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Sample records for ag nps decorated

  1. Decorating CdTe QD-Embedded Mesoporous Silica Nanospheres with Ag NPs to Prevent Bacteria Invasion for Enhanced Anticounterfeit Applications.

    PubMed

    Gao, Yangyang; Dong, Qigeqi; Lan, Shi; Cai, Qian; Simalou, Oudjaniyobi; Zhang, Shiqi; Gao, Ge; Chokto, Harnoode; Dong, Alideertu

    2015-05-13

    Quantum dots (QDs) as potent candidates possess advantageous superiority in fluorescence imaging applications, but they are susceptible to the biological circumstances (e.g., bacterial environment), leading to fluorescence quenching or lose of fluorescent properties. In this work, CdTe QDs were embedded into mesoporous silica nanospheres (m-SiO2 NSs) for preventing QD agglomeration, and then CdTe QD-embedded m-SiO2 NSs (m-SiO2/CdTe NSs) were modified with Ag nanoparticles (Ag NPs) to prevent bacteria invasion for enhanced anticounterfeit applications. The m-SiO2 NSs, which serve as intermediate layers to combine CdTe QDs with Ag NPs, help us establish a highly fluorescent and long-term antibacterial system (i.e., m-SiO2/CdTe/Ag NSs). More importantly, CdTe QD-embedded m-SiO2 NSs showed fluorescence quenching when they encounter bacteria, which was avoided by attaching Ag NPs outside. Ag NPs are superior to CdTe QDs for preventing bacteria invasion because of the structure (well-dispersed Ag NPs), size (small diameter), and surface charge (positive zeta potentials) of Ag NPs. The plausible antibacterial mechanisms of m-SiO2/CdTe/Ag NSs toward both Gram-positive and Gram-negative bacteria were established. As for potential applications, m-SiO2/CdTe/Ag NSs were developed as fluorescent anticounterfeiting ink for enhanced imaging applications.

  2. 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

  3. Enhanced conductivity of rGO/Ag NPs composites for electrochemical immunoassay of prostate-specific antigen.

    PubMed

    Han, Lu; Liu, Cheng-Mei; Dong, Shi-Lei; Du, Cai-Xia; Zhang, Xiao-Yong; Li, Lu-Hai; Wei, Yen

    2017-01-15

    Electrode materials play a vital role in the development of electrochemical immunosensors (EIs), particularly of label-free EIs. In this study, composites containing reduced graphene oxide with silver nanoparticles (rGO/Ag NPs) were synthesized using binary reductants, i.e. hydrazine hydrate and sodium citrate. Due to the fact that graphene oxide (GO) was fully restored to rGO, and rGO stacking was effectively inhibited by insertion of small Ag NPs between the graphene sheets, the electrical conductivity of rGO/Ag NPs composites was significantly improved compared to rGO alone, with an enhancement factor of 346% at 40wt% of rGO. Moreover, the conducting path between rGO and Ag NPs formed because the structural defects in rGO were effectively repaired by decoration with Ag NPs. Subsequently, based on a screen-printed three-electrode system, a label-free EI for detecting prostate-specific antigen (PSA) was constructed using rGO/Ag NPs composites as a support material. The fabricated EIs demonstrated a wide linear response range (1.0-1000ng/ml), low detection limit (0.01ng/ml) and excellent specificity, reproducibility and stability. Thus, the proposed EIs based on rGO/Ag NPs composites can be easily extended for the ultrasensitive detection of different protein biomarkers.

  4. Instantly AgNPs deposition through facile solventless technique for poly-functional cotton fabrics.

    PubMed

    Emam, Hossam E; Saleh, N H; Nagy, Khaled S; Zahran, M K

    2016-03-01

    Nowadays, functional clothes are employed for human body protection in addition to be fashionable clothes. Hence functionalization of clothes increases the attention of scientists and business. In the current study, poly-functional cotton fabric was carried out by instantly deposition of AgNPs using two solventless techniques namely; sorption and padding. Sorption technique was exhibited extremely high efficiency than padding one by ca. 10 times. By using the same concentrations of AgNO3, Ag content was ranged 69.3-6094.8 mg/kg and 33.8-609.3 mg/kg for sorption and padding, respectively. After AgNPs deposition, fabrics color was turned to gray-reddish yellow. By applying 5912.3 mgAg/kg fabric, bacterial reduction and UPF value were reached 99% and 12.59. Bacterial reduction and UPF were lessened to 90% and 10.19 after 20 washings. These findings proved that the direct AgNPs deposition into cotton using solventless/sorption technique is applicable in manufacturing of antibacterial/UV resistant fabrics with acquired decorative color.

  5. The preparation and antibacterial effects of dopa-cotton/AgNPs

    NASA Astrophysics Data System (ADS)

    Xu, Hong; Shi, Xue; Ma, Hui; Lv, Yihang; Zhang, Linping; Mao, Zhiping

    2011-05-01

    Silver nanoparticles (AgNPs) have been known to have powerful antibacterial activity. In this paper, in situ generation of AgNPs on the surface of dopamine modified cotton fabrics (dopa-cotton/AgNPs) in aqueous solution under room temperature is presented. X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscope (FE-SEM) were used to analyze the surface chemical composition and the morphology of the modified cotton fabrics, respectively. The results indicated that the surface of cotton fabrics was successfully coated with polydopamine and AgNPs. The cotton fabrics with AgNPs showed durable antibacterial activity.

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

    PubMed

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

    2015-01-01

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

  7. Improvement of polypyrrole nanowire devices by plasmonic space charge generation: high photocurrent and wide spectral response by Ag nanoparticle decoration

    NASA Astrophysics Data System (ADS)

    Lee, S.-H.; Bae, J.; Lee, S. W.; Jang, J.-W.

    2015-10-01

    In this study, improvement of the opto-electronic properties of non-single crystallized nanowire devices with space charges generated by localized surface plasmon resonance (LSPR) is demonstrated. The photocurrent and spectral response of single polypyrrole (PPy) nanowire (NW) devices are increased by electrostatically attached Ag nanoparticles (Ag NPs). To take advantage of plasmon-exciton coupling in the photocurrent of the device, 80 nm of Ag NPs (454 nm = λmax) were chosen for matching the maximum absorption with PPy NWs (442 nm = λmax). The photocurrent density is remarkably improved, up to 25.3 times (2530%), by the Ag NP decoration onto the PPy NW (PPyAgNPs NW) under blue light (λ = 425-475 nm) illumination. In addition, the PPyAgNPs NW shows a photocurrent decay time twice that of PPy NW, as well as an improved spectral response of the photocurrent. The improved photocurrent efficiency, decay time, and spectral response resulted from the space charges generated by the LSPR of Ag NPs. Furthermore, the increasing exponent (m) of the photocurrent (JPC ~ Vm) and finite-differential time domain (FDTD) simulation straightforwardly indicate relatively large plasmonic space charge generation under blue light illumination. These results prove that the performance of non-single crystallized polymer nanowire devices can also be improved by plasmonic enhancement.In this study, improvement of the opto-electronic properties of non-single crystallized nanowire devices with space charges generated by localized surface plasmon resonance (LSPR) is demonstrated. The photocurrent and spectral response of single polypyrrole (PPy) nanowire (NW) devices are increased by electrostatically attached Ag nanoparticles (Ag NPs). To take advantage of plasmon-exciton coupling in the photocurrent of the device, 80 nm of Ag NPs (454 nm = λmax) were chosen for matching the maximum absorption with PPy NWs (442 nm = λmax). The photocurrent density is remarkably improved, up to 25.3 times

  8. A highly sensitive hydrogen peroxide sensor based on (Ag-Au NPs)/poly[o-phenylenediamine] modified glassy carbon electrode.

    PubMed

    Shamsipur, Mojtaba; Karimi, Ziba; Amouzadeh Tabrizi, Mahmoud

    2015-11-01

    Herein, the poly(o-phenylenediamine) decorated with gold-silver nanoparticle (Ag-Au NPs) nanocomposite modified glassy carbon was used for the determination of hydrogen peroxide. Electrochemical experiments indicated that the proposed sensor possesses an excellent sensitivity toward the reduction of hydrogen peroxide. The resulting sensor exhibited a good response to hydrogen peroxide over linear range from 0.2 to 60.0μM with a limit of detection of 0.08μM, good reproducibility, long-term stability and negligible interference from ascorbic acid, uric acid and dopamine. The proposed sensor was successfully applied to the determination of hydrogen peroxide in human serum sample.

  9. Improvement of polypyrrole nanowire devices by plasmonic space charge generation: high photocurrent and wide spectral response by Ag nanoparticle decoration.

    PubMed

    Lee, S-H; Bae, J; Lee, S W; Jang, J-W

    2015-11-07

    In this study, improvement of the opto-electronic properties of non-single crystallized nanowire devices with space charges generated by localized surface plasmon resonance (LSPR) is demonstrated. The photocurrent and spectral response of single polypyrrole (PPy) nanowire (NW) devices are increased by electrostatically attached Ag nanoparticles (Ag NPs). To take advantage of plasmon-exciton coupling in the photocurrent of the device, 80 nm of Ag NPs (454 nm = λmax) were chosen for matching the maximum absorption with PPy NWs (442 nm = λmax). The photocurrent density is remarkably improved, up to 25.3 times (2530%), by the Ag NP decoration onto the PPy NW (PPyAgNPs NW) under blue light (λ = 425-475 nm) illumination. In addition, the PPyAgNPs NW shows a photocurrent decay time twice that of PPy NW, as well as an improved spectral response of the photocurrent. The improved photocurrent efficiency, decay time, and spectral response resulted from the space charges generated by the LSPR of Ag NPs. Furthermore, the increasing exponent (m) of the photocurrent (JPC ∼ V(m)) and finite-differential time domain (FDTD) simulation straightforwardly indicate relatively large plasmonic space charge generation under blue light illumination. These results prove that the performance of non-single crystallized polymer nanowire devices can also be improved by plasmonic enhancement.

  10. Improved nonlinear optical and optical limiting properties in non-covalent functionalized reduced graphene oxide/silver nanoparticle (NF-RGO/Ag-NPs) hybrid

    NASA Astrophysics Data System (ADS)

    Sakho, El hadji Mamour; Oluwafemi, Oluwatobi S.; Sreekanth, P.; Philip, Reji; Thomas, Sabu; Kalarikkal, Nandakumar

    2016-08-01

    Nonlinear optical (NLO) response under near infrared (800 nm) and visible (532 nm) laser excitations, of 100 fs (fs) and 5 ns (ns) pulse durations respectively, of reduced graphene oxide (RGO), non-covalent functionalized reduced graphene oxide (NF-RGO) and NF-RGO decorated with various concentration of silver nanoparticles (NF-RGO/Ag-NPs) have been investigated using the Open-aperture Z-Scan technique. For both femtosecond and nanosecond laser excitations, the studied graphene-based materials exhibit good nonlinear optical power limiting properties (OL), with NF-RGO/Ag-NPs sample prepared with 0.1 M AgNO3 showing the best nonlinear optical properties. For the ns regime, the optical limiting threshold decreased from 8.3 J/cm2 in NF-RGO to 4.3 J/cm2 in NF-RGO/Ag-NPs, while at fs regime, the nonlinear absorption coefficient (β) was found to increase with decrease in concentration of Ag-NPs in the hybrid. Two-photon absorption (2 PA) in combination with saturable absorption (SA) in femtosecond regime, and reverse saturable absorption (RSA) along with saturable absorption (SA) in the nanosecond regime, are responsible for the observed nonlinear optical absorption (NLA) behavior in these materials. These findings show that the as-synthesized NF-RGO/Ag-NPs hybrid is a relatively better material for nonlinear optical limiting applications.

  11. Fabrication LSPR sensor chip of Ag NPs and their biosensor application based on interparticle coupling

    NASA Astrophysics Data System (ADS)

    Ghodselahi, T.; Neishaboorynejad, T.; Arsalani, S.

    2015-07-01

    We introduce a simple method to synthesize localized surface plasmon resonance (LSPR) sensor chip of Ag NPs on the hydrogenated amorphous carbon by co-deposition of RF-Sputtering and RF-PECVD. The X-ray photoelectron spectroscopy revealed the content of Ag and C atoms. X-ray diffraction profile and atomic force microscopy indicate that the Ag NPs have fcc crystal structure and spherical shape and by increasing deposition time, particle sizes do not vary and only Ag NPs aggregation occurs, resulting in LSPR wavelength shift. Firstly, by increasing Ag NPs content, in-plan interparticles coupling is dominant and causes redshift in LSPR. At the early stage of agglomeration, out-plane coupling occurs and in-plane coupling is reduced, resulting a blueshift in the LSPR. By further increasing of Ag NPs content, agglomeration is completed on the substrate and in-plan coupling rises, resulting significant redshift in the LSPR. Results were used to implement biosensor application of chips. Detection of DNA primer at fM concentration was achieved based on breaking interparticles coupling of Ag NPs. A significant wavelength shift sensitivity of 30 nm and a short response time of 30 min were obtained, where both of these are prerequisite for biosensor applications.

  12. Improvement of polypyrrole nanowire devices by plasmonic space charge generation: high photocurrent and wide spectral response by Ag nanoparticle decoration

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Hoon; Lee, Seung Woo; Jang, Jaw-Won

    In this study, improvement of the opto-electronic properties of non-single crystallized nanowire devices with space charges generated by localized surface plasmon resonance (LSPR) is demonstrated. The photocurrent and spectral response of single polypyrrole (PPy) nanowire (NW) devices are increased by electrostatically attached Ag nanoparticles (Ag NPs). The photocurrent density is remarkably improved, up to 25.3 times, by the Ag NP decoration onto the PPy NW (PPyAgNPs NW) under blue light illumination. In addition, the PPyAgNPs NW shows a photocurrent decay time twice that of PPy NW, as well as an improved spectral response of the photocurrent. The improved photocurrent efficiency, decay time, and spectral response resulted from the space charges generated by the LSPR of Ag NPs. Furthermore, the increasing exponent (m) of the photocurrent (JPC ~Vm) and finite-differential time domain (FDTD) simulation straightforwardly indicate relatively large plasmonic space charge generation. Supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (no. 2013K1A3A1A32035429 and 2015R1A1A1A05027681).

  13. Highly Reproducible Ag NPs/CNT-Intercalated GO Membranes for Enrichment and SERS Detection of Antibiotics.

    PubMed

    Qu, Lu Lu; Liu, Ying-Ya; Liu, Ming-Kai; Yang, Guo-Hai; Li, Da-Wei; Li, Hai-Tao

    2016-10-05

    The increasing pollution of aquatic environments by antibiotics makes it necessary to develop efficient enrichment and sensitive detection methods for environmental antibiotics monitoring. In this work, silver nanoparticles and carbon nanotube-intercalated graphene oxide laminar membranes (Ag NPs/CNT-GO membranes) were successfully prepared for enrichment and surface-enhanced Raman scattering (SERS) detection of antibiotics. The prepared Ag NPs/CNT-GO membranes exhibited a high enrichment ability because of the π-π stacking and electrostatic interactions of GO toward antibiotic molecules, which enhanced the sensitivity of SERS measurements and enabled the antibiotics to be determined at sub-nM concentrations. In addition, the nanochannels created by the intercalation of CNTs into GO layers resulted in an 8-fold enhancement in the water permeance of Ag NPs/CNT-GO membranes compared to that of pure GO membranes. More importantly, the Ag NPs/CNT-GO membranes exhibited high reproducibility and long-term stability. The spot-to-spot variation in SERS intensity was less than 15%, and the SERS performance was maintained for at least 70 days. The Ag NPs/CNT-GO membranes were also used for SERS detection of antibiotics in real samples; the results showed that the characteristic peaks of antibiotics were obviously recognizable. Thus, the sensitive SERS detection of antibiotics based on Ag NPs/CNT-GO offers great potential for practical applications in environmental analysis.

  14. Novel Asymmetric Wettable AgNPs/Chitosan Wound Dressing: In Vitro and In Vivo Evaluation.

    PubMed

    Liang, Donghui; Lu, Zhong; Yang, Hao; Gao, Jingting; Chen, Rong

    2016-02-17

    A novel silver nanoparticles (AgNPs)/chitosan composite dressing with asymmetric wettability surfaces was successfully prepared via a simple two-step method for biomedical applications as wound healing materials. First, AgNPs were assembled into the chitosan sponge which was prepared by lyophilization process. Then one side of the sponge was modified by a thin layer of stearic acid. The incorporation of AgNPs into chitosan dressing could enhance the antibacterial activity against drug-sensitive and drug-resistant pathogenic bacteria. The asymmetric surface modification endows the dressing with both highly hydrophobic property and inherent hydrophilic nature of chitosan. The hydrophobic surface of the dressing shows waterproof and antiadhesion for contaminant properties, whereas the hydrophilic surface preserves its water-absorbing capability and efficiently inhibits the growth of bacteria. Furthermore, the AgNPs/chitosan composite dressing displays improved moisture retention and blood clotting ability compared to the unmodified dressings. Cytocompatibility test evaluated in vitro and in a wound infection model illustrates the nontoxic nature of the composite dressing. More importantly, the in vivo wound healing model evaluation in mice reveals that the asymmetric AgNPs/chitosan dressing promotes the wound healing and accelerates the reepithelialization and collagen deposition. The silver accumulation in mice body treated by the composite dressing is far lower than that of the clinically used Acasin nanosilver dressing treated mice. This work indicates the huge potential of the novel AgNPs/chitosan wound dressing with asymmetrical wettability for clinical use.

  15. 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.

  16. Toxicokinetics of Ag in the terrestrial isopod Porcellionides pruinosus exposed to Ag NPs and AgNO₃ via soil and food.

    PubMed

    Tourinho, Paula S; van Gestel, Cornelis A M; Morgan, A John; Kille, Peter; Svendsen, Claus; Jurkschat, Kerstin; Mosselmans, J Fred W; Soares, Amadeu M V M; Loureiro, Susana

    2016-03-01

    Silver nanoparticles (Ag NPs) have been used in numerous consumer products and may enter the soil through the land application of biosolids. However, little is known about the relationship between Ag NP exposure and their bioavailability for soil organisms. This study aims at comparing the uptake and elimination kinetics of Ag upon exposures to different Ag forms (NPs and ionic Ag (as AgNO3)) in the isopod Porcellionides pruinosus. Isopods were exposed to contaminated Lufa 2.2 soil or alder leaves as food. Uptake and elimination rate constants for soil exposure did not significantly differ between Ag NPs and ionic Ag at 30 and 60 mg Ag/kg. For dietary exposure, the uptake rate constant was up to 5 times higher for Ag NPs than for AgNO3, but this was related to feeding activity and exposure concentrations, while no difference in the elimination rate constants was found. When comparing both routes, dietary exposure resulted in lower Ag uptake rate constants but elimination rate constants did not differ. A fast Ag uptake was observed from both routes and most of the Ag taken up seemed not to be eliminated. Synchrotron X-ray fluorescence showed Ag in the S-cells of the hepatopancreas, thus supporting the observations from the kinetic experiment (i.e. low elimination). In addition, our results show that isopods have an extremely high Ag accumulation capacity, suggesting the presence of an efficient Ag storage compartment.

  17. Improved thermal conductivity of Ag decorated carbon nanotubes water based nanofluids

    NASA Astrophysics Data System (ADS)

    Farbod, Mansoor; Ahangarpour, Ameneh

    2016-12-01

    The effect of Ag decoration of carbon nanotubes on thermal conductivity enhancement of Ag decorated MWCNTs water based nanofluids has been investigated. The pristine and functionalized MWCNTs were decorated with Ag nanoparticles by mass ratios of 1%, 2% and 4% and used to prepare water based nanofluids with 0.1 vol.%. An enhancement of 1-20.4 percent in thermal conductivity was observed. It was found that the decoration of functionalized MWCNTs can increase the thermal conductivity about 0.16-8.02 percent compared to the undecorated ones. The maximum enhancement of 20.4% was measured for the sample containing 4 wt.% Ag at 40 °C.

  18. Green Synthesis of AgNPs Stabilized with biowaste and their antimicrobial activities

    PubMed Central

    Jasuja, Nakuleshwar Dut; Gupta, Deepak Kumar; Reza, Mohtashim; Joshi, Suresh C.

    2014-01-01

    In the present study, rapid reduction and stabilization of Ag+ ions with different NaOH molar concentration (0.5 mM, 1.0 mM and 1.5 mM) has been carried out in the aqueous solution of silver nitrate by the bio waste peel extract of P.granatum. Generally, chemical methods used for the synthesis of AgNPs are quite toxic, flammable and have adverse effect in medical application but green synthesis is a better option due to eco-friendliness, non-toxicity and safe for human. Stable AgNPs were synthesized by treating 90 mL aqueous solution of 2 mM AgNO3 with the 5 mL plant peels extract (0.4% w/v) at different NaOH concentration (5 mL). The synthesized AgNPs were characterized by UV-Vis spectroscopy, TEM and SEM. Further, antimicrobial activities of AgNPs were performed on Gram positive i.e. Staphylococcus aureus, Bacillus subtilius and Gram negative i.e. E. coli, Pseudomonas aeruginosa bacteria. The AgNPs synthesized at 1.5 mM NaOH concentration had shown maximum zone of inhibition (ZOI) i.e. 49 ± 0.64 in E. coli, whereas Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilius had shown 40 ± 0.29 mm, 28 ± 0.13 and 42 ± 0.49 mm ZOI respectively. The MIC value of 30 μg/mL observed for E. coli Whereas, Staphylococcus aureus, Bacillus subtilius and Pseudomonas aeruginosa had shown 45 μg/mL, 38 μg/mL, 35 μg/mL respectively. The study revealed that AgNPs had shown significant antimicrobial activity as compared to Streptomycin. PMID:25763037

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

    PubMed

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

    2016-01-01

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

  20. 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.

  1. 77 FR 75169 - Silver Nanoparticles (AgNPs); Information and Comment Request

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-19

    ... responses, and (3) histopathology changes in the kidney and especially in the liver, in which bile duct... to the liver . Studies also indicate that AgNPs can be transported and deposited in major organs and... histopathological effects to the liver in exposed Sprague-Dawley and F344 rats [Sung et al. 2009; Kim et al....

  2. 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.

  3. Integrated mRNA and micro RNA profiling reveals epigenetic mechanism of differential sensitivity of Jurkat T cells to AgNPs and Ag ions.

    PubMed

    Eom, Hyun-Jeong; Chatterjee, Nivedita; Lee, Jeongsoo; Choi, Jinhee

    2014-08-17

    In our previous in vitro study of the toxicity on silver nanoparticles (AgNPs), we observed a dramatically higher sensitivity of Jurkat T cells to AgNPs than to Ag ions, and DNA damage and apoptosis were found to be involved in that toxicity. In this study, to understand underlying mechanism of different sensitivity of Jurket T cells to AgNPs and Ag ions, mRNA microarray and micro RNA microarray were concomitantly conducted on AgNPs and Ag ions exposed Jurkat T cells. Surprisingly only a small number of genes were differentially expressed by exposure to each of the silver (15 altered mRNA by AgNPs exposure, whereas 4 altered mRNA by Ag ions exposure, as determined 1.5-fold change as the cut-off value). miRNA microarray revealed that the expression of 63 miRNAs was altered by AgNPs exposure, whereas that of 32 miRNAs was altered by Ag ions exposure. An integrated analysis of mRNA and miRNA expression revealed that the expression of hsa-miR-219-5p, was negatively correlated with the expression of metallothionein 1F (MT1F) and tribbles homolog 3 (TRIB3), in cells exposed to AgNPs; whereas, the expression of hsa-miR-654-3p was negatively correlated with the expression of mRNA, endonuclease G-like 1 (EDGL1) in cells exposed to Ag ions. Network analysis were further conducted on mRNA-miRNA pairs, which revealed that miR-219-5p-MT1F and -TRIB3 pairs by AgNPs are being involved in various cellular processes, such as, oxidative stress, cell cycle and apoptosis, whereas, miR-654-3p and ENDOGL1 pair by Ag ions generated a much simpler network. The putative target genes of AgNPs-induced miR-504, miR-33 and miR-302 identified by Tarbase 6.0 are also found to be involved in DNA damage and apoptosis. These results collectively suggest that distinct epigenetic regulation may be an underlying mechanism of different sensitivity of Jurkat T cells to AgNPs and Ag ion. Further identification of putative target genes of DE miRNA by AgNPs and Ag ions may provide additional clues for the

  4. Rapid Biosynthesis of AgNPs Using Soil Bacterium Azotobacter vinelandii With Promising Antioxidant and Antibacterial Activities for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Karunakaran, Gopalu; Jagathambal, Matheswaran; Gusev, Alexander; Torres, Juan Antonio Lopez; Kolesnikov, Evgeny; Kuznetsov, Denis

    2016-11-01

    Silver nanoparticles (AgNPs) are applied in various fields from electronics to biomedical applications as a result of their high surface-to-volume ratio. Even though different approaches are available for synthesis of AgNPs, a nontoxic method for the synthesis has not yet been developed. Thus, this study focused on developing an easy and ecofriendly approach to synthesize AgNPs using Azotobacter vinelandii culture extracts. The biosynthesized nanoparticles were further characterized by ultraviolet-visible (UV-Vis) spectroscopy, x-ray diffraction (XRD), Fourier transform infrared (FTIR), energy-dispersive spectrum, particle size distribution (PSD), and transmission electron microscopy (TEM). UV absorption noticed at 435 nm showed formation of AgNPs. The XRD pattern showed a face-centered cubic structure with broad peaks of 28.2°, 32.6°, 46.6°, 55.2°, 57.9°, and 67.8°. The FTIR confirmed the involvement of various functional groups in the biosynthesis of AgNPs. The PSD and TEM analyses showed spherical, well-distributed nanoparticles with an average size of 20-70 nm. The elemental studies confirmed the existence of pure AgNPs. The bacterial extract containing extracellular enzyme nitrate reductase converted silver nitrate into AgNPs. AgNPs significantly inhibited the growth of pathogenic bacteria such as Streptomyces fradiae (National Collection of Industrial Microorganisms (NCIM) 2419), Staphylococcus aureus (NCIM 2127), Escherichia coli (NCIM 2065), and Serratia marcescens (NCIM 2919). In addition, biosynthesized AgNPs were found to possess strong antioxidant activity. Thus, the results of this study revealed that biosynthesized AgNPs could serve as a lead in the development of nanomedicine.

  5. Preparation of melamine sponge decorated with silver nanoparticles-modified graphene for water disinfection.

    PubMed

    Deng, Can-Hui; Gong, Ji-Lai; Zhang, Peng; Zeng, Guang-Ming; Song, Biao; Liu, Hong-Yu

    2017-02-15

    This paper reports the fabrication of melamine sponge decorated with silver nanoparticles-modified graphene (G/AgNPs-MS) for water disinfection. The G/AgNPs-MS composites with the high porosity and elasticity were used in an antibacterial process in which the composite was first immersed in bacterial suspension, and subsequently squeezed via hand compression. G/AgNPs-MS exhibited more excellent bactericidal activity against Escherichia coli and Staphylococcus aureus bacteria compared with melamine sponge (MS), melamine sponge decorated with graphene (G-MS), and melamine sponge decorated with silver nanoparticles (AgNPs-MS). The superior antibacterial effect was possibly ascribed to the coordination of graphene oxide (GO) and silver nanoparticles (Ag NPs). Compared to AgNPs-MS, G/AgNPs-MS displayed better stability with fewer Ag(+) release. G/AgNPs-MS composites were highly reusable with no significant differences in the loss of bacterial viability over 12 operational cycles. The possible antibacterial mechanism of G/AgNPs-MS was also investigated. It was found that the destruction of bacterial membrane by G/AgNPs-MS played an important role in the bactericidal activity. The generation of intercellular ROS and scavenging assays confirmed the involvement of Ag(+) and ROS in the antibacterial process of G/AgNPs-MS. All the results demonstrated that the prepared G/AgNPs-MS composites, as innovative antibacterial materials, showed a great potential for water disinfection.

  6. 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.

  7. Surface modification of cotton fabrics for antibacterial application by coating with AgNPs-alginate composite.

    PubMed

    Zahran, M K; Ahmed, Hanan B; El-Rafie, M H

    2014-08-08

    In recent years nano-sized particles have been focused on bacteriostasis. We investigated antimicrobial activities by applying AgNPs-alginate composite on cotton fabric, using a simple one-step rapid synthetic route by reduction of silver nitrate using alkali hydrolyzed alginate solution which acts as both reducing and capping agent. FTIR spectra, color coordinates, silver content, silver release percent and SEM images of treated fabric samples confirmed the successful physical deposition of AgNPs-alginate composite on the fabric. The treated fabrics demonstrated an excellent antibacterial activity against the tested bacteria, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. A slight decrease in the antibacterial feature of the cotton fabrics was observed after successive washings. However, an efficient antibacterial activity still remained on the fabrics.

  8. Polymers effects on synthesis of AuNPs, and Au/Ag nanoalloys: indirectly generated AuNPs and versatile sensing applications including anti-leukemic agent.

    PubMed

    Jahan, Shanaz; Mansoor, Farrukh; Kanwal, Shamsa

    2014-03-15

    Polymers either serve as shielding or capping agents to restrict the nanoparticle size. This study demonstrates the polymer depositions and their effects in synthesis and sharp stabilization of gold nanoparticles (AuNPs) and to develop gold/silver nanoalloys (Au/Ag nanoalloys). Effects of different polymers are tested to justify their role in synthesis and stability of phloroglucinol (PG) coated AuNPs and Au/Ag nanoalloys. Cationic and anionic i.e. [Polydiallyldimethylammonium](+) (PDDA), [Polyethyleneimine](+) (PEI), [Polystyrene sulfonate](2-) (PSS) and neutral polymer Polychlorotriflouroethylene (PCTFE) produce praiseworthy stable AuNPs and Au/Ag nanoalloy. To prove polymer effects characterization protocols including UV-vis, Fluorescence (PL), IR and AFM imaging are performed to fully investigate the mechanism and size characteristics of these nanoparticles/nanoalloys. In this study sharp size controlling/sheilding effects were observed particularly with cationic polymers simply through the favorable electrostatic interactions with the terminal ends of PG Potent/significant detection of doxorubicin (DOX, an antileukemic agent) via fluorescence resonance energy transfer (FRET) between PEI shielded AuNPs (AuNPEI) and DOX was achieved upto 10 pM level, while PDDA protected AuNPs facilitated the detection of ascorbic acid based on fluorescence enhancement effects in wide range (10-200 nM) and with detection limit of 200 pM. Similarly sensing performance of PEI stabilized Au/Ag nanoalloys on addition of halides (Cl(-), Br(-), I(-)) is evaluated through red shifted SPR along with continuous increase in absorbance and also through AFM. Moreover the addition of halide ions also helped the regeneration of AuNPs by taking away silver from the Au/Ag nanoalloys enabling their detections upto subnanomolar levels.

  9. 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.

  10. Amperometric detection of Sudan I in red chili powder samples using Ag nanoparticles decorated graphene oxide modified glassy carbon electrode.

    PubMed

    Prabakaran, E; Pandian, K

    2015-01-01

    A simple and sensitive electrochemical method was developed to determine the concentration of Sudan I in chili powder based on silver nanoparticles decorated graphene oxide modified glassy carbon electrode (AgNPs@GO/GCE). The voltammetry behaviour of Sudan I on modified GCE was investigated in phosphate buffer medium (PBS) with various pH ranges and the electron transfer properties were studied. It is found that the AgNPs@GO/GCE can catalyse the reduction of azo group, -N=N- followed by electrochemical oxidation of (-)OH group present in Sudan I dye molecule. Quantitative detection of Sudan I present in food products was carried out by amperometry method in which reduction potential was fixed at -0.77 V vs. Ag/AgCl. The amperometry method showed an excellent performance with a sensitivity of 6.83 μA mM(-1) and a detection limit of 11.4 × 10(-7)ML(-1). A linear calibration graph was constructed in the ranging 3.90 × 10(-6) to 3.19 × 10(-5)ML(-1). The method was successfully applied for the determination of Sudan I in red chili powder samples.

  11. Ag-nanoparticle-decorated porous ZnO-nanosheets grafted on a carbon fiber cloth as effective SERS substrates.

    PubMed

    Wang, Zhiwei; Meng, Guowen; Huang, Zhulin; Li, Zhongbo; Zhou, Qitao

    2014-12-21

    We report on the large-scale synthesis of Ag-nanoparticle (Ag-NP) decorated ZnO-mesoporous-nanosheets (NSs) grafted on a flexible carbon fiber cloth (CFC), as sensitive and reproducible surface enhanced Raman scattering (SERS) substrates with excellent flexibility. The composite SERS-substrates are achieved by a combination of atomic layer deposition of ZnO-seeds on each fiber of the CFC (denoted as ZnO-seeds@CFC), chemical bath deposition and subsequent pyrolysis for the creation of ZnO-mesoporous-NSs grafted on ZnO-seeds@CFC, and ion-sputtering of Ag-NPs on the ZnO-mesoporous-NSs. As abundant SERS "hot spots" are generated from the electromagnetic coupling of the densely distributed Ag-NPs, and the semiconducting ZnO-mesoporous-NSs also have chemical supporting enhancement and distinct molecule adsorbing abilities, the composite SERS-substrates demonstrate high SERS-sensitivity with good signal reproducibility. As a trial for potential applications, the composite SERS-substrates were used to identify pesticides and highly toxic polychlorinated biphenyls (PCBs), and low concentrations down to 10(-7) M for methyl parathion and 5 × 10(-6) M for PCB-77 were reached, respectively, showing promising potential for the SERS-based rapid detection of toxic organic pollutants in the environment.

  12. 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

  13. Enhanced 1.53 μm band fluorescence in Er3+/Ce3+ codoped tellurite glasses containing Ag NPs

    NASA Astrophysics Data System (ADS)

    Wu, Libo; Huang, Bo; Yang, Fengjing; Qi, Yawei; Peng, Shengxi; Zhou, Yaxun; Li, Jun

    2015-05-01

    The silver nanoparticles (Ag NPs) was introduced into Er3+/Ce3+ codoped tellurite glasses with composition of TeO2-ZnO-La2O3 and the effects of Ag NPs on the 1.53 μm band spectroscopic properties of Er3+ ions, structural nature and thermal stability of glass hosts were investigated. The absorption spectra, upconversion emission spectra, 1.53 μm band fluorescence spectra together with the X-ray diffraction (XRD) patterns, differential scanning calorimeter (DSC) curves and transmission electron microscopy (TEM) image were measured. It was found that the near-spherical shape Ag NPs with average diameter of about 19 nm dispersed uniformly in the glass matrix, and the Er3+/Ce3+ codoped tellurite glasses containing Ag NPs exhibited an obvious enhancement in the 1.53 μm band fluorescence, which is attributed to the intensified local electric field induced by Ag NPs and the possible energy transfer from Ag NPs to Er3+ ions. The enhanced effect of Ag NPs on the 1.53 μm band fluorescence was elucidated by the obtained large Judd-Ofelt intensity parameter Ω6 and the calculated quantum efficiency of Er3+:4I13/2 level. In addition, the thermal stability of prepared glass samples increased with the introduction of Ag NPs and the amorphous structural nature was demonstrated by the measured XRD patterns with no sharp diffraction peak. The present results indicate that the prepared Er3+/Ce3+ codoped tellurite glass with Ag NPs has good prospect as a gain medium applied for 1.53 μm band Er3+-doped fiber amplifiers (EDFAs).

  14. Facile biosynthesis of Ag-NPs using Otostegia limbata plant extract: Physical characterization and auspicious biological activities

    NASA Astrophysics Data System (ADS)

    Kausar, Rizwan; Shaheen, Muhammad Ashraf; Maqbool, Qaisar; Naz, Sania; Nazar, Mudassar; Abbas, Fazal; Hussain, Talib; Younas, Umer; Shams, Muhammad Fahad

    2016-09-01

    Silver nanoparticles (Ag-NPs) synthesized through reduction by Otostegia limbata green extract are, hereby, reported for the first time. It is very interesting to observe that in this case, O. limbata plant extract acts as a strong chelating agent in Ag-NPs formation through AgNO3. Scanning electron microscope (SEM) studies expose that Ag-NPs formation is highly homogenous and spherical with mean particle size of 32 ±0.8 nm. A typical Ag absorption peak has been observed at 419 nm by ultra violet (UV)-visible spectroscopy which have endorsed the successful formation of single phase Ag-NPs. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) examination further validates the crystalline pure phase structure of Ag-NPs. Promising results have been recorded against protein kinase inhibition assay and antibacterial assay having prominent pathogenic strains. Our present study explores that biosynthesized eco-friendly Ag-NPs have great potential, in the future, for anticancer drug development with wide range pharmaceutical applications.

  15. SiO(2) /TiO(2) hollow nanoparticles decorated with Ag nanoparticles: enhanced visible light absorption and improved light scattering in dye-sensitized solar cells.

    PubMed

    Hwang, Sun Hye; Shin, Dong Hoon; Yun, Juyoung; Kim, Chanhoi; Choi, Moonjung; Jang, Jyongsik

    2014-04-07

    Hollow SiO2 /TiO2 nanoparticles decorated with Ag nanoparticles (NPs) of controlled size (Ag@HNPs) were fabricated in order to enhance visible-light absorption and improve light scattering in dye-sensitized solar cells (DSSCs). They exhibited localized surface plasmon resonance (LSPR) and the LSPR effects were significantly influenced by the size of the Ag NPs. The absorption peak of the LSPR band dramatically increased with increasing Ag NP size. The LSPR of the large Ag NPs mainly increased the light absorption at short wavelengths, whereas the scattering from the SiO2 /TiO2 HNPs improved the light absorption at long wavelengths. This enabled the working electrode to use the full solar spectrum. Furthermore, the SiO2 layer thickness was adjusted to maximize the LSPR from the Ag NPs and avoid corrosion of the Ag NPs by the electrolyte. Importantly, the power conversion efficiency (PCE) increased from 7.1 % with purely TiO2 -based DSSCs to 8.1 % with HNP-based DSSCs, which is an approximately 12 % enhancement and can be attributed to greater light scattering. Furthermore, the PCEs of Ag@HNP-based DSSCs were 11 % higher (8.1 vs. 9.0 %) than the bare-HNP-based DSSCs, which can be attributed to LSPR. Together, the PCE of Ag@HNP-based DSSCs improved by a total of 27 %, from 7.1 to 9.0 %, due to these two effects. This comparative research will offer guidance in the design of multifunctional nanomaterials and the optimization of solar-cell performance.

  16. Both enhanced biocompatibility and antibacterial activity in Ag-decorated TiO2 nanotubes.

    PubMed

    Lan, Ming-Ying; Liu, Chia-Pei; Huang, Her-Hsiung; Lee, Sheng-Wei

    2013-01-01

    In this study, Ag is electron-beam evaporated to modify the topography of anodic TiO2 nanotubes of different diameters to obtain an implant with enhanced antibacterial activity and biocompatibility. We found that highly hydrophilic as-grown TiO2 nanotubes became poorly hydrophilic with Ag incorporation; however they could effectively recover their wettability to some extent under ultraviolet light irradiation. The results obtained from antibacterial tests suggested that the Ag-decorated TiO2 nanotubes could greatly inhibit the growth of Staphylococcus aureus. In vitro biocompatibility evaluation indicated that fibroblast cells exhibited an obvious diameter-dependent behavior on both as-grown and Ag-decorated TiO2 nanotubes. Most importantly, of all samples, the smallest diameter (25-nm-diameter) Ag-decorated nanotubes exhibited the most obvious biological activity in promoting adhesion and proliferation of human fibroblasts, and this activity could be attributed to the highly irregular topography on a nanometric scale of the Ag-decorated nanotube surface. These experimental results demonstrate that by properly controlling the structural parameters of Ag-decorated TiO2 nanotubes, an implant surface can be produced that enhances biocompatibility and simultaneously boosts antibacterial activity.

  17. Nanosilver as a disinfectant in dental unit waterlines: Assessment of the physicochemical transformations of the AgNPs.

    PubMed

    Gitipour, Alireza; Al-Abed, Souhail R; Thiel, Stephen W; Scheckel, Kirk G; Tolaymat, Thabet

    2017-04-01

    Dental unit water lines (DUWL) are susceptible to biofilm development and bacterial growth leading to water contamination, causing health and ecological effects. This study monitors the interactions between a commonly used nanosilver disinfectant (ASAP-AGX-32, an antimicrobial cleaner for dental units, 0.0032% Ag) and biofilm development in DUWL. To simulate the disinfection scenario, an in-house DUWL model was assembled and biofilm accumulation was allowed. Subsequent to biofilm development, the disinfection process was performed according to the manufacturer's instructions. The pristine nanosilver particles in the cleaner measured between 3 and 5 nm in diameter and were surrounded by a stabilizing polymer. However, the polymeric stabilizing agent diminished over the disinfection process, initiating partial AgNPs aggregation. Furthermore, surface speciation of the pristine AgNPs were identified as primarily AgO, and after the disinfection process, transformations to AgCl were observed. The physicochemical characteristics of AgNPs are known to govern their fate, transport and environmental implications. Hence, knowledge of the AgNPs characteristics after the disinfection process (usage scenario) is of significance. This study demonstrates the adsorption of AgNPs onto biofilm surfaces and, therefore, will assist in illustration of the toxicity mechanisms of AgNPs to bacteria and biofilms. This work can be an initial step in better understanding how AgNPs transform depending on the conditions they are exposed to during their lifetime. Until this date, most research has been focused on assessing the impacts of pristine (lab synthesized) nanomaterials on various systems. However, it is our belief that nanoparticles may undergo transformations during usage, which must be taken into consideration. Furthermore, this experiment is unique as it was conducted with a commonly used, commercially available nanosilver suspension leading to more realistic and applicable findings.

  18. Synthesis and optical properties study of nanocomposites based on AuNPs and AgNPs obtained by laser ablation in liquid monomer

    NASA Astrophysics Data System (ADS)

    Zulina, Natalia A.; Pavlovetc, Ilia M.; Baranov, Mikhail A.; Kaliabin, Viacheslav O.; Denisyuk, Igor Yu.

    2017-01-01

    In this work, Ag and Au nanoparticles (AgNPs and AuNPs) stable colloid solution were prepared by laser ablation of chemically pure silver rod and gold film in liquid monomer isodecyl acrylate (IDA). Sizes of obtained nanoparticles were determined by scanning electron microscope and vary from 30 to 130 nm. Nanocomposites films were prepared from obtained stable colloid solution by photocuring. To prepare solid film based on aliphatic polymer IDA long molecules cross-linking, 1,6-Hexandiol diacrylate was used. Obtained films were transparent, homogenous and colored in brown for AgNPs and purple for AuNPs-filled nanocomposites. Prepared nanomaterials exhibit strong third-order nonlinear optical responses under CW laser irradiation at 532 nm, which was estimated by using z-scan technique performed with open and close aperture. The real and imaginary parts of third-order nonlinear optical coefficients of the studied nanocomposites were found to be up to Reχ (3) = 1.31 × 10-5 (esu) and Imχ (3) = 7.64 × 10-5 (esu), for samples negative nonlinear refractive index was obtained, which corresponds to self-defocusing effect.

  19. Fabrication of Au@Ag core-shell NPs as enhanced CT contrast agents with broad antibacterial properties.

    PubMed

    Huo, Da; He, Jian; Li, Hui; Yu, Haiping; Shi, Tingting; Feng, Yahui; Zhou, Zhengyang; Hu, Yong

    2014-05-01

    Au@Ag core-shell nanoparticles (NPs) integrating both antibacterial and X-ray attenuation capabilities were facilely synthesized in aqueous solution. These NPs modified with methoxy-PEG-SH (m-PEG) on the surface rendered them favorable dispersity and stability in water, resulting in enhancement of their blood circulation time. X-ray photoelectron spectroscope (XPS) and high-resolution transmission electron microscope (HRTEM) results confirmed the core-shell structure of m-PEG-Au@Ag NPs. The m-PEG-Au@Ag NPs showed low cytotoxicity and strong X-ray absorption potency in vitro. Further in vivo study showed that as-synthesized NPs offered a pronounced contrast and prolonged their circulation time in the blood stream with negligible toxic effect in vivo. Besides, m-PEG-Au@Ag NPs had significant bacteriostatic effect toward common bacteria like Escherichia coli and Staphylococcus aureus as demonstrated by broth dilution assay. Given their low-cytotoxicity and high CT attenuation efficacy, m-PEG-Au@Ag NPs had a promising potential for use as CT enhancing and antibacterial agents.

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

    PubMed

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

    2015-03-05

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

  1. Palladium-phosphorus/sulfur nanoparticles (NPs) decorated on graphene oxide: synthesis using the same precursor for NPs and catalytic applications in Suzuki-Miyaura coupling.

    PubMed

    Joshi, Hemant; Sharma, Kamal Nayan; Sharma, Alpesh K; Singh, Ajai Kumar

    2014-05-07

    PdP2 and Pd4S nanoparticles (NPs) (size: ∼2-6 and 9-15 nm respectively) have been prepared for the first time from a single source precursor complex [Pd(L)Cl2] (1) by its one pot thermolysis at 200 °C in TOP and OA/ODE (1 : 1) respectively. These NPs were stirred with graphene oxide (GO) at room temperature to prepare NP composites, GO-PdP2 and GO-Pd4S. The GO-PdP2 NPs have been synthesized for the first time. The thioether ligand L prepared by reaction of 1,3-dibromo-2-propanol with the in situ generated PhSNa reacts with [PdCl2(CH3CN)2] in CH3CN at 70 °C resulting in 1. The L and 1 have been characterized by (1)H and (13)C{(1)H} NMR and HR-MS. The single crystal structure of 1 determined by X-ray diffraction reveals nearly square planar geometry around the Pd metal centre. The catalytic activities of two palladium nano-phases having phosphorus and sulphur respectively as a co-constituent for Suzuki-Miyaura coupling have been found to be exceptionally different, as PdP2 nanoparticles (NPs) grafted on graphene oxide (GO-PdP2) are significantly more efficient than Pd4S NPs grafted on GO. Without grafting PdP2 and Pd4S both have low efficiency. This is the first report comparing the influence of P and S on the catalytic activity of Pd NPs. TEM, SEM-EDX and powder-XRD have been used to authenticate all NPs. The GO-PdP2 NPs have been found to be efficient catalysts for Suzuki-Miyaura coupling reactions (yield up to 96% in 30 min) at room temperature to 80 °C. Their recyclability has been found up to 6 cycles. In contrast, GO-Pd4S NPs are little active in comparison with GO-PdP2 NPs. The size of NPs and their distribution on GO appear to be key factors affecting the catalytic efficiency of the composite NPs. Leaching of Pd from GO-PdP2 NPs contributes significantly to the catalysis as evidenced by the three phase test, hot-filtration and recycling experiments. The catalysis is almost homogeneous.

  2. Antibacterial and antifouling activities of chitosan/TiO2/Ag NPs nanocomposite films against packaged drinking water bacterial isolates.

    PubMed

    Natarajan, Saravanan; Bhuvaneshwari, M; Lakshmi, D Shanthana; Mrudula, P; Chandrasekaran, N; Mukherjee, Amitava

    2016-10-01

    TiO2 and Ag NPs are widely used as antibacterial agents against many bacterial pathogens. Chitosan (polymer) itself acts as a strong antibacterial agent. Hence, chitosan/TiO2/Ag NPs incorporated nanocomposite film was prepared against packed drinking water bacterial strains. A concentration-dependent increase in the reduction of cell viability was observed in all the isolates under UV-C and dark exposure conditions. The bacteria consortium showed greater resistance against antibacterial effects of chitosan/TiO2/Ag nanocomposite as compared to single isolates. Glycocalyx test and mass assessment conclude the effective antibacterial activity by inhibiting bacterial adhesion on the film surface. The release of LDH and generation of ROS act as the predominant antibacterial mechanism induced by TiO2/Ag NPs. Surface characterization of chitosan/TiO2/Ag nanocomposite was studied by FTIR and XRD analyses and SEM analysis after interaction with the bacteria.

  3. Palladium-phosphorus/sulfur nanoparticles (NPs) decorated on graphene oxide: synthesis using the same precursor for NPs and catalytic applications in Suzuki-Miyaura coupling

    NASA Astrophysics Data System (ADS)

    Joshi, Hemant; Sharma, Kamal Nayan; Sharma, Alpesh K.; Singh, Ajai Kumar

    2014-04-01

    PdP2 and Pd4S nanoparticles (NPs) (size: ~2-6 and 9-15 nm respectively) have been prepared for the first time from a single source precursor complex [Pd(L)Cl2] (1) by its one pot thermolysis at 200 °C in TOP and OA/ODE (1 : 1) respectively. These NPs were stirred with graphene oxide (GO) at room temperature to prepare NP composites, GO-PdP2 and GO-Pd4S. The GO-PdP2 NPs have been synthesized for the first time. The thioether ligand L prepared by reaction of 1,3-dibromo-2-propanol with the in situ generated PhSNa reacts with [PdCl2(CH3CN)2] in CH3CN at 70 °C resulting in 1. The L and 1 have been characterized by 1H and 13C{1H} NMR and HR-MS. The single crystal structure of 1 determined by X-ray diffraction reveals nearly square planar geometry around the Pd metal centre. The catalytic activities of two palladium nano-phases having phosphorus and sulphur respectively as a co-constituent for Suzuki-Miyaura coupling have been found to be exceptionally different, as PdP2 nanoparticles (NPs) grafted on graphene oxide (GO-PdP2) are significantly more efficient than Pd4S NPs grafted on GO. Without grafting PdP2 and Pd4S both have low efficiency. This is the first report comparing the influence of P and S on the catalytic activity of Pd NPs. TEM, SEM-EDX and powder-XRD have been used to authenticate all NPs. The GO-PdP2 NPs have been found to be efficient catalysts for Suzuki-Miyaura coupling reactions (yield up to 96% in 30 min) at room temperature to 80 °C. Their recyclability has been found up to 6 cycles. In contrast, GO-Pd4S NPs are little active in comparison with GO-PdP2 NPs. The size of NPs and their distribution on GO appear to be key factors affecting the catalytic efficiency of the composite NPs. Leaching of Pd from GO-PdP2 NPs contributes significantly to the catalysis as evidenced by the three phase test, hot-filtration and recycling experiments. The catalysis is almost homogeneous.PdP2 and Pd4S nanoparticles (NPs) (size: ~2-6 and 9-15 nm respectively) have

  4. Impurity Decoration for Crystal Shape Control: C60 on Ag(111)

    NASA Astrophysics Data System (ADS)

    Stasevich, T. J.; Tao, C. G.; Cullen, W. G.; Williams, E. D.; Einstein, T. L.

    2008-03-01

    The decoration of hexagonal Ag/Ag(111) monolayer islands by chains of C60, observed via STM at 300K, dramatically changes their shape and fluctuations. We tune coverage so that a single C60 chain fully decorates each Ag island boundary.ootnotetextC.G. Tao et al., PRB 73, 125436 (2006); Nano Letters 7, 1495 (2007). The C60-induced rounding appears due to competing energetic and entropic effects.ootnotetextT.J. Stasevich & TLE, (SIAM) Multiscale Model. Simul. 6, 90 (2007) We estimate the Ag - C60 and C60 - C60 attractions as ˜0.13 eV and ˜0.04 eV, respectively.ootnotetextT.J. Stasevich et al., submitted. The edge fluctuations are remarkable: 1) C60 decoration does not notably impede the step-edge diffusion (SED) and 2) while the bare-island fluctuations are driven by SED, the decorated island has the signature of non-conserved dynamics, even though the C60s remain at the island edge. We suggest that rapidly diffusing Ag atoms randomly attracting the nearby C60s. Generalizations of our model show that both spherical and rectangular decorating molecules will similarly lower the energy of highly-kinked boundaries, leading to similar island shape changes.

  5. Evolution of a high local strain in rolling up MoS2 sheets decorated with Ag and Au nanoparticles for surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Hwang, Da Young; Hack Suh, Dong

    2017-01-01

    We report that a high local strain was obtained for multilayer MoS2 nanoscrolls decorated with noble nanoparticles (Ag and Au NPs) using a rolling process beyond breaking or slipping of MoS2. The local strain was estimated through the bending strain in the nanoscrolls and the extent of coverage of Ag and Au NPs decorated on MoS2, exhibiting magnified surface-enhanced Raman scattering. TEM images showed that the MoS2-Ag and MoS2-Au nanoscrolls have a tube-like morphology decorated with NPs on the inner and outer sides of the MoS2 nanoscrolls. In the Raman spectra, we confirmed the red shift and broadness of the FWHM for nanoscrolls in the eigenvectors of the {{{E}}}{2{{g}}+}1 and {{{E}}}{2g+}1 modes. From the Grüneisen parameter γ and the shear deformation potential β, we obtained peak shifts of ˜4.9 cm-1/% at {{{E}}}{2g-}1 and ˜1.1 cm-1/% strain at {{{E}}}{2g+}1 for free-standing MoS2. According to the obtained relationship of the Raman shift and the induced uniaxial tensile strain, the {{{E}}}{2g-}1 and {{{E}}}{2g+}1 peaks shifted upwards to around -12.8 cm-1 and -2.9 cm-1, respectively, and can be converted to an induced uniaxial tensile strain of about 2.6% for MoS2-Ag nanoscrolls.

  6. 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.

  7. 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.

  8. Electrostatic Assemblies of Well-Dispersed AgNPs on the Surface of Electrospun Nanofibers as Highly Active SERS Substrates for Wide-Range pH Sensing.

    PubMed

    Yang, Tong; Ma, Jun; Zhen, Shu Jun; Huang, Cheng Zhi

    2016-06-15

    Surface-enhanced Raman scattering (SERS) has shown high promise in analysis and bioanalysis, wherein noble metal nanoparticles (NMNPs) such as silver nanoparticles were employed as substrates because of their strong localized surface plasmon resonance (LSPR) properties. However, SERS-based pH sensing was restricted because of the aggregation of NMNPs in acidic medium or biosamples with high ionic strength. Herein, by using the electrostatic interaction as a driving force, AgNPs are assembled on the surface of ethylene imine polymer (PEI)/poly(vinyl alcohol) (PVA) electrospun nanofibers, which are then applied as highly sensitive and reproducible SERS substrate with an enhancement factor (EF) of 10(7)-10(8). When p-aminothiophenol (p-ATP) is used as an indicator with its b2 mode, a good and wide linear response to pH ranging from 2.56 to 11.20 could be available, and the as-prepared nanocomposite fibers then could be fabricated as excellent pH sensors in complicated biological samples such as urine, considering that the pH of urine could reflect the acid-base status of a person. This work not only emerges a cost-effective, direct, and convenient approach to homogeneously decorate AgNPs on the surface of polymer nanofibers but also supplies a route for preparing other noble metal nanofibrous sensing membranes.

