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Sample records for ag nanoparticle arrays

  1. Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties

    NASA Astrophysics Data System (ADS)

    Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

    2015-03-01

    Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

  2. An ultrasensitive, uniform and large-area surface-enhanced Raman scattering substrate based on Ag or Ag/Au nanoparticles decorated Si nanocone arrays

    NASA Astrophysics Data System (ADS)

    Zhang, P. P.; Gao, J.; Sun, X. H.

    2015-01-01

    Large-area and highly ordered Si nanocone arrays decorated with Ag or Au/Ag nanoparticles have been fabricated via a mask-free lithography with reaction ion etching, followed by metal deposition process. Ultrasensitive surface enhanced Raman scattering signals with an enhancement factor of 1012 were achieved even at the concentration of the Rhodamine 6G as low as 10-15 M. The surface-enhanced Raman spectroscopy (SERS) substrate was also applied on the detection of Sudan I dye and the Raman signals were substantially enhanced as well. The stability of the SERS substrate can be significantly improved by covering Ag nanoparticles with Au thin layer, which maintain a high SERS performance even after one month storage. This nanofabrication process appears to be a feasible approach to prepare uniform and reproducible SERS-active substrates with high sensitivity and stability for practical SERS applications.

  3. Recyclable three-dimensional Ag nanoparticle-decorated TiO2 nanorod arrays for surface-enhanced Raman scattering.

    PubMed

    Fang, Hui; Zhang, Chang Xing; Liu, Luo; Zhao, Yong Mei; Xu, Hai Jun

    2015-02-15

    Multifunctional Ag nanoparticle-decorated TiO2 nanorod arrays were prepared by two simple processes. TiO2 nanorod arrays were first fabricated by the hydrothermal route and then Ag nanoparticles were decorated on the nanorods by the chemical reduction impregnation method. Three-dimensional Ag/TiO2 arrays were used as an active substrate for surface-enhanced Raman scattering (SERS). The results show that the detection limit for rhodamine 6G (R6G) was as low as 10(-7)M and the Raman enhancement factor was as large as 10(5). After calibrating the Raman peak intensities of R6G, it could be quantitatively detected. More importantly, the photocatalytic activity of TiO2 provides a self-cleaning capability to the SERS substrate, which can be recycled and used to degrade many Ag surface adsorbates such as R6G, methyl orange, Congo red, and methylene blue after exposure to visible light. The absorbed small molecules can all be rapidly and completely removed from the SERS substrate, which has been successfully reused four times without a decrease in accuracy or sensitivity. Our results reveal that the unique recyclable property not only paves a new way to solve the single-use problem of traditional SERS substrates but also provides more SERS platforms for multiple detections of other organic molecular species.

  4. Ag Nanoparticle-Grafted PAN-Nanohump Array Films with 3D High-Density Hot Spots as Flexible and Reliable SERS Substrates.

    PubMed

    Li, Zhongbo; Meng, Guowen; Huang, Qing; Hu, Xiaoye; He, Xuan; Tang, Haibin; Wang, Zhiwei; Li, Fadi

    2015-10-28

    A facile fabrication approach of large-scale flexible films is reported, with one surface side consisting of Ag-nanoparticle (Ag-NP) decorated polyacrylonitrile (PAN) nanohump (denoted as Ag-NPs@PAN-nanohump) arrays. This is achieved via molding PAN films with ordered nanohump arrays on one side and then sputtering much smaller Ag-NPs onto each of the PAN-nanohumps. Surface-enhanced Raman scattering (SERS) activity of the Ag-NPs@PAN-nanohump array films can be improved by curving the flexible PAN film with ordered nanohump arrays during the Ag-sputtering process to increase the density of the Ag-NPs on the sidewalls of the PAN-nanohumps. More 3D hot spots are thus achieved on a large-scale. The Ag-NPs@PAN-nanohump array films show high SERS activity with good Raman signal reproducibility for Rhodamine 6G probe molecules. To trial their practical application, the Ag-NPs@PAN-nanohump array films are employed as SERS substrates for trace detection of trinitrotoluene and a congener of polychlorinated biphenyls. A lower detection limit of 10(-12) m and 10(-5) m can be achieved, respectively. Furthermore, the flexible Ag-NPs@PAN-nanohump array films can also be utilized as swabs to probe traces of methyl parathion on the surface of fruits such as apples. The as-fabricated SERS substrates therefore have promising potential for applications in rapid safety inspection and environmental protection.

  5. Ag nanoparticle-filled TiO2 nanotube arrays prepared by anodization and electrophoretic deposition for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Wei, Xing; Sugri Nbelayim, Pascal; Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

    2017-03-01

    A layer of TiO2 nanotube (TNT) arrays with a thickness of 13 μm is synthesized by a two-step anodic oxidation from Ti metal foil. Surface charged Ag nanoparticles (NPs) are prepared by chemical reduction. After a pretreatment of the TNT arrays by acetone vapor, Ag NP filled TNT arrays can be achieved by electrophoretic deposition (EPD). Effects of the applied voltage during EPD such as DC–AC difference, frequency and waveform are investigated by quantitative analysis using atomic absorption spectroscopy. The results show that the best EPD condition is using DC 2 V + AC 4 V and a square wave of 1 Hz as the applied voltage. Back illuminated dye-sensitized solar cells are fabricated from TNT arrays with and without Ag NPs. The efficiency increased from 3.70% to 5.01% by the deposition of Ag NPs.

  6. Ag nanoparticle-filled TiO2 nanotube arrays prepared by anodization and electrophoretic deposition for dye-sensitized solar cells.

    PubMed

    Wei, Xing; Nbelayim, Pascal Sugri; Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

    2017-03-01

    A layer of TiO2 nanotube (TNT) arrays with a thickness of 13 μm is synthesized by a two-step anodic oxidation from Ti metal foil. Surface charged Ag nanoparticles (NPs) are prepared by chemical reduction. After a pretreatment of the TNT arrays by acetone vapor, Ag NP filled TNT arrays can be achieved by electrophoretic deposition (EPD). Effects of the applied voltage during EPD such as DC-AC difference, frequency and waveform are investigated by quantitative analysis using atomic absorption spectroscopy. The results show that the best EPD condition is using DC 2 V + AC 4 V and a square wave of 1 Hz as the applied voltage. Back illuminated dye-sensitized solar cells are fabricated from TNT arrays with and without Ag NPs. The efficiency increased from 3.70% to 5.01% by the deposition of Ag NPs.

  7. 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

  8. 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.

  9. Generation of Localized Surface Plasmon Resonance Using Hybrid Au–Ag Nanoparticle Arrays as a Sensor of Polychlorinated Biphenyls Detection

    PubMed Central

    Liu, Jing; Cai, Haoyuan; Chen, Chaoyang; Yang, Guangsong; Yang, Cheng-Fu

    2016-01-01

    In this study, the hybrid Au–Ag hexagonal lattice of triangular and square lattice of quadrate periodic nanoparticle arrays (PNAs) were designed to investigate their extinction spectra of the localized surface plasmon resonances (LSPRs). First, their simulating extinction spectra were calculated by discrete dipole approximation (DDA) numerical method by changing the media refractive index. Simulation results showed that as the media refractive index was changed from 1.0 to 1.2, the maximum peak intensity of LSPRs spectra had no apparent change and the wavelength to reveal the maximum peak intensity of LSPRs spectra was shifted lower value. Polystyrene (PS) nanospheres with two differently arranged structures were used as the templates to deposit the hybrid Au–Ag hexagonal lattice of triangular and square lattice of quadrate periodic PNAs by evaporation method. The hybrid Au–Ag hexagonal lattice of triangular and square lattice of quadrate PNAs were grown on single crystal silicon (c-Si) substrates, and their measured extinction spectra were compared with the calculated results. Finally, the fabricated hexagonal lattices of triangular PNAs were investigated as a sensor of polychlorinated biphenyl solution (PCB-77) by observing the wavelength to reveal the maximum extinction efficiency (λmax). We show that the adhesion of β-cyclodextrins (SH-β-CD) on the hybrid Au–Ag hexagonal lattice of triangular PNAs could be used to increase the variation of λmax. We also demonstrate that the adhesion of SH-β-CD increases the sensitivity and detection effect of PCB-77 in hexagonal lattice of triangular PNAs. PMID:27527188

  10. Ag Nanoparticles Located on Three-Dimensional Pine Tree-Like Hierarchical TiO2 Nanotube Array Films as High-Efficiency Plasmonic Photocatalysts

    NASA Astrophysics Data System (ADS)

    Xu, Jinxia; Wang, Zhenhuan; Li, Wenqing; Zhang, Xingang; He, Dong; Xiao, Xiangheng

    2017-01-01

    High specific surface area three-dimensional pine tree-like hierarchical TiO2 nanotube array films loaded with Ag nanoparticles were successfully prepared by one-step hydrothermal reaction combining with simple and feasible magnetron sputtering. The composite Ag/TiO2-branched nanotube arrays show outstanding photocatalytic property, which is attributed to the boost of plasmonic enhancement carrier generation and separation, higher specific surface area, higher organic pollutant absorption, faster charge transport, and superior light-harvesting efficiency for efficient charge collection. The work provides a cost-effective and flexible pathway to develop high-performance photocatalyst or optoelectronic devices.

  11. Plasmon enhanced CdS-quantum dot sensitized solar cell using ZnO nanorods array deposited with Ag nanoparticles as photoanode

    NASA Astrophysics Data System (ADS)

    Eskandari, M.; Ahmadi, V.; Yousefi rad, M.; Kohnehpoushi, S.

    2015-04-01

    CdS-quantum dot sensitized solar cell using ZnO nanorods (ZnO NRs) array deposited with Ag nanoparticles (Ag NPs) as photoanode was fabricated. Light absorption effect of Ag NPs on improvement of the cell performance was investigated. Performance improvement of metal nanoparticles (MNPs) was controlled by the structure design and architecture. Different decorations and densities of Ag NPs were utilized on the photoanode. Results showed that using 5% Ag NPs in the photoanode results in the increased efficiency, fill factor, and circuit current density from 0.28% to 0.60%, 0.22 to 0.29, and 2.18 mA/cm2 to 3.25 mA/cm2, respectively. Also, incident photon-to-current efficiencies (IPCE) results showed that cell performance improvement is related to enhanced absorption in the photoanode, which is because of the surface plasmonic resonance and light scattering of Ag NPs in the photoanode. Measurements of electrochemical impedance spectroscopy revealed that hole transfer kinetics increases with introduction of Ag NPs into photoanode. Also, it is shown that chemical capacitance increases with introduction of Ag NPs. Such increase can be attributed to the surface palsmonic resonance of Ag NPs which leads to absorption of more light in the photoanode and generation of more photoelectron in the photoanode.

  12. Ag Nanoparticle-Functionalized Open-Ended Freestanding TiO₂ Nanotube Arrays with a Scattering Layer for Improved Energy Conversion Efficiency in Dye-Sensitized Solar Cells.

    PubMed

    Rho, Won-Yeop; Chun, Myeung-Hwan; Kim, Ho-Sub; Kim, Hyung-Mo; Suh, Jung Sang; Jun, Bong-Hyun

    2016-06-15

    Dye-sensitized solar cells (DSSCs) were fabricated using open-ended freestanding TiO₂ nanotube arrays functionalized with Ag nanoparticles (NPs) in the channel to create a plasmonic effect, and then coated with large TiO₂ NPs to create a scattering effect in order to improve energy conversion efficiency. Compared to closed-ended freestanding TiO₂ nanotube array-based DSSCs without Ag or large TiO₂ NPs, the energy conversion efficiency of closed-ended DSSCs improved by 9.21% (actual efficiency, from 5.86% to 6.40%) with Ag NPs, 6.48% (actual efficiency, from 5.86% to 6.24%) with TiO₂ NPs, and 14.50% (actual efficiency, from 5.86% to 6.71%) with both Ag NPs and TiO₂ NPs. By introducing Ag NPs and/or large TiO₂ NPs to open-ended freestanding TiO₂ nanotube array-based DSSCs, the energy conversion efficiency was improved by 9.15% (actual efficiency, from 6.12% to 6.68%) with Ag NPs and 8.17% (actual efficiency, from 6.12% to 6.62%) with TiO₂ NPs, and by 15.20% (actual efficiency, from 6.12% to 7.05%) with both Ag NPs and TiO₂ NPs. Moreover, compared to closed-ended freestanding TiO₂ nanotube arrays, the energy conversion efficiency of open-ended freestanding TiO₂ nanotube arrays increased from 6.71% to 7.05%. We demonstrate that each component-Ag NPs, TiO₂ NPs, and open-ended freestanding TiO₂ nanotube arrays-enhanced the energy conversion efficiency, and the use of a combination of all components in DSSCs resulted in the highest energy conversion efficiency.

  13. Ag-nanoparticle-decorated Ge nanocap arrays protruding from porous anodic aluminum oxide as sensitive and reproducible surface-enhanced Raman scattering substrates.

    PubMed

    Liu, Jing; Meng, Guowen; Li, Xiangdong; Huang, Zhulin

    2014-11-25

    We report on the fabrication of Ag nanoparticle (Ag NP) decorated germanium (Ge) nanocap (Ag-NPs@Ge-nanocap) arrays protruding from highly ordered porous anodic aluminum oxide (AAO) template as highly sensitive and uniform surface-enhanced Raman scattering (SERS) substrates. The hybrid SERS substrates are fabricated via a combinatorial process of AAO template-assisted growth of Ge nanotubes with each tube having a hemispherical nanocap on the AAO pore bottom, wet chemical etching of the remaining aluminum and the AAO barrier layer to expose the Ge nanocaps, and sputtering Ag NPs on the Ge nanocap arrays. Because sufficient SERS "hot spots" are created from the electromagnetic coupling among the Ag NPs on the Ge nanocap and the highly ordered Ge nanocap arrays also have semiconducting chemical supporting enhancement, the hybrid SERS substrates have high SERS sensitivity and good signal reproducibility. Using the hybrid SERS substrates, Rhodamine 6G with a concentration down to 10(-11) M is identified, and one congener of highly toxic polychlorinated biphenyls with a concentration as low as 10(-6) M is also recognized, showing great potential for SERS-based rapid detection of organic pollutants in the environment.

  14. Effects of morphology, diameter and periodic distance of the Ag nanoparticle periodic arrays on the enhancement of the plasmonic field absorption in the CdSe quantum dots

    NASA Astrophysics Data System (ADS)

    Kohnehpoushi, Saman; Eskandari, Mehdi; Ahmadi, Vahid; Yousefirad, Mansooreh; Nabavi, Elham

    2016-09-01

    In this work, the numerical calculations of plasmonic field absorption of Ag nanoparticles (Ag NPs) periodic arrays in the CdSe quantum dot (QD) film are investigated by the three-dimensional finite difference time domain (FDTD). Diameter (D), periodic distance (P), and morphology effects of Ag NPs are investigated on the improvement of the plasmonic field absorption in CdSe QD film. Results show that plasmonic field absorption in CdSe QD film is enhanced with reduction of D of Ag NPs until 5 nm and reduces thereafter. It is observed that with raising D of Ag NPs, optimum plasmonic field absorption in CdSe QD film is shifted toward the higher P. Moreover, with varying morphology of Ag NPs from spherical to cylindrical, cubic, ringing and pyramid, the plasmonic field absorption is considerably enhanced in CdSe QD film and position of quadrupole plasmon mode (QPPM) is shifted toward further wavelength. For cylindrical Ag NPs, the QPPM intensity increased with raising height (H) until 15 nm and reduces thereafter.

  15. Numerical calculation of plasmonic field absorption enhancement in CdSe-quantum dot sensitized ZnO nanorods by Ag nanoparticle periodic arrays

    NASA Astrophysics Data System (ADS)

    Kohnehpoushi, Saman; Eskandari, Mehdi; Nejand, Bahram Abdollahi; Ahmadi, Vahid

    2016-12-01

    Plasmonic field absorption enhancement (PFAE) of Ag nanoparticles (Ag NPs) periodic arrays in CdSe-quantum dot (QD) sensitized ZnO nanorods was numerically investigated by the three-dimensional finite difference time domain (FDTD). The Ag NPs with spherical morphology were found to have an optimum PFAE compared to other Ag NP morphologies such as cubic and pyramidal. The results also showed that PFAE intensity in CdSe-QD-sensitized ZnO nanorods is increased with the reduction of Ag NP diameter until 10 nm and decreases thereafter. Moreover, the optimum density of spherical Ag NPs for optimum PFAE was observed as 20%. PFAE in CdSe-QD-sensitized ZnO nanorods is improved with increasing space between ZnO nanorods until 180 nm and reduces thereafter. Finally, the results showed that PFAE of Ag NPs for the high distance between ZnO nanorods is dependent on radiation angle; while for the low distance between ZnO nanorods it is free of radiation angle.

  16. Enhanced photocatalytic, electrochemical and photoelectrochemical properties of TiO2 nanotubes arrays modified with Cu, AgCu and Bi nanoparticles obtained via radiolytic reduction

    NASA Astrophysics Data System (ADS)

    Nischk, Michał; Mazierski, Paweł; Wei, Zhishun; Siuzdak, Katarzyna; Kouame, Natalie Amoin; Kowalska, Ewa; Remita, Hynd; Zaleska-Medynska, Adriana

    2016-11-01

    TiO2 nanotubes arrays (NTs), obtained via electrochemical anodization of Ti foil, were modified with monometallic (Cu, Bi) and bimetallic (AgCu) nanoparticles. Different amounts of metals' precursors were deposited on the surface of NTs by the spin-coating technique, and the reduction of metals was performed via gamma radiolysis. Surface modification of titania was studied by EDS and XPS analysis. The results show that AgCu nanoparticles exist in a Agcore-Cushell form. Photocatalytic activity was examined under UV irradiation and phenol was used as a model pollutant of water. Over 95% of phenol degradation was achieved after 60 min of irradiation for almost all examined samples, but only slight difference in degradation efficiency (about 3%) between modified and bare NTs was observed. However, the initial phenol degradation rate and TOC removal efficiency was significantly enhanced for the samples modified with 0.31 and 0.63 mol% of Bi as well as for all the samples modified with Cu and AgCu nanoparticles in comparison with bare titania nanotubes. The saturated photocurrent, under the influence of simulated solar light irradiation, for the most active Bi- and AgCu-modified samples, was over two times higher than for pristine NTs. All the examined materials were resistant towards photocorrosion processes that enables their application for long term processes induced by light.

  17. Label free sub-picomole level DNA detection with Ag nanoparticle decorated Au nanotip arrays as surface enhanced Raman spectroscopy platform.

    PubMed

    Lo, Hung-Chun; Hsiung, Hsin-I; Chattopadhyay, Surojit; Han, Hsieh-Cheng; Chen, Chia-Fu; Leu, Jih Perng; Chen, Kuei-Hsien; Chen, Li-Chyong

    2011-01-15

    Label free optical sensing of adenine and thymine oligonucleotides has been achieved at the sub-picomole level using self assembled silver nanoparticles (AgNPs) decorated gold nanotip (AuNT) arrays. The platform consisting of the AuNTs not only aids in efficient bio-immobilization, but also packs AgNPs in a three dimensional high surface area workspace, assisting in surface enhanced Raman scattering (SERS). The use of sub-10 nm AgNPs with optimum inter-particle distance ensures amplification of the chemically specific Raman signals of the adsorbed adenine, thymine, cytosine and guanine molecules in SERS experiments. High temporal stability of the Raman signals ensured reliable and repeatable DNA detection even after three weeks of ambient desk-top conservation. This facile architecture, being three dimensional and non-lithographic, differs from conventional SERS platforms.

  18. Efficiency Enhancement of Quantum Dot Sensitized TiO2/ZnO Nanorod Arrays Solar Cells by Plasmonic Ag Nanoparticles.

    PubMed

    Zhao, Haifeng; Huang, Fei; Hou, Juan; Liu, Zhiyong; Wu, Qiang; Cao, Haibin; Jing, Qun; Peng, Shanglong; Cao, Guozhong

    2016-10-12

    A high efficiency quantum dot sensitized solar cell (QDSC) based on Ag nanoparticles (NPs) decorated TiO2/ZnO nanorod arrays (NAs) photoelectrode has been constructed. The incorporation of Ag NPs to TiO2/ZnO NAs photoelectrode not only increases light harvesting efficiency and facilitates exciton dissociation but also decreases surface charge recombination and prolongs electron lifetime, which collectively contribute to improving the Jsc of the CdS/CdSe QDs cosensitized solar cells. The direct contact of Ag NPs with TiO2 NPs is undergoing Fermi level alignment; thus, the apparent Fermi level is supposed to trigger an upward shift of more negative potential, which results in an increase the Voc of the QDSCs. As a result, the power conversion efficiency of the QDSCs with Ag NPs decorated TiO2/ZnO NAs photoelectrode reached 5.92%, which is about 22% enhancement of the efficiency for the solar cells without Ag NPs (4.80%).

  19. Tailor-made Au@Ag core-shell nanoparticle 2D arrays on protein-coated graphene oxide with assembly enhanced antibacterial activity

    NASA Astrophysics Data System (ADS)

    Wang, Huiqiao; Liu, Jinbin; Wu, Xuan; Tong, Zhonghua; Deng, Zhaoxiang

    2013-05-01

    Water-dispersible two-dimensional (2D) assemblies of Au@Ag core-shell nanoparticles are obtained through a highly selective electroless silver deposition on pre-assembled gold nanoparticles on bovine serum albumin (BSA)-coated graphene oxide (BSA-GO). While neither BSA-GO nor AuNP-decorated BSA-GO shows any antibacterial ability, the silver-coated GO@Au nanosheets (namely GO@Au@Ag) exhibit an enhanced antibacterial activity against Gram-negative Escherichia coli (E. coli) bacteria, superior to unassembled Au@Ag nanoparticles and even ionic Ag. Such an improvement may be attributed to the increased local concentration of silver nanoparticles around a bacterium and a polyvalent interaction with the bacterial surface. In addition, the colloidal stability of this novel nano-antimicrobial against the formation of random nanoparticle aggregates guarantees a minimized activity loss of the Au@Ag nanoparticles. The antibacterial efficacy of GO@Au@Ag is less sensitive to the existence of Cl-, in comparison with silver ions, providing another advantage for wound dressing applications. Our research unambiguously reveals a strong and very specific interaction between the GO@Au@Ag nanoassembly and E. coli, which could be an important clue toward a rational design, synthesis and assembly of innovative and highly active antibacterial nanomaterials.

  20. Ultrasound aided photochemical synthesis of Ag loaded TiO2 nanotube arrays to enhance photocatalytic activity.

    PubMed

    Sun, Lan; Li, Jing; Wang, Chenglin; Li, Sifang; Lai, Yuekun; Chen, Hongbo; Lin, Changjian

    2009-11-15

    This work presents a novel approach for preparing TiO(2) nanotube array photocatalyst loaded with highly dispersed Ag nanoparticles through an ultrasound aided photochemical route. The Ag content loaded on the array was controlled by changing the concentration of AgNO(3) solution. The Ag-TiO(2) nanotube arrays were characterized by SEM, XRD, XPS and UV-vis absorption. The effects of Ag content on the photoelectrochemical (PEC) property and photocatalytic activity of TiO(2) nanotube array electrode were studied. The results showed that Ag loading significantly enhanced the photocurrent and photocatalytic degradation rate of TiO(2) nanotube array under UV-light irradiation. The photocurrent and photocatalytic degradation rate of Ag-TiO(2) nanotube array prepared in 0.006 M AgNO(3) solution were about 1.2 and 3.7 times as that of pure TiO(2) nanotube array, respectively.

  1. Biotemplated magnetic nanoparticle arrays.

    PubMed

    Galloway, Johanna M; Bramble, Jonathan P; Rawlings, Andrea E; Burnell, Gavin; Evans, Stephen D; Staniland, Sarah S

    2012-01-23

    Immobilized biomineralizing protein Mms6 templates the formation of uniform magnetite nanoparticles in situ when selectively patterned onto a surface. Magnetic force microscopy shows that the stable magnetite particles maintain their magnetic orientation at room temperature, and may be exchange coupled. This precision-mixed biomimetic/soft-lithography methodology offers great potential for the future of nanodevice fabrication.

  2. Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction as a highly efficient and stable visible light photocatalyst.

    PubMed

    Liu, Chengbin; Cao, Chenghao; Luo, Xubiao; Luo, Shenglian

    2015-03-21

    A unique Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction (Ag-Ag2O/TiO2 NT) was fabricated by simple electrochemical method. Ag nanoparticles were firstly electrochemically deposited onto the surface of TiO2 NT and then were partly oxidized to Ag2O nanowires while the rest of Ag mother nanoparticles were located at the junctions of Ag2O nanowire network. The Ag-Ag2O/TiO2 NT heterostructure exhibited strong visible-light response, effective separation of photogenerated carriers, and high adsorption capacity. The integration of Ag-Ag2O self-stability structure and p-n heterojunction permitted high and stable photocatalytic activity of Ag-Ag2O/TiO2 NT heterostructure photocatalyst. Under 140-min visible light irradiation, the photocatalytic removal efficiency of both dye acid orange 7 (AO7) and industrial chemical p-nitrophenol (PNP) over Ag-Ag2O/TiO2 NT reached nearly 100% much higher than 17% for AO7 or 13% for PNP over bare TiO2 NT. After 5 successive cycles under 600-min simulated solar light irradiation, Ag-Ag2O/TiO2 NT remained highly stable photocatalytic activity.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Optical scattering from isolated metal nanoparticles and arrays.

    SciTech Connect

    Wurtz, G. A.; Im, J. S.; Gray, S. K.; Wiederrecht, G. P.; Chemistry

    2003-12-25

    Near-field scanning optical microscopy (NSOM) is used to explore the optical scattering from isolated metal nanoparticles (MNPs) and arrays of MNPs. The optical excitation source is an evanescent wave created through total internal reflection of a continuous wave laser beam at the sample-air interface. For optical excitation of isolated Ag and Au MNPs, experimental results show that the scattered light propagates into the far field at an angle of 19{sup o} from the substrate. Finite-difference time-domain (FDTD) calculations are used to study simpler but related metallic nanowire systems under evanescent wave excitation. The FDTD results are found to be similar to the experimental results, indicating the generality of the scattering phenomenon. NSOM characterization of plasmonic arrays that consist of closely spaced Ag MNPs are subsequently reported. Confined optical signals within the array are observed along with a reduction in the far-field scattered signal. Simultaneous collection of the atomic force microscopy signal and near-field signals also shows that the spatial distribution of the near-field is strongly modified in the arrays compared to isolated MNPs. FDTD studies on arrays of nanowires also show large differences from the isolated metal nanoparticle calculations, including a decrease in the forward scattered angle (with chain length) and diminished overall forward scattering.

  9. Optical impedance matching using coupled plasmonic nanoparticle arrays.

    PubMed

    Spinelli, P; Hebbink, M; de Waele, R; Black, L; Lenzmann, F; Polman, A

    2011-04-13

    Silver nanoparticle arrays placed on top of a high-refractive index substrate enhance the coupling of light into the substrate over a broad spectral range. We perform a systematic numerical and experimental study of the light incoupling by arrays of Ag nanoparticle arrays in order to achieve the best impedance matching between light propagating in air and in the substrate. We identify the parameters that determine the incoupling efficiency, including the effect of Fano resonances in the scattering, interparticle coupling, as well as resonance shifts due to variations in the near-field coupling to the substrate and spacer layer. The optimal configuration studied is a square array of 200 nm wide, 125 nm high spheroidal Ag particles, at a pitch of 450 nm on a 50 nm thick Si(3)N(4) spacer layer on a Si substrate. When integrated over the AM1.5 solar spectral range from 300 to 1100 nm, this particle array shows 50% enhanced incoupling compared to a bare Si wafer, 8% higher than a standard interference antireflection coating. Experimental data show that the enhancement occurs mostly in the spectral range near the Si band gap. This study opens new perspectives for antireflection coating applications in optical devices and for light management in Si solar cells.

  10. Construction of Ag/AgCl nanostructures from Ag nanoparticles as high-performance visible-light photocatalysts

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Liu, Dongzhi; Wang, Tianyang; Li, Wei; Hu, Wenping; Zhou, Xueqin

    2016-11-01

    A combined strategy of in situ oxidation and assembly is developed to prepare Ag/AgCl nanospheres and nanocubes from Ag nanoparticles under room temperature. It is a new facile way to fabricate Ag/AgCl with small sizes and defined morphologies. Ag/AgCl nanospheres with an average size of 80 nm were achieved without any surfactants, while Ag/AgCl nanocubes with a mean edge length of 150 nm were obtained by introduction of N-dodecyl- N, N-dimethyl-2-ammonio-acetate. The possible formation mechanism involves the self-assembly of AgCl nanoparticles, Ostwald ripening and photoreduction of Ag+ into Ag0 by the room light. The as-prepared Ag/AgCl nanospheres and nanocubes exhibit excellent photocatalytic activity and stability toward degradation of organic pollutants under visible-light irradiation. It is demonstrated that Ag/AgCl nanocubes display enhanced photocatalytic activity in comparison with Ag/AgCl nanospheres due to the more efficient charge transfer. This work may pave an avenue to construct various functional materials via the assembly strategy using nanoparticles as versatile building blocks.

  11. Plasmon-induced optical switching of electrical conductivity in porous anodic aluminum oxide films encapsulated with silver nanoparticle arrays.

    PubMed

    Huang, Chen-Han; Lin, Hsing-Ying; Lau, Ben-Chao; Liu, Chih-Yi; Chui, Hsiang-Chen; Tzeng, Yonhua

    2010-12-20

    We report on plasmon induced optical switching of electrical conductivity in two-dimensional (2D) arrays of silver (Ag) nanoparticles encapsulated inside nanochannels of porous anodic aluminum oxide (AAO) films. The reversible switching of photoconductivity greatly enhanced by an array of closely spaced Ag nanoparticles which are isolated from each other and from the ambient by thin aluminum oxide barrier layers are attributed to the improved electron transport due to the localized surface plasmon resonance and coupling among Ag nanoparticles. The photoconductivity is proportional to the power, and strongly dependent on the wavelength of light illumination. With Ag nanoparticles being isolated from the ambient environments by a thin layer of aluminum oxide barrier layer of controlled thickness in nanometers to tens of nanometers, deterioration of silver nanoparticles caused by environments is minimized. The electrochemically fabricated nanostructured Ag/AAO is inexpensive and promising for applications to integrated plasmonic circuits and sensors.

  12. Refracting surface plasmon polaritons with nanoparticle arrays.

    PubMed

    Radko, Ilya P; Evlyukhin, Andrey B; Boltasseva, Alexandra; Bozhevolnyi, Sergey I

    2008-03-17

    Refraction of surface plasmon polaritons (SPPs) by various structures formed by a 100-nm-period square lattice of gold nanoparticles on top of a gold film is studied by leakage radiation microscopy. SPP refraction by a triangular-shaped nanoparticle array indicates that the SPP effective refractive index increases inside the array by a factor of approximately 1.08 (for the wavelength 800 nm) with respect to the SPP index at a flat surface. Observations of SPP focusing and deflection by circularly shaped areas as well as SPP waveguiding inside rectangular arrays are consistent with the SPP index increase deduced from the SPP refraction by triangular arrays. The SPP refractive index is found to decrease slightly for longer wavelengths within the wavelength range of 700-860 nm. Modeling based on the Green's tensor formalism is in a good agreement with the experimental results, opening the possibility to design nanoparticle arrays for specific applications requiring in-plane SPP manipulation.

  13. Design of highly ordered Ag-SrTiO{sub 3} nanotube arrays for photocatalytic degradation of methyl orange

    SciTech Connect

    Sun Yue; Liu Jiawen; Li Zhonghua

    2011-08-15

    Ag-SrTiO{sub 3} nanotube arrays were successfully prepared for the degradation of methyl orange (MO) under ultraviolet irradiation. In order to form highly ordered SrTiO{sub 3} nanotube arrays, the preparation of TiO{sub 2} nanotube arrays by anodic oxidation of titanium foil in different electrolytes was investigated. The selected organic solvents in electrolytes include glycerol, dimethyl sulfoxide and glycol. The results indicate that the morphology of TiO{sub 2} nanotube arrays prepared in glycol containing ammonium fluoride electrolyte is more regular. Then SrTiO{sub 3} nanotube arrays were synthesized by a hydrothermal method using TiO{sub 2} nanotube arrays as the precursor. In order to further improve the photocatalytic activity of SrTiO{sub 3} nanotube arrays, Ag nanoparticles were loaded on SrTiO{sub 3} nanotube arrays by two sets of experiments. The loaded Ag results in an enhancement of photocatalytic activity of SrTiO{sub 3} nanotube arrays. Moreover, the effect of pH on the photocatalytic degradation of MO was also studied. - Graphical abstract: Ag-SrTiO{sub 3} nanotube arrays were successfully prepared. The photocatalytic activity was evaluated by degradation of methyl orange under ultraviolet irradiation. Highlights: > TiO{sub 2} nanotube arrays prepared in glycol+NH{sub 4}F electrolyte are more regular. > Highly ordered Ag-SrTiO{sub 3} nanotube arrays were successfully synthesized. > Ag loading could enhance the photocatalytic activity of SrTiO{sub 3} nanotube arrays. > Ag-SrTiO{sub 3} nanotube arrays show excellent catalytic activity at a low pH value.

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

    PubMed

    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.

  15. 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

  16. STM-assisted manipulation of Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Radojkovic, P.; Schwartzkopff, M.; Gabriel, T.; Hartmann, E.

    We report scanning tunneling microscope (STM) investigations of inert-gas-evaporated Ag nanoparticles deposited on atomically flat, H-terminated Si(111) surfaces, to which they weakly stick. For the present purpose, nanoparticles having an average size of 3 nm are fabricated and the particle coverage on the substrate fluctuates between one and three monolayers. The weakly coupling particle network can repeatedly be imaged with the STM without inadvertently manipulating the fundamental building blocks. When the STM is operated in the field-emission regime and the tunnel current is kept between 50 pA and 39 μA, the temperature of the nanoparticles rises, thus stimulating local manipulation processes. Depending on the power density dissipated in the particles, we distinguish between a local sintering process leading to the formation of narrow necks to the nearest neighbors, while the original granular nature of the particle layer is maintained, and a complete fusion. In the latter case, stable nanometer-scale structures are fabricated which strongly interconnect with the underlying substrate. In combining nanoparticle-inherent properties with existing theory, we roughly estimate the temperature rise of the nanoparticles and confirm the possibility of particle liquefaction for the highest power densities generated.

  17. 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.

  18. 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.

  19. 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

  20. Ag colloids and arrays for plasmonic non-radiative energy transfer from quantum dots to a quantum well

    NASA Astrophysics Data System (ADS)

    Murphy, Graham P.; Gough, John J.; Higgins, Luke J.; Karanikolas, Vasilios D.; Wilson, Keith M.; Garcia Coindreau, Jorge A.; Zubialevich, Vitaly Z.; Parbrook, Peter J.; Bradley, A. Louise

    2017-03-01

    Non-radiative energy transfer (NRET) can be an efficient process of benefit to many applications including photovoltaics, sensors, light emitting diodes and photodetectors. Combining the remarkable optical properties of quantum dots (QDs) with the electrical properties of quantum wells (QWs) allows for the formation of hybrid devices which can utilize NRET as a means of transferring absorbed optical energy from the QDs to the QW. Here we report on plasmon-enhanced NRET from semiconductor nanocrystal QDs to a QW. Ag nanoparticles in the form of colloids and ordered arrays are used to demonstrate plasmon-mediated NRET from QDs to QWs with varying top barrier thicknesses. Plasmon-mediated energy transfer (ET) efficiencies of up to ∼25% are observed with the Ag colloids. The distance dependence of the plasmon-mediated ET is found to follow the same d ‑4 dependence as the direct QD to QW ET. There is also evidence for an increase in the characteristic distance of the interaction, thus indicating that it follows a Förster-like model with the Ag nanoparticle-QD acting as an enhanced donor dipole. Ordered Ag nanoparticle arrays display plasmon-mediated ET efficiencies up to ∼21%. To explore the tunability of the array system, two arrays with different geometries are presented. It is demonstrated that changing the geometry of the array allows a transition from overall quenching of the acceptor QW emission to enhancement, as well as control of the competition between the QD donor quenching and ET rates.

  1. Nanoparticle Array Assembly Using Chemical Templates

    NASA Astrophysics Data System (ADS)

    Adams, Sarah Marie

    This dissertation demonstrates chemically-driven self-assembly techniques to produce assemblies of closely-spaced metal nanoparticles from colloidal nanoparticle solution in order to engineer enhanced optical fields. Planar nanoparticle assemblies provide a platform for a multitude of applications and material architectures. With nanoscale inter-particle spacing, metallic nanoparticles enable increased efficiency of photovoltaic devices due to light focusing and enhancement of electromagnetic fields useful for optical sensing of molecules due to coupling of the plasmon resonance in nanoparticle gaps. For molecular sensors, development of self-assembled two-dimensional assemblies of closely-spaced nanoparticles is useful for producing surface plasmon resonance sensors and surface-enhanced Raman spectroscopy (SERS) based sensing. Using chemical self-assembly, monodisperse, colloidal gold nanoparticles were attached on self-organized polymer templates in order to pattern assemblies of nanoparticle clusters with sub-10 nanometer inter-particle spacing. First citrate-stabilized Au nanoparticles were functionalized with thioctic acid ligands in solution. Then poly(methyl methacrylate) domains in phase-separated poly(styrene-block-methyl methacrylate) (PS-b-PMMA) thin films were chemically modified with surface amine functional groups. Au nanoparticles were preferentially attached to the functionalized PMMA surface domains using cross-linking chemistry. This method allows for versatility of size, shape, and composition. In this dissertation, we demonstrated attachment of 5, 10, and 20 nm Au and 20 nm Ag nanoparticles. PS-b-PMMA thin films also exhibit versatility of domain size and morphology by varying polymer molecular weights. The nanoparticle diameter to PMMA domain size ratio influenced the cluster size. As the ratio decreased, larger clusters were observed on PMMA domains with increased frequency. SERS measurement of nanoparticle assemblies showed uniform signal

  2. Using Ag-embedded TiO2 nanotubes array as recyclable SERS substrate

    NASA Astrophysics Data System (ADS)

    Ling, Yunhan; Zhuo, Yuqing; Huang, Liang; Mao, Duolu

    2016-12-01

    A simple strategy for synthesizing Ag-loaded TiO2 nanotube film for use as multifunctional photocatalyst and recyclable surface-enhanced Raman scattering (SERS) substrate is introduced. Highly aligned TiO2 nanotube arrays (TNTA) prepared via electrochemical anodization were used as a 3D rough host for silver nanoparticles. Ag deposits were sputtered in a vacuum, and it was found that their morphologies were mainly influenced by the diameters of nanotubes and the UV irradiation induced aging process, especially the self-migration of silver along the tubular wall. SERS and the self-cleaning effect were observed using Rhodamine 6G (R6G) as the probe molecule. The results showed that narrow nanotube and silver nanoparticles embedment contributed significantly to both the phenomenal SERS and recyclability.

  3. 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.

  4. Advances of Ag, Cu, and Ag-Cu alloy nanoparticles synthesized via chemical reduction route

    NASA Astrophysics Data System (ADS)

    Tan, Kim Seah; Cheong, Kuan Yew

    2013-04-01

    Silver (Ag) and copper (Cu) nanoparticles have shown great potential in variety applications due to their excellent electrical and thermal properties resulting high demand in the market. Decreasing in size to nanometer scale has shown distinct improvement in these inherent properties due to larger surface-to-volume ratio. Ag and Cu nanoparticles are also shown higher surface reactivity, and therefore being used to improve interfacial and catalytic process. Their melting points have also dramatically decreased compared with bulk and thus can be processed at relatively low temperature. Besides, regularly alloying Ag into Cu to create Ag-Cu alloy nanoparticles could be used to improve fast oxidizing property of Cu nanoparticles. There are varieties methods have been reported on the synthesis of Ag, Cu, and Ag-Cu alloy nanoparticles. This review aims to cover chemical reduction means for synthesis of those nanoparticles. Advances of this technique utilizing different reagents namely metal salt precursors, reducing agents, and stabilizers, as well as their effects on respective nanoparticles have been systematically reviewed. Other parameters such as pH and temperature that have been considered as an important factor influencing the quality of those nanoparticles have also been reviewed thoroughly.

  5. Photoacoustic emission from Au nanoparticles arrayed on thermal insulation layer.

    PubMed

    Namura, Kyoko; Suzuki, Motofumi; Nakajima, Kaoru; Kimura, Kenji

    2013-04-08

    Efficient photoacoustic emission from Au nanoparticles on a porous SiO(2) layer was investigated experimentally and theoretically. The Au nanoparticle arrays/porous SiO(2)/SiO(2)/Ag mirror sandwiches, namely, local plasmon resonators, were prepared by dynamic oblique deposition (DOD). Photoacoustic measurements were performed on the local plasmon resonators, whose optical absorption was varied from 0.03 (3%) to 0.95 by varying the thickness of the dielectric SiO(2) layer. The sample with high absorption (0.95) emitted a sound that was eight times stronger than that emitted by graphite (0.94) and three times stronger than that emitted by the sample without the porous SiO(2) layer (0.93). The contribution of the porous SiO(2) layer to the efficient photoacoustic emission was analyzed by means of a numerical method based on a one-dimensional heat transfer model. The result suggested that the low thermal conductivity of the underlying porous layer reduces the amount of heat escaping from the substrate and contributes to the efficient photoacoustic emission from Au nanoparticle arrays. Because both the thermal conductivity and the spatial distribution of the heat generation can be controlled by DOD, the local plasmon resonators produced by DOD are suitable for the spatio-temporal modulation of the local temperature.

  6. Ag-NP@Ge-nanotaper/Si-micropillar ordered arrays as ultrasensitive and uniform surface enhanced Raman scattering substrates

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Meng, Guowen; Li, Zhongbo; Huang, Zhulin; Li, Xiangdong

    2015-10-01

    Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) ``hot spots'' created from the large quantities of the neighboring Ag-NPs and large-scale uniform morphology, the hierarchical Ag-NP@Ge-nanotaper/Si-micropillar arrays exhibit strong and reproducible SERS activity. Using our hierarchical 3D SERS-substrates, both methyl parathion (a commonly used pesticide) and PCB-2 (one congener of highly toxic polychlorinated biphenyls) with concentrations down to 10-7 M and 10-5 M have been detected respectively, showing great potential in SERS-based rapid trace-level detection of toxic organic pollutants in the environment.Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) ``hot spots'' created from the large quantities of the neighboring Ag-NPs and large-scale uniform

  7. 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...

  8. Fabrication of Ag/TiO2 nanotube array with enhanced photo-catalytic degradation of aqueous organic pollutant

    NASA Astrophysics Data System (ADS)

    Ma, Jie; Yang, Mingxuan; Sun, Yiran; Li, Chenlu; Li, Qiang; Gao, Fangfang; Yu, Fei; Chen, Junhong

    2014-04-01

    In this paper, the fabrication of Ag/TiO2 nanotube arrays and their photo-catalytic activity have been studied. The SEM, TEM and XRD were performed to characterize the morphology and crystalline phase of the TiO2 nanotube array and Ag/TiO2 nanotube array. Ag nanoparticles with different loadings, which are aimed to suppress the electron-hole recombination so as to enhance the photo-catalytic oxidation efficiency, were systematically coated onto TiO2 nanotubes. The photo-catalytic activity of these nano-materials was evaluated by the degradation of two different pollutants: methyl orange and glyphosate. The effects of various parameters, such as the amount of the photo-catalyst, the illumination time, and pH value on the photo-catalytic oxidation activity, were studied.

  9. Quantum plasmonics with a metal nanoparticle array

    NASA Astrophysics Data System (ADS)

    Lee, Changhyoup; Tame, Mark; Lim, James; Lee, Jinhyoung

    2012-06-01

    We investigate an array of metal nanoparticles as a channel for nanophotonic quantum communication and the generation of quantum plasmonic interference. We consider the transfer of quantum states, including single qubits as plasmonic wave packets, and highlight the necessity of a quantum-mechanical description by comparing the predictions of quantum theory with those of classical electromagnetic theory. The effects of loss in the metal are included, thus putting our investigation into a practical setting and enabling the quantification of the performance of realistic nanoparticle arrays as plasmonic quantum channels. We explore the interference of single plasmons, finding nonlinear absorption effects associated with the quantum properties of the plasmon excitations. This work highlights the benefits and drawbacks of using nanophotonic periodic systems for quantum plasmonic applications, such as quantum communication and the generation of quantum interference.

  10. Nanoparticles alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle alloying.

    PubMed

    Semaltianos, N G; Chassagnon, R; Moutarlier, V; Blondeau-Patissier, V; Assoul, M; Monteil, G

    2017-04-18

    Laser irradiation of a mixture of single-element micro/nanomaterials may lead to their alloying and fabrication of multi-element structures. In addition to the laser induced alloying of particulates in the form of micro/nanopowders in ambient atmosphere (which forms the basis of the field of additive manufacturing technology), another interesting problem is the laser-induced alloying of a mixture of single-element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed-nanoparticle colloidal solutions. In this work, bare-surface ligand-free Ag and Pd nanoparticles in solution were prepared by laser ablation of the corresponding bulk target materials, separately in water. The two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser-induced nanoparticles alloying in liquid. Nanoparticles alloying and the formation of AgPd alloyed nanoparticles takes place with a decrease of the intensity of the surface-plasmon resonance peak of the Ag nanoparticles (at ∼405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for a time duration even as long as 30 min. The nanoalloys have lattice constants with values between those of the pure metals, which indicates that they consist of Ag and Pd in an approximately 1:1 ratio similar to the atomic composition of the starting mixed-nanoparticle solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles that remain as single elements (even after the end of the irradiation), joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time, which is also a typical characteristic of AgPd alloyed nanoparticles. The mechanisms of nanoparticles alloying and network formation are also

  11. Nanoparticles alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle alloying

    NASA Astrophysics Data System (ADS)

    Semaltianos, N. G.; Chassagnon, R.; Moutarlier, V.; Blondeau-Patissier, V.; Assoul, M.; Monteil, G.

    2017-04-01

    Laser irradiation of a mixture of single-element micro/nanomaterials may lead to their alloying and fabrication of multi-element structures. In addition to the laser induced alloying of particulates in the form of micro/nanopowders in ambient atmosphere (which forms the basis of the field of additive manufacturing technology), another interesting problem is the laser-induced alloying of a mixture of single-element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed-nanoparticle colloidal solutions. In this work, bare-surface ligand-free Ag and Pd nanoparticles in solution were prepared by laser ablation of the corresponding bulk target materials, separately in water. The two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser-induced nanoparticles alloying in liquid. Nanoparticles alloying and the formation of AgPd alloyed nanoparticles takes place with a decrease of the intensity of the surface-plasmon resonance peak of the Ag nanoparticles (at ∼405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for a time duration even as long as 30 min. The nanoalloys have lattice constants with values between those of the pure metals, which indicates that they consist of Ag and Pd in an approximately 1:1 ratio similar to the atomic composition of the starting mixed-nanoparticle solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles that remain as single elements (even after the end of the irradiation), joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time, which is also a typical characteristic of AgPd alloyed nanoparticles. The mechanisms of nanoparticles alloying and network formation are also

  12. A convenient phase transfer route for Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhao, Shi-Yong; Chen, Shen-Hao; Li, De-Gang; Yang, Xue-Geng; Ma, Hou-Yi

    2004-06-01

    Generally, phase transfer of metal nanoparticles between aqueous phase and organic phase need two reagents at last. One is stabilizer of nanoparticles, the other is phase-transfer agent (Chem. Lett. 21 (1992) 1527; J. Colloid Interface Sci. 161 (1993) 471; J. Phys. Chem B 101 (1997) 9876; Chem. Commun. (1997) 537; Langmuir 14 (1998) 602; J. Phys. Chem B 103 (1999) 7238; Chem. Mater. 13 (2001) 4692; Langmuir 17 (2001) 733; Langmuir 16 (2000) 9775; Langmuir 18 (2002) 3364; J. Am. Chem. Soc. 123 (2001) 11148). In this paper, Ag nanoparticle prepared by tannic acid reduction of AgNO 3 in aqueous medium were transferred to chloroform solution via a remarkably simple one-step route under the effect of phase-transfer inducer dimethyldioctadecylammonium chloride (DDAC), where no special stabilizer was required. Monolayer of Ag nanoparticles is obtained on carbon film by self-assembly using chloroform organosol. The effect of the inducer DDAC concentration is checked, and it was found that 5×10 -3 mol dm -3 of DDAC was the optimum concentration for phase transfer of Ag nanoparticles. The organosol, Ag nanoparticle self-assembled monolayer and phase transfer were characterized by UV-vis spectra, TEM, ED and TF-IR.

  13. Radiochemical synthesis of 105gAg-labelled silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Ichedef, C.; Simonelli, F.; Holzwarth, U.; Bagaria, J. Piella; Puntes, V. F.; Cotogno, G.; Gilliland, D.; Gibson, N.

