WorldWideScience

Sample records for stable silver colloids

  1. Antimicrobial polyethyleneimine-silver nanoparticles in a stable colloidal dispersion.

    Science.gov (United States)

    Lee, Hyun Ju; Lee, Se Guen; Oh, Eun Jung; Chung, Ho Yun; Han, Sang Ik; Kim, Eun Jung; Seo, Song Yi; Ghim, Han Do; Yeum, Jeong Hyun; Choi, Jin Hyun

    2011-11-01

    Excellent colloidal stability and antimicrobial activity are important parameters for silver nanoparticles (AgNPs) in a range of biomedical applications. In this study, polyethyleneimine (PEI)-capped silver nanoparticles (PEI-AgNPs) were synthesized in the presence of sodium borohydride (NaBH(4)) and PEI at room temperature. The PEI-AgNPs had a positive zeta potential of approximately +49 mV, and formed a stable nanocolloid against agglomeration due to electrostatic repulsion. The particle size and hydrodynamic cluster size showed significant correlations with the amount of PEI and NaBH(4). PEI-AgNPs and even PEI showed excellent antimicrobial activity against Staphylococus aureus and Klebsiella pneumoniae. The cytotoxic effects of PEI and PEI-AgNPs were confirmed by an evaluation of the cell viability. The results suggest that the amount of PEI should be minimized to the level that maintains the stability of PEI-AgNPs in a colloidal dispersion. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Silver coated aluminium microrods as highly colloidal stable SERS platforms.

    Science.gov (United States)

    Pazos-Perez, Nicolas; Borke, Tina; Andreeva, Daria V; Alvarez-Puebla, Ramon A

    2011-08-01

    We report on the fabrication of a novel material with the ability to remain in solution even under the very demanding conditions required for structural and dynamic characterization of biomacromolecule assays. This stability is provided by the increase in surface area of a low density material (aluminium) natively coated with a very hydrophilic surface composed of aluminium oxide (Al(2)O(3)) and metallic silver nanoparticles. Additionally, due to the dense collection of active hot spots on their surface, this material offers higher levels of SERS intensity as compared with the same free and aggregated silver nanoparticles. This journal is © The Royal Society of Chemistry 2011

  3. [Bactericidal activity of colloidal silver against grampositive and gramnegative bacteria].

    Science.gov (United States)

    Afonina, I A; Kraeva, L A; Tseneva, G Ia

    2010-01-01

    It was shown that colloidal silver solution prepared in cooperation with the A. F. Ioffe Physical Technical Institute of the Russian Academy of Sciences, had significant bactericidal activity. Stable bactericidal effect on gramnegative microorganisms was observed after their 2-hour exposition in the solution of colloidal silver at a concentration of 10 ppm. Grampositive capsule-forming microorganisms were less susceptible to the colloidal silver solution: their death was observed after the 4-hour exposition in the solution.

  4. Colloidal silver solutions with antimicrobial properties

    International Nuclear Information System (INIS)

    Petica, A.; Gavriliu, S.; Lungu, M.; Buruntea, N.; Panzaru, C.

    2008-01-01

    Some colloidal silver solutions involving the electrochemical technique with 'sacrificial anode method and different stabilizers and co-stabilizers' have been prepared. A constant current pulse generator with stirrer at different working times has been used. To achieve stable colloidal silver solutions, a mix of different tensioactive agents namely [poly (N-vinylpyrrolidone)], Na-naphthalene sulphonate, Na-lauryl sulfate and Na-dodecyl sulphonate were tested. The effects of these various mixes of polymer and ionic surfactants upon the Ag concentration and UV-vis spectra of silver nanoparticles were determined by spectrophotometer techniques. The nanoparticles sizes have been analyzed through dynamic light scattering technique and the silver nanoparticle morphology has been evidenced by transmission electron microscopy (TEM). Micobiological analysis has been made by determining minimal inhibitorial concentration upon the following germs: Staphylococcus aureus (ATCC) (Gram-positive cocci), Pseudomonas aeruginosa (ATTC), Escherichia coli (ATCC) and Acinetobacter spp. (Gram-negative coccobacillus). To evaluate the antifungal effect, the antibiogram method involving various tests using a fungi mix of Aspergillus, Penicillium and Trichoderma species has been used. The presented method allows obtaining of some stable colloidal solutions containing up to 35 ppm of Ag with very good antimicrobial and antifungal properties

  5. Colloidal silver solutions with antimicrobial properties

    Energy Technology Data Exchange (ETDEWEB)

    Petica, A. [INCDIE ICPE-Advanced Research, Bucharest (Romania)], E-mail: petica@icpe-ca.ro; Gavriliu, S.; Lungu, M.; Buruntea, N. [INCDIE ICPE-Advanced Research, Bucharest (Romania); Panzaru, C. [Institute of Medicine and Pharmacy, Iassy (Romania)

    2008-08-25

    Some colloidal silver solutions involving the electrochemical technique with 'sacrificial anode method and different stabilizers and co-stabilizers' have been prepared. A constant current pulse generator with stirrer at different working times has been used. To achieve stable colloidal silver solutions, a mix of different tensioactive agents namely [poly (N-vinylpyrrolidone)], Na-naphthalene sulphonate, Na-lauryl sulfate and Na-dodecyl sulphonate were tested. The effects of these various mixes of polymer and ionic surfactants upon the Ag concentration and UV-vis spectra of silver nanoparticles were determined by spectrophotometer techniques. The nanoparticles sizes have been analyzed through dynamic light scattering technique and the silver nanoparticle morphology has been evidenced by transmission electron microscopy (TEM). Micobiological analysis has been made by determining minimal inhibitorial concentration upon the following germs: Staphylococcus aureus (ATCC) (Gram-positive cocci), Pseudomonas aeruginosa (ATTC), Escherichia coli (ATCC) and Acinetobacter spp. (Gram-negative coccobacillus). To evaluate the antifungal effect, the antibiogram method involving various tests using a fungi mix of Aspergillus, Penicillium and Trichoderma species has been used. The presented method allows obtaining of some stable colloidal solutions containing up to 35 ppm of Ag with very good antimicrobial and antifungal properties.

  6. Green synthesis of silver nanoparticles and silver colloidal solutions

    International Nuclear Information System (INIS)

    Nguyen Thi Phuong Phong; Ngo Hoang Minh; Ngo Vo Ke Thanh; Dang Mau Chien

    2009-01-01

    In this paper, silver colloidal solutions have been synthesized rapidly in green conditions by using microwave irradiation and non-toxic chemistry substances (acid oxalic, silver nitrate, polyvinyl pyrolidone (PVP; Mw = 55 000)). The particle size and morphology of these solutions can be controlled by altering several factors like the time, the power of microwave exposure, and the ratio of silver oxalate and PVP etc. The silver nanoparticles were fabricated by thermal decomposition of silver oxalate. The synthesized silver colloidal solutions and silver nanoparticles were characterized by several analytical techniques like UV- VIS, XRD, TEM, FESEM/EDS and ICP-AAS studies. Finally, we used the synthesized silver colloidal solutions for antibacterial purpose. The obtained results showed that the synthesized silver colloidal solutions, even at very low concentrations, have highly efficient anti-bacterial property.

  7. Detection of colloidal silver chloride near solubility limit

    Science.gov (United States)

    Putri, K. Y.; Adawiah, R.

    2018-03-01

    Detection of nanoparticles in solution has been made possible by several means; one of them is laser-induced breakdown detection (LIBD). LIBD is able to distinguish colloids of various sizes and concentrations. This technique has been used in several solubility studies. In this study, the formation of colloids in a mixed system of silver nitrate and sodium chloride was observed by acoustic LIBD. Silver chloride has low solubility limit, therefore LIBD measurement is appropriate. Silver and chloride solutions with equal concentrations, set at below and above the solubility of silver chloride as the expected solid product, were mixed and the resulting colloids were observed. The result of LIBD measurement showed that larger particles were present as more silver and chloride introduced. However, once the concentrations exceeded the solubility limit of silver chloride, the detected particle size seemed to be decreasing, hence suggested the occurrence of coprecipitation process. This phenomenon indicated that the ability of LIBD to detect even small changes in colloid amounts might be a useful tool in study on formation and stability of colloids, i.e. to confirm whether nanoparticles synthesis has been successfully performed and whether the system is stable or not.

  8. Towards conducting inks: Polypyrrole–silver colloids

    International Nuclear Information System (INIS)

    Omastová, Mária; Bober, Patrycja; Morávková, Zuzana; Peřinka, Nikola; Kaplanová, Marie; Syrový, Tomáš; Hromádková, Jiřina; Trchová, Miroslava; Stejskal, Jaroslav

    2014-01-01

    Graphical abstract: - Highlights: • Composite colloidal particles combining conducting polymer and metal have been prepared. • Conducting colloids are suitable for printing applications. • Polypyrrole/silver colloids are prepared in a single reaction step. • The conductivity control is discussed and still needs improvement. - Abstract: The oxidation of pyrrole with silver nitrate in the presence of suitable water-soluble polymers yields composite polypyrrole–silver colloids. The polypyrrole–silver nanoparticles stabilized with poly(N-vinylpyrrolidone) have a typical size around 350 nm and polydispersity index 0.20, i.e. a moderate polydispersity in size. Similar results have been obtained with poly(vinyl alcohol) as stabilizer. The effect of stabilizer concentration on the particle size is marginal. In the present study, several types of stabilizers have been tested in addition to currently used poly(N-vinylpyrrolidone). Transmission electron microscopy and optical microscopy revealed the gemini morphology of polypyrrole and silver colloidal nanoparticles and confirmed their size and size-distribution determined by dynamic light scattering. The use of colloidal dispersions provides an efficient tool for the UV–vis and FT Raman spectroscopic characterization of polypyrrole, including the transition between polypyrrole salt and corresponding polypyrrole base. The dispersions were used for the preparation of coatings on polyethylene terephthalate foils, and the properties for polypyrrole–silver composites have been compared with those produced from polypyrrole colloids alone

  9. Colloidal Silver Not Approved for Treating Animals

    OpenAIRE

    Bagley, Clell V, DVM

    1997-01-01

    FDA has received reports that products containing colloidal silver are being promoted for use in the treatment of mastitis and other serious disease conditions of dairy cattle, as well as for various conditions of companion animals. For example, FDA’s Center for Veterinary Medicine has received reports from the Agency's regional milk specialists and State inspectors that colloidal silver products have been found on some dairy farms. Also, recent articles in some farm newspapers and journals p...

  10. Sensitive chemical neutron dosimetry using silver colloids

    International Nuclear Information System (INIS)

    Brede, O.; Boes, J.; Hoesselbarth, B.

    1982-01-01

    The radiation-induced formation of silver colloid was checked for its use as a sensitive dosimeter for neutron irradiation. For non-monoenergetic pulsed neutron irradiation in the Dubna IBR-30 reactor, the colloid dosimeter was found to be suitable to indicate the chemical neutron effect, i.e., to determine the sum concentration of the primary particles of water radiolysis: esub(aq)sup(-), OH and H. (author)

  11. Synthesis and characterization of colloidal fluorescent silver nanoclusters.

    Science.gov (United States)

    Huang, Sherry; Pfeiffer, Christian; Hollmann, Jana; Friede, Sebastian; Chen, Justin Jin-Ching; Beyer, Andreas; Haas, Benedikt; Volz, Kerstin; Heimbrodt, Wolfram; Montenegro Martos, Jose Maria; Chang, Walter; Parak, Wolfgang J

    2012-06-19

    Ultrasmall water-soluble silver nanoclusters are synthesized, and their properties are investigated. The silver nanoclusters have high colloidal stability and show fluorescence in the red. This demonstrates that like gold nanoclusters also silver nanoclusters can be fluorescent.

  12. Radiolytic reduction reaction of colloidal silver bromide solution

    International Nuclear Information System (INIS)

    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)

  13. Nonlinear optical properties of colloidal silver nanoparticles produced by laser ablation in liquids

    International Nuclear Information System (INIS)

    Karavanskii, V A; Krasovskii, V I; Ivanchenko, P V; Simakin, Aleksandr V

    2004-01-01

    The optical and nonlinear optical properties of colloidal solutions of silver obtained by laser ablation in water and ethanol are studied. It is shown that freshly prepared colloids experience a full or partial sedimentation by changing their nonlinear optical properties. Aqueous colloids undergo a partial sedimentation and their nonlinear optical absorption changes to nonlinear optical transmission. The obtained results are interpreted using the Drude model for metal particles taking the particle size into account and can be explained by the sedimentation of larger silver particles accompanied by the formation of a stable colloid containing silver nanoparticles with a tentatively silver oxide shell. The characteristic size of particles forming such a stable colloid is determined and its optical nonlinearity is estimated. (nonlinear optical phenomena)

  14. Synthesis of dextrin-stabilized colloidal silver nanoparticles and their application as modifiers of cement mortar.

    Science.gov (United States)

    Konował, Emilia; Sybis, Marta; Modrzejewska-Sikorska, Anna; Milczarek, Grzegorz

    2017-11-01

    Various commercial dextrins were used as reducing and stabilizing agents for a novel one-step synthesis of silver nanoparticles from ammonia complexes of silver ions. As a result, stable colloids of silver were formed during the reaction with the particle size being the function of the dextrin type. The obtained colloids were characterized by UV-vis spectrophotometry, size distribution (using Non-Invasive Backscatter optics) and transmission electron microscopy (TEM). The achieved results clearly indicate the possibility of low-cost production of large quantities of colloidal silver nanoparticles using materials derived from renewable sources. The resulting silver colloids can be used for different purposes, e.g. as bactericidal agents. Combination of the aforementioned properties of nanosilver particles with plasticizing properties of dextrin enables to obtain cement mortars with increased workability and enhanced compressive strength. Moreover, the obtained material is also characterized by increased immunity to adverse impact of microorganisms. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Sunlight-assisted synthesis of colloidal silver nanoparticles using chitosan as reducing agent

    Science.gov (United States)

    Susilowati, E.; Maryani; Ashadi

    2018-04-01

    The present study we explore an environmentally friendly colloidal silver nanoparticles preparation using chitosan as reducing agent and stabilizer. It develops a new strategy on preparation of silver nanoparticles through the gel phase using sodium hydroxide (NaOH) as accelerator reagent. Sunlight irradiation was employed to assisted reducing process of silver ions to silver nanoparticles. Localized surface plasmon resonance (LSPR) phenomenon of silver nanoparticles was investigated using UV-Vis spectrophotometer. The shape and size of silver particles were analyzed using TEM. The formation of silver nanoparticles was confirmed by the appearance of LSPR absorption peak at 396.0–412.0 nm. The absorption peak of LSPR were affected by NaOH amount, time of sulight irradiation and concentration of AgNO3. The produced silver nanoparticles were spherical with dominant size range of 5 to 8 nm as shown by TEM images. All colloidals were stable without any aggregation for 30 days after preparation.

  16. Silver carbonate and stability in colloidal silver: A by-product of the electric spark discharge method

    International Nuclear Information System (INIS)

    Tseng, Kuo-Hsiung; Liao, Chih-Yu; Tien, Der-Chi

    2010-01-01

    Many methods of producing colloidal silver (CS) include the introduction of surfactants to improve the suspensivity of the silver particles. The electric spark discharge method (ESDM) which involves pulses of direct current being passed through a silver electrode submerged in deionized water has been shown to successfully produce colloidal silver in a stable suspension without the use of chemical additives. A by-product of the electric spark discharge method, a silver ion compound (AgX), is shown to be the cause of the high suspensivity of the silver nanoparticles (AgNPs). The silver ion compound has been identified as Ag 2 CO 3 using X-ray diffraction, and it has been determined that the Ag 2 CO 3 is formed during the electric spark discharge process through a reaction with atmospheric CO 2 . It has been shown that an Ag 2 CO 3 concentration of 10 ppm or more is sufficient to generate a stable suspension of silver particles. Because of the occurrence of Ag 2 CO 3 , the electric spark discharge method can produce stable colloidal silver.

  17. Spectrum of antimicrobial activity associated with ionic colloidal silver.

    Science.gov (United States)

    Morrill, Kira; May, Kathleen; Leek, Daniel; Langland, Nicole; Jeane, La Deana; Ventura, Jose; Skubisz, Corey; Scherer, Sean; Lopez, Eric; Crocker, Ephraim; Peters, Rachel; Oertle, John; Nguyen, Krystine; Just, Scott; Orian, Michael; Humphrey, Meaghan; Payne, David; Jacobs, Bertram; Waters, Robert; Langland, Jeffrey

    2013-03-01

    Silver has historically and extensively been used as a broad-spectrum antimicrobial agent. However, the Food and Drug Administration currently does not recognize colloidal silver as a safe and effective antimicrobial agent. The goal of this study was to further evaluate the antimicrobial efficacy of colloidal silver. Several strains of bacteria, fungi, and viruses were grown under multicycle growth conditions in the presence or absence of ionic colloidal silver in order to assess the antimicrobial activity. For bacteria grown under aerobic or anaerobic conditions, significant growth inhibition was observed, although multiple treatments were typically required. For fungal cultures, the effects of ionic colloidal silver varied significantly between different genera. No viral growth inhibition was observed with any strains tested. The study data support ionic colloidal silver as a broad-spectrum antimicrobial agent against aerobic and anaerobic bacteria, while having a more limited and specific spectrum of activity against fungi.

  18. 21 CFR 310.548 - Drug products containing colloidal silver ingredients or silver salts offered over-the-counter...

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 5 2010-04-01 2010-04-01 false Drug products containing colloidal silver... Drug products containing colloidal silver ingredients or silver salts offered over-the-counter (OTC) for the treatment and/or prevention of disease. (a) Colloidal silver ingredients and silver salts have...

  19. Synthesis of nanosized silver colloids by microwave dielectric heating

    Indian Academy of Sciences (India)

    Silver nanosized crystallites have been synthesized in aqueous and polyols viz., ethylene glycol and glycerol, using a microwave technique. Dispersions of colloidal silver have been prepared by the reduction of silver nitrate both in the presence and absence of stabilizer poly(vinylpyrolidone) (PVP). It was observed that ...

  20. Synthesis and characterization of silver colloidal nanoparticles with different coatings for SERS application

    International Nuclear Information System (INIS)

    Mikac, L.; Ivanda, M.; Gotić, M.; Mihelj, T.; Horvat, L.

    2014-01-01

    Silver colloids were produced by chemical reduction of silver salt (silver nitrate, AgNO 3 ) solution. As reducing agents, trisodium citrate, sodium borohydride, ascorbic acid, polyvinylpyrrolidone, and glucose were used. The colloids were characterized by UV–Vis, DLS, zeta potential measurements, and SEM. The colloids were stabilized with negative groups or large molecules attached to their surface. The surface-enhanced Raman scattering (SERS) effect of stabilized nanoparticles was measured by using pyridine and rhodamine 6G molecules as analytes and NaNO 3 , KCl, and KBr at different concentrations as aggregating agents. The best Raman signal enhancement was achieved using silver nanoparticles of 40 nm size reduced and stabilized with citrate. The SERS signal of analyte molecules was further enhanced with the addition of sodium borohydride as an alternative aggregating agent. The borohydride had the strongest impact on the SERS effect of the colloid consistent of large (0.5 µm) silver nanoparticles stabilized with aminodextran. The mixture colloid-borohydride-pyridine was stable for hours. The mechanism of borohydride in the colloids is discussed

  1. Synthesis and characterization of silver colloidal nanoparticles with different coatings for SERS application

    Energy Technology Data Exchange (ETDEWEB)

    Mikac, L.; Ivanda, M., E-mail: ivanda@irb.hr [Ruđer Bošković Institute, Laboratory for Molecular Physics (Croatia); Gotić, M. [Ruđer Bošković Institute, Laboratory for Synthesis of New Materials (Croatia); Mihelj, T. [Ruđer Bošković Institute, Laboratory for Synthesis and Processes of Self-assembling of Organic Molecules (Croatia); Horvat, L. [Ruđer Bošković Institute, Laboratory for Electron Microscopy (Croatia)

    2014-12-15

    Silver colloids were produced by chemical reduction of silver salt (silver nitrate, AgNO{sub 3}) solution. As reducing agents, trisodium citrate, sodium borohydride, ascorbic acid, polyvinylpyrrolidone, and glucose were used. The colloids were characterized by UV–Vis, DLS, zeta potential measurements, and SEM. The colloids were stabilized with negative groups or large molecules attached to their surface. The surface-enhanced Raman scattering (SERS) effect of stabilized nanoparticles was measured by using pyridine and rhodamine 6G molecules as analytes and NaNO{sub 3}, KCl, and KBr at different concentrations as aggregating agents. The best Raman signal enhancement was achieved using silver nanoparticles of 40 nm size reduced and stabilized with citrate. The SERS signal of analyte molecules was further enhanced with the addition of sodium borohydride as an alternative aggregating agent. The borohydride had the strongest impact on the SERS effect of the colloid consistent of large (0.5 µm) silver nanoparticles stabilized with aminodextran. The mixture colloid-borohydride-pyridine was stable for hours. The mechanism of borohydride in the colloids is discussed.

  2. Colloidal silver: a novel treatment for Staphylococcus aureus biofilms?

    Science.gov (United States)

    Goggin, Rachel; Jardeleza, Camille; Wormald, Peter-John; Vreugde, Sarah

    2014-03-01

    Colloidal silver is an alternative medicine consisting of silver particles suspended in water. After using this solution as a nasal spray, the symptoms of a previously recalcitrant Staphylococcus aureus (S. aureus)-infected chronic rhinosinusitis patient were observed to have improved markedly. The aim of this study was to determine whether colloidal silver has any direct bactericidal effects on these biofilms in vitro. S. aureus biofilms were grown from the ATCC 25923 reference strain on Minimum Biofilm Eradication Concentration (MBEC) device pegs, and treated with colloidal silver. Concentrations tested ranged from 10 to 150 μL colloidal silver diluted to 200 μL with sterile water in 50 μL cerebrospinal fluid (CSF) broth. Control pegs were exposed to equivalent volumes of CSF broth and sterile water. The sample size was 4 biomass values per treatment or control group. Confocal scanning laser microscopy and COMSTAT software were used to quantify biofilms 24 hours after treatment. Significant differences from control were found for all concentrations tested bar the lowest of 10 μL colloidal silver in 200 μL. At 20 μL colloidal silver, the reduction in biomass was 98.9% (mean difference between control and treatment = -4.0317 μm(3) /μm(2) , p colloidal silver (mean differences = -4.0681 and -4.0675μm(3) /μm(2) , respectively, p Colloidal silver directly attenuates in vitro S. aureus biofilms. © 2014 ARS-AAOA, LLC.

  3. Single Molecule Raman Detection of Enkephalin on Silver Colloidal Particles

    DEFF Research Database (Denmark)

    Kneipp, Katrin; Kneipp, Holger; Abdali, Salim

    2004-01-01

    the Raman signal the enkephalin molecules have been attached to silver colloidal cluster structures. The experiments demonstrate that the SERS signal of the strongly enhanced ring breathing vibration of phenylalanine at 1000 cm-1 can be used as “intrinsic marker” for detecting a single enkephalin molecule...... and for monitoring its diffusion on the surface of the silver colloidal cluster without using a specific label molecule....

  4. Colloidal silver ingestion with copper and caeruloplasmin deficiency.

    Science.gov (United States)

    Stepien, Karolina M; Taylor, Andrew

    2012-05-01

    The copper concentration in serum can be affected by the presence of other trace elements such as silver. Low serum copper may result in decreased caeruloplasmin synthesis. We report the case of a 59-year-old woman, who was admitted to hospital with acute psychosis and who had been ingesting chronically, colloidal silver.

  5. Synthesis of Silver-Chitosan Nanocomposites Colloidal by Glucose as Reducing Agent

    Directory of Open Access Journals (Sweden)

    Endang Susilowati

    2015-03-01

    Full Text Available Silver-chitosan nanocomposites colloidal was successfully performed by chemical reduction method at room temperature using glucose as reducing agent, sodium hydroxide (NaOH as accelerator reagent, silver nitrate (AgNO3 as metal precursor and chitosan as stabilizing agent. Compared to other synthetic methods, this work is green and simple. The effect of the amount of NaOH, molar ratio of AgNO3 to glucose and AgNO3 concentration towards Localized Surface Plasmon Resonance (LSPR absorption band of silver nanoparticles was investigated using UV-Vis spectrophotometer. The stability of the colloid was also studied for the first 16 weeks of storage at ambient temperature. The formation of silver nanoparticles was confirmed by the appearance of LSPR absorption peak at 402.4–414.5 nm. It is also shown that the absorption peak of LSPR were affected by NaOH amount, ratio molar AgNO3/glucose and concentration of AgNO3. The produced silver nanoparticles were spherical with dominant size range of 6 to 18 nm as shown by TEM images. All colloidals were stable without any aggregation for 16 weeks after preparation. The newly prepared silver-chitosan nanocomposites colloidal may have potential for antibacterial applications.

  6. Characterization of engineered nanoparticles in commercially available spray disinfectant products advertised to contain colloidal silver

    Science.gov (United States)

    Given the potential for human exposure to silver nanoparticles from spray disinfectants and dietary supplements, we characterized the silver-containing nanoparticles in 22 commercial products that advertised the use of silver or colloidal silver as the active ingredient. Characte...

  7. A Case of Argyria Following Colloidal Silver Ingestion

    OpenAIRE

    Kwon, Hyok Bu; Lee, Joon Ho; Lee, Seung Ho; Lee, Ai Young; Choi, Jong Sun; Ahn, Yeon Soon

    2009-01-01

    Argyria is a rare cutaneous discoloration caused by the intake of silver or various compounds containing silver. We report a case of argyria in a 73-year-old male following ingestion of colloidal silver as an alternative medicine over 5 years. He had a diffuse, slate gray discoloration of his face and hands. A biopsy specimen from the face revealed brown-black extracellular granules in the upper dermis and between collagen bundles. We also found silver particles in the mucous of the colon. Th...

  8. [Antimicrobial activity of stable silver nanoparticles of a certain size].

    Science.gov (United States)

    Mukha, Iu P; Eremenko, A M; Smirnova, N P; Mikhienkova, A I; Korchak, G I; Gorchev, V F; Chunikhin, A Iu

    2013-01-01

    Conditions for obtaining stable silver nanoparticles smaller than 10 nm were developed using a binary stabilizer polyvinylpyrrolidone/sodium dodecylsulphate in optimal ratio. Optical spectra, morphology and dependence of size of the nanoparticles on the amount of reducing agent were studied. Colloidal solutions of nanosilver showed a high bactericidal activity against strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, and fungicidal activity against Candida albicans. The mechanism of action of nanosized silver on microbial cell was examined by laser scanning confocal microscope using fluorescent label. First step of antimicrobial effect on microorganisms was membrane damage and penetration of silver nanoparticles into the cell. Prolonged stability of nanoparticles and their antimicrobial activity over the past two years were showed.

  9. Tuning the localized surface plasmon resonance of silver nanoplatelet colloids

    International Nuclear Information System (INIS)

    Singh, Asha; Jayabalan, J; Chari, Rama; Srivastava, Himanshu; Oak, S M

    2010-01-01

    The effect of femtosecond laser irradiation on silver nanoplatelet colloids is described. It is shown that irradiation with a femtosecond laser of appropriate fluence can be used to tune the localized surface plasmon resonances of triangular silver nanoplatelets by a few tens of nanometres. This peak shift is shown to be caused by the structural modifications of the particle tips. We have also shown that post-preparation addition of poly-vinyl pyrrolidone to the nanocolloid arrests the peak shift.

  10. Tuning the localized surface plasmon resonance of silver nanoplatelet colloids

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Asha; Jayabalan, J; Chari, Rama [Laser Physics Applications Division, Raja Ramanna Centre for Advanced Technology, Indore (India); Srivastava, Himanshu [Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore (India); Oak, S M, E-mail: jjaya@rrcat.gov.i [Solid State Laser Division, Raja Ramanna Centre for Advanced Technology, Indore (India)

    2010-08-25

    The effect of femtosecond laser irradiation on silver nanoplatelet colloids is described. It is shown that irradiation with a femtosecond laser of appropriate fluence can be used to tune the localized surface plasmon resonances of triangular silver nanoplatelets by a few tens of nanometres. This peak shift is shown to be caused by the structural modifications of the particle tips. We have also shown that post-preparation addition of poly-vinyl pyrrolidone to the nanocolloid arrests the peak shift.

  11. Silver Colloid Nanoparticles: Synthesis, Characterization, and Their Antibacterial Activity

    Czech Academy of Sciences Publication Activity Database

    Panáček, A.; Kvítek, L.; Prucek, R.; Kolář, M.; Večeřová, R.; Pizúrová, Naděžda; Sharma, V. K.; Nevěčná, T.; Zbořil, R.

    2006-01-01

    Roč. 110, č. 33 (2006), s. 16248-16253 ISSN 1520-6106 R&D Projects: GA MŠk(CZ) 1M0512 Institutional research plan: CEZ:AV0Z20410507 Keywords : silver colloid nanoparticles * antimicrobial and bactericidal assays * particle size Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.115, year: 2006

  12. Adsorption of iodide and iodate on colloidal silver surface

    International Nuclear Information System (INIS)

    Zhang Aiping; Tie Xiaoyun; Zhang Jinzhi; An Yanwei; Li Lingjie

    2008-01-01

    'Chemically pure' silver colloids were prepared by laser ablated method to investigate their adsorption-induced spectral and morphologic changes, using UV-visible absorption, Raman and transmission electron microscopy (TEM) techniques, when nucleophilic different anions (IO 3 - and I - ) were added into sols. It reveals that the adsorption of nucleophiles on silver surfaces leads to an excess negative charge in the metal interior and modifies both surface charge density and the Fermi levels of metal, which is responsible for the colloidal aggregation, reconstruction and appearance of new resonance absorption bands or with wavelength shift. In addition, two models regarding different adsorption effects of these two anions on silver surfaces were proposed to explain their variant spectral and TEM phenomena.

  13. Photochemical Synthesis and Properties of Colloidal Copper, Silver and Gold Adsorbed on Quartz

    International Nuclear Information System (INIS)

    Loginov, Anatoliy V.; Gorbunova, Valentina V.; Boitsova, Tatiana B.

    2002-01-01

    Original methods for the photochemical production of stable copper, silver and gold colloids in the form of films on quartz, and dispersion in liquids were devised. It is shown that photochemical synthesis of colloidal metals is a difficult multiphase process, and includes the formation of low-valence forms of Cu(I), Au(I) and nonmetal clusters, colloidal particles and their agglomerates. Cluster stabilization and further growth to colloidal particles are achieved by adsorption onto the solid surface (quartz) or by increasing the viscosity of photolyte. In the absence of these methods of stabilization, the processes of intermediate reoxidation to Cu(II) and Au(III) and agglomeration of Ag and Au colloids proceed in a photolyte. Adsorption and the rate of cluster growth on a quartz surface are speeded up by the action of monochromatic UV light. Experimental models of the mechanism of colloidal formation are suggested. The dependence of the growth rate and the properties of the colloids on conditions of the photochemical procedure (energy and light intensity, concentration of initial complex) has been established

  14. Towards conducting inks: polypyrrole-silver colloids

    Czech Academy of Sciences Publication Activity Database

    Omastová, M.; Bober, Patrycja; Morávková, Zuzana; Peřinka, N.; Kaplanová, M.; Syrový, T.; Hromádková, Jiřina; Trchová, Miroslava; Stejskal, Jaroslav

    2014-01-01

    Roč. 122, 10 March (2014), s. 296-302 ISSN 0013-4686 R&D Projects: GA TA ČR TE01020022; GA ČR(CZ) GA13-00270S Institutional support: RVO:61389013 Keywords : conducting inks * polypyrrole * colloids Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 4.504, year: 2014

  15. Stability of colloidal silver nanoparticles trapped in lipid bilayer: effect of lecithin concentration and applied temperature

    NARCIS (Netherlands)

    Barani, H.; Montazer, M.; Braun, H.G.; Dutschk, Victoria

    2014-01-01

    The use of silver nanoparticle on various substrates has been widespread because of its good antibacterial properties that directly depend on the stability of the silver nanoparticles in a colloidal suspension. In this study, the colloidal solutions of the silver nanoparticles were synthesised by a

  16. Silver distribution and release from an antimicrobial denture base resin containing silver colloidal nanoparticles.

    Science.gov (United States)

    Monteiro, Douglas Roberto; Gorup, Luiz Fernando; Takamiya, Aline Satie; de Camargo, Emerson Rodrigues; Filho, Adhemar Colla Ruvolo; Barbosa, Debora Barros

    2012-01-01

    The aim of this study was to evaluate a denture base resin containing silver colloidal nanoparticles through morphological analysis to check the distribution and dispersion of these particles in the polymer and by testing the silver release in deionized water at different time periods. A Lucitone 550 denture resin was used, and silver nanoparticles were synthesized by reduction of silver nitrate with sodium citrate. The acrylic resin was prepared in accordance with the manufacturers' instructions, and silver nanoparticle suspension was added to the acrylic resin monomer in different concentrations (0.05, 0.5, and 5 vol% silver colloidal). Controls devoid of silver nanoparticles were included. The specimens were stored in deionized water at 37°C for 7, 15, 30, 60, and 120 days, and each solution was analyzed using atomic absorption spectroscopy. Silver was not detected in deionized water regardless of the silver nanoparticles added to the resin and of the storage period. Micrographs showed that with lower concentrations, the distribution of silver nanoparticles was reduced, whereas their dispersion was improved in the polymer. Moreover, after 120 days of storage, nanoparticles were mainly located on the surface of the nanocomposite specimens. Incorporation of silver nanoparticles in the acrylic resin was evidenced. Moreover, silver was not detected by the detection limit of the atomic absorption spectrophotometer used in this study, even after 120 days of storage in deionized water. Silver nanoparticles are incorporated in the PMMA denture resin to attain an effective antimicrobial material to help control common infections involving oral mucosal tissues in complete denture wearers. © 2011 by the American College of Prosthodontists.

  17. Plasmonic resonance of colloidal silver in nanoporous matrix

    International Nuclear Information System (INIS)

    Andreeva, O V; Saitov, S V; Andreeva, N V; Sidorov, A I

    2014-01-01

    The object of the study in this paper – silver nanoporous silicate matrix with pore size less than 20 nm. Colloidal silver particles with volume concentration about 10 −4 are formed within free volume of pores of silicate matrix by chemical method. Changes in the attenuation spectra of the investigated object during changing of the refractive index of free volume of pores from 1.0 to 1.5 are reviewed. Comparison of the obtained experimental data with the results of calculations was carried out

  18. Taking the Silver Bullet Colloidal Silver Particles for the Topical Treatment of Biofilm-Related Infections.

    Science.gov (United States)

    Richter, Katharina; Facal, Paula; Thomas, Nicky; Vandecandelaere, Ilse; Ramezanpour, Mahnaz; Cooksley, Clare; Prestidge, Clive A; Coenye, Tom; Wormald, Peter-John; Vreugde, Sarah

    2017-07-05

    Biofilms are aggregates of bacteria residing in a self-assembled matrix, which protects these sessile cells against external stress, including antibiotic therapies. In light of emerging multidrug-resistant bacteria, alternative strategies to antibiotics are emerging. The present study evaluated the activity of colloidal silver nanoparticles (AgNPs) of different shapes against biofilms formed by Staphylococcus aureus (SA), methicillin-resistant SA (MRSA), and Pseudomonas aeruginosa (PA). Colloidal quasi-spherical, cubic, and star-shaped AgNPs were synthesized, and their cytotoxicity on macrophages (THP-1) and bronchial epithelial cells (Nuli-1) was analyzed by the lactate dehydrogenase assay. The antibiofilm activity was assessed in vitro by the resazurin assay and in an in vivo infection model in Caenorhabditis elegans. Cubic and star-shaped AgNPs induced cytotoxicity, while quasi-spherical AgNPs were not toxic. Quasi-spherical AgNPs showed substantial antibiofilm activity in vitro with 96% (±2%), 97% (±1%), and 98% (±1%) biofilm killing of SA, MRSA, and PA, respectively, while significantly reducing mortality of infected nematodes. The in vivo antibiofilm activity was linked to the accumulation of AgNPs in the intestinal tract of C. elegans as observed by 3D X-ray tomography. Quasi-spherical AgNPs were physically stable in suspension for over 6 months with no observed loss in antibiofilm activity. While toxicity and stability limited the utilization of cubic and star-shaped AgNPs, quasi-spherical AgNPs could be rapidly synthesized, were stable and nontoxic, and showed substantial in vitro and in vivo activity against clinically relevant biofilms. Quasi-spherical AgNPs hold potential as pharmacotherapy, for example, as topical treatment for biofilm-related infections.

  19. Green synthesis of colloidal silver nanoparticles using natural rubber latex extracted from Hevea brasiliensis.

    Science.gov (United States)

    Guidelli, Eder José; Ramos, Ana Paula; Zaniquelli, Maria Elisabete D; Baffa, Oswaldo

    2011-11-01

    Colloidal silver nanoparticles were synthesized by an easy green method using thermal treatment of aqueous solutions of silver nitrate and natural rubber latex (NRL) extracted from Hevea brasiliensis. The UV-Vis spectra detected the characteristic surface plasmonic absorption band around 435 nm. Both NRL and AgNO(3) contents in the reaction medium have influence in the Ag nanoparticles formation. Lower AgNO(3) concentration led to decreased particle size. The silver nanoparticles presented diameters ranging from 2 nm to 100 nm and had spherical shape. The selected area electron diffraction (SAED) patterns indicated that the silver nanoparticles have face centered cubic (fcc) crystalline structure. FTIR spectra suggest that reduction of the silver ions are facilitated by their interaction with the amine groups from ammonia, which is used for conservation of the NRL, whereas the stability of the particles results from cis-isoprene binding onto the surface of nanoparticles. Therefore natural rubber latex extracted from H. brasiliensis can be employed in the preparation of stable aqueous dispersions of silver nanoparticles acting as a dispersing and/or capping agent. Moreover, this work provides a new method for the synthesis of silver nanoparticles that is simple, easy to perform, pollutant free and inexpensive. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. Photonic Crystal Fibre SERS Sensors Based on Silver Nanoparticle Colloid

    International Nuclear Information System (INIS)

    Zhi-Guo, Xie; Yong-Hua, Lu; Pei, Wang; Kai-Qun, Lin; Jie, Yan; Hai, Ming

    2008-01-01

    A photonic crystal fibre (PCF) surface enhanced Raman scattering (SERS) sensor is developed based on silver nanoparticle colloid. Analyte solution and silver nanoparticles are injected into the air holes of PCF by a simple modified syringe to overcome mass-transport constraints, allowing more silver nanoparticles involved in SERS activity. This sensor offers significant benefit over the conventional SERS sensor with high flexibility, easy manufacture. We demonstrate the detection of 4-mercaptobenzoic acid (4-MBA) molecules with the injecting way and the common dipping measurement. The injecting way shows obviously better results than the dipping one. Theoretical analysis indicates that this PCF SERS substrate offers enhancement of about 7 orders of magnitude in SERS active area

  1. A novel wound rinsing solution based on nano colloidal silver

    Directory of Open Access Journals (Sweden)

    Soheila Kordestani

    2014-10-01

    Full Text Available Objective(s: The present study aimed to investigate the antiseptic properties of a colloidal nano silver wound rinsing solution to inhibit a wide range of pathogens including bacteria, viruses and fungus present in chronic and acute wounds. Materials and Methods:The wound rinsing solution named SilvoSept® was prepared using colloidal nano silver suspension. Physicochemical properties, effectiveness against microorganism including  Staphylocoocous aureus ATCC 6538P, Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 8739 ,Candida albicans ATCC 10231, Aspergillus niger ATCC 16404, MRSA , Mycobacterium spp. , HSV-1 and H1N1, and biocompatibility tests were carried out according to relevant standards . Results: X-ray diffraction (XRD scan was performed on the sample and verify single phase of silver particles in the compound. The size of the silver particles in the solution, measured by dynamic light scattering (DLS techniqu, ranged 80-90 nm. Transmission electron microscopy (TEM revealed spherical shape with smooth surface of the silver nanoparticles. SilvoSept® reduced 5 log from the initial count of 107 CFU/mL of Staphylocoocous aureus ATCC 6538P, Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 8739, Candida albicans ATCC 10231, Aspergillus niger ATCC 16404, MRSA, Mycobacterium spp. Further assessments of SilvoSept solution exhibited a significant inhibition on the replication of HSV-1 and H1N1. The biocompatibility studies showed that the solution was non-allergic, non-irritant and noncytotoxic. Conclusion: Findings of the present study showed that SilvoSept® wound rinsing solution containing nano silver particles is an effective antiseptic solution against a wide spectrum of microorganism. This compound can be a suitable candidate for wound irrigation.   

  2. Non-hazardous anticancerous and antibacterial colloidal 'green' silver nanoparticles.

    Science.gov (United States)

    Barua, Shaswat; Konwarh, Rocktotpal; Bhattacharya, Satya Sundar; Das, Pallabi; Devi, K Sanjana P; Maiti, Tapas K; Mandal, Manabendra; Karak, Niranjan

    2013-05-01

    Poly(ethylene glycol) stabilized colloidal silver nanoparticles were prepared using the reductive potency of the aqueous extract of Thuja occidentalis leaves under ambient conditions. The nanoparticles were well dispersed within a narrow size spectrum (7-14 nm) and displayed characteristic surface plasmon resonance peak at around 420 nm and Bragg's reflection planes of fcc structure. MTT assay revealed the dose-dependent cytocompatibility and toxicity of the nanoparticles with the L929 normal cell line. On the other hand, the antiproliferative action of the nanoparticles was evaluated on HeLa cell (cancerous cells) line. Fluorescence and phase contrast microscopic imaging indicated the appearance of multinucleate stages with aggregation and nuclear membrane disruption of the HeLa cells post treatment with the nanoparticles. The interaction at the prokaryotic level was also assessed via differential antibacterial efficacy against Staphylococcus aureus (MTCC 3160) and Escherichia coli (MTCC 40). Under these perspectives, it is also necessary to observe the environmental impact of the prepared silver nanoparticles. Hence, the dose dependent toxicity of silver nanoparticles was evaluated upon the earthworm species Eisenia fetida. Neither the survival nor the reproduction was affected by the addition of silver nanoparticles up to 1000 ppm. Thus these 'green' silver nanoparticles have promising potential as future materials. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. Stabilization of sputtered gold and silver nanoparticles in PEG colloid solutions

    International Nuclear Information System (INIS)

    Slepička, P.; Elashnikov, R.; Ulbrich, P.; Staszek, M.; Kolská, Z.; Švorčík, V.

    2015-01-01

    In this study, a simple technique for preparation of colloid solution of metal nanoparticles in polyethylene glycol (PEG)/H 2 O is described. By this technique, stable colloidal metal solutions can be prepared ready for use without application of chemical reactions, stabilizers, or reducing agents. The nanoparticles are created by direct sputtering of metal into PEG. The influence of sputter conditions and the concentration of PEG/H 2 O on the properties of nanoparticles was studied. The nanoparticles were characterized by transmission electron microscopy, atomic absorption spectrometry, dynamic light scattering, and UV–Vis spectroscopy. UV–Vis spectra of gold nanoparticle solution exhibit localized surface plasmon resonance characteristic peaks located in the region 513–560 nm (PEG/H 2 O—1/1), 509–535 nm (PEG/H 2 O—1/9), and for silver nanoparticles in the region from 401 to 421 nm. Silver nanoparticles have a broader size distribution compared with gold ones. An appropriate choice of concentration, mixing, and deposition conditions allows preparing the stable solution of gold or silver nanoparticles

  4. Stabilization of sputtered gold and silver nanoparticles in PEG colloid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Slepička, P., E-mail: petr.slepicka@vscht.cz; Elashnikov, R. [University of Chemistry and Technology Prague, Department of Solid State Engineering (Czech Republic); Ulbrich, P. [University of Chemistry and Technology Prague, Department of Biochemistry and Microbiology (Czech Republic); Staszek, M. [University of Chemistry and Technology Prague, Department of Solid State Engineering (Czech Republic); Kolská, Z. [University of J. E. Purkyně, Faculty of Science (Czech Republic); Švorčík, V. [University of Chemistry and Technology Prague, Department of Solid State Engineering (Czech Republic)

    2015-01-15

    In this study, a simple technique for preparation of colloid solution of metal nanoparticles in polyethylene glycol (PEG)/H{sub 2}O is described. By this technique, stable colloidal metal solutions can be prepared ready for use without application of chemical reactions, stabilizers, or reducing agents. The nanoparticles are created by direct sputtering of metal into PEG. The influence of sputter conditions and the concentration of PEG/H{sub 2}O on the properties of nanoparticles was studied. The nanoparticles were characterized by transmission electron microscopy, atomic absorption spectrometry, dynamic light scattering, and UV–Vis spectroscopy. UV–Vis spectra of gold nanoparticle solution exhibit localized surface plasmon resonance characteristic peaks located in the region 513–560 nm (PEG/H{sub 2}O—1/1), 509–535 nm (PEG/H{sub 2}O—1/9), and for silver nanoparticles in the region from 401 to 421 nm. Silver nanoparticles have a broader size distribution compared with gold ones. An appropriate choice of concentration, mixing, and deposition conditions allows preparing the stable solution of gold or silver nanoparticles.

  5. Colloidal stability of silver nanoparticles in biologically relevant conditions

    International Nuclear Information System (INIS)

    MacCuspie, Robert I.

    2011-01-01

    Understanding the colloidal stability of nanoparticles (NPs) plays a key role in phenomenological interpretation of toxicological experiments, particularly if single NPs or their aggregates or agglomerates determine the dominant experimental result. This report examines a variety of instrumental techniques for surveying the colloidal stability of aqueous suspensions of silver nanoparticles (AgNPs), including atomic force microscopy, dynamic light scattering, and colorimetry. It was found that colorimetry can adequately determine the concentration of single AgNPs that remained in solution if morphological information about agglomerates is not required. The colloidal stability of AgNPs with various surface capping agents and in various solvents ranging from cell culture media to different electrolytes of several concentrations, and in different pH conditions was determined. It was found that biocompatible bulky capping agents, such as bovine serum albumin or starch, that provided steric colloidal stabilization, as opposed to purely electrostatic stabilization such as with citrate AgNPs, provided better retention of single AgNPs in solution over a variety of conditions for up to 64 h of observation.

  6. Laser ablation studies of Deposited Silver Colloids Active in SERS

    International Nuclear Information System (INIS)

    La Porte, R.T.; Moreno, D.S.; Striano, M.C.; Munnoz, M.M.; Garcia-Ramos, J.V.; Cortes, S.S.; Koudoumas, E.

    2002-01-01

    Laser ablation of deposited silver colloids, active in SERS, is carried out at three different laser wavelengths (KrF, XeCl and Nd:YAG at λ = 248, 308 and 532 nm respectively). Emission form excited neutral Ag and Na atoms, present in the ablation plume, is detected with spectral and temporal resolution. The expansion velocity of Ag in the plume is estimated in ∼1x104m s-1, Low-fluence laser ablation of the colloids yields ionized species that are analyzed by time-of-flight mass spectroscopy. Na+ and Agn+(n≤3) are observed. Composition of the mass spectra and widths of the mass peaks are found to be dependent on laser wavelength, suggesting that the dominant ablation mechanisms are different at the different wavelenghts.

  7. [MAXIMUM SINGLE DOSE OF COLLOIDAL SILVER NEGATIVELY AFFECTS ERYTHROPOIESIS IN VITRO].

    Science.gov (United States)

    Tishevskayal, N V; Zakharovl, Y M; Bolotovl, A A; Arkhipenko, Yu V; Sazontova, T G

    2015-01-01

    Erythroblastic islets (EI) of rat bone marrow were cultured for 24 h in the presence of silver nanoparticles (1.07 · 10(-4) mg/ml; 1.07 · 10(-3) mg/ml; and 1.07 · 10(-2) mg/mL). The colloidal silver at 1.07 · 10(-3) mg/ml concentration inhibited the formation of new Elby disrupting contacts of bone marrow macrophages with CFU-E (erythropoiesis de novo) by 65.3% (p Colloidal silver nanoparticles suppressed the reconstruction of erythropoiesis and inhibited the formation of new EI by disrupting contacts of CFU-E and central macrophages with matured erythroidal "crown" (erythropoiesis de repeto). The colloidal silver concentration of 1.07 · 10(-3) mg/ml in the culture medium also reduced the number of self-reconstructing EI by 67.5% (p colloidal silver reduced this value by 93.7% (p Silver nanoparticles retarded maturation of erythroid cells at the stage of oxiphylic normoblast denucleation: 1.07 · 10(-3) mg/ml colloidal silver increased the number of mature El by 53% (p colloidal silver in concentration equivalent to the maximum single dose is related to the effect of silver nanoparticles rather than glycerol present in the colloidal suspension.

  8. An evaluation of acute toxicity of colloidal silver nanoparticles.

    Science.gov (United States)

    Maneewattanapinyo, Pattwat; Banlunara, Wijit; Thammacharoen, Chuchaat; Ekgasit, Sanong; Kaewamatawong, Theerayuth

    2011-11-01

    Tests for acute oral toxicity, eye irritation, corrosion and dermal toxicity of colloidal silver nanoparticles (AgNPs) were conducted in laboratory animals following OECD guidelines. Oral administration of AgNPs at a limited dose of 5,000 mg/kg produced neither mortality nor acute toxic signs throughout the observation period. Percentage of body weight gain of the mice showed no significant difference between control and treatment groups. In the hematological analysis, there was no significant difference between mice treated with AgNPs and controls. Blood chemistry analysis also showed no differences in any of the parameter examined. There was neither any gross lesion nor histopathological change observed in various organs. The results indicated that the LD(50) of colloidal AgNPs is greater than 5,000 mg/kg body weight. In acute eye irritation and corrosion study, no mortality and toxic signs were observed when various doses of colloidal AgNPs were instilled in guinea pig eyes during 72 hr observation period. However, the instillation of AgNPs at 5,000 ppm produced transient eye irritation during early 24 hr observation time. No any gross abnormality was noted in the skins of the guinea pigs exposed to various doses of colloidal AgNPs. In addition, no significant AgNPs exposure relating to dermal tissue changes was observed microscopically. In summary, these findings of all toxicity tests in this study suggest that colloidal AgNPs could be relatively safe when administered to oral, eye and skin of the animal models for short periods of time.

  9. Production of silver ions from colloidal silver by nanoparticle iontophoresis system.

    Science.gov (United States)

    Tseng, Kuo-Hsiung; Liao, Chih-Yu

    2011-03-01

    Metal ions, especially the silver ion, were used to treat infection before the initiation of antibiotic therapy. Unfortunately, there is a lack of research on the metallic nanoparticle suspension as a reservoir for metal ion release application. For medical purposes, conversion of colloidal silver into an ionic form is necessary, but not using silver salts (e.g., AgNO3, Ag2SO4), due to the fact that the counter-ion of silver salts may cause problems to the body as the silver ion (Ag+) is consumed. The goal of this research is to develop a silver nanoparticle iontophoresis system (NIS) which can provide a relatively safe bactericidal silver ion solution with a controllable electric field. In this study, ion-selective electrodes were used to identify and observe details of the system's activity. Both qualitative and quantitative data analyses were performed. The experimental results show that the ion releasing peak time (R(PT)) has an inversely proportional relationship with the applied current and voltage. The ion releasing maximum level (R(ML)) and dosage (R(D)) are proportional to the current density and inversely proportional to the voltage, respectively. These results reveal that the nanoparticle iontophoresis system (NIS) is an alternative method for the controlled release of a metal ion and the ion's concentration profile, by controlling the magnitude of current density (1 microA/cm2 equal to 1 ppm/hour) and applied voltage.

  10. Powerful colloidal silver nanoparticles for the prevention of gastrointestinal bacterial infections

    International Nuclear Information System (INIS)

    Le, Anh-Tuan; Le, Thi Tam; Nguyen, Van Quy; Tran, Huy Hoang; Dang, Duc Anh; Tran, Quang Huy; Vu, Dinh Lam

    2012-01-01

    In this work we have demonstrated a powerful disinfectant ability of colloidal silver nanoparticles (NPs) for the prevention of gastrointestinal bacterial infections. The silver NPs colloid was synthesized by a UV-enhanced chemical precipitation. Two gastrointestinal bacterial strains of Escherichia coli (ATCC 43888-O157:k-:H7) and Vibrio cholerae (O1) were used to verify the antibacterial activity of the as-prepared silver NPs colloid by means of surface disinfection assay in agar plates and turbidity assay in liquid media. Transmission electron microscopy was also employed to analyze the ultrastructural changes of bacterial cells caused by silver NPs. Noticeably, our silver NPs colloid displayed a highly effective bactericidal effect against two tested gastrointestinal bacterial strains at a silver concentration as low as ∼3 mg l −1 . More importantly, the silver NPs colloid showed an enhancement of antibacterial activity and long-lasting disinfectant effect as compared to conventional chloramin B (5%) disinfection agent. These advantages of the as-prepared colloidal silver NPs make them very promising for environmental treatments contaminated with gastrointestinal bacteria and other infectious pathogens. Moreover, the powerful disinfectant activity of silver-containing materials can also help in controlling and preventing further outbreak of diseases. (paper)

  11. Colloidal silver fabrication using the spark discharge system and its antimicrobial effect on Staphylococcus aureus.

    Science.gov (United States)

    Tien, Der-Chi; Tseng, Kuo-Hsiung; Liao, Chih-Yu; Tsung, Tsing-Tshih

    2008-10-01

    Nanoscale techniques for silver production may assist the resurgence of the medical use of silver, especially given that pathogens are showing increasing resistance to antibiotics. Traditional chemical synthesis methods for colloidal silver (CS) may lead to the presence of toxic chemical species or chemical residues, which may inhibit the effectiveness of CS as an antibacterial agent. To counter these problems a spark discharge system (SDS) was used to fabricate a suspension of colloidal silver in deionized water with no added chemical surfactants. SDS-CS contains both metallic silver nanoparticles (Ag(0)) and ionic silver forms (Ag(+)). The antimicrobial affect of SDS-CS on Staphylococcus aureus was studied. The results show that CS solutions with an ionic silver concentration of 30 ppm or higher are strong enough to destroy S. aureus. In addition, it was found that a solution's antimicrobial potency is directly related to its level of silver ion concentration.

  12. A case of generalized argyria after ingestion of colloidal silver solution.

    Science.gov (United States)

    Kim, Yangho; Suh, Ho Seok; Cha, Hee Jeong; Kim, Suk Hwan; Jeong, Kyoung Sook; Kim, Dong Hoon

    2009-03-01

    A 58-year-old woman was referred to our hospital due to progressive skin darkening, which began 5 months previously. The patient had strikingly diffuse blue-gray discoloration of the skin, most prominent in sun-exposed areas, especially her face and hands. The oral mucosa, tongue, gums, eye conjunctiva, ears, nail beds, and trunk were also involved. Bluish-gray discoloration of all nails was aggravated by cold weather. She had ingested 1 L of colloidal silver solution daily for approximately 16 months as a traditional remedy. Her serum silver concentration was 381 ng/ml which was a very high (reference level: silver and sulfur in the dense black deposits. The ingestion of colloidal silver appears to be an increasing practice among patients using alternative health practices. All silver-containing products including colloidal silver should be labeled with a clear warning to prevent argyria, especially in alternative health practices.

  13. Colloid bands in silver chloride induced by reactor irradiation at low temperature

    International Nuclear Information System (INIS)

    Atobe, K.; Okada, M.; Nakagawa, M.

    1978-01-01

    It is well known that no trapped electron center exists stably in irradiated silver chlorides even at low temperatures. On the other hand, irradiation by ultra-violet light at room temperature produces a broad absorption (colloid bands) on the long wavelength side of the fundamental absorption. In this report, it is shown that one of the colloid bands appears in undoped AgCl crystals by reactor irradiation at low temperature (20 K) and the other colloid band by thermal annealing after the irradiation. The relation between the bands, which correspond to two types of colloidal silver, is represented. (author)

  14. Controlled synthesis of colloidal silver nanoparticles in capillary micro-flow reactor

    International Nuclear Information System (INIS)

    He Shengtai; Liu Yulan; Maeda, Hideaki

    2008-01-01

    In this study, using a polytetrafluoroethylene (PTFE) capillary tube as a micro-flow reactor, well-dispersed colloidal silver nanoparticles were controllably synthesized with different flow rates of precursory solution. Scanning transmission electron microscopy images and UV-visible absorbance spectra showed that silver nanoparticles with large size can be prepared with slow flow rate in the PTFE capillary reactor. The effects of tube diameters on the growth of colloidal silver nanoparticles were investigated. Experiment results demonstrated that using tube with small diameter was more propitious for the controllable synthesis of silver nanoparticles with different sizes.

  15. Investigation of antibacterial activity of cotton fabric incorporating nano silver colloid

    International Nuclear Information System (INIS)

    Ngo Vo Ke Thanh; Nguyen Thi Phuong Phong

    2009-01-01

    In this work, silver nanoparticles were prepared by polyol process with microwave heating and incorporated on cotton fabric surfaces. The antibacterial performance of the antibacterial cotton fabric was tested for different concentration of nano-sized silver colloid, contact time germs, and washing times. It was found that antibacterial activity increased with the increasing concentration of nano-sized silver colloid. The antibacterial fabric with 758 mg/kg of silver nanoparticles on surface cotton was highly effective in killing test bacteria and had excellent water resisting property.

  16. Source of cytotoxicity in a colloidal silver nanoparticle suspension.

    Science.gov (United States)

    Hatipoglu, Manolya Kukut; Keleştemur, Seda; Altunbek, Mine; Culha, Mustafa

    2015-05-15

    Silver nanoparticles (AgNPs) are increasingly used in a variety of applications because of their potential antimicrobial activity and their plasmonic and conductivity properties. In this study, we investigated the source of cytotoxicity, genotoxicity, and reactive oxygen species (ROS) production on human dermal fibroblast and human lung cancer (A549) cell lines upon exposure to AgNP colloidal suspensions prepared with the simplest and most commonly used Lee–Meisel method with a variety of reaction times and the concentrations of the reducing agent. The AgNPs synthesized with shorter reaction times were more cytotoxic and genotoxic due to the presence of a few nanometer-sized AgNP seeds. The suspensions prepared with an increased citrate concentration were not cytotoxic, but they induced more ROS generation on A549 cells due to the high citrate concentration. The genotoxicity of the suspension decreased significantly at the higher citrate concentrations. The analysis of both transmission electron microscopy images from the dried droplet areas of the colloidal suspensions and toxicity data indicated that the AgNP seeds were the major source of toxicity. The completion of the nucleation step and the formation of larger AgNPs effectively decreased the toxicity.

  17. Colloidal complexed silver and silver nanoparticles in extrapallial fluid of Mytilus edulis.

    Science.gov (United States)

    Zuykov, Michael; Pelletier, Emilien; Demers, Serge

    2011-02-01

    Metal transport in mollusk extrapallial fluid (EPF) that acts as a "bridge" between soft tissues and shell has surprisingly received little attention until now. Using ultrafiltration and radiotracer techniques we determined silver concentrations and speciation in the EPF of the blue mussel Mytilus edulis after short-term uptake and depuration laboratory experiments. Radiolabelled silver ((¹¹⁰m)Ag) was used in dissolved or nanoparticulate phases (AgNPs silver nanoparticles were transported to the EPF of blue mussels at a level similar to the Ag ionic form. Bulk activity of radiolabelled silver in the EPF represented only up to 7% of the bulk activity measured in the whole mussels. The EPF extracted from mussels exposed to both treatments exhibited an Ag colloidal complexed form based on EPF ultrafiltration through a 3 kDa filter. This original study brings new insights to internal circulation of nanoparticles in living organisms and contributes to the international effort in studying the potential impacts of engineered nanomaterials on marine bivalves which play an essential role in coastal ecosystems, and are important contributors to human food supply from the sea. © 2010 Elsevier Ltd. All rights reserved.

  18. Antitumor activity of colloidal silver on MCF-7 human breast cancer cells.

    Science.gov (United States)

    Franco-Molina, Moisés A; Mendoza-Gamboa, Edgar; Sierra-Rivera, Crystel A; Gómez-Flores, Ricardo A; Zapata-Benavides, Pablo; Castillo-Tello, Paloma; Alcocer-González, Juan Manuel; Miranda-Hernández, Diana F; Tamez-Guerra, Reyes S; Rodríguez-Padilla, Cristina

    2010-11-16

    Colloidal silver has been used as an antimicrobial and disinfectant agent. However, there is scarce information on its antitumor potential. The aim of this study was to determine if colloidal silver had cytotoxic effects on MCF-7 breast cancer cells and its mechanism of cell death. MCF-7 breast cancer cells were treated with colloidal silver (ranged from 1.75 to 17.5 ng/mL) for 5 h at 37°C and 5% CO2 atmosphere. Cell Viability was evaluated by trypan blue exclusion method and the mechanism of cell death through detection of mono-oligonucleosomes using an ELISA kit and TUNEL assay. The production of NO, LDH, and Gpx, SOD, CAT, and Total antioxidant activities were evaluated by colorimetric assays. Colloidal silver had dose-dependent cytotoxic effect in MCF-7 breast cancer cells through induction of apoptosis, shown an LD50 (3.5 ng/mL) and LD100 (14 ng/mL) (*P colloidal silver. The present results showed that colloidal silver might be a potential alternative agent for human breast cancer therapy.

  19. ANTIOXIDANT AND ANTIMICROBIAL PROPERTIES OF STEVIA LEAVES EXTRACTS AND SILVER NANOPARTICLES COLLOIDS

    Directory of Open Access Journals (Sweden)

    Iryna Laguta

    2016-12-01

    Full Text Available Three extracts of Stevia rebaudiana (Bertoni were prepared using various types of raw materials: leaves of plants grown ex situ, leaves of plants grown in vitro, callus culture formed on damaged leaves. Composition of the extracts, their activity in the synthesis of silver nanoparticles colloids, as well as antioxidant and antimicrobial properties of the extracts and the colloids were investigated.

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

    Science.gov (United States)

    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.

  1. Oral toxicity of silver ions, silver nanoparticles and colloidal silver – a review

    DEFF Research Database (Denmark)

    Hadrup, Niels; Lam, Henrik Rye

    2014-01-01

    Orally administered silver has been described to be absorbed in a range of 0.4-18% in mammals with a human value of 18%. Based on findings in animals, silver seems to be distributed to all of the organs investigated, with the highest levels being observed in the intestine and stomach. In the skin......, silver induces a blue-grey discoloration termed argyria. Excretion occurs via the bile and urine. The following dose-dependent animal toxicity findings have been reported: death, weight loss, hypoactivity, altered neurotransmitter levels, altered liver enzymes, altered blood values, enlarged hearts...... and immunological effects. Substantial evidence exists suggesting that the effects induced by particulate silver are mediated via silver ions that are released from the particle surface. With the current data regarding toxicity and average human dietary exposure, a Margin of Safety calculation indicates at least...

  2. Sweet Nanochemistry: A Fast, Reliable Alternative Synthesis of Yellow Colloidal Silver Nanoparticles Using Benign Reagents

    Science.gov (United States)

    Cooke, Jason; Hebert, Dominique; Kelly, Joel A.

    2015-01-01

    This work describes a convenient and reliable laboratory experiment in nanochemistry that is flexible and adaptable to a wide range of educational settings. The rapid preparation of yellow colloidal silver nanoparticles is achieved by glucose reduction of silver nitrate in the presence of starch and sodium citrate in gently boiling water, using…

  3. Eco-friendly synthesis of colloidal silver nanospheres, nanorings and nanonetworks

    NARCIS (Netherlands)

    Singh, A.K.; Rai, A.K.; Bicanic, D.D.

    2009-01-01

    Colloidal silver nanospheres, nanorings, and nanonetworks were synthesized by the nanosecond pulsed laser ablation of a silver metal plate in a pure distilled water (at room temperature) using the fundamental (1064 nm), second harmonic (532 nm), and third harmonic (355 nm) wavelengths of the Nd:YAG

  4. The electrochemical reduction rate of colloidal particles of silver halides as a function of the electrolyte composition

    International Nuclear Information System (INIS)

    Selivanov, V.N.

    1997-01-01

    Influence of silver halide colloid particles concentration (AgI), electrolyte composition and signs of the electrode and colloids charges on their reduction threshold current densities has been studied. It has been discovered that reduction threshold current densities of positively charged colloid particles exceed by a factor of 3-4 the threshold densities of silver ions diffusion current. It is shown that the threshold density of colloids reduction current is limited by the rates of their electrophoretic transfer and diffusion

  5. Studies on the antimicrobial properties of colloidal silver nanoparticles stabilized by bovine serum albumin.

    Science.gov (United States)

    Mathew, Thomas V; Kuriakose, Sunny

    2013-01-01

    Colloidal silver nanoparticles were synthesised using sol-gel method and these nanoparticles were stabilised by encapsulated into the scaffolds of bovine serum albumin. Silver nanoparticles and encapsulated products were characterised by FTIR, NMR, XRD, TG, SEM and TEM analyses. Silver nanoparticle encapsulated bovine serum albumin showed highly potent antibacterial activity towards the bacterial strains such as Staphylococcus aureus, Serratia marcescens, Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Characterization samples of Tigris river water treated with nano colloidal silver (physically, chemically, microbiologically)

    International Nuclear Information System (INIS)

    Dumboos, H. I.; Beden, S. J.; Zouari, K.; Chkir, N.; Ahmed, H. A.

    2012-12-01

    Many researches of using nano silver in purification of drinking water from bacteria and its effect on stan dared properties as drinking water were established. Two stages accomplished in these projects. First stage include preparation of colloidal silver with characterization process and prepare water samples through sedimentation, filtration process, PH and turbidity measure then treated with colloidal silver in volume ratio (0.1-Λ) ml/100ml. The second stage represent select the better results from stage one and take samples to determine the standard characterization values with chemical, physical and microbiological taste. Results will be compared with Iraq standard certification. (Author)

  7. Low molecular weight compounds as effective dispersing agents in the formation of colloidal silver nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Natsuki, Jun; Natsuki, Toshiaki, E-mail: natsuki@shinshu-u.ac.jp; Abe, Takao [Shinshu University, Faculty of Textile Science and Technology (Japan)

    2013-03-15

    A convenient method to synthesize uniform, well-dispersed colloidal silver nanoparticles is described. Aldonic acid or {alpha}-hydroxy acid compounds of low molecular weight are used instead of polymeric compounds as dispersing agents to prepare silver nanoparticles. The size, conformation, and electrical conductivity of the silver nanoparticles, and the effect and function of the dispersing agents are investigated in detail. Using these low molecular weight compounds as dispersing agents, silver nanoparticles with a diameter of 10 nm or less and high electrical conductivity can be obtained. In addition, this procedure allows silver nanoparticles to be sintered at 150 Degree-Sign C, which is lower than that required for silver nanoparticle formulation using polymeric compounds (200 Degree-Sign C). The silver nanoparticles produced by this process can be used to prepare various inks and to manufacture electronic circuits. It is found that low molecular weight compounds are more effective dispersing agents than polymeric compounds in the formation of silver nanoparticles.

  8. Colloidal Photonic Crystals Containing Silver Nanoparticles with Tunable Structural Colors

    Directory of Open Access Journals (Sweden)

    Chun-Feng Lai

    2016-05-01

    Full Text Available Polystyrene (PS colloidal photonic crystals (CPhCs containing silver nanoparticles (AgNPs present tunable structural colors. PS CPhC color films containing a high concentration of AgNPs were prepared using self-assembly process through gravitational sedimentation method. High-concentration AgNPs were deposited on the bottom of the substrate and acted as black materials to absorb background and scattering light. Brilliant structural colors were enhanced because of the absorption of incoherent scattering light, and color saturation was increased by the distribution AgNPs on the PS CPhC surfaces. The vivid iridescent structural colors of AgNPs/PS hybrid CPhC films were based on Bragg diffraction and backward scattering absorption using AgNPs. The photonic stop band of PS CPhCs and AgNPs/PS hybrid CPhCs were measured by UV–visible reflection spectrometry and calculated based on the Bragg–Snell law. In addition, the tunable structural colors of AgNPs/PS hybrid CPhC films were evaluated using color measurements according to the Commission International d’Eclairage standard colorimetric system. This paper presents a simple and inexpensive method to produce tunable structural colors for numerous applications, such as textile fabrics, bionic colors, catalysis, and paints.

  9. A concetration-dependent model for silver colloids in nanostructured sol-gel materials

    Science.gov (United States)

    Garcia-Macedo, Jorge A.; Franco, Alfredo; Renteria, Victor; Valverde-Aguilar, Guadalupe

    2005-08-01

    We report on the physical modelling of the photoconductive response of nanostructured sol-gel films in function of the silver nitrate concentration (ions and colloids). This model considers several factors as the silver nitrate concentration and the transport parameters obtained. The model is compared with others commonly used. 2d-hexagonal nanostructured sol-gel thin films were prepared by dip-coating method using a non-ionic diblock copolymer Brij58 (surfactant) to produce channels into the film. Silver colloids (metallic Ag0 nanoparticles ) were obtained by spontaneous reduction process of Ag+ ions to Ag0. These nanoparticles were deposited into the channels formed by the surfactant. The structure was identified by X-ray diffraction and TEM. An absorption band located at 430 nm was detected by optical absorption; it corresponds to the plasmon surface. Fit to this band with modified Gans theory is presented. Photoconductivity studies were performed on films with silver ions and films with silver colloids to characterized their mechanisms of charge transport in the darkness and under illumination at 420, 633 nm wavelengths. Transport parameters were calculated. The films with silver colloids exhibit a photovoltaic effect stronger than the films with silver ions. While, the last ones possesses a photoconductivity behaviour.