  9. High-performance SERS substrate based on hybrid structure of graphene oxide/AgNPs/Cu film@pyramid Si

    NASA Astrophysics Data System (ADS)

    Li, Zhe; Xu, Shi Cai; Zhang, Chao; Liu, Xiao Yun; Gao, Sai Sai; Hu, Li Tao; Guo, Jia; Ma, Yong; Jiang, Shou Zhen; Si, Hai Peng

    2016-12-01

    We present a novel surface-enhanced Raman scattering (SERS) substrate based on graphene oxide/silver nanoparticles/copper film covered silicon pyramid arrays (GO/AgNPs/PCu@Si) by a low-cost and simple method. The GO/AgNPs/PCu@Si substrate presents high sensitivity, good homogeneity and well stability with R6G molecules as a probe. The detected concentration of Rhodamine 6 G (R6G) is as low as 10‑15 M. These sensitive SERS behaviors are also confirmed in theory via a commercial COMSOL software, the electric field enhancement is not only formed between the AgNPs, but also formed between the AgNPs and Cu film. And the GO/AgNPs/PCu@Si substrates also present good property on practical application for the detection of methylene blue (MB) and crystal violet (CV). This work may offer a novel and practical method to facilitate the SERS applications in areas of medicine, food safety and biotechnology.

  10. High-performance SERS substrate based on hybrid structure of graphene oxide/AgNPs/Cu film@pyramid Si

    PubMed Central

    Li, Zhe; Xu, Shi Cai; Zhang, Chao; Liu, Xiao Yun; Gao, Sai Sai; Hu, Li Tao; Guo, Jia; Ma, Yong; Jiang, Shou Zhen; Si, Hai Peng

    2016-01-01

    We present a novel surface-enhanced Raman scattering (SERS) substrate based on graphene oxide/silver nanoparticles/copper film covered silicon pyramid arrays (GO/AgNPs/PCu@Si) by a low-cost and simple method. The GO/AgNPs/PCu@Si substrate presents high sensitivity, good homogeneity and well stability with R6G molecules as a probe. The detected concentration of Rhodamine 6 G (R6G) is as low as 10−15 M. These sensitive SERS behaviors are also confirmed in theory via a commercial COMSOL software, the electric field enhancement is not only formed between the AgNPs, but also formed between the AgNPs and Cu film. And the GO/AgNPs/PCu@Si substrates also present good property on practical application for the detection of methylene blue (MB) and crystal violet (CV). This work may offer a novel and practical method to facilitate the SERS applications in areas of medicine, food safety and biotechnology. PMID:27924863

  11. High-performance SERS substrate based on hybrid structure of graphene oxide/AgNPs/Cu film@pyramid Si.

    PubMed

    Li, Zhe; Xu, Shi Cai; Zhang, Chao; Liu, Xiao Yun; Gao, Sai Sai; Hu, Li Tao; Guo, Jia; Ma, Yong; Jiang, Shou Zhen; Si, Hai Peng

    2016-12-07

    We present a novel surface-enhanced Raman scattering (SERS) substrate based on graphene oxide/silver nanoparticles/copper film covered silicon pyramid arrays (GO/AgNPs/PCu@Si) by a low-cost and simple method. The GO/AgNPs/PCu@Si substrate presents high sensitivity, good homogeneity and well stability with R6G molecules as a probe. The detected concentration of Rhodamine 6 G (R6G) is as low as 10(-15) M. These sensitive SERS behaviors are also confirmed in theory via a commercial COMSOL software, the electric field enhancement is not only formed between the AgNPs, but also formed between the AgNPs and Cu film. And the GO/AgNPs/PCu@Si substrates also present good property on practical application for the detection of methylene blue (MB) and crystal violet (CV). This work may offer a novel and practical method to facilitate the SERS applications in areas of medicine, food safety and biotechnology.

  12. Ag-nanoparticle-decorated porous ZnO-nanosheets grafted on a carbon fiber cloth as effective SERS substrates

    NASA Astrophysics Data System (ADS)

    Wang, Zhiwei; Meng, Guowen; Huang, Zhulin; Li, Zhongbo; Zhou, Qitao

    2014-11-01

    We report on the large-scale synthesis of Ag-nanoparticle (Ag-NP) decorated ZnO-mesoporous-nanosheets (NSs) grafted on a flexible carbon fiber cloth (CFC), as sensitive and reproducible surface enhanced Raman scattering (SERS) substrates with excellent flexibility. The composite SERS-substrates are achieved by a combination of atomic layer deposition of ZnO-seeds on each fiber of the CFC (denoted as ZnO-seeds@CFC), chemical bath deposition and subsequent pyrolysis for the creation of ZnO-mesoporous-NSs grafted on ZnO-seeds@CFC, and ion-sputtering of Ag-NPs on the ZnO-mesoporous-NSs. As abundant SERS ``hot spots'' are generated from the electromagnetic coupling of the densely distributed Ag-NPs, and the semiconducting ZnO-mesoporous-NSs also have chemical supporting enhancement and distinct molecule adsorbing abilities, the composite SERS-substrates demonstrate high SERS-sensitivity with good signal reproducibility. As a trial for potential applications, the composite SERS-substrates were used to identify pesticides and highly toxic polychlorinated biphenyls (PCBs), and low concentrations down to 10-7 M for methyl parathion and 5 × 10-6 M for PCB-77 were reached, respectively, showing promising potential for the SERS-based rapid detection of toxic organic pollutants in the environment.We report on the large-scale synthesis of Ag-nanoparticle (Ag-NP) decorated ZnO-mesoporous-nanosheets (NSs) grafted on a flexible carbon fiber cloth (CFC), as sensitive and reproducible surface enhanced Raman scattering (SERS) substrates with excellent flexibility. The composite SERS-substrates are achieved by a combination of atomic layer deposition of ZnO-seeds on each fiber of the CFC (denoted as ZnO-seeds@CFC), chemical bath deposition and subsequent pyrolysis for the creation of ZnO-mesoporous-NSs grafted on ZnO-seeds@CFC, and ion-sputtering of Ag-NPs on the ZnO-mesoporous-NSs. As abundant SERS ``hot spots'' are generated from the electromagnetic coupling of the densely

  13. 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

  14. Fabrication and Formation Mechanism of Ag Nanoplate-Decorated Nanofiber Mats and Their Application in SERS.

    PubMed

    Jia, Peng; Chang, Jiao; Wang, Jianqiang; Zhang, Pan; Cao, Bing; Geng, Yuting; Wang, Xiuxing; Pan, Kai

    2016-01-01

    We report a new simple method to fabricate a highly active SERS substrate consisting of poly-m-phenylenediamine/polyacrylonitrile (PmPD/PAN) decorated with Ag nanoplates. The formation mechanism of Ag nanoplates is investigated. The synthetic process of the Ag nanoplate-decorated PmPD/PAN (Ag nanoplates@PmPD/PAN) nanofiber mats consists of the assembly of Ag nanoparticles on the surface of PmPD/PAN nanofibers as crystal nuclei followed by in situ growth of Ag nanoparticles exclusively into nanoplates. Both the reducibility of the polymer and the concentration of AgNO3 are found to play important roles in the formation and the density of Ag nanoplates. The optimized Ag nanoplates@PmPD/PAN nanofiber mats exhibit excellent activity and reproducibility in surface-enhanced Raman scattering (SERS) detection of 4-mercaptobenzoic acid (4-MBA) with a detection limit of 10(-10)  m, making the Ag nanoplates@PmPD/PAN nanofiber mats a promising substrate for SERS detection of chemical molecules. In addition, this work also provides a design and fabrication process for a 3D SERS substrate made of a reducible polymer with noble metals.

  15. Controllable synthesis of silver nanoparticle-decorated reduced graphene oxide hybrids for ammonia detection.

    PubMed

    Cui, Shumao; Mao, Shun; Wen, Zhenhai; Chang, Jingbo; Zhang, Yang; Chen, Junhong

    2013-05-21

    We demonstrate controllable fabrication of Ag nanoparticle (NP)-decorated reduced graphene oxide (RGO/Ag) hybrids and their application for fast and selective detection of ammonia at room temperature. Ag NPs greatly improved the sensitivity of RGO. The response time (6 s) and recovery time (10 s) are comparable with our previous Ag NP-decorated multiwalled carbon nanotube (MWCNT/Ag) NH3 sensors; however, the sensitivity is about twice that of MWCNT/Ag hybrids. We found that the loading density of NPs greatly affects the sensing performance of RGO/Ag hybrids and a proper NP loading leads to maximum sensitivity.

  16. Aminated polyethersulfone-silver nanoparticles (AgNPs-APES) composite membranes with controlled silver ion release for antibacterial and water treatment applications.

    PubMed

    Haider, M Salman; Shao, Godlisten N; Imran, S M; Park, Sung Soo; Abbas, Nadir; Tahir, M Suleman; Hussain, Manwar; Bae, Wookeun; Kim, Hee Taik

    2016-05-01

    The present study reports the antibacterial disinfection properties of a series of silver nanoparticle (AgNP) immobilized membranes. Initially, polyethersulfone (PES) was functionalized through the introduction of amino groups to form aminated polyethersulfone (NH2-PES, APES). AgNPs were then coordinately immobilized on the surface of the APES composite membrane to form AgNPs-APES. The properties of the obtained membrane were examined by FT-IR, XPS, XRD, TGA, ICP-OES and SEM-EDAX analyses. These structural characterizations revealed that AgNPs ranging from 5 to 40 nm were immobilized on the surface of the polymer membrane. Antibacterial tests of the samples showed that the AgNPs-APES exhibited higher activity than the AgNPs-PES un-functionalized membrane. Generally, the AgNPs-APES 1 cm × 3 cm strip revealed a four times longer life than the un-functionalized AgNPs polymer membranes. The evaluation of the Ag(+) leaching properties of the obtained samples indicated that approximately 30% of the AgNPs could be retained, even after 12 days of operation. Further analysis indicated that silver ion release can be sustained for approximately 25 days. The present study provides a systematic and novel approach to synthesize water treatment membranes with controlled and improved silver (Ag(+)) release to enhance the lifetime of the membranes.

  17. Silver nanoparticles (AgNPs) biosynthesized using pod extract of Cola nitida enhances antioxidant activity and phytochemical composition of Amaranthus caudatus Linn

    NASA Astrophysics Data System (ADS)

    Azeez, Luqmon; Lateef, Agbaje; Adebisi, Segun A.

    2017-02-01

    This study investigates the influence of different concentrations of AgNPs biologically synthesized using pod extract of Cola nitida on antioxidant activity, phenolic contents, flavonoid contents and compositions of Amaranthus caudatus L. AgNPs of 25, 50, 75, 100 and 150 ppm were utilized in growing A. caudatus while water was used as control. Delayed germination for two days was observed for A. caudatus grown with 150 ppm of AgNPs, while others showed no difference. There were 43.3, 38.7, 26.7 and 6.48% improvements in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant activity of A. caudatus grown with 25, 50, 75 and 100 ppm of AgNPs, respectively, compared to control. Antioxidant activity of A. caudatus grown with AgNPs reduced with increase in the concentrations of AgNPs. A. caudatus grown with 50 ppm of AgNPs was the most potent with the least IC50 of 0.67 mg/ml. Significant improvements obtained for phenolic and flavonoid contents grown with AgNPs were concentration dependent. Enhancements of 21.9, 68.19, and 1.98% in phenolic contents were achieved in treatments with 25, 50 and 75 ppm AgNPs, respectively, while 32.58, 35.80, and 7.20% improvement in flavonoids were obtained for 25, 50 and 100 ppm treatments, respectively. Kaempferol and quercetin were the most abundant flavonoids in A. caudatus treated with 50 ppm of AgNPs, showing the highest flavonoid composition. This further confirms A. caudatus grown with 50 ppm of AgNPs as the most potent. This study has shown that concentration-dependent AgNPs can be used to boost antioxidant activity and phytochemical contents of vegetables.

  18. Silver nanoparticles (AgNPs) biosynthesized using pod extract of Cola nitida enhances antioxidant activity and phytochemical composition of Amaranthus caudatus Linn

    NASA Astrophysics Data System (ADS)

    Azeez, Luqmon; Lateef, Agbaje; Adebisi, Segun A.

    2017-01-01

    This study investigates the influence of different concentrations of AgNPs biologically synthesized using pod extract of Cola nitida on antioxidant activity, phenolic contents, flavonoid contents and compositions of Amaranthus caudatus L. AgNPs of 25, 50, 75, 100 and 150 ppm were utilized in growing A. caudatus while water was used as control. Delayed germination for two days was observed for A. caudatus grown with 150 ppm of AgNPs, while others showed no difference. There were 43.3, 38.7, 26.7 and 6.48% improvements in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant activity of A. caudatus grown with 25, 50, 75 and 100 ppm of AgNPs, respectively, compared to control. Antioxidant activity of A. caudatus grown with AgNPs reduced with increase in the concentrations of AgNPs. A. caudatus grown with 50 ppm of AgNPs was the most potent with the least IC50 of 0.67 mg/ml. Significant improvements obtained for phenolic and flavonoid contents grown with AgNPs were concentration dependent. Enhancements of 21.9, 68.19, and 1.98% in phenolic contents were achieved in treatments with 25, 50 and 75 ppm AgNPs, respectively, while 32.58, 35.80, and 7.20% improvement in flavonoids were obtained for 25, 50 and 100 ppm treatments, respectively. Kaempferol and quercetin were the most abundant flavonoids in A. caudatus treated with 50 ppm of AgNPs, showing the highest flavonoid composition. This further confirms A. caudatus grown with 50 ppm of AgNPs as the most potent. This study has shown that concentration-dependent AgNPs can be used to boost antioxidant activity and phytochemical contents of vegetables.

  19. Antimicrobial kinetics of Alstonia scholaris bark extract-mediated AgNPs

    NASA Astrophysics Data System (ADS)

    Supraja, N.; Prasad, T. N. V. K. V.; David, E.; Giridhara Krishna, T.

    2016-06-01

    Nanobiotechnology is considered as one of the important branches of nanotechnology, and research on synthesis of nanoscale materials, silver in particular, using plant and plant parts has been progressing rapidly. Herein, we used bark extract of Alstonia scholaris one of the most important medicinal plants to synthesize silver nanoparticles (AgNPs) which exhibited excellent antimicrobial properties against biofilm formed in drinking water PVC pipes. The biosynthesis of silver nanoparticles was done by treating 90 mL of 1 mM AgNO3 aqueous solution with 10 mL of 5 % bark extract. As-prepared silver nanoparticles were characterized using the biophysical techniques such as UV-Vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, transmission electron microscopy, and dynamic light scattering for the measurement of hydrodynamic diameter and zeta potential. The kinetics of the antimicrobial activity against PVC biofilm of prepared silver nanoparticles were done using comparative solution suspension time-killing assessments and which are evidenced in Epi-fluorescent microscopic observations.

  20. 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.

  1. Low-temperature photoluminescence behaviour of Ag decorated ZnO Nanorods

    NASA Astrophysics Data System (ADS)

    Amutha, A.; Amirthapandian, S.; Sundaravel, B.; Panigrahi, B. K.; Saravanan, K.; Thangadurai, P.

    2016-11-01

    The Ag nanoparticles decorated ZnO nanorods (Ag:ZnO) were prepared by irradiating the precursor solution with ultra-violet radiation for two irradiation times (6 and 17 h). Structural and microstructural studies were done by X-ray diffraction and transmission electron microscopy, respectively. Optical properties were studied by UV-Vis spectroscopy at room temperature (300 K) and photoluminescence (PL) spectroscopy at low-temperature in the temperature range from 5 to 300 K. The Ag:ZnO nanorods possessed the wurtzite structure of ZnO along with the cubic fcc phase of Ag nanoparticles. Average size of Ag nanoparticles in Ag:ZnO nanorods prepared with 6 and 17 h of UV irradiation time was 4 and 16 nm, respectively. The 4 nm Ag nanoparticles had played a crucial role for enhanced PL emission (in the UV region) in the Ag:ZnO nanorods at 60 K. In the case of 16 nm sized Ag nanoparticles, violet emission has been enhanced about 3.5 times compared to that of pure ZnO nanorods and 4 nm-Ag:ZnO nanorods at 5 K. Thermal activation energy of 4 nm-Ag:ZnO and 16 nm-Ag:ZnO nanorods was found to be 0.6 and 0.7 meV, respectively, at low temperature region (5 to 60 K).

  2. 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.

  3. Fabrication of Au@Ag core/shell nanoparticles decorated TiO2 hollow structure for efficient light-harvesting in dye-sensitized solar cells.

    PubMed

    Yun, Juyoung; Hwang, Sun Hye; Jang, Jyongsik

    2015-01-28

    Improving the light-harvesting properties of photoanodes is promising way to enhance the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). We synthesized Au@Ag core/shell nanoparticles decorated TiO2 hollow nanoparticles (Au@Ag/TiO2 HNPs) via sol-gel reaction and chemical deposition. The Au@Ag/TiO2 HNPs exhibited multifunctions from Au@Ag core/shell NPs (Au@Ag CSNPs) and TiO2 hollow nanoparticles (TiO2 HNPs). These Au@Ag CSNPs exhibited strong and broadened localized surface plasmon resonance (LSPR), together with a large specific surface area of 129 m(2) g(-1), light scattering effect, and facile oxidation-reduction reaction of electrolyte from TiO2 HNPs, which resulted in enhancement of the light harvesting. The optimum PCE of η = 9.7% was achieved for the DSSCs using photoanode materials based on TiO2 HNPs containing Au@Ag/TiO2 HNPs (0.2 wt % Au@Ag CSNPs with respect to TiO2 HNPs), which outperformed by 24% enhancement that of conventional photoanodes formed using P25 (η = 7.8%).

  4. 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.

  5. Mechanism of strong visible light photocatalysis by Ag2O-nanoparticle-decorated monoclinic TiO2(B) porous nanorods.

    PubMed

    Paul, Kamal Kumar; Ghosh, Ramesh; Giri, P K

    2016-08-05

    We report on the ultra-high rate of photodegradation of organic dyes under visible light illumination on Ag2O-nanoparticle-decorated (NP) porous pure B-phase TiO2 (TiO2(B)) nanorods (NRs) grown by a solvothermal route. The as-grown TiO2(B) NRs are found to be nanoporous in nature and the Ag2O NPs are uniformly decorated over its surface, since most of the pores work as nucleation sites for the growth of Ag2O NPs. The effective band gap of the TiO2(B)/Ag2O heterostructure (HS), with a weight ratio of 1:1, has been significantly reduced to 1.68 eV from the pure TiO2(B) band gap of 2.8 eV. Steady state and time-resolved photoluminescence (PL) studies show the reduced intensity of visible PL and slower recombination dynamics in the HS samples. The photocatalytic degradation efficiency of the TiO2(B)/Ag2O HS has been investigated using aqueous methyl orange and methylene blue as reference dyes under visible light (390-800 nm) irradiation. It is found that photodegradation by the TiO2(B)/Ag2O HS is about one order of magnitude higher than that of bare TiO2(B) NRs and Ag2O NPs. The optimized TiO2(B)/Ag2O HS exhibited the highest photocatalytic efficiency, with 88.2% degradation for 30 min irradiation. The corresponding first order degradation rate constant is 0.071 min(-1), which is four times higher than the reported values. Furthermore, cyclic stability studies show the high stability of the HS photocatalyst for up to four cycles of use. The major improvement in photocatalytic efficiency has been explained on the basis of enhanced visible light absorption and band-bending-induced efficient charge separation in the HS. Our results demonstrate the long-term stability and superiority of the TiO2(B)/Ag2O HS over the bare TiO2(B) NRs and other TiO2-based photocatalysts for its cutting edge application in hydrogen production and environmental cleaning driven by solar light photocatalysis.

  6. Mechanism of strong visible light photocatalysis by Ag2O-nanoparticle-decorated monoclinic TiO2(B) porous nanorods

    NASA Astrophysics Data System (ADS)

    Paul, Kamal Kumar; Ghosh, Ramesh; Giri, P. K.

    2016-08-01

    We report on the ultra-high rate of photodegradation of organic dyes under visible light illumination on Ag2O-nanoparticle-decorated (NP) porous pure B-phase TiO2 (TiO2(B)) nanorods (NRs) grown by a solvothermal route. The as-grown TiO2(B) NRs are found to be nanoporous in nature and the Ag2O NPs are uniformly decorated over its surface, since most of the pores work as nucleation sites for the growth of Ag2O NPs. The effective band gap of the TiO2(B)/Ag2O heterostructure (HS), with a weight ratio of 1:1, has been significantly reduced to 1.68 eV from the pure TiO2(B) band gap of 2.8 eV. Steady state and time-resolved photoluminescence (PL) studies show the reduced intensity of visible PL and slower recombination dynamics in the HS samples. The photocatalytic degradation efficiency of the TiO2(B)/Ag2O HS has been investigated using aqueous methyl orange and methylene blue as reference dyes under visible light (390-800 nm) irradiation. It is found that photodegradation by the TiO2(B)/Ag2O HS is about one order of magnitude higher than that of bare TiO2(B) NRs and Ag2O NPs. The optimized TiO2(B)/Ag2O HS exhibited the highest photocatalytic efficiency, with 88.2% degradation for 30 min irradiation. The corresponding first order degradation rate constant is 0.071 min-1, which is four times higher than the reported values. Furthermore, cyclic stability studies show the high stability of the HS photocatalyst for up to four cycles of use. The major improvement in photocatalytic efficiency has been explained on the basis of enhanced visible light absorption and band-bending-induced efficient charge separation in the HS. Our results demonstrate the long-term stability and superiority of the TiO2(B)/Ag2O HS over the bare TiO2(B) NRs and other TiO2-based photocatalysts for its cutting edge application in hydrogen production and environmental cleaning driven by solar light photocatalysis.

  7. Effects of reducibility of graphene oxide nanosheets on preparation of AgNPs/GO nanocomposites and their electrocatalytic performance

    NASA Astrophysics Data System (ADS)

    Dou, Yanpeng; Peng, Junjun; Li, Wei; Li, Ming; Liu, Huihong; Zhang, Hanmin

    2015-12-01

    Silver nanoparticles/graphene oxide (AgNPs/GO) nanocomposites were prepared in a solution of AgNO3 and GO. The GO serves not only as a reductant but also as a substrate to support the as-reduced silver nanoparticles. The reducibility of GO was investigated by analyzing the influence factors such as pH, duration, the reaction temperature, and the weight ratio of AgNO3 and GO in the AgNP/GO nanocomposite mixture, which were evaluated by the UV-vis absorption spectroscopy. The results demonstrated that Ag nanoparticles with an average diameter of 5-10 nm were uniformly dispersed on the surface of GO nanosheets under the optimum synthesis conditions of pH between 8 and 11, weight ratio of AgNO3 and GO between 55 % and 60 %, and at 80 °C for 6 h. Moreover, the obtained AgNPs/GO nanocomposites exhibit good electrocatalytic activity for the reduction of p-nitrophenol to 4-(hydroxyamino) phenol.

  8. Enhanced photocatalytic performance of sandwiched ZnO@Ag@Cu₂O nanorod films: the distinct role of Ag NPs in the visible light and UV region.

    PubMed

    Ren, Shoutian; Zhao, Guoliang; Wang, Yingying; Wang, Benyang; Wang, Qiang

    2015-03-27

    Sandwiched ZnO@Ag@Cu2O nanorod films were synthesized by successive electrodeposition, magnetron sputtering and the second electrodeposition. The as-synthesized composites were characterized by x-ray diffraction patterns, field emission scanning electron microscopy, low- and high-resolution transmission electron microscopy and a UV-vis spectrophotometer. Their photocatalytic performance was estimated by the degradation of a methyl orange solution under UV or visible-light irradiation, respectively. In the visible region, due to localized surface plasmon resonance absorption of Ag NPs, ZnO@Ag@Cu2O showed a significantly enhanced photocatalytic performance. The enhancement factor of Ag NPs on the catalytic performance of ZnO@Ag@Cu2O was estimated as a function of the Cu2O deposition time, and the corresponding enhancement mechanism was also evaluated by the monochromatic photocatalytic experiment and discrete dipole approximation simulation. In the UV region, due to the formation of a Schottky junction (e.g. Ag/ZnO, Ag/Cu2O), a limited enhanced photocatalytic performance was also realized for ZnO@Ag@Cu2O photocatalysts.

  9. Green synthesis, characterisation and biological evaluation of AgNPs using Agave americana, Mentha spicata and Mangifera indica aqueous leaves extract.

    PubMed

    Ahmad, Bashir; Shireen, Farah; Bashir, Shumaila; Khan, Ibrar; Azam, Sadiq

    2016-10-01

    The current study was performed to synthesize stable, eco-friendly and bio-compatible silver nano-particles (AgNPs) of Agave americana, Mentha spicata and Mangifera indica leaves and to screen them for biological activities. The ultraviolet-visible spectroscopic analysis revealed that λ-max for AgNPs range from 350-500 nm. All AgNPs possessed polycrystalline structure as notified as intense graphical peaks in complete spectrum of 20 values ranging from 10-80° in X-ray diffraction measurements and supported by scanning electron microscopy data. The size of the nano-particles was confirmed by transmission electron microscopy (30-150 nm). Mass loss at variable temperatures was evaluated by simultaneous thermogravimetric and differential thermal analysis revealed reduction in mass and activity of compounds was notified by temperature increase from 200 to 800 °C, thus concluding it as thermally sensitive compounds. A. americana AgNPs showed significant (96%) activity against Methicillin resistant Staphylococcus aureus, Escherichia coli (95%) and Fusarium oxysporum (89%). Good antioxidant activity was shown by M. spicata AgNPs at 300 µl (79%). M. indica AgNPs showed significant phytotoxic activity (88%) at highest concentration. No haemagglutination reaction was observed for the test samples. The above results revealed that AgNPs synthesized from selected plant species possesses significant antimicrobial and phytotoxic effect.

  10. Synthesis, kinetics and photocatalytic study of "ultra-small" Ag-NPs obtained by a green chemistry method using an extract of Rosa 'Andeli' double delight petals.

    PubMed

    Suárez-Cerda, Javier; Alonso-Nuñez, Gabriel; Espinoza-Gómez, Heriberto; Flores-López, Lucía Z

    2015-11-15

    This paper reports the effect of different concentrations of Rosa 'Andeli' double delight petals aqueous extract (PERA) in the synthesis of silver nanoparticles (Ag-NPs), using an easy green chemistry method. Its kinetics study and photocatalytic activity were also evaluated. The Ag-NPs were obtained using an aqueous silver nitrate solution (AgNO3) with 9.66% w/v, 7.25% w/v, and 4.20% w/v PERA as both reducing-stabilizing agent. The formation of the Ag-NPs was demonstrated by analysis of UV-vis spectroscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). TEM analysis shows spherical nanoparticles in shape and size between ∼0.5 and 1.4nm. A comparative study was done to determine which concentration was the best reducing-stabilizing agent, and we found out that "ultra-small" nanoparticles (0.5-1.1nm) were obtained with 9.66% w/v of PERA. The size of the Ag-NPs depends on the concentration of PERA and Ag(I). The reaction of formation of "ultra-small" Ag-NPs, proved to be first order for metallic precursor (silver) and second order for reducing-stabilizing agent (PERA). The Ag-NPs showed photocatalytic activity, in degradation of commercial dye with an efficiency of 95%.

  11. 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.

  12. Dye decorated ZnO-NWs /CdS-NPs heterostructures for efficiency improvement of quantum dots sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Nayeri, Fatemeh Dehghan; Akbarnejad, Elaheh; Ghoranneviss, Mahmood; Soleimani, Ebrahim Asl; Hashemizadeh, S. A.

    2016-03-01

    High density vertically aligned ZnO nanowire was coated with CdS nanocrystals of different thicknesses by the RF magnetron sputtering process and applied as photoanode in CdS quantum dot sensitized solar cells. Field emission scanning electron microscopy (FESEM), photoluminescence, and X-Ray diffraction (XRD) were utilized to characterize the samples and study their properties. Results demonstrated that, after dye decoration co-sensitized process, the ZnO/CdS heterostructures showed an overall power conversion efficiency of 2.68%, which is 76.3% improvement over that of pristine ZnO/CdS-QDSSC. Thereby, the QDSSC was assembled with modified ZnO/CdS heterostructures by Dye exhibited high performance.

  13. Low-dose AgNPs reduce lung mechanical function and innate immune defense in the absence of cellular toxicity

    PubMed Central

    Botelho, Danielle J.; Leo, Bey Fen; Massa, Christopher B.; Sarkar, Srijata; Tetley, Terry D.; Chung, Kian Fan; Chen, Shu; Ryan, Mary P.; Porter, Alexandra E.; Zhang, Junfeng; Schwander, Stephan K.; Gow, Andrew J.

    2016-01-01

    Multiple studies have examined the direct cellular toxicity of silver nanoparticles (AgNPs). However, the lung is a complex biological system with multiple cell types and a lipid-rich surface fluid; therefore, organ level responses may not depend on direct cellular toxicity. We hypothesized that interaction with the lung lining is a critical determinant of organ level responses. Here, we have examined the effects of low dose intratracheal instillation of AgNPs (0.05 µg/g body weight) 20 and 110nm diameter in size, and functionalized with citrate or polyvinylpyrrolidone. Both size and functionalization were significant factors in particle aggregation and lipid interaction in vitro. One day post-intratracheal instillation lung function was assessed, and bronchoalveolar lavage (BAL) and lung tissue collected. There were no signs of overt inflammation. There was no change in surfactant protein-B content in the BAL but there was loss of surfactant protein-D with polyvinylpyrrolidone (PVP)-stabilized particles. Mechanical impedance data demonstrated a significant increase in pulmonary elastance as compared to control, greatest with 110nm PVP-stabilized particles. Seven days post-instillation of PVP-stabilized particles increased BAL cell counts, and reduced lung function was observed. These changes resolved by 21 days. Hence, AgNP-mediated alterations in the lung lining and mechanical function resolve by 21 days. Larger particles and PVP stabilization produce the largest disruptions. These studies demonstrate that low dose AgNPs elicit deficits in both mechanical and innate immune defense function, suggesting that organ level toxicity should be considered. PMID:26152688

  14. Low-dose AgNPs reduce lung mechanical function and innate immune defense in the absence of cellular toxicity.

    PubMed

    Botelho, Danielle J; Leo, Bey Fen; Massa, Christopher B; Sarkar, Srijata; Tetley, Terry D; Chung, Kian Fan; Chen, Shu; Ryan, Mary P; Porter, Alexandra E; Zhang, Junfeng; Schwander, Stephan K; Gow, Andrew J

    2016-01-01

    Multiple studies have examined the direct cellular toxicity of silver nanoparticles (AgNPs). However, the lung is a complex biological system with multiple cell types and a lipid-rich surface fluid; therefore, organ level responses may not depend on direct cellular toxicity. We hypothesized that interaction with the lung lining is a critical determinant of organ level responses. Here, we have examined the effects of low dose intratracheal instillation of AgNPs (0.05 μg/g body weight) 20 and 110 nm diameter in size, and functionalized with citrate or polyvinylpyrrolidone. Both size and functionalization were significant factors in particle aggregation and lipid interaction in vitro. One day post-intratracheal instillation lung function was assessed, and bronchoalveolar lavage (BAL) and lung tissue collected. There were no signs of overt inflammation. There was no change in surfactant protein-B content in the BAL but there was loss of surfactant protein-D with polyvinylpyrrolidone (PVP)-stabilized particles. Mechanical impedance data demonstrated a significant increase in pulmonary elastance as compared to control, greatest with 110 nm PVP-stabilized particles. Seven days post-instillation of PVP-stabilized particles increased BAL cell counts, and reduced lung function was observed. These changes resolved by 21 days. Hence, AgNP-mediated alterations in the lung lining and mechanical function resolve by 21 days. Larger particles and PVP stabilization produce the largest disruptions. These studies demonstrate that low dose AgNPs elicit deficits in both mechanical and innate immune defense function, suggesting that organ level toxicity should be considered.

  15. Photoconversion of 4-nitrophenol in the presence of hydrazine with AgNPs-TiO2 nanoparticles prepared by the sol-gel method.

    PubMed

    Hernández-Gordillo, Agileo; Arroyo, Missael; Zanella, R; Rodríguez-González, V

    2014-03-15

    The photocatalytic properties of functionalized TiO2 with silver nanoparticles (AgNPs) for the conversion of 4-nitrophenol to 4-aminophenol in the presence of hydrazine were investigated. The TiO2 semiconductor synthesized by the sol-gel method was functionalized with AgNPs at different loadings, and their structural and optical properties were characterized by several techniques. The functionalized TiO2 with 1.5wt% AgNPs presented the highest photocatalytic activity for the conversion of 4-nitrophenol with appropriate hydrazine concentrations (0.5M). The photoefficiency enhancement under UV light irradiation was attributed to the electron transfer from the TiO2 semiconductor surface to the adsorbed acceptor reactant (4-nitrophenol) through the deposited AgNPs.

  16. Aniline as a dispersing and stabilizing agent for reduced graphene oxide and its subsequent decoration with Ag nanoparticles for enzymeless hydrogen peroxide detection.

    PubMed

    Liu, Sen; Wang, Lei; Tian, Jingqi; Luo, Yonglan; Zhang, Xinxin; Sun, Xuping

    2011-11-15

    An aqueous dispersion of reduced graphene oxide (rGO) has been successfully prepared via chemical reduction of graphene oxide (GO) by hydrazine hydrate in the presence of aniline for the first time. The noncovalent functionalization of rGO by aniline leads to a rGO dispersion that can be very stable for several months without the observation of any floating or precipitated particles. Several analytical techniques including Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) have been used to characterize the resulting rGO. Taking advantages of the fact reducing ability of aniline toward AgNO(3), we further demonstrated the subsequent decoration of rGO with Ag nanoparticles (AgNPs) by in situ chemical reduction of silver salts. It was found that such AgNP/rGO nanocomposites exhibit good catalytic activity toward the reduction of hydrogen peroxide (H(2)O(2)), leading to an enzymeless sensor with a fast amperometric response time of less than 2s. The linear detection range is estimated to be from 100 μM to 80 mM (r=0.9991), and the detection limit is estimated to be 7.1 μM at a signal-to-noise ratio of 3.

  17. Composite structure of SiO2@AgNPs@p-SiNWs for enhanced broadband optical antireflection.

    PubMed

    Lu, Ren; Wang, Yewu; Gu, Lin; Wang, Wei; Fang, Yanjun; Sha, Jian

    2013-07-29

    The composite structure of SiO(2)@AgNPs@p-SiNWs based on silicon nanowires (SiNWs) produced by metal-assisted chemical etching (MaCE) method has been designed to realize the significant reflection suppression over a broad wavelength range (300 - 2500 nm). Especially, the reflectivity of the structure even below 0.3% at a wide range of 620 - 1950 nm can be achieved. It also has been demonstrated that SiO(2) capers play a dominant role in the significant reflection suppression of the composite structure.

  18. Selective colorimetric sensors based on the monitoring of an unmodified silver nanoparticles (AgNPs) reduction for a simple and rapid determination of mercury

    NASA Astrophysics Data System (ADS)

    Jarujamrus, Purim; Amatatongchai, Maliwan; Thima, Araya; Khongrangdee, Thatsanee; Mongkontong, Chakrit

    2015-05-01

    In this work, selective colorimetric sensors for simple and rapid detection of Hg(II) ions based on the monitoring of an unmodified silver nanoparticles (AgNPs) reduction were developed. The average diameter of synthesized AgNPs was 8.3 ± 1.4 nm which was characterized by transmission electron microscopy (TEM). The abrupt change in absorbance of the unmodified AgNPs was observed which progressively decreased and slightly shifted to the blue wavelength as the concentration of Hg(II) increased, indicating the oxidation of Ag(0) to Ag(I) occurred. It appears that the AgNPs were oxidized by Hg(II), resulting in disintegration of the AgNPs into smaller particles as well as mediating the reduction of Hg(II) to Hg(0) adsorbed onto the surface of AgNPs. The adsorption of Hg(0) resulted in the lack of sufficient charges on AgNPs surfaces due to the decrease in the surface coverage of negatively charged citrate molecules, which then leaded to enlargement of AgNPs. The calibration curve of this technique was demonstrated from 0.5 to 7 ppm (r2 = 0.995), the limit of detection (LOD) was 0.06 ppm (SDblank/slope of calibration curve) with the precision (RSD, n = 4) of 3.24-4.53. Interestingly, the results show a significant enhance in the Hg(II) analytical sensitivity when Cu(II) is doped onto the unmodified AgNPs, which improves the quantitative detection limit to 0.008 ppm. In addition, greater selectivity toward Hg(II) compared with the other metal ions tested was observed. Furthermore, the percentage recoveries of spiked drinking water, tap water and SRM1641d (mercury in water) were in acceptable range with a good precision (RSD) which were in agreement with the values obtained from graphite furnace atomic absorption spectrometer (GFAAS). The technique proposed in this study provides a rapid, simple, sensitive and selective detection method for Hg(II) in water samples.

  19. Selective colorimetric sensors based on the monitoring of an unmodified silver nanoparticles (AgNPs) reduction for a simple and rapid determination of mercury.

    PubMed

    Jarujamrus, Purim; Amatatongchai, Maliwan; Thima, Araya; Khongrangdee, Thatsanee; Mongkontong, Chakrit

    2015-05-05

    In this work, selective colorimetric sensors for simple and rapid detection of Hg(II) ions based on the monitoring of an unmodified silver nanoparticles (AgNPs) reduction were developed. The average diameter of synthesized AgNPs was 8.3±1.4nm which was characterized by transmission electron microscopy (TEM). The abrupt change in absorbance of the unmodified AgNPs was observed which progressively decreased and slightly shifted to the blue wavelength as the concentration of Hg(II) increased, indicating the oxidation of Ag(0) to Ag(I) occurred. It appears that the AgNPs were oxidized by Hg(II), resulting in disintegration of the AgNPs into smaller particles as well as mediating the reduction of Hg(II) to Hg(0) adsorbed onto the surface of AgNPs. The adsorption of Hg(0) resulted in the lack of sufficient charges on AgNPs surfaces due to the decrease in the surface coverage of negatively charged citrate molecules, which then leaded to enlargement of AgNPs. The calibration curve of this technique was demonstrated from 0.5 to 7ppm (r(2)=0.995), the limit of detection (LOD) was 0.06ppm (SDblank/slope of calibration curve) with the precision (RSD, n=4) of 3.24-4.53. Interestingly, the results show a significant enhance in the Hg(II) analytical sensitivity when Cu(II) is doped onto the unmodified AgNPs, which improves the quantitative detection limit to 0.008ppm. In addition, greater selectivity toward Hg(II) compared with the other metal ions tested was observed. Furthermore, the percentage recoveries of spiked drinking water, tap water and SRM1641d (mercury in water) were in acceptable range with a good precision (RSD) which were in agreement with the values obtained from graphite furnace atomic absorption spectrometer (GFAAS). The technique proposed in this study provides a rapid, simple, sensitive and selective detection method for Hg(II) in water samples.

  20. 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.

  1. Influences of Ag-NPs doping chitosan/calcium silicate nanocomposites for optical and antibacterial activity.

    PubMed

    El-Nahrawy, Amany M; Ali, Ahmed I; Abou Hammad, Ali B; Youssef, Ahmed M

    2016-12-01

    Chitosan (CS)/calcium silicate nanocomposites pure and doped with Ag ions (1, 2mol%) were prepared via sol-gel method. The prepared CS/calcium silicate nanocomposites were investigated through X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The XRD results, indicating that after increasing the Ag ions in the CS/calcium silicate nanocomposite the crystallinity degree increased regularly in the prepared nanocomposites accompanying to the continuously rearrangement in the internal structure of nanocomposite under the effect of inorganic nanoparticles. Correspondingly, the optical properties of the prepared nanocomposites films were measured using UV/vis spectroscopy. The reflectance increased while the energy band gap decreased from 3.96eV to 2.43eV with Ag-ions concentration. More over the transition type changed from direct into indirect by adding Ag-ions, indicate that new band between valence and conduction band were formed. In addition, the optical parameters showed an increase in refractive indices and decrease in the surface and volume energies losses with increasing Ag-ions. Correspondingly, the prepared nanocomposites exhibited good antibacterial activity against gram positive (Staphylococcus aureus), gram negative (Pseudomonas aeruginosa) bacteria and fungi (Candidia albicans). The results suggested that the prepared CS/calcium silicate nanocomposites can be a promised candidate for optical sensors applications and smart packaging materials.

  2. Synthesis of Ag-decorated porous TiO2 nanowires through a sunlight induced reduction method and its enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Yao, Yun-Chang; Dai, Xin-Rong; Hu, Xiao-Ye; Huang, Su-Zhen; Jin, Zhen

    2016-11-01

    In this work, Ag-decorated porous TiO2 nanowires were successfully synthesized via a facile and low-cost sunlight induced reduction method. The cooperation of sunlight irradiation and ethanol reduction results the formation and decoration of the Ag nanoparticles on the porous TiO2 nanowires. The structure of the Ag-decorated porous TiO2 nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Energy dispersive spectroscopy (EDS) measurements. It can be seen that the Ag nanoparticles are well dispersed within the porous TiO2 nanowires. The as-prepared Ag-decorated porous TiO2 nanowires exhibits excellent photocatalytic properties. The photocatalytic tests show that 10 ppm methylene blue can be photodegraded within 60 min. And the photodegradation ratio of the Ag-decorated porous TiO2 nanowires much higher than that of P25 and porous TiO2 nanowires. Moreover, the Ag-decorated porous TiO2 nanowires also reveal good photocatalytic activity towards to other organic pollutions, such as phenol and R6G. Therefore, it is believed that the Ag-decorated porous TiO2 nanowires can be used as a potential high performance photocatalyst in wastewater treatment.

  3. Biosynthesis of AgNPs using Carica Papaya peel extract and evaluation of its antioxidant and antimicrobial activities.

    PubMed

    Kokila, T; Ramesh, P S; Geetha, D

    2016-12-01

    Waste fruit peel mediated synthesis of silver nanoparticles (AgNPs) is a green chemistry approach that links nanotechnology and biotechnology. Using biological medium such as peel extract for the biosynthesis of nanoparticles is an ecofriendly and emerging scientific trend. With this back drop the present study focused on the biosynthesis of AgNPs using Carica Papaya peel extract (CPPE) and evaluation of its antimicrobial potentials of the nanoparticles against different human pathogens and to investigate the free radical scavenging activity. Water soluble antioxidant constituents present in Carica Papaya peel extract were mainly responsible for the reduction of silver ions to nanosized Ag particles. UV-vis spectral analysis shows surface plasmon resonance band at 430nm. The presence of active proteins and phenolic groups present in the biomass before and after reduction was identified by Fourier transform infrared spectroscopy. X-ray diffraction study shows the average size of the silver nanoparticles is in the range of 28nm, as well as revealed their face centered cubic structure. Atomic force microscope image gives the 3D topological characteristic of silver nanoparticles and the particle size ranges from 10 to 30nm. The average particle size distribution of silver nanoparticles is 161nm (Dynamic light scattering) and the corresponding average zeta potential value is -20.5mV, suggesting higher stability of silver nanoparticles. Biologically synthesized nanoparticles efficiently inhibited pathogenic organisms both gram-positive and gram-negative bacteria. The biosynthesized nanoparticles might serve as a potent antioxidant as revealed by DPPH and ABT(S+)assay.

  4. Simultaneous determination of epinephrine and dopamine by electrochemical reduction on the hybrid material SiO₂/graphene oxide decorated with Ag nanoparticles.

    PubMed

    Cincotto, Fernando H; Canevari, Thiago C; Campos, Anderson M; Landers, Richard; Machado, Sérgio A S

    2014-09-21

    This paper describes the synthesis, characterization and applications of a new hybrid material composed of mesoporous silica (SiO2) modified with graphene oxide (GO), SiO2/GO, obtained by the sol-gel process using HF as the catalyst. The hybrid material, SiO2/GO, was decorated with silver nanoparticles (AgNPs) with a size of less than 20 nanometres, prepared directly on the surface of the material using N,N-dimethylformamide (DMF) as the reducing agent. The resulting material was designated as AgNP/SiO2/GO. The Ag/SiO2/GO material was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and high-resolution transmission electron microscopy (HR-TEM). A glassy carbon electrode modified with AgNP/SiO2/GO was used in the development of a sensitive electrochemical sensor for the simultaneous determination of epinephrine and dopamine employing electrocatalytic reduction using squarewave voltammetry. Well-defined and separate reduction peaks were observed in PBS buffer at pH 7. No significant interference was seen for primarily biological interferents such as uric acid and ascorbic acid in the detection of dopamine and epinephrine. Our study demonstrated that the resultant AgNP/SiO2/GO-modified electrode is highly sensitive for the simultaneous determination of dopamine and epinephrine, with the limits of detection being 0.26 and 0.27 μmol L(-1), respectively. The AgNP/SiO2/GO-modified electrode is highly selective and can be used to detect dopamine and epinephrine in a human urine sample.

  5. Core-Shell γ-Fe2O3/SiO2/PCA/Ag-NPs Hybrid Nanomaterials as a New Candidate for Future Cancer Therapy

    NASA Astrophysics Data System (ADS)

    Soleyman, R.; Pourjavadi, A.; Masoud, N.; Varamesh, A.

    2014-04-01

    In the current study, γ-Fe2O3/SiO2/PCA/Ag-NPs hybrid nanomaterials were successfully synthesized and characterized. At first, prepared γ-Fe2O3 core nanoparticles were modified by SiO2 layer. Then they were covered by poly citric acid (PCA) via melting esterification method as well. PCA shell acts as an effective linker, and provides vacancies for conveying drugs. Moreover, this shell as an effective capping agent directs synthesis of silver nanoparticles (Ag-NPs) via in situ photo-reduction of silver ions by sunlight-UV irradiation. This system has several benefits as a suitable cancer therapy nanomaterial. Magnetic nanoparticles (MNPs) can guide Ag-NPs and drugs to cancer cells and then Ag-NPs can affect those cells via Ag-NPs anti-angiogenesis effect. Size and structure of the prepared magnetic hybrid nanomaterials were characterized using FTIR and UV-Vis spectra, AFM and TEM pictures and XRD data.

  6. Metabolic responses of the growing Daphnia similis to chronic AgNPs exposure as revealed by GC-Q-TOF/MS and LC-Q-TOF/MS.

    PubMed

    Zhang, Bo; Zhang, Hui; Du, Chunlei; Ng, Qin Xiang; Hu, Chaoyang; He, Yiliang; Ong, Choon Nam

    2017-05-01

    Silver nanoparticles (AgNPs) are one of the most widely used nanomaterials. Their fast-growing utilization has increased the occurrence of AgNPs in the environment, posing potential health and ecological risks. In this study, we conducted chronic toxicity tests and investigated the metabolic changes of the growing Daphna similis with exposure to 0, 0.02, and 1 ppb AgNPs, using non-targeted mass spectrometry-based metabolomics. To the best of our knowledge, this study is the first to report the baseline metabolite change of a common aquatic organism Daphnia crustacean through its life-cycle. The results show a dynamic kinetic pattern of the growing Daphnia's metabolome underwent a cycle from day 0 to day 21, with the level of metabolites gradually increasing from day 0 to day 13, before falling back to the baseline level of day 0 on day 21. As for the samples exposed to environmental concentrations of AgNPs, although without morphological or structural changes, numerous metabolite changes occurred abruptly during the first 10 days, and these changes reached steady state by day 13. The significant changes in certain metabolites, such as amino acids (serine, threonine and tyrosine), sugars (d-allose) and fatty acids (arachidonic acid) revealed new insights into how these metabolites in Daphnia respond to chronic AgNPs stress. These findings highlight the capability of metabolomics to discover early metabolic responses to environmental silver nanoparticles.

  7. Ag-Decorated Localized Surface Plasmon-Enhanced Ultraviolet Electroluminescence from ZnO Quantum Dot-Based/GaN Heterojunction Diodes by Optimizing MgO Interlayer Thickness

    NASA Astrophysics Data System (ADS)

    Chen, Cheng; Chen, Jingwen; Zhang, Jun; Wang, Shuai; Zhang, Wei; Liang, Renli; Dai, Jiangnan; Chen, Changqing

    2016-10-01

    We demonstrate the fabrication and characterization of localized surface plasmon (LSP)-enhanced n-ZnO quantum dot (QD)/MgO/p-GaN heterojunction light-emitting diodes (LEDs) by embedding Ag nanoparticles (Ag-NPs) into the ZnO/MgO interface. The maximum enhancement ration of the Ag-NP-decorated LEDs in electroluminescence (EL) is 4.3-fold by optimizing MgO electron-blocking layer thickness. The EL origination was investigated qualitatively in terms of photoluminescence (PL) results. Through analysis of the energy band structure of device and carrier transport mechanisms, it suggests that the EL enhancement is attributed to the increased rate of spontaneous emission and improved internal quantum efficiency induced by exciton-LSP coupling.

  8. Application of cow milk-derived carbon dots/Ag NPs composite as the antibacterial agent

    NASA Astrophysics Data System (ADS)

    Han, Shuai; Zhang, He; Xie, Yujie; Liu, Liangliang; Shan, Changfu; Li, Xiangkai; Liu, Weisheng; Tang, Yu

    2015-02-01

    Cow milk-derived carbon dots (CMCDs) were prepared by hydrothermal treatment of cow milk, and the as-prepared CMCDs were further extracted by ethyl acetate to obtain amphiphilic CMCDs (ACMCDs). Using the ACMCDs both as a reducing agent and a template, the ACMCDs-supported silver nanoparticles (ACMCD-Ag nanocomposites) were prepared, which showed good biocidal effect on both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacterias. After that, a novel ACMCD-Ag/polymethylmethacrylate nanocomposite antibacterial film was fabricated by solvent casting method. Due to the excellent antibacterial, light admitting, and flexible properties, the nanocomposite antibacterial film is considered to be of great potential in applications.

  9. Antibacterial activity and synergistic effect of biosynthesized AgNPs with antibiotics against multidrug-resistant biofilm-forming coagulase-negative staphylococci isolated from clinical samples.

    PubMed

    Thomas, Roshmi; Nair, Aswathi P; Kr, Soumya; Mathew, Jyothis; Ek, Radhakrishnan

    2014-05-01

    Silver nanoparticles form promising template for designing antimicrobial agents against drug resistant pathogenic microorganisms. Thus, the development of a reliable green approach for the synthesis of nanoparticles is an important aspect of current nanotechnology research. In the present investigation, silver nanoparticles synthesized by a soil Bacillus sp. were characterized using UV-vis spectroscopy, FTIR, SEM, and EDS. The antibacterial potential of biosynthesized silver nanoparticles, standard antibiotics, and their conjugates were evaluated against multidrug-resistant biofilm-forming coagulase-negative S. epidermidis strains, S. aureus, Salmonella Typhi, Salmonella Paratyphi, and V. cholerae. Interestingly, silver nanoparticles (AgNPs) showed remarkable antibacterial activity against all the test strains with the highest activity against S. epidermidis strains 145 and 152. In addition, the highest synergistic effect of AgNPs was observed with chloramphenicol against Salmonella typhi. The results of the study clearly indicate the promising biomedical applications of biosynthesized AgNPs.

  10. Comparative effects on rat primary astrocytes and C6 rat glioma cells cultures after 24-h exposure to silver nanoparticles (AgNPs)

    NASA Astrophysics Data System (ADS)

    Salazar-García, Samuel; Silva-Ramírez, Ana Sonia; Ramirez-Lee, Manuel A.; Rosas-Hernandez, Hector; Rangel-López, Edgar; Castillo, Claudia G.; Santamaría, Abel; Martinez-Castañon, Gabriel A.; Gonzalez, Carmen

    2015-11-01

    The aim of this work was to compare the effects of 24-h exposure of rat primary astrocytes and C6 rat glioma cells to 7.8 nm AgNPs. Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor and current treatments lead to diverse side-effects; for this reason, it is imperative to investigate new approaches, including those alternatives provided by nanotechnology, like nanomaterials (NMs) such as silver nanoparticles. Herein, we found that C6 rat glioma cells, but no primary astrocytes, decreased cell viability after AgNPs treatment; however, both cell types diminished their proliferation. The decrease of glioma C6 cells proliferation was related with necrosis, while in primary astrocytes, the decreased proliferation was associated with the induction of apoptosis. The ionic control (AgNO3) exerted a different profile than AgNPs; the bulk form did not modify the basal effect in each determination, whereas cisplatin, a well-known antitumoral drug used as a comparative control, promoted cytotoxicity in both cell types at specific concentrations. Our findings prompt the need to determine the fine molecular and cellular mechanisms involved in the differential biological responses to AgNPs in order to develop new tools or alternatives based on nanotechnology that may contribute to the understanding, impact and use of NMs in specific targets, like glioblastoma cells.

  11. Ag-NPs embedded in two novel Zn3/Zn5-cluster-based metal-organic frameworks for catalytic reduction of 2/3/4-nitrophenol.

    PubMed

    Wu, Xue-Qian; Huang, Dan-Dan; Zhou, Zhi-Hang; Dong, Wen-Wen; Wu, Ya-Pan; Zhao, Jun; Li, Dong-Sheng; Zhang, Qichun; Bu, Xianhui

    2017-02-21

    By utilizing symmetrical pentacarboxylate ligands, 3,5-di(2',5'-dicarboxylphenyl)benzoic acid (H5L1) and 3,5-di(2',4'-dicarboxylphenyl)benzoic acid (H5L2), two novel porous Zn-MOFs, [Zn5(μ3-H2O)2(L1)2]·3DMA·4H2O (CTGU-3) and [Zn3(μ3-OH)L2(H2O)3]·H2O (CTGU-4) have been synthesized under solvothermal conditions. CTGU-3 and CTGU-4 exhibit 3D microporous frameworks with flu and dia topologies and possess unique secondary building units [Zn5(μ3-H2O)2(RCO2)6] and [Zn3(μ3-OH)(RCO2)3], respectively. Such porous systems create a unique space or surface to accommodate Ag nanoparticles (Ag NPs), which could efficiently prevent Ag NPs from aggregation and leaching. In this work, two new Ag@Zn-MOF composites, denoted as Ag@CTGU, have been successfully fabricated through solution infiltration, for the reduction of nitrophenol. Compared with CTGU-4, CTGU-3 shows enhanced catalytic efficiency toward the reaction when it is used as a catalyst support of Ag NPs. Moreover, gas sorption and luminescence properties of two compounds were also investigated.