    2013-11-01

    A method for synthesis of radiolabelled silver nanoparticles is reported. The method is based on proton activation of silver metal powder, enriched in 107Ag, with a 30.7 MeV proton beam. At this proton energy 105gAg is efficiently created, mainly via the 107Ag(p,3n)105Cd → 105gAg reaction. 105gAg has a half-life of 41.29 days and emits easily detectable gamma radiation on decay to 105Pd. This makes it very useful as a tracing radionuclide for experiments over several weeks or months. Following activation and a period to allow short-lived radionuclides to decay, the powder was dissolved in concentrated nitric acid in order to form silver nitrate (AgNO3), which was used to synthesise radiolabelled silver nanoparticles via the process of sodium borohydride reduction. For comparison, non-radioactive silver nanoparticles were synthesised using commercially supplied AgNO3 in order to check if the use of irradiated Ag powder as a starting material would alter in any way the final nanoparticle characteristics. Both nanoparticle types were characterised using dynamic light scattering, zeta-potential and X-ray diffraction measurements, while additionally the non-radioactive samples were analysed by transmission electron microscopy and UV-Vis spectrometry. A hydrodynamic diameter of about 16 nm was determined for both radiolabelled and non-radioactive nanoparticles, while the electron microscopy on the non-radioactive samples indicated that the physical size of the metal NPs was (7.3 ± 1.4) nm.

  14. Low temperature sintering of Ag nanoparticles for flexible electronics packaging

    NASA Astrophysics Data System (ADS)

    Hu, A.; Guo, J. Y.; Alarifi, H.; Patane, G.; Zhou, Y.; Compagnini, G.; Xu, C. X.

    2010-10-01

    We achieve robust bonding of Cu wires to Cu pads on polyimide with silver nanopaste cured at 373 K. The paste is prepared by simply condensing Ag nanoparticle (NP) solution via centrifuging. The bonding is formed by solid state sintering of Ag NPs through neck growth and direct metallic bonding between clean Ag-Cu interfaces. Both experiment and Monte Carlo simulation confirm that the melting point of joint clusters increases during sintering. This creates improved bonds for use at an elevated operating temperature using Ag NPs.

  15. Au nanoparticle sensitized ZnO nanopencil arrays for photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Wang, Tuo; Lv, Rui; Zhang, Peng; Li, Changjiang; Gong, Jinlong

    2014-11-01

    This paper describes the synthesis of Au nanoparticle sensitized ZnO nanopencil arrays on F-doped SnO2 substrates by an aqueous chemical growth and subsequent photoreduction method. The Au-ZnO nanopencil arrays yield a photocurrent of ~1.5 mA cm-2 at 1 V versus Ag/AgCl. The enhanced photocurrent is attributed to the surface plasmon resonance effect of Au nanoparticles and the prolonged lifetime of the photo-generated electron-hole pairs. The improved stability of ZnO is due to the plasmon resonance energy transfer process enabled by the Au nanoparticles, which enhances the electric field intensity in a small, well-defined location of the ZnO semiconductor.This paper describes the synthesis of Au nanoparticle sensitized ZnO nanopencil arrays on F-doped SnO2 substrates by an aqueous chemical growth and subsequent photoreduction method. The Au-ZnO nanopencil arrays yield a photocurrent of ~1.5 mA cm-2 at 1 V versus Ag/AgCl. The enhanced photocurrent is attributed to the surface plasmon resonance effect of Au nanoparticles and the prolonged lifetime of the photo-generated electron-hole pairs. The improved stability of ZnO is due to the plasmon resonance energy transfer process enabled by the Au nanoparticles, which enhances the electric field intensity in a small, well-defined location of the ZnO semiconductor. Electronic supplementary information (ESI) available: Illustrative schematic of PEC measurements, XPS of ZnO nanorods and nanopencils. See DOI: 10.1039/c4nr03735a

  16. Ultrasensitive SERS performance in 3D "sunflower-like" nanoarrays decorated with Ag nanoparticles.

    PubMed

    Zhang, Xiaolei; Xiao, Xiangheng; Dai, Zhigao; Wu, Wei; Zhang, Xingang; Fu, Lei; Jiang, Changzhong

    2017-03-02

    Low-cost, stabilized and ultrasensitive three-dimensional (3D) hierarchical surface-enhanced Raman scattering substrates ("sunflower-like" nanoarrays decorated with Ag nanoparticles, denoted as SLNAs-Ag) have been obtained by fabricating binary colloidal crystals and then decorating with Ag nanoparticles. In order to provide a larger density of hot spots within the laser-illumination area, the silica sphere arrays were chosen as the island-type platform for the polystyrene (PS) nanosphere deposition, and the distances between the PS nanospheres were tuned by etching for different durations. Compared with conventional 2D planar systems, the as-fabricated 3D SLNAs-Ag exhibited extremely high SERS sensitivity ascribed to the larger SERS active regions. Quantitative detection of molecules with an extremely low incident laser power was achieved on the "sunflower-like" nanoarrays in which the PS nanospheres were etched for 5 minutes and decorated with Ag nanoparticles, and the corresponding analytical enhancement factor is calculated to be 2 × 10(14) with the concentration of rhodamine 6G down to 10(-15) M. Based on the achieved SERS substrates, we have further demonstrated the highly sensitive detection of molecules such as melamine for food safety inspection.

  17. 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.

  18. 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.

  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.

  20. Strongly visible-light responsive plasmonic shaped AgX:Ag (X = Cl, Br) nanoparticles for reduction of CO2 to methanol

    NASA Astrophysics Data System (ADS)

    An, Changhua; Wang, Jizhuang; Jiang, Wen; Zhang, Meiyu; Ming, Xijuan; Wang, Shutao; Zhang, Qinhui

    2012-08-01

    Plasmonic shaped AgX:Ag (X = Cl, Br) nanoparticles have been synthesized by a facile and versatile glycerol-mediated solution route. The as-prepared AgX:Ag nanoparticles exhibit regular shapes, i.e., cube-tetrapod-like AgCl:Ag nanoparticles and AgBr:Ag nanoplates. Compared with the pristine AgX, AgX:Ag nanocomposites display stronger absorption in the visible region due to the surface plasmon resonance of silver nanoparticles. The calculation of bandgaps and band positions indicates the as-achieved AgX:Ag nanoparticles can be used as a class of potential photocatalyst for the reduction of CO2. For example, reduction of CO2 under visible light irradiation with the assistance of the anisotropic AgX:Ag nanoparticles yields as much as 100 μmol methanol in the products. Furthermore, the AgX:Ag nanoparticles can maintain its structure and activity after 3 runs of reactions. Therefore, the present route opens an avenue to acquire plasmonic photocatalysts for conversion of CO2 into useful organic compounds.Plasmonic shaped AgX:Ag (X = Cl, Br) nanoparticles have been synthesized by a facile and versatile glycerol-mediated solution route. The as-prepared AgX:Ag nanoparticles exhibit regular shapes, i.e., cube-tetrapod-like AgCl:Ag nanoparticles and AgBr:Ag nanoplates. Compared with the pristine AgX, AgX:Ag nanocomposites display stronger absorption in the visible region due to the surface plasmon resonance of silver nanoparticles. The calculation of bandgaps and band positions indicates the as-achieved AgX:Ag nanoparticles can be used as a class of potential photocatalyst for the reduction of CO2. For example, reduction of CO2 under visible light irradiation with the assistance of the anisotropic AgX:Ag nanoparticles yields as much as 100 μmol methanol in the products. Furthermore, the AgX:Ag nanoparticles can maintain its structure and activity after 3 runs of reactions. Therefore, the present route opens an avenue to acquire plasmonic photocatalysts for conversion of CO2

  1. 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.

  2. Synthesis of one-dimensional silver oxide nanoparticle arrays and silver nanorods templated by Langmuir monolayers.

    PubMed

    Liu, Hong-Guo; Xiao, Fei; Wang, Chang-Wei; Xue, Qingbin; Chen, Xiao; Lee, Yong-Ill; Hao, Jingcheng; Jiang, Jianzhuang

    2007-10-01

    One-dimensional (1D) silver oxide nanoparticle arrays were synthesized by illuminating the composite Langmuir-Blodgett monolayers of porphyrin derivatives/Ag(+) and n-hexadecyl dihydrogen phosphate (n-HDP)/Ag(+) deposited on carbon-coated copper grids with daylight and then exposing them to air. Transmission electron microscopy (TEM) observation shows that the nanoparticle size is around 3 nm, with the separation of about 2-3 nm. High-resolution TEM (HRTEM) investigation indicates that the particles are made up of Ag(2)O. Ag nanorods with the width of 15-35 nm and the length of several hundreds of nanometers were synthesized by irradiating the composite Langmuir monolayers of porphyrin derivatives/Ag(+) and n-HDP/Ag(+) by UV-light directly at the air/water interface at room temperature. HRTEM image and selected-area electron diffraction (SAED) pattern indicate that the nanorods are single crystals with the (110) face of the face-centered cubic (fcc) silver parallel to the air/water interface. The formation of the 1D arrays and the nanorods should be attributed to the templating effect of the linear supramolecules formed by porphyrin derivative or n-HDP molecules in Langmuir monolayers through non-covalent interactions.

  3. DC electric field induced phase array self-assembly of Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Yadavali, S.; Sachan, R.; Dyck, O.; Kalyanaraman, R.

    2014-11-01

    In this work we report the discovery of phase array self-assembly, a new way to spontaneously make periodic arrangements of metal nanoparticles. An initially random arrangement of gold (Au) or silver (Ag) nanoparticles on SiO2/Si substrates was irradiated with linearly polarized (P) laser light in the presence of a dc electric (E) field applied to the insulating substrate. For E fields parallel to the laser polarization (E \\parallel P), the resulting periodic ordering was single-crystal like with extremely low defect density and covered large macroscopic areas. The E field appears to be modifying the phase between radiation scattered by the individual nanoparticles thus leading to enhanced interference effects. While phase array behavior is widely known in antenna technology, this is the first evidence that it can also aid in nanoscale self-assembly. These results provide a simple way to produce periodic metal nanoparticles over large areas.

  4. Ag colloids and arrays for plasmonic non-radiative energy transfer from quantum dots to a quantum well.

    PubMed

    Murphy, Graham P; Gough, John J; Higgins, Luke J; Karanikolas, Vasilios D; Wilson, Keith M; Garcia Coindreau, Jorge A; Zubialevich, Vitaly Z; Parbrook, Peter J; Bradley, A Louise

    2017-03-17

    Non-radiative energy transfer (NRET) can be an efficient process of benefit to many applications including photovoltaics, sensors, light emitting diodes and photodetectors. Combining the remarkable optical properties of quantum dots (QDs) with the electrical properties of quantum wells (QWs) allows for the formation of hybrid devices which can utilize NRET as a means of transferring absorbed optical energy from the QDs to the QW. Here we report on plasmon-enhanced NRET from semiconductor nanocrystal QDs to a QW. Ag nanoparticles in the form of colloids and ordered arrays are used to demonstrate plasmon-mediated NRET from QDs to QWs with varying top barrier thicknesses. Plasmon-mediated energy transfer (ET) efficiencies of up to ∼25% are observed with the Ag colloids. The distance dependence of the plasmon-mediated ET is found to follow the same d (-4) dependence as the direct QD to QW ET. There is also evidence for an increase in the characteristic distance of the interaction, thus indicating that it follows a Förster-like model with the Ag nanoparticle-QD acting as an enhanced donor dipole. Ordered Ag nanoparticle arrays display plasmon-mediated ET efficiencies up to ∼21%. To explore the tunability of the array system, two arrays with different geometries are presented. It is demonstrated that changing the geometry of the array allows a transition from overall quenching of the acceptor QW emission to enhancement, as well as control of the competition between the QD donor quenching and ET rates.

  5. Enzyme immobilization on Ag nanoparticles/polyaniline nanocomposites.

    PubMed

    Crespilho, Frank N; Iost, Rodrigo M; Travain, Silmar A; Oliveira, Osvaldo N; Zucolotto, Valtencir

    2009-06-15

    We show a simple strategy to obtain an efficient enzymatic bioelectrochemical device, in which urease was immobilized on electroactive nanostructured membranes (ENMs) made with polyaniline and silver nanoparticles (AgNP) stabilized in polyvinyl alcohol (PAni/PVA-AgNP). Fabrication of the modified electrodes comprised the chemical deposition of polyaniline followed by drop-coating of PVA-AgNP and urease, resulting in a final ITO/PAni/PVA-AgNP/urease electrode configuration. For comparison, the electrochemical performance of ITO/PAni/urease electrodes (without Ag nanoparticles) was also studied. The performance of the modified electrodes toward urea hydrolysis was investigated via amperometric measurements, revealing a fast increase in cathodic current with a well-defined peak upon addition of urea to the electrolytic solution. The cathodic currents for the ITO/PAni/PVA-AgNP/urease electrodes were significantly higher than for the ITO/PAni/urease electrodes. The friendly environment provided by the ITO/PAni/PVA-AgNP electrode to the immobilized enzyme promoted efficient catalytic conversion of urea into ammonium and bicarbonate ions. Using the Michaelis-Menten kinetics equation, a K(M)(app) of 2.7 mmol L(-1) was obtained, indicating that the electrode architecture employed may be advantageous for fabrication of enzymatic devices with improved biocatalytic properties.

  6. Synergistic bactericidal activity of Ag-TiO₂ nanoparticles in both light and dark conditions.

    PubMed

    Li, Minghua; Noriega-Trevino, Maria Eugenia; Nino-Martinez, Nereyda; Marambio-Jones, Catalina; Wang, Jinwen; Damoiseaux, Robert; Ruiz, Facundo; Hoek, Eric M V

    2011-10-15

    High-throughput screening was employed to evaluate bactericidal activities of hybrid Ag-TiO₂ nanoparticles comprising variations in TiO₂ crystalline phase, Ag content, and synthesis method. Hybrid Ag-TiO₂ nanoparticles were prepared by either wet-impregnation or UV photo deposition onto both Degussa P25 and DuPont R902 TiO₂ nanoparticles. The presence of Ag was confirmed by ICP, TEM, and XRD analysis. The size of Ag nanoparticles formed on anatase/rutile P25 TiO₂ nanoparticles was smaller than those formed on pure rutile R902. When activated by UV light, all hybrid Ag-TiO₂ nanoparticles exhibited stronger bactericidal activity than UV alone, Ag/UV, or UV/TiO₂. For experiments conducted in the dark, bactericidal activity of Ag-TiO₂ nanoparticles was greater than either bare TiO₂ (inert) or pure Ag nanoparticles, suggesting that the hybrid materials produced a synergistic antibacterial effect unrelated to photoactivity. Moreover, less Ag(+) dissolved from Ag-TiO₂ nanoparticles than from Ag nanoparticles, indicating the antibacterial activities of Ag-TiO₂ was not only caused by releasing of toxic metal ions. It is clear that nanotechnology can produce more effective bactericides; however, the challenge remains to identify practical ways to take advantage of these exciting new material properties.

  7. SERS detection of low-concentration adenosine by silver nanoparticles on silicon nanoporous pyramid arrays structure

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Man, B. Y.; Jiang, S. Z.; Yang, C.; Liu, M.; Chen, C. S.; Xu, S. C.; Qiu, H. W.; Li, Z.

    2015-08-01

    A novel surface-enhanced Raman spectroscopy (SERS) substrate based on uniform silver nanoparticles/silicon nanoporous pyramid arrays (Ag/PS) is prepared and SERS behaviors to adenosine are discussed and compared. With a low concentration of 10-7 M, the characteristic Raman bands of adenosine demonstrate the significantly high SERS sensitivity of the prepared Ag/PS substrate. A reasonable linear correlation is obtained between the intensity of SERS signal and the adenosine concentration from 10-2 to 10-7M in log scale. These results imply that the Ag/PS with regular pyramids array might be an effective substrate for performing label-free sensitive SERS detections of biomolecule.

  8. Enhanced chemiluminescence of the luminol-AgNO3 system by Ag nanoparticles.

    PubMed

    Li, Shifeng; Sun, Huimin; Wang, Dong; Hong, Jianguo; Tao, Shanjun; Yu, Haiyin; Wang, Xiuhua; Wei, Xianwen

    2012-01-01

    The oxidation reaction of luminol with AgNO(3) can produce chemiluminescence (CL) in the presence of silver nanoparticles (NPs) in alkaline solution. Based on the studies of UV-vis absorption spectra, photoluminescence (PL) spectra and CL spectra, a CL enhancement mechanism is proposed. The CL emission spectrum of the luminol-AgNO(3)-Ag NPs system indicated that the luminophore was still 3-aminophthalate. On injection of silver nanoparticles into the mixture of luminol and AgNO(3), they catalysed the reduction of AgNO(3) by luminol. The product luminol radicals reacted with the dissolved oxygen, to produce a strong CL emission. As a result, the CL intensity was substantially increased. Moreover, the influences of 18 amino acids, e.g. cystine, tyrosine and asparagine, and 25 organic compounds, including gallic acid, tannic acid and hydroquinone, on the luminol-AgNO(3)-Ag NPs CL system were studied by a flow-injection procedure, which led to an effective method for detecting these compounds.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. 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.

  11. Dynamically tunable chemiluminescence of luminol-functionalized silver nanoparticles and its application to protein sensing arrays.

    PubMed

    He, Yi; He, Xiao; Liu, Xiaoying; Gao, Lingfeng; Cui, Hua

    2014-12-16

    It is still a great challenge to develop an array-based sensing system that can obtain only multiparameters, according to a single experiment and device. The role of conventional chemiluminescence (CL) in biosensing has been limited to a signal transducer in which a single signal (CL intensity) can be obtained for quantifying the concentrations of analytes. In this work, we have developed an dynamically tunable CL system, based on the reaction of luminol-functionalized silver nanoparticles (luminol-AgNPs) with H2O2, which could be tunable via adjusting various conditions such as the concentration of H2O2, pH value, and addition of protein. A single experiment operation could obtain multiparameters including CL intensity, the time to appear CL emission and the time to reach CL peak value. The tunable, low-background, and highly reproducible CL system based on luminol-AgNPs is applied, for the first time, as a sensing platform with trichannel properties for protein sensing arrays by principal component analysis. Identification of 35 unknowns demonstrated a success rate of >96%. The developed sensing arrays based on the luminol-AgNPs provide a new way to use nanoparticles-based CL for the fabrication of sensing arrays and hold great promise for biomedical application in the future.

  12. SERS detection of R6G based on a novel graphene oxide/silver nanoparticles/silicon pyramid arrays structure.

    PubMed

    Zhang, C; Jiang, S Z; Huo, Y Y; Liu, A H; Xu, S C; Liu, X Y; Sun, Z C; Xu, Y Y; Li, Z; Man, B Y

    2015-09-21

    We present a novel surface-enhanced Raman scattering (SERS) substrate based on graphene oxide/silver nanoparticles/silicon pyramid arrays structure (GO/Ag/PSi). The SERS behaviors are discussed and compared by the detection of R6G. Based on the contrast experiments with PSi, GO/PSi, Ag/PSi and GO/AgA/PSi as SERS substrate, the perfect bio-compatibility, good homogeneity and chemical stability were confirmed. We also calculated the electric field distributions using Finite-difference time-domain (FDTD) analysis to further understand the GO/Ag/PSi structure as a perfect SERS platform. These experimental and theoretical results imply that the GO/Ag/PSi with regular pyramids array is expected to be an effective substrate for label-free sensitive SERS detections in areas of medicine, food safety and biotechnology.

  13. Systematic investigation of the SERS efficiency and SERS hotspots in gas-phase deposited Ag nanoparticle assemblies.

    PubMed

    He, L B; Wang, Y L; Xie, X; Han, M; Song, F Q; Wang, B J; Chen, W L; Xu, H X; Sun, L T

    2017-02-15

    Gas-phase deposited Ag nanoparticle assemblies are one of the most commonly used plasmonic substrates benefiting from their remarkable advantages such as clean particle surface, tunable particle density, available inter-particle gaps, low-cost and scalable fabrication, and excellent industry compatibility. However, their performance efficiencies are difficult to optimize due to the lack of knowledge of the hotspots inside their structures. We here report a design of delicate rainbow-like Ag nanoparticle assemblies, based on which the hotspots can be revealed through a combinatorial approach. The findings show that the hotspots in gas-phase deposited Ag nanoparticle assemblies are uniquely entangled by the excitation energy and specific inter-particle gaps, differing from the matching conditions in periodic arrays. For Ag nanoparticle assemblies deposited on Formvar-filmed substrates, the mean particle size is maintained around 10 nm, while the particle density can be widely tuned. The one possessing the highest SERS efficiency (under 473 nm excitation) have a particle number density of around 7100 μm(-2). Gaps with an inter-particle spacing of around 3 nm are found to serve as SERS hotspots, and these hotspots contribute to 68% of the overall SERS intensity. For Ag nanoparticle assemblies fabricated on carbon-filmed substrates, the mean particle size can be feasibly tuned. The one possessing the highest SERS efficiency under 473 nm excitation has a particle number density of around 460 μm(-2) and a mean particle size of around 42.1 nm. The construction of Ag-analyte-Ag sandwich-like nanoparticle assemblies by a two-step-deposition method slightly improves the SERS efficiency when the particle number density is low, but suppresses the SERS efficiency when the particle number density is high.

  14. Antibacterial performance of Ag nanoparticles and AgGO nanocomposites prepared via rapid microwave-assisted synthesis method

    NASA Astrophysics Data System (ADS)

    Chook, Soon Wei; Chia, Chin Hua; Zakaria, Sarani; Ayob, Mohd Khan; Chee, Kah Leong; Huang, Nay Ming; Neoh, Hui Min; Lim, Hong Ngee; Jamal, Rahman; Rahman, Raha Mohd Fadhil Raja Abdul

    2012-09-01

    Silver nanoparticles and silver-graphene oxide nanocomposites were fabricated using a rapid and green microwave irradiation synthesis method. Silver nanoparticles with narrow size distribution were formed under microwave irradiation for both samples. The silver nanoparticles were distributed randomly on the surface of graphene oxide. The Fourier transform infrared and thermogravimetry analysis results showed that the graphene oxide for the AgNP-graphene oxide (AgGO) sample was partially reduced during the in situ synthesis of silver nanoparticles. Both silver nanoparticles and AgGO nanocomposites exhibited stronger antibacterial properties against Gram-negative bacteria ( Salmonella typhi and Escherichia coli) than against Gram-positive bacteria ( Staphyloccocus aureus and Staphyloccocus epidermidis). The AgGO nanocomposites consisting of approximately 40 wt.% silver can achieve antibacterial performance comparable to that of neat silver nanoparticles.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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.

  17. 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

  18. High Visible Photoelectrochemical Activity of Ag Nanoparticle-Sandwiched CdS/Ag/ZnO Nanorods.

    PubMed

    Yang, Xu; Li, Hui; Zhang, Wu; Sun, Mingxuan; Li, Lequn; Xu, Ning; Wu, Jiada; Sun, Jian

    2017-01-11

    We report on the sensitizing of CdS-coated ZnO (CdS/ZnO) nanorods (NRs) by Ag nanoparticles (NPs) embedded between the CdS coating and the ZnO nanorod and the improved optical and photoelectrochemical properties of the Ag NP-sandwiched nanostructure CdS/Ag/ZnO NRs. The CdS/Ag/ZnO NRs were fabricated by growing Ag NPs on hydrothermally grown ZnO NRs and subsequently depositing CdS coatings followed by subsequent N2 annealing. The structure of the fabricated CdS/Ag/ZnO NRs was characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman backscattering, revealing that the ZnO NRs and the CdS coatings are both structured with hexagonal wurtzite and the Ag NPs contact well with ZnO and CdS. Optical properties were evaluated by measuring optical absorption and photoluminescence, showing that the Ag NPs behave well as sensitizers for optical property improvement and the CdS/Ag/ZnO NRs exhibit better photoresponse in a wide spectral region than CdS/ZnO because of plasmon-enhanced absorption due to the embedment of Ag NPs. The Ag NPs also serve as electron relays from CdS to ZnO, facilitating electron transfer from the CdS coatings to the ZnO NRs. The excellent photoresponse and efficient electron transfer make the CdS/Ag/ZnO NRs highly photoelectrochemically active. The CdS/Ag/ZnO NRs fabricated on indium-tin oxide present much better photoelectrochemical performance as photoanodes working in the visible region than CdS/ZnO NRs without Ag NPs. Under visible illumination, a maximum optical-to-chemical conversion efficiency of 3.13% is obtained for CdS/Ag/ZnO NR photoanodes against 1.35% for CdS/ZnO NR photoanodes.

  19. Ag/FeCo/Ag core/shell/shell magnetic nanoparticles with plasmonic imaging capability.

    PubMed

    Takahashi, Mari; Mohan, Priyank; Nakade, Akiko; Higashimine, Koichi; Mott, Derrick; Hamada, Tsutomu; Matsumura, Kazuaki; Taguchi, Tomohiko; Maenosono, Shinya

    2015-02-24

    Magnetic nanoparticles (NPs) have been used to separate various species such as bacteria, cells, and proteins. In this study, we synthesized Ag/FeCo/Ag core/shell/shell NPs designed for magnetic separation of subcellular components like intracellular vesicles. A benefit of these NPs is that their silver metal content allows plasmon scattering to be used as a tool to observe detection by the NPs easily and semipermanently. Therefore, these NPs are considered a potential alternative to existing fluorescent probes like dye molecules and colloidal quantum dots. In addition, the Ag core inside the NPs suppresses the oxidation of FeCo because of electron transfer from the Ag core to the FeCo shell, even though FeCo is typically susceptible to oxidation. The surfaces of the Ag/FeCo/Ag NPs were functionalized with ε-poly-L-lysine-based hydrophilic polymers to make them water-soluble and biocompatible. The imaging capability of the polymer-functionalized NPs induced by plasmon scattering from the Ag core was investigated. The response of the NPs to a magnetic field using liposomes as platforms and applying a magnetic field during observation by confocal laser scanning microscopy was assessed. The results of the magnetophoresis experiments of liposomes allowed us to calculate the magnetic force to which each liposome was subjected.

  20. 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,; Lead, Jamie

    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.

  1. Multifunctional ZnO/Ag nanorod array as highly sensitive substrate for surface enhanced Raman detection.

    PubMed

    Shan, Guiye; Zheng, Shujing; Chen, Shaopeng; Chen, Yanwei; Liu, Yichun

    2012-06-01

    A multifunctional ZnO/Ag nanorod arrays has been prepared to construct SERS-active and photocatalytic substrate by a hydrothermal method. The morphology, microstructure and optical properties of ZnO/Ag nanorod arrays are characterized by X-ray diffraction spectra, field emission scanning electron microscopy, energy-dispersive, ultraviolet-visible (UV-vis) absorption and photoluminescence measurement to confirm the successful Ag deposition on the ZnO nanorod arrays. Such arrays exhibit strong and reproducible SERS signals of the Raman probe molecules. The mechanism of SERS enhancement was discussed due to the formation of interfacial electric field between ZnO nanorods and Ag. Furthermore, ZnO/Ag nanorod arrays also show catalytic properties by photocatalytic degradation of target molecules adsorbed to the substrate, which provides promising application for detecting and eliminating organic pollutant.

  2. Fabrication and characterization of extended arrays of Ag{sub 2}S/Ag nanodot resistive switches

    SciTech Connect

    Wang Daoai; Liu Lifeng; Kim, Yunseok; Pantel, Daniel; Hesse, Dietrich; Alexe, Marin; Huang Zhipeng

    2011-06-13

    Well-ordered Ag{sub 2}S/Ag nanodot arrays with a density of >60 Gbit/in.{sup 2} have been fabricated by sputtering Ag on a silicon substrate using ultrathin porous anodic aluminum oxide membranes as shadow masks, followed by sulfurization treatment at room temperature. The morphology, microstructure, and electrical properties of the as-prepared nanodots were characterized by scanning electron microscopy, x-ray diffractometry, transmission electron microscopy, and conductive atomic force microscopy, respectively. Well-defined resistive switching behavior was observed in these nanodots, and the ON/OFF ratio was found to be higher than 10{sup 2}. The Ag{sub 2}S/Ag nanodot arrays hold substantial promise for use as ultrahigh density nonvolatile memory devices.

  3. 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.

  4. Optical nonlinearities of Au nanoparticles and Au/Ag coreshells.

    PubMed

    Seo, Jae Tae; Yang, Qiguang; Kim, Wan-Joong; Heo, Jinhwa; Ma, Seong-Min; Austin, Jasmine; Yun, Wan Soo; Jung, Sung Soo; Han, Sang Woo; Tabibi, Bagher; Temple, Doyle

    2009-02-01

    Au nanoparticles exhibited both negative and positive nonlinear absorptions with ground-state plasmon bleaching and free-carrier absorption that could be origins of the saturable and reverse-saturable optical properties. Au/Ag coreshells displayed only positive nonlinear absorption and reverse-saturable optical properties as a function of excitation intensity at the edge of surface-plasmon resonance, which implies no ground-state plasmon bleaching and the existence of two-photon absorption.

  5. Inverted Linear Halbach Array for Separation of Magnetic Nanoparticles.

    PubMed

    Ijiri, Y; Poudel, C; Williams, P S; Moore, L R; Orita, T; Zborowski, M

    2013-07-01

    A linear array of Nd-Fe-B magnets has been designed and constructed in an inverted Halbach configuration for use in separating magnetic nanoparticles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient in agreement with finite element modeling calculations. The magnet assembly has been combined with a flow channel for magnetic nanoparticle suspensions, such that for an appropriate distance away from the assembly, nanoparticles of higher moment aggregate and accumulate against the channel wall, with lower moment nanoparticles flowing unaffected. The device is demonstrated for iron oxide nanoparticles with diameters of ~ 5 and 20 nm. In comparison to other approaches, the inverted Halbach array is more amenable to modeling and to scaling up to preparative quantities of particles.

  6. Inverted Linear Halbach Array for Separation of Magnetic Nanoparticles

    PubMed Central

    Ijiri, Y.; Poudel, C.; Williams, P.S.; Moore, L.R.; Orita, T.; Zborowski, M.

    2014-01-01

    A linear array of Nd-Fe-B magnets has been designed and constructed in an inverted Halbach configuration for use in separating magnetic nanoparticles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient in agreement with finite element modeling calculations. The magnet assembly has been combined with a flow channel for magnetic nanoparticle suspensions, such that for an appropriate distance away from the assembly, nanoparticles of higher moment aggregate and accumulate against the channel wall, with lower moment nanoparticles flowing unaffected. The device is demonstrated for iron oxide nanoparticles with diameters of ~ 5 and 20 nm. In comparison to other approaches, the inverted Halbach array is more amenable to modeling and to scaling up to preparative quantities of particles. PMID:25382864

  7. Strongly visible-light responsive plasmonic shaped AgX:Ag (X = Cl, Br) nanoparticles for reduction of CO2 to methanol.

    PubMed

    An, Changhua; Wang, Jizhuang; Jiang, Wen; Zhang, Meiyu; Ming, Xijuan; Wang, Shutao; Zhang, Qinhui

    2012-09-21

    Plasmonic shaped AgX:Ag (X = Cl, Br) nanoparticles have been synthesized by a facile and versatile glycerol-mediated solution route. The as-prepared AgX:Ag nanoparticles exhibit regular shapes, i.e., cube-tetrapod-like AgCl:Ag nanoparticles and AgBr:Ag nanoplates. Compared with the pristine AgX, AgX:Ag nanocomposites display stronger absorption in the visible region due to the surface plasmon resonance of silver nanoparticles. The calculation of bandgaps and band positions indicates the as-achieved AgX:Ag nanoparticles can be used as a class of potential photocatalyst for the reduction of CO(2). For example, reduction of CO(2) under visible light irradiation with the assistance of the anisotropic AgX:Ag nanoparticles yields as much as 100 μmol methanol in the products. Furthermore, the AgX:Ag nanoparticles can maintain its structure and activity after 3 runs of reactions. Therefore, the present route opens an avenue to acquire plasmonic photocatalysts for conversion of CO(2) into useful organic compounds.

  8. Facile synthesis of AgCl/polydopamine/Ag nanoparticles with in-situ laser improving Raman scattering effect

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Zhang, Wenqi; Wang, Lin; Wang, Feng; Yang, Haifeng

    2017-01-01

    We reported a simple and fast method to prepare a composite material of polydopamine (PDA) adlayer covered cubic AgCl core, which was inlaid with Ag nanoparticles (NPs), shortly named as AgCl/PDA/AgNPs. The resultant AgCl/PDA/AgNPs could be employed as surface-enhanced Raman scattering (SERS) substrate for in-situ detection and the SERS activity could be further greatly improved due to the production of more AgNPs upon laser irradiation. With 4-mercaptopyridine (4-Mpy) as the probe molecule, the enhancement factor could reach 107. Additionally, such SERS substrate shows good reproducibility with relative standard deviation of 7.32% and long term stability (after storage for 100 days under ambient condition, SERS intensity decay is less than 25%). In-situ elevating SERS activity of AgCl/PDA/AgNPs induced by laser may be beneficial to sensitive analysis in practical fields.

  9. Preparation and antibacterial activity of titanium nanotubes loaded with Ag nanoparticles in the dark and under the UV light

    NASA Astrophysics Data System (ADS)

    Zhao, Chanjuan; Feng, Bo; Li, Yiting; Tan, Jing; Lu, Xiong; Weng, Jie

    2013-09-01

    Highly ordered anatase-type titanium nanotubes (TNTs) arrays were prepared on the surface of titanium by anodization and subsequently heat treatment at 450 °C for 5 h. Three different diameters of TNTs (50 nm, 75 nm, 100 nm) were fabricated via the voltage changed. Then Ag was loaded on these TNTs through a photo-reduction method of AgNO3 solution. Ag particles with the size of approximately 10 nm were uniformly distributed on the surface of TNTs. Samples were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, atomic absorption spectrometry and contact angle test. Meanwhile, the antibacterial activities of Ag-loaded TiO2 nanotubes (TNTs-Ag) were evaluated through antibacterial experiment against both Escherichia coli and Staphylococcus aureus in the dark and under the UV light (λ = 365 nm) irradiation respectively. The results indicated that under the UV light TNTs-Ag had higher antibacterial activities to the two bacteria than TNTs, though the later also showed antibacterial ability. While in the dark environment, the loading of Ag nanoparticles largely enhanced the antibacterial activities of the titanium nanotubes. In addition, the antibacterial efficiencies of all samples increased with increase of nanotube diameters both in the dark and under the UV light. Therefore, TNTs loaded with Ag nanoparticles are expected to be well suited for endo-prosthetic applications due to their excellent antibacterial activities in the dark. And their antibacterial efficiencies can be controlled by adjusting diameters of TNTs, distribution and size of Ag nanoparticles.

  10. Selective photochemical synthesis of Ag nanoparticles on position-controlled ZnO nanorods for the enhancement of yellow-green light emission.

    PubMed

    Park, Hyeong-Ho; Zhang, Xin; Lee, Keun Woo; Sohn, Ahrum; Kim, Dong-Wook; Kim, Joondong; Song, Jin-Won; Choi, Young Su; Lee, Hee Kwan; Jung, Sang Hyun; Lee, In-Geun; Cho, Young-Dae; Shin, Hyun-Beom; Sung, Ho Kun; Park, Kyung Ho; Kang, Ho Kwan; Park, Won-Kyu; Park, Hyung-Ho

    2015-12-28

    A novel technique for the selective photochemical synthesis of silver (Ag) nanoparticles (NPs) on ZnO nanorod arrays is established by combining ultraviolet-assisted nanoimprint lithography (UV-NIL) for the definition of growth sites, hydrothermal reaction for the position-controlled growth of ZnO nanorods, and photochemical reduction for the decoration of Ag NPs on the ZnO nanorods. During photochemical reduction, the size distribution and loading of Ag NPs on ZnO nanorods can be tuned by varying the UV-irradiation time. The photochemical reduction is hypothesized to facilitate the adsorbed citrate ions on the surface of ZnO, allowing Ag ions to preferentially form Ag NPs on ZnO nanorods. The ratio of visible emission to ultraviolet (UV) emission for the Ag NP-decorated ZnO nanorod arrays, synthesized for 30 min, is 20.5 times that for the ZnO nanorod arrays without Ag NPs. The enhancement of the visible emission is believed to associate with the surface plasmon (SP) effect of Ag NPs. The Ag NP-decorated ZnO nanorod arrays show significant SP-induced enhancement of yellow-green light emission, which could be useful in optoelectronic applications. The technique developed here requires low processing temperatures (120 °C and lower) and no high-vacuum deposition tools, suitable for applications such as flexible electronics.

  11. 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.

  12. 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.

  13. Effect of Ag nanoparticles deposition on photocatalytic activity of Ag{sub 2}SO{sub 3}

    SciTech Connect

    Zhang, Xuan Wang, Qi; Hu, Jin-Wen; Zou, Lan-Hua; You, Jia-Wen

    2016-03-15

    Highlights: • Ag{sub 2}SO{sub 3} was developed as novel photocatalyst. • The effect of Ag nanoparticles deposition on photocatalytic activity was investigated. • The activation and deactivation mechanism was proposed. - Abstract: A novel photocatalyst Ag{sub 2}SO{sub 3} was prepared and the effect of Ag nanoparticles, photo-deposited on the surface of Ag{sub 2}SO{sub 3}, on its photocatalytic activity was investigated. The as-prepared photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflection spectroscopy (DRS). The photocatalytic activity was evaluated by photo-degradation of rhodamine B dye under UV light irradiation. It was found that the photocatalytic activity of Ag{sub 2}SO{sub 3} was initially enhanced with deposition of Ag nanoparticles, but subsequently declined with Ag nanoparticles overloaded. The possible mechanism was proposed based on experimental results. These findings may contribute to developing novel photocatalysts and understanding of fundamentals of Ag-based photocatalytic materials.

  14. Comparison of antibacterial activities of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Dhanalekshmi, K. I.; Meena, K. S.

    2014-07-01

    Core-shell type Ag@TiO2 nanoparticles were prepared by one pot simultaneous reduction of AgNO3 and hydrolysis of Ti (IV) isopropoxide and Ag@SiO2 core-shell nanoparticles were prepared by Stober's method. They were characterized by absorption, XRD, and HR-TEM techniques. XRD patterns show the presence of anatase form of TiO2 and amorphous form of SiO2 and the noble metal (Ag). High resolution transmission electron microscopy measurements revealed that their size is below 50 nm. The antibacterial properties of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were examined by the agar diffusion method. As a result E. coli and S. aureus were shown to be substantially inhibited by Ag@TiO2 and Ag@SiO2 core-shell nanoparticles. These results demonstrated that TiO2 and SiO2 supported on the surface of Ag NPs without aggregation was proved to have enhanced antibacterial activity.

  15. Photo-catalytic activity of Plasmonic Ag@AgCl nanoparticles (synthesized via a green route) for the effective degradation of Victoria Blue B from aqueous phase.

    PubMed

    Devi, Th Babita; Begum, Shamima; Ahmaruzzaman, M

    2016-07-01

    This study reports a green process for the fabrication of Ag@AgCl (silver@silver chloride) nanoparticles by using Aquilaria agallocha (AA) leaves juice without using any external reagents. The effect of various reaction parameters, such as reaction temperature, reaction time and concentration of Aquilaria agallocha leaves juice in the formation of nanoparticles have also been investigated. From the FTIR spectra of leaves juice and phytochemicals test, it was found that flavonoids present in the leaves are responsible for the reduction of Ag(+) ions to Ag(0) species and leads to the formation of Ag@AgCl NPs. The synthesized Ag@AgCl NPs were utilized for the removal of toxic and hazardous dyes, such as Victoria Blue B from aqueous phase. Approximately, 99.46% degradation of Victoria Blue B dye were observed with Ag@AgCl NPs. Furthermore, the photocatalytic activity of the Ag@AgCl nanoparticles was unchanged after 5cycles of operation.

  16. Single-pulse transformation of Ag thin film into nanoparticles via laser-induced dewetting

    NASA Astrophysics Data System (ADS)

    Oh, Yoonseok; Lee, Myeongkyu

    2017-03-01

    In this study, we show that Ag thin films deposited on glass can be transformed into nanoparticles by laser-induced dewetting using a nanosecond-pulsed Nd:YAG laser. The film could be completely dewetted by a single pulse and the pulse energy density required for a 10 nm-thick Ag film was 86 mJ/cm2 at λ = 1064 nm. This made it possible to dewet a film area of ∼10 cm2 by a single pulse with energy of 850 mJ. The produced particles exhibited a monomodal size distribution and the mean particle size increased as the initial film thickness increased. Repeated exposure to pulses induced no noticeable change in the particle size distribution. The initial film thickness was the only factor that determined the mean particle size. The absorption spectra of dewetted films were well consistent with the surface plasma resonance behaviors of metal nanoparticles. This process provides a facile and scalable method of forming metal nanoparticle arrays for plasmonic and other applications.

  17. 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.

  18. Magnetic nanoparticle assembly arrays prepared by hierarchical self-assembly on a patterned surface.

    PubMed

    Wen, Tianlong; Zhang, Dainan; Wen, Qiye; Zhang, Huaiwu; Liao, Yulong; Li, Qiang; Yang, Qinghui; Bai, Feiming; Zhong, Zhiyong

    2015-03-21

    Inverted pyramid hole arrays were fabricated by photolithography and used as templates to direct the growth of colloidal nanoparticle assemblies. Cobalt ferrite nanoparticles deposit in the holes to yield high quality pyramid magnetic nanoparticle assembly arrays by carefully controlling the evaporation of the carrier fluid. Magnetic measurements indicate that the pyramid magnetic nanoparticle assembly arrays preferentially magnetize perpendicular to the substrate.

  19. 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.

  20. Preparation of AgBr Nanoparticles in Microemulsions Via Reaction of AgNO3 with CTAB Counterion

    NASA Astrophysics Data System (ADS)

    Husein, Maen M.; Rodil, Eva; Vera, Juan H.

    2007-10-01

    Nanoparticles of AgBr were prepared by precipitating AgBr in the water pools of microemulsions consisting of CTAB, n-butanol, isooctane and water. An aqueous solution of AgNO3 added to the microemulsion was the source of Ag+ ions. The formation of AgBr nanoparticles in microemulsions through direct reaction with the surfactant counterion is a novel approach aimed at decreasing the role of intermicellar nucleation on nanoparticle formation for rapid reactions. The availability of the surfactant counterion in every reverse micelle and the rapidity of the reaction with the counterion trigger nucleation within individual reverse micelles. The effect of the following variables on the particle size and size distribution was investigated: the surfactant and cosurfactant concentrations, moles of AgNO3 added, and water to surfactant mole ratio, R. High concentration of the surfactant or cosurfactant, or high water content of the microemulsion favored intermicellar nucleation and resulted in the formation of large particles with broad size distribution, while high amounts of AgNO3 favored nucleation within individual micelles and resulted in small nanoparticles with narrow size distribution. A blue shift in the UV absorption threshold corresponding to a decrease in the particle size was generally observed. Notably, the variation of the absorption peak size with the nanoparticle size was opposite to those reported by us in previous studies using different surfactants.

  1. Array-based electrical detection of DNA with nanoparticle probes.

    PubMed

    Park, So-Jung; Taton, T Andrew; Mirkin, Chad A

    2002-02-22

    A DNA array detection method is reported in which the binding of oligonucleotides functionalized with gold nanoparticles leads to conductivity changes associated with target-probe binding events. The binding events localize gold nanoparticles in an electrode gap; silver deposition facilitated by these nanoparticles bridges the gap and leads to readily measurable conductivity changes. An unusual salt concentration-dependent hybridization behavior associated with these nanoparticle probes was exploited to achieve selectivity without a thermal-stringency wash. Using this method, we have detected target DNA at concentrations as low as 500 femtomolar with a point mutation selectivity factor of approximately 100,000:1.

  2. Electrodeposition of silver nanoparticle arrays on transparent conductive oxides

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  3. Self-assembled dendrite Ag arrays with tunable morphologies for surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Huang, Pingping; Wang, Zhezhe; Lin, Lin; Feng, Zhuohong; Wen, Xin; Zheng, Zhiqiang

    2016-11-01

    Highly ordered dendrite Ag arrays are fabricated by using photosensitive sol-gel and electrochemical reaction self-assembly strategy to achieve large field enhancement for Surface-Enhanced Raman scattering (SERS) application. The effects of applied voltage, reaction time and KH550 have been investigated to tailor the growth of Ag dendrite. At an applied voltage of 25 V and reaction time of 30 min, orderly dendrite Ag arrays are obtained and show strong SERS effect. Meanwhile, the additive KH550 also shows a unique effect on the morphologies of Ag dendrite and contributes to increase the SERS. This kind of substrate can be used to detect R6G with the concentration of as low as 10-13 M obviously. Our results suggest that the dendrite Ag arrays as SERS substrate with strong SERS effect having vast potential applications in biosensors and nanodevices with molecule-level detection.

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

    NASA Astrophysics Data System (ADS)

    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

    2015-09-01

    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.

  5. Surface-enhanced Raman spectroscopy for DNA detection by the self-assembly of Ag nanoparticles onto Ag nanoparticle-graphene oxide nanocomposites.

    PubMed

    Lin, Tsung-Wu; Wu, Hong-Yi; Tasi, Ting-Ti; Lai, Ying-Huang; Shen, Hsin-Hui

    2015-07-28

    A novel surface-enhanced Raman scattering (SERS) sensing system which operates by the self-assembly of Ag nanoparticles (AgNPs) onto the nanocomposite of AgNPs and graphene oxide (AgNP-GO) in the presence of two complementary DNAs has been developed. In this system, AgNP-GO serves as a SERS-active substrate. The AgNPs with the modification of non-fluorescent 4-mercaptobenzoic acid (4-MBA) act as highly efficient Raman probes for DNA hybridization. When probe DNAs on AgNP-GO are complementary to target DNAs on AgNPs functionalized with 4-MBA, the DNA hybridization occurring directs the self-assembly of AgNPs onto AgNP-GO, leading to the creation of SERS hot spots. Due to the fact that partial 4-MBA molecules are located in the region of the hot spots, their SERS signals are greatly enhanced, indicating successful DNA hybridization. It is noteworthy that the size of AgNPs contributes significantly to the enhancement of SERS activity. The detection limit of the target DNAs at the pM level can be achieved through the self-assembly of large sized AgNPs onto AgNP-GO. More importantly, the AgNP-AgNP-GO system shows reproducible SERS signals in proportion to the logarithm of the target DNA concentrations spanning from 10(-6) to 10(-12) M and the excellent capability for multiplex DNA detection.

  6. Composition dependence of magneto-optical response in Ag/Co dimer nanodot arrays

    NASA Astrophysics Data System (ADS)

    Yan, Yaning; Deng, Chenhua; Yan, Lijuan; Tang, Zhixiong; Tang, Shaolong; Xu, Xiaohong

    2016-12-01

    In this work, we fabricated ordered Ag/Co dimer nanodot arrays by using anodic aluminum oxide (AAO) templates combined with magnetron sputtering. First of all, we studied the optical properties of the nanodot arrays with different Ag/Co ratios while keeping the total thickness constant. The sharp absorption peaks were found in visible spectral range due to the excitation of localized surface plasmon resonances (LSPR) of Ag/Co nanodot arrays, and the absorption peak decreases and slightly blue shifts with the decreasing of Ag ratio. Further, we explored the magneto-optical (MO) properties of nanodot arrays, and found that the excitation of LSPR induces electromagnetic (EM) enhancement near the surface of the Co, which exhibits a sizable MO activity.

  7. Controlled joining of Ag nanoparticles with femtosecond laser radiation

    NASA Astrophysics Data System (ADS)

    Huang, H.; Liu, L.; Peng, P.; Hu, A.; Duley, W. W.; Zhou, Y.

    2012-12-01

    We show that it is possible to tailor the gap separation and interface geometry between adjacent Ag nanoparticles (NPs) by controlling fluence when irradiating with pulses from a fs laser. Unirradiated samples extracted from aqueous solution consist of networks of Ag NPs coated with polyvinylpyrrolidone (PVP). At low laser fluence, bonding between NPs occurs via the formation of an intervening hydrogenated amorphous carbon (α-C:H) layer resulting from the laser-induced decomposition of PVP. This occurs when electrons are emitted at hot-spots created by the trapping of plasmons. The thickness of the α-C:H layer determines the minimum separation between NPs. Ag NPs with different contact geometries can be produced by irradiation of the networks in solution at fluences exceeding the threshold for the formation of α-C:H. At fluences between 200 and 380 μJ/cm2, the α-C:H interface layer is replaced with a metallic neck. Surface enhanced Raman scattering (SERS) has been used to quantify the electromagnetic field enhancement in joined NP samples. We find that Ag NPs bonded by α-C:H and exhibiting a narrow gap possess the highest SERS enhancement.

  8. 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.

  9. Biotic and abiotic interactions in aquatic microcosms determine fate and toxicity of Ag nanoparticles: part 2-toxicity and Ag speciation.

    PubMed

    Bone, Audrey J; Colman, Benjamin P; Gondikas, Andreas P; Newton, Kim M; Harrold, Katherine H; Cory, Rose M; Unrine, Jason M; Klaine, Stephen J; Matson, Cole W; Di Giulio, Richard T

    2012-07-03

    To study the effects of complex environmental media on silver nanoparticle (AgNP) toxicity, AgNPs were added to microcosms with freshwater sediments and two species of aquatic plants (Potamogeton diversifolius and Egeria densa), followed by toxicity testing with microcosm surface water. Microcosms were designed with four environmental matrices in order to determine the contribution of each environmental compartment to changes in toxicity: water only (W), water + sediment (WS), water + plants (WP), and water + plants + sediment (WPS). Silver treatments included AgNPs with two different coatings, gum arabic (GA-AgNPs) or polyvinylpyrollidone (PVP-AgNPs), as well as AgNO(3). Water samples taken from the microcosms at 24 h postdosing were used in acute toxicity tests with two standard model organisms, early life stage zebrafish (Danio rerio) and Daphnia magna. Speciation of Ag in these samples was analyzed using Ag L3-edge X-ray absorption near edge spectroscopy (XANES). Silver speciation patterns for the nanoparticle treatments varied significantly by coating type. While PVP-AgNPs were quite stable and resisted transformation across all matrices (>92.4% Ag(0)), GA-AgNP speciation patterns suggest significantly higher transformation rates, especially in treatments with plants (<69.2% and <58.8% Ag(0) in WP and WPS, respectively) and moderately increased transformation with sediments (<85.6% Ag(0)). Additionally, the presence of plants in the microcosms (with and without sediments) reduced both the concentration of Ag in the water column and toxicity for all Ag treatments. Reductions in toxicity may have been related to decreased water column concentrations as well as changes in the surface chemistry of the particles induced by organic substances released from the plants.

