• Title, Summary, Keyword: Ag nanoparticles

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Synthesis of Ni-Ag Core-shell Nanoparticles by Polyol process and Microemulsion Process

  • Nguyen, Ngoc Anh Thu;Park, Joseph G.;Kim, Sang-Hern
    • Bulletin of the Korean Chemical Society
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    • v.34 no.10
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    • pp.2865-2870
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    • 2013
  • Ni-Ag core-shell nanoparticles were synthesized by polyol process and microemulsion technique successfully. In the polyol process, a chemical reduction method for preparing highly dispersed pure nickel and Ag shell formation have been reported. The approach involved the control of reaction temperature and reaction time in presence of organic solvent (ethylene glycol) as a reducing agent for Ag cation with poly(vinyl-pyrrolidone) (PVP. Mw = 40000) as a capping agent. In microemulsion method, the emulsion was prepared by water/cetyltrimetylammonium bromide (CTAB)/cyclohexane. The size of microemulsion droplet was determined by the molar ratio of water to surfactant (${\omega}_o$). The core-shell formation along with the change in structural phase and stability against oxidation at high temperature heat treatments of nanoparticles were investigated by X-ray diffraction and TEM analysis. Under optimum conditions the polyol process gives the Ni-Ag core-shell structures with 13 nm Ni core covered with 3 nm Ag shell, while the microemulsion method gives Ni core diameter of 8 nm with Ag shell of thickness 6 nm. The synthesized Ni-Ag core-shell nanoparticles were stable against oxidation up to $300^{\circ}C$.

Synthesis of Cysteine Capped Silver Nanoparticles by Electrochemically Active Biofilm and their Antibacterial Activities

  • Khan, Mohammad Mansoob;Kalathil, Shafeer;Lee, Jin-Tae;Cho, Moo-Hwan
    • Bulletin of the Korean Chemical Society
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    • v.33 no.8
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    • pp.2592-2596
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    • 2012
  • Cysteine capped silver nanoparticles (Cys-AgNPs) have been synthesized by employing electrochemically active biofilm (EAB), $AgNO_3$ as precursor and sodium acetate as electron donor in aqueous solution at $30^{\circ}C$. Cys-AgNPs of 5-10 nm were synthesized and characterized by UV-Vis, FT-IR, XRD and TEM. Capping of the silver nanoparticles with cysteine provides stability to nanoparticles by a thiolate bond between the amino acid and the nanoparticle surface and hydrogen bonding among the Cys-AgNPs. In addition, the antibacterial effects of as-synthesized Cys-AgNPs have been tested against two pathogenic bacteria Escherichia coli (O157:H7) and Pseudomonas aeruginosa (PAO1). The results demonstrate that the as-synthesized Cys-AgNPs can proficiently inhibit the growth and multiplication of E. coli and P. aeruginosa.

Controllable Biogenic Synthesis of Intracellular Silver/Silver Chloride Nanoparticles by Meyerozyma guilliermondii KX008616

  • Alamri, Saad A.M.;Hashem, Mohamed;Nafady, Nivien A.;Sayed, Mahmoud A.;Alshehri, Ali M.;El-Shaboury, Gamal A.
    • Journal of Microbiology and Biotechnology
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    • v.28 no.6
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    • pp.917-930
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    • 2018
  • Intracellular synthesis of silver/silver chloride nanoparticles (Ag/AgCl-NPs) using Meyerozyma guilliermondii KX008616 is reported under aerobic and anaerobic conditions for the first time. The biogenic synthesis of Ag-NP types has been proposed as an easy and cost-effective alternative for various biomedical applications. The interaction of nanoparticles with ethanol production was mentioned. The purified biogenic Ag/AgCl-nanoparticles were characterized by different spectroscopic and microscopic approaches. The purified nanoparticles exhibited a surface plasmon resonance band at 419 and 415 nm, confirming the formation of Ag/AgCl-NPs under aerobic and anaerobic conditions, respectively. The planes of the cubic crystalline phase of the Ag/AgCl-NPs were confirmed by X-ray diffraction. Fourier-transform infrared spectra showed the interactions between the yeast cell constituents and silver ions to form the biogenic Ag/AgCl-NPs. The intracellular Ag/AgCl-NPs synthesized under aerobic condition were homogenous and spherical in shape, with an approximate particle size of 2.5-30nm as denoted by the transmission electron microscopy (TEM). The reaction mixture was optimized by varying reaction parameters, including temperature and pH. Analysis of ultrathin sections of yeast cells by TEM indicated that the biogenic nanoparticles were formed as clusters, known as nanoaggregates, in the cytoplasm or in the inner and outer regions of the cell wall. The study recommends using the biomass of yeast that is used in industrial or fermentation purposes to produce Ag/AgCl-NPs as associated by-products to maximize benefit and to reduce the production cost.