  12. 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.

  13. Ag-decorated TiO2 photocatalytic membrane with hierarchical architecture: photocatalytic and anti-bacterial activities.

    PubMed

    Goei, Ronn; Lim, Teik-Thye

    2014-08-01

    Ag-decorated TiO2 (Ag-TiO2) photocatalytic membranes have been fabricated by using Pluronic P-123 as a pore-forming and structure-directing agent. Six different hierarchical architectures were obtained by multilayer coating of different Ag-TiO2 sols. The porous structure of the resulting layers could be fine-tuned by altering the amounts of P-123 and AgNO3 added during the preparation of TiO2 sols. Physico-chemical and morphological properties of different Ag-TiO2 layers were thoroughly investigated. Ag nanoparticles were successfully incorporated into the TiO2 matrix. The Ag-TiO2 membranes possessed multi-functionality of membrane retention, Ag-enhanced TiO2 photocatalytic activity and anti-bacterial action. They were evaluated through experiments using a batch reactor and a photocatalytic membrane reactor (PMR). The best performing membrane was able to remove up to 1007 mg m(-2) h(-1) of Rhodamine B in the PMR. Two phenomena (photocatalytic degradation and adsorptive-membrane retention) that were responsible for the RhB removal were evaluated. In the batch reactor operated in dark, the membranes were able to remove greater than 5-logs of Escherichia coli. The membrane with the highest percentage of Ag incorporated was able to remove close to 7-logs of E. coli when operated in the PMR.

  14. Au or Ag nanoparticle-decorated 3D urchin-like TiO2 nanostructures: synthesis, characterization, and enhanced photocatalytic activity.

    PubMed

    Xiang, Liqin; Zhao, Xiaopeng; Shang, Chaohong; Yin, Jianbo

    2013-08-01

    The semiconductors decorated with noble metals have attracted increasing attention due to their interesting physical and chemical properties. Here, 3D urchin-like hierarchical TiO2 nanostructures decorated with Au or Ag nanoparticles were prepared by wet-chemical process. The morphology and structure were characterized by different techniques. It shows that Au or Ag nanoparticles with narrow distribution are uniformly loaded on urchin-like TiO2 nanostructures, and the resulted composite nanostructures show distinct surface plasmon absorption band and quenched photoluminence compared to pure TiO2 nanostructures. Photocatalytic tests show both Au-decorated TiO2 and Ag-decorated TiO2 exhibit enhanced photocatalytic activity for photodegradation of methyl blue in water.

  15. 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.

  16. 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.

  17. 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.

  18. Gas-phase self-assembly of uniform silica nanostructures decorated and doped with silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Lai, Chao-Shun; Chen, Yi-Chen; Wang, Hsiao-Fang; Ho, Hsin-Chia; Ho, Rong-Ming; Tsai, De-Hao

    2017-01-01

    We report a systematic study of the controlled gas-phase synthesis of silver-silica hybrid nanostructures (Ag-SiO2 NP) using the concept of evaporation-induced self-assembly. The approach includes the use of a direct gas-phase electrophoresis for size classification and in situ characterization of mobility size. Transmission electron microscopy and ultraviolet-visible light spectroscopy were employed complementarily to determine the morphology and surface plasmon resonance of Ag-SiO2 NP. Results show that two types of Ag-SiO2 NPs were successfully synthesized: (1) AgNPs decorated on a SiO2-NP (Ag-T-SiO2 NP), and (2) AgNPs doped in a cluster of SiO2-NPs (Ag-C-SiO2 NP). The physical size, morphology, and compositions of Ag-SiO2 NPs were tunable through the adjustments of precursor concentrations and the selected mobility sizes. The results also show that SPR performance, colloidal stability, and dispersibility of AgNPs enhanced significantly in an aqueous environment after the hybridization with SiO2-NP (especially for Ag-C-SiO2 NP). The results and corresponding methodology summarized here provide the proof of concept to fabricate high-purity AgNP-based hybrid nanostructures through gas-phase evaporation-induced self-assembly for future biomedical applications (e.g., hyperthermal therapy, targeted drug delivery, and antibacterial applications).

  19. The antimicrobial effect of silicon nanowires decorated with silver and copper nanoparticles.

    PubMed

    Fellahi, Ouarda; Sarma, Rupak K; Das, Manash R; Saikia, Ratul; Marcon, Lionel; Coffinier, Yannick; Hadjersi, Toufik; Maamache, Mustapha; Boukherroub, Rabah

    2013-12-13

    The paper reports on the preparation and antibacterial activity of silicon nanowire (SiNW) substrates coated with Ag or Cu nanoparticles (NPs) against Escherichia coli (E. coli) bacteria. The substrates are easily prepared using the metal-assisted chemical etching of crystalline silicon in hydrofluoric acid/silver nitrate (HF/AgNO3) aqueous solution. Decoration of the SiNWs with metal NPs is achieved by simple immersion in HF aqueous solutions containing silver or copper salts. The SiNWs coated with Ag NPs are biocompatible with human lung adenocarcinoma epithelial cell line A549 while possessing strong antibacterial properties to E. coli. In contrast, the SiNWs decorated with Cu NPs showed higher cytotoxicity and slightly lower antibacterial activity. Moreover, it was also observed that leakage of sugars and proteins from the cell wall of E. coli in interaction with SiNWs decorated with Ag NPs is higher compared to SiNWs modified with Cu NPs.

  20. The antimicrobial effect of silicon nanowires decorated with silver and copper nanoparticles

    NASA Astrophysics Data System (ADS)

    Fellahi, Ouarda; Sarma, Rupak K.; Das, Manash R.; Saikia, Ratul; Marcon, Lionel; Coffinier, Yannick; Hadjersi, Toufik; Maamache, Mustapha; Boukherroub, Rabah

    2013-12-01

    The paper reports on the preparation and antibacterial activity of silicon nanowire (SiNW) substrates coated with Ag or Cu nanoparticles (NPs) against Escherichia coli (E. coli) bacteria. The substrates are easily prepared using the metal-assisted chemical etching of crystalline silicon in hydrofluoric acid/silver nitrate (HF/AgNO3) aqueous solution. Decoration of the SiNWs with metal NPs is achieved by simple immersion in HF aqueous solutions containing silver or copper salts. The SiNWs coated with Ag NPs are biocompatible with human lung adenocarcinoma epithelial cell line A549 while possessing strong antibacterial properties to E. coli. In contrast, the SiNWs decorated with Cu NPs showed higher cytotoxicity and slightly lower antibacterial activity. Moreover, it was also observed that leakage of sugars and proteins from the cell wall of E. coli in interaction with SiNWs decorated with Ag NPs is higher compared to SiNWs modified with Cu NPs.

  1. Boron nitride nanosheets decorated with silver nanoparticles through mussel-inspired chemistry of dopamine.

    PubMed

    Roy, Arup Kumer; Park, Byoungnam; Lee, Kang Seok; Park, Sung Young; In, Insik

    2014-11-07

    Boron nitride nanosheet (BNNS) decorated with silver nanoparticles (AgNPs) was successfully synthesized via mussel-inspired chemistry of dopamine. Poly(dopamine)-functionalized BNNS (PDA-BNNS) was prepared by adding dopamine into the aqueous dispersion of hydroxylated BNNS (OH-BNNS) at alkaline condition. AgNPs were decorated on PDA-BNNS through spontaneous reduction of silver cations by catechol moieties of a PDA layer on BNNS, resulting in AgNP-BNNS with good dispersion stability. Incorporation of PDA on BNNS not only played a role as a surface functionalization method of BNNS, but also provided a molecular platform for creating very sophisticated two-dimensional (2D) BNNS-based hybrid nanomaterials such as metal nanoparticle-decorated BNNS.

  2. Boron nitride nanosheets decorated with silver nanoparticles through mussel-inspired chemistry of dopamine

    NASA Astrophysics Data System (ADS)

    Kumer Roy, Arup; Park, Byoungnam; Lee, Kang Seok; Park, Sung Young; In, Insik

    2014-11-01

    Boron nitride nanosheet (BNNS) decorated with silver nanoparticles (AgNPs) was successfully synthesized via mussel-inspired chemistry of dopamine. Poly(dopamine)-functionalized BNNS (PDA-BNNS) was prepared by adding dopamine into the aqueous dispersion of hydroxylated BNNS (OH-BNNS) at alkaline condition. AgNPs were decorated on PDA-BNNS through spontaneous reduction of silver cations by catechol moieties of a PDA layer on BNNS, resulting in AgNP-BNNS with good dispersion stability. Incorporation of PDA on BNNS not only played a role as a surface functionalization method of BNNS, but also provided a molecular platform for creating very sophisticated two-dimensional (2D) BNNS-based hybrid nanomaterials such as metal nanoparticle-decorated BNNS.

  3. Bioinspired anchoring AgNPs onto micro-nanoporous TiO2 orthopedic coatings: Trap-killing of bacteria, surface-regulated osteoblast functions and host responses.

    PubMed

    Jia, Zhaojun; Xiu, Peng; Li, Ming; Xu, Xuchen; Shi, Yuying; Cheng, Yan; Wei, Shicheng; Zheng, Yufeng; Xi, Tingfei; Cai, Hong; Liu, Zhongjun

    2016-01-01

    The therapeutic applications of silver nanoparticles (AgNPs) against biomedical device-associated infections (BAI), by local delivery, are encountered with risks of detachment, instability and nanotoxicity in physiological milieus. To firmly anchor AgNPs onto modified biomaterial surfaces through tight physicochemical interactions would potentially relieve these concerns. Herein, we present a strategy for hierarchical TiO2/Ag coating, in an attempt to endow medical titanium (Ti) with anticorrosion and antibacterial properties whilst maintaining normal biological functions. In brief, by harnessing the adhesion and reactivity of bioinspired polydopamine, silver nanoparticles were easily immobilized onto peripheral surface and incorporated into interior cavity of a micro/nanoporous TiO2 ceramic coating in situ grown from template Ti. The resulting coating protected the substrate well from corrosion and gave a sustained release of Ag(+) up to 28 d. An interesting germicidal effect, termed "trap-killing", was observed against Staphylococcus aureus strain. The multiple osteoblast responses, i.e. adherence, spreading, proliferation, and differentiation, were retained normal or promoted, via a putative surface-initiated self-regulation mechanism. After subcutaneous implantation for a month, the coated specimens elicited minimal, comparable inflammatory responses relative to the control. Moreover, this simple and safe functionalization strategy manifested a good degree of flexibility towards three-dimensional sophisticated objects. Expectedly, it can become a prospective bench to bedside solution to current challenges facing orthopedics.

  4. Gas Sensing Analysis of Ag-Decorated Graphene for Sulfur Hexafluoride Decomposition Products Based on the Density Functional Theory.

    PubMed

    Zhang, Xiaoxing; Huang, Rong; Gui, Yingang; Zeng, Hong

    2016-11-01

    Detection of decomposition products of sulfur hexafluoride (SF₆) is one of the best ways to diagnose early latent insulation faults in gas-insulated equipment, and the occurrence of sudden accidents can be avoided effectively by finding early latent faults. Recently, functionalized graphene, a kind of gas sensing material, has been reported to show good application prospects in the gas sensor field. Therefore, calculations were performed to analyze the gas sensing properties of intrinsic graphene (Int-graphene) and functionalized graphene-based material, Ag-decorated graphene (Ag-graphene), for decomposition products of SF₆, including SO₂F₂, SOF₂, and SO₂, based on density functional theory (DFT). We thoroughly investigated a series of parameters presenting gas-sensing properties of adsorbing process about gas molecule (SO₂F₂, SOF₂, SO₂) and double gas molecules (2SO₂F₂, 2SOF₂, 2SO₂) on Ag-graphene, including adsorption energy, net charge transfer, electronic state density, and the highest and lowest unoccupied molecular orbital. The results showed that the Ag atom significantly enhances the electrochemical reactivity of graphene, reflected in the change of conductivity during the adsorption process. SO₂F₂ and SO₂ gas molecules on Ag-graphene presented chemisorption, and the adsorption strength was SO₂F₂ > SO₂, while SOF₂ absorption on Ag-graphene was physical adsorption. Thus, we concluded that Ag-graphene showed good selectivity and high sensitivity to SO₂F₂. The results can provide a helpful guide in exploring Ag-graphene material in experiments for monitoring the insulation status of SF₆-insulated equipment based on detecting decomposition products of SF₆.

  5. Gas Sensing Analysis of Ag-Decorated Graphene for Sulfur Hexafluoride Decomposition Products Based on the Density Functional Theory

    PubMed Central

    Zhang, Xiaoxing; Huang, Rong; Gui, Yingang; Zeng, Hong

    2016-01-01

    Detection of decomposition products of sulfur hexafluoride (SF6) is one of the best ways to diagnose early latent insulation faults in gas-insulated equipment, and the occurrence of sudden accidents can be avoided effectively by finding early latent faults. Recently, functionalized graphene, a kind of gas sensing material, has been reported to show good application prospects in the gas sensor field. Therefore, calculations were performed to analyze the gas sensing properties of intrinsic graphene (Int-graphene) and functionalized graphene-based material, Ag-decorated graphene (Ag-graphene), for decomposition products of SF6, including SO2F2, SOF2, and SO2, based on density functional theory (DFT). We thoroughly investigated a series of parameters presenting gas-sensing properties of adsorbing process about gas molecule (SO2F2, SOF2, SO2) and double gas molecules (2SO2F2, 2SOF2, 2SO2) on Ag-graphene, including adsorption energy, net charge transfer, electronic state density, and the highest and lowest unoccupied molecular orbital. The results showed that the Ag atom significantly enhances the electrochemical reactivity of graphene, reflected in the change of conductivity during the adsorption process. SO2F2 and SO2 gas molecules on Ag-graphene presented chemisorption, and the adsorption strength was SO2F2 > SO2, while SOF2 absorption on Ag-graphene was physical adsorption. Thus, we concluded that Ag-graphene showed good selectivity and high sensitivity to SO2F2. The results can provide a helpful guide in exploring Ag-graphene material in experiments for monitoring the insulation status of SF6-insulated equipment based on detecting decomposition products of SF6. PMID:27809269

  6. 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.

  7. Enhanced ferroelectric photoelectrochemical properties of polycrystalline BiFeO{sub 3} film by decorating with Ag nanoparticles

    SciTech Connect

    Liu, Qing; Shen, Mingrong; Fang, Liang; Zhou, Yang; You, Lu; Wang, Junling

    2016-01-11

    Polycrystalline BiFeO{sub 3} (BFO) films are fabricated on Pt/Ti/SiO{sub 2}/Si(100) substrate as photoelectrode using sol-gel method. The microstructure, optical, and photoelectrochemical (PEC) properties of the films are characterized and optimized by controlling the film thickness. Moreover, the PEC properties of the BFO films are dependent on ferroelectric polarization, which is mainly ascribed to the modulation of band structure at the BFO/electrolyte interface by the polarization. Further enhancement of PEC properties is obtained by decorating the samples with appropriate amounts of Ag nanoparticles, which is attributed to the reduced electron-hole recombination, and localized surface plasmon resonance effect of Ag nanoparticles.

  8. A hydrogen peroxide electrochemical sensor based on silver nanoparticles decorated three-dimensional graphene

    SciTech Connect

    Zhan, Beibei; Liu, Changbing; Shi, Huaxia; Li, Chen; Wang, Lianhui; Huang, Wei E-mail: iamwhuang@njtech.edu.cn; Dong, Xiaochen E-mail: iamwhuang@njtech.edu.cn

    2014-06-16

    A facile strategy has been developed to synthesize sliver nanoparticles (Ag NPs) decorated three-dimensional graphene (3DG) through hydrothermal process. The AgNPs-3DG composites are directly fabricated into a free standing sensing electrode for electrochemical detection of hydrogen peroxide (H{sub 2}O{sub 2}) in phosphate buffered solutions. Various techniques equipments including scanning electron microscopy, X-ray diffraction, and Raman spectroscopy are used to characterize the morphology and structure of the as-prepared composite. The electrochemical experiments reveal the AgNPs-3DG based biosensor exhibits fast amperometric sensing, low detection limitation, wide linear responding range, and perfect selectivity for non-enzyme H{sub 2}O{sub 2} detection, indicating the well synergistic effect of Ag NPs high electrocatalytic activity and 3DG high conductivity and large surface area.

  9. One-pot synthesis of GO/AgNPs/luminol composites with electrochemiluminescence activity for sensitive detection of DNA methyltransferase activity.

    PubMed

    Zhao, Hui-Fang; Liang, Ru-Ping; Wang, Jing-Wu; Qiu, Jian-Ding

    2015-01-15

    DNA methyltransferases catalyze the transfer of a methyl group from S-adenosylmethionine to the target adenine or cytosine, eventually inducing the DNA methylation in both prokaryotes and eukaryotes. Herein, we developed a novel electrochemiluminescence biosensor to quantify DNA adenine methylation (Dam) methyltransferase (MTase) employing signal amplification of GO/AgNPs/luminol composites to enhance the assay sensitivity. The method was developed by designing a capture probe DNA, which was immobilized on gold electrode surface, to hybridize with azide complementary DNA to form the azide-terminated dsDNA. Then, alkynyl functionalized GO/AgNPs/luminol composites as the signal probe were immobilized to azide-terminated dsDNA modified electrode via click chemistry, resulting in a high electrochemiluminescence (ECL) signal. Once the DNA hybrid was methylated (under catalysis of Dam MTase) and further cleaved by Dpn I endonuclease (a site-specific endonuclease recognizing the duplex symmetrical sequence of 5'-G-Am-T-C-3'), GO/AgNPs/luminol composites release from the electrode surface to the solution, leading to significant reduction of the ECL signal. The change of the ECL intensity is related to the methylation status and MTase activity, which forms the basis of MTase activity assay and site-specific methylation determination. This novel strategy can be further used as a universal method for other transferase determination by designing various transferase-specific DNA sequences. In addition, this method can be used for the screening of antimicrobial drugs and has a great potential to be further applied in early clinical diagnosis.

  10. 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.

  11. UV-visible light-activated Ag-decorated, monodisperse TiO2 aggregates for treatment of the pharmaceutical oxytetracycline.

    PubMed

    Han, Changseok; Likodimos, Vlassis; Khan, Javed Ali; Nadagouda, Mallikarjuna N; Andersen, Joel; Falaras, Polycarpos; Rosales-Lombardi, Pablo; Dionysiou, Dionysios D

    2014-10-01

    Noble metal Ag-decorated, monodisperse TiO2 aggregates were successfully synthesized by an ionic strength-assisted, simple sol-gel method and were used for the photocatalytic degradation of the antibiotic oxytetracycline (OTC) under both UV and visible light (UV-visible light) irradiation. The synthesized samples were characterized by X-ray diffraction analysis (XRD); UV-vis diffuse reflectance spectroscopy; environmental scanning electron microscopy (ESEM); transmission electron microscopy (TEM); high-resolution TEM (HR-TEM); micro-Raman, energy-dispersive X-ray spectroscopy (EDS); and inductively coupled plasma optical emission spectrometry (ICP-OES). The results showed that the uniformity of TiO2 aggregates was finely tuned by the sol-gel method, and Ag was well decorated on the monodisperse TiO2 aggregates. The absorption of the samples in the visible light region increased with increasing Ag loading that was proportional to the amount of Ag precursor added in the solution over the tested concentration range. The Brunauer, Emmett, and Teller (The BET) surface area slightly decreased with increasing Ag loading on the TiO2 aggregates. Ag-decorated TiO2 samples demonstrated enhanced photocatalytic activity for the degradation of OTC under UV-visible light illumination compared to that of pure TiO2. The sample containing 1.9 wt% Ag showed the highest photocatalytic activity for the degradation of OTC under both UV-visible light and visible light illumination. During the experiments, the detected Ag leaching for the best TiO2-Ag photocatalyst was much lower than the National Secondary Drinking Water Regulation for Ag limit (0.1 mg L(-1)) issued by the US Environmental Protection Agency.

  12. Bactericidal mechanisms revealed for rapid water disinfection by superabsorbent cryogels decorated with silver nanoparticles.

    PubMed

    Loo, Siew-Leng; Krantz, William B; Fane, Anthony G; Gao, Yiben; Lim, Teik-Thye; Hu, Xiao

    2015-02-17

    The authors have recently reported the fabrication of superabsorbent cryogels decorated with silver nanoparticles (PSA/AgNP cryogels) that demonstrate rapid water disinfection. This paper provides a systematic elucidation of the bactericidal mechanisms of AgNPs (silver nanoparticles), both generally and in the specific context of cryogels. Direct contact between the PSA/AgNP cryogel interface and the bacterial cells is required to accomplish disinfection. Specifically, the disinfection efficacy is closely correlated to the cell-bound Ag concentration, which constitutes >90% of the Ag released. Cells exposed to PSA/AgNP cryogels show a significant depletion of intracellular adenosine triphosphate (ATP) content and cell-membrane lesions. A positive ROS (reactive oxygen species) scavenging test confirms the involvement of ROS (·O2(-), H2O2, and ·OH) in the bactericidal mechanism. Furthermore, exposed bacterial cells show an enhanced level of thiobarbituric acid reactive substances, indicating the occurrence of cell-membrane peroxidation mediated by ROS. In addition, this study reveals that both Ag(+) and Ag(0) are involved in the bactericidal mechanism of AgNPs via tests conducted using PSA cryogels with bound Ag(+) ions (or PSA/Ag(+) cryogels without reducing Ag(+) to Ag(0)). Significantly, bacterial cells exposed to PSA/Ag(+) cryogels did not show any cell-membrane damage even though the former had a higher cell-bound Ag concentration than that of the PSA/AgNP cryogels, thus indicating the differential action of Ag(+) and Ag(0).

  13. Studies on the impact of biosynthesized silver nanoparticles (AgNPs) in relation to malaria and filariasis vector control against Anopheles stephensi Liston and Culex quinquefasciatus Say (Diptera: Culicidae).

    PubMed

    Subarani, Selladurai; Sabhanayakam, Selvi; Kamaraj, Chinnaperumal

    2013-02-01

    Biosynthesized nanoparticles have been achieved using environmentally acceptable plant extract and eco-friendly reducing and capping agents. The present study was based on assessments of the larvicidal activities to determine the efficacies of synthesized silver nanoparticles (AgNPs) using aqueous leaf extract of Vinca rosea (L.) (Apocynaceae) against the larvae of malaria vector Anopheles stephensi Liston and filariasis vector Culex quinquefasciatus Say (Diptera: Culicidae). Larvae were exposed to varying concentrations of aqueous extract of V. rosea and synthesized AgNPs for 24, 48, and 72 h. AgNPs were rapidly synthesized using the leaf extract of V. rosea, and the formation of nanoparticles was observed within 15 min. The results recorded from UV-Vis spectrum, Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) support the biosynthesis and characterization of AgNPs. The formation of the AgNPs synthesized from the XRD spectrum compared with the Bragg reflections at 2θ = 29.36, 38.26, 44.51, 63.54, and 77.13° which can be indexed to the (121), (111), (200), (220), and (311) orientations, respectively, confirmed the presence of AgNPs. The FTIR spectra of AgNPs exhibited prominent peaks at the spectra showed sharp and strong absorption band at 3,406.71 to 3,431.90 cm(-1) double in case of NH(2) group of a primary amine (N-H stretch). The presence of the sharp peak at 2,926.54 to 2,925.80 cm(-1) very broad often looks like distorted baseline (O-H carboxylic acids). The band 1,633.26 to 1,625.81 cm(-1) was assigned to C = C alkenes, aromatic ring stretching vibration, respectively. SEM analysis of the synthesized AgNPs clearly showed the clustered and irregular shapes, mostly aggregated and having the size of 120 nm. TEM reveals spherical shape of synthesized AgNPs. Particle size analysis revealed that the size of particles ranges from 25 to 47 nm with average size of 34.61 nm

  14. Synthesis of silver nanoparticles (Ag NPs) for anticancer activities (MCF 7 breast and A549 lung cell lines) of the crude extract of Syzygium aromaticum.

    PubMed

    Venugopal, K; Rather, H A; Rajagopal, K; Shanthi, M P; Sheriff, K; Illiyas, M; Rather, R A; Manikandan, E; Uvarajan, S; Bhaskar, M; Maaza, M

    2017-02-01

    In the present report, silver nanoparticles were synthesized using Piper nigrum extract for in vitro cytotoxicity efficacy against MCF-7 and HEP-2 cells. The silver nanoparticles (AgNPs) were formed within 20min and after preliminarily confirmation by UV-Visible spectroscopy (strong peak observed at ~441nm), they were characterized by using FT-IR and HR-TEM. The TEM images show spherical shape of biosynthesized AgNPs with particle size in the range 5-40nm while as compositional analysis were observed by EDAX. MTT assays were carried out for cytotoxicity of various concentrations of biosynthesized silver nanoparticles and Piper nigrum extract ranging from 10 to 100μg. The biosynthesized silver nanoparticles showed a significant anticancer activity against both MCF-7 and Hep-2 cells compared to Piper nigrum extract which was dose dependent. Our study thus revealed an excellent application of greenly synthesized silver nanoparticles using Piper nigrum. The study further suggested the potential therapeutic use of these nanoparticles in cancer study.

  15. Enzyme-free colorimetric determination of EV71 virus using a 3D-MnO2-PEG nanoflower and 4-MBA-MA-AgNPs.

    PubMed

    Chu, Chengchao; Ge, Shengxiang; Zhang, Jing; Lin, Huirong; Liu, Gang; Chen, Xiaoyuan

    2016-09-15

    We present a simple colorimetric assay for EV71 virus detection based on the aggregation of 4-mercaptobenzoic acid (4-MBA) and melamine (MA) modified silver nanoparticles (4-MBA-MA-AgNPs) in the presence of Mn(2+). The EV71-Ab1 was incubated on a 96-well plate and the EV71-Ab2 was labeled on the surface of three-dimensional nanoflower-like MnO2-PEG (3D-MnO2-PEG). After layer-by-layer immunoreactions, the EV71 virus and the corresponding 3D-MnO2-PEG-Ab2 were captured on the plate. With the addition of Vitamin C (Vc), Mn(2+) was released from the 3D-MnO2-PEG and then the aggregation of the 4-MBA-MA-AgNPs was induced, allowing a naked-eye detection limit of EV71 virus to be as low as 5 × 10(4) particles per mL, which is about three orders of magnitude lower than the conventional enzyme-linked immunosorbent assay (ELISA). This enzyme-free immunoassay based on a hybrid 3D-MnO2 features signal amplification strategies via a simple reduction reaction.

  16. Silver nanoparticle gated, mesoporous silica coated gold nanorods (AuNR@MS@AgNPs): low premature release and multifunctional cancer theranostic platform.

    PubMed

    Zhang, Zhehua; Liu, Changhui; Bai, Junhui; Wu, Cuichen; Xiao, Yue; Li, Yinhui; Zheng, Jing; Yang, Ronghua; Tan, Weihong

    2015-03-25

    Multifunctional nanoparticles integrated with an imaging module and therapeutic drugs are promising candidates for future cancer diagnosis and therapy. Mesoporous silica coated gold nanorods (AuNR@MS) have emerged as a novel multifunctional cancer theranostic platform combining the large specific surface area of mesoporous silica, which guarantees a high drug payload, and the photothermal modality of AuNRs. However, premature release and side effects of exogenous stimulus still hinder the further application of AuNR@MS. To address these issues, herein, we proposed a glutathione (GSH)-responsive multifunctional AuNR@MS nanocarrier with in situ formed silver nanoparticles (AgNPs) as the capping agent. The inner AuNR core functions as a hyperthermia agent, while the outer mesoporous silica shell exhibits the potential to allow a high drug payload, thus posing itself as an effective drug carrier. With the incorporation of targeting aptamers, the constructed nanocarriers show drug release in accordance with an intracellular GSH level with maximum drug release into tumors and minimum systemic release in the blood. Meanwhile, the photothermal effect of the AuNRs upon application to near-infrared (NIR) light led to a rapid rise in the local temperature, resulting in an enhanced cell cytotoxicity. Such a versatile theranostic system as AuNR@MS@AgNPs is expected to have a wide biomedical application and may be particularly useful for cancer therapy.

  17. Green synthesis of nanosilver-decorated graphene oxide sheets.

    PubMed

    Rodríguez-González, Claramaría; Velázquez-Villalba, Pamela; Salas, Pedro; Castaño, Víctor M

    2016-10-01

    A green facile method has been successfully used for the synthesis of graphene oxide sheets decorated with silver nanoparticles (rGO/AgNPs), employing graphite oxide as a precursor of graphene oxide (GO), AgNO3 as a precursor of Ag nanoparticles (AgNPs), and geranium (Pelargonium graveolens) extract as reducing agent. Synthesis was accomplished using the weight ratios 1:1 and 1:3 GO/Ag, respectively. The synthesised nanocomposites were characterised by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction, UV-visible spectroscopy, Raman spectroscopy, energy dispersive X-ray spectroscopy and thermogravimetric analysis. The results show a more uniform and homogeneous distribution of AgNPs on the surface of the GO sheets with the weight ratio 1:1 in comparison with the ratio 1:3. This eco-friendly method provides a rGO/AgNPs nanocomposite with promising applications, such as surface enhanced Raman scattering, catalysis, biomedical material and antibacterial agent.

  18. 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.

  19. Multiplex paper-based colorimetric DNA sensor using pyrrolidinyl peptide nucleic acid-induced AgNPs aggregation for detecting MERS-CoV, MTB and HPV oligonucleotides.

    PubMed

    Tee-Ngam, Prinjaporn; Siangproh, Weena; Tuantranont, Adisorn; Vilaivan, Tirayut; Chailapakul, Orawon; Henry, Charles S

    2017-04-10

    The development of simple fluorescent and colorimetric assays that enable point-of-care DNA and RNA detection has been a topic of significant research because of the utility of such assays in resource limited settings. The most common motifs utilize hybridization to a complementary detection strand coupled with a sensitive reporter molecule. Here, apaper-based colorimetric assay for DNA detection based on pyrrolidinyl peptide nucleic acid (acpcPNA)-induced nanoparticle aggregationis reported as an alternative to traditional colorimetric approaches. PNA probes are an attractive alternative to DNA and RNA probes because they are chemically and biologically stable, easily synthesized, and hybridize efficiently with the complementary DNA strands. The acpcPNA probe contains a single positive charge from the lysine at C-terminus and causes aggregation of citrate anion-stabilized silver nanoparticles (AgNPs) in the absence of complementary DNA. In the presence of target DNA, formation of the anionic DNA-acpcPNA duplex results in dispersion of the AgNPs as a result of electrostatic repulsion, giving rise to a detectable color change. Factors affecting the sensitivity and selectivity of this assay were investigated, including ionic strength, AgNP concentration, PNA concentration, and DNA strand mismatches. The method was used for screening of synthetic Middle East respiratory syndrome coronavirus (MERS-CoV), mycobacterium tuberculosis (MTB) and human papillomavirus (HPV)DNA based on a colorimetric paper-based analytical device developed using the aforementioned principle. The oligonucleotide targets were detected by measuring the color change of AgNPs, giving detection limits of 1.53 nM (MERS-CoV), 1.27 nM (MTB) and 1.03 nM (HPV).The acpcPNA probe exhibited high selectivity for the complementary oligonucleotides over single-base-mismatch, two-base-mismatch and non-complementary DNA targets. The proposed paper-based colorimetric DNA sensor has potential to be an alternative

  20. Realization of low power-laser induced thermionic emission from Ag nanoparticle-decorated CNT forest: A consequence of surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Monshipouri, Mahta; Abdi, Yaser; Darbari, Sara

    2016-11-01

    Enhancement of electron emission from Ag nanoparticle-decorated carbon nanotube (CNT) forest, using low power-lasers, is reported in this work. Realization of thermionic emission from CNTs using the low power laser can be achievable when the CNT forest is illuminated by a narrow laser beam which leads to localized heating of the CNT forest surface. For this purpose, CNT forest was decorated with Ag nanoparticles. Surface plasmon resonance of Ag nano-particles led to intense local electric field which is responsible for localized heating and thermionic emission from CNTs. Enhancement of emission current from CNTs depends on the wavelength of the excitation laser, so that matching the wavelength of laser to the wavelength of the plasmon resonance leaded to a maximum enhancement in electron emission.

  1. 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.

  2. Hollow fiber membrane decorated with Ag/MWNTs: toward effective water disinfection and biofouling control.

    PubMed

    Gunawan, Poernomo; Guan, Cong; Song, Xianghua; Zhang, Quanyuan; Leong, Susanna Su Jan; Tang, Chuyang; Chen, Yuan; Chan-Park, Mary B; Chang, Matthew Wook; Wang, Kean; Xu, Rong

    2011-12-27

    The currently applied disinfection methods during water treatment provide effective solutions to kill pathogens, but also generate harmful byproducts, which are required to be treated with additional efforts. In this work, an alternative and safer water disinfection system consisting of silver nanoparticle/multiwalled carbon nanotubes (Ag/MWNTs) coated on a polyacrylonitrile (PAN) hollow fiber membrane, Ag/MWNTs/PAN, has been developed. Silver nanoparticles of controlled sizes were coated on polyethylene glycol-grafted MWNTs. Ag/MWNTs were then covalently coated on the external surface of a chemically modified PAN hollow fiber membrane to act as a disinfection barrier. A continuous filtration test using E. coli containing feedwater was conducted for the pristine PAN and Ag/MWNTs/PAN composite membranes. The Ag/MWNT coating significantly enhanced the antimicrobial activities and antifouling properties of the membrane against E. coli. Under the continuous filtration mode using E. coli feedwater, the relative flux drop over Ag/MWNTs/PAN was 6%, which was significantly lower than that over the pristine PAN (55%) at 20 h of filtration. The presence of the Ag/MWNT disinfection layer effectively inhibited the growth of bacteria in the filtration module and prevented the formation of biofilm on the surface of the membrane. Such distinctive antimicrobial properties of the composite membrane is attributed to the proper dispersion of silver nanoparticles on the external surface of the membrane, leading to direct contact with bacterium cells.

  3. A mixture toxicity approach to predict the toxicity of Ag decorated ZnO nanomaterials.

    PubMed

    Azevedo, S L; Holz, T; Rodrigues, J; Monteiro, T; Costa, F M; Soares, A M V M; Loureiro, S

    2017-02-01

    Nanotechnology is a rising field and nanomaterials can now be found in a vast variety of products with different chemical compositions, sizes and shapes. New nanostructures combining different nanomaterials are being developed due to their enhancing characteristics when compared to nanomaterials alone. In the present study, the toxicity of a nanostructure composed by a ZnO nanomaterial with Ag nanomaterials on its surface (designated as ZnO/Ag nanostructure) was assessed using the model-organism Daphnia magna and its toxicity predicted based on the toxicity of the single components (Zn and Ag). For that ZnO and Ag nanomaterials as single components, along with its mixture prepared in the laboratory, were compared in terms of toxicity to ZnO/Ag nanostructures. Toxicity was assessed by immobilization and reproduction tests. A mixture toxicity approach was carried out using as starting point the conceptual model of Concentration Addition. The laboratory mixture of both nanomaterials showed that toxicity was dependent on the doses of ZnO and Ag used (immobilization) or presented a synergistic pattern (reproduction). The ZnO/Ag nanostructure toxicity prediction, based on the percentage of individual components, showed an increase in toxicity when compared to the expected (immobilization) and dependent on the concentration used (reproduction). This study demonstrates that the toxicity of the prepared mixture of ZnO and Ag and of the ZnO/Ag nanostructure cannot be predicted based on the toxicity of their components, highlighting the importance of taking into account the interaction between nanomaterials when assessing hazard and risk.

  4. 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.

  5. Large-scale homogeneously distributed Ag-NPs with sub-10 nm gaps assembled on a two-layered honeycomb-like TiO2 film as sensitive and reproducible SERS substrates.

    PubMed

    Hu, Xiaoye; Meng, Guowen; Huang, Qing; Xu, Wei; Han, Fangming; Sun, Kexi; Xu, Qiaoling; Wang, Zhaoming

    2012-09-28

    We present a surface-enhanced Raman scattering (SERS) substrate featured by large-scale homogeneously distributed Ag nanoparticles (Ag-NPs) with sub-10 nm gaps assembled on a two-layered honeycomb-like TiO(2) film. The two-layered honeycomb-like TiO(2) film was achieved by a two-step anodization of pure Ti foil, with its upper layer consisting of hexagonally arranged shallow nano-bowls of 160 nm in diameter, and the lower layer consisting of arrays of about fifty vertically aligned sub-20 nm diameter nanopores. The shallow nano-bowls in the upper layer divide the whole TiO(2) film into regularly arranged arrays of uniform hexagonal nano-cells, leading to a similar distribution pattern for the ion-sputtered Ag-NPs in each nano-cell. The lower layer with sub-20 nm diameter nanopores prevents the aggregation of the sputtered Ag-NPs, so that the Ag-NPs can get much closer with gaps in the sub-10 nm range. Therefore, large-scale high-density and quasi-ordered sub-10 nm gaps between the adjacent Ag-NPs were achieved, which ensures homogeneously distributed 'hot spots' over a large area for the SERS effect. Moreover, the honeycomb-like structure can also facilitate the capture of target analyte molecules. As expected, the SERS substrate exhibits an excellent SERS effect with high sensitivity and reproducibility. As an example, the SERS substrate was utilized to detect polychlorinated biphenyls (PCBs, a kind of persistent organic pollutants as global environmental hazard) such as 3,3',4,4'-pentachlorobiphenyl (PCB-77) with concentrations down to 10(-9) M. Therefore the large-scale Ag-NPs with sub-10 nm gaps assembled on the two-layered honeycomb-like TiO (2) film have potentials in SERS-based rapid trace detection of PCBs.

  6. 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.

  7. A highly reproducible and sensitive fiber SERS probe fabricated by direct synthesis of closely packed AgNPs on the silanized fiber taper.

    PubMed

    Cao, Jie; Zhao, Di; Mao, Qinghe

    2017-01-27

    A surface-enhanced Raman scattering (SERS) tapered fiber probe has been developed by using a chemically-etched tapered fiber tip and silanization of the surface of the fiber taper, followed by the hydrothermal growth of silver nanoparticles (AgNPs) on the silanized fiber taper. 4-Aminothiophenol (4-ATP) was selected as the target analyte to study the SERS responses of the prepared fiber SERS probe in an optrode remote detection mode. The experimental results show that the prepared fiber probe exhibited the ability to detect the 4-ATP molecule at a concentration as low as 10(-9) M and good reproducibility with the relative standard deviation (RSD) values being less than 9.1% for the strongest Raman peak. This work gives a novel and reliable way to realize a fiber SERS probe with high sensitivity, long-term stability, good reproducibility, and superior recyclability, exhibiting potential in SERS-based in situ detection application.

  8. Surface chemical bonds, surface-enhanced Raman scattering, and dielectric constant of SiO2 nanospheres in-situ decorated with Ag-nanoparticles by electron-irradiation

    NASA Astrophysics Data System (ADS)

    Phatangare, A. B.; Dhole, S. D.; Dahiwale, S. S.; Mathe, V. L.; Bhoraskar, S. V.; Late, D. J.; Bhoraskar, V. N.

    2016-12-01

    Nanostructures of dielectric materials decorated with metal nanoparticles are of great scientific interest; however, the involved synthesis methods are complicated and require multistep chemical processing, including functionalization of the dielectric surfaces. In the present work, without chemical processes, silver nanoparticles of average sizes in the range of 11 to 15 nm were in-situ synthesized and decorated on SiO2 nanospheres in a single step process by irradiating a solution (AgNO3-polyvinylpyrrolidone (PVP)-SiO2 nanospheres) with 6 MeV electrons at 1.5 × 1015 e-/cm2, 3.0 × 1015 e-/cm2, and 4.5 × 1015 e-/cm2 fluences. The electron irradiated solutions were characterized with different surface and other techniques. The results revealed that the SiO2 nanospheres were uniformly decorated with Ag nanoparticles, and the prominent chemical bonds involved were Ag-O, Si-O-Ag, and Si-Ag. Moreover, the sizes and the decoration density of Ag nanoparticles could be tailored by varying electron fluence. The Surface-enhanced Raman scattering (SERS) of 4-aminothiophenol (4-ATP) solutions was studied using substrates in the form of thin coatings of the solutions of Ag-decorated SiO2 nanospheres. The appearance of the characteristic SERS peaks of both 4-ATP and 4, 4'-dimercaptoazobenzene (4, 4'-DMAB) in Raman spectra confirmed the conversion of a fraction of 4-ATP into 4, 4'-DMAB in the presence of Ag nanoparticles. Composites in the form of thin films were synthesized from the mixture solutions of PVP and Ag-decorated SiO2 nanospheres. The dielectric constant of each thin film was higher as compared to polymers, and could be tailored by varying electron fluence used for decorating Ag nanoparticles.

  9. Highly Wavelength-Selective Enhancement of Responsivity in Ag Nanoparticle-Modified ZnO UV Photodetector.

    PubMed

    Wang, Xiao; Liu, Kewei; Chen, Xing; Li, Binghui; Jiang, Mingming; Zhang, Zhenzhong; Zhao, Haifeng; Shen, Dezhen

    2017-02-15

    We proposed and demonstrated Ag nanoparticles (NPs)-decorated ZnO photodetectors for UV light sensing. After decoration of their surface with random Ag NPs, the dark current density of ZnO UV photodetectors decreases obviously. Moreover, the device exhibits an obvious increase in peak responsivity at around 380 nm, which can be attributed to the narrow-band quadrupole plasmon resonance of Ag NPs in the UV range. Meanwhile, the responsivity at the other wavelengths decreases a lot. As a result, the response peak becomes more significant, and the response of the devices presents an excellent wavelength selectivity after covering with Ag NPs. The detailed mechanism for this phenomenon was explained. We believe that our findings would open a way to harness the high-order plasmon modes in the field of UV optoelectronic devices.

  10. SPR studies of the adsorption of silver/bovine serum albumin nanoparticles (Ag/BSA NPs) onto the model biological substrates.

    PubMed

    Bhan, Chandra; Brower, Tina Louise; Raghavan, Dharmaraj

    2013-07-15

    The primary objective of this study is to investigate the interactive forces that promote the adsorption of bio-conjugated nanoparticles onto proteins. To elucidate the interactive forces, we demonstrate an approach using synthetic and model biological surfaces to study adsorption of bio-conjugated nanoparticles. Real-time adsorption of BSA conjugated silver nanoparticles (Ag/BSA NPs) on the immobilized substrates was followed by surface plasmon resonance (SPR). The extent of adsorption of the nanoparticles on the synthetic surface was found to be larger for self-assembled monolayers (SAMs) with ionizable terminal groups and lower for SAMs with unionizable terminal groups. For model biological substrate, the extent of nanoparticles adsorption was found to relate to the pKa of immobilized proteins. For collagen immobilized substrate, the adsorption of Ag/BSA nanoparticles showed a significantly higher SPR response than that of free BSA. The extent of nanoparticles adsorption on the collagen immobilized substrate was also influenced by the type and concentration of electrolyte used in dispersing nanoparticles. Our findings indicate that the adsorption of nanoparticles to immobilized surface has contributions from electrostatic interactions, hydrophobic, and/or hydrogen bonding. This work provides the framework to study interactions that may arise when bio-conjugated nanoparticles are transported in biological systems.

  11. In situ decoration of plasmonic Ag nanocrystals on the surface of (BiO)2CO3 hierarchical microspheres for enhanced visible light photocatalysis.

    PubMed

    Dong, Fan; Li, Qiuyan; Zhou, Ying; Sun, Yanjun; Zhang, Haidong; Wu, Zhongbiao

    2014-07-07

    Novel plasmonic 0D Ag nanocrystal decorated 3D (BiO)2CO3 hierarchical microspheres were fabricated with a one-pot hydrothermal method. The as-prepared samples were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, photoluminescence spectra, ns-level time-resolved fluorescence spectra, photocurrent generation and EIS measurement. The results indicated that the 0D Ag nanoparticles were deposited on the surface of 3D (BiO)2CO3 hierarchical microspheres. The deposited Ag nanoparticles were reduced from Ag(+) by the citrate ions from bismuth citrate. The photocatalytic activity of the as-prepared samples was evaluated towards the degradation of NO at ppb-level under visible light irradiation. The intermediate NO2 was monitored on-line during the photocatalytic reaction. The pure (BiO)2CO3 microspheres exhibited decent visible light photocatalytic activity because of the surface scattering and reflecting (SSR effect) resulting from the special 3D hierarchical architecture. The Ag-decorated (BiO)2CO3 microspheres (Ag/BOC) exhibited greatly enhanced photocatalytic activity, photocurrent generation and promoted NO2 oxidation compared to the pure (BiO)2CO3 microspheres. The enhanced photocatalytic activity and photocurrent generation of Ag/BOC was ascribed to the cooperative contribution of the surface plasmon resonance (SPR effect), efficient separation of electron-hole pairs and prolonged lifetime of charge carriers induced by Ag nanoparticles. The photocatalytic performance of Ag/BOC was dependent on the content of Ag loading. When the amount of Ag is controlled at 5%, the highest photocatalytic performance can be achieved. Further increasing the Ag loading content promotes aggregation of the Ag particles and transforms the uniform microspheres into non-uniform microspheres, which is not beneficial

  12. Influence of silver decoration on the nonlinear optical absorption exhibited by multiwall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Mercado-Zúñiga, C.; Torres-Torres, C.; Trejo-Valdez, M.; Torres-Martínez, R.; Cervantes-Sodi, F.; Vargas-García, J. R.

    2014-04-01

    A study about the optical and electrical response exhibited by multi-wall carbon nanotubes (MWCNTs) decorated by silver nanoparticles (Ag NPs) is presented. The size of the NPs varies in the range from 35 to 65 nm, with an average size of 47 nm. The samples were prepared by a chemical vapor deposition method. The third-order nonlinear optical response of the samples was evaluated by using single pulses of 1 ns at 532 nm wavelength. A vectorial two-wave mixing configuration was employed in order to measure the absorptive and refractive nonlinearities. An optical Kerr effect and a two-photon absorption process were identified as the main physical phenomena responsible for the third-order optical nonlinearities in the MWCNTs; however, a saturated optical absorption was developed by the sample when the tubes were decorated by Ag. Moreover, an important modification in the electrical capacitance exhibited by the studied sample after the inclusion of Ag NPs was observed. It is estimated that metallic NPs are capable to modulate nonlinear optical processes in decorated CNTs by selective near-resonant energy transfers.

  13. Silver nanoparticle (AgNPs) doped gum acacia-gelatin-silica nanohybrid: an effective support for diastase immobilization.

    PubMed

    Singh, Vandana; Ahmed, Shakeel

    2012-03-01

    An effective carrier matrix for diastase alpha amylase immobilization has been fabricated by gum acacia-gelatin dual templated polymerization of tetramethoxysilane. Silver nanoparticle (AgNp) doping to this hybrid could significantly enhance the shelf life of the impregnated enzyme while retaining its full bio-catalytic activity. The doped nanohybrid has been characterized as a thermally stable porous material which also showed multipeak photoluminescence under UV excitation. The immobilized diastase alpha amylase has been used to optimize the conditions for soluble starch hydrolysis in comparison to the free enzyme. The optimum pH for both immobilized and free enzyme hydrolysis was found to be same (pH=5), indicating that the immobilization made no major change in enzyme conformation. The immobilized enzyme showed good performance in wide temperature range (from 303 to 323 K), 323 K being the optimum value. The kinetic parameters for the immobilized, (K(m)=10.30 mg/mL, V(max)=4.36 μmol mL(-1)min(-1)) and free enzyme (K(m)=8.85 mg/mL, V(max)=2.81 μmol mL(-1)min(-1)) indicated that the immobilization improved the overall stability and catalytic property of the enzyme. The immobilized enzyme remained usable for repeated cycles and did not lose its activity even after 30 days storage at 40°C, while identically synthesized and stored silver undoped hybrid lost its ~31% activity in 48 h. Present study revealed the hybrids to be potentially useful for biomedical and optical applications.

  14. Catalytic activity of silicon nanowires decorated with silver and copper nanoparticles

    NASA Astrophysics Data System (ADS)

    Amdouni, Sonia; Coffinier, Yannick; Szunerits, Sabine; Zaïbi, Mohammed Ali; Oueslati, Meherzi; Boukherroub, Rabah

    2016-01-01

    The paper reports on the elaboration of silicon nanowires decorated with silver (SiNWs-Ag NPs) or copper (SiNWs-Cu NPs) nanoparticles and the investigation of their catalytic properties for the reduction of 4-nitrophenol to 4-aminophenol. The SiNW arrays were produced through chemical etching of crystalline silicon in HF/AgNO3 aqueous solution. The metal nanoparticles were deposited on the SiNW substrates through chemical bath immersion in a metal salt/hydrofluoric acid aqueous solution. The SiNWs decorated with Ag NPs and Cu NPs were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). The catalytic activity of the SiNWs loaded with metal nanoparticles was evaluated for the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride (NaBH4). The substrates exhibited good catalytic performance toward nitrophenol with a full reduction in less than 30 s for the SiNWs-Cu NPs.

  15. Silver nanoparticles-decorated polyphosphazene nanotubes: synthesis and applications.

    PubMed

    Wang, Minghuan; Fu, Jianwei; Huang, Dandan; Zhang, Chao; Xu, Qun

    2013-09-07

    Herein, we report the preparation of poly (cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) nanotubes decorated with Ag nanoparticles (NPs). The PZS nanotubes have been synthesized firstly via an in situ template approach, and then Ag nanoparticles were prepared via in situ reduction of AgNO3 with NaBH4 as the reductant, supported on the surface of the PZS nanotubes. The as-obtained PZS nanotubes and PZS@Ag NPs composites were characterized by means of Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and UV-vis spectroscopy. Characterization results showed that Ag NPs with good dispersibility were well anchored onto the surface of the PZS nanotubes with superior thermal stability. In addition, the catalytic activities and reusability of these composites were investigated by employing the reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) by NaBH4 as a model reaction.

  16. 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.

  17. 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.

  18. Silver nanoparticle-decorated carbon nanotubes as bifunctional gas-diffusion electrodes for zinc-air batteries

    NASA Astrophysics Data System (ADS)

    Wang, T.; Kaempgen, M.; Nopphawan, P.; Wee, G.; Mhaisalkar, S.; Srinivasan, M.

    Thin, lightweight, and flexible gas-diffusion electrodes (GDEs) based on freestanding entangled networks of single-walled carbon nanotubes (SWNTs) decorated with Ag nanoparticles (AgNPs) are tested as the air-breathing cathode in a zinc-air battery. The SWNT networks provide a highly porous surface for active oxygen absorption and diffusion. The high conductivity of SWNTs coupled with the catalytic activity of AgNPs for oxygen reduction leads to an improvement in the performance of the zinc-air cell. By modulating the pH value and the reaction time, different sizes of AgNPs are decorated uniformly on the SWNTs, as revealed by transmission electron microscopy and powder X-ray diffraction. AgNPs with sizes of 3-5 nm double the capacity and specific energy of a zinc-air battery as compared with bare SWNTs. The simplified, lightweight architecture shows significant advantages over conventional carbon-based GDEs in terms of weight, thickness and conductivity, and hence may be useful for mobile and portable applications.

  19. Novel AgI-decorated β-Bi₂O₃ nanosheet heterostructured Z-scheme photocatalysts for efficient degradation of organic pollutants with enhanced performance.

    PubMed

    Zhang, Zhengyuan; Jiang, Deli; Xing, Chaosheng; Chen, Linlin; Chen, Min; He, Minqiang

    2015-07-07

    The low photocatalytic activity of single semiconductor photocatalysts mainly originates from their fast recombination of photogenerated electron-hole pairs. Constructing nanosheet-based composite photocatalysts is an effective way to enhance the charge separation efficiency of photogenerated electron-hole pairs. In this work, AgI-decorated β-Bi2O3 nanosheet heterostructured photocatalysts were prepared by a facile method. The as-obtained AgI/β-Bi2O3 heterostructures exhibited enhanced visible-light-driven photocatalytic activity towards the degradation of methyl orange (MO) and tetracycline hydrochloride (TC) in aqueous solution. The optimum photocatalytic activity of 20%-AgI/β-Bi2O3 for the degradation of MO was about 4.1 and 6.2 times higher than that of AgI and β-Bi2O3. The photocatalytic activity enhancement of AgI/β-Bi2O3 heterostructures could be ascribed to the formation of a Z-scheme system, which results in the efficient space separation of photo-induced charge carriers.

  20. 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.

  1. Facile fabrication and upconversion luminescence enhancement of LaF3:Yb3+/Ln3+@SiO2 (Ln = Er, Tm) nanostructures decorated with Ag nanoparticles.

    PubMed

    He, Enjie; Zheng, Hairong; Dong, Jun; Gao, Wei; Han, Qingyan; Li, Junna; Hui, Le; Lu, Ying; Tian, Huani

    2014-01-31

    A novel hybrid nanostructure, that is a Ag nanoparticle decorated LaF(3):Yb(3+)/Ln(3+)@SiO(2) nanosphere (Ln=Er, Tm), was constructed by a facile strategy, and characterized by XRD, TEM, FTIR, XPS and UV-vis-NIR absorption. Obvious spectral broadening and red-shift on the surface plasmon resonance were obtained by adjusting the size and configuration of Ag nanoparticles. Effective upconversion luminescence enhancements for Er(3+) and Tm(3+) containing samples were obtained. It is suggested that the luminescence enhancement results from both the excitation and emission processes, and the configuration of the studied hybrid nanostructure is an efficient system to enhance the luminescence emission of rare earth doped nanomaterials. It is believed that the enhancement from the hybrid nanostructure will find great potential in the development of photovoltaic solar cells.