  10. Oral toxicity of silver ions, silver nanoparticles and colloidal silver--a review.

    Science.gov (United States)

    Hadrup, Niels; Lam, Henrik R

    2014-02-01

    Orally administered silver has been described to be absorbed in a range of 0.4-18% in mammals with a human value of 18%. Based on findings in animals, silver seems to be distributed to all of the organs investigated, with the highest levels being observed in the intestine and stomach. In the skin, silver induces a blue-grey discoloration termed argyria. Excretion occurs via the bile and urine. The following dose-dependent animal toxicity findings have been reported: death, weight loss, hypoactivity, altered neurotransmitter levels, altered liver enzymes, altered blood values, enlarged hearts and immunological effects. Substantial evidence exists suggesting that the effects induced by particulate silver are mediated via silver ions that are released from the particle surface. With the current data regarding toxicity and average human dietary exposure, a Margin of Safety calculation indicates at least a factor of five before a level of concern to the general population is reached. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. Localized surface plasmon resonance enhanced photoluminescence of CdSe QDs in PMMA matrix on silver colloids with different shapes

    International Nuclear Information System (INIS)

    Lu Liu; Xu Xiaoliang; Shi Chaoshu; Ming Hai

    2010-01-01

    Localized surface plasmon resonance (LSPR) enhanced photoluminescences (PL) from CdSe quantum dots (QDs) on worm-like or quasi-spherical silver colloids have been investigated. The shape of silver colloid film is controlled by annealing temperature (200 o C∼350 o C). Strong PL enhancements of CdSe QDs on both as-grown and annealed silver colloid films are observed. The results show that the PL enhancement factor of CdSe QDs on worm-like silver colloid film reaches as high as 15-fold. Moreover, the enhancement factor is 5 times larger than that obtained from the quasi-spherical silver colloids. The superiority of worm-like silver nanostructure on LSPR enhanced photoluminescence is attributed to its larger size, hot spots and multiple dipole resonance modes coupling, which are induced by aggregation effect.

  12. A Study of Antibioactivity of Nanosilver Colloid and Silver Ion Solution

    Directory of Open Access Journals (Sweden)

    Kuo-Hsiung Tseng

    2014-01-01

    Full Text Available The colloidal silver solution was successfully prepared in dielectric fluid by using electrical spark discharge (ESD without any surfactants. It does not require the toxic chemical agents in the process, which may affect the effectiveness of nanosilver colloid as an antibacterial agent. Nanocolloidal silver produced by ESD is characterized as low cost, zero environmental pollution, continuous, and rapid mass production process. In order to test the effect of antibioactivity, nanosilver dough was tested; the silver nanofluid was prepared by ESD machine, made into dough at different concentrations, and fermented for three hours in order to observe changes in the diameter of the dough. The results showed that the effect of effectiveness of nanosilver at the concentration of 100 ppm was weak, whereas the effect of 60 ppm silver ion (100 ppm AgNO3 was significant, as the dissociation rate of silver ion concentration correlates to the antibioactivity.

  13. Green synthesis of highly concentrated aqueous colloidal solutions of large starch-stabilised silver nanoplatelets.

    Science.gov (United States)

    Cheng, Fei; Betts, Jonathan W; Kelly, Stephen M; Hector, Andrew L

    2015-01-01

    A simple, environmentally friendly and cost-effective method has been developed to prepare a range of aqueous silver colloidal solutions, using ascorbic acid as a reducing agent, water-soluble starch as a combined crystallising, stabilising and solubilising agent, and water as the solvent. The diameter of silver nanoplatelets increases with higher concentrations of AgNO3 and starch. The silver nanoparticles are also more uniform in shape the greater the diameter of the nanoparticles. Colloidal solutions with a very high concentration of large, flat, hexagonal silver nanoplatelets (~230 nm in breadth) have been used to deposit and fix an antibacterial coating of these large starch-stabilised silver nanoplates on commercial cotton fibres, using a simple dip-coating process using water as the solvent, in order to study the dependence of the antibacterial properties of these nanoplatelets on their size. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. [Morphological changes of the intestine in experimental acute intestinal infection in the treatment of colloidal silver].

    Science.gov (United States)

    Polov'ian, E S; Chemich, N D; Moskalenko, R A; Romaniuk, A N

    2012-06-01

    At the present stage of infectionist practice in the treatment of acute intestinal infections caused by opportunistic microorganisms, colloidal silver is used with a particle size of 25 nm as an alternative to conventional causal therapy. In 32 rats, distributed in 4 groups of 8 animals each (intact; healthy, got colloidal silver; with a modeled acute intestinal infection in the basic treatment and with the addition of colloidal silver), histological examination was performed of small and large intestine of rats. Oral administration of colloidal silver at a dose of 0.02 mg/day to intact rats did not lead to changes in morphometric parameters compared to the norm, and during early convalescence in rats with acute intestinal infections were observed destructive and compensatory changes in the intestine, which depended on the treatment regimen. With the introduction of colloidal silver decreased activity of the inflammatory process and the severity of morphological changes in tissues of small and large intestine, indicating that the positive effect of study drug compared with baseline therapy.

  15. Antitumor activity of colloidal silver on MCF-7 human breast cancer cells

    Directory of Open Access Journals (Sweden)

    Franco-Molina Moisés A

    2010-11-01

    Full Text Available Abstract Background Colloidal silver has been used as an antimicrobial and disinfectant agent. However, there is scarce information on its antitumor potential. The aim of this study was to determine if colloidal silver had cytotoxic effects on MCF-7 breast cancer cells and its mechanism of cell death. Methods MCF-7 breast cancer cells were treated with colloidal silver (ranged from 1.75 to 17.5 ng/mL for 5 h at 37°C and 5% CO2 atmosphere. Cell Viability was evaluated by trypan blue exclusion method and the mechanism of cell death through detection of mono-oligonucleosomes using an ELISA kit and TUNEL assay. The production of NO, LDH, and Gpx, SOD, CAT, and Total antioxidant activities were evaluated by colorimetric assays. Results Colloidal silver had dose-dependent cytotoxic effect in MCF-7 breast cancer cells through induction of apoptosis, shown an LD50 (3.5 ng/mL and LD100 (14 ng/mL (*P Conclusions The present results showed that colloidal silver might be a potential alternative agent for human breast cancer therapy.

  16. SERS and DFT study of p-hydroxybenzoic acid adsorbed on colloidal silver particles.

    Science.gov (United States)

    Chen, Y; Chen, S J; Li, S; Wei, J J

    2015-10-16

    In this study, normal Raman spectra of p—hydroxybenzoic acid (PHBA) powder and its surface—enhanced Raman scattering (SERS) spectra in silver colloidal solutions were measured under near infrared excitation conditions. In theoretical calculation, two models of PHBA adsorbed on the surfaces of silver nanoparticles were established. The Raman frequencies of these two models using density functional theory (DFT) method were calculated, and compared with the experimental results. It was found that the calculated Raman frequencies were in good agreement with experimental values, which indicates that there are two enhanced mechanism physical (electromagnetic, EM) enhancement and chemical (charge—transfer, CT) enhancement, in silver colloidal solutions regarding SERS effect. Furthermore, from high—quality SERS spectrum of PHBA obtained in silver colloids, we inferred that PHBA molecules in silver colloids adsorb onto the metal surfaces through carboxyl at a perpendicular orientation. The combination of SERS spectra and DFT calculation is thus useful for studies of the adsorption—orientation of a molecule on a metal colloid.

  17. Sustainable colloidal-silver-impregnated ceramic filter for point-of-use water treatment.

    Science.gov (United States)

    Oyanedel-Craver, Vinka A; Smith, James A

    2008-02-01

    Cylindrical colloidal-silver-impregnated ceramic filters for household (point-of-use) water treatment were manufactured and tested for performance in the laboratory with respect to flow rate and bacteria transport. Filters were manufactured by combining clay-rich soil with water, grog (previously fired clay), and flour, pressing them into cylinders, and firing them at 900 degrees C for 8 h. The pore-size distribution of the resulting ceramic filters was quantified by mercury porosimetry. Colloidal silver was applied to filters in different quantities and ways (dipping and painting). Filters were also tested without any colloidal-silver application. Hydraulic conductivity of the filters was quantified using changing-head permeability tests. [3H]H2O water was used as a conservative tracer to quantify advection velocities and the coefficient of hydrodynamic dispersion. Escherichia coli (E. coli) was used to quantify bacterial transport through the filters. Hydraulic conductivity and pore-size distribution varied with filter composition; hydraulic conductivities were on the order of 10(-5) cm/s and more than 50% of the pores for each filter had diameters ranging from 0.02 to 15 microm. The filters removed between 97.8% and 100% of the applied bacteria; colloidal-silver treatments improved filter performance, presumably by deactivation of bacteria. The quantity of colloidal silver applied per filter was more important to bacteria removal than the method of application. Silver concentrations in effluent filter water were initially greater than 0.1 mg/L, but dropped below this value after 200 min of continuous operation. These results indicate that colloidal-silver-impregnated ceramic filters, which can be made using primarily local materials and labor, show promise as an effective and sustainable point-of-use water treatment technology for the world's poorest communities.

  18. A general method for synthesis continuous silver nanoshells on dielectric colloids

    International Nuclear Information System (INIS)

    Chen Dong; Liu Huiyu; Liu Jianshu; Ren Xianglin; Meng Xianwei; Wu Wei; Tang Fangqiong

    2008-01-01

    A method for the controlled synthesis of silver nanoshells on various dielectric colloids, such as silica and polystyrene is presented in this study. The complexation of triethanolamine and silver ions is applied here to moderate the availability of the silver ions in the reaction solution, which directly affect the coating process. The morphologies of the particles were studied with transmission electron microscopy and their crystallinity and chemical composition were confirmed by X-ray and electron diffraction. The synthesis conditions were investigated and experimental results show that compact silver shells with easily controlled thickness can be deposited on dielectric cores by this method

  19. [A clinical study of gelatamp colloidal silver gelatin sponge on preventing the complication of teeth extraction].

    Science.gov (United States)

    Cai, Yong-hai; Lu, Chang-shou

    2008-10-01

    To study the clinical effect of Gelatamp colloidal silver gelatin sponge on preventing the complication of teeth extraction. 672 teeth were divided into experimental group and control group semi-randomly. All teeth were extracted after local anesthesia and sockets were cleaned. Gelatamp colloidal silver gelatin sponge was implanted into socket in experimental group and nothing was implanted into alveolar socket in control group. The complication of teeth extraction was observed on 0.5 h, 2 d and 7 d after extraction. The incidence rate of complication was calculated. The incidence rate of complication of teeth extraction in experimental group was 7.72%, which was lower than that of control group (24.43%). There was significant difference in the incidence rates of complication between experimental group and control group (P colloidal silver gelatin sponge can prevent the occurrence of complication of teeth extraction, this can be used in clinic.

  20. Continuous synthesis of colloidal silver nanoparticles by electrochemical discharge in aqueous solutions

    International Nuclear Information System (INIS)

    Tseng, Kuo-Hsiung; Chen, Yu-Chun; Shyue, Jing-Jong

    2011-01-01

    This article presents an electrochemical discharge (ECD) method that consists of a combination of chemical methods and electric arc discharges. In the method, 140 V is applied to an Ag electrode from a DC power supply. The arc-discharge between the electrodes produces metallic silver nanoparticles and silver ions in the aqueous solution. Compared with the original arc discharge, this ECD method creates smaller nanoparticles, prevents clumping of the nanoparticles, and shortens the production time. The citrate ions also reduce the silver ions to silver nanoparticles. In addition, the citrate ions cap the surface of the produced silver nanoparticles and the zeta potential increases. In this article, the weight loss of the electrodes and the reduction of silver ions to silver nanoparticles as a function of citrate concentration and electric conductivity of the medium are discussed. Furthermore, the properties of the colloidal silver prepared with ECD are analyzed by UV–Vis spectroscopy, dynamic light scattering, electrophoresis light scattering, and scanning electron microscopy. Finally, a continuous production apparatus is presented for the continuous production of colloidal silver.

  1. A novel 'green' synthesis of colloidal silver nanoparticles (SNP) using Dillenia indica fruit extract.

    Science.gov (United States)

    Singh, Susmita; Saikia, Jyoti P; Buragohain, Alak K

    2013-02-01

    In the present research we have defined a novel green method of silver nanoparticles synthesis using Dillenia indica fruit extract. D. indica is an edible fruit widely distributed in the foothills of Himalayas and known for its antioxidant and further predicted for cancer preventive potency. The maximum absorbance of the colloidal silver nanoparticle solution was observed at 421 nm when examined with UV-vis spectrophotometer. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Air-stable n-type colloidal quantum dot solids

    KAUST Repository

    Ning, Zhijun; Voznyy, Oleksandr; Pan, Jun; Hoogland, Sjoerd H.; Adinolfi, Valerio; Xu, Jixian; Li, Min; Kirmani, Ahmad R.; Sun, Jonpaul; Minor, James C.; Kemp, Kyle W.; Dong, Haopeng; Rollny, Lisa R.; Labelle, André J.; Carey, Graham H.; Sutherland, Brandon R.; Hill, Ian G.; Amassian, Aram; Liu, Huan; Tang, Jiang; Bakr, Osman; Sargent, E. H.

    2014-01-01

    Colloidal quantum dots (CQDs) offer promise in flexible electronics, light sensing and energy conversion. These applications rely on rectifying junctions that require the creation of high-quality CQD solids that are controllably n-type (electron-rich) or p-type (hole-rich). Unfortunately, n-type semiconductors made using soft matter are notoriously prone to oxidation within minutes of air exposure. Here we report high-performance, air-stable n-type CQD solids. Using density functional theory we identify inorganic passivants that bind strongly to the CQD surface and repel oxidative attack. A materials processing strategy that wards off strong protic attack by polar solvents enabled the synthesis of an air-stable n-type PbS CQD solid. This material was used to build an air-processed inverted quantum junction device, which shows the highest current density from any CQD solar cell and a solar power conversion efficiency as high as 8%. We also feature the n-type CQD solid in the rapid, sensitive, and specific detection of atmospheric NO2. This work paves the way for new families of electronic devices that leverage air-stable quantum-tuned materials. © 2014 Macmillan Publishers Limited. All rights reserved.

  3. Air-stable n-type colloidal quantum dot solids

    KAUST Repository

    Ning, Zhijun

    2014-06-08

    Colloidal quantum dots (CQDs) offer promise in flexible electronics, light sensing and energy conversion. These applications rely on rectifying junctions that require the creation of high-quality CQD solids that are controllably n-type (electron-rich) or p-type (hole-rich). Unfortunately, n-type semiconductors made using soft matter are notoriously prone to oxidation within minutes of air exposure. Here we report high-performance, air-stable n-type CQD solids. Using density functional theory we identify inorganic passivants that bind strongly to the CQD surface and repel oxidative attack. A materials processing strategy that wards off strong protic attack by polar solvents enabled the synthesis of an air-stable n-type PbS CQD solid. This material was used to build an air-processed inverted quantum junction device, which shows the highest current density from any CQD solar cell and a solar power conversion efficiency as high as 8%. We also feature the n-type CQD solid in the rapid, sensitive, and specific detection of atmospheric NO2. This work paves the way for new families of electronic devices that leverage air-stable quantum-tuned materials. © 2014 Macmillan Publishers Limited. All rights reserved.

  4. Stability of colloidal silver nanoparticles trapped in lipid bilayer: effect of lecithin concentration and applied temperature.

    Science.gov (United States)

    Barani, Hossein; Montazer, Majid; Braun, Hans-Georg; Dutschk, Victoria

    2014-12-01

    The use of silver nanoparticle on various substrates has been widespread because of its good antibacterial properties that directly depend on the stability of the silver nanoparticles in a colloidal suspension. In this study, the colloidal solutions of the silver nanoparticles were synthesised by a simple and safe method by using lecithin as a stabilising agent and their stability was examined at various temperatures. The effect of the lecithin concentrations on the stability of the synthesised silver nanoparticles was examined from 25 to 80°C at 5°C intervals, by recording the changes in the UV-vis absorption spectra, the hydrodynamic diameter and the light scattering intensity of the silver nanoparticles. In addition, the morphology of the synthesised silver nanoparticles was investigated with the low-voltage scanning electron microscopy and transmission electron microscopy. The results indicated that increasing temperature caused different changes in the size of the stabilised and the unstabilised silver nanoparticles. The size of the stabilised silver nanoparticles reduced from 38 to 36 nm during increasing temperature, which confirmed good stability.

  5. Surface-enhanced Raman spectrum of Gly-Gly adsorbed on the silver colloidal surface

    Science.gov (United States)

    Xiaojuan, Yuan; Huaimin, Gu; Jiwei, Wu

    2010-08-01

    Raman and SERS spectra of homodipeptide Gly-Gly and Gly were recorded and compared in this paper, and band assignment for the functional groups contained in these molecules was analyzed in detail. Time-dependent and pH-dependent SERS spectra of Gly-Gly molecule adsorbed on nano-colloidal silver surface were also studied. The time-dependent SERS spectra of Gly-Gly are characterized by the increase in intensity of bands primarily representing the vibrational signatures emanating from the amino and amide moiety of Gly-Gly molecule. It is found that the adsorption style of Gly-Gly on the silver colloid changes as time goes on; at 5 min after adding the sample to the silver colloid, Gly-Gly adsorbs on silver surface firstly through the carboxylate, amino and amide groups, and then the carboxylate group is far away from the silver surface at 10 min to 3 days. The SERS variation of Gly-Gly with the change of pH suggests that the adsorption style is pH-dependent, the different adsorption behavior of the Gly-Gly occurs on silver surface at different pH values.

  6. Synthesis of pure colloidal silver nanoparticles with high electroconductivity for printed electronic circuits: the effect of amines on their formation in aqueous media.

    Science.gov (United States)

    Natsuki, Jun; Abe, Takao

    2011-07-01

    This paper describes a practical and convenient method to prepare stable colloidal silver nanoparticles for use in printed electronic circuits. The method uses a dispersant and two kinds of reducing agents including 2-(dimethylamino) ethanol (DMAE), which play important roles in the reduction of silver ions in an aqueous medium. The effect of DMAE and dispersant, as well as the factors affecting particle size and morphology are investigated. In the formation of the silver nanoparticles, reduction occurs rapidly at room temperature and the silver particles can be separated easily from the mixture in a short time. In addition, organic solvents are not used. Pure, small and relatively uniform particles with a diameter less than 10 nm can be obtained that exhibit high electroconductivity. The silver nanoparticles are stable, and can be isolated as a dried powder that can be fully redispersed in deionized water. This method of producing colloidal silver nanoparticles will find practical use in electronics applications. Copyright © 2011 Elsevier Inc. All rights reserved.

  7. Synthesis of highly stable silver nanoparticles through a novel green method using Mirabillis jalapa for antibacterial, nonlinear optical applications

    Science.gov (United States)

    Pugazhendhi, S.; Palanisamy, P. K.; Jayavel, R.

    2018-05-01

    Green synthesis techniques are developing as more simplistic and eco-friendly approach for the synthesis of metal nanoparticles compared to chemical reduction methods. Herein we report Synthesis of highly stable silver nanoparticles using Mirabillis jalapa seed extract as a reducing and capping agent. The as-prepared silver nanoparticles were characterized by UV-vis spectroscopy (UV-vis) to confirm the formation of silver nanoparticles by its characteristic surface plasmon resonance peak observed at 420 nm. The Powder X-ray diffraction (P-XRD) revealed the structure and crystalline nature of synthesized silver nanoparticles, The Fourier transform infra-red spectroscopic (FT-IR) revealed the presence of the biomolecules in the extract that acted as reducing as well stabilizing agent. The high resolution transmission electron microscopic (HRTEM) images divulged that the synthesized silver nanoparticles were spherical in shape and poly dispersed. The energy dispersive X-ray diffraction (EDX) profile revealed the elements present in the as-synthesized colloidal silver nanoparticles and its percentages. The Zeta potential measured for silver nanoparticles evidenced that the prepared silver nanoparticles owned high stability in room temperature itself. The as-synthesized silver nanoparticles (AgNPs) in colloidal form were showed good antimicrobial effects and it's were found to exhibit third order optical nonlinearity as studied by Z-scan technique using 532 nm Nd:YAG (SHG) CW laser beam (COHERENT-Compass 215 M-50 diode pumped) output as source. The negative nonlinearity observed was well utilized for the study of optical limiting behavior of the silver nanoparticles.

  8. Laser induced morphology change of silver colloids: formation of nano-size wires

    International Nuclear Information System (INIS)

    Tsuji, Takeshi; Watanabe, Norihisa; Tsuji, Masaharu

    2003-01-01

    We have performed laser irradiation at 355 nm onto spherical silver colloids in pure water, which were prepared by laser ablation of silver plate in pure water. In addition to size-reduced particles due to fragmentation, we have found that nano-size wire structures were formed in solution for the first time. The width of the wires was in the 10-100 nm range, and the length of long wires was more than 1 μm. Electron diffraction patterns revealed that these wires were composed of pure silver. It was suggested that the wires were formed via fusion of particles photo-thermally melted by laser irradiation

  9. Colloidal silver nanoparticles/rhamnolipid (SNPRL) composite as novel chemotactic antibacterial agent.

    Science.gov (United States)

    Bharali, P; Saikia, J P; Paul, S; Konwar, B K

    2013-10-01

    The antibacterial activity of silver nanoparticles and rhamnolipid are well known individually. In the present research, antibacterial and chemotactic activity due to colloidal silver nanoparticles (SNP), rhamnolipid (RL) and silver nanoparticles/rhamnolipid composite (SNPRL) were evaluated using Staphylococcus aureus (MTCC3160), Escherichia coli (MTCC40), Pseudomonas aeruginosa (MTCC8163) and Bacillus subtilis (MTCC441) as test strains. Further, the SNPRL nanoparticles were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The observation clearly indicates that SNPRL shows prominent antibacterial and chemotactic activity in comparison to all of its individual precursor components. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Efficient intracellular delivery and improved biocompatibility of colloidal silver nanoparticles towards intracellular SERS immuno-sensing.

    Science.gov (United States)

    Bhardwaj, Vinay; Srinivasan, Supriya; McGoron, Anthony J

    2015-06-21

    High throughput intracellular delivery strategies, electroporation, passive and TATHA2 facilitated diffusion of colloidal silver nanoparticles (AgNPs) are investigated for cellular toxicity and uptake using state-of-art analytical techniques. The TATHA2 facilitated approach efficiently delivered high payload with no toxicity, pre-requisites for intracellular applications of plasmonic metal nanoparticles (PMNPs) in sensing and therapeutics.

  11. [Use of "gelatamp" colloidal silver gelatin sponge to prevent dry socket after extracting mandibular impacted teeth].

    Science.gov (United States)

    Wang, Yao-zhong; Guan, Qun-li; Li, Ya-xin; Guo, Ji-lai; Jiang, Ling; Jia, Mu-yun; Deng, Yue

    2013-02-01

    To study the clinical effect of "gelatamp" colloidal silver gelatin sponge on preventing dry socket after extracting the mandibular impacted teeth. 1350 teeth extracted from 976 patients who needed to extract the mandibular impacted teeth were divided into group A, group B and group C randomly. "Gelatamp" colloidal silver gelatin sponge was implanted into alveolar socket after teeth extraction in group A, with absorbable gelatin sponge was implanted into alveolar socket in group B and nothing was implanted into alveolar socket in group C. The incidence of dry socket was observed, the data was analyzed using SPSS10.0 software package. The incidence of dry socket was 0.44% in group A, 2% in group B and 4.44% in group C. There was significant difference in the incidence of dry socket between group A and group C(Pcolloidal silver gelatin sponge can prevent the occurrence of dry socket after teeth extraction, which is of wide clinical use.

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

    Science.gov (United States)

    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.

  13. Preparation of silver colloid and enhancement of dispersion stability in organic solvent

    International Nuclear Information System (INIS)

    Kim, Ki Young; Choi, Young Tai; Seo, Dae Jong; Park, Seung Bin

    2004-01-01

    Silver colloid of nanometer size was prepared in liquid phase by a reduction method. AgNO 3 , FeSO 4 .7H 2 O, and Na 3 C 6 H 5 O 7 .2H 2 O were used as silver precursor, reducing agent and dispersing agent, respectively. As precursor concentration was decreased or the concentration of dispersing agent was increased, the prepared particle size was decreased from 180 nm to 20 nm. Apparently, the particle size seemed to be decreased with the increase of stirring rate, but it was confirmed by TEM that the size of primary particle remained the same. This result indicates that the uniformity of precursor concentration in the reactor affects the particle size and the stirring rate should be kept higher than the critical value to prevent the agglomeration of particles. In order to make the dispersion stability of the prepared silver colloid maintained even in non-polar organic solvent, electrodialysis technique was applied. As ionic species in colloidal solution were removed by electrodialysis, the dispersability of the colloid in the organic solvent of long carbon chain was confirmed to be increased

  14. Effect of laundry surfactants on surface charge and colloidal stability of silver nanoparticles.

    Science.gov (United States)

    Skoglund, Sara; Lowe, Troy A; Hedberg, Jonas; Blomberg, Eva; Wallinder, Inger Odnevall; Wold, Susanna; Lundin, Maria

    2013-07-16

    The stability of silver nanoparticles (Ag NPs) potentially released from clothing during a laundry cycle and their interactions with laundry-relevant surfactants [anionic (LAS), cationic (DTAC), and nonionic (Berol)] have been investigated. Surface interactions between Ag NPs and surfactants influence their speciation and stability. In the absence of surfactants as well as in the presence of LAS, the negatively charged Ag NPs were stable in solution for more than 1 day. At low DTAC concentrations (≤1 mM), DTAC-Ag NP interactions resulted in charge neutralization and formation of agglomerates. The surface charge of the particles became positive at higher concentrations due to a bilayer type formation of DTAC that prevents from agglomeration due to repulsive electrostatic forces between the positively charged colloids. The adsorption of Berol was enhanced when above its critical micelle concentration (cmc). This resulted in a surface charge close to zero and subsequent agglomeration. Extended DLVO theory calculations were in compliance with observed findings. The stability of the Ag NPs was shown to depend on the charge and concentration of the adsorbed surfactants. Such knowledge is important as it may influence the subsequent transport of Ag NPs through different chemical transients and thus their potential bioavailability and toxicity.

  15. Influence of dose on particle size of colloidal silver nanoparticles synthesized by gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Naghavi, Kazem, E-mail: Kazem.naghavi@gmail.co [Universiti Putra Malaysia, Physics Department, 43400 UPM SERDANG, Selangor (Malaysia); Saion, Elias [Universiti Putra Malaysia, Physics Department, 43400 UPM SERDANG, Selangor (Malaysia); Rezaee, Khadijeh [Department of Nuclear Engineering, Faculty of Modern Sciences and Technologies, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Yunus, Wan Mahmood Mat [Universiti Putra Malaysia, Physics Department, 43400 UPM SERDANG, Selangor (Malaysia)

    2010-12-15

    Colloidal silver nanoparticles were synthesized by {gamma}-irradiation-induced reduction method of an aqueous solution containing silver nitrate as a precursor in various concentrations between 7.40x10{sup -4} and 1.84x10{sup -3} M, polyvinyl pyrrolidone for capping colloidal nanoparticles, isopropanol as radical scavenger of hydroxyl radicals and deionised water as a solvent. The irradiations were carried out in a {sup 60}Co {gamma} source chamber at doses up to 70 kGy. The optical absorption spectra were measured using UV-vis spectrophotometer and used to study the particle distribution and electronic structure of silver nanoparticles. As the radiation dose increases from 10 to 70 kGy, the absorption intensity increases with increasing dose. The absorption peak {lambda}{sub max} blue shifted from 410 to 403 nm correspond to the increase of absorption conduction electron energy from 3.02 to 3.08 eV, indicating the particle size decreases with increasing dose. The particle size was determined by photon cross correlation spectroscopy and the results showed that the particle diameter decreases exponentially with the increase of dose. The transmission electron microscopy images were taken at doses of 20 and 60 kGy and the results confirmed that as the dose increases the diameter of colloidal silver nanoparticle decreases and the particle distribution increases.

  16. Influence of dose on particle size of colloidal silver nanoparticles synthesized by gamma radiation

    International Nuclear Information System (INIS)

    Naghavi, Kazem; Saion, Elias; Rezaee, Khadijeh; Yunus, Wan Mahmood Mat

    2010-01-01

    Colloidal silver nanoparticles were synthesized by γ-irradiation-induced reduction method of an aqueous solution containing silver nitrate as a precursor in various concentrations between 7.40x10 -4 and 1.84x10 -3 M, polyvinyl pyrrolidone for capping colloidal nanoparticles, isopropanol as radical scavenger of hydroxyl radicals and deionised water as a solvent. The irradiations were carried out in a 60 Co γ source chamber at doses up to 70 kGy. The optical absorption spectra were measured using UV-vis spectrophotometer and used to study the particle distribution and electronic structure of silver nanoparticles. As the radiation dose increases from 10 to 70 kGy, the absorption intensity increases with increasing dose. The absorption peak λ max blue shifted from 410 to 403 nm correspond to the increase of absorption conduction electron energy from 3.02 to 3.08 eV, indicating the particle size decreases with increasing dose. The particle size was determined by photon cross correlation spectroscopy and the results showed that the particle diameter decreases exponentially with the increase of dose. The transmission electron microscopy images were taken at doses of 20 and 60 kGy and the results confirmed that as the dose increases the diameter of colloidal silver nanoparticle decreases and the particle distribution increases.

  17. Radiation induced synthesis of colloidal silver nanoparticles stabilized by PVP/chitosan

    International Nuclear Information System (INIS)

    Dang Van Phu; Nguyen Trieu; Vo Thi Kim Lang; Nguyen Quoc Hien; Bui Duy Du

    2008-01-01

    Colloidal silver nanoparticle solution (10 mmol) was prepared by gamma 60 Co irradiation using polyvinyl pyrrolidone (PVP), water soluble chitosan (WSC) and mixture of PVP/WSC as stabilizers. Saturated conversion doses (Ag + → Ag 0 ) and maximum absorption wavelengths (λ max ) were determined by UV-vis spectra to be of 28 kGy (405.5 nm), 20 kGy (418.5 nm), 24 kGy (415.0 nm) and 24 kGy (407.0 nm) for PVP 1% (C1), WSC 0.5% (C2), PVP 1%/WSC 0.5% (C3) and PVP 1%/ethanol 1 M (C4), respectively. Results of the conversion doses indicated that WSC and ethanol plays a role in scavenging the OH* and H* arising from radiolysis of water, which reduced the conversion dose from 28 kGy (C1) to 20 kGy (C2). The average size of silver nanoparticles was characterized by Transmission Electron Microscopy (TEM) as 15.96 ± 0.51, 5.55 ± 0.25, 2.92 ± 0.05, and 11.44 ±2.07 nm for C1, C2, C3 and C4, respectively. The obtained result of silver nanoparticle sizes showed that WSC exhibited the effect of reducing silver nanoparticle size in colloids, especially the mixture of PVP/WSC that reduced the size of silver nanoparticle from ∼16 nm (C1) to about 3 nm (C3). The effect of NaNO 3 on stability of colloidal silver nanoparticles has been also investigated. (author)

  18. Synthesis of colloidal silver nanoparticle clusters and their application in ascorbic acid detection by SERS.

    Science.gov (United States)

    Cholula-Díaz, Jorge L; Lomelí-Marroquín, Diana; Pramanick, Bidhan; Nieto-Argüello, Alfonso; Cantú-Castillo, Luis A; Hwang, Hyundoo

    2018-03-01

    Ascorbic acid (vitamin C) has an essential role in the human body mainly due to its antioxidant function. In this work, metallic silver nanoparticle (AgNP) colloids were used in SERS experiments to detect ascorbic acid in aqueous solution. The AgNPs were synthesized by a green method using potato starch as reducing and stabilizing agent, and water as the solvent. The optical properties of the yellowish as-synthesized silver colloids were characterized by UV-vis spectroscopy, in which besides a typical band at 410 nm related to the localized surface plasmon resonance of the silver nanoparticles, a shoulder band around 500 nm, due to silver nanoparticle cluster formation, is presented when relatively higher concentrations of starch are used in the synthesis. These starch-capped silver nanoparticles show an intrinsic Raman peak at 1386 cm -1 assigned to deformation modes of the starch structure. The increase of the intensity of the SERS peak at 1386 cm -1 with an increase in the concentration of the ascorbic acid is related to a decrease of the gap between dimers and trimers of the silver nanoparticle clusters produced by the presence of ascorbic acid in the colloid. The limit of detection of this technique for ascorbic acid is 0.02 mM with a measurement concentration range of 0.02-10 mM, which is relevant for the application of this method for detecting ascorbic acid in biological specimen. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Radiation stability of colloidal metals in aqueous solutions: silver and other metals

    International Nuclear Information System (INIS)

    Ershov, B.G.

    1998-01-01

    The effect of accelerated electrons and γ-rays of 60N i on the stability of aqueous solutions of colloidal silver was studied. The threshold of absorbed dose, at which the stability dramatically decreases and coagulation of the metal occurs, was found. This critical dose corresponds to the reduction of silver ions determining the electrical potential of the sols. Radiation neutralization was also found for cadmium was not observed in the case of thallium, copper and platinum. A mechanism of the effect of radiation, taking into account the electrostatic factor in the stability of metal sols, was considered. (author)

  20. Investigation on the adsorption characteristics of anserine on the surface of colloidal silver nanoparticles.

    Science.gov (United States)

    Thomas, S; Maiti, N; Mukherjee, T; Kapoor, S

    2013-08-01

    The surface-enhanced Raman scattering (SERS) studies of anserine (beta-alanyl-N-methylhistidine) was carried out on colloidal silver nanoparticles to understand its adsorption characteristics. The experimentally observed Raman bands were assigned based on the results of DFT calculations. The studies suggest that the interaction of anserine is primarily through the carboxylate group with the imidazole ring in an upright position with respect to the silver surface. Concentration dependent SERS studies suggest a change in orientation at sub-monolayer concentration. Copyright © 2013 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

    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.)

  2. Laser-assisted immobilization of colloid silver nanoparticles on polyethyleneterephthalate

    Czech Academy of Sciences Publication Activity Database

    Siegel, J.; Lyutakov, O.; Polívková, M.; Staszek, M.; Hubáček, Tomáš; Švorčík, V.

    2017-01-01

    Roč. 420, OCT (2017), s. 661-668 ISSN 0169-4332 R&D Projects: GA MŠk LM2015075 Institutional support: RVO:60077344 Keywords : silver nanoparticles * polyethyleneterephthalate * excimer laser * immobilization Subject RIV: JJ - Other Materials OBOR OECD: Materials engineering Impact factor: 3.387, year: 2016

  3. Antimicrobial potentials of silver colloidal (nanorods) on clinical ...

    African Journals Online (AJOL)

    Antimicrobial resistance in developing countries has long been an issue of major concern. Nanotechnology has become an eye opener for the intervention on multiple drug resistance organisms. In this study we investigated the antimicrobial potentials of Silver Nitrate (nanorods) solution used in managing infectious ...

  4. The study of the antimicrobial activity of colloidal solutions of silver nanoparticles prepared using food stabilizers.

    Science.gov (United States)

    Balandin, G V; Suvorov, O A; Shaburova, L N; Podkopaev, D O; Frolova, Yu V; Ermolaeva, G A

    2015-06-01

    The bactericidal effect of colloidal solutions of silver nanoparticles based on food stabilizers, gum arabic and chitosan, against bacterial cultures of microorganisms in food production is described. The antibacterial activity of nanotechnology products containing different amounts of stabilizing additives when applied to solid pH-neutral substrates is studied. For its evaluation a method making it possible to take into account the capability of nanoparticles to diffuse in solid media was applied. Minimal inhibitory concentrations of nanoparticles used against Erwinia herbicola, Pseudomonas fluorescens, Bacillus subtilis, Sarcina flava were found. A suggestion was made concerning the influence of the spatial structure of bacteria on the antibacterial activity of colloidal solutions of silver nanoparticles. The data concerning the antibacterial activity and minimal inhibiting concentrations of nanoparticles may be used for development of products suppressing activity of microorganisms hazardous for food production.

  5. Colloidal silver iodide characterization within the framework of nuclear spent fuel dissolution

    International Nuclear Information System (INIS)

    Bernard-Mozziconacci, O.; Devisme, F.; Marignier, JL.; Belloni, J.

    2004-01-01

    Iodine-129 partitioning during the dissolution stage of the Purex reprocessing, based on volatile molecular iodine formation and stripping, is mainly limited by dissolved oxidized species such as iodate and insoluble forms such as colloidal silver iodide. The study of their formation and stability, not completely clarified, requires to prepare the colloid in a reproducible way under various conditions and to characterize it. The work reported here describes a first step towards this objective. Carried out under simplified operating conditions, speciation and physical characterization (spectrophotometry and TEM) made it possible to evaluate, for the first time, the molar extinction coefficient of the colloid per monomer and its variation with the nuclearity, ε(n), on the basis of a simplified coalescence model: ε(n) = ε max (1 - e -αn ) where ε max ∼ 7000 L mol -1 cm -1 and α = 4.3 x 10 -6 per monomer number in a particle. (authors)

  6. In Vitro Evaluation of Colloidal Silver on Immune Function: Anti lymphoproliferative Activity

    International Nuclear Information System (INIS)

    Franco-Molina, M. A.; Mendoza-Gamboa, E.; Zarate-Trivino, D. G.; Coronado-Cerda, E.E.; Alcocer-Gonzalez, J. M.; Resendez-Perez, D.; Rodriguez-Salazar, M.C.; Rivera-Morales, L.G.; Tamez-Guerra, R.; Rodriguez-Padilla, C.

    2016-01-01

    Colloidal silver (AgC) is currently used by humans and it can be internalized through inhalation, injection, ingestion, and dermal contact. However, there is limited information about immunological activity; more investigations using colloidal silver are needed. In the present study, the effects of AgC (17.5 ng/m L) on immunological parameters (proliferation and immuno phenotyping) using human peripheral blood mononuclear cells (PBMC) and macrophages (phagocytosis) and cytotoxicity on leukemia and lymphoma cancer cell lines (1.75 to 17.5 ng/m L) were investigated. AgC was observed to significantly ρ) decrease interleukin-2 (I L-2) production and proliferation induced by phytohemagglutinin or concanavalin A in PBMC without affecting its cell viability but with cytotoxic effect on cancer cells. IL-2, IL-4, IL-6, IL-10, INF-γ, and IL_-17 A cytokines production and CD3"+, CD3"-CD19"+, CD3"+CD4"+, CD3"+CD8"+, and CD16"+CD56"+ PBMC phenotypes were not affected by AgC. The present study demonstrates that colloidal silver is harmless and nontoxic to the immune system cells and its ability to interfere with the immune response by decreasing cell proliferation when stimulated with mitogens demonstrated the anti lymphoproliferative potential of AgC

  7. In Vitro Evaluation of Colloidal Silver on Immune Function: Antilymphoproliferative Activity

    Directory of Open Access Journals (Sweden)

    M. A. Franco-Molina

    2016-01-01

    Full Text Available Colloidal silver (AgC is currently used by humans and it can be internalized through inhalation, injection, ingestion, and dermal contact. However, there is limited information about immunological activity; more investigations using colloidal silver are needed. In the present study, the effects of AgC (17.5 ng/mL on immunological parameters (proliferation and immunophenotyping using human peripheral blood mononuclear cells (PBMC and macrophages (phagocytosis and cytotoxicity on leukemia and lymphoma cancer cell lines (1.75 to 17.5 ng/mL were investigated. AgC was observed to significantly (p<0.05 decrease interleukin-2 (IL-2 production and proliferation induced by phytohemagglutinin or concanavalin A in PBMC without affecting its cell viability but with cytotoxic effect on cancer cells. IL-2, IL-4, IL-6, IL-10, INF-γ, and IL-17A cytokines production and CD3+, CD3−CD19+, CD3+CD4+, CD3+CD8+, and CD16+CD56+ PBMC phenotypes were not affected by AgC. The present study demonstrates that colloidal silver is harmless and nontoxic to the immune system cells and its ability to interfere with the immune response by decreasing cell proliferation when stimulated with mitogens demonstrated the antilymphoproliferative potential of AgC.

  8. Formation of silver colloids on ion exchanged soda lime silicate glasses by irradiation

    International Nuclear Information System (INIS)

    Yoshimura, E.M.; Okuno, E.

    1998-01-01

    The effect of ionizing radiation (gamma rays, X-rays and electrons) on soda lime silicate glasses, in which part of the Na + was substituted by Ag + by means of an ionic exchange process, was studied. The techniques of thermally stimulated depolarization current (TSDC) and transmission electron microscopy (TEM) were employed to follow the formation of silver colloids by irradiation. Also the thermoluminescence (TL) of the samples was measured and three peaks between room temperature and 450 C were observed. The TEM and TSDC results agree that, as expected, ionizing radiation promotes the formation of silver colloids on the ion exchanged surface of soda lime glasses. Soft X-rays are much more efficient in the process than gamma rays and electrons. The correlation with thermoluminescence glow curves indicates that the intensity of a TL peak at 230 C can provide a rapid means of evaluating the presence of silver colloids. TL sensitivities, measured as area under the glow curve per unit mass and unit dose, are very similar for ion exchanged and not exchanged samples submitted to X-ray irradiation, although the peak temperatures differ in about 40 C in the two cases. For both electron and gamma irradiated samples, the TL sensitivity drops about an order of magnitude when compared to the X-ray irradiated ones. (orig.)

  9. Interactions between colloidal silver and photosynthetic pigments located in cyanobacteria fragments and in solution.

    Science.gov (United States)

    Siejak, Przemysław; Frackowiak, Danuta

    2007-09-25

    Changes in the yield of the fluorescence emitted by pigments of photosynthetic organisms could be used for the establishment of the presence of some toxic substances. The presence of colloidal metals can be indicated by enhancement of pigments' emission as a result of plasmons generation. The spectra of the pigments of cyanobacterium Synechocystis located in the bacterium fragments and in solutions with and without colloidal silver additions have been measured. The quantum yield of the pigments' fluorescence in solution has been observed to increase at some wavelength of excitation, while the fluorescence of the pigments in the bacteria fragments has been only quenched as a consequence of interactions with colloidal silver particles. Close contact between pigment molecules located in bacteria fragments and silver particles is probably not possible. We plan in future to investigate the influence of other, more typical metal pollutants of water, using similar spectral methods and several other photosynthetic bacteria pigments, in solution, in cell fragments and in the whole bacteria organisms.

  10. Antibacterial Activity of Electrochemically Synthesized Colloidal Silver Nanoparticles Against Hospital-Acquired Infections

    Science.gov (United States)

    Thuc, Dao Tri; Huy, Tran Quang; Hoang, Luc Huy; Hoang, Tran Huy; Le, Anh-Tuan; Anh, Dang Duc

    2017-06-01

    This study evaluated the antibacterial activity of electrochemically synthesized colloidal silver nanoparticles (AgNPs) against hospital-acquired infections. Colloidal AgNPs were synthesized via a single process using bulk silver bars, bi-distilled water, trisodium citrate, and direct current voltage at room temperature. Colloidal AgNPs were characterized by transmission electron microscopy, field-emission scanning electron microscopy, and energy-dispersive x-ray analyses. The antibacterial activity of colloidal AgNPs against four bacterial strains isolated from clinical samples, including methicillin-resistant Staphylococcus aureus, Escherichia coli O157:H7, multidrug-resistant Pseudomonas aeruginosa, and carbapenem-resistant Klebsiella pneumonia, was evaluated by disc diffusion, minimum inhibitory concentration (MIC), and ultrathin sectioning electron microscopy. The results showed that the prepared AgNPs were 19.7 ± 4.3 nm in size, quasi-spherical, and of high purity. Zones of inhibition approximately 6-10 mm in diameter were found, corresponding to AgNPs concentrations of 50 μg/mL to 100 μg/mL. The MIC results revealed that the antibacterial activity of the prepared AgNPs was strongly dependent on the concentration and strain of the tested bacteria.

  11. Multifaceted adsorption of α-cyano-4-hydroxycinnamic acid on silver colloidal and island surfaces

    Science.gov (United States)

    Jung, Dawoon; Jeon, Kooknam; Yeo, Juhyun; Hussain, Shafqat; Pang, Yoonsoo

    2017-12-01

    The surface adsorption of organic nitrile compounds on the silver colloidal and island surfaces has been studied using surface-enhanced Raman scattering (SERS). α-Cyano-4-hydroxycinnamic acid (CHCA) with nitrile and carboxyl groups shows various surface adsorption on the silver surfaces. In acidic conditions, the surface adsorption of CHCA via the nitrile group with a more or less tilted geometry to the surface was found. When the solution pH increases, the carboxylate and nitrile groups of deprotonated CHCA participate in the surface adsorption, whereas the molecular plane of CHCA becomes more parallel to the surface. The ν(Ctbnd N) band in SERS of CHCA is the indicator of the surface adsorption geometry. The strongly red-shifted and broadened ν(Ctbnd N) band in SERS represents the surface adsorption via π-electrons of the Ctbnd N bond (side-on geometry; π-coordination). Nitriles adsorbed on the surface via the nonbonding electron pair of the nitrogen atom (end-on geometry; σ-coordination) often cause the blue-shifts and small band broadening in ν(Ctbnd N) in SERS. The surface adsorption geometry of organic nitriles based on many previous experimental results was further confirmed by the surface adsorption of CHCA on the silver island surfaces and dinitrile compounds on the silver colloidal surfaces.

  12. Study of optical and physicochemical properties of colloidal silver nanoparticles as an efficient substrate for SERS

    International Nuclear Information System (INIS)

    Cyrankiewicz, M; Kruszewski, S

    2011-01-01

    The unique optical and physicochemical properties of the noble metal colloidal nanoparticles enable their use in a wide range of applications, especially as a substrate in SERS and MEF study. The aim of this work is to characterize the conditions for the enhancement of Raman scattering by molecules adsorbed on silver surface. Silver sol is prepared by slightly modified Lee-Meisel's method and rhodamine 6G is used as a probe adsorbate. Pure colloidal silver suspension containing isolated nanoparticles exhibits relatively poor SERS efficiency. The extremely large electromagnetic field is induced in the junctions between two or more metallic nanocrystalites so some degree of their aggregation is necessary. The influence of potassium chloride and nitric acid as the aggregating agents is investigated here. The experiments show that both of them can promote the controlled aggregation process but chloride anions, unlike nitrate, much more effectively affect both electromagnetic and chemical mechanisms contributing to SERS. Due to the co-adsorption with rhodamine 6G they allow the dye molecules to directly interact with metallic surface. Moreover, the results clearly indicate that chloride in the presence of silver particles can induce the dimerization of the dye molecules.

  13. Fermi level equilibration between colloidal lead and silver particles in aqueous solution

    International Nuclear Information System (INIS)

    Henglein, A.; Holzwarth, A.; Mulvaney, P.

    1992-01-01

    Colloidal solutions of lead and silver were mixed under the exclusion of air. The equilibration of the Fermi levels in the two different types of metal particles took place over a few days at room temperature. The equilibration took place by the transfer of lead atoms from lead to silver particles until the latter carried a lead mantle of one to two monolayers. This could be concluded from the observed changes in the optical spectrum of the silver particles. The results are discussed in terms of two mechanisms: (1) Pb atom transfer following heterocoagulation of the lead and silver particles and (2) electron transfer during Brownian encounters, followed by Pb 2+ desorption from the lead particles and subsequent Pb 2+ reductor on the silver particles carrying the transferred electrons. Traces of methylviologen, MV 2+ , in the solution drastically increase the rate of equilibration; this is explained by a relay mechanism in which electrons in the lead particles are first picked up by MV 2+ and are then transferred from MV + to the silver particles. 2 refs., 4 figs

  14. Study of the spectra of silica colloidal crystals with assembled silver obtained from a photolysis method

    Science.gov (United States)

    Li, Wenjiang; He, Jinglong; He, Sailing

    2005-02-01

    The colorful artificial 3D silica colloidal crystals (opal) were prepared through self-assembly of silica spheres in the visible frequency range. We directly synthesized nano silver particles in the void of the silica artificial opal film using the photolysis of silver nitrate under UV light, nano silver particles were self-deposited around the surface of silica sphere. The shifts of the stop band of the artificial crystals after exposing different time under UV light were studied. Synthetic silica opal with three-dimensional (3D) structure is potentially useful for the development of diffractive optical devices, micro mechanical systems, and sensory elements because photonic band gaps obtained from self-assembled closely packed periodic structures.

  15. Microwave-assisted one-step patterning of aqueous colloidal silver.

    Science.gov (United States)

    Yang, G; Zhou, Y W; Guo, Z R; Wan, Y; Ding, Q; Bai, T T; Wang, C L; Gu, N

    2012-07-05

    A new approach of utilizing microwave to pattern gradient concentric silver nanoparticle ring structures has been presented. The width and height of a single ring and the space between adjacent rings can be adjusted by changing the silver colloidal concentration and the microwave output power. By simply enhancing the ambient vapour pressure to the saturated value during microwave-assisted evaporation, sub-100 nm rings can be deposited in between adjacent micro-rings over a distance of millimetres. Combined with microwave sintering, this approach can also create conductive silver tracks in a single step, showing huge potential in fabricating micro- and nano-electronic devices in an ultra-fast and cost-effective fashion.

  16. Hydrothermal-induced assembly of colloidal silver spheres into various nanoparticles on the basis of HTAB-modified silver mirror reaction.

    Science.gov (United States)

    Yu, Dabin; Yam, Vivian Wing-Wah

    2005-03-31

    Small colloidal silver spheres (diameter synthesis process. Adjustment of the synthesis parameters, in particular the concentrations of HTAB and [Ag(NH3)2]+, led to an obvious shape evolution of silver nanoparticles, thus resulting in the shape-selective formation of the silver nanoparticles. The monodisperse nanocubes with a well-defined crystallographical structure (a single crystal bounded by six {200} facets) have a strong tendency to assemble into two-dimensional arrays on substrates. The nanowires with uniform diameter usually existed in the form of two-dimensional alignments. The findings suggested that hydrothermal-induced assembly of small silver colloidal particles should be a convenient and effective approach to the preparation of various silver nanoparticles.

  17. Particulate and colloidal silver in sewage effluent and sludge discharged from British wastewater treatment plants.

    Science.gov (United States)

    Johnson, Andrew C; Jürgens, Monika D; Lawlor, Alan J; Cisowska, Iwona; Williams, Richard J

    2014-10-01

    Differential filtration was used to measure silver (>2 nm) entering and leaving nine sewage treatment plants (STPs). The mean concentration of colloidal (2-450 nm) silver, which includes nanosilver, was found to be 12 ng L(-1) in the influent and 6 ng L(-1) in the effluent. For particulate silver (>450 nm) the mean values were 3.3 μg L(-1) for influent and 0.08 μg L(-1) for effluent. Thus, removal was around 50% and 98% for colloidal and particulate silver respectively. There was no significant difference in performance between the different types of STP investigated (three examples each of activated sludge, biological filter and biological filter with tertiary treatment located across England, UK). In addition, treated sewage sludge samples (biosolids) were taken from several STPs to measure the total silver likely to be discharged to soils. Total silver was 3-14 mg kg(-1) DW in the sludge (median 3.6), which if the sludge were added at the recommended rate to soil, would add 11 μg kg(-1) yr(-1) to the top 20 cm soil layer. Predicted concentrations using the LF2000-WQX model for all the rivers of England and Wales for nanosilver were typically in the 0-1 ng L(-1) range but levels up to 4 ng L(-1) are possible in a high discharge and low flow scenario. Predicted concentrations for the total particulate forms were mostly below 50 ng L(-1) except for a high discharge and low flow scenario where concentrations could reach 135 ng L(-1). Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Laser-assisted immobilization of colloid silver nanoparticles on polyethyleneterephthalate

    Science.gov (United States)

    Siegel, Jakub; Lyutakov, Oleksiy; Polívková, Markéta; Staszek, Marek; Hubáček, Tomáš; Švorčík, Václav

    2017-10-01

    Immobilization of nanoobjects on the surface of underlying material belongs to current issues of material science. Such altered materials exhibits completely exceptional properties exploitable in a broad spectrum of industrially important applications ranging from catalysts up to health-care industry. Here we present unique approach for immobilization of electrochemically synthesized silver nanoparticles on polyethyleneterephthalate (PET) foil whose essence lies in physical incorporation of particles into thin polymer surface layer induced by polarized excimer laser light. Changes in chemical composition and surface structure of polymer after particle immobilization were recorded by wide range of analytical techniques such as ARXPS, EDX, RBS, AAS, Raman, ICP-MS, DLS, UV-vis, SEM, TEM, and AFM. Thorough analysis of both nanoparticles entering the immobilization step as well as modified PET surface allowed revealing the mechanism of immobilization process itself. Silver nanoparticles were physically embedded into a thin surface layer of polymer reaching several nanometers beneath the surface rather than chemically bonded to PET macromolecules. Laser-implanted nanoparticles open up new possibilities especially in the development of the next generation cell-conform antimicrobial coatings of polymeric materials, namely due to the considerable immobilization strength which is strong enough to prevent particle release into the surrounding environment.

  19. Silver nanoparticle colloids with γ-cyclodextrin: enhanced stability and Gibbs–Marangoni flow

    Energy Technology Data Exchange (ETDEWEB)

    Amiri, Setareh; Duroux, Laurent; Larsen, Kim Lambertsen, E-mail: kll@bio.aau.dk [Aalborg University, Department of Chemistry and Bioscience (Denmark)

    2015-01-15

    Although cyclodextrins (CD) are effective stabilizers for metal nanoparticle colloids, differences between α-, β- and γ-CD in stabilizing such colloids have not been previously reported. In this study, silver nanoparticles (AgNP) were synthesized using NaBH{sub 4} as reducing agent and cyclodextrins as stabilizers. Long-term stability of AgNP colloids in equilibrium conditions showed no marked differences between CD types. Transmission electron microscopy and quantitative image analysis revealed only marginal differences in particle sizes for CD-AgNP, although statistically significant. CD-AgNP colloids showed dispersed particles with average diameters of 7.3 ± 2.2, 6.3 ± 2.9 and 4.9 ± 1.9 nm for α-, β- and γ-CD, respectively, and with similar ζ-potentials about −25 to −30 mV. AgNP without CD showed bigger and aggregated particles of 15.0 ± 2.0 nm with lower ζ-potentials of about −40 mV. When subjected to centrifugal forces, i.e. non-equilibrium conditions, γ-CD was markedly more efficient than α- and β-CD in stabilizing the colloids. Drying patterns of colloid droplets showed a typical self-pinned coffee ring for all but the colloid stabilized by γ-CD, which showed a pattern resulting from a dominant Gibbs–Marangoni flow inside the drying droplet. Calculations using the Derjaguin, Landau, Verwey and Overbeek (DLVO) theory supported the stabilizing effect of CD in equilibrium conditions; it however did not provide clues for the superior stabilization by γ-CD in conditions of hydrodynamic stress.

  20. Silver nanoparticle colloids with γ-cyclodextrin: enhanced stability and Gibbs–Marangoni flow

    International Nuclear Information System (INIS)

    Amiri, Setareh; Duroux, Laurent; Larsen, Kim Lambertsen

    2015-01-01

    Although cyclodextrins (CD) are effective stabilizers for metal nanoparticle colloids, differences between α-, β- and γ-CD in stabilizing such colloids have not been previously reported. In this study, silver nanoparticles (AgNP) were synthesized using NaBH 4 as reducing agent and cyclodextrins as stabilizers. Long-term stability of AgNP colloids in equilibrium conditions showed no marked differences between CD types. Transmission electron microscopy and quantitative image analysis revealed only marginal differences in particle sizes for CD-AgNP, although statistically significant. CD-AgNP colloids showed dispersed particles with average diameters of 7.3 ± 2.2, 6.3 ± 2.9 and 4.9 ± 1.9 nm for α-, β- and γ-CD, respectively, and with similar ζ-potentials about −25 to −30 mV. AgNP without CD showed bigger and aggregated particles of 15.0 ± 2.0 nm with lower ζ-potentials of about −40 mV. When subjected to centrifugal forces, i.e. non-equilibrium conditions, γ-CD was markedly more efficient than α- and β-CD in stabilizing the colloids. Drying patterns of colloid droplets showed a typical self-pinned coffee ring for all but the colloid stabilized by γ-CD, which showed a pattern resulting from a dominant Gibbs–Marangoni flow inside the drying droplet. Calculations using the Derjaguin, Landau, Verwey and Overbeek (DLVO) theory supported the stabilizing effect of CD in equilibrium conditions; it however did not provide clues for the superior stabilization by γ-CD in conditions of hydrodynamic stress

  1. Topical colloidal silver as an anti-biofilm agent in a Staphylococcus aureus chronic rhinosinusitis sheep model.

    Science.gov (United States)

    Rajiv, Sukanya; Drilling, Amanda; Bassiouni, Ahmed; James, Craig; Vreugde, Sarah; Wormald, Peter-John

    2015-04-01

    Treatment of recalcitrant chronic rhinosinusitis (CRS) is a challenge with increasing antibiotic resistance, leading to re-emergence of topical therapies. The aim of this study was to assess safety and efficacy of topical colloidal silver solution for the treatment of Staphylococcus aureus biofilms in a sheep model. In the safety study, normal saline (control) and 30-ppm colloidal silver solution (test) was used to flush the frontal sinuses for 14 days in 8 sheep (4 sheep each). In the efficacy study, following frontal sinus infection with Staphylococcus aureus, sheep were treated with either control saline or topical silver solution of varying concentrations (30 ppm/20 ppm/10 ppm/5 ppm) for 5 days, with 4 sheep in each group. Blood silver level, full blood counts, and biochemical parameters were analyzed in both safety and efficacy studies. Sinus tissue was harvested for histological examination and ciliary structure analysis in safety and for biofilm biomass quantification by fluorescence in situ hybridization (FISH) technique and COMSTAT 2 software in the efficacy study. Results were analyzed using appropriate statistical tests. Sheep treated with silver showed a significant decrease in biofilm biomass (0.004, 0.004, 0.004, and 0.007, in the 4 silver-treated groups, respectively) compared to saline control (0.175), p silver levels were higher in the treated groups compared to controls (p colloidal silver solution has effective antibiofilm activity in Staphylococcus aureus CRS in a sheep model and appears safe. © 2015 ARS-AAOA, LLC.

  2. Reactions of organic free radicals at colloidal silver in aqueous solution. Electron pool effect and water decomposition

    International Nuclear Information System (INIS)

    Henglein, A.

    1979-01-01

    Organic free radicals of high negative redox potential such as α-alcohol radicals were found to transfer electrons to colloidal silver particles stabilized by sodium dodecyl sulfate in aqueous solution. The colloidal particles thus became a pool of stored electrons that could reduce water to form hydrogen or react with suitable acceptors in solution. The organic radicals were produced by irradiation, using suitable scavengers for the primary radicals from the radiolysis of the aqueous solvent. The solutions initially contained silver ions at 1 x 10 -4 - 2 x 10 -3 M. At doses below 10 5 rd, the silver ions were completely reduced to form the colloidal catalyst. In this dose range, the corresponding hydrogen yield amounted to 1 molecule per 100 eV. It increased steeply at higher doses up to 3 molecules per 100 eV. The H 2 yield decreased with increasing dose rate and with increasing pH in alkaline solutions. It was highest at a concentration of sodium dodecyl sulfate of 1 x 10 -3 M, i.e., far below the critical micelle concentration of this surfactant. Changes in the absorption spectrum of the colloid are attributed to changes in the size of the silver particles upon charging up with electrons. The competition of radical-colloid reactions with radical-radical deactivation in the bulk of solution or at the surface of the colloidal particles is also discussed. 11 figures

  3. Effect of halideions on the surface-enhanced Raman spectroscopy of methylene blue for borohydride-reduced silver colloid

    International Nuclear Information System (INIS)

    Dong Xiao; Gu Huaimin; Liu Fang

    2011-01-01

    The surface enhanced Raman scattering (SERS) spectrum of methylene blue (MB) was studied when adding a range of halideions to borohydride-reduced silver colloid. The halideions such as chloride, bromide and iodide were added as aggregating agents to study the effects of halideions on SERS spectroscopy of MB and observe which halideion gives the greatest enhancement for borohydride-reduced silver colloids. The SERS spectra of MB were also detected over a wide range of concentrations of halideions to find the optimum concentration of halideions for SERS enhancement. From the results of this study, the intensity of SERS signal of MB was enhanced significantly when adding halideions to the colloid. Among the three kinds of halideions, chloride gives the greatest enhancement on SERS signal. The enhancement factors for MB with optimal concentration of chloride, bromide and iodide are 3.44x10 4 , 2.04x10 4 , and 1.0x10 4 , respectively. The differences of the SERS spectra of MB when adding different kinds and concentrations of halideions to the colloid may be attributed to the both effects of extent of aggregation of the colloid and the modification of silver surface chemistry. The purpose of this study is to further investigate the effect of halideions on borohydride-reduced silver colloid and to make the experimental conditions suitable for detecting some analytes in high efficiency on rational principles.

  4. Evaluation of Soft Tissue Reaction to Corundum Ceramic Implants Infiltrated with Colloidal Silver.

    Science.gov (United States)

    Wnukiewicz, Witold; Rutowski, Roman; Zboromirska-Wnukiewicz, Beata; Reichert, Paweł; Gosk, Jerzy

    2016-01-01

    Corundum ceramic is a biomaterial used as a bone graft substitute. Silver is a well known antiseptic substance with many practical, clinical applications. The aim of this study was to estimate soft tissue (in vivo) reaction to a new kind of ceramic implants. In our experiment, we examined the soft tissue reaction after implantation of corundum ceramic infiltrated with colloidal silver in the back muscles of 18 Wistar rats. The use of colloidal silver as a coating for the implant was designed to protect it against colonization by bacteria and the formation of bacterial biofilm. In our study, based on the experimental method, we performed implantation operations on 18 Wistar rats. We implanted 18 modified ceramic implants and, as a control group, 18 unmodified implants. As a follow up, we observed the animals operated upon, and did postoperative, autopsy and histopathological examinations 14, 30, 90 and 180 days after implantation. We didn't observe any pathological reactions and significant differences between the soft tissue reaction to the modified implants and the control group. Lack of pathological reaction to the modified implants in the living organism is the proof of their biocompatibility. This is, of course, the first step on the long path to introduce a new kind of biocompatible ceramic implant with antiseptic cottage. Our experiment has an only introductory character and we plan to perform other, more specific, tests of this new kind of implant.

  5. Nonlinear-Optical and Fluorescent Properties of Ag Aqueous Colloid Prepared by Silver Nitrate Reduction

    Directory of Open Access Journals (Sweden)

    Xiaoqiang Zhang

    2010-01-01

    Full Text Available The nonlinear-optical properties of metal Ag colloidal solutions, which were prepared by the reduction of silver nitrate, were investigated using Z-scan method. Under picosecond 532 nm excitation, the Ag colloidal solution exhibited negative nonlinear refractive index (n2=−5.17×10−4 cm2/W and reverse saturable absorption coefficient (β=4.32 cm/GW. The data fitting result of optical limiting (OL response of metal Ag colloidal solution indicated that the nonlinear absorption was attributed to two-photon absorption effect at 532 nm. Moreover, the fluorescence emission spectra of Ag colloidal solution were recorded under excitations at both 280 nm and 350 nm. Two fluorescence peaks, 336 nm and 543 nm for 280 nm excitation, while 544 nm and 694 nm for 350 nm excitation, were observed.

  6. pH-dependent fluorescence property of methyl red isomers in silver colloids

    International Nuclear Information System (INIS)

    Wong, Jian-How; Lee, Szetsen

    2012-01-01

    We report the use of silver (Ag) colloids in the spectroscopic differentiation of methyl red (MR) isomers (o-MR, m-MR, p-MR) by fluorescence techniques. Under different pH conditions, the formation of MR-Ag complex has an impact on the fluorescence band shapes and peak position shift, which are distinctive between MR isomers. The fluorescence quenching between 400 and 414 nm accompanied by simultaneous enhancement between 510 and 541 nm changes with pH are closely related to energy transfer efficiency and the interaction between the MR isomers and the Ag surface.

  7. Sunlight based irradiation strategy for rapid green synthesis of highly stable silver nanoparticles using aqueous garlic (Allium sativum) extract and their antibacterial potential

    International Nuclear Information System (INIS)

    Rastogi, Lori; Arunachalam, J.

    2011-01-01

    Highlights: → We report green synthetic route for the production crystalline silver nanoparticles using garlic as both reducing and stabilizing agent. → Synthesis has been achieved by exposing the solution mixture of [Ag(NH 3 ) 2 ] + and aqueous garlic extract under sunlight. → Role of light in the synthesis process has been investigated and is discussed in detail. → The antibacterial effect of the synthesized silver nanoparticles has been assessed against both Gram classes of bacteria. → Synthesized silver colloidal solutions were found to be stable for a very long period and retained their bactericidal potential. - Abstract: A green synthetic route for the production of highly stable silver nanoparticles using aqueous garlic extract is being reported for the first time. The silver nanoparticles were synthesized by exposing a mixture of 0.1 M [Ag(NH 3 ) 2 ] + and diluted aqueous garlic extract under bright sunlight for 15 min. The garlic extract components served as both reducing and capping agents in the synthesis of silver nanoparticles while the sunlight acted as catalyst in the synthesis process. The synthesized nanoparticles were characterized using UV-visible (UV-vis) spectrophotometer; transmission electron microscopy (TEM), glancing angle X-ray diffraction (GA-XRD) and Fourier transform infra red (FTIR) spectrometry. The nanoparticles were found to be poly-dispersed in nature, spherical in shape and of 7.3 ± 4.4 nm in size. The FTIR analysis was suggestive of proteins as capping agents around the nanoparticles. The yield of synthesized nanoparticles was calculated to be approximately 80% by dry weight and 85% ICP-AES method. The synthesized silver nanoparticles exhibited good antibacterial potential against both Gram positive and Gram negative bacterial strains, as measured using well diffusion assay. Most importantly, the silver colloidal solutions thus synthesized were found to be stable for a very long period (more than a year) and retained

  8. Sunlight based irradiation strategy for rapid green synthesis of highly stable silver nanoparticles using aqueous garlic (Allium sativum) extract and their antibacterial potential

    Energy Technology Data Exchange (ETDEWEB)

    Rastogi, Lori [National Center for Chemical Characterization of Materials, Bhabha Atomic Research Centre, ECIL-PO, Hyderabad 500 062 (India); Arunachalam, J., E-mail: aruncccm@rediffmail.com [National Center for Chemical Characterization of Materials, Bhabha Atomic Research Centre, ECIL-PO, Hyderabad 500 062 (India)

    2011-09-15

    Highlights: {yields} We report green synthetic route for the production crystalline silver nanoparticles using garlic as both reducing and stabilizing agent. {yields} Synthesis has been achieved by exposing the solution mixture of [Ag(NH{sub 3}){sub 2}]{sup +} and aqueous garlic extract under sunlight. {yields} Role of light in the synthesis process has been investigated and is discussed in detail. {yields} The antibacterial effect of the synthesized silver nanoparticles has been assessed against both Gram classes of bacteria. {yields} Synthesized silver colloidal solutions were found to be stable for a very long period and retained their bactericidal potential. - Abstract: A green synthetic route for the production of highly stable silver nanoparticles using aqueous garlic extract is being reported for the first time. The silver nanoparticles were synthesized by exposing a mixture of 0.1 M [Ag(NH{sub 3}){sub 2}]{sup +} and diluted aqueous garlic extract under bright sunlight for 15 min. The garlic extract components served as both reducing and capping agents in the synthesis of silver nanoparticles while the sunlight acted as catalyst in the synthesis process. The synthesized nanoparticles were characterized using UV-visible (UV-vis) spectrophotometer; transmission electron microscopy (TEM), glancing angle X-ray diffraction (GA-XRD) and Fourier transform infra red (FTIR) spectrometry. The nanoparticles were found to be poly-dispersed in nature, spherical in shape and of 7.3 {+-} 4.4 nm in size. The FTIR analysis was suggestive of proteins as capping agents around the nanoparticles. The yield of synthesized nanoparticles was calculated to be approximately 80% by dry weight and 85% ICP-AES method. The synthesized silver nanoparticles exhibited good antibacterial potential against both Gram positive and Gram negative bacterial strains, as measured using well diffusion assay. Most importantly, the silver colloidal solutions thus synthesized were found to be stable for

  9. In situ spectroscopy of ligand exchange reactions at the surface of colloidal gold and silver nanoparticles

    International Nuclear Information System (INIS)

    Dinkel, Rebecca; Peukert, Wolfgang; Braunschweig, Björn

    2017-01-01

    Gold and silver nanoparticles with their tunable optical and electronic properties are of great interest for a wide range of applications. Often the ligands at the surface of the nanoparticles have to be exchanged in a second step after particle formation in order to obtain a desired surface functionalization. For many techniques, this process is not accessible in situ . In this review, we present second-harmonic scattering (SHS) as an inherently surface sensitive and label-free optical technique to probe the ligand exchange at the surface of colloidal gold and silver nanoparticles in situ and in real time. First, a brief introduction to SHS and basic features of the SHS of nanoparticles are given. After that, we demonstrate how the SHS intensity decrease can be correlated to the thiol coverage which allows for the determination of the Gibbs free energy of adsorption and the surface coverage. (topical review)

  10. Surface-enhanced raman spectroscopic studies of ellagic acid in silver colloids

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Jang; Cheong, Byeong Seo; Cho, Han Gook [Dept. of Chemistry, Incheon National University, Incheon (Korea, Republic of)

    2015-06-15

    Surface-enhanced Raman scattering (SERS) spectroscopy has been applied for the vibrational characterization of ellagic acid (EA), a natural organic dye, using citrate-reduced silver colloids. The infrared and FT-Raman spectra of EA in the solid state were examined for comparison. Spectral assignments of the observed bands were aided by density functional theory (DFT) calculations employing the B3LYP functional. The variations in the SERS spectrum with pH and excitation wavelength were analyzed to gain information on the adsorption- and pH-dependent behaviors of the natural dye on the metal surface. On the basis of the observed spectral features and DFT calculations, the adsorption configuration of EA on the silver metal surface is proposed.