  10. 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.

  11. 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.

  12. Controlled plasmon enhanced fluorescence by silver nanoparticles deposited onto nanotube arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenglong; Wu, Yanni; Dong, Jun; Gao, Wei; Han, Qingyan; Zheng, Hairong

    2016-09-01

    Three-dimensional (3D) plasmonic nanostructures of porous alumina array (PAA) with silver nanoparticles (AgNPs) were prepared for enhancing fluorescence emission. In order to avoid fluorescence quenching effects and obtain clear fluorescence enhancement, the molecules were separated by using such 3D substrates, and the mean distance between the molecules and nanoparticles’ surface can be easily controlled by changing the diameters of the PAA tube. It was found that the PAA tube with smaller size provides better fluorescence enhancement. Enhanced cross section, a new fluorescence enhanced factor, combined with the simulation of localized electromagnetic field enhancement was presented to understand the experimental results.

  13. Graphene oxide-Ag nanoparticles-pyramidal silicon hybrid system for homogeneous, long-term stable and sensitive SERS activity

    NASA Astrophysics Data System (ADS)

    Guo, Jia; Xu, Shicai; Liu, Xiaoyun; Li, Zhe; Hu, Litao; Li, Zhen; Chen, Peixi; Ma, Yong; Jiang, Shouzhen; Ning, Tingyin

    2017-02-01

    In our work, few layers graphene oxide (GO) were directly synthesized on Ag nanoparticles (AgNPs) by spin-coating method to fabricate a GO-AgNPs hybrid structure on a pyramidal silicon (PSi) substrate for surface-enhanced Raman scattering (SERS). The GO-AgNPs-PSi substrate showed excellent Raman enhancement effect, the minimum detected concentration for Rhodamine 6G (R6G) can reach 10-12 M, which is one order of magnitude lower than the AgNPs-PSi substrate and two order of magnitude lower than the GO-AgNPs-flat-Si substrate. The linear fit calibration curve with error bars is presented and the value of R2 of 612 and 773 cm-1 can reach 0.986 and 0.980, respectively. The excellent linear response between the Raman intensity and R6G concentrations prove that the prepared GO-AgNPs-PSi substrates can serve as good SERS substrate for molecule detection. The maximum deviations of SERS intensities from 20 positions of the GO-AgNPs-PSi substrate are less than 8%, revealing the high homogeneity of the SERS substrate. The excellent homogeneity of the enhanced Raman signals can be attributed to well-separated pyramid arrays of PSi, the uniform morphology of AgNPs and multi-functions of GO layer. Besides, the uniform GO film can effectively protect AgNPs from oxidation and endow the hybrid system a good stability and long lifetime. This GO-AgNPs-PSi substrate may provide a new way toward practical applications for the ultrasensitive and label-free SERS detection in areas of medicine, food safety and biotechnology.

  14. 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.

  15. 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.

  16. 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.

  17. Hyperbolic and plasmonic properties of silicon/Ag aligned nanowire arrays.

    PubMed

    Prokes, S M; Glembocki, Orest J; Livenere, J E; Tumkur, T U; Kitur, J K; Zhu, G; Wells, B; Podolskiy, V A; Noginov, M A

    2013-06-17

    The hyperbolic and plasmonic properties of silicon nanowire/Ag arrays have been investigated. The aligned nanowire arrays were formed and coated by atomic layer deposition of Ag, which itself is a metamaterial due to its unique mosaic film structure. The theoretical and numerical studies suggest that the fabricated arrays have hyperbolic dispersion in the visible and IR ranges of the spectrum. The theoretical predictions have been indirectly confirmed by polarized reflection spectra, showing reduction of the reflection in p polarization in comparison to that in s polarization. Studies of dye emission on top of Si/Ag nanowire arrays show strong emission quenching and shortening of dye emission kinetics. This behavior is also consistent with the predictions for hyperbolic media. The measured SERS signals were enhanced by almost an order of magnitude for closely packed and aligned nanowires, compared to random nanowire composites. These results agree with electric field simulations of these array structures.

  18. 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.

  19. Cu-Ag core-shell nanoparticles with enhanced oxidation stability for printed electronics

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    In this work, we synthesized uniform Cu-Ag core-shell nanoparticles using a facile two-step process that consists of thermal decomposition and galvanic displacement methods. The core-shell structure of these nanoparticles was confirmed through characterization using transmission electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Furthermore, we investigated the oxidation stability of the Cu-Ag core-shell nanoparticles in detail. Both qualitative and quantitative x-ray photoelectron spectroscopy analyses confirm that the Cu-Ag core-shell nanoparticles have considerably higher oxidation stability than Cu nanoparticles. Finally, we formulated a conductive ink using the synthesized nanoparticles and coated it onto glass substrates. Following the sintering process, we compared the resistivity of the Cu-Ag core-shell nanoparticles with that of the Cu nanoparticles. The results of this study clearly show that the Cu-Ag core-shell nanoparticles can potentially be used as an alternative to Ag nanoparticles because of their superior oxidation stability and electrical properties.

  20. Cu-Ag core-shell nanoparticles with enhanced oxidation stability for printed electronics.

    PubMed

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

    2015-11-13

    In this work, we synthesized uniform Cu-Ag core-shell nanoparticles using a facile two-step process that consists of thermal decomposition and galvanic displacement methods. The core-shell structure of these nanoparticles was confirmed through characterization using transmission electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Furthermore, we investigated the oxidation stability of the Cu-Ag core-shell nanoparticles in detail. Both qualitative and quantitative x-ray photoelectron spectroscopy analyses confirm that the Cu-Ag core-shell nanoparticles have considerably higher oxidation stability than Cu nanoparticles. Finally, we formulated a conductive ink using the synthesized nanoparticles and coated it onto glass substrates. Following the sintering process, we compared the resistivity of the Cu-Ag core-shell nanoparticles with that of the Cu nanoparticles. The results of this study clearly show that the Cu-Ag core-shell nanoparticles can potentially be used as an alternative to Ag nanoparticles because of their superior oxidation stability and electrical properties.

  1. Tunable plasmon polaritons in arrays of interacting metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Weick, Guillaume; Mariani, Eros

    2015-01-01

    We consider a simple cubic array of metallic nanoparticles supporting extended collective plasmons that arise from the near-field dipolar interaction between localized surface plasmons in each nanoparticle. We develop a fully analytical quantum theory of the strong-coupling regime between these collective plasmons and photons resulting in plasmon polaritons in the nanoparticle array. Remarkably, we show that the polaritonic band gap and the dielectric function of the metamaterial can be significantly modulated by the polarization of light. We unveil how such an anisotropic behavior in the plasmonic metamaterial is crucially mediated by the dipolar interactions between the nanoparticles despite the symmetry of the underlying lattice. Our results thus pave the way towards the realization of tunable quantum plasmonic metamaterials presenting interaction-driven birefringence.

  2. Light manipulation of nanoparticles in arrays of topological defects

    PubMed Central

    Kasyanyuk, D.; Pagliusi, P.; Mazzulla, A.; Reshetnyak, V.; Reznikov, Yu.; Provenzano, C.; Giocondo, M.; Vasnetsov, M.; Yaroshchuk, O.; Cipparrone, G.

    2016-01-01

    We report a strategy to assemble and manipulate nanoparticles arrays. The approach is based on the use of topological defects, namely disclination lines, created in chiral liquid crystals. The control of nanoparticle-loaded topological defects by low power light is demonstrated. Large-scale rotation, translation and deformation of quantum dots light-emitting chains is achieved by homogeneous LED illumination. Full reconfigurability and time stability make this approach attractive for future developments and applications. PMID:26882826

  3. Light manipulation of nanoparticles in arrays of topological defects

    NASA Astrophysics Data System (ADS)

    Kasyanyuk, D.; Pagliusi, P.; Mazzulla, A.; Reshetnyak, V.; Reznikov, Yu.; Provenzano, C.; Giocondo, M.; Vasnetsov, M.; Yaroshchuk, O.; Cipparrone, G.

    2016-02-01

    We report a strategy to assemble and manipulate nanoparticles arrays. The approach is based on the use of topological defects, namely disclination lines, created in chiral liquid crystals. The control of nanoparticle-loaded topological defects by low power light is demonstrated. Large-scale rotation, translation and deformation of quantum dots light-emitting chains is achieved by homogeneous LED illumination. Full reconfigurability and time stability make this approach attractive for future developments and applications.

  4. Preparation and characterization of Ag nanoparticle-embedded blank and ligand-anchored silica gels.

    PubMed

    Im, Hee-Jung; Lee, Byung Cheol; Yeon, Jei-Won

    2013-11-01

    Ag nanoparticles, used for halogen (especially iodine) adsorption and an evaluation of halogen behavior, were embedded in synthesized inorganic-organic hybrid gels. In particular, an irradiation method using an electron beam plays a part in introducing Ag nanoparticles to the organofunctionalized silica gels from AgNO3 solutions in a simple way at atmospheric pressure and room temperature. For preparation of the Ag nanoparticle-embedded inorganic-organic hybrid gels, ligands of ethylenediamine (NH2CH2CH2NH-, TMSen) and mercapto (HS-) functionalized three-dimensional porous SiO2 sol-gels were first synthesized through hydrolysis and condensation reactions, and Ag nanoparticles were then embedded into the ethylenediamine- and mercapto-anchored silica gels each, through electron-beam irradiation. The addition of ligands yielded larger average pore sizes than the absence of any ligand. Moreover, the ethylenediamine ligand led to looser structures and better access of the Ag nanoparticles to the ethylenediamine-anchored gel. As a result, more Ag nanoparticles were introduced into the ethylenediamine-anchored gel. The preparation and characterization of Ag nanoparticle-embedded blank and ligand-anchored silica gels are discussed in detail.

  5. Template-Stripped Smooth Ag Nanohole Arrays with Silica Shells for Surface Plasmon Resonance Biosensing

    PubMed Central

    Im, Hyungsoon; Lee, Si Hoon; Wittenberg, Nathan J.; Johnson, Timothy W.; Lindquist, Nathan C.; Nagpal, Prashant; Norris, David J.; Oh, Sang-Hyun

    2011-01-01

    Inexpensive, reproducible and high-throughput fabrication of nanometric apertures in metallic films can benefit many applications in plasmonics, sensing, spectroscopy, lithography and imaging. Here we use template stripping to pattern periodic nanohole arrays in optically thick, smooth Ag films with a silicon template made via nanoimprint lithography. Ag is a low-cost material with good optical properties, but it suffers from poor chemical stability and biocompatibility. However, a thin silica shell encapsulating our template-stripped Ag nanoholes facilitates biosensing applications by protecting the Ag from oxidation as well as providing a robust surface that can be readily modified with a variety of biomolecules using well-established silane chemistry. The thickness of the conformal silica shell can be precisely tuned by atomic layer deposition, and a 15-nm-thick silica shell can effectively prevent fluorophore quenching. The Ag nanohole arrays with silica shells can also be bonded to polydimethylsiloxane (PDMS) microfluidic channels for fluorescence imaging, formation of supported lipid bilayers, and real-time, label-free SPR sensing. Additionally, the smooth surfaces of the template-stripped Ag films enhance refractive index sensitivity compared with as-deposited, rough Ag films. Because nearly centimeter-sized nanohole arrays can be produced inexpensively without using any additional lithography, etching or lift-off, this method can facilitate widespread applications of metallic nanohole arrays for plasmonics and biosensing. PMID:21770414

  6. Ordering Ag nanowire arrays by spontaneous spreading of volatile droplet on solid surface

    PubMed Central

    Dai, Han; Ding, Ruiqiang; Li, Meicheng; Huang, Jinjer; Li, Yingfeng; Trevor, Mwenya

    2014-01-01

    Large-area Ag nanowires are ordered by spontaneous spreading of volatile droplet on a wettable solid surface. Compared with other nanowires orientation methods, radial shaped oriented Ag nanowires in a large ring region are obtained in an extremely short time. Furthermore, the radial shaped oriented Ag nanowires are transferred and aligned into one direction. Based on the hydrodynamics, the coactions among the microfluid, gravity effect and the adhesion of substrate on the orientation of the Ag nanowires are clearly revealed. This spreading method opens an efficient way for extreme economic, efficient and “green” way for commercial producing ordered nanowire arrays. PMID:25339118

  7. Silver nanoparticle-initiated chemiluminescence reaction of luminol-AgNO3 and its analytical application.

    PubMed

    Liu, Cui; Li, Baoxin

    2011-07-01

    Ag(+) has been regarded as an inert chemiluminescent oxidant. In this work, it was found that in the presence of silver nanoparticles (AgNPs), AgNO(3) could react with luminol to produce strong chemiluminescence (CL). The AgNPs with smaller size could initiate stronger CL emission. To investigate the CL mechanism of the AgNPs-luminol-AgNO(3) system, the UV-visible spectra and the CL spectrum of the CL system were obtained. The CL reaction mechanism involving catalysis was proposed. Compared with the reported nanoparticles-luminol-H(2)O(2) CL system, the AgNPs-luminol-AgNO(3) CL system has the advantages of low background and good stability. Moreover, the new CL system was used in immunoassay for IgG.

  8. Bottom-Up Nanofabrication of Supported Noble Metal Alloy Nanoparticle Arrays for Plasmonics.

    PubMed

    Nugroho, Ferry A A; Iandolo, Beniamino; Wagner, Jakob B; Langhammer, Christoph

    2016-02-23

    Mixing different elements at the nanoscale to obtain alloy nanostructures with fine-tuned physical and chemical properties offers appealing opportunities for nanotechnology and nanoscience. However, despite widespread successful application of alloy nanoparticles made by colloidal synthesis in heterogeneous catalysis, nanoalloy systems have been used very rarely in solid-state devices and nanoplasmonics-related applications. One reason is that such applications require integration in arrays on a surface with compelling demands on nanoparticle arrangement, uniformity in surface coverage, and optimization of the surface density. These cannot be fulfilled even using state-of-the-art self-assembly strategies of colloids. As a solution, we present here a generic bottom-up nanolithography-compatible fabrication approach for large-area arrays of alloy nanoparticles on surfaces. To illustrate the concept, we focus on Au-based binary and ternary alloy systems with Ag, Cu, and Pd, due to their high relevance for nanoplasmonics and complete miscibility, and characterize their optical properties. Moreover, as an example for the relevance of the obtained materials for integration in devices, we demonstrate the superior and hysteresis-free plasmonic hydrogen-sensing performance of the AuPd alloy nanoparticle system.

  9. Efficient removal of herbicide 2,4-dichlorophenoxyacetic acid from water using Ag/reduced graphene oxide co-decorated TiO2 nanotube arrays.

    PubMed

    Tang, Yanhong; Luo, Shenglian; Teng, Yarong; Liu, Chengbin; Xu, Xiangli; Zhang, Xilin; Chen, Liang

    2012-11-30

    A new photocatalyst, Ag nanoparticles (NPs) and reduced graphene oxide (RGO) co-decorated TiO(2) nanotube arrays (NTs) (Ag/RGO-TiO(2) NTs), was designed and facilely produced by combining electrodeposition and photoreduction processes. The structures and properties of the photocatalysts were characterized. The ternary catalyst exhibited almost 100% photocatalytic removal efficiency of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from water under simulated solar light irradiation. The photodegradation rate toward 2,4-D over Ag/RGO-TiO(2) NTs is 11.3 times that over bare TiO(2) NTs. After 10 successive cycles with 1600 min of irradiation, Ag/RGO-TiO(2) NTs maintained as high 2,4-D removal efficiency as 97.3% with excellent stability and easy recovery, which justifies the photocatalytic system a promising application for herbicide removal from water.

  10. 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

  11. 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.

  12. DNA/Ag Nanoparticles as Antibacterial Agents against Gram-Negative Bacteria

    PubMed Central

    Takeshima, Tomomi; Tada, Yuya; Sakaguchi, Norihito; Watari, Fumio; Fugetsu, Bunshi

    2015-01-01

    Silver (Ag) nanoparticles were produced using DNA extracted from salmon milt as templates. Particles spherical in shape with an average diameter smaller than 10 nm were obtained. The nanoparticles consisted of Ag as the core with an outermost thin layer of DNA. The DNA/Ag hybrid nanoparticles were immobilized over the surface of cotton based fabrics and their antibacterial efficiency was evaluated using E. coli as the typical Gram-negative bacteria. The antibacterial experiments were performed according to the Antibacterial Standard of Japanese Association for the Functional Evaluation of Textiles. The fabrics modified with DNA/Ag nanoparticles showed a high enough inhibitory and killing efficiency against E. coli at a concentration of Ag ≥ 10 ppm. PMID:28347012

  13. 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.

  14. Optical diffraction in ordered VO2 nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Lopez, Rene; Feldman, Leonard; Haglund, Richard

    2006-03-01

    The potential of oxide electronic materials as multifunctional building blocks is one of the driving concepts of the field. In this presentation, we show how nanostructured particle arrays with long-range order can be used to modulate an optical response through exploiting the metal-insulator transition of vanadium dioxide. Arrays of VO2 nanoparticles with long-range order were fabricated by pulsed laser deposition in an arbitrary pattern defined by focused ion-beam lithography. The interaction of light with the nanoparticles is controlled by the nanoparticle size, spacing and geometrical arrangement and by switching between the metallic and semiconducting phases of VO2. In addition to the near-infrared surface plasmon response observed in previous VO2 studies, the VO2 nanoparticle arrays exhibit size-dependent optical resonances in the visible region that likewise show an enhanced optical contrast between the semiconducting and metallic phases. The collective optical response as a function of temperature gives rise to an enhanced scattering state during the evolving phase transition, while the incoherent coupling between the nanoparticles produces an order-disorder-order transition.

  15. Supported Membranes Embedded with Fixed Arrays of Gold Nanoparticles

    PubMed Central

    2011-01-01

    We present a supported membrane platform consisting of a fluid lipid bilayer membrane embedded with a fixed array of gold nanoparticles. The system is realized by preforming a hexagonal array of gold nanoparticles (∼5–7 nm) with controlled spacing (∼50–150 nm) fixed to a silica or glass substrate by block copolymer lithography. Subsequently, a supported membrane is assembled over the intervening bare substrate. Proteins or other ligands can be associated with the fluid lipid component, the fixed nanoparticle component, or both, providing a hybrid interface consisting of mobile and immobile components with controlled geometry. We test different biochemical coupling strategies to bind individual proteins to the particles surrounded by a fluid lipid membrane. The coupling efficiency to nanoparticles and the influence of nanoparticle arrays on the surrounding membrane integrity are characterized by fluorescence imaging, correlation spectroscopy, and super-resolution fluorescence microscopy. Finally, the functionality of this system for live cell experiments is tested using the ephrin-A1–EphA2 juxtacrine signaling interaction in human breast epithelial cells. PMID:21967595

  16. Microfluidic-based metal enhanced fluorescence for capillary electrophoresis by Ag nanorod arrays

    NASA Astrophysics Data System (ADS)

    Xiao, Chenyu; Cao, Zhen; Deng, Junhong; Huang, Zhifeng; Xu, Zheng; Fu, Junxue; Yobas, Levent

    2014-06-01

    As metal nanorods show much higher metal enhanced fluorescence (MEF) than metal nanospheres, microfluidic-based MEF is first explored with Ag nanorod (ND) arrays made by oblique angle deposition. By measuring the fluorescein isothiocyanate (FITC) solution sandwiched between the Ag NDs and a piece of cover slip, the enhancement factors (EFs) are found as 3.7 ± 0.64 and 6.74 ± 2.04, for a solution thickness at 20.8 μm and 10 μm, respectively. Because of the strong plasmonic coupling between the adjacent Ag NDs, only the emission of the fluorophores present in the three-dimensional NDs array gets enhanced. Thus, the corresponding effective enhancement factors (EEFs) are revealed to be relatively close, 259 ± 92 and 340 ± 102, respectively. To demonstrate the application of MEF in microfluidic systems, a multilayer of SiO2 NDs/Ag NDs is integrated with a capillary electrophoresis device. At a microchannel depth of 10 μm, an enhancement of 6.5 fold is obtained for amino acids separation detection. These results are very encouraging and open the possibility of MEF applications for the Ag ND arrays decorated microchannels. With the miniaturization of microfluidic devices, microfluidic-based MEF by Ag ND arrays will likely find more applications with further enhancement.

  17. Microfluidic-based metal enhanced fluorescence for capillary electrophoresis by Ag nanorod arrays.

    PubMed

    Xiao, Chenyu; Cao, Zhen; Deng, Junhong; Huang, Zhifeng; Xu, Zheng; Fu, Junxue; Yobas, Levent

    2014-06-06

    As metal nanorods show much higher metal enhanced fluorescence (MEF) than metal nanospheres, microfluidic-based MEF is first explored with Ag nanorod (ND) arrays made by oblique angle deposition. By measuring the fluorescein isothiocyanate (FITC) solution sandwiched between the Ag NDs and a piece of cover slip, the enhancement factors (EFs) are found as 3.7 ± 0.64 and 6.74 ± 2.04, for a solution thickness at 20.8 μm and 10 μm, respectively. Because of the strong plasmonic coupling between the adjacent Ag NDs, only the emission of the fluorophores present in the three-dimensional NDs array gets enhanced. Thus, the corresponding effective enhancement factors (EEFs) are revealed to be relatively close, 259 ± 92 and 340 ± 102, respectively. To demonstrate the application of MEF in microfluidic systems, a multilayer of SiO2 NDs/Ag NDs is integrated with a capillary electrophoresis device. At a microchannel depth of 10 μm, an enhancement of 6.5 fold is obtained for amino acids separation detection. These results are very encouraging and open the possibility of MEF applications for the Ag ND arrays decorated microchannels. With the miniaturization of microfluidic devices, microfluidic-based MEF by Ag ND arrays will likely find more applications with further enhancement.

  18. Fabrication of composite based on GeSi with Ag nanoparticles using ion implantation

    NASA Astrophysics Data System (ADS)

    Batalov, R. I.; Vorobev, V. V.; Nuzhdin, V. I.; Valeev, V. F.; Bayazitov, R. M.; Lyadov, N. M.; Osin, Yu. N.; Stepanov, A. L.

    2016-12-01

    Comparative analysis of the structural and optical properties of composite layers fabricated with the aid of implantation of single-crystalline silicon ( c-Si) using Ge+ (40 keV/1 × 1017 ions/cm2) and Ag+ (30 keV/1.5 × 1017 ions/cm2) ions and sequential irradiation using Ge+ and Ag+ ions is presented. The implantation of the Ge+ ions leads to the formation of Ge: Si fine-grain amorphous surface layer with a thickness of 60 nm and a grain size of 20-40 nm. The implantation of c-Si using Ag+ ions results in the formation of submicron porous amorphous a-Si structure with a thickness of about 50 nm containing ion-synthesized Ag nanoparticles. The penetration of the Ag+ ions in the Ge: Si layer stimulates the formation of pores with Ag nanoparticles with more uniform size distribution. The reflection spectra of the implanted Ag: Si and Ag: GeSi layers exhibit a sharp decrease in the intensity in the UV (220-420 nm) spectral interval relative to the intensity of c-Si by more than 50% owing to the amorphization and structuring of surface. The formation of Ag nanoparticles in the implanted layers gives rise to a selective band of the plasmon resonance at a wavelength of about 820 nm in the optical spectra. Technological methods for fabrication of a composite based on GeSi with Ag nanoparticles are demonstrated in practice.

  19. Highly selective and quantitative colorimetric detection of mercury(II) ions by carrageenan-functionalized Ag/AgCl nanoparticles.

    PubMed

    Narayanan, Kannan Badri; Han, Sung Soo

    2017-03-15

    The natural algal polysaccharide carrageenan was used for the greener synthesis of silver/silver chloride nanoparticles (Carr-Ag/AgCl NPs) without any toxic chemicals. We report the robust, highly selective, and sensitive colorimetric sensing of Hg(2+) ions using Carr-Ag/AgCl NPs without any further surface modification. The dark-brown color of a solution of Carr-Ag/AgCl NPs turned to white in a concentration-dependent manner with the addition of Hg(2+) ions, confirming the interaction of Carr-Ag/AgCl NPs with Hg(2+) ions. The plot of the extinction ratio of absorbance at 350nm to 450nm (A350/A450) for Carr-Ag/AgCl NPs against the concentration of [Hg(2+)] ions was linear, and the calibration curve was A350/A450=1.05254+0.00318×CHg with a lower detection limit of 1μM. This portable and cost-effective method for mercury(II) ion sensing is widely applicable in on-field qualitative and quantitative measurements of [Hg(2+)] ions in environmental or biological samples.

  20. Facile fabrication of AgCl@polypyrrole-chitosan core-shell nanoparticles and polymeric hollow nanospheres.

    PubMed

    Cheng, Daming; Xia, Haibing; Chan, Hardy Sze On

    2004-11-09

    A one-step sequential method for preparing AgCl@polypyrrole-chitosan core-shell nanoparticles and subsequently the formation of polypyrrole-chitosan hollow nanospheres is reported. The formation of the core and the shell is performed in one reaction medium almost simultaneously. Transmission electron microscopy (TEM) images show the presence of core-shell nanoparticles and hollow nanospheres. Ultraviolet-visible (UV-vis) studies reveal that AgCl was formed first followed by polypyrrole. X-ray diffration (XRD) and UV-vis studies show that AgCl was present in the core-shell nanoparticles and could be removed completely from the core.

  1. 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%.

  2. Selective photochemical synthesis of Ag nanoparticles on position-controlled ZnO nanorods for the enhancement of yellow-green light emission

    NASA Astrophysics Data System (ADS)

    Park, Hyeong-Ho; Zhang, Xin; Lee, Keun Woo; Sohn, Ahrum; Kim, Dong-Wook; Kim, Joondong; Song, Jin-Won; Choi, Young Su; Lee, Hee Kwan; Jung, Sang Hyun; Lee, In-Geun; Cho, Young-Dae; Shin, Hyun-Beom; Sung, Ho Kun; Park, Kyung Ho; Kang, Ho Kwan; Park, Won-Kyu; Park, Hyung-Ho

    2015-12-01

    A novel technique for the selective photochemical synthesis of silver (Ag) nanoparticles (NPs) on ZnO nanorod arrays is established by combining ultraviolet-assisted nanoimprint lithography (UV-NIL) for the definition of growth sites, hydrothermal reaction for the position-controlled growth of ZnO nanorods, and photochemical reduction for the decoration of Ag NPs on the ZnO nanorods. During photochemical reduction, the size distribution and loading of Ag NPs on ZnO nanorods can be tuned by varying the UV-irradiation time. The photochemical reduction is hypothesized to facilitate the adsorbed citrate ions on the surface of ZnO, allowing Ag ions to preferentially form Ag NPs on ZnO nanorods. The ratio of visible emission to ultraviolet (UV) emission for the Ag NP-decorated ZnO nanorod arrays, synthesized for 30 min, is 20.5 times that for the ZnO nanorod arrays without Ag NPs. The enhancement of the visible emission is believed to associate with the surface plasmon (SP) effect of Ag NPs. The Ag NP-decorated ZnO nanorod arrays show significant SP-induced enhancement of yellow-green light emission, which could be useful in optoelectronic applications. The technique developed here requires low processing temperatures (120 °C and lower) and no high-vacuum deposition tools, suitable for applications such as flexible electronics.A novel technique for the selective photochemical synthesis of silver (Ag) nanoparticles (NPs) on ZnO nanorod arrays is established by combining ultraviolet-assisted nanoimprint lithography (UV-NIL) for the definition of growth sites, hydrothermal reaction for the position-controlled growth of ZnO nanorods, and photochemical reduction for the decoration of Ag NPs on the ZnO nanorods. During photochemical reduction, the size distribution and loading of Ag NPs on ZnO nanorods can be tuned by varying the UV-irradiation time. The photochemical reduction is hypothesized to facilitate the adsorbed citrate ions on the surface of ZnO, allowing Ag ions to

  3. Observation of Multipeak Collision Behavior during the Electro-Oxidation of Single Ag Nanoparticles.

    PubMed

    Oja, Stephen M; Robinson, Donald A; Vitti, Nicholas J; Edwards, Martin A; Liu, Yuwen; White, Henry S; Zhang, Bo

    2017-01-18

    The dynamic collision behavior of the electro-oxidation of single Ag nanoparticles is observed at Au microelectrodes using stochastic single-nanoparticle collision amperometry. Results show that an Ag nanoparticle collision/oxidation event typically consists of a series of 1 to ∼10 discrete "sub-events" over an ∼20 ms interval. Results also show that the Ag nanoparticles typically undergo only partial oxidation prior to diffusing away from the Au electrode into the bulk solution. Both behaviors are characterized and shown to exist under a variety of experimental conditions. These previously unreported behaviors suggest that nanoparticle collision and electro-dissolution is a highly dynamic process driven by fast particle-electrode interactions and nanoparticle diffusion.

  4. Electrochemically Created Highly Surface Roughened Ag Nanoplate Arrays for SERS Biosensing Applications

    PubMed Central

    Slotcavage, Daniel; Mai, John D.; Guo, Feng; Li, Sixing; Zhao, Yanhui; Lei, Yong; Cameron, Craig E.

    2014-01-01

    Highly surface-roughened Ag nanoplate arrays are fabricated using a simple electrodeposition and in situ electrocorrosion method with inorganic borate ions as capping agent. The electrocorrosion process is induced by a change in the local pH value during the electrochemical growth, which is used to intentionally carve the electrodeposited structures. The three dimensionally arranged Ag nanoplates are integrated with substantial surface-enhanced Raman scattering (SERS) hot spots and are free of organic contaminations widely used as shaping agents in previous works, making them excellent candidate substrates for SERS biosensing applications. The SERS enhancement factor of the rough Ag nanoplates is estimated to be > 109. These Ag nanoplate arrays are used for SERS-based analysis of DNA hybridization monitoring, protein detection, and virus differentiation without any additional surface modifications or labelling. They all exhibit an extremely high detection sensitivity, reliability, and reproducibility. PMID:25383191

  5. Halloysite Nanotubes Supported Ag and ZnO Nanoparticles with Synergistically Enhanced Antibacterial Activity.

    PubMed

    Shu, Zhan; Zhang, Yi; Yang, Qian; Yang, Huaming

    2017-12-01

    Novel antimicrobial nanocomposite incorporating halloysite nanotubes (HNTs) and silver (Ag) into zinc oxide (ZnO) nanoparticles is prepared by integrating HNTs and decorating Ag nanoparticles. ZnO nanoparticles (ZnO NPs) and Ag nanoparticles (Ag NPs) with a size of about 100 and 8 nm, respectively, are dispersively anchored onto HNTs. The synergistic effects of ZnO NPs, Ag NPs, and HNTs led to the superior antibacterial activity of the Ag-ZnO/HNTs antibacterial nanocomposites. HNTs facilitated the dispersion and stability of ZnO NPs and brought them in close contact with bacteria, while Ag NPs could promote the separation of photogenerated electron-hole pairs and enhanced the antibacterial activity of ZnO NPs. The close contact with cell membrane enabled the nanoparticles to produce the increased concentration of reactive oxygen species and the metal ions to permeate into the cytoplasm, thus induced quick death of bacteria, indicating that Ag-ZnO/HNTs antibacterial nanocomposite is a promising candidate in the antibacterial fields.

  6. Halloysite Nanotubes Supported Ag and ZnO Nanoparticles with Synergistically Enhanced Antibacterial Activity

    NASA Astrophysics Data System (ADS)

    Shu, Zhan; Zhang, Yi; Yang, Qian; Yang, Huaming

    2017-02-01

    Novel antimicrobial nanocomposite incorporating halloysite nanotubes (HNTs) and silver (Ag) into zinc oxide (ZnO) nanoparticles is prepared by integrating HNTs and decorating Ag nanoparticles. ZnO nanoparticles (ZnO NPs) and Ag nanoparticles (Ag NPs) with a size of about 100 and 8 nm, respectively, are dispersively anchored onto HNTs. The synergistic effects of ZnO NPs, Ag NPs, and HNTs led to the superior antibacterial activity of the Ag-ZnO/HNTs antibacterial nanocomposites. HNTs facilitated the dispersion and stability of ZnO NPs and brought them in close contact with bacteria, while Ag NPs could promote the separation of photogenerated electron-hole pairs and enhanced the antibacterial activity of ZnO NPs. The close contact with cell membrane enabled the nanoparticles to produce the increased concentration of reactive oxygen species and the metal ions to permeate into the cytoplasm, thus induced quick death of bacteria, indicating that Ag-ZnO/HNTs antibacterial nanocomposite is a promising candidate in the antibacterial fields.

  7. 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

  8. Broadband light absorption of silicon nanowires embedded in Ag nano-hole arrays

    NASA Astrophysics Data System (ADS)

    Rao, Lei; Ji, Chun-Lei; Li, Ming

    2016-09-01

    Silicon nanowires (SiNWs) embedded in Ag nano-hole arrays with broadband light absorption is proposed in this paper. Finite Difference Time Domain (FDTD) simulations were utilized to obtain absorptivity and band diagrams for both SiNWs and SiNWs embedded in Ag nano-hole arrays. A direct relationship between waveguide modes and extraordinary absorptivity is established qualitatively, which helps to optimal design the structure parameters to achieve broadband absorptivity. After introducing Ag nano-hole arrays at the rear side of SiNWs, the band modes are extended into leaky regions and light energy can be fully absorbed, resulting in high absorptivity at long wavelength. Severe reflection is also suppressed by light trapping capability of SiNWs at short wavelength. Over 70% average absorptivity from 400 nm to 1100 nm is realized finally. This kinds of design give promising route for high efficiency solar cells and optical absorbers.

  9. 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.

  10. Metal enhanced fluorescence improved protein and DNA detection by zigzag Ag nanorod arrays.

    PubMed

    Ji, Xiaofan; Xiao, Chenyu; Lau, Wai-Fung; Li, Jianping; Fu, Junxue

    2016-08-15

    As metal nano-arrays show great potential on metal enhanced fluorescence (MEF) than random nanostructures, MEF of Ag zigzag nanorod (ZNR) arrays made by oblique angle deposition has been studied for biomolecule-protein interaction and DNA hybridization. By changing the folding number and the deposition substrate temperature, a 14-fold enhancement factor (EF) is obtained for biotin-neutravidin detection. The optimal folding number is decided as Z=7, owing to the high scattering intensity of Ag ZNRs. The substrate temperature T=25°C and 0°C slightly alters the morphology of Ag ZNRs but has no big difference in EF. Further, Ag ZNRs deposited on a layer of Ag film have been introduced to the DNA hybridization and a significant signal enhancement has been observed through the fluorescence microscope. Through a detailed quantitative EF analysis, which excludes the enhancing effect from the increased surface area of ZNRs and only considers the contribution of MEF, an EF of 28 is achieved for the hybridization of two single-stranded oligonucleotides with 33 bases. Furthermore, a limit of detection is determined as 0.01pM. We believe that the Ag ZNR arrays can serve as a universal and sensitive bio-detection platform.

  11. Self-assembled nanoparticle arrays for multiphase trace analyte detection

    NASA Astrophysics Data System (ADS)

    Cecchini, Michael P.; Turek, Vladimir A.; Paget, Jack; Kornyshev, Alexei A.; Edel, Joshua B.

    2013-02-01

    Nanoplasmonic structures designed for trace analyte detection using surface-enhanced Raman spectroscopy typically require sophisticated nanofabrication techniques. An alternative to fabricating such substrates is to rely on self-assembly of nanoparticles into close-packed arrays at liquid/liquid or liquid/air interfaces. The density of the arrays can be controlled by modifying the nanoparticle functionality, pH of the solution and salt concentration. Importantly, these arrays are robust, self-healing, reproducible and extremely easy to handle. Here, we report on the use of such platforms formed by Au nanoparticles for the detection of multi-analytes from the aqueous, organic or air phases. The interfacial area of the Au array in our system is ≈25 mm2 and can be made smaller, making this platform ideal for small-volume samples, low concentrations and trace analytes. Importantly, the ease of assembly and rapid detection make this platform ideal for in-the-field sample testing of toxins, explosives, narcotics or other hazardous chemicals.

  12. ZnO Nanorod Array Grown on Ag Layer: A Highly Efficient Fluorescence Enhancement Platform

    PubMed Central

    Yin, Yongqi; Sun, Ye; Yu, Miao; Liu, Xiao; Jiang, Tingting; Yang, Bin; Liu, Danqing; Liu, Shaoqin; Cao, Wenwu

    2015-01-01

    ZnO nanorods (NRs) are known for ultra-sensitive biomolecule detection through fluorescence enhancement. In this work, we demonstrate that ZnO NR arrays grown on Ag layers can significantly improve the enhancement up to 86 times compared to that grown on bare Si, and the enhancement can be modified in a controlled manner by varying Ag thickness. The much improved waveguide properties are attributed to the high reflectance of the Ag layers and their tuning effect on the diameters of ZnO NRs. Our results provide a deep insight into the mechanism of NRs-based fluorescence enhancement platform. PMID:25633246

  13. Core-shell nanoparticle arrays double the strength of steel

    NASA Astrophysics Data System (ADS)

    Seol, J.-B.; Na, S.-H.; Gault, B.; Kim, J.-E.; Han, J.-C.; Park, C.-G.; Raabe, D.

    2017-02-01

    Manipulating structure, defects and composition of a material at the atomic scale for enhancing its physical or mechanical properties is referred to as nanostructuring. Here, by combining advanced microscopy techniques, we unveil how formation of highly regular nano-arrays of nanoparticles doubles the strength of an Fe-based alloy, doped with Ti, Mo, and V, from 500 MPa to 1 GPa, upon prolonged heat treatment. The nanoparticles form at moving heterophase interfaces during cooling from the high-temperature face-centered cubic austenite to the body-centered cubic ferrite phase. We observe MoC and TiC nanoparticles at early precipitation stages as well as core-shell nanoparticles with a Ti-C rich core and a Mo-V rich shell at later precipitation stages. The core-shell structure hampers particle coarsening, enhancing the material’s strength. Designing such highly organized metallic core-shell nanoparticle arrays provides a new pathway for developing a wide range of stable nano-architectured engineering metallic alloys with drastically enhanced properties.

  14. Core-shell nanoparticle arrays double the strength of steel

    PubMed Central

    Seol, J.-B.; Na, S.-H.; Gault, B.; Kim, J.-E.; Han, J.-C.; Park, C.-G.; Raabe, D.

    2017-01-01

    Manipulating structure, defects and composition of a material at the atomic scale for enhancing its physical or mechanical properties is referred to as nanostructuring. Here, by combining advanced microscopy techniques, we unveil how formation of highly regular nano-arrays of nanoparticles doubles the strength of an Fe-based alloy, doped with Ti, Mo, and V, from 500 MPa to 1 GPa, upon prolonged heat treatment. The nanoparticles form at moving heterophase interfaces during cooling from the high-temperature face-centered cubic austenite to the body-centered cubic ferrite phase. We observe MoC and TiC nanoparticles at early precipitation stages as well as core-shell nanoparticles with a Ti-C rich core and a Mo-V rich shell at later precipitation stages. The core-shell structure hampers particle coarsening, enhancing the material’s strength. Designing such highly organized metallic core-shell nanoparticle arrays provides a new pathway for developing a wide range of stable nano-architectured engineering metallic alloys with drastically enhanced properties. PMID:28225022

  15. Core-shell nanoparticle arrays double the strength of steel.

    PubMed

    Seol, J-B; Na, S-H; Gault, B; Kim, J-E; Han, J-C; Park, C-G; Raabe, D

    2017-02-22

    Manipulating structure, defects and composition of a material at the atomic scale for enhancing its physical or mechanical properties is referred to as nanostructuring. Here, by combining advanced microscopy techniques, we unveil how formation of highly regular nano-arrays of nanoparticles doubles the strength of an Fe-based alloy, doped with Ti, Mo, and V, from 500 MPa to 1 GPa, upon prolonged heat treatment. The nanoparticles form at moving heterophase interfaces during cooling from the high-temperature face-centered cubic austenite to the body-centered cubic ferrite phase. We observe MoC and TiC nanoparticles at early precipitation stages as well as core-shell nanoparticles with a Ti-C rich core and a Mo-V rich shell at later precipitation stages. The core-shell structure hampers particle coarsening, enhancing the material's strength. Designing such highly organized metallic core-shell nanoparticle arrays provides a new pathway for developing a wide range of stable nano-architectured engineering metallic alloys with drastically enhanced properties.

  16. 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

  17. Interfacial magnetic coupling between Fe nanoparticles in Fe–Ag granular alloys.

    PubMed

    Alonso, J; Fdez-Gubieda, M L; Sarmiento, G; Chaboy, J; Boada, R; García Prieto, A; Haskel, D; Laguna-Marco, M A; Lang, J C; Meneghini, C; Fernández Barquín, L; Neisius, T; Orue, I

    2012-01-20

    The role of the interface in mediating interparticle magnetic interactions has been analysed in Fe50Ag50 and Fe55Ag45 granular thin films deposited by the pulsed laser deposition technique (PLD). These samples are composed of crystalline bcc Fe (2–4 nm) nanoparticles and fcc Ag (10–12 nm) nanoparticles, separated by an amorphous Fe50Ag50 interface, occupying around 20% of the sample volume, as determined by x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS), and high resolution transmission electron microscopy (HRTEM). Interfacial magnetic coupling between Fe nanoparticles is studied by dc magnetization and x-ray magnetic circular dichroism (XMCD) measurements at the Fe K and Ag L2,3 edges. This paper reveals that these thin films present two magnetic transitions, at low and high temperatures, which are strongly related to the magnetic state of the amorphous interface, which acts as a barrier for interparticle magnetic coupling.

  18. 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.

  19. 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).

  20. A Sustainable Approach to Fabricating Ag Nanoparticles/PVA Hybrid Nanofiber and Its Catalytic Activity

    PubMed Central

    Meng, Yongde

    2015-01-01

    Ag nanoparticles were synthesized by using Ficus altissima Blume leaf extract as a reducing agent at room temperature. The resulting Ag nanoparticles/PVA mixture was employed to create Ag nanoparticles/PVA (polyvinyl alcohol) hybrid nanofibers via an electrospinning technique. The obtained nanofibers were confirmed by means of UV-Vis spectroscopy, The X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and then tested to catalyze KBH4 reduction of methylene blue (MB). The catalytic results demonstrate that the MB can be reduced completely within 15 min. In addition, the Ag nanoparticles/PVA hybrid nanofibers show reusability for three cycles with no obvious losses in degradation ratio of the MB.

  1. 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

  2. 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.

  3. 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

    2016-09-12

    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.

  4. Highly anisotropic effective dielectric functions of silver nanoparticle arrays.

    PubMed

    Oates, Thomas W H; Ranjan, Mukesh; Facsko, Stefan; Arwin, Hans

    2011-01-31

    Variable-angle and Mueller matrix spectroscopic ellipsometry are used to determine the effective dielectric tensors of random and aligned silver nanoparticles and nanorods thin films. Randomly arranged particles are uniaxially anisotropic while aligned particles are biaxially anisotropic, with the anisotropy predominantly at the plasmonic resonances. The strong resonances in nanorod arrays result in the real part of the effective in-plane permittivities being opposite in sign over a significant range in the visible, suggesting the potential to design materials that display tunable negative-refraction. A structural tilt in the particle arrays results in monoclinic dielectric properties.

  5. 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.

  6. Preparation of a novel silk microfiber covered by AgCl nanoparticles with antimicrobial activity.

    PubMed

    Xie, Qifan; Xu, Zongpu; Hu, Binhui; He, Xiuling; Zhu, Liangjun

    2017-03-01

    We prepared silk fibroin microfibers in which silver chloride (AgCl) nanoparticles were dispersed, by sequential dipping of microfibers obtained using alkaline hydrolysis in alternating solutions of silver nitrate and potassium chloride. Scanning and transmission electron microscopy showed an increase in nanoparticle size and quantity with increase in dipping cycles and solution concentration, but ultrasound irradiation did not affect nanoparticle formation. The presence of cubic AgCl crystals was confirmed by energy dispersive X-ray spectroscopy and X-ray diffractometry. Differential scanning calorimetry and Fourier transform infrared spectroscopy revealed that the nanoparticles do not affect the microfiber properties. The growth of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria was inhibited by microfiber covered with AgCl nanoparticles. This antimicrobial activity allows to use microfiber as a reinforced or surface additive biomaterial. Microsc. Res. Tech. 80:272-279, 2017. © 2016 Wiley Periodicals, Inc.

  7. Disordered antireflective subwavelength structures using Ag nanoparticles on fused silica windows.

    PubMed

    Shang, Peng; Xiong, Sheng Ming; Deng, Qi Ling; Shi, Li Fang; Zhang, Mian

    2014-10-10

    In this paper, we have demonstrated an effective method for fabricating disordered subwavelength structures (d-SWSs) on fused silica using thermal dewetted Ag nanoparticles at lower temperatures (<300°C) with a vacuum. Theoretically and experimentally, we investigate the effects of the film thickness, annealing temperature, and etching time on the antireflective properties of the d-SWS arrays. The measured data and calculated results obtained by rigorous coupled-wave analysis exhibit reasonably similar tendencies. For the sample with a 10-nm-thick Ag film, good optical transmission characteristics (on one side, T(ave)∼95.6%) over a wide wavelength region of 500-1300 nm were obtained, and a maximum value of ∼96% at a wavelength of 850 nm was also obtained. Furthermore, the d-SWSs exhibit excellent optical and thermal stability at high temperatures of 800°C and 1000°C compared to a conventional Ta2O5/SiO2 multilayer coating.

  8. Improving g-C3N4 photocatalysis for NOx removal by Ag nanoparticles decoration

    NASA Astrophysics Data System (ADS)

    Sun, Yanjuan; Xiong, Ting; Ni, Zilin; Liu, Jie; Dong, Fan; Zhang, Wei; Ho, Wing-Kei

    2015-12-01

    In order to overcome the intrinsic drawback of pristine g-C3N4, we prepared g-C3N4 nanosheets with enhanced photocatalytic performance by Ag nanoparticles decoration using urea as the precursor. It was revealed that the monodispersed Ag nanoparticles were deposited on the surface of g-C3N4 nanosheets. The Ag/g-C3N4 nanocomposites were applied in removal of NOx in air under visible light irradiation. The results showed that the decoration of Ag nanoparticles not only enhanced the photocatalytic activity of g-C3N4 nanosheets, but also benefited the oxidation of NO to final products. The increased visible light absorption arising from the surface plasmon resonance of Ag and improved separation and transfer of photoinduced carriers over Ag/g-C3N4 composites were demonstrated by the UV-vis diffuse reflectance spectra and photoluminescence spectra, respectively. It was therefore proposed that the enhanced photocatalytic activity of Ag/g-C3N4 composites could be attributed to the extended light response range and enhanced charge separation due to the introduction of Ag nanoparticles.

  9. Ag-Mn nanoparticles: Three-dimensional finite size effect of the spin glass state

    NASA Astrophysics Data System (ADS)

    Ederth, J.; Hoel, A.; Johansson, C. I.; Kiss, L. B.; Olsson, E.; Granqvist, C. G.; Nordblad, P.

    1999-12-01

    Ag-Mn nanoparticles were prepared by advanced gas evaporation. Their composition corresponded to Ag0.89Mn0.11, and the particle size distribution was log normal. The particles demonstrated an unambiguous spin glass behavior with the temperature dependent magnetic susceptibility displaying a plateau at ˜25 K. The magnetic domains were limited by the size of the particles.

  10. Growth of Ag nanoparticles using plasma-modified multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tseng, Chun-Hao; Chen, Chuh-Yung

    2008-01-01

    This study presents a novel method for preparing multi-walled carbon nanotubes (MWNTs) grafted with a poly(2-hydroxyethyl methacrylate) (HEMA)-silver complex (CNTs-HEMA-Ag complex) through plasma-induced grafting polymerization. The characteristics of the MWNTs after being grafted with HEMA polymer are monitored by Fourier transform infrared (FT-IR) spectroscopy. The chelating groups in the HEMA polymer grafted on the surface of the CNTs-HEMA are the coordination sites for chelating silver ions, and are further used as nanotemplates for the growing of Ag nanoparticles (quantum dots). Transmission electron microscopy (TEM) reveals that the particle size of Ag nanoparticles on the CNT surfaces increases with the Ag+ chelating concentration, reaction time, and reaction temperature. Moreover, the crystalline phase of Ag nanoparticles is identified by using x-ray diffraction (XRD). In addition, high-resolution x-ray photoelectron spectroscopy (XPS) is used to characterize the functional groups on the surface of the MWNTs after chemical modification through plasma treatment; it demonstrates that the growing amount of the Ag nanoparticles on the nanotubes increases with the Ag+ chelating concentration due to the blocking effect of the Ag particles forming on the MWNTs.