  2. Electrospun nanofibrous membranes surface-decorated with silver nanoparticles as flexible and active/sensitive substrates for surface-enhanced Raman scattering.

    PubMed

    Zhang, Lifeng; Gong, Xiao; Bao, Ying; Zhao, Yong; Xi, Min; Jiang, Chaoyang; Fong, Hao

    2012-10-09

    The development of novel nanomaterials with well-controlled morphologies/structures to achieve excellent activities/sensitivities in surface-enhanced Raman scattering (SERS) is crucial in advancing the high-performance SERS detections of chemical and biological species. In this study, amidoxime surface-functionalized polyacrylonitrile (ASFPAN) nanofibrous membranes surface-decorated with silver nanoparticles (Ag NPs) were prepared via the technique of electrospinning followed by the method of seed-mediated electroless plating. High SERS activities/sensitivities were observed from the ASFPAN-Ag NPs nanofibrous membranes, while the density and size of Ag NPs had an important impact on the SERS activity/sensitivity. The results confirmed that the enhancement of Raman signals is due to the presence of hot spots between/among Ag NPs on the nanofiber surfaces. Electrospun nanofibrous membranes surface-decorated with Ag NPs were mechanical flexible/resilient and could be used as highly active/sensitive SERS substrates for a broad range of applications.

  3. 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

  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. A novel green synthesis approach for polymer nanocomposites decorated with silver nanoparticles and their antibacterial activity.

    PubMed

    Chen, Guofang; Lu, Jingran; Lam, Clarissa; Yu, Yong

    2014-11-21

    A novel, low-cost and direct green synthesis strategy was developed for the preparation of polymer composite spheres composed of silver nanoparticles (AgNPs) decorated on the polymer colloids in a raspberry-like fashion. The polymer colloids were employed as both the reductant and the substrate support. The environmentally benign reaction system consists of AgNO3, polymer spheres and an ethanol solvent, without any additional reducing agents or stabilizers. The obtained composite spheres are surprisingly stable. The size range of the formed AgNPs is from several to tens of nanometers, dependent on the reaction time, AgNO3 concentration, and the amount of polymer spheres. A four-step mechanism was proposed for the formation of AgNPs-coated polymer spheres emphasizing the role of ethanol for saturating the external surface of the polymer spheres first. These composites exhibit excellent antibacterial activity, which is dependent on both the concentration of the composite spheres and the size of coated AgNPs.

  6. Electrospun TiO₂ nanofelt surface-decorated with Ag nanoparticles as sensitive and UV-cleanable substrate for surface enhanced Raman scattering.

    PubMed

    Zhao, Yong; Sun, Lei; Xi, Min; Feng, Quan; Jiang, Chaoyang; Fong, Hao

    2014-04-23

    In this study, the free-standing electrospun nanofibrous mat (i.e., nanofelt) consisting of anatase-phase TiO2 nanofibers with diameters of ∼200 nm was prepared, and the nanofelt was subsequently surface-decorated with Ag nanoparticles via an electroless plating method. The sensitivity toward surface enhanced Raman scattering (SERS) and UV-cleanable property of electrospun TiO2/Ag nanofelt were then investigated. In the SERS tests, the target analyte (i.e., 4-mercaptobenzoic acid, Rhodamine 6G, and 4-aminothiophenol) was first adsorbed onto the TiO2/Ag nanofelt as the probe analyte; this was followed by the measurements of Raman intensity and SERS maps. Thereafter, the nanofelt adsorbed with target analyte was cleaned and regenerated/recovered upon UV irradiation in O2-saturated water, and the removal of target analyte was attributed to photodegradation property of anatase-phase TiO2. This study suggested that the electrospun TiO2/Ag nanofelt would be promising as SERS-active substrate with UV-cleanable property for cost-effective and reproducible SERS applications.

  7. A double signal electrochemical human immunoglobulin G immunosensor based on gold nanoparticles-polydopamine functionalized reduced graphene oxide as a sensor platform and AgNPs/carbon nanocomposite as signal probe and catalytic substrate.

    PubMed

    Zhang, Si; Huang, Na; Lu, Qiujun; Liu, Meiling; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

    2016-03-15

    In this paper, a double signal electrochemical Human immunoglobulin G (HIgG) immunosensor based on AgNPs/carbon nanocomposite (Ag/C NC) as the signal probe and catalytic substrate was developed for fast and sensitive detection of HIgG. The as-prepared AuNPs-PDA-rGO nanocomposite and Ag/C NC were confirmed by UV-vis, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. Electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical properties of the proposed immunosensor. The AuNPs-PDA-rGO nanocomposite can improve the electron transfer rate and capture more Ab1. In the sandwich-type immunoassay process, the Ag/C NC functionalized bioconjugates were captured on HIgG/Ab1/AuNPs-PDA-rGO surface and the electrochemical double-signal strategy was employed. These double electrochemical detection signals were directly monitored the oxidation current originated from Ag/C NC and indirectly detected the reduction current of benzoquinone which was produced from the reaction of H2O2 and HQ by catalysis of Ag/C NC in electrochemical detection of HIgG. Under the optimized conditions, the current responses were changed with the concentrations of HIgG for the proposed immunosensor with wide linear ranges of 0.1 to 100 ngmL(-1) and 0.01-100 ngmL(-1) with the lowest detection concentration of 0.001 ng mL(-1) in the absence and presence of H2O2 and HQ. The double-signal strategy is used for detection of HIgG, and the results came from the two signals were well consistent with each other. The proposed immunosensor was successfully applied in analysis of human IgG in real samples and this strategy may provide a relative simple and effective method for construction of other immunsensors in detection of other biomarkers in clinical medicine.

  8. Decoration of silicon nanowires with silver nanoparticles for ultrasensitive surface enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    D'Andrea, Cristiano; Lo Faro, Maria J.; Bertino, Giulia; Ossi, Paolo M.; Neri, Fortunato; Trusso, Sebastiano; Musumeci, Paolo; Galli, Matteo; Cioffi, Nicola; Irrera, Alessia; Priolo, Francesco; Fazio, Barbara

    2016-09-01

    Silicon nanowires (Si NWs), produced by the chemical etching technique, were decorated with silver nanoparticles (NPs) produced at room temperature by the pulsed laser deposition (PLD) technique. Silver NPs were obtained by means of nanosecond pulsed laser ablation of a target in the presence of a controlled Ar atmosphere. Two different laser pulse numbers and Si NWs having different lengths were used to change the NP number density on the Si NW surface. The resulting Ag NP morphologies were studied by scanning electron microscopy imaging. The results show that this industrially compatible technological approach allows the coverage of the Si NW walls with Ag NPs with a strong control of the NP size distribution and spatial arrangement. The obtained Ag NP decorated Si NWs are free from chemicals contamination and there is no need of post deposition high temperature processes. The optical properties of Si NW arrays were investigated by reflectance spectroscopy that showed the presence of a plasmon related absorption peak, whose position and width is dependent on the Ag NP surface morphology. Coupling the huge surface-to-volume ratio of Si NW arrays with the plasmonic properties of silver nanoparticles resulted in a 3D structure suitable for very sensitive surface enhanced Raman scattering (SERS) applications, as demonstrated by the detection of Rhodamine 6G in aqueous solution at a concentration level of 10-8 M.

  9. ZnWO4 nanorods decorated with Ag/AgBr nanoparticles as highly efficient visible-light-responsive photocatalyst for dye AR18 photodegradation

    NASA Astrophysics Data System (ADS)

    Li, Kebin; Xue, Jie; Zhang, Yanhui; Wei, Hong; Liu, Yalan; Dong, Chengxing

    2014-11-01

    A novel Ag-AgBr/ZnWO4 nanorod heterostructure composite was prepared via a facile deposition-precipitation method with ZnWO4 nanorods as the substrate, and characterized by XRD, SEM-EDX, TEM, XPS, and DRS to confirm its structure, morphology, composition, and optical property. The composite was used as a photocatalyst to destroy azo dye Acid Red 18 (AR18) under visible light irradiation. The effects of catalyst composition, solution pH, catalyst loading, and initial dye concentration on photocatalytic degradation rate and efficiency were examined. It was revealed that the photocatalytic activity of Ag-AgBr/ZnWO4 nanojunction system was higher than that of the single ZnWO4 or Ag-AgBr for AR18 degradation under visible light irradiation. The optimal content of Ag-AgBr in Ag-AgBr/ZnWO4 composite was 0.58:1 of Ag/W molar ratio using in the catalyst preparation. Acid pH and decreasing dye initial concentration were favorable to AR18 photodegradation, but the catalyst loading had an optimal value. The catalyst was stable and recyclable, after five successive cycles the photoactivity was fully maintained and the XRD patterns of AgBr displayed no evident change. Photoluminescence spectra revealed the enhanced photocatalytic activity and stability were closely related to the efficient separation of photogenerated carriers in Ag-AgBr/ZnWO4 nanojunction system. Superoxide radicals and holes were found to be main active species for AR18 photodegradation. Finally, the possible mechanism for AR18 degradation over Ag-AgBr/ZnWO4 nanorods under visible light irradiation was proposed as well.

  10. Transcriptome Analysis Reveals Silver Nanoparticle-Decorated Quercetin Antibacterial Molecular Mechanism.

    PubMed

    Sun, Dongdong; Zhang, Weiwei; Mou, Zhipeng; Chen, Ying; Guo, Feng; Yang, Endong; Wang, Weiyun

    2017-03-22

    Facile and simple method is developed to synthesize silver-nanoparticle-decorated quercetin nanoparticles (QA NPs). Modification suggests that synergistic quercetin (Qe) improves the antibacterial effect of silver nanoparticles (Ag NPs). Characterization experiment indicates that QA NPs have a diameter of approximately 10 nm. QA NPs show highly effective antibacterial activities against drug-resistant Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). We explore antibacterial mechanisms using S. aureus and E. coli treated with QA NPs. Through morphological changes in E. coli and S. aureus, mechanisms are examined for bacterial damage caused by particulate matter from local dissociation of silver ion and Qe from QA NPs trapped inside membranes. Moreover, we note that gene expression profiling methods, such as RNA sequencing, can be used to predict discover mechanisms of toxicity of QA NPs. Gene ontology (GO) assay analyses demonstrate the molecular mechanism of the antibacterial effect of QA NPs. Regarding cellular component ontology, "cell wall organization or biogenesis" (GO: 0071554) and "cell wall macromolecule metabolic process" (GO: 0044036) are the most represented categories. The present study reports that transcriptome analysis of the mechanism offers novel insights into the molecular mechanism of antibacterial assays.

  11. NPS AUV Integrated Simulator

    DTIC Science & Technology

    1992-03-01

    147 3. GRAPHIC OBJECT MODEI’QUSING OBJECTFILE FORMAT (cIF)...................... ........... 149. APPENDIX -C. NPS, AUV SONAR CLASSIFICATION SYSTEM...Monterey Bay .. 15 Figure 2.8 Graphics simulation for NPS AUV sonar visualization .......... 15’ Figure 3.1 Integrated simulator network physical...3.11 Integrated simulation display of AUV minefield searh ........ 39 Figure4.1 NPS AUV sonar beam profiles in the NPS pool .......... 43 Figure 42 NPS

  12. A model electrode of well-defined geometry prepared by direct laser-induced decoration of nanoporous templates with Au-Ag@C nanoparticles.

    PubMed

    Schlicht, Stefanie; Kireev, Alexey; Vasileva, Anna; Grachova, Elena V; Tunik, Sergey P; Manshina, Alina A; Bachmann, Julien

    2017-02-10

    We present an original type of model electrode system consisting of bimetallic Au-Ag nanoparticles embedded in an amorphous carbon matrix with an extremely well-defined geometry of parallel, straight, cylindrical macropores. The samples are prepared in one step by direct laser deposition of the metal/carbon composite onto the inner walls of a porous 'anodic' alumina matrix serving as a template. The coating is homogeneous from top to bottom of the pores, and the amount of material deposited can be tuned by the duration of the deposition procedure. As a test system, we demonstrate that a bimetallic Ag-Au@C system is catalytically active for the electrochemical oxidation of glucose in alkaline solution, the anodic reaction of a direct glucose fuel cell. Furthermore, the electrocatalytic current density increases with the amount of Ag-Au@C NPs deposited, up to a point at which the pores are clogged with it. This type of model system allows for the systematic study of geometric effects in fuel cell electrodes. It can be generalized to a number of different nanoparticle compositions, and thereby, to various electrocatalytic reactions.

  13. A model electrode of well-defined geometry prepared by direct laser-induced decoration of nanoporous templates with Au-Ag@C nanoparticles

    NASA Astrophysics Data System (ADS)

    Schlicht, Stefanie; Kireev, Alexey; Vasileva, Anna; Grachova, Elena V.; Tunik, Sergey P.; Manshina, Alina A.; Bachmann, Julien

    2017-02-01

    We present an original type of model electrode system consisting of bimetallic Au-Ag nanoparticles embedded in an amorphous carbon matrix with an extremely well-defined geometry of parallel, straight, cylindrical macropores. The samples are prepared in one step by direct laser deposition of the metal/carbon composite onto the inner walls of a porous ‘anodic’ alumina matrix serving as a template. The coating is homogeneous from top to bottom of the pores, and the amount of material deposited can be tuned by the duration of the deposition procedure. As a test system, we demonstrate that a bimetallic Ag-Au@C system is catalytically active for the electrochemical oxidation of glucose in alkaline solution, the anodic reaction of a direct glucose fuel cell. Furthermore, the electrocatalytic current density increases with the amount of Ag-Au@C NPs deposited, up to a point at which the pores are clogged with it. This type of model system allows for the systematic study of geometric effects in fuel cell electrodes. It can be generalized to a number of different nanoparticle compositions, and thereby, to various electrocatalytic reactions.

  14. Eco-friendly decoration of graphene oxide with biogenic silver nanoparticles: antibacterial and antibiofilm activity

    NASA Astrophysics Data System (ADS)

    de Faria, Andreia Fonseca; de Moraes, Ana Carolina Mazarin; Marcato, Priscyla Daniely; Martinez, Diego Stéfani Teodoro; Durán, Nelson; Filho, Antônio Gomes Souza; Brandelli, Adriano; Alves, Oswaldo Luiz

    2014-02-01

    This work reports on preparation, characterization, and antibacterial activity of graphene oxide (GO) decorated with biogenic silver nanoparticles (Bio-AgNPs) produced by the fungus Fusarium oxysporum. This nanocomposite (Bio-GOAg) was prepared by an ex situ process through the physical mixture of a GO dispersion with the previously prepared Bio-AgNPs. The adsorption of the Bio-AgNPs onto the GO sheets was confirmed by transmission electron microscopy. The average size of the Bio-AgNPs anchored onto the GO surface was found to be 3.5 nm. The antibacterial activity of the Bio-GOAg nanocomposite against Gram-positive and Gram-negative microorganisms was investigated and a very promising result was found for the Gram-negative strains. In addition, the Bio-GOAg nanocomposite displayed a very strong biocidal activity against the Salmonella typhimurium strain at a concentration of 2.0 μg/mL. The antibiofilm activity toward S. typhimurium adhered on stainless steel surfaces was also investigated. The results showed 100 % inhibition of the adhered cells after exposure to the Bio-GOAg nanocomposite for 1 h.

  15. 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%).

  16. Synthesis and improved SERS performance of silver nanoparticles-decorated surface mesoporous silica microspheres

    NASA Astrophysics Data System (ADS)

    Jiang, Tao; Wang, Xiaolong; Zhang, Li; Zhou, Jun; Zhao, Ziqi

    2016-08-01

    This study reported the improved Raman enhancement ability of silver nanoparticles (Ag NPs) decorated on surface mesoporous silica microspheres (MSiO2@Ag) than that of Ag NPs on solid silica microspheres (SSiO2@Ag). These two kinds of hybrid structures were prepared by a facile single-step hydrothermal reaction with polyvinylpyrrolidone (PVP) serves as both a reductant and stabilizer. The as-synthesized MSiO2@Ag microspheres show more significant surface-enhanced Raman scattering (SERS) activity for 4-mercaptobenzoic acid (4MBA) than SSiO2@Ag microspheres with enhancement factors as 9.20 × 106 and 4.39 × 106, respectively. The proposed reason for the higher SERS activity is estimated to be the contribution of more Raman probe molecules at the mesoporous channels where an enhanced electromagnetic field exists. Such a field was identified by theoretical calculation result. The MSiO2@Ag microspheres were eventually demonstrated for the SERS detection of a typical chemical toxin namely methyl parathion with a detection limit as low as 1 × 10-3 ppm, showing its promising potential in biosensor application.

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

    PubMed

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

    2015-04-01

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

  18. Enhanced photoelectrochemical water-splitting effect with a bent ZnO nanorod photoanode decorated with Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Wei, Yuefan; Ke, Lin; Kong, Junhua; Liu, Hong; Jiao, Zhihui; Lu, Xuehong; Du, Hejun; Sun, Xiao Wei

    2012-06-01

    Zinc oxide (ZnO) nanorods coated with silver (Ag) film on a polyethylene terephthalate (PET) flexible substrate were used as the photoanode for water splitting. The hybrid nanostructures were prepared via low-temperature hydrothermal growth and electron beam evaporation. The effects of plasmonic enhanced absorption, surface recombination inhibition and improved charge transport are investigated by varying the Ag thickness. Light trapping and absorption enhancement are further studied by optimizing the curvature of the PET substrates. The maximum short circuit current density (JSC, 0.616 mA cm-2) and the photoelectron conversion efficiency (PCE, 0.81%) are achieved with an optimized Ag film thickness of 10 nm and substrate bending radius of 6.0 mm. The maximum JSC and PCE are seven times and ten times, respectively, higher than those of the bare ZnO nanorods on flexible substrates without bending. The overall PEC performance improvement is attributed to the plasmonic effects induced by Ag film and improved charge transport due to inhibition of ZnO surface charge recombination. Enhanced light trapping (harvesting) induced by bending the PET substrates further improved the overall efficiency.

  19. Core-satellite ZnS-Ag nanoassemblies: Synthesis, structure, and optical properties.

    PubMed

    Rohani, Parham; Sharma, Munish K; Swihart, Mark T

    2016-02-01

    We synthesized hollow core-satellite nanoassemblies comprised of hollow zinc sulfide (ZnS) shells decorated with silver nanoparticles (Ag NPs). This was achieved by solution-phase attachment of Ag NPs to hollow ZnS nanospheres (NSs) prepared by spray pyrolysis. This produces an aqueous dispersion of ZnS-Ag hybrid structures, 50-500nm in overall diameter. We characterized the nanostructures by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDX) to elucidate the ZnS (core)-Ag (satellite) morphology and optimize conditions for producing such structures. Optical spectroscopy showed that photoluminescence of ZnS was quenched by Ag while absorbance was enhanced. This work provides a simple and general means of producing hollow core-satellite structures that could be of broad applicability.

  20. Hybrid opto-chemical doping in Ag nanoparticle-decorated monolayer graphene grown by chemical vapor deposition probed by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Maiti, R.; Haldar, S.; Majumdar, D.; Singha, A.; Ray, S. K.

    2017-02-01

    The novel opto-chemical doping effect in Ag nanoparticle-decorated monolayer graphene grown by chemical vapor deposition has been investigated using Raman spectroscopy for the first time. We used both noble metal nanoparticles and optical excitation, in a hybrid opto-chemical route, to tune the doping level in graphene. Metal nanoparticle-induced chemical effects and laser power-induced substrate effects alter the doping nature of graphene from p- to n-type. Compared with earlier studies, the proposed method significantly lowers the laser intensity required for optical power-dependent doping, resulting in prevention of damage to the sample due to local heating. Some other interesting observations are the enhanced peak intensity in the Raman spectrum of graphene, enhancement of the D-band intensity and the introduction of G-band splitting. This novel, cheap and easily implemented hybrid optical-chemical doping strategy could be very useful for tuning graphene plasmons on the widely used Si/SiO2 substrates for various photonic device applications.

  1. Hybrid opto-chemical doping in Ag nanoparticle-decorated monolayer graphene grown by chemical vapor deposition probed by Raman spectroscopy.

    PubMed

    Maiti, R; Haldar, S; Majumdar, D; Singha, A; Ray, S K

    2017-02-17

    The novel opto-chemical doping effect in Ag nanoparticle-decorated monolayer graphene grown by chemical vapor deposition has been investigated using Raman spectroscopy for the first time. We used both noble metal nanoparticles and optical excitation, in a hybrid opto-chemical route, to tune the doping level in graphene. Metal nanoparticle-induced chemical effects and laser power-induced substrate effects alter the doping nature of graphene from p- to n-type. Compared with earlier studies, the proposed method significantly lowers the laser intensity required for optical power-dependent doping, resulting in prevention of damage to the sample due to local heating. Some other interesting observations are the enhanced peak intensity in the Raman spectrum of graphene, enhancement of the D-band intensity and the introduction of G-band splitting. This novel, cheap and easily implemented hybrid optical-chemical doping strategy could be very useful for tuning graphene plasmons on the widely used Si/SiO2 substrates for various photonic device applications.

  2. Hybrid nanostructured Ag/ZnO decorated powder cellulose fillers for medical plastics with enhanced surface antibacterial activity.

    PubMed

    Bazant, Pavel; Kuritka, Ivo; Munster, Lukas; Machovsky, Michal; Kozakova, Zuzana; Saha, Petr

    2014-11-01

    Hybrid inorganic-organic fillers based on nanostructured silver/zinc oxide decorations on micro-cellulose carrier particles were prepared by stepwise microwave assisted hydrothermal synthesis using soluble salts as precursors of silver and zinc oxide. Hexamethylenetetramine was used as precipitating agent for zinc oxide and reducing agent for silver. The inorganics covered all available surfaces of the cellulose particles with a morphology resembling a coral reef. Prepared particulate fillers were compounded to medical grade poly(vinyl chloride) matrix. Scanning electron microscopy and powder X-ray diffractometry were used to investigate the morphology and crystalline phase structure of fillers. The scanning electron microscopy was used for morphological study of composites. With respect to prospective application, the composites were tested on electrical and antibacterial properties. A small effect of water absorption in polymer composites on their dielectric properties was observed but no adverse effect of water exposure on prepared materials was manifested. Electrical conductivity of fillers and composites was measured and no influence of water soaking of composites was found at all. The surface antibacterial activity of prepared composites was evaluated according to the standard ISO 22196. Excellent performance against Escherichia coli and very high against Staphylococcus aureus was achieved.

  3. Capillary electrophoresis with online stacking in combination with AgNPs@MCM-41 reinforced hollow fiber solid-liquid phase microextraction for quantitative analysis of Capecitabine and its main metabolite 5-Fluorouracil in plasma samples isolated from cancer patients.

    PubMed

    Forough, Mehrdad; Farhadi, Khalil; Molaei, Rahim; Khalili, Hedayat; Shakeri, Ramin; Zamani, Asghar; Matin, Amir Abbas

    2017-01-01

    The purpose of this study is the development and validation of a simple, novel, selective and fast off-line microextraction technique combining capillary electrophoresis with in-column field-amplified sample injection (FASI) for the simultaneous determination of capecitabine (CAP) and its active metabolite, 5-Fluorouracil (5-FU), in human plasma. At the moment, there is a lack of using cost-effective CE tool combined with novel miniaturized sample clean-up techniques for analysis of these important anti-cancer agents in plasma samples. This paper intends to fill this gap and describe a simple off-line sample pretreatment by means of AgNPs@MCM-41 reinforced hollow fiber Solid/Liquid phase microextraction (AgNPs@MCM41-HF-SLPME) with subsequent quantitation by FASI-CE. The separation of analytes was performed using a BGE containing 60mM phosphate-Tris buffer (pH 7) with 10% methanol as an organic modifier. Before sample loading, a short water plug (50mbar, 3s) was injected to permit FASI for stacking. Various parameters affecting the off-line microextraction efficiency as well as FASI were optimized. Migration time was found to be 6.6 (±0.1)min for 5-FU and 7.4 (±0.2)min for CAP. The linearity, precision, accuracy, recovery, selectivity, specificity, stability as well as the robustness of the method was evaluated from spiked plasma samples during the course of validation. The results revealed that the presented technique demonstrates acceptable accuracy and precision, miniaturized sample preparation and a reduced need for complicated equipment along with an acceptable analysis time. The validated method was successfully applied to determine CAP and 5-FU in patient's plasma samples.

  4. 3D Ag/ZnO hybrids for sensitive surface-enhanced Raman scattering detection

    NASA Astrophysics Data System (ADS)

    Huang, Chenyue; Xu, Chunxiang; Lu, Junfeng; Li, Zhaohui; Tian, Zhengshan

    2016-03-01

    To combine the surface plasma resonance of metal and local field enhancement in metal/semiconductor interface, Ag nanoparticles (NPs) were assembled on a ZnO nanorod array which was grown by hydrothermally on carbon fibers. The construction of dimensional (3D) Surface-Enhanced Raman Scattering (SERS) substrate is used for the sensitive detection of organic pollutants with the advantages such as facile synthesis, short detection time and low cost. The hybrid substrate was manifested a high sensitivity to phenol red at a lower concentration of 1 × 10-9 M and a higher enhancement factor of 3.18 × 109. Moreover, the ZnO nanostructures decorated with Ag NPs were demonstrated self-cleaning function under UV irradiation via photocatalytic degradation of the analytic molecules. The fabrication process of the materials and sensors, optimization of the SERS behaviors for different sized Ag NPs, the mechanism of SERS and recovery were presented with a detailed discussion.

  5. 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.

  6. Direct synthesis of mesostructured carbon nanofibers decorated with silver-nanoparticles as a multifunctional membrane for water treatment

    NASA Astrophysics Data System (ADS)

    Aboueloyoun Taha, Ahmed

    2015-12-01

    One-dimensional (1D) porous carbon nanofibers (CNFs) decorated by silver (Ag) nanoparticles (NPs) were prepared using a one-pot/self-template synthesis strategy by combining electrospinning and carbonization methods. The characterization results revealed that AgNPs were homogenously distributed along the CNFs and possessed a relatively uniform nano-size of about 12 nm. The novel membrane distinctively displayed enhanced photocatalytic activity under visible-light irradiation. The membrane exhibited excellent dye degradation and bacteria disinfection in batch experiments. The high photocatalytic activity can be attributed to the highly accessible surface areas, good light absorption capability, and high separation efficiency of photogenerated electron-hole pairs. The as-prepared membranes can be easily recycled because of their 1D property.

  7. Antibacterial properties of amino acid functionalized silver nanoparticles decorated on graphene oxide sheets.

    PubMed

    Chandraker, Kumudini; Nagwanshi, Rekha; Jadhav, S K; Ghosh, Kallol K; Satnami, Manmohan L

    2017-03-16

    Graphene oxide (GO) sheets decorated with amino acid L-cysteine (L-cys) functionalized silver nanoparticles (GO-L-cys-Ag) was synthesized by AgNO3, trisodium citrate, and NaBH4. GO-L-cys-Ag nanocomposite was characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-vis) absorption spectra, which demonstrated that a diameter of L-cys-AgNPs compactly deposited on GO. Antibacterial activity tests of GO-L-cys-Ag nanocomposite were carried out using Escherichia coli MTCC 1687 and Staphylococcus aureus MTCC 3160 as model strains of Gram-negative and Gram-positive bacteria, respectively. The effect of bactericide dosage on antibacterial activity of GO-L-cys-Ag nanocomposite was examined by plate count, well diffusion and broth dilution methods. Morphological observation of bacterial cells by scanning electron microscope (SEM) showed that GO-L-cys-Ag nanocomposite was more destructive to cell membrane of Escherichia coli than that of Staphylococcus aureus. The above technique establish that the bactericidal property of GO-L-cys-Ag nanocomposite with wide range of applications in biomedical science.

  8. 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

  9. Tuning the performance of nanocarbon-based gas sensors through nanoparticle decoration

    NASA Astrophysics Data System (ADS)

    Cui, Shumao

    Tin dioxide (SnO2) is a well-known gas sensing material, but it becomes sensitive only at elevated temperatures (e.g., above 200 °C). Nanoparticles (NPs) combined with nanocarbons, such as carbon nanotubes (CNTs) and graphene, form a new class of hybrid nanomaterials that can exhibit fascinating gas sensing performance due to tunable electron transfer between NPs and nanocarbons induced by gas adsorption. Indeed, sensors made of SnO2 NPs-coated CNTs have shown outstanding room-temperature sensing performance to various gases, including those that are undetectable by either SnO2 or CNTs alone. The objectives of this dissertation study are to synthesize various NP-nanocarbon hybrid materials and to fabricate and characterize sensing platforms based on the resulting hybrid nanomaterials. Two simple and efficient methods have been used for the hybrid synthesis. One is a simple NP synthesis and assembly system for NP-nanocarbon hybrid nanomaterials production through combining a mini-arc plasma reactor with electrostatic force-directed assembly. The other is a simple wet-chemical method for direct fabrication of doped SnO 2 NP-decorated reduced graphene oxide (RGO) sheets. In particular, CNT/Ag NP and RGO/Ag NP hybrids have been produced for fast, sensitive, and selective detection of NH3. Furthermore, a ternary hybrid of Ag NPs and SnO2 NPs-decorated CNTs has been demonstrated and showed better sensing performance than CNT/SnO2 NP hybrids likely due to the enhanced gas adsorption and electron transfer. Additionally, hybrid sensors of In-doped SnO2 NPs on RGO are shown to exhibit high selectivity to NO2 sensing. Finally, the sensing mechanism for the NP-nanocarbon system has been extensively discussed. Based on this study, we conclude that the sensing performance (including sensitivity, selectivity, and response time) can be fine-tuned by coating nanocarbons with carefully-selected NPs (pure or doped). An attempt has been made to compare the sensing performance of

  10. Designing an ultra-sensitive aptasensor based on an AgNPs/thiol-GQD nanocomposite for TNT detection at femtomolar levels using the electrochemical oxidation of Rutin as a redox probe.

    PubMed

    Shahdost-Fard, Faezeh; Roushani, Mahmoud

    2017-01-15

    In this paper, for the first time a highly sensitive and low-cost electrochemical aptasensor was fabricated based on a silver nanoparticles/thiol functionalized graphene quantum dot (AgNPs/thiol-GQD) nanocomposite for the measurement of 2,4,6-Trinitrotoluen (TNT) as a nitroaromatic explosive. For the first time Rutin (RU) as a biological molecule with inherent properties was used as the redox probe in the development of the TNT aptasensor was used. The system was based on a TNT-binding aptamer which is covalently attached onto the surface of a glassy carbon electrode (GCE) modified with the nanocomposite for the formation of a sensing layer and improving the performance of the aptasensor. Using the proposed nanocomposite provides a specific platform with increased surface area which is capable of loading more Aptamer (Ap) molecules as a receptor element of TNT on the electrode surface. So, TNT molecules is in an upward position to be measured and the obtained results indicate that the aptasensor exhibits two wide linear ranges and an unprecedented LOD compared with previously reported analytical methods for TNT detection. Applicability of the developed aptasensor to easily detect TNT in real samples was evaluated. It seems that the proposed strategy can be expanded to other nanoparticles and is expected to have promising implications in the design of electrochemical sensors or biosensors for the detection of various targets.

  11. Pt74Ag26 nanoparticle-decorated ultrathin MoS2 nanosheets as novel peroxidase mimics for highly selective colorimetric detection of H2O2 and glucose

    NASA Astrophysics Data System (ADS)

    Cai, Shuangfei; Han, Qiusen; Qi, Cui; Lian, Zheng; Jia, Xinghang; Yang, Rong; Wang, Chen

    2016-02-01

    To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating ultrathin MoS2 nanosheets with octahedral Pt74Ag26 alloy nanoparticles has been reported. The as-prepared MoS2-Pt74Ag26 nanohybrids were investigated as novel peroxidase mimics to catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, producing a blue colored reaction and exhibiting typical Michaelis-Menten kinetics. MoS2-Pt74Ag26 has a higher affinity for H2O2 than horseradish peroxidase (HRP) and a higher vmax value with TMB as the substrate than MoS2. The improved catalytic activity of hybrids for colorimetric reactions could be attributed to the synergistic effects of octahedral Pt74Ag26 nanoparticles and ultrathin MoS2 nanosheets as supports. Meanwhile, the generation of active oxygen species (&z.rad;OH) by H2O2 decomposition with MoS2-Pt74Ag26 was responsible for the oxidation of TMB. On the basis of these findings, a colorimetric method based on MoS2-Pt74Ag26 nanohybrids that is highly sensitive and selective was developed for glucose detection. Lower values of the limit of detection (LOD) were obtained, which is more sensitive than MoS2 nanosheets.To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating

  12. 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.

  13. Highly-Sensitive Surface-Enhanced Raman Spectroscopy (SERS)-based Chemical Sensor using 3D Graphene Foam Decorated with Silver Nanoparticles as SERS substrate

    PubMed Central

    Srichan, Chavis; Ekpanyapong, Mongkol; Horprathum, Mati; Eiamchai, Pitak; Nuntawong, Noppadon; Phokharatkul, Ditsayut; Danvirutai, Pobporn; Bohez, Erik; Wisitsoraat, Anurat; Tuantranont, Adisorn

    2016-01-01

    In this work, a novel platform for surface-enhanced Raman spectroscopy (SERS)-based chemical sensors utilizing three-dimensional microporous graphene foam (GF) decorated with silver nanoparticles (AgNPs) is developed and applied for methylene blue (MB) detection. The results demonstrate that silver nanoparticles significantly enhance cascaded amplification of SERS effect on multilayer graphene foam (GF). The enhancement factor of AgNPs/GF sensor is found to be four orders of magnitude larger than that of AgNPs/Si substrate. In addition, the sensitivity of the sensor could be tuned by controlling the size of silver nanoparticles. The highest SERS enhancement factor of ∼5 × 104 is achieved at the optimal nanoparticle size of 50 nm. Moreover, the sensor is capable of detecting MB over broad concentration ranges from 1 nM to 100 μM. Therefore, AgNPs/GF is a highly promising SERS substrate for detection of chemical substances with ultra-low concentrations. PMID:27020705

  14. Facile in situ growth of highly monodispersed Ag nanoparticles on electrospun PU nanofiber membranes: Flexible and high efficiency substrates for surface enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Amarjargal, Altangerel; Tijing, Leonard D.; Shon, Ho Kyong; Park, Chan-Hee; Kim, Cheol Sang

    2014-07-01

    In this study, by utilizing a two-step route of electrospinning and polyol immersion, in the absence of any surfactant or sensitizing and stabilizing reagent, a well-distributed assembly of Ag NPs on the electrospun polyurethane (PU) nanofibers was successfully fabricated through a simple and controllable manner. Based on the FE-SEM, XRD and FT-IR analyses, the polyol medium plays an important role in the growth of highly monodispersed Ag NPs, wherein the hydroxyl group of ethylene glycol (EG) can be bridged to the amide group on the surface of the PU nanofibers through intermolecular hydrogen bonds. Fabrication of a polymer fibrous membrane effectively attached/decorated with noble metal NPs, which is essential as flexible and high efficiency substrates for SERS application where the molecule analytes are directly adsorbed on their surfaces is important, could be realized by the present electrospun PU-Ag(EG) nanofibers, employing 4-mercaptobenzoic acid (4-MBA) as probe molecules.

  15. A novel approach for electromembrane extraction based on the use of silver nanometallic-decorated hollow fibers.

    PubMed

    Ramos-Payán, María; Fernández-Torres, Rut; Pérez-Bernal, Juan Luis; Callejón-Mochón, Manuel; Bello-López, Miguel Ángel

    2014-11-07

    A novel approach based on the use of nanometallic-decorated hollow fibers to assist electromembrane extraction is proposed. Microporous polypropylene hollow fibers, on which nanometallic silver was deposited, have been used for the first time as liquid membrane support in electromembrane extraction (EME). Different methods for the generation/deposition of silver nanoparticles (AgNPs) were studied. The best results were obtained with chemical reduction of silver nitrate using NaBH4 in aqueous solution followed by direct deposition on the hollow fibers. The extraction performance of the new supports was compared with a previously developed EME procedure used for the extraction of selected non-steroidal anti-inflammatory drugs (NSAIDs), resulting in an increase in the extraction ratio by a factor of 1.2-2 with a 30% reduction in the extraction time. The new nanometallic-decorated supports open new possibilities for EME due to the singular properties of nanometallic particles, including chemical fiber functionalization.

  16. The fabrication and photocatalytic performances of flower-like Ag nanoparticles/ZnO nanosheets-assembled microspheres

    NASA Astrophysics Data System (ADS)

    Deng, Quan; Tang, Haibin; Liu, Gang; Song, Xiaoping; Xu, Guoping; Li, Qian; Ng, Dickon H. L.; Wang, Guozhong

    2015-03-01

    A new micro/nanostructure photocatalyst, Ag nanoparticles decorated ZnO nanosheets-assembled microspheres (Ag-NPs/ZnOs), was synthesised by a two-step method. The flower-like micron-sized ZnO spheres assembled with ∼25 nm thick ZnO nanosheets were initially fabricated via a facile solvothermal method. Then, highly dispersed Ag nanoparticles (Ag-NPs) with dimension ranging from 15 to 50 nm were anchored onto the surface of the each ZnO nanosheet by the Sn(II) ion activation method. The as-prepared Ag-NPs/ZnOs demonstrated enhanced photocatalytic performance in eliminating methylene blue and methyl orange aqueous solutions under UV irradiation, showing twice faster reaction rate than the bare ZnOs. The enhanced photocatalytic activity was due to the suppression of electron/hole pair recombination and the acceleration of surface charge transfer induced by the highly dispersive Ag-NPs, which was further demonstrated by the cyclic voltammetry and impedance spectra measurements.

  17. Enhanced photoelectrochemical performance of ZnO nanorod arrays decorated with CdS shell and Ag2S quantum dots

    NASA Astrophysics Data System (ADS)

    Holi, Araa Mebdir; Zainal, Zulkarnain; Talib, Zainal Abidin; Lim, Hong-Ngee; Yap, Chi-Chin; Chang, Sook-Keng; Ayal, Asmaa Kadim

    2017-03-01

    Ternary nanostructured Ag2S/CdS/ZnO thin film was prepared by using a simple low-cost hydrothermal method. The hexagonal phase of ZnO nanorods and CdS shells combined with monoclinic Ag2S quantum dots resulted in improved optical and photoelectrochemical properties. CdS shell with high absorption property efficiently compliment the energy levels of ZnO and improved the ability of light absorption. Furthermore, narrow band gap Ag2S also played a vital part in the light harvesting. The photoelectrochemical performance of the ternary nanostructured Ag2S/CdS/ZnO NRs was investigated in a mixture of Na2S and Na2SO3 aqueous solutions under visible light illumination. The Ag2S/CdS/ZnO NRs were found to be more efficient than ZnO NRs, CdS/ZnO NRs, and Ag2S/ZnO NRs as this particular sample gave a maximum photocurrent of 5.69 mA cm-2, which is around 2 and 1.5 times greater than CdS/ZnO NRs and Ag2S/ZnO NRs, respectively. Besides that, it was found that this ternary film possessed 15 times higher photocurrent density than plain ZnO NRs. This is attributed to the larger amount of visible light absorbed by the ternary nanostructured composite.

  18. Synthesis of spherical Ag/ZnO heterostructural composites with excellent photocatalytic activity under visible light and UV irradiation

    NASA Astrophysics Data System (ADS)

    Liu, Hairui; Hu, Yanchun; Zhang, Zhuxia; Liu, Xuguang; Jia, Husheng; Xu, Bingshe

    2015-11-01

    Ag nanoparticles (Ag-NPs) decorated ZnO microspheres (ZnO-MSs) heterostructural composites were fabricated via a two-step chemical method. The ZnO-MSs with the diameter about 700 nm was initially prepared by ultrasonic technology. Subsequently, Ag-NPs with a diameter of 20-50 nm were anchored onto the surface of the as-prepared ZnO-MSs by a microwave polyol process. The morphology, structural and optical properties of the as-synthesized materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-visible absorption spectroscopy, and photoluminescence spectroscopy. The results show that the surface plasmon absorption band of Ag/ZnO composites is distinctly broadened and the PL intensity of Ag/ZnO heterostructural composites varies with the increase of Ag loading. The photocatalytic activity of the Ag/ZnO composites were evaluated by the degradation of rhodamine B (RhB) solution under ultraviolet (UV) and visible light irradiation. The rate of degradation of the as-prepared Ag/ZnO composites was more than triple times faster than that of pure ZnO-MSs under UV light, which was ascribed to the formation of Schottky barriers in the regions between Ag-NPs and ZnO-MSs. Furthermore, Ag/ZnO composites exhibit superior photocatalytic activity over ZnO-MSs in the visible light region owing to the effective electron transfer from plasmon-excited Ag(0) nanoparticles to ZnO-MSs by strong localization of surface plasmon resonance (SPR). This can effectively decrease the recombination of electron-hole pairs, lead to a prolonged lifetime of the electron-holes pairs that promotes the degradation efficiency. The chemical stability and reusability of Ag/ZnO powders were also investigated.

  19. Enhanced magneto-optical effects in composite coaxial nanowires embedded with Ag nanoparticles

    PubMed Central

    Liu, Qianwen; Zheng, Xuanli; He, Jialun; Wang, Weiping; Fu, Mingming; Cao, Yiyan; Li, Heng; Wu, Yaping; Chen, Ting; Zhang, Chunmiao; Chen, Xiaohong; Yu, Binbin; Li, Shuping; Kang, Junyong; Wu, Zhiming

    2016-01-01

    Nanostructures decorated with noble metal nanoparticles (NPs) exhibit potential for use in highly sensitive optoelectronic devices through the localized surface plasmon resonance (LSPR) effect. In this study, Faraday rotation was significantly enhanced through the structural optimization of ferromagnetic (FM)/semiconductor composite nanostructures. Experimental and theoretical results revealed that the position of noble metal NPs significantly influenced the coupling of the LSPR-enhanced electromagnetic field with FM materials. Furthermore, nanostructures embedded with noble metals demonstrated an improved capability to efficiently use the electromagnetic field compared to other structures. The Faraday rotation of ZnO/Ag(NPs)/Fe was enhanced 58 fold compared to that of the ZnO(film)/Fe. This work provides a basis for the design of nanoarchitectures for miniaturized high-performance magneto-optical devices. PMID:27403716

  20. Nanoparticles decorated with proteolytic enzymes, a promising strategy to overcome the mucus barrier.

    PubMed

    Pereira de Sousa, Irene; Cattoz, Beatrice; Wilcox, Matthew D; Griffiths, Peter C; Dalgliesh, Robert; Rogers, Sarah; Bernkop-Schnürch, Andreas

    2015-11-01

    The intestinal mucus gel layer represents a stumbling block for drug adsorption. This study is aimed to formulate a nanoparticulate system able to overcome this barrier by cleaving locally the glycoprotein substructures of the mucus. Mucolytic enzymes such as papain (PAP) and bromelain (BRO) were covalently conjugated to poly(acrylic acid) (PAA). Nanoparticles (NPs) were then formulated via ionic gelation method and characterized by particle size, zeta potential, enzyme content and enzymatic activity. The NPs permeation quantified by rotating tube studies was correlated with changes in the mucus gel layer structure determined by pulsed-gradient-spin-echo NMR (PGSE-NMR), small-angle neutron scattering (SANS) and spin-echo SANS (SESANS). PAP and BRO functionalized NPs had an average size in the range of 250 and 285 nm and a zeta potential that ranged between -6 and -5 mV. The enzyme content was 242 μg enzyme/mg for PAP modified NPs and 253 μg enzyme/mg for BRO modified NPs. The maintained enzymatic activity was 43% for PAP decorated NPs and 76% for BRO decorated NPs. The rotating tube technique revealed a better performance of BRO decorated NPs compared to PAA decorated NPs, with a 4.8-fold higher concentration of NPs in the inner slice of mucus. Addition of 0.5 wt% of enzyme functionalized NPs to 5 wt% intestinal mucin led to c.a. 2-fold increase in the mobility of the mucin as measured by PGSE-NMR indicative of a significant break-up of the structure of the mucin. SANS and SESANS measurements further revealed a change in structure of the intestinal mucus induced by the incorporation of the functionalized NPs mostly occurring at a length scale longer than 0.5 μm. Accordingly, BRO decorated NPs show higher potential than PAP functionalized NPs as mucus permeating drug delivery systems.

  1. Reproducible preparation of a stable polypyrrole-coated-silver nanoparticles decorated polypyrrole-coated-polycaprolactone-nanofiber-based cloth electrode for electrochemical sensor application.

    PubMed

    Li, Li; Wang, Xiaoping; Liu, Guiting; Wang, Zhenzhen; Wang, Feng; Guo, Xiaoyu; Wen, Ying; Yang, Haifeng

    2015-11-06

    A piece of conductive cloth has been successfully constructed from polypyrrole-coated silver nanoparticle (Ag@PPy) composites decorated on electrospun polycaprolactone (PCL) nanofibers that formed the core-shell structure of Ag@PPy/PCL@PPy via a photo-induced one-step redox reaction. The photochemical reaction method both accelerated the rate of formation of silver nanoparticles (Ag NPs) and enhanced the dispersion of Ag NPs at the surface of PCL@PPy film. The resulting Ag@PPy/PCL@PPy-based cloth was flexible enough to be cut and pasted onto a glass carbon electrode for the preparation of a biosensor. The resulting biosensor showed good electrochemical activity toward the reduction of H2O2 with low detection limit down to 1 μM (S/N = 3) and wide linear detection ranging from 0.01 mM to 3.5 mM (R(2) = 0.990). This sensor has been applied to detect the trace H2O2 residual in milk. The cloth electrode has been proved to exhibit long-term stability, high selectivity, and excellent reproducibility.

  2. Cost-Effective Plasmonic Platforms: Glass Capillaries Decorated with Ag@SiO2 Nanoparticles on Inner Walls as SERS Substrates.

    PubMed

    Shanthil, M; Fathima, Hemna; George Thomas, K

    2017-03-01

    A cost-effective method for the fabrication of a glass capillary based plasmonic platform for the selective detection and identification of analytes of importance in health, environment, and safety is demonstrated. This was achieved by coating Ag@SiO2 nanoparticles (Ag ∼ 60 nm) having silica shell of varying thickness (∼2 and ∼25 nm) on the inside walls of glass capillaries, over 2 cm in length, with uniform coverage. It was found that the particle density on the surface plays a decisive role on the enhancement of Raman signals. Multiple hot spots, which are essentially junctions of amplified electric field, were generated when ∼30 Ag@SiO2 particles/μm(2) were bound onto the walls of glass capillaries. The pores of the silica shell allow the localization of analyte molecules to the vicinity of hot spots resulting in signal enhancements of the order of 10(10) (using pyrene as analyte; excitation wavelength, 632.8 nm). The applicability of Ag@SiO2 coated capillaries for the detection of a wide range of molecules has been explored, by taking representative examples of polyaromatic hydrocarbons (pyrene), amino acids (tryptophan), proteins (bovine serum albumin), and explosives (trinitrotoluene). By increasing the thickness of the silica shell of Ag@SiO2 nanoparticles, an effective filtration cum detection method has been developed for the selective identification of small molecules such as amino acids, without the interference of large proteins.

  3. Visible light photo catalytic inactivation of bacteria and photo degradation of methylene blue with Ag/TiO2 nanocomposite prepared by a novel method.

    PubMed

    Tahir, Kamran; Ahmad, Aftab; Li, Baoshan; Nazir, Sadia; Khan, Arif Ullah; Nasir, Tabassum; Khan, Zia Ul Haq; Naz, Rubina; Raza, Muslim

    2016-09-01

    Water purification is one of the worldwide problem and most of the conventional methods are associated with a number of drawbacks. Therefore it is the need of the day to develop new methods and materials to overcome the problem of water purification. In this research work we present a simple and green approach to synthesize silver decorated titanium dioxide (Ag/TiO2) nanocomposite with an efficient photo catalytic activities. Phytochemicals of the Cestrum nocturnum leaf extract were used to synthesize silver nanoparticles (AgNPs), Titanium dioxide (TiO2) and Ag/TiO2 nanocomposite. To confirm the formation, crystal structure, particle size and shape of green synthesized nanoparticles and nanocomposite, they were characterized by UV-visible spectroscopy (UV-vis), X-ray diffraction spectroscopy (XRD), high resolution transmission electron microscopy (HRTEM), Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The AgNPs, TiO2 and Ag/TiO2 were evaluated for photo degradation of methylene blue (MB) and photo inhibition of Bacteria. The bio-synthesized Ag/TiO2 nanocomposite was observed to have strong catalytic activities for photo reduction of MB and photo inactivation of bacteria as compared to bare AgNPs and TiO2. In the presence of Ag/TiO2, 90% of MB was degraded only in 40min of irradiation. Alternatively the bare AgNPs and TiO2 degraded less than 30% and 80% respectively of MB even in more than 100min of irradiation. Similarly the Ag/TiO2 has very strong photo inhibition efficiency towards Escherichia coli and Pseudomonas aeruginosa. The zone of inhibition of irradiated Ag/TiO2 nanocomposites against E. coli and P. aeruginosa was 19mm and 17mm respectively which was two times higher than in dark. These promising photocatalytic activities of nanocomposite may be due to the highly decorated AgNPs over the surface of TiO2.

  4. DNA-embedded Au-Ag core-shell nanoparticles assembled on silicon slides as a reliable SERS substrate.

    PubMed

    Zhang, Zhong; Zhang, Sha; Lin, Mengshi

    2014-05-07

    This study aimed at developing a sensitive and reliable SERS substrate by assembling DNA-embedded Au-Ag core-shell nanoparticles (NPs) on silicon slides. First, a monolayer of well separated DNA-functionalized Au NPs (40 nm) was decorated on (3-aminopropyl)triethoxysilane modified silicon slides. The DNA-embedded Au-Ag core-shell NPs were assembled on the 40 nm Au-DNA NPs to form a core-satellite structure through DNA hybridization. Using 4-MBA as a Raman dye, the SERS performance of the substrates was evaluated after being cleaned by low oxygen and argon plasma. The Raman intensity of the assembly using DNA-embedded Au-Ag core-shell NPs was 8-10 times higher than the intensity of the assembly using Au NPs as satellites. In addition, the signal-to-noise ratio of the assembly was 2.6 times higher than that of a commercial substrate (Klarite™) when a 785 nm laser was used. The SERS enhancements of the assembled substrates were 2.2 to 2.8 times higher than the Klarite when an acquisition time of 5 s was used at an excitation wavelength of 633 nm. The assembled substrates also show a good spot-to-spot and substrate-to-substrate reproducibility at the excitation wavelengths of 633 and 785 nm. These results demonstrate that the fabrication process is simple and cost-effective for assembling DNA-embedded Au-Ag core-shell NPs on silicon slides that can be used as a reliable SERS substrate.

  5. Collection Development "Budget Decorating": Decorating Cents

    ERIC Educational Resources Information Center

    Kumaran, Maha

    2008-01-01

    Home decorating is a popular idea these days as seen in the rise of cable television channels like TLC and HGTV (Home & Garden Television) and TV shows like "Trading Spaces, Take This House and Sell It, Design on a Dime, Decorating Cents," and many others. Throughout history, humans have always expressed the desire to personalize and beautify…

  6. Plasmonic enhancement of the optical absorption and catalytic efficiency of BiVO₄ photoanodes decorated with Ag@SiO₂ core-shell nanoparticles.

    PubMed

    Abdi, Fatwa F; Dabirian, Ali; Dam, Bernard; van de Krol, Roel

    2014-08-07

    Recent progress in the development of bismuth vanadate (BiVO4) photoanodes has firmly established it as a promising material for solar water splitting applications. Performance limitations due to intrinsically poor catalytic activity and slow electron transport have been successfully addressed through the application of water oxidation co-catalysts and novel doping strategies. The next bottleneck to tackle is the modest optical absorption in BiVO4, particularly close to its absorption edge of 2.4 eV. Here, we explore the modification of the BiVO4 surface with Ag@SiO2 core-shell plasmonic nanoparticles. A photocurrent enhancement by a factor of ~2.5 is found under 1 sun illumination (AM1.5). We show that this enhancement consists of two contributions: optical absorption and catalysis. The optical absorption enhancement is induced by the excitation of localized surface plasmon resonances in the Ag nanoparticles, and agrees well with our full-field electromagnetic simulations. Far-field effects (scattering) are found to be dominant, with a smaller contribution from near-field plasmonic enhancement. In addition, a significant catalytic enhancement is observed, which is tentatively attributed to the electrocatalytic activity of the Ag@SiO2 nanoparticles.

  7. Silver decorated multiwalled carbon nanotubes and their characterization

    NASA Astrophysics Data System (ADS)

    Gahlot, Swati; Kulshrestha, Vaibhav; Shahi, V. K.

    2014-04-01

    Deposition of silver nanoparticles on functionalized multiwalled carbon nanotubes is done in the present study. To decorate silver nanoparticles on CNT walls silver nitrate (AgNO3) was used as precursor. Finally prepared nanotubes (Ag-CNT) were analyzed by TEM, XRD and FTIR for the structural and chemical characterization.

  8. Magnesium nanoparticles with transition metal decoration for hydrogen storage

    NASA Astrophysics Data System (ADS)

    Pasquini, Luca; Callini, Elsa; Brighi, Matteo; Boscherini, Federico; Montone, Amelia; Jensen, Torben R.; Maurizio, Chiara; Vittori Antisari, Marco; Bonetti, Ennio

    2011-11-01

    We report on the hydrogen storage behaviour of Mg nanoparticles (NPs) (size range 100 nm-1 μm) with metal-oxide core-shell morphology synthesized by inert gas condensation and decorated by transition metal (TM) (Pd or Ti) clusters via in situ vacuum deposition. The structure and morphology of the as-prepared and hydrogenated NPs is studied by electron microscopy, X-ray diffraction including in situ experiments and X-ray absorption spectroscopy, in order to investigate the relationships with the hydrogen storage kinetics measured by the volumetric Sieverts method. With both Pd and Ti, the decoration deeply improves the hydrogen sorption properties: previously inert NPs exhibit complete hydrogenation with fast transformation kinetics, good stability and reversible gravimetric capacity that can attain 6 wt%. In the case of Pd-decoration, the occurrence of Mg-Pd alloying is observed at high temperatures and in dependence of the hydrogen pressure conditions. These structural transformations modify both the kinetics and thermodynamics of hydride formation, while Ti-decoration has an effect only on the kinetics. The experimental results are discussed in relation with key issues such as the amount of decoration, the heat of mixing between TM and Mg and the binding energy between TM and hydrogen.