  11. Wound healing applications of biogenic colloidal silver and gold nanoparticles: recent trends and future prospects.

    Science.gov (United States)

    Ovais, Muhammad; Ahmad, Irshad; Khalil, Ali Talha; Mukherjee, Sudip; Javed, Rabia; Ayaz, Muhammad; Raza, Abida; Shinwari, Zabta Khan

    2018-05-01

    Nanotechnology has emerged as a prominent scientific discipline in the technological revolution of this millennium. The scientific community has focused on the green synthesis of metal nanoparticles as compared to physical and chemical methods due to its eco-friendly nature and high efficacy. Medicinal plants have been proven as the paramount source of various phytochemicals that can be used for the biogenic synthesis of colloidal silver and gold nanoparticles as compared to other living organisms, e.g., microbes and fungi. According to various scientific reports, the biogenic nanoparticles have shown promising potential as wound healing agents. However, not a single broad review article was present that demonstrates the wound healing application of biogenic silver and gold nanoparticles. Foreseeing the overall literature published, we for the first time intended to discuss the current trends in wound healing via biogenic silver and gold nanoparticles. Furthermore, light has been shed on the mechanistic aspects of wound healing along with futuristic discussion on the faith of biogenic silver and gold nanoparticles as potential wound healing agents.

  12. ETAAS determination of thallium and silver from water matrix after colloidal precipitate flotation using lead(II) hexamethylenedithiocarbamate

    OpenAIRE

    TRAJCE STAFILOV; KATARINA CUNDEVA; GORICA PAVLOVSKA

    2001-01-01

    Afast method for the preconcentration of thallium and silver in nanogram quantities in fresh drinking waters (source, well, tap) and waters for irrigation using colloidal precipitate flotation is described. Lead(II) hexamethylenedithiocarbamate, Pb(HMDTC)2 played the role of flotation collector. The experimental conditions for the successful separation of thallium and silver (mass of Pb, amount ofHMDTC-, pHof the system, induction time, type of surfactant etc.) were optimized. After flotation...

  13. Surface-enhanced raman spectroscopy of quinomethionate adsorbed on silver colloids

    International Nuclear Information System (INIS)

    Kim, Mak Soon; Kang, Jae Soo; Park, Si Bum; Lee, Mu Sang

    2003-01-01

    We have studied the surface-enhanced Raman spectroscopy (SERS) spectrum of quinomethionate (6-methyl-1,3-dithiolo(4,5-b)quinoxalin-2-one), which is an insecticide or fungicide used on vegetables and wheat. We observed no signals in the ordinary Raman spectra of solid-state quinomethionate, but when it was adsorbed on a colloidal silver surface, strong vibrational signals were obtained at a very low concentration. The SERS spectra were obtained by silver colloids prepared by the Creighton et al. method. The influence of pH and the aggregation inductors (Cl - , Br - , I - , F - ) on the adsorption mechanism was investigated. Two different adsorption mechanisms were deduced, depending on the experimental conditions: The one N atom or two N atoms are chemisorbed on an Ag surface. An important contribution of the chemical mechanism was inferred when the one N atom was perpendicularly adsorbed on a surface. It is possible that quinomethionate can be detected to about 10 -5 M

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

    Science.gov (United States)

    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

    Science.gov (United States)

    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. Enhancing the stability of colloidal silver nanoparticles using polyhydroxyalkanoates (PHA) from Bacillus circulans (MTCC 8167) isolated from crude oil contaminated soil.

    Science.gov (United States)

    Phukon, Pinkee; Saikia, Jyoti Prasad; Konwar, Bolin Kumar

    2011-09-01

    Polyhydroxyalkanoate (PHA) was produced by growing Bacillus circulans (MTCC 8167) in the specific detection medium. The identification of the polymer as PHA was confirmed by fluorescence microscopy. The PHA was purified and characterized using FT-IR. The silver nanoparticles (SNP) were synthesized from AgNO3 in the dispersed colloids of PHA (0.085%) using NaBH4 (sodium borohydrate as reducing agent). The stability was tested using wave length scanning with a UV-Vis spectrophotometer and finally with transmission electron microscopy. The PHA stabilized solution was found to be stable for 30 days as against the low stability of silver nanoparticles (SNP) solution alone. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Nanostructured Silver Substrates With Stable and Universal SERS Properties: Application to Organic Molecules and Semiconductor Nanoparticles

    Directory of Open Access Journals (Sweden)

    Waurisch C

    2009-01-01

    Full Text Available Abstract Nanostructured silver films have been prepared by thermal deposition on silicon, and their properties as SERS substrates investigated. The optimal conditions of the post-growth annealing of the substrates were established. Atomic force microscopy study revealed that the silver films with relatively dense and homogeneous arrays of 60–80-nm high pyramidal nanoislands are the most efficient for SERS of both organic dye and inorganic nanoparticles analytes. The noticeable enhancement of the Raman signal from colloidal nanoparticles with the help of silver island films is reported for the first time.

  18. Surface-enhanced Raman difference between bombesin and its modified analogues on the colloidal and electrochemically roughen silver surfaces.

    Science.gov (United States)

    Podstawka, Edyta; Ozaki, Yukihiro

    2008-10-01

    In this article, surface-enhanced Raman scattering (SERS) spectra of bombesin (BN) and its six modified analogues ([D-Phe(12)]BN, [Tyr(4)]BN, [Tyr(4),D-Phe(12)]BN, [D-Phe(12),Leu(14)]BN, [Leu(13)-(R)-Leu(14)]BN, and [Lys(3)]BN) on a colloidal silver surface are reported and compared with SERS spectra of these species immobilized onto an ellectrochemically roughen silver electrode. Changes in enhancement and wavenumber of proper bands upon adsorption on different silver surfaces are consistent with BN and its analogues adsorption primarily through Trp(8). Slightly different adsorption states of these molecules are observed depending upon natural amino acids substitution. For example, the indole ring in all the peptides interacts with silver nanoparticles in a edge-on orientation. It is additionally coordinated to the silver through the N(1)--H bond for all the peptides, except [Phe(12)]BN. This is in contrary to the results obtained for the silver roughen electrode that show direct but not strong N(1)--H/Ag interaction for all peptides except [D-Phe(12),Leu(14)]BN and [Leu(13)-(R)-Leu(14)]BN. For BN only C==O is not involved in the chemical coordination with the colloidal surface. [Lys(3)]BN and BN also adsorb with the C--N bond of NH(2) group normal and horizontal, respectively, to the colloidal surface, whereas C--NH(2) in other peptides is tilted to this surface. Also, the Trp(8) --CH(2)-- moiety of only [Tyr(4)]BN, [Lys(3)]BN, and [Tyr(4),D-Phe(12)]BN coordinates to Ag, whereas the Phe(12) ring of [Phe(12)]BN, [Tyr(4),D-Phe(12)]BN, and [D-Phe(12),Leu(14)]BN assists in the peptides binding only on the colloidal silver. (c) 2008 Wiley Periodicals, Inc.

  19. Catalysis of the reduction of Tl+ and of CH2Cl2 by colloidal silver in aqueous solution

    International Nuclear Information System (INIS)

    Henglein, A.

    1979-01-01

    (CH 3 ) 2 COH radicals (1-hydroxy-1-methylethyl) do not reduce Tl + or CH 2 Cl 2 in homogeneous aqueous solution. In the presence of 2.5 x 10 -4 g atom/L of colloidal silver, Tl + is reduced to yield colloidal thallium, and CH 2 Cl 2 to yield Cl - plus CH 3 Cl. These reactions occur in competition with the silver-catalyzed reduction of water. Tl + is reduced in a one-electron transfer reaction and CH 2 Cl 2 in a two-electron transfer process. The effects are understood in terms of the colloidal particles acting as a pool for electrons that is continuously charged by the organic radicals and discharged by water or dissolved substrates. The specific rate for the CH 2 Cl 2 reduction at the silver pool is 4.3 x 10 3 times greater than that of the water reduction. Electrochemical considerations are carried out to estimate a stationary potential of -0.62 V (vs the standard hydrogen electrode) for the electron pool and to discuss the energetics of the observed reactions and the possible role of adsorbed hydrogen atoms. Colloidal silver and organic radicals were radiolytically produced. 7 figures

  20. Silver nanoparticle-E. coli colloidal interaction in water and effect on E. coli survival.

    Science.gov (United States)

    Dror-Ehre, A; Mamane, H; Belenkova, T; Markovich, G; Adin, A

    2009-11-15

    Silver nanoparticles exhibit antibacterial properties via bacterial inactivation and growth inhibition. The mechanism is not yet completely understood. This work was aimed at elucidating the effect of silver nanoparticles on inactivation of Escherichia coli, by studying particle-particle interactions in aqueous suspensions. Stable, molecularly capped, positively or negatively charged silver nanoparticles were mixed at 1 to 60microgmL(-1) with suspended E. coli cells to examine their effect on inactivation of the bacteria. Gold nanoparticles with the same surfactant were used as a control, being of similar size but made up of a presumably inert metal. Log reduction of 5log(10) and complete inactivation were obtained with the silver nanoparticles while the gold nanoparticles did not show any inactivation ability. The effect of molecularly capped nanoparticles on E. coli survival was dependent on particle number. Log reduction of E. coli was associated with the ratio between the number of nanoparticles and the initial bacterial cell count. Electrostatic attraction or repulsion mechanisms in silver nanoparticle-E. coli cell interactions did not contribute to the inactivation process.

  1. Highly stable colloidal TiO2 nanocrystals with strong violet-blue emission

    International Nuclear Information System (INIS)

    Ghamsari, Morteza Sasani; Gaeeni, Mohammad Reza; Han, Wooje; Park, Hyung-Ho

    2016-01-01

    Improved sol–gel method has been applied to prepare highly stable colloidal TiO 2 nanocrystals. The synthesized titania nanocrystals exhibit strong emission in the violet-blue wavelength region. Very long evolution time was obtained by preventing the sol to gel conversion with reflux process. FTIR, XRD, UV–vis absorption, photoluminescence and high resolution transmission electron microscope (HRTEM) were used to study the optical properties, crystalline phase, morphology, shape and size of prepared TiO 2 colloidal nanocrystals. HRTEM showed that the diameter of TiO 2 colloidal nanocrystals is about 5 nm. Although the PL spectra show similar spectral features upon excitation wavelengths at 280, 300 and 350 nm, but their emission intensities are significantly different from each other. Photoluminescence quantum yield for TiO 2 colloidal nanocrystals is estimated to be 49% with 280 nm excitation wavelength which is in agreement and better than reported before. Obtained results confirm that the prepared colloidal TiO 2 sample has enough potential for optoelectronics applications.

  2. Highly stable colloidal TiO{sub 2} nanocrystals with strong violet-blue emission

    Energy Technology Data Exchange (ETDEWEB)

    Ghamsari, Morteza Sasani, E-mail: msghamsari@yahoo.com [Laser & Optics Research School, NSTRI, 11155-3486 Tehran (Iran, Islamic Republic of); Gaeeni, Mohammad Reza [Laser & Optics Research School, NSTRI, 11155-3486 Tehran (Iran, Islamic Republic of); Han, Wooje; Park, Hyung-Ho [Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749 (Korea, Republic of)

    2016-10-15

    Improved sol–gel method has been applied to prepare highly stable colloidal TiO{sub 2} nanocrystals. The synthesized titania nanocrystals exhibit strong emission in the violet-blue wavelength region. Very long evolution time was obtained by preventing the sol to gel conversion with reflux process. FTIR, XRD, UV–vis absorption, photoluminescence and high resolution transmission electron microscope (HRTEM) were used to study the optical properties, crystalline phase, morphology, shape and size of prepared TiO{sub 2} colloidal nanocrystals. HRTEM showed that the diameter of TiO{sub 2} colloidal nanocrystals is about 5 nm. Although the PL spectra show similar spectral features upon excitation wavelengths at 280, 300 and 350 nm, but their emission intensities are significantly different from each other. Photoluminescence quantum yield for TiO{sub 2} colloidal nanocrystals is estimated to be 49% with 280 nm excitation wavelength which is in agreement and better than reported before. Obtained results confirm that the prepared colloidal TiO{sub 2} sample has enough potential for optoelectronics applications.

  3. Colloidal silver nanoparticles prepared by UV-light induced citrate reduction technique for the quantitative detection of uric acid

    Science.gov (United States)

    Maity, Anupam; Panda, Sovan Kumar

    2018-04-01

    Reddish-yellow color colloid consisting of silver nanoparticles (Ag NPs) has been synthesized by reducing aqueous AgNO3 solution by photo-induced citrate reduction technique under UV light. As prepared colloid exhibits single and intense plasmonic absorption peak in the violet region of the visible spectra with the peak centered at 405 nm. The NPs are fine and spherical with diameter ranging from 5 to 10 nm. These colloidal NPs have been used for the quantitative detection of uric acid by UV-VIS spectroscopy. A linear red shifting of the characteristics Plasmonic absorption peak of Ag NPs is observed with uric acid concentration. Uric acid can be detected by UV-VIS spectroscopy down to 5 nM limit using the prepared colloid.

  4. The Challenge of Producing and Marketing Colloidal Silver Water Filters in Nepal

    Directory of Open Access Journals (Sweden)

    Anne Bogler

    2015-07-01

    Full Text Available Background: Obtaining safe drinking water can be a challenge in Nepal. By training potters and setting up production sites for Colloidal Silver Filters, several non-governmental organizations have tried to provide local people with a low-cost option for household water treatment. Out of 19 trained entrepreneurs, only four are currently producing filters. The goal of this evaluation was to find out what conditions lead to the successful continuation of the production and the reasons for failure. Methods: The evaluation of the potters was based on a Qualitative Comparative Analysis and the conditions looked at were: “Production”, “Collaboration”, “Market” and “Potter”. Results: Analysis showed that production problems and insufficient demand led to the termination of ceramic filter production and that both trouble-free production and high demand are necessary for a sustainable business.

  5. Colloidal silver nanoparticle gradient layer prepared by drying between two walls of different wettability

    International Nuclear Information System (INIS)

    Roth, S V; Kuhlmann, M; Walter, H; Snigirev, A; Snigireva, I; Burghammer, M; Riekel, C; Lengeler, B; Schroer, C G; Mueller-Buschbaum, P

    2009-01-01

    A one-dimensional silver (Ag) nanoparticle gradient layer is prepared from an aqueous colloidal solution upon a polystyrene (PS) coated silicon (Si) substrate. For preparation two walls of different wettability are used. The 40 nm PS-layer exhibits a locally constant film thickness due to the strong roughness correlation with the underlying Si-substrate and is less wettable as compared to the glass plate placed above. The Ag nanoparticles have a triangular prism-like shape. The structural characterization of the obtained complex gradient formed by drying is performed with microbeam grazing incidence small-angle x-ray scattering based on compound refractive lenses. Due to the adsorption from aqueous solution in the selective geometry a double gradient type structure defined by two areas with characteristic lateral lengths and a cross-over regime between both is observed.

  6. Study of the surface-enhanced Raman spectroscopy of residual impurities in hydroxylamine-reduced silver colloid and the effects of anions on the colloid activity.

    Science.gov (United States)

    Dong, Xiao; Gu, Huaimin; Liu, Fangfang

    2012-03-01

    The paper investigated the residual ions in hydroxylamine-reduced silver colloid (HRSC) and the relationship between the condition of HRSC and the enhanced mechanisms of this colloid. We also detected the SERS of MB and studied the effects of anions on the Raman signal. In the case of HRSC, the bands of residual ions diminish while the bands of Ag-anions increase gradually with increasing the concentrations of Cl(-) and NO(3)(-). It means the affinity of residual ions on the silver surface is weaker than that of Cl(-) and NO(3)(-) and the residual ions are replaced gradually by the added Cl(-) or NO(3)(-). The Raman signal of residual ions can be detected by treatment with anions that do not bind strongly to the silver surface, such as SO(4)(2-). The most intense band of Ag-anions bonds can be also observed when adding weakly binding anions to the colloid. However, the anions which make up the Ag-anions bonds are residual Cl(-) and the effect of weakly binding anions is only to aggregate the silver particles. Residual Cl(-) can be replaced by I(-) which has the highest affinity. From the detection of methylene blue (MB), the effects of anions on the enhancement of Raman signal are discussed in detail, and these findings could make the conditions suitable for detecting analytes in high efficiency. This study will have a profound implication to SERS users about their interpretation of SERS spectra when obtaining these anomalous bands. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Formation of stable uranium(VI) colloidal nanoparticles in conditions relevant to radioactive waste disposal.

    Science.gov (United States)

    Bots, Pieter; Morris, Katherine; Hibberd, Rosemary; Law, Gareth T W; Mosselmans, J Frederick W; Brown, Andy P; Doutch, James; Smith, Andrew J; Shaw, Samuel

    2014-12-09

    The favored pathway for disposal of higher activity radioactive wastes is via deep geological disposal. Many geological disposal facility designs include cement in their engineering design. Over the long term, interaction of groundwater with the cement and waste will form a plume of a hyperalkaline leachate (pH 10-13), and the behavior of radionuclides needs to be constrained under these extreme conditions to minimize the environmental hazard from the wastes. For uranium, a key component of many radioactive wastes, thermodynamic modeling predicts that, at high pH, U(VI) solubility will be very low (nM or lower) and controlled by equilibrium with solid phase alkali and alkaline-earth uranates. However, the formation of U(VI) colloids could potentially enhance the mobility of U(VI) under these conditions, and characterizing the potential for formation and medium-term stability of U(VI) colloids is important in underpinning our understanding of U behavior in waste disposal. Reflecting this, we applied conventional geochemical and microscopy techniques combined with synchrotron based in situ and ex situ X-ray techniques (small-angle X-ray scattering and X-ray adsorption spectroscopy (XAS)) to characterize colloidal U(VI) nanoparticles in a synthetic cement leachate (pH > 13) containing 4.2-252 μM U(VI). The results show that in cement leachates with 42 μM U(VI), colloids formed within hours and remained stable for several years. The colloids consisted of 1.5-1.8 nm nanoparticles with a proportion forming 20-60 nm aggregates. Using XAS and electron microscopy, we were able to determine that the colloidal nanoparticles had a clarkeite (sodium-uranate)-type crystallographic structure. The presented results have clear and hitherto unrecognized implications for the mobility of U(VI) in cementitious environments, in particular those associated with the geological disposal of nuclear waste.

  8. ETAAS determination of thallium and silver from water matrix after colloidal precipitate flotation using lead(II hexamethylenedithiocarbamate

    Directory of Open Access Journals (Sweden)

    TRAJCE STAFILOV

    2001-10-01

    Full Text Available Afast method for the preconcentration of thallium and silver in nanogram quantities in fresh drinking waters (source, well, tap and waters for irrigation using colloidal precipitate flotation is described. Lead(II hexamethylenedithiocarbamate, Pb(HMDTC2 played the role of flotation collector. The experimental conditions for the successful separation of thallium and silver (mass of Pb, amount ofHMDTC-, pHof the system, induction time, type of surfactant etc. were optimized. After flotation separation from the mother liquor, the solid sublate containing traces of thallium and silver was dissolved and the analytes were determined by electrothermal atomic absorption spectrometry (ETAAS. The results of the ETAAS analysis are compared with those obtained by inductively coupled plasma-atomic emission spectrometry. The detection limit for thallium by this method is 0.027 mg/l, and for silver 0.005 microg/l.

  9. Highly Stable Monocrystalline Silver Clusters for Plasmonic Applications

    DEFF Research Database (Denmark)

    Novikov, Sergey M.; Popok, Vladimir N.; Evlyukhin, Andrey B.

    2017-01-01

    Plasmonic sensor configurations utilizing localized plasmon resonances in silver nanostructures typically suffer from the rapid degradation of silver under ambient atmospheric conditions. In this work, we report on the fabrication and detailed characterization of ensembles of monocrystalline silver......-beam technique and characterized by linear spectroscopy, two-photon-excited photoluminescence, surface-enhanced Raman scattering microscopy, and transmission electron, helium ion, and atomic force microscopies. It is found that the fabricated ensembles of monocrystalline silver NPs preserve their plasmonic...... properties (monitored with optical spectroscopy) and strong field enhancements (revealed by surface-enhanced Raman spectroscopy) at least 5 times longer as compared to chemically synthesized silver NPs with similar sizes. The obtained results are of high practical relevance for the further development...

  10. Characterization of a silica-PVA hybrid for high density and stable silver dissolution

    Energy Technology Data Exchange (ETDEWEB)

    Dorin, Bryce, E-mail: bryce.dorin@postgrad.manchester.ac.uk [The Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); School of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Zhu, Guangyu, E-mail: g.zhu@liverpool.ac.uk [Lairdside Laser Engineering Centre, The University of Liverpool, Campbeltown Road, Merseyside, CH41 9HP (United Kingdom); Parkinson, Patrick, E-mail: patrick.parkinson@manchester.ac.uk [The Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Perrie, Walter, E-mail: wpfemto1@liverpool.ac.uk [Lairdside Laser Engineering Centre, The University of Liverpool, Campbeltown Road, Merseyside, CH41 9HP (United Kingdom); Benyezzar, Med, E-mail: med.benyezzar@manchester.ac.uk [The Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Scully, Patricia, E-mail: patricia.scully@manchester.ac.uk [The Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); School of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

    2016-07-01

    A silica and polyvinyl alcohol (PVA) hybrid material mixed with a high density of silver ions is synthesised and characterized in this work. The hybrid material can be cast into thick films, which we determined to be homogeneous using Raman spectroscopy. We observed that the silver ions remain stable in the material over time and at temperatures of 100 °C, which represents a marked improvement over previous solid solutions of silver. Differential scanning calorimetry and thermogravimetric analysis indicate the rapid activation of silver at 173 °C, resulting in a dense formation of silver nanoparticles within the hybrid. The activation of silver was also demonstrated in 3-dimensional geometries using femtosecond duration laser pulses. These results illustrate the silica-PVA hybrid is an attractive material for developing silver-insulator composites. - Highlights: • A novel PVA-silica hybrid is developed for silver ion dissolution. • The hybrid exhibits a high silver saturation point and good silver stability. • Heating and laser irradiation are capable of converting the silver ions to metal. • The hybrid material enables the fabrication of 3D metal-insulator composites.

  11. Catalysis of the reduction of Tl+ and of CH2Cl2 by colloidal silver in aqueous solution

    International Nuclear Information System (INIS)

    Henglein, A.

    1979-01-01

    (CH 3 ) 2 COH radicals (1-hydroxy-1-methylethyl) do not reduce Tl + or CH 2 CL 2 in homogeneous aqueous solution. In the presence of 2.5 x 10 -4 g atom/L of colloidal silver, Tl + is reduced to yield colloidal thallium, and CH 2 Cl 2 to yield Cl - plus CH 3 Cl. These reactions occur in competition with the silver-catalyzed reduction of water. Tl + is reduced in a one-electron transfer reaction and CH 2 Cl 2 in a two-electron transfer process. The effects are understood in terms of the colloidal particles acting as a pool for electrons that is continuously charged by the organic radicals and discharged by water or dissolved substrates. The specific rate for the CH 2 Cl 2 reduction at the silver pool is 4.3 x 10 3 times greater than that of the water reduction. Electrochemical considerations are carried out to estimate a stationary potential of -0.62 V (vs the standard hydrogen electrode) for the electron pool and to discuss the energetics of the observed reactions and tha materials handling point of view, are being determined

  12. Evaluation of medicinal plants and colloidal silver efficiency against Vibrio parahaemolyticus infection in Litopenaeus vannamei cultured at low salinity.

    Science.gov (United States)

    Morales-Covarrubias, María Soledad; García-Aguilar, Noemí; Bolan-Mejía, María Del; Puello-Cruz, Ana Carmela

    2016-11-22

    In shrimp aquaculture, reduction in the use of synthetic antibiotics is a priority due to the high incidence of resistant bacteria (Vibrio) in the white shrimp Litopenaeus vannamei. An increasing number of studies show bactericidal activity of natural treatments in aquaculture. The effectiveness of neem (Azadirachta indica) and oregano (Lippia berlandieri) aqueous extracts and colloidal silver against V. parahaemolyticus were evaluated in low salinity shrimp culture. Results show that aqueous extracts of oregano and neem each present a minimum inhibitory concentration (MIC) of 62.50 mg ml-1 and inhibitory halos of 12.0 to 19.0 mm. Colloidal silver gave a MIC of 2 mg ml-1, and the inhibitory halos were found to be between 11.8 and 18.8 mm, depending on treatment concentrations. An in vivo challenge test was conducted on white shrimp postlarvae cultured at low salinity (5 practical salinity units, PSU), and a significant increase (p colloidal silver 90%), when compared to the control (0%) in the challenge test. However, no significant differences were observed between treatments, suggesting that they all act as alternative bactericidal source agents against V. parahaemolyticus infections for L. vannamei postlarvae when cultured at 5 PSU.

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

    Science.gov (United States)

    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.

  14. Silver nanoparticles in complex biological media: assessment of colloidal stability and protein corona formation

    Energy Technology Data Exchange (ETDEWEB)

    Argentiere, Simona, E-mail: simona.argentiere@fondazionefilarete.com; Cella, Claudia, E-mail: claudia.cella@unimi.it [Fondazione Filarete (Italy); Cesaria, Maura, E-mail: maura.cesaria@le.infn.it [Università del Salento, Dipartimento di Matematica e Fisica “Ennio De Giorgi” (Italy); Milani, Paolo, E-mail: paolo.milani@mi.infn.it; Lenardi, Cristina, E-mail: cristina.lenardi@mi.infn.it [Università degli Studi di Milano, CIMAINA and Dipartimento di Fisica (Italy)

    2016-08-15

    Engineered silver nanoparticles (AgNPs) are among the most used nanomaterials in consumer products, therefore concerns are raised about their potential for adverse effects in humans and environment. Although an increasing number of studies in vitro and in vivo are being reported on the toxicity of AgNPs, most of them suffer from incomplete characterization of AgNPs in the tested biological media. As a consequence, the comparison of toxicological data is troublesome and the toxicity evaluation still remains an open critical issue. The development of a reliable protocol to evaluate interactions of AgNPs with surrounding proteins as well as to assess their colloidal stability is therefore required. In this regard, it is of importance not only to use multiple, easy-to-access and simple techniques but also to understand limitations of each characterization methods. In this work, the morphological and structural behaviour of AgNPs has been studied in two relevant biological media, namely 10 % FBS and MP. Three different techniques (Dynamic Light Scattering, Transmission Electron Microscopy, UV–Vis spectroscopy) were tested for their suitability in detecting AgNPs of three different sizes (10, 40 and 100 nm) coated with either citrate or polyvinylpyrrolidone. Results showed that UV–Vis spectroscopy is the most versatile and informative technique to gain information about interaction between AgNPs and surrounding proteins and to determine their colloidal stability in the tested biological media. These findings are expected to provide useful insights in characterizing AgNPs before performing any further in vitro/in vivo experiment.

  15. Study on the synthesis of colloidal silver nanoparticles by γ-irradiation for using as an antimicrobial substance

    International Nuclear Information System (INIS)

    Dang Van Phu; Nguyen Trieu; Vo Thi Kim Lang; Doan Thi The; Nguyen Quoc Hien; Bui Duy Du

    2007-01-01

    Colloidal silver nanoparticles of different sizes less than 20 nm were synthesized by γ Co-60 irradiation of Ag + in solution containing polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP) as stabilizer. The saturated conversion dose (D) of Ag + to Ag 0 and particle size (d) depended on Ag + concentration from 1 to 50 mM were found out to be as: D (kGy) = - 0.0041[Ag + ] 2 + 0.8674[Ag + ] + 3.2262, d (nm) = 0.0029[Ag + ] 2 + 0.0529[Ag + ] + 0.9259 for PVA 2 g/100 ml and D (kGy) = -0.0151[Ag + ] 2 + 1.5258[Ag + ] + 9.2441, d (nm) = -0.0016[Ag + ] 2 + 0.3757[Ag + ] + 6.2886 for PVP 2 g/100 ml. Colloidal silver nanoparticles showed the maximal absorption peak at λ max ∼ 400-420 nm. The size and size distribution of silver nanoparticles were characterized by transmission electron microscopy (TEM). The silver nanoparticle size of approximate 10 nm showed highly antimicrobial effect against E.coli and S.aureus. (author)

  16. Durable antibacterial and cross-linking cotton with colloidal silver nanoparticles and butane tetracarboxylic acid without yellowing.

    Science.gov (United States)

    Montazer, Majid; Alimohammadi, Farbod; Shamei, Ali; Rahimi, Mohammad Karim

    2012-01-01

    Colloidal nano silver was applied on the surface of cotton fabric and stabilized using 1,2,3,4-butanetetracarboxylic acid (BTCA). The two properties of antimicrobial activity and resistance against creasing were imparted to the samples of fabric as a result of the treatment with silver nano colloid and BTCA. The antimicrobial property of samples was evaluated using two pathogenic bacteria including Escherichia coli and Staphylococcus aureus as outstanding barometers in this field. The durability of applied nanoparticles, color variation, wettability and wrinkle recovery angle of the treated samples were investigated employing related credible standards. The presence of nano silver particles on the surface of treated cotton fabric was proved using EDS spectrum as well as the SEM images. Furthermore, the creation of cross-links was confirmed by the means of both ATR-FTIR and Raman spectra. In conclusion, it was observed that BTCA plays a prominent role in stabilizing silver nanoparticle. Besides, Wettability and winkle recovery angle of finished samples decreased and increased, respectively. In addition, it is noteworthy that no obvious color variation was observed. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Chronic effect of waterborne colloidal silver nanoparticles on plasma biochemistry and hematology of rainbow trout (Oncorhynchus mykiss

    Directory of Open Access Journals (Sweden)

    Seyed Ali Johari

    2016-05-01

    Full Text Available Objective: To investigate the possible effects of silver nanoparticles (AgNPs on some blood and plasma indices of rainbow trout (Oncorhynchus mykiss. Methods: Hence, fish were exposed for 21 days to sub-lethal concentrations of colloidal AgNPs and blood parameters including erythrocyte size and hematocrit, plasma parameters including cholinesterase, cortisol, sodium, chloride, and potassium, and also silver concentration in plasma were measured following the 11th and 21st days of exposure. Results: According to the results of present study, higher concentrations of AgNPs had more significant effects on plasma biochemistry and hematology of trout. The greatest impacts were decline of chloride ions and increase of cortisol and cholinesterase. Also fish exposed to AgNPs significantly increased silver concentration in the plasma. Conclusions: Further studies are needed to identify appropriate blood biomarkers following fish exposed to nanomaterials, especially AgNPs.

  18. Adsorbed States of phosphonate derivatives of N-heterocyclic aromatic compounds, imidazole, thiazole, and pyridine on colloidal silver: comparison with a silver electrode.

    Science.gov (United States)

    Podstawka, Edyta; Olszewski, Tomasz K; Boduszek, Bogdan; Proniewicz, Leonard M

    2009-09-03

    Here, we report a systematic surface-enhanced Raman spectroscopy (SERS) study of the structures of phosphonate derivatives of the N-heterocyclic aromatic compounds imidazole (ImMeP ([hydroxy(1H-imidazol-5-yl)methyl]phosphonic acid) and (ImMe)(2)P (bis[hydroxy-(1H-imidazol-4-yl)-methyl]phosphinic acid)), thiazole (BAThMeP (butylaminothiazol-2-yl-methyl)phosphonic acid) and BzAThMeP (benzylaminothiazol-2-yl-methyl)phosphonic acid)), and pyridine ((PyMe)(2)P (bis[(hydroxypyridin-3-yl-methyl)]phosphinic acid)) adsorbed on nanometer-sized colloidal particles. We compared these structures to those on a roughened silver electrode surface to determine the relationship between the adsorption strength and the geometry. For example, we showed that all of these biomolecules interact with the colloidal surface through aromatic rings. However, for BzAThMeP, a preferential interaction between the benzene ring and the colloidal silver surface is observed more so than that between the thiazole ring and this substrate. The PC(OH)C fragment does not take part in the adsorption process, and the phosphonate moiety of ImMeP and (ImMe)(2)P, being removed from the surface, only assists in this process.

  19. Silver colloidal nanoparticle stability: influence on Candida biofilms formed on denture acrylic.

    Science.gov (United States)

    Monteiro, Douglas Roberto; Takamiya, Aline Satie; Feresin, Leonardo Perina; Gorup, Luiz Fernando; de Camargo, Emerson Rodrigues; Delbem, Alberto Carlos Botazzo; Henriques, Mariana; Barbosa, Debora Barros

    2014-08-01

    Our aim in this study was to evaluate how the chemical stability of silver nanoparticles (SNs) influences their efficacy against Candida albicans and C. glabrata biofilms. Several parameters of SN stability were tested, namely, temperature (50ºC, 70ºC, and 100ºC), pH (5.0 and 9.0), and time of contact (5 h and 24 h) with biofilms. The control was defined as SNs without temperature treatment, pH 7, and 24 h of contact. These colloidal suspensions at 54 mg/L were used to treat mature Candida biofilms (48 h) formed on acrylic. Their efficacy was determined by total biomass and colony-forming unit quantification. Data were analyzed using analysis of variance and the Bonferroni post hoc test (α = 0.05). The temperature and pH variations of SNs did not affect their efficacy against the viable cells of Candida biofilms (P > 0.05). Moreover, the treatment periods were not decisive in terms of the susceptibility of Candida biofilms to SNs. These findings provide an important advantage of SNs that may be useful in the treatment of Candida-associated denture stomatitis. © The Author 2014. Published by Oxford University Press on behalf of The International Society for Human and Animal Mycology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  20. Impacts of select organic ligands on the colloidal stability, dissolution dynamics, and toxicity of silver nanoparticles.

    Science.gov (United States)

    Pokhrel, Lok R; Dubey, Brajesh; Scheuerman, Phillip R

    2013-11-19

    Key understanding of potential transformations that may occur on silver nanoparticle (AgNP) surface upon interaction with naturally ubiquitous organic ligands (e.g., -SH (thoil), humic acid, or -COO (carboxylate)) is limited. Herein we investigated how dissolved organic carbon (DOC), -SH (in cysteine, a well-known Ag(+) chelating agent), and -COO (in trolox, a well-known antioxidant) could alter the colloidal stability, dissolution rate, and toxicity of citrate-functionalized AgNPs (citrate-AgNPs) against a keystone crustacean Daphnia magna. Cysteine, DOC, or trolox amendment of citrate-AgNPs differentially modified particle size, surface properties (charge, plasmonic spectra), and ion release dynamics, thereby attenuating (with cysteine or trolox) or promoting (with DOC) AgNP toxicity. Except with DOC amendment, the combined toxicity of AgNPs and released Ag under cysteine or trolox amendment was lower than of AgNO3 alone. The results of this study show that citrate-AgNP toxicity can be associated with oxidative stress, ion release, and the organism biology. Our evidence suggests that specific organic ligands available in the receiving waters can differentially surface modify AgNPs and alter their environmental persistence (changing dissolution dynamics) and subsequently the toxicity; hence, we caveat to generalize that surface modified nanoparticles upon environmental release may not be toxic to receptor organisms.

  1. Immobilization, direct electrochemistry and electrocatalysis of hemoglobin on colloidal silver nanoparticles-chitosan film

    Energy Technology Data Exchange (ETDEWEB)

    Yu Chunmei [College of Chemistry and Chemical Engineering and Materials Science, Suzhou University, Suzhou 215123 (China); Institute of Analytical Chemistry for Life Science, School of Public Health, Nantong University, Nantong 226007 (China); Zhou Xiaohui [Institute of Analytical Chemistry for Life Science, School of Public Health, Nantong University, Nantong 226007 (China); Gu Haiying, E-mail: hygu@ntu.edu.c [Institute of Analytical Chemistry for Life Science, School of Public Health, Nantong University, Nantong 226007 (China)

    2010-12-01

    This paper reports on the fabrication and characterization of hemoglobin (Hb)-colloidal silver nanoparticles (CSNs)-chitosan film on the glassy carbon electrode and its application on electrochemical biosensing. CSNs could greatly enhance the electron transfer reactivity of Hb as a bridge. In the phosphate buffer solution with pH value of 7.0, Hb showed a pair of well-defined redox peaks with the formal potential (E{sup 0'}) of -0.325 V (vs. SCE). The immobilized Hb in the film maintained its biological activity, showing a surface-controlled process with the heterogeneous electron transfer rate constant (k{sub s}) of 1.83 s{sup -1} and displayed the same features of a peroxidase in the electrocatalytic reduction of oxygen and hydrogen peroxide (H{sub 2}O{sub 2}). The linear range for the determination of H{sub 2}O{sub 2} was from 0.75 {mu}M to 0.216 mM with a detection limit of 0.5 {mu}M (S/N = 3). Such a simple assemble method could offer a promising platform for further study on the direct electrochemistry of other redox proteins and the development of the third-generation electrochemical biosensors.

  2. Enhanced optical output of InGaN/GaN near-ultraviolet light-emitting diodes by localized surface plasmon of colloidal silver nanoparticles

    International Nuclear Information System (INIS)

    Hong, Sang-Hyun; Kim, Jae-Joon; Jung, Yen-Sook; Kim, Dong-Yu; Park, Seong-Ju; Kang, Jang-Won; Yim, Sang-Youp

    2015-01-01

    We report on the characteristics of localized surface plasmon (LSP)-enhanced near-ultraviolet light-emitting diodes (NUV-LEDs) fabricated by using colloidal silver (Ag) nanoparticles (NPs). Colloidal Ag NPs were deposited on the 20 nm thick p-GaN spacer layer using a spray process. The optical output power of NUV-LEDs with colloidal Ag NPs was increased by 48.7% at 20 mA compared with NUV-LEDs without colloidal Ag NPs. The enhancement was attributed to increased internal quantum efficiency caused by the resonance coupling between excitons in the multiple quantum wells and the LSPs in the Ag NPs. (paper)

  3. Colloid stable sorbents for cesium removal: Preparation and application of latex particles functionalized with transition metals ferrocyanides

    Energy Technology Data Exchange (ETDEWEB)

    Avramenko, Valentin [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation); Bratskaya, Svetlana, E-mail: sbratska@ich.dvo.ru [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation); Zheleznov, Veniamin; Sheveleva, Irina [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation); Voitenko, Oleg [Far Eastern Federal University, Laboratory of Electron Microscopy and Image Processing, 27, Oktyabr' skaya Street, Vladivostok 690950 (Russian Federation); Sergienko, Valentin [Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159 ave 100-letiya Vladivostoka, Vladivostok 690022 (Russian Federation)

    2011-02-28

    In this paper we suggest a principally new approach to preparation of colloid stable selective sorbents for cesium uptake using immobilization of transition metals (cobalt, nickel, and copper) ferrocyanides in nanosized carboxylic latex emulsions. The effects of ferrocyanide composition, pH, and media salinity on the sorption properties of the colloid stable sorbents toward cesium ions were studied in solutions containing up to 200 g/L of sodium nitrate or potassium chloride. The sorption capacities of the colloid sorbents based on mixed potassium/transition metals ferrocyanides were in the range 1.3-1.5 mol Cs/mol ferrocyanide with the highest value found for the copper ferrocyanide. It was shown that the obtained colloid-stable sorbents were capable to penetrate through bulk materials without filtration that made them applicable for decontamination of solids, e.g. soils, zeolites, spent ion-exchange resins contaminated with cesium radionuclides. After decontamination of liquid or solid radioactive wastes the colloid-stable sorbents can be easily separated from solutions by precipitation with cationic flocculants providing localization of radionuclides in a small volume of the precipitates formed.

  4. The effectiveness of topical colloidal silver in recalcitrant chronic rhinosinusitis: a randomized crossover control trial.

    Science.gov (United States)

    Scott, John R; Krishnan, Rohin; Rotenberg, Brian W; Sowerby, Leigh J

    2017-11-25

    Recalcitrant chronic rhinosinusitis without polyposis (CRSsP) is a challenging condition to manage as traditional medical therapies and surgery fail to provide satisfactory clinical improvements. Colloidal silver (CS), a widely used naturopathic agent, has recently shown anti-biofilm properties both in vitro and within a rhinosinusitis animal model. To date, no trials involving humans have been published in world literature. The purpose of this study was to assess the efficacy of CS as a topical nasal spray in patients with refractory CRSsP. A prospective cohort study was conducted using a convenience sample of 20 randomized patients with crossover methodology, comparing nasal sprays with CS versus saline. Patients sprayed twice daily for six weeks with the first intervention and then switched to the second for the next six weeks, with measurements made at baseline and each time point. Primary outcomes were changes in SNOT-22 and Lund-Kennedy (LK) endoscopic scores. All analysis was non-parametric and was conducted using STATA 14. Twenty-two patients were enrolled in the study with 20 completing the entire protocol. Mean 6-week change in SNOT-22 scores were -2.8 and 1.0 for saline and CS, respectively (p = 0.373). Similarly, mean 6-week change in LK scores were -1.4 and -1.1 for saline and CS, respectively (p = 0.794). Significant period effects were observed with the SNOT-22 score between the randomized groups. No participants experienced negative health effects directly attributable to the administration of intranasal CS. Commercially available CS nasal spray did not demonstrate any meaningful subjective or objective improvements in patients with recalcitrant CRSsP. NCT02403479 . Registered on March 1, 2015.

  5. Formation of plasmonic colloidal silver for flexible and printed electronics using laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Kassavetis, S., E-mail: skasa@physics.auth.gr [University of Ioannina, Department of Materials Science and Engineering, 45110 Ioannina (Greece); Kaziannis, S. [University of Ioannina, Department of Physics, 45110 Ioannina (Greece); Pliatsikas, N. [University of Ioannina, Department of Materials Science and Engineering, 45110 Ioannina (Greece); Aristotle University of Thessaloniki, Department of Physics, 54124 Thessaloniki (Greece); Avgeropoulos, A.; Karantzalis, A.E. [University of Ioannina, Department of Materials Science and Engineering, 45110 Ioannina (Greece); Kosmidis, C. [University of Ioannina, Department of Physics, 45110 Ioannina (Greece); Lidorikis, E. [University of Ioannina, Department of Materials Science and Engineering, 45110 Ioannina (Greece); Patsalas, P. [Aristotle University of Thessaloniki, Department of Physics, 54124 Thessaloniki (Greece)

    2015-05-01

    Highlights: • Silver plasmonic colloidal in organic solvents by ps laser ablation process. • Ag NPs that meet size requirements of the printed organic electronics technology. • Ag NPs size refinement by secondary process using the 355 nm beam of a ns laser. - Abstract: Laser ablation (LA) in liquids has been used for the development of various nanoparticles (NPs); among them, Ag NPs in aqueous solutions (usually produced by nanosecond (ns) LA) have attracted exceptional interest due to its strong plasmonic response. In this work, we present a comprehensive study of the LA of Ag in water, chloroform and toluene, with and without PVP, using a picosecond (ps) Nd:YAG laser and we consider a wide range of LA parameters such as the laser wavelength (1064, 532, 355 nm), the pulse energy (0.3–17 mJ) and the number of pulses. In addition, we consider the use of a secondary nanosecond laser beam for the refinement of the NPs size distribution. The optical properties of the NPs were evaluated by in situ optical transmittance measurements in the UV–vis spectral ranges. The morphology of the NPs and the formation of aggregates were investigated by Scanning Electron Microscopy and High-Resolution Transmission Electron Microscopy. The ps LA process resulted in the development of bigger Ag NPs, compared to the ns LA, compatible with the size requirements of the printed organic electronics technology. The optimum conditions for the ps LA of Ag in organic solvents include the use of the 355 nm beam at low pulse energy (<1 mJ); these conditions rendered isolated Ag nanoparticles manifesting strong and well defined surface plasmon resonance peak. The use of the secondary ns laser beam was proven to be able to refine the nanoparticles to intermediate size between those produced by the single ns or ps LA.

  6. Evaluation of Flexural Strength of Polymethyl Methacrylate modified with Silver Colloidal Nanoparticles subjected to Two Different Curing Cycles: An in vitro Study.

    Science.gov (United States)

    Munikamaiah, Ranganath L; Jain, Saket K; Pal, Kapil S; Gaikwad, Ajay

    2018-03-01

    Silver colloidal nanoparticles have been incorporated into acrylic resins to induce antimicrobial properties. However, as additives, they can influence the mechanical properties of the final product. Mechanical properties are also dependent on different curing cycles. The aim of this study was to evaluate flexural strength of a denture base resin incorporated with different concentrations of silver colloidal nanoparticles subjected to two different curing cycles. Lucitone 199 denture base resin was used into which silver colloidal nanoparticles were incorporated at 0.5 and 5% by polymer mass. Specimens devoid of nanoparticles were used as controls. A total of 60 specimens were fabricated and divided into two groups. Each group was divided into three subgroups consisting of 10 specimens each. The specimens were fabricated according to American Dental Association (ADA) specification No. 12 and tested for flexural strength using universal testing machine. Silver colloidal nanoparticle incorporation at 0.5% concentration increased the mean flexural strength in both curing cycles by 7.5 and 4.4%, respectively, when compared with the control group. The study suggested that the mean flexural strength value of 0.5% silver colloidal nanoparticles in denture base resin was above the value of the control group both in short and long curing cycles, which makes it clinically suitable as a denture base material. However, at 5% concentration, the statistically significant amount of decrease in flexural strength compared with the value of control group both in short and long curing cycles gives it a questionable prognosis. The specimens incorporated with the antimicrobial agent 0.5% silver colloidal nanoparticles and processed by long curing cycles showed significant increase in its flexural strength compared with the control group, which makes it clinically suitable as a denture base material.

  7. Silver colloidal effects on excited-state structure and intramolecular charge transfer of p-N, N-dimethylaminobenzoic acid in aqueous cyclodextrin solutions

    International Nuclear Information System (INIS)

    Choi, Jung Kwon; Kim, Yang Hee; Yoon, Min Joong; Lee, Seung Joon; Kim, Kwan; Jeoung, Sae Chae

    2001-01-01

    The silver colloidal effects on the excited-state structure and intramolecular charge transfer (ICT) of p-N,N-dimethylaminobenzoic acid (DMABA) in aqueous cyclodextrin (CD) solutions have been investigated by UV-VIS absorption, steady-state and time-resolved fluorescence, and transient Raman spectroscopy. As the concentration of silver colloids increases, the ratio of the ICT emission to the normal emission (I a /I b ) of DMABA in the aqueous α-CD solutions are greatly decreased while the I a /I b values in the aqueous β-CD solutions are significantly enhanced. It is also noteworthy that the ICT emission maxima are red-shifted by 15-40 nm upon addition of silver colloids, implying that DMABA encapsulated in α-CD or β-CD cavity is exposed to more polar environment. The transient resonance Raman spectra of DMABA in silver colloidal solutions demonstrate that DMABA in the excited-state is desorbed from silver colloidal surfaces as demonstrated by the disappearance of v s (CO 2 - )(1380 cm -1 ) with appearance of v (C-OH)(1280 cm -1 ) band, respectively. Thus, in the aqueous β-CD solutions the carboxylic acid group of DMABA in the excited-state can be readily hydrogen bonded with the secondary hydroxyl group of β-CD while in aqueous and α-CD solutions the carboxylic acid group of DMABA has the hydrogen-bonding interaction with water. Consequently, in the aqueous β-CD solutions the enhancement of the I a /I b value arises from the intermolecular hydrogen-bonding interaction between DMABA and the secondary hydroxyl group of β-CD as well as the lower polarity of the rim of the β-CD cavity compared to bulk water. This is also supported by the increase of the association constant for DMABA/β-CD complex in the presence of silver colloids

  8. Mechanically stable antimicrobial chitosan-PVA-silver nanocomposite coatings deposited on titanium implants.

    Science.gov (United States)

    Mishra, Sandeep K; Ferreira, J M F; Kannan, S

    2015-05-05

    Bionanocomposite coatings with antimicrobial activity comprising polyvinyl alcohol (PVA)-capped silver nanoparticles embedded in chitosan (CS) matrix were developed by a green soft chemistry synthesis route. Colloidal sols of PVA-capped silver nanoparticles (AgNPs) were synthesized by microwave irradiating an aqueous solution comprising silver nitrate and PVA. The bionanocomposites were prepared by adding an aqueous solution of chitosan to the synthesized PVA-capped AgNPs sols in appropriate ratios. Uniform bionanocomposite coatings with different contents of PVA-capped AgNPs were deposited onto titanium substrates by "spread casting" followed by solvent evaporation. Nanoindentation and antimicrobial activity tests performed on CS and bionanocomposites revealed that the incorporation of PVA-capped AgNPs enhanced the overall functional properties of the coatings, namely their mechanical stability and bactericidal activity against Escherichia coli and Staphylococcus aureus. The coated specimens maintained their antimicrobial activity for 8h due to the slow sustained release of silver ions. The overall benefits for the relevant functional properties of the coatings were shown increase with increasing contents of PVA-capped AgNPs in the bionanocomposites. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Toxicological evaluation of nano-sized colloidal silver in experiments on mice. behavioral reactions, morphology of internals

    Directory of Open Access Journals (Sweden)

    N.V. Zaitseva

    2015-06-01

    Full Text Available The results of toxicity studies of nano-sized colloidal silver (NCC, the most widely used in medicine, food and life, are given. When evaluating safe doses of silver NP (using commercially available NCC solution stabilized with polyvinylpyrrolidone (PVP, with the size of silver NP at the range of 5-80 nm when orally administered to male mice, BALB/c mice at doses of 0.1; 1.0 and 10 mg/kg of body weight per silver different effects from the motor and orienting-exploratory activity were revealed, for the part of them the dependence on the dose of the NCC was typical. The following peculiarities were found: reduction in motor activity to reduce the frequency of activities requiring physical effort, reduction of the execution time of these actions; increasing anxiety in terms of frequency and duration of attacks of orienting-investigative activity and animals washing. Morphological examination revealed a series of tissue changes of internal organs (especially liver and spleen, to a lesser extent – kidney, heart and colon with increase of the spectrum and severity of structural changes with increasing doses of the NCC. From the combination of the data the conclusion was made that maximal ineffective dose (NOAEL of this nanomaterial at subacute oral administration is no more than 0.1 mg/kg body weight.

  10. Sodium deoxycholate-decorated zein nanoparticles for a stable colloidal drug delivery system.

    Science.gov (United States)

    Gagliardi, Agnese; Paolino, Donatella; Iannone, Michelangelo; Palma, Ernesto; Fresta, Massimo; Cosco, Donato

    2018-01-01

    The use of biopolymers is increasing in drug delivery, thanks to the peculiar properties of these compounds such as their biodegradability, availability, and the possibility of modulating their physico-chemical characteristics. In particular, protein-based systems such as albumin are able to interact with many active compounds, modulating their biopharmaceutical properties. Zein is a protein of 20-40 kDa made up of many hydrophobic amino acids, generally regarded as safe (GRAS) and used as a coating material. In this investigation, zein was combined with various surfactants in order to obtain stable nanosystems by means of the nanoprecipitation technique. Specific parameters, eg, temperature, pH value, Turbiscan Stability Index, serum stability, in vitro cytotoxicity and entrapment efficiency of various model compounds were investigated, in order to identify the nanoformulation most useful for a systemic drug delivery application. The use of non-ionic and ionic surfactants such as Tween 80, poloxamer 188, and sodium deoxycholate allowed us to obtain nanoparticles characterized by a mean diameter of 100-200 nm when a protein concentration of 2 mg/mL was used. The surface charge was modulated by means of the protein concentration and the nature of the stabilizer. The most suitable nanoparticle formulation to be proposed as a colloidal drug delivery system was obtained using sodium deoxycholate (1.25% w/v) because it was characterized by a narrow size distribution, a good storage stability after freeze-drying and significant feature of retaining lipophilic and hydrophilic compounds. The sodium deoxycholate-coated zein nanoparticles are stable biocompatible colloidal carriers to be used as useful drug delivery systems.

  11. Efficacy of some colloidal silver preparations and silver salts against Proteus bacteria, one possible cause of rheumatoid arthritis.

    Science.gov (United States)

    Disaanayake, D M B T; Faoagali, Joan; Laroo, Hans; Hancock, Gerald; Whitehouse, Michael

    2014-04-01

    There has been increased interest in the role of anti-Proteus antibodies in the aetiology of rheumatoid arthritis (RA) and whether chemotherapeutic agents active against Proteus species might reduce the risk and/or exacerbations of RA. We examined the in vitro antibacterial effects of ten different silver preparations which were either ionic silver [Ag(I)] solutions or nanoparticulate silver (NPS) (Ag(0)) suspensions against ATCC and two wild (clinical) strains of Proteus. The data establish the low minimum inhibitory concentration and minimum bactericidal concentration of all the silver formulations tested against these four Proteus strains. In a pilot study, a potent NPS preparation ex vivo showed long-lasting anti-Proteus activity in a normal human volunteer.

  12. Biological sensing with surface-enhanced Raman spectroscopy (SERS) using a facile and rapid silver colloid-based synthesis technique

    Science.gov (United States)

    Smyth, C.; Mehigan, S.; Rakovich, Y. P.; Bell, S. E. J.; McCabe, E. M.

    2011-03-01

    Optical techniques towards the realisation of sensitive and selective biosensing platforms have received a considerable amount of attention in recent times. Techniques based on interferometry, surface plasmon resonance, field-effect transistors and waveguides have all proved popular, and in particular, spectroscopy offers a large range of options. Raman spectroscopy has always been viewed as an information rich technique in which the vibrational frequencies reveal a lot about the structure of a compound. The issue with Raman spectroscopy has traditionally been that its rather low cross section leads to poor limits-of-detection. In response to this problem, Surface-enhanced Raman Scattering (SERS), which increases sensitivity by bringing the sample in contact with many types of enhanceing substrates, has been developed. Here we discuss a facile and rapid technique for the detection of pterins using colloidal silver suspensions. Pteridine compounds are a family of biochemicals, heterocyclic in structure, and employed in nature as components of colour pigmentation and also as facilitators for many metabolic pathways, particularly those relating to the amino acid hydroxylases. In this work, xanthopterin, isoxanthopterin and 7,8- dihydrobiopterin have been examined whilst absorbed to SERS-active silver colloids. SERS, while far more sensitive than regular Raman spectroscopy, has its own issues relating to the reproducibility of substrates. In order to obtain quantitative data for the pteridine compounds mentioned above, exploratory studies of methods for introducing an internal standard for normalisation of the signals have been carried out.e

  13. Study of fungicidal properties of colloidal silver nanoparticles (AgNPs on trout egg pathogen, Saprolegnia sp.

    Directory of Open Access Journals (Sweden)

    Seyed Ali Johari

    2015-05-01

    Full Text Available Silver nanoparticles (AgNPs are known to have bactericidal and fungicidal effects. Since, there is few information available on the interaction of colloidal nanosilver with fish pathogens. Hence, the current study investigated the effects of colloidal AgNPs on the in vitro growth of the fish pathogen Saprolegnia sp.. Before the experiments, various important properties of AgNPs were well-characterized. The antifungal activity of AgNPs was then evaluated by determining the minimum inhibitory concentrations (MICs using two-fold serial dilutions of colloidal nanosilver in a glucose yeast extract agar at 22ºC. The growth of Saprolegnia sp. on the AgNPs agar treatments was compared to that of nanosilver-free agar as controls. The results showed that AgNPs have an inhibitory effect on the in vitro growth of the tested fungi. The MIC of AgNPs for Saprolegnia sp. was calculated at 1800 mg/L, which is equal to 0.18 percent. It seems that AgNPs could be a proper replacement for teratogenic and toxic agents, such as malachite green. In addition, the indirect use of AgNPs could be a useful method for providing new antifungal activity in aquaculture systems.

  14. The irradiation influence on the properties of silver sulfide (Ag2S) colloidal nanoparticles

    Science.gov (United States)

    Rempel, S. V.; Kuznetsova, Yu. V.; Gerasimov, E. Yu.; Rempel', A. A.

    2017-08-01

    The aqueous solutions of different stability containing silver sulfide (Ag2S) nanoparticles are studied. The stable, transparent, and turbid solutions have been subjected to daylight for 7 months, to ultraviolet and laser irradiation, as well as to an electron beam. Solar radiation is found to favor the Ag2S reduction to Ag and/or the formation of Ag2S/Ag hybrid nanoparticles in the solution. At a high amount of hybrid nanoparticles, the exciton-plasmon interaction causes asymmetry in the absorption spectra. The exposure of Ag2S particles precipitated from the solution with the electron beam leads to the reversible growth of Ag threads. The possible exciton-plasmon interplay mechanisms in Ag2S/Ag hybrid nanoparticles are considered. The physical mechanisms of the changing Ag2S stoichiometry, the formation of metallic Ag and Ag2S/Ag hybrid nanoparticles are the generation of hot carriers and the energy transfer (exciton-plasmon interaction) in a metal-semiconductor hybrid nanosystem are elucidated, as well.

  15. Colloidal silver-based nanogel as nonocclusive dressing for multiple superficial pellet wounds.

    Science.gov (United States)

    Dharmshaktu, Ganesh Singh; Singhal, Aanshu; Pangtey, Tanuja

    2016-01-01

    A good dressing is mandatory to an uncomplicated wound healing, especially when foreign particles contaminate the wound. Various forms of dressing preparations are available for use and differ in chemical composition and efficacy. Silver has been a known agent with good antimicrobial and healing properties and recent times has seen an upsurge in various silver-based dressing supplements. We describe our report of use and efficacy of a silver nanoparticle- based gel dressing in the healing of multiple superficial firearm pellet wounds.

  16. [Toxicological evaluation of nanosized colloidal silver, stabilized with polyvinylpyrrolidone, in 92-day experiment on rats. II. Internal organs morphology].

    Science.gov (United States)

    Zaytseva, N V; Zemlyanova, M A; Zvezdin, V N; Dovbysh, A A; Gmoshinsky, I V; Khotimchenko, S A; Akafieva, T I

    2016-01-01

    The aim of the study was to evaluate the safe doses of commercially available nanosized colloidal silver (NCS), stabilized with polyvinilpirrolidone (PVP, food additive E1201) when administered in gastrointestinal tract of rats in the 92-day experiment in terms of the morphological changes in the internals of animals. The sample studied contained non-aggregated nanoparticles (NPs) of silver belonging to size fractions with a diameter of less than 5 nm, 10-20 nm or 50-80 nm. 80% of NPs were inside the range of hydrodynamic diameters 10.6-61.8 nm. The preparation of NCS was administered to growing male Wistar rats. (initial body weight 80 ± 10 g) for 1 month by intragastric gavage and then consumed with food at doses of 0.1, 1.0 and 10 mg/kg of body weight based on silver. The control animals received water or vehicle of nanomaterial--water solution of PVP. After withdrawal of animals from the experiment by exsanguination under ether anesthesia organs (liver, spleen, kidney, ileum) were isolated and their slides were prepared by standard methods following 'by staining with hematoxylin-eosin. Analysis was performed in light optical microscope equipped with a digital camera at a magnification from 1 x 100 to 1 x 1000. It was shown that the experimental animals treated with the NCS developed series of morphological changes in the tissues of the internal organs (liver, spleen and kidney) with the elevation of the range and severity of structural changes with increasing doses of silver. The most sensitive target of NCS action was apparently liver, which has already shown at a dose of 0.1 mg of silver NP/kg of body weight marked eosinophilic infiltration of portal tracts, which was accompanied at doses of 1.0 and 10.0 mg/kg by the emergence of medium and large-drop fat vacuoles in the cytoplasm of hepatocytes, swelling and lympho-macrophage. infiltration of the portal tracts. Detectable changes can be regarded as symptoms of inflammation of hepatocytes, at least, at a

  17. Synthesis and spectroscopic studies of stable aqueous dispersion of silver nanoparticles.

    Science.gov (United States)

    El-Shishtawy, Reda M; Asiri, Abdullah M; Al-Otaibi, Maha M

    2011-09-01

    A facile approach for the synthesis of stable aqueous dispersion of silver nanoparticles (AgNPs) using glucose as the reducing agent in water/micelles system, in which cetyltrimethylammonium bromide (CTAB) was used as capping agent (stabilizer) is described. The evolution of plasmon band of AgNPs was monitored under different conditions such as (a) concentration of sodium hydroxide, (b) concentration of glucose, (c) concentration of silver nitrate (d) concentration of CTAB, and (e) reaction time. AgNPs were characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), fluorescence spectroscopy and FT-IR spectroscopy. The results revealed an easy and viable strategy for obtaining stable aqueous dispersion of AgNPs with well controlled shape and size below 30 nm in diameter. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Tangential flow ultrafiltration: a "green" method for the size selection and concentration of colloidal silver nanoparticles.

    Science.gov (United States)

    Anders, Catherine B; Baker, Joshua D; Stahler, Adam C; Williams, Austin J; Sisco, Jackie N; Trefry, John C; Wooley, Dawn P; Pavel Sizemore, Ioana E

    2012-10-04

    Nowadays, AgNPs are extensively used in the manufacture of consumer products,(1) water disinfectants,(2) therapeutics,(1, 3) and biomedical devices(4) due to their powerful antimicrobial properties.(3-6) These nanoparticle applications are strongly influenced by the AgNP size and aggregation state. Many challenges exist in the controlled fabrication(7) and size-based isolation(4,8) of unfunctionalized, homogenous AgNPs that are free from chemically aggressive capping/stabilizing agents or organic solvents.(7-13) Limitations emerge from the toxicity of reagents, high costs or reduced efficiency of the AgNP synthesis or isolation methods (e.g., centrifugation, size-dependent solubility, size-exclusion chromatography, etc.).(10,14-18) To overcome this, we recently showed that TFU permits greater control over the size, concentration and aggregation state of Creighton AgNPs (300 ml of 15.3 μg ml(-1) down to 10 ml of 198.7 μg ml(-1)) than conventional methods of isolation such as ultracentrifugation.(19) TFU is a recirculation method commonly used for the weight-based isolation of proteins, viruses and cells.(20,21) Briefly, the liquid sample is passed through a series of hollow fiber membranes with pore size ranging from 1,000 kD to 10 kD. Smaller suspended or dissolved constituents in the sample will pass through the porous barrier together with the solvent (filtrate), while the larger constituents are retained (retentate). TFU may be considered a "green" method as it neither damages the sample nor requires additional solvent to eliminate toxic excess reagents and byproducts. Furthermore, TFU may be applied to a large variety of nanoparticles as both hydrophobic and hydrophilic filters are available. The two main objectives of this study were: 1) to illustrate the experimental aspects of the TFU approach through an invited video experience and 2) to demonstrate the feasibility of the TFU method for larger volumes of colloidal nanoparticles and smaller volumes of

  19. Enhancement of single-molecule fluorescence signals by colloidal silver nanoparticles in studies of protein translation.

    Science.gov (United States)

    Bharill, Shashank; Chen, Chunlai; Stevens, Benjamin; Kaur, Jaskiran; Smilansky, Zeev; Mandecki, Wlodek; Gryczynski, Ignacy; Gryczynski, Zygmunt; Cooperman, Barry S; Goldman, Yale E

    2011-01-25

    Metal-enhanced fluorescence (MEF) increased total photon emission of Cy3- and Cy5-labeled ribosomal initiation complexes near 50 nm silver particles 4- and 5.5-fold, respectively. Fluorescence intensity fluctuations above shot noise, at 0.1-5 Hz, were greater on silver particles. Overall signal-to-noise ratio was similar or slightly improved near the particles. Proximity to silver particles did not compromise ribosome function, as measured by codon-dependent binding of fluorescent tRNA, dynamics of fluorescence resonance energy transfer between adjacent tRNAs in the ribosome, and tRNA translocation induced by elongation factor G.

  20. Enhancement of Single Molecule Fluorescence Signals by Colloidal Silver Nanoparticles in Studies of Protein Translation

    Science.gov (United States)

    Bharill, Shashank; Chen, Chunlai; Stevens, Benjamin; Kaur, Jaskiran; Smilansky, Zeev; Mandecki, Wlodek; Gryczynski, Ignacy; Gryczynski, Zygmunt; Cooperman, Barry S.; Goldman, Yale E.

    2011-01-01

    Metal enhanced fluorescence (MEF) increased total photon emission of Cy3- and Cy5-labeled ribosomal initiation complexes near 50 nm silver particles 4- and 5.5-fold respectively. Fluorescence intensity fluctuations above shot noise, at 0.1 – 5 Hz, were greater on silver particles. Overall signal to noise ratio was similar or slightly improved near the particles. Proximity to silver particles did not compromise ribosome function, as measured by codon-dependent binding of fluorescent tRNA, dynamics of fluorescence resonance energy transfer between adjacent tRNAs in the ribosome, and tRNA translocation induced by elongation factor G. PMID:21158483

  1. Colloidal silver-based nanogel as nonocclusive dressing for multiple superficial pellet wounds

    Directory of Open Access Journals (Sweden)

    Ganesh Singh Dharmshaktu

    2016-01-01

    Full Text Available A good dressing is mandatory to an uncomplicated wound healing, especially when foreign particles contaminate the wound. Various forms of dressing preparations are available for use and differ in chemical composition and efficacy. Silver has been a known agent with good antimicrobial and healing properties and recent times has seen an upsurge in various silver-based dressing supplements. We describe our report of use and efficacy of a silver nanoparticle- based gel dressing in the healing of multiple superficial firearm pellet wounds.

  2. Characterization and antibacterial properties of stable silver substituted hydroxyapatite nanoparticles synthesized through surfactant assisted microwave process

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Nida [Medical Implant Technology Group (MEDITEG), Faculty of Bioscience and Medical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Abdul Kadir, Mohammed Rafiq, E-mail: rafiq@biomedical.utm.my [Medical Implant Technology Group (MEDITEG), Faculty of Bioscience and Medical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Nik Malek, Nik Ahmad Nazim [Faculty of Bioscience and Medical Engineering (FBME), Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Mahmood, Nasrul Humaimi Bin [Medical Implant Technology Group (MEDITEG), Faculty of Bioscience and Medical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor Darul Takzim (Malaysia); Murali, Malliga Raman; Kamarul, T. [Tissue Engineering Group, NOCERAL, Department of Orthopaedic Surgery, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2013-09-01

    Highlights: • Stable nano sized silver substitute hydroxyapatite is prepared under surfactant assisted microwave process at 600 W power for 7 min. • The nanoparticles are in the size range of 58–72 nm and exert uniform elongated spheroid morphology. • Increase in silver concentration resulted in better dielectric properties. • Good antibacterial activity and silver release. - Abstract: The present study reports a relatively simple method for the synthesis of stable silver substituted hydroxyapatite nanoparticles with controlled morphology and particle size. In order to achieve this, CTAB is included as a surfactant in the microwave refluxing process (600 W for 7 min). The nanoparticles produced with different silver ion concentrations (0.05, 0.1 and 0.2 wt%) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX) and Brunauer–Emmett–Teller (BET) analysis. XRD and FTIR analyses reveal that the Ag-HA nanoparticles were phase pure at 1000 °C. FESEM images showed that the produced nanoparticles are in the size range of 58–72 nm and exert uniform elongated spheroid morphology. The dielectric properties suggest that the increase in dielectric constant (ε′) and dissipation factor (D) values with increasing Ag concentrations. Antibacterial performance of the Ag-HA samples elucidated using disk diffusion technique (DDT) and minimum inhibitory concentration (MIC) demonstrates anti-bacterial activity against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli. This effect was dose dependent and was more pronounced against Gram-negative bacteria than Gram-positive organisms.