  11. Ordered array of Ag semishells on different diameter monolayer polystyrene colloidal crystals: An ultrasensitive and reproducible SERS substrate

    PubMed Central

    Yi, Zao; Niu, Gao; Luo, Jiangshan; Kang, Xiaoli; Yao, Weitang; Zhang, Weibin; Yi, Yougen; Yi, Yong; Ye, Xin; Duan, Tao; Tang, Yongjian

    2016-01-01

    Ag semishells (AgSS) ordered arrays for surface-enhanced Raman scattering (SERS) spectroscopy have been prepared by depositing Ag film onto polystyrene colloidal particle (PSCP) monolayer templates array. The diversified activity for SERS activity with the ordered AgSS arrays mainly depends on the PSCP diameter and Ag film thickness. The high SERS sensitivity and reproducibility are proved by the detection of rhodamine 6G (R6G) and 4-aminothiophenol (4-ATP) molecules. The prominent enhancements of SERS are mainly from the “V”-shaped or “U”-shaped nanogaps on AgSS, which are experimentally and theoretically investigated. The higher SERS activity, stability and reproducibility make the ordered AgSS a promising choice for practical SERS low concentration detection applications. PMID:27586562

  12. Ordered array of Ag semishells on different diameter monolayer polystyrene colloidal crystals: An ultrasensitive and reproducible SERS substrate

    NASA Astrophysics Data System (ADS)

    Yi, Zao; Niu, Gao; Luo, Jiangshan; Kang, Xiaoli; Yao, Weitang; Zhang, Weibin; Yi, Yougen; Yi, Yong; Ye, Xin; Duan, Tao; Tang, Yongjian

    2016-09-01

    Ag semishells (AgSS) ordered arrays for surface-enhanced Raman scattering (SERS) spectroscopy have been prepared by depositing Ag film onto polystyrene colloidal particle (PSCP) monolayer templates array. The diversified activity for SERS activity with the ordered AgSS arrays mainly depends on the PSCP diameter and Ag film thickness. The high SERS sensitivity and reproducibility are proved by the detection of rhodamine 6G (R6G) and 4-aminothiophenol (4-ATP) molecules. The prominent enhancements of SERS are mainly from the “V”-shaped or “U”-shaped nanogaps on AgSS, which are experimentally and theoretically investigated. The higher SERS activity, stability and reproducibility make the ordered AgSS a promising choice for practical SERS low concentration detection applications.

  13. Lattice plasmons in dielectric nanoparticle arrays arranged on metal film

    NASA Astrophysics Data System (ADS)

    Zhang, Lianxue; Ge, Chaoyang; Zhang, Kun; Tian, Cheng; Fang, Xin; Zhai, Wenhao; Tao, Li; Li, Yanping; Ran, Guangzhao

    2016-12-01

    We propose a hybrid plasmonic photonic crystal consisting of a square array of dielectric nanoparticles arranged on a metal film with a gap inbetween. Simulations show that this plasmonic crystal supports lattice plasmon modes just like the metal nanoparticle array, exhibiting an extremely narrow and deep reflection dip. When interparticle spacing increases from 800 to 1000 nm, the full width at half the maximum of lattice plasmons decreases from 21 to 4 nm, and the lowest reflectance is close to zero. The resonant wavelength of this plasmonic crystal is highly sensitive to the local environment. It yields a sensitivity of 700 nm RIU-1 and a figure of merit of 33, which can be used in sensing of the refractive index.

  14. 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; ...

    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

  15. 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.

  16. 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.

  17. Diffusive Dynamics of Nanoparticles in Arrays of Nanoposts

    SciTech Connect

    He, Kai; Korasani, Firoozeh; Thomas, Darrell Keith; Retterer, Scott T; Conrad, Jacinta; Krishnamoorti, Ramanan

    2013-01-01

    The diffusive dynamics of dilute dispersions of nanoparticles of diameter 200 400 nm were studied in microfabricated arrays of nanoposts using differential dynamic microscopy and single particle tracking. Posts of diameter 500 nm and height 10 m were spaced by 1.2 10 m on a square lattice. As the spacing between posts was decreased, the dynamics of the nanoparticles slowed. Moreover, the dynamics at all length scales were best represented by a stretched exponential rather than a simple exponential. Both the relative diffusivity and the stretching exponent decreased linearly with increased confinement and, equivalently, with decreased void volume. The slowing of the overall diffusive dynamics and the broadening distribution of nanoparticle displacements with increased confinement are consistent with the onset of cooperative dynamics.

  18. 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.

  19. Morphology and electrochemical behavior of Ag-Cu nanoparticle-doped amalgams.

    PubMed

    Chung, Kwok-Hung; Hsiao, Li-Yin; Lin, Yu-Sheng; Duh, Jenq-Gong

    2008-05-01

    The aim of this study was to introduce Ag-Cu phase nanopowder as an additive to improve the corrosion behavior of dental amalgams. A novel Ag-Cu nanopowder was synthesized by the precipitation method. An amalgam alloy powder (World-Cap) was added and mixed with 5 wt.% and 10 wt.% of Ag-Cu nanopowders, respectively, to form experimental amalgam alloy powders. The original alloy powder was used as a control. Alloy powders were examined using X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy and electron probe microanalysis. Amalgam disk specimens of metallurgically prepared were tested in 0.9% NaCl solution using electrochemical methods. The changes in the corrosion potential and anodic polarization characteristics were determined. Corrosion potential data were analyzed statistically (n=3, analysis of variance, Tukey's test, p<0.05). The diameters of lamellar structure Ag-Cu nanoparticles were measured to be approximately 30 nm. The composition of the Ag-Cu nanoparticles determined by TEM-energy-dispersive spectroscopy was 56.28 at.% Ag-43.72 at.% Cu. A light-shaded phase was found mixing with dark Cu-Sn reaction particles in the reaction zones of Ag-Cu nanoparticle-doped amalgams. The Ag-Cu nanoparticle-doped amalgams exhibited zero current potentials more positive than the control (p<0.05) and no current peak was observed at -325mV that related to Ag-Hg phase and Cu6Sn5 phase in anodic polarization curves. The results indicated that the corrosion resistance of high-copper single-composition amalgam could be improved by Ag-Cu nanoparticle-doping.

  20. Subsurface Synthesis and Characterization of Ag Nanoparticles Embedded in MgO

    SciTech Connect

    Vilayur Ganapathy, Subramanian; Devaraj, Arun; Colby, Robert J.; Pandey, Archana; Varga, Tamas; Shutthanandan, V.; Manandhar, Sandeep; El-Khoury, Patrick Z.; Kayani, Asghar N.; Hess, Wayne P.; Thevuthasan, Suntharampillai

    2013-03-08

    Metal nanoparticles exhibit localized surface plasmon resonance (LSPR) which is very sensitive to the size and shape of the nanoparticle and the dielectric medium surrounding it. LSPR causes field enhancement near the surface of the nanoparticle making them interesting candidates for plasmonic applications. In particular, partially exposed metallic nanoparticles distributed in a dielectric matrix form hotspots which are prime locations for LSPR spectroscopy and sensing. This study involves synthesizing partially buried Ag nanoparticles in MgO and investigating the characteristics of this material system. 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 10000C for 10 and 30 hours. A detailed optical and structural characterization was carried out to understand the evolution of Ag nanoparticle microstructure and size distribution inside the MgO matrix. Micro x-ray diffraction (MicroXRD) was employed to investigate the structural properties and estimate the crystallite size. The nanoparticles evolved from a spherical to faceted morphology with annealing time, assuming an octahedral shape truncated at the (001) planes as seen 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 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.

  1. Nanoparticle-Assisted Diffusion Brazing of Metal Microchannel Arrays: Nanoparticle Synthesis, Deposition, and Characterization

    NASA Astrophysics Data System (ADS)

    Eluri, Ravindranadh T.

    Microchannel process technology (MPT) offers several advantages to the field of nanomanufacturing: 1) improved process control over very short time intervals owing to shorter diffusional distances; and 2) reduced reactor size due to high surface area to volume ratios and enhanced heat and mass transfer. The objective of this thesis was to consider how nanomaterials, produced in part using MPT, could be used to solve problems associated with the fabrication of MPT devices. Specifically, many MPT devices are produced using transient liquid-phase brazing involving an electroplated interlayer consisting of a brazing alloy designed for melting temperature suppression. Unfortunately, these alloys can form brittle secondary phases which significantly reduce bond strength. In contrast, prior efforts have shown that it is possible to leverage the size-dependent properties of nanomaterials to suppress brazing temperatures. In this prior work, thin films of off-the-shelf elemental nanoparticles were used as interlayers yielding joints with improved mechanical properties. In the present investigation, efforts have been made to characterize the synthesis and deposition of various elemental nanoparticle suspensions for use in the transient liquid-phase brazing of aluminum and stainless steel. Advances were used to demonstrate the nanoparticle-assisted diffusion brazing of a microchannel array. In the first section, a silver nanoparticle (AgNP) interlayer was produced for the diffusion brazing of heat exchanger aluminum. Efforts are made to examine the effect of braze filler particle size (˜5 nm and ˜50 nm) and processing parameters (heating rate: 5ºC/min and 25ºC/min; brazing temperature: 550ºC and 570ºC) on thin coupons of diffusion-brazed 3003 Al. A tensile strength of 69.7 MPa was achieved for a sample brazed at 570°C for 30 min under 1 MPa with an interlayer thickness of approximately 7 microm. Further suppression of the brazing temperature to 500ºC was achieved by

  2. Fabrication of graphene oxide enwrapped Z-scheme Ag2SO3/AgBr nanoparticles with enhanced visible-light photocatalysis

    NASA Astrophysics Data System (ADS)

    Wan, Yujuan; Liang, Chunyan; Xia, Yue; Huang, Wei; Li, Zelin

    2017-02-01

    A novel graphene oxide (GO) enwrapped Ag2SO3/AgBr (GO/Ag2SO3/AgBr) composite was fabricated through a facile solution approach via electrostatic interaction and precipitation transformation reaction for the first time. The results of XRD, Raman, SEM, TEM and XPS confirmed the structure, morphology and composition of the GO/Ag2SO3/AgBr composite very well. The Ag2SO3/AgBr nanoparticles were found to be encapsulated by GO sheets. The photocatalytic activity of the composite was investigated by the degradation of methyl orange (MO), rhodamine B (RhB) and methylene blue (MB) in water under visible light. The incorporation of GO sheets not only significantly enhanced the photocatalytic activity but also improved the reusability of Ag2SO3/AgBr nanoparticles. The photocatalytic ability of GO/Ag2SO3/AgBr can be maintained at a high level for 4 times cycle experiments. The trapping experiments confirmed that holes and superoxide ion radicals were the main active species responsible for the degradation reaction. A plasmonic Z-scheme photocatalytic mechanism was proposed to illustrate the possible transferred and separated behavior of electron-hole pairs among Ag, Ag2SO3, AgBr and GO quaternary system under visible light irradiation.

  3. Ordered nanoparticle arrays formed on engineered chaperonin protein templates

    NASA Technical Reports Server (NTRS)

    McMillan, R. Andrew; Paavola, Chad D.; Howard, Jeanie; Chan, Suzanne L.; Zaluzec, Nestor J.; Trent, Jonathan D.

    2002-01-01

    Traditional methods for fabricating nanoscale arrays are usually based on lithographic techniques. Alternative new approaches rely on the use of nanoscale templates made of synthetic or biological materials. Some proteins, for example, have been used to form ordered two-dimensional arrays. Here, we fabricated nanoscale ordered arrays of metal and semiconductor quantum dots by binding preformed nanoparticles onto crystalline protein templates made from genetically engineered hollow double-ring structures called chaperonins. Using structural information as a guide, a thermostable recombinant chaperonin subunit was modified to assemble into chaperonins with either 3 nm or 9 nm apical pores surrounded by chemically reactive thiols. These engineered chaperonins were crystallized into two-dimensional templates up to 20 microm in diameter. The periodic solvent-exposed thiols within these crystalline templates were used to size-selectively bind and organize either gold (1.4, 5 or 10nm) or CdSe-ZnS semiconductor (4.5 nm) quantum dots into arrays. The order within the arrays was defined by the lattice of the underlying protein crystal. By combining the self-assembling properties of chaperonins with mutations guided by structural modelling, we demonstrate that quantum dots can be manipulated using modified chaperonins and organized into arrays for use in next-generation electronic and photonic devices.

  4. In situ preparation of monodispersed Ag/polyaniline/Fe3O4 nanoparticles via heterogeneous nucleation

    PubMed Central

    2013-01-01

    Acrylic acid and styrene were polymerized onto monodispersed Fe3O4 nanoparticles using a grafting copolymerization method. Aniline molecules were then bonded onto the Fe3O4 nanoparticles by electrostatic self-assembly and further polymerized to obtain uniform polyaniline/Fe3O4 (PANI/Fe3O4) nanoparticles (approximately 35 nm). Finally, monodispersed Ag/PANI/Fe3O4 nanoparticles were prepared by an in situ reduction reaction between emeraldine PANI and silver nitrate. Fourier transform infrared and UV-visible spectrometers and a transmission electron microscope were used to characterize both the chemical structure and the morphology of the resulting nanoparticles. PMID:23819820

  5. 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.

  6. 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

  7. 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

    2007-02-07

    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.

  8. Cross-linked block copolymer templated assembly of nanoparticle arrays with high density and position selectivity

    NASA Astrophysics Data System (ADS)

    Liu, Zhicheng; Chang, Tongxin; Huang, Haiying; Bai, Lu

    2016-10-01

    Patterning ordered nanoparticle arrays is crucial for the fascinating collective properties of nanoparticles. Block copolymer template provides us a platform for the simple and efficient assembly of nanoparticle arrays. In this work, cylinder-forming poly(styrene-block-2-vinylpyridine) thin film was firstly plasma-etched to expose poly(2-vinylpyridine) cylinders. Then the templates were cross-linked by small molecules so as to access gold nanoparticle arrays with both high density and excellent position selectivity. The cross-linking process significantly restrains the unfavorable surface reconstruction of the thin film. It is demonstrated that the quality of the nanoparticle array was affected by the degree of the cross-linking and the immersion time in nanoparticle solution. The highly ordered gold nanoparticle arrays are promising in several fields such as optics and surface enhanced Raman scattering (SERS).

  9. Influence of silver content on rifampicin adsorptivity for magnetite/Ag/rifampicin nanoparticles

    NASA Astrophysics Data System (ADS)

    Ivashchenko, Olena; Coy, Emerson; Peplinska, Barbara; Jarek, Marcin; Lewandowski, Mikołaj; Załęski, Karol; Warowicka, Alicja; Wozniak, Anna; Babutina, Tatiana; Jurga-Stopa, Justyna; Dolinsek, Janez; Jurga, Stefan

    2017-02-01

    Magnetite nanoparticles (NPs) decorated with silver (magnetite/Ag) are intensively investigated due to their application in the biomedical field. We demonstrate that the increase of silver content on the surface of nanoparticles improves the adsorptivity of antibiotic rifampicin as well as antibacterial properties. The use of ginger extract allowed to improve the silver nucleation on the magnetite surface that resulted in an increase of silver content. Physicochemical and functional characterization of magnetite/Ag NPs was performed. Our results show that 5%-10% of silver content in magnetite/Ag NPs is already sufficient for antimicrobial properties against Streptococcus salivarius and Staphylococcus aureus. The rifampicin molecules on the magnetite/Ag NPs surface made the spectrum of antimicrobial activity wider. Cytotoxicity evaluation of the magnetite/Ag/rifampicin NPs showed no harmful action towards normal human fibroblasts, whereas the effect on human embryonic kidney cell viability was time and dose dependent.

  10. Titanium dioxide encapsulation of supported Ag nanoparticles on the porous silica bead for increased photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Liu, Hui; Deng, Lu; Sun, Chaochao; Li, Junqi; Zhu, Zhenfeng

    2015-01-01

    A new synthetic strategy has been developed to encapsulate Ag nanoparticles in heterogeneous catalysts to prevent their dropping and sintering. Ag nanoparticles with diameters about 5-10 nm were first supported on the porous silica bead. These were then covered with a fresh layer of titanium dioxide with the thickness about 5 nm. SEM and TEM images were used to confirm the success of each synthesis step, and the photocatalytic activity of the as-synthesized samples was evaluated by photocatalytic decolorization of Rhodamine B (Rh B) aqueous solution at ambient temperature under both UV and visible light irradiation. The resulting titanium dioxide encapsulated Ag nanoparticles exhibited an enhanced photocatalytic activity under both UV and visible light irradiation, this can be attributed to effective charge separation and light harvesting of the plasmonic silver nanoparticles decoration, even the reducing of the exciton recombination rate caused by the small grain size of anatase TiO2 nanocrystals.

  11. 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

  12. Biosynthesis of quasi-spherical Ag nanoparticle by Pseudomonas aeruginosa as a bioreducing agent

    NASA Astrophysics Data System (ADS)

    Taheri Otaqsara, S. M.

    2011-12-01

    Use of microorganism as a novel and eco-friendly strategy to production of nanomaterials is an important aspect of modern nanotechnology. Biosynthesis of quasi-spherical silver nanoparticles (Ag-NPs) has been investigated using Pseudomonas aeruginosa. We observe that silver (Ag+) ions when exposed to P. aeruginosa biomass are reduced in solution, thereby leading to the formation of Ag-NPs. Quasi-spherical shape and nearly well distribution and FCC crystal structure of Ag-NPs were confirmed by XRD pattern, STM and TEM micrographs. UV-Vis spectra show a surface plasmon resonance (SPR) band at ~ 435 nm.

  13. The role of Ag on dynamics of superspins in MnFe2- x Ag x O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Aslibeiki, B.; Kameli, P.; Salamati, H.

    2013-02-01

    The effect of dipole-dipole and exchange interactions on dynamics of superspins in a system of MnFe2- x Ag x O4 (where x = 0, 0.1, 0.2, 0.3, and 0.6) nanoparticles has been studied by Ac magnetic susceptibility measurements. Average crystallite size of samples was estimated to be 7 to 4 nm, with respect to the doping level of x = 0-0.6. It was found that the nanoparticles are superparamagnetic at room temperature with almost zero coercivity. Saturation magnetization of samples showed a remarkable reduction by increasing non-magnetic Ag doping level. By decreasing the temperature, a transition to frustrated superspin glass state was observed in all samples. Freezing temperatures of superspins were decreased by increasing the Ag content, as a result of decreasing size of crystallites, magnetization of nanoparticles, and consequently weakening of dipole-dipole interactions. The estimated values of zυ, τ 0, and T 0, using critical slowing down model, justify the observed variation of freezing temperatures. Furthermore it was realized that sensitivity of samples to the variation of applied frequency, an important parameter in hyperthermia based therapy, is affected by magnetic interactions between nanoparticles.

  14. 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.

  15. Physical and magnetic properties of magnetic nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Mohtasebzadeh, Abdul Rahman

    Using Scanning Electron Microscope (SEM) , Atomic Force Microscope (AFM) and Vibrating Sample Magnetometer (VSM) I studied magnetic-field directed selfassembly of magnetic nanoparticles into patterned arrays on the surface of perpendicular magnetic recording media. A controllable machine was used to coat super paramagnetic nano particles onto the surface of perpendicular recording media for different time intervals. Self assembled nano particles on the surface of the media, were transferred to a polymer layer to observe physical properties. Results from imaging shows that the average width and height of arrays is increasing as a function of time. Width of arrays with assembly time varies from 100nm at 5 minutes to 500nm at 120 minutes. Similarly, height changes from 13nm at 5 minutes to 37nm at 120 minutes. Therefore the pattern aspect ratio changes from 8:1 at 5 minutes to 14:1 at 120 minutes. For large widths compared with pattern spacing, array interaction appears as a slope change in VSM hysteresis loops. The hypothesis is that the difference in slope as a function of time for two cases; patterns oriented parallel and perpendicular to the external field is caused by array interaction; in other words wider patterns interact with each other more than narrower patterns.

  16. Halloysite nanotube supported Ag nanoparticles heteroarchitectures as catalysts for polymerization of alkylsilanes to superhydrophobic silanol/siloxane composite microspheres.

    PubMed

    Li, Cuiping; Li, Xueyuan; Duan, Xuelan; Li, Guangjie; Wang, Jiaqiang

    2014-12-15

    Halloysite nanotube supported Ag nanoparticles heteroarchitectures have been prepared through a very simple electroless plating method. Robust Ag nanocrystals can be reproducibly fabricated by soaking halloysite nanotubes in ethanolic solutions of AgNO3 and butylamine. By simply adjusting the molar ratio of AgNO3 and butylamine, Ag nanoparticles with tunable size and quantity on halloysite nanotube are achieved. It reveals that the Ag nanoparticles are well-dispersed on the surface of halloysite nanotubes. The halloysite nanotube supported Ag nanoparticles heteroarchitectures can serve as active catalysts for the polymerization of an alkylsilane C18H37SiH3 with water to form silanol/siloxane composite microspheres and exhibit interesting superhydrophobicity ascribed to the micro/nanobinary structure.

  17. Controlled growth of thermally stable uniform-sized Ag nanoparticles on flat support and their electrochemical activity

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    A method consisting of spin coating of Ag+ ions (AgNO3) solution followed by chemical reduction in aqueous hydrazine solution has been presented for controlled growth of thermally stable uniform-sized Ag nanoparticles on flat substrate. Scanning electron microscopy images and local surface plasmon resonance absorption studies imply that most of the Ag nanoparticles grow with unique preferable size. This preferable size can be controlled by changing AgNO3 solution characteristics (drop size and concentration), spin-coating parameters (rpm and ramp) and annealing temperatures. With increase in rpm or ramp, particle size decreases with enhanced particles density. The Ag nanoparticles are thermally stable up to 450 °C, and the preferable size is increased with annealing temperature. The grown particles are catalytic active for oxygen reduction reaction, and activity was found to be dependent on size and density of Ag nanoparticles.

  18. 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.

  19. Hollow Au-Ag Nanoparticles Labeled Immunochromatography Strip for Highly Sensitive Detection of Clenbuterol

    NASA Astrophysics Data System (ADS)

    Wang, Jingyun; Zhang, Lei; Huang, Youju; Dandapat, Anirban; Dai, Liwei; Zhang, Ganggang; Lu, Xuefei; Zhang, Jiawei; Lai, Weihua; Chen, Tao

    2017-01-01

    The probe materials play a significant role in improving the detection efficiency and sensitivity of lateral-flow immunochromatographic test strip (ICTS). Unlike conventional ICTS assay usually uses single-component, solid gold nanoparticles as labeled probes, in our present study, a bimetallic, hollow Au-Ag nanoparticles (NPs) labeled ICTS was successfully developed for the detection of clenbuterol (CLE). The hollow Au-Ag NPs with different Au/Ag mole ratio and tunable size were synthesized by varying the volume ratio of [HAuCl4]:[Ag NPs] via the galvanic replacement reaction. The surface of hollow Ag-Au NPs was functionalized with 11-mercaptoundecanoic acid (MUA) for further covalently bonded with anti-CLE monoclonal antibody. Overall size of the Au-Ag NPs, size of the holes within individual NPs and also Au/Ag mole ratio have been systematically optimized to amplify both the visual inspection signals and the quantitative data. The sensitivity of optimized hollow Au-Ag NPs probes has been achieved even as low as 2 ppb in a short time (within 15 min), which is superior over the detection performance of conventional test strip using Au NPs. The optimized hollow Au-Ag NPs labeled test strip can be used as an ideal candidate for the rapid screening of CLE in food samples.

  20. Hollow Au-Ag Nanoparticles Labeled Immunochromatography Strip for Highly Sensitive Detection of Clenbuterol

    PubMed Central

    Wang, Jingyun; Zhang, Lei; Huang, Youju; Dandapat, Anirban; Dai, Liwei; Zhang, Ganggang; Lu, Xuefei; Zhang, Jiawei; Lai, Weihua; Chen, Tao

    2017-01-01

    The probe materials play a significant role in improving the detection efficiency and sensitivity of lateral-flow immunochromatographic test strip (ICTS). Unlike conventional ICTS assay usually uses single-component, solid gold nanoparticles as labeled probes, in our present study, a bimetallic, hollow Au-Ag nanoparticles (NPs) labeled ICTS was successfully developed for the detection of clenbuterol (CLE). The hollow Au-Ag NPs with different Au/Ag mole ratio and tunable size were synthesized by varying the volume ratio of [HAuCl4]:[Ag NPs] via the galvanic replacement reaction. The surface of hollow Ag-Au NPs was functionalized with 11-mercaptoundecanoic acid (MUA) for further covalently bonded with anti-CLE monoclonal antibody. Overall size of the Au-Ag NPs, size of the holes within individual NPs and also Au/Ag mole ratio have been systematically optimized to amplify both the visual inspection signals and the quantitative data. The sensitivity of optimized hollow Au-Ag NPs probes has been achieved even as low as 2 ppb in a short time (within 15 min), which is superior over the detection performance of conventional test strip using Au NPs. The optimized hollow Au-Ag NPs labeled test strip can be used as an ideal candidate for the rapid screening of CLE in food samples. PMID:28134263

  1. Application of Multi-Species Microbial Bioassay to Assess the Effects of Engineered Nanoparticles in the Aquatic Environment: Potential of a Luminous Microbial Array for Toxicity Risk Assessment (LumiMARA) on Testing for Surface-Coated Silver Nanoparticles

    PubMed Central

    Jung, YounJung; Park, Chang-Beom; Kim, Youngjun; Kim, Sanghun; Pflugmacher, Stephan; Baik, Seungyun

    2015-01-01

    Four different manufactured surface-coated silver nanoparticles (AgNPs) with coating of citrate, tannic acid, polyethylene glycol, and branched polyethylenimine were used in this study. The toxicity of surface-coated AgNPs was evaluated by a luminous microbial array for toxicity risk assessment (LumiMARA) using multi-species of luminescent bacteria. The salt stability of four different AgNPs was measured by UV absorbance at 400 nm wavelength, and different surface-charged AgNPs in combination with bacteria were observed using scanning electron microscopy (SEM). Both branched polyethylenimine (BPEI)-AgNPs and polyethylene glycol (PEG)-AgNPs were shown to be stable with 2% NaCl (non-aggregation), whereas both citrate (Cit)-AgNPs and tannic acid (Tan)-AgNPs rapidly aggregated in 2% NaCl solution. The values of the 50% effective concentration (EC50) for BPEI-AgNPs in marine bacteria strains (1.57 to 5.19 mg/L) were lower than those for the other surface-coated AgNPs (i.e., Cit-AgNPs, Tan-AgNPs, and PEG-AgNPs). It appears that the toxicity of AgNPs could be activated by the interaction of positively charged AgNPs with the negatively charged bacterial cell wall from the results of LumiMARA. LumiMARA for toxicity screening has advantageous compared to a single-species bioassay and is applicable for environmental samples as displaying ranges of assessment results. PMID:26184279

  2. TiO2 modified with Ag nanoparticles synthesized via ultrasonic atomization-UV reduction and the use of kinetic models to determine the acetic acid photocatalytic degradation

    NASA Astrophysics Data System (ADS)

    Xu, Yingcao; You, Hong

    2014-12-01

    TiO2 surfaces modified with noble metal nanoparticles have been found to effectively reduce the photogenerated carrier recombination rate and significantly extend the light absorption properties of TiO2, thereby greatly increasing its photocatalytic activity. In this paper, highly ordered, double-sided TiO2 nanotube arrays were prepared using an anodic oxidation method in a home-made reactor using glycerol/water (volume ratio 2:1) and NH4F (0.25 mol/L) as the electrolyte, titanium plates (10 cm × 2 cm × 0.5 mm) as the anode and graphite as the cathode at a constant voltage of 25 V. After a 2-h reaction, anatase TiO2 nanotubes were obtained upon calcination at 450 °C for 4 h. The Ag nanoparticles on the surfaces of the TiO2 were prepared via ultrasonic atomization-ultraviolet light reduction. First, a silver nitrate solution was sputtered into small droplets under ultrasonication. Then, the Ag+ droplets were reduced to Ag nanoparticles. The surface morphologies, structures and elemental compositions were characterized using SEM, EDS, XRD and XPS. The photocatalytic activities were determined in acetic acid solutions (40-200 mg/L), and a mathematical model for catalytic degradation was established based on a hyperbolic model. The SEM results showed that the diameters of the as-prepared Ag/TiO2 are approximately 100 nm and that the lengths are approximately 1.8 μm. The XRD crystal structure analysis shows that the anatase phase of the TiO2 does not change during the Ag modification, and there was a peak from Ag (2 2 0). The XPS determined that the Ag atom percentage was 1.11%. The degradation of acetic acid indicated that Ag/TiO2 has a higher photocatalytic activity than the undoped TiO2.

  3. Nanoparticle-lipid bilayer interactions studied with lipid bilayer arrays

    NASA Astrophysics Data System (ADS)

    Lu, Bin; Smith, Tyler; Schmidt, Jacob J.

    2015-04-01

    The widespread environmental presence and commercial use of nanoparticles have raised significant health concerns as a result of many in vitro and in vivo assays indicating toxicity of a wide range of nanoparticle species. Many of these assays have identified the ability of nanoparticles to damage cell membranes. These interactions can be studied in detail using artificial lipid bilayers, which can provide insight into the nature of the particle-membrane interaction through variation of membrane and solution properties not possible with cell-based assays. However, the scope of these studies can be limited because of the low throughput characteristic of lipid bilayer platforms. We have recently described an easy to use, parallel lipid bilayer platform which we have used to electrically investigate the activity of 60 nm diameter amine and carboxyl modified polystyrene nanoparticles (NH2-NP and COOH-NP) with over 1000 lipid bilayers while varying lipid composition, bilayer charge, ionic strength, pH, voltage, serum, particle concentration, and particle charge. Our results confirm recent studies finding activity of NH2-NP but not COOH-NP. Detailed analysis shows that NH2-NP formed pores 0.3-2.3 nm in radius, dependent on bilayer and solution composition. These interactions appear to be electrostatic, as they are regulated by NH2-NP surface charge, solution ionic strength, and bilayer charge. The ability to rapidly measure a large number of nanoparticle and membrane parameters indicates strong potential of this bilayer array platform for additional nanoparticle bilayer studies.The widespread environmental presence and commercial use of nanoparticles have raised significant health concerns as a result of many in vitro and in vivo assays indicating toxicity of a wide range of nanoparticle species. Many of these assays have identified the ability of nanoparticles to damage cell membranes. These interactions can be studied in detail using artificial lipid bilayers, which

  4. Real-time imaging and elemental mapping of AgAu nanoparticle transformations.

    PubMed

    Lewis, E A; Slater, T J A; Prestat, E; Macedo, A; O'Brien, P; Camargo, P H C; Haigh, S J

    2014-11-21

    We report the controlled alloying, oxidation, and subsequent reduction of individual AgAu nanoparticles in the scanning transmission electron microscope (STEM). Through sequential application of electron beam induced oxidation and in situ heating and quenching, we demonstrate the transformation of Ag-Au core-shell nanoparticles into: AgAu alloyed, Au-Ag core-shell, hollow Au-Ag2O core-shell, and Au-Ag2O yolk-shell nanoparticles. We are able to directly image these morphological transformations in real-time at atomic resolution and perform energy dispersive X-ray (EDX) spectrum imaging to map changing elemental distributions with sub-nanometre resolution. By combining aberration corrected STEM imaging and high efficiency EDX spectroscopy we are able to quantify not only the growth and coalescence of Kirkendall voids during oxidation but also the compositional changes occurring during this reaction. This is the first time that it has been possible to track the changing distribution of elements in an individual nanoparticle undergoing oxidation driven shell growth and hollowing.

  5. 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.

  6. Electrical Transport in Semiconductor Nanoparticle Arrays: Conductivity, Sensing and Modeling

    NASA Astrophysics Data System (ADS)

    Hartner, Sonja; Schwesig, Dominik; Plümel, Ingo; Wolf, Dietrich E.; Lorke, Axel; Wiggers, Hartmut

    Electrical properties of nanoparticle ensembles are dominated by interparticle transport processes, mainly due to particle-particle and particle-contact interactions. This makes their electrical properties dependent on the network properties such as porosity and particle size and is a main prerequisite for solid- state gas sensors, as the surrounding gas atmosphere influences the depletion layer surrounding each particle. Different kinds of nanoparticle arrays such as pressed pellets, printed layer, and thin films prepared by molecular beam-assisted deposition are characterized with respect to their electrical transport properties. Experimental results are shown for the electrical and sensing properties of several metal oxide nanoparticle ensembles and the influence of porosity is investigated during compaction of nanoparticle powders exposed to an external force. A model describing these properties is developed and it is shown that for a given material only porosity, geometry, and particle size influence the overall electrical properties. The model developed for the description of current transport in particulate matter can also be utilized to describe current-assisted sintering.

  7. Sulfur-doped graphene-supported Ag nanoparticles for nonenzymatic hydrogen peroxide detection

    NASA Astrophysics Data System (ADS)

    Tian, Ye; Liu, Yu; Wang, Weiping; Zhang, Xiao; Peng, Wei

    2015-04-01

    Heteroatom doping is an effective way to modulate the physicochemical properties of graphene and its hybrid materials. In this work, sulfur-doped graphene (SG) was used for the first time as a supporting material for loading Ag nanoparticles, and the resulting Ag/SG hybrid with a high S-doping level (2.8 at.%) and a uniform Ag NP decoration was successfully prepared by a microwave-assisted method. Electrochemical measurements revealed that the Ag/SG exhibited a better electrocatalytic activity toward H2O2 reduction than undoped Ag/reduced graphene oxide, which highlighted the important role of S-doping that could not only improve the charge transfer, but also introduce more defects as active sites. The nonenzymatic sensor based on Ag/SG displayed good sensing performances for highly sensitive, selective, and stable detection of H2O2, demonstrating that SG is indeed a promising catalyst-supporting material for electrochemical sensing.

  8. Large-scale fabrication of polymer/Ag core-shell nanorod array as flexible SERS substrate by combining direct nanoimprint and electroless deposition

    NASA Astrophysics Data System (ADS)

    Liu, Sisi; Xu, Zhimou; Sun, Tangyou; Zhao, Wenning; Wu, Xinghui; Ma, Zhichao; Xu, Haifeng; He, Jian; Chen, Cunhua

    2014-06-01

    We demonstrate a highly sensitive surface-enhanced Raman scattering (SERS) substrate, which consists of Ag nanoparticles (NPs) assembled on the surface of a nanopatterned polymer film. The fabrication route of a polymer/Ag core-shell nanorod (PACSN) array employed a direct nanoimprint technique to create a high-resolution polymer nanorod array. The obtained nanopatterned polymer film was subjected to electroless deposition to form a sea-cucumber-like Ag shell over the surface of the polymer nanorod. The morphology and structures of PACSNs were analyzed by using scanning electron microscopy and X-ray diffraction. The as-synthesized PACSNs exhibited a remarkable SERS activity and Raman signal reproducibility to rhodamine 6G, and a concentration down to 10-12 M can be identified. The effect of electroless deposition time of Ag NPs onto the polymer nanorod surface was investigated. It was found that the electroless deposition time played an important role in SERS activity. Our results revealed that the combination of direct nanoimprint and electroless deposition provided a convenient and cost-effective way for large-scale fabrication of reliable SERS substrates without the requirement of expensive instruments.

  9. Determining the Concentration Dependent Transformations of Ag Nanoparticles in Complex Media: Using SP-ICP-MS and Au@Ag Core-Shell Nanoparticles as Tracers.

    PubMed

    Merrifield, Ruth C; Stephan, Chady; Lead, Jamie

    2017-03-01

    The fate, behavior, and impact of engineered nanoparticles (NPs) in toxicological and environmental media are driven by complex processes which are difficult to quantify. A key limitation is the ability to perform measurements at low and environmentally relevant concentrations, since concentration may be a key factor determining fate and effects. Here, we use single particle inductively coupled mass spectroscopy (SP-ICP-MS) to measure directly NP diameter and particle number concentration of suspensions containing gold-silver core-shell (Au@Ag) NPs in EPA moderately hard water (MHW) and MHW containing 2.5 mg L(-1) Suwannee River fulvic acid. The Au core of the Au@Ag NPs acts as an internal standard, and aids in the analysis of the complex Ag transformations. The high sensitivity of SP-ICP-MS, along with the Au@Ag NPs, enabled us to track the NP transformations in the range 0.01 and 50 μg L(-1), without further sample preparation. On the basis of the analysis of both Au and Ag parameters (size, size distribution, and particle number), concentration was shown to be a key factor in NP behavior. At higher concentration, NPs were in an aggregation-dominated regime, while at the lower and environmentally representative concentrations, dissolution of Ag was dominant and aggregation was negligible. In addition, further formation of ionic silver as Ag NPs in the form of AgS or AgCl was shown to occur. Between 1 and 10 μg L(-1), both aggregation and dissolution were important. The results suggest that, under realistic conditions, the role of NP homoaggregation may be minimal. In addition, the complexity of exposure and dose in dose-response relationships is highlighted.

  10. 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.

  11. Fabrication and SERS performance of silver-nanoparticle-decorated Si/ZnO nanotrees in ordered arrays.

    PubMed

    Cheng, Chuanwei; Yan, Bin; Wong, She Mein; Li, Xianglin; Zhou, Weiwei; Yu, Ting; Shen, Zexiang; Yu, Hongyu; Fan, Hong Jin

    2010-07-01

    Highly ordered treelike Si/ZnO hierarchical nanostructures are successfully prepared in a large scale by combining two common techniques, viz., photolithography-assisted wafer-scale fabrication of Si nanopillars and bottom-up hydrothermal growth of ZnO nanorods. Silver nanoparticles are decorated onto the nanotrees by photochemical reduction and deposition. The Si/ZnO/Ag hybrid nanotrees are employed as SERS-active substrates, which exhibit good performance in terms of high sensitivity and good reproducibility. In addition to the SERS application, such ordered Si/ZnO arrays might also find potential applications in light-emitting diodes and solar cells.

  12. 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.

  13. 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...

  14. A distance-controlled nanoparticle array using PEGylated ferritin

    NASA Astrophysics Data System (ADS)

    He, Chao; Uenuma, Mutsunori; Okamoto, Naofumi; Kamitake, Hiroki; Ishikawa, Yasuaki; Yamashita, Ichiro; Uraoka, Yukiharu

    2014-12-01

    A distance-controlled nanoparticle (NP) array was investigated using a simple spin coating process. It was found that the separation distance of NPs was controlled at the nanoscale by using polyethylene glycols (PEGs). Ferritin was used to synthesize NPs and carry them to a substrate by using the different molecular weight of PEGs. In order to control the distance of the NPs, PEGs with molecular weights of 2k, 5k, 10k and 20k were modified on ferritin with 10 mM ion strength and 0.01 mg ml-1 ferritin concentration. The separated distances of NPs increased along with increase in PEG molecular weight.

  15. 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.

  16. 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.

  17. Small nickel nanoparticle arrays from long chain imidazolium ionic liquids

    DOE PAGES

    Yang, Mei; Campbell, Paul S.; Santini, Catherine C.; ...

    2013-11-08

    A series of six long chain alkyl mono- and bi-cationic imidazolium based salts with bis(trifluoromethylsulfonyl)imide (NTf2–) as the anion were synthesized and characterized. Single crystal structure of 1-methyl-3-octadecylimidazolium bis(trifluoromethylsulfonyl)imide could be obtained by X-ray analysis. All these long chain alkyl imidazolium based ILs were applied in the synthesis of nickel nanoparticles via chemical decomposition of an organometallic precursor of nickel. In these media, spontaneous decomposition of Ni(COD)2 (COD = 1,5-cyclooctadiene) in the absence of H2 occurred giving small NPs (≤4 nm) with narrow size distributions. Interestingly, formation of regularly interspaced NP arrays was also observed in long chain ILs. Lastly,more » such array formation could be interesting for potential applications such as carbon nanotube growth.« less

  18. Small nickel nanoparticle arrays from long chain imidazolium ionic liquids

    SciTech Connect

    Yang, Mei; Campbell, Paul S.; Santini, Catherine C.; Mudring, Anja -Verena

    2013-11-08

    A series of six long chain alkyl mono- and bi-cationic imidazolium based salts with bis(trifluoromethylsulfonyl)imide (NTf2–) as the anion were synthesized and characterized. Single crystal structure of 1-methyl-3-octadecylimidazolium bis(trifluoromethylsulfonyl)imide could be obtained by X-ray analysis. All these long chain alkyl imidazolium based ILs were applied in the synthesis of nickel nanoparticles via chemical decomposition of an organometallic precursor of nickel. In these media, spontaneous decomposition of Ni(COD)2 (COD = 1,5-cyclooctadiene) in the absence of H2 occurred giving small NPs (≤4 nm) with narrow size distributions. Interestingly, formation of regularly interspaced NP arrays was also observed in long chain ILs. Lastly, such array formation could be interesting for potential applications such as carbon nanotube growth.

  19. Hydrophobic interactions increase attachment of gum Arabic- and PVP-coated Ag nanoparticles to hydrophobic surfaces.

    PubMed

    Song, Jee Eun; Phenrat, Tanapon; Marinakos, Stella; Xiao, Yao; Liu, Jie; Wiesner, Mark R; Tilton, Robert D; Lowry, Gregory V

    2011-07-15

    A fundamental understanding of attachment of surface-coated nanoparticles (NPs) is essential to predict the distribution and potential risks of NPs in the environment. Column deposition studies were used to examine the effect of surface-coating hydrophobicity on NP attachment to collector surfaces in mixtures with varying ratios of octadecylichlorosilane (OTS)-coated (hydrophobic) glass beads and clean silica (hydrophilic) glass beads. Silver nanoparticles (AgNPs) coated with organic coatings of varying hydrophobicity, including citrate, polyvinylpyrrolidone (PVP), and gum arabic (GA), were used. The attachment efficiencies of GA and PVP AgNPs increased by 2- and 4-fold, respectively, for OTS-coated glass beads compared to clean glass beads. Citrate AgNPs showed no substantial change in attachment efficiency for hydrophobic compared to hydrophilic surfaces. The attachment efficiency of PVP-, GA-, and citrate-coated AgNPs to hydrophobic collector surfaces correlated with the relative hydrophobicity of the coatings. The differences in the observed attachment efficiencies among AgNPs could not be explained by classical DLVO, suggesting that hydrophobic interactions between AgNPs and OTS-coated glass beads were responsible for the increase in attachment of surface-coated AgNPs with greater hydrophobicity. This study indicates that the overall attachment efficiency of AgNPs will be influenced by the hydrophobicity of the NP coating and the fraction of hydrophobic surfaces in the environment.

  20. Ordering Ag nanowire arrays by a glass capillary: a portable, reusable and durable SERS substrate.

    PubMed

    Liu, Jian-Wei; Wang, Jin-Long; Huang, Wei-Ran; Yu, Le; Ren, Xi-Feng; Wen, Wu-Cheng; Yu, Shu-Hong

    2012-01-01

    Assembly of nanowires into ordered macroscopic structures with new functionalities has been a recent focus. In this Letter, we report a new route for ordering hydrophilic Ag nanowires with high aspect ratio by flowing through a glass capillary. The present glass capillary with well-defined silver nanowire films inside can serve as a portable and reusable substrate for surface-enhanced Raman spectroscopy (SERS), which may provide a versatile and promising platform for detecting mixture pollutions. By controlling the flow parameters of nanowire suspensions, initially random Ag nanowires can be aligned to form nanowire arrays with tunable density, forming cambered nanowire films adhered onto the inner wall of the capillary. Compared with the planar ordered Ag nanowire films by the Langmuir-Blodgett (LB) technique, the cambered nanowire films show better SERS performance.

  1. Synthesis of Ag/ZnO nanorods array with enhanced photocatalytic performance.

    PubMed

    Ren, Chunlei; Yang, Beifang; Wu, Min; Xu, Jiao; Fu, Zhengping; Lv, Yan; Guo, Ting; Zhao, Yongxun; Zhu, Changqiong

    2010-10-15

    Silver-modified ZnO nanorods array has been prepared and the effect of silver modification has been studied. ZnO nanorods array were fabricated through a wet chemical route and a photo deposition method was taken to fabricate silver nano particulate on the ZnO nanorods. The structural and optical properties were characterized by field emission scanning electron microscope, high resolution transmission electron microscope, X-ray photoelectron spectroscopy, Raman, UV-vis and photoluminescence (PL) spectra. The UV photocatalytic activity of these materials was studied by analyzing the degradation of methylene blue (MB) in aqueous solution. The photocatalytic performance indicated that Ag deposit acted as not only electron sinks to enhance the separation of photoexcited electrons from holes, but also charge carrier recombination centers, so the optimized amount of Ag deposit was investigated.

  2. 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

    2016-11-05

    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.

  3. Focused-ion-beam-fabricated Au nanorods coupled with Ag nanoparticles used as surface-enhanced Raman scattering-active substrate for analyzing trace melamine constituents in solution.

    PubMed

    Sivashanmugan, Kundan; Liao, Jiunn-Der; Liu, Bernard Haochih; Yao, Chih-Kai

    2013-10-24

    A well-ordered Au-nanorod array with a controlled tip ring diameter (Au_NRsd) was fabricated using the focused ion beam method. Au_NRsd was then coupled with Ag nanoparticles (Ag NPs) to bridge the gaps among Au nanorods. The effect of surface-enhanced Raman scattering (SERS) on Au_NRsd and Ag NPs/Au_NRsd was particularly verified using crystal violet (CV) as the molecular probe. Raman intensity obtained from a characteristic peak of CV on Au_NRsd was estimated by an enhancement factor of ≈10(7) in magnitude, which increased ≈10(12) in magnitude for that on Ag NPs/Au_NRsd. A highly SERS-active Ag NPs/Au_NRsd was furthermore applied for the detection of melamine (MEL) at very low concentrations. Raman-active peaks of MEL (10(-3) to 10(-12)M) in water or milk solution upon Au_NRsd or Ag NPs/Au_NRsd were well distinguished. The peaks at 680 and 702 cm(-1) for MEL molecules were found suitable to be used as the index for sensing low-concentration MEL in a varied solution, while that at 1051 cm(-1) was practical to interpret MEL molecules in water or milk solution bonded with Au (i.e., Au_NRsd) or Ag (i.e., Ag NPs/Au_NRsd) surface. At the interface of Ag NPs/Au_NRsd and MEL molecules in milk solution, a laser-induced electromagnetic field or hotspot effect was produced and competent to sense low-concentration MEL molecules interacting with Ag and Au surfaces. Accordingly, Ag NPs/Au_NRsd is very promising to be used as a fast and sensitive tool for screening MEL in complex matrices such as adulteration in e.g., food and pharmaceutical products.

  4. 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.

  5. 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...

  6. Synthesis and characterization of Co@Ag core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Garcia-Torres, Jose; Vallés, Elisa; Gómez, Elvira

    2010-08-01

    A micellar method has been used to prepare silver-coated cobalt (Co@Ag) nanoparticles. The synthesized particles have been deeply characterized by several methods, i.e., XRD, UV-Vis, TEM, XPS, and electrochemical techniques. There is every indication that the obtained particles show a truly core-shell structure. All the nanoparticles obtained under different conditions are in the size range 3-5 nm. High-resolution TEM (HRTEM), Fast Fourier Transformation (FFT), and Selected Area Electron Diffraction (SAED) indicated that the presence of hcp-Co and fcc-Ag, in which cobalt is located in the central area; meanwhile silver is at the edges of the nanoparticle. The absorption band of the Co@Ag colloid shifts to a longer wavelength and broadens relative to that of pure silver colloid. Voltammetric characterization allowed to determine the coverage of the cobalt core.

  7. Preparation and thermoelectric properties of sulfur doped Ag2Te nanoparticles via solvothermal methods.

    PubMed

    Zhou, Wenwen; Zhao, Weiyun; Lu, Ziyang; Zhu, Jixin; Fan, Shufen; Ma, Jan; Hng, Huey Hoon; Yan, Qingyu

    2012-07-07

    In this work, n-type Ag(2)Te nanoparticles are prepared by a solvothermal approach with uniform and controllable sizes, e.g. 5-15 nm. The usage of dodecanethiol during the synthesis effectively introduces sulfur doping into the sample, which optimizes the charge carrier concentration of the nanoparticles to >1 × 10(20) cm(-3). This allows us to achieve the desired electrical resistivities of <5 × 10(-6)Ω m. It is demonstrated that Ag(2)Te particles prepared by this solvothermal process can exhibit high ZT values, e.g. 15 nm Ag(2)Te nanoparticles with effective sulphur doping show a maximum ZT value of ~0.62 at 550 K.

  8. 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.

  9. Studies on plasmon characteristics and the local density of states of Au and Ag based nanoparticles

    NASA Astrophysics Data System (ADS)

    Vinod, M.; Biju, V.; Gopchandran, K. G.

    2016-01-01

    Knowledge about the conductive properties and the local density of states of chemically pure Au, Ag, Ag@Au core-shell and Au-Ag bimetallic nanoparticles is technologically important. Herein, the I-V characteristics and the density of states derived from scanning tunneling microscopy measurements made under atmospheric conditions is reported. The nanoparticles in thin film form used in this study were prepared by laser ablation in water followed by drop and evaporation. The morphology of the surface of the nanostructures was observed from optimizing tunneling current in each case. The monometallic Au and Ag particles shows almost similar current characteristics as well as discrete energy states but the slope of I-V characteristics was different for bimetallic structures. An attempt has also been made to compare the current measurements done in the nanoscale with the surface plasmon characteristics.