  9. Development of a supramolecular ensemble of an AIEE active hexaphenylbenzene derivative and Ag@Cu2O core-shell NPs: an efficient photocatalytic system for C-H activation.

    PubMed

    Chopra, Radhika; Kumar, Manoj; Bhalla, Vandana

    2016-08-09

    A supramolecular ensemble having Ag@Cu2O core-shell nanoparticles stabilized by aggregates of a hexaphenylbenzene derivative has been developed which exhibits excellent photocatalytic efficiency in reactions involving preparation of imidazole and benzimidazole derivatives via C-H activation.

  10. Synthesis, characterization, and application of Fe3O4/Ag magnetic composites for mercury removal from water

    NASA Astrophysics Data System (ADS)

    Elhouderi, Z. A.; Beesley, D. P.; Nguyen, T. T.; Lai, P.; Sheehan, K.; Trudel, S.; Prenner, E.; Cramb, D. T.; Anikovskiy, M.

    2016-04-01

    Engineered nanocomposites (NCs) have recently emerged as materials of great scientific and technological interest. In these materials, different components are combined to yield a nanoentity with desired properties not afforded by the constituent materials. Designing novel NCs and synthetic routes that enable controlling the size and functionalities remains an active area of research. Here, we present a two-step method of synthesizing Ag-Fe3O4 NCs with tunable sizes. Unlike previously reported structures, the prepared NCs do not have a familiar core-shell architecture. Instead, small Fe3O4 nanoparticles (NPs) are embedded in a larger silver matrix. The superparamagnetic Fe3O4 NPs endow the NC with magnetic properties, enabling easy separation from solution. The degree of the NC response to an external magnetic field can be controlled by varying the concentration of Fe3O4 NPs during the synthesis. The Ag matrix serves to protect the embedded Fe3O4 NPs from degradation and can be used for further functionalization of the NCs with different sulfhydryl containing linkers. To demonstrate utility, we show how decorating the outer layer of the Ag NC with diphenyl-4,4‧-dithiol transforms the NCs into a water purifying system capable of sequestering highly toxic Hg2+ ions from solution magnetically.

  11. Exploration of silver decoration concentration to enhance photocatalytic efficiency of titanium dioxide photocatalysts

    NASA Astrophysics Data System (ADS)

    Chang, Lee-Hong; Cho, Chun-Pei

    2016-12-01

    Ag decoration on TiO2 is favorable to absorption of visible light and wider absorption range. Ag nanoparticles playing the role of electron receivers on TiO2 surface enhance photodegradation. However, excess Ag nanoparticles caused reduced specific surface area of photocatalysts and increased probability of charge recombination, resulting in lower photocatalytic efficiency. In this study, the influence of various Ag decoration concentrations on photocatalytic activity was investigated. Surface treatment by nitric acid after Ag decoration was performed to avoid excessive Ag deposition. The extent of Ag elimination and its impacts on photocatalytic activity were also explored. An optimum Ag content in the photocatalyst was achieved and photocatalytic efficiency was obviously improved. It was found that the number of calcination times affected the crystallinity and stability of photocatalysts. Better photocatalytic efficiency could be obtained after twice calcinations.

  12. P25 nanoparticles decorated on titania nanotubes arrays as effective drug delivery system for ibuprofen

    NASA Astrophysics Data System (ADS)

    Wang, Zhang; Xie, Chunlin; Luo, Fei; Li, Ping; Xiao, Xiufeng

    2015-01-01

    In this study, uniformly distributed layer of P25 nanoparticles (NPs) decorated on titania (TiO2) nanotubes (TNTs) arrays was prepared in a teflon-lined stainless steel autoclave by the hydrothermal treatment. To investigate the influence of the P25 concentration, different concentrations of P25 NPs were added into the solution to obtain the optimal decorative effect. TNTs decorated with P25 (TNTs-P25) and TNTs without P25 decorated on its surface were loaded with ibuprofen (IBU) via vacuum drying and its release properties were investigated. The samples were characterized by field emission scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicated that P25 NPs were successfully decorated on the surface of TNTs by hydrothermal method and the optimal concentration was found to be 7.5 × 10-4 M. P25 NPs decorated on TNTs led to a significant increase in the specific surface area of TNTs which was conducive to improve the loading effect of IBU. Importantly, the diameters of the decorated nanotubes were reduced to 100 ± 10 nm and the increase in roughness led to an effective and prolonged drug release.

  13. Novel magnetically separable silver-iron oxide nanoparticles decorated graphitic carbon nitride nano-sheets: A multifunctional photocatalyst via one-step hydrothermal process.

    PubMed

    Pant, Bishweshwar; Park, Mira; Lee, Joong Hee; Kim, Hak-Yong; Park, Soo-Jin

    2017-06-15

    Development of photocatalytic materials with magnetic and antibacterial properties is highly desirable in wastewater treatment. In this study, a novel magnetically separable silver-iron oxide nanoparticles (Ag-Fe3O4 NPs) decorated graphitic carbon nitride (g-C3N4) nanocomposite via hydrothermal treatment has been presented for the multifaceted applications. The physiochemical properties of the as-synthesized ternary nanocomposite were characterized by the field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) studies. The experimental results showed that loading of Ag on Fe3O4/g-C3N4 nanocomposite significantly improved the catalytic activity of the composite material in terms of photocatalytic degradation of methylene blue (Mdestruction of Escherichia coli (E. coli) bacteria. More importantly, the as-synthesized silver-iron oxide nanoparticles decorated graphitic carbon nitride (Ag-Fe3O4/g-C3N4) nanocomposite catalyst could be recovered by an applied external magnet and reused without the loss of photocatalytic activity. The obtained results showed that the synthesized material has potential as an economically friendly photocatalyst for environmental and energy applications.

  14. Monodisperse raspberry-like multihollow polymer/Ag nanocomposite microspheres for rapid catalytic degradation of methylene blue.

    PubMed

    Tian, Qiong; Yu, Xiaojing; Zhang, Lifeng; Yu, Demei

    2017-04-01

    Raspberry-like multihollow polymer microspheres were prepared by seeded swelling polymerization and decorated with silver nanoparticles (AgNPs) in the presence of polyvinylpyrrolidone (PVP) which acted as both reducing and stabilizing agent. Formation mechanism of the raspberry-like multihollow microsphere was discussed on the basis of water absorption of sulfonated groups in the seeded swelling polymerization. Effects of weight ratio of sodium 4-vinylbenzenesulfonate to styrene (NaSS/St) of the seed particles, the concentration of PVP and [Ag(NH3)2](+) ions on the properties of polymer/Ag nanocomposite microspheres were investigated by microscopic observation, nitrogen adsorption/desorption isotherms, UV-vis absorption spectra, X-ray diffraction patterns and thermogravimetric analysis. The results demonstrated that the raspberry-like multihollow microspheres were successfully fabricated by controlling over the NaSS/St of the seed particles in the seeded swelling polymerization by which the fabrication of hollow structure became simple and convenient. The spherical AgNPs were loaded on the polymer microsphere by in-situ chemical reduction due to the stabilization and reduction of PVP and the attraction between sulfonated groups and [Ag(NH3)2](+) ions. The raspberry-like multihollow polymer/Ag microspheres showed good catalytic activity and reusability in the degradation of methylene blue in the presence of NaBH4.

  15. ZnO/Ag composite nanoflowers as substrates for surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Zhang, Guling; Deng, Chaoyue; Shi, Honglong; Zou, Bin; Li, Yongchao; Liu, Tengteng; Wang, Wenzhong

    2017-04-01

    We used a simple two-step hydrothermal method to synthesize ZnO nanoflowers (NFs) evenly decorated with silver nanoparticles (NPs) and evaluated their efficiency as organic-molecule detectors during surface-enhanced Raman scattering (SERS). These three-dimensional (3D) hierarchically structured substrates exhibited high SERS sensitivity with respect to Rhodamine 6G (R6G), with the enhancement factor being as high as 107. And the characteristic peaks of R6G could be identified even at the concentration as low as 10-12 M. SERS maps collected through a point-by-point evaluation suggested that only some parts of the substrates could yield "hot spots," which exhibited extremely high spectral intensities even at relatively low concentrations of the analyte organic molecule. Owing to the synergistic effects of the hierarchically structured semiconductor nanocrystals and the metal NPs, the degree of increase in SERS was much higher than that in the case of Ag NPs alone. This could be ascribed to the high-intensity electromagnetic fields induced at the junction spots formed between the Ag NPs, the chemical enhancement properties of the ZnO NFs, and the ability of the 3D hierarchical nanostructures to create a large number of the adsorption sites and hot spots necessary for SERS.

  16. Effects of PVP/PEI coated and uncoated silver NPs and PVP/PEI coating agent on three species of marine microalgae.

    PubMed

    Schiavo, S; Duroudier, N; Bilbao, E; Mikolaczyk, M; Schäfer, J; Cajaraville, M P; Manzo, S

    2017-01-15

    In the last years, applications for silver nanoparticles (Ag NPs) continue to increase together with the concerns about their potential input and hazards in aquatic ecosystems, where microalgae are key organisms. The aim of the present study was to assess the relative sensitivity of three marine microalgae species with differences in cell wall composition/structure exposed to Poly N-vinyl-2-pirrolidone/Polyethyleneimine (PVP/PEI) coated 5nm Ag NPs and uncoated 47nm Ag NP. As limited attention has been paid to the role of coating agents in NP toxicity, the effect of PVP/PEI alone was also evaluated. After 72h in artificial seawater, 47nm Ag NPs formed around 1400nm size aggregates while PVP/PEI coated 5nm Ag NPs reached around 90nm. Ag(+) release in seawater was around 3% for 47nm Ag NPs and 30% for PVP/PEI coated 5nm Ag NPs. PVP/PEI coated 5nm Ag NP aggregates entrapped the algal cells in a network of heteroaggregates, while uncoated 47nm Ag NPs interacted to a lesser extent with algae. The concentration of PVP/PEI coated 5nm Ag NPs that exerted the median effect (EC50) on algae growth pointed out differences in algae sensitivity: T. suecica was about 10 times more sensitive than I. galbana and P. tricornutum. Further, the coating agent alone was as toxic to algae as PVP/PEI coated 5nm Ag NPs, suggesting that presence of the coating agent was the main driver of toxicity of coated NPs. Uncoated 47nm Ag NPs instead, showed similar toxicity towards algae although P. tricornutum was slightly less sensitive than T. suecica and I. galbana, which agrees with the presence of a resistant silicified cell wall in the diatom. The present work demonstrates differences in sensitivity of three marine microalgae, possibly related to their cell surface and size characteristics.

  17. Decoration of vertical graphene with aerosol nanoparticles for gas sensing

    NASA Astrophysics Data System (ADS)

    Cui, Shumao; Guo, Xiaoru; Ren, Ren; Zhou, Guihua; Chen, Junhong

    2015-08-01

    A facile method was demonstrated to decorate aerosol Ag nanoparticles onto vertical graphene surfaces using a mini-arc plasma reactor. The vertical graphene was directly grown on a sensor electrode using a plasma-enhanced chemical vapor deposition (PECVD) method. The aerosol Ag nanoparticles were synthesized by a simple vapor condensation process using a mini-arc plasma source. Then, the nanoparticles were assembled on the surface of vertical graphene through the assistance of an electric field. Based on our observation, nonagglomerated Ag nanoparticles formed in the gas phase and were assembled onto vertical graphene sheets. Nanohybrids of Ag nanoparticle-decorated vertical graphene were characterized for ammonia gas detection at room temperature. The vertical graphene served as the conductance channel, and the conductance change upon exposure to ammonia was used as the sensing signal. The sensing results show that Ag nanoparticles significantly improve the sensitivity, response time, and recovery time of the sensor.

  18. Basic Cake Decorating Workbook.

    ERIC Educational Resources Information Center

    Bogdany, Mel

    Included in this student workbook for basic cake decorating are the following: (1) Drawings of steps in a basic way to ice a layer cake, how to make a paper cone, various sizes of flower nails, various sizes and types of tin pastry tubes, and special rose tubes; (2) recipes for basic decorating icings (buttercream, rose paste, and royal icing);…

  19. Silver nanowire decorated heatable textiles

    NASA Astrophysics Data System (ADS)

    Doganay, Doga; Coskun, Sahin; Polat Genlik, Sevim; Emrah Unalan, Husnu

    2016-10-01

    The modification of insulating fabrics with electrically conductive nanomaterials has opened up a novel application field. With the help of Joule heating mechanism, conductive fabrics can be used as mobile heaters. In this work, heatable textiles are fabricated using silver nanowires (Ag NWs). Cotton fabrics are decorated with polyol synthesized Ag NWs via a simple dip-and-dry method. The time-dependent thermal response of the fabrics under different applied voltages is investigated. It is found that the fabrics can be heated to 50 °C under an applied power density of as low as 0.05 W cm-2. Uniform deposition of Ag NWs resulted in the homogeneous generation of heat. In addition, the stability of the fabrics with time and under different bending and washing conditions is examined. Moreover, a simple control circuit is fabricated and integrated in order to demonstrate the high potential of the fabrics for mobile applications. This work provides a roadmap for researchers who would like to work on heatable textiles with metallic NWs.

  20. Silver nanowire decorated heatable textiles.

    PubMed

    Doganay, Doga; Coskun, Sahin; Genlik, Sevim Polat; Unalan, Husnu Emrah

    2016-10-28

    The modification of insulating fabrics with electrically conductive nanomaterials has opened up a novel application field. With the help of Joule heating mechanism, conductive fabrics can be used as mobile heaters. In this work, heatable textiles are fabricated using silver nanowires (Ag NWs). Cotton fabrics are decorated with polyol synthesized Ag NWs via a simple dip-and-dry method. The time-dependent thermal response of the fabrics under different applied voltages is investigated. It is found that the fabrics can be heated to 50 °C under an applied power density of as low as 0.05 W cm(-2). Uniform deposition of Ag NWs resulted in the homogeneous generation of heat. In addition, the stability of the fabrics with time and under different bending and washing conditions is examined. Moreover, a simple control circuit is fabricated and integrated in order to demonstrate the high potential of the fabrics for mobile applications. This work provides a roadmap for researchers who would like to work on heatable textiles with metallic NWs.

  1. Composition dependent Fermi level shifting of Au decorated MoS{sub 2} nanosheets

    SciTech Connect

    Shakya, Jyoti; Patel, Arun Singh; Mohanty, Tanuja E-mail: tanujajnu@gmail.com; Singh, Fouran

    2016-01-04

    In the present work, shifting of Fermi level of MoS{sub 2} nanosheets due to decoration of Au nanoparticles (Au NPs) is reported. Au NPs are grown on MoS{sub 2} nanosheets by chemical reduction method. The structural analysis of pristine MoS{sub 2} and Au NPs decorated MoS{sub 2} has been done using X-ray diffraction and transmission electron microscopy. The effect of Au NPs decoration on the Fermi energy level of MoS{sub 2} nanosheets have been monitored by scanning Kelvin probe microscopy, which measures the work function in terms of contact potential difference. The work function of pristine MoS{sub 2} is found to be 4.994 eV, and it increases linearly for Au-MoS{sub 2} with increasing concentration of Au NPs. The gradual increase in the work function values indicate a systematic shifting of Fermi energy level of MoS{sub 2} towards valence band due to decoration of Au NPs.

  2. Installing multifunctionality on titanium with RGD-decorated polyurethane-polyurea roxithromycin loaded nanoparticles: toward new osseointegrative therapies.

    PubMed

    Rocas, Pau; Hoyos-Nogués, Mireia; Rocas, Josep; Manero, José M; Gil, Javier; Albericio, Fernando; Mas-Moruno, Carlos

    2015-09-16

    A novel class of polyurethane-polyurea nanoparticles (PUUa NPs) to install multifunctionality on biomaterials is presented. Biofunctionalization of titanium with roxithromycin loaded RGD-decorated PUUa NPs results in an outstanding improvement of osteoblast adhesion and strong suppression of bacterial attachment. This strategy represents a powerful approach to enhance the osseointegration of implant materials.

  3. 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.

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

    USGS Publications Warehouse

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

  5. Preparation and antibacterial property of silver decorated carbon microspheres

    NASA Astrophysics Data System (ADS)

    Li, Sha; Yan, Xiaoliang; Yang, Zhi; Yang, Yongzhen; Liu, Xuguang; Zou, Jing

    2014-02-01

    Carbon microspheres (CMSs) were prepared by glucose hydrothermal method. The effects of glucose concentration and reaction time on the size and morphology of CMSs were studied. CMSs with surface area of 642.5 m2/g and pore size of 0.8 nm were exploited to design hybrid material of CMSs with Ag decoration by radio frequency plasma (RF plasma). A series of investigations using X-ray diffraction, UV-vis spectrometry, Fourier transform infrared spectrometry, X-ray photoelectron spectrometry, thermogravimetric analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy was carried out to characterize the Ag decorated CMSs. RF plasma was employed to reduce Ag+ ions to metallic nano-particles with the particle size of 10-20 nm and form a clean metal-support (Ag-CMSs) interface. The mechanism for the structure formation of Ag decorated CMSs was discussed. Plasma produced Ag/CMSs showed antibacterial property and proved suitable for potential biological and environmental applications.

  6. Gas sensing properties of MWCNT layers electrochemically decorated with Au and Pd nanoparticles

    PubMed Central

    Alvisi, Marco; Rossi, Riccardo; Cassano, Gennaro; Di Franco, Cinzia; Palmisano, Francesco; Torsi, Luisa

    2017-01-01

    Multiwalled carbon nanotube (MWCNT)-based chemiresistors were electrochemically decorated with Au and Pd nanoparticles (NPs), resulting in an improvement in the detection of gaseous pollutants as compared to sensors based on pristine MWCNTs. Electrophoresis was used to decorate MWCNTs with preformed Au or Pd NPs, thus preserving their nanometer-sized dimensions and allowing the metal content to be tuned by simply varying the deposition time. The sensing response of unmodified and metal-decorated MWCNTs was evaluated towards different gaseous pollutants (e.g., NO2, H2S, NH3 and C4H10) at a wide range of concentrations in the operating temperature range of 45–200 °C. The gas sensing results were related to the presence, type and loading of metal NPs used in the MWCNT functionalization. Compared to pristine MWCNTs, metal-decorated MWCNTs revealed a higher gas sensitivity, a faster response, a better stability, reversibility and repeatability, and a low detection limit, where all of these sensing properties were controlled by the type and loading of the deposited metal catalytic NPs. Specifically, in the NO2 gas sensing experiments, MWCNTs decorated with the lowest Au content revealed the highest sensitivity at 150 °C, while MWCNTs with the highest Pd loading showed the highest sensitivity when operated at 100 °C. Finally, considering the reported gas sensing results, sensing mechanisms have been proposed, correlating the chemical composition and gas sensing responses. PMID:28382249

  7. 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.

  8. 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

  9. 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.

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

    PubMed

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

    2016-09-12

    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.

  11. Antimicrobial wound dressing nanofiber mats from multicomponent (chitosan/silver-NPs/polyvinyl alcohol) systems.

    PubMed

    Abdelgawad, Abdelrahman M; Hudson, Samuel M; Rojas, Orlando J

    2014-01-16

    Novel hybrid nanomaterials have been developed for antimicrobial applications. Here we introduce a green route to produce antibacterial nanofiber mats loaded with silver nanoparticles (Ag-NPs, 25 nm diameter) enveloped in chitosan after reduction with glucose. The nanofiber mats were obtained from colloidal dispersions of chitosan-based Ag-NPs blended with polyvinyl alcohol. Nanofibers (150 nm average diameter and narrow size distribution) were obtained by electrospinning and cross-linked with glutaraldhyde. The effect of crosslinking on the release of silver was studied by atomic absorption spectroscopy. Antimicrobial activity was studied by the viable cell-counting; mats loaded with silver and control samples (chitosan/PVA) with different degrees of cross-linking were compared for their effectiveness in reducing or halting the growth of aerobic bacteria. The results showed superior properties and synergistic antibacterial effects by combining chitosan with Ag-NPs.

  12. 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.

  13. Silver bioaccumulation dynamics in a freshwater invertebrate after aqueous and dietary exposures to nanosized and ionic Ag

    USGS Publications Warehouse

    le Croteau, Marie-Noe; Misra, Superb K.; Luoma, Samuel N.; Valsami-Jones, Eugenia

    2011-01-01

    We compared silver (Ag) bioavailability and toxicity to a freshwater gastropod after exposure to ionic silver (Ag+) and to Ag nanoparticles (Ag NPs) capped with citrate or with humic acid. Silver form, exposure route, and capping agent influence Ag bioaccumulation dynamics in Lymnaea stagnalis. Snails efficiently accumulated Ag from all forms after either aqueous or dietary exposure. For both exposure routes, uptake rates were faster for Ag+ than for Ag NPs. Snails efficiently assimilated Ag from Ag NPs mixed with diatoms (assimilation efficiency (AE) ranged from 49 to 58%) and from diatoms pre-exposed to Ag+ (AE of 73%). In the diet, Ag NPs damaged digestion. Snails ate less and inefficiently processed the ingested food, which adversely impacted their growth. Loss rates of Ag were faster after waterborne exposure to Ag NPs than after exposure to dissolved Ag+. Once Ag was taken up from diet, whether from Ag+ or Ag NPs, Ag was lost extremely slowly. Large Ag body concentrations are thus expected in L. stagnalis after dietborne exposures, especially to citrate-capped Ag NPs. Ingestion of Ag associated with particulate materials appears as the most important vector of uptake. Nanosilver exposure from food might trigger important environmental risks.

  14. 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.

  15. Investigation on the electrical conductivity of ZnO nanoparticles-decorated bacterial nanowires

    NASA Astrophysics Data System (ADS)

    Maruthupandy, Muthuchamy; Anand, Muthusamy; Maduraiveeran, Govindhan; Suresh, Santhanakrishnan; Sait Hameedha Beevi, Akbar; Jeeva Priya, Radhakrishnan

    2016-12-01

    Electrical conductivity of zinc oxide nanoparticles (ZnO NPs)-decorated bacterial nanowires is investigated in the present work. The ZnO NPs are prepared through a simple precipitation method and characterized by UV-vis spectrophotometer, Fourier transform infrared spectroscopy, x-ray diffraction, atomic force microscopy (AFM), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The SEM analysis discloses that the prepared ZnO NPs are spherical in shape with an average particle size of 3.5 nm. The ZnO NPs are decorated on the surface of bacterial nanowires and the same are characterized by AFM and HRTEM. The electrochemical performance of the bare bacterial nanowires and ZnO NPs-decorated bacterial nanowires is analyzed by cyclic voltammetry and linear sweep voltammetry, whereas their electrical conductivity is measured by electrochemical impedance spectroscopy. The results of the electrochemical investigations indicate that the ZnO NPs coating on the surface of bacterial nanowires improve the electrical conductivity of the bacterial nanowires.

  16. Heterostructured Ag3PO4/AgBr/Ag plasmonic photocatalyst with enhanced photocatalytic activity and stability under visible light

    NASA Astrophysics Data System (ADS)

    Wang, Wan-Sheng; Du, Hong; Wang, Rui-Xia; Wen, Tao; Xu, An-Wu

    2013-03-01

    A heterostructured Ag3PO4/AgBr/Ag plasmonic photocatalyst was prepared by a rational in situ ion exchange reaction between Ag3PO4 micro-cubes and Br- in aqueous solution followed by photoreduction. The photocatalytic activities of obtained photocatalysts were measured by the degradation of methyl orange (MO) and methylene blue (MB) under visible light irradiation (λ >= 400 nm). Compared to AgBr/Ag, Ag3PO4/AgBr heterocrystals and pure Ag3PO4 crystals, the heterostructured Ag3PO4/AgBr/Ag plasmonic photocatalysts exhibit much higher photocatalytic activity and stability. This enhanced photocatalytic activity suggests that the synergetic effects of the heterostructured Ag3PO4/AgBr/Ag and the strong SPR of Ag NPs on the surface result in the high efficiencies of the photocatalytic activity and the improved stability. With the assistance of Ag3PO4/AgBr/Ag heterostructures, only 8 min and 12 min are taken to completely decompose MO and MB molecules under visible-light irradiation, respectively. Furthermore, the photodegradation rate does not show an obvious decrease during ten successive cycles, indicating that our heterostructured Ag3PO4/AgBr/Ag plasmonic photocatalysts are extremely stable under visible-light irradiation.A heterostructured Ag3PO4/AgBr/Ag plasmonic photocatalyst was prepared by a rational in situ ion exchange reaction between Ag3PO4 micro-cubes and Br- in aqueous solution followed by photoreduction. The photocatalytic activities of obtained photocatalysts were measured by the degradation of methyl orange (MO) and methylene blue (MB) under visible light irradiation (λ >= 400 nm). Compared to AgBr/Ag, Ag3PO4/AgBr heterocrystals and pure Ag3PO4 crystals, the heterostructured Ag3PO4/AgBr/Ag plasmonic photocatalysts exhibit much higher photocatalytic activity and stability. This enhanced photocatalytic activity suggests that the synergetic effects of the heterostructured Ag3PO4/AgBr/Ag and the strong SPR of Ag NPs on the surface result in the high

  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. Robust platforms for creating organic-inorganic nanocomposite microspheres: decorating polymer microspheres containing mussel-inspired adhesion layers with inorganic nanoparticles.

    PubMed

    Satoh, H; Saito, Y; Yabu, H

    2014-12-07

    We describe a method for creating robust and stable core-shell polymer microspheres decorated with inorganic (IO) nanoparticles (NPs) by a self-organization process and heterocoagulation using a mussel-inspired polymer adhesive layer between the IO NPs and the microspheres.

  19. Fabrication of small-sized silver NPs/graphene sheets for high-quality surface-enhanced Raman scattering.

    PubMed

    Zhao, Hong; Fu, Honggang; Zhao, Tianshou; Wang, Lei; Tan, Taixing

    2012-06-01

    In this paper, small-sized and highly dispersed Ag nanoparticles (NPs) supported on graphene nanosheets are fabricated via a strategy for etching a copper template with Ag(+). Firstly, big-sized Cu NPs are supported on graphene, and then the small-sized and highly dispersed Ag NPs are supported on graphene by replacement reaction, mainly making use of graphene passing electrons between Cu and Ag(+). The graphene used in the experiment is prepared by in situ self-generating template and has good dispersion, excellent crystallinity and little defects. Thus, in the process of Ag/graphene synthesis, there is no any intervention of surfactant, which ensures that SERS activity sites have not been passivated. And, the little defects of graphene benefit the excellent conductivity of graphene and ensured the replacement reaction between Cu and Ag(+). The obtained material exhibits significant high-quality and distinctive SERS activity. Especially, a serial new peak of p-aminothiophenol (PATP) is observed, this is suggested two reasons: one is "surface geometry" of the PATP on small-sized Ag NPs and another is the charge-transfer between Ag and graphene.

  20. Effect of Ag Templates on the Formation of Au-Ag Hollow/Core-Shell Nanostructures.

    PubMed

    Tsai, Chi-Hang; Chen, Shih-Yun; Song, Jenn-Ming; Haruta, Mitsutaka; Kurata, Hiroki

    2015-12-01

    Au-Ag alloy nanostructures with various shapes were synthesized using a successive reduction method in this study. By means of galvanic replacement, twined Ag nanoparticles (NPs) and single-crystalline Ag nanowires (NWs) were adopted as templates, respectively, and alloyed with the same amount of Au(+) ions. High angle annular dark field-scanning TEM (HAADF-STEM) images observed from different rotation angles confirm that Ag NPs turned into AuAg alloy rings with an Au/Ag ratio of 1. The shifts of surface plasmon resonance and chemical composition reveal the evolution of the alloy ring formation. On the other hand, single-crystalline Ag NWs became Ag@AuAg core-shell wires instead of hollow nanostructure through a process of galvanic replacement. It is proposed that in addition to the ratio of Ag templates and Au ion additives, the twin boundaries of the Ag templates were the dominating factor causing hollow alloy nanostructures.

  1. Hierarchically Structured Recommender System for Improving NPS

    ERIC Educational Resources Information Center

    Kuang, Jieyan

    2016-01-01

    Net Promoter System (NPS) is well known as an evaluation measure of the growth engine of big companies in the business area. The ultimate goal of my research is to build an action rules and meta-actions based recommender system for improving NPS scores of 34 companies (clients) dealing with similar businesses in the US and Canada. With the given…

  2. Preparation of iron oxide nanoparticles-decorated carbon nanotube using laser ablation in liquid and their antimicrobial activity.

    PubMed

    Khashan, Khawla S; Sulaiman, Ghassan M; Mahdi, Rafal

    2017-02-01

    The antimicrobial activity was investigated for iron oxide IO nanoparticles (NPs)-decorated carbon nanotubes CNT prepared successfully by Nd:YAG-pulsed laser ablation in the liquid process. TEM reveals the composite NP and exhibits semispherical of iron oxide NPs, which aggregate around rolled and unrolled graphene sheet. XRD pattern proved the presence of carbon and different phases of IO NPs. Then, the antibacterial activity of the NPs was examined against different bacteria using nutrient broth and nutrient agar methods, which was enhanced using IO. In addition, the wound-healing activity for the best antibacterial concentration is tested by using animal models successfully.

  3. Three dimensional design of large-scale TiO(2) nanorods scaffold decorated by silver nanoparticles as SERS sensor for ultrasensitive malachite green detection.

    PubMed

    Tan, En-Zhong; Yin, Peng-Gang; You, Ting-Ting; Wang, Hua; Guo, Lin

    2012-07-25

    We have designed a large-scale three-dimensional (3D) hybrid nanostructure as surface-enhanced Raman scattering (SERS) sensor by decorating silver nanoparticles on TiO2 nanorods scaffold (Ag/TiO2). Taking p-mercaptobenzoic acid (PMBA) as the probe molecule, the SERS signals collected by point-to-point and time mapping modes show that the relative standard deviation (RSD) in the intensity of the main Raman vibration modes (1079, 1586 cm(-1)) is less than 10%, demonstrating good spatial uniformity and time stability. This hybrid substrate also exhibits excellent SERS enhancement effect due to the formation of high-density hot spots among the AgNPs, which was proved by finite-difference time-domain (FDTD) simulations. The application of the new nanostructures as SERS sensors was demonstrated with the detection of malachite green (MG). The quantification of MG can be accomplished with the detection limit of 1 × 10(-12) M based on the Raman intensity. The results show that the Ag/TiO2 nanostructure can be a promising candidate for SERS sensor.

  4. 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.

  5. Photo- and thermo-chemical transformation of AgCl and Ag2S in environmental matrices and its implication.

    PubMed

    Yin, Yongguang; Xu, Wei; Tan, Zhiqiang; Li, Yanbin; Wang, Weidong; Guo, Xiaoru; Yu, Sujuan; Liu, Jingfu; Jiang, Guibin

    2017-01-01

    AgCl and Ag2S prevalently exist in the environment as minerals and/or the chlorination and sulfidation products of ionic silver and elemental silver nanoparticles (AgNPs). In this work, we investigated the chemical transformation of AgCl and Ag2S under simulated sunlight (in water) and incineration (in sludge and simulated municipal solid waste, SMSW). In the presence of natural organic matter, AgCl in river water was observed to be transformed into AgNPs under simulated sunlight, while photo-reduction of Ag2S could not take place under the same experimental conditions. During the course of incineration, pure Ag2S was transformed into elemental silver while AgCl remained stable; however, both Ag2S in sludge and AgCl in SMSW can be transformed to elemental silver under incineration, evident by the results of X-ray absorption spectroscopy and scanning electron microscopy measurements. Incineration temperature played an important role in the transformation of Ag2S and AgCl into elemental silver. These results suggest that chemical transformations of Ag2S and AgCl into elemental silver could be a possible source of naturally occurring or unintentionally produced AgNPs, affecting the fate, transport, bioavailability and toxicity of silver. Therefore, it is necessary to include the contributions of this transformation process when assessing the risk of ionic silver/AgNPs and the utilization and management of incineration residues.

  6. Surface decoration by Spirulina polysaccharide enhances the cellular uptake and anticancer efficacy of selenium nanoparticles

    PubMed Central

    Yang, Fang; Tang, Quanming; Zhong, Xueyun; Bai, Yan; Chen, Tianfeng; Zhang, Yibo; Li, Yinghua; Zheng, Wenjie

    2012-01-01

    A simple and solution-phase method for functionalization of selenium nanoparticles (SeNPs) with Spirulina polysaccharides (SPS) has been developed in the present study. The cellular uptake and anticancer activity of SPS-SeNPs were also evaluated. Monodisperse and homogeneous spherical SPS-SeNPs with diameters ranging from 20 nm to 50 nm were achieved under optimized conditions, which were stable in the solution phase for at least 3 months. SPS surface decoration significantly enhanced the cellular uptake and cytotoxicity of SeNPs toward several human cancer cell lines. A375 human melanoma cells were found extremely susceptible to SPS-SeNPs with half maximal (50%) inhibitory concentration value of 7.94 μM. Investigation of the underlying mechanisms revealed that SPS-SeNPs inhibited cancer cell growth through induction of apoptosis, as evidenced by an increase in sub-G1 cell population, deoxyribonucleic acid fragmentation, chromatin condensation, and phosphatidylserine translocation. Results suggest that the strategy to use SPS as a surface decorator could be an effective way to enhance the cellular uptake and anticancer efficacy of nanomaterials. SPS-SeNPs may be a potential candidate for further evaluation as a chemopreventive and chemotherapeutic agent against human cancers. PMID:22359460

  7. Antibody decoration of neurofilaments

    PubMed Central

    1981-01-01

    We have decorated neurofilaments with antibodies against three polypeptides (designated here as H [mol wt = 195,000], 45[mol wt = 145,000], and 46[mol wt = 73,000]) in an effort to understand the arrangement of these polypeptides within neurofilaments. The three polypeptides were purified and antibodies were raised against each. The cross-reactivity of the antibodies suggested that each polypeptide contains both shared and unique antigenic determinants. The differential reactivities of each antibody preparation were enhanced by adsorption with the two heterologous polypeptides, and the resulting preparations were used to decorate purified neurofilaments, which were then negatively stained and examined in an electron microscope. The appearance of the antibody-decorated structures led to the following conclusions: All three polypeptides are physically associated with the same neurofilament. However, the disposition of H and 46 within a filament is different; 46 antigens appear to be associated with a "central core" of the filament, whereas H antigens compose a structure more loosely and peripherally attached to the central core and periodically arranged along its axis. The antibody-decorated H- containing structure assumes variable configurations; in some cases it appears asa bridge connecting two filaments; in other cases it appears as a helix wrapping the central core with a period of approximately 1,000 A and an apparent unit length of approximately 1.5 periods. These configurations suggest several functional implications, including the possibility that H is a component of the cross-bridges observed between filaments in situ. We also note that the central core-helix relationship could be used in the design of an intracellular transport motor. PMID:6788775

  8. Photoluminescence Behaviour of Sm3+ Ions in presence of Ag Nanoparticles in Methanol

    NASA Astrophysics Data System (ADS)

    Dehingia, N.; Gogoi, P.; Boruah, A.; Kakoti, D.; Rajkonwar, N.; Dutta, P.

    2016-10-01

    In the present work, capped Ag NPs prepared by reduction of Ag (NO3)3 by Dimethyl Formamide is doped with Sm3+ in methanol and its photoluminescence behavior is studied. Significant modifications of the Sm3+ ions’ emission as well as quantum yield, were observed with the concentration of Ag NPs. Local field enhancement induced by neutral Ag NPs were found to be responsible for enhancement in efficiency of the Sm3+ ions.

  9. Gold nanoparticles-decorated single silver nanowire as an efficient SERS-active substrate

    NASA Astrophysics Data System (ADS)

    Tan, En-zhong

    2014-07-01

    A novel surface-enhanced Raman scattering (SERS)-active substrate based on Au nanoparticles (AuNPs)-coated silver nanowire (AgNW) is obtained by an effective and simple method. The results show that the hybrid structures prepared by this method are powerful SERS-active substrates for the detection of malachite green (MG) molecules with the limit of 1 nmol/L. The excellent enhancing ability mainly comes from two kinds of hot spots. One is from the gaps among the adjacent AuNPs, and the other is the presence of zone between AuNPs and AgNW. In particular, the AuNPs-coated AgNW can be viewed through the objective of the confocal Raman spectrometer due to the length of the AgNW reaches microns, which can improve the repeatability of detection. Moreover, it is of great significance in research of SERS mechanism and application.

  10. Virus-Surface-Mimicking Surface Clustering of AuNPs onto DNA-Entrapped Polymeric Nanoparticle for Enhanced Cellular Internalization and Nanocluster-Induced NIR Photothermal Therapy.

    PubMed

    Jia, Hui-Zhen; Chen, Wei-Hai; Wang, Xuli; Lei, Qi; Yin, Wei-Na; Wang, Yan; Zhuo, Ren-Xi; Feng, Jun; Zhang, Xian-Zheng

    2015-12-01

    Virus-surface-mimicking decoration of deoxyribonucleic acid (DNA)-entrapped polymeric nanoparticle with AuNPs is demonstrated to lead to enhanced cellular uptake, improved gene transfection, and particularly efficient near-infrared photothermal therapy that cannot be achieved by both of them separately. This hybrid nanosystem represents a novel paradigm of multipurpose organic-inorganic nanoplatform, especially for cancer treatments.

  11. Intranasally Administered Neuropeptide S (NPS) Exerts Anxiolytic Effects Following Internalization Into NPS Receptor-Expressing Neurons

    PubMed Central

    Ionescu, Irina A; Dine, Julien; Yen, Yi-Chun; Buell, Dominik R; Herrmann, Leonie; Holsboer, Florian; Eder, Matthias; Landgraf, Rainer; Schmidt, Ulrike

    2012-01-01

    Experiments in rodents revealed neuropeptide S (NPS) to constitute a potential novel treatment option for anxiety diseases such as panic and post-traumatic stress disorder. However, both its cerebral target sites and the molecular underpinnings of NPS-mediated effects still remain elusive. By administration of fluorophore-conjugated NPS, we pinpointed NPS target neurons in distinct regions throughout the entire brain. We demonstrated their functional relevance in the hippocampus. In the CA1 region, NPS modulates synaptic transmission and plasticity. NPS is taken up into NPS receptor-expressing neurons by internalization of the receptor–ligand complex as we confirmed by subsequent cell culture studies. Furthermore, we tracked internalization of intranasally applied NPS at the single-neuron level and additionally demonstrate that it is delivered into the mouse brain without losing its anxiolytic properties. Finally, we show that NPS differentially modulates the expression of proteins of the glutamatergic system involved inter alia in synaptic plasticity. These results not only enlighten the path of NPS in the brain, but also establish a non-invasive method for NPS administration in mice, thus strongly encouraging translation into a novel therapeutic approach for pathological anxiety in humans. PMID:22278093

  12. 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.

  13. 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

  14. 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.

  15. 7. WEST PORTAL. NOTE DECORATIVE ELEMENTS, INCLUDING DECORATIVE CAPS COVERING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. WEST PORTAL. NOTE DECORATIVE ELEMENTS, INCLUDING DECORATIVE CAPS COVERING COMPRESSION BLOCKS. NAME OF THE BRIDGE COMPANY WITH HERALDIC CARTOUCHE BEARING NAMES OF THREE COUNTY COMMISSIONERS BELOW, AND OPEN SCROLL WORK IN WROUGHT IRON. - Peevy Road Bridge, Peevy Road spanning Perkiomen Creek in Upper Hanover Township, East Greenville, Montgomery County, PA

  16. 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 ...

  17. 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.

  18. Complications of decorative tattoo.

    PubMed

    Shinohara, Michi M

    2016-01-01

    Decorative tattoo is a popular practice that is generally safe when performed in the professional setting but can be associated with a variety of inflammatory, infectious, and neoplastic complications, risks that may be increased with current trends in home tattooing. Modern tattoo inks contain azo dyes and are often of unknown composition and not currently regulated for content or purity. Biopsy of most (if not all) tattoo reactions presenting to the dermatologist is recommended, given recent clusters of nontuberculous mycobacterial infections occurring within tattoo, as well as associations between tattoo reactions and systemic diseases such as sarcoidosis.

  19. Synthesis of Water Dispersible and Catalytically Active Gold-Decorated Cobalt Ferrite Nanoparticles.

    PubMed

    Silvestri, Alessandro; Mondini, Sara; Marelli, Marcello; Pifferi, Valentina; Falciola, Luigi; Ponti, Alessandro; Ferretti, Anna Maria; Polito, Laura

    2016-07-19

    Hetero-nanoparticles represent an important family of composite nanomaterials that in the past years are attracting ever-growing interest. Here, we report a new strategy for the synthesis of water dispersible cobalt ferrite nanoparticles (CoxFe3-xO4 NPs) decorated with ultrasmall (2-3 nm) gold nanoparticles (Au NPs). The synthetic procedure is based on the use of 2,3-meso-dimercaptosuccinic acid (DMSA), which plays a double role. First, it transfers cobalt ferrite NPs from the organic phase to aqueous media. Second, the DMSA reductive power promotes the in situ nucleation of gold NPs in proximity of the magnetic NP surface. Following this procedure, we achieved a water dispersible nanosystem (CoxFe3-xO4-DMSA-Au NPs) which combines the cobalt ferrite magnetic properties with the catalytic features of ultrasmall Au NPs. We showed that CoxFe3-xO4-DMSA-Au NPs act as an efficient nanocatalyst to reduce 4-nitrophenol to 4-aminophenol and that they can be magnetically recovered and recycled. It is noteworthy that such nanosystem is more catalytically active than Au NPs with equal size. Finally, a complete structural and chemical characterization of the hetero-NPs is provided.

  20. 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

  1. 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.

  2. 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.

  3. Antibacterial carboxymethyl cellulose/Ag nanocomposite hydrogels cross-linked with layered double hydroxides.

    PubMed

    Yadollahi, Mehdi; Namazi, Hassan; Aghazadeh, Mohammad

    2015-08-01

    This paper deals with the preparation of antibacterial nanocomposite hydrogels through the combination of carboxy methyl cellulose (CMC), layered double hydroxides (LDH), and silver nanoparticles (AgNPs). CMC-LDH hydrogels were prepared by intercalating CMC into different LDHs. Then, Ag/CMC-LDH nanocomposite hydrogels were prepared through in situ formation of AgNPs within the CMC-LDHs. XRD analysis confirmed the intercalating CMC into the LDH sheets and formation of intercalated structures, as well as formation of AgNPs within the CMC-LDHs. SEM and TEM micrographs indicated well distribution of AgNPs within the Ag/CMC-LDHs. The prepared hydrogels showed a pH sensitive swelling behavior. The Ag/CMC-LDH nanocomposite hydrogels have rather higher swelling in different aqueous solutions in comparison with CMC-LDHs. The antibacterial activity of CMC-LDHs increased considerably after formation of AgNPs and was stable for more than one month.

  4. A flexible lab-on-a-chip for the synthesis and magnetic separation of magnetite decorated with gold nanoparticles.

    PubMed

    Cabrera, Flávio C; Melo, Antonio F A A; de Souza, João C P; Job, Aldo E; Crespilho, Frank N

    2015-04-21

    Magnetite decorated with gold nanoparticles (Fe3O4-AuNPs) is a ferrimagnetic material with unprecedented applications in immunosensors, as a contrast agent for imaging diagnosis, and for the photothermal ablation of tumor cells. Here, we show the preparation of controlled amounts of Fe3O4-AuNPs without organic solvents, surfactants, or heat treatment. For this, we have developed a customized natural-rubber-based microfluidic device (NRMD) as a flexible lab-on-a-chip for the decoration of Fe3O4 with AuNPs. With a novel NRMD configuration, monodisperse Fe3O4-NPs (ϕ = 10 nm) decorated with AuNPs (ϕ = 4 nm) were readily obtained. The AuNPs were homogenous in terms of their size and their distribution on the Fe3O4-NP surfaces. Furthermore, the lab-on-a-chip was projected with an internal system for magnetic separation, an innovation in terms of aqueous/carrier phase separation. Finally, the nanomaterials produced with this NRMD are free of organic solvents and surfactants, allowing them to be used directly for medical applications.

  5. Enhanced photocatalytic properties of the 3D flower-like Mg-Al layered double hydroxides decorated with Ag{sub 2}CO{sub 3} under visible light illumination

    SciTech Connect

    Ao, Yanhui Wang, Dandan; Wang, Peifang; Wang, Chao; Hou, Jun; Qian, Jin

    2016-08-15

    Highlights: • 3D flower-like Ag{sub 2}CO{sub 3}/Mg-Al layered double hydroxide composite was prepared. • The nanocomposites exhibited high photocatalytic activities on different organic pollutants. • The mechanism of the enhanced activity were investigated. - Abstract: A facile anion-exchange precipitation method was employed to synthesize 3D flower-like Ag{sub 2}CO{sub 3}/Mg-Al layered double hydroxide composite photocatalyst. Results showed that Ag{sub 2}CO{sub 3} nanoparticles dispersed uniformly on the petals of the flower-like Mg-Al LDH. The obtained nanocomposites exhibited high photocatalytic activities on different organic pollutants (cationic and anionic dyes, phenol) under visible light illumination. The high photocatalytic activity can be ascribed to the special structure which accomplishes the wide-distribution of Ag{sub 2}CO{sub 3} nanoparticles on the surfaces of the 3D flower-like nanocomposites. Therefore, it can provide much more active sites for the degradation of organic pollutant. Then the photocatalytic mechanism was also verified by reactive species trapping experiments in detail. The work would pave a facile way to prepare LDHs based hierarchical photocatalysts with high activity for the degradation of wide range organic pollutants under visible light irradiation.

  6. Gracilaria lemaneiformis polysaccharide as integrin-targeting surface decorator of selenium nanoparticles to achieve enhanced anticancer efficacy.

    PubMed

    Jiang, Wenting; Fu, Yuanting; Yang, Fang; Yang, Yufeng; Liu, Ting; Zheng, Wenjie; Zeng, Lilan; Chen, Tianfeng

    2014-08-27

    The poor permeability of glioma parenchyma represents a major limit for antiglioblastoma drug delivery. Gracilaria lemaneiformis polysaccharide (GLP), which has a high binding affinity to αvβ3 integrin overexpressed in glioma cells, was employed in the present study to functionalize selenium nanoparticles (SeNPs) to achieve antiglioblastoma efficacy. GLP-SeNPs showed satisfactory size distribution, high stability, and selectivity between cancer and normal cells. In U87 glioma cell membrane, which has a high integrin expression level, GLP-SeNPs exhibited significantly higher cellular uptake than unmodified SeNPs. As expected, U87 cells exhibited a greater uptake of GLP-SeNPs than C6 cells with low integrin expression level. Furthermore, the internalization of GLP-SeNPs was inhibited by cyclo-(Arg-Gly-Asp-Phe-Lys) peptides, suggesting that cellular uptake into U87 cells and C6 cells occurred via αvβ3 integrin-mediated endocytosis. For U87 cells, the cytotoxicity of SeNPs decorated by GLP was enhanced significantly because of the induction of various apoptosis signaling pathways. Internalized GLP-SeNPs triggered intracellular reactive oxygen species downregulation. Therefore, p53, MAPKs, and AKT pathways were activated to advance cell apoptosis. These findings suggest that surface decoration of nanomaterials with GLP could be an efficient strategy for design and preparation of glioblastoma targeting nanodrugs.

  7. 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.

  8. Gold nanoparticles decorated on cobalt porphyrin-modified glassy carbon electrode for the sensitive determination of nitrite ion.

    PubMed

    Muthukumar, Palanisamy; Abraham John, S

    2014-05-01

    The present study reports the electrochemical determination of nitrite ion using citrate-gold nanoparticles (cit-AuNPs) decorated on meso-tetra(para-aminophenyl)porphyrinatocobalt(II) (Co(II)MTpAP) self-assembled glassy carbon electrode (GCE). The decoration of cit-AuNPs on Co(II)MTpAP was achieved with the aid of amine groups present on the surface of the self-assembled monolayer (SAM) of Co(II)MTpAP. The SEM image shows that the cit-AuNPs were densely packed on Co(II)MTpAP. The AuNPs decorated electrode was successfully used for the determination of nitrite ion. The cit-AuNPs decorated electrode not only shifted nitrite ion oxidation potential towards less positive potential but also greatly enhanced its current when compared to bare and Co(II)MTpAP SAM modified electrodes. The amperometric current increases linearly while increasing the concentration of nitrite ion ranging from 0.5×10(-6) to 4.7×10(-3) M and the detection limit was found to be 60 nM (S/N=3). Further, the modified electrode was successfully used to determine nitrite ion in the presence of 200-fold excess of common interferents such as Na+, NO3-, I-, K+, CO3(2-), Ca2+, SO4(2-), NH4+, Cl- and glucose. The practical application of the cit-AuNPs decorated electrode was demonstrated by determining nitrite ion in water samples.

  9. Gold nanoparticles-decorated graphene field-effect transistor biosensor for femtomolar MicroRNA detection.

    PubMed

    Cai, Bingjie; Huang, Le; Zhang, Hong; Sun, Zhongyue; Zhang, Zhiyong; Zhang, Guo-Jun

    2015-12-15

    Early detection is proven to be the best chance for successful cancer treatment. MiRNAs, as ideal biomarkers, can identify cancer in the early stage. Therefore, development of highly sensitive and selective detection methods for miRNA is still anticipated. Here we report on a gold nanoparticles (AuNPs)-decorated graphene field-effect transistor (FET) biosensor for highly sensitive, selective and label-free detection of miRNA. The AuNPs-decorated graphene FET biosensor was fabricated by drop-casting the reduced graphene oxide (R-GO) suspension onto the sensor surface, and subsequently decorating AuNPs onto the surface of R-GO. After peptide nucleic acid (PNA) probe was immobilized on the AuNPs surface, miRNA detection was carried out via PNA-miRNA hybridization. It was found that the developed FET biosensor was able to achieve a detection limit as low as 10 fM. In addition, the biosensor enabled an accurate distinction of complementary miRNA from one-base mismatched miRNA and noncomplementary miRNA. What's more, this highly sensitive and selective assay was also applied to the detection of miRNA in serum samples, making it a potential method for diagnosis of gene-related diseases.

  10. Bimetallic non-alloyed NPs for improving the broadband optical absorption of thin amorphous silicon substrates

    PubMed Central

    2014-01-01

    We propose the use of bimetallic non-alloyed nanoparticles (BNNPs) to improve the broadband optical absorption of thin amorphous silicon substrates. Isolated bimetallic NPs with uniform size distribution on glass and silicon are obtained by depositing a 10-nm Au film and annealing it at 600°C; this is followed by an 8-nm Ag film annealed at 400°C. We experimentally demonstrate that the deposition of gold (Au)-silver (Ag) bimetallic non-alloyed NPs (BNNPs) on a thin amorphous silicon (a-Si) film increases the film's average absorption and forward scattering over a broad spectrum, thus significantly reducing its total reflection performance. Experimental results show that Au-Ag BNNPs fabricated on a glass substrate exhibit resonant peaks at 437 and 540 nm and a 14-fold increase in average forward scattering over the wavelength range of 300 to 1,100 nm in comparison with bare glass. When deposited on a 100-nm-thin a-Si film, Au-Ag BNNPs increase the average absorption and forward scattering by 19.6% and 95.9% compared to those values for Au NPs on thin a-Si and plain a-Si without MNPs, respectively, over the 300- to 1,100-nm range. PMID:24725390

  11. Ultrasensitive luminol electrochemiluminescence for protein detection based on in situ generated hydrogen peroxide as coreactant with glucose oxidase anchored AuNPs@MWCNTs labeling.

    PubMed

    Cao, Yaling; Yuan, Ruo; Chai, Yaqin; Mao, Li; Niu, Huan; Liu, Huijing; Zhuo, Ying

    2012-01-15

    In this study, an ultrasensitive luminol electrochemiluminescence (ECL) immunosensor was constructed using carboxyl group functionalized multi-walled carbon nanotubes (MWCNTs) as platform and glucose oxidase (GOD) supported on Au nanoparticles (AuNPs) decorated MWCNTs (AuNPs@MWCNTs-GOD) as labels. Firstly, using poly(ethylenimine) (PEI) as linkage reagents, AuNPs@MWCNTs were prepared and introduced for binding of the secondary antibody (Ab(2)) and glucose oxidase (GOD) with high loading amount and good biological activity due to the improved surface area of AuNPs@MWCNTs and excellent biocompatibility of AuNPs. Then the GOD and Ab(2) labeled AuNPs@MWCNTs were linked to the electrode surface via sandwich immunoreactions. These localized GOD and AuNPs amplified luminol ECL signals dramatically, which was achieved by efficient catalysis of the GOD and AuNPs towards the oxidation of glucose to in situ generate improved amount of hydrogen peroxide (H(2)O(2)) as coreactant and the enhancement of AuNPs to the ECL reaction of luminol-H(2)O(2). The experimental results demonstrated that the proposed immunosensor exhibited sensitive and stable response for the detection of α-1-fetoprotein (AFP), ranging from 0.0001 to 80 ng mL(-1) with a limit of detection down to 0.03 pg mL(-1) (S/N=3). With excellent stability, sensitivity, selectivity and simplicity, the proposed luminol ECL immunosensor showed great potential in clinical applications.

  12. 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

  13. The utilization of SiNWs/AuNPs-modified indium tin oxide (ITO) in fabrication of electrochemical DNA sensor.

    PubMed

    Rashid, Jahwarhar Izuan Abdul; Yusof, Nor Azah; Abdullah, Jaafar; Hashim, Uda; Hajian, Reza

    2014-12-01

    This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using self-assembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0-178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4°C in silica gel.

