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Sample records for ag nanoparticles prepared

  1. Preparation and antibacterial activities of Ag/Ag+/Ag3+ nanoparticle composites made by pomegranate (Punica granatum) rind extract

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Ren, Yan-yu; Wang, Tao; Wang, Chuang

    Nano-silver and its composite materials are widely used in medicine, food and other industries due to their strong conductivity, size effect and other special performances. So far, more microbial researches have been applied, but a plant method is rarely reported. In order to open up a new way to prepare AgNP composites, pomegranate peel extract was used in this work to reduce Ag+ to prepare Ag/Ag+/Ag3+ nanoparticle composites. UV-Vis was employed to detect and track the reduction of Ag+ and the forming process of AgNPs. The composition, structure and size of the crystal were analyzed by XRD and TEM. Results showed that, under mild conditions, pomegranate peel extract reacted with dilute AgNO3 solution to produce Ag/Ag+/Ag3+ nanoparticle composites. At pH = 8 and 10 mmol/L of AgNO3 concentration, the size of the achieved composites ranged between 15 and 35 nm with spherical shapes and good crystallinity. The bactericidal experiment indicated that the prepared Ag/Ag+/Ag3+ nanoparticles had strong antibacterial activity against gram positive bacteria and gram negative bacteria. FTIR analysis revealed that biological macromolecules with groups of sbnd NH2, sbnd OH, and others were distributed on the surface of the newly synthesized Ag/Ag+/Ag3+ nanoparticles. This provided a useful clue to further study the AgNP biosynthesis mechanism.

  2. Preparation of conducting silver paste with Ag nanoparticles prepared by e-beam irradiation

    NASA Astrophysics Data System (ADS)

    Sohn, Jong Hwa; Pham, Long Quoc; Kang, Hyun Suk; Park, Ji Hyun; Lee, Byung Cheol; Kang, Young Soo

    2010-11-01

    Conducting silver paste was prepared by using Ag nanoparticles which were synthesized by e-beam irradiation method (from KAERI); its conductivity was comparatively determined with Ag nanoparticles which were prepared by thermolysis method (commercial). The silver nanoparticles with the diameter of approximately 150 nm size prepared by e-beam irradiation were mixed with glass frit and sintered for 1 h at 500 °C. It is presumably concluded that the wt% of silver nanoparticle, size distribution and homogenous dispersibility of Ag nanoparticles in the pastes are the critical factors for the high conductivity of the paste. Among the various wt% of silver nanoparticle in the conducting silver pastes, silver paste with 90 wt% of silver nanoparticle has the highest conductivity as 1.6×10 4 S cm -1. This conductivity value is 1.6 times higher than the Ag pastes which were prepared with silver nanoparticles obtained by thermolysis method.

  3. Phytotoxicity of Ag nanoparticles prepared by biogenic and chemical methods

    NASA Astrophysics Data System (ADS)

    Choudhury, Rupasree; Majumder, Manna; Roy, Dijendra Nath; Basumallick, Srijita; Misra, Tarun Kumar

    2016-06-01

    Silver nanoparticles (Ag NPs) are now widely used as antibacterial and antifungal materials in different consumer products. We report here the preparation of Ag NPs by neem leaves extract ( Azadirachta) reduction and trisodium citrate-sodium borohydride reduction methods, and study of their phytotoxicity. The nanoparticles were characterized by UV-Vis spectroscopy, FTIR, and atomic force microscopy (AFM) techniques. Both neem-coated and citrate-coated Ag NPs exhibit surface plasmon around 400 nm, and their average sizes measured by AFM are about 100 and 20 nm, respectively. Antibacterial and antifungal activities of these nanomaterials have been studied by simple pea seed germination and disk diffusion methods. It has been observed from the growth of root and shoot, citrate-coated Ag NPs significantly affect seedling growth, but neem-coated Ag NPs exhibit somehow mild toxicity toward germination process due to the nutrient supplements from neem. On the other hand, antifungal activity of neem-coated Ag NPs has been found much higher than that of citrate-coated Ag NPs due to the combined effects of antifungal activity of neem and Ag NPs. Present research primarily indicates a possible application of neem-coated Ag NPs as a potential fungicide.

  4. Preparation of highly dispersed core/shell-type titania nanocapsules containing a single Ag nanoparticle.

    PubMed

    Sakai, Hideki; Kanda, Takashi; Shibata, Hirobumi; Ohkubo, Takahiro; Abe, Masahiko

    2006-04-19

    Core/shell-type titania nanocapsules containing a single Ag nanoparticle were prepared. Ag nanoparticles were prepared using the reduction of silver nitrate with hydrazine in the presence of cetyltrimethylammonium bromide (CTAB) as protective agent. The sol-gel reaction of titanium tetraisopropoxide (TTIP) was used to prepare core/shell-type titania nanocapsules with CTAB-coated Ag nanoparticles as the core. TEM observations revealed that the size of the core (Ag particle) and the thickness of the shell (titania) of the core/shell particles obtained are about 10 nm and 5-10 nm, respectively. In addition, the nanocapsules were found to be dispersed in the medium as individual particles without aggregation. Moreover, titania coating caused the surface plasmon absorption of Ag nanoparticles to shift toward the longer wavelength side. PMID:16608315

  5. Application of a new coordination compound for the preparation of AgI nanoparticles

    SciTech Connect

    Mohandes, Fatemeh; Salavati-Niasari, Masoud

    2013-10-15

    Graphical abstract: Silver iodide nanoparticles have been sonochemically synthesized by using silver salicylate complex, [Ag(HSal)], as silver precursor. A series of control experiments were carried out to investigate the effects of solvent, surfactant concentration, sonication time and temperature on the morphology of AgI nanostructures. - Highlights: • Silver salicylate as a new precursor was applied to fabricate γ-AgI nanoparticles. • To further decrease the particle size of AgI, SDS was used as surfactant. • The effect of preparation parameters on the particle size of AgI was investigated. - Abstract: AgI nanoparticles have been sonochemically synthesized by using silver salicylate, [Ag(HSal)], as silver precursor. To investigate the effects of solvent, surfactant concentration, sonication time and temperature on the morphology of AgI nanostructures, several experiments were carried out. The products were characterized by SEM, TEM, XRD, TGA/DTA, UV–vis, and FT-IR. Based on the experimental findings in this research, it was found that the size of AgI nanoparticles was dramatically dependent on the silver precursor, sonochemical irradiation, and surfactant concentration. Sodium dodecyl sulfate (SDS) was applied as surfactant. When the concentration of SDS was 0.055 mM, very uniform sphere-like AgI nanoparticles with grain size of about 25–30 nm were obtained. These results indicated that the high concentration of SDS could prevent the aggregation between colloidal nanoparticles due to its steric hindrance effect.

  6. A simple way to prepare Cupric oleate capped AgI nanoparticles

    SciTech Connect

    Song Meirong; Zhang Zhijun . E-mail: s234soow@henu.edu.cn

    2004-12-02

    Cupric oleate capped AgI (Cu(OA){sub 2}-AgI) nanoparticles were prepared by a simple method and they have good dispersibility in organic solvents. X-ray diffraction (XRD), transmission electron microscope (TEM), FTIR, X-ray photoelectron spectrometer (XPS) and ultraviolet-visible (UV-vis) spectrometer were used to characterize the Cu(OA){sub 2}-AgI nanoparticles. The results show that the mean size is about 80 nm; the modified reagent has been chemically bonded on the surface of AgI. In addition, new absorption peaks in the UV region appear.

  7. Preparation and antibacterial activity of Fe3O4@Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Gong, Ping; Li, Huimin; He, Xiaoxiao; Wang, Kemin; Hu, Jianbing; Tan, Weihong; Zhang, Shouchun; Yang, Xiaohai

    2007-07-01

    Bifunctional Fe3O4@Ag nanoparticles with both superparamagnetic and antibacterial properties were prepared by reducing silver nitrate on the surface of Fe3O4 nanoparticles using the water-in-oil microemulsion method. Formation of well-dispersed nanoparticles with sizes of 60 ± 20 nm was confirmed by transmission electron microscopy and dynamic light scattering. X-ray diffraction patterns and UV-visible spectroscopy indicated that both Fe3O4 and silver are present in the same particle. The superparamagnetism of Fe3O4@Ag nanoparticles was confirmed with a vibrating sample magnetometer. Their antibacterial activity was evaluated by means of minimum inhibitory concentration value, flow cytometry, and antibacterial rate assays. The results showed that Fe3O4@Ag nanoparticles presented good antibacterial performance against Escherichia coli (gram-negative bacteria), Staphylococcus epidermidis (gram-positive bacteria) and Bacillus subtilis (spore bacteria). Furthermore, Fe3O4@Ag nanoparticles can be easily removed from water by using a magnetic field to avoid contamination of surroundings. Reclaimed Fe3O4@Ag nanoparticles can still have antibacterial capability and can be reused.

  8. Preparation of graphene-Ag nanoparticles hybrids and their SERS activities

    NASA Astrophysics Data System (ADS)

    Wang, Xinyu; Wang, Ning; Gong, Tiancheng; Zhu, Yong; Zhang, Jie

    2016-11-01

    Surface-enhanced Raman scattering (SERS) substrates based on graphene and Ag nanoparticles hybrid structures with low cost, high uniformity were prepared by a standard process of immobilization of silver nanoparticles with 3-aminopropyltrimethoxysilane (APTMS). Thermal annealing was used for removing residual APTMS and adjusting the morphology of silver nanoparticles, and the effectiveness of this method was verified experimentally. The influence of annealing temperature, dipping duration, and APTMS volume on the distribution of Ag nanoparticles and Raman enhancement was investigated experimentally and analyzed in detail. Our samples were prepared under the preparation conditions of 10% ν/ν APTMS, dipping time of 48 h, annealing temperature of 450 °C, duration of 30 min, and Ar flow rate of 40 sccm. SERS activities with enhancement of 107 and relative standard deviation of <20% were observed using rhodamine 6G (R6G) as probe molecule with a concentration of 10-6 M and 10-7 M.

  9. Magnetic properties of Co/Ag core/shell nanoparticles prepared by successive reactions in microemulsions

    NASA Astrophysics Data System (ADS)

    Rivas, J.; Garcia-Bastida, A. J.; Lopez-Quintela, M. A.; Ramos, C.

    2006-05-01

    Co nanoparticles with an Ag covering layer have been prepared by successive reactions in microemulsions. Their magnetic behavior was studied as a function of heat treatment. It was confirmed that, under the experimental conditions of this study, the size of the Co nuclei is limited by the reactant concentration, whereas the Ag covering is fixed by microemulsion droplet size. The as-prepared particles contain mainly Co 3O 4 nuclei, and present high effective moments that agree with the spin state of Co 3+. The observed magnetic behaviors were explained taking into account the intra- and inter-particle structural evolution of the particle assemblies annealed under different experimental conditions.

  10. Scalable preparation of ultrathin silica-coated Ag nanoparticles for SERS application.

    PubMed

    Hu, Yanjie; Shi, Yunli; Jiang, Hao; Huang, Guangjian; Li, Chunzhong

    2013-11-13

    Silica-coated Ag nanoparticles (Ag@SiO2 NPs) have been successfully prepared by a scalable flame spray pyrolysis (FSP) technique with production rate up to 4 g/h in laboratory-scale. The ultrathin SiO2 shell, with a thickness 1 nm, not only effectively avoids the intersintering of Ag nanoparticles core at the high temperature, but also serves as a protective layer of the SERS-active nanostructure. The silica-coated Ag nanoparticles form agglomerates in the large temperature gradient zone, which with several nanometers gaps from each other but not contact. Such an intriguing feature can result in more Raman hot-spots generated at the gaps among Ag core active sites, which will beneficial for the whole SERS substrate enhancement. The results demonstrate that a maximum enhancement factor can reach ~10(5) with a detectable concentration as low as 10(-10) M for rhodamine 6G (R6G) molecules, indicating that the as-obtained unique nanostructure will be a promising candidate for SERS applications. PMID:24117322

  11. [Preparation Polyacrylonitrile/Ag Nanoparticle Composite Nanofibers Via an Elelctrospinning Technique and Their Surface Enhanced Raman Scattering Study].

    PubMed

    Song, Wei; Li, Ting-ting; Wang, Xu; Zhao, Bing

    2015-07-01

    In this paper, we have prepared polyacrylonitrile (PAN) /Ag nanoparticle composite nanofibers as a surface enhanced Raman scattering (SERS) substrate via an electrospinning technique. First, the PAN and AgNO3 were dissolved in N, N'-dimethylformamide solvent to get PAN/Ag seed solution; then the PAN/Ag seed solution was electrospun for the preparation of PAN/Ag seed composite nanofibers; Finally, the PAN/Ag seed composite nanofibers were treated by hydrazine hydrate to syn- thesize PAN/Ag nanoparticle composite nanofibers. The as-prepared PAN/Ag nanoparticle composite nanofibers were mixed with the probes for the SERS detection to get the SERS spectrum of the probes. The PAN/Ag nanoparticle composite nanofibers substate showed a good SERS signal when the concentration of PATP is as low as 10(-6) mol x L(-1). Furthermore, this kind of SERS substrate could be large-scale prepared, which showed a high commercial value. PMID:26717748

  12. Preparation of Novel Europium Complex Doped Ag@SiO2 Nanoparticles with Intense Fluorescence.

    PubMed

    Liu, Bing; Yin, Dongguang; Song, Kailin; Yang, Juan Ou; Wang, Chengcheng; Wu, Minghong

    2015-01-01

    In this study, a new europium complex of 4,4'-bis (1",1",1",2",2",3",3"-heptafluoro-4",6"- hexanedion-6"-yl)-o-terpheny-Eu(3+)-4,7-diphenyl-1,10-phenanthroline-2,9-dicarboxylic acid-(3-aminopropyl) trimethoxysilane (BHHT-Eu(3+)-DPPDA-APTMS) was prepared first. Then novel core-shell Ag@SiO2 nanoparticles with BHHT-Eu(3+)-DPPDA-APTMS doped in shell were synthesized by a facile water-in-oil microemulsion method. The properties of the prepared complex and nanoparticles, and the effect of metal enhanced fluorescence for the nanoparticles were investigated. The prepared nanopartilces exhibited intense fluorescence, uniform morphology and good water-solubility. The fluorescent intensities of silver core-present nanopartciles were significant higher than that of silver core-absent nanoparticles owing to the metal enhanced fluorescence of silver core. It is expectable that the as-prepared nanoparticles can serve as a potential fluorescent nanoprobe, applying in high sensitive biological and medical detections.

  13. Production of antibacterial colored viscose fibers using in situ prepared spherical Ag nanoparticles.

    PubMed

    Emam, Hossam E; Mowafi, Salwa; Mashaly, Hamada M; Rehan, Mohamed

    2014-09-22

    In situ incorporation technique was used for coloration and acquiring excellent antibacterial properties for viscose fibers by silver nanoparticles (AgNPs). AgNPs were prepared in situ and incorporated in viscose matrix directly without using any other reducing and stabilizing agents. The main objective of this research was to successfully employ the reducing and stabilizing features of cellulose to produce nanosilver-viscose composites. Coloration of fibers after in situ AgNPs incorporation is related to surface plasmon resonance of silver. Colorimetric data were recorded as a function of washings to characterize the final colored fibers. Fastness properties and silver release were all measured to study the washable and wear off properties. Depending on the silver concentration, yellowish colored fibers with different shades were produced. Good fastness properties were obtained after 20 washings without using any crosslinker or binder. The colored fibers had excellent antibacterial activities against Escherichia coli, even after 20 washings. PMID:24906741

  14. Synthesis of silver nanoparticles deposited on silica by γ-irradiation and preparation of PE/Ag nano compound masterbatches

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi Kim Lan; Trinh Nguyen, Thuy Ai; Phu Dang, Van; Duy Nguyen, Ngoc; Le, Anh Quoc; Hien Nguyen, Quoc

    2013-12-01

    Silver nanoparticles (AgNPs) deposited on silica were synthesized by gamma Co-60 irradiation of Ag+ dispersion in silica/ethanol/water mixture (9/80/20:w/v/v). The reduction of Ag+ is occurred by hydrated electron (e-aq) and hydrogen atom (H•) generated during radiolysis of ethanol/water. The conversion doses (Ag+ → Ag0) were determined by UV-Vis spectroscopy. The synthesized AgNPs/silica were characterized by transmission electron microscopy (TEM) and x-ray diffraction (XRD), which showed the size of AgNPs to be in the range of 5-40 nm for Ag+ concentrations from 5 to 20 mM. Masterbatches of PE/AgNPs/silica compound with silver content from 250 to 1000 mg kg-1 were also prepared. These masterbatches can be suitably used for various applications such as antimicrobial food containers and packing films, etc.

  15. Preparation of an agar-silver nanoparticles (A-AgNp) film for increasing the shelf-life of fruits.

    PubMed

    Gudadhe, Janhavi A; Yadav, Alka; Gade, Aniket; Marcato, Priscyla D; Durán, Nelson; Rai, Mahendra

    2014-12-01

    Preparation of protective coating possessing antimicrobial properties is present day need as they increase the shelf life of fruits and vegetables. In the present study, preparation of agar-silver nanoparticle film for increasing the shelf life of fruits is reported. Silver nanoparticles (Ag-NPs) biosynthesised using an extract of Ocimum sanctum leaves, were mixed with agar-agar to prepare an agar-silver nanoparticles (A-AgNp) film. This film was surface-coated over the fruits, Citrus aurantifolium (Thornless lime) and Pyrus malus (Apple), and evaluated for the determination of antimicrobial activity of A-AgNp films using disc diffusion method, weight loss and shelf life of fruits. This study demonstrates that these A-AgNp films possess antimicrobial activity and also increase the shelf life of fruits. PMID:25429496

  16. The preparation and characterization of nanoparticle Ag-SiO2 composite films with super low refractive index

    NASA Astrophysics Data System (ADS)

    Sun, Yu-Long; Wang, Jian; Li, Shou-Yi; He, Xin; Wang, Cheng-Wei

    2014-09-01

    The spin coating technique is used to prepare the porous Ag-SiO2 composite films, and the subsequent annealing process makes the nanoparticle Ag-SiO2 composite films formed. As the increase of the annealing temperature from 300 °C to 500 °C, the size of Ag-SiO2 composite nanoparticles gradually decreases. The SEM, TEM and XRD measurements of Ag-SiO2 composite films indicate that the single crystal metal nanoparticles are uniformly embedded into the SiO2 particles, forming Ag-SiO2 composite nanoparticles. The SPR absorption spectra of the Ag-SiO2 composite films show the content of metal Ag increases with the increase of annealing temperature, but when the annealing temperature increases to 500 °C, the SPR absorption is not observed on the absorption spectra although the total absorption of Ag-SiO2 composite films is enhanced. Furthermore, the optical constants of Ag-SiO2 composite films have been determined based on the measurement of ellipsometric parameters. It is more important the refractive index lower than 1 is obtained after annealing process of Ag-SiO2 composite films under 300 and 400 °C, but the extinction coefficient is low, which makes the film have low absorption.

  17. Preparation and application of conducting polymer/Ag/clay composite nanoparticles formed by in situ UV-induced dispersion polymerization

    PubMed Central

    Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

    2016-01-01

    In this work, composite nanoparticles containing polypyrrole, silver and attapulgite (PPy/Ag/ATP) were prepared via UV-induced dispersion polymerization of pyrrole using ATP clay as a templet and silver nitrate as photoinitiator. The effects of ATP concentration on morphology, structure and electrical conductivity were studied. The obtained composite nanoparticles with an interesting beads-on-a-string morphology can be obtained in a short time (10 min), which indicates the preparation method is facile and feasible. To explore the potential applications of the prepared PPy/Ag/ATP composite nanoparticles, they were served as multifunctional filler and blended with poly(butylene succinate) (PBS) matrix to prepare biodegradable composite material. The distribution of fillers in polymer matrix and the interfacial interaction between fillers and PBS were confirmed by scanning electron microscope, elemental mapping and dynamic mechanical analysis. The well dispersed fillers in PBS matrix impart outstanding antibacterial property to the biodegradable composite material as well as enhanced storage modulus due to Ag nanoparticles and ATP clay. The biodegradable composite material also possesses modest surface resistivity (106 ~ 109 Ω/◻). PMID:26839126

  18. Preparation and application of conducting polymer/Ag/clay composite nanoparticles formed by in situ UV-induced dispersion polymerization.

    PubMed

    Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

    2016-02-03

    In this work, composite nanoparticles containing polypyrrole, silver and attapulgite (PPy/Ag/ATP) were prepared via UV-induced dispersion polymerization of pyrrole using ATP clay as a templet and silver nitrate as photoinitiator. The effects of ATP concentration on morphology, structure and electrical conductivity were studied. The obtained composite nanoparticles with an interesting beads-on-a-string morphology can be obtained in a short time (10 min), which indicates the preparation method is facile and feasible. To explore the potential applications of the prepared PPy/Ag/ATP composite nanoparticles, they were served as multifunctional filler and blended with poly(butylene succinate) (PBS) matrix to prepare biodegradable composite material. The distribution of fillers in polymer matrix and the interfacial interaction between fillers and PBS were confirmed by scanning electron microscope, elemental mapping and dynamic mechanical analysis. The well dispersed fillers in PBS matrix impart outstanding antibacterial property to the biodegradable composite material as well as enhanced storage modulus due to Ag nanoparticles and ATP clay. The biodegradable composite material also possesses modest surface resistivity (10(6)~ 10(9) Ω/◻).

  19. Preparation and application of conducting polymer/Ag/clay composite nanoparticles formed by in situ UV-induced dispersion polymerization

    NASA Astrophysics Data System (ADS)

    Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

    2016-02-01

    In this work, composite nanoparticles containing polypyrrole, silver and attapulgite (PPy/Ag/ATP) were prepared via UV-induced dispersion polymerization of pyrrole using ATP clay as a templet and silver nitrate as photoinitiator. The effects of ATP concentration on morphology, structure and electrical conductivity were studied. The obtained composite nanoparticles with an interesting beads-on-a-string morphology can be obtained in a short time (10 min), which indicates the preparation method is facile and feasible. To explore the potential applications of the prepared PPy/Ag/ATP composite nanoparticles, they were served as multifunctional filler and blended with poly(butylene succinate) (PBS) matrix to prepare biodegradable composite material. The distribution of fillers in polymer matrix and the interfacial interaction between fillers and PBS were confirmed by scanning electron microscope, elemental mapping and dynamic mechanical analysis. The well dispersed fillers in PBS matrix impart outstanding antibacterial property to the biodegradable composite material as well as enhanced storage modulus due to Ag nanoparticles and ATP clay. The biodegradable composite material also possesses modest surface resistivity (106 ~ 109 Ω/◻).

  20. Preparation, characterization, and photocatalytic activity of porous AgBr@Ag and AgBrI@Ag plasmonic photocatalysts

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Tian, Baozhu; Zhang, Jinlong; Xiong, Tianqing; Wang, Tingting

    2014-02-01

    Porous AgBr@Ag and AgBrI@Ag plasmonic photocatalysts were synthesized by a multistep route, including a dealloying method to prepare porous Ag, a transformation from Ag to AgBr and AgBrI, and a photo-reduction process to form Ag nanoparticles on the surface of AgBr and AgBrI. It was found that the porous structure kept unchanged during Ag was transferred into AgBr, AgBrI, AgBr@Ag, and AgBrI@Ag. Both porous AgBr@Ag and porous AgBrI@Ag showed much higher visible-light photocatalytic activity than cubic AgBr@Ag for the degradation of methyl orange, which is because the interconnected pore channels not only provide more reactive sites but also favor the transportation of photo-generated electrons and holes. For AgBrI@Ag, AgBrI solid solution formed at the interface of AgBr and AgI, and the phase junction can effectively separate the photo-generated electrons and holes, favorable to the improvement of photocatalytic activity. The optimal I content for obtaining the highest activity is ∼10 at.%.

  1. Preparation of AgX (X = Cl, I) nanoparticles using ionic liquids

    NASA Astrophysics Data System (ADS)

    Rodil, Eva; Aldous, Leigh; Hardacre, Christopher; Lagunas, M. Cristina

    2008-03-01

    Nanoparticles of silver halides have been prepared by mixing silver halide powder with a single liquid phase consisting of an ionic liquid, isooctane, n-decanol and water. Much higher nanoparticle concentrations may be formed with ionic liquids using this new simple method than are found with conventionally applied surfactants. This method also emphasizes the applicability of ionic liquids as versatile components in microemulsions and as solvents for the synthesis of nanomaterials. The effect on the nanoparticles of changing the composition of the liquid mixtures and the nature of the ionic liquid is analysed. High nanoparticle concentrations were only found with chloride based ionic liquids, indicating the importance of the ionic liquid anion in the mechanism of the reaction.

  2. Novel method for the preparation of core-shell nanoparticles with movable Ag core and polystyrene loop shell

    SciTech Connect

    Liu Weijun; Zhang Zhicheng . E-mail: lwj3600@ustc.edu; He Weidong; Zheng Cheng; Ge Xuewu; Li, Jian; Liu Huarong; Jiang Hao

    2006-04-15

    Core/shell nanoparticles with movable silver (Ag) core and polystyrene (PSt) shell (Ag at PSt nanoparticle) were successfully synthesized at room temperature and under ambient pressure via two steps: {gamma}-irradiation and interfacial-initiated polymerization. Firstly, mono-dispersed Ag nanoparticles with diameters 20 nm were synthesized in inversed microemulsion by reducing silver nitrate under {gamma}-irradiation. Then, Ag nanoparticles were coated with PSt via interfacial-initiated polymerization with cumene hydroperoxide/ferrous sulfate/disodium ethylenediaminetetraacetate/sodium formaldehyde sulfoxylate (CHPO-Fe {sup 2+}-EDTA-SFS) as the redox initiation pair. The resulted Ag at PSt nanoparticles were identified by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS)

  3. In-situ preparation of binary-phase silver nanoparticles at a high Ag+ concentration.

    PubMed

    Ullah, Md Habib; Kim, Il; Ha, Chang-Sik

    2006-03-01

    Stable and monodisperse silver nanoparticles (NPs) have been synthesized using high metal salt concentration (up to 0.735 M) through a simple but novel technique. It is based on one-step procedure that uses glycerol for reducing Ag+ in the presence of o-phenylenediamine (o-PDA) resulting the nanoparticles are in two forms (one water-soluble, the other a precipitated). The water-soluble phase contains NPs that have a bimodal size distribution (2-3 and 5-6 nm); the other comprises precipitated NPs, having a unimodal size distribution (2-3 nm). The water-soluble NPs are covalently bonded to the aromatic amine molecules to form isolated units, while the precipitated nanoparticles are embedded in the networks formed by cross-linking between COOH groups of hydroxypyruvic acid (oxidized form of glycerol) and NH2 groups of o-PDA molecules. We used transmission electron microscopy (TEM), UV-Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) to characterize the silver products obtained.

  4. Core–shell Ag@SiO{sub 2} nanoparticles of different silica shell thicknesses: Preparation and their effects on photoluminescence of lanthanide complexes

    SciTech Connect

    Kang, Jie; Li, Yuan; Chen, Yingnan; Wang, Ailing; Yue, Bin; Qu, Yanrong; Zhao, Yongliang; Chu, Haibin

    2015-11-15

    Highlights: • Ag@SiO{sub 2} nanoparticles of different silica shell thicknesses were prepared via the Stöber process. • Sm and Dy complexes with benzoate, 1,10-phenanthroline and 2,2′-bipyridine were synthesized. • The complex-doped Ag@SiO{sub 2} composites show stronger luminescent intensities than pure complexes. • The luminescent intensities of the composites strongly depend on the SiO{sub 2} shell thickness. - Abstract: Three kinds of almost spherical core–shell Ag@SiO{sub 2} nanoparticles of different silica shell thicknesses (10, 25 and 80 nm) were prepared via the Stöber process. The Ag core nanoparticles were prepared by reducing silver nitrate with sodium citrate. The size, morphology and structure of core–shell Ag@SiO{sub 2} nanoparticles were characterized by transmission electron microscopy. Subsequently, eight kinds of lanthanide complexes with benzoate, 1,10-phenanthroline and 2,2′-bipyridine were synthesized. The composition of the lanthanide complexes was characterized by elemental analysis, IR and UV spectra. Finally, lanthanide complexes were attached to the surface of Ag@SiO{sub 2} nanoparticles to form lanthanide-complex-doped Ag@SiO{sub 2} nanocomposites. The results show that the complex-doped Ag@SiO{sub 2} nanocomposites display much stronger luminescence intensities than the lanthanide complexes. Furthermore, the luminescence intensities of the lanthanide-complex-doped Ag@SiO{sub 2} nanocomposites with SiO{sub 2} shell thickness of 25 nm are stronger than those of the nanocomposites with SiO{sub 2} shell thickness of 10 and 80 nm.

  5. Y{sub 2}O{sub 3}:Eu{sup 3+} (5 mol%) with Ag nanoparticles prepared by citrate precursor

    SciTech Connect

    Ferrari, J.L.; Cebim, M.A.; Pires, A.M.; Couto dos Santos, M.A.

    2010-09-15

    Y{sub 2}O{sub 3}:Eu{sup 3+} (5 mol% Eu{sup 3+}) and Y{sub 2}O{sub 3}:Eu{sup 3+} (5 mol% Eu{sup 3+}) containing 1 mol% of Ag nanoparticles were prepared by heat treatment of a viscous resin obtained via citrate precursor. TEM and EDS analyses showed that Y{sub 2}O{sub 3}:Eu{sup 3+} (5 mol% Eu{sup 3+}) is formed by nanoparticles with an average size of 12 nm, which increases to 30 nm when Ag is present because the effect of metal induced crystallization occurs. Ag nanoparticles with a size of 9 nm dispersed in Y{sub 2}O{sub 3}:Eu{sup 3+} (5 mol% Eu{sup 3+}) were obtained and the surface plasmon effect on Ag nanoparticles was observed. The emission around 612 nm assigned to the Eu{sup 3+} ({sup 5}D{sub 0{yields}}{sup 7}F{sub 2}) transition enhanced when the Ag nanoparticles were present in the Y{sub 2}O{sub 3}:Eu{sup 3+} luminescent material. - Graphical abstract: The presence of Ag nanoparticles together Y{sub 2}O{sub 3}:Eu{sup 3+} 5 mol% phosphor showed to affect directly the optical and crystallinity of the material. Luminescence spectra show directly the effect observed.

  6. A simple and large-scale strategy for the preparation of Ag nanoparticles supported on resin-derived carbon and their antibacterial properties

    NASA Astrophysics Data System (ADS)

    Wang, Baoli; Tian, Chungui; Zheng, Chunying; Wang, Lei; Fu, Honggang

    2009-01-01

    A simple strategy was developed for preparing stable Ag nanoparticles supported on carbon by carbonizing Ag+/acrylic acid type ion-exchange resin complexes under N2 atmosphere. The products were characterized by x-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-visible absorption spectroscopy. The results indicated that the Ag nanoparticles were well dispersed on the surface of carbon, and their size could be regulated by tuning the carbonization temperature. The antibacterial assay showed that the Ag/C composites possess good antibacterial properties that are determined largely by the Ag particle size. Furthermore, the composites are very stable and they do not show obviously change even after storing at ambient conditions for more than one year.

  7. Preparation of the egg membrane bandage contained the antibacterial Ag nanoparticles

    SciTech Connect

    Zhang, Jin; Duan, Guangwen; Fu, Yunzhi; Zhao, Jinsheng

    2015-02-15

    Silver nanoparticles were synthesized using a rapid, single step, and completely green biosynthetic method employing aqueous aloe leaf extracts as both the reducing and capping agent. Transmission electron microscopy analysis revealed the average size of silver nanoparticles approximately 18.05 nm. Fourier transform infrared spectroscopy observation showed the estimation of two kinds of binding sites between aqueous aloe leaf and aqueous aloe leaf with silver nanoparticles. In addition, the critical roles of the concentration of silver nitrate, temperature, and reaction time in the formation of silver nanoparticles had been illustrated. Furthermore, silver nanoparticles were deposited on egg membrane bandage, forming a new egg membrane bandage that contained silver nanoparticles that exhibiting excellent antibacterial effects against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, which was 2.5 times stronger than the commercially available bandage. - Graphical Abstract: Display Omitted.

  8. Multifunctional Fe{sub 3}O{sub 4}@C@Ag hybrid nanoparticles: Aqueous solution preparation, characterization and photocatalytic activity

    SciTech Connect

    Liang, Hongxia; Niu, Helin; Li, Ping; Tao, Zhiyin; Mao, Changjie; Song, Jiming; Zhang, Shengyi

    2013-07-15

    Highlights: ► Ag-loaded Fe{sub 3}O{sub 4}@C magnetic-optical bifunctional materials have been investigated. ► The magnetism was studied at the room temperature. ► The photocatalytic activity was evaluated under visible light irradiation. ► Ag-loaded Fe{sub 3}O{sub 4}@C nanocomposites show superior magnetism and photocatalytic activity. ► A simple synthetic process was discussed. - Abstract: The paper describes a kind of multifunctional Fe{sub 3}O{sub 4}@C@Ag hybrid nanoparticles, which can be successfully synthesized using a simple route based on directly adsorption and spontaneous reduction of silver ions onto the surface shell of carbon-coated magnetic nanoparticles. The as-prepared samples have been characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectrum, vibrating sample magnetometer (VSM) and UV–vis spectrum (UV–vis). The Ag nanocrystals loaded on the surface shell of carbon-coated magnetic nanoparticles are nearly spherical with an average diameter of 10 nm. And the carbonaceous polysaccharides shell obtained using an glucose hydrothermal reaction act as a role of a bridge between magnetic Fe{sub 3}O{sub 4} core and noble metallic Ag nanocrystals. The as-prepared samples can be used as an effective catalyst for the photodegradation of organic dyes (neutral red) under the exposure of visible light. Results show that the as-prepared samples have a degradation rate of 93.7% for dyes within 30 min, which indicates their high-efficiency and rapid photocatalytic activity.

  9. Comparative Study of Antimicrobial Activity of AgBr and Ag Nanoparticles (NPs)

    PubMed Central

    Suchomel, Petr; Kvitek, Libor; Panacek, Ales; Prucek, Robert; Hrbac, Jan; Vecerova, Renata; Zboril, Radek

    2015-01-01

    The diverse mechanism of antimicrobial activity of Ag and AgBr nanoparticles against gram-positive and gram-negative bacteria and also against several strains of candida was explored in this study. The AgBr nanoparticles (NPs) were prepared by simple precipitation of silver nitrate by potassium bromide in the presence of stabilizing polymers. The used polymers (PEG, PVP, PVA, and HEC) influence significantly the size of the prepared AgBr NPs dependently on the mode of interaction of polymer with Ag+ ions. Small NPs (diameter of about 60–70 nm) were formed in the presence of the polymer with low interaction as are PEG and HEC, the polymers which interact with Ag+ strongly produce nearly two times bigger NPs (120–130 nm). The prepared AgBr NPs were transformed to Ag NPs by the reduction using NaBH4. The sizes of the produced Ag NPs followed the same trends – the smallest NPs were produced in the presence of PEG and HEC polymers. Prepared AgBr and Ag NPs dispersions were tested for their biological activity. The obtained results of antimicrobial activity of AgBr and Ag NPs are discussed in terms of possible mechanism of the action of these NPs against tested microbial strains. The AgBr NPs are more effective against gram-negative bacteria and tested yeast strains while Ag NPs show the best antibacterial action against gram-positive bacteria strains. PMID:25781988

  10. Preparation of PdAg and PdAu nanoparticle-loaded carbon black catalysts and their electrocatalytic activity for the glycerol oxidation reaction in alkaline medium

    NASA Astrophysics Data System (ADS)

    Lam, Binh Thi Xuan; Chiku, Masanobu; Higuchi, Eiji; Inoue, Hiroshi

    2015-11-01

    PdAg and PdAu alloy nanoparticle catalysts for the glycerol oxidation reaction (GOR) were prepared at room temperature by a wet method. The molar ratio of the precursors controlled the bulk composition of the PdAg and PdAu alloys, and their surface composition was Ag-enriched and Pd-enriched, respectively. On PdAg-loaded carbon black (PdAg/CB) electrodes, the onset potential of GOR was 0.10-0.15 V more negative than on the Pd/CB electrode due to the electronic effect. The ratio of GOR peak current densities in the backward and forward sweeps of CVs (ib/if) was smaller because of the improved tolerance to the poisoning species. The ratio of the GOR current density at 60 and 5 min (i60/i5) for the PdAg/CB electrodes was higher for more negative potentials than the Pd/CB electrode. In contrast, the PdAu-loaded CB (PdAu/CB) electrodes had an onset potential of GOR similar to the Pd/CB electrode and a higher GOR peak current density owing to the bi-functional effect. However, the ib/if ratio was higher for PdAu/CB because of the increase in ib as the Pd surface was recovered, and the i60/i5 ratio was higher for more positive potentials, similar to the Pd/CB electrode.

  11. Fast preparation of Bi{sub 2}GeO{sub 5} nanoflakes via a microwave-hydrothermal process and enhanced photocatalytic activity after loading with Ag nanoparticles

    SciTech Connect

    Li, Zhao-Qian; Lin, Xin-Shan; Zhang, Lei; Chen, Xue-Tai; Xue, Zi-Ling

    2012-09-15

    Highlights: ► Bi{sub 2}GeO{sub 5} nanoflakes were successfully synthesized via a microwave-assisted solution-phase approach. ► Ag nanoparticles were deposited on the Bi{sub 2}GeO{sub 5} nanoflakes by a photoreduction procedure. ► Catalytic activity of the Ag/Bi{sub 2}GeO{sub 5} nanocomposite in the photo-degradation of rhodamine B (RhB) was much higher than that of pure Bi{sub 2}GeO{sub 5}. -- Abstract: In this work, a facile and rapid microwave-assisted hydrothermal route has been developed to prepare Bi{sub 2}GeO{sub 5} nanoflakes. Ag nanoparticles were subsequently deposited on the Bi{sub 2}GeO{sub 5} nanoflakes by a photoreduction procedure. The phases and morphologies of the products were characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV–vis diffuse reflectance spectroscopy. Photocatalytic experiments indicate that such Ag/Bi{sub 2}GeO{sub 5} nanocomposite possesses higher photocatalytic activity for RhB degradation under UV light irradiation in comparison to pure Bi{sub 2}GeO{sub 5}. The amount of Ag in the nanocomposite affects the catalytic activity, and 3 wt% Ag showed the highest photodegradation efficiency. Moreover, the catalyst remains active after four consecutive tests. The present study provides a new strategy to design composite materials with enhanced photocatalytic activity.

  12. Study of antibacterial activity of Ag and Ag2CO3 nanoparticles stabilized over montmorillonite

    NASA Astrophysics Data System (ADS)

    Sohrabnezhad, Sh.; Pourahmad, A.; Mehdipour Moghaddam, M. J.; Sadeghi, A.

    2015-02-01

    Silver carbonate and silver nanoparticles (NPs) over of stabilizer montmorillonite (MMT) have been synthesized in aqueous and polyol solvent, respectively. Dispersions of silver nanoparticles have been prepared by the reduction of silver nitrate over of MMT in presence and absence of Na2CO3 compound in ethylene glycol. It was observed that montmorillonite was capable of stabilizing formed Ag nanoparticles through the reduction of Ag+ ions in ethylene glycol. Na2CO3 was used as carbonate source in synthesis of Ag2CO3 NPs in water solvent and also for controlling of Ag nanoparticles size in ethylene glycol medium. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and ultraviolet-visible diffuse reflectance spectroscopy (DRS). The TEM images showed that Ag NPs size in presence Na2CO3 salts was smaller than without that. The results indicated intercalation of Ag and Ag2CO3 nanoparticles into the montmorillonite clay layers. The diffuse reflectance spectra exhibited a strong surface plasmon resonance (SPR) adsorption peak in the visible region, resulting from Ag nanoparticles. The antibacterial testing results showed that the Ag2CO3-MMT nanocomposite exhibited an antibacterial activity higher than Ag-MMT sample against Escherichia coli.

  13. Preparation and enhanced visible light photocatalytic activity of novel g-C3N4 nanosheets loaded with Ag2CO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Yunfeng; Fang, Lin; Jin, Renxi; Yang, Yang; Fang, Xu; Xing, Yan; Song, Shuyan

    2014-12-01

    As a potential visible-light photocatalyst, the photocatalytic performance of the bulk g-C3N4 synthesized by heating melamine (denote as g-C3N4-M) is limited due to its low specific surface area and the high recombination rate of the photo-induced electron-hole pair. In this paper, a novel g-C3N4-M nanosheet (g-C3N4-MN) obtained from the bulk g-C3N4-M through a thermal exploitation method is employed as an excellent substrate and different amounts of Ag2CO3 nanoparticles are loaded at room temperature. The phase and chemical structure, electronic and optical properties of the Ag2CO3/g-C3N4-MN heterostructures are well-characterized. The photocatalytic activities of the as-prepared Ag2CO3/g-C3N4-MN are evaluated by the degradation of methyl orange (MO) and rhodamine B (RhB) pollutants under visible light irradiation. More importantly, the Ag2CO3/g-C3N4-MN heterostructure has been proved to be an excellent photocatalytic system with an enhanced specific surface area and charge separation rate compared with those of the Ag2CO3/g-C3N4-M system.As a potential visible-light photocatalyst, the photocatalytic performance of the bulk g-C3N4 synthesized by heating melamine (denote as g-C3N4-M) is limited due to its low specific surface area and the high recombination rate of the photo-induced electron-hole pair. In this paper, a novel g-C3N4-M nanosheet (g-C3N4-MN) obtained from the bulk g-C3N4-M through a thermal exploitation method is employed as an excellent substrate and different amounts of Ag2CO3 nanoparticles are loaded at room temperature. The phase and chemical structure, electronic and optical properties of the Ag2CO3/g-C3N4-MN heterostructures are well-characterized. The photocatalytic activities of the as-prepared Ag2CO3/g-C3N4-MN are evaluated by the degradation of methyl orange (MO) and rhodamine B (RhB) pollutants under visible light irradiation. More importantly, the Ag2CO3/g-C3N4-MN heterostructure has been proved to be an excellent photocatalytic system

  14. Preparation of Ag nanoparticles on PAN/TiO2 nanofibers and their photocatalytic and antibacterial properties

    NASA Astrophysics Data System (ADS)

    Jeun, Joon-Pyo; Seo, Dong-Kwon; Kim, Hyun-Bin; Kang, Phil-Hyun

    2010-06-01

    Polyacrylonitrile/titania (PAN/TiO2) nanofibrous mats were prepared by an electrospinning method and silver nanoparticles were deposited by electron beam (e-beam) irradiation of silver ions in aqueous solutions. The morphology of the electrospun fibers was characterized by SEM analysis. The deposition of silver particles was not of a uniform coverage on the PAN/TiO2 surface, but of a heterogeneous growth of the silver particles on the PAN/TiO2 surface. The photocatalytic efficiency of the composites against methylene blue dye in an aqueous solution improved and the actibacterial activity against E. coli and S. aureus was found to increase with the silver nanoparticles being induced.

  15. Biosynthesis of Au, Ag and Au-Ag nanoparticles using edible mushroom extract

    NASA Astrophysics Data System (ADS)

    Philip, Daizy

    2009-07-01

    Integration of green chemistry principles to nanotechnology is one of the key issues in nanoscience research. There is growing need to develop environmentally benign metal nanoparticle synthesis process that do not use toxic chemicals in the synthesis protocols to avoid adverse effects in medical applications. Here, it is a report on extracellular synthesis method for the preparation of Au, Ag and Au-Ag nanoparticles in water, using the extract of Volvariella volvacea, a naturally occurring edible mushroom, as reducing and protecting agents. Gold nanoparticles of different sizes (20-150 nm) and shapes from triangular nanoprisms to nearly spherical and hexagonal are obtained by this novel method. The size and shape of gold nanoparticles are also found to depend on temperature of the extract. The silver nanoparticles are spherical with size ˜15 nm. There is increased productivity of nanoparticles as shown by sharp and intense surface plasmon resonance bands for the nanoparticles prepared using an excess of the extract. The Au-Ag nanoparticles prepared by co-reduction has only one plasmon band due to alloying of the constituents. All the synthesized nanoparticles are found to be photoluminescent and are highly crystalline as shown by SAED and XRD patterns with fcc phase oriented along the (1 1 1) plane. FTIR measurements were carried out to identify the possible biomolecules responsible for capping and efficient stabilization of the nanoparticles. It is found that Au nanoparticles are bound to proteins through free amino groups and silver nanoparticles through the carboxylate group of the amino acid residues. The position and intensity of the emission band is found to depend on composition of the nanoparticles indicating the possible use in therapeutic applications.

  16. Noble-metal Ag nanoparticle chains: annealing Ag/Bi superlattice nanowires in vacuum

    NASA Astrophysics Data System (ADS)

    Xu, Shao Hui; Fei, Guang Tao; You, Qiao; Gao, Xu Dong; Huo, Peng Cheng; De Zhang, Li

    2016-09-01

    One-dimensional noble-metal Ag nanoparticle chains have been prepared by electrodepositing Ag/Bi superlattice nanowires in a porous anodic alumina oxide (AAO) template and following an annealing process in vacuum. It is found that Bi, as a sacrificial metal, can be removed completely after annealing at 450 °C with a vacuum degree of 10-5 Torr. The regulation of particle size, shape and interparticle spacing of Ag NP chains has been realized by adjusting the segment length of the Ag/Bi superlattice nanowires and the annealing condition. With an extension of the annealing time, it is observed that Ag particles display the transform trend from ellipsoid to sphere. Our findings could inspire further investigation on the design and fabrication of metal nanoparticle chains.

  17. Noble-metal Ag nanoparticle chains: annealing Ag/Bi superlattice nanowires in vacuum

    NASA Astrophysics Data System (ADS)

    Xu, Shao Hui; Fei, Guang Tao; You, Qiao; Gao, Xu Dong; Huo, Peng Cheng; De Zhang, Li

    2016-09-01

    One-dimensional noble-metal Ag nanoparticle chains have been prepared by electrodepositing Ag/Bi superlattice nanowires in a porous anodic alumina oxide (AAO) template and following an annealing process in vacuum. It is found that Bi, as a sacrificial metal, can be removed completely after annealing at 450 °C with a vacuum degree of 10‑5 Torr. The regulation of particle size, shape and interparticle spacing of Ag NP chains has been realized by adjusting the segment length of the Ag/Bi superlattice nanowires and the annealing condition. With an extension of the annealing time, it is observed that Ag particles display the transform trend from ellipsoid to sphere. Our findings could inspire further investigation on the design and fabrication of metal nanoparticle chains.

  18. Noble-metal Ag nanoparticle chains: annealing Ag/Bi superlattice nanowires in vacuum.

    PubMed

    Xu, Shao Hui; Fei, Guang Tao; You, Qiao; Gao, Xu Dong; Huo, Peng Cheng; De Zhang, Li

    2016-09-16

    One-dimensional noble-metal Ag nanoparticle chains have been prepared by electrodepositing Ag/Bi superlattice nanowires in a porous anodic alumina oxide (AAO) template and following an annealing process in vacuum. It is found that Bi, as a sacrificial metal, can be removed completely after annealing at 450 °C with a vacuum degree of 10(-5) Torr. The regulation of particle size, shape and interparticle spacing of Ag NP chains has been realized by adjusting the segment length of the Ag/Bi superlattice nanowires and the annealing condition. With an extension of the annealing time, it is observed that Ag particles display the transform trend from ellipsoid to sphere. Our findings could inspire further investigation on the design and fabrication of metal nanoparticle chains.

  19. Noble-metal Ag nanoparticle chains: annealing Ag/Bi superlattice nanowires in vacuum.

    PubMed

    Xu, Shao Hui; Fei, Guang Tao; You, Qiao; Gao, Xu Dong; Huo, Peng Cheng; De Zhang, Li

    2016-09-16

    One-dimensional noble-metal Ag nanoparticle chains have been prepared by electrodepositing Ag/Bi superlattice nanowires in a porous anodic alumina oxide (AAO) template and following an annealing process in vacuum. It is found that Bi, as a sacrificial metal, can be removed completely after annealing at 450 °C with a vacuum degree of 10(-5) Torr. The regulation of particle size, shape and interparticle spacing of Ag NP chains has been realized by adjusting the segment length of the Ag/Bi superlattice nanowires and the annealing condition. With an extension of the annealing time, it is observed that Ag particles display the transform trend from ellipsoid to sphere. Our findings could inspire further investigation on the design and fabrication of metal nanoparticle chains. PMID:27487089

  20. Functionalization of Ag nanoparticles using local hydrophilic pool segment designed on their particle surface

    NASA Astrophysics Data System (ADS)

    Iijima, Motoyuki; Kurumiya, Aki; Esashi, Junki; Miyazaki, Hayato; Kamiya, Hidehiro

    2014-10-01

    The preparation of SiO2-coated Ag nanoparticles dispersible in various organic solvents has been achieved using a solgel reaction of tetraethylorthosilicate (TEOS), in the localized hydrophilic pool segments designed on Ag nanoparticle surfaces. First, oleylamine-capped core Ag nanoparticles were synthesized, followed by ligand exchange with polyethyleneimine (PEI) and further adsorption of an anionic surfactant comprising hydrophilic polyethylene glycol (PEG) chains and hydrophobic alkyl chains, which has previously been reported to improve the stability of nanoparticles in various solvents. Then, a reaction of TEOS with the localized hydrophilic PEI layer on the Ag nanoparticles' surface was conducted by stirring a toluene/TEOS solution of surface-modified Ag nanoparticles at various temperatures. It was found that a SiO2 layer was successfully formed on Ag nanoparticles when the reaction temperature was increased to 60 °C. It was also found, however, that at this elevated temperature, the primary particle size of Ag nanoparticles increased to several tens of nm, attributable to the dissolution and re-reduction of Ag+. Because the surface modifier, PEI and anionic surfactant all remained on the nanoparticle surface during the SiO2 coating process, the prepared SiO2-coated Ag nanoparticles were found to be dispersible in various organic solvents near to their primary particle size.

  1. Synthesis of Cu core Ag shell nanoparticles using chemical reduction method

    NASA Astrophysics Data System (ADS)

    Chinh Trinh, Dung; Dung Dang, Thi My; Khanh Huynh, Kim; Fribourg-Blanc, Eric; Chien Dang, Mau

    2015-01-01

    A simple chemical reduction method is used to prepare colloidal bimetallic Cu-Ag core-shell (Cu@Ag) nanoparticles. Polyvinyl pyrrolidone (PVP) was used as capping agent, and ascorbic acid (C6H8O6) and sodium borohydride (NaBH4) were used as reducing agents. The obtained Cu@Ag nanoparticles were characterized by powder x-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis spectrophotometry. The influence of [Ag]/[Cu] molar ratios on the formation of Ag coatings on the Cu particles was investigated. From the TEM results we found that the ratio [Ag+]/[Cu2+] = 0.2 is the best for the stability of Cu@Ag nanoparticles with an average size of 22 nm. It is also found out that adding ammonium hydroxide (NH4OH) makes the obtained Cu@Ag nanoparticles more stable over time when pure deionized water is used as solvent.

  2. Photocurrent enhancement of chemically synthesized Ag nanoparticle-embedded BiFeO3 thin films

    NASA Astrophysics Data System (ADS)

    Maruyama, Rika; Sakamoto, Wataru; Yuitoo, Isamu; Takeuchi, Teruaki; Hayashi, Koichiro; Yogo, Toshinobu

    2016-10-01

    BiFeO3 and Ag nanoparticle-embedded BiFeO3 thin films were prepared on Pt/TiO x /SiO2/Si and MgO(100) substrates using colloidal silver and BiFeO3 metal-organic precursor solutions. Colloidal silver solution was prepared by a chemical reductive method using NaBH4 as a reductant. The prepared Ag nanoparticles exhibited characteristic optical absorption properties based on their surface plasmon resonance related to particle size. The synthesized BiFeO3 and Ag nanoparticle/BiFeO3 thin films demonstrated rapid on/off responses of photocurrent to visible light. The Ag nanoparticle-incorporated BiFeO3 film exhibited a 2-4-fold higher photocurrent than the BiFeO3 film. Optical and ferroelectric properties did not change markedly even when Ag nanoparticles were embedded in the BiFeO3 thin film within the quantities of this study. Furthermore, in the Ag nanoparticle/BiFeO3 composite structure, Ag nanoparticles were introduced in the near-metallic state with maintained their nanometer size. In the Ag nanoparticle-embedded BiFeO3 film, photoinduced charge separation and transport of photoexcited carriers were enhanced by the surface plasmon effect of nanosized Ag particles as well as the internal bias electric field existed in the narrow-bandgap BiFeO3 thin film.

  3. Spectroscopic Study on Eu3+ Doped Borate Glasses Containing Ag Nanoparticles and Ag Aggregates.

    PubMed

    Fu, Shaobo; Zheng, Hui; Zhang, Jinsu; Li, Xiangping; Sun, Jiashi; Hua, Ruinian; Dong, Bin; Xia, Haiping; Chen, Baojiu

    2015-01-01

    Transparent Eu(3+)-doped borate glasses containing Ag nanoparticles and Ag aggregates with composition (40 - x) CaO-59.5B2O3-0.5Eu2O3-xAgNO3 were prepared by a simple one-step melt-quenching technique. The X-ray diffraction (XRD) patterns of the glasses reveal amorphous structural properties and no diffraction peaks belonging to metal Ag particles. Ag particles and Ag aggregates were observed from the absorption spectra. Effective energy transfers from the Ag aggregates to the Eu3+ ions were observed in the excitation spectra from monitoring the intrinsic emission of Eu3+x .5D0 --> 7F2. The glasses with higher Ag content can be effectively excited by light in a wide wavelength region, indicating that these glasses have potential application in the solid state lighting driven by semiconductor light emitting diodes (LEDs). The emission spectra of the samples with higher Ag contents exhibit plenteous spectral components covering the full visible region from violet to red, thus indicating that these glass materials possess an excellent and tunable color rendering index. The color coordinates for all the glass samples were calculated by using the intensity-corrected emission spectra and the standard data issued by the CIE (Commission International de l' Eclairage) in 1931. It was found that the color coordinates for most samples with higher Ag contents fall into the white region in the color space. PMID:26328363

  4. Highly quasi-monodisperse ag nanoparticles on titania nanotubes by impregnative aqueous ion exchange.

    PubMed

    Toledo-Antonio, J A; Cortes-Jácome, M A; Angeles-Chavez, C; López-Salinas, E; Quintana, P

    2009-09-01

    Silver nanoparticles were homogenously dispersed on titania nanotubes (NT), which were prepared by alkali hydrothermal methodology and dried at 373 K. Ag(+) incorporation was done by impregnative ion exchange of aqueous silver nitrate onto NT. First, Ag(+) ions incorporate into the layers of nanotube walls, and then, upon heat treatment under N(2) at 573 and 673 K, they migrate and change into Ag(2)O and Ag(0) nanoparticles, respectively. In both cases, Ag nanoparticles are highly dispersed, decorating the nanotubes in a polka-dot pattern. The Ag particle size distribution is very narrow, being ca. 4 +/- 2 nm without any observable agglomeration. The reduction of Ag(2)O into Ag(0) octahedral nanoparticles occurs spontaneously and topotactically when annealing, without the aid of any reducing agent. The population of Ag(0) nanoparticles can be controlled by adjusting the annealing temperature. An electron charge transfer from NT support to Ag(0) nanoparticles, because of a strong interaction, is responsible for considerable visible light absorption in Ag(0) nanoparticles supported on NT.

  5. Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers prepared by atmospheric plasma treatment and electrospinning

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers were prepared by atmospheric plasma treatment and electrospinning. Atmospheric helium plasma treatment was first used to reduce the silver nitrate precursor in pre-electrospinning solutions into metallic silver nanoparticles, foll...

  6. Spin coating of Ag nanoparticles: Effect of reduction

    SciTech Connect

    Ansari, A. A. Sartale, S. D.

    2014-04-24

    A surfactant free method for the growth of Ag nanoparticles on glass substrate by spin coating of Ag ions solution followed by chemical reduction in aqueous hydrazine hydrate (HyH) solution has been presented. Appearance of surface plasmon resonance confirms the formation of Ag nanoparticles. Morphology and absorbance spectra of Ag nanoparticles films are used to examine effect of hydrazine concentration on the growth of Ag nanoparticles. SEM images show uniformly distributed Ag nanoparticles. Rate constant was found to be dependent on HyH concentration as a consequence influence particle size.

  7. Study of structural modification of PVA by incorporating Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Saini, Isha; Sharma, Annu; Rozra, Jyoti; Aggarwal, Sanjeev; Dhiman, Rajnish; Sharma, Pawan K.

    2016-05-01

    Nanocomposites of PVA with Ag nanoparticles dispersed in it were synthesized using solution casting method. The morphology and size distribution of Ag nanoparticles embedded in PVA matrix were obtained by transmission electron microscopy (TEM) and Field emission scanning electron microscopy (FE-SEM). Raman spectroscopy was used to examine structural changes taking place inside polyvinyl alcohol (PVA) matrix due to incorporation of Ag nanoparticle. Raman analysis indicates that Ag nanoparticles interact with PVA through H-bonding.

  8. Laser-based synthesis of core Ag-shell AgI nanoparticles

    NASA Astrophysics Data System (ADS)

    Tan, Hua; Fan, Wai Yip

    2005-05-01

    A laser-controlled synthesis of silver iodide (AgI) nanoparticles with isolable AgI shell-Ag core stable intermediates is achieved via molecular iodine photodissociation in the presence of pure Ag nanoparticles dispersed in water. Ag nanoparticles were introduced into the solution containing sodium dodecylsulphate surfactants and iodine by ablating a piece of silver foil with a 532 nm pulsed Nd-YAG laser. Transmission electron microscopy images showed that different AgI shell-Ag core sizes could be achieved by controlling the photolysis of I 2 in solution. These nanoparticles were also found to catalyse an atom-economy Grignard-Barbier organic reaction.

  9. Annealing behaviour of c-SiO 2 implanted layer distributed with high density Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Zhengxin; Wang, Honghong

    1997-01-01

    High volume density Ag nanoparticles embedded in c-SiO 2 matrix have been prepared by Ag ion implantation at an energy of 200 keV and a current density of about 20 μA/cm 2 to a nominal dose of 6.7 × 10 16ions/cm 2 at RT. Bright-field transmission electron microscopy (TEM) image indicates that Ag nanoparticles show two groups of sizes: the larger diameter is about 25 nm and the smaller is less than 10 nm. RBS spectra show that the distribution of implanted Ag atoms is bimodal which is associated with the two groups of nanoparticles above. Thermal stability of the implanted layer which consists of Ag nanoparticles, dissolved Ag atoms and c-SiO 2 matrix has been investigated by RBS, TEM and Raman spectroscopy. RBS spectra prove that little migration of Ag atoms is found and Ag nanoparticles are considerably stable at 300°C annealing. Though the obvious change in the distribution of Ag is observed at 400°C annealing in RBS spectra, TEM image identifies that both the larger and the smaller Ag nanoparticles still exist at relatively stable state. Following 750°C annealing, Ag atoms drastically move, and furthermore, the bimodal character of the distribution disappears. On the other hand, the amorphized SiO 2 implanted layer recrystal after 300°C, 400°C annealing.

  10. Preparation of silver nanoparticles fabrics against multidrug-resistant bacteria

    NASA Astrophysics Data System (ADS)

    Hanh, Truong Thi; Thu, Nguyen Thi; Hien, Nguyen Quoc; An, Pham Ngoc; Loan, Truong Thi Kieu; Hoa, Phan Thi

    2016-04-01

    The silver nanoparticles (AgNPs)/peco fabrics were prepared by immobilization of AgNPs on fabrics in which AgNPs were synthesized by γ-irradiation of the 10 mM AgNO3 chitosan solution at the dose of 17.6 kGy. The AgNPs size has been estimated to be about 11 nm from TEM image. The AgNPs content onto peco fabrics was of 143±6 mg/kg at the initial AgNPs concentration of 100 ppm. The AgNPs colloidal solution was characterized by UV-vis spectroscopy and TEM image. The antibacterial activity of AgNPs/peco fabrics after 60 washings against Staphylococcus aureus and Klebsiella pneumoniae was found to be over 99%. Effects of AgNPs fabics on multidrug-resistant pathogens from the clinical specimens were also tested.

  11. Beet juice utilization: Expeditious green synthesis of nobel metal nanoparticles (Ag, Au, Pt, and Pd) using microwaves

    EPA Science Inventory

    Metal nanoparticles of Ag, Au, Pt, and Pd were prepared in aqueous solutions via a rapid microwave-assisted green method using beet juice, an abundant sugar-rich agricultural produce, served as both a reducing and a capping reagent. The Ag nanoparticles with capping prepared by b...

  12. Preparation of AgInS2 nanoparticles by a facile microwave heating technique; study of effective parameters, optical and photovoltaic characteristics

    NASA Astrophysics Data System (ADS)

    Tadjarodi, Azadeh; Cheshmekhavar, Amir Hossein; Imani, Mina

    2012-12-01

    In this work, AgInS2 (AIS) semiconductor nanoparticles were synthesized by an efficient and facile microwave heating technique using several sulfur sources and solvents in the different reaction times. The SEM images presented the particle morphology for all of the obtained products in the arranged reaction conditions. The particle size of 70 nm was obtained using thioacetamide (TAA), ethylene glycol (EG) as the sulfur source and solvent, respectively at the reaction time of 5 min. It was found that the change of the mentioned parameters lead to alter on the particle size of the resulting products. The average particle size was estimated using a microstructure measurement program and Minitab statistical software. The optical band gap energy of 1.96 eV for the synthesized AIS nanoparticles was determined by the diffuse reflectance spectroscopy (DRS). AgInS2/CdS/CuInSe2 heterojunction solar cell was constructed and photovoltaic parameters, i.e., open-circuit voltage (Voc), short-circuit current (Jsc) and fill factor (FF) were estimated by photocurrent-voltage (I-V) curve. The calculated fill factor of 30% and energy conversion efficiency of 1.58% revealed the capability of AIS nanoparticles to use in the solar cell devices.

  13. High Resolution PDF Measurements on Ag Nanoparticles

    SciTech Connect

    Rocha, Tulio C. R.; Martin, Chris; Kycia, Stefan; Zanchet, Daniela

    2009-01-29

    The quantitative analysis of structural defects in Ag nanoparticles was addressed in this work. We performed atomic scale structural characterization by a combination of x-ray diffraction (XRD) using the Pair Distribution Function analysis (PDF) and High Resolution Transmission Electron Microscopy (HRTEM). The XRD measurements were performed using an innovative instrumentation setup to provide high resolution PDF patterns.

  14. Nanoparticle Ag-enhanced textured-powder Bi-2212/Ag wire technology

    NASA Astrophysics Data System (ADS)

    Kellams, J. N.; McIntyre, P.; Pogue, N.; Vandergrifft, J.

    2015-12-01

    A new approach to the preparation of cores for Bi-2212/Ag wire is being developed. Nanoparticle Ag is homogeneously dispersed in Bi-2212 fine powder, and the mixture is uniaxially compressed to form highly textured, cold-sintered core rods. The rods can be assembled in a silver matrix, drawn to form multifilament wire, and restacked and drawn to form multifilament wire. Preliminary studies using tablet geometry demonstrate that a nonmelt heat treatment produces densification, grain growth, intergrowth among grains, and macroscopic current transport. The status of the development is reported.

  15. Synthesis and Characterization of BSA Conjugated Silver Nanoparticles (Ag/BSA Nanoparticles) and Evaluation of Biological Properties of Ag/BSA Nanoparticles and Ag/BSA Nanoparticles Loaded Poly(hydroxy butyrate valerate) PHBV Films

    NASA Astrophysics Data System (ADS)

    Ambaye, Almaz

    Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa are the etiological agents of several infectious diseases. Antibiotic resistance by these three microbes has emerged as a prevalent problem due in part to the misuse of existing antibiotics and the lack of novel antibiotics. Nanoparticles have emerged as an alternative antibacterial agents to conventional antibiotics owing to their high surface area to volume ratio and their unique chemical and physical properties. Among the nanoparticles, silver nanoparticles have gained increasing attention because silver nanoparticles exhibit antibacterial activity against a range of gram positive and gram negative bacteria. Nanoparticles of well-defined chemistry and morphology can be used in broad biomedical applications, especially in bone tissue engineering applications, where bone infection by bacteria can be acute and lethal. It is commonly noted in the literature that the activity of nanoparticles against microorganisms is dependent upon the size and concentration of the nanoparticles as well as the chemistry of stabilizing agent. To the best of our knowledge, a comprehensive study that evaluates the antibacterial activity of well characterized silver nanoparticles in particular Bovine Serum Albumin (BSA) stabilized against S. aureus and E. coli and cytotoxicity level of BSA stabilized silver nanoparticles towards osteoblast cells (MC3T3-E1) is currently lacking. Therefore, the primary objective of this study was to characterize protein conjugated silver nanoparticles prepared by chemical reduction of AgNO3 and BSA mixture. The formation of Ag/BSA nanoparticles was studied by UV-Vis spectroscopy. The molar ratio of silver to BSA in the Ag/BSA nanoparticles was established to be 27+/- 3: 1, based on Thermogravimetric Analysis and Atomic Absorption Spectroscopy. Based on atomic force microscopy, dynamic light scattering,and transmission electron microscopy(TEM) measurements, the particle size (diameter) of

  16. Fabrication of plasmonic AgBr/Ag nanoparticles-sensitized TiO2 nanotube arrays and their enhanced photo-conversion and photoelectrocatalytic properties

    NASA Astrophysics Data System (ADS)

    Wang, Qingyao; Qiao, Jianlei; Jin, Rencheng; Xu, Xiaohui; Gao, Shanmin

    2015-03-01

    Plasmonic photosensitizer AgBr/Ag nanospheres supported on TiO2 nanotube arrays (TiO2 NTs) are prepared by successive ionic layer adsorption and reaction (SILAR) technique followed by photoreduction methods. The structural and surface morphological properties of AgBr/Ag nanoparticles sensitized TiO2 NTs and their photoelectrochemical performance are investigated and discussed. A detailed formation mechanism of the TiO2 NTs/AgBr/Ag is proposed. The TiO2 NTs/AgBr/Ag exhibit excellent photocurrent and photoelectrocatalytic activities under visible light irradiation. Efficient utilization of solar energy to create electron-hole pairs is attributed to the significant visible light response and surface plasmon resonance of Ag nanoparticles. This finding indicates that the high photosensitivity of the TiO2 NTs-based surface plasmon resonance materials could be applied toward the development of new plasmonic visible-light-sensitive photovoltaic fuel cells and photocatalysts.

  17. Solution structure of peptide AG4 used to form silver nanoparticles

    SciTech Connect

    Lee, Eunjung; Kim, Dae-Hee; Woo, Yoonkyung; Hur, Ho-Gil; Lim, Yoongho

    2008-11-21

    The preparation of silver nanoparticles (AgNPs) is of great interest due to their various biological activities, such as observed in their antimicrobial and wound healing actions. Moreover, the formation of AgNPs using silver-binding peptide has certain advantages because they can be made in aqueous solution at ambient temperature. The solution structure of the silver-binding peptide AG4 was determined using nuclear magnetic resonance spectroscopy, and the site of the AG4 interaction with AgNPs was elucidated.

  18. Ag/CuO nanoparticles prepared from a novel trinuclear compound [Cu(Imdz)4(Ag(CN)2)2] (Imdz = imidazole) by a pyrolysis display excellent antimicrobial activity

    NASA Astrophysics Data System (ADS)

    Adhikary, Jaydeep; Das, Balaram; Chatterjee, Sourav; Dash, Sandeep Kumar; Chattopadhyay, Sourav; Roy, Somenath; Chen, Jeng-Wei; Chattopadhyay, Tanmay

    2016-06-01

    One copper and two silver containing one hetero tri-nuclear precursor compound [Cu(Imdz)4(Ag(CN)2)2] (1) (Imdz = Imidazole) has been synthesized and characterized by single crystal X-ray diffraction. Simple pyrolysis of the complex at 550 °C for 4 h afforded Ag/CuO nanoparticles (NPs). The synthesized nanoparticles were characterized by ultraviolet-visible (UV-Vis), Fourier transform infrared (FT-IR), X-ray powder diffraction (XRPD), dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and X-ray photo electron spectroscopy (XPS). Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) have been employed as model microbial species to study the anti-microbial activity of the synthesized NPs. The NPs showed potent anti-microbial activity evidenced from the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values. Very high level of cell uptake and then generation of reactive oxygen species (ROS) are the origin of such strong antimicrobial activity for the NPs. However, the cytotoxicity level of the NPs towards normal human cell is very low.

  19. Preparation of surface plasmon resonance biosensor based on magnetic core/shell Fe3O4/SiO2 and Fe3O4/Ag/SiO2 nanoparticles.

    PubMed

    Wang, Liying; Sun, Ying; Wang, Jing; Wang, Jian; Yu, Aimin; Zhang, Hanqi; Song, Daqian

    2011-06-01

    In this paper, surface plasmon resonance biosensors based on magnetic core/shell Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were developed for immunoassay. With Fe(3)O(4) and Fe(3)O(4)/Ag nanoparticles being used as seeding materials, Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were formed by hydrolysis of tetraethyl orthosilicate. The aldehyde group functionalized magnetic nanoparticles provide organic functionality for bioconjugation. The products were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), FTIR and UV-vis absorption spectrometry. The magnetic nanoparticles possess the unique superparamagnetism property, exceptional optical properties and good compatibilities, and could be used as immobilization matrix for goat anti-rabbit IgG. The magnetic nanoparticles can be easily immobilized on the surface of SPR biosensor chip by a magnetic pillar. The effects of Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles on the sensitivity of SPR biosensors were also investigated. As a result, the SPR biosensors based on Fe(3)O(4)/SiO(2) nanoparticles and Fe(3)O(4)/Ag/SiO(2) nanoparticles exhibit a response for rabbit IgG in the concentration range of 1.25-20.00 μg ml(-1) and 0.30-20.00 μg ml(-1), respectively.

  20. Preparation of core-shell Ag@CeO2 nanocomposite by LSPR photothermal induced interface reaction

    NASA Astrophysics Data System (ADS)

    Zhong, H. X.; Wei, Y.; Yue, Y. Z.; Zhang, L. H.; Liu, Y.

    2016-04-01

    The core-shell structure of Ag@CeO2 was prepared by a novel and facile method, which was based on the photothermal effect of localized surface plasmon resonance (LSPR). Nanoparticles (NPs) of Ag were dispersed in a solution containing citric acid, ethylene glycol and cerium nitrate, then under irradiation, Ag NPs generated heat from LSPR and the heat-induced polymerization reaction in the interface between Ag and the sol resulted in cerium gel formation only on the surface of the Ag NPs. After calcination, Ag@CeO2 was successfully obtained, then Ag@CeO2/SiO2 was prepared by loading Ag@CeO2 on SiO2. The resultant catalyst exhibited favorable activity and stability for CO oxidation. The preparation method proposed here should be extendable to other composites with metallic cores and oxide shells in which the metallic nanoparticle possesses LSPR properties.

  1. Preparation of core-shell Ag@CeO2 nanocomposite by LSPR photothermal induced interface reaction.

    PubMed

    Zhong, H X; Wei, Y; Yue, Y Z; Zhang, L H; Liu, Y

    2016-04-01

    The core-shell structure of Ag@CeO2 was prepared by a novel and facile method, which was based on the photothermal effect of localized surface plasmon resonance (LSPR). Nanoparticles (NPs) of Ag were dispersed in a solution containing citric acid, ethylene glycol and cerium nitrate, then under irradiation, Ag NPs generated heat from LSPR and the heat-induced polymerization reaction in the interface between Ag and the sol resulted in cerium gel formation only on the surface of the Ag NPs. After calcination, Ag@CeO2 was successfully obtained, then Ag@CeO2/SiO2 was prepared by loading Ag@CeO2 on SiO2. The resultant catalyst exhibited favorable activity and stability for CO oxidation. The preparation method proposed here should be extendable to other composites with metallic cores and oxide shells in which the metallic nanoparticle possesses LSPR properties.

  2. Monodispersed bimetallic PdAg nanoparticles with twinned structures: Formation and enhancement for the methanol oxidation

    PubMed Central

    Yin, Zhen; Zhang, Yining; Chen, Kai; Li, Jing; Li, Wenjing; Tang, Pei; Zhao, Huabo; Zhu, Qingjun; Bao, Xinhe; Ma, Ding

    2014-01-01

    Monodispersed bimetallic PdAg nanoparticles can be fabricated through the emulsion-assisted ethylene glycol (EG) ternary system. Different compositions of bimetallic PdAg nanoparticles, Pd80Ag20, Pd65Ag35 and Pd46Ag54 can be obtained via adjusting the reaction parameters. For the formation process of the bimetallic PdAg nanoparticles, there have two-stage growth processes: firstly, nucleation and growth of the primary nanoclusters; secondly, formation of the secondary nanoparticles with the size-selection and relax process via the coalescence or aggregation of the primary nanoclusters. The as-prepared PdAg can be supported on the carbon black without any post-treatment, which exhibited high electro-oxidation activity towards methanol oxidation under alkaline media. More importantly, carbon-supported Pd80Ag20 nanoparticles reveal distinctly superior activities for the methanol oxidation, even if compared with commercial Pt/C electro-catalyst. It is concluded that the enhanced activity is dependant on the unique twinning structure with heterogeneous phase due to the dominating coalescence growth in EG ternary system. PMID:24608736

  3. Optical properties of Ag nanoparticle-polymer composite film based on two-dimensional Au nanoparticle array film

    PubMed Central

    2014-01-01

    The nanocomposite polyvinyl pyrrolidone (PVP) films containing Ag nanoparticles and Rhodamine 6G are prepared on the two-dimensional distinctive continuous ultrathin gold nanofilms. We investigate the optical properties and the fluorescence properties of silver nanoparticles-PVP polymer composite films influenced by Ag nanoparticles and Au nanoparticles. Absorption spectral analysis suggests that the prominently light absorption in Ag nanowire/PVP and Ag nanowire/PVP/Au film arises from the localized surface plasmon resonance of Ag nanowire and Au nanofilm. The enhanced fluorescence is observed in the presence of Ag nanowire and Au nanofilm, which is attributed to the excitation of surface plasmon polariton resonance of Ag nanowire and Au nanofilm. The gold nanofilm is proven to be very effective fluorescence resonance energy transfer donors. The fabricated novel structure, gold ultrathin continuous nanofilm, possesses high surface plasmon resonance properties and prominent fluorescence enhancement effect. Therefore, the ultrathin continuous gold nanofilm is an active substrate on nanoparticle-enhanced fluorescence. PMID:24685186

  4. Preparation and Sintering Properties of Ag27Cu2Sn Nanopaste as Die Attach Material

    NASA Astrophysics Data System (ADS)

    Liu, Xiaojian; Liu, Wei; Wang, Chunqing; Zheng, Zhen; Kong, Lingchao

    2016-10-01

    Ag27Cu2Sn nanopaste has been prepared by mixing Ag, Cu, and Sn nanoparticles with an organic solvent system. Sintering and mechanical properties of this nanopaste were characterized and investigated. Effects of sintering temperature and time on the sintered microstructure of the nanopaste and shear strength of Cu/Ag27Cu2Sn/Cu structure were analyzed. The results showed that the organic shells coated on the outside of metal nanoparticles could effectively prevent metal nanoparticles from being oxidized below 480°C. When the paste was sintered at 480°C without pressure, few voids or large particles formed within the sintered layer and distributions of Ag, Cu, and Sn were quite uniform. This sintering temperature was much lower than the eutectic temperature (779°C) of Ag-Cu bulk material. Moreover, mutual solid solubilities of Ag and Cu were increased remarkably, which may be caused by high surface activity of Ag and Cu nanoparticles and the important role of the Sn addition. Shear strength of samples with Cu/Ag27Cu2Sn/Cu structure could reach 21 MPa, which could compare with that of Ag nanopaste or conductive adhesives.