  10. Highly reproducible and uniform SERS substrates based on Ag nanoparticles with optimized size and gap

    NASA Astrophysics Data System (ADS)

    Bai, Yiming; Yan, Lingling; Wang, Jun; Su, Lin; Chen, Nuofu; Tan, Zhanao

    2017-02-01

    It's quite necessary to fabricate reproducible and uniform surface-enhanced Raman scattering (SERS) composite substrate with high enhancement factor simply. Therefore, in this work, in order to obtain the SERS substrates with optimized size and gap, Ag films with different thickness deposited by magnetron sputtering and following annealing are performed. The results both elucidate the function relationship between the size, gap of nanoparticles and the thickness of Ag films, and ascertain the optimized parameters for silver nanoparticles on the basis of finite-difference time-domain simulation, the SERS signal using graphene and Rhodamine 6G (R6G) as probe molecules for Ag-NPs/Si substrates. Moreover, our findings highlight the Ag NPs with optimized size and gap as SERS substrates present high reproducibility and uniformity.

  11. 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.

  12. A significant cathodic shift in the onset potential and enhanced photoelectrochemical water splitting using Au nanoparticles decorated WO3 nanorod array.

    PubMed

    Xu, Fang; Yao, Yanwen; Bai, Dandan; Xu, Ruishu; Mei, Jingjing; Wu, Dapeng; Gao, Zhiyong; Jiang, Kai

    2015-11-15

    Au nanoparticles decorated WO3 nanorod array was prepared and applied for solar water oxidation. Scanning electron microscopy and transmission electron microscop images showed that Au distributed on the surface of WO3 nanorod array. The surface plasmon resonance effect of Au nanoparticles contributed to the enhancement of photoelectrochemical performance of Au-WO3 photoanode, such as enhanced photocurrent density of 1.17mA/cm(2) at 1.0V vs Ag/AgCl, a cathodic shift of onset of ∼0.2V and higher stability. UV-vis absorption, electrochemical impedance and Mott-Schottky measurements proved that Au-WO3 photoanode has enhanced light absorption, lower transfer resistance, increased photogenerated carriers density and higher hole injection yield. Therefore, Au-WO3 photoanode exhibited higher photoelectrochemical performance than WO3 photoanode.

  13. Studies on interaction of colloidal Ag nanoparticles with Bovine Serum Albumin (BSA).

    PubMed

    Ravindran, Aswathy; Singh, Anupam; Raichur, Ashok M; Chandrasekaran, N; Mukherjee, Amitava

    2010-03-01

    Biofunctionalization of noble metal nanoparticles like Ag, Au is essential to obtain biocompatibility for specific biomedical applications. Silver nanoparticles are being increasingly used in bio-sensing applications owing to excellent optoelectronic properties. Among the serum albumins, the most abundant proteins in plasma, a wide range of physiological functions of Bovine Serum Albumin (BSA) has made it a model system for biofunctionalization. In absence of adequate prior reports, this study aims to investigate the interaction between silver nanoparticles and BSA. The interaction of BSA [0.05-0.85% concentrations] with Ag nanoparticles [50ppm concentration] in aqueous dispersion was studied through UV-vis spectral changes, morphological and surface structural changes. At pH 7, which is more than the isoelectric point of BSA, a decrease in absorbance at plasmon peak of uninteracted nanoparticles (425nm) was noted till 0.45% BSA, beyond that a blue shift towards 410nm was observed. The blue shift may be attributed to enhanced electron density on the particle surfaces. Increasing pH to 12 enhanced the blue shift further to 400nm. The conformational changes in BSA at alkaline pH ranges and consequent hydrophobic interactions also played an important role. The equilibrium adsorption data fitted better to Freundlich isotherm compared to Langmuir curve. The X-ray diffraction study revealed complete coverage of Ag nanoparticles by BSA. The scanning electron microscopic study of the interacted nanoparticles was also carried out to decipher morphological changes. This study established that tailoring the concentration of BSA and pH of the interaction it was possible to reduce aggregation of nanoparticles. Biofunctionalized Ag nanoparticles with reduced aggregation will be more amenable towards bio-sensing applications.

  14. 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.

  15. Size tuning of Ag-decorated TiO₂ nanotube arrays for improved bactericidal capacity of orthopedic implants.

    PubMed

    Esfandiari, N; Simchi, A; Bagheri, R

    2014-08-01

    Surface modification of orthopedic implants using titanium dioxide nanotubes and silver nanoparticles (SNs) is a promising approach to prevent bacteria adhesion, biofilm formation, and implant infection. Herein, we utilized a straightforward and all-solution process to prepare silver-decorated TiO2 nanotube arrays with surface density of 10(3) to 10(4) per µm(2). With controlling the synthesis conditions, hexagonal closed-packed nanotubes with opening diameter of 30-100 nm that are decorated with SNs with varying sizes (12-40 nm) were prepared. Various analytical techniques were utilized to characterize the size, morphology, distribution, valance state, surface roughness, and composition of the prepared antibacterial films. The bactericidal capacity of the films were studied on Escherichia coli (E. coli) by drop-test method and correlated with the size and percentage of Ag as well as the surface density of TiO2 nanotube arrays. Synergetic effect of TiO2 nanotubes and SNs on the antibacterial activity of the composite films is shown. The bactericidal capacity is found to depend on the size characteristics of the Ag-TiO2 coating. The highest antibacterial activity is obtained for TiO2 nanotubes with opening diameter of about 100 nm and SNs with an average size of 20 nm. MTT assay using osteoblast MG63 cells was performed to examine the cell viability. We suggest that release rate of the silver ions is an important factor controlling the antibacterial activity. Additionally, the size dependency of the bactericidal capacity implies that electrical coupling between silver and TiO2 nanotubes and improved hydrophobicity of the coating might influence the bacterial behavior of the hybrid nanostructures.

  16. 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)

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

    NASA Astrophysics Data System (ADS)

    Liu, Wei-Jun; Zhang, Zhi-Cheng; He, Wei-Dong; Zheng, Cheng; Ge, Xue-Wu; Li, Jian; Liu, Hua-Rong; Jiang, Hao

    2006-04-01

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

  18. Negligible particle-specific toxicity mechanism of silver nanoparticles: the role of Ag+ ion release in the cytosol.

    PubMed

    De Matteis, Valeria; Malvindi, Maria Ada; Galeone, Antonio; Brunetti, Virgilio; De Luca, Elisa; Kote, Sachin; Kshirsagar, Prakash; Sabella, Stefania; Bardi, Giuseppe; Pompa, Pier Paolo

    2015-04-01

    Toxicity of silver nanoparticles (AgNPs) is supported by many observations in literature, but no mechanism details have been proved yet. Here we confirm and quantify the toxic potential of fully characterized AgNPs in HeLa and A549 cells. Notably, through a specific fluorescent probe, we demonstrate the intracellular release of Ag(+) ions in living cells after nanoparticle internalization, showing that in-situ particle degradation is promoted by the acidic lysosomal environment. The activation of metallothioneins in response to AgNPs and the possibility to reverse the main toxic pathway by Ag(+) chelating agents demonstrate a cause/effect relationship between ions and cell death. We propose that endocytosed AgNPs are degraded in the lysosomes and the release of Ag(+) ions in the cytosol induces cell damages, while ions released in the cell culture medium play a negligible effect. These findings will be useful to develop safer-by-design nanoparticles and proper regulatory guidelines of AgNPs. From the clinical editor: The authors describe the toxic potential of silver nanoparticles (AgNP) in human cancer cell lines. Cell death following the application of AgNPs is dose-dependent, and it is mostly due to Ag+ ions. Further in vivo studies should be performed to gain a comprehensive picture of AgNP-toxicity in mammals.

  19. 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.

  20. Electromagnetic wave propagation in a Ag nanoparticle-based plasmonic power divider.

    PubMed

    Ahmed, Iftikhar; Png, Ching Eng; Li, Er-Ping; Vahldieck, Rüdiger

    2009-01-05

    In this paper a new silver (Ag) nanoparticle-based structure is presented which shows potential as a device for front end applications, in nano-interconnects or power dividers. A novel oxide bar ensures waveguiding and control of the signal strength with promising results. The structure is simulated by the two dimensional finite difference time domain (FDTD) method considering TM polarization and the Drude model. The effect of different wavelengths, material loss, gaps and particle sizes on the overall performance is discussed. It is found that the maximum signal strength remains along the Ag metallic nanoparticles and can be guided to targeted end points.

  1. Correlating second harmonic optical responses of single Ag nanoparticles with morphology.

    PubMed

    Jin, Rongchao; Jureller, Justin E; Kim, Hee Y; Scherer, Norbert F

    2005-09-14

    Femtosecond laser excited second harmonic (SH) activity from single Ag nanoparticles is reported. A correlation of SH single-particle measurements with high-resolution imaging of particle morphology by TEM was achieved by creating position markers on an optical and electron transparent substrate (Si3N4 thin film, approximately 100 nm). We compared the SH activity of single Ag nanoparticles (nanospheres versus nanorods) and cluster structures (composed of two or multiple particles, e.g., dimers and trimers). The direct correlation of single-particle structures and SH activity, spectral and power dependence, strongly suggests one-photon resonant driven nonlinear oscillator response mechanism.

  2. 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.

  3. 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

  4. Microfluidic synthesis of Ag@Cu2O core-shell nanoparticles with enhanced photocatalytic activity.

    PubMed

    Tao, Sha; Yang, Mei; Chen, Huihui; Ren, Mingyue; Chen, Guangwen

    2017-01-15

    A microfluidic-based method for the continuous synthesis of Ag@Cu2O core-shell nanoparticles (NPs) has been developed. It only took 32s to obtain Ag@Cu2O core-shell NPs, indicating a high efficiency of this microfluidic-based method. Triangular Ag nanoprisms were employed as the cores for the overgrowth of Cu2O through the reduction of Cu(OH)4(2-) with ascorbic acid. The as-synthesized samples were characterized by XRD, TEM, SEM, HAADF-STEM, EDX, HRTEM, UV-vis spectra and N2 adsorption-desorption. The characterization results revealed that the as-synthesized Ag@Cu2O core-shell NPs exhibited a well-defined core-shell nanostructure with a polycrystalline shell, which was composed of numbers of Cu2O domains epitaxially growing on the triangular Ag nanoprism. It was concluded that the synthesis parameters such as the molar ratio of trisodium citrate to AgNO3, H2O2 to AgNO3, NaOH to CuSO4, ascorbic acid to CuSO4 and AgNO3 to CuSO4 had significant effect on the synthesis of Ag@Cu2O core-shell NPs. Moreover, Ag@Cu2O core-shell NPs exhibited superior catalytic activity in comparison with pristine Cu2O NPs towards the visible light-driven degradation of methyl orange. This enhanced photocatalytic activity of Ag@Cu2O core-shell NPs was attributed to the larger BET surface area and improved charge separation efficiency. The trapping experiment indicated that holes and superoxide anion radicals were the major reactive species in the photodegradation of methyl orange over Ag@Cu2O core-shell NPs. In addition, Ag@Cu2O core-shell NPs showed no obvious deactivation in the cyclic test.

  5. 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.

  6. Controlled synthesis of Ag nanoparticles with different morphologies and their antibacterial properties.

    PubMed

    Gao, Minjie; Sun, Lei; Wang, Zhiqiang; Zhao, Yanbao

    2013-01-01

    In this paper, Ag triangle nanoplates and nanospheres were synthesized by liquid chemical reduction method in the presence of seeds, with L-ascorbic acid as the reductant and polyvinyl pyrrolidone (PVP) as the surface modification agent, respectively. Characterizations of the particles were conducted by various techniques such as X-ray powder diffraction, transmission electron microscopy, ultraviolet-visible absorption spectroscopy, Fourier transformation infrared spectrometry, and thermal analysis. The antibacterial properties of Ag nanoparticles against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were investigated by disk diffusion and broth dilution methods. The results indicate that Ag nanospheres exhibit better antibacterial properties than that of triangle nanoplates.

  7. 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.

  8. 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.

  9. Effects of Ag Nanoparticles on Growth and Fat Body Proteins in Silkworms (Bombyx mori).

    PubMed

    Meng, Xu; Abdlli, Nouara; Wang, Niannian; Lü, Peng; Nie, Zhichao; Dong, Xin; Lu, Shuang; Chen, Keping

    2017-03-30

    Ag nanoparticles (AgNPs), a widely used non-antibiotic, antibacterial material, have shown toxic and other potentially harmful effects in mammals. However, the deleterious effects of AgNPs on insects are still unknown. Here, we studied the effects of AgNPs on the model invertebrate organism Bombyx mori. After feeding silkworm larvae different concentrations of AgNPs, we evaluated the changes of B. mori body weights, survival rates, and proteomic differences. The results showed that low concentrations (<400 mg/L) of AgNPs promoted the growth and cocoon weights of B. mori. Although high concentrations (≥800 mg/L) of AgNPs also improved B. mori growth, they resulted in silkworm death. An analysis of fat body proteomic differences revealed 13 significant differences in fat body protein spots, nine of which exhibited significantly downregulated expression, while four showed significantly upregulated expression. Reverse transcription-polymerase chain reaction results showed that at an AgNP concentration of 1600 mg/L, the expression levels of seven proteins were similar to the transcription levels of their corresponding genes. Our results suggest that AgNPs lowered the resistance to oxidative stress, affected cell apoptosis, and induced cell necrosis by regulating related protein metabolism and metabolic pathways in B. mori.

  10. Green synthesis of halloysite nanotubes supported Ag nanoparticles for photocatalytic decomposition of methylene blue

    NASA Astrophysics Data System (ADS)

    Zou, MeiLing; Du, MingLiang; Zhu, Han; Xu, CongSheng; Fu, YaQin

    2012-08-01

    Using tea polyphenols (TPs) as a reductant, Ag nanoparticles (AgNPs) supported on halloysite nanotubes (HNTs) were simply and greenly synthesized for the photocatalytic decomposition of methylene blue (MB). HNTs were initially functionalized by N-β-aminoethyl-γ-aminopropyl trimethoxysilane (AEAPTMS) to introduce amino groups to form N-HNTs to fasten the AgNPs; then AgNPs were synthesized and ‘anchored’ on the surface of the HNTs. Fourier transform infrared spectroscopy was employed to testify the amino groups on the surface of the HNTs. Transmission electron microscopy, field-emission scanning electron microscopy and x-ray diffraction were utilized to characterize the structure and morphology of the synthesized HNTs supported by the AgNPs (AgNPs@N-HNTs). The results showed that the AgNPs had been synthesized and ‘anchored’ onto the surface of the HNTs with a diameter of about 20-30 nm. X-ray photoelectron spectroscopy analysis revealed the chelating interaction between the AgNPs and N atoms together with the TP molecular. The photocatalytic activity of the as-prepared AgNPs@N-HNTs catalyst was evaluated by decomposition of MB; the results showed that the prepared catalyst exhibited excellent catalytic activity and high adsorption capability to MB.

  11. Ag nanoparticles loaded on porous graphitic carbon nitride with enhanced photocatalytic activity for degradation of phenol

    NASA Astrophysics Data System (ADS)

    Han, Zhenwei; Wang, Nan; Fan, Hai; Ai, Shiyun

    2017-03-01

    Highly efficient photocatalyst of visible-light-driven Ag nanoparticles loaded on porous graphitic carbon nitride (g-C3N4) was prepared by the reduction of Ag ions on porous g-C3N4. The obtained Ag/porous g-C3N4 composite products were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflection spectra (DRS), thermal gravimetric analysis (TGA). The results demonstrated that a homogeneous distribution of Ag NPs of 10 nm was attached onto the surface of the porous g-C3N4. The prepared Ag/porous g-C3N4 samples were applied for catalyzing the degradation of phenol in water under visible light irradiation. Porous g-C3N4 demonstrated an excellent support for the formation and dispersion of small uniform Ag NPs. When the weight percentage of Ag reaches 5%, the nanohybrid exhibits superior photocatalytic activities compared to bulk g-C3N4, porous g-C3N4, and 2% Ag/porous g-C3N4 hybrids. The enhanced photocatalytic performance is due to the synergic effect between Ag and porous g-C3N4, which suppressed the recombination of photogenerated electron-hole pairs.

  12. The role of Ag nanoparticles in inverted polymer solar cells: Surface plasmon resonance and backscattering centers

    NASA Astrophysics Data System (ADS)

    Xu, Peng; Shen, Liang; Meng, Fanxu; Zhang, Jiaqi; Xie, Wenfa; Yu, Wenjuan; Guo, Wenbin; Jia, Xu; Ruan, Shengping

    2013-03-01

    Here, we demonstrate silver (Ag) nanoparticles (NPs) existing in molybdenum trioxide (MoO3) buffer layers can improve the photocurrent by surface plasmon resonance (SPR) and backscattering enhancement. The device structure is glass/indium tin oxides/titanium dioxide (TiO2)/regioregular poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester/MoO3/Ag NPs/MoO3/Ag. Compared to the device without Ag NPs, the short current density (Jsc) is improved from 7.76 ± 0.14 mA/cm2 to 8.89 ± 0.12 mA/cm2, and the power conversion efficiency is also enhanced from 2.70% ± 0.11% to 3.35% ± 0.08%. The transmittance spectra show that the device with Ag NPs has weaker transmittance than the device without, which could be attributed to the photons absorption of Ag NPs and light scattering by Ag NPs. The absorption profile of the devices with or without Ag NPs is simulated using finite-difference time-domain methods. It is approved that the Ag NPs result in the absorption improvement by SPR and backscattering enhancement.

  13. Engineering structured light with Vogel spiral arrays of nanoparticles

    NASA Astrophysics Data System (ADS)

    Lawrence, Nate; Trevino, Jacob; Dal Negro, Luca

    2013-03-01

    We present a general analytical model for light scattering by arbitrary Vogel spiral arrays of circular apertures uniformly illuminated at normal incidence. This model suffices to unveil the fundamental mathematical structure of their complex Fraunhofer diffraction patterns and enables the engineering of optical beams carrying multiple values of orbital angular momentum (OAM). By performing analytical Fourier-Hankel decomposition of spiral arrays and far field patterns, we rigorously demonstrate the ability to encode specific numerical sequences onto the OAM values of diffracted optical beams. In particular, we show that these OAM values are determined by the rational approximations of the continued fraction expansions of the irrational angles utilized to generate Vogel spirals. Finally, we experimentally demonstrate structured light carrying multiple values of OAM in the far-field scattering region of Vogel spiral arrays of metallic nanoparticles. Using Fourier-Hankel mode decomposition analysis and interferometric reconstruction of the complex amplitude of scattered waves, we show the ability to encode well-defined numerical sequences, determined by the aperiodic spiral geometry, into azimuthal OAM values, in excellent agreement with analytical scattering theory. The generation of sequences of OAM values by light scattering from engineered aperiodic surfaces is relevant to a number of device applications for secure optical communication, classical and quantum cryptography.

  14. 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.

  15. Pressure-driven assembly of spherical nanoparticles and formation of 1D nanostructure arrays.

    SciTech Connect

    Wu, Huimeng

    2010-08-01

    External pressure was used to engineer nanoparticle assembly. Reversible manipulation of the unit-cell dimensions of a 3D ordered nanoparticle array under a hydrostatic pressure field enabled the fine-tuning of the interparticle distance. Under a uniaxial pressure field, nanoparticles were forced to contact and coalesce into nanorods or nanowires and ordered ultrahigh-density arrays (see picture; small arrows denote pressure).

  16. Assemblies of silicate sol-gel matrix encapsulated core/shell Au/Ag nanoparticles: interparticles surface plasmon coupling

    NASA Astrophysics Data System (ADS)

    Manivannan, Shanmugam; Ramaraj, Ramasamy

    2012-06-01

    Cluster-like assemblies of bimetal core/shell Au/Ag nanoparticles were prepared. The Ag shell was deposited on the preformed Au nanoparticles using two different types of preformed Au nanoparticles in the presence of EDAS silane monomer, one stabilized by citrate and other by β-cyclodextrin. The Ag shell was deposited on the preformed Au nanoparticles by the reduction of Ag+ ions by β-cyclodextrin and EDAS silane composite. Interestingly, productive Ag shell deposition occurred only on the β-cyclodextrin-stabilized Au nanoparticles and led to the assembly formation, whereas aggregation occurred with the citrate-stabilized Au nanoparticles. The average particle size of the core/shell Au/Ag nanoparticles was found to be 6.5 nm. Spectral features of this assembly of core/shell Au/Ag nanoparticles resembled the longitudinal surface plasmon resonance behavior of Au nanorod-like structures arising from the interparticles surface plasmon coupling. The assemblies so prepared were characterized by uv-vis absorption spectroscopy and high-resolution transmission electron microscopy.

  17. 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.

  18. Ag/Pd core-shell nanoparticles by a successive method: Pulsed laser ablation of Ag in water and reduction reaction of PdCl2

    NASA Astrophysics Data System (ADS)

    Mottaghi, N.; Ranjbar, M.; Farrokhpour, H.; Khoshouei, M.; Khoshouei, A.; Kameli, P.; Salamati, H.; Tabrizchi, M.; Jalilian-Nosrati, M.

    2014-02-01

    In this study Ag/Pd nanoparticles (NPs) have been fabricated by a successive method; first, colloids of Ag nanoparticles (NPs) have been prepared in water by pulsed laser ablation in liquid (PLAL) method. Then PdCl2 solution (up to 0.2 g/l) were added to the as-prepared or aged colloidal Ag NPs. Characterizations were done using UV-vis spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmissions electron microscopy (TEM) techniques. Spectroscopy data showed that surface plasmon resonance (SPR) peaks of as-prepared Ag NPs at about λ = 400 nm were completely extinguished after addition of PdCl2 solution while this effect was not observed when aged Ag NPs are used. XRD and XPS results revealed that by addition of the PdCl2 solution into the as-prepared Ag NPs, metallic palladium, and silver chloride composition products are generated. TEM images revealed that as a result of this reaction, single and core-shell nanoparticles are obtained and their average sizes are 2.4 nm (Ag) and 3.2 nm (Ag/Pd). The calculated d-spacing values form XRD data with observations on high magnification TEM images were able to explain the chemical nature of different parts of Ag/Pd NPs.

  19. Fabrication of silver nanoparticle-doped hydroxyapatite coatings with oriented block arrays for enhancing bactericidal effect and osteoinductivity.

    PubMed

    Tian, Bo; Chen, Wei; Yu, Degang; Lei, Yong; Ke, Qinfei; Guo, Yaping; Zhu, Zhenan

    2016-08-01

    Implant-associated infection is a common postoperative complication and remains a serious problem in orthopedic surgery. This work describes the synthesis of silver nanoparticle-doped hydroxyapatite coatings with oriented block arrays (AgNP-BHAC). The resulting nanostructure was investigated using scanning electron microscopy, energy-dispersive spectrometry, transmission electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. AgNP-BHAC exhibited excellent antimicrobial activity toward gram-negative Escherichia coli and gram-positive Staphylococcus aureus owing to the antibacterial effects of the silver nanoparticles. Human bone marrow stromal cells (hBMSC) culture revealed that the AgNP-BHAC exhibited better biocompatibility, and permitted improved cell proliferation, attachment, and osteoinductivity than uncoated Ti-6Al-4V titanium alloy, the favored material for biomedical applications. In summary, this study presents a convenient and effective method for the incorporation of silver into HA coatings with block morphology. This method can be utilized to modify a variety of metallic implant surfaces to improve their antimicrobial effects and reduce potential long-term cytotoxicity.

  20. 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.

  1. Visual determination of Cu2+ through copper-catalysed in situ formation of Ag nanoparticles.

    PubMed

    Yuan, Xun; Chen, Yi

    2012-10-07

    A new strategy was explored for the visual determination of Cu(2+) using copper-catalysed in situ formation of Ag nanoparticles. In this method, only common reagents were used and the pre-synthesis and modification of nanoparticles are avoided. Ag(+) can form a milk-white suspension (AgBr) with Br(-) in an aqueous solution composed of AgNO(3), cetyltrimethylammonium bromide, ascorbic acid, bovine serum albumin, and NaNO(3). The reaction will be stopped by addition of Cu(2+), accompanied by a colour change from milk-white to orange or brilliant yellow. Cu(+) (the reduction product of Cu(2+)) consumes the dissolved O(2) and prevents the O(2) from oxidizing the newly reduced Ag atoms (by ascorbic acid) back to Ag(+), facilitating the further aggregation of Ag atoms to become Ag nanoparticles. The visible colour change was shown to be specific towards Cu(2+) over most other metal ions. The limit of detection was 0.75 μM Cu(2+) by the naked eye and 0.25 μM by spectrometer. Quantitation of Cu(2+) was achieved in a linear range from 0.25 to 2.0 μM. This method was validated by measuring real water and serum samples, giving results agreeing well with the data reported and measured by inductively coupled plasma mass spectrometry. The recovery was 95.6-106% for untreated tap water and 96.0-100% for resin-pre-treated water and serum samples.

  2. 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

  3. 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.

  4. Size-selected ag nanoparticles with five-fold symmetry.

    PubMed

    Gracia-Pinilla, Miguelángel; Ferrer, Domingo; Mejía-Rosales, Sergio; Pérez-Tijerina, Eduardo

    2009-05-15

    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.

  5. 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

  6. 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

  7. 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.

  8. On-the-fly green generation and dispersion of AgI nanoparticles for cloud seeding nuclei

    NASA Astrophysics Data System (ADS)

    Hu, Xiuli; Zhou, Wenbo; Wang, Xizheng; Wu, Tao; Delisio, Jeffery B.; Zachariah, Michael R.

    2016-07-01

    This study reports on an on-the-fly green synthesis/dispersion of silver iodide (AgI) nanoparticles from the combustion of AgIO3/carbon black (CB)/nitrocellulose (NC) composites, which could be used as a candidate for a cloud-seeding pyrotechnic. Films were formed by direct electrospray deposition of a mixture of synthesized silver iodate with CB and NC. The decomposition pathways of AgIO3/CB and AgIO3/CB/NC were evaluated by temperature jump time of flight mass spectrometry (T-jump TOFMS) and XRD, showing that AgI particles and CO2 are released from the reaction between AgIO3 and CB without other toxic residuals. The flame propagation velocity of AgIO3/CB/NC films increases with the increasing of particle mass loading of AgIO3 and CB and peaks at 40 wt%, which is much higher than that of an AgI/AP/NC film. The mean diameter of the resultant AgI nanoparticles is from 51 to 97 nm. The mass loading of AgIO3 and CB was found to play a major role in size control of the AgI nanoparticles.

  9. Ag nanoparticles/PPV composite nanofibers with high and sensitive opto-electronic response

    NASA Astrophysics Data System (ADS)

    Chen, Jinfeng; Yang, Peipei; Wang, Chunjiao; Zhan, Sumei; Zhang, Lianji; Huang, Zonghao; Li, Wenwen; Wang, Cheng; Jiang, Zijiang; Shao, Chen

    2011-12-01

    The novel Ag nanoparticles/poly( p-phenylene vinylene) [PPV] composite nanofibers were prepared by electrospinning. The transmission electron microscope image shows that the average diameter of composite fibers is about 500 nm and Ag nanoparticles are uniformly dispersed in the PPV matrix with an average diameter of about 25 nm. The Fourier transform infrared spectra suggest that there could be a coordination effect to a certain extent between the Ag atom and the π system of PPV, which is significantly favorable for the dissociation of photoexcitons and the charge transfer at the interface between the Ag nanoparticle and the PPV. The Au top electrode device of the single Ag/PPV composite nanofiber exhibits high and sensitive opto-electronic responses. Under light illumination of 5.76 mW/cm2 and voltage of 20 V, the photocurrent is over three times larger than the dark current under same voltage, which indicates that this kind of composite fiber is an excellent opto-electronic nanomaterial.

  10. 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.

  11. 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.

  12. Enrichment of anodic MgO layers with Ag nanoparticles for biomedical applications.

    PubMed

    Necula, B S; Fratila-Apachitei, L E; Berkani, A; Apachitei, I; Duszczyk, J

    2009-01-01

    The growing fight against infections caused by bacteria poses new challenges for development of materials and medical devices with antimicrobial properties. Silver is a well known antimicrobial agent and has recently started to be used in nanoparticulate form, with the advantage of a high specific surface area and a continuous release of enough concentration of silver ions/radicals. The synthesis of MgO-Ag nanocomposite coatings by in situ deposition of silver nanoparticles during plasma electrolytic oxidation of a magnesium substrate is presented in this study. The process was performed in an electrolyte containing Ag nanoparticles under different oxidation conditions (i.e., current density, oxidizing time, silver nanoparticles concentration in the electrolyte). Surface morphology, phase composition and elemental composition (on the surface and across the thickness of MgO-Ag nanocomposite coatings) were assessed by scanning electron microscopy, X-ray diffraction, energy X-ray dispersive spectrometry and radio frequency glow discharge optical emission spectroscopy, respectively. The coatings were found to be porous, around 7 mum thick, consisting of a crystalline oxide matrix embedded with silver nanoparticles. The findings suggest that plasma electrolytic oxidation process has potential for the synthesis of MgO-Ag nanocomposite coatings.

  13. 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

  14. Femtomolar Detection of Silver Nanoparticles by Flow-Enhanced Direct-Impact Voltammetry at a Microelectrode Array

    PubMed Central

    2016-01-01

    We report the femtomolar detection of silver (Ag) nanoparticles by direct-impact voltammetry. This is achieved through the use of a random array of microelectrodes (RAM) integrated into a purpose-built flow cell, allowing combined diffusion and convection to the electrode surface. A coupled RAM-flow cell system is implemented and is shown to give reproducible wall-jet type flow characteristics, using potassium ferrocyanide as a molecular redox species. The calibrated flow system is then used to detect and quantitatively size Ag nanoparticles at femtomolar concentrations. Under flow conditions, it is found the nanoparticle impact frequency increases linearly with the volumetric flow rate. The resulting limit of detection is more than 2 orders of magnitude smaller than the previous detection limit for direct-impact voltammetry (900 fM) [J. Ellison et al. Sens. Actuators, B2014, 200, 47], and is more than 30 times smaller than the previous detection limit for mediated-impact voltammetry (83 fM) [T. M. Alligrant et al. Langmuir2014, 30, 13462]. PMID:27494652

  15. Femtomolar Detection of Silver Nanoparticles by Flow-Enhanced Direct-Impact Voltammetry at a Microelectrode Array.

    PubMed

    Sokolov, Stanislav V; Bartlett, Thomas R; Fair, Peter; Fletcher, Stephen; Compton, Richard G

    2016-09-06

    We report the femtomolar detection of silver (Ag) nanoparticles by direct-impact voltammetry. This is achieved through the use of a random array of microelectrodes (RAM) integrated into a purpose-built flow cell, allowing combined diffusion and convection to the electrode surface. A coupled RAM-flow cell system is implemented and is shown to give reproducible wall-jet type flow characteristics, using potassium ferrocyanide as a molecular redox species. The calibrated flow system is then used to detect and quantitatively size Ag nanoparticles at femtomolar concentrations. Under flow conditions, it is found the nanoparticle impact frequency increases linearly with the volumetric flow rate. The resulting limit of detection is more than 2 orders of magnitude smaller than the previous detection limit for direct-impact voltammetry (900 fM) [J. Ellison et al. Sens. Actuators, B 2014, 200, 47], and is more than 30 times smaller than the previous detection limit for mediated-impact voltammetry (83 fM) [T. M. Alligrant et al. Langmuir 2014, 30, 13462].

  16. Directed liquid phase assembly of highly ordered metallic nanoparticle arrays

    DOE PAGES

    Wu, Yueying; Dong, Nanyi; Fu, Shaofang; ...

    2014-04-01

    Directed assembly of nanomaterials is a promising route for the synthesis of advanced materials and devices. We demonstrate the directed-assembly of highly ordered two-dimensional arrays of hierarchical nanostructures with tunable size, spacing and composition. The directed assembly is achieved on lithographically patterned metal films that are subsequently pulse-laser melted; during the brief liquid lifetime, the pattened nanostructures assemble into highly ordered primary and secondary nanoparticles, with sizes below that which was originally patterned. Complementary fluid-dynamics simulations emulate the resultant patterns and show how the competition of capillary forces and liquid metal–solid substrate interaction potential drives the directed assembly. Lastly, asmore » an example of the enhanced functionality, a full-wave electromagnetic analysis has been performed to identify the nature of the supported plasmonic resonances.« less

  17. Directed liquid phase assembly of highly ordered metallic nanoparticle arrays

    SciTech Connect

    Wu, Yueying; Dong, Nanyi; Fu, Shaofang; Fowlkes, Jason D.; Kondic, Lou; Vincenti, Maria A.; de Ceglia, Domenico; Rack, Philip D.

    2014-04-01

    Directed assembly of nanomaterials is a promising route for the synthesis of advanced materials and devices. We demonstrate the directed-assembly of highly ordered two-dimensional arrays of hierarchical nanostructures with tunable size, spacing and composition. The directed assembly is achieved on lithographically patterned metal films that are subsequently pulse-laser melted; during the brief liquid lifetime, the pattened nanostructures assemble into highly ordered primary and secondary nanoparticles, with sizes below that which was originally patterned. Complementary fluid-dynamics simulations emulate the resultant patterns and show how the competition of capillary forces and liquid metal–solid substrate interaction potential drives the directed assembly. Lastly, as an example of the enhanced functionality, a full-wave electromagnetic analysis has been performed to identify the nature of the supported plasmonic resonances.

  18. Green synthesis of Ag nanoparticles using Tamarind fruit extract for the antibacterial studies.

    PubMed

    Jayaprakash, N; Vijaya, J Judith; Kaviyarasu, K; Kombaiah, K; Kennedy, L John; Ramalingam, R Jothi; Munusamy, Murugan A; Al-Lohedan, Hamad A

    2017-04-01

    In the present study, first time we report the microwave-assisted green synthesis of silver nanoparticles (AgNPs) using Tamarindus indica natural fruit extract. The plant extract plays a dual role of reducing and capping agent for the synthesis of AgNPs. The formation of spherical shape AgNPs is confirmed by XRD, HR-SEM, and HR-TEM. The presence of face-centered cubic (FCC) silver is confirmed by XRD studies and the average crystallite size of AgNPs is calculated to be around 6-8nm. The average particle diameter is found to be around 10nm, which is identified from HR-TEM images. The purity of AgNPs is confirmed by EDX analysis. The presence of sigmoid curve in UV-Visible absorption spectra suggests that the reaction has complicated kinetic features. To investigate the functional groups of the extract and their involvement in the reduction of AgNO3 to form AgNPs, FT-IR studies are carried out. The redox peaks are observed in cyclic voltammetry in the potential range of -1.2 to +1.2V, due to the redox active components of the T. indica fruit extract. In photoluminescence spectroscopy, the excited and emission peaks were obtained at 432nm and 487nm, respectively. The as-prepared AgNPs showed good results towards antibacterial activities. Hence, the present approach is a facile, cost- effective, reproducible, eco-friendly, and green method.

  19. 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.

  20. Laser fabrication of 2D and 3D metal nanoparticle structures and arrays.

    PubMed

    Kuznetsov, A I; Kiyan, R; Chichkov, B N

    2010-09-27

    A novel method for fabrication of 2D and 3D metal nanoparticle structures and arrays is proposed. This technique is based on laser-induced transfer of molten metal nanodroplets from thin metal films. Metal nanoparticles are produced by solidification of these nanodroplets. The size of the transferred nanoparticles can be controllably changed in the range from 180 nm to 1500 nm. Several examples of complex 2D and 3D microstructures generated form gold nanoparticles are demonstrated.

  1. Photocatalytic activity of Ag/ZnO core–shell nanoparticles with shell thickness as controlling parameter under green environment

    NASA Astrophysics Data System (ADS)

    Rajbongshi, Himanshu; Bhattacharjee, Suparna; Datta, Pranayee

    2017-02-01

    Plasmonic Ag/ZnO core–shell nanoparticles have been synthesized via a simple two-step wet chemical method for application in Photocatalysis. The morphology, size, crystal structure, composition and optical properties of the nanoparticles are investigated by x-ray diffraction, transmission electron microscopy (TEM), FTIR spectroscopy, ultraviolet–visible (UV–Vis) absorption spectroscopy and photoluminescence (PL) spectroscopy. The shell thicknesses are varied by varying the concentration of zinc nitrate hexa-hydrate and triethanolamine. The ZnO shell coating over Ag core enhances the charge separation, whereas the larger shell thickness and increased refractive index of surrounding medium cause red shifts of surface Plasmon resonance (SPR) peak of Ag core. The photoluminescence (PL) spectra of Ag/ZnO core–shell show that the larger shell thickness quenches the near band edge UV emission of ZnO. The electrochemical impedance spectra (EIS) i.e. Nyquist plots also confirm the higher charge transfer efficiency of the Ag/ZnO core–shell nanoparticles. The Photocatalytic activities of Ag/ZnO core–shell nanoparticles are investigated by the degradation of methylene blue (MB) dye under direct sunlight irradiation. Compared to pure ZnO nanoparticles (NPs), Ag/ZnO core–shell NPs display efficient sunlight plasmonic photocatalytic activity because of the influence of SPR of Ag core and the electron sink effect. The photocatalytic activity of Ag/ZnO core–shell NPs is found to be enhanced with increase in shell thickness.

  2. 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.

  3. Preparation and structural properties of pure and codoped (Mg, Ag) ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Reddy, B. Sankara; Reddy, S. Venkatramana; Reddy, N. Koteeswara

    2013-06-01

    Pure and co-doped (Mg, Ag) ZnO nanoparticles (Zn0.90Mg0.05Ag0.05O) are synthesized by chemical co-precipitation method in the presence of capping agent Polyethylene glycol 600 (PEG 600) and annealed at 500°C in air ambient for 1h. The XRD measurements reveals that the pure and co-doped ZnO samples have hexagonal structure without any change and the size of ZnO nanoparicles were decreased from 17 nm to 13 nm. FESEM images indicates that they are flake like structures of the ZnO and co-doped ZnO samples and ED AX spectra reveals that the successful doping concentration of Mg and Ag. From the TEM results, the size of the ZnO nanoparticles which are in good agreement with the XRD results.

  4. Cyto/hemocompatible magnetic hybrid nanoparticles (Ag2S-Fe3O4) with luminescence in the near-infrared region as promising theranostic materials.

    PubMed

    Hocaoglu, Ibrahim; Asik, Didar; Ulusoy, Gulen; Grandfils, Christian; Ojea-Jimenez, Isaac; Rossi, François; Kiraz, Alper; Doğan, Nurcan; Acar, Havva Yagci

    2015-09-01

    Small hybrid nanoparticles composed of highly biocompatible Ag2S quantum dots (QD) emitting in the near-infrared region and superparamagnetic iron oxide (SPION) are produced in a simple extraction method utilizing ligand exchange mechanism. Hybrid nanoparticles luminesce at the same wavelength as the parent QD, therefore an array of hybrid nanoparticles with emission between 840 and 912nm were easily produced. Such hybrid structures have (1) strong luminescence in the medical imaging window eliminating the autofluoresence of cells as effective optical probes, (2) strong magnetic response for magnetic targeting and (3) good cyto/hemocompatibility. An interesting size dependent cytotoxicity behavior was observed in HeLa and NIH/3T3 cell lines: smallest particles are internalized significantly more by both of the cell lines, yet showed almost no significant cytotoxicity in HeLa between 10 and 25μg/mL Ag concentration but were most toxic in NIH/3T3 cells. Cell internalization and hence the cytotoxicity enhanced when cells were incubated with the hybrid nanoparticles under magnetic field, especially with the hybrid nanoparticles containing larger amounts of SPION in the hybrid composition. These results prove them as effective optical imaging agents and magnetic delivery vehicles. Combined with the known advantages of SPIONs as a contrast agent in MRI, these particles are a step forward for new theranostics for multimode imaging and magnetic targeting.

  5. 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.

  6. 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

  7. 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.

  8. Structural and plasmonic studies of Ag nanoparticles in silica glass hosts

    NASA Astrophysics Data System (ADS)

    R, Rejikumar P.; Thomas, Vinoy; George, Jacob; Joseph, Cyriac; R, Biju P.; V, Unnikrishnan N.

    2013-05-01

    Silica glassy materials doped with Ag were prepared through sol gel route. The structural studies of the prepared samples showed an icosahedral morphology of the nanocrystals formed along with spherical morphology. The XRD and TEM data confirmed the formation of silver nanoparticles of size between 20 and 22nm. The surface plasmon resonance (SPR) of silver nanoparticles with spherical morphology was studied with the discrete dipole approximation . The shape and size effects of the nanoparticles can induce distinctive features of the SPR spectrum. It has been shown that such effects can induce peak intensity enhancement, wavelength shift and spectral broadening of the SPR spectra of the nanoparticles. The results obtained depend on the existence of highly localized plasmonic oscillations. An attempt has also been made to calculate the van der Waals force between nanoparticles.

  9. Cooperative plasmonic effect of Ag and Au nanoparticles on enhancing performance of polymer solar cells.

    PubMed

    Lu, Luyao; Luo, Zhiqiang; Xu, Tao; Yu, Luping

    2013-01-09

    This article describes a cooperative plasmonic effect on improving the performance of polymer bulk heterojunction solar cells. When mixed Ag and Au nanoparticles are incorporated into the anode buffer layer, dual nanoparticles show superior behavior on enhancing light absorption in comparison with single nanoparticles, which led to the realization of a polymer solar cell with a power conversion efficiency of 8.67%, accounting for a 20% enhancement. The cooperative plasmonic effect aroused from dual resonance enhancement of two different nanoparticles. The idea was further unraveled by comparing Au nanorods with Au nanoparticles for solar cell application. Detailed studies shed light into the influence of plasmonic nanostructures on exciton generation, dissociation, and charge recombination and transport inside thin film devices.

  10. 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

  11. Absorption and scattering of light by VO2 nanoparticle array

    NASA Astrophysics Data System (ADS)

    Yu, Xiaojing; Li, Yi; Wang, Haifang; Zhang, Hu; Zhang, Wei; Huang, Yize

    2009-07-01

    Much attention has been paid to the semiconductor-metal phase transition in vanadium dioxide nanomaterials, accompanied with an abrupt change in its resistivity and near-infrared transmission. The phase transition and optical properties of vanadium dioxide nanoparticles were studied by the mathematical model based on the complex refractive changing with the temperature and wavelength. The optical properties of nano-array were investigated by using the discrete dipole approximation and Mie scattering theory, as well as the absorption and scattering properties of small particles. The results show that the main contribution to the optical response with variational wavelength in the infrared is from absorption cross section comparing with the scattering cross section. It is obvious that the absorption peak of metal phase occurs near 980nm. With the change of temperature, the variation of extinction coefficient is larger in the infrared region than in the visible region. The largest change of extinction coefficient occurs in the near-infrared region. The extincition coefficient is very small in the visible region and there is a maximal value in the infrared region in the nano-array.

  12. 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.

  13. 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

  14. Memristive behavior of Al2O3 film with bottom electrode surface modified by Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Qin, Shu-Chao; Dong, Rui-Xin; Yan, Xun-Ling

    2014-09-01

    The memristive behavior of Al2O3-based device is significantly improved by introducing Ag nanoparticles (NPs). Inserting Ag NPs can effectively reduce the switching voltages, increase the resistance ratio (about 104) and enhance the sweep endurance (300 cycles). In particular, the stable switching properties are obtained by inserting an Ag NPs layer with an average diameter of 14 nm on the surface of bottom electrode, and the devices show a long retention time (more than 106 s) compared with the devices without Ag NPs. The switching mechanism is related to the oxygen-vacancy-based conducting filaments and the interfacial effect. The local enhancement and nonuniform distribution of electric field have the benefits to promote, induce and modulate the growth of conducting filaments, such as shape, location and orientation, which are responsible for the improvement performance of the devices.

  15. Memristive behavior of Al2O3 film with bottom electrode surface modified by Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Qin, Shu-Chao; Dong, Rui-Xin; Yan, Xun-Ling

    2015-02-01

    The memristive behavior of Al2O3-based device is significantly improved by introducing Ag nanoparticles (NPs). Inserting Ag NPs can effectively reduce the switching voltages, increase the resistance ratio (about 104) and enhance the sweep endurance (300 cycles). In particular, the stable switching properties are obtained by inserting an Ag NPs layer with an average diameter of 14 nm on the surface of bottom electrode, and the devices show a long retention time (more than 106 s) compared with the devices without Ag NPs. The switching mechanism is related to the oxygen-vacancy-based conducting filaments and the interfacial effect. The local enhancement and nonuniform distribution of electric field have the benefits to promote, induce and modulate the growth of conducting filaments, such as shape, location and orientation, which are responsible for the improvement performance of the devices.

  16. Experimental investigation of nonlinear optical properties of Ag nanoparticles: Effects of size quantization

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    The effects of size quantization on the nonlinear optical response of Ag nanoparticles are experimentally studied by spectroscopic ellipsometry and femtosecond spectroscopic pump-and-probe techniques. In the vicinity of a localized surface-plasmon resonance (2.0-3.5 eV), we have investigated the optical nonlinearity of Ag particles embedded in silica glass for particle diameters ranging from 3.0 to 16 nm. The intrinsic third-order optical susceptibility χm(3) of Ag particles exhibited significant spectral and size dependences. These results are explained as quantum and dielectric confinements and are compared to the results of theoretical quantum finite-size effects calculation for metallic particles. In light of these results, we discuss the contribution of interband transitions to the size dependence of χm(3). Quantum size effects lead to an increase in nonlinearity in small Ag particles.

  17. 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.

  18. 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

    2016-06-07

    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%.

  19. 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

  20. Luminescent Ag-doped In2S3 nanoparticles stabilized by mercaptoacetate in water and glycerol

    NASA Astrophysics Data System (ADS)

    Raevskaya, Alexandra E.; Ivanchenko, Maria V.; Stroyuk, Oleksandr L.; Kuchmiy, Stepan Ya.; Plyusnin, Victor F.

    2015-03-01

    Colloidal nanoparticles (NPs) of tetragonal β-In2S3 were stabilized in water and glycerol by mercaptoacetate anions. Doping of In2S3 NPs with AgI cations at the time of the synthesis imparts the NPs with the photoluminescence (PL) in the visible part of the spectrum. The doping results also in a shift of the absorption threshold and the PL band maximum to longer wavelengths proportional to the AgI content. The PL band maximum of AgI-doped In2S3 NPs can be varied from 575-580 to 760-765 nm by augmenting the silver(I) amount and the duration and temperature of the post-synthesis aging. The average radiative life-time of AgI-doped In2S3 NPs also depends on the silver(I) content and reaches the maximal value, 960 ns, at a molar Ag:In ratio of 1:4. The maximal quantum yield of stationary PL, 12 %, is observed at this Ag:In ratio as well. Deposition of a ZnS "shell" on the surface of AgI-doped In2S3 NPs results in an increase of the PL quantum yield to 30 %.

  1. Ag Nanoparticle-Sensitized WO3 Hollow Nanosphere for Localized Surface Plasmon Enhanced Gas Sensors.

    PubMed

    Yao, Yao; Ji, Fangxu; Yin, Mingli; Ren, Xianpei; Ma, Qiang; Yan, Junqing; Liu, Shengzhong Frank

    2016-07-20

    Ag nanoparticle (NP)-sensitized WO3 hollow nanospheres (Ag-WO3-HNSs) are fabricated via a simple sonochemical synthesis route. It is found that the Ag-WO3-HNS shows remarkable performance in gas sensors. Field-emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) images reveal that the Agx-WO3 adopts the HNS structure in which WO3 forms the outer shell framework and the Ag NPs are grown on the inner wall of the WO3 hollow sphere. The size of the Ag NPs can be controlled by adjusting the addition amount of WCl6 during the reaction. The sensor Agx-WO3 exhibits extremely high sensitivity and selectivity toward alcohol vapor. In particular, the Ag(15nm)-WO3 sensor shows significantly lower operating temperature (230 °C), superior detection limits as low as 0.09 ppb, and faster response (7 s). Light illumination was found to boost the sensor performance effectively, especially at 405 and 900 nm, where the light wavelength resonates with the absorption of Ag NPs and the surface oxygen vacancies of WO3, respectively. The improved sensor performance is attributed to the localized surface plasmon resonance (LSPR) effect.

  2. Ag2S/CdS/TiO2 Nanotube Array Films with High Photocurrent Density by Spotting Sample Method

    NASA Astrophysics Data System (ADS)

    Sun, Hong; Zhao, Peini; Zhang, Fanjun; Liu, Yuliang; Hao, Jingcheng

    2015-10-01

    Ag2S/CdS/TiO2 hybrid nanotube array films (Ag2S/CdS/TNTs) were prepared by selectively depositing a narrow-gap semiconductor—Ag2S (0.9 eV) quantum dots (QDs)—in the local domain of the CdS/TiO2 nanotube array films by spotting sample method (SSM). The improvement of sunlight absorption ability and photocurrent density of titanium dioxide (TiO2) nanotube array films (TNTs) which were obtained by anodic oxidation method was realized because of modifying semiconductor QDs. The CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs fabricated by uniformly depositing the QDs into the TNTs via the successive ionic layer adsorption and reaction (SILAR) method were synthesized, respectively. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared. In comparison with the four films of TNTs, CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs by SILAR, the Ag2S/CdS/TNTs prepared by SSM showed much better absorption capability and the highest photocurrent density in UV-vis range (320~800 nm). The cycles of local deposition have great influence on their photoelectric properties. The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

  3. AC Conductivity and Diffuse Reflectance Studies of Ag-TiO2 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Abdul Gafoor, A. K.; Musthafa, M. M.; Pradyumnan, P. P.