  14. Immunomodulatory of selenium nano-particles decorated by sulfated Ganoderma lucidum polysaccharides.

    PubMed

    Wang, Jianguo; Zhang, Yifeng; Yuan, Yahong; Yue, Tianli

    2014-06-01

    In this study, we employed a one-step method to prepare selenium nanoparticles (SeNPs) decorated by the water-soluble derivative of Ganoderma lucidum polysaccharides (SPS). The SeNPs-SPS complexes were stable, and the diameter of the SeNPs was homogeneous at around 25 nm. We investigated the anti-inflammatory activity of SeNPs-SPS against murine Raw 264.7 macrophage cells induced by LPS. SeNPs-SPS were found to significantly inhibit LPS-stimulated nitric oxide (NO) production against Raw 264.7 macrophages. RT-PCR results reveal the down-regulation of mRNA gene expressions for pro-inflammatory cytokines, including inducible NO synthase (iNOS), interleukin (IL)-1 and TNF-α in a dose-dependent manner. However, the anti-inflammation cytokine IL-10 was markedly increased. In the NF-κB signal pathway, SeNPs-SPS significantly inhibited the phosphorylation of Iκ-Bα. Similar results were observed for inhibition of the phosphorylation of JNK1/2 and p38 mitogen-activated protein kinase(MAPKs), whereas ERK1/2 MAPK was not apparently affected by SeNPs-SPS. All of these results suggest that SeNPs-SPS complexes have anti-inflammatory potential modulating pro-/anti-inflammation cytokine secretion profiles, and that the mechanism is partially due to inhibition of activations of NF-κB, JNK1/2 and p38 MAPKs.

  15. 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.

  16. Decoration of cesium iodide nano particles on patterned carbon nanotube emitter arrays to improve their field emission

    NASA Astrophysics Data System (ADS)

    Shahi, Monika; Gautam, S.; Shah, P. V.; Rawat, J. S.; Chaudhury, P. K.; Harsh; Tandon, R. P.

    2013-03-01

    Arrays of aligned carbon nanotube (CNT) bundles were synthesized on the pre-patterned silicon substrate using thermal chemical vapor deposition. Silicon substrate was patterned with square arrays of 10 × 10 μm iron catalyst using photolithography, iron sputtering, and a lift-off process. After field emission (FE) measurement in diode configuration, CNT emitter arrays (CEAs) were decorated with cesium iodide (CsI) nano particles (NPs) using thermal evaporation with substrate heating at 300 °C. FE of pristine CEAs and CsI NPs decorated CEAs were carried out under same vacuum condition and constant inter-electrode separation. Pristine CEAs and CsI NPs decorated CEAs were characterized using scanning electron microscope, transmission electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman characterization. From FE comparison plots, it was observed that CsI NPs decoration on the CEAs had significantly lowered the turn-on electric field from 3.00 to 2.13 V/μm. A remarkable improvement of more than 50 % in the current density, from 11.02 to 17.33 mA/cm2, was also observed at a constant applied electric field of 5 V/μm.

  17. 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

  18. In-site synthesis of monodisperse, oleylamine-capped Ag nanoparticles through microemulsion approach

    NASA Astrophysics Data System (ADS)

    Chen, Shun; Ju, Yanyun; Guo, Yi; Xiong, Chuanxi; Dong, Lijie

    2017-03-01

    Ag NPs were in-site synthesized through microemulsion method by reducing silver acetate with oleylamine-mediated at 70 °C with highly monodisperse and narrow size from 10 to 20 nm. The synthesis of Ag NPs was aided by oleylamine and the role of oleylamine was researched. This in-site synthesis approach to Ag NPs was reproducibility and high yield more than 80% with stable store about 6 months.

  19. Fire-Retardant, Decorative Inks

    NASA Technical Reports Server (NTRS)

    Kourtides, D.; Nir, Z.; Mikroyannidis, J.

    1987-01-01

    Effectiveness of fire-retardant additives evaluated. Fire retardance of decorative acrylic printing inks for aircraft interiors enhanced by certain commercial and experimental fire-retardant additives, according to study.

  20. 3D Woven-Like Carbon Micropattern Decorated with Silicon Nanoparticles for Use in Lithium-Ion Batteries.

    PubMed

    Kang, Da-Young; Kim, Cheolho; Gueon, Donghee; Park, Gyulim; Kim, Jung Sub; Lee, Joong Kee; Moon, Jun Hyuk

    2015-10-26

    Carbon/silicon composite materials are a promising anode substrate for use in lithium-ion batteries. In this study, we suggest a new architecture for a composite electrode made of a woven-like carbon material decorated with silicon nanoparticles. The 3D woven-like carbon (WLC) structure was fabricated using direct carbonization of multi-beam interference lithography polymer patterns. Subsequent solution coating was applied to decorate the WLC with silicon nanoparticles (SiNPs). The SiNP/WLC electrode exhibited a specific capacity of 930 mAh g(-1) , which is three times higher than the specific capacity of the bare electrode. Specifically, the SiNP/WLC electrode exhibited an outstanding retention capacity of 81 % after 50 cycles and a Coulombic efficiency of more than 98 %. This rate capability performance was attributed to the WLC structure and the uniform decoration of the SiNPs.

  1. 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.

  2. pH-sensitive nanocarrier based on gold/silver core-shell nanoparticles decorated multi-walled carbon manotubes for tracing drug release in living cells.

    PubMed

    Chen, Peng; Wang, Zhuyuan; Zong, Shenfei; Zhu, Dan; Chen, Hui; Zhang, Yizhi; Wu, Lei; Cui, Yiping

    2016-01-15

    We fabricate a multifunctional nanocarrier based on multi-walled carbon nanotubes (MWCNTs) decorated with gold/silver core-shell nanoparticles (Au@Ag NPs) and fluorescein isothiocyanate (FITC) for tracking the intracellular drug release process. In the demonstrated nanocarrier, the Au@Ag NPs adsorbed on the surface of MWCNTs were labeled with the pH-dependent SERS reporter 4-Mercaptobenzoic acid (4MBA) for SERS based pH sensing. FITC was conjugated on MWCNTs to provide fluorescence signal for tracing the MWCNTs. Fluorescent doxorubicin (DOX) was used as the model drug which can be loaded onto MWCNTs via π-π stacking and released from the MWCNTs under acidic condition. By detecting the SERS spectrum of 4MBA, the pH value around the nanocarrier could be monitored. Besides, by tracing the fluorescence of FITC and DOX, we can also investigate the drug release process in cells. Experimental results show that the proposed nanocarrier retained a well pH-sensitive performance in living cells, and the DOX detached from MWCNTs inside the lysosomes and entered into the cytoplasm with the MWCNTs being left in lysosomes. To further investigate the drug release dynamics, 2-D color-gradient pH mapping were plotted, which were calculated from the SERS spectra of 4MBA. The detailed release process and carrier distribution have been recorded as environmental pH changes during cell endocytosis. Furthermore, we also confirmed that the proposed nanocarrier has a good biocompatibility. It indicates that the designed nanocarrier have a great potential in intraceable drug delivery, cancer cells imaging and pH monitoring.

  3. 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.

  4. 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

  5. Hyaluronan-decorated polymer nanoparticles targeting the CD44 receptor for the combined photo/chemo-therapy of cancer

    NASA Astrophysics Data System (ADS)

    Maiolino, Sara; Moret, Francesca; Conte, Claudia; Fraix, Aurore; Tirino, Pasquale; Ungaro, Francesca; Sortino, Salvatore; Reddi, Elena; Quaglia, Fabiana

    2015-03-01

    In the attempt to develop novel concepts in designing targeted nanoparticles for combination therapy of cancer, we propose here CD44-targeted hyaluronan-decorated double-coated nanoparticles (dcNPs) delivering the lipophilic chemotherapeutic docetaxel (DTX) and an anionic porphyrin (TPPS4). dcNPs are based on electrostatic interactions between a negative DTX-loaded nanoscaffold of poly(lactide-co-glycolide), a polycationic shell of polyethyleneimine entangling negatively-charged TPPS4 and finally decorated with hyaluronan (HA) to promote internalization through CD44 receptor-mediated endocytosis. DTX/TPPS4-dcNPs, prepared through layer-by-layer deposition, showed a hydrodynamic diameter of around 180 nm, negative zeta potential and efficient loading of both DTX and TPPS4. DTX/TPPS4-dcNPs were freeze-dried with trehalose giving a powder that could be easily dispersed in different media. Excellent stability of dcNPs in specific salt- and protein-containing media was found. Spectroscopic behavior of DTX/TPPS4-dcNPs demonstrated a face-to-face arrangement of the TPPS4 units in non-photoresponsive H-type aggregates accounting for an extensive aggregation of the porphyrin embedded in the shell. Experiments in MDA-MB-231 cells overexpressing the CD44 receptor demonstrated a 9.4-fold increase in the intracellular level of TPPS4 delivered from dcNPs as compared to free TPPS4. Light-induced death increased tremendously in cells that had been treated with a combination of TPPS4 and DTX delivered through dcNPs as compared with free drugs, presumably due to efficient uptake and co-localization inside the cells. In perspective, the strategy proposed here to target synergistic drug combinations through HA-decorated nanoparticles seems very attractive to improve the specificity and efficacy of cancer treatment.In the attempt to develop novel concepts in designing targeted nanoparticles for combination therapy of cancer, we propose here CD44-targeted hyaluronan-decorated double

  6. Biotin decorated PLGA nanoparticles containing SN-38 designed for cancer therapy.

    PubMed

    Mehdizadeh, Mozhdeh; Rouhani, Hasti; Sepehri, Nima; Varshochian, Reyhaneh; Ghahremani, Mohammad Hossein; Amini, Mohsen; Gharghabi, Mehdi; Ostad, Seyed Nasser; Atyabi, Fatemeh; Baharian, Azin; Dinarvand, Rassoul

    2017-05-01

    Active targeted chemotherapy is expected to provide more specific delivery of cytotoxic drugs to the tumor cells and hence reducing the side effects on healthy tissues. Due to the over expression of biotin receptors on cancerous cells as a result of further requirement for rapid proliferations, biotin can be a good candidate as a targeting agent. In this study, biotin decorated PLGA nanoparticles (NPs) containing SN-38 were prepared and in vitro studies were evaluated for their improved anti-cancer properties. In conclusion, biotin targeted PLGA NPs containing SN-38 showed preferential anticancer properties against tumor cells with biotin receptor over expression.

  7. Highly Sensitive Ethanol Sensor Based on Au-Decorated SnO2 Nanoparticles Synthesized Through Precipitation and Microwave Irradiation

    NASA Astrophysics Data System (ADS)

    Li, Yan; Zhao, Fang-Xian; Lian, Xiao-Xue; Zou, Yun-Ling; Wang, Qiong; Zhou, Qing-Jun

    2016-06-01

    Gold (Au)-decorated SnO2 nanoparticles (NPs) were synthesized through a precipitation and microwave irradiation process. The as-prepared products were characterized by x-ray diffraction and scanning electron microscopy. The results indicated that the as-prepared products consisted of nanometer-scale tetragonal crystalline SnO2 and face-centered cubic gold metal NPs. The gas sensing measurements showed that the sensor based on Au-decorated SnO2 NPs exhibited an extremely high response (239.5) toward 500-ppm ethanol at a relatively low working temperature (220°C). In addition, the response and recovery times of this sensor to ethanol were 1 s and 31 s, respectively. The excellent gas sensing performance of the synthesized NPs in terms of high response, fast response-recovery, superior selectivity, and good stability was attributed to the small nanometer size of the particles, Schottky barrier, and Au NP catalysis. Finally, we demonstrated that our Au-decorated SnO2 NPs could be a potential candidate for use in highly sensitive and selective gas sensors for ethanol.

  8. NPS Solar Cell Array Tester Cubesat Flight Testing and Integration

    DTIC Science & Technology

    2014-09-01

    AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE NPS SOLAR CELL ARRAY TESTER CUBESAT FLIGHT TESTING AND INTEGRATION 5. FUNDING NUMBERS 6...DISTRIBUTION CODE A 13. ABSTRACT (maximum 200 words) The Naval Postgraduate School Solar Cell Array Tester (NPS-SCAT) is the first CubeSat for the...Naval Postgraduate School (NPS). The NPS-SCAT mission was designed to measure solar cell performance degradation in low earth orbit . NPS-SCAT serves as

  9. Gold nanoparticles-decorated silicon nanowires as highly efficient near-infrared hyperthermia agents for cancer cells destruction.

    PubMed

    Su, Yuanyuan; Wei, Xinpan; Peng, Fei; Zhong, Yiling; Lu, Yimei; Su, Shao; Xu, Tingting; Lee, Shuit-Tong; He, Yao

    2012-04-11

    Near-infrared (NIR) hyperthermia agents are of current interest because they hold great promise as highly efficacious tools for cancer photothermal therapy. Although various agents have been reported, a practical NIR hyperthermia agent is yet unavailable. Here, we present the first demonstration that silicon nanomaterials-based NIR hyperthermia agent, that is, gold nanoparticles-decorated silicon nanowires (AuNPs@SiNWs), is capable of high-efficiency destruction of cancer cells. AuNPs@SiNWs are found to possess strong optical absorbance in the NIR spectral window, producing sufficient heat under NIR irradiation. AuNPs@SiNWs are explored as novel NIR hyperthermia agents for photothermal ablation of tumor cells. In particular, three different cancer cells treated with AuNPs@SiNWs were completely destructed within 3 min of NIR irradiation, demonstrating the exciting potential of AuNPs@SiNWs for NIR hyperthermia agents.

  10. NPS-SCAT: Electrical Power System

    DTIC Science & Technology

    2009-09-01

    DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE NPS-SCAT; Electrical Power System 6. AUTHOR( S ) Lawrence Tyrone Dorn Jr. 5. FUNDING...NUMBERS 7. PERFORMING ORGANIZATION NAME( S ) AND ADDRESS(ES) Naval Postgraduate School Monterey, CA 93943-5000 8. PERFORMING ORGANIZATION REPORT NUMBER...9. SPONSORING /MONITORING AGENCY NAME( S ) AND ADDRESS(ES) N/A 10. SPONSORING/MONITORING AGENCY REPORT NUMBER 11. SUPPLEMENTARY NOTES The

  11. Biotin-decorated silica coated PbS nanocrystals emitting in the second biological near infrared window for bioimaging

    NASA Astrophysics Data System (ADS)

    Corricelli, M.; Depalo, N.; di Carlo, E.; Fanizza, E.; Laquintana, V.; Denora, N.; Agostiano, A.; Striccoli, M.; Curri, M. L.

    2014-06-01

    Nanoparticles (NPs) emitting in the second biological near infrared (NIR) window of the electromagnetic spectrum have been successfully synthesized by growing a silica shell on the hydrophobic surface of OLEA/TOP PbS nanocrystals (NCs), by means of a reverse microemulsion approach, and subsequently decorated with biotin molecules. The fabrication of very uniform and monodisperse NPs, formed of SiO2 shell coated single core PbS NCs, has been demonstrated by means of a set of complementary optical and structural techniques (Vis-NIR absorption and photoluminescence spectroscopy, transmission electron microscopy) that have highlighted how experimental parameters, such as PbS NC and silica precursor concentration, are crucial to direct the morphology and optical properties of silica coated PbS NPs. Subsequently, the silica surface of the core-shell NPs has been grafted with amino groups, in order to achieve covalent binding of biotin to NIR emitting silica coated NPs. Finally the successful reaction with a green-fluorescent labelled streptavidin has verified the molecular recognition response of the biotin molecules decorating the PbS@SiO2 NP surface. Dynamic light scattering (DLS) and ζ-potential techniques have been used to monitor the hydrodynamic diameter and colloidal stability of both PbS@SiO2 and biotin decorated NPs, showing their high colloidal stability in physiological media, as needed for biomedical applications. Remarkably the obtained biotinylated PbS@SiO2 NPs have been found to retain emission properties in the `second optical window' of the NIR region of the electromagnetic spectrum, thus representing attractive receptor-targeted NIR fluorescent probes for in vivo tumour imaging.Nanoparticles (NPs) emitting in the second biological near infrared (NIR) window of the electromagnetic spectrum have been successfully synthesized by growing a silica shell on the hydrophobic surface of OLEA/TOP PbS nanocrystals (NCs), by means of a reverse microemulsion

  12. NPS Gas Gun for Planar Impact Studies

    NASA Astrophysics Data System (ADS)

    Cheong Ho, Chien; Hixson, Robert

    2009-11-01

    The Naval Postgraduate School (NPS) commissioned a Gas Gun for shock wave studies on 9^th October 2009, by performing the first experiment. The Gas Gun is the key element of NPS Shock Wave Research Program within the Physics Department, where well-characterized planar impacts are essential for obtaining high quality data, to characterize a solid material. This first experiment was very successful, and returned key data on the quality of the impact conditions created. The Gas Gun is designed by SANDIA NATIONAL LABORATORIES, and the NPS spent twelve months fabricating the components of the Gas Gun and six months assembling the Gas Gun. Three inch projectile are launched at velocities up to 0.5 km/s, creating high pressure and temperature states that can be used to characterize the fundamental response of relevant materials to dynamic loading. The projectile is launched from a `wrap around' gas breech where helium gas is pressurized to relatively low pressure. This gas is used to accelerate the projectile down a 3m barrel. Upon impact, the speed of the projectile and the flatness of the impact is measured, via a stepped circular pin array circuit. The next stage of development for the Gas Gun is to integrate a Velocity Interferometer System for Any Reflector (VISAR). The VISAR sees all the waves that flow through the target plate as a result of the impact. This is a key diagnostic for determining material properties under dynamic loading conditions.

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

    PubMed

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

    2017-06-01

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

  14. Ag@AgHPW as a plasmonic catalyst for visible-light photocatalytic degradation of environmentally harmful organic pollutants

    SciTech Connect

    Zhou, Wenhui; Cao, Minhua Li, Na; Su, Shuangyue; Zhao, Xinyu; Wang, Jiangqiang; Li, Xianghua; Hu, Changwen

    2013-06-01

    Graphical abstract: Ag@Ag{sub x}H{sub 3−x}PW12O40 (Ag@AgHPW) nanoparticles (NPs), a new visible-light driven plasmonic photocatalyst, are prepared by a green photoreduction strategy without the addition of any surfactant, which show a high activity and stability for the degradation of methyl blue (MB) under visible light irradiation. - Highlights: • A new visible-light driven photocatalyst Ag@Ag{sub x}H{sub 3−x}PW{sub 12}O{sub 40} was designed. • The photocatalyst shows a high activity for the degradation of methyl blue. • The high activity can be ascribed to the synergy of photoexcited AgHPW and Ag. - Abstract: Ag@Ag{sub x}H{sub 3−x}PW{sub 12}O{sub 40} (Ag@AgHPW) nanoparticles (NPs), a new visible-light driven plasmonic photocatalyst, are prepared by a green photoreduction strategy without the addition of any surfactant. They show strong absorption in the visible region because of the localized surface plasmon resonance (LSPR) of Ag NPs. This plasmonic photocatalyst shows a high activity and stability for the degradation of methyl blue (MB) under visible light irradiation, which could be attributed to the highly synergy of photoexcited Ag{sub x}H{sub 3−x}PW{sub 12}O{sub 40} (AgHPW) and plasmon-excited Ag NPs and the confinement effects at interfaces between polyoxometalates (POMs) and silver. POM anions have redox ability and high photocatalytic activity, whereas Ag NPs could effectively accelerate the separation of electrons and holes, both of which contribute to their high activity.

  15. ZnO decorated germanium nanoparticles as anode materials in Li-ion batteries.

    PubMed

    Kim, Tae-Hee; Park, Song Yi; Lee, Tack Ho; Jeong, Jaeki; Kim, Dong Suk; Swihart, Mark T; Song, Hyun-Kon; Kim, Jin Young; Kim, Seongbeom

    2017-03-03

    Germanium exhibits high charge capacity and high lithium diffusivity, both are the key requirements for electrode materials in high performance lithium ion batteries (LIBs). However, high volume expansion and segregation from the electrode during charge-discharge cycling have limited use of germanium in LIBs. Here, we demonstrate that ZnO decorated Ge nanoparticles (Ge@ZnO NPs) can overcome these limitations of Ge as an LIB anode material. We produced Ge NPs at high rates by laser pyrolysis of GeH4, then coated them with solution phase synthesized ZnO NPs. Half-cell tests revealed dramatically enhanced cycling stability and higher rate capability of Ge@ZnO NPs compared to Ge NPs. Enhancements arise from the core-shell structure of Ge@ZnO NPs as well as production of metallic Zn from the ZnO layer. These findings not only demonstrate a new surface treatment for Ge NPs, but also provide a new opportunity for development of high-rate LIBs.

  16. ZnO decorated germanium nanoparticles as anode materials in Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Hee; Park, Song Yi; Lee, Tack Ho; Jeong, Jaeki; Kim, Dong Suk; Swihart, Mark T.; Song, Hyun-Kon; Kim, Jin Young; Kim, Seongbeom

    2017-03-01

    Germanium exhibits high charge capacity and high lithium diffusivity, both are the key requirements for electrode materials in high performance lithium ion batteries (LIBs). However, high volume expansion and segregation from the electrode during charge–discharge cycling have limited use of germanium in LIBs. Here, we demonstrate that ZnO decorated Ge nanoparticles (Ge@ZnO NPs) can overcome these limitations of Ge as an LIB anode material. We produced Ge NPs at high rates by laser pyrolysis of GeH4, then coated them with solution phase synthesized ZnO NPs. Half-cell tests revealed dramatically enhanced cycling stability and higher rate capability of Ge@ZnO NPs compared to Ge NPs. Enhancements arise from the core–shell structure of Ge@ZnO NPs as well as production of metallic Zn from the ZnO layer. These findings not only demonstrate a new surface treatment for Ge NPs, but also provide a new opportunity for development of high-rate LIBs.

  17. 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.

  18. Selective Decoration of Au Nanoparticles on Monolayer MoS2 Single Crystals

    PubMed Central

    Shi, Yumeng; Huang, Jing-Kai; Jin, Limin; Hsu, Yu-Te; Yu, Siu Fung; Li, Lain-Jong; Yang, Hui Ying

    2013-01-01

    We report a controllable wet method for effective decoration of 2-dimensional (2D) molybdenum disulfide (MoS2) layers with Au nanoparticles (NPs). Au NPs can be selectively formed on the edge sites or defective sites of MoS2 layers. The Au-MoS2 nano-composites are formed by non-covalent bond. The size distribution, morphology and density of the metal nanoparticles can be tuned by changing the defect density in MoS2 layers. Field effect transistors were directly fabricated by placing ion gel gate dielectrics on Au-decorated MoS2 layers without the need to transfer these MoS2 layers to SiO2/Si substrates for bottom gate devices. The ion gel method allows probing the intrinsic electrical properties of the as-grown and Au-decorated MoS2 layers. This study shows that Au NPs impose remarkable p-doping effects to the MoS2 transistors without degrading their electrical characteristics. PMID:23670611

  19. 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.

  20. 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.

  1. Individual and Co Transport Study of Titanium Dioxide NPs and Zinc Oxide NPs in Porous Media

    PubMed Central

    Kumari, Jyoti; Mathur, Ankita; Rajeshwari, A.; Venkatesan, Arthi; S, Satyavati; Pulimi, Mrudula; Chandrasekaran, Natarajan; Nagarajan, R.; Mukherjee, Amitava

    2015-01-01

    The impact of pH and ionic strength on the mobility (individual and co-transport) and deposition kinetics of TiO2 and ZnO NPs in porous media was systematically investigated in this study. Packed column experiments were performed over a series of environmentally relevant ionic strengths with both NaCl (0.1−10 mM) and CaCl2 (0.01–0.1mM) solutions and at pH 5, 7, and 9. The transport of TiO2 NPs at pH 5 was not significantly affected by ZnO NPs in solution. At pH 7, a decrease in TiO2 NP transport was noted with co-existence of ZnO NPs, while at pH 9 an increase in the transport was observed. At pH 5 and 7, the transport of ZnO NPs was decreased when TiO2 NPs was present in the solution, and at pH 9, an increase was noted. The breakthrough curves (BTC) were noted to be sensitive to the solution chemistries; the decrease in the breakthrough plateau with increasing ionic strength was observed under all examined pH (5, 7, and 9). The retention profiles were the inverse of the plateaus of BTCs, as expected from mass balance considerations. Overall, the results from this study suggest that solution chemistries (ionic strength and pH) are likely the key factors that govern the individual and co-transport behavior of TiO2 and ZnO NPs in sand. PMID:26252479

  2. Tunable superconductivity in decorated graphene

    NASA Astrophysics Data System (ADS)

    Han, Zheng; Allain, Adrien; Marty, Laetitia; Bendiab, Nedjma; Toulemonde, Pierre; Strobel, Pierre; Coraux, Johann; Bouchiat, Vincent

    2013-03-01

    Graphene offers an exposed bidimensional gas of high mobility charge carriers with gate tunable density. Its chemical inertness offers an outstanding platform to explore exotic 2D superconductivity. Superconductivity can be induced in graphene by means of proximity effect (by depositing a set of superconducting metal clusters such as lead or tin nanoparticles). The influence of decoration material, density or particles and disorder of graphene will be discussed. In the case of disordered graphene, Tin decoration leads to a gate-tunable superconducting-to-insulator quantum phase transition. Superconductivity in graphene is also expected to occur under strong charge doping (induced either by gating or under chemical decoration, in analogy with graphite intercalated compounds). I will also show preliminary results showing the influence of Calcium intercalation of few layer graphene and progress toward the demonstration of intrinsic superconductivity in such systems. Work supported by EU GRANT FP7-NMP GRENADA.

  3. 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.

  4. 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.

  5. Au nanostructure-decorated TiO2 nanowires exhibiting photoactivity across entire UV-visible region for photoelectrochemical water splitting.

    PubMed

    Pu, Ying-Chih; Wang, Gongming; Chang, Kao-Der; Ling, Yichuan; Lin, Yin-Kai; Fitzmorris, Bob C; Liu, Chia-Ming; Lu, Xihong; Tong, Yexiang; Zhang, Jin Z; Hsu, Yung-Jung; Li, Yat

    2013-08-14

    Here we demonstrate that the photoactivity of Au-decorated TiO2 electrodes for photoelectrochemical water oxidation can be effectively enhanced in the entire UV-visible region from 300 to 800 nm by manipulating the shape of the decorated Au nanostructures. The samples were prepared by carefully depositing Au nanoparticles (NPs), Au nanorods (NRs), and a mixture of Au NPs and NRs on the surface of TiO2 nanowire arrays. As compared with bare TiO2, Au NP-decorated TiO2 nanowire electrodes exhibited significantly enhanced photoactivity in both the UV and visible regions. For Au NR-decorated TiO2 electrodes, the photoactivity enhancement was, however, observed in the visible region only, with the largest photocurrent generation achieved at 710 nm. Significantly, TiO2 nanowires deposited with a mixture of Au NPs and NRs showed enhanced photoactivity in the entire UV-visible region. Monochromatic incident photon-to-electron conversion efficiency measurements indicated that excitation of surface plasmon resonance of Au is responsible for the enhanced photoactivity of Au nanostructure-decorated TiO2 nanowires. Photovoltage experiment showed that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was attributable to the effective surface passivation of Au NPs. Furthermore, 3D finite-difference time domain simulation was performed to investigate the electrical field amplification at the interface between Au nanostructures and TiO2 upon SPR excitation. The results suggested that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was partially due to the increased optical absorption of TiO2 associated with SPR electrical field amplification. The current study could provide a new paradigm for designing plasmonic metal/semiconductor composite systems to effectively harvest the entire UV-visible light for solar fuel production.

  6. 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.

  7. Enhanced antibacterial activity of silver/polyrhodanine-composite-decorated silica nanoparticles.

    PubMed

    Song, Jooyoung; Kim, Hyunyoung; Jang, Yoonsun; Jang, Jyongsik

    2013-11-27

    This work describes the synthesis of silver/polyrhodanine-composite-decorated silica nanoparticles and their antibacterial activity. Polymerization of polyrhodanine proceeded preferentially on the surface of the silica nanoparticles where Ag(+) ions were located. In addition, the embedded Ag(+) ions were reduced to form metallic Ag nanoparticles; consequently, silver/polyrhodanine-composite nanoparticles (approximately 7 nm in diameter) were formed on the surface of the silica nanoparticles. The resulting nanostructure was investigated using electron microscopy, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy. The silver/polyrhodanine-nanocomposite-decorated silica nanoparticles exhibited excellent antimicrobial activity toward gram-negative Escherichia coli and gram-positive Staphylococcus aureus because of the antibacterial effects of the silver nanoparticles and the polyrhodanine. The silver/polyrhodanine-composite nanoparticles may therefore have potential for use as a long-term antibacterial agent.

  8. Methods for preparing polymer-decorated single exchange-biased magnetic nanoparticles for application in flexible polymer-based films

    PubMed Central

    2017-01-01

    Background: Magnetic nanoparticles (NPs) must not only be well-defined in composition, shape and size to exhibit the desired properties (e.g., exchange-bias for thermal stability of the magnetization) but also judiciously functionalized to ensure their stability in air and their compatibility with a polymer matrix, in order to avoid aggregation which may seriously affect their physical properties. Dipolar interactions between NPs too close to each other favour a collective magnetic glass state with lower magnetization and coercivity because of inhomogeneous and frustrated macrospin cluster freezing. Consequently, tailoring chemically (through surface functionalization) and magnetically stable NPs for technological applications is of primary importance. Results: In this work, well-characterized exchange-biased perfectly epitaxial CoxFe3− xO4@CoO core@shell NPs, which were isotropic in shape and of about 10 nm in diameter, were decorated by two different polymers, poly(methyl methacrylate) (PMMA) or polystyrene (PS), using radical-controlled polymerization under various processing conditions. We compared the influence of the synthesis parameters on the structural and microstructural properties of the resulting hybrid systems, with special emphasis on significantly reducing their mutual magnetic attraction. For this, we followed two routes: the first one consists of the direct grafting of bromopropionyl ester groups at the surface of the NPs, which were previously recovered and redispersed in a suitable solvent. The second route deals with an “all in solution” process, based on the decoration of NPs by oleic acid followed by ligand exchange with the desired bromopropionyl ester groups. We then built various assemblies of NPs directly on a substrate or suspended in PMMA. Conclusion: The alternative two-step strategy leads to better dispersed polymer-decorated magnetic particles, and the resulting nanohybrids can be considered as valuable building blocks for

  9. 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.

  10. 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.

  11. Gold Decorated Graphene for Rapid Dye Reduction and Efficient Electro Catalytic Oxidation of Ethanol

    NASA Astrophysics Data System (ADS)

    Siddhardha, R. S.; Kumar v, Lakshman; Kaniyoor, A.; Podila, R.; Kumar, V. S.; Venkataramaniah, K.; Ramaprabhu, S.; Rao, A.; Ramamurthy, S. S.; Clemson University Team; Sri Sathya Sai Institute of Higher Learning Team; IITMadras Team

    2013-03-01

    A well known disadvantage in fabrication of metal-graphene composite is the use of surfactants that strongly adsorb on the surface and reduce the performance of the catalyst. Here, we demonstrate a novel one pot synthesis of gold nanoparticles (AuNPs) by laser ablation of gold strip and simultaneous decoration of these on functionalized graphene derivatives. Not only the impregnation of AuNPs was linker free, but also the synthesis by itself was surfactant free. This resulted in in-situ decoration of pristine AuNPs on functionalized graphene derivatives. These materials were well characterized and tested for catalytic applications pertaining to dye reduction and electrooxidation. The catalytic reduction rates are 1.4 x 102 and 9.4x102 times faster for Rhodamine B and Methylene Blue dyes respectively, compared to earlier reports. The enhanced rate involves synergistic interplay of electronic relay between AuNPs and the dye, also charge transfer between the graphene system and dye. In addition, the onset potential for ethanol oxidation was found to be more negative ~ 100 mV, an indication of its promising application in direct ethanol fuel cells.

  12. Terahertz conductivity engineering in surface decorated carbon nanotube films by gold nanoparticles.

    PubMed

    Polley, Debanjan; Patra, Animesh; Barman, Anjan; Mitra, Rajib Kumar

    2017-02-01

    We report the controllable conductivity of single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes with their surface walls decorated by gold nanoparticles (Au NPs) with varying concentration in terahertz (THz) frequency range. Colloidal Au NPs of nominal diameter ∼15  nm are synthesized by the reduction of gold chloride solution using tri-sodium citrate. A simple chemical route is followed to attach Au NPs on the surfaces of both types of carbon nanotubes (CNTs). The attachment of Au NPs on the sidewalls of CNTs is confirmed by UV-visible spectroscopy and scanning electron microscope images. THz spectroscopic measurements are carried out at room temperature in transmission geometry in the frequency range of 0.3-2.0 THz. It is found that the THz conductivity of the surface decorated SWNT composites can either be increased or decreased by ±15% than that of the as-prepared SWNT composites by carefully choosing the Au NP concentration. The conductivity variation is qualitatively explained in terms of carrier trapping potential for low Au NP density, and alternative carrier conduction pathways at higher Au NP density and analyzed with the help of a modified universal dielectric relaxation model.

  13. Metal Decoration Effects on the Gas-Sensing Properties of 2D Hybrid-Structures on Flexible Substrates

    PubMed Central

    Cho, Byungjin; Yoon, Jongwon; Lim, Sung Kwan; Kim, Ah Ra; Choi, Sun-Young; Kim, Dong-Ho; Lee, Kyu Hwan; Lee, Byoung Hun; Ko, Heung Cho; Hahm, Myung Gwan

    2015-01-01

    We have investigated the effects of metal decoration on the gas-sensing properties of a device with two-dimensional (2D) molybdenum disulfide (MoS2) flake channels and graphene electrodes. The 2D hybrid-structure device sensitively detected NO2 gas molecules (>1.2 ppm) as well as NH3 (>10 ppm). Metal nanoparticles (NPs) could tune the electronic properties of the 2D graphene/MoS2 device, increasing sensitivity to a specific gas molecule. For instance, palladium NPs accumulate hole carriers of graphene/MoS2, electronically sensitizing NH3 gas molecules. Contrarily, aluminum NPs deplete hole carriers, enhancing NO2 sensitivity. The synergistic combination of metal NPs and 2D hybrid layers could be also applied to a flexible gas sensor. There was no serious degradation in the sensing performance of metal-decorated MoS2 flexible devices before/after 5000 bending cycles. Thus, highly sensitive and endurable gas sensor could be achieved through the metal-decorated 2D hybrid-structure, offering a useful route to wearable electronic sensing platforms. PMID:26404279

  14. 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.

  15. 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.

  16. Stimulus Response of Au-NPs@GMP-Tb Core-Shell Nanoparticles: Toward Colorimetric and Fluorescent Dual-Mode Sensing of Alkaline Phosphatase Activity in Algal Blooms of a Freshwater Lake.

    PubMed

    Zhang, Xiaolei; Deng, Jingjing; Xue, Yumeng; Shi, Guoyue; Zhou, Tianshu

    2016-01-19

    In this study, we demonstrate a colorimetric and fluorescent dual-mode method for alkaline phosphatase activity (APA) sensing in freshwater lake with stimuli-responsive gold nanoparticles@terbium-guanosine monophosphate (Au-NPs@GMP-Tb) core-shell nanoparticles. Initially, the core-shell nanoparticles were fabricated based on Au-NPs decorated with a fluorescent GMP-Tb shell. Upon being excited at 290 nm, the as-formed Au-NPs@GMP-Tb core-shell nanoparticles emit green fluorescence, and the decorated GMP-Tb shell causes the aggregation of Au-NPs. However, the addition of ALP destroys GMP-Tb shell, resulting in the release of Au-NPs from the shell into the solvent. As a consequence, the aggregated Au-NPs solubilizes with the changes in the UV-vis spectrum of the dispersion, and in the meantime, the fluorescence of GMP-Tb shell turns off, which constitutes a new mechanism for colorimetric and fluorescent dual-mode sensing of APA. With the method developed here, we could monitor the dynamic change of APA during an algal bloom of a freshwater lake, both by the naked eye and further confirmed by fluorometric determination. This study not only offers a new method for on-site visible detection of APA but also provides a strategy for dual-mode sensing mechanisms by the rational design of the excellent optical properties of Au-NPs and the adaptive inclusion properties of the luminescent infinite coordination polymers.

  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. The evolutionary ecology of decorating behaviour

    PubMed Central

    Ruxton, Graeme D.; Stevens, Martin

    2015-01-01

    Many animals decorate themselves through the accumulation of environmental material on their exterior. Decoration has been studied across a range of different taxa, but there are substantial limits to current understanding. Decoration in non-humans appears to function predominantly in defence against predators and parasites, although an adaptive function is often assumed rather than comprehensively demonstrated. It seems predominantly an aquatic phenomenon—presumably because buoyancy helps reduce energetic costs associated with carrying the decorative material. In terrestrial examples, decorating is relatively common in the larval stages of insects. Insects are small and thus able to generate the power to carry a greater mass of material relative to their own body weight. In adult forms, the need to be lightweight for flight probably rules out decoration. We emphasize that both benefits and costs to decoration are rarely quantified, and that costs should include those associated with collecting as well as carrying the material. PMID:26041868

  19. Development of biofuel cells based on gold nanoparticle decorated multi-walled carbon nanotubes.

    PubMed

    Naruse, Junichi; Hoa, Le Quynh; Sugano, Yasuhito; Ikeuchi, Tomohiko; Yoshikawa, Hiroyuki; Saito, Masato; Tamiya, Eiichi

    2011-12-15

    This study focused on developing the synthesis of Au nanoparticle-decorated functionalized multi-walled carbon nanotubes (Au-NPs/f-MWCNTs) for monosaccharide (bio-fuel) oxidation reactions and practical application in air-biofuel cells. We developed a scalable and straightforward method to synthesize Au-NPs/f-MWCNTs which allow us to control the loading and size of the Au-NPs. The Au-NPs/f-MWCNTs exhibited better catalytic activities and stability than the Au sheet and subsequently resulted in a threefold increase in the power density of the air-glucose fuel cell with an exceptionally high open circuit voltage (~1.3 V). The catalytic efficiency was confirmed by high performance liquid chromatography with the superior of the Au-NPs/f-MWCNTs over a bare gold electrode. In addition, the application of this advanced catalyst to other monosaccharide oxidation reactions figured out that the configuration of -OH groups at C(2) and C(3) of the reactants plays an important role in the initial adsorption process, and thus, affects the required activation energy for further oxidation. The different monosaccharides lead to significantly different fuel cell performances in terms of power density, which coherently corresponds to the difference in the configuration of C(2) and C(3). Because two small air-glucose fuel cells using Au-NPs/f-MWCNTs can run a LED lamp, further applications of other monosaccharides as fuel in biofuel cells for equivalent required power devices may be possible.

  20. Water-dispersible silver nanoparticles-decorated carbon nanomaterials: synthesis and enhanced antibacterial activity

    NASA Astrophysics Data System (ADS)

    Dinh, Ngo Xuan; Chi, Do Thi; Lan, Nguyen Thi; Lan, Hoang; Van Tuan, Hoang; Van Quy, Nguyen; Phan, Vu Ngoc; Huy, Tran Quang; Le, Anh-Tuan

    2015-04-01

    In recent years, a growing number of outbreak of infectious diseases have emerged all over the world. The outbreak of re-emerging and emerging infectious diseases is a considerable burden on global economies and public health. Nano-antimicrobials have been studied as an effective solution for the prevention of infectious diseases. In this work, we demonstrated a modified photochemical approach for the preparation of carbon nanotubes-silver nanoparticles (CNTs-Ag) and graphene oxide-silver nanoparticles (GO-Ag) nanocomposites, which can be stably dispersible in aqueous solution. The formation of silver nanoparticles (Ag-NPs) on the functionalized CNTs and GO nanosheets was analyzed by X-ray diffraction, transmission electron microscopy, Raman spectroscopy and UV-Vis measurements. These analyses indicated that the average particle sizes of Ag-NPs deposited on GO/CNTs nanostructures were ~6-7 nm with nearly uniform size distribution. Moreover, these nanocomposites were found to exhibit enhanced antibacterial activity against two strains of infectious bacteria including Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria as compared to bare Ag-NPs. Our obtained studies showed a high potential of GO-Ag and CNTs-Ag nanocomposites as effective and long-term disinfection solution to eliminate infectious bacterial pathogens.

  1. 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

  2. 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.

  3. Green synthesized gold nanoparticles decorated graphene oxide for sensitive determination of chloramphenicol in milk, powdered milk, honey and eye drops.

    PubMed

    Karthik, R; Govindasamy, Mani; Chen, Shen-Ming; Mani, Veerappan; Lou, Bih-Show; Devasenathipathy, Rajkumar; Hou, Yu-Shen; Elangovan, A

    2016-08-01

    A simple and rapid green synthesis using Bischofia javanica Blume leaves as reducing agent was developed for the preparation of gold nanoparticles (AuNPs). AuNPs decorated graphene oxide (AuNPs/GO) was prepared and employed for the sensitive amperometric determination of chloramphenicol. The green biosynthesis requires less than 40s to reduce gold salts to AuNPs. The formations of AuNPs and AuNPs/GO were evaluated by scanning electron and atomic force microscopies, UV-Visible and energy dispersive X-ray spectroscopies, X-ray diffraction studies, and electrochemical methods. AuNPs/GO composite film modified electrode was fabricated and shown excellent electrocatalytic ability towards chloramphenicol. Under optimal conditions, the amperometric sensing platform has delivered wide linear range of 1.5-2.95μM, low detection limit of 0.25μM and high sensitivity of 3.81μAμM(-1)cm(-2). The developed sensor exhibited good repeatability and reproducibility, anti-interference ability and long-term storage stability. Practical feasibility of the sensor has been demonstrated in food samples (milk, powdered milk and honey) and pharmaceutical sample (eye drops). The green synthesized AuNPs/GO composite has great potential for analysis of food samples in food safety measures.

  4. 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).

  5. 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.

  6. 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.

  7. Understanding the sensor response of metal-decorated carbon nanotubes.

    PubMed

    Kauffman, Douglas R; Sorescu, Dan C; Schofield, Daniel P; Allen, Brett L; Jordan, Kenneth D; Star, Alexander

    2010-03-10

    We have explored the room temperature response of metal nanoparticle decorated single-walled carbon nanotubes (NP-SWNTs) using a combination of electrical transport, optical spectroscopy, and electronic structure calculations. We have found that upon the electrochemical growth of Au NPs on SWNTs, there is a transfer of electron density from the SWNT to the NP species, and that adsorption of CO molecules on the NP surface is accompanied by transfer of electronic density back into the SWNT. Moreover, the electronic structure calculations indicate dramatic variations in the charge density at the NP-SWNT interface, which supports our previous observation that interfacial potential barriers dominate the electrical behavior of NP-SWNT systems.

  8. An Au/AgBr-Ag heterostructure plasmonic photocatalyst with enhanced catalytic activity under visible light.

    PubMed

    Purbia, Rahul; Paria, Santanu

    2017-01-17

    This study reports an easy synthesis protocol of a novel bimetallic silver halide (Au/AgBr-Ag) plasmonic heterostructure as a visible light induced photocatalyst. In this process, first CTAB capped Au NPs were coated with AgBr, and then Ag nanoparticles were formed on the surface of AgBr by photoreduction, while exposing to daylight at room temperature. The presence of Au and Ag improves the visible absorption ability of NPs and avoids charge recombination of the semiconductor AgBr during photoexcitation, which in turn enhances 16 and 8.9 fold the photocatalytic efficiency of Rhodamine B dye degradation under visible light irradiation compared to that of pure AgBr and AgBr/Ag, respectively. The recycling tests of the photocatalyst show only ∼8.7% decrease in efficiency after the 5(th) cycle of reuse without changing the morphology. During the photocatalytic process, active superoxide radicals (O2˙(-)) play a major role, proved through scavenger trapping and photoluminescence experiments. The presence of two plasmonic metals (Au and Ag) in the heterostructure helps to improve visible light absorption as well as avoid charge recombination of the semiconductor AgBr to act as a better photocatalyst. Since this heteronanostructure can be easily synthesized by a one-step method, this study could provide a new approach for the development of efficient bimetallic/semiconductor halide plasmonic photocatalysts with enhanced visible absorption and better charge separation.

  9. Synthesis of Metal Nanoparticle-decorated Carbon Nanotubes under Ambient Conditions

    NASA Technical Reports Server (NTRS)

    Lin, Yi; Watson, Kent A.; Ghose, Sayata; Smith, Joseph G.; Connell, John W.

    2008-01-01

    This viewgraph presentation reviews the production of Metal Nanoparticle-decorated carbon Nanotubes. Multi-walled carbon nanotubes (MWCNTs) were efficiently decorated with metal nanoparticles (e.g. Ag, Pt, etc.) using the corresponding metal acetate in a simple mixing process without the need of chemical reagents or further processing. The conversion of acetate compounds to the corresponding metal reached over 90%, forming nanoparticles with average diameters less than 10 nm under certain conditions. The process was readily scalable allowing for the convenient preparation of multi-gram quantities of metal nanoparticle-decorated MWCNTs in a matter of a few minutes. These materials are under evaluation for a variety of electrical and catalytic applications. The preparation and characterization of these materials will be presented. The microscopic views of the processed MWCNTs are shown

  10. 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.

  11. Surface decorated platinum carbonyl clusters

    NASA Astrophysics Data System (ADS)

    Ciabatti, Iacopo; Femoni, Cristina; Iapalucci, Maria Carmela; Longoni, Giuliano; Zacchini, Stefano; Zarra, Salvatore

    2012-06-01

    Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2- (1), [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2- (2), [H2Pt26(CO)20(CdBr)12]8- (3) and [H4Pt26(CO)20(CdBr)12(PtBr)x]6- (4) (x = 0-2), have been obtained from the reactions between [Pt3n(CO)6n]2- (n = 2-6) and CdBr2.H2O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt26Cd12 metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters.Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2- (1), [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2- (2), [H2Pt26(CO)20(CdBr)12]8- (3) and [H4Pt26(CO)20(CdBr)12(PtBr)x]6- (4) (x = 0-2), have been obtained from the reactions between [Pt3n(CO)6n]2- (n = 2-6) and CdBr2.H2O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt26Cd12 metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters. CCDC 867747 and 867748. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30400g

  12. New insight into daylight photocatalysis of AgBr@Ag: synergistic effect between semiconductor photocatalysis and plasmonic photocatalysis.

    PubMed

    Jiang, Jing; Li, Hao; Zhang, Lizhi

    2012-05-14

    Noble metal nanoparticles (NPs) are often used as electron scavengers in conventional semiconductor photocatalysis to suppress electron-hole (e(-)-h(+) ) recombination and promote interfacial charge transfer, and thus enhance photocatalytic activity of semiconductors. In this contribution, it is demonstrated that noble metal NPs such as Ag NPs function as visible-light harvesting and electron-generating centers during the daylight photocatalysis of AgBr@Ag. Novel Ag plasmonic photocatalysis could cooperate with the conventional AgBr semiconductor photocatalysis to enhance the overall daylight activity of AgBr@Ag greatly because of an interesting synergistic effect. After a systematic investigation of the daylight photocatalysis mechanism of AgBr@Ag, the synergistic effect was attributed to surface plasmon resonance induced local electric field enhancement on Ag, which can accelerate the generation of e(-)-h(+) pairs in AgBr, so that more electrons are produced in the conduction band of AgBr under daylight irradiation. This study provides new insight into the photocatalytic mechanism of noble metal/semiconductor systems as well as the design and fabrication of novel plasmonic photocatalysts.

  13. 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.

  14. Palladium nanoparticle decorated silicon nanowire field-effect transistor with side-gates for hydrogen gas detection

    SciTech Connect

    Ahn, Jae-Hyuk; Yun, Jeonghoon; Park, Inkyu; Choi, Yang-Kyu

    2014-01-06

    A silicon nanowire field-effect transistor (SiNW FET) with local side-gates and Pd surface decoration is demonstrated for hydrogen (H{sub 2}) detection. The SiNW FETs are fabricated by top-down method and functionalized with palladium nanoparticles (PdNPs) through electron beam evaporation for H{sub 2} detection. The drain current of the PdNP-decorated device reversibly responds to H{sub 2} at different concentrations. The local side-gates allow individual addressing of each sensor and enhance the sensitivity by adjusting the working region to the subthreshold regime. A control experiment using a non-functionalized device verifies that the hydrogen-sensitivity is originated from the PdNPs functionalized on the SiNW surface.

  15. A novel flexible C2H2 gas sensor based on Ag-ZnO nanorods on PI/PTFE substrate

    NASA Astrophysics Data System (ADS)

    Uddin, A. S. M. Iftekhar; Chung, Gwiy-Sang

    2016-02-01

    In this work a novel flexible acetylene (C2H2) gas sensor based on Ag nanoparticles decorated vertical ZnO nanorods (Ag-ZnO NRs) on PI/PTFE substrate has been investigated. The grown structure was synthesized through a simple, rapid, and low-temperature hydrothermal-RF magnetron sputtering method. The successful immobilization of Ag nanoparticles (NPs) onto the surface of ZnO nanorods contributed large effective surface area and facilitated the charge transfer process. The as-fabricated sensor exhibited enhanced C2H2 sensing performances at low temperature (200°C) including a broad detection range (3 - 1000 ppm), and short recovery time (39 sec). Mechanical robustness and device flexibility were investigated at different curvature angle (0 - 90°) and several times bending-relaxing process (0 - 5 × 105 times). The sensor exhibited stable response magnitude with a negligible drift of ~ 2.1% for a maximum bending angle of 90o and a response drop of 8% after 5 × 104 bending/relaxing processes. The superior sensing features along with outstanding flexibility to extreme bending stress indicate the sensor a promising candidate for the development of practical flexible C2H2 gas sensors.

  16. 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.

  17. Influence of size, shape and core-shell interface on surface plasmon resonance in Ag and Ag@MgO nanoparticle films deposited on Si/SiO x.

    PubMed

    D'Addato, Sergio; Pinotti, Daniele; Spadaro, Maria Chiara; Paolicelli, Guido; Grillo, Vincenzo; Valeri, Sergio; Pasquali, Luca; Bergamini, Luca; Corni, Stefano

    2015-01-01

    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 SiO x (Si/SiO x ). 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.

  18. Spontaneous decoration of silicon surfaces with MoOx nanoparticles for the sunlight-assisted hydrogen evolution reaction.

    PubMed

    Truong, T-G; Mériadec, C; Fabre, B; Bergamini, J-F; de Sagazan, O; Ababou-Girard, S; Loget, G

    2017-02-02

    The immersion of oxide-free Si surfaces in MoS4(2-) aqueous solutions induces their spontaneous decoration with isolated MoOx nanoparticles (NPs). The process is versatile and was used on planar Si (100) as well as on antireflective Si (111) micro-pyramid (SimPy) arrays. The NP decoration does not affect the optical properties of the surface in the visible range and improves the performance of the hydrogen evolution reaction (HER) under simulated sunlight. The simplicity and the scalability of the technique make it highly promising for the fabrication of catalytically active photoelectrodes. More specifically, the MoOx-decorated SimPy produced H2 at a rate of 11 μmol cm(-2) min(-1) with a faradaic efficiency higher than 90% at -0.35 V vs. RHE. Furthermore, this process can be of great interest for other applications in high-performance electronic devices.

  19. 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.

  20. Novel Psychoactive Substances (NPS): a Study on Persian Language Websites

    PubMed Central

    BIGDELI, Imanollah; CORAZZA, Ornella; ASLANPOUR, Zoe; SCHIFANO, Fabrizio

    2013-01-01

    Background During the past few years, there has been an increasing recognition that Internet is playing a significant role in the synthesis, the distribution and the consumption of Novel Psychoactive Substances (NPS).The aim of this study was to assess the online availability of NPS in Persian language websites. Methods: The Google search engine was used to carry out an accurate qualitative assessment of information available on NPS in a sample of 104 websites. Results: The monitoring has led to the identification of 14 NPS including herbal, synthetic, pharmaceutical and combination drugs that have been sold online. Conclusion: The availability of online marketing of NPS in Persian language websites may constitute a public health challenge at least across three Farsi-speaking countries in the Middle East. Hence, descriptions of this phenomenon are valuable to clinicians and health professional in this region. Further international collaborative efforts may be able to tackle the growth and expansion of regular offer of NPS. PMID:23802109

  1. Jointed toxicity of TiO2 NPs and Cd to rice seedlings: NPs alleviated Cd toxicity and Cd promoted NPs uptake.

    PubMed

    Ji, Ye; Zhou, Yun; Ma, Chuanxin; Feng, Yan; Hao, Yi; Rui, Yukui; Wu, Wenhao; Gui, Xin; Le, Van Nhan; Han, Yaning; Wang, Yingcai; Xing, Baoshan; Liu, Liming; Cao, Weidong

    2017-01-01

    Previous studies have reported that nanoparticles (NPs) and heavy metals are toxic to the environment. However, the jointed toxicity is not yet well understood. This study was aimed to investigate the combined toxicity of TiO2 NPs and the heavy metal cadmium (Cd) to plants. Rice (Oryzasativa L.) was selected as the target plant. The rice seedlings were randomly separated into 12 groups and treated with CdCl2 (0, 10 and 20 mg/L) and TiO2 NPs (0, 10, 100 and 1000 mg/L). The plant height, biomass and root length indicated significant toxicity of Cd to the growth, but TiO2 NPs exhibited the potential ability to alleviate the Cd toxicity. Transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS) confirmed the existence of TiO2 NPs in plants. Elemental analysis of Ti and Cd suggested that the presences of Cd significantly decreased the Ti accumulation in the rice roots in the co-exposure treatments. Interestingly, TiO2 NPs could lower the Cd uptake and distribution in rice roots and leaves. The results of antioxidant enzyme activity, lipid peroxide as well as phytohormones varied in the different treatments. Comparing with the Cd alone treatment, the net photosynthetic rate and chlorophyll content were significantly increased in the co-exposure treatments, suggesting that TiO2 NPs could tremendously reduce the Cd toxicity.

  2. 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...