  5. Spherically-clustered porous Au-Ag alloy nanoparticle prepared by partial inhibition of galvanic replacement and its application for efficient multimodal therapy.

    PubMed

    Jang, Hongje; Min, Dal-Hee

    2015-03-24

    The polyvinylpyrrolidone (PVP)-coated spherically clustered porous gold-silver alloy nanoparticle (PVP-SPAN) was prepared by low temperature mediated, partially inhibited galvanic replacement reaction followed by silver etching process. The prepared porous nanostructures exhibited excellent photothermal conversion efficiency under irradiation of near-infrared light (NIR) and allowed a high payload of both doxorubicin (Dox) and thiolated dye-labeled oligonucleotide, DNAzyme (FDz). Especially, PVP-SPAN provided 10 times higher loading capacity for oligonucleotide than conventional hollow nanoshells due to increased pore diameter and surface-to-volume ratio. We demonstrated highly efficient chemo-thermo-gene multitherapy based on codelivery of Dox and FDz with NIR-mediated photothermal therapeutic effect using a model system of hepatitis C virus infected human liver cells (Huh7 human hepatocarcinoma cell line containing hepatitis C virus NS3 gene replicon) compared to conventional hollow nanoshells.

  6. Oxidation of Ag nanoparticles in aqueous media: Effect of particle size and capping

    NASA Astrophysics Data System (ADS)

    Mikhlin, Yuri L.; Vishnyakova, Elena A.; Romanchenko, Alexander S.; Saikova, Svetlana V.; Likhatski, Maxim N.; Larichev, Yurii V.; Tuzikov, Fedor V.; Zaikovskii, Vladimir I.; Zharkov, Sergey M.

    2014-04-01

    Many applications and environmental impact of silver-bearing nanomaterials critically depend upon their specific reactivity, which is still poorly understood. Here, silver nanoparticles (Ag NPs) of about 3-5 nm and 10-12 nm in diameter, uncapped and capped with L-glucose or citrate, were prepared, characterized using UV-vis absorption spectroscopy, SAXS, TEM, and their (electro)chemical oxidation was examined in comparison with each other and bulk metal applying scanning tunneling microscopy and spectroscopy, cyclic voltammetry, and XPS. A resistive switching effect was found in the tunneling spectra measured in air at the smaller uncapped Ag NPs deposited on HOPG and was interpreted in terms of Ag transfer between the particle and the probe. The anodic oxidation of these Ag NPs in 1 M NaOH yielded 3D Ag2O, while only a layer of "primary" Ag(I) oxide emerged on larger uncapped nanoparticles during the potential sweep. The formation of AgO at higher potentials proceeded readily at the "primary" oxide but was retarded at the smaller NPs. The citrate- and glucose-capping substantially impeded the formation both of Ag2O and AgO. The findings highlighted, particularly, a non-trivial effect of particle size and transient mobilization of Ag species on the reactions of silver nanoparticles.

  7. Size and alloying induced shift in core and valence bands of Pd-Ag and Pd-Cu nanoparticles

    SciTech Connect

    Sengar, Saurabh K.; Mehta, B. R.; Govind

    2014-03-28

    In this report, X-ray photoelectron spectroscopy studies have been carried out on Pd, Ag, Cu, Pd-Ag, and Pd-Cu nanoparticles having identical sizes corresponding to mobility equivalent diameters of 60, 40, and 20 nm. The nanoparticles were prepared by the gas phase synthesis method. The effect of size on valence and core levels in metal and alloy nanoparticles has been studied by comparing the values to those with the 60 nm nanoparticles. The effect of alloying has been investigated by comparing the valence and core level binding energies of Pd-Cu and Pd-Ag alloy nanoparticles with the corresponding values for Pd, Ag, and Cu nanoparticles of identical sizes. These effects have been explained in terms of size induced lattice contractions, alloying induced charge transfer, and hybridization effects. The observation of alloying and size induced binding energy shifts in bimetallic nanoparticles is important from the point of view of hydrogen reactivity.

  8. Preparation and characterization of nanosized Ag/SLN composite and its viability for improved occlusion

    NASA Astrophysics Data System (ADS)

    Cynthia Jemima Swarnavalli, G.; Dinakaran, S.; Divya, S.

    2016-10-01

    Nanocomposites consisting of silver and solid lipid nanoparticles (SLN) elicit interest for their synergistic effect based enhanced properties in skin hydration. The nanocomposite preparation aims at combining the antimicrobial activity of silver with skin hydration performance of SLN. The nanocomposites designated Ag/SAN (silver/stearic acid nanoparticles), Ag/PAN (silver/palmitic acid nanoparticles) were prepared by incorporating silver nanoparticles into the dispersion of SLN and sonicating for 10 min followed by heating for 1 h at 50 °C in a thermostat. The occlusive property of the two nanocomposites was evaluated in comparison with the pure SLN by adopting de Vringer-de Ronde in vitro occlusion test. The incorporation of silver nanoparticles has improved occlusion factor by 10 % in the case of both composites at SLN concentration of 0.14 mmol. Characterization studies include XRD, DSC, HRSEM, DLS and zeta potential measurement. High resolution scanning electron microscopy (HRSEM) images divulge that the nanoparticles of composite (Ag/SAN) shows halo effect where the hydrophobic stearic acid is oriented at the core and is surrounded by silver nanoparticles while Ag/PAN shows cashew shaped SLN dispersed in silver nanoparticles matrix.

  9. Visible-light photocatalytic degradation of methylene blue with laser-induced Ag/ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Whang, Thou-Jen; Hsieh, Mu-Tao; Chen, Huang-Han

    2012-01-01

    The preparation of Ag doped ZnO nanoparticles conducted through the method of laser-induction is presented in this work. The Ag/ZnO nanoparticles attained from various weight percentages of added AgNO3 relative to ZnO were applied under visible-light irradiation for evaluating the heterogeneous photocatalytic degradations of methylene blue (MB) solutions. It was shown that the catalytic behavior of Ag/ZnO nanoparticles in the visible-light range is notably improved through the Ag deposition onto ZnO nanoparticles by the method of laser-induction with a maximum effectiveness of 92% degradation. The properties of the nanoparticles were characterized by the employments of UV-vis spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and selected-area electron diffraction (SAED).

  10. Characterization of Silver/Bovine Serum Albumin (Ag/BSA) nanoparticles structure: morphological, compositional, and interaction studies.

    PubMed

    Gebregeorgis, A; Bhan, C; Wilson, O; Raghavan, D

    2013-01-01

    The primary objective of this study was to elucidate the structure of protein conjugated silver nanoparticles prepared by chemical reduction of AgNO(3) and bovine serum albumin (BSA) mixture. The role of BSA in the formation of Ag/BSA nanoparticles was established by UV-Vis Spectroscopy. The association of silver with BSA in Ag/BSA nanoparticles was studied by the decrease in the intensity of absorbance peak at 278 nm in UV-Vis spectra and shift in cathodic peak potential in cyclic voltammogram. The molar ratio of silver to BSA in the Ag/BSA nanoparticles is 27:1, as ascertained by thermogravimetric analysis and atomic absorption spectrometry. Based on atomic force microscopy, dynamic light scattering and transmission electron microscopy (TEM) measurements, the average particle size of nanoparticles was found to be range of 11-15 nm. TEM image showed that the nanoparticle has two distinct phases and selected area electron diffraction pattern of nanoparticles indicated that the silver phase in Ag/BSA is fcc. X-ray photo electron spectroscopy measurements of freshly prepared and argon sputtered nanoparticles provided evidence that the outer and inner region of nanoparticles are mainly composed of BSA and silver respectively. The structural and compositional findings of nanoparticles could have a strong bearing on the bioavailability and antimicrobial activity of nanoparticles.

  11. Facile synthesis of Ag2S nanoparticles functionalized by carbon-containing citrate shell

    NASA Astrophysics Data System (ADS)

    Sadovnikov, S. I.; Gusev, A. I.; Gerasimov, E. Yu.; Rempel, A. A.

    2015-12-01

    Silver sulfide nanoparticles with non-toxic citrate shell are synthesized by chemical bath deposition from aqueous mixtures of silver nitrate and sodium sulfide in the presence of sodium citrate used as a complexing and stabilizing agent. The prepared nanoparticles have Ag2S core with monoclinic crystal structure functionalized by a carbon-containing citrate shell. By varying the concentrations of reagents it was possible to prepare core-shell nanoparticles with pre-assigned size of Ag2S core from 10 and 50 nm and pre-assigned thickness from 1.5 to 10 nm of citrate shell. A probable mechanism of formation of carbon-containing citrate shell on Ag2S core has been proposed.

  12. Bimetallic PdAg nanoparticle arrays from monolayer films of diblock copolymer micelles

    NASA Astrophysics Data System (ADS)

    Ehret, E.; Beyou, E.; Mamontov, G. V.; Bugrova, T. A.; Prakash, S.; Aouine, M.; Domenichini, B.; Cadete Santos Aires, F. J.

    2015-07-01

    The self-assembly technique provides a highly efficient route to generate well-ordered structures on a nanometer scale. In this paper, well-ordered arrays of PdAg alloy nanoparticles on flat substrates with narrow distributions of particle size (6-7 nm) and interparticle spacing (about 60 nm) were synthesized by the block copolymer micelle approach. A home-made PS-b-P4VP diblock copolymer was prepared to obtain a micellar structure in toluene. Pd and Ag salts were then successfully loaded in the micellar core of the PS-b-P4VP copolymer. A self-assembled monolayer of the loaded micelles was obtained by dipping the flat substrate in the solution. At this stage, the core of the micelles was still loaded with the metal precursor rather than with a metal. Physical and chemical reducing methods were used to reduce the metal salts embedded in the P4VP core into PdAg nanoparticles. HRTEM and EDX indicated that Pd-rich PdAg alloy nanoparticles were synthesized by chemical or physical reduction; UV-visible spectroscopy observations confirmed that metallic PdAg nanoparticles were quickly formed after chemical reduction; XPS measurements revealed that the PdAg alloy nanoparticles were in a metallic state after a short time of exposure to O2 plasma and after hydrazine reduction.

  13. Surface spin polarization induced ferromagnetic Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Shih, Po-Hsun; Li, Wen-Hsien; Wu, Sheng Yun

    2016-05-01

    We report on the observation of ferromagnetic spin polarized moments in 4.5 nm Ag nanoparticles. Both ferromagnetic and diamagnetic responses to an applied magnetic field were detected. The spin polarized moments shown under non-linear thermoinduced magnetization appeared on the surface atoms, rather than on all the atoms in particles. The saturation magnetization departed substantially from the Bloch T3/2-law, showing the existence of magnetic anisotropy. The Heisenberg ferromagnetic spin wave model for Ha-aligned moments was then employed to identify the magnetic anisotropic energy gap of ~0.12 meV. Our results may be understood by assuming the surface magnetism model, in which the surface atoms give rise to polarized moments while the core atoms produce diamagnetic responses.

  14. Hydroxyapatite supported Ag3PO4 nanoparticles with higher visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Hong, Xiaoting; Wu, Xiaohui; Zhang, Qiuyun; Xiao, Mingfeng; Yang, Gelin; Qiu, Meirong; Han, Guocheng

    2012-03-01

    Hydroxyapatite supported Ag3PO4 nanocomposites have been synthesized by a wet impregnation process. UV-vis absorption spectra show a red shift of the absorption edges for the composite systems compared to pure hydroxyapatite support. The surface structure and morphology of the nanocomposites were characterized by Brunauer-Emmett-Teller (BET) apparatus, X-ray diffraction (XRD), transmission electron microscopy (TEM). The results suggest that Ag3PO4 nanoparticles (6-17 nm in diameter) are well dispersed on the hydroxyapatite support and Ag3PO4 nanoparticles density is larger for the higher Ag+ loading sample. The as-prepared nanocomposite photocatalysts showed a pronounced photocatalytic activity upon decomposition of methylene blue dye in aqueous solution under both visible light (wavelength > 400 nm) and UV-vis light irradiation. A synergic mechanism of inherent photocatalytic capability of Ag3PO4 and the accelerated electron/hole separation resulting from the photoinduced electrons captured by the slow-released Ag+ at the interface of Ag3PO4 and hydroxyapatite is proposed for the nanocomposites on the enhancement of photocatalytic performance in comparison to that of pure Ag3PO4 nanoparticles. The support of hydroxyapatite may also act as an absorbent which favors the mass transfer in heterogeneous photocatalysis reaction.

  15. Synthesis and formation mechanism of Ag-Ni alloy nanoparticles at room temperature

    NASA Astrophysics Data System (ADS)

    Yan, Shi; Sun, Dongbai; Tan, Yuanyuan; Xing, Xueqing; Yu, Hongying; Wu, Zhonghua

    2016-11-01

    Ag-Ni nanoparticles were prepared with a chemical reduction method in the presence of polyvinylpyrrolidone (PVP) used as a stabilizing agent. During the synthesis of Ag-Ni nanoparticles, silver nitrate was used as the Ag+ source while nickel sulfate hexahydrate was used as Ni2+ source. Mixed solutions of Ag+ source and Ni2+ source were used as the precursors and sodium borohydride was used as the reducing agent. Five ratios of Ag+/Ni2+ (9:1, 3:1, 1:1, 1:3, and 1:9) suspensions were prepared in the corresponding precursors. Ag-Ni alloy nanoparticles were obtained with this method at room temperature. Scanning electronic microscope (SEM), energy dispersive spectrum (EDS), high resolution transmission electron microscope (HRTEM) were used to characterize the morphology, composition and crystal structure of the nanoparticles. The crystal structure was also investigated with X-ray diffraction (XRD). In all five Ag/Ni ratios, two kinds of particle structures were observed that are single crystal structure and five-fold twinned structure respectively. Free energy of nanoparticles with different crystal structures were calculated at each Ag/Ni ratio. Calculated results revealed that, with identical volume, free energy of single crystal particle is lower than multi-twinned particle and the difference becomes smaller with the increase of particle size; increase of Ni content will lead the increase of free energy for both structures. Formation of different crystal structures are decided by the structure of the original nuclei at the very early stage of the reduction process.

  16. Photocatalytic performance of Ag doped SnO2 nanoparticles modified with curcumin

    NASA Astrophysics Data System (ADS)

    Vignesh, K.; Hariharan, R.; Rajarajan, M.; Suganthi, A.

    2013-07-01

    Visible light active Ag doped SnO2 nanoparticles modified with curcumin (Cur-Ag-SnO2) have been prepared by a combined precipitation and chemical impregnation route. The optical properties, phase structures and morphologies of the as-prepared nanoparticles were characterized using UV-visible diffuse reflectance spectra (UV-vis-DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The surface area was measured by Brunauer. Emmett. Teller (B.E.T) analysis. Compared to bare SnO2, the surface modified photocatalysts (Ag-SnO2 and Cur-Ag-SnO2) showed a red shift in the visible region. The photocatalytic activity was monitored via the degradation of rose bengal (RB) dye and the results revealed that Cur-Ag-SnO2 shows better photocatalytic activity than that of Ag-SnO2 and SnO2. The superior photocatalytic activity of Cur-Ag-SnO2 could be attributed to the effective electron-hole separation by surface modification. The effect of photocatalyst concentration, initial dye concentration and electron scavenger on the photocatalytic activity was examined in detail. Furthermore, the antifungal activity of the photocatalysts and the reusability of Cur-Ag-SnO2 were tested.

  17. Evidence for avoidance of Ag nanoparticles by earthworms (Eisenia fetida).

    PubMed

    Shoults-Wilson, W A; Zhurbich, Oksana I; McNear, David H; Tsyusko, Olga V; Bertsch, Paul M; Unrine, Jason M

    2011-03-01

    Silver nanoparticles have been incorporated into a wide variety of consumer products, ideally acting as antimicrobial agents. Silver exposure has long been known to cause toxic effects to a wide variety of organisms, making large scale production of silver nanoparticles a potential hazard to environmental systems. Here we describe the first evidence that an organism may be able to sense manufactured nanoparticles in a complex, environmentally relevant exposure and that the presence of nanoparticles alters the organism's behavior. We found that earthworms (Eisenia fetida) consistently avoid soils containing silver nanoparticles and AgNO(3) at similar concentrations of Ag. However, avoidance of silver nanoparticles occurred over 48 h, while avoidance of AgNO(3) was immediate. It was determined that avoidance of silver nanoparticles could not be explained by release of silver ions or any changes in microbial communities caused by the introduction of Ag. This leads us to conclude that the earthworms were in some way sensing the presence of nanoparticles over the course of a 48 h exposure and choosing to avoid exposure to them. Our results demonstrate that nanoparticle interactions with organisms may be unpredictable and that these interactions may result in ecologically significant effects on behavior at environmentally relevant concentrations. PMID:21229389

  18. Immobilization of Highly Dispersed Ag Nanoparticles on Carbon Nanotubes Using Electron-Assisted Reduction for Antibacterial Performance.

    PubMed

    Yan, Xiaoliang; Li, Sha; Bao, Jiehua; Zhang, Nan; Fan, Binbin; Li, Ruifeng; Liu, Xuguang; Pan, Yun-Xiang

    2016-07-13

    Silver nanoparticles (Ag NPs) supported on certain materials have been widely used as disinfectants. Yet, to date, the antibacterial activity of the supported Ag NPs is still far below optimum. This is mainly associated with the easy aggregation of Ag NPs on the supporting materials. Herein, an electron-assisted reduction (EAR) method, which is operated at temperatures as low as room temperature and without using any reduction reagent, was employed for immobilizing highly dispersed Ag NPs on aminated-CNTs (Ag/A-CNTs). The average Ag NPs size on the EAR-prepared Ag/A-CNTs is only 3.8 nm, which is much smaller than that on the Ag/A-CNTs fabricated from the traditional thermal calcination (25.5 nm). Compared with Ag/A-CNTs fabricated from traditional thermal calcination, EAR-prepared Ag/A-CNTs shows a much better antibacterial activity to E. coli/S. aureus and antifouling performance to P. subcordiformis/T. lepidoptera. This is mainly originated from the significantly enhanced Ag(+) ion releasing rate and highly dispersed Ag NPs with small size on the EAR-prepared Ag/A-CNTs. The findings from the present work are helpful for fabricating supported Ag NPs with small size and high dispersion for efficient antibacterial process. PMID:27327238

  19. Contribution of Eu ions on the precipitation of silver nanoparticles in Ag-Eu co-doped borate glasses

    SciTech Connect

    Jiao, Qing; Qiu, Jianbei; Zhou, Dacheng; Xu, Xuhui

    2014-03-01

    Graphical abstract: - Highlights: • Silver nanoparticles are precipitated from the borate glasses during the melting process without any further heat treatment. • The reduction of Eu{sup 3+} ions to Eu{sup 2+} ions is presented in this material. • The intensity of Ag{sup +} luminescence. • The introduction of Eu ions accelerated the reaction between Eu{sup 2+} ions and silver ions inducing the silver clusters formation. - Abstract: Ag{sup +} doped sodium borate glasses with different Eu ions concentration were prepared by the melt-quenching method. The absorption at about 410 nm which was caused by the surface plasmon resonance (SPR) of Ag nanoparticles (NPs) is promoted with increasing of Eu ions concentration. Meanwhile, the luminescent spectra showed that the emission intensity of Ag{sup +} decreased while that of the Ag aggregates increased simultaneously. The results indicated that the Ag ions intend to form the high-polymeric state such as Ag aggregates and nanoparticles with increasing of europium ions. Owing to the self-reduction of Eu{sup 3+} to Eu{sup 2+} in our glass system, it revealed that Ag{sup +} has been reduced by the neighboring Eu{sup 2+} which leads to the formation of Ag aggregates and the precipitation of Ag NPs in the matrix. In addition, energy transfer (ET) process from Ag{sup +}/Ag aggregates to the Eu{sup 3+} was investigated for the enhancement of Eu{sup 3+} luminescence.

  20. Beet Juice-Induced Green Fabrication of Plasmonic AgCl/Ag Nanoparticles

    EPA Science Inventory

    A simple, green, and fast approach (complete within 5 min) was explored for the fabrication of hybrid AgCl/Ag plasmonic nanoparticles under microwave (MW) irradiation. In this method, beet juice served as a reducing reagent, which is an abundant sugar-rich agricultural produce. I...

  1. Preparation, characterization, and photocatalytic performance of pear-shaped ZnO/Ag core-shell submicrospheres

    NASA Astrophysics Data System (ADS)

    Guo, Xiao-Hua; Ma, Jian-Qi; Ge, Hong-Guang

    2013-05-01

    Pear-shaped ZnO/Ag core-shell submicrospheres with good monodispersity were prepared via a seed-mediated particle growth procedure, where metal Ag (by reducing Ag+ with Sn2+) deposited on the as-prepared ZnO submicrospheres served as seeds (nucleation sites) for further growth of Ag nanoparticles. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, ultraviolet-visible and photoluminescence spectra. Structure characterization demonstrates that the ZnO/Ag composites are composed of pear-shaped wurtzite ZnO submicrosphere core and Ag nanoparticles (nanoshell). Photoluminescence indicates that Ag nanoshell can effectively inhibit the recombination of the photoinduced electrons and holes of ZnO. This is responsible for the higher photocatalytic activity of the ZnO/Ag core-shell composites. The photocatalytic performance of the prepared ZnO/Ag samples for degradation of Rhodamine B was evaluated with a comparative study. The relationship between the structure of the samples and their photocatalytic performance shows that Ag deposits can significantly enhance the photocatalytic efficiency of ZnO submicrospheres.

  2. Synthesis and characterization of AgCl nanoparticles produced by laser ablation of Ag in NaCl solution

    NASA Astrophysics Data System (ADS)

    Mahmoodi, Afsaneh; Shoorshinie, Seyedeh Zahra; Dorranian, Davoud

    2016-04-01

    In this work, the structural and optical properties of silver chloride nanoparticles produced by laser ablation of Ag plate in NaCl solution were investigated. Five different concentrations of NaCl solution were used as the ablation environment. The beam of a Q-switched Nd:YAG laser of 1064 nm wavelength and 7 ns pulse width was employed to irradiate the Ag target in NaCl solutions. Fluence of laser pulse was 1.5 J/cm2, and repetition rate was 5 Hz. Samples were prepared using 1500 pulses. Produced nanoparticles were characterized using UV-visible-NIR absorption, and transmission spectrum, transmission electron microscopy, scanning electron microscopy, X-ray diffraction pattern, photoluminescence spectrum, and dynamic light scattering method. Results show that laser ablation is a promising method to produce AgCl nanoparticles. Size of nanoparticles, their lattice structure, and bandgap energy as well as the production rate may be controlled by the concentration of NaCl in the ablation environment.

  3. Gold core@silver semishell Janus nanoparticles prepared by interfacial etching

    NASA Astrophysics Data System (ADS)

    Chen, Limei; Deming, Christopher P.; Peng, Yi; Hu, Peiguang; Stofan, Jake; Chen, Shaowei

    2016-07-01

    Gold core@silver semishell Janus nanoparticles were prepared by chemical etching of Au@Ag core-shell nanoparticles at the air/water interface. Au@Ag core-shell nanoparticles were synthesized by chemical deposition of a silver shell onto gold seed colloids followed by the self-assembly of 1-dodecanethiol onto the nanoparticle surface. The nanoparticles then formed a monolayer on the water surface of a Langmuir-Blodgett trough, and part of the silver shell was selectively etched away by the mixture of hydrogen peroxide and ammonia in the water subphase, where the etching was limited to the side of the nanoparticles that was in direct contact with water. The resulting Janus nanoparticles exhibited an asymmetrical distribution of silver on the surface of the gold cores, as manifested in transmission electron microscopy, UV-vis absorption, and X-ray photoelectron spectroscopy measurements. Interestingly, the Au@Ag semishell Janus nanoparticles exhibited enhanced electrocatalytic activity in oxygen reduction reactions, as compared to their Au@Ag and Ag@Au core-shell counterparts, likely due to a synergistic effect between the gold cores and silver semishells that optimized oxygen binding to the nanoparticle surface.Gold core@silver semishell Janus nanoparticles were prepared by chemical etching of Au@Ag core-shell nanoparticles at the air/water interface. Au@Ag core-shell nanoparticles were synthesized by chemical deposition of a silver shell onto gold seed colloids followed by the self-assembly of 1-dodecanethiol onto the nanoparticle surface. The nanoparticles then formed a monolayer on the water surface of a Langmuir-Blodgett trough, and part of the silver shell was selectively etched away by the mixture of hydrogen peroxide and ammonia in the water subphase, where the etching was limited to the side of the nanoparticles that was in direct contact with water. The resulting Janus nanoparticles exhibited an asymmetrical distribution of silver on the surface of the gold

  4. Metal Nanoparticles Preparation In Supercritical Carbon Dioxide Solutions

    SciTech Connect

    Harry W. Rollins

    2004-04-01

    The novel optical, electronic, and/or magnetic properties of metal and semiconductor nanoparticles have resulted in extensive research on new methods for their preparation. An ideal preparation method would allow the particle size, size distribution, crystallinity, and particle shape to be easily controlled, and would be applicable to a wide variety of material systems. Numerous preparation methods have been reported, each with its inherent advantages and disadvantages; however, an ideal method has yet to emerge. The most widely applied methods for nanoparticle preparation include the sonochemical reduction of organometallic reagents,(1&2) the solvothermal method of Alivisatos,(3) reactions in microemulsions,(4-6) the polyol method (reduction by alcohols),(7-9) and the use of polymer and solgel materials as hosts.(10-13) In addition to these methods, there are a variety of methods that take advantage of the unique properties of a supercritical fluid.(14&15) Through simple variations of temperature and pressure, the properties of a supercritical fluid can be continuously tuned from gas-like to liquid-like without undergoing a phase change. Nanoparticle preparation methods that utilize supercritical fluids are briefly reviewed below using the following categories: Rapid Expansion of Supercritical Solutions (RESS), Reactive Supercritical Fluid Processing, and Supercritical Fluid Microemulsions. Because of its easily accessible critical temperature and pressure and environmentally benign nature, carbon dioxide is the most widely used supercritical solvent. Supercritical CO2 is unfortunately a poor solvent for many polar or ionic species, which has impeded its use in the preparation of metal and semiconductor nanoparticles. We have developed a reactive supercritical fluid processing method using supercritical carbon dioxide for the preparation of metal and metal sulfide particles and used it to prepare narrowly distributed nanoparticles of silver (Ag) and silver sulfide

  5. Ag(I)-triggered one-pot synthesis of Ag nanoparticles onto natural nanorods as a multifunctional nanocomposite for efficient catalysis and adsorption.

    PubMed

    Tian, Guangyan; Wang, Wenbo; Mu, Bin; Kang, Yuru; Wang, Aiqin

    2016-07-01

    A multifunctional palygorskite/polyaniline/Ag nanoparticles (PAL/PANI/AgNPs) nanocomposite was prepared at room temperature using a simple one-pot in-situ polymerization reaction of aniline monomers triggered by Ag(I) on the surface of natural PAL nanorods. Ag(I) served as both the oxidant and the precursor of the AgNPs, which initiated the polymerization of aniline monomers on PAL nanorods while simultaneously being reduced to form Ag(0) nanoparticles (AgNPs). The in-situ formed AgNPs were evenly distributed on the surface of the PAL nanorods because the interfacial effect of PAL prevents their aggregation. The density and size of the AgNPs and the catalytic activity of the nanocomposites could be controlled by altering the molar ratio of aniline to Ag(I). The performance evaluation revealed that the nanocomposites could be used as highly active catalysts, which rapidly catalyzed the reduction of 4-nitrophenol (4-NP) within 2min and Congo red (CR) within 10min. The nanocomposites are also an effective adsorbent for H2PO4(-) able to remove 99.40% of H2PO4(-) (only 61.77% for raw PAL) from a solution with an initial concentration of 50mg/L. This multifunctional nanocomposite synthesized by a simple one-pot approach is a promising material for environmental applications.

  6. Monodispersed bimetallic PdAg nanoparticles with twinned structures: formation and enhancement for the methanol oxidation.

    PubMed

    Yin, Zhen; Zhang, Yining; Chen, Kai; Li, Jing; Li, Wenjing; Tang, Pei; Zhao, Huabo; Zhu, Qingjun; Bao, Xinhe; Ma, Ding

    2014-01-01

    Monodispersed bimetallic PdAg nanoparticles can be fabricated through the emulsion-assisted ethylene glycol (EG) ternary system. Different compositions of bimetallic PdAg nanoparticles, Pd₈₀Ag₂₀, Pd₆₅Ag₃₅ and Pd₄₆Ag₅₄ can be obtained via adjusting the reaction parameters. For the formation process of the bimetallic PdAg nanoparticles, there have two-stage growth processes: firstly, nucleation and growth of the primary nanoclusters; secondly, formation of the secondary nanoparticles with the size-selection and relax process via the coalescence or aggregation of the primary nanoclusters. The as-prepared PdAg can be supported on the carbon black without any post-treatment, which exhibited high electro-oxidation activity towards methanol oxidation under alkaline media. More importantly, carbon-supported Pd₈₀Ag₂₀ nanoparticles reveal distinctly superior activities for the methanol oxidation, even if compared with commercial Pt/C electro-catalyst. It is concluded that the enhanced activity is dependant on the unique twinning structure with heterogeneous phase due to the dominating coalescence growth in EG ternary system. PMID:24608736

  7. Highly luminescent material based on Alq3:Ag nanoparticles.

    PubMed

    Salah, Numan; Habib, Sami S; Khan, Zishan H

    2013-09-01

    Tris (8-hydroxyquinoline) aluminum (Alq3) is an organic semiconductor molecule, widely used as an electron transport layer, light emitting layer in organic light-emitting diodes and a host for fluorescent and phosphorescent dyes. In this work thin films of pure and silver (Ag), cupper (Cu), terbium (Tb) doped Alq3 nanoparticles were synthesized using the physical vapor condensation method. They were fabricated on glass substrates and characterized by X-ray diffraction, scanning electron microscope (SEM), energy dispersive spectroscopy, atomic force microscope (AFM), UV-visible absorption spectra and studied for their photoluminescence (PL) properties. SEM and AFM results show spherical nanoparticles with size around 70-80 nm. These nanoparticles have almost equal sizes and a homogeneous size distribution. The maximum absorption of Alq3 nanoparticles is observed at 300 nm, while the surface plasmon resonant band of Ag doped sample appears at 450 nm. The PL emission spectra of Tb, Cu and Ag doped Alq3 nanoparticles show a single broad band at around 515 nm, which is similar to that of the pure one, but with enhanced PL intensity. The sample doped with Ag at a concentration ratio of Alq3:Ag = 1:0.8 is found to have the highest PL intensity, which is around 2 times stronger than that of the pure one. This enhancement could be attributed to the surface plasmon resonance of Ag ions that might have increased the absorption and then the quantum yield. These remarkable result suggest that Alq3 nanoparticles incorporated with Ag ions might be quite useful for future nano-optoelectronic devices. PMID:23653126

  8. Tyrosine-assisted preparation of Ag/ZnO nanocomposites with enhanced photocatalytic performance and synergistic antibacterial activities

    NASA Astrophysics Data System (ADS)

    Lu, Weiwei; Liu, Guosheng; Gao, Shuyan; Xing, Shantao; Wang, Jianji

    2008-11-01

    In this paper, Ag/ZnO metal-semiconductor nanocomposites were prepared through a facile one-pot hydrothermal method with the assistance of tyrosine. The synthesized samples were structurally characterized by x-ray diffraction, scanning electron microscope, transmission electron microscope and x-ray photoelectron spectroscopy. It was shown that the added tyrosine served both as a shape conductor for the formation of ZnO faceted nanorods and as a reducing agent of Ag+ ions. In the reaction process, the complexation of Ag+ with NH3 and OH- decreased the redox potential of Ag+/Ag, which prevented the formation of isolated Ag nanoparticles in solution. The prepared Ag/ZnO nanocomposites showed potential applications in photodegradation of organic dye pollutants and destruction of bacteria.

  9. Synthesis and the enhanced visible-light-driven photocatalytic activity of BiVO4 nanocrystals coupled with Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, W. Z.; Meng, Shan; Tan, Miao; Jia, L. J.; Zhou, Y. X.; Wu, Shuang; Huang, X. W.; Liang, Y. J.; Shi, H. L.

    2015-03-01

    BiVO4 nanocrystals coupled with Ag nanoparticles (Ag-BiVO4 heterogeneous nanostructures) have been prepared by a new strategy via combining a hydrothermal route with a polyol process, in which BiVO4 nanocrystals were first synthesized by a hydrothermal route, and then, Ag nanoparticles were grown on the surfaces of the presynthesized BiVO4 nanocrystals through a polyol process. The photocatalytic evaluations demonstrate that BiVO4 nanocrystals coupled with Ag nanoparticles exhibit the enhanced visible-light-driven photocatalytic activity for the degradation of methylene blue (MB) and rhodamine B (RhB). The energy alignment and diffuse reflectance property of Ag-BiVO4 heterogeneous nanostructures demonstrate that Ag nanoparticles attached on the surfaces of BiVO4 nanocrystals play double roles for the enhanced visible-light-driven photocatalytic activity. First, the Ag nanoparticles grown on the surfaces of BiVO4 nanocrystals may act as electron sinks to retard the recombination of the photogenerated electrons and holes in BiVO4 so as to improve the charge separation on its surfaces. Second, the Ag nanoparticles increase the visible light absorption of the Ag-BiVO4 photocatalyst due to surface plasmon resonance (SPR) of Ag nanoparticles. These double roles of Ag nanoparticles make Ag-BiVO4 heterogeneous nanostructures to exhibit the enhanced photocatalytic activity to decompose MB and RhB under visible light irradiation, compared to the pure BiVO4 nanocrystals. The enhanced photocatalytic activity is attributed to the charge transfer from BiVO4 to the attached Ag nanoparticles as well as SPR absorption of Ag nanoparticles. The present work not only provides an efficient route to enhance visible-light-driven photocatalytic activity of BiVO4, but also offers a new strategy for fabricating metal-semiconductor heterogeneous nanostructure photocatalysts, which are expected to show considerable potential applications in solar-driven wastewater treatment and water

  10. Synthesis, Characterizations of Superparamagnetic Fe3O4-Ag Hybrid Nanoparticles and Their Application for Highly Effective Bacteria Inactivation.

    PubMed

    Tung, Le Minh; Cong, Nguyen Xuan; Huy, Le Thanh; Lan, Nguyen Thi; Phan, Vu Ngoc; Hoa, Nguyen Quang; Vinh, Le Khanh; Thinh, Nguyen Viet; Tai, Le Thanh; Ngo, Duc-The; Mølhave, Kristian; Huy, Tran Quang; Le, Anh-Tuan

    2016-06-01

    In recent years, outbreaks of infectious diseases caused by pathogenic micro-organisms pose a serious threat to public health. In this work, Fe3O4-Ag hybrid nanoparticles were synthesized by simple chemistry method and these prepared nanoparticles were used to investigate their antibacterial properties and mechanism against methicilline-resistant Staphylococcus aureus (MRSA) pathogen. The formation of dimer-like nanostructure of Fe3O4-Ag hybrid NPs was confirmed by X-ray diffraction and High-resolution Transmission Electron Microscopy. Our biological analysis revealed that the Fe3O4-Ag hybrid NPs showed more noticeable bactericidal activity than that of plain Fe3O4 NPs and Ag-NPs. We suggest that the enhancement in bactericidal activity of Fe3O4-Ag hybrid NPs might be likely from main factors such as: (i) enhanced surface area property of hybrid nanoparticles; (ii) the high catalytic activity of Ag-NPs with good dispersion and aggregation stability due to the iron oxide magnetic carrier, and (iii) large direct physical contacts between the bacterial cell membrane and the hybrid nanoparticles. The superparamagnetic hybrid nanoparticles of iron oxide magnetic nanoparticles decorated with silver nanoparticles can be a potential candidate to effectively treat infectious MRSA pathogen with recyclable capability, targeted bactericidal delivery and minimum release into environment. PMID:27427651

  11. Preparation and properties of silver nanoparticles loaded in activated carbon for biological and environmental applications.

    PubMed

    Tran, Quoc Tuan; Nguyen, Van Son; Hoang, Thi Kim Dung; Nguyen, Hoang Luong; Bui, Thu Thuy; Nguyen, Thi Van Anh; Nguyen, Dinh Hoa; Nguyen, Hoang Hai

    2011-09-15

    Silver nanoparticles colloid has been prepared by a modified sonoelectrodeposition technique in which a silver plate was used as the source of silver ions. This technique allows producing Ag nanoparticles with the size of 4-30 nm dispersed in a non-toxic solution. The Ag nanoparticles were loaded in a high surface activated carbon produced from coconut husk, a popular agricultural waste in Vietnam by thermal activation. The surface area of the best activated carbon is 890 m(2)/g. The presence of Ag nanoparticles does not change significantly properties of the activated carbon in terms of morphology and methylene blue adsorption ability. The Ag nanoparticle-loaded activated carbon shows a good antibacterial activity against Escherichia coli with very low minimal inhibitory concentration of 16 μg/ml and strong As(V) adsorption. The materials are potential for prevention and treatment of microbial infection and contamination for environmental applications.

  12. Label-Free Detection of Ag+ Based on Gold Nanoparticles and Ag+-Specific DNA.

    PubMed

    Pu, Wendan; Zhao, Zhao; Wu, Liping; Liu, Yue; Zhao, Huawen

    2015-08-01

    A sensitive label-free method was presented for the determination of silver ion (Ag+) in this paper. Cytosine-rich DNA (C-DNA) was used as Ag+ specific DNA. Without Ag+ in the solution, fluorescence of fluorescein (FAM) is quenched by C-DNA stabilized gold nanoparticles (AuNPs) in high salt environment. When Ag+ is present in the solution, however, Ag+-mediated cytosine-Ag+-cytosine (C-Ag+-C) base pairs induced the C-DNA folding into a hairpin structure, which can not stabilize AuNPs in high salt environment, thus causing AuNPs aggregation. After centrifugation to remove the aggregated AuNPs, the quenching ability of the supernatant for FAM is decreased and the fluorescence intensity of solution increases with increasing the Ag+ concentration. Due to the highly specific interaction of the C-DNA towards Ag+ and the strong fluorescent quenching ability of AuNPs for FAM, the method has high selectivity and sensitivity for Ag+. Under the optimal conditions, the fluorescence intensity at 515 nm increased linearly with the concentration of Ag+ ranging from 15 nM to 700 nM, and the detection limit was determined as 6 nM based on 3 σ/slope. This method is simple, sensitive, and may be applied to other detection systems by selecting the appropriate DNA sequences. PMID:26369112

  13. Extranuclear dynamics of 111Ag(→111Cd) doped in AgI nanoparticles

    NASA Astrophysics Data System (ADS)

    Sato, W.; Mizuuchi, R.; Irioka, N.; Komatsuda, S.; Kawata, S.; Taoka, A.; Ohkubo, Y.

    2014-08-01

    Dynamic behavior of the extranuclear field relative to the 111Ag(→111Cd) probe nucleus introduced in a superionic conductor silver iodide (AgI) was investigated by means of the time-differential perturbed angular correlation technique. For poly-N-vinyl-2-pyrrolidone (PVP)-coated AgI nanoparticles, we observed nuclear spin relaxation of the probe at room temperature. This result signifies that Ag+ ions in the polymer-coated sample make hopping motion from site to site at this low temperature. The activation energy for the dynamic motion was successfully estimated to be 46(10) meV. The first atomic-level observation of the temperature-dependent dynamic behavior of Ag+ ions in the polymer-coated AgI is reported.

  14. Investigation of antibacterial properties silver nanoparticles prepared via green method

    PubMed Central

    2012-01-01

    Background This study aims to investigate the influence of different stirring times on antibacterial activity of silver nanoparticles in polyethylene glycol (PEG) suspension. The silver nanoparticles (Ag-NPs) were prepared by green synthesis method using green agents, polyethylene glycol (PEG) under moderate temperature at different stirring times. Silver nitrate (AgNO3) was taken as the metal precursor while PEG was used as the solid support and polymeric stabilizer. The antibacterial activity of different sizes of nanosilver was investigated against Gram–positive [Staphylococcus aureus] and Gram–negative bacteria [Salmonella typhimurium SL1344] by the disk diffusion method using Müeller–Hinton Agar. Results Formation of Ag-NPs was determined by UV–vis spectroscopy where surface plasmon absorption maxima can be observed at 412–437 nm from the UV–vis spectrum. The synthesized nanoparticles were also characterized by X-ray diffraction (XRD). The peaks in the XRD pattern confirmed that the Ag-NPs possessed a face-centered cubic and peaks of contaminated crystalline phases were unable to be located. Transmission electron microscopy (TEM) revealed that Ag-NPs synthesized were in spherical shape. The optimum stirring time to synthesize smallest particle size was 6 hours with mean diameter of 11.23 nm. Zeta potential results indicate that the stability of the Ag-NPs is increases at the 6 h stirring time of reaction. The Fourier transform infrared (FT-IR) spectrum suggested the complexation present between PEG and Ag-NPs. The Ag-NPs in PEG were effective against all bacteria tested. Higher antibacterial activity was observed for Ag-NPs with smaller size. These suggest that Ag-NPs can be employed as an effective bacteria inhibitor and can be applied in medical field. Conclusions Ag-NPs were successfully synthesized in PEG suspension under moderate temperature at different stirring times. The study clearly showed that the Ag-NPs with different stirring times

  15. Vibrational Dynamics and Thermodynamics of AgCu nanoparticles

    NASA Astrophysics Data System (ADS)

    Kara, Abdelkader; Yildirim, Handan; Rahman, Talat S.; Ferrando, Ricardo

    2006-03-01

    We present results of a systematic study of the structure, vibrational dynamics and thermodynamics of AgnCu34-n nanoparticles including. The starting structure were generated using a structural optimization using a genetic algorithm [1]. Using the embedded atom method potentials, we have calculated the vibrational densities of states for all stoichiometries and the corresponding vibrational free energies, in the harmonic approximations. At 300K, the vibrational free energy is found to behave linearly with the increasing number of Ag atoms in the nanoparticles. The vibrational contributions to the free energy increase from 5.5% for Ag0Cu34 to 8.3% Ag34Cu0. Selected force constants for several nanoparticles were calculated using density functional theory (DFT) and were found to be very close to those determined using EAM potentials. [1] G. Rossi, A. Rapallo, C. Mottet, A. Fortunelli, F. Baletto and R. Ferrando Phys. Rev. Lett, 93, 105503 (2004)

  16. Synthesis and anti-bacterial activity of Cu, Ag and Cu-Ag alloy nanoparticles: A green approach

    SciTech Connect

    Valodkar, Mayur; Modi, Shefaly; Pal, Angshuman; Thakore, Sonal

    2011-03-15

    Research highlights: {yields} Synthesis of novel nanosized copper-silver alloys of different compositions. {yields} Completely green approach for synthesis of water soluble bimetallic nanoparticle. {yields} Interesting anti-bacterial activity of as synthesized metal and alloy nanoparticle. -- Abstract: Metallic and bimetallic nanoparticles of copper and silver in various proportions were prepared by microwave assisted chemical reduction in aqueous medium using the biopolymer, starch as a stabilizing agent. Ascorbic acid was used as the reducing agent. The silver and copper nanoparticles exhibited surface plasmon absorption resonance maxima (SPR) at 416 and 584 nm, respectively; while SPR for the Cu-Ag alloys appeared in between depending on the alloy composition. The SPR maxima for bimetallic nanoparticles changes linearly with increasing copper content in the alloy. Transmission electron micrograph (TEM) showed monodispersed particles in the range of 20 {+-} 5 nm size. Both silver and copper nanoparticles exhibited emission band at 485 and 645 nm, respectively. The starch-stabilized nanoparticles exhibited interesting antibacterial activity with both gram positive and gram negative bacteria at micromolar concentrations.

  17. Ag nanoparticle dispersed PbTiO3 percolative composite thin film with high permittivity

    NASA Astrophysics Data System (ADS)

    Wang, Zongrong; Hu, Tao; Tang, Liwen; Ma, Ning; Song, Chenlu; Han, Gaorong; Weng, Wenjian; Du, Piyi

    2008-12-01

    Ag nanoparticle dispersed PbTiO3 percolative composite thin films were prepared in situ by sol-gel method using Pb(NO3)2, Ti(C4H9O)4, and AgNO3 as raw materials and lactic acid along with citric acid as complexing agent. The size of the Ag nanoparticles measured by ultraviolet-visible spectra is about 3nm. The percolation effect occurs in composite thin films. The composite exhibits relatively high dielectric constant which is about five times higher than that of PbTiO3 thin film and comparatively low dielectric loss comparable to pure PbTiO3 system. It is highly attractive in application of high quality dielectric devices and miniaturization.

  18. Enhanced resistive switching effect in Ag nanoparticle embedded BaTiO{sub 3} thin films

    SciTech Connect

    Au, K.; Wang, Juan; Bao, Z. Y.; Dai, J. Y.; Gao, X. S.; Liu, J. M.

    2013-07-14

    Ag nanoparticle (NP) embedded BaTiO{sub 3} (BTO) thin films on SrRuO{sub 3}-coated SrTiO{sub 3} (STO) substrates are prepared by the integrated nanocluster beam deposition and laser-molecular beam epitaxy. Enhanced resistive switching, up to an ON/OFF ration of 10{sup 4}, has been achieved at low switching voltage (less than 1 V) without a forming voltage. These characteristics make such nanocomposite film very promising for application of low voltage non-volatile random access memory. The enhanced resistive switching effect may be attributed to the charge storage effect of the Ag nanoparticles and easy formation of Ag filament inside the BTO film.

  19. In situ assembly of well-dispersed Ag nanoparticles (AgNPs) on electrospun carbon nanofibers (CNFs) for catalytic reduction of 4-nitrophenol.

    PubMed

    Zhang, Peng; Shao, Changlu; Zhang, Zhenyi; Zhang, Mingyi; Mu, Jingbo; Guo, Zengcai; Liu, Yichun

    2011-08-01

    Carbon nanofibers/silver nanoparticles (CNFs/AgNPs) composite nanofibers were fabricated by two steps consisting of the preparation of the CNFs by electrospinning and the hydrothermal growth of the AgNPs on the CNFs. The as-prepared nanofibers were characterized by scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, resonant Raman spectra, thermal gravimetric and differential thermal analysis, and X-ray photoelectron spectroscopy, respectively. The results indicated that not only were AgNPs (25-50 nm) successfully grown on the CNFs but also the AgNPs were distributed without aggregation on the CNFs. Further more, by adjusting the parameters in hydrothermal processing, the content of silver supported on the CNFs could be easily controlled. The catalytic activities of the CNFs/AgNPs composite nanofibers to the reduction of 4-nitrophenol (4-NP) with NaBH(4) were tracked by UV-visible spectroscopy. It was suggested that the CNFs/AgNPs composite nanofibers exhibited high catalytic activity in the reduction of 4-NP, which might be attributed to the high surface areas of AgNPs and synergistic effect on delivery of electrons between CNFs and AgNPs. And, the catalytic efficiency was enhanced with the increasing of the content of silver on the CNFs/AgNPs composite nanofibers. Notably, the CNFs/AgNPs composite nanofibers could be easily recycled due to their one-dimensional nanostructural property.

  20. SERS enhancement of silver nanoparticles prepared by a template-directed triazole ligand strategy.

    PubMed

    Kashmery, Heba A; Thompson, David G; Dondi, Ruggero; Mabbott, Samuel; Graham, Duncan; Clark, Alasdair W; Burley, Glenn A

    2015-08-21

    Two advances in the development of a one-pot method to prepare silver nanoparticles (AgNPs) using the Tollens' reagent are described. First, a template-directed process of AgNP synthesis using resorcinol triazole ligands bearing two pendent galactose sugars is shown. Second, the conversion of these AgNPs into SERS nanotags is demonstrated using malachite green isothiocyanate as the Raman reporter molecule. PMID:26179948

  1. Coupling of Ag Nanoparticle with Inverse Opal Photonic Crystals as a Novel Strategy for Upconversion Emission Enhancement of NaYF4: Yb(3+), Er(3+) Nanoparticles.

    PubMed

    Shao, Bo; Yang, Zhengwen; Wang, Yida; Li, Jun; Yang, Jianzhi; Qiu, Jianbei; Song, Zhiguo

    2015-11-18

    Rare-earth-ion-doped upconversion (UC) nanoparticles have generated considerable interest because of their potential application in solar cells, biological labeling, therapeutics, and imaging. However, the applications of UC nanoparticles were still limited because of their low emission efficiency. Photonic crystals and noble metal nanoparticles are applied extensively to enhance the UC emission of rare earth ions. In the present work, a novel substrate consisting of inverse opal photonic crystals and Ag nanoparticles was prepared by the template-assisted method, which was used to enhance the UC emission of NaYF4: Yb(3+), Er(3+) nanoparticles. The red or green UC emissions of NaYF4: Yb(3+), Er(3+) nanoparticles were selectively enhanced on the inverse opal substrates because of the Bragg reflection of the photonic band gap. Additionally, the UC emission enhancement of NaYF4: Yb(3+), Er(3+) nanoparticles induced by the coupling of metal nanoparticle plasmons and photonic crystal effects was realized on the Ag nanoparticles included in the inverse opal substrate. The present results demonstrated that coupling of Ag nanoparticle with inverse opal photonic crystals provides a useful strategy to enhance UC emission of rare-earth-ion-doped nanoparticles. PMID:26496243

  2. Coupling of Ag Nanoparticle with Inverse Opal Photonic Crystals as a Novel Strategy for Upconversion Emission Enhancement of NaYF4: Yb(3+), Er(3+) Nanoparticles.

    PubMed

    Shao, Bo; Yang, Zhengwen; Wang, Yida; Li, Jun; Yang, Jianzhi; Qiu, Jianbei; Song, Zhiguo

    2015-11-18

    Rare-earth-ion-doped upconversion (UC) nanoparticles have generated considerable interest because of their potential application in solar cells, biological labeling, therapeutics, and imaging. However, the applications of UC nanoparticles were still limited because of their low emission efficiency. Photonic crystals and noble metal nanoparticles are applied extensively to enhance the UC emission of rare earth ions. In the present work, a novel substrate consisting of inverse opal photonic crystals and Ag nanoparticles was prepared by the template-assisted method, which was used to enhance the UC emission of NaYF4: Yb(3+), Er(3+) nanoparticles. The red or green UC emissions of NaYF4: Yb(3+), Er(3+) nanoparticles were selectively enhanced on the inverse opal substrates because of the Bragg reflection of the photonic band gap. Additionally, the UC emission enhancement of NaYF4: Yb(3+), Er(3+) nanoparticles induced by the coupling of metal nanoparticle plasmons and photonic crystal effects was realized on the Ag nanoparticles included in the inverse opal substrate. The present results demonstrated that coupling of Ag nanoparticle with inverse opal photonic crystals provides a useful strategy to enhance UC emission of rare-earth-ion-doped nanoparticles.

  3. Preparation of metallic nanoparticles by irradiation in starch aqueous solution

    SciTech Connect

    Nemţanu, Monica R. Braşoveanu, Mirela Iacob, Nicuşor

    2014-11-24

    Colloidal silver nanoparticles (AgNPs) were synthesized in a single step by electron beam irradiation reduction of silver ions in aqueous solution containing starch. The nanoparticles were characterized by spectrophotocolorimetry and compared with those obtained by chemical (thermal) reduction method. The results showed that the smaller sizes of AgNPs were prepared with higher yields as the irradiation dose increased. The broadening of particle size distribution occurred by increasing of irradiation dose and dose rate. Chromatic parameters such as b* (yellow-blue coordinate), C* (chroma) and ΔE{sub ab} (total color difference) could characterize the nanoparticles with respect of their concentration. Hue angle h{sup o} was correlated to the particle size distribution. Experimental data of the irradiated samples were also subjected to factor analysis using principal component extraction and varimax rotation in order to reveal the relation between dependent variables and independent variables and to reduce their number. The radiation-based method provided silver nanoparticles with higher concentration and narrower size distribution than those produced by chemical reduction method. Therefore, the electron beam irradiation is effective for preparation of silver nanoparticles using starch aqueous solution as dispersion medium.

  4. Preparation of metallic nanoparticles by irradiation in starch aqueous solution

    NASA Astrophysics Data System (ADS)

    NemÅ£anu, Monica R.; Braşoveanu, Mirela; Iacob, Nicuşor

    2014-11-01

    Colloidal silver nanoparticles (AgNPs) were synthesized in a single step by electron beam irradiation reduction of silver ions in aqueous solution containing starch. The nanoparticles were characterized by spectrophotocolorimetry and compared with those obtained by chemical (thermal) reduction method. The results showed that the smaller sizes of AgNPs were prepared with higher yields as the irradiation dose increased. The broadening of particle size distribution occurred by increasing of irradiation dose and dose rate. Chromatic parameters such as b* (yellow-blue coordinate), C* (chroma) and ΔEab (total color difference) could characterize the nanoparticles with respect of their concentration. Hue angle ho was correlated to the particle size distribution. Experimental data of the irradiated samples were also subjected to factor analysis using principal component extraction and varimax rotation in order to reveal the relation between dependent variables and independent variables and to reduce their number. The radiation-based method provided silver nanoparticles with higher concentration and narrower size distribution than those produced by chemical reduction method. Therefore, the electron beam irradiation is effective for preparation of silver nanoparticles using starch aqueous solution as dispersion medium.

  5. Stability of Ag nanoparticles dispersed in amphiphilic organic matrix

    NASA Astrophysics Data System (ADS)

    Suvorova, Elena I.; Klechkovskaya, Vera V.; Kopeikin, Victor V.; Buffat, Philippe A.

    2005-02-01

    Nano- and thin-film technologies based on novel systems associating metals particles to polymer matrix open a broad range of different applications. Such composites were found to be more efficient and safe, for instance, in biomedical needs. The Ag/poly(N-vinyl-2-pyrrolidone) (Ag/PVP) composite investigated in the present work is a new bactericide mean applied in complicated cases of infected burns and purulent wounds. High-resolution transmission electron microscopy (HRTEM) and X-ray energy-dispersive (EDS) microanalysis were used to bring chemical and structural information in a study of the properties and stability of thin-film nanocomposite whih consisted of Ag nanoparticles dispersed in water-soluble organic matrix poly(N-vinyl-2-pyrrolidone). The nanostructural investigation of Ag/PVP composite by HRTEM and EDS exposed to SO 2 and H 2S from the atmosphere and some traces of S-containing substances explains the limited stability of this system by a structural modification associated with a phase change and formation of Ag 2S and Ag 2SO 3. However, formation of the hardly water-soluble Ag 2S and Ag 2SO 3 salts may play an important role in the suppression of bacterial growth. On the one hand, silver could block S-H groups in vital proteins and conduced to their destruction, in that way revealing the antibacterial power. On the other hand, antiseptic properties of Ag consist in binding the products of the protein decay.

  6. Fungal biomolecules assisted biosynthesis of Au-Ag alloy nanoparticles and evaluation of their catalytic property.

    PubMed

    Tripathi, Ravi Mani; Gupta, Rohit Kumar; Bhadwal, Akhshay Singh; Singh, Priti; Shrivastav, Archana; Shrivastav, B R

    2015-08-01

    The catalytic reduction of methylene blue was studied using biosynthesised gold-silver (Au-Ag) alloy nanoparticles (NPs). The fungal biomass of Trichoderma harzianum was used as a reducing and stabilising agent in the synthesis of Au-Ag alloy NPs. The synthesised NPs were well characterised by UV-vis spectroscopy, dynamic light scattering, X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The plausible synthesis mechanism involved in the formation of Au-Ag alloy NPs was also discussed with diagrammatic representation. A series of experiments was performed to investigate the catalytic activity of the as-prepared Au-Ag alloy NPs and found that the alloy NPs show excellent catalytic activity. PMID:26224346

  7. Photostability of gold nanoparticles with different shapes: the role of Ag clusters.

    PubMed

    Attia, Yasser A; Buceta, David; Requejo, Félix G; Giovanetti, Lisandro J; López-Quintela, M Arturo

    2015-07-14

    Anisotropic gold nanostructures prepared by the seed method in the presence of Ag ions have been used to study their photostability to low-power UV irradiation (254 nm) at room temperature. It has been observed that, whereas spheres are very stable to photoirradiation, rods and prisms suffer from photocorrosion and finally dissolve completely with the production of Au(III) ions. Interpretation of these differences is based on the presence of semiconductor-like Ag clusters, adsorbed onto rods and prisms, able to photocorrode the Au nanoparticles, which are absent in the case of Au spheres. We further show direct evidence of the presence of Ag clusters in Au nanorods by XANES. These results confirm a previous hypothesis (J. Am. Chem. Soc., 2014, 136, 1182-1185) about the major influence of very stable small Ag clusters, not only on the anisotropic formation of nanostructures but also on their photostability.

  8. Stellated Ag-Pt bimetallic nanoparticles: An effective platform for catalytic activity tuning

    PubMed Central

    Liu, Hui; Ye, Feng; Yao, Qiaofeng; Cao, Hongbin; Xie, Jianping; Lee, Jim Yang; Yang, Jun

    2014-01-01

    The usefulness of Pt-based nanomaterials for catalysis can be greatly enhanced by coupling morphology engineering to the strategic presence of a second or even third metal. Here we demonstrate the design and preparation of stellated Ag-Pt bimetallic nanoparticles where significant activity difference between the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR) may be realized by relegating Ag to the core or by hollowing out the core. In particular the stellated Pt surface, with an abundance of steps, edges, corner atoms, and {111} facets, is highly effective for the ORR but is ineffective for MOR. MOR activity is only observed in the presence of a Ag core through electronic coupling to the stellated Pt shell. The bimetallic Ag-Pt stellates therefore demonstrate the feasibility of tuning a Pt surface for two very different structure sensitive catalytic reactions. Stellated bimetallics may therefore be an effective platform for highly tunable catalyst designs. PMID:24495979

  9. Transport of silver nanoparticles (AgNPs) in soil.

    PubMed

    Sagee, Omer; Dror, Ishai; Berkowitz, Brian

    2012-07-01

    The effect of soil properties on the transport of silver nanoparticles (AgNPs) was studied in a set of laboratory column experiments, using different combinations of size fractions of a Mediterranean sandy clay soil. The AgNPs with average size of ~30nm yielded a stable suspension in water with zeta potential of -39mV. Early breakthrough of AgNPs in soil was observed in column transport experiments. AgNPs were found to have high mobility in soil with outlet relative concentrations ranging from 30% to 70%, depending on experimental conditions. AgNP mobility through the column decreased when the fraction of smaller soil aggregates was larger. The early breakthrough pattern was not observed for AgNPs in pure quartz columns nor for bromide tracer in soil columns, suggesting that early breakthrough is related to the nature of AgNP transport in natural soils. Micro-CT and image analysis used to investigate structural features of the soil, suggest that soil aggregate size strongly affects AgNP transport in natural soil. The retention of AgNPs in the soil column was reduced when humic acid was added to the leaching solution, while a lower flow rate (Darcy velocity of 0.17cm/min versus 0.66cm/min) resulted in higher retention of AgNPs in the soil. When soil residual chloride was exchanged by nitrate prior to column experiments, significantly improved mobility of AgNPs was observed in the soil column. These findings point to the importance of AgNP-soil chemical interactions as a retention mechanism, and demonstrate the need to employ natural soils rather than glass beads or quartz in representative experimental investigations.

  10. Preparation and characterization of BC/PAM-AgNPs nanocomposites for antibacterial applications.

    PubMed

    Yang, Guang; Wang, Caixia; Hong, Feng; Yang, Xuexia; Cao, Zhangjun

    2015-01-22

    In this work, a bacterial cellulose/polyacrylamide (BC/PAM) double network composite was prepared to act as the template for in situ synthesis of silver nanoparticles (AgNPs). Effects of reaction conditions of the BC/PAM composite were investigated on its microstructure, mechanical properties and thermal stabilities. Both the BC/PAM composite and pure BC were utilized to prepare the corresponding silver impregnated nanocomposites, i.e., BC/PAM-AgNPs and BC-AgNPs, by an environmental friendly method, UV irradiation. The influences of the templates were investigated on the AgNPs formation and the antibacterial activities of the nanocomposites by both the zone of inhibition and dynamic shake flask methods. It was shown that the BC/PAM composite displayed a denser microstructure and higher thermal stabilities than pure BC. The BC/PAM-AgNPs nanocomposite exhibited a bigger particle size and lower mass content of AgNPs than the BC-AgNPs one. For the antibacterial test, two nanocomposites exhibited a close antibacterial effect, with a high log reduction above 3 and killing ratio above 99.9%, respectively. PMID:25439942

  11. Preparation and characterization of BC/PAM-AgNPs nanocomposites for antibacterial applications.

    PubMed

    Yang, Guang; Wang, Caixia; Hong, Feng; Yang, Xuexia; Cao, Zhangjun

    2015-01-22

    In this work, a bacterial cellulose/polyacrylamide (BC/PAM) double network composite was prepared to act as the template for in situ synthesis of silver nanoparticles (AgNPs). Effects of reaction conditions of the BC/PAM composite were investigated on its microstructure, mechanical properties and thermal stabilities. Both the BC/PAM composite and pure BC were utilized to prepare the corresponding silver impregnated nanocomposites, i.e., BC/PAM-AgNPs and BC-AgNPs, by an environmental friendly method, UV irradiation. The influences of the templates were investigated on the AgNPs formation and the antibacterial activities of the nanocomposites by both the zone of inhibition and dynamic shake flask methods. It was shown that the BC/PAM composite displayed a denser microstructure and higher thermal stabilities than pure BC. The BC/PAM-AgNPs nanocomposite exhibited a bigger particle size and lower mass content of AgNPs than the BC-AgNPs one. For the antibacterial test, two nanocomposites exhibited a close antibacterial effect, with a high log reduction above 3 and killing ratio above 99.9%, respectively.

  12. Pulsed laser deposition of Mg-Al layered double hydroxide with Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Matei, A.; Birjega, R.; Vlad, A.; Luculescu, C.; Epurescu, G.; Stokker-Cheregi, F.; Dinescu, M.; Zavoianu, R.; Pavel, O. D.

    2013-03-01

    Powdered layered double hydroxides (LDHs)—also known as hydrotalcite-like (HT)—compounds have been widely studied due to their applications as catalysts, anionic exchangers or host materials for inorganic or organic molecules. Assembling thin films of nano-sized LDHs onto flat solid substrates is an expanding area of research, with promising applications as sensors, corrosion-resistant coatings, components in optical and magnetic devices. The exploitation of LDHs as vehicles to carry dispersed metal nanoparticles onto a substrate is a new approach to obtain composite thin films with prospects for biomedical and optical applications. We report the deposition of thin films of Ag nanoparticles embedded in a Mg-Al layered double hydroxide matrix by pulsed laser deposition (PLD). The Ag-LDH powder was prepared by co-precipitation at supersaturation and pH = 10 using aqueous solutions of Mg and Al nitrates, Na hydroxide and carbonate, and AgNO3, having atomic ratios of Mg/Al = 3 and Ag/Al = 0.55. The target to be used in laser ablation experiments was a dry pressed pellet obtained from the prepared Ag-LDH powder. Three different wavelengths of a Nd:YAG laser (266, 532 and 1064 nm) working at a repetition rate of 10 Hz were used. X-Ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and secondary ions mass spectrometry (SIMS) were used to investigate the structure, surface morphology and composition of the deposited films.

  13. Dielectric performance of polymer-based composites containing core-shell Ag@TiO2 nanoparticle fillers

    NASA Astrophysics Data System (ADS)

    Liang, Fei; Zhang, Lu; Lu, Wen-Zhong; Wan, Qian-Xing; Fan, Gui-Fen

    2016-02-01

    This paper reports composites prepared by embedding core-shell Ag@TiO2 fillers into polytetrafluoroethylene. Ag nanoparticles were homogeneously coated with TiO2, to give a shell thickness of approximately ˜8-10 nm. The composite containing Ag@TiO2 nanoparticles with rutile shells exhibited better dielectric properties than the composite containing Ag@TiO2 nanoparticles with anatase shells. The relative permittivity (ɛr) of the composite containing 70 vol. % filler was approximately 240 at 100 Hz, which was more than 100 times higher than that of pure polytetrafluoroethylene (ɛr = 2.1). An effective medium percolation theory model is used to account for the dielectric constant of the composite.

  14. Ag nanoparticle decorated nanoporous ZnO microrods and their enhanced photocatalytic activities.

    PubMed

    Deng, Quan; Duan, Xiaowei; Ng, Dickon H L; Tang, Haibin; Yang, Yong; Kong, Mingguang; Wu, Zhikun; Cai, Weiping; Wang, Guozhong

    2012-11-01

    Nanostructured Ag nanoparticles (Ag-NPs)/nanoporous ZnO micrometer-rods (n-ZnO MRs) have been synthesized by a two-step method. The n-ZnO MRs was initially prepared by solvothermal-assisted heat treatment. The rods had the diameter ranged from 90 to 150 nm and length between 0.5 and 3 μm. They were found to be porous and were composited of ZnO nanopartiles with size of about 20 nm. In the second stage, Ag-NPs with a diameter of 20-50 nm were anchored onto the surface of the as-prepared n-ZnO MRs by a photoreduction method. The Ag-NPs/n-ZnO MRs were evaluated for their ability to degrade methylene blue (MB) solution under visible to ultraviolet (UV) light irradiation. The rate of degradation of the as-prepared Ag-NPs/n-ZnO MRs was more than twice and nearly 5.6 times faster than that of using bare n-ZnO MRs under the UV and solar light irradiation, respectively. The formation of Schottky barriers in the regions between the Ag-NPs and n-ZnO MRs had improved the charge separation and consequently enhanced the efficiency of the degradation process. Moreover, the as-prepared hybrid structure exhibited high photostability, and 98% of degradation efficiency could be maintained even after being used five times. This endurance was attributed to the retardation of photocorrosion of ZnO as a result of the low concentration of surface defects in the as-prepared n-ZnO MRs. It also minimized the surface defects of the as-prepared n-ZnO MRs and consequently further inhibited the photocorrosion of ZnO when the deposited Ag-NPs were much more inclined to combine with the chemisorbed oxygen.

  15. Transport of engineered silver (Ag) nanoparticles through partially fractured sandstones.

    PubMed

    Neukum, Christoph; Braun, Anika; Azzam, Rafig

    2014-08-01

    Transport behavior and fate of engineered silver nanoparticles (AgNP) in the subsurface is of major interest concerning soil and groundwater protection in order to avoid groundwater contamination of vital resources. Sandstone aquifers are important groundwater resources which are frequently used for public water supply in many regions of the world. The objective of this study is to get a better understanding of AgNP transport behavior in partially fractured sandstones. We executed AgNP transport studies on partially fissured sandstone drilling cores in laboratory experiments. The AgNP concentration and AgNP size in the effluent were analyzed using flow field-flow fractionation mainly. We employed inverse mathematical models on the measured AgNP breakthrough curves to identify and quantify relevant transport processes. Physicochemical filtration, time-dependent blocking due to filling of favorable attachment sites and colloid-facilitated transport were identified as the major processes for AgNP mobility. Physicochemical filtration was found to depend on solute chemistry, mineralogy, pore size distribution and probably on physical and chemical heterogeneity. Compared to AgNP transport in undisturbed sandstone matrix reported in the literature, their mobility in partially fissured sandstone is enhanced probably due to larger void spaces and higher hydraulic conductivity.

  16. Determination of Anthracene on Ag-Au Alloy Nanoparticles/Overoxidized-Polypyrrole Composite Modified Glassy Carbon Electrodes

    PubMed Central

    Mailu, Stephen N.; Waryo, Tesfaye T.; Ndangili, Peter M.; Ngece, Fanelwa R.; Baleg, Abd A.; Baker, Priscilla G.; Iwuoha, Emmanuel I.

    2010-01-01

    A novel electrochemical sensor for the detection of anthracene was prepared by modifying a glassy carbon electrode (GCE) with over-oxidized polypyrrole (PPyox) and Ag-Au (1:3) bimetallic nanoparticles (Ag-AuNPs). The composite electrode (PPyox/Ag-AuNPs/GCE) was prepared by potentiodynamic polymerization of pyrrole on GCE followed by its overoxidation in 0.1 M NaOH. Ag-Au bimetallic nanoparticles were chemically prepared by the reduction of AgNO3 and HAuCl4 using C6H5O7Na3 as the reducing agent as well as the capping agent and then immobilized on the surface of the PPyox/GCE. The nanoparticles were characterized by UV-visible spectroscopy technique which confirmed the homogeneous formation of the bimetallic alloy nanoparticles. Transmission electron microscopy showed that the synthesized bimetallic nanoparticles were in the range of 20–50 nm. The electrochemical behaviour of anthracene at the PPyox/Ag-AuNPs/GCE with Ag: Au atomic ratio 25:75 (1:3) exhibited a higher electrocatalytic effect compared to that observed when GCE was modified with each constituent of the composite (i.e., PPyox, Ag-AuNPs) and bare GCE. A linear relationship between anodic current and anthracene concentration was attained over the range of 3.0 × 10−6 to 3.56 × 10−4 M with a detection limit of 1.69 × 10−7 M. The proposed method was simple, less time consuming and showed a high sensitivity. PMID:22163419

  17. One pot synthesis of Ag nanoparticle modified ZnO microspheres in ethylene glycol medium and their enhanced photocatalytic performance

    SciTech Connect

    Tian Chungui; Li Wei; Pan Kai; Zhang Qi; Tian Guohui; Zhou Wei; Fu Honggang

    2010-11-15

    Ag nanoparticles (NPs) modified ZnO microspheres (Ag/ZnO microspheres) were prepared by a facile one pot strategy in ethylene glycol (EG) medium. The EG played two important roles in the synthesis: it could act as a reaction media for the formation of ZnO and reduce Ag{sup +} to Ag{sup 0}. A series of the characterizations indicated the successful combination of Ag NPs with ZnO microspheres. It was shown that Ag modification could greatly enhance the photocatalytic efficiency of ZnO microspheres by taking the photodegradation of Rhodamine B as a model reaction. With appropriate ratio of Ag and ZnO, Ag/ZnO microspheres showed the better photocatalytic performance than commercial Degussa P-25 TiO{sub 2}. Photoluminescence and surface photovoltage spectra demonstrated that Ag modification could effectively inhibit the recombination of the photoinduced electron and holes of ZnO. This is responsible for the higher photocatalytic activity of Ag/ZnO composites. -- Graphical abstract: A 'one-pot' strategy was developed for preparing the Ag/ZnO microspheres in ethylene glycol. The composites exhibited superior photocatalytic performance for photodegradation of Rhodamine B dye in water. Display Omitted

  18. Shape manipulation of ion irradiated Ag nanoparticles embedded in lithium niobate

    NASA Astrophysics Data System (ADS)

    Wolf, Steffen; Rensberg, Jura; Johannes, Andreas; Thomae, Rainer; Smit, Frederick; Neveling, Retief; Moodley, Mathew; Bierschenk, Thomas; Rodriguez, Matias; Afra, Boshra; Hasan, Shakeeb Bin; Rockstuhl, Carsten; Ridgway, Mark; Bharuth-Ram, Krish; Ronning, Carsten

    2016-04-01

    Spherical silver nanoparticles were prepared by means of ion beam synthesis in lithium niobate. The embedded nanoparticles were then irradiated with energetic 84Kr and 197Au ions, resulting in different electronic energy losses between 8.1 and 27.5 keV nm-1 in the top layer of the samples. Due to the high electronic energy losses of the irradiating ions, molten ion tracks are formed inside the lithium niobate in which the elongated Ag nanoparticles are formed. This process is strongly dependent on the initial particle size and leads to a broad aspect ratio distribution. Extinction spectra of the samples feature the extinction maximum with shoulders on either side. While the maximum is caused by numerous remaining spherical nanoparticles, the shoulders can be attributed to elongated particles. The latter could be verified by COMSOL simulations. The extinction spectra are thus a superposition of the spectra of all individual particles.

  19. Shape manipulation of ion irradiated Ag nanoparticles embedded in lithium niobate.

    PubMed

    Wolf, Steffen; Rensberg, Jura; Johannes, Andreas; Thomae, Rainer; Smit, Frederick; Neveling, Retief; Moodley, Mathew; Bierschenk, Thomas; Rodriguez, Matias; Afra, Boshra; Bin Hasan, Shakeeb; Rockstuhl, Carsten; Ridgway, Mark; Bharuth-Ram, Krish; Ronning, Carsten

    2016-04-01

    Spherical silver nanoparticles were prepared by means of ion beam synthesis in lithium niobate. The embedded nanoparticles were then irradiated with energetic (84)Kr and (197)Au ions, resulting in different electronic energy losses between 8.1 and 27.5 keV nm(-1) in the top layer of the samples. Due to the high electronic energy losses of the irradiating ions, molten ion tracks are formed inside the lithium niobate in which the elongated Ag nanoparticles are formed. This process is strongly dependent on the initial particle size and leads to a broad aspect ratio distribution. Extinction spectra of the samples feature the extinction maximum with shoulders on either side. While the maximum is caused by numerous remaining spherical nanoparticles, the shoulders can be attributed to elongated particles. The latter could be verified by COMSOL simulations. The extinction spectra are thus a superposition of the spectra of all individual particles. PMID:26902734

  20. Accelerated CO2 transport on surface of AgO nanoparticles in ionic liquid BMIMBF4

    PubMed Central

    Ji, Dahye; Kang, Yong Soo; Kang, Sang Wook

    2015-01-01

    The AgO nanoparticles were utilized for a CO2 separation membrane. The AgO nanoparticles were successfully generated in ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF4) by favorable interaction between the surface of particles and the counteranion of BMIMBF4. The generated AgO nanoparticles were confirmed by TEM, and the average size was 20 nm. Coordinative interactions of dissociated AgO particles with BMIM+BF4− were investigated by FT-Raman spectroscopy. When the ionic liquid BMIMBF4 containing AgO nanoparticles was utilized as a CO2 separation membrane, the separation performance was largely enhanced. PMID:26549605

  1. Influence of temperature and precursor concentration on the synthesis of HDA-capped Ag{sub 2}Se nanoparticles

    SciTech Connect

    Mlambo, M.; Moloto, M.J.; Moloto, N.; Mdluli, P.S.

    2013-06-01

    Graphical abstract: The temperature effect on the growth and size of silver selenide nanoparticles with the size distribution and XRD patterns. Highlights: ► The HDA-capped Ag{sub 2}Se nanoparticles were synthesized via the colloidal route. ► Temperature and monomer concentration of the reaction were varied. ► The concentration as a factor influenced particles with a decrease observed as the amount of Ag{sup +} ion source is increased. ► Temperature has expected influence on the growth of particles resulting in increase as the temperature is increased. ► TEM images shows spherical particles and their orthorhombic phase from structural analysis by XRD. - Abstract: The size dependent of temperature and precursor concentration on the synthesis of hexadecylamine capped Ag{sub 2}Se nanoparticles via the colloidal route were studied using the combination of optical and structural analysis. The as-prepared Ag{sub 2}Se nanoparticles showed the quantum confinement with all the obtained absorption band edges blue-shifted from the bulk and their corresponding emission maxima displaying a red-shift from band edges characterised by UV–vis absorption and photoluminescence spectroscopy. The particle sizes were obtained from transmission electron microscopy analysis. The increase in precursor concentration resulted in a decrease in nanoparticle sizes. The increase in reaction temperature showed an increase in the nanoparticle sizes, when the critical temperature at 160 °C was reached, the nanoparticle sizes decreased.

  2. Characterization and Evaluation of Reverse Osmosis Membranes Modified with Ag2O Nanoparticles to Improve Performance.

    PubMed

    Al-Hobaib, Abdullah S; Al-Sheetan, Khalid M; Shaik, Mohammed Rafi; Al-Andis, Naser M; Al-Suhybani, M S

    2015-12-01

    The objective of this work was to prepare and characterize a new and highly efficient modified membrane by in situ interfacial polymerization on porous polysulfone supports. The process used m-phenylenediamine and trimesoyl chloride in hexane, incorporating silver oxide Ag2O nanoparticles of varied concentrations from 0.001 to 0.1 wt%. Ag2O nanoparticles were prepared at different sizes varying between 20 and 50 nm. The modified membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle measurement. The results showed a smooth membrane surface and average surface roughness from 31 to 74 nm. Moreover, hydrophilicity improved and the contact angle decreased to 41° at 0.009 wt% silver oxide. The performances of the developed membranes were investigated by measuring permeate fluxes and salt rejection capability by passing NaCl solutions (2000 ppm) through the membranes at 225 psi. The results showed that the flux increased from 26 to 40.5 L/m(2) h, while the salt rejection was high, at 99 %, with 0.003 wt% Ag2O nanoparticles.

  3. Characterization and Evaluation of Reverse Osmosis Membranes Modified with Ag2O Nanoparticles to Improve Performance

    NASA Astrophysics Data System (ADS)

    Al-Hobaib, Abdullah S.; AL-Sheetan, Khalid M.; Shaik, Mohammed Rafi; Al-Andis, Naser M.; Al-Suhybani, M. S.

    2015-09-01

    The objective of this work was to prepare and characterize a new and highly efficient modified membrane by in situ interfacial polymerization on porous polysulfone supports. The process used m-phenylenediamine and trimesoyl chloride in hexane, incorporating silver oxide Ag2O nanoparticles of varied concentrations from 0.001 to 0.1 wt%. Ag2O nanoparticles were prepared at different sizes varying between 20 and 50 nm. The modified membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle measurement. The results showed a smooth membrane surface and average surface roughness from 31 to 74 nm. Moreover, hydrophilicity improved and the contact angle decreased to 41° at 0.009 wt% silver oxide. The performances of the developed membranes were investigated by measuring permeate fluxes and salt rejection capability by passing NaCl solutions (2000 ppm) through the membranes at 225 psi. The results showed that the flux increased from 26 to 40.5 L/m2 h, while the salt rejection was high, at 99 %, with 0.003 wt% Ag2O nanoparticles.

  4. Effect of cysteine and humic acids on bioavailability of Ag from Ag nanoparticles to a freshwater snail

    USGS Publications Warehouse

    Luoma, Samuel N.; Tasha Stoiber,; Croteau, Marie-Noele; Isabelle Romer,; Ruth Merrifeild,; Jamie Lead,

    2016-01-01

    Metal-based engineered nanoparticles (NPs) will undergo transformations that will affect their bioavailability, toxicity and ecological risk when released to the environment, including interactions with dissolved organic material. The purpose of this paper is to determine how interactions with two different types of organic material affect the bioavailability of silver nanoparticles (AgNPs). Silver uptake rates by the pond snail Lymnaea stagnalis were determined after exposure to 25 nmol l-1 of Ag as PVP AgNPs, PEG AgNPs or AgNO3, in the presence of either Suwannee River humic acid or cysteine, a high-affinity thiol-rich organic ligand. Total uptake rate of Ag from the two NPs was either increased or not strongly affected in the presence of 1 – 10 mg 1-1 humic acid. Humic substances contain relatively few strong ligands for Ag explaining their limited effects on Ag uptake rate. In contrast, Ag uptake rate was substantially reduced by cysteine. Three components of uptake from the AgNPs were quantified in the presence of cysteine using a biodynamic modeling approach: uptake of dissolved Ag released by the AgNPs, uptake of a polymer or large (>3kD) Ag-cysteine complex and uptake of the nanoparticle itself. Addition of 1:1 Ag:cysteine reduced concentrations of dissolved Ag, which contributed to, but did not fully explain the reductions in uptake. A bioavailable Ag-cysteine complex (> 3kD) appeared to be the dominant avenue of uptake from both PVP AgNPs and PEG AgNPs in the presence of cysteine. Quantifying the different avenues of uptake sets the stage for studies to assess toxicity unique to NPs.

  5. Spectral anion sensing and γ-radiation induced magnetic modifications of polyphenol generated Ag-nanoparticles

    NASA Astrophysics Data System (ADS)

    Ansari, Zarina; Dhara, Susmita; Bandyopadhyay, Bilwadal; Saha, Abhijit; Sen, Kamalika

    2016-03-01

    A fast one step bio-synthesis for in situ preparation of silver nanoparticles is proposed. The method involves reduction of AgNO3 with an aqueous extract of peanut skin, which is a good source of polyphenols. The silver nanoparticles thus synthesized were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis absorption spectroscopy, Fourier Transform infrared (FTIR) spectroscopy and magnetic measurements. Effect of low dose γ irradiation during the synthesis was studied and their physico-chemical properties were compared with those produced without irradiation. On the contrary to the diamagnetic behavior of bulk silver, the silver nanoparticles thus prepared show a significant ferromagnetic moment component. Variable time exposure to γ-irradiation results in an exponential decay of ferromagnetic component. A freshly prepared solution of silver nanoparticles shows selective spectral changes towards iodide ions at trace concentration (below 50 μM) among a series of 16 other competing anions. The prepared nanoparticles are therefore suitable for anion sensing application.

  6. Nanoporous Ag prepared from the melt-spun Cu-Ag alloys

    NASA Astrophysics Data System (ADS)

    Li, Guijing; Song, Xiaoping; Sun, Zhanbo; Yang, Shengchun; Ding, Bingjun; Yang, Sen; Yang, Zhimao; Wang, Fei

    2011-07-01

    Nanoporous Ag ribbons with different morphology and porosity were achieved by the electrochemical corrosion of the melt-spun Cu-Ag alloys. The Cu-rich phase in the alloys was removed, resulting in the formation of the nanopores distributed across the whole ribbon. It is found that the structures, morphology and porosity of the nanoporous Ag ribbons were dependent on the microstructures of the parent alloys. The most of ligaments presented a rod-like shape due to the formation of pseudoeutectic microstructure in the melt-spun Cu 55Ag 45 and Cu 70Ag 30 alloys. For nanoporous Ag prepared from Cu 85Ag 15 alloys, the ligaments were camber-like because of the appearance of the divorced microstructures. Especially, a novel bamboo-grove-like structure could be observed at the cross-section of the nanoporous Ag ribbons. The experiment reveals that nanoporous Ag ribbons exhibited excellent enhancement of surface-enhanced Raman scattering (SERS) effect, but a slight difference existed due to the discrepancy of their morphology.

  7. Fabrication of Au@Ag core-shell nanoparticles using polyelectrolyte multilayers as nanoreactors.

    PubMed

    Zhang, Xin; Wang, Hui; Su, Zhaohui

    2012-11-01

    A new synthetic strategy has been developed for the fabrication of Au-Ag bimetallic core-shell nanoparticles (NPs) using polyelectrolyte multilayers (PEMs) as unique nanoreactors. Bimetallic NPs composed of Au core and Ag shell were successively incorporated into PEMs by repeating anion/cation exchange/reduction cycle multiple times in a stepwise manner. The strategy described here allows for the facile preparation of Au@Ag core-shell NPs with well-controlled core and shell dimensions and geometrically tunable optical properties by simply varying the number of ion-exchange/reduction cycles in the PEM matrix. The strategy can be extended to synthesize in situ other core-shell NPs in polymer matrix.

  8. Magnetite Nanoparticles Prepared By Spark Erosion

    NASA Astrophysics Data System (ADS)

    Maiorov, M.; Blums, E.; Kronkalns, G.; Krumina, A.; Lubane, M.

    2016-08-01

    In the present research, we study a possibility of using the electric spark erosion method as an alternative to the method of chemical co-precipitation for preparation of magnetic nanoparticles. Initiation of high frequency electric discharge between coarse iron particles under a layer of distilled water allows obtaining pure magnetite nanoparticles.

  9. Preparation of DPPE-Stabilized Gold Nanoparticles

    ERIC Educational Resources Information Center

    Dungey, Keenan E.; Muller, David P.; Gunter, Tammy

    2005-01-01

    An experiment is presented that introduces students to nanotechnology through the preparation of nanoparticles and their visualization using transmission electron microscopy (TEM). The experiment familiarizes the students with nonaqueous solvents, biphasic reactions, phase-transfer agents, ligands to stabilize growing nanoparticles, and bidentate…

  10. Synthesis, characterization, and 3D-FDTD simulation of Ag@SiO2 nanoparticles for shell-isolated nanoparticle-enhanced Raman spectroscopy.

    PubMed

    Uzayisenga, Viviane; Lin, Xiao-Dong; Li, Li-Mei; Anema, Jason R; Yang, Zhi-Lin; Huang, Yi-Fan; Lin, Hai-Xin; Li, Song-Bo; Li, Jian-Feng; Tian, Zhong-Qun

    2012-06-19

    Au-seed Ag-growth nanoparticles of controllable diameter (50-100 nm), and having an ultrathin SiO(2) shell of controllable thickness (2-3 nm), were prepared for shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Their morphological, optical, and material properties were characterized; and their potential for use as a versatile Raman signal amplifier was investigated experimentally using pyridine as a probe molecule and theoretically by the three-dimensional finite-difference time-domain (3D-FDTD) method. We show that a SiO(2) shell as thin as 2 nm can be synthesized pinhole-free on the Ag surface of a nanoparticle, which then becomes the core. The dielectric SiO(2) shell serves to isolate the Raman-signal enhancing core and prevent it from interfering with the system under study. The SiO(2) shell also hinders oxidation of the Ag surface and nanoparticle aggregation. It significantly improves the stability and reproducibility of surface-enhanced Raman scattering (SERS) signal intensity, which is essential for SERS applications. Our 3D-FDTD simulations show that Ag-core SHINERS nanoparticles yield at least 2 orders of magnitude greater enhancement than Au-core ones when excited with green light on a smooth Ag surface, and thus add to the versatility of our SHINERS method.

  11. Rapid synthesis of ordered hexagonal mesoporous silica and their incorporation with Ag nanoparticles by solution plasma

    SciTech Connect

    Pootawang, Panuphong; Saito, Nagahiro; Takai, Osamu; Lee, Sang Yul

    2012-10-15

    Graphical abstract: Overall reactions of mesoporous silica and AgNPs-incorporated mesoporous silica syntheses by solution plasma process (SPP). Highlights: ► SPP for rapid synthesis of mesoporous silica. ► SPP for rapid synthesis of mesoporous silica and AgNPs incorporation. ► Higher surface area and larger pore diameter of mesoporous silica synthesized by SPP. -- Abstract: Rapid synthesis of silica with ordered hexagonal mesopore arrangement was obtained using solution plasma process (SPP) by discharging the mixture of P123 triblock copolymer/TEOS in acid solution. SPP, moreover, was utilized for Ag nanoparticles (AgNPs) incorporation in silica framework as one-batch process using silver nitrate (AgNO{sub 3}) solution as precursor. The turbid silicate gel was clearly observed after discharge for 1 min and the white precipitate formed at 3 min. The mesopore with hexagonal arrangement and AgNPs were observed in mesoporous silica. Two regions of X-ray diffraction patterns (2θ < 2° and 2θ = 35–90°) corresponded to the mesoporous silica and Ag nanocrystal characteristics. Comparing with mesoporous silica prepared by a conventional sol–gel route, surface area and pore diameter of mesoporous silica prepared by solution plasma were observed to be larger. In addition, the increase in Ag loading resulted in the decrease in surface area with insignificant variation in the pore diameter of mesoporous silica. SPP could be successfully utilized not only to enhance gelation time but also to increase surface area and pore diameter of mesoporous silica.

  12. Ag nanoparticle-deposited TiO2 nanotube arrays for electrodes of Dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Kawamura, Go; Ohmi, Hayato; Tan, Wai Kian; Lockman, Zainovia; Muto, Hiroyuki; Matsuda, Atsunori

    2015-05-01

    Dye-sensitized solar cells composed of a photoanode of Ag nanoparticle (NP)-deposited TiO2 nanotube (TNT) arrays were fabricated. The TNT arrays were prepared by anodizing Ti films on fluorine-doped tin oxide (FTO)-coated glass substrates. Efficient charge transportation through the ordered nanostructure of TNT arrays should be carried out compared to conventional particulate TiO2 electrodes. However, it has been a big challenge to grow TNT arrays on FTO glass substrates with the lengths needed for sufficient light-harvesting (tens of micrometers). In this work, we deposited Ag nanoparticles (NPs) on the wall of TNT arrays to enhance light-harvesting property. Dye-sensitized solar cells with these Ag NP-deposited TNT arrays yielded a higher power conversion efficiency (2.03 %) than those without Ag NPs (1.39 %).

  13. Carbon supported Ag nanoparticles as high performance cathode catalyst for H2/O2 anion exchange membrane fuel cell

    PubMed Central

    Xin, Le; Zhang, Zhiyong; Wang, Zhichao; Qi, Ji; Li, Wenzhen

    2013-01-01

    A solution phase-based nanocapsule method was successfully developed to synthesize non-platinum metal catalyst—carbon supported Ag nanoparticles (Ag/C). XRD patterns and TEM image show Ag nanoparticles with a small average size (5.4 nm) and narrow size distribution (2–9 nm) are uniformly dispersed on the carbon black Vulcan XC-72 support. The intrinsic activity and pathway of oxygen reduction reaction (ORR) on the Ag/C and commercial Pt/C were investigated using rotating ring disk electrode (RRDE) tests at room temperature. The results confirmed that the 4-electron pathway of ORR proceeds on small Ag nanoparticles, and showed comparable ORR activities on the self-prepared Ag/C and a commercial Pt/C. A single H2-O2 anion exchange membrane fuel cell (AEMFC) with the Ag/C cathode catalyst exhibited an open circuit potential of 0.98 V and a peak power density of 190 mW/cm2 at 80°C. PMID:24790944

  14. Narrow size distributed Ag nanoparticles grown by spin coating and thermal reduction: effect of processing parameters

    NASA Astrophysics Data System (ADS)

    Ansari, A. A.; Sartale, S. D.

    2016-08-01

    A simple method to grow uniform sized Ag nanoparticles with narrow size distribution on flat support (glass and Si substrates) via spin coating of Ag+ ions (AgNO3) solution followed by thermal reduction in H2 is presented. These grown nanoparticles can be used as model catalytic system to study size dependent oxygen reduction reaction (ORR) activity. Ag nanoparticles formation was confirmed by local surface plasmon resonance and x-ray photoelectron spectroscopy measurements. Influences of process parameters (revolution per minute (rpm), ramp and salt concentration) on grown Ag nanoparticles size, density and size uniformity are studied. With increase in rpm and ramp the size decreases and the particle number density increases, whereas the size dispersion improves. The catalytic activity of the grown Ag particles for ORR is studied and it is found that the catalytic performance is dependent on the size as well as the number density of the grown Ag nanoparticles.

  15. Synthesis of polydopamine at the femtoliter scale and confined fabrication of Ag nanoparticles on surfaces.

    PubMed

    Guardingo, M; Esplandiu, M J; Ruiz-Molina, D

    2014-10-25

    Nanoscale polydopamine motifs are fabricated on surfaces by deposition of precursor femtolitre droplets using an AFM tip and employed as confined reactors to fabricate Ag nanoparticle patterns by in situ reduction of a Ag(+) salt. PMID:25195667

  16. Core-shell Au@Pd nanoparticles with enhanced catalytic activity for oxygen reduction reaction via core-shell Au@Ag/Pd constructions

    PubMed Central

    Chen, Dong; Li, Chengyin; Liu, Hui; Ye, Feng; Yang, Jun

    2015-01-01

    Core-shell nanoparticles often exhibit improved catalytic properties due to the lattice strain created in these core-shell particles. Herein, we demonstrate the synthesis of core-shell Au@Pd nanoparticles from their core-shell Au@Ag/Pd parents. This strategy begins with the preparation of core-shell Au@Ag nanoparticles in an organic solvent. Then, the pure Ag shells are converted into the shells made of Ag/Pd alloy by galvanic replacement reaction between the Ag shells and Pd2+ precursors. Subsequently, the Ag component is removed from the alloy shell using saturated NaCl solution to form core-shell Au@Pd nanoparticles with an Au core and a Pd shell. In comparison with the core-shell Au@Pd nanoparticles upon directly depositing Pd shell on the Au seeds and commercial Pd/C catalysts, the core-shell Au@Pd nanoparticles via their core-shell Au@Ag/Pd templates display superior activity and durability in catalyzing oxygen reduction reaction, mainly due to the larger lattice tensile effect in Pd shell induced by the Au core and Ag removal. PMID:26144550

  17. New methods for lipid nanoparticles preparation.

    PubMed

    Corrias, Francesco; Lai, Francesco

    2011-09-01

    Lipid nanoparticles have attracted many researchers during recent years due to the excellent tolerability and advantages compared to liposomes and polymeric nanoparticles. High pressure homogenization is the main technique used to prepare solid lipid nanoparticles (SLN) encapsulating different type of drugs, however this method involves some critical process parameters. For this reason and in order to overcome patented methods, different production techniques for lipid nanoparticles have been widely investigated in recent years (last decade). The paper reviews new methods for lipid nanoparticles preparation, and their recent applications in pharmaceutical field, especially focusing on coacervation, microemulsions templates, supercritical fluid technology, phase-inversion temperature (PIT) techniques. References of the most relevant literature and patents published by various research groups on these fields are provided. PMID:21834772

  18. M4Ag44(p-MBA)30 Molecular Nanoparticles

    NASA Astrophysics Data System (ADS)

    Conn, Brian E.

    In recent years, molecular nanoparticles have attracted much attention due to their unique physical, optical, and electronic properties. The properties of molecular nanoparticles are shown to deviate from their larger bulk counterparts, due to quantum confinement effects and large surface-to-volume ratios. As the size of the nanoparticle shrinks to a cluster of metal atoms (<3 nm in diameter), there is an emergence of a HOMO-LUMO band gap, which is not present in transitional d-block metals. The HOMO-LUMO band gap gives rise to discrete electronic states, leading to new chemical and physical properties. Molecular nanoparticles have had a substantial impact across a diverse range of fields, including catalysis, sensing, photochemistry, optoelectronic, energy conversion, and medicine. Currently many of the synthetic procedures for molecular nanoparticles require low temperatures, long incubation times, multistep purification and hazardous reagents that produce low yields and polydisperse molecular nanoparticles with poor stability. Although silver has very desirable physical properties, good relative abundance and low cost, gold molecular nanoparticles have been widely favored owing to their proved stability and ease of use. Unlike gold, silver is notorious for its susceptibility to oxidation, i.e., tarnishing, which has limited the development of silver-based nanotechnologies. Despite two decades of synthetic efforts, silver molecular nanoparticles that are inert or have long-term stability have remained unrealized. Herein we report a simple synthetic protocol for producing ultrastable M4Ag44(p-MBA)30 nanoparticles as a single-sized molecular product and in exceptionally large quantities. The stability, purity, and yield are substantially better than other metal nanoparticles, including gold, due to several stabilization mechanisms. Also, reported are the structural and mechanical properties of extended crystalline solids of Na4Ag44(p-MBA)30 from large-scale quantum

  19. Single molecule detection using SERS study in PVP functionalized Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Garg, Parul; Dhara, S.

    2013-02-01

    Non-spherical functionalized Ag nanoparticles (NPs) with homogenous size ˜ 40 nm have been grown using soft chemical route. Solution of silver nitrate and polyvinylpyrrolidone is reduced in excess of ethylene glycol for the preparation of the NPs. Substrates has been prepared by dip coating of the NPs on c-Si for Raman studies. Rhodamine (R6G) is used as a test molecule to study the surface enhanced Raman spectroscopy (SERS) effect. A single molecule detection of R6G along with an enhancement factor of ˜ 4×103 orders of magnitude in the intensity, for the concentration as low as 10-12 M using polymer coated Ag NPs as SERS substrates, has been achieved.

  20. In situ growth of Ag nanoparticles on α-Ag2WO4 under electron irradiation: probing the physical principles

    NASA Astrophysics Data System (ADS)

    San-Miguel, Miguel A.; da Silva, Edison Z.; Zannetti, Sonia M.; Cilense, Mario; Fabbro, Maria T.; Gracia, Lourdes; Andrés, Juan; Longo, Elson

    2016-06-01

    Exploiting the plasmonic behavior of Ag nanoparticles grown on α-Ag2WO4 is a widely employed strategy to produce efficient photocatalysts, ozone sensors, and bactericides. However, a description of the atomic and electronic structure of the semiconductor sites irradiated by electrons is still not available. Such a description is of great importance to understand the mechanisms underlying these physical processes and to improve the design of silver nanoparticles to enhance their activities. Motivated by this, we studied the growth of silver nanoparticles to investigate this novel class of phenomena using both transmission electron microscopy and field emission scanning electron microscopy. A theoretical framework based on density functional theory calculations (DFT), together with experimental analysis and measurements, were developed to examine the changes in the local geometrical and electronic structure of the materials. The physical principles for the formation of Ag nanoparticles on α-Ag2WO4 by electron beam irradiation are described. Quantum mechanical calculations based on DFT show that the (001) of α-Ag2WO4 displays Ag atoms with different coordination numbers. Some of them are able to diffuse out of the surface with a very low energy barrier (less than 0.1 eV), thus, initiating the growth of metallic Ag nanostructures and leaving Ag vacancies in the bulk material. These processes increase the structural disorder of α-Ag2WO4 as well as its electrical resistance as observed in the experimental measurements.

  1. In situ growth of Ag nanoparticles on α-Ag2WO4 under electron irradiation: probing the physical principles.

    PubMed

    San-Miguel, Miguel A; da Silva, Edison Z; Zannetti, Sonia M; Cilense, Mario; Fabbro, Maria T; Gracia, Lourdes; Andrés, Juan; Longo, Elson

    2016-06-01

    Exploiting the plasmonic behavior of Ag nanoparticles grown on α-Ag2WO4 is a widely employed strategy to produce efficient photocatalysts, ozone sensors, and bactericides. However, a description of the atomic and electronic structure of the semiconductor sites irradiated by electrons is still not available. Such a description is of great importance to understand the mechanisms underlying these physical processes and to improve the design of silver nanoparticles to enhance their activities. Motivated by this, we studied the growth of silver nanoparticles to investigate this novel class of phenomena using both transmission electron microscopy and field emission scanning electron microscopy. A theoretical framework based on density functional theory calculations (DFT), together with experimental analysis and measurements, were developed to examine the changes in the local geometrical and electronic structure of the materials. The physical principles for the formation of Ag nanoparticles on α-Ag2WO4 by electron beam irradiation are described. Quantum mechanical calculations based on DFT show that the (001) of α-Ag2WO4 displays Ag atoms with different coordination numbers. Some of them are able to diffuse out of the surface with a very low energy barrier (less than 0.1 eV), thus, initiating the growth of metallic Ag nanostructures and leaving Ag vacancies in the bulk material. These processes increase the structural disorder of α-Ag2WO4 as well as its electrical resistance as observed in the experimental measurements. PMID:27114472

  2. Large 2D-arrays of size-controllable silver nanoparticles prepared by hybrid deposition

    NASA Astrophysics Data System (ADS)

    Dieu Thuy Ung, Thi; Hoa Nguyen, Thi; Liem Nguyen, Quang

    2016-09-01

    Two main results are presented in this paper. (i) Silver nanoparticles (AgNPs) with uniform size-distribution and controllability in the range of 20-50 nm were synthesized by seeding and growing at ambient conditions. The single-crystal Ag nano-seeds were created by reduction of AgNO3 in presence of citrate surfactant at 70 °C. Then, importantly, the fresh AgCl precursor was used in the presence of polyvinylpyrrolidone to adjust the reaction rate with ascorbic acid to generate Ag for growing on the surface of single-crystal Ag nano-seeds. The AgNPs size could be well-controlled by varying the amount of Ag nano-seeds while keeping the AgCl precursor concentration to be constant. (ii) The large 2D-arrays with homogeneous and dense monolayers of AgNPs were prepared on ITO substrates by hybrid method, in which the key technological point is the surface functionalization of AgNPs using mixed alkanethiols (dodecanethiol:octadecanethiol = 6:1). We have used the fabricated 2D-arrays from the 50 nm AgNPs as a surface enhanced Raman scattering substrate to take the Raman scattering spectra of rhodamine B (RhB), glucose and viral pathogen (H5N1) at very low concentrations of 10-10 M, 10-12 M and 4 ng μl-1, respectively.

  3. Large 2D-arrays of size-controllable silver nanoparticles prepared by hybrid deposition

    NASA Astrophysics Data System (ADS)

    Dieu Thuy Ung, Thi; Hoa Nguyen, Thi; Liem Nguyen, Quang

    2016-09-01

    Two main results are presented in this paper. (i) Silver nanoparticles (AgNPs) with uniform size-distribution and controllability in the range of 20–50 nm were synthesized by seeding and growing at ambient conditions. The single-crystal Ag nano-seeds were created by reduction of AgNO3 in presence of citrate surfactant at 70 °C. Then, importantly, the fresh AgCl precursor was used in the presence of polyvinylpyrrolidone to adjust the reaction rate with ascorbic acid to generate Ag for growing on the surface of single-crystal Ag nano-seeds. The AgNPs size could be well-controlled by varying the amount of Ag nano-seeds while keeping the AgCl precursor concentration to be constant. (ii) The large 2D-arrays with homogeneous and dense monolayers of AgNPs were prepared on ITO substrates by hybrid method, in which the key technological point is the surface functionalization of AgNPs using mixed alkanethiols (dodecanethiol:octadecanethiol = 6:1). We have used the fabricated 2D-arrays from the 50 nm AgNPs as a surface enhanced Raman scattering substrate to take the Raman scattering spectra of rhodamine B (RhB), glucose and viral pathogen (H5N1) at very low concentrations of 10‑10 M, 10‑12 M and 4 ng μl‑1, respectively.

  4. Synthesis of spindle-shaped AgI/TiO2 nanoparticles with enhanced photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Yang, Liu; Gao, Minggang; Dai, Bin; Guo, Xuhong; Liu, Zhiyong; Peng, Banghua

    2016-11-01

    A novel synthetic route has been developed to prepare silver iodide (AgI) loaded spindle-shaped TiO2 nanoparticles (NPs). The morphology and crystallinity characterization revealed that small AgI NPs, with an average diameter of 15 nm were dispersed on the surface and interior of nanoporous anatase TiO2 support. High-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET) surface area, Raman and X-ray photoelectron spectroscopy (XPS) were used to identify the nanoporous structure of TiO2 and the existence of AgI NPs. Diffuse reflectance spectra (DRS) showed that AgI/TiO2 composite exhibited a remarkable enhancement of visible light absorption, which is ascribed to the addition of AgI. For illustrating the superior property of this hybrid as photocatalyst, the degradation experiments were carried out for processing rhodamine B (RhB) solution under visible light irradiation and it was found that the photocatalytic activity was dramatically improved for AgI/TiO2 compared with nanoporous TiO2 and commercial P25 TiO2. The enhanced photocatalytic properties could be attributed to the large surface area of porous TiO2, good stability of AgI particles, and the effective charge separation due to the synergetic effect between AgI and TiO2 that can facilitate the separation of electron-hole pairs. Our novel composite based on nanoporous spindle-shaped TiO2 represents a promising new pathway for the design of high-performance photocatalysts for environmental applications.

  5. Conversion of Ag nanowires to AgCI nanowires decorated with Au nanoparticles and their photocatalytic activity.

    SciTech Connect

    Sun, Y.; Center for Nanoscale Materials

    2010-02-11

    A two-step approach has been developed to synthesize AgCl nanowires decorated with Au nanoparticles by using Ag nanowires as chemical templates. In the first step, the Ag nanowires are oxidized with FeCl{sub 3} followed by a simultaneous precipitation reaction between Ag{sup +} and Cl{sup -} ions at room temperature, resulting in conversion of the Ag nanowires to AgCl nanowires as well as reduction of Fe{sup 3+} to Fe{sup 2+} ions. In the second step, the Fe{sup 2+} ions generated in the first step reduce Au precursors (e.g., NaAuCl{sub 4}) to deposit Au nanoparticles on the surfaces of the AgCl nanowires, resulting in the formation of AgCl:Au composite nanowires. Because of strong surface plasmon resonance and chemical inertness of Au nanoparticles, the as-synthesized AgCl:Au nanowires exhibit enhanced absorption coefficient in the visible region and enhanced chemical stability to prevent them from degradation and aggregation. These unique properties enable the AgCl:Au nanowires to be used as a class of promising plasmonic photocatalysts driven by visible light. Preliminary results demonstrate these composite nanowires can efficiently decompose organics, such as methylene blue molecules, under illumination of white light.

  6. Synthesis and characterization of PVK/AgNPs nanocomposites prepared by laser ablation.

    PubMed

    Abd El-Kader, F H; Hakeem, N A; Elashmawi, I S; Menazea, A A

    2015-03-01

    Nanocomposites of Poly (n-vinylcarbazole) PVK/Ag nanoparticles were prepared by laser ablation of a silver plate in aqueous solution of chlorobenzene. The influences of laser parameters such as; time of irradiation, source power and wavelength (photon energy) on structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Ultraviolet-visible (UV-Vis) and Photoluminescence (PL). A correlation between the investigated properties has been discussed. XRD, TEM and PL indicated that the complexation between AgNPs and PVK in the composite system is possible. Only the reflection peak at 2θ=38° of AgNPs appeared in the composite nanoparticles while the other reflection peaks were destroyed. The nanoparticles shape and size distribution were evaluated from TEM images. TEM analysis revealed a lower average particle size at long laser irradiation time 40min and short laser wavelength 532nm together with high laser power 570mW. From UV-Visible spectra the values of absorption coefficient, absorption edge and energy tail were calculated. The reduction of band tail value with increasing the laser ablation parameters confirms the decrease of the disorder in such composite system. The PL and UV-Vis. spectra confirm that nanocomposite samples showed quantum confinement effect. PMID:25506650

  7. Synthesis and characterization of PVK/AgNPs nanocomposites prepared by laser ablation

    NASA Astrophysics Data System (ADS)

    Abd El-kader, F. H.; Hakeem, N. A.; Elashmawi, I. S.; Menazea, A. A.

    2015-03-01

    Nanocomposites of Poly (n-vinylcarbazole) PVK/Ag nanoparticles were prepared by laser ablation of a silver plate in aqueous solution of chlorobenzene. The influences of laser parameters such as; time of irradiation, source power and wavelength (photon energy) on structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Ultraviolet-visible (UV-Vis) and Photoluminescence (PL). A correlation between the investigated properties has been discussed. XRD, TEM and PL indicated that the complexation between AgNPs and PVK in the composite system is possible. Only the reflection peak at 2θ = 38° of AgNPs appeared in the composite nanoparticles while the other reflection peaks were destroyed. The nanoparticles shape and size distribution were evaluated from TEM images. TEM analysis revealed a lower average particle size at long laser irradiation time 40 min and short laser wavelength 532 nm together with high laser power 570 mW. From UV-Visible spectra the values of absorption coefficient, absorption edge and energy tail were calculated. The reduction of band tail value with increasing the laser ablation parameters confirms the decrease of the disorder in such composite system. The PL and UV-Vis. spectra confirm that nanocomposite samples showed quantum confinement effect.

  8. Synthesis and characterization of PVK/AgNPs nanocomposites prepared by laser ablation.

    PubMed

    Abd El-Kader, F H; Hakeem, N A; Elashmawi, I S; Menazea, A A

    2015-03-01

    Nanocomposites of Poly (n-vinylcarbazole) PVK/Ag nanoparticles were prepared by laser ablation of a silver plate in aqueous solution of chlorobenzene. The influences of laser parameters such as; time of irradiation, source power and wavelength (photon energy) on structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Ultraviolet-visible (UV-Vis) and Photoluminescence (PL). A correlation between the investigated properties has been discussed. XRD, TEM and PL indicated that the complexation between AgNPs and PVK in the composite system is possible. Only the reflection peak at 2θ=38° of AgNPs appeared in the composite nanoparticles while the other reflection peaks were destroyed. The nanoparticles shape and size distribution were evaluated from TEM images. TEM analysis revealed a lower average particle size at long laser irradiation time 40min and short laser wavelength 532nm together with high laser power 570mW. From UV-Visible spectra the values of absorption coefficient, absorption edge and energy tail were calculated. The reduction of band tail value with increasing the laser ablation parameters confirms the decrease of the disorder in such composite system. The PL and UV-Vis. spectra confirm that nanocomposite samples showed quantum confinement effect.

  9. One pot preparation of silver nanoparticles decorated TiO2 mesoporous microspheres with enhanced antibacterial activity.

    PubMed

    Chen, Yuemei; Deng, Yuanming; Pu, Yitao; Tang, Bijun; Su, Yikun; Tang, Jiaoning

    2016-08-01

    We report a simple "one-pot" solvothermal preparation of silver nanoparticles (Ag NPs) decorated mesoporous titania (TiO2) microspheres as an effective antibacterial agent. TBOT as Ti source was hydrolyzed and crystallized in media composed of acetic acid and ethanol, in which esterification catalyzed by TBOT occurred for in-situ "controlled water release". AgNO3 as Ag source was reduced by ethanol to form Ag NPs embedded in the TiO2 microspheres. The effect of AgNO3 and HAc on the morphology of Ag/TiO2 was investigated. The Ag/TiO2 with various Ag content showed excellent antibacterial activities with extremely low minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Escherichia coli and Staphylococcus aureus when compared with colloidal Ag NPs. PMID:27157724

  10. The synthesis of Pt/Ag bimetallic nanoparticles using a successive solution plasma process.

    PubMed

    Kim, Sung Min; Lee, Sang Yul; Lee, Min Hyung; Kim, Jung Wan

    2014-12-01

    A successive solution plasma process was developed for the synthesis of Pt/Ag bimetallic nanoparticles. Ag nanoparticles were made first by applying a high voltage of bipolar pulsed DC to anode and cathode electrodes composed of Ag rods. The solution containing Ag nanoparticles was discharged successively using Pt electrodes. The joule heating and electrolysis between electrodes generated vapors, and solution plasma was sustained due to progressive ionization and excitation in the vapor phase. The maximum current and voltage breakdown was observed at approximately 8.9 A and 900 V with an interval of 25 μs, which indicated that an intense solution plasma was sustained continuously. The Pt-on-Ag heterogeneous nanostructures formed, and finally, the Ag nanoparticles were completely covered by Pt nanoparticles after a discharge duration of 1,200 s. PMID:25970983

  11. Preparation of the CNC/Ag/beeswax composites for enhancing antibacterial and water resistance properties of paper.

    PubMed

    Liu, Kai; Liang, Hunan; Nasrallah, Joseph; Chen, Lihui; Huang, Liulian; Ni, Yonghao

    2016-05-20

    An effective method of preparing composites containing inorganic (Ag) and organic (beeswax) particles was established in this study. Ag nanoparticles were first immobilized on the cellulose nanocrystals (CNC) during the reduction of AgNO3 in the presence of CNC, then mixed with beeswax by high speed stirring. Scanning transmission electron microscopy (STEM) images indicated that Ag and beeswax particles were uniformly dispersed and stable in the network structure formed by CNC. Upon coating on a paper surface, a layer of beeswax film was evident based on scanning electron microscopy (SEM) images. The dynamic contact angle and antibacterial activity tests indicated that the contact angle of coated paper reached 113.06° and the growth inhibition of Escherichia coli increased to 99.96%, respectively, at a coating amount of 21.53 g/m(2). When applied onto paper surface by coating, the CNC/Ag/beeswax composites can impact paper with antibacterial property and improved water resistance.

  12. Fabrication of Ag-Decorated CaTiO₃ Nanoparticles and Their Enhanced Photocatalytic Activity for Dye Degradation.

    PubMed

    Xian, T; Yang, H; Huo, Y S; Ma, J Y; Zhang, H M; Su, J Y; Feng, W J

    2016-01-01

    CaTiO₃nanoparticles of 30-40 nm in size were synthesized via a polyacrylamide gel route. Ag nanoparticles with size of 8-16 nm were deposited onto CaTiO₃particles by a photochemical reduction method to yield CaTiO₃@Ag composites. The photocatalytic activity of prepared samples was evaluated by degrading methyl orange under ultraviolet irradiation. It is demonstrated that Ag-decorated CaTiO₃ particles exhibit an enhanced photocatalytic activity compared to bare CaTiO₃ particles. After 60 min of photocatalysis, the degradation percentage of MO increases from 54% for bare CaTiO₃particles to 72% for CaTiO₃@Ag composites. This can be explained by the fact that photogenerated electrons are captured by Ag nanoparticles and photogenerated holes are therefore increasingly available to react with OH⁻/H₂O to generate hydroxyl (·OH) radicals. ·OH radicals were detected by fluorimetry using terephthalic acid as a probe molecule, revealing an enhanced yield on the irradiated CaTiO₃@Ag composites. In addition, it is found that the addition of ethanol, which acts as an ·OH scavenger, leads to a quenching of ·OH radicals and simultaneous decrease in the photocatalytic efficiency. This suggests that ·OH radicals are the dominant active species responsible for the dye degradation. PMID:27398489

  13. Exposure-dependent Ag+ release from silver nanoparticles and its complexation in AgS2 sites in primary murine macrophages

    NASA Astrophysics Data System (ADS)

    Veronesi, G.; Aude-Garcia, C.; Kieffer, I.; Gallon, T.; Delangle, P.; Herlin-Boime, N.; Rabilloud, T.; Carrière, M.

    2015-04-01

    Silver nanoparticle (AgNP) toxicity is related to their dissolution in biological environments and to the binding of the released Ag+ ions in cellulo; the chemical environment of recombined Ag+ ions is responsible for their toxicological outcome, moreover it is indicative of the cellular response to AgNP exposure, and can therefore shed light on the mechanisms governing AgNP toxicity. This study probes the chemistry of Ag species in primary murine macrophages exposed to AgNPs by making use of X-ray Absorption Fine Structure spectroscopy under cryogenic conditions: the linear combination analysis of the near-edge region of the spectra provides the fraction of Ag+ ions released from the AgNPs under a given exposure condition and highlights their complexation with thiolate groups; the ab initio modelling of the extended spectra allows measuring the Ag-S bond length in cellulo. Dissolution rates depend on the exposure scenario, chronicity leading to higher Ag+ release than acute exposure; Ag-S bond lengths are 2.41 +/- 0.03 Å and 2.38 +/- 0.01 Å in acute and chronic exposure respectively, compatible with digonal AgS2 coordination. Glutathione is identified as the most likely putative ligand for Ag+. The proposed method offers a scope for the investigation of metallic nanoparticle dissolution and recombination in cellular models.Silver nanoparticle (AgNP) toxicity is related to their dissolution in biological environments and to the binding of the released Ag+ ions in cellulo; the chemical environment of recombined Ag+ ions is responsible for their toxicological outcome, moreover it is indicative of the cellular response to AgNP exposure, and can therefore shed light on the mechanisms governing AgNP toxicity. This study probes the chemistry of Ag species in primary murine macrophages exposed to AgNPs by making use of X-ray Absorption Fine Structure spectroscopy under cryogenic conditions: the linear combination analysis of the near-edge region of the spectra provides

  14. Raman gas sensing of modified Ag nanoparticle SERS

    NASA Astrophysics Data System (ADS)

    Myoung, NoSoung; Yoo, Hyung Keun; Hwang, In-Wook

    2014-03-01

    Recent progress in modified Surface Enhanced Raman Scattering (SERS) using Ag nanoparticles makes them promising optical technique for direct gas sensing of interest. However, SERS has been shown to provide sub ppb level detection of the compounds in the vapor phase. The major problem with the sensitivity scaling-up was in the development of fabrication technology for stability and reproducibility of SERS substrates. We report an optimization of 1-propanethiol coated multiple Ag nanoparticle layers on SiO2 substrate as well as new records of real-time, simultaneous vapor phase detection of toluene and 1-2 dichlorobenzene by the radiation of fiber optic coupled 785 nm diode laser and spectrograph. Multiple depositions of Ag NPs were loaded on SiO2 and soaked in 1-propanethiol solution for 24 hours to modify the surface into hydrophobic due to the characteristics of vapor phase of our interests. Raman bands at 1003 cm-1 and 1130 cm-1 for toluene and 12DCB, respectively were compared to 1089 cm-1 and each gas concentration in 1000 mL flask were calculated as a function of each vapor phase ratio. The saturation of toluene and 12DCB were limited only by 800 ppm and the detectable range was 0.6-800 ppm.

  15. Surface-enhanced Raman scattering from Ag nanoparticles formed by visible laser irradiation of thermally annealed AgO{sub x} thin films

    SciTech Connect

    Fujimaki, Makoto; Awazu, Koichi; Tominaga, Junji; Iwanabe, Yasuhiko

    2006-10-01

    Visible laser irradiation of AgO{sub x} thin films forms Ag nanoparticles, which then results in surface-enhanced Raman scattering (SERS). The efficiency of this Ag nanoparticle formation strongly depends on the properties of the AgO{sub x} thin films. Thermal annealing causes changes in physical properties such as deoxidization of the films and aggregation of Ag atoms in the films. In the present research, the effects of the changes induced by thermal annealing on SERS efficiency were examined. It was found that AgO{sub x} thin films annealed at 300 deg. C for 5 min in a N{sub 2} atmosphere were suitable for the formation of Ag nanoparticles effective for SERS, while films that were not annealed were not. From these results, it was deduced that the Ag aggregation resulting from thermal annealing in AgO{sub x} thin films promotes the Ag nanoparticle formation.

  16. Preparation, characterization and photocatalytic activities of ZrWMoO8/Ag composites with core-shell structure

    NASA Astrophysics Data System (ADS)

    Liu, Qinqin; Sun, Shuai; Li, Haohua; Yang, Xiaofei; Shen, Hao; Cheng, Xiaonong; Dong, Shubin

    2012-11-01

    A novel photocatalytic ZrWMoO8/Ag composite with core-shell structure was prepared. The composites were composed of ZrWMoO8 rods with negative thermal expansion (NTE) property as cores and Ag nanoparticles as shell. The resulting products were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible spectrophotometer (UV-vis DRS). The results showed that ZrWMoO8 rods displayed not only negative thermal expansion but also photocatalytic efficiency toward Rhodamine B (RB) degradation under UV-irradiation. The as-prepared ZrWMoO8/Ag composites exhibited a higher photocatalytic activity than that of pure ZrWMoO8, thereby implying that the ZrWMoO8/Ag interfaces promote the separation of photogenerated electron-hole pairs and enhance the photocatalytic activity.

  17. Hydroquinone-assisted synthesis of branched au-ag nanoparticles with polydopamine coating as highly efficient photothermal agents.

    PubMed

    Li, Jing; Wang, Wenjing; Zhao, Liang; Rong, Li; Lan, Shijie; Sun, Hongchen; Zhang, Hao; Yang, Bai

    2015-06-01

    Despite the success of galvanic replacement in preparing hollow nanostructures with diversified morphologies via the replacement reaction between sacrificial metal nanoparticles (NPs) seeds and less active metal ions, limited advances are made for producing branched alloy nanostructures. In this paper, we report an extended galvanic replacement for preparing branched Au-Ag NPs with Au-rich core and Ag branches using hydroquinone (HQ) as the reductant. In the presence of HQ, the preformed Ag seeds are replaceable by Au and, in turn, supply the growth of Ag branches. By altering the feed ratio of Ag seeds, HAuCl4, and HQ, the size and morphology of the NPs are tunable. Accordingly, the surface plasmon resonance absorption is tuned to near-infrared (NIR) region, making the branched NPs as potential materials in photothermal therapy. The branched NPs are further coated with polydopamine (PDA) shell via dopamine polymerization at room temperature. In comparison with bare NPs, PDA-coated branched Au-Ag (Au-Ag@PDA) NPs exhibit improved stability, biocompatibility, and photothermal performance. In vitro experiments indicate that the branched Au-Ag@PDA NPs are competitive agents for photothermal ablation of cancer cells. PMID:25969998

  18. Hydroquinone-assisted synthesis of branched au-ag nanoparticles with polydopamine coating as highly efficient photothermal agents.

    PubMed

    Li, Jing; Wang, Wenjing; Zhao, Liang; Rong, Li; Lan, Shijie; Sun, Hongchen; Zhang, Hao; Yang, Bai

    2015-06-01

    Despite the success of galvanic replacement in preparing hollow nanostructures with diversified morphologies via the replacement reaction between sacrificial metal nanoparticles (NPs) seeds and less active metal ions, limited advances are made for producing branched alloy nanostructures. In this paper, we report an extended galvanic replacement for preparing branched Au-Ag NPs with Au-rich core and Ag branches using hydroquinone (HQ) as the reductant. In the presence of HQ, the preformed Ag seeds are replaceable by Au and, in turn, supply the growth of Ag branches. By altering the feed ratio of Ag seeds, HAuCl4, and HQ, the size and morphology of the NPs are tunable. Accordingly, the surface plasmon resonance absorption is tuned to near-infrared (NIR) region, making the branched NPs as potential materials in photothermal therapy. The branched NPs are further coated with polydopamine (PDA) shell via dopamine polymerization at room temperature. In comparison with bare NPs, PDA-coated branched Au-Ag (Au-Ag@PDA) NPs exhibit improved stability, biocompatibility, and photothermal performance. In vitro experiments indicate that the branched Au-Ag@PDA NPs are competitive agents for photothermal ablation of cancer cells.

  19. Aging Induced Ag Nanoparticle Rearrangement under Ambient Atmosphere and Consequences for Nanoparticle-Enhanced DNA Biosensing

    PubMed Central

    Peng, Hsin-I; Krauss, Todd D.; Miller, Benjamin L.

    2010-01-01

    Localized surface plasmons of metallic nanoparticles can strongly amplify the magnitude of the surrounding electric field. This in turn enhances fluorescence from nearby fluorophores. However, little is known regarding how time-dependent changes in nanoparticle structure due to exposure to the ambient environment affect their behavior in plasmonic devices. Here, we report the interesting finding that the aging of a nanostructured Ag substrate in ambient atmosphere markedly improves the fluorescence signal of a plasmonic-based DNA detection system. The effect can be observed with an exposure time as short as two days, and a nearly 17-fold signal enhancement can be achieved with 30 days of aging. Analysis of substrate surface topography by atomic force microscopy (AFM) reveals a substantial change in nanoparticle morphology as the substrates age despite being covalently attached to a solid dry substrate. Nanoparticle morphological changes also manifest in extinction spectra. This process can be further accelerated by light. Together, our findings address the important question of Ag nanoparticle stability over time and its potential ramifications for plasmon-enabled sensors. They also imply that nanoparticle aging may be used strategically to tune nanoparticle size and geometry and plasmon spectrum, which may be beneficial for studies on plasmonics as well as sensor optimization. PMID:20857925

  20. Method to prepare nanoparticles on porous mediums

    DOEpatents

    Vieth, Gabriel M [Knoxville, TN; Dudney, Nancy J [Oak Ridge, TN; Dai, Sheng [Knoxville, TN

    2010-08-10

    A method to prepare porous medium decorated with nanoparticles involves contacting a suspension of nanoparticles in an ionic liquid with a porous medium such that the particles diffuse into the pores of the medium followed by heating the resulting composition to a temperature equal to or greater than the thermal decomposition temperature of the ionic liquid resulting in the removal of the liquid portion of the suspension. The nanoparticles can be a metal, an alloy, or a metal compound. The resulting compositions can be used as catalysts, sensors, or separators.

  1. Preparation and Characterization of Gelatin Nanofibers Containing Silver Nanoparticles

    PubMed Central

    Jeong, Lim; Park, Won Ho

    2014-01-01

    Ag nanoparticles (NPs) were synthesized in formic acid aqueous solutions through chemical reduction. Formic acid was used for a reducing agent of Ag precursor and solvent of gelatin. Silver acetate, silver tetrafluoroborate, silver nitrate, and silver phosphate were used as Ag precursors. Ag+ ions were reduced into Ag NPs by formic acid. The formation of Ag NPs was characterized by a UV-Vis spectrophotometer. Ag NPs were quickly generated within a few minutes in silver nitrate (AgNO3)/formic acid solution. As the water content of formic acid aqueous solution increased, more Ag NPs were generated, at a higher rate and with greater size. When gelatin was added to the AgNO3/formic acid solution, the Ag NPs were stabilized, resulting in smaller particles. Moreover, gelatin limits further aggregation of Ag NPs, which were effectively dispersed in solution. The amount of Ag NPs formed increased with increasing concentration of AgNO3 and aging time. Gelatin nanofibers containing Ag NPs were fabricated by electrospinning. The average diameters of gelatin nanofibers were 166.52 ± 32.72 nm, but these decreased with the addition of AgNO3. The average diameters of the Ag NPs in gelatin nanofibers ranged between 13 and 25 nm, which was confirmed by transmission electron microscopy (TEM). PMID:24758929

  2. Photocurrent enhancements of organic solar cells by altering dewetting of plasmonic Ag nanoparticles

    PubMed Central

    Fleetham, Tyler; Choi, Jea-Young; Choi, Hyung Woo; Alford, Terry; Jeong, Doo Seok; Lee, Taek Sung; Lee, Wook Seong; Lee, Kyeong-Seok; Li, Jian; Kim, Inho

    2015-01-01

    Incorporation of metal nanoparticles into active layers of organic solar cells is one of the promising light trapping approaches. The size of metal nanoparticles is one of key factors to strong light trapping, and the size of thermally evaporated metal nanoparticles can be tuned by either post heat treatment or surface modification of substrates. We deposited Ag nanoparticles on ITO by varying nominal thicknesses, and post annealing was carried out to increase their size in radius. PEDOT:PSS was employed onto the ITO substrates as a buffer layer to alter the dewetting behavior of Ag nanoparticles. The size of Ag nanoparticles on PEDOT:PSS were dramatically increased by more than three times compared to those on the ITO substrates. Organic solar cells were fabricated on the ITO and PEDOT:PSS coated ITO substrates with incorporation of those Ag nanoparticles, and their performances were compared. The photocurrents of the cells with the active layers on PEDOT:PSS with an optimal choice of the Ag nanoparticles were greatly enhanced whereas the Ag nanoparticles on the ITO substrates did not lead to the photocurrent enhancements. The origin of the photocurrent enhancements with introducing the Ag nanoparticles on PEDOT:PSS are discussed. PMID:26388104

  3. Non-covalent functionalization of graphene oxide by polyindole and subsequent incorporation of Ag nanoparticles for electrochemical applications

    NASA Astrophysics Data System (ADS)

    Dubey, Prashant; Kumar, Ashish; Prakash, Rajiv

    2015-11-01

    Reduced graphene oxide (r-GO) sheets have been modified by polyindole (PIn) via in situ chemical oxidation method to obtain stable dispersion in water and furthermore incorporation of Ag nanoparticles (Ag NPs); the resulting Ag NPs/PIn-r-GO nanocomposite is demonstrated for electrochemical applications. Ag NPs/r-GO and PIn/GO nanocomposites have also been prepared for its comparative study with Ag NPs/PIn-r-GO. Non-covalent functionalization of GO by PIn polymer leads to PIn-GO dispersion, which is stable for several months without any precipitation. This dispersed solution is used for formation of Ag NPs/PIn-r-GO nanocomposite. Various experimental tools like UV-vis, FTIR and TEM have been used to characterize as-synthesized materials. Thereafter electrochemical performance of as-synthesized nanocomposites have been compared for their charge capacitive behaviour (without its poisoning compared to Ag NPs/r-GO) which leads to be an excellent candidate for the possible applications such as electrocatalysis, charge storage devices, etc. We observed that Ag NPs/PIn-r-GO nanocomposite exhibits better processability and electroactivity as electrode material in comparison to Ag NPs/r-GO and PIn/GO nanocomposites due to synergistic effect of individual components.

  4. LSP spectral changes correlating with SERS activation and quenching for R6G on immobilized Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Futamata, M.; Maruyama, Y.

    2008-10-01

    In terms of chemical enhancement in Surface Enhanced Raman Scattering (SERS), we investigated the effect of halide and other anions to rhodamine 6G (R6G) adsorbed Ag particles that were immobilized on the substrates. The residual species on chemically prepared Ag particles such as citrate or a-carbon were thoroughly substituted by various anions, e.g., Cl-, Br-, I-, SCN-, CN-, or S2O3 2- anions, whose adsorption features are elucidated by the formation constants for AgX2 ( m-1)-, here X denotes the above anions. In particular, Cl-, Br-, or SCN- ions activated SERS of R6G via intrinsic electronic interaction with Ag, whereas CN-, S2O3 2-, or I- anions quenched it due to their exclusive adsorption onto the Ag surfaces. We found that the activation process with the anions commonly yields a marked blue-shift of the coupled plasmon peak from ca. 650-700 to 500-550 nm in elastic scattering. It is rationalized by slight increase of the gap size between adjacent Ag nanoparticles by only ca. 1 nm based on theoretical simulations. This is probably caused by slight dissolution, oxidative etching, of the particles according to large formation constants of the complexes. Consequently, partly remaining negative charges on the Ag surface, and a slight increase in the gap size, providing huge electric field, facilitated R6G cations to adsorb on the nanoparticles, especially at the junction.

  5. Synthesis of triangular Au core-Ag shell nanoparticles

    SciTech Connect

    Rai, Akhilesh; Chaudhary, Minakshi; Ahmad, Absar; Bhargava, Suresh; Sastry, Murali . E-mail: msastry@tatachemicals.com

    2007-07-03

    In this paper, we demonstrate a simple and reproducible method for the synthesis of triangular Au core-Ag shell nanoparticles. The triangular gold core is obtained by the reduction of gold ions by lemongrass extract. Utilizing the negative charge on the gold nanotriangles, silver ions are bound to their surface and thereafter reduced by ascorbic acid under alkaline conditions. The thickness of the silver shell may be modulated by varying the pH of the reaction medium. The formation of the Au core-Ag shell triangular nanostructures has been followed by UV-vis-NIR Spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements. The sharp vertices of the triangles coupled with the core-shell structure is expected to have potential for application in surface enhanced Raman spectroscopy and in the sensitive detection of biomolecules.

  6. Morphological and electrochemical characterization of electrodeposited Zn–Ag nanoparticle composite coatings

    SciTech Connect

    Punith Kumar, M.K.; Srivastava, Chandan

    2013-11-15

    Silver nanoparticles with an average size of 23 nm were chemically synthesized and used to fabricate Zn–Ag composite coatings. The Zn–Ag composite coatings were generated by electrodeposition method using a simple sulfate plating bath dispersed with 0.5, 1 and 1.5 g/l of Ag nanoparticles. Scanning electron microscopy, X-ray diffraction and texture co-efficient calculations revealed that Ag nanoparticles appreciably influenced the morphology, micro-structure and texture of the deposit. It was also noticed that agglomerates of Ag nanoparticles, in the case of high bath load conditions, produced defects and dislocations on the deposit surface. Ag nanoparticles altered the corrosion resistance property of Zn–Ag composite coatings as observed from Tafel polarization, electrochemical impedance analysis and an immersion test. Reduction in corrosion rate with increased charge transfer resistance was observed for Zn–Ag composite coatings when compared to a pure Zn coating. However, the particle concentration in the plating bath and their agglomeration state directly influenced the surface morphology and the subsequent corrosion behavior of the deposits. - Highlights: • Synthesis of Ag nanoparticles with an average size of 23 nm • Fabrication of Zn/nano Ag composite coating on mild steel • Composite coatings showed better corrosion resistance. • Optimization of particle concentration is necessary.

  7. Spectral investigation of nonlinear local field effects in Ag nanoparticles

    SciTech Connect

    Sato, Rodrigo Takeda, Yoshihiko; Ohnuma, Masato; Oyoshi, Keiji

    2015-03-21

    The capability of Ag nanoparticles to modulate their optical resonance condition, by optical nonlinearity, without an external feedback system was experimentally demonstrated. These optical nonlinearities were studied in the vicinity of the localized surface plasmon resonance (LSPR), using femtosecond pump-and-probe spectroscopy with a white-light continuum probe. Transient transmission changes ΔT/T exhibited strong photon energy and particle size dependence and showed a complex and non-monotonic change with increasing pump light intensity. Peak position and change of sign redshift with increasing pump light intensity demonstrate the modulation of the LSPR. These features are discussed in terms of the intrinsic feedback via local field enhancement.

  8. Dendritic macromolecules supported Ag nanoparticles as efficient catalyst for the reduction of 4-nitrophenol

    NASA Astrophysics Data System (ADS)

    Safari, Javad; Zarnegar, Zohre; Sadeghi, Masoud; Enayati-Najafabadi, Azadeh

    2016-12-01

    Polymer supported Ag nanoparticles, generated in situ by silver nitrate (AgNO3) reduction under reaction conditions, catalyzed the hydrogenation of 4-nitrophenol with high efficiency in water at room temperature in the presence of an excess amount of NaBH4. Amphiphilic linear-dendritic copolymers containing a poly(ethylene glycol) (PEG) core and poly(2-ethyl-2-oxazoline)-poly(ε-caprolactone) arms were able to load the Ag nanoparticles. The Ag nanoparticles with a diameter of 8-10 nm were found to show a comparable catalytic activity towards formation of the aromatic amine as single product with short reaction time.

  9. Reversibly phototunable TiO{sub 2} photonic crystal modulated by Ag nanoparticles' oxidation/reduction

    SciTech Connect

    Liu Jian; Zhou Jinming; Ye Changqing; Li Mingzhu; Wang Jingxia; Jiang Lei; Song Yanlin

    2011-01-10

    We report a reversibly phototunable photonic crystal system whose reflectance at the stop band position can be modulated by alternating UV/visible (UV/Vis) irradiation. The phototunable system consists of Ag nanoparticles and TiO{sub 2} photonic crystal. The stop bands intensity of Ag loaded TiO{sub 2} photonic crystals were found to be dependent on the redox states of Ag nanoparticles. The quasi 'on' and 'off' states of the stop band were reversibly modulated by the Ag nanoparticles' oxidation/reduction through alternating UV/Vis light irradiation.

  10. Double Detection of Mycotoxins Based on SERS Labels Embedded Ag@Au Core-Shell Nanoparticles.

    PubMed

    Zhao, Yuan; Yang, Yaxin; Luo, Yaodong; Yang, Xuan; Li, Manli; Song, Qijun

    2015-10-01

    A sensitive surface-enhanced Raman scattering (SERS) signal dependent double detection of mycotoxins is achieved for the first time, without the aid of nucleic acid amplification strategies. SERS labels embedded Ag@Au core-shell (CS) nanoparticles (NPs) as novel SERS tags are successfully prepared through a galvanic replacement-free deposition. SERS tags produce stable and quantitative SERS signal, emerging from the plasmonic coupling at the junction of Ag core and Au shell. SERS tags engineered Raman aptasensors are developed for the double detection of ochratoxin A (OTA) and aflatoxin B1 (AFB1) in maize meal. The limits of detection (LODs) are as low as 0.006 ng/mL for OTA and 0.03 ng/mL for AFB1. The developed protocol can be extended to a large set of different SERS tags for the sensitive detection of multiple targets that possess different lengths of aptamers.

  11. Facile preparation of silver nanoparticle films as an efficient surface-enhanced Raman scattering substrate

    NASA Astrophysics Data System (ADS)

    Sun, Yujing; Zhang, Yue; Shi, Yan; Xiao, Xianping; Dai, Haichao; Hu, Jingting; Ni, Pengjuan; Li, Zhuang

    2013-10-01

    Here, we report a new and facile method to prepare silver nanoparticles (Ag NPs) film for surface-enhanced Raman scattering (SERS)-based sensing. The porous Ni foam was used as a template to generate high quality of Ag NPs by seed-mediated growth of metallic nanoparticles. The preparation process is very economic and environment-friendly, can achieve the recovery of the raw materials. We found that the type of silver-plating solution and the growth time are two key factors to determine the magnitude of SERS signal enhancement. Using rhodamine 6G (R6G) and 4-animothiophenol (4-ATP) as probe molecules, the created Ag NP films exhibited relatively high enhancement ability, good stability, and well reproducibility. The synthesized SERS-active substrate was further used to detect melamine molecules, an illegal additive in infant milk powder, and the limitation of detection can reach 1 μM.

  12. Raman scattering of 4-aminobenzenethiol sandwiched between Ag nanoparticle and macroscopically smooth Au substrate: effects of size of Ag nanoparticles and the excitation wavelength.

    PubMed

    Kim, Kwan; Choi, Jeong-Yong; Lee, Hyang Bong; Shin, Kuan Soo

    2011-09-28

    A nanogap formed by a metal nanoparticle and a flat metal substrate is one kind of "hot site" for surface-enhanced Raman scattering (SERS). Accordingly, although no Raman signal is observable when 4-aminobenzenethiol (4-ABT), for instance, is self-assembled on a flat Au substrate, a distinct spectrum is obtained when Ag or Au nanoparticles are adsorbed on the pendent amine groups of 4-ABT. This is definitely due to the electromagnetic coupling between the localized surface plasmon of Ag or Au nanoparticle with the surface plasmon polariton of the planar Au substrate, allowing an intense electric field to be induced in the gap even by visible light. To appreciate the Raman scattering enhancement and also to seek the optimal condition for SERS at the nanogap, we have thoroughly examined the size effect of Ag nanoparticles, along with the excitation wavelength dependence, by assembling 4-ABT between planar Au and a variable-size Ag nanoparticle (from 20- to 80-nm in diameter). Regarding the size dependence, a higher Raman signal was observed when larger Ag nanoparticles were attached onto 4-ABT, irrespective of the excitation wavelength. Regarding the excitation wavelength, the highest Raman signal was measured at 568 nm excitation, slightly larger than that at 632.8 nm excitation. The Raman signal measured at 514.5 and 488 nm excitation was an order of magnitude weaker than that at 568 nm excitation, in agreement with the finite-difference time domain simulation. It is noteworthy that placing an Au nanoparticle on 4-ABT, instead of an Ag nanoparticle, the enhancement at the 568 nm excitation was several tens of times weaker than that at the 632.8 nm excitation, suggesting the importance of the localized surface plasmon resonance of the Ag nanoparticles for an effective coupling with the surface plasmon polariton of the planar Au substrate to induce a very intense electric field at the nanogap.

  13. Oleate-Assisted Room Temperature Synthesis and High Photocatalytic Activity of Ag3PO4 Nanoparticles for no Decomposition

    NASA Astrophysics Data System (ADS)

    Huang, Lijun; Yin, Shu; Guo, Chongshen; Huang, Yunfang; Wang, Ming; Dong, Qiang; Li, Huihui; Kimura, Takeshi; Tanaka, Miyuki; Sato, Tsugio

    2012-06-01

    An oleate-assisted approach was used to synthesize nanosized spherical silver phosphate (Ag3PO4) in different solvents. The silver phosphate nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible-infrared diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TDA), and surface area measurement by nitrogen adsorption and decomposition evolution of NOx gas. The as-prepared nanoparticles showed narrow size distribution. The black colored nanoparticles could absorb most of visible light with a wavelength up to 530 nm. The DeNOx experiments revealed that the nanosized Ag3PO4 possessed a photocatalytic ability being superior to commercial P25 sample both in ultraviolet light and visible light regions.

  14. Preparation of Hydrochlorothiazide Nanoparticles for Solubility Enhancement.

    PubMed

    Vaculikova, Eliska; Cernikova, Aneta; Placha, Daniela; Pisarcik, Martin; Peikertova, Pavlina; Dedkova, Katerina; Devinsky, Ferdinand; Jampilek, Josef

    2016-01-01

    Nanoparticles can be considered as a useful tool for improving properties of poorly soluble active ingredients. Hydrochlorothiazide (Class IV of the Biopharmaceutical Classification System) was chosen as a model compound. Antisolvent precipitation-solvent evaporation and emulsion solvent evaporation methods were used for preparation of 18 samples containing hydrochlorothiazide nanoparticles. Water solutions of surfactants sodium dodecyl sulfate, Tween 80 and carboxymethyl dextran were used in mass concentrations of 1%, 3% and 5%. Acetone and dichloromethane were used as solvents of the model compound. The particle size of the prepared samples was measured by dynamic light scattering. The selected sample of hydrochlorothiazide nanoparticles stabilized with carboxymethyl dextran sodium salt with particle size 2.6 nm was characterized additionally by Fourier transform mid-infrared spectroscopy and scanning electron microscopy. It was found that the solubility of this sample was 6.5-fold higher than that of bulk hydrochlorothiazide. PMID:27490530

  15. Preparation and characterization of Mg nanoparticles

    SciTech Connect

    Song Meirong; Chen Miao Zhang Zhijun

    2008-05-15

    In this paper, Mg nanoparticles were prepared in tetrahydrofuran via lithium reduction of the corresponding Mg salt. X-ray diffraction and scanning electron microscope investigations confirm the formation of hexagonal phase Mg particles with an average size of 300 nm. X-ray photoelectron spectrometer analysis indicates that the as-prepared Mg nanoparticles are covered with a protecting layer consisting of residue solvents, naphthalene and Mg(OH){sub 2}, which slows down further oxidation under ambient conditions. Thermal analysis shows that the rapid oxidation and nitridation processes of the particles take place at around 500 deg. C and 553 deg. C, respectively. Furthermore, the addition of a small amount of magnesium nanoparticles remarkably catalyzes the decomposition process of ammonium perchlorate by lowering the decomposition temperature and enhancing its heat output.

  16. Preparation, characterization and utilization of starch nanoparticles.

    PubMed

    Kim, Hee-Young; Park, Sung Soo; Lim, Seung-Taik

    2015-02-01

    Starch is one of the most abundant biopolymers in nature and is typically isolated from plants in the form of micro-scale granules. Recent studies reported that nano-scale starch particles could be readily prepared from starch granules, which have unique physical properties. Because starch is environmentally friendly, starch nanoparticles are suggested as one of the promising biomaterials for novel utilization in foods, cosmetics, medicines as well as various composites. An overview of the most up-to-date information regarding the starch nanoparticles including the preparation processes and physicochemical characterization will be presented in this review. Additionally, the prospects and outlooks for the industrial utilization of starch nanoparticles will be discussed.

  17. High-value utilization of lignin to synthesize Ag nanoparticles with detection capacity for Hg²⁺.

    PubMed

    Shen, Zuguang; Luo, Yuqiong; Wang, Qun; Wang, Xiaoying; Sun, Runcang

    2014-09-24

    This study reports the rapid preparation of silver nanoparticles (AgNPs) from Tollens' reagent under microwave irradiation. In the synthesis, lignin with reducing groups and spatial three-dimensional structure was used as reducing and stabilizing agents without other chemical reagents, and the effects of the ratio of lignin to Ag(+), reaction temperature, and heating time on the synthesis of AgNPs were investigated. The obtained AgNPs were further characterized by UV-vis, Malvern particle size, TEM, XRD, and XPS analyses. The structural changes of lignin before and after reaction were also studied by FT-IR, (1)H NMR, (13)C NMR, and GC-MS. The results revealed that the obtained AgNPs were mostly spherical with diameters of around 24 nm. The optimum reaction conditions were a ratio 50 mg of lignin to 0.3 mM of Ag(+), a microwave irradiation temperature of 60 °C, and a heating time of 10 min. Moreover, AgNPs redispersed well in water and ethanol after centrifugation for the removal of lignin. During the formation of AgNPs, lignin was oxidized, and the side chains of lignin were partly disrupted into small molecules, such as hydrocarbon and alcohol. The resultant lignin-AgNPs showed highly selective sensing detection for Hg(2+), and the color of the lignin-AgNP solution containing Hg(2+) decreased gradually with increasing amounts of Hg(2+) within seconds, but the other 19 metal ions had little effect on the color and surface plasmon absorption band of the lignin-AgNPs. Also, there was a linear relationship between the absorbance and Hg(2+) concentration, with a limit of detection concentration of 23 nM. This study provides not only a new way to take advantage of agricultural and forestry residues, but also a green and rapid method for the synthesis of AgNPs to detect the toxic ion Hg(2+) selectively and sensitively.

  18. Ultrafine Au and Ag Nanoparticles Synthesized from Self-Assembled Peptide Fibers and Their Excellent Catalytic Activity.

    PubMed

    Xu, Wenlong; Hong, Yue; Hu, Yuanyuan; Hao, Jingcheng; Song, Aixin

    2016-07-18

    The self-assembly of an amphiphilic peptide molecule to form nanofibers facilitated by Ag(+) ions was investigated. Ultrafine AgNPs (NPs=nanoparticles) with an average size of 1.67 nm were synthesized in situ along the fibers due to the weak reducibility of the -SH group on the peptide molecule. By adding NaBH4 to the peptide solution, ultrafine AgNPs and AuNPs were synthesized with an average size of 1.35 and 1.18 nm, respectively. The AuNPs, AgNPs, and AgNPs/nanofibers all exhibited excellent catalytic activity toward the reduction of 4-nitrophenol, with turnover frequency (TOF) values of 720, 188, and 96 h(-1) , respectively. Three dyes were selected for catalytic degradation by the prepared nanoparticles and the nanoparticles showed selective catalysis activity toward the different dyes. It was a surprising discovery that the ultrafine AuNPs in this work had an extremely high catalytic activity toward methylene blue, with a reaction rate constant of 0.21 s(-1) and a TOF value of 1899 h(-1) .

  19. Sonochemically synthesized Ag nanoparticles as a SERS active substrate and effect of surfactant

    NASA Astrophysics Data System (ADS)

    Dar, Nitzan; Chen, Kuang-Yu; Nien, Yung-Tang; Perkas, Nina; Gedanken, Aharon; Chen, In-Gann

    2015-03-01

    Surface enhanced Raman scattering (SERS) enables the detection of substances at low concentrations using silver or gold nanostructure. The SERS technique has many applications, such as environmental detection and biosensing. Sonochemistry is an excellent and cheap deposition technique for coating substrates in a form of nanostructure at ambient temperature. It can also be utilized to prepare large SERS substrates. Here, we used the advantages of sonochemistry to deposit solid SERS substrates immobilized on GaN nanostructure. Morphology was studied by scanning electron microscopy. The elemental composition and the spatial distribution were examined by energy dispersive X-ray spectroscopy. The crystal structure and atomic presence was confirmed by X-ray diffraction. SERS substrates were examined with the analytes crystal violet (10-5 M) and rhodamine 6G (10-6 M), they showed prominent characteristic peaks. We discovered that the SERS intensity of poly-vinyl-pyrrolidinone aided sonochemical deposition of Ag nanoparticles was increased. The reason for the effect is morphological changes of the Ag nanoparticles. Smaller nanoparticles were fabricated, which increase their SERS intensity.

  20. Preparation and Characterization of SnO2/Ag Hollow Microsphere via a Convenient Hydrothermal Route.

    PubMed

    Qiao, Xiuqing; Hu, Fuchao; Hou, Dongfang; Li, Dongsheng

    2016-04-01

    SnO2/Ag hollow microsphere, assembled form SnO2 and Ag nanoparticles, was synthesized via a facile one-step hydrothermal synthesis method using Na2SnO3.3H2O, CO(NH2)2 and AgNO3 as raw materials. XRD, SEM, and TEM results revealed that the obtained SnO2/Ag hollow microsphere with diameters of ca.3-5 µm was built from uniformly distributed rutile SnO2 and cubic Ag nanoparticles. Moreover, XPS results indicate the existence of strong interaction between Ag and SnO2 nanoparticles, rather than simply physical contact, endowing the SnO2/Ag hollow microspheres with excellent photocatalytic performance in the degradation of RhB solution under visible light irradiation. PMID:27451773

  1. Ablation and optical third-order nonlinearities in Ag nanoparticles

    PubMed Central

    Torres-Torres, Carlos; Peréa-López, Néstor; Reyes-Esqueda, Jorge Alejandro; Rodríguez-Fernández, Luis; Crespo-Sosa, Alejandro; Cheang-Wong, Juan Carlos; Oliver, Alicia

    2010-01-01

    The optical damage associated with high intensity laser excitation of silver nanoparticles (NPs) was studied. In order to investigate the mechanisms of optical nonlinearity of a nanocomposite and their relation with its ablation threshold, a high-purity silica sample implanted with Ag ions was exposed to different nanosecond and picosecond laser irradiations. The magnitude and sign of picosecond refractive and absorptive nonlinearities were measured near and far from the surface plasmon resonance (SPR) of the Ag NPs with a self-diffraction technique. Saturable optical absorption and electronic polarization related to self-focusing were identified. Linear absorption is the main process involved in nanosecond laser ablation, but non-linearities are important for ultrashort picosecond pulses when the absorptive process become significantly dependent on the irradiance. We estimated that near the resonance, picosecond intraband transitions allow an expanded distribution of energy among the NPs, in comparison to the energy distribution resulting in a case of far from resonance, when the most important absorption takes place in silica. We measured important differences in the ablation threshold and we estimated that the high selectiveness of the SPR of Ag NPs as well as their corresponding optical nonlinearities can be strongly significant for laser-induced controlled explosions, with potential applications for biomedical photothermal processes. PMID:21187944

  2. Fluoride-induced reduction of Ag(I) cation leading to formation of silver mirrors and luminescent Ag-nanoparticles.

    PubMed

    Maity, Krishnendu; Panda, Dillip K; Lochner, Eric; Saha, Sourav

    2015-03-01

    In aprotic solvents, Lewis basic F(-) anion reduces Lewis acidic Ag(I) cation to Ag(0), forming metallic silver mirrors on the inner surfaces of reaction vessels and luminescent Ag-nanoparticles (AgNPs) in supernatant solutions, which emit blue light upon UV irradiation. The F(-)-induced formation of silver mirrors and AgNPs was confirmed through X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), fluorescence spectroscopy, and mass spectrometry, whereas the Ag(I)-induced oxidation of F(-) to Ḟ radical, followed by its conversion to HF2(-) via H-abstraction and H-bonding, was evident from (19)F NMR spectroscopy. This redox reaction is deactivated in water, as the reducing power of hydrated F(-) diminishes drastically. Less Lewis basic Cl(-), Br(-), and I(-) ions do not reduce Ag(I) to Ag(0), instead they can only form Ag(I) halide precipitates irrespective of protic or aprotic solvents. The Ag-coated surfaces, luminescent AgNPs, and Ḟ radicals produced by this unprecedented redox reaction could be exploited as electrodes, light-emitting materials, and radical initiators, respectively.

  3. Core-size-dependent catalytic properties of bimetallic Au/Ag core-shell nanoparticles.

    PubMed

    Haldar, Krishna Kanta; Kundu, Simanta; Patra, Amitava

    2014-12-24

    Bimetallic core-shell nanoparticles have recently emerged as a new class of functional materials because of their potential applications in catalysis, surface enhanced Raman scattering (SERS) substrate and photonics etc. Here, we have synthesized Au/Ag bimetallic core-shell nanoparticles with varying the core diameter. The red-shifting of the both plasmonic peaks of Ag and Au confirms the core-shell structure of the nanoparticles. Transmission electron microscopy (TEM) analysis, line scan EDS measurement and UV-vis study confirm the formation of core-shell nanoparticles. We have examined the catalytic activity of these core-shell nanostructures in the reaction between 4-nitrophenol (4-NP) and NaBH4 to form 4-aminophenol (4-AP) and the efficiency of the catalytic reaction is found to be increased with increasing the core size of Au/Ag core-shell nanocrystals. The catalytic efficiency varies from 41.8 to 96.5% with varying core size from 10 to 100 nm of Au/Ag core-shell nanoparticles, and the Au100/Ag bimetallic core-shell nanoparticle is found to be 12-fold more active than that of the pure Au nanoparticles with 100 nm diameter. Thus, the catalytic properties of the metal nanoparticles are significantly enhanced because of the Au/Ag core-shell structure, and the rate is dependent on the size of the core of the nanoparticles.

  4. Low temperature sintering of Ag nanoparticles/graphene composites for paper based writing electronics

    NASA Astrophysics Data System (ADS)

    Wang, Fuliang; Zhu, Haixin; He, Hu

    2016-10-01

    With the great demand in the applications of flexible electronics, the methods leading to improvements in the electrical and mechanical performance have been widely investigated. In this work, we firstly prepared a hybrid composite ink using Ag nanoparticles and graphene. Then, a hot-press sintering process was deployed to obtain the desired electrical tracks which could be applied in flexible electronics. We have systematically investigated the effects of sintering time, pressure and temperature, as well as the different percentage of weight (wt%) of graphene for the electrical and mechanical performance of sintered electrical tracks. We achieved reasonably low electrical resistivity at low sintering temperature (120 °C). Specifically, the resistivity reaches 6.19  ×  10-8 Ω · m which is just 3.87 times higher than the value of bulk silver. Additionally, the prepared hybrid composite ink obtained better electrical reliability against bending test comparing with Ag nanoparticle ink. Finally, the optimal wt% of graphene and potential effect to the electrical and mechanical performance were also investigated.

  5. The Antimicrobial Properties of Silver Nanoparticles in Bacillus subtilis Are Mediated by Released Ag+ Ions

    PubMed Central

    Hsueh, Yi-Huang; Lin, Kuen-Song; Ke, Wan-Ju; Hsieh, Chien-Te; Chiang, Chao-Lung; Tzou, Dong-Ying; Liu, Shih-Tung

    2015-01-01

    The superior antimicrobial properties of silver nanoparticles (Ag NPs) are well-documented, but the exact mechanisms underlying Ag-NP microbial toxicity remain the subject of intense debate. Here, we show that Ag-NP concentrations as low as 10 ppm exert significant toxicity against Bacillus subtilis, a beneficial bacterium ubiquitous in the soil. Growth arrest and chromosomal DNA degradation were observed, and flow cytometric quantification of propidium iodide (PI) staining also revealed that Ag-NP concentrations of 25 ppm and above increased membrane permeability. RedoxSensor content analysis and Phag-GFP expression analysis further indicated that reductase activity and cytosolic protein expression decreased in B. subtilis cells treated with 10–50 ppm of Ag NPs. We conducted X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses to directly clarify the valence and fine structure of Ag atoms in B. subtilis cells placed in contact with Ag NPs. The results confirmed the Ag species in Ag NP-treated B. subtilis cells as Ag2O, indicating that Ag-NP toxicity is likely mediated by released Ag+ ions from Ag NPs, which penetrate bacterial cells and are subsequently oxidized intracellularly to Ag2O. These findings provide conclusive evidence for the role of Ag+ ions in Ag-NP microbial toxicity, and suggest that the impact of inappropriately disposed Ag NPs to soil and water ecosystems may warrant further investigation. PMID:26669836

  6. The Antimicrobial Properties of Silver Nanoparticles in Bacillus subtilis Are Mediated by Released Ag+ Ions.

    PubMed

    Hsueh, Yi-Huang; Lin, Kuen-Song; Ke, Wan-Ju; Hsieh, Chien-Te; Chiang, Chao-Lung; Tzou, Dong-Ying; Liu, Shih-Tung

    2015-01-01

    The superior antimicrobial properties of silver nanoparticles (Ag NPs) are well-documented, but the exact mechanisms underlying Ag-NP microbial toxicity remain the subject of intense debate. Here, we show that Ag-NP concentrations as low as 10 ppm exert significant toxicity against Bacillus subtilis, a beneficial bacterium ubiquitous in the soil. Growth arrest and chromosomal DNA degradation were observed, and flow cytometric quantification of propidium iodide (PI) staining also revealed that Ag-NP concentrations of 25 ppm and above increased membrane permeability. RedoxSensor content analysis and Phag-GFP expression analysis further indicated that reductase activity and cytosolic protein expression decreased in B. subtilis cells treated with 10-50 ppm of Ag NPs. We conducted X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses to directly clarify the valence and fine structure of Ag atoms in B. subtilis cells placed in contact with Ag NPs. The results confirmed the Ag species in Ag NP-treated B. subtilis cells as Ag2O, indicating that Ag-NP toxicity is likely mediated by released Ag+ ions from Ag NPs, which penetrate bacterial cells and are subsequently oxidized intracellularly to Ag2O. These findings provide conclusive evidence for the role of Ag+ ions in Ag-NP microbial toxicity, and suggest that the impact of inappropriately disposed Ag NPs to soil and water ecosystems may warrant further investigation. PMID:26669836

  7. Thermal Behavior of Ag Micro/Nano Wires Formed by Low-Temperature Sintering of Ag Nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Wen; Zhong, Yinghui; Li, Dongxue; Wang, Pan; Cai, Yuwei; Duan, Zhiyong

    2015-12-01

    Ag nanoparticles of 30 nm size were deposited onto a Si substrate to form Ag microwires. The nanoparticles were transformed into continuous Ag wires with low-temperature heat treatment at temperatures not higher than 200°C. The morphology, electrical properties, and interface of the sintered Ag nanoparticle wires are described. It is shown that the neck between the nanoparticles begins to form at 150°C, and obvious metallization was found at 170°C. The changes of the crystal structure of the Ag wires at different sintering temperatures were analyzed by x-ray diffractometry. The grain boundary resistance decreased as the crystal grain size increased above 130 nm. The corresponding resistivity of the microstructure is close to that of the bulk. Through the comparison between the Mayadas-Shatzkes's model and experimental data, the range of the grain boundary reflection coefficient C at different temperatures is obtained. This research lays the foundation for the study of nanoimprint lithography with a pseudoplastic metal nanoparticle fluid.

  8. Preparation of magnetic Fe3O4/TiO2/Ag composite microspheres with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Wu, Zheng; Chen, Liangwei; Zhang, Lianjie; Li, Xuelian; Xu, Haifeng; Wang, Hongyan; Zhu, Guang

    2016-02-01

    The novel three-component Fe3O4/TiO2/Ag composite mircospheres were prepared via a facile chemical deposition route. The Fe3O4/TiO2 mircospheres were first prepared by the solvothermal method, and then Ag nanoparticles were anchored onto the out-layer of TiO2 by the tyrosine-reduced method. The as-prepared magnetic Fe3O4/TiO2/Ag composite mircospheres were applied as photocatalysis for the photocatalytic degradation of methylene blue. The results indicate that the photocatalytic activity of Fe3O4/TiO2/Ag composite microspheres is superior to that of Fe3O4/TiO2 due to the dual effects of the enhanced light absorption and reduction of photoelectron-hole pair recombination in TiO2 with the introduction of Ag NPs. Moreover, these magnetic Fe3O4/TiO2/Ag composite microspheres can be completely removed from the dispersion with the help of magnetic separation and reused with little or no loss of catalytic activity.

  9. Preparation of sensitive and recyclable porous Ag/TiO2 composite films for SERS detection

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengyi; Yu, Jiajie; Yang, Jingying; Lv, Xiang; Wang, Tianhe

    2015-12-01

    Porous Ag/TiO2 composite films were prepared by spin coating of titania on normal glass slides and subsequent photochemical deposition of silver nanoparticles (AgNPs). The films were characterized by XRD and FESEM to reveal micro structural and morphological differences between films obtained under varied conditions. The SERS properties of these films were investigated using aqueous crystal violet (CV) as probe molecules. The results indicate that the content of polyethylene glycol (PEG) and photo-reduction time had significant influences on both the microstructure and SERS performance of Ag/TiO2 films. The highest SERS sensitivity that allowed as low as 10-10 M aqueous CV to be detected, was achieved with the PEG/(C4H9O)4Ti molar ratio being 0.08% and with 30 min of UV irradiation. With this film a linear relationship was established through experiment between SERS intensity and CV concentration from 10-10 to 10-5 M, which could be used as a calibration curve for CV concentration measurement. In addition, the film could be reused as a SERS substrate for up to four times without significantly losing SERS sensitivity if a simple regeneration was followed. It is visualized that the Ag/TiO2 film on glass has potentials for being developed into a practical SERS substrate with high sensitivity and good reusability.

  10. Preparation and self-sterilizing properties of Ag@TiO2-styrene-acrylic complex coatings.

    PubMed

    Zhou, Xiang-dong; Chen, Feng; Yang, Jin-tao; Yan, Xiao-hui; Zhong, Ming-qiang

    2013-04-01

    In this study, we report a simple and cost-effective method for self-sterilized complex coatings obtained by Ag@TiO2 particle incorporation into styrene-acrylic latex. The Ag@TiO2 particles were prepared via a coupling agent modification process. The composite latices characterized by transmission electron microscopy (TEM) study were highly homogeneous at the nanometric scale, and the Ag@TiO2 particles were well dispersed and exhibited an intimate contact between both the organic and inorganic components. The Ag@TiO2 nanoparticles significantly enhanced the absorption in the visible region and engendered a good heat-insulating effect of the complex coatings. Moreover, the Ag@TiO2 nanoparticle incorporation into this polymer matrix renders self-sterilized nanocomposite materials upon light excitation, which are tested against Escherichia coli and Staphylococcus aureus. The complex coatings display an impressive performance in the killing of all micro-organisms with a maximum for a Ag@TiO2 loading concentration of 2-5 wt.%. The weathering endurance of the complex coating was also measured.

  11. Mechanisms of Toxicity of Ag Nanoparticles in Comparison to Bulk and Ionic Ag on Mussel Hemocytes and Gill Cells

    PubMed Central

    Katsumiti, Alberto; Gilliland, Douglas; Arostegui, Inmaculada; Cajaraville, Miren P.

    2015-01-01

    Silver nanoparticles (Ag NPs) are increasingly used in many products and are expected to end up in the aquatic environment. Mussels have been proposed as marine model species to evaluate NP toxicity in vitro. The objective of this work was to assess the mechanisms of toxicity of Ag NPs on mussel hemocytes and gill cells, in comparison to ionic and bulk Ag. Firstly, cytotoxicity of commercial and maltose stabilized Ag NPs was screened in parallel with the ionic and bulk forms at a wide range of concentrations in isolated mussel cells using cell viability assays. Toxicity of maltose alone was also tested. LC50 values were calculated and the most toxic Ag NPs tested were selected for a second step where sublethal concentrations of each Ag form were tested using a wide array of mechanistic tests in both cell types. Maltose-stabilized Ag NPs showed size-dependent cytotoxicity, smaller (20 nm) NPs being more toxic than larger (40 and 100 nm) NPs. Maltose alone provoked minor effects on cell viability. Ionic Ag was the most cytotoxic Ag form tested whereas bulk Ag showed similar cytotoxicity to the commercial Ag NPs. Main mechanisms of action of Ag NPs involved oxidative stress and genotoxicity in the two cell types, activation of lysosomal AcP activity, disruption of actin cytoskeleton and stimulation of phagocytosis in hemocytes and increase of MXR transport activity and inhibition of Na-K-ATPase in gill cells. Similar effects were observed after exposure to ionic and bulk Ag in the two cell types, although generally effects were more marked for the ionic form. In conclusion, results suggest that most observed responses were due at least in part to dissolved Ag. PMID:26061169

  12. Fabrication of SWCNT-Ag nanoparticle hybrid included self-assemblies for antibacterial applications.

    PubMed

    Brahmachari, Sayanti; Mandal, Subhra Kanti; Das, Prasanta Kumar

    2014-01-01

    The present article reports the development of soft nanohybrids comprising of single walled carbon nanotube (SWCNT) included silver nanoparticles (AgNPs) having superior antibacterial property. In this regard aqueous dispersing agent of carbon nanotube (CNT) containing a silver ion reducing unit was synthesised by the inclusion of tryptophan and tyrosine within the backbone of the amphiphile. The dispersions were characterized spectroscopically and microscopically using TEM, AFM and Raman spectroscopy. The nanotube-nanoparticle conjugates were prepared by the in situ photoreduction of AgNO3. The phenolate residue and the indole moieties of tyrosine and tryptophan, respectively reduces the sliver ion as well as acts as stabilizing agents for the synthesized AgNPs. The nanohybrids were characterized using TEM and AFM. The antibacterial activity of the nanohybrids was studied against Gram-positive (Bacillus subtilis and Micrococcus luteus) and Gram-negative bacteria (Escherichia coli and Klebsiella aerogenes). The SWCNT dispersions showed moderate killing ability (40-60%) against Gram-positive bacteria however no antibacterial activity was observed against the Gram negative ones. Interestingly, the developed SWCNT-amphiphile-AgNP nanohybrids exhibited significant killing ability (∼90%) against all bacteria. Importantly, the cell viability of these newly developed self-assemblies was checked towards chinese hamster ovarian cells and high cell viability was observed after 24 h of incubation. This specific killing of bacterial cells may have been achieved due to the presence of higher -SH containing proteins in the cell walls of the bacteria. The developed nanohybrids were subsequently infused into tissue engineering scaffold agar-gelatin films and the films similarly showed bactericidal activity towards both kinds of bacterial strains while allowing normal growth of eukaryotic cells on the surface of the films. PMID:25191756

  13. AgI/TiO2 nanocomposites: ultrasound-assisted preparation, visible-light induced photocatalytic degradation of methyl orange and antibacterial activity.

    PubMed

    Xue, Bin; Sun, Tao; Wu, Ji-Kui; Mao, Fang; Yang, Wei

    2015-01-01

    AgI/TiO2 nanocomposites were prepared by an ultrasound-assisted precipitation process and subsequent low-temperature (350°C) calcination. The crystal phase, morphology and optical properties of the AgI/TiO2 nanocomposites were characterized by X-ray diffraction, transmission electron microscopy and UV-vis absorption spectroscopy. After calcination, the crystallite size of AgI nanoparticles in the AgI/TiO2 nanocomposites decreased, and visible light absorption intensity of the AgI/TiO2 nanocomposites was significantly enhanced. The AgI/TiO2 nanocomposites after calcination exhibited the superior photocatalytic activity for methyl orange degradation and killing of Escherichia coli under visible light irradiation. The improvement of photocatalytic activity could be attributed to two reasons, namely, reduced crystallite size and enhanced visible light absorption of AgI nanoparticles in calcined AgI/TiO2 nanocomposites. The trapping experiments demonstrated that superoxide radical (O2(-)) and holes (h(+)) were the main reactive species for the photodegradation of methyl orange under visible light irradiation. The ultrasound-assisted preparation approach is efficient and facile, which promotes large-scale production and application of AgI/TiO2 nanocomposites in photocatalytic degradation of organic pollutants, disinfection and other fields.

  14. SERS detection and antibacterial activity from uniform incorporation of Ag nanoparticles with aligned Si nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Chia-Yun; Hsu, Li-Jen; Hsiao, Po-Hsuan; Yu, Chang-Tze Ricky

    2015-11-01

    We present a facile, reliable and controllable two-steps electroless deposition for uniformly decorating the silver (Ag) nanoparticles (NPs) on the highly aspect ratio of silicon (Si) nanowire arrays. Different from the direct Ag-loading process, which is normally challenged by the non-uniform coating of Ag, the formation of Ag NPs using such innovative electroless process is no longer to be limited at top nanowire surfaces solely; instead, each Ag+/Si interface can initiate the galvanic reduction of Ag+ ions, thus resulting in the uniform formation of Ag NPs on the entire Si nanowire arrays. In addition, systematic explorations of surface-enhanced Raman scattering (SERS) capability as well as antibacterial activity of the Ag/Si-incorporated nanostructures were performed, and the optimized Ag loadings on Si nanowire-based substrates along with the kinetic investigations were further revealed, which may benefit their practical applications in sensing, medical and biological needs.

  15. Facile Decoration of Polyaniline Fiber with Ag Nanoparticles for Recyclable SERS Substrate.

    PubMed

    Mondal, Sanjoy; Rana, Utpal; Malik, Sudip

    2015-05-20

    Facile synthesis of polyaniline@Ag composite has been successfully demonstrated by a simple solution-dipping method using high-aspect-ratio benzene tetracarboxylic acid-doped polyaniline (BDP) fiber as a nontoxic reducing agent as well as template cum stabilizer. In BDP@Ag composite, BDP fibers are decorated with spherical Ag nanoparticles (Ag NPs), and the population of Ag NPs on BDP fibers is controlled by changing the molar concentration of AgNO3. Importantly, Ag-NP-decorated BDP fibers (BDP@Ag composites) have been evolved as a sensitive materials for the detection of trace amounts of 4-mercaptobenzoic acid and rhodamine 6G as an analyte of surface-enhanced Raman scattering (SERS), and the detection limit is down to nanomolar concentrations with excellent recyclability. Furthermore, synthesized BDP@Ag composites are applied simultaneously as an active SERS substrate and a superior catalyst for reduction of 4-nitrothiophenol.

  16. The impact of Ag nanoparticles on the parameters of DSS- cells sensitized by Z907

    NASA Astrophysics Data System (ADS)

    Ibrayev, N. Kh; Aimukhanov, A. K.; Zeinidenov, A. K.

    2016-02-01

    Research of influence of Ag nanoparticles are in-process undertaken on absorption and on parameters CVC DSS-cells sensitized Z907. It is set that with the height of concentration Ag nanoparticles in tape to the concentration of 0.3% wt%. the absorbance of Z907 in a short-wave stripe grew to the value 1,6. It is set that under reaching the concentration of Ag nanoparticles in the cell of value the 0.3% wt%. efficiency of cell increased to 2.2%.

  17. Janus nanoparticles: preparation, characterization, and applications.

    PubMed

    Song, Yang; Chen, Shaowei

    2014-02-01

    In chemical functionalization of colloidal particles, the functional moieties are generally distributed rather homogeneously on the particle surface. Recently, a variety of synthetic protocols have been developed in which particle functionalization may be carried out in a spatially controlled fashion, leading to the production of structurally asymmetrical particles. Janus particles represent the first example in which the two hemispheres exhibit distinctly different chemical and physical properties, which is analogous to the dual-faced Roman god, Janus. Whereas a variety of methods have been reported for the preparation of (sub)micron-sized polymeric Janus particles, it has remained challenging for the synthesis and (unambiguous) structural characterization of much smaller nanometer-sized Janus particles. Herein, several leading methods for the preparation of nanometer-sized Janus particles are discussed and the important properties and applications of these Janus nanoparticles in electrochemistry, sensing, and catalysis are highlighted. Some perspectives on research into functional patchy nanoparticles are also given. PMID:24376180

  18. Mixed-valence metal oxide nanoparticles as electrochemical half-cells: substituting the Ag/AgCl of reference electrodes by CeO(2-x) nanoparticles.

    PubMed

    Nagarale, Rajaram K; Hoss, Udo; Heller, Adam

    2012-12-26

    Cations of mixed valence at surfaces of metal oxide nanoparticles constitute electrochemical half-cells, with potentials intermediate between those of the dissolved cations and those in the solid. When only cations at surfaces of the particles are electrochemically active, the ratio of electrochemically active/all cations is ~0.1 for 15 nm diameter CeO(2-x) particles. CeO(2-x) nanoparticle-loaded hydrogel films on printed carbon and on sputtered gold constitute reference electrodes having a redox potential similar to that of Ag/AgCl in physiological (0.14 M) saline solutions. In vitro the characteristics of potentially subcutaneously implantable glucose monitoring sensors made with CeO(2-x) nanoparticle reference electrodes are undistinguishable from those of sensors made with Ag/AgCl reference electrodes. Cerium is 900 times more abundant than silver, and commercially produced CeO(2-x) nanoparticle solutions are available at prices well below those of the Ag/AgCl pastes used in the annual manufacture of ~10(9) reference electrodes of glucose monitoring strips for diabetes management. PMID:23171288

  19. Fabrication of silver nanoparticles embedded into polyvinyl alcohol (Ag/PVA) composite nanofibrous films through electrospinning for antibacterial and surface-enhanced Raman scattering (SERS) activities.

    PubMed

    Zhang, Zhijie; Wu, Yunping; Wang, Zhihua; Zou, Xueyan; Zhao, Yanbao; Sun, Lei

    2016-12-01

    Silver nanoparticle-embedded polyvinyl alcohol (PVA) nanofibers were prepared through electrospinning technique, using as antimicrobial agents and surface-enhanced Raman scattering (SERS) substrates. Ag nanoparticles (NPs) were synthesized in liquid phase, followed by evenly dispersing in PVA solution. After electrospinning of the mixed solution at room temperature, the PVA embedded with Ag NPs (Ag/PVA) composite nanofibers were obtained. The morphologies and structures of the as-synthesized Ag nanoparticles and Ag/PVA fibers were characterized by the techniques of transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Ag NPs have an average diameter of 13.8nm, were found to be uniformly dispersed in PVA nanofibers. The Ag/PVA nanofibers provided robust antibacterial activities against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) microorganisms. It's also found that Ag/PVA nanofibers make a significant contribution to the high sensitivity of SERS to 4-mercaptophenol (4-MPh) molecules. PMID:27612736

  20. Fabrication of silver nanoparticles embedded into polyvinyl alcohol (Ag/PVA) composite nanofibrous films through electrospinning for antibacterial and surface-enhanced Raman scattering (SERS) activities.

    PubMed

    Zhang, Zhijie; Wu, Yunping; Wang, Zhihua; Zou, Xueyan; Zhao, Yanbao; Sun, Lei

    2016-12-01

    Silver nanoparticle-embedded polyvinyl alcohol (PVA) nanofibers were prepared through electrospinning technique, using as antimicrobial agents and surface-enhanced Raman scattering (SERS) substrates. Ag nanoparticles (NPs) were synthesized in liquid phase, followed by evenly dispersing in PVA solution. After electrospinning of the mixed solution at room temperature, the PVA embedded with Ag NPs (Ag/PVA) composite nanofibers were obtained. The morphologies and structures of the as-synthesized Ag nanoparticles and Ag/PVA fibers were characterized by the techniques of transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Ag NPs have an average diameter of 13.8nm, were found to be uniformly dispersed in PVA nanofibers. The Ag/PVA nanofibers provided robust antibacterial activities against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) microorganisms. It's also found that Ag/PVA nanofibers make a significant contribution to the high sensitivity of SERS to 4-mercaptophenol (4-MPh) molecules.

  1. In situ plasmonic Ag nanoparticle anchored TiO2 nanotube arrays as visible-light-driven photocatalysts for enhanced water splitting

    NASA Astrophysics Data System (ADS)

    Ge, Ming-Zheng; Cao, Chun-Yan; Li, Shu-Hui; Tang, Yu-Xin; Wang, Lu-Ning; Qi, Ning; Huang, Jian-Ying; Zhang, Ke-Qin; Al-Deyab, S. S.; Lai, Yue-Kun

    2016-02-01

    An ultrasonication-assisted in situ deposition strategy was utilised to uniformly decorate plasmonic Ag nanoparticles on vertically aligned TiO2 nanotube arrays (NTAs) to construct a Ag@TiO2 NTA composite. The Ag nanoparticles act as efficient surface plasmon resonance (SPR) photosensitizers to drive photocatalytic water splitting under visible light irradiation. The Ag nanoparticles were uniformly deposited on the surface and inside the highly oriented TiO2 nanotubes. The visible-light-driven hydrogen production activities of silver nanoparticle anchored TiO2 nanotube array photocatalysts were evaluated using methanol as a sacrificial reagent in water under a 500 W Xe lamp with a UV light cutoff filter (λ >= 420 nm). It was found that the hydrogen production rate of the Ag@TiO2 NTAs prepared with ultrasonication-assisted deposition for 5 min was approximately 15 times higher than that of its pristine TiO2 NTAs counterpart. The highly efficient photocatalytic hydrogen evolution is attributed to the SPR effect of Ag for enhanced visible light absorption and boosting the photogenerated electron-hole separation/transfer. This strategy is promising for the design and construction of high efficiency TiO2 based photocatalysts for solar energy conversion.An ultrasonication-assisted in situ deposition strategy was utilised to uniformly decorate plasmonic Ag nanoparticles on vertically aligned TiO2 nanotube arrays (NTAs) to construct a Ag@TiO2 NTA composite. The Ag nanoparticles act as efficient surface plasmon resonance (SPR) photosensitizers to drive photocatalytic water splitting under visible light irradiation. The Ag nanoparticles were uniformly deposited on the surface and inside the highly oriented TiO2 nanotubes. The visible-light-driven hydrogen production activities of silver nanoparticle anchored TiO2 nanotube array photocatalysts were evaluated using methanol as a sacrificial reagent in water under a 500 W Xe lamp with a UV light cutoff filter (λ >= 420 nm

  2. Sample preparation and EFTEM of Meat Samples for Nanoparticle Analysis in Food

    NASA Astrophysics Data System (ADS)

    Lari, L.; Dudkiewicz, A.

    2014-06-01

    Nanoparticles are used in industry for personal care products and the preparation of food. In the latter application, their functions include the prevention of microbes' growth, increase of the foods nutritional value and sensory quality. EU regulations require a risk assessment of the nanoparticles used in foods and food contact materials before the products can reach the market. However, availability of validated analytical methodologies for detection and characterisation of the nanoparticles in food hampers appropriate risk assessment. As part of a research on the evaluation of the methods for screening and quantification of Ag nanoparticles in meat we have tested a new TEM sample preparation alternative to resin embedding and cryo-sectioning. Energy filtered TEM analysis was applied to evaluate thickness and the uniformity of thin meat layers acquired at increasing input of the sample demonstrating that the protocols used ensured good stability under the electron beam, reliable sample concentration and reproducibility.

  3. Surface modification of oleylamine-capped Ag-Cu nanoparticles to fabricate low-temperature-sinterable Ag-Cu nanoink

    NASA Astrophysics Data System (ADS)

    Kim, Na Rae; Jong Lee, Yung; Lee, Changsoo; Koo, Jahyun; Lee, Hyuck Mo

    2016-08-01

    By treating oleylamine (OA)-capped Ag-Cu nanoparticles with tetramethylammonium hydroxide (TMAH), we obtained metal nanoparticles that are suspended in polar solvents and sinterable at low temperatures. The simple process with ultra sonication enables synthesis of monodispersed and high purity nanoparticles in an organic base, where the resulting nanoparticles are dispersible in polar solvents such as ethanol and isopropyl alcohol. To investigate the surface characteristics, we conducted Fourier-transform infrared and zeta-potential analyses. After thermal sintering at 200 °C, which is approximately 150 °C lower than the thermal decomposition temperature of OA, an electrically conductive thin film was obtained. Electrical resistivity measurements of the TMAH-treated ink demonstrate that surface modified nanoparticles have a low resistivity of 13.7 × 10-6 Ω cm. These results confirm the prospects of using low-temperature sinterable nanoparticles as the electrode layer for flexible printed electronics without damaging other stacked polymer layers.

  4. Sensitive and selective detection of Ag+ in aqueous solutions using Fe3O4@Au nanoparticles as smart electrochemical nanosensors.

    PubMed

    Yang, Huicui; Liu, Xiaoxiao; Fei, Ruihua; Hu, Yonggang

    2013-11-15

    Owing to the selective deposition reaction on the surface of magnetic nanoparticles, we reported a simple and selective magnetic electrochemical method for the detection of Ag(+) ions in aqueous solutions. The analyte deposited on the nanoparticles was brought to the surface of a homemade magnetic electrode and detected electrochemically in 0.1 mol/L KCl solution based on the reaction of Ag0 transferred to AgCl. Under the optimal conditions, the linear response range of Ag(+) ions was 0.117-17.7 μmol/L (R(2)=0.9909) with a detection limit of 59 nmol/L (S/N=3). A series of repeatability measurements 1.0 μmol/L Ag(+) gave reproducible results with a relative standard deviation (RSD) of 4.5% (n=11). The interference from other metal cations can be eliminated by adding EDTA as a co-additive to mask the metal cations. The recoveries ranging from 98.6% to 103.99% after standard additions demonstrate that this sensor has great potential in practical applications. The advantages of this developed method include remarkable simplicity, low cost, and no requirement for probe preparation, among others.

  5. Oxidative Stress Mechanisms Caused by Ag Nanoparticles (NM300K) are Different from Those of AgNO3: Effects in the Soil Invertebrate Enchytraeus crypticus

    PubMed Central

    Ribeiro, Maria J.; Maria, Vera L.; Scott-Fordsmand, Janeck J.; Amorim, Mónica J. B.

    2015-01-01

    The mechanisms of toxicity of Ag nanoparticles (NPs) are unclear, in particular in the terrestrial environment. In this study the effects of AgNP (AgNM300K) were assessed in terms of oxidative stress in the soil worm Enchytraeus crypticus, using a range of biochemical markers [catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), glutathione reductase (GR), total glutathione (TG), metallothionein (MT), lipid peroxidation (LPO)]. E. crypticus were exposed during 3 and 7 days (d) to the reproduction EC20, EC50 and EC80 levels of both AgNP and AgNO3. AgNO3 induced oxidative stress earlier (3 d) than AgNP (7 d), both leading to LPO despite the activation of the anti-redox system. MT increased only for AgNP. The Correspondence Analysis showed a clear separation between AgNO3 and AgNP, with e.g., CAT being the main descriptor for AgNP for 7 d. LPO, GST and GPx were for both 3 and 7 d associated with AgNO3, whereas MT and TG were associated with AgNP. These results may reflect a delay in the effects of AgNP compared to AgNO3 due to the slower release of Ag+ ions from the AgNP, although this does not fully explain the observed differences, i.e., we can conclude that there is a nanoparticle effect. PMID:26287225

  6. Vertically oriented TiO(x)N(y) nanopillar arrays with embedded Ag nanoparticles for visible-light photocatalysis.

    PubMed

    Jiang, Weitao; Ullah, Najeeb; Divitini, Giorgio; Ducati, Caterina; Kumar, R Vasant; Ding, Yucheng; Barber, Zoe H

    2012-03-27

    We present a straightforward method to produce highly crystalline, vertically oriented TiO(x)N(y) nanopillars (up to 1 μm in length) with a band gap in the visible-light region. This process starts with reactive dc sputtering to produce a TiN porous film, followed by a simple oxidation process at elevated temperatures in oxygen or air. By controlling the oxidation conditions, the band gap of the prepared TiO(x)N(y) can be tuned to different wavelength within the range of visible light. Furthermore, in order to inhibit carrier recombination to enhance the photocatalytic activity, Ag nanoparticles have been embedded into the nanogaps between the TiO(x)N(y) pillars by photoinduced reduction of Ag(+) (aq) irradiated with visible light. Transmission electron microscopy reveals that the Ag nanoparticles with a diameter of about 10 nm are uniformly dispersed along the pillars. The prepared TiO(x)N(y) nanopillar matrix and Ag:TiO(x)N(y) network show strong photocatalytic activity under visible-light irradiation, evaluated via degradation of Rhodamine B.

  7. Loading Ag nanoparticles on Cd(II) boron imidazolate framework for photocatalysis

    NASA Astrophysics Data System (ADS)

    Liu, Min; Zhang, De-Xiang; Chen, Shumei; Wen, Tian

    2016-05-01

    An amine-functionalized Cd(II) boron imidazolate framework (BIF-77) with three-dimensional open structure has been successfully synthesized, which can load Ag nanoparticles (NPs) for photocatalytic degradation of methylene blue (MB).

  8. In vitro and in vivo study of hazardous effects of Ag nanoparticles and Arginine-treated multi walled carbon nanotubes on blood cells: application in hemodialysis membranes.

    PubMed

    Zare-Zardini, Hadi; Amiri, Ahmad; Shanbedi, Mehdi; Taheri-Kafrani, Asghar; Kazi, S N; Chew, B T; Razmjou, Amir

    2015-09-01

    One of the novel applications of the nanostructures is the modification and development of membranes for hemocompatibility of hemodialysis. The toxicity and hemocompatibility of Ag nanoparticles and arginine-treated multiwalled carbon nanotubes (MWNT-Arg) and possibility of their application in membrane technology are investigated here. MWNT-Arg is prepared by amidation reactions, followed by characterization by FTIR spectroscopy, Raman spectroscopy, and thermogravimetric analysis. The results showed a good hemocompatibility and the hemolytic rates in the presence of both MWNT-Arg and Ag nanoparticles. The hemolytic rate of Ag nanoparticles was lower than that of MWNT-Arg. In vivo study revealed that Ag nanoparticle and MWNT-Arg decreased Hematocrit and mean number of red blood cells (RBC) statistically at concentration of 100 µg mL(-1) . The mean decrease of RBC and Hematocrit for Ag nanoparticles (18% for Hematocrit and 5.8 × 1,000,000/µL) was more than MWNT-Arg (20% for Hematocrit and 6 × 1000000/µL). In addition, MWNT-Arg and Ag nanoparticles had a direct influence on the White Blood Cell (WBC) drop. Regarding both nanostructures, although the number of WBC increased in initial concentration, it decreased significantly at the concentration of 100 µg mL(-1) . It is worth mentioning that the toxicity of Ag nanoparticle on WBC was higher than that of MWNT-Arg. Because of potent antimicrobial activity and relative hemocompatibility, MWNT-Arg could be considered as a new candidate for biomedical applications in the future especially for hemodialysis membranes.

  9. Preparation of Ag{sub 2}S-Graphene nanocomposite from a single source precursor and its surface-enhanced Raman scattering and photoluminescent activity

    SciTech Connect

    Pan Shugang; Liu Xiaoheng Wang Xin

    2011-11-15

    Ag{sub 2}S-Graphene nanocomposite was prepared via a relatively facile hydrothermal method, using a single-source molecular (silver diethyldithiocarbamate [Ag(DDTC)]) as precursor and graphene sheets as a support material. The composite was characterized by X-ray power diffraction, X-ray photoelectron spectroscopy, Field-emission scanning electron microscope, transmission electron microscopy, Fourier transform infrared, Raman spectra and fluorescence spectroscopy. The experimental results show that the Ag{sub 2}S-Graphene nanocomposite displays surface-enhanced Raman scattering (SERS) activity for graphene oxide and reveals relatively better fluorescence property compared with pure Ag{sub 2}S. Highlights: {yields} Ag{sub 2}S nanoparticles are deposited on graphene sheets via a single source precursor. {yields} Graphene oxide is reduced to graphene in the hydrothermal reaction process. {yields} Ag{sub 2}S-Graphene system displays surface-enhanced Raman scattering activity and relatively better fluorescence property.

  10. The role of exopolymeric substances in the bioaccumulation and toxicity of Ag nanoparticles to algae.

    PubMed

    Zhou, Kaijun; Hu, Yi; Zhang, Luqing; Yang, Kun; Lin, Daohui

    2016-01-01

    Exopolymeric substances (EPS) have an important role in bioaccumulation and toxicity of nanoparticles (NPs) to algae, which warrants specific studies. The interaction of EPS with citrate and polyvinyl pyrrolidone (PVP) coated AgNPs (C-AgNPs and P-AgNPs, respectively) and its roles in bioaccumulation and toxicity of the AgNPs to Chlorella pyrenoidosa were investigated. The amino and aromatic carboxylic groups in the EPS were involved in the EPS-AgNP interactions. Compared with Ag(+), C-AgNPs had comparable total bioaccumulation but greater absorption by intact algae with EPS; P-AgNPs had the smallest total bioaccumulation and were mainly adsorbed on algal surfaces. With EPS removed, the total bioaccumulations and surface adsorptions for the three Ag species decreased but the cell internalizations increased; the 96 h half growth inhibition concentrations decreased, indicating EPS alleviated the algal toxicity of Ag. The cell-internalized but not the adsorbed AgNPs could contribute to the nanotoxicity. The EPS could bind both AgNPs and Ag(+), and thus inhibited the cell internalization and the nanotoxicity. However, the EPS-bound Ag on the cell surfaces would migrate along with the algae and be biologically amplified in the aquatic food chains, presenting ecological risks. These results are helpful for understanding the fate and ecological effects of NPs. PMID:27615743

  11. The role of exopolymeric substances in the bioaccumulation and toxicity of Ag nanoparticles to algae

    PubMed Central

    Zhou, Kaijun; Hu, Yi; Zhang, Luqing; Yang, Kun; Lin, Daohui

    2016-01-01

    Exopolymeric substances (EPS) have an important role in bioaccumulation and toxicity of nanoparticles (NPs) to algae, which warrants specific studies. The interaction of EPS with citrate and polyvinyl pyrrolidone (PVP) coated AgNPs (C-AgNPs and P-AgNPs, respectively) and its roles in bioaccumulation and toxicity of the AgNPs to Chlorella pyrenoidosa were investigated. The amino and aromatic carboxylic groups in the EPS were involved in the EPS-AgNP interactions. Compared with Ag+, C-AgNPs had comparable total bioaccumulation but greater absorption by intact algae with EPS; P-AgNPs had the smallest total bioaccumulation and were mainly adsorbed on algal surfaces. With EPS removed, the total bioaccumulations and surface adsorptions for the three Ag species decreased but the cell internalizations increased; the 96 h half growth inhibition concentrations decreased, indicating EPS alleviated the algal toxicity of Ag. The cell-internalized but not the adsorbed AgNPs could contribute to the nanotoxicity. The EPS could bind both AgNPs and Ag+, and thus inhibited the cell internalization and the nanotoxicity. However, the EPS-bound Ag on the cell surfaces would migrate along with the algae and be biologically amplified in the aquatic food chains, presenting ecological risks. These results are helpful for understanding the fate and ecological effects of NPs. PMID:27615743

  12. The role of exopolymeric substances in the bioaccumulation and toxicity of Ag nanoparticles to algae

    NASA Astrophysics Data System (ADS)

    Zhou, Kaijun; Hu, Yi; Zhang, Luqing; Yang, Kun; Lin, Daohui

    2016-09-01

    Exopolymeric substances (EPS) have an important role in bioaccumulation and toxicity of nanoparticles (NPs) to algae, which warrants specific studies. The interaction of EPS with citrate and polyvinyl pyrrolidone (PVP) coated AgNPs (C-AgNPs and P-AgNPs, respectively) and its roles in bioaccumulation and toxicity of the AgNPs to Chlorella pyrenoidosa were investigated. The amino and aromatic carboxylic groups in the EPS were involved in the EPS-AgNP interactions. Compared with Ag+, C-AgNPs had comparable total bioaccumulation but greater absorption by intact algae with EPS; P-AgNPs had the smallest total bioaccumulation and were mainly adsorbed on algal surfaces. With EPS removed, the total bioaccumulations and surface adsorptions for the three Ag species decreased but the cell internalizations increased; the 96 h half growth inhibition concentrations decreased, indicating EPS alleviated the algal toxicity of Ag. The cell-internalized but not the adsorbed AgNPs could contribute to the nanotoxicity. The EPS could bind both AgNPs and Ag+, and thus inhibited the cell internalization and the nanotoxicity. However, the EPS-bound Ag on the cell surfaces would migrate along with the algae and be biologically amplified in the aquatic food chains, presenting ecological risks. These results are helpful for understanding the fate and ecological effects of NPs.

  13. Reducing Strength Prevailing at Root Surface of Plants Promotes Reduction of Ag+ and Generation of Ag0/Ag2O Nanoparticles Exogenously in Aqueous Phase

    PubMed Central

    Pardha-Saradhi, Peddisetty; Yamal, Gupta; Peddisetty, Tanuj; Sharmila, Peddisetty; Nagar, Shilpi; Singh, Jyoti; Nagarajan, Rajamani; Rao, Kottapalli S.

    2014-01-01

    Potential of root system of plants from wide range of families to effectively reduce membrane impermeable ferricyanide to ferrocyanide and blue coloured 2,6-dichlorophenol indophenol (DCPIP) to colourless DCPIPH2 both under non-sterile and sterile conditions, revealed prevalence of immense reducing strength at root surface. As generation of silver nanoparticles (NPs) from Ag+ involves reduction, present investigations were carried to evaluate if reducing strength prevailing at surface of root system can be exploited for reduction of Ag+ and exogenous generation of silver-NPs. Root system of intact plants of 16 species from 11 diverse families of angiosperms turned clear colorless AgNO3 solutions, turbid brown. Absorption spectra of these turbid brown solutions showed silver-NPs specific surface plasmon resonance peak. Transmission electron microscope coupled with energy dispersive X-ray confirmed the presence of distinct NPs in the range of 5–50 nm containing Ag. Selected area electron diffraction and powder X-ray diffraction patterns of the silver NPs showed Bragg reflections, characteristic of crystalline face-centered cubic structure of Ag0 and cubic structure of Ag2O. Root system of intact plants raised under sterile conditions also generated Ag0/Ag2O-NPs under strict sterile conditions in a manner similar to that recorded under non-sterile conditions. This revealed the inbuilt potential of root system to generate Ag0/Ag2O-NPs independent of any microorganism. Roots of intact plants reduced triphenyltetrazolium to triphenylformazon and impermeable ferricyanide to ferrocyanide, suggesting involvement of plasma membrane bound dehydrogenases in reduction of Ag+ and formation of Ag0/Ag2O-NPs. Root enzyme extract reduced triphenyltetrazolium to triphenylformazon and Ag+ to Ag0 in presence of NADH, clearly establishing potential of dehydrogenases to reduce Ag+ to Ag0, which generate Ag0/Ag2O-NPs. Findings presented in this manuscript put forth a novel, simple

  14. A simple method for preparation of Ag nanofilm used as active, stable, and biocompatible SERS substrate by using electrostatic self-assembly.

    PubMed

    Liu, Renming; Si, Minzhen; Kang, Yipu; Zi, Xingfa; Liu, Zhenquan; Zhang, Deqing

    2010-03-01

    A new SERS-active Ag nanofilm on the surface of a glass slide has been prepared by a low-cost electrochemical strategy using polyvinyl alcohol (PVA) at a proper voltage. The two-dimensional morphology of the Ag nanofilm has been examined by scanning electron microscopy (SEM). The average size of the aggregated particles on the surface of the Ag nanofilm is up to ca. 200+/-50 nm, which is much larger than that of PVA-protected Ag colloidal nanoparticles (PVA-Ag CNPs, 45+/-8 nm). Meanwhile, many nano-scale regions with average sizes of ca. 300+/-50 nm are formed between the adjacent Ag nanoparticles. By the SERS measurements of human serum (HS) and hemoglobin (Hb), this Ag nanofilm is shown to be an excellent SERS substrate with good stability and biocompatibility. As the fabrication process of this SERS substrate is simple and inexpensive, this method may be used in large-scale preparation of substrates that have been widely applied in Raman analysis. In addition, this SERS-active Ag nanofilm can serve as a novel SERS substrate in biochemical analysis due to the biocompatibility.

  15. A nanosized Ag-silica hybrid complex prepared by γ-irradiation activates the defense response in Arabidopsis

    NASA Astrophysics Data System (ADS)

    Chu, Hyosub; Kim, Hwa-Jung; Su Kim, Joong; Kim, Min-Soo; Yoon, Byung-Dae; Park, Hae-Jun; Kim, Cha Young

    2012-02-01

    Silver nanoparticles have antimicrobial activity against many pathogenic microbes. Here, the preparation of a nanosized Ag-silica hybrid complex (NSS) prepared by γ-irradiation is described. The effects of both NSS and reduced Ag nanoparticles (Ag 0) on the growth of the model plant Arabidopsis thaliana were tested. The application of 1-10 ppm NSS complex improved Arabidopsis growth in soil, whereas 100 ppm NSS resulted in weakly curled leaves. In addition, supplementation of Murashige and Skoog (MS) growth medium with 1 ppm NSS promoted the root growth of Arabidopsis seedlings, but root growth was inhibited by supplementation with 10 ppm NSS. To investigate whether the NSS complex could induce plant defense responses, the expression of pathogenesis-related ( PR) genes that are implicated in systemic acquired resistance (SAR) in Arabidopsis plants was examined. PR1, PR2 and PR5 were significantly up-regulated by each application of 10 ppm NSS complex or Ag 0 to the rosette leaves. Furthermore, pretreatment with the NSS complex induced more pathogen resistance to the virulent pathogen Pseudomonas syringae pv. tomato DC3000 ( Pst) compared to water treatment in Arabidopsis plants.

  16. Fabrication of uniformly dispersed Ag nanoparticles loaded TiO{sub 2} nanotube arrays for enhancing photoelectrochemical and photocatalytic performances under visible light irradiation

    SciTech Connect

    Yi, Junhui; Zhang, Shengsen; Wang, Hongjuan; Yu, Hao; Peng, Feng

    2014-12-15

    Graphical abstract: Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO{sub 2} nanotube arrays (NTs) through a simple polyol method, which exhibited the enhanced photoelectrochemical and photocatalytic performances under visible-light irradiation due to the more effective separation of photo-generated electron–hole pairs and faster interfacial charge transfer. - Highlights: • Highly dispersed Ag nanoparticles (NPs) are successfully prepared by polyol method. • Ag NPs are uniformly loaded on the surface of the TiO{sub 2} nanotube arrays (NTs). • Ag/TiO{sub 2}-NTs exhibit the enhanced photocatalytic activity under visible-light. • The enhanced photocurrent is explained by electrochemical impedance spectroscopy. - Abstract: Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO{sub 2} nanotube arrays (NTs) through a simple polyol method. The as-prepared Ag/TiO{sub 2}-NTs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV–vis diffusion reflectance spectroscopy. Photoelectrochemical behaviors were investigated via photocurrent response and electrochemical impedance spectroscopy (EIS). Photocatalytic activity of Ag/TiO{sub 2}-NTs was evaluated by degradation of acid orange II under visible light irradiation. The results showed that photocatalytic efficiency of Ag/TiO{sub 2}-NTs is more than 5 times higher than that of pure TiO{sub 2} NTs. Comparing with the electrochemical deposition method, the photocatalytic activity of Ag/TiO{sub 2}-NTs prepared by polyol method has been obviously increased.

  17. Room-temperature solution synthesis of Ag nanoparticle functionalized molybdenum oxide nanowires and their catalytic applications

    NASA Astrophysics Data System (ADS)

    Dong, Wenjun; Huang, Huandi; Zhu, Yanjun; Li, Xiaoyun; Wang, Xuebin; Li, Chaorong; Chen, Benyong; Wang, Ge; Shi, Zhan

    2012-10-01

    A simple chemical solution route for the synthesis of large-scale high-quality Ag nanoparticle functionalized molybdenum oxide nanowire at room temperature has been developed. In the synthesis, the protonated amine was intercalated into the molybdenum bronze layers to reduce the electrostatic force of the lamellar structures, and then the Ag nanoparticle functionalized long nanowires could be easily induced by a redox reaction between a molybdenum oxide-amine intermediate and Ag+ at room temperature. The intercalation lamellar structures improved the nucleation and growth of the Ag nanoparticles, with the result that uniform Ag nanoparticles occurred on the surface of the MoO3 nanowire. In this way Ag nanoparticles with average sizes of around 6 nm, and high-purity nanowires with mean diameter of around 50 nm and with typical lengths of several tens to hundreds of micrometers were produced. The heteronanostructured nanowires were intricately and inseparably connected to each other with hydrogen bonds and/or bridge oxygen atoms and packed together, forming a paper-like porous network film. The Ag-MoO3 nanowire film performs a promoted catalytic property for the epoxidation of cis-cyclooctene, and the heteronanostructured nanowire film sensor shows excellent sensing performance to hydrogen and oxygen at room temperature.

  18. Impact of Ag and Al₂O₃ nanoparticles on soil organisms: in vitro and soil experiments.

    PubMed

    Fajardo, C; Saccà, M L; Costa, G; Nande, M; Martin, M

    2014-03-01

    In vitro analyses were conducted to assess the impact of Al2O3 and Ag nanoparticles on two common soil bacteria, Bacillus cereus and Pseudomonas stutzeri. Al2O3 nanoparticles did not show significant toxicity at any dose or time assayed, whereas exposure to 5 mg L(-1) Ag nanoparticles for 48 h caused bactericidal effects. Moreover, alterations at the morphological level were observed by transmission electron microscopy (TEM); Ag but not Al2O3 nanoparticles evoked the entrance of B. cereus cells in an early sporulation stage and both nanoparticles penetrated P. stutzeri cells. At the molecular level, a dramatic increase (8.2-fold) in katB gene expression was found in P. stutzeri following Al2O3 nanoparticles exposure, indicative of an oxidative stress-defence system enhancement in this bacterium. In the microcosm experiment, using two different natural soils, Al2O3 or Ag nanoparticles did not affect the Caenorhabditis elegans toxicity endpoints growth, survival, or reproduction. However, differences in microbial phylogenetic compositions were detected by fluorescence in situ hybridization (FISH). The use of katB- and pykA-based sequences showed that the microbial transcriptional response to nanoparticle exposure decreased, suggesting a decrease in cellular activity. These changes were attributable to both the nanoparticles treatment and soil characteristics, highlighting the importance of considering the soil matrix on a case by case basis.

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

    SciTech Connect

    Han, Kun; Miao, Peng; Tang, Yuguo; Tong, Hui; Zhu, Xiaoli; Liu, Tao; Cheng, Wenbo

    2014-02-03

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

  20. In situ plasmonic Ag nanoparticle anchored TiO2 nanotube arrays as visible-light-driven photocatalysts for enhanced water splitting.

    PubMed

    Ge, Ming-Zheng; Cao, Chun-Yan; Li, Shu-Hui; Tang, Yu-Xin; Wang, Lu-Ning; Qi, Ning; Huang, Jian-Ying; Zhang, Ke-Qin; Al-Deyab, S S; Lai, Yue-Kun

    2016-03-01

    An ultrasonication-assisted in situ deposition strategy was utilised to uniformly decorate plasmonic Ag nanoparticles on vertically aligned TiO2 nanotube arrays (NTAs) to construct a Ag@TiO2 NTA composite. The Ag nanoparticles act as efficient surface plasmon resonance (SPR) photosensitizers to drive photocatalytic water splitting under visible light irradiation. The Ag nanoparticles were uniformly deposited on the surface and inside the highly oriented TiO2 nanotubes. The visible-light-driven hydrogen production activities of silver nanoparticle anchored TiO2 nanotube array photocatalysts were evaluated using methanol as a sacrificial reagent in water under a 500 W Xe lamp with a UV light cutoff filter (λ ≥ 420 nm). It was found that the hydrogen production rate of the Ag@TiO2 NTAs prepared with ultrasonication-assisted deposition for 5 min was approximately 15 times higher than that of its pristine TiO2 NTAs counterpart. The highly efficient photocatalytic hydrogen evolution is attributed to the SPR effect of Ag for enhanced visible light absorption and boosting the photogenerated electron-hole separation/transfer. This strategy is promising for the design and construction of high efficiency TiO2 based photocatalysts for solar energy conversion. PMID:26878901

  1. A novel green synthesis of Fe3O4-Ag core shell recyclable nanoparticles using Vitis vinifera stem extract and its enhanced antibacterial performance

    NASA Astrophysics Data System (ADS)

    Venkateswarlu, Sada; Natesh Kumar, B.; Prathima, B.; Anitha, K.; Jyothi, N. V. V.

    2015-01-01

    We described a novel and eco-friendly method for preparing Fe3O4-Ag core shell nanoparticles (CSNPs) with high magnetism and potent antibacterial activity. The Fe3O4-Ag CSNPs were obtained using waste material of Vitis vinifera (grape) stem extract as the green solvent, reducing and capping agent. The result recorded from X-ray powder diffraction (XRD), UV-vis spectrum, energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) supports the biosynthesis and characterization of Fe3O4-Ag CSNPs. From transmission electron microscopy (TEM) the size of the Fe3O4-Ag nanoparticles was measured below 50 nm; high-resolution TEM (HRTEM) indicates the core shell structure; and selected area electron diffraction (SAED) has revealed polycrystalline nature. Vibrating sample magnetometer (VSM) shows the ferromagnetic nature of Fe3O4-Ag CSNPs at room temperature with saturation magnetization of 15.74 emu/g. Further, these biogenic nanoparticles were highly hazardous to microorganisms. The antibacterial activity of biogenic Fe3O4-Ag CSNPs showed potent inhibitory activity against both Gram-positive and Gram-negative pathogens. These nanoparticles may also be reusable because of its excellent ferromagnetic property.

  2. Effect of Ag nanoparticle concentration on the electrical and ferroelectric properties of Ag/P(VDF-TrFE) composite films

    PubMed Central

    Paik, Haemin; Choi, Yoon-Young; Hong, Seungbum; No, Kwangsoo

    2015-01-01

    We investigated the effect of the Ag nanoparticles on the ferroelectric and piezoelectric properties of Ag/poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) composite films. We found that the remanent polarization and direct piezoelectric coefficient increased up to 12.14 μC/cm2 and 20.23 pC/N when the Ag concentration increased up to 0.005 volume percent (v%) and decreased down to 9.38 μC/cm2 and 13.45 pC/N when it increased up to 0.01 v%. Further increase in Ag concentration resulted in precipitation of Ag phase and significant leakage current that hindered any meaningful measurement of the ferroelectric and piezoelectric properties. 46% increase of the remanent polarization value and 27% increase of the direct piezoelectric coefficient were observed in the film with the 0.005 v% of the Ag nanoparticles added without significant changes to the crystalline structure confirmed by both X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) experiments. These enhancements of both the ferroelectric and piezoelectric properties are attributed to the increase in the effective electric field induced by the reduction in the effective volume of P(VDF-TrFE) that results in more aligned dipoles. PMID:26336795

  3. Effect of Ag nanoparticle concentration on the electrical and ferroelectric properties of Ag/P(VDF-TrFE) composite films

    DOE PAGES

    Paik, Haemin; Choi, Yoon -Young; Hong, Seungbum; No, Kwangsoo

    2015-09-04

    We investigated the effect of the Ag nanoparticles on the ferroelectric and piezoelectric properties of Ag/poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) composite films. We found that the remanent polarization and direct piezoelectric coefficient increased up to 12.14 μC/cm2 and 20.23 pC/N when the Ag concentration increased up to 0.005 volume percent (v%) and decreased down to 9.38 μC/cm2 and 13.45 pC/N when it increased up to 0.01 v%. Further increase in Ag concentration resulted in precipitation of Ag phase and significant leakage current that hindered any meaningful measurement of the ferroelectric and piezoelectric properties. 46% increase of the remanent polarization value and 27% increasemore » of the direct piezoelectric coefficient were observed in the film with the 0.005 v% of the Ag nanoparticles added without significant changes to the crystalline structure confirmed by both X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) experiments. The enhancements of both the ferroelectric and piezoelectric properties are attributed to the increase in the effective electric field induced by the reduction in the effective volume of P(VDF-TrFE) that results in more aligned dipoles.« less

  4. Effect of Ag nanoparticle concentration on the electrical and ferroelectric properties of Ag/P(VDF-TrFE) composite films

    SciTech Connect

    Paik, Haemin; Choi, Yoon -Young; Hong, Seungbum; No, Kwangsoo

    2015-09-04

    We investigated the effect of the Ag nanoparticles on the ferroelectric and piezoelectric properties of Ag/poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) composite films. We found that the remanent polarization and direct piezoelectric coefficient increased up to 12.14 μC/cm2 and 20.23 pC/N when the Ag concentration increased up to 0.005 volume percent (v%) and decreased down to 9.38 μC/cm2 and 13.45 pC/N when it increased up to 0.01 v%. Further increase in Ag concentration resulted in precipitation of Ag phase and significant leakage current that hindered any meaningful measurement of the ferroelectric and piezoelectric properties. 46% increase of the remanent polarization value and 27% increase of the direct piezoelectric coefficient were observed in the film with the 0.005 v% of the Ag nanoparticles added without significant changes to the crystalline structure confirmed by both X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) experiments. The enhancements of both the ferroelectric and piezoelectric properties are attributed to the increase in the effective electric field induced by the reduction in the effective volume of P(VDF-TrFE) that results in more aligned dipoles.

  5. Photocatalytic performances and activities of Ag-doped CuFe{sub 2}O{sub 4} nanoparticles

    SciTech Connect

    Zhu, Zhengru; Li, Xinyong; Zhao, Qidong; Li, Yonghua; Sun, Caizhi; Cao, Yongqiang

    2013-08-01

    Graphical abstract: - Highlights: • CuFe{sub 2}O{sub 4} nanocrystals were synthesized by a co-precipitation method. • Ag/CuFe{sub 2}O{sub 4} catalyst was prepared by the wetness impregnation strategy. • The structural properties of Ag/CuFe{sub 2}O{sub 4} were investigated by XRD, TEM, DRS, and XPS techniques. • Ag/CuFe{sub 2}O{sub 4} has higher photocatalytic activity. - Abstract: In this work, CuFe{sub 2}O{sub 4} nanoparticles were synthesized by a chemical co-precipitation route. The Ag/CuFe{sub 2}O{sub 4} catalyst was prepared based on the CuFe{sub 2}O{sub 4} nanoparticles by the incipient wetness impregnation strategy, which showed excellent photoelectric property and catalytic activity. The structural properties of these samples were systematically investigated by X-ray powder diffraction (XRD), transmission electronic microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) techniques. The photo-induced charge separation in the samples was demonstrated by surface photovoltage (SPV) measurement. The photocatalytic degradation of 4-CP by the Ag/CuFe{sub 2}O{sub 4} and CuFe{sub 2}O{sub 4} samples were comparatively studied under xenon lamp irradiation. The results indicate that the Ag/CuFe{sub 2}O{sub 4} sample exhibited the higher efficiency for the degradation of 4-CP.

  6. Graphite-like C3N4 modified Ag3PO4 nanoparticles with highly enhanced photocatalytic activities under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Xiu, Zhiliang; Bo, Hai; Wu, Yongzhong; Hao, Xiaopeng

    2014-01-01

    Graphite-like C3N4 (g-C3N4) modified Ag3PO4 nanoparticles with highly enhanced photocatalytic activities under visible light irradiation (λ ≥ 400 nm) compared to the bare Ag3PO4 nanoparticles were prepared by a facile chemisorption method. The resulting C3N4/Ag3PO4 composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible diffuse reflectance spectra (DRS). Enhanced charge separation efficiency was confirmed by electrochemical impedance spectroscopy (EIS) measurements. The enhanced photocatalytic activities were mainly ascribed to the synergistic effect between C3N4 and Ag3PO4 which led to an improved separation efficiency of electron-hole pairs. The high-efficient hybrid photocatalysts are expected to show considerable potential applications in wastewater treatment and water splitting.

  7. Ag@Au core-shell nanoparticles synthesized by pulsed laser ablation in water: Effect of plasmon coupling and their SERS performance.

    PubMed

    Vinod, M; Gopchandran, K G

    2015-01-01

    Ag@Au core-shell nanoparticles are synthesised by pulsed laser ablation in water using low energy laser pulses. The plasmon characteristics of these core-shell nanoparticles are found to be highly sensitive to the thickness of Au coating. In the synthesis, at first silver nanocolloid was prepared by ablating Ag target and then it is followed by ablation of Au target for different time durations to form Ag@Au core-shell nanostructures. The effect of plasmon-plasmon coupling on the absorption spectra is investigated by decreasing the effective distance between the nanoparticles. This is achieved by reducing the total volume of the colloidal suspension by simple evaporation of water, the solvent used. The suitability of these core-shell nanostructures for application as surface enhanced Raman scattering substrates are tested with crystal violet as probe molecules. Influence of plasmon coupling on the enhancement of Raman bands is found to be different for different bands.

  8. Silica Cladding of Ag Nanoparticles for High Stability and Surface-Enhanced Raman Spectroscopy Performance

    NASA Astrophysics Data System (ADS)

    Zhao, Miaomiao; Guo, Hao; Liu, Wenyao; Tang, Jun; Wang, Lei; Zhang, Binzhen; Xue, Chenyang; Liu, Jun; Zhang, Wendong

    2016-09-01

    For high-precision biochemical sensing, surface-enhanced Raman spectroscopy (SERS) has been demonstrated to be a highly sensitive spectroscopic analytical method and Ag is considered to be the best material for SERS performance. Due to the high surface activity of Ag nanoparticles, the high stability of Ag nanostructures, especially in moist environments, is one of the key issues that need to be solved. A method for silica (SiO2) cladding of Ag nanoparticles (NPs) is demonstrated here for high sensitivity and long-term stability when putted in aqueous solution. The chemically inert, transparent, hydrophilic, and bio-compatible SiO2 surface acts as the protection layer for the Ag nanoparticles, which can also enhance the Raman intensity to a certain extent. In our study, the Ag@SiO2 core-shell substrate can detect crystal violet solutions with molar concentrations down to 10-12 M. After 24 h of immersion, the reduction in Raman scattering intensity is about 85 % for sole Ag NP films, compared to 12 % for the Ag coated with a 10-nm SiO2 layer. This thickness was found to be optimum for Ag@SiO2 core-shell substrates with long-term stability and high SERS activity.

  9. Silica Cladding of Ag Nanoparticles for High Stability and Surface-Enhanced Raman Spectroscopy Performance.

    PubMed

    Zhao, Miaomiao; Guo, Hao; Liu, Wenyao; Tang, Jun; Wang, Lei; Zhang, Binzhen; Xue, Chenyang; Liu, Jun; Zhang, Wendong

    2016-12-01

    For high-precision biochemical sensing, surface-enhanced Raman spectroscopy (SERS) has been demonstrated to be a highly sensitive spectroscopic analytical method and Ag is considered to be the best material for SERS performance. Due to the high surface activity of Ag nanoparticles, the high stability of Ag nanostructures, especially in moist environments, is one of the key issues that need to be solved. A method for silica (SiO2) cladding of Ag nanoparticles (NPs) is demonstrated here for high sensitivity and long-term stability when putted in aqueous solution. The chemically inert, transparent, hydrophilic, and bio-compatible SiO2 surface acts as the protection layer for the Ag nanoparticles, which can also enhance the Raman intensity to a certain extent. In our study, the Ag@SiO2 core-shell substrate can detect crystal violet solutions with molar concentrations down to 10(-12) M. After 24 h of immersion, the reduction in Raman scattering intensity is about 85 % for sole Ag NP films, compared to 12 % for the Ag coated with a 10-nm SiO2 layer. This thickness was found to be optimum for Ag@SiO2 core-shell substrates with long-term stability and high SERS activity. PMID:27637895

  10. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles.

    PubMed

    Chaffin, Elise; O'Connor, Ryan T; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ∼410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods. PMID:27497571

  11. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles

    NASA Astrophysics Data System (ADS)

    Chaffin, Elise; O'Connor, Ryan T.; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ˜410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods.

  12. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles.

    PubMed

    Chaffin, Elise; O'Connor, Ryan T; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ∼410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods.

  13. Preparation and gas sensing property of Ag-supported vanadium oxide nanotubes

    NASA Astrophysics Data System (ADS)

    Jin, Wei; Yan, Shilin; Chen, Wen; Yang, Shuang; Zhao, Chunxia; Dai, Ying

    2014-03-01

    A facile microwave irradiation was used to synthesize Ag nanoparticle supported on vanadium oxide nanotubes (VONTs) in this paper. The VONTs on alumina tube installed with Pt electrodes were tested for gas sensing towards C2H5OH, NH3 and C6H5CH3 gases. Detailed studies showed that the sensing capabilities were greatly enhanced in comparison to those of pure nanotubes. It was found that the Ag nanoparticles supported on VONTs sensing films exhibited a high C2H5OH selectivity compared with NH3 and C6H5CH3 gases. When the sensor is exposed to C2H5OH, the ethanol molecules interact with the preadsorbed oxygen ions on the Ag nanoparticles surface. The ethanol oxidation on the Ag nanoparticles leads to the transfer of electrons into the semiconducting VONTs and this is reflected as the change in conductance of sensor. The presence of Ag nanoparticles on the surface of VONTs serves to enhance the C2H5OH oxidation due to a higher oxygen ion-chemisorption on the conductive Ag nanoparticle surfaces.

  14. Facile method to prepare poly(S-co-HEA)/Ag nanocomposite particles with high efficient catalytic activity and surface enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Chao, Zhiyin; Wang, Lan; Song, Linyong; Zhou, Yifeng; Nie, Wangyan; Chen, Pengpeng

    2015-02-01

    Surface hydroxyl-functionalized poly(styrene-co-hydroxyethyl acrylate) [P(S-co-HEA)] microsphere were used to prepare P(S-co-HEA)/silver composite particles. Based on the weak interaction between silver ions and hydroxyl, silver ions were adsorbed onto the polymer surface and reduced by diethanolamine (DEA). The morphology of P(S-co-HEA)/Ag was easily controlled by the molar ratio of DEA/AgNO3. The composite particles were characterized by SEM, XRD, and UV-vis spectroscopy. The obtained P(S-co-HEA)/Ag particles with small and denser silver nanoparticles showed a high efficient activity to catalyze reduction of methylene blue (MB). While the P(S-co-HEA)/Ag particles with big and denser silver nanoparticles showed highly sensitive Raman enhanced performance.

  15. Bimetallic Ag-Au nanoparticles: Extracting meaningful optical constants from the surface-plasmon extinction spectrum

    NASA Astrophysics Data System (ADS)

    Moskovits, M.; Srnova-Sloufova, I.; Vlckova, B.

    2002-06-01

    We report an approach for extracting the optical constants of bimetallic Ag-Au nanoparticles from the measured surface-plasmon (SP) extinction spectra. The dielectric function of the metal is expressed as an analytic function of the wavelength in which the interband (and all other non-Drude) contributions to the dielectric function are represented by a sum of Lorentz functions. This expression is then used to fit the experimental extinction spectra to appropriate functions based on Mie theory. Three Lorentz functions (plus a Drude term) were found to be sufficient to reproduce the dielectric functions of Ag and Au [P. B. Johnson and R. W. Christy, Phys. Rev. B 6, 4370 (1972)] over the entire 0.6-6.5 eV range reported. With functions of this type, an excellent multiparameter fit of the measured extinction spectrum of colloidal Ag was obtained. Extinction spectra of a series of (Ag)Au hydrosols, prepared by reducing a gold precursor in the presence of previously synthesized silver seed particles with Au mole fractions ranging from 0.1 to 0.8, were measured. The extinction spectra show a single band (attributed to the surface plasmon) for all of the colloids produced, suggesting alloy formation. Transmission electron microscopy (TEM) images, however, indicate clear core-shell contrast for nanoparticles with Au mole fractions 0.4 and higher. With a presumed particle structure consisting of Ag core and Ag/Au alloy shell, very good fits were obtained for all of the measured extinction spectra by using a fitting strategy that restricted the number of parameters allowed to vary freely in the aforementioned dielectric function. The values of the dielectric function of the presumed shells were extracted in this manner as a function of wavelength. For particles with Au mole fraction 0.1-0.3, the results suggest an incompletely formed shell. For particles with higher Au mole fractions, the dielectric function of the shell gradually approaches that of Au. Overall, the results

  16. Subsurface synthesis and characterization of Ag nanoparticles embedded in MgO.

    PubMed

    Vilayurganapathy, S; Devaraj, A; Colby, R; Pandey, A; Varga, T; Shutthanandan, V; Manandhar, S; El-Khoury, P Z; Kayani, Asghar; Hess, W P; Thevuthasan, S

    2013-03-01

    Metal nanoparticles exhibit a localized surface plasmon resonance (LSPR) which is very sensitive to the size and shape of the nanoparticle and the surrounding dielectric medium. The coupling between the electromagnetic radiation and the localized surface plasmon in metallic nanoparticles results in a sizable enhancement of the incident fields, making them possible candidates for plasmonic applications. In particular, partially exposed metallic nanoparticles distributed in a dielectric matrix can provide prime locations for LSPR spectroscopy and sensing. We report the synthesis and characterization of a plasmonic substrate consisting of Ag nanoparticles partially buried in MgO. Ag nanoparticles of different shapes and size distributions were synthesized below the surface of MgO by implanting 200 keV Ag(+) ions followed by annealing at 1000 °C for 10 and 30 h. A detailed optical and structural characterization was carried out to understand the evolution of the Ag nanoparticle and size distribution inside the MgO matrix. Micro x-ray diffraction (Micro-XRD) was employed to investigate the structural properties and estimate the crystallite size. The nanoparticles evolved from a spherical to a faceted morphology with annealing time, assuming an octahedral shape truncated at the (001) planes, as visualized from aberration-corrected transmission electron microscopy (TEM) images. The nanoparticles embedded in MgO were shown to be pure metallic Ag using atom probe tomography (APT). The nanoparticles were partially exposed to the surface by employing plasma etch techniques to remove the overlaying MgO. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to study the surface morphology and obtain a height distribution for the partially exposed nanoparticles. PMID:23403363

  17. Subsurface synthesis and characterization of Ag nanoparticles embedded in MgO

    NASA Astrophysics Data System (ADS)

    Vilayurganapathy, S.; Devaraj, A.; Colby, R.; Pandey, A.; Varga, T.; Shutthanandan, V.; Manandhar, S.; El-Khoury, P. Z.; Kayani, Asghar; Hess, W. P.; Thevuthasan, S.

    2013-03-01

    Metal nanoparticles exhibit a localized surface plasmon resonance (LSPR) which is very sensitive to the size and shape of the nanoparticle and the surrounding dielectric medium. The coupling between the electromagnetic radiation and the localized surface plasmon in metallic nanoparticles results in a sizable enhancement of the incident fields, making them possible candidates for plasmonic applications. In particular, partially exposed metallic nanoparticles distributed in a dielectric matrix can provide prime locations for LSPR spectroscopy and sensing. We report the synthesis and characterization of a plasmonic substrate consisting of Ag nanoparticles partially buried in MgO. Ag nanoparticles of different shapes and size distributions were synthesized below the surface of MgO by implanting 200 keV Ag+ ions followed by annealing at 1000 °C for 10 and 30 h. A detailed optical and structural characterization was carried out to understand the evolution of the Ag nanoparticle and size distribution inside the MgO matrix. Micro x-ray diffraction (Micro-XRD) was employed to investigate the structural properties and estimate the crystallite size. The nanoparticles evolved from a spherical to a faceted morphology with annealing time, assuming an octahedral shape truncated at the (001) planes, as visualized from aberration-corrected transmission electron microscopy (TEM) images. The nanoparticles embedded in MgO were shown to be pure metallic Ag using atom probe tomography (APT). The nanoparticles were partially exposed to the surface by employing plasma etch techniques to remove the overlaying MgO. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to study the surface morphology and obtain a height distribution for the partially exposed nanoparticles.

  18. New SERS-active alumina-based sorbents containing Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Yurova, Nadezhda S.; Markina, Natalia E.; Galushka, Victor V.; Burashnikova, Marina M.; Zakharevich, Andrey M.; Markin, Alexey V.; Rusanova, Tatiana Y.

    2016-04-01

    New SERS-active materials were obtained by preparation of alumina with embedded silver nanoparticles and their application both as sorbents for pre-concentration and SERS platforms was studied. The influence of ionic strength on Ag NPs size, absorption spectra and SERS signal was investigated. Synthesized materials were examined by Raman spectroscopy, scanning electron microscopy, and UV-visible spectroscopy. The optimal conditions for SERSmeasurements were chosen. Synthesized materials were applied for pre-concentration of model analytes (Rhodamine 6G, folic acid and pyrene) and their SERS detection directly within the sorbent. It was shown that the recovery of analytes could be improved by alumina modification. The combination of surface-enhanced Raman spectroscopy with preconcentration is a promising instrument for analytical applications.

  19. MMT-supported Ag nanoparticles for chitosan nanocomposites: structural properties and antibacterial activity.

    PubMed

    Lavorgna, M; Attianese, I; Buonocore, G G; Conte, A; Del Nobile, M A; Tescione, F; Amendola, E

    2014-02-15

    Multifunctional bionanocomposites have been prepared by loading chitosan matrix with silver-montmorillonite antimicrobial nanoparticles obtained by replacing Na(+) ions of natural montmorillonite with silver ions. This filler has been chosen for its twofold advantage to serve as silver supporting material and to confer new and better performance to the obtained material. It has been proved that the achievement of the intercalation of chitosan into the silicate galleries of montomorillonite as well as the interaction between chitosan and Ag ions and silver particles lead to an enhancement of the thermal stability, to an improvement of mechanical strengths and to a reduction of the liquid water uptake of the obtained bionanocomposites. Results also show that silver ions are released in a steady and prolonged manner providing, after 24 h, a significant reduction in the microbial growth of Pseudomonas spp. PMID:24507295

  20. Deposition of Ag nanoparticles on fluoroalkylsilane self-assembled monolayers with varying chain length

    NASA Astrophysics Data System (ADS)

    Zuo, Juan; Keil, Patrick; Valtiner, Markus; Thissen, Peter; Grundmeier, Guido

    2008-12-01

    Silver nanoparticles were prepared by means of electron beam evaporation of silver on top of self-assembled fluoroalkylsilane monolayers with different fluoroalkyl chain length. The surface properties of the different self-assembled monolayers (SAMs) were evaluated by surface energy measurements and X-ray photoelectron spectroscopy. The morphology of the silver nanostructures, characterized by their size, size distribution, shape and interparticle separation, was observed to be dependent on the chemical composition, fluoroalkyl chain length and surface energy of the sub-layer as well as the degradation of the monolayer during the deposition process. The resulting morphology of the evaporated Ag nanostructures on the different surfaces could be explained based on the basis of surface energy and the role of ordering, disordering and defects of the monolayers caused by the impinging silver atoms during evaporation. Depending on the fluoroalkyl chain length significant changes in the chemical and physical structure of the SAMs after the evaporation process could be detected.

  1. Synthesis of rattle-type Ag@Al2O3 nanostructure by laser-induced heating of Ag and Al nanoparticles

    NASA Astrophysics Data System (ADS)

    Singh, Rina; Soni, R. K.

    2015-10-01

    A simple and flexible method has been presented for the fabrication of rattle-type Ag@Al2O3 nanostructures in water and polyvinyl pyrrolidone polymer solution based on laser-induced heating of mixture of silver (Ag) and aluminium (Al) nanoparticles by 532-nm laser. Silver and aluminium nanoparticles were prepared by pulsed laser ablation in liquid using same laser wavelength. The transmission electron micrographs revealed morphological changes from sintered-/intermediate-type structure in water medium and jointed structure (heterostructures) in polymer solution to rattle-type structure with changing irradiation time. At longer irradiation time, the Kirkendall effect becomes dominant due to diffusion rate mismatch between the two metals at the interface and facilitates the formation of porous alumina shell over silver core. The morphology and chemical composition of the nanostructures were characterized by transmission electron micrograph, high-resolution transmission electron micrograph and energy-dispersive X-ray analysis. The melting response of alumina (Al2O3), aluminium and silver nanoparticles with 532-nm laser wavelength provides novel pathway for rattle-type formation.

  2. Bio-inspired sustainable and green synthesis of plasmonic Ag/AgCl nanoparticles for enhanced degradation of organic compound from aqueous phase.

    PubMed

    Devi, Th Babita; Ahmaruzzaman, M

    2016-09-01

    In the current study, we report the utilization of the biogenic potential of Benincasa hispida (ash gourd) peel extract for the synthesis of Ag embedded AgCl nanoparticles nanoparticles (Ag/AgCl NPs) without the use of any external organic solvents. The appearance of dark brown color from the pale yellow color confirmed the formation of Ag/AgCl nanoparticles which was further validated by absorbance peak using UV-visible spectroscopy. The phytochemicals (flavones) present in the B. hispida peel extract acts as a reducing/stabilizing agents. The morphology and size of the synthesized NPs were characterized by transmission electron microscope (TEM), selected area electron microscope (SAED) and high resolution transmission electron microscope (HR-TEM). FT-IR spectra of the B. hispida peel extract and after the development of nanoparticles are determined to identify the functional groups responsible for the conversion of metal ions to metal nanoparticles. The synthesized nanoparticles showed an excellent photocatalytic property in the degradation of toxic dye like malachite green oxalate under sunlight irradiation. For the first time, malachite green oxalate dye was degraded by Ag/AgCl nanoparticles under sunlight irradiation. PMID:27246560

  3. Bio-inspired sustainable and green synthesis of plasmonic Ag/AgCl nanoparticles for enhanced degradation of organic compound from aqueous phase.

    PubMed

    Devi, Th Babita; Ahmaruzzaman, M

    2016-09-01

    In the current study, we report the utilization of the biogenic potential of Benincasa hispida (ash gourd) peel extract for the synthesis of Ag embedded AgCl nanoparticles nanoparticles (Ag/AgCl NPs) without the use of any external organic solvents. The appearance of dark brown color from the pale yellow color confirmed the formation of Ag/AgCl nanoparticles which was further validated by absorbance peak using UV-visible spectroscopy. The phytochemicals (flavones) present in the B. hispida peel extract acts as a reducing/stabilizing agents. The morphology and size of the synthesized NPs were characterized by transmission electron microscope (TEM), selected area electron microscope (SAED) and high resolution transmission electron microscope (HR-TEM). FT-IR spectra of the B. hispida peel extract and after the development of nanoparticles are determined to identify the functional groups responsible for the conversion of metal ions to metal nanoparticles. The synthesized nanoparticles showed an excellent photocatalytic property in the degradation of toxic dye like malachite green oxalate under sunlight irradiation. For the first time, malachite green oxalate dye was degraded by Ag/AgCl nanoparticles under sunlight irradiation.

  4. Preparing of Highly Conductive Patterns on Flexible Substrates by Screen Printing of Silver Nanoparticles with Different Size Distribution

    NASA Astrophysics Data System (ADS)

    Ding, Jin; Liu, Jun; Tian, Qingyong; Wu, Zhaohui; Yao, Weijing; Dai, Zhigao; Liu, Li; Wu, Wei

    2016-09-01

    A facile one-step polyol method is employed to synthesize the Ag nanoparticles (NPs) in large scale. The Ag NPs with different average diameter (from 52 to 120 nm) and particle size distribution are prepared by changing the mass ratio of AgNO3 and PVP. Furthermore, the as-obtained Ag NPs are prepared as conductive inks, which could be screen printed on various flexible substrates and formed as conductive patterns after sintering treatment. During the reaction process, PVP is used as the capping reagent for preventing the agglomeration of Ag NPs, and the influence of the mass ratio of AgNO3 and PVP to the size distribution of Ag NPs is investigated. The results of electronic properties reveal that the conductivity of printed patterns is highly dependent on the size distribution of as-obtained Ag NPs. Among all the samples, the optimal conductivity is obtained when the mass ratio of AgNO3 and PVP is 1:0.4. Subsequently, the sintering time and temperature are further investigated for obtaining the best conductivity; the optimal electrical resistivity value of 3.83 μΩ · cm is achieved at 160 °C for 75 min, which is close to the resistivity value of the bulk silver (1.58 μΩ · cm). Significantly, there are many potential advantages in printed electronics applications because of the as-synthesized Ag NPs with a low sintering temperature and low electrical resistivity.

  5. Nanoparticles of Ag with a Pt and Pd rich surface supported on carbon as a new catalyst for the oxygen electroreduction reaction (ORR) in acid electrolytes: Part 1

    NASA Astrophysics Data System (ADS)

    Pech-Pech, I. E.; Gervasio, Dominic F.; Godínez-Garcia, A.; Solorza-Feria, O.; Pérez-Robles, J. F.

    2015-02-01

    Silver (Ag) nanoparticles enriched with platinum (Pt) and palladium (Pd) on their surfaces (Ag@Pt0.1Pd0.1) are supported on Vulcan XC-72 carbon (C) to form a new catalyst (Ag@Pt0.1Pd0.1/C) for the oxygen reduction reaction (ORR) in acid electrolytes. This catalyst is prepared in one pot by reducing Ag and then Pt and Pd metal salts with sodium borohydride in the presence of trisodium citrate then adding XC-72 while applying intense ultrasound. The metallic Ag@Pt0.1Pd0.1 nanoparticles contain 2 weight percent of Pt, are spherical and have an average size less than 10 nm as determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). At the ORR potentials, Ag nanoparticles on carbon (Ag/C) rapidly lose Ag by dissolution and show no more catalytic activity for the ORR than the carbon support, whereas Ag@Pt0.1Pd0.1/C is a stable catalyst and exhibits 1.4 and 1.6 fold greater specific activity, also 3.6 and 2.8 fold greater mass activity for ORR in 0.5 M H2SO4 solution than comparable Pt/C and Pt0.5Pd0.5/C catalysts with the same Pt loading as determined for thin-films of these catalysts on a rotating-disk electrode (TF-RDE). Using silver nanoparticles increases Pt utilization and therefore decreases Pt-loading and cost of a catalyst for a proton exchange membrane fuel cell (PEMFC) electrode.

  6. Silver sulfide nanoparticles (Ag2S-NPs) are taken up by plants and are phytotoxic.

    PubMed

    Wang, Peng; Menzies, Neal W; Lombi, Enzo; Sekine, Ryo; Blamey, F Pax C; Hernandez-Soriano, Maria C; Cheng, Miaomiao; Kappen, Peter; Peijnenburg, Willie J G M; Tang, Caixian; Kopittke, Peter M

    2015-01-01

    Silver nanoparticles (NPs) are used in more consumer products than any other nanomaterial and their release into the environment is unavoidable. Of primary concern is the wastewater stream in which most silver NPs are transformed to silver sulfide NPs (Ag2S-NPs) before being applied to agricultural soils within biosolids. While Ag2S-NPs are assumed to be biologically inert, nothing is known of their effects on terrestrial plants. The phytotoxicity of Ag and its accumulation was examined in short-term (24 h) and longer-term (2-week) solution culture experiments with cowpea (Vigna unguiculata L. Walp.) and wheat (Triticum aestivum L.) exposed to Ag2S-NPs (0-20 mg Ag L(-1)), metallic Ag-NPs (0-1.6 mg Ag L(-1)), or ionic Ag (AgNO3; 0-0.086 mg Ag L(-1)). Although not inducing any effects during 24-h exposure, Ag2S-NPs reduced growth by up to 52% over a 2-week period. This toxicity did not result from their dissolution and release of toxic Ag(+) in the rooting medium, with soluble Ag concentrations remaining below 0.001 mg Ag L(-1). Rather, Ag accumulated as Ag2S in the root and shoot tissues when plants were exposed to Ag2S-NPs, consistent with their direct uptake. Importantly, this differed from the form of Ag present in tissues of plants exposed to AgNO3. For the first time, our findings have shown that Ag2S-NPs exert toxic effects through their direct accumulation in terrestrial plant tissues. These findings need to be considered to ensure high yield of food crops, and to avoid increasing Ag in the food chain. PMID:25686712

  7. Ag Nanoparticles (Ag NM300K) in the Terrestrial Environment: Effects at Population and Cellular Level in Folsomia candida (Collembola)

    PubMed Central

    Mendes, Luís André; Maria, Vera L.; Scott-Fordsmand, Janeck J.; Amorim, Mónica J. B.

    2015-01-01

    The effects of nanomaterials have been primarily assessed based on standard ecotoxicity guidelines. However, by adapting alternative measures the information gained could be enhanced considerably, e.g., studies should focus on more mechanistic approaches. Here, the environmental risk posed by the presence of silver nanoparticles (Ag NM300K) in soil was investigated, anchoring population and cellular level effects, i.e., survival, reproduction (28 days) and oxidative stress markers (0, 2, 4, 6, 10 days). The standard species Folsomia candida was used. Measured markers included catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), total glutathione (TG), metallothionein (MT) and lipid peroxidation (LPO). Results showed that AgNO3 was more toxic than AgNPs at the population level: reproduction EC20 and EC50 was ca. 2 and 4 times lower, respectively. At the cellular level Correspondence Analysis showed a clear separation between AgNO3 and AgNP throughout time. Results showed differences in the mechanisms, indicating a combined effect of released Ag+ (MT and GST) and of AgNPs (CAT, GR, TG, LPO). Hence, clear advantages from mechanistic approaches are shown, but also that time is of importance when measuring such responses. PMID:26473892

  8. 1,10-Phenanthroline as an accelerator for Ag nanoparticle-catalysed electroless copper deposition

    NASA Astrophysics Data System (ADS)

    Liu, Chia-Ru; Chou, Nan-Kuang; Li, Cheng-Hsing; Chen, Ho-Rei; Lee, Chien-Liang

    2014-10-01

    1,10-Phenanthroline (phen) can be successfully used as an accelerator for Ag-catalysed electroless copper deposition (ECD) processes. Electrochemical quartz crystal microbalance analyses indicate that the mass activity in terms of thickness of deposited Cu layer and average ECD rate within a deposition time of 110 s for Ag nanoparticles activated by phen are 7.86 × 10-3 μm μg-1 and 1.43 × 10-4 μm μg-1 s-1, respectively, whereas Ag nanoparticles without phen cannot catalyse the reaction. Furthermore, Tafel and cyclic voltammetric results show that the addition of phen to the ECD bath significantly enhances the ability of the Ag nanoparticles to catalyse the oxidation of HCHO and suppresses the formation of CuO.

  9. DNA-modulated photo-transformation of AgCl to silver nanoparticles: visiting the formation mechanism.

    PubMed

    Wang, Guoqing; Mitomo, Hideyuki; Matsuo, Yasutaka; Niikura, Kenichi; Maeda, Mizuo; Ijiro, Kuniharu

    2015-08-15

    Solution-phase synthesis and post-synthetic bio-modification have continued to play a dominant role in preparation of nanostructured biomaterials. Heterogeneous nucleation and growth that occur much more often in nature, however, remain rarely explored in nano-biomaterials research. We have newly developed a DNA-modulated photoconversion approach to uniform silver nanoparticles that afford DNA-directed recognition and multi-mode imaging. The present study was aimed at understanding the rapid heterogeneous nucleation and growth of AgNPs at the solid-liquid interface with the aid of DNA. Dynamic changes in absorbance, size and morphology of silver nanostructures were monitored and analyzed to clarify the growth kinetics, which indicated a synthetic route involving synchronous growth of silver nanostructures and the fragmentation and consumption of AgCl. Various stabilizers, including polymer and amino acids, were assessed and compared with respect to the efficacy in photoconversion of AgCl. DNA was found to offer the best monodispersity and the smallest diameter for the resultant AgNPs, due to its strong interactions to silver species as well as excellent charge dispersion ability. By controlling the physicochemical property of DNA through choice of pH and ionic strength, we have demonstrated tunable structure and composition of the nanoparticles.

  10. Controlled formation of ag nanoparticles by means of long-chain sodium polyacrylates in dilute solution.

    PubMed

    Huber, Klaus; Witte, Thomas; Hollmann, Jutta; Keuker-Baumann, Susanne

    2007-02-01

    A new tool is presented to control formation of Ag nanoparticles. Small amounts of silver ions were added to dilute solutions of long-chain sodium polyacrylates (NaPA). Four NaPA samples covering a molar mass regime of 97 kD < or = Mw < or = 650 kD have been used. With amounts of added Ag(+) as low as 1-2% of the COO(-) groups of the polyanionic chains, significant changes could already be induced in the NaPA coils with 650 kD. If the NaPA concentration was kept below 0.1 g/L, the coils with 650 kD exhibited a significant coil shrinking in stable solutions. At larger NaPA concentrations, addition of Ag+ initiates an aggregation of the polyacrylate coils toward compact structures. Coil shrinking and aggregation was revealed by means of time-resolved static light scattering. If exposed to UV-radiation, small Ag particles formed within the shrunken anionic polyacrylate coils. The Ag nanoparticles were identified by means of an enhanced light scattering and a characteristic plasmon absorption band around 410 nm. No such Ag particle formation could be observed even at 5 times larger concentrations of Ag(+) and NaPA if the two smallest polyacrylate samples have been used under otherwise equal conditions. This molar mass sensitive response of NaPA to Ag(+)-addition suggests an interesting phenomenon: if the coil size of the NaPa chains, which act as Ag(+) collectors, is large enough, local Ag(+) concentration in these coil-shaped Ag(+) containers exceeds a critical value, and irradiation with UV generates Ag nanoparticles. PMID:17263389

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

    PubMed

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

    2015-04-01

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

  12. Fabrication of Sn-3.5Ag Eutectic Alloy Powder by Annealing Sub-Micrometer Sn@Ag Powder Prepared by Citric Acid-Assisted Ag Immersion Plating.

    PubMed

    Chee, Sang-Soo; Choi, Eun Byeol; Lee, Jong-Hyun

    2015-11-01

    A Sn-3.5Ag eutectic alloy powder has been developed by chemically synthesizing sub-micrometer Sn@Ag powder at room temperature. This synthesis was achieved by first obtaining a sub-micrometer Sn powder for the core using a modified variant of the polyol method, and then coating this with a uniformly thin and continuous Ag layer through immersion plating in 5.20 mM citric acid. The citric acid was found to play multiple roles in the Ag coating process, acting as a chelating agent, a reducing agent and a stabilizer to ensure coating uniformity; and as such, the amount used has an immense influence on the coating quality of the Ag shells. It was later verified by transmission electron microscopy and X-ray diffraction analysis that the coated Ag layer transfers to the Sn core via diffusion to form an Ag3Sn phase at room temperature. Differential scanning calorimetry also revealed that the synthesized Sn@Ag powder is nearly transformed into Sn-3.5Ag eutectic alloy powder upon annealing three times at a temperature of up to 250 degrees C, as evidenced by a single melting peak at 220.5 degrees C. It was inferred from this that Sn-3.5Ag eutectic alloy powder can be successfully prepared through the synthesis of core Sn powders by a modified polyol method, immersion plating using citric acid, and annealing, in that order.

  13. Size-controlled stabilization of the superionic phase to room temperature in polymer-coated AgI nanoparticles.

    PubMed

    Makiura, Rie; Yonemura, Takayuki; Yamada, Teppei; Yamauchi, Miho; Ikeda, Ryuichi; Kitagawa, Hiroshi; Kato, Kenichi; Takata, Masaki

    2009-06-01

    Solid-state ionic conductors are actively studied for their large application potential in batteries and sensors. From the view of future nanodevices, nanoscaled ionic conductors are attracting much interest. Silver iodide (AgI) is a well-known ionic conductor for which the high-temperature alpha-phase shows a superionic conductivity greater than 1 Omega(-1) cm(-1). Below 147 degrees C, alpha-AgI undergoes a phase transition into the poorly conducting beta- and gamma-polymorphs, thereby limiting its applications. Here, we report the facile synthesis of variable-size AgI nanoparticles coated with poly-N-vinyl-2-pyrrolidone (PVP) and the controllable tuning of the alpha- to beta-/gamma-phase transition temperature (Tc). Tc shifts considerably to lower temperatures with decreasing nanoparticle size, leading to a progressively enlarged thermal hysteresis. Specifically, when the size approaches 10-11 nm, the alpha-phase survives down to 30 degrees C--the lowest temperature for any AgI family material. We attribute the suppression of the phase transition not only to the increase of the surface energy, but also to the presence of defects and the accompanying charge imbalance induced by PVP. Moreover, the conductivity of as-prepared 11 nm beta-/gamma-AgI nanoparticles at 24 degrees C is approximately 1.5 x 10(-2) Omega(-1) cm(-1)--the highest ionic conductivity for a binary solid at room temperature. The stabilized superionic phase and the remarkable transport properties at a practical temperature reported here suggest promising applications in silver-ion-based electrochemical devices.

  14. Size-controlled stabilization of the superionic phase to room temperature in polymer-coated AgI nanoparticles

    NASA Astrophysics Data System (ADS)

    Makiura, Rie; Yonemura, Takayuki; Yamada, Teppei; Yamauchi, Miho; Ikeda, Ryuichi; Kitagawa, Hiroshi; Kato, Kenichi; Takata, Masaki

    2009-06-01

    Solid-state ionic conductors are actively studied for their large application potential in batteries and sensors. From the view of future nanodevices, nanoscaled ionic conductors are attracting much interest. Silver iodide (AgI) is a well-known ionic conductor for which the high-temperature α-phase shows a superionic conductivity greater than 1Ω-1cm-1 (ref. 6). Below 147∘C, α-AgI undergoes a phase transition into the poorly conducting β- and γ-polymorphs, thereby limiting its applications. Here, we report the facile synthesis of variable-size AgI nanoparticles coated with poly-N-vinyl-2-pyrrolidone (PVP) and the controllable tuning of the α- to β-/γ-phase transition temperature (Tc↓). Tc↓ shifts considerably to lower temperatures with decreasing nanoparticle size, leading to a progressively enlarged thermal hysteresis. Specifically, when the size approaches 10-11nm, the α-phase survives down to 30∘C-the lowest temperature for any AgI family material. We attribute the suppression of the phase transition not only to the increase of the surface energy, but also to the presence of defects and the accompanying charge imbalance induced by PVP. Moreover, the conductivity of as-prepared 11nm β-/γ-AgI nanoparticles at 24∘C is ~1.5×10-2Ω-1cm-1-the highest ionic conductivity for a binary solid at room temperature. The stabilized superionic phase and the remarkable transport properties at a practical temperature reported here suggest promising applications in silver-ion-based electrochemical devices.

  15. Evaluation of the Cytotoxic Behavior of Fungal Extracellular Synthesized Ag Nanoparticles Using Confocal Laser Scanning Microscope

    PubMed Central

    Salaheldin, Taher A.; Husseiny, Sherif M.; Al-Enizi, Abdullah M.; Elzatahry, Ahmed; Cowley, Alan H.

    2016-01-01

    Silver nanoparticles have been synthesized by subjecting a reaction medium to a Fusarium oxysporum biomass at 28 °C for 96 h. The biosynthesized Ag nanoparticles were characterized on the basis of their anticipated peak at 405 nm using UV-Vis-NIR spectroscopy. Structural confirmation was evident from the characteristic X-ray diffraction (XRD) pattern, high-resolution transmission electron Microscopy (HRTEM) and the particle size analyzer. The Ag nanoparticles were of dimension 40 ± 5 nm and spherical in shape. The study mainly focused on using the confocal laser scanning microscope (CLSM) to examine the cytotoxic activities of fungal synthesized Ag nanoparticles on a human breast carcinoma cell line MCF7 cell, which featured remarkable vacuolation, thus indicating a potent cytotoxic activity. PMID:26950118

  16. Evaluation of the Cytotoxic Behavior of Fungal Extracellular Synthesized Ag Nanoparticles Using Confocal Laser Scanning Microscope.

    PubMed

    Salaheldin, Taher A; Husseiny, Sherif M; Al-Enizi, Abdullah M; Elzatahry, Ahmed; Cowley, Alan H

    2016-03-03

    Silver nanoparticles have been synthesized by subjecting a reaction medium to a Fusarium oxysporum biomass at 28 °C for 96 h. The biosynthesized Ag nanoparticles were characterized on the basis of their anticipated peak at 405 nm using UV-Vis-NIR spectroscopy. Structural confirmation was evident from the characteristic X-ray diffraction (XRD) pattern, high-resolution transmission electron Microscopy (HRTEM) and the particle size analyzer. The Ag nanoparticles were of dimension 40 ± 5 nm and spherical in shape. The study mainly focused on using the confocal laser scanning microscope (CLSM) to examine the cytotoxic activities of fungal synthesized Ag nanoparticles on a human breast carcinoma cell line MCF7 cell, which featured remarkable vacuolation, thus indicating a potent cytotoxic activity.

  17. Organic-inorganic hybrid nanoparticles for bacterial inhibition: synthesis and characterization of doped and undoped ONPs with Ag/Au NPs.

    PubMed

    Aguilar, Carlos Alberto Huerta; Jiménez, Adriana Berenice Pérez; Silva, Antonio Romero; Kaur, Navneet; Thangarasu, Pandiyan; Ramos, Jorge Manuel Vázquez; Singh, Narinder

    2015-01-01

    Organic nanoparticles (ONPs) of lipoic acid and its doped derivatives ONPs/Ag and ONPs/Au were prepared and characterized by UV-Visible, EDS, and TEM analysis. The antibacterial properties of the ONPs ONPs/Ag and ONPs/Au were tested against bacterial strains (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Salmonella typhi). Minimal Inhibitory Concentration (MIC) and bacterial growth inhibition tests show that ONPs/Ag are more effective in limiting bacterial growth than other NPs, particularly, for Gram positive than for Gram-negative ones. The order of bacterial cell growth inhibition was ONPs/Ag > ONPs > ONPs/Au. The morphology of the cell membrane for the treated bacteria was analyzed by SEM. The nature of bond formation of LA with Ag or Au was analyzed by molecular orbital and density of state (DOS) using DFT. PMID:25853317

  18. Facile route for preparation of silver nanoparticle-coated precipitated silica

    NASA Astrophysics Data System (ADS)

    Quang, Dang Viet; Sarawade, Pradip B.; Hilonga, Askwar; Park, Sung Dae; Kim, Jong-Kil; Kim, Hee Taik

    2011-02-01

    In this research, a facile route was used to prepare silver nanoparticle-coated precipitated silica using sodium silicate, a cheap precursor. Precipitated silica (PS) was synthesized by dropping 8% H2SO4 into a mixed solution of sodium silicate 24% (Na2O·3.4SiO2) and NaCl 4%; under constant stirring. The precipitated silica was then modified by simultaneous addition of 3-aminopropyltriethoxysilane (3-APTES) and 8% H2SO4. The resulting material was aged at 80 °C for 1 h to produce amino-functionalized precipitated silica (AFPS). Silver nanoparticle-coated precipitated silica (Ag-NPS) was synthesized by adding silver nitrate (AgNO3). The synthesis procedure also involved mixing for 2 h and dropping 0.05 M sodium borohydride (NaBH4). The final products, namely, PS, AFPS, and Ag-NPS were characterized using BET analyzer, FE-SEM, TEM and XRD. Silver nanoparticles with an average size ranging from 18 to 25 nm were found mostly coated on the exterior layer of the precipitated silica. The synthesis method reported in this work is facile and might be used for large-scale industrial production of inexpensive Ag-NPS.

  19. Green and Tunable Decoration of Graphene with Spherical Nanoparticles Based on Laser Ablation in Water: A Case of Ag Nanoparticle/Graphene Oxide Sheet Composites.

    PubMed

    He, Hui; Wang, Haibo; Li, Kai; Zhu, Jun; Liu, Jianshuang; Meng, Xiangdong; Shen, Xiaoshuang; Zeng, Xianghua; Cai, Weiping

    2016-02-23

    A simple and green strategy is presented to decorate graphene with nanoparticles, based on laser ablation of targets in graphene auqeous solution. Ag and graphene oxide (GO) are chosen as model materials. The surface of GO sheets is strongly anchored with spherical Ag nanoparticles. The density and size of the Ag nanoparticles can be easily tuned by laser ablation conditions. Further, the GO sheets can be decorated with other nanoparticles from simple metals or semiconductors to multicomponent hybrids. Additionally, the Ag nanoparticle/GO sheet colloids can be utilized as blocks to build three-dimensional structures, such as sandwich membranes by evaporation-induced self-assembly. These graphene-based composite materials could be very useful in catalysis, sensors, and nanodevices. Particularly, the Ag nanoparticle/GO sheet sandwich composite membranes exhibit excellent surface-enhanced Raman scattering performance and possess the huge potential in trace-detecting persistent organic pollutants in the environment.

  20. Effect of toxicity of Ag nanoparticles on SERS spectral variance of bacteria

    NASA Astrophysics Data System (ADS)

    Cui, Li; Chen, Shaode; Zhang, Kaisong

    2015-02-01

    Ag nanoparticles (NPs) have been extensively utilized in surface-enhanced Raman scattering (SERS) spectroscopy for bacterial identification. However, Ag NPs are toxic to bacteria. Whether such toxicity can affect SERS features of bacteria and interfere with bacterial identification is still unknown and needed to explore. Here, by carrying out a comparative study on non-toxic Au NPs with that on toxic Ag NPs, we investigated the influence of nanoparticle concentration and incubation time on bacterial SERS spectral variance, both of which were demonstrated to be closely related to the toxicity of Ag NPs. Sensitive spectral alterations were observed on Ag NPs with increase of NPs concentration or incubation time, accompanied with an obvious decrease in number of viable bacteria. In contrast, SERS spectra and viable bacterial number on Au NPs were rather constant under the same conditions. A further analysis on spectral changes demonstrated that it was cell response (i.e. metabolic activity or death) to the toxicity of Ag NPs causing spectral variance. However, biochemical responses to the toxicity of Ag were very different in different bacteria, indicating the complex toxic mechanism of Ag NPs. Ag NPs are toxic to a great variety of organisms, including bacteria, fungi, algae, protozoa etc., therefore, this work will be helpful in guiding the future application of SERS technique in various complex biological systems.

  1. Effect of toxicity of Ag nanoparticles on SERS spectral variance of bacteria.

    PubMed

    Cui, Li; Chen, Shaode; Zhang, Kaisong

    2015-02-25

    Ag nanoparticles (NPs) have been extensively utilized in surface-enhanced Raman scattering (SERS) spectroscopy for bacterial identification. However, Ag NPs are toxic to bacteria. Whether such toxicity can affect SERS features of bacteria and interfere with bacterial identification is still unknown and needed to explore. Here, by carrying out a comparative study on non-toxic Au NPs with that on toxic Ag NPs, we investigated the influence of nanoparticle concentration and incubation time on bacterial SERS spectral variance, both of which were demonstrated to be closely related to the toxicity of Ag NPs. Sensitive spectral alterations were observed on Ag NPs with increase of NPs concentration or incubation time, accompanied with an obvious decrease in number of viable bacteria. In contrast, SERS spectra and viable bacterial number on Au NPs were rather constant under the same conditions. A further analysis on spectral changes demonstrated that it was cell response (i.e. metabolic activity or death) to the toxicity of Ag NPs causing spectral variance. However, biochemical responses to the toxicity of Ag were very different in different bacteria, indicating the complex toxic mechanism of Ag NPs. Ag NPs are toxic to a great variety of organisms, including bacteria, fungi, algae, protozoa etc., therefore, this work will be helpful in guiding the future application of SERS technique in various complex biological systems. PMID:25291503

  2. Determination of 2-methoxyestradiol in serum samples and pharmaceutical preparations by silver nanoparticles-enhanced chemiluminescence.

    PubMed

    Zhang, Min; Xiao, Xiangqin; Zeng, Wenyuan; Zeng, Xiaoying; Yao, Hanchun

    2014-03-01

    Silver nanoparticles (AgNPs) exhibited better chemiluminescence (CL) catalysis activity and smaller nanoparticles have stronger catalysis ability in luminol-K3Fe(CN)6 system among the synthesized AgNPs of different size. 10±2 nm nanoparticles was used as catalysts to enhance the reaction sensitivity. It was found that the CL intensity of AgNPs-luminol-K3Fe(CN)6 was strongly inhibited in the presence of 2-methoxyestradiol (2-ME) and the relative CL intensity was in linear correlation with the concentration of 2-ME. Thus, the silver nanoparticles-enhanced CL method for the determination of 2-ME was developed. The proposed method has a detection limit (3 Sb/K) of 5.0×10(-10) mol L(-1) with a relative standard deviation of 0.75% for 5.0×10(-8) mol L(-1) 2-ME. The method was successfully applied for determination of 2-ME in human serum and pharmaceutical preparations. The possible CL reaction mechanism was also discussed briefly. Oxygen radicals played an important role in the catalytic process.

  3. Synthesis of Ag/CNT hybrid nanoparticles and fabrication of their nylon-6 polymer nanocomposite fibers for antimicrobial applications.

    PubMed

    Rangari, Vijaya K; Mohammad, Ghouse M; Jeelani, Shaik; Hundley, Angel; Vig, Komal; Singh, Shree Ram; Pillai, Shreekumar

    2010-03-01

    Ag-coated CNTs hybrid nanoparticles (Ag/CNTs) were prepared by ultrasonic irradiation of dimethylformamide (DMF) and silver (I) acetate precursors in the presence of CNTs. The morphology of Ag/CNTs was characterized using x-ray diffraction and transmission electron microscopy (TEM) techniques. The Nylon-6 powder and 1 wt% Ag/CNTs mixture was dispersed uniformly using a noncontact spinning technique. The dried mixture was melted in a single screw extrusion machine and then extruded through an orifice. Extruded filaments were later stretched and stabilized by sequentially passing them through a set of tension adjusters and a secondary heater. The Nylon-6/Ag/CNT hybrid polymer nanocomposite (HPNC) fibers, which were of approximately 80 microm size, were tested for their tensile properties. The failure stress and modulus of the extruded HPNC fibers (doped with 1% Ag/CNTs) was about 72.19 % and 342.62% higher than the neat extruded Nylon-6 fiber, respectively. DSC results indicated an increase in the thermal stability and crystallization for HPNC fibers. The antibacterial activity of the Ag-coated CNTs, commercial Ag, neat Nylon-6 and plain CNTs were evaluated. Ag-coated CNTs at 25 microg demonstrated good antimicrobial activity against four common bacterial pathogens as tested by the Kirby-Bauer assay. The mean diameters of the zones of inhibition were 27.9 +/- 6.72 mm, 19.4 +/- 3.64 mm, 21.9 +/- 4.33 mm, and 24.1 +/- 4.14 mm, respectively, for Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Salmonella enterica serovar Typhimurium. By comparison, those obtained using the broad spectrum antibiotic amoxicillin-clavulanic acid were 37.7 +/- 2.13 mm, 28.6 +/- 4.27 mm, 22.6 +/- 1.27 mm, and 27.0 +/- 1.41 mm, respectively, for the same strains. The zones of inhibition obtained for Nylon-6 Ag-coated CNT powder at 25 microg were also high, ranging from 15.2 to 25.3 mm in contrast to commercial silver or neat Nylon-6, which did not inhibit the bacterial

  4. Synthesis of Ag/CNT hybrid nanoparticles and fabrication of their Nylon-6 polymer nanocomposite fibers for antimicrobial applications

    NASA Astrophysics Data System (ADS)

    Rangari, Vijaya K.; Mohammad, Ghouse M.; Jeelani, Shaik; Hundley, Angel; Vig, Komal; Ram Singh, Shree; Pillai, Shreekumar

    2010-03-01

    Ag-coated CNTs hybrid nanoparticles (Ag/CNTs) were prepared by ultrasonic irradiation of dimethylformamide (DMF) and silver (I) acetate precursors in the presence of CNTs. The morphology of Ag/CNTs was characterized using x-ray diffraction and transmission electron microscopy (TEM) techniques. The Nylon-6 powder and 1 wt% Ag/CNTs mixture was dispersed uniformly using a noncontact spinning technique. The dried mixture was melted in a single screw extrusion machine and then extruded through an orifice. Extruded filaments were later stretched and stabilized by sequentially passing them through a set of tension adjusters and a secondary heater. The Nylon-6/Ag/CNT hybrid polymer nanocomposite (HPNC) fibers, which were of ~ 80 µm size, were tested for their tensile properties. The failure stress and modulus of the extruded HPNC fibers (doped with 1% Ag/CNTs) was about 72.19 % and 342.62% higher than the neat extruded Nylon-6 fiber, respectively. DSC results indicated an increase in the thermal stability and crystallization for HPNC fibers. The antibacterial activity of the Ag-coated CNTs, commercial Ag, neat Nylon-6 and plain CNTs were evaluated. Ag-coated CNTs at 25 µg demonstrated good antimicrobial activity against four common bacterial pathogens as tested by the Kirby-Bauer assay. The mean diameters of the zones of inhibition were 27.9 ± 6.72 mm, 19.4 ± 3.64 mm, 21.9 ± 4.33 mm, and 24.1 ± 4.14 mm, respectively, for Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Salmonella enterica serovar Typhimurium. By comparison, those obtained using the broad spectrum antibiotic amoxicillin-clavulanic acid were 37.7 ± 2.13 mm, 28.6 ± 4.27 mm, 22.6 ± 1.27 mm, and 27.0 ± 1.41 mm, respectively, for the same strains. The zones of inhibition obtained for Nylon-6 Ag-coated CNT powder at 25 µg were also high, ranging from 15.2 to 25.3 mm in contrast to commercial silver or neat Nylon-6, which did not inhibit the bacterial strains tested. Further, the

  5. Preparation and Characterization of Calcium Carbonate Nanoparticles

    NASA Astrophysics Data System (ADS)

    Hassim, Aqilah; Rachmawati, Heni

    2010-10-01

    Taking calcium supplements can reduce the risk of developing osteoporosis, but they are not readily absorbed in the gastrointestinal tract. Nanotechnology is expected to resolve this problem. In this study, we prepared and characterized calcium carbonate nanoparticle to improve the solubility by using bottom-up method. The experiment was done by titrating calcium chloride with sodium carbonate with the addition of polyvinylpyrrolidone (PVP) as stabilizer, using ultra-turrax. Various concentrations of calcium chloride and sodium carbonate as well as various speed of stirring were used to prepare the calcium carbonate nanoparticles. Evaluations studied were including particle size, polydispersity index (PI) and zeta potential with particle analyzer, surface morphology with scanning electron microscope, and saturated solubility. In addition, to test the ability of PVP to prevent particles growth, short stability study was performed by storing nano CaCO3 suspension at room temperature for 2 weeks. Results show that using 8000 rpm speed of stirring, the particle size tends to be bigger with the range of 500-600 nm (PI between 0.2-0.4) whereas with stirring speed of 4000 rpm, the particle size tends to be smaller with 300-400 nm (PI between 0.2-0.4). Stirring speed of 6000 rpm produced particle size within the range of 400-500 nm (PI between 0.2-0.4). SEM photograph shows that particles are monodisperse confirming that particles were physically stable without any agglomeration within 2 weeks storage. Taken together, nano CaCO3 is successfully prepared by bottom-up method and PVP is a good stabilizer to prevent the particle growth.

  6. Hyperspectral reflected light microscopy of plasmonic Au/Ag alloy nanoparticles incubated as multiplex chromatic biomarkers with cancer cells.

    PubMed

    Patskovsky, Sergiy; Bergeron, Eric; Rioux, David; Simard, Mikaël; Meunier, Michel

    2014-10-21

    A hyperspectral microscopy system based on a reflected light method for plasmonic nanoparticle (NP) imaging was designed and compared with a conventional darkfield method for spatial localization and spectroscopic identification of single Au, Ag and Au/Ag alloy NPs incubated with fixed human cancer cell preparations. A new synthesis protocol based on co-reduction of Au and Ag salts combined with the seeded growth technique was used for the fabrication of monodispersed alloy NPs with sizes ranging from 30 to 100 nm in diameter. We validated theoretically and experimentally the performance of 60 nm Au, Ag and Au/Ag (50 : 50) NPs as multiplexed biological chromatic markers for biomedical diagnostics and optical biosensing. The advantages of the proposed reflected light microscopy method are presented for NP imaging in a complex and highly diffusing medium such as a cellular environment. The obtained information is essential for the development of a high throughput, selective and efficient strategy for cancer detection and treatment. PMID:25133743

  7. Synthesis of wheatear-like ZnO nanoarrays decorated with Ag nanoparticles and its improved SERS performance through hydrogenation.

    PubMed

    Shan, Yufeng; Yang, Yong; Cao, Yanqin; Fu, Chaoli; Huang, Zhengren

    2016-04-01

    Semiconductor/noble metal composite SERS substrates have been extensively studied due to their unique bifunctionality. In this work, wheatear-like ZnO nanoarrarys have been fabricated via a modified low-temperature solution method. The hierarchical nanostructures that are constructed by stacked nanoflakes and long whiskers of ZnO possess a substantial number of characteristic nano corners and edges, which are proved to be beneficial to deposit more Ag nanoparticles (NPs). Furthermore, hydrogenated wheatear-like ZnO/AgNP composite substrates are achieved via a safe and facile solid hydrogen source (NaBH4). The hydrogenated ZnO/AgNPs (H-ZnO/Ag) substrates exhibit greatly improved SERS activity in detecting R6G molecules with an enhancement factor (EF) up to ∼0.49 × 10(8), over two orders of magnitude higher than that of the substrates before hydrogenation. The outstanding SERS performance of wheatear-like H-ZnO/Ag substrates benefits from the emerging porous structure of ZnO and abundant surface defects introduced by hydrogenation. In addition, the as-prepared substrates also show high detection sensitivity, good repeatability and recyclability, indicating great potential for practical applications. PMID:26916627

  8. Large-scale preparation of strawberry-like, AgNP-doped SiO2 microspheres using the electrospraying method

    NASA Astrophysics Data System (ADS)

    Ma, Zhijun; Ji, Huijiao; Tan, Dezhi; Dong, Guoping; Teng, Yu; Zhou, Jiajia; Guan, Miaojia; Qiu, Jianrong; Zhang, Ming

    2011-07-01

    In this paper, we report on a novel strategy for the preparation of silver nanoparticle-doped SiO2 microspheres (Ag-SMSs) with an interesting strawberry-like morphology using a simple and efficient electrospraying method. SEM (scanning electron microscopy), TEM (transmission electron microscopy), XRD (x-ray diffraction), EDS (energy-dispersive spectroscopy) and UV-vis spectra (ultraviolet-visible spectra) were applied to investigate the morphology, structure, composition and optical properties of the hybrid microspheres, and E. coli (Escherichia coli) was used as a model microbe to evaluate their antibacterial ability. The results showed that the Ag-SMSs were environmentally stable and washing resistant. The Ag-SMSs exhibited effective inhibition against proliferation of E. coli, and their antibacterial ability could be well preserved for a long time. The environmental stability, washing resistance, efficient antibacterial ability and simple but productive preparation method endowed the Ag-SMSs with great potential for practical biomedical applications.

  9. Magnetic properties of self-organized L1 0 FePtAg nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Wang, S.; Kang, S. S.; Nikles, D. E.; Harrell, J. W.; Wu, X. W.

    2003-10-01

    The magnetic properties of chemically synthesized high anisotropy L1 0 [Fe 49Pt 51] 88Ag 12 nanoparticle arrays have been studied as a function of annealing temperature. Particles were prepared by the simultaneous polyol reduction of platinum acetylacetonate and silver acetate and the thermal decomposition of iron carbonyl, yielding monodispersed particles of diameter ˜3.5 nm. Addition of Ag lowers the ordering temperature of self-assembled arrays by ˜150°C. After annealing at Ta=500°C for 30 min in an Ar/H 2 atmosphere, the coercivity was 13,800 Oe. TEM and delta- M measurements indicate weak particle aggregation up to Ta=400°C, with evidence of sintering at higher temperatures. Large ratios of remanent to hysteresis coercivity indicate a large distribution in anisotropy energies. Anomalously large thermal stability constants, KV/ kBT, and switching volumes were measured, even in samples with very little evidence of sintering. Zero field viscosity versus remanence curves show evidence of exchange interactions.

  10. Ag Nanoparticles (Ag NM300K) in the Terrestrial Environment: Effects at Population and Cellular Level in Folsomia candida (Collembola).

    PubMed

    Mendes, Luís André; Maria, Vera L; Scott-Fordsmand, Janeck J; Amorim, Mónica J B

    2015-10-01

    The effects of nanomaterials have been primarily assessed based on standard ecotoxicity guidelines. However, by adapting alternative measures the information gained could be enhanced considerably, e.g., studies should focus on more mechanistic approaches. Here, the environmental risk posed by the presence of silver nanoparticles (Ag NM300K) in soil was investigated, anchoring population and cellular level effects, i.e., survival, reproduction (28 days) and oxidative stress markers (0, 2, 4, 6, 10 days). The standard species Folsomia candida was used. Measured markers included catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), total glutathione (TG), metallothionein (MT) and lipid peroxidation (LPO). Results showed that AgNO₃ was more toxic than AgNPs at the population level: reproduction EC₂₀ and EC₅₀ was ca. 2 and 4 times lower, respectively. At the cellular level Correspondence Analysis showed a clear separation between AgNO₃ and AgNP throughout time. Results showed differences in the mechanisms, indicating a combined effect of released Ag⁺ (MT and GST) and of AgNPs (CAT, GR, TG, LPO). Hence, clear advantages from mechanistic approaches are shown, but also that time is of importance when measuring such responses. PMID:26473892

  11. Gamma ray irradiated AgFeO{sub 2} nanoparticles with enhanced gas sensor properties

    SciTech Connect

    Wang, Xiuhua; Shi, Zhijie; Yao, Shangwu; Liao, Fan; Ding, Juanjuan; Shao, Mingwang

    2014-11-15

    AgFeO{sub 2} nanoparticles were synthesized via a facile hydrothermal method and irradiated by various doses of gamma ray. The products were characterized with X-ray powder diffraction, UV–vis absorption spectrum and transmission electron microscope. The results revealed that the crystal structure, morphology and size of the samples remained unchanged after irradiation, while the intensity of UV–Vis spectra increased with irradiation dose increasing. In addition, gamma ray irradiation improved the performance of gas sensor based on the AgFeO{sub 2} nanoparticles including the optimum operating temperature and sensitivity, which might be ascribed to the generation of defects. - Graphical abstract: Gamma ray irradiation improved the performance of gas sensor based on the AgFeO{sub 2} nanoparticles including sensitivity and optimum operating temperature, which might be ascribed to the generation of defects. - Highlights: • AgFeO{sub 2} nanoparticles were synthesized and irradiated with gamma ray. • AgFeO{sub 2} nanoparticles were employed to fabricate gas sensors to detect ethanol. • Gamma ray irradiation improved the sensitivity and optimum operating temperature.

  12. The influence of Ag nanoparticles on random laser from dye-doped nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Ye, Lihua; Liu, Bo; Li, Fangjie; Feng, Yangyang; Cui, Yiping; Lu, Yanqing

    2016-10-01

    The threshold energy and electric field response characteristic of random laser have been investigated in dye-doped nematic liquid crystal (DDNLC) with the addition of different concentrations of Ag nanoparticles (NPs). Due to the localized surface plasmon resonance (LSPR) induced by Ag NPs, random laser from DDNLC with Ag NP doping had a lower threshold energy. From another point of view, nematic liquid crystals (LCs) in a DDNLC cell with the addition of Ag NPs could be more easily influenced by the electric field, which allowed the random laser to be controlled at a lower applied voltage. The turn-off time and turn-on time of random laser also decreased in the DDNLC cells with increasing the concentration of Ag NPs. This is due to the enhancement of the electro-optical characteristic of LC and the restoring force imparted by the locally ordered LCs induced by the Ag NPs, respectively.

  13. Electrospun polyacrylonitrile nanofibers supported Ag/Pd nanoparticles for hydrogen generation from the hydrolysis of ammonia borane

    NASA Astrophysics Data System (ADS)

    Tong, Yan; Lu, Xiaofeng; Sun, Weining; Nie, Guangdi; Yang, Liu; Wang, Ce

    2014-09-01

    A high-performance hydrogen generation system based on the electrospun polyacrylonitrile (PAN)/Ag/Pd composite nanofibers, which were prepared by microwave reducing the electrospun PAN/AgNO3 nanofibers and followed by a replacement reaction has been demonstrated. The morphology of the as-prepared PAN/Ag/Pd composite nanofibers and the metal nanoparticles on the fibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. It has been demonstrated that the obtained PAN/Ag/Pd composite nanofibers possess fine morphology and high catalytic activities for H2 generation from aqueous solution of ammonia borane (NH3BH3, AB). The H2 generation test exhibited that the catalyst had excellent catalytic activity (with turnover frequency (TOF) of 377.2 mol H2 h-1 (mol Pd)-1), good recycle stability and easy-separation from the reaction system. This new kind of nanofibers possesses great potential application for the new clean energy development.

  14. Voltammetric studies of Azathioprine on the surface of graphite electrode modified with graphene nanosheets decorated with Ag nanoparticles.

    PubMed

    Asadian, Elham; Iraji Zad, Azam; Shahrokhian, Saeed

    2016-01-01

    By using graphene nanosheets decorated with Ag nanoparticles (AgNPs-G) as an effective approach for the surface modification of pyrolytic graphite electrode (PGE), a sensing platform was fabricated for the sensitive voltammetric determination of Azathioprine (Aza). The prepared AgNPs-G nanosheets were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis and Raman spectroscopy techniques. The electrochemical behavior of Aza was investigated by means of cyclic voltammetry. Comparing to the bare PGE, a remarkable enhancement was observed in the response characteristics of Aza on the surface of the modified electrode (AgNPs-G/PGE) as well as a noticeable decrease in its reduction overpotential. These results can be attributed to the incredible enlargement in the microscopic surface area of the electrode due to the presence of graphene nanosheets together with strong adsorption of Aza on its surface. The effect of experimental parameters such as accumulation time, the amount of modifier suspension and pH of the supporting electrolyte were also optimized toward obtaining the maximum sensitivity. Under the optimum conditions, the calibration curve studies demonstrated that the peak current increased linearly with Aza concentrations in the range of 7 × 10(-7) to 1 × 10(-4)mol L(-1) with the detection limit of 68 nM. Further experiments revealed that the modified electrode can be successfully applied for the accurate determination of Aza in pharmaceutical preparations.

  15. Ordered silicon nanowire arrays prepared by an improved nanospheres self-assembly in combination with Ag-assisted wet chemical etching

    NASA Astrophysics Data System (ADS)

    Jia, Guobin; Westphalen, Jasper; Drexler, Jan; Plentz, Jonathan; Dellith, Jan; Dellith, Andrea; Andrä, Gudrun; Falk, Fritz

    2016-04-01

    An improved Langmuir-Blodgett self-assembly process combined with Ag-assisted wet chemical etching for the preparation of ordered silicon nanowire arrays is presented in this paper. The new process is independent of the surface conditions (hydrophilic or hydrophobic) of the substrate, allowing for depositing a monolayer of closely packed polystyrene nanospheres onto any flat surface. A full control of the morphology of the silicon nanowire is achieved. Furthermore, it is observed that the formation of porous-Si at the tips of the nanowires is closely related to the release of Ag nanoparticles from the Ag mask during the etching, which subsequently redeposit on the surface initially free of Ag, and these Ag nanoparticles catalyze the etching of the tips and lead to the porous-Si formation. This finding will help to improve the resulting nano- and microstructures to get them free of pores, and renders it a promising technology for low-cost high throughput fabrication of specific optical devices, photonic crystals, sensors, MEMS, and NEMS by substituting the costly BOSCH process. It is shown that ordered nanowire arrays free of porous structures can be produced if all sources of Ag nanoparticles are excluded, and structures with aspect ratio more than 100 can be produced.

  16. Ag2Mo3O10 Nanorods Decorated with Ag2S Nanoparticles: Visible-Light Photocatalytic Activity, Photostability, and Charge Transfer.

    PubMed

    Chen, Xianjie; Liu, Fenglin; Yan, Xiaodong; Yang, Yang; Chen, Qian; Wan, Juan; Tian, Lihong; Xia, Qinghua; Chen, Xiaobo

    2015-12-14

    Ag2Mo3O10 nanorods decorated with Ag2 S nanoparticles have been synthesized by an anion-exchange route. With thiourea as the sulfur source, sulfur ions replace [Mo3O10](2-) units of active sites on the surface of Ag2Mo3O10 nanorods, forming Ag2Mo3O10 nanorods decorated with Ag2S nanoparticles. This induces enhanced absorption in the visible-light region. Ag2 S nanoparticles decorate the surface of Ag2Mo3O10 nanorods uniformly with a suitable amount of thiourea. The Ag2S/Ag2Mo3O10 nanoheterostructure enhances the photocatalytic activity on the degradations of Rhodamine B and glyphosate under visible light. This enhancement is attributed to the improved absorption of visible light and effective separation of charge carriers in the nanoheterostructure. Meanwhile, the Ag2S/Ag2Mo3O10 nanoheterostructure displays good photocatalytic stability based on cyclic photocatalytic experiments.

  17. Formation of Ag Nanoparticles on β-Ag2WO4 through Electron Beam Irradiation: A Synergetic Computational and Experimental Study.

    PubMed

    Roca, Roman A; Gouveia, Amanda F; Lemos, Pablo S; Gracia, Lourdes; Andrés, Juan; Longo, Elson

    2016-09-01

    In the present work, a combined theoretical and experimental study was performed on the structure, optical properties, and growth of Ag nanoparticles in metastable β-Ag2WO4 microcrystals. This material was synthesized using the precipitation method without the presence of surfactants. The structural behavior was analyzed using X-ray diffraction and Raman and infrared spectroscopy. Field-emission scanning electron microscopy revealed the presence of irregular spherical-like Ag nanoparticles on the β-Ag2WO4 microcrystals, which were induced by electron beam irradiation under high vacuum conditions. A detailed analysis of the optimized β-Ag2WO4 geometry and theoretical results enabled interpretation of both the Raman and infrared spectra and provided deeper insight into rationalizing the observed morphology. In addition, first-principles calculations, within the quantum theory of atoms in molecules framework, provided an in-depth understanding of the nucleation and early evolution of Ag nanoparticles. The Ag nucleation and formation is the result of structural and electronic changes of the [AgO6] and [AgO5] clusters as a constituent building block of β-Ag2WO4, which is consistent with Ag metallic formation. PMID:27533109

  18. Speciation and Lability of Ag-, AgCl- and Ag2S-Nanoparticles in Soil Determined by X-ray Absorption Spectroscopy and Diffusive Gradients in Thin Films

    EPA Science Inventory

    Long-term speciation and lability of silver (Ag-), silver chloride (AgCl-) and silver sulfide nanoparticles (Ag2S-NPs) in soil were studied by X-ray absorption spectroscopy (XAS), and newly developed "nano" Diffusive Gradients in Thin Films (DGT) devices. These nano-D...

  19. Preparation of the CNC/Ag/beeswax composites for enhancing antibacterial and water resistance properties of paper.

    PubMed

    Liu, Kai; Liang, Hunan; Nasrallah, Joseph; Chen, Lihui; Huang, Liulian; Ni, Yonghao

    2016-05-20

    An effective method of preparing composites containing inorganic (Ag) and organic (beeswax) particles was established in this study. Ag nanoparticles were first immobilized on the cellulose nanocrystals (CNC) during the reduction of AgNO3 in the presence of CNC, then mixed with beeswax by high speed stirring. Scanning transmission electron microscopy (STEM) images indicated that Ag and beeswax particles were uniformly dispersed and stable in the network structure formed by CNC. Upon coating on a paper surface, a layer of beeswax film was evident based on scanning electron microscopy (SEM) images. The dynamic contact angle and antibacterial activity tests indicated that the contact angle of coated paper reached 113.06° and the growth inhibition of Escherichia coli increased to 99.96%, respectively, at a coating amount of 21.53 g/m(2). When applied onto paper surface by coating, the CNC/Ag/beeswax composites can impact paper with antibacterial property and improved water resistance. PMID:26917389

  20. Dual layer hollow fiber PVDF ultra-filtration membranes containing Ag nano-particle loaded zeolite with longer term anti-bacterial capacity in salt water.

    PubMed

    Shi, Huyan; Xue, Lixin; Gao, Ailin; Zhou, Qingbo

    2016-01-01

    Dual layer polyvinylidene fluoride (PVDF), antibacterial, hollow fiber, ultra-filtration composite membranes with antibacterial particles (silver (Ag) nano-particles loaded zeolite (Z-Ag)) in the outer layer were prepared with high water flux and desired pore sizes. The amounts of Ag(+) released from the composite membranes, freshly made and stored in water and salt solution, were measured. The result indicated that dual layer PVDF antibacterial hollow fiber containing Z-Ag (M-1-Ag) still possessed the ability of continuous release of Ag(+) even after exposure to water with high ionic content, showing a longer term resistance to bacterial adhesion and antibacterial activity than membrane doped with Z-Ag(+) (M-1). Results from an anti-adhesion and bacteria killing test with Escherichia coli supported that the antibacterial efficiency of dual hollow fiber PVDF membranes with Z-Ag was much higher than those with Z-Ag(+) after long time storage in water or exposure to phosphate buffered saline (PBS) solution. This novel hollow fiber membrane may find applications in constructing sea water pretreatment devices with long term antifouling capability for the desalination processes.

  1. Dual layer hollow fiber PVDF ultra-filtration membranes containing Ag nano-particle loaded zeolite with longer term anti-bacterial capacity in salt water.

    PubMed

    Shi, Huyan; Xue, Lixin; Gao, Ailin; Zhou, Qingbo

    2016-01-01

    Dual layer polyvinylidene fluoride (PVDF), antibacterial, hollow fiber, ultra-filtration composite membranes with antibacterial particles (silver (Ag) nano-particles loaded zeolite (Z-Ag)) in the outer layer were prepared with high water flux and desired pore sizes. The amounts of Ag(+) released from the composite membranes, freshly made and stored in water and salt solution, were measured. The result indicated that dual layer PVDF antibacterial hollow fiber containing Z-Ag (M-1-Ag) still possessed the ability of continuous release of Ag(+) even after exposure to water with high ionic content, showing a longer term resistance to bacterial adhesion and antibacterial activity than membrane doped with Z-Ag(+) (M-1). Results from an anti-adhesion and bacteria killing test with Escherichia coli supported that the antibacterial efficiency of dual hollow fiber PVDF membranes with Z-Ag was much higher than those with Z-Ag(+) after long time storage in water or exposure to phosphate buffered saline (PBS) solution. This novel hollow fiber membrane may find applications in constructing sea water pretreatment devices with long term antifouling capability for the desalination processes. PMID:27148717

  2. Preparation and characterization of porphyrin nanoparticles.

    PubMed

    Gong, Xianchang; Milic, Tatjana; Xu, Chang; Batteas, James D; Drain, Charles Michael

    2002-12-01

    The synthesis, characterization, and stability of porphyrin nanoparticles of 20-200 nm diameter presented herein is general for meso arylporphyrins. The elegance of the method lies in its simplicity. This work shows that the agent used to prevent agglomeration can be covalently attached to the dye forming the particle or be part of the solvent system. It also demonstrates that these and other types of dyes with a range of photonic properties do not need to be prepared by inclusion in external matrices or by designed self-assembly a priori. The matrix may severely limit the functionality of the particles in the former case, and at present this size of particle is difficult to achieve via the latter.

  3. Decorated TiO2 Nanoparticles with La and Ag Elements to Improve Photocatalytic Activity Under Visible Light for the Degradation of MO.

    PubMed

    Wang, Qinghua; Gao, Xuechuan; Zhang, Renfei; Shen, Beibei; Tan, Zhibing; Li, Zhao; Yu, Shiyong

    2016-04-01

    Visible-light photocatalyst of TiO2/La/Ag nanocomposites were successfully synthesized via the conventional sol-gel method and reducing agent of Ag+. The photocatalytic activities were evaluated by methyl orange (MO) degradation. They have remarkable photocatalytic activities compared to TiO2-Anatase, which is thanks to the separation of electron-hole pairs by Ag nanoparticles and lanthanum. The products were characterized by a series of techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Uv-vis. The results show that spherical nanocomposites have been prepared with the size 300 nm and Ag nanoparticles (~10 nm) are dispersed uniformly onto the surface of TiO2/La, which forms TiO2/La/Ag nanocomposites. TiO2/La/Ag nanocomposites have good absorption in the visible region (700 nm > λ > 400 nm). The reasons are as follows: (1) the efficient separation of photogenerated electrons and holes of the photocatalysts on the surface of TiO2/La/Ag nanocomposites and (2) a wide visible-light photoabsorption range (700 nm > λ > 400 nm). Therefore, this study may provide some new idea for the rational design and the facile synthesis of composite catalysts with a green, efficient pathway. PMID:27451670

  4. Influence of Ag/TiO2 nanoparticle on the surface hydrophilicity and visible-light response activity of polyvinylidene fluoride membrane

    NASA Astrophysics Data System (ADS)

    Li, Jian-Hua; Yan, Bang-Feng; Shao, Xi-Sheng; Wang, Shuang-Shuang; Tian, Hai-Yan; Zhang, Qi-Qing

    2015-01-01

    A novel polyvinylidene fluoride (PVDF) membrane, i.e. Ag/TiO2/PVDF composite membrane, was prepared via the blending/photo reduction combined method in this paper. And the influence of Ag/TiO2 embedment on the surface property of PVDF membrane was discussed, including the surface hydrophilicity and visible-light response activity. ATR/FTIR characterization certified that amount of hydroxyl group (sbnd OH) was formed on the PVDF membrane surface owing to the embedment of Ag/TiO2. The results suggested that the increased hydrophilicity of PVDF membrane can be achieved through the addition of Ag/TiO2 nanoparticles because the surface hydroxyl group (sbnd OH) had great contribution to membrane hydrophilicity. The increased hydrophilicity was also demonstrated by the contact angle measurement. In a word, Ag/TiO2 improved the surface hydrophilicity of PVDF membrane in contrast with virgin PVDF membrane. Besides, Ag/TiO2 nanoparticle provided PVDF membrane with an enhanced visible-light response activity. Ag/TiO2/PVDF composite membrane showed excellent activity on degradation of methylene blue (MB) and inactivation of bacterial under visible-light illumination. I hope this research can provide a new way for PVDF surface modification.

  5. Sequential laser and ultrasonic wave generation of TiO2@Ag core-shell nanoparticles and their anti-bacterial properties.

    PubMed

    Hamad, Abubaker Hassan; Li, Lin; Liu, Zhu; Zhong, Xiang Li; Wang, Tao

    2016-02-01

    Core-shell nanoparticles have unusual physical, chemical and biological properties. Until now, for the Ag and TiO2 combination, only Ag core and TiO2 shell nanoparticles have been practically demonstrated. In this investigation, novel TiO2@Ag core-shell (TiO2 core and Ag shell) nanoparticles were produced via ultrasonic vibration of Ag-TiO2 compound nanoparticles. A bulk Ti/Ag alloy plate was used to generate colloidal Ag-TiO2 compound nanoparticles via picosecond laser ablation in deionised water. The colloidal nanoparticles were then sonicated in an ultrasonic bath to generate TiO2@Ag core-shell nanoparticles. They were characterised using a UV-VIS spectrometer, transmission electron microscopy (TEM), high-angle annular dark-field-Scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The Ag-TiO2 compound and the TiO2@Ag core-shell nanoparticles were examined for their antibacterial activity against Escherichia coli (E. coli) JM109 strain bacteria and compared with those of Ag and TiO2 nanoparticles. The antibacterial activity of the core-shell nanoparticles was slightly better than that of the compound nanoparticles at the same concentration under standard laboratory light conditions and both were better than the TiO2 nanoparticles but not as good as the Ag nanoparticles.

  6. Preparation of silver nano-particles immobilized onto chitin nano-crystals and their application to cellulose paper for imparting antimicrobial activity.

    PubMed

    Li, Zhihan; Zhang, Ming; Cheng, Dong; Yang, Rendang

    2016-10-20

    Immobilized silver nano-particles (Ag NPs) possess excellent antimicrobial properties due to their unique surface characteristics. In this paper, immobilized silver nano-particles were synthesized in the presence of chitin nano-crystals (CNC) based on the Tollens mechanism (reduction of silver ion by aldehydes in the chitosan oligosaccharides (COS)) under microwave-assisted conditions. The prepared Ag NPs-loaded CNC nano-composites were then applied onto the paper surface via coating for the preparation of antibacterial paper. Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) results confirmed that the Ag NPs were immobilized onto the CNC. The transmission electron microscope (TEM) and scanning electron microscopy (SEM) results further revealed that the spherical Ag NPs (5-12nm) were well dispersed on the surface of CNC. The coated paper made from the Ag NPs-loaded CNC nano-composites exhibited a high effectiveness of the antibacterial activity against E. coli or S. aureus.

  7. The disinfection performance and mechanisms of Ag/lysozyme nanoparticles supported with montmorillonite clay.

    PubMed

    Jiang, Jing; Zhang, Chang; Zeng, Guang-Ming; Gong, Ji-Lai; Chang, Ying-Na; Song, Biao; Deng, Can-Hui; Liu, Hong-Yu

    2016-11-01

    The fabrication of montmorillonite (Mt) decorated with lysozyme-modified silver nanoparticles (Ag/lyz-Mt) was reported. The lysozyme (lyz) was served as both reducing and capping reagent. Coupling the bactericidal activity of the lyz with AgNPs, along with the high porous structure and large specific surface area of the Mt, prevented aggregation of AgNPs and promoted nanomaterial-bacteria interactions, resulting in a greatly enhanced bactericidal capability against both Gram positive and Gram negative bacteria. This paper systematically elucidated the bactericidal mechanisms of Ag/lyz-Mt. Direct contact between the Ag/lyz-Mt surface and the bacterial cell was essential to the disinfection. Physical disruption of bacterial membrane was considered to be one of the bactericidal mechanisms of Ag/lyz-Mt. Results revealed that Ag(+) was involved in the bactericidal activity of Ag/lyz-Mt via tests conducted using Ag(+) scavengers. A positive ROS (reactive oxygen species) scavenging test indirectly confirmed the involvement of ROS (O2(-), H2O2, and OH) in the bactericidal mechanism. Furthermore, the concentrations of individual ROS were quantified. Results showed that Ag/lyz-Mt nanomaterial could be a promising bactericide for water disinfection.

  8. The disinfection performance and mechanisms of Ag/lysozyme nanoparticles supported with montmorillonite clay.

    PubMed

    Jiang, Jing; Zhang, Chang; Zeng, Guang-Ming; Gong, Ji-Lai; Chang, Ying-Na; Song, Biao; Deng, Can-Hui; Liu, Hong-Yu

    2016-11-01

    The fabrication of montmorillonite (Mt) decorated with lysozyme-modified silver nanoparticles (Ag/lyz-Mt) was reported. The lysozyme (lyz) was served as both reducing and capping reagent. Coupling the bactericidal activity of the lyz with AgNPs, along with the high porous structure and large specific surface area of the Mt, prevented aggregation of AgNPs and promoted nanomaterial-bacteria interactions, resulting in a greatly enhanced bactericidal capability against both Gram positive and Gram negative bacteria. This paper systematically elucidated the bactericidal mechanisms of Ag/lyz-Mt. Direct contact between the Ag/lyz-Mt surface and the bacterial cell was essential to the disinfection. Physical disruption of bacterial membrane was considered to be one of the bactericidal mechanisms of Ag/lyz-Mt. Results revealed that Ag(+) was involved in the bactericidal activity of Ag/lyz-Mt via tests conducted using Ag(+) scavengers. A positive ROS (reactive oxygen species) scavenging test indirectly confirmed the involvement of ROS (O2(-), H2O2, and OH) in the bactericidal mechanism. Furthermore, the concentrations of individual ROS were quantified. Results showed that Ag/lyz-Mt nanomaterial could be a promising bactericide for water disinfection. PMID:27318738

  9. Synthesis and characterization of Au-core Ag-shell nanoparticles from unmodified apoferritin

    SciTech Connect

    Li, T.; Chattopadhyay, S.; Shibata, T.; Cook, R. E.; Miller, J. T.; Suthiwangcharoen, N.; Lee, S.; Winans, R. E.; Lee, B.

    2012-01-01

    Narrow-size distributed, water-soluble Au-core Ag-shell nanoparticles with a size range from 1 to 5 nm are synthesized using unmodified apoferritin as a template. Fast protein liquid chromatography reveals that the nanoparticles are formed inside the apoferritin cavity and are stable in aqueous solution. Electron microscopy shows that the particles are uniform in size and composed of both Au and Ag. In addition, extended X-ray absorption fine structure confirms that the particles have a core-shell structure with a Au core covered with a Ag shell. By varying the loading amounts of the silver precursor, the Ag shell thickness is controlled from one layer to several layers.

  10. Prediction of size distribution of Ag nanoparticles synthesized via gamma-ray radiolysis

    NASA Astrophysics Data System (ADS)

    Liang, Jia-liang; Shen, Sheng-wen; Ye, Sheng-ying; Ye, Lü-meng

    2015-09-01

    The spherical shape Ag nanoparticles synthesized via gamma-ray radiolysis were observed with the transmission electron microscope (TEM). Diameters of Ag nanoparticles were measured from the TEM photographs. Statistical analysis showed that the particle diameter complied with a linear-converted Poisson distribution. The distribution parameter, which was the average of diameters, was related to the ultraviolet-visible spectrum peak position of the nanosilver collosol. An empirical equation was established to predicting size distribution of Ag nanoparticles with the peak position. Nanosilver of different sizes could be synthesized by adjusting the intensity of γ-irradiation, the kind and the addition amount of the stabilizing agent. Because particle size affects the physiochemical properties of nanosilver material, results of this paper would be of practical significance for the application of nanosilver.

  11. Biofabrication of Ag nanoparticles using Moringa oleifera leaf extract and their antimicrobial activity

    PubMed Central

    Prasad, TNVKV; Elumalai, EK

    2011-01-01

    Objective To formulate a simple rapid procedure for bioreduction of silver nanoparticles using aqueous leaves extract of Moringa oleifera (M. oleifera). Methods 10 mL of leaf extract was mixed to 90 mL of 1 mM aqueous of AgNO3 and was heated at 60 - 80 °C for 20 min. A change from brown to reddish color was observed. Characterization using UV-Vis spectrophotometry, Transmission Electron Microscopy (TEM) was performed. Results TEM showed the formation of silver nanoparticles with an average size of 57 nm. Conclusions M. oleifera demonstrates strong potential for synthesis of silver nanoparticles by rapid reduction of silver ions (Ag+ to Ag0). Biological methods are good competents for the chemical procedures, which are eco-friendly and convenient. PMID:23569809

  12. Synthesis of Starch-Stabilized Ag Nanoparticles and Hg2+ Recognition in Aqueous Media

    NASA Astrophysics Data System (ADS)

    Fan, Yingju; Liu, Zhen; Wang, Le; Zhan, Jinhua

    2009-10-01

    The starch-stabilized Ag nanoparticles were successfully synthesized via a reduction approach and characterized with SPR UV/Vis spectroscopy, TEM, and HRTEM. By utilizing the redox reaction between Ag nanoparticles and Hg2+, and the resulted decrease in UV/Vis signal, we develop a colorimetric method for detection of Hg2+ ion. A linear relationship stands between the absorbance intensity of the Ag nanoparticles and the concentration of Hg2+ ion over the range from 10 ppb to 1 ppm at the absorption of 390 nm. The detection limit for Hg2+ ions in homogeneous aqueous solutions is estimated to be ~5 ppb. This system shows excellent selectivity for Hg2+ over other metal ions including Na+, K+, Ba2+, Mg2+, Ca2+, Fe3+, and Cd2+. The results shown herein have potential implications in the development of new colorimetric sensors for easy and selective detection and monitoring of mercuric ions in aqueous solutions.

  13. The characteristics of novel bimodal Ag-TiO2 nanoparticles generated by hybrid laser-ultrasonic technique

    NASA Astrophysics Data System (ADS)

    Hamad, Abubaker; Li, Lin; Liu, Zhu; Zhong, Xiang Li; Burke, Grace; Wang, Tao

    2016-04-01

    Silver-titania (Ag-TiO2) nanoparticles with smaller Ag nanoparticles attached to larger TiO2 nanoparticles were generated by hybrid ultrasonic vibration and picosecond laser ablation of Ag and Ti bulk targets in deionised water, for the first time. The laser has a wavelength of 1064 nm and a pulse duration of 10 ps. It was observed that without the ultrasonic vibration, Ag and TiO2 nanoparticles did not combine, thus the role of ultrasonic vibration is essential. In addition, colloidal TiO2 and Ag nanoparticles were generated separately for comparison under the same laser beam characteristics and process conditions. The absorption spectra of colloidal Ag-TiO2 cluster nanoparticles were examined by UV-Vis spectroscopy, and size distribution was characterised using transmission electron microscopy. The morphology and composition of Ag-TiO2 nanoparticles were examined using scanning transmission electron microscopy in high-angle annular dark field, and energy-dispersive X-ray spectroscopy. The crystalline structures were investigated by X-ray diffraction. The size of larger TiO2 particles was in the range 30-150 nm, and the smaller-sized Ag nanoparticles attached to the TiO2 was mainly in the range of 10-15 nm. The yield is more than 50 % with the remaining nanoparticles in the form of uncombined Ag and TiO2. The nanoparticles generated had strong antibacterial effects as tested against E. coli. A discussion is given on the role of ultrasonic vibration in the formation of Ag-TiO2 hybrid nanoparticles by picosecond laser ablation.

  14. Preparations, characterizations and applications of chitosan-based nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Chenguang; Tan, Yulong; Liu, Chengsheng; Chen, Xiguang; Yu, Lejun

    2007-07-01

    Chitosan is a natural polysaccharide prepared by the N-deacetylation of chitin. In this paper we have reviewed the methods of preparation of chitosan-based nanoparticles and their pharmaceutical applications. There are five methods of their preparations: emulsion cross-linking, emulsion-droplet coalescence, ionic gelation, reverse micellar method and chemically modified chitosan method. Chitosan nanoparticles are used as carriers for low molecular weight drug, vaccines and DNA. Releasing characteristics, biodistribution and applications are also summarized.

  15. In situ biosynthesis of Ag, Au and bimetallic nanoparticles using Piper pedicellatum C.DC: green chemistry approach.

    PubMed

    Tamuly, Chandan; Hazarika, Moushumi; Borah, Sarat Ch; Das, Manash R; Boruah, Manas P

    2013-02-01

    The synthesis of Ag, Au and Ag-Au bimetallic nanoparticles using Piper pedicellatum C.DC leaf extract is demonstrated here. The rapid formation of stable Ag and Au nanoparticles has been found using P. pedicellatum C.DC leaf extract in aqueous medium at normal atmospheric condition. Competitive reduction of Ag(+) and Au(3+) ions present simultaneously in solution during exposure to P. pedicellatum C.DC leaf extract leads to the synthesis of bimetallic Ag-Au nanoparticles in solution. Transmission electron microscopy (TEM) analysis revealed that the Ag nanoparticles predominantly form spherical in shape with the size range of 2.0±0.5-30.0±1.2 nm. In case of Au nanoparticles, the particles are spherical in shape along with few triangular, hexagonal and pentagonal shaped nanoparticles also observed. X-ray diffraction (XRD) studies revealed that the nanoparticles were face centered cubic (fcc) in shape. Fourier transform infrared spectroscopy (FTIR) showed nanoparticles were capped with plant compounds. The chemical constituents, viz. catechin, gallic acid, courmaric acid and protocatechuic acid of the leaf extract were identified which may act as a reducing, stabilizing and capping agent. The expected reaction mechanism in the formation of Ag and Au nanoparticles is also reported. PMID:23107941

  16. In situ biosynthesis of Ag, Au and bimetallic nanoparticles using Piper pedicellatum C.DC: green chemistry approach.

    PubMed

    Tamuly, Chandan; Hazarika, Moushumi; Borah, Sarat Ch; Das, Manash R; Boruah, Manas P

    2013-02-01

    The synthesis of Ag, Au and Ag-Au bimetallic nanoparticles using Piper pedicellatum C.DC leaf extract is demonstrated here. The rapid formation of stable Ag and Au nanoparticles has been found using P. pedicellatum C.DC leaf extract in aqueous medium at normal atmospheric condition. Competitive reduction of Ag(+) and Au(3+) ions present simultaneously in solution during exposure to P. pedicellatum C.DC leaf extract leads to the synthesis of bimetallic Ag-Au nanoparticles in solution. Transmission electron microscopy (TEM) analysis revealed that the Ag nanoparticles predominantly form spherical in shape with the size range of 2.0±0.5-30.0±1.2 nm. In case of Au nanoparticles, the particles are spherical in shape along with few triangular, hexagonal and pentagonal shaped nanoparticles also observed. X-ray diffraction (XRD) studies revealed that the nanoparticles were face centered cubic (fcc) in shape. Fourier transform infrared spectroscopy (FTIR) showed nanoparticles were capped with plant compounds. The chemical constituents, viz. catechin, gallic acid, courmaric acid and protocatechuic acid of the leaf extract were identified which may act as a reducing, stabilizing and capping agent. The expected reaction mechanism in the formation of Ag and Au nanoparticles is also reported.

  17. Preparation and characterization of magnetic nanoparticles with chitosan coating

    NASA Astrophysics Data System (ADS)

    Dung, Doan Thi Kim; Hoang Hai, Tran; Phuc, Le Hong; Long, Bui Duc; Khanh Vinh, Le; Nha Truc, Phan

    2009-09-01

    Magnetic chitosan nanoparticles were prepared by the suspension cross-linking technique for use in the application of magnetic carrier technology. The Fe3O4 magnetic nanoparticles were synthesized by co-precipitation of FeCl2 and FeCl3 solution in base medium for using in the preparation of the magnetic chitosan. The morphological and magnetic properties of the magnetic nanoparticles were characterized by different techniques (TEM, XRD, VSM, FTIR, etc.). The magnetic properties of chitosan - magnetic nanoparticles were analyzed by VSM, and MS around 15 emu/g.

  18. Preparation of drug nanoparticles by emulsion evaporation method

    NASA Astrophysics Data System (ADS)

    Hoa, Le Thi Mai; Chi, Nguyen Tai; Triet, Nguyen Minh; Thanh Nhan, Le Ngoc; Mau Chien, Dang

    2009-09-01

    Polymeric drug nanoparticles were prepared by emulsion solvent evaporation method. In this study, prepared the polymeric drug nanoparticles consist of ketoprofen and Eudragit E 100. The morphology structure was investigated by scanning electron microscopy (SEM). The interactions between the drug and polymer were investigated by Fourier transform infrared spectroscopy (FTIR). The size distribution was measured by means of Dynamic Light Scattering. The nanoparticles have an average size of about 150 nm. The incorporation ability of drugs in the polymeric nanoparticles depended on the integration between polymer and drug as well as the glass transition temperature of the polymer.

  19. Electrochemical preparation of carbon chains and nanoparticles

    NASA Astrophysics Data System (ADS)

    Kavan, Ladislav

    1999-09-01

    The composite of carbon with alkali metal fluoride, C-MF(M=Li, Na) was prepared by cathodic defluorination of perfluorinated hydrocarbons at room temperature. Raman spectra of C-MF from PTFE indicate carbon chains (oligoynes, 1974-2024 cm-1) in addition to graphite-like carbon (1300-1500 cm-1). The oligoyne-containing carbon is partly selforganized by cross linking towards graphene. Highly-organized carbons were prepared from friction-deposited PTFE films. AFM confirms perfect ordering of the precursor molecules (up to atomic resolution), but the corresponding carbonization product is rapidly reconstructed upon contact to air. Raman spectra of oriented carbons display high conjugation lengths (up to 18 sp-bonded carbon atoms). Cyclic perfluorinated precursors are also smoothly defluorinated to elemental carbon. TEM indicates that these carbons contain about 1% of carbonaceous nanoparticles, i.e. nanotubes and onions. Also small quantity of fullerene C60(≈0.01%) was detected in the toluene extract.

  20. Effect of Ag nanowire addition into nanoparticle paste on the conductivity of Ag patterns printed by gravure offset method.

    PubMed

    Ok, Ki-Hun; Lee, Chan-Jae; Kwak, Min-Gi; Choi, Duck-Kyun; Kim, Kwang-Seok; Jung, Seung-Boo; Kim, Jong-Woong

    2014-11-01

    This paper focuses on the effect of Ag nanowire addition into a commercial Ag nanopaste and the printability evaluation of the mixed paste by the gravure offset printing methodology. Ag nanowires were synthesized by a modified polyol method, and a small amount of them was added into a commercial metallic paste based on Ag nanoparticles of 50 nm in diameter. Two annealing temperatures were selected for comparison, and electrical conductivity was measured by four point probe method. As a result, the hybrid mixture could be printed by the gravure offset method for patterning fine lines up to 15 μm width with sharp edges and scarce spreading. The addition of the Ag nanowires was significantly efficient for enhancement of electrical conductivity of the printed lines annealed at a low temperature (150 degrees C), while the effect was somewhat diluted in case of high temperature annealing (200 degrees C). The experimental results were discussed with the conduction mechanism in the printed conductive circuits with a schematic description of the electron flows in the printed lines.

  1. Volume-labeled nanoparticles and methods of preparation

    DOEpatents

    Wang, Wei; Gu, Baohua; Retterer, Scott T; Doktycz, Mitchel J

    2015-04-21

    Compositions comprising nanosized objects (i.e., nanoparticles) in which at least one observable marker, such as a radioisotope or fluorophore, is incorporated within the nanosized object. The nanosized objects include, for example, metal or semi-metal oxide (e.g., silica), quantum dot, noble metal, magnetic metal oxide, organic polymer, metal salt, and core-shell nanoparticles, wherein the label is incorporated within the nanoparticle or selectively in a metal oxide shell of a core-shell nanoparticle. Methods of preparing the volume-labeled nanoparticles are also described.

  2. In vitro assessment of Ag2O nanoparticles toxicity against Gram-positive and Gram-negative bacteria.

    PubMed

    Negi, Harshita; Rathinavelu Saravanan, Palaniyandi; Agarwal, Tithi; Ghulam Haider Zaidi, Mohd; Goel, Reeta

    2013-01-01

    In view of antibiotic resistance among pathogens, the present study is to address the toxicity of Ag2O nanoparticles against the Gram-positive and Gram-negative bacteria through in vitro assays. The preliminary screening by agar diffusion assay confirms the antibacterial activity of Ag2O nanoparticles against all the test bacteria. Comparative antibacterial activity of Ag2O nanoparticles and respective antibiotics reveals their broad range of activity and lower inhibitory dose against the used bacterial strains. Further, they can inhibit E. coli with an effective dose of 0.036 mg/ml within 1 h of exposure time as determined by luciferin based ATP assay. Moreover, the Ag2O nanoparticles exhibit higher antibacterial efficacy against Gram-negative bacteria than Gram-positive bacteria, as revealed by their MIC & MBC values. Therefore, Ag2O nanoparticles pave the way for a new generation of antibacterial agents against the emerging multidrug resistant pathogens.

  3. Speciation and lability of Ag-, AgCl-, and Ag2S-nanoparticles in soil determined by X-ray absorption spectroscopy and diffusive gradients in thin films.

    PubMed

    Sekine, R; Brunetti, G; Donner, E; Khaksar, M; Vasilev, K; Jämting, Å K; Scheckel, K G; Kappen, P; Zhang, H; Lombi, E

    2015-01-20

    Long-term speciation and lability of silver (Ag-), silver chloride (AgCl-), and silver sulfide nanoparticles (Ag2S-NPs) in soil were studied by X-ray absorption spectroscopy (XAS), and newly developed “nano” Diffusive Gradients in Thin Films (DGT) devices. These nano-DGT devices were designed specifically to avoid confounding effects when measuring element lability in the presence of nanoparticles. The aging profile and stabilities of the three nanoparticles and AgNO3 (ionic Ag) in soil were examined at three different soil pH values over a period of up to 7 months. Transformation of ionic Ag, Ag-NP and AgCl-NPs were dependent on pH. AgCl formation and persistence was observed under acidic conditions, whereas sulfur-bound forms of Ag dominated in neutral to alkaline soils. Ag2S-NPs were found to be very stable under all conditions tested and remained sulfur bound after 7 months of incubation. Ag lability was characteristically low in soils containing Ag2S-NPs. Other forms of Ag were linked to higher DGT-determined lability, and this varied as a function of aging and related speciation changes as determined by XAS. These results clearly indicate that Ag2S-NPs, which are the most environmentally relevant form of Ag that enter soils, are chemically stable and have profoundly low Ag lability over extended periods. This may minimize the long-term risks of Ag toxicity in the soil environment. PMID:25436975

  4. Impact of ZnO and Ag Nanoparticles on Bacterial Growth and Viability

    NASA Astrophysics Data System (ADS)

    Olson, M. S.; Digiovanni, K. A.

    2007-12-01

    Hundreds of consumer products containing nanomaterials are currently available in the U.S., including computers, clothing, cosmetics, sports equipment, medical devices and product packaging. Metallic nanoparticles can be embedded in or coated on product surfaces to provide antimicrobial, deodorizing, and stain- resistant properties. Although these products have the potential to provide significant benefit to the user, the impact of these products on the environment remains largely unknown. The purpose of this project is to study the effect of metallic nanoparticles released to the environment on bacterial growth and viability. Inhibition of bacterial growth was tested by adding doses of suspended ZnO and Ag nanoparticles into luria broth prior to inoculation of Escherichia coli cells. ZnO particles (approximately 40 nm) were obtained commercially and Ag particles (12-14 nm) were fabricated by reduction of silver nitrate with sodium borohydride. Toxicity assays were performed to test the viability of E. coli cells exposed to both ZnO and Ag nanoparticles using the LIVE/DEAD BacLight bacterial viability kit (Invitrogen). Live cells stain green whereas cells with compromised membranes that are considered dead or dying stain red. Cells were first grown, stained, and exposed to varying doses of metallic nanoparticles, and then bacterial viability was measured hourly using fluorescence microscopy. Results indicate that both ZnO and Ag nanoparticles inhibit the growth of E. coli in liquid media. Preliminary results from toxicity assays confirm the toxic effect of ZnO and Ag nanoparticles on active cell cultures. Calculated death rates resulting from analyses of toxicity studies will be presented.

  5. Surface modification of oleylamine-capped Ag-Cu nanoparticles to fabricate low-temperature-sinterable Ag-Cu nanoink.

    PubMed

    Kim, Na Rae; Lee, Yung Jong; Lee, Changsoo; Koo, Jahyun; Lee, Hyuck Mo

    2016-08-26

    By treating oleylamine (OA)-capped Ag-Cu nanoparticles with tetramethylammonium hydroxide (TMAH), we obtained metal nanoparticles that are suspended in polar solvents and sinterable at low temperatures. The simple process with ultra sonication enables synthesis of monodispersed and high purity nanoparticles in an organic base, where the resulting nanoparticles are dispersible in polar solvents such as ethanol and isopropyl alcohol. To investigate the surface characteristics, we conducted Fourier-transform infrared and zeta-potential analyses. After thermal sintering at 200 °C, which is approximately 150 °C lower than the thermal decomposition temperature of OA, an electrically conductive thin film was obtained. Electrical resistivity measurements of the TMAH-treated ink demonstrate that surface modified nanoparticles have a low resistivity of 13.7 × 10(-6) Ω cm. These results confirm the prospects of using low-temperature sinterable nanoparticles as the electrode layer for flexible printed electronics without damaging other stacked polymer layers. PMID:27454465

  6. Chemical and phase distributions in a multilayered organic matter-Ag nanoparticle thin film system

    NASA Astrophysics Data System (ADS)

    Michel, F. M.; Levard, C.; Wang, Y.; Choi, Y.; Eng, P.; Brown, G. E.

    2010-12-01

    Rapid development of nanotechnologies raises concern regarding the environmental impact of nanoparticles on ecosystems. Among the types of nanoparticles currently in production, metallic silver is the most widely used in nanotechnology (1). Synthetic Ag nanoparticles (Ag-NPs) are most often used for their antimicrobial and antifungal properties that are, in part, explained by the release of highly toxic Ag+ species (2). While such properties are desirable in certain applied cases, the release of Ag-NPs and soluble Ag+ species to the environment is expected to impact biota as well as soil and water quality (3). With the production of Ag-NPs projected to increase (1), the amount of Ag-NPs that will be released to the environment through waste streams is also likely to increase. As such, a deeper understanding of the fundamental processes associated with Ag-NPs toxicity and reactivity is needed to evaluate their impact on the environment. We have studied the interaction during aging of poly-acrylic acid (PAA) and Ag-NPs with average particle sizes of 20 ±5 nm. The sample studied was composed of thin films of PAA and Ag-NPs deposited on a Si-wafer support. PAA served as a model compound and a simplified surrogate for exopolysaccharide, an organic substance produced through metabolic activity by most microorganisms. We applied a novel combination of long-period x-ray standing wave fluorescence yield (XSW-FY) spectroscopy, grazing-incidence x-ray diffraction (GI-XRD), and XRD-based standing wave profiles (XSW-XRD) to obtain chemical- and phase-specific information on this sample. After 24 hours, we observed the formation of AgCl(s) in the PAA film of the sample, which suggests oxidation and dissolution of a portion of the Ag-NPs during aging, resulting in the release of Ag+. In addition, we see partitioning of Cl and Br, both present initially in the PAA, to the intact Ag-NPs thin film. To our knowledge, this is the first application of this suite of techniques to this

  7. Localized surface plasmon resonance-based hybrid Au-Ag nanoparticles for detection of Staphylococcus aureus enterotoxin B

    NASA Astrophysics Data System (ADS)

    Zhu, Shaoli; Du, ChunLei; Fu, Yongqi

    2009-09-01

    A triangular hybrid Au-Ag nanoparticles array was proposed for the purpose of biosensing in this paper. Constructing the hybrid nanoparticles, an Au thin film is capped on the Ag nanoparticles which are attached on glass substrate. The hybrid nanoparticles array was designed by means of finite-difference and time-domain (FDTD) algorithm-based computational numerical calculation and optimization. Sensitivity of refractive index of the hybrid nanoparticles array was obtained by the computational calculation and experimental detection. Moreover, the hybrid nanoparticles array can prevent oxidation of the pure Ag nanoparticles from atmosphere environment because the Au protective layer was deposited on top of the Ag nanoparticles so as to isolate the Ag particles from the atmosphere. We presented a novel surface covalent link method between the localized surface plasmon resonance (LSPR) effect-based biosensors with hybrid nanoparticles array and the detected target molecules. The generated surface plasmon wave from the array carries the biological interaction message into the corresponding spectra. Staphylococcus aureus enterotoxin B (SEB), a small protein toxin was directly detected at nanogramme per milliliter level using the triangular hybrid Au-Ag nanoparticles. Hence one more option for the SEB detection is provided by this way.

  8. Phase transitions in CuS-Ag2S nanoparticle system

    NASA Astrophysics Data System (ADS)

    Sheela Christy, R.; Thanka Kumaran, J. T.; Bansal, C.; Brightson, M.

    2016-02-01

    (Ag2)xCu1-xS, x = .2, .4, .6 and .8 nanoparticles were synthesized by the solvothermal method. The as-synthesized nanoparticles were characterized by X-ray diffraction to study the crystal structure and size. The surface morphologies of the above samples were studied using scanning electron microscope. As there is continuous shift in the lower wavelength absorption edge of the UV-VIS spectrum of these samples with concentration, (Ag2)xCu1-xS nanoparticles can be tuned to different band gap energies by varying the composition. The D.C. electrical resistance was measured in the temperature range 310-485 K. As Ag2S transforms from monoclinic to bcc at around 450 K, copper sulfide nanoparticles also shows a phase transition at around 470 K, the effects of these two transitions are seen in the resistance measurements and in the UV-VIS spectra of the entire system. The electrical resistance of (Ag2)xCu1-xS nanoparticles rapidly reduces as more and more copper sulfide is added.

  9. Biogenic synthesis of Au and Ag nanoparticles by Indian propolis and its constituents.

    PubMed

    Roy, Nayan; Mondal, Samiran; Laskar, Rajibul A; Basu, Saswati; Mandal, Debabrata; Begum, Naznin Ara

    2010-03-01

    In an attempt to find natural, environmentally benign, green-chemical agents for the synthesis of metal nanoparticles, we have demonstrated for the first time the excellent efficiency of ethanol and water extracts of a natural, non-toxic material, Indian propolis and two of its chemical constituents, pinocembrin and galangin in the rapid synthesis of stable Ag and Au nanoparticles having wide spectrum of fascinating morphologies. Both of these two extracts were found to be extremely efficient in the synthesis of Ag and Au nanoparticles under alkaline condition. For a given metal ion precursor, the kinetics of particle synthesis were remarkably similar in all the cases, as it is evident from the absorption spectra monitored over time. Moreover they exhibited similar redox behavior under alkaline condition (pH approximately 10.62). The efficiency of the ethanol and water extracts of Indian propolis towards Ag and Au nanoparticles synthesis was compared with that of naturally occurring hydroxyflavonoids, pinocembrin and galangin isolated from Indian propolis; which are equally efficient in the rapid synthesis of Ag and Au nanoparticles and stabilization of the resultant particles.

  10. Preparation of silver nanoparticle containing silica micro beads and investigation of their antibacterial activity

    NASA Astrophysics Data System (ADS)

    Quang, Dang Viet; Sarawade, Pradip B.; Hilonga, Askwar; Kim, Jong-Kil; Chai, Young Gyu; Kim, Sang Hoon; Ryu, Jae-Yong; Kim, Hee Taik

    2011-05-01

    Silver nanoparticle containing silica micro beads (Ag-NPBs) were successfully prepared by using sodium silicate, a cheap precursor, involving chemical reductive method. First, silica gel was synthesized and crushed into micro beads which have sizes ranging from 0.5 to 1 mm. Silica micro beads were then modified with 3-aminopropyltriethoxysilane to graft amino functional groups onto their surface. Silver ions were loaded onto the surface of the modified silica and reduced to silver crystal by adding NaBH 4. The presence of silver nanoparticles as well as structure of materials was characterized with FT-IR, XRD, BET, FE-SEM, TEM, UV-vis spectrophotometer, and optical microscope. Silver nanoparticles with an average size about 5 nm were found in the pore and on the surface of amino functionalized silica beads. Ag-NPBs samples were tested for their antibacterial activity against Escherichia coli ( E. coli). The antibacterial activity was examined by both zone inhibition and test tube test method. Biological results indicated that the synthesized materials have an excellent antibacterial performance against E. coli which was completely inhibited after 5 min contact with Ag-NPBs.

  11. The enhanced SERS effect of Ag/ZnO nanoparticles through surface hydrophobic modification

    NASA Astrophysics Data System (ADS)

    Li, Zhenjiang; Zhu, Kaixing; Zhao, Qian; Meng, Alan

    2016-07-01

    Ag/ZnO nanocomposites modified by a mixture of stearic acid (SA) and polyvinylpyrrolidone (PVP) were obtained using a heating reflux method. Fourier transform infrared spectroscopy (FT-IR) suggests that organic SA/PVP was bonded onto the surface of Ag/ZnO nanocrystals, converting the wettability property of the nanostructures from hydrophilic to hydrophobic. The modified Ag/ZnO nanostructures were confirmed as effective Raman substrates, with a 3-fold signal enhancement compared to the ordinary hydrophilic Ag/ZnO substrate for detecting Rh B molecules due to the hydrophobic condensation effect. It is expected that the modified Ag/ZnO nanoparticles have potential for SERS-based rapid detection of molecules.

  12. Ag nanowire percolating network embedded in indium tin oxide nanoparticles for printable transparent conducting electrodes

    SciTech Connect

    Jeong, Jin-A; Kim, Han-Ki

    2014-02-17

    Solution-based printable transparent conducting electrodes consisting of Ag nanowire (NW) and indium tin oxide (ITO) nanoparticles (NPs) were fabricated by simple brush painting at room temperature under atmospheric ambient conditions. Effectively embedding the Ag NW percolating network into the ITO NPs provided a conduction path, led to a metallic conduction behavior of the ITO NPs/Ag NW/ITO NPs multilayer and supplied electrons into the ITO NPs. The optimized ITO NPs/Ag NW/ITO NPs multilayer showed a sheet resistance of 16.57 Ω/sq and an optical transparency of 79.50% without post annealing. Based on high resolution transmission electron microscope analysis, we investigated the microstructure and interface structure of the ITO NPs/Ag NW/ITO NPs multilayer electrodes and suggested a possible mechanism to explain the low resistivity of the multilayers.

  13. Low-temperature ferromagnetic properties in Co-doped Ag{sub 2}Se nanoparticles

    SciTech Connect

    Yang, Fengxia E-mail: xia9020@hust.edu.cn; Yu, Gen; Han, Chong; Liu, Tingting; Zhang, Duanming; Xia, Zhengcai E-mail: xia9020@hust.edu.cn

    2014-01-06

    β-Ag{sub 2}Se is a topologically nontrivial insulator. The magnetic properties of Co-doped Ag{sub 2}Se nanoparticles with Co concentrations up to 40% were investigated. The cusp of zero-field-cooling magnetization curves and the low-temperature hysteresis loops were observed. With increasing concentration of Co{sup 2+} ions mainly substituting Ag{sub I} sites in the Ag{sub 2}Se structure, the resistivity, Curie temperature T{sub c}, and magnetization increased. At 10 T, a sharp drop of resistance near T{sub c} was detected due to Co dopants. The ferromagnetic behavior in Co-doped Ag{sub 2}Se might result from the intra-layer ferromagnetic coupling and surface spin. This magnetic semiconductor is a promising candidate in electronics and spintronics.

  14. A simple preparation of Ag@graphene nanocomposites for surface-enhanced Raman spectroscopy of fluorescent anticancer drug

    NASA Astrophysics Data System (ADS)

    Meng, Ying; Yan, Xueying; Wang, Yi

    2016-05-01

    A simple method was developed to synthesize Ag@graphene nanocomposites with rough Ag nanoparticles (AgNPs) conjugated with graphene nanosheets, and the nanocomposites could be used as substrates for effective surface-enhanced Raman spectroscopy (SERS) of fluorescent anticancer drug (Dox) since they could not only enhance the Raman signals but also suppress the fluorescent signals.

  15. A novel sonication route to prepare anthracene nanoparticles

    SciTech Connect

    Kang Peng; Chen Chunnian; Hao Lingyun; Zhu Chunling; Hu Yuan; Chen Zuyao

    2004-04-02

    A novel sonication method has been successfully developed for the preparation of anthracene nanoparticles. The as-prepared nanoparticles are characterized using transmission electron microscopy, ultraviolet-visible absorption spectroscopy, fluorescence excitation and emission spectroscopy. Nanoparticles prepared with sonication are smaller and better dispersed than with magnetic stirring. Surfactants cetyltrimethylammonium bromide, bis(2-ethylhexyl)sodium sulfosuccinate, sodium dodecyl sulfonate and polyvinylpyrrolidone are used to control the size and morphology. Excimer band is found at 445 and 472 nm and possible mechanism is discussed.

  16. IgA response and protection following nasal vaccination of chickens with Newcastle disease virus DNA vaccine nanoencapsulated with Ag@SiO2 hollow nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Rong, Guangyu; Hao, Yan; Yu, Lu; Kang, Hong; Wang, Xin; Wang, Xiaohua; Jin, Zheng; Ren, Zhiyu; Li, Zejun

    2016-05-01

    Newcastle disease caused by ND virus (NDV) is a highly contagious disease of birds. Vaccine for effective protection of poultry animals from NDV infection is urgently needed. Mucosal immunity plays a very important role in the antiviral immune response. In this study, a NDV F gene-containing DNA vaccine encapsulated in Ag@SiO2 hollow nanoparticles (pFDNA-Ag@SiO2-NPs) with an average diameter of 500 nm were prepared to assess the mucosal immune response. These nanoparticles exhibited low cytotoxicity and did not destroy the bioactivity of plasmid DNA, which could be expressed in vitro. The plasmid DNA was sustainably released after an initial burst release. In vivo immunization showed that the intranasal immunization of chickens with pFDNA-Ag@SiO2-NPs induced high titers of serum antibody, significantly promoted lymphocyte proliferation and induced higher expression levels of IL-2 and IFN-γ in a dose-dependent manner. These results indicated that the Ag@SiO2 hollow nanoparticles could serve as an efficient and safe delivery carrier for NDV DNA vaccine to induce mucosal immunity. This study has provided promising results for the further development of mucosal vaccines encapsulated in inorganic nanoparticles.

  17. IgA response and protection following nasal vaccination of chickens with Newcastle disease virus DNA vaccine nanoencapsulated with Ag@SiO2 hollow nanoparticles.

    PubMed

    Zhao, Kai; Rong, Guangyu; Hao, Yan; Yu, Lu; Kang, Hong; Wang, Xin; Wang, Xiaohua; Jin, Zheng; Ren, Zhiyu; Li, Zejun

    2016-01-01

    Newcastle disease caused by ND virus (NDV) is a highly contagious disease of birds. Vaccine for effective protection of poultry animals from NDV infection is urgently needed. Mucosal immunity plays a very important role in the antiviral immune response. In this study, a NDV F gene-containing DNA vaccine encapsulated in Ag@SiO2 hollow nanoparticles (pFDNA-Ag@SiO2-NPs) with an average diameter of 500 nm were prepared to assess the mucosal immune response. These nanoparticles exhibited low cytotoxicity and did not destroy the bioactivity of plasmid DNA, which could be expressed in vitro. The plasmid DNA was sustainably released after an initial burst release. In vivo immunization showed that the intranasal immunization of chickens with pFDNA-Ag@SiO2-NPs induced high titers of serum antibody, significantly promoted lymphocyte proliferation and induced higher expression levels of IL-2 and IFN-γ in a dose-dependent manner. These results indicated that the Ag@SiO2 hollow nanoparticles could serve as an efficient and safe delivery carrier for NDV DNA vaccine to induce mucosal immunity. This study has provided promising results for the further development of mucosal vaccines encapsulated in inorganic nanoparticles. PMID:27170532

  18. IgA response and protection following nasal vaccination of chickens with Newcastle disease virus DNA vaccine nanoencapsulated with Ag@SiO2 hollow nanoparticles

    PubMed Central

    Zhao, Kai; Rong, Guangyu; Hao, Yan; Yu, Lu; Kang, Hong; Wang, Xin; Wang, Xiaohua; Jin, Zheng; Ren, Zhiyu; Li, Zejun

    2016-01-01

    Newcastle disease caused by ND virus (NDV) is a highly contagious disease of birds. Vaccine for effective protection of poultry animals from NDV infection is urgently needed. Mucosal immunity plays a very important role in the antiviral immune response. In this study, a NDV F gene-containing DNA vaccine encapsulated in Ag@SiO2 hollow nanoparticles (pFDNA-Ag@SiO2-NPs) with an average diameter of 500 nm were prepared to assess the mucosal immune response. These nanoparticles exhibited low cytotoxicity and did not destroy the bioactivity of plasmid DNA, which could be expressed in vitro. The plasmid DNA was sustainably released after an initial burst release. In vivo immunization showed that the intranasal immunization of chickens with pFDNA-Ag@SiO2-NPs induced high titers of serum antibody, significantly promoted lymphocyte proliferation and induced higher expression levels of IL-2 and IFN-γ in a dose-dependent manner. These results indicated that the Ag@SiO2 hollow nanoparticles could serve as an efficient and safe delivery carrier for NDV DNA vaccine to induce mucosal immunity. This study has provided promising results for the further development of mucosal vaccines encapsulated in inorganic nanoparticles. PMID:27170532

  19. Preparation of carbon microspheres decorated with silver nanoparticles and their ability to remove dyes from aqueous solution.

    PubMed

    Chen, Qingchun; Wu, Qingsheng

    2015-01-01

    Solid, but not hollow or porous, carbon microspheres decorated with silver nanoparticles (AgNP-CMSs) were prepared from silver nitrate and CMSs by a redox reaction at room temperature. The CMSs and AgNP-CMSs were characterized using X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and UV-vis spectrophotometry. Though with non-high specific surface area, the AgNP-CMSs exhibited a high adsorption capacity toward methylene blue (MB) in an aqueous solution. The AgNP-CMSs were able to remove all the MB from a solution of 30 mg/L MB in water within 1 min when the adsorbent concentration was 0.12 g/L. The AgNP-CMSs also exhibited good adsorption and photocatalytic activity in the decomposition of aqueous Rhodamine B as well as MB under visible light. FTIR was used to examine the interaction between AgNP-CMSs and MB, and the spectrum and more extra experiments suggest ionic interactions between cationic dyes and the negatively charged groups can be formed but not the presence of abundant π-π conjugations between dye molecules and the aromatic rings. The origin of the photocatalytic activity of AgNP-CMSs was attributed to a surface plasmon resonance (SPR) effect of the silver nanoparticles on the CMSs.

  20. Tuning the SERS Response with Ag-Au Nanoparticle-Embedded Polymer Thin Film Substrates.

    PubMed

    Rao, V Kesava; Radhakrishnan, T P

    2015-06-17

    Development of facile routes to the fabrication of thin film substrates with tunable surface enhanced Raman scattering (SERS) efficiency and identification of the optimal conditions for maximizing the enhancement factor (EF) are significant in terms of both fundamental and application aspects of SERS. In the present work, polymer thin films with embedded bimetallic nanoparticles of Ag-Au are fabricated by a simple two-stage protocol. Ag nanoparticles are formed in the first stage, by the in situ reduction of silver nitrate by the poly(vinyl alcohol) (PVA) film through mild thermal annealing, without any additional reducing agent. In the second stage, aqueous solutions of chloroauric acid spread on the Ag-PVA thin film under ambient conditions, lead to the galvanic displacement of Ag by Au in situ inside the film, and the formation of Ag-Au particles. Evolution of the morphology of the bimetallic nanoparticles into hollow cage structures and the distribution of Au on the nanoparticles are revealed through electron microscopy and energy dispersive X-ray spectroscopy. The localized surface plasmon resonance (LSPR) extinction of the nanocomposite thin film evolves with the Ag-Au composition; theoretical simulation of the extinction spectra provides insight into the observed trends. The Ag-Au-PVA thin films are found to be efficient substrates for SERS. The EF follows the variation of the LSPR extinction vis-à-vis the excitation laser wavelength, but with an offset, and the maximum SERS effect is obtained at very low Au content; experiments with Rhodamine 6G showed EFs on the order of 10(8) and a limit of detection of 0.6 pmol. The present study describes a facile and simple fabrication of a nanocomposite thin film that can be conveniently deployed in SERS investigations, and the utility of the bimetallic system to tune and maximize the EF.

  1. All-thiol-stabilized Ag44 and Au12Ag32 nanoparticles with single-crystal structures.

    PubMed

    Yang, Huayan; Wang, Yu; Huang, Huaqi; Gell, Lars; Lehtovaara, Lauri; Malola, Sami; Häkkinen, Hannu; Zheng, Nanfeng

    2013-01-01

    Noble metal nanoparticles stabilized by organic ligands are important for applications in assembly, site-specific bioconjugate labelling and sensing, drug delivery and medical therapy, molecular recognition and molecular electronics, and catalysis. Here we report crystal structures and theoretical analysis of three Ag44(SR)30 and three Au12Ag32(SR)30 intermetallic nanoclusters stabilized with fluorinated arylthiols (SR=SPhF, SPhF2 or SPhCF3). The nanocluster forms a Keplerate solid of concentric icosahedral and dodecahedral atom shells, protected by six Ag2(SR)5 units. Positive counterions in the crystal indicate a high negative charge of 4(-) per nanoparticle, and density functional theory calculations explain the stability as an 18-electron superatom shell closure in the metal core. Highly featured optical absorption spectra in the ultraviolet-visible region are analysed using time-dependent density functional perturbation theory. This work forms a basis for further understanding, engineering and controlling of stability as well as electronic and optical properties of these novel nanomaterials. PMID:24005600

  2. All-thiol-stabilized Ag44 and Au12Ag32 nanoparticles with single-crystal structures.

    PubMed

    Yang, Huayan; Wang, Yu; Huang, Huaqi; Gell, Lars; Lehtovaara, Lauri; Malola, Sami; Häkkinen, Hannu; Zheng, Nanfeng

    2013-01-01

    Noble metal nanoparticles stabilized by organic ligands are important for applications in assembly, site-specific bioconjugate labelling and sensing, drug delivery and medical therapy, molecular recognition and molecular electronics, and catalysis. Here we report crystal structures and theoretical analysis of three Ag44(SR)30 and three Au12Ag32(SR)30 intermetallic nanoclusters stabilized with fluorinated arylthiols (SR=SPhF, SPhF2 or SPhCF3). The nanocluster forms a Keplerate solid of concentric icosahedral and dodecahedral atom shells, protected by six Ag2(SR)5 units. Positive counterions in the crystal indicate a high negative charge of 4(-) per nanoparticle, and density functional theory calculations explain the stability as an 18-electron superatom shell closure in the metal core. Highly featured optical absorption spectra in the ultraviolet-visible region are analysed using time-dependent density functional perturbation theory. This work forms a basis for further understanding, engineering and controlling of stability as well as electronic and optical properties of these novel nanomaterials.

  3. Enhanced Raman Scattering of Silicon Nanowires by Ag Nanoparticles in-situ Decoration

    NASA Astrophysics Data System (ADS)

    Peng, Zeping; Hu, Hailong; Wang, Shijie; Shen, Zexiang; Xiong, Qihua

    2010-08-01

    Recently, metallic nanoparticles decorated semiconductor nanowires, especially silicon, attract considerable attention, due to their potential applications in photocatalysis, photovoltaics, surface enhanced Raman scattering and biosensing. A common method that has been used to decorate silicon nanowires with metallic nanoparticles, e.g. Au or Pt, is galvanic displacement, in which metallic ions are reduced with electrons supplied by virtue of silicon half-cell reaction. Here we report a method to decorate silicon nanowires with Ag nanoparticles by surface reduction, in which a freshly etched silicon surface reduces Ag ions in-situ in aqueous silver nitrate solution. The as-grown Ag nanoparticles exhibit either highly single crystallinity or twinning boundaries, with most probably diameter ˜25 nm (Figure 1). Raman mapping experiments suggest that 1st order Raman band of silicon nanowires exhibit uniform contrast along wire axis for pristine silicon nanowires, while for Ag nanoparticle decorated silicon nanowires a series of "hot-spot," i.e., substantially enhanced Raman scattering were discovered along the wire axis. This was explained by local electric field enhancement due to Ag nanoparticle "nano-antenna," which was supported by the correlation between atomic force microscopy (AFM) analysis and Raman mapping (Figure 2). The enhancement is more or less delocalized in Raman mapping due to diffraction limit in our far-field mapping experiments. In addition, we also noticed a new side band feature ˜495 cm-1 for nanowires appeared after HF etching, this new feature sustained after sequential Oxygen plasma and UV/ozone treatment which excluded the possibility due to any possible surface dangling bonds. We now suspect this feature is due to porosity resulted from HF etching and it is now being subjected to further investigations.

  4. Preparation and Characterization of Nateglinide Loaded Hydrophobic Biocompatible Polymer Nanoparticles

    NASA Astrophysics Data System (ADS)

    Naik, Jitendra; Lokhande, Amolkumar; Mishra, Satyendra; Kulkarni, Ravindra

    2016-09-01

    The aim of the present study was to develop sustained release Nateglinide loaded Ethylcellulose nanoparticles and characterize the properties of recovered nanoparticles. The sustained release nanoparticles were prepared by oil in water single emulsion solvent evaporation method. The developed nanoparticles were characterised for their particle size, morphology, encapsulation efficiency, drug polymer compatibility and in vitro drug release. The drug polymer compatibility was investigated by XRPD. Imaging of particles was performed by field emission scanning electron microscopy. The highest particle size and encapsulation efficiency of recovered nanoparticles were 248.37 nm and 91.16 % respectively. The recovered nanoparticles are spherical in nature and uniform in size. Developed nanoparticles have low crystallinity than the pure Nateglinide. The highest drug-polymer ratio formulation showed drug release 61.1 ± 1.76 % up to 24 h.

  5. Preparation and in vitro investigation of antigastric cancer activities of carvacrol-loaded human serum albumin nanoparticles.

    PubMed

    Maryam, Keshavarzi; Shakeri, Shahryar; Kiani, Keyhaneh

    2015-10-01

    In this study, carvacrol-loaded human serum albumin (HSA) nanoparticles were developed and characterised. Nanoparticles were prepared by desolvation and emulsion/desolvation methods. Encapsulation efficiency (EE%) and loading capacity (LC%) of nanoparticles prepared by desolvation method were 48.4 and 45.1%, respectively. Carvacrol-loaded nanoparticles had 132±42 nm in diameter with monomodal distribution. Carvacrol-loaded nanoparticles which is prepared by emulsion/desolvation method had EE% and LC% of 32 and 32.3%, respectively, and 230±38 nm in size. The release of carvacrol from nanoparticles was monitored in phosphate-buffered saline (pH=7.4), 100 rpm at 37°C for 10 days. About 21.4% of carvacrol was released after 3 h from nanoparticles that were prepared by desolvation method. In emulsion/desolvation method, 26.8% of total carvacrol was released during 3 h of incubation. Cytotoxicity effect of loaded carvacrol was assessed by 3-[4, 5 dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test on gastric cancer cells line (AGS). Cell line was exposed to the free carvacrol, unloaded and carvacrol-loaded nanoparticles for 48 h. The half maximal inhibitory concentration (IC50) for free carvacrol, unloaded and carvacrol-loaded HSA nanoparticles were 30, 1070 and 120 µg/ml, respectively. In conclusion, the results of this study showed applications of HSA nanoparticles for entrapment of carvacrol and antigastric cancer activity. Moreover, loading of carvacrol in combination with chemotherapy agents into the HSA nanoparticles may treat cancer cells better than single drug loaded nanoparticles. PMID:26435283

  6. Ag2CrO4 nanoparticles loaded on two-dimensional large surface area graphite-like carbon nitride sheets: simple synthesis and excellent photocatalytic performance.

    PubMed

    Shi, Lei; Liang, Lin; Wang, Fangxiao; Liu, Mengshuai; Sun, Jianmin

    2016-04-01

    Graphite-like carbon nitride (g-C3N4) with a large surface area was prepared through thermal condensation of guanidine hydrochloride at 650 °C. Various amounts of silver chromate (Ag2CrO4) nanoparticles with small size were highly loaded on the g-C3N4 by a simple co-precipitation method at room temperature. The chemical constituents, surface structure and optical properties of the resultant Ag2CrO4/g-C3N4 composites were thoroughly characterized. And the photocatalytic performances were evaluated by degradation of Rhodamine B (RhB) and phenol, the experimental results indicated that the as-prepared Ag2CrO4/g-C3N4 composites presented excellent photocatalytic activity under visible-light irradiation. With the mass ratio of Ag2CrO4 to g-C3N4 at 1 : 2, the Ag2CrO4/g-C3N4 composites exhibited optimal photocatalytic activity for degrading RhB, approximately 6.1 and 10.4 times higher than those on pure g-C3N4 and bare Ag2CrO4 particles. The improved photocatalytic activity was mainly attributed to the combined effect including the larger surface area, highly dispersed smaller Ag2CrO4 nanoparticles, stronger visible absorption and higher charge separation efficiency of the Ag2CrO4/g-C3N4 composites. Moreover, the possible mechanism for the photocatalytic activity was tentatively proposed.

  7. Ag2CrO4 nanoparticles loaded on two-dimensional large surface area graphite-like carbon nitride sheets: simple synthesis and excellent photocatalytic performance.

    PubMed

    Shi, Lei; Liang, Lin; Wang, Fangxiao; Liu, Mengshuai; Sun, Jianmin

    2016-04-01

    Graphite-like carbon nitride (g-C3N4) with a large surface area was prepared through thermal condensation of guanidine hydrochloride at 650 °C. Various amounts of silver chromate (Ag2CrO4) nanoparticles with small size were highly loaded on the g-C3N4 by a simple co-precipitation method at room temperature. The chemical constituents, surface structure and optical properties of the resultant Ag2CrO4/g-C3N4 composites were thoroughly characterized. And the photocatalytic performances were evaluated by degradation of Rhodamine B (RhB) and phenol, the experimental results indicated that the as-prepared Ag2CrO4/g-C3N4 composites presented excellent photocatalytic activity under visible-light irradiation. With the mass ratio of Ag2CrO4 to g-C3N4 at 1 : 2, the Ag2CrO4/g-C3N4 composites exhibited optimal photocatalytic activity for degrading RhB, approximately 6.1 and 10.4 times higher than those on pure g-C3N4 and bare Ag2CrO4 particles. The improved photocatalytic activity was mainly attributed to the combined effect including the larger surface area, highly dispersed smaller Ag2CrO4 nanoparticles, stronger visible absorption and higher charge separation efficiency of the Ag2CrO4/g-C3N4 composites. Moreover, the possible mechanism for the photocatalytic activity was tentatively proposed. PMID:26937621

  8. Immunoassay for tumor markers in human serum based on Si nanoparticles and SiC@Ag SERS-active substrate.

    PubMed

    Zhou, Lu; Zhou, Jun; Feng, Zhao; Wang, Fuyan; Xie, Shushen; Bu, Shizhong

    2016-04-21

    Based on a sandwich structure consisting of nano-Si immune probes and a SiC@Ag SERS-active immune substrate, a kind of ultra-sensitive immunoassay protocol is presented to detect tumor markers in human serum. The nano-Si immune probes were prepared by immobilizing the detecting antibodies onto the surfaces of SiO2-coated Si nanoparticles (NPs) which were modified with 3-(aminopropyl)trimethoxysilane, and the SiC@Ag SERS-active immune substrates were prepared by immobilizing the captured antibodies on Ag film sputtered on SiC sandpaper. To the best of our knowledge, it is the first time that Si NPs are directly used as Raman tags in an immunoassay strategy. And, the SiC@Ag SERS-active substrates exhibit excellent surface enhanced Raman scattering (SERS) performances with an enhancement factor of ∼10(5), owing to the plasmonic effect of the Ag film on the rough surface of the SiC sandpaper. In our experiments, the sandwich immunoassay structure has been successfully applied to detect prostate specific antigen (PSA), α-fetoprotein (AFP) and carbohydrate antigen 19-9 (CA19-9) in a human serum sample and the limit of detections are as low as 1.79 fg mL(-1), 0.46 fg mL(-1) and 1.3 × 10(-3) U mL(-1), respectively. It reveals that the proposed immunoassay protocol has demonstrated a high sensitivity for tumor markers in human serum and a potential practicability in biosensing and clinical diagnostics. PMID:27003871

  9. In-situ preparation of Z-scheme AgI/Bi5O7I hybrid and its excellent photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Cui, Min; Yu, Jingxiong; Lin, Hongjun; Wu, Ying; Zhao, Leihong; He, Yiming

    2016-11-01

    The aim of this work was to synthesize, characterize and evaluate the photocatalytic activity of AgI/Bi5O7I composite photocatalyst under visible light irradiation. The photocatalyst was prepared by a simple one-step ionic reaction between Bi5O7I microrods and AgNO3 solutions, and was characterized by various techniques including X-ray diffraction (XRD), Raman spectroscopy (Raman), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL). The characterizations indicate that AgI particles were closely anchored on Bi5O7I micronods. During the photocataytic reaction, the composite was actually an Ag-AgI-Bi5O7I ternary system. The plasmonic effect of the formed Ag nanoparticles improved the visible light absorption performance, which benefits the photocatalytic reaction. However, more important was the formed heterojunction structure in the composite, which efficiently promoted the separation of electron-hole pairs by a plasmonic Z-scheme mechanism, and ultimately enhanced the photocatalytic activity. The optimal AgI/Bi5O7I composite showed a RhB degradation rate of 0.046 min-1, which was 3.83 and 6.57 times higher than those of Bi5O7I and AgI, respectively. This work may provide some insight into the design of novel and highly efficient Z-scheme visible-light photocatalysts.

  10. Influence of formulation factors on the preparation of zein nanoparticles.

    PubMed

    Podaralla, Satheesh; Perumal, Omathanu

    2012-09-01

    The main objective of the present study was to investigate the influence of various formulation parameters on the preparation of zein nanoparticles. 6,7-dihydroxycoumarin (DHC) was used as a model hydrophobic compound. The influence of pH of the aqueous phase, buffer type, ionic strength, surfactant, and zein concentration on particle size, polydispersity index, and zeta potential of DHC-loaded zein nanoparticles were studied. Smaller nanoparticles were formed when the pH was close to the isoelectric point of zein. DHC-loaded zein nanoparticles prepared using citrate buffer (pH 7.4) was better than phosphate buffer in preventing particle aggregation during lyophilization. The ionic strength did not have a significant influence on the particle size of DHC-loaded zein nanoparticles. A combination of Pluronic F68 and lecithin in 2:1 ratio stabilized the zein nanoparticles. An increase in zein concentration led to increase in particle size of DHC-loaded zein nanoparticles. The use of optimal conditions produced DHC-loaded nanoparticles of 256 ± 30 nm and an encapsulation efficiency of 78 ± 7%. Overall, the study demonstrated the optimal conditions to prepare zein nanoparticles for drug encapsulation.

  11. Exposure medium: key in identifying free Ag+ as the exclusive species of silver nanoparticles with acute toxicity to Daphnia magna.

    PubMed

    Shen, Mo-Hai; Zhou, Xiao-Xia; Yang, Xiao-Ya; Chao, Jing-Bo; Liu, Rui; Liu, Jing-Fu

    2015-04-10

    It is still not very clear what roles the various Ag species play in the toxicity of silver nanoparticles (AgNPs). In this study, we found that traditional exposure media result in uncontrollable but consistent physicochemical transformation of AgNPs, causing artifacts in determination of median lethal concentration (LC50) and hindering the identification of Ag species responsible for the acute toxicity of AgNPs to Daphnia magna. This obstacle was overcome by using 8 h exposure in 0.1 mmol L(-1) NaNO3 medium, in which we measured the 8-h LC50 of seven AgNPs with different sizes and coatings, and determined the concentrations of various Ag species. The LC50 as free Ag(+) of the seven AgNPs (0.37-0.44 μg L(-1)) agreed very well with that of AgNO3 (0.40 μg L(-1)), and showed the lowest value compared to that as total Ag, total Ag(+), and dissolved Ag, demonstrating free Ag(+) is exclusively responsible for the acute toxicity of AgNPs to D. magna, while other Ag species in AgNPs have no contribution to the acute toxicity. Our results demonstrated the great importance of developing appropriate exposure media for evaluating risk of nanomaterials.

  12. Exposure Medium: Key in Identifying Free Ag+ as the Exclusive Species of Silver Nanoparticles with Acute Toxicity to Daphnia magna

    NASA Astrophysics Data System (ADS)

    Shen, Mo-Hai; Zhou, Xiao-Xia; Yang, Xiao-Ya; Chao, Jing-Bo; Liu, Rui; Liu, Jing-Fu

    2015-04-01

    It is still not very clear what roles the various Ag species play in the toxicity of silver nanoparticles (AgNPs). In this study, we found that traditional exposure media result in uncontrollable but consistent physicochemical transformation of AgNPs, causing artifacts in determination of median lethal concentration (LC50) and hindering the identification of Ag species responsible for the acute toxicity of AgNPs to Daphnia magna. This obstacle was overcome by using 8 h exposure in 0.1 mmol L-1 NaNO3 medium, in which we measured the 8-h LC50 of seven AgNPs with different sizes and coatings, and determined the concentrations of various Ag species. The LC50 as free Ag+ of the seven AgNPs (0.37-0.44 μg L-1) agreed very well with that of AgNO3 (0.40 μg L-1), and showed the lowest value compared to that as total Ag, total Ag+, and dissolved Ag, demonstrating free Ag+ is exclusively responsible for the acute toxicity of AgNPs to D. magna, while other Ag species in AgNPs have no contribution to the acute toxicity. Our results demonstrated the great importance of developing appropriate exposure media for evaluating risk of nanomaterials.

  13. Exposure Medium: Key in Identifying Free Ag+ as the Exclusive Species of Silver Nanoparticles with Acute Toxicity to Daphnia magna

    PubMed Central

    Shen, Mo-Hai; Zhou, Xiao-Xia; Yang, Xiao-Ya; Chao, Jing-Bo; Liu, Rui; Liu, Jing-Fu

    2015-01-01

    It is still not very clear what roles the various Ag species play in the toxicity of silver nanoparticles (AgNPs). In this study, we found that traditional exposure media result in uncontrollable but consistent physicochemical transformation of AgNPs, causing artifacts in determination of median lethal concentration (LC50) and hindering the identification of Ag species responsible for the acute toxicity of AgNPs to Daphnia magna. This obstacle was overcome by using 8 h exposure in 0.1 mmol L−1 NaNO3 medium, in which we measured the 8-h LC50 of seven AgNPs with different sizes and coatings, and determined the concentrations of various Ag species. The LC50 as free Ag+ of the seven AgNPs (0.37–0.44 μg L−1) agreed very well with that of AgNO3 (0.40 μg L−1), and showed the lowest value compared to that as total Ag, total Ag+, and dissolved Ag, demonstrating free Ag+ is exclusively responsible for the acute toxicity of AgNPs to D. magna, while other Ag species in AgNPs have no contribution to the acute toxicity. Our results demonstrated the great importance of developing appropriate exposure media for evaluating risk of nanomaterials. PMID:25858866

  14. Size-selected ag nanoparticles with five-fold symmetry.

    PubMed

    Gracia-Pinilla, Miguelángel; Ferrer, Domingo; Mejía-Rosales, Sergio; Pérez-Tijerina, Eduardo

    2009-01-01

    Silver nanoparticles were synthesized using the inert gas aggregation technique. We found the optimal experimental conditions to synthesize nanoparticles at different sizes: 1.3 ± 0.2, 1.7 ± 0.3, 2.5 ± 0.4, 3.7 ± 0.4, 4.5 ± 0.9, and 5.5 ± 0.3 nm. We were able to investigate the dependence of the size of the nanoparticles on the synthesis parameters. Our data suggest that the aggregation of clusters (dimers, trimer, etc.) into the active zone of the nanocluster source is the predominant physical mechanism for the formation of the nanoparticles. Our experiments were carried out in conditions that kept the density of nanoparticles low, and the formation of larges nanoparticles by coalescence processes was avoided. In order to preserve the structural and morphological properties, the impact energy of the clusters landing into the substrate was controlled, such that the acceleration energy of the nanoparticles was around 0.1 eV/atom, assuring a soft landing deposition. High-resolution transmission electron microscopy images showed that the nanoparticles were icosahedral in shape, preferentially oriented with a five-fold axis perpendicular to the substrate surface. Our results show that the synthesis by inert gas aggregation technique is a very promising alternative to produce metal nanoparticles when the control of both size and shape are critical for the development of practical applications.

  15. Size-Selected Ag Nanoparticles with Five-Fold Symmetry

    PubMed Central

    2009-01-01

    Silver nanoparticles were synthesized using the inert gas aggregation technique. We found the optimal experimental conditions to synthesize nanoparticles at different sizes: 1.3 ± 0.2, 1.7 ± 0.3, 2.5 ± 0.4, 3.7 ± 0.4, 4.5 ± 0.9, and 5.5 ± 0.3 nm. We were able to investigate the dependence of the size of the nanoparticles on the synthesis parameters. Our data suggest that the aggregation of clusters (dimers, trimer, etc.) into the active zone of the nanocluster source is the predominant physical mechanism for the formation of the nanoparticles. Our experiments were carried out in conditions that kept the density of nanoparticles low, and the formation of larges nanoparticles by coalescence processes was avoided. In order to preserve the structural and morphological properties, the impact energy of the clusters landing into the substrate was controlled, such that the acceleration energy of the nanoparticles was around 0.1 eV/atom, assuring a soft landing deposition. High-resolution transmission electron microscopy images showed that the nanoparticles were icosahedral in shape, preferentially oriented with a five-fold axis perpendicular to the substrate surface. Our results show that the synthesis by inert gas aggregation technique is a very promising alternative to produce metal nanoparticles when the control of both size and shape are critical for the development of practical applications. PMID:20596397

  16. Bioaccumulation of Zn and Ag Nanoparticles in the Earthworms (Eisenia fetida)

    NASA Astrophysics Data System (ADS)

    Ha, Lee Seung; Sung-Dae, Kim; Yi, Yang Song; Byeong-Gweon, Lee

    2014-05-01

    Many studies are carried out to evaluate environmental effects of engineered nanoparticles (ENPs). Most of the previous studies primarily focused on the effects of nanoparticles into the aquatic environment and human. Model studies predict that ENPs released into environment would transferred primarily to the soil of the terrestrial environment. Despite this prediction, biogeochemical behavior of ENPs in soil environment as well as bioavailability of ENPs to soil-dwelling organisms such as earthworm, springtail, isopod and nematodes are poorly understood. The main goal of this study was to compare the bioaccumulation factor (BAFs) and subcellular partitioning of nanoparticles in the soil-dwelling earthworm (Eisenia fetida) from ENP (ZnO and Ag nanoparticles) or ionic metal (Zn2+, Ag+) contaminated soil. And the sequential extraction was also used to determine the mobility of metals in soil which could be used as to predict bioavailability and compare that with bioaccumulation factor. The radiotracer method was employed to trace the transfer of ENPs and ionic metal among different environmental media and animals. Radiolabeled 65ZnO, 110mAgNPs coated with PVP or citrate were synthesized in the laboratory and their chemical and biological behavior was compared to ionic 65Zn and 110mAg. The BAFs of Zn and Ag in the earthworms were determined after animals exposed to the contaminated soils. After the 7 days of elimination phase, subcellular partitioning of metals were also obtained. BAF for ZnO(0.06) was 31 times lower than that for Zn ion (1.86), suggesting that ZnO was less bioavailable than its ionic form from contaminated soil. On the other hands, BAFs for AgNPs coated with PVP (0.12) or with citrate (0.11) were comparable to those for Ag ion (0.17), indicating that Ag from contaminated soil was bioavailable in a similar rate regardless of chemical forms. The subcellular partitioning results showed that bioaccumulated Zn from Zn ion and ZnO contaminated soil were

  17. Magnetic hyperthermia in brick-like Ag@Fe3O4 core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Brollo, M. E. F.; Orozco-Henao, J. M.; López-Ruiz, R.; Muraca, D.; Dias, C. S. B.; Pirota, K. R.; Knobel, M.

    2016-01-01

    Heating efficiency of multifunctional Ag@Fe3O4 brick-like nanoparticles under alternating magnetic field was investigated by means of specific absorption rate (SAR) measurements, and compared with equivalent measurements for plain magnetite and dimer heteroparticles. The samples were synthesized by thermal decomposition reactions and present narrow size polydispersity and high degree of crystallinity. The SAR values are analyzed using the superparamagnetic theory, in which the basic morphology, size and dispersion of sizes play key roles. The results suggest that these novel brick-like nanoparticles are good candidates for hyperthermia applications, displaying heating efficiencies comparable with the most efficient plain nanoparticles.

  18. 77 FR 75169 - Silver Nanoparticles (AgNPs); Information and Comment Request

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-19

    ... HUMAN SERVICES Centers for Disease Control and Prevention Silver Nanoparticles (AgNPs); Information and Comment Request AGENCY: National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control and Prevention (CDC), Department of Health and Human Services (HHS). ACTION: Request...

  19. Ag Nanoparticle/Polydopamine-Coated Inverse Opals as Highly Efficient Catalytic Membranes.

    PubMed

    Choi, Gwan H; Rhee, Do Kyung; Park, A Reum; Oh, Min Jun; Hong, Sunghwan; Richardson, Joseph J; Guo, Junling; Caruso, Frank; Yoo, Pil J

    2016-02-10

    Polymeric three-dimensional inverse-opal (IO) structures provide unique structural properties useful for various applications ranging from optics to separation technologies. Despite vast needs for IO functionalization to impart additional chemical properties, this task has been seriously challenged by the intrinsic limitation of polymeric porous materials that do not allow for the easy penetration of waterborne moieties or precursors. To overcome this restriction, we present a robust and straightforward method of employing a dipping-based surface modification with polydopamine (PDA) inside the IO structures, and demonstrate their application to catalytic membranes via synthetic incorporation of Ag nanoparticles. The PDA coating offers simultaneous advantages of achieving the improved hydrophilicity required for the facilitated infiltration of aqueous precursors and successful creation of nucleation sites for a reduction of growth of the Ag nanoparticles. The resulting Ag nanoparticle-incorporated IO structures are utilized as catalytic membranes for the reduction of 4-nitrophenol to its amino derivatives in the presence of NaBH4. Synergistically combined characteristics of high reactivity of Ag nanoparticles along with a greatly enhanced internal surface area of IO structures enable the implementation of remarkably improved catalytic performance, exhibiting a good conversion efficiency greater than 99% while minimizing loss in the membrane permeability. PMID:26780371

  20. Trimetallic nanostructures: the case of AgPd/Pt multiply twinned nanoparticles

    PubMed Central

    Khanal, Subarna; Bhattarai, Nabraj; Velázquez-Salazar, J. Jesús; Bahena, Daniel; Soldano, German; Ponce, Arturo; Mariscal, Marcelo M.; Mejía-Rosales, Sergio; José-Yacamán, Miguel

    2013-01-01

    We report the synthesis, structural characterization, and atomistic simulations of AgPd/Pt trimetallic (TM) nanoparticles. Two types of structure were synthesized using a relatively facile chemical method: multiply twinned core-shell, and hollow particles. The nanoparticles were small in size, with an average diameter of 11 nm and a narrow distribution, and their characterization by aberration corrected scanning transmission electron microscopy allowed us to probe the structure of the particles at atomistic level. In some nanoparticles, the formation of a hollow structure was also observed, that facilitates the alloying of Ag and Pt in the shell region and the segregation of Ag atoms in the surface, affecting the catalytic activity and stability. We also investigated the growth mechanism of the nanoparticles using grand canonical Monte Carlo simulations, and we have found that Pt regions grow at overpotentials on the AgPd nanoalloys, forming 3D islands at the early stages of the deposition process. We found very good agreement between the simulated structures and those observed experimentally. PMID:24165796

  1. Ag Nanoparticle/Polydopamine-Coated Inverse Opals as Highly Efficient Catalytic Membranes.

    PubMed

    Choi, Gwan H; Rhee, Do Kyung; Park, A Reum; Oh, Min Jun; Hong, Sunghwan; Richardson, Joseph J; Guo, Junling; Caruso, Frank; Yoo, Pil J

    2016-02-10

    Polymeric three-dimensional inverse-opal (IO) structures provide unique structural properties useful for various applications ranging from optics to separation technologies. Despite vast needs for IO functionalization to impart additional chemical properties, this task has been seriously challenged by the intrinsic limitation of polymeric porous materials that do not allow for the easy penetration of waterborne moieties or precursors. To overcome this restriction, we present a robust and straightforward method of employing a dipping-based surface modification with polydopamine (PDA) inside the IO structures, and demonstrate their application to catalytic membranes via synthetic incorporation of Ag nanoparticles. The PDA coating offers simultaneous advantages of achieving the improved hydrophilicity required for the facilitated infiltration of aqueous precursors and successful creation of nucleation sites for a reduction of growth of the Ag nanoparticles. The resulting Ag nanoparticle-incorporated IO structures are utilized as catalytic membranes for the reduction of 4-nitrophenol to its amino derivatives in the presence of NaBH4. Synergistically combined characteristics of high reactivity of Ag nanoparticles along with a greatly enhanced internal surface area of IO structures enable the implementation of remarkably improved catalytic performance, exhibiting a good conversion efficiency greater than 99% while minimizing loss in the membrane permeability.

  2. Collagen-chitosan scaffold modified with Au and Ag nanoparticles: Synthesis and structure

    NASA Astrophysics Data System (ADS)

    Rubina, M. S.; Kamitov, E. E.; Zubavichus, Ya. V.; Peters, G. S.; Naumkin, A. V.; Suzer, S.; Vasil'kov, A. Yu.

    2016-03-01

    Nowadays, the dermal biomimetic scaffolds are widely used in regenerative medicine. Collagen-chitosan scaffold one of these materials possesses antibacterial activity, good compatibility with living tissues and has been already used as a wound-healing material. In this article, collagen-chitosan scaffolds modified with Ag and Au nanoparticles have been synthesized using novel method - the metal-vapor synthesis. The nanocomposite materials are characterized by XPS, TEM, SEM and synchrotron radiation-based X-ray techniques. According to XRD data, the mean size of the nanoparticles (NPs) is 10.5 nm and 20.2 nm in Au-Collagen-Chitosan (Au-CollCh) and Ag-Collagen-Chitosan (Ag-CollCh) scaffolds, respectively in fair agreement with the TEM data. SAXS analysis of the composites reveals an asymmetric size distribution peaked at 10 nm for Au-CollCh and 25 nm for Ag-CollCh indicative of particle's aggregation. According to SEM data, the metal-carrying scaffolds have layered structure and the nanoparticles are rather uniformly distributed on the surface material. XPS data indicate that the metallic nanoparticles are in their unoxidized/neutral states and dominantly stabilized within the chitosan-rich domains.

  3. Preparation of starch-stabilized silver nanoparticles from amylose-sodium palmitate inclusion complexes.

    PubMed

    Fanta, George F; Kenar, James A; Felker, Frederick C; Byars, Jeffrey A

    2013-01-30

    Starch-stabilized silver nanoparticles (AgNP) were prepared from amylose-sodium palmitate helical inclusion complexes by first converting sodium palmitate within the amylose helix to silver palmitate by an ion-exchange reaction with silver nitrate, and then reducing the complexed silver palmitate salt with NaBH(4). This process yielded stable aqueous solutions that could be dried and then re-dispersed in water for end-use applications. Reaction products were characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), UV-VIS spectroscopy, X-ray diffraction, TEM, SEM and light microscopy. Addition of acid to reduce the pH of aqueous starch-AgNP solutions produced an increase in viscosity, and nearly quantitative precipitation of starch-AgNP was observed at low pH. Smaller AgNP and higher conversions of silver nitrate to water-soluble starch-AgNP were obtained in this process, as compared with a process carried out under similar conditions using a commercial soluble starch as a stabilizer. PMID:23218293

  4. Polyvinyl alcohol electrospun nanofibers containing Ag nanoparticles used as sensors for the detection of biogenic amines.

    PubMed

    Marega, Carla; Maculan, Jenny; Andrea Rizzi, Gian; Saini, Roberta; Cavaliere, Emanuele; Gavioli, Luca; Cattelan, Mattia; Giallongo, Giuseppe; Marigo, Antonio; Granozzi, Gaetano

    2015-02-20

    Polyvinyl alcohol (PVA) electrospun nanofibers containing Ag nanoparticles (NPs) have been deposited on glass substrates. The aim of the work was to test the feasibility of this approach for the detection of biogenic amines by using either the Ag localized surface plasmon resonance quenching caused by the adsorption of amines on Ag NPs or by detecting the amines by surface enhanced Raman spectroscopy (SERS) after adsorption, from the gas phase, on the metal NPs. Two different approaches have been adopted. In the first one an ethanol/water solution containing AgNO3 was used directly in the electrospinning apparatus. In this way, a simple heat treatment of the nanofibers mat was sufficient to obtain the formation of Ag NPs inside the nanofibers and a partial cross-link of PVA. In the second procedure, the Ag NPs were deposited on PVA nanofibers by using the supersonic cluster beam deposition method, so that a beam of pure Ag NPs of controlled size was obtained. Exposure of the PVA mat to the beam produced a uniform distribution of the NPs on the nanofibers surface. Ethylendiamine vapors and volatile amines released from fresh shrimp meat were chemisorbed on the nanofibers mats. A SERS spectrum characterized by a diagnostic Ag-N stretching vibration at 230 cm(-1) was obtained. The results allow to compare the two different approaches in the detection of ammines.

  5. Ag nanoparticles generated using bio-reduction and -coating cause microbial killing without cell lysis.

    PubMed

    Gade, Aniket; Adams, Joshua; Britt, David W; Shen, Fen-Ann; McLean, Joan E; Jacobson, Astrid; Kim, Young-Cheol; Anderson, Anne J

    2016-04-01

    Cost-effective "green" methods of producing Ag nanoparticles (NPs) are being examined because of the potential of these NPs as antimicrobials. Ag NPs were generated from Ag ions using extracellular metabolites from a soil-borne Pythium species. The NPs were variable in size, but had one dimension less than 50 nm and were biocoated; aggregation and coating changed with acetone precipitation. They had dose-dependent lethal effects on a soil pseudomonad, Pseudomonas chlororaphis O6, and were about 30-fold more effective than Ag(+) ions. A role of reactive oxygen species in cell death was demonstrated by use of fluorescent dyes responsive to superoxide anion and peroxide accumulation. Also mutants of the pseudomonad, defective in enzymes that protect against oxidative stress, were more sensitive than the wild type strain; mutant sensitivity differed between exposure to Ag NPs and Ag(+) ions demonstrating a nano-effect. Imaging of bacterial cells treated with the biocoated Ag NPs revealed no cell lysis, but there were changes in surface properties and cell height. These findings support that biocoating the NPs results in limited Ag release and yet they retained potent antimicrobial activity. PMID:26805711

  6. Polyvinyl alcohol electrospun nanofibers containing Ag nanoparticles used as sensors for the detection of biogenic amines

    NASA Astrophysics Data System (ADS)

    Marega, Carla; Maculan, Jenny; Rizzi, Gian Andrea; Saini, Roberta; Cavaliere, Emanuele; Gavioli, Luca; Cattelan, Mattia; Giallongo, Giuseppe; Marigo, Antonio; Granozzi, Gaetano

    2015-02-01

    Polyvinyl alcohol (PVA) electrospun nanofibers containing Ag nanoparticles (NPs) have been deposited on glass substrates. The aim of the work was to test the feasibility of this approach for the detection of biogenic amines by using either the Ag localized surface plasmon resonance quenching caused by the adsorption of amines on Ag NPs or by detecting the amines by surface enhanced Raman spectroscopy (SERS) after adsorption, from the gas phase, on the metal NPs. Two different approaches have been adopted. In the first one an ethanol/water solution containing AgNO3 was used directly in the electrospinning apparatus. In this way, a simple heat treatment of the nanofibers mat was sufficient to obtain the formation of Ag NPs inside the nanofibers and a partial cross-link of PVA. In the second procedure, the Ag NPs were deposited on PVA nanofibers by using the supersonic cluster beam deposition method, so that a beam of pure Ag NPs of controlled size was obtained. Exposure of the PVA mat to the beam produced a uniform distribution of the NPs on the nanofibers surface. Ethylendiamine vapors and volatile amines released from fresh shrimp meat were chemisorbed on the nanofibers mats. A SERS spectrum characterized by a diagnostic Ag-N stretching vibration at 230 cm-1 was obtained. The results allow to compare the two different approaches in the detection of ammines.

  7. Enhanced photocatalysis by coupling of anatase TiO2 film to triangular Ag nanoparticle island.

    PubMed

    Xu, Jinxia; Xiao, Xiangheng; Ren, Feng; Wu, Wei; Dai, Zhigao; Cai, Guangxu; Zhang, Shaofeng; Zhou, Juan; Mei, Fei; Jiang, Changzhong

    2012-01-01

    In order to overcome the low utilization ratio of solar light and high electron-hole pair recombination rate of TiO2, the triangular Ag nanoparticle island is covered on the surface of the TiO2 thin film. Enhancement of the photocatalytic activity of the Ag/TiO2 nanocomposite system is observed. The increase of electron-hole pair generation is caused by the enhanced near-field amplitudes of localized surface plasmon of the Ag nanoparticles. The efficiently suppressed recombination of electron-hole pair caused by the metal-semiconductor contact can also enhance the photocatalytic activity of the TiO2 film. PMID:22548875

  8. Enhanced photocatalysis by coupling of anatase TiO2 film to triangular Ag nanoparticle island

    PubMed Central

    2012-01-01

    In order to overcome the low utilization ratio of solar light and high electron-hole pair recombination rate of TiO2, the triangular Ag nanoparticle island is covered on the surface of the TiO2 thin film. Enhancement of the photocatalytic activity of the Ag/TiO2 nanocomposite system is observed. The increase of electron-hole pair generation is caused by the enhanced near-field amplitudes of localized surface plasmon of the Ag nanoparticles. The efficiently suppressed recombination of electron-hole pair caused by the metal-semiconductor contact can also enhance the photocatalytic activity of the TiO2 film. PMID:22548875

  9. The IP6 micelle-stabilized small Ag cluster for synthesizing Ag-Au alloy nanoparticles and the tunable surface plasmon resonance effect

    NASA Astrophysics Data System (ADS)

    Wang, Na; Wen, Ying; Wang, Yao; Zhang, Rui; Chen, Xiyao; Ling, Bo; Huan, Shuangyan; Yang, Haifeng

    2012-04-01

    The stable small Ag seeds (size in diameter < 10 nm) were obtained in the presence of inositol hexakisphosphoric (IP6) micelles. Then Ag-Au bimetallic nanoparticles were synthesized through a replacement reaction with the rapid interdiffusion process between such small Ag seeds in nanoclusters and HAuCl4. Adjusting the dosage of HAuCl4 resulted in different products, which possessed unique surface plasmon resonances (SPR). The morphologies of the as-made nanoparticles were observed using transmission electron microscopy and field emission scanning electron microscopy and their compositions were determined by energy-dispersive x-ray spectroscopy. Among them, the Ag-Au alloy nanoparticles with the cauliflower-like structure had a suitable SPR for highly sensitive Raman detection application as a surface-enhanced Raman scattering (SERS) substrate with a long-term stability of six months.

  10. Adsorption of DNA on colloidal Ag nanoparticles: effects of nanoparticle surface charge, base content and length of DNA.

    PubMed

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

    2014-04-01

    The adsorption of single and double stranded DNA on colloidal silver nanoparticles has been studied to investigate the effects of surface charge of the nanoparticles, the composition of the oligonucleotide and its length on the adsorption characteristics. The results explain that the nanoparticle surface charge is a key parameter determining the propensity of oligonucleotides to adsorb on nanoparticles. The adsorption also depends on the length and composition of oligonucleotide. The protective effects of both single and double stranded DNA against salt-induced aggregation dramatically increase as the DNA length increases. In contrast to other available reports, we observed that long oligonucleotides (single-stranded and double stranded) can well be adsorbed on the nanoparticles as the short ones leading to almost complete protection of nanoparticles against salt induced aggregation and hence are not suitable for the sensing applications. Finally, the light scattering from the Ag nanoparticles has been simulated and the results compared with the experiments. Our understanding should improve development of colorimetric assays for DNA detection based on aggregation of unmodified metallic nanoparticles.

  11. Energetics of the formation of Cu-Ag core–shell nanoparticles

    DOE PAGES

    Chandross, Michael

    2014-10-06

    Our work presents molecular dynamics and Monte Carlo simulations aimed at developing an understanding of the formation of core–shell Cu-Ag nanoparticles. The effects of surface and interfacial energies were considered and used to form a phenomenological model that calculates the energy gained upon the formation of a core–shell structure from two previously distinct, non-interacting nanoparticles. In most cases, the core–shell structure was found to be energetically favored. Specifically, the difference in energy as a function of the radii of the individual Cu and Ag particles was examined, with the assumption that a core–shell structure forms. In general, it was foundmore » that the energetic gain from forming such a structure increased with increasing size of the initial Ag particle. This result was interpreted as a result of the reduction in surface energy. Moreover, for two separate particles, both Cu and Ag contribute to the surface energy; however, for a core–shell structure, the only contribution to the surface energy is from the Ag shell and the Cu contribution is changed to a Cu–Ag interfacial energy, which is always smaller.« less

  12. Energetics of the formation of Cu-Ag core–shell nanoparticles

    SciTech Connect

    Chandross, Michael

    2014-10-06

    Our work presents molecular dynamics and Monte Carlo simulations aimed at developing an understanding of the formation of core–shell Cu-Ag nanoparticles. The effects of surface and interfacial energies were considered and used to form a phenomenological model that calculates the energy gained upon the formation of a core–shell structure from two previously distinct, non-interacting nanoparticles. In most cases, the core–shell structure was found to be energetically favored. Specifically, the difference in energy as a function of the radii of the individual Cu and Ag particles was examined, with the assumption that a core–shell structure forms. In general, it was found that the energetic gain from forming such a structure increased with increasing size of the initial Ag particle. This result was interpreted as a result of the reduction in surface energy. Moreover, for two separate particles, both Cu and Ag contribute to the surface energy; however, for a core–shell structure, the only contribution to the surface energy is from the Ag shell and the Cu contribution is changed to a Cu–Ag interfacial energy, which is always smaller.

  13. Preparation and photocatalytic properties of AgI–SnO{sub 2} nano-composites

    SciTech Connect

    Wen, Biao; Wang, Xiao-Hui; Lu, Juan; Cao, Jia-Lei; Wang, Zuo-Shan

    2013-05-15

    Highlights: ► AgI–SnO{sub 2} nano-composites have been successfully synthesized. ► As-prepared AgI–SnO{sub 2} nano-composites own the excellent visible light photocatalytic activity. ► As-prepared AgI–SnO{sub 2} nano-composites own the excellent stability. - Abstract: AgI doped SnO{sub 2} nano-composites were prepared by the chemical coprecipitation method and were characterized by the X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Results showed that main of the I{sup −} ions remained in the AgI lattice which is highly dispersed in the system. The photo-catalytic experiments performed under visible light irradiation using methylene blue as the pollutant revealed that not only the photo-catalytic activity but also the stability of SnO{sub 2} based photocatalyst could be improved by introduction of an appropriate amount of AgI, and the result was further supported by the UV–Vis diffuse reflection spectra and the electron spin-resonance spectra. Among all of the samples, AgI–SnO{sub 2} nano-composite with 2At% AgI exhibited the best catalytic efficiency and stability.

  14. Facile Preparation of Ag/NiO Composite Nanosheets and Their Antibacterial Activity

    NASA Astrophysics Data System (ADS)

    Shi, Cui-E.; Pan, Lu; Wang, Cheng-Run; He, Yi; Wu, Yong-Feng; Xue, Sai-Sai

    2016-01-01

    Sheet-like precursors of NiO and Ag/NiO with different Ag contents were synthesized by a facile and easily controlled hydrothermal method. The NiO and Ag/NiO composite nanosheets were prepared by calcination of the corresponding precursors at 400°C for 3 h. The as-synthesized samples were characterized by thermogravimetric analysis, x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The antibacterial activity of NiO and Ag/NiO composites to several gram-positive and gram-negative bacteria was examined. Results showed that NiO nanosheets hardly exhibited antibacterial activity; however, Ag/NiO composites displayed higher activity even with low Ag content.

  15. Supercapacitors Based on Metal Electrodes Prepared from Nanoparticle Mixtures at Room Temperature

    SciTech Connect

    Nakanishi, Hideyuki; Grzybowski, Bartosz A.

    2010-01-01

    Films comprising Au and Ag nanoparticles are transformed into porous metal electrodes by desorption of weak organic ligands followed by wet chemical etching of silver. Thus prepared electrodes provide the basis for supercapacitors whose specific capacitances approach 70 F/g. Cyclic voltammetry measurement yield “rectangular” I-V curves even at high scan rates, indicating that the supercapacitors have low internal resistance. Owing to this property, the supercapacitors have a high power density ~12 kW/kg, comparable with that of the state-of-the-art carbon-based devices. The entire assembly protocol does not require high-temperature processing or the use of organic binders.

  16. Novel Methods of Lipidic Nanoparticle Preparation and Drug Loading

    NASA Astrophysics Data System (ADS)

    Maitani, Y.

    2013-09-01

    In improving cancer chemotherapy, lipidic nanoparticle systems for drug delivery, such as liposomes and emulsions, have received much attention because they are capable of delivering their drug payload selectively to cancer cells and of circulating for a long period in the bloodstream. In addition, lipidic nanoparticles have been examined for use in gene delivery as a non-viral vector. Preparation methods of particles and drug loading methods are crucial for the physicochemical properties of nanoparticles, which are the key aspects for pharmaceutical applications. This review describes new preparation methods for nanoparticles and a loading method for drugs using nanotechnology, including an evaluation of nanoparticles from the point of drug release for applications in cancer therapy and gene delivery.

  17. Preparation of nanoparticles in reverse microemulsions

    NASA Astrophysics Data System (ADS)

    Tovstun, Sergey A.; Razumov, Vladimir F.

    2011-10-01

    Experimental data and results of theoretical studies dealing with the synthesis of nanoparticles by the condensation of products of chemical reactions in reverse microemulsions are generalized. Attention is focused on the analysis of mechanisms of nanoparticle nucleation and growth. The bibliography includes 252 references.

  18. Zero-valent iron nanoparticles preparation

    SciTech Connect

    Oropeza, S.; Corea, M.; Gómez-Yáñez, C.; Cruz-Rivera, J.J.; Navarro-Clemente, M.E.

    2012-06-15

    Graphical abstract: Zero-valent iron nanoparticles were synthesized by hydrogenating [Fe[N(Si(CH{sub 3}){sub 3}){sub 2}]{sub 2}] at room temperature and a pressure of 3 atm. The synthesized nanoparticles were spherical and had diameters less than 5 nm. Highlights: ► Zero-valent iron nanoparticles were synthesized by hydrogenating [Fe[N(Si(CH{sub 3}){sub 3}){sub 2}]{sub 2}]. ► The conditions of reaction were at room temperature and a pressure of 3 atm. ► The synthesized nanoparticles were spherical and had diameters less than 5 nm. -- Abstract: Zero-valent iron nanoparticles were synthesized by hydrogenating [Fe[N(Si(CH{sub 3}){sub 3}){sub 2}]{sub 2}] at room temperature and a pressure of 3 atm. To monitor the reaction, a stainless steel pressure reactor lined with PTFE and mechanically stirred was designed. This design allowed the extraction of samples at different times, minimizing the perturbation in the system. In this way, the shape and the diameter of the nanoparticles produced during the reaction were also monitored. The results showed the production of zero-valent iron nanoparticles that were approximately 5 nm in diameter arranged in agglomerates. The agglomerates grew to 900 nm when the reaction time increased up to 12 h; however, the diameter of the individual nanoparticles remained almost the same. During the reaction, some byproducts constituted by amino species acted as surfactants; therefore, no other surfactants were necessary.

  19. Resonant surface enhancement of Raman scattering of Ag nanoparticles on silicon substrates fabricated by dc sputtering

    SciTech Connect

    Fang Yingcui; Li Xiaxi; Blinn, Kevin; Mahmoud, Mahmoud A.; Liu Meilin

    2012-09-15

    Ag nanoparticles (AgNPs) were deposited onto silicon substrates by direct current (dc) magnetron sputtering. The influences of sputtering power and sputtering time on the AgNP film morphology were studied using atomic force microscopy. The particle size was successfully tuned from 19 nm to 53 nm by varying the sputtering time at a dc power of 10 W. When Rhodamine 6 G (R6G) was used as the probe molecule, the AgNP films showed significant surface enhanced Raman scattering effect. In particular, it is found that larger particles show stronger enhancement for lower concentrations of R6G while smaller particles display stronger enhancement for higher concentrations of R6G.

  20. Fabrication of high aspect ratio nanogrid transparent electrodes via capillary assembly of Ag nanoparticles.

    PubMed

    Kang, Juhoon; Park, Chang-Goo; Lee, Su-Han; Cho, Changsoon; Choi, Dae-Geun; Lee, Jung-Yong

    2016-06-01

    In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq(-1) and an optical transmittance of 85.4%. PMID:27187802

  1. Antifungal activity of gold nanoparticles prepared by solvothermal method

    SciTech Connect

    Ahmad, Tokeer; Wani, Irshad A.; Lone, Irfan H.; Ganguly, Aparna; Manzoor, Nikhat; Ahmad, Aijaz; Ahmed, Jahangeer; Al-Shihri, Ayed S.

    2013-01-15

    Graphical abstract: Gold nanoparticles (7 and 15 nm) of very high surface area (329 and 269 m{sup 2}/g) have been successfully synthesized through solvothermal method by using tin chloride and sodium borohydride as reducing agents. As-prepared gold nanoparticles shows very excellent antifungal activity against Candida isolates and activity increases with decrease in the particle size. Display Omitted Highlights: ► Effect of reducing agents on the morphology of gold nanoparticles. ► Highly uniform and monodisperse gold nanoparticles (7 nm). ► Highest surface area of gold nanoparticles (329 m{sup 2/}g). ► Excellent antifungal activity of gold nanoparticles against Candida strains. -- Abstract: Gold nanoparticles have been successfully synthesized by solvothermal method using SnCl{sub 2} and NaBH{sub 4} as reducing agents. X-ray diffraction studies show highly crystalline and monophasic nature of the gold nanoparticles with face centred cubic structure. The transmission electron microscopic studies show the formation of nearly spherical gold nanoparticles of average size of 15 nm using SnCl{sub 2}, however, NaBH{sub 4} produced highly uniform, monodispersed and spherical gold nanoparticles of average grain size of 7 nm. A high surface area of 329 m{sup 2}/g for 7 nm and 269 m{sup 2}/g for 15 nm gold nanoparticles was observed. UV–vis studies assert the excitations over the visible region due to transverse and longitudinal surface plasmon modes. The gold nanoparticles exhibit excellent size dependant antifungal activity and greater biocidal action against Candida isolates for 7 nm sized gold nanoparticles restricting the transmembrane H{sup +} efflux of the Candida species than 15 nm sized gold nanoparticles.

  2. Fractal structure formation from Ag nanoparticle films on insulating substrates.

    PubMed

    Tang, Jing; Li, Zhiyong; Xia, Qiangfei; Williams, R Stanley

    2009-07-01

    Two dimensional (2D) fractal structures were observed to form from fairly uniform Ag island films (equivalent mass thicknesses of 1.5 and 5 nm) on insulating silicon dioxide surfaces (thermally grown silicon oxide on Si or quartz) upon immersion in deionized water. This result is distinctly different from the previously observed three-dimensional (3D) growth of faceted Ag nanocrystals on conductive surfaces (ITO and graphite) as the result of an electrochemical Ostwald ripening process, which also occurs on native oxide covered silicon surfaces as reported here. The fractal structures formed by diffusion-limited aggregation (DLA) of Ag species on the insulating surfaces. We present the experimental observation of this phenomenon and discuss some possible mechanisms for the DLA formation. PMID:19496573

  3. Evaluation of Postharvest Washing on Removal of Silver Nanoparticles (AgNPs) from Spinach Leaves.

    PubMed

    Zhang, Zhiyun; Guo, Huiyuan; Carlisle, Thomas; Mukherjee, Arnab; Kinchla, Amanda; White, Jason C; Xing, Baoshan; He, Lili

    2016-09-21

    There is increasing use of silver nanoparticles (AgNPs) as pesticides for fruits and vegetables due to the particles' unique antimicrobial and insecticidal properties. However, residual AgNPs in harvested produce may transfer through the food chain and pose a potential risk to public health. The objective of this study is to determine whether postharvest washing can effectively remove AgNPs that had accumulated on fresh produce. Ten microliters of commercially available 40 nm citrate coated AgNPs (0.4 mg/L) was dropped to a (1 × 1 cm(2)) spot on spinach leaves, followed by washing with deionized water (DI water), Tsunami 100 (80 mg/L), or Clorox bleach (200 mg/L). Then, the AgNP removal efficiency of the three treatments was evaluated by surface-enhanced Raman spectroscopy (SERS), scanning electron microscopy (SEM)-energy dispersive spectrometry (EDS), and inductively coupled plasma mass spectrometry (ICP-MS). ICP-MS results showed that deionized water removed statistically insignificant amounts of total Ag (5%), whereas Tsunami 100 and Clorox bleach yielded 21 and 10% decreases in total Ag, respectively (P < 0.05). The increased removal efficiency resulted from AgNP dissolution and Ag(+) release upon contact with the oxidizing agents in Tsunami 100 (peroxyacetic acid, hydrogen peroxide) and Clorox bleach (sodium hypochlorite). According to the SERS results, the deionized water and Tsunami 100 treatments removed nonsignificant amounts of AgNPs. Clorox bleach decreased Ag NPs by >90% (P < 0.05); however, SEM-EDS images revealed the formation of large silver chloride (AgCl) crystals (162 ± 51 nm) on the leaf, which explained the low total Ag removal from ICP-MS. This study indicates current factory washing methods for fresh produce may not be effective in reducing AgNPs (by water and Tsunami 100) and total Ag (by all three means). This highlights the necessity to develop an efficient washing method for NP removal from food surfaces in the future. PMID:27548506

  4. Evaluation of Postharvest Washing on Removal of Silver Nanoparticles (AgNPs) from Spinach Leaves.

    PubMed

    Zhang, Zhiyun; Guo, Huiyuan; Carlisle, Thomas; Mukherjee, Arnab; Kinchla, Amanda; White, Jason C; Xing, Baoshan; He, Lili

    2016-09-21

    There is increasing use of silver nanoparticles (AgNPs) as pesticides for fruits and vegetables due to the particles' unique antimicrobial and insecticidal properties. However, residual AgNPs in harvested produce may transfer through the food chain and pose a potential risk to public health. The objective of this study is to determine whether postharvest washing can effectively remove AgNPs that had accumulated on fresh produce. Ten microliters of commercially available 40 nm citrate coated AgNPs (0.4 mg/L) was dropped to a (1 × 1 cm(2)) spot on spinach leaves, followed by washing with deionized water (DI water), Tsunami 100 (80 mg/L), or Clorox bleach (200 mg/L). Then, the AgNP removal efficiency of the three treatments was evaluated by surface-enhanced Raman spectroscopy (SERS), scanning electron microscopy (SEM)-energy dispersive spectrometry (EDS), and inductively coupled plasma mass spectrometry (ICP-MS). ICP-MS results showed that deionized water removed statistically insignificant amounts of total Ag (5%), whereas Tsunami 100 and Clorox bleach yielded 21 and 10% decreases in total Ag, respectively (P < 0.05). The increased removal efficiency resulted from AgNP dissolution and Ag(+) release upon contact with the oxidizing agents in Tsunami 100 (peroxyacetic acid, hydrogen peroxide) and Clorox bleach (sodium hypochlorite). According to the SERS results, the deionized water and Tsunami 100 treatments removed nonsignificant amounts of AgNPs. Clorox bleach decreased Ag NPs by >90% (P < 0.05); however, SEM-EDS images revealed the formation of large silver chloride (AgCl) crystals (162 ± 51 nm) on the leaf, which explained the low total Ag removal from ICP-MS. This study indicates current factory washing methods for fresh produce may not be effective in reducing AgNPs (by water and Tsunami 100) and total Ag (by all three means). This highlights the necessity to develop an efficient washing method for NP removal from food surfaces in the future.

  5. Facile synthesis of S-Ag nanocomposites and Ag2S short nanorods by the interaction of sulfur with AgNO3 in PEG400

    NASA Astrophysics Data System (ADS)

    Zhang, Yan-Li; Xie, Xin-Yuan; Liang, Ming; Xie, Shu-Ming; Chen, Jie-Mei; Zheng, Wen-Jie

    2016-06-01

    A facile, eco-friendly and inexpensive method to prepare Ag2S short nanorods and S-Ag nanocomposites using sublimed sulfur, AgNO3, PVP and PEG400 was studied. According to x-ray diffraction and scanning electron microscopy of the Ag2S, the products are highly crystalline and pure Ag2S nanorods with diameters of 70-160 nm and lengths of 200-360 nm. X-ray diffraction of the S-Ag nanocomposites shows that we obtained cubic Ag and S nanoparticles. Transmission electron microscopy shows that the molar ratio of PVP to Ag+ plays an important role in controlling the size and morphology of the S-Ag nanocomposites. When the molar ratio of PVP to Ag+ was 10:1, smaller sizes, better dispersibility and narrower distribution of S-Ag nanocomposites with diameters of 10-40 nm were obtained. The formation mechanism of the S-Ag nanocomposites was studied by designing a series of experiments using ultraviolet-visible measurement, and it was found that S nanoparticles are produced first and act as seed crystals; then Ag+ becomes Ag nanocrystals on the surfaces of the S nanoparticles by the reduction of PVP. PEG400 acts as a catalyzer, accelerating the reaction rate, and protects the S-Ag nanocomposites from reacting to produce Ag2S. The antimicrobial experiments show that the S-Ag nanocomposites have greater antimicrobial activity on Staphylococcus aureus, Aspergillus niger and blue mold than Ag nanoparticles.

  6. Facile synthesis of S–Ag nanocomposites and Ag2S short nanorods by the interaction of sulfur with AgNO3 in PEG400

    NASA Astrophysics Data System (ADS)

    Zhang, Yan-Li; Xie, Xin-Yuan; Liang, Ming; Xie, Shu-Ming; Chen, Jie-Mei; Zheng, Wen-Jie

    2016-06-01

    A facile, eco-friendly and inexpensive method to prepare Ag2S short nanorods and S–Ag nanocomposites using sublimed sulfur, AgNO3, PVP and PEG400 was studied. According to x-ray diffraction and scanning electron microscopy of the Ag2S, the products are highly crystalline and pure Ag2S nanorods with diameters of 70–160 nm and lengths of 200–360 nm. X-ray diffraction of the S–Ag nanocomposites shows that we obtained cubic Ag and S nanoparticles. Transmission electron microscopy shows that the molar ratio of PVP to Ag+ plays an important role in controlling the size and morphology of the S–Ag nanocomposites. When the molar ratio of PVP to Ag+ was 10:1, smaller sizes, better dispersibility and narrower distribution of S–Ag nanocomposites with diameters of 10–40 nm were obtained. The formation mechanism of the S–Ag nanocomposites was studied by designing a series of experiments using ultraviolet–visible measurement, and it was found that S nanoparticles are produced first and act as seed crystals; then Ag+ becomes Ag nanocrystals on the surfaces of the S nanoparticles by the reduction of PVP. PEG400 acts as a catalyzer, accelerating the reaction rate, and protects the S–Ag nanocomposites from reacting to produce Ag2S. The antimicrobial experiments show that the S–Ag nanocomposites have greater antimicrobial activity on Staphylococcus aureus, Aspergillus niger and blue mold than Ag nanoparticles.

  7. Graphene-supported Ag-based core-shell nanoparticles for hydrogen generation in hydrolysis of ammonia borane and methylamine borane.

    PubMed

    Yang, Lan; Luo, Wei; Cheng, Gongzhen

    2013-08-28

    Well-dispersed magnetically recyclable core-shell Ag@M (M = Co, Ni, Fe) nanoparticles (NPs) supported on graphene have been synthesized via a facile in situ one-step procedure, using methylamine borane (MeAB) as a reducing agent under ambient condition. Their catalytic activity toward hydrolysis of ammonia borane (AB) were studied. Although the Ag@Fe/graphene NPs are almost inactive, the as-prepared Ag@Co/graphene NPs are the most reactive catalysts, followed by Ag@Ni/graphene NPs. Compared with AB and NaBH4, the as-synthesized Ag@Co/graphene catalysts which reduced by MeAB exert the highest catalytic activity. Additionally, the Ag@Co NPs supported on graphene exhibit higher catalytic activity than the catalysts with other conventional supports, such as the SiO2, carbon black, and γ-Al2O3. The as-synthesized Ag@Co/graphene NPs exert satisfied catalytic activity, with the turnover frequency (TOF) value of 102.4 (mol H2 min(-1) (mol Ag)(-1)), and the activation energy Ea value of 20.03 kJ/mol. Furthermore, the as-synthesized Ag@Co/graphene NPs show good recyclability and magnetically reusability for the hydrolytic dehydrogenation of AB and MeAB, which make the practical reusing application of the catalysts more convenient. Moreover, this simple synthetic method indicates that MeAB could be used as not only a potential hydrogen storage material but also an efficient reducing agent. It can be easily extended to facile preparation of other graphene supported metal NPs. PMID:23927435

  8. Fabrication of high aspect ratio nanogrid transparent electrodes via capillary assembly of Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Kang, Juhoon; Park, Chang-Goo; Lee, Su-Han; Cho, Changsoon; Choi, Dae-Geun; Lee, Jung-Yong

    2016-05-01

    In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq-1 and an optical transmittance of 85.4%.In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq-1 and an optical transmittance of 85.4%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01896c

  9. Green synthesis, characterization, photocatalytic, fluorescence and antimicrobial activities of Cochlospermum gossypium capped Ag2S nanoparticles.

    PubMed

    Ayodhya, Dasari; Veerabhadram, Guttena

    2016-04-01

    The study describes a simple and green method for the synthesis of silver sulfide nanoparticles (Ag2S NPs) using gum kondagogu (Cochlospermum gossypium) (GK). The synthesized NPs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), fluorescence, UV-vis absorption, zeta potential and thermogravimetric analysis (TGA) techniques. The optical properties and quantum confinement effect of the products were confirmed by means of spectroscopic measurements. The morphologies and sizes were characterized by SEM and TEM. The Ag2S NPs were spherical in shape with an effective diameter size of 25 nm. The photocatalytic property of Ag2S NPs was evaluated by the degradation of fluorescein (FL) dye under solar light. The effect of Ag2SNPs on the photocatalytic degradation of FL dye and influence of other parameters such as Ag2S loading, H2O2, temperature and under solar light irradiation was also evaluated. The degradation reaction follows the pseudo-first order kinetics. The apparent reaction rate was used to calculate the apparent activation energy (Ea=13.95 kJ/mol) of the degradation process. The activation thermodynamic parameters (ΔG*, ΔH* and ΔS*) were obtained from variable temperature kinetic studies. The interaction between Ag2S NPs and bovine serum albumin (BSA) was studied by using fluorescence spectroscopic measurements. The synthesized Ag2S NPs were showing good antimicrobial activity.

  10. Preparing of Highly Conductive Patterns on Flexible Substrates by Screen Printing of Silver Nanoparticles with Different Size Distribution.

    PubMed

    Ding, Jin; Liu, Jun; Tian, Qingyong; Wu, Zhaohui; Yao, Weijing; Dai, Zhigao; Liu, Li; Wu, Wei

    2016-12-01

    A facile one-step polyol method is employed to synthesize the Ag nanoparticles (NPs) in large scale. The Ag NPs with different average diameter (from 52 to 120 nm) and particle size distribution are prepared by changing the mass ratio of AgNO3 and PVP. Furthermore, the as-obtained Ag NPs are prepared as conductive inks, which could be screen printed on various flexible substrates and formed as conductive patterns after sintering treatment. During the reaction process, PVP is used as the capping reagent for preventing the agglomeration of Ag NPs, and the influence of the mass ratio of AgNO3 and PVP to the size distribution of Ag NPs is investigated. The results of electronic properties reveal that the conductivity of printed patterns is highly dependent on the size distribution of as-obtained Ag NPs. Among all the samples, the optimal conductivity is obtained when the mass ratio of AgNO3 and PVP is 1:0.4. Subsequently, the sintering time and temperature are further investigated for obtaining the best conductivity; the optimal electrical resistivity value of 3.83 μΩ · cm is achieved at 160 °C for 75 min, which is close to the resistivity value of the bulk silver (1.58 μΩ · cm). Significantly, there are many potential advantages in printed electronics applications because of the as-synthesized Ag NPs with a low sintering temperature and low electrical resistivity. PMID:27644238

  11. Raman enhancement of rhodamine adsorbed on Ag nanoparticles self-assembled into nanowire-like arrays

    PubMed Central

    2011-01-01

    This work reports on Raman scattering of rhodamine (R6G) molecules absorbed on either randomly distributed or grating-like arrays of approximately 8-nm Ag nanoparticles developed by inert gas aggregation. Optimal growth and surface-enhanced Raman scattering (SERS) parameters have been obtained for the randomly distributed nanoparticles, while effects related to the aging of the silver nanoparticles were studied. Grating-like arrays of nanoparticles have been fabricated using line arrays templates formed either by fracture-induced structuring or by standard lithographic techniques. Grating structures fabricated by both methods exhibit an enhancement of the SERS signal, in comparison to the corresponding signal from randomly distributed Ag nanoparticles, as well as a preferential enhancement in the areas of the sharp features, and a dependence on the polarization direction of the incident exciting laser beam, with respect to the orientation of the gratings structuring. The observed spectroscopic features are consistent with a line-arrangement of hot-spots due to the self- alignment of metallic nanoparticles, induced by the grating-like templates. PMID:22168792

  12. [Three-dimensional vertically aligned CNTs coated by Ag nanoparticles for surface-enhanced Raman scattering].

    PubMed

    Zhang, Xiao-Lei; Zhang, Jie; Fan, Tuo; Ren, Wen-Jie; Lai, Chun-Hong

    2014-09-01

    In order to make surface-enhanced Raman scattering (SERS) substrates contained more "hot spots" in a three-dimensional (3D) focal volume, and can be adsorbed more probe molecules and metal nanoparticles, to obtain stronger Raman spectral signal, a new structure based on vertically aligned carbon nanotubes (CNTs) coated by Ag nanoparticles for surface Raman enhancement is presented. The vertically aligned CNTs are synthesized by chemical vapor deposition (CVD). A silver film is first deposited on the vertically aligned CNTs by magnetron sputtering. The samples are then annealed at different temperature to cause the different size silver nanoparticles to coat on the surface and sidewalls of vertically aligned CNTs. The result of scanning electron microscopy(SEM) shows that Ag nanoparticles are attached onto the sidewalls and tips of the vertically aligned CNTs, as the annealing temperature is different , pitch size, morphology and space between the silver nanoparticles is vary. Rhodamine 6G is served as the probe analyte. Raman spectrum measurement indicates that: the higher the concentration of R6G, the stronger the Raman intensity, but R6G concentration increase with the enhanced Raman intensity varies nonlinearly; when annealing temperature is 450 °C, the average size of silver nanoparticles is about 100 to 120 nm, while annealing temperature is 400 °C, the average size is about 70 nm, and the Raman intensity of 450 °C is superior to the annealing temperature that of 400 °C and 350 °C. PMID:25532342

  13. M3Ag17(SPh)12 Nanoparticles and Their Structure Prediction.

    PubMed

    Wickramasinghe, Sameera; Atnagulov, Aydar; Yoon, Bokwon; Barnett, Robert N; Griffith, Wendell P; Landman, Uzi; Bigioni, Terry P

    2015-09-16

    Although silver nanoparticles are of great fundamental and practical interest, only one structure has been determined thus far: M4Ag44(SPh)30, where M is a monocation, and SPh is an aromatic thiolate ligand. This is in part due to the fact that no other molecular silver nanoparticles have been synthesized with aromatic thiolate ligands. Here we report the synthesis of M3Ag17(4-tert-butylbenzene-thiol)12, which has good stability and an unusual optical spectrum. We also present a rational strategy for predicting the structure of this molecule. First-principles calculations support the structural model, predict a HOMO-LUMO energy gap of 1.77 eV, and predict a new "monomer mount" capping motif, Ag(SR)3, for Ag nanoparticles. The calculated optical absorption spectrum is in good correspondence with the measured spectrum. Heteroatom substitution was also used as a structural probe. First-principles calculations based on the structural model predicted a strong preference for a single Au atom substitution in agreement with experiment.

  14. Environmentally friendly preparation of metal nanoparticles

    EPA Science Inventory

    The book chapter summarizes the “state of the art” in the exploitation of various environmentally-friendly synthesis approaches, reaction precursors and conditions to manufacture metal and metal oxide nanoparticles for a vast variety of purposes.

  15. Preparation of silver nanoparticles at low temperature

    NASA Astrophysics Data System (ADS)

    Mishra, Mini; Chauhan, Pratima

    2016-04-01

    Silver from ancient time is used as antimicrobial agent in the bulk form but now with the advancement in nanotechnology silver in the form of nanoparticles shown potential effect against microbes which make us easy to fight with many diseases plants and animals. In this work silver nanoparticles were synthesized by chemical routes using sodium borohydride as reducing agent at low temperature. The particles were characterized through UV-Visible spectroscopy as well as X-Ray Diffraction. The UV-visible spectra of silver nanoparticles exhibited absorption at 425 cm; the crystallite size of the particles is between 19nm to 39nm. EDAX graph shows two peaks of silver and oxygen. Water absorbed by silver nanoparticles was removed by the calcinations.

  16. Microstructure of interface between Si chip and tape-type Ag nanoparticle sheet

    NASA Astrophysics Data System (ADS)

    Mutoh, Hayato; Moriyama, Naoki; Kaneko, Keiya; Miyazawa, Yasuyuki; Kida, Hitoshi

    2014-08-01

    A Ag nanoparticles-based technology for joining semiconductor materials through sintering has been developed. Currently, a paste consisting of Ag nanoparticles is used for die bonding in the electronics industry. A binder-free Ag nanojoining material has been developed for fabricating electronic devices. In this study, we investigated the joining ability of this binder-free tape-type Ag nanojoining material with respect to Si chips. A paste-type Ag nanojoining material that contained an organic binder was also investigated for comparison. The microstructures of the Si-joining material interfaces were observed using a focused ion beam system. The cleaved surfaces of the joints were observed using scanning electron microscopy. High-quality joints that contained only a few pores could be formed between a Au thin film electroplated on the Si chip and the tape-type material after sintering, owing to the simplicity of the joining process and the binder-free nature of the joining material.

  17. Formation Mechanism and Characterization of Ag-Metal Chelate Polymer Prepared by a Wet Chemical Process

    NASA Astrophysics Data System (ADS)

    Huang, Chueh-Jung; Lin, Jiang-Jen; Shieu, Fuh-Sheng

    2005-08-01

    In this study, a metal chelate polymer (MCP) contained Ag(0) was prepared from commercial polyvinyl acetate (PVAc) and silver nitrate (AgNO3) by a wet chemical method using concentrate formic acid (HCOOH) as solvent. The characterization of these MCP materials, and the formation mechanism that involved in the MCP system, were studied by the analyses of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM). The Ag(I) cations of silver nitrate (AgNO3) were found coordinated with polymer functional groups to form polymer-Ag(I) complexes. The XRD analysis revealed that these complexed Ag(I) ions were in-situ reduced to generate Ag(0) metal by HCOOH solvent in MCP system. The results of FTIR and NMR analyses demonstrated that there are hydrolyzed hydroxyl groups present in the MCP chains. The XPS analysis showed that the oxygen ligands that interacted with the Ag(0) were mostly contributed from the OH groups. The interaction between the reduced Ag(0) metal and the polymer chains was confirmed by transmission electron microscopy (TEM) investigation on the MCP materials.

  18. Breathing Raman modes in Ag2S nanoparticles obtained from F9 zeolite matrix

    NASA Astrophysics Data System (ADS)

    Delgado-Beleño, Y.; Cortez-Valadez, M.; Martinez-Nuñez, C. E.; Britto Hurtado, R.; Alvarez, Ramón A. B.; Rocha-Rocha, O.; Arizpe-Chávez, H.; Perez-Rodríguez, A.; Flores-Acosta, M.

    2015-12-01

    Ag2S nanoparticles were synthesized with a combination of synthetic F9, silver nitrate (AgNO3) and monohydrated sodium sulfide (Na2S9H2O). An ionic exchange was achieved via hydrothermal reaction. Nanoparticles with a predominant size ranging from 2 to 3 nm were obtained through Transmission Electron Microscopy (TEM). The nanoparticles feature a phase P21/n (14) monoclinic structure. A Raman band can be observed at around 250 cm-1 in the nanoparticles. Furthermore, the vibrational properties and stability parameters of the clusters (AgS)n, (with n = 2-9) were studied by the Density Functional Theory (DFT). The approximation levels used with DFT were: Local Spin Density Approximation (LSDA) and Becke's three-parameter and the gradient corrected functional of Lee, Yang and Puar (B3LYP) in combination with the basis set LANL2DZ (the effective core potentials and associated double-zeta valence). The Radial Breathing Mode (RBM) for B3LYP was found between 227 and 295 cm-1 as well as in longer wavelengths for LSDA.

  19. Enhanced and tunable optical quantum efficiencies from plasmon bandwidth engineering in bimetallic CoAg nanoparticles

    NASA Astrophysics Data System (ADS)

    Malasi, A.; Taz, H.; Ehrsam, M.; Goodwin, J.; Garcia, H.; Kalyanaraman, R.

    2016-10-01

    Plasmonic nanoparticles are amongst the most effective ways to resonantly couple optical energy into and out of nanometer sized volumes. However, controlling and/or tuning the transfer of this incident energy to the surrounding near and far field is one of the most interesting challenges in this area. Due to the dielectric properties of metallic silver (Ag), its nanoparticles have amongst the highest radiative quantum efficiencies (η), i.e., the ability to radiatively transfer the incident energy to the surrounding. Here we report the discovery that bimetallic nanoparticles of Ag made with immiscible and plasmonically weak Co metal can show comparable and/or even higher η values. The enhancement is a result of the narrowing of the plasmon bandwidth from these bimetal systems. The phenomenological explanation of this effect based on the dipolar approximation points to the reduction in radiative losses within the Ag nanoparticles when in contact with cobalt. This is also supported by a model of coupling between poor and good conductors based on the surface to volume ratio. This study presents a new type of bandwidth engineering, one based on using bimetal nanostructures, to tune and/or enhance the quality factor and quantum efficiency for near and far-field plasmonic applications.

  20. Formation and Cytotoxicity of Nanoparticles and Nanocubes Prepared from Gold and Silver Salts

    NASA Astrophysics Data System (ADS)

    Banker, Daniel; Dorrell, Skyler; Ivey, Prescott; Scurti, Joseph; Dobbins, Tabbetha

    Photothermal therapy is the use of electromagnetic radiation as the treatment for medical conditions such as cancer. Noble metal nanoparticles and nanocubes are brought to an excited state with laser light and as a result they release vibrational energy in the form of heat, which can be used to kill targeted cancer cells. Wet chemistry gives the basics for the preparation of nanoparticles and nanocubes. Using HAuCl4, AgNO3, tri-sodium citrate and other chemicals, we were able to successfully create gold and silver nanoparticles and nanocubes. The goal is to make sure that 3T3 cells can survive in a nanoparticle or nanocube doped medium so that we can then observe their reaction to photothermal effects. Cell culture techniques were done to 3T3 cells to keep them alive before the testing of cytotoxicity. Photothermal effect refers to the way that our nanoparticles or nanocubes can be photoexcited to release enough heat to kill the cells. We used a UV-Vis spectrophotometer to ensure that the correct wavelength laser. Assuming that the cells will survive living in the doped medium, a medium that has had nanomaterials introduced into it, we will use a high powered laser to observe what the excitation does to the cells since the photothermal effect should result in dead cells.

  1. Preparation of TiO(2)/Ag colloids with ultraviolet resistance and antibacterial property using short chain polyethylene glycol.

    PubMed

    Su, W; Wei, S S; Hu, S Q; Tang, J X

    2009-12-30

    TiO(2)/Ag nano-antibacterial material was prepared at low temperature using polyethylene glycol (PEG-600) as reducing and stabilizing agent. The size and shape as well as the optical properties of the nano-materials were characterized with transmission electron microscopy (TEM) and UV-vis spectroscopy (UV-vis). The results showed that the average particle size of TiO(2) among these nano-materials was around 50-150 nm, and the average particle size of nano-silver was around 20 nm. Formation of Ag nano-particles on the surface of TiO(2) was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the antibacterial activity was also investigated. By the antibacterial activity study and ultraviolet resistance test, it is noted that growth inhibition rates against E. coli was 99.99% as the concentration of nano-particles dispersion solution was 10 ppm, the minimum UV protective effect could be achieved as the concentration was 290 ppm.

  2. Preparation and evaluations in vitro of oxaliplatin polylactic acid nanoparticles.

    PubMed

    Cui, Zhaoyuan; Sun, Yong; Liu, Xiaohong; Ju, Fang; Chen, Qian; Gao, Wen; Wei, Haitian

    2013-08-01

    The oxaliplatin nanoparticles were prepared with polylactic acid matrix, orthogonal test was applied to optimize the prescriptions, and the qualities of oxaliplatin nanoparticles were characterized by the shape, particle size, encapsulation efficiency (EE), and drug loading (DL). Oxaliplatin nanoparticle was prepared by solution replacement method. The formation of 0.25% Tween80, DMF-water 1:8 (v/v), oxaliplatin-polylactic acid 1:5 (w/w), and 20 mg/ml polylactic acid showed the suitable EE (17.4 ± 0.47%), DL (3.52 ± 0.07%). We observed the shape of oxaliplatin nanoparticles through SEM. The average size of the particles was 120.5 ± 8.7 nm, which was detected by N5 submicron particle size analyzer.

  3. Preparation and characterization of biopolymeric nanoparticles used in drug delivery.

    PubMed

    Ramachandran, Radhika; Shanmughavel, Piramanayagam

    2010-02-01

    Nanotechnology plays an important role in advanced biology and medicine research particularly in the development of potential site-specific delivery systems with lower drug toxicity and greater efficiency. These include microcapsules, liposomes, polymeric microspheres, microemulsions, polymer micelles, hydrogels, solid nanoparticles etc. In the present study, preparation and characterization of biopolymeric gelatin nanoparticles for encapsulating the antimicrobial drug sulfadiazine and its in vivo drug release in phosphate buffer saline (PBS) have been investigated. The nanoparticles prepared by second desolvation process varied in a size range 200 nm and 600 nm with a drug entrapment efficiency of 50% characterized by atomic force microscopy and dynamic light scattering. The drug release from the nanoparticles occurred up to 30% in a controlled manner.

  4. Preparation and characterization of biopolymeric nanoparticles used in drug delivery.

    PubMed

    Ramachandran, Radhika; Shanmughavel, Piramanayagam

    2010-02-01

    Nanotechnology plays an important role in advanced biology and medicine research particularly in the development of potential site-specific delivery systems with lower drug toxicity and greater efficiency. These include microcapsules, liposomes, polymeric microspheres, microemulsions, polymer micelles, hydrogels, solid nanoparticles etc. In the present study, preparation and characterization of biopolymeric gelatin nanoparticles for encapsulating the antimicrobial drug sulfadiazine and its in vivo drug release in phosphate buffer saline (PBS) have been investigated. The nanoparticles prepared by second desolvation process varied in a size range 200 nm and 600 nm with a drug entrapment efficiency of 50% characterized by atomic force microscopy and dynamic light scattering. The drug release from the nanoparticles occurred up to 30% in a controlled manner. PMID:21086757

  5. Synthesis of silver nanoparticles prepared in aqueous solutions using helium dc microplasma jet

    NASA Astrophysics Data System (ADS)

    Li Thong, Ying; Hoong Chin, Oi; Hoong Ong, Boon; Huang, Nay Ming

    2016-01-01

    Silver nanoparticles (AgNPs) were synthesized in aqueous solutions by reduction of silver nitrate (AgNO3) assisted by a helium dc microplasma jet at atmospheric pressure without additional chemical reducing agents. Surfactant-free AgNPs were obtained at low initial AgNO3 precursor concentrations ≤0.5 mM. A surface plasmon resonance peak at approximately 400 nm confirmed the presence of AgNPs. At higher concentrations, sucrose was used to prevent agglomeration and cap the growth of nanoparticles. The effects of the molar ratio of sucrose/AgNO3 on the size distribution and morphologies of AgNPs were investigated. The average sizes of AgNPs synthesized at molar ratios of 20, 50, and 60% were 11.2 ± 0.4, 10.0 ± 0.2, and 6.2 ± 0.1 nm, respectively.

  6. Enhanced high thermal conductivity and low permittivity of polyimide based composites by core-shell Ag@SiO2 nanoparticle fillers

    NASA Astrophysics Data System (ADS)

    Zhou, Yongcun; Wang, Lu; Zhang, Hu; Bai, Yuanyuan; Niu, Yujuan; Wang, Hong

    2012-07-01

    A kind of polymer based composites was prepared by embedding the fillers of core-shell Ag@SiO2 nanoparticles into the polyimide (PI) matrix. The obtained Ag@SiO2/PI (50% vf of fillers) composites show remarkably improved high thermal conductivity and low relative permittivity. The maximum value of the thermal conductivity of composites is 7.88 W/(mK) and the relative permittivity and dielectric loss are about 11.7 and 0.015 at 1 MHz, respectively. Compared with self-passivated nanometer Al* particles composites, core-shell Ag@SiO2 nano-composite is beneficial to increase the thermal conductivity and reduce the permittivity of the composites. The relative mechanism was studied and discussed.

  7. Direct laser writing of μ-chips based on hybrid C-Au-Ag nanoparticles for express analysis of hazardous and biological substances.

    PubMed

    Bashouti, M Y; Manshina, A; Povolotckaia, A; Povolotskiy, A; Kireev, A; Petrov, Y; Mačković, M; Spiecker, E; Koshevoy, I; Tunik, S; Christiansen, S

    2015-04-01

    Micro-chips based on organic-inorganic hybrid nanoparticles (NPs) composed of nanoalloys of gold (Au) and silver (Ag) embedded in an amorphous carbonaceous matrix (C-Au-Ag NPs) were prepared directly on a substrate by the laser-induced deposition (for short: LID) method. The C-Au-Ag NPs show a unique plasmon resonance which enhances Raman scattering of analytes, making the μ-chips suitable to detect ultra-low-volumes (10(-12) liter) and concentrations (10(-9) M) of bio-agents and a hazardous compound. These micro-chips constitute a novel, flexible solid-state device that can be used for applications in point-of-care diagnostics, consumer electronics, homeland security and environmental monitoring. PMID:25673275

  8. Direct laser writing of μ-chips based on hybrid C-Au-Ag nanoparticles for express analysis of hazardous and biological substances.

    PubMed

    Bashouti, M Y; Manshina, A; Povolotckaia, A; Povolotskiy, A; Kireev, A; Petrov, Y; Mačković, M; Spiecker, E; Koshevoy, I; Tunik, S; Christiansen, S

    2015-04-01

    Micro-chips based on organic-inorganic hybrid nanoparticles (NPs) composed of nanoalloys of gold (Au) and silver (Ag) embedded in an amorphous carbonaceous matrix (C-Au-Ag NPs) were prepared directly on a substrate by the laser-induced deposition (for short: LID) method. The C-Au-Ag NPs show a unique plasmon resonance which enhances Raman scattering of analytes, making the μ-chips suitable to detect ultra-low-volumes (10(-12) liter) and concentrations (10(-9) M) of bio-agents and a hazardous compound. These micro-chips constitute a novel, flexible solid-state device that can be used for applications in point-of-care diagnostics, consumer electronics, homeland security and environmental monitoring.

  9. An efficient photocatalyst for degradation of various organic dyes: Ag@Ag2MoO4-AgBr composite.

    PubMed

    Bai, Yu-Yang; Lu, Yi; Liu, Jin-Ku

    2016-04-15

    The Ag2MoO4-AgBr composite was prepared by a facile in-situ anion-exchange method, then the Ag nanoparticles were coated on this composite through photodeposition route to form a novel Ag@Ag2MoO4-AgBr composite. The in-situ Br(-) replacement in a crystal lattice node position of Ag2MoO4 crystal allows for overcoming the resistance of electron transition effectively. Meanwhile silver nano-particles on the surface of Ag@Ag2MoO4-AgBr composite could act as electron traps to intensify the photogeneration electron-hole separation and the subsequent transfer of the trapped electron to the adsorbed O2 as an electron acceptor. As an efficient visible light catalyst, the Ag@Ag2MoO4-AgBr composite exhibited superior photocatalytic activity for the degradation of various organic dyes. The experimental results demonstrated superior photocatalytic rate of Ag@Ag2MoO4-AgBr composite compared to pure AgBr and Ag2MoO4 crystals (37.6% and 348.4% enhancement respectively). The Ag@Ag2MoO4-AgBr composite cloud degraded Rhodamin B, bromophenol blue, and amino black 10b completed in 7min. PMID:26775100

  10. An efficient photocatalyst for degradation of various organic dyes: Ag@Ag2MoO4-AgBr composite.

    PubMed

    Bai, Yu-Yang; Lu, Yi; Liu, Jin-Ku

    2016-04-15

    The Ag2MoO4-AgBr composite was prepared by a facile in-situ anion-exchange method, then the Ag nanoparticles were coated on this composite through photodeposition route to form a novel Ag@Ag2MoO4-AgBr composite. The in-situ Br(-) replacement in a crystal lattice node position of Ag2MoO4 crystal allows for overcoming the resistance of electron transition effectively. Meanwhile silver nano-particles on the surface of Ag@Ag2MoO4-AgBr composite could act as electron traps to intensify the photogeneration electron-hole separation and the subsequent transfer of the trapped electron to the adsorbed O2 as an electron acceptor. As an efficient visible light catalyst, the Ag@Ag2MoO4-AgBr composite exhibited superior photocatalytic activity for the degradation of various organic dyes. The experimental results demonstrated superior photocatalytic rate of Ag@Ag2MoO4-AgBr composite compared to pure AgBr and Ag2MoO4 crystals (37.6% and 348.4% enhancement respectively). The Ag@Ag2MoO4-AgBr composite cloud degraded Rhodamin B, bromophenol blue, and amino black 10b completed in 7min.

  11. Green synthesis and applications of Au-Ag bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Meena Kumari, M.; Jacob, John; Philip, Daizy

    2015-02-01

    This paper reports for the first time the synthesis of bimetallic nanoparticles at room temperature using the fruit juice of pomegranate. Simultaneous reduction of gold and silver ions in different molar ratios leads to the formation of alloy as well as core-shell nanostructures. The nanoparticles have been characterized using UV-vis spectroscopy, transmission electron microscopy, Fourier Transform Infrared Spectroscopy and X-ray diffraction. The synthesized alloy particles are used as catalysts in the reduction of 2-, 3-, 4-nitrophenols to the corresponding amines and in the degradation of methyl orange. The reduction kinetics for all the reactions follows pseudo-first order. The rate constants follow the order k4-nitrophenol < k2-nitrophenol < k3-nitrophenol. Thermal conductivity is measured as a function of volume fraction and it is observed that the incorporation of the alloy nanoparticles enhances the thermal conductivity of the base fluid (water) showing nanofluid application. The nitric oxide and hydroxyl radical scavenging activity shown by the nanoparticles promise the potential application in biomedical field.

  12. Green synthesis and applications of Au-Ag bimetallic nanoparticles.

    PubMed

    Meena Kumari, M; Jacob, John; Philip, Daizy

    2015-02-25

    This paper reports for the first time the synthesis of bimetallic nanoparticles at room temperature using the fruit juice of pomegranate. Simultaneous reduction of gold and silver ions in different molar ratios leads to the formation of alloy as well as core-shell nanostructures. The nanoparticles have been characterized using UV-vis spectroscopy, transmission electron microscopy, Fourier Transform Infrared Spectroscopy and X-ray diffraction. The synthesized alloy particles are used as catalysts in the reduction of 2-, 3-, 4-nitrophenols to the corresponding amines and in the degradation of methyl orange. The reduction kinetics for all the reactions follows pseudo-first order. The rate constants follow the order k4-nitrophenolnanoparticles enhances the thermal conductivity of the base fluid (water) showing nanofluid application. The nitric oxide and hydroxyl radical scavenging activity shown by the nanoparticles promise the potential application in biomedical field. PMID:25218228

  13. Effective medium analysis of thermally evaporated Ag nanoparticle films for plasmonic enhancement in organic solar cell

    NASA Astrophysics Data System (ADS)

    Haidari, Gholamhosain; Hajimahmoodzadeh, Morteza; Fallah, Hamid Reza; Varnamkhasti, Mohsen Ghasemi

    2015-09-01

    Films of silver nanoparticles have optical properties that are useful for applications such as plasmonic light trapping in solar cells. We report on the simple fabrication of Ag nanoparticle films via thermal evaporation, with and without subsequent annealing. These films result in a random array of particles of various shapes and sizes. The modeling of such a vast collection of particles is still beyond reach of the modern computers. We show that it is possible to represent the silver island films by the Bergman effective mediums with the same optical properties. The effective medium method provides us with deep insight about the shape, the size and the distribution of nanoparticles. The far field simulations of solar cells, in which the silver island film is replaced with an effective medium layer, show a reduction in the absorption of active layer. Besides, the near field simulations based on finite-difference time-domain technique demonstrate that the near field effects on active layer absorption are negligible and this method highlights the importance of nanoparticles shapes. The PCPDTBT:PCBM solar cells with embedded silver island films are fabricated, and it is found that their performances show the similar trend. This insight can be used for the optical analysis of thermally evaporated Ag nanoparticle films for the improvement of organic solar cells.

  14. A composition and size controllable approach for Au-Ag alloy nanoparticles

    PubMed Central

    2012-01-01

    A capillary micro-reaction was established for the synthesis of Au-Ag alloy nanoparticles (NPs) with a flexible and controllable composition and grain size by tuning the synthesis temperature, the residence time, or the mole ratio of Au3+:Ag+. By extending the residence time from 5 to 900 s, enhancing the temperature from 120°C to 160°C, or decreasing the mole ratio of Au3+:Ag+ from 1:1 to 1:20, the composition of samples was changed continuously from Au-rich to Ag-rich. The particles became large with the increase of the residence time; however, synthesis temperatures showed less effect on the particle size change. The particle size of the Au-Ag alloy NPs with various composition could be kept by adjusting the mole ratio of Au3+:Ag+. TEM observation displayed that the as-obtained NPs were sphere-like with the smallest average size of 4.0 nm, which is half of those obtained by the traditional flask method. PMID:22513005

  15. Enhanced hydrogenation and reduced lattice distortion in size selected Pd-Ag and Pd-Cu alloy nanoparticles

    SciTech Connect

    Sengar, Saurabh K.; Mehta, B. R.; Kulriya, P. K.; Khan, S. A.

    2013-10-21

    Important correlation between valence band spectra and hydrogenation properties in Pd alloy nanoparticles is established by studying the properties of size selected and monocrystalline Pd, Ag, Cu, Pd-Ag, and Pd-Cu nanoparticles. The X-ray photoelectron spectroscopy and elastic recoil detection analysis show that size induced Pd4d centroid shift is related to enhanced hydrogenation with H/Pd ratio of 0.57 and 0.49 in Pd-Ag and Pd-Cu nanoparticles in comparison to reported bulk values of 0.2 and 0.1, respectively. Pd-alloy nanoparticles show lower hydrogen induced lattice distortion. The reduced distortion and higher hydrogen reactivity of Pd-alloy nanoparticles is important for numerous hydrogen related applications.

  16. Preparation and evaluation of thiomer nanoparticles via high pressure homogenization.

    PubMed

    Hoyer, Herbert; Schlocker, Wolfgang; Greindl, Melanie; Ostermann, Thomas; Bernkop-Schnürch, Andreas

    2010-01-01

    The aim of this study was to establish and evaluate a high pressure homogenization method for the preparation of thiomer nanoparticles. Particles were formulated by incorporation of the model protein horseradish peroxidase in chitosan-glutathione (Ch-GSH) and poly(acrylic acid)-glutathione (PAA-GSH) via co-precipitation followed by air jet milling. The resulting microparticles were suspended in distilled water using an Ultraturax and subsequently micronized by high pressure homogenization. Finally, resulting particles were evaluated regarding size distribution, shape, zeta potential, drug load, protein activity and release behaviour. The mean particle size after 30 cycles with a pressure of 1500 bar was 538 +/- 94 nm for particles consisting of Ch-GSH and 638 +/- 94 nm for particles consisting of PAA-GSH. Nanoparticles of Ch-GSH had a positive zeta-potential of +1.03 mv, whereas nanoparticles from PAA-GSH had a negative zeta potential of -6.21 mv. The maximum protein load for nanoparticles based on Ch-GSH and based on PAA-GSH was 45 +/- 2% and 37 +/- %, respectively. The release profile of nanoparticles followed a first order release kinetic. Thiolated nanoparticles prepared by a high pressure homogenization technique were shown to be stable and provide controlled drug release characteristics. The preparation method described here might be a useful tool for a more upscaled production of nanoparticulate drug delivery systems. PMID:20367028

  17. Nano-Ag complexes prepared by γ-radiolysis and their structures and physical properties

    NASA Astrophysics Data System (ADS)

    Kim, Hwa-Jung; Choi, Seong-Ho; Park, Hae-Jun

    2012-10-01

    In this study, nano-silver (nano-Ag) complexes showing different properties have been synthesized as follows. Polypyrrolidone (PVP)-stabilized silver colloids (NAg), nano-Ag bound to silica (SiO2) (NSS), and nano-Ag bound to a complex of SiO2 and polyaniline (PANI) (NSSPAI) were prepared via γ-irradiation at room temperature. NAg and NSS used PVP as a colloidal stabilizer, while NSSPAI did not use PVP as a colloidal stabilizer. Interesting bonding properties occurred in the nano-Ag complex and anticipated structural changes were clearly shown through a surface analysis of x-ray photoelectron spectroscopy (XPS). The morphologies by field emission-scanning electron microscopy (FE-SEM) analysis showed that nano-Ag complexes have various particle sizes ranging from 10 to 30 nm. NSS (average, 10 nm) and NSSPAI (average, 30 nm) showed a uniformly spherical shape and size, while NAg did not. From the reflection peaks in the x-ray diffraction (XRD) patterns, surface crystallinity of the nano-Ag complexes was indicated to be in the same degree as that of NSSPAI>NSS>NAg. Also, in the contact angle (CA) determination, surface hydrophobicity of NSSPAI was stronger than those of NSS and NAg, relatively. The different nano-Ag complexes prepared by γ-irradiation can be applicable in various industry fields due to the increase in specific property.

  18. Porous silicon nanowire arrays decorated by Ag nanoparticles for surface enhanced Raman scattering study

    NASA Astrophysics Data System (ADS)

    Su, L.; Xu, H. J.; Chan, Y. F.; Sun, X. M.

    2012-02-01

    A large scale and highly ordered Ag nanoparticle-decorated porous silicon nanowire array was fabricated for a uniform and reproducible surface-enhanced Raman scattering (SERS) substrate. The overall process for the proposed structure is simple and reliable with the use of only chemical etching and metal reduction processes. The SERS sensitivity of the novel substrate as low as 10-16 M for rhodamine 6G (R6G) and the Raman enhancement factor as high as 10^14 were obtained. The excellent SERS performances were mainly attributed to the strong local electromagnetic effect which is associated with the formation of large-quantity Ag nanoparticles on porous silicon nanowire array and the existence of semiconductor silicon nanowires. Significantly, the quadratic relation between the logarithmic concentrations and the logarithmic integrated Raman peak intensities provided quantitative detection of R6G. Our results open new possibilities for applying SERS to trace detection of low-concentration biomolecules.

  19. Improved nonlinear optical and optical limiting properties in non-covalent functionalized reduced graphene oxide/silver nanoparticle (NF-RGO/Ag-NPs) hybrid

    NASA Astrophysics Data System (ADS)

    Sakho, El hadji Mamour; Oluwafemi, Oluwatobi S.; Sreekanth, P.; Philip, Reji; Thomas, Sabu; Kalarikkal, Nandakumar

    2016-08-01

    Nonlinear optical (NLO) response under near infrared (800 nm) and visible (532 nm) laser excitations, of 100 fs (fs) and 5 ns (ns) pulse durations respectively, of reduced graphene oxide (RGO), non-covalent functionalized reduced graphene oxide (NF-RGO) and NF-RGO decorated with various concentration of silver nanoparticles (NF-RGO/Ag-NPs) have been investigated using the Open-aperture Z-Scan technique. For both femtosecond and nanosecond laser excitations, the studied graphene-based materials exhibit good nonlinear optical power limiting properties (OL), with NF-RGO/Ag-NPs sample prepared with 0.1 M AgNO3 showing the best nonlinear optical properties. For the ns regime, the optical limiting threshold decreased from 8.3 J/cm2 in NF-RGO to 4.3 J/cm2 in NF-RGO/Ag-NPs, while at fs regime, the nonlinear absorption coefficient (β) was found to increase with decrease in concentration of Ag-NPs in the hybrid. Two-photon absorption (2 PA) in combination with saturable absorption (SA) in femtosecond regime, and reverse saturable absorption (RSA) along with saturable absorption (SA) in the nanosecond regime, are responsible for the observed nonlinear optical absorption (NLA) behavior in these materials. These findings show that the as-synthesized NF-RGO/Ag-NPs hybrid is a relatively better material for nonlinear optical limiting applications.

  20. Synthesis of Ag(2) S-Ag nanoprisms and their use as DNA hybridization probes.

    PubMed

    Liu, Bing; Ma, Zhanfang

    2011-06-01

    A simple synthetic route to prepare Ag(2) S-Ag nanoprisms consists of the facile addition of Na(2) S to a solution of triangular Ag nanoprisms. The resulting Ag(2) S-Ag nanoparticles are more stable in solution than the original Ag nanoprisms, and two surface plasmon resonance (SPR) bands of the original Ag nanoprisms still remain. In addition, the SPR bands of the Ag(2) S-Ag nanoprisms are tunable over a wide range. The Ag(2) S-Ag nanoprisms can be directly bioconjugated via well-established stable Ag(2) S surface chemistry with readily available sulfur coupling agents. The nanoprisms are used in the hybridization of functionalized oligonucleotides, and show promise as probes for future biosensing applications. PMID:21538868

  1. Cell outer membrane mimetic chitosan nanoparticles: preparation, characterization and cytotoxicity.

    PubMed

    Zhao, Jing; Liang, Fei; Kong, Lingheng; Zheng, Lina; Fan, Tao

    2015-01-01

    A negatively charged copolymer poly (MPC-co-AMPS) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-acrylamide-2-methyl propane sulfonic acid (AMPS) was designed and synthesized. Chitosan nanoparticles with cell outer membrane mimetic structure were prepared by electrostatic interaction between the sulfonic acid groups of poly (MPC-co-AMPS) and the protonated amino groups of chitosan. Effects of factors on influencing the particle size, distribution, and stability were investigated. The experimental results showed that cell membrane mimetic chitosan nanoparticles with controllable and homogeneous size ranged from 100 to 300 nm were prepared at the concentration of 0.1-2.0 mg/mL and the charge ratio of 0.5-1.1. Chitosan nanoparticles prepared can exist stably for more than 45 days when placed at 4 °C and pH < 7.5. The cytotoxicity of the chitosan nanoparticles reduced significantly after surface modification with cell membrane mimetic structure, meeting the basic requirements of biomedical materials. The results suggest cell membrane mimetic chitosan nanoparticles prepared with polyanion and polycation obtain good biological compatibility and immune stealth ability, which has important academic significance and great application prospects.

  2. Synthesis and thermal behavior of tin-based alloy (Sn-Ag-Cu) nanoparticles.

    PubMed

    Roshanghias, Ali; Yakymovych, Andriy; Bernardi, Johannes; Ipser, Herbert

    2015-03-19

    The prominent melting point depression of nanoparticles has been the subject of a considerable amount of research. For their promising applications in electronics, tin-based nano-alloys such as near-eutectic Sn-Ag-Cu (SAC) alloys have been synthesized via various techniques. However, due to issues such as particle aggregation and oxidation or introduced impurities, the application of these nano-size particles has been confined or aborted. For instance, thermal investigations by DTA/DSC in a large number of studies revealed exothermic peaks in the range of 240-500 °C, i.e. above the melting point of SAC nanoparticles, with different and quite controversial explanations for this unclear phenomenon. This represents a considerable drawback for the application of nanoparticles. Correspondingly, in the current study, the thermal stability of SAC nanoparticles has been investigated via electron microscopy, XRD, FTIR, and DSC/TG analysis. It was found that the nanoparticles consist mainly of a metallic β-Sn core and an amorphous tin hydroxide shell structure. The SnO crystalline phase formation from this amorphous shell has been associated with the exothermic peaks on the first heating cycle of the nanoparticles, followed by a disproportionation reaction into metallic Sn and SnO₂.The results also revealed that the surfactant and reducing agent cannot only affect the size and size distribution of the nanoparticles, they might also alter the ratio between the amorphous shell and the crystalline core in the structure of particles. PMID:25757694

  3. Influence of Ag thickness on structural, optical, and electrical properties of ZnS/Ag/ZnS multilayers prepared by ion beam assisted deposition

    SciTech Connect

    Leng Jian; Yu Zhinong; Xue Wei; Zhang Ting; Jiang Yurong; Zhang Jie; Zhang Dongpu

    2010-10-15

    The structural, optical, and electrical characteristics of zinc sulfide (ZnS)/Ag/ZnS (ZAZ) multilayer films prepared by ion beam assisted deposition on k9 glass have been investigated as a function of Ag layer thickness. The characteristics of ZAZ multilayer are significantly improved up insertion of optimal Ag thickness between ZnS layers. The results show that due to bombardment of Ar ion beam, distinct Ag islands evolve into continuous Ag films at a thin Ag thickness of about 4 nm. The thinner Ag film as a thickness of 2 nm leads to high sheet resistance and low transmittance for the interface scattering induced by the Ag islands or noncontinuous films; and when the Ag thickness is over 4 nm, the ZAZ multilayer exhibits a remarkably reduced sheet resistance between 7-80 {Omega}/sq for the increase in carrier concentration and mobility of Ag layer, and a high transmittance over 90% for the interference phenomena of multilayers and low absorption and surface scattering of Ag layer. The ZAZ multilayer with 14 nm Ag film has a figure of merit up to 6.32x10{sup -2} {Omega}{sup -1}, an average transmittance over 92% and a sheet resistance of 7.1 {Omega}/sq. The results suggest that ZAZ film has better optoelectrical properties than conditional indium tin oxide single layer.

  4. Preparation, characterization and photocatalytic activity of visible-light-driven plasmonic Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposites

    SciTech Connect

    Li, Xiaojuan Tang, Duanlian; Tang, Fan; Zhu, Yunyan; He, Changfa; Liu, Minghua Lin, Chunxiang; Liu, Yifan

    2014-08-15

    Highlights: • A plasmonic Ag/AgBr/ZnFe{sub 2}O{sub 4} photocatalyst has been successfully synthesized. • Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposites exhibit high visible light photocatalytic activity. • Ag/AgBr/ZnFe{sub 2}O{sub 4} photocatalyst is stable and magnetically separable. - Abstract: A visible-light-driven plasmonic Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposite has been successfully synthesized via a deposition–precipitation and photoreduction through a novel one-pot process. X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy were employed to investigate the crystal structure, chemical composition, morphology, and optical properties of the as-prepared nanocomposites. The photocatalytic activities of the nanocomposites were evaluated by photodegradation of Rhodamine B (RhB) and phenol under visible light. The results demonstrated that the obtained Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposites exhibited higher photocatalytic activity as compared to pure ZnFe{sub 2}O{sub 4}. In addition, the sample photoreduced for 20 min and calcined at 500 °C achieved the highest photocatalytic activity. Furthermore, the Ag/AgBr/ZnFe{sub 2}O{sub 4} nanocomposite has high stability under visible light irradiation and could be conveniently separated by using an external magnetic field.

  5. Tuning the properties of ZnO, hematite, and Ag nanoparticles by adjusting the surface charge.

    PubMed

    Zhang, Jianhui; Dong, Guanjun; Thurber, Aaron; Hou, Yayi; Gu, Min; Tenne, Dmitri A; Hanna, C B; Punnoose, Alex

    2012-03-01

    A poly (acryl acid) (PAA) post-treatment method is performed to modify the surface charge of ZnO nanospheres, hematite nanocubes, and Ag nanoprisms from highly positive to very negative by adjusting the PAA concentration, to and greatly modify their photoluminescence, cytotoxicity, magnetism, and surface plasmon resonance. This method provides a general way to tune the nanoparticle properties for broad physicochemical and biological applications. PMID:22298490

  6. Visible-light photoactive Ag-AgBr/α-Ag3VO4 nanostructures prepared in a water-soluble ionic liquid for degradation of wastewater

    NASA Astrophysics Data System (ADS)

    Padervand, Mohsen

    2016-03-01

    Ag-AgBr/α-Ag3VO4 photocatalysts, prepared by an ionic liquid-assisted precipitation method, were used as an efficient visible light-driven photocatalytic system for removal of wastewater and pathogenic bacteria from the aqueous medium. X-ray diffraction powder, diffuse reflectance spectroscopy, Fourier transform infrared, scanning electron microscopy, and nitrogen adsorption-desorption isotherm (BET) analysis methods were used to characterize the nanostructures. Photodegradation mechanism was investigated and the results showed that the prepared samples were too efficient for the degradation of Acid Blue 92 (AB92) azo dye, and E. coli cells under visible light. The photogenerated electron-hole pairs reacted with the species in the solution and produced super active radicals such as {{O}}{{{H}}^ \\cdot } , {{H}}{{{O}}^ \\cdot }_{{2}} , and {{{O}}^{ \\cdot - }}_{{2}} which are responsible for the degradation of the environmental pollutions. TEM images were used to clarify the antibacterial activity of the products. Finally, as a practical application of the prepared photocatalysts, their ability evaluated for degradation of a real wastewater sample which was provided from the textile industries.

  7. Enhanced formation of silver nanoparticles in Ag+-NOM-iron(II, III) systems and antibacterial activity studies.

    PubMed

    Adegboyega, Nathaniel F; Sharma, Virender K; Siskova, Karolina M; Vecerova, Renata; Kolar, Milan; Zbořil, Radek; Gardea-Torresdey, Jorge L

    2014-03-18

    This work reports the role of iron redox pair (Fe(3+)/Fe(2+)) in the formation of naturally occurring silver nanoparticles (AgNPs) in the aquatic environment. The results showed that Fe(3+) or Fe(2+) ions in the mixtures of Ag(+) and natural organic matter enhanced the formation of AgNPs. The formation of AgNPs depended on pH and types of organic matter. Increase in pH enhanced the formation of AgNPs, and humic acids as ligands showed higher formation of AgNPs compared to fulvic acids. The observed results were described by considering the potentials of redox pairs of silver and iron species and the possible species involved in reducing silver ions to AgNPs. Dynamic light scattering and transmission electron microscopy measurements of AgNPs revealed mostly bimodal size distribution with decrease in size of AgNPs due to iron species in the reaction mixture. Minimum inhibitory concentration of AgNPs needed to inhibit the growth of various bacterial species suggested the role of surfaces of tested Gram-positive and Gram-negative bacteria. Stability study of AgNPs, formed in Ag(+)-humic acid/fulvic acids-Fe(3+) mixtures over a period of several months showed high stability of the particles with significant increase in surface plasmon resonance peak. The environmental implications of the results in terms of fate, transport, and ecotoxicity of organic-coated AgNPs are briefly presented. PMID:24524189

  8. Preparation and Properties of Various Magnetic Nanoparticles

    PubMed Central

    Drbohlavova, Jana; Hrdy, Radim; Adam, Vojtech; Kizek, Rene; Schneeweiss, Oldrich; Hubalek, Jaromir

    2009-01-01

    The fabrications of iron oxides nanoparticles using co-precipitation and gadolinium nanoparticles using water in oil microemulsion method are reported in this paper. Results of detailed phase analysis by XRD and Mössbauer spectroscopy are discussed. XRD analysis revealed that the crystallite size (mean coherence length) of iron oxides (mainly γ-Fe2O3) in the Fe2O3 sample was 30 nm, while in Fe2O3/SiO2 where the ε-Fe2O3 phase dominated it was only 14 nm. Gd/SiO2 nanoparticles were found to be completely amorphous, according to XRD. The samples showed various shapes of hysteresis loops and different coercivities. Differences in the saturation magnetization (MS) correspond to the chemical and phase composition of the sample materials. However, we observed that MS was not reached in the case of Fe2O3/SiO2, while for Gd/SiO2 sample the MS value was extremely low. Therefore we conclude that only unmodified Fe2O3 nanoparticles are suitable for intended biosensing application in vitro (e.g. detection of viral nucleic acids) and the phase purification of this sample for this purpose is not necessary. PMID:22574017

  9. Raman scattering of linear chains of strongly coupled Ag nanoparticles on SWCNTs

    PubMed Central

    Valmalette, Jean-Christophe; Tan, Zhenquan; Abe, Hiroya; Ohara, Satoshi

    2014-01-01

    We compare the Raman scattering properties of hybrid nanostructures consisting of Ag nanoparticles (NPs) in disordered and aligned arrangements on single-walled carbon nanotubes (SWCNTs) as a result of chemical and photoreduction methods. In the latter case, the unique structure of the very small Ag NP (from 4 to 7 nm) chains generated an extremely large mode at 969 cm−1 that was assigned to the sulphate-silver interaction at the NP surface. Another strong mode was present at 1201 cm−1 and was assigned to an IR-active mode of sodium dodecyl sulphate (SDS); this mode was observed because the symmetry changes altered the selection rules. We demonstrate that both the UV photoreduction of silver and the presence of SWCNTs are necessary to produce this very strong Raman scattering. The Raman modes of the SWCNTs are also significantly modified by the presence of Ag NP chains along the nanotubes. PMID:24912409

  10. Green synthesis of silver nanoparticles in aloe vera plant extract prepared by a hydrothermal method and their synergistic antibacterial activity

    PubMed Central

    Phromviyo, Nutthakritta; Boueroy, Parichart; Chompoosor, Apiwat

    2016-01-01

    Background There is worldwide interest in silver nanoparticles (AgNPs) synthesized by various chemical reactions for use in applications exploiting their antibacterial activity, even though these processes exhibit a broad range of toxicity in vertebrates and invertebrates alike. To avoid the chemical toxicity, biosynthesis (green synthesis) of metal nanoparticles is proposed as a cost-effective and environmental friendly alternative. Aloe vera leaf extract is a medicinal agent with multiple properties including an antibacterial effect. Moreover the constituents of aloe vera leaves include lignin, hemicellulose, and pectins which can be used in the reduction of silver ions to produce as AgNPs@aloe vera (AgNPs@AV) with antibacterial activity. Methods AgNPs were prepared by an eco-friendly hydrothermal method using an aloe vera plant extract solution as both a reducing and stabilizing agent. AgNPs@AV were characterized using XRD and SEM. Additionally, an agar well diffusion method was used to screen for antimicrobial activity. MIC and MBC were used to correlate the concentration of AgNPs@AV its bactericidal effect. SEM was used to investigate bacterial inactivation. Then the toxicity with human cells was investigated using an MTT assay. Results The synthesized AgNPs were crystalline with sizes of 70.70 ± 22-192.02 ± 53 nm as revealed using XRD and SEM. The sizes of AgNPs can be varied through alteration of times and temperatures used in their synthesis. These AgNPs were investigated for potential use as an antibacterial agent to inhibit pathogenic bacteria. Their antibacterial activity was tested on S. epidermidis and P. aeruginosa. The results showed that AgNPs had a high antibacterial which depended on their synthesis conditions, particularly when processed at 100 oC for 6 h and 200 oC for 12 h. The cytotoxicity of AgNPs was determined using human PBMCs revealing no obvious cytotoxicity. These results indicated that AgNPs@AV can be effectively utilized in

  11. Anisotropic effective medium properties from interacting Ag nanoparticles in silicon dioxide.

    PubMed

    Menegotto, Thiago; Horowitz, Flavio

    2014-05-01

    Films containing a layer of Ag nanoparticles embedded in silicon dioxide were produced by RF magnetron sputtering. Optical transmittance measurements at several angles of incidence (from normal to 75°) revealed two surface plasmon resonance (SPR) peaks, which depend on electric field direction: one in the ultraviolet and another red-shifted from the dilute Ag/SiO₂ system resonance at 410 nm. In order to investigate the origin of this anisotropic behavior, the structural properties were determined by transmission electron microscopy, revealing the bidimensional plane distribution of Ag nanoparticles with nearly spherical shape as well as the filling factor of metal in the composite. A simple model linked to these experimental parameters allowed description of the most relevant features of the SPR positions, which, depending on the field direction, were distinctly affected by the coupling of oscillations between close nanoparticles, as described by a modified Drude-Lorentz dielectric function introduced into the Maxwell-Garnett relation. This approach allowed prediction of the resonance for light at 75° incidence from the SPR position for light at normal incidence, in good agreement with experimental observation. PMID:24921871

  12. Hotspots engineering by grafting Au@Ag core-shell nanoparticles on the Au film over slightly etched nanoparticles substrate for on-site paraquat sensing.

    PubMed

    Wang, Chaoguang; Wu, Xuezhong; Dong, Peitao; Chen, Jian; Xiao, Rui

    2016-12-15

    Paraquat (PQ) pollutions are ultra-toxic to human beings and hard to be decomposed in the environment, thus requiring an on-site detection strategy. Herein, we developed a robust and rapid PQ sensing strategy based on the surface-enhanced Raman scattering (SERS) technique. A hybrid SERS substrate was prepared by grafting the Au@Ag core-shell nanoparticles (NPs) on the Au film over slightly etched nanoparticles (Au FOSEN). Hotspots were engineered at the junctions as indicated by the finite difference time domain calculation. SERS performance of the hybrid substrate was explored using p-ATP as the Raman probe. The hybrid substrate gives higher enhancement factor comparing to either the Au FOSEN substrate or the Au@Ag core-shell NPs, and exhibits excellent reproducibility, homogeneity and stability. The proposed SERS substrates were prepared in batches for the practical PQ sensing. The total analysis time for a single sample, including the pre-treatment and measurement, was less than 5min with a PQ detection limit of 10nM. Peak intensities of the SERS signal were plotted as a function of the PQ concentrations to calibrate the sensitivity by fitting the Hill's equation. The plotted calibration curve showed a good log-log linearity with the coefficient of determination of 0.98. The selectivity of the sensing proposal was based on the "finger print" Raman spectra of the analyte. The proposed substrate exhibited good recovery when it applied to real water samples, including lab tap water, bottled water, and commercially obtained apple juice and grape juice. This SERS-based PQ detection method is simple, rapid, sensitive and selective, which shows great potential in pesticide residue and additives abuse monitoring. PMID:27498319

  13. Investigating the versatility of multifunctional silver nanoparticles: preparation and inspection of their potential as wound treatment agents

    NASA Astrophysics Data System (ADS)

    Nam, Geewoo; Purushothaman, Baskaran; Rangasamy, Sabarinathan; Song, Joon Myong

    2016-11-01

    Silver nanoparticles (AgNPs) are capable of inhibiting the growth of a broad spectrum of bacterial species. The minute size of the nanoparticulates enhances their biocidal activity and is thus widely utilized as antibacterial agents. The most recently researched and recognized antibacterial and wound-healing properties of published AgNPs were investigated in this article. The following parameters of the AgNPs affecting their properties and potency were explored: particle size, shape, and type of ligand or stabilizing agent. Research regarding the antibacterial activity enhancement of high-valent silver nanoparticles compared to those of the lower valent forms were summarized and analyzed. Nanocrystalline silver is capable of binding to components that may enhance their preparation and antibacterial properties. By forming complexes with ligands that exhibit desired properties, silver nanoparticles can be synthesized to exhibit those desired properties without compromising their performance. This review will provide a detailed discussion regarding the parameter-dependent bactericidal properties of silver nanoparticles and nanocomposite silver complexes as potent multifunctional wound-healing agents.

  14. A vaccine prepared from the 22 nm particles of surface hepatitis B antigen (HBsAg)

    SciTech Connect

    Karelin, V.P.; Babaeva, E.E.; Gubenko, E.F.; Kaulen, D.K.; Zhdanov, V.M.

    1980-01-01

    A method for obtaining a subunit inactivated vaccine preparation from the 22-nm particles of HBsAg is proposed. For inactivation of the residual infectious hepatitis B virus (HBV) the preparations were successively treated with 1% sodium dodecyl sulfate (SDS) and nucleases. In addition, thermal denaturation and ultraviolet irradiation of HBV DNA were used. As a control the biologic activity of a reference virus (SV40) was tested after the same treatment. The effectiveness of DNA inactivation was monitored by adding 3H-thymidine labeled reference virus to the vaccine preparations. The purified and inactivated HBsAg was adsorbed on Al2O3. Antigenicity was calculated on the basis of the determination of antibody in guinea pigs immunized with various doses of the vaccine, and the release of /sup 125/I- HBsAg from blood and kidneys in immunized and control mice was analyzed. Possible methods of inactivation and control of HBV vaccine is discussed.

  15. Morphology and Shear Strength of Lead-Free Solder Joints with Sn3.0Ag0.5Cu Solder Paste Reinforced with Ceramic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Yakymovych, A.; Plevachuk, Yu.; Švec, P.; Švec, P.; Janičkovič, D.; Šebo, P.; Beronská, N.; Roshanghias, A.; Ipser, H.

    2016-08-01

    To date, additions of different oxide nanoparticles is one of the most widespread procedures to improve the mechanical properties of metals and metal alloys. This research deals with the effect of minor ceramic nanoparticle additions (SiO2, TiO2 and ZrO2) on the microstructure and mechanical properties of Cu/solder/Cu joints. The reinforced Sn3.0Ag0.5Cu (SAC305) solder alloy with 0.5 wt.% and 1.0 wt.% of ceramic nanoparticles was prepared through mechanically stirring. The microstructure of as-solidified Cu/solder/Cu joints was studied using scanning electron microscopy. The additions of ceramic nanoparticles suppressed the growth of the intermetallic compound layer Cu6Sn5 at the interface solder/Cu and improved the microstructure of the joints. Furthermore, measurements of mechanical properties showed improved shear strength of Cu/composite solder/Cu joints compared to joints with unreinforced solder. This fact related to all investigated ceramic nanoinclusions and should be attributed to the adsorption of nanoparticles on the grain surface during solidification. However, this effect is less pronounced on increasing the nanoinclusion content from 0.5 wt.% to 1.0 wt.% due to agglomeration of nanoparticles. Moreover, a comparison analysis showed that the most beneficial influence was obtained by minor additions of SiO2 nanoparticles into the SAC305 solder alloy.

  16. Preparation of Ag deposited TiO2 (Ag/TiO2) composites and investigation on visible-light photocatalytic degradation activity in magnetic field

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Ma, C. H.; Wang, J.; Li, S. G.; Li, Y.

    2014-12-01

    In this study, Ag deposited TiO2 (Ag/TiO2) composites were prepared by three different methods (Ultraviolet Irradiation Deposition (UID), Vitamin C Reduction (VCR) and Sodium Borohydride Reduction (SBR)) for the visible-light photocatalytic degradation of organic dyes in magnetic field. And then the prepared Ag deposited TiO2 (Ag/TiO2) composites were characterized physically by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The visible-light photocatalytic activities of these three kinds of Ag deposited TiO2 (Ag/TiO2) composites were examined and compared through the degradation of several organic dyes under visible-light irradiation in magnetic field. In addition, some influence factors such as visible-light irradiation time, organic dye concentration, revolution speed, magnetic field intensity and organic dye kind on the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composite were reviewed. The research results showed that the presence of magnetic field significantly enhanced the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composites and then contributed to the degradation of organic dyes.

  17. Toxicological Effects of Caco-2 Cells Following Short-Term and Long-Term Exposure to Ag Nanoparticles

    PubMed Central

    Chen, Ni; Song, Zheng-Mei; Tang, Huan; Xi, Wen-Song; Cao, Aoneng; Liu, Yuanfang; Wang, Haifang

    2016-01-01

    Extensive utilization increases the exposure of humans to Ag nanoparticles (NPs) via the oral pathway. To comprehensively address the action of Ag NPs to the gastrointestinal systems in real situations, i.e., the long-term low-dose exposure, we evaluated and compared the toxicity of three Ag NPs (20–30 nm with different surface coatings) to the human intestine cell Caco-2 after 1-day and 21-day exposures, using various biological assays. In both the short- and long-term exposures, the variety of surface coating predominated the toxicity of Ag NPs in a descending order of citrate-coated Ag NP (Ag-CIT), bare Ag NP (Ag-B), and poly (N-vinyl-2-pyrrolidone)-coated Ag NP (Ag-PVP). The short-term exposure induced cell growth inhibition and death. The cell viability loss appeared after cells were exposed to 0.7 μg/mL Ag-CIT, 0.9 μg/mL Ag-B or >1.0 μg/mL Ag-PVP for 24 h. The short-term and higher-dose exposure also induced reactive oxygen species (ROS) generation, mitochondrial damage, cell membrane leakage, apoptosis, and inflammation (IL-8 level). The long-term exposure only inhibited the cell proliferation. After 21-day exposure to 0.4 μg/mL Ag-CIT, the cell viability dropped to less than 50%, while cells exposed to 0.5 μg/mL Ag-PVP remained normal as the control. Generally, 0.3 μg/mL is the non-toxic dose for the long-term exposure of Caco-2 cells to Ag NPs in this study. However, cells presented inflammation after exposure to Ag NPs with the non-toxic dose in the long-term exposure. PMID:27338357

  18. Facile fabrication of Pt-Ag bimetallic nanoparticles decorated reduced graphene oxide for highly sensitive non-enzymatic hydrogen peroxide sensing.

    PubMed

    Zhang, Cong; Zhang, Yanyan; Du, Xin; Chen, Yuan; Dong, Wenhao; Han, Bingkai; Chen, Qiang

    2016-10-01

    A new electrocatalyst, Pt-Ag bimetallic nanoparticles decorated reduced graphene oxide nanocomposite, was successfully synthesized by a facile, eco-friendly and controllable route. The morphological characterization of RGO/Pt-Ag NPs nanocomposite was examined by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) analyzer, X-ray diffraction (XRD) spectrum, and Fourier transform infrared spectrum (FT-IR), respectively. And then, the RGO/Pt-Ag NPs nanocomposite was immobilized on the surface of glassy carbon (GC) electrode to fabricate a novel and highly sensitive non-enzymatic hydrogen peroxide sensor. The electrochemical behaviors of the prepared sensor were investigated by cyclic voltammetry and chronoamperometry. The sensor showed excellent performance toward H2O2 with sensitivity as high as 699.6 μA mM(-1)cm(-2) and 402.7 μA mM(-1)cm(-2), wide linear range of 0.005-1.5mM and 1.5-7mM, and low detection limit of 0.04μM (S/N=3). Moreover, the prepared hydrogen peroxide sensor was applied to in real samples with satisfactory results. These excellent results indicate that the prepared RGO/Pt-Ag NPs nanocomposite has broad application prospect in the field of sensors. PMID:27474309

  19. Ag-TiO2 nanoparticle codoped SiO2 films on ZrO2 barrier-coated glass substrates with antibacterial activity in ambient condition.

    PubMed

    Mukhopadhyay, Anindita; Basak, Sujit; Das, Jugal Kishore; Medda, Samar Kumar; Chattopadhyay, Krishnananda; De, Goutam

    2010-09-01

    Anatase TiO2 and Ag nanoparticles (NPs) codoped SiO2 films were prepared by the sol-gel method. Proportionate amounts of 3-(glycidoxypropyl)trimethoxysilane (GLYMO), tetraethylorthosilicate (TEOS) and 3-(methacryloxypropyl)trimethoxysilane (MEMO) derived inorganic-organic silica sol, commercially available dispersed anatase TiO2 NPs, and AgNO3 were used to prepare the sols. The films were prepared on ZrO2 (cubic) precoated soda-lime glass substrates by a single-dipping technique and heat-treated at 450 °C in air and H2/Ar atmosphere to obtain hard, relatively porous, and transparent coatings of thickness>600 nm. The ZrO2 barrier layer was previously applied on soda-lime glass to restrict the diffusion of Ag into the substrate. The Ag-TiO2 NPs incorporated SiO2 films were intense yellow in color and found to be fairly stable at ambient condition for several days under fluorescent light. These films show a considerable growth inhibition on contact with the gram negative bacteria E. coli.

  20. Facile fabrication of Pt-Ag bimetallic nanoparticles decorated reduced graphene oxide for highly sensitive non-enzymatic hydrogen peroxide sensing.

    PubMed

    Zhang, Cong; Zhang, Yanyan; Du, Xin; Chen, Yuan; Dong, Wenhao; Han, Bingkai; Chen, Qiang

    2016-10-01

    A new electrocatalyst, Pt-Ag bimetallic nanoparticles decorated reduced graphene oxide nanocomposite, was successfully synthesized by a facile, eco-friendly and controllable route. The morphological characterization of RGO/Pt-Ag NPs nanocomposite was examined by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) analyzer, X-ray diffraction (XRD) spectrum, and Fourier transform infrared spectrum (FT-IR), respectively. And then, the RGO/Pt-Ag NPs nanocomposite was immobilized on the surface of glassy carbon (GC) electrode to fabricate a novel and highly sensitive non-enzymatic hydrogen peroxide sensor. The electrochemical behaviors of the prepared sensor were investigated by cyclic voltammetry and chronoamperometry. The sensor showed excellent performance toward H2O2 with sensitivity as high as 699.6 μA mM(-1)cm(-2) and 402.7 μA mM(-1)cm(-2), wide linear range of 0.005-1.5mM and 1.5-7mM, and low detection limit of 0.04μM (S/N=3). Moreover, the prepared hydrogen peroxide sensor was applied to in real samples with satisfactory results. These excellent results indicate that the prepared RGO/Pt-Ag NPs nanocomposite has broad application prospect in the field of sensors.

  1. Drastic nickel ion removal from aqueous solution by curcumin-capped Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Bettini, S.; Pagano, R.; Valli, L.; Giancane, G.