  3. Characterization and antibacterial properties of stable silver substituted hydroxyapatite nanoparticles synthesized through surfactant assisted microwave process

    International Nuclear Information System (INIS)

    Iqbal, Nida; Abdul Kadir, Mohammed Rafiq; Nik Malek, Nik Ahmad Nazim; Mahmood, Nasrul Humaimi Bin; Murali, Malliga Raman; Kamarul, T.

    2013-01-01

    Highlights: • Stable nano sized silver substitute hydroxyapatite is prepared under surfactant assisted microwave process at 600 W power for 7 min. • The nanoparticles are in the size range of 58–72 nm and exert uniform elongated spheroid morphology. • Increase in silver concentration resulted in better dielectric properties. • Good antibacterial activity and silver release. - Abstract: The present study reports a relatively simple method for the synthesis of stable silver substituted hydroxyapatite nanoparticles with controlled morphology and particle size. In order to achieve this, CTAB is included as a surfactant in the microwave refluxing process (600 W for 7 min). The nanoparticles produced with different silver ion concentrations (0.05, 0.1 and 0.2 wt%) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX) and Brunauer–Emmett–Teller (BET) analysis. XRD and FTIR analyses reveal that the Ag-HA nanoparticles were phase pure at 1000 °C. FESEM images showed that the produced nanoparticles are in the size range of 58–72 nm and exert uniform elongated spheroid morphology. The dielectric properties suggest that the increase in dielectric constant (ε′) and dissipation factor (D) values with increasing Ag concentrations. Antibacterial performance of the Ag-HA samples elucidated using disk diffusion technique (DDT) and minimum inhibitory concentration (MIC) demonstrates anti-bacterial activity against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli. This effect was dose dependent and was more pronounced against Gram-negative bacteria than Gram-positive organisms

  4. Ultra-thin layer chromatography with integrated silver colloid-based SERS detection.

    Science.gov (United States)

    Wallace, Ryan A; Lavrik, Nickolay V; Sepaniak, Michael J

    2017-01-01

    Simplified lab-on-a-chip techniques are desirable for quick and efficient detection of analytes of interest in the field. The following work involves the use of deterministic pillar arrays on the micro-scale as a platform to separate compounds, and the use of Ag colloid within the arrays as a source of increased signal via surface enhanced Raman spectroscopy (SERS). One problem traditionally seen with SERS surfaces containing Ag colloid is oxidation; however, our platforms are superhydrophobic, reducing the amount of oxidation taking place on the surface of the Ag colloid. This work includes the successful separation and SERS detection of a fluorescent dye compounds (resorufin and sulforhodamine 640), fluorescent anti-tumor drugs (Adriamycin and Daunomycin), and purine and pyrimidine bases (adenine, cytosine, guanine, hypoxanthine, and thymine). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Non-labile silver species in biosolids remain stable throughout 50 years of weathering and ageing

    International Nuclear Information System (INIS)

    Donner, E.; Scheckel, K.; Sekine, R.; Popelka-Filcoff, R.S.; Bennett, J.W.; Brunetti, G.; Naidu, R.; McGrath, S.P.; Lombi, E.

    2015-01-01

    Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that biosolids Ag concentrations have decreased significantly over recent decades. XANES revealed the importance of reduced-sulfur binding environments for Ag speciation in materials ranging from freshly produced sludge to biosolids weathered under ambient environmental conditions for more than 50 years. Isotopic dilution with 110m Ag showed that Ag was predominantly non-labile in both fresh and aged biosolids (13.7% mean lability), with E-values ranging from 0.3 to 60 mg/kg and 5 mM CaNO 3 extractable Ag from 1.2 to 609 μg/kg (0.002–3.4% of the total Ag). This study indicates that at the time of soil application, biosolids Ag will be predominantly Ag-sulfides and characterised by low isotopic lability. - Highlights: • Biosolids silver (Ag) concentrations appear to have decreased in recent decades. • Ag 2 S dominates Ag speciation in freshly produced sludge. • Ag 2 S is also the dominant species in aged biosolids. • Upon land application biosolids will mainly contain Ag-sulfides and have low isotopic lability. - Analysis of historic and contemporary biosolids from three continents indicated decreasing wastewater silver releases, and non-labile, extremely stable silver speciation

  6. In situ growth of hollow gold-silver nanoshells within porous silica offers tunable plasmonic extinctions and enhanced colloidal stability.

    Science.gov (United States)

    Li, Chien-Hung; Jamison, Andrew C; Rittikulsittichai, Supparesk; Lee, Tai-Chou; Lee, T Randall

    2014-11-26

    Porous silica-coated hollow gold-silver nanoshells were successfully synthesized utilizing a procedure where the porous silica shell was produced prior to the transformation of the metallic core, providing enhanced control over the structure/composition of the bimetallic hollow core. By varying the reaction time and the precise amount of gold salt solution added to a porous silica-coated silver-core template solution, composite nanoparticles were tailored to reveal a readily tunable surface plasmon resonance that could be centered across the visible and near-IR spectral regions (∼445-800 nm). Characterization by X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that the synthetic methodology afforded particles having uniform composition, size, and shape. The optical properties were evaluated by absorption/extinction spectroscopy. The stability of colloidal solutions of our composite nanoparticles as a function of pH was also investigated, revealing that the nanoshells remain intact over a wide range of conditions (i.e., pH 2-10). The facile tunability, enhanced stability, and relatively small diameter of these composite particles (∼110 nm) makes them promising candidates for use in tumor ablation or as photothermal drug-delivery agents.

  7. Infrared Emitting and Photoconducting Colloidal Silver Chalcogenide Nanocrystal Quantum Dots from a Silylamide-Promoted Synthesis

    NARCIS (Netherlands)

    Yarema, Maksym; Pichler, Stefan; Sytnyk, Mykhailo; Seyrkammer, Robert; Lechner, Rainer T.; Fritz-Popovski, Gerhard; Jarzab, Dorota; Szendrei, Krisztina; Resel, Roland; Korovyanko, Oleksandra; Loi, Maria Antonietta; Paris, Oskar; Hesser, Guenter; Heiss, Wolfgang; Hesser, Günter

    Here, we present a hot injection synthesis of colloidal Ag chalcogenide nanocrystals (Ag(2)Se, Ag(2)Te, and Ag(2)S) that resulted in exceptionally small nanocrystal sizes in the range between 2 and 4 nm. Ag chalcogenide nanocrystals exhibit band gap energies within the near-infrared spectral region,

  8. [Toxicological evaluation of colloidal nano-sized silver stabilized polyvinylpyrrolidone. III. Enzymological, biochemical markers, state of antioxidant defense system].

    Science.gov (United States)

    Gmoshinsky, I V; Shipelin, V A; Vorozhko, I V; Sentsova, T B; Soto, S Kh; Avren'eva, L I; Guseva, G V; Kravchenko, L V; Khotimchenko, S A; Tutelyan, V A

    2016-01-01

    Nanosized colloidal silver (NCS) with primary nanoparticles (NPs) size in the range of 10-80 nm in aqueous suspension was administered to rats with initial weight 80±10 gfor the first 30 day intragastrically and for lasting 62 days with the diet consumed in doses of 0.1; 1.0 and 10 mg/kg of body weight b.w) per day based on silver (Ag). The control animals received deionized water and carrier of NPs - aqueous solution of stabilizer polyvinylpyrrolidone. Activity (Vmax) was determined in liver of microsomal mixed function monooxygenase isoforms CYP 1A1, 1A2 and 2B1 against their specific substrates, the activity of liver conjugating enzymes (glutathione-S-transferase and UDP-glucuronosyltransferase) in the microsomal fraction and a cytosol, and the overall and non-sedimentable activities of lysosomal hydrolases. In blood plasma there were evaluated malonic dialdehyde, PUFA diene conjugates, in erythrocytes - the activity of antioxidant enzymes. A set of standard biochemical indicators of blood serum was also determined. The studies revealed changes in a number of molecular markers of toxic action. Among them - the increase in the activity of key enzymes I and II stages of detoxification of xenobiotics, indicating its functional overvoltage; reducing the activity of glutathione peroxidase (GP), the total arylsulfatase A and B, β-galactosidase (in the absence of changes in their non-sedimentable activity), levels of uric acid, increased alkaline phosphatase activity. These changes occurred mainly at the dose Ag of 10 mg/kg b.w., except for the GP to which the threshold dose was 1 mg/kg b.w. No significant changes in the studied markers in a dose Ag 0,1 mg/kg b.w. were identified. Possible mechanisms of the toxic action of silver NPs are discussed.

  9. Dilated cardiomyopathy and left bundle branch block associated with ingestion of colloidal gold and silver is reversed by British antiLewisite and vitamin E: The potential toxicity of metals used as health supplements

    Science.gov (United States)

    Archer, Stephen Lawrence

    2008-01-01

    A case of left bundle branch block and a dilated, nonhypertrophic cardiomyopathy associated with ingestion of colloidal gold and silver as an ‘energy tonic’ is described. The cardiac disease was reversed within two months by a course of dimercaprol (Akorn Inc, USA) (British antiLewisite) and vitamin E. This is the first case of gold and silver cardiomyopathy in humans, and highlights the risks of these colloidal metal ‘health supplements’. PMID:18464946

  10. A Widely Applicable Silver Sol for TLC Detection with Rich and Stable SERS Features

    Science.gov (United States)

    Zhu, Qingxia; Li, Hao; Lu, Feng; Chai, Yifeng; Yuan, Yongfang

    2016-04-01

    Thin-layer chromatography (TLC) coupled with surface-enhanced Raman spectroscopy (SERS) has gained tremendous popularity in the study of various complex systems. However, the detection of hydrophobic analytes is difficult, and the specificity still needs to be improved. In this study, a SERS-active non-aqueous silver sol which could activate the analytes to produce rich and stable spectral features was rapidly synthesized. Then, the optimized silver nanoparticles (AgNPs)-DMF sol was employed for TLC-SERS detection of hydrophobic (and also hydrophilic) analytes. SERS performance of this sol was superior to that of traditional Lee-Meisel AgNPs due to its high specificity, acceptable stability, and wide applicability. The non-aqueous AgNPs would be suitable for the TLC-SERS method, which shows great promise for applications in food safety assurance, environmental monitoring, medical diagnoses, and many other fields.

  11. Large third-order optical nonlinearity of silver colloids in silica glasses synthesized by ion implantation

    International Nuclear Information System (INIS)

    Ghosh, Binita; Chakraborty, Purushottam

    2011-01-01

    Silver ion implantations in fused silica glasses have been made to synthesize silver nanocluster-glass composites and a combination of 'Anti-Resonant Interferometric Nonlinear Spectroscopy (ARINS)' and 'Z-scan' techniques has been employed for the measurement of the third-order optical susceptibility of these nanocomposites. The ARINS technique utilizes the dressing of two unequal-intensity counter-propagating pulsed optical beams with differential nonlinear phases, which occurs upon traversing the sample. This difference in phase manifests itself in the intensity-dependent transmission, measurement of which enables us to extract the values of nonlinear refractive index (η 2 ) and nonlinear absorption coefficient (β), finally yielding the real and imaginary parts of the third-order dielectric susceptibility (χ (3) ). The real and imaginary parts of χ (3) are obtained in the orders of 10 -10 e.s.u for silver nanocluster-glass composites. The present value of χ (3) , to our knowledge, is extremely accurate and much more reliable compared to the values previously obtained by other workers for similar silver-glass nanocomposites using only Z-scan technique. Optical nonlinearity has been explained to be due to two-photon absorption in the present nanocomposite glasses and is essentially of electronic origin.

  12. Biological properties of printable polyaniline and polyaniline-silver colloidal dispersions stabilized by gelatin

    Czech Academy of Sciences Publication Activity Database

    Bober, Patrycja; Humpolíček, P.; Syrový, T.; Capáková, Z.; Syrová, L.; Hromádková, Jiřina; Stejskal, Jaroslav

    2017-01-01

    Roč. 232, October (2017), s. 52-59 ISSN 0379-6779 R&D Projects: GA ČR(CZ) GP14-05568P; GA ČR(CZ) GA17-05095S; GA TA ČR(CZ) TE01020022 Institutional support: RVO:61389013 Keywords : conducting polymer * colloidal dispersion * hybrid composite Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 2.435, year: 2016

  13. Nanostructured silver sulfide: synthesis of various forms and their application

    Science.gov (United States)

    Sadovnikov, S. I.; Rempel, A. A.; Gusev, A. I.

    2018-04-01

    The results of experimental studies on nanostructured silver sulfide are analyzed and generalized. The influence of small particle size on nonstoichiometry of silver sulfide is discussed. Methods for the synthesis of various forms of nanostructured Ag2S including nanopowders, stable colloidal solutions, quantum dots, core–shell nanoparticles and heteronanostructures are described. The advantages and drawbacks of different synthetic procedures are analyzed. Main fields of application of nanostructured silver sulfide are considered. The bibliography includes 184 references.

  14. A novel polyol method to synthesize colloidal silver nanoparticles by ultrasonic irradiation.

    Science.gov (United States)

    Byeon, Jeong Hoon; Kim, Young-Woo

    2012-01-01

    A polyol synthesis of silver nanoparticles in the presence of ultrasonic irradiation was compared with other configurations (at ambient temperature, 120° C, and 120 °C with injected solutions) in the absence of ultrasonic irradiation in order to obtain systematic results for morphology and size distribution. For applying ultrasonic irradiation, rather fine and uniform spherical silver particles (21±3.7 nm) were obtained in a simple (at ambient temperature without mechanical stirring) and fast (within 4 min, 3.61×10(-3) mol min(-1)) manner than other cases (at ambient temperature (for 8 h, 0.03×10(-3) mol min(-1)): 86±16.8 nm, 120 °C (for 12 min, 1.16×10(-3) mol min(-1)): 64±14.9 nm, and 120 °C with injected solutions (during 12 min): 35±6.8 nm; all other cases contained anisotropic shaped particles). Even though the temperature of polyol reaction reached only at 80 °C (silver particle and surrounding components) by ultrasonic irradiation might induce a better formation kinetics and morphological uniformity. Copyright © 2011 Elsevier B.V. All rights reserved.

  15. Robust one pot synthesis of colloidal silver nanoparticles by simple redox method and absorbance recovered sensing.

    Science.gov (United States)

    Salman, Muhammad; Iqbal, Mahwish; El Ashry, El Sayed H; Kanwal, Shamsa

    2012-01-01

    Conventional synthesis of silver nanoparticles employs a reducing agent and a capping agent. In this report water-soluble silver nanoparticles (AgNPs) were prepared facilely by chemical reduction of Ag(I) ions. 4-Amino-3-(d-gluco-pentitol-1-yl)-4,5-dihydro-1,2,4-triazole-5-thione (AGTT) was used both as reducing and stabilizing agent. Direct heating methodology was found to be more suitable for achieving particles with a hydrodynamic diameter of ~20 nm. AGTT exists as tautomer in solution form and our studies indicate that -NH(2) group is involved in the reduction and stabilization of Ag(+) and thione (Δ=S) group of AGTT is possibly involved in stabilizing the nanoparticles via coordinate covalent linkage. Characterization of synthesized silver nanoparticles was performed by UV-vis, FT-IR and by FESEM. Based on the absorption properties of synthesized AgNPs, we used AgNPs to detect bovine serum albumin (BSA) and AgNPs-BSA composite nanoprobe was further applied to detect Cu(2+) based on absorbance recovery. The proposed method has advantages over existing methods in terms of rapid synthesis and stability of AgNPs and their applications. Analysis is reproducible, cost effective and highly sensitive. The lowest detectable concentration of BSA in this approach is 3 nM, and for Cu(2+) it can detect upto 200 pM. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Protein-silver nanoparticle interactions to colloidal stability in acidic environments.

    Science.gov (United States)

    Tai, Jui-Ting; Lai, Chao-Shun; Ho, Hsin-Chia; Yeh, Yu-Shan; Wang, Hsiao-Fang; Ho, Rong-Ming; Tsai, De-Hao

    2014-11-04

    We report a kinetic study of Ag nanoparticles (AgNPs) under acidic environments (i.e., pH 2.3 to pH ≈7) and systematically investigate the impact of protein interactions [i.e., bovine serum albumin (BSA) as representative] to the colloidal stability of AgNPs. Electrospray-differential mobility analysis (ES-DMA) was used to characterize the particle size distributions and the number concentrations of AgNPs. Transmission electron microscopy was employed orthogonally to provide visualization of AgNPs. For unconjugated AgNPs, the extent of aggregation, or the average particle size, was shown to be increased significantly with an increase of acidity, where a partial coalescence was found between the primary particles of unconjugated AgNP clusters. Aggregation rate constant, kD, was also shown to be proportional to acidity, following a correlation of log(kD) = -1.627(pH)-9.3715. Using ES-DMA, we observe BSA had a strong binding affinity (equilibrium binding constant, ≈ 1.1 × 10(6) L/mol) to the surface of AgNPs, with an estimated maximum molecular surface density of ≈0.012 nm(-2). BSA-functionalized AgNPs exhibited highly-improved colloidal stability compared to the unconjugated AgNPs under acidic environments, where both the acid-induced interfacial dissolution and the particle aggregation became negligible. Results confirm a complex mechanism of colloidal stability of AgNPs: the aggregation process was shown to be dominant, and the formation of BSA corona on AgNPs suppressed both particle aggregation and interfacial dissolution of AgNP samples under acidic environments.

  17. Synthesis of anti-aggregation silver nanoparticles based on inositol hexakisphosphoric micelles for a stable surface enhanced Raman scattering substrate

    International Nuclear Information System (INIS)

    Wang Na; Yang Haifeng; Zhu Xuan; Zhang Rui; Wang Yao; Huang Guanfeng; Zhang Zongrang

    2009-01-01

    We report a novel method of synthesizing a kind of silver nanoparticles aided by the inositol hexakisphosphoric micelle as a soft template and stabilizer. By controlling the reaction time, UV-vis and TEM observations of the size growth of the nanoparticles are performed. Careful examinations of surface enhanced Raman scattering (SERS) spectra of 2-mercaptopyridine (2-Mpy) on the as-produced silver nanoparticles exhibit very stable and reproducible Raman signals within about 4 months.

  18. Structure of magnetic particles studied by small angle neutron scattering. [Magnetic colloid particles in stable liquid dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Cebula, D J; Charles, S W; Popplewell, J

    1981-03-01

    The purpose of this note is to show how the use of small angle neutron scattering (SANS) can provide fundamental information on the structure of magnetic colloid particles in stable liquid dispersion. A more detailed account elaborating the use of the technique to provide fundamental information on interactions will appear later. This contribution contains some principal results on particle structure. The technique of SANS provides a very sensitive means of measuring particle size by measuring the scattered neutron intensity, I(Q), as a function of scattered wave vector, Q.

  19. Efficient, air-stable colloidal quantum dot solar cells encapsulated using atomic layer deposition of a nanolaminate barrier

    KAUST Repository

    Ip, Alexander H.; Labelle, André J.; Sargent, Edward H.

    2013-01-01

    Atomic layer deposition was used to encapsulate colloidal quantum dot solar cells. A nanolaminate layer consisting of alternating alumina and zirconia films provided a robust gas permeation barrier which prevented device performance degradation over a period of multiple weeks. Unencapsulated cells stored in ambient and nitrogen environments demonstrated significant performance losses over the same period. The encapsulated cell also exhibited stable performance under constant simulated solar illumination without filtration of harsh ultraviolet photons. This monolithically integrated thin film encapsulation method is promising for roll-to-roll processed high efficiency nanocrystal solar cells. © 2013 AIP Publishing LLC.

  20. Efficient, air-stable colloidal quantum dot solar cells encapsulated using atomic layer deposition of a nanolaminate barrier

    KAUST Repository

    Ip, Alexander H.

    2013-12-23

    Atomic layer deposition was used to encapsulate colloidal quantum dot solar cells. A nanolaminate layer consisting of alternating alumina and zirconia films provided a robust gas permeation barrier which prevented device performance degradation over a period of multiple weeks. Unencapsulated cells stored in ambient and nitrogen environments demonstrated significant performance losses over the same period. The encapsulated cell also exhibited stable performance under constant simulated solar illumination without filtration of harsh ultraviolet photons. This monolithically integrated thin film encapsulation method is promising for roll-to-roll processed high efficiency nanocrystal solar cells. © 2013 AIP Publishing LLC.

  1. Demonstration of vessels in CNS and other organs by AMG silver enhancement of colloidal gold particles dispersed in gelatine.

    Science.gov (United States)

    Danscher, G; Andreasen, A

    1997-12-01

    We present a new autometallographic technique for demonstrating vessels and other small cavities at light microscopy (LM) and electron microscopy (EM) levels. It is possible to obtain detailed knowledge of the 3-D appearance of the vascular system by exchanging blood with a 40 degrees C, 8% gelatine solution containing colloidal gold particles (gold gelatine solution, GGS) and ensuing silver enhancement of the gold particles by autometallography (AMG). The GGS-AMG technique demonstrates the vascular system as a dark web that can be studied in cryostat, vibratome, methacrylate, paraffin and Epon sections at all magnifications. The infused GGS becomes increasingly viscous and finally becomes rigid when the temperature falls below 20 degrees C. An additional advantage of this technique is the fact that none of the tested counterstains or immunotechniques interfere with this AMG approach. The GGS-AMG technique is demonstrated on rat brains but can be applied to any organ. We believe that the present technique is valuable for both experimental studies and routine pathology.

  2. Colloidal lithography with electrochemical nickel deposition as a unique method for improved silver decorated nanocavities in SERS applications

    Science.gov (United States)

    Petruš, Ondrej; Oriňak, Andrej; Oriňaková, Renáta; Orságová Králová, Zuzana; Múdra, Erika; Kupková, Miriam; Kovaľ, Karol

    2017-11-01

    Two types of metallised nanocavities (single and hybrid) were fabricated by colloid lithography followed by electrochemical deposition of Ni and subsequently Ag layers. Introductory Ni deposition step iniciates more homogenous decoration of nanocavities with Ag nanoparticles. Silver nanocavity decoration has been so performed with lower nucleation rate and with Ag nanoparticles homogeinity increase. By this, two step Ni and Ag deposition trough polystyrene nanospheres (100, 300, 500, 700, 900 nm), the various Ag surfaces were obtained. Ni layer formation in the first step of deposition enabled more precise controlling of Ag film deposition and thus final Ag surface morphology. Prepared substrates were tested as active surfaces in SERS application. The best SERS signal enhancement was observed at 500 nm Ag nanocavities with normalised thickness Ni layer ∼0.5. Enhancement factor has been established at value 1.078 × 1010; time stability was determined within 13 weeks; charge distribution at nanocavity Ag surfaces as well as reflection spectra were calculated by FDTD method. Newly prepared nanocavity surface can be applied in SERS analysis, predominantly.

  3. Silver colloidal nanoparticles: antifungal effect against adhered cells and biofilms of Candida albicans and Candida glabrata.

    Science.gov (United States)

    Monteiro, D R; Gorup, L F; Silva, S; Negri, M; de Camargo, E R; Oliveira, R; Barbosa, D B; Henriques, M

    2011-08-01

    The aim of this study was to evaluate the effect of silver nanoparticles (SN) against Candida albicans and Candida glabrata adhered cells and biofilms. SN (average diameter 5 nm) were synthesized by silver nitrate reduction with sodium citrate and stabilized with ammonia. Minimal inhibitory concentration (MIC) tests were performed for C. albicans (n = 2) and C. glabrata (n = 2) grown in suspension following the Clinical Laboratory Standards Institute microbroth dilution method. SN were applied to adhered cells (2 h) or biofilms (48 h) and after 24 h of contact their effect was assessed by enumeration of colony forming units (CFUs) and quantification of total biomass (by crystal violet staining). The MIC results showed that SN were fungicidal against all strains tested at very low concentrations (0.4-3.3 μg ml(-1)). Furthermore, SN were more effective in reducing biofilm biomass when applied to adhered cells (2 h) than to pre-formed biofilms (48 h), with the exception of C. glabrata ATCC, which in both cases showed a reduction ∼90%. Regarding cell viability, SN were highly effective on adhered C. glabrata and respective biofilms. On C. albicans the effect was not so evident but there was also a reduction in the number of viable biofilm cells. In summary, SN may have the potential to be an effective alternative to conventional antifungal agents for future therapies in Candida-associated denture stomatitis.

  4. SERS spectrum of gallic acid obtained from a modified silver colloid

    Science.gov (United States)

    Garrido, C.; Diaz-Fleming, G.; Campos-Vallette, M. M.

    2016-06-01

    Two different crystals of the gallic acid were microscopically separated from a p.a. commercial product. The Raman spectra analysis allowed distinguishing monomeric and dimeric structures. The vibrational wave numbers were computed using DFT quantum chemical calculations. The data obtained from wave number calculations are used to assign vibrational bands obtained in the Raman spectrum. The dimer, characterized as ellagic acid, involves the carboxyl and hydroxyl moieties. The Raman spectrum in water solution of each species is dominated by the monomeric form. A low negatively charged Ag colloid allowed obtain to the best of our knowledge, the first surface enhanced Raman scattering (SERS) spectrum of the gallic acid. The possible electrophilic attacking sites of the title molecule are identified using MEP surface plot study and the orientation of the analyte on the metal surface is proposed tilted to the surface.

  5. Elaboration of Stable and Antibody Functionalized Positively Charged Colloids by Polyelectrolyte Complexation between Chitosan and Hyaluronic Acid

    Directory of Open Access Journals (Sweden)

    Ramona C. Polexe

    2013-07-01

    Full Text Available In this study, we describe the elaboration of multifunctional positively charged polyelectrolyte complex (PEC nanoparticles, designed to be stable at physiological salt concentration and pH, for effective targeted delivery. These nanoparticles were obtained by charge neutralization between chitosan (CS as polycation and hyaluronic acid (HA as polyanion. We showed that the course of the complexation process and the physico-chemical properties of the resulting colloids were impacted by (i internal parameters such as the Degree of Acetylation (DA, i.e., the molar ration of acetyl glucosamine residues and molar mass of CS, the HA molar mass and (ii external parameters like the charge mixing ratio and the polymer concentrations. As a result, nonstoichiometric colloidal PECs were obtained in water or PBS (pH 7.4 and remained stable over one month. The polymer interactions were characterized by thermal analysis (DSC and TGA and the morphology was studied by scanning electron microscopy. A model antibody, anti-ovalbumine (OVA immunoglobulin A (IgA was sorbed on the particle surface in water and PBS quantitatively in 4 h. The CS-HA/IgA nanoparticles average size was between 425–665 nm with a positive zeta potential. These results pointed out that CS-HA can be effective carriers for use in targeted drug delivery.

  6. Synthesis colloidal Kyllinga brevifolia-mediated silver nanoparticles at different temperature for methylene blue removal

    Science.gov (United States)

    Isa, Norain; Sarijo, Siti Halimah; Aziz, Azizan; Lockman, Zainovia

    2017-09-01

    Metallic nanoparticles are well known of having wide applications in various fields such as, catalysis, electronics, energy, chemistry and medicine due to its unique physico-chemical properties. In this study, nanocatalyst Kyllinga brevifolia-mediated silver nanoparticles (AgNPs) were prepared by reduction of silver nitrate using aqueous extract of Kyllinga brevifolia at different temperature. The formations of AgNPs were monitored using UV-visible spectroscopy. Transmission electron microscope (TEM) results reveal that the AgNPs well dispersed with average particle size are 22.34 and 6.73 nm for synthesized at room temperature and cold temperature respectively. The biomolecules present in the Kyllinga brevifolia aqueous extract responsible for the formation of AgNPs were identified using Fourier transform infrared (FTIR). Our AgNPs performed excellent catalytic activity in degradation of methylene blue (MB) dyes via electron relay effect. MB is toxic to ecological system and also has carcinogenic properties. The AgNPs nanocatalysts synthesized in this study are highly dispersed, quasi-spherical and due to their size in nanoscale, they have shown effectiveness for degradation of MB dyes. More importantly, our AgNPs were prepared using biomolecules as capping and reducing agent, which make our product "greener" than available AgNPs that are commonly prepared using hydrazine and borohydride; which are harmful substances to human and environment. Not only the AgNPs can act as nanocatalyst for degradation of MB, they can also be expected to degrade other types of toxic dyes used in textiles industry.

  7. Infrared emitting and photoconducting colloidal silver chalcogenide nanocrystal quantum dots from a silylamide-promoted synthesis.

    Science.gov (United States)

    Yarema, Maksym; Pichler, Stefan; Sytnyk, Mykhailo; Seyrkammer, Robert; Lechner, Rainer T; Fritz-Popovski, Gerhard; Jarzab, Dorota; Szendrei, Krisztina; Resel, Roland; Korovyanko, Oleksandra; Loi, Maria Antonietta; Paris, Oskar; Hesser, Günter; Heiss, Wolfgang

    2011-05-24

    Here, we present a hot injection synthesis of colloidal Ag chalcogenide nanocrystals (Ag(2)Se, Ag(2)Te, and Ag(2)S) that resulted in exceptionally small nanocrystal sizes in the range between 2 and 4 nm. Ag chalcogenide nanocrystals exhibit band gap energies within the near-infrared spectral region, making these materials promising as environmentally benign alternatives to established infrared active nanocrystals containing toxic metals such as Hg, Cd, and Pb. We present Ag(2)Se nanocrystals in detail, giving size-tunable luminescence with quantum yields above 1.7%. The luminescence, with a decay time on the order of 130 ns, was shown to improve due to the growth of a monolayer thick ZnSe shell. Photoconductivity with a quantum efficiency of 27% was achieved by blending the Ag(2)Se nanocrystals with a soluble fullerene derivative. The co-injection of lithium silylamide was found to be crucial to the synthesis of Ag chalcogenide nanocrystals, which drastically increased their nucleation rate even at relatively low growth temperatures. Because the same observation was made for the nucleation of Cd chalcogenide nanocrystals, we conclude that the addition of lithium silylamide might generally promote wet-chemical synthesis of metal chalcogenide nanocrystals, including in as-yet unexplored materials.

  8. Directly deposited quantum dot solids using a colloidally stable nanoparticle ink

    KAUST Repository

    Fischer, Armin H.; Rollny, Lisa R.; Pan, Jun; Carey, Graham H.; Thon, Susanna; Hoogland, Sjoerd H.; Voznyy, Oleksandr; Zhitomirsky, David; Kim, Jinyoung; Bakr, Osman; Sargent, E. H.

    2013-01-01

    We develop a photovoltaic colloidal quantum dot ink that allows for lossless, single-step coating of large areas in a manufacturing-compatible process. Our materials strategy involves a solution-phase ligand exchange to transport compatible linkers that yield 1-thioglycerol-capped PbS quantum dots in dimethyl sulfoxide with a photoluminescence quantum yield of 24%. A proof-of-principle solar cell made from the ink exhibits 2.1% power conversion efficiency. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Directly deposited quantum dot solids using a colloidally stable nanoparticle ink

    KAUST Repository

    Fischer, Armin H.

    2013-08-12

    We develop a photovoltaic colloidal quantum dot ink that allows for lossless, single-step coating of large areas in a manufacturing-compatible process. Our materials strategy involves a solution-phase ligand exchange to transport compatible linkers that yield 1-thioglycerol-capped PbS quantum dots in dimethyl sulfoxide with a photoluminescence quantum yield of 24%. A proof-of-principle solar cell made from the ink exhibits 2.1% power conversion efficiency. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Feasibility Study on the Use of the Seeding Growth Technique in Producing a Highly Stable Gold Nanoparticle Colloidal System

    Directory of Open Access Journals (Sweden)

    Kim Han Tan

    2015-01-01

    Full Text Available Stable colloidal gold nanoparticles (Au NPs are synthesized successfully using a seeding growth technique. The size of the nanoparticles is determined using transmission electron microscopy (TEM, and it is observed that the size of the nanoparticles ranges from 7 to 30 nm. The TEM images and optical absorption spectra of the Au NPs reveal that the suspension is well dispersed and consistent with the particle size. The feasibility of the seeding growth technique is investigated using Turbiscan Classic MA 2000 screening stability tester. Based on the peak thickness kinetics and mean value kinetics, the backscattered light profiles indicate that the suspension is highly stable without particle sedimentation as well as negligible agglomeration. In addition, the Au NPs are proven to remain stable over a period of 2 months. Particle sedimentation eventually occurs due to the weight of nanoparticles. It is concluded that the seeding growth technique is feasible in synthesizing stable Au NPs. Controlling the stability, size and shape of Au NPs are technologically important because of the strong correlation between these parameters and the optical, electrical, and catalytic properties of the nanoparticles.

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

    Science.gov (United States)

    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.

  12. Silver colloidal nanoparticles: effect on matrix composition and structure of Candida albicans and Candida glabrata biofilms.

    Science.gov (United States)

    Monteiro, D R; Silva, S; Negri, M; Gorup, L F; de Camargo, E R; Oliveira, R; Barbosa, D B; Henriques, M

    2013-04-01

    The aim of this study was to assess the effect of different silver nanoparticles (SN) concentrations on the matrix composition and structure of Candida albicans and Candida glabrata biofilms. Candida biofilms were developed in 6-well microtiter plates during 48 h. After, these biofilms were exposed to 13.5 or 54 μg SN ml(-1) for 24 h. Then, extracellular matrices were extracted from biofilms and analysed chemically in terms of proteins, carbohydrates and DNA. To investigate the biofilm structure, scanning electron microscopy (SEM) and epifluorescence microscopy were used. SN interfered with the matrix composition of Candida biofilms tested in terms of protein, carbohydrate and DNA, except for the protein content of C. albicans biofilm. By SEM, Candida biofilms treated with SN revealed structural differences, when compared with the control groups. Further, SN showed a trend of agglomeration within the biofilms. Epifluorescence microscopy images suggest that SN induced damage on cell walls of the Candida isolates tested. In general, irrespective of concentration, SN affected the matrix composition and structure of Candida biofilms and these findings may be related to the mechanisms of biocide action of SN. This study reveals new insights about the behaviour of SN when in contact with Candida biofilms. SN may contribute to the development of therapies to prevent or control Candida infections. © 2012 The Society for Applied Microbiology.

  13. Studies on interaction of colloidal silver nanoparticles (SNPs) with five different bacterial species.

    Science.gov (United States)

    Khan, S Sudheer; Mukherjee, Amitava; Chandrasekaran, N

    2011-10-01

    Silver nanoparticles (SNPs) are being increasingly used in many consumer products like textile fabrics, cosmetics, washing machines, food and drug products owing to its excellent antimicrobial properties. Here we have studied the adsorption and toxicity of SNPs on bacterial species such as Pseudomonas aeruginosa, Micrococcus luteus, Bacillus subtilis, Bacillus barbaricus and Klebsiella pneumoniae. The influence of zeta potential on the adsorption of SNPs on bacterial cell surface was investigated at acidic, neutral and alkaline pH and with varying salt (NaCl) concentrations (0.05, 0.1, 0.5, 1 and 1.5 M). The survival rate of bacterial species decreased with increase in adsorption of SNPs. Maximum adsorption and toxicity was observed at pH 5, and NaCl concentration of 0.5 M, there by resulting in less toxicity. The zeta potential study suggests that, the adsorption of SNPs on the cell surface was related to electrostatic force of attraction. The equilibrium and kinetics of the adsorption process were also studied. The adsorption equilibrium isotherms fitted well to the Langmuir model. The kinetics of adsorption fitted best to pseudo-first-order. These findings form a basis for interpreting the interaction of nanoparticles with environmental bacterial species. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Colloidal stability of carbonate-coated silver nanoparticles in synthetic and natural freshwater.

    Science.gov (United States)

    Piccapietra, Flavio; Sigg, Laura; Behra, Renata

    2012-01-17

    To gain important information on fate, mobility, and bioavailability of silver nanoparticles (AgNP) in aquatic systems, the influence of pH, ionic strength, and humic substances on the stability of carbonate-coated AgNP (average diameter 29 nm) was systematically investigated in 10 mM carbonate and 10 mM MOPS buffer, and in filtered natural freshwater. Changes in the physicochemical properties of AgNP were measured using nanoparticle tracking analysis, dynamic light scattering, and ultraviolet-visible spectroscopy. According to the pH-dependent carbonate speciation, below pH 4 the negatively charged surface of AgNP became positive and increased agglomeration was observed. Electrolyte concentrations above 2 mM Ca(2+) and 100 mM Na(+) enhanced AgNP agglomeration in the synthetic media. In the considered concentration range of humic substances, no relevant changes in the AgNP agglomeration state were measured. Agglomeration of AgNP exposed in filtered natural freshwater was observed to be primarily controlled by the electrolyte type and concentration. Moreover, agglomerated AgNP were still detected after 7 days of exposure. Consequently, slow sedimentation and high mobility of agglomerated AgNP could be expected under the considered natural conditions. A critical evaluation of the different methods used is presented as well.

  15. Applications of plant terpenoids in the synthesis of colloidal silver nanoparticles.

    Science.gov (United States)

    Mashwani, Zia-Ur-Rehman; Khan, Mubarak Ali; Khan, Tariq; Nadhman, Akhtar

    2016-08-01

    Green chemistry is the design of chemical products and processes that reduce or eliminate the generation of hazardous substances. Since the last few years, natural products especially plant secondary metabolites have been extensively explored for their potency to synthesize silver nanoparticles (AgNPs). The plant-based AgNPs are safer, energy efficient, eco-friendly, and less toxic than chemically synthesized counterparts. The secondary metabolites, ubiquitously found in plants especially the terpenoid-rich essential oils, have a significant role in AgNPs synthesis. Terpenoids belong to the largest family of natural products and are found in all kinds of organisms. Their involvement in the synthesis of plant-based AgNPs has got much attention in the recent years. The current article is not meant to provide an exhaustive overview of green synthesis of nanoparticles, but to present the pertinent role of plant terpenoids in the biosynthesis of AgNPs, as capping and reducing agents for development of uniform size and shape AgNPs. An emphasis on the important role of FTIR in the identification and elucidation of major functional groups in terpenoids for AgNPs synthesis has also been reviewed in this manuscript. It was found that no such article is available that has discussed the role of plant terpenoids in the green synthesis of AgNPs. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Characterization of silver colloids formed in LiBbO3 by Ag and O implantation at room and elevated temperatures

    International Nuclear Information System (INIS)

    Williams, E.K.; Ila, D.; Darwish, A.; Poker, D.B.; Sarkisov, S.S.; Curley, M.J.; Wang, J.-C.; Svetchnikov, V.L.; Zandbergen, H.W.

    1999-01-01

    To address the issue of dispersion of Ag colloids in LiNbO 3 at heat treatment temperatures of 400-500 deg. C, Ag and O were implanted at energies of 160 and 35 keV, respectively, at room temperature (Rt) and at 500 deg. C. Fluences were 4x10 16 and 8x10 16 /cm 2 and the order of the Ag and O implants was varied. Electron paramagnetic resonance spectra indicated that only O followed by Ag implantation of 500 deg. C produced silver oxide. Optical absorption spectrometry and RBS showed significant differences in the dispersion of the colloids with implant temperature and implant order. Implantation of Ag at 1.5 MeV to a fluence of 2x10 16 /cm 2 followed by heat treatment at 500 deg. C for 1 h produced nonlinear optical waveguides with a nonlinear index of the order of 10 -10 cm 2 /W at 532 nm

  17. A Highly Sensitive Nonenzymatic Glucose Biosensor Based on the Regulatory Effect of Glucose on Electrochemical Behaviors of Colloidal Silver Nanoparticles on MoS₂†.

    Science.gov (United States)

    Anderson, Kash; Poulter, Benjamin; Dudgeon, John; Li, Shu-En; Ma, Xiang

    2017-08-05

    A novel and highly sensitive nonenzymatic glucose biosensor was developed by nucleating colloidal silver nanoparticles (AgNPs) on MoS₂. The facile fabrication method, high reproducibility (97.5%) and stability indicates a promising capability for large-scale manufacturing. Additionally, the excellent sensitivity (9044.6 μA mM -1 cm -2 ), low detection limit (0.03 μM), appropriate linear range of 0.1-1000 μM, and high selectivity suggests that this biosensor has a great potential to be applied for noninvasive glucose detection in human body fluids, such as sweat and saliva.

  18. One-pot synthesis of stable colloidal solutions of MFe2O4 nanoparticles using oleylamine as solvent and stabilizer

    International Nuclear Information System (INIS)

    Pérez-Mirabet, Leonardo; Solano, Eduardo; Martínez-Julián, Fernando; Guzmán, Roger; Arbiol, Jordi; Puig, Teresa; Obradors, Xavier; Pomar, Alberto; Yáñez, Ramón; Ros, Josep; Ricart, Susagna

    2013-01-01

    Highlights: ► One-pot synthesis of ferrite magnetic nanoparticles ( 3 and M(acac) 2 (M = Co, Mn, Cu and Zn) in oleylamine, which also acts as a capping ligand, by producing stable colloidal dispersions of nanoparticles in non-polar solvents. The properties of the nanoparticles have been studied via different techniques, such as transmission electron microscopy, which shows that nanoparticles are monocrystallines and a narrow dispersion in size; magnetic analyses have demonstrated that the resulting ferrite nanoparticles show high saturation values and superparamagnetic behavior at room temperature; X-ray diffraction has also been performed, and it confirms that the synthesized nanoparticles have a spinel structure. Complementarily, ligand exchange has been also carried out in order to produce dispersions of the synthesized nanoparticles in polar media

  19. In situ probing of cholesterol in astrocytes at the single-cell level using laser desorption ionization mass spectrometric imaging with colloidal silver.

    Science.gov (United States)

    Perdian, D C; Cha, Sangwon; Oh, Jisun; Sakaguchi, Donald S; Yeung, Edward S; Lee, Young Jin

    2010-04-30

    Mass spectrometric imaging has been utilized to localize individual astrocytes and to obtain cholesterol populations at the single-cell level in laser desorption ionization (LDI) with colloidal silver. The silver ion adduct of membrane-bound cholesterol was monitored to detect individual cells. Good correlation between mass spectrometric and optical images at different cell densities indicates the ability to perform single-cell studies of cholesterol abundance. The feasibility of quantification is confirmed by the agreement between the LDI-MS ion signals and the results from a traditional enzymatic fluorometric assay. We propose that this approach could be an effective tool to study chemical populations at the cellular level. Published in 2010 by John Wiley & Sons, Ltd.

  20. Facile SILAR approach to air-stable naked silver and gold nanoparticles supported by alumina.

    Science.gov (United States)

    Stamplecoskie, Kevin G; Manser, Joseph S

    2014-10-22

    A synthetically convenient and scalable SILAR (successive ion layer adsorption and reaction) method is used to make air-stable films of silver and gold nanoparticles supported on alumina scaffolds. This solution-based deposition technique yields particles devoid of insulating capping agents or ligands. The optical properties of the nanoparticle films were investigated using femtosecond transient absorption spectroscopy. A linear absorption arising from intraband excitation (775 nm laser pulse) is seen only for Au nanoparticles at low intensity. However, both Au and Ag particles exhibit plasmon resonance responses at high excitation intensity via two photon absorption of the 775 nm pump pulse. The difference in optical response to near-IR laser excitation is rationalized based on the known density of states for each metal. To demonstrate the potential applications of these films, alumina-supported Ag nanoparticles were utilized as substrates for surface enhanced Raman spectroscopy, resulting in a 65-fold enhancement in the Raman signal of the probe molecule rhodamine 6G. The exceptional stability and scalability of these SILAR films opens the door for further optical and photocatalytic studies and applications, particularly with ligand-free Ag nanoparticles that typically oxidize under ambient conditions. Additionally, isolating plasmonic and interband electronic excitations in stable AgNP under visible light irradiation could enable elucidation of the mechanisms that drive noble metal-assisted photocatalytic processes.

  1. Influence of the laser light absorption by the colloid on the properties of silver nanoparticles produced by laser ablation in stirred and stationary liquid

    International Nuclear Information System (INIS)

    Resano-Garcia, A.; Battie, Y.; Koch, A.; En Naciri, A.; Chaoui, N.

    2015-01-01

    Silver nanoparticles were produced by nanosecond pulsed-laser ablation at 1064 nm of Ag in pure water. These experiments were performed using an alternative ablation cell design where a cylindrical shaped Ag target was horizontally irradiated, while the liquid was stirred by a stir rod coaxially arranged to the target. The repeatability of the generated colloids properties (extinction and size distribution) is assessed by statistical tools. The colloids properties prepared under stationary liquid are found to be unpredictable, while they are highly repeatable at high stirring speed. At the same time, electronic microscopy examinations of the irradiated Ag targets revealed that the width of the laser-machined grooves exponentially decays in stationary liquid and almost linearly under high stirring speed as the ablation proceeds. In the latter case, the decay rate was found to be constant from one experiment to the other, while it was not repeatable stationary liquid. We show that the decay of the groove width is due to an attenuation of the laser energy reaching the target surface due to the formation of a more or less dense NPs layer in front of the target as the ablation proceeds. Using the ablation time-dependence of the groove width, we can quantify the attenuation factor of the laser energy with exposure time. Finally, the relationship between the laser energy attenuation, stirring speed, and repeatability of the colloids properties is interpreted and discussed in terms of mass transfer

  2. Silver enhancement of nanogold and undecagold

    Energy Technology Data Exchange (ETDEWEB)

    Hainfield, J.F.; Furuya, F.R.

    1995-07-01

    A recent advance in immunogold technology has been the use of molecular gold instead of colloidal gold. A number of advantages are realized by this approach, such as stable covalent, site-specific attachment, small probe size and absence of aggregates for improved penetration. Silver enhancement has led to improved and unique results for electron and light microscopy, as well as their use with blots and gels. Most previous work with immunogold silver staining has been done with colloidal gold particles. More recently, large gold compounds (``clusters``) having a definite number of gold atoms and defined organic shell, have been used, frequently with improved results. These gold dusters, large compared to simple compounds, are, however, at the small end of the colloidal gold scale in size; undecagold is 0.8 nm and Nanogold is 1.4 nm. They may be used in practically all applications where colloidal gold is used (Light and electron microscopy, dot blots, etc.) and in some unique applications, where at least the larger colloidal golds don`t work, such as running gold labeled proteins on gels (which are later detected by silver enhancement). The main differences between gold clusters and colloidal golds are the small size of the dusters and their covalent attachment to antibodies or other molecules.

  3. Stable silver nanoclusters electrochemically deposited on nitrogen-doped graphene as efficient electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Jin, Shi; Chen, Man; Dong, Haifeng; He, Bingyu; Lu, Huiting; Su, Lei; Dai, Wenhao; Zhang, Qiaochu; Zhang, Xueji

    2015-01-01

    Metal nanoclusters exhibit unusually high catalytic activity toward oxygen reduction reaction (ORR) due to their small size and unique electronic structures. However, controllable synthesis of stable metal nanoclusters is a challenge, and the durability of metal clusters suffers from the deficiency of dissolution, aggregation, and sintering during catalysis reactions. Herein, silver nanoclusters (AgNCs) (diameter , which is vital in high performance fuel cells, batteries and nanodevices.

  4. Preparation and dispersive properties of Ag colloid by electrical explosion of wire

    International Nuclear Information System (INIS)

    Yun, G.S.; Bac, L.H.; Kim, J.S.; Kwon, Y.S.; Choi, H.S.; Kim, J.C.

    2011-01-01

    Research highlights: → Wire diameter and synthetic temperature affect on properties of Ag colloid by EEW. → The lower temperature and smaller diameter make smaller size and narrower size distribution. → Ag colloid are more stable at lower synthetic temperature and smaller size. - Abstract: In this work, Ag colloid was prepared by electrical explosion of wire in deionized water with 0.2 mm and 0.3 mm wire diameter. The temperature of water used for medium of explosion process was change from 20 deg. C to 80 deg. C. Morphology and particle size of nanoparticles was observed by transmission electron microscope. The particle size and size distribution of nanoparticles was found to shift to a smaller size with a decrease of temperature and smaller wire diameter. Surface plasmon resonance of the silver colloids was studied by UV-vis spectroscopy. Stability of silver colloids was investigated by zeta-potential and Turbiscan techniques. The results indicated that temperature of medium during explosion affects much on the stability of Ag colloid. The silver colloidal stability prepared at lower temperature and smaller wire diameter was more stable.

  5. Stable and Controllable Synthesis of Silver Nanowires for Transparent Conducting Film

    Science.gov (United States)

    Liu, Bitao; Yan, Hengqing; Chen, Shanyong; Guan, Youwei; Wu, Guoguo; Jin, Rong; Li, Lu

    2017-03-01

    Silver nanowires without particles are synthesized by a solvothermal method at temperature 150 °C. Silver nanowires are prepared via a reducing agent of glycerol and a capping agent of polyvinylpyrrolidone ( M w ≈ 1,300,000). Both of them can improve the purity of the as-prepared silver nanowires. With controllable shapes and sizes, silver nanowires are grown continuously up to 10-20 μm in length with 40-50 nm in diameter. To improve the yield of silver nanowires, the different concentrations of AgNO3 synthesis silver nanowires are discussed. The characterizations of the synthesized silver nanowires are analyzed by UV-visible absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscope (AFM), and silver nanowires are pumped on the cellulose membrane and heated stress on the PET. Then, the cellulose membrane is dissolved by the steam of acetone to prepare flexible transparent conducting thin film, which is detected 89.9 of transmittance and 58 Ω/□. Additionally, there is a close loop connected by the thin film, a blue LED, a pair of batteries, and a number of wires, to determinate directly the film if conductive or not.

  6. Colloidal Silver Products

    Science.gov (United States)

    ... Events Multimedia (Video, Images, and Audio) NCCIH Clinical Digest A monthly newsletter with evidence-based information on ... require a viewer such as the free Adobe Reader . NCCIH Pub No.: D209 Last Updated: April 2017 ...

  7. Climatic correlations in the stable isotope records of silver fir (Abies pindrow) trees from Kashmir, India

    International Nuclear Information System (INIS)

    Ramesh, R.; Bhattacharya, S.K.; Gopalan, K.

    1986-01-01

    A high degree of coherence in the annual stable isotopic records along different radial directions of a silver fir tree and between two members of this species from the Kashmir Valley has recently been reported by us. Since such a common pattern of isotopic variability is most likely due to the climatic fluctuations in the site, we have compared the mean δD, δ 13 C and δ 18 O records of these trees with instrumentally measured climatic parameters recorded in a nearby weather station to identify the climatic parameters predominantly influencing the isotopic record. A multiple regression analysis of the two records for the period 1903-1932 yields the following: δD is most sensitive to the amount of growing season precipitation, followed by mean maximum temperature. Tree cellulose shows an amount effect analogous to precipitation samples. The temperature coefficient for δD is in good agreement with earlier estimates based on spatial correlations. δ 13 C is significantly related to humidity and cloud amount. The signs of the regression coefficients are consistent with the recent model of Francey and Farquhar for 13 C/ 12 C fractionation in C 3 plants. δ 18 O of cellulose appears to be controlled significantly by relative humidity. δ 18 O shows less overall correlation with climatic parameters than δD and δ 13 C. δD of carbon bound hydrogen and δ 18 O of tree cellulose are linearly related with a slope of 7.9±0.3, suggesting evaporative enrichment in leaf water. (orig.)

  8. Tangential Flow Ultrafiltration: A “Green” Method for the Size Selection and Concentration of Colloidal Silver Nanoparticles

    Science.gov (United States)

    Anders, Catherine B.; Baker, Joshua D.; Stahler, Adam C.; Williams, Austin J.; Sisco, Jackie N.; Trefry, John C.; Wooley, Dawn P.; Pavel Sizemore, Ioana E.

    2012-01-01

    Nowadays, AgNPs are extensively used in the manufacture of consumer products,1 water disinfectants,2 therapeutics,1, 3 and biomedical devices4 due to their powerful antimicrobial properties.3-6 These nanoparticle applications are strongly influenced by the AgNP size and aggregation state. Many challenges exist in the controlled fabrication7 and size-based isolation4,8 of unfunctionalized, homogenous AgNPs that are free from chemically aggressive capping/stabilizing agents or organic solvents.7-13 Limitations emerge from the toxicity of reagents, high costs or reduced efficiency of the AgNP synthesis or isolation methods (e.g., centrifugation, size-dependent solubility, size-exclusion chromatography, etc.).10,14-18 To overcome this, we recently showed that TFU permits greater control over the size, concentration and aggregation state of Creighton AgNPs (300 ml of 15.3 μg ml-1 down to 10 ml of 198.7 μg ml-1) than conventional methods of isolation such as ultracentrifugation.19 TFU is a recirculation method commonly used for the weight-based isolation of proteins, viruses and cells.20,21 Briefly, the liquid sample is passed through a series of hollow fiber membranes with pore size ranging from 1,000 kD to 10 kD. Smaller suspended or dissolved constituents in the sample will pass through the porous barrier together with the solvent (filtrate), while the larger constituents are retained (retentate). TFU may be considered a "green" method as it neither damages the sample nor requires additional solvent to eliminate toxic excess reagents and byproducts. Furthermore, TFU may be applied to a large variety of nanoparticles as both hydrophobic and hydrophilic filters are available. The two main objectives of this study were: 1) to illustrate the experimental aspects of the TFU approach through an invited video experience and 2) to demonstrate the feasibility of the TFU method for larger volumes of colloidal nanoparticles and smaller volumes of retentate. First

  9. [AgBr colloids prepared by electrolysis and their SERS activity research].

    Science.gov (United States)

    Si, Min-Zhen; Fang, Yan; Dong, Gang; Zhang, Peng-Xiang

    2008-01-01

    Ivory-white AgBr colloids were prepared by means of electrolysis. Two silver rods 1.0 cm in diameter and 10.0 cm long were respectively used as the negative and positive electrodes, the aqueous solution of hexadecyl trimethyl ammonium bromide was used as the electrolyte, and a 7 V direct current was applied on the silver rods for three hours. The obtained AgBr colloids were characterized by UV-Vis spectroscopy, transmission electron microscopy, and SERS using a 514. 5 nm laser line on Renishaw 2000 Raman spectrometer. These particles are about nanometer size and their shapes are as spherical or elliptic, with a slight degree of particle aggregation. The UV-Vis spectra exhibit a large plasmon resonance band at about 292.5 nm, similar to that reported in the literature. The AgBr colloids were very stable at room temperature for months. In order to test if these AgBr colloids can be used for SERS research, methyl orange, Sudan red and pyridine were used. It was found that AgBr colloids have SERS activity to these three molicules. For methyl orange, the intense Raman peaks are at 1 123, 1 146, 1 392, 1 448 and 1 594 cm(-1); for Sudan red, the intense Raman peaks are at 1 141, 1 179, 1 433 and 1 590 cm(-1); and for pyridine, the intense Raman peaks are at 1 003, 1 034 and 1 121 cm(-1). It is noticeable that SERS of methyl orange was observed on AgBr colloids, but not on the gray and yellow silver colloids prepared by traditional means. The possible reason was explained. One major advantage of this means is the absence of the spectral interference such as citrate, BH4- arising from reaction products of the colloids formation process. On AgBr colloids, one can get some molecular SERS impossible to get on the gray and yellow silver colloids.

  10. Increasing surface enhanced Raman spectroscopy effect of RNA and DNA components by changing the pH of silver colloidal suspensions.

    Science.gov (United States)

    Primera-Pedrozo, Oliva M; Rodríguez, Gabriela Del Mar; Castellanos, Jorge; Felix-Rivera, Hilsamar; Resto, Oscar; Hernández-Rivera, Samuel P

    2012-02-15

    This work focused on establishing the parameters for enhancing the Raman signals of DNA and RNA constituents: nitrogenous bases, nucleosides and nucleotides, using metallic nanoparticles as surface enhanced Raman scattering substrates. Silver nanospheres were synthesized using sodium borohydride as a reducing agent and sodium citrate as a capping agent. The prepared nanoparticles had a surface plasmon band at ∼384nm and an average size of 12±3nm. The nanoparticles' surface charge was manipulated by changing the pH of the Ag colloidal suspensions in the range of 1-13. Low concentrations as 0.7μM were detected under the experimental conditions. The optimum pH values were: 7 for adenine, 9 for AMP, 5 for adenosine, 7 for dAMP and 11 for deoxyadenosine. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. Acute and subacute pulmonary toxicity caused by a single intratracheal instillation of colloidal silver nanoparticles in mice: pathobiological changes and metallothionein responses.

    Science.gov (United States)

    Kaewamatawong, Theerayuth; Banlunara, Wijit; Maneewattanapinyo, Pattwat; Thammachareon, Chuchaat; Ekgasit, Sanong

    2014-01-01

    To study the acute and subacute pulmonary toxicity of colloidal silver nanoparticles (Ag-NPs), 0 or 100 ppm of Ag-NPs were instilled intratracheally in mice. Cellular and biochemical parameters in bronchoalveolar lavage fluid (BALF) and histological alterations were determined 1, 3, 7, 15, and 30 days after instillation. Ag-NPs induced moderate pulmonary inflammation and injury on BALF indices during the acute period; however, these changes gradually regressed in a time-dependent manner. Concomitant histopathological and laminin immunohistochemical findings generally correlated to BALF data. Superoxide dismutase and metallothionein expression occurred in particle-laden macrophages and alveolar epithelial cells, which correlated to lung lesions in mice treated with Ag-NPs. These findings suggest that instillation of Ag-NPs causes transient moderate acute lung inflammation and tissue damage. Oxidative stress may underlie the induction of injury to lung tissue. Moreover, the expression of metallothionein in tissues indicated the protective response to exposure to Ag-NPs.

  12. Charge density modification of carboxylated cellulose nanocrystals for stable silver nanoparticles suspension preparation

    International Nuclear Information System (INIS)

    Hoeng, Fanny; Denneulin, Aurore; Neuman, Charles; Bras, Julien

    2015-01-01

    Synthesis of silver nanoparticles using cellulose nanocrystals (CNC) has been found to be a great method for producing metallic particles in a sustainable way. In this work, we propose to evaluate the influence of the charge density of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-oxidized CNC on the morphology and the stability of synthetized silver nanoparticles. Silver nanoparticles were obtained by sol–gel reaction using borohydride reduction, and charge density of TEMPO-oxidized CNC was tuned by an amine grafting. The grafting was performed at room temperature and neutral pH. Crystallinity and morphology were kept intact during the peptidic reaction on CNC allowing knowing the exact impact of the charge density. Charge density has been found to have a strong impact on shape, organization, and suspension stability of resulting silver particles. Results show an easy way to tune the charge density of CNC and propose a sustainable way to control the morphology and stability of silver nanoparticles in aqueous suspension

  13. Photobiosynthesis of stable and functional silver/silver chloride nanoparticles with hydrolytic activity using hyperthermophilic β-glucosidases with industrial potential.

    Science.gov (United States)

    Araújo, Juscemácia N; Tofanello, Aryane; da Silva, Viviam M; Sato, Juliana A P; Squina, Fabio M; Nantes, Iseli L; Garcia, Wanius

    2017-09-01

    The β-glucosidases are important enzymes employed in a large number of processes and industrial applications, including biofuel production from biomass. Therefore, in this study, we reported for the first time the photobiosynthesis of stable and functional silver/silver chloride nanoparticles (Ag/AgCl-NPs) using two hyperthermostable bacterial β-glucosidases with industrial potential. The syntheses were straightforward and rapid processes carried out by mixing β-glucosidase and silver nitrate (in buffer 10mM Tris-HCl, pH 8) under irradiation with light (over a wavelength range of 450-600nm), therefore, compatible with the green chemistry procedure. Synthesized Ag/AgCl-NPs were characterized using a series of physical techniques. Absorption spectroscopy showed a strong absorption band centered at 460nm due to surface plasmon resonance of the Ag-NPs. X-ray diffraction analysis revealed that the Ag/AgCl-NPs were purely crystalline in nature. Under electron microscopy, Ag/AgCl-NPs of variable diameter ranging from 10 to 100nm can be visualized. Furthermore, electron microscopy, zeta potential and Fourier transform infrared spectroscopy results confirmed the presence of β-glucosidases coating and stabilizing the Ag/AgCl-NPs. Finally, the results showed that the enzymatic activities were maintained in the β-glucosidases assisted Ag/AgCl-NPs. The information described here should provide a useful basis for future studies of β-glucosidases assisted Ag/AgCl-NPs, including biotechnological applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. [Toxicological evaluation of nanosized colloidal silver, stabilized with polyvinylpyrrolidone. I. Characterization of nanomaterial, integral, hematological parameters, level of thiol compounds and liver cell apoptosis].

    Science.gov (United States)

    Shumakova, A A; Shipelin, V A; Sidorova, Yu S; Trushina, E N; Mustafina, O K; Pridvorova, S M; Gmoshinsky, I V; Khotimchenko, S A

    2015-01-01

    Nano-sized colloidal silver (NCS) is currently one of the most widely used nanomaterials in medicine and consumer’s products. Nanoparticles (NPs) of silver, in addition to the direct exposition through products may expose human via various environmental objects. The aim of the study is to assess the safe doses of silver NP received orally. The investigated NCS contained silver NPs with diameter of 10–60 nm, predominantly with a nearly spherical form stabilized with polyvinylpyrrolidone (PVP). The experiment was performed during 92 days in 5 groups of male Wistar rats (n=15 in each group), receiving a balanced semisynthetic diet. Animal of group 1 (control) received vehicle (deionized water) intragastrically for 30 days and then with food, groups from 2nd to 4th – PVP and groups from 3rd to 5th NCS, in doses respectively, 0.1; 1.0 and 10 mg/kg body weight (b.w.) in terms of silver. The dose of PVP in groups from 2nd to 5th did not differ, amounting to 200 mg/kg b.w. During the experiment, the weight gain, skin condition, activity, stool, cognitive function were assessed. At the end of the feeding period weight of internal organs, intestinal wall permeability to protein macromolecules, liver thiols, standard values of blood erythrocytes, leukocytes and platelets, hepatocyte apoptosis by flow cytometry were studied. These results suggest that in terms of weight gain, lung relative mass, average erythrocyte volume, hemoglobin content and concentration in erythrocytes, the relative proportion of lymphocytes and neutrophils adverse changes have been observed at a dose of 10 mg NPs per kg of b.w. At lower levels of exposure (0.1 and 1.0 mg/kg b.w.) some specific changes were also observed (in terms of thiols pool in liver, cognitive function, relative abundance of monocytes, the number of dead hepatocytes), which, however, did not possess an unambiguous dependence on the dose. Possible mechanisms of the toxic action of the NCS have been discussed.

  15. Raspberry Extract as Both a Stabilizer and a Reducing Agent in Environmentally Friendly Process of Receiving Colloidal Silver

    Directory of Open Access Journals (Sweden)

    Jolanta Pulit

    2013-01-01

    Full Text Available An ecofriendly method of nanosilver obtaining has been studied. The process involves the chemical reduction method carried out in aqueous environment. Silver nitrate (V was applied as a silver ions source. Raspberry extract was used as a natural source of both reducing and stabilizing agents. The total amount of phenolic compounds was determined by the Folin-Ciocalteu method. Obtained nanoparticles were analyzed by the dynamic light scattering technique so as to determine the particles size and suspension stability which was characterized by an electrokinetic potential. The results confirmed that the size of some nanoparticles was under 100 nm.

  16. [Study of the effect of colloidal solution of silver nanoparticles on parameters of cardio- and hemo-dynamics in rabbits].

    Science.gov (United States)

    Pryskoka, A O

    2014-01-01

    Metal nanoparticles and silver nanoparticles in particular are extensively studied recently considering their prominent antimicrobial properties. Nevertheless, their toxicity aspects and probable side effects remain not well studied. In this article the results of study of the influence of silver nanoparticles onto a cardiovascular system in an in vivo experiment were provided, changes in parameters of cardio- and hemodynamics were defined, and the principles of such influence were identified. Dose-dependent effect of these nanoparticles was established when administered in dose of 4.3 mg/kg three times and 20 mg/kg once.

  17. Adsorption and sub-nanomolar sensing of thioflavin T on colloidal gold nanoparticles, silver nanoparticles and silver-coated films studied using surface-enhanced Raman scattering.

    Science.gov (United States)

    Maiti, Nandita; Chadha, Ridhima; Das, Abhishek; Kapoor, Sudhir

    2015-01-01

    Raman and surface-enhanced Raman scattering (SERS) studies of thioflavin T (ThT) in solid, solution, gold nanoparticles (GNPs), silver nanoparticles (SNPs) and silver-coated films (SCFs) were investigated. Concentration-dependent SERS spectrum of ThT in GNPs and SNPs indicated the existence of two possible structures, one with the torsional angle (φ) between benzothiazole and dimethylaminobenzene rings being 37° and the other with φ=90°. The SERS spectrum of ThT in SCFs were similar to the Raman spectrum of solid and solution that suggests φ=37°. In this paper, the high sensitivity of the SERS technique was employed for sub-nanomolar (picomolar) sensing of ThT. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Non-labile silver species in biosolids remain stable throughout 50 years of weathering and ageing.

    Science.gov (United States)

    Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that...

  19. A radiometric method for the characterization of particulate processes in colloidal suspensions. II

    International Nuclear Information System (INIS)

    Subotic, B.

    1979-01-01

    A radiometric method for the characterization of particulate processes is verified using stable hydrosols of silver iodide. Silver iodide hydrosols satisfy the conditions required for the applications of the proposed method. Comparison shows that the values for the change of particle size measured in silver iodide hydrosols by the proposed method are in excellent agreement with the values obtained by other methods on the same systems (electron microscopy, sedimentation analysis, light scattering). This shows that the proposed method is suitable for the characterization of particulate processes in colloidal suspensions. (Auth.

  20. Preparation of smooth, flexible and stable silver nanowires- polyurethane composite transparent conductive films by transfer method

    Science.gov (United States)

    Bai, Shengchi; Wang, Haifeng; Yang, Hui; Zhang, He; Guo, Xingzhong

    2018-02-01

    Silver nanowires (AgNWs)-polyurethane (PU) composite transparent conductive films were fabricated via transfer method using AgNWs conductive inks and polyurethane as starting materials, and the effects of post-treatments including heat treatment, NaCl solution bath and HCl solution bath for AgNWs film on the sheet resistance and transmittance of the composite films were respectively investigated in detail. AgNWs networks are uniformly embedded in the PU layer to improve the adhesion and reduce the surface roughness of AgNWs-PU composite films. Heat treatment can melt and weld the nanowires, and NaCl and HCl solution baths promote the dissolution and re-deposition of silver and the dissolving of the polymer, both which form conduction pathways and improve contact of AgNWs for reducing the sheet resistance. Smooth and flexible AgNWs-PU composite film with a transmittance of 85% and a sheet resistance of 15 Ω · sq‑1 is obtained after treated in 0.5 wt% HCl solution bath for 60 s, and the optoelectronic properties of the resultant composite film can maintain after 1000 cycles of bending and 100 days.

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

    Science.gov (United States)

    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.

  2. Colloidal systems of silver nanoparticles and high-regioregular cationic polythiophene with ionic-liquid-like pendant groups: Optical properties and SERS.

    Science.gov (United States)

    Kazim, Samrana; Pfleger, Jiří; Procházka, Marek; Bondarev, Dmitrij; Vohlídal, Jiří

    2011-02-15

    We report tuning of structure dependent optical properties of colloidal systems of borate-stabilized silver nanoparticles (Ag NPs) and polythiophene-based cationic polyelectrolyte with ionic-liquid like side groups: poly{3-[6-(1-methylimidazolium-3-yl)hexyl]thiophene-2,5-diyl bromide} (PMHT-Br) towards obtaining local electromagnetic field enhancement effects. Surface-enhanced Raman scattering (SERS) studies showed that the strong electromagnetic field enhancement is related to the formation of aggregates of Ag NPs achieved at the components ratio providing the charge balance between Ag NPs and cationic polythiophene, at which Ag NPs are nearly single-polymer-layer coated, their zeta potential is close to zero and they easily form aggregates in which the mean inter-particle distance enables the occurrence of desired plasmonic effects. Fluorescence quenching is efficient only in the systems with low concentrations of PMHT-Br, in which almost all polymer chains directly interact with the Ag NPs surface. Copyright © 2010 Elsevier Inc. All rights reserved.

  3. [The study of antimicrobial properties of silver nanoparticles in the form of a colloidal solution in the matrix of finely dispersed silica].

    Science.gov (United States)

    Korchak, G I; Surmasheva, E V; Mikhienkova, A I; Nikonova, N A; Romanenko, L I; Oliĭnyk, Z A; Gorval', A K; Rosada, M A

    2012-01-01

    In the experimental study obtained with chemical method colloid solution of nanoparticles (NPs) of silver (Ag) and a composite on his base in the matrix of finely dispersed silica with particle size of 8-12 nm and NPs concentration in basic solution of 0,0016% (0,016 mg/cm3) were established to exhibit high antimicrobial activity against the test organisms: E. coli, P. aeruginosa, S. Aureus and C. Albicans, which depended on a set of factors. Antibacterial properties of tissue impregnated with Ag-NPs were studied. As stabilizing substances a mixture of surface-active substance sodium dodecyl sulfate and polymer polyvinylpyrrolidone was used Before the beginning of the study effective neutralizer was tailored. Times of preservation of antimicrobial activity of test samples have been established, and also their stability throughout long term of supervision (24 months) has been shown. Effect of organic pollution on antimicrobal activity of the samples has been studied. Based on obtained results the algorithm of the study of antimicrobial properties of nanopreparations has been elaborated.