  3. Surface Plasmon Enhanced Photocatalysis of Au/Pt-decorated TiO2 Nanopillar Arrays

    PubMed Central

    Shuang, Shuang; Lv, Ruitao; Xie, Zheng; Zhang, Zhengjun

    2016-01-01

    The low quantum yields and lack of visible light utilization hinder the practical application of TiO2 in high-performance photocatalysis. Herein, we present a design of TiO2 nanopillar arrays (NPAs) decorated with both Au and Pt nanoparticles (NPs) directly synthesized through successive ion layer adsorption and reaction (SILAR) at room temperature. Au/Pt NPs with sizes of ~4 nm are well-dispersed on the TiO2 NPAs as evidenced by electron microscopic analyses. The present design of Au/Pt co-decoration on the TiO2 NPAs shows much higher visible and ultraviolet (UV) light absorption response, which leads to remarkably enhanced photocatalytic activities on both the dye degradation and photoelectrochemical (PEC) performance. Its photocatalytic reaction efficiency is 21 and 13 times higher than that of pure TiO2 sample under UV-vis and visible light, respectively. This great enhancement can be attributed to the synergy of electron-sink function of Pt and surface plasmon resonance (SPR) of Au NPs, which significantly improves charge separation of photoexcited TiO2. Our studies demonstrate that through rational design of composite nanostructures one can harvest visible light through the SPR effect to enhance the photocatalytic activities initiated by UV-light, and thus realize more effectively utilization of the whole solar spectrum for energy conversion. PMID:27215703

  4. Decoration of gold nanoparticles on thin multiwall carbon nanotubes and their use as a glucose sensor

    NASA Astrophysics Data System (ADS)

    Gangwar, Rajesh K.; Dhumale, Vinayak A.; Date, Kalyani S.; Alegaonkar, Prashant; Sharma, Rishi B.; Datar, Suwarna

    2016-03-01

    Thin multiwall carbon nanotubes (MWCNTs) have been decorated with gold nanoparticles (Au NPs) with polyaniline (PANI) as an inter-linker by a simple wet chemical method. The synthesized AuNPs:MWCNT:PANI composite was studied with UV-vis, FTIR, Raman spectroscopy, x-ray diffractometer, transmission electron microscopy (TEM) and atomic force microscopy (AFM). Conducting AFM (C-AFM) images of the composite reveal the role played by the two components in electrochemical reactions. The size of the Au NPs was found to be 13 ± 2 nm in the composite as observed from TEM. The synthesized AuNPs:MWCNT:PANI composite was further drop casted onto a glassy carbon electrode (GCE) for electrocatalytic study. The resulting composite exhibits good electrocatalytic activity towards reduction of H2O2 and O2. A glucose biosensor was developed by immobilizing glucose oxidase into AuNPs:MWCNT:PANI composite film on GCE. The fabricated sensor demonstrates good linear response to glucose (i.e. R = 0.9975) in the range of 2 to 12 mM.

  5. Palladium nanoparticles decorated on activated fullerene modified screen printed carbon electrode for enhanced electrochemical sensing of dopamine.

    PubMed

    Palanisamy, Selvakumar; Thirumalraj, Balamurugan; Chen, Shen-Ming; Ali, M Ajmal; Al-Hemaid, Fahad M A

    2015-06-15

    In the present work, an enhanced electrochemical sensor for dopamine (DA) was developed based on palladium nanoparticles decorated activated fullerene-C60 (AC60/PdNPs) composite modified screen printed carbon electrode (SPCE). The scanning electron microscopy and elemental analysis confirmed the formation of PdNPs on AC60. The fabricated AC60/PdNPs composite modified electrode exhibited an enhanced electrochemical response to DA with a lower oxidation potential than that of SPCE modified with PdNPs and C60, indicating the excellent electrooxidation behavior of the AC60/PdNPs composite modified electrode. The electrochemical studies confirmed that the electrooxidation of DA at the composite electrode is a diffusion controlled electrochemical process. The differential pulse voltammetry was employed for the determination of DA; under optimum conditions, the electrochemical oxidation signal of DA increased linearly at the AC60/PdNPs composite from 0.35 to 133.35 μM. The limit of detection was found as 0.056 μM with a sensitivity of 4.23 μA μM(-1) cm(-2). The good recovery of DA in the DA injection samples further revealed the good practicality of AC60/PdNPs modified electrode.

  6. 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.

  7. Plasmon-induced photodegradation of toxic pollutants with Ag-AgI/Al2O3 under visible-light irradiation.

    PubMed

    Hu, Chun; Peng, Tianwei; Hu, Xuexiang; Nie, Yulun; Zhou, Xuefeng; Qu, Jiuhui; He, Hong

    2010-01-20

    A plasmonic photocatalyst Ag-AgI supported on mesoporous alumina (Ag-AgI/Al(2)O(3)) was prepared by deposition-precipitation and photoreduction methods. The catalyst showed high and stable photocatalytic activity for the degradation and mineralization of toxic persistent organic pollutants, as demonstrated with 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), and trichlorophenol (TCP) under visible light or simulated solar light irradiation. On the basis of electron spin resonance, cyclic voltammetry analyses under a variety of experimental conditions, two electron transfer processes were verified from the excited Ag NPs to AgI and from 2-CP to the Ag NPs, and the main active species of O(2)(*-) and excited h(+) on Ag NPs were involved in the photoreaction system of Ag-AgI/Al(2)O(3). A plasmon-induced photocatalytic mechanism was proposed. Accordingly, the plasmon-induced electron transfer processes elucidated the photostability of Ag-AgI/Al(2)O(3). This finding indicates that the high photosensitivity of noble metal NPs due to surface plasmon resonance could be applied toward the development of new plasmonic visible-light-sensitive photocatalysts and photovoltaic fuel cells.

  8. Antibacterial activity and cytotoxicity of multi-walled carbon nanotubes decorated with silver nanoparticles

    PubMed Central

    Seo, Youngmin; Hwang, Jangsun; Kim, Jieun; Jeong, Yoon; Hwang, Mintai P; Choi, Jonghoon

    2014-01-01

    Recently, various nanoscale materials, including silver (Ag) nanoparticles, have been actively studied for their capacity to effectively prevent bacterial growth. A critical challenge is to enhance the antibacterial properties of nanomaterials while maintaining their biocompatibility. The conjugation of multiple nanomaterials with different dimensions, such as spherical nanoparticles and high-aspect-ratio nanotubes, may increase the target-specific antibacterial capacity of the consequent nanostructure while retaining an optimal biocompatibility. In this study, multi-walled carbon nanotubes (MWCNTs) were treated with a mixture of acids and decorated with Ag nanoparticles via a chemical reduction of Ag cations by ethanol solution. The synthesized Ag-MWCNT complexes were characterized by transmission electron microscopy, X-ray diffractometry, and energy-dispersive X-ray spectroscopy. The antibacterial function of Ag-MWCNTs was evaluated against Methylobacterium spp. and Sphingomonas spp. In addition, the biocompatibility of Ag-MWCNTs was evaluated using both mouse liver hepatocytes (AML 12) and human peripheral blood mononuclear cells. Finally, we determined the minimum amount of Ag-MWCNTs required for a biocompatible yet effective antibacterial treatment modality. We report that 30 μg/mL of Ag-MWCNTs confers antibacterial functionality while maintaining minimal cytotoxicity toward both human and animal cells. The results reported herein would be beneficial for researchers interested in the efficient preparation of hybrid nanostructures and in determining the minimum amount of Ag-MWCNTs necessary to effectively hinder the growth of bacteria. PMID:25336943

  9. Antibacterial activity and cytotoxicity of multi-walled carbon nanotubes decorated with silver nanoparticles.

    PubMed

    Seo, Youngmin; Hwang, Jangsun; Kim, Jieun; Jeong, Yoon; Hwang, Mintai P; Choi, Jonghoon

    2014-01-01

    Recently, various nanoscale materials, including silver (Ag) nanoparticles, have been actively studied for their capacity to effectively prevent bacterial growth. A critical challenge is to enhance the antibacterial properties of nanomaterials while maintaining their biocompatibility. The conjugation of multiple nanomaterials with different dimensions, such as spherical nanoparticles and high-aspect-ratio nanotubes, may increase the target-specific antibacterial capacity of the consequent nanostructure while retaining an optimal biocompatibility. In this study, multi-walled carbon nanotubes (MWCNTs) were treated with a mixture of acids and decorated with Ag nanoparticles via a chemical reduction of Ag cations by ethanol solution. The synthesized Ag-MWCNT complexes were characterized by transmission electron microscopy, X-ray diffractometry, and energy-dispersive X-ray spectroscopy. The antibacterial function of Ag-MWCNTs was evaluated against Methylobacterium spp. and Sphingomonas spp. In addition, the biocompatibility of Ag-MWCNTs was evaluated using both mouse liver hepatocytes (AML 12) and human peripheral blood mononuclear cells. Finally, we determined the minimum amount of Ag-MWCNTs required for a biocompatible yet effective antibacterial treatment modality. We report that 30 μg/mL of Ag-MWCNTs confers antibacterial functionality while maintaining minimal cytotoxicity toward both human and animal cells. The results reported herein would be beneficial for researchers interested in the efficient preparation of hybrid nanostructures and in determining the minimum amount of Ag-MWCNTs necessary to effectively hinder the growth of bacteria.

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

    PubMed

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

    2015-06-03

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

  11. Synthesis of fluorescent and low cytotoxicity phenol formaldehyde resin (PFR)@Ag composites for cell imaging and antibacterial activity.

    PubMed

    Yang, Ping; Dong, Hao; Xia, Jun; Xu, Andong; Shi, Jianjun; He, Jie; Ding, Jianzhong; Li, Dewei

    2015-12-01

    Ag nanoparticles (NPs) were loaded onto the surface of phenol formaldehyde resin (PFR) NPs without any reducing agent. The as-synthesized PFR@Ag composites have low cytotoxicity, which makes them promising antibacterial agents. Furthermore, the good fluorescence of PFR could be used for cell imaging.

  12. 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.

  13. The Role of Decorative Pictures in Learning

    ERIC Educational Resources Information Center

    Lenzner, Alwine; Schnotz, Wolfgang; Müller, Andreas

    2013-01-01

    Three experiments with students from 7th and 8th grade were performed to investigate the effects of decorative pictures in learning as compared to instructional pictures. Pictures were considered as instructional, when they were primarily informative, and as decorative, when they were primarily aesthetically appealing. The experiments…

  14. Painter and Decorator. Occupational Analyses Series.

    ERIC Educational Resources Information Center

    Chapman, Mike; MacCallum, Marilyn; Maddocks, Christopher

    This analysis covers tasks performed by a painter and decorator, an occupational title some provinces and territories of Canada have also identified as painter and painter and decorator--commercial and residential. A guide to analysis discusses development, structure, and validation method; scope of the occupation; trends; and safety. To…

  15. 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

  16. Chitosan based polymer matrix with silver nanoparticles decorated multiwalled carbon nanotubes for catalytic reduction of 4-nitrophenol.

    PubMed

    Alshehri, Saad M; Almuqati, Turki; Almuqati, Naif; Al-Farraj, Eida; Alhokbany, Norah; Ahamad, Tansir

    2016-10-20

    A novel catalyst for the reduction of 4-nitrophenol (4-NP) was prepared using carboxyl group-functionalized multiwalled carbon nanotubes (MWCNTs), polymer matrix, and silver nanoparticles (AgNPs). The AgNPs were prepared by the reduction of silver nitrate by trisodium citrate in the MWCNTs-polymer nanocomposite; the size of the synthesized AgNPs was found to be 3nm (average diameter). The synthesized nanocomposites were characterized using several analytical techniques. Ag@MWCNTs-polymer composite in the presence of sodium borohydride (NaBH4) in aqueous solution is an effective catalyst for the reduction of 4-NP. The apparent kinetics of reduction has a pseudo-first-order kinetics, and the rate constant and catalytic activity parameter were found to be respectively 7.88×10(-3)s(-1)and 11.64s(-1)g(-1). The MWCNTs-polymer nanocomposite renders stability to AgNPs against the environment and the reaction medium, which means that the Ag@MWCNTs-polymer composite can be re-used for many catalytic cycles.

  17. Improving the photocatalytic activity of s-triazine based graphitic carbon nitride through metal decoration: an ab initio investigation.

    PubMed

    Srinivasu, K; Modak, Brindaban; Ghosh, Swapan K

    2016-09-29

    Graphitic carbon nitride based semiconductor materials are found to be potential photocatalysts for generating hydrogen through solar water splitting. Through more accurate hybrid density functional theory calculations, we attempted to tune the electronic band structure of poly s-triazine based graphitic carbon nitride by decorating it with different metal atoms and clusters for improving its visible light absorption efficiency. For deposition on the two-dimensional carbon nitride surface, a range of metals have been considered which include all the 3d transition metals and the noble metals (Ag, Au, Pt and Pd). Our study reveals that though the band gaps of all the metal decorated systems were less than that of pristine carbon nitride, in most of the cases, metal decoration leads to the formation of mid gap impurity states, which can hinder the mobility of charge carriers. However, in the case of Ag and its four atom cluster deposited systems, no mid gap states were observed. In all the metal decorated systems, the measured band edge potentials were also found to satisfy the thermodynamic criterion for overall water splitting. The calculated optical absorption spectra show a shift in the absorption band towards the visible region upon metal decoration. Our results indicate that among all the considered metal atoms silver is the preferred candidate for deposition on the carbon nitride surface for improved photocatalytic activity.

  18. 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.

  19. The effect of Fe segregation on the photocatalytic growth of Ag nanoparticles on rutile TiO2(001)

    NASA Astrophysics Data System (ADS)

    Busiakiewicz, Adam; Kisielewska, Aneta; Piwoński, Ireneusz; Batory, Damian

    2017-04-01

    The photocatalytic growth of silver nanoparticles (AgNPs) on rutile TiO2(001) and Fe-modified rutile TiO2(001) monocrystals was investigated. Various amount of Fe was segregated in a controlled way from the doped TiO2 substrates in ultra-high vacuum conditions resulting in low- medium- and high- content of Fe on TiO2 substrates. AgNPs were grown on pristine TiO2 and substrates containing Fe by photoreduction of Ag+ ions under UV illumination. It was found that the size of AgNPs was larger on Fe/TiO2 than on TiO2 while the surface density exhibited the opposite behavior - a large number of AgNPs were present on the TiO2 surface but only a few AgNPs were visible on the Fe/TiO2 substrates. The reason for the differences in size and number of AgNPs on TiO2 and Fe/TiO2 is the limited access of Ag+ to the TiO2 surface caused by the large number of Fe grains segregated onto the TiO2 surface. Another possible reason for the various AgNPs morphologies is alteration in the mechanism of Ag+ photoreduction caused by iron present as Fe3+ ions and by newly formed AgNPs playing the role of electron traps. The surface elemental analysis of the investigated materials was performed with the use of X-ray photoelectron spectroscopy (XPS) and confirmed the composition of AgNPs/Fe/TiO2 systems. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed sizes, morphology and distribution of the nanostructures.

  20. Ag-Fe2O3 nanocomposites with enhanced catalytic activity for reduction of 4-nitrophenol

    NASA Astrophysics Data System (ADS)

    Liu, Shiben; Chen, Yingjie; Dong, Lifeng

    2016-07-01

    Hybrid nanostructures can be multifunctional and even possess enhanced properties. Ag-Fe2O3 nanocomposites and Ag nanoparticles (NPs) were fabricated and applied to catalyze the reduction of 4-nitrophenol. Compared with Ag NPs, Ag-Fe2O3 nanocomposites demonstrated enhanced catalytic activities. Furthermore, due to their magnetic properties, Ag-Fe2O3 nanocomposites could be easily separated from the reaction mixture and recycled through an external magnetic field. These findings will help us design hybrid nanostructures with catalytic activity and explore other potential applications of magnetic nanocomposites.

  1. Decoration Increases the Conspicuousness of Raptor Nests.

    PubMed

    Canal, David; Mulero-Pázmány, Margarita; Negro, Juan José; Sergio, Fabrizio

    2016-01-01

    Avian nests are frequently concealed or camouflaged, but a number of species builds noticeable nests or use conspicuous materials for nest decoration. In most cases, nest decoration has a role in mate choice or provides thermoregulatory or antiparasitic benefits. In territorial species however, decorations may serve additional or complementary functions, such as extended phenotypic signaling of nest-site occupancy and social status to potential intruders. The latter may benefit both signaler and receiver by minimizing the risk of aggressive interactions, especially in organisms with dangerous weaponry. Support for this hypothesis was recently found in a population of black kites (Milvus migrans), a territorial raptor that decorates its nest with white artificial materials. However, the crucial assumption that nest decorations increased nest-site visibility to conspecifics was not assessed, a key aspect given that black kite nests may be well concealed within the canopy. Here, we used an unmanned aircraft system to take pictures of black kite nests, with and without an experimentally placed decoration, from different altitudes and distances simulating the perspective of a flying and approaching, prospecting intruder. The pictures were shown to human volunteers through a standardized routine to determine whether detection rates varied according the nest decoration status and distance. Decorated nests consistently showed a higher detection frequency and a lower detection-latency, compared to undecorated versions of the same nests. Our results confirm that nest decoration in this species may act as a signaling medium that enhances nest visibility for aerial receivers, even at large distances. This finding complements previous work on this communication system, which showed that nest decoration was a threat informing trespassing conspecifics on the social dominance, territory quality and fighting capabilities of the signaler.

  2. Decoration Increases the Conspicuousness of Raptor Nests

    PubMed Central

    Canal, David; Mulero-Pázmány, Margarita; Negro, Juan José; Sergio, Fabrizio

    2016-01-01

    Avian nests are frequently concealed or camouflaged, but a number of species builds noticeable nests or use conspicuous materials for nest decoration. In most cases, nest decoration has a role in mate choice or provides thermoregulatory or antiparasitic benefits. In territorial species however, decorations may serve additional or complementary functions, such as extended phenotypic signaling of nest-site occupancy and social status to potential intruders. The latter may benefit both signaler and receiver by minimizing the risk of aggressive interactions, especially in organisms with dangerous weaponry. Support for this hypothesis was recently found in a population of black kites (Milvus migrans), a territorial raptor that decorates its nest with white artificial materials. However, the crucial assumption that nest decorations increased nest-site visibility to conspecifics was not assessed, a key aspect given that black kite nests may be well concealed within the canopy. Here, we used an unmanned aircraft system to take pictures of black kite nests, with and without an experimentally placed decoration, from different altitudes and distances simulating the perspective of a flying and approaching, prospecting intruder. The pictures were shown to human volunteers through a standardized routine to determine whether detection rates varied according the nest decoration status and distance. Decorated nests consistently showed a higher detection frequency and a lower detection-latency, compared to undecorated versions of the same nests. Our results confirm that nest decoration in this species may act as a signaling medium that enhances nest visibility for aerial receivers, even at large distances. This finding complements previous work on this communication system, which showed that nest decoration was a threat informing trespassing conspecifics on the social dominance, territory quality and fighting capabilities of the signaler. PMID:27455066

  3. Photocatalytic oxidation removal of Hg0 using ternary Ag/AgI-Ag2CO3 hybrids in wet scrubbing process under fluorescent light

    NASA Astrophysics Data System (ADS)

    Zhang, Anchao; Zhang, Lixiang; Chen, Xiaozhuan; Zhu, Qifeng; Liu, Zhichao; Xiang, Jun

    2017-01-01

    A series of ternary Ag/AgI-Ag2CO3 photocatalysts synthesized using a facile coprecipitation method were employed to investigate their performances of Hg0 removal in a wet scrubbing reactor. The hybrids were characterized by N2 adsorption-desorption, XRD, SEM-EDS, HRTEM, XPS, DRS and ESR. The photocatalytic activities of Hg0 removal were evaluated under fluorescent light. The results showed that AgI content, fluorescent light irradiation, reaction temperature all showed significant influences on Hg0 removal. NO exhibited significant effect on Hg0 removal in comparison to SO2. Among these ternary Ag/AgI-Ag2CO3 hybrids, Ag/AgI(0.1)-Ag2CO3 showed the highest Hg0 removal efficiency, which could be ascribed to the effective separation of photogenerated electron-hole pairs between AgI and Ag2CO3 and the surface plasmon resonance (SPR) effect in the visible region by metallic silver nanoparticles (Ag0 NPs). The trapping studies of reactive radicals showed that the superoxide radicals (rad O2-) may play a key role in Hg0 removal under fluorescent light. According to the experimental and characterization results, a possible photocatalytic oxidation mechanism for enhanced Hg0 removal over Ag/AgI(0.1)-Ag2CO3 hybrid under fluorescent light was proposed.

  4. Green fabrication of quaternized chitosan/rectorite/Ag NP nanocomposites with antimicrobial activity.

    PubMed

    Luo, Jiwen; Xie, Meijia; Wang, Xiaoying

    2014-02-01

    Silver nanoparticles (Ag NPs) were synthesized rapidly in one pot via the Tollens reaction, in which quaternized chitosan (QCS) and rectorite (REC) acted as the reducing and stabilizing agent, while other chemical reducing and stabilizing agents and the surfactant were not included. X-ray diffraction, scanning electron microscopy and transmission electron microscopy results showed that spherical Ag NPs with uniform sizes were obtained, the layers of clay were peeled and thus exfoliated QCS/REC/Ag NP (QCRAg) nanocomposite was achieved. Moreover, Ag NPs dispersed well in the exfoliated nanocomposite matrix, some Ag NPs even entered into the interlayer of REC. QCRAg nanocomposites showed strong antimicrobial activity; the lowest minimum inhibitory concentration against Staphyloccocus aureus was only 0.0001% (w/v). The study reveals that the obtained QCRAg nanocomposites have great potential for biomedical applications.

  5. 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.

  6. Easily separated silver nanoparticle-decorated magnetic graphene oxide: Synthesis and high antibacterial activity.

    PubMed

    Zhang, Huai-Zhi; Zhang, Chang; Zeng, Guang-Ming; Gong, Ji-Lai; Ou, Xiao-Ming; Huan, Shuang-Yan

    2016-06-01

    Silver nanoparticle-decorated magnetic graphene oxide (MGO-Ag) was synthesized by doping silver and Fe3O4 nanoparticles on the surface of GO, which was used as an antibacterial agent. MGO-Ag was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy dispersive X-ray (EDS), X-ray diffraction (XRD), Raman spectroscopy and magnetic property tests. It can be found that magnetic iron oxide nanoparticles and nano-Ag was well dispersed on graphene oxide; and MGO-Ag exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus. Several factors were investigated to study the antibacterial effect of MGO-Ag, such as temperature, time, pH and bacterial concentration. We also found that MGO-Ag maintained high inactivation rates after use six times and can be separated easily after antibacterial process. Moreover, the antibacterial mechanism is discussed and the synergistic effect of GO, Fe3O4 nanoparticles and nano-Ag accounted for high inactivation of MGO-Ag.

  7. 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

  8. Silica decorated on porous activated carbon nanofiber composites for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Kim, So Yeun; Kim, Bo-Hye

    2016-10-01

    A hybrid of silica decorated on porous activated carbon nanofibers (ACNFs) is fabricated in the form of a web via electrospinning and an activation process as an electrode material for electrochemical capacitors in an organic electrolyte. The introduction of PhSiH3 (PS) into the polyacrylonitrile (PAN) solution induces a porous ACNF structure containing silica nanoparticles (NPs) via the spontaneous sol-gel process of PS by steam in the subsequent physical activation process. These inorganic-organic hybrid composites of porous ACNF containing silica NPs show superior specific capacitance and energy density in electrochemical tests, along with good rate capability and excellent cycle life in an organic electrolyte, which is attributed to the combination of ACNF's high surface area and silica's hydrophilicity. The electrochemical performance decreases with increasing PS concentration, and this trend is consistent with the specific surface area results, which reveal the rapid formation of a double layer.

  9. Surface decorated poly(ester-ether-urethane)s nanoparticles: a versatile approach towards clinical translation.

    PubMed

    Piras, Anna Maria; Sandreschi, Stefania; Malliappan, Sivakumar Ponnurengam; Dash, Mamoni; Bartoli, Cristina; Dinucci, Dinuccio; Guarna, Francesco; Ammannati, Enrico; Masa, Marc; Múčková, Marta; Schmidtová, Ludmila; Chiellini, Emo; Chiellini, Federica

    2014-11-20

    Poly(ester-ether-urethane)s copolymers are a resourceful class of biopolymers for the preparation of nanocarriers for drug delivery applications. However, a simple clinical translation for this synthetic material with biological and quality features is still needed. In this view, poly(ε-caprolactone)-co-poly(ethylene glycol) copolymers were synthesized as semi-bulk pilot (Kg) scale under mild conditions in absence of catalyst, bearing functional termini such as fluorescein tag and anticancer targeting moieties. The obtained materials were processed into surface decorated paclitaxel (PTX) loaded nanoparticles (NPs). The NPs were fully characterized in vitro and in vivo biodistribution in healthy mice evidenced no sign of toxicity and lower levels of PTX in lung and spleen, compared to clinically applied PTX dosage form.

  10. 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.

  11. 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

  12. Metal-Particle-Decorated ZnO Nanocrystals: Photocatalysis and Charge Dynamics.

    PubMed

    Lin, Wei-Hao; Chiu, Yi-Hsuan; Shao, Pao-Wen; Hsu, Yung-Jung

    2016-12-07

    Understanding of charge transfer processes is determinant to the performance optimization for semiconductor photocatalysts. As a representative model of composite photocatalysts, metal-particle-decorated ZnO has been widely employed for a great deal of photocatalytic applications; however, the dependence of charge carrier dynamics on the metal content and metal composition and their correlation with the photocatalytic properties have seldom been reported. Here, the interfacial charge dynamics for metal-decorated ZnO nanocrystals were investigated and their correspondence with the photocatalytic properties was evaluated. The samples were prepared with a delicate antisolvent approach, in which ZnO nanocrystals were grown along with metal particle decoration in a deep eutectic solvent. By modulating the experimental conditions, the metal content (from 0.6 to 2.3 at%) and metal composition (including Ag, Au, and Pd) in the resulting metal-decorated ZnO could be readily controlled. Time-resolved photoluminescence spectra showed that an optimal Au content of 1.3 at% could effectuate the largest electron transfer rate constant for Au-decorated ZnO nanocrystals, in conformity with the highest photocatalytic efficiency observed. The relevance of charge carrier dynamics to the metal composition was also inspected and realized in terms of the energy level difference between ZnO and metal. Among the three metal-decorated ZnO samples tested, ZnO-Pd displayed the highest photocatalytic activity, fundamentally according with the largest electron transfer rate constant deduced in carrier dynamics measurements. The current work was the first study to present the correlations among charge carrier dynamics, metal content, metal composition, and the resultant photocatalytic properties for semiconductor/metal heterostructures. The findings not only helped to resolve the standing issues regarding the mechanistic foundation of photocatalysis but also shed light on the intelligent design

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  14. A sensitive sandwich-type electrochemical aptasensor for thrombin detection based on platinum nanoparticles decorated carbon nanocages as signal labels.

    PubMed

    Gao, Fenglei; Du, Lili; Zhang, Yu; Zhou, Fuyi; Tang, Daoquan

    2016-12-15

    In this work, a novel and sensitive sandwich-type electrochemical aptasensor has been developed for thrombin detection based on platinum nanoparticles (Pt NPs) decorated carbon nanocages (CNCs) as signal tags. The morphological and compositional of the Pt NPs/CNCs were examined using transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The results showed that the Pt NPs with about 3-5nm in diameter were well dispersed on the surface of CNCs. The thiolated aptamer was firstly immobilized on the gold electrode to capture the thrombin molecules, and then aptamer functionalized Pt NPs/CNCs nanocomposites were used to fabricate a sandwich sensing platform. Then, the high-content Pt NPs on carbon nanocages acting as hydrogen peroxide-mimicking enzyme catalyzed the reduction of H2O2, resulting in significant electrochemical signal amplification. Differential pulse voltammetry is employed to detect thrombin with different concentrations. Under optimized conditions, the approach provided a good linear response range from 0.05 pM to 20nM with a low detection limit of 10fM. This Pt NPs/CNCs-based aptasensor shows good precision, acceptable stability and reproducibility, which provided a promising strategy for electrochemical aptamer-based detection of other biomolecules.

  15. Spontaneous decoration of Au nanoparticles on micro-patterned reduced graphene oxide shaped by focused laser beam

    SciTech Connect

    Wan, Y. C.; Tok, E. S.; Teoh, H. F.; Sow, C. H.

    2015-02-07

    We report a facile, two-step method for the micro-landscaping of Au nanoparticles(NPs) on reduced graphene oxide (rGO) film en route to micro-patterned Au(NPs)-rGO hybrid functional materials. This method employs a focused laser beam to first locally convert GO to rGO before immersing the micro-patterned GO-rGO film into HAuCl{sub 4} solution. The rGO micro-pattern, shaped by the focused laser beam, serves as nucleation sites for the reduction of Au ions. The reduction mechanism that governs the decoration of Au NPs on rGO films is akin to electroless deposition process. In this instance, surface charges that are formed during laser reduction of GO to rGO provide active nucleation sites for Au{sup 3+} ions to form Au NPs when HAuCl{sub 4} solution is introduced. The number density, the size, and size distribution of the Au NPs can thus be directly tuned and preferentially anchored onto the rGO micro-pattern by varying the incident laser power, the scanning speed of the laser, or the concentration of HAuCl{sub 4}. The resulting hybrid materials can be used as a substrate for Surface Enhanced Raman Spectroscopy (SERS). Using Rhodamine 6G as the test subject, we found an improvement of SERS enhancement over bare rGO of up to four times, depending on the size of the Au NPs.

  16. Polyoxometalate (POM) Macroion Decorated Polymersomes

    NASA Astrophysics Data System (ADS)

    Jing, Benxin; Connor, Erin; Zhu, Y. Elaine

    2014-03-01

    Polymersomes as one of the common self-assembled forms of amphiphilic block copolymers have been widely developed for applications from drug delivery to mirco/nanoreactors. The tunability of their materials properties, such as mechanical strength and permeability often relies on the chemistry of the selected polymer in a liquid medium. We have recently employed the emergent polyoxometalate (POM) nanoclusters as macroions to control their interaction and assembly with different polymersomes. For both neutral and cationic polymersomes decorated with highly charged anionic POM nanoclusters, the dispersion stability and mechanic strength can be significantly enhanced. AFM and TEM characterization further confirms the encapsulation of POM macroions into polymersomes to form inorganic-organic hybrid complexes, which lead to new potential applications in anticancer and antibacterial medicines and catalysts.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. Synthesis of metal oxide nanoparticles (CuO and ZnO NPs) via biological template and their optical sensor applications

    NASA Astrophysics Data System (ADS)

    Maruthupandy, Muthuchamy; Zuo, Yong; Chen, Jing-Shuai; Song, Ji-Ming; Niu, He-Lin; Mao, Chang-Jie; Zhang, Sheng-Yi; Shen, Yu-Hua

    2017-03-01

    The present study is focused on employing Camellia japonica leaf extract as inductive and stabilizing agent to synthesis CuO and ZnO nanoparticles (NPs). The chemicals, such as (Cu(NO3)2·3H2O) and (Zn(NO3)2·6H2O) were converted into copper and zinc ions, respectively because of the different natural products present in the C. japonica leaf extract. The UV-vis spectra of CuO and ZnO NPs showed absorption peak at 290 nm and 301 nm, respectively. The XRD result revealed crystalline nature of the metal oxide NPs and the TEM images indicated that average sizes of the synthesized CuO and ZnO NPs were ∼17 nm and ∼20 nm, respectively. The FTIR spectra of C. japonica leaf extract showed the presence of organic groups, such as, sbnd OH, sbnd Csbnd N, and N-H, which would be responsible for forming CuO and ZnO NPs. The synthesized CuO and ZnO NPs were tested for the optical sensing of metal ions, viz. Li+ and Ag+ that illustrated excellent outcome and hence this method offers a novel lane for the synthesis of metal oxide NPs, which can be used as optical sensor for the detection of metal ions.

  2. β-CD Dimer-immobilized Ag Assembly Embedded Silica Nanoparticles for Sensitive Detection of Polycyclic Aromatic Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Hahm, Eunil; Jeong, Daham; Cha, Myeong Geun; Choi, Jae Min; Pham, Xuan-Hung; Kim, Hyung-Mo; Kim, Hwanhee; Lee, Yoon-Sik; Jeong, Dae Hong; Jung, Seunho; Jun, Bong-Hyun

    2016-05-01

    We designed a β-CD dimer on silver nanoparticles embedded with silica nanoparticles (Ag@SiO2 NPs) structure to detect polycyclic aromatic hydrocarbons (PAHs). Silica NPs were utilized as a template for embedding silver NPs to create hot spot structures and enhance the surface-enhanced Raman scattering (SERS) signal, and a thioether-bridged dimeric β-CD was immobilized on Ag NPs to capture PAHs. The assembled Ag NPs on silica NPs were confirmed by TEM and the presence of β-CD dimer on Ag@SiO2 was confirmed by UV-vis and attenuated total reflection-Fourier transform infrared spectroscopy. The β-CD dimer@Ag@SiO2 NPs were used as SERS substrate for detecting perylene, a PAH, directly and in a wide linearity range of 10‑7 M to 10‑2 M with a low detection limit of 10‑8 M. Also, the β-CD dimer@Ag@SiO2 NPs exhibited 1000-fold greater sensitivity than Ag@SiO2 NPs in terms of their perylene detection limit. Furthermore, we demonstrated the possibility of detecting various PAH compounds using the β-CD dimer@Ag@SiO2 NPs as a multiplex detection tool. Various PAH compounds with the NPs exhibited their distinct SERS bands by the ratio of each PAHs. This approach of utilizing the assembled structure and the ligands to recognize target has potential for use in sensitive analytical sensors.

  3. β-CD Dimer-immobilized Ag Assembly Embedded Silica Nanoparticles for Sensitive Detection of Polycyclic Aromatic Hydrocarbons

    PubMed Central

    Hahm, Eunil; Jeong, Daham; Cha, Myeong Geun; Choi, Jae Min; Pham, Xuan-Hung; Kim, Hyung-Mo; Kim, Hwanhee; Lee, Yoon-Sik; Jeong, Dae Hong; Jung, Seunho; Jun, Bong-Hyun

    2016-01-01

    We designed a β-CD dimer on silver nanoparticles embedded with silica nanoparticles (Ag@SiO2 NPs) structure to detect polycyclic aromatic hydrocarbons (PAHs). Silica NPs were utilized as a template for embedding silver NPs to create hot spot structures and enhance the surface-enhanced Raman scattering (SERS) signal, and a thioether-bridged dimeric β-CD was immobilized on Ag NPs to capture PAHs. The assembled Ag NPs on silica NPs were confirmed by TEM and the presence of β-CD dimer on Ag@SiO2 was confirmed by UV-vis and attenuated total reflection-Fourier transform infrared spectroscopy. The β-CD dimer@Ag@SiO2 NPs were used as SERS substrate for detecting perylene, a PAH, directly and in a wide linearity range of 10−7 M to 10−2 M with a low detection limit of 10−8 M. Also, the β-CD dimer@Ag@SiO2 NPs exhibited 1000-fold greater sensitivity than Ag@SiO2 NPs in terms of their perylene detection limit. Furthermore, we demonstrated the possibility of detecting various PAH compounds using the β-CD dimer@Ag@SiO2 NPs as a multiplex detection tool. Various PAH compounds with the NPs exhibited their distinct SERS bands by the ratio of each PAHs. This approach of utilizing the assembled structure and the ligands to recognize target has potential for use in sensitive analytical sensors. PMID:27184729

  4. 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.

  5. 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.

  6. 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

  7. Phytosynthesis of stable Au, Ag and Au-Ag alloy nanoparticles using J. Sambac leaves extract, and their enhanced antimicrobial activity in presence of organic antimicrobials

    NASA Astrophysics Data System (ADS)

    Yallappa, S.; Manjanna, J.; Dhananjaya, B. L.

    2015-02-01

    A green chemistry approach for the synthesis of Au, Ag and Au-Ag alloy nanoparticles (NPs) using the corresponding metal precursors and Jasminum sambac leaves extract as both reducing and capping media, under microwave irradiation, is reported. During the formation, as expected, the reaction mixture shows marginal decrease in pH and an increase in solution potential. The formation of NPs is evident from their surface plasmon resonance (SPR) peak observed at ∼555 nm for Au, ∼435 nm for Ag and ∼510 nm for Au-Ag alloy. The XRD pattern shows fcc structure while the FTIR spectra indicate the presence of plant residues adsorbed on these NPs. Such a bio-capping of NPs is characterized by their weight loss, ∼35% due to thermal degradation of biomass, as observed in TG analysis. The colloidal dispersion of NPs is stable for about 6 weeks. The near spherical shape of NPs (ϕ20-50 nm) is observed by FE-SEM/TEM images and EDAX gives the expected elemental composition. Furthermore, these NPs showed enhanced antimicrobial activity (∼1-4-fold increase in zone of inhibition) in combination with antimicrobials against test strains. Thus, the phytosynthesized NPs could be used as effective growth inhibitors for various microorganisms.

  8. Phytosynthesis of stable Au, Ag and Au-Ag alloy nanoparticles using J. sambac leaves extract, and their enhanced antimicrobial activity in presence of organic antimicrobials.

    PubMed

    Yallappa, S; Manjanna, J; Dhananjaya, B L

    2015-02-25

    A green chemistry approach for the synthesis of Au, Ag and Au-Ag alloy nanoparticles (NPs) using the corresponding metal precursors and Jasminum sambac leaves extract as both reducing and capping media, under microwave irradiation, is reported. During the formation, as expected, the reaction mixture shows marginal decrease in pH and an increase in solution potential. The formation of NPs is evident from their surface plasmon resonance (SPR) peak observed at ∼555 nm for Au, ∼435 nm for Ag and ∼510 nm for Au-Ag alloy. The XRD pattern shows fcc structure while the FTIR spectra indicate the presence of plant residues adsorbed on these NPs. Such a bio-capping of NPs is characterized by their weight loss, ∼35% due to thermal degradation of biomass, as observed in TG analysis. The colloidal dispersion of NPs is stable for about 6 weeks. The near spherical shape of NPs (ϕ20-50 nm) is observed by FE-SEM/TEM images and EDAX gives the expected elemental composition. Furthermore, these NPs showed enhanced antimicrobial activity (∼1-4-fold increase in zone of inhibition) in combination with antimicrobials against test strains. Thus, the phytosynthesized NPs could be used as effective growth inhibitors for various microorganisms.

  9. Use of Single-Layer g-C3N4/Ag Hybrids for Surface-Enhanced Raman Scattering (SERS)

    PubMed Central

    Jiang, Jizhou; Zou, Jing; Wee, Andrew Thye Shen; Zhang, Wenjing

    2016-01-01

    Surface-enhanced Raman scattering (SERS) substrates with high activity and stability are desirable for SERS sensing. Here, we report a new single atomic layer graphitic-C3N4 (S-g-C3N4) and Ag nanoparticles (NPs) hybrid as high-performance SERS substrates. The SERS mechanism of the highly stable S-g-C3N4/Ag substrates was systematically investigated by a combination of experiments and theoretical calculations. From the results of XPS and Raman spectroscopies, it was found that there was a strong interaction between S-g-C3N4 and Ag NPs, which facilitates the uniform distribution of Ag NPs over the edges and surfaces of S-g-C3N4 nanosheets, and induces a charge transfer from S-g-C3N4 to the oxidizing agent through the silver surface, ultimately protecting Ag NPs from oxidation. Based on the theoretical calculations, we found that the net surface charge of the Ag atoms on the S-g-C3N4/Ag substrates was positive and the Ag NPs presented high dispersibility, suggesting that the Ag atoms on the S-g-C3N4/Ag substrates were not likely to be oxidized, thereby ensuring the high stability of the S-g-C3N4/Ag substrate. An understanding of the stability mechanism in this system can be helpful for developing other effective SERS substrates with long-term stability. PMID:27687573

  10. Use of Single-Layer g-C3N4/Ag Hybrids for Surface-Enhanced Raman Scattering (SERS)

    NASA Astrophysics Data System (ADS)

    Jiang, Jizhou; Zou, Jing; Wee, Andrew Thye Shen; Zhang, Wenjing

    2016-09-01

    Surface-enhanced Raman scattering (SERS) substrates with high activity and stability are desirable for SERS sensing. Here, we report a new single atomic layer graphitic-C3N4 (S-g-C3N4) and Ag nanoparticles (NPs) hybrid as high-performance SERS substrates. The SERS mechanism of the highly stable S-g-C3N4/Ag substrates was systematically investigated by a combination of experiments and theoretical calculations. From the results of XPS and Raman spectroscopies, it was found that there was a strong interaction between S-g-C3N4 and Ag NPs, which facilitates the uniform distribution of Ag NPs over the edges and surfaces of S-g-C3N4 nanosheets, and induces a charge transfer from S-g-C3N4 to the oxidizing agent through the silver surface, ultimately protecting Ag NPs from oxidation. Based on the theoretical calculations, we found that the net surface charge of the Ag atoms on the S-g-C3N4/Ag substrates was positive and the Ag NPs presented high dispersibility, suggesting that the Ag atoms on the S-g-C3N4/Ag substrates were not likely to be oxidized, thereby ensuring the high stability of the S-g-C3N4/Ag substrate. An understanding of the stability mechanism in this system can be helpful for developing other effective SERS substrates with long-term stability.

  11. Use of Single-Layer g-C3N4/Ag Hybrids for Surface-Enhanced Raman Scattering (SERS).

    PubMed

    Jiang, Jizhou; Zou, Jing; Wee, Andrew Thye Shen; Zhang, Wenjing

    2016-09-30

    Surface-enhanced Raman scattering (SERS) substrates with high activity and stability are desirable for SERS sensing. Here, we report a new single atomic layer graphitic-C3N4 (S-g-C3N4) and Ag nanoparticles (NPs) hybrid as high-performance SERS substrates. The SERS mechanism of the highly stable S-g-C3N4/Ag substrates was systematically investigated by a combination of experiments and theoretical calculations. From the results of XPS and Raman spectroscopies, it was found that there was a strong interaction between S-g-C3N4 and Ag NPs, which facilitates the uniform distribution of Ag NPs over the edges and surfaces of S-g-C3N4 nanosheets, and induces a charge transfer from S-g-C3N4 to the oxidizing agent through the silver surface, ultimately protecting Ag NPs from oxidation. Based on the theoretical calculations, we found that the net surface charge of the Ag atoms on the S-g-C3N4/Ag substrates was positive and the Ag NPs presented high dispersibility, suggesting that the Ag atoms on the S-g-C3N4/Ag substrates were not likely to be oxidized, thereby ensuring the high stability of the S-g-C3N4/Ag substrate. An understanding of the stability mechanism in this system can be helpful for developing other effective SERS substrates with long-term stability.

  12. 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

  13. 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 %.

  14. Two-dimensional ZnO ultrathin nanosheets decorated with Au nanoparticles for effective photocatalysis

    NASA Astrophysics Data System (ADS)

    Hu, Jin; You, Ning; Yu, Zhe; Zhou, Gang; Xu, Xiaoyong

    2016-08-01

    Two-dimensional (2D) materials, especially the inorganic 2D nanosheets (NSs), are of particular interest due to their unique structural and electronic properties, which are favorable for photoelectronic applications such as photocatalysis. Here, we design and fabricate the ultrathin 2D ZnO NSs decorated with Au nanoparticles (AuNPs), though molecular modelling 2D hydrothermal growth and followed by surface modification are used as an effective photocatalyst for photocatalytic organic dye degradation and hydrogen production. The ultrathin 2D nature enables ultrahigh atom ratio near surface to proliferate the active sites, and the Au plasmon plays a promoting role in the visible-light absorption and photogenerated charge separation, thus integrating the synergistic benefits to boost the redox reactions at catalyst/electrolyte interface. The AuNPs-decorated ZnO NSs yield the impressive photocatalytic activities such as the dye degradation rate constant of 7.69 × 10-2 min-1 and the hydrogen production rate of 350 μmol h-1 g-1.

  15. NPS-SCAT: Systems Engineering and Payload Subsystem Design, Integration, and Testing of NPS’ First CubeSat

    DTIC Science & Technology

    2010-06-01

    20 Figure 13 NPS-SCAT Prototype (From [39]) ..................................................................22 Figure 14 Pumpkin FM430 PCB...of a prototype unit by Alex Bein [39]. The initial prototype consisted of a Pumpkin CubeSat Kit that included a 1U Pumpkin Structure, Pumpkin Linear...NPS-SCAT satellite was the Microhard MHX-2420 2.4 GHz radio transceiver [39]. This component is strictly COTS and was marketed by the Pumpkin

  16. Ag-plasma modification enhances bone apposition around titanium dental implants: an animal study in Labrador dogs.

    PubMed

    Qiao, Shichong; Cao, Huiliang; Zhao, Xu; Lo, Hueiwen; Zhuang, Longfei; Gu, Yingxin; Shi, Junyu; Liu, Xuanyong; Lai, Hongchang

    2015-01-01

    Dental implants with proper antibacterial ability as well as ideal osseointegration are being actively pursued. The antimicrobial ability of titanium implants can be significantly enhanced via modification with silver nanoparticles (Ag NPs). However, the high mobility of Ag NPs results in their potential cytotoxicity. The silver plasma immersion ion-implantation (Ag-PIII) technique may remedy the defect. Accordingly, Ag-PIII technique was employed in this study in an attempt to reduce the mobility of Ag NPs and enhance osseointegration of sandblasted and acid-etched (SLA) dental implants. Briefly, 48 dental implants, divided equally into one control and three test groups (further treated by Ag-PIII technique with three different implantation parameters), were inserted in the mandibles of six Labrador dogs. Scanning electron microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma optical emission spectrometry were used to investigate the surface topography, chemical states, and silver release of SLA- and Ag-PIII-treated titanium dental implants. The implant stability quotient examination, Microcomputed tomography evaluation, histological observations, and histomorphometric analysis were performed to assess the osseointegration effect in vivo. The results demonstrated that normal soft tissue healing around dental implants was observed in all the groups, whereas the implant stability quotient values in Ag-PIII groups were higher than that in the SLA group. In addition, all the Ag-PIII groups, compared to the SLA-group, exhibited enhanced new bone formation, bone mineral density, and trabecular pattern. With regard to osteogenic indicators, the implants treated with Ag-PIII for 30 minutes and 60 minutes, with the diameter of the Ag NPs ranging from 5-25 nm, were better than those treated with Ag-PIII for 90 minutes, with the Ag NPs diameter out of that range. These results suggest that Ag-PIII technique can reduce the mobility of Ag NPs and enhance

  17. Ag-plasma modification enhances bone apposition around titanium dental implants: an animal study in Labrador dogs

    PubMed Central

    Qiao, Shichong; Cao, Huiliang; Zhao, Xu; Lo, Hueiwen; Zhuang, Longfei; Gu, Yingxin; Shi, Junyu; Liu, Xuanyong; Lai, Hongchang

    2015-01-01

    Dental implants with proper antibacterial ability as well as ideal osseointegration are being actively pursued. The antimicrobial ability of titanium implants can be significantly enhanced via modification with silver nanoparticles (Ag NPs). However, the high mobility of Ag NPs results in their potential cytotoxicity. The silver plasma immersion ion-implantation (Ag-PIII) technique may remedy the defect. Accordingly, Ag-PIII technique was employed in this study in an attempt to reduce the mobility of Ag NPs and enhance osseointegration of sandblasted and acid-etched (SLA) dental implants. Briefly, 48 dental implants, divided equally into one control and three test groups (further treated by Ag-PIII technique with three different implantation parameters), were inserted in the mandibles of six Labrador dogs. Scanning electron microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma optical emission spectrometry were used to investigate the surface topography, chemical states, and silver release of SLA- and Ag-PIII-treated titanium dental implants. The implant stability quotient examination, Microcomputed tomography evaluation, histological observations, and histomorphometric analysis were performed to assess the osseointegration effect in vivo. The results demonstrated that normal soft tissue healing around dental implants was observed in all the groups, whereas the implant stability quotient values in Ag-PIII groups were higher than that in the SLA group. In addition, all the Ag-PIII groups, compared to the SLA-group, exhibited enhanced new bone formation, bone mineral density, and trabecular pattern. With regard to osteogenic indicators, the implants treated with Ag-PIII for 30 minutes and 60 minutes, with the diameter of the Ag NPs ranging from 5–25 nm, were better than those treated with Ag-PIII for 90 minutes, with the Ag NPs diameter out of that range. These results suggest that Ag-PIII technique can reduce the mobility of Ag NPs and

  18. The valence band structure of Ag{sub x}Rh{sub 1–x} alloy nanoparticles

    SciTech Connect

    Yang, Anli; Sakata, Osami; Kusada, Kohei; Kobayashi, Hirokazu; Yayama, Tomoe; Ishimoto, Takayoshi; Yoshikawa, Hideki; Koyama, Michihisa; and others

    2014-10-13

    The valence band (VB) structures of face-centered-cubic Ag-Rh alloy nanoparticles (NPs), which are known to have excellent hydrogen-storage properties, were investigated using bulk-sensitive hard x-ray photoelectron spectroscopy. The observed VB spectra profiles of the Ag-Rh alloy NPs do not resemble simple linear combinations of the VB spectra of Ag and Rh NPs. The observed VB hybridization was qualitatively reproduced via a first-principles calculation. The electronic structure of the Ag{sub 0.5}Rh{sub 0.5} alloy NPs near the Fermi edge was strikingly similar to that of Pd NPs, whose superior hydrogen-storage properties are well known.

  19. Pollutant capturing SERS substrate: porous boron nitride microfibers with uniform silver nanoparticle decoration.

    PubMed

    Dai, Pengcheng; Xue, Yanming; Wang, Xuebin; Weng, Qunhong; Zhang, Chao; Jiang, Xiangfen; Tang, Daiming; Wang, Xi; Kawamoto, Naoyuki; Ide, Yusuke; Mitome, Masanori; Golberg, Dmitri; Bando, Yoshio

    2015-12-07

    How to concentrate target molecules on the surface of a SERS substrate is a key problem in the practical application of SERS. Herein, we designed for the first time a pollutant capturing surface enhanced Raman spectroscopy (SERS) substrate, namely porous BN microfibers uniformly decorated with Ag nanoparticles, in which the BN microfibers adsorb pollutants, while the Ag nanoparticles provide SERS activity. This SERS substrate captures pollutants from an aqueous solution completely and accumulates them all on its surface without introducing noise signals. The pores of BN protect the silver particles from aggregation which makes BN/Ag a stable and recyclable SERS substrate. What's more, while the dyes are thoroughly concentrated from a diluted solution, the SERS detection limit is easily enhanced, from 10(-6) M to 10(-9) M.

  20. Effects of reducing agents on the synthesis of Ag/rGO nanocomposites

    NASA Astrophysics Data System (ADS)

    Li, Yaya; Song, Qiong; Fan, Bingbing; Zhang, Rui

    2017-01-01

    A facile and rapid microwave-assisted green route has been used for the formation of Ag nanoparticles (AgNPs) and the reduction of graphene oxide (GO) simultaneously with five different reducing agents, sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium citrate, urea and ascorbic acid. The experimental results show that the structural properties and phase of Ag/reduced graphene oxide (Ag/rGO) nanocomposites are connected with reducing agent. AgNPs can be uniformly and compactly anchored on reduced GO (rGO) surface in the microwave field for 2 min by the assist of NaOH or KOH as reducing agent. The OH‑ can not only accelerate the ionization of acidic functional groups but also act as the nucleophile for Ag+. By addition of sodium citrate and urea, the GO sample remains its original structure, and Ag+ tends to form Ag2CO3, which then decomposes into Ag2O. While in the urea solution, Ag2O turns into [Ag(NH3)2]+ ions with abundant urea, then [Ag(NH3)2]+ ions are reduced to Ag0 by electrons, which leads to both Ag and Ag2O phase coexisting in the urea treated samples. In addition, it can be found that NaOH shows the best results in terms of the crystallinity and purity of Ag grains anchored on rGO surface.

  1. Reversible modulated mid-infrared absorption of Ag/TiO{sub 2} by photoinduced interfacial charge transfer

    SciTech Connect

    Xu, S. C. E-mail: ghli@issp.ac.cn; Li, L.; Pan, S. S.; Luo, Y. Y.; Zhang, Y. X.; Li, G. H. E-mail: ghli@issp.ac.cn

    2014-10-06

    An enhanced mid-infrared absorption in Ag nanoparticles-decorated TiO{sub 2} microflowers was reported. It was found that the mid-infrared absorption of the Ag/TiO{sub 2} complex depends strongly on the content and size of Ag nanoparticles, the higher the Ag nanoparticles content, the stronger the infrared absorption. The average reflectivity in the entire mid-infrared region of the microflowers drops from 57.6% to 10.5% after Ag nanoparticles decoration. Reversible modulated mid-infrared absorption properties were found in the Ag/TiO{sub 2} complexes upon alternative illumination of visible and UV light due to the photoinduced interfacial electron transfer between TiO{sub 2} semiconductor and Ag nanoparticles.

  2. Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene

    PubMed Central

    Hazarika, Ankita; Deka, Biplab K.; Kim, DoYoung; Kong, Kyungil; Park, Young-Bin; Park, Hyung Wook

    2017-01-01

    We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90–100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene. PMID:28074877

  3. Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene

    NASA Astrophysics Data System (ADS)

    Hazarika, Ankita; Deka, Biplab K.; Kim, Doyoung; Kong, Kyungil; Park, Young-Bin; Park, Hyung Wook

    2017-01-01

    We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90–100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene.

  4. Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene.

    PubMed

    Hazarika, Ankita; Deka, Biplab K; Kim, DoYoung; Kong, Kyungil; Park, Young-Bin; Park, Hyung Wook

    2017-01-11

    We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90-100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene.

  5. Antibacterial and hemolysis activity of polypyrrole nanotubes decorated with silver nanoparticles by an in-situ reduction process.

    PubMed

    Upadhyay, J; Kumar, A; Gogoi, B; Buragohain, A K

    2015-09-01

    Polypyrrole nanotube-silver nanoparticle nanocomposites (PPy-NTs:Ag-NPs) have been synthesized by in-situ reduction of silver nitrate (AgNO3) to suppress the agglomeration of Ag-NPs. The morphology and chemical structure of the nanocomposites have been studied by HRTEM, SEM, XRD, FTIR and UV-vis spectroscopy. The average diameter of the polypyrrole nanotubes (PPy-NTs) is measured to be 130.59±5.5 nm with their length in the micrometer range, while the silver nanoparticles (Ag-NPs) exhibit spherical shape with an average diameter of 23.12±3.23 nm. In-vitro blood compatibility of the nanocomposites has been carried out via hemolysis assay. Antimicrobial activity of the nanocomposites has been investigated with Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. The results depict that the hemolysis and antimicrobial activities of the nanocomposites increase with increasing Ag-NP concentration that can be controlled by the AgNO3 precursor concentration in the in-situ process.