    2012-09-01

    Silver (Ag)-TiO2 nanoparticles synthesized by a low-temperature hydrothermal method in the anatase phase have been investigated by x-ray diffraction. Transmission electron microscopy has been used for morphological studies. Surface areas were studied by the Brunauer-Emmett-Teller method. Alternating-current (AC) conductivity and dielectric properties were studied for various dopant levels of 0.25 wt.%, 0.5 wt.%, and 1.0 wt.% at 300 K in the frequency range from 42 Hz to 5 MHz. AC conductivity and dielectric properties of TiO2 nanoparticles were greatly affected by loading with Ag. At high frequencies, the materials showed high AC conductivity and low dielectric constant. Diffuse reflectance studies were carried out for various dopant levels at 300 K by ultraviolet-visible (UV-Vis) spectroscopy. Considerable absorption of visible light by 0.5 wt.% and 1.0 wt.% Ag-TiO2 nanoparticles was observed due to the decrease of the energy band gap on Ag loading.

  4. Green rapid biogenic synthesis of bioactive silver nanoparticles (AgNPs) using Pseudomonas aeruginosa.

    PubMed

    Busi, Siddhardha; Rajkumari, Jobina; Ranjan, Bibhuti; Karuganti, Sukumar

    2014-12-01

    The present work was focused on isolating a bacterial strain of Pseudomonas sp. with the ability to synthesise AgNPs rapidly. A strain of Pseudomonas aeruginosa designated JO was found to be a potential candidate for rapid synthesis of AgNPs with a synthesis time of 4h in light, at room temperature which is a shorter time period noticed for the synthesis when compared to the previous reports Biosynthesis of AgNPs was achieved by addition of culture supernatant with aqueous silver nitrate solution (1 mM). The reaction mixture exhibits change in colour from green to brown with a peak at 420 nm corresponding to the plasmon absorbance of AgNPs by UV-vis spectroscopy. The nanoparticles were characterised by X-ray diffraction (XRD), energy-dispersive X-ray analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), Zetasizer and transmission electron microscopy (TEM). The XRD spectrum exhibited 2θ values corresponding to the silver nanocrystals. TEM and SEM micrographs revealed the extracellular formation of polydispersed elongated nanoparticles with an average size of 27.5 nm. Synthesised nanoparticles showed antibacterial property against both gram-positive and gram-negative microorganisms, but more effective towards gram-negative.

  5. Ag Nanoparticle–Functionalized Open-Ended Freestanding TiO2 Nanotube Arrays with a Scattering Layer for Improved Energy Conversion Efficiency in Dye-Sensitized Solar Cells

    PubMed Central

    Rho, Won-Yeop; Chun, Myeung-Hwan; Kim, Ho-Sub; Kim, Hyung-Mo; Suh, Jung Sang; Jun, Bong-Hyun

    2016-01-01

    Dye-sensitized solar cells (DSSCs) were fabricated using open-ended freestanding TiO2 nanotube arrays functionalized with Ag nanoparticles (NPs) in the channel to create a plasmonic effect, and then coated with large TiO2 NPs to create a scattering effect in order to improve energy conversion efficiency. Compared to closed-ended freestanding TiO2 nanotube array–based DSSCs without Ag or large TiO2 NPs, the energy conversion efficiency of closed-ended DSSCs improved by 9.21% (actual efficiency, from 5.86% to 6.40%) with Ag NPs, 6.48% (actual efficiency, from 5.86% to 6.24%) with TiO2 NPs, and 14.50% (actual efficiency, from 5.86% to 6.71%) with both Ag NPs and TiO2 NPs. By introducing Ag NPs and/or large TiO2 NPs to open-ended freestanding TiO2 nanotube array–based DSSCs, the energy conversion efficiency was improved by 9.15% (actual efficiency, from 6.12% to 6.68%) with Ag NPs and 8.17% (actual efficiency, from 6.12% to 6.62%) with TiO2 NPs, and by 15.20% (actual efficiency, from 6.12% to 7.05%) with both Ag NPs and TiO2 NPs. Moreover, compared to closed-ended freestanding TiO2 nanotube arrays, the energy conversion efficiency of open-ended freestanding TiO2 nanotube arrays increased from 6.71% to 7.05%. We demonstrate that each component—Ag NPs, TiO2 NPs, and open-ended freestanding TiO2 nanotube arrays—enhanced the energy conversion efficiency, and the use of a combination of all components in DSSCs resulted in the highest energy conversion efficiency. PMID:28335245

  6. 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.

  7. Sequential repetitive chemical reduction technique to study size-property relationships of graphene attached Ag nanoparticle

    NASA Astrophysics Data System (ADS)

    Haider, M. Salman; Badejo, Abimbola Comfort; Shao, Godlisten N.; Imran, S. M.; Abbas, Nadir; Chai, Young Gyu; Hussain, Manwar; Kim, Hee Taik

    2015-06-01

    The present study demonstrates a novel, systematic and application route synthesis approach to develop size-property relationship and control the growth of silver nanoparticles (AgNPs) embedded on reduced graphene oxide (rGO). A sequential repetitive chemical reduction technique to observe the growth of silver nanoparticles (AgNPs) attached to rGO, was performed on a single solution of graphene oxide (GO) and silver nitrate solution (7 runs, R1-R7) in order to manipulate the growth and size of the AgNPs. The physical-chemical properties of the samples were examined by RAMAN, XPS, XRD, SEM-EDAX, and HRTEM analyses. It was confirmed that AgNPs with diameter varying from 4 nm in first run (R1) to 50 nm in seventh run (R7) can be obtained using this technique. A major correlation between particle size and activities was also observed. Antibacterial activities of the samples were carried out to investigate the disinfection performance of the samples on the Gram negative bacteria (Escherichia coli). It was suggested that the sample obtained in the third run (R3) exhibited the highest antibacterial activity as compared to other samples, toward disinfection of bacteria due to its superior properties. This study provides a unique and novel application route to synthesize and control size of AgNPs embedded on graphene for various applications.

  8. Ag/AgO Nanoparticles Grown via Time Dependent Double Mechanism in a 2D Layered Ni-PCP and Their Antibacterial Efficacy

    PubMed Central

    Agarwal, Rashmi A.; Gupta, Neeraj K.; Singh, Rajan; Nigam, Shivansh; Ateeq, Bushra

    2017-01-01

    A simple synthesis route for growth of Ag/AgO nanoparticles (NPs) in large quantitative yields with narrow size distribution from a functional, non-activated, Ni (II) based highly flexible porous coordination polymer (PCP) as a template has been demonstrated. This template is a stable storage media for the NPs larger than the pore diameters of the PCP. From EPR study it was concluded that NPs were synthesized via two mechanisms i.e. acid formation and the redox activity of the framework. Size range of Ag/AgO NPs is sensitive to choice of solvent and reaction time. Direct use of Ag/AgO@Ni-PCP shows influential growth inhibition towards Escherichia coli and the pathogen Salmonella typhimurium at extremely low concentrations. The pristine template shows no cytotoxic activity, even though it contains Ni nodes in the framework. PMID:28322256

  9. Ag/AgO Nanoparticles Grown via Time Dependent Double Mechanism in a 2D Layered Ni-PCP and Their Antibacterial Efficacy

    NASA Astrophysics Data System (ADS)

    Agarwal, Rashmi A.; Gupta, Neeraj K.; Singh, Rajan; Nigam, Shivansh; Ateeq, Bushra

    2017-03-01

    A simple synthesis route for growth of Ag/AgO nanoparticles (NPs) in large quantitative yields with narrow size distribution from a functional, non-activated, Ni (II) based highly flexible porous coordination polymer (PCP) as a template has been demonstrated. This template is a stable storage media for the NPs larger than the pore diameters of the PCP. From EPR study it was concluded that NPs were synthesized via two mechanisms i.e. acid formation and the redox activity of the framework. Size range of Ag/AgO NPs is sensitive to choice of solvent and reaction time. Direct use of Ag/AgO@Ni-PCP shows influential growth inhibition towards Escherichia coli and the pathogen Salmonella typhimurium at extremely low concentrations. The pristine template shows no cytotoxic activity, even though it contains Ni nodes in the framework.

  10. 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.

  11. 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.

  12. Decoration of crumpled rGO sheets with Ag nanoparticles by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Papailias, I.; Giannouri, M.; Trapalis, A.; Todorova, N.; Giannakopoulou, T.; Boukos, N.; Lekakou, C.

    2015-12-01

    In this work, crumpled reduced graphene oxide (rGO) nanostructures were produced using spray pyrolysis technique. Graphite oxide (GtO) prepared through a modified Hummers method was used as starting material. Water dispersions of graphene oxide (GO) were prepared and sprayed in a tube furnace at 300 °C, 500 °C and 700 °C using Argon (Ar) as carrier gas. Also, precursor dispersions with different AgNO3 concentrations were processed at the same conditions. During the treatment, the sprayed droplets underwent rapid heating and then gradual cooling until the exit of the oven, where crumpled rGO and Ag/rGO powders were collected. The prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and FT-IR spectroscopy. It was established that the crumpling of the nanosheets was slightly affected by the increase of the process temperature. Crumpled morphologies were obtained even at low temperature of 300 °C. In contrast, the degree of GO reduction was temperature dependent and increased with the increase of the temperature. The incorporation of Ag nanoparticles was evidenced by the XRD and TEM analysis with the size of the Ag nanoparticles to grow as the concentration of AgNO3 and/or the process temperature increased. SERS effect in the Raman spectra of the Ag/rGO materials was observed that reached a maximum at 500 °C. Spray pyrolysis was suggested as a simple, controllable and scalable route for the instantaneous crumpling, reduction and decoration of GO nanosheets with metal/metal oxide nanoparticles.

  13. Plasmonic effects of au/ag bimetallic multispiked nanoparticles for photovoltaic applications.

    PubMed

    Sharma, Manisha; Pudasaini, Pushpa Raj; Ruiz-Zepeda, Francisco; Vinogradova, Ekaterina; Ayon, Arturo A

    2014-09-10

    In recent years, there has been considerable interest in the use of plasmons, that is, free electron oscillations in conductors, to boost the performance of both organic and inorganic thin film solar cells. This has been driven by the possibility of employing thin active layers in solar cells in order to reduce materials costs, and is enabled by significant advances in fabrication technology. The ability of surface plasmons in metallic nanostructures to guide and confine light in the nanometer scale has opened up new design possibilities for solar cell devices. Here, we report the synthesis and characterization of highly monodisperse, reasonably stable, multipode Au/Ag bimetallic nanostructures using an inorganic additive as a ligand for photovoltaic applications. A promising surface enhanced Raman scattering (SERS) effect has been observed for the synthesized bimetallic Au/Ag multispiked nanoparticles, which compare favorably well with their Au and Ag spherical nanoparticle counterparts. The synthesized plasmonic nanostructures were incorporated on the rear surface of an ultrathin planar c-silicon/organic polymer hybrid solar cell, and the overall effect on photovoltaic performance was investigated. A promising enhancement in solar cell performance parameters, including both the open circuit voltage (VOC) and short circuit current density (JSC), has been observed by employing the aforementioned bimetallic multispiked nanoparticles on the rear surface of solar cell devices. A power conversion efficiency (PCE) value as high as 7.70% has been measured in a hybrid device with Au/Ag multispiked nanoparticles on the rear surface of an ultrathin, crystalline silicon (c-Si) membrane (∼ 12 μm). This value compares well to the measured PCE value of 6.72% for a similar device without nanoparticles. The experimental observations support the hope for a sizable PCE increase, due to plasmon effects, in thin-film, c-Si solar cells in the near future.

  14. Screening sensitive nanosensors via the investigation of shape-dependent localized surface plasmon resonance of single Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Yue; Huang, Cheng Zhi

    2013-07-01

    Understanding the localized surface plasmon resonance (LSPR) of differently shaped plasmonic nanoparticles benefits screening and designing highly sensitive single nanoparticle sensors. Herein, in the present work, we systematically investigated the shape-dependent scattering light colours and refractive index (RI) sensitivity of Ag nanoparticles (AgNPs) at the single nanoparticle level using conventional dark-field light scattering microscopy and spectroscopy. AgNPs in various shapes and scattering colourful light were synthesized, and the shape effect on the scattering light colour was determined by the colocalization of the same nanoparticles with dark-field microscopy (DFM) and scanning electron microscopy (SEM). The results showed that the AgNPs that scattered blue, cyan, yellow, and red light are spheres, cubes, triangular bipyramids, and rods, respectively, which enable us to directly recognize the shape of AgNPs through dark-field microscopy instead of electron microscopy. Further studies on investigation of the scattering spectral responses of single AgNPs to their surrounding solvents show that the RI sensitivity of AgNPs of different shapes followed the order of rods > cubes > triangular bipyramids > spheres. Among the commonly studied AgNPs, Ag nanorods have the highest RI sensitivity, which increases as the aspect ratio increases. Then, AgNPs of various shapes were used as single nanoparticle sensors for probing the adsorption of small molecules.Understanding the localized surface plasmon resonance (LSPR) of differently shaped plasmonic nanoparticles benefits screening and designing highly sensitive single nanoparticle sensors. Herein, in the present work, we systematically investigated the shape-dependent scattering light colours and refractive index (RI) sensitivity of Ag nanoparticles (AgNPs) at the single nanoparticle level using conventional dark-field light scattering microscopy and spectroscopy. AgNPs in various shapes and scattering colourful

  15. Ag-nanoparticle fractionation by low melting point agarose gel electrophoresis

    NASA Astrophysics Data System (ADS)

    Guarrotxena, Nekane; Braun, Gary

    2012-10-01

    The separation of surface-enhanced raman scattering (SERS)-active Ag-multi-nanoparticle (NP) assemblies by low melting point agarose gel electrophoresis was accomplished here by controlling surface charge using NP capping agents, and the pore size of agarose gel matrix. Detailed transmission electron microscopy analysis of excised gel fractions showed dimers and small clusters to have the greatest SERS activity and a mobility in between the monomers and large aggregates. This strategy enables one to: (1) stabilize small multispherical Ag clusters against further aggregation during purification; (2) fractionate and recover spherical assemblies by nuclearity; and (3) analyze SERS-enhancements for each fraction to optimize purification conditions.

  16. Electromagnetic resonances of solar-selective absorbers with nanoparticle arrays embedded in a dielectric layer

    NASA Astrophysics Data System (ADS)

    Sakurai, Atsushi; Kawamata, Tomoaki

    2016-11-01

    We numerically investigate a solar-selective absorber with tungsten core-shell nanoparticle arrays embedded in an SiO2 layer. The 3D full-wave finite-difference time-domain (FDTD) simulations are performed to investigate the geometric effects of different types of solar-selective absorbers. Consequently, broadband light absorption was achieved with either a tungsten nanoparticle array or a tungsten core-shell nanoparticle array because of the strong electric field enhancement in the gap between the core nanoparticles. The solar performance of the proposed structure is shown for high-efficiency solar light absorption. This study enhances understanding of the light absorption mechanism of metallic nanoparticle/dielectric composite and facilitates the design of high-efficiency solar-selective absorbers.

  17. 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.

  18. The structural conversion from α-AgVO3 to β-AgVO3: Ag nanoparticle decorated nanowires with application as cathode materials for Li-ion batteries.

    PubMed

    McNulty, David; Ramasse, Quentin; O'Dwyer, Colm

    2016-09-15

    The majority of electrode materials in batteries and related electrochemical energy storage devices are fashioned into slurries via the addition of a conductive additive and a binder. However, aggregation of smaller diameter nanoparticles in current generation electrode compositions can result in non-homogeneous active materials. Inconsistent slurry formulation may lead to inconsistent electrical conductivity throughout the material, local variations in electrochemical response, and the overall cell performance. Here we demonstrate the hydrothermal preparation of Ag nanoparticle (NP) decorated α-AgVO3 nanowires (NWs) and their conversion to tunnel structured β-AgVO3 NWs by annealing to form a uniform blend of intercalation materials that are well connected electrically. The synthesis of nanostructures with chemically bound conductive nanoparticles is an elegant means to overcome the intrinsic issues associated with electrode slurry production, as wire-to-wire conductive pathways are formed within the overall electrode active mass of NWs. The conversion from α-AgVO3 to β-AgVO3 is explained in detail through a comprehensive structural characterization. Meticulous EELS analysis of β-AgVO3 NWs offers insight into the true β-AgVO3 structure and how the annealing process facilitates a higher surface coverage of Ag NPs directly from ionic Ag content within the α-AgVO3 NWs. Variations in vanadium oxidation state across the surface of the nanowires indicate that the β-AgVO3 NWs have a core-shell oxidation state structure, and that the vanadium oxidation state under the Ag NP confirms a chemically bound NP from reduction of diffused ionic silver from the α-AgVO3 NWs core material. Electrochemical comparison of α-AgVO3 and β-AgVO3 NWs confirms that β-AgVO3 offers improved electrochemical performance. An ex situ structural characterization of β-AgVO3 NWs after the first galvanostatic discharge and charge offers new insight into the Li(+) reaction mechanism for β-Ag

  19. 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.

  20. Simple and Sensitive Colorimetric Assay for Pb2+ Based on Glutathione Protected Ag Nanoparticles by Salt Amplification.

    PubMed

    Chen, Zhang; Li, Huidong; Chu, Lin; Liu, Chenbin; Luo, Shenglian

    2015-02-01

    A simple and sensitive colorimetric assay for Pb2+ detection has been reported using glutathione protected silver nanoparticles (AgNPs) by salt amplification. The naked AgNPs aggregate under the influence of salt. Glutathione (GSH) can bind to AgNPs via Ag-S bond, helping AgNPs to against salt-induced aggregation. However, GSH binding to AgNPs can be compromised by the interaction between Pb2+ and GSH. As a result, Pb2+-mediated aggregation of AgNPs under the influence of salt is reflected by the UV-Visible spectrum, and the qualitative and quantitative detection for Pb2+ is accomplished, with the detection range 0.5-4 µM and a detection limit of 0.5 µM. At the same time, Pb2+ in real water sample is detected. Furthermore, the high selectivity and low cost of the assay means it is promising for enviromental applications.

  1. Preparation of carboxylated Ag nanoparticles as a coating material for medical devices and control of antibacterial activity.

    PubMed

    Furuzono, Tsutomu; Iwamoto, Takashi; Azuma, Yoshinao; Okada, Masahiro; Sawa, Yoshiki

    2013-12-01

    Carboxyl group-donated silver (Ag) nanoparticles for coating on medical devices were prepared by a two-phase reduction system in situ. AgNO3 was the Ag ion source, tetraoctylammonium bromide [N(C8H17)4Br] the phase-transfer agent, sodium tetrahydroborate (NaBH4) the reducing agent and 10-carboxy-1-decanthiol (C11H22O2S, CDT) the capping agent. The characterizations of the Ag nanoparticles were conducted by diffuse reflectance Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric differential thermal analysis (TG/DTA) and transmission electron microscope. With CDT capped on Ag nanoparticles, we found that the band around 3,100 cm(-1) was attributed to COO-H stretching vibration, two adsorptions at 2,928 and 2,856 cm(-1) to C-H symmetric/anti-symmetric stretching vibration, and at 1,718 cm(-1) to C=O stretching vibration in the FT-IR spectra. The organic components of the carboxylated Ag nanoparticles were 5.8-25.9 wt%, determined by TG/DTA. The particle sizes of the carboxylated Ag nanoparticles were well controlled by the addition of the capping agent, CDT, into the reaction system. The antimicrobial activity of the Ag nanoparticles covered with different contents of CDT against E. coli was evaluated. Smaller-size Ag nanoparticles showed higher antibacterial activity, which depended on a surface area that attached easily to a microorganism cell membrane.

  2. Enhanced Electronic Properties of Pt@Ag Heterostructured Nanoparticles

    PubMed Central

    Dao, Anh Thi Ngoc; Mott, Derrick M.; Higashimine, Koichi; Maenosono, Shinya

    2013-01-01

    Platinum coated by silver nanoparticles was synthesized, which displays a unique structure where polycrystalline platinum particles are completely encapsulated in continuous monocrystalline silver shells. These particles display accentuated electronic properties, where the silver shells gain electron density from the platinum cores, imparting enhanced properties such as oxidation resistance. This electron transfer phenomenon is highly interfacial in nature, and the degree of electron transfer decreases as the thickness of silver shell increases. The nanoparticle structure and electronic properties are studied and the implication to creating sensing probes with enhanced robustness, sensitivity and controllable plasmonic properties is discussed. PMID:23778193

  3. 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.

  4. Dipolar interaction effects in the magnetic and magnetotransport properties of ordered nanoparticle arrays.

    PubMed

    Kechrakos, D; Trohidou, K N

    2008-06-01

    Assemblies of magnetic nanoparticles exhibit interesting physical properties arising from the competition of intraparticle dynamics and interparticle interactions. In ordered arrays of magnetic nanoparticles magnetostatic interparticle interactions introduce collective dynamics acting competitively to random anisotropy. Basic understanding, characterization and control of dipolar interaction effects in arrays of magnetic nanoparticles is an issue of central importance. To this end, numerical simulation techniques offer an indispensable tool. We report on Monte Carlo studies of the magnetic hysteresis and spin-dependent transport in thin films formed by ordered arrays of magnetic nanoparticles. Emphasis is given to the modifications of the single-particle behavior due to interparticle dipolar interactions as these arise in quantities of experimental interest, such as, the magnetization, the susceptibility and the magnetoresistance. We investigate the role of the structural parameters of an array (interparticle separation, number of stacked monolayers) and the role of the internal structure of the nanoparticles (single phase, core-shell). Dipolar interactions are responsible for anisotropic magnetic behavior between the in-plane and out-of-plane directions of the sample, which is reflected on the investigated magnetic properties (magnetization, transverse susceptibility and magnetoresistance) and the parameters of the array (remanent magnetization, coercive field, and blocking temperature). Our numerical results are compared to existing measurements on self-assembled arrays of Fe-based and Co nanoparticles is made.

  5. Surface plasmon resonance-induced visible light photocatalytic reduction of graphene oxide: using Ag nanoparticles as a plasmonic photocatalyst.

    PubMed

    Wu, Tongshun; Liu, Sen; Luo, Yonglan; Lu, Wenbo; Wang, Lei; Sun, Xuping

    2011-05-01

    The present communication reports on the first preparation of reduced graphene oxide (rGO) via surface plasmon resonance (SPR)-induced visible light photocatalytic reduction of GO with the use of Ag nanoparticles (AgNPs) as a plasmonic photocatalyst in the presence of an electron donor (ED).

  6. Highly dynamic PVP-coated silver nanoparticles in aquatic environments: chemical and morphology change induced by oxidation of Ag(0) and reduction of Ag(+).

    PubMed

    Yu, Su-Juan; Yin, Yong-Guang; Chao, Jing-Bo; Shen, Mo-Hai; Liu, Jing-Fu

    2014-01-01

    The fast growing and abundant use of silver nanoparticles (AgNPs) in commercial products alerts us to be cautious of their unknown health and environmental risks. Because of the inherent redox instability of silver, AgNPs are highly dynamic in the aquatic system, and the cycle of chemical oxidation of AgNPs to release Ag(+) and reconstitution to form AgNPs is expected to occur in aquatic environments. This study investigated how inevitable environmentally relevant factors like sunlight, dissolved organic matter (DOM), pH, Ca(2+)/Mg(2+), Cl(-), and S(2-) individually or in combination affect the chemical transformation of AgNPs. It was demonstrated that simulated sunlight induced the aggregation of AgNPs, causing particle fusion or self-assembly to form larger structures and aggregates. Meanwhile, AgNPs were significantly stabilized by DOM, indicating that AgNPs may exist as single particles and be suspended in natural water for a long time or delivered far distances. Dissolution (ion release) kinetics of AgNPs in sunlit DOM-rich water showed that dissolved Ag concentration increased gradually first and then suddenly decreased with external light irradiation, along with the regeneration of new tiny AgNPs. pH variation and addition of Ca(2+) and Mg(2+) within environmental levels did not affect the tendency, showing that this phenomenon was general in real aquatic systems. Given that a great number of studies have proven the toxicity of dissolved Ag (commonly regarded as the source of AgNP toxicity) to many aquatic organisms, our finding that the effect of DOM and sunlight on AgNP dissolution can regulate AgNP toxicity under these conditions is important. The fact that the release of Ag(+) and regeneration of AgNPs could both happen in sunlit DOM-rich water implies that previous results of toxicity studies gained by focusing on the original nature of AgNPs should be reconsidered and highlights the necessity to monitor the fate and toxicity of AgNPs under more

  7. 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.

  8. Ag nanoparticles enhanced near-IR emission from Er3+ ions doped glasses

    NASA Astrophysics Data System (ADS)

    Qi, Jiani; Xu, Tiefeng; Wu, Yi; Shen, Xiang; Dai, Shixun; Xu, Yinsheng

    2013-10-01

    Vitreous materials containing rare-earth (RE) ions and metallic nanoparticles (NPs) attract considerable interest because the presence of the NPs may lead to an intensification of luminescence. In this work, the characteristics of 1.54 μm luminescence for the Er3+ ions doped bismuthate glasses containing Ag NPs were studied under 980 nm excitation. The surface plasmon resonance (SPR) band of Ag NPs appears from 500 to 1500 nm. Transmission electron microscopic (TEM) image reveals that the Ag NPs are dispersed homogeneously with the size from 2 to 7 nm. The strength parameters Ωt(t = 2, 4, 6), spontaneous emission probability (A), radiative lifetime (τ) and stimulated emission section (σem) of Er3+ ions were calculated by the Judd-Ofelt theory. When the glass contains 0.2 wt% AgCl, the 1.54 μm fluorescence intensity of Er3+ reaches a maximum value, which is 7.2 times higher than that of glass without Ag NPs. The Ag NPs embedded glasses show significantly fluorescence enhancement of Er3+ ions by local field enhancement from SPR.

  9. Cu/Ag-based bifunctional nanoparticles obtained by one-pot laser-assisted galvanic replacement

    NASA Astrophysics Data System (ADS)

    Giorgetti, Emilia; Marsili, Paolo; Canton, Patrizia; Muniz-Miranda, Maurizio; Caporali, Stefano; Giammanco, Francesco

    2013-01-01

    We have prepared, for the first time, stable and uncapped Ag/Cu-based bifunctional nanoparticles (NPs) (BFNPs) in water, by combining ps laser ablation in liquid environment and galvanic replacement. The particles were obtained in a single step by 1,064 nm irradiation of a Cu target in water solutions of AgNO3 or AgNO2. Under proper salt concentration and irradiation conditions, the laser beam activates formation of deep orange colloids, which are positively charged and stable for weeks. High resolution transmission electron microscopy (HRTEM) analysis showed a predominance of composite crystalline nanostructures with size in the 1-15 nm range and consisting of fcc Ag and fcc Cu (or its oxides). While CuO tenorite crystalline phase was detected by HRTEM, X-ray photoelectron spectroscopy analysis permitted to observe also the Cu(I) oxidation state of Cu, being the Cu(I)/Cu(II) ratio different in the samples obtained in AgNO3 or AgNO2 baths. Functionalization with organic ligands and subsequent Raman tests demonstrated the SERS activity of the BFNPs and the existence of different complexing surface sites.

  10. Evaluation of genotoxic effect of silver nanoparticles (Ag-Nps) in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Tavares, Priscila; Balbinot, Fernanda; de Oliveira, Hugo Martins; Fagundes, Gabriela Elibio; Venâncio, Mireli; Ronconi, João Vitor Vieira; Merlini, Aline; Streck, Emílio L.; da Silva Paula, Marcos Marques; de Andrade, Vanessa Moraes

    2012-03-01

    Silver nanoparticles (Ag-NPs) are the most prominent nanoproducts. Due to their antimicrobial activity, they have been incorporated in different materials, such as catheters, clothes, electric home appliance, and many others. The genotoxicity of Ag-NPs (5-45 nm), in different concentrations and times of exposure, was evaluated by the comet assay in in vitro and in vivo conditions, respectively, using human peripheral blood and Swiss mice. The results showed the genotoxic effect of Ag-NPs in vitro , in all the doses tested in the initial hour of exposure, possibly through the reactive oxygen species generation. Nevertheless, the values for this damage decrease with time, indicating that the DNA may have been restored by the repair system. In the in vivo conditions, we found no genotoxicity of Ag-NPs in any hour of exposure and any dose investigated, which can be attributed to the activation of a cellular antioxidant network and the hydrophobic nature of Ag-NPs. Now, it is absolutely necessary to investigate the role of Ag-NPs in different cell lines in vivo.

  11. Catalytic kinetics of single gold nanoparticles observed via optical microwell arrays

    NASA Astrophysics Data System (ADS)

    Mayer, Kathryn M.; Shnipes, Jason; Davis, Douglas; Walt, David R.

    2015-02-01

    Catalytic activities and kinetics are measured at the single-particle level for gold nanoparticles catalyzing a fluorogenic oxidation reaction. This measurement is accomplished by confining the reactions in optically addressable microwell arrays. Citrate-capped gold nanoparticles are isolated in sealed ˜70 fL microwells along with a substrate, and the accumulation of a fluorescent product over time is observed. Thousands of reactions are measured in parallel. Catalytic activities are calculated for each nanoparticle and the activity distribution is analyzed.

  12. Array-based sensing with nanoparticles: “Chemical noses” for sensing biomolecules and cell surfaces

    PubMed Central

    Miranda, Oscar R.; Creran, Brian; Rotello, Vincent M.

    2010-01-01

    Nanoparticle-based arrays have been used to distinguish a wide range of biomolecular targets through pattern recognition. In this report, we highlight new “chemical nose” methodologies that use nanoparticle systems to provide high sensitivity sensing of biomolecular targets, including fluorescent polymer/gold nanoparticle complexes that can discriminate between different bioanalytes including proteins, bacteria, and mammalian cells as well as dye-based micellar systems for the detection of clinically important metallo- and non-metallo proteins. PMID:20801707

  13. Laser tailored nanoparticle arrays to detect molecules at dilute concentration

    NASA Astrophysics Data System (ADS)

    Zanchi, Chiara; Lucotti, Andrea; Tommasini, Matteo; Trusso, Sebastiano; de Grazia, Ugo; Ciusani, Emilio; Ossi, Paolo M.

    2017-02-01

    By nanosecond pulsed laser ablation in an ambient gas gold nanoparticles (NPs) were produced that self-assemble on a substrate resulting in increasingly elaborated architectures of growing thickness, from isolated NP arrays up to percolated films. NPs nucleate and grow in the plasma plume propagating through the gas. Process parameters including laser wavelength, laser energy density, target to substrate distance, nature and pressure of the gas affect plasma expansion, thus asymptotic NP size and kinetic energy. NP size, energy and mobility at landing determine film growth and morphology that affect the physico-chemical properties of the film. Keeping fixed the other process parameters, we discuss the sensitive dependence of film surface nanostructure on Ar pressure and on laser pulse number. The initial plume velocity and average ablated mass per pulse allow predicting the asymptotic NP size. The control of growth parameters favors fine-tuning of NP aggregation, relevant to plasmonics to get optimized substrates for surface enhanced Raman spectroscopy (SERS). Their behavior is discussed for testing conditions of interest for clinical application. Both in aqueous and in biological solutions we obtained good sensitivity and reproducibility of the SERS signals for the anti-Parkinson drug apomorphine, and for the anti-epilepsy drug carbamazepine.

  14. 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.

  15. Light induced diffusion driven self assembly of Ag nanoparticles in a-Se/Ag bi-layer thin film with ultrafast optical response

    NASA Astrophysics Data System (ADS)

    Bapna, Mukund; Sharma, Rituraj; Barik, A. R.; Khan, Pritam; Ranjan Kumar, Rakesh; Adarsh, K. V.

    2013-05-01

    In this Letter, we demonstrate that femtosecond light-induced interdiffusion of Ag driven by the electrostatic attraction between photo-excited Ag+ ions and negatively charged amorphous layer can act as an efficient single step method for hybrid integration of spatially ordered and interconnected nanoparticles on the surface of amorphous films. Such self assembled complex hybrid structures of silver nanoparticles via bottom-up nano-construction method on a-Se thin film show an ultrafast optical response over an unusually broad wavelength range that can be used to construct optical modulators operating at switching speed of ˜5 ps.

  16. Antifungal mechanisms of ZnO and Ag nanoparticles to Sclerotinia homoeocarpa.

    PubMed

    Li, Junli; Sang, Hyunkyu; Guo, Huiyuan; Popko, James T; He, Lili; White, Jason C; Parkash Dhankher, Om; Jung, Geunhwa; Xing, Baoshan

    2017-04-18

    Fungicides have extensively been used to effectively combat fungal diseases on a range of plant species, but resistance to multiple active ingredients has developed in pathogens such as Sclerotinia homoeocarpa, the causal agent of dollar spot on cool-season turfgrasses. Recently, ZnO and Ag nanoparticles (NPs) have received increased attention due to their antimicrobial activities. In this study, the NPs' toxicity and mechanisms of action were investigated as alternative antifungal agents against S. homoeocarpa isolates that varied in their resistance to demethylation inhibitor (DMI) fungicides. S. homoeocarpa isolates were treated with ZnO NPs and ZnCl2 (25-400 μg ml(-1)) and Ag NPs and AgNO3 (5-100 μg ml(-1)) to test antifungal activity of the NPs and ions. The mycelial growth of S. homoeocarpa isolates regardless of their DMI sensitivity was significantly inhibited on ZnO NPs (≥200 μg ml(-1)), Ag NPs (≥25 μg ml(-1)), Zn(2+) ions (≥200 μg ml(-1)), and Ag(+) ions (≥10 μg ml(-1)) amended media. Expression of stress response genes, glutathione S-transferase (Shgst1) and superoxide dismutase 2 (ShSOD2), was significantly induced in the isolates by exposure to the NPs and ions. In addition, a significant increase in the nucleic acid contents of fungal hyphae, which may be due to stress response, was observed upon treatment with Ag NPs using Raman spectroscopy. We further observed that a zinc transporter (Shzrt1) might play an important role in accumulating ZnO and Ag NPs into the cells of S. homoeocarpa due to overexpression of Shzrt1 significantly induced by ZnO or Ag NPs within 3 h of exposure. Yeast mutants complemented with Shzrt1 became more sensitive to ZnO and Ag NPs as well as Zn(2+) and Ag(+) ions than the control strain and resulted in increased Zn or Ag content after exposure. This is the first report of involvement of the zinc transporter in the accumulation of Zn and Ag from NP exposure in filamentous plant pathogenic fungi. Understanding

  17. Antifungal mechanisms of ZnO and Ag nanoparticles to Sclerotinia homoeocarpa

    NASA Astrophysics Data System (ADS)

    Li, Junli; Sang, Hyunkyu; Guo, Huiyuan; Popko, James T.; He, Lili; White, Jason C.; Parkash Dhankher, Om; Jung, Geunhwa; Xing, Baoshan

    2017-04-01

    Fungicides have extensively been used to effectively combat fungal diseases on a range of plant species, but resistance to multiple active ingredients has developed in pathogens such as Sclerotinia homoeocarpa, the causal agent of dollar spot on cool-season turfgrasses. Recently, ZnO and Ag nanoparticles (NPs) have received increased attention due to their antimicrobial activities. In this study, the NPs’ toxicity and mechanisms of action were investigated as alternative antifungal agents against S. homoeocarpa isolates that varied in their resistance to demethylation inhibitor (DMI) fungicides. S. homoeocarpa isolates were treated with ZnO NPs and ZnCl2 (25–400 μg ml‑1) and Ag NPs and AgNO3 (5–100 μg ml‑1) to test antifungal activity of the NPs and ions. The mycelial growth of S. homoeocarpa isolates regardless of their DMI sensitivity was significantly inhibited on ZnO NPs (≥200 μg ml‑1), Ag NPs (≥25 μg ml‑1), Zn2+ ions (≥200 μg ml‑1), and Ag+ ions (≥10 μg ml‑1) amended media. Expression of stress response genes, glutathione S-transferase (Shgst1) and superoxide dismutase 2 (ShSOD2), was significantly induced in the isolates by exposure to the NPs and ions. In addition, a significant increase in the nucleic acid contents of fungal hyphae, which may be due to stress response, was observed upon treatment with Ag NPs using Raman spectroscopy. We further observed that a zinc transporter (Shzrt1) might play an important role in accumulating ZnO and Ag NPs into the cells of S. homoeocarpa due to overexpression of Shzrt1 significantly induced by ZnO or Ag NPs within 3 h of exposure. Yeast mutants complemented with Shzrt1 became more sensitive to ZnO and Ag NPs as well as Zn2+ and Ag+ ions than the control strain and resulted in increased Zn or Ag content after exposure. This is the first report of involvement of the zinc transporter in the accumulation of Zn and Ag from NP exposure in filamentous plant pathogenic fungi. Understanding the

  18. Quantitative determination of melamine in milk using Ag nanoparticle monolayer film as SERS substrate

    NASA Astrophysics Data System (ADS)

    Li, Ruoping; Yang, Jingliang; Han, Junhe; Liu, Junhui; Huang, Mingju

    2017-04-01

    A Raman method employing silver nanoparticle (Ag NP) monolayer film as Surface-enhanced Raman Scattering (SERS) substrate was presented to rapidly detect melamine in milk. The Ag NPs with 80 nm diameter were modified by polyvinylpyrrolidone to improve their uniformity and chemical stability. The treatment procedure of liquid milk required only addition of acetic acid and centrifugation, and required time is less than 15 min. The Ag NP monolayer film significantly enhanced Raman signal from melamine and allowed experimentally reproducible determination of the melamine concentration. A good linear relationship (R2=0.994) between the concentration and Raman peak intensity of melamine at 681 cm-1 was obtained for melamine concentrations between 0.10 mg L-1 and 5.00 mg L-1. This implies that this method can detect melamine concentrations below 1.0 mg L-1, the concentration currently considered unsafe.

  19. 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.

  20. 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.

  1. 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.

  2. Growth of different morphologies (quantum dots to nanorod) of Ag-nanoparticles: role of cysteine concentrations.

    PubMed

    Khan, Zaheer; Talib, Abou

    2010-03-01

    This work describes an easy chemical method for the preparation of orange-red color silver sol by the cysteine reduction of silver (I) in the presence of cetyltrimethylammonium bromide (CTAB). The obtained sol was found to have very small particles in the order of quantum dots for the first time. Transmission electron microscope (TEM) images show that the silver sol consists of aggregated as well as cross-linking arrangement of spherical silver quantum dots (size in the range ca. Ag-nanoparticles from quantum dots to nanorod of diameter 60nm and pearl-necklace shaped which occurred due to the cross-linking aggregation of silver quantum dots. For a certain reaction time, i.e., 100min, the absorbance of reaction mixture first increased until it reached a maximum, then decreased with [cysteine]. The rate of Ag-nanoparticles formation decreases with the increase in [cysteine] whereas [CTAB] and [Ag(+)] have no effect on the reaction rate. Interestingly, at higher [cysteine] (>or=20.0x10(-4)mol dm(-3)), white precipitate was formed instead of transparent silver sol. Cysteine acts as a reducing, cross-linking, stabilizing and buffering agent during the growth of different shape and size of silver nanoparticles.

  3. Ag-nanoparticle as a Q switched device for tunable C-band fiber laser

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Ruslan, N. E.; Ali, Z. A.; Reduan, S. A.; Lee, C. S. J.; Shaharuddin, R. A.; Nayan, N.; Ismail, M. A.

    2016-12-01

    The use of silver (Ag)-nanoparticle as saturable absorber (SA) to induce tunable Q-switched fiber laser in C-band is demonstrated. The Ag-nanoparticle SA exhibits modulation depth of 31.6% and saturation intensity of 0.54 MW cm-2. The SA is integrated into the laser cavity by sandwiching it between two fiber ferrules. Lasing in CW region starts at 10 mW, whereas stable self-starting Q-switching with a central wavelength of 1558.4 nm begins at 20 mW. As the pump power increases, the repetition rate varies from 10.5 kHz to 24.4 kHz and the narrowest pulse width obtained is around 6.5 μs. The Q-switched laser has a tuning range of 27.3 nm (1552.9-1580.2 nm). The stability of the pulse is verified from the radio-freqeuncy (RF) spectrum with a measured signal-to-noise ratio (SNR) of 46.22 dB. The ability of Ag-nanoparticle as an effective SA may lead to further development of pulsed fiber laser in the field of photonics.

  4. Photocatalytic degradation of phenol using Ag core-TiO2 shell (Ag@TiO2) nanoparticles under UV light irradiation.

    PubMed

    Shet, Amruta; Shetty K, Vidya

    2016-10-01

    Ag@TiO2 nanoparticles were synthesized by one pot synthesis method with postcalcination. These nanoparticles were tested for their photocatalytic efficacies in degradation of phenol both in free and immobilized forms under UV light irradiation through batch experiments. Ag@TiO2 nanoparticles were found to be the effective photocatalysts for degradation of phenol. The effects of factors such as pH, initial phenol concentration, and catalyst loading on phenol degradation were evaluated, and these factors were found to influence the process efficiency. The optimum values of these factors were determined to maximize the phenol degradation. The efficacy of the nanoparticles immobilized on cellulose acetate film was inferior to that of free nanoparticles in UV photocatalysis due to light penetration problem and diffusional limitations. The performance of fluidized bed photocatalytic reactor operated under batch with recycle mode was evaluated for UV photocatalysis with immobilized Ag@TiO2 nanoparticles. In the fluidized bed reactor, the percentage degradation of phenol was found to increase with the increase in catalyst loading.

  5. Long-term transformation and fate of manufactured ag nanoparticles in a simulated large scale freshwater emergent wetland.

    PubMed

    Lowry, Gregory V; Espinasse, Benjamin P; Badireddy, Appala Raju; Richardson, Curtis J; Reinsch, Brian C; Bryant, Lee D; Bone, Audrey J; Deonarine, Amrika; Chae, Soryong; Therezien, Mathieu; Colman, Benjamin P; Hsu-Kim, Heileen; Bernhardt, Emily S; Matson, Cole W; Wiesner, Mark R

    2012-07-03

    Transformations and long-term fate of engineered nanomaterials must be measured in realistic complex natural systems to accurately assess the risks that they may pose. Here, we determine the long-term behavior of poly(vinylpyrrolidone)-coated silver nanoparticles (AgNPs) in freshwater mesocosms simulating an emergent wetland environment. AgNPs were either applied to the water column or to the terrestrial soils. The distribution of silver among water, solids, and biota, and Ag speciation in soils and sediment was determined 18 months after dosing. Most (70 wt %) of the added Ag resided in the soils and sediments, and largely remained in the compartment in which they were dosed. However, some movement between soil and sediment was observed. Movement of AgNPs from terrestrial soils to sediments was more facile than from sediments to soils, suggesting that erosion and runoff is a potential pathway for AgNPs to enter waterways. The AgNPs in terrestrial soils were transformed to Ag(2)S (~52%), whereas AgNPs in the subaquatic sediment were present as Ag(2)S (55%) and Ag-sulfhydryl compounds (27%). Despite significant sulfidation of the AgNPs, a fraction of the added Ag resided in the terrestrial plant biomass (~3 wt % for the terrestrially dosed mesocosm), and relatively high body burdens of Ag (0.5-3.3 μg Ag/g wet weight) were found in mosquito fish and chironomids in both mesocosms. Thus, Ag from the NPs remained bioavailable even after partial sulfidation and when water column total Ag concentrations are low (<0.002 mg/L).

  6. 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

  7. High-density ordered Ag@Al2O3 nanobowl arrays in applications of surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Kang, Mengyang; Zhang, Xiaoyan; Liu, Liwei; Zhou, Qingwei; Jin, Mingliang; Zhou, Guofu; Gao, Xingsen; Lu, Xubing; Zhang, Zhang; Liu, Junming

    2016-04-01

    In this paper, we demonstrate a high-performance surface-enhanced Raman scattering (SERS) substrate based on high-density ordered Ag@Al2O3 nanobowl arrays. By ion beam etching (IBE) the anodized aluminum oxide (AAO) and subsequent Ag coating, ordered Ag@Al2O3 nanobowl arrays were created on the Si substrate. Unlike the ‘hot spots’ generated between adjacent metallic nanostructures, the Ag@Al2O3 nanobowl introduced ‘hot spots’ on the metal boundary of its hemispherical cavity. Based on the analysis of SERS signals, the optimized SERS substrate of Ag@Al2O3 nanobowl arrays had both high sensitivity and large-area uniformity. A detection limit as low as 10-10 M was obtained using chemisorbed p-thiocresol (p-Tc) molecules, and the SERS signal was highly reproducible with a small standard deviation. The method opens up a new way to create highly sensitive SERS sensors with high-density ‘hot spots’, and it could play an important role in device design and corresponding biological and food safety monitoring applications.

  8. Large third-order optical nonlinearity in vertically oriented mesoporous silica thin films embedded with Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Tan, Min; Liu, Qiming

    2016-12-01

    Taking advantage of the channel confinement of mesoporous films to prevent the agglomeration of Ag nanoparticles to achieve large third-order optical nonlinearity in amorphous materials, Ag-loaded composite mesoporous silica film was prepared by the electrochemical deposition method on ITO substrate. Ag ions were firstly transported into the channels of mesoporous film by the diffusion and binding force of channels, which were reduced to nanoparticles by applying suitable voltage. The existence and uniform distribution of Ag nanoparticles ranging in 1-10 nm in the mesoporous silica thin films were exhibited by UV spectrophotometer, X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) measurements. The third-order optical nonlinearity induced by Ag nanoparticles was studied by the Z-scan technique. Due to the local field surface plasmon resonance, the maximum third-order nonlinear optical susceptibility of Ag-loaded composite mesoporous silica film is 1.53×10-10 esu, which is 1000 times larger than that of the Ag-contained chalcogenide glasses which showed large nonlinearity in amorphous materials.

  9. Doping effect of Ag+, Mn2+ ions on Structural and Optical Properties of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Sankara Reddy, B.; Venkatramana Reddy, S.; Venkateswara Reddy, P.; Koteeswara Reddy, N.; Vijayalakshmi, R. P.

    2015-02-01

    Pure ZnO and co-doped (Mn, Ag) ZnO nanoparticles have been successfully prepared by chemical co-precipitation method without using a capping agent. X-ray diffraction (XRD) studies confirms the presence of wurtzite (hexagonal) crystal structure similar to undoped ZnO, suggesting that doped Mn, Ag ions are substituted to the regular Zn sites. The morphology of the samples were studied by scanning electron microscopy (SEM). The chemical composition of pure and co-doped ZnO nanoparticles were characterized by energy dispersive X-ray analysis spectroscopy (EDAX). Optical absorption properties were determined by UV-vis Diffuse Reflectance Spectrophotometer. The incorporation of Ag+, Mn2+ in the place of Zn2+ provoked to decrease the size of nanocrystals as compared to pure ZnO. Optical absorption measurements indicates blue shift in the absorption band edge upon Ag, Mn ions doped ZnO nanoparticles.

  10. Fluorescence enhancement of europium complexes by core-shell Ag@SiO₂ nanoparticles.

    PubMed

    Zhang, Hai-Xia; Lin, Xue-Mei; Wang, Ai-Ling; Zhao, Yong-Liang; Chu, Hai-Bin

    2015-12-05

    Three kinds of core-shell Ag@SiO2 nanoparticles with shell thickness of around 10, 15, and 25 nm, respectively, have been prepared by modified Stöber method and used for fluorescence enhancement. Six kinds of europium complexes with halobenzoic acid have been synthesized. Elemental analysis and lanthanide coordination titration show that the complexes have the compositions of Eu(p-XBA)3·H2O and Eu(o-XBA)3·2H2O (X=F, Cl, Br). The fluorescence spectra investigation indicates that the introduction of Ag@SiO2 nanoparticles into the europium complexes' solution can significantly enhance the fluorescence intensities of the complexes. The sequence of enhancement factors for halobenzoic acid complexes with different halogen atoms is Fnanoparticles. And the nanoparticles near the complexes can effectively prevent complexes from the interaction with the solvent molecules, leading to a decrease of nonradiative energy transfer and the suppression of luminescence quench.

  11. 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

  12. 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

    2014-10-02

    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.

  13. Optimum Conditions for the Fabrication of Zein/Ag Composite Nanoparticles from Ethanol/H2O Co-Solvents Using Electrospinning

    PubMed Central

    Yang, Seong Baek; Rabbani, Mohammad Mahbub; Ji, Byung Chul; Han, Dong-Wook; Lee, Joon Seok; Kim, Jong Won; Yeum, Jeong Hyun

    2016-01-01

    The optimum conditions for the fabrication of zein/Ag composite nanoparticles from ethanol/H2O cosolvents using electrospinning and the properties of the composite were investigated. The zein/Ag nanoparticles were characterized using field-emission scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis. The antibacterial activity of the zein/Ag composite nanoparticles was also investigated. The XRD patterns and TEM images indicate the coexistence of a zein matrix and well-distributed Ag nanoparticles. PMID:28335358

  14. 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.

  15. 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).

  16. 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

  17. Structural characterization of rotavirus-directed synthesis and assembly of metallic nanoparticle arrays.

    PubMed

    Plascencia-Villa, Germán; Medina, Ariosto; Palomares, Laura A; Ramírez, Octavio T; Ascencio, Jorge A

    2013-08-01

    Self-assembled structures derived of viral proteins display sophisticated structures that are difficult to obtain with even advanced synthesis methods and the use of protein nanotubes for synthesis and organization of inorganic nanoarrays into well-defined architectures are here reported. Nanoparticle arrays derived of rotavirus VP6 nanotubes were synthesized by in situ functionalization with silver and gold nanoparticles. The size and morphology of metal nanoparticles were characterized by transmission electron microscopy (TEM) and high resolution TEM (HR-TEM). Processing of micrographs to obtain fast Fourier transforms (FFT) patterns of nanoparticles shown that the preferred morphologies are fcc-like and multiple twinned ones. Micrographs were used to assign structure and orientation, and the elemental composition analysis was performed with energy dispersive spectroscopy (EDS). Structural characterization of functionalized rotavirus VP6 demonstrated its utility for directed construction of hybrid anisotropic nanomaterials formed by arrays of metallic nanoparticles.

  18. Facet-mediated growth of silver nanoparticles on biaxial calcium fluoride nanorod arrays

    NASA Astrophysics Data System (ADS)

    Auer, Mathias; Ye, Dexian

    2017-01-01

    The surface orientation of metal nanoparticles is critical to their physical and chemical properties. This study aims on the understanding of the effect of surface orientation as well as heterogeneous epitaxy of metal nanoparticles at an interface between two materials with a large lattice mismatch. Silver nanoparticles of different diameters were grown on arrays of calcium fluoride (CaF2) nanorods using oblique angle deposition as a model system for this study. Scanning electron microscopy and transmission electron microscopy (TEM) imaging were used to verify that the nanoparticles were selectively grown on the desired {111} facets of the nanorod tips. Using selected area diffraction and dark field imaging in TEM, it was shown that the nanoparticles were grown at a (111) orientation at the CaF2 interface with large lattice strains. Thus biaxially textured CaF2 nanorod arrays can be used as a catalytic support.

  19. 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

  20. Self-Assembly of Ag Nanoparticles Induced by Centrifuging and Broken by Silanization.

    PubMed

    Yang, Ping; Zhang, Yulan

    2015-08-01

    A novel method was developed to assemble Ag nanoparticles (NPs) into chain-like structures. The assembly of the NPs was created by suspending in an ethanol and water solution as well as centrifuging at a high speed (a force of more than 29 Kg for the NPs with an average diameter of 18 nm). The composition of solvents and centrifuged speeds of samples play important roles for the formation of regular assemblies. The number of Ag NPs in the chain-like assemblies was adjusted by changing centrifuging forces. The assemblies of the NPs were fixed by a SiO2 coating through a St6ber synthesis. In addition, the assemblies were broken through a silanization process because of partially hydrolyzed tetraethyl-orthosilicate molecules adsorbed on the surface of Ag NPs to form a SiO2 layer opposite aggregation. A slow silanization process made Ag NPs monodispersed in solutions, in which Ag/SiO2 core/shell NPs were created.

  1. Efficient photon management with Ag nanoparticles coated TiO2 nanowire clusters for photodetector application

    NASA Astrophysics Data System (ADS)

    Ngangbam, Chitralekha; Mondal, Aniruddha; Choudhuri, Bijit

    2015-09-01

    TiO2 nanowire clusters (NWCs) covered with Ag nanoparticles (NPs) were synthesized on Si substrates using GLAD technique. Ag NPs/TiO2 NWCs showed enhanced optical absorption all over the spectrum compared to bare TiO2 NWCs. The leakage current of the TiO2 NWCs device (-10.8 μA) was reduced by ˜9 × 103 times for Ag NPs/TiO2 NWCs detector (-1.2 nA) at -1 V applied bias. Ag NPs/TiO2 NWCs detector exhibited maximum photoresponsivity ˜2.4 times (-2 V) as compared to the bare TiO2 NWCs detector. Using 10 K photocapacitance measurement, a sharp peak at 355 nm (˜3.5 eV) was detected due to the main band transition. The other sub band gap defects were observed within 410-490 nm along with a broad hump between 595-700 nm. The light dependent capacitance-time (I-T) characteristic of the Ag/TiO2 NWCs detector shows rise-time ( T r ) of 9.6 s and decay time ( T d ) of 10 s. [Figure not available: see fulltext.

  2. 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.

  3. Study on surface-enhanced Raman scattering efficiency of Ag core-Au shell bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Dong, Xiao; Gu, Huaimin; Kang, Jian; Yuan, Xiaojuan

    2009-08-01

    In this article, the relationship between the states of Ag core-Au shell (core-shell) nanoparticles (NP) and the intensity of Raman scattering of analytes dissolved in the water and adsorbed on the NP was studied. The core-shell NP were synthesised by coating Au layers over Ag seeds by the method of "seed-growth". To highlight the advantage of the core-shell NP, Ag colloid and Au colloid were chosen for contrasting. The analyte that were chosen for this testing were methylene blue (MB) for the reason that MB has very strong signal in surface-enhanced Raman scattering (SERS). The SERS activity of optimalizing states of Ag and Au colloids were compared with that of core-shell NP when MB was used as analyte. In this study, sodium chloride, sodium sulfate and sodium nitrate were used as aggregating agents for Ag, Au colloids and core-shell NP, because anions have a strong influence on the SERS efficiency and the stability of colloids. The results indicate that core-shell NP can obviously enhance the SERS of MB. The aim of this study is to prove that compared with the metal colloid, the core-shell NP is a high efficiency SERS active substrate.

  4. Room temperature nanojoining of Cu-Ag core-shell nanoparticles and nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Jiaqi; Shin, Seungha

    2017-02-01

    Room temperature ( T room, 300 K) nanojoining of Ag has been widely employed in fabrication of microelectronic applications where the shapes and structures of microelectronic components must be maintained. In this research, the joining processes of pure Ag nanoparticles (NPs), Cu-Ag core-shell NPs, and nanowires (NWs) are studied using molecular dynamics simulations at T room. The evolution of densification, potential energy, and structural deformation during joining process are analyzed to identify joining mechanisms. Depending on geometry, different joining mechanisms including crystallization-amorphization, reorientation, Shockley partial dislocation are determined. A three-stage joining scenario is observed in both joining process of NPs and NWs. Besides, the Cu core does not participate in all joining processes, however, it enhances the mobility of Ag shell atoms, contributing to a higher densification and bonding strength at T room, compared with pure Ag nanomaterials. The tensile test shows that the nanojoint bears higher rupture strength than the core-shell NW itself. This study deepens understanding in the underlying joining mechanisms and thus nanojoint with desirable thermal, electrical, and mechanical properties could be potentially achieved.

  5. Fabrication, characterization and screen printing of conductive ink based on carbon@Ag core-shell nanoparticles.

    PubMed

    Wu, Wei; Yang, Shuanglei; Zhang, Shaofeng; Zhang, Hongbo; Jiang, Changzhong

    2014-08-01

    The large-scale synthesis and characterization of carbon-core/Ag-shell (C@Ag) nanoparticles by the successive reduction of silver ammonia are described. The resultant C@Ag nanoparticles had a mean core diameter of 360 nm and a controllable shell thickness from 10 to 40 nm by simple adjustments of repeat coating times. Various analysis techniques confirmed that the carbon cores were fully covered by Ag nanoshells. The results also show that C/Ag composite nanomaterials-based conductive inks, which can be easily produced on a large scale and possess outstanding electronic properties, have great potential for the convenient fabrication of flexible and low-cost carbon-based electronic devices and replace the traditional pure silver paste, by using a simple screen printing technique.

  6. An investigation of localised surface plasmon resonance (LSPR) of Ag nanoparticles produced by pulsed laser deposition (PLD) technique

    NASA Astrophysics Data System (ADS)

    Gezgin, Serap Yiǧit; Kepceoǧlu, Abdullah; Kılıç, Hamdi Şükür

    2017-02-01

    Noble metal nano-structures such as Ag, Cu, Au are used commonly to increase power conversion efficiency of the solar cell by using their surface plasmons. The plasmonic metal nanoparticles of Ag among others that have strong LSPR in near UV range. They increase photon absorbance via embedding in the active semiconductor of the solar cell. Thin films of Ag are grown in the desired particle size and interparticle distance easily and at low cost by PLD technique. Ag nanoparticle thin films were grown on micro slide glass at 25-36 mJ laser pulse energies under by PLD using ns-Nd:YAG laser. The result of this work have been presented by carrying out UV-VIS and AFM analysis. It was concluded that a laser energy increases, the density and size of Ag-NPs arriving on the substrate increases, and the interparticle distance was decreases. Therefore, LSPR wavelength shifts towards to longer wavelength region.

  7. Synthesis of beta-cyclodextrin-modified water-dispersible Ag-TiO2 core-shell nanoparticles and their photocatalytic activity.

    PubMed

    Shown, Indrajit; Ujihara, Masaki; Imae, Toyoko

    2011-04-01

    The beta-cyclodextrin-modified Ag-TiO2 core-shell nanoparticles were prepared by sodium borohydrate reduction of AgNO3 and the subsequent hydrolysis of the tetraisopropyl orthotitanate in an aqueous medium. Inversely in the preparation of beta-cyclodextrin-modified TiO2-Ag core-shell nanoparticles, first hydrolysis and then following reduction were carried out. The synthesized spherical core-shell nanoparticles were highly water-dispersible and had an average diameter in the range of 9 to 12 nm. A significant shifting of surface plasmon band was observed for the synthesized Ag-TiO2 and TiO2-Ag core-shell nanoparticles. On a model reaction, namely, the photodegradation of phenol by the UV light irradiation, the photocatalytic property of TiO2 nanoparticles was enhanced, when the Ag nanoparticle was embedded in the core of TiO2 nanoparticles but TiO2 nanoparticles coated by Ag shell decreased the photocatalytic property of TiO2 nanoparticles. The mechanism is ascribed to the surface plasmon characteristics of Ag in the core of the TiO2 nanoparticles under the acceleration by host-guest inclusion characteristics.

  8. 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.

  9. Ag-doped manganite nanoparticles: new materials for temperature-controlled medical hyperthermia.

    PubMed

    Melnikov, O V; Gorbenko, O Yu; Markelova, M N; Kaul, A R; Atsarkin, V A; Demidov, V V; Soto, C; Roy, E J; Odintsov, B M

    2009-12-15

    The purpose of this study was to introduce newly synthesized nanomaterials as an alternative to superparamagnetic ironoxide based particles (SPIO) and thus to launch a new platform for highly controllable hyperthermia cancer therapy and imaging. The new material that forms the basis for this article is lanthanum manganite particles with silver ions inserted into the perovskite lattice: La(1-x)Ag(x)MnO(3+delta). Adjusting the silver doping level, it is possible to control the Curie temperature (T(c)) in the hyperthermia range of interest (41-44 degrees C). A new class of nanoparticles based on silver-doped manganites La(1-x)Ag(x)MnO(3+delta) is suggested. New nanoparticles are stable, and their properties were not affected by the typical ambient conditions in the living tissue. It is possible to monitor the particle uptake and retention by MRI. When these particles are placed into an alternating magnetic field, their temperature increases to the definite value near T(c) and then remains constant if the magnetic field is maintained. During the hyperthermia procedure, the temperature can be restricted, thereby preventing the necrosis of normal tissue. A new class of nanoparticles based on silver-doped manganites La(1-x)Ag(x)MnO(3+delta) was suggested. Ag-doped perovskite manganites particles clearly demonstrated the effect of adjustable Curie temperature necessary for highly controllable cellular hyperthermia. The magnetic relaxation properties of the particles are comparable with that of SPIO, and so we were able to monitor the particle movement and retention by MRI. Thus, the new material combines the MRI contrast enhancement capability with targeted hyperthermia treatment.

  10. 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.

  11. Synthesis of novel AuPd nanoparticles decorated one-dimensional ZnO nanorod arrays with enhanced photoelectrochemical water splitting activity.

    PubMed

    Lu, Yan; Zhang, Junlong; Ge, Lei; Han, Changcun; Qiu, Ping; Fang, Siman

    2016-12-01

    The vertically aligned one-dimensional (1D) ZnO nanorod arrays decorated with AuPd alloy nanoparticles have been synthesized with ZnO nanorod arrays as template via a mild hydrothermal method. In this work, the as-prepared AuPd/ZnO nanorod arrays demonstrated high light-harvesting efficiency. The microstructures, morphologies and chemical properties of the obtained AuPd/ZnO composite photocatalyst were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscopy (XPS). The photoelectrochemical (PEC) performances of as-obtained AuPd/ZnO nanorod arrays were examined, and the photocurrent density was up to 0.98mAcm(-2) at 0.787V versus Ag/AgCl, which was about 2.4 times higher than the pure ZnO sample. A possible photocatalytic mechanism of the AuPd/ZnO hybrid nanostructures under the simulated sunlight irradiation was proposed to guide further improvement of other desirable materials. According to the above experiment results, it can be clearly found that AuPd/ZnO composite nanorod arrays showed excellent PEC performance and had promising applications in the utilization of solar energy.

  12. 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.

  13. A facile and green strategy for the synthesis of Au, Ag and Au-Ag alloy nanoparticles using aerial parts of R. hypocrateriformis extract and their biological evaluation.

    PubMed

    Godipurge, S S; Yallappa, S; Biradar, Naveen J; Biradar, J S; Dhananjaya, B L; Hegde, Gajanan; Jagadish, K; Hegde, Gurumurthy

    2016-12-01

    A facile and green strategy is reported here to synthesize gold (Au), silver (Ag) and gold-silver (Au-Ag) alloy nanoparticles (NPs) through bio-reduction reactions of aqueous corresponding metal precursors mediated by extracts of aerial parts of R. hypocrateriformis, which act as both reducing and stabilizing agents, under microwave irradiation. UV-vis spectrophotometer, XRD, FT-IR, FESEM/TEM, TGA and EDAX analysis were used to characterize the obtained NPs. The formation of NPs is evident from their surface plasmon resonance peak observed at λmax=∼550, 450 and 500nm for Au, Ag and Au-Ag alloy NPs respectively. XRD pattern revealed that fcc structure, while FT-IR spectra signify the presence of phytochemicals adsorbed on NPs. Such a biofunctionalized NPs were characterized by their weight loss, 30% due to thermal degradation of plant phytochemicals observed in TG analysis. The spherical shape of Au, Ag and Au-Ag alloy NPs (∼10-50nm) is observed by FE-SEM/TEM images. EDAX analysis confirms the expected elemental composition. Moreover, these NPs showed enhanced antimicrobial, antioxidant, and anticancer activities, though it is more pronounced for Au-Ag alloy NPs, which is due to the combining effect of phytochemicals, Au and Ag metals. Thus, the biosynthesized NPs could be applied as effective growth inhibitors for various biomedical applications.

  14. W 18O 49 nanorods decorated with Ag/AgCl nanoparticles as highly-sensitive gas-sensing material and visible-light-driven photocatalyst

    NASA Astrophysics Data System (ADS)

    Sun, Shibin; Chang, Xueting; Dong, Lihua; Zhang, Yidong; Li, Zhenjiang; Qiu, Yanyan

    2011-08-01

    A novel gas-sensing material and photocatalyst was successfully obtained by decorating Ag/AgCl nanoparticles on the W 18O 49 nanorods through a clean photochemical route. The as-prepared samples were characterized using combined techniques of X-ray diffractometry, electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Gas-sensing measurements indicate that the Ag/AgCl/W 18O 49 NRs sensors exhibit superior reducing gas-sensing properties to those of bare W 18O 49 NRs, and they are highly selective and sensitive to NH 3, acetone, and H 2S with short response and recovery times. The Ag/AgCl/W 18O 49 NRs photocatlysts also possess higher photocatalytic performance than bare W 18O 49 NRs for degradation of methyl orange under simulated sunlight irradiation. Possible mechanisms concerning the enhancement of gas-sensing and photocatalytic activities of the Ag/AgCl/W 18O 49 NRs composite were proposed.

  15. Au-Ag template stripped pattern for scanning probe investigations of DNA arrays produced by dip pen nanolithography.

    PubMed

    Baserga, Andrea; Viganò, Marco; Casari, Carlo S; Turri, Stefano; Li Bassi, Andrea; Levi, Marinella; Bottani, Carlo E

    2008-11-18

    We report on DNA arrays produced by dip pen nanolithography (DPN) on a novel Au-Ag micropatterned template stripped surface. DNA arrays have been investigated by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) showing that the patterned template stripped substrate enables easy retrieval of the DPN-functionalized zone with a standard optical microscope permitting multi-instrument and multitechnique local detection and analysis. Moreover the smooth surface of the Au squares ( approximately 5-10 A roughness) allows AFM/STM to be sensitive to the hybridization of the oligonucleotide array with label-free target DNA. Our Au-Ag substrates, combining the retrieving capabilities of the patterned surface with the smoothness of the template stripped technique, are candidates for the investigation of DPN nanostructures and for the development of label-free detection methods for DNA nanoarrays based on the use of scanning probes.

  16. 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.

  17. Selective turn-on fluorescence sensor for Ag+ using cysteamine capped CdS quantum dots: determination of free Ag+ in silver nanoparticles solution.

    PubMed

    Khantaw, Thitima; Boonmee, Chanida; Tuntulani, Thawatchai; Ngeontae, Wittaya

    2013-10-15

    Cadmium sulfide quantum dots capped with cysteamine (Cys-CdS QDs) were demonstrated as a selective fluorescence probe for sensing of free trace silver ions. The fluorescence intensity of the Cys-CdS QDs can be enhanced only in the presence of free Ag(+) and the fluorescence spectrum was slightly red shift from the original spectra. In addition, the fluorescence intensities were linearly increased upon increasing Ag(+) concentration. At the optimized condition for Ag(+) detection, when adding other metal ions to the Cys-CdS QDs solution, fluorescence spectra of Cys-CdS QDs did not change significantly revealing good selectivity of the sensors towards Ag(+). The working linear concentration range was found to be 0.1-1.5 µM with LOD of 68 nM. The proposed sensor was then applied to detect free Ag(+) in the silver nanoparticles solution. The results showed that the proposed sensor can be efficiently used with good accuracy and precision providing the simple method for detection of free Ag(+) in silver nanoparticles of quality control products.

  18. 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

    2012-06-04

    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.

  19. Ag nanoparticle mediated growth of CdS nanobelts

    NASA Astrophysics Data System (ADS)

    Sreejith, K.; Nuwad, J.; Thinaharan, C.; Dey, G. K.; Pillai, C. G. S.

    2007-06-01

    Catalytic growth of CdS have been carried out on large scale by evaporation of bulk CdS on Ag deposited Si (1 1 1) at atmospheric pressure. The as prepared CdS had wurtzite structure as evidenced by X-ray diffraction. The nanostructures were beltlike with several tens of micrometers length, several micrometers width and few nanometers to tens of nanometers thick as seen by scanning electron microscope and confirmed by TEM studies. The nanobelts were single crystalline in nature and showed reflection corresponding to (1 1 2) and (0 0 2) planes in SAED. The PL studies revealed the green band due to band gap emission and red band due to emission from the surface states. The higher intensity of the defect emission indicated the presence of considerable concentration of surface defects in the as prepared sample. The deposition of CdS could be explained on the basis of catalyst assisted vapor-liquid-solid and vapor-solid mechanism.

  20. 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

  1. Ag Nanoparticles-Modified 3D Graphene Foam for Binder-Free Electrodes of Electrochemical Sensors

    PubMed Central

    Han, Tao; Jin, Jianli; Wang, Congxu; Sun, Youyi; Zhang, Yinghe; Liu, Yaqing

    2017-01-01

    Ag nanoparticles-modified 3D graphene foam was synthesized through a one-step in-situ approach and then directly applied as the electrode of an electrochemical sensor. The composite foam electrode exhibited electrocatalytic activity towards Hg(II) oxidation with high limit of detection and sensitivity of 0.11 µM and 8.0 µA/µM, respectively. Moreover, the composite foam electrode for the sensor exhibited high cycling stability, long-term durability and reproducibility. These results were attributed to the unique porous structure of the composite foam electrode, which enabled the surface of Ag nanoparticles modified reduced graphene oxide (Ag NPs modified rGO) foam to become highly accessible to the metal ion and provided more void volume for the reaction with metal ion. This work not only proved that the composite foam has great potential application in heavy metal ions sensors, but also provided a facile method of gram scale synthesis 3D electrode materials based on rGO foam and other electrical active materials for various applications. PMID:28336878

  2. 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.

  3. Ag Nanoparticles-Modified 3D Graphene Foam for Binder-Free Electrodes of Electrochemical Sensors.

    PubMed

    Han, Tao; Jin, Jianli; Wang, Congxu; Sun, Youyi; Zhang, Yinghe; Liu, Yaqing

    2017-02-16

    Ag nanoparticles-modified 3D graphene foam was synthesized through a one-step in-situ approach and then directly applied as the electrode of an electrochemical sensor. The composite foam electrode exhibited electrocatalytic activity towards Hg(II) oxidation with high limit of detection and sensitivity of 0.11 μM and 8.0 μA/μM, respectively. Moreover, the composite foam electrode for the sensor exhibited high cycling stability, long-term durability and reproducibility. These results were attributed to the unique porous structure of the composite foam electrode, which enabled the surface of Ag nanoparticles modified reduced graphene oxide (Ag NPs modified rGO) foam to become highly accessible to the metal ion and provided more void volume for the reaction with metal ion. This work not only proved that the composite foam has great potential application in heavy metal ions sensors, but also provided a facile method of gram scale synthesis 3D electrode materials based on rGO foam and other electrical active materials for various applications.

  4. 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.

  5. Autocatalytic synthesis of multifunctional precursors for fabricating silica microspheres with well-dispersed Ag and Co3O4 nanoparticles.

    PubMed

    Xu, Linxu; Cui, Fang; Zhang, Jiajia; Hao, Yanjun; Wang, Yan; Cui, Tieyu

    2017-01-05

    Herein, an autocatalytic route to fabricate dual metal ion-equipped organic/inorganic hybrid silica, an ideal precursor for multifunctional silica-based composites integrated with well-dispersed Ag and Co3O4 nanoparticles was demonstrated. Significantly, by rational selection of reactants, such dual metal ion-equipped organic/inorganic hybrid silica can be synthesized through successive spontaneous reactions under near neutral conditions without an additional catalyst. Both the Ag(+) and Co(2+) ions are introduced into silica by chemical bonds, which favor the formation of small-sized and well-dispersed Ag and Co3O4 nanoparticles without aggregation in the entire silica matrix. After calcination, multifunctional silica composites equipped with well-dispersed Ag and Co3O4 nanoparticles were obtained. The as-obtained silica composites, as indicated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), have a spherical morphology and smooth surface. TEM tests also reveal the well dispersed fashion of Ag and Co3O4 nanoparticles. In addition, the obtained Ag-Co3O4@SiO2 composites exhibit good catalytic performance in the reduction of methylene blue (MB) with NaBH4 as a reducing agent, and can be readily recycled by an external magnetic field due to their superparamagnetic properties.

  6. Synthesis and characterization of AgI nanoparticles in β-CD/PAN nanofibers by electrospinning method

    NASA Astrophysics Data System (ADS)

    Liang, Haiou; Li, Chunping; Bai, Jie; Zhang, Lijuan; Guo, Liping; Huang, Yarong

    2013-04-01

    AgI nanoparticles/β-cyclodextrin (β-CD)/polyacrylonitrile (PAN) composite nanofibers film were prepared via a new route which combined electrospinning technology with the reaction of solid-liquid process. In this article, AgI nanoparticles were successfully prepared in β-CD/PAN nanofibers which contained different concentration β-CD by the new route. Firstly, the AgNO3-β-CD/PAN nanofibers were obtained via electrospinning method, then put the nanofibers into the solution of potassium iodide to prepare AgI-β-CD/PAN nanofibers. The morphology and structure of the composite nanofibers and nanoparticles have been investigated by scanning electron microscopy (SEM) and transmission electro microscopy (TEM). The existence of the AgI nanoparticles was proved by X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD) patterns. The results of various characterizations indicated that the sample of AgI-β-CD (2 wt%)/PAN have the optimum morphology and structure.

  7. Biosynthesis of Cu, ZVI, and Ag nanoparticles using Dodonaea viscosa extract for antibacterial activity against human pathogens

    NASA Astrophysics Data System (ADS)

    Kiruba Daniel, S. C. G.; Vinothini, G.; Subramanian, N.; Nehru, K.; Sivakumar, M.

    2013-01-01

    Biosynthesis of copper, zero-valent iron (ZVI), and silver nanoparticles using leaf extract of Dodonaea viscosa has been investigated in this report. There are no additional surfactants/polymers used as capping or reducing agents for these syntheses. The synthesized nanoparticles were characterized by UV-Vis spectroscopy, X-ray diffraction, atomic force microscopy, and high-resolution transmission electron microscopy. The phase analysis was performed using selected area electron diffraction. The pH dependence of surface plasmon resonance and subsequent size variation has been determined. The synthesized nanoparticles showed spherical morphology and the average size of 29, 27, and 16 nm for Cu, ZVI, and Ag nanoparticles, respectively. Finally, biosynthesized Cu, ZVI, and Ag nanoparticles were tested against human pathogens viz. Gram-negative Escherichia coli, Klebsiella pneumonia, Pseudomonas fluorescens and Gram-positive Staphylococcus aureus and Bacillus subtilis, and showed good antimicrobial activity.

  8. Determination of anthracene on Ag-Au alloy nanoparticles/overoxidized-polypyrrole composite modified glassy carbon electrodes.

    PubMed

    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 AgNO(3) and HAuCl(4) using C(6)H(5)O(7)Na(3) 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.

  9. Photo-bioreduction of Ag(+) ions towards the generation of multifunctional silver nanoparticles: Mechanistic perspective and therapeutic potential.

    PubMed

    Jena, Satyapriya; Singh, Rohit Kumar; Panigrahi, Bijayananda; Suar, Mrutyunjay; Mandal, Dindyal

    2016-11-01

    In this article, light induced plant extract mediated one pot synthesis of silver nanoparticles (AgNPs) has been demonstrated and potential mechanistic insight in the synthesis has been investigated. Bioactive molecules containing medicinal plant Cassytha filiformis has been explored for the synthesis of silver nanoparticles. The as-synthesized silver nanoparticles were characterized by various analytical techniques including Ultraviolet-visible spectroscopy (UV-Vis), High Resolution Transmission Electron Microscopy (HR-TEM), Dynamic Light Scattering (DLS) and Fourier Transform Infrared Spectroscopy (FT-IR). Among different light sources (sunlight, room light, UV) applied the sunlight was found to be efficient external stimuli to induce rapid synthesis of AgNPs at room temperature. Modified DPPH assay indicated that polyphenolic compounds were most likely involved in the synthesis of AgNPs. Possible molecule responsible for the synthesis of AgNPs was identified, purified and characterized. Potential biomedical applications such as antibacterial, antifungal and anticancer activities of AgNPs have been evaluated. Irrespective of nature of pathogenic strains nanoparticles exhibited significant antibacterial activities against Gram positive (Streptococcus aureus) and Gram negative (Escherichia coli) bacterial pathogens. It showed higher activity on E. coli than on S. aureus. Distinct antifungal activity (MIC=5.244μg/ml) and remarkable anticancer activity (IC50=10μg/ml) was found against Candida albicans and HCT116 (colorectal carcinoma) cells, respectively. Taken together, these findings suggested that light induced plant generated silver nanoparticles could be used for various biomedical purposes.

  10. 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.

  11. 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.

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

    PubMed

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

    2016-03-05

    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.

  13. Photodeposition of Ag2S on TiO2 nanorod arrays for quantum dot-sensitized solar cells.

    PubMed

    Hu, Hongwei; Ding, Jianning; Zhang, Shuai; Li, Yan; Bai, Li; Yuan, Ningyi

    2013-01-03

    Ag2S quantum dots were deposited on the surface of TiO2 nanorod arrays by a two-step photodeposition. The prepared TiO2 nanorod arrays as well as the Ag2S deposited electrodes were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscope, suggesting a large coverage of Ag2S quantum dots on the ordered TiO2 nanorod arrays. UV-vis absorption spectra of Ag2S deposited electrodes show a broad absorption range of the visible light. The quantum dot-sensitized solar cells (QDSSCs) based on these electrodes were fabricated, and the photoelectrochemical properties were examined. A high photocurrent density of 10.25 mA/cm2 with a conversion efficiency of 0.98% at AM 1.5 solar light of 100 mW/cm2 was obtained with an optimal photodeposition time. The performance of the QDSSC at different incident light intensities was also investigated. The results display a better performance at a lower incident light level with a conversion efficiency of 1.25% at 47 mW/cm2.

  14. Photodeposition of Ag2S on TiO2 nanorod arrays for quantum dot-sensitized solar cells

    PubMed Central

    2013-01-01

    Ag2S quantum dots were deposited on the surface of TiO2 nanorod arrays by a two-step photodeposition. The prepared TiO2 nanorod arrays as well as the Ag2S deposited electrodes were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscope, suggesting a large coverage of Ag2S quantum dots on the ordered TiO2 nanorod arrays. UV–vis absorption spectra of Ag2S deposited electrodes show a broad absorption range of the visible light. The quantum dot-sensitized solar cells (QDSSCs) based on these electrodes were fabricated, and the photoelectrochemical properties were examined. A high photocurrent density of 10.25 mA/cm2 with a conversion efficiency of 0.98% at AM 1.5 solar light of 100 mW/cm2 was obtained with an optimal photodeposition time. The performance of the QDSSC at different incident light intensities was also investigated. The results display a better performance at a lower incident light level with a conversion efficiency of 1.25% at 47 mW/cm2. PMID:23286551

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. Synthesis and optical properties of silver nanoparticles and arrays.

    PubMed

    Evanoff, David D; Chumanov, George

    2005-07-11

    This Minireview systematically examines optical properties of silver nanoparticles as a function of size. Extinction, scattering, and absorption cross-sections and distance dependence of the local electromagnetic field, as well as the quadrupolar coupling of 2D assemblies of such particles are experimentally measured for a wide range of particle sizes. Such measurements were possible because of the development of a novel synthetic method for the size-controlled synthesis of chemically clean, highly crystalline silver nanoparticles of narrow size distribution. The method and its unique advantages are compared to other methods for synthesis of metal nanoparticles. Synthesis and properties of nanocomposite materials using these and other nanoparticles are also described. Important highlights in the history of the field of metal nanoparticles as well as an examination of the basic principles of plasmon resonances are included.

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

    NASA Astrophysics Data System (ADS)

    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 NaBH4 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.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

  1. Patterning of plasmonic nanoparticles into multiplexed one-dimensional arrays based on spatially modulated electrostatic potential.

    PubMed

    Jiang, Lin; Sun, Yinghui; Nowak, Christoph; Kibrom, Asmorom; Zou, Changji; Ma, Jan; Fuchs, Harald; Li, Shuzhou; Chi, Lifeng; Chen, Xiaodong

    2011-10-25

    We report a new strategy to pattern plasmonic nanoparticles into multiplexed one-dimensional arrays based on the spatially modulated electrostatic potential. The 32 nm Au nanoparticles can be simultaneously deposited on one chip with tunable interparticle distance by solely adjusting the width of the grooves. Furthermore, 32 and 13 nm Au nanoparticles can be selectively deposited in grooves of different widths on one chip. As a result, the surface plasmon absorption bands on the chip can be tuned depending on the interparticle distance or the particle size of multiplex 1D arrays, which could enhance the Raman scattering cross section of the adsorbed molecules and result in multiplex surface-enhanced Raman scattering (SERS) response on the chip. This strategy provides a general method to fabricate 1D multiplex arrays with different particle sizes and interparticle distances on one chip.

  2. Flexible Textile-Based Organic Transistors Using Graphene/Ag Nanoparticle Electrode.

    PubMed

    Kim, Youn; Kwon, Yeon Ju; Lee, Kang Eun; Oh, Youngseok; Um, Moon-Kwang; Seong, Dong Gi; Lee, Jea Uk

    2016-08-16

    Highly flexible and electrically-conductive multifunctional textiles are desirable for use in wearable electronic applications. In this study, we fabricated multifunctional textile composites by vacuum filtration and wet-transfer of graphene oxide films on a flexible polyethylene terephthalate (PET) textile in association with embedding Ag nanoparticles (AgNPs) to improve the electrical conductivity. A flexible organic transistor can be developed by direct transfer of a dielectric/semiconducting double layer on the graphene/AgNP textile composite, where the textile composite was used as both flexible substrate and conductive gate electrode. The thermal treatment of a textile-based transistor enhanced the electrical performance (mobility = 7.2 cm²·V(-1)·s(-1), on/off current ratio = 4 × 10⁵, and threshold voltage = -1.1 V) due to the improvement of interfacial properties between the conductive textile electrode and the ion-gel dielectric layer. Furthermore, the textile transistors exhibited highly stable device performance under extended bending conditions (with a bending radius down to 3 mm and repeated tests over 1000 cycles). We believe that our simple methods for the fabrication of graphene/AgNP textile composite for use in textile-type transistors can potentially be applied to the development of flexible large-area electronic clothes.

  3. Flexible Textile-Based Organic Transistors Using Graphene/Ag Nanoparticle Electrode

    PubMed Central

    Kim, Youn; Kwon, Yeon Ju; Lee, Kang Eun; Oh, Youngseok; Um, Moon-Kwang; Seong, Dong Gi; Lee, Jea Uk

    2016-01-01

    Highly flexible and electrically-conductive multifunctional textiles are desirable for use in wearable electronic applications. In this study, we fabricated multifunctional textile composites by vacuum filtration and wet-transfer of graphene oxide films on a flexible polyethylene terephthalate (PET) textile in association with embedding Ag nanoparticles (AgNPs) to improve the electrical conductivity. A flexible organic transistor can be developed by direct transfer of a dielectric/semiconducting double layer on the graphene/AgNP textile composite, where the textile composite was used as both flexible substrate and conductive gate electrode. The thermal treatment of a textile-based transistor enhanced the electrical performance (mobility = 7.2 cm2·V−1·s−1, on/off current ratio = 4 × 105, and threshold voltage = −1.1 V) due to the improvement of interfacial properties between the conductive textile electrode and the ion-gel dielectric layer. Furthermore, the textile transistors exhibited highly stable device performance under extended bending conditions (with a bending radius down to 3 mm and repeated tests over 1000 cycles). We believe that our simple methods for the fabrication of graphene/AgNP textile composite for use in textile-type transistors can potentially be applied to the development of flexible large-area electronic clothes. PMID:28335276

  4. 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.

  5. Homogeneous synthesis of Ag nanoparticles-doped water-soluble cellulose acetate for versatile applications.

    PubMed

    Cao, Jie; Sun, Xunwen; Zhang, Xinxing; Lu, Canhui

    2016-11-01

    We report a facile and efficient approach for synthesis of well-dispersed and stable silver nanoparticles (Ag NPs) using water-soluble cellulose acetate (CA) as both reductant and stabilizer. Partially substituted CA with highly active hydroxyl groups and excellent water-solubility is able to reduce silver ions in homogeneous aqueous medium effectively. The synthesized Ag NPs were characterized by UV-vis spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive X-ray spectroscope analysis. The as-prepared Ag NPs were well-dispersed, showing a surface plasmon resonance peak at 426nm. The resulted Ag NPs@CA nanohybrids exhibit high catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. Meanwhile, the nanohybrids are also effective in inhibiting the growth of bacterial. This environmentally friendly method promotes the use of renewable natural resources to prepare a variety of inorganic-organic materials for catalysis, antibacterial, sensors and other applications.

  6. Ion Beam Stabilization of FePt Nanoparticle Arrays for Magnetic Storage Media

    SciTech Connect

    Toney, Michael F

    2003-07-31

    The authors describe the use of ion beam induced crosslinking to harden the organic matrix material of self-assembled arrays of monodisperse (4 nm) FePt nanoparticles, providing diamondlike carbon barriers to inhibit agglomeration of the nanoparticles under heat treatment. Such stabilization is necessary for the particles to survive the > 500 C annealing required for growth of the fct L 1{sub 0} phase of FePt, whose magnetic anisotropy is necessary for application of such arrays for high density perpendicular recording. Selective area irradiation of continuous nanoparticle coatings, using ion beams patterned over a full disk by stencil mask or with ion projection optics, followed by dissolution of the unexposed coating, is proposed as a means of fabricating extended bit patterns consisting of isolated islands of FePt nanoparticles, with characteristic dimensions of tens of nanometers.

  7. The fabrication of polymer-nanocone-based 3D Au nanoparticle array and its SERS performance

    NASA Astrophysics Data System (ADS)

    Zhao, Wenning; Wu, Yiyao; Liu, Xiaoguang; Xu, Yebin; Wang, Shuangbao; Xu, Zhimou

    2017-01-01

    By combining conical-pore-AAO template and NIL technology, we realized the transfer of three-dimensional nanoparticle array to polymer materials. Au nanoparticles were deposited on the surface of conical-pore-AAO template, then the nanostructure was duplicated onto the polymer wafer via NIL method and the nanoparticles were inlaid onto the nanocones. Polymer-nanocone-based 3D Au nanoparticle array was obtained. The product possesses excellent flexibility and transparency in visual and infrared range. As a new class of SERS substrate, the product exhibits excellent sensitivity and reproducibility. Compared with the traditional SERS substrates, it provides unique advantages, such as being flexible, transparent, lightweight, portable, easily handled and low cost.

  8. Polarization sensitivity of light diffraction for periodic array of anisotropic gold nanoparticles

    SciTech Connect

    Tsai, Ming-shan Liu, Tung-kai; Tsen, Chun-yu; Ting, Chen-ching

    2015-06-15

    This article aims to analyze the first order diffraction intensity of the incident polarized light which is diffracted by the gold nanoparticles array in terms of the surface plasmon effect. The inspected gold nanoparticles array films are built in grating pattern with stripe thickness of 4 μm and diameters of gold nanoparticles ca. 10–56 nm, which are formed by annealing at temperatures of 400, 450, 500, and 550 °C, respectively. The probing light is linearly polarized with wavelengths of 450–800 nm and counterclockwise turns its polarization direction from 0° to 90° during measurements. The results show that the diffraction intensity depends on the anisotropic configuration samples which gold nanoparticles are orientated by analyzing the scanning electron microscope images. It results that the localized surface plasmon effect induced by incident field depends on orientation and causes the sample polarization-sensitive.

  9. Microwave properties of La0.8Ag0.2MnO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Rostamnejadi, Ali

    2016-11-01

    In this research, single-phase nanoparticles of La0.8Ag0.2MnO3 with mean particle size of 15 nm have been synthesized by sol-gel method. The microwave properties of La0.8Ag0.2MnO3/paraffin nanocomposite are studied by measuring the complex permittivity and permeability in the frequency range of 1-18 GHz. The composite shows both reflection and absorption electromagnetic shielding effectiveness with maximum total value of 36 dB, which is suitable for defense and microwave radiation shielding applications at high temperatures. The electromagnetic absorption properties are described in terms of dielectric relaxation processes.

  10. 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

  11. 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

    2015-12-07

    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.

  12. Montmorillonite-supported Ag/TiO(2) nanoparticles: an efficient visible-light bacteria photodegradation material.

    PubMed

    Wu, Tong-Shun; Wang, Kai-Xue; Li, Guo-Dong; Sun, Shi-Yang; Sun, Jian; Chen, Jie-Sheng

    2010-02-01

    Montmorillonite (MMT)-supported Ag/TiO(2) composite (Ag/TiO(2)/MMT) has been prepared through a one-step, low-temperature solvothermal technique. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) reveal that the Ag particles coated with TiO(2) nanoparticles are well-dispersed on the surface of MMT in the composite. As a support for the Ag/TiO(2) composite, the MMT prevents the loss of the catalyst during recycling test. This Ag/TiO(2)/MMT composite exhibits high photocatalytic activity and good recycling performance in the degradation of E. coli under visible light. The high visible-light photocatalytic activity of the Ag/TiO(2)/MMT composite is ascribed to the increase in surface active centers and the localized surface plasmon effect of the Ag nanoparticles. The Ag/TiO(2)/MMT materials with excellent stability, recyclability, and bactericidal activities are promising photocatalysts for application in decontamination.

  13. 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.

  14. 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.

  15. Marangoni flow of Ag nanoparticles from the fluid-fluid interface.

    PubMed

    Johnson, Donald D; Kang, Barry; Vigorita, John L; Amram, Alec; Spain, Eileen M

    2008-10-02

    Fluid flow is observed when a volume of passivated Ag nanoparticles suspended in chloroform is mixed with a water/ethanol (v/v) mixture containing acidified 11-mercaptoundecanoic acid. Following mechanical agitation, Ag nanoparticles embedded in a film are driven from the organic-aqueous interface. A reddish-brown colored film, verified by transmission electron microscopy to contain uniformly dispersed Ag nanoparticles, is observed to spontaneously climb the interior surface of an ordinary, laboratory glass vial. This phenomenon is recorded by a digital video recorder, and a measurement of the distance traveled by the film front versus time is extracted. Surface (interfacial) tension gradients due to surfactant concentration, temperature, and electrostatic potential across immiscible fluids are known to drive interface motion; this well-known phenomenon is termed Marangoni flow or the Marangoni effect. Experimental results are presented that show the observed mass transfer is dependent on an acid surfactant concentration and on the volume fraction of water in the aqueous phase, consistent with fluid flow induced by interfacial tension gradients. In addition, an effective desorption rate constant for the Marangoni flow is measured in the range of approximately 0.01 to approximately 1 s(-1) from a fit to the relative film front distance traveled versus time data. The fit is based on a time-dependent expression for the surface (interface) excess for desorption kinetics. Such flow suggests that purposeful creation of interfacial tension gradients may aid in the transfer of 2- and 3-dimensional assemblies, made with nanostructures at the liquid-liquid interface, to solid surfaces.

  16. W{sub 18}O{sub 49} nanorods decorated with Ag/AgCl nanoparticles as highly-sensitive gas-sensing material and visible-light-driven photocatalyst

    SciTech Connect

    Sun Shibin; Chang Xueting; Dong Lihua; Zhang Yidong; Li Zhenjiang; Qiu Yanyan

    2011-08-15

    A novel gas-sensing material and photocatalyst was successfully obtained by decorating Ag/AgCl nanoparticles on the W{sub 18}O{sub 49} nanorods through a clean photochemical route. The as-prepared samples were characterized using combined techniques of X-ray diffractometry, electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Gas-sensing measurements indicate that the Ag/AgCl/W{sub 18}O{sub 49} NRs sensors exhibit superior reducing gas-sensing properties to those of bare W{sub 18}O{sub 49} NRs, and they are highly selective and sensitive to NH{sub 3}, acetone, and H{sub 2}S with short response and recovery times. The Ag/AgCl/W{sub 18}O{sub 49} NRs photocatlysts also possess higher photocatalytic performance than bare W{sub 18}O{sub 49} NRs for degradation of methyl orange under simulated sunlight irradiation. Possible mechanisms concerning the enhancement of gas-sensing and photocatalytic activities of the Ag/AgCl/W{sub 18}O{sub 49} NRs composite were proposed. - Graphical Abstract: The Ag/AgCl nanoparticles adhered well to the W{sub 18}O{sub 49} nanorod. The Ag could act as transfer center of the photoexcited carriers, prohibiting their recombinations in both W{sub 18}O{sub 49} and AgCl. Highlights: > Ag/AgCl/W{sub 18}O{sub 49} NRs were successfully obtained via a clean photochemical route. > The Ag/AgCl nanoparticles decorated on the W{sub 18}O{sub 49} NRs possessed cladding structure. > The Ag/AgCl/W{sub 18}O{sub 49} NRs exhibited excellent gas-sensing and photocatalytic properties.

  17. 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

    2012-07-03

    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.

  18. Asymmetric transport of light in linearly arrayed metallic nano-particles

    NASA Astrophysics Data System (ADS)

    Horchani, R.

    2016-02-01

    A strong asymmetric light transport in a linear chain of spherical and equidistantly spaced silver metal nano-particles (MNPs) located near a substrate is reported. The contrast ratio of the proposed structure is above 0.95. We have studied the propagation of light in the array with respect to the metal and the size of the last nano-particle of the chain and the nature of the substrate. It is shown also that the presence of a copper or gold substrate enhance the guiding properties of the array. This structure opens the possibility to design various optical devices such as broadband antennae and optical diodes.

  19. Asymmetric transport of light in linearly arrayed metallic nano-particles

    NASA Astrophysics Data System (ADS)

    Aroua, W.; Horchani, R.; AbdelMalek, F.; Haxha, S.; Kamli, Ali A.

    2016-09-01

    A strong asymmetric light transport in a linear chain of spherical and equidistantly spaced silver metal nano-particles (MNPs) located near a substrate is reported. The contrast ratio of the proposed structure is above 0.95. We have studied the propagation of light in the array with respect to the metal and the size of the last nano-particle of the chain and the nature of the substrate. It is shown also that the presence of a copper or gold substrate enhance the guiding properties of the array. This structure opens the possibility to design various optical devices such as broadband antennae and optical diodes.

  20. Laser fabrication of large-scale nanoparticle arrays for sensing applications.

    PubMed

    Kuznetsov, Arseniy I; Evlyukhin, Andrey B; Gonçalves, Manuel R; Reinhardt, Carsten; Koroleva, Anastasia; Arnedillo, Maria Luisa; Kiyan, Roman; Marti, Othmar; Chichkov, Boris N

    2011-06-28

    A novel method for high-speed fabrication of large scale periodic arrays of nanoparticles (diameters 40-200 nm) is developed. This method is based on a combination of nanosphere lithography and laser-induced transfer. Fabricated spherical nanoparticles are partially embedded into a polymer substrate. They are arranged into a hexagonal array and can be used for sensing applications. An optical sensor with the sensitivity of 365 nm/RIU and the figure of merit of 21.5 in the visible spectral range is demonstrated.

  1. Quasi-periodic distribution of plasmon modes in two-dimensional Fibonacci arrays of metal nanoparticles.

    PubMed

    Dallapiccola, Ramona; Gopinath, Ashwin; Stellacci, Francesco; Dal Negro, Luca

    2008-04-14

    In this paper we investigate for the first time the near-field optical behavior of two-dimensional Fibonacci plasmonic lattices fabricated by electron-beam lithography on transparent quartz substrates. In particular, by performing near-field optical microscopy measurements and three dimensional Finite Difference Time Domain simulations we demonstrate that near-field coupling of nanoparticle dimers in Fibonacci arrays results in a quasi-periodic lattice of localized nanoparticle plasmons. The possibility to accurately predict the spatial distribution of enhanced localized plasmon modes in quasi-periodic Fibonacci arrays can have a significant impact for the design and fabrication of novel nano-plasmonics devices.

  2. Steady-state and time-resolved fluorescence spectroscopic studies on the interaction between bovine serum albumin and Ag-nanoparticles

    NASA Astrophysics Data System (ADS)

    Ye, Manping; Shi, Yarong; Chen, Huacai

    2016-10-01

    The interaction between bovine serum albumin(BSA) and Ag-nanoparticles was studied under a pH 7.4 buffer system by time-resolved fluorescence technique combined with the steady-state absorption and fluorescence spectrum. With Ag-nanoparticles, the BSA showed blue shift of fluorescence from 335nm to 332.5nm, accompanied by the fluorescence intensity decreasing. When adding the Ag-nanoparticles to the three fluorescent amino acids tryptophan(Trp), tyrosine(Tyr)and phenylalanine(Phe), only Trp displayed peak shift which from 346.5nm to 341nm. Strong interaction between BSA and the Ag-nanoparticles may come from Trp residue. Time-resolved fluorescence gave that BSA had only one fluorescence lifetime around 6ns from 308 to 313K. When adding Ag-nanoparticles, two fluorescence lifetimes appeared. One is a little above than 6ns and the other is around 3ns. The two Trp residues in 134th and 212th position may give contribution to the changes of the fluorescence lifetime. The 134th Trp residue is probably protected by BSA molecule structure and basically don't contact with Ag-nanoparticles, which shows little change of fluorescence lifetime. The 212th Trp residue is likely the target of the Ag-nanoparticles. The Ag-nanoparticles changed the microenvironment of BSA around the 212th Trp residue and therefore increases the exposure of the 212th Trp and the 134th Trp .

  3. Effects of concentration of Ag nanoparticles on surface structure and in vitro biological responses of oxide layer on pure titanium via plasma electrolytic oxidation

    NASA Astrophysics Data System (ADS)

    Shin, Ki Ryong; Kim, Yeon Sung; Kim, Gye Won; Yang, Hae Woong; Ko, Young Gun; Shin, Dong Hyuk

    2015-08-01

    This study was to investigate how Ag nanoparticles with various concentrations affect the surface structure and in vitro biological properties of oxide layers on the pure titanium produced by a plasma electrolytic oxidation (PEO) process. For this aim, PEO processes were carried out at an AC current density of 100 mA/cm2 for 300 s in potassium pyrophosphate (K4P2O7) electrolytes containing 0, 0.1, 0.3 and 0.5 g/l Ag nanoparticles. Structural investigations using scanning electron microscopy evidenced that the oxide layers showed the successful incorporation of Ag nanoparticles, and the topographical deformation of the porous surface was found when the concentration of Ag nanoparticles was more than 0.1 g/l. Based on the anti-bacterial activity of all oxide layers, the Ag nanoparticles uniformly spread were of considerable importance in triggering the disinfection of E. coli bacteria. The bone forming abilities and cell (MC3T3-E1) proliferation rates of oxide layers produced in electrolytes containing 0 and 0.1 g/l Ag nanoparticles were higher than those containing 0.3 and 0.5 g/l Ag nanoparticles. Consequently, the oxide layer on pure titanium via PEO process in the electrolyte with 0.1 g/l Ag nanoparticles exhibited better the bioactivity accompanying the anti-bacterial activity.

  4. 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.

  5. Current bistability and carrier transport mechanisms of organic bistable devices based on hybrid Ag nanoparticle-polymethyl methacrylate polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Kim, Won Tae; Jung, Jae Hun; Kim, Tae Whan; Son, Dong Ick

    2010-06-01

    The current bistability and the carrier transport mechanisms of organic bistable devices (OBDs) using Ag nanoparticle-polymethyl methacrylate (PMMA) nanocomposites have been investigated. Current-voltage measurements at 300 K on the Al/Ag nanoparticles embedded in the PMMA layer/indium-tin-oxide devices exhibit a current bistability with an ON/OFF ratio of 103. Write-read-erase-read sequence results demonstrate the switching characteristics of the OBD. The cycling endurance number of the ON/OFF switching for the OBD is above 7×104. The current bistability and carrier transport mechanisms of the OBD fabricated utilizing hybrid Ag nanoparticle-PMMA polymer nanocomposites are described on the basis of the experimental data.

  6. Ag Nanoparticles-enhanced Fluorescence of Terbium-Deferasirox Complexes for the Highly Sensitive Determination of Deferasirox.

    PubMed

    Abolhasani, Jafar; Naderali, Roza; Hassanzadeh, Javad

    2016-01-01

    We describe the effect of different sized gold and silver nanoparticles on the terbium sensitized fluorescence of deferasirox. It is indicated that silver nanostructures, especially 18 nm Ag nanoparticles (AgNPs), have a remarkable amplifying effect compared to Au nanoparticles. Based on this observation, a highly sensitive and selective method was developed for the determination of deferasirox. Effects of various parameters like AgNPs and Tb(3+) concentration and pH of media were investigated. Under the optimal conditions, a calibration curve was plotted as the fluorescence intensities versus the concentration of deferasirox in the range of 0.1 to 200 nmol L(-1), and detection limit of 0.03 nmol L(-1) was obtained. The method has good linearity, recovery, reproducibility and sensitivity, and was satisfactorily applied for the determination of deferasirox in urine and pharmaceutical samples.

  7. AuAg bimetallic nonalloyed nanoparticles on a periodically nanostructured GaAs substrate for enhancing light trapping.

    PubMed

    Lee, Soo Kyung; Tan, Chee Leong; Ju, Gun Wu; Song, Jae Hong; Yeo, Chan Il; Lee, Yong Tak

    2015-12-15

    We present a light trapping structure consisting of AuAg bimetallic nonalloyed nanoparticles (BNNPs) on cone-shaped GaAs subwavelength structures (SWSs), combining the advantages of plasmonic structures and SWSs for GaAs-based solar cell applications. To obtain efficient light trapping in solar cells, the optical properties' dependence on the size and composition of the Ag and Au metal nanoparticles was systematically investigated. Cone-shaped GaAs SWSs with AuAg BNNPs formed from an Au film of 12 nm and an Ag film of 10 nm exhibited the extremely low average reflectance (R(avg)) of 2.43% and the solar-weighted reflectance (SWR) of 2.38%, compared to that of a bare GaAs substrate (R(avg), 37.50%; SWR, 36.72%) in the wavelength range of 300 to 870 nm.

  8. Anchoring of Ag-Au alloy nanoparticles on reduced graphene oxide sheets for the reduction of 4-nitrophenol

    NASA Astrophysics Data System (ADS)

    Hareesh, K.; Joshi, R. P.; D. V., Sunitha; Bhoraskar, V. N.; Dhole, S. D.

    2016-12-01

    One-step gamma radiation assisted method has been used for the synthesis of Silver-Gold (Ag-Au) alloy nanoparticles with simultaneous reduction of graphene oxide (GO). UV-vis spectroscopic results along with X-ray diffraction analysis, X-ray Photoelectron spectroscopy and Transmission electron microscopy confirmed the decoration face centered cubic structured Ag-Au nanoparticles of size (5-19) nm on reduced graphene oxide (rGO) sheets. The increase in disorder parameter in Raman spectroscopy indicates the formation of more number of small sp2 domains. The synthesized Ag-Au-rGO nanocomposite showed enhanced catalytic activity towards the reduction of 4-Nitrophenol compared to individual Ag-Au and rGO components.

  9. Sensor Arrays from Multicomponent Micropatterned Nanoparticles and Graphene

    DTIC Science & Technology

    2013-10-10

    tetrahydrate in the presence of ammonia into Fe3O4 nanoparticles. The resultant Fe3O4/Au multicomponent micropatterned-graphene films were found to be highly...alkalization of ferrous chloride tetrahydrate in the presence of ammonia into Fe3O4 nanoparticles. The resultant Fe3O4/Au multicomponent...alkalization reaction of ferrous ions with ammonium hydroxide (NH4OH) in the presence of ammonia to form Fe3O4 nanoparticles within the plasma-treated areas

  10. Design a New Strategy Based on Nanoparticle-Enhanced Chemiluminescence Sensor Array for Biothiols Discrimination

    PubMed Central

    Shahrajabian, Maryam; Hormozi-Nezhad, M. Reza

    2016-01-01

    Array-based sensor is an interesting approach that suggests an alternative to expensive analytical methods. In this work, we introduce a novel, simple, and sensitive nanoparticle-based chemiluminescence (CL) sensor array for discrimination of biothiols (e.g., cysteine, glutathione and glutathione disulfide). The proposed CL sensor array is based on the CL efficiencies of four types of enhanced nanoparticle-based CL systems. The intensity of CL was altered to varying degrees upon interaction with biothiols, producing unique CL response patterns. These distinct CL response patterns were collected as “fingerprints” and were then identified through chemometric methods, including linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA). The developed array was able to successfully differentiate between cysteine, glutathione and glutathione disulfide in a wide concentration range. Moreover, it was applied to distinguish among the above analytes in human plasma. PMID:27574247

  11. Design a New Strategy Based on Nanoparticle-Enhanced Chemiluminescence Sensor Array for Biothiols Discrimination

    NASA Astrophysics Data System (ADS)

    Shahrajabian, Maryam; Hormozi-Nezhad, M. Reza

    2016-08-01

    Array-based sensor is an interesting approach that suggests an alternative to expensive analytical methods. In this work, we introduce a novel, simple, and sensitive nanoparticle-based chemiluminescence (CL) sensor array for discrimination of biothiols (e.g., cysteine, glutathione and glutathione disulfide). The proposed CL sensor array is based on the CL efficiencies of four types of enhanced nanoparticle-based CL systems. The intensity of CL was altered to varying degrees upon interaction with biothiols, producing unique CL response patterns. These distinct CL response patterns were collected as “fingerprints” and were then identified through chemometric methods, including linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA). The developed array was able to successfully differentiate between cysteine, glutathione and glutathione disulfide in a wide concentration range. Moreover, it was applied to distinguish among the above analytes in human plasma.

  12. Fluorescence enhancement in large-scale self-assembled gold nanoparticle double arrays

    SciTech Connect

    Chekini, M.; Bierwagen, J.; Cunningham, A.; Bürgi, T.; Filter, R.; Rockstuhl, C.

    2015-12-21

    Localized surface plasmon resonances excited in metallic nanoparticles confine and enhance electromagnetic fields at the nanoscale. This is particularly pronounced in dimers made from two closely spaced nanoparticles. When quantum emitters, such as dyes, are placed in the gap of those dimers, their absorption and emission characteristics can be modified. Both processes have to be considered when aiming to enhance the fluorescence from the quantum emitters. This is particularly challenging for dimers, since the electromagnetic properties and the enhanced fluorescence sensitively depend on the distance between the nanoparticles. Here, we use a layer-by-layer method to precisely control the distances in such systems. We consider a dye layer deposited on top of an array of gold nanoparticles or integrated into a central position of a double array of gold nanoparticles. We study the effect of the spatial arrangement and the average distance on the plasmon-enhanced fluorescence. We found a maximum of a 99-fold increase in the fluorescence intensity of the dye layer sandwiched between two gold nanoparticle arrays. The interaction of the dye layer with the plasmonic system also causes a spectral shift in the emission wavelengths and a shortening of the fluorescence life times. Our work paves the way for large-scale, high throughput, and low-cost self-assembled functionalized plasmonic systems that can be used as efficient light sources.

  13. 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.

  14. 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.

  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. Cobalt-substituted magnetite nanoparticles and their assembly into ferrimagnetic nanoparticle arrays.

    PubMed

    Yu, Yongsheng; Mendoza-Garcia, Adriana; Ning, Bo; Sun, Shouheng

    2013-06-11

    A simple process to prepare monodisperse ferrimagnetic cobalt-substituted magnetite Co(x)Fe(3-x)O4 nanoparticles is reported. These ferrimagnetic nanoparticles are readily dispersed in hexane, forming a stable ferrimagnetic nanoparticle dispersion, and allowing easy nanoparticle self-assembly. When assembled under an external magnetic field (5.5 kOe), these nanoparticles show preferred magnetic alignment with their H(c) reaching 2.49 kOe.

  17. Antimicrobial effects of TiO(2) and Ag(2)O nanoparticles against drug-resistant bacteria and leishmania parasites.

    PubMed

    Allahverdiyev, Adil M; Abamor, Emrah Sefik; Bagirova, Malahat; Rafailovich, Miriam

    2011-08-01

    Nanotechnology is the creation of functional materials, devices and systems at atomic and molecular scales (1-100 nm), where properties differ significantly from those at a larger scale. The use of nanotechnology and nanomaterials in medical research is growing rapidly. Recently, nanotechnologic developments in microbiology have gained importance in the field of chemotherapy. Bacterial strains that are resistant to current antibiotics have become serious public health problems that raise the need to develop new bactericidal materials. Metal oxide nanoparticles, especially TiO(2) and Ag(2)O nanoparticles, have demonstrated significant antibacterial activity. Therefore, it is thought that this property of metal oxide nanoparticles could effectively be used as a novel solution strategy. In this review, we focus on the unique properties of nanoparticles, their mechanism of action as antibacterial agents and recent studies in which the effects of visible and UV-light induced TiO(2) and Ag(2)O nanoparticles on drug-resistant bacteria have been documented. In addition, from to previous results of our studies, antileishmanial effects of metal oxide nanoparticles are also demonstrated, indicating that metal oxide nanoparticles can also be effective against eukaryotic infectious agents. Conversely, despite their significant potential in antimicrobial applications, the toxicity of metal oxide nanoparticles restricts their use in humans. However, recent studies infer that metal oxide nanoparticles have considerable potential to be the first-choice for antibacterial and antiparasitic applications in the future, provided that researchers can bring new ideas in order to cope with their main problem of toxicity.

  18. Asymmetric light reflectance from metal nanoparticle arrays on dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Huang, K.; Pan, W.; Zhu, J. F.; Li, J. C.; Gao, N.; Liu, C.; Ji, L.; Yu, E. T.; Kang, J. Y.

    2015-12-01

    Asymmetric light reflectance associated with localized surface plasmons excited in metal nanoparticles on a quartz substrate is observed and analyzed. This phenomenon is explained by the superposition of two waves, the wave reflected by the air/quartz interface and that reflected by the metal nanoparticles, and the resulting interference effects. Far field behavior investigation suggests that zero reflection can be achieved by optimizing the density of metal nanoparticles. Near field behavior investigation suggests that the coupling efficiency of localized surface plasmon can be additionally enhanced by separating the metal NPs from substrates using a thin film with refractive index smaller than the substrate. The latter behavior is confirmed via surface-enhanced Raman spectroscopy studies using metal nanoparticles on Si/SiO2 substrates.

  19. Asymmetric light reflectance from metal nanoparticle arrays on dielectric surfaces.

    PubMed

    Huang, K; Pan, W; Zhu, J F; Li, J C; Gao, N; Liu, C; Ji, L; Yu, E T; Kang, J Y

    2015-12-18

    Asymmetric light reflectance associated with localized surface plasmons excited in metal nanoparticles on a quartz substrate is observed and analyzed. This phenomenon is explained by the superposition of two waves, the wave reflected by the air/quartz interface and that reflected by the metal nanoparticles, and the resulting interference effects. Far field behavior investigation suggests that zero reflection can be achieved by optimizing the density of metal nanoparticles. Near field behavior investigation suggests that the coupling efficiency of localized surface plasmon can be additionally enhanced by separating the metal NPs from substrates using a thin film with refractive index smaller than the substrate. The latter behavior is confirmed via surface-enhanced Raman spectroscopy studies using metal nanoparticles on Si/SiO2 substrates.

  20. Near-field heat transfer between gold nanoparticle arrays

    SciTech Connect

    Phan, Anh D.; Phan, The-Long; Woods, Lilia M.

    2013-12-07

    The radiative heat transfer between gold nanoparticle layers is presented using the coupled dipole method. Gold nanoparticles are modelled as effective electric and magnetic dipoles interacting via electromagnetic fluctuations. The effect of higher-order multipoles is implemented in the expression of electric polarizability to calculate the interactions at short distances. Our findings show that the near-field radiation reduces as the radius of the nanoparticles is increased. Also, the magnetic dipole contribution to the heat exchange becomes more important for larger particles. When one layer is displayed in parallel with respect to the other layer, the near-field heat transfer exhibits oscillatory-like features due to the influence of the individual nanostructures. Further details about the effect of the nanoparticles size are also discussed.

  1. Nanostructured gold architectures formed through high pressure-driven sintering of spherical nanoparticle arrays.

    PubMed

    Wu, Huimeng; Bai, Feng; Sun, Zaicheng; Haddad, Raid E; Boye, Daniel M; Wang, Zhongwu; Huang, Jian Yu; Fan, Hongyou

    2010-09-22

    We have demonstrated pressure-directed assembly for preparation of a new class of chemically and mechanically stable gold nanostructures through high pressure-driven sintering of nanoparticle assemblies at room temperature. We show that under a hydrostatic pressure field, the unit cell dimension of a 3D ordered nanoparticle array can be reversibly manipulated allowing fine-tuning of the interparticle separation distance. In addition, 3D nanostructured gold architecture can be formed through high pressure-induced nanoparticle sintering. This work opens a new pathway for engineering and fabrication of different metal nanostructured architectures.

  2. Modulation of localized surface plasmon resonance for an array of Ag nanostructures layered with nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Shang, Zhenzhen; Huang, Haishen; Wan, Yuan; Deng, Luogen

    2016-08-01

    Sensitivity of the localized surface plasmon resonance (LSPR) for an array of Ag (silver) nanostructures layered with nematic liquid crystals (NLC) is investigated. Calculations are made by using finite-difference time-domain (FDTD) method under different geometrical and environmental parameters. Results show that the LSPR wavelength in this array can be controlled and tuned to infrared wavelength range by the rotation of the NLC optical-axis. The rotation of the array and the modifications to height of the NLC layer, the size and periods of the array can affect the sensitivity of the LSPR. The sensitivity is higher when the optical-axis is in xoz plane, than that for the optical-axis in xoy plane. An improved sensitivity has been obtained in the simulation.

  3. Internally dispersed synthesis of uniform silver nanoparticles via in situ reduction of [Ag(NH3)2]+ along natural microfibrillar substructures of cotton fiber

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Silver nanoparticles (Ag NPs) are known to have efficient antimicrobial properties, but the direct application of Ag NPs onto the surface of textiles has shown to be ineffective and raise environmental concerns because Ag NPs leach out during washing. In this study, non-leaching and stable Agcotton ...

  4. Nonlinear optical characterization of the Ag nanoparticles doped in polyvinyl alcohol films

    NASA Astrophysics Data System (ADS)

    Ghanipour, Mahshad; Dorranian, Davoud

    2015-06-01

    The effect of silver nanoparticles doped in polyvinyl alcohol (PVA) on the nonlinear optical properties of composite films is studied experimentally. Samples are PVA films of 0.14 mm thickness doped with different concentrations of silver nanoparticles. Nonlinear optical properties of doped polymer films are studied experimentally employing Z-scan techniques. Experiments are performed using the second harmonic of a continuous Nd-Yag laser beam at 532 nm wavelength and 45 mW power. The effect of nonlinear refractive index of samples is obtained by measuring the profile of propagated beam through the samples and their nonlinear refractive index is found to be negative. The nonlinear absorption coefficient is calculated using open aperture Z-scan data while its nonlinear refractive index is measured using the closed aperture Z-scan data, leads to measuring the third order susceptibility |χ(3)|. Real and imaginary parts of the third-order nonlinear optical susceptibility |χ(3)| are decrease with increasing the concentration of Ag nanoparticles in the films. The values of thermo-optic coefficient are determined at different concentrations of silver nanoparticles for samples.

  5. Microbial disinfection of water with endotoxin degradation by photocatalysis using Ag@TiO2 core shell nanoparticles.

    PubMed

    S, Sreeja; K, Vidya Shetty

    2016-09-01

    The studies on photocatalytic disinfection of water contaminated with Escherichia coli using Ag core and TiO2 shell (Ag@TiO2) nanoparticles under UV irradiation showed that these nanoparticles are very efficient in water disinfection both in their free and immobilised form. Complete disinfection of 40 × 10(8) CFU/mL could be achieved in 60 min with 0.4 g/L catalyst loading and in 35 min with 1 g/L catalyst loading. Ag@TiO2 nanoparticles were found to be superior to TiO2 nanoparticles in photocatalytic disinfection of water. Kinetics of disinfection followed Chick's law, and the pseudo-first-order rate constant was 0.0168 min(-1) for a catalyst loading of 0.1 g/L. Disinfection of water and degradation of endotoxins (harmful disinfection residual) occurred simultaneously during photocatalysis thereby making the treated water safe for use. Endotoxin degradation showed a shifting order of kinetics. The rate of photocatalysis with nanoparticles immobilised in cellulose acetate film was marginally lower as compared to that of free nanoparticles. Negligible Ag ion leakage and re-growth of cells post-photo-catalytic treatment of water confirmed that complete disintegration of E. coli occurred during photocatalysis making the treated water safe for use. Therefore, Ag@TiO2 nanoparticles have a potential for large-scale application in drinking water treatment plants and household purification units.

  6. Microfluidic separation of magnetic nanoparticles on an ordered array of magnetized micropillars

    NASA Astrophysics Data System (ADS)

    Orlandi, G.; Kuzhir, P.; Izmaylov, Y.; Alves Marins, J.; Ezzaier, H.; Robert, L.; Doutre, F.; Noblin, X.; Lomenech, C.; Bossis, G.; Meunier, A.; Sandoz, G.; Zubarev, A.

    2016-06-01

    Microfluidic separation of magnetic particles is based on their capture by magnetized microcollectors while the suspending fluid flows past the microcollectors inside a microchannel. Separation of nanoparticles is often challenging because of strong Brownian motion. Low capture efficiency of nanoparticles limits their applications in bioanalysis. However, at some conditions, magnetic nanoparticles may undergo field-induced aggregation that amplifies the magnetic attractive force proportionally to the aggregate volume and considerably increases nanoparticle capture efficiency. In this paper, we have demonstrated the role of such aggregation on an efficient capture of magnetic nanoparticles (about 80 nm in diameter) in a microfluidic channel equipped with a nickel micropillar array. This array was magnetized by an external uniform magnetic field, of intensity as low as 6-10 kA/m, and experiments were carried out at flow rates ranging between 0.3 and 30 μ L /min . Nanoparticle capture is shown to be mostly governed by the Mason number Ma, while the dipolar coupling parameter α does not exhibit a clear effect in the studied range, 1.4 < α < 4.5. The capture efficiency Λ shows a strongly decreasing Mason number behavior, Λ ∝M a-1.78 within the range 32 ≤ Ma ≤ 3250. We have proposed a simple theoretical model which considers destructible nanoparticle chains and gives the scaling behavior, Λ ∝M a-1.7 , close to the experimental findings.

  7. Microfluidic separation of magnetic nanoparticles on an ordered array of magnetized micropillars.

    PubMed

    Orlandi, G; Kuzhir, P; Izmaylov, Y; Alves Marins, J; Ezzaier, H; Robert, L; Doutre, F; Noblin, X; Lomenech, C; Bossis, G; Meunier, A; Sandoz, G; Zubarev, A

    2016-06-01

    Microfluidic separation of magnetic particles is based on their capture by magnetized microcollectors while the suspending fluid flows past the microcollectors inside a microchannel. Separation of nanoparticles is often challenging because of strong Brownian motion. Low capture efficiency of nanoparticles limits their applications in bioanalysis. However, at some conditions, magnetic nanoparticles may undergo field-induced aggregation that amplifies the magnetic attractive force proportionally to the aggregate volume and considerably increases nanoparticle capture efficiency. In this paper, we have demonstrated the role of such aggregation on an efficient capture of magnetic nanoparticles (about 80 nm in diameter) in a microfluidic channel equipped with a nickel micropillar array. This array was magnetized by an external uniform magnetic field, of intensity as low as 6-10 kA/m, and experiments were carried out at flow rates ranging between 0.3 and 30 μL/min. Nanoparticle capture is shown to be mostly governed by the Mason number Ma, while the dipolar coupling parameter α does not exhibit a clear effect in the studied range, 1.4 < α < 4.5. The capture efficiency Λ shows a strongly decreasing Mason number behavior, Λ∝Ma^{-1.78} within the range 32 ≤ Ma ≤ 3250. We have proposed a simple theoretical model which considers destructible nanoparticle chains and gives the scaling behavior, Λ∝Ma^{-1.7}, close to the experimental findings.

  8. Electron photoemission in plasmonic nanoparticle arrays: analysis of collective resonances and embedding effects

    NASA Astrophysics Data System (ADS)

    Zhukovsky, Sergei V.; Babicheva, Viktoriia E.; Uskov, Alexander V.; Protsenko, Igor E.; Lavrinenko, Andrei V.

    2014-09-01

    We theoretically study the characteristics of photoelectron emission in plasmonic nanoparticle arrays. Nanoparticles are partially embedded in a semiconductor, forming Schottky barriers at metal/semiconductor interfaces through which photoelectrons can tunnel from the nanoparticle into the semiconductor; photodetection in the infrared range, where photon energies are below the semiconductor band gap (insufficient for band-to-band absorption in semiconductor), is therefore possible. The nanoparticles are arranged in a sparse rectangular lattice so that the wavelength of the lattice-induced Rayleigh anomalies can overlap the wavelength of the localized surface plasmon resonance of the individual particles, bringing about collective effects from the nanoparticle array. Using full-wave numerical simulations, we analyze the effects of lattice constant, embedding depth, and refractive index step between the semiconductor layer and an adjacent transparent conductive oxide layer. We show that the presence of refractive index mismatch between media surrounding the nanoparticles disrupts the formation of a narrow absorption peak associated with the Rayleigh anomaly, so the role of collective lattice effects in the formation of plasmonic resonance is diminished. We also show that 5-20 times increase of photoemission can be achieved on embedding of nanoparticles without taking into account dynamics of ballistic electrons. The results obtained can be used to increase efficiency of plasmon-based photodetectors and photovoltaic devices. The results may provide clues to designing an experiment where the contributions of surface and volume photoelectric effects to the overall photocurrent would be defined.

  9. Enhanced optical second harmonic generation in hybrid polymer nanoassemblies based on coupled surface plasmon resonance of a gold nanoparticle array

    NASA Astrophysics Data System (ADS)

    Ishifuji, Miki; Mitsuishi, Masaya; Miyashita, Tokuji

    2006-07-01

    Effective utilization of coupled surface plasmon resonance from gold nanoparticles was demonstrated experimentally for optoelectronic applications based on second-order nonlinear optics. Hybrid polymer nanoassemblies were constructed by manipulating gold nanoparticle arrays with nonlinear optical active polymer nanosheets to investigate the second harmonic generation. The gold nanoparticle arrays were assembled on heterodeposited polymer nanosheets. The second harmonic light intensity was enhanced by a factor of 8. The observed enhancement was attributed to coupling of surface plasmons between two adjacent gold nanoparticles, thereby enhancing the surface electromagnetic field around the nanoparticles at the fundamental light wavelength (1064nm).

  10. Carbon nanotube supported PdAg nanoparticles for electrocatalytic oxidation of glycerol in anion exchange membrane fuel cells

    DOE PAGES

    Benipal, Neeva; Qi, Ji; Liu, Qi; ...

    2017-03-10

    Electro-oxidation of alcohol is the key reaction occurring at the anode of a direct alcohol fuel cell (DAFC), in which both reaction kinetics (rate) and selectivity (to deep oxidation products) need improvement to obtain higher power density and fuel utilization for a more efficient DAFC. We recently found that a PdAg bimetallic nanoparticle catalyst is more efficient than Pd for alcohol oxidation: Pd can facilitate deprotonation of alcohol in a base electrolyte, while Ag can promote intermediate aldehyde oxidation and cleavage of C-single bondC bond of C3 species to C2 species. Furthermore, a combination of the two active sites (Pdmore » and Ag) with two different functions, can simultaneously improve the reaction rates and deeper oxidation products of alcohols. In this continuing work, Pd, Ag mono, and bimetallic nanoparticles supported on carbon nanotubes (Ag/CNT, Pd/CNT, Pd1Ag1/CNT, and Pd1Ag3/CNT) were prepared using an aqueous-phase reduction method; they served as working catalysts for studying electrocatalytic oxidation of glycerol in an anion-exchange membrane-based direct glycerol fuel cell. Combined XRD, TEM, and HAADF-STEM analyses performed to fully characterize as-prepared catalysts suggested that they have small particle sizes: 2.0 nm for Pd/CNT, 2.3 nm for PdAg/CNT, 2.4 nm for PdAg3/CNT, and 13.9 nm for Ag/CNT. XPS further shows that alloying with Ag results in more metal state Pd presented on the surface, and this may be related to their higher direct glycerol fuel cell (DGFC) performances. Single DGFC performance and product analysis results show that PdAg bimetallic nanoparticles can not only improve the glycerol reaction rate so that higher power output can be achieved, but also facilitate deep oxidation of glycerol so that a higher faradaic efficiency and fuel utilization can be achieved along with optimal reaction conditions (increased base-to-fuel ratio). Half-cell electrocatalytic activity measurement and single fuel cell product analysis

  11. Synthesis of ZnS:Ag,Co water-soluble blue afterglow nanoparticles and application in photodynamic activation

    NASA Astrophysics Data System (ADS)

    Ma, Lun; Zou, Xiaoju; Hossu, Marius; Chen, Wei

    2016-08-01

    Silver and cobalt co-doped ZnS (ZnS:Ag,Co) water-soluble afterglow nanoparticles were synthesized using a wet chemistry method followed by aging at room temperature. The nanoparticles had a cubic zinc blende structure with average sizes of approximately 4 nm and emitted a blue fluorescence emission centered at 441 nm due to radiative transitions from surface defects to Ag+ luminescent centers. Intense afterglow emission peaking at 475 nm from the obtained nanoparticles was observed and was red-shifted compared to the fluorescence emission peak. X-ray photoelectron spectroscopy revealed a large increase of O/S ratio, indicating a surface oxidation process during aging. The S vacancies produced accordingly may contribute to form more electron traps and enhance afterglow. The ZnS:Ag,Co afterglow nanoparticles have a very low dark-toxicity and are applied as a light source for photodynamic therapy activation by conjugating with protoporphyrin together. Our preliminary study has shown that the ZnS:Ag,Co afterglow nanoparticles can significantly reduce the x-ray dosage used in activation and thus may be a very promising candidate for future x-ray excited photodynamic therapy in deep cancer treatment.

  12. Impact of Ag nanoparticle exposure on p,p'-DDE bioaccumulation by Cucurbita pepo (zucchini) and Glycine max (soybean).

    PubMed

    De La Torre-Roche, Roberto; Hawthorne, Joseph; Musante, Craig; Xing, Baoshan; Newman, Lee A; Ma, Xingmao; White, Jason C

    2013-01-15

    The effect of nanoparticle (NP), bulk, or ionic Ag exposure on dichlorodiphenyldichloroethylene (p,p'-DDE; DDT metabolite) accumulation by Glycine max L. (soybean) and Cucurbita pepo L. (zucchini) was investigated. The plants were grown in 125-mL jars of vermiculite amended with 500 or 2000 mg/L of bulk or NP Ag; ion controls at 5 and 20 mg/L were established. During 19 d of growth, plants were amended with solution containing 100 ng/mL of p,p'-DDE. Total shoot p,p'-DDE levels in non-Ag exposed G. max and C. pepo were 500 and 970 ng, respectively; total root DDE content was 13,700 and 20,300 ng, respectively. Ag decreased the p,p'-DDE content of G. max tissues by up to 40%, with NP exposure resulting in less contaminant uptake than bulk Ag. Total Ag content of exposed G. max ranged from 50.5 to 373 μg; NP-exposed plants had 1.9-2.2 times greater overall Ag than corresponding bulk particle treatments and also significantly greater relative Ag transport to shoot tissues. Bulk and NP Ag at 500 mg/L suppressed DDE uptake by C. pepo by 21-29%, although Ag exposure at 2000 mg/L had no impact on contaminant uptake. Similar to G. max , C. pepo whole plant Ag content ranged from 50.5 to 182 μg, with tissue element content generally being greater for NP exposed plants. These findings show that the Ag may significantly alter the accumulation and translocation of cocontaminants in agricultural systems. Notably, the cocontaminant interactions vary both with Ag particle size (NP vs bulk) and plant species. Future investigations will be needed to clarify the mechanisms responsible for the cocontaminant interactions and assess the impact on overall exposure and risk.

  13. A method for the formation of Pt metal nanoparticle arrays using nanosecond pulsed laser dewetting

    SciTech Connect

    Owusu-Ansah, Ebenezer; Horwood, Corie A.; Birss, Viola I.; Shi, Yujun J.; El-Sayed, Hany A.

    2015-05-18

    Nanosecond pulsed laser dewetting of Pt thin films, deposited on a dimpled Ta (DT) surface, has been studied here in order to form ordered Pt nanoparticle (NP) arrays. The DT substrate was fabricated via a simple electrochemical anodization process in a highly concentrated H{sub 2}SO{sub 4} and HF solution. Pt thin films (3–5 nm) were sputter coated on DT and then dewetted under vacuum to generate NPs using a 355 nm laser radiation (6–9 ns, 10 Hz). The threshold laser fluence to fully dewet a 3.5 nm thick Pt film was determined to be 300 mJ/cm{sup 2}. Our experiments have shown that shorter irradiation times (≤60 s) produce smaller nanoparticles with more uniform sizes, while longer times (>60 s) give large nanoparticles with wider size distributions. The optimum laser irradiation time of 1 s (10 pulses) has led to the formation of highly ordered Pt nanoparticle arrays with an average nanoparticle size of 26 ± 3 nm with no substrate deformation. At the optimum condition of 1 s and 500 mJ/cm{sup 2}, as many as 85% of the dewetted NPs were found neatly in the well-defined dimples. This work has demonstrated that pulsed laser dewetting of Pt thin films on a pre-patterned dimpled substrate is an efficient and powerful technique to produce highly ordered Pt nanoparticle arrays. This method can thus be used to produce arrays of other high-melting-point metal nanoparticles for a range of applications, including electrocatalysis, functionalized nanomaterials, and analytical purposes.

  14. A method for the formation of Pt metal nanoparticle arrays using nanosecond pulsed laser dewetting

    NASA Astrophysics Data System (ADS)

    Owusu-Ansah, Ebenezer; Horwood, Corie A.; El-Sayed, Hany A.; Birss, Viola I.; Shi, Yujun J.

    2015-05-01

    Nanosecond pulsed laser dewetting of Pt thin films, deposited on a dimpled Ta (DT) surface, has been studied here in order to form ordered Pt nanoparticle (NP) arrays. The DT substrate was fabricated via a simple electrochemical anodization process in a highly concentrated H2SO4 and HF solution. Pt thin films (3-5 nm) were sputter coated on DT and then dewetted under vacuum to generate NPs using a 355 nm laser radiation (6-9 ns, 10 Hz). The threshold laser fluence to fully dewet a 3.5 nm thick Pt film was determined to be 300 mJ/cm2. Our experiments have shown that shorter irradiation times (≤60 s) produce smaller nanoparticles with more uniform sizes, while longer times (>60 s) give large nanoparticles with wider size distributions. The optimum laser irradiation time of 1 s (10 pulses) has led to the formation of highly ordered Pt nanoparticle arrays with an average nanoparticle size of 26 ± 3 nm with no substrate deformation. At the optimum condition of 1 s and 500 mJ/cm2, as many as 85% of the dewetted NPs were found neatly in the well-defined dimples. This work has demonstrated that pulsed laser dewetting of Pt thin films on a pre-patterned dimpled substrate is an efficient and powerful technique to produce highly ordered Pt nanoparticle arrays. This method can thus be used to produce arrays of other high-melting-point metal nanoparticles for a range of applications, including electrocatalysis, functionalized nanomaterials, and analytical purposes.

  15. Uniformly dispersed and controllable ligand-free silver-nanoparticle-decorated TiO2 nanotube arrays with enhanced photoelectrochemical behaviors.

    PubMed

    Bian, Haidong; Shu, Xia; Zhang, Jianfang; Yuan, Bao; Wang, Yan; Liu, Lingjuan; Xu, Guangqing; Chen, Zhong; Wu, Yucheng

    2013-11-01

    Homogeneously dispersed silver nanoparticles (AgNPs) were successfully decorated onto the surface of TiO2 nanotube arrays (TNTA) by means of an in situ photoreduction method. TNTA films as supports exhibit excellent properties to prevent agglomeration of AgNPs, and they also avoid using polymer ligands, which is deleterious to enhancing the properties of the fabricated NPs. The silver particle size and its content could be controlled just by changing the immersion time. Detailed SEM and TEM analyses combined with energy-dispersive X-ray spectroscopy analyses with different immersion times (5, 10, 30, 60 min) have revealed the variation tendency. The prepared Ag/TNTA composite films were also characterized by XRD, X-ray photoelectron spectroscopy, and high-resolution TEM. The UV/Vis diffuse reflectance spectra displayed a redshift of the absorption peak with the growth of AgNPs. The photocurrent response and the photoelectrocatalytic degradation of methyl orange (MO) were used to evaluate the photoelectrochemical properties of the fabricated samples. The results showed that the photocurrent response and photoelectrocatalytic activity largely depended on the loaded Ag particle size and content. TNTA films with a diameter of 17.92 nm and silver content of 1.15 at% showed the highest photocurrent response and degradation rate of MO. The enhanced properties could be attributed to the synergistic effect between AgNPs and TiO2. To make good use of this effect, particle size and silver content should be well controlled to develop the electron charge and discharge process during the photoelectrical process. Neither smaller nor larger AgNPs caused decreased photoelectrical properties.

  16. Laser-induced periodic alignment of Ag nanoparticles in soda-lime glass.

    PubMed

    Goutaland, François; Colombier, Jean-Philippe; Sow, Mohamed Cherif; Ollier, Nadège; Vocanson, Francis

    2013-12-30

    One-, two- or three-dimensional arrays of closely spaced silver nanoparticles may lead to new optical properties, due to short or long range coupling between their resonant surface plasmons, so that the spatially controlled growth of silver nanoparticles provides an efficient way to tune their optical properties. Towards this way, we present here the periodic pattern of a glass surface with silver nanoparticles by continuous ultraviolet laser exposure. The formation of the 160 nm period pattern is well described by an interference-based model which agrees with the experimental conclusions, mainly obtained by various forms of microscopy. Statistical approach based on the autocorrelation function gives quantitative description about the quality of the order in the periodic structure and about the nanoparticles averaged diameter (80 nm). We also present the optical extinction spectrum of the Laser Induced Periodic Surface Structure (LIPSS)-containing area of the glass, which unusually shows several bands in the visible range. The period of 160 nm of the periodic structure is short enough to allow coupling between nanoparticles, which makes it a possible candidate for plasmon-based optical applications.

  17. Enhanced photoresponse of conformal TiO{sub 2}/Ag nanorod array-based Schottky photodiodes fabricated via successive glancing angle and atomic layer deposition

    SciTech Connect

    Haider, Ali; Biyikli, Necmi; Cansizoglu, Hilal; Cansizoglu, Mehmet Fatih; Karabacak, Tansel; Okyay, Ali Kemal

    2015-01-01

    In this study, the authors demonstrate a proof of concept nanostructured photodiode fabrication method via successive glancing angle deposition (GLAD) and atomic layer deposition (ALD). The fabricated metal-semiconductor nanorod (NR) arrays offer enhanced photoresponse compared to conventional planar thin-film counterparts. Silver (Ag) metallic NR arrays were deposited on Ag-film/Si templates by utilizing GLAD. Subsequently, titanium dioxide (TiO{sub 2}) was deposited conformally on Ag NRs via ALD. Scanning electron microscopy studies confirmed the successful formation of vertically aligned Ag NRs deposited via GLAD and conformal deposition of TiO{sub 2} on Ag NRs via ALD. Following the growth of TiO{sub 2} on Ag NRs, aluminum metallic top contacts were formed to complete the fabrication of NR-based Schottky photodiodes. Nanostructured devices exhibited a photo response enhancement factor of 1.49 × 10{sup 2} under a reverse bias of 3 V.

  18. Foliar exposure of the crop Lactuca sativa to silver nanoparticles: evidence for internalization and changes in Ag speciation.

    PubMed

    Larue, Camille; Castillo-Michel, Hiram; Sobanska, Sophie; Cécillon, Lauric; Bureau, Sarah; Barthès, Véronique; Ouerdane, Laurent; Carrière, Marie; Sarret, Géraldine

    2014-01-15

    The impact of engineered nanomaterials on plants, which act as a major point of entry of contaminants into trophic chains, is little documented. The foliar pathway is even less known than the soil-root pathway. However, significant inputs of nanoparticles (NPs) on plant foliage may be expected due to deposition of atmospheric particles or application of NP-containing pesticides. The uptake of Ag-NPs in the crop species Lactuca sativa after foliar exposure and their possible biotransformation and phytotoxic effects were studied. In addition to chemical analyses and ecotoxicological tests, micro X-ray fluorescence, micro X-ray absorption spectroscopy, time of flight secondary ion mass spectrometry and electron microscopy were used to localize and determine the speciation of Ag at sub-micrometer resolution. Although no sign of phytotoxicity was observed, Ag was effectively trapped on lettuce leaves and a thorough washing did not decrease Ag content significantly. We provide first evidence for the entrapment of Ag-NPs by the cuticle and penetration in the leaf tissue through stomata, for the diffusion of Ag in leaf tissues, and oxidation of Ag-NPs and complexation of Ag(+) by thiol-containing molecules. Such type of information is crucial for better assessing the risk associated to Ag-NP containing products.

  19. 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.

  20. DNA origami based Au-Ag-core-shell nanoparticle dimers with single-molecule SERS sensitivity

    NASA Astrophysics Data System (ADS)

    Prinz, J.; Heck, C.; Ellerik, L.; Merk, V.; Bald, I.

    2016-03-01

    DNA origami nanostructures are a versatile tool to arrange metal nanostructures and other chemical entities with nanometer precision. In this way gold nanoparticle dimers with defined distance can be constructed, which can be exploited as novel substrates for surface enhanced Raman scattering (SERS). We have optimized the size, composition and arrangement of Au/Ag nanoparticles to create intense SERS hot spots, with Raman enhancement up to 1010, which is sufficient to detect single molecules by Raman scattering. This is demonstrated using single dye molecules (TAMRA and Cy3) placed into the center of the nanoparticle dimers. In conjunction with the DNA origami nanostructures novel SERS substrates are created, which can in the future be applied to the SERS analysis of more complex biomolecular targets, whose position and conformation within the SERS hot spot can be precisely controlled.DNA origami nanostructures are a versatile tool to arrange metal nanostructures and other chemical entities with nanometer precision. In this way gold nanoparticle dimers with defined distance can be constructed, which can be exploited as novel substrates for surface enhanced Raman scattering (SERS). We have optimized the size, composition and arrangement of Au/Ag nanoparticles to create intense SERS hot spots, with Raman enhancement up to 1010, which is sufficient to detect single molecules by Raman scattering. This is demonstrated using single dye molecules (TAMRA and Cy3) placed into the center of the nanoparticle dimers. In conjunction with the DNA origami nanostructures novel SERS substrates are created, which can in the future be applied to the SERS analysis of more complex biomolecular targets, whose position and conformation within the SERS hot spot can be precisely controlled. Electronic supplementary information (ESI) available: Additional information about materials and methods, designs of DNA origami templates, height profiles, additional SERS spectra, assignment of DNA

  1. A reusable laser wrapped graphene-Ag array based SERS sensor for trace detection of genomic DNA methylation.

    PubMed

    Ouyang, Lei; Hu, Yaowu; Zhu, Lihua; Cheng, Gary J; Irudayaraj, Joseph

    2017-06-15

    Methylation is an important epigenetic DNA modification that governs gene expression. The genomic level of methylated DNA and its derivatives may serve as important indicators for the initiation and progression of cancers among other diseases. In this effort we propose a new laser wrapped graphene-Ag array as a highly sensitive Surface-enhanced Raman spectroscopy (SERS) sensor for the detection of methylated DNA (5-methylcytosine, 5mC) and its oxidation derivatives namely 5-hydroxymethylcytosine (5-hmC) and 5-carboxylcytosine (5-caC). Excellent sensitivity and reproducibility were achieved with the laser wrapped graphene-Ag array as a substrate, with the graphene layer acting as an enhancer of the SERS signal due to the effective coupling of the electromagnetic field. In summary, fast (less than 60min) and sensitive (at a limit of detection 0.2pgμL(-1), ie. 1.8pmolL(-1)) detection of methylated DNA and its derivatives was realized with the ability to distinguish methylation levels from a mixture at 0.1%. The sensitive and accurate detection in DNA extracted from cells was also accomplished. Furthermore our graphene wrapped approach circumvents the direct interaction between Ag array and the analytes, thus improving the reusability of the SERS substrate even after five cycles of use.

  2. Evolution of ion-induced nanoparticle arrays on GaAs surfaces

    NASA Astrophysics Data System (ADS)

    Kang, M.; Beskin, I.; Al-Heji, A. A.; Shende, O.; Huang, S.; Jeon, S.; Goldman, R. S.

    2014-05-01

    We have examined the evolution of irradiation-induced Ga nanoparticle (NP) arrays on GaAs surfaces. Focused-ion-beam irradiation of pre-patterned GaAs surfaces induces monotonic increases in the NP volume and aspect ratio up to a saturation ion dose, independent of NP location within the array. Beyond the saturation ion dose, the NP volume continues to increase monotonically while the NP aspect ratio decreases monotonically. In addition, the NP volumes (aspect ratios) are highest (lowest) for the corner NPs. We discuss the relative influences of bulk and surface diffusion on the evolution of Ga NP arrays.

  3. 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.

  4. Design and Implementation of Noble Metal Nanoparticle Cluster Arrays for Plasmon Enhanced Biosensing

    PubMed Central

    Yan, Bo; Boriskina, Svetlana V.; Reinhard, Björn M.

    2011-01-01

    Nanoparticle Cluster Arrays (NCAs) are a class of electromagnetic materials that comprise chemically defined nanoparticles assembled into clusters of defined size in an extended deterministic arrangement. NCAs are fabricated through integration of chemically synthesized building blocks into predefined patterns using a hybrid top-down/bottom-up fabrication approach that overcomes some of the limitations of conventional top-down fabrication methods with regard to minimum available feature size and structural complexity. NCAs can sustain near-field interactions between nanoparticles within individual clusters as well as between entire neighboring clusters. The availability of near-field interactions on multiple length scales - together with the ability to further enhance the coupled plasmon modes through photonic modes in carefully designed array morphologies - leads to a multiscale cascade electromagnetic field enhancement throughout the array. This feature article introduces the design and fabrication fundamentals of NCAs and characterizes the electromagnetic coupling mechanisms in the arrays. Furthermore, it reviews how the optical properties of NCAs can be tuned through the size and shape of the nanoparticle building blocks and the geometry, size, and separation of the assembled clusters. NCAs have potential applications in many different areas; this feature article focuses on plasmon enhanced biosensing and surface enhanced Raman spectroscopy (SERS), in particular. PMID:22299057

  5. Trapping and Detection of Nanoparticles and Cells Using a Parallel Photonic Nanojet Array.

    PubMed

    Li, Yuchao; Xin, Hongbao; Liu, Xiaoshuai; Zhang, Yao; Lei, Hongxiang; Li, Baojun

    2016-06-28

    In advanced nanoscience, there is a strong desire to trap and detect nanoscale objects with high-throughput, single-nanoparticle resolution and high selectivity. Although emerging optical methods have enabled the selective trapping and detection of multiple micrometer-sized objects, it remains a great challenge to extend this functionality to the nanoscale. Here, we report an approach to trap and detect nanoparticles and subwavelength cells at low optical power using a parallel photonic nanojet array produced by assembling microlenses on an optical fiber probe. Benefiting from the subwavelength confinement of the photonic nanojets, tens to hundreds of nanotraps were formed in three dimensions. Backscattering signals were detected in real time with single-nanoparticle resolution and enhancement factors of 10(3)-10(4). Selective trapping of nanoparticles and cells from a particle mixture or human blood solution was demonstrated using the nanojet array. The developed nanojet array is potentially a powerful tool for nanoparticle assembly, biosensing, single-cell analysis, and optical sorting.

  6. Photodegradation of nalidixic acid assisted by TiO(2) nanorods/Ag nanoparticles based catalyst.

    PubMed

    Petronella, F; Diomede, S; Fanizza, E; Mascolo, G; Sibillano, T; Agostiano, A; Curri, M L; Comparelli, R

    2013-05-01

    Two different nanosized TiO2-based catalysts supported onto glass with tailored photocatalytic properties upon irradiation by UV light were successfully employed for the degradation of nalidixid acid, a widely diffused antibacterial agent of environmental relevance known to be non-biodegradable. Anatase rod-like TiO2 nanocrystals (TiO2NRs) and a semiconductor oxide-noble metal nanocomposite TiO2 NRs/Ag nanoparticles (NPs), synthesized by colloidal chemistry routes, were cast onto glass slide and employed as photocatalysts. A commercially available catalyst (TiO2 P25), also immobilized onto a glass slide, was used as a reference material. It was found that both TiO2 NRs/Ag NPs composite and TiO2 NRs demonstrated a photocatalytic efficiency significantly higher than the reference TiO2 P25. Specifically, TiO2 NRs/Ag NPs showed a photoactivity in nalidixic acid degradation 14 times higher than TiO2 P25 and 4 times higher than bare TiO2 NRs in the first 60min of reaction. Several by-products were identified by HPLC-MS along the nalidixic acid degradation, thus getting useful insight on the degradation pathway. All the identified by-products resulted completely removed after 6h of reaction.

  7. Suspension arrays based on nanoparticle-encoded microspheres for high-throughput multiplexed detection

    PubMed Central

    Leng, Yuankui

    2017-01-01

    Spectrometrically or optically encoded microsphere based suspension array technology (SAT) is applicable to the high-throughput, simultaneous detection of multiple analytes within a small, single sample volume. Thanks to the rapid development of nanotechnology, tremendous progress has been made in the multiplexed detecting capability, sensitivity, and photostability of suspension arrays. In this review, we first focus on the current stock of nanoparticle-based barcodes as well as the manufacturing technologies required for their production. We then move on to discuss all existing barcode-based bioanalysis patterns, including the various labels used in suspension arrays, label-free platforms, signal amplification methods, and fluorescence resonance energy transfer (FRET)-based platforms. We then introduce automatic platforms for suspension arrays that use superparamagnetic nanoparticle-based microspheres. Finally, we summarize the current challenges and their proposed solutions, which are centered on improving encoding capacities, alternative probe possibilities, nonspecificity suppression, directional immobilization, and “point of care” platforms. Throughout this review, we aim to provide a comprehensive guide for the design of suspension arrays, with the goal of improving their performance in areas such as multiplexing capacity, throughput, sensitivity, and cost effectiveness. We hope that our summary on the state-of-the-art development of these arrays, our commentary on future challenges, and some proposed avenues for further advances will help drive the development of suspension array technology and its related fields. PMID:26021602

  8. Self-Assembled Array of Tethered Manganese Oxide Nanoparticles for the Next Generation of Energy Storage

    NASA Astrophysics Data System (ADS)

    Stevens, Tyler E.; Pearce, Charles J.; Whitten, Caleah N.; Grant, Richard P.; Monson, Todd C.

    2017-03-01

    Many challenges must be overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. To begin addressing these challenges (and others), we report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers. The tethered array of nanoparticles, MnO in this case, bound directly to a gold current collector via short conducting linkages eliminates the need for fillers, resulting in a material which achieves 99.9% active material by mass (excluding the current collector). This strategy is expected to be both scalable as well as effective for alternative tethers and metal oxide nanoparticles.

  9. Self-Assembled Array of Tethered Manganese Oxide Nanoparticles for the Next Generation of Energy Storage

    PubMed Central

    Stevens, Tyler E.; Pearce, Charles J.; Whitten, Caleah N.; Grant, Richard P.; Monson, Todd C.

    2017-01-01

    Many challenges must be overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. To begin addressing these challenges (and others), we report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers. The tethered array of nanoparticles, MnO in this case, bound directly to a gold current collector via short conducting linkages eliminates the need for fillers, resulting in a material which achieves 99.9% active material by mass (excluding the current collector). This strategy is expected to be both scalable as well as effective for alternative tethers and metal oxide nanoparticles. PMID:28287183

  10. Electrochemical oxidation of methanol on Pt nanoparticles composited MnO 2 nanowire arrayed electrode

    NASA Astrophysics Data System (ADS)

    Zhao, Guang-Yu; Li, Hu-Lin

    2008-03-01

    By use of the membrane-template synthesis route, MnO 2 nanowire arrayed electrodes are successfully synthesized by means of the anodic deposition technique. The Pt nanoparticles composited MnO 2 nanowire arrayed electrodes (PME) are obtained through depositing Pt on MnO 2 nanowire arrayed electrode by cathode deposition technique. For comparison of electrochemical performance, Pt nanowire arrayed electrodes which have the same amount of Pt with PME are also prepared. The electro-oxidation of methanol on PME and Pt nanowire arrayed electrodes is investigated at room temperature by cyclic voltammetry, which show that about 110 mV decreased overpotential and 2.1-fold enhanced votammetric current are achieved on PME. The chronoamperometry result demonstrates that the resistance to carbon monoxide for PME is improved.

  11. 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.

  12. The effect of Fe segregation on the photocatalytic growth of