Poly(ethylenimine)-Stabilized Hollow Gold-Silver Bimetallic Nanoparticles: Fabrication and Catalytic Application

  • Shin, Kuan-Soo;Kim, Ji-Hoon;Kim, In-Hyun;Kim, Kwan
    • Bulletin of the Korean Chemical Society
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    • v.33 no.3
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    • pp.906-910
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    • 2012
  • Hollow gold-silver bimetallic nanoparticles (AuAg-HNPs) have been synthesized and their optical and structural properties were characterized. Initially Ag nanoparticles (Ag-NPs) were prepared using poly(ethylenimine) (PEI) as a reducing and a stabilizing agent simultaneously. AuAg-HNPs could then be synthesized via galvanic replacement reaction in a PEI aqueous solution by reacting sacrificial Ag template with a precursor compound of Au, i.e., $HAuCl_4$. Due to the presence of abundant amine functional groups in PEI, which could act as the dissolving ligand for AgCl, the precipitation problem of $Ag^+$ in the presence of Cl from $HAuCl_4$ salt was avoided. On this basis, the relatively high concentrations of $HAuCl_4$ and PEI-stabilized Ag nanoparticles could be used for the fabrication of AuAg-HNPs. Because of their increased surface areas and reduced densities, the AuAg-HNPs were expected and confirmed to outperform their solid counterparts in applications such as catalysis for the reduction of 4-nitrophenol in the presence of $NaBH_4$.

Localized Surface Plasmon Resonance Coupling in Self-Assembled Ag Nanoparticles by Using 3-Dimensional FDTD Simulation (3차원 FDTD Simulation을 이용한 자기조립된 Ag 나노입자의 국소표면플라즈몬공명 상호작용 현상 연구)

  • Lee, Kyung-Min;Yoon, Soon-Gil;Jeong, Jong-Ryul
    • Korean Journal of Materials Research
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    • v.24 no.8
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    • pp.417-422
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    • 2014
  • In this study, we investigated localized surface plasmon resonance and the related coupling phenomena with respect to various geometric parameters of Ag nanoparticles, including the size and inter-particle distance. The plasmon resonances of Ag nanoparticles were studied using three-dimensional finite difference time domain(FDTD) calculations. From the FDTD calculations, we discovered the existence of a symmetric and an anti-symmetric plasmon coupling modes in the coupled Ag nanoparticles. The dependence of the resonance wavelength with respect to the inter-particle distance was also investigated, revealing that the anti-symmetric mode is more closely correlated with the inter-particle distance of the Ag nanoparticles than the symmetric mode. We also found that higher order resonance modes are appeared in the extinction spectrum for closely spaced Ag nanoparticles. Plasmon resonance calculations for the Ag particles coated with a $SiO_2$ layer showed enhanced plasmon coupling due to the strengthened plasmon resonance, suggesting that the inter-particle distance of the Ag nanoparticles can be estimated by measuring the transmission and absorption spectra with the plasmon resonance of symmetric and anti-symmetric localized surface plasmons.

Fabrication of Poly(ethylene oxide)/Ag Nanoparticles/p-benzoquinone Composite Membrane Using AgNO3 Precursor for Olefin/Paraffin Separation (올레핀/파라핀 분리용 AgNO3 전구체를 활용한 poly(ethylene oxide)/Ag nanoparticles/p-benzoquinone 복합체 분리막 제조)

  • kim, Minsu;Kang, Sang Wook
    • Membrane Journal
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    • v.28 no.4
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    • pp.260-264
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    • 2018
  • Poly (ethylene oxide) (PEO)/Ag nanoparticles (AgNPs)(precursor : $AgBF_4$)/p-benzoquinone (p-BQ) composite membrane was prepared for olefin/paraffin separation. As a result, the performance of composite membrane was observed to be maintained at selectivity of 10 and permeance of 15 GPU up to 100 hours. The performance of the membrane was maintained for 100 hours was attributable to that Ag ions could be converted into stable Ag NPs by addition of p-BQ. Furthermore, the surface was partially polarized by the electron acceptor p-BQ, resulting in the formation of olefin carrier. In this study, since the cost of $AgBF_4$ used as a precursor of Ag NPs was relatively higher, $AgNO_3$ was utilized. As a result, it was confirmed that $AgNO_3$ couldn't show the stable formation of nanoparticle, resulting in the poor separation performance.