  6. 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.

  7. 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.

  8. 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).

  9. Pollutant capturing SERS substrate: porous boron nitride microfibers with uniform silver nanoparticle decoration

    NASA Astrophysics Data System (ADS)

    Dai, Pengcheng; Xue, Yanming; Wang, Xuebin; Weng, Qunhong; Zhang, Chao; Jiang, Xiangfen; Tang, Daiming; Wang, Xi; Kawamoto, Naoyuki; Ide, Yusuke; Mitome, Masanori; Golberg, Dmitri; Bando, Yoshio

    2015-11-01

    How to concentrate target molecules on the surface of a SERS substrate is a key problem in the practical application of SERS. Herein, we designed for the first time a pollutant capturing surface enhanced Raman spectroscopy (SERS) substrate, namely porous BN microfibers uniformly decorated with Ag nanoparticles, in which the BN microfibers adsorb pollutants, while the Ag nanoparticles provide SERS activity. This SERS substrate captures pollutants from an aqueous solution completely and accumulates them all on its surface without introducing noise signals. The pores of BN protect the silver particles from aggregation which makes BN/Ag a stable and recyclable SERS substrate. What's more, while the dyes are thoroughly concentrated from a diluted solution, the SERS detection limit is easily enhanced, from 10-6 M to 10-9 M.How to concentrate target molecules on the surface of a SERS substrate is a key problem in the practical application of SERS. Herein, we designed for the first time a pollutant capturing surface enhanced Raman spectroscopy (SERS) substrate, namely porous BN microfibers uniformly decorated with Ag nanoparticles, in which the BN microfibers adsorb pollutants, while the Ag nanoparticles provide SERS activity. This SERS substrate captures pollutants from an aqueous solution completely and accumulates them all on its surface without introducing noise signals. The pores of BN protect the silver particles from aggregation which makes BN/Ag a stable and recyclable SERS substrate. What's more, while the dyes are thoroughly concentrated from a diluted solution, the SERS detection limit is easily enhanced, from 10-6 M to 10-9 M. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05625j

  10. Antibacterial polylactic acid/chitosan nanofibers decorated with bioactive glass

    NASA Astrophysics Data System (ADS)

    Goh, Yi-fan; Akram, Muhammad; Alshemary, Ammarz; Hussain, Rafaqat

    2016-11-01

    In this study, we have presented the structural and in vitro characterization of electrospun polylactic acid (PLA)/Chitosan nanofibers coated with cerium, copper or silver doped bioactive glasses (CeBG/CuBG/AgBG). Bead-free, smooth surfaced nanofibers were successfully prepared by using electrospinning technique. The nanocomposite fibers were obtained using a facile dip-coating method, their antibacterial activities against E. coliE. coli (ATCC 25922 strains) were measured by the disk diffusion method after 24 h of incubation at 37 °C. CeBG and CuBG decorated PLA/Chitosan nanofibers did not develop an inhibition zone against the bacteria. On the other hand, nanofibers coated with AgBG developed an inhibition zone against the bacteria. The as-prepared nanocomposite fibers were immersed in SBF for 1, 3 and 7 days in Simulated Body Fluid (SBF) for evaluation of in vitro bioactivity. All samples induced the formation of crystallites with roughly ruffled morphology and the pores of fibers were covered with the extensive growth of crystallites. Energy Dispersive X-ray (EDX) composition analysis showed that the crystallites possessed Ca/P ratio close to 1.67, confirming the good in-vitro bioactivity of the fibers.

  11. Two-step synthesis of Ag@GQD hybrid with enhanced photothermal effect and catalytic performance

    NASA Astrophysics Data System (ADS)

    Wu, Cong; Yuan, Yali; He, Qian; Song, Rui

    2016-12-01

    A novel Ag@GQD (graphene quantum dot) hybrid fabricated by a facile two-step strategy is presented: the GQDs are prepared by citrate acid and AgNO3 is reduced. Catalytic studies showed that the Ag@GQD hybrid exhibited excellent photothermal effect and catalytic performance for 4-nitrophenol (4-NP) reduction, suggesting that the GQDs enhanced the catalytic activity via a synergistic effect and the Ag NPs boosted the catalytic efficiency through SPR-mediated photothermal local heating.

  12. Effects of ZnO Quantum Dots Decoration on the Field Emission Behavior of Graphene.

    PubMed

    Sun, Lei; Zhou, Xiongtu; Lin, Zhixian; Guo, Tailiang; Zhang, Yongai; Zeng, Yongzhi

    2016-11-23

    ZnO quantum dots (QDs) have been decorated on graphene deposited on patterned Ag electrodes as a field emission cathode by a solution process. Effects of ZnO QDs on the field emission behavior of graphene are studied by experiment and first-principles calculations. The results indicate that the attachment of ZnO QDs with a C atom leads to the enhancement of electron emission from graphene, which is mainly attributed to the reduction of the work function and ionization potential, and the increase of the Fermi level of graphene after the decoration. A change in the local density distribution and the density of states near the Fermi level may also account for this behavior. Our study may help to develop new field emission composites and expand ZnO QDs in applications for electron emission devices as well.

  13. Preparation and antibacterial properties of Ag@polydopamine/graphene oxide sheet nanocomposite

    NASA Astrophysics Data System (ADS)

    Zhou, Hao; Liu, Yunfang; Chi, Weidong; Yu, Changyuan; Yu, Yingjie

    2013-10-01

    Immobilization of silver nanoparticles (Ag NPs) on poly-dopamine (PDA) functionalized graphene oxide sheets (GOSs) were carried out by an easy in situ reduction method. The PDA layer was coated on the surface of the GOSs via the self-polymerization of dopamine under atmosphere condition. The PDA layer not only works as the chemisorption and reduction sites for silver ions to form Ag NPs but also stabilizes them. High-resolution transmission electron microscopy observation shows that the average size of the Ag NPs anchored on the PDA/GOS composite is about 2.8 nm. The inhibition zone diameter of the Ag@PDA/GOS nanocomposite is about 23.7 mm, whereas said diameter of the Ag NPs is only 18.5 mm. The minimum bactericidal concentration of the Ag@PDA/GOS nanocomposite is about 25 μg/ml that is only half of said concentration of the Ag NPs. The Ag@PDA/GOS nanocomposite exhibits an excellent antibacterial property.

  14. 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

  15. 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.

  16. 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.

  17. Preparation of AgBr@SiO2 core@shell hybrid nanoparticles and their bactericidal activity.

    PubMed

    Li, Yuanyuan; Yang, Lisu; Zhao, Yanbao; Li, Binjie; Sun, Lei; Luo, Huajuan

    2013-04-01

    AgBr@SiO2 core@shell hybrid nanoparticles (NPs) were successfully prepared by sol-gel method. Their morphology and structure were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The hybrid NPs are predominantly spherical in shape, with an average diameter of 180-200 nm, and each NP contains one inorganic core. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the hybrid NPs were examined against Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli), respectively. Results indicated that the AgBr@SiO2 NPs had excellent antibacterial activity.

  18. 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

  19. Cellular Energy Allocation to Assess the Impact of Nanomaterials on Soil Invertebrates (Enchytraeids): The Effect of Cu and Ag.

    PubMed

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

    2015-06-16

    The effects of several copper (Cu) and silver (Ag) nanomaterials were assessed using the cellular energy allocation (CEA), a methodology used to evaluate the energetic status and which relates with organisms' overall condition and response to toxic stress. Enchytraeus crypticus (Oligochatea), was exposed to the reproduction effect concentrations EC20/50 of several Cu and Ag materials (CuNO3, Cu-Field, Cu-Nwires and Cu-NPs; AgNO3, Ag NM300K, Ag-NPs Non-coated and Ag-NPs PVP-coated) for 7 days (0-3-7d). The parameters measured were the total energy reserves available (protein, carbohydrate and lipid budgets) and the energy consumption (Ec) integrated to obtain the CEA. Results showed that these parameters allowed a clear discrimination between Cu and Ag, but less clearly within each of the various materials. For Cu there was an increase in Ec and protein budget, while for Ag a decrease was observed. The results corroborate known mechanisms, e.g., with Cu causing an increase in metabolic rate whereas Ag induces mitochondrial damage. The various Cu forms seem to activate different mechanisms with size and shape (e.g., Cu-NPs versus Cu-Nwires), causing clearly different effects. For Ag, results are in line with a slower oxidation rate of Ag-NMs in comparison with Ag-salt and hence delayed effects.

  20. A simple preparation of Ag@graphene nanocomposites for surface-enhanced Raman spectroscopy of fluorescent anticancer drug

    NASA Astrophysics Data System (ADS)

    Meng, Ying; Yan, Xueying; Wang, Yi

    2016-05-01

    A simple method was developed to synthesize Ag@graphene nanocomposites with rough Ag nanoparticles (AgNPs) conjugated with graphene nanosheets, and the nanocomposites could be used as substrates for effective surface-enhanced Raman spectroscopy (SERS) of fluorescent anticancer drug (Dox) since they could not only enhance the Raman signals but also suppress the fluorescent signals.

  1. The Catalytic Behaviour of NanoAg@montmorillonite Composite Materials

    NASA Astrophysics Data System (ADS)

    Karlíková, Martina; Kvítek, Libor; Prucek, Robert; Panáček, Aleš; Filip, Jan; Pechoušek, Jiří; Adegboyega, Nathaniel F.

    The preparation of nanoAg@montmorillonite composite materials and their catalytic activity is reported in this article. The nanoAg@montmorillonite composite materials were prepared by the adsorption of silver NPs, with an average size about 30 nm, from their aqueous dispersion onto two types of montmorillonite with different chemical composition. Silver NPs were prepared via modified Tollens process, which involves the reduction of [Ag(NH3)2]+ complex cation by maltose. The amount of silver NPs anchored onto the MMT surfaces was determined by UV-VIS spectroscopy; the decrease in absorbance of the dispersion after the adsorption was monitored. Prepared nanocomposite materials were subsequently characterized by means of transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). The reduction of 4-nitrophenol by sodium borohydride was chosen to examine the catalytic properties of the synthesized silver nanocomposite materials.

  2. Noble metal nanoparticle-decorated TiO2 nanobelts for enhanced photocatalysis

    NASA Astrophysics Data System (ADS)

    He, Haiyan; Yang, Ping; Jia, Changchao; Miao, Yanping; Zhao, Jie; Du, Yingying

    2014-07-01

    TiO2 nanobelts have been fabricated through a hydrothermal method and subsequently sulfuric-acid-corrosion-treated for a rough surface. Noble metal nanoparticles such as Ag and Au were deposited on the coarse surface of TiO2 nanobelts via a coprecipitation procedure. Ag-TiO2 nanobelts were prepared in ethanolic solution contained silver nitrate (AgNO3) and sodium hydroxide (NaOH). Au-TiO2 nanobelts were obtained in chloroauric acid (HAuCl4) using sodium borohydride (NaBH4) as the reductant. It is confirmed by the results of XRD patterns together with the SEM images that the composite of noble metal and TiO2 nanobelts were obtained successfully and the Ag or Au nanoparticles were well-dispersed on the TiO2 nanobelts. Moreover, the as-prepared Ag and Au nanoparticle-decorated TiO2 nanobelts represent an enhanced photocatalytic activity compared with pure TiO2 nanobelts, which is due to the fact that the Ag and Au nanoparticles on the surface of TiO2 nanobelts act as sinks for the photogenerated electrons and promote the separation of the electrons and holes.

  3. Development and Exploration of Nanoparticle Decorated Carbon Supports (Graphene and Graphene Oxide) for Energy Collection, Storage, and Conversion

    DTIC Science & Technology

    2012-12-17

    hybrid films as an alternative to organic-based photoactive materials in flexible photodetectors and solar cells . Figure 3. Solution...a wide range of metal nanoparticle-decorated (Pt, Au, Ag, Pt/Ru) graphene oxide (GO) hybrids as well as inorganic particle-graphene ( TiO2 /PbSe/G... hybrids . These hybrids were then evaluated for their performance in energy conversion devices and two examples were chosen, namely stacked fuel cells

  4. A study on Cu and Ag doped ZnO nanoparticles for the photocatalytic degradation of brilliant green dye: synthesis and characterization.

    PubMed

    Gnanaprakasam, A; Sivakumar, V M; Thirumarimurugan, M

    2016-09-01

    Novel polyvinyl pyrrolidone capped pure, Ag (1-3%) and Cu doped (1-3%) zinc oxide (ZnO) nanoparticles (NPs) were successfully synthesized via the co-precipitation method. The synthesized NPs were characterized by UV-visible spectrophotometry, X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and field emission scanning electron microscopy (FE-SEM). Compared to pure ZnO, the absorption bands of Ag and Cu doped ZnO NPs were shifted and, further, the band gap energy was also decreased which confirms the incorporation of Ag and Cu into the ZnO lattice. The XRD diffraction peak confirms that all the synthesized compounds are found to be of highly crystalline hexagonal wurtzite structure. In addition, the presence of Ag and Cu in the ZnO NPs was further evidenced from EDS analysis. FE-SEM images established the morphology of the doped ZnO NPs which was not affected by the addition of Ag and Cu. The photocatalytic activity of undoped, Ag doped (1-3%) and Cu doped (1-3%) ZnO NPs were tested with brilliant green dye under UV irradiation. Degradation study reveals that doping has a distinct effect on the photocatalytic behavior of ZnO NPs. In addition to that, kinetic, thermodynamic and reusability studies have been performed for the 2% Ag doped ZnO NPs.

  5. USGS-NPS Servicewide Benthic Mapping Program (SBMP) workshop report

    USGS Publications Warehouse

    Moses, Christopher S.; Nayagandhi, Amar; Brock, John; Beavers, Rebecca

    2010-01-01

    The National Park Service (NPS) Inventory and Monitoring (I&M) Program recently allocated funds to initiate a benthic mapping program in ocean and Great Lakes parks in alignment with the NPS Ocean Park Stewardship 2007-2008 Action Plan. Seventy-four (ocean and Great Lakes) parks, spanning more than 5,000 miles of coastline, many affected by increasing coastal storms and other natural and anthropogenic processes, make the development of a Servicewide Benthic Mapping Program (SBMP) timely. The resulting maps and associated reports will be provided to NPS managers in a consistent servicewide format to help park managers protect and manage the 3 million acres of submerged National Park System natural and cultural resources. Of the 74 ocean and Great Lakes park units, the 40 parks with submerged acreage will be the focus in the early years of the SBMP. The NPS and U.S. Geological Survey (USGS) convened a workshop (June 3-5, 2008) in Lakewood, CO. The assembly of experts from the NPS and other Federal and non-Federal agencies clarified the needs and goals of the NPS SBMP and was one of the key first steps in designing the benthic mapping program. The central needs for individual parks, park networks, and regions identified by workshop participants were maps including bathymetry, bottom type, geology, and biology. This workshop, although not an exhaustive survey of data-acquisition technologies, highlighted the more promising technologies being used, existing sources of data, and the need for partnerships to leverage resources. Workshop products include recommended classification schemes and management approaches for consistent application and products similar to other long-term NPS benthic mapping efforts. As part of the SBMP, recommendations from this workshop, including application of an improved version of the Coastal and Marine Ecological Classification Standard (CMECS), will be tested in several pilot parks. In 2008, in conjunction with the findings of this workshop

  6. 5. EAST ELEVATION (OFFICE BLOCK), DETAIL SHOWING DECORATIVE PILASTERS AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. EAST ELEVATION (OFFICE BLOCK), DETAIL SHOWING DECORATIVE PILASTERS AND STYLIZED EGG-AND-DART DECORATION AROUND WINDOWS OF UPPER FLOORS - Delaware, Lackawanna & Western Railroad & Ferry Terminal, Hudson Place, Hoboken, Hudson County, NJ

  7. Encapsulated Fluorescent Ag NPs as Novel Indicators for High-Energy Ionizing Radiation

    DTIC Science & Technology

    2014-06-01

    angstrom atmosphere (normal) bar barn British thermal unit (thermochemical) calorie (thermochemical) cal (thermochemical/cm 2 ) curie degree...which yielded levels near zero (the background spectra were subtracted). However, for the 50 Gy dosage the 16 hr equilibration time was optimal, leading

  8. Gamma radiation synthesis of colloidal AgNPs for its potential application in antimicrobial fabrics

    NASA Astrophysics Data System (ADS)

    Bera, Anuradha; Garai, Purabi; Singh, Rita; Prakash Gupta, P.; Malav, Shatrughan; Singh, Durgeshwer; Kumar, Devendra; Tiwari, B. L.; Vaijapurkar, S. G.

    2015-10-01

    Highly stable colloidal solution of silver nanoparticles in a water-isopropanol-polyvinyl alcohol system was prepared through 60Co-gamma radiation at total dose of 35 kGy at dose rate of 5.67 kGy/h under nitrogen atmosphere. Ultraviolet-visible (UV-vis), X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) of the obtained colloidal solution indicated the formation of spherical shaped well mono dispersed silver nanoparticles with average diameter about 30 nm having very narrow size distribution. The radiolytically obtained nanosilver colloid was coated onto cotton fabrics by a simple industrial screen printing method and its adhesion with the fabric was found out by leaching studies using Atomic Absorption Spectrophotometry (AAS). Good adhesion was achieved by the adopted method wherein 89.5% of the coated nanosilver was retained in the fabric even after keeping the fabrics soaked in water for more than 60 h. Antimicrobial efficacy tests of the nanosilver coated cotton fabric showed that nanosilver coating is effective in killing both bacterial and fungal strains even at very low nanosilver loading (21.81 μgm/cm2). Nanosilver coating on the cotton fabric did not allow microbes (Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Candida albicans) to adhere and proliferate on fabric surface. Staphylococci (Staphylococcus aureus) and Yeast (Candida albicans) showed inhibition zones in presence of these nanosilver coated fabrics while no inhibition zone was observed with the uncoated control fabric.

  9. Kraft lignin/silica-AgNPs as a functional material with antibacterial activity.

    PubMed

    Klapiszewski, Łukasz; Rzemieniecki, Tomasz; Krawczyk, Magdalena; Malina, Dagmara; Norman, Małgorzata; Zdarta, Jakub; Majchrzak, Izabela; Dobrowolska, Anna; Czaczyk, Katarzyna; Jesionowski, Teofil

    2015-10-01

    Advanced functional silica/lignin hybrid materials, modified with nanosilver, were obtained. The commercial silica Syloid 244 was used, modified with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to increase its chemical affinity to lignin. Similarly, kraft lignin was oxidized using a solution of sodium periodate to activate appropriate functional groups on its surface. Silver nanoparticles were grafted onto the resulting silica/lignin hybrids. The systems obtained were comprehensively tested using available techniques and methods, including transmission electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, elemental analysis and atomic absorption spectroscopy. An evaluation was also made of the electrokinetic stability of the systems with and without silver nanoparticles. Conclusions were drawn concerning the chemical nature of the bonds between the precursors and the effectiveness of the method of binding nanosilver to the hybrid materials. The antimicrobial activity of the studied materials was tested against five species of Gram-positive and Gram-negative bacteria. The addition of silver nanoparticles to the silica/lignin hybrids led to inhibition of the growth of the analyzed bacteria. The best results were obtained against Pseudomonas aeruginosa, a dangerous human pathogen.

  10. Plasmon coupling-enhanced two-photon photoluminescence of Au@Ag core-shell nanoparticles and applications in the nuclease assay

    NASA Astrophysics Data System (ADS)

    Yuan, Peiyan; Ma, Rizhao; Gao, Nengyue; Garai, Monalisa; Xu, Qing-Hua

    2015-05-01

    Au and Ag nanoparticles (NPs) have been known to display significantly enhanced two-photon photoluminescence (2PPL) upon the formation of nanoparticle aggregates. The enhancement effect of the core-shell nanoparticles has not been explored so far. Here we have prepared Au@Ag bimetallic core-shell nanoparticles with different thicknesses (1.1, 2.1, 3.5, 4.5, and 5.5 nm) of silver coating on 19 nm Au NPs to investigate the composition effects on plasmon coupling-enhanced 2PPL. A maximum 2PPL enhancement factor (IcoupledNPs/IisolatedNPs) of up to 840-fold was obtained for Au@Ag NPs with ~3.5 nm Ag nanoshells. These Au@Ag NPs were subsequently utilized in two-photon detection of S1 nuclease as a photoluminescence turn on probe. This method displayed high sensitivity with the limit of detection of 1.4 × 10-6 U μL-1 and an excellent selectivity.Au and Ag nanoparticles (NPs) have been known to display significantly enhanced two-photon photoluminescence (2PPL) upon the formation of nanoparticle aggregates. The enhancement effect of the core-shell nanoparticles has not been explored so far. Here we have prepared Au@Ag bimetallic core-shell nanoparticles with different thicknesses (1.1, 2.1, 3.5, 4.5, and 5.5 nm) of silver coating on 19 nm Au NPs to investigate the composition effects on plasmon coupling-enhanced 2PPL. A maximum 2PPL enhancement factor (IcoupledNPs/IisolatedNPs) of up to 840-fold was obtained for Au@Ag NPs with ~3.5 nm Ag nanoshells. These Au@Ag NPs were subsequently utilized in two-photon detection of S1 nuclease as a photoluminescence turn on probe. This method displayed high sensitivity with the limit of detection of 1.4 × 10-6 U μL-1 and an excellent selectivity. Electronic supplementary information (ESI) available: TEM images, histograms of the sizes of Au@Ag NPs; extinction, 2PPL spectra of aggregated NPs, cysteamine, ssDNA and S1 nuclease; 2-photon action cross section of aggregated NPs; lengths of ssDNA and [NaCl] effect; excitation power

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

    PubMed

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

    2016-07-18

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

  12. Thermal conductivity studies of novel nanofluids based on metallic silver decorated mesoporous silica nanoparticles

    SciTech Connect

    Tadjarodi, Azadeh; Zabihi, Fatemeh

    2013-10-15

    Graphical abstract: - Highlights: • Metallic silver was decorated in mSiO{sub 2} with grafted hemiaminal functional groups. • Synthesized nanoparticles were used for preparation of glycerol based nanofluids. • The effect of temperature, weight fraction of mSiO{sub 2} and concentration of silver nanoparticles on thermal conductivity of nanofluids was investigated. - Abstract: In the present study, the mesoporous structure of silica (mSiO{sub 2}) nanoparticles as well as hemiaminal grafted mSiO{sub 2} decorated by metallic silver (Ag/mSiO{sub 2}) has been used for the preparation of glycerol based nanofluids. Structural and morphological characterization of the synthesized products have been carried out using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), UV–vis spectroscopy, inductively coupled plasma (ICP) and N{sub 2} adsorption–desorption isotherms. The thermal conductivity and viscosity of the nanofluids have been measured as a function of temperature for various weight fractions and silver concentrations of mSiO{sub 2} and Ag/mSiO{sub 2} nanoparticles, respectively. The results show that the thermal conductivity of the nanofluids increase up to 9.24% as the weight fraction of mSiO{sub 2} increases up to 4 wt%. Also, increasing the percent of the silver decorated mSiO{sub 2} (Ag/mSiO{sub 2}) up to 2.98% caused an enhancement in the thermal conductivity of the base fluid up to 10.95%. Furthermore, the results show that the nanofluids have Newtonian behavior in the tested temperature range for various concentrations of nanoparticles.

  13. Revamped NPS Brings More Focus to CTE Issues

    ERIC Educational Resources Information Center

    Techniques: Connecting Education and Careers (J3), 2008

    2008-01-01

    In March, attendees at the annual ACTE National Policy Seminar (NPS) got more than they bargained for. With a new hotel and a completely reorganized agenda, career and technical educators were more than energized to bring the career and technical education (CTE) message to Capitol Hill. This year marked the first time ACTE held a special briefing…

  14. 252. Mabry Mill. View of the mill and the NPS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    252. Mabry Mill. View of the mill and the NPS dredged reflecting pond which illustrates how the parkway has manipulated the landscape to make it more picturesque. Looking north-northwest from interpretative trail. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  15. Complete Genome Sequence of Streptococcus sp. Strain NPS 308

    PubMed Central

    Ogura, Yoshitoshi; Sato, Keiko; Imamura, Keigo; Hoshino, Tomonori; Nishiguchi, Miyuki; Hasuwa, Tomoyuki; Moriuchi, Hiroyuki; Hayashi, Tetsuya; Fujiwara, Taku

    2016-01-01

    Streptococcus sp. strain NPS 308, isolated from an 8-year-old girl diagnosed with infective endocarditis, likely presents a novel species of Streptococcus. Here, we present a complete genome sequence of this species, which will contribute to better understanding of the pathogenesis of infective endocarditis. PMID:28007849

  16. Phenylboronic acid-decorated gelatin nanoparticles for enhanced tumor targeting and penetration

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Wei, Bing; Cheng, Xu; Wang, Jun; Tang, Rupei

    2016-09-01

    Phenylboronic acid-decorated nanoparticles (NPs) were prepared for tumor-targeted drug delivery. 3-carboxyphenylboronic acid (3-CPBA) was modified on the surface of conventional gelatin NPs (designated as NP1) to give tumor-targeting NPs (designated as NP2). The morphology and stability of NP1 and NP2 were then investigated using transmission electron microscopy, scanning electron microscopy, and dynamic light scattering. The results show that both NP1 and NP2 are spherical-like and kinetically stable under various conditions. Doxorubicin hydrochloride (DOX) was used as a model anticancer drug and was loaded into NP1 (NP1-DOX) and NP2 (NP2-DOX). The i n vitro cellular uptake and cytotoxicity of NP1-DOX and NP2-DOX were measured using SH-SY5Y cells, H22 cells, and HepG2 cells. Tumor penetration, accumulation, and antitumor activity were investigated using SH-SY5Y tumor-like spheroids and H22 tumor-bearing mice. All results demonstrated that the conjugation of 3-CPBA can efficiently enhance non-targeted NPs’ tumor-homing activity, thus improving their tumor accumulation and antitumor effect.

  17. Synthesis, characterization and multifunctional properties of plasmonic Ag-TiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Prakash, Jai; Kumar, Promod; Harris, R. A.; Swart, Chantel; Neethling, J. H.; Janse van Vuuren, A.; Swart, H. C.

    2016-09-01

    We report on the synthesis of multifunctional Ag-TiO2 nanocomposites and their optical, physio-chemical, surface enhanced Raman scattering (SERS) and antibacterial properties. A series of Ag-TiO2 nanocomposites were synthesized by sol-gel technique and characterized by x-ray diffraction, scanning and transmission electron microscopy, energy-dispersed x-ray analysis, photoluminescence, UV-vis, x-ray photoelectron and Raman spectroscopy and Brunauer-Emmett-Teller method. The Ag nanoparticles (NPs) (7-20 nm) were found to be uniformly distributed around and strongly attached to TiO2 NPs. The novel optical responses of the nanocomposites are due to the strong electric field from the localized surface plasmon (LSP) excitation of the Ag NPs and decreased recombination of photo-induced electrons and holes at Ag-TiO2 interface providing potential materials for photocatalysis. The nanocomposites show enhancement in the SERS signals of methyl orange (MO) molecules with increasing Ag content attributed to the long-range electromagnetic enhancement from the excited LSP of the Ag NPs. To further understand the SERS activity, molecular mechanics and molecular dynamics simulations were used to study the geometries and SERS enhancement of MO adsorbed onto Ag-TiO2 respectively. Simulation results indicate that number of ligands (MO) that adsorb onto the Ag NPs as well as binding energy per ligand increases with increasing NP density and molecule-to-surface orientation is mainly flat resulting in strong bond strength between MO and Ag NP surface and enhanced SERS signals. The antimicrobial activity of the Ag-TiO2 nanocomposites was tested against the bacterium Staphylococcus aureus and enhanced antibacterial effect was observed with increasing Ag content explained by contact killing action mechanism. These results foresee promising applications of the plasmonic metal-semiconductor based nano-biocomposites for both chemical and biological samples.

  18. Synthesis of Au nanoparticles decorated graphene oxide nanosheets: noncovalent functionalization by TWEEN 20 in situ reduction of aqueous chloroaurate ions for hydrazine detection and catalytic reduction of 4-nitrophenol.

    PubMed

    Lu, Wenbo; Ning, Rui; Qin, Xiaoyun; Zhang, Yingwei; Chang, Guohui; Liu, Sen; Luo, Yonglan; Sun, Xuping

    2011-12-15

    In this paper, we develop a cost-effective and simple route for the synthesis of Au nanoparticles (AuNPs) decorated graphene oxide (GO) nanosheets using polyoxyethylene sorbitol anhydride monolaurate (TWEEN 20) as a stabilizing agent for GO as well as a reducing and immobilizing agent for AuNPs. The AuNPs assemble on the surface of TWEEN-functionalized GO by the in situ reduction of HAuCl(4) aqueous solution. The morphologies of these composites were characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is found that the resultant AuNPs decorated GO nanosheets (AuNPs/TWEEN/GO) exhibit remarkable catalytic performance for hydrazine oxidation. This hydrazine sensor has a fast amperometric response time of less than 3s. The linear range is estimated to be from 5 μM to 3 mM (r=0.999), and the detection limit is estimated to be 78 nM at a signal-to-noise ratio of 3. The AuNPs/TWEEN/GO composites also exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the GO supports also enhance the catalytic activity via a synergistic effect.

  19. Morphology Effect of Ni-Ag/CARBON Nanomaterials on Their Electrocatalytic Activity for Glucose Oxidation

    NASA Astrophysics Data System (ADS)

    Ouyang, Ruizhuo; Li, Weiwei; Yang, Yang; Zhang, Wangyao; Feng, Kai; Zong, Tianyu; An, Yarui; Zhou, Shuang; Miao, Yuqing

    2016-06-01

    We presented here three carbon-nanomaterials-based modified glassy carbon electrodes (GCE) with Ni-Ag nanohybrid nanoparticles (NPs) deposited upon, including single-wall carbon nanotubes (SWCNTs), multi-wall carbon nanotubes (MWCNTs) and the mesoporous carbons (MPCs), and compared their morphology effects on both Ni-Ag deposition quality and electrocatalytic performances toward Glu oxidation. After being deposited with Ni-Ag NPs, a homogenous surface with very small Ni-Ag NPs was obtained for Ni-Ag/SWCNTs/GCE, while heterogeneous, coarse surfaces with obvious embedment with large Ni-Ag particles were observed for both Ni-Ag/MWCNTs/GCE and Ni-Ag/MPC/GCE. All three modified electrodes were well characterized in terms of surface morphology, electron transfer rate, hydrophilicity, interference resistance, stability, electrocatalytic behaviors as well as practicability in real samples, based on which Ni-Ag/SWCNTs/GCE was always proved to be more advantageous over other two composite electrodes. Such advantage of Ni-Ag/SWCNTs/GCE was attributed to its desirable surface morphology good for Ni-Ag deposition and exposure of as many active sites as possible to Glu oxidation, leading to the extraordinary electrocatalytic performance.

  20. 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

  1. Total synthesis of isotopically enriched Si-29 silica NPs as potential spikes for isotope dilution quantification of natural silica NPs.

    PubMed

    Pálmai, Marcell; Szalay, Roland; Bartczak, Dorota; Varga, Zoltán; Nagy, Lívia Naszályi; Gollwitzer, Christian; Krumrey, Michael; Goenaga-Infante, Heidi

    2015-05-01

    A new method was developed for the preparation of highly monodisperse isotopically enriched Si-29 silica nanoparticles ((29)Si-silica NPs) with the purpose of using them as spikes for isotope dilution mass spectrometry (IDMS) quantification of silica NPs with natural isotopic distribution. Si-29 tetraethyl orthosilicate ((29)Si-TEOS), the silica precursor was prepared in two steps starting from elementary silicon-29 pellets. In the first step Si-29 silicon tetrachloride ((29)SiCl4) was prepared by heating elementary silicon-29 in chlorine gas stream. By using a multistep cooling system and the dilution of the volatile and moisture-sensitive (29)SiCl4 in carbon tetrachloride as inert medium we managed to reduce product loss caused by evaporation. (29)Si-TEOS was obtained by treating (29)SiCl4 with absolute ethanol. Structural characterisation of (29)Si-TEOS was performed by using (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform infrared (FTIR) spectroscopy. For the NP preparation, a basic amino acid catalysis route was used and the resulting NPs were analysed using transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), dynamic light scattering (DLS) and zeta potential measurements. Finally, the feasibility of using enriched NPs for on-line field-flow fractionation coupled with multi-angle light scattering and inductively coupled plasma mass spectrometry (FFF/MALS/ICP-MS) has been demonstrated.

  2. Agglomeration in core-shell structure of CuAg nanoparticles synthesized by the laser ablation of Cu target in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Petrović, S.; Salatić, B.; Milovanović, D.; Lazović, V.; Živković, Lj; Trtica, M.; Jelenković, B.

    2015-02-01

    Metallic copper Cu and bimetallic copper-silver CuAg nanoparticles (NPs) are generated by the ablation of copper bulk target in water and aqueous Ag colloidal solution, respectively. The experiments were performed using nanosecond Nd:YAG laser operating at 1064 nm. The generated NPs are characterized by UV-vis absorption spectroscopy, laser-induced breakdown spectroscopy, dynamic light scattering and scanning electron microscopy. The conducted investigations can be summarized as follows: (i) CuAg NPs colloidal solution possess the absorption in UV-vis spectral region, which can be attributed to the Cu-component; (ii) the primary bimetallic CuAg NPs have near uniform dimensions with diameter of about 15 nm, and as a rule, they are grouped into larger agglomerates without defined morphology; (iii) the obtained Cu NPs have mainly spherical form with average diameters up to 20 nm. Both types of NPs show a tendency towards the formation of large agglomerates with different morphology. Bimetallic NPs show the plasmon resonance in the vicinity of 640 nm with a good coincidence with formation of the colloidal solution of pure Cu NPs. The results also demonstrate that the core-shell structure (Ag-rich core/Cu-rich shell) is important for the formation of the bimetallic NPs, also agreeing very well with theory.

  3. Synthesis of Pt nanoparticles decorated 1,5-diaminoanthraquinone nanofibers and their application toward catalytic reduction of 4-nitrophenol.

    PubMed

    Chang, Guohui; Luo, Yonglan; Qin, Xiaoyun; Lu, Wenbo; Asiri, Abdullah M; Al-Youbi, Abdulrahman O; Sun, Xuping

    2012-09-01

    The present communication reports on the rapid preparation of 1,5-diaminoanthraquinone nanofibers (DAAQNFs) on a large scale by a reprecipitation method and their subsequent decoration with small platinum nanoparticles (PtNPs) using tannic acid (TA) as a reducing agent. It suggests the resultant PtNP/DAAQNF composites exhibit a good catalytic activity toward reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4. It also suggests that the composites exhibit higher catalytic activity than the PtNPs due to that the DAAQNF support may play an active part in the catalysis, yielding a synergistic effect. The possible mechanism involved has also been discussed.

  4. Connections on decorated path space bundles

    NASA Astrophysics Data System (ADS)

    Chatterjee, Saikat; Lahiri, Amitabha; Sengupta, Ambar N.

    2017-02-01

    For a principal bundle P → M equipped with a connection A ¯ , we study an infinite dimensional bundle PA¯ dec P over the space of paths on M, with the points of PA¯ dec P being horizontal paths on P decorated with elements of a second structure group. We construct parallel transport processes on such bundles and study holonomy bundles in this setting.

  5. 10 Ways to...Decorate Your Classroom

    ERIC Educational Resources Information Center

    Prescott, Jennifer

    2005-01-01

    Recruit the best decorating corps you have for this year's classroom makeover--your students! Not only does involving kids save money and effort on your part, teachers agree that it increases kids' sense of involvement and respect. In this article, the author presents 10 teacher-tested ideas for a classroom that shines with color and learning: (1)…

  6. Synergistic interactions between silver decorated graphene and carbon nanotubes yield flexible composites to attenuate electromagnetic radiation

    NASA Astrophysics Data System (ADS)

    Patangrao Pawar, Shital; Kumar, Sachin; Jain, Shubham; Gandi, Mounika; Chatterjee, Kaushik; Bose, Suryasarathi

    2017-01-01

    The need of today’s highly integrated electronic devices, especially working in the GHz frequencies, is to protect them from unwanted interference from neighbouring devices. Hence, lightweight, flexible, easy to process microwave absorbers were designed here by dispersing conductive multiwall carbon nanotubes (MWNTs) and silver nanoparticles decorated onto two-dimensional graphene sheets (rGO@Ag) in poly(ɛ-caprolactone) (PCL). In this study, we have shown how dielectric losses can be tuned in the nanocomposites by rGO@Ag nano-hybrid; an essential criterion for energy dissipation within a material resulting in effective shielding of the incoming electromagnetic (EM) radiation. Herein, the conducting pathway for nomadic charge transfer in the PCL matrix was established by MWNTs and the attenuation was tuned by multiple scattering due to the large specific surface area of rGO@Ag. The latter was possible because of the fine dispersion state of the Ag nanoparticles which otherwise often agglomerate if mixed separately. The effect of individual nanoparticles on microwave attenuation was systematically assessed here. It was observed that this strategy resulted in strikingly enhanced microwave attenuation in PCL nanocomposites in contrast to addition of individual particles. For instance, PCL nanocomposites containing both MWNTs and rGO@Ag manifested in a SET of -37 dB and, interestingly, at arelatively smaller fraction. The SE shown by this particular composite makes it a potential candidate for many commercial applications as reflected by its exceptional absorption capability (91.3%).

  7. Supercritical Fluid Synthesis and Tribological Applications of Silver Nanoparticle-decorated Graphene in Engine Oil Nanofluid.

    PubMed

    Meng, Yuan; Su, Fenghua; Chen, Yangzhi

    2016-08-04

    Silver nanoparticle-decorated graphene nanocomposites were synthesized by a facile chemical reduction approach with the assistance of supercritical CO2 (ScCO2). The silver nanoparticles with diameters of 2-16 nm are uniformly distributed and firmly anchored on graphene nanosheets. The tribological properties of the as-synthesized nanocomposites as lubricant additives in engine oil were investigated by a four-ball tribometer. The engine oil with 0.06~0.10 wt.% Sc-Ag/GN nanocomposites displays remarkable lubricating performance, superior than the pure engine oil, the engine oil containing zinc dialkyl dithiophosphate (ZDDP), as well as the oil dispersed with the single nanomaterial of graphene oxides (GOs) and nano-Ag particles alone. The remarkable lubricating behaviors of Sc-Ag/GN probably derive from the synergistic interactions of nano-Ag and graphene in the nanocomposite and the action of the formed protective film on the contact balls. The anchored nano-Ag particles on graphene expand the interlamination spaces of graphene nanosheets and can prevent them from restacking during the rubbing process, resulting in the full play of lubricating activity of graphene. The formed protective film on the friction pairs significantly reduces the surface roughness of the sliding balls and hence preventing them from direct interaction during the sliding process.

  8. Supercritical Fluid Synthesis and Tribological Applications of Silver Nanoparticle-decorated Graphene in Engine Oil Nanofluid

    NASA Astrophysics Data System (ADS)

    Meng, Yuan; Su, Fenghua; Chen, Yangzhi

    2016-08-01

    Silver nanoparticle-decorated graphene nanocomposites were synthesized by a facile chemical reduction approach with the assistance of supercritical CO2 (ScCO2). The silver nanoparticles with diameters of 2–16 nm are uniformly distributed and firmly anchored on graphene nanosheets. The tribological properties of the as-synthesized nanocomposites as lubricant additives in engine oil were investigated by a four-ball tribometer. The engine oil with 0.06~0.10 wt.% Sc-Ag/GN nanocomposites displays remarkable lubricating performance, superior than the pure engine oil, the engine oil containing zinc dialkyl dithiophosphate (ZDDP), as well as the oil dispersed with the single nanomaterial of graphene oxides (GOs) and nano-Ag particles alone. The remarkable lubricating behaviors of Sc-Ag/GN probably derive from the synergistic interactions of nano-Ag and graphene in the nanocomposite and the action of the formed protective film on the contact balls. The anchored nano-Ag particles on graphene expand the interlamination spaces of graphene nanosheets and can prevent them from restacking during the rubbing process, resulting in the full play of lubricating activity of graphene. The formed protective film on the friction pairs significantly reduces the surface roughness of the sliding balls and hence preventing them from direct interaction during the sliding process.

  9. Supercritical Fluid Synthesis and Tribological Applications of Silver Nanoparticle-decorated Graphene in Engine Oil Nanofluid

    PubMed Central

    Meng, Yuan; Su, Fenghua; Chen, Yangzhi

    2016-01-01

    Silver nanoparticle-decorated graphene nanocomposites were synthesized by a facile chemical reduction approach with the assistance of supercritical CO2 (ScCO2). The silver nanoparticles with diameters of 2–16 nm are uniformly distributed and firmly anchored on graphene nanosheets. The tribological properties of the as-synthesized nanocomposites as lubricant additives in engine oil were investigated by a four-ball tribometer. The engine oil with 0.06~0.10 wt.% Sc-Ag/GN nanocomposites displays remarkable lubricating performance, superior than the pure engine oil, the engine oil containing zinc dialkyl dithiophosphate (ZDDP), as well as the oil dispersed with the single nanomaterial of graphene oxides (GOs) and nano-Ag particles alone. The remarkable lubricating behaviors of Sc-Ag/GN probably derive from the synergistic interactions of nano-Ag and graphene in the nanocomposite and the action of the formed protective film on the contact balls. The anchored nano-Ag particles on graphene expand the interlamination spaces of graphene nanosheets and can prevent them from restacking during the rubbing process, resulting in the full play of lubricating activity of graphene. The formed protective film on the friction pairs significantly reduces the surface roughness of the sliding balls and hence preventing them from direct interaction during the sliding process. PMID:27488733

  10. 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.

  11. Long and short term impacts of CuO, Ag and CeO2 nanoparticles on anaerobic digestion of municipal waste activated sludge.

    PubMed

    Ünşar, E Kökdemir; Çığgın, A S; Erdem, A; Perendeci, N A

    2016-02-01

    In this study, long and short term inhibition impacts of Ag, CuO and CeO2 nanoparticles (NPs) on anaerobic digestion (AD) of waste activated sludge (WAS) were investigated. CuO NPs were detected as the most toxic NPs on AD. As the CuO NP concentration increased from 5 to 1000 mg per gTS, an increase in the inhibition of AD from 5.8 to 84.0% was observed. EC50 values of short and long term inhibitions were calculated as 224.2 mgCuO per gTS and 215.1 mgCuO per gTS, respectively. Ag and CeO2 NPs did not cause drastic impacts on AD as compared to CuO NPs. In the long term test, Ag NPs created 12.1% decrease and CeO2 NPs caused 9.2% increase in the methane production from WAS at the highest dosage. FISH imaging also revealed that the abundance of Archaea in raw WAS was similar in short and long term tests carried out with WAS containing Ag and CeO2 NPs. On the other hand, CuO NPs caused inhibition of Archaea in the long term test. Digestion kinetics of WAS containing Ag, CeO2, CuO NPs were also evaluated with Gompertz, Logistic, Transference and First Order models. The hydrolysis rate constant (kH) for each concentration of Ag and CeO2 NPs and the raw WAS was 0.027745 d(-1) while the kH of WAS containing high concentrations of CuO NPs was found to be 0.001610 d(-1).

  12. Icosahedral quasicrystal decoration models. I. Geometrical principles

    SciTech Connect

    Mihalkovic, M. |; Zhu, W.; Henley, C.L.; Oxborrow, M. |

    1996-04-01

    It is proposed that quasicrystal structure determination should include the calculation of cohesive energies using realistic potentials. A class of atomic decoration models for {ital i}-AlMn is then presented, adopting the {open_quote}{open_quote}canonical-cell{close_quote}{close_quote} tiling geometry, with {open_quote}{open_quote}Mackay icosahedron{close_quote}{close_quote} clusters placed on all its nodes. The remaining atomic positions are based, as far as possible, on the known structure of {alpha}-AlMnSi. These models guarantee good local packing of the atoms, whose displacements away from {open_quote}{open_quote}ideal{close_quote}{close_quote} positions are specified by only a moderate number of parameters. Certain atomic sites are uncertain as regards their occupancy and/or chemistry; variations of the decoration rules on these sites must be compared, in order to discover the correct one. Our models are well adapted to be relaxed under an effective Hamiltonian to optimize the cohesive energy; we show how the energies found in such relaxations can be used to extract an effective tile-tile Hamiltonian, as would be needed for future studies of phason elasticity and the development of long-range order. In addition, we clarify concepts needed for decoration models in general (in particular, the ways in which elaborate, more realistic decorations may be evolved from simpler ones). We also show that these decoration models are closely related, but not identical, to quasiperiodic structures defined using six-dimensional formalism. {copyright} {ital 1996 The American Physical Society.}

  13. One-Step Fabrication of 3D Nanohierarchical Nickel Nanomace Array To Sinter with Silver NPs and the Interfacial Analysis.

    PubMed

    Zhou, Wei; Zheng, Zhen; Wang, Chunqing; Wang, Zhongtao; An, Rong

    2017-02-08

    Three-dimensional (3D) nanohierarchical Ni nanomace (Ni NM) array was fabricated on copper substrate by only one step with electroplating method, the unique structure was covered with Au film (Ni/Au NM) without changing its morphology, and in the following step, it was sintered with silver nanoparticle (Ag NP) paste. The structure of the Ni NM array and its surface morphology were characterized by X-ray diffraction, scanning electron microscope (SEM), and atomic force microscope. The sintered interface was investigated by SEM, transmission electron microscopy, and energy-dispersive X-ray spectroscopy to analyze the sintering mechanism. The results showed that a metallurgical bond was successfully achieved at 250 °C without any gas or vacuum shield and extra pressure. The Cu substrate with Ni/Au NM array was able to join with the Ag NP paste without obvious voids. Due to the compatible chemical potential between Ag NPs and Ni/Au NM array, the Au element was able to diffuse into the Ag layer with about 800 nm distance. Based on the excellent 3D nanohierarchical structure, the shear strength of Ni/Au NM array was 6 times stronger than the flat Ni/Au coated substrate. It turned out that the substrate surface played a crucial role in improving the shear strength and sintering efficiency. The 3D Ni NM array had achieved an excellent bonding interface and had great potential application in the microelectronics packaging field.

  14. Synthesis of Ag-ZnO with multiple rods (multipods) morphology and its application in the simultaneous photo-catalytic degradation of methyl orange and methylene blue.

    PubMed

    Arab Chamjangali, M; Bagherian, G; Javid, A; Boroumand, S; Farzaneh, N

    2015-11-05

    In this study, the photo-decolorization of a mixture of methylene blue (MB) and methyl orange (MO) was investigated using Ag-ZnO multipods. The photo-catalyst used, ZnO multipods, was successfully synthesized. The surface of ZnO microstructure was modified by deposition of different amounts of Ag nanoparticles (Ag NPs) using the photo-reduction method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis and atomic absorption spectroscopy. The photo-catalytic efficiency of Ag-ZnO is mainly controlled by the amount of Ag NPs deposited on the ZnO surface. The results obtained suggest that Ag-ZnO containing 6.5% Ag NPs, has the highest photo-catalytic performance in the simultaneous photo-degradation of dyes at a shorter time.

  15. 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.

  16. Mass Transportation for NPS: A Financial Feasibility Study

    DTIC Science & Technology

    1992-06-01

    approximately 20 MPG) multiplied by a fuel cost of $1.20 per gallon. The average automobile MPG was obtained from 1992 World Almanac . 23 Fortunately for the NPS... Almanac , The World Almanac and Book of Facts 1992, Pharos Books, 1991. 23. Stickney, Clyde P., Weil, Roman L., and Davidson, Sidney, Financial Accounting...You Want It? Cleaner Air Will Require Dramatic Changes in How We Live, Work and Get Around," Motorland, p.44, November/December 1991. 22. World

  17. NPS Government Purchase Card Program: An Analysis of Internal Controls

    DTIC Science & Technology

    2014-03-18

    monthly AO and CH account statements (GSA, n.d.-d). The government has partnerships with Citibank , JP Morgan Chase, and U.S. Bank (GSA, n.d.-b), and... Citibank to process all types of transactions, including those made with the purchase, travel, and fleet card. However, the DoD’s independent agencies also...purchase card training. Furthermore, DoD annual ethics training is required as well. Initial training with Citibank is required, and NPS also requires that

  18. California Current Monitoring Using the NPS Ocean Acoustic Observatory

    DTIC Science & Technology

    2016-06-07

    term research goals are: 1. To achieve a permanent, real-time capability in monitoring the meso- to large-scale temperature variability off Central...frequency sound traveling initially downslope from a seamount, through the California Current Front over deep water, and then upslope through inshore...Nicholas and Centerville SOSUS arrays, and an autonomous low-frequency sound source. While the Pt Sur array is operated by the NPS OAO, the San

  19. Biofabrication of Ag nanoparticles using Sterculia foetida L. seed extract and their toxic potential against mosquito vectors and HeLa cancer cells.

    PubMed

    Rajasekharreddy, Pala; Rani, Pathipati Usha

    2014-06-01

    A one-step and eco-friendly process for the synthesis of silver-(protein-lipid) nanoparticles (Ag-PL NPs) (core-shell) has been developed using the seed extract from wild Indian Almond tree, Sterculia foetida (L.) (Sterculiaceae). The reaction temperature played a major role in controlling the size and shell formation of NPs. The amount of NPs synthesized and qualitative characterization was done by UV-vis spectroscopy and transmission electron microscopy (TEM), respectively. TEM studies exhibited controlled dispersity of spherical shaped NPs with an average size of 6.9±0.2nm. Selected area electron diffraction (SAED) and X-ray diffraction (XRD) revealed 'fcc' phase and crystallinity of the particles. X-ray photoelectron spectroscopy (XPS) was used to identify the protein-lipid (PL) bilayer that appears as a shell around the Ag core particles. The thermal stability of the Ag-PL NPs was examined using thermogravimetric analysis (TGA). Further analysis was carried out by using Fourier transform infrared spectroscopy (FTIR), where the spectra provided evidence for the presence of proteins and lipid moieties ((2n-octylcycloprop-1-enyl)-octanoic acid (I)), and their role in synthesis and stabilization of Ag NPs. This is the first report of plant seed assisted synthesis of PL conjugated Ag NPs. These formed Ag-PL NPs showed potential mosquito larvicidal activity against Aedes aegypti (L.), Anopheles stephensi Liston and Culex quinquefasciatus Say. These Ag-PL NPs can also act as promising agents in cancer therapy. They exhibited anti-proliferative activity against HeLa cancer cell lines and a promising toxicity was observed in a dose dependent manner. Toxicity studies were further supported by the cellular DNA fragmentation in the Ag-PL NPs treated HeLa cells.

  20. Ag@Ag8W4O16 nanoroasted rice beads with photocatalytic, antibacterial and anticancer activity.

    PubMed

    Selvamani, Muthamizh; Krishnamoorthy, Giribabu; Ramadoss, Manigandan; Sivakumar, Praveen Kumar; Settu, Munusamy; Ranganathan, Suresh; Vengidusamy, Narayanan

    2016-03-01

    Increasing resistance of pathogens and cancer cell line towards antibiotics and anticancer agents has caused serious health problems in the past decades. Due to these problems in recent years, researchers have tried to combine nanotechnology with material science to have intrinsic antimicrobial and anticancer activity. The metals and metal oxides were investigated with respect to their antimicrobial and anticancer effects towards bacteria and cancer cell line. In the present work metal@metal tungstate (Ag@Ag8W4O16 nanoroasted rice beads) is investigated for antibacterial activity against Escherichia coli and Staphylococcus aureus using Mueller-Hinton broth and the anticancer activity against B16F10 cell line was studied. Silver decorated silver tungstate (Ag@Ag8W4O16) was synthesized by the microwave irradiation method using Cetyl Trimethyl Ammonium Bromide (CTAB). Ag@Ag8W4O16 was characterized by using various spectroscopic techniques. The phase and crystalline nature were analyzed by using XRD. The morphological analysis was carried out using Field Emission Scanning Electron Microscopy (FE-SEM), and High Resolution Transmission Electron Microscopy (HR-TEM). Further, Fourier Transform Infrared Spectroscopy (FT-IR) and Raman spectral analysis were carried out in order to ascertain the presence of functional groups in Ag@Ag8W4O16. The optical property was investigated using Diffuse Reflectance Ultraviolet-Visible Spectroscopy (DRS-UV-Vis) and the band gap was found to be 3.08eV. Surface area of the synthesized Ag@Ag8W4O16 wasanalyzed by BET analysis and Ag@Ag8W4O16 was utilized for the degradation of organic dyes methylene blue and rhodamine B. The morphology of the Ag@Ag8W4O16 resembles roasted rice beads with breath and length in nm range. The oxidation state of tungsten (W) and silver (Ag) was investigated using X-ray photoelectron spectroscopy (XPS).

  1. Earthworm coelomocytes as nanoscavenger of ZnO NPs

    NASA Astrophysics Data System (ADS)

    Gupta, Shruti; Kushwah, Tanuja; Yadav, Shweta

    2014-05-01

    Earthworms can `biotransform' or `biodegrade' chemical contaminants, rendering them harmless in their bodies, and can bioaccumulate them in their tissues. They `absorb' the dissolved chemicals through their moist `body wall' due to the interstitial water and also ingest by `mouth' while soil passes through the gut. Since the advent of the nanotechnology era, the environmental sink has been continuously receiving engineered nanomaterials as well as their derivatives. Our current understanding of the potential impact of nanomaterials and their natural scavenger is limited. In the present investigation, we studied the cellular uptake of ZnO nanoparticles (NPs) by coelomocytes especially by chloragocytes of Eisenia fetida and their role as nanoscavenger. Results from exposure to 100- and 50-nm ZnO NPs indicate that coelomocytes of the earthworm E. fetida show no significant DNA damage at a dose lower than 3 mg/l and have the potential ability to uptake ZnO NPs from the soil ecosystem and transform them into microparