2003-01-01

    Silver oxide thin films have been prepared on soda lime glass substrates at room temperature (300 K) by reactive DC Magnetron sputtering technique using pure silver metal target; the oxygen flow rates have been varied in the range 0.00-2.01 sccm. The X-ray diffraction data on these films show a systematic change from metallic silver to silver (sub) oxides. The electrical resistivity increases with increasing oxygen flow. The films show a p-type behavior (by both Hall and Seebeck measurements) for the oxygen flow rates of 0.54, 1.09 and 1.43 sccm. The refractive index of the films (at 632.8 nm) decreases with increasing oxygen content and is in the range 1.167-1.145, whereas the p-type films show a higher refractive index (1.186-1.204). The work function of these silver oxide films has been measured by Kelvin Probe technique. The results, in specific, the p-type conductivity in the silver oxide films, have been explained on the basis of the theory of partial ionic charge proposed by Sanderson

  2. In vitro assessment of the antimicrobial activity of silver and zinc oxide nanoparticles against fish pathogens.

    Shaalan, Mohamed Ibrahim; El-Mahdy, Magdy Mohamed; Theiner, Sarah; El-Matbouli, Mansour; Saleh, Mona

    2017-07-21

    Antibiotic resistance is a global issue that threatens public health. The excessive use of antibiotics contributes to this problem as the genes of antibiotic resistance can be transferred between the bacteria in humans, animals and aquatic organisms. Metallic nanoparticles could serve as future substitutes for some conventional antibiotics because of their antimicrobial activity. The aim of this study was to evaluate the antimicrobial effects of silver and zinc oxide nanoparticles against major fish pathogens and assess their safety in vitro. Silver nanoparticles were synthesized by chemical reduction and characterized with UV-Vis spectroscopy, transmission electron microscopy and zeta sizer. The concentrations of silver and zinc oxide nanoparticles were measured using inductively coupled plasma-mass spectrometry. Subsequently, silver and zinc oxide nanoparticles were tested for their antimicrobial activity against Aeromonas hydrophila, Aeromonas salmonicida subsp. salmonicida, Edwardsiella ictaluri, Edwardsiella tarda, Francisella noatunensis subsp. orientalis, Yersinia ruckeri and Aphanomyces invadans and the minimum inhibitory concentrations were determined. MTT assay was performed on eel kidney cell line (EK-1) to determine the cell viability after incubation with nanoparticles. The interaction between silver nanoparticles and A. salmonicida was investigated by transmission electron microscopy. The tested nanoparticles exhibited marked antimicrobial activity. Silver nanoparticles inhibited the growth of both A. salmonicida and A. invadans at a concentration of 17 µg/mL. Zinc oxide nanoparticles inhibited the growth of A. salmonicida, Y. ruckeri and A. invadans at concentrations of 15.75, 31.5 and 3.15 µg/mL respectively. Silver nanoparticles showed higher cell viability when compared to zinc oxide nanoparticles in the MTT assay. Transmission electron microscopy showed the attachment of silver nanoparticles to the bacterial membrane and disruption of its

  3. The scavenging of silver by manganese and iron oxides in stream sediments collected from two drainage areas of Colorado

    Chao, T.T.; Anderson, B.J.

    1974-01-01

    Stream sediments of two well-weathered and aerated drainage areas of Colorado containing anomalous amounts of silver were allowed to react by shaking with nitric acid of different concentrations (1-10M). Silver, manganese, and iron simultaneously dissolved were determined by atomic absorption. The relationship between silver dissolution and the dissolution of manganese and/or iron was evaluated by linear and multiple regression analyses. The highly significant correlation coefficient (r = 0.913) between silver and manganese dissolution suggests that manganese oxides are the major control on the scavenging of silver in these stream sediments, whereas iron oxides only play a secondary role in this regard. ?? 1974.

  4. Antibacterial properties of composite resins incorporating silver and zinc oxide nanoparticles on Streptococcus mutans and Lactobacillus

    Shahin Kasraei

    2014-05-01

    Full Text Available Objectives Recurrent caries was partly ascribed to lack of antibacterial properties in composite resin. Silver and zinc nanoparticles are considered to be broad-spectrum antibacterial agents. The aim of the present study was to evaluate the antibacterial properties of composite resins containing 1% silver and zinc-oxide nanoparticles on Streptococcus mutans and Lactobacillus. Materials and Methods Ninety discoid tablets containing 0%, 1% nano-silver and 1% nano zinc-oxide particles were prepared from flowable composite resin (n = 30. The antibacterial properties of composite resin discs were evaluated by direct contact test. Diluted solutions of Streptococcus mutans (PTCC 1683 and Lactobacillus (PTCC 1643 were prepared. 0.01 mL of each bacterial species was separately placed on the discs. The discs were transferred to liquid culture media and were incubated at 37℃ for 8 hr. 0.01 mL of each solution was cultured on blood agar and the colonies were counted. Data was analyzed with Kruskall-Wallis and Mann-Whitney U tests. Results Composites containing nano zinc-oxide particles or silver nanoparticles exhibited higher antibacterial activity against Streptococcus mutans and Lactobacillus compared to the control group (p < 0.05. The effect of zinc-oxide on Streptococcus mutans was significantly higher than that of silver (p < 0.05. There were no significant differences in the antibacterial activity against Lactobacillus between composites containing silver nanoparticles and those containing zinc-oxide nanoparticles. Conclusions Composite resins containing silver or zinc-oxide nanoparticles exhibited antibacterial activity against Streptococcus mutans and Lactobacillus.

  5. Silver-graphene oxide based plasmonic spacer for surface plasmon-coupled fluorescence emission enhancements

    Badiya, Pradeep Kumar; Srinivasan, Venkatesh; Sathish Ramamurthy, Sai

    2017-06-01

    We report the application of single layered graphene oxide (SLGO) and silver decorated SLGO (Ag-SLGO) as plasmonic spacer material for obtaining enhanced fluorescence from a Rhodamine 6G (Rh6G) radiating dipole in a surface plasmon-coupled emission platform. To this end, we have decorated SLGO with biphasic silver nanoparticles using an in situ deposition technique to achieve 112-fold fluorescence enhancements.

  6. Structural and silver/vanadium ratio effects on silver vanadium phosphorous oxide solution formation kinetics: impact on battery electrochemistry.

    Bock, David C; Takeuchi, Kenneth J; Marschilok, Amy C; Takeuchi, Esther S

    2015-01-21

    The detailed understanding of non-faradaic parasitic reactions which diminish battery calendar life is essential to the development of effective batteries for use in long life applications. The dissolution of cathode materials including manganese, cobalt and vanadium oxides in battery systems has been identified as a battery failure mechanism, yet detailed dissolution studies including kinetic analysis are absent from the literature. The results presented here provide a framework for the quantitative and kinetic analyses of the dissolution of cathode materials which will aid the broader community in more fully understanding this battery failure mechanism. In this study, the dissolution of silver vanadium oxide, representing the primary battery powering implantable cardioverter defibrillators (ICD), is compared with the dissolution of silver vanadium phosphorous oxide (Ag(w)VxPyOz) materials which were targeted as alternatives to minimize solubility. This study contains the first kinetic analyses of silver and vanadium solution formation from Ag0.48VOPO4·1.9H2O and Ag2VP2O8, in a non-aqueous battery electrolyte. The kinetic results are compared with those of Ag2VO2PO4 and Ag2V4O11 to probe the relationships among crystal structure, stoichiometry, and solubility. For vanadium, significant dissolution was observed for Ag2V4O11 as well as for the phosphate oxide Ag0.49VOPO4·1.9H2O, which may involve structural water or the existence of multiple vanadium oxidation states. Notably, the materials from the SVPO family with the lowest vanadium solubility are Ag2VO2PO4 and Ag2VP2O8. The low concentrations and solution rates coupled with their electrochemical performance make these materials interesting alternatives to Ag2V4O11 for the ICD application.

  7. FDTD Modelling of Silver Nanoparticles Embedded in Phase Separation Interface of H-PDLC

    Kun Gui

    2015-01-01

    Full Text Available We report localized surface plasmon resonance (LSPR of silver nanoparticles (NPs embedded in interface of phase separation of holographic polymer-dispersed liquid crystal (H-PDLC gratings using Finite-Difference Time Domain method. We show that silver NPs exhibit double resonance peak at the interface, and these peaks are influenced by the angle of incident light. We observe a blue shift of the wavelength of resonance peak as the incident angle increases. However, the location of silver NPs at the interface has nearly no effect on the wavelength of resonance peak. Also we show near-field and far-field properties surrounding silver NPs and find that field distribution can be controlled through rotation of incident angle. Therefore, LSPR properties of silver NPs within H-PDLC gratings can be excited by appropriate wavelength and angle of the incident light.

  8. Comparison of properties of silver-metal oxide electrical contact materials

    Ćosović V.

    2012-01-01

    Full Text Available Changes in physical properties such as density, porosity, hardness and electrical conductivity of the Ag-SnO2 and Ag-SnO2In2O3 electrical contact materials induced by introduction of metal oxide nanoparticles were investigated. Properties of the obtained silver-metal oxide nanoparticle composites are discussed and presented in comparison to their counterparts with the micro metal oxide particles as well as comparable Ag-SnO2WO3 and Ag-ZnO contact materials. Studied silvermetal oxide composites were produced by powder metallurgy method from very fine pure silver and micro- and nanoparticle metal oxide powders. Very uniform microstructures were obtained for all investigated composites and they exhibited physical properties that are comparable with relevant properties of equivalent commercial silver based electrical contact materials. Both Ag-SnO2 and Ag- SnO2In2O3 composites with metal oxide nanoparticles were found to have lower porosity, higher density and hardness than their respective counterparts which can be attributed to better dispersion hardening i.e. higher degree of dispersion of metal oxide in silver matrix.

  9. Apoptosis inducing ability of silver decorated highly reduced graphene oxide nanocomposites in A549 lung cancer

    Khan M

    2016-03-01

    Full Text Available Merajuddin Khan,1 Mujeeb Khan,1 Abdulhadi H Al-Marri,1 Abdulrahman Al-Warthan,1 Hamad Z Alkhathlan,1 Mohammed Rafiq H Siddiqui,1 Vadithe Lakshma Nayak,2 Ahmed Kamal,2 Syed F Adil1 1Department of Chemistry, College of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia; 2Department of Medicinal Chemistry and Pharmacology, CSIR – Indian Institute of Chemical Technology, Hyderabad, India Abstract: Recently, graphene and graphene-based materials have been increasingly used for various biological applications due to their extraordinary physicochemical properties. Here, we demonstrate the anticancer properties and apoptosis-inducing ability of silver doped highly reduced graphene oxide nanocomposites synthesized by employing green approach. These nano­composites (PGE-HRG-Ag were synthesized by using Pulicaria glutinosa extract (PGE as a reducing agent and were evaluated for their anticancer properties against various human cancer cell lines with tamoxifen as the reference drug. A correlation between the amount of Ag nanoparticles on the surface of highly reduced graphene oxide (HRG and the anticancer activity of nanocomposite was observed, wherein an increase in the concentration of Ag nanoparticles on the surface of HRG led to the enhanced anticancer activity of the nanocomposite. The nanocomposite PGE-HRG-Ag-2 exhibited more potent cytotoxicity than standard drug in A549 cells, a human lung cancer cell line. A detailed investigation was undertaken and Fluorescence activated cell sorting (FACS analysis demonstrated that the nanocomposite PGE-HRG-Ag-2 showed G0/G1 phase cell cycle arrest and induced apoptosis in A549 cells. Studies such as, measurement of mitochondrial membrane potential, generation of reactive oxygen species (ROS and Annexin V-FITC staining assay suggested that this compound induced apoptosis in human lung cancer cells. Keywords: plant extract, graphene/silver nanocomposites, anticancer, apoptosis

  10. Waste treatment in NUCEF facility with silver mediated electrochemical oxidation technique

    Umeda, M.; Sugikawa, S.

    2000-01-01

    Silver mediated electrochemical oxidation technique has been considered one of promising candidates for alpha-bearing waste treatment. Destruction tests of organic compounds, such as insoluble tannin, TBP and dodecane, were carried out by this technique and the experimental data such as destruction rates, current efficiencies and intermediates were obtained. These compounds could be completely mineralized without the formation of reactive organic nitrate associated to safety hazards. On the basis of these results, the applicability of silver mediated electrochemical oxidation technique to waste treatment in NUCEF was evaluated. (authors)

  11. Kinetics of oxidic phase dissolution in acids

    Gorichev, I.G.; Kipriyanov, N.A.

    1981-01-01

    The critical analysis of the experimental data on dissolution kinetics of metal oxides (BeO, V 2 O 5 , UO 2 , Nb 2 O 5 , Ta 2 O 5 etc.) in acid media is carried out. Kinetic peculiarities of oxide dissolution are explained on the basis of the notions of electron- proton theory. It is established that the surface nonstoichiometric ccomposition of oxide phase and potential jump, appearing on the interface of the oxide-electrolyte phase are the important factors, determining the dissolution rate of a solid phase. The dissolution rate of metal oxides is limited by the transition of protons into the solid oxide phase. Morphological models of heterogeneous kinetics are used when explaining kinetic regularities of oxide dissolution process [ru

  12. Electric radiation mapping of silver/zinc oxide nanoantennas by using electron holography

    Sanchez, J. E.; Mendoza-Santoyo, F.; Cantu-Valle, J.; Velazquez-Salazar, J.; José Yacaman, M.; Ponce, A. [Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio 78249 (United States); González, F. J. [Coordinación para la Innovación y la Aplicación de la Ciencia y la Tecnología, Universidad Autónoma de San Luís Potosí, San Luis Potosí 78210 (Mexico); Diaz de Leon, R. [Instituto Tecnológico de San Luis Potosí, San Luis Potosi 78437 (Mexico)

    2015-01-21

    In this work, we report the fabrication of self-assembled zinc oxide nanorods grown on pentagonal faces of silver nanowires by using microwaves irradiation. The nanostructures resemble a hierarchal nanoantenna and were used to study the far and near field electrical metal-semiconductor behavior from the electrical radiation pattern resulting from the phase map reconstruction obtained using off-axis electron holography. As a comparison, we use electric numerical approximations methods for a finite number of ZnO nanorods on the Ag nanowires and show that the electric radiation intensities maps match closely the experimental results obtained with electron holography. The time evolution of the radiation pattern as generated from the nanostructure was recorded under in-situ radio frequency signal stimulation, in which the generated electrical source amplitude and frequency were varied from 0 to 5 V and from 1 to 10 MHz, respectively. The phase maps obtained from electron holography show the change in the distribution of the electric radiation pattern for individual nanoantennas. The mapping of this electrical behavior is of the utmost importance to gain a complete understanding for the metal-semiconductor (Ag/ZnO) heterojunction that will help to show the mechanism through which these receiving/transmitting structures behave at nanoscale level.

  13. Silver Modified Degussa P25 for the Photocatalytic Removal of Nitric Oxide

    Neil Bowering

    2007-01-01

    Full Text Available A study of the photocatalytic behaviour of silver modified titanium dioxide materials for the decomposition and reduction of nitric oxide (NO gas has been carried out. The effects of silver loading, calcination temperature, and reaction conditions have been investigated. Prepared photocatalysts were characterised using XRD, TEM, and XPS. A continuous flow reactor was used to determine the photocatalytic activity and selectivity of NO decomposition in the absence of oxygen as well as NO reduction using CO as the reducing agent, over the prepared photocatalysts. XRD and TEM analysis of the photocatalysts showed that crystalline silver nitrate particles were present on the titanium dioxide surface after calcination at temperatures of up to 200∘C. The silver nitrate particles are thermally decomposed to form metallic silver clusters at higher temperatures. XPS analysis of the photocatalysts showed that for each of the temperatures used, both Ag+ and Ag0 were present and that the Ag0/Ag+ ratio increased with increasing calcination temperature. The presence of metallic silver species on the TiO2 surface dramatically increased the selectivity for N2 formation of both decomposition and reduction reactions. When CO was present in the reaction gas, selectivities of over 90% were observed for all the Ag-TiO2 photocatalysts that had been calcined at temperatures above 200∘C. Unfortunately these high selectivities were at the expense of photocatalytic activity, with lower NO conversion rates than those achieved over unmodified TiO2 photocatalysts.

  14. Reconstruction mechanisms of tantalum oxide coatings with low concentrations of silver for high temperature tribological applications

    Stone, D. S.; Bischof, M.; Aouadi, S. M., E-mail: samir.aouadi@unt.edu [Department of Material Science and Engineering, University of North Texas, Denton, Texas 76207 (United States); Gao, H.; Martini, A. [School of Engineering, University of California Merced, Merced, California 95343 (United States); Chantharangsi, C.; Paksunchai, C. [Department of Physics, King Mongkut' s University of Technology Thonburi, Bangkok 10140 (Thailand)

    2014-11-10

    Silver tantalate (AgTaO{sub 3}) coatings have been found to exhibit outstanding tribological properties at elevated temperatures. To understand the mechanisms involved in the tribological behavior of the Ag-Ta-O system, tantalum oxide coatings with a small content of silver were produced to investigate the metastable nature of this self-lubricating material. The coatings were produced by unbalanced magnetron sputtering, ball-on-disk wear tested at 750 °C, and subsequently characterized by X-ray diffraction, Scanning Auger Nanoprobe, cross-sectional Scanning Electron Microscopy, and Transmission Electron Microscopy. Complementary molecular dynamic simulations were carried out to investigate changes in the chemical and structural properties at the interface due to sliding for films with varying silver content. Both the experimental characterization and the theoretical modeling showed that silver content affects friction and wear, through the role of silver in film reconstruction during sliding. The results suggest that the relative amount of silver may be used to tune film performance for a given application.

  15. Reconstruction mechanisms of tantalum oxide coatings with low concentrations of silver for high temperature tribological applications

    Stone, D. S.; Bischof, M.; Aouadi, S. M.; Gao, H.; Martini, A.; Chantharangsi, C.; Paksunchai, C.

    2014-01-01

    Silver tantalate (AgTaO 3 ) coatings have been found to exhibit outstanding tribological properties at elevated temperatures. To understand the mechanisms involved in the tribological behavior of the Ag-Ta-O system, tantalum oxide coatings with a small content of silver were produced to investigate the metastable nature of this self-lubricating material. The coatings were produced by unbalanced magnetron sputtering, ball-on-disk wear tested at 750 °C, and subsequently characterized by X-ray diffraction, Scanning Auger Nanoprobe, cross-sectional Scanning Electron Microscopy, and Transmission Electron Microscopy. Complementary molecular dynamic simulations were carried out to investigate changes in the chemical and structural properties at the interface due to sliding for films with varying silver content. Both the experimental characterization and the theoretical modeling showed that silver content affects friction and wear, through the role of silver in film reconstruction during sliding. The results suggest that the relative amount of silver may be used to tune film performance for a given application

  16. Graphene supported silver@silver chloride & ferroferric oxide hybrid, a magnetically separable photocatalyst with high performance under visible light irradiation

    Zhong, Suting; Jiang, Wei, E-mail: superfine_jw@126.com; Han, Mei; Liu, Gongzong; Zhang, Na; Lu, Yue

    2015-08-30

    Graphical abstract: - Highlights: • The composites were synthesized via a facile and effective process. • Plenty of Fe{sub 3}O{sub 4} and Ag@AgCl nanoparticles are deposited on the reduced graphene oxide nanosheets. • The catalyst exhibited an enhanced photocatalytic performance and magnetic property. • The catalyst is stable under the visible light irradiation. - Abstract: A stable magnetic separable plasmonic photocatalyst was successfully fabricated by grafting silver@silver chloride (Ag@AgCl) and ferroferric oxide (Fe{sub 3}O{sub 4}) nanoparticles on graphene sheets. The composite exhibited high activity degrading methylene blue (MB) and rhodamine B (RB) under visible light irradiation: decomposition 97.4% of MB in 100 min and 97.9% of RB in 120 min. The enhanced photocatalytic activities can be attributed to synergistic effect between Ag@AgCl and graphene: the effective charge transfer from Ag@AgCl to graphene thus promotes the separation of electron–hole pairs. Moreover, the excellent magnetic property gives a more convenient way to recycle the photocatalysts.

  17. Silver-mediated oxidative C-H difluoromethylation of phenanthridines and 1,10-phenanthrolines.

    Zhu, Sheng-Qing; Xu, Xiu-Hua; Qing, Feng-Ling

    2017-10-17

    A silver-mediated oxidative difluoromethylation of phenanthridines and 1,10-phenanthrolines with TMSCF 2 H is disclosed. This C-H difluoromethylation of N-containing polycyclic aromatics constitutes an efficient method for the regioselective synthesis of difluoromethylated N-heterocycles.

  18. Intrinsic and extrinsic resistive switching in a planar diode based on silver oxide nanoparticles

    Kiazadeh, A.; Gomes, H.L.; Rosa da Costa, A.M.; Moreira, J.A.; Leeuw, de D.M.; Meskers, S.C.J.

    2012-01-01

    Resistive switching is investigated in thin-film planar diodes using silver oxide nanoparticles capped in a polymer. The conduction channel is directly exposed to the ambient atmosphere. Two types of switching are observed. In air, the hysteresis loop in the current–voltage characteristics is

  19. Enhanced Bonding of Silver Nanoparticles on Oxidized TiO2(110)

    Hansen, Jonas Ørbæk; Salazar, Estephania Lira; Galliker, Patrick

    2010-01-01

    The nucleation and growth of silver nanoclusters on TiO2(110) surfaces with on-top O adatoms (oxidized TiO2), surface O vacancies and H adatoms (reduced TiO2) have been studied. From the interplay of scanning tunneling microscopy/photoelectron spectroscopy experiments and density functional theor...

  20. Sequestration of radioactive iodine in silver-palladium phases in commercial spent nuclear fuel

    Buck, Edgar C., E-mail: edgar.buck@pnnl.gov; Mausolf, Edward J.; McNamara, Bruce K.; Soderquist, Chuck Z.; Schwantes, Jon M.

    2016-12-15

    Radioactive iodine is the Achilles' heel in the design for the safe geological disposal of spent uranium oxide (UO{sub 2}) nuclear fuel. Furthermore, iodine's high volatility and aqueous solubility were mainly responsible for the high early doses released during the accident at Fukushima Daiichi in 2011. Studies Kienzler et al., however, have indicated that the instant release fraction (IRF) of radioiodine ({sup 131/129}I) does not correlate directly with increasing fuel burn-up. In fact, there is a peak in the release of iodine at around 50–60 MW d/kgU, and with increasing burn-up, the IRF of {sup 131/129}I decreases. The reasons for this decrease have not fully been understood. We have performed microscopic analysis of chemically processed high burn-up UO{sub 2} fuel (80 MW d/kgU) and have found recalcitrant nano-particles containing, Pd, Ag, I, and Br, possibly consistent with a high pressure phase of silver iodide in the undissolved residue. It is likely that increased levels of Ag and Pd from {sup 239}Pu fission in high burnup fuels leads to the formation of these metal halides. The occurrence of these phases in UO{sub 2} nuclear fuels may reduce the impact of long-lived {sup 129}I on the repository performance assessment calculations. - Highlights: • A Pd-Ag halide phase has been observed in a high burn-up UO{sub 2} reactor fuel. • The phases contains iodine and bromine. • Iodine release in high burnup fuels may be reduced through the formation of recalcitrant phases.

  1. Phase-transfer and film formation of silver nanoparticles.

    Sarkar, Anjana; Chadha, Ridhima; Biswas, Nandita; Mukherjee, Tulsi; Kapoor, Sudhir

    2009-04-01

    In this article, a simple method for either transfer of silver nanoparticles from formamide to chloroform or to form a film at their interface is demonstrated. The transfer of the particles is a two-step size-dependent process. The size distribution of the colloidal hydrophobic silver particles in chloroform was almost the same as that before its transfer. Particles can be isolated by evaporation of chloroform. During evaporation, the hydrophobic particles become hydrophilic (charged) due to the formation of bilayer of CTAB over their surface. The isolated particles can be re-dispersed easily in polar solvents such as water and methanol. Nanocrystalline film of Ag is also prepared at the formamide-chloroform interface using suitable stabilizers in two immiscible layers. The nanocrystals have been characterized by various microscopic and spectroscopic techniques. The free standing film could be easily transferred on solid support.

  2. Sorption of microamount of colloidal silver iodide on hydrated iron(III) oxide

    Kepak, F.; Nova, J.

    1975-01-01

    Sorption of a microamount of colloidal silver iodide labelled with 131 I on hydrated iron/III/ oxide suspension was studied. The sorption dependence upon pH, sorbent amount, and inert electrolyte concentration has revealed that sorption of silver iodide reaches no more than 63%. The sorption lasted one hour during which the maximum value was reached. Desorption time was one hour, as well. Except for measuring the sorption dependence on pH, the sorption pH was 7.0, temperature 24+-2 0 C. (F.G.)

  3. Oxidative Pressure Leaching of Silver from Flotation Concentrates with Ammonium Thiocyanate Solution

    Yang, Sheng-Hai; Yang, Jian-Guang; Liu, Wei; Chen, Geng-Tao; Tang, Mo-Tang; Qiu, Guan-Zhou

    2010-02-01

    The thermodynamics and technologies of the selective pressure leaching of silver from flotation concentrates were investigated in an ammonium thiocyanate medium. Thermodynamic analyses, which include silver solubility in NH4SCN solution and Eh-pH diagrams of the Me-MeS-NH4SCN-H2O system at 25 °C, were discussed. The effects of several factors, such as temperature, leaching time, oxidant, pH value, flotation concentrates concentration, surfactant concentration, and so on, on the extraction percentages of silver and zinc were investigated. The following optimal leaching conditions were obtained: NH4SCN concentration 1.5 M, lignin concentration 0.5 g/L, Fe3+ concentration 2 g/L, flotation concentrates addition 200 g/L, and oxygen pressure 1.2 MPa at 130 °C for 3 hours. Under these optimum conditions, the average extraction percentage of silver exceeded 94 pct, whereas the average extraction percentage of zinc was less than 3 pct. Only 7 pct of ammonium thiocyanate was consumed after 4 cycles, which indicated that ammonium thiocyanate hardly was oxidized under these oxidative pressure leaching conditions.

  4. Synthesis of tungsten oxide, silver, and gold nanoparticles by radio frequency plasma in water

    Hattori, Yoshiaki; Nomura, Shinfuku; Mukasa, Shinobu; Toyota, Hiromichi; Inoue, Toru; Usui, Tomoya

    2013-01-01

    Highlights: •RF plasma in water was used for nanoparticle synthesis. •Nanoparticles were produced from erosion of metallic electrode. •Rectangular and spherical tungsten oxide nanoparticles were produced. •No oxidations of the silver and gold spherical nanoparticles were produced. -- Abstract: A process for synthesis of nanoparticles using plasma in water generated by a radio frequency of 27.12 MHz is proposed. Tungsten oxide, silver, and gold nanoparticles were produced at 20 kPa through erosion of a metallic electrode exposed to plasma. Characterization of the produced nanoparticles was carried out by XRD, absorption spectrum, and TEM. The nanoparticle sizes were compared with those produced by a similar technique using plasma in liquid

  5. The influence of water on the oxygen-silver interaction and on the oxidative dehydrogenation of methanol

    Lefferts, Leon; Van Ommen, Jan G.; Ross, Julian R H

    1988-01-01

    Experiments carried out using temperature-programmed desorption and reduction could detect no interaction between water and silver at 200 °C. However, separate experiments on the effect of water on the oxidative dehydrogenation of methanol over a silver catalyst showed that water affected the

  6. Argentation gas chromatography revisited: Separation of light olefin/paraffin mixtures using silver-based ionic liquid stationary phases.

    Nan, He; Zhang, Cheng; Venkatesh, Amrit; Rossini, Aaron J; Anderson, Jared L

    2017-11-10

    Silver ion or argentation chromatography utilizes stationary phases containing silver ions for the separation of unsaturated compounds. In this study, a mixed-ligand silver-based ionic liquid (IL) was evaluated for the first time as a gas chromatographic (GC) stationary phase for the separation of light olefin/paraffin mixtures. The selectivity of the stationary phase toward olefins can be tuned by adjusting the ratio of silver ion and the mixed ligands. The maximum allowable operating temperature of these stationary phases was determined to be between 125°C and 150°C. Nuclear magnetic resonance (NMR) spectroscopy was used to characterize the coordination behavior of the silver-based IL as well as provide an understanding into the retention mechanism of light olefins. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Quantitative characterization of colloidal assembly of graphene oxide-silver nanoparticle hybrids using aerosol differential mobility-coupled mass analyses.

    Nguyen, Thai Phuong; Chang, Wei-Chang; Lai, Yen-Chih; Hsiao, Ta-Chih; Tsai, De-Hao

    2017-10-01

    In this work, we develop an aerosol-based, time-resolved ion mobility-coupled mass characterization method to investigate colloidal assembly of graphene oxide (GO)-silver nanoparticle (AgNP) hybrid nanostructure on a quantitative basis. Transmission electron microscopy (TEM) and zeta potential (ZP) analysis were used to provide visual information and elemental-based particle size distributions, respectively. Results clearly show a successful controlled assembly of GO-AgNP by electrostatic-directed heterogeneous aggregation between GO and bovine serum albumin (BSA)-functionalized AgNP under an acidic environment. Additionally, physical size, mass, and conformation (i.e., number of AgNP per nanohybrid) of GO-AgNP were shown to be proportional to the number concentration ratio of AgNP to GO (R) and the selected electrical mobility diameter. An analysis of colloidal stability of GO-AgNP indicates that the stability increased with its absolute ZP, which was dependent on R and environmental pH. The work presented here provides a proof of concept for systematically synthesizing hybrid colloidal nanomaterials through the tuning of surface chemistry in aqueous phase with the ability in quantitative characterization. Graphical Abstract Colloidal assembly of graphene oxide-silver nanoparticle hybrids characterized by aerosol differential mobility-coupled mass analyses.

  8. Polyaniline-silver composites prepared by the oxidation of aniline with mixed oxidants, silver nitrate and ammonium peroxydisulfate: the control of silver content

    Bober, Patrycja; Stejskal, Jaroslav; Trchová, Miroslava; Prokeš, J.

    2011-01-01

    Roč. 52, č. 26 (2011), s. 5947-5952 ISSN 0032-3861 R&D Projects: GA AV ČR IAA400500905; GA AV ČR IAA100500902; GA MŠk LA09028 Institutional research plan: CEZ:AV0Z40500505 Keywords : conducting polymer * polyaniline * silver Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.438, year: 2011

  9. Photocatalytic activity of silver oxide capped Ag nanoparticles constructed by air plasma irradiation

    Fang, Yingcui; Wu, Qingmeng; Li, Huanhuan; Zhang, Bing; Yan, Rong; Chen, Junling; Sun, Mengtao

    2018-04-01

    We construct a kind of structure of silver oxide capped silver nanoparticles (AgNPs) by cost-efficient air plasma irradiation, and study its visible-light driven photocatalytic activity (PA). By controlling the oxidization time, the relationship between the intensity of the localized surface plasmon resonance (LSPR) and the PA is well established. The PA reaches the maximum when the LSPR of AgNPs is nearly completely damped (according to absorption spectra); however, under this condition, the LSPR still works, confirmed with the high efficient selective transformation of p-Aminothiophenol (PATP) to p, p'-dimercaptoazobenzene (DMAB) under visible light. The mechanism of the LSPR damping induced PA improvement is discussed. We not only provide a cost-efficient approach to construct a LSPR strong damping structure but also promote the understanding of LSPR strong damping and its relationship with photocatalysis.

  10. Processing and properties of silver-metal oxide electrical contact materials

    Nadežda M. Talijan

    2012-12-01

    Full Text Available The presented study gives a brief overview of the experimental results of investigations of different production technologies of silver-metal oxide electrical contact materials in relation: processing method - properties. The two most common routes of production, i.e. internal oxidation/ingot metallurgy and powder metallurgy are demonstrated on the example of Ag-CdO and Ag-ZnO materials. For illustration of alternative processing routes that provide higher dispersion of metal-oxide particles in silver matrix more environmentally friendly Ag-SnO2 contact materials are used. Processing of electrical contact materials by mechanical mixing of starting powders in high energy ball mill is presented. The obtained experimental results of application of different methods of introduction of SnO2 nanoparticles in the silver matrix such as conventional powder metallurgy mixing and template method are given and discussed in terms of their influence on microstructure and physical properties (density, hardness and electrical conductivity of the prepared Ag-SnO2 electrical contact materials.

  11. The effect of copper and silver on the properties of Au-ZnO catalyst and its activity in glycerol oxidation

    Kaskow, Iveta; Decyk, Piotr; Sobczak, Izabela

    2018-06-01

    The goal of this work was to use ZnO as a support for gold and copper (Au-Cu system) or gold and silver (Au-Ag system) and comparison of the effect of copper and silver on the properties of gold and its activity in glycerol oxidation with oxygen in the liquid phase. The samples prepared were fully characterized by XRD, TEM techniques and UV-vis, XPS, ESR spectroscopic methods. It was found that the introduction of copper and silver changed the electronic state of gold loaded on ZnO by the electron transfer between metals. Three different metallic gold species were identified in calcined catalysts: (Au°)δ- (Au-ZnO), (Au°)η- (AuCu-ZnO) and (Au°)γ- (AuAg-ZnO), where δ-,η-,γ- indicate a different partial negative charge on metallic gold and γ > δ > η. The results showed that (Au°)η- centers (metallic gold with the lowest negative charge) formed on AuCu-ZnO were the most active in glycerol oxidation. The increase in the negative charge on metallic gold loaded on AuAg-ZnO reduced the gold activity in silver containing sample. The glyceric acid adsorption and desorption rate influenced the selectivity of the catalysts.

  12. Preparation of silver nanoparticles/graphene nanosheets as a catalyst for electrochemical oxidation of methanol

    Han, Kun; Miao, Peng; Tang, Yuguo, E-mail: tangyg@sibet.ac.cn [Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Tong, Hui; Zhu, Xiaoli [Laboratory of Biosensing Technology, School of Life Sciences, Shanghai University, Shanghai 200444 (China); Liu, Tao; Cheng, Wenbo [Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163 (China)

    2014-02-03

    In this report, silver nanoparticles (AgNPs) decorated graphene nanosheets have been prepared based on the reduction of Ag ions by hydroquinone, and their catalytic performance towards the electrochemical oxidation of methanol is investigated. The synthesis of the nano-composite is confirmed by transmission electron microscope measurements and UV-vis absorption spectra. Excellent electrocatalytic performance of the material is demonstrated by cyclic voltammograms. This material also contributes to the low peak potential of methanol oxidation compared with most of the other materials.

  13. Surface modification of indium tin oxide for direct writing of silver nanoparticulate ink micropatterns

    Vunnam, Swathi; Ankireddy, Krishnamraju; Kellar, Jon; Cross, William

    2013-01-01

    Surface treatment techniques were deployed to alter the surface of indium tin oxide (ITO) samples to attain a favorable interface between printed nano-inks and ITO surface. Surface free energy components of treated ITO substrates were calculated for each treatment using the van Oss–Chaudhury–Good method. The surface treatments of ITO changed the Lifshitz–van der Waals and Lewis acid–base components, and contact angle hysteresis significantly. Among all the surface treatments, air plasma treated samples showed high polar in nature, whereas dodecyltrichlorosilane self-assembled monolayer treated sample showed the lowest. In addition to the polarity and homogeneity, the surface roughness of the ITO was studied with respect to the surface treatment. Silver nanoparticulate ink was printed on treated ITO surfaces using aerosol jet printing system. Printed silver nano-ink line width and morphology strongly depended on the surface treatment of the ITO, ink properties and printing parameters. - Highlights: ► Surface treatments on indium tin oxide (ITO) altered its surface free energy. ► Surface free energies were studied in terms of acid–base components. ► ITO surface morphology and roughness were changed with the surface treatment. ► Silver ink was printed on treated ITO samples using aerosol jet printing system. ► Line widths of printed patterns clearly depended on the surface free energy of ITO

  14. Surface modification of indium tin oxide for direct writing of silver nanoparticulate ink micropatterns

    Vunnam, Swathi, E-mail: swathi.vunnam@mines.sdsmt.edu [Nanoscience and Nanoengineering Department, South Dakota School of Mines and Technology, Rapid City, SD-57701 (United States); Ankireddy, Krishnamraju; Kellar, Jon; Cross, William [Department of Materials and Metallurgical Engineering, South Dakota School of Mines and Technology, Rapid City, SD-57701 (United States)

    2013-03-01

    Surface treatment techniques were deployed to alter the surface of indium tin oxide (ITO) samples to attain a favorable interface between printed nano-inks and ITO surface. Surface free energy components of treated ITO substrates were calculated for each treatment using the van Oss–Chaudhury–Good method. The surface treatments of ITO changed the Lifshitz–van der Waals and Lewis acid–base components, and contact angle hysteresis significantly. Among all the surface treatments, air plasma treated samples showed high polar in nature, whereas dodecyltrichlorosilane self-assembled monolayer treated sample showed the lowest. In addition to the polarity and homogeneity, the surface roughness of the ITO was studied with respect to the surface treatment. Silver nanoparticulate ink was printed on treated ITO surfaces using aerosol jet printing system. Printed silver nano-ink line width and morphology strongly depended on the surface treatment of the ITO, ink properties and printing parameters. - Highlights: ► Surface treatments on indium tin oxide (ITO) altered its surface free energy. ► Surface free energies were studied in terms of acid–base components. ► ITO surface morphology and roughness were changed with the surface treatment. ► Silver ink was printed on treated ITO samples using aerosol jet printing system. ► Line widths of printed patterns clearly depended on the surface free energy of ITO.

  15. Fabrication of dendritic silver-coated copper powders by galvanic displacement reaction and their thermal stability against oxidation

    Park, Yu-Seon [School of Chemical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Farad Materials Co., Ltd., Suwon 16419 (Korea, Republic of); An, Chang Yong; Kannan, Padmanathan Karthick; Seo, Nary [School of Chemical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Zhuo, Kai [School of Chemical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Farad Materials Co., Ltd., Suwon 16419 (Korea, Republic of); Yoo, Tae Kyong [School of Chemical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Chung, Chan-Hwa, E-mail: chchung@skku.edu [School of Chemical Engineering, Sungkyunkwan University, Suwon 16419 (Korea, Republic of); Farad Materials Co., Ltd., Suwon 16419 (Korea, Republic of)

    2016-12-15

    Highlights: • The dendritic silver-coated copper powders with high specific surface area have been prepared using a simple wet chemical reduction process at room temperature. • It is found that the Cu starts to be oxidized into Cu{sub 2}O followed by CuO at elevated temperatures. • The more amount of Ag-coating provides the less oxidation, which confirms that the Ag-shell prevents the Cu-core from oxidation. • The resistivity of dendritic 33.27 wt.% Ag-coated Cu powders was measured to 25.67 μΩ cm after the annealing at 150 °C for 30 min. - Abstract: Two steps of wet chemical processes have been developed for the preparation of core-shell nanostructures of copper and silver, which is a facile and low cost method for the production of large quantity of dendritic powders. First step involves a galvanic displacement reaction with hydrogen evolution which is the motive force of spontaneous electrochemical reaction. To achieve the core-shell structure, silver has been coated on the dendritic copper using the galvanic displacement reaction. The dendritic silver-coated copper powders exhibit high surface-area, excellent conductivity, and good oxidation resistance. It has been found that silver-coated copper powders maintain the electrical conductivity even after annealing at 150 °C for several to tens of minutes, thus it is a promising material and an alternative to pure silver powders in printed electronics application.

  16. Water treatment with exceptional virus inactivation using activated carbon modified with silver (Ag) and copper oxide (CuO) nanoparticles.

    Shimabuku, Quelen Letícia; Arakawa, Flávia Sayuri; Fernandes Silva, Marcela; Ferri Coldebella, Priscila; Ueda-Nakamura, Tânia; Fagundes-Klen, Márcia Regina; Bergamasco, Rosangela

    2017-08-01

    Continuous flow experiments (450 mL min -1 ) were performed in household filter in order to investigate the removal and/or inactivation of T4 bacteriophage, using granular activated carbon (GAC) modified with silver and/or copper oxide nanoparticles at different concentrations. GAC and modified GAC were characterized by X-ray diffractometry, specific surface area, pore size and volume, pore average diameter, scanning electron microscopy, transmission electron microscopy, zeta potential and atomic absorption spectroscopy. The antiviral activity of the produced porous media was evaluated by passing suspensions of T4 bacteriophage (∼10 5  UFP/mL) through filters. The filtered water was analyzed for the presence of the bacteriophage and the release of silver and copper oxide. The porous media containing silver and copper oxide nanoparticles showed high inactivation capacity, even reaching reductions higher than 3 log. GAC6 (GAC/Ag0.5%Cu1.0%) was effective in the bacteriophage inactivation, reaching 5.53 log reduction. The levels of silver and copper released in filtered water were below the recommended limits (100 ppb for silver and 1000 ppb for copper) in drinking water. From this study, it is possible to conclude that activated carbon modified with silver and copper oxide nanoparticles can be used as a filter for virus removal in the treatment of drinking water.

  17. Fabrication of dendritic silver-coated copper powders by galvanic displacement reaction and their thermal stability against oxidation

    Park, Yu-Seon; An, Chang Yong; Kannan, Padmanathan Karthick; Seo, Nary; Zhuo, Kai; Yoo, Tae Kyong; Chung, Chan-Hwa

    2016-01-01

    Highlights: • The dendritic silver-coated copper powders with high specific surface area have been prepared using a simple wet chemical reduction process at room temperature. • It is found that the Cu starts to be oxidized into Cu_2O followed by CuO at elevated temperatures. • The more amount of Ag-coating provides the less oxidation, which confirms that the Ag-shell prevents the Cu-core from oxidation. • The resistivity of dendritic 33.27 wt.% Ag-coated Cu powders was measured to 25.67 μΩ cm after the annealing at 150 °C for 30 min. - Abstract: Two steps of wet chemical processes have been developed for the preparation of core-shell nanostructures of copper and silver, which is a facile and low cost method for the production of large quantity of dendritic powders. First step involves a galvanic displacement reaction with hydrogen evolution which is the motive force of spontaneous electrochemical reaction. To achieve the core-shell structure, silver has been coated on the dendritic copper using the galvanic displacement reaction. The dendritic silver-coated copper powders exhibit high surface-area, excellent conductivity, and good oxidation resistance. It has been found that silver-coated copper powders maintain the electrical conductivity even after annealing at 150 °C for several to tens of minutes, thus it is a promising material and an alternative to pure silver powders in printed electronics application.

  18. Graphene oxide-silver nanocomposite as a promising biocidal agent against methicillin-resistant Staphylococcus aureus

    de Moraes ACM

    2015-11-01

    Full Text Available Ana Carolina Mazarin de Moraes,1 Bruna Araujo Lima,2 Andreia Fonseca de Faria,1 Marcelo Brocchi,2 Oswaldo Luiz Alves1 1Laboratory of Solid State Chemistry, Institute of Chemistry, University of Campinas, Campinas, São Paulo, Brazil; 2Department of Genetics, Evolution and Bioagents, Institute of Biology, University of Campinas, Campinas, São Paulo, Brazil Background: Methicillin-resistant Staphylococcus aureus (MRSA has been responsible for serious hospital infections worldwide. Nanomaterials are an alternative to conventional antibiotic compounds, because bacteria are unlikely to develop microbial resistance against nanomaterials. In the past decade, graphene oxide (GO has emerged as a material that is often used to support and stabilize silver nanoparticles (AgNPs for the preparation of novel antibacterial nanocomposites. In this work, we report the synthesis of the graphene-oxide silver nanocomposite (GO-Ag and its antibacterial activity against relevant microorganisms in medicine. Materials and methods: GO-Ag nanocomposite was synthesized through the reduction of silver ions (Ag+ by sodium citrate in an aqueous GO dispersion, and was extensively characterized using ultraviolet-visible absorption spectroscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, and transmission electron microscopy. The antibacterial activity was evaluated by microdilution assays and time-kill experiments. The morphology of bacterial cells treated with GO-Ag was investigated via transmission electron microscopy. Results: AgNPs were well distributed throughout GO sheets, with an average size of 9.4±2.8 nm. The GO-Ag nanocomposite exhibited an excellent antibacterial activity against methicillin-resistant S. aureus, Acinetobacter baumannii, Enterococcus faecalis, and Escherichia coli. All (100% MRSA cells were inactivated after 4 hours of exposure to GO-Ag sheets. In addition, no toxicity was found for either pristine GO or bare Ag

  19. Phase recording for formation of holographic optical elements on silver-halide photographic emulsions

    Ganzherli, Nina M.; Gulyaev, Sergey N.; Maurer, Irina A.; Chernykh, Dmitrii F.

    2009-05-01

    Holographic fabrication methods of regular and nonregular relief-phase structures on silver-halide photographic emulsions are considered. Methods of gelatin photodestruction under short-wave ultra-violet radiation and chemical hardening with the help of dichromated solutions were used as a technique for surface relief formation. The developed techniques permitted us to study specimens of holographic diffusers and microlens rasters with small absorption and high light efficiency.

  20. Rapid dehalogenation of pesticides and organics at the interface of reduced graphene oxide-silver nanocomposite.

    Koushik, Dibyashree; Sen Gupta, Soujit; Maliyekkal, Shihabudheen M; Pradeep, T

    2016-05-05

    This paper reports dehalogenation of various organohalides, especially aliphatic halocarbons and pesticides at reduced graphene oxide-silver nanocomposite (RGO@Ag). Several pesticides as well as chlorinated and fluorinated alkyl halides were chosen for this purpose. The composite and the products of degradation were characterized thoroughly by means of various microscopic and spectroscopic techniques. A sequential two-step mechanism involving dehalogenation of the target pollutants by silver nanoparticles followed by adsorption of the degraded compounds onto RGO was revealed. The composite showed unusual adsorption capacity, as high as 1534 mg/g, which facilitated the complete removal of the pollutants. Irrespective of the pollutants tested, a pseudo-second-order rate equation best described the adsorption kinetics. The affinity of the composite manifested chemical differences. The high adsorption capacity and re-usability makes the composite an excellent substrate for purification of water. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Stability of silver nanoparticles: agglomeration and oxidation in biological relevant conditions

    Valenti, Laura E.; Giacomelli, Carla E.

    2017-05-01

    Silver nanoparticles (Ag-NP) are the most used nanomaterial in consumer products due to the intrinsic antimicrobial capacity of silver. However, Ag-NP may be also harmful to algae, aquatic species, mammalian cells, and higher plants because both Ag+ and nanoparticles are responsible of cell damages. The oxidative dissolution of Ag-NP would proceed to completion under oxic conditions, but the rate and extent of the dissolution depend on several factors. This work correlates the effect of the capping agent (albumin and citrate) with the stability of Ag-NP towards agglomeration in simulated body fluid (SBF) and oxidation in the presence of ROS species (H2O2). Capping provides colloidal stability only through electrostatic means, whereas albumin acts as bulky ligands giving steric and electrostatic repulsion, inhibiting the agglomeration in SBF. However, citrate capping protects Ag-NP from dissolution to a major extent than albumin does because of its reducing power. Moreover, citrate in solution minimizes the oxidation of albumin-coated Ag-NP even after long incubation times. H2O2-induced dissolution proceeds to completion with Ag-NP incubated in SBF, while incubation in citrate leads to an incomplete oxidation. In short, albumin is an excellent capping agent to minimize Ag-NP agglomeration whereas citrate provides a mild-reductive medium that prevents dissolution in biological relevant media as well as in the presence of ROS species. These results provide insight into how the surface properties and media composition affect the release of Ag+ from Ag-NP, related to the cell toxicity and relevant to the storage and lifetime of silver-containing nanomaterials.

  2. Stability of silver nanoparticles: agglomeration and oxidation in biological relevant conditions

    Valenti, Laura E.; Giacomelli, Carla E., E-mail: giacomel@fcq.unc.edu.ar [Universidad Nacional de Córdoba, Ciudad Universitaria, Instituto de Investigaciones en Físico Química de Córdoba (INFIQC) CONICET-UNC, Departamento de Fisicoquímica, Facultad de Ciencias Químicas (Argentina)

    2017-05-15

    Silver nanoparticles (Ag-NP) are the most used nanomaterial in consumer products due to the intrinsic antimicrobial capacity of silver. However, Ag-NP may be also harmful to algae, aquatic species, mammalian cells, and higher plants because both Ag{sup +} and nanoparticles are responsible of cell damages. The oxidative dissolution of Ag-NP would proceed to completion under oxic conditions, but the rate and extent of the dissolution depend on several factors. This work correlates the effect of the capping agent (albumin and citrate) with the stability of Ag-NP towards agglomeration in simulated body fluid (SBF) and oxidation in the presence of ROS species (H{sub 2}O{sub 2}). Capping provides colloidal stability only through electrostatic means, whereas albumin acts as bulky ligands giving steric and electrostatic repulsion, inhibiting the agglomeration in SBF. However, citrate capping protects Ag-NP from dissolution to a major extent than albumin does because of its reducing power. Moreover, citrate in solution minimizes the oxidation of albumin-coated Ag-NP even after long incubation times. H{sub 2}O{sub 2}-induced dissolution proceeds to completion with Ag-NP incubated in SBF, while incubation in citrate leads to an incomplete oxidation. In short, albumin is an excellent capping agent to minimize Ag-NP agglomeration whereas citrate provides a mild-reductive medium that prevents dissolution in biological relevant media as well as in the presence of ROS species. These results provide insight into how the surface properties and media composition affect the release of Ag{sup +} from Ag-NP, related to the cell toxicity and relevant to the storage and lifetime of silver-containing nanomaterials.

  3. Selective and efficient reduction of carbon dioxide to carbon monoxide on oxide-derived nanostructured silver electrocatalysts

    Ma, Ming; Trześniewski, Bartek J.; Xie, Jie; Smith, Wilson A.

    2016-01-01

    In this work, the selective electrocatalytic reduction of carbon dioxide to carbon monoxide on oxide-derived silver electrocatalysts is presented. By a simple synthesis technique, the overall high faradaic efficiency for CO production on the oxide-derived Ag was shifted by more than 400 mV towards a

  4. Study of the electrochemical oxidation of Am with lacunary heteropolyanions and silver nitrate

    Chartier, D.

    1999-01-01

    Electrochemical oxidation of Am(III) with certain lacunary heteropolyanions (LHPA α 2 -P 2 W 17 O 61 10- or αSiW 11 O 39 8- ) and silver nitrate is an efficient way to prepare Am(VI). This document presents bibliographic data and an experimental study of the process. Thus, it has been established that Am(IV) is an intermediate species in the reaction and occurs in 1:1 (Amt IV LHPA) or 1:2 (Am IV (LHAP) 2 ) complexes with the relevant LHPA. These 1:1 complexes of Am(IV) have been identified and isolated in this work whereas 1:2 complexes were known from previous studies. The reactivity of these complexes in oxidation shows that 1:1 complexes of Am(IV) are oxidised much more quickly than 1:2 complexes. Apparent stability constants of Am(III) and Am(IV) complexes with the relevant LHPA have been measured for a 1 M nitric acid medium. Thermodynamic data of the reaction are then assessed: redox potentials of Am pairs are computed for a 1 M nitric acid medium containing various amount of LHPA ligands. Those results show that the role of LHPA is to stabilize the intermediate species Am(IV) by lowering the Am(IV)/Am(III) pair potential of about 1 Volt. Nevertheless, if this stabilisation is too strong (i.e. of tungsto-silicate), the oxidation of Am(IV) requires high anodic potential (more than 2 V/ENH). Then, the faradic yield of the oxidation of americium is poor because of water oxidation. This study has also shown that the main role of silver is to catalyze the electrochemical oxidation of Am IV (LHPA) X complexes. Indeed, these oxidations without silver are extremely slow. An oxygen tracer experiment has been performed during the oxidation of Am(III) in Am(VI). It has been shown that the oxygen atoms of Am(VI) (AMO 2 2+ ) come from water molecules of the solvent and not from the complexing oxygen atoms of the ligands. (author)

  5. Polyethyleneglycol/silver functionalized reduced graphene oxide aerogel for environmental application

    Kumari, G. Vanitha; Asha, S.; Ananth, A. Nimrodh; Rajan, M. A. Jothi; Mathavan, T.

    2018-04-01

    Polyethylene glycol (PEG)/Silver (Ag) functionalized reduced graphene oxide aerogel (RGOA) was synthesized. PEG/Ag decorated reduced graphene oxide aerogel was characterized using XRD, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR). The surface morphology of PEG/Ag/RGOA was analyzed using scanning electron microscope. The non-covalent interaction between reduced graphene oxide layers and the interaction between PEG and Ag on RGOA were studied by FT-IR spectra. It was observed that the interaction between Ag and PEG could enhance the properties of RGOA. Methyl Orange (MO) dye degradation was observed from UV-Vis Spectra. The process was studied by monitoring the simultaneous decrease in the height of UV-Vis absorption peak of dye solution. The results show that PEG/RGOA and PEG/Ag/RGOA are an efficient catalyst for dye degradation.

  6. [Effects of silver nitrate on the phase state of model multibilayer membranes].

    Vashchenko, O V; Iermak, Yu L; Krasnikova, A O; Lisetski, L N

    2015-01-01

    In order to study the effects caused by silver nitrate (AgNO3) on model lipid membranes, we studied multibilayer membranes based on L-α-dipalmitoylphosphatidylcholine (DPPC) and AgNO3 aqueous soluitions in a wide concentration range (up to 30 wt%) by means of differential scanning calorimetry. It has been shown that the presence of AgNO3 leads both to an increase in the main phase transition temperature (T(m)) and appearance of an additional phase transition peak (T(m)), suggesting increasing of both density and heterogeneity of the lipid membrane. The effect of nitrate ions (NO ) was shown to be of the opposite nature (bilayer fluidizing), so the integral densifying effect of AgNO3 can be referred solely to the action of silver ions (Ag(+)). With increasing AgNO3 concentration, the tendency was observed to opposite changes in T(m) and T'(m) peaks intensity, thereby at about 26. wt% of AgNO3 the initial peak (T(m)) disappeared. In the range of Ag+ therapeutic concentrations (up to 2 wt%) no significant changes in the DPPC membrane were revealed. This can be one of the reasons of the absence of a damaging effect of silver drugs on a host organism with simultaneous pronounced bactericidal effect.

  7. Antibacterial TiO2Coating Incorporating Silver Nanoparticles by Micro arc Oxidation and Ion Implantation

    Zhang, P.; Zhang, Z.; Li, W.

    2013-01-01

    Infection associated with titanium implants remains the most common serious complication in hard tissue replacement surgery. Since such postoperative infections are usually difficult to cure, it is critical to find optimal strategies for preventing infections. In this study, TiO 2 coating incorporating silver (Ag) nanoparticles were fabricated on pure titanium by micro arc oxidation and ion implantation. The antibacterial activity was evaluated by exposing the specimens to Staphylococcus aureus and comparing the reaction of the pathogens to Ti-MAO-Ag with Ti-MAO controls. Ti-MAO-Ag clearly inhibited bacterial colonization more than the control specimen. The coating’s antibacterial ability was enhanced by increasing the dose of silver ion implantation, and Ti-MAO-Ag 20.0 had the best antibacterial ability. In addition, cytocompatibility was assessed by culturing cell colonies on the specimens. The cells grew well on both specimens. These findings indicate that surface modification by means of this process combining MAO and silver ion implantation is useful in providing antibacterial activity and exhibits cytocompatibility with titanium implants

  8. Structural phase transitions in niobium oxide nanocrystals

    Yuvakkumar, R.; Hong, Sun Ig

    2015-09-01

    Niobium oxide nanocrystals were successfully synthesized employing the green synthesis method. Phase formation, microstructure and compositional properties of 1, 4 and 7 days incubation treated samples after calcinations at 450 °C were examined using X-ray diffraction, Raman, photoluminescence (PL), infrared, X-ray photoelectron spectra and transmission electron microscopic characterizations. It was observed that phase formation of Nb2O5 nanocrystals was dependent upon the incubation period required to form stable metal oxides. The characteristic results clearly revealed that with increasing incubation and aging, the transformation of cubic, orthorhombic and monoclinic phases were observed. The uniform heating at room temperature (32 °C) and the ligation of niobium atoms due to higher phenolic constituents of utilized rambutan during aging processing plays a vital role in structural phase transitions in niobium oxide nanocrystals. The defects over a period of incubation and the intensities of the PL spectra changing over a period of aging were related to the amount of the defects induced by the phase transition.

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

    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.

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

    Hannemann, Stefan; Grunwaldt, Jan-Dierk; Krumeich, Frank; Kappen, Peter; Baiker, Alfons

    2006-01-01

    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 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

  11. Effects of silver nanoparticles to soil invertebrates: Oxidative stress biomarkers in Eisenia fetida

    Gomes, Susana I.L.; Hansen, Ditte; Scott-Fordsmand, Janeck J.; Amorim, Mónica J.B.

    2015-01-01

    Silver nanoparticles (Ag-NPs) are among the most produced NPs worldwide having several applications in consumer products. Ag-NPs are known to cause oxidative stress in several organisms and cell lines, however comparatively less information is available regarding their effects on soil living invertebrates. The purpose of this study was to investigate if Ag-NPs cause oxidative stress on soil invertebrates. The model soil species Eisenia fetida was used. Our results showed that total glutathione (TG) is the first mechanism triggered by Ag-NPs, followed by glutathione peroxidase (GPx) and glutathione reductase (GR), however oxidative damage was observed for higher doses and exposure time (increased lipid peroxidation, LPO). AgNO 3 exposure caused impairment in GPx and glutathione-S-transferase (GST), probably as result of the higher bioavailability of Ag in the salt-form. The current results indicate that effects are partly caused by Ag ions released from Ag-NPs, but specific particle effects cannot be excluded. - Highlights: • Oxidative stress of Ag-NPs and AgNO 3 was assessed in Eisenia fetida. • Both Ag forms induced oxidative damage (LPO) via different mechanisms. • Ag-NPs activated total glutathione, followed by GPx and GR. • AgNO 3 impaired GPx and GST. • Overall results indicated effects from Ag ionization and NPs specific effects. - Oxidative stress to Ag in Eisenia fetida occurs via different mechanisms for Ag nanoparticles and AgNO 3

  12. Graphene oxide-silver nanocomposite as a promising biocidal agent against methicillin-resistant Staphylococcus aureus.

    de Moraes, Ana Carolina Mazarin; Lima, Bruna Araujo; de Faria, Andreia Fonseca; Brocchi, Marcelo; Alves, Oswaldo Luiz

    2015-01-01

    Methicillin-resistant Staphylococcus aureus (MRSA) has been responsible for serious hospital infections worldwide. Nanomaterials are an alternative to conventional antibiotic compounds, because bacteria are unlikely to develop microbial resistance against nanomaterials. In the past decade, graphene oxide (GO) has emerged as a material that is often used to support and stabilize silver nanoparticles (AgNPs) for the preparation of novel antibacterial nanocomposites. In this work, we report the synthesis of the graphene-oxide silver nanocomposite (GO-Ag) and its antibacterial activity against relevant microorganisms in medicine. GO-Ag nanocomposite was synthesized through the reduction of silver ions (Ag(+)) by sodium citrate in an aqueous GO dispersion, and was extensively characterized using ultraviolet-visible absorption spectroscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, and transmission electron microscopy. The antibacterial activity was evaluated by microdilution assays and time-kill experiments. The morphology of bacterial cells treated with GO-Ag was investigated via transmission electron microscopy. AgNPs were well distributed throughout GO sheets, with an average size of 9.4±2.8 nm. The GO-Ag nanocomposite exhibited an excellent antibacterial activity against methicillin-resistant S. aureus, Acinetobacter baumannii, Enterococcus faecalis, and Escherichia coli. All (100%) MRSA cells were inactivated after 4 hours of exposure to GO-Ag sheets. In addition, no toxicity was found for either pristine GO or bare AgNPs within the tested concentration range. Transmission electronic microscopy images offered insights into how GO-Ag nanosheets interacted with bacterial cells. Our results indicate that the GO-Ag nanocomposite is a promising antibacterial agent against common nosocomial bacteria, particularly antibiotic-resistant MRSA. Morphological injuries on MRSA cells revealed a likely loss of viability as a result of the

  13. Distance-dependent metal enhanced fluorescence by flowerlike silver nanostructures fabricated in liquid crystalline phase

    Zhang, Ying; Yang, Chengliang; Zhang, Guiyang; Peng, Zenghui; Yao, Lishuang; Wang, Qidong; Cao, Zhaoliang; Mu, Quanquan; Xuan, Li

    2017-10-01

    Flowerlike silver nanostructure substrates were fabricated in liquid crystalline phase and the distance dependent property of metal enhanced fluorescence for such substrate was studied for the first time. The distance between silver nanostructures and fluorophore was controlled by the well-established layer-by-layer (LbL) technique constructing alternate layers of poly (allylamine hydrochloride) (PAH) and poly (sodium 4-styrenesulfonate) (PSS). The Rhodamine 6G (R6G) molecules were electrostatically attached to the outmost negative charged PSS layer. The fluorescence enhancement factor of flowerlike nanostructure substrate increased firstly and then decreased with the distance increasing. The best enhanced fluorescence intensity of 71 fold was obtained at a distance of 5.2 nm from the surface of flowerlike silver nanostructure. The distance for best enhancement effect is an instructive parameter for the applications of such substrates and could be used in the practical MEF applications with the flowerlike nanostructure substrates fabricated in such way which is simple, controllable and cost-effective.

  14. Oxygen reduction reaction catalysts of manganese oxide decorated by silver nanoparticles for aluminum-air batteries

    Sun, Shanshan; Miao, He; Xue, Yejian; Wang, Qin; Li, Shihua; Liu, Zhaoping

    2016-01-01

    In this paper, the hybrid catalysts of manganese oxide decorated by silver nanoparticles (Ag-MnO x ) are fully investigated and show the excellent oxygen reduction reaction (ORR) activity. The Ag-MnO 2 is synthesized by a facile strategy of the electroless plating of silver on the manganese oxide. The catalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Then, the ORR activities of the catalysts are systematically investigated by the rotating disk electrode (RDE) and aluminum-air battery technologies. The Ag nanoparticles with the diameters at about 10 nm are anchored on the surface of α-MnO 2 and a strong interaction between Ag and MnO 2 components in the hybrid catalyst are confirmed. The electrochemical tests show that the activity and stability of the 50%Ag-MnO 2 composite catalyst (the mass ratio of Ag/MnO 2 is 1:1) toward ORR are greatly enhanced comparing with single Ag or MnO 2 catalyst. Moreover, the peak power density of the aluminum-air battery with 50%Ag-MnO 2 can reach 204 mW cm −2 .

  15. Participation of the Third Order Optical Nonlinearities in Nanostructured Silver Doped Zinc Oxide Thin Solid Films

    C. Torres-Torres

    2012-01-01

    Full Text Available We report the transmittance modulation of optical signals in a nanocomposite integrated by two different silver doped zinc oxide thin solid films. An ultrasonic spray pyrolysis approach was employed for the preparation of the samples. Measurements of the third-order nonlinear optical response at a nonresonant 532 nm wavelength of excitation were performed using a vectorial two-wave mixing. It seems that the separated contribution of the optical nonlinearity associated with each film noticeable differs in the resulting nonlinear effects with respect to the additive response exhibited by the bilayer system. An enhancement of the optical Kerr nonlinearity is predicted for prime number arrays of the studied nanoclusters in a two-wave interaction. We consider that the nanostructured morphology of the thin solid films originates a strong modification of the third-order optical phenomena exhibited by multilayer films based on zinc oxide.

  16. Electrochemical intercalation of lithium into polypyrrole/silver vanadium oxide composite used for lithium primary batteries

    Lee, Jong-Won; Popov, Branko N. [Center for Electrochemical Engineering, Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208 (United States)

    2006-10-20

    Hybrid composites of polypyrrole (PPy) and silver vanadium oxide (SVO) used for lithium primary batteries were chemically synthesized by an oxidative polymerization of pyrrole monomer on the SVO surface in an acidic medium. The composite electrode exhibited higher discharge capacity and better rate capability as compared with the pristine SVO electrode. The improvement in electrochemical performance of the composite electrode was due to PPy which accommodates lithium ions and also enhances the SVO utilization. Chronoamperometric and ac-impedance measurements indicated that lithium intercalation proceeds under the mixed control by interfacial charge transfer and diffusion. The enhanced SVO utilization in the composite electrode results from a facilitated kinetics of interfacial charge transfer in the presence of PPy. (author)

  17. Electrochemical intercalation of lithium into polypyrrole/silver vanadium oxide composite used for lithium primary batteries

    Lee, Jong-Won; Popov, Branko N.

    Hybrid composites of polypyrrole (PPy) and silver vanadium oxide (SVO) used for lithium primary batteries were chemically synthesized by an oxidative polymerization of pyrrole monomer on the SVO surface in an acidic medium. The composite electrode exhibited higher discharge capacity and better rate capability as compared with the pristine SVO electrode. The improvement in electrochemical performance of the composite electrode was due to PPy which accommodates lithium ions and also enhances the SVO utilization. Chronoamperometric and ac-impedance measurements indicated that lithium intercalation proceeds under the mixed control by interfacial charge transfer and diffusion. The enhanced SVO utilization in the composite electrode results from a facilitated kinetics of interfacial charge transfer in the presence of PPy.

  18. Efficient electrochemical water oxidation in neutral and near-neutral systems by nanoscale silver-oxide catalyst

    Joya, Khurram Saleem; Ahmad, Zahoor; Joya, Yasir Faheem; Garcia Esparza, Angel T.; de Groot, Huub

    2016-01-01

    In electrocatalytic water splitting systems pursuing for renewable energy using sun light, developing robust, stable and easy accessible materials operating under mild chemical conditions is pivotal. We present here unique nano-particulate type silver-oxide (AgOx-NP) based robust and highly stable electrocatalyst for efficient water oxidation. The AgOx-NP is generated in situ in a HCO3–/CO2 system under benign conditions. Mircographs show that they exhibit nanoscale box type squared nano-bipyramidal configuration. The oxygen generation is initiated at low overpotential, and a sustained O2 evolution current density of > 1.1 mA cm–2 is achieved during prolonged-period water electrolysis. The AgOx-NP electrocatalyst performs exceptionally well in metal-ions free neutral or near-neutral carbonate, phosphate and borate buffers relative to recently reported Co-oxide and Ni-oxide based heterogeneous electrocatalysts, which are unstable in metal-ions free electrolyte and tend to degrade with time and lose catalytic performance during long-term experimental tests.