Biological Synthesis of Au Core-Ag Shell Bimetallic Nanoparticles Using Magnolia kobus Leaf Extract (목련잎 추출액을 이용한 Au Core-Ag Shell 합금 나노입자의 생물학적 합성)

  • Song, Jae Yong;Kim, Beom Soo
    • Korean Chemical Engineering Research
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    • v.48 no.1
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    • pp.98-102
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    • 2010
  • Magnolia kobus leaf extract was used for the synthesis of bimetallic Au core-Ag shell nanoparticles. Gold seeds and silver shells were formed by first treating aqueous solution of $HAuCl_4$ and then $AgNO_3$ with the plant leaf extract as reducing agent. UV-visible spectroscopy was monitored as a function of reaction time to follow the formation of bimetallic nanoparticles. The synthesized bimetallic nanoparticles were characterized with transmission electron microscopy(TEM), energy dispersive X-ray spectroscopy(EDS), and X-ray photoelectron spectroscopy(XPS). TEM images showed that the bimetallic nanoparticles are a mixture of plate(triangles, pentagons, and hexagons) and spherical structures. The atomic Ag contents of the bimetallic Au/Ag nanoparticles determined from EDS and XPS analysis were 34 and 65 wt%, respectively, suggesting the formation of bimetallic Au core-Ag shell nanostructure. This core-shell type nanostructure is expected to have potential for application in surface enhanced Raman spectroscopy and in the sensitive detection of biomolecules.

Synthesis and Optoelectronic Characteristics of Ag2Se Nanoparticle for NIR Sensor Application (근적외선 센서를 위한 Ag2Se 나노 입자 합성 및 광전기적 특성)

  • Jang, Jaewon
    • Journal of Sensor Science and Technology
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    • v.28 no.4
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    • pp.266-269
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    • 2019
  • In this study, $Ag_2Se$ nanoparticles were synthesized by employing the colloidal method. The synthesized $Ag_2Se$ nanocrystals were spherical in shape with a diameter of approximately 4 nm and had high crystallinity. These attributes of $Ag_2Se$ nanocrystals were determined through images obtained from a high resolution transmission electron microscope. Thin films comprising the synthesized $Ag_2Se$ nanoparticles had an optical band gap of 1.5 eV. Furthermore, fabricated NIR sensors comprising $Ag_2Se$ nanoparticles exhibited a high detectivity of $5.5{\times}10^9$ Jones (above $1{\times}10^9$) at room temperature, leading to low power consumption

Nano-sized Effect on the Magnetic Properties of Ag Clusters

  • Jo, Y.;Jung, M.H.;Kyum, M.C.;Park, K.H.;Kim, Y.N.
    • Journal of Magnetics
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    • v.11 no.4
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    • pp.160-163
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    • 2006
  • We have prepared crystalline Ag nanoparticles with an average size of 4 nm in diameter by using an inductively coupled plasma reactor equipped with the liquid nitrogen cooling system. Our magnetic data show that the nano-sized effect of Ag nanoparticles on the magnetic properties is ferromagnetic, instead of a diamagnetic component of the Ag bulk and a superparamagnetic component of magnetic nanoparticles. We have also studied the magnetic properties of Ag-Cu nanocomposites with an opposite concentration profile between surface and core. These comparisons indicate that the ferromagnetic component strongly depends on the surface of Ag nanoparticles, while the paramagnetic component is strongly affected by the outer oxide layer, with the background of a diamagnetic component from the core of Ag.

Preparation of Polyurethane Nanofiber Mats Containing Silver Nanoparticles (은 나노입자를 함유한 폴리우레탄 나노섬유 매트의 제조)

  • Jin Wen-Ji;Jeon Hyun-Jeong;Hong Ji-Hye;Jeong Eun-Hwan;Youk Ji-Ho
    • Textile Science and Engineering
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    • v.43 no.1
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    • pp.1-6
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    • 2006
  • Poly(urethane)(PU) nanofibers containing silver nanoparticles were prepared via a simple one-step method. PU was dissolved in DMAc/THF(7/3 w/w) with a small amount of $AgNO_3.Ag^+$ ions in the PU solution were reduced by DMAc into Ag nanoparticles, which was confirmed by UV-vis spectroscopy and TEM analysis. DMAc was used as a solvent for PU as well as a reducing agent for the Ag+ ions. The resulting solutions were directly electrospun into PU nanofibers. The Ag nanoparticles were all sphere shaped and evenly distributed in the PU nanofibers. The average sizes of Ag nanoparticles in PU nanofibers electro spun with 0.2 and 0.5 wt% $AgNO_3$ were 3.6 and 4.0 nm, respectively.