  4. Structural, optical, electrochemical and photovoltaic studies of spider web like Silver Indium Diselenide Quantum dots synthesized by ligand mediated colloidal sol-gel approach

    Science.gov (United States)

    Adhikari, Tham; Pathak, Dinesh; Wagner, Tomas; Jambor, Roman; Jabeen, Uzma; Aamir, Muhammad; Nunzi, Jean-Michel

    2017-11-01

    Silver indium diselenide quantum dots were successively synthesized by colloidal sol-gel method by chelating with organic ligand oleylamine (OLA). The particle size was studied by transmission electron microscopy (TEM) and the size was found about 10 nm. X-ray diffraction (XRD) was used to study crystalline structure of the nanocrystals. The grain size and morphology were further studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elemental composition was studied by X-ray photon electron spectroscopy (XPS) and energy dispersive x-ray spectroscopy (EDAX). The capping property of OLA in nanocrystal was also demonstrated by Fourier Transform Infrared spectroscopy (FTIR). The band gap was calculated from both cyclic voltammetry and optical absorption and suggest quantum confinement. The solution processed bilayer thin film solar cells were fabricated with n-type Zinc oxide using doctor blading/spin coating method and their photovoltaic performance was studied. The best device sintered at 450 °C showed an efficiency 0.75% with current density of 4.54 mAcm-2, open-circuit voltage 0.44 V and fill factor 39.4%.

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

    International Nuclear Information System (INIS)

    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)

  6. Fabrication of antibacterial water filter by coating silver nanoparticles on flexible polyurethane foams

    International Nuclear Information System (INIS)

    Nguyen Thi Phuong Phong; Ngo Vo Ke Thanh; Phan Hue Phuong

    2009-01-01

    In this paper, we fabricated silver-coated polyurethane foams and used it as a bacterial filter for contaminated drinking water. Flexible PU foams were soaked in silver colloidal solutions for 10 h, then washed and air-dried at room temperature. The prepared silver colloidal solutions and silver-coated PU materials were characterized by several techniques including TEM, FESEM/EDS, UV-VIS, ICP-AAS, and Raman spectroscopy. The TEM images showed that the size of silver nanoparticles in colloidal solutions varies from 6 to 12nm. The Raman, FE-SEM/EDS and ICP-AAS data illustrated that silver nanoparticles were stable on the PU foam and were not washed away by water. Furthermore, the microbiological tests (tube tests and flow test) were carried out on silver-coated PU materials with the Coliforms, E. coli, and B. subtilis. The obtained results showed that the bacteria was killed completely with antibacterial efficiency of 100% being observed. Our research suggests that silver-coated polyurethane foams can be used as excellent antibacterial water filters and would have several applications in other sectors.

  7. Biofilm Removal and Antimicrobial Activities of Agar Hydrogel Containing Colloid Nano-Silver against Staphylococcus aureus and Salmonella typhimurium

    Directory of Open Access Journals (Sweden)

    Leyla Sadat Bouryabaf

    2017-10-01

    Full Text Available Background:    Antibacterial and biofilm removal effects of agar hydrogel incorporating silver nanoparticles (SNP at various concentrations were studied against Staphylococcus aureus and Salmonella typhimurium in vitro.Methods:      The minimum inhibitory concentrations (MIC of SNP was determined by agar dilution method. Then, hydrogels were prepared by mixing of 0.5% w/v agar and SNP (1/2 MIC, MIC, and 2 MIC and their inhibitory efficacies against planktonic and biofilm forms of bacteria were measured using agar spot and microtiter test, respectively.Results:    The MIC value was 125 µg/ mL for both bacteria. All SNP hydrogels represented antibacterial activity against Staphylococcus aureus and S. typhimurium on agar culture, which was significant compared to control group (silver sulfadiazine cream. The developed biofilm of S. aureus and S. typhimurium were strongly (85% reduction and modernly affected (60% reduction by SNP hydrogels during 15 min contact time, respectively. A dose-dependent biofilm reduction was not demonstrated when different SNP concentrations were tested. Moreover, the results from this study confirmed the moderate sanitizing ability of SNP loaded hydrogel against planktonic forms of both bacteria, which SNP (2MIC hydrogel decreased only 2.3 log10 CFU/ mL in a primary population of S. typhimurium during 15 min exposure time.Conclusion:     We recommended SNP incorporated agar hydrogel as an effective biofilm removal sanitizer.

  8. Aggregation-based colorimetric sensor for determination of prothioconazole fungicide using colloidal silver nanoparticles (AgNPs)

    Science.gov (United States)

    Ivrigh, Zahra Jafar-Nezhad; Fahimi-Kashani, Nafiseh; Hormozi-Nezhad, M. Reza

    2017-12-01

    There is a growing interest in developing high-performance sensors monitoring fungicides, due to their broadly usage and their adverse effects on humans and wildlife. In the present study, a colorimetric probe has been proposed for detection of prothioconazole based on aggregation of unmodified silver nanoparticles (AgNPs). Under optimized condition, linear relationships between the concentration of prothioconazole and the absorbance ratio of A500/A395 were found over the range of 0.01 μg·mL- 1 to 0.4 μg·mL- 1 with quantification limit as low as 1.7 ng·mL- 1. Furthermore, AgNPs color change from yellow to pink-orange in presence of prothioconazole, indicates highly sensitive naked-eye colorimetric assay for quantifying prothioconazole in real applications. The proposed approach was successfully used for the determination of prothioconazole in wheat flour and paddy water sample.

  9. Silver micro- and nano-particles obtained using different glycols as reducing agents and measurement of their conductivity

    Directory of Open Access Journals (Sweden)

    Moudir Naïma

    2016-01-01

    Full Text Available Synthesis of silver micro- and nano-particles for the preparation of conductive pastes for the metallization of solar cells was realized by chemical reduction in the presence and absence of poly(vinyl-pyrrolidone (PVP. Silver nitrate was used as a precursor in the presence of three polyols (ethylene glycol, di-ethylene glycol and propylene glycol tested at experimental temperatures near their boiling points. Six samples were obtained by this protocol. Three silver powders obtained without the use of PVP have a metallic luster appearance; however, the samples produced using an excess of PVP are in the form of stable colloidal dispersions of silver nano-particles. Structural characterizations of samples using a scanning electron microscope and X-ray diffractometer show a good crystallinity and spherical morphology. From DSC and TGA analyses, it was noticed that all the nano-silvers present in the colloidal suspension have the same thermal behavior.

  10. Radiometric method for the characterization of particulate processes in colloidal suspensions. II. Experimental verification of the method

    Energy Technology Data Exchange (ETDEWEB)

    Subotic, B. [Institut Rudjer Boskovic, Zagreb (Yugoslavia)

    1979-09-15

    A radiometric method for the characterization of particulate processes is verified using stable hydrosols of silver iodide. Silver iodide hydrosols satisfy the conditions required for the applications of the proposed method. Comparison shows that the values for the change of particle size measured in silver iodide hydrosols by the proposed method are in excellent agreement with the values obtained by other methods on the same systems (electron microscopy, sedimentation analysis, light scattering). This shows that the proposed method is suitable for the characterization of particulate processes in colloidal suspensions. (Auth.).

  11. Controllable fabrication of large-scale hierarchical silver nanostructures for long-term stable and ultrasensitive SERS substrates

    Science.gov (United States)

    Wu, Jing; Fang, Jinghuai; Cheng, Mingfei; Gong, Xiao

    2016-09-01

    In this work, we aim to prepare effective and long-term stable hierarchical silver nanostructures serving as surface-enhanced Raman scattering (SERS) substrates simply via displacement reaction on Aluminum foils. In our experiments, Hexadecyltrimethylammonium bromide (CTAB) is used as cationic surfactant to control the velocity of displacement reaction as well as the hierarchical morphology of the resultant. We find that the volume ratio of CTAB to AgNO3 plays a dominant role in regulating the hierarchical structures besides the influence of displacement reaction time. These as-prepared hierarchical morphologies demonstrate excellent SERS sensitivity, structural stability and reproducibility with low values of relative standard deviation less than 20 %. The high SERS analytical enhancement factor of ~6.7 × 108 is achieved even at the concentration of Crystal Violet (CV) as low as 10-7 M, which is sufficient for single-molecule detection. The detection limit of CV is 10-9 M in this study. We believe that this simple and rapid approach integrating advantages of low-cost production and high reproducibility would be a promising way to facilitate routine SERS detection and will get wide applications in chemical synthesis.

  12. Silver nanoparticle aggregation not triggered by an ionic strength mechanism

    International Nuclear Information System (INIS)

    Botasini, Santiago; Méndez, Eduardo

    2013-01-01

    The synthesis of stable colloidal solutions of silver nanoparticles is a major goal in the industry to control their fate in aqueous solutions. The present work studies 10–20-nm silver nanoparticle aggregation triggered by the presence of chloride ions. The aggregation process was followed by UV–Vis–NIR spectroscopy and transmission electron microscopy. We found that the mechanism involved differs from the classic explanation of nanoparticle aggregation triggered by an increase in the ionic strength. Moreover, our results give evidence that even when nanoparticles are resistant to an increment of the total amount of ions, the formation of insoluble salts in the vicinity of the nanoparticle is enough to induce the aggregation. The presence of silver chloride around the silver nanoparticles was documented by an X-ray diffraction pattern and electrochemical methods because chloride anions are ubiquitous in real media; this alternative process jeopardized the development of many applications with silver nanoparticles that depend on the use of stable colloids.

  13. Silver nanoparticle aggregation not triggered by an ionic strength mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Botasini, Santiago; Mendez, Eduardo, E-mail: emendez@fcien.edu.uy [Instituto de Quimica Biologica, Universidad de la Republica, Laboratorio de Biomateriales (Uruguay)

    2013-04-15

    The synthesis of stable colloidal solutions of silver nanoparticles is a major goal in the industry to control their fate in aqueous solutions. The present work studies 10-20-nm silver nanoparticle aggregation triggered by the presence of chloride ions. The aggregation process was followed by UV-Vis-NIR spectroscopy and transmission electron microscopy. We found that the mechanism involved differs from the classic explanation of nanoparticle aggregation triggered by an increase in the ionic strength. Moreover, our results give evidence that even when nanoparticles are resistant to an increment of the total amount of ions, the formation of insoluble salts in the vicinity of the nanoparticle is enough to induce the aggregation. The presence of silver chloride around the silver nanoparticles was documented by an X-ray diffraction pattern and electrochemical methods because chloride anions are ubiquitous in real media; this alternative process jeopardized the development of many applications with silver nanoparticles that depend on the use of stable colloids.

  14. Attachment of 13 Types of Foodborne Bacteria to Jalapeño and Serrano Peppers and Antibacterial Effect of Roselle Calyx Extracts, Sodium Hypochlorite, Colloidal Silver, and Acetic Acid against These Foodborne Bacteria on Peppers.

    Science.gov (United States)

    Rangel-Vargas, Esmeralda; Gómez-Aldapa, Carlos A; Falfan-Cortes, Reyna N; Rodríguez-Marín, María L; Godínez-Oviedo, Angélica; Acevedo-Sandoval, Otilio A; Castro-Rosas, Javier

    2017-03-01

    Chili peppers are a very important crop in Mexico. However, these peppers have been associated with Salmonella infection outbreaks in the United States, and Salmonella and diarrheagenic Escherichia coli pathotypes have been isolated from jalapeño and serrano peppers in Mexico. To decrease microbial contamination of fruits and vegetables, chemical agents are commonly used; however, chemical agents used to eliminate pathogenic bacteria on vegetables have a limited antimicrobial effect. Roselle ( Hibiscus sabdariffa ) calyces have been reported to have an antimicrobial effect on pathogenic bacteria. In the present study, the antibacterial effect of four roselle calyx extracts (water, methanol, acetone, and ethyl acetate), sodium hypochlorite, colloidal silver, and acetic acid against foodborne bacteria was evaluated on contaminated jalapeño and serrano peppers. The 13 types of foodborne bacteria evaluated were Listeria monocytogenes , Shigella flexneri , Salmonella Typhimurium, Salmonella Typhi, Salmonella Montevideo, Staphylococcus aureus , E. coli O157:H7, five E. coli pathotypes (Shiga toxin producing, enteropathogenic, enterotoxigenic, enteroinvasive, and enteroaggregative), and Vibrio cholerae O1. All 13 types attached to both pepper types, with no significant differences in attachment between jalapeño and serrano peppers. Roselle calyx extract treatment resulted in a greater reduction in levels of all foodborne bacteria than did treatment with sodium hypochlorite, colloidal silver, and acetic acid on both pepper types. Roselle calyx extracts may be a useful for disinfection of chili peppers in the field, processing plants, restaurants, and homes.

  15. Size-tunable silver nanoparticles synthesized by using aminopolycarboxylic acids at ambient-temperature

    International Nuclear Information System (INIS)

    Malkar, Vishwabharati V.; Chadha, R.; Biswas, N.; Mukherjee, T.; Kapoor, S.

    2009-01-01

    Full text: Stable aqueous sols of silver nanoparticles are prepared by using various aminopolycarboxylic acids as stabilizing agents at ambient temperature. The precursor silver perchlorate is reduced using γ radiations. Interestingly, it was observed that size of silver nanoparticles obtained could be tuned using various aminopolycarboxylic acids of varying carboxylic acid groups The silver sols synthesized by this method were stable for months and particles obtained were monodisperse in almost all cases. Particle formation was observed at equimolar concentration of silver and aminopolycarboxylic acids. The stabilization of particles even in the absence of any polymer indicates that the adsorption of aminopolycarboxylic acids on silver particle is a spontaneous process. The adsorbed aminopolycarboxylic acids can saturate the residual valence force of the silver atom on the particle surface by coordinating with unoccupied orbital. Adsorption of aminopolycarboxylic acids does not lead to any change in surface plasmon band of silver nanoparticles; this indicates that anions in the double layer on the colloidal particle have different chemical properties from the free anions. Synthesized silver nanoparticles were characterized by UV-visible spectrophotometer, X-ray Diffraction, Dynamic Light Scattering and Transmission Electron Microscope

  16. Colloidal organization

    CERN Document Server

    Okubo, Tsuneo

    2015-01-01

    Colloidal Organization presents a chemical and physical study on colloidal organization phenomena including equilibrium systems such as colloidal crystallization, drying patterns as an example of a dissipative system and similar sized aggregation. This book outlines the fundamental science behind colloid and surface chemistry and the findings from the author's own laboratory. The text goes on to discuss in-depth colloidal crystallization, gel crystallization, drying dissipative structures of solutions, suspensions and gels, and similar-sized aggregates from nanosized particles. Special emphas

  17. Production of putrescine-capped stable silver nanoparticle: its characterization and antibacterial activity against multidrug-resistant bacterial strains

    Science.gov (United States)

    Saha, Saswati; Gupta, Bhaskar; Gupta, Kamala; Chaudhuri, Mahua Ghosh

    2016-11-01

    Integration of biology with nanotechnology is now becoming attention-grabbing area of research. The antimicrobial potency of silver has been eminent from antiquity. Due to the recent desire for the enhancement of antibacterial efficacy of silver, various synthesis methods of silver in their nano dimensions are being practiced using a range of capping material. The present work highlights a facile biomimetic approach for production of silver nanoparticle being capped and stabilized by putrescine, possessing a diameter of 10-25 ± 1.5 nm. The synthesized nanoparticles have been analyzed spectrally and analytically. Morphological studies are carried out by high-resolution transmission electron microscopy and crystallinity by selected area electron diffraction patterns. Moreover, the elemental composition of the capped nanoparticles was confirmed by energy-dispersive X-ray spectroscopy analysis. A comparative study (zone of inhibition and minimum inhibitory concentration) regarding the interactions and antibacterial potentiality of the capped silver nanoparticles with respect to the bare ones reveal the efficiency of the capped one over the bare one. The bacterial kinetic study was executed to monitor the interference of nanoparticles with bacterial growth rate. The results also highlight the efficacy of putrescine-capped silver nanoparticles as effective growth inhibitors against multi-drug resistant human pathogenic bacterial strains, which may, thus, potentially be applicable as an effective antibacterial control system to fight diseases.

  18. Laser induced augmentation of silver nanospheres to nanowires in ethanol fostered by Poly Vinyl Pyrrolidone

    Energy Technology Data Exchange (ETDEWEB)

    Sebastian, Suneetha, E-mail: sunikutty@gmail.com; Linslal, C.L.; Vallabhan, C.P.G.; Nampoori, V.P.N.; Radhakrishnan, P.; Kailasnath, M.

    2014-11-30

    Highlights: • Silver nanospheres are synthesised in ethanol containing Poly Vinyl Pyrrolidone which acts as a polymeric capping agent to nanoparticles thus improving its stability. • Laser irradiation onto the colloidal solution of silver nanoparticles produced well defined nanowires through ripening mechanism promoted by Poly Vinyl Pyrrolidone. • Nanowires so formed are having an average length of 8.7 μm and width of 160 nm. - Abstract: Stable uniform silver nanospheres having an average diameter of 45 nm are synthesised in ethanol containing Poly Vinyl Pyrrolidone using Laser Ablation in Liquid technique. Further irradiation of the nanocolloidal solution by focussed laser beam produced stable well defined silver nanowires through ripening mechanism fostered by the presence of Poly Vinyl Pyrrolidone. Confirmation of the mechanism is obtained from Transmission Electron Microscopic images of the nanocolloidal solution irradiated for different time durations.

  19. Facile and efficient one-pot solvothermal and microwave-assisted synthesis of stable colloidal solutions of MFe2O4 spinel magnetic nanoparticles

    International Nuclear Information System (INIS)

    Solano, Eduardo; Perez-Mirabet, Leonardo; Martinez-Julian, Fernando; Guzmán, Roger; Arbiol, Jordi; Puig, Teresa; Obradors, Xavier; Yañez, Ramón; Pomar, Alberto; Ricart, Susagna; Ros, Josep

    2012-01-01

    Well-defined synthesis conditions of high quality MFe 2 O 4 (M = Mn, Fe, Co, Ni, Zn, and Cu) spinel ferrite magnetic nanoparticles, with diameters below 10 nm, have been described based on facile and efficient one-pot solvothermal or microwave-assisted heating procedures. Both methods are reproducible and scalable and allow forming concentrated stable colloidal solutions in polar solvents, but microwave-assisted heating allows reducing 15 times the required annealing time and leads to an enhanced monodispersity of the nanoparticles. Non-agglomerated nanoparticles dispersions have been achieved using a simple one-pot approach where a single compound, triethyleneglycol, behaves at the same time as solvent and capping ligand. A narrow nanoparticle size distribution and high quality crystallinity have been achieved through selected nucleation and growth conditions. High resolution transmission electron microscopy images and electron energy loss spectroscopy analysis confirm the expected structure and composition and show that similar crystal faceting has been formed in both synthetic approaches. The spinel nanoparticles behave as ferrimagnets with a high saturation magnetization and are superparamagnetic at room temperature. The influence of synthesis route on phase purity and unconventional magnetic properties is discussed in some particular cases such as CuFe 2 O 4 , CoFe 2 O 4 , and ZnFe 2 O 4 .

  20. One-pot synthesis of stable colloidal solutions of MFe{sub 2}O{sub 4} nanoparticles using oleylamine as solvent and stabilizer

    Energy Technology Data Exchange (ETDEWEB)

    Pérez-Mirabet, Leonardo [Departament de Química, Universitat Autònoma de Barcelona, Campus de la UAB, 08193 Bellaterra (Spain); Solano, Eduardo, E-mail: eduardo.solano@uab.cat [Departament de Química, Universitat Autònoma de Barcelona, Campus de la UAB, 08193 Bellaterra (Spain); Martínez-Julián, Fernando; Guzmán, Roger [Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra (Spain); Arbiol, Jordi [Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra (Spain); Institució Catalana de Recerca i Estudis Avançats (ICREA), 08019 Barcelona (Spain); Puig, Teresa; Obradors, Xavier; Pomar, Alberto [Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra (Spain); Yáñez, Ramón; Ros, Josep [Departament de Química, Universitat Autònoma de Barcelona, Campus de la UAB, 08193 Bellaterra (Spain); Ricart, Susagna [Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra (Spain)

    2013-03-15

    Highlights: ► One-pot synthesis of ferrite magnetic nanoparticles (<10 nm) in non-polar media. ► Nanoparticles present high monocrystal quality and monodispersion. ► Superparamagnetic behavior at room temperature. ► Nanoparticles transfer to polar media via ligand exchange. - Abstract: An easy, efficient, reproducible and scalable one-pot synthetic methodology to obtain magnetic spinel ferrite nanoparticles has been developed. This approach is based on one-pot thermal decomposition of Fe(acac){sub 3} and M(acac){sub 2} (M = Co, Mn, Cu and Zn) in oleylamine, which also acts as a capping ligand, by producing stable colloidal dispersions of nanoparticles in non-polar solvents. The properties of the nanoparticles have been studied via different techniques, such as transmission electron microscopy, which shows that nanoparticles are monocrystallines and a narrow dispersion in size; magnetic analyses have demonstrated that the resulting ferrite nanoparticles show high saturation values and superparamagnetic behavior at room temperature; X-ray diffraction has also been performed, and it confirms that the synthesized nanoparticles have a spinel structure. Complementarily, ligand exchange has been also carried out in order to produce dispersions of the synthesized nanoparticles in polar media.

  1. Lysine-functionalized nanodiamonds as gene carriers: development of stable colloidal dispersion for in vitro cellular uptake studies and siRNA delivery application

    Science.gov (United States)

    Alwani, Saniya; Kaur, Randeep; Michel, Deborah; Chitanda, Jackson M; Verrall, Ronald E; Karunakaran, Chithra; Badea, Ildiko

    2016-01-01

    Purpose Nanodiamonds (NDs) are emerging as an attractive tool for gene therapeutics. To reach their full potential for biological application, NDs should maintain their colloidal stability in biological milieu. This study describes the behavior of lysine-functionalized ND (lys-ND) in various dispersion media, with an aim to limit aggregation and improve the colloidal stability of ND-gene complexes called diamoplexes. Furthermore, cellular and macromolecular interactions of lys-NDs are also analyzed in vitro to establish the understanding of ND-mediated gene transfer in cells. Methods lys-NDs were synthesized earlier through covalent conjugation of lysine amino acid to carboxylated NDs surface generated through re-oxidation in strong oxidizing acids. In this study, dispersions of lys-NDs were prepared in various media, and the degree of sedimentation was monitored for 72 hours. Particle size distributions and zeta potential measurements were performed for a period of 25 days to characterize the physicochemical stability of lys-NDs in the medium. The interaction profile of lys-NDs with fetal bovine serum showed formation of a protein corona, which was evaluated by size and charge distribution measurements. Uptake of lys-NDs in cervical cancer cells was analyzed by scanning transmission X-ray microscopy, flow cytometry, and confocal microscopy. Cellular uptake of diamoplexes (complex of lys-NDs with small interfering RNA) was also analyzed using flow cytometry. Results Aqueous dispersion of lys-NDs showed minimum sedimentation and remained stable over a period of 25 days. Size distributions showed good stability, remaining under 100 nm throughout the testing period. A positive zeta potential of >+20 mV indicated a preservation of surface charges. Size distribution and zeta potential changed for lys-NDs after incubation with blood serum, suggesting an interaction with biomolecules, mainly proteins, and a possible formation of a protein corona. Cellular internalization

  2. Lysine-functionalized nanodiamonds as gene carriers: development of stable colloidal dispersion for in vitro cellular uptake studies and siRNA delivery application.

    Science.gov (United States)

    Alwani, Saniya; Kaur, Randeep; Michel, Deborah; Chitanda, Jackson M; Verrall, Ronald E; Karunakaran, Chithra; Badea, Ildiko

    2016-01-01

    Nanodiamonds (NDs) are emerging as an attractive tool for gene therapeutics. To reach their full potential for biological application, NDs should maintain their colloidal stability in biological milieu. This study describes the behavior of lysine-functionalized ND (lys-ND) in various dispersion media, with an aim to limit aggregation and improve the colloidal stability of ND-gene complexes called diamoplexes. Furthermore, cellular and macromolecular interactions of lys-NDs are also analyzed in vitro to establish the understanding of ND-mediated gene transfer in cells. lys-NDs were synthesized earlier through covalent conjugation of lysine amino acid to carboxylated NDs surface generated through re-oxidation in strong oxidizing acids. In this study, dispersions of lys-NDs were prepared in various media, and the degree of sedimentation was monitored for 72 hours. Particle size distributions and zeta potential measurements were performed for a period of 25 days to characterize the physicochemical stability of lys-NDs in the medium. The interaction profile of lys-NDs with fetal bovine serum showed formation of a protein corona, which was evaluated by size and charge distribution measurements. Uptake of lys-NDs in cervical cancer cells was analyzed by scanning transmission X-ray microscopy, flow cytometry, and confocal microscopy. Cellular uptake of diamoplexes (complex of lys-NDs with small interfering RNA) was also analyzed using flow cytometry. Aqueous dispersion of lys-NDs showed minimum sedimentation and remained stable over a period of 25 days. Size distributions showed good stability, remaining under 100 nm throughout the testing period. A positive zeta potential of >+20 mV indicated a preservation of surface charges. Size distribution and zeta potential changed for lys-NDs after incubation with blood serum, suggesting an interaction with biomolecules, mainly proteins, and a possible formation of a protein corona. Cellular internalization of lys-NDs was confirmed

  3. A general method to coat colloidal particles with titiana

    NARCIS (Netherlands)

    Demirors, A.F.; van Blaaderen, A.; Imhof, A.

    2010-01-01

    We describe a general one-pot method for coating colloidal particles with amorphous titania. Various colloidal particles such as silica particles, large silver colloids, gibbsite platelets, and polystyrene spheres were successfully coated with a titania shell. Although there are several ways of

  4. Synthesis and characterization of silver nanoparticles by sol-gel route from silver nitrate

    International Nuclear Information System (INIS)

    Morales, Jorge; Moran, Jose; Quintana, Maria; Estrada, Walter

    2009-01-01

    Silver nanoparticles colloids have been synthesized by sol-gel method. This synthesis consists in silver nitrate reduction by ethylene glycol in a process called polyol. The growth of the nanoparticles have been controlled by the steric stabilization of the colloid with polyvinylpyrrolidone (PVP, M w = 40 000). The silver nanoparticle size and structure was depending on the control of parameters such as: molar concentrations ratio of silver nitrate and PVP, temperature of reaction and the reflux time. Colloids have been characterized by UV-vis spectroscopy in the range from 300 to 1000 nm. The results show that the typical peak of surface plasmon resonance is formed at 400-450 nm indicating the formation of silver nanoparticles. The presences of silver nanoparticles of spherical shape with size among 20-40 nm were observed by transmission electronic microscopy (TEM). Electron diffraction patterns confirmed that synthesized colloids contain metallic silver with a crystal structure face centered cubic FCC. (author)

  5. Lysine-functionalized nanodiamonds as gene carriers: development of stable colloidal dispersion for in vitro cellular uptake studies and siRNA delivery application

    Directory of Open Access Journals (Sweden)

    Alwani S

    2016-02-01

    Full Text Available Saniya Alwani,1 Randeep Kaur,1 Deborah Michel,1 Jackson M Chitanda,2 Ronald E Verrall,3 Chithra Karunakaran,4 Ildiko Badea1 1Drug Design and Discovery Research Group, College of Pharmacy and Nutrition, 2Department of Chemical & Biological Engineering, 3Department of Chemistry, University of Saskatchewan, 4Canadian Light Source, Saskatoon, SK, Canada Purpose: Nanodiamonds (NDs are emerging as an attractive tool for gene therapeutics. To reach their full potential for biological application, NDs should maintain their colloidal stability in biological milieu. This study describes the behavior of lysine-functionalized ND (lys-ND in various dispersion media, with an aim to limit aggregation and improve the colloidal stability of ND-gene complexes called diamoplexes. Furthermore, cellular and macromolecular interactions of lys-NDs are also analyzed in vitro to establish the understanding of ND-mediated gene transfer in cells. Methods: lys-NDs were synthesized earlier through covalent conjugation of lysine amino acid to carboxylated NDs surface generated through re-oxidation in strong oxidizing acids. In this study, dispersions of lys-NDs were prepared in various media, and the degree of sedimentation was monitored for 72 hours. Particle size distributions and zeta potential measurements were performed for a period of 25 days to characterize the physicochemical stability of lys-NDs in the medium. The interaction profile of lys-NDs with fetal bovine serum showed formation of a protein corona, which was evaluated by size and charge distribution measurements. Uptake of lys-NDs in cervical cancer cells was analyzed by scanning transmission X-ray microscopy, flow cytometry, and confocal microscopy. Cellular uptake of diamoplexes (complex of lys-NDs with small interfering RNA was also analyzed using flow cytometry. Results: Aqueous dispersion of lys-NDs showed minimum sedimentation and remained stable over a period of 25 days. Size distributions showed

  6. Quantum-size colloid metal systems

    International Nuclear Information System (INIS)

    Roldugin, V.I.

    2000-01-01

    In the review dealing with quantum-dimensional metallic colloid systems the methods of preparation, electronic, optical and thermodynamic properties of metal nanoparticles and thin films are considered, the effect of ionizing radiation on stability of silver colloid sols and existence of a threshold radiation dose affecting loss of stability being discussed. It is shown that sol stability loss stems from particles charge neutralization due to reduction of sorbed silver ions induced by radiation, which results in destruction of double electric layer on colloid particles boundary [ru

  7. Silver Nanoparticles and Studies on Using in Poultry Nutrition

    OpenAIRE

    Mehmet Akif Özcan

    2015-01-01

    The use of colloidal silver as an antibiotic was becoming widespread until the 1940s. However, with the discovery of antibiotics, usage of colloidal silver had been reduced because of being expensive. The fact that bacteria develop resistance to antibiotics lead to prohibiton the usage of antibiotics in poultry diets as growth promoters. Based on these developments reuse of colloidal silver has been raised as an alternative to antibiotics. Without prejudice to the beneficial enzymes, colloida...

  8. Photochemical Synthesis of Silver Nanodecahedrons and Related Nanostructures for Plasmonic Field Enhancement Applications

    Science.gov (United States)

    Lu, Haifei

    Noble-metal nanocrystals have received considerable attention in recent years for their size and shape dependent localized surface Plasmon resonances (LSPR). Various applications based on colloidal nanoparticles, such as surface enhanced Raman scattering (SERS), surface enhanced fluorescence (SEF), plasmonic sensing, photothermal therapy etc., have been broadly explored in the field of biomedicine, because of their extremely large optical scattering and absorption cross sections, as well as giant electric field enhancement on their surface. However, despite its high chemical stability, gold exhibits quite large losses and electric field enhancement is comparatively weaker than silver. Silver nanoparticles synthesized by the traditional technique only cover an LSPR ranged from 420~500 nm. On the other hand, the range of 500~660 nm, which is covered by several easily available commercial laser lines, very limited colloidal silver nanostructures with controllable size and shape have been reported, and realization of tuning the resonance to longer wavelengths is very important for the practical applications. In this thesis, a systematic study on photochemical synthesis of silver nanodecahedrons (NDs) and related nanostructures, and their plasmonic field enhancements are presented. First, the roles of chemicals and the light source during the formation of silver nanoparticles have been studied. We have also developed a preparation route for the production size-controlled silver nanodecahedrons (LSPR range 420 ~ 660 nm) in high purity. Indeed our experiments indicate that both the chemicals and the light sources can affect the shape and purity of final products. Adjusting the molar ratio between sodium citrate and silver nitrate can help to control the crystal structure following rapid reduction from sodium borohydride. Light from a blue LED (465 nm) can efficiently transform the polyvinylpyrrolidone stabilized small silver nanoparticles into silver NDs through photo

  9. Microwave-assisted rapid extracellular synthesis of stable bio-functionalized silver nanoparticles from guava (Psidium guajava) leaf extract

    Energy Technology Data Exchange (ETDEWEB)

    Raghunandan, Deshpande [H.K.E.S' s College of Pharmacy (India); Mahesh, Bedre D. [Gulbarga University, Materials Chemistry Laboratory, Department of Material Science (India); Basavaraja, S. [Jawaharlal Nehru Centre for Advanced Scientific Research, Veeco-India Nanotechnology Laboratory (India); Balaji, S. D. [Gulbarga University, Materials Chemistry Laboratory, Department of Material Science (India); Manjunath, S. Y. [Sri Krupa, Institute of Pharmaceutical Science (India); Venkataraman, A., E-mail: raman_chem@rediffmail.com [Gulbarga University, Materials Chemistry Laboratory, Department of Material Science (India)

    2011-05-15

    Our research interest centers on microwave-assisted rapid extracellular synthesis of bio-functionalized silver nanoparticles of 26 {+-} 5 nm from guava (Psidium guajava) leaf extract with control over dimension and composition. The reaction occurs very rapidly as the formation of spherical nanoparticles almost completed within 90 s. The probable pathway of the biosynthesis is suggested. Appearance, crystalline nature, size and shape of nanoparticles are understood by UV-vis (UV-vis spectroscopy), FTIR (fourier transform infrared spectroscopy), XRD (X-ray diffraction), FESEM (field emission scanning electron microscopy) and TEM (transmission electron microscopy) techniques. Microwave-assisted route is selected for the synthesis of silver nanoparticles to carry out the reaction fast, suppress the enzymatic action and to keep the process environmentally clean and green.

  10. Microwave-assisted rapid extracellular synthesis of stable bio-functionalized silver nanoparticles from guava (Psidium guajava) leaf extract

    International Nuclear Information System (INIS)

    Raghunandan, Deshpande; Mahesh, Bedre D.; Basavaraja, S.; Balaji, S. D.; Manjunath, S. Y.; Venkataraman, A.

    2011-01-01

    Our research interest centers on microwave-assisted rapid extracellular synthesis of bio-functionalized silver nanoparticles of 26 ± 5 nm from guava (Psidium guajava) leaf extract with control over dimension and composition. The reaction occurs very rapidly as the formation of spherical nanoparticles almost completed within 90 s. The probable pathway of the biosynthesis is suggested. Appearance, crystalline nature, size and shape of nanoparticles are understood by UV–vis (UV–vis spectroscopy), FTIR (fourier transform infrared spectroscopy), XRD (X-ray diffraction), FESEM (field emission scanning electron microscopy) and TEM (transmission electron microscopy) techniques. Microwave-assisted route is selected for the synthesis of silver nanoparticles to carry out the reaction fast, suppress the enzymatic action and to keep the process environmentally clean and green.

  11. Microwave-assisted rapid extracellular synthesis of stable bio-functionalized silver nanoparticles from guava ( Psidium guajava) leaf extract

    Science.gov (United States)

    Raghunandan, Deshpande; Mahesh, Bedre D.; Basavaraja, S.; Balaji, S. D.; Manjunath, S. Y.; Venkataraman, A.

    2011-05-01

    Our research interest centers on microwave-assisted rapid extracellular synthesis of bio-functionalized silver nanoparticles of 26 ± 5 nm from guava ( Psidium guajava) leaf extract with control over dimension and composition. The reaction occurs very rapidly as the formation of spherical nanoparticles almost completed within 90 s. The probable pathway of the biosynthesis is suggested. Appearance, crystalline nature, size and shape of nanoparticles are understood by UV-vis (UV-vis spectroscopy), FTIR (fourier transform infrared spectroscopy), XRD (X-ray diffraction), FESEM (field emission scanning electron microscopy) and TEM (transmission electron microscopy) techniques. Microwave-assisted route is selected for the synthesis of silver nanoparticles to carry out the reaction fast, suppress the enzymatic action and to keep the process environmentally clean and green.

  12. Shape transformation of silver nanospheres to silver nanoplates induced by redox reaction of hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Parnklang, Tewarak; Lamlua, Banjongsak; Gatemala, Harnchana; Thammacharoen, Chuchaat [Department of Chemistry, Faculty of Science, Chulalongkorn University, 254 Phyathai Road, Patumwan, Bangkok 10330 (Thailand); Kuimalee, Surasak [Industrial Chemistry and Textile Technology Programme, Faculty of Science, Maejo University, Chiang Mai 50290 (Thailand); Lohwongwatana, Boonrat [Metallurgical Engineering Department, Faculty of Engineering, Chulalongkorn University, 254 Phyathai Road, Patumwan, Bangkok 10330 (Thailand); Ekgasit, Sanong, E-mail: sanong.e@chula.ac.th [Department of Chemistry, Faculty of Science, Chulalongkorn University, 254 Phyathai Road, Patumwan, Bangkok 10330 (Thailand)

    2015-03-01

    In this paper we demonstrate a simple and rapid shape transformation of silver nanospheres (AgNSs) to silver nanoplates (AgNPls) using the oxidation and reduction capabilities of hydrogen peroxide. AgNPls having tunable surface plasmon resonance across the visible region with average size of 40–100 nm and thickness of 10–15 nm can be fabricated within 2 min simply by adding H{sub 2}O{sub 2} into a colloid of AgNSs with average particle size of 7 nm. The efficiency of H{sub 2}O{sub 2} as a shape-transforming agent depends strongly on its concentration, pH of the AgNS colloid, and the employed stabilizers. H{sub 2}O{sub 2} oxidizes AgNSs to silver ions while concertedly reduces silver ions to silver atom necessary for the growth of AgNPls. The shape transformation reaction was conducted at a relatively low concentration of H{sub 2}O{sub 2} in order to minimize the oxidative dissolution while facilitating kinetically controlled growth of AgNPls under a near neutral pH. Polyvinyl-pyrrolidone is an effective steric stabilizer preventing aggregation while assisting the growth of AgNPls. Trisodium citrate inhibits the formation of AgNPls under the H{sub 2}O{sub 2} reduction as it forms a stable complex with silver ions capable of withstanding the weakly reducing power of H{sub 2}O{sub 2}. After a complete consumption of AgNSs, large nanoplates grows with an expense of smaller nanoplates. The growth continues until H{sub 2}O{sub 2} is exhausted. A high concentration H{sub 2}O{sub 2} promotes catalytic decomposition of H{sub 2}O{sub 2} on the surface of AgNSs and oxidative dissolution of AgNSs without a formation of AgNPls. - Graphical abstract: Proposed mechanism for the shape transformation of AgNSs to AgNPls induced by the oxidation/reduction of H{sub 2}O{sub 2}. - Highlights: • Rapid shape transformation of silver nanospheres to nanoplates by H{sub 2}O{sub 2}. • Structural change completes in 2 min with a yellow-to-blue color change. • Selective fabrication of

  13. Active colloids

    International Nuclear Information System (INIS)

    Aranson, Igor S

    2013-01-01

    A colloidal suspension is a heterogeneous fluid containing solid microscopic particles. Colloids play an important role in our everyday life, from food and pharmaceutical industries to medicine and nanotechnology. It is useful to distinguish two major classes of colloidal suspensions: equilibrium and active, i.e., maintained out of thermodynamic equilibrium by external electric or magnetic fields, light, chemical reactions, or hydrodynamic shear flow. While the properties of equilibrium colloidal suspensions are fairly well understood, active colloids pose a formidable challenge, and the research is in its early exploratory stage. One of the most remarkable properties of active colloids is the possibility of dynamic self-assembly, a natural tendency of simple building blocks to organize into complex functional architectures. Examples range from tunable, self-healing colloidal crystals and membranes to self-assembled microswimmers and robots. Active colloidal suspensions may exhibit material properties not present in their equilibrium counterparts, e.g., reduced viscosity and enhanced self-diffusivity, etc. This study surveys the most recent developments in the physics of active colloids, both in synthetic and living systems, with the aim of elucidation of the fundamental physical mechanisms governing self-assembly and collective behavior. (physics of our days)

  14. EDITORIAL: Colloidal suspensions Colloidal suspensions

    Science.gov (United States)

    Petukhov, Andrei; Kegel, Willem; van Duijneveldt, Jeroen

    2011-05-01

    fluid-fluid interface [2]. Together with Remco Tuinier, Henk has recently completed a book in this area which is to appear later this year. A major theme in Henk's research is that of phase transitions in lyotropic liquid crystals. Henk, together with Daan Frenkel and Alain Stroobants, realized in the 1980s that a smectic phase in dispersions of rod-like particles can be stable without the presence of attractive interactions, similar to nematic ordering as predicted earlier by Onsager [3]. Together with Gert-Jan Vroege he wrote a seminal review in this area [4]. Henk once said that 'one can only truly develop one colloidal model system in one's career' and in his case this must be that of gibbsite platelets. Initially Henk's group pursued another polymorph of aluminium hydroxide, boehmite, which forms rod-like particles [5], which already displayed nematic liquid crystal phases. The real breakthrough came when the same precursors treated the produced gibbsite platelets slightly differently. These reliably form a discotic nematic phase [6] and, despite the polydispersity in their diameter, a columnar phase [7]. A theme encompassing a wide range of soft matter systems is that of colloidal dynamics and phase transition kinetics. Many colloidal systems have a tendency to get stuck in metastable states, such as gels or glasses. This is a nuisance if one wishes to study phase transitions, but it is of great practical significance. Such issues feature in many of Henk's publications, and with Valerie Anderson he wrote a highly cited review in this area [8]. Henk Lekkerkerker has also invested significant effort into the promotion of synchrotron radiation studies of colloidal suspensions. He was one of the great supporters of the Dutch-Belgian beamline 'DUBBLE' project at the ESRF [9]. He attended one of the very first experiments in Grenoble in 1999, which led to a Nature publication [7]. He was strongly involved in many other experiments which followed and also has been a

  15. Highly Stable Double-Stranded DNA Containing Sequential Silver(I)-Mediated 7-Deazaadenine/Thymine Watson-Crick Base Pairs.

    Science.gov (United States)

    Santamaría-Díaz, Noelia; Méndez-Arriaga, José M; Salas, Juan M; Galindo, Miguel A

    2016-05-17

    The oligonucleotide d(TX)9 , which consists of an octadecamer sequence with alternating non-canonical 7-deazaadenine (X) and canonical thymine (T) as the nucleobases, was synthesized and shown to hybridize into double-stranded DNA through the formation of hydrogen-bonded Watson-Crick base pairs. dsDNA with metal-mediated base pairs was then obtained by selectively replacing W-C hydrogen bonds by coordination bonds to central silver(I) ions. The oligonucleotide I adopts a duplex structure in the absence of Ag(+) ions, and its stability is significantly enhanced in the presence of Ag(+) ions while its double-helix structure is retained. Temperature-dependent UV spectroscopy, circular dichroism spectroscopy, and ESI mass spectrometry were used to confirm the selective formation of the silver(I)-mediated base pairs. This strategy could become useful for preparing stable metallo-DNA-based nanostructures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Highly stable polymer coated nano-clustered silver plates: a multimodal optical contrast agent for biomedical imaging

    International Nuclear Information System (INIS)

    Ray, Aniruddha; Mukundan, Ananya; Karamchand, Leshern; Kopelman, Raoul; Xie, Zhixing; Wang, Xueding

    2014-01-01

    Here, we present a new optical contrast agent based on silver nanoplate clusters embedded inside of a polymer nano matrix. Unlike nanosphere clusters, which have been well studied, nanoplate clusters have unique properties due to the different possible orientations of interaction between the individual plates, resulting in a significant broadening of the absorption spectra. These nanoclusters were immobilized inside of a polymer cladding so as to maintain their stability and optical properties under in vivo conditions. The polymer-coated silver nanoplate clusters show a lower toxicity compared to the uncoated nanoparticles. At high nanoparticle concentrations, cell death occurs mostly due to apoptosis. These nanoparticles were used for targeted fluorescence imaging in a rat glioma cell line by incorporating a fluorescent dye into the matrix, followed by conjugation of a tumor targeting an F3 peptide. We further used these nanoparticles as photoacoustic contrast agents in vivo to enhance the contrast of the vasculature structures in a rat ear model. We observed a contrast enhancement of over 90% following the nanoparticle injection. It is also shown that these NPs can serve as efficient contrast agents, with specific targeting abilities for broadband multimodal imaging that are usable for diagnostic applications and that extend into use as therapeutic agents as well. (paper)

  17. Polypyrrole-silver Nanocomposite: Synthesis and Characterization

    OpenAIRE

    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...

  18. Effect of concentration and pH on the surface-enhanced Raman scattering of captopril on nano-colloidal silver surface

    Science.gov (United States)

    Gao, Junxiang; Gu, Huaimin; Liu, Fangfang; Dong, Xiao; Xie, Min; Hu, Yongjun

    2011-07-01

    In this report, Raman and surface-enhanced Raman scattering (SERS) spectra of captopril are studied in detail. Herein, the Raman bands are assigned by the density functional theory (DFT) calculations and potential energy distributions (PED) based on internal coordinates of the molecule, which are found to be in good agree with the experimental values. Furthermore, the concentration and pH dependence of the SERS intensity of the molecule is discussed. By analyzing the intensities variation of SERS bands of the different concentrations of captopril solution, it can be concluded that the molecules orientation adsorbed on the silver nanoparticles surface change with the change of the concentrations. The variation of SERS spectra of captopril with the change of pH suggests that the interaction among the adsorbates with Ag cluster depend on the protonated state of the adsorbate and the aggregation of silver nanoparticles.

  19. In situ photoactivated plasmonic Ag{sub 3}PO{sub 4}@silver as a stable catalyst with enhanced photocatalytic activity under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Dongfang; Wang, Jiaxun, E-mail: zdfbb66@aliyun.com [College of Science, Huazhong Agricultural University, Wuhan (China)

    2017-05-15

    Silver orthophosphate (Ag{sub 3}PO{sub 4}) had been reported as an excellent candidate to split water or decompose pollutants with high efficiency in visible light region, yet is not stable due to the reduction of silver ion. In this work, an easy-fabricated method (in situ photoinduced reduction) was provided to enhance the stability of Ag{sub 3}PO{sub 4} for its possible application as a visible-light sensitive photocatalyst. The as-prepared samples were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra, photoluminescence spectra (PL) and Photoelectrochemical measurements. The Ag{sub 3}PO{sub 4}/Ag photocatalysts showed strong photocatalytic activity for decomposition of RhB dye or phenol-X-3B mixture under visible light irradiation (λ> 420 nm) and can be used repeatedly. The possible mechanism for the enhanced photocatalytic properties of the Ag{sub 3}PO{sub 4} /Ag hybrid was also discussed. It was found that •OH and holes take priority over •O{sub 2}{sup -} radicals in serving as the main oxidant in the Ag{sub 3}PO{sub 4}/Ag photocatalytic system. Especially, the experimental results indicate that the surface plasmon resonance of Ag nanoparticles and a large negative charge of PO{sub 4}{sup 3-} ions as well as high separation efficiency of {sup e-} --h{sup +} pairs, facilitated the enhancement of the photocatalytic activity of the Ag{sub 3} PO{sub 4} /Ag composite. The results indicated that Ag{sub 3} PO{sub 4} /Ag is an efficient and stable visible-light-driven photocatalyst. (author)

  20. Colloidal glasses

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Colloidal glasses. Glassy state is attained when system fails to reach equilibrium due to crowding of constituent particles. In molecular glasses, glassy state is reached by rapidly lowering the temperature. In colloidal glasses, glassy state is reached by increasing the ...

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

    International Nuclear Information System (INIS)

    Nikov, R.G.; Nikolov, A.S.; Nedyalkov, N.N.; Dimitrov, I.G.; Atanasov, P.A.; Alexandrov, M.T.

    2012-01-01

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

  2. UV Treatment of the Stabilizing Shell for Improving the Photostability of Silver Nanoparticles

    Directory of Open Access Journals (Sweden)

    Silvia Rinaldi

    2016-01-01

    Full Text Available Silver nanoparticles or nanoclusters are quite sensitive to light exposure. In particular, irradiation in the localized surface plasmon resonance (LSPR region brings about a drastic modification of their optical properties due to growth and reshaping of the nanoparticles. In order to obtain luminescent colloids, small silver colloidal nanoparticles were prepared in chloroform using vinylpyrrolidone oligomers as capping agent and their luminescence properties were used to control their stability upon prolonged exposure to visible light. The polymeric shell around the metal clusters was hardened through photo-cross-linking by UV light. This process did not alter the morphology and the optical properties of the nanoparticles but greatly improved the particle photostability as confirmed also by confocal laser scanning microscopy measurements. The data clearly show that UV curing of the stabilizing layer could be a simple postsynthetic procedure to obtain materials with stable properties.

  3. Tuning the thermal diffusivity of silver based nanofluids by controlling nanoparticle aggregation

    International Nuclear Information System (INIS)

    Agresti, Filippo; Barison, Simona; Battiston, Simone; Pagura, Cesare; Fabrizio, Monica; Colla, Laura; Fedele, Laura

    2013-01-01

    With the aim of preparing stable nanofluids for heat exchange applications and to study the effect of surfactant on the aggregation of nanoparticles and thermal diffusivity, stable silver colloids were synthesized in water by a green method, reducing AgNO 3 with fructose in the presence of poly-vinylpyrollidone (PVP) of various molecular weights. A silver nanopowder was precipitated from the colloids and re-dispersed at 4 vol% in deionized water. The Ag colloids were characterized by UV–visible spectroscopy, combined dynamic light scattering and ζ-potential measurements, and laser flash thermal diffusivity. The Ag nanopowders were characterized by scanning electron microscopy and thermal gravimetric analysis. It was found that the molecular weight of PVP strongly affects the ζ-potential and the aggregation of nanoparticles, thereby affecting the thermal diffusivity of the obtained colloids. In particular, it was observed that on increasing the molecular weight of PVP the absolute value of the ζ-potential is reduced, leading to increased aggregation of nanoparticles. A clear relation was identified between thermal diffusivity and aggregation, showing higher thermal diffusivity for nanofluids having higher aggregation. A maximum improvement of thermal diffusivity by about 12% was found for nanofluids prepared with PVP having higher molecular weight. (paper)

  4. In Vitro and In Vivo Toxicity Evaluation of Colloidal Silver Nanoparticles Used in Endodontic Treatments.

    Science.gov (United States)

    Takamiya, Aline Satie; Monteiro, Douglas Roberto; Bernabé, Daniel Galera; Gorup, Luiz Fernando; Camargo, Emerson Rodrigues; Gomes-Filho, João Eduardo; Oliveira, Sandra Helena Penha; Barbosa, Debora Barros

    2016-06-01

    Silver nanoparticles have been used for different purposes in dentistry, including endodontic treatments. The aim of this study was to determine the cytotoxicity of different types of silver nanoparticles on mouse fibroblast cell line L929 and the reaction of subcutaneous connective tissue of Wistar rats to these nanoparticles. Silver nanoparticles of an average size of 5 nm were synthesized with ammonia (SNA) or polyvinylpyrrolidone (SNP). L929 was exposed to SNA and SNP (0.1-100 μg/mL), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and enzyme-linked immunosorbent assays were performed after 6, 24, and 48 hours. Culture medium was used as the control. Sixteen rats received, individually, 3 polyethylene tubes filled with a fibrin sponge embedded in 100 μL SNA or SNP (1 μg/mL). A fibrin sponge with no embedding was the control. Tissue reaction was performed qualitatively and quantitatively after 7, 15, 30, and 90 days of implantation in the dorsal connective tissue of Wistar rats. SNA and SNP were cytotoxic to L929 in higher concentrations, with SNA significantly more toxic than SNP. SNA and SNP did not induce significant interleukin-1β and interleukin-6 production. The release of stem cell factor by L929 increased 48 hours after the treatment with SNP at 5 μg/mL. Histologic examination showed that the inflammatory responses caused by SNA and SNP at 1 μg/mL were similar to the control in all experimental periods. It was concluded that SNA and SNP were not cytotoxic at 25 μg/mL or lower concentrations. However, for safe clinical use, further studies establishing others points of its toxicologic profile are recommended. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  5. Enzyme-mediated formulation of stable elliptical silver nanoparticles tested against clinical pathogens and MDR bacteria and development of antimicrobial surgical thread.

    Science.gov (United States)

    Thapa, Rupak; Bhagat, Chintan; Shrestha, Pragya; Awal, Suvash; Dudhagara, Pravin

    2017-05-16

    Silver nanoparticles (AgNPs) are believed to be emerging tool against various infectious diseases including multi-drug resistant (MDR) bacteria. In the present study, in vitro synthesis of AgNPs was optimized using 1:50 ratio of macerozyme (25 μg/μl) and 1 mM AgNO 3 incubated at 80 °C for 8 h. AgNPs were characterized by UV-Visible spectroscopy, dynamic light scattering (DLS), scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD). Characterization studies suggest the synthesis of elliptical, stable and crystalline AgNPs with an average size of 38.26 ± 0.4 nm calculated using TEM. The XRD pattern revealed the face-centered-cubic (fcc) form of metallic silver. Good shape integrity and dispersion of AgNPs after 1 year of incubation confirmed their stability. AgNPs were exibited the antimicrobial property against ten pathogenic bacteria, three molds and one yeast. The AgNPs also revealed remarkable antimicrobial activity against three MDR strains i.e. Extended spectrum beta-lactamase positive Escherichia coli, Staphylococcus aureus (MRSA) and Teicoplanin resistant Streptococcus Pneumoniae. The AgNPs coated surgical threads (suture) were revealed the remarkble antibacterial activity against three MDR strains. This is the first report to synthesize antimicrobial elliptical AgNPs using enzymes. The results suggest the possibilities to develop the nanoparticles coated antimicrobial medical fabric to combat against MDR infection.

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

    Energy Technology Data Exchange (ETDEWEB)

    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%.

  7. Single-step biological fabrication of colloidal silver nanoparticles using Hugonia mystax: larvicidal potential against Zika virus, dengue, and malaria vector mosquitoes.

    Science.gov (United States)

    Govindarajan, Marimuthu; Kadaikunnan, Shine; Alharbi, Naiyf S; Benelli, Giovanni

    2017-11-01

    Mosquito control is facing key challenges, including outbreaks of new arbovirus threats. We proposed an eco-friendly synthesis of silver nanoparticles (AgNPs) employing a low-cost extract of Hugonia mystax. AgNPs were specified by UV, XRD, FTIR and EDX spectroscopy, SEM and TEM. AgNPs were more toxic to Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus larvae (LC 50 : 14.45, 15.86, and 17.46 μg/mL) if compared to aquatic biocontrol organisms Gambusia affinis, Diplonychus indicus, and Anisops bouvieri (LC 50 : 2567.15, 1075.16, and 829.63 μg/ml). Overall, we shed light on the mosquito larvicidal efficacy of H. mystax, a possible biological resource for low-cost fabrication of AgNPs.

  8. The Synthesis of Silver Nanoparticles Produced by Chemical Reduction of Silver Salt Solution

    International Nuclear Information System (INIS)

    Sri Budi Harmani; Dewi Sondari; Agus Haryono

    2008-01-01

    Described in this research are the synthesis of silver nanoparticle produced by chemical reduction of silver salt (silver nitrate AgNO 3 ) solution. As a reducer, sodium citrate (C 6 H 5 O 7 Na 3 ) was used. Preparation of silver colloid is done by using chemical reduction method. In typical experiment 150 ml of 1.10 -3 M AgNO 3 solution was heated with temperature variation such as 90, 100, 110 degree of Celsius. To this solution 15 ml of 1 % trisodium citrate was added into solution drop by drop during heating. During the process, solution was mixed vigorously. Solution was heated until colour's change is evident (pale yellow solution is formed). Then it was removed from the heating element and stirred until cooled to room temperature. Experimental result showed that diameter of silver nanoparticles in colloid solution is about 28.3 nm (Ag colloid, 90 o C); 19.9 nm (Ag colloid, 100 o C)and 26.4 nm (Ag colloid, 110 o C). Characterization of the silver nanoparticle colloid conducted by using UV-Vis Spectroscopy, Particles Size Analyzer (PSA) and Scanning Electron Microscope (SEM) indicate the produced structures of silver nanoparticles. (author)

  9. Biosynthesis of silver fine particles and particles decorated with nanoparticles using the extract of Illicium verum (star anise) seeds.

    Science.gov (United States)

    Luna, Carlos; Chávez, V H G; Barriga-Castro, Enrique Díaz; Núñez, Nuria O; Mendoza-Reséndez, Raquel

    2015-04-15

    Given the upsurge of new technologies based on nanomaterials, the development of sustainable methods to obtain functional nanostructures has become an imperative task. In this matter, several recent researches have shown that the biodegradable natural antioxidants of several plant extracts can be used simultaneously as reducing and stabilizing agents in the wet chemical synthesis of metallic nanoparticles, opening new opportunities to design greener synthesis. However, the challenge of these new techniques is to produce stable colloidal nanoparticles with controlled particle uniformity, size, shape and aggregation state, in similar manner than the well-established synthetic methods. In the present work, colloidal metallic silver nanoparticles have been synthesized using silver nitrate and extracts of Illicium verum (star anise) seeds at room temperature in a facile one-step procedure. The resulting products were colloidal suspensions of two populations of silver nanoparticles, one of them with particle sizes of few nanometers and the other with particles of tens of nm. Strikingly, the variation of the AgNO3/extract weight ratio in the reaction medium yielded to the variation of the spatial distribution of the nanoparticles: high AgNO3/extract concentration ratios yielded to randomly dispersed particles, whereas for lower AgNO3/extract ratios, the biggest particles appeared coated with the finest nanoparticles. This biosynthesized colloidal system, with controlled particle aggregation states, presents plasmonic and SERS properties with potential applications in molecular sensors and nanophotonic devices. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Coherent Plasmon-Exciton Coupling in Silver Platelet-J-aggregate Nanocomposites

    Science.gov (United States)

    2015-02-27

    visible spectra of colloidal suspensions containing silver nanoplatelets and a cyanine dye, 1,1?-diethyl-2,2?-cyanine iodide (PIC). PIC was...highest reported for colloidal nanoparticles. The optical properties of the silver platelet-J-aggregate nanocomposites were supported numerically and...visible spectra of colloidal suspensions containing silver nanoplatelets and a cyanine dye, 1,1′-diethyl-2,2′-cyanine iodide (PIC). PIC was electrostati

  11. Microwave Accelerated Green Synthesis of Stable Silver Nanoparticles with Eucalyptus globulus Leaf Extract and Their Antibacterial and Antibiofilm Activity on Clinical Isolates.

    Directory of Open Access Journals (Sweden)

    Khursheed Ali

    Full Text Available A simple and rapid microwave assisted method of green synthesis of silver nanoparticles (AgNPs was developed using aqueous leaf extract of Eucalyptus globulus(ELE, and their antibacterial and antibiofilm potential investigated. With this aim, the aqueous solutions of ELE and AgNO3(1 mM were mixed (1:4 v/v, and microwave irradiated at 2450 Mhz, for 30 sec. The instant color change of the ELE-AgNO3 mixture from pale yellow to dark brown indicated ELE-AgNPs synthesis. The intensity of peak at 428 nm in UV-Vis spectra, due to the surface plasmon resonance of AgNPs, varied with the amount of ELE, AgNO3 concentration, pH and time of incubation. The biosynthesized ELE-AgNPs were characterized by UV-visible spectroscopy, XRD, TEM, SEM-EDX, FTIR and TGA analyses. The size of ELE-AgNPs was determined to be in range of 1.9-4.3 nm and 5-25 nm, with and without microwave treatment, respectively. SEM exhibited the capping of AgNPs with the ELE constituents, and validated by FTIR analysis. The FTIR data revealed the presence of plant organic constituents and metabolites bound to ELE-AgNPs, which contributes for their stability. The antimicrobial activity of ELE-AgNPs was assessed by growth and biofilm inhibition of extended spectrum β-lactamase (ESBL producing Pseudomonas aeruginosa, Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA and methicillin-sensitive Staphylococcus aureus (MSSA clinical bacterial isolates. The results demonstrated that S. aureus were more sensitive to ELE-AgNPs than E. coli and P. aeruginosa. MRSA exhibited higher sensitive than MSSA, whereas P. aeruginosa were more sensitive than E. coli to ELE-AgNPs treatment. Also, significant (83 ± 3% and 84 ± 5% biofilm inhibition was observed in case of S. aureus and P. aeruginosa, respectively. The results elucidated environmentally friendly, economical and quick method for production of colloidal bio-functionalized ELE-AgNPs, for effectual clinical applications, as broad

  12. Green synthesis and antibacterial effects of aqueous colloidal solutions of silver nanoparticles using camomile terpenoids as a combined reducing and capping agent.

    Science.gov (United States)

    Parlinska-Wojtan, Magdalena; Kus-Liskiewicz, Małgorzata; Depciuch, Joanna; Sadik, Omowunmi

    2016-08-01

    Green synthesis method using camomile extract was applied to synthesize silver nanoparticles to tune their antibacterial properties merging the synergistic effect of camomile and Ag. Scanning transmission electron microscopy revealed that camomile extract (CE) consisted of porous globular nanometer sized structures, which were a perfect support for Ag nanoparticles. The Ag nanoparticles synthesized with the camomile extract (AgNPs/CE) of 7 nm average sizes, were uniformly distributed on the CE support, contrary to the pure Ag nanoparticles synthesized with glucose (AgNPs/G), which were over 50 nm in diameter and strongly agglomerated. The energy dispersive X-ray spectroscopy chemical analysis showed that camomile terpenoids act as a capping and reducing agent being adsorbed on the surface of AgNPs/CE enabling their reduction from Ag(+) and preventing them from agglomeration. Fourier transform infrared and ultraviolet-visible spectroscopy measurements confirmed these findings, as the spectra of AgNPs/CE, compared to pure CE, did not contain the 1109 cm(-1) band, corresponding to -C-O groups of terpenoids and the peaks at 280 and 320 nm, respectively. Antibacterial tests using four bacteria strains showed that the AgNPs/CE performed five times better compared to CE AgNPs/G samples, reducing totally all the bacteria in 2 h.

  13. Production of Silver Nanoparticles with Strong and Stable Antimicrobial Activity against Highly Pathogenic and Multidrug Resistant Bacteria

    Science.gov (United States)

    Saeb, Amr T. M.; Alshammari, Ahmad S.; Al-Brahim, Hessa; Al-Rubeaan, Khalid A.

    2014-01-01

    Aims. To synthesize, characterize, and analyze antimicrobial activity of AgNPs of Escherichia hermannii (SHE), Citrobacter sedlakii (S11P), and Pseudomonas putida (S5). Methods. The synthesized AgNPs were examined using ultraviolet-visible spectroscopy (UV-vis) and, zeta potential, and the size and the morphology obtained from the three different isolates were also confirmed by TEM. Results. Among the three isolates tested, SHE showed the best antimicrobial activity due to the presence of small (4–12 nm) and stable (−22 mV) AgNPs. Stability of AgNPs was also investigated and found to be dependent on the nature of isolates. Conclusion. Produced AgNPs showed particle stability and antimicrobial efficacy up to 90 days of production. Our AgNPs exhibited greater antimicrobial activity compared with gentamicin against P. aeruginosa isolates and vancomycin against S. aureus and MRSA isolates at very low concentration (0.0002 mg per Microliters). PMID:25093206

  14. Colloidal nematostatics

    Directory of Open Access Journals (Sweden)

    V.M. Pergamenshchik

    2010-01-01

    Full Text Available We give a review of the theory of large distance colloidal interaction via the nematic director field. The new area of nematic colloidal systems (or nematic emulsions has been guided by the analogy between the colloidal nematostatics and electrostatics. The elastic charge density representation of the colloidal nematostatics [V.M. Pergamenshchik, V.O. Uzunova, Eur. Phys. J. E, 2007, 23, 161; Phys. Rev. E, 2007, 76, 011707] develops this analogy at the level of charge density and Coulomb interaction. The analogy is shown to lie in common mathematics based on the solutions of Laplace equation. However, the 3d colloidal nematostatics substantially differs from electrostatics both in its mathematical structure and physical implications. The elastic charge is a vector fully determined by the torque exerted upon colloid, the role of Gauss' theorem is played by conservation of the torque components. Elastic multipoles consist of two tensors (dyads. Formulas for the elastic multipoles, the Coulomb-like, dipole-dipole, and quadrupole-quadrupole pair interaction potentials are derived and illustrated by particular examples. Based on the tensorial structure, we list possible types of elastic dipoles and quadrupoles. An elastic dipole is characterized by its isotropic strength, anisotropy, chirality, and its longitudinal component. An elastic quadrupole can be uniaxial and biaxial. Relation between the multipole type and its symmetry is discussed, sketches of some types of multipoles are given. Using the mirror image method of electrostatics as a guiding idea, we develop the mirror image method in nematostatics for arbitrary director tilt at the wall. The method is applied to the charge-wall and dipole-wall interaction.

  15. Radioactive colloids

    International Nuclear Information System (INIS)

    Bergqvist, L.

    1987-01-01

    Different techniques for the characterization of radioactive colloids, used in nuclear medicine, have been evaluated and compared. Several radioactive colloids have been characterized in vitro and in vivo and tested experimentally. Colloid biokinetics following interstitial or intravenous injection were evaluated with a scintillation camera technique. Lymphoscintigraphy with a Tc-99-labelled antimony sulphur colloid was performed in 32 patients with malignant melanoma in order to evaluate the technique. Based on the biokinetic results, absorbed doses in tissues and organs were calculated. The function of the reticuloendothelial system has been evaluated in rats after inoculation with tumour cells. Microfiltration and photon correlation spectroscopy were found to be suitable in determining activity-size and particle size distributions, respectively. Maximal lymph node uptake following subcutaneous injection was found to correspond to a colloid particle size between 10 and 50 nm. Lymphoscintigraphy was found to be useful in the study of lymphatic drainage from the primary tumour site in patients with malignant melanoma on the trunk. Quantitative analysis of ilio-inguinal lymph node uptake in patients with malignant melanoma on the lower extremities was, however, found to be of no value for the detection of metastatic disease in lymph nodes. High absorbed doses may be received in lymph nodes (up to 1 mGy/MBq) and at the injection site (about 10 mGy/MBq). In an experimental study it was found that the relative colloid uptake in bone marrow and spleen depended on the total number of intravenously injected particles. This may considerably affect the absorbed dose in these organs. (author)

  16. Systematic optimization of quantum junction colloidal quantum dot solar cells

    KAUST Repository

    Liu, Huan

    2012-01-01

    The recently reported quantum junction architecture represents a promising approach to building a rectifying photovoltaic device that employs colloidal quantum dot layers on each side of the p-n junction. Here, we report an optimized quantum junction solar cell that leverages an improved aluminum zinc oxide electrode for a stable contact to the n-side of the quantum junction and silver doping of the p-layer that greatly enhances the photocurrent by expanding the depletion region in the n-side of the device. These improvements result in greater stability and a power conversion efficiency of 6.1 under AM1.5 simulated solar illumination. © 2012 American Institute of Physics.

  17. Silver Nanoparticles Modification of Ultra High Molecular Weight Polyethylene in Non-Aqueous Medium

    OpenAIRE

    V. N. Glushko; L. I. Blokhina; E. E. Anisimova; M. V. Bogdanovskaya; V. I. Kozhukhov; T. A. Cherdyntseva

    2016-01-01

    A series of experiments for obtaining modified with silver nanoparticles ultra-high molecular weight polyethylene (UHMWPE) is done. Optimal precursors are silver trifluoroacetate, silver nitrate and silver methanesulfonate. Three variants of UHMWPE modification is studied: 1) the polyol synthesis, 2) polymer processing silver nanoparticle colloid and 3) reduction of silver salt solution in the UHMWPE polymer matrix. It is found that the last method is optimal. The specific surface of obtained...

  18. Preparation of silver nanocrystals in microemulsion by the γ-radiation method

    International Nuclear Information System (INIS)

    Hongkai Wu; Xiangling Xu; Xuewu Ge; Zhicheng Zhang

    1997-01-01

    Silver colloids of well-defined shape, size were synthesized by γ-ray irradiating silver salt in reversed microemulsions, and then pure silver dry powders were obtained. The sols were studied by absorption spectroscopy, and the silver powders were characterized by Transmission Electron Micrographs (TEM) and X-ray Diffraction (XRD). The effect of radiation dose and aging time was discussed. (Author)

  19. Monodisperse Silver Nanoparticles Synthesized by a Microwave-Assisted Method

    International Nuclear Information System (INIS)

    Shao-Peng, Zhu; Shao-Chun, Tang; Xiang-Kang, Meng

    2009-01-01

    Silver nanoparticles with an average size of about 20 nm are synthesized in a colloidal solution with the aid of microwave irradiation. Neither additional reductant nor stabilizer is required in this microwave-assisted method. The color of the colloidal solution is found to be dark green, different from the characteristic yellow of silver colloidal solutions. The silver nanoparticles in the colloidal solution have a narrow size distribution and large yield quantity. UV-visible absorption spectroscopy analysis reveals that the as-synthesized monodisperse silver nanoparticles have exceptional optical properties. Raman spectroscopy measurements demonstrate that these silver nanoparticles exhibit a notable surface-enhanced Raman scattering ability. (cross-disciplinary physics and related areas of science and technology)

  20. Liquid crystal boojum-colloids

    International Nuclear Information System (INIS)

    Tasinkevych, M; Silvestre, N M; Telo da Gama, M M

    2012-01-01

    Colloidal particles dispersed in a liquid crystal (LC) lead to distortions of the director field. The distortions are responsible for long-range effective colloidal interactions whose asymptotic behaviour is well understood. The short-distance behaviour depends on the structure and dynamics of the topological defects nucleated near the colloidal particles and a full nonlinear theory is required to describe it. Spherical colloidal particles with strong planar degenerate anchoring nucleate a pair of antipodal surface topological defects, known as boojums. We use the Landau-de Gennes theory to resolve the mesoscopic structure of the boojum cores and to determine the pairwise colloidal interactions. We compare the results in three (3D) and two (2D) spatial dimensions for spherical and disc-like colloidal particles, respectively. The corresponding free energy functionals are minimized numerically using finite elements with adaptive meshes. Boojums are always point-like in 2D, but acquire a rather complex structure in 3D, which depends on the combination of the anchoring potential, the radius of the colloid, the temperature and the LC elastic anisotropy. We identify three types of defect cores in 3D that we call single, double and split-core boojums, and investigate the associated structural transitions. The split-core structure is favoured by low temperatures, strong anchoring and small twist to splay or bend ratios. For sufficiently strong anchoring potentials characterized by a well-defined uniaxial minimum, the split-core boojums are the only stable configuration. In the presence of two colloidal particles, we observe substantial re-arrangements of the inner defects in both 3D and 2D. These re-arrangements lead to qualitative changes in the force-distance profile when compared to the asymptotic quadrupole-quadrupole interaction. In line with the experimental results, the presence of the defects prevents coalescence of the colloidal particles in 2D, but not in 3D

  1. Colloidal superballs

    NARCIS (Netherlands)

    Rossi, L.

    2012-01-01

    This thesis is organized in four parts as follows. Part 1 focuses on the synthetic aspects of the colloidal model systems that will be used throughout the work described in this thesis. In Chapter 2 we describe synthetic procedures for the preparation of polycrystalline hematite superballs and

  2. Effect of poly-α, γ, L-glutamic acid as a capping agent on morphology and oxidative stress-dependent toxicity of silver nanoparticles

    Science.gov (United States)

    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

  3. Characterization of Electrochemically Generated Silver

    Science.gov (United States)

    Adam, Niklas; Martinez, James; Carrier, Chris

    2014-01-01

    Silver biocide offers a potential advantage over iodine, the current state of the art in US spacecraft disinfection technology, in that silver can be safely consumed by the crew. Low concentrations of silver (Silver does not require hardware to remove it from a water system, and therefore can provide a simpler means for disinfecting water. The Russian segment of the International Space Station has utilized an electrochemically generated silver solution, which is colloidal in nature. To be able to reliably provide a silver biocide to drinking water by electrochemical means would reduce mass required for removing another biocide such as iodine from the water. This would also aid in crew time required to replace iodine removal cartridges. Future long term missions would benefit from electrochemically produced silver as the biocide could be produced on demand and requires only a small concentration to be effective. Since it can also be consumed safely, there is less mass in removal hardware and little consumables required for production. The goal of this project initially is to understand the nature of the electrochemically produced silver, the particle sizes produced by the electrochemical cell and the effect that voltage adjustment has on the particle size. In literature, it has been documented that dissolved oxygen and pH have an effect on the ionization of the electrochemical silver so those parameters would be measured and possibly adjusted to understand their effect on the silver.

  4. Controlled generation of silver nanocolloid in amorphous silica materials

    International Nuclear Information System (INIS)

    Gil, C.; Garcia-Heras, M.; Carmona, N.; Villages, M. A.

    2004-01-01

    Amorphous silica-based materials bulk and superficially doped with silver nano colloids were prepared. Bulk doped glasses were obtained by conventional melting and doped monolithic slabs by sol-gel. Superficially doped glasses were obtained by ion-exchange and doped coatings by sol-gel. The samples were characterised by TEM and UV-VIS spectrometry. Depending on the composition, the silver incorporation process, and the thermal treatments, several colourings were obtained. By controlling these parameters, metallic silver nano colloids can be generated in the matrices studied. Colloids aggregation and growing up depends on the matrix nature and on the experimental process carried out. (Author) 10 refs

  5. Relaxation of the silver/silver iodide electrode in aqueous solution

    NARCIS (Netherlands)

    Peverelli, K.J.

    1979-01-01

    The aim of this study is to detect and characterize relaxation processes on silver/silver iodide electrodes in aqueous electrolyte solution. The information obtained is to be used for an estimation of the consequences of similar processes on colloidal AgI

  6. The Effects of Subsurface Bioremediation on Soil Structure, Colloid Formation, and Contaminant Transport

    Science.gov (United States)

    Wang, Y.; Liang, X.; Zhuang, J.; Radosevich, M.

    2016-12-01

    Anaerobic bioremediation is widely applied to create anaerobic subsurface conditions designed to stimulate microorganisms that degrade organic contaminants and immobilize toxic metals in situ. Anaerobic conditions that accompany such techniques also promotes microbially mediated Fe(III)-oxide mineral reduction. The reduction of Fe(III) could potentially cause soil structure breakdown, formation of clay colloids, and alternation of soil surface chemical properties. These processes could then affect bioremediation and the migration of contaminants. Column experiments were conducted to investigate the impact of anaerobic bioreduction on soil structure, hydraulic properties, colloid formation, and transport of three tracers (bromide, DFBA, and silica shelled silver nanoparticles). Columns packed with inoculated water stable soil aggregates were placed in anaerobic glovebox, and artificial groundwater media was pumped into the columns to simulate anaerobic bioreduction process for four weeks. Decent amount of soluble Fe(II) accompanied by colloids were detected in the effluent from bioreduction columns a week after initiation of bioreduction treatment, which demonstrated bioreduction of Fe(III) and formation of colloids. Transport experiments were performed in the columns before and after bioreduction process to assess the changes of hydraulic and surface chemical properties through bioreduction treatment. Earlier breakthrough of bromide and DFBA after treatment indicated alterations in flow paths (formation of preferential flow paths). Less dispersion of bromide and DFBA, and less tailing of DFBA after treatment implied breakdown of soil aggregates. Dramatically enhanced transport and early breakthrough of silica shelled silver nanoparticles after treatment supported the above conclusion of alterations in flow paths, and indicated changes of soil surface chemical properties.

  7. Green synthesis of zero valent colloidal nanosilver targeting A549 lung cancer cell: In vitro cytotoxicity

    Directory of Open Access Journals (Sweden)

    Minakshi Jha

    2018-06-01

    Full Text Available An eco-friendly green approach was proposed to synthesise stable, cytotoxic colloidal silver nanoparticles (AgNPs using Momordica charantia (M. charantia fruit extract. Bioinspired green method adopted for fabrication of AgNPs because of easy, fast, low-cost and benign bioprocess. Phytocomponents played the crucial role in capping, stabilisation and inherent cytotoxic potential of colloidal nanosilver. The physiochemical, crystalline, optical and morphological properties of AgNPs were characterized using UV-vis, FT-IR, XRD, SEM, TEM, EDX and AFM. FT-IR reveals the presence of carbonyl, methyl, polyphenol (flavonoid, primary and secondary amine (protein, carboxyl group, ester as major functional groups over the surface of nanomaterials. Mechanistic pathway for formation and stabilisation of colloidal nanosilver has been discussed. Average crystalline size of AgNPs was found to be 12.55 nm from XRD. TEM shows AgNPs nanosphere with size range 1–13.85 nm. Consistency in spherical morphology was also confirmed through Atomic Force Microscopy (AFM. AFM measurement provided image Rq value 3.62, image Ra 2.47, roughness Rmax 36.4 nm, skewness 1.99 and kurtosis 9.87. The SRB assay revealed substantial in vitro noticeable anti-cancer activity of colloidal nanosilver on A549 and HOP-62 human lung cancer cells in a dose dependent manner with IC50 value of 51.93 µg/ml and 76.92 µg/ml. In addition, M. charantia capped AgNPs were found to be more biocompatible in comparison to M. charantia FE. Our study demonstrated the integration of green chemistry principle in nanomaterials fabrication and focused on the potential use of M. charantia fruit extract as an efficient precursor for biocompatible AgNPs anodrug formulation with improved cytotoxic applications. Keywords: M. charantia, Silver nanoparticles, TEM, Anticancer activity, A549, HOP-62

  8. One-pot silver nanoring synthesis.

    OpenAIRE

    Drogat , Nicolas; Granet , Robert; Sol , Vincent; Krausz , Pierre

    2009-01-01

    Abstract Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV–vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH...

  9. Novel silver tubing method for quantitative introduction of water into high temperature conversion systems for stable hydrogen and oxygen isotopic measurements

    Science.gov (United States)

    Qi, Haiping; Groning, Manfred; Coplen, Tyler B.; Buck, Bryan; Mroczkowski, Stanley J.; Brand, Willi A.; Geilmann, Heike; Gehre, Matthias

    2010-01-01

    A new method to seal water in silver tubes for use in a TC/EA reduction unit using a semi-automated sealing apparatus can yield reproducibilities (1 standard deviation) of δ2H and &delta18O measurements of 1.0 ‰ and 0.06 ‰, respectively. These silver tubes containing reference waters may be preferred for calibration of H- and O-bearing materials analyzed with a TC/EA reduction unit. The new sealing apparatus employs a computer controlled stepping motor to produce silver tubes identical in length. The reproducibility of mass of water sealed in tubes (in a range of 200 to 400 µg) can be as good as 1 percent. Although silver tubes sealed with reference waters are robust and can be shaken or heated to 110 °C with no loss of integrity, they should not be frozen because the expansion during the phase transition of water to ice will break the cold seals and all water will be lost. They should be shipped in insulated containers. This new method eliminates air inclusions and isotopic fractionation of water associated with the loading of water into capsules using a syringe. The method is also more than an order of magnitude faster than preparing water samples in ordinary Ag capsules. Nevertheless, some laboratories may prefer loading water into silver capsules because expensive equipment is not needed, but they are cautioned to apply the necessary corrections for evaporation, back exchange with laboratory atmospheric moisture, and blank.

  10. Entropy favours open colloidal lattices

    Science.gov (United States)

    Mao, Xiaoming; Chen, Qian; Granick, Steve

    2013-03-01

    Burgeoning experimental and simulation activity seeks to understand the existence of self-assembled colloidal structures that are not close-packed. Here we describe an analytical theory based on lattice dynamics and supported by experiments that reveals the fundamental role entropy can play in stabilizing open lattices. The entropy we consider is associated with the rotational and vibrational modes unique to colloids interacting through extended attractive patches. The theory makes predictions of the implied temperature, pressure and patch-size dependence of the phase diagram of open and close-packed structures. More generally, it provides guidance for the conditions at which targeted patchy colloidal assemblies in two and three dimensions are stable, thus overcoming the difficulty in exploring by experiment or simulation the full range of conceivable parameters.

  11. Highly transparent and thermal-stable silver nanowire conductive film covered with ZnMgO by atomic-layer-deposition

    Science.gov (United States)

    Wang, Lei; Huang, Dongchen; Li, Min; Xu, Hua; Zou, Jianhua; Tao, Hong; Peng, Junbiao; Xu, Miao

    2017-12-01

    Solution-processed silver nanowires (AgNWs) have been considered as a promising material for next generation flexible transparent conductive electrodes. However AgNWs films have several intrinsic drawbacks, such as thermal stability and storage stability. Herein, we demonstrate a laminated ZnO/MgO (ZnMgO, ZMO) as a protective layer on the AgNWs films using atomic layer deposition (ALD). The fabricated films exhibited a low sheet resistance of 16 Ω/sq with high transmittance of 91% at 550 nm, an excellent thermal stability and bending property. The ZMO film grows perpendicularly on the surface of the AgNWs, making a perfect coverage of bulk silver nanowires and junction, which can effectively prompt the electrical transport behavior and enhance stability of the silver nanowires network.

  12. Biosynthesis of silver nanoparticles using lingonberry and cranberry juices and their antimicrobial activity.

    Science.gov (United States)

    Puišo, Judita; Jonkuvienė, Dovilė; Mačionienė, Irena; Šalomskienė, Joana; Jasutienė, Ina; Kondrotas, Rokas

    2014-09-01

    In this study lingonberry and cranberry juices were used for silver nanoparticle synthesis. The berry juices were characterized by total phenolics, total anthocyanins and benzoic acid content, respectively 1.9-2.7mg/ml, 55.2-83.4mg/l and 590.8-889.2mg/l. The synthesis of silver nanoparticles was performed at room temperature assisting in solutions irradiated by ultraviolet for 30min. Ultraviolet-visible (UV-vis) spectroscopy and microscopy confirmed the formation of nanoparticles as well as the dark red color of colloid of silver samples showed the formation of stable nanoparticles. Broad localized surface plasmon resonance (LSPR) peaks in UV-vis spectra indicated the formation of polydispersive silver nanoparticles and LSPR was observed at 485nm and 520nm for the silver nanoparticles synthesis using lingonberry and cranberry juices, respectively. The antimicrobial activity of silver nanoparticles was determined against the reference strains of microorganisms that could be found in food products: Staphylococcus aureus ATCC 25923, Salmonella typhimurium ATCC 13076, Listeria monocytogenes ATCC 19111, Bacillus cereus ATCC 11778, Escherichia coli ATCC 25922, Bacillus subtilis ATCC 6633, Candida albicans ATCC 10231 and foodborne B. cereus producing and non-producing enterotoxins. Silver nanoparticles showed a broad spectrum of antimicrobial activity and were most active against S. aureus ATCC 25923, B. subtilis ATCC 6633 and B. cereus ATCC 11778 reference cultures, and less active against C. albicans ATCC 10231 and foodborne B. cereus. It can be concluded that lingonberry and cranberry juices could be used as bioreductants for silver ions. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Synthesis and antimicrobial effects of silver nanoparticles

    Directory of Open Access Journals (Sweden)

    S kheybari

    2010-09-01

    Full Text Available "n  "n "nBackground and the purpose of the study:The most prominent nanoparticles for medical uses are nanosilver particles which are famous for their high anti-microbial activity. Silver ion has been known as a metal ion that exhibit anti-mold, anti-microbial and anti-algal properties for a long time. In particular, it is widely used as silver nitrate aqueous solution which has disinfecting and sterilizing actions. The purpose of this study was to evaluate the antimicrobial activity as well as physical properties of the silver nanoparticles prepared by chemical reduction method. "nMethods:Silver nanoparticles (NPs were prepared by reduction of silver nitrate in the presence of a reducing agent and also poly [N-vinylpyrolidone] (PVP as a stabilizer. Two kinds of NPs were synthesized by ethylene glycol (EG and glucose as reducing agent. The nanostructure and particle size of silver NPs were confirmed by scanning electron microscopy (SEM and laser particle analyzer (LPA. The formations of the silver NPs were monitored using ultraviolet-visible spectroscopy. The anti-bacterial activity of silver NPs were assessed by determination of their minimum inhibitory concentrations (MIC against the Gram positive (Staphylococcus aureus and Staphylococcus epidermidis as well as Gram-negative (Escherichia coli and Pseudomonas aeruginosa bacteria. "nResults and Conclusion:The silver nanoparticles were spherical with particle size between 10 to 250 nm. Analysis of the theoretical (Mie light scattering theory and experimental results showed that the silver NPs in colloidal solution had a diameter of approximately 50 nm. "nBoth colloidal silver NPs showed high anti-bacterial activity against Gram positive and Gram negative bacteria. Glucose nanosilver colloids showed a shorter killing time against most of the tested bacteria which could be due to their nanostructures and uniform size distribution patterns.

  14. Anisotropic Model Colloids

    NARCIS (Netherlands)

    van Kats, C.M.

    2008-01-01

    The driving forces for fundamental research in colloid science are the ability to manage the material properties of colloids and to unravel the forces that play a role between colloids to be able to control and understand the processes where colloids play an important role. Therefore we are

  15. Colloid Transport and Retention

    DEFF Research Database (Denmark)

    Yuan, Hao; Shapiro, Alexander

    2012-01-01

    related to historical prospective, synthesis, characterization, theoretical modeling and application of unique class of colloidal materials starting from colloidal gold to coated silica colloid and platinum, titania colloids. This book is unique in its design, content, providing depth of science about...

  16. Silver Nanoparticles and Studies on Using in Poultry Nutrition

    Directory of Open Access Journals (Sweden)

    Mehmet Akif Özcan

    2015-02-01

    Full Text Available The use of colloidal silver as an antibiotic was becoming widespread until the 1940s. However, with the discovery of antibiotics, usage of colloidal silver had been reduced because of being expensive. The fact that bacteria develop resistance to antibiotics lead to prohibiton the usage of antibiotics in poultry diets as growth promoters. Based on these developments reuse of colloidal silver has been raised as an alternative to antibiotics. Without prejudice to the beneficial enzymes, colloidal silver disables certain enzymes needed by bacteria, viruses, yeasts, and fungus resulting in the destruction of these enzymes. It is reported that increase in surface area of nano-particles of silver increase antibacterial activity. The most important limitation on the widespread use of silver nanoparticles as feed additives is uncertainty about the possible toxic effects. In this review, studies for the use of colloidal silver particles in poultry feed were evaluated and tried to seek answer the question “may be a new resource that can be used as an alternative to antibiotics?

  17. Preparation and characterization of biocompatible silver nanoparticles using pomegranate peel extract.

    Science.gov (United States)

    Nasiriboroumand, Majid; Montazer, Majid; Barani, Hossein

    2018-02-01

    The potential application of any nanoparticles, including silver nanoparticles (AgNPs), strongly depends on their stability against aggregation. In the current study, an aqueous extract of pomegranate peel was used as a stabilizer during synthesis of AgNPs. Nanoparticles have been prepared by the chemical reduction method from an aqueous solution of silver nitrate in the presence of sodium borohydride as a reducing agent. The AgNPs were characterized by dynamic light scattering (DLS), zeta-potential measurements, UV-Vis spectroscopy and transmission electron microscopy (TEM). The antibacterial efficiency of AgNPs against Escherichia coli was investigated. The size, polydispersity index, FWHM, and colloidal stability of nanoparticles in dispersion depends on the extract concentrations. In the presence of pomegranate peel extract, the nanoparticles suspension shows colloidal stability at least for a week. Our studies show that synthesized AgNPs with the above described procedure were stable at pH = 3-12 and in the temperature range of 25-85 °C. Additionally, AgNPs exhibit antibacterial properties, especially at the lowest amount of extract to silver ratio (K Extract/Ag ). Copyright © 2018. Published by Elsevier B.V.

  18. Preparation, characterization, and antibacterial activity of γ-irradiated silver nanoparticles in aqueous gelatin

    Science.gov (United States)

    Darroudi, Majid; Ahmad, Mansor B.; Hakimi, Mohammad; Zamiri, Reza; Zak, Ali Khorsand; Hosseini, Hasan Ali; Zargar, Mohsen

    2013-04-01

    Colloidal silver nanoparticles (Ag-NPs) were obtained through γ-irradiation of aqueous solutions containing AgNO3 and gelatin as a silver source and stabilizer, respectively. The absorbed dose of γ-irradiation influences the particle diameter of the Ag-NPs, as evidenced from surface plasmon resonance (SPR) and transmission electron microscopy (TEM) images. When the γ-irradiation dose was increased (from 2 to 50 kGy), the mean particle size was decreased continuously as a result of γ-induced Ag-NPs fragmentation. The antibacterial properties of the Ag-NPs were tested against Methicillinresistant Staphylococcus aureus (MRSA) (Gram-positive) and Pseudomonas aeruginosa (P.a) (Gram-negative) bacteria. This approach reveals that the γ-irradiation-mediated method is a promising simple route for synthesizing highly stable Ag-NPs in aqueous solutions with good antibacterial properties for different applications.

  19. A Novel Photosynthesis of Carboxymethyl Starch-Stabilized Silver Nanoparticles

    Science.gov (United States)

    El-Sheikh, M. A.

    2014-01-01

    The water soluble photoinitiator (PI) 4-(trimethyl ammonium methyl) benzophenone chloride is used for the first time in the synthesis of silver nanoparticles (AgNPs). A new green synthesis method involves using PI/UV system, carboxymethyl starch (CMS), silver nitrate, and water. A mechanism of the reduction of silver ions to AgNPs by PI/UV system as well as by the newly born aldehydic groups was proposed. The synthesis process was assessed by UV-vis spectra and TEM of AgNPs colloidal solution. The highest absorbance was obtained using CMS, PI and AgNO3 concentrations of 10 g/L, 1 g/L, and 1 g/L, respectively; 40°C; 60 min; pH 7; and a material : liquor ratio 1 : 20. AgNPs so-obtained were stable in aqueous solution over a period of three weeks at room temperature (~25°C) and have round shape morphology. The sizes of synthesized AgNPs were in the range of 1–21 nm and the highest counts % of these particles were for particles of 6–10 and 1–3 nm, respectively. PMID:24672325

  20. A Novel Photosynthesis of Carboxymethyl Starch-Stabilized Silver Nanoparticles

    Directory of Open Access Journals (Sweden)

    M. A. El-Sheikh

    2014-01-01

    Full Text Available The water soluble photoinitiator (PI 4-(trimethyl ammonium methyl benzophenone chloride is used for the first time in the synthesis of silver nanoparticles (AgNPs. A new green synthesis method involves using PI/UV system, carboxymethyl starch (CMS, silver nitrate, and water. A mechanism of the reduction of silver ions to AgNPs by PI/UV system as well as by the newly born aldehydic groups was proposed. The synthesis process was assessed by UV-vis spectra and TEM of AgNPs colloidal solution. The highest absorbance was obtained using CMS, PI and AgNO3 concentrations of 10 g/L, 1 g/L, and 1 g/L, respectively; 40°C; 60 min; pH 7; and a material : liquor ratio 1 : 20. AgNPs so-obtained were stable in aqueous solution over a period of three weeks at room temperature (~25°C and have round shape morphology. The sizes of synthesized AgNPs were in the range of 1–21 nm and the highest counts % of these particles were for particles of 6–10 and 1–3 nm, respectively.

  1. Gravimetric and volumetric determination of the purity of electrolytically refined silver and the produced silver nitrate

    Directory of Open Access Journals (Sweden)

    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

  2. Effect of poly-α, γ, L-glutamic acid as a capping agent on morphology and oxidative stress-dependent toxicity of silver nanoparticles

    Directory of Open Access Journals (Sweden)

    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

  3. Electron-transfer reactions of extremely small AgI colloids

    International Nuclear Information System (INIS)

    Vucemilovic, M.I.; Micic, O.I.

    1988-01-01

    Small colloidal AgI particles (particle diameter 20-50 A) have been prepared in water and acetonitrile, and optical effects due to size quantization have been observed. Electron transfer reactions involving electron donors and electron acceptors with AgI have been studied by pulse radiolysis techniques. Both reduction and oxidation of the colloids led to transient bleaching of semiconductor absorption. The recovery of the bleaching has been attributed to corrosion processes. Electrons injected into AgI colloids produce metallic silver and hydrogen. Hydrogen evolution is catalyzed by metallic silver formation. (author)

  4. The colloid investigations conducted at the Aespoe Hard Rock Laboratory during 2000-2004

    Energy Technology Data Exchange (ETDEWEB)

    Laaksoharju, Marcus [Geopoint AB, Stockholm (Sweden); Wold, Susanna [Royal Inst. of Tech., Stockholm (Sweden). School of Chemical Science and Engineering, Nuclear Chemistry] (eds.)

    2005-12-15

    In 2000, SKB decided to initiate an international colloid project at the Aespoe Hard Rock Laboratory in Sweden. The objectives of the colloid project are to: (i) study the role of bentonite as a colloid source, (ii) verify the background colloid concentration at Aespoe HRL and, (iii) investigate the potential for colloid formation/transport in natural groundwater concentrations. The experimental concepts for the colloid project are: laboratory experiments with bentonite, background field measurements of natural colloids, borehole specific bentonite colloid stability experiments and a fracture specific transport experiment. The activities concerning the laboratory experiments and background field measurements are described in this work; the other activities are ongoing or planned. The following conclusions were made: The bentonite colloid stability is strongly dependent on the groundwater ionic strength. Natural colloids are organic degradation products such as humic and fulvic acids, inorganic colloids (clay, calcite, iron hydroxide) and microbes. Microbes form few but large particles and their concentration increase with increasing organic carbon concentrations. The small organic colloids are present in very low concentrations in deep granitic groundwater. The concentrations can be rather high in shallow waters. The colloid concentration decreases with depth and salinity, since colloids are less stable in saline waters. The colloid content at Aespoe is less than 300 ppb. The colloid content at repository level is less than 50 ppb. The groundwater variability obtained in the boreholes reflects well the natural groundwater variability along the whole HRL tunnel.

  5. The colloid investigations conducted at the Aespoe Hard Rock Laboratory during 2000-2004

    International Nuclear Information System (INIS)

    Laaksoharju, Marcus; Wold, Susanna

    2005-12-01

    In 2000, SKB decided to initiate an international colloid project at the Aespoe Hard Rock Laboratory in Sweden. The objectives of the colloid project are to: (i) study the role of bentonite as a colloid source, (ii) verify the background colloid concentration at Aespoe HRL and, (iii) investigate the potential for colloid formation/transport in natural groundwater concentrations. The experimental concepts for the colloid project are: laboratory experiments with bentonite, background field measurements of natural colloids, borehole specific bentonite colloid stability experiments and a fracture specific transport experiment. The activities concerning the laboratory experiments and background field measurements are described in this work; the other activities are ongoing or planned. The following conclusions were made: The bentonite colloid stability is strongly dependent on the groundwater ionic strength. Natural colloids are organic degradation products such as humic and fulvic acids, inorganic colloids (clay, calcite, iron hydroxide) and microbes. Microbes form few but large particles and their concentration increase with increasing organic carbon concentrations. The small organic colloids are present in very low concentrations in deep granitic groundwater. The concentrations can be rather high in shallow waters. The colloid concentration decreases with depth and salinity, since colloids are less stable in saline waters. The colloid content at Aespoe is less than 300 ppb. The colloid content at repository level is less than 50 ppb. The groundwater variability obtained in the boreholes reflects well the natural groundwater variability along the whole HRL tunnel

  6. Reproducible preparation of a stable polypyrrole-coated-silver nanoparticles decorated polypyrrole-coated-polycaprolactone-nanofiber-based cloth electrode for electrochemical sensor application

    Science.gov (United States)

    Li, Li; Wang, Xiaoping; Liu, Guiting; Wang, Zhenzhen; Wang, Feng; Guo, Xiaoyu; Wen, Ying; Yang, Haifeng

    2015-11-01

    A piece of conductive cloth has been successfully constructed from polypyrrole-coated silver nanoparticle (Ag@PPy) composites decorated on electrospun polycaprolactone (PCL) nanofibers that formed the core-shell structure of Ag@PPy/PCL@PPy via a photo-induced one-step redox reaction. The photochemical reaction method both accelerated the rate of formation of silver nanoparticles (Ag NPs) and enhanced the dispersion of Ag NPs at the surface of PCL@PPy film. The resulting Ag@PPy/PCL@PPy-based cloth was flexible enough to be cut and pasted onto a glass carbon electrode for the preparation of a biosensor. The resulting biosensor showed good electrochemical activity toward the reduction of H2O2 with low detection limit down to 1 μM (S/N = 3) and wide linear detection ranging from 0.01 mM to 3.5 mM (R2 = 0.990). This sensor has been applied to detect the trace H2O2 residual in milk. The cloth electrode has been proved to exhibit long-term stability, high selectivity, and excellent reproducibility.

  7. Reproducible preparation of a stable polypyrrole-coated-silver nanoparticles decorated polypyrrole-coated-polycaprolactone-nanofiber-based cloth electrode for electrochemical sensor application

    International Nuclear Information System (INIS)

    Li, Li; Wang, Xiaoping; Liu, Guiting; Wang, Zhenzhen; Wang, Feng; Guo, Xiaoyu; Wen, Ying; Yang, Haifeng

    2015-01-01

    A piece of conductive cloth has been successfully constructed from polypyrrole-coated silver nanoparticle (Ag@PPy) composites decorated on electrospun polycaprolactone (PCL) nanofibers that formed the core–shell structure of Ag@PPy/PCL@PPy via a photo-induced one-step redox reaction. The photochemical reaction method both accelerated the rate of formation of silver nanoparticles (Ag NPs) and enhanced the dispersion of Ag NPs at the surface of PCL@PPy film. The resulting Ag@PPy/PCL@PPy-based cloth was flexible enough to be cut and pasted onto a glass carbon electrode for the preparation of a biosensor. The resulting biosensor showed good electrochemical activity toward the reduction of H 2 O 2 with low detection limit down to 1 μM (S/N = 3) and wide linear detection ranging from 0.01 mM to 3.5 mM (R 2  = 0.990). This sensor has been applied to detect the trace H 2 O 2 residual in milk. The cloth electrode has been proved to exhibit long-term stability, high selectivity, and excellent reproducibility. (paper)

  8. A facile biomimetic preparation of highly stabilized silver nanoparticles derived from seed extract of Vigna radiata and evaluation of their antibacterial activity

    Science.gov (United States)

    Choudhary, Manoj Kumar; Kataria, Jyoti; Cameotra, Swaranjit Singh; Singh, Jagdish

    2016-01-01

    The significant antibacterial activity of silver nanoparticles draws the major attention toward the present nanobiotechnology. Also, the use of plant material for the synthesis of metal nanoparticles is considered as a green technology. In this context, a non-toxic, eco-friendly, and cost-effective method has been developed for the synthesis of silver nanoparticles using seed extract of mung beans ( Vigna radiata). The synthesized nanoparticles have been characterized by UV-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), atomic absorption spectroscopy (AAS), and X-ray diffraction (XRD). The UV-visible spectrum showed an absorption peak at around 440 nm. The different types of phytochemicals present in the seed extract synergistically reduce the Ag metal ions, as each phytochemical is unique in terms of its structure and antioxidant function. The colloidal silver nanoparticles were observed to be highly stable, even after 5 months. XRD analysis showed that the silver nanoparticles are crystalline in nature with face-centered cubic geometry and the TEM micrographs showed spherical particles with an average size of 18 nm. Further, the antibacterial activity of silver nanoparticles was evaluated by well-diffusion method and it was observed that the biogenic silver nanoparticles have an effective antibacterial activity against Escherichia coli and Staphylococcus aureus. The outcome of this study could be useful for nanotechnology-based biomedical applications.

  9. Implant materials modified by colloids

    Directory of Open Access Journals (Sweden)

    Zboromirska-Wnukiewicz Beata

    2016-03-01

    Full Text Available Recent advances in general medicine led to the development of biomaterials. Implant material should be characterized by a high biocompatibility to the tissue and appropriate functionality, i.e. to have high mechanical and electrical strength and be stable in an electrolyte environment – these are the most important properties of bioceramic materials. Considerations of biomaterials design embrace also electrical properties occurring on the implant-body fluid interface and consequently the electrokinetic potential, which can be altered by modifying the surface of the implant. In this work, the surface of the implants was modified to decrease the risk of infection by using metal colloids. Nanocolloids were obtained using different chemical and electrical methods. It was found that the colloids obtained by physical and electrical methods are more stable than colloids obtained by chemical route. In this work the surface of modified corundum implants was investigated. The implant modified by nanosilver, obtained by electrical method was selected. The in vivo research on animals was carried out. Clinical observations showed that the implants with modified surface could be applied to wounds caused by atherosclerotic skeleton, for curing the chronic and bacterial inflammations as well as for skeletal reconstruction surgery.

  10. Method for the preparation of metal colloids in inverse micelles and product preferred by the method

    Science.gov (United States)

    Wilcoxon, Jess P.

    1992-01-01

    A method is provided for preparing catalytic elemental metal colloidal particles (e.g. gold, palladium, silver, rhodium, iridium, nickel, iron, platinum, molybdenum) or colloidal alloy particles (silver/iridium or platinum/gold). A homogeneous inverse micelle solution of a metal salt is first formed in a metal-salt solvent comprised of a surfactant (e.g. a nonionic or cationic surfactant) and an organic solvent. The size and number of inverse micelles is controlled by the proportions of the surfactant and the solvent. Then, the metal salt is reduced (by chemical reduction or by a pulsed or continuous wave UV laser) to colloidal particles of elemental metal. After their formation, the colloidal metal particles can be stabilized by reaction with materials that permanently add surface stabilizing groups to the surface of the colloidal metal particles. The sizes of the colloidal elemental metal particles and their size distribution is determined by the size and number of the inverse micelles. A second salt can be added with further reduction to form the colloidal alloy particles. After the colloidal elemental metal particles are formed, the homogeneous solution distributes to two phases, one phase rich in colloidal elemental metal particles and the other phase rich in surfactant. The colloidal elemental metal particles from one phase can be dried to form a powder useful as a catalyst. Surfactant can be recovered and recycled from the phase rich in surfactant.

  11. One-Pot Silver Nanoring Synthesis

    Directory of Open Access Journals (Sweden)

    Drogat Nicolas

    2009-01-01

    Full Text Available Abstract Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV–vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation.

  12. One-Pot Silver Nanoring Synthesis

    Science.gov (United States)

    Drogat, Nicolas; Granet, Robert; Sol, Vincent; Krausz, Pierre

    2010-03-01

    Silver colloidal nanorings have been synthesized by reducing silver ions with NaBH4 in trisodium citrate buffers. pH increase, by addition of NaOH, was used to speed up reduction reaction. The UV-vis absorption spectra of resulting silver nanorings showed two peaks accounting for transverse and longitudinal surface plasmon resonance, at ≈400 nm, and between 600 and 700 nm, respectively. The shapes of these silver nanoparticles (nanorings) depended on AgNO3/NaBH4 ratio, pH and reaction temperature. Particles were analysed by transmission electron microscopy, scanning electron microscopy and X-ray diffraction. A reaction pathway is proposed to explain silver nanoring formation.

  13. Tailoring particle size and morphology of colloidal Ag particles via chemical precipitation for Ag-BSCCO composites

    International Nuclear Information System (INIS)

    Medendorp, N.W. Jr.; Bowman, K.J.; Trumble, K.P.

    1996-01-01

    The chemical precipitation of silver particles is an effective method for tailoring the particle size and morphology. This article investigates a chemical precipitation method for producing silver colloids, and how processing parameters affected particle size, morphology and adherence. Decreasing the silver nitrate concentration during precipitation with sodium borohydride decreased the colloidal silver particle size. Decreasing the addition rate of the reducing agent produced faceted particles. Reversing the reactant addition order also changed the particle size and the morphology. Precipitated colloids demonstrated a difference between the growth-dominated and the equilibrium structures. Co-dispersing Bi-based superconducting platelets during precipitation allowed Ag colloids to preferentially nucleate on the platelets and to remain adhered even after the additional processing. (orig.)

  14. Radiation formation of colloidal metallic particles in aqueous systems

    International Nuclear Information System (INIS)

    Cuba, Vaclav; Nemec, Mojmir; Gbur, Tomas; John, Jan; Pospisil, Milan; Mucka, Viliam

    2008-01-01

    Full text: Radiation and photochemical methods have been successfully utilized in various steps of nanoparticles preparation. Presented study deals with formation of silver nanoparticles in various aqueous solutions initiated by UV and gamma radiation. Silver nitrate and silver cyanide were used as precursors for radiation and/or photochemical reduction of Ag + ions to the metallic form. Influence of various parameters (dose of radiation, dose rate, exposition time) on nucleation and formation of colloid particles was studied. Attention was also focused on composition of irradiated solution. Aliphatic alcohols were used as scavengers of OH radicals and other oxidizing species. Various organic stabilizers of formed nanoparticles were used, among others ethylenediaminetetraacetic acid, citric acid and polyvinyl alcohol. Irradiation effects were evaluated using UV/Vis absorption spectra in colloid solution, solid phase formed after long-term irradiation was analysed via X-ray structural analysis

  15. Preparation of counterion stabilized concentrated silver sols.

    Science.gov (United States)

    LaPlante, Sylas; Halaciuga, Ionel; Goia, Dan V

    2011-07-01

    A strategy for obtaining stable concentrated silver dispersions without dedicated stabilizing agents is presented. This approach consists of rapidly mixing aqueous solutions of silver salicylate and ascorbic acid. By using salicylate as Ag(+) counterion, it is possible to prepare stable sols with metal concentrations up to two orders of magnitude higher than with silver nitrate. The stabilizing effect of the counterion is the result of a decreased ionic strength due to salicylate protonation and its adsorption on the surface of silver. Both effects increase the range of the electrostatic repulsive forces by expanding the electrical double layer. Copyright © 2011 Elsevier Inc. All rights reserved.

  16. Saturated Zone Colloid Transport

    International Nuclear Information System (INIS)

    H. S. Viswanathan

    2004-01-01

    This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, R col is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of R col that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, k att , and detachment rate constants, k det , of colloids to the fracture surface have been measured for the fractured volcanics, and separate R col uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant retardation. Radionuclides irreversibly

  17. Random packing of colloids and granular matter

    NARCIS (Netherlands)

    Wouterse, A.

    2008-01-01

    This thesis deals with the random packing of colloids and granular matter. A random packing is a stable disordered collection of touching particles, without long-range positional and orientational order. Experimental random packings of particles with the same shape but made of different materials

  18. Autometallography: tissue metals demonstrated by a silver enhancement kit

    DEFF Research Database (Denmark)

    Danscher, G; Nørgaard, J O; Baatrup, E

    1987-01-01

    , primarily intended for the amplification of colloidal gold particles, has been used to demonstrate these catalytic tissue metals. Sections from animals exposed intravitally to aurothiomalatate, silver lactate, mercury chloride, sodium selenite or perfused with sodium sulphide were subjected to a commercial......In biological tissue, minute accumulations of gold, silver, mercury and zinc can be visualized by a technique whereby metallic silver is precipitated on tiny accumulations of the two noble metals, or on selenites or sulphides of all four metals. In the present study a silver enhancement kit...... silver enhancement kit (IntenSE, Janssen Pharmaceutica). It was found that the kit performs adequately to the silver lactate gum arabic developer and to the photographic emulsion technique. The kit can be used as a silver enhancement medium for the demonstration of zinc by the Neo-Timm and selenium...

  19. Surface-enhanced Raman Spectroscopy of Ethephone Adsorbed on Silver Surface

    International Nuclear Information System (INIS)

    Lee, Chul Jae; Kim, Hee Jin; Karim, Mohammad Rezaul; Lee, Mu Sang

    2006-01-01

    We investigated the Surface-enhanced Raman Spectroscopy (SERS) spectrum of ethephone (2- chloroethylphosphonic acid). We observed significant signals in the ordinary Raman spectrum for solid-state ethephone as well as when it was adsorbed on a colloidal silver surface, strong vibrational signals were obtained at a very low concentration. The SERS spectra were obtained by silver colloids that were prepared by the γ - irradiation method. The influence of pH and the influence of anion (Cl - , Br - , I - ) on the adsorption orientation were investigated. Two different adsorption mechanisms were deduced, depending on the experimental conditions. The chlorine atom or the chlorine and two oxygen atoms were adsorbed on the colloidal silver surface. Among halide ions, Br - and I - were more strongly adsorbed on the colloidal silver surfaces. As a result, the adsorption of ethephone was less effective due to their steric hinderance

  20. Silica colloids and their effect on radionuclide sorption. A literature review

    International Nuclear Information System (INIS)

    Hoelttae, P.; Hakanen, M.

    2008-05-01

    Silica sol, commercial colloidal silica manufactured by Eka Chemicals in Bohus, Sweden is a promising inorganic grout material for sealing small fractures in low permeable rock. This literature review collects information about the use of silica sol as an injection grout material, the properties of inorganic, especially silica colloids, colloid contents in granitic groundwater conditions, essential characterization methods and colloid-mediated transport of radionuclides. Objective was to evaluate the release and mobility of silica sol colloids, the effect of the groundwater conditions, the amount of colloids compared with natural colloids in Olkiluoto conditions, radionuclide sorption on colloids and their contribution to radionuclide transport. Silica sol seems to be a feasible material to seal fractures with an aperture as small as 10 μm in low permeable rock. The silica sol gel is sufficiently stable to limit to water ingress during the operational phase, the requirement that the pH should be below 11 is fulfilled and the compatibility with Engineered Barrier System (EBS) materials is expected to be good. No significant influence on the bentonite properties caused by the silica sol is expected when calcium chloride is used as an accelerator but the influence of sodium chloride has not been examined. No significant release of colloids is expected under prevailing groundwater conditions. The long-term (100 y) stability of silica sol gel has not yet been clearly demonstrated and a long-term release of silica colloids cannot be excluded. The question is the amount of colloids, how mobile they are and the influence of possible glacial melt waters. The bentonite buffer used in the EBS system is assumed to be a potential source of colloids. In a study in Olkiluoto, bentonite colloids were found only in low salinity groundwater. In general, low salinity water (total dissolved solids -1 ) favours colloid stability and bentonite colloids can remain stable over long

  1. Analysis of colloid transport

    International Nuclear Information System (INIS)

    Travis, B.J.; Nuttall, H.E.

    1985-01-01

    The population balance methodology is described and applied to the transport and capture of polydispersed colloids in packed columns. The transient model includes particle growth, capture, convective transport, and dispersion. We also follow the dynamic accumulation of captured colloids on the solids. The multidimensional parabolic partial differential equation was solved by a recently enhanced method of characteristics technique. This computational technique minimized numerical dispersion and is computationally very fast. The FORTRAN 77 code ran on a VAX-780 in less than a minute and also runs on an IBM-AT using the Professional FORTRAN compiler. The code was extensively tested against various simplified cases and against analytical models. The packed column experiments by Saltelli et al. were re-analyzed incorporating the experimentally reported size distribution of the colloid feed material. Colloid capture was modeled using a linear size dependent filtration function. The effects of a colloid size dependent filtration factor and various initial colloid size distributions on colloid migration and capture were investigated. Also, we followed the changing colloid size distribution as a function of position in the column. Some simple arguments are made to assess the likelihood of colloid migration at a potential NTS Yucca Mountain waste disposal site. 10 refs., 3 figs., 1 tab

  2. Colloid process engineering

    CERN Document Server

    Peukert, Wolfgang; Rehage, Heinz; Schuchmann, Heike

    2015-01-01

    This book deals with colloidal systems in technical processes and the influence of colloidal systems by technical processes. It explores how new measurement capabilities can offer the potential for a dynamic development of scientific and engineering, and examines the origin of colloidal systems and its use for new products. The future challenges to colloidal process engineering are the development of appropriate equipment and processes for the production and obtainment of multi-phase structures and energetic interactions in market-relevant quantities. The book explores the relevant processes and for controlled production and how they can be used across all scales.

  3. UZ Colloid Transport Model

    International Nuclear Information System (INIS)

    McGraw, M.

    2000-01-01

    The UZ Colloid Transport model development plan states that the objective of this Analysis/Model Report (AMR) is to document the development of a model for simulating unsaturated colloid transport. This objective includes the following: (1) use of a process level model to evaluate the potential mechanisms for colloid transport at Yucca Mountain; (2) Provide ranges of parameters for significant colloid transport processes to Performance Assessment (PA) for the unsaturated zone (UZ); (3) Provide a basis for development of an abstracted model for use in PA calculations

  4. How do 10-camphorsulfonic acid, silver or aluminum nanoparticles influence optical, electrochemical, electrochromic and photovoltaic properties of air and thermally stable triphenylamine-based polyazomethine with carbazole moieties?

    International Nuclear Information System (INIS)

    Iwan, Agnieszka; Boharewicz, Bartosz; Tazbir, Igor; Filapek, Michal; Korona, Krzysztof P.; Wróbel, Piotr; Stefaniuk, Tomasz; Ciesielski, Arkadiusz; Wojtkiewicz, Jacek; Wronkowska, Aleksandra A.; Wronkowski, Andrzej; Zboromirska-Wnukiewicz, Beata; Grankowska-Ciechanowicz, Sylwia; Kaminska, Maria; Szoplik, Tomasz

    2015-01-01

    Organic (10-camphorsulfonic acid, CSA), organic-inorganic (Ag-poly(vinylpyrrolidone), Ag-PVP with 10 and 20 nm size of Ag) or inorganic (Al, 18 nm) compounds were applied as new components of active layer in bulk heterojunction polymer solar cells based on a new polyazomethine (PAZ-Car-TPA) resulting in significant change of optical and electrical properties. Moreover, colloidal Ag (100 nm) and Ag-PVP in aqueous solution (10 nm) were tested as an addition to the hole transporting layer based on PEDOT:PSS in polyazomethine solar cells. CSA added to PAZ-Car-TPA decrease its energy gap from 1.91 to 1.20 eV and causes a significant bathochromic shift of the maximum of absorption band along with the change of the polymer color from yellow to red (electrochromic behavior). Photoluminescence maximum of PAZ-Car-TPA protonated with CSA showed 120 nm redshift from 500 to 620 nm in comparison to undoped PAZ-Car-TPA. HOMO-LUMO of PAZ-Car-TPA and its mixture with CSA were analyzed by cyclic voltammetry and quantum mechanical calculations using Density Functional Theory method. Refraction index and extinction coefficient of PAZ-Car-TPA and its mixtures with PC 71 BM as well as Ag or Al nanoparticles were investigated taking into consideration various thickness of polymer layer. The power conversion efficiency of the ITO/PEDOT:PSS/PAZ-Car-TPA:PCBM:CSA/Al device was five time higher than that of the device based on PAZ-Car-TPA:PCBM. Such an enhancement was found to be primarily due to the increase of the short-circuit current, suggesting that the charge collection increases upon the incorporation of CSA in the active layer. Moreover, presence of Ag-PVP (20 nm) or Al (18 nm) in device increased short circuit current of the constructed polymer solar cells. Additionally, devices were tested by external quantum efficiency measurements and electrochemical impedance spectroscopy in dark and under illumination. The polymer solar cell with PAZ-Car-TPA as donor in active layer showed good

  5. Synthesis and characterization of monodispersed silver nanoparticles

    Science.gov (United States)

    Jegatha Christy, A.; Umadevi, M.

    2012-09-01

    Synthesis of silver nanoparticles (NPs) has become a fascinating and important field of applied chemical research. In this paper silver NPs were prepared using silver nitrate (AgNO3), gelatin, and cetyl trimethyl ammonium bromide (CTAB). The prepared silver NPs were exposed under the laser ablation. In our photochemical procedure, gelatin acts as a biopolymer and CTAB acts as a reducing agent. The appearance of surface plasmon band around 410 nm indicates the formation of silver NPs. The nature of the prepared silver NPs in the face-centered cubic (fcc) structure are confirmed by the peaks in the x-ray diffraction (XRD) pattern corresponding to (111), (200), (220) and (311) planes. Monodispersed, stable, spherical silver NPs with diameter about 10 nm were obtained and confirmed by high-resolution transmission electron microscope (HRTEM).

  6. Synthesis and characterization of monodispersed silver nanoparticles

    International Nuclear Information System (INIS)

    Christy, A Jegatha; Umadevi, M

    2012-01-01

    Synthesis of silver nanoparticles (NPs) has become a fascinating and important field of applied chemical research. In this paper silver NPs were prepared using silver nitrate (AgNO 3 ), gelatin, and cetyl trimethyl ammonium bromide (CTAB). The prepared silver NPs were exposed under the laser ablation. In our photochemical procedure, gelatin acts as a biopolymer and CTAB acts as a reducing agent. The appearance of surface plasmon band around 410 nm indicates the formation of silver NPs. The nature of the prepared silver NPs in the face-centered cubic (fcc) structure are confirmed by the peaks in the x-ray diffraction (XRD) pattern corresponding to (111), (200), (220) and (311) planes. Monodispersed, stable, spherical silver NPs with diameter about 10 nm were obtained and confirmed by high-resolution transmission electron microscope (HRTEM). (paper)

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

    Science.gov (United States)

    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.

  8. Synthesis and optical properties of silver nanoparticles

    Science.gov (United States)

    Singh, Jaiveer; Kaurav, Netram; Choudhary, K. K.; Okram, Gunadhor S.

    2015-07-01

    The preparation of stable, uniform silver nanoparticles by reduction of silver acetate by ethylene glycol (EG) is reported in the present paper. It is a simple process of recent interest for obtaining silver nanoparticles. The samples were characterized by X-Ray diffraction (XRD), which reveals an average particle size (D) of 38 nm. The UV/Vis spectra show that an absorption peak, occurring due to surface plasmon resonance (SPR), exists at 319 nm.

  9. Silver niobates

    International Nuclear Information System (INIS)

    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

  10. Green synthesis of silver nanoparticles using tannins

    Science.gov (United States)

    Raja, Pandian Bothi; Rahim, Afidah Abdul; Qureshi, Ahmad Kaleem; Awang, Khalijah

    2014-09-01

    Colloidal silver nanoparticles were prepared by rapid green synthesis using different tannin sources as reducing agent viz. chestnut (CN), mangrove (MG) and quebracho (QB). The aqueous silver ions when exposed to CN, MG and QB tannins were reduced which resulted in formation of silver nanoparticles. The resultant silver nanoparticles were characterized using UV-Visible, X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), and transmission electron microscopy (TEM) techniques. Furthermore, the possible mechanism of nanoparticles synthesis was also derived using FT-IR analysis. Spectroscopy analysis revealed that the synthesized nanoparticles were within 30 to 75 nm in size, while XRD results showed that nanoparticles formed were crystalline with face centered cubic geometry.

  11. Interface colloidal robotic manipulator

    Science.gov (United States)

    Aronson, Igor; Snezhko, Oleksiy

    2015-08-04

    A magnetic colloidal system confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters. The colloidal system exhibits locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, structures can capture, transport, and position target particles.

  12. Transport of Intrinsic Plutonium Colloids in Saturated Porous Media

    Science.gov (United States)

    Zhou, D.; Abdel-Fattah, A.; Boukhalfa, H.; Ware, S. D.; Tarimala, S.; Keller, A. A.

    2011-12-01

    Actinide contaminants were introduced to the subsurface environment as a result of nuclear weapons development and testing, as well as for nuclear power generation and related research activities for defense and civilian applications. Even though most actinide species were believed to be fairly immobile once in the subsurface, recent studies have shown the transport of actinides kilometers away from their disposal sites. For example, the treated liquid wastes released into Mortandad Canyon at the Los Alamos National Laboratory were predicted to travel less than a few meters; however, plutonium and americium have been detected 3.4 km away from the waste outfall. A colloid-facilitated mechanism has been suggested to account for this unexpected transport of these radioactive wastes. Clays, oxides, organic matters, and actinide hydroxides have all been proposed as the possible mobile phase. Pu ions associated with natural colloids are often referred to as pseudo-Pu colloids, in contrast with the intrinsic Pu colloids that consist of Pu oxides. Significant efforts have been made to investigate the role of pseudo-Pu colloids, while few studies have evaluated the environmental behavior of the intrinsic Pu colloids. Given the fact that Pu (IV) has extremely low solubility product constant, it can be inferred that the transport of Pu in the intrinsic form is highly likely at suitable environmental conditions. This study investigates the transport of intrinsic Pu colloids in a saturated alluvium material packed in a cylindrical column (2.5-cm Dia. x 30-cm high) and compares the results to previous data on the transport of pseudo Pu colloids in the same material. A procedure to prepare a stable intrinsic Pu colloid suspension that produced consistent and reproducible electrokinetic and stability data was developed. Electrokinetic properties and aggregation stability were characterized. The Pu colloids, together with trillium as a conservative tracer, were injected into the

  13. Ultrasonic electrodeposition of silver nanoparticles on dielectric silica spheres

    International Nuclear Information System (INIS)

    Tang Shaochun; Tang Yuefeng; Gao Feng; Liu Zhiguo; Meng Xiangkang

    2007-01-01

    In the present study, a facile and one-step ultrasonic electrodeposition method is first applied to controllably coat colloidal silica spheres with silver nanoparticles. This method is additive-free and very direct, because processes necessary in many other approaches, such as pretreatment of the silica sphere surface and pre-preparation of silver nanoparticles, are not involved in it. Furthermore, it makes possible the coating of dielectric substrates with metal through an electrodeposition route. Under appropriate conditions, silver nanoparticles with sizes of 8-10 nm in diameter can be relatively homogeneously deposited onto the surface of preformed colloidal silica spheres. Silver particles with different sizes and dispersive uniformity on silica sphere surfaces can also be obtained by adjusting the current density (I), the concentration of electrolyte (C) and the electrolysis time (t). The possible ultrasonic electrodeposition mechanism is also suggested according to the experimental results

  14. Micellized sequestered silver atoms and small silver clusters

    International Nuclear Information System (INIS)

    Borgarello, E.; Lawless, D.; Serpone, N.; Pelizzetti, E.; Meisel, D.

    1990-01-01

    Pulse radiolysis was used to examine the nature of the silver species obtained when an aqueous solution containing sequestered Ag + ions was reduced by hydrated electrons in the presence of a surfactant macrocyclic crown ether, labeled L, and/or a maltoside surfactant. The initially formed product is the Ag 0 (L) species which rapidly loses its ligand (half-life ≤5 μs) and reacts with another Ag + (L) ion to form Ag 2 + (L). The latter species decays by a bimolecular process to form the Ag 4 2+ (L) n species at a faster rate than its ligand free analogue. Ultimately, colloidal metallic silver, (Ag) n , forms which is stabilized by the surfactant moieties. No long-term stability to the reduced monomolecular species could be obtained

  15. ANTISEPTIC SPRAY BASED ON STABILIZED SILVER PARTICLES: AN ANALYSIS OF ANTISEPTIC PROPERTIES AND COMPREHENSIVE COMPARISON

    Directory of Open Access Journals (Sweden)

    Manuilov, A.M.

    2018-04-01

    Full Text Available Introduction. It's known that some antiseptic sprays based on alcohols can provoke the formation of multi-resistant strains of pathogenic microorganisms. In addition, alcoholic antiseptics has a number of restrictions to use, for example, they can't to be used in even the presence of micro-trauma on the skin, their ingression into the body and mucous membranes is unacceptable. Alternative can be natural antiseptics based on colloidal silver or silver nanoparticles, as well as silver in ionic form. However, such antiseptics has low efficacy against the most dangerous strains. Company Modern Biochem Technologies Ltd. announced the development of a portable device that generates a natural and safe antiseptic Dew, based on stabilized silver particles. Antiseptic Dew surpasses the vast majority of antiseptics based on silver, and is not inferior in effectiveness to antiseptics based on alcohols. This work is devoted to testing the declared characteristics of Dew and its comparison with antiseptics based on colloidal silver, silver nanoparticles and isopropyl alcohol. Materials and methods. To test the antiseptic effect of these agents, we used four test strains from the American Type Culture Collection: E. Coli ATCC 25922, Staphylococcus Aureus ATCC 25923, Candida Albicans ATCC 885-653 and Proteus Vulgaris ATCC 4636 with billion concentration of colony forming units in 1 ml (108 – 109 CFU/mL, ln CFU/mL = 19.57 ... 20.72. Sowing and screening of cultures were performed on sterile Petri dishes according to the standard procedure. Antiseptic Dew was prepared by prototype provided by Modern Biochem Technologies. The antiseptics of comparison were purchased in Kharkiv, Ukraine. The treatment of contaminated surfaces was performed using mechanical pump sprayers. In accordance with the internal protocol, 1 ml of antiseptic was sprayed from the distance of 10 cm onto the infected surface. To determine the silver content in the Dew, we were used atomic

  16. Synthesis and characterization of nanophased silver tungstate

    Indian Academy of Sciences (India)

    nanoparticles were examined with scanning electron microscope (A Lieca Stereoscan. 440 model SEM) at an ... SEM image of rod-like nanocrystalline silver tungstate. Figure 3. ... Thermal analysis shows that the compound is thermally stable ...

  17. A study of the uptake and toxicity of some stable and radioactive pollutants in marine organisms: antimony, silver, cobalt and strontium in mollusks, crustaceans and teleosts

    International Nuclear Information System (INIS)

    Amiard, J.-C.

    1978-10-01

    Qualitative and quantitative results following direct aquatic contamination of mollusks, crustaceans and teleosts by 125 Sb, 110 Ag, 60 Co, 85 Sr are reported. The effects of a number of biotic and abiotic parameters on the contamination of the various organisms and the distribution and elimination of the radionuclides in the tissues were investigated. The transfer of sup(110m)Ag, 60 Co and 125 Sb was studied in several benthic food chains. The transfer factor (F.T.) between a given trophic level and the initial environment (seawater) was determined as well as various physiological parameters (percentages ingested, assimilated, eliminated via the feces or urine and/or the gills. Elimination and tissue uptake were followed in mollusks and crustaceans. The consequences of contamination by stable and radioactive pollutants on plants and animals were considered. Acute (lethal) toxicity of various metals or metalloids on marine organisms were quantified. More sensitive sublethal tests considering physiological functions or behaviour were used. Irradiation doses to experiment animals were calculated, showing the importance of the (internal or external distribution of radionuclides and individual geometries on the total exposure dose [fr

  18. Behavior and chronic toxicity of two differently stabilized silver nanoparticles to Daphnia magna

    DEFF Research Database (Denmark)

    Sakka, Yvonne; Skjolding, Lars Michael; Mackevica, Aiga

    2016-01-01

    While differences in silver nanoparticle (AgNP) colloidal stability, surface potential, or acute aquatic toxicity for differently stabilized AgNP have often been reported, these have rarely been studied in long-term ecotoxicity tests. In the current study, we investigated the chronic toxicity of Ag...... types of AgNP during a typical media exchange period in the D. magna test for chronic toxicity. As expected, the sterically stabilized AgNP were more stable in the test medium, also in the presence of food; however, a higher uptake of silver after 24 h exposure of the charge stabilized AgNP was found...... compared to the detergent-stabilized AgNP (0.046 ± 0.006 μg Ag μg DW−1 and 0.023 ± 0.005 μg Ag μg DW−1, respectively). In accordance with this, the higher reproductive effects and mortality were found for the charge-stabilized than for the sterically-stabilized silver nanoparticles in 21-d tests...

  19. Synthesis and characterization of silver nanoparticles in AOT microemulsion system

    International Nuclear Information System (INIS)

    Zhang Wanzhong; Qiao Xueliang; Chen Jianguo

    2006-01-01

    Colloidal silver nanoparticles have been synthesized in water-in-oil microemulsion using silver nitrate solubilized in the water core of one microemulsion as source of silver ions, hydrazine hydrate solubilized in the water core of another microemulsion as reducing agent, dodecane as the oil phase, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as the surfactant. The UV-vis absorption spectra and transmission electron microscopy (TEM) have been used to trace the growth process and elucidate the structure of the silver nanoparticles. UV-vis spectra show that the Ag 4 + intermediates formed at early stages of the reaction and then the clusters grow or aggregate to larger nanoparticles. TEM micrographs confirm that the silver nanoparticles are all spherical. The resulting particles have a very narrow size distribution. Meanwhile, the diameter size of the particles is so small that the smallest mean diameter is only 1.6nm. IR results show that the surfactant molecules are strongly adsorbed on the surface of silver particles through a coordination bond between the silver atom and the sulfonic group of AOT molecules, which endows the particles with a good stability in oil solvents. As dodecane is used as oil solvent to prepare silver nanoparticles, the formed nano-silver sol is almost nontoxic. As a result, the silver nanoparticles need not be separated from the reaction solution and the silver sol may be directly used in antibacterial fields

  20. Saturated Zone Colloid Transport

    Energy Technology Data Exchange (ETDEWEB)

    H. S. Viswanathan

    2004-10-07

    This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, R{sub col} is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of R{sub col} that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, k{sub att}, and detachment rate constants, k{sub det}, of colloids to the fracture surface have been measured for the fractured volcanics, and separate R{sub col} uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant

  1. On the aging and colloid properties of AgI soils

    International Nuclear Information System (INIS)

    Despotovicj, R.; Kapetanovicj, J.

    1977-01-01

    A study of the changes of silver iodide sol properties has shown the role of the ageing process in the characterization of the colloid system. An analysis of the critical coagulation concentration changes and of the sedimentation rates with time and electrophoretic mobility of sols has revealed, that sols in the presence of various counter ions do not exhibit strictly equal colloid properties, although counter ions are present at the critical coagulation concentration

  2. Biosynthesis of Silver and Gold Crystals Using Grapefruit Extract

    OpenAIRE

    Chen Long; Wang Jianli; Wang Hongfeng; Qi Zhaopeng; Zheng Yuchuan; Wang Junbo; Pan Le; Chang Guanru; Yang Yongmei

    2016-01-01

    In this paper, biological synthesis of silver and gold crystals using grapefruit extract is reported. On treatment of aqueous solutions of silver nitrate and chloroauric acid with grapefruit extract, the formation of stable silver and gold particles at high concentrations is observed to occur. The silver particles formed are quasi-spherical or irregular with sizes ranging from several hundred nanometers to several microns. The gold quasi-spheres with holes on surfaces and with diameters rangi...

  3. Grimsel colloid exercise

    International Nuclear Information System (INIS)

    Degueldre, C.; Longworth, G.; Vilks, P.

    1989-11-01

    The Grimsel Colloid Exercise was an intercomparison exercise which consisted of an in situ sampling phase followed by a colloid characterisation step. The goal of this benchmark exercise, which involved 12 laboratories, was to evaluate both sampling and characterisation techniques with emphasis on the colloid specific size distribution. The sampling phase took place at the Grimsel Test Site between February 1 and 13, 1988 and the participating groups produced colloid samples using the following methods: 1. Cross-flow ultrafiltration with production of membranes loaded with colloids. 2. Tangential diaultrafiltration and production of colloid concentrates. 3. Filtrates produced by each group. 4. Unfiltered water was also collected by PSI in glass bottles, under controlled anaerobic conditions, and by the other sampling groups in various plastic bottles. In addition, on-line monitoring of pH, χ, [O-2] and T of the water and of [O-2] in the atmosphere of the sampling units was carried out routinely. All samples were shipped according to the CoCo Club scheme for characterisation, with emphasis on the size distribution. The exercise differentiates the colloid samples produced on site from those obtained after transfer of the fluid samples to the laboratories. The colloid concentration and size distribution can be determined by scanning electron microscopy (SEM), gravimetry (GRAV), chemical analysis of fluid samples after micro/ultrafiltration (MF/UF) and by transmission single particle counting (PC). The colloid concentration can also be evaluated by transmission electron microscopy (TEM), static and dynamic light scattering (SLS,DLS) and by laser-induced photoacoustic spectroscopy (LPAS). The results are discussed on the basis of the detection limit, lateral resolution and counting conditions of the technique (precision) as well as sample preparation, artefact production and measurement optimisation (accuracy). A good agreement between size distribution results was

  4. Clusters in attractive colloids

    Energy Technology Data Exchange (ETDEWEB)

    Coniglio, A [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario di Monte Sant' Angelo, via Cintia 80126 Naples (Italy); Arcangelis, L de [Dipartimento di Ingegneria dell' Informazione and CNISM II Universita di Napoli, Aversa (CE) (Italy); Candia, A de [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario di Monte Sant' Angelo, via Cintia 80126 Naples (Italy); Gado, E Del [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario di Monte Sant' Angelo, via Cintia 80126 Naples (Italy); Fierro, A [Dipartimento di Scienze Fisiche, Universita di Napoli ' Federico II' , Complesso Universitario di Monte Sant' Angelo, via Cintia 80126 Naples (Italy); Sator, N [Laboratoire de Physique Theorique de la Matiere Condensee, Universite Pierre et Marie Curie-Paris6, UMR (CNRS) 7600 Case 121, 4 Place Jussieu 75252 Paris Cedex 05 (France)

    2006-09-13

    We discuss how the anomalous increase of the viscosity in colloidal systems with short-range attraction can be related to the formation of long-living clusters. Based on molecular dynamics and Monte Carlo numerical simulations of different models, we propose a similar picture for colloidal gelation at low and intermediate volume fractions. On this basis, we analyze the distinct role played by the formation of long-living bonds and the crowding of the particles in the slow dynamics of attractive colloidal systems.

  5. Colloids in Biotechnology

    CERN Document Server

    Fanun, Monzer

    2010-01-01

    Colloids have come a long way from when Thomas Graham coined the term colloid to describe 'pseudo solutions'. This book enables scientists to close the gap between extensive research and translation into commercial options in biomedicine and biotechnology. It covers biosurfactants and surface properties, phase behavior, and orientational change of surfactant mixtures with peptides at the interface. It also covers adsorption of polymers and biopolymers on the surface and interface, discusses colloidal nanoparticles and their use in biotechnology, and delves into bioadhesion and microencapsulati

  6. Distribution of silver in rats following 28 days of repeated oral exposure to silver nanoparticles or silver acetate

    DEFF Research Database (Denmark)

    Löschner, Katrin; Hadrup, Niels; Qvortrup, Klaus

    2011-01-01

    Background: The study investigated the distribution of silver after 28 days repeated oral administration of silver nanoparticles (AgNPs) and silver acetate (AgAc) to rats. Oral administration is a relevant route of exposure because of the use of silver nanoparticles in products related to food...... and food contact materials. Results: AgNPs were synthesized with a size distribution of 14 ± 4 nm in diameter (90% of the nanoparticle volume) and stabilized in aqueous suspension by the polymer polyvinylpyrrolidone (PVP). The AgNPs remained stable throughout the duration of the 28-day oral toxicity study...... in rats. The organ distribution pattern of silver following administration of AgNPs and AgAc was similar. However the absolute silver concentrations in tissues were lower following oral exposure to AgNPs. This was in agreement with an indication of a higher fecal excretion following administration of Ag...

  7. Fast microbial reduction of ferrihydrite colloids from a soil effluent

    Science.gov (United States)

    Fritzsche, Andreas; Bosch, Julian; Rennert, Thilo; Heister, Katja; Braunschweig, Juliane; Meckenstock, Rainer U.; Totsche, Kai U.

    2012-01-01

    Recent studies on the microbial reduction of synthetic iron oxide colloids showed their superior electron accepting property in comparison to bulk iron oxides. However, natural colloidal iron oxides differ in composition from their synthetic counterparts. Besides a potential effect of colloid size, microbial iron reduction may be accelerated by electron-shuttling dissolved organic matter (DOM) as well as slowed down by inhibitors such as arsenic. We examined the microbial reduction of OM- and arsenic-containing ferrihydrite colloids. Four effluent fractions were collected from a soil column experiment run under water-saturated conditions. Ferrihydrite colloids precipitated from the soil effluent and exhibited stable hydrodynamic diameters ranging from 281 (±146) nm in the effluent fraction that was collected first and 100 (±43) nm in a subsequently obtained effluent fraction. Aliquots of these oxic effluent fractions were added to anoxic low salt medium containing diluted suspensions of Geobacter sulfurreducens. Independent of the initial colloid size, the soil effluent ferrihydrite colloids were quickly and completely reduced. The rates of Fe2+ formation ranged between 1.9 and 3.3 fmol h-1 cell-1, and are in the range of or slightly exceeding previously reported rates of synthetic ferrihydrite colloids (1.3 fmol h-1 cell-1), but greatly exceeding previously known rates of macroaggregate-ferrihydrite reduction (0.07 fmol h-1 cell-1). The inhibition of microbial Fe(III) reduction by arsenic is unlikely or overridden by the concurrent enhancement induced by soil effluent DOM. These organic species may have increased the already high intrinsic reducibility of colloidal ferrihydrite owing to quinone-mediated electron shuttling. Additionally, OM, which is structurally associated with the soil effluent ferrihydrite colloids, may also contribute to the higher reactivity due to increasing solubility and specific surface area of ferrihydrite. In conclusion, ferrihydrite

  8. Fabrication of Phase-Change Polymer Colloidal Photonic Crystals

    Directory of Open Access Journals (Sweden)

    Tianyi Zhao

    2014-01-01

    Full Text Available This paper presents the preparation of phase-change polymer colloidal photonic crystals (PCs by assembling hollow latex spheres encapsulated with dodecanol for the first time. The monodispersed hollow latex spheres were obtained by phase reversion of monodispersed core-shell latex spheres in the n-hexane, which dissolves the PS core and retains the PMMA/PAA shell. The as-prepared phase-change colloidal PCs show stable phase-change behavior. This fabrication of phase-change colloidal PCs would be significant for PC’s applications in functional coatings and various optic devices.

  9. Green Synthesis of Silver Nanoparticles and the Study of Optical Properties

    OpenAIRE

    Vasireddy, Ramakrishna; Paul, Rima; Mitra, Apurba Krishna

    2012-01-01

    The synthesis of silver nanoparticles of varying size has been achieved using different molar concentrations of NaOH while the effect of changing the temperature has been studied. AgNO3, gelatine, glucose and NaOH are used as a silver precursor, stabilizer, reducing agent and accelerator respectively. The synthesized nanoparticles have been characterized by a FESEM study, X‐ray diffractometry, Raman spectroscopy and UV‐vis spectroscopy. The colloidal sols of the silver nanoparticles in a biop...

  10. Natural analogue studies of the role of colloids, natural organics and microorganisms on radionuclide transport

    International Nuclear Information System (INIS)

    McCarthy, J.F.