  19. Efficient electrochemical water oxidation in neutral and near-neutral systems by nanoscale silver-oxide catalyst

    Joya, Khurram Saleem

    2016-07-19

    In electrocatalytic water splitting systems pursuing for renewable energy using sun light, developing robust, stable and easy accessible materials operating under mild chemical conditions is pivotal. We present here unique nano-particulate type silver-oxide (AgOx-NP) based robust and highly stable electrocatalyst for efficient water oxidation. The AgOx-NP is generated in situ in a HCO3–/CO2 system under benign conditions. Mircographs show that they exhibit nanoscale box type squared nano-bipyramidal configuration. The oxygen generation is initiated at low overpotential, and a sustained O2 evolution current density of > 1.1 mA cm–2 is achieved during prolonged-period water electrolysis. The AgOx-NP electrocatalyst performs exceptionally well in metal-ions free neutral or near-neutral carbonate, phosphate and borate buffers relative to recently reported Co-oxide and Ni-oxide based heterogeneous electrocatalysts, which are unstable in metal-ions free electrolyte and tend to degrade with time and lose catalytic performance during long-term experimental tests.

  20. Realization of ultrathin silver layers in highly conductive and transparent zinc tin oxide/silver/zinc tin oxide multilayer electrodes deposited at room temperature for transparent organic devices

    Winkler, Thomas; Schmidt, Hans; Fluegge, Harald; Nikolayzik, Fabian; Baumann, Ihno; Schmale, Stephan; Johannes, Hans-Hermann; Rabe, Torsten [Institut fuer Hochfrequenztechnik, Technische Universitaet Braunschweig, Schleinitzstr. 22, 38106 Braunschweig (Germany); Hamwi, Sami, E-mail: sami.hamwi@ihf.tu-bs.de [Institut fuer Hochfrequenztechnik, Technische Universitaet Braunschweig, Schleinitzstr. 22, 38106 Braunschweig (Germany); Riedl, Thomas [Institute of Electronic Devices, Bergische Universitaet Wuppertal, Rainer-Gruenter Str. 21, 42119 Wuppertal (Germany); Kowalsky, Wolfgang [Institut fuer Hochfrequenztechnik, Technische Universitaet Braunschweig, Schleinitzstr. 22, 38106 Braunschweig (Germany)

    2012-05-01

    We report on transparent and highly conductive multilayer electrodes prepared at room temperature by RF sputtering of zinc tin oxide (ZTO) and thermal evaporation of ultrathin silver (Ag) as top contact for transparent organic light emitting diodes (TOLED). Specifically, we study the morphological, electrical and optical properties of the multilayer structure in particular of the thin Ag film. The tendency of Ag to form agglomerates over time on top of ZTO is shown by atomic force microscopy. From the optical constants derived from ellipsometric measurements we evidenced a bulk like behavior of an Ag film with a thickness of 8 nm embedded in ZTO leading to a low sheet resistance of 9 {Omega}/sq. Furthermore we verify the optical constants by simulation of an optimized ZTO/Ag/ZTO structure. As an application we present a highly efficient TOLED providing a device transmittance of > 82% in the visible part of the spectrum. The TOLED shows no damage caused by sputtering on a lighting area of 80 mm{sup 2} and exhibits efficiencies of 43 cd/A and 36 lm/W.

  1. Inkjet-Printed Porous Silver Thin Film as a Cathode for a Low-Temperature Solid Oxide Fuel Cell.

    Yu, Chen-Chiang; Baek, Jong Dae; Su, Chun-Hao; Fan, Liangdong; Wei, Jun; Liao, Ying-Chih; Su, Pei-Chen

    2016-04-27

    In this work we report a porous silver thin film cathode that was fabricated by a simple inkjet printing process for low-temperature solid oxide fuel cell applications. The electrochemical performance of the inkjet-printed silver cathode was studied at 300-450 °C and was compared with that of silver cathodes that were fabricated by the typical sputtering method. Inkjet-printed silver cathodes showed lower electrochemical impedance due to their porous structure, which facilitated oxygen gaseous diffusion and oxygen surface adsorption-dissociation reactions. A typical sputtered nanoporous silver cathode became essentially dense after the operation and showed high impedance due to a lack of oxygen supply. The results of long-term fuel cell operation show that the cell with an inkjet-printed cathode had a more stable current output for more than 45 h at 400 °C. A porous silver cathode is required for high fuel cell performance, and the simple inkjet printing technique offers an alternative method of fabrication for such a desirable porous structure with the required thermal-morphological stability.

  2. Electrical and optical properties of reactive dc magnetron sputtered silver-doped indium oxide thin films: role of oxygen

    Subrahmanyam, A.; Barik, U.K.

    2006-01-01

    Silver-doped indium oxide thin films have been prepared on glass and quartz substrates at room temperature (300 K) by a reactive dc magnetron sputtering technique using an alloy target of pure indium and silver (80:20 at. %). During sputtering, the oxygen flow rates are varied in the range 0.00-2.86 sccm keeping the magnetron power constant at 40 W. The resistivity of these films is in the range 10 0 -10 -3 Ωcm and they show a negative temperature coefficient of resistivity. The films exhibit p-type conductivity at an oxygen flow rate of 1.71 sccm. The work function of these silver-indium oxide films has been measured by a Kelvin probe technique. The refractive index of the films (at 632.8 nm) varies in the range 1.13-1.20. Silver doping in indium oxide narrows the band gap of indium oxide (3.75 eV). (orig.)

  3. Electrical and optical properties of reactive dc magnetron sputtered silver-doped indium oxide thin films: role of oxygen

    Subrahmanyam, A; Barik, U K [Indian Institute of Technology Madras, Semiconductor Physics Laboratory, Department of Physics, Chennai (India)

    2006-07-15

    Silver-doped indium oxide thin films have been prepared on glass and quartz substrates at room temperature (300 K) by a reactive dc magnetron sputtering technique using an alloy target of pure indium and silver (80:20 at. %). During sputtering, the oxygen flow rates are varied in the range 0.00-2.86 sccm keeping the magnetron power constant at 40 W. The resistivity of these films is in the range 10{sup 0}-10{sup -3} {omega}cm and they show a negative temperature coefficient of resistivity. The films exhibit p-type conductivity at an oxygen flow rate of 1.71 sccm. The work function of these silver-indium oxide films has been measured by a Kelvin probe technique. The refractive index of the films (at 632.8 nm) varies in the range 1.13-1.20. Silver doping in indium oxide narrows the band gap of indium oxide (3.75 eV). (orig.)

  4. In vitro cardiotoxicity screening of silver and metal oxide nanoparticles using human induced pluripotent stem cell-derived cardiomyocytes

    Exposure risk to silver and metal oxide nanoparticles (NPs) continues to increase due to their widespread use in products and applications. In vivo studies have shown Ag, TiO2 and CeO2 NPs translocate to the heart following various routes of exposure. Thus, it is critical to asse...

  5. Influence of different synthesis approach on doping behavior of silver nanoparticles onto the iron oxide-silica coreshell surfaces

    Mahmed, N.; Jiang, H.; Heczko, Oleg; Söderberg, O.; Hannula, S.-P.

    2012-01-01

    Roč. 14, č. 8 (2012), s. 1-15 ISSN 1388-0764 Institutional research plan: CEZ:AV0Z10100520 Keywords : stroble method * silver nanoparticles * iron oxide * amourphous silica Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.175, year: 2012

  6. A comparative study of silver-graphene oxide nanocomposites as a recyclable catalyst for the aerobic oxidation of benzyl alcohol: Support effect

    Zahed, Bahareh; Hosseini-Monfared, Hassan, E-mail: monfared@znu.ac.ir

    2015-02-15

    Graphical abstract: - Highlights: • Characteristics of three different graphene oxide (GO) are studied as a support for Ag nanoparticles. • The required conditions for a best support are determined. • For the first time the silver nanoparticles decorated GO as catalyst for aerobic oxidation of benzyl alcohol and the effects of the degree of reduction of GO on AgNPs on GO are reported. - Abstract: Three different nanocomposites of silver and graphene oxide, namely silver nanoparticles (AgNPs) immobilized on reduced graphene oxide (AgNPs/rGO), partially reduced graphene oxide (AgNPs/GO) and thiolated partially reduced graphene oxide (AgNPs/GOSH), were synthesized in order to compare their properties. Characterizations were carried out by infrared and UV–Vis and Raman spectroscopy, ICP, X-ray diffraction, SEM and TEM, confirming both the targeted chemical modification and the composite formation. The nanocomposites were successfully employed in the aerobic oxidation of benzyl alcohol at atmospheric pressure. AgNPs/GOSH is stable and recyclable catalyst which showed the highest activity in the aerobic oxidation of benzyl alcohol in the presence of N-hydroxyphthalimide (NHPI) to give benzaldehyde with 58% selectivity in 24 h at 61% conversion. The favorite properties of AgNPs/GOSH are reasonably attributed to the stable and well distributed AgNPs over GOSH due to strong adhesion between AgNPs and GOSH.

  7. Oxidation phase growth diagram of vanadium oxides film fabricated by rapid thermal annealing

    Tamura KOZO; Zheng-cao LI; Yu-quan WANG; Jie NI; Yin HU; Zheng-jun ZHANG

    2009-01-01

    Thermal evaporation deposited vanadium oxide films were annealed in air by rapid thermal annealing (RTP). By adjusting the annealing temperature and time, a series of vanadium oxide films with various oxidation phases and surface morphologies were fabricated, and an oxidation phase growth diagram was established. It was observed that different oxidation phases appear at a limited and continuous annealing condition range, and the morphologic changes are related to the oxidation process.

  8. The Green Synthesis and Evaluation of Silver Nanoparticles and Zinc Oxide Nanoparticles

    Gebear-Eigzabher, Bellsabel

    Nanoparticle (NP) research has received exceptional attention as the field of study that contributes to transforming the world of materials science. When implementing NPs in consumer and industrial products, their unique properties improve technologies to the extent of significant game-changing breakthroughs. Conversely, the increased production of NPs, their use, their disposal or inadvertent release in the environment drove the need for processes and policies that ensures consumer and environmental safety. Mitigation of any harmful effects that NPs could potentially have combines methods of safe preparation, safe handling and safe disposal as well as containment of any inadvertent release. Our focus is in safe preparation of nanomaterials and we report green and energy efficient synthesis methods for metal NPs and metal oxide NPs of two popular materials: silver (Ag) and zinc oxide (ZnO). The thesis explained: 1) The impact of NPs in nowadays' world; 2) Synthesis methods that were designed to include environmentally-friendly staring materials and energy-saving fabrication processes, with emphasis on maintaining NPs final size and morphology when compared with existing methods; and 3) Nanoparticles characterization and data collection which allowed us to determine and/or validate their properties. Nanoparticles were studied using transmission electron microscope (TEM), X-Ray powder diffraction (XRD), low-voltage (5 keV) transmission electron microscopy (LV EM 5), Fourier-Transform Infrared Spectroscopy (FT-IR), and Ultraviolet-Visible (UV-Vis) spectroscopy. We developed an aqueous-based preparation of zinc oxide nanoparticles (ZnO NPs) using microwave-assisted chemistry to render a well-controlled particle size distribution within each set of reaction conditions in the range of 15 nm to 75 nm. We developed a scalable silver nanoparticles synthesis by chemical reduction methods. The NPs could be used in consumer products. The measurement tools for consumer products

  9. The influence of narrow optical gap silver oxide on zinc oxide nanoparticles produced by microwave-assisted colloidal synthesis: photocatalytic studies

    Prakoso, S. P.; Paramarta, V.; Tju, H.; Taufik, A.; Saleh, R.

    2016-11-01

    This paper reports a photocatalytic study on wide band gap zinc oxide (ZnO) incorporated by narrow band gap silver oxide (Ag2O), namely Ag2O/ZnO nanocomposites, which were prepared by colloidal synthesis with microwave supports. The Ag2O/ZnO nanocomposites were prepared with three different molar ratios (MR) of Ag2O to ZnO (MR: 0.25, 0.5 and 0.75). In order to confirm qualitatively the concentration ratio of Ag2O in ZnO, crystal phase intensity ratio was executed by peak indexing from x-ray diffraction. The Ag2O/ZnO nanocomposites properties were further investigated using diffuse reflectance spectroscopy. The nanocomposites were tested for the degradation of organic dyes solutions under visible and UV light irradiations. The photocatalytic activity of Ag2O/ZnO nanocomposites under visible light increased with increasing molar ratio of Ag2O to ZnO, while the opposite trends observed under UV light irradiation. The improvement of photoabsorption together with photocatalytic activities might be suspected due to the p-n heterojunction structure in Ag2O/ZnO nanocomposites. The corresponding mechanism will be discussed in detail.

  10. The influence of narrow optical gap silver oxide on zinc oxide nanoparticles produced by microwave-assisted colloidal synthesis: photocatalytic studies

    Prakoso, S. P.; Paramarta, V.; Tju, H.; Taufik, A.; Saleh, R.

    2016-01-01

    This paper reports a photocatalytic study on wide band gap zinc oxide (ZnO) incorporated by narrow band gap silver oxide (Ag 2 O), namely Ag 2 O/ZnO nanocomposites, which were prepared by colloidal synthesis with microwave supports. The Ag 2 O/ZnO nanocomposites were prepared with three different molar ratios (MR) of Ag 2 O to ZnO (MR: 0.25, 0.5 and 0.75). In order to confirm qualitatively the concentration ratio of Ag 2 O in ZnO, crystal phase intensity ratio was executed by peak indexing from x-ray diffraction. The Ag 2 O/ZnO nanocomposites properties were further investigated using diffuse reflectance spectroscopy. The nanocomposites were tested for the degradation of organic dyes solutions under visible and UV light irradiations. The photocatalytic activity of Ag 2 O/ZnO nanocomposites under visible light increased with increasing molar ratio of Ag 2 O to ZnO, while the opposite trends observed under UV light irradiation. The improvement of photoabsorption together with photocatalytic activities might be suspected due to the p-n heterojunction structure in Ag 2 O/ZnO nanocomposites. The corresponding mechanism will be discussed in detail. (paper)

  11. Preparation, characterization, and antibacterial activity of silver nanoparticle-decorated graphene oxide nanocomposite.

    Shao, Wei; Liu, Xiufeng; Min, Huihua; Dong, Guanghui; Feng, Qingyuan; Zuo, Songlin

    2015-04-01

    In this work, we report a facile and green approach to prepare a uniform silver nanoparticles (AgNPs) decorated graphene oxide (GO) nanocomposite (GO-Ag). The nanocomposite was fully characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-vis) absorption spectra, and X-ray photoelectron spectroscopy (XPS), which demonstrated that AgNPs with a diameter of approximately 22 nm were uniformly and compactly deposited on GO. To investigate the silver ion release behaviors, HEPES buffers with different pH (5.5, 7, and 8.5) were selected and the mechanism of release actions was discussed in detail. The cytotoxicity of GO-Ag nanocomposite was also studied using HEK 293 cells. GO-Ag nanocomposite displayed good cytocompatibility. Furthermore, the antibacterial properties of GO-Ag nanocomposite were studied using Gram-negative E. coli ATCC 25922 and Gram-positive S. aureus ATCC 6538 by both the plate count method and disk diffusion method. The nanocomposite showed excellent antibacterial activity. These results demonstrated that GO-Ag nanocomposite, as a kind of antibacterial material, had a great promise for application in a wide range of biomedical applications.

  12. Ambipolar transport of silver nanoparticles decorated graphene oxide field effect transistors

    Sarkar, Kalyan Jyoti; Sarkar, K.; Pal, B.; Kumar, Aparabal; Das, Anish; Banerji, P.

    2018-05-01

    In this article, we report ambipolar field effect transistor (FET) by using graphene oxide (GO) as a gate dielectric material for silver nanoparticles (AgNPs) decorated GO channel layer. GO was synthesized by Hummers' method. The AgNPs were prepared via photochemical reduction of silver nitrate solution by using monoethanolamine as a reducing agent. Morphological properties of channel layer were characterized by Field Effect Scanning Electron Microscopy (FESEM). Fourier Transform Infrared Spectroscopy (FTIR) was carried out to characterize GO thin film. For device fabrication gold (Au) was deposited as source-drain contact and aluminum (Al) was taken as bottom contact. Electrical measurements were performed by back gate configuration. Ambipolar transport behavior was explained from transfer characteristics. A maximum electron mobiliy of 6.65 cm2/Vs and a hole mobility of 2.46 cm2/Vs were extracted from the transfer characteristics. These results suggest that GO is a potential candidate as a gate dielectric material for thin film transistor applications and also provides new insights in GO based research.

  13. Synthesis of supported silver nano-spheres on zinc oxide nanorods for visible light photocatalytic applications

    Saoud, Khaled [Virginia Commonwealth University-Qatar, Doha (Qatar); Alsoubaihi, Rola [Virginia Commonwealth University, Richmond, VA (United States); Bensalah, Nasr [Qatar University, Doha (Qatar); Bora, Tanujjal [Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, P.O. Box 33, Al-Khoudh-123 (Oman); Bertino, Massimo [Virginia Commonwealth University, Richmond, VA (United States); Dutta, Joydeep, E-mail: dutta@squ.edu.om [Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, P.O. Box 33, Al-Khoudh-123 (Oman)

    2015-03-15

    Highlights: • Synthesis of supported Ag NPs on ZnO nanorods using open vessel microwave reactor. • Use of the Ag/ZnO NPs as an efficient visible light photocatalyst. • Complete degradation of methylene blue in 1 h with 0.5 g/L Ag/ZnO NPs. - Abstract: We report the synthesis of silver (Ag) nano-spheres (NS) supported on zinc oxide (ZnO) nanorods through two step mechanism, using open vessel microwave reactor. Direct reduction of ZnO from zinc nitrates was followed by deposition precipitation of the silver on the ZnO nanorods. The supported Ag/ZnO nanoparticles were then characterized by electron microscopy, X-ray diffraction, FTIR, photoluminescence and UV–vis spectroscopy. The visible light photocatalytic activity of Ag/ZnO system was investigated using a test contaminant, methylene blue (MB). Almost complete removal of MB in about 60 min for doses higher than 0.5 g/L of the Ag/ZnO photocatalyst was achieved. This significant improvement in the photocatalytic efficiency of Ag/ZnO photocatalyst under visible light irradiation can be attributed to the presence of Ag nanoparticles on the ZnO nanoparticles which greatly enhances absorption in the visible range of solar spectrum enabled by surface plasmon resonance effect from Ag nanoparticles.

  14. Synthesis of colloidal silver iron oxide nanoparticles--study of their optical and magnetic behavior.

    Kumar, Anil; Singhal, Aditi

    2009-07-22

    Silver iron oxide nanoparticles of fairly small size (average diameter approximately 1 nm) with narrow size distribution have been synthesized by the interaction of colloidal beta- Fe2O3 and silver nanoparticles. The surface morphology and size of these particles have been analyzed by using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Their structural analysis has been carried out by employing x-ray diffraction (XRD), selected-area electron diffraction (SAED), optical and infrared (IR) spectroscopic techniques. The ageing of these particles exhibits the formation of self-assembly, possibly involving weak supramolecular interactions between Ag(I)O4 and Fe(III)O4 species. These particles display the onset of absorption in the near-infrared region and have higher absorption coefficient in the visible range compared to that of its precursors. Magnetic measurements reveal an interesting transition in their magnetic behavior from diamagnetic to superparamagnetic. The magnetic moment of these particles attains a limiting value of about 0.19 emu cm(-2), which is more than two times higher than that of colloidal beta- Fe2O3. With enhanced optical and magnetic properties, this system is suggested to have possible applications in optoelectronic and magnetic devices.

  15. Synthesis of colloidal silver iron oxide nanoparticles—study of their optical and magnetic behavior

    Kumar, Anil; Singhal, Aditi

    2009-07-01

    Silver iron oxide nanoparticles of fairly small size (average diameter ~1 nm) with narrow size distribution have been synthesized by the interaction of colloidal β- Fe2O3 and silver nanoparticles. The surface morphology and size of these particles have been analyzed by using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Their structural analysis has been carried out by employing x-ray diffraction (XRD), selected-area electron diffraction (SAED), optical and infrared (IR) spectroscopic techniques. The ageing of these particles exhibits the formation of self-assembly, possibly involving weak supramolecular interactions between AgIO4 and FeIIIO4 species. These particles display the onset of absorption in the near-infrared region and have higher absorption coefficient in the visible range compared to that of its precursors. Magnetic measurements reveal an interesting transition in their magnetic behavior from diamagnetic to superparamagnetic. The magnetic moment of these particles attains a limiting value of about 0.19 emu cm-2, which is more than two times higher than that of colloidal β- Fe2O3. With enhanced optical and magnetic properties, this system is suggested to have possible applications in optoelectronic and magnetic devices.

  16. Green synthesis of silver nanoparticle-reduced graphene oxide using Psidium guajava and its application in SERS for the detection of methylene blue

    Chettri, Prajwal; Vendamani, V. S.; Tripathi, Ajay; Singh, Manish Kumar; Pathak, Anand P.; Tiwari, Archana

    2017-06-01

    Here we present the synthesis of reduced graphene oxide and silver nanoparticle-reduced graphene oxide composites using aqueous extract of dry leaves of Psidium guajava by one pot reflux method. Psidium guajava extract simultaneously reduces silver nitrate and graphene oxide in the reaction mixture which is confirmed by various spectroscopic techniques. Variable concentrations of silver nitrate solution are used to obtain reduced graphene oxide with different dosage of silver nanoparticles and the resultant composites are examined using surface enhanced Raman scattering measurements. Considering methylene blue as a probe molecule, it is found that the surface enhanced Raman scattering activity increases with the increase in the dose of silver nanoparticles. Our as-synthesised silver nanoparticle-reduced graphene oxide composite shows remarkable performance in detecting methylene blue with concentration as low as 10-8 M for which the enhancement factor is 4.6 × 105. In addition, we report that the reduced graphene oxide quenches the photoluminescence of methylene blue more efficiently than silver nanoparticle-reduced graphene oxide composite. The charge transfer states have been extracted which are mainly responsible for the quenching processes.

  17. Structural and Optical Properties of Chemical Bath Deposited Silver Oxide Thin Films: Role of Deposition Time

    A. C. Nwanya

    2013-01-01

    Full Text Available Silver oxide thin films were deposited on glass substrates at a temperature of 50°C by chemical bath deposition technique under different deposition times using pure AgNO3 precursor and triethanolamine as the complexing agent. The chemical analysis based on EDX technique shows the presence of Ag and O at the appropriate energy levels. The morphological features obtained from SEM showed that the AgxO structures varied as the deposition time changes. The X-ray diffraction showed the peaks of Ag2O and AgO in the structure. The direct band gap and the refractive index increased as the deposition time increased and was in the range of 1.64–1.95 eV and 1.02–2.07, respectively. The values of the band gap and refractive index obtained indicate possible applications in photovoltaic and photothermal systems.

  18. Controlled Deposition of Tin Oxide and Silver Nanoparticles Using Microcontact Printing

    Joo C. Chan

    2015-02-01

    Full Text Available This report describes extensive studies of deposition processes involving tin oxide (SnOx nanoparticles on smooth glass surfaces. We demonstrate the use of smooth films of these nanoparticles as a platform for spatially-selective electroless deposition of silver by soft lithographic stamping. The edge and height roughness of the depositing metallic films are 100 nm and 20 nm, respectively, controlled by the intrinsic size of the nanoparticles. Mixtures of alcohols as capping agents provide further control over the size and shape of nanoparticles clusters. The distribution of cluster heights obtained by atomic force microscopy (AFM is modeled through a modified heterogeneous nucleation theory as well as Oswald ripening. The thermodynamic modeling of the wetting properties of nanoparticles aggregates provides insight into their mechanism of formation and how their properties might be further exploited in wide-ranging applications.

  19. Graphene Oxide-Based Nanocomposites Decorated with Silver Nanoparticles as an Antibacterial Agent

    Jaworski, Sławomir; Wierzbicki, Mateusz; Sawosz, Ewa; Jung, Anna; Gielerak, Grzegorz; Biernat, Joanna; Jaremek, Henryk; Łojkowski, Witold; Woźniak, Bartosz; Wojnarowicz, Jacek; Stobiński, Leszek; Małolepszy, Artur; Mazurkiewicz-Pawlicka, Marta; Łojkowski, Maciej; Kurantowicz, Natalia; Chwalibog, André

    2018-04-01

    One of the most promising methods against drug-resistant bacteria can be surface-modified materials with biocidal nanoparticles and nanocomposites. Herein, we present a nanocomposite with silver nanoparticles (Ag-NPs) on the surface of graphene oxide (GO) as a novel multifunctional antibacterial and antifungal material. Ultrasonic technologies have been used as an effective method of coating polyurethane foils. Toxicity on gram-negative bacteria ( Escherichia coli), gram-positive bacteria ( Staphylococcus aureus and Staphylococcus epidermidis), and pathogenic yeast ( Candida albicans) was evaluated by analysis of cell morphology, assessment of cell viability using the PrestoBlue assay, analysis of cell membrane integrity using the lactate dehydrogenase assay, and reactive oxygen species production. Compared to Ag-NPs and GO, which have been widely used as antibacterial agents, our nanocomposite shows much higher antimicrobial efficiency toward bacteria and yeast cells.

  20. Fabrication of highly catalytic silver nanoclusters/graphene oxide nanocomposite as nanotag for sensitive electrochemical immunoassay

    Wang, Jiamian; Wang, Xiuyun; Wu, Shuo, E-mail: wushuo@dlut.edu.cn; Song, Jie; Zhao, Yanqiu; Ge, Yanqiu; Meng, Changgong

    2016-02-04

    Silver nanoclusters and graphene oxide nanocomposite (AgNCs/GRO) is synthesized and functionalized with detection antibody for highly sensitive electrochemical sensing of carcinoembryonic antigen (CEA), a model tumor marker involved in many cancers. AgNCs with large surface area and abundant amount of low-coordinated sites are synthesized with DNA as template and exhibit high catalytic activity towards the electrochemical reduction of H{sub 2}O{sub 2}. GRO is employed to assemble with AgNCs because it has large specific surface area, super electronic conductivity and strong π-π stacking interaction with the hydrophobic bases of DNA, which can further improve the catalytic ability of the AgNCs. Using AgNCs/GRO as signal amplification tag, an enzyme-free electrochemical immunosensing protocol is designed for the highly sensitive detection of CEA on the capture antibody functionalized immunosensing interface. Under optimal conditions, the designed immunosensor exhibits a wide linear range from 0.1 pg mL{sup −1} to 100 ng mL{sup −1} and a low limit of detection of 0.037 pg mL{sup −1}. Practical sample analysis reveals the sensor has good accuracy and reproducibility, indicating the great application prospective of the AgNCs/GRO in fabricating highly sensitive immunosensors, which can be extended to the detection of various kinds of low abundance disease related proteins. - Highlights: • An enzyme-free electrochemical immunosensor is reported for detecting proteins. • A silver nanocluster/graphene oxide composite is synthesized as nanotag. • The nanotags exhibit highly catalytic activity to the electro-reduction of H{sub 2}O{sub 2}. • The as-fabricated immunosensor could detect protein in serum samples.

  1. Synthesis of silver/silver chloride/graphene oxide composite and its surface-enhanced Raman scattering activity and self-cleaning property

    Zhao, Nan; Fei, Xiao; Cheng, Xiaonong; Yang, Juan

    2017-09-01

    Recently, silver nanoparticles decorated with graphene and graphene oxide (GO) sheets can be employed as surface-enhanced Raman scattering (SERS) substrates. However, their SERS activity on macromolecular compound detection is all one-time process. In order to solve this issue and decrease the cost of routine SERS detection, silver/silver chloride (Ag/AgCl) with photocatalytic activity under visible light was introduced. In this study, a novel, simple and clean approach is carried out for synthesis of the Ag/AgCl/GO composite. The Ag/AgCl colloidal solution is obtained by hydrothermal method and then mixed with GO solution to obtain the Ag/AgCl/GO composite using a facile electrostatic self-assembly method. Results showed that the Ag/AgCl/GO composite has the optimized SERS activity to Rhodamine 6G molecules with the maximum enhancement factor value of 3.8×107. Furthermore, the Ag/AgCl particles with high efficient and stable photocatalytic activity under visible light lead to an outstanding self-cleaning property of the Ag/AgCl/GO composite.

  2. Effects of silver nanoparticles on nitrification and associated nitrous oxide production in aquatic environments.

    Zheng, Yanling; Hou, Lijun; Liu, Min; Newell, Silvia E; Yin, Guoyu; Yu, Chendi; Zhang, Hongli; Li, Xiaofei; Gao, Dengzhou; Gao, Juan; Wang, Rong; Liu, Cheng

    2017-08-01

    Silver nanoparticles (AgNPs) are the most common materials in nanotechnology-based consumer products globally. Because of the wide application of AgNPs, their potential environmental impact is currently a highly topical focus of concern. Nitrification is one of the processes in the nitrogen cycle most susceptible to AgNPs but the specific effects of AgNPs on nitrification in aquatic environments are not well understood. We report the influence of AgNPs on nitrification and associated nitrous oxide (N 2 O) production in estuarine sediments. AgNPs inhibited nitrification rates, which decreased exponentially with increasing AgNP concentrations. The response of nitrifier N 2 O production to AgNPs exhibited low-dose stimulation (production could be enhanced by >100% at low doses of AgNPs. This result was confirmed by metatranscriptome studies showing up-regulation of nitric oxide reductase (norQ) gene expression in the low-dose treatment. Isotopomer analysis revealed that hydroxylamine oxidation was the main N 2 O production pathway, and its contribution to N 2 O emission was enhanced when exposed to low-dose AgNPs. This study highlights the molecular underpinnings of the effects of AgNPs on nitrification activity and demonstrates that the release of AgNPs into the environment should be controlled because they interfere with nitrifying communities and stimulate N 2 O emission.

  3. Reduced temperature phase diagrams of the silver-rare earths binary systems

    Ferro, R.; Delfino, S.; Capelli, R.; Borsese, A.

    1975-01-01

    Phase equilibria of the silver-rare earth binary systems have been reported in ''reduced temperature'' diagrams (the ''reduced temperature'' being defined as the ratio between a characteristic temperature of the Agsub(x)R.E. phase and the melting temperature of the corresponding R.E. metal, both in 0 K). The smooth trends of the various characteristic reduced temperatures, when plotted against the R.E. atomic number, have been demonstrated. On passing from the light- to the heavy-rare-earths, a correlation has been found between the crossing of these curves and other phenomena, such as the disappearing of the Ag 5 R.E. phases from incongruently, to congruently melting compounds. The trends of the reduced-temperature curves have been briefly discussed in terms of the treatment suggested by Gschneidner together with the volumetric data known for the different Agsub(x)R.E. phases. In addition, the characteristic data of the 1:1 AgR.E. compounds have been compared with those of the analogous AuR.E. phases. (Auth.)

  4. Oxidative Stress, Inflammation, and DNA Damage Responses Elicited by Silver, Titanium Dioxide, and Cerium Oxide Nanomaterials

    Previous literature on the biological effects of engineered nanomaterials has focused largely on oxidative stress and inflammation endpoints without further investigating potential pathways. Here we examine time-sensitive biological response pathways affected by engineered nanoma...

  5. Polyaniline–silver composites prepared by the oxidation of aniline with silver nitrate in solutions of sulfonic acids

    Bober, Patrycja; Trchová, Miroslava; Prokeš, J.; Varga, M.; Stejskal, Jaroslav

    2011-01-01

    Roč. 56, č. 10 (2011), s. 3580-3585 ISSN 0013-4686 R&D Projects: GA AV ČR IAA400500905; GA AV ČR IAA100500902; GA ČR GA203/08/0686 Institutional research plan: CEZ:AV0Z40500505 Keywords : conductivity * polyaniline * silver Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.832, year: 2011

  6. Polyaniline silver nanoparticle coffee waste extracted porous graphene oxide nanocomposite structures as novel electrode material for rechargeable batteries

    Sundriyal, Poonam; Bhattacharya, Shantanu

    2017-03-01

    The exploration of new and advanced electrode materials are required in electronic and electrical devices for power storage applications. Also, there has been a continuous endeavour to formulate strategies for extraction of high performance electrode materials from naturally obtained waste products. In this work, we have developed an in situ hybrid nanocomposite from coffee waste extracted porous graphene oxide (CEPG), polyaniline (PANI) and silver nanoparticles (Ag) and have found this novel composite to serve as an efficient electrode material for batteries. The successful interaction among the three phases of the nano-composite i.e. CEPG-PANI-Ag have been thoroughly understood through RAMAN, Fourier transform infrared and x-ray diffraction spectroscopy, morphological studies through field emission scanning electron microscope and transmission electron microscope. Thermo-gravimetric analysis of the nano-composite demonstrates higher thermal stability up-to a temperature of 495 °C. Further BET studies through nitrogen adsorption-desorption isotherms confirm the presence of micro/meso and macro-pores in the nanocomposite sample. The cyclic-voltammetry (CV) analysis performed on CEPG-PANI-Ag nanocomposite exhibits a purely faradic behaviour using nickel foam as a current collector thus suggests the prepared nanocomposite as a battery electrode material. The nanocomposite reports a maximum specific capacity of 1428 C g-1 and excellent cyclic stability up-to 5000 cycles.

  7. Silver oxide nanocrystals anchored on titanate nanotubes and nanofibers: promising candidates for entrapment of radioactive iodine anions.

    Yang, Dongjiang; Liu, Hongwei; Liu, Long; Sarina, Sarina; Zheng, Zhanfeng; Zhu, Huaiyong

    2013-11-21

    Iodine radioisotopes are released into the environment by the nuclear industry and medical research institutions using radioactive materials. The (129)I(-) anion is one of the more mobile radioactive species due to a long half-life, and it is a great challenge to design long-term management solutions for such radioactive waste. In this study, a new adsorbent structure with the potential to efficiently remove radioactive iodine anions (I(-)) from water is devised: silver oxide (Ag2O) nanocrystals firmly anchored on the surface of titanate nanotubes and nanofibers via coherent interfaces between Ag2O and titanate phases. I(-) anions in fluids can easily access the Ag2O nanocrystals and be efficiently trapped by forming AgI precipitate that firmly attaches to the adsorbent. Due to their one-dimensional morphology, the new adsorbents can be readily dispersed in liquids and easily separated after purification; and the adsorption beds loaded with the adsorbents can permit high flux. This significantly enhances the adsorption efficiency and reduces the separation costs. The proposed structure reveals a new direction in developing efficient adsorbents for the removal of radioactive anions from wastewater.

  8. Formation of random and regular relief-phase structures on silver halide photographic emulsions by holographic methods

    Ganzherli, N. M.; Gulyaev, S. N.; Gurin, A. S.; Kramushchenko, D. D.; Maurer, I. A.; Chernykh, D. F.

    2009-07-01

    The formation of diffusers and microlens rasters on silver halide emulsions by holographic methods is considered. Two techniques for converting amplitude holographic recording to relief-phase recording, selective curing and irradiation of the emulsion gelatin by short-wavelength UV radiation, are compared.

  9. Effect of thermal processing on silver thin films of varying thickness deposited on zinc oxide and indium tin oxide

    Sivaramakrishnan, K.; Ngo, A. T.; Alford, T. L.; Iyer, S.

    2009-01-01

    Silver films of varying thicknesses (25, 45, and 60 nm) were deposited on indium tin oxide (ITO) on silicon and zinc oxide (ZnO) on silicon. The films were annealed in vacuum for 1 h at different temperatures (300-650 deg. C). Four-point-probe measurements were used to determine the resistivity of the films. All films showed an abrupt change in resistivity beyond an onset temperature that varied with thickness. Rutherford backscattering spectrometry measurements revealed agglomeration of the Ag films upon annealing as being responsible for the resistivity change. X-ray pole figure analysis determined that the annealed films took on a preferential texturing; however, the degree of texturing was significantly higher in Ag/ZnO/Si than in Ag/ITO/Si samples. This observation was accounted for by interface energy minimization. Atomic force microscopy (AFM) measurements revealed an increasing surface roughness of the annealed films with temperature. The resistivity behavior was explained by the counterbalancing effects of increasing crystallinity and surface roughness. Average surface roughness obtained from the AFM measurements were also used to model the agglomeration of Ag based on Ostwald ripening theory

  10. Silver niobates

    Tanirbergenov, B.; Rozhenko, S.P.

    1979-01-01

    By means of determination of residual concentrations and pH measurements investigated are the AgNO 3 -KNbO 3 -H 2 O, AgNO 3 -K 3 NbO 4 -H 2 O, AgNO 3 -K 8 Nb 16 O 19 -H 2 O systems and established is formation of meta-, ortho-and hexaniobates of silver. AgNbO 3 x H 2 O, Ag 8 Nb 6 O 19 x 6H 2 O and Ag 3 NbO 3 x 2.5H 2 O are separated from aqueous solution. Using the methods of differential-thermal, thermogravimetric and X-ray-phase analyses it is shown that silver metaniobate transforms into the crystal state at 530 deg C. Ortho- and hexaniobate of silver decompose at 500 deg C with formation of silver metaniobate and metal silver

  11. Influence of daylight on the fate of silver and zinc oxide nanoparticles in natural aquatic environments

    Odzak, Niksa; Kistler, David; Sigg, Laura

    2017-01-01

    Nanoparticles, such as silver (Ag-NP) and zinc oxide (ZnO-NP), are increasingly used in many consumer products. These nanoparticles (NPs) will likely be exposed to the aquatic environment (rain, river, lake water) and to light (visible and UV) in the products where they are applied, or after those products are discharged. Dissolution of Ag-NP and ZnO-NP is an important process because the dissolved Ag + and Zn 2+ are readily available and toxic for aquatic organisms. The objective of this study was to investigate the role of daylight (UV and visible) for the fate of engineered Ag-NP and ZnO-NPs in different types of natural waters. Ag-NP and ZnO-NP were exposed to rainwater, river Rhine, and lake waters (Greifen, Lucerne, Cristallina, Gruère) under different light conditions (no light, UV 300–400 nm and visible light 400–700 nm) for up to 8 days. Stronger agglomeration of Ag-NP was observed in the waters with higher ionic strength in comparison to those with lower ionic strength. Visible light tended to increase the dissolution of Ag-NP under most natural water conditions in comparison to dark conditions, whereas UV-light led to decreased dissolved Ag + after longer exposure time. These effects illustrate the dynamic interactions of Ag-NP with light, which may lead both to increased oxidation and to increased reduction of Ag + by organic compounds under UV-light. In the case of ZnO-NP, agglomeration occurred at higher ionic strength, but the effects of pH were predominant for dissolution, which occurred up to concentrations close to the solubility limit of ZnO(s) at pH around 8.2 and to nearly complete dissolution of ZnO-NP at lower pH (pH 4.8–6.5), with both visible and UV-light facilitating dissolution. This study thus shows that light conditions play an important role in the dissolution processes of nanoparticles. - Highlights: • Effects of visible and UV-light on dissolution of silver and zinc oxide nanoparticles were examined. • Natural waters

  12. Silver nanoparticle formation in thin oxide layer on silicon by silver-negative-ion implantation for Coulomb blockade at room temperature

    Tsuji, Hiroshi; Arai, Nobutoshi; Matsumoto, Takuya; Ueno, Kazuya; Gotoh, Yasuhito; Adachi, Kouichiro; Kotaki, Hiroshi; Ishikawa, Junzo

    2004-01-01

    Formation of silver nanoparticles formed by silver negative-ion implantation in a thin SiO 2 layer and its I-V characteristics were investigated for development single electron devices. In order to obtain effective Coulomb blockade phenomenon at room temperature, the isolated metal nanoparticles should be in very small size and be formed in a thin insulator layer such as gate oxide on the silicon substrate. Therefore, conditions of a fine particles size, high particle density and narrow distribution should be controlled at their formation without any electrical breakdown of the thin insulator layer. We have used a negative-ion implantation technique with an advantage of 'charge-up free' for insulators, with which no breakdown of thin oxide layer on Si was obtained. In the I-V characteristics with Au electrode, the current steps were observed with a voltage interval of about 0.12 V. From the step voltage the corresponded capacitance was calculated to be 0.7 aF. In one nanoparticle system, this value of capacitance could be given by a nanoparticle of about 3 nm in diameter. This consideration is consistent to the measured particle size in the cross-sectional TEM observation. Therefore, the observed I-V characteristics with steps are considered to be Coulomb staircase by the Ag nanoparticles

  13. Room-temperature synthesis and enhanced catalytic performance of silver-reduced graphene oxide nanohybrids

    Thu, Tran Viet; Ko, Pil Ju; Phuc, Nguyen Huu Huy; Sandhu, Adarsh

    2013-01-01

    The synthesis of supported, ultrasmall metallic nanoparticles (NPs) is of great importance for catalytic applications. In this study, silver-reduced graphene oxide nanohybrids (Ag–rGO NHs) were prepared by reducing Ag ions and graphene oxide (GO) at room temperature using sodium borohydride (NaBH 4 ) and trisodium citrate. The resulting products were characterized using UV–Vis spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy. The rich chemistry of GO surface provided many sites for the nucleation of Ag ions and efficiently limited their growth. Ag NPs were uniformly grown on basal planes of rGO with a high density (∼1,700 NPs μm −2 ) and well-defined size (3.6 ± 0.6 nm) as evidenced in SEM and HRTEM studies. The resulting Ag–rGO NHs were readily dispersed in water and exhibited enhanced catalytic activity toward the reduction of 4-nitrophenol by NaBH 4 in comparison to unsupported Ag NPs. The role of rGO as an excellent support for Ag catalyst is discussed

  14. Room-temperature synthesis and enhanced catalytic performance of silver-reduced graphene oxide nanohybrids

    Thu, Tran Viet, E-mail: thu@eiiris.tut.ac.jp; Ko, Pil Ju, E-mail: ko@eiiris.tut.ac.jp [Toyohashi University of Technology, Electronics-Inspired Interdisciplinary Research Institute (Japan); Phuc, Nguyen Huu Huy [Toyohashi University of Technology, Department of Electrical and Electronic Information Engineering (Japan); Sandhu, Adarsh [Toyohashi University of Technology, Electronics-Inspired Interdisciplinary Research Institute (Japan)

    2013-10-15

    The synthesis of supported, ultrasmall metallic nanoparticles (NPs) is of great importance for catalytic applications. In this study, silver-reduced graphene oxide nanohybrids (Ag-rGO NHs) were prepared by reducing Ag ions and graphene oxide (GO) at room temperature using sodium borohydride (NaBH{sub 4}) and trisodium citrate. The resulting products were characterized using UV-Vis spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy. The rich chemistry of GO surface provided many sites for the nucleation of Ag ions and efficiently limited their growth. Ag NPs were uniformly grown on basal planes of rGO with a high density ({approx}1,700 NPs {mu}m{sup -2}) and well-defined size (3.6 {+-} 0.6 nm) as evidenced in SEM and HRTEM studies. The resulting Ag-rGO NHs were readily dispersed in water and exhibited enhanced catalytic activity toward the reduction of 4-nitrophenol by NaBH{sub 4} in comparison to unsupported Ag NPs. The role of rGO as an excellent support for Ag catalyst is discussed.

  15. Oxidized multiwalled carbon nanotubes decorated with silver nanoparticles for fluorometric detection of dimethoate.

    Hsu, Chun-Wei; Lin, Zhong-Yi; Chan, Tzu-Yi; Chiu, Tai-Chia; Hu, Cho-Chun

    2017-06-01

    A novel method for the detection of dimethoate based on the peroxidase-like activity of silver-nanoparticles-modified oxidized multiwalled carbon nanotubes (AgNPs/oxMWCNTs) has been developed. The synthesized AgNPs/oxMWCNTs showed excellent peroxidease-like catalytic activity in hydrogen peroxide-Amplex red (AR) system (AR is oxidized to resorufinat, with the resorufin fluorescence at 584nm being used to monitor the catalytic activity). After dimethoate was added to AgNPs/oxMWCNTs, the interaction between dimethoate and the AgNPs inhibited the catalytic activity of AgNPs/oxMWCNTs. The decrease in fluorescence was used for the detection of dimethoate in the range of 0.01-0.35μgmL -1 (R 2 =0.998) with a detection limit of 0.003μgmL -1 (signal/noise=3). This method exhibited good selectivity for the detection of dimethoate even in the presence of high concentration of other pesticides. Consequently, the method was applied to measure the concentration of dimethoate residue in lake water and fruit, thus obtaining satisfactory results. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Theoretical Study On The Interaction Between Xenon And Positive Silver Clusters In Gas Phase And On The (001) Chabazite Surface

    Hunter, D.

    2009-01-01

    A systematic study on the adsorption of xenon on silver clusters in the gas phase and on the (001) surface of silver-exchanged chabazite is reported. Density functional theory at the B3LYP level with the cluster model was employed. The results indicate that the dominant part of the binding is the σ donation, which is the charge transfer from the 5p orbital of Xe to the 5s orbital of Ag and is not the previously suggested d π -d π back-donation. A correlation between the binding energy and the degree of σ donation is found. Xenon was found to bind strongly to silver cluster cations and not to neutral ones. The binding strength decreases as the cluster size increases for both cases, clusters in the gas-phase and on the chabazite surface. The Ag + cation is the strongest binding site for xenon both in gas phase and on the chabazite surface with the binding energies of 73.9 and 14.5 kJ/mol, respectively. The results also suggest that the smaller silver clusters contribute to the negative chemical shifts observed in the 129 Xe NMR spectra in experiments.

  17. Templated electrodeposition of Ag7NO11 nanowires with very high oxidation states of silver

    Rodijk, E.J.B.; Maijenburg, A.W.; Maas, M.G.; Blank, David H.A.; ten Elshof, Johan E.

    2011-01-01

    The templated electrodeposition of 200 nm diameter nanowires of the argentic oxynitrate Ag(Ag3O4)2NO3 phase is reported. Their high surface-to-volume ratio and the high average oxidation state of Ag make these wires promising candidates for nanoscale redox processes in which both a high volumetric

  18. Graphene Oxide/Silver Nanohybrid as Multi-functional Material for Highly Efficient Bacterial Disinfection and Detection of Organic Dye

    Tam, L.T.; Dinh, N. X.; Cuong, N. V.

    2016-01-01

    In this work, a multi-functional hybrid system consisting of graphene oxide and silver nanoparticles (GO-Ag NPs) was successfully synthesized by using a two-step chemical process. We firstly demonstrated noticeable bactericidal ability of the GO-Ag hybrid system. We provide more chemo-physical ev......In this work, a multi-functional hybrid system consisting of graphene oxide and silver nanoparticles (GO-Ag NPs) was successfully synthesized by using a two-step chemical process. We firstly demonstrated noticeable bactericidal ability of the GO-Ag hybrid system. We provide more chemo...... media. With the aforementioned properties, the GO-Ag hybrid system is found to be very promising as a multi-functional material for advanced biomedicine and environmental monitoring applications....

  19. Reusable fluorescent sensor for captopril based on energy transfer from photoluminescent graphene oxide self-assembly multilayers to silver nanoparticles.

    Sun, Xiangying; Liu, Bin; Li, Shuchun; Li, Fang

    2016-05-15

    In this work we designed a self-assembly multilayers, in which photoluminescent graphene oxide was employed as a fluorescence probe. This multilayers film can effectively recognize captopril by resonance energy transfer from graphite oxide to silver nanoparticles. A new interfacial sensing method for captopril with high signal to noise ratio was established, by means of that multilayers was quenched by silver nanoparticles and subsequently recovered by adding captopril. The linear relation between intensity and captopril concentration was good, and the detection limit was found to be 0.1578 μM. Also, this novel detection platform demonstrated intriguing reusable properties, and the sensor could be repeated more than ten times without obviously losing its sensing performance. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Silver nanoparticles induced heat shock protein 70, oxidative stress and apoptosis in Drosophila melanogaster.

    Ahamed, Maqusood; Posgai, Ryan; Gorey, Timothy J; Nielsen, Mark; Hussain, Saber M; Rowe, John J

    2010-02-01

    Due to the intensive commercial application of silver nanoparticles (Ag NPs), risk assessment of this nanoparticle is of great importance. Our previous in vitro study demonstrated that Ag NPs caused DNA damage and apoptosis in mouse embryonic stem cells and fibroblasts. However, toxicity of Ag NPs in vivo is largely lacking. This study was undertaken to examine the toxic effects of well-characterized polysaccharide coated 10 nm Ag NPs on heat shock stress, oxidative stress, DNA damage and apoptosis in Drosophila melanogaster. Third instar larvae of D. melanogaster were fed a diet of standard cornmeal media mixed with Ag NPs at the concentrations of 50 and 100 microg/ml for 24 and 48 h. Ag NPs up-regulated the expression of heat shock protein 70 and induced oxidative stress in D. melanogaster. Malondialdehyde level, an end product of lipid peroxidation was significantly higher while antioxidant glutathione content was significantly lower in Ag NPs exposed organisms. Activities of antioxidant enzyme superoxide dismutase and catalase were also significantly higher in the organisms exposed to Ag NPs. Furthermore, Ag NPs up-regulated the cell cycle checkpoint p53 and cell signaling protein p38 that are involved in the DNA damage repair pathway. Moreover, activities of caspase-3 and caspase-9, markers of apoptosis were significantly higher in Ag NPs exposed organisms. The results indicate that Ag NPs in D. melanogaster induce heat shock stress, oxidative stress, DNA damage and apoptosis. This study suggests that the organism is stressed and thus warrants more careful assessment of Ag NPs using in vivo models to determine if chronic exposure presents developmental and reproductive toxicity. Copyright 2009 Elsevier Inc. All rights reserved.

  1. Silver nanoparticles induced heat shock protein 70, oxidative stress and apoptosis in Drosophila melanogaster

    Ahamed, Maqusood; Posgai, Ryan; Gorey, Timothy J.; Nielsen, Mark; Hussain, Saber M.; Rowe, John J.

    2010-01-01

    Due to the intensive commercial application of silver nanoparticles (Ag NPs), risk assessment of this nanoparticle is of great importance. Our previous in vitro study demonstrated that Ag NPs caused DNA damage and apoptosis in mouse embryonic stem cells and fibroblasts. However, toxicity of Ag NPs in vivo is largely lacking. This study was undertaken to examine the toxic effects of well-characterized polysaccharide coated 10 nm Ag NPs on heat shock stress, oxidative stress, DNA damage and apoptosis in Drosophila melanogaster. Third instar larvae of D. melanogaster were fed a diet of standard cornmeal media mixed with Ag NPs at the concentrations of 50 and 100 μg/ml for 24 and 48 h. Ag NPs up-regulated the expression of heat shock protein 70 and induced oxidative stress in D. melanogaster. Malondialdehyde level, an end product of lipid peroxidation was significantly higher while antioxidant glutathione content was significantly lower in Ag NPs exposed organisms. Activities of antioxidant enzyme superoxide dismutase and catalase were also significantly higher in the organisms exposed to Ag NPs. Furthermore, Ag NPs up-regulated the cell cycle checkpoint p53 and cell signaling protein p38 that are involved in the DNA damage repair pathway. Moreover, activities of caspase-3 and caspase-9, markers of apoptosis were significantly higher in Ag NPs exposed organisms. The results indicate that Ag NPs in D. melanogaster induce heat shock stress, oxidative stress, DNA damage and apoptosis. This study suggests that the organism is stressed and thus warrants more careful assessment of Ag NPs using in vivo models to determine if chronic exposure presents developmental and reproductive toxicity.

  2. Improvement of corrosion resistance of transparent conductive multilayer coating consisting of silver layers and transparent metal oxide layers

    Koike, Katsuhiko; Yamazaki, Fumiharu; Okamura, Tomoyuki; Fukuda, Shin

    2007-01-01

    An optical filter for plasma display panel (PDP) requires an electromagnetic shield with very high ability. The authors investigated a transparent conductive multilayer coating consisting of silver (Ag) layers and transparent metal oxide layers. The durability of the multilayer sputter coating, including the silver layer, is very sensitive to the surrounding atmosphere. For example, after an exposure test they found discolored points on the multilayer sputter coatings, possibly caused by migration of silver atoms in the silver layers. In their investigation, they modified the top surface of the multilayer sputter coatings with transition metals to improve the corrosion resistance of the multilayer coating. Specifically, they deposited transition metals 0.5-2 nm thick on the top surface of the multilayer coatings by sputtering. They chose indium tin oxide (ITO) as the transparent metal oxide. They applied the multilayer sputter coatings of seven layers to a polyethylene terephthalate (PET) film substrate. A cross-sectional structure of the film with the multilayer coatings is PET film/ITO/Ag/ITO/Ag/ITO/Ag/ITO. They evaluated the corrosion resistance of the films by a salt-water immersion test. In the test, they immersed the film with multilayer coatings into salt water, and then evaluated the appearance, transmittance, and electrical resistance of the multilayer coatings. They investigated several transition metals as the modifying material, and found that titanium and tantalum drastically improved the resistance of the multilayer coatings to the salt-water exposure without a significant decline in transmittance. They also investigated the relation between elapsed time after deposition of the modifying materials and resistance to the salt water. Furthermore, they investigated the effects of a heat treatment and an oxide plasma treatment on resistance to the salt water

  3. Hydrophobic silver nanoparticles trapped in lipid bilayers: Size distribution, bilayer phase behavior, and optical properties

    Bothun Geoffrey D

    2008-11-01

    Full Text Available Abstract Background Lipid-based dispersion of nanoparticles provides a biologically inspired route to designing therapeutic agents and a means of reducing nanoparticle toxicity. Little is currently known on how the presence of nanoparticles influences lipid vesicle stability and bilayer phase behavior. In this work, the formation of aqueous lipid/nanoparticle assemblies (LNAs consisting of hydrophobic silver-decanethiol particles (5.7 ± 1.8 nm embedded within 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC bilayers is demonstrated as a function of the DPPC/Ag nanoparticle (AgNP ratio. The effect of nanoparticle loading on the size distribution, bilayer phase behavior, and bilayer fluidity is determined. Concomitantly, the effect of bilayer incorporation on the optical properties of the AgNPs is also examined. Results The dispersions were stable at 50°C where the bilayers existed in a liquid crystalline state, but phase separated at 25°C where the bilayers were in a gel state, consistent with vesicle aggregation below the lipid melting temperature. Formation of bilayer-embedded nanoparticles was confirmed by differential scanning calorimetry and fluorescence anisotropy, where increasing nanoparticle concentration suppressed the lipid pretransition temperature, reduced the melting temperature, and disrupted gel phase bilayers. The characteristic surface plasmon resonance (SPR wavelength of the embedded nanoparticles was independent of the bilayer phase; however, the SPR absorbance was dependent on vesicle aggregation. Conclusion These results suggest that lipid bilayers can distort to accommodate large hydrophobic nanoparticles, relative to the thickness of the bilayer, and may provide insight into nanoparticle/biomembrane interactions and the design of multifunctional liposomal carriers.

  4. Surface Species and Metal Oxidation State during H2-Assisted NH3-SCR of NOx over Alumina-Supported Silver and Indium

    Linda Ström

    2018-01-01

    Full Text Available Alumina-supported silver and indium catalysts are investigated for the hydrogen-assisted selective catalytic reduction (SCR of NOx with ammonia. Particularly, we focus on the active phase of the catalyst and the formation of surface species, as a function of the gas environment. Diffuse reflectance ultraviolet-visible (UV-vis spectroscopy was used to follow the oxidation state of the silver and indium phases, and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS was used to elucidate the formation of surface species during SCR conditions. In addition, the NOx reduction efficiency of the materials was evaluated using H2-assisted NH3-SCR. The DRIFTS results show that the Ag/Al2O3 sample forms NO-containing surface species during SCR conditions to a higher extent compared to the In/Al2O3 sample. The silver sample also appears to be more reduced by H2 than the indium sample, as revealed by UV-vis spectroscopic experiments. Addition of H2, however, may promote the formation of highly dispersed In2O3 clusters, which previously have been suggested to be important for the SCR reaction. The affinity to adsorb NH3 is confirmed by both temperature programmed desorption (NH3-TPD and in situ DRIFTS to be higher for the In/Al2O3 sample compared to Ag/Al2O3. The strong adsorption of NH3 may inhibit (self-poison the NH3 activation, thereby hindering further reaction over this catalyst, which is also shown by the lower SCR activity compared to Ag/Al2O3.

  5. Densification, phase stability and in vitro biocompatibility property of hydroxyapatite-10 wt% silver composites.

    Nath, Shekhar; Kalmodia, Sushma; Basu, Bikramjit

    2010-04-01

    In this paper, we demonstrate how a simple fabrication route, i.e., pressureless sintering of mechanically mixed powders can be employed to develop hydroxyapatite (HAp, Ca(10)(PO(4))(6)(OH)(2))-silver (Ag) bioceramic composites with superior combination of physical (hardness, toughness), non-cytotoxicity, cytocompatiblity and anti-microbial property. The densification results show that such composites can be sintered at 1200 degrees C for 2 h near to theoretical density (>98% rho(th).) An important observation is that the dissociation of HAp phase can be prevented during sintering up to 1300 degrees C for 2 h in HAp-10 wt% Ag composites. The stability of HAp in presence of silver is discussed in reference to the results obtained using XRD, FTIR and Raman spectroscopy. The hardness values of the composites are comparable (approximately 6.5 GPa) to that of pure HAp, despite of the presence of softer Ag particles. The sintered composites exhibit modest crack growth resistance property and their toughness varies in the range of 0.9-1.2 MPa m(0.5), depending on sintering temperature. For selected samples, the in vitro characterization was performed using mouse fibroblast (L929) and human osteosarcoma (MG63) cell lines. The combination of biochemical assays (MTT, ALP and osteocalcin) confirm that HAp-10 wt% Ag biocomposites have comparable or even better cellular viability, osteogenic differentiation and bone mineralization as well as osteoinduction property. Antibacterial experiments involving gram-negative bacteria, Escherichia coli confirm excellent bactericidal property of HAp-10 wt% Ag composites, sintered using mechanically mixed powders.

  6. Mixed phase-amplitude holographic gratings recorded in bleached silver halide materials

    Neipp, C.; Pascual, C.; Belendez, A.

    2002-01-01

    The coupled wave theory of Kogelnik has given a well-established basis for the comprehension of how light propagates inside a volume hologram. This theory gives a good approximation for the diffraction efficiency of both volume phase holograms and volume absorption holograms. Mixed holograms (phase and absorption) have also been dealt with from the point of view of the coupled wave theory. In this paper we use Kogelnik's coupled wave theory to give quantitative information about the mechanisms which produce mixed gratings in photographic emulsions. In particular, we demonstrate that mixed amplitude-phase gratings are recorded on photographic emulsions when fixation-free bleaching techniques are used to obtain volume holograms. We will prove that the oxidation products of the bleach can give rise to an absorption modulation at high values of exposure and high concentrations of potassium bromide in the bleach bath. We will also give quantitative data regarding the absorption created by these oxidation products. (author)

  7. Two-Phase Bactericidal Mechanism of Silver Nanoparticles against Burkholderia pseudomallei.

    Pawinee Siritongsuk

    Full Text Available Silver nanoparticles (AgNPs have a strong antimicrobial activity against a variety of pathogenic bacteria. The killing mechanism of AgNPs involves direct physical membrane destruction and subsequent molecular damage from both AgNPs and released Ag+. Burkholderia pseudomallei is the causative agent of melioidosis, an endemic infectious disease primarily found in northern Australia and Southeast Asia. B. pseudomallei is intrinsically resistant to most common antibiotics. In this study, the antimicrobial activity and mechanism of AgNPs (10-20 nm against B. pseudomallei were investigated. The MIC and MBC for nine B. pseudomallei strains ranged from 32-48 μg/mL and 96-128 μg/mL, respectively. Concentrations of AgNPs less than 256 μg/mL were not toxic to human red blood cells. AgNPs exhibited a two-phase mechanism: cell death induction and ROS induction. The first phase was a rapid killing step within 5 min, causing the direct damage of the cytoplasmic membrane of the bacterial cells, as observed by a time-kill assay and fluorescence microscopy. During the period of 5-30 min, the cell surface charge was rapidly neutralized from -8.73 and -7.74 to 2.85 and 2.94 mV in two isolates of B. pseudomallei, as revealed by zeta potential measurement. Energy-dispersive X-ray (EDX spectroscopy showed the silver element deposited on the bacterial membrane, and TEM micrographs of the AgNP-treated B. pseudomallei cells showed severe membrane damage and cytosolic leakage at 1/5 MIC and cell bursting at MBC. During the killing effect the released Ag+ from AgNPs was only 3.9% from the starting AgNPs concentration as observed with ICP-OES experiment. In the second phase, the ROS induction occurred 1-4 hr after the AgNP treatment. Altogether, we provide direct kinetic evidence of the AgNPs killing mechanism, by which cell death is separable from the ROS induction and AgNPs mainly contributes in the killing action. AgNPs may be considered a potential candidate to

  8. Green synthesis of dimension-controlled silver nanoparticle–graphene oxide with in situ ultrasonication

    Hui, K.S.; Hui, K.N.; Dinh, D.A.; Tsang, C.H.; Cho, Y.R.; Zhou, Wei; Hong, Xiaoting; Chun, Ho-Hwan

    2014-01-01

    Graphical abstract: -- Abstract: A green chemical approach to control the dimensions of Ag nanoparticle-decorated graphene oxide (AgNP–GO) composites was proposed by in situ ultrasonication of a mixture of AgNO 3 and GO solution with the assistance of vitamin C acting as an environmentally friendly reducing agent at room temperature. The AgNP–GO composites were characterized by X-ray diffraction, transmission electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, Raman spectra and ultraviolet–visible absorption spectra. The results demonstrated that Ag nanoparticles with an average diameter of ∼15 nm were uniformly dispersed on the surface of GO nanosheets by in situ ultrasonication of 1 min with vitamin C. Increasing the ultrasonication times resulted in Ag nanoparticles with tunable dimensions ranging from 15 to 55 nm being formed on the surface of GO nanosheets. The amount of silver nitrate and the ultrasonication time play a key role in the control of the dimension of Ag nanoparticles on GO, and a formation mechanism of the as-prepared AgNP–GO composites is proposed. This study provides a guide to controlling the dimensions of AgNP–GO composites, which may hold promise as advanced materials for various analytical applications such as catalysis, sensors and microchips

  9. Electrochemical immunosensor for ethinylestradiol using diazonium salt grafting onto silver nanoparticles-silica-graphene oxide hybrids.

    Cincotto, Fernando H; Martínez-García, Gonzalo; Yáñez-Sedeño, Paloma; Canevari, Thiago C; Machado, S A S; Pingarrón, José M

    2016-01-15

    This work describes the preparation of an electrochemical immunosensor for ethinylestradiol (EE2) based on grafting of diazonium salt of 4-aminobenzoic acid onto a glassy carbon electrode modified with silver nanoparticles/SiO2/graphene oxide hybrid followed by covalent binding of anti-ethinylestradiol (anti-EE2) to activated carboxyl groups. A competitive immunoassay was developed for the determination of the hormone using peroxidase-labeled ethinylestradiol (HRP-EE2) and measurement of the amperometric response at -200mV in the presence of hydroquinone (HQ) as redox mediator. The calibration curve for EE2 exhibited a linear range between 0.1 and 50ng/mL (r(2)=0.996), with a detection limit of 65pg/mL. Interference studies with other hormones related with EE2 revealed the practical specificity of the developed method for the analyte. A good reproducibility, with RSD=4.5% (n=10) was also observed. The operating stability of a single bioelectrode modified with anti-EE2 was maintained at least for 15 days when it was stored at 4°C under humid conditions between measurements. The developed immunosensor was applied to the analysis of spiked urine with good results. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Electrochemical performance of polypyrrole/silver vanadium oxide composite cathodes in lithium primary batteries

    Anguchamy, Yogesh K.; Lee, Jong-Won; Popov, Branko N.

    Polypyrrole (PPy)/silver vanadium oxide (SVO) composite cathode materials were synthesized by polymerizing pyrrole onto the surface of pure SVO particles. Electrochemical characterization was carried out by performing galvanostatic discharge, pulse discharge and ac-impedance experiments. The composite electrode exhibited better performance than pristine SVO in all the experiments. The composite electrodes yielded a higher discharge capacity and a better pulse discharge capability when compared to the pristine SVO electrode. The pulse discharge and ac-impedance studies indicated that PPy forms an effective conductive network on the SVO surface and thereby reduces the particle-to-particle contact resistance and facilitates the interfacial charge transfer kinetics. To determine the thermal stability of the composite cathode, galvanostatic discharge and ac-impedance experiments were performed at different temperatures. The capacity increased with temperature due to enhanced charge transfer kinetics and low mass transfer limitations. The peak capacity was obtained at 60 °C, after which the performance degraded with any further increase in temperature.

  11. Electrochemical performance of polypyrrole/silver vanadium oxide composite cathodes in lithium primary batteries

    Anguchamy, Yogesh K.; Lee, Jong-Won; Popov, Branko N. [Center for Electrochemical Engineering, Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208 (United States)

    2008-09-15

    Polypyrrole (PPy)/silver vanadium oxide (SVO) composite cathode materials were synthesized by polymerizing pyrrole onto the surface of pure SVO particles. Electrochemical characterization was carried out by performing galvanostatic discharge, pulse discharge and ac-impedance experiments. The composite electrode exhibited better performance than pristine SVO in all the experiments. The composite electrodes yielded a higher discharge capacity and a better pulse discharge capability when compared to the pristine SVO electrode. The pulse discharge and ac-impedance studies indicated that PPy forms an effective conductive network on the SVO surface and thereby reduces the particle-to-particle contact resistance and facilitates the interfacial charge transfer kinetics. To determine the thermal stability of the composite cathode, galvanostatic discharge and ac-impedance experiments were performed at different temperatures. The capacity increased with temperature due to enhanced charge transfer kinetics and low mass transfer limitations. The peak capacity was obtained at 60 C, after which the performance degraded with any further increase in temperature. (author)

  12. Photochemical decoration of silver nanoparticles on graphene oxide nanosheets and their optical characterization

    Lan, Nguyen Thi; Chi, Do Thi; Dinh, Ngo Xuan; Hung, Nguyen Duy; Lan, Hoang [Department of Nanoscience and Nanotechnology, Advanced Institute for Science and Technology (AIST), Hanoi University of Science and Technology (HUST), No. 1 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam); Tuan, Pham Anh [Vietnam Metrology Institute, 08 Hoang Quoc Viet Road, Cau Giay District, Hanoi (Viet Nam); Thang, Le Hong [School of Materials Science and Engineering, Hanoi University of Science and Technology (HUST), 01 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam); Trung, Nguyen Ngoc [School of Engineering Physics, Hanoi University of Science and Technology (HUST), 01 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam); Hoa, Nguyen Quang [Department of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); Huy, Tran Quang [Laboratory for Ultrastructure and Bionanotechnology (LUBN), National Institute of Hygiene and Epidemiology (NIHE), No. 1 Yecxanh Street, Hai Ba Trung District, Hanoi (Viet Nam); Quy, Nguyen Van [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST), 01 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam); Duong, Thanh-Tung [Department of Materials Engineering, Chungnam National University, Daeduk Science Town, 305-764 Daejeon (Korea, Republic of); Phan, Vu Ngoc [Department of Nanoscience and Nanotechnology, Advanced Institute for Science and Technology (AIST), Hanoi University of Science and Technology (HUST), No. 1 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam); Le, Anh-Tuan, E-mail: tuan.leanh1@hust.edu.vn [Department of Nanoscience and Nanotechnology, Advanced Institute for Science and Technology (AIST), Hanoi University of Science and Technology (HUST), No. 1 Dai Co Viet Street, Hai Ba Trung District, Hanoi (Viet Nam)

    2014-12-05

    Highlights: • A photochemical method for effective decoration of the Ag-NPs on GO nanosheets is presented. • The average size of the Ag-NPs on the GO nanosheets obtained ∼6–7 nm with uniform size distribution. • Surface interaction of Ag-NPs with GO nanosheets leads to surface plasmon-enhanced luminescence. - Abstract: Nanohybrid materials based on silver nanoparticles (Ag-NPs) and graphene oxide (GO) are attracting considerable research interest because of their potential many applications including surface-enhanced Raman scattering, catalysis, sensors, biomedicine and antimicrobials. In this study, we established a simple and effective method of preparing a finely dispersed Ag-GO aqueous solution using modified Hummer and photochemical technique. The Ag-NPs formation on GO nanosheets was analyzed by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The average size of Ag-NPs on the GO nanosheets was approximately 6–7 nm with nearly uniform size distribution. The Ag-GO nanohybrid also exhibits an adsorption band at 435 nm because of the presence of Ag-NPs on the GO nanosheets. Photoluminescence emission of the Ag-GO nanohybrid was found at 400 and 530 nm, which can be attributed to the interaction between the luminescence of exploited GO nanosheets and localized surface plasmon resonance from metallic Ag-NPs. The observed excellent optical properties of the as-prepared Ag-GO nanohybrid showed a significant potential for optoelectronics applications.

  13. Physical transformations of iron oxide and silver nanoparticles from an intermediate scale field transport study

    Emerson, Hilary P.; Hart, Ashley E.; Baldwin, Jonathon A.; Waterhouse, Tyler C.; Kitchens, Christopher L.; Mefford, O. Thompson; Powell, Brian A.

    2014-02-01

    In recent years, there has been increasing concern regarding the fate and transport of engineered nanoparticles (NPs) in environmental systems and the potential impacts on human and environmental health due to the exponential increase in commercial and industrial use worldwide. To date, there have been relatively few field-scale studies or laboratory-based studies on environmentally relevant soils examining the chemical/physical behavior of the NPs following release into natural systems. The objective of this research is to demonstrate the behavior and transformations of iron oxide and silver NPs with different capping ligands within the unsaturated zone. Here, we show that NP transport within the vadose zone is minimal primarily due to heteroaggregation with soil surface coatings with results that >99 % of the NPs remained within 5 cm of the original source after 1 year in intermediate-scale field lysimeters. These results suggest that transport may be overestimated when compared to previous laboratory-scale studies on pristine soils and pure minerals and that future work must incorporate more environmentally relevant parameters.

  14. Silver nanoparticles cause osmoregulatory impairment and oxidative stress in Caspian kutum (Rutilus kutum, Kamensky 1901)

    Masouleh, Fatemeh F.; Amiri, Bagher M.; Mirvaghefi, Alireza

    2017-01-01

    Silver nanoparticles (AgNPs) are increasingly used in several industrial and household products because of their antibacterial and antifungal properties. Hence, there is an inevitable risk that these chemicals may end up in aquatic biotopes and have adverse effects on the fauna. In order to asses...... compared to controls. Whole-body cortisol and thyroid hormones decreased compared to controls. In conclusion, the study demonstrates that AgNPs cause oxidative stress and gill osmoregulatory disruption in Caspian kutum juveniles....... potential health effects on aquatic organisms, this study evaluated the effects of waterborne AgNP exposure for 7 days on a set of critical stress parameters in juvenile Caspian kutum (Rutilus kutum), an economically important fish in the Caspian Sea. The applied level 11 μg/l of AgNP is high compared......) and alkaline phosphatase (ALP), and whole-body cortisol and thyroid hormones (T3 and T4) were measured as endpoints. Gill hsp70 mRNA expression increased and gill Na+/K+-ATPase activity decreased in AgNP-exposed fish compared to controls. The specific activities of all liver enzymes decreased significantly...

  15. Criticality safety analysis for plutonium dissolver using silver mediated electrolytic oxidation method

    Umeda, Miki; Sugikawa, Susumu; Nakamura, Kazuhito; Egashira, Tetsurou

    1998-08-01

    Design and construction of a plutonium dissolver using silver mediated electrolytic oxidation method are promoted in NUCEF. Criticality safety analysis for the plutonium dissolver is described in this report. The electrolytic plutonium dissolver consists of connection pipes and three pots for MOX powder supply, circulation and electrolysis. The criticality control for the dissolver is made by geometrically safe shape with mass limitation. Monte Carlo code KENO-IV using MGCL-137 library based on ENDF/B-IV was used for the criticality safety analysis for the plutonium dissolver. Considering the required size for construction and criticality safety, diameter of pot and distance between two pots were determined. On this condition, the criticality safety analysis for the plutonium dissolver with connection pipes was carried out. As the result of the criticality safety analysis, an effective neutron multiplication factor keff of 0.91 was obtained and the criticality safety of the plutonium dissolver was confirmed on the basis of criteria of ≤0.95. (author)

  16. Zinc oxide and silver nanoparticles toxicity in the baker's yeast, Saccharomyces cerevisiae.

    Galván Márquez, Imelda; Ghiyasvand, Mergan; Massarsky, Andrey; Babu, Mohan; Samanfar, Bahram; Omidi, Katayoun; Moon, Thomas W; Smith, Myron L; Golshani, Ashkan

    2018-01-01

    Engineered nanomaterials (ENMs) are increasingly incorporated into a variety of commercial applications and consumer products; however, ENMs may possess cytotoxic properties due to their small size. This study assessed the effects of two commonly used ENMs, zinc oxide nanoparticles (ZnONPs) and silver nanoparticles (AgNPs), in the model eukaryote Saccharomyces cerevisiae. A collection of ≈4600 S. cerevisiae deletion mutant strains was used to deduce the genes, whose absence makes S. cerevisiae more prone to the cytotoxic effects of ZnONPs or AgNPs. We demonstrate that S. cerevisiae strains that lack genes involved in transmembrane and membrane transport, cellular ion homeostasis, and cell wall organization or biogenesis exhibited the highest sensitivity to ZnONPs. In contrast, strains that lack genes involved in transcription and RNA processing, cellular respiration, and endocytosis and vesicular transport exhibited the highest sensitivity to AgNPs. Secondary assays confirmed that ZnONPs affected cell wall function and integrity, whereas AgNPs exposure decreased transcription, reduced endocytosis, and led to a dysfunctional electron transport system. This study supports the use of S. cerevisiae Gene Deletion Array as an effective high-throughput technique to determine cellular targets of ENM toxicity.

  17. Photochemical decoration of silver nanoparticles on graphene oxide nanosheets and their optical characterization

    Lan, Nguyen Thi; Chi, Do Thi; Dinh, Ngo Xuan; Hung, Nguyen Duy; Lan, Hoang; Tuan, Pham Anh; Thang, Le Hong; Trung, Nguyen Ngoc; Hoa, Nguyen Quang; Huy, Tran Quang; Quy, Nguyen Van; Duong, Thanh-Tung; Phan, Vu Ngoc; Le, Anh-Tuan

    2014-01-01

    Highlights: • A photochemical method for effective decoration of the Ag-NPs on GO nanosheets is presented. • The average size of the Ag-NPs on the GO nanosheets obtained ∼6–7 nm with uniform size distribution. • Surface interaction of Ag-NPs with GO nanosheets leads to surface plasmon-enhanced luminescence. - Abstract: Nanohybrid materials based on silver nanoparticles (Ag-NPs) and graphene oxide (GO) are attracting considerable research interest because of their potential many applications including surface-enhanced Raman scattering, catalysis, sensors, biomedicine and antimicrobials. In this study, we established a simple and effective method of preparing a finely dispersed Ag-GO aqueous solution using modified Hummer and photochemical technique. The Ag-NPs formation on GO nanosheets was analyzed by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The average size of Ag-NPs on the GO nanosheets was approximately 6–7 nm with nearly uniform size distribution. The Ag-GO nanohybrid also exhibits an adsorption band at 435 nm because of the presence of Ag-NPs on the GO nanosheets. Photoluminescence emission of the Ag-GO nanohybrid was found at 400 and 530 nm, which can be attributed to the interaction between the luminescence of exploited GO nanosheets and localized surface plasmon resonance from metallic Ag-NPs. The observed excellent optical properties of the as-prepared Ag-GO nanohybrid showed a significant potential for optoelectronics applications

  18. Silver nanoplates with ground or metastable structures obtained from template-free two-phase aqueous/organic synthesis

    Zhelev, Doncho V., E-mail: dontcho.jelev@nih.gov; Zheleva, Tsvetanka S. [Army Research Laboratory, 2800 Adelphi, Maryland 20783 (United States)

    2014-01-28

    Silver has unique electrical, catalytic, and plasmonic characteristics and has been widely sought for fabrication of nanostructures. The properties of silver nanostructures are intimately coupled to the structure of silver crystals. Two crystal structures are known for silver: the stable (ground) state cubic face centered 3C-Ag structure and the metastable hexagonal 4H-Ag structure. Recently, Chackraborty et al. [J. Phys.: Condens. Matter 23, 325401 (2011)] discovered a low density, highly reactive metastable hexagonal 2H-Ag structure accessible during electrodeposition of silver nanowires in porous anodic alumina templates. This 2H-Ag structure has enhanced electrical and catalytic characteristics. In the present work we report template-free synthesis of silver nanoplates with the metastable 2H-Ag crystal structure, which appears together with the ground 3C-Ag and the metastable 4H-Ag structures in a two-phase solution synthesis with citric acid as the capping agent. The capacity of citric acid to stabilize both the stable and the metastable structures is explained by its preferential binding to the close packed facets of Ag crystals, which are the (111) planes for 3C-Ag and the (0001) planes for 4H-Ag and 2H-Ag. Nanoplate morphology and structure are characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The synthesized nanoplates have thickness from 15 to 17 nm and edge length from 1 to 10 μm. Transmission electron microscopy selected area electron diffraction is used to uniquely identify and distinguish between nanoplates with 2H-Ag or 4H-Ag or 3C-Ag structures.

  19. The interaction between silver and N2O in relation to the oxidative dehydrogenation of methanol

    Lefferts, Leonardus; van Ommen, J.G.; Ross, J.R.H.

    1988-01-01

    The interaction of N2O with pure silver at temperatures up to 900 °C has been studied using temperature-programmed reduction and desorption; the interaction is compared with that of oxygen with silver. The effect of addition of N2O, as well as of the complete replacement of oxygen by N2O, on the

  20. Silver nanoparticles deposited on graphene oxide for ultrasensitive surface-enhanced Raman scattering immunoassay of cancer biomarker.

    Yang, Lin; Zhen, Shu Jun; Li, Yuan Fang; Huang, Cheng Zhi

    2018-06-14

    Graphene oxide (GO) exhibits distinctive Raman scattering features for its high frequency D (disordered) and tangential modes (G-band), which are characteristically sharp at 1580 cm-1 and 1350 cm-1, respectively, but are too weak for sensitive quantitation purposes. By depositing silver nanoparticles on the surface of GO in this contribution, both D and G bands of GO become enhanced. The enzyme label of this method controls the dissolution of silver nanoparticles on the surface of GO through hydrogen peroxide which is produced by the oxidation of the enzyme substrate. With the dissolution of the silver nanoparticles a greatly decreased SERS signal of GO was obtained. This strategy involves dual signal amplification of the enzyme and nanocomposites to improve the detection sensitivity. As a proof of concept, prostate specific antigen (PSA), a biomarker for prostate cancer, is successfully detected as a target by forming a sandwich structure in immunoassay. The SERS immunoassay possesses excellent analytical performance in the range 0.5 pg mL-1 to 500 pg mL-1 with a limit of detection of 0.23 pg mL-1, making the detection of PSA serum samples from prostate cancer patients satisfactory, demonstrating that the sensitive enzyme-assisted dissolved AgNPs SERS immunoassay of PSA has potential applications in clinical diagnosis.

  1. Amalgamation based optical and colorimetric sensing of mercury(II) ions with silver graphene oxide nanocomposite materials

    Kamali, Khosro Zangeneh; Pandikumar, Alagarsamy; Jayabal, Subramaniam; Huang, Nay Ming; Ramaraj, Ramasamy; Lim, Hong Ngee; Ong, Boon Hoong; Bien, Chia Sheng Daniel; Kee, Yeh Yee

    2016-01-01

    The article describes a facile method for the preparation of a conjugate composed of silver nanoparticles and graphene oxide (Ag GO) via chemical reduction of silver precursors in the presence of graphene oxide (GO) while sonicating the solution. The Ag GO was characterized by X-ray photoelectron spectroscopy, X-ray powder diffraction, and energy-dispersive X-ray spectroscopy. The nanocomposite undergoes a color change from yellow to colorless in presence of Hg(II), and this effect is based on the disappearance of the localized surface plasmon resonance absorption of the AgNPs due to the formation of silver-mercury amalgam. The presence of GO, on the other hand, prevents the agglomeration of the AgNPs and enhances the stability of the nanocomposite material in solution. Hence, the probe represents a viable optical probe for the determination of mercury(II) ions in that it can be used to visually detect Hg(II) concentrations as low as 100 μM. The instrumental LOD is 338 nM. (author)

  2. Evaluation of three telemetry transmitter attachment methods for female silver-phase American eels ( Anguilla rostrata Lesueur)

    Cottrill, R.A.; Økland, F.; Aarestrup, Kim

    2006-01-01

    Declines in juvenile American eel (Anguilla rostrata Lesueur) abundance have led to concern about the impacts of anthropogenic structures on eel migration patterns. Telemetry provides an insightful tool for examining the movements of eels around these structures. Although there have been a number...... of studies investigating movements of Anguillid eels, using a variety of transmitter attachment techniques, there are few published evaluations of the effects of various tag attachment procedures. Hence, the effects of three telemetry attachment procedures were evaluated for female silver phase American eels...... of silver-phase American eels is not affected by the presence of telemetry transmitters or the method of transmitter attachment, even though swim performance decreases. However, transmitter retention rates varied considerably after the 12-week experimental period. Three gastric tags were regurgitated...

  3. Ergonomic Synthesis Suitable for Industrial Production of Silver-Festooned Zinc Oxide Nanorods

    Khan, G. R.; Khan, R. A.

    2015-07-01

    For maximizing productivity, minimizing cost, time-boxing process and optimizing human effort, a single-step, cost-effective, ultra-fast and environmentally benign synthesis suitable for industrial production of nanocrystalline ZnO, and Ag-doped ZnO has been reported in this paper. The synthesis based on microwave-supported aqueous solution method used zinc acetate dehydrate and silver nitrate as precursors for fabrication of nanorods. The synthesized products were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and UV-Vis-NIR spectroscopy. The undoped and Ag-doped ZnO nanorods crystallized in a hexagonal wurtzite structure having spindle-like morphology. The blue shift occurred at absorption edge of Ag-doped ZnO around 260 nm compared to 365 nm of bulk ZnO. The red shift occurred at Raman peak site of 434 cm-1 compared to characteristic wurtzite phase peak of ZnO (437 cm-1). The bandgap energies were found to be 3.10 eV, 3.11 eV and 3.18 eV for undoped, 1% Ag-doped, and 3% Ag-doped ZnO samples, respectively. The TEM results provided average particle sizes of 17 nm, 15 nm and 13 nm for undoped, and 1% and 3% Ag-doped ZnO samples, respectively.

  4. Continuous synthesis of magnesium-hydroxide, zinc-oxide, and silver nanoparticles by microwave plasma in water

    Hattori, Yoshiaki; Mukasa, Shinobu; Toyota, Hiromichi; Inoue, Toru; Nomura, Shinfuku

    2011-01-01

    Nanoparticles are continuously synthesized from submerged magnesium, zinc, and silver rods 1–2 mm in diameter by microwave plasma in pure water at 20 kPa. Magnesium-hydroxide nanoplates shaped as triangles, truncated triangles or hexagons with 25–125 nm in size are synthesized with a production rate of 60 g h −1 . Zinc-oxide nanoparticles formed as sharp sticks with diameters of 50 nm and lengths of 150–200 nm are synthesized with a production rate of 14 g h −1 . Silver nanoparticles with a diameter of approximately 6 nm are synthesized with a production rate of 0.8 g h −1 . The excitation temperature is estimated by applying the Boltzmann plot method in assumption of local thermodynamic equilibrium. The excitation temperatures obtained from hydrogen, magnesium, and zinc lines are 3300 ± 100 K, 4000 ± 500 K, and 3200 ± 500 K, respectively.

  5. Silver nanoparticles deposited on anodic aluminum oxide template using magnetron sputtering for surface-enhanced Raman scattering substrate

    Wong-ek, Krongkamol [Nanoscience and Technology Program, Chulalongkorn University, Bangkok 10330 (Thailand); Eiamchai, Pitak; Horprathum, Mati; Patthanasettakul, Viyapol [National Electronics and Computer Technology Center, 112 Thailand Science Park, Phahonyothin Rd., Klong Luang, Pathumthani 12120 (Thailand); Limnonthakul, Puenisara [Department of Physics, Faculty of Science, King Mongkut' s University of Technology Thonburi, Bangkok 10140 (Thailand); Chindaudom, Pongpan [National Electronics and Computer Technology Center, 112 Thailand Science Park, Phahonyothin Rd., Klong Luang, Pathumthani 12120 (Thailand); Nuntawong, Noppadon, E-mail: noppadon.nuntawong@nectec.or.t [National Electronics and Computer Technology Center, 112 Thailand Science Park, Phahonyothin Rd., Klong Luang, Pathumthani 12120 (Thailand)

    2010-09-30

    Low-cost and highly sensitive surface-enhanced Raman scattering (SERS) substrates have been fabricated by a simple anodizing process and a magnetron sputtering deposition. The substrates, which consist of silver nanoparticles embedded on anodic aluminum oxide (AAO) templates, are investigated by a scanning electron microscope and a confocal Raman spectroscopy. The SERS activities are demonstrated by Raman scattering from adsorbed solutions of methylene blue and pyridine on the SERS substrate surface. The most optimized SERS substrate contains the silver nanoparticles, with a size distribution of 10-30 nm, deposited on the AAO template. From a calculation, the SERS enhancement factor is as high as 8.5 x 10{sup 7}, which suggests strong potentials for direct applications in the chemical detection and analyses.

  6. Influence of Experimental Conditions on Deposition of Silver Nanoparticles Onto Surface of Graphene Oxide / Wpływ Warunków Eksperymentalnych Na Proces Osadzania Nanocząstek Srebra Na Powierzchni Tlenku Grafenu

    Wojnicki M.

    2015-12-01

    Full Text Available Present work describes the influence of silver nanoparticles precursor form as well as the impact of graphene oxide initial concentration on deposition of the silver nanoparticles onto graphene oxide. Borane dimethylamine complex (DMAB was used as the reducing agent. It was observed that application of silver ammonia complexes as the silver nanoparticles precursor as well as alkaline solution effect in higher quantity of deposited AgNPs in comparison to deposition process with the use of silver(I nitrate in acidic solution.

  7. Self-Assembly of Single-Crystal Silver Microflakes on Reduced Graphene Oxide and their Use in Ultrasensitive Sensors

    Chen, Ye

    2016-01-19

    Compared to 1D structures, 2D structures have higher specific and active surface, which drastically improves electron transfer and extensibility along 2D plane. Herein, 2D-single crystal silver microflakes (AgMFs) are prepared for the first time in situ on reduced graphene oxide (RGO) by solvothermal synthesis with thickness around 100 nm and length around 10 μm. The oriented attachment mechanism is hypothesized to control the silver crystal growth and self-assembly of reduced silver units to form single-crystal AgMF structure on RGO sheets. Employing it as an electrode to fabricate reliable and extremely sensitive pressure sensors verifies the applicability of this novel 2D structure. Contrary to nanowires, 2D microflakes can intercalate better within the polymer matrix to provide an enhanced network for electron movement. The designed sensor can retain more than 4.7 MPa-1 after 10 000 cycles. The design proves functional for monitoring various actions such as wrist movement, squatting, walking, and delicate finger touch with high durability. A highly sensitive and flexible pressure sensor is fabricated based on the self-assembly of silver microflakes on reduced graphene oxide. This sensor exhibits an excellent pressure sensitivity as it can retain more than 4.7 MPa-1 after 10 000 cycles. This system is successfully used to monitor wrist movement, walking, and squatting and can be applied in touch screen panels, robotic systems, and prosthetics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Effects of γ- and x-irradiation upon activity and selectivity of a supported silver catalyst in the oxidation of ethylene and carbon monoxide

    Mora Vallejo, R.J.

    1975-01-01

    Effects of γ and x-radiation on catalytic selectivity of supported silver catalysts for production of ethylene oxide via ethylene oxidation were compared by determination of radio-induced changes in conversion-yield profiles. Influence of photon energy on the kinetics of the irradiation process was studied by determination of conversion-yield profiles, using samples of catalyst exposed to x-rays of different mean photon energy and γ-rays for different cumulative periods of time. The effect of γ-radiation on catalytic activity of the same silver catalysts for carbon monoxide oxidation was analyzed by determination of the reaction kinetics before and after catalyst irradiation

  9. Improvement of mechanical reliability by patterned silver/Indium-Tin-Oxide structure for flexible electronic devices

    Baek, Kyunghyun; Jang, Kyungsoo; Lee, Youn-Jung; Ryu, Kyungyul; Choi, Woojin; Kim, Doyoung; Yi, Junsin

    2013-01-01

    We report the effect of silver (Ag)-buffer layer Indium-Tin-Oxide (ITO) film on a polyethylene terephthalate substrate on the electrical, optical and reliable properties for transparent–flexible displays. The electrical and optical characteristics of an ITO-only film and an Ag-layer-inserted ITO film are measured and compared to assess the applicability of the triple layered structure in flexible displays. The sheet resistance, the resistivity and the light transmittance of the ITO-only film were 400 Ω/sq, 1.33 × 10 −3 Ω-cm and 99.2%, while those of the ITO film inserted with a 10 nm thick Ag layer were 165 Ω/sq, 4.78 × 10 −4 Ω-cm and about 97%, respectively. To evaluate the mechanical reliability of the different ITO films, bending tests were carried out. After the dynamic bending test of 900 cycles, the sheet resistance of the ITO film inserted with the Ag layer changed from 154 Ω/sq to 475 Ω/sq, about a 3-time increase but that of the ITO-only film changed from 400 Ω/sq to 61,986 Ω/sq, about 150-time increase. When the radius is changed from 25 mm to 20 mm in the static bending test, the sheet resistance of the ITO-only film changed from 400 to 678.3 linearly whereas that of the Ag-layer inserted ITO film changed a little from 154.4 to 154.9. These results show that Ag-layer inserted ITO film had better mechanical characteristics than the ITO-only film. - Highlights: ► Transparent flexible electrode fabricated on glass substrate. ► Electrode fabricated using vertically-patterned design on glass substrate. ► Optimization of the vertical patterns ► Application of the vertically-patterned electrode in transparent–flexible electronics

  10. Problems of selectivity in liquid-phase oxidation

    Emanuel, N M

    1978-07-01

    Based on a kinetic analysis of a generalized scheme for radical-chain process and on published experimental results, factors determining the selectivities of various liquid-phase oxidations of organic compounds are examined, including the kinetic chain length, molecular and chain decomposition of products, and competing routes in the initiated oxidation or autoxidation of hydrocarbons to peroxides. Also discussed are selective inhibition of undesirable routes in chain reactions, e.g., styrene and acetaldehyde co-oxidation; activation of molecular oxygen by variable-valence metal compounds used as homogeneous catalysts; modeling of fermentative processes by oxidation of hydrocarbons in complex catalytic systems, e.g., hydroxylation of alkanes, epoxidation or carbonylation of olefins, or oxidation of alcohols and ketones to acids; and the mechanisms of heterogeneous catalysis in liquid-phase reactions, e.g., oxidation of alkylaromatic hydrocarbons to peroxides and co-oxidation of propylene and acetaldehyde.

  11. Compact Chemical Monitor for Silver Ions in Spacecraft Water Systems, Phase I

    National Aeronautics and Space Administration — NASA has identified silver ions as the best candidate biocide for use in the potable water system on next-generation spacecraft. Though significant work has been...

  12. Influence of daylight on the fate of silver and zinc oxide nanoparticles in natural aquatic environments.

    Odzak, Niksa; Kistler, David; Sigg, Laura

    2017-07-01

    Nanoparticles, such as silver (Ag-NP) and zinc oxide (ZnO-NP), are increasingly used in many consumer products. These nanoparticles (NPs) will likely be exposed to the aquatic environment (rain, river, lake water) and to light (visible and UV) in the products where they are applied, or after those products are discharged. Dissolution of Ag-NP and ZnO-NP is an important process because the dissolved Ag + and Zn 2+ are readily available and toxic for aquatic organisms. The objective of this study was to investigate the role of daylight (UV and visible) for the fate of engineered Ag-NP and ZnO-NPs in different types of natural waters. Ag-NP and ZnO-NP were exposed to rainwater, river Rhine, and lake waters (Greifen, Lucerne, Cristallina, Gruère) under different light conditions (no light, UV 300-400 nm and visible light 400-700 nm) for up to 8 days. Stronger agglomeration of Ag-NP was observed in the waters with higher ionic strength in comparison to those with lower ionic strength. Visible light tended to increase the dissolution of Ag-NP under most natural water conditions in comparison to dark conditions, whereas UV-light led to decreased dissolved Ag + after longer exposure time. These effects illustrate the dynamic interactions of Ag-NP with light, which may lead both to increased oxidation and to increased reduction of Ag + by organic compounds under UV-light. In the case of ZnO-NP, agglomeration occurred at higher ionic strength, but the effects of pH were predominant for dissolution, which occurred up to concentrations close to the solubility limit of ZnO(s) at pH around 8.2 and to nearly complete dissolution of ZnO-NP at lower pH (pH 4.8-6.5), with both visible and UV-light facilitating dissolution. This study thus shows that light conditions play an important role in the dissolution processes of nanoparticles. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Electrochemical preparation of new uranium oxide phases

    Smolenskij, V.V.; Lyalyushkin, N.V.; Bove, A.L.; Komarov, V.K.; Kapshukov, I.I.

    1992-01-01

    Behaviour of uranium ions in oxidation states 3+ and 4+ in molten chlorides of alkali metals in the temperature range of 700-900 degC in the atmosphere of an inert gas was studied by the method of cyclic voltametry. It is shown that as a result of introduction of crystal uranium dioxide into the salt melt formation of uranium oxide ions of the composition UO + and UO 2+ occurs, the ions participating in electrode reactions and bringing about formation of the following uranium oxides on the cathode: UO and, presumably, U 3 O 4 . Oxides UO and U 3 O 4 are thermodynamically unstable at low temperatures and decompose into uranium oxide of the composition UO 2-x , where x varies from 0 to 0.05, and metal uranium

  14. Phase Transformation of Hot Dipped Aluminium during High Temperature Oxidation

    Zaifol Samsu; Muhammad Daud; Hishamuddin Husain; Mohd Saari Ripin; Rusni Rejab; Zaiton Selamat; Mohd Shariff Sattar

    2014-01-01

    Low alloy carbon steel was coated by hot-dipping into a molten aluminum bath. Isothermal oxidations were carried out at 750 degree Celsius in static air to study the oxidation behaviour of the hot-dipped aluminide steel. The phase transformation in the aluminide layer during diffusion at 750 degree Celsius in static air was analyzed by SEM-EDX and XRD. After hot-dip treatment, the coating layers consisted of three phases, where Al, thinner layer of FeAl 3 , and thicker layer of Fe 2 Al 5 were detected from external topcoat to the aluminide/ steel substrate. After oxidation, the Fe 2 Al 5 formed during the immersion process completely transformed to Fe 2 Al 5 , FeAl 2 , FeAl and Al-Fe(Al) phases because of the composition gradient and the chemical diffusion by oxidation. After oxidation, there are some voids were found at the coating/ substrate interface due to the rapid inter-diffusion of iron and aluminium during oxidation. The FeAl phase kept growing with increasing exposure time at 750 degree Celsius, while the Fe 2 Al 5 was consumed during oxidation. After 168 hrs oxidation, the Fe 2 Al 5 phase was going disappeared as the aluminum layer was consumed. (author)

  15. Silver Vanadium Phosphorous Oxide, Ag(2)VO(2)PO(4): Chimie Douce Preparation and Resulting Lithium Cell Electrochemistry.

    Kim, Young Jin; Marschilok, Amy C; Takeuchi, Kenneth J; Takeuchi, Esther S

    2011-08-15

    Recently, we have shown silver vanadium phosphorous oxide (Ag(2)VO(2)PO(4), SVPO) to be a promising cathode material for lithium based batteries. Whereas the first reported preparation of SVPO employed an elevated pressure, hydrothermal approach, we report herein a novel ambient pressure synthesis method to prepare SVPO, where our chimie douce preparation is readily scalable and provides material with a smaller, more consistent particle size and higher surface area relative to SVPO prepared via the hydrothermal method. Lithium electrochemical cells utilizing SVPO cathodes made by our new process show improved power capability under constant current and pulse conditions over cells containing cathode from SVPO prepared via the hydrothermal method.

  16. A new liquid-phase-separation glaze containing neodymium oxide

    Jing, S.; Xianque, C.; Luxing, K.; Pentecost, J.L.

    1986-01-01

    A color-changeable opaque glaze containing neodymium oxide was investigated. Results show that the glaze is a new example of the liquid-phase-separation type. The discrete phase droplets are from 50 to 500 nm in size. They are rich in Nd, Zn, Ca, and Mg and the continuous phase is rich in Si, Al, and K. The concentration of the discrete phase is approx. =45%. The large number of discrete droplets and the zinc oxide in the glaze increase its opacity to cover the selective light absorption and scattering of the neodymium ion and reduce the opalescence effect

  17. Preparation of silver-cuprous oxide/stearic acid composite coating with superhydrophobicity on copper substrate and evaluation of its friction-reducing and anticorrosion abilities

    Li, Peipei [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Chen, Xinhua [College of Chemistry and Chemical Engineering, Xuchang University, Xuchang 461000 (China); Yang, Guangbin; Yu, Laigui [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Zhang, Pingyu, E-mail: pingyu@henu.edu.cn [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China)

    2014-01-15

    A simple two-step solution immersion process was combined with surface-modification by stearic acid to prepare superhydrophobic coatings on copper substrates so as to reduce friction coefficient, increase wear resistance and improve the anticorrosion ability of copper. Briefly, cuprous oxide (Cu{sub 2}O) crystal coating with uniform and compact tetrahedron structure was firstly created by immersing copper substrate in 2 mol L{sup −1} NaOH solution. As-obtained Cu{sub 2}O coating was then immersed in 0.33 mmol L{sup −1} AgNO{sub 3} solution to incorporate silver nanoparticles, followed by modification with stearic acid (denoted as SA) coating to achieve hydrophobicity. The surface morphology and chemical composition of silver-cuprous oxide/stearic acid (denoted as Ag-Cu{sub 2}O/SA) composite coating were investigated using a scanning electron microscope and an X-ray photoelectron spectroscope (XPS); and its phase structure was examined with an X-ray diffractometer (XRD). Moreover, the contact angle of water on as-prepared Ag-Cu{sub 2}O/SA composite coating was measured, and its friction-reducing and anticorrosion abilities were evaluated. It was found that as-prepared Ag-Cu{sub 2}O/SA composite coating has a water contact angle of as high as 152.4{sup o} and can provide effective friction-reducing, wear protection and anticorrosion protection for copper substrate, showing great potential for surface-modification of copper.

  18. Resonating Nitrous Oxide Thruster, Phase I

    National Aeronautics and Space Administration — AeroAstro proposes decomposing nitrous oxide (N2O) as an alternative propellant to existing spacecraft propellants. Decomposing N2O can be used as either a high Isp,...

  19. Diffusionless phase transitions and related structures in oxides

    Boulesteix, C.

    1992-01-01

    The relative importance of oxides in the field of materials science has been spectacularly increasing during the last twenty years. First the study of ferroelectrics kept the attention of scientists. Nevertheless this domain is far from being worked out and a lot of new results and of new fields of interest were recently discovered. Other ferroic oxides, especially ferroelastics, have also been the subject of a very great number of new results. In these cases the properties of oxides are at room temperature very tightly related to the phase transition that is generally occurring a few hundred of degrees above this room temperature. In many other cases also properties of oxides can be related to the existence of a phase transition or to a rather similar phenomenon. This book has been specially devoted to the study of the properties of oxides which are in some way related to the existence of a phase transition. The first chapters are focussed on general considerations: the first one is devoted to a general study of phase transitions, the second one to the twinning phenomenon which is of special interest for many oxides. Chapters 3 and 4 are focussed on ferroelectric and ferroelastic materials. These four chapters consitute the first part of the book. Chapters 5 to 8 are devoted to the study of oxides of special interest which have some of their properties related to a phase transition or to a rather similar phenomenon: rare earth oxides, oxides with a diffuse phase transition, zirconia and alumina systems, tungsten oxides and their relatives. These four chapters constitute the second part of the book. (orig.)

  20. Multifunctional silver nanoparticle-doped silica for solid-phase extraction and surface-enhanced Raman scattering detection

    Markina, Natalia E.; Markin, Alexey V.; Zakharevich, Andrey M.; Gorin, Dmitry A.; Rusanova, Tatiana Yu.; Goryacheva, Irina Yu.

    2016-12-01

    Multifunctional silica gel with embedded silver nanoparticles (SiO2-AgNP) is proposed for application as sorbent for solid-phase extraction (SPE) and simultaneously as substrate for surface-enhanced Raman spectroscopy (SERS) due to their high sorption properties and ability to enhance Raman signal (SERS-active sorbents). SiO2-AgNP was synthesized via alkaline hydrolysis of tetraethyl orthosilicate with simultaneous reduction of silver ions to silver nanoparticles (AgNP) within the SiO2 bulk. Synthesis of AgNP directly to the SiO2 matrix enables to exclude any additional stabilizers for the nanoparticles that educes signal-to-noise ratio during SERS measurement. Apart from Raman spectroscopy, obtained sorbents were also characterized by scanning electron microscopy and UV-visible diffuse reflectance spectroscopy. The influence of AgNO3 concentration used during the SiO2-AgNP synthesis on its gelling time, color, diffuse reflectance spectra, and enhancement of Raman signal was investigated. A Raman enhancement factor of SiO2-AgNP with optimal composition was around 105. Finally, the sorbents were applied for SPE and subsequent SERS detection of model compounds (rhodamine 6G and folic acid). It was found that SPE enables to decrease detectable concentrations by two orders. Therefore, SPE combined with SERS has high potential for further analytical investigations.

  1. Multifunctional silver nanoparticle-doped silica for solid-phase extraction and surface-enhanced Raman scattering detection

    Markina, Natalia E.; Markin, Alexey V., E-mail: av-markin@mail.ru; Zakharevich, Andrey M.; Gorin, Dmitry A.; Rusanova, Tatiana Yu.; Goryacheva, Irina Yu. [Saratov State University (Russian Federation)

    2016-12-15

    Multifunctional silica gel with embedded silver nanoparticles (SiO{sub 2}–AgNP) is proposed for application as sorbent for solid-phase extraction (SPE) and simultaneously as substrate for surface-enhanced Raman spectroscopy (SERS) due to their high sorption properties and ability to enhance Raman signal (SERS-active sorbents). SiO{sub 2}–AgNP was synthesized via alkaline hydrolysis of tetraethyl orthosilicate with simultaneous reduction of silver ions to silver nanoparticles (AgNP) within the SiO{sub 2} bulk. Synthesis of AgNP directly to the SiO{sub 2} matrix enables to exclude any additional stabilizers for the nanoparticles that educes signal-to-noise ratio during SERS measurement. Apart from Raman spectroscopy, obtained sorbents were also characterized by scanning electron microscopy and UV-visible diffuse reflectance spectroscopy. The influence of AgNO{sub 3} concentration used during the SiO{sub 2}–AgNP synthesis on its gelling time, color, diffuse reflectance spectra, and enhancement of Raman signal was investigated. A Raman enhancement factor of SiO{sub 2}–AgNP with optimal composition was around 10{sup 5}. Finally, the sorbents were applied for SPE and subsequent SERS detection of model compounds (rhodamine 6G and folic acid). It was found that SPE enables to decrease detectable concentrations by two orders. Therefore, SPE combined with SERS has high potential for further analytical investigations.

  2. Zinc oxide nanotubes decorated with silver nanoparticles as an ultrasensitive substrate for surface-enhanced Raman scattering

    Gao, M.; Feng, B.; Sun, Y.; Xing, G.; Li, S.; Yang, J.; Yang, L.; Zhang, Y.; Liu, H.; Fan, H.; Sui, Y.; Zhang, Z.; Liu, S.; Song, H.

    2012-01-01

    We report on the fabrication of a highly aligned silver-decorated array of zinc oxide nanotubes for use in surface-enhanced Raman spectroscopy (SERS). The ZnO nanotube array was first prepared by chemical etching, and the silver nanoparticles (AgNPs) were then deposited on their surface by magnetron sputtering. Such ZnO/Ag hybrid structures are shown to act as SERS-active substrates with remarkable sensitivity. The enhancement factor can be as high as 10 5 when using 4-mercaptopyridine in solution as a SERS probe. The synergistic combination between SERS 'hot spots' and the formation of an interfacial electric field between the zinc oxide nanotubes and the AgNPs in our opinion contribute to the high sensitivity. The relative standard deviations of signal intensities for the major SERS peaks are <7 %. This demonstrates that the optimized ZnO/Ag hybrid represents an excellent SERS substrate that may be used in trace analysis and ultrasensitive molecular sensing. (author)

  3. Measurement of Nitrate Concentration in Aqueous Media Using an Electrochemical Nanosensor Based on Silver Nanoparticles-Nanocellulose/Graphene Oxide

    Majid Shadfar

    2017-11-01

    Full Text Available Nitrate pollution is at the forefront of groundwater contamination which poses serious environmental and public health hazards.  Nitrate is usually released in solution from agricultural activities and finds its way into groundwater resources. The objective of the present study was to determine, accurately concentrations of nitrate ions in water samples from the environment using sensitive electrochemical methods. For this purpose, a modified glassy carbon electrode modified with a nanocomposite consisting of silver nanoparticles, nanocellulose, and graphene oxide (Ag/NC/GO-GCE was used. The characterization of the nanocomposite was investigated using scanning electron microscope (SEM, X-Ray diffraction (XRD, and electrochemical impedance spectroscopy (EIS. The modified Ag/NC/GO-GCE electrode was used as nanosensor for the electrocatalytic determination of nitrate using the voltammetric method. The effects of the parameters of scan rate, pH, and different nitrate concentrations were studied and the optimum conditions were obtained. A limit of detection of 0.016 µM (S/N=3 was found in the linear range of 0.005 to 10 mM nitrate. The Ag/NC/GO-GCE electrode exhibited a synergistic effect toward voltammetric determination of nitrate in the presence of graphene oxide, nanocellulose, and silver nanocatalyst. The nanosensor developed here showed excellent sensitivity, selectivity, and stability toward nitrate determination in aqueous solutions without any significant interference.

  4. Liquid phase oxidation chemistry in continuous-flow microreactors.

    Gemoets, Hannes P L; Su, Yuanhai; Shang, Minjing; Hessel, Volker; Luque, Rafael; Noël, Timothy

    2016-01-07

    Continuous-flow liquid phase oxidation chemistry in microreactors receives a lot of attention as the reactor provides enhanced heat and mass transfer characteristics, safe use of hazardous oxidants, high interfacial areas, and scale-up potential. In this review, an up-to-date overview of both technological and chemical aspects of liquid phase oxidation chemistry in continuous-flow microreactors is given. A description of mass and heat transfer phenomena is provided and fundamental principles are deduced which can be used to make a judicious choice for a suitable reactor. In addition, the safety aspects of continuous-flow technology are discussed. Next, oxidation chemistry in flow is discussed, including the use of oxygen, hydrogen peroxide, ozone and other oxidants in flow. Finally, the scale-up potential for continuous-flow reactors is described.

  5. l-Cysteine-modified silver-functionalized silica-based material as an efficient solid-phase extraction adsorbent for the determination of bisphenol A.

    Li, Yuanyuan; Zhu, Nan; Li, Bingxiang; Chen, Tong; Ma, Yulong; Li, Qiang

    2018-02-01

    A new silver-functionalized silica-based material with a core-shell structure based on silver nanoparticle-coated silica spheres was synthesized, and silver nanoparticles were modified using strongly bound l-cysteine. l-Cysteine-silver@silica was characterized by scanning electron microscopy and FTIR spectroscopy. Then, a solid-phase extraction method based on l-cysteine-silver@silica was developed and successfully used for bisphenol A determination prior to HPLC analysis. The results showed that the l-cysteine-silver@silica as an adsorbent exhibited good enrichment capability for bisphenol A, and the maximum adsorption saturation was 20.93 mg/g. Moreover, a short adsorption equilibrium time was obtained due to the presence of silver nanoparticles on the surface of the silica. The extraction efficiencies were then optimized by varying the eluents and pH. Under the optimized conditions, good linearity for bisphenol A was obtained in the range from 0.4 to 4.0 μM (R 2  > 0.99) with a low limit of detection (1.15 ng/mL). The spiked recoveries from tap water and milk samples were satisfactory (85-102%) with relative standard deviations below 5.2% (n = 3), which indicated that the method was suitable for the analysis of bisphenol A in complex samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Gas phase chemistry of N-benzylbenzamides with silver(I) cations: characterization of benzylsilver cation.

    Sun, Hezhi; Jin, Zhe; Quan, Hong; Sun, Cuirong; Pan, Yuanjiang

    2015-03-07

    The benzylsilver cation which emerges from the collisional dissociation of silver(I)-N-benzylbenzamide complexes was characterized by deuterium-labeling experiments, theoretical calculations, breakdown curves and substituent effects. The nucleophilic attack of the carbonyl oxygen on an α-hydrogen results in the generation of the benzylsilver cation, which is competitive to the AgH loss with the α-hydrogen.

  7. The emerging case of nanopollutants in the aquatic environment: analytical challenges for the exposure assessment of silver and zinc oxide nanoparticles

    Thwala, Melusi

    2016-09-01

    Full Text Available of emerging environmental contaminants partly due to limited capability to detect and quantify them in environmental matrices. The current paper presents findings from the exposure assessments of silver and zinc oxide nanoparticles (Ag and ZnO NPs...

  8. Influence of pH and media composition on suspension stability of silver, zinc oxide, and titanium dioxide nanoparticles and immobilization of Daphnia magna under guideline testing conditions

    Cupi, Denisa; Hartmann, Nanna B.; Baun, Anders

    2016-01-01

    sterically stabilized, test suspensions of silver (Ag) ENPs formed large agglomerates in both VS EPA and M7 media; and toxicity was found to be higher in VS EPA medium due to increased dissolution. Low-agglomerate suspensions for zinc oxide (ZnO) could be obtained at pH 7 in VS EPA medium, but the increase...

  9. Evaluation of developmental responses of two crop plants exposed to silver and zinc oxide nanoparticles

    Pokhrel, Lok R. [Department of Environmental Health, College of Public Health, East Tennessee State University, Johnson City, TN 37614–1700 (United States); Dubey, Brajesh, E-mail: bdubey@uoguelph.ca [Environmental Engineering, School of Engineering, University of Guelph, 50 Stone Road East, Guelph, Ontario (Canada)

    2013-05-01

    The increasing applications of different nanomaterials in the myriad of nano-enabled products and their potential for leaching have raised considerable environmental, health and safety (EHS) concerns. As systematic studies investigating potential anomalies in the morphology and anatomy of crop plants are scarce, herein we report on the developmental responses of two agriculturally significant crop plants, maize (Zea mays L.) and cabbage (Brassica oleracea var. capitata L.), upon in vitro exposure to nanoparticles of citrate-coated silver (Citrate–nAg) and zinc oxide (nZnO). Analyses involve histology of the primary root morphology and anatomy using light microscopy, metal biouptake, moisture content, rate of germination, and root elongation. Comparative toxicity profiles of the ionic salts (AgNO{sub 3} and ZnSO{sub 4}) are developed. Notably, we uncover structural changes in maize primary root cells upon exposure to Citrate–nAg, nZnO, AgNO{sub 3}, and ZnSO{sub 4}, possibly due to metal biouptake, suggesting potential for functional impairments in the plant growth and development. Citrate–nAg exposure results in lower Ag biouptake compared to AgNO{sub 3} treatment in maize. Microscopic evidence reveals ‘tunneling-like effect’ with nZnO treatment, while exposure to AgNO{sub 3} leads to cell erosion in maize root apical meristem. In maize, a significant change in metaxylem count is evident with Citrate–nAg, AgNO{sub 3}, and ZnSO{sub 4} treatment, but not with nZnO treatment (p > 0.1). In both maize and cabbage, measures of germination and root elongation reveal lower nanoparticle toxicity compared to free ions. As moisture data do not support osmotically-induced water stress hypothesis for explaining toxicity, we discuss other proximate mechanisms including the potential role of growth hormones and transcription factors. These findings highlight previously overlooked, anatomically significant effects of metal nanoparticles, and recommend considering

  10. A novel electro analytical nanosensor based on graphene oxide/silver nanoparticles for simultaneous determination of quercetin and morin

    Yola, Mehmet Lütfi; Gupta, Vinod Kumar; Eren, Tanju; Şen, Arif Emre; Atar, Necip

    2014-01-01

    Graphical abstract: - Abstract: In this report, silver nanoparticles (AgNPs) with the mean diameters of 10-30 nm were self-assembled onto the surfaces of 2-aminoethanethiol (2-AET) functionalized graphene oxide (AETGO) sheets. The graphene oxide (GO) and AgNPs-AETGO nanocomposites were characterized by a transmission electron microscope (TEM), x-ray photoelectron spectroscopy (XPS), reflection–absorption infrared spectroscopy (RAIRS) and the x-ray diffraction (XRD). The simultaneous determination of quercetin (QR) and morin (MR) has been performed on glassy carbon electrode (GCE) modified with AgNPs-AETGO (AgNPs-AETGO/GCE). QR presented an oxidation step at Ea of 200 mV and reduction step at Ec of 150 mV and RT presented an oxidation step at Ea of 600 mV at AgNPs-AETGO/GCE by cyclic voltammetry (CV). The linearity ranges and the detection limits of QR and MR were 1.0 × 10-8 - 5.0 × 10-6 M and 3.3 × 10-9 M, respectively. The AgNPs-AETGO/GCE was also applied to real samples for the simultaneous determination of QR and MR. Thus the developed method can be adopted as an alternative to the published chromatographic, spectrophotometric and electroanalytical methods for simultaneous determination of QR and MR

  11. Effect of metallic silver nanoparticles on the alignment and relaxation behaviour of liquid crystalline material in smectic C* phase

    Vimal, Tripti; Kumar Gupta, Swadesh; Katiyar, Rohit; Srivastava, Atul; Czerwinski, Michal; Krup, Katarzyna; Kumar, Sandeep; Manohar, Rajiv

    2017-09-01

    The influence of silver nanoparticles dispersed in a Ferroelectric Liquid Crystal (FLC) on the properties of the resultant composite system has been investigated by thermal, electro-optical, and dielectric methods. We show that the concentration of thiol capped silver nanoparticles is a critical factor in governing the alignment of nanoparticles (NPs) in the host FLC. The orientation of NPs in composite samples affects the ordering of the LC (Liquid Crystal) phase and consequently changes the various phase transition temperatures of the host LC. Formation of self-assembled 2D (two dimensional) arrays of nanoparticles is observed for high concentration of dopant in the LC, oriented perpendicular to the direction of rubbing. We propose that the molecular interaction between the thiol capped NPs and LC molecules is the key factor behind such an arrangement of NPs. Orientation of NPs has affected the relaxation behaviour and various other material parameters, significantly. A noteworthy change in DC conductivity articulates our proposed idea of the formation of 2D array of NPs perpendicular to the direction of rubbing. This comprehensive study endorses the importance of dopant concentration in modifying the properties of the host LC material.

  12. Initial oxidation of silver surfaces by S2-and S4+ species

    Kleber, Ch.; Wiesinger, R.; Schnoeller, J.; Hilfrich, U.; Hutter, H.; Schreiner, M.

    2008-01-01

    Silver has been exposed to each of the sulphurous gases under the influence of different humidity contents in the ambient atmosphere and in the presence and absence of aerial oxygen. The samples were investigated by means of in situ quartz crystal microbalance (QCM), tapping-mode atomic force microscopy (TM-AFM) and time of flight secondary ion mass spectrometry (TOF-SIMS) which enables to characterize the corrosion layer formed, the morphology and the chemical structure of the weathered surfaces. The investigations revealed that sulfidation by both gases is strongly dependent on the relative humidity (% RH) content and the aerial oxygen content in the ambient atmosphere. The results obtained are used to suggest new mechanisms for the sulfidation of silver surfaces exposed to humidified atmospheres with addition of SO 2 and H 2 S, respectively

  13. Novel electrospun polyvinylidene fluoride-graphene oxide-silver nanocomposite membranes with protein and bacterial antifouling characteristics

    C. Liu

    2018-04-01

    Full Text Available We developed and fabricated novel polyvinylidene fluoride (PVDF-(0.5–2%Ag and PVDF-(0.5–2%Ag-1% graphene oxide (GO nanocomposite membranes with antifouling properties through electrospinning. Silver nanoparticles (AgNPs were in situ synthesized from silver nitrate precursor directly. The tensile properties, wetting, antifouling characteristics of pristine PVDF and its nanocomposite membranes were studied. Tensile tests showed that the addition of 0.5–2% AgNPs to PVDF improves its elastic modulus and tensile strength markedly. A further increase in both tensile modulus and strength of PVDF were obtained by hybridizing AgNPs with 1% GO. Water contact angle measurements revealed that the incorporation of AgNPs or AgNPs/GO nanofillers into PVDF decreases its degree of hydrophobicity. This led to the nanocomposite membranes having higher water flux permeation. In addition, AgNPs and AgNPs/GO fillers played a crucial role against protein and bacterial fouling of the resulting composite membranes. The antibacterial activities of electrospun nanocomposite membranes were assessed against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. On the basis of water contact angle, water permeation flux and antifouling results, electrospun PVDF-2% Ag-GO composite membrane was found to exhibit excellent filtration performance, protein antifouling and bactericidal activities. Thus such a fibrous nanocomposite is considered as a high-potential membrane for water purification and disinfection applications.

  14. Enhanced antibacterial activity of silver-decorated sandwich-like mesoporous silica/reduced graphene oxide nanosheets through photothermal effect

    Liu, Rong; Wang, Xuandong; Ye, Jun; Xue, Ximei; Zhang, Fangrong; Zhang, Huicong; Hou, Xuemei; Liu, Xiaolong; Zhang, Yun

    2018-03-01

    Drug resistance of bacteria has become a global health problem, as it makes conventional antibiotics less efficient. It is urgently needed to explore novel antibacterial materials and develop effective treatment strategies to overcome the drug resistance of antibiotics. Herein, we successfully synthesized silver decorated sandwich-like mesoporous silica/reduced graphene oxide nanosheets (rGO/MSN/Ag) as a novel antibacterial material through facile method. The rGO and Ag nanoparticles can be reduced in the reaction system without adding any other reductants. In addition, the rGO/MSN/Ag showed higher photothermal conversion capacity due to the modification of silver nanoparticles and exhibited excellent antibacterial activities against Pseudomonas putida, Escherichia coli and Rhodococcus at relatively low dosages, which was confirmed by the minimum inhibitory concentration (MIC) test. Meanwhile, the E. coli with a high concentration was selected for exposure using an 808 nm laser, and the antibacterial effect was obviously enhanced by the near-infrared irradiation induced photothermal effect. Moreover, the hepatocyte LO2 were used for the cytotoxicity evaluation, and the rGO/MSN/Ag showed low toxicity and were without detectable cytotoxicity at the antimicrobial dose. As the prepared rGO/MSN/Ag nanosheets have the advantages of low-cost and high antibacterial activity, they might be of promising and useful antibacterial agents for different applications.

  15. Silver nanoparticle induced cytotoxicity, oxidative stress, and DNA damage in CHO cells

    Awasthi, Kumud Kant [University of Rajasthan, Department of Zoology (India); Awasthi, Anjali; Kumar, Narender; Roy, Partha [Indian Institute of Technology Roorkee, Department of Biotechnology (India); Awasthi, Kamlendra, E-mail: kamlendra.awasthi@gmail.com [Malaviya National Institute of Technology, Department of Physics (India); John, P. J., E-mail: placheriljohn@yahoo.com [University of Rajasthan, Department of Zoology (India)

    2013-09-15

    Silver nanoparticles (Ag NPs) are being used increasingly in wound dressings, catheters, and in various household products due to their antimicrobial activity. The present study reports the toxicity evaluation of synthesized and well characterized Ag NPs using Chinese hamster ovary (CHO) cells. The UV-Vis spectroscopy reveals the formation of silver nanoparticles by exhibiting the typical surface plasmon absorption maxima at 408-410 nm. Transmission electron microscopy (TEM) reveals that the average diameter of silver nanoparticles is about 5.0 {+-} 1.0 nm and that they have spherical shape. Cell visibility and cell viability percentage show dose-dependent cellular toxicity of Ag NPs. The half maximal inhibitory concentration (IC{sub 50}) for CHO cells is 68.0 {+-} 2.65 {mu}g/ml after 24 h Ag NPs exposure. Toxicity evaluations, including cellular morphology, mitochondrial function (MTT assay), reactive oxygen species (ROS), and DNA fragmentation assay (Ladder pattern) were assessed in unexposed CHO cells (control) and the cells exposed to Ag NPs concentrations of 15, 30, and 60 {mu}g/ml for 24 h. The findings may assist in the designing of Ag NPs for various applications and provide insights into their toxicity.

  16. Zirconium metal-water oxidation kinetics. III. Oxygen diffusion in oxide and alpha Zircaloy phases

    Pawel, R.E.

    1976-10-01

    The reaction of Zircaloy in steam at elevated temperature involves the growth of discrete layers of oxide and oxygen-rich alpha Zircaloy from the parent beta phase. The multiphase, moving boundary diffusion problem involved is encountered in a number of important reaction schemes in addition to that of Zircaloy-oxygen and can be completely (albeitly ideally) characterized through an appropriate model in terms of oxygen diffusion coefficients and equilibrium concentrations for the various phases. Conversely, kinetic data for phase growth and total oxygen consumption rates can be used to compute diffusion coefficients. Equations are developed that express the oxygen diffusion coefficients in the oxide and alpha phases in terms of the reaction rate constants and equilibrium solubility values. These equations were applied to recent experimental kinetic data on the steam oxidation of Zircaloy-4 to determine the effective oxygen diffusion coefficients in these phases over the temperature range 1000--1500 0 C

  17. Nanotechnology in plant disease management: DNA-directed silver nanoparticles on graphene oxide as an antibacterial against Xanthomonas perforans.

    Ocsoy, Ismail; Paret, Mathews L; Ocsoy, Muserref Arslan; Kunwar, Sanju; Chen, Tao; You, Mingxu; Tan, Weihong

    2013-10-22

    Bacterial spot caused by Xanthomonas perforans is a major disease of tomatoes, leading to reduction in production by 10-50%. While copper (Cu)-based bactericides have been used for disease management, most of the X. perforans strains isolated from tomatoes in Florida and other locations worldwide are Cu-resistant. We have developed DNA-directed silver (Ag) nanoparticles (NPs) grown on graphene oxide (GO). These Ag@dsDNA@GO composites effectively decrease X. perforans cell viability in culture and on plants. At the very low concentration of 16 ppm of Ag@dsDNA@GO, composites show excellent antibacterial capability in culture with significant advantages in improved stability, enhanced antibacterial activity, and stronger adsorption properties. Application of Ag@dsDNA@GO at 100 ppm on tomato transplants in a greenhouse experiment significantly reduced the severity of bacterial spot disease compared to untreated plants, giving results similar to those of the current grower standard treatment, with no phytotoxicity.

  18. Structural, electronic and optical properties of silver delafossite oxides: A first-principles study with hybrid functional

    Kumar, Mukesh; Persson, Clas

    2013-01-01

    Ternary delafossite compounds are potential materials for optoelectronic devices. Employing a first-principles method, we calculate the structural, electronic, and optical properties of the silver based compounds AgMO 2 (M=Al, Ga or In), which crystallize in delafossite structure. Our calculations show that these AgMO 2 oxides have indirect band gaps and the gap energies are in the region of 1.6–3.0 eV whereas, the lowest direct band gap energies are estimated in the range of 2.6–4.3 eV. Furthermore, we find that AgMO 2 compounds exhibit a strong anisotropy for the dielectric function and absorption spectra. The absorption onset for these compounds occurs well above the band gap energies. Overall, we show that the hybrid functional improves the lattice parameters and band gap energies and the calculated values are in good agreement with the experimental values

  19. Amperometric detection and electrochemical oxidation of aliphatic amines and ammonia on silver-lead oxide thin-film electrodes

    Ge, Jisheng [Iowa State Univ., Ames, IA (United States)

    1996-01-08

    This thesis comprises three parts: Electrocatalysis of anodic oxygen-transfer reactions: aliphatic amines at mixed Ag-Pb oxide thin-film electrodes; oxidation of ammonia at anodized Ag-Pb eutectic alloy electrodes; and temperature effects on oxidation of ethylamine, alanine, and aquated ammonia.

  20. A novel non-enzymatic H{sub 2}O{sub 2} sensor based on polypyrrole nanofibers–silver nanoparticles decorated reduced graphene oxide nano composites

    Moozarm Nia, Pooria, E-mail: pooriamn@yahoo.com; Lorestani, Farnaz, E-mail: farnaz.lorestani@siswa.um.edu.my; Meng, Woi Pei, E-mail: pmwoi@um.edu.my; Alias, Y., E-mail: yatimah70@um.edu.my

    2015-03-30

    Graphical abstract: - Highlights: • Decorating silver nanoparticles on the surface of graphene oxide nanocomposites. • Using and comparing two different electrochemical methods for reducing graphene oxide. • Investigating the effect of cyclic voltammetry and amperometry on electropolymerization of polypyrrole nanofibers. • The senor shows superior performances (LOD, LOQ, selectivity, repeatability, reproducibility and stability) towards H{sub 2}O{sub 2}. - Abstract: Graphene oxide (GO) decorated with silver nanoparticles (AgNPs), was electrochemically reduced on glassy carbon electrode (GCE) by an amperometry method (AMP-AgNPs-rGO/GCE). Then, Pyrrole was electropolymerized on the surface of the modified electrode through amperometry process in order to obtain nanofibers of polypyrrole (AMP-PpyNFs-AgNPs-rGO). Fourier-transform infrared transmission spectroscopy and X-ray diffraction approved that during the amperometry process, the GO and Ppy nanofibers were reduced and polymerized respectively and the silver nanoparticles were formed. Field emission scanning electron microscope images indicated that the silver nanoparticles were homogeneously distributed on the rGO surface with a narrow nano size distribution and polypyrrole synthesized in the form of nanofibers with diameter around 100 nm. The first linear section was in the range of 0.1–5 mM with a limit of detection of 1.099 and the second linear section raised to 90 mM with a correlation factor of 0.085 (S/N of 3)

  1. A novel non-enzymatic H2O2 sensor based on polypyrrole nanofibers–silver nanoparticles decorated reduced graphene oxide nano composites

    Moozarm Nia, Pooria; Lorestani, Farnaz; Meng, Woi Pei; Alias, Y.

    2015-01-01

    Graphical abstract: - Highlights: • Decorating silver nanoparticles on the surface of graphene oxide nanocomposites. • Using and comparing two different electrochemical methods for reducing graphene oxide. • Investigating the effect of cyclic voltammetry and amperometry on electropolymerization of polypyrrole nanofibers. • The senor shows superior performances (LOD, LOQ, selectivity, repeatability, reproducibility and stability) towards H 2 O 2 . - Abstract: Graphene oxide (GO) decorated with silver nanoparticles (AgNPs), was electrochemically reduced on glassy carbon electrode (GCE) by an amperometry method (AMP-AgNPs-rGO/GCE). Then, Pyrrole was electropolymerized on the surface of the modified electrode through amperometry process in order to obtain nanofibers of polypyrrole (AMP-PpyNFs-AgNPs-rGO). Fourier-transform infrared transmission spectroscopy and X-ray diffraction approved that during the amperometry process, the GO and Ppy nanofibers were reduced and polymerized respectively and the silver nanoparticles were formed. Field emission scanning electron microscope images indicated that the silver nanoparticles were homogeneously distributed on the rGO surface with a narrow nano size distribution and polypyrrole synthesized in the form of nanofibers with diameter around 100 nm. The first linear section was in the range of 0.1–5 mM with a limit of detection of 1.099 and the second linear section raised to 90 mM with a correlation factor of 0.085 (S/N of 3)

  2. Studies on the electrical properties of reactive DC magnetron-sputtered indium-doped silver oxide thin films: The role of oxygen

    Subrahmanyam, A [Semiconductor Physics Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Barik, Ullash Kumar [Semiconductor Physics Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)

    2007-03-15

    Indium ({approx}10 at.%)-doped silver oxide (AIO) thin films have been prepared on glass substrates at room temperature (300 K) by reactive DC magnetron sputtering technique using an alloy target made of pure (99.99%) silver and indium (90:10 at.%) metals. The oxygen flow rates have been varied in the range 0.00-3.44 sccm during sputtering. The X-ray diffraction data on these indium-doped silver oxide films show polycrystalline nature. With increasing oxygen flow rate, the carrier concentration, the Hall mobility and the electron mean free path decrease. These films show a very low positive temperature coefficient of resistivity {approx}3.40x10{sup -8} ohm-cm/K. The work function values for these films (measured by Kelvin probe technique) are in the range 4.81-5.07 eV. The high electrical resistivity indicate that the films are in the island state (size effects). Calculations of the partial ionic charge (by Sanderson's theory) show that indium doping in silver oxide thin films enhance the ionicity.

  3. Studies on the electrical properties of reactive DC magnetron-sputtered indium-doped silver oxide thin films: The role of oxygen

    Subrahmanyam, A.; Barik, Ullash Kumar

    2007-01-01

    Indium (∼10 at.%)-doped silver oxide (AIO) thin films have been prepared on glass substrates at room temperature (300 K) by reactive DC magnetron sputtering technique using an alloy target made of pure (99.99%) silver and indium (90:10 at.%) metals. The oxygen flow rates have been varied in the range 0.00-3.44 sccm during sputtering. The X-ray diffraction data on these indium-doped silver oxide films show polycrystalline nature. With increasing oxygen flow rate, the carrier concentration, the Hall mobility and the electron mean free path decrease. These films show a very low positive temperature coefficient of resistivity ∼3.40x10 -8 ohm-cm/K. The work function values for these films (measured by Kelvin probe technique) are in the range 4.81-5.07 eV. The high electrical resistivity indicate that the films are in the island state (size effects). Calculations of the partial ionic charge (by Sanderson's theory) show that indium doping in silver oxide thin films enhance the ionicity

  4. Zinc oxide and silver nanoparticles influence the antioxidative status in a higher aquatic plant, Spirodela punctata

    Thwala, Melusi

    2012-09-01

    Full Text Available during the 14-d exposure. The biochemical anti-oxidative status of the plant specimens were investigated using quantitative analysis of total antioxidant capacity, peroxidase and activity of catalase and superoxide dismutase. The anti-oxidative defence...

  5. A gold electrode modified with silver oxide nanoparticle decorated carbon nanotubes for electrochemical sensing of dissolved ammonia

    Rahman, Mohammed M.; Asiri, Abdullah M.; Balkhoyor, Hasan B.; Marwani, Hadi M.

    2016-01-01

    We have prepared silver oxide nanoparticles with a diameter of ∼ 15 nm and decorated with carbon nanotube nanocomposites (Ag_2O/CNT NCs) by a facile wet chemical method using reducing agents in alkaline medium. These NCs were characterized by UV/vis, FTIR and energy dispersive X-ray spectroscopy, by X-ray powder diffraction and field emission scanning electron microscopy. The NCs were then deposited on a flat gold electrode with the help of a conducting binder to result in an electrochemical sensor for aqueous ammonia using the I-V technique. Response is based on surface oxidation of ammonium hydroxide with electrode-adsorbed oxygen to form nitrogen oxide, these simultaneously liberating free electrons in the conduction band. Sensor features include a sensitivity of 32.856 μA.μM"-"1.cm"-"2, a low detection limit (1.3 pM at a signal to noise ratio of 3), reliability, reproducibility, ease of integration, and long term stability. The response to dissolved ammonia is linear (r"2: 0.9778) over the 0.01 nM to 0.1 mM concentration range. (author)

  6. Solution processed zinc oxide nanopyramid/silver nanowire transparent network films with highly tunable light scattering properties

    Mehra, Saahil

    2013-01-01

    Metal nanowire transparent networks are promising replacements to indium tin oxide (ITO) transparent electrodes for optoelectronic devices. While the transparency and sheet resistance are key metrics for transparent electrode performance, independent control of the film light scattering properties is important to developing multifunctional electrodes for improved photovoltaic absorption. Here we show that controlled incorporation of ZnO nanopyramids into a metal nanowire network film affords independent, highly tunable control of the scattering properties (haze) with minimal effects on the transparency and sheet resistance. Varying the zinc oxide/silver nanostructure ratios prior to spray deposition results in sheet resistances, transmission (600 nm), and haze (600 nm) of 6-30 Ω □-1, 68-86%, and 34-66%, respectively. Incorporation of zinc oxide nanopyramid scattering agents into the conducting nanowire mesh has a negligible effect on mesh connectivity, providing a straightforward method of controlling electrode scattering properties. The decoupling of the film scattering power and electrical characteristics makes these films promising candidates for highly scattering transparent electrodes in optoelectronic devices and can be generalized to other metal nanowire films as well as carbon nanotube transparent electrodes. © 2013 The Royal Society of Chemistry.

  7. High pressure phase transitions in Europous oxide

    Kremser, D.T.

    1982-01-01

    The pressure-volume relationship for EuO was investigated to 630 kilobars at room temperature with a diamond-anvil, high-pressure cell. Volumes were determined by x-ray diffraction; pressures were determined by the ruby R 1 fluorescence method. The preferred interpretation involves normal compression behavior for EuO, initially in the B1 (NaCl-type) structure, to about 280 kilobars. Between approx. =280 and approx. =350 kilobars a region of anomalous compressibility in which the volume drops continuously by approximately 2% is observed. A second-order electronic transition is proposed with the 6s band overlapping with the 4f levels, thereby reducing the volume of EuO without changing the structure. This is not a semiconductor-to-metal transition. In reflected light, this transition is correlated with a subtle and continuous change in color from brown-black to a light brown. The collapsed B1 phase (postelectronic transition) is stable between approx. =350 and approx. =400 kilobars. At about 400 kilobars the collapsed B1 structure transforms to the B2 (CsCl-type) structure, with a zero pressure-volume change of approximately 12 +/- 1.5%

  8. A versatile silver oxide-zinc battery for synchronous orbit and planetary missions

    Schwartz, H. J.; Soltis, D. G.

    1973-01-01

    A new kind of silver-zinc cell has been developed and tested under NASA support which can withstand severe heat sterilization requirements and does not display the traditional life limiting aspect of zinc electrodes - i.e., shape change. These cells could be used on a planetary lander mission which requires wet-stand periods of over a year, a modest number of cycles (400 to 500) and may require dry heat sterilization. The weight advantage of these cells over the traditional nickel-cadmium batteries makes them also an attractive alternative for synchronous orbit service where 400 to 500 cycles would be required over a five-year period.

  9. Polyvinylidene Fluoride Micropore Membranes as Solid-Phase Extraction Disk for Preconcentration of Nanoparticulate Silver in Environmental Waters.

    Zhou, Xiao-Xia; Lai, Yu-Jian; Liu, Rui; Li, Sha-Sha; Xu, Jing-Wen; Liu, Jing-Fu

    2017-12-05

    Efficient separation and preconcentration of trace nanoparticulate silver (NAg) from large-volume environmental waters is a prerequisite for reliable analysis and therefore understanding the environmental processes of silver nanoparticles (AgNPs). Herein, we report the novel use of polyvinylidene fluoride (PVDF) filter membrane for disk-based solid phase extraction (SPE) of NAg in 1 L of water samples with the disk-based SPE system, which consists of a syringe pump and a syringe filter holder to embed the filter membrane. While the PVDF membrane can selectively adsorb NAg in the presence of Ag + , aqueous solution of 2% (m/v) FL-70 is found to efficiently elute NAg. Analysis of NAg is performed following optimization of filter membrane and elution conditions with an enrichment factor of 1000. Additionally, transmission electron microscopy (TEM), UV-vis spectroscopy, and size-exclusion chromatography coupled with ICP-MS (SEC-ICP-MS) analysis showed that the extraction gives rise to no change in NAg size or shape, making this method attractive for practical applications. Furthermore, feasibility of the protocol is verified by applying it to extract NAg in four real waters with recoveries of 62.2-80.2% at 0.056-0.58 μg/L spiked levels. This work will facilitate robust studies of trace NAg transformation and their hazard assessments in the environment.

  10. Formation of tungsten blue oxide and its phase constitution

    Zou, Z.; Wu, E.; Tan, A.; Qian, C.

    1984-01-01

    By means of X-ray diffraction structure analysis, SEM observation, chemical analysis and particle specific surface analysis etc., an investigation was made in order to determine the regularity of tungsten blue oxide formation during reductional calcine process of APT. It was found that the oxygen index (OI) decreased continuously with increasing calcine temperature. The decrease rate of OI variated as the calcine atmosphere being changed, the stronger the reductivity of the atmosphere is, the more OI decreases. The deammonia-dewater process and the phase constitution variation during calcine was studied, some idea for description of phase transformation path was suggested. It was found that the most important parameter affecting phase constitution and transformation is calcine temperature. At the temperature lower than 450 0 C, the main formed phase was ATB, while at higher temperature, the different phase like W/sub 20/O/sub 58/, WO/sub 3/ etc., could be formed by different ways depending on the atmosphere reductivity. The composition and the OI of ATB are changeable. An experiment for some blue oxides reduction at low temperature was carried out. It was found that OI and the constitution of blue oxide strongly affected the particle size of the formed W-powder

  11. Aqueous phase oxidation techniques as an alternative to incineration

    Gray, L.W.; Adamson, M.G.; Hickman, R.G.; Farmer, J.C.; Chiba, Z.; Gregg, D.W.; Wang, F.T.

    1992-03-01

    The Lawrence Livermore National Laboratory (LLNL) has three aqueous phase techniques under development for oxidation of high value or high risk waste steams. One is direct electrochemical oxidation and one is mediated electrochemical oxidation utilizing regenerable, strongly oxidizing cations such as Ag(II), Co (III), Ce(IV), etc. These cations can either attack oxidizable materials directly and/or indirectly via first reacting with water to generate OH radicals which then attack the oxidizable materials. The third system utilizes H 2 O 2 and UV light to generate OH radicals directly which in turn attack the oxidizable materials. All systems have the advantage of a chemical off-switch in that when the power is turned off, the reaction quickly subsides. All systems operate with low concentrations (typically <5 wt %) of oxidizable materials, therefore, the stored energy for possible run-away reactions is very low. 15 figures, 22 references

  12. Laser-induced partial oxidation of cyclohexane in liquid phase

    Oshima, Y.; Wu, X.W.; Koda, S.

    1995-01-01

    A laser-induced partial oxidation of cyclohexane was studied in the liquid phase. With KrF excimer laser (248 nm) irradiation to neat liquid cyclohexane in which O 2 was dissolved, cyclohexanol and cyclohexanone were obtained with very high selectivities, together with cyclohexane as a minor product. Radical recombination reactions to produce dicyclohexyl ether and bicyclohexyl also took place, while these products were not observed in the gas phase reaction. These experimental results were considered to be due not only to higher concentration of cyclohexane but to the cage effect in the liquid phase oxidation. To clarify the reaction progress including the photoabsorption process, the effects of laser intensity and O 2 pressure on product distribution were studied. (author)

  13. Nucleation and characterization of hydroxyapatite on thioglycolic acid-capped reduced graphene oxide/silver nanoparticles in simplified simulated body fluid

    Zhao, Jun; Zhang, Zhaochun, E-mail: zhangzhaochun@shu.edu.cn; Yu, Zhenwei; He, Zhenni; Yang, Shanshan; Jiang, Huiyi

    2014-01-15

    Herein hydroxyapatite (HA) has been synthesized by the nucleation on the surfaces of reduced graphene oxide/silver nanoparticles (rGO/AgNPs) chemisorbed with thioglycolic acid (TGA). The self-assembled monolayer of TGA formed on rGO/AgNPs was immersed in simplified simulated body fluid under gentle growth conditions, forming rGO/AgNPs/TGA/HA biocomposite. The phase structures and functional groups of biocomposite were analyzed by X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Enhanced Raman spectrum of TGA on prepared rGO/AgNPs was obtained with excitation at 633 nm, showing that TGA was chemisorbed on AgNPs through S atom and TGA molecular plane exhibited a tilted orientation with respect to AgNPs. The morphologies of biocomposite were investigated by means of atomic force microscope and transmission electron microscope coupled with energy dispersive spectrum. Analysis shows that the AgNPs uniformly distributed on the rGO nanosheets with the size of about 15–20 nm and HA formation initiated through Ca{sup 2+}-adsorption upon complexation with -COO{sup −} groups of TGA on AgNPs. The results obtained indicated that the rGO/AgNPs/TGA/HA biocomposite may have immense potential application in bone tissue engineering fields for its outstanding and stable activities.

  14. Nucleation and characterization of hydroxyapatite on thioglycolic acid-capped reduced graphene oxide/silver nanoparticles in simplified simulated body fluid

    Zhao, Jun; Zhang, Zhaochun; Yu, Zhenwei; He, Zhenni; Yang, Shanshan; Jiang, Huiyi

    2014-01-01

    Herein hydroxyapatite (HA) has been synthesized by the nucleation on the surfaces of reduced graphene oxide/silver nanoparticles (rGO/AgNPs) chemisorbed with thioglycolic acid (TGA). The self-assembled monolayer of TGA formed on rGO/AgNPs was immersed in simplified simulated body fluid under gentle growth conditions, forming rGO/AgNPs/TGA/HA biocomposite. The phase structures and functional groups of biocomposite were analyzed by X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Enhanced Raman spectrum of TGA on prepared rGO/AgNPs was obtained with excitation at 633 nm, showing that TGA was chemisorbed on AgNPs through S atom and TGA molecular plane exhibited a tilted orientation with respect to AgNPs. The morphologies of biocomposite were investigated by means of atomic force microscope and transmission electron microscope coupled with energy dispersive spectrum. Analysis shows that the AgNPs uniformly distributed on the rGO nanosheets with the size of about 15-20 nm and HA formation initiated through Ca2+-adsorption upon complexation with sbnd COO- groups of TGA on AgNPs. The results obtained indicated that the rGO/AgNPs/TGA/HA biocomposite may have immense potential application in bone tissue engineering fields for its outstanding and stable activities.

  15. Nucleation and characterization of hydroxyapatite on thioglycolic acid-capped reduced graphene oxide/silver nanoparticles in simplified simulated body fluid

    Zhao, Jun; Zhang, Zhaochun; Yu, Zhenwei; He, Zhenni; Yang, Shanshan; Jiang, Huiyi

    2014-01-01

    Herein hydroxyapatite (HA) has been synthesized by the nucleation on the surfaces of reduced graphene oxide/silver nanoparticles (rGO/AgNPs) chemisorbed with thioglycolic acid (TGA). The self-assembled monolayer of TGA formed on rGO/AgNPs was immersed in simplified simulated body fluid under gentle growth conditions, forming rGO/AgNPs/TGA/HA biocomposite. The phase structures and functional groups of biocomposite were analyzed by X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Enhanced Raman spectrum of TGA on prepared rGO/AgNPs was obtained with excitation at 633 nm, showing that TGA was chemisorbed on AgNPs through S atom and TGA molecular plane exhibited a tilted orientation with respect to AgNPs. The morphologies of biocomposite were investigated by means of atomic force microscope and transmission electron microscope coupled with energy dispersive spectrum. Analysis shows that the AgNPs uniformly distributed on the rGO nanosheets with the size of about 15–20 nm and HA formation initiated through Ca 2+ -adsorption upon complexation with -COO − groups of TGA on AgNPs. The results obtained indicated that the rGO/AgNPs/TGA/HA biocomposite may have immense potential application in bone tissue engineering fields for its outstanding and stable activities.

  16. Fabrication of silver nanowires and metal oxide composite transparent electrodes and their application in UV light-emitting diodes

    Yan, Xingzhen; Ma, Jiangang; Xu, Haiyang; Wang, Chunliang; Liu, Yichun

    2016-08-01

    In this paper, we prepared the silver nanowires (AgNWs)/aluminum-doped zinc oxide (AZO) composite transparent conducting electrodes for n-ZnO/p-GaN heterojunction light emitting-diodes (LEDs) by drop casting AgNW networks and subsequent atomic layer deposition (ALD) of AZO at 150 °C. The contact resistances between AgNWs were dramatically reduced by pre-annealing in the vacuum chamber before the ALD of AZO. In this case, AZO works not only as the conformal passivation layer that protects AgNWs from oxidation, but also as the binding material that improves AgNWs adhesion to substrates. Due to the localized surface plasmons (LSPs) of the AgNWs resonant coupling with the ultraviolet (UV) light emission from the LEDs, a higher UV light extracting efficiency is achieved from LEDs with the AgNWs/AZO composite electrodes in comparison with the conventional AZO electrodes. Additionally, the antireflective nature of random AgNW networks in the composite electrodes caused a broad output light angular distribution, which could be of benefit to certain optoelectronic devices like LEDs and solar cells.

  17. Silver nanoparticles in combination with acetic acid and zinc oxide quantum dots for antibacterial activities improvement—A comparative study

    Sedira, Sofiane, E-mail: sofianebilel@gmail.com [Ceramic Laboratory, University of Constantine1, Constantine (Algeria); Ayachi, Ahmed Abdelhakim, E-mail: ayachi-med@hotmail.fr [Ceramic Laboratory, University of Constantine1, Constantine (Algeria); Lakehal, Sihem, E-mail: lakehal.lakehal@gmail.com [Ceramic Laboratory, University of Constantine1, Constantine (Algeria); Fateh, Merouane, E-mail: merouane.fateh@gmail.com [Microbiological Laboratory Engineering and Application, University of Constantine1, Constantine (Algeria); Achour, Slimane, E-mail: achourslimane11@yahoo.fr [Ceramic Laboratory, University of Constantine1, Constantine (Algeria)

    2014-08-30

    Graphical abstract: - Highlights: • Ag NPs and ZnO Qds were synthesized using polyol and hydrothermal method. • Ag NPs exert their bactericidal effect mainly by Ag{sup +} ions. • CH{sub 3}COOH addition to Ag NPs improves bactericidal effect more than ZnO Qds addition. • E. coli and P. aeruginosa are more sensitive to NPs than K. pneumonia and S. aureus. - Abstract: Due to their remarkable antibacterial/antivirus properties, silver nanoparticles (Ag NPs) and zinc oxide quantum dots (ZnO Qds) have been widely used in the antimicrobial field. The mechanism of action of Ag NPs on bacteria was recently studied and it has been proven that Ag NPs exerts their antibacterial activities mainly by the released Ag{sup +}. In this work, Ag NPs and ZnO Qds were synthesized using polyol and hydrothermal method, respectively. It was demonstrated that Ag NPs can be oxidized easily in aqueous solution and the addition of acetic acid can increase the Ag{sup +} release which improves the antibacterial activity of Ag NPs. A comparative study between bactericidal effect of Ag NPs/acetic acid and Ag NPs/ZnO Qds on Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia and Staphylococcus aureus was undertaken using agar diffusion method. The obtained colloids were characterized using UV–vis spectroscopy, Raman spectrometry, X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM)

  18. Silver Nanowire Embedded Colorless Polyimide Heater for Wearable Chemical Sensors: Improved Reversible Reaction Kinetics of Optically Reduced Graphene Oxide.

    Choi, Seon-Jin; Kim, Sang-Joon; Jang, Ji-Soo; Lee, Ji-Hyun; Kim, Il-Doo

    2016-09-14

    Optically reduced graphene oxide (ORGO) sheets are successfully integrated on silver nanowire (Ag NW)-embedded transparent and flexible substrate. As a heating element, Ag NWs are embedded in a colorless polyimide (CPI) film by covering Ag NW networks using polyamic acid and subsequent imidization. Graphene oxide dispersed aqueous solution is drop-coated on the Ag NW-embedded CPI (Ag NW-CPI) film and directly irradiated by intense pulsed light to obtain ORGO sheets. The heat generation property of Ag NW-CPI film is investigated by applying DC voltage, which demonstrates unprecedentedly reliable and stable characteristics even in dynamic bending condition. To demonstrate the potential application in wearable chemical sensors, NO 2 sensing characteristic of ORGO is investigated with respect to the different heating temperature (22.7-71.7 °C) of Ag NW-CPI film. The result reveals that the ORGO sheets exhibit high sensitivity of 2.69% with reversible response/recovery sensing properties and minimal deviation of baseline resistance of around 1% toward NO 2 molecules when the temperature of Ag NW-CPI film is 71.7 °C. This work first demonstrates the improved reversible NO 2 sensing properties of ORGO sheets on flexible and transparent Ag NW-CPI film assisted by Ag NW heating networks. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Preparation of graphene oxide-wrapped carbon sphere@silver spheres for high performance chlorinated phenols sensor

    Gan, Tian, E-mail: gantsjy@163.com [College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000 (China); State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008 (China); Lv, Zhen; Sun, Junyong; Shi, Zhaoxia; Liu, Yanming [College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000 (China)

    2016-01-25

    Highlights: • Hierarchical CS@Ag@GO composite was obtained by a simple solution route. • Signal amplification is achieved for sensitive detection of chlorinated phenols. • The low-cost method exhibits wide concentration range and acceptable accuracy. • The method can be successfully applied to detect chlorinated phenols in waters. - Abstract: A template-activated strategy was developed to construct core/shell structured carbon sphere@silver composite based on one-pot hydrothermal treatment. The CS@Ag possessed a uniform three-dimensional interconnected microstructure with an enlarged surface area and catalytic activity, which was further mechanically protected by graphene oxide (GO) nanolayers to fabricate intriguing configuration, which was beneficial for efficiently preventing the aggregation and oxidation of AgNPs and improving the electrical conductivity through intimate contact. By immobilizing this special material on electrode surface, the CS@Ag@GO was further used for sensitive determination of chlorinated phenols including 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. The tailored structure, fast electron transfer ability and facile preparation of CS@Ag@GO made it a promising electrode material for practical applications in phenols sensing.

  20. Mercury Oxidation via Catalytic Barrier Filters Phase II

    Wayne Seames; Michael Mann; Darrin Muggli; Jason Hrdlicka; Carol Horabik

    2007-09-30

    In 2004, the Department of Energy National Energy Technology Laboratory awarded the University of North Dakota a Phase II University Coal Research grant to explore the feasibility of using barrier filters coated with a catalyst to oxidize elemental mercury in coal combustion flue gas streams. Oxidized mercury is substantially easier to remove than elemental mercury. If successful, this technique has the potential to substantially reduce mercury control costs for those installations that already utilize baghouse barrier filters for particulate removal. Completed in 2004, Phase I of this project successfully met its objectives of screening and assessing the possible feasibility of using catalyst coated barrier filters for the oxidation of vapor phase elemental mercury in coal combustion generated flue gas streams. Completed in September 2007, Phase II of this project successfully met its three objectives. First, an effective coating method for a catalytic barrier filter was found. Second, the effects of a simulated flue gas on the catalysts in a bench-scale reactor were determined. Finally, the performance of the best catalyst was assessed using real flue gas generated by a 19 kW research combustor firing each of three separate coal types.

  1. Silver nanoparticles: green synthesis using Phoenix dactylifera fruit extract, characterization, and anti-oxidant and anti-microbial activities

    Shaikh, Anas Ejaz; Satardekar, Kshitij Vasant; Khan, Rummana Rehman; Tarte, Nanda Amit; Barve, Siddhivinayak Satyasandha

    2018-03-01

    Hydro-alcoholic (2:8 v/v) extract of the pulp of Phoenix dactylifera fruit pulp obtained using Soxhlet extraction (70 °C, 6 h) was found to contain alkaloids, sterols, tannins, flavonoids, cardiac glycosides, proteins, and carbohydrates. An aqueous solution (20% v/v) of the extract led to the synthesis of silver nanoparticles (AgNPs) from 0.01 M AgNO3 solution as confirmed by the surface plasmon resonance at 445 nm determined using UV-visible spectroscopy after 24 h. The synthesized AgNPs were found to be mostly spherical and complexed with phytochemicals from the extract. The size of AgNPs ranged from 12.2-140.2 nm with mean diameter of 47.0 nm as characterized by scanning electron microscopy (SEM). The elemental composition of the AgNPs complexed with the phytochemicals was found to be 80.49% silver (Ag), 15.21% carbon (C), and 4.30% oxygen (O) on a weight basis by energy-dispersive spectroscopy (EDS). Using the α,α-diphenyl-β-picrylhydrazyl (DPPH) assay, an anti-oxidant activity of 89.15% for 1 µg L-1 ultrasonically homogenized ethanolic solution of complexed AgNPs was obtained (equivalent to 0.20 mg mL-1 gallic acid solution), while methanolic solution of plant extract possessed an EC50 value of 3.45% (v/v) (equivalent to 0.11 mg mL-1 gallic acid solution). The plant-nanosilver broth was also found to possess effective anti-microbial activity against Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 6538, and Candida albicans ATCC 10231 as assessed by the disc diffusion assay. However, the plant extract showed negligible anti-microbial activity.

  2. High performance flexible metal oxide/silver nanowire based transparent conductive films by a scalable lamination-assisted solution method

    Hua Yu

    2017-03-01

    Full Text Available Flexible MoO3/silver nanowire (AgNW/MoO3/TiO2/Epoxy electrodes with comparable performance to ITO were fabricated by a scalable solution-processed method with lamination assistance for transparent and conductive applications. Silver nanoparticle-based electrodes were also prepared for comparison. Using a simple spin-coating and lamination-assisted planarization method, a full solution-based approach allows preparation of AgNW-based composite electrodes at temperatures as low as 140 °C. The resulting flexible AgNW-based electrodes exhibit higher transmittance of 82% at 550 nm and lower sheet resistance about 12–15 Ω sq−1, in comparison with the values of 68% and 22–25 Ω sq−1 separately for AgNP based electrodes. Scanning electron microscopy (SEM and Atomic force microscopy (AFM reveals that the multi-stacked metal-oxide layers embedded with the AgNWs possess lower surface roughness (<15 nm. The AgNW/MoO3 composite network could enhance the charge transport and collection efficiency by broadening the lateral conduction range due to the built of an efficient charge transport network with long-sized nanowire. In consideration of the manufacturing cost, the lamination-assisted solution-processed method is cost-effective and scalable, which is desire for large-area fabrication. While in view of the materials cost and comparable performance, this AgNW-based transparent and conductive electrodes is potential as an alternative to ITO for various optoelectronic applications.

  3. Solid-phase vibrational redox reactions in coordinated oxides

    Kostikova, G.P.; Korol'kov, D.V.; Kostikov, Yu.P.

    1996-01-01

    The properties of multicomponent oxides (YBa 2 Cu 3 O 7-x , etc.), incorporating different valency forms of each of two (or more) different elements have been compared with the properties of the known chemical systems, where vibrational (periodic) redox-reactions are realized a fortiori. The essence of the new theoretical concept suggested consists in the following: high-T c superconductivity of the complex oxides and similar compounds originates from vibrational redox reaction proceeding in solid phase and involving different valency atoms of every element

  4. Polypyrrole-silver Nanocomposite: Synthesis and Characterization

    D. M. Nerkar

    2016-07-01

    Full Text Available Polypyrrole-Silver (PPy-Ag nanocomposite has been successfully synthesized by the chemical oxidative polymerization of pyrrole with iron (III chloride as an oxidant, in the presence of a colloidal suspension of silver nanoparticles. Turkevich method (Citrate reduction method was used for the synthesis of silver nanoparticles (Ag NPs. The silver nanoparticles were characterized by UV-Visible spectroscopy which showed an absorption band at 423 nm confirming the formation of nanoparticles. PPy-Ag nanocomposite was characterized by Transmission Electron Microscopy (TEM, Scanning Electron Microscopy (SEM, Fourier Transform Infrared Spectroscopy (FTIR and X-ray diffraction (XRD techniques for morphological and structural confirmations. TEM and SEM images revealed that the silver nanoparticles were well dispersed in the PPy matrix. XRD pattern showed that PPy is amorphous but the presence of the peaks at 2q values of 38.24°, 44.57°, 64.51° and 78.45° corresponding to a cubic phase of silver, revealed the incorporation of silver nanoparticles in the PPy matrix. A possible formation mechanism of PPy-Ag nanocomposite was also proposed. The electrical conductivity of PPy-Ag nanocomposite was studied using two probe method. The electrical conductivity of the PPy-Ag nanocomposite prepared was found to be 4.657´10- 2 S/cm, whereas that of pure PPy was found to be 9.85´10-3 S/cm at room temperature (303 K. The value of activation energy (Ea for pure PPy was 0.045 eV while it decreased to 0.034 eV for PPy-Ag nanocomposite. The synthesized nanocomposite powder can be utilized as a potential material for fabrication of gas sensors operating at room temperature.

  5. Silver-Nanowire-Embedded Transparent Metal-Oxide Heterojunction Schottky Photodetector.

    Abbas, Sohail; Kumar, Mohit; Kim, Hong-Sik; Kim, Joondong; Lee, Jung-Ho

    2018-05-02

    We report a self-biased and transparent Cu 4 O 3 /TiO 2 heterojunction for ultraviolet photodetection. The dynamic photoresponse improved 8.5 × 10 4 % by adding silver nanowires (AgNWs) Schottky contact and maintaining 39% transparency. The current density-voltage characteristics revealed a strong interfacial electric field, responsible for zero-bias operation. In addition, the dynamic photoresponse measurement endorsed the effective holes collection by embedded-AgNWs network, leading to fast rise and fall time of 0.439 and 0.423 ms, respectively. Similarly, a drastic improvement in responsivity and detectivity of 187.5 mAW -1 and of 5.13 × 10 9 Jones, is observed, respectively. The AgNWs employed as contact electrode can ensure high-performance for transparent and flexible optoelectronic applications.

  6. Brush-Painting and Photonic Sintering of Copper Oxide and Silver Inks on Wood and Cardboard Substrates to Form Antennas for UHF RFID Tags

    Erja Sipilä

    2016-01-01

    Full Text Available Additive deposition of inks with metallic inclusions provides compelling means to embed electronics into versatile structures. The need to integrate electronics into environmentally friendly components and structures increases dramatically together with the increasing popularity of the Internet of Things. We demonstrate a novel brush-painting method for depositing copper oxide and silver inks directly on wood and cardboard substrates and discuss the optimization of the photonic sintering process parameters for both materials. The optimized parameters were utilized to manufacture passive ultra high frequency (UHF radio frequency identification (RFID tag antennas. The results from wireless testing show that the RFID tags based on the copper oxide and silver ink antennas on wood substrate are readable from ranges of 8.5 and 11 meters, respectively, and on cardboard substrate from read ranges of 8.5 and 12 meters, respectively. These results are well sufficient for many future wireless applications requiring remote identification with RFID.

  7. Nematic phase formation in suspensions of graphene oxide

    Fresneau, Nathalie; Campidelli, Stéphane

    The last decade has seen the rise of graphene. Graphene is a single layer of graphite; it can be obtained by direct liquid phase exfoliation of the latter through harsh sonication. This technique presents the disadvantage to produce small graphene flakes (typically in the 0.05 to 0.4 μm2 range for the monolayers) and multilayer graphene with uncontrolled thickness distributions. In order to improve the exfoliation process, one has to counter the strong van der Waals interactions between the carbon planes of graphite. This implies to increase the distance between two planes and it can be done, for example, by oxidizing graphite to introduce oxygen species in the graphenic planes. The fabrication of graphite oxide is known for almost 150 years, and it became popular again these last ten years. Generally, the oxidation of graphite is performed following a method described by Hummers in the 1950's and the material produced by this technique exfoliates quasi-spontaneously into monolayer species called graphene oxide (GO). The highly anisotropic shape of GO (several μm in length and width for a thickness of ca. 1 nm) combined with the presence of oxygenated functions on the sp2 carbon structure of graphene lead to the formation of a lyotropic liquid crystalline phase in water. Above a certain concentration of graphene flakes the gain in translational entropy for a long-range ordered phase outweighs the loss in rotational entropy, and the liquid crystal phase then forms. The value of the threshold is affected by the aspect ratio of the graphene flakes but other factors such as the interactions also play a strong role.

  8. One-step synthesis of high conductivity silver nanoparticle-reduced graphene oxide composite films by electron beam irradiation

    Liu, Gang; Wang, Yujia; Pu, Xianjuan; Jiang, Yong; Cheng, Lingli, E-mail: chenglingli@shu.edu.cn; Jiao, Zheng, E-mail: zjiao@shu.edu.cn

    2015-09-15

    Graphical abstract: - Highlights: • Both graphene oxide and silver ion were reduced simultaneously by electron beam-based method. • The size of AgNPs can be controlled by changing the irradiation dose of electron beam. • The AgNPs/rGO nanocomposite exhibits much lower sheet resistivity (0.06 Ω m). - Abstract: A rapid, eco-friendly, one-step electron beam (EB)-based method for both the reduction of graphene oxide and loading of Ag nanoparticles (AgNPs) were achieved. Further, the effects of irradiation dose on the morphology of AgNPs and the sheet resistance of Ag nanoparticles/reduced graphene oxide (AgNPs/rGO) were studied. The results reveal that when the irradiation dose increased from 70 kGy to 350 kGy, the size of the AgNPs decreased and became uniformly distributed over the surface of the rGO nanosheets. However the size of the AgNPs increased when the irradiation dose reached 500 kGy. Four-point probe measurement showed that the sheet resistance of the AgNPs/rGO films decreased with decreasing AgNPs size. The lowest sheet resistivity of 0.06 Ω m was obtained in the film corresponding to 350 kGy irradiation dose, which showed a much lower resistivity than the GO film (5.04 × 10{sup 5} Ω m). The formation mechanisms of the as-prepared AgNPs/rGO nanocomposites were proposed. This study provides a fast and eco-friendly EB irradiation induced method to controlling the dimensions of AgNPs/rGO nanocomposites, which can strongly support the mass production of AgNPs/rGO nanocomposites for practical applications.

  9. One-step synthesis of high conductivity silver nanoparticle-reduced graphene oxide composite films by electron beam irradiation

    Liu, Gang; Wang, Yujia; Pu, Xianjuan; Jiang, Yong; Cheng, Lingli; Jiao, Zheng

    2015-01-01

    Graphical abstract: - Highlights: • Both graphene oxide and silver ion were reduced simultaneously by electron beam-based method. • The size of AgNPs can be controlled by changing the irradiation dose of electron beam. • The AgNPs/rGO nanocomposite exhibits much lower sheet resistivity (0.06 Ω m). - Abstract: A rapid, eco-friendly, one-step electron beam (EB)-based method for both the reduction of graphene oxide and loading of Ag nanoparticles (AgNPs) were achieved. Further, the effects of irradiation dose on the morphology of AgNPs and the sheet resistance of Ag nanoparticles/reduced graphene oxide (AgNPs/rGO) were studied. The results reveal that when the irradiation dose increased from 70 kGy to 350 kGy, the size of the AgNPs decreased and became uniformly distributed over the surface of the rGO nanosheets. However the size of the AgNPs increased when the irradiation dose reached 500 kGy. Four-point probe measurement showed that the sheet resistance of the AgNPs/rGO films decreased with decreasing AgNPs size. The lowest sheet resistivity of 0.06 Ω m was obtained in the film corresponding to 350 kGy irradiation dose, which showed a much lower resistivity than the GO film (5.04 × 10 5 Ω m). The formation mechanisms of the as-prepared AgNPs/rGO nanocomposites were proposed. This study provides a fast and eco-friendly EB irradiation induced method to controlling the dimensions of AgNPs/rGO nanocomposites, which can strongly support the mass production of AgNPs/rGO nanocomposites for practical applications

  10. Oxidative C-C bond cleavage of 1,2-diols by silver(II)

    Kumar, A.

    1981-01-01

    Oxidation of ethylene glycol and related compounds by Ag(II) has been investigated. Complexation of these substrates by Ag(II) precedes their oxidation. Oxidation occurs through electron transfer from an OH group to the Ag(II) within the complex resulting in the formation of alkoxyl-type radicals. The radicals thus formed undergo β-scission to give cleavage products. For ethylene glycol a complexation rate 1.3 x 10 6 M -1 s -1 and oxidation rate approx. 3 x 10 3 s -1 were observed. A general trend for the type of the substrates which would undergo C-C bond scission by Ag(II) is discussed

  11. From Two-Phase to Three-Phase: The New Electrochemical Interface by Oxide Electrocatalysts

    Xu, Zhichuan J.

    2018-03-01

    Electrochemical reactions typically occur at the interface between a solid electrode and a liquid electrolyte. The charge exchange behaviour between these two phases determines the kinetics of electrochemical reactions. In the past few years, significant advances have been made in the development of metal oxide electrocatalysts for fuel cell and electrolyser reactions. However, considerable gaps remain in the fundamental understanding of the charge transfer pathways and the interaction between the metal oxides and the conducting substrate on which they are located. In particular, the electrochemical interfaces of metal oxides are significantly different from the traditional (metal) ones, where only a conductive solid electrode and a liquid electrolyte are considered. Oxides are insulating and have to be combined with carbon as a conductive mediator. This electrode configuration results in a three-phase electrochemical interface, consisting of the insulating oxide, the conductive carbon, and the liquid electrolyte. To date, the mechanistic insights into this kind of non-traditional electrochemical interface remain unclear. Consequently conventional electrochemistry concepts, established on classical electrode materials and their two-phase interfaces, are facing challenges when employed for explaining these new electrode materials. [Figure not available: see fulltext.

  12. In vitro cytotoxicity of silver nanoparticles and zinc oxide nanoparticles to human epithelial colorectal adenocarcinoma (Caco-2) cells

    Song, Yijuan; Guan, Rongfa; Lyu, Fei; Kang, Tianshu; Wu, Yihang; Chen, Xiaoqiang

    2014-01-01

    Highlights: • The characterization of Ag NPs and ZnO NPs. • The various morphologies of Caco-2 cells stained with AO/EB. • The viability of Caco-2 cells after Ag NPs and ZnO NPs exposure. • The cytotoxicity of Ag NPs and ZnO NPs on Caco-2 cells by oxidative stress assays. - Abstract: With the increasing applications of silver nanoparticles (Ag NPs) and zinc oxide nanoparticles (ZnO NPs) in foods and cosmetics, the concerns about the potential toxicities to human have been raised. The aims of this study are to observe the cytotoxicity of Ag NPs and ZnO NPs to human epithelial colorectal adenocarcinoma (Caco-2) cells in vitro, and to discover the toxicity mechanism of nanoparticles on Caco-2 cells. Caco-2 cells were exposed to 10, 25, 50, 100, 200 μg/mL of Ag NPs and ZnO NPs (90 nm). AO/EB double staining was used to characterize the morphology of the treated cells. The cell counting kit-8 (CCK-8) assay was used to detect the proliferation of the cells. Reactive oxygen species (ROS), superoxide dismutase (SOD) and glutathione (GSH) assay were used to explore the oxidative damage of Caco-2 cells. The results showed that Ag NPs and ZnO NPs (0–200 μg/mL) had highly significant effect on the Caco-2 cells activity. ZnO NPs exerted higher cytotoxicity than Ag NPs in the same concentration range. ZnO NPs have dose-depended toxicity. The LD 50 of ZnO NPs in Caco-2 cells is 0.431 mg/L. Significant depletion of SOD level, variation in GSH level and release of ROS in cells treated by ZnO NPs were observed, which suggests that cytotoxicity of ZnO NPs in intestine cells might be mediated through cellular oxidative stress. While Caco-2 cells treated with Ag NPs at all experimental concentrations showed no cellular oxidative damage. Moreover, the cells’ antioxidant capacity increased, and reached the highest level when the concentration of Ag NPs was 50 μg/mL. Therefore, it can be concluded that Ag NPs are safer antibacterial material in food packaging materials than

  13. In vitro cytotoxicity of silver nanoparticles and zinc oxide nanoparticles to human epithelial colorectal adenocarcinoma (Caco-2) cells

    Song, Yijuan [Zhejiang Provincial Key Laboratory of Biometrology and Inspection and Quarantine, China Jiliang University, Hangzhou 310018 (China); Guan, Rongfa, E-mail: rongfaguan@163.com [Zhejiang Provincial Key Laboratory of Biometrology and Inspection and Quarantine, China Jiliang University, Hangzhou 310018 (China); Lyu, Fei [Department of Food Science and Technology, Zhejiang University of Technology, Hangzhou 310014 (China); Kang, Tianshu; Wu, Yihang [Zhejiang Provincial Key Laboratory of Biometrology and Inspection and Quarantine, China Jiliang University, Hangzhou 310018 (China); Chen, Xiaoqiang [Hubei University of Technology, Wuhan 430068 (China)

    2014-11-15

    Highlights: • The characterization of Ag NPs and ZnO NPs. • The various morphologies of Caco-2 cells stained with AO/EB. • The viability of Caco-2 cells after Ag NPs and ZnO NPs exposure. • The cytotoxicity of Ag NPs and ZnO NPs on Caco-2 cells by oxidative stress assays. - Abstract: With the increasing applications of silver nanoparticles (Ag NPs) and zinc oxide nanoparticles (ZnO NPs) in foods and cosmetics, the concerns about the potential toxicities to human have been raised. The aims of this study are to observe the cytotoxicity of Ag NPs and ZnO NPs to human epithelial colorectal adenocarcinoma (Caco-2) cells in vitro, and to discover the toxicity mechanism of nanoparticles on Caco-2 cells. Caco-2 cells were exposed to 10, 25, 50, 100, 200 μg/mL of Ag NPs and ZnO NPs (90 nm). AO/EB double staining was used to characterize the morphology of the treated cells. The cell counting kit-8 (CCK-8) assay was used to detect the proliferation of the cells. Reactive oxygen species (ROS), superoxide dismutase (SOD) and glutathione (GSH) assay were used to explore the oxidative damage of Caco-2 cells. The results showed that Ag NPs and ZnO NPs (0–200 μg/mL) had highly significant effect on the Caco-2 cells activity. ZnO NPs exerted higher cytotoxicity than Ag NPs in the same concentration range. ZnO NPs have dose-depended toxicity. The LD{sub 50} of ZnO NPs in Caco-2 cells is 0.431 mg/L. Significant depletion of SOD level, variation in GSH level and release of ROS in cells treated by ZnO NPs were observed, which suggests that cytotoxicity of ZnO NPs in intestine cells might be mediated through cellular oxidative stress. While Caco-2 cells treated with Ag NPs at all experimental concentrations showed no cellular oxidative damage. Moreover, the cells’ antioxidant capacity increased, and reached the highest level when the concentration of Ag NPs was 50 μg/mL. Therefore, it can be concluded that Ag NPs are safer antibacterial material in food packaging materials

  14. Heterogeneously Catalyzed Oxidation Reactions Using Molecular Oxygen

    Beier, Matthias Josef

    Heterogeneously catalyzed selective oxidation reactions have attracted a lot of attention in recent time. The first part of the present thesis provides an overview over heterogeneous copper and silver catalysts for selective oxidations in the liquid phase and compared the performance and catalytic...... that both copper and silver can function as complementary catalyst materials to gold showing different catalytic properties and being more suitable for hydrocarbon oxidation reactions. Potential opportunities for future research were outlined. In an experimental study, the potential of silver as a catalyst...... revealed that all catalysts were more active in combination with ceria nanoparticles and that under the tested reaction conditions silver was equally or even more efficient than the gold catalysts. Calcination at 900 °C of silver on silica prepared by impregnation afforded a catalyst which was used...

  15. Colloidal silver nanoparticles improve anti-leukemic drug efficacy via amplification of oxidative stress.

    Guo, Dawei; Zhang, Junren; Huang, Zhihai; Jiang, Shanxiang; Gu, Ning

    2015-02-01

    Recently, increased reactive oxygen species (ROS) levels and altered redox status in cancer cells have become a novel therapeutic strategy to improve cancer selectivity over normal cells. It has been known that silver nanoparticles (AgNPs) display anti-leukemic activity via ROS overproduction. Hence, we hypothesized that AgNPs could improve therapeutic efficacy of ROS-generating agents against leukemia cells. In the current study, N-(4-hydroxyphenyl)retinamide (4-HPR), a synthetic retinoid, was used as a drug model of ROS induction to investigate its synergistic effect with AgNPs. The data exhibited that AgNPs with uniform size prepared by an electrochemical method could localize in the lysosomes, mitochondria and cytoplasm of SHI-1 cells. More importantly, AgNPs together with 4-HPR could exhibit more cytotoxicity and apoptosis via overproduction of ROS in comparison with that alone. Taken together, these results reveal that AgNPs combined with ROS-generating drugs could potentially enhance therapeutic efficacy against leukemia cells, thereby providing a novel strategy for AgNPs in leukemia therapy. Copyright © 2015. Published by Elsevier B.V.

  16. Effects of silver nanoparticle (Ag NP on oxidative stress biomarkers in rat

    Akram Ranjbar

    2014-04-01

    Full Text Available Objective(s: Nanotechnology and nanoparticles are increasingly recognized for their potential applications in aerospace engineering, nanoelectronics, and environmental remediation, medicine and consumer products. More importantly is the potential for the application of silver nanoparticles (Ag NPs in the treatment of diseases that require maintenance of circulating drug concentration or targeting of specific cells or organs the aim of this study was to investigate the possible protective role of Ag NP antioxidative biomarkers in rats. Ag NPs are used to investigate the potential risks for the environment and health. Materials and Methods: Rats received Ag NP, 5, 50, 250 and 500 mg/kg/day IP. After two week of treatment, the activity of enzymatic scavengers such as glutathione peroxidase (GPx, superoxide dismutase (SOD and total antioxidant capacity (TAC of blood samples were measured. Results: Ag NP in 5, 50, 250 and 500 mg/kg reduced activities of CAT, SOD and increased TAC in plasma. Conclusion: In this study, Ag NP with 500mg/kg induced activities of CAT, SOD and decreased TAC. It is concluded that antioxidative properties of Ag NP is dose dependent.

  17. Phase Behavior and Equations of State of the Actinide Oxides

    Chidester, B.; Pardo, O. S.; Panero, W. R.; Fischer, R. A.; Thompson, E. C.; Heinz, D. L.; Prescher, C.; Prakapenka, V. B.; Campbell, A.

    2017-12-01

    The distribution of the long-lived heat-producing actinide elements U and Th in the deep Earth has important implications for the dynamics of the mantle and possibly the energy budget of Earth's core. The low shear velocities of the Large Low-Shear Velocity Provinces (LLSVPs) on the core-mantle boundary suggests that these regions are at least partially molten and may contain concentrated amounts of the radioactive elements, as well as other large cations such as the rare Earth elements. As such, by exploring the phase behavior of actinide-bearing minerals at extreme conditions, some insight into the mineralogy, formation, and geochemical and geodynamical effects of these regions can be gained. We have performed in situ high-pressure, high-temperature synchrotron X-ray diffraction experiments and calculations on two actinide oxide materials, UO2 and ThO2, to determine their phase behavior at the extreme conditions of the lower mantle. Experiments on ThO2 reached 60 GPa and 2500 K, and experiments on UO2 reached 95 GPa and 2500 K. We find that ThO2 exists in the fluorite-type structure to 20 GPa at high temperatures, at which point it transforms to the high-pressure cotunnite-type structure and remains thus up to 60 GPa. At room temperature, an anomalous expansion of the fluorite structure is observed prior to the transition, and may signal anion sub-lattice disorder. Similarly, UO2 exists in the fluorite-type structure at ambient conditions and up to 28 GPa at high temperatures. Above these pressures, we have observed a previously unidentified phase of UO2 with a tetragonal structure as the lower-temperature phase and the cotunnite-type phase at higher temperatures. Above 78 GPa, UO2 undergoes another transition or possible dissociation into two separate oxide phases. These phase diagrams suggest that the actinides could exist as oxides in solid solution with other analogous phases (e.g. ZrO2) in the cotunnite-type structure throughout much of Earth's lower mantle.

  18. Pulsed cathodoluminescence of nanoscale aluminum oxide with different phase compositions

    Kortov, V.S.; Zvonarev, S.V.; Medvedev, A.I.

    2011-01-01

    The methods of pulsed cathodoluminescence have been used to study compacted powders and ceramics containing different phases of aluminum oxide. An intensive luminescence of the samples under study in the visible, NIR, and UV regions of the spectrum has been found. The luminescence bands are very broad and include a few components. The number of the bands depends on the phase composition of the samples. The oxygen vacancies, which capture one or two electrons, produce luminescence centers in the near UV region. The most probable in the visible region is the luminescence of aggregate defects, impurities, and surface centers. - Highlights: → We investigate pulsed cathodoluminescence spectra of nanoscale alumina. → We found the intensive luminescence in the visible, NIR, and UV regions. → The transformation of R-line structure depends on phase composition of alumina. → We substantiate the relation of luminescence bands with concrete centers.

  19. ALTERATION OF U(VI)-PHASES UNDER OXIDIZING CONDITIONS

    A.P. Deditius; S. Utsunomiya; R.C. Ewing

    2006-02-21

    Uranium-(VI) phases are the primary alteration products of the UO{sub 2} in spent nuclear fuel and the UO{sub 2+x}, in natural uranium deposits. The U(VI)-phases generally form sheet structures of edge-sharing UO{sub 2}{sup 2+} polyhedra. The complexity of these structures offers numerous possibilities for coupled-substitutions of trace metals and radionuclides. The incorporation of radionuclides into U(VI)-structures provides a potential barrier to their release and transport in a geologic repository that experiences oxidizing conditions. In this study, we have used natural samples of UO{sub 2+x}, to study the U(VI)-phases that form during alteration and to determine the fate of the associated trace elements.

  20. ALTERATION OF U(VI)-PHASES UNDER OXIDIZING CONDITIONS

    A.P. Deditius; S. Utsunomiya; R.C. Ewing

    2006-01-01

    Uranium-(VI) phases are the primary alteration products of the UO 2 in spent nuclear fuel and the UO 2+x , in natural uranium deposits. The U(VI)-phases generally form sheet structures of edge-sharing UO 2 2+ polyhedra. The complexity of these structures offers numerous possibilities for coupled-substitutions of trace metals and radionuclides. The incorporation of radionuclides into U(VI)-structures provides a potential barrier to their release and transport in a geologic repository that experiences oxidizing conditions. In this study, we have used natural samples of UO 2+x , to study the U(VI)-phases that form during alteration and to determine the fate of the associated trace elements

  1. Antibacterial properties and cytocompatibility of tantalum oxide coatings with different silver content

    Huang, Heng-Li; Chang, Yin-Yu; Chen, Hung-Jui; Chou, Yu-Kai; Lai, Chih-Ho; Chen, Michael Y. C.

    2014-01-01

    Tantalum (Ta) oxides and their coatings have been proved to increase their applications in the biomedical fields by improving osseointegration and wear resistance. In this study, Ta oxide coatings containing different proportions of Ag are deposited on SS304 materials. A twin-gun magnetron sputtering system is used to deposit the tantalum oxide-Ag coating. In this study, Staphylococcus aureus, which exhibits physiological commensalism on the human skin, nares, and mucosal and oral areas, is chosen as the model for in vitro antibacterial analyses via a fluorescence staining method using Syto9. The cytocompatibility and adhesive morphology of human skin fibroblast cells (CCD-966SK) on the coatings are also determined by using the microculture tetrazolium assay. This study shows that Ta 2 O 5 and Ta 2 O 5 -Ag coatings with 12.5 at. % of Ag exhibit improved antibacterial effects against S. aureus and have good skin fibroblast cell cellular biocompatibility

  2. Polypyrrole-silver Nanocomposite: Synthesis and Characterization

    D. M. Nerkar; S. V. Panse; S. P. Patil; S. E. Jaware; G. G. Padhye

    2016-01-01

    Polypyrrole-Silver (PPy-Ag) nanocomposite has been successfully synthesized by the chemical oxidative polymerization of pyrrole with iron (III) chloride as an oxidant, in the presence of a colloidal suspension of silver nanoparticles. Turkevich method (Citrate reduction method) was used for the synthesis of silver nanoparticles (Ag NPs). The silver nanoparticles were characterized by UV-Visible spectroscopy which showed an absorption band at 423 nm confirming the formation of nanoparticles. P...

  3. Fractionation of silver isotopes in native silver explained by redox reactions

    Mathur, Ryan; Arribas, Antonio; Megaw, Peter; Wilson, Marc; Stroup, Steven; Meyer-Arrivillaga, Danilo; Arribas, Isabel

    2018-03-01

    Scant data exist on the silver isotope composition of native silver specimens because of the relative newness of the technique. This study increases the published dataset by an order of magnitude and presents 80 silver new isotope analyses from native silver originating from a diverse set of worldwide deposits (8 deposit types, 33 mining districts in five continents). The measured isotopic range (defined as δ109Ag/107Ag in per mil units compared to NIST 978 Ag isotope standard) is +2.1 to -0.86‰ (2σ errors less than 0.015); with no apparent systematic correlations to date with deposit type or even within districts. Importantly, the data centering on 0‰ all come from high temperature hypogene/primary deposits whereas flanking and overlapping data represent secondary supergene deposits. To investigate the causes for the more fractionated values, several laboratory experiments involving oxidation of silver from natural specimens of Ag-rich sulfides and precipitation and adsorption of silver onto reagent grade MnO2 and FeOOH were conducted. Simple leach experiments demonstrate little Ag isotope fractionation occurred through oxidation of Ag from native Ag (Δsolution-native109Ag = 0.12‰). In contrast, significant fractionation occurred through precipitation of native Ag onto MnO2 (up to Δsolution-MnO2109Ag = 0.68‰, or 0.3amu). Adsorption of silver onto the MnO2 and FeOOH did not produce as large fractionation as precipitation (mean value of Δsolution-MnO2109Ag = 0.10‰). The most likely cause for the isotopic variations seen relates to redox effects such as the reduction of silver from Ag (I) to Ag° that occurs during precipitation onto the mineral surface. Since many Ag deposits have halos dominated by MnO2 and FeOOH phases, potential may exist for the silver isotope composition of ores and surrounding geochemical haloes to be used to better understand ore genesis and potential exploration applications. Aside from the Mn oxides, surface fluid silver

  4. Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on reduced graphene oxide and silver nanoparticles nanocomposite modified electrode.

    Palanisamy, Selvakumar; Karuppiah, Chelladurai; Chen, Shen-Ming

    2014-02-01

    The direct electrochemistry of glucose oxidase (GOx) was successfully realized on electrochemically reduced graphene oxide and silver nanoparticles (RGO/Ag) nanocomposite modified electrode. The fabricated nanocomposite was characterized by field emission scanning electron microscope and energy dispersive spectroscopy. The GOx immobilized nanocomposite modified electrode showed a pair of well-defined redox peaks with a formal potential (E°) of -0.422 V, indicating that the bioactivity of GOx was retained. The heterogeneous electron transfer rate constant (Ks) of GOx at the nanocomposite was calculated to be 5.27 s(-1), revealing a fast direct electron transfer of GOx. The GOx immobilized RGO/Ag nanocomposite electrode exhibited a good electrocatalytic activity toward glucose over a linear concentration range from 0.5 to 12.5 mM with a detection limit of 0.16 mM. Besides, the fabricated biosensor showed an acceptable sensitivity and selectivity for glucose. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Enhanced mechanical, thermal and antimicrobial properties of poly(vinyl alcohol)/graphene oxide/starch/silver nanocomposites films.

    Usman, Adil; Hussain, Zakir; Riaz, Asim; Khan, Ahmad Nawaz

    2016-11-20

    In the present work, synthesis of poly(vinyl alcohol)/graphene oxide/starch/silver (PVA/GO/Starch/Ag) nanocomposites films is reported. Such films have been characterized and investigated for their mechanical, thermal and antimicrobial properties. The exfoliation of GO in the PVA matrix occurs owing to the non-covalent interactions of the polymer chains of PVA and hydrophilic surface of the GO layers. Presence of GO in PVA and PVA/starch blends were found to enhance the tensile strength of the nanocomposites system. It was found that the thermal stability of PVA as well as PVA/starch blend systems increased by the incorporation of GO where strong physical bonding between GO layers and PVA/starch blends is assumed to cause thermal barrier effects. Antimicrobial properties of the prepared films were investigated against Escherichia coli and Staphylococcus aureus. Our results show enhanced antimicrobial properties of the prepared films where PVA-GO, PVA-Ag, PVA-GO-Ag and PVA-GO-Ag-Starch showed antimicrobial activity in ascending order. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Stretchable, Transparent, and Stretch-Unresponsive Capacitive Touch Sensor Array with Selectively Patterned Silver Nanowires/Reduced Graphene Oxide Electrodes.

    Choi, Tae Young; Hwang, Byeong-Ung; Kim, Bo-Yeong; Trung, Tran Quang; Nam, Yun Hyoung; Kim, Do-Nyun; Eom, Kilho; Lee, Nae-Eung

    2017-05-31

    Stretchable and transparent touch sensors are essential input devices for future stretchable transparent electronics. Capacitive touch sensors with a simple structure of only two electrodes and one dielectric are an established technology in current rigid electronics. However, the development of stretchable and transparent capacitive touch sensors has been limited due to changes in capacitance resulting from dimensional changes in elastomeric dielectrics and difficulty in obtaining stretchable transparent electrodes that are stable under large strains. Herein, a stretch-unresponsive stretchable and transparent capacitive touch sensor array was demonstrated by employing stretchable and transparent electrodes with a simple selective-patterning process and by carefully selecting dielectric and substrate materials with low strain responsivity. A selective-patterning process was used to embed a stretchable and transparent silver nanowires/reduced graphene oxide (AgNWs/rGO) electrode line into a polyurethane (PU) dielectric layer on a polydimethylsiloxane (PDMS) substrate using oxygen plasma treatment. This method provides the ability to directly fabricate thin film electrode lines on elastomeric substrates and can be used in conventional processes employed in stretchable electronics. We used a dielectric (PU) with a Poisson's ratio smaller than that of the substrate (PDMS), which prevented changes in the capacitance resulting from stretching of the sensor. The stretch-unresponsive touch sensing capability of our transparent and stretchable capacitive touch sensor has great potential in wearable electronics and human-machine interfaces.

  7. An ultrasensitive sandwich type electrochemiluminescence immunosensor for triiodothyronine detection using silver nanoparticle-decorated graphene oxide as a nanocarrier.

    Chou, Hung-Tao; Fu, Chien-Yu; Lee, Chi-Young; Tai, Nyan-Hwa; Chang, Hwan-You

    2015-09-15

    An ultrasensitive electrochemiluminescence (ECL) immunosensor was constructed to detect 3,3',5-triiodothyronine (T3). The system employed T3-conjugated, silver nanoparticle-decorated carboxylic graphene oxide (Ag@fGO-T3) as a carrier and anti-T3 antibody-tris(2,2'-bipyridyl) ruthenium(II) (Ru(bpy)3(2+)) as a probe. The Ag@fGO-T3 and Ru(bpy)3(2+) complex could be mobilized rapidly to the anode in the reaction chamber through electrophoresis. The fGO is reduced electrochemically at the electrode, and the electrons could transfer from an anode to the Ru(bpy)3(2+). The complex is excited at the electrode and an ECL signal is produced upon reacting with tripropylamine (TPrA). Because of its large surface area and excellent conductivity, Ag@fGO could enhance ECL signal significantly in the system. Quantitative measurement of T3 could be achieved in the range from 0.1 pg/mL to 0.8 ng/mL with a detection limit of 0.05 pg/mL. In addition, the novel immunosensor showed good specificity in the presence of serum, indicating its high potential in clinical use. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Synthesis and characterization of self-bridged silver vanadium oxide/CNTs composite and its enhanced lithium storage performance.

    Liang, Liying; Liu, Haimei; Yang, Wensheng

    2013-02-07

    The improvement of the electrochemical properties of electrode materials with large capacity and good capacity retention is becoming an important task in the field of lithium ion batteries (LIBs). We designed a function-oriented hybrid material consisting of silver vanadium oxide (β-AgVO(3)) nanowires modified with uniform Ag nanoparticles and multi-walled carbon nanotubes (CNTs) as a high-performance cathode material for LIBs. The Ag nanoparticles which precipitated automatically in the synthetic process act as a bridge between the β-AgVO(3) nanowires and CNTs, creating a self-bridged network structure. The Ag particles at the junction of the nanowires and CNTs facilitate electron transport from the CNTs to the nanowires, and thereby improve the electrical conductivity of the β-AgVO(3) nanowires and the composite. Moreover, the self-bridged network is hierarchically porous with a high surface area. When used as a cathode material, this composite electrode reveals high discharge capacities, excellent rate capability, and good cycling stability. The improved performance of the composite arises from its unique nanosized β-AgVO(3) nanowires with short diffusion pathway for lithium ions, efficient electron collection and transfer in the presence of Ag nanoparticles, together with excellent electrical conductivity of CNTs.

  9. Silver-choline chloride modified graphene oxide: Novel nano-bioelectrochemical sensor for celecoxib detection and CCD-RSM model.

    Parsaee, Zohreh; Karachi, Nima; Abrishamifar, Seyyed Milad; Kahkha, Mohammad Reza Rezaei; Razavi, Razieh

    2018-07-01

    In this study, silver nanoparticles modified choline chloride functionalized graphene oxide (AgNPs-ChCl-GO) was synthesized using sonochemical method and utilized as a bioelectrochemical sensor for detection of celecoxib (CEL). The characterization studies were ultimately performed in order to acheive a more complete understanding of the morphological and structural features of the AgNPs-ChCl-GO using different techniques including FT-IR, AFM, FE-SEM, EDX, and XRD. AgNPs-ChCl-GO demonstrated a significant improvement in the reduction activity of CEL due to the enhancement in the current response compared to the bare carbon paste electrode (CPE). The optimum experimental conditions, were optimized using central composite design (CCD) methodology. The differential pulse voltammetry (DPVs) showed an expanded linear dynamic ranges of 9.6 × 10 -9 -7.4 × 10 -7  M for celecoxib in Britton-Robinson buffer in pH 5.0 with. LOD (S/N = 3) and LOQ (S/N = 10) were obtained 2.51 × 10 -9  M and 6.58 × 10 -9  M respectively. AgNPs-ChCl-GO-carbon paste electrode exhibited suitable properties and high accuracy determination of celecoxib in the human plasma sample. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Detrimental effects of commercial zinc oxide and silver nanomaterials on bacterial populations and performance of wastewater systems

    Mboyi, Anza-vhudziki; Kamika, Ilunga; Momba, MaggyN. B.

    2017-08-01

    The widespread use of commercial nanomaterials (NMs) in consumer products has raised environmental concerns as they can enter and affect the efficiency of the wastewater treatment plants. In this study the effect of various concentrations of zinc oxide NMs (nZnO) and silver NMs (nAg) on the selected wastewater bacterial species (Bacillus licheniformis, Brevibacillus laterosporus and Pseudomonas putida) was ascertained at different pH levels (pH 2, 7 and 10). Lethal concentrations (LC) of NMs and parameters such as chemical oxygen demand (COD) and dissolved oxygen (DO) were taken into consideration to assess the performance of a wastewater batch reactor. Bacterial isolates were susceptible to varying concentrations of both nZnO and nAg at pH 2, 7 and 10. It was found that a change in pH did not significantly affect the toxicity of test NMs towards target bacterial isolates. All bacterial species were significantly inhibited (p 0.05) in COD removal in the presence of increasing concentrations of NMs, which resulted in increasing releases of COD. Noticeably, there was no significant difference (p > 0.05) in the decrease in DO uptake in the presence of increasing NM concentrations for all bacterial isolates. The toxic effects of the target NMs on bacterial populations in wastewater may negatively impact the performance of biological treatment processes and may thus affect the efficiency of wastewater treatment plants in producing effluent of high quality.

  11. Zinc oxide and silver nanoparticles influence the antioxidative status in a higher aquatic plant, Spirodela punctata

    Thwala, Melusi

    2012-09-01

    Full Text Available The authors present evidence of free radical activity and resultant anti-oxidative defence in Spirodela plants after exposure to 0.01-1000 mg/L of ZnO and Ag nanoparticles (NPs) over 96-h and 14-d. The quantification of reactive nitrogen...

  12. Multifunctional Silver Coated E-33/Iron Oxide Water Filters: Inhibition of Biofilm Growth and Arsenic Removal

    Bayoxide® E33 (E-33, Goethite) is a widely used commercial material for arsenic adsorption. It is a mixture of iron oxyhydroxide and oxides. E-33 is primarily used to remove arsenic from water and to a lesser extent, other anions, but generally lacks multifunctuality. It is a non...

  13. Heterogeneous nanocomposites composed of silver sulfide and hollow structured Pd nanoparticles with enhanced catalytic activity toward formic acid oxidation

    Chen, Dong; Cui, Penglei; Liu, Hui; Yang, Jun

    2015-01-01

    Highlights: • Core–shell Ag-Ag/Pd nanoparticles with an Ag core and an Ag/Pd alloy shell are prepared via galvanic replacement reaction. • Heterogeneous Ag2S-hollow Pd nanocomposites are fabricated by converting the Ag component into Ag2S using element sulfur. • The heterogeneous Ag2S-hollow Pd nanocomposites display enhanced activity for formic acid oxidation due to electronic coupling effect. • The methodology may find applications to produce the semiconductor-metal nanocomposites with interesting architectures and tailored functionalities. - Abstract: Nanocomposites consisting semiconductor and noble metal domains are of great interest for their synergistic effect-based enhanced properties in a given application. Herein, we demonstrate a facile approach for the synthesis of heterogeneous nanocomposites consisting of silver sulfide (Ag 2 S) and hollow structured Pd nanoparticles (hPd). It begins with the preparation of core–shell nanoparticles with an Ag core and an alloy Ag/Pd shell in an organic solvent via galvanic replacement reaction (GRR) between Ag seed particles pre-synthesized and Pd 2+ ion precursors. The Ag component is then removed from the core and shell regions of core–shell Ag-Ag/Pd nanoparticles, and converted into Ag 2 S by elemental sulfur (S). The Ag 2 S forms the semiconductor domain in the nanocomposite and shares the solid-state interface with the resultant hollow structured Pd nanoparticle. As demonstrated, the Ag 2 S-hPd nanocomposites exhibit superior catalytic activity and durability for formic acid oxidation, compared to the pure Pd nanoparticles prepared by oleylamine reduction of Pd ion precursors and commercial Pd/C catalyst, due to the electronic coupling between semiconductor and noble metal domains in the nanocomposites. In addition, the structural transformation from core–shell to heterogeneous nanocomposites may provide new opportunities to design and fabricate hybrid nanostructures with interesting

  14. Oxidation of Alumina-Forming MAX Phases in Turbine Environments

    Smialek, James; Garg, Anita; Harder, Bryan; Nesbitt, James; Gabb, Timothy; Gray, SImon

    2017-01-01

    Protective coatings for high temperature turbine components are based on YSZ thermal barriers and oxidation resistant, alumina-forming NiAl or NiCoCrAlY bond coats. Ti2AlC and Cr2AlC MAX phases are thus of special interest because of good oxidation resistance and CTE that can match Al2O3 and YSZ. Their alumina scales grow according to cubic kinetics due to grain growth in the scale, with initial heating dominated by fast TiO2 growth. Protective cubic kinetics are also found in high pressure burner rig tests of MAXthal 211 Ti2AlC, but with reduced rates due to volatile TiO(OH)2 formation in water vapor. YSZ-coatings on bulk Ti2AlC exhibit remarkable durability up to 1300C in furnace tests and at least a 25x life advantage compared to superalloys. At another extreme, Cr2AlC is resistant to low temperature Na2SO4 hot corrosion and exhibits thermal cycling stability bonded to a superalloy disk material. Accordingly, sputtered Cr2AlC coatings on disk specimens prevented hot corrosion detriments on LCF. Breakaway oxidation (Ti2AlC), scale spallation (Cr2AlC), interdiffusion, and processing as coatings still present serious challenges. However the basic properties of MAX phases provide some unusual opportunities for use in high temperature turbines.

  15. Sol–gel-based silver nanoparticles-doped silica – Polydiphenylamine nanocomposite for micro-solid-phase extraction

    Bagheri, Habib, E-mail: bagheri@sharif.edu; Banihashemi, Solmaz

    2015-07-30

    A nanocomposite of silica-polydiphenylamine doped with silver nanoparticles (Ag–SiO{sub 2}-PDPA) was successfully synthesized by the sol–gel process. For its preparation, PDPA was mixed with butanethiol capped Ag nanoparticles (NPs) and added to the silica sol solution. The Ag NPs were stabilized as a result of their adsorption on the SiO{sub 2} spheres. The surface characteristic of nanocomposite was investigated using scanning electron microscopy (SEM). In this work the Ag–SiO{sub 2}-PDPA nanocomposite was employed as an efficient sorbent for micro-solid-phase extraction (μ-SPE) of some selected pesticides. An amount of 15 mg of the prepared sorbent was used to extract and determine the representatives from organophosphorous, organochlorine and aryloxyphenoxy propionic acids from aqueous samples. After the implementation of extraction process, the analytes were desorbed by methanol and determined using gas chromatography–mass spectrometry (GC–MS). Important parameters influencing the extraction and desorption processes such as pH of sample solution, salting out effect, type and volume of the desorption solvent, the sample loading and eluting flow rates along with the sample volume were experimentally optimized. Limits of detection (LODs) and the limits of quantification (LOQs) were in the range of 0.02–0.05 μg L{sup −1} and 0.1–0.2 μg L{sup −1}, respectively, using time scheduled selected ion monitoring (SIM) mode. The relative standard deviation percent (RSD %) with four replicates was in the range of 6–10%. The applicability of the developed method was examined by analyzing different environmental water samples and the relative recovery (RR %) values for the spiked water samples were found to be in the range of 86–103%. - Highlights: • A sol–gel-based silver nanoparticles doped silica-polydiphenylamine nanocomposite was synthesized. • The sorbent was applied to micro-solid-phase extraction of some selected pesticides in water

  16. Gas phase reactions of nitrogen oxides with olefins

    Altshuller, A P; Cohen, I

    1961-01-01

    The nature of the condensation products formed in the gas phase reactions of nitrogen dioxide and nitric oxide with pentene-1, 2-methylbutene-2, and 2-methylbutadiene-1,3 was investigated. The reactants were combined at partial pressures in the range of 0.1 to 2.5 mm with the total pressure at one atmosphere. The products were determined by infrared and ultraviolet spectroscopy and colorimetry. The condensates included primary and secondary nitro compounds and alkyl nitrates. Strong hydroxyl and single bond carbon to oxygen stretching vibrations indicate the presence of either nitroalcohols or simple aliphatic alcohols formed through oxidation reactions. Carbonyl stretching frequencies observable in some of the reactions support the conclusion that a portion of the reactants disappear by oxidation rather than by nitration processes. The available results do not indicate the presence of appreciable amounts of tert.-nitro compounds, conjugated nitro-olefins, or gem-dinitro-alkanes. The reactivities of the olefins with the nitrogen oxides are in the decreasing order: 2-methyl-butadiene-1,3, 2-methylbutene-2, pentene-1. 20 references.

  17. Reaction pathways for catalytic gas-phase oxidation of glycerol over mixed metal oxides

    Suprun, W.; Glaeser, R.; Papp, H. [Leipzig Univ. (Germany). Inst. of Chemical Technology

    2011-07-01

    Glycerol as a main by-product from bio-diesel manufacture is a cheap raw material with large potential for chemical or biochemical transformations to value-added C3-chemicals. One possible way of glycerol utilization involves its catalytic oxidation to acrylic acid as an alternative to petrochemical routes. However, this catalytic conversion exhibits various problems such as harsh reaction conditions, severe catalyst coking and large amounts of undesired by-products. In this study, the reaction pathways for gas-phase conversion of glycerol over transition metal oxides (Mo, V und W) supported on TiO{sub 2} and SiO{sub 2} were investigated by two methods: (i) steady state experiments of glycerol oxidation and possible reactions intermediates, i.e., acrolein, 3-hydroxy propionaldehyde and acetaldehyde, and (ii) temperature-programmed surface reaction (TPSR) studies of glycerol conversion in the presence and in the absence of gas-phase oxygen. It is shown that the supported W-, V and Mo-oxides possess an ability to catalyze the oxidation of glycerol to acrylic acid. These investigations allowed us to gain a deeper insight into the reaction mechanism. Thus, based on the obtained results, three possible reactions pathways for the selective oxidation of glycerol to acrylic acid on the transition metal-containing catalysts are proposed. The major pathways in presence of molecular oxygen are a fast successive destructive oxidation of glycerol to CO{sub x} and the dehydration of glycerol to acrolein which is a rate-limiting step. (orig.)

  18. Antibacterial properties and cytocompatibility of tantalum oxide coatings with different silver content

    Huang, Heng-Li [School of Dentistry, China Medical University, Taichung 404, Taiwan (China); Chang, Yin-Yu, E-mail: yinyu@mail2000.com.tw; Chen, Hung-Jui; Chou, Yu-Kai [Department of Mechanical and Computer-Aided Engineering, National Formosa University, Yunlin 632, Taiwan (China); Lai, Chih-Ho [School of Medicine, China Medical University, Taichung 404, Taiwan (China); Chen, Michael Y. C. [Division of Oral and Maxillofacial Surgery, China Medical University Hospital, Taichung 404, Taiwan (China)

    2014-03-15

    Tantalum (Ta) oxides and their coatings have been proved to increase their applications in the biomedical fields by improving osseointegration and wear resistance. In this study, Ta oxide coatings containing different proportions of Ag are deposited on SS304 materials. A twin-gun magnetron sputtering system is used to deposit the tantalum oxide-Ag coating. In this study, Staphylococcus aureus, which exhibits physiological commensalism on the human skin, nares, and mucosal and oral areas, is chosen as the model for in vitro antibacterial analyses via a fluorescence staining method using Syto9. The cytocompatibility and adhesive morphology of human skin fibroblast cells (CCD-966SK) on the coatings are also determined by using the microculture tetrazolium assay. This study shows that Ta{sub 2}O{sub 5} and Ta{sub 2}O{sub 5}-Ag coatings with 12.5 at. % of Ag exhibit improved antibacterial effects against S. aureus and have good skin fibroblast cell cellular biocompatibility.

  19. Study on silicon oxide coated on silver nanocrystal to enhance fluorescence intensity of rare earth complexes

    Qu, Yan-rong; Lin, Xue-mei; Wang, Ai-ling; Wang, Zhong-xia; Kang, Jie; Chu, Hai-bin, E-mail: binghai99@gmail.com; Zhao, Yong-liang, E-mail: hxzhaoyl@163.com

    2014-10-15

    Twelve kinds of rare earth complexes were synthesized using halo-benzoic acid as anion ligand and Sm{sup 3+} and Dy{sup 3+} as central ions, respectively. The complexes were characterized by elemental analysis, rare earth coordination titration and electrospray ionization mass spectra, from which the compositions of the complexes were confirmed to be RE(p-FBA){sub 3}·H{sub 2}O, RE(p-ClBA){sub 3}·2H{sub 2}O, RE(p-BrBA){sub 3}·H{sub 2}O, RE(o-FBA){sub 3}·2H{sub 2}O, RE(o-ClBA){sub 3}·H{sub 2}O, RE(o-BrBA){sub 3}·H{sub 2}O (RE=Sm{sup 3+}, Dy{sup 3+}). Besides, IR spectra and UV–visible absorption spectroscopy indicated that the carboxyl oxygen atoms of ligands coordinated to the rare earth ions. Moreover, Ag@SiO{sub 2} core–shell nanoparticles (NPs) were prepared via a modified Stöber method. The average diameters of silver cores were typically between 60 nm and 70 nm, and the thicknesses of the SiO{sub 2} shells were around 10 nm, 15 nm and 25 nm, respectively. The influence of Ag@SiO{sub 2} NPs on the luminescence properties of the rare earth complexes showed that the luminescence intensities of rare earth complexes were enhanced remarkably. As the thickness of SiO{sub 2} shell increases in the range of 10–25 nm, the effect of metal-enhanced fluorescence become obvious. The mechanism of the changes of the fluorescence intensity is also discussed. - Highlights: • Among 10–25 nm, the thicker the shell thickness, the better the fluorescence effect. • The strong the intensity of the pure complexes, the smaller the multiple enhanced. • The intensity of Sm(p-BrBA){sub 3}·H{sub 2}O is the strongest among Sm(p-XBA){sub 3}·nH{sub 2}O complexes. • The intensity of Dy(p-ClBA){sub 3}·2H{sub 2}O is the strongest among Dy(p-XBA){sub 3}·nH{sub 2}O complexes. • When halogen is in o-position, the intensity of RE(o-ClBA){sub 3}·H{sub 2}O is the strongest.

  20. Relative SHG measurements of metal thin films: Gold, silver, aluminum, cobalt, chromium, germanium, nickel, antimony, titanium, titanium nitride, tungsten, zinc, silicon and indium tin oxide

    Franklin Che

    Full Text Available We have experimentally measured the surface second-harmonic generation (SHG of sputtered gold, silver, aluminum, zinc, tungsten, copper, titanium, cobalt, nickel, chromium, germanium, antimony, titanium nitride, silicon and indium tin oxide thin films. The second-harmonic response was measured in reflection using a 150 fs p-polarized laser pulse at 1561 nm. We present a clear comparison of the SHG intensity of these films relative to each other. Our measured relative intensities compare favorably with the relative intensities of metals with published data. We also report for the first time to our knowledge the surface SHG intensity of tungsten and antimony relative to that of well known metallic thin films such as gold and silver. Keywords: Surface second-harmonic generation, Nonlinear optics, Metal thin films

  1. Sulfonated nanocellulose for the efficient dispersive micro solid-phase extraction and determination of silver nanoparticles in food products.

    Ruiz-Palomero, Celia; Soriano, M Laura; Valcárcel, Miguel

    2016-01-08

    This paper reports a simple approach to Analytical Nanoscience and Nanotechnology (AN&N) that integrates the nanotool, sulfonated nanocellulose (s-NC), and nanoanalyte, silver nanoparticles (AgNPs), in the same analytical process by using an efficient, environmentally friendly dispersive micro solid-phase extraction (D-μSPE) capillary electrophoresis (CE) method with s-NC as sorbent material. Introducing negatively charged sulfate groups onto the surface of cellulose enhances its surface chemistry and enables the extraction and preconcentration of AgNPs of variable diameter (10, 20 and 60nm) and shell composition (citrate and polyvinylpyrrolidone coatings) from complex matrices into a cationic surfactant. In this way, AgNPs of diverse nature were successfully extracted onto the s-NC sorbent and then desorbed into an aqueous solution containing thiotic acid (TA) prior to CE without the need for any labor-intensive cleanup. The ensuing eco-friendly D-μSPE method exhibited a linear response to AgNPs with a limit of detection (LOD) of 20μg/L. Its ability to specifically recognize AgNPs of different sizes was checked in orange juice and mussels, which afforded recoveries of 70.9-108.4%. The repeatability of the method at the limit of quantitation (LOQ) level was 5.6%. Based on the results, sulfonated nanocellulose provides an efficient, cost-effective analytical nanotool for the extraction of AgNPs from food products. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Green synthesis of high conductivity silver nanoparticle-reduced graphene oxide composite films

    Dinh, D. A.; Hui, K. S.; Hui, K. N.; Cho, Y. R.; Zhou, Wei; Hong, Xiaoting; Chun, Ho-Hwan

    2014-04-01

    A green facile chemical approach to control the dimensions of Ag nanoparticles-graphene oxide (AgNPs/GO) composites was performed by the in situ ultrasonication of a mixture of AgNO3 and graphene oxide solutions with the assistance of vitamin C acting as an environmentally friendly reducing agent at room temperature. With decreasing ultrasonication time, the size of the Ag nanoparticles decreased and became uniformly distributed over the surface of the GO nanosheets. The as-prepared AgNPs/rGO composite films were then formed using a spin coating method and reduced at 500 °C under N2/H2 gas flow for 1 h. Four-point probe measurements showed that the sheet resistance of the AgNPs/rGO films decreased with decreasing AgNPs size. The lowest sheet resistance of 270 Ω/sq was obtained in the film corresponding to 1 min of ultrasonication, which showed a 40 times lower resistivity than the rGO film (10.93 kΩ/sq). The formation mechanisms of the as-prepared AgNPs/rGO films are proposed. This study provides a guide to controlling the dimensions of AgNPs/rGO films, which might hold promise as advanced materials for a range of analytical applications, such as catalysis, sensors and microchips.

  3. Strain-induced topological quantum phase transition in phosphorene oxide

    Kang, Seoung-Hun; Park, Jejune; Woo, Sungjong; Kwon, Young-Kyun

    Using ab initio density functional theory, we investigate the structural stability and electronic properties of phosphorene oxides (POx) with different oxygen compositions x. A variety of configurations are modeled and optimized geometrically to search for the equilibrium structure for each x value. Our electronic structure calculations on the equilibrium configuration obtained for each x reveal that the band gap tends to increase with the oxygen composition of x 0.5. We further explore the strain effect on the electronic structure of the fully oxidized phosphorene, PO, with x = 1. At a particular strain without spin-orbit coupling (SOC) is observed a band gap closure near the Γ point in the k space. We further find the strain in tandem with SOC induces an interesting band inversion with a reopened very small band gap (5 meV), and thus gives rise to a topological quantum phase transition from a normal insulator to a topological insulator. Such a topological phase transition is confirmed by the wave function analysis and the band topology identified by the Z2 invariant calculation.

  4. Closed-cage tungsten oxide clusters in the gas phase.

    Singh, D M David Jeba; Pradeep, T; Thirumoorthy, Krishnan; Balasubramanian, Krishnan

    2010-05-06

    During the course of a study on the clustering of W-Se and W-S mixtures in the gas phase using laser desorption ionization (LDI) mass spectrometry, we observed several anionic W-O clusters. Three distinct species, W(6)O(19)(-), W(13)O(29)(-), and W(14)O(32)(-), stand out as intense peaks in the regular mass spectral pattern of tungsten oxide clusters suggesting unusual stabilities for them. Moreover, these clusters do not fragment in the postsource decay analysis. While trying to understand the precursor material, which produced these clusters, we found the presence of nanoscale forms of tungsten oxide. The structure and thermodynamic parameters of tungsten clusters have been explored using relativistic quantum chemical methods. Our computed results of atomization energy are consistent with the observed LDI mass spectra. The computational results suggest that the clusters observed have closed-cage structure. These distinct W(13) and W(14) clusters were observed for the first time in the gas phase.

  5. Green synthesis of high conductivity silver nanoparticle-reduced graphene oxide composite films

    Dinh, D.A. [School of Materials Science and Engineering, Pusan National University, San 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Hui, K.S., E-mail: kshui@hanyang.ac.kr [Department of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Hui, K.N., E-mail: bizhui@pusan.ac.kr [School of Materials Science and Engineering, Pusan National University, San 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Cho, Y.R. [School of Materials Science and Engineering, Pusan National University, San 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Zhou, Wei [Department of Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005 (China); Hong, Xiaoting [School of Chemistry and Environment, South China Normal University, Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, Guangzhou 510006 (China); Chun, Ho-Hwan [Global Core Research Center for Ships and Offshore Plants (GCRC-SOP), Pusan National University, San 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of)

    2014-04-01

    Graphical abstract: - Highlights: • A green facile chemical approach to control the dimensions of Ag nanoparticles–graphene oxide (AgNPs/GO) composites was performed at room temperature. • With decreasing ultrasonication time, the size of the Ag nanoparticles decreased and became uniformly distributed over the surface of the GO nanosheets. • The as-prepared AgNPs/rGO composite films were then formed using a spin coating method and reduced at 500 °C under N{sub 2}/H{sub 2} gas flow for 1 h. • The lowest sheet resistance of 270 Ω/sq was obtained in the film corresponding to 1 min of ultrasonication, which showed a 40 times lower resistivity than the rGO film (10.93 kΩ/sq). - Abstract: A green facile chemical approach to control the dimensions of Ag nanoparticles–graphene oxide (AgNPs/GO) composites was performed by the in situ ultrasonication of a mixture of AgNO{sub 3} and graphene oxide solutions with the assistance of vitamin C acting as an environmentally friendly reducing agent at room temperature. With decreasing ultrasonication time, the size of the Ag nanoparticles decreased and became uniformly distributed over the surface of the GO nanosheets. The as-prepared AgNPs/rGO composite films were then formed using a spin coating method and reduced at 500 °C under N{sub 2}/H{sub 2} gas flow for 1 h. Four-point probe measurements showed that the sheet resistance of the AgNPs/rGO films decreased with decreasing AgNPs size. The lowest sheet resistance of 270 Ω/sq was obtained in the film corresponding to 1 min of ultrasonication, which showed a 40 times lower resistivity than the rGO film (10.93 kΩ/sq). The formation mechanisms of the as-prepared AgNPs/rGO films are proposed. This study provides a guide to controlling the dimensions of AgNPs/rGO films, which might hold promise as advanced materials for a range of analytical applications, such as catalysis, sensors and microchips.

  6. Green synthesis of high conductivity silver nanoparticle-reduced graphene oxide composite films

    Dinh, D.A.; Hui, K.S.; Hui, K.N.; Cho, Y.R.; Zhou, Wei; Hong, Xiaoting; Chun, Ho-Hwan

    2014-01-01

    Graphical abstract: - Highlights: • A green facile chemical approach to control the dimensions of Ag nanoparticles–graphene oxide (AgNPs/GO) composites was performed at room temperature. • With decreasing ultrasonication time, the size of the Ag nanoparticles decreased and became uniformly distributed over the surface of the GO nanosheets. • The as-prepared AgNPs/rGO composite films were then formed using a spin coating method and reduced at 500 °C under N 2 /H 2 gas flow for 1 h. • The lowest sheet resistance of 270 Ω/sq was obtained in the film corresponding to 1 min of ultrasonication, which showed a 40 times lower resistivity than the rGO film (10.93 kΩ/sq). - Abstract: A green facile chemical approach to control the dimensions of Ag nanoparticles–graphene oxide (AgNPs/GO) composites was performed by the in situ ultrasonication of a mixture of AgNO 3 and graphene oxide solutions with the assistance of vitamin C acting as an environmentally friendly reducing agent at room temperature. With decreasing ultrasonication time, the size of the Ag nanoparticles decreased and became uniformly distributed over the surface of the GO nanosheets. The as-prepared AgNPs/rGO composite films were then formed using a spin coating method and reduced at 500 °C under N 2 /H 2 gas flow for 1 h. Four-point probe measurements showed that the sheet resistance of the AgNPs/rGO films decreased with decreasing AgNPs size. The lowest sheet resistance of 270 Ω/sq was obtained in the film corresponding to 1 min of ultrasonication, which showed a 40 times lower resistivity than the rGO film (10.93 kΩ/sq). The formation mechanisms of the as-prepared AgNPs/rGO films are proposed. This study provides a guide to controlling the dimensions of AgNPs/rGO films, which might hold promise as advanced materials for a range of analytical applications, such as catalysis, sensors and microchips

  7. High-transparency and low-resistivity poly (methylmethacrylate) films containing silver nanowires and graphene-oxide nanoplatelets

    Bang, Yo Han; Choo, Dong Chul; Kim, Tae Whan

    2016-01-01

    Highlights: • PMMA films containing both Ag-NWs and GONPs were formed by using a transfer method. • Scanning electron microscopy images showed that the Ag-NWs on the PMMA film were partially covered with the GONPs. • Transmittance and the sheet resistance of the PMMA films were approximately 90% at 550 nm and 24 Ω/sq, respectively. • Uniformity of the sheet resistance was significantly improved due to the GONP treatment. • XPS spectra showed that the enhancement in the sheet resistance originated from the quaternary nitrogen in the GONPs. - Abstract: Nanocomposite films containing silver nanowires (Ag NWs) and graphene-oxide nanoplatelets (GONPs) were formed on glass, and the nanocomposite films were then transferred to poly(methylmethacrylate) (PMMA) films. Scanning electron microscopy images showed that Ag NWs with a length of 20 μm and a width of 80 nm, together with GONPs with a size of 15 μm, had been formed on the PMMA film and that the Ag NWs on the PMMA film were partially covered with the GONPs. While the transmittance of the PMMA film with the Ag NWs and the GONPs was almost the same as that of the PMMA film with the Ag NWs alone, the corresponding sheet resistance was decreased due to the generation of quaternary nitrogen in the GONPs, which the results of X-ray photoelectron spectroscopy and Raman spectroscopy confirmed. The transmittance and the sheet resistance of the PMMA film containing Ag NWs and GONPs were approximately 90% at 550 nm and 24 Ohm/sq, respectively.

  8. No evidence of the genotoxic potential of gold, silver, zinc oxide and titanium dioxide nanoparticles in the SOS chromotest.

    Nam, Sun-Hwa; Kim, Shin Woong; An, Youn-Joo

    2013-10-01

    Gold nanoparticles (Au NPs), silver nanoparticles (Ag NPs), zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO2 NPs) are widely used in cosmetic products such as preservatives, colorants and sunscreens. This study investigated the genotoxicity of Au NPs, Ag NPs, ZnO NPs and TiO2 NPs using the SOS chromotest with Escherichia coli PQ37. The maximum exposure concentrations for each nanoparticle were 3.23 mg l(-1) for Au NPs, 32.3 mg l(-1) for Ag NPs and 100 mg l(-1) for ZnO NPs and TiO2 NPs. Additionally, in order to compare the genotoxicity of nanoparticles and corresponding dissolved ions, the ions were assessed in the same way as nanoparticles. The genotoxicity of the titanium ion was not assessed because of the extremely low solubility of TiO2 NPs. Au NPs, Ag NPs, ZnO NPs, TiO2 NPs and ions of Au, Ag and Zn, in a range of tested concentrations, exerted no effects in the SOS chromotest, evidenced by maximum IF (IFmax) values of below 1.5 for all chemicals. Owing to the results, nanosized Au NPs, Ag NPs, ZnO NPs, TiO2 NPs and ions of Au, Ag and Zn are classified as non-genotoxic on the basis of the SOS chromotest used in this study. To the best of our knowledge, this is the first study to evaluate the genotoxicity of Au NPs, Ag NPs, ZnO NPs and TiO2 NPs using the SOS chromotest. Copyright © 2012 John Wiley & Sons, Ltd.

  9. Peculiarities of the diffusion of silver and sodium ions in phosphate glasses with a high content of sodium oxide

    Syutkin, V.M.; Tolkatchev, V.A.

    1996-01-01

    The phosphate glasses with a high content of alkali metal ions are good ionic conductors. Despite active studies, the mechanism of ion diffusion is not so far clear. The present work discusses the characteristics of ion diffusion in phosphate glasses with a high content of sodium oxide. An effective method to study ion transport is the investigation of relaxation processes the kinetics of which depends on ion diffusion. We use the data for two types of relaxation processes the kinetics of which is determined by ion diffusion. This is the conductivity relaxation due to sodium (host) ions and the decay of radiation-induced centers controlled by silver (guest) ion diffusion. Both of the processes being actually the first-order processes display a nonexponential kinetic behavior. The relaxation law can be interpreted either as the inherently nonexponential function or as the weighted sum of exponential decay functions with a distribution of relaxation times. It has been demonstrated that on the molecular level the relaxation function should be interpreted in the frame of the scheme of parallel first-order processes. This fact allows one to formulate a number of features of ion diffusion: (i) the mean square displacement of ions does not exceed several angstrom when transport becomes non-dispersive; (ii) the diffusion coefficient of ions is the function of coordinates. In this case, a characteristic distance at which D(r) noticeably varies is no less than a hundred of angstrom; (iii) the instantaneous concentration of mobile ions is well below the overall concentration ions

  10. Highly sensitive, reproducible and stable SERS substrate based on reduced graphene oxide/silver nanoparticles coated weighing paper

    Xiao, Guina, E-mail: xiaoguina@shnu.edu.cn; Li, Yunxiang; Shi, Wangzhou; Shen, Leo; Chen, Qi; Huang, Lei, E-mail: leihuang@shnu.edu.cn

    2017-05-15

    Highlights: • We developed a paper-based SERS substrate by gravure and inkjet printing methods. • The S-RGO/AgNPs comoposite structure had higher SERS activity than the pure AgNPs. • The Raman enhancement factor of S-RGO/AgNPs substrate was calculated to be 10{sup 9}. • The paper-based substrate exhibited good reproducibility and long-term stability. - Abstract: Paper-based surface-enhanced Raman scattering (SERS) substrates receive a great deal of attention due to low cost and high flexibility. Herein, we developed an efficient SERS substrate by gravure printing of sulfonated reduced graphene-oxide (S-RGO) thin film and inkjet printing of silver nanoparticles (AgNPs) on weighing paper successively. Malachite green (MG) and rhodamine 6G (R6G) were chosen as probe molecules to evaluate the enhanced performance of the fabricated SERS-active substrates. It was found that the S-RGO/AgNPs composite structure possessed higher enhancement ability than the pure AgNPs. The Raman enhancement factor of S-RGO/AgNPs was calculated to be as large as 10{sup 9}. The minimum detection limit for MG and R6G was down to 10{sup −7} M with good linear responses (R{sup 2} = 0.9996, 0.9983) range from 10{sup −4} M to 10{sup −7} M. In addition, the S-RGO/AgNPs exhibited good uniformity with a relative standard deviation (RSD) of 7.90% measured by 572 points, excellent reproducibility with RSD smaller than 3.36%, and long-term stability with RSD less than 7.19%.

  11. Graphene oxide directed in-situ deposition of electroactive silver nanoparticles and its electrochemical sensing application for DNA analysis

    Gao, Ningning [College of Chemistry and Environment, Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou, 363000 (China); Gao, Feng, E-mail: fgao1981@mnnu.edu.cn [College of Chemistry and Environment, Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou, 363000 (China); Department of Chemistry, Graduate School of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue, Shimane, 690-8504 (Japan); He, Suyu; Zhu, Qionghua; Huang, Jiafu [College of Chemistry and Environment, Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou, 363000 (China); Tanaka, Hidekazu [Department of Chemistry, Graduate School of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue, Shimane, 690-8504 (Japan); Wang, Qingxiang, E-mail: axiang236@126.com [College of Chemistry and Environment, Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou, 363000 (China)

    2017-01-25

    The development of high-performance biosensing platform is heavily dependent on the recognition property of the sensing layer and the output intensity of the signal probe. Herein, we present a simple and highly sensitive biosensing interface for DNA detection on the basis of graphene oxide nanosheets (GONs) directed in-situ deposition of silver nanoparticles (AgNPs). The fabrication process and electrochemical properties of the biosensing interface were probed by electrochemical techniques and scanning electron microscopy. The results indicate that GONs can specifically adsorb at the single-stranded DNA probe surface, and induces the deposition of highly electroactive AgNPs. Upon hybridization with complementary oligonucleotides to generate the duplex DNA on the electrode surface, the GONs with the deposited AgNPs will be liberated from the sensing interface due to the inferior affinity of GONs and duplex DNA, resulting in the reduction of the electrochemical signal. Such a strategy combines the superior recognition of GONs toward single-stranded DNA and double-stranded DNA, and the strong electrochemical response of in-situ deposited AgNPs. Under optimal conditions, the biosensor can detect target DNA over a wide range from 10 fM to 10 nM with a detection limit of 7.6 fM. Also, the developed biosensor shows outstanding discriminating ability toward oligonucleotides with different mismatching degrees. - Highlights: • An novel DNA biosensor was constructed based on GONs with deposited AgNPs. • GONs catalyze the in-situ deposition of AgNPs on the sensing interface. • Unique π-stacking of GONs with probe DNA contributes high selectivity of the biosensor. • High electroactivity of AgNPs leads to low detection limit (7.6 fM) for target DNA.

  12. Nanoscale current spreading analysis in solution-processed graphene oxide/silver nanowire transparent electrodes via conductive atomic force microscopy

    Shaw, Joseph E.; Perumal, Ajay; Bradley, Donal D. C.; Stavrinou, Paul N.; Anthopoulos, Thomas D., E-mail: t.anthopoulos@ic.ac.uk [Department of Physics and Centre for Plastic Electronics, Blackett Laboratory, Imperial College London, London SW7 2AZ (United Kingdom)

    2016-05-21

    We use conductive atomic force microscopy (CAFM) to study the origin of long-range conductivity in model transparent conductive electrodes composed of networks of reduced graphene oxide (rGO{sub X}) and silver nanowires (AgNWs), with nanoscale spatial resolution. Pristine networks of rGO{sub X} (1–3 monolayers-thick) and AgNWs exhibit sheet resistances of ∼100–1000 kΩ/□ and 100–900 Ω/□, respectively. When the materials are deposited sequentially to form bilayer rGO{sub X}/AgNW electrodes and thermally annealed at 200 °C, the sheet resistance reduces by up to 36% as compared to pristine AgNW networks. CAFM was used to analyze the current spreading in both systems in order to identify the nanoscale phenomena responsible for this effect. For rGO{sub X} networks, the low intra-flake conductivity and the inter-flake contact resistance is found to dominate the macroscopic sheet resistance, while for AgNW networks the latter is determined by the density of the inter-AgNW junctions and their associated resistance. In the case of the bilayer rGO{sub X}/AgNWs' networks, rGO{sub X} flakes are found to form conductive “bridges” between AgNWs. We show that these additional nanoscopic electrical connections are responsible for the enhanced macroscopic conductivity of the bilayer rGO{sub X}/AgNW electrodes. Finally, the critical role of thermal annealing on the formation of these nanoscopic connections is discussed.

  13. Silver/iron oxide/graphitic carbon composites as bacteriostatic catalysts for enhancing oxygen reduction in microbial fuel cells

    Ma, Ming; You, Shijie; Gong, Xiaobo; Dai, Ying; Zou, Jinlong; Fu, Honggang

    2015-06-01

    Biofilms from anode heterotrophic bacteria are inevitably formed over cathodic catalytic sites, limiting the performances of single-chamber microbial fuel cells (MFCs). Graphitic carbon (GC) - based nano silver/iron oxide (AgNPs/Fe3O4/GC) composites are prepared from waste pomelo skin and used as antibacterial oxygen reduction catalysts for MFCs. AgNPs and Fe3O4 are introduced in situ into the composites by one-step carbothermal reduction, enhancing their conductivity and catalytic activity. To investigate the effects of Fe species on the antibacterial and catalytic properties, AgNPs/Fe3O4/GC is washed with sulfuric acid (1 mol L-1) for 0.5 h, 1 h, and 5 h and marked as AgNPs/Fe3O4/GC-x (x = 0.5 h, 1 h and 5 h, respectively). A maximum power density of 1712 ± 35 mW m-2 is obtained by AgNPs/Fe3O4/GC-1 h, which declines by 4.12% after 17 cycles. Under catalysis of all AgNP-containing catalysts, oxygen reduction reaction (ORR) proceeds via the 4e- pathway, and no toxic effects to anode microorganisms result from inhibiting the cathodic biofilm overgrowth. With the exception of AgNPs/Fe3O4/GC-5 h, the AgNPs-containing composites exhibit remarkable power output and coulombic efficiency through lowering proton transfer resistance and air-cathode biofouling. This study provides a perspective for the practical application of MFCs using these efficient antibacterial ORR catalysts.

  14. A novel solution-phase route for the synthesis of crystalline silver nanowires

    Liu Yang; Chu Ying; Yang Likun; Han Dongxue; Lue Zhongxian

    2005-01-01

    A unique solution-phase route was devised to synthesize crystal Ag nanowires with high aspect-ratio (8-10 nm in diameter and length up to 10 μm) by the reduction of AgNO 3 with Vitamin C in SDS/ethanol solution. The resultant nanoproducts were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD) and electron diffraction (ED). A soft template mechanism was put forward to interpret the formation of metal Ag nanowires

  15. Kinetics of the gas-phase tritium oxidation reaction

    Failor, R.A.

    1989-01-01

    Homogeneous gas-phase kinetics of tritium oxidation (2T 2 + O 2 →2T 2 O) have been studied with a model that accounts explicitly for radiolysis of the major species and the kinetics of the subsequent reactions of ionic, excited-state, and neutral species. Results from model calculations are given for 10 -4 -1.0 mol% T 2 in O 2 (298 K, 1 atm). As the reaction evolves three different mechanisms control T 2 O production, each with a different overall rate expression and a different order with respect to the T 2 concentration. The effects of self-radiolysis of pure T 2 on the tritium oxidation reaction were calculated. Tritium atoms, the primary product of T 2 self-radiolysis, altered the oxidation mechanism only during the first few seconds following the initiation of the T 2 -O 2 reaction. Ozone, an important intermediate in T 2 oxidation, was monitored in-situ by U.V. absorption spectroscopy for 0.01-1.0 mol% T 2 an 1 atm O 2 . The shape of the experimental ozone time profile agreed with the model predictions. As predicted, the measured initial rate of ozone production varied linearly with initial T 2 concentration ([T 2 ] 0.6 o ), but at an initial rate one-third the predicted value. The steady-state ozone concentration ([O 3 ]ss) was predicted to be dependent on [T 2 ] 0.3 o , but the measured value was [T 2 ] 0.6 o , resulting in four times higher [O 3 ]ss than predicted for a 1.0% T 2 -O 2 mixture. Adding H 2 to the T 2 -O 2 mixture, to provide insight into the differences between the radiolytic and chemical behavior of the tritium, produced a greater decrease in [O 3 ]ss than predicted. Adjusting the reaction cell surface-to-volume ratio showed implications of minor surface removal of ozone

  16. Aqueously Dispersed Silver Nanoparticle-Decorated Boron Nitride Nanosheets for Reusable, Thermal Oxidation-Resistant Surface Enhanced Raman Spectroscopy (SERS) Devices

    Lin, Yi; Bunker, Christopher E.; Fernandos, K. A. Shiral; Connell, John W.

    2012-01-01

    The impurity-free aqueous dispersions of boron nitride nanosheets (BNNS) allowed the facile preparation of silver (Ag) nanoparticle-decorated BNNS by chemical reduction of an Ag salt with hydrazine in the presence of BNNS. The resultant Ag-BNNS nanohybrids remained dispersed in water, allowing convenient subsequent solution processing. By using substrate transfer techniques, Ag-BNNS nanohybrid thin film coatings on quartz substrates were prepared and evaluated as reusable surface enhanced Raman spectroscopy (SERS) sensors that were robust against repeated solvent washing. In addition, because of the unique thermal oxidation-resistant properties of the BNNS, the sensor devices may be readily recycled by short-duration high temperature air oxidation to remove residual analyte molecules in repeated runs. The limiting factor associated with the thermal oxidation recycling process was the Ostwald ripening effect of Ag nanostructures.

  17. Kinetics Study of Silver Electrocrystallization on (3-mercaptopropyl)trimethoxysilane-grafted Indium Tin Oxide Plastic Substrate

    Hau, Nga Yu; Chang, Ya-Huei; Feng, Shien-Ping

    2015-01-01

    Highlights: • The larger charge transfer coefficient supports that MPS promotes electrodeposition. • ACV shows that electron-transfer rate enhanced by 2.5 times after MPS treatment. • The fitting of CA defined the Ag nucleation mode on blank and MPS-grafted ITO-PEN. • MPS treatment changed the nucleation mode from 2-step to a single step one. - Abstract: 3-mercaptopropyl-trimethoxysilane (MPS) self-assembled monolayer (SAM) has been demonstrated as effective promoters to enable direct electroplated metallization on indium tin oxide (ITO) plastic substrate. In this paper, the detail kinetics in Ag electrocrystallization on MPS-grafted ITO-PEN is reported. Contact angle measurement provides evidence of bridging-link effect between the sulfur head groups of MPS and the Ag + ions in the electrolyte. Electrochemical techniques including cyclic voltammetry and Tafel plot were used to investigate the redox kinetics. Quantitative evaluation was conducted by alternating current voltammetry to determine the rate constant of electron transfer. The chronoamperograms and their fitting results suggest a combined model with two-dimensional/three-dimensional nucleation transition and Shariker-Hills model for electroplated Ag on blank ITO-PEN and MPS-grafted ITO-PEN respectively

  18. Mixed conductivity studies in silver oxide based barium vanado-tellurite glasses

    Pant, Meenakshi; Kanchan, D.K.; Sharma, Poonam; Jayswal, Manish S.

    2008-01-01

    The dc conductivity and frequency dependent ac conductivity of the quaternary glass system x(BaO:1.5 Ag 2 O)-(95 - x)V 2 O 5 -5TeO 2 , are reported in the frequency range 1 Hz to 32 MHz in the temperature range from room temperature to 433 K. The dc conductivity measured in high temperature range increased with transition metal oxide content while the activation range decreased. The conductivity arises mainly from polaron hopping between V 4+ and V 5+ ions. High temperature conductivity data satisfy Mott's small polaron hopping model. It is found that a mechanism of non-adiabatic hopping is the most appropriate conduction model for these glasses. A power law behavior σ(ω) = σ dc + Aω n (with 0 < n < 1) is well exhibited by the ac conductivity data of the glasses. The activation energy calculated from both the relaxation time and dc conductivity is found to be nearly same in both the cases. A scaling of the conductivity spectra with respect to temperature and composition is attempted and it is observed that the relaxation dynamics of charge carriers in the present glasses is independent of temperature and composition

  19. Growth and optical properties of silver nanostructures obtained on connected anodic aluminum oxide templates

    Giallongo, G.; Durante, C.; Pilot, R.; Garoli, D.; Bozio, R.; Romanato, F.; Gennaro, A.; Rizzi, G. A.; Granozzi, G.

    2012-08-01

    Ag nanostructures are grown by AC electrodeposition on anodic alumina oxide (AAO) connected membranes acting as templates. Depending on the thickness of the template and on the voltage applied during the growth process, different Ag nanostructures with different optical properties are obtained. When AAO membranes about 1 μm thick are used, the Ag nanostructures consist in Ag nanorods, at the bottom of the pores, and Ag nanotubes departing from the nanorods and filling the pores almost for the whole length. When AAO membranes about 3 μm thick are used, the nanostructures are Ag spheroids, at the bottom of the pores, and Ag nanowires that do not reach the upper part of the alumina pores. The samples are characterized by angle resolved x-ray photoelectron spectroscopy, scanning electron microscopy and UV-vis and Raman spectroscopies. A simple NaOH etching procedure, followed by sonication in ethanol, allows one to obtain an exposed ordered array of Ag nanorods, suitable for surface-enhanced Raman spectroscopy, while in the other case (3 μm thick AAO membranes) the sample can be used in localized surface plasmon resonance sensing.

  20. Growth and optical properties of silver nanostructures obtained on connected anodic aluminum oxide templates

    Giallongo, G; Durante, C; Pilot, R; Bozio, R; Gennaro, A; Rizzi, G A; Granozzi, G; Garoli, D; Romanato, F

    2012-01-01

    Ag nanostructures are grown by AC electrodeposition on anodic alumina oxide (AAO) connected membranes acting as templates. Depending on the thickness of the template and on the voltage applied during the growth process, different Ag nanostructures with different optical properties are obtained. When AAO membranes about 1 μm thick are used, the Ag nanostructures consist in Ag nanorods, at the bottom of the pores, and Ag nanotubes departing from the nanorods and filling the pores almost for the whole length. When AAO membranes about 3 μm thick are used, the nanostructures are Ag spheroids, at the bottom of the pores, and Ag nanowires that do not reach the upper part of the alumina pores. The samples are characterized by angle resolved x-ray photoelectron spectroscopy, scanning electron microscopy and UV–vis and Raman spectroscopies. A simple NaOH etching procedure, followed by sonication in ethanol, allows one to obtain an exposed ordered array of Ag nanorods, suitable for surface-enhanced Raman spectroscopy, while in the other case (3 μm thick AAO membranes) the sample can be used in localized surface plasmon resonance sensing. (paper)

  1. A novel non-enzymatic H2O2 sensor based on polypyrrole nanofibers-silver nanoparticles decorated reduced graphene oxide nano composites

    Moozarm Nia, Pooria; Lorestani, Farnaz; Meng, Woi Pei; Alias, Y.

    2015-03-01

    Graphene oxide (GO) decorated with silver nanoparticles (AgNPs), was electrochemically reduced on glassy carbon electrode (GCE) by an amperometry method (AMP-AgNPs-rGO/GCE). Then, Pyrrole was electropolymerized on the surface of the modified electrode through amperometry process in order to obtain nanofibers of polypyrrole (AMP-PpyNFs-AgNPs-rGO). Fourier-transform infrared transmission spectroscopy and X-ray diffraction approved that during the amperometry process, the GO and Ppy nanofibers were reduced and polymerized respectively and the silver nanoparticles were formed. Field emission scanning electron microscope images indicated that the silver nanoparticles were homogeneously distributed on the rGO surface with a narrow nano size distribution and polypyrrole synthesized in the form of nanofibers with diameter around 100 nm. The first linear section was in the range of 0.1-5 mM with a limit of detection of 1.099 and the second linear section raised to 90 mM with a correlation factor of 0.085 (S/N of 3)

  2. Antimicrobial effect, frictional resistance, and surface roughness of stainless steel orthodontic brackets coated with nanofilms of silver and titanium oxide: a preliminary study.

    Ghasemi, Tania; Arash, Valiollah; Rabiee, Sayed Mahmood; Rajabnia, Ramazan; Pourzare, Amirhosein; Rakhshan, Vahid

    2017-06-01

    Nano-silver and nano-titanium oxide films can be coated over brackets in order to reduce bacterial aggregation and friction. However, their antimicrobial efficacy, surface roughness, and frictional resistance are not assessed before. Fifty-five stainless-steel brackets were divided into 5 groups of 11 brackets each: uncoated brackets, brackets coated with 60 µm silver, 100 µm silver, 60 µm titanium, and 100 µm titanium. Coating was performed using physical vapor deposition method. For friction test, three brackets from each group were randomly selected and tested. For scanning electron microscopy and atomic-force microscopy assessments, one and one brackets were selected from each group. For antibacterial assessment, six brackets were selected from each group. Of them, three were immediately subjected to direct contact with S. mutans. Colonies were counted 3, 6, 24, and 48 h of contact. The other three were stored in water for 3 months. Then were subjected to a similar direct contact test. Results pertaining to both subgroups were combined. Groups were compared statistically. Mean (SD) friction values of the groups 'control, silver-60, silver-100, titanium-60, and titanium-100' were 0.55 ± 0.14, 0.77 ± 0.08, 0.82 ± 0.11, 1.52 ± 0.24, and 1.57 ± 0.41 N, respectively (p = .0004, Kruskal-Wallis). Titanium frictions were significantly greater than control (p  .05, Dunn). In the uncoated group, colony count increased exponentially within 48 h. The coated groups showed significant reductions in colony count (p < .05, two-way-repeated-measures ANOVA). In conclusions, all four explained coatings reduce surface roughness and bacterial growth. Nano-titanium films are not suitable for friction reduction. Nano-silver results were not conclusive and need future larger studies. © 2016 Wiley Periodicals, Inc.

  3. Electrical transport and phase stability in silver iodide-cadmium iodide

    Brightwell, J.W.; Buckley, C.N.; Miller, L.S.; Ray, B.

    1983-01-01

    A form of the equilibrium diagram for the system AgI-CdI 2 is proposed on the basis of thermal, X-ray diffractometer, and electrical conductivity data. Only one intermediate equilibrium phase, of composition Ag 2 CdI 4 , of tetragonal form with a 0 = 6.35 A and c 0 = 12.7 A is apparent; the previously reported hexagonal form of this composition being metastable. Low levels of CdI 2 are found to enhance the formation of the cubic, #betta#-form, af AgI and to increase the electrical conductivity. For various levels of CdI 2 inclusion in AgI, the principal increase in conductivity occurs in the region of 110 0 C instead of at 146 0 C as in pure AgI. (author)

  4. Electrical transport and phase stability in silver iodide-cadmium iodide

    Brightwell, J.W.; Buckley, C.N.; Miller, L.S.; Ray, B. (Lanchester Polytechnic, Coventry (UK))

    1983-03-16

    A form of the equilibrium diagram for the system AgI-CdI/sub 2/ is proposed on the basis of thermal, X-ray diffractometer, and electrical conductivity data. Only one intermediate equilibrium phase, of composition Ag/sub 2/CdI/sub 4/, of tetragonal form with a/sub 0/ = 6.35 A and c/sub 0/ = 12.7 A is apparent; the previously reported hexagonal form of this composition being metastable. Low levels of CdI/sub 2/ are found to enhance the formation of the cubic, ..gamma..-form, af AgI and to increase the electrical conductivity. For various levels of CdI/sub 2/ inclusion in AgI, the principal increase in conductivity occurs in the region of 110 /sup 0/C instead of at 146 /sup 0/C as in pure AgI.

  5. Highly flexible transparent thin film heaters based on silver nanowires and aluminum zinc oxides

    Cheong, Hahn-Gil; Kim, Jin-Hoon; Song, Jun-Hyuk; Jeong, Unyong; Park, Jin-Woo, E-mail: jwpark09@yonsei.ac.kr

    2015-08-31

    In this work, we developed highly flexible transparent film heaters (f-TFHs) composed of Ag nanowire networks (AgNWs) and aluminum zinc oxide (AZO). Uniform AgNWs were roll-to-roll coated on polyethylene terephthalate (PET) substrates using the Mayer rod method, and AZO was sputter-deposited atop the AgNWs at room temperature. The sheet resistance (R{sub s}) and transparency (T{sub opt}) of the AZO-coated AgNWs changed only slightly compared with the uncoated AgNWs. AZO is thermally less conductive than the heat pipes, but increases the thermal efficiency of the heaters blocking the heat convection through the air. Based on Joule heating, a higher average film temperature (T{sub ave}) is attained at a fixed electric potential drop between electrodes (ϕ) as the R{sub s} of the film decreases. Our experimental results revealed that T{sub ave} of the hybrid f-TFH is higher than AgNWs when the ratio of the area coverage of AgNWs to AZO is over a certain value. When a ϕ as low as 3 V/cm was applied to 5 cm × 5 cm f-TFHs, the maximum temperature of the hybrid film was over 100 °C, which is greater than that of AgNWs by more than 30 °C. Furthermore, uniform heating throughout the surfaces is achieved in the hybrid films while heating begins in small areas where densities of the nanowires (NWs) are the highest in the bare network. The non-uniform heating decreases the lifetime of f-TFHs by forming hot spots. Cyclic bending test results indicated that the hybrid films were as flexible as the AgNWs, and the R{sub s} of the hybrid films changes only slightly until 5000 cycles. Combined with the high-throughput coating technology presented here, the hybrid films will provide a robust and scalable strategy for large-area f-TFHs with highly enhanced performance. - Highlights: • We developed highly efficient flexible thin film heaters based on Ag nanowires and AZO composites. • In the composite, AZO plays an important role as an insulation blanket to block heat loss to

  6. Heteroaggregation of graphene oxide with minerals in aqueous phase.

    Zhao, Jian; Liu, Feifei; Wang, Zhenyu; Cao, Xuesong; Xing, Baoshan

    2015-03-03

    Upon release into waters, sediments, and soils, graphene oxide (GO) may interact with fine mineral particles. We investigated the heteroaggregation of GO with different minerals, including montmorillonite, kaolinite, and goethite, in aqueous phase. GO significantly enhanced the dispersion of positively charged goethite (>50%) via heteroaggregation, while there was no interaction between GO and negatively charged montmorillonite or kaolinite. Electrostatic attraction was the dominant force in the GO-goethite heteroaggregation (pH 4.0-8.5), and the dissolved Fe ions (formation of multilayered GO-goethite complex with high configurational stability. These findings are useful for understanding the interaction of GO with mineral surfaces, and potential fate and toxicity of GO under natural conditions in aquatic environments, as well as in soils and sediments.

  7. Gas-Phase Thermolysis of a Thioketen-S-Oxide

    Carlsen, Lars; Egsgaard, Helge; Schaumann, Ernst

    1980-01-01

    The unimolecular gas-phase thermolytic decomposition of 1,1,3,3-tetramethyl-2-thiocarbonylcyclohexane S-oxide (3) has been studied as a function of temperature by a flash vacuum thermolysis (f.v.t.) technique. The products detected are the carbenes (4) and (5), the ketone (6), the keten (7......), the thioketone (8), and the thioketen (9). The product ratio is highly dependent on the thermolysis temperature. The thermolysis of (3) is mechanistically rationalized by assuming the existence of only two concurrent primary processes, which are (a) extrusion of atomic oxygen, leading to the thioketen (9...... and CSO leading to the carbenes (5) and (4), respectively, are observed. Owing to an apparently very short half-life of the oxathiiran (10), only the decomposition products of the three-membered ring compound have been detected. These are the thioketone (8), formed by rearrangement of (10) into the α...

  8. Tailoring silver nanoparticle construction using dendrimer templated silica networks

    Liu Xiaojun; Kakkar, Ashok

    2008-01-01

    We have examined the role of the internal environment of dendrimer templated silica networks in tailoring the construction of silver nanoparticle assemblies. Silica networks from which 3,5-dihydroxybenzyl alcohol based dendrimer templates have been completely removed, slowly wet with an aqueous solution of silver acetate. The latter then reacts with internal silica silanol groups, leading to chemisorption of silver ions, followed by the growth of silver oxide nanoparticles. Silica network constructed using generation 4 dendrimer contains residual dendrimer template, and mixes with aqueous silver acetate solution easily. Upon chemisorption, silver ions get photolytically reduced to silver metal under a stabilizing dendrimer environment, leading to the formation of silver metal nanoparticles

  9. Metal Oxide-Carbon Nanocomposites for Aqueous and Nonaqueous Supercapacitors, Phase I

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I effort focuses on development of novel metal-oxide-carbon nanocomposites for application in pseudocapacitive...

  10. Cooperative properties of single phases of complex oxide catalyst for oxidation of propylene to acrolein

    Orel, L.I.; Udalova, O.V.; Korchak, V.N.; Isaev, O.V.; Krylov, O.V.; Gershenzon, Yu.M.; Aptekar', E.L.

    1992-01-01

    Synergetic effect of increase of acrolein yield during propylene oxidation on mechanical mixture of (α + β)CoMoO 4 and MoO 3 , as well as CO and CO 2 yield on mixture of CoMoO 4 and Bi 2 O 3 ·2MoO 3 was revealed. It is shown that CoMoO 4 generates allyl radicals, desorption of these radicals to gaseous phase is not practically observed with MoO 3 , bismuth molybdates and Fe 2 O 3 · Fe 2 O 3 ·3MoO 3

  11. Structural phase transitions and superconductivity in lanthanum copper oxides

    Crawford, M.K.; Harlow, R.L.; McCarron, E.M.

    1996-01-01

    Despite the enormous effort expended over the past ten years to determine the mechanism underlying high temperature superconductivity in cuprates there is still no consensus on the physical origin of this fascinating phenomenon. This is a consequence of a number of factors, among which are the intrinsic difficulties in understanding the strong electron correlations in the copper oxides, determining the roles played by antiferromagnetic interactions and low dimensionality, analyzing the complex phonon dispersion relationships, and characterizing the phase diagrams which are functions of the physical parameters of temperature and pressure, as well as the chemical parameters of stoichiometry and hole concentration. In addition to all of these intrinsic difficulties, extrinsic materials issues such as sample quality and homogeneity present additional complications. Within the field of high temperature superconductivity there exists a subfield centered around the material originally reported to exhibit high temperature superconductivity by Bednorz and Mueller, Ba doped La 2 CuO 4 . This is structurally the simplest cuprate superconductor. The authors report on studies of phase differences observed between such base superconductors doped with Ba or Sr. What these studies have revealed is a fascinating interplay of structural, magnetic and superconducting properties which is unique in the field of high temperature superconductivity and is summarized in this paper

  12. Evaluation the effect of silver nanoparticles on oxidative stress biomarkers in blood serum and liver and kidney tissues

    Mahsa Tashakori Miyanroudi

    2016-07-01

    Full Text Available Objective(s: Silver nanoparticles (Ag-NPs are one of the most widely used nanomaterials recently. Despite the wide application of nanomaterials, there is limited information concerning their impact on human health and the environment. This study aimed to find the effects of Ag-NPs (40 nm on blood serum, liver and kidney tissues of homing pigeons (Columbia livia.Materials and Methods: Columba livia, in vivo model used in ecotoxicity experiments were gavaged 3 times daily with 75 and 150 ppm of Ag-NPs within 14 days. A group of 30 Pigeon were randomly divided into three groups: Ag-NPs exposed and control groups (n=10. Data analysis was counducted by performing one-way variance (ANOVA in SPSS.v.16.0                                                                         Results: The results of this study illustrated that in the enzyme activity of Glutathione S –transferase (GST, Aspartate amino transferase (AST, Alanine amino transferase (ALT and lactate dehydrogenas (LDH there is a significant difference between treatment groups with Ag-NPs and the control group. Also, lipid peroxidation (LPO analysis and catalase activity CAT suggest Ag-NPs cause the main damage to the liver tissue. On the other hand: Ag-NPs have toxic and harmful effects in both concentrations (75 and 150 ppm, and cause LPO induction, oxidative stress and increase of biomarkers of liver necrosis in under treatment pigeons.Conclusion: The results of this study show that the organism’s exposure to Ag-NPs cause toxicity that is dose-dependant. in this study, the highest damage was observed in the liver. However, this issue will have to be considered more extensively in further studies.

  13. Nonequilibrium phase formation in oxides prepared at low temperature: Fergusonite-related phases

    Mather, S.A.; Davies, P.K.

    1995-01-01

    Sol-gel methods have been developed to prepare YNbO 4 , YTaO 4 , and other rare-earth niobates and tantalates with fergusonite-related crystal structures. At low temperatures, all of the fergusonites, with the exception of SmTaO 4 , crystallize in a metastable tetragonal (T') structure similar to that of tetragonal zirconia. Although all of the equilibrium forms of these oxides adopt a crystal structure containing an ordered distribution of the trivalent and pentavalent cations, a random cation distribution is obtained in the metastable T' phase. Metastable phase formation is often ascribed solely to kinetically limited topotactic crystallization. However, the changes in the grain size and unit-cell volumes that accompany the metastable-to-equilibrium fergusonite conversions imply that other physical phenomena induced by small-particle synthesis, namely the Gibbs-Thompson pressure effect and the increased contribution of surface energy, cannot be ignored

  14. Development of HSPA1A promoter-driven luciferase reporter gene assays in human cells for assessing the oxidative damage induced by silver nanoparticles

    Xin, Lili; Wang, Jianshu; Zhang, Leshuai W.; Che, Bizhong; Dong, Guangzhu; Fan, Guoqiang; Cheng, Kaiming

    2016-01-01

    The exponential increase in the total number of engineered nanoparticles in consumer products requires novel tools for rapid and cost-effective toxicology screening. In order to assess the oxidative damage induced by nanoparticles, toxicity test systems based on a human HSPA1A promoter-driven luciferase reporter in HepG2, LO2, A549, and HBE cells were established. After treated with heat shock and a group of silver nanoparticles (AgNPs) with different primary particle sizes, the cell viability, oxidative damage, and luciferase activity were determined. The time-dependent Ag + ions release from AgNPs in cell medium was also evaluated. Our results showed that heat shock produced a strong time-dependent induction of relative luciferase activity in the four luciferase reporter cells. Surprisingly, at 4 h of recovery, the relative luciferase activity was > 98 × the control level in HepG2-luciferase cells. Exposure to different sizes of AgNPs resulted in activation of the HSPA1A promoter in a dose-dependent manner, even at low cytotoxic or non-cytotoxic doses. The smaller (5 nm) AgNPs were more potent in luciferase induction than the larger (50 and 75 nm) AgNPs. These results were generally in accordance with the oxidative damage indicated by malondialdehyde concentration, reactive oxygen species induction and glutathione depletion, and Ag + ions release in cell medium. Compared with the other three luciferase reporter cells, the luciferase signal in HepG2-luciferase cells is obviously more sensitive and stable. We conclude that the luciferase reporter cells, especially the HepG2-luciferase cells, could provide a valuable tool for rapid screening of the oxidative damage induced by AgNPs. - Highlights: • We established the stable HSPA1A promoter-driven luciferase reporter cells. • Silver nanoparticles induced dose-dependent increases in luciferase activity. • HSPA1A promoter activity is a sensitive and responsive indicator of oxidative stress. • HepG2-luciferase

  15. Development of HSPA1A promoter-driven luciferase reporter gene assays in human cells for assessing the oxidative damage induced by silver nanoparticles

    Xin, Lili, E-mail: llxin@suda.edu.cn [School of Public Health, Medical College of Soochow University, 199 Renai Road, Suzhou 215123, Jiangsu (China); Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, School of Public Health, Soochow University, Suzhou 215123 (China); Wang, Jianshu [Suzhou Center for Disease Prevention and Control, 72 Sanxiang Road, Suzhou, Jiangsu (China); Zhang, Leshuai W. [School of Radiation Medicine and Protection & School for Radiological and Interdisciplinary Sciences (RAD-X), Soochow University, 215123 (China); Che, Bizhong; Dong, Guangzhu [School of Public Health, Medical College of Soochow University, 199 Renai Road, Suzhou 215123, Jiangsu (China); Fan, Guoqiang; Cheng, Kaiming [Suzhou Industrial Park Centers for Disease Control and Prevention, 58 Suqian Road, Suzhou, Jiangsu (China)

    2016-08-01

    The exponential increase in the total number of engineered nanoparticles in consumer products requires novel tools for rapid and cost-effective toxicology screening. In order to assess the oxidative damage induced by nanoparticles, toxicity test systems based on a human HSPA1A promoter-driven luciferase reporter in HepG2, LO2, A549, and HBE cells were established. After treated with heat shock and a group of silver nanoparticles (AgNPs) with different primary particle sizes, the cell viability, oxidative damage, and luciferase activity were determined. The time-dependent Ag{sup +} ions release from AgNPs in cell medium was also evaluated. Our results showed that heat shock produced a strong time-dependent induction of relative luciferase activity in the four luciferase reporter cells. Surprisingly, at 4 h of recovery, the relative luciferase activity was > 98 × the control level in HepG2-luciferase cells. Exposure to different sizes of AgNPs resulted in activation of the HSPA1A promoter in a dose-dependent manner, even at low cytotoxic or non-cytotoxic doses. The smaller (5 nm) AgNPs were more potent in luciferase induction than the larger (50 and 75 nm) AgNPs. These results were generally in accordance with the oxidative damage indicated by malondialdehyde concentration, reactive oxygen species induction and glutathione depletion, and Ag{sup +} ions release in cell medium. Compared with the other three luciferase reporter cells, the luciferase signal in HepG2-luciferase cells is obviously more sensitive and stable. We conclude that the luciferase reporter cells, especially the HepG2-luciferase cells, could provide a valuable tool for rapid screening of the oxidative damage induced by AgNPs. - Highlights: • We established the stable HSPA1A promoter-driven luciferase reporter cells. • Silver nanoparticles induced dose-dependent increases in luciferase activity. • HSPA1A promoter activity is a sensitive and responsive indicator of oxidative stress. • HepG2

  16. Microwave assisted facile synthesis of reduced graphene oxide-silver (RGO-Ag) nanocomposite and their application as active SERS substrate

    Wadhwa, Heena; Kumar, Devender; Mahendia, Suman; Kumar, Shyam

    2017-01-01

    The present paper represents the facile and rapid synthesis of reduced graphene oxide-silver (RGO-Ag) nanocomposite with the help of microwave irradiation. The graphene oxide (GO) solution has been prepared in bulk using Hummer's method followed by microwave assisted in-situ reduction of GO and silver nitrate (AgNO_3) by hydrazine hydrate in a short spam of 5 min. The prepared nanocomposite has been characterized using Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) Scanning Electron Microscopy (SEM) and UV–Visible spectroscopy. TEM analysis shows that Ag nanoparticles with average size 32 nm are uniformly entangled with in RGO layers. The UV–Visible absorption spectrum of nanocomposite depicts the reduction of GO to RGO along with the formation of Ag nanoparticles with the presence of characteristic surface Plasmon resonance (SPR) peak of Ag nanoparticles at 422 nm. The performance of prepared nanocomposite has been tested as the active Surface Enhanced Raman Scattering (SERS) substrate for Rhodamine 6G with detection limit 0.1 μM. - Highlights: • The RGO and RGO-Ag nanocomposite were synthesized with microwave irradiation. • Ag nanoparticles of average size 32 nm are uniformly entangled within RGO layers. • RGO itself is a florescence quencher with SERS detection limit 1 μM for R6G. • RGO-Ag nanocomposite show good SERS activity for R6G with detection limit 0.1 μM.

  17. Microwave assisted facile synthesis of reduced graphene oxide-silver (RGO-Ag) nanocomposite and their application as active SERS substrate

    Wadhwa, Heena, E-mail: heenawadhwa1988@gmail.com; Kumar, Devender, E-mail: devkumsaroha@kuk.ac.in; Mahendia, Suman, E-mail: mahendia@gmail.com; Kumar, Shyam, E-mail: profshyam@gmail.com

    2017-06-15

    The present paper represents the facile and rapid synthesis of reduced graphene oxide-silver (RGO-Ag) nanocomposite with the help of microwave irradiation. The graphene oxide (GO) solution has been prepared in bulk using Hummer's method followed by microwave assisted in-situ reduction of GO and silver nitrate (AgNO{sub 3}) by hydrazine hydrate in a short spam of 5 min. The prepared nanocomposite has been characterized using Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) Scanning Electron Microscopy (SEM) and UV–Visible spectroscopy. TEM analysis shows that Ag nanoparticles with average size 32 nm are uniformly entangled with in RGO layers. The UV–Visible absorption spectrum of nanocomposite depicts the reduction of GO to RGO along with the formation of Ag nanoparticles with the presence of characteristic surface Plasmon resonance (SPR) peak of Ag nanoparticles at 422 nm. The performance of prepared nanocomposite has been tested as the active Surface Enhanced Raman Scattering (SERS) substrate for Rhodamine 6G with detection limit 0.1 μM. - Highlights: • The RGO and RGO-Ag nanocomposite were synthesized with microwave irradiation. • Ag nanoparticles of average size 32 nm are uniformly entangled within RGO layers. • RGO itself is a florescence quencher with SERS detection limit 1 μM for R6G. • RGO-Ag nanocomposite show good SERS activity for R6G with detection limit 0.1 μM.

  18. Electrodeposited Silver Nanoparticles Patterned Hexagonally for SERS

    Gu, Geun Hoi; Lee, Sue Yeone; Suh, Jung Sang

    2010-01-01

    We have fabricated hexagonally patterned silver nanoparticles for surface-enhanced Raman scattering (SERS) by electrodepositing silver on the surface of an aluminum plate prepared by completely removing the oxide from anodic aluminum oxide (AAO) templates. Even after completely removing the oxide, well-ordered hexagonal patterns, similar to the shape of graphene, remained on the surface of the aluminum plate. The borders of the hexagonal pattern protruded up to form sorts of nano-mountains at both the sides and apexes of the hexagon, with the apexes protruding even more significantly than the sides. The aluminum plate prepared by completely removing the oxide has been used in the preparation of SERS substrates by sputter-coating of gold or silver on it. Instead of sputter-coating, here we have electro-deposited silver on the aluminum plate. When silver was electro-deposited on the plate, silver nanoparticles were made along the hexagonal margins.

  19. Preparation of solid silver nanoparticles for inkjet printed flexible electronics with high conductivity.

    Shen, Wenfeng; Zhang, Xianpeng; Huang, Qijin; Xu, Qingsong; Song, Weijie

    2014-01-01

    Silver nanoparticles (NPs) which could be kept in solid form and were easily stored without degeneration or oxidation at room temperature for a long period of time were synthesized by a simple and environmentally friendly wet chemistry method in an aqueous phase. Highly stable dispersions of aqueous silver NP inks, sintered at room temperature, for printing highly conductive tracks (∼8.0 μΩ cm) were prepared simply by dispersing the synthesized silver NP powder in water. These inks are stable, fairly homogeneous and suitable for a wide range of patterning techniques. The inks were successfully printed on paper and polyethylene terephthalate (PET) substrates using a common color printer. Upon annealing at 180 °C, the resistivity of the printed silver patterns decreased to 3.7 μΩ cm, which is close to twice that of bulk silver. Various factors affecting the resistivity of the printed silver patterns, such as annealing temperature and the number of printing cycles, were investigated. The resulting high conductivity of the printed silver patterns reached over 20% of the bulk silver value under ambient conditions, which enabled the fabrication of flexible electronic devices, as demonstrated by the inkjet printing of conductive circuits of LED devices.

  20. Chemical interactions between the metallic silver aerosols and the iodide compounds in the containment building of a PWR reactor during a serious accident; Interactions chimiques entre les aerosols d'argent metallique et les composes iodes dans l'enceinte de confinement d'un reacteur nucleaire a eau pressurisee en cas d'accident grave

    Serra, D.; Saint-Raymond, O.; Zoulalian, A. [Universite Henri Poincare, LERMAB-ENSTIB, 54 - Vandoeuvre-les-Nancy (France); Montanelli, T. [CEA/Cadarache, Inst. de Protection et de Surete Nucleaire, IPSN/DRS/SESHP/LEATS, 13 - Saint-Paul-lez-Durance (France)

    2000-07-01

    During an hypothetical severe accident in a PWR, the iodide fission products can be transferred into the liquid phase of the containment with silver particles (or silver colloid) resulting from the fusion and the vaporization of neutronic control rods. The chemical interactions between the iodide ions and the molecular iodine with the silver particles are studied in an aqueous phase separately and without radiation. The interaction between the iodide ions and silver particles requires a preliminary oxidation step of the silver particles the rate of which depends on the pH, the temperature and the liquid oxygen concentration. A kinetic model including two independent stoichiometries allows to represent correctly the whole experimental runs. At pH = 3, the chemical interactions between molecular iodine and silver particles do not require an oxidation step and a second order kinetic model is able to represent the experimental results considering the operating conditions studied. (authors)

  1. Self-Assembly of Single-Crystal Silver Microflakes on Reduced Graphene Oxide and their Use in Ultrasensitive Sensors

    Chen, Ye; Tao, Jing; Hammami, Mohamed Amen; Hoang, Phuong Mai; Khashab, Niveen M.

    2016-01-01

    Compared to 1D structures, 2D structures have higher specific and active surface, which drastically improves electron transfer and extensibility along 2D plane. Herein, 2D-single crystal silver microflakes (AgMFs) are prepared for the first time

  2. Exposure to silver nanoparticles induces size- and dose-dependent oxidative stress and cytotoxicity in human colon carcinoma cells

    Miethling-Graff, Rona; Rumpker, Rita; Richter, Madeleine

    2014-01-01

    The antimicrobial properties of silver nanoparticles (AgNPs) have made these particles one of the most frequently utilized nanomaterials in consumer products; therefore, a comprehensive understanding of their toxicity is necessary. In particular, information about the cellular uptake and size...

  3. Variable Charge and Electrical Double Layer of Mineral-Water Interfaces: Silver Halides versus Metal (Hydr)Oxides

    Hiemstra, T.

    2012-01-01

    Classically, silver (Ag) halides have been used to understand thermodynamic principles of the charging process and the corresponding development of the electrical double layer (EDL). A mechanistic approach to the processes on the molecular level has not yet been carried out using advanced surface

  4. Silver oxide-containing hydroxyapatite coating supports osteoblast function and enhances implant anchorage strength in rat femur.

    Eto, Shuichi; Miyamoto, Hiroshi; Shobuike, Takeo; Noda, Iwao; Akiyama, Takayuki; Tsukamoto, Masatsugu; Ueno, Masaya; Someya, Shinsuke; Kawano, Shunsuke; Sonohata, Motoki; Mawatari, Masaaki

    2015-09-01

    Antibacterial silver with hydroxyapatite (Ag-HA) is a promising coating material for imparting antibacterial properties to implants. We previously reported that 3% (w/w) silver with HA (3% Ag-HA) has both antibacterial activity and osteoconductivity. In this study, we investigated the effects of Ag-HA on the in vitro osteoblast function and the in vivo anchorage strength and osteoconductivity of implants. Production of the osteoblast marker alkaline phosphatase, but not cytotoxicity, was observed in cells of the osteoblast cell line MC3T3-E1 cultured on the 3% Ag-HA-coated surface. These results were similar to those observed with silver-free HA coating. In contrast, a significant high level of cytotoxicity was observed when the cells were cultured on a 50% Ag-HA-coated surface. The anchorage strength of implants inserted into the femur of Sprague-Dawley (SD) rats was enhanced by coating the implants with 3% Ag-HA. On the 3% Ag-HA-coated surface, both metaphyseal and diaphyseal areas were largely covered with new bone and had adequate osteoconductivity. These results suggest that 3% Ag-HA, like conventional HA, promotes osteogenesis by supporting osteoblast viability and function and thereby contributes to sufficient anchorage strength of implants. Application of 3% Ag-HA, which combines the osteoconductivity of HA and the antibacterial activity of silver, to prosthetic joints will help prevent postoperative infections. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  5. Disinfection of Spacecraft Potable Water Systems by Passivation with Ionic Silver

    Birmele, Michele N.; McCoy, LaShelle e.; Roberts, Michael S.

    2011-01-01

    Microbial growth is common on wetted surfaces in spacecraft environmental control and life support systems despite the use of chemical and physical disinfection methods. Advanced control technologies are needed to limit microorganisms and increase the reliability of life support systems required for long-duration human missions. Silver ions and compounds are widely used as antimicrobial agents for medical applications and continue to be used as a residual biocide in some spacecraft water systems. The National Aeronautics and Space Administration (NASA) has identified silver fluoride for use in the potable water system on the next generation spacecraft. Due to ionic interactions between silver fluoride in solution and wetted metallic surfaces, ionic silver is rapidly depleted from solution and loses its antimicrobial efficacy over time. This report describes research to prolong the antimicrobial efficacy of ionic silver by maintaining its solubility. Three types of metal coupons (lnconel 718, Stainless Steel 316, and Titanium 6AI-4V) used in spacecraft potable water systems were exposed to either a continuous flow of water amended with 0.4 mg/L ionic silver fluoride or to a static, pre-treatment passivation in 50 mg/L ionic silver fluoride with or without a surface oxidation pre-treatment. Coupons were then challenged in a high-shear, CDC bioreactor (BioSurface Technologies) by exposure to six bacteria previously isolated from spacecraft potable water systems. Continuous exposure to 0.4 mg/L ionic silver over the course of 24 hours during the flow phase resulted in a >7-log reduction. The residual effect of a 24-hour passivation treatment in 50 mg/L of ionic silver resulted in a >3-log reduction, whereas a two-week treatment resulted in a >4-log reduction. Results indicate that 0.4 mg/L ionic silver is an effective biocide against many bacteria and that a prepassivation of metal surfaces with silver can provide additional microbial control.

  6. Eco-Friendly Synthesis of Silver Nanoparticles Through Economical Methods and Assessment of Toxicity Through Oxidative Stress Analysis in the Labeo Rohita.

    Khan, Muhammad Saleem; Qureshi, Naureen Aziz; Jabeen, Farhat; Asghar, Muhammad Saleem; Shakeel, Muhammad; Fakhar-E-Alam, Muhammad

    2017-04-01

    The physicochemical and biological properties of metals change as the particles are reduced to nanoscale. This ability increases the application of nanoparticles in commercial and medical industry. Keeping in view this importance, Silver nanoparticles (Ag-NPs) were synthesized by reduction methods using formaldehyde as reducing agent in the chemical route and lemon extracts in the biological route. The scanning electron microscope (SEM) images of nanoparticles suggested that the particles were either agglomerated or spherical in shape with mean diameter of 16.59 nm in the chemical route and 42.93 nm in the biological route. The particles were between 5 and 80 nm with maximum frequency between 5 and 20 nm in the chemical route and between 5 and 100 nm with maximum frequency between 15 and 50 nm in the biological method. In the second phase of the study, the effect of Ag-NPs on the oxidative stress was studied. For this purpose, Labeo rohita (20 ± 2.5 g in weight and 12 ± 1.4 cm in length) were involved. Six treatments were applied in three replicates having five fishes in each replicate. The first treatment was used as control group, and the other five treatments were exposed to either 10 or 20 or 30 or 45 or 55 mg L -1 of Ag-NPs for 28 days. The treatment of Ag-NPs caused oxidative stress in the liver and gill tissues, which induced alterations in the activities of antioxidant enzymes. The level of catalase (CAT) was decreased in response to Ag-NPs concentration in dose-dependent manner. Ag-NPs treatment stimulated the liver and gill tissues to significantly increase the level of superoxide dismutase (SOD), which might be due to synthesis of SOD and addition in the pre-existing SOD level. The level decreases again due to depletion of SOD level. There was a sharp decline in the activities of glutathione S-transferase (GST) in both gills and liver tissues even at lower concentration, and this decrease in the GST activity was significantly

  7. Reaction kinetics of oxygen on single-phase alloys, oxidation of nickel and niobium alloys

    Lalauze, Rene

    1973-01-01

    This research thesis first addresses the reaction kinetics of oxygen on alloys. It presents some generalities on heterogeneous reactions (conventional theory, theory of jumps), discusses the core reaction (with the influence of pressure), discusses the influence of metal self-diffusion on metal oxidation kinetics (equilibrium conditions at the interface, hybrid diffusion regime), reports the application of the hybrid diffusion model to the study of selective oxidation of alloys (Wagner model, hybrid diffusion model) and the study of the oxidation kinetics of an alloy forming a solid solution of two oxides. The second part reports the investigation of the oxidation of single phase nickel and niobium alloys (phase α, β and γ)

  8. Development studies for a novel wet oxidation process. Phase 2

    1994-07-01

    DETOX SM is a catalyzed wet oxidation process which destroys organic materials in an acidic water solution of iron at 373 to 473 K. The solution can be used repeatedly to destroy great amounts of organic materials. Since the process is conducted in a contained vessel, air emissions from the process can be well controlled. The solution is also capable of dissolving and concentrating many heavy and radioactive metals for eventual stabilization and disposal. The Phase 2 effort for this project is site selection and engineering design for a DETOX demonstration unit. Site selection was made using a set of site selection criteria and evaluation factors. A survey of mixed wastes at DOE sites was conducted using the Interim Mixed Waste Inventory Report. Sites with likely suitable waste types were identified. Potential demonstration sites were ranked based on waste types, interest, regulatory needs, scheduling, ability to provide support, and available facilities. Engineering design for the demonstration unit is in progress and is being performed by Jacobs Applied Technology. The engineering design proceeded through preliminary process flow diagrams (PFDs), calculation of mass and energy balances for representative waste types, process and instrumentation diagrams (P and IDs), preparation of component specifications, and a firm cost estimate for fabrication of the demonstration unit

  9. High Performance Nitrous Oxide Analyzer for Atmospheric Research, Phase I

    National Aeronautics and Space Administration — This project targets the development of a highly sensitive gas sensor to monitor atmospheric nitrous oxide. Nitrous oxide is an important species in Earth science...

  10. Enhancement of as-sputtered silver-tantalum oxide thin film coating on biomaterial stainless steel by surface thermal treatment

    Alias, Rodianah; Mahmoodian, Reza; Shukor, Mohd Hamdi Abd; Yew, Been Seok; Muhamad, Martini

    2018-04-01

    Stainless steel 316L (SS316L) is extensively used as surgical/clinical tools due to its low carbon content and excellent mechanical characteristic. The fabrication of metal ceramic based on this metallic biomaterial favor its biofunctionality properties. However, instability phase of amorphous thin film lead to degradation, corrosion and oxidation. Thus, thin film coating requires elevated adhesion strength and higher surface hardness to meet clinical tools criteria. In this study, the SS316L was deposited with micron thickness of Ag-TaO thin film by using magnetron sputtering. The microstructure, elemental analysis and phase identification of Ag-TaO thin film were characterized by using FESEM, EDX and XRD, respectively; whereas the micro scratch test and micro hardness test were performed by using Micro Scratch Testing System and Vickers Micro Hardness Tester, respectively. It was found that the coating thin film's adhesion and hardness strength were improved from 672 to 2749 mN and 142 to 158 Hv respectively. It was found that the as-deposited surface were treated at 500 °C of temperatures with 2 °C/min ramping rate enhance 4.1 times of the adhesion strength value. Furthermore, FESEM characterization revealed coarsening structure of the thin film coating which can provide high durability service.

  11. Comparison between a commercial solid-phase extraction cartridge and a home-made silver containing charcoal column: purification of Mo-99 from I-131 and Te-121

    Dias, Carla Roberta; Teodoro, Rodrigo; Osso Junior, Joao

    2011-01-01

    Among the radioisotopes used for medical application in Nuclear Medicine, 99m Tc, readily available from the elution of 99 Mo/ 99m Tc generators, is the most used, responsible for more than eighty percent of the total applications. These generators use the 99 Mo radioisotope that is produced in nuclear reactors and IPEN imports all the 99 Mo used in Brazil, mainly from Canada (Nordion). Due to the increasing needs of the Nuclear Medicine in Brazil and the world shortage of 99 Mo observed since 2008, IPEN decided to construct a new research reactor named Brazilian Multipurpose Reactor (BMR) as well as to develop the production of 99 Mo through the route of 235 U fission using a CINTICHEM modified separation process. The 99 Mo obtained from this process contains some contaminants and need to be purified. The aim of this work is to compare the preliminary results of the purification step of the solution containing 99 Mo and the contaminants, 131 I and 121 Te in the silver containing charcoal column and a solid-phase extraction cartridge. The purification process of 99 Mo coming from fission LEU foils was performed by adsorption chromatography using a home-made activated charcoal containing silver column (AC-Ag) and a commercial solid-phase extraction cartridge (OnGuard II Ag). High yields of 99 Mo elution and high retention of 131 I were achieved in the AC-Ag column and silver cartridge but 121 Te was more retained in the cartridge than in the AC-Ag column. (author)

  12. Phyto-assisted synthesis of bio-functionalised silver nanoparticles and their potential anti-oxidant, anti-microbial and wound healing activities.

    Mohanta, Yugal Kishore; Biswas, Kunal; Panda, Sujogya Kumar; Bandyopadhyay, Jaya; De, Debashis; Jayabalan, Rasu; Bastia, Akshaya Kumar; Mohanta, Tapan Kumar

    2017-12-01

    Bio- synthesis of silver nanoparticles (AgNPs) was made by using the aqueous leaf extract of Ardisia solanacea. Rapid formation of AgNPs was observed from silver nitrate upon treatment with the aqueous extract of A. solanacea leaf. The formation and stability of the AgNPs in the colloidal solution were monitored by UV-visible spectrophotometer. The mean particle diameter of AgNPs was calculated from the DLS with an average size ∼4 nm and ∼65 nm. ATR-FTIR spectroscopy confirmed the presence of alcohols, aldehydes, flavonoids, phenols and nitro compounds in the leaf which act as the stabilizing agent. Antimicrobial activity of the synthesized AgNPs was performed using agar well diffusion and broth dilution method against the Gram-positive and Gram-negative bacteria. Further, robust anti-oxidative potential was evaluated by DPPH assay. The highest antimicrobial activity of synthesized AgNPs was found against Pseudomonas aeruginosa (28.2 ± 0.52 mm) whereas moderate activity was found against Bacillus subtilis (16.1 ± 0.76), Candida kruseii (13.0 ± 1.0), and Trichophyton mentagrophytes (12.6 ± 1.52). Moreover, the potential wound healing activity was observed against the BJ-5Ta normal fibroblast cell line. Current research revealed that A. solanacea was found to be a suitable source for the green synthesis of silver nanoparticles.

  13. Kinetics, Mechanism, and Secondary Organic Aerosol Yield of Aqueous Phase Photo-oxidation of α-Pinene Oxidation Products.

    Aljawhary, Dana; Zhao, Ran; Lee, Alex K Y; Wang, Chen; Abbatt, Jonathan P D

    2016-03-10

    Formation of secondary organic aerosol (SOA) involves atmospheric oxidation of volatile organic compounds (VOCs), the majority of which are emitted from biogenic sources. Oxidation can occur not only in the gas-phase but also in atmospheric aqueous phases such as cloudwater and aerosol liquid water. This study explores for the first time the aqueous-phase OH oxidation chemistry of oxidation products of α-pinene, a major biogenic VOC species emitted to the atmosphere. The kinetics, reaction mechanisms, and formation of SOA compounds in the aqueous phase of two model compounds, cis-pinonic acid (PIN) and tricarballylic acid (TCA), were investigated in the laboratory; TCA was used as a surrogate for 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA), a known α-pinene oxidation product. Aerosol time-of-flight chemical ionization mass spectrometry (Aerosol-ToF-CIMS) was used to follow the kinetics and reaction mechanisms at the molecular level. Room-temperature second-order rate constants of PIN and TCA were determined to be 3.3 (± 0.5) × 10(9) and 3.1 (± 0.2) × 10(8) M(-1) s(-1), respectively, from which were estimated their condensed-phase atmospheric lifetimes. Aerosol-ToF-CIMS detected a large number of products leading to detailed reaction mechanisms for PIN and MBTCA. By monitoring the particle size distribution after drying, the amount of SOA material remaining in the particle phase was determined. An aqueous SOA yield of 40 to 60% was determined for PIN OH oxidation. Although recent laboratory studies have focused primarily on aqueous-phase processing of isoprene-related compounds, we demonstrate that aqueous formation of SOA materials also occurs from monoterpene oxidation products, thus representing an additional source of biogenically driven aerosol formation.

  14. Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

    Ngah Demon, Siti Zulaikha; Miyauchi, Yoshihiro; Mizutani, Goro; Matsushima, Toshinori; Murata, Hideyuki

    2014-08-01

    We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕinterface with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°.

  15. Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

    Ngah Demon, Siti Zulaikha; Miyauchi, Yoshihiro; Mizutani, Goro; Matsushima, Toshinori; Murata, Hideyuki

    2014-01-01

    We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕ_ with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°.

  16. Oxidation of aniline with silver nitrate accelerated by p-phenylenediamine: A new route to conducting composites

    Bober, Patrycja; Stejskal, Jaroslav; Trchová, Miroslava; Prokeš, J.; Sapurina, I.

    2010-01-01

    Roč. 43, č. 24 (2010), s. 10406-10413 ISSN 0024-9297 R&D Projects: GA AV ČR IAA400500905; GA AV ČR IAA100500902; GA ČR GA203/08/0686; GA MŠk ME 847 Institutional research plan: CEZ:AV0Z40500505 Keywords : polyaniline * p-phenylenediamine * silver Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.838, year: 2010

  17. Effect of rose water on structural, optical and electrical properties of composites of reduced graphene oxide-poly (vinyl alcohol) (PVA) grafted with silver nanoparticles

    Kumar, Devender; Wadhwa, Heena; Mahendia, Suman; Chand, Fakir; Kumar, Shyam

    2017-02-01

    In this work, nanocomposites of reduced graphene oxide-poly (vinyl alcohol) (PVA) grafted with silver nanoparticles (rGO-PVA-Ag) were prepared in the absence and presence of rose water. The optical characterizations of prepared nanocomposites were done through UV-visible spectroscopy and Transmission Electron Microscopy (TEM) and Raman spectroscopy was employed for the surface characterization. The grafted silver (Ag) nanoparticles are found to be almost spherical in shape with reduction in their mean diameter from 47 nm to 26 nm after addition of rose water. The UV-visible absorption spectra of as-prepared rGO-PVA-Ag nanocomposites without and with rose water depicted surface plasmon resonance (SPR) peak at around 448 nm which coincides with the predicted spectra from simulation based on the Mie Theory. The electrical dc conductivity measurements as the function of temperature from room temperature to 55 °C were investigated. It has been found that use of rose water in synthesis process increases the electrical conductivity of the rGO-PVA-Ag. The mode of the electrical conduction in the composites can be explained using Efros-Shklovskii Variable Range Hopping mechanism (ES VRH).

  18. Surface functionalization of copper via oxidative graft polymerization of 2,2'-bithiophene and immobilization of silver nanoparticles for combating biocorrosion.

    Wan, Dong; Yuan, Shaojun; Neoh, K G; Kang, E T

    2010-06-01

    An environmentally benign approach to surface modification was developed to impart copper surface with enhanced resistance to corrosion, bacterial adhesion and biocorrosion. Oxidative graft polymerization of 2,2'-bithiophene from the copper surface with self-assembled 2,2'-bithiophene monolayer, and subsequent reduction of silver ions to silver nanoparticles (Ag NPs) on the surface, give rise to a homogeneous bithiophene polymer (PBT) film with densely coupled Ag NPs on the copper surface (Cu-g-PBT-Ag NP surface). The immobilized Ag NPs were found to significantly inhibit bacterial adhesion and enhance the antibacterial properties of the PBT modified copper surface. The corrosion inhibition performance of the functionalized copper substrates was evaluated by Tafel polarization curves and electrochemical impedance spectroscopy. Arising from the chemical affinity of thiols for the noble and coinage metals, the copper surface functionalized with both PBT brushes and Ag NPs also exhibits long-term stability, and is thus potentially useful for combating the combined problems of corrosion and biocorrosion in harsh marine and aquatic environments.

  19. Phase chemistry and microstructure evolution in silver-clad (Bi2-xPbx)Sr2Ca2Cu3Oy filaments

    Luo, J.S.; Merchant, N.; Maroni, V.A.; Escorcia-Aparicio, E.; Gruen, D.M.; Tani, B.S.; Riley, G.N. Jr.; Carter, W.L.

    1992-08-01

    The reaction kinetics and mechanism that control the conversion of (Bi,Pb) 2 Sr 2 CaCu 2 O z (Bi-2212) + alkaline earth cuporates to (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O y (Bi-2223) in silver-clad wires were investigated as a function of equilibration temperature and time at a fixed oxygen partial pressure (7.5% O 2 ). Measured values for the fractional conversion of Bi-2223 versus time have been evaluated based on the Avrami equation. SEM and TEM studies of partially and fully converted wires have revealed that (1) the growth of Bi-2223 is two-dimensional and controlled by a diffusion process, (2) liquid phases are present during part of the Bi-2212 -> Bi-2212 conversion, and (3) segregation of the second phases occurs in early time domains of the reaction

  20. Low temperature phase transition of the stoichiometric Ln2NiO4 oxides

    Fernandez, F.; Saez-Puche, R.; Botto, I.L.; Baran, E.J.

    1991-01-01

    In this paper we will present a comparative study of the structural phase transition in Ln 2 NiO 4 oxides, by means of neutron diffraction and infrared(IR) spectroscopy. In the Ln 2 NiO 4 oxides (Ln=La, Pr and Nd), there is a low temperature structural phase transition from the orthorhombic symmetry to a tetragonal phase, of first order character. The IR spectra show, at low temperature, a splitting of the bands related with the stretching Ni-O, strongly correlated with the phase transformation. From the neutron data, the phase transition can be visualized as a sudden tilt of the nickel octahedra

  1. Characterization of Schottky barrier diodes fabricated from electrochemical oxidation of {alpha} phase brass

    Bond, John W., E-mail: jwb13@le.ac.u [Forensic Research Centre, University of Leicester, Leicester LE1 7 EA (United Kingdom)

    2011-04-01

    By careful selection of chloride ion concentration in aqueous sodium chloride, electrochemical oxidation of {alpha} phase brass is shown to permit fabrication of either p-type copper (I) oxide/metal or n-type zinc oxide/metal Schottky barrier diodes. X-ray photoelectron and Auger electron spectroscopies provide evidence that barrier formation and rectifying qualities depend on the relative surface abundance of copper (I) oxide and zinc oxide. X-ray diffraction of the resulting diodes shows polycrystalline oxides embedded in amorphous oxidation products that have a lower relative abundance than the diode forming oxide. Conventional I/V characteristics of these diodes show good rectifying qualities. When neither of the oxides dominate, the semiconductor/metal junction displays an absence of rectification.

  2. Monolithic Approach to Oxide Dispersion Strengthened Aluminum, Phase I

    National Aeronautics and Space Administration — Nassau Stern Company is investigating an approach for manufacturing oxide dispersion strengthened (ODS) aluminum in bulk rather than powder form. The approach...

  3. Advanced Wastewater Photo-oxidation System, Phase I

    National Aeronautics and Space Administration — Pioneer Astronautics proposes an advanced photocatalytic oxidation reactor for enhancing the reliability and performance of Water Recovery Post Processing systems...

  4. Highly Efficient, Durable Regenerative Solid Oxide Stack, Phase I

    National Aeronautics and Space Administration — Precision Combustion, Inc. (PCI) proposes to develop a highly efficient regenerative solid oxide stack design. Novel structural elements allow direct internal...

  5. Oxidation kinetics of zircaloy-4 in the temperature range correspondent to alpha phase

    Medeiros, L.F.

    1975-12-01

    Oxidation kinetics of Zry-4 in the alpha phase is isothermally studied in the temperature range from 600 0 C to 800 0 C, by continuous and discontinuous gravimetric methods. The total mass gain during the oxidation takes place by two distinct ways: oxide formation and solid solution formation. The first one has been studied by microscopy: the latter by microhardness. The oxygen diffusion coefficients in the zirconium are experimentally determined by microhardness measurements and are compared with those obtained by the oxide layer thickness and by oxygen mass in the oxide. The oxygen diffusion coefficients in the oxide are obtained too by oxide layer thickness and by oxygen diffusivities in the alpha phase and compared with literature. (author)

  6. Improvement of optical and electrical properties of indium tin oxide layer of GaN-based light-emitting diode by surface plasmon in silver nanoparticles

    Cho, Chu-Young; Hong, Sang-Hyun; Park, Seong-Ju

    2015-01-01

    We report on the effect of silver (Ag) nanoparticles on the optical transmittance and electrical conductivity of indium tin oxide (ITO) transparent conducting layer deposited on p-GaN layer of light-emitting diodes (LEDs). The sheet resistance of ITO and the series resistance of LEDs were decreased due to the increased electrical conductivity of ITO by Ag nanoparticles, compared with those of the LEDs with a bare ITO only. The ITO transmittance was also improved by localized surface plasmon resonance between the incident light and the randomly distributed Ag nanoparticles on ITO. The optical output power of LEDs with Ag nanoparticles on ITO was increased by 16% at 20 mA of injection current. - Highlights: • We studied the effect of Ag nanoparticles deposited on ITO on the properties of LED. • The optical power of LED and transmittance of ITO were improved by Ag surface plasmon. • The electrical conductivity of ITO was increased by Ag nanoparticles

  7. The influence of natural organic matter and aging on suspension stability in guideline toxicity testing of silver, zinc oxide, and titanium dioxide nanoparticles with Daphnia magna

    Cupi, Denisa; Hartmann, Nanna Isabella Bloch; Baun, Anders

    2015-01-01

    The present study investigated changes in suspension stability and ecotoxicity of engineered nanoparticles (ENPs) by addition of Suwannee River natural organic matter and aging of stock and test suspensions prior to testing. Acute toxicity tests of silver (Ag), zinc oxide (ZnO), and titanium...... not decrease toxicity significantly. Conversely, the presence of Suwannee River natural organic matter (NOM; 20mgL-1) completely alleviated Ag ENP toxicity in all testing scenarios and did not aid in stabilizing suspensions. In contrast, addition of Suwannee River NOM stabilized ZnO ENP suspensions and did...... in stock suspensions. The authors' results suggest that aging and presence of Suwannee River NOM are important parameters in standard toxicity testing of ENPs, which in some cases may aid in gaining better control over the exposure conditions but in other cases might contribute to agglomeration...

  8. Reduction of silver nanoparticles onto graphene oxide nanosheets with N,N-dimethylformamide and SERS activities of GO/Ag composites

    Yang Yingkui; He Chengen; He Wenjie; Yu Linjuan; Peng Rengui; Xie Xiaolin; Wang Xianbao; Mai Yiuwing

    2011-01-01

    Silver nanoparticles (Ag NPs) have been homogeneously deposited onto graphene oxide (GO) nanosheets by an optimal method, in which N,N-dimethylformamide (DMF) as a co-dispersant of GO and reductant of sliver ions is added to an aqueous suspension of GO and AgNO 3 . GO nanosheets are uniformly covered by Ag NPs with a narrow size distribution and inter-particle gap. Raman signals of GO are greatly enhanced after deposition owing to the charge transfer interaction of GO with Ag NPs. The GO/Ag composite can be further utilized as an effective surface-enhanced Raman scattering (SERS) active substrate. Several new Raman bands and frequency shifts are clearly observed in using 4-aminothiophenol (4-ATP) as a Raman probe on GO/Ag compared to the normal Raman spectrum of solid 4-ATP. The Raman enhancement arises from a major electromagnetic effect and a minor chemical effect.

  9. Oxidation studies of β-sialon ceramics containing amorphous and / or crystalline intergranular phases

    Persson, J.; Kall, P.O.; Jansson, K.; Nygren, M.

    1992-01-01

    β-sialon ceramics of equal overall compositions but containing amorphous, partly crystalline and almost completely crystalline intergranular phase(s) have been oxidized in oxygen at 1350 deg C for 20 hours. The obtained weight gain curves do not follow the parabolic rate law (ΔW/A 0 ) 2 = k p t + β. To the extent that crystallization occurs in the oxide scale during the oxidation experiment, the amorphous cross section area through which oxygen most easily diffuses will decrease with time. A brief description of this new rate law is given, and the obtained oxidation curves will be discussed within that framework. 4 refs., 2 tabs., 2 figs

  10. Phase-field modeling of corrosion kinetics under dual-oxidants

    Wen, You-Hai; Chen, Long-Qing; Hawk, Jeffrey A.

    2012-04-01

    A phase-field model is proposed to simulate corrosion kinetics under a dual-oxidant atmosphere. It will be demonstrated that the model can be applied to simulate corrosion kinetics under oxidation, sulfidation and simultaneous oxidation/sulfidation processes. Phase-dependent diffusivities are incorporated in a natural manner and allow more realistic modeling as the diffusivities usually differ by many orders of magnitude in different phases. Simple free energy models are then used for testing the model while calibrated free energy models can be implemented for quantitative modeling.

  11. Silver oxide nanoparticles embedded silk fibroin spuns: Microwave mediated preparation, characterization and their synergistic wound healing and anti-bacterial activity.

    Babu, Punuri Jayasekhar; Doble, Mukesh; Raichur, Ashok M

    2018-03-01

    The synergistic wound healing and antibacterial activity of silver oxide nanoparticles embedded silk fibroin (Ag 2 O-SF) spuns is reported here. UV-Vis spectro photometric analysis of these spuns showed the surface plasmon resonance (SPR) confirming the formation of the silver oxide nanoparticles (Ag 2 O NPs) on the surface of the silk fibroin (SF). Scanning electron microscope (SEM) and Differential scanning calorimetry (DSC) also confirmed the presence of Ag 2 O NPs on surface of SF. X-ray diffraction (XRD) analysis revealed the crystalline nature of both SF and Ag 2 O-SF. Fourier transform infrared spectroscopy (FT-IR) results showed the different forms of silk (I and II) and their corresponding protein (amide I, II, III) confirmations. Biodegradation study revealed insignificant changes in the morphology of Ag 2 O-SF spuns even after 14 days of immersion in phosphate buffered saline (PBS). Ag 2 O-SF spuns showed excellent antibacterial activity against both pathogen (S. aureus and M. tuberculosis) and non-pathogen (E. coli) bacteria. More importantly, In vitro wound healing (scratch assay) assay revealed fast migration of the T3T fibroblast cells through the scratch area treated with extract of Ag 2 O-SF spuns and the area was completely covered within 24 h. Cytotoxicity assay confirmed the biocompatible nature of the Ag 2 O-SF spuns, thus suggesting an ideal material for wound healing and anti-bacterial applications. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. A glassy carbon electrode modified with a composite consisting of reduced graphene oxide, zinc oxide and silver nanoparticles in a chitosan matrix for studying the direct electron transfer of glucose oxidase and for enzymatic sensing of glucose

    Li, Zhenjiang; Sheng, Liying; Xie, Cuicui; Meng, Alan; Zhao, Kun

    2016-01-01

    The authors describe the fabrication of a nanocomposite consisting of reduced graphene oxide, zinc oxide and silver nanoparticles by microwave-assisted synthesis. The composite was further reduced in-situ with hydrazine hydrate and then placed, along with the enzyme glucose oxidase, on a glassy carbon electrode. The synergistic effect of the materials employed in the nanocomposite result in excellent electrocatalytic activity. The Michaelis-Menten constant of the adsorbed GOx is 0.25 mM, implying a remarkable affinity of the GOx for glucose. The amperometric response of the modified GCE is linearly proportional to the concentration of glucose in 0.1 to 12.0 mM concentration range, and the detection limit is 10.6 µM. The biosensor is highly selective, well reproducible and stable. (author)

  13. Photocatalytic production of 1O2 and ·OH mediated by silver oxidation during the photoinactivation of Escherichia coli with TiO2

    Castro, Camilo A.; Osorio, Paula; Sienkiewicz, Andrzej; Pulgarin, Cesar; Centeno, Aristóbulo; Giraldo, Sonia A.

    2012-01-01

    Highlights: ► Metallic silver enhances the Ag–TiO 2 photoinactivation of Escherichia coli under Vis irradiation. ► 1 O 2 and ·OH were identified in Vis irradiated Ag–TiO 2 suspensions. ► UV oxidized the Ag metallic species in the material decreasing photoactivity. ► Dark contact of the UV oxidized material with E. coli regenerates the photocatalyst. - Abstract: Ag loaded TiO 2 was applied in the photocatalytic inactivation of Escherichia coli under ultraviolet (UV) and visible (Vis) light irradiations. Ag enhanced the TiO 2 photodisinfecting effect under Vis irradiation promoting the formation of singlet oxygen and hydroxyl radicals as identified by EPR analyses. Ag nanoparticles, determined on TEM analyses, undergo an oxidation process on the TiO 2 's surface under UV or Vis irradiation as observed by XPS. In particular, UV pre-irradiation of the material totally diminished its photodisinfection activity under a subsequent Vis irradiation test. Under UV, photodegradation of dichloroacetic acid (DCA), attributed to photoproduced holes in TiO 2 , was inhibited by the presence of Ag suggesting that oxidation of Ag 0 to Ag + and Ag 2+ is faster than the oxidative path of the TiO 2 's holes on DCA molecules. Furthermore, photoassisted increased of Ag + concentration on TiO 2 's surface enhances the bacteriostatic activity of the material in dark periods. Indeed, this latter dark contact of Ag + –TiO 2 and E. coli seems to induce recovering of the Vis light photoactivity promoted by the surface Ag photoactive species.

  14. Three-phase solvent bar micro-extraction as an approach to silver ultra-traces speciation in estuarine water samples.

    López-López, José Antonio; Herce-Sesa, Belén; Moreno, Carlos

    2015-01-01

    Silver ion inputs into the environment due to human activities have been increased in the last years because it has been used as a bactericide with application in medical, homecare and self-care products. In addition, it is toxic at low concentration for aquatic organisms. In estuarine waters, salinity and dissolved organic matter (DOM) regulate Ag(+) concentration by the formation of complexes as AgCln((n-1)-) and Ag-DOM. Difficulties of Ag(+) analysis in estuaries are associated to its low concentration level and interferences of sample matrix. Liquid and solid phase extraction methods have been used for speciation of silver in waters; however, miniaturized methods that offer a better environmental profile are desirable. Hollow fiber liquid phase micro-extraction (HFLPME) allows obtaining higher pre-concentration factors with a reduction of waste generation. Notwithstanding, some operational improvements are needed to permit their use as a routine method that can be afforded using a configuration of three-phase solvent bar micro-extraction (3PSBME). In this work, tri-isobutylphosphine sulphide (TIBPS) has been used as an extractant for Ag(+) pre-concentration in estuarine waters by 3PSBME. Under optimized conditions, Ag(+) has been pre-concentrated 60 times and the method presents a limit of detection of 1.53 ng L(-1). To evaluate which Ag species is transported by TIBPS, Cl(-) and DOM have been added to synthetic samples. As a result, a decrease in Ag pre-concentration efficiency after additions has been observed and quantified. Results showed that Ag(+) is selectively transported by TIBPS from estuarine water samples after comparison of the results with those obtained by the reference method of liquid extraction with APDC/DDDC. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Preparation of glasses and glass ceramics of heavy metal oxides containing silver: optical, structural and electrochemical properties; Preparacao de vidros e vitroceramicas de oxidos de metais pesados contendo prata: propriedades opticas, estruturais e eletroquimicas

    Bregadiolli, Bruna A. [Departamento de Fisica, Faculdade de Ciencias, Universidade Estadual Paulista, Bauru - SP (Brazil); Souza, Ernesto R.; Sigoli, Fernando A. [Instituto de Quimica, Universidade Estadual de Campinas, Campinas - SP (Brazil); Caiut, Jose M.A. [Departamento de Quimica, Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto - SP (Brazil); Alencar, Monica A.S.; Benedetti, Assis V. [Instituto de Quimica, Universidade Estadual Paulista, Araraquara - SP (Brazil); Nalin, Marcelo, E-mail: mnalin@ufscar.br [Departamento de Quimica, Universidade Federal de Sao Carlos, SP, (Brazil)

    2012-07-01

    Silver containing heavy metal oxide glasses and glass ceramics of the system WO{sub 3}-SbPO{sub 4} -PbO-AgCl with different AgCl contents have been prepared and their thermal, structural and optical properties characterized. Glass ceramics containing metallic silver nanoparticles have been prepared by annealing glass samples at temperatures above the glass transition and analyzed by transmission electron microscopy and energy dispersive X-ray microanalysis. The presence of the metallic clusters has been also confirmed by the observation of a surface plasmon resonance band in the visible range. Cyclic voltammetric measurements indicated the presence of metallic silver into the glasses, even before to perform the thermal treatment. (author)

  16. Gravimetric and volumetric determination of the purity of electrolytically refined silver and the produced silver nitrate

    Ačanski Marijana M.

    2007-01-01

    Full Text Available Silver is, along with gold and the platinum-group metals, one of the so called precious metals. Because of its comparative scarcity, brilliant white color, malleability and resistance to atmospheric oxidation, silver has been used in the manufacture of coins and jewelry for a long time. Silver has the highest known electrical and thermal conductivity of all metals and is used in fabricating printed electrical circuits, and also as a coating for electronic conductors. It is also alloyed with other elements such as nickel or palladium for use in electrical contacts. The most useful silver salt is silver nitrate, a caustic chemical reagent, significant as an antiseptic and as a reagent in analytical chemistry. Pure silver nitrate is an intermediate in the industrial preparation of other silver salts, including the colloidal silver compounds used in medicine and the silver halides incorporated into photographic emulsions. Silver halides become increasingly insoluble in the series: AgCl, AgBr, AgI. All silver salts are sensitive to light and are used in photographic coatings on film and paper. The ZORKA-PHARMA company (Sabac, Serbia specializes in the production of pharmaceutical remedies and lab chemicals. One of its products is chemical silver nitrate (argentum-nitricum (l. Silver nitrate is generally produced by dissolving pure electrolytically refined silver in hot 48% nitric acid. Since the purity of silver nitrate, produced in 2002, was not in compliance with the p.a. level of purity, there was doubt that the electrolytically refined silver was pure. The aim of this research was the gravimetric and volumetric determination of the purity of electrolytically refined silver and silver nitrate, produced industrially and in a laboratory. The purity determination was carried out gravimetrically, by the sedimentation of silver(I ions in the form of insoluble silver salts: AgCl, AgBr and Agi, and volumetrically, according to Mohr and Volhardt. The

  17. Phase stability of oxide dispersion-strengthened ferritic steels in neutron irradiation

    Yamashita, S.; Oka, K.; Ohnuki, S.; Akasaka, N.; Ukai, S.

    2002-01-01

    Oxide dispersion-strengthened ferritic steels were irradiated by neutrons up to 21 dpa and studied by microstructural observation and microchemical analysis. The original high dislocation density did not change after neutron irradiation, indicating that the dispersed oxide particles have high stability under neutron irradiation. However, there is potential for recoil resolution of the oxide particles due to ballistic ejection at high dose. From the microchemical analysis, it was implied that some of the complex oxides have a double-layer structure, such that TiO 2 occupied the core region and Y 2 O 3 the outer layer. Such a structure may be more stable than the simple mono-oxides. Under high-temperature irradiation, Laves phase was the predominant precipitate occurring at grain boundaries α phase and χ phase were not observed in this study

  18. Single Molecule Scanning of DNA Radiation Oxidative Damage, Phase I

    National Aeronautics and Space Administration — This proposal will develop an assay to map genomic DNA, at the single molecule level and in a nanodevice, for oxidative DNA damage arising from radiation exposure;...

  19. Nytrox Oxidizers for NanoSat Launch Vehicles, Phase I

    National Aeronautics and Space Administration — Space Propulsion Group, Inc. proposes to conduct systems studies to quantify the performance and cost advantages of Nytrox oxidizers for small launch vehicles. This...

  20. Phase Identification and Internal Stress Analysis of Steamside Oxides on Plant Exposed Superheater Tubes

    Pantleon, Karen; Montgomery, Melanie

    2012-01-01

    During long-term, high-temperature exposure of superheater tubes in thermal power plants, various oxides are formed on the inner side (steamside) of the tubes, and oxide spallation is a serious problem for the power plant industry. Most often, oxidation in a steam atmosphere is investigated...... in laboratory experiments just mimicking the actual conditions in the power plant for simplified samples. On real plant-exposed superheater tubes, the steamside oxides are solely investigated microscopically. The feasibility of X-ray diffraction for the characterization of steamside oxidation on real plant......-exposed superheater tubes was proven in the current work; the challenges for depth-resolved phase analysis and phase-specific residual stress analysis at the inner side of the tubes with concave surface curvature are discussed. Essential differences between the steamside oxides formed on two different steels...

  1. Phase-Field Simulations of Topological Structures and Topological Phase Transitions in Ferroelectric Oxide Heterostructures

    Zijian Hong

    Ferroelectrics are materials that exhibit spontaneous electric polarization which can be switched between energy-degenerated states by external stimuli (e.g., mechanical force and electric field) that exceeds a critical value. They have wide potential applications in memories, capacitors, piezoelectric and pyroelectric sensors, and nanomechanical systems. Topological structures and topological phase transitions have been introduced to the condensed matter physics in the past few decades and have attracted broad attentions in various disciplines due to the rich physical insights and broad potential applications. Ferromagnetic topological structures such as vortex and skyrmion are known to be stabilized by the antisymmetric chiral interaction (e.g., Dzyaloshinskii-Moriya interaction). Without such interaction, ferroelectric topological structures (i.e., vortex, flux-closure, skyrmions, and merons) have been studied only recently with other designing strategies, such as reducing the dimension of the ferroelectrics. The overarching goal of this dissertation is to investigate the topological structures in ferroelectric oxide perovskites as well as the topological phase transitions under external applied forces. Pb(Zr,Ti)O3 (PZT) with morphotropic phase boundary is widely explored for high piezoelectric and dielectric properties. The domain structure of PZT tetragonal/rhombohedral (T/R) bilayer is investigated. Strong interfacial coupling is shown, with large polarization rotation to a lower symmetry phase near the T/R interface. Interlayer domain growth can also be captured, with T-domains in the R layer and R-domains in the T layer. For thin PZT bilayer with 5nm of T-layer and 20 nm of R-layer, the a1/a 2 twin domain structure is formed in the top T layer, which could be fully switched to R domains under applied bias. While a unique flux-closure pattern is observed both theoretically and experimentally in the thick bilayer film with 50 nm of thickness for both T and R

  2. Liquid phase oxidation via heterogeneous catalysis organic synthesis and industrial applications

    Clerici, Mario G

    2013-01-01

    Sets the stage for environmentally friendly industrial organic syntheses From basic principles to new and emerging industrial applications, this book offers comprehensive coverage of heterogeneous liquid-phase selective oxidation catalysis. It fully examines the synthesis, characterization, and application of catalytic materials for environmentally friendly organic syntheses. Readers will find coverage of all the important classes of catalysts, with an emphasis on their stability and reusability. Liquid Phase Oxidation via Heterogeneous Catalysis features contributions from an internation

  3. Characterization of fatty acid and triacylglycerol composition in animal fats using silver-ion and non-aqueous reversed-phase high-performance liquid chromatography/mass spectrometry and gas chromatography/flame ionization detection

    Lísa, M.; Netušilová, K.; Franěk, L.; Dvořáková, H.; Vrkoslav, Vladimír; Holčapek, M.

    2011-01-01

    Roč. 1218, č. 42 (2011), s. 7499-7510 ISSN 0021-9673 R&D Projects: GA ČR GA203/09/0139 Institutional research plan: CEZ:AV0Z40550506 Keywords : silver-ion HPLC * non-aqueous reversed-phase HPLC * triacylglycerol Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.531, year: 2011

  4. How Pt nanoparticles affect TiO2-induced gas-phase photocatalytic oxidation reactions

    Fraters, B.D.; Amrollahi Buky, Rezvaneh; Mul, Guido

    2015-01-01

    The effect of Pt nanoparticles on the gas-phase photocatalytic oxidation activity of TiO2 is shown to be largely dependent on the molecular functionality of the substrate. We demonstrate that Pt nanoparticles decrease rates in photocatalytic oxidation of propane, whereas a strong beneficial effect

  5. Finite element analysis of the tetragonal to monoclinic phase transformation during oxidation of zirconium alloys

    Platt, P.; Frankel, P.; Gass, M.; Howells, R.; Preuss, M.

    2014-11-01

    Corrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal-oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations.

  6. Finite element analysis of the tetragonal to monoclinic phase transformation during oxidation of zirconium alloys

    Platt, P.; Frankel, P.; Gass, M.; Howells, R.; Preuss, M.

    2014-01-01

    Corrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal–oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations

  7. Finite element analysis of the tetragonal to monoclinic phase transformation during oxidation of zirconium alloys

    Platt, P., E-mail: Philip.Platt@manchester.ac.uk [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom); Frankel, P. [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom); Gass, M.; Howells, R. [AMEC, Walton House, Faraday Street, Birchwood Park, Risley, Warrington WA3 6GA (United Kingdom); Preuss, M. [University of Manchester, School of Materials, Materials Performance Centre, Manchester M13 9PL (United Kingdom)

    2014-11-15

    Corrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal–oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations.

  8. High Transparent Metal Oxide / Polyimide Antistatic Coatings, Phase II

    National Aeronautics and Space Administration — Through this Phase I program, Agiltron has successfully produced an innovative transparent conductive nanocomposite paint that holds the promise of meeting space...

  9. Thermochemical properties of silver tellurides including empressite (AgTe) and phase diagrams for Ag-Te and Ag-Te-O

    Voronin, Mikhail V.; Osadchii, Evgeniy G.; Brichkina, Ekaterina A.

    2017-10-01

    This study compiles original experimental and literature data on the thermodynamic properties (ΔfG°, S°, ΔfH°) of silver tellurides (α-Ag2Te, β-Ag2Te, Ag1.9Te, Ag5Te3, AgTe) obtained by the method of solid-state galvanic cell with the RbAg4I5 and AgI solid electrolytes. The thermodynamic data for empressite (AgTe, pure fraction from Empress Josephine Mine, Colorado USA) have been obtained for the first time by the electrochemical experiment with the virtual reaction Ag + Te = AgTe. The Ag-Te phase diagrams in the T - x and log fTe2 (gas) - 1/ T coordinates have been refined, and the ternary Ag-Te-O diagrams with Ag-Te-TeO2 (paratellurite) composition range have been calculated.

  10. Oxidation behaviour of a Ti2AlN MAX-phase coating

    Wang Qimin; Kim, Kwangho; Garkas, W; Renteria, A Flores; Leyens, C; Sun Chao

    2011-01-01

    In this paper, we reported the oxidation behaviour of Ti 2 AlN coatings on a -TiAl substrate. The coatings composed mainly of Ti 2 AlN MAX phase were obtained by magnetron sputtering and subsequent vacuum annealing. Isothermal oxidation tests at 700-900 deg. C were performed in air. The results indicated that the oxidation resistance of the -TiAl alloy can be improved by depositing a Ti 2 AlN layer on the alloy surface, especially at high temperatures. An Al-rich oxide scale formed on the coating surfaces during oxidation. This scale acts as diffusion barrier blocking the ingress of oxidation, and effectively protects the coated alloys from further oxidation attack.

  11. Oxidation behaviour of a Ti{sub 2}AlN MAX-phase coating

    Wang Qimin; Kim, Kwangho [National Core Research Center for Hybrid Materials Solution, Pusan National University, Busan 609-735 (Korea, Republic of); Garkas, W; Renteria, A Flores [Chair of Physical Metallurgy and Materials Technology, Technical University of Brandenburg at Cottbus, 03046 Cottbus (Germany); Leyens, C [Institute of Materials Science, Technical University of Dresden, Helmholtzstrasse 7, 01069 Dresden (Germany); Sun Chao, E-mail: qmwang@pusan.ac.kr, E-mail: kwhokim@pusan.ac.kr [Division of Surface Engineering of Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2011-10-29

    In this paper, we reported the oxidation behaviour of Ti{sub 2}AlN coatings on a -TiAl substrate. The coatings composed mainly of Ti{sub 2}AlN MAX phase were obtained by magnetron sputtering and subsequent vacuum annealing. Isothermal oxidation tests at 700-900 deg. C were performed in air. The results indicated that the oxidation resistance of the -TiAl alloy can be improved by depositing a Ti{sub 2}AlN layer on the alloy surface, especially at high temperatures. An Al-rich oxide scale formed on the coating surfaces during oxidation. This scale acts as diffusion barrier blocking the ingress of oxidation, and effectively protects the coated alloys from further oxidation attack.

  12. Nanoporous silver cathode surface treated by atomic layer deposition of CeO_x for low-temperature solid oxide fuel cells

    Neoh, Ke Chean; Han, Gwon Deok; Kim, Manjin; Kim, Jun Woo; Choi, Hyung Jong; Park, Suk Won; Shim, Joon Hyung

    2016-01-01

    We evaluated the performance of solid oxide fuel cells (SOFCs) with a 50 nm thin silver (Ag) cathode surface treated with cerium oxide (CeO_x) by atomic layer deposition (ALD). The performances of bare and ALD-treated Ag cathodes were evaluated on gadolinia-doped ceria (GDC) electrolyte supporting cells with a platinum (Pt) anode over 300 °C–450 °C. Our work confirms that ALD CeO_x treatment enhances cathodic performance and thermal stability of the Ag cathode. The performance difference between cells using a Ag cathode optimally treated with an ALD CeO_x surface and a reference Pt cathode is about 50% at 450 °C in terms of fuel cell power output in our experiment. The bare Ag cathode completely agglomerated into islands during fuel cell operation at 450 °C, while the ALD CeO_x treatment effectively protects the porosity of the cathode. We also discuss the long-term stability of ALD CeO_x-treated Ag cathodes related to the microstructure of the layers. (paper)

  13. On the catalytic gas phase oxidation of butadiene to furan

    Kubias, B.; Rodemerck, U. [Institut fuer Angewandte Chemie Berlin-Adlershof e.V., Berlin (Germany); Ritschl, F.; Meisel, M. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Chemie

    1998-12-31

    Applying the thermochemical selectivity criterion of Hadnett et al. It is shown that the selectivity of the furan formation is not limited by a too low strength of the C-H bonds in furan when compared with the C-H bond dissociation energy in the educt molecule butadiene. In the oxidation of butadiene on a CsH{sub 2}PMo{sub 12}O{sub 40} catalyst a maximum yield of 22 mol% furan has been obtained. To improve this comparatively low furan yield oxidation activity of the catalyst must be lowered to prevent the consecutive reaction to maleic anhydride. (orig.)

  14. Using Spin-Coated Silver Nanoparticles/Zinc Oxide Thin Films to Improve the Efficiency of GaInP/(InGaAs/Ge Solar Cells

    Po-Hsun Lei

    2018-06-01

    Full Text Available We synthesized a silver nanoparticle/zinc oxide (Ag NP/ZnO thin film by using spin-coating technology. The treatment solution for Ag NP/ZnO thin film deposition contained zinc acetate (Zn(CH3COO2, sodium hydroxide (NaOH, and silver nitrate (AgNO3 aqueous solutions. The crystalline characteristics, surface morphology, content of elements, and reflectivity of the Ag NPs/ZnO thin film at various concentrations of the AgNO3 aqueous solution were investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and ultraviolet–visible–near infrared spectrophotometry. The results indicated that the crystalline structure, Ag content, and reflectance of Ag NP/ZnO thin films depended on the AgNO3 concentration. Hybrid antireflection coatings (ARCs composed of SiNx and Ag NPs/ZnO thin films with various AgNO3 concentrations were deposited on GaInP/(InGaAs/Ge solar cells. We propose that the optimal ARC consists of SiNx and Ag NP/ZnO thin films prepared using a treatment solution of 0.0008 M AgNO3, 0.007 M Zn(CH3COO2, and 1 M NaOH, followed by post-annealing at 200 °C. GaInP/(AlGaAs/Ge solar cells with the optimal hybrid ARC and SiNx ARC exhibit a conversion efficiency of 34.1% and 30.2% with Voc = 2.39 and 2.4 V, Jsc = 16.63 and 15.37 mA/cm2, and fill factor = 86.1% and 78.8%.

  15. Three-phase boundary length in solid-oxide fuel cells: A mathematical model

    Janardhanan, Vinod M.; Heuveline, Vincent; Deutschmann, Olaf

    A mathematical model to calculate the volume specific three-phase boundary length in the porous composite electrodes of solid-oxide fuel cell is presented. The model is exclusively based on geometrical considerations accounting for porosity, particle diameter, particle size distribution, and solids phase distribution. Results are presented for uniform particle size distribution as well as for non-uniform particle size distribution.

  16. Phase change induced by polypyrrole in iron-oxide polypyrrole ...

    Unknown

    polymer. Polypyrrole, one of the conducting polymers, has received lot of attention in the preparation of nanocomposites due to its high stability in conducting oxidized form (Partch et al 1991; Huang and Matijevic. 1995; Maeda and Armes 1995). Nanocomposite materials based on nanosized magnetic materials have been ...

  17. Stability of nanoscale secondary phases in an oxide dispersion strengthened Fe-12Cr alloy

    Castro, V. de; Marquis, E.A.; Lozano-Perez, S.; Pareja, R.; Jenkins, M.L.

    2011-01-01

    Transmission electron microscopy and atom-probe tomography were used to characterize on a near-atomic scale the microstructure and oxide and carbide phases that form during thermo-mechanical treatments of a model oxide dispersion strengthened Fe-12 wt.% Cr-0.4 wt.% Y 2 O 3 alloy. It was found that some of the Y-rich nanoparticles retained their initial crystallographic structure but developed a Cr-enriched shell, while others evolved into ternary oxide phases during the initial processing. The Y- and Cr-rich oxide phases formed remained stable after annealing at 1023 K for 96 h. However, the number of Cr-rich carbides appeared to increase, inducing Cr depletion in the matrix.

  18. Stability of nanoscale secondary phases in an oxide dispersion strengthened Fe-12Cr alloy

    Castro, V. de, E-mail: vanessa.decastro@uc3m.es [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Marquis, E.A.; Lozano-Perez, S. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Pareja, R. [Departamento de Fisica, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganes, Madrid (Spain); Jenkins, M.L. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom)

    2011-06-15

    Transmission electron microscopy and atom-probe tomography were used to characterize on a near-atomic scale the microstructure and oxide and carbide phases that form during thermo-mechanical treatments of a model oxide dispersion strengthened Fe-12 wt.% Cr-0.4 wt.% Y{sub 2}O{sub 3} alloy. It was found that some of the Y-rich nanoparticles retained their initial crystallographic structure but developed a Cr-enriched shell, while others evolved into ternary oxide phases during the initial processing. The Y- and Cr-rich oxide phases formed remained stable after annealing at 1023 K for 96 h. However, the number of Cr-rich carbides appeared to increase, inducing Cr depletion in the matrix.

  19. Gas-Phase Photocatalytic Oxidation of Dimethylamine: The Reaction Pathway and Kinetics

    Anna Kachina

    2007-01-01

    Full Text Available Gas-phase photocatalytic oxidation (PCO and thermal catalytic oxidation (TCO of dimethylamine (DMA on titanium dioxide was studied in a continuous flow simple tubular reactor. Volatile PCO products of DMA included ammonia, formamide, carbon dioxide, and water. Ammonia was further oxidized in minor amounts to nitrous oxide and nitrogen dioxide. Effective at 573 K, TCO resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide, and water. The PCO kinetic data fit well to the monomolecular Langmuir-Hinshelwood model, whereas TCO kinetic behaviour matched the first-order process. No deactivation of the photocatalyst during the multiple long-run experiments was observed.

  20. In vitro assessment of activity of graphene silver composite sheets ...

    Purpose: To synthesize graphene-based silver nanocomposites and evaluate their antimicrobial and anti-Tomato Bushy Stunt Virus (TBSV) activities. Methods: A graphene-based silver composite was prepared by adsorbing silver nanoparticles AgNPs to the surfaces of graphene oxide (GO) sheets. Scanning electron ...

  1. Phases quantification in titanium oxides by means of X-ray diffraction

    Macias B, L.R.; Garcia C, R.M.; Ita T, A. de; Chavez R, A.

    2001-01-01

    In this work two phases of titanium oxides are quantified which belong to the same crystalline system and by means of a computer program named Quanto created by the first author, contains the information for calculating the absorption coefficients, it can be quantified phases having one of the pure phases and the problem samples. In order to perform this work different mixtures of different titanium oxides were prepared measuring by means of the X-ray diffraction technique in the Siemens X-ray diffractometer of ININ which were processed with the Peakfit package and also they were evaluated by means of the computer program with the necessary information finding acceptable results. (Author)

  2. Analysis of impurities in silver matrix by atomic absorption spectrophotometry

    Hussain, R.; Ishaque, M.; Mohammad, D.

    1999-01-01

    A procedure for the analysis of aluminium, chromium, copper, lead, mercury, nickel and zinc mainly using flame lens atomic absorption spectrophotometry has been described. The results depict that the presence of silver does not introduce any significant interference, when standards are prepared in matching silver matrix solutions. The calibration curves obey the straight-line equations passing through the origin. Thus the separation of silver matrix from the analyte solutions is not necessary. The method has successfully been applied for the analysis of silver foils, wires, battery grade silver oxides and silver nitrate samples containing analyte elements in the concentration range 2 to 40 ppm. (author)

  3. Combined gas-phase oxidation of methane and ethylene

    Pogosyan, N.M.; Pogosyan, M.D.

    2009-01-01

    It is established that depending on the reaction conditions combined oxidation of methane and ethylene may result in ethylene and propylene oxides with high selectivity with respect to the process, where in the initial reaction mixture methane is replaced by the same quantity of nitrogen. The formed additional methyl radicals increase the yield of all reaction products except CO. At low temperatures methyl radicals react with oxygen resulting in methyl peroxide radicals, which in turn, reacting with ethylene provide its epoxidation and formation of other oxygen-containing products. At high temperatures as a result of addition reaction between methyl radicals and ethylene, propyl radicals are formed that, in turn yield propylene. Alongside with positive influence on the yield of reaction products, methane exerts negative influence upon the conversion, that is it decreases the rate of ethylene and oxygen conversion, simultaneously decreasing significantly the yield of CO

  4. The analysis of magnesium oxide hydration in three-phase reaction system

    Tang, Xiaojia; Guo, Lin; Chen, Chen; Liu, Quan; Li, Tie; Zhu, Yimin, E-mail: ntp@dlmu.edu.cn

    2014-05-01

    In order to investigate the magnesium oxide hydration process in gas–liquid–solid (three-phase) reaction system, magnesium hydroxide was prepared by magnesium oxide hydration in liquid–solid (two-phase) and three-phase reaction systems. A semi-empirical model and the classical shrinking core model were used to fit the experimental data. The fitting result shows that both models describe well the hydration process of three-phase system, while only the semi-empirical model right for the hydration process of two-phase system. The characterization of the hydration product using X-Ray diffraction (XRD) and scanning electron microscope (SEM) was performed. The XRD and SEM show hydration process in the two-phase system follows common dissolution/precipitation mechanism. While in the three-phase system, the hydration process undergo MgO dissolution, Mg(OH){sub 2} precipitation, Mg(OH){sub 2} peeling off from MgO particle and leaving behind fresh MgO surface. - Graphical abstract: There was existence of a peeling-off process in the gas–liquid–solid (three-phase) MgO hydration system. - Highlights: • Magnesium oxide hydration in gas–liquid–solid system was investigated. • The experimental data in three-phase system could be fitted well by two models. • The morphology analysis suggested that there was existence of a peel-off process.

  5. Cadmium, lead and silver adsorption in hydrous niobium oxide(V) prepared by precipitation in homogeneous solution method; Adsorcao de chumbo, cadmio e prata em oxido de niobio(V) hidratado preparado pelo metodo da precipitacao em solucao homogenea

    Tagliaferro, Geronimo V.; Pereira, Paulo Henrique F.; Rodrigues, Liana Alvares; Silva, Maria Lucia Caetano Pinto da, E-mail: fernandes_eng@yahoo.com.b [Universidade de Sao Paulo (USP), Lorena, SP (Brazil). Escola de Engenharia. Dept. de Engenharia Quimica

    2011-07-01

    This paper describes the adsorption of heavy metals ions from aqueous solution by hydrous niobium oxide. Three heavy metals were selected for this study: cadmium, lead and silver. Adsorption isotherms were well fitted by Langmuir model. Maximum adsorption capacity (Q{sub 0}) for Pb{sup 2+}, Ag{sup +} and Cd{sup 2+} was found to be 452.5, 188.68 and 8.85 mg g{sup -1}, respectively. (author)

  6. Influence of Silver nanoparticles addition on the phase transformation, mechanical properties and corrosion behaviour of Cu–Al–Ni shape memory alloys

    Saud, Safaa N.; Hamzah, E., E-mail: esah@fkm.utm.my; Abubakar, T.; Bakhsheshi-Rad, H.R.; Farahany, S.; Abdolahi, A.; Taheri, M.M.

    2014-11-05

    Highlights: • Thermal analysis showed four different phase β, α, NiAl and γ2 during solidification. • The martensite appeared in the microstructure as a plate and needle like shape. • Shape recovery ratio of 80% was obtained after Ag nanoparticles addition. • Effect of Ag nanoparticles on the corrosion behaviour of Cu–Al–Ni SMA was investigated. - Abstract: Incorporation of silver nanoparticles into Cu-based shape memory alloys is recommended to enhance their phase transformation behaviour. However, this incorporation can affect their transformation temperatures, mechanical, microstructural and corrosion characteristics. Four different phase reactions β, α, NiAl and γ{sub 2} were detected on a derivative curve during the solidification by-computer-aided cooling curve thermal analysis. The highest fraction solid (82%) was calculated for the parent phase (β) based on the Newtonian baseline method. The microstructural changes and mechanical properties were investigated using field emission scanning electron microscopy, X-ray diffraction tensile test and shape memory effect test. It was found that the addition of Ag can control the phase morphology and orientations along with the formation of the Ag-rich precipitates, and thus the tensile strength, elongation, fracture stress–strain, yield strength and shape memory effect are improved. Remarkably, the shape recovery ratio reached approximately 80% of the original shape. The corrosion behaviour of the Cu–Al–Ni shape memory alloy were investigated using electrochemical tests in NaCl solution and their results showed that the corrosion potential (E{sub corr}) of Cu–Al–Ni SMA is shifted towards the nobler direction from −307.4 to −277.1 m V{sub SCE} with the addition of 0.25 wt.% Ag.

  7. Liquid Phase Plasma Synthesis of Iron Oxide/Carbon Composite as Dielectric Material for Capacitor

    Heon Lee

    2014-01-01

    Full Text Available Iron oxide/carbon composite was synthesized using a liquid phase plasma process to be used as the electrode of supercapacitor. Spherical iron oxide nanoparticles with the size of 5~10 nm were dispersed uniformly on carbon powder surface. The specific capacitance of the composite increased with increasing quantity of iron oxide precipitate on the carbon powder up to a certain quantity. When the quantity of the iron oxide precipitate exceeds the threshold, however, the specific capacitance was rather reduced by the addition of precipitate. The iron oxide/carbon composite containing an optimum quantity (0.33 atomic % of iron oxide precipitate exhibited the smallest resistance and the largest initial resistance slope.

  8. Silver Clear Nylon Dressing is Effective in Preventing Radiation-Induced Dermatitis in Patients With Lower Gastrointestinal Cancer: Results From a Phase III Study

    Niazi, Tamim M. [Segal Cancer Centre, Department of Radiation Oncology, Jewish General Hospital, McGill University (Canada); Vuong, Te, E-mail: tvuong@jgh.mcgill.ca [Segal Cancer Centre, Department of Radiation Oncology, Jewish General Hospital, McGill University (Canada); Azoulay, Laurant [Department of Epidemiology, Jewish General Hospital, McGill University (Canada); Marijnen, Corrie [Department of Clinical Oncology, Leiden University Medical Center, Amsterdam (Netherlands); Bujko, Kryzstof [Department of Radiotherapy, The Maria Sklodowska-Curie Memorial Cancer Centre, Warsaw (Poland); Nasr, Elie [Department of Radiation Oncology, Hotel-Dieu de France Hospital (Lebanon); Lambert, Christine; Duclos, Marie; Faria, Sergio; David, Marc [Department of Radiation Oncology, Montreal-General-Hospital, McGill University, Montreal (Canada); Cummings, Bernard [Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto (Canada)

    2012-11-01

    Purpose: For patients with anal canal and advanced rectal cancer, chemoradiation therapy is a curative modality or an important adjunct to surgery. Nearly all patients treated with chemoradiation experience some degree of radiation-induced dermatitis (RID). Prevention and effective treatment of RID, therefore, is of considerable clinical relevance. The present phase III randomized trial compared the efficacy of silver clear nylon dressing (SCND) with that of standard skin care for these patients. Methods and Materials: A total of 42 rectal or anal canal cancer patients were randomized to either a SCND or standard skin care group. SCND was applied from Day 1 of radiation therapy (RT) until 2 weeks after treatment completion. In the control arm, sulfadiazine cream was applied at the time of skin dermatitis. Printed digital photographs taken 2 weeks prior to, on the last day, and two weeks after the treatment completion were scored by 10 blinded readers, who used the common toxicity scoring system for skin dermatitis. Results: The radiation dose ranged from 50.4 to 59.4 Gy, and there were no differences between the 2 groups. On the last day of RT, when the most severe RID occurs, the mean dermatitis score was 2.53 (standard deviation [SD], 1.17) for the standard and 1.67 (SD, 1.2; P=.01) for the SCND arm. At 2 weeks after RT, the difference was 0.39 points in favor of SCND (P=.39). There was considerable intraclass correlation among the 10 observers. Conclusions: Silver clear nylon dressing is effective in reducing RID in patients with lower gastrointestinal cancer treated with combined chemotherapy and radiation treatment.

  9. Development of new portable miniaturize solid phase microextraction of silver-APDC complex using micropipette tip in-syringe system couple with electrothermal atomic absorption spectrometry

    Naeemullah; Kazi, Tasneem Gul; Afridi, Hassan Imran; Shah, Faheem; Arain, Sadaf Sadia; Arain, Salma Aslam; Panhwar, Abdul Haleem; Arain, Mariam Shahzadi; Samoon, Muhammad Kashif

    2016-02-01

    An innovative and simple miniaturized solid phase microextraction (M-SPME) method, was developed for preconcentration and determination of silver(I) in the fresh and waste water samples. For M-SPME, a micropipette tip packed with activated carbon cloth (ACC) as sorbent, in a syringe system. The size, morphology and elemental composition of ACC before and after adsorption of analyte have been characterized by scanning electron microscopy and energy dispersive spectroscopy. The sample solution treated with a complexing reagent, ammonium pyrrolidine dithiocarbamate (APDC), was drawn into the syringe filled with ACC and dispensed manually for 2 to 10 aspirating/dispensing cycle. Then the Ag- complex sorbed on the ACC in micropipette was quantitatively eluted by drawing and dispensing of different concentrations of acids for 2 to 5 aspirating/dispensing cycles. The extracted Ag ions with modifier were injected directly into the electrothermal atomic absorption spectrometry for analysis. The influence of different variables on the extraction efficiency, including the concentration of ligand, pH, sample volume, eluent type, concentration and volume was investigated. Validity and accuracy of the developed method was checked by the standard addition method. Reliability of the proposed methodology was checked by the relative standard deviation (%RSD), which was found to be < 5%. Under the optimized experimental variables, the limits of detection (LOD) and enhancement factors (EF), were obtained to be 0.86 ng L- 1 and 120, respectively. The proposed method was successfully applied for the determination of trace levels of silver ions in fresh and waste water samples.

  10. Silver Clear Nylon Dressing is Effective in Preventing Radiation-Induced Dermatitis in Patients With Lower Gastrointestinal Cancer: Results From a Phase III Study

    Niazi, Tamim M.; Vuong, Te; Azoulay, Laurant; Marijnen, Corrie; Bujko, Kryzstof; Nasr, Elie; Lambert, Christine; Duclos, Marie; Faria, Sergio; David, Marc; Cummings, Bernard

    2012-01-01

    Purpose: For patients with anal canal and advanced rectal cancer, chemoradiation therapy is a curative modality or an important adjunct to surgery. Nearly all patients treated with chemoradiation experience some degree of radiation-induced dermatitis (RID). Prevention and effective treatment of RID, therefore, is of considerable clinical relevance. The present phase III randomized trial compared the efficacy of silver clear nylon dressing (SCND) with that of standard skin care for these patients. Methods and Materials: A total of 42 rectal or anal canal cancer patients were randomized to either a SCND or standard skin care group. SCND was applied from Day 1 of radiation therapy (RT) until 2 weeks after treatment completion. In the control arm, sulfadiazine cream was applied at the time of skin dermatitis. Printed digital photographs taken 2 weeks prior to, on the last day, and two weeks after the treatment completion were scored by 10 blinded readers, who used the common toxicity scoring system for skin dermatitis. Results: The radiation dose ranged from 50.4 to 59.4 Gy, and there were no differences between the 2 groups. On the last day of RT, when the most severe RID occurs, the mean dermatitis score was 2.53 (standard deviation [SD], 1.17) for the standard and 1.67 (SD, 1.2; P=.01) for the SCND arm. At 2 weeks after RT, the difference was 0.39 points in favor of SCND (P=.39). There was considerable intraclass correlation among the 10 observers. Conclusions: Silver clear nylon dressing is effective in reducing RID in patients with lower gastrointestinal cancer treated with combined chemotherapy and radiation treatment.

  11. Development of new portable miniaturize solid phase microextraction of silver-APDC complex using micropipette tip in-syringe system couple with electrothermal atomic absorption spectrometry.

    Naeemullah; Kazi, Tasneem Gul; Afridi, Hassan Imran; Shah, Faheem; Arain, Sadaf Sadia; Arain, Salma Aslam; Panhwar, Abdul Haleem; Arain, Mariam Shahzadi; Samoon, Muhammad Kashif

    2016-02-05

    An innovative and simple miniaturized solid phase microextraction (M-SPME) method, was developed for preconcentration and determination of silver(I) in the fresh and waste water samples. For M-SPME, a micropipette tip packed with activated carbon cloth (ACC) as sorbent, in a syringe system. The size, morphology and elemental composition of ACC before and after adsorption of analyte have been characterized by scanning electron microscopy and energy dispersive spectroscopy. The sample solution treated with a complexing reagent, ammonium pyrrolidine dithiocarbamate (APDC), was drawn into the syringe filled with ACC and dispensed manually for 2 to 10 aspirating/dispensing cycle. Then the Ag- complex sorbed on the ACC in micropipette was quantitatively eluted by drawing and dispensing of different concentrations of acids for 2 to 5 aspirating/dispensing cycles. The extracted Ag ions with modifier were injected directly into the electrothermal atomic absorption spectrometry for analysis. The influence of different variables on the extraction efficiency, including the concentration of ligand, pH, sample volume, eluent type, concentration and volume was investigated. Validity and accuracy of the developed method was checked by the standard addition method. Reliability of the proposed methodology was checked by the relative standard deviation (%RSD), which was found to be <5%. Under the optimized experimental variables, the limits of detection (LOD) and enhancement factors (EF), were obtained to be 0.86 ng L(-1) and 120, respectively. The proposed method was successfully applied for the determination of trace levels of silver ions in fresh and waste water samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Ytterbia doped nickel–manganese mixed oxide catalysts for liquid phase oxidation of benzyl alcohol

    S.S.P. Sultana

    2017-11-01

    Full Text Available Nickel–manganese mixed oxides doped with 1, 3, 5 mol% ytterbia have been prepared by co-precipitation method and used in the catalytic oxidation of benzyl alcohol. Catalytic activity of these oxides calcined at 400 °C and 500 °C was studied for selective oxidation of benzyl alcohol to the corresponding aldehyde using molecular oxygen as an oxidizing agent. The results showed that thermally stable 5 mol% ytterbia doped nickel–manganese oxide [Yb2O3-(5%-Ni6MnO8] exhibited highest catalytic performance when it was calcined at 400 °C. A 100% conversion of the benzyl alcohol was achieved with >99% selectivity to benzaldehyde within a reaction period of 5 h at 100 °C. The mixed oxide prepared has been characterized by scanning election microscopy (SEM and energy dispersive X-ray analysis (EDXA, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR, thermogravimetric analysis (TGA, Brunauer–Emmett–Teller (BET and temperature programed reduction (H2-TPR.

  13. Gas phase deposition of oxide and metal-oxide coatings on fuel particles

    Patokin, A.P.; Khrebtov, V.L.; Shirokov, B.M.

    2008-01-01

    Production processes and properties of oxide (Al 2 O 3 , ZrO 2 ) and metal-oxide (Mo-Al 2 O 3 , Mo-ZrO 2 , W-Al 2 O 3 , W-ZrO 2 ) coatings on molybdenum substrates and uranium dioxide fuel particles were investigated. It is shown that the main factors that have an effect on the deposition rate, density, microstructure and other properties of coatings are the deposition temperature, the ratio of H 2 and CO 2 flow rates, the total reactor pressure and the ratio of partial pressures of corresponding metal chlorides during formation of metal-oxide coatings

  14. Catalytic oxidation of cyanides in an aqueous phase over individual and manganese-modified cobalt oxide systems

    Christoskova, St.; Stoyanova, M.

    2009-01-01

    The possibility for purification of wastewaters containing free cyanides by applying of a new method based on cyanides catalytic oxidation with air to CO 2 and N 2 at low temperature and atmospheric pressure was investigated. On this purpose, individual and modified with manganese Co-oxide systems as active phase of environmental catalysts were synthesized. The applied method of synthesis favours the preparation of oxide catalytic systems with high active oxygen content (total-O* and surface-O* s ) possessing high mobility, and the metal ions being in a high oxidation state and in an octahedral coordination-factors determining high activity in reactions of complete oxidation. The catalysts employed were characterized by powder X-ray diffraction, Infrared spectroscopy, and chemical analysis. The effect of pH of the medium and catalyst loading on the effectiveness of the cyanide oxidation process, expressed by the degree of conversion (α, %), by the rate constant (k, min -1 ), and COD was studied. The results obtained reveal that using catalysts investigated a high cyanide removal efficiency could be achieved even in strong alkaline medium. The higher activity of the manganese promoted catalytic sample could be explained on the basis of higher total active oxygen content and its higher mobility both depending on the conditions, under which the synthesis of catalyst is being carried out.

  15. Electrically conductive nanostructured silver doped zinc oxide (Ag:ZnO) prepared by solution-immersion technique

    Afaah, A. N.; Asib, N. A. M.; Aadila, A.; Khusaimi, Z.; Mohamed, R.; Rusop, M.

    2016-01-01

    p-type ZnO films have been fabricated on ZnO-seeded glass substrate, using AgNO_3 as a source of silver dopant by facile solution-immersion. Cleaned glass substrate were seeded with ZnO by mist-atomisation, and next the seeded substrates were immersed in Ag:ZnO solution. The effects of Ag doping concentration on the Ag-doped ZnO have been investigated. The substrates were immersed in different concentrations of Ag dopant with variation of 0, 1, 3, 5 and 7 at. %. The surface morphology of the films was characterized by field emission scanning electron microscope (FESEM). In order to investigate the electrical properties, the films were characterized by Current-Voltage (I-V) measurement. FESEM micrographs showed uniform distribution of nanostructured ZnO and Ag:ZnO. Besides, the electrical properties of Ag-doped ZnO were also dependent on the doping concentration. The I-V measurement result indicated the electrical properties of 1 at. % Ag:ZnO thin film owned highest electrical conductivity.

  16. Nitrous oxide: Saturation properties and the phase diagram

    Ferreira, A.G.M.; Lobo, L.Q.

    2009-01-01

    The experimental values of the coordinates of the triple point and of the critical point of nitrous oxide registered in the literature were assessed and those judged as most reliable have been selected. Empirical equations have been found for the vapour pressure, sublimation and fusion curves. The virial coefficients and saturation properties as functions of temperature along the equilibrium curves are described by reduced equations. They were used in arriving at the molar enthalpies at the triple point and the normal boiling temperature. Equations for the sublimation and fusion curves resulting from the exactly integrated Clapeyron equation compare favourably with the results from the empirical treatment and the experimental data.

  17. Oxidation kinetics of a Pb-64 at.% In single-phase alloy

    Zhang, M.X.; Chang, Y.A.; Marcotte, V.C.

    1991-01-01

    The solid-state oxidation kinetics of a Pb-64 at.% IN(50 wt.%) single-phase alloy were studied from room temperature to 150C using AES (Auger Electron Spectroscopy) depth profiling technique. The general oxidation behavior of this alloy is different from that of a Pb-3 at.% In alloy but similar to that of a Pb-30 at.% In alloy. The oxide formed on this alloy is almost pure In oxide (In 2 O 3 ) with the possible existence of some In suboxide near the oxide/alloy interface. At room temperature, oxidation of the alloy follows a direct logarithmic law, and the results can be described by the model proposed previously by Zhang, Chang, and Marcotte. At temperatures higher than 75C, rapid oxidation occurred initially followed by a slower parabolic oxidation at longer time. These data were described quantitatively by the model which assumes the existence of short-circuit diffusion in addition to lattice diffusion in the oxide as proposed by Smeltzer, Haering, and Kirkaldy. The effects of alloy composition in the oxidation kinetics of (pb, In) alloy are also examined by comparing the data for Pb-3, 30, and 64 at.% In alloys

  18. Thermal conductivity and stability of a three-phase blend of carbon nanotubes, conductive polymer, and silver nanoparticles incorporated into polycarbonate nanocomposites

    Patole, Archana

    2015-04-16

    Metallic and non-metallic nanofillers can be used together in the design of polycarbonate (PC) nanocomposites with improved electrical properties. Here, the preparation of three-phase blend (carbon nanotubes (CNT), silver nanoparticles, and conductive polymer) in a two-step process before incorporation in the PC is reported. First, ethylene diamine functionalized multiwall carbon nanotubes (MWCNT-EDA) were decorated with Ag nanoparticles. Next, the Ag-decorated CNTs were coated with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Due to the high thermal conductivity instrinsic to both metallic and non-metallic phases, it is expected that the thermal properties of the resulting nanocomposite would largely differ from those of pristine PC. We thus investigated in detail how this hybrid conductive blend affected properties such as the glass transition temperature, the thermal stability, and the thermal conductivity of the nanocomposite. It was found that this strategy results in improved thermal conductivity and thermal stability of the material. © 2015 Wiley Periodicals, Inc.

  19. Thermal conductivity and stability of a three-phase blend of carbon nanotubes, conductive polymer, and silver nanoparticles incorporated into polycarbonate nanocomposites

    Patole, Archana; Ventura, Isaac Aguilar; Lubineau, Gilles

    2015-01-01

    Metallic and non-metallic nanofillers can be used together in the design of polycarbonate (PC) nanocomposites with improved electrical properties. Here, the preparation of three-phase blend (carbon nanotubes (CNT), silver nanoparticles, and conductive polymer) in a two-step process before incorporation in the PC is reported. First, ethylene diamine functionalized multiwall carbon nanotubes (MWCNT-EDA) were decorated with Ag nanoparticles. Next, the Ag-decorated CNTs were coated with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Due to the high thermal conductivity instrinsic to both metallic and non-metallic phases, it is expected that the thermal properties of the resulting nanocomposite would largely differ from those of pristine PC. We thus investigated in detail how this hybrid conductive blend affected properties such as the glass transition temperature, the thermal stability, and the thermal conductivity of the nanocomposite. It was found that this strategy results in improved thermal conductivity and thermal stability of the material. © 2015 Wiley Periodicals, Inc.

  20. Vanadium oxide monolayer catalysts : The vapor-phase oxidation of methanol

    Roozeboom, Fred; Cordingley, Peter D.; Gellings, P.J.

    1981-01-01

    The oxidation of methanol over vanadium oxide, unsupported and applied as a monolayer on γ-Al2O3, CeO2, TiO2, and ZrO2, was studied between 100 and 400 °C in a continuous-flow reactor. At temperatures from 150 to about 250 °C two main reactions take place, (a) dehydration of methanol to dimethyl

  1. Potential Impacts of two SO2 oxidation pathways on regional sulfate concentrations: acqueous-hase oxidation by NO2 and gas-phase oxidation by Stabilized Criegee Intermediates

    We examine the potential impacts of two additional sulfate production pathways using the Community Multiscale Air Quality modeling system. First we evaluate the impact of the aqueous-phase oxidation of S(IV) by nitrogen dioxide using two published rate constants, differing by 1-2...

  2. Simple approach to detection and estimation of photoactivity of silver particles on graphene oxide in aqueous-organic dispersion

    Vlasov, D. V.; Vlasova, T. D.; Apresyan, L. A.; Krasovskiy, V. I.; Feofanov, I. N.; Kazaryan, M. A.

    2015-12-01

    The effect of sediment flotation was observed in dispersion of graphene oxide flakes with Ag-particles deposited thereon in the aqueous-organic (containing dimethylformamide) under the visible light action, with subsequent stabilization of the dispersion, which does not occur in the absence of Ag-particles. The main reason for this laser light induced movement of sediment graphene oxide flakes may be associated with the appearance of small bubbles. The further development of this approach seem to be able to estimate the of graphene flakes photoactivity with different activating particles.

  3. Influence of cobalt oxide on structure and phase composition of zirconium-containing materials

    Vladimirova, O.S.; Gruzdev, A.I.; Koposova, Z.L.; Lyutsareva, L.A.

    1986-01-01

    Effect of Co 3 O 4 addition in a quantity from 10 to 90% on microstructure, phase content, lattice parameter and structure of ZrO 2 ceramics spallings stabilized with yttrium oxide, is studied. It is found out that in the process of ceramics synthesis the formation of three-phased heterogeneous system of matrix type occurs. At cobalt oxide content within the range of 10-30% a matrix consist of ZrO 2 base solid solution, at cobalt oxide content from 50 to 90% it is a matrix base, at 40% Co 3 O 4 the regions with both type matrixes exist. Cobalt oxide introduction decreases the sintering temperature without loss in operation indices of heat sensitive ceramics for resistance transducers

  4. Treatment of reduced sulphur compounds and SO2 by Gas Phase Advanced Oxidation

    Meusinger, Carl; Bluhme, Anders Brostrøm; Ingemar, Jonas L.

    2017-01-01

    Reduced sulphur compounds (RSCs) emitted from pig farms are a major problem for agriculture, due to their health and environmental impacts and foul odour. This study investigates the removal of RSCs, including H2S, and their oxidation product SO2 using Gas Phase Advanced Oxidation (GPAO). GPAO...... is a novel air cleaning technique which utilises accelerated atmospheric chemistry to oxidise pollutants before removing their oxidation products as particles. Removal efficiencies of 24.5% and 3.9% were found for 461 ppb of H2S and 714 ppb of SO2 in a laboratory system (volumetric flow Q = 75 m3/h......). A numerical model of the reactor system was developed to explore the basic features of the system; its output was in fair agreement with the experiment. The model verified the role of OH radicals in initiating the oxidation chemistry. All sulphur removed from the gas phase was detected as particulate matter...

  5. Silver linings.

    Bultas, Margaret W; Pohlman, Shawn

    2014-01-01

    The purpose of this interpretive phenomenological study was to gain a better understanding of the experiences of 11 mothers of preschool children with autism spectrum disorder (ASD). Mothers were interviewed three times over a 6 week period. Interviews were analyzed using interpretive methods. This manuscript highlights one particular theme-a positive perspective mothers described as the "silver lining." This "silver lining" represents optimism despite the adversities associated with parenting a child with ASD. A deeper understanding of this side of mothering children with ASD may help health care providers improve rapport, communication, and result in more authentic family centered care. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. Pro-inflammatory responses of RAW264.7 macrophages when treated with ultralow concentrations of silver, titanium dioxide, and zinc oxide nanoparticles

    Giovanni, Marcella; Yue, Junqi; Zhang, Lifeng; Xie, Jianping; Ong, Choon Nam; Leong, David Tai

    2015-01-01

    Highlights: • Ultralow levels of common nanoparticles exist in environment and consumer products. • Common nanoparticles at ultralow levels induce mild pro-inflammation by macrophages. • The nanoparticles are cytotoxic only at high doses. - Abstract: To cellular systems, nanoparticles are considered as foreign particles. Upon particles and cells contact, innate immune system responds by activating the inflammatory pathway. However, excessive inflammation had been linked to various diseases ranging from allergic responses to cancer. Common nanoparticles, namely silver, titanium dioxide, and zinc oxide exist in the environment as well as in consumer products at ultralow level of 10 −6 –10 −3 μg mL −1 . However, so far the risks of such low NPs concentrations remain unexplored. Therefore, we attempted to screen the pro-inflammatory responses after ultralow concentration treatments of the three nanoparticles on RAW264.7 macrophages, which are a part of the immune system, at both cellular and gene levels. Even though cytotoxicity was only observed at nanoparticles concentrations as high as 10 μg mL −1 , through the level of NF-κB and upregulation of pro-inflammatory genes, we observed activation of the induction of genes encoding pro-inflammatory cytokines starting already at 10 −7 μg mL −1 . This calls for more thorough characterization of nanoparticles in the environment as well as in consumer products to ascertain the health and safety of the consumers and living systems in general

  7. One-Step Process for High-Performance, Adhesive, Flexible Transparent Conductive Films Based on p-Type Reduced Graphene Oxides and Silver Nanowires.

    Lai, Yi-Ting; Tai, Nyan-Hwa

    2015-08-26

    This work demonstrates a one-step process to synthesize uniformly dispersed hybrid nanomaterial containing silver nanowires (AgNWs) and p-type reduced graphene (p-rGO). The hybrid nanomaterial was coated onto a polyethylene terephthalate (PET) substrate for preparing high-performance flexible transparent conductive films (TCFs). The p-rGO plays the role of bridging discrete AgNWs, providing more electron holes and lowering the resistance of the contacted AgNWs; therefore, enhancing the electrical conductivity without sacrificing too much transparence of the TCFs. Additionally, the p-rGO also improves the adhesion between AgNWs and substrate by covering the AgNWs on the substrate tightly. The study shows that coating of the hybrid nanomaterials on the PET substrate demonstrates exceptional optoelectronic properties with a transmittance of 94.68% (at a wavelength of 550 nm) and a sheet resistance of 25.0 ± 0.8 Ω/sq. No significant variation in electric resistance can be detected even when the film was subjected to a bend loading with a radius of curvature of 5.0 mm or the film was loaded with a reciprocal tension or compression for 1000 cycles. Furthermore, both chemical corrosion resistance and haze effect were improved when p-rGO was introduced. The study shows that the fabricated flexible TCFs have the potential to replace indium tin oxide film in the optoelectronic industry.

  8. Determination of Zinc, Cadmium, Lead, Copper and Silver Using a Carbon Paste Electrode and a Screen Printed Electrode Modified with Chromium(III Oxide

    Zuzana Koudelkova

    2017-08-01

    Full Text Available In this study, the preparation and electrochemical application of a chromium(III oxide modified carbon paste electrode (Cr-CPE and a screen printed electrode (SPE, made from the same material and optimized for the simple, cheap and sensitive simultaneous determination of zinc, cadmium, lead, copper and the detection of silver ions, is described. The limits of detection and quantification were 25 and 80 µg·L−1 for Zn(II, 3 and 10 µg·L−1 for Cd(II, 3 and 10 µg·L−1 for Pb(II, 3 and 10 µg·L−1 for Cu(II, and 3 and 10 µg·L−1 for Ag(I, respectively. Furthermore, this promising modification was transferred to the screen-printed electrode. The limits of detection for the simultaneous determination of zinc, cadmium, copper and lead on the screen printed electrodes were found to be 350 µg·L−1 for Zn(II, 25 µg·L−1 for Cd(II, 3 µg·L−1 for Pb(II and 3 µg·L−1 for Cu(II. Practical usability for the simultaneous detection of these heavy metal ions by the Cr-CPE was also demonstrated in the analyses of wastewaters.

  9. Determination of Zinc, Cadmium, Lead, Copper and Silver Using a Carbon Paste Electrode and a Screen Printed Electrode Modified with Chromium(III) Oxide.

    Koudelkova, Zuzana; Syrovy, Tomas; Ambrozova, Pavlina; Moravec, Zdenek; Kubac, Lubomir; Hynek, David; Richtera, Lukas; Adam, Vojtech

    2017-08-09

    In this study, the preparation and electrochemical application of a chromium(III) oxide modified carbon paste electrode (Cr-CPE) and a screen printed electrode (SPE), made from the same material and optimized for the simple, cheap and sensitive simultaneous determination of zinc, cadmium, lead, copper and the detection of silver ions, is described. The limits of detection and quantification were 25 and 80 µg·L -1 for Zn(II), 3 and 10 µg·L -1 for Cd(II), 3 and 10 µg·L -1 for Pb(II), 3 and 10 µg·L -1 for Cu(II), and 3 and 10 µg·L -1 for Ag(I), respectively. Furthermore, this promising modification was transferred to the screen-printed electrode. The limits of detection for the simultaneous determination of zinc, cadmium, copper and lead on the screen printed electrodes were found to be 350 µg·L -1 for Zn(II), 25 µg·L -1 for Cd(II), 3 µg·L -1 for Pb(II) and 3 µg·L -1 for Cu(II). Practical usability for the simultaneous detection of these heavy metal ions by the Cr-CPE was also demonstrated in the analyses of wastewaters.

  10. The liquid phase oxidation of n-butane: a search for plausible mechanisms

    Hobbs, C.C. [Celanese Ltd., TX (United States). Corpus Christi Technical Center

    1998-12-31

    This articles deals with an approach that has given some key information about the mechanisms of the liquid phase oxidation of butane to acetic acid. This procedure has been developed over the last 34 years; however, much of what will be discussed represents a synthesis of previous insights. Many of the observations are relatively recent and have not been previously published. In principle, this approach should be applicable to many oxidation processes. (orig.)

  11. Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

    Ngah Demon, Siti Zulaikha; Miyauchi, Yoshihiro; Mizutani, Goro; Matsushima, Toshinori; Murata, Hideyuki

    2014-01-01

    Highlights: • SHG phase from the interfaces of ITO/CuPc and ITO/pentacene was observed. • Optical dispersion of the organic thin film was taken into account. • Phase shift from bare ITO was 140° for ITO/CuPc and 160° for ITO/pentacene. - Abstract: We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕ interface with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°

  12. Optical second harmonic generation phase measurement at interfaces of some organic layers with indium tin oxide

    Ngah Demon, Siti Zulaikha [School of Materials Science, Japan Advanced Institute of Science and Technology, 923-1292 Ishikawa (Japan); Department of Physics, Centre of Defence Foundation Studies, National Defence University of Malaysia, 53 000 Kuala Lumpur (Malaysia); Miyauchi, Yoshihiro [Department of Applied Physics, School of Applied Sciences, National Defense Academy of Japan, 239-8686 Kanagawa (Japan); Mizutani, Goro, E-mail: mizutani@jaist.ac.jp [School of Materials Science, Japan Advanced Institute of Science and Technology, 923-1292 Ishikawa (Japan); Matsushima, Toshinori; Murata, Hideyuki [School of Materials Science, Japan Advanced Institute of Science and Technology, 923-1292 Ishikawa (Japan)

    2014-08-30

    Highlights: • SHG phase from the interfaces of ITO/CuPc and ITO/pentacene was observed. • Optical dispersion of the organic thin film was taken into account. • Phase shift from bare ITO was 140° for ITO/CuPc and 160° for ITO/pentacene. - Abstract: We observed phase shift in optical second harmonic generation (SHG) from interfaces of indium tin oxide (ITO)/copper phthalocyanine (CuPc) and ITO/pentacene. Phase correction due to Fresnel factors of the sample was taken into account. The phase of SHG electric field at the ITO/pentacene interface, ϕ{sub interface} with respect to the phase of SHG of bare substrate ITO was 160°, while the interface of ITO/CuPc had a phase of 140°.

  13. Nickel oxide/polypyrrole/silver nanocomposites with core/shell/shell structure: Synthesis, characterization and their electrochemical behaviour with antimicrobial activities

    Das, Dhaneswar; Nath, Bikash C. [Department of Chemical Sciences, Tezpur University, Tezpur 784028, Assam (India); Phukon, Pinkee [Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur 784028, Assam (India); Saikia, Bhaskar J.; Kamrupi, Isha R. [Department of Chemical Sciences, Tezpur University, Tezpur 784028, Assam (India); Dolui, Swapan K., E-mail: dolui@tezu.ernet.in [Department of Chemical Sciences, Tezpur University, Tezpur 784028, Assam (India)

    2013-10-01

    Magnetic and conducting Nickel oxide–polypyrrole (NiO/PPy) nanoparticles with core–shell structure were prepared in the presence of Nickel oxide (NiO) in aqueous solution containing sodium dodecyl benzenesulfonate (SDBS) as a surfactant as well as dopant. A stable dispersion of silver (Ag) nanoparticles was synthesized by chemical (citrate reduction) method. NiO/PPy nanocomposites were added to the Ag colloid under stirring. Ag nanoparticles could be electrostatically attracted on the surface of NiO/PPy nanocomposites, leading to formation of NiO/PPy/Ag nanocomposites with core/shell/shell structure. The morphology, structure, particle size and composition of the products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV) and current–voltage (I–V) analysis. The resultant nanocomposites have the good conductivity and excellent electrochemical and catalytic properties of PPy and Ag nanoparticles. Furthermore, the nanocomposites showed excellent antibacterial behaviour due to the presence of Ag nanoparticles in the composite. The thermal stability of NiO–PPy as well as NiO/PPy/Ag nanocomposites was higher than that of pristine PPy. Studies of IR spectra suggest that the increased thermal stability may be due to interactions between NiO and Ag nanoparticles with the PPy backbone. - Highlights: • NiO nanoparticles were synthesized by two step soft chemical synthesis route. • Ag nanoparticles were prepared by using citrate reduction method. • NiO/PPy nanocomposites are synthesized by chemical oxidative polymerization process. • NiO/PPy/Ag nanocomposites can be used in the water purification technology.

  14. Facile synthesis of silver nanoparticles supported on three dimensional graphene oxide/carbon black composite and its application for oxygen reduction reaction

    Yuan, Lizhi; Jiang, Luhua; Liu, Jing; Xia, Zhangxun; Wang, Suli; Sun, Gongquan

    2014-01-01

    Graphical abstract: - Highlights: • Ag nanoparticles were prepared using GO as reductant without any stabilizers. • A composite support with a 3D structure was constructed by GO and carbon black. • The Ag/GO/C composite shows enhanced ORR activity compared with Ag/GO. - Abstract: A 3D graphene oxide/carbon sphere supported silver composite (Ag/GO/C) was synthesized using graphene oxide as the reducing agent. The reducing process of Ag + was monitored by the ultra violet-visible (UV-vis) absorption spectrometer and the physical properties of the Ag/GO/C composite were characterized by Fourier transform infrared spectrometer (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the dispersive Ag nanoparticles are anchored uniformly on the surface of GO sheets with a mean size of about 6.9 nm. With introducing carbon black, the Ag nanoparticles aggregated slightly. Compared with its counterpart Ag/GO, the Ag/GO/C composite showed a significantly enhanced activity towards the oxygen reduction reaction in alkaline media. The enhancement can be ascribed to the 3D composite support, which not only improves the electrical conductivity, but also enforces the mass transport in the catalyst layer facilitating the reactants access to the active sites. Moreover, the Ag/GO/C composite exhibits good tolerance to alcohols, carbonates and tetramethylammonium hydroxide. This work is expected to open a new pathway to use GO as a reducing agent to synthesize electrocatalysts without surfactants

  15. Nickel oxide/polypyrrole/silver nanocomposites with core/shell/shell structure: Synthesis, characterization and their electrochemical behaviour with antimicrobial activities

    Das, Dhaneswar; Nath, Bikash C.; Phukon, Pinkee; Saikia, Bhaskar J.; Kamrupi, Isha R.; Dolui, Swapan K.

    2013-01-01

    Magnetic and conducting Nickel oxide–polypyrrole (NiO/PPy) nanoparticles with core–shell structure were prepared in the presence of Nickel oxide (NiO) in aqueous solution containing sodium dodecyl benzenesulfonate (SDBS) as a surfactant as well as dopant. A stable dispersion of silver (Ag) nanoparticles was synthesized by chemical (citrate reduction) method. NiO/PPy nanocomposites were added to the Ag colloid under stirring. Ag nanoparticles could be electrostatically attracted on the surface of NiO/PPy nanocomposites, leading to formation of NiO/PPy/Ag nanocomposites with core/shell/shell structure. The morphology, structure, particle size and composition of the products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV) and current–voltage (I–V) analysis. The resultant nanocomposites have the good conductivity and excellent electrochemical and catalytic properties of PPy and Ag nanoparticles. Furthermore, the nanocomposites showed excellent antibacterial behaviour due to the presence of Ag nanoparticles in the composite. The thermal stability of NiO–PPy as well as NiO/PPy/Ag nanocomposites was higher than that of pristine PPy. Studies of IR spectra suggest that the increased thermal stability may be due to interactions between NiO and Ag nanoparticles with the PPy backbone. - Highlights: • NiO nanoparticles were synthesized by two step soft chemical synthesis route. • Ag nanoparticles were prepared by using citrate reduction method. • NiO/PPy nanocomposites are synthesized by chemical oxidative polymerization process. • NiO/PPy/Ag nanocomposites can be used in the water purification technology

  16. Study of the phase composition of nanostructures produced by the local anodic oxidation of titanium films

    Avilov, V. I.; Ageev, O. A.; Konoplev, B. G.; Smirnov, V. A.; Solodovnik, M. S.; Tsukanova, O. G.

    2016-01-01

    The results of experimental studies of the phase composition of oxide nanostructures formed by the local anodic oxidation of a titanium thin film are reported. The data of the phase analysis of titanium-oxide nanostructures are obtained by X-ray photoelectron spectroscopy in the ion profiling mode of measurements. It is established that the surface of titanium-oxide nanostructures 4.5 ± 0.2 nm in height possesses a binding energy of core levels characteristic of TiO_2 (458.4 eV). By analyzing the titanium-oxide nanostructures in depth by X-ray photoelectron spectroscopy, the formation of phases with binding energies of core levels characteristic of Ti_2O_3 (456.6 eV) and TiO (454.8 eV) is established. The results can be used in developing the technological processes of the formation of a future electronic-component base for nanoelectronics on the basis of titanium-oxide nanostructures and probe nanotechnologies.

  17. Process for forming a homogeneous oxide solid phase of catalytically active material

    Perry, Dale L.; Russo, Richard E.; Mao, Xianglei

    1995-01-01

    A process is disclosed for forming a homogeneous oxide solid phase reaction product of catalytically active material comprising one or more alkali metals, one or more alkaline earth metals, and one or more Group VIII transition metals. The process comprises reacting together one or more alkali metal oxides and/or salts, one or more alkaline earth metal oxides and/or salts, one or more Group VIII transition metal oxides and/or salts, capable of forming a catalytically active reaction product, in the optional presence of an additional source of oxygen, using a laser beam to ablate from a target such metal compound reactants in the form of a vapor in a deposition chamber, resulting in the deposition, on a heated substrate in the chamber, of the desired oxide phase reaction product. The resulting product may be formed in variable, but reproducible, stoichiometric ratios. The homogeneous oxide solid phase product is useful as a catalyst, and can be produced in many physical forms, including thin films, particulate forms, coatings on catalyst support structures, and coatings on structures used in reaction apparatus in which the reaction product of the invention will serve as a catalyst.

  18. Direct gas-phase epoxidation of propylene to propylene oxide through radical reactions: A theoretical study

    Kizilkaya, Ali Can; Fellah, Mehmet Ferdi; Onal, Isik

    2010-03-01

    The gas-phase radical chain reactions which utilize O 2 as the oxidant to produce propylene oxide (PO) are investigated through theoretical calculations. The transition states and energy profiles were obtained for each path. The rate constants were also calculated. The energetics for the competing pathways indicate that PO can be formed selectively due to its relatively low activation barrier (9.3 kcal/mol) which is in a good agreement with the experimental value (11 kcal/mol) of gas-phase propylene epoxidation. The formation of the acrolein and combustion products have relatively high activation barriers and are not favored. These results also support the recent experimental findings.

  19. Kinetics and mechanism of the selective oxidation of primary aliphatic alcohols under phase transfer catalysis

    K. Bijudas

    2014-03-01

    Full Text Available Kinetics of the oxidation of primary aliphatic alcohols has been carried out using phase transferred monochromate in benzene. Tetrabutylammonium bromide (TBAB and tetrabutylphosphonium bromide (TBPB are used as phase transfer catalysts (PT catalyst. The reaction shows first order dependence on both [alcohol] and [monochromate ion]. The oxidation leads to the formation of corresponding aldehyde and no traces of carboxylic acid has been detected. The reaction mixture failed to induce the polymerization of added acrylonitrile which rules out the presence radical intermediates in the reaction. Various thermodynamic parameters have been evaluated and a suitable mechanism has been proposed.

  20. Heterogeneous Oxidation of Atmospheric Organic Aerosol: Kinetics of Changes to the Amount and Oxidation State of Particle-Phase Organic Carbon.

    Kroll, Jesse H; Lim, Christopher Y; Kessler, Sean H; Wilson, Kevin R

    2015-11-05

    Atmospheric oxidation reactions are known to affect the chemical composition of organic aerosol (OA) particles over timescales of several days, but the details of such oxidative aging reactions are poorly understood. In this study we examine the rates and products of a key class of aging reaction, the heterogeneous oxidation of particle-phase organic species by the gas-phase hydroxyl radical (OH). We compile and reanalyze a number of previous studies from our laboratories involving the oxidation of single-component organic particles. All kinetic and product data are described on a common basis, enabling a straightforward comparison among different chemical systems and experimental conditions. Oxidation chemistry is described in terms of changes to key ensemble properties of the OA, rather than to its detailed molecular composition, focusing on two quantities in particular, the amount and the oxidation state of the particle-phase carbon. Heterogeneous oxidation increases the oxidation state of particulate carbon, with the rate of increase determined by the detailed chemical mechanism. At the same time, the amount of particle-phase carbon decreases with oxidation, due to fragmentation (C-C scission) reactions that form small, volatile products that escape to the gas phase. In contrast to the oxidation state increase, the rate of carbon loss is nearly uniform among most systems studied. Extrapolation of these results to atmospheric conditions indicates that heterogeneous oxidation can have a substantial effect on the amount and composition of atmospheric OA over timescales of several days, a prediction that is broadly in line with available measurements of OA evolution over such long timescales. In particular, 3-13% of particle-phase carbon is lost to the gas phase after one week of heterogeneous oxidation. Our results indicate that oxidative aging represents an important sink for particulate organic carbon, and more generally that fragmentation reactions play a major

  1. Gas-phase copper and silver complexes with phosphorothioate and phosphorodithioate pesticides investigated using electrospray ionization mass spectrometry.

    Mustapha, Adetayo M; Pasilis, Sofie P

    2015-01-01

    Efforts to improve agricultural productivity have led to a growing dependency on organophosphorus pesticides. Phosphorothioate and phosphorodithioate pesticides are organophosphorus pesticide subclasses with widespread application for the control of insects feeding on vegetables and fruits. However, even low doses of these pesticides can cause neurological problems in humans; thus, their determination and monitoring in agricultural foodstuffs is important for human health. Phosphorothioate and phosphorodithioate pesticides may be poorly ionized during electrospray, adversely affecting limits of detection. These pesticides can form complexes with Cu(2+) and Ag(+) , however, potentially improving ionization. In the present work, we used electrospray ionization/mass spectrometry (ESI/MS) to study fenitrothion, parathion, diazinon, and malathion coordination complexes with silver and copper ions. Stable 1 : 1 and 1 : 2 metal/pesticide complexes were detected. Mass spectra acquired from pesticide solutions containing Ag(+) or Cu(2+) showed a significant increase in signal-to-background ratio over those acquired from solutions containing only the pesticides, with Ag(+) improving detection more effectively than Cu(2+). Addition of Ag(+) to a pesticide solution improved the limit of detection by ten times. The relative affinity of each pesticide for Ag(+) was related to complex stability, following the order diazinon > malathion > fenitrothion > parathion. The formation of Ag(+)-pesticide complexes can significantly improve the detection of phosphorothioate and phosphorodithioate pesticides using ESI/MS. The technique could potentially be used in reactive desorption electrospray ionization/mass spectrometry to detect phosphorothioate and phosphorodithioate pesticides on fruit and vegetable skins. Copyright © 2015 John Wiley & Sons, Ltd.

  2. Hierarchical porous silver metal using Pluronic F-127 and graphene oxide as reinforcing agents for the reduction of o-nitroaniline to 1, 2-benzenediamine

    Bano, Mustri; Ahirwar, Devendra; Thomas, Molly; Sheikh, Mehraj Ud Din; Khan, Farid, E-mail: faridkhan58@yahoo.com

    2017-04-15

    An elegant method is used to prepare silver monoliths with Pluronic F-127(F-127) as sacrificial template by modified sol-gel method. Si nanoparticles (SiNPs) and graphene oxide (GO) are added in situ to Ag/F-127 hydrogel for the reduction of ο-nitroaniline (ο-NA) to 1, 2-benzenediamine. Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Thermogravimetric analysis (TGA), Raman Spectroscopy, Powder X-Ray Diffraction (PXRD) analysis and Brunauer-Emmett-Teller (BET) Nitrogen adsorption techniques were used for characterization of monoliths. An epoch-making catalytic activity of Ag/F-127/GO monoliths is observed in the reduction of ο-NA to 1, 2-benzenediamine in presence of NaBH{sub 4} in aqueous media. The catalyst Ag/F-127/GO took only 2 min which is the minimum time reported so far with significant rate constant claimed itself a leading catalyst for the reduction of ο-NA to 1,2-benzenediamine. Pseudo first order rate constant (k) and Turn over frequency (TOF) values are 0.231 min{sup −1} and 30.053×10{sup 19} molecules min{sup −1} respectively suggest that the catalyst has industrial importance. Recyclability and stability of Ag/F-127/GO catalyst are studied successfully up to 10 cycles. Energy of activation (E{sub a}), and thermodynamic parameters viz. activation enthalpy (ΔH{sup ≠}), activation Gibbs free energy (ΔG{sup ≠}), and entropy of activation (ΔS{sup ≠}) were also ascertained. Catalytic activities of Ag/F-127, Ag/F-127/Dextran, Ag/F-127/Trimethylbenzene (TMB), Ag/F-127/SiNPs, and Ag/F-127/Si/GO monoliths were also studied. - Graphical abstract: Significant catalytic activities of silver monoliths against the reduction of ο-NA to 1,2 benzenediamine. - Highlights: • A new catalyst synthesized Ag/F-127/GO for the reduction of ο- NA to 1, 2- benzenediamine took only 2 min. • Turn over frequency of as synthesized catalyst was 30.053×10{sup 19} molecules min{sup

  3. Phase and structural transformations in annealed copper coatings in relation to oxide whisker growth

    Dorogov, M.V.; Priezzheva, A.N. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Vlassov, S., E-mail: vlassovs@ut.ee [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia); Kink, I.; Shulga, E. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Dorogin, L.M. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); ITMO University, Kronverkskiy 49, 197101 Saint Petersburg (Russian Federation); Lõhmus, R. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Tyurkov, M.N.; Vikarchuk, A.A. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Romanov, A.E. [Togliatti State University, Belorusskaya 14, 445667 Togliatti (Russian Federation); Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); ITMO University, Kronverkskiy 49, 197101 Saint Petersburg (Russian Federation); Ioffe Physical Technical Institute, RAS, Polytechnicheskaya 26, 194021 Saint Petersburg (Russian Federation)

    2015-08-15

    Highlights: • Coatings prepared by Cu microparticle electrodeposition. • Structural and phase transformation in Cu coatings annealed at 400 °C. • Annealing is accompanied by intensive growth of CuO whiskers. • Layered oxide phases (Cu{sub 2}O and CuO) in the coating are characterized. • Formation of volumetric defects in the coating is demonstrated. - Abstract: We describe structural and phase transformation in copper coatings made of microparticles during heating and annealing in air in the temperature range up to 400 °C. Such thermal treatment is accompanied by intensive CuO nanowhisker growth on the coating surface and the formation of the layered oxide phases (Cu{sub 2}O and CuO) in the coating interior. X-ray diffraction and focused ion beam (FIB) are employed to characterize the multilayer structure of annealed copper coatings. Formation of volumetric defects such as voids and cracks in the coating is demonstrated.

  4. Experimental study of the oxide film structural phase state in the E635 and E110 alloys

    Shevyakov, A. Yu.; Shishov, V. N.; Novikov, V. V.

    2013-01-01

    The microstructure, phase and element compositions of oxide films of E110 (Zr-1%Nb) and E635 (Zr-1%Nb-0,35%Fe-1,2%Sn) alloys after autoclave tests in pure water had been studied by the method of transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS). TEM investigations of oxide film structure were carried on different oxide layers according to their thickness (near interface of “metal-oxide”, in central part of the oxide film and near outer surface) and in cross-section. The results of the tests show that oxide films of the alloys have different microstructure (grain size, fraction of tetragonal phase, content of defects, etc) and the phase compositions. The crystal structure of oxide films is mainly monoclinic, however, at the “metal-oxide” interface there are a significant fraction of the tetragonal phase. Researching of oxides on different stages of oxidation allow us to determine the kinetics of the second phase precipitate structure change: a) in E635 alloy at early oxidation stages of the amorphization process of the Laves phase precipitates begins with decreasing the content of iron and niobium; b) in E110 alloy the amorphization process of β-Nb precipitates begins at a later stage of oxidation. The influence of changes of the crystal structure and the chemical composition of the second phase precipitates on protective properties of the oxides had been determined. Researching of alloying element redistribution in E635 alloy oxide film shows that iron and niobium are concentrated in pores. Increased porosity of the E635 alloy oxide films at a later oxidation stage, in comparison with the E110 alloy, shows the influence of change composition and subsequent dissolution of the Laves phase particles on the pore formation in the oxide. (authors)

  5. Oxidative decarboxylation of glycolic and phenylacetic acids with cerium(4) catalyzed by silver ions in the sulfuric acid media

    Venkatesvar Rao, G.; Nagardzhun Rao, Ch.; Sajprakash, P.K.

    1981-01-01

    Oxidative decarboxylation of glycolic and phenylacetic acids by cerium (4) in the presence of Ag + ions is studied. The Ce(4) order equals 1, glycolic acid order in the absence of a catalyst also equals 1 and is fractional (0.5) for a catalytic reaction. The phenylacetic acid order is fractional (0.75). The Ag + ion reaction order is fractional and constitutes 0.32 for glycolic and 0.36 for phenylacetic acids. The reaction mechanism is proposed [ru

  6. Aqueous-Phase Synthesis of Silver Nanodiscs and Nanorods in Methyl Cellulose Matrix: Photophysical Study and Simulation of UV–Vis Extinction Spectra Using DDA Method

    Sarkar Priyanka

    2010-01-01

    Full Text Available Abstract We present a very simple and effective way for the synthesis of tunable coloured silver sols having different morphologies. The procedure is based on the seed-mediated growth approach where methyl cellulose (MC has been used as soft-template in the growth solution. Nanostructures of varying morphologies as well as colour of the silver sols are controlled by altering the concentration of citrate in the growth solution. Similar to the polymers in the solution, citrate ions also dynamically adsorbed on the growing silver nanoparticles and promote one (1-D and two-dimensional (2-D growth of nanoparticles. Silver nanostructures are characterized using UV–vis and HR-TEM spectroscopic study. Simulation of the UV–vis extinction spectra of our synthesized silver nanostructures has been carried out using discrete dipole approximation (DDA method.

  7. A heterojunction photocatalyst composed of zinc rhodium oxide, single crystal-derived bismuth vanadium oxide, and silver for overall pure-water splitting under visible light up to 740 nm.

    Kobayashi, Ryoya; Takashima, Toshihiro; Tanigawa, Satoshi; Takeuchi, Shugo; Ohtani, Bunsho; Irie, Hiroshi

    2016-10-12

    We recently reported the synthesis of a solid-state heterojunction photocatalyst consisting of zinc rhodium oxide (ZnRh 2 O 4 ) and bismuth vanadium oxide (Bi 4 V 2 O 11 ), which functioned as hydrogen (H 2 ) and oxygen (O 2 ) evolution photocatalysts, respectively, connected with silver (Ag). Polycrystalline Bi 4 V 2 O 11 (p-Bi 4 V 2 O 11 ) powders were utilized to form ZnRh 2 O 4 /Ag/p-Bi 4 V 2 O 11 , which was able to photocatalyze overall pure-water splitting under red-light irradiation with a wavelength of 700 nm (R. Kobayashi et al., J. Mater. Chem. A, 2016, 4, 3061). In the present study, we replaced p-Bi 4 V 2 O 11 with a powder obtained by pulverizing single crystals of Bi 4 V 2 O 11 (s-Bi 4 V 2 O 11 ) to form ZnRh 2 O 4 /Ag/s-Bi 4 V 2 O 11 , and demonstrated that this heterojunction photocatalyst had enhanced water-splitting activity. In addition, ZnRh 2 O 4 /Ag/s-Bi 4 V 2 O 11 was able to utilize nearly the entire range of visible light up to a wavelength of 740 nm. These properties were attributable to the higher O 2 evolution activity of s-Bi 4 V 2 O 11 .

  8. Three-phase boundary length in solid-oxide fuel cells: A mathematical model

    Janardhanan, Vinod M. [Institutefor Chemical Technology and Polymer Chemistry, University of Karlsruhe (TH), Kaiserstr. 12, D-76128 Karlsruhe (Germany); Heuveline, Vincent; Deutschmann, Olaf [Institute for Applied and Numerical Mathematics, University of Karlsruhe (TH), Kaiserstr. 12, D-76128 Karlsruhe (Germany)

    2008-03-15

    A mathematical model to calculate the volume specific three-phase boundary length in the porous composite electrodes of solid-oxide fuel cell is presented. The model is exclusively based on geometrical considerations accounting for porosity, particle diameter, particle size distribution, and solids phase distribution. Results are presented for uniform particle size distribution as well as for non-uniform particle size distribution. (author)

  9. Long-term oxidization and phase transition of InN nanotextures

    Dražic Goran

    2011-01-01

    Full Text Available Abstract The long-term (6 months oxidization of hcp-InN (wurtzite, InN-w nanostructures (crystalline/amorphous synthesized on Si [100] substrates is analyzed. The densely packed layers of InN-w nanostructures (5-40 nm are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-O x -N y (indium oxynitride phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture. High-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction are used to identify amorphous In-O x -N y oxynitride phase. When the oxidized area exceeds the critical size of 5 nm, the amorphous In-O x -N y phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase.

  10. Silver deposition on stainless steel container surfaces in contact with disinfectant silver aqueous solutions

    Petala, M.; Tsiridis, V.; Mintsouli, I.; Pliatsikas, N.; Spanos, Th.; Rebeyre, P.; Darakas, E.; Patsalas, P.; Vourlias, G.; Kostoglou, M.; Sotiropoulos, S.; Karapantsios, Th.

    2017-01-01

    Highlights: • Silver is one of the biocides of water consumed in the International Space Station. • Ionic silver is depleted from potable water when in contact with stainless steel (SS). • SEM and XPS analysis reveal a uniform silver deposition over the SS surface. • Silver deposits in its metallic form, in line with a galvanic deposition mechanism. • Evidence is provided that Cr and/ or Ni oxide builds-up on SS surfaces. - Abstract: Silver is the preservative used on the Russian segment of the International Space Station (ISS) to prevent microbial proliferation within potable water supplies. Yet, in the frame of the European Automated Transfer Vehicle (ATV) missions to ISS, silver depletion from water has been detected during ground transportation of this water to launch site, thereby indicating a degradation of water quality. This study investigates the silver loss from water when in contact with stainless steel surfaces. Experiments are conducted with several types of stainless steel surfaces being exposed to water containing 10 or 0.5 mg/L silver ions. Results show that silver deposits on stainless steel surfaces even when a passivation layer protects the metallic surface. The highest protection to silver deposition is offered by acid passivated and electropolished SS 316L. SEM and XPS experiments were carried out at several locations of the sample area that was in contact with the Ag solution and found similar morphological (SEM) and compositional (sputter-etch XPS) results. The results reveal that silver deposits uniformly across the wetted surface to a thickness larger than 3 nm. Moreover, evidence is provided that silver deposits in its metallic form on all stainless steel surfaces, in line with a galvanic deposition mechanism. Combination of ICP-MS and XPS results suggests a mechanism for Ag deposition/reduction with simultaneous substrate oxidation resulting in oxide growth at the exposed stainless steel surface.

  11. Silver deposition on stainless steel container surfaces in contact with disinfectant silver aqueous solutions

    Petala, M., E-mail: petala@civil.auth.gr [Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Tsiridis, V. [Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Mintsouli, I. [Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Pliatsikas, N. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Spanos, Th. [Department of Petroleum and Mechanical Engineering Sciences, Eastern Macedonia and Thrace Institute of Technology, Kavala, 65404 (Greece); Rebeyre, P. [ESA/ESTEC, P.O.Box 299, 2200 AG, Noordwijk (Netherlands); Darakas, E. [Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Patsalas, P.; Vourlias, G. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Kostoglou, M.; Sotiropoulos, S.; Karapantsios, Th. [Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece)

    2017-02-28

    Highlights: • Silver is one of the biocides of water consumed in the International Space Station. • Ionic silver is depleted from potable water when in contact with stainless steel (SS). • SEM and XPS analysis reveal a uniform silver deposition over the SS surface. • Silver deposits in its metallic form, in line with a galvanic deposition mechanism. • Evidence is provided that Cr and/ or Ni oxide builds-up on SS surfaces. - Abstract: Silver is the preservative used on the Russian segment of the International Space Station (ISS) to prevent microbial proliferation within potable water supplies. Yet, in the frame of the European Automated Transfer Vehicle (ATV) missions to ISS, silver depletion from water has been detected during ground transportation of this water to launch site, thereby indicating a degradation of water quality. This study investigates the silver loss from water when in contact with stainless steel surfaces. Experiments are conducted with several types of stainless steel surfaces being exposed to water containing 10 or 0.5 mg/L silver ions. Results show that silver deposits on stainless steel surfaces even when a passivation layer protects the metallic surface. The highest protection to silver deposition is offered by acid passivated and electropolished SS 316L. SEM and XPS experiments were carried out at several locations of the sample area that was in contact with the Ag solution and found similar morphological (SEM) and compositional (sputter-etch XPS) results. The results reveal that silver deposits uniformly across the wetted surface to a thickness larger than 3 nm. Moreover, evidence is provided that silver deposits in its metallic form on all stainless steel surfaces, in line with a galvanic deposition mechanism. Combination of ICP-MS and XPS results suggests a mechanism for Ag deposition/reduction with simultaneous substrate oxidation resulting in oxide growth at the exposed stainless steel surface.

  12. Application of mid-infrared pulses for quasi-phase-matching of high-order harmonics in silver plasma.

    Ganeev, Rashid A; Husakou, Anton; Suzuki, Masayuki; Kuroda, Hiroto

    2016-02-22

    We demonstrate the quasi-phase-matching of a group of harmonics generated in Ag multi-jet plasma using tunable pulses in the region of 1160 - 1540 nm and their second harmonic emission. The numerical treatment of this effect includes microscopic description of the harmonic generation, propagation of the pump pulse, and the propagation of the generated harmonics. We obtained more than 30-fold growth of harmonics at the conditions of quasi-phase-matching in the region of 35 nm using eight-jet plasma compared with the case of imperforated plasma.

  13. Gas-Phase Oxidation of Aqueous Ethanol by Nanoparticle Vanadia/Anatase Catalysts

    Jørgensen, Betina; Kristensen, Steffen Buus; Kunov-Kruse, Andreas Jonas

    2009-01-01

    The gas-phase oxidation of aqueous ethanol with dioxygen has been examined with a new nanoparticle V2O5/TiO2 catalyst. Product selectivity could to a large extent be controlled by small alterations of reaction parameters, allowing production of acetaldehyde at a selectivity higher than 90%, near...

  14. Zinc oxide crystal whiskers as a novel sorbent for solid-phase extraction of flavonoids.

    Wang, Licheng; Shangguan, Yangnan; Hou, Xiudan; Jia, Yong; Liu, Shujuan; Sun, Yingxin; Guo, Yong

    2017-08-15

    As a novel solid-phase extraction material, zinc oxide crystal whiskers were used to extract flavonoid compounds and showed good extraction abilities. X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy and surface area/pore volume characterized the sorbent. The zinc oxide was packed into a solid-phase extraction micro-column and its extraction ability was evaluated by four model flavonoid compounds. The sample loading and elution parameters were optimized and the zinc oxide based analytical method for flavonoids was established. It showed that the method has wide linearities from 1 to 150μg/L and low limits of detection at 0.25μg/L. The relative standard deviations of a single column repeatability and column to column reproducibility were less than 6.8% and 10.6%. Several real samples were analyzed by the established method and satisfactory results were obtained. The interactions between flavonoids and zinc oxide were calculated and proved to be from the Van der Waals' forces between the 4p and 5d orbitals from zinc atom and the neighboring π orbitals from flavonoid phenyl groups. Moreover, the zinc oxide crystal whiskers showed good stability and could be reused more than 50 times under the operation conditions. This work proves that the zinc oxide crystal whiskers are a good candidate for flavonoids enrichment. Copyright © 2017. Published by Elsevier B.V.

  15. Selective oxidation of dual phase steel after annealing at different dew points

    Lins, Vanessa de Freitas Cunha; Madeira, Laureanny; Vilela, Jose Mario Carneiro; Andrade, Margareth Spangler; Buono, Vicente Tadeu Lopes; Guimarães, Juliana Porto; Alvarenga, Evandro de Azevedo

    2011-04-01

    Hot galvanized steels have been extensively used in the automotive industry. Selective oxidation on the steel surface affects the wettability of zinc on steel and the grain orientation of inhibition layer (Fe-Al-Zn alloy) and reduces the iron diffusion to the zinc layer. The aim of this work is to identify and quantify selective oxidation on the surface of a dual phase steel, and an experimental steel with a lower content of manganese, annealed at different dew points. The techniques employed were atomic force microscopy, X-ray photoelectron spectroscopy, and glow discharge optical emission spectroscopy. External selective oxidation was observed for phosphorus on steel surface annealed at 0 °C dp, and for manganese, silicon, and aluminum at a lower dew point. The concentration of manganese was higher on the dual phase steel surface than on the surface of the experimental steel. The concentration of molybdenum on the surface of both steels increased as the depth increased.

  16. Synergistic effect of shape-selective silver nanostructures decorating reduced graphene oxide nanoplatelets for enhanced cytotoxicity against breast cancer

    Derakhshi, Maryam; Ashkarran, Ali Akbar; Bahari, Ali; Bonakdar, Shahin

    2018-07-01

    Graphene-based nanomaterials contain unique physicochemical properties and have been widely investigated due to a variety of applications particularly in cancer therapy. Furthermore, Ag has been known for its extensive historical background for biomedical applications. Therefore, conjugation of shape-selective Ag nanostructures with graphene may provide new horizons for pharmaceutical applications such as cancer treatments. Here we report on the synthesis of Ag nanoparticles (NPs)/reduced graphene oxide (AgNPs/RGO) conjugate nanomaterials containing various shapes of AgNPs by a novel and simple synthesis route using the deformation of dimethylformamide (DMF) as the reducing and coupling agent. The cytotoxicity and anticancer properties of AgNPs, AgNPs/RGO conjugate nanomaterials, RGO and graphene oxide (GO) were probed against MDA-MB-231 cancer and MCF-10A normal human breast cells in vitro. The AgNPs/RGO nanocomposites exhibited a strong anticancer effect by penetration and apoptosis in cancer cells as well as the lowest influence on the viability of normal cells. It was found that cancer cell viability not only depends on the geometry of Ag nanostructures but also on the interaction between AgNPs and RGO nanoplatelets. It is suggested that AgNPs/RGO conjugate nanomaterials with various shapes of AgNPs is a promising therapeutic platform for cancer therapy.

  17. Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H2O2, O3 and iron catalysis

    J. N. Crowley

    2012-01-01

    Full Text Available The oxidation of SO2 to sulfate is a key reaction in determining the role of sulfate in the environment through its effect on aerosol size distribution and composition. Sulfur isotope analysis has been used to investigate sources and chemical processes of sulfur dioxide and sulfate in the atmosphere, however interpretation of measured sulfur isotope ratios is challenging due to a lack of reliable information on the isotopic fractionation involved in major transformation pathways. This paper presents laboratory measurements of the fractionation factors for the major atmospheric oxidation reactions for SO2: Gas-phase oxidation by OH radicals, and aqueous oxidation by H2O2, O3 and a radical chain reaction initiated by iron. The measured fractionation factor for 34S/32S during the gas-phase reaction is αOH = (1.0089±0.0007−((4±5×10−5 T(°C. The measured fractionation factor for 34S/32S during aqueous oxidation by H2O2 or O3 is αaq = (1.0167±0.0019−((8.7±3.5 ×10−5T(°C. The observed fractionation during oxidation by H2O2 and O3 appeared to be controlled primarily by protonation and acid-base equilibria of S(IV in solution, which is the reason that there is no significant difference between the fractionation produced by the two oxidants within the experimental error. The isotopic fractionation factor from a radical chain reaction in solution catalysed by iron is αFe = (0.9894±0.0043 at 19 °C for 34S/32S. Fractionation was mass-dependent with regards to 33S/32S for all the reactions investigated. The radical chain reaction mechanism was the only measured reaction that had a faster rate for the light isotopes. The results presented in this study will be particularly useful to determine the importance of the transition metal-catalysed oxidation pathway compared to other oxidation pathways, but other main oxidation pathways can not be distinguished based on stable sulfur isotope measurements alone.

  18. Metastable phases in yttrium oxide plasma spray deposits and their effect on coating properties

    Gourlaouen, V.; Schnedecker, G.; Boncoeur, M.; Lejus, A.M.; Collongues, R.

    1993-01-01

    Yttrium oxide coatings were obtained by plasma spray. Structural investigations on these deposits show that, due to the drastic conditions of this technique, a minor monoclinic B phase is formed in the neighborhood of the major cubic C form. The authors discuss here the influence of different plasma spray parameters on the amount of the B phase formed. They describe also the main properties of Y 2 O 3 B and C phases in these deposits such as structural characteristics, thermal stability and mechanical behavior

  19. Method of forming an oxide superconducting thin film having an R1A2C3 crystalline phase over an R2A1C1 crystalline phase

    Lelental, M.; Romanofsky, H.J.

    1992-01-01

    This patent describes a process which comprises forming a mixed rare earth alkaline earth copper oxide layer on a substrate and converting the mixed rare earth alkaline earth copper oxide layer to an electrically conductive layer. It comprises crystalline R 1 A 2 C 3 oxide phase by heating in the presence of oxygen, wherein rare earth and R is in each instance chosen from among yttrium, lanthanum, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium and alkaline earth and A is in each instance chosen from among calcium, strontium and barium, characterized in that a crystalline R 2 A 1 C 1 oxide phase is first formed as a layer on the substrate and the crystalline R 1 A 2 C 3 oxide phase is formed over the crystalline R 2 A 1 C 1 oxide phase by coating a mixed rare earth alkaline earth copper oxide on the crystalline R 2 A 1 C 1 oxide phase and heating the mixed rare earth alkaline earth copper oxide to a temperature of at least 1000 degrees C

  20. Russell-Silver syndrome

    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 ...

  1. Crystalline oxides on semiconductors: A structural transition of the interface phase

    Walker, F. J.; Buongiorno-Nardelli, Marco; Billman, C. A.; McKee, R. A.

    2004-03-01

    The growth of crystalline oxides on silicon is facilitated by the preparation of a surface phase of alkaline earth silicide. We describe how the surface phase serves as a precursor of the final interface phase using reflection high energy electron diffraction (RHEED) and density functional theory (DFT). RHEED intensity oscillations of the growth of BaSrO show layer-by-layer build up of the oxide on the interface. The 2x1 symmetry of the surface precursor persists up to 3 ML BaSrO coverage at which point a 1x1 pattern characteristic of the rock-salt structure of BaSrO is observed. Prior to 3 ML growth of alkaline earth oxide, DFT calculations and RHEED show that the surface precursor persists as the interface phase and induces large displacements in the growing oxide layer away from the rock-salt structure and having a 2x1 symmetry. These distortions of the rock-salt structure are energetically unfavorable and become more unfavorable as the oxide thickness increases. At 3 ML, the stability of the rock-salt structure drives a structural transformation of the film and the interface phase to a structure that is distinct from the surface precursor. Research sponsored jointly by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy at Oak Ridge National Laboratory under contract DE-AC05-00OR22725 with UT-Battelle, LLC and at the University of Tennessee under contract DE-FG02-01ER45937. Calculations have been performed on CCS supercomputers at Oak Ridge National Laboratory.

  2. Opto-electronic properties of bismuth oxide films presenting different crystallographic phases

    Gomez, Celia L. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Posgrado en Ciencia e Ingeniería de Materiales, UNAM, Unidad de Posgrado, Edificio C, Piso 1, Zona Cultural de CU, México, D.F. 04510 (Mexico); Depablos-Rivera, Osmary, E-mail: osmarydep@yahoo.com [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Posgrado en Ciencia e Ingeniería de Materiales, UNAM, Unidad de Posgrado, Edificio C, Piso 1, Zona Cultural de CU, México, D.F. 04510 (Mexico); Silva-Bermudez, Phaedra [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Instituto Nacional de Rehabilitación, Calz. México Xochimilco No. 289 Col. Arenal de Guadalupe, C.P.14389, Ciudad de México, D.F. (Mexico); Muhl, Stephen [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Zeinert, Andreas; Lejeune, Michael; Charvet, Stephane; Barroy, Pierre [Laboratoire de Physique de la Matière Condensée, Université de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens Cedex 1 (France); Camps, Enrique [Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca S/N, kilómetro 36.5. La Marquesa, Municipio de Ocoyoacac, CP 52750, Estado de México (Mexico); Rodil, Sandra E. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico)

    2015-03-02

    The optical, electrical and structural properties of bismuth oxide thin films deposited by radio frequency reactive magnetron sputtering were studied. The Bi{sub 2}O{sub 3} thin films were grown on Si and glass substrates under different power and substrate temperatures in an oxygen-enriched plasma leading to films with different crystalline phase as evidenced by X-ray diffraction and Raman spectroscopy. The optical properties of the films were measured using ellipsometric spectroscopy and optical transmission spectra. In order to parameterize the optical dispersion functions (n, k) of the films, the Tauc–Lorentz dispersion model was used. The optical bandgap was then assessed by different methods and the results are compared to the thermal variations of the electrical resistivity of the films. It was found that the refractive index, extinction coefficient and optical gap strongly depend on the deposition conditions and the crystalline phase; the fluorite defect cubic δ-Bi{sub 2}O{sub 3} phase showed the lowest optical gap and lower resistivity. - Highlights: • Different bismuth oxide phases were obtained by sputtering. • The power and substrate temperature were the two key parameters. • Room temperature delta-Bi{sub 2}O{sub 3} thin films were obtained. • The optical bandgap was around 1.5 and 2.2 eV, depending on the phase. • The bismuth oxide films presented activation energies around 1 eV.

  3. Opto-electronic properties of bismuth oxide films presenting different crystallographic phases

    Gomez, Celia L.; Depablos-Rivera, Osmary; Silva-Bermudez, Phaedra; Muhl, Stephen; Zeinert, Andreas; Lejeune, Michael; Charvet, Stephane; Barroy, Pierre; Camps, Enrique; Rodil, Sandra E.

    2015-01-01

    The optical, electrical and structural properties of bismuth oxide thin films deposited by radio frequency reactive magnetron sputtering were studied. The Bi 2 O 3 thin films were grown on Si and glass substrates under different power and substrate temperatures in an oxygen-enriched plasma leading to films with different crystalline phase as evidenced by X-ray diffraction and Raman spectroscopy. The optical properties of the films were measured using ellipsometric spectroscopy and optical transmission spectra. In order to parameterize the optical dispersion functions (n, k) of the films, the Tauc–Lorentz dispersion model was used. The optical bandgap was then assessed by different methods and the results are compared to the thermal variations of the electrical resistivity of the films. It was found that the refractive index, extinction coefficient and optical gap strongly depend on the deposition conditions and the crystalline phase; the fluorite defect cubic δ-Bi 2 O 3 phase showed the lowest optical gap and lower resistivity. - Highlights: • Different bismuth oxide phases were obtained by sputtering. • The power and substrate temperature were the two key parameters. • Room temperature delta-Bi 2 O 3 thin films were obtained. • The optical bandgap was around 1.5 and 2.2 eV, depending on the phase. • The bismuth oxide films presented activation energies around 1 eV

  4. Immobilization of Radioactive Rare Earth oxide Waste by Solid Phase Sintering

    Ahn, Byung Gil; Park, Hwan Seo; Kim, Hwan Young; Lee, Han Soo; Kim, In Tae

    2010-01-01

    In the pyroprocessing of spent nuclear fuels, LiCl-KCl waste salt containing radioactive rare earth chlorides are generated. The radioactive rare earth oxides are recovered by co-oxidative precipitation of rare earth elements. The powder phase of rare earth oxide waste must be immobilized to produce a monolithic wasteform suitable for storage and ultimate disposal. The immobilization of these waste developed in this study involves a solid state sintering of the waste with host borosilicate glass and zinc titanate based ceramic matrix (ZIT). And the rare-earth monazite which synthesised by reaction of ammonium di-hydrogen phosphate with the rare earth oxides waste, were immobilized with the borosilicate glass. It is shown that the developed ZIT ceramic wasteform is highly resistant the leaching process, high density and thermal conductivity.

  5. Heterogeneous inhibition of the liquid phase oxidation of hydrocarbons by molybdenum compounds

    Tavadyan, L.A.; Karapetyan, A.P.; Madatovyan, V.M.

    1988-05-01

    The heterogeneous action of molybdenum compounds: MoB, MoSe/sub 2/, MoSi/sub 2/, Mo/sub 2/C, MoO/sub 3/, Mo on the oxidation of n-decane, ethylbenzene, and nonene-1 has been investigated. A parameter representing the inhibiting effect of the heterogeneous catalyst was calculated theoretically. It was found that NoB, MoSe/sub 2/, and MoSi/sub 2/ inhibited the oxidation of n-decane at 408 K while the remaining heterogeneous contacts catalyzed it. A critical phenomenon was detected in the inhibition by MoSi/sub 2/. All the molybdenum compounds investigated inhibited the oxidation of ethylbenzene at 393 K owing to the formation of phenol by catalytic decomposition of the hydroperoxide. The liquid phase oxidation autoinhibited by phenol is described theoretically.

  6. Synthesizing A Phase Changing Bistable Electroactive Polymer And Silver Nanoparticles Coated Fabric As A Resistive Heating Element

    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 strategy of the wearable heater can potentially play influential roles in energy saving and consumer experience in a localized thermal management system. (Abstract shortened by ProQuest.).

  7. Ion irradiation-induced diffusion in bixbyite-fluorite related oxides: Dislocations and phase transformation

    Rolly, Gaboriaud, E-mail: Rolly.gaboriaud@univ-poitiers.fr [Institut Pprime, CNRS-University of Poitiers, SP2MI-BP 30179, 86962 Chasseneuil-Futuroscope (France); Fabien, Paumier [Institut Pprime, CNRS-University of Poitiers, SP2MI-BP 30179, 86962 Chasseneuil-Futuroscope (France); Bertrand, Lacroix [CSIC – University of Sevilla, Avenida Américo Vespucio, 49, 41092 Sevilla (Spain)

    2014-05-01

    Ion-irradiation induced diffusion and the phase transformation of a bixbyite-fluorite related rare earth oxide thin films are studied. This work is focused on yttrium sesquioxide, Y{sub 2}O{sub 3}, thin films deposited on Si (1 0 0) substrates using the ion beam sputtering technique (IBS). As-deposited samples were annealed ant then irradiated at cryogenic temperature (80 K) with 260 keV Xe{sup 2+} at different fluences. The irradiated thin oxide films are characterized by X-ray diffraction. A cubic to monoclinic phase transformation was observed. Analysis of this phenomenon is done in terms of residual stresses. Stress measurements as a function of irradiation fluences were realised using the XRD-sin{sup 2}ψ method. Stress evolution and kinetic of the phase transformation are compared and leads to the role-played by the nucleation of point and extended defects.

  8. Stability-Indicating RP-HPLC Method for Assay of Silver Lactate

    V. Srinivasan

    2011-01-01

    Full Text Available A simple, economic and time-efficient stability-indicating, reverse-phase high-performance liquid chromatographic (RP-HPLC method has been developed for analysis of silver lactate in the presence of degradation products generated by decomposition. When silver lactate was subjected to acid hydrolysis, base hydrolysis, oxidative, photolytic, humidity and thermal stress, degradation was observed during base hydrolysis, oxidation, humidity and thermal stress. The drug was found to be stable to other stress conditions. Successful chromatographic condition of the drug from the degradation products formed under stress conditions was achieved on a phenomenex Gemini column with potassium dihydrogen phosphate buffer, pH adjusted to 2.2 with orthophosphoric acid, as mobile phase. The method was validated for linearity, precision, specificity and robustness and can be used for quality-control during manufacture and assessment of the stability of samples of silver lactate. To the best of our knowledge, a validated stability-indicating LC assay method for silver lactate based on lactic acid is reported for the first time.

  9. Synthesis and characterization of gadolinia-doped ceria-silver cermet cathode material for solid oxide fuel cells

    Datta, Pradyot; Majewski, Peter; Aldinger, Fritz

    2008-01-01

    A series of Ce 0.9 Gd 0.1 O 2-δ -Ag cermets with different Ag contents were prepared by conventional sintering process aiming at assessing the suitability of using them as cathode material for solid oxide fuel cell (SOFC) with Gadolinia-doped ceria electrolyte. The chemical compatibility between Ce 0.9 Gd 0.1 O 2-δ (CGO) and Ag was investigated by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. Thermal expansion coefficients of the cermets were measured as a function of Ag content and were found to increase with metallic content. Although oxygen adsorption at the surface of the cermets could be detected, no reaction or solid solubility between CGO and Ag was found

  10. Influence of pH and media composition on suspension stability of silver, zinc oxide, and titanium dioxide nanoparticles and immobilization of Daphnia magna under guideline testing conditions.

    Cupi, Denisa; Hartmann, Nanna B; Baun, Anders

    2016-05-01

    In aquatic toxicity testing of engineered nanoparticles (ENPs) the process of agglomeration is very important as it may alter bioavailability and toxicity. In the present study, we aimed to identify test conditions that are favorable for maintaining stable ENP suspensions. We evaluated the influence of key environmental parameters: pH (2-12) and ionic strength using M7, Soft EPA (S EPA) medium, and Very Soft EPA (VS EPA) medium; and observed the influence of these parameters on zeta potential, zeta average, and acute immobilization of Daphnia magna for three different ENPs. Despite being sterically stabilized, test suspensions of silver (Ag) ENPs formed large agglomerates in both VS EPA and M7 media; and toxicity was found to be higher in VS EPA medium due to increased dissolution. Low-agglomerate suspensions for zinc oxide (ZnO) could be obtained at pH 7 in VS EPA medium, but the increase in dissolution caused higher toxicity than in M7 medium. Titanium dioxide (TiO2) ENPs had a point of zero charge in the range of pH 7-8. At pH 7 in VS EPA, agglomerates with smaller hydrodynamic diameters (~200nm) were present compared to the high ionic strength M7 medium where hydrodynamic diameters reached micrometer range. The stable suspensions of TiO2 ENPs caused immobilization of D. magna, 48-h EC50 value of 13.7mgL(-1) (95% CI, 2.4mg-79.1mgL(-1)); whereas no toxicity was seen in the unstable, highly agglomerated M7 medium suspensions, 48-h EC50 >100mgL(-1). The current study provides a preliminary approach for methodology in testing and assessing stability and toxicity of ENPs in aquatic toxicity tests of regulatory relevance. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Novel biomolecule lycopene-reduced graphene oxide-silver nanoparticle enhances apoptotic potential of trichostatin A in human ovarian cancer cells (SKOV3).

    Zhang, Xi-Feng; Huang, Feng-Hua; Zhang, Guo-Liang; Bai, Ding-Ping; Massimo, De Felici; Huang, Yi-Fan; Gurunathan, Sangiliyandi

    2017-01-01

    Recently, there has been much interest in the field of nanomedicine to improve prevention, diagnosis, and treatment. Combination therapy seems to be most effective when two different molecules that work by different mechanisms are combined at low dose, thereby decreasing the possibility of drug resistance and occurrence of unbearable side effects. Based on this consideration, the study was designed to investigate the combination effect of reduced graphene oxide-silver nanoparticles (rGO-AgNPs) and trichostatin A (TSA) in human ovarian cancer cells (SKOV3). The rGO-AgNPs were synthesized using a biomolecule called lycopene, and the resultant product was characterized by various analytical techniques. The combination effect of rGO-Ag and TSA was investigated in SKOV3 cells using various cellular assays such as cell viability, cytotoxicity, and immunofluorescence analysis. AgNPs were uniformly distributed on the surface of graphene sheet with an average size between 10 and 50 nm. rGO-Ag and TSA were found to inhibit cell viability in a dose-dependent manner. The combination of rGO-Ag and TSA at low concentration showed a significant effect on cell viability, and increased cytotoxicity by increasing the level of malondialdehyde and decreasing the level of glutathione, and also causing mitochondrial dysfunction. Furthermore, the combination of rGO-Ag and TSA had a more pronounced effect on DNA fragmentation and double-strand breaks, and eventually induced apoptosis. This study is the first to report that the combination of rGO-Ag and TSA can cause potential cytotoxicity and also induce significantly greater cell death compared to either rGO-Ag alone or TSA alone in SKOV3 cells by various mechanisms including reactive oxygen species generation, mitochondrial dysfunction, and DNA damage. Therefore, this combination chemotherapy could be possibly used in advanced cancers that are not suitable for radiation therapy or surgical treatment and facilitate overcoming tumor

  12. Pro-inflammatory responses of RAW264.7 macrophages when treated with ultralow concentrations of silver, titanium dioxide, and zinc oxide nanoparticles

    Giovanni, Marcella [Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585 (Singapore); Yue, Junqi; Zhang, Lifeng [PUB, 40 Scotts Road, Singapore 228231 (Singapore); Xie, Jianping [Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585 (Singapore); Ong, Choon Nam [Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, Singapore 117549 (Singapore); NUS Environmental Research Institute, National University of Singapore, 5A Engineering Drive 1, Singapore 117411 (Singapore); Leong, David Tai, E-mail: cheltwd@nus.edu.sg [Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585 (Singapore)

    2015-10-30

    Highlights: • Ultralow levels of common nanoparticles exist in environment and consumer products. • Common nanoparticles at ultralow levels induce mild pro-inflammation by macrophages. • The nanoparticles are cytotoxic only at high doses. - Abstract: To cellular systems, nanoparticles are considered as foreign particles. Upon particles and cells contact, innate immune system responds by activating the inflammatory pathway. However, excessive inflammation had been linked to various diseases ranging from allergic responses to cancer. Common nanoparticles, namely silver, titanium dioxide, and zinc oxide exist in the environment as well as in consumer products at ultralow level of 10{sup −6}–10{sup −3} μg mL{sup −1}. However, so far the risks of such low NPs concentrations remain unexplored. Therefore, we attempted to screen the pro-inflammatory responses after ultralow concentration treatments of the three nanoparticles on RAW264.7 macrophages, which are a part of the immune system, at both cellular and gene levels. Even though cytotoxicity was only observed at nanoparticles concentrations as high as 10 μg mL{sup −1}, through the level of NF-κB and upregulation of pro-inflammatory genes, we observed activation of the induction of genes encoding pro-inflammatory cytokines starting already at 10{sup −7} μg mL{sup −1}. This calls for more thorough characterization of nanoparticles in the environment as well as in consumer products to ascertain the health and safety of the consumers and living systems in general.

  13. Radiolytic reduction reaction of colloidal silver bromide solution

    Oya, Yasuhisa; Zushi, Takehiro; Hasegawa, Kunihiko; Matsuura, Tatsuo.

    1995-01-01

    The reduction reaction of colloidal silver bromide (AgBr 3 ) 2- in nitrous oxide gas saturated solution of some alcohols: methanol, ethanol, 2-propanol and 2-methyl-2-propanol by γ-irradiation was studied spectrophotometrically in order to elucidate the mechanism of the formation of colloidal silver bromide (AgBr 3 ) 3- at ambient temperature. The amount of colloidal silver bromide formed increases in the order: i-PrOH, EtOH, MeOH. In t-BuOH, colloidal silver bromide did not form. The relative reactivities of alcohols for colloidal silver bromide was also studied kinetically. (author)

  14. Biological evaluation of silver nanoparticles incorporated into chitosan-based membranes

    Shao, J.; Yu, N.; Kolwijck, E.; Wang, B.; Tan, K.W.; Jansen, J.A.; Walboomers, X.F.; Yang, F.

    2017-01-01

    AIM: To evaluate the antibacterial potential and biological performance of silver nanoparticles in chitosan-based membranes. MATERIALS & METHODS: Electrospun chitosan/poly(ethylene oxide) membranes with different amounts of silver nanoparticles were evaluated for antibacterial properties and

  15. Effect of poly-α, γ, L-glutamic acid as a capping agent on morphology and oxidative stress-dependent toxicity of silver nanoparticles

    Stevanović, Magdalena; Kovačević, Branimir; Petković, Jana; Filipič, Metka; Uskoković, Dragan

    2011-01-01

    Highly stable dispersions of nanosized silver particles were synthesized using a straightforward, cost-effective, and ecofriendly method. Nontoxic glucose was utilized as a reducing agent and poly-α, γ, L-glutamic acid (PGA), a naturally occurring anionic polymer, was used as a capping agent to protect the silver nanoparticles from agglomeration and render them biocompatible. Use of ammonia during synthesis was avoided. Our study clearly demonstrates how the concentration of the capping agent plays a major role in determining the dimensions, morphology, and stability, as well as toxicity of a silver colloidal solution. Hence, proper optimization is necessary to develop silver colloids of narrow size distribution. The samples were characterized by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and zeta potential measurement. MTT assay results indicated good biocompatibility of the PGA-capped silver nanoparticles. Formation of intracellular reactive oxygen species was measured spectrophotometrically using 2,7-dichlorofluorescein diacetate as a fluorescent probe, and it was shown that the PGA-capped silver nanoparticles did not induce intracellular formation of reactive oxygen species. PMID:22131829

  16. Mono and bimetallic nanoparticles of gold, silver and palladium-catalyzed NADH oxidation-coupled reduction of Eosin-Y

    Santhanalakshmi, J.; Venkatesan, P.

    2011-02-01

    Mono metallic (Au, Ag, Pd) and bimetallic (Au-Ag, Ag-Pd, Au-Pd) with 1:1 mol stoichiometry, nanoparticles are synthesized using one-pot, temperature controlled chemical method using cetyltrimethylammonium bromide (CTAB) as the capping agent. The particle sizes (Au = 5.6, Ag = 5.0, Pd = 6.0, Au-Ag = 9.2, Ag-Pd = 9.6, Au-Pd = 9.4 nm) are characterized by UV-Vis, HRTEM, and XRD measurements, respectively. CTAB bindings onto mono and bimetallic nanoparticles are analyzed by FTIR spectra. The catalytic activities of mono and bimetallic nanoparticles are tested on the reaction between NADH oxidation and Eosin-Y reduction. The effects of base, pH, ionic strength, nature of mono and bimetallic catalysts are studied and the reaction conditions are optimized. Bimetallic nanoparticles exhibited better catalysis than the mono metallic nanoparticles, which may be due to the electronic effects of the core to shell metal atoms.

  17. Mono and bimetallic nanoparticles of gold, silver and palladium-catalyzed NADH oxidation-coupled reduction of Eosin-Y

    Santhanalakshmi, J.; Venkatesan, P.

    2011-01-01

    Mono metallic (Au, Ag, Pd) and bimetallic (Au–Ag, Ag–Pd, Au–Pd) with 1:1 mol stoichiometry, nanoparticles are synthesized using one-pot, temperature controlled chemical method using cetyltrimethylammonium bromide (CTAB) as the capping agent. The particle sizes (Au = 5.6, Ag = 5.0, Pd = 6.0, Au–Ag = 9.2, Ag–Pd = 9.6, Au–Pd = 9.4 nm) are characterized by UV–Vis, HRTEM, and XRD measurements, respectively. CTAB bindings onto mono and bimetallic nanoparticles are analyzed by FTIR spectra. The catalytic activities of mono and bimetallic nanoparticles are tested on the reaction between NADH oxidation and Eosin-Y reduction. The effects of base, pH, ionic strength, nature of mono and bimetallic catalysts are studied and the reaction conditions are optimized. Bimetallic nanoparticles exhibited better catalysis than the mono metallic nanoparticles, which may be due to the electronic effects of the core to shell metal atoms.Graphical Abstract

  18. Synthesis of battery grade reduced silver powder

    Qadeer, R.; Hameed, M.; Ikram, S.; Munir, A.

    2002-01-01

    Process for production of battery grade reduced silver powder, an active positive material for zinc-silver oxide batteries, having specific characteristics has been optimized and the synthesized reduced silver powder was characterized. Results reveal that the values of bulk density (1.25 0.1 g/cm3) and activity (73.27 %) of synthesized reduced silver powder lies within the recommended range for use as battery material. It has purity ≥ 98% and contains Fe and Cu as traces in the concentration range of 30 5 ppm and 15 7 ppm respectively. Others determined values of surface and pores parameters are: surface area 2.6 .4 m2/g: pore volume 3.10 cm3/g: pore diameter 0.043 mu m and porosity 20%. XRD studies reveal that reduced silver powder has a cubic structure. (author)

  19. A new polyethylene glycol fiber prepared by coating porous zinc electrodeposited onto silver for solid-phase microextraction of styrene

    Sungkaew, Sakchaibordee; Thammakhet, Chongdee; Thavarungkul, Panote; Kanatharana, Proespichaya

    2010-01-01

    A new polyethylene glycol fiber was developed for solid-phase microextraction (SPME) of styrene by electrodepositing porous Zn film on Ag wire substrate followed by coating with polyethylene glycol sol-gel (Ag/Zn/PEG sol-gel fiber). The scanning electron micrographs of fibers surface revealed a highly porous structure. The extraction property of the developed fiber-to-styrene residue from polystyrene packaged food was investigated by headspace solid-phase microextraction (HS-SPME) and analyzed with a gas chromatograph coupled with flame ionization detection (GC-FID). The new Ag/Zn/PEG sol-gel fiber is simple to prepare, low cost, robust, has high thermal stability and long lifetime, up to 359 extractions. Repeatability of one fiber (n = 6) was in the range of 4.7-7.5% and fiber-to-fiber reproducibility (n = 4) for five concentration values were in the range 3.4-10%. This Ag/Zn/PEG sol-gel fiber was compared to two commercial SPME fibers, 75 μm carboxen/polydimethylsiloxane (CAR/PDMS) and 100 μm polydimethylsiloxane (PDMS). Under their optimum conditions, Ag/Zn/PEG sol-gel fiber showed the highest sensitivity and the lowest detection limit at 0.28 ± 0.01 ng mL -1 .

  20. Deep desulfurization of diesel via peroxide oxidation using phosphotungstic acid as phase transfer catalyst

    Sachdeva, T.O.; Pant, K.K. [Department of Chemical Engineering, Indian Institute of Technology, Delhi, New Delhi, 110016 (India)

    2010-09-15

    High sulfur level in diesel fuel has been identified as a major contributor to air pollutant in term of sulfur dioxide (SO{sub x}) through diesel fueled vehicles. The main aim of the present work is to develop a promising methodology for ultra deep desulfurization of diesel fuel using oxidation followed by phase transfer of oxidized sulfur. Experiments were carried out in a batch reactor using n-decane as the model diesel compound and also using commercial diesel feedstock. To remove sulfur tetraoctylammonium bromide, phosphotungstic acid, and hydrogen peroxide were used as phase transfer agent, catalyst and oxidant respectively. The percent sulfur removal increases with increasing the initial concentration of sulfur in fuel and with increasing the reaction temperature. Similar trends were observed when commercial diesel was used to carry out desulfurization studies. The amphiphilic catalyst serves as a catalyst and also as an emulsifying agent to stabilize the emulsion droplets. The effects of temperature, agitation speed, quantity of catalyst and the phase transfer agent were studied to estimate the optimal conditions for the reactions. The sulfur removal from a commercial diesel by phase transfer catalysis has been found effective and removal efficiency was more than 98%. Kinetic experiments carried out for the desulfurization revealed that the sulfur removal results are best fitted to a pseudo first order kinetics and the apparent activation energy of desulfurization was 30.6 kJ/mol. (author)

  1. Deep desulfurization of diesel via peroxide oxidation using phosphotungstic acid as phase transfer catalyst

    Sachdeva, T.O.; Pant, K.K.

    2010-01-01

    High sulfur level in diesel fuel has been identified as a major contributor to air pollutant in term of sulfur dioxide (SO x ) through diesel fueled vehicles. The main aim of the present work is to develop a promising methodology for ultra deep desulfurization of diesel fuel using oxidation followed by phase transfer of oxidized sulfur. Experiments were carried out in a batch reactor using n-decane as the model diesel compound and also using commercial diesel feedstock. To remove sulfur tetraoctylammonium bromide, phosphotungstic acid, and hydrogen peroxide were used as phase transfer agent, catalyst and oxidant respectively. The percent sulfur removal increases with increasing the initial concentration of sulfur in fuel and with increasing the reaction temperature. Similar trends were observed when commercial diesel was used to carry out desulfurization studies. The amphiphilic catalyst serves as a catalyst and also as an emulsifying agent to stabilize the emulsion droplets. The effects of temperature, agitation speed, quantity of catalyst and the phase transfer agent were studied to estimate the optimal conditions for the reactions. The sulfur removal from a commercial diesel by phase transfer catalysis has been found effective and removal efficiency was more than 98%. Kinetic experiments carried out for the desulfurization revealed that the sulfur removal results are best fitted to a pseudo first order kinetics and the apparent activation energy of desulfurization was 30.6 kJ/mol. (author)

  2. Online Measurements of Highly Oxidized Organics in the Gas and Particle phase during SOAS and SENEX

    Lopez-Hilfiker, F.; Lee, B. H.; Mohr, C.; Ehn, M.; Rubach, F.; Mentel, T. F.; Kleist, E.; Thornton, J. A.

    2014-12-01

    We present measurements of a large suite of gas and particle phase organic compounds made with a Filter Inlet for Gas and AEROsol (FIGAERO) coupled to a high resolution time of flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington and with airborne HR-ToF-CIMS measurements. The FIGAERO instrument was deployed on the Jülich Plant Atmosphere Chamber to study α-pinene oxidation, and subsequently at the SMEAR II forest station in Hyytiälä, Finland and the SOAS ground site, in Brent Alabama. During the Southern Atmosphere Study, a gas-phase only version of the HR-ToF-CIMS was deployed on the NOAA WP-3 aircraft as part of SENEX. We focus here on highly oxygenated organic compounds derived from monoterpene oxidation detected both aloft during SENEX and at the ground-based site during SOAS. In both chamber and the atmosphere, many highly oxidized, low volatility compounds were observed in the gas and particles and many of the same compositions detected in the gas-phase were detected in the particles upon temperature programmed thermal desorption. The fraction of a given compound measured in the particle phase follows expected trends with elemental composition such as O/C ratios, but many compounds would not be well described by an absorptive partitioning model assuming unity activity coefficients. The detailed structure in the thermograms reveals a significant contribution from large molecular weight organics and/or oligomers in both chamber and ambient aerosol samples. Approximately 50% of the measured organics in the particle phase are associated with compounds having effective vapour pressures 4 or more orders of magnitude lower than commonly measured monoterpene oxidation products. We discuss the implications of these findings for measurements of gas-particle partitioning and for evaluating the contribution of monoterpene oxidation to organic aerosol formation and growth. We also use the aircraft measurements and a

  3. A study of the oxidation of nickel-titanium intermetallics. II. Phase composition of the scale

    Chuprina, V G [Institut Problem Materialovedeniia, Kiev (Ukrainian SSR)

    1989-06-01

    The phase composition of the scale formed on NiTi during oxidation in air in the temperature range 600-1000 C was investigated by X-ray diffraction and layer-by-layer metallographic analyses. The scale was found to contain NiO, NiO.TiO2, TiO2, Ti2O3, Ti3O5, Ni, and Ni(Ti) solid solution; an Ni3Ti sublayer was present at the scale-alloy boundary. Oxygen diffusion in the scale toward the sublayer and counterdiffusion of Ni(+2) were found to be the principal processes responsible for NiTi oxidation. 8 refs.

  4. Detection of OH on photolysis of styrene oxide at 193 nm in gas phase

    Kumar, Awadhesh; SenGupta, Sumana; Pushpa, K. K.; Naik, P. D.; Bajaj, P. N.

    2006-10-01

    Photodissociation of styrene oxide at 193 nm in gas phase generates OH, as detected by laser-induced fluorescence technique. Under similar conditions, OH was not observed from ethylene and propylene oxides, primarily because of their low absorption cross-sections at 193 nm. Mechanism of OH formation involves first opening of the three-membered ring from the ground electronic state via cleavage of either of two C sbnd O bonds, followed by isomerization to enolic forms of phenylacetaldehyde and acetophenone, and finally scission of the C sbnd OH bond of enols. Ab initio molecular orbital calculations support the proposed mechanism.

  5. Preparation of a Microspherical Silver-Reduced Graphene Oxide-Bismuth Vanadate Composite and Evaluation of Its Photocatalytic Activity

    Mao Du

    2016-03-01

    Full Text Available A novel Ag-reduced graphene oxide (rGO-bismuth vanadate (BiVO4 (AgGB ternary composite was successfully synthesized via a one-step method. The prepared composite was characterized by X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, scanning electron microscopy (SEM, energy dispersive X-ray (EDX, Brunauer-Emmett-Teller (BET surface area measurement, Raman scattering spectroscopy, and ultraviolet-visible diffuse-reflection spectroscopy (UV-vis DRS. The results showed that bulk monoclinic needle-like BiVO4 and Ag nanoparticles with a diameter of approximately 40 nm formed microspheres (diameter, 5–8 μm with a uniform size distribution that could be loaded on rGO sheets to facilitate the transport of electrons photogenerated in BiVO4, thereby reducing the rate of recombination of photogenerated charge carriers in the coupled AgGB composite system. Ag nanoparticles were dispersed on the surface of the rGO sheets, which exhibited a localized surface plasmon resonance phenomenon and enhanced visible light absorption. The removal efficiency of rhodamine B dye by AgGB (80.2% was much higher than that of pure BiVO4 (51.6% and rGO-BiVO4 (58.3% under visible light irradiation. Recycle experiments showed that the AgGB composite still presented significant photocatalytic activity after five successive cycles. Finally, we propose a possible pathway and mechanism for the photocatalytic degradation of rhodamine B dye using the composite photocatalyst under visible light irradiation.

  6. Analysis of volatiles in silver carp by headspace solid phase micro-extraction coupled with GC-MS

    Yang Yuping; Xiong Guangquan; Cheng Wei; Liao Tao; Lin Ruotai; Geng Shengrong; Li Xin; Li Xiaoding; Wu Wenjin

    2010-01-01

    In this paper, a method for the determination of volatiles using headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) was presented. The extraction conditions were optimized with reference to these volatiles as hexanal, heptanal, benzaldehyde, 1-Octen-3-ol, octanal, nonanal, decenal, 2,4-heptadienal and 2,4-decadienal. The extraction of fish muscle followed by incubation on a StableFlex divinyl benzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber during 50 in at 60 obtained the most effective extraction of the analytes. The methods by HS-SPME and GC-MS were effective in detecting volatiles in the gills, scales, viscera and fish muscles. The types of volatiles in the gill were more than other organs and the number of odors compounds was 63, and the number of volatiles in scales, viscera and fish muscles was 48, 44 and 42 respectively. (authors)

  7. Highly Efficient Gas-Phase Oxidation of Renewable Furfural to Maleic Anhydride over Plate Vanadium Phosphorus Oxide Catalyst.

    Li, Xiukai; Ko, Jogie; Zhang, Yugen

    2018-02-09

    Maleic anhydride (MAnh) and its acids are critical intermediates in chemical industry. The synthesis of maleic anhydride from renewable furfural is one of the most sought after processes in the field of sustainable chemistry. In this study, a plate vanadium phosphorus oxide (VPO) catalyst synthesized by a hydrothermal method with glucose as a green reducing agent catalyzes furfural oxidation to MAnh in the gas phase. The plate catalyst-denoted as VPO HT -has a preferentially exposed (200) crystal plane and exhibited dramatically enhanced activity, selectivity and stability as compared to conventional VPO catalysts and other state-of-the-art catalytic systems. At 360 °C reaction temperature with air as an oxidant, about 90 % yield of MAnh was obtained at 10 vol % of furfural in the feed, a furfural concentration value that is much higher than those (<2 vol %) reported for other catalytic systems. The catalyst showed good long-term stability and there was no decrease in activity or selectivity for MAnh during the time-on-stream of 25 h. The high efficiency and catalyst stability indicate the great potential of this system for the synthesis of maleic anhydride from renewable furfural. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. The influence of surfactant on the synthesis of gamma ferric oxide: implications on phase composition and magnetic properties

    Narasimhan, B.R.V.; Prabhakar, S.; Manohar, P.; Gnanam, F.D.

    2002-01-01

    It has already been established that ferrous carbonate precipitated from the reaction of ferrous sulphate and sodium carbonate, on direct thermal decomposition yields gamma ferric oxide. The present work describes the effect of sodium lauryl sulphate (Sodium dodecyl sulphate) on the synthesis of gamma ferric oxide when it is introduced during the precipitation of ferrous carbonate. Since ferrous carbonate undergoes rapid oxidation on standing in air, the extent of oxidation in presence of sodium lauryl sulphate is also studied using oxidation-reduction potential measurements. The ferric oxide powders are characterized for phase analysis (XRD), magnetic properties (VSM) and particle size analysis. (author)

  9. Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

    Matthias Augustin

    2015-01-01

    Full Text Available Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mnx+ oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous α-Mn2O3 particles were synthesized by calcination of Mn(II glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure–property relationships. The oxidation process related to the different MnOx species was observed by in situ X-ray diffraction (XRD measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II glycolate precursor to α-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnOx species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnOx species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous α-Mn2O3 species.

  10. Effect of poly-α, γ, L-glutamic acid as a capping agent on morphology and oxidative stress-dependent toxicity of silver nanoparticles

    Stevanović M

    2011-11-01

    Full Text Available Magdalena Stevanović1, Branimir Kovačević2, Jana Petković3, Metka Filipič3, Dragan Uskoković11Institute of Technical Sciences of Serbian Academy of Sciences and Arts, 2Institute of General and Physical Chemistry, Belgrade, Serbia; 3Department of Genetic Toxicology and Cancer Biology, National Institute of Biology, Ljubljana, SloveniaAbstract: Highly stable dispersions of nanosized silver particles were synthesized using a straightforward, cost-effective, and ecofriendly method. Nontoxic glucose was utilized as a reducing agent and poly- α, γ, L-glutamic acid (PGA, a naturally occurring anionic polymer, was used as a capping agent to protect the silver nanoparticles from agglomeration and render them biocompatible. Use of ammonia during synthesis was avoided. Our study clearly demonstrates how the concentration of the capping agent plays a major role in determining the dimensions, morphology, and stability, as well as toxicity of a silver colloidal solution. Hence, proper optimization is necessary to develop silver colloids of narrow size distribution. The samples were characterized by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and zeta potential measurement. MTT assay results indicated good biocompatibility of the PGA-capped silver nanoparticles. Formation of intracellular reactive oxygen species was measured spectrophotometrically using 2,7-dichlorofluorescein diacetate as a fluorescent probe, and it was shown that the PGA-capped silver nanoparticles did not induce intracellular formation of reactive oxygen species.Keywords: silver nanoparticles, poly-α, γ, L-glutamic, green synthesis, morphology, cytotoxicity

  11. Dynamic\tmodelling of catalytic three-phase reactors for hydrogenation and oxidation processes

    Salmi T.

    2000-01-01

    Full Text Available The dynamic modelling principles for typical catalytic three-phase reactors, batch autoclaves and fixed (trickle beds were described. The models consist of balance equations for the catalyst particles as well as for the bulk phases of gas and liquid. Rate equations, transport models and mass balances were coupled to generalized heterogeneous models which were solved with respect to time and space with algorithms suitable for stiff differential equations. The aspects of numerical solution strategies were discussed and the procedure was illustrated with three case studies: hydrogenation of aromatics, hydrogenation of aldehydes and oxidation of ferrosulphate. The case studies revealed the importance of mass transfer resistance inside the catalyst pallets as well as the dynamics of the different phases being present in the reactor. Reliable three-phase reactor simulation and scale-up should be based on dynamic heterogeneous models.

  12. In situ synthesis of silver nanoparticles on the cotton fabrics modified by plasma induced vapor phase graft polymerization of acrylic acid for durable multifunction

    Wang, C.X., E-mail: cxwang@mail.dhu.edu.cn [College of Textiles and Clothing, Yancheng Institute of Technology, Jiangsu, 224003 (China); Collaborative Innovation Center for Ecological Building, Materials and Environmental Protection Equipments, Jiangsu, 224051 (China); Laboratory for Advanced Technology in Environmental Protection, Jiangsu, 224051 (China); School of Textile and Clothing, Nantong University, Jiangsu, 226019 (China); Ren, Y. [School of Textile and Clothing, Nantong University, Jiangsu, 226019 (China); Lv, J.C.; Zhou, Q.Q.; Ma, Z.P.; Qi, Z.M.; Chen, J.Y.; Liu, G.L.; Gao, D.W. [College of Textiles and Clothing, Yancheng Institute of Technology, Jiangsu, 224003 (China); Lu, Z.Q. [College of Textiles and Clothing, Yancheng Institute of Technology, Jiangsu, 224003 (China); Collaborative Innovation Center for Ecological Building, Materials and Environmental Protection Equipments, Jiangsu, 224051 (China); Laboratory for Advanced Technology in Environmental Protection, Jiangsu, 224051 (China); Zhang, W. [College of Textiles and Clothing, Yancheng Institute of Technology, Jiangsu, 224003 (China); Jin, L.M. [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201204 (China)

    2017-02-28

    Highlights: • A new means for multifunctional cotton fabrics by PIVPGP of AA and AgNPs synthesis. • Surface modification by PIVPGP of AA had a positive effect on AgNPs loading. • Antibacterial, self-cleaning and thermal stability were greatly improved. • AgNP loaded cotton fabric exhibited excellent laundering durability. • Mechanism of AgNPs in situ synthesis on cotton fabrics by PIVPGP of AA was proposed. - Abstract: A practical and ecological method for preparing the multifunctional cotton fabrics with excellent laundering durability was explored. Cotton fabrics were modified by plasma induced vapor phase graft polymerization (PIVPGP) of acrylic acid (AA) and subsequently silver nanoparticles (AgNPs) were in situ synthesized on the treated cotton fabrics. The AgNP loaded cotton fabrics were characterized by scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), antibacterial activity, self-cleaning activity, thermal stability and laundering durability, respectively. SEM observation and EDX, XPS and XRD analysis demonstrated the much more AgNPs deposition on the cotton fabrics modified by PIVPGP of AA. The AgNP loaded cotton fabrics also exhibited better antibacterial activity, self-cleaning activity, thermal stability and laundering durability. It was concluded that the surface modification of the cotton fabrics by PIVPGP of AA could increase the loading efficiency and binding fastness of AgNPs on the treated cotton fabrics, which could fabricate the cotton fabrics with durable multifunction. In addition, the mechanism of in situ synthesis of AgNPs on the cotton fabrics modified by PIVPGP of AA was proposed.

  13. Nanoscale Phase Stability Reversal During the Nucleation and Growth of Titanium Oxide Minerals

    Hummmer, D. R.; Heaney, P. J.; Kubicki, J. D.; Kent, P. R.; Post, J. E.

    2008-12-01

    Fine-grained titanium oxide minerals are important in soils, where they affect a variety of geochemical processes. They are also industrially important as catalysts, pigments, food additives, and dielectrics. Recent research has indicated an apparent reversal of thermodynamic stability between TiO2 phases at the nanoscale thought to be caused by an increased contribution of surface energy to the total free energy. Time-resolved X-ray diffraction (XRD) experiments in which titanium oxides crystallize from aqueous TiCl4 solutions confirm that anatase, a metastable phase, is always the first phase to nucleate under our range of initial conditions. Rutile peaks are observed only minutes after the first appearance of anatase, after which anatase abundance slowly decreases while rutile continues to form. Whole pattern refinement of diffraction data reveals that lattice constants of both phases increase throughout the crystallization process. In addition, transmission electron microscope (TEM) observations and kinetic modeling indicate that anatase does not undergo a solid-state transformation to the rutile structure as once thought. Instead, anatase appears to re-dissolve and then feed the growth of already nucleated rutile nanocrystals. Density functional theory (DFT) calculations were employed to model 1, 2, and 3 nm particles of both mineral phases. The total surface energies calculated from these models did yield lower values for anatase than for rutile by 8-13 kJ/mol depending on particle size, indicating that surface free energy is sufficient to account for stability reversal. However, these whole-particle surface energies were much higher than the sum of energies of each particle's constituent crystallographic surfaces. We attribute the excess energy to defects associated with the edges and corners of nanoparticles, which are not present on a 2-D periodic surface. This previously unreported edge and corner energy may play a dominant role in the stability reversal

  14. Kinematics and thermodynamics across a propagating non-stoichiometric oxidation phase front in spent fuel grains

    Stout, R.B.; Kansa, E.J.; Wijesinghe, A.M.

    1993-09-01

    Spent fuel contains mixtures, alloy and compound, but are dominated by U and O except for some UO 2 fuels with burnable poisons (gadolinia in BWR rods), the other elements evolve during reactor operation from neutron reaction and fission + fission decay events. Due to decay, chemical composition and activity of spent fuel will continue to evolve after removal from reactors. During the time interval with significant radioactivity levels relevant for a geological repository, it is important to develop models for potential chemical responses in spent fuel and potential degradation of repository. One such potential impact is the oxidation of spent fuel, which results in initial phase change of UO 2 lattice to U 4 O 9 and the next phase change is probably to U 3 O 8 although it has not been observed yet below 200C. The U 4 O 9 lattice is nonstoichiometric with a O/U weight ratio at 2.4. Preliminary indications are that the UO 2 has a O/U of 2. 4 at the time just before it transforms into the U 4 O 9 phase. In the oxygen weight gain versus time response, a plateau appears as the O/U approaches 2.4. Part of this plateau is due to geometrical effects of a U 4 O 9 phase change front propagating into UO 2 grain volumes; however, this may indicate a metastable phase change delay kinetics or a diffusional related delay time until the oxygen density can satisfy stoichiometry and energy conditions for phase changes. Experimental data show a front of U 4 O 9 lattice structure propagating into grains of the UO 2 lattice. To describe this spatially inhomogenous oxidation phase transition, as well as the expected U 3 O 8 phase transition from the U 4 O 9 lattice, lattice models are developed and spatially discontinuous kinematic and energetic expressions are derived. 9 refs

  15. Phase stability of zirconium oxide films during focused ion beam milling

    Baxter, Felicity; Garner, Alistair; Topping, Matthew; Hulme, Helen; Preuss, Michael; Frankel, Philipp

    2018-06-01

    Focused ion beam (FIB) is a widely used technique for preparation of electron transparent samples and so it is vital to understand the potential for introduction of FIB-induced microstructural artefacts. The bombardment of both Xe+ and Ga+ ions is observed to cause extensive monoclinic to tetragonal phase transformation in ZrO2 corrosion films, however, this effect is diminished with reduced energy and is not observed below 5 KeV. This study emphasises the importance of careful FIB sample preparation with a low energy cleaning step, and also gives insight into the stabilisation mechanism of the tetragonal phase during oxidation.

  16. Separation of silver ions and starch modified silver nanoparticles using high performance liquid chromatography with ultraviolet and inductively coupled mass spectrometric detection

    Hanley, Traci A.; Saadawi, Ryan; Zhang, Peng; Caruso, Joseph A.; Landero-Figueroa, Julio

    2014-01-01

    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

  17. Separation of silver ions and starch modified silver nanoparticles using high performance liquid chromatography with ultraviolet and inductively coupled mass spectrometric detection

    Hanley, Traci A.; Saadawi, Ryan; Zhang, Peng; Caruso, Joseph A., E-mail: joseph.caruso@uc.edu; 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{sup +}) 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{sup −1} detection limit, and 90% chromatographic recovery for silver solutions containing ions and starch stabilized silver nanoparticles smaller than 100 nm.

  18. Hysteresis phenomena at metal-semiconductor phase transformation in vanadium oxides

    Lanskaya, T.G.; Merkulov, I.A.; Chudnovski , F.A.

    1978-01-01

    The hysteresis phenomena during the metal-semiconductor phase transformation (MSPT) in vanadium oxides are investigated. It is shown experimentally that the hysteresis effects during MSPT in vanadium oxides are associated not only with the martensite nature of the transformation, but also with activation processes. It is shown that the hysteresis phenomena during MSPT may be described by the distribution function of microregions of the crystal in the phase transformation temperature T 0 and the coercive temperature Tsub(c). An experimental method for constructing this distribution function was worked out. An analysis of the experimental data shows that finely dispersed films are characterized by a wide range of values of T 0 and Tsub(c) (55 deg C 0 <65 deg C, 6 deg C< Tsub(c)<12 deg C). The peculiarities of the optical recording of information on monocrystal and finely dispersed films are considered

  19. Gas-phase advanced oxidation for effective, efficient in situ control of pollution

    Johnson, Matthew Stanley; Nilsson, Elna Johanna Kristina; Svensson, Erik Anders

    2014-01-01

    In this article, gas-phase advanced oxidation, a new method for pollution control building on the photo-oxidation and particle formation chemistry occurring in the atmosphere, is introduced and characterized. The process uses ozone and UV-C light to produce in situ radicals to oxidize pollution......, generating particles that are removed by a filter; ozone is removed using a MnO2 honeycomb catalyst. This combination of in situ processes removes a wide range of pollutants with a comparatively low specific energy input. Two proof-of-concept devices were built to test and optimize the process...... particulate mass. Secondary pollution including formaldehyde and ultrafine particles might be generated, depending on the composition of the primary pollution....

  20. US-UK Phase 3 Task 1 Oxidation in Supercritical Fluids

    Holcomb, Gordon R. [National Energy Technology Lab. (NETL), Albany, OR (United States)

    2017-03-20

    A presentation of the US-UK Phase 3 Task 1 Oxidation in Supercritical Fluids. Includes slides on Supercritical Steam, sCO2 Power Cycles – Indirect, sCO2 Power Cycles – Direct, Experimental Exposures, Alloys, Why Si, Results—Ni-xCr Alloys (5-24Cr), Fatigue Crack Growth$-$Experiment, and Alloys and Samples, Fatigue Crack Growth—Results (H282).

  1. Rhodium and Hafnium Influence on the Microstructure, Phase Composition, and Oxidation Resistance of Aluminide Coatings

    Maryana Zagula-Yavorska; Małgorzata Wierzbińska; Jan Sieniawski

    2017-01-01

    A 0.5 μm thick layer of rhodium was deposited on the CMSX 4 superalloy by the electroplating method. The rhodium-coated superalloy was hafnized and aluminized or only aluminized using the Chemical vapour deposition method. A comparison was made of the microstructure, phase composition, and oxidation resistance of three aluminide coatings: nonmodified (a), rhodium-modified (b), and rhodium- and hafnium-modified (c). All three coatings consisted of two layers: the additive layer and the interdi...

  2. Phase Separation and Elastic Properties of Poly(Trimethylene Terephthalate)-block-poly(Ethylene Oxide) Copolymers

    Elżbieta Piesowicz; Sandra Paszkiewicz; Anna Szymczyk

    2016-01-01

    A series of poly(trimethylene terephthalate)-block-poly(ethylene oxide) (PTT-b-PEOT) copolymers with different compositions of rigid PTT and flexible PEOT segments were synthesized via condensation in the melt. The influence of the block length and the block ratio on the micro-separated phase structure and elastic properties of the synthesized multiblock copolymers was studied. The PEOT segments in these copolymers were kept constant at 1130, 2130 or 3130 g/mol, whereas the PTT content varied...

  3. Electrical wire explosion process of copper/silver hybrid nano-particle ink and its sintering via flash white light to achieve high electrical conductivity.

    Chung, Wan-Ho; Hwang, Yeon-Taek; Lee, Seung-Hyun; Kim, Hak-Sung

    2016-05-20

    In this work, combined silver/copper nanoparticles were fabricated by the electrical explosion of a metal wire. In this method, a high electrical current passes through the metal wire with a high voltage. Consequently, the metal wire evaporates and metal nanoparticles are formed. The diameters of the silver and copper nanoparticles were controlled by changing the voltage conditions. The fabricated silver and copper nano-inks were printed on a flexible polyimide (PI) substrate and sintered at room temperature via a flash light process, using a xenon lamp and varying the light energy. The microstructures of the sintered silver and copper films were observed using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). To investigate the crystal phases of the flash-light-sintered silver and copper films, x-ray diffraction (XRD) was performed. The absorption wavelengths of the silver and copper nano-inks were measured using ultraviolet-visible spectroscopy (UV-vis). Furthermore, the resistivity of the sintered silver and copper films was measured using the four-point probe method and an alpha step. As a result, the fabricated Cu/Ag film shows a high electrical conductivity (4.06 μΩcm), which is comparable to the resistivity of bulk copper (1.68 μΩcm). In addition, the fabricated Cu/Ag nanoparticle film shows superior oxidation stability compared to the Cu nanoparticle film.

  4. Electrocatalytic activity of bismuth doped silver electrodes

    Amjad, M

    2002-01-01

    Investigation of redox reactions on silver, and bismuth doped silver electrodes in aqueous KOH solutions, by using potentiostatic steady-state polarization technique, has been carried out. The redox wave potential and current displacements along with multiplicity of the latter have been examined. These electrodes were employed for the oxidation of organic molecules such as ethylamine in alkaline media. Subsequently, these electrodes were ranked with respect to their activity for the redox reactions. (author)

  5. Comparative analysis of oxide phase formation and its effects on electrical properties of SiO{sub 2}/InSb metal-oxide-semiconductor structures

    Lee, Jaeyel [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Park, Sehun [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Kim, Jungsub; Yang, Changjae; Kim, Sujin; Seok, Chulkyun [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Park, Jinsub [Department of Electronic Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Yoon, Euijoon, E-mail: eyoon@snu.ac.kr [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Department of Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Suwon 443-270 (Korea, Republic of); Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of)

    2012-06-01

    We report on the changes in the interfacial phases between SiO{sub 2} and InSb caused by various deposition temperatures and heat treatments. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to evaluate the relative amount of each phase present at the interface. The effect of interfacial phases on the electrical properties of SiO{sub 2}/InSb metal-oxide-semiconductor (MOS) structures was investigated by capacitance-voltage (C-V) measurements. The amount of both In and Sb oxides increased with the deposition temperature. The amount of interfacial In oxide was larger for all samples, regardless of the deposition and annealing temperatures and times. In particular, the annealed samples contained less than half the amount of Sb oxide compared with the as-deposited samples, indicating a strong interfacial reaction between Sb oxide and the InSb substrate during annealing. The interface trap density sharply increased for deposition temperatures above 240 Degree-Sign C. The C-V measurements and Raman spectroscopy indicated that elemental Sb accumulation due to the interfacial reaction of Sb oxide with InSb substrate was responsible for the increased interfacial trap densities in these SiO{sub 2}/InSb MOS structures. - Highlights: Black-Right-Pointing-Pointer We report the quantitative analysis of interfacial oxides at the SiO{sub 2}/InSb interface. Black-Right-Pointing-Pointer Interfacial oxides were measured quantitatively by X-ray Photoelectron Spectroscopy. Black-Right-Pointing-Pointer As-grown and annealed samples showed different compositions of oxide phases. Black-Right-Pointing-Pointer Considerable reduction of antimony oxide phases was observed during annealing. Black-Right-Pointing-Pointer Interface trap densities at the SiO{sub 2}/InSb interface were calculated.

  6. Heavy haze in winter Beijing driven by fast gas phase oxidation

    Lu, K.; Tan, Z.; Wang, H.; Li, X.; Wu, Z.; Chen, Q.; Wu, Y.; Ma, X.; Liu, Y.; Chen, X.; Shang, D.; Dong, H.; Zeng, L.; Shao, M.; Hu, M.; Fuchs, H.; Novelli, A.; Broch, S.; Hofzumahaus, A.; Holland, F.; Rohrer, F.; Bohn, B.; Georgios, G.; Schmitt, S. H.; Schlag, P.; Kiendler-Scharr, A.; Wahner, A.; Zhang, Y.

    2017-12-01

    Heavy haze conditions were frequently presented in the airsheds of Beijing and surrounding areas, especially during winter time. To explore the trace gas oxidation and the subsequent formation of aerosols, a comprehensive field campaign was performed at a regional site (in the campus of University of Chinese Academy of Science, UCAS) in Beijing winter 2016. Serious haze pollution processes were often observed with the fast increase of inorganic salt (especially nitrate) and these pollutions were always associated with enhanced humidity and the concentrations of PAN (PeroxyAcyl Nitrates) which is normally a marker of gas phase oxidations from NOx and VOCs. Moreover, based on the measurements of OH, HO2, RO2, total OH reactivity, N2O5, NO, NO2, SO2, particle concentrations/distributions/chemical compositions, and meteorological parameters, the gas phase oxidation rates that leads to the formation of sulfate, nitrate and secondary organic aerosols were estimated. These determined formation rates were clearly enhanced by several folds during pollution episodes compared to that of the clean air masses. Preliminary analysis result showed that the gas phase formation potential of nitrate and secondary organic aerosols were larger than the observed concentrations of nitrate and SOA of which the excess production may be explained by deposition and dilution.

  7. Kinematics and thermodynamics of non-stoichiometric oxidation phase transitions in spent fuel

    Stout, R.B.; Kansa, E.J.; Wijesinghe, A.M.

    1993-01-01

    At low temperatures ( 2 lattice to a U 4 O 9 lattice but with an oxygen-to-uranium (O/U) ratio of ∼2.4. Also, the weight gain time response has a plateau as the O/U approaches 2.4. Part of this response results from a geometrical dependency as a U 4 O 9 oxidation front propagates into grain volumes Of UO 2 It may also be indicative of a metastable, non-stoichiometric U 4 O 9 phase whose existence may inhibit the transition kinetics to the next expected phase Of U 3 O 8 . To gain a mechanistic understanding and to plan future oxidation tests, lattice kinematic and thermodynamic models are developed for lattice deformations and energetics of lattice phase changes (UO 2 → U 4 O 9 → U 3 0 7 → U 3 O 8) that include zeroth order influences on oxidation kinetics due to interstitial oxygen atoms and vacancies plus interstitial and substitutional actinides and fission decay products in spent fuel

  8. Gas-phase advanced oxidation as an integrated air pollution control technique

    Getachew A. Adnew

    2016-03-01

    Full Text Available Gas-phase advanced oxidation (GPAO is an emerging air cleaning technology based on the natural self-cleaning processes that occur in the Earth’s atmosphere. The technology uses ozone, UV-C lamps and water vapor to generate gas-phase hydroxyl radicals that initiate oxidation of a wide range of pollutants. In this study four types of GPAO systems are presented: a laboratory scale prototype, a shipping container prototype, a modular prototype, and commercial scale GPAO installations. The GPAO systems treat volatile organic compounds, reduced sulfur compounds, amines, ozone, nitrogen oxides, particles and odor. While the method covers a wide range of pollutants, effective treatment becomes difficult when temperature is outside the range of 0 to 80 °C, for anoxic gas streams and for pollution loads exceeding ca. 1000 ppm. Air residence time in the system and the rate of reaction of a given pollutant with hydroxyl radicals determine the removal efficiency of GPAO. For gas phase compounds and odors including VOCs (e.g. C6H6 and C3H8 and reduced sulfur compounds (e.g. H2S and CH3SH, removal efficiencies exceed 80%. The method is energy efficient relative to many established technologies and is applicable to pollutants emitted from diverse sources including food processing, foundries, water treatment, biofuel generation, and petrochemical industries.

  9. Comprehensive Analysis of the Gas- and Particle-Phase Products of VOC Oxidation

    Bakker-Arkema, J.; Ziemann, P. J.

    2017-12-01

    Controlled environmental chamber studies are important for determining atmospheric reaction mechanisms and gas and aerosol products formed in the oxidation of volatile organic compounds (VOCs). Such information is necessary for developing detailed chemical models for use in predicting the atmospheric fate of VOCs and also secondary organic aerosol (SOA) formation. However, complete characterization of atmospheric oxidation reactions, including gas- and particle-phase product yields, and reaction branching ratios, are difficult to achieve. In this work, we investigated the reactions of terminal and internal alkenes with OH radicals in the presence of NOx in an attempt to fully characterize the chemistry of these systems while minimizing and accounting for the inherent uncertainties associated with environmental chamber experiments. Gas-phase products (aldehydes formed by alkoxy radical decomposition) and particle-phase products (alkyl nitrates, β-hydroxynitrates, dihydroxynitrates, 1,4-hydroxynitrates, 1,4-hydroxycarbonyls, and dihydroxycarbonyls) formed through pathways involving addition of OH to the C=C double bond as well as H-atom abstraction were identified and quantified using a suite of analytical techniques. Particle-phase products were analyzed in real time with a thermal desorption particle beam mass spectrometer; and off-line by collection onto filters, extraction, and subsequent analysis of functional groups by derivatization-spectrophotometric methods developed in our lab. Derivatized products were also separated by liquid chromatography for molecular quantitation by UV absorbance and identification using chemical ionization-ion trap mass spectrometry. Gas phase aldehydes were analyzed off-line by collection onto Tenax and a 5-channel denuder with subsequent analysis by gas chromatography, or by collection onto DNPH-coated cartridges and subsequent analysis by liquid chromatography. The full product identification and quantitation, with careful

  10. Effect of boron oxide on the cubic-to-monoclinic phase transition in yttria-stabilized zirconia

    Florio, D.Z. de; Muccillo, R.

    2004-01-01

    Specimens of yttria fully stabilized zirconia with different amounts of boron oxide have been studied by X-ray diffraction at room temperature and at higher temperatures up to 1250 deg. C. A boron oxide-assisted cubic-to-monoclinic phase transformation was determined in the temperature range 800-1250 deg. C. In situ high temperature X-ray diffraction experiments gave evidences of the dependence of the phase transformation on the heating rate. The possibility of tuning the cubic-monoclinic phase ratio by suitable addition of boron oxide before pressing and sintering is proposed

  11. Oxidation behaviour of Ti2AIN films composed mainly of nanolaminated MAX phase.

    Wang, Q M; Garkas, W; Renteria, A Flores; Leyens, C; Kim, K H

    2011-10-01

    In this paper, we reported the oxidation behaviour of Ti2AIN films on polycrystalline Al2O3 substrates. The Ti2AIN films composed mainly of nanolaminated MAX phase was obtained by first depositing Ti-Al-N films using reactive sputtering of two elemental Ti and Al targets in Ar/N2 atmosphere and subsequent vacuum annealing at 800 degrees C for 1 h. The Ti2AIN films exhibited excellent oxidation resistance and thermal stability at 600-900 degrees C in air. Very low mass gain was observed. At low temperature (600 degrees C), no oxide crystals were observed on film surface. Blade-like Theta-Al2O3 fine crystals formed on film surfaces at 700-800 degrees C. At high temperature (900 degrees C), firstly Theta-Al2O3 formed on film surface and then transformed into alpha-Al2O3. At 700-900 degrees C, a continuous Al2O3 layer formed on Ti2AIN films surface, acting as diffusion barrier preventing further oxidation attack. The mechanism of the excellent oxidation resistance of Ti2AIN films was discussed based on the experimental results.

  12. Room temperature ferromagnetism in liquid-phase pulsed laser ablation synthesized nanoparticles of nonmagnetic oxides

    Singh, S. C.; Gopal, R.; Kotnala, R. K.

    2015-01-01

    Intrinsic Room Temperature Ferromagnetism (RTF) has been observed in undoped/uncapped zinc oxide and titanium dioxide spherical nanoparticles (NPs) obtained by a purely green approach of liquid phase pulsed laser ablation of corresponding metal targets in pure water. Saturation magnetization values observed for zinc oxide (average size, 9 ± 1.2 nm) and titanium dioxide (average size, 4.4 ± 0.3 nm) NPs are 62.37 and 42.17 memu/g, respectively, which are several orders of magnitude larger than those of previous reports. In contrast to the previous works, no postprocessing treatments or surface modification is required to induce ferromagnetism in the case of present communication. The most important result, related to the field of intrinsic ferromagnetism in nonmagnetic materials, is the observation of size dependent ferromagnetism. Degree of ferromagnetism in titanium dioxide increases with the increase in particle size, while it is reverse for zinc oxide. Surface and volume defects play significant roles for the origin of RTF in zinc oxide and titanium dioxide NPs, respectively. Single ionized oxygen and neutral zinc vacancies in zinc oxide and oxygen and neutral/ionized titanium vacancies in titanium dioxide are considered as predominant defect centres responsible for observed ferromagnetism. It is expected that origin of ferromagnetism is a consequence of exchange interactions between localized electron spin moments resulting from point defects

  13. Synthesis of high-oxidation Y-Ba-Cu-O phases in superoxygenated thin films

    Zhang, H.; Gauquelin, N.; McMahon, C.; Hawthorn, D. G.; Botton, G. A.; Wei, J. Y. T.

    2018-03-01

    It is known that solid-state reaction in high-pressure oxygen can stabilize high-oxidation phases of Y-Ba-Cu-O superconductors in powder form. We extend this superoxygenation concept of synthesis to thin films which, due to their large surface-to-volume ratio, are more reactive thermodynamically. Epitaxial thin films of YBa2Cu3O7 -δ grown by pulsed laser deposition are annealed at up to 700 atm O2 and 900 ∘C , in conjunction with Cu enrichment by solid-state diffusion. The films show the clear formation of Y2Ba4Cu7O15 -δ and Y2Ba4Cu8O16 as well as regions of YBa2Cu5O9 -δ and YBa2Cu6O10 -δ phases, according to scanning transmission electron microscopy, x-ray diffraction, and x-ray absorption spectroscopy. Similarly annealed YBa2Cu3O7 -δ powders show no phase conversion. Our results demonstrate a route of synthesis towards discovering more complex phases of cuprates and other superconducting oxides.

  14. Laser Processed Silver Nanowire Network Transparent Electrodes for Novel Electronic Devices

    Spechler, Joshua Allen

    Silver nanowire network transparent conducting layers are poised to make headway into a space previously dominated by transparent conducting oxides due to the promise of a flexible, scaleable, lab-atmosphere processable alternative. However, there are many challenges standing in the way between research scale use and consumer technology scale adaptation of this technology. In this thesis we will explore many, and overcome a few of these challenges. We will address the poor conductivity at the narrow nanowire-nanowire junction points in the network by developing a laser based process to weld nanowires together on a microscopic scale. We address the need for a comparative metric for transparent conductors in general, by taking a device level rather than a component level view of these layers. We also address the mechanical, physical, and thermal limitations to the silver nanowire networks by making composites from materials including a colorless polyimide and titania sol-gel. Additionally, we verify our findings by integrating these processes into devices. Studying a hybrid organic/inorganic heterojunction photovoltaic device we show the benefits of a laser processed electrode. Green phosphorescent organic light emitting diodes fabricated on a solution phase processed silver nanowire based electrode show favorable device metrics compared to a conductive oxide electrode based control. The work in this thesis is intended to push the adoption of silver nanowire networks to further allow new device architectures, and thereby new device applications.

  15. Silver ion imprinted polymer nanobeads based on a aza-thioether crown containing a 1,10-phenanthroline subunit for solid phase extraction and for voltammetric and potentiometric silver sensors

    Shamsipur, Mojtaba, E-mail: mshamsipur@yahoo.com [Department of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Hashemi, Beshare; Dehdashtian, Sara; Mohammadi, Moslem; Gholivand, Mohammad Bagher [Department of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Garau, Alessandra; Lippolis, Vito [Dipartimento di Scienze Chimiche e Geologiche, Universita' degli Studi di Cagliari, S.S. 554 Bivio per Sestu, 09042 Monserrato, CA (Italy)

    2014-12-10

    Highlights: • Preparation of Ag{sup +} imprinted polymeric nanobeads via precipitation polymerization. • Use of a mixed aza-thioether crown containing a 1,10-phenanthroline subunit a selective host for Ag{sup +} ion. • Highly selective, sensitive and fast recognition of traces of Ag{sup +} ions. • Use of the prepared Ag{sup +}-IIP for preparation of an Ag{sup +}-voltammetric sensor with LOD of 9.0 × 10{sup −10} M. • Use of the prepared Ag{sup +}-IIP for preparation of Ag{sup +}-ISEs with LOD of 1.2 × 10{sup −9} M 9.0 × 10{sup −10} M. - Abstract: A new nano-sized silver(I) ion-imprinted polymer (IIP) was prepared via precipitation copolymerization using ethyleneglycol dimethacrylate, as a cross-linking agent in the presence of Ag{sup +} and an aza-thioether crown containing a 1,10-phenanthroline subunit as a highly selective complexing agent. The imprint silver(I) ion was removed from the polymeric matrix using a 1.0 M HNO{sub 3} solution. The resulting powder material was characterized using IR spectroscopy and scanning electron microscopy. The SEM micrographs showed colloidal nanoparticles of about 52 nm and 75 nm in diameter and slightly irregular in shape for leached and unleached IIPs, respectively. The optimal pH for quantitative enrichment was 6.0 and maximum sorbent capacity of the prepared IIP for Ag{sup +} was 18.08 μmol g{sup −1}. The relative standard deviation and limit of detection (LOD = 3S{sub b}/m) for flame atomic absorption spectrometric determination of silver(I) ion, after its selective extraction by the prepared IIP nanobeads, were evaluated as 2.42% and 2.2 × 10{sup −8} M, respectively. The new Ag{sup +}-IIP was also applied as a suitable sensing element to the preparation of highly selective and sensitive voltammetric and potentiometric sensors for ultra trace detection of silver(I) ion in water samples, with limits of detection of 9.0 × 10{sup −10} and 1.2 × 10{sup −9} M, respectively.

  16. Effective oxidation of benzylic and alkane C-H bonds catalyzed by sodium o-iodobenzenesulfonate with Oxone as a terminal oxidant under phase-transfer conditions.

    Cui, Li-Qian; Liu, Kai; Zhang, Chi

    2011-04-07

    Catalytic oxidation of benzylic C-H bonds could be efficiently realized using IBS as a catalyst which was generated in situ from the oxidation of sodium 2-iodobenzenesulfonate (1b) by Oxone in the presence of a phase-transfer catalyst, tetra-n-butylammonium hydrogen sulfate, in anhydrous acetonitrile at 60 °C. Various alkylbenzenes, including toluenes and ethylbenzenes, several oxygen-containing functionalities substituted alkylbenzenes, and a cyclic benzyl ether could be efficiently oxidized. And, the same reagent system of cat. 1b/Oxone/cat. n-Bu(4)NHSO(4) could be applied to the effective oxidation of alkanes as well.

  17. PHASE CHANGES ON 4H AND 6H SIC AT HIGH TEMPERATURE OXIDATION

    Jan Setiawan

    2016-10-01

    Full Text Available ABSTRACT PHASE CHANGES ON 4H AND 6H SIC AT HIGH TEMPERATURE OXIDATION. The oxidation on two silicon carbide contain 6H phase and contains 6H and 4H phases has been done.  Silicon carbide is ceramic non-oxide with excellent properties that potentially used in industry.  Silicon carbide is used in nuclear industry as structure material that developed as light water reactor (LWR fuel cladding and as a coating layer in the high temperature gas-cooled reactor (HTGR fuel.  In this study silicon carbide oxidation simulation take place in case the accident in primary cooling pipe is ruptured.  Sample silicon carbide made of powder that pressed into pellet with diameter 12.7 mm and thickness 1.0 mm, then oxidized at temperature 1000 oC, 1200 oC dan 1400 oC for 1 hour.  The samples were weighted before and after oxidized.  X-ray diffraction con-ducted to the samples using Panalytical Empyrean diffractometer with Cu as X-ray source.  Diffraction pattern analysis has been done using General Structure Analysis System (GSAS software. This software was resulting the lattice parameter changes and content of SiC phases.  The result showed all of the oxidation samples undergoes weight gain.  The 6S samples showed the highest weight change at oxidation temperature 1200 oC, for the 46S samples showed increasing tendency with the oxidation temperature.  X-ray diffraction pattern analysis showed the 6S samples contain dominan phase 6H-SiC that matched to ICSD 98-001-5325 card.  Diffraction pattern on 6S showed lattice parameter, composition and crystallite size changes.  Lattice parameters changes had smaller tendency from the model and before oxidation.  However, the lowest silicon carbide composition or the highest converted into other phases up to 66.85 %, occurred at oxidation temperature 1200 oC.  The 46S samples contains two polytypes silicon car-bide.  The 6H-SiC phases matched by ICSD 98-016-4972 card and 4H-SiC phase matched by ICSD 98

  18. For cermet inert anode containing oxide and metal phases useful for the electrolytic production of metals

    Ray, Siba P.; Liu, Xinghua; Weirauch, Douglas A.

    2002-01-01

    A cermet inert anode for the electrolytic production of metals such as aluminum is disclosed. The inert anode comprises a ceramic phase including an oxide of Ni, Fe and M, where M is at least one metal selected from Zn, Co, Al, Li, Cu, Ti, V, Cr, Zr, Nb, Ta, W, Mo, Hf and rare earths, preferably Zn and/or Co. Preferred ceramic compositions comprise Fe.sub.2 O.sub.3, NiO and ZnO or CoO. The cermet inert anode also comprises a metal phase such as Cu, Ag, Pd, Pt, Au, Rh, Ru, Ir and/or Os. A preferred metal phase comprises Cu and Ag. The cermet inert anodes may be used in electrolytic reduction cells for the production of commercial purity aluminum as well as other metals.

  19. Preconcentration of silver as silver xanthate on activated carbon

    Ramadevi, P.; Naidu, U.V.; Naidu, G.R.K.

    1988-01-01

    Silver from aqueous solution was preconcentrated by adsorption on activated carbon as silver xanthate. Factors influencing the adsorption of silver were studied. Optimum conditions for the preconcentration of silver were established. (author) 9 refs.; 3 tabs

  20. Silvering of European eel (Anguilla anguilla L.): seasonal changes of morphological and metabolic parameters

    Ginneken, van V.; Durif, C.; Paul Balm, S.; Boot, R.; Verstegen, M.W.A.; Antonissen, E.; Thillart, van den G.

    2007-01-01

    The transformation of yellow eel into silver eel is called `silvering¿, and takes place prior to migration. We found the sedentary yellow phase in spring, the migratory silver phase in autumn, while August was a cross-over month. We used principal component analysis (PCA) to characterise the