    2014-08-01

    A completely green synthesis protocol has been adopted to obtain silver nanoaggregates capped by the natural compound (1E, 6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-diene), also known as curcumin. The synthesis has been monitored by infrared, Raman, visible and fluorescence spectroscopies. Characterization confirms that curcumin reduces and caps the nanoparticles, and such a procedure allows its solubility in water and drastically increases curcumin stability. Silver nanoparticles (AgNPs)/curcumin complex has been dispersed in a water solution containing a known nickel ion concentration. After three days, a grey precipitate is observed and nickel concentration in the solution is reduced by about 70%.A completely green synthesis protocol has been adopted to obtain silver nanoaggregates capped by the natural compound (1E, 6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-diene), also known as curcumin. The synthesis has been monitored by infrared, Raman, visible and fluorescence spectroscopies. Characterization confirms that curcumin reduces and caps the nanoparticles, and such a procedure allows its solubility in water and drastically increases curcumin stability. Silver nanoparticles (AgNPs)/curcumin complex has been dispersed in a water solution containing a known nickel ion concentration. After three days, a grey precipitate is observed and nickel concentration in the solution is reduced by about 70%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02583k

  2. Preparation of platinum nanoparticle catalyst for propane dehydrogenation.

    PubMed

    Li, Jun; Wang, Jun; Ma, Zhanhua; Sun, Lanyi; Hu, Yangdong

    2014-09-01

    Supported Pt nanoparticle catalysts were prepared by combing a chemical reduction method with an ultrasonic sonication loading method. Several techniques including transmission electron microscopy (TEM), nitrogen sorption technique and pyridine adsorption Fourier-transform infrared (Py-IR) were applied to characterize the physicochemical properties of these catalysts. The catalytic performance of catalysts was evaluated in the dehydrogenation of propane. The influence of the preparation method of Pt nanoparticles, the ratio of Polyvinyl Pyrrolidone (PVP) to Pt, loading method and different supports on the catalytic performance was investigated. PVP is useful for controlling the size of Pt nanoparticles and a PVP/Pt ratio of 15 is favorable to achieve a good catalytic performance. NaBH4 reduction is better than ethanol refluxing in preparing Pt nanoparticles. The ultrasonic sonication is effective to load the Pt nanoparticles onto the support channels. The mesoporous alumina proved to be a good catalyst support due to its high surface area and unique pore structure. PMID:25924358

  3. Preparation, characterization and optimization of glipizide controlled release nanoparticles

    PubMed Central

    Emami, J.; Boushehri, M.S. Shetab; Varshosaz, J.

    2014-01-01

    The purpose of the present study was to develop glipizide controlled release nanoparticles using alginate and chitosan thorough ionotropic controlled gelation method. Glipizide is a frequently prescribed second generation sulfonylurea which lowers the blood glucose in type-two diabetics. Quick absorption of the drug from the gastrointestinal tract along with short half- life of elimination makes it a good candidate for controlled release formulations. Alginate-chitosan nanoparticles (ACNP) are convenient controlled delivery systems for glipizide, due to both the release limiting properties of the system, and the bioadhesive nature of the polymers. In the present study, glipizide loaded alginate-chitosan nanoparticles (GlACNP) were prepared, and the particle characteristics including particle size (PS), zeta potential (ZP), entrapment efficiency (EE%), loading percent (LP), and mean release time (MRT), as well as the morphology of the nanoparticles, the drug-excipient compatibility, and the release kinetics along with the drug diffusion mechanism were evaluated. The results suggested that ionotropic controlled gelation method offers the possibility of preparing the nanoparticles in mild conditions in an aqueous environment, and can lead to the preparation of particles with favorable size, controlled release characteristics, and high entrapment efficiency, serving as a convenient delivery system for glipizide. The particle and release characteristics can be efficiently optimized using the Box-Behnken design. Based on the findings of the present study, it is expected that this novel formulation be a superior therapeutic alternative to the currently available glipizide delivery systems. PMID:25657802

  4. Factors Affecting the Morphology of Pb-Based Glass Frit Coated with Ag Material Prepared by Electroless Silver Plating

    NASA Astrophysics Data System (ADS)

    Huang, Bei; Gan, Weiping; Zhou, Jian; Li, Yingfen; Lin, Tao; Liu, Xiaogang

    2014-05-01

    Pb-based glass frit coated with nanosilver material for Si solar cell applications has been directly prepared by electroless silver plating. Activation of the glass frit was accomplished by using glycol, with the aim of reducing the silver ions to elemental silver on the surface of the glass frit. Electroless silver plating onto the glass frit was successfully realized using two kinds of electroless plating bath. However, the morphology of the composite powder greatly affected the modality, sheet resistance, series resistance, and photoelectric conversion efficiency of the conducting silver films. We found that the activation temperature affected the number and distribution of silver nanoparticles. Meanwhile, the average grain size of the silver particles and the silver content in the Pb-based glass frit coated with Ag material could be controlled by adjusting the pH value and loading capacity, respectively, during plating.

  5. Kinetic trapping through coalescence and the formation of patterned Ag-Cu nanoparticles

    NASA Astrophysics Data System (ADS)

    Grammatikopoulos, Panagiotis; Kioseoglou, Joseph; Galea, Antony; Vernieres, Jerome; Benelmekki, Maria; Diaz, Rosa E.; Sowwan, Mukhles

    2016-05-01

    In recent years, due to its inherent flexibility, magnetron-sputtering has been widely used to synthesise bi-metallic nanoparticles (NPs) via subsequent inert-gas cooling and gas-phase condensation of the sputtered atomic vapour. Utilising two separate sputter targets allows for good control over composition. Simultaneously, it involves fast kinetics and non-equilibrium processes, which can trap the nascent NPs into metastable configurations. In this study, we observed such configurations in immiscible, bi-metallic Ag-Cu NPs by scanning transmission electron microscopy (S/TEM) and electron energy-loss spectroscopy (EELS), and noticed a marked difference in the shape of NPs belonging to Ag- and Cu-rich samples. We explained the formation of Janus or Ag@Cu core/shell metastable structures on the grounds of in-flight mixed NP coalescence. We utilised molecular dynamics (MD) and Monte Carlo (MC) computer simulations to demonstrate that such configurations cannot occur as a result of nanoalloy segregation. Instead, sintering at relatively low temperatures can give rise to metastable structures, which eventually can be stabilised by subsequent quenching. Furthermore, we compared the heteroepitaxial diffusivities along various surfaces of both Ag and Cu NPs, and emphasised the differences between the sintering mechanisms of Ag- and Cu-rich NP compositions: small Cu NPs deform as coherent objects on large Ag NPs, whereas small Ag NPs dissolve into large Cu NPs, with their atoms diffusing along specific directions. Taking advantage of this observation, we propose controlled NP coalescence as a method to engineer mixed NPs of a unique, patterned core@partial-shell structure, which we refer to as a ``glass-float'' (ukidama) structure.In recent years, due to its inherent flexibility, magnetron-sputtering has been widely used to synthesise bi-metallic nanoparticles (NPs) via subsequent inert-gas cooling and gas-phase condensation of the sputtered atomic vapour. Utilising two

  6. Synthesis of silver nanoparticles by solar irradiation of cell-free Bacillus amyloliquefaciens extracts and AgNO3.

    PubMed

    Wei, Xuetuan; Luo, Mingfang; Li, Wei; Yang, Liangrong; Liang, Xiangfeng; Xu, Lin; Kong, Peng; Liu, Huizhou

    2012-01-01

    Silver nanoparticles (AgNPs) were obtained by solar irradiation of cell-free extracts of Bacillusamyloliquefaciens and AgNO3. Light intensity, extract concentration, and NaCl addition influenced the synthesis of AgNPs. Under optimized conditions (solar intensity 70,000 lx, extract concentration 3 mg/mL, and NaCl content 2 mM), 98.23±0.06% of the Ag+ (1 mM) was reduced to AgNPs within 80 min, and the ζ-potential of AgNPs reached -70.84±0.66 mV. TEM (Transmission electron microscopy) and XRD (X-ray diffraction) analysis confirmed that circular and triangular crystalline AgNPs with mean diameter of 14.6 nm were synthesized. Since heat-inactivated extracts also mediated the formation of AgNPs, enzymatic reactions are likely not involved in AgNPs formation. A high absolute ζ-potential value of the AgNPs, possibly caused by interaction with proteins likely explains the high stability of AgNPs suspensions. AgNPs showed antimicrobial activity against Bacillussubtilis and Escherichiacoli in liquid and solid medium.

  7. Effect of Synthesis Techniques on Crystallization and Optical Properties of Ag-Cu Bimetallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Xiong, Ziye; Qin, Fen; Huang, Po-Shun; Nettleship, Ian; Lee, Jung-Kun

    2016-04-01

    Silver (Ag)-copper (Cu) bimetallic nanoparticles (NPs) were synthesized by the reduction of silver nitrate and copper (II) acetate monohydrate using ethylene glycol in a microwave (MW) heating system with controlled reaction times ranging from 5 min to 30 min. The molar ratio Ag/Cu was varied from 1:1 to 1:3. The effect of reaction conditions on the bimetallic NPs structures and compositions were characterized by x-ray photoelectron spectroscopy, x-ray diffraction and transmission electron microscopy. The average particle size was approximately 150 nm. The surface plasmon resonance (SPR) of Ag-Cu bimetallic NPs was investigated by monitoring the SPR band peak behavior via UV/Vis spectrophotometry. The resonance peak positions and peak widths varied due to the different structures of the bimetallic NPs created under the synthesis conditions. In the MW heating method, the reduction of Cu was increased and Cu was inhomogeneously deposited over the Ag cores. As the composition of Cu becoming higher in the Ag-Cu bimetallic NPs, the absorption between 400 nm to 600 nm was greatly enhanced.

  8. Platinum adlayered ruthenium nanoparticles, method for preparing, and uses thereof

    DOEpatents

    Tong, YuYe; Du, Bingchen

    2015-08-11

    A superior, industrially scalable one-pot ethylene glycol-based wet chemistry method to prepare platinum-adlayered ruthenium nanoparticles has been developed that offers an exquisite control of the platinum packing density of the adlayers and effectively prevents sintering of the nanoparticles during the deposition process. The wet chemistry based method for the controlled deposition of submonolayer platinum is advantageous in terms of processing and maximizing the use of platinum and can, in principle, be scaled up straightforwardly to an industrial level. The reactivity of the Pt(31)-Ru sample was about 150% higher than that of the industrial benchmark PtRu (1:1) alloy sample but with 3.5 times less platinum loading. Using the Pt(31)-Ru nanoparticles would lower the electrode material cost compared to using the industrial benchmark alloy nanoparticles for direct methanol fuel cell applications.

  9. Comparison of Ag and SiO2 Nanoparticles for Light Trapping Applications in Silicon Thin Film Solar Cells.

    PubMed

    Theuring, Martin; Wang, Peng Hui; Vehse, Martin; Steenhoff, Volker; von Maydell, Karsten; Agert, Carsten; Brolo, Alexandre G

    2014-10-01

    Plasmonic and photonic light trapping structures can significantly improve the efficiency of solar cells. This work presents an experimental and computational comparison of identically shaped metallic (Ag) and nonmetallic (SiO2) nanoparticles integrated to the back contact of amorphous silicon solar cells. Our results show comparable performance for both samples, suggesting that minor influence arises from the nanoparticle material. Particularly, no additional beneficial effect of the plasmonic features due to metallic nanoparticles could be observed. PMID:26278435

  10. Partitioning of silver and chemical speciation of free Ag in soils amended with nanoparticles

    PubMed Central

    2013-01-01

    Background Knowledge about silver nanoparticles in soils is limited even if soils are a critical pathway for their environmental fate. In this paper, speciation results have been acquired using a silver ion selective electrode in three different soils. Results Soil organic matter and pH were the most important soil properties controlling the occurrence of silver ions in soils. In acidic soils, more free silver ions are available while in the presence of organic matter, ions were tightly bound in complexes. The evolution of the chemical speciation of the silver nanoparticles in soils was followed over six months. Conclusion During the first few hours, there appeared to be a strong sorption of the silver with soil ligands, whereas over time, silver ions were released, the final concentration being approximately 10 times higher than at the beginning. Ag release was associated with either the oxidation of the nanoparticles or a dissociation of adsorbed silver from the soil surfaces. PMID:23617903

  11. Development of Novel Cadmium-Free AgInS2 Semiconductor Nanoparticles.

    PubMed

    Yang, Wentao; Gong, Xiaoqun; Chang, Jin

    2016-03-01

    AgInS2 (AIS) semiconductor nanoparticles as the novel alternatives to cadmium- or lead-containing semiconductors have attracted much attention both on the theory and application research, based on their tunable fluorescence emission wavelengths, high photostability and low toxicity of chemical composition. The bandgap of AIS nanoparticles can be adjusted from 1.54 to 2.03 eV, which makes AIS nanocrystalline suitable for applications in solar energy conversion. Moreover, the fluorescence emission wavelengths can be tuned in the near-infrared regions, and thus make it the next-generation low-toxicity materials for the applications in bioimaging. In this review, the research progress of the AIS nanoparticles is summarized, including synthetic methods, properties and the possibilities to influence their shape and crystallographic structure. Furthermore, we discuss the potential applications of this novel material in photocatalysis, solar energy conversion and biological area. PMID:27455616

  12. Raman bands in Ag nanoparticles obtained in extract of Opuntia ficus-indica plant

    NASA Astrophysics Data System (ADS)

    Bocarando-Chacon, J.-G.; Cortez-Valadez, M.; Vargas-Vazquez, D.; Rodríguez Melgarejo, F.; Flores-Acosta, M.; Mani-Gonzalez, P. G.; Leon-Sarabia, E.; Navarro-Badilla, A.; Ramírez-Bon, R.

    2014-05-01

    Silver nanoparticles have been obtained in an extract of Opuntia ficus-indica plant. The size and distribution of nanoparticles were quantified by atomic force microscopy (AFM). The diameter was estimated to be about 15 nm. In addition, energy dispersive X-ray spectroscopy (EDX) peaks of silver were observed in these samples. Three Raman bands have been experimentally detected at 83, 110 and 160 cm-1. The bands at 83 and 110 cm-1 are assigned to the silver-silver Raman modes (skeletal modes) and the Raman mode located at 160 cm-1 has been assigned to breathing modes. Vibrational assignments of Raman modes have been carried out based on the Density Functional Theory (DFT) quantum mechanical calculation. Structural and vibrational properties for small Agn clusters with 2≤n≤9 were determined. Calculated Raman modes for small metal clusters have an approximation trend of Raman bands. These Raman bands were obtained experimentally for silver nanoparticles (AgNP).

  13. Development of Novel Cadmium-Free AgInS2 Semiconductor Nanoparticles.

    PubMed

    Yang, Wentao; Gong, Xiaoqun; Chang, Jin

    2016-03-01

    AgInS2 (AIS) semiconductor nanoparticles as the novel alternatives to cadmium- or lead-containing semiconductors have attracted much attention both on the theory and application research, based on their tunable fluorescence emission wavelengths, high photostability and low toxicity of chemical composition. The bandgap of AIS nanoparticles can be adjusted from 1.54 to 2.03 eV, which makes AIS nanocrystalline suitable for applications in solar energy conversion. Moreover, the fluorescence emission wavelengths can be tuned in the near-infrared regions, and thus make it the next-generation low-toxicity materials for the applications in bioimaging. In this review, the research progress of the AIS nanoparticles is summarized, including synthetic methods, properties and the possibilities to influence their shape and crystallographic structure. Furthermore, we discuss the potential applications of this novel material in photocatalysis, solar energy conversion and biological area.

  14. Preparation of mesoporous cadmium sulfide nanoparticles with moderate pore size

    SciTech Connect

    Han Zhaohui Zhu, Huaiyong; Shi, Jeffrey; Parkinson, Gordon; Lu, G.Q.

    2007-03-15

    The preparation of cadmium sulfide nanoparticles that have a moderate pore size is reported. This preparation method involves a hydrothermal process that produces a precursor mixture and a following acid treatment of the precursor to get the porous material. The majority of the particles have a pore size close to 20nm, which complements and fills in the gap between the existing cadmium sulfide materials, which usually have a pore size either less than 10nm or are well above 100nm.

  15. Green synthesis, characterization, photocatalytic, fluorescence and antimicrobial activities of Cochlospermum gossypium capped Ag2S nanoparticles.

    PubMed

    Ayodhya, Dasari; Veerabhadram, Guttena

    2016-04-01

    The study describes a simple and green method for the synthesis of silver sulfide nanoparticles (Ag2S NPs) using gum kondagogu (Cochlospermum gossypium) (GK). The synthesized NPs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), fluorescence, UV-vis absorption, zeta potential and thermogravimetric analysis (TGA) techniques. The optical properties and quantum confinement effect of the products were confirmed by means of spectroscopic measurements. The morphologies and sizes were characterized by SEM and TEM. The Ag2S NPs were spherical in shape with an effective diameter size of 25 nm. The photocatalytic property of Ag2S NPs was evaluated by the degradation of fluorescein (FL) dye under solar light. The effect of Ag2SNPs on the photocatalytic degradation of FL dye and influence of other parameters such as Ag2S loading, H2O2, temperature and under solar light irradiation was also evaluated. The degradation reaction follows the pseudo-first order kinetics. The apparent reaction rate was used to calculate the apparent activation energy (Ea=13.95 kJ/mol) of the degradation process. The activation thermodynamic parameters (ΔG*, ΔH* and ΔS*) were obtained from variable temperature kinetic studies. The interaction between Ag2S NPs and bovine serum albumin (BSA) was studied by using fluorescence spectroscopic measurements. The synthesized Ag2S NPs were showing good antimicrobial activity. PMID:26894846

  16. Kinetic trapping through coalescence and the formation of patterned Ag-Cu nanoparticles.

    PubMed

    Grammatikopoulos, Panagiotis; Kioseoglou, Joseph; Galea, Antony; Vernieres, Jerome; Benelmekki, Maria; Diaz, Rosa E; Sowwan, Mukhles

    2016-05-14

    In recent years, due to its inherent flexibility, magnetron-sputtering has been widely used to synthesise bi-metallic nanoparticles (NPs) via subsequent inert-gas cooling and gas-phase condensation of the sputtered atomic vapour. Utilising two separate sputter targets allows for good control over composition. Simultaneously, it involves fast kinetics and non-equilibrium processes, which can trap the nascent NPs into metastable configurations. In this study, we observed such configurations in immiscible, bi-metallic Ag-Cu NPs by scanning transmission electron microscopy (S/TEM) and electron energy-loss spectroscopy (EELS), and noticed a marked difference in the shape of NPs belonging to Ag- and Cu-rich samples. We explained the formation of Janus or Ag@Cu core/shell metastable structures on the grounds of in-flight mixed NP coalescence. We utilised molecular dynamics (MD) and Monte Carlo (MC) computer simulations to demonstrate that such configurations cannot occur as a result of nanoalloy segregation. Instead, sintering at relatively low temperatures can give rise to metastable structures, which eventually can be stabilised by subsequent quenching. Furthermore, we compared the heteroepitaxial diffusivities along various surfaces of both Ag and Cu NPs, and emphasised the differences between the sintering mechanisms of Ag- and Cu-rich NP compositions: small Cu NPs deform as coherent objects on large Ag NPs, whereas small Ag NPs dissolve into large Cu NPs, with their atoms diffusing along specific directions. Taking advantage of this observation, we propose controlled NP coalescence as a method to engineer mixed NPs of a unique, patterned core@partial-shell structure, which we refer to as a "glass-float" (ukidama) structure. PMID:27119383

  17. Preparation and Characterization of Polymeric Nanoparticles: An Interdisciplinary Experiment

    ERIC Educational Resources Information Center

    Ramalho, Maria J.; Pereira, M. Carmo

    2016-01-01

    In this work, a laboratory experiment to introduce graduate students to nanotechnology is described. Students prepared poly(lactic-"co"-glycolic acid) (PLGA) nanoparticles using two different synthesis procedures, a single and a double emulsion-solvent evaporation method. The students also performed a physicochemical characterization of…

  18. Effects of soil and dietary exposures to Ag nanoparticles and AgNO₃ in the terrestrial isopod Porcellionides pruinosus.

    PubMed

    Tourinho, Paula S; van Gestel, Cornelis A M; Jurkschat, Kerstin; Soares, Amadeu M V M; Loureiro, Susana

    2015-10-01

    The effects of Ag-NPs and AgNO3 on the isopod Porcellionides pruinosus were determined upon soil and dietary exposures. Isopods avoided Ag in soil, with EC50 values of ∼16.0 and 14.0 mg Ag/kg for Ag-NPs and AgNO3, respectively. Feeding inhibition tests in soil showed EC50s for effects on consumption ratio of 127 and 56.7 mg Ag/kg, respectively. Although similar EC50s for effects on biomass were observed for nanoparticulate and ionic Ag (114 and 120 mg Ag/kg dry soil, respectively), at higher concentrations greater biomass loss was found for AgNO3. Upon dietary exposure, AgNO3 was more toxic, with EC50 for effects on biomass change being >1500 and 233 mg Ag/kg for Ag-NPs and AgNO3, respectively. The difference in toxicity between Ag-NPs and AgNO3 could not be explained from Ag body concentrations. This suggests that the relation between toxicity and bioavailability of Ag-NPs differs from that of ionic Ag in soils.

  19. Preparation of homogeneous gold-silver alloy nanoparticles using the apoferritin cavity as a nanoreactor

    SciTech Connect

    Shin, Yongsoon; Dohnalkova, Alice; Lin, Yuehe

    2010-04-08

    Homogeneous Au-Ag alloy nanoparticles have been synthesized in the cavity of horse spleen apoferritin (HSAF) by a diffusion technique. Low concentration of NH4OH solution has been used stabilize Ag(I) ions at pH 8.3, where channels between the subunits of HASF are open for the diffusion of metal ions. The Au-Ag nanoparticle cores are 5.6-6.3 nm in diameter with narrow size distribution (≤ 1.0 nm), and their average diameter was gradually increased with an increase of Ag content. The core formation ratios of Au-Ag-HASF samples are higher than 80%. These series of nanoparticles were applied for the reduction of 4-nitrophenol in the presence of NaBH4. As the Au content was increased in the Au-Ag-HSAF nanoparticles, the rate constant of the reduction was exponentially increased from 1.3 x 10-3 s-1 (pure Ag-HSAF) to 7.58 x 10-2 s-1 (pure Au-HSAF). These synthesized Au-Ag nanoparticles with different compositions will be further applicable in catalysis, sensing, and biomedical areas.

  20. Pt74Ag26 nanoparticle-decorated ultrathin MoS2 nanosheets as novel peroxidase mimics for highly selective colorimetric detection of H2O2 and glucose

    NASA Astrophysics Data System (ADS)

    Cai, Shuangfei; Han, Qiusen; Qi, Cui; Lian, Zheng; Jia, Xinghang; Yang, Rong; Wang, Chen

    2016-02-01

    To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating ultrathin MoS2 nanosheets with octahedral Pt74Ag26 alloy nanoparticles has been reported. The as-prepared MoS2-Pt74Ag26 nanohybrids were investigated as novel peroxidase mimics to catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, producing a blue colored reaction and exhibiting typical Michaelis-Menten kinetics. MoS2-Pt74Ag26 has a higher affinity for H2O2 than horseradish peroxidase (HRP) and a higher vmax value with TMB as the substrate than MoS2. The improved catalytic activity of hybrids for colorimetric reactions could be attributed to the synergistic effects of octahedral Pt74Ag26 nanoparticles and ultrathin MoS2 nanosheets as supports. Meanwhile, the generation of active oxygen species (&z.rad;OH) by H2O2 decomposition with MoS2-Pt74Ag26 was responsible for the oxidation of TMB. On the basis of these findings, a colorimetric method based on MoS2-Pt74Ag26 nanohybrids that is highly sensitive and selective was developed for glucose detection. Lower values of the limit of detection (LOD) were obtained, which is more sensitive than MoS2 nanosheets.To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating

  1. E-beam deposited Ag-nanoparticles plasmonic organic solar cell and its absorption enhancement analysis using FDTD-based cylindrical nano-particle optical model.

    PubMed

    Kim, Richard S; Zhu, Jinfeng; Park, Jeung Hun; Li, Lu; Yu, Zhibin; Shen, Huajun; Xue, Mei; Wang, Kang L; Park, Gyechoon; Anderson, Timothy J; Pei, Qibing

    2012-06-01

    We report the plasmon-assisted photocurrent enhancement in Ag-nanoparticles (Ag-NPs) embedded PEDOT:PSS/P3HT:PCBM organic solar cells, and systematically investigate the causes of the improved optical absorption based on a cylindrical Ag-NPs optical model which is simulated with a 3-Dimensional finite difference time domain (FDTD) method. The proposed cylindrical Ag-NPs optical model is able to explain the optical absorption enhancement by the localized surface plasmon resonance (LSPR) modes, and to provide a further understanding of Ag-NPs shape parameters which play an important role to determine the broadband absorption phenomena in plasmonic organic solar cells. A significant increase in the power conversion efficiency (PCE) of the plasmonic solar cell was experimentally observed and compared with that of the solar cells without Ag-NPs. Finally, our conclusion was made after briefly discussing the electrical effects of the fabricated plasmonic organic solar cells.

  2. Pt74Ag26 nanoparticle-decorated ultrathin MoS2 nanosheets as novel peroxidase mimics for highly selective colorimetric detection of H2O2 and glucose.

    PubMed

    Cai, Shuangfei; Han, Qiusen; Qi, Cui; Lian, Zheng; Jia, Xinghang; Yang, Rong; Wang, Chen

    2016-02-14

    To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating ultrathin MoS2 nanosheets with octahedral Pt74Ag26 alloy nanoparticles has been reported. The as-prepared MoS2-Pt74Ag26 nanohybrids were investigated as novel peroxidase mimics to catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, producing a blue colored reaction and exhibiting typical Michaelis-Menten kinetics. MoS2-Pt74Ag26 has a higher affinity for H2O2 than horseradish peroxidase (HRP) and a higher vmax value with TMB as the substrate than MoS2. The improved catalytic activity of hybrids for colorimetric reactions could be attributed to the synergistic effects of octahedral Pt74Ag26 nanoparticles and ultrathin MoS2 nanosheets as supports. Meanwhile, the generation of active oxygen species (˙OH) by H2O2 decomposition with MoS2-Pt74Ag26 was responsible for the oxidation of TMB. On the basis of these findings, a colorimetric method based on MoS2-Pt74Ag26 nanohybrids that is highly sensitive and selective was developed for glucose detection. Lower values of the limit of detection (LOD) were obtained, which is more sensitive than MoS2 nanosheets.

  3. Preaggregated Ag nanoparticles in dry swellable gel films for off-the-shelf surface-enhanced Raman spectroscopy.

    PubMed

    Lee, Wendy W Y; Silverson, Victoria A D; McCoy, Colin P; Donnelly, Ryan F; Bell, Steven E J

    2014-08-19

    Large, thin (50 μm) dry polymer sheets containing numerous surface-enhanced Raman spectroscopy (SERS) active Ag nanoparticle aggregates have been prepared by drying aqueous mixtures of hydroxyethylcelloulose (HEC) and preaggregated Ag colloid in 10 × 10 cm molds. In these dry films, the particle aggregates are protected from the environment during storage and are easy to handle; for example, they can be cut to size with scissors. When in use, the highly swellable HEC polymer allowed the films to rapidly absorb aqueous analyte solutions while simultaneously releasing the Ag nanoparticle aggregates to interact with the analyte and generate large SERS signals. Either the films could be immersed in the analyte solution or 5 μL droplets were applied to the surface; in the latter method, the local swelling caused the active area to dome upward, but the swollen film remained physically robust and could be handled as required. Importantly, encapsulation and release did not significantly compromise the SERS performance of the colloid; the signals given by the swollen films were similar to the very high signals obtained from the parent citrate-reduced colloid and were an order of magnitude larger than a commercially available nanoparticle substrate. These "Poly-SERS" films retained 70% of their SERS activity after being stored for 1 year in air. The films were sufficiently homogeneous to give a standard deviation of 3.2% in the absolute signal levels obtained from a test analyte, primarily due to the films' ability to suppress "coffee ring" drying marks, which meant that quantitative analysis without an internal standard was possible. The majority of the work used aqueous thiophenol as the test analyte; however, preliminary studies showed that the Poly-SERS films could also be used with nonaqueous solvents and for a range of other analytes including theophylline, a therapeutic drug, at a concentration as low as 1.0 × 10(-5) mol dm(-3) (1.8 mg/dm(3)), well below the

  4. Antibacterial property of Ag nanoparticle-impregnated N-doped titania films under visible light

    NASA Astrophysics Data System (ADS)

    Wong, Ming-Show; Chen, Chun-Wei; Hsieh, Chia-Chun; Hung, Shih-Che; Sun, Der-Shan; Chang, Hsin-Hou

    2015-07-01

    Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet-visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films.

  5. Antibacterial property of Ag nanoparticle-impregnated N-doped titania films under visible light

    PubMed Central

    Wong, Ming-Show; Chen, Chun-Wei; Hsieh, Chia-Chun; Hung, Shih-Che; Sun, Der-Shan; Chang, Hsin-Hou

    2015-01-01

    Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet–visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films. PMID:26156001

  6. Role of silver nanoparticles (AgNPs) on the cardiovascular system.

    PubMed

    Gonzalez, Carmen; Rosas-Hernandez, Hector; Ramirez-Lee, Manuel Alejandro; Salazar-García, Samuel; Ali, Syed F

    2016-03-01

    With the advent of nanotechnology, the use and applications of silver nanoparticles (AgNPs) have increased, both in consumer products as well as in medical devices. However, little is known about the effects of these nanoparticles on human health, more specific in the cardiovascular system, since this system represents an important route of action in terms of distribution, bioaccumulation and bioavailability of the different circulating substances in the bloodstream. A collection of studies have addressed the effects and applications of different kinds of AgNPs (shaped, sized, coated and functionalized) in several components of the cardiovascular system, such as endothelial cells, isolated vessels and organs as well as integrative animal models, trying to identify the underlying mechanisms involved in their actions, to understand their implication in the field of biomedicine. The purpose of the present review is to summarize the most relevant studies to date of AgNPs effects in the cardiovascular system and provide a broader picture of the potential toxic effects and exposure risks, which in turn will allow pointing out the directions of further research as well as new applications of these versatile nanomaterials.

  7. Antibacterial property of Ag nanoparticle-impregnated N-doped titania films under visible light.

    PubMed

    Wong, Ming-Show; Chen, Chun-Wei; Hsieh, Chia-Chun; Hung, Shih-Che; Sun, Der-Shan; Chang, Hsin-Hou

    2015-07-09

    Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet-visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films.

  8. Role of silver nanoparticles (AgNPs) on the cardiovascular system.

    PubMed

    Gonzalez, Carmen; Rosas-Hernandez, Hector; Ramirez-Lee, Manuel Alejandro; Salazar-García, Samuel; Ali, Syed F

    2016-03-01

    With the advent of nanotechnology, the use and applications of silver nanoparticles (AgNPs) have increased, both in consumer products as well as in medical devices. However, little is known about the effects of these nanoparticles on human health, more specific in the cardiovascular system, since this system represents an important route of action in terms of distribution, bioaccumulation and bioavailability of the different circulating substances in the bloodstream. A collection of studies have addressed the effects and applications of different kinds of AgNPs (shaped, sized, coated and functionalized) in several components of the cardiovascular system, such as endothelial cells, isolated vessels and organs as well as integrative animal models, trying to identify the underlying mechanisms involved in their actions, to understand their implication in the field of biomedicine. The purpose of the present review is to summarize the most relevant studies to date of AgNPs effects in the cardiovascular system and provide a broader picture of the potential toxic effects and exposure risks, which in turn will allow pointing out the directions of further research as well as new applications of these versatile nanomaterials. PMID:25543135

  9. Systematic study on the preparation of BSA nanoparticles.

    PubMed

    Galisteo-González, F; Molina-Bolívar, J A

    2014-11-01

    Albumins, in the form of nanoparticles, are increasingly used as drug carriers in the medical field, and the size effect of these nanomaterials is of major importance since it may affect their bioavailability and the in vivo behaviour after intravenous injection. This research provides a comprehensive study on the preparation of BSA nanoparticles, based on a simple coacervation method, with suitable size, size distribution, and surface charge for drug-delivery applications. Numerous experimental variables were examined in order to characterize their impact on nanoparticle size, distribution, electrophoretic mobility, and yield. Particle size was controlled by adjusting self-assembly phenomena of the protein molecules, which was affected by preparation conditions including BSA content, pH, and ionic strength (a parameter that strongly influences nanoparticle formation but surprisingly has not been previously studied in detail). Small particles with a narrow size distribution were obtained under experimental conditions where the repulsion between BSA molecules was high, i.e. at pH values far from the isoelectric point of the protein and low salt concentration. Changes in temperature, volume, and rate of addition of the dehydrating agent (ethanol) also affect nanoparticle characteristics, as they influence the nucleation rate and particle growth. The effect of these experimental conditions on the quantity of protein still dissolved in the aqueous phase after desolvation (i.e. the yield of BSA nanoparticles) was also studied. Nanoparticles surface charge was modulated with the extension of cross-linking. Finally, long-term colloidal stability of samples was evaluated after 2 months of storage.

  10. Preparation and characterization of Au nanoparticles capped with mercaptocarboranyl clusters.

    PubMed

    Cioran, Ana M; Teixidor, Francesc; Krpetić, Željka; Brust, Mathias; Viñas, Clara

    2014-04-01

    The preparation of 3-4 nm and 10 nm gold nanoparticles capped with neutral carborane-based mercaptocarboranes, via two different preparative routes, is reported. The resulting boron-enriched nanomaterials exhibit complete dispersibility in water, opening the way for the use of these monolayer protected clusters (MPCs) in medical applications, such as boron neutron capture therapy (BNCT). These newly prepared MPCs have been characterized by FTIR, (1)H and (11)B NMR spectroscopy, UV-visible, centrifugal particle sizing (CPS), and, in some cases, inductively coupled plasma atomic emission spectrometry (ICP-AES). Water dispersibility exhibited by these MPCs allowed the study of the cellular uptake by HeLa cells.

  11. Dispensing of high concentration Ag nano-particles ink for ultra-low resistivity paper-based writing electronics.

    PubMed

    Wang, Fuliang; Mao, Peng; He, Hu

    2016-02-17

    Paper-based writing electronics has received a lot of interest recently due to its potential applications in flexible electronics. To obtain ultra-low resistivity paper-based writing electronics, we developed a kind of ink with high concentration of Ag Nano-particles (up to 80 wt%), as well as a related dispensing writing system consisting an air compressor machine and a dispenser. Additionally, we also demonstrated the writability and practical application of our proposed ink and writing system. Based on the study on the effect of sintering time and pressure, we found the optimal sintering time and pressure to obtain high quality Ag NPs wires. The electrical conductivity of nano-silver paper-based electronics has been tested using the calculated resistivity. After hot-pressure sintering at 120 °C, 25 MPa pressure for 20 minutes, the resistivity of silver NPs conductive tracks was 3.92 × 10(-8) (Ωm), only 2.45 times of bulk silver. The mechanical flexibility of nano-silver paper-based electronics also has been tested. After 1000 bending cycles, the resistivity slightly increased from the initial 4.01 × 10(-8) to 5.08 × 10(-8) (Ωm). With this proposed ink preparation and writing system, a kind of paper-based writing electronics with ultra-low resistivity and good mechanical flexibility was achieved.

  12. Dispensing of high concentration Ag nano-particles ink for ultra-low resistivity paper-based writing electronics.

    PubMed

    Wang, Fuliang; Mao, Peng; He, Hu

    2016-01-01

    Paper-based writing electronics has received a lot of interest recently due to its potential applications in flexible electronics. To obtain ultra-low resistivity paper-based writing electronics, we developed a kind of ink with high concentration of Ag Nano-particles (up to 80 wt%), as well as a related dispensing writing system consisting an air compressor machine and a dispenser. Additionally, we also demonstrated the writability and practical application of our proposed ink and writing system. Based on the study on the effect of sintering time and pressure, we found the optimal sintering time and pressure to obtain high quality Ag NPs wires. The electrical conductivity of nano-silver paper-based electronics has been tested using the calculated resistivity. After hot-pressure sintering at 120 °C, 25 MPa pressure for 20 minutes, the resistivity of silver NPs conductive tracks was 3.92 × 10(-8) (Ωm), only 2.45 times of bulk silver. The mechanical flexibility of nano-silver paper-based electronics also has been tested. After 1000 bending cycles, the resistivity slightly increased from the initial 4.01 × 10(-8) to 5.08 × 10(-8) (Ωm). With this proposed ink preparation and writing system, a kind of paper-based writing electronics with ultra-low resistivity and good mechanical flexibility was achieved. PMID:26883558

  13. Dispensing of high concentration Ag nano-particles ink for ultra-low resistivity paper-based writing electronics

    NASA Astrophysics Data System (ADS)

    Wang, Fuliang; Mao, Peng; He, Hu

    2016-02-01

    Paper-based writing electronics has received a lot of interest recently due to its potential applications in flexible electronics. To obtain ultra-low resistivity paper-based writing electronics, we developed a kind of ink with high concentration of Ag Nano-particles (up to 80 wt%), as well as a related dispensing writing system consisting an air compressor machine and a dispenser. Additionally, we also demonstrated the writability and practical application of our proposed ink and writing system. Based on the study on the effect of sintering time and pressure, we found the optimal sintering time and pressure to obtain high quality Ag NPs wires. The electrical conductivity of nano-silver paper-based electronics has been tested using the calculated resistivity. After hot-pressure sintering at 120 °C, 25 MPa pressure for 20 minutes, the resistivity of silver NPs conductive tracks was 3.92 × 10-8 (Ωm), only 2.45 times of bulk silver. The mechanical flexibility of nano-silver paper-based electronics also has been tested. After 1000 bending cycles, the resistivity slightly increased from the initial 4.01 × 10-8 to 5.08 × 10-8 (Ωm). With this proposed ink preparation and writing system, a kind of paper-based writing electronics with ultra-low resistivity and good mechanical flexibility was achieved.

  14. The optical nonlinearity of gold nanoparticles prepared by bioreduction method

    NASA Astrophysics Data System (ADS)

    Balbuena Ortega, A.; Arroyo Carrasco, M. L.; Gayou, V. L.; Orduña Díaz, A.; Delgado Macuil, R.; Rojas López, Marlon

    2013-11-01

    Nonlinear optical and electronic properties of nanosized metal particles have drawn considerable attention because of their strong and size-dependent plasmon resonance absorption. In a metal nanoparticle system such as gold dispersed in a transparent matrix, an absorption peak due to surface plasmon resonance is usually observed in the visible spectral region. Metal nanoparticles are of special interest as nonlinear materials for optical switching and computing because of their relatively large third-order nonlinearity (χ3) and ultrafast response time. The purpose of this study was to analyze the nonlinear optical properties of biosynthesized gold nanoparticles. The samples were prepared by biosynthesis method using yeast extract as reducing agent and the nonlinear optical properties of the nanoparticles were investigated using a single beam Z-scan technique with a beam power of 20 mW and operated at wavelength of 514 nm. The reaction between metal ions and yeast extracts were monitored by UV-visible spectra of Au nanoparticles in aqueous solution with different pH (3-6). The surface plasmon peak position was shifted from 528 nm to 573 nm, according to of pH variation 4 to 6. The average particle size was calculated by the absorption peak position using the Fernig method, from 42 to 103 nm. The z-scan curves showed a negative nonlocal nonlinear refractive index with a magnitude dependent on the nanoparticle size.

  15. Study of Ag-Pd bimetallic nanoparticles modified glassy carbon electrode for detection of L-cysteine

    NASA Astrophysics Data System (ADS)

    Murugavelu, M.; Karthikeyan, B.

    2014-11-01

    Ag-Pd bimetallic nanoparticles (Ag-Pd BNPs) as an enhanced sensing material with improved electronic transmission rates in the electrochemical sensing of L-cysteine (L-cys) has been reported. The morphology of Ag-Pd BNPs was characterized with X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and cyclic voltammetry (CV). Oxidation of L-cys on Ag-Pd BNPs is investigated in detail by discussing the effect of the structure and from the electrocatalytic oxidation of L-cys. We found that the Ag-Pd BNPs exhibited high electrocatalytic activity towards L-cys oxidation in neutral condition and could be used for the development of nonenzymatic L-cys sensor. Based on the efficient catalytic ability of Ag-Pd BNPs, the fabricated biosensor exhibited a wide linear range of responses to the L-cys with the concentration detection limit of nearly down to 2 mM with fast response time.

  16. Unaffected features of BSA stabilized Ag nanoparticles after storage and reconstitution in biological relevant media.

    PubMed

    Valenti, Laura E; Giacomelli, Carla E

    2015-08-01

    Silver-coated orthopedic implants and silver composite materials have been proposed to produce local biocidal activity at low dose to reduce post-surgery infection that remains one of the major contributions to the patient morbidity. This work presents the synthesis combined with the characterization, colloidal stability in biological relevant media, antimicrobial activity and handling properties of silver nanoparticles (Ag-NP) before and after freeze dry and storage. The nanomaterial was synthesized in aqueous solution with simple, reproducible and low-cost strategies using bovine serum albumin (BSA) as the stabilizing agent. Ag-NP were characterized by means of the size distribution and morphology (UV-vis spectra, dynamic light scattering measurements and TEM images), charge as a function of the pH (zeta potential measurements) and colloidal stability in biological relevant media (UV-vis spectra and dynamic light scattering measurements). Further, the interactions between the protein and Ag-NP were evaluated by surface enhanced Raman spectroscopy (SERS) and the antimicrobial activity was tested with two bacteria strains (namely Staphylococcus aureus and Staphylococcus epidermidis) mainly present in the infections caused by implants and prosthesis in orthopedic surgery. Finally, the Ag-NP dispersed in aqueous solution were dried and stored as long-lasting powders that were easily reconstituted without losing their stability and antimicrobial properties. The proposed methods to stabilize Ag-NP not only produce stable dispersions in media of biological relevance but also long-lasting powders with optimal antimicrobial activity in the nanomolar range. This level is much lower than the cytotoxicity determined in vitro on osteoblasts, osteoclasts and osteoarthritic chondrocytes. The synthesized Ag-NP can be incorporated as additive of biomaterials or pharmaceutical products to confer antimicrobial activity in a powdered form in different formulations, dispersed in

  17. Assessing Pistia stratiotes for phytoremediation of silver nanoparticles and Ag(I) contaminated waters.

    PubMed

    Hanks, Nicole A; Caruso, Joseph A; Zhang, Peng

    2015-12-01

    To study the phytoremediation capabilities of Pistia stratiotes in silver nanoparticle (AgNP) and silver ion contaminated wastewaters, individual plants were grown in media spiked with different concentrations of silver nanoparticle and silver ions (0.02, 0.2, and 2 mg L(-1)). Control experiments were carried out at the same time for comparison purposes. Visual changes in the plants were also recorded periodically during each experiment. Total silver concentrations were monitored in the media before, during, and at the termination of the experiments. In addition, analysis of total silver in plant root and leaf samples after termination were carried out to determine the effect of the different media concentrations. The results showed that P. stratiotes can survive in AgNP and ions under 0.02 mg L(-1) and contaminants are retained within the plant. The use of P. stratiotes as a phytoremediator shows potential in removing heavy metal nanoparticles and is competitive in its removal of the ion counterpart. Even higher concentrations of silver, regardless of form, can be reduced to lower levels than the World Health Organization's maximum contamination limit.

  18. The antibacterial properties of a novel chitosan-Ag-nanoparticle composite.

    PubMed

    Sanpui, Pallab; Murugadoss, A; Prasad, P V Durga; Ghosh, Siddhartha Sankar; Chattopadhyay, Arun

    2008-05-31

    Escherichia coli expressing recombinant green fluorescent protein was used to test the bactericidal efficacy of a newly synthesized chitosan-Ag-nanoparticle composite. The composite was found to have significantly higher antimicrobial activity than its components at their respective concentrations. The one-pot synthesis method led to the formation of small Ag nanoparticles attached to the polymer which can be dispersed in media of pH< or =6.3. The presence of a small percentage (2.15%, w/w) of metal nanoparticles in the composite was enough to significantly enhance inactivation of E. coli as compared with unaltered chitosan. Fluorescence spectroscopy indicated that bacterial growth stopped immediately after exposure of E. coli to the composite, with release of cellular green fluorescent protein into the medium at a faster rate than with chitosan. Fluorescence confocal laser scanning and scanning electron microscopy showed attachment of the bacteria to the composite and their subsequent fragmentation. Native protein gel electrophoresis experiments indicated no effect of the composite on bacterial proteins.

  19. Polymer Assisted Core-shell Ag-C nanoparticles Synthesis via Green hydrothermal Technique

    NASA Astrophysics Data System (ADS)

    Williams, James; Mishra, Sanjay

    2009-03-01

    Core-Shell Ag-C nanoparticles were synthesized in the presence of glucose through a one-pot green hydrothermal wet chemical process. An aqueous solution of glucose and Ag nitrate was hydrothermally treated to produce porous carbonaceous shell over silver core nanoparticles. The growth of carbon shells was regulated by either of the polymers (poly) vinyl pyrrolidone (PVP) or poly vinyl alcohol (PVA). The two polymers were compared to take a measure of different tunable sizes of cores, and shells. The effects of hydrothermal temperature, time, and concentration of reagents on the final formation of nanostructures were studied using UV-vis extinction spectra, transmission electron microscope, and Raman spectroscopy. The polymer molecules were found to be incorporated into carbonaceous shell. The resulting opacity of the shell was found to be hydrothermal time and temperature dependent. The shell structure was found to be more uniform with PVP than PVA. Furthermore, the polymer concentration was found to influence size and shape of the core-silver particles as well. The core-shelled nanoparticles have surfaces with organic groups capable of assembling with different reagents that could be useful in drug-delivery, optical nanodevices or biochemistry.

  20. Preparation of graphene–Ag composites and their application for electrochemical detection of chloride

    SciTech Connect

    Yu, Mei; Liu, Pengrui; Zhang, Shilu; Liu, Jianhua; An, Junwei; Li, Songmei

    2012-11-15

    Highlights: ► Graphene–Ag composites were prepared in situ using ascorbic acid as green reducing agent. ► The morphology of Ag particles was irregular sheet and Ag particles homogeneously distributed on the graphene matrix. ► The surface-enhanced Raman scattering enhancement factor of D band is 5.85 for composites. ► The composites exhibited good sensitivity for the detection of chloride ions. -- Abstract: Graphene–Ag composites were prepared in situ using ascorbic acid as green reducing agent. The composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected-area electronic diffraction (SAED), and Raman spectrometer. It was showed that Ag particles homogeneously distributed on the graphene matrix. The morphology of Ag particles was irregular sheet with (1 1 1) basal plane. The surface-enhanced Raman scattering (SERS) enhancement factor of D band is 5.85 for composites. The application of the composites for electrochemical detection of chloride was studied by cyclic voltammetry. The composites exhibited good sensitivity for the detection of chloride ions. The maximum peak current of cyclic voltammetry curve in 5 mM KCl was 0.80 mA. In the range of 500 μM to 50 mM for Cl{sup −}, the current response was proportional and linear to the Cl{sup −} concentration. The sensitivity to the detection for Cl{sup −} was 0.059 (mA/mM) and the detection limit was 61 μM for Cl{sup −}. It indicates graphene–Ag composites would be a competitive material for detection of halide.

  1. Synthesis and thermal behavior of tin-based alloy (Sn-Ag-Cu) nanoparticles

    NASA Astrophysics Data System (ADS)

    Roshanghias, Ali; Yakymovych, Andriy; Bernardi, Johannes; Ipser, Herbert

    2015-03-01

    The prominent melting point depression of nanoparticles has been the subject of a considerable amount of research. For their promising applications in electronics, tin-based nano-alloys such as near-eutectic Sn-Ag-Cu (SAC) alloys have been synthesized via various techniques. However, due to issues such as particle aggregation and oxidation or introduced impurities, the application of these nano-size particles has been confined or aborted. For instance, thermal investigations by DTA/DSC in a large number of studies revealed exothermic peaks in the range of 240-500 °C, i.e. above the melting point of SAC nanoparticles, with different and quite controversial explanations for this unclear phenomenon. This represents a considerable drawback for the application of nanoparticles. Correspondingly, in the current study, the thermal stability of SAC nanoparticles has been investigated via electron microscopy, XRD, FTIR, and DSC/TG analysis. It was found that the nanoparticles consist mainly of a metallic β-Sn core and an amorphous tin hydroxide shell structure. The SnO crystalline phase formation from this amorphous shell has been associated with the exothermic peaks on the first heating cycle of the nanoparticles, followed by a disproportionation reaction into metallic Sn and SnO2.The results also revealed that the surfactant and reducing agent cannot only affect the size and size distribution of the nanoparticles, they might also alter the ratio between the amorphous shell and the crystalline core in the structure of particles.The prominent melting point depression of nanoparticles has been the subject of a considerable amount of research. For their promising applications in electronics, tin-based nano-alloys such as near-eutectic Sn-Ag-Cu (SAC) alloys have been synthesized via various techniques. However, due to issues such as particle aggregation and oxidation or introduced impurities, the application of these nano-size particles has been confined or aborted. For

  2. Preparation and properties of poly(vinyl alcohol)/chitosan blend bionanocomposites reinforced with cellulose nanocrystals/ZnO-Ag multifunctional nanosized filler

    PubMed Central

    Azizi, Susan; Ahmad, Mansor Bin; Hussein, Mohd Zobir; Ibrahim, Nor Azowa; Namvar, Farideh

    2014-01-01

    A series of novel bionanocomposites were cast using different contents of zinc oxide-silver nanoparticles (ZnO-AgNPs) stabilized by cellulose nanocrystals (CNC) as multifunctional nanosized fillers in poly(vinyl alcohol)/chitosan (PVA/Cs) matrices. The morphological structure, mechanical properties, ultraviolet-visible absorption, and antimicrobial properties of the prepared films were investigated as a function of their CNC/ZnO-AgNP content and compared with PVA/chitosan/CNC bionanocomposite films. X-ray diffraction and field emission scanning electron microscopic analyses showed that the CNC/ZnO-AgNPs were homogeneously dispersed in the PVA/Cs matrix and the crystallinity increased with increasing nanosized filler content. Compared with pure PVA/Cs, the tensile strength and modulus in the films increased from 0.055 to 0.205 GPa and from 0.395 to 1.20 GPa, respectively. Ultraviolet and visible light can be efficiently absorbed by incorporating ZnO-AgNPs into a PVA/Cs matrix, suggesting that these bionanocomposite films show good visibility and ultraviolet-shielding effects. The bionanocomposite films had excellent antimicrobial properties, killing both Gram-negative Salmonella choleraesuis and Gram-positive Staphylococcus aureus. The enhanced physical properties achieved by incorporating CNC/ZnO-AgNPs could be beneficial in various applications. PMID:24790433

  3. Blood surface-enhanced Raman spectroscopy based on Ag and Au nanoparticles for nasopharyngeal cancer detection

    NASA Astrophysics Data System (ADS)

    Lin, Duo; Ge, Xiaosong; Lin, Xueliang; Chen, Guannan; Chen, Rong

    2016-05-01

    This study aims to evaluate and compare the utility of blood surface-enhanced Raman spectroscopy (SERS) based on Au or Ag nanoparticles (NPs), respectively, for detection of nasopharyngeal cancer (NPC). A rapid home-made Raman system was employed for SERS measurement, and high quality SERS spectra can be recorded from blood plasma samples belonging to 60 healthy volunteers and 100 NPC patients, using both metallic NPs. The spectral differences under Ag-SERS measurement between the normal and cancer groups are more significant than Au-SERS. Principal component analysis combined with linear discriminant analysis (PCA-LDA) was used for differentiating the two blood groups with a diagnostic sensitivity and specificity of 90% and 95%, respectively, using Ag-SERS method, which has almost a 20% improvement in diagnostic specificity in comparison to Au-SERS. This exploratory study demonstrates that blood SERS based on Ag NPs is capable of achieving a better diagnostic performance for NPC detection, and has promising potential for improving NPC screening.

  4. Influence of size, shape and core–shell interface on surface plasmon resonance in Ag and Ag@MgO nanoparticle films deposited on Si/SiOx

    PubMed Central

    Pinotti, Daniele; Spadaro, Maria Chiara; Paolicelli, Guido; Grillo, Vincenzo; Valeri, Sergio; Pasquali, Luca; Bergamini, Luca; Corni, Stefano

    2015-01-01

    Summary Ag and Ag@MgO core–shell nanoparticles (NPs) with a diameter of d = 3–10 nm were obtained by physical synthesis methods and deposited on Si with its native ultrathin oxide layer SiOx (Si/SiOx). Scanning electron microscopy and transmission electron microscopy (TEM) images of bare Ag NPs revealed the presence of small NP aggregates caused by diffusion on the surface and agglomeration. Atomic resolution TEM gave evidence of the presence of crystalline multidomains in the NPs, which were due to aggregation and multitwinning occurring during NP growth in the nanocluster source. Co-deposition of Ag NPs and Mg atoms in an oxygen atmosphere gave rise to formation of a MgO shell matrix surrounding the Ag NPs. The behaviour of the surface plasmon resonance (SPR) excitation in surface differential reflectivity (SDR) spectra with p-polarised light was investigated for bare Ag and Ag@MgO NPs. It was shown that the presence of MgO around the Ag NPs caused a red shift of the plasmon excitation, and served to preserve its existence after prolonged (five months) exposure to air, realizing the possibility of technological applications in plasmonic devices. The Ag NP and Ag@MgO NP film features in the SDR spectra could be reproduced by classical electrodynamics simulations by treating the NP-containing layer as an effective Maxwell Garnett medium. The simulations gave results in agreement with the experiments when accounting for the experimentally observed aggregation. PMID:25821680

  5. Redox-Robust Pentamethylferrocene Polymers and Supramolecular Polymers, and Controlled Self-Assembly of Pentamethylferricenium Polymer-Embedded Ag, AgI, and Au Nanoparticles.

    PubMed

    Gu, Haibin; Ciganda, Roberto; Castel, Patricia; Vax, Amélie; Gregurec, Danijela; Irigoyen, Joseba; Moya, Sergio; Salmon, Lionel; Zhao, Pengxiang; Ruiz, Jaime; Hernández, Ricardo; Astruc, Didier

    2015-12-01

    We report the first pentamethylferrocene (PMF) polymers and the redox chemistry of their robust polycationic pentamethylferricenium (PMFium) analogues. The PMF polymers were synthesized by ring-opening metathesis polymerization (ROMP) of a PMF-containing norbornene derivative by using the third-generation Grubbs ruthenium metathesis catalyst. Cyclic voltammetry studies allowed us to determine confidently the number of monomer units in the polymers through the Bard-Anson method. Stoichiometric oxidation by using ferricenium hexafluorophosphate quantitatively and instantaneously provided fully stable (even in aerobic solutions) blue d(5) Fe(III) metallopolymers. Alternatively, oxidation of the PMF-containing polymers was conducted by reactions with Ag(I) or Au(III) , to give PMFium polymer-embedded Ag and Au nanoparticles (NPs). In the presence of I2 , oxidation by using Ag(I) gave polymer-embedded Ag/AgI NPs and AgNPs at the surface of AgI NPs. Oxidation by using Au(III) also produced an Au(I) intermediate that was trapped and characterized. Engineered single-electron transfer reactions of these redox-robust nanomaterial precursors appear to be a new way to control their formation, size, and environment in a supramolecular way.

  6. Redox-Robust Pentamethylferrocene Polymers and Supramolecular Polymers, and Controlled Self-Assembly of Pentamethylferricenium Polymer-Embedded Ag, AgI, and Au Nanoparticles.

    PubMed

    Gu, Haibin; Ciganda, Roberto; Castel, Patricia; Vax, Amélie; Gregurec, Danijela; Irigoyen, Joseba; Moya, Sergio; Salmon, Lionel; Zhao, Pengxiang; Ruiz, Jaime; Hernández, Ricardo; Astruc, Didier

    2015-12-01

    We report the first pentamethylferrocene (PMF) polymers and the redox chemistry of their robust polycationic pentamethylferricenium (PMFium) analogues. The PMF polymers were synthesized by ring-opening metathesis polymerization (ROMP) of a PMF-containing norbornene derivative by using the third-generation Grubbs ruthenium metathesis catalyst. Cyclic voltammetry studies allowed us to determine confidently the number of monomer units in the polymers through the Bard-Anson method. Stoichiometric oxidation by using ferricenium hexafluorophosphate quantitatively and instantaneously provided fully stable (even in aerobic solutions) blue d(5) Fe(III) metallopolymers. Alternatively, oxidation of the PMF-containing polymers was conducted by reactions with Ag(I) or Au(III) , to give PMFium polymer-embedded Ag and Au nanoparticles (NPs). In the presence of I2 , oxidation by using Ag(I) gave polymer-embedded Ag/AgI NPs and AgNPs at the surface of AgI NPs. Oxidation by using Au(III) also produced an Au(I) intermediate that was trapped and characterized. Engineered single-electron transfer reactions of these redox-robust nanomaterial precursors appear to be a new way to control their formation, size, and environment in a supramolecular way. PMID:26494439

  7. Photodeposition of Ag or Pt onto TiO2 nanoparticles decorated on step edges of HOPG.

    PubMed

    Taing, James; Cheng, Ming H; Hemminger, John C

    2011-08-23

    Ordered linear arrays of titanium dioxide nanoparticles were fabricated on highly oriented pyrolytic graphite utilizing a step edge decoration method. Ag- or Pt-based nanoparticles were then photodeposited onto the titanium dioxide nanoparticles (∼18 nm) to simultaneously verify photocatalytic activity and to demonstrate a viable route to load the titanium dioxide nanoparticles with metals. Scanning electron microscopy and atomic force microscopy determined the morphology, size, and distribution of the particles. X-ray photoelectron spectroscopy confirmed the identity of the titanium dioxide nanoparticles, and transmission electron microscopy showed that some of the particles were rutile single crystals. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy determined the chemical composition of the metal-based nanoparticles selectively loaded on the linear arrays of titanium dioxide nanoparticles.

  8. Preparation and characterization of supported magnetic nanoparticles prepared by reverse micelles

    PubMed Central

    Han, Luyang; Biskupek, Johannes; Kaiser, Ute; Ziemann, Paul

    2010-01-01

    Summary Monatomic (Fe, Co) and bimetallic (FePt and CoPt) nanoparticles were prepared by exploiting the self-organization of precursor loaded reverse micelles. Achievements and limitations of the preparation approach are critically discussed. We show that self-assembled metallic nanoparticles can be prepared with diameters d = 2–12 nm and interparticle distances D = 20–140 nm on various substrates. Structural, electronic and magnetic properties of the particle arrays were characterized by several techniques to give a comprehensive view of the high quality of the method. For Co nanoparticles, it is demonstrated that magnetostatic interactions can be neglected for distances which are at least 6 times larger than the particle diameter. Focus is placed on FePt alloy nanoparticles which show a huge magnetic anisotropy in the L10 phase, however, this is still less by a factor of 3–4 when compared to the anisotropy of the bulk counterpart. A similar observation was also found for CoPt nanoparticles (NPs). These results are related to imperfect crystal structures as revealed by HRTEM as well as to compositional distributions of the prepared particles. Interestingly, the results demonstrate that the averaged effective magnetic anisotropy of FePt nanoparticles does not strongly depend on size. Consequently, magnetization stability should scale linearly with the volume of the NPs and give rise to a critical value for stability at ambient temperature. Indeed, for diameters above 6 nm such stability is observed for the current FePt and CoPt NPs. Finally, the long-term conservation of nanoparticles by Au photoseeding is presented. PMID:21977392

  9. The effect of silver nanoparticles (AgNPs) on proliferation and apoptosis of in ovo cultured glioblastoma multiforme (GBM) cells

    NASA Astrophysics Data System (ADS)

    Urbańska, Kaja; Pająk, Beata; Orzechowski, Arkadiusz; Sokołowska, Justyna; Grodzik, Marta; Sawosz, Ewa; Szmidt, Maciej; Sysa, Paweł

    2015-03-01

    Recently, it has been shown that silver nanoparticles (AgNPs) provide a unique approach to the treatment of tumors, especially those of neuroepithelial origin. Thus, the aim of this study was to evaluate the impact of AgNPs on proliferation and activation of the intrinsic apoptotic pathway of glioblastoma multiforme (GBM) cells cultured in an in ovo model. Human GBM cells, line U-87, were placed on chicken embryo chorioallantoic membrane. After 8 days, the tumors were divided into three groups: control (non-treated), treated with colloidal AgNPs (40 μg/ml), and placebo (tumors supplemented with vehicle only). At the end of the experiment, all tumors were isolated. Assessment of cell proliferation and cell apoptosis was estimated by histological, immunohistochemical, and Western blot analyses. The results show that AgNPs can influence GBM growth. AgNPs inhibit proliferation of GBM cells and seem to have proapoptotic properties. Although there were statistically significant differences between control and AgNP groups in the AI and the levels of active caspase 9 and active caspase 3, the level of these proteins in GBM cells treated with AgNPs seems to be on the border between the spontaneous apoptosis and the induced. Our results indicate that the antiproliferative properties of silver nanoparticles overwhelm proapoptotic ones. Further research focused on the cytotoxic effect of AgNPs on tumor and normal cells should be conducted.

  10. Electrochemical detection of Cu2+ through Ag nanoparticle assembly regulated by copper-catalyzed oxidation of cysteamine.

    PubMed

    Cui, Lin; Wu, Jie; Li, Jie; Ge, Yanqiu; Ju, Huangxian

    2014-05-15

    A highly sensitive and selective electrochemical sensor was developed for the detection of Cu(2+) by the assembly of Ag nanoparticles (AgNPs) at dithiobis[succinimidylpropionate] encapsulated Au nanoparticles (DSP-AuNPs), which was regulated by copper-catalyzed oxidation of cysteamine (Cys). The electrochemical sensor was constructed by layer-by-layer modification of glassy carbon electrode with carbon nanotubes, poly(amidoamine) dendrimers and DSP-AuNPs. In the absence of Cu(2+), Cys could bind to the surface of citrate-stabilized AgNPs via Ag-S bond, thus AgNPs could be assembled on the sensor surface through the reaction between DSP and Cys. In contrast, the copper-catalyzed oxidation of Cys by dissolved oxygen in the presence of Cu(2+) inhibited the Cys-induced aggregation of AgNPs, leading to the decrease of the electrochemical stripping signal of AgNPs. Under the optimized conditions, this method could detect Cu(2+) in the range of 1.0-1000 nM with a detection limit of 0.48 nM. The proposed Cu(2+) sensor showed good reproducibility, stability and selectivity. It has been satisfactorily applied to determine Cu(2+) in water samples.

  11. Preparation and luminescence of bulk oxyfluoride glasses doped with Ag nanoclusters.

    PubMed

    Tikhomirov, V K; Rodríguez, V D; Kuznetsov, A; Kirilenko, D; Van Tendeloo, G; Moshchalkov, V V

    2010-10-11

    Bulk oxyfluoride glasses doped with Ag nanoclusters have been prepared using the melt quenching technique. When pumped in the absorption band of Ag nanoclusters between 300 to 500 nm, these glasses emit a very broad luminescence band covering all the visible range with a weak tail extending into the near infrared. The maximum of the luminescence band and its color shifts to the blue with a shortening of the excitation wavelength and an increasing ratio of oxide to fluoride components, resulting in white color luminescence at a particular ratio of oxide to fluoride; with a quantum yield above 20%. PMID:20941104

  12. Biotic and abiotic interactions in aquatic microcosms determine fate and toxicity of Ag nanoparticles. Part 1. Aggregation and dissolution.

    PubMed

    Unrine, Jason M; Colman, Benjamin P; Bone, Audrey J; Gondikas, Andreas P; Matson, Cole W

    2012-07-01

    To better understand their fate and toxicity in aquatic environments, we compared the aggregation and dissolution behavior of gum arabic (GA) and polyvinylpyrrolidone (PVP) coated Ag nanoparticles (NPs) in aquatic microcosms. There were four microcosm types: surface water; water and sediment; water and aquatic plants; or water, sediment, and aquatic plants. Dissolution and aggregation behavior of AgNPs were examined using ultracentrifugation, ultrafiltration, and asymmetrical flow field flow fractionation coupled to ultraviolet-visible spectroscopy, dynamic and static laser light scattering, and inductively coupled plasma mass spectrometry. Plants released dissolved organic matter (DOM) into the water column either through active or passive processes in response to Ag exposure. This organic matter fraction readily bound Ag ions. The plant-derived DOM had the effect of stabilizing PVP-AgNPs as primary particles, but caused GA-AgNPs to be removed from the water column, likely by dissolution and binding of released Ag ions on sediment and plant surfaces. The destabilization of the GA-AgNPs also corresponded with X-ray absorption near edge spectroscopy results which suggest that 22-28% of the particulate Ag was associated with thiols and 5-14% was present as oxides. The results highlight the potential complexities of nanomaterial behavior in response to biotic and abiotic modifications in ecosystems, and may help to explain differences in toxicity of Ag observed in realistic exposure media compared to simplified laboratory exposures.

  13. Self-organization and photo-induced formation of cyanine dye aggregates on the plasmonic Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Starovoytov, Anton A.; Nabiullina, Rezida D.; Toropov, Nikita A.

    2016-04-01

    The optical properties of hybrid film based on plasmon Ag nanoparticles of different size and cyanine dyes with different length of conjugation chain depending on the relative position of the plasmon resonance and the absorption of organic molecules were studied. The absorption spectra of the films revealed several molecular forms, such as all-trans- and cisisomers, dimers and J-aggregate, which also exist in pure organic films without Ag nanoparticles. It's shown that the absorption of aggregate bands increased after exposure by nanosecond laser on the hybrid films due to photo-induced additional self-organization of aggregates. In the presence of Ag nanoparticles, laser radiation leads to the change of molecular forms at a comparatively low threshold.

  14. Preparation, characterization, and bacteriostasis of AgNP-coated β-CD grafting cellulose beads.

    PubMed

    Wang, Ting; Li, Bin; Lin, Li

    2013-03-01

    A novel functional material of β-cyclodextrin (β-CD) grafting cellulose beads containing immobilized silver nanoparticles (AgNPs) is presented in this paper. The morphology was characterized by scanning electron microscopy, energy-dispersive X-ray, and X-ray photoelectron spectroscopy. Phenolphthalein probe molecule technique was used to detect the activity of the grafting β-CD, and the results demonstrated that the deposition of AgNPs had no influence on its encapsulation ability. Acid resistance of the AgNPs on the bead material was studied by atomic absorption spectrometry. The stability of the AgNPs was enhanced due to the grafting of β-CD. Tube dilution method was applied to study the bacteriostatic effect, and the minimal inhibitory doses of the novel material against Escherichia coli and Staphylococcus aureus were 12.5 and 25 mg, respectively. The minimal bactericidal doses for the two bacteria were 25 and 25 mg, respectively. PMID:23340866

  15. Coating geometry of Ag, Ti, Co, Ni, and Al nanoparticles on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Barberio, M.; Stranges, F.; Xu, F.

    2015-04-01

    We present a morphology study on laser ablation produced metal nanoparticles (NPs) deposited on carbon nanotube (CNT) substrates. We analyzed the coating geometry and topography by processing AFM and SEM images. Our results show that Ag NPs aggregate together to form large agglomerates, that Ti NPs are well dispersed on the substrate surface forming a quasi-continuous layer, and that Co, Ni, and Al NPs coat quite uniformly CNTs and locally grow in a layer like fashion. We interpret the coating and clustering geometries in terms of cohesion, surface, and interfacial energies and diffusion barriers. Fractal analysis of composites morphology suggests the formation of structures with a smoother topography relative to pure carbon nanotubes for reactive metal nanoparticles.

  16. Preparation, structural and morphological studies of Ni doped titania nanoparticles.

    PubMed

    Rajamannan, B; Mugundan, S; Viruthagiri, G; Shanmugam, N; Gobi, R; Praveen, P

    2014-07-15

    TiO2 nanoparticles doped with different weight percentages (4%, 8%, 12% and 16%) of nickel contents were prepared by a modified sol-gel method using Titanium tetra iso propoxide and nickel nitrate as precursors and 2-propanol as a solvent. X-ray diffraction studies show that the as prepared and annealed products show anatase structure with average particle sizes running between of 8 and 16 nm. FTIR results demonstrate the presence of strong chemical bonding at the interface of TiO2 nanoparticles. The optical properties of bare and doped samples were carried out using UV-DRS and photoluminescence measurements. The surface morphology and the element constitution of the nickel doped TiO2 nanoparticles were studied by scanning electron microscope attached with energy dispersive X-ray spectrometer arrangement. The non linear optical properties of the products were confirmed by Kurtz second harmonic generation (SHG) test and the output power generated by the nanoparticle was compared with that of potassium di hydrogen phosphate (KDP).

  17. Preparation, structural and morphological studies of Ni doped titania nanoparticles

    NASA Astrophysics Data System (ADS)

    Rajamannan, B.; Mugundan, S.; Viruthagiri, G.; Shanmugam, N.; Gobi, R.; Praveen, P.

    2014-07-01

    TiO2 nanoparticles doped with different weight percentages (4%, 8%, 12% and 16%) of nickel contents were prepared by a modified sol-gel method using Titanium tetra iso propoxide and nickel nitrate as precursors and 2-propanol as a solvent. X-ray diffraction studies show that the as prepared and annealed products show anatase structure with average particle sizes running between of 8 and 16 nm. FTIR results demonstrate the presence of strong chemical bonding at the interface of TiO2 nanoparticles. The optical properties of bare and doped samples were carried out using UV-DRS and photoluminescence measurements. The surface morphology and the element constitution of the nickel doped TiO2 nanoparticles were studied by scanning electron microscope attached with energy dispersive X-ray spectrometer arrangement. The non linear optical properties of the products were confirmed by Kurtz second harmonic generation (SHG) test and the output power generated by the nanoparticle was compared with that of potassium di hydrogen phosphate (KDP).

  18. Preparation of nanoporous titania spherical nanoparticles

    NASA Astrophysics Data System (ADS)

    Shiba, Kota; Sato, Soh; Matsushita, Takayuki; Ogawa, Makoto

    2013-03-01

    Preparation of nanoporous titania particles from well-defined titania-octadecylamine (titania-ODA) hybrid spherical particles with 450 nm in size, which were prepared by the method reported previously (Chem. Commun., 2009, pp. 6851-6853 [39]; RSC Adv., 2012, vol. 2, pp. 1343-1349 [40]), was studied. ODA was removed by solvent extraction with acidic ethanol to obtain nanoporous titania particles and subsequent calcination led to the formation of nanoporous titania particles with the nanopore size ranging from 2 to 4 nm depending on the calcination temperature. The as-synthesized titania was amorphous and was transformed into anatase (at around 300 °C) and rutile (at around 600 °C) by the heat treatment. The phase transition behavior was discussed in comparison with that of as-synthesized titania-ODA particles without ODA removal. Spherical particles of titania-ODA hybrids with 70 nm in size were also transformed into nanoporous titania particles composed of anatase crystallites by the washing and calcination at 500 °C for 1 h.

  19. Ag doped hollow TiO2 nanoparticles as an effective green fungicide against Fusarium solani and Venturia inaequalis phytopathogens

    NASA Astrophysics Data System (ADS)

    Sankar Boxi, Siddhartha; Mukherjee, Khushi; Paria, Santanu

    2016-02-01

    Chemical-based pesticides are widely used in agriculture to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumor, cancer) and environmental problems. Therefore nanoparticle-based green pesticides have become of special importance in recent years. The antifungal activities of pure and Ag doped (solid and hollow) TiO2 nanoparticles are studied against two potent phytopathogens, Fusarium solani (which causes Fusarium wilt disease in potato, tomato, etc) and Venturia inaequalis (which causes apple scab disease) and it is found that hollow nanoparticles are more effective than the other two. The antifungal activities of the nanoparticles were further enhanced against these two phytopathogens under visible light exposure. The fungicidal effect of the nanoparticles depends on different parameters, such as particle concentration and the intensity of visible light. The minimum inhibitory dose of the nanoparticles for V. inaequalis and F. solani are 0.75 and 0.43 mg/plate. The presence of Ag as a dopant helps in the formation of stable Ag-S and disulfide bonds (R-S-S-R) in cellular protein, which leads to cell damage. During photocatalysis generated •OH radicals loosen the cell wall structure and this finally leads to cell death. The mechanisms of the fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses and field emission electron microscopy. Apart from the fungicidal effect, at a very low dose (0.015 mg/plate) the nanoparticles are successful in arresting production of toxic napthoquinone pigment for F. solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective in protecting potatoes affected by F. solani or other fungi from spoiling.

  20. Ag doped hollow TiO2 nanoparticles as an effective green fungicide against Fusarium solani and Venturia inaequalis phytopathogens.

    PubMed

    Boxi, Siddhartha Sankar; Mukherjee, Khushi; Paria, Santanu

    2016-02-26

    Chemical-based pesticides are widely used in agriculture to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumor, cancer) and environmental problems. Therefore nanoparticle-based green pesticides have become of special importance in recent years. The antifungal activities of pure and Ag doped (solid and hollow) TiO2 nanoparticles are studied against two potent phytopathogens, Fusarium solani (which causes Fusarium wilt disease in potato, tomato, etc) and Venturia inaequalis (which causes apple scab disease) and it is found that hollow nanoparticles are more effective than the other two. The antifungal activities of the nanoparticles were further enhanced against these two phytopathogens under visible light exposure. The fungicidal effect of the nanoparticles depends on different parameters, such as particle concentration and the intensity of visible light. The minimum inhibitory dose of the nanoparticles for V. inaequalis and F. solani are 0.75 and 0.43 mg/plate. The presence of Ag as a dopant helps in the formation of stable Ag-S and disulfide bonds (R-S-S-R) in cellular protein, which leads to cell damage. During photocatalysis generated (•)OH radicals loosen the cell wall structure and this finally leads to cell death. The mechanisms of the fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses and field emission electron microscopy. Apart from the fungicidal effect, at a very low dose (0.015 mg/plate) the nanoparticles are successful in arresting production of toxic napthoquinone pigment for F. solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective in protecting potatoes affected by F. solani or other fungi from spoiling. PMID:26808118

  1. Ag doped hollow TiO2 nanoparticles as an effective green fungicide against Fusarium solani and Venturia inaequalis phytopathogens.

    PubMed

    Boxi, Siddhartha Sankar; Mukherjee, Khushi; Paria, Santanu

    2016-02-26

    Chemical-based pesticides are widely used in agriculture to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumor, cancer) and environmental problems. Therefore nanoparticle-based green pesticides have become of special importance in recent years. The antifungal activities of pure and Ag doped (solid and hollow) TiO2 nanoparticles are studied against two potent phytopathogens, Fusarium solani (which causes Fusarium wilt disease in potato, tomato, etc) and Venturia inaequalis (which causes apple scab disease) and it is found that hollow nanoparticles are more effective than the other two. The antifungal activities of the nanoparticles were further enhanced against these two phytopathogens under visible light exposure. The fungicidal effect of the nanoparticles depends on different parameters, such as particle concentration and the intensity of visible light. The minimum inhibitory dose of the nanoparticles for V. inaequalis and F. solani are 0.75 and 0.43 mg/plate. The presence of Ag as a dopant helps in the formation of stable Ag-S and disulfide bonds (R-S-S-R) in cellular protein, which leads to cell damage. During photocatalysis generated (•)OH radicals loosen the cell wall structure and this finally leads to cell death. The mechanisms of the fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses and field emission electron microscopy. Apart from the fungicidal effect, at a very low dose (0.015 mg/plate) the nanoparticles are successful in arresting production of toxic napthoquinone pigment for F. solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective in protecting potatoes affected by F. solani or other fungi from spoiling.

  2. Indomethacin-loaded poly(butylcyanoacrylate) nanoparticles: preparation and characterization.

    PubMed

    Liu, Haiyan; Chen, Jinchun

    2009-01-01

    This paper describes a method to prepare indomethacin-loaded poly(butylcyanoacrylate) (PBCA) nanoparticles based on the anionic polymerization procedure, often used in the synthesis of poly(alkylcyanoacrylate) (PACA) nanoparticles for drug delivery. A detailed investigation into the capability of the polymeric nanoparticles to load this drug is discussed, along with the effect of the technique parameters on characteristics of the nanoparticles. The results indicated that indomethacin-loaded PBCA nanoparticles showed a particle size distribution that could be successfully exploited for the formulation of colloidal pharmaceutical systems. The particles were predominantly less than 200 nm in size with a negative charge, and rather stable when pH was adjusted to neutral. In addition, X-ray diffraction experiments revealed that the drug would be molecularly dispersed in the polymers in an amorphous state and crystalline with very small size. In vitro drug release revealed that indomethacin incorporation and/or adsorption led to a rapid drug release followed by a slower release in biological phosphate buffer and that the release rate decreased with increasing indomethacin content in the particle.

  3. Preparation of platinum nanoparticles in liquids by laser ablation method