    1994-01-01

    Colloids may be important as a geochemical transport mechanism for radionuclides at geological repositories if they are (1) present in the groundwater, (2) stable with respect to both colloidal and chemical stabilities, (3) capable of adsorbing radionuclides, especially if the sorption is irreversible, and (4) mobile in the subsurface. The available evidence from natural analogue and other field studies relevant to these issues is reviewed, as is the potential role of mobile microorganisms (open-quotes biocolloidsclose quotes) on radionuclide migration. Studies have demonstrated that colloids are ubiquitous in groundwater, although colloid concentrations in deep, geochemically stable systems may be too low to affect radionuclide transport. However, even low colloid populations cannot be dismissed as a potential concern because colloids appear to be stable, and many radionuclides that adsorb to colloids are not readily desorbed over long periods. Field studies offer somewhat equivocal evidence concerning colloid mobility and cannot prove or disprove the significance of colloid transport in the far-field environment. Additional research is needed at new sites to properly represent a repository far-field. Performance assessment would benefit from natural analogue studies to examine colloid behavior at sites encompassing a suite of probable groundwater chemistries and that mimic the types of formations selected for radioactive waste repositories

  11. Liquid crystal colloids

    CERN Document Server

    Muševič, Igor

    2017-01-01

    This book brings together the many concepts and discoveries in liquid crystal colloids contributed over the last twenty years and scattered across numerous articles and book chapters. It provides both a historical overview of the development of the field and a clear perspective on the future applications in photonics. The book covers all phenomena observed in liquid crystal colloids with an emphasis on experimental tools and applications of topology in condensed matter, as well as practical micro-photonics applications. It includes a number of spectacular manifestations of new topological phenomena not found or difficult to observe in other systems. Starting from the early works on nematic colloids, it explains the basics of topological defects in ordered media, charge and winding, and the elastic forces between colloidal particles in nematics. Following a detailed description of experimental methods, such as optical tweezing and particle tracking, the book eases the reader into the theoretical part, which de...

  12. Liquid Crystal Colloids

    Science.gov (United States)

    Smalyukh, Ivan I.

    2018-03-01

    Colloids are abundant in nature, science, and technology, with examples ranging from milk to quantum dots and the colloidal atom paradigm. Similarly, liquid crystal ordering is important in contexts ranging from biological membranes to laboratory models of cosmic strings and liquid crystal displays in consumer devices. Some of the most exciting recent developments in both of these soft matter fields emerge at their interface, in the fast-growing research arena of liquid crystal colloids. Mesoscale self-assembly in such systems may lead to artificial materials and to structures with emergent physical behavior arising from patterning of molecular order and nano- or microparticles into precisely controlled configurations. Liquid crystal colloids show exceptional promise for new discovery that may impinge on composite material fabrication, low-dimensional topology, photonics, and so on. Starting from physical underpinnings, I review the state of the art in this fast-growing field, with a focus on its scientific and technological potential.

  13. Antimicrobial effects of zinc oxide nanoparticles modified with silver

    International Nuclear Information System (INIS)

    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)

  14. Antimicrobial effects of zinc oxide nanoparticles modified with silver

    Energy Technology Data Exchange (ETDEWEB)

    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)

  15. Filtration of polydispersed colloids

    International Nuclear Information System (INIS)

    Nuttall, H.E.

    1988-01-01

    In this study, the dynamic microscopic form of the population balance model is applied to the problem of polydispersed particle capture in one spatial diffusion. This mathematical modeling approach can be applied to the difficult and potentially important problem of particulate (radiocolloid) transport in the groundwater surrounding a nuclear waste disposal site. To demonstrate the population balance methodology, the equations were developed and used to investigate transport and capture of polydispersed colloids in packed columns. Modeling simulations were compared to experimental column data. The multidimensional form of the population balance equation was used to analyze the transport and capture of polydispersed colloids. A numerical model was developed to describe transport of polydispersed colloids through a one-dimensional porous region. The effects of various size distributions were investigated in terms of capture efficiency. For simulating the column data, it was found by trial and error that as part of the population balance model a linear size dependent filtration function gave a good fit to the measured colloid concentration profile. The effects of constant versus size dependent filtration coefficients were compared and the differences illustrated by the calculated colloid profile within the column. Also observed from the model calculations was the dramatically changing liquid-phase colloid-size distribution which was plotted as a function of position down the column. This modeling approach was excellent for describing and understanding microscopic filtration in porous media

  16. Interaction between the surface of the silver nanoparticles prepared by γ-irradiation and organic molecules containing thiol group

    International Nuclear Information System (INIS)

    Choi, S.-H.; Lee, S.-H.; Hwang, Y.-M.; Lee, K.-P.; Kang, H.-D.

    2003-01-01

    The colloidal silver nanoparticles were prepared by the γ-irradiation of silver nitrate (AgNO 3 ) in a mixture solution of water and 2-propanol in the presence of poly(vinylpyrrolidone) as a colloidal stabilizer. The Ag colloids obtained by γ-irradiation were characterized by use of XRD and TEM. The surface of the Ag colloids were modified by use of mercaptosuccinic acid (MSA), (D)-cysteine (Cys), and (L)-Cys, respectively. The MSA and (L)-Cys-capped Ag colloids were aggregated because of hydrogen bonding of the carboxylic acid and amino acid group, respectively. From the analysis by CD spectroscopy, it was shown that chiral-enhanced phenomena were obtained in (L)- and (D)-Cys-capped Ag colloids

  17. Formation and stability of aluminosilicate colloids by coprecipitation

    Energy Technology Data Exchange (ETDEWEB)

    Putri, Kirana Yuniati

    2011-02-15

    Colloids are ubiquitous in natural waters. Colloid-facilitated migration is of importance in safety assessment of a nuclear waste disposal. Aluminosilicate colloids are considered to be the kernel of aquatic colloids. Their stability is affected by a number of geochemical parameters. This work aims to study qualitatively and quantitatively the stability of aluminosilicate colloids formed by coprecipitation under various geochemical conditions, i.e. pH, concentration of Al and Si metal ions, ionic strength, and omnipresent cations (Na{sup +}, Ca{sup 2+}, and Mg{sup 2+}). The work is performed by colorimetric method and laser-induced breakdown detection (LIBD). Two consecutive phase separations at 450 nm and 1 kDa are applied to separate the precipitates and colloids from the ionic species. By means of colorimetry, Si and Al can be detected down to 5.8 x10{sup -8} M and 7.4x10{sup -7} M, respectively. On the other hand, LIBD is able to quantify the colloidal size and its number density down to several ppt. Depending on the concentration of Al and Si metal ions, the formation trend of aluminosilicate colloid changes following its solubility curve. The lower the concentration, the higher the pH range in which the colloids start to emerge. Furthermore, the colloids are stable at higher Al and Si concentration and at low ionic strength. In the low pH range, cations provide different effects at low and high ionic strengths. At high ionic strength, the colloids are stable in the presence of a larger cation, while all cations exhibit similar effects at low ionic strength. However, in the high pH range, valence seems to have a stronger effect than ionic radius; colloids are more stable in the presence of monovalent cations than divalent ones. Meanwhile, XRD shows non- and/or poor crystalline structure of the aluminosilicate species. Nevertheless, results from XPS may suggest that the chemical composition (Si/Al ∼ 0.6) of the aluminosilicate precipitates is sillimanite or

  18. An evidence-based environmental perspective of manufactured silver nanoparticle in syntheses and applications: A systematic review and critical appraisal of peer-reviewed scientific papers

    International Nuclear Information System (INIS)

    Tolaymat, Thabet M.; El Badawy, Amro M.; Genaidy, Ash; Scheckel, Kirk G.; Luxton, Todd P.; Suidan, Makram

    2010-01-01

    research articles. Data and information extraction relied on the type of synthesis methods, that is, synthesized silver nanoparticles in general and specific applications, nanocomposites, and bimetallic techniques. The following items were gathered for: type of silver salt, solvent, reducing agent, stabilizing agent, size, and type of application/nanocomposite/bimetallic, and template (for nanocomposites). The description of evidence was presented in tabular format. The critical appraisal was analyzed in graphical format and discussed. Results: An analysis of the scientific literature suggests that most synthesis processes produce spherical silver nanoparticles with less than 20 nm diameter. Silver nanoparticles are often synthesized via reduction of AgNO 3 , dissolution in water, and utilization of reductants also acting as capping or stabilizing agents for the control of particle size to ensure a relatively stable suspension. Two of the most commonly used reductants and stabilizing agents are NaBH 4 and citrate which yield particles with a negative surface charge over the environmental pH range (3-10). The environmental perspectives of these parameters are discussed. Concluding remarks: It is expected that the antibacterial property of bulk silver is carried over and perhaps enhanced, to silver nanoparticles. Therefore, when one examines the environmental issues associated with the manufacture and use of silver nanoparticle-based products, the antibacterial effects should always be taken into account particularly at the different stages of the product lifecycle. Currently, there are two arguments in the scientific literature about the mechanisms of antimicrobial properties of silver nanoparticles as they relate to colloidal silver particles and inonic silver. Methodologies of risk assessment and control have to account for both arguments.

  19. An evidence-based environmental perspective of manufactured silver nanoparticle in syntheses and applications: A systematic review and critical appraisal of peer-reviewed scientific papers

    Energy Technology Data Exchange (ETDEWEB)

    Tolaymat, Thabet M., E-mail: tolaymat.thabet@epa.gov [USEPA Office of Research and Development, National Risk Management Laboratory, 26 West Martin Luther King Drive, Cincinnati, OH 45224 (United States); El Badawy, Amro M. [Dept. of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, OH (United States); Genaidy, Ash [WorldTek Inc, Cincinnati, OH (United States); Scheckel, Kirk G.; Luxton, Todd P. [USEPA Office of Research and Development, National Risk Management Laboratory, 26 West Martin Luther King Drive, Cincinnati, OH 45224 (United States); Suidan, Makram [Dept. of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, OH (United States)

    2010-02-01

    research articles. Data and information extraction relied on the type of synthesis methods, that is, synthesized silver nanoparticles in general and specific applications, nanocomposites, and bimetallic techniques. The following items were gathered for: type of silver salt, solvent, reducing agent, stabilizing agent, size, and type of application/nanocomposite/bimetallic, and template (for nanocomposites). The description of evidence was presented in tabular format. The critical appraisal was analyzed in graphical format and discussed. Results: An analysis of the scientific literature suggests that most synthesis processes produce spherical silver nanoparticles with less than 20 nm diameter. Silver nanoparticles are often synthesized via reduction of AgNO{sub 3}, dissolution in water, and utilization of reductants also acting as capping or stabilizing agents for the control of particle size to ensure a relatively stable suspension. Two of the most commonly used reductants and stabilizing agents are NaBH{sub 4} and citrate which yield particles with a negative surface charge over the environmental pH range (3-10). The environmental perspectives of these parameters are discussed. Concluding remarks: It is expected that the antibacterial property of bulk silver is carried over and perhaps enhanced, to silver nanoparticles. Therefore, when one examines the environmental issues associated with the manufacture and use of silver nanoparticle-based products, the antibacterial effects should always be taken into account particularly at the different stages of the product lifecycle. Currently, there are two arguments in the scientific literature about the mechanisms of antimicrobial properties of silver nanoparticles as they relate to colloidal silver particles and inonic silver. Methodologies of risk assessment and control have to account for both arguments.

  20. Actinide colloid generation in groundwater

    International Nuclear Information System (INIS)

    Kim, J.I.

    1990-05-01

    The progress made in the investigation of actinide colloid generation in groundwaters is summarized and discussed with particular examples relevant to an understanding of the migration behaviour of actinides in natural aquifer systems. The first part deals with the characterization of colloids: groundwater colloids, actinide real-colloids and actinide pseudocolloids. The second part concentrates on the generation processes and migration behaviour of actinide pseudocolloids, which are discussed with some notable experimental examples. Importance is stressed more on the chemical aspects of the actinide colloid generation in groundwater. This work is a contribution to the CEC project MIRAGE II, particularly, to research area: complexation and colloids. (orig.)

  1. Field-scale colloid migration experiments in a granite fracture

    International Nuclear Information System (INIS)

    Vilks, P.; Frost, L.H.; Bachinski, D.B.

    1997-01-01

    An understanding of particle migration in fractured rock, required to assess the potential for colloid-facilitated transport of radionuclides, can best be evaluated when the results of laboratory experiments are demonstrated in the field. Field-scale migration experiments with silica colloids were carried out at AECL's Underground Research Laboratory (URL), located in southern Manitoba, to develop the methodology for large-scale migration experiments and to determine whether colloid transport is possible over distances up to 17 m. In addition, these experiments were designed to evaluate the effects of flow rate and flow path geometry, and to determine whether colloid tracers could be used to provide additional information on subsurface transport to that provided by conservative tracers alone. The colloid migration studies were carried out as part of AECL's Transport Properties in Highly Fractured Rock Experiment, the objective of which was to develop and demonstrate methods for evaluating the solute transport characteristics of zones of highly fractured rock. The experiments were carried out within fracture zone 2 as two-well recirculating, two-well non-recirculating, and convergent flow tests, using injection rates of 5 and 101 min -1 . Silica colloids with a 20 nm size were used because they are potentially mobile due to their stability, small size and negative surface charge. The shapes of elution profiles for colloids and conservative tracers were similar, demonstrating that colloids can migrate over distances of 17 m. The local region of drawdown towards the URL shaft affected colloid migration and, to a lesser extent, conservative tracer migration within the flow field established by the two-well tracer tests. These results indicate that stable colloids, with sizes as small as 20 nm, have different migration properties from dissolved conservative tracers. (author)

  2. Silver linings.

    Science.gov (United States)

    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.

  3. Green synthesis and characterization of silver nanoparticles using Artemisia absinthium aqueous extract — A comprehensive study

    International Nuclear Information System (INIS)

    Ali, Mohammad; Kim, Bosung; Belfield, Kevin D.; Norman, David; Brennan, Mary; Ali, Gul Shad

    2016-01-01

    Unlike chemical synthesis, biological synthesis of nanoparticles is gaining tremendous interest, and plant extracts are preferred over other biological sources due to their ample availability and wide array of reducing metabolites. In this project, we investigated the reducing potential of aqueous extract of Artemisia absinthium L. for synthesizing silver nanoparticles (AgNPs). Optimal synthesis of AgNPs with desirable physical and biological properties was investigated using ultra violet–visible spectroscopy (UV–vis), dynamic light scattering (DLS), transmission electron microscopy (TEM) and energy-dispersive X-ray analysis (EDX). To determine their appropriate concentrations for AgNP synthesis, two-fold dilutions of silver nitrate (20 to 0.62 mM) and aqueous plant extract (100 to 0.79 mg ml"−"1) were reacted. The results showed that silver nitrate (2 mM) and plant extract (10 mg ml"−"1) mixed in different ratios significantly affected size, stability and yield of AgNPs. Extract to AgNO_3 ratio of 6:4 v/v resulted in the highest conversion efficiency of AgNO_3 to AgNPs, with the particles in average size range of less than 100 nm. Furthermore, the direct imaging of synthesized AgNPs by TEM revealed polydispersed particles in the size range of 5 to 20 nm. Similarly, nanoparticles with the characteristic peak of silver were observed with EDX. This study presents a comprehensive investigation of the differential behavior of plant extract and AgNO_3 to synthesize biologically stable AgNPs. - Graphical abstract: Aqueous extract from Artemisia absinthium when used in appropriate ratio (shown in Eppendorf tubes and microtiter plate) is highly active in reducing elemental silver to colloidal silver nanoparticles in the 5–20 nm size range (shown in TEM image, bottom left panel; DLS histogram, upper left panel; EDX analysis, bottom right panel). - Highlights: • Artemisia absinthium extract provides excellent reducing potential for biosynthesis of silver

  4. Green synthesis and characterization of silver nanoparticles using Artemisia absinthium aqueous extract — A comprehensive study

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Mohammad [Mid-Florida Research and Education Center and Department of Plant Pathology, University of Florida/Institute of Food and Agricultural Sciences, 2725 Binion Rd., Apopka, FL 32703 (United States); Kim, Bosung [Department of Chemistry, University of Central Florida, Orlando, FL 32816 (United States); Belfield, Kevin D. [Department of Chemistry, University of Central Florida, Orlando, FL 32816 (United States); College of Science and Liberal Arts, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Norman, David; Brennan, Mary [Mid-Florida Research and Education Center and Department of Plant Pathology, University of Florida/Institute of Food and Agricultural Sciences, 2725 Binion Rd., Apopka, FL 32703 (United States); Ali, Gul Shad, E-mail: gsali@ufl.edu [Mid-Florida Research and Education Center and Department of Plant Pathology, University of Florida/Institute of Food and Agricultural Sciences, 2725 Binion Rd., Apopka, FL 32703 (United States)

    2016-01-01

    Unlike chemical synthesis, biological synthesis of nanoparticles is gaining tremendous interest, and plant extracts are preferred over other biological sources due to their ample availability and wide array of reducing metabolites. In this project, we investigated the reducing potential of aqueous extract of Artemisia absinthium L. for synthesizing silver nanoparticles (AgNPs). Optimal synthesis of AgNPs with desirable physical and biological properties was investigated using ultra violet–visible spectroscopy (UV–vis), dynamic light scattering (DLS), transmission electron microscopy (TEM) and energy-dispersive X-ray analysis (EDX). To determine their appropriate concentrations for AgNP synthesis, two-fold dilutions of silver nitrate (20 to 0.62 mM) and aqueous plant extract (100 to 0.79 mg ml{sup −1}) were reacted. The results showed that silver nitrate (2 mM) and plant extract (10 mg ml{sup −1}) mixed in different ratios significantly affected size, stability and yield of AgNPs. Extract to AgNO{sub 3} ratio of 6:4 v/v resulted in the highest conversion efficiency of AgNO{sub 3} to AgNPs, with the particles in average size range of less than 100 nm. Furthermore, the direct imaging of synthesized AgNPs by TEM revealed polydispersed particles in the size range of 5 to 20 nm. Similarly, nanoparticles with the characteristic peak of silver were observed with EDX. This study presents a comprehensive investigation of the differential behavior of plant extract and AgNO{sub 3} to synthesize biologically stable AgNPs. - Graphical abstract: Aqueous extract from Artemisia absinthium when used in appropriate ratio (shown in Eppendorf tubes and microtiter plate) is highly active in reducing elemental silver to colloidal silver nanoparticles in the 5–20 nm size range (shown in TEM image, bottom left panel; DLS histogram, upper left panel; EDX analysis, bottom right panel). - Highlights: • Artemisia absinthium extract provides excellent reducing potential for

  5. Colloids and composite materials Au/Pvp and Ag/Pvp generated by laser ablation in polymeric liquid environment

    Energy Technology Data Exchange (ETDEWEB)

    Larez, J.; Rojas, C. [Universidad Central de Venezuela, Faculty of Science, Center of Experimental Solid State Physics, Paseo Los Ilustres, Los Chaguaramos, Apdo. Postal 20513, Caracas 1020-A (Venezuela, Bolivarian Republic of); Castell, R., E-mail: jlarez@fisica.ciens.ucv.ve [Universidad Simon Bolivar, Department of Physics, Plasma and Laser Spectroscopy Laboratory, Valle de Sartenejas, Baruta, Apdo. Postal 89000, Caracas 1080-A (Venezuela, Bolivarian Republic of)

    2016-11-01

    Pulsed laser ablation of silver and gold targets, immersed in a polymeric solution of Polyvinylpyrrolidone (Pvp), is used to generate colloids and composite metal-polymer. Solutions of Pvp in deionized water at different concentrations are employed. Two Pvp number average molecular weights were considered, 10000 g/mol and 55000 g/mol. The high purity targets are irradiated between 20 min and 40 min with the third harmonic (Thg) (λ = 335 nm) of a Nd:YAG laser operating at a rate of 10 Hz with pulses of 8 ns. Optical spectroscopy in UV and vis regions, scanning electron microscopy, high resolution scanning electron microscopy and X-ray are used to identify and determine the shape and size of the produced particles. Very stable sub-micrometric spherical particles for Au/Pvp and Ag/Pvp samples are obtained with diameters of 0.72 μm and 0.40 μm, respectively. The preparation of colloids is performed in one step and no surfactant or dispersing agent is used in this process. (Author)

  6. Silver nitrate based gel dosimeter

    International Nuclear Information System (INIS)

    Titus, D; Samuel, E J J; Srinivasan, K; Roopan, S M; Madhu, C S

    2017-01-01

    A new radiochromic gel dosimeter based on silver nitrate and a normoxic gel dosimeter was investigated using UV-Visible spectrophotometry in the clinical dose range. Gamma radiation induced the synthesis of silver nanoparticles in the gel and is confirmed from the UV-Visible spectrum which shows an absorbance peak at around 450 nm. The dose response function of the dosimeter is found to be linear upto12Gy. In addition, the gel samples were found to be stable which were kept under refrigeration. (paper)

  7. Impact of Redox Reactions on Colloid Transport in Saturated Porous Media: An Example of Ferrihydrite Colloids Transport in the Presence of Sulfide.

    Science.gov (United States)

    Liao, Peng; Yuan, Songhu; Wang, Dengjun

    2016-10-18

    Transport of colloids in the subsurface is an important environmental process with most research interests centered on the transport in chemically stable conditions. While colloids can be formed under dynamic redox conditions, the impact of redox reactions on their transport is largely overlooked. Taking the redox reactions between ferrihydrite colloids and sulfide as an example, we investigated how and to what extent the redox reactions modulated the transport of ferrihydrite colloids in anoxic sand columns over a range of environmentally relevant conditions. Our results reveal that the presence of sulfide (7.8-46.9 μM) significantly decreased the breakthrough of ferrihydrite colloids in the sand column. The estimated travel distance of ferrihydrite colloids in the absence of sulfide was nearly 7-fold larger than that in the presence of 46.9 μM sulfide. The reduced breakthrough was primarily attributed to the reductive dissolution of ferrihydrite colloids by sulfide in parallel with formation of elemental sulfur (S(0)) particles from sulfide oxidation. Reductive dissolution decreased the total mass of ferrihydrite colloids, while the negatively charged S(0) decreased the overall zeta potential of ferrihydrite colloids by attaching onto their surfaces and thus enhanced their retention in the sand. Our findings provide novel insights into the critical role of redox reactions on the transport of redox-sensitive colloids in saturated porous media.

  8. Search for an optimal colloid for sentinel node imaging

    International Nuclear Information System (INIS)

    Imam, S.K.; Killingsworth, M.

    2005-01-01

    This study aims at finding a cost-effective and stable colloid of appropriate size to replace antimony sulfide colloid which is now in routine use in Australia for sentinel lymph node (SLN) imaging. For this reason we evaluated three colloids; namely phytate, hepatate and stannous fluoride (SnF 2 ). As colloids of particle size of 100-200 nm seem to be appropriate for sentinel node imaging, the three radiolabelled colloid preparations were filtered through 0.1 and 0.22 μm filters and then studied on electron microscope. Electron microscopy showed that unlike phytate, the particle size of the hepatate and SnF 2 colloids did not increase beyond the size limit of 200 nm over a period of as long as 26 hours. Instead, they remained well within the size limits chosen. The stability of particle size is required for intra-operative gamma probe lymphatic mapping that sometimes may be performed on the following day. Hepatate and SnF 2 colloids appeared to be more suited for sentinel lymph node imaging, the latter being an inhouse product is more cost-effective. Further studies based on nodal uptake and the behavior of these two radiopharmaceuticals in animals is suggested in order to evaluate their potential for future wide-spread application in human sentinel node imaging. (author)

  9. Experimental Studies to Evaluate the Role of Colloids on the Radionuclide Migration in a Crystalline Medium

    International Nuclear Information System (INIS)

    Albarran, Nairoby; Missana, Tiziana; Alonso, Ursula; Garcia-Gutierrez, Miguel; Mingarro, Manuel; Lopez, Trinidad

    2008-01-01

    In a deep geological repository (DGR) of high level radioactive waste, all the possible phenomena affecting radionuclide migration have to be studied to assess its security over time. Colloids can play an important role for contaminant transport if the following conditions are fulfilled: colloids exist in a non negligible concentration, they are mobile and stable in the environment of interest, and they are able to adsorb radionuclides irreversibly. In this study, different transport experiments where performed to improve the knowledge on the main mechanisms affecting the radionuclide migration in the presence of colloids in a crystalline medium. Firstly, colloid stability was analysed and then transport experiments in an artificial granite longitudinal fracture were carried out. Synthetic colloids of different size and bentonite clay colloids were used to evaluate the effects of colloid size, charge, and water flow rate on their mobility. Results showed that both major importance of the water flow rate on the mobility of colloids and their recovery and a higher interaction of smaller particles with the surface. Finally, the migration behaviour of Sr, and Sr adsorbed onto bentonite colloids was compared. The elution curves of Sr adsorbed onto colloid were significantly different from the ones of Sr alone, pointing out that sorption/desorption mechanisms must be taken into account to understand the radionuclide migration in the fracture in the presence of colloids. (authors)

  10. Analytic solutions for colloid transport with time- or depth-dependent retention in porous media

    Science.gov (United States)

    Elucidating and quantifying the transport of industrial nanoparticles (e.g. silver, carbon nanotubes, and graphene oxide) and other colloid-size particles such as viruses and bacteria is important to safeguard and manage the quality of the subsurface environment. Analytic solutions were derived for...

  11. Controlled assembly of jammed colloidal shells on fluid droplets

    Science.gov (United States)

    Subramaniam, Anand Bala; Abkarian, Manouk; Stone, Howard A.

    2005-07-01

    Assembly of colloidal particles on fluid interfaces is a promising technique for synthesizing two-dimensional microcrystalline materials useful in fields as diverse as biomedicine, materials science, mineral flotation and food processing. Current approaches rely on bulk emulsification methods, require further chemical and thermal treatments, and are restrictive with respect to the materials used. The development of methods that exploit the great potential of interfacial assembly for producing tailored materials have been hampered by the lack of understanding of the assembly process. Here we report a microfluidic method that allows direct visualization and understanding of the dynamics of colloidal crystal growth on curved interfaces. The crystals are periodically ejected to form stable jammed shells, which we refer to as colloidal armour. We propose that the energetic barriers to interfacial crystal growth and organization can be overcome by targeted delivery of colloidal particles through hydrodynamic flows. Our method allows an unprecedented degree of control over armour composition, size and stability.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  13. Piperidine adsorption on two different silver electrodes: A combined surface enhanced Raman spectroscopy and density functional theory study

    International Nuclear Information System (INIS)

    Hao Yanling; Fang Yan

    2007-01-01

    The surface enhanced Raman scattering (SERS) spectra of piperidine in silver colloid solution, on roughened silver electrode and on roughened silver electrode modified with silver nanoparticles were studied, and the high-quality SERS spectra of piperidine on roughened silver electrode modified with silver nanoparticles were obtained for the first time. Surface selection rules derived from the EM enhancement model were employed to deduce piperidine orientations on the different surfaces. On the basis of this, two models of piperidine adsorbed on the surface of the silver nanoparticles were built, and DFT-B3PW91/LanL2dz was applied to calculate the Raman frequencies. It proves that, at higher potential values, the piperidine is perpendicularly standing on the roughened silver electrode surface though its lone-electron pair, but in silver colloid solution and on the silver nanoparticles modified silver electrode the piperidine molecular lies flat on the silver surface. In the meantime, the potential dependent SERS of piperidine on the modified electrode were studied

  14. Effects of electrolytes and surfactants on the morphology and stability of advanced silver nano-materials

    Energy Technology Data Exchange (ETDEWEB)

    Obaid, Abdullah Yousif; AL-Thabaiti, Shaeel Ahmed; El-Mossalamy, E.H. [Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21413 (Saudi Arabia); Hussain, Javed Ijaz [Nano-science Research Lab, Department of Chemistry, Jamia Millia Islamia (Central University), New Delhi 110 025 (India); Khan, Zaheer, E-mail: drkhanchem@yahoo.co.in [Nano-science Research Lab, Department of Chemistry, Jamia Millia Islamia (Central University), New Delhi 110 025 (India)

    2013-03-15

    Highlights: ► Stoichiometric ratio of S{sub 2}O{sub 3}{sup 2−} and Ag{sup +} ions are responsible to the formation of prefect transparent yellow colored silver sol. ► Higher S{sub 2}O{sub 3}{sup 2−} concentrations has damping effect. ► Head group of the surfactants and nature of the electrolytes have significant effect on the stability of silver nanoparticles. - Abstract: The impact of electrolytes, stabilizing and/or capping agents on morphology of colloidal silver nano-materials (AgNPs) has been studied spectroscopically. Sodium thiosulfate acts as reducing-, stabilizing- and damping-agents. Stoichiometric ratios of S{sub 2}O{sub 3}{sup 2−} and Ag{sup +} ions were responsible to the formation stable and prefect transparent dark yellow colored AgNPs. The S{sub 2}O{sub 3}{sup 2−}-stabilized AgNPs were significantly more stable in inorganic electrolytes (NaNO{sub 3}, Na{sub 2}SO{sub 4}, Na{sub 2}CO{sub 3} and KBr). S{sub 2}O{sub 3}{sup 2−} is adsorbed more strongly than the used other anions. The addition of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) has significant effects on the absorbance of S{sub 2}O{sub 3}{sup 2−}-stabilized AgNPs which can be rationalized in terms of electrostatic attraction and repulsion between the adsorbed S{sub 2}O{sub 3}{sup 2−} ions on to the surface of AgNPs and cationic and/or anionic head groups of used surfactants, respectively. Transmission electron microscopy images suggest that AgNPs are polydispersed, spherical and exhibiting an interesting irregular morphology.

  15. Green synthesis and antimicrobial activity of monodisperse silver nanoparticles synthesized using Ginkgo Biloba leaf extract

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Yan-yu [School of Food and Biological Engineering, Shaanxi University of Science & Technology, Xi' an 710021 (China); Yang, Hui, E-mail: 549456369@qq.com [School of Food and Biological Engineering, Shaanxi University of Science & Technology, Xi' an 710021 (China); Wang, Tao [School of Food and Biological Engineering, Shaanxi University of Science & Technology, Xi' an 710021 (China); Wang, Chuang [Department of Highway & Bridge, Shaanxi Railway Institute, Weinan 714000 (China)

    2016-11-25

    Various parts of plants can be used as a raw material for the synthesis of nanoparticles, which is eco-friendly way and does not involve any harmful chemicals. In this project, Ginkgo biloba leaf, an abundantly available medicinal plant in China, was for the first time adopted as a reducing and stabilizing agent to synthesize smaller sized and stable silver nanoparticles (AgNPs). To improve the quality of AgNPs, the reduction was accelerated by changing the concentrations of initial Ag{sup +} (0.02, 0.04, 0.06 and 0.08 mol/L) of the reaction mixture consisting of silver nitrate solution (AgNO{sub 3}) and Ginkgo biloba leaf extract. At pH = 8 and lower AgNO{sub 3} concentration (0.02 mol/L), a colloid consisting of well-dispersed spherical nanoparticles was obtained. The synthesized nanocrystals were successfully characterized by UV–vis and XRD. TEM images revealed the size of the spherical AgNPs ranged between 10–16 nm. FTIR analysis revealed that biological macromolecules with groups of −NH{sub 2}, −OH, and others were distributed on the surface of the nanoparticles. The biosynthesized AgNPs exhibited good antibacterial activities against gram-negative bacteria and gram-positive bacteria. Compared to traditional chemical methods, Ginkgo biloba leaf extract provides an easy green synthetical way. It is anticipated that the biosynthesized AgNPs can be used in areas such as cosmetics, foods and medical applications. - Highlights: • Monodisperse silver nanoparticles were first prepared by a green synthetical way through Ginkgo Biloba leaf extract. • The synthesized AgNPs is of high crystallinity, stable and good dispersion with smaller sizes between 10–16 nm. • The achieved AgNPs exhibits good antibacterial activities. • The biosynthesis method is advantageous for its cost effectiveness, availability, portability, nontoxic and environmentally benign.

  16. Green synthesis and antimicrobial activity of monodisperse silver nanoparticles synthesized using Ginkgo Biloba leaf extract

    International Nuclear Information System (INIS)

    Ren, Yan-yu; Yang, Hui; Wang, Tao; Wang, Chuang

    2016-01-01

    Various parts of plants can be used as a raw material for the synthesis of nanoparticles, which is eco-friendly way and does not involve any harmful chemicals. In this project, Ginkgo biloba leaf, an abundantly available medicinal plant in China, was for the first time adopted as a reducing and stabilizing agent to synthesize smaller sized and stable silver nanoparticles (AgNPs). To improve the quality of AgNPs, the reduction was accelerated by changing the concentrations of initial Ag + (0.02, 0.04, 0.06 and 0.08 mol/L) of the reaction mixture consisting of silver nitrate solution (AgNO 3 ) and Ginkgo biloba leaf extract. At pH = 8 and lower AgNO 3 concentration (0.02 mol/L), a colloid consisting of well-dispersed spherical nanoparticles was obtained. The synthesized nanocrystals were successfully characterized by UV–vis and XRD. TEM images revealed the size of the spherical AgNPs ranged between 10–16 nm. FTIR analysis revealed that biological macromolecules with groups of −NH 2 , −OH, and others were distributed on the surface of the nanoparticles. The biosynthesized AgNPs exhibited good antibacterial activities against gram-negative bacteria and gram-positive bacteria. Compared to traditional chemical methods, Ginkgo biloba leaf extract provides an easy green synthetical way. It is anticipated that the biosynthesized AgNPs can be used in areas such as cosmetics, foods and medical applications. - Highlights: • Monodisperse silver nanoparticles were first prepared by a green synthetical way through Ginkgo Biloba leaf extract. • The synthesized AgNPs is of high crystallinity, stable and good dispersion with smaller sizes between 10–16 nm. • The achieved AgNPs exhibits good antibacterial activities. • The biosynthesis method is advantageous for its cost effectiveness, availability, portability, nontoxic and environmentally benign.

  17. Green Synthesis of Silver Nanoparticles Using Pimpinella anisum L. Seed Aqueous Extract and Its Antioxidant Activity

    Directory of Open Access Journals (Sweden)

    Hashem Akhlaghi

    2015-09-01

    Full Text Available An aqueous extract of Pimpinella anisum was used for green synthesis of silver nanoparticles by bio reduction of an aqueous solution of silver nitrate. Silver nanoparticles were characterized by UV–Vis spectrometry, Fourier transform infrared spectroscopy (FTIR, X-ray diffraction (XRD analysis, scanning electron microscopy (SEM and energy-dispersive X-ray analysis (EDAX. The increase in absorption at 420 nm was used for recording the formation of a colloidal suspension of silver nanoparticles. The binding properties of the capped Ag nanoparticles synthesized from aqueous extract of P. anisum were analyzed by FTIR. XRD studies revealed that most of the nanoparticles were cubic and face centered cubic in shape. SEM analysis showed the size and shape of silver nanoparticles and EDAX confirmed the presence of silver. The synthesized silver nanoparticles showed DPPH free radical scavenging activity.

  18. Medical applications of colloids

    CERN Document Server

    Matijevic, Egon

    2008-01-01

    The first book of its type on the medical and biomedical applications of colloids, although there are some related titles on different topicsDiscusses the effects of uniform particles in drug formulations and releaseEvaluates particle transport and deposition in the human body.

  19. Simulation of dense colloids

    NARCIS (Netherlands)

    Herrmann, H.J.; Harting, J.D.R.; Hecht, M.; Ben-Naim, E.

    2008-01-01

    We present in this proceeding recent large scale simulations of dense colloids. On one hand we simulate model clay consisting of nanometric aluminum oxide spheres in water using realistic DLVO potentials and a combination of MD and SRD. We find pronounced cluster formation and retrieve the shear

  20. Colloid Release From Differently Managed Loess Soil

    DEFF Research Database (Denmark)

    Vendelboe, Anders Lindblad; Schjønning, Per; Møldrup, Per

    2012-01-01

    The content of water-dispersible colloids (WDC) in a soil can have a major impact on soil functions, such as permeability to water and air, and on soil strength, which can impair soil fertility and workability. In addition, the content of WDC in the soil may increase the risk of nutrient loss...... and of colloid-facilitated transport of strongly sorbing compounds. In the present study, soils from the Bad Lauchsta¨dt longterm static fertilizer experiment with different management histories were investigated to relate basic soil properties to the content of WDC, the content of water-stable aggregates (WSA......), and aggregate tensile strength. Our studies were carried out on soils on identical parent material under controlled management conditions, enabling us to study the long-term effects on soil physical properties with few explanatory variables in play. The content of WDC and the amount of WSA were measured...

  1. Russell-Silver syndrome

    Science.gov (United States)

    Silver-Russell syndrome; Silver syndrome; RSS; Russell-Silver syndrome ... One in 10 children with this syndrome has a problem involving chromosome 7. In other people with the syndrome, it may affect chromosome 11. Most of the time, it ...

  2. Optimizing colloidal nanocrystals for applications

    International Nuclear Information System (INIS)

    Sytnyk, M.

    2015-01-01

    In the scientific literature colloidal nanocrystals are presented as promising materials for multiple applications, in areas covering optoelectronics, photovoltaics, spintronics, catalysis, and bio-medicine. On the marked are, however, only a very limited number of examples found, indeed implementing colloidal nanocrystals. Thus the scope of this thesis was to modify nanocrystals and to tune their properties to fulfill specific demands. While some modifications could be achieved by post synthetic treatments, one key problem of colloidal nanocrystals, hampering there widespread application is the toxicity of their constituents. To develop nanocrystals from non-toxic materials has been a major goal of this thesis as well. Roughly, the results in this thesis could be subdivided into three parts: (i) the development of ion exchange methods to tailor the properties of metallic and metal-oxide based nanocrystal heterostructures, (ii), the synthesis of semiconductor nanocrystals from non-toxic materials, and (iii) the characterization of the nanocrystals by measurements of their morphology, chemical composition, magnetic-, optical-, and electronic properties. In detail, the thesis is subdivided into an introductory chapter, 4 chapters reporting on scientific results, a chapter reporting the used methods, and the conclusions. The 4 chapters devoted to the scientific results correspond to manuscripts, which are either currently in preparation, or have been published in highly ranked scientific journals such as NanoLetters (chapter 2), ACS Nano (chapter 4), or JACS (chapter 5). Thus, these chapters provide also an extra introduction and conclusion section, as well as separate reference lists. Chapter 2 describes a cation exchange process which is used to tune and improve the magnetic properties of different iron-oxide based colloidal nanocrystal-heterostructures. The superparamagnetic blocking temperature, magnetic remanence, and coercivity is tuned by replacing Fe2+ by Co2

  3. Reduction and aggregation of silver in aqueous gelatin and silica suspensions

    International Nuclear Information System (INIS)

    Kapoor, S.; Lawless, D.; Kennepohl, P.; Meisel, D.; Serpone, N.

    1994-01-01

    The investigation of silver reduction and aggregation processes are of specific interest to the photographic industry, which relies heavily on photochemical equivalents of these reactions. Mechanistic insights into the formation of small silver clusters in aqueous solution have been obtained from both pulse and γ-radiolytic studies. This paper examines the reduction of silver ions and the subsequent formation of silver clusters in aqueous gelatin solutions and on colloidal silica particles using the pulse radiolysis technique. The aggregation processes are compared with the parallel reactions in aqueous solutions

  4. Silver nanoprisms self-assembly on differently functionalized silica surface

    International Nuclear Information System (INIS)

    Pilipavicius, J; Chodosovskaja, A; Beganskiene, A; Kareiva, A

    2015-01-01

    In this work colloidal silica/silver nanoprisms (NPRs) composite coatings were made. Firstly colloidal silica sols were synthesized by sol-gel method and produced coatings on glass by dip-coating technique. Next coatings were silanized by (3-Aminopropyl)triethoxysilane (APTES), N-[3-(Trimethoxysilyl)propyl]ethylenediamine (AEAPTMS), (3- Mercaptopropyl)trimethoxysilane (MPTMS). Silver NPRs where synthesized via seed-mediated method and high yield of 94±15 nm average edge length silver NPRs were obtained with surface plasmon resonance peak at 921 nm. Silica-Silver NPRs composite coatings obtained by selfassembly on silica coated-functionalized surface. In order to find the most appropriate silanization way for Silver NPRs self-assembly, the composite coatings were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), water contact angle (CA) and surface free energy (SFE) methods. Results have showed that surface functionalization is necessary to achieve self-assembled Ag NPRs layer. MPTMS silanized coatings resulted sparse distribution of Ag NPRs. Most homogeneous, even distribution composite coatings obtained on APTES functionalized silica coatings, while AEAPTMS induced strong aggregation of Silver NPRs

  5. Enzymatic functionalization of cork surface with antimicrobial hybrid biopolymer/silver nanoparticles.

    Science.gov (United States)

    Francesko, Antonio; Blandón, Lucas; Vázquez, Mario; Petkova, Petya; Morató, Jordi; Pfeifer, Annett; Heinze, Thomas; Mendoza, Ernest; Tzanov, Tzanko

    2015-05-13

    Laccase-assisted assembling of hybrid biopolymer-silver nanoparticles and cork matrices into an antimicrobial material with potential for water remediation is herein described. Amino-functional biopolymers were first used as doping agents to stabilize concentrated colloidal dispersions of silver nanoparticles (AgNP), additionally providing the particles with functionalities for covalent immobilization onto cork to impart a durable antibacterial effect. The solvent-free AgNP synthesis by chemical reduction was carried out in the presence of chitosan (CS) or 6-deoxy-6-(ω-aminoethyl) aminocellulose (AC), leading to simultaneous AgNP biofunctionalization. This approach resulted in concentrated hybrid NP dispersion stable to aggregation and with hydrodynamic radius of particles of about 250 nm. Moreover, laccase enabled coupling between the phenolic groups in cork and amino moieties in the biopolymer-doped AgNP for permanent modification of the material. The antibacterial efficiency of the functionalized cork matrices, aimed as adsorbents for wastewater treatment, was evaluated against Escherichia coli and Staphylococcus aureus during 5 days in conditions mimicking those in constructed wetlands. Both intrinsically antimicrobial CS and AC contributed to the bactericidal effect of the enzymatically grafted on cork AgNP. In contrast, unmodified AgNP were easily washed off from the material, confirming that the biopolymers potentiated a durable antibacterial functionalization of the cork matrices.

  6. Green synthesis and antimicrobial activity of monodisperse silver nanoparticles synthesized using Ginkgo Biloba leaf extract

    Science.gov (United States)

    Ren, Yan-yu; Yang, Hui; Wang, Tao; Wang, Chuang

    2016-11-01

    Various parts of plants can be used as a raw material for the synthesis of nanoparticles, which is eco-friendly way and does not involve any harmful chemicals. In this project, Ginkgo biloba leaf, an abundantly available medicinal plant in China, was for the first time adopted as a reducing and stabilizing agent to synthesize smaller sized and stable silver nanoparticles (AgNPs). To improve the quality of AgNPs, the reduction was accelerated by changing the concentrations of initial Ag+ (0.02, 0.04, 0.06 and 0.08 mol/L) of the reaction mixture consisting of silver nitrate solution (AgNO3) and Ginkgo biloba leaf extract. At pH = 8 and lower AgNO3 concentration (0.02 mol/L), a colloid consisting of well-dispersed spherical nanoparticles was obtained. The synthesized nanocrystals were successfully characterized by UV-vis and XRD. TEM images revealed the size of the spherical AgNPs ranged between 10-16 nm. FTIR analysis revealed that biological macromolecules with groups of sbnd NH2, sbnd OH, and others were distributed on the surface of the nanoparticles. The biosynthesized AgNPs exhibited good antibacterial activities against gram-negative bacteria and gram-positive bacteria. Compared to traditional chemical methods, Ginkgo biloba leaf extract provides an easy green synthetical way. It is anticipated that the biosynthesized AgNPs can be used in areas such as cosmetics, foods and medical applications.

  7. Synthesis and Characterization of Polyethylene Glycol Mediated Silver Nanoparticles by the Green Method

    Directory of Open Access Journals (Sweden)

    Yadollah Abdollahi

    2012-05-01

    Full Text Available The roles of green chemistry in nanotechnology and nanoscience fields are very significant in the synthesis of diverse nanomaterials. Herein, we report a green chemistry method for synthesized colloidal silver nanoparticles (Ag NPs in polymeric media. The colloidal Ag NPs were synthesized in an aqueous solution using silver nitrate, polyethylene glycol (PEG, and β-d-glucose as a silver precursor, stabilizer, and reducing agent, respectively. The properties of synthesized colloidal Ag NPs were studied at different reaction times. The ultraviolet-visible spectra were in excellent agreement with the obtained nanostructure studies performed by transmission electron microscopy (TEM and their size distributions. The Ag NPs were characterized by utilizing X-ray diffraction (XRD, zeta potential measurements and Fourier transform infrared (FT-IR. The use of green chemistry reagents, such as glucose, provides green and economic features to this work.

  8. Liquid radiation detectors based on nano-silver surface plasmon resonance phenomena

    International Nuclear Information System (INIS)

    Puiso, J.; Laurikaitiene, J.; Adliene, D.; Prosycevas, I.

    2010-01-01

    The rapid development of micro- and nano-structures containing silver nano-particles is based on their unique physical properties. Despite the new applications of silver nano-particles in nano-medicine are under heavy discussions, silver nano-particles could be used in liquid radiation detectors thanks to the irradiation-induced surface plasmon resonance (SPR) phenomena observed in the colloidal solutions. Silver nitrate (1 mM AgNO 3 ) and sodium citrate (1 wt% and 5 wt% C 6 H 5 O 7 Na 3 ) were used as precursors for the fabrication of colloidal solutions. Prepared solutions were exposed to gamma-rays from a 60 Co gamma therapy unit 'Rokus-M' to varying absorbed doses, from 2 to 250 Gy. A UV/VIS/NIR spectrometer (Avantes-2048) was used for the measurement of the optical properties (absorbance) of the silver solutions. It was found that an initial absorbed dose of 2 Gy induced the formation of spherical silver nano-particles as it was indicated in the absorbance spectrum of the solution, which had a well-pronounced absorption maximum at the wavelength of 410 nm. There is a potential to measure absorbed doses down to around 20 mGy. The SPR peaks at the wavelengths of 500-700 nm were found at the highest investigated doses > 100 Gy, indicating the presence of silver nano-rods. The colour of colloidal solutions ranged from pale yellow to green and was dependent on the absorbed dose. The investigation has shown that density, size and shape of synthesised silver nano-particles are dependent on the absorbed dose and that shape transformations of the particles due to irradiation are possible. Application of colloidal solutions containing silver nano-particles for dosimetric purposes is discussed on the basis of the obtained results. (authors)

  9. Assessing antibacterial effect of filter media coated with silver nanoparticles against Bacillus spp

    Directory of Open Access Journals (Sweden)

    Mahmood Nafisi Bahabadi

    2016-04-01

    Full Text Available Background: Nanotechnology is a field of applied science and technology covering a broad range of topics. Use of nanotechnology and especially silver nanoparticles in control of bacterial diseases and infections has been studied in the recent years. The aim of the present study was to investigate the in vitro antibacterial effect of filter media coated with silver nanoparticles against Bacillus spp. Materials and methods: In this research, first, the antibacterial effects of silver nanoparticles against mentioned bacteria were evaluated by microdilution method in Broth medium. After confidence of inhibitory effect of colloidal silver nanoparticles, antibacterial effect of filter media coated with silver nanoparticles was evaluated via in vitro microbiology tests (zone of inhibition test and test tube test. Results: Present study showed that colloidal silver nanoparticles have good antimicrobial effects against tested bacteria, so that MIC and MBC of silver nanoparticles for Bacillus spp. were calculated 3.9 and 31.25 mg/L, respectively. Also significant decrease was observed in bacterial growth after exposure to filter media coated with silver nanoparticles in test tube test and  zone of inhibition test (P≤ 5%. Conclusion: The results of this research indicate that filter media coated with silver nanoparticles have considerable antimicrobial effects; therefore they could possibly be used as excellent antibacterial water filters and would have several applications in other sectors.

  10. Preparation of colloidal gold for staining proteins electrotransferred onto nitrocellulose membranes.

    Science.gov (United States)

    Yamaguchi, K; Asakawa, H

    1988-07-01

    This paper describes a simple method of preparing colloidal gold for staining protein blots. Colloidal gold was prepared from 0.005 or 0.01% HAuCl4 by the addition of formalin as a reductant and potassium hydroxide. Staining of small cell carcinoma tissue extract blotted onto nitrocellulose membranes with this colloidal gold solution resulted in the appearance of a large number of clear wine-red bands. The sensitivity of gold staining was 60 times higher than that of Coomassie brilliant blue staining and almost comparable to that of silver staining of proteins in polyacrylamide gel. The sensitivity of this method was also satisfactory in comparison with that of enzyme immunoblotting. The colloidal gold prepared by this method is usable for routine work.

  11. Polypyrrole-silver Nanocomposite: Synthesis and Characterization

    Directory of Open Access Journals (Sweden)

    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.

  12. Patterned Colloidal Photonic Crystals.

    Science.gov (United States)

    Hou, Jue; Li, Mingzhu; Song, Yanlin

    2018-03-01

    Colloidal photonic crystals (PCs) have been well developed because they are easy to prepare, cost-effective, and versatile with regards to modification and functionalization. Patterned colloidal PCs contribute a novel approach to constructing high-performance PC devices with unique structures and specific functions. In this review, an overview of the strategies for fabricating patterned colloidal PCs, including patterned substrate-induced assembly, inkjet printing, and selective immobilization and modification, is presented. The advantages of patterned PC devices are also discussed in detail, for example, improved detection sensitivity and response speed of the sensors, control over the flow direction and wicking rate of microfluidic channels, recognition of cross-reactive molecules through an array-patterned microchip, fabrication of display devices with tunable patterns, well-arranged RGB units, and wide viewing-angles, and the ability to construct anti-counterfeiting devices with different security strategies. Finally, the perspective of future developments and challenges is presented. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Flocking ferromagnetic colloids.

    Science.gov (United States)

    Kaiser, Andreas; Snezhko, Alexey; Aranson, Igor S

    2017-02-01

    Assemblages of microscopic colloidal particles exhibit fascinating collective motion when energized by electric or magnetic fields. The behaviors range from coherent vortical motion to phase separation and dynamic self-assembly. Although colloidal systems are relatively simple, understanding their collective response, especially under out-of-equilibrium conditions, remains elusive. We report on the emergence of flocking and global rotation in the system of rolling ferromagnetic microparticles energized by a vertical alternating magnetic field. By combing experiments and discrete particle simulations, we have identified primary physical mechanisms, leading to the emergence of large-scale collective motion: spontaneous symmetry breaking of the clockwise/counterclockwise particle rotation, collisional alignment of particle velocities, and random particle reorientations due to shape imperfections. We have also shown that hydrodynamic interactions between the particles do not have a qualitative effect on the collective dynamics. Our findings shed light on the onset of spatial and temporal coherence in a large class of active systems, both synthetic (colloids, swarms of robots, and biopolymers) and living (suspensions of bacteria, cell colonies, and bird flocks).

  14. Bacterial resistance to silver nanoparticles and how to overcome it

    Science.gov (United States)

    Panáček, Aleš; Kvítek, Libor; Smékalová, Monika; Večeřová, Renata; Kolář, Milan; Röderová, Magdalena; Dyčka, Filip; Šebela, Marek; Prucek, Robert; Tomanec, Ondřej; Zbořil, Radek

    2018-01-01

    Silver nanoparticles have already been successfully applied in various biomedical and antimicrobial technologies and products used in everyday life. Although bacterial resistance to antibiotics has been extensively discussed in the literature, the possible development of resistance to silver nanoparticles has not been fully explored. We report that the Gram-negative bacteria Escherichia coli 013, Pseudomonas aeruginosa CCM 3955 and E. coli CCM 3954 can develop resistance to silver nanoparticles after repeated exposure. The resistance stems from the production of the adhesive flagellum protein flagellin, which triggers the aggregation of the nanoparticles. This resistance evolves without any genetic changes; only phenotypic change is needed to reduce the nanoparticles' colloidal stability and thus eliminate their antibacterial activity. The resistance mechanism cannot be overcome by additional stabilization of silver nanoparticles using surfactants or polymers. It is, however, strongly suppressed by inhibiting flagellin production with pomegranate rind extract.

  15. Colloid migration in fractured media

    International Nuclear Information System (INIS)

    Hunt, J.R.

    1989-01-01

    Field studies at the Nevada Test Site by researchers at Lawrence Livermore National Laboratory have demonstrated that radionuclides are being transported by colloidal material suspended in groundwater. This observation is counter to most predictions from contaminant transport models because the models assume adsorbed species are immobile. The purpose of this research is to quantify the transport processes for colloidal materials and develop the mechanistic understanding necessary to predict radionuclide transport in fractured media. There were three areas of investigation during this year that have addressed these issues: chemical control of colloid deposition on clean mineral surfaces, colloid accumulation on fracture surfaces, and the influence of deposited colloids on colloid and tracer migration. 7 refs

  16. Strontium migration in a crystalline medium: effects of the presence of bentonite colloids.

    Science.gov (United States)

    Albarran, Nairoby; Missana, Tiziana; García-Gutiérrez, Miguel; Alonso, Ursula; Mingarro, Manuel

    2011-03-25

    The effects of bentonite colloids on strontium migration in fractured crystalline medium were investigated. We analyzed first the transport behaviour of bentonite colloids alone at different flow rates; then we compared the transport behaviour of strontium as solute and of strontium previously adsorbed onto stable bentonite colloids at a water velocity of approximately 7.1·10(-6)m/s-224m/yr. Experiments with bentonite colloids alone showed that - at the lowest water flow rate used in our experiments (7.1·10(-6)m/s) - approximately 70% of the initially injected colloids were retained in the fracture. Nevertheless, the mobile colloidal fraction, moved through the fracture without retardation, at any flow rate. Bentonite colloids deposited over the fracture surface were identified during post-mortem analyses. The breakthrough curve of strontium as a solute, presented a retardation factor, R(f)~6, in agreement with its sorption onto the granite fracture surface. The breakthrough curve of strontium in the presence of bentonite colloids was much more complex, suggesting additional contributions of colloids to strontium transport. A very small fraction of strontium adsorbed on mobile colloids moved un-retarded (R(f)=1) and this fraction was much lower than the expected, considering the quantity of strontium initially adsorbed onto colloids (90%). This behaviour suggests the hypothesis of strontium sorption reversibility from colloids. On the other hand, bentonite colloids retained within the granite fracture played a major role, contributing to a slower strontium transport in comparison with strontium as a solute. This was shown by a clear peak in the breakthrough curve corresponding to a retardation factor of approximately 20. Copyright © 2010 Elsevier B.V. All rights reserved.

  17. Generation of colloidal granules and capsules from double emulsion drops

    Science.gov (United States)

    Hess, Kathryn S.

    Assemblies of colloidal particles are extensively used in ceramic processing, pharmaceuticals, inks and coatings. In this project, the aim was to develop a new technique to fabricate monodispersed colloidal assemblies. The use of microfluidic devices and emulsion processing allows for the fabrication of complex materials that can be used in a variety of applications. A microfluidic device is used to create monodispersed water/oil/water (w/o/w) double emulsions with interior droplets of colloidal silica suspension ranging in size from tens to hundreds of microns. By tailoring the osmotic pressure using glycerol as a solute in the continuous and inner phases of the emulsion, we can control the final volume size of the monodispersed silica colloidal crystals that form in the inner droplets of the double emulsion. Modifying the ionic strength in the colloidal dispersion can be used to affect the particle-particle interactions and crystal formation of the final colloidal particle. This w/o/w technique has been used with other systems of metal oxide colloids and cellulose nanocrystals. Encapsulation of the colloidal suspension in a polymer shell for the generation of ceramic-polymer core-shell particles has also been developed. These core-shell particles have spawned new research in the field of locally resonant acoustic metamaterials. Systems and chemistries for creating cellulose hydrogels within the double emulsions have also been researched. Water in oil single emulsions and double emulsions have been used to create cellulose hydrogel spheres in the sub-100 micron diameter range. Oil/water/oil double emulsions allow us to create stable cellulose capsules. The addition of a second hydrogel polymer, such as acrylate or alginate, further strengthens the cellulose gel network and can also be processed into capsules and particles using the microfluidic device. This work could have promising applications in acoustic metamaterials, personal care products, pharmaceuticals

  18. Noble silver nanoparticles (AgNPs) synthesis and characterization ...

    African Journals Online (AJOL)

    Nanotechnology is rapidly growing with nanoparticles produced and utilized in a wide range of pharmaceutical and commercial products throughout the world. In this study, fig (Ficus carica) leaf extracts were used for ecofriendly extracellular synthesis of stable silver nanoparticles (AgNPs) by treating an aqueous silver ...

  19. Green synthesis of silver nanoparticles from seed extract of Brassica nigra and its antibacterial activity

    Directory of Open Access Journals (Sweden)

    RAKSHA PANDIT

    2015-05-01

    Full Text Available Pandit R. 2015. Green synthesis of silver nanoparticles from seed extract of Brassica nigra and its antibacterial activity. Nusantara Bioscience 7: 15-19. We report the green synthesis of silver nanoparticles using seed extract of Brassica nigra. UV-visible spectroscopic analysis showed the absorbance peak at 432 nm which indicated the synthesis of silver nanoparticles. Nanoparticles Tracking and Analysis (NTA was used to determine the size of synthesized silver nanoparticles. Zeta potential analysis was carried out to study the stability of nanoparticles while FTIR analysis confirmed the presence of proteins as capping agents that provided stability to nanoparticles in colloid. Antibacterial activity of silver nanoparticles was evaluated against Propionibacterium acnes, Pseudomonas aeruginosa and Klebsiella pneumoniae. The activity of Vancomycin was significantly increased in combination with silver nanoparticles showing synergistic activity against all bacteria while the maximum activity was noted against P. acnes.

  20. Influence of surfactant on the preparation of silver nanoparticles by polyol method

    International Nuclear Information System (INIS)

    Dung Dang, Thi My; Tuyet Le, Thi Thu; Dang, Mau Chien; Fribourg-Blanc, Eric

    2012-01-01

    In this study, silver nanoparticles were synthesized from silver nitrate via a polyol method in ambient atmosphere. In our synthesis route, polyvinylpyrrolidone (PVP) is used as both size controller and capping agent, ethylene glycol acts both as solvent and reducing agent. The obtained silver nanoparticles were characterized by ultraviolet-visible spectrophotometry which indicated the formation of nanoparticles. Investigation of Fourier transform infrared spectroscopy clearly demonstrated the coordination between silver nanoparticles and PVP. Transmission electron microscopy (TEM) contributed to the particle size analysis. The surface plasmon resonance peak in absorption spectra of silver colloidal solution showed absorption from 406 to 409 nm. The average size of the resulting silver nanoparticles was below 10 nm with a dependency on the PVP concentration. (paper)

  1. Synthesis and characterization of silver nanoparticles: effect on phytopathogen Colletotrichum gloesporioides

    Science.gov (United States)

    Aguilar-Méndez, Miguel A.; San Martín-Martínez, Eduardo; Ortega-Arroyo, Lesli; Cobián-Portillo, Georgina; Sánchez-Espíndola, Esther

    2011-06-01

    Colloidal silver nanoparticles were synthesized by reducing silver nitrate solutions with glucose, in the presence of gelatin as capping agent. The obtained nanoparticles were characterized by means of UV-Vis spectroscopy, transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The response surface methodology (RSM) was also used to determine the influence of the variables on the size of the nanoparticles. The antifungal activity of the silver nanoparticles was evaluated on the phytopathogen Colletotrichum gloesporioides, which causes anthracnose in a wide range of fruits. The UV-Vis spectra indicated the formation of silver nanoparticles preferably spherical and of relatively small size (silver nanoparticles. By means of FTIR spectroscopy it was determined that gelatin, through their amide and hydroxyl groups, interacts with nanoparticles preventing their agglomeration. The growth of C. gloesporioides in the presence of silver nanoparticles was significantly delayed in a dose dependent manner.

  2. Moderating effect of ammonia on particle growth and stability of quasi-monodisperse silver nanoparticles synthesized by the Turkevich method.

    Science.gov (United States)

    Gorup, Luiz F; Longo, Elson; Leite, Edson R; Camargo, Emerson R

    2011-08-15

    A new method to stabilize silver nanoparticles by the addition of ammonia is proposed. 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. After approximately 12 min, a diluted ammonia solution was added to the reaction flask to form soluble diamine silver (I) complexes that played an important growth moderating role, making it possible to stabilize metallic silver nanoparticles with sizes as small as 1.6 nm after 17 min of reaction. Colloidal dispersions were characterized by UV-visible absorption spectroscopy, X-ray diffraction, and transmission electronic microscopy. Copyright © 2011 Elsevier Inc. All rights reserved.

  3. Facile synthesis and catalytic properties of silver colloidal ...

    Indian Academy of Sciences (India)

    Administrator

    al 2011). Organic thiol compounds, long-chain amines ... synthesis of nanomaterials by mixing with other co- surfactants such ... example, Zhang and co-workers (2006) used SDBS as a capping .... of AgCNPs, we considered that monolayer micelle model could be ... significantly with pH value, when AgCNPs are suspended.

  4. Synthesis of nanosized silver colloids by microwave dielectric heating

    Indian Academy of Sciences (India)

    Unknown

    Radiation Chemistry and Chemical Dynamics Division, Bhabha Atomic Research Centre,. Mumbai 400 085 ... wave heating is well known in the food industry and of late has ... AgNO3 (BDH), ethylene glycol (UV spectroscopy grade, Spectro-.

  5. Characterization of spray disinfectant products advertised to contain colloidal silver

    Data.gov (United States)

    U.S. Environmental Protection Agency — Included in dataset. This dataset is associated with the following publication: Rogers, K., J. Navratilova, A. Stefaniak, L. Bowers, A. Knepp, S. Al-Abed, P. Potter,...

  6. Preconcentration of silver as silver xanthate on activated carbon

    International Nuclear Information System (INIS)

    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

  7. A facile route to synthesize nanogels doped with silver nanoparticles

    Science.gov (United States)

    Coll Ferrer, M. Carme; Ferrier, Robert C.; Eckmann, David M.; Composto, Russell J.

    2013-01-01

    In this study, we describe a simple method to prepare hybrid nanogels consisting of a biocompatible core-shell polymer host containing silver nanoparticles. First, the nanogels (NG, 160 nm) containing a lysozyme rich core and a dextran rich shell, are prepared via Maillard and heat-gelation reactions. Second, silver nanoparticles (Ag NPs, 5 nm) are synthesized "in situ" in the NG solution without requiring additional reducing agents. This approach leads to stable Ag NPs located in the NG. Furthermore, we demonstrate that the amount of Ag NPs in the NG can be tuned by varying silver precursor concentration. Hybrid nanogels with silver nanoparticles have potential in antimicrobial, optical, and therapeutic applications.

  8. Polymers and colloids

    International Nuclear Information System (INIS)

    Schurtenberger, P.

    1996-01-01

    A wealth of structural information from colloid and polymer solutions on a large range of length scales can be obtained using small angle neutron scattering (SANS) experiments. After a general introduction to the field of soft condensed matter, I shall give a few selected examples on how SANS combined with suitable contrast variation schemes can be used to extract information on the size and conformation of polymer coils in solution and in the melt, and on the local structure and flexibility of polymerlike micelles and microemulsions. (author) 8 figs., tabs., 44 refs

  9. Polymers and colloids

    Energy Technology Data Exchange (ETDEWEB)

    Schurtenberger, P [ETH Zurich, Inst. fuer Polymere, Zurich (Switzerland)

    1996-11-01

    A wealth of structural information from colloid and polymer solutions on a large range of length scales can be obtained using small angle neutron scattering (SANS) experiments. After a general introduction to the field of soft condensed matter, I shall give a few selected examples on how SANS combined with suitable contrast variation schemes can be used to extract information on the size and conformation of polymer coils in solution and in the melt, and on the local structure and flexibility of polymerlike micelles and microemulsions. (author) 8 figs., tabs., 44 refs.

  10. The silver lining: towards the responsible and limited usage of silver.

    Science.gov (United States)

    Naik, K; Kowshik, M

    2017-11-01

    Silver has attracted a lot of attention as a powerful, broad spectrum and natural antimicrobial agent since the ancient times because of its nontoxic nature to the human body at low concentrations. It has been used in treatment of various infections and ulcers, storage of water and prevention of bacterial growth on the surfaces and within materials. However, there are numerous medical and health benefits of colloidal or nanosilver apart from its microbicidal ability which as yet has not been fully embraced by the medical community. These include antiplatelet activity, antioxidant effect, anticancer activity, wound healing and bone regeneration, enhancement of immunity, and increase in antibiotic efficiency. Additionally silver also provides protection against alcohol toxicity, upper respiratory tract infections and stomach ailments. Although nanosilver has been proposed for various topical applications, its usage by ingestion and inhalation remains controversial due to the lack of detailed and precise toxicity information. These beneficial properties of silver can be utilized by using silver at very low concentrations which are not harmful to the human body and environment. The following review discusses the diverse medical applications of silver and further recommends human clinical studies for its in vivo usage. #x00A9; 2017 The Society for Applied Microbiology.

  11. Sustainable steric stabilization of colloidal titania nanoparticles

    Science.gov (United States)

    Elbasuney, Sherif

    2017-07-01

    A route to produce a stable colloidal suspension is essential if mono-dispersed particles are to be successfully synthesized, isolated, and used in subsequent nanocomposite manufacture. Dispersing nanoparticles in fluids was found to be an important approach for avoiding poor dispersion characteristics. However, there is still a great tendency for colloidal nanoparticles to flocculate over time. Steric stabilization can prevent coagulation by introducing a thick adsorbed organic layer which constitutes a significant steric barrier that can prevent the particle surfaces from coming into direct contact. One of the main features of hydrothermal synthesis technique is that it offers novel approaches for sustainable nanoparticle surface modification. This manuscript reports on the sustainable steric stabilization of titanium dioxide nanoparticles. Nanoparticle surface modification was performed via two main approaches including post-synthesis and in situ surface modification. The tuneable hydrothermal conditions (i.e. temperature, pressure, flow rates, and surfactant addition) were optimized to enable controlled steric stabilization in a continuous fashion. Effective post synthesis surface modification with organic ligand (dodecenyl succinic anhydride (DDSA)) was achieved; the optimum surface coating temperature was reported to be 180-240 °C to ensure DDSA ring opening and binding to titania nanoparticles. Organic-modified titania demonstrated complete change in surface properties from hydrophilic to hydrophobic and exhibited phase transfer from the aqueous phase to the organic phase. Exclusive surface modification in the reactor was found to be an effective approach; it demonstrated surfactant loading level 2.2 times that of post synthesis surface modification. Titania was also stabilized in aqueous media using poly acrylic acid (PAA) as polar polymeric dispersant. PAA-titania nanoparticles demonstrated a durable amorphous polymeric layer of 2 nm thickness. This

  12. Testing single extraction methods and in vitro tests to assess the geochemical reactivity and human bioaccessibility of silver in urban soils amended with silver nanoparticles

    NARCIS (Netherlands)

    Cruz, N.; Rodrigues, S.M.; Tavares, D.; Monteiro, R.J.R.; Carvalho, L.; Trindade, T.; Duarte, A.C.; Pereira, E.; Romkens, Paul

    2015-01-01

    To assess if the geochemical reactivity and human bioaccessibility of silver nanoparticles (AgNPs) in soils can be determined by routine soil tests commonly applied to other metals in soil, colloidal Ag was introduced to five pots containing urban soils (equivalent to 6.8mgAgkg-1

  13. Laboratory investigation of the factors impact on bubble size, pore blocking and enhanced oil recovery with aqueous Colloidal Gas Aphron.

    Science.gov (United States)

    Shi, Shenglong; Wang, Yefei; Li, Zhongpeng; Chen, Qingguo; Zhao, Zenghao

    Colloidal Gas Aphron as a mobility control in enhanced oil recovery is becoming attractive; it is also designed to block porous media with micro-bubbles. In this paper, the effects of surfactant concentration, polymer concentration, temperature and salinity on the bubble size of the Colloidal Gas Aphron were studied. Effects of injection rates, Colloidal Gas Aphron fluid composition, heterogeneity of reservoir on the resistance to the flow of Colloidal Gas Aphron fluid through porous media were investigated. Effects of Colloidal Gas Aphron fluid composition and temperature on residual oil recovery were also studied. The results showed that bubble growth rate decreased with increasing surfactant concentration, polymer concentration, and decreasing temperature, while it decreased and then increased slightly with increasing salinity. The obvious increase of injection pressure was observed as more Colloidal Gas Aphron fluid was injected, indicating that Colloidal Gas Aphron could block the pore media effectively. The effectiveness of the best blend obtained through homogeneous sandpack flood tests was modestly improved in the heterogeneous sandpack. The tertiary oil recovery increased 26.8 % by Colloidal Gas Aphron fluid as compared to 20.3 % by XG solution when chemical solution of 1 PV was injected into the sandpack. The maximum injected pressure of Colloidal Gas Aphron fluid was about three times that of the XG solution. As the temperature increased, the Colloidal Gas Aphron fluid became less stable; the maximum injection pressure and tertiary oil recovery of Colloidal Gas Aphron fluid decreased.

  14. Comment on “A re-assessment of the safety of silver in household water treatment: rapid systematic review of mammalian in vivo genotoxicity studies”

    OpenAIRE

    Lantagne, Daniele; Rayner, Justine; Mittelman, Anjuliee; Pennell, Kurt

    2017-01-01

    We wish to thank Fewtrell, Majuru, and Hunter for their article highlighting genotoxic risks associated with the use of particulate silver for primary drinking water treatment. The recent promotion of colloidal silver products for household water treatment in developing countries is problematic due to previously identified concerns regarding manufacturing quality and questionable advertising practices, as well as the low efficiency of silver nanoparticles to treat bacteria, viruses, and proto...

  15. Colloidal copper in aqueous solutions: radiation-chemical reduction, mechanism of formation and properties

    International Nuclear Information System (INIS)

    Ershov, B.G.

    1994-01-01

    Colloidal copper was obtained upon γ-irradiation of aqueous solutions of divalent copper perchlorate in the presence of alcohol and polyethyleneimine (PEI). The sols were in the form of spherical particles 4 nm in diameter, which were promptly oxidized by oxygen or other oxidants. The copper ions were reduced on the surface of silver sols. The optical parameters of the obtained bimetallic particles were studied. The copper ions led to the broadening and shift of the absorption bands of the silver sols to the UV region

  16. Preparation of rhenium-186 tin colloid as radio synovectomy agent

    International Nuclear Information System (INIS)

    Cecep T Rustendi; Martalena Ramli; M Subur

    2010-01-01

    Radio synovectomy is an alternative therapy besides surgery whereby a beta-emitting radiopharmaceutical is delivered into the affected synovial compartment in order to threat rheumatoid arthritis. One of radiopharmaceuticals that could be applied as radio synovectomy agent is 186 Re-Sn colloid. Preparation of 186 Re-Sn colloid has been carried out by searching the best condition of the reaction to obtain a high labeling efficiency (>95%), appropriate particle size and stable at room temperature. Preparation of 186 Re-Sn colloid has been done successfully using a mol ratio of Sn to Re with value 1000:1 (~50 mg SnCl 2 .2H 2 O) by heating for 90 minutes and resulting >95% labeling efficiency. Stability of 186 Re-Sn colloid was found to be good enough when it was stored at room temperature for 24 hours. The 186 Re-Sn colloid was also found to have an appropriate particle size for radiopharmaceutical agent for radio synovectomy. (author)

  17. Microrheology of colloidal systems

    International Nuclear Information System (INIS)

    Puertas, A M; Voigtmann, T

    2014-01-01

    Microrheology was proposed almost twenty years ago as a technique to obtain rheological properties in soft matter from the microscopic motion of colloidal tracers used as probes, either freely diffusing in the host medium, or subjected to external forces. The former case is known as passive microrheology, and is based on generalizations of the Stokes–Einstein relation between the friction experienced by the probe and the host-fluid viscosity. The latter is termed active microrheology, and extends the measurement of the friction coefficient to the nonlinear-response regime of strongly driven probes. In this review article, we discuss theoretical models available in the literature for both passive and active microrheology, focusing on the case of single-probe motion in model colloidal host media. A brief overview of the theory of passive microrheology is given, starting from the work of Mason and Weitz. Further developments include refined models of the host suspension beyond that of a Newtonian-fluid continuum, and the investigation of probe-size effects. Active microrheology is described starting from microscopic equations of motion for the whole system including both the host-fluid particles and the tracer; the many-body Smoluchowski equation for the case of colloidal suspensions. At low fluid densities, this can be simplified to a two-particle equation that allows the calculation of the friction coefficient with the input of the density distribution around the tracer, as shown by Brady and coworkers. The results need to be upscaled to agree with simulations at moderate density, in both the case of pulling the tracer with a constant force or dragging it at a constant velocity. The full many-particle equation has been tackled by Fuchs and coworkers, using a mode-coupling approximation and the scheme of integration through transients, valid at high densities. A localization transition is predicted for a probe embedded in a glass-forming host suspension. The

  18. Colloidal suspensions hydrodynamic retention mechanisms in model porous media

    International Nuclear Information System (INIS)

    Salehi, N.

    1996-01-01

    This study deals with the retention mechanisms of colloidal particles in porous media flows, and the subsequent reduction in permeability in the case of stable and non adsorbing colloids. It combines experimental results and modelling. This study has been realised with stable dispersion of monodispersed carboxylate polystyrene latexes negatively charged injected through negatively charged polycarbonate membranes having mono-sized cylindrical pores. The mean particle diameter is smaller than the mean pore diameter. Both batch and flow experiments in Nuclepore membranes have been done. The results of batch experiments have proved no adsorption of the colloidal latex particles on the surface of the Nuclepore membranes without flow at low salinity. In flow experiments at low particle concentration, only deposition on the upstream side of the membrane have been induced by hydrodynamic forces even for non adsorbing particles without creating any permeability reduction. The retention levels are zero at low and high Peclet numbers with a maximum at intermediate values. Partial plugging was observed at higher colloid concentration even at low salinity without any upstream surface deposition. The modelling of plugging processes is achieved by considering the particle concentration, fluid rate and ratio between the mean pore diameter and the mean particle diameter. This study can be particularly useful in the fields of water treatment and of restoration of lands following radioactive contamination. (author). 96 refs., 99 figs., 29 tabs

  19. Magnetically actuated and controlled colloidal sphere-pair swimmer

    International Nuclear Information System (INIS)

    Ran, Sijie; Guez, Allon; Friedman, Gary

    2016-01-01

    Magnetically actuated swimming of microscopic objects has been attracting attention partly due to its promising applications in the bio-medical field and partly due to interesting physics of swimming in general. While colloidal particles that are free to move in fluid can be an attractive swimming system due it its simplicity and ability to assemble in situ , stability of their dynamics and the possibility of stable swimming behavior in periodically varying magnetic fields has not been considered. Dynamic behavior of two magnetically interacting colloidal particles subjected to rotating magnetic field of switching frequency is analyzed here and is shown to result in stable swimming without any stabilizing feedback. A new mechanism of swimming that relies only on rotations of the particles themselves and of the particle pair axis is found to dominate the swimming dynamics of the colloidal particle pair. Simulation results and analytical arguments demonstrate that this swimming strategy compares favorably to dragging the particles with an external magnetic force when colloidal particle sizes are reduced. (paper)

  20. Actinide colloid generation in groundwater. Part 2

    International Nuclear Information System (INIS)

    Kim, J.I.

    1991-01-01

    The progress made in the investigation of actinide colloid generation in groundwater is summarized and discussed with particular examples relevant to an understanding of the migration behaviour of actinides in natural aquifer systems. The first part deals with the characterization of colloids: groundwater colloids, actinide real-colloids and actinide pseudocolloids. The second part concentrates on the generation processes and migration behaviour of actinide pseudo colloids, which are discussed with some notable experimental examples. Importance is stressed more on the chemical aspects of the actinide colloid generation in groundwater. This work is a contribution to the CEC Mirage II project, in particular the complexation and colloids research area

  1. Pharmacology of colloids and crystalloids.

    Science.gov (United States)

    Griffel, M I; Kaufman, B S

    1992-04-01

    We have attempted to review body fluid distribution by compartments so that the reader understands the physiology of ICF and ECF, and the relationship between interstitial and intravascular fluids. Crystalloids such as NS and RL are distributed to the ECF, whereas colloids primarily remain intravascular for longer periods. Although effective, crystalloids tend to require larger volumes for infusion, and edema remains a problem. Colloids as a group are extremely effective volume expanders, but none is ideal. Albumin, hetastarch, dextran, and the less commonly used colloids each have significant toxicities that must be considered when using them. Intelligent choices can be made to optimize use of these fluids.

  2. Driving dynamic colloidal assembly using eccentric self-propelled colloids

    OpenAIRE

    Ma, Zhan; Lei, Qun-li; Ni, Ran

    2017-01-01

    Designing protocols to dynamically direct the self-assembly of colloidal particles has become an important direction in soft matter physics because of the promising applications in fabrication of dynamic responsive functional materials. Here using computer simulations, we found that in the mixture of passive colloids and eccentric self-propelled active particles, when the eccentricity and self-propulsion of active particles are high enough, the eccentric active particles can push passive coll...

  3. Microwave flash sintering of inkjet-printed silver tracks on polymer substrates

    NARCIS (Netherlands)

    Perelaer, J.; Klokkenburg, M.; Hendriks, C.E.; Schubert, U.S.

    2009-01-01

    Microwave flash sintering of inkjet printed colloidal silver dispersions on thin polymer substrates was studied as a function of the antenna area and initial resistance. The presence of conductive antennae promotes nanoparticle sintering in predried ink lines. For dried nanoparticle inks connected

  4. Time-dependent effect in green synthesis of silver nanoparticles

    Directory of Open Access Journals (Sweden)

    Darroudi M

    2011-04-01

    Full Text Available Majid Darroudi1,2, Mansor Bin Ahmad3, Reza Zamiri4, AK Zak5, Abdul Halim Abdullah1,3, Nor Azowa Ibrahim31Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA, Universiti Putra Malaysia, Selangor, Malaysia; 2Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran; 3Department of Chemistry, 4Department of Physics, Faculty of Science, Universiti Putra Malaysia, Selangor, Malaysia; 5Low Dimensional Materials Research Center, Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur, MalaysiaAbstract: The application of “green” chemistry rules to nanoscience and nanotechnology is very important in the preparation of various nanomaterials. In this work, we successfully developed an eco-friendly chemistry method for preparing silver nanoparticles (Ag-NPs in natural polymeric media. The colloidal Ag-NPs were synthesized in an aqueous solution using silver nitrate, gelatin, and glucose as a silver precursor, stabilizer, and reducing agent, respectively. The properties of synthesized colloidal Ag-NPs were studied at different reaction times. The ultraviolet-visible (UV-vis spectra were in excellent agreement with the obtained nanostructure studies performed by transmission electron microscopy (TEM and their size distributions. The prepared samples were also characterized by X-ray diffraction (XRD and atomic force microscopy (AFM. The use of eco-friendly reagents, such as gelatin and glucose, provides green and economic attributes to this work.Keywords: silver nanoparticles, gelatin, green chemistry, time-dependent effect, ultraviolet-visible spectra

  5. Frost Heave in Colloidal Soils

    KAUST Repository

    Peppin, Stephen; Majumdar, Apala; Style, Robert; Sander, Graham

    2011-01-01

    We develop a mathematical model of frost heave in colloidal soils. The theory accountsfor heave and consolidation while not requiring a frozen fringe assumption. Two solidificationregimes occur: a compaction regime in which the soil consolidates

  6. Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

    Directory of Open Access Journals (Sweden)

    M. Vinod

    2014-12-01

    Full Text Available Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation. The dependence of laser fluence on the surface plasmon characteristics of the nanoparticles was investigated. Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids. The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process. The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones. The surface enhanced Raman scattering activity of the Au, Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules. Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.

  7. Effect of Accelerator in Green Synthesis of Silver Nanoparticles

    Directory of Open Access Journals (Sweden)

    Kamyar Shameli

    2010-10-01

    Full Text Available Silver nanoparticles (Ag-NPs were successfully synthesized in the natural polymeric matrix. Silver nitrate, gelatin, glucose, and sodium hydroxide have been used as silver precursor, stabilizer, reducing agent, and accelerator reagent, respectively. This study investigated the role of NaOH as the accelerator. The resultant products have been confirmed to be Ag-NPs using powder X-ray diffraction (PXRD, UV-vis spectroscopy, and transmission electron microscopy (TEM. The colloidal sols of Ag-NPs obtained at different volumes of NaOH show strong and different surface plasmon resonance (SPR peaks, which can be explained from the TEM images of Ag-NPs and their particle size distribution. Compared with other synthetic methods, this work is green, rapid, and simple to use. The newly prepared Ag-NPs may have many potential applications in chemical and biological industries.

  8. Hetero-Colloidal Metal Particle Multilayer Films Grown Using Electrostatic Interactions at the Air-water Interface

    International Nuclear Information System (INIS)

    Sastry, Murali; Mayya, K.S.

    2000-01-01

    The formation of nanoparticle multilayer films by electrostatic immobilization of surface-modified colloidal particles at the air-water interface has been recently demonstrated by us. In this paper, we extend our study to show that multilayer assemblies consisting of metal particles of different chemical nature (hetero-colloidal particle superlattices) and size can be deposited by the versatile Langmuir-Blodgett technique. Multilayer films consisting of a different number of bilayers of gold and silver colloidal particles have been deposited and characterized using quartz crystal microgravimetry and UV-visible spectroscopy measurements. It is observed that while layer-by-layer deposition of the different colloidal particle assemblies is possible by this technique without a detectable variation in the cluster density in the different layers, a degree of post-deposition reorganization of the clusters occurs in the film. In addition to this aging behavior, the effect of different organic solvents on the reorganization process has also been studied

  9. Hemocompatibility of ultrafine systems on the basis of chitosan and its derivatives polymer-colloid complexes

    Directory of Open Access Journals (Sweden)

    M.V. Bazunova

    2015-03-01

    Full Text Available This article presents the results of the development process for the preparation of micro and nano-sized polymer-colloid com-plexes (РСС on the basis of water-soluble natural polymer chitosan (СTZ and the sodium salt of chitosan succinylamid (SСTZ with silver halide sols in aqueous media. Results of research of СTZ, sodium salt of SСTZ solutions and PСС of CTZ and SСTZ with colloidal parti-cles of silver iodide influence on structurally-functional properties of erythrocytes’ membranes on model of acidic hemolisis are presented in the article. Their influence on the nature of erythrocytes distribution by degree of their stability and on kinetic parameters (the beginning, intensity and completion of process of their destruction under the influence of the damaging agent (HCl is shown. The comparative analysis of results convinces that СTZ, SСTZ solutions and disperse systems on the basis of PСС of СTZ and SСTZ with colloidal particles of the silver iodide are capable of modulating variously matrix properties of erythrocytes of blood.

  10. Optimization of silver-dielectric-silver nanoshell for sensing applications

    International Nuclear Information System (INIS)

    Shirzaditabar, Farzad; Saliminasab, Maryam

    2013-01-01

    In this paper, resonance light scattering (RLS) properties of a silver-dielectric-silver nanoshell, based on quasi-static approach and plasmon hybridization theory, are investigated. Scattering spectrum of silver-dielectric-silver nanoshell has two intense and clearly separated RLS peaks and provides a potential for biosensing based on surface plasmon resonance and surface-enhanced Raman scattering. The two RLS peaks in silver-dielectric-silver nanoshell are optimized by tuning the geometrical dimensions. In addition, the optimal geometry is discussed to obtain the high sensitivity of silver-dielectric-silver nanoshell. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness increases the sensitivity of silver-dielectric-silver nanoshell

  11. Stable isotopes

    International Nuclear Information System (INIS)

    Evans, D.K.

    1986-01-01

    Seventy-five percent of the world's stable isotope supply comes from one producer, Oak Ridge Nuclear Laboratory (ORNL) in the US. Canadian concern is that foreign needs will be met only after domestic needs, thus creating a shortage of stable isotopes in Canada. This article describes the present situation in Canada (availability and cost) of stable isotopes, the isotope enrichment techniques, and related research programs at Chalk River Nuclear Laboratories (CRNL)

  12. Colloid migration in porous media

    International Nuclear Information System (INIS)

    Hunt, J.R.; McDowell-Boyer; Sitar, N.

    1985-01-01

    Retention of radionuclides for long periods near waste repositories depends upon multiple barriers, one of which is adsorption to immobile solid surfaces. Since small particles and colloidal matter have high adsorption capacities per unit mass and can be mobile in subsurface flows, colloidal transport of waste components requires analysis. Theories for predicting colloid migration through porous media have been developed in the filtration literature. The applicability of filtration theories for predicting particle and colloid transport. Emphasis is on suspended matter much smaller than pore sizes, where physical and chemical forces control migration rather than size dependent physical straining. In general, experimentally verifiable theories exist for particle filtration by clean media, and a sensitivity analysis is possible on particle and media properties and fluid flow rate. When particle aggregates accumulate within pores, media permeability decreases, resulting in flow field alteration and possible radionuclide isolation. An analysis of the limited experimental data available indicates that present theories cannot predict long-term colloid transport when permeability reduction occurs. The coupling of colloid attachment processes and the hydrologic flow processes requires more extensive laboratory field research than has currently been carried out. An emphasis on the fundamental mechanisms is necessary to enhance long-term predictability

  13. Characterization of colloids in groundwater

    International Nuclear Information System (INIS)

    Kim, J.I.; Buckau, G.; Klenze, R.

    1987-07-01

    Natural colloids in the Gorleben aquifer systems have been investigated as for their chemical composition, quantification and size distribution. Humic substances appear to be the major organic materials in these groundwaters, generating humic colloids which are analysed to be humic acid (and fulvic acid) loaded with a large number of trace heavy metal ions. These metal ions include natural homologues of actinides and some fission products in trivalent, tetravalent and hexavalent state. Concentrations of trivalent and tetravalent heavy metal ions are linearly correlated with the dissolved organic carbon (DDC) concentration in different groundwaters. The DOC is found to be present as humic colloids. The Am 3+ ions introduced in such a groundwater readily undergo the generation of its pseudocolloids through sorption or ion exchange reactions with humic colloids. The chemical behaviour of Am(III), being similar to the trivalent metal ions, e.g. Fe 3+ , REE etc. found in natural colloids, has been investigated by laser induced photoacoustic spectroscopy (LPAS). Groundwaters from Ispra, Markham Clinton and Felslabor Grimsel. Bidistilled water and one of Gorleben groundwaters, Gohy 1011, are taken for the purpose of comparison. This groundwater contains the least amount of natural colloids of all Gorleben groundwaters hitherto investigated. An indirect quantification is made by comparison of the LPAS results with experiment from Latex solution. (orig./IRB)

  14. Colloid remediation in groundwater by polyelectrolyte capture

    International Nuclear Information System (INIS)

    Nuttall, H.E.; Rao, S.; Jain, R.

    1992-01-01

    This paper describes an ongoing study to characterize groundwater colloids, to understand the geochemical factors affecting colloid transport in groundwater, and to develop an in-situ colloid remediation process. The colloids and suspended particulate matter used in this study were collected from a perched aquifer site that has radiation levels several hundred times the natural background and where previous researchers have measured and reported the presence of radiocolloids containing plutonium and americium. At this site, radionuclides have spread over several kilometers. Inorganic colloids collected from water samples are characterized with respect to concentration, mineralogy, size distribution, electrophoretic mobility (zeta potential), and radioactivity levels. Presented are the methods used to investigate the physiochemical factors affecting colloid transport and the preliminary analytical results. Included below are a description of a colloid transport model and the corresponding computational code, water analyses, characterization of the inorganic colloids, and a conceptual description of a process for in-situ colloid remediation using the phenomenon of polyelectrolyte capture

  15. Green synthesis of silver nanoparticles using Alternanthera dentata leaf extract at room temperature and their antimicrobial activity.

    Science.gov (United States)

    Kumar, Deenadayalan Ashok; Palanichamy, V; Roopan, Selvaraj Mohana

    2014-06-05

    A green rapid biogenic synthesis of silver nanoparticles AgNPs using Alternanthera dentata (A. dentata) aqueous extract was demonstrated in this present study. The formation of silver nanoparticles was confirmed by Surface Plasmon Resonance (SPR) at 430nm using UV-visible spectrophotometer. The reduction of silver ions to silver nanoparticles by A. dentata extract was completed within 10min. Synthesized nanoparticles were characterized using UV-visible spectroscopy; Fourier transformed infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy (TEM). The extracellular silver nanoparticles synthesis by aqueous leaf extract demonstrates rapid, simple and inexpensive method comparable to chemical and microbial methods. The colloidal solution of silver nanoparticles were found to exhibit antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia and, Enterococcus faecalis. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. The study of antibacterial activity and stability of dyed cotton fabrics modified with different forms of silver

    Directory of Open Access Journals (Sweden)

    Lazić Vesna

    2012-01-01

    Full Text Available This study compares the effect of colloidal silver nanoparticles and commercial RUCO-BAC AGP agent with silver chloride as an active component on antibacterial activity of dyed cotton fabrics. Cotton fabrics were dyed with vat dyes Bezanthren olive T and Bezanthren grey FFB. Antibacterial activity of silver loaded dyed cotton fabrics was tested against Gram-positive bacterium Staphylococcus aureus and Gram-negative bacterium Escherichia coli. Unlike RUCO-BAC AGP synthesized silver nanoparticles deposited onto dyed cotton fabrics provided maximum bacteria reduction independently of applied dye. The stability of modified cotton fabrics was analyzed in artificial sweat at pH 5.5 and 8.0. Approximately the same amount of silver was released from differently modified cotton fabrics in artificial sweat. Larger amount of silver was released in the sweat at pH 8.0.

  17. Comment on "A re-assessment of the safety of silver in household water treatment: rapid systematic review of mammalian in vivo genotoxicity studies".

    Science.gov (United States)

    Lantagne, Daniele; Rayner, Justine; Mittelman, Anjuliee; Pennell, Kurt

    2017-11-13

    We wish to thank Fewtrell, Majuru, and Hunter for their article highlighting genotoxic risks associated with the use of particulate silver for primary drinking water treatment. The recent promotion of colloidal silver products for household water treatment in developing countries is problematic due to previously identified concerns regarding manufacturing quality and questionable advertising practices, as well as the low efficiency of silver nanoparticles to treat bacteria, viruses, and protozoa in source waters. However, in the conclusion statement of the manuscript, Fewtrell et al. state, "Before colloidal Ag or AgNP are used in filter matrices for drinking water treatment, consideration needs to be given to how much silver is likely to be released from the matrix during the life of the filter." Unfortunately, it appears Fewtrell et al. were unaware that studies of silver nanoparticle and silver ion elution from ceramic filters manufactured and used in developing countries have already been completed. These existing studies have found that: 1) silver ions, not silver nanoparticles, are eluted from ceramic filters treated with silver nanoparticles or silver nitrate; and, 2) silver ions have not been shown to be genotoxic. Thus, the existing recommendation of applying silver nanoparticles to ceramic filters to prevent biofilm formation within the filter and improve microbiological efficacy should still be adhered to, as there is no identified risk to people who drink water from ceramic filters treated with silver nanoparticles or silver nitrate. We note that efforts should continue to minimize exposure to silver nanoparticles (and silica) to employees in ceramic filter factories in collaboration with the organizations that provide technical assistance to ceramic filter factories.

  18. Two step continuous method to synthesize colloidal spheroid gold nanorods.

    Science.gov (United States)

    Chandra, S; Doran, J; McCormack, S J

    2015-12-01

    This research investigated a two-step continuous process to synthesize colloidal suspension of spheroid gold nanorods. In the first step; gold precursor was reduced to seed-like particles in the presence of polyvinylpyrrolidone and ascorbic acid. In continuous second step; silver nitrate and alkaline sodium hydroxide produced various shape and size Au nanoparticles. The shape was manipulated through weight ratio of ascorbic acid to silver nitrate by varying silver nitrate concentration. The specific weight ratio of 1.35-1.75 grew spheroid gold nanorods of aspect ratio ∼1.85 to ∼2.2. Lower weight ratio of 0.5-1.1 formed spherical nanoparticle. The alkaline medium increased the yield of gold nanorods and reduced reaction time at room temperature. The synthesized gold nanorods retained their shape and size in ethanol. The surface plasmon resonance was red shifted by ∼5 nm due to higher refractive index of ethanol than water. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. One stone, two birds: silica nanospheres significantly increase photocatalytic activity and colloidal stability of photocatalysts

    Science.gov (United States)

    Rasamani, Kowsalya D.; Foley, Jonathan J., IV; Sun, Yugang

    2018-03-01

    Silver-doped silver chloride [AgCl(Ag)] nanoparticles represent a unique class of visible-light-driven photocatalysts, in which the silver dopants introduce electron-abundant mid-gap energy levels to lower the bandgap of AgCl. However, free-standing AgCl(Ag) nanoparticles, particularly those with small sizes and large surface areas, exhibit low colloidal stability and low compositional stability upon exposure to light irradiation, leading to easy aggregation and conversion to metallic silver and thus a loss of photocatalytic activity. These problems could be eliminated by attaching the small AgCl(Ag) nanoparticles to the surfaces of spherical dielectric silica particles with submicrometer sizes. The high optical transparency in the visible spectral region (400-800 nm), colloidal stability, and chemical/electronic inertness displayed by the silica spheres make them ideal for supporting photocatalysts and significantly improving their stability. The spherical morphology of the dielectric silica particles can support light scattering resonances to generate significantly enhanced electric fields near the silica particle surfaces, on which the optical absorption cross-section of the AgCl(Ag) nanoparticles is dramatically increased to promote their photocatalytic activity. The hybrid silica/AgCl(Ag) structures exhibit superior photocatalytic activity and stability, suitable for supporting photocatalysis sustainably; for instance, their efficiency in the photocatalytic decomposition of methylene blue decreases by only ˜9% even after ten cycles of operation.

  20. Thermodynamic stabilization of colloids

    NARCIS (Netherlands)

    Stol, R.J.; Bruyn, P.L. de

    An analysis is given of the conditions necessary for obtaining a thermodynamically stable dispersion (TSD) of solid particles in a continuous aqueous solution phase. The role of the adsorption of potential-determining ions at the planar interface in lowering the interfacial free energy (γ) to

  1. Synthesis of Silver Nanoparticles in Cotton Fabric by Polyvinyl-2-pyrrolidone as a Reducing and Stabilizing Agent

    Directory of Open Access Journals (Sweden)

    Farbod Alimohammadi

    2012-12-01

    Full Text Available Silver nanoparticles have been extensively applied in various fields suchas polymers and textile fibers considering their well known antimicrobialproperties. In conventional methods nano silver is synthesized through chemical reduction however, in this paper a novel synthesis method based on aqueous solution of ammonia/silver complex with cationic stabilizer along with UV-C irradiation is introduced. On this basis, silver nitrate was oxidized with sodium hydroxide and then transformed into [Ag(NH32]+ aqueous solution with ammonia followed by adding PVP as a reducing and stabilizing agent and irradiated by UV-C. The formation of silver nanoparticles was confirmed from the appearance of surface plasmon absorption and the X-ray diffraction (XRD demonstrated that the colloidal nanoparticles were pure silver and Zeta sizer showed particle size distribution. Cotton fabric finishing was accomplished in pad process with various concentrations of nano-sized colloidal silver. Some characteristics of the fabric such as antimicrobial against different microorganisms including gram positive bacteria (Staphylococcous aureus, one gram negative bacteria (Escherichia coli, UV–vis spectrophotometry, color space a*, b* and L*, scanning electron microscopy, EDAX were investigated. Very good antibacterial efficacy against S. aureus and E. coli (higher than 97% appeared even by applying a low nanosilver content (200 ppm for twenty cycles of home laundering. Polyvinyl pyrrolidone resulted in a remarkable control in the release of silver nanoparticle from the coating and can improve the long-term microbiological activity, especially against home laundering.

  2. Wave oscillations in colloid oxyhydrates wave oscillations in colloid oxyhydrates

    CERN Document Server

    Sucharev, Yuri I

    2010-01-01

    The importance of coherent chemistry, that is, the chemistry of periodic oscillatory processes, is increasing at a rapid rate in specific chemical disciplines. While being perfectly understood and highly developed in the fields of physical chemistry, chemical physics and biological chemistry, the periodic developmental paradigm of processes and phenomena still remains poorly developed and misunderstood in classical inorganic chemistry and related branches, such as colloid chemistry. The probability is that we miss subtle colloid chemical phenomena that could be of utmost importance if taken into consideration when catalysis or adsorption is involved. The author here reveals all of the astonishing vistas that periodic wave paradigms open up to researchers in certain colloid chemical systems, and will doubtless stimulate researchers to look at them in a new light.Review from Book News Inc.: Coherent chemistry, the chemistry of periodical oscillatory processes, is well established in physical chemistry, chemical...

  3. Sustainable steric stabilization of colloidal titania nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Elbasuney, Sherif, E-mail: sherif_basuney2000@yahoo.com

    2017-07-01

    Graphical abstract: Controlled surface properties of titania nanoparticles via surface modification, flocculation from aqueous phase (a), stabilization in aqueous phase (b), extraction to organic phase (c). - Highlights: • Complete change in surface properties of titania nanoparticles from hydrophilic to hydrophobic. • Harvesting the formulated nanoparticles from the aqueous phase to the organic phase. • Exclusive surface modification in the reactor during nanoparticle synthesis. • Sustainable stabilization of titania nanoparticles in aqueous media with polar polymeric dispersant. - Abstract: A route to produce a stable colloidal suspension is essential if mono-dispersed particles are to be successfully synthesized, isolated, and used in subsequent nanocomposite manufacture. Dispersing nanoparticles in fluids was found to be an important approach for avoiding poor dispersion characteristics. However, there is still a great tendency for colloidal nanoparticles to flocculate over time. Steric stabilization can prevent coagulation by introducing a thick adsorbed organic layer which constitutes a significant steric barrier that can prevent the particle surfaces from coming into direct contact. One of the main features of hydrothermal synthesis technique is that it offers novel approaches for sustainable nanoparticle surface modification. This manuscript reports on the sustainable steric stabilization of titanium dioxide nanoparticles. Nanoparticle surface modification was performed via two main approaches including post-synthesis and in situ surface modification. The tuneable hydrothermal conditions (i.e. temperature, pressure, flow rates, and surfactant addition) were optimized to enable controlled steric stabilization in a continuous fashion. Effective post synthesis surface modification with organic ligand (dodecenyl succinic anhydride (DDSA)) was achieved; the optimum surface coating temperature was reported to be 180–240 °C to ensure DDSA ring opening

  4. The radiation chemistry of colloids

    International Nuclear Information System (INIS)

    Sellers, R.M.

    1976-08-01

    One of the most important problems associated with water cooled reactors is the accumulation on the pipework of radio-active deposits. These are formed from corrosion products which become activated during their passage through the reactor core. The first step of the activation process involves the deposition of the corrosion products, which are present as either colloidal or particulate matter, onto surfaces in the reactor core, i.e. within the radiation zone. A review of the literature on the effect of radiation on colloids is presented. Particular emphasis is given to the dependence of colloidal parameters such as particle size, turbidity and electrophoretic mobility on radiation dose. Most of the data available is of a qualitative nature only. Evidence is presented that colloids of iron are affected (in some cases precipitated) by radiation, and it is suggested that this process plays a part in the deposition of corrosion products in nuclear reactor cores. The bulk of the information available can be rationalized in terms of the radiation chemistry of aqueous solutions, and the interaction of the radicals produced with the atoms or molecules at the surface of the colloidal particles. This approach is very successful in explaining the variation of the mean particle size of monodisperse sulphur hydrosols with dose, for which quantitative experimental data are available. (author)

  5. Crack formation and prevention in colloidal drops

    Science.gov (United States)

    Kim, Jin Young; Cho, Kun; Ryu, Seul-A.; Kim, So Youn; Weon, Byung Mook

    2015-08-01

    Crack formation is a frequent result of residual stress release from colloidal films made by the evaporation of colloidal droplets containing nanoparticles. Crack prevention is a significant task in industrial applications such as painting and inkjet printing with colloidal nanoparticles. Here, we illustrate how colloidal drops evaporate and how crack generation is dependent on the particle size and initial volume fraction, through direct visualization of the individual colloids with confocal laser microscopy. To prevent crack formation, we suggest use of a versatile method to control the colloid-polymer interactions by mixing a nonadsorbing polymer with the colloidal suspension, which is known to drive gelation of the particles with short-range attraction. Gelation-driven crack prevention is a feasible and simple method to obtain crack-free, uniform coatings through drying-mediated assembly of colloidal nanoparticles.

  6. Colloid Thrusters, Physics, Fabrication and Performance

    National Research Council Canada - National Science Library

    Martinez-Sanchez, Manuel; Akinwande, Akintunde I

    2005-01-01

    ... discovered pure ionic mode, the microfabrication in Silicon of two types of arrays of colloid or electrospray emitters, and the development of a quantitative theory for the colloidal regime (no ions...

  7. Anisotropic deformation of metallo-dielectric core-shell colloids under MeV ion irradiation

    International Nuclear Information System (INIS)

    Penninkhof, J.J.; Dillen, T. van; Roorda, S.; Graf, C.; Blaaderen, A. van; Vredenberg, A.M.; Polman, A.

    2006-01-01

    We have studied the deformation of metallo-dielectric core-shell colloids under 4 MeV Xe, 6 and 16 MeV Au, 30 MeV Si and 30 MeV Cu ion irradiation. Colloids of silica surrounded by a gold shell, with a typical diameter of 400 nm, show anisotropic plastic deformation under MeV ion irradiation, with the metal flowing conform the anisotropically deforming silica core. The 20 nm thick metal shell imposes a mechanical constraint on the deforming silica core, reducing the net deformation strain rate compared to that of pure silica. In colloids consisting of a Au core and a silica shell, the silica expands perpendicular to the ion beam, while the metal core shows a large elongation along the ion beam direction, provided the silica shell is thick enough (>40 nm). A minimum electronic energy loss of 3.3 keV/nm is required for shape transformation of the metal core. Silver cores embedded in a silica shell show no elongation, but rather disintegrate. Also in planar SiO 2 films, Au and Ag colloids show entirely different behavior under MeV irradiation. We conclude that the deformation model of core-shell colloids must include ion-induced particle disintegration in combination with thermodynamical effects, possibly in combination with mechanical effects driven by stresses around the ion tracks

  8. Anisotropic deformation of metallo-dielectric core shell colloids under MeV ion irradiation

    Science.gov (United States)

    Penninkhof, J. J.; van Dillen, T.; Roorda, S.; Graf, C.; van Blaaderen, A.; Vredenberg, A. M.; Polman, A.

    2006-01-01

    We have studied the deformation of metallo-dielectric core-shell colloids under 4 MeV Xe, 6 and 16 MeV Au, 30 MeV Si and 30 MeV Cu ion irradiation. Colloids of silica surrounded by a gold shell, with a typical diameter of 400 nm, show anisotropic plastic deformation under MeV ion irradiation, with the metal flowing conform the anisotropically deforming silica core. The 20 nm thick metal shell imposes a mechanical constraint on the deforming silica core, reducing the net deformation strain rate compared to that of pure silica. In colloids consisting of a Au core and a silica shell, the silica expands perpendicular to the ion beam, while the metal core shows a large elongation along the ion beam direction, provided the silica shell is thick enough (>40 nm). A minimum electronic energy loss of 3.3 keV/nm is required for shape transformation of the metal core. Silver cores embedded in a silica shell show no elongation, but rather disintegrate. Also in planar SiO2 films, Au and Ag colloids show entirely different behavior under MeV irradiation. We conclude that the deformation model of core-shell colloids must include ion-induced particle disintegration in combination with thermodynamical effects, possibly in combination with mechanical effects driven by stresses around the ion tracks.

  9. Colloid Release from Soil Aggregates

    DEFF Research Database (Denmark)

    Vendelboe, Anders Lindblad; Møldrup, Per; Schjønning, Per

    2012-01-01

    The content of water-dispersible colloids (WDC) has a major impact on soil functions and structural stability. In addition, the presence of mobile colloids may increase the risk of colloid-facilitated transport of strongly sorbing environmental contaminants. The WDC content was measured in 39 soils......, using laser diffraction, by agitating the samples using a wet-dispersion unit. This approach eliminated the need for long sedimentation times required by the more classical end-over-end shaking approach and provided information about the time-dependent release of WDC. The total clay content of the soils...... ranged from 0.1 to 0.44 kg kg−1. The WDC content was measured on air-dry and moist 1- to 2-mm aggregates. The WDC content at a reference time was highly correlated to the total clay content (r > 0.91, P soils. Only for two sites was the WDC content correlated to the content of clay...

  10. Agglomeration, colloidal stability, and magnetic separation of magnetic nanoparticles: collective influences on environmental engineering applications

    Science.gov (United States)

    Yeap, Swee Pin; Lim, JitKang; Ooi, Boon Seng; Ahmad, Abdul Latif

    2017-11-01

    Magnetic nanoparticles (MNPs) which exhibit magnetic and catalytic bifunctionalities have been widely accepted as one of the most promising nanoagents used in water purification processes. However, due to the magnetic dipole-dipole interaction, MNPs can easily lose their colloidal stability and tend to agglomerate. Thus, it is necessary to enhance their colloidal stability in order to maintain the desired high specific surface area. Meanwhile, in order to successfully utilize MNPs for environmental engineering applications, an effective magnetic separation technology has to be developed. This step is to ensure the MNPs that have been used for pollutant removal can be fully reharvested back. Unfortunately, it was recently highlighted that there exists a conflicting role between colloidal stability and magnetic separability of the MNPs, whereby the more colloidally stable the particle is, the harder for it to be magnetically separated. In other words, attaining a win-win scenario in which the MNPs possess both good colloidal stability and fast magnetic separation rate becomes challenging. Such phenomenon has to be thoroughly understood as the colloidal stability and the magnetic separability of MNPs play a pivotal role on affecting their effective implementation in water purification processes. Accordingly, it is the aim of this paper to provide reviews on (i) the colloidal stability and (ii) the magnetic separation of MNPs, as well as to provide insights on (iii) their conflicting relationship based on recent research findings. [Figure not available: see fulltext.

  11. From silver nanoparticles to nanostructures through matrix chemistry

    International Nuclear Information System (INIS)

    Ayyad, Omar; Munoz-Rojas, David; Oro-Sole, Judith; Gomez-Romero, Pedro

    2010-01-01

    Direct in situ reduction of silver ions by a biopolymer such as agar, without any other reducing nor capping agent is shown in this article to lead either to nanoparticles (typically 12(2) nm in an optimized case) or to more complex nanostructures depending on the reaction conditions used. This approach takes advantage of the porous polymer lattice acting as a template and leads to hybrid Ag-Agar materials with long-term synergic stability. Silver acts as an antibacterial agent for agar whereas the biopolymer prevents agglomeration of the inorganic nanoparticles leading to a stable nanocomposite formed by a thermoreversible biopolymer from which silver nanoparticles can eventually be recovered.

  12. Limitations and possibilities of green synthesis and long-term stability of colloidal Ag nanoparticles

    Science.gov (United States)

    Velgosová, Oksana; Mražíková, Anna

    2017-12-01

    In this paper the influence of algae life cycle and the solutions pH on the green synthesis of colloidal Ag nanoparticles (AgNPs) as well as effect of different storage conditions on AgNPs long-term stability was investigated. Silver nanoparticles were biologically synthesized using extracts of Parachlorella kessleri algae cultivated 1, 2, 3 and 4 weeks. The formation of AgNPs was monitored using a UV-vis spectrophotometer and verified by TEM observation. The results confirmed formation of polyhedron and/or near polyhedron AgNPs, ranging between 5 and 60 nm in diameter. The age of algae influenced the synthesis rate and an amount of AgNPs in solution. The best results were obtained using tree weeks old algae. UV-vis analysis and TEM observation also revealed that the size and the stability of AgNPs depend on the pH of solution. AgNPs formed in solutions of higher pH (8 and 10) are polyhedron, fine, with narrow size interval and stabile. Nanoparticles formed in solutions of low pH (2, 4 and 6) started to lose their stability on 10th day of experiment, and the particle size interval was wide. The long-term stability of AgNPs can be influenced by light and temperature conditions. The most significant stability loss was observed at day light and room temperature (21°C). After 200-days significant amount of agglomerated particles settled on the bottom of the Erlenmeyer flask. AgNPs stored at dark and room temperature showed better long-term stability, weak particles agglomeration was observed. AgNPs stored at dark and at temperature 5°C showed the best long-term stability. Such AgNPs remained spherical, fine (5-20 nm), with narrow size interval and stable (no agglomeration) even after more than six months.

  13. Formation mechanisms of metal colloids

    Science.gov (United States)

    Halaciuga, Ionel

    Highly dispersed uniform metallic particles are widely used in various areas of technology and medicine and are likely to be incorporated into many other applications in the future. It is commonly accepted that size, shape and composition of the particles represent critical factors in most applications. Thus, understanding the mechanisms of formation of metal particles and the ways to control the physical (e.g. shape, size) and chemical (e.g. composition) properties is of great importance. In the current research, the formation of uniform silver spheres is investigated experimentally. The parameters that influence the formation of silver particles when concentrated iso-ascorbic acid and silver-polyamine complex solutions are rapidly mixed were studied in the absence of dispersants. We found that by varying the nature of the amine, temperature, concentration of reactants, silver/amine molar ratio, and the nature of the silver salt, the size of the resulting silver particles can be varied in a wide range (0.08--1.5 microm). The silver particles were formed by aggregation of nanosize subunits as substantiated by both electron microscopy and X-ray diffraction techniques and by the vivid rapid color changes during the chemical precipitation process. From the practical standpoint, the goal of this research was to prepare well dispersed spherical silver particles having a relatively smooth surface and a diameter of about 1 microm to satisfy the demands of the current electronic materials market. A two stage particle growth model previously developed to explain the narrow size distribution occurring in synthesis of gold spheres was applied to the present experimental system, and the parameters that control the size distribution characteristics were identified. The kinetic parameter required to match the final particle size was found to be in agreement with the one used previously in modeling formation of gold spheres, suggesting that similar kinetics governs the

  14. Colloidal phytosterols: synthesis, characterization and bioaccessibility

    NARCIS (Netherlands)

    Rossi, L.; Seijen ten Hoorn, J.W.M.; Melnikov, S.M.; Velikov, K.P.

    2010-01-01

    We demonstrate the synthesis of phytosterol colloidal particles using a simple food grade method based on antisolvent precipitation in the presence of a non-ionic surfactant. The resulting colloidal particles have a rod-like shape with some degree of crystallinity. The colloidal dispersions display

  15. Self-Assembly of Faceted Colloidal Particles

    NARCIS (Netherlands)

    Gantapara, A.P.

    2015-01-01

    A colloidal dispersion consists of insoluble microscopic particles that are suspended in a solvent. Typically, a colloid is a particle for which at least one of its dimension is within the size range of a nanometer to a micron. Due to collisions with much smaller solvent molecules, colloids perform

  16. Colloid formation during waste glass corrosion

    International Nuclear Information System (INIS)

    Mertz, C.J.; Buck, E.C.; Fortner, J.A.; Bates, J.K.

    1996-01-01

    The long-term behavior of nuclear waste glass in a geologic repository may require a technical consideration of the role of colloids in the release and transport of radionuclides. The neglect of colloidal properties in assessing the near- and far-field migration behavior of actinides may lead to significant underestimates and poor predictions of biosphere exposure from high-level waste (HLW) disposal. Existing data on colloid-facilitated transport suggests that radionuclide migration may be enhanced, but the importance of colloids is not adequately assessed. Indeed, the occurrence of radionuclide transport, attributed to colloidal species, has been reported at Mortandad Canyon, Los Alamos and at the Nevada Test Site; both unsaturated regions are similar to the proposed HLW repository at Yucca Mountain. Although some developments have been made on understanding the transport characteristics of colloids, the characterization of colloids generated from the corrosion of the waste form has been limited. Colloids are known to incorporate radionuclides either from hydrolysis of dissolved species (real colloids) or from adsorption of dissolved species onto existing groundwater colloids (pseudocolloids); however, these colloids may be considered secondary and solubility limited when compared to the colloids generated during glass alteration

  17. Sampling and physical and actinide characterization of colloids from the Grimsel test site

    International Nuclear Information System (INIS)

    Longworth, G.; Ivanovich, M.

    1990-01-01

    Samples of groundwater from a granite fracture at the Grimsel test site in Switzerland have been collected as part of a second intercomparison of groundwater colloid sampling and characterization techniques carried out by members of the Coco Club (colloids and complexes) sponsored by the CEC. This report describes the Harwell contribution to this exercise. The bulk of naturally occurring actinides were found to reside in solution with 10 particles/I (detection limit ∼50 nm) for samples determined by three laboratories. The colloids were shown to be negatively charged using microelectrophoresis and to be relatively stable. There was evidence of a reduction in the pH of the water after storage due to air contamination. This work has served to identify the problems associated with colloid sampling and characterization techniques

  18. Bonding assembled colloids without loss of colloidal stability

    NARCIS (Netherlands)

    Vutukuri, H.R.; Stiefelhagen, J.C.P.; Vissers, T; Imhof, A.; van Blaaderen, A.

    2012-01-01

    In recent years the diversity of self-assembled colloidal structures has strongly increased, as it is fueled by a wide range of applications in materials science and also in soft condensed-matter physics.[1–4] Some potential applications include photonic bandgap (PBG) crystals, materials for

  19. Biomimetic synthesis of silver nanoparticles using microalgal secretory carbohydrates as a novel anticancer and antimicrobial

    International Nuclear Information System (INIS)

    Ebrahiminezhad, Alireza; Bagheri, Mahboobeh; Taghizadeh, Seyedeh-Masoumeh; Ghasemi, Younes; Berenjian, Aydin

    2016-01-01

    Secreted carbohydrates by Chlorella vulgaris cells were used for reducing and capping Silver nanoparticles (AgNPs). Oxygen-bearing functional groups on the carbohydrates found to be the main biochemical groups responsible for anchoring the metal nanoparticles. Transmission electron microscopy (TEM) micrographs showed that isotropic small particles with mean particles size of 7 nm were synthesized. Comparing the TEM results with DLS analysis revealed that the thickness of carbohydrate capping was about 2 nm. A zeta potential of +26 mV made the particles colloidally stable and desirable for anticancer and antimicrobial applications. The MIC against gram positive (Staphylococcus aureus) and gram negative bacteria (Escherichia coli) were determined to be 37.5 μg ml −1 and 9.4 μg ml −1 , respectively. Treatment of Hep-G2 cells with 4.7 μg ml −1 AgNPs for 24 h reduced the cell viability to 61%. This concentration was also reduced the cell viability to 37% after 48 h of exposure. (paper)

  20. Biomimetic synthesis of silver nanoparticles using microalgal secretory carbohydrates as a novel anticancer and antimicrobial

    Science.gov (United States)

    Ebrahiminezhad, Alireza; Bagheri, Mahboobeh; Taghizadeh, Seyedeh-Masoumeh; Berenjian, Aydin; Ghasemi, Younes

    2016-03-01

    Secreted carbohydrates by Chlorella vulgaris cells were used for reducing and capping Silver nanoparticles (AgNPs). Oxygen-bearing functional groups on the carbohydrates found to be the main biochemical groups responsible for anchoring the metal nanoparticles. Transmission electron microscopy (TEM) micrographs showed that isotropic small particles with mean particles size of 7 nm were synthesized. Comparing the TEM results with DLS analysis revealed that the thickness of carbohydrate capping was about 2 nm. A zeta potential of +26 mV made the particles colloidally stable and desirable for anticancer and antimicrobial applications. The MIC against gram positive (Staphylococcus aureus) and gram negative bacteria (Escherichia coli) were determined to be 37.5 μg ml-1 and 9.4 μg ml-1, respectively. Treatment of Hep-G2 cells with 4.7 μg ml-1 AgNPs for 24 h reduced the cell viability to 61%. This concentration was also reduced the cell viability to 37% after 48 h of exposure.

  1. Experimental and theoretical study of the transport of silver nanoparticles at their prolonged administration into a mammal organism

    Science.gov (United States)

    Antsiferova, A. A.; Buzulukov, Yu. P.; Kashkarov, P. K.; Kovalchuk, M. V.

    2016-11-01

    The transport of silver nanoparticles in the organism of laboratory animals has been investigated. A mathematical model of the biokinetics of prolonged administration of nonmetabolizable and nonaglomerating pharmaceutical preparations is proposed, and its analytical solution is found. Based on the experimental data on the prolonged introduction and excretion of colloidal silver nanoparticles and the numerical approximation of the solutions to the equations for the proposed model, time dependences of the silver mass content in brain and blood are obtained and some other important biokinetic parameters are determined. It is concluded that both chronic1 and subchronic2 peroral application of these nanoparticles as an biologically active additive or antiseptic is potentially dangerous.

  2. Radiation-electrochemistry of the colloidal gold micro-electrode: Hydrogen formation by organic free radicals

    International Nuclear Information System (INIS)

    Westerhausen, J.; Henglein, A.; Lilie, J.

    1981-01-01

    Various organic free radicals as well as Ni + ions produce hydrogen in the presence of some 10 -4 M of colloidal gold. The gold catalyst was prepared via the reduction of HAuCl 4 either thermally by citrate or by γ-irradiation. The organic radicals were radiolytically produced. The mechanism of H 2 formation includes electron transfer from the organic radicals to the gold particles, storage of a large number of electrons per gold particle, conversion of the electrons into adsorbed H-atoms and desorption of the latter to form H 2 . - The rates of some of these steps were measured using the method of pulse radiolysis. 1-Hydroxy-1-methyl ethyl radicals, (CH 3 ) 2 COH, react with colloidal gold particles almost diffusion controlled provided that the gold particles are not charged with excess electrons. Charged gold particles react at a substantially lower rate. The stored electrons live seconds or even minutes depending on their number per gold particle. In the stationary state, up to 0.38 Coulomb of electrons could be stored per liter of a 2.9x10 -4 molar gold solution, each gold particle carrying about 39 electrons. A comparison is also made between the catalytic activities of colloidal gold and silver. Due to the relative fast conversion of electrons into adsorbed H-atoms, colloidal gold has less capacity for the storage of electrons than colloidal silver. - The dependence of the hydrogen yield on the pH of the solution, the concentration of gold, the size of the gold particles, the concentration of the polyvinyl alcohol stabilizer, and the intensity of radiation was also investigated. At high intensities, some of the radicals are destroyed in a gold catalysed disproportionation. (orig.)

  3. Colloid properties in groundwaters from crystalline formations

    International Nuclear Information System (INIS)

    Degueldre, C.A.

    1994-09-01

    Colloids are present in all groundwaters. The role they may play in the migration of safety-relevant radionuclides in the geosphere therefore must be studied. Colloid sampling and characterisation campaigns have been carried out in Switzerland. On the bases of the results from studies in the Grimsel area, Northern Switzerland and the Black Forest, as well as those obtained by other groups concerned with crystalline waters, a consistent picture is emerging. The groundwater colloids in crystalline formations are predominantly comprised of phyllosilicates and silica originating from the aquifer rock. Under constant hydrogeochemical conditions, the colloid concentration is not expected to exceed 100 ng.ml -1 when the calcium concentration is greater than 10 -4 . However, under transient chemical or physical conditions, such as geothermal or tectonic activity, colloid generation may be enhanced and the colloid concentration may reach 10 μg.ml -1 or more, if both the calcium and sodium concentrations are low. In the Nagra Crystalline Reference Water the expected colloid concentration is -1 . This can be compared, for example, to a colloid concentration of about 10 ng.ml -1 found in Zurzach water. The small colloid concentration in the reference water is a consequence of an attachment factor for clay colloids (monmorillonite) close to 1. A model indicates that at pH 8, the nuclide partition coefficients between water and colloid (K p ) must be smaller than 10 7 ml.g -1 if sorption takes place by surface complexation on colloids, = AIOH active groups forming the dominant sorption sites. This pragmatic model is based on the competition between the formation of nuclide hydroxo complexes in solution and their sorption on colloids. Experimental nuclide sorption data on colloids are compared with those obtained by applying this model. For a low colloid concentration, a sorption capacity of the order of 10 -9 M and reversible surface complexation, their presence in the

  4. A re-assessment of the safety of silver in household water treatment: rapid systematic review of mammalian in vivo genotoxicity studies.

    Science.gov (United States)

    Fewtrell, Lorna; Majuru, Batsirai; Hunter, Paul R

    2017-06-20

    Despite poor evidence of their effectiveness, colloidal silver and silver nanoparticles are increasingly being promoted for treating potentially contaminated drinking water in low income countries. Recently, however, concerns have been raised about the possible genotoxicity of particulate silver. The goal of this paper was to review the published mammalian in vivo genotoxicity studies using silver micro and nanoparticles. SCOPUS and Medline were searched using the following search string: ("DNA damage" OR genotox* OR Cytotox* OR Embryotox*) AND (silver OR AgNP). Included papers were any mammalian in vivo experimental studies investigating genotoxicity of silver particles. Studies were quality assessed using the ToxRTool. 16 relevant papers were identified. There were substantial variations in study design including the size of silver particles, animal species, target organs, silver dose, route of administration and the method used to detect genotoxicity. Thus, it was not possible to produce a definitive pooled result. Nevertheless, most studies showed evidence of genotoxicity unless using very low doses. We also identified one human study reporting evidence of "severe DNA damage" in silver jewellery workers occupationally exposed to silver particles. With the available evidence it is not possible to be definitive about risks to human health from oral exposure to silver particulates. However, the balance of evidence suggests that there should be concerns especially when considering the evidence from jewellery workers. There is an urgent need to determine whether people exposed to particulate silver as part of drinking water treatment have evidence of DNA damage.

  5. Chloride ion-dependent surface-enhanced Raman scattering study of biotin on the silver surface

    International Nuclear Information System (INIS)

    Liu Fangfang; Gu Huaimin; Yuan Xiaojuan; Dong Xiao; Lin Yue

    2011-01-01

    In the present paper, the surface enhanced Raman scattering (SERS) technique was employed to study the SERS spectra of biotin molecules formed on the silver surface. The adsorption geometries of biotin molecules on the silver surface were analyzed based on the SERS data. It can be found that most vibration modes show a Raman shift in silver sol after the addition of sodium chloride solution. In addition, The Raman signals of biotin become weaker and weaker with the increase of the concentration of sodium chloride. This may be due to that the interaction between chloride ions and silver particles is stronger than the interaction between biotin molecules and silver particles. When the concentration of sodium chloride in silver colloid is higher than 0.05mol/L, superfluous chloride ions may form an absorption layer so that biotin can not be adsorbed on silver surface directly. The changes in intensity and profile shape in the SERS spectra suggest different adsorption behavior and surface-coverage of biotin on silver surface. The SERS spectra of biotin suggest that the contribution of the charge transfer mechanism to SERS may be dominant.

  6. Copper and silver halates

    CERN Document Server

    Woolley, EM; Salomon, M

    2013-01-01

    Copper and Silver Halates is the third in a series of four volumes on inorganic metal halates. This volume presents critical evaluations and compilations for halate solubilities of the Group II metals. The solubility data included in this volume are those for the five compounds, copper chlorate and iodate, and silver chlorate, bromate and iodate.

  7. Microbial effects on colloidal agglomeration

    International Nuclear Information System (INIS)

    Hersman, L.

    1995-11-01

    Colloidal particles are known to enhance the transport of radioactive metals through soil and rock systems. This study was performed to determine if a soil microorganism, isolated from the surface samples collected at Yucca Mountain, NV, could affect the colloidal properties of day particles. The agglomeration of a Wyoming bentonite clay in a sterile uninoculated microbial growth medium was compared to the agglomeration in the medium inoculated with a Pseudomonas sp. In a second experiment, microorganisms were cultured in the succinate medium for 50 h and removed by centrifugation. The agglomeration of the clay in this spent was compared to sterile uninoculated medium. In both experiments, the agglomeration of the clay was greater than that of the sterile, uninoculated control. Based on these results, which indicate that this microorganism enhanced the agglomeration of the bentonite clay, it is possible to say that in the presence of microorganisms colloidal movement through a rock matrix could be reduced because of an overall increase in the size of colloidal particle agglomerates. 32 refs

  8. Characterization of Complex Colloidal Suspensions

    Science.gov (United States)

    Seaman, J. C.; Guerin, M.; Jackson, B. P.; Ranville, J. M.

    2003-04-01

    Surface chemical reactions play a major role in controlling contaminant fate and transport in the subsurface environment. Recent field and laboratory evidence suggests that mobile soil and groundwater colloids may facilitate the migration of sparingly soluble groundwater contaminants. Colloidal suspensions collected in the field or generated in laboratory column experiments tend to be fairly dilute in nature and comprised of relatively small particulates (reserved for studying ideal systems to the characterization of mobile colloids. However, many of these analytical techniques, including total/selective dissolution methods, dynamic light scattering, micro-electrophoresis, streaming potential, and even scanning electron microscopy (SEM), can be biased in of larger size fractions, and therefore, extremely sensitive to sampling, storage, and fractionation artifacts. In addition, surface modifiers such as sorbed oxides or organics can alter particulate appearance, composition, and behavior when compared to synthetic analogues or mineral standards. The current presentation will discuss the limitations and inherent biases associated with a number of analytical characterization techniques that are commonly applied to the study of mobile soil and groundwater colloids, including field flow fractionation (FFF) and acoustic based methods that have only recently become available.

  9. A short textbook of colloid chemistry

    CERN Document Server

    Jirgensons, B

    1962-01-01

    A Short Textbook of Colloid Chemistry, Second Revised Edition details the factual aspect of colloid chemistry that includes the basic facts, established empirical and mathematical relationships, and practical applications. The chapters of the title are organized into two parts. In the first part, the text discusses the general concepts of colloid chemistry, such as the history and scope, basic terms, and basic methods in experiment with colloids. Part Two covers the technical aspect of colloid chemistry, such as the optical properties, electrical properties, and viscosity. The book will be of

  10. Microstrain and residual stress in thin-films made from silver nanoparticles deposited by inkjet-printing technology

    NARCIS (Netherlands)

    Cauchois, R.; Borbély, A.; Gergaud, P.; Saadaoui, M.; Inal, K.

    2014-01-01

    Colloidal suspensions of nanoparticles are increasingly employed in the fabrication process of electronic devices using inkjet-printing technology and a consecutive thermal treatment. The evolution of internal stresses during the conversion of silver nanoparticle-based ink into a metallic thin-film

  11. Interactive Relationship between Silver Ions and Silver Nanoparticles with PVA Prepared by the Submerged Arc Discharge Method

    Directory of Open Access Journals (Sweden)

    Kuo-Hsiung Tseng

    2018-01-01

    Full Text Available This study uses the submerged arc discharge method (SADM and the concentrated energy of arc to melt silver metal in deionized water (DW so as to prepare metal fluid with nanoparticles and submicron particles. The process is free from any chemical agent; it is rapid and simple, and rapid and mass production is available (0.5 L/min. Aside from the silver nanoparticle (Ag0, silver ions (Ag+ exist in the colloidal Ag prepared by the system. In the preparation of colloidal Ag, polyvinyl alcohol (PVA is used as an additive so that the Ag0/Ag+ concentration, arcing rate, peak, and scanning electron microscopic (SEM images in the cases with and without PVA can be analyzed. The findings show that the Ag0/Ag+ concentration increases with the addition level of PVA, while the nano-Ag and Ag+ electrode arcing rate rises. The UV-Vis absorption peak increases Ag0 absorbance and shifts as the dispersity increases with PVA addition. Lastly, with PVA addition, the proposed method can prepare smaller and more amounts of Ag0 nanoparticles, distributed uniformly. PVA possesses many distinct features such as cladding, dispersion, and stability.

  12. Unpredictably Stable

    DEFF Research Database (Denmark)

    Failla, Virgilio; Melillo, Francesca; Reichstein, Toke

    2014-01-01

    Is entrepreneurship a more stable career choice for high employment turnover individuals? We find that a transition to entrepreneurship induces a shift towards stayer behavior and identify job matching, job satisfaction and lock-in effects as main drivers. These findings have major implications...

  13. Modeling of the geochemical behaviour and of the radionuclide transport in the presence of colloids

    International Nuclear Information System (INIS)

    Van der Lee, Jan

    1997-01-01

    CHESS, a complete geochemical model, especially developed for coupling purposes in a transparent manner with transport codes. The second topic concerns the development of a probabilistic theory for colloid retention, as well as for the kinetics involved in the reaction. The proposed theory seem to be robust, predicts correctly the impact of System parameters such as pH, ionic strength and colloid size, and is applicable to real Systems, at least at the scale of laboratory experiments. The thesis also presents the theory of adsorption kinetics. This theory is more rigorous than the theories available in the literature, and applies for porous as well as fractured media. A comparison with models provided by the literature and with experimental data seems to confirm the correctness of the theory. The third topic involves reactive transport modelling of chemical species and colloids and has lead to the development of a new transport model, HYTEC. This tool includes convective-diffusive-dispersive transport of colloids, aqueous species and gases, calculates the thermodynamic equilibrium state of the solution and incorporates the newly developed theory of colloid retention. As far as we know, this is the first model which integrates colloids as well as the complete geochemistry in a transport model. Resuming, this work shows the importance of the adsorption capacity of most of the natural colloids with respect to actinides, such as uranium, americium and europium. The complexation capacity of organic colloids is even greater than that of inorganic colloids, such as silica, clays and hydrous ferric oxide. This study also indicates that colloids are capable of keeping the radioactive load during their journey through the geological medium, even if the complexing affinity of the medium is much stronger than of the colloids. Accordingly, colloids may act as a very rapid transport vehicle for radionuclides, provided they are chemically and electrostatically stable in suspension

  14. Glass/Jamming Transition in Colloidal Aggregation

    Science.gov (United States)

    Segre, Philip N.; Prasad, Vikram; Weitz, David A.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We have studied colloidal aggregation in a model colloid plus polymer system with short-range attractive interactions. By varying the colloid concentration and the strength of the attraction, we explored regions where the equilibrium phase is expected to consist of colloidal crystallites in coexistance with colloidal gas (i.e. monomers). This occurs for moderate values of the potential depth, U approximately equal to 2-5 kT. Crystallization was not always observed. Rather, over an extended sub-region two new metastable phases appear, one fluid-like and one solid-like. These were examined in detail with light scattering and microscopy techniques. Both phases consist of a near uniform distribution of small irregular shaped clusters of colloidal particles. The dynamical and structural characteristics of the ergodic-nonergodic transition between the two phases share much in common with the colloidal hard sphere glass transition.

  15. Morphology-controlled synthesis of silver nanostructures via a seed catalysis process

    Science.gov (United States)

    Chen, Chang; Wang, Li; Yu, Haojie; Wang, Jianjun; Zhou, Junfeng; Tan, Qiaohua; Deng, Libo

    2007-03-01

    A novel, effective strategy named 'seed catalysis' has been described here to synthesize silver nanostructures with controllable morphology. Typically, we added Na2S into the reaction system and the Ag2S semiconductor colloids formed at the initial stage would act as both seeds and catalyst in the silver reduction. The morphology of products is controlled by the concentration of Na2S added to the system. Low concentration of Na2S gives nanocubes of 40-50 nm in size, while a high concentration of Na2S is of benefit to obtain nanowires. The growth of the silver crystal is also accelerated by the catalysis of Ag2S. Electron microscopy and UV-vis absorption spectra have been used to investigate the evolution of silver nanowires, and a reasonable mechanism to explain the role of Ag2S seeds has also been suggested. This semiconductor seed catalysis strategy will provide wide applications in the fabrication of metal nanomaterials.

  16. Green Synthesis of Silver Nanoparticles and the Study of Optical Properties

    Directory of Open Access Journals (Sweden)

    Ramakrishna Vasireddy

    2012-08-01

    Full Text Available The synthesis of silver nanoparticles of varying size has been achieved using different molar concentrations of NaOH while the effect of changing the temperature has been studied. AgNO3, gelatine, glucose and NaOH are used as a silver precursor, stabilizer, reducing agent and accelerator respectively. The synthesized nanoparticles have been characterized by a FESEM study, X‐ray diffractometry, Raman spectroscopy and UV‐vis spectroscopy. The colloidal sols of the silver nanoparticles in a biopolymer gelatine show strong surface plasmon resonance absorption peaks. The visible photoluminescence emission from the synthesized silver nanocrystals has been recorded within the wavelength range of 400‐600 nm under UV excitation. The synthesized nanoparticles may be extremely useful in making biosensor devices as well as for other applications.

  17. Morphology-controlled synthesis of silver nanostructures via a seed catalysis process

    International Nuclear Information System (INIS)

    Chen Chang; Wang Li; Yu Haojie; Wang Jianjun; Zhou Junfeng; Tan Qiaohua; Deng Libo

    2007-01-01

    A novel, effective strategy named 'seed catalysis' has been described here to synthesize silver nanostructures with controllable morphology. Typically, we added Na 2 S into the reaction system and the Ag 2 S semiconductor colloids formed at the initial stage would act as both seeds and catalyst in the silver reduction. The morphology of products is controlled by the concentration of Na 2 S added to the system. Low concentration of Na 2 S gives nanocubes of 40-50 nm in size, while a high concentration of Na 2 S is of benefit to obtain nanowires. The growth of the silver crystal is also accelerated by the catalysis of Ag 2 S. Electron microscopy and UV-vis absorption spectra have been used to investigate the evolution of silver nanowires, and a reasonable mechanism to explain the role of Ag 2 S seeds has also been suggested. This semiconductor seed catalysis strategy will provide wide applications in the fabrication of metal nanomaterials

  18. Mineral commodity profiles: Silver

    Science.gov (United States)

    Butterman, W.C.; Hilliard, Henry E.

    2005-01-01

    Overview -- Silver is one of the eight precious, or noble, metals; the others are gold and the six platinum-group metals (PGM). World mine production in 2001 was 18,700 metric tons (t) and came from mines in 60 countries; the 10 leading producing countries accounted for 86 percent of the total. The largest producer was Mexico, followed by Peru, Australia, and the United States. About 25 percent of the silver mined in the world in 2001 came from silver ores; 15 percent, from gold ores and the remaining 60 percent, from copper, lead, and zinc ores. In the United States, 14 percent of the silver mined in 2001 came from silver ores; 39 percent, from gold ores; 10 percent, from copper and copper-molybdenum ores; and 37 percent, from lead, zinc, and lead-zinc ores. The precious metal ores (gold and silver) came from 30 lode mines and 10 placer mines; the base-metal ores (copper, lead, molybdenum, and zinc) came from 24 lode mines. Placer mines yielded less than 1 percent of the national silver production. Silver was mined in 12 States, of which Nevada was by far the largest producer; it accounted for nearly one-third of the national total. The production of silver at domestic mines generated employment for about 1,100 mine and mill workers. The value of mined domestic silver was estimated to be $290 million. Of the nearly 27,000 t of world silver that was fabricated in 2001, about one-third went into jewelry and silverware, one-fourth into the light-sensitive compounds used in photography, and nearly all the remainder went for industrial uses, of which there were 7 substantial uses and many other small-volume uses. By comparison, 85 percent of the silver used in the United States went to photography and industrial uses, 8 percent to jewelry and silverware, and 7 percent to coins and medals. The United States was the largest consumer of silver followed by India, Japan, and Italy; the 13 largest consuming countries accounted for nearly 90 percent of the world total. In the

  19. Evaluation of colloidal Ag and Ag-alloys as anode electrocatalysts for direct borohydride fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Atwan, Mohammed H.; Northwood, Derek O. [Mechanical, Auto, and Materials Engineering, University of Windsor, Windsor, N9B 3P4 (Canada); Gyenge, Elod L. [Chemical and Biological Engineering, The University of British Colombia, Vancouver, BC, V6T 1Z4 (Canada)

    2007-10-15

    In this study, colloidal silver and silver-alloys (Ag-Pt, Ag-Au, Ag-Ir, and Ag-Pd) prepared by the Boenneman technique were evaluated as anode catalysts for sodium borohydride oxidation using cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP) and rotating disk electrode (RDE) voltammetry. The CV results show that the colloidal Ag-alloys were electrochemically active towards borohydride oxidation with oxidation potentials ranging between -0.7 and 0.4 V vs. Hg/HgO (MOE). The most negative oxidation potential was recorded on Ag-Pt. CA results show that the steady state current density was highest on Ag-Pt, followed by Ag-Ir, Ag-Au, and Ag-Pd. The lowest overpotential was recorded on Ag-Ir for a current step change of 10mAcm{sup -2}. A significant temperature effect and a small rotation speed effect were found in the rotating disc voltammetry for all the investigated colloids. The highest peak current was recorded on Ag-Au, while the most negative peak potential was recorded on Ag-Ir. (author)

  20. Determination of silver in fresh water by atomic absorption spectrometry following flotation preconcentration by iron(III) collectors

    Energy Technology Data Exchange (ETDEWEB)

    Cundeva, K.; Stafilov, T. [Institute of Chemistry, Faculty of Science, St. Cyril and Methodius University, Skopje (Yugoslavia)

    1997-08-01

    Colloid precipitate flotation of silver from fresh water is applied for preconcentration and separation. Optimal conditions using hydrated iron(III) oxide and iron(III) tetramethylenedithiocarbamate as collectors were investigated. Various factors affecting the silver recovery, including collector mass, nature of the supporting electrolyte, pH of the working medium, electrokinetic potential of the collector particle surfaces, type of surfactant, induction time etc., were checked. Within the optimal pH range (5.5-6.5) silver was separated quantitatively (94.9- 100.0%) with 30 mg Fe(III) as collector. The content of silver was determined by electrothermal atomic absorption spectrometry and compared to that from inductively coupled plasma-atomic emission spectrometry. The detection limit of silver by the method described is 0.01 {mu}g/L. (orig.) With 2 figs., 3 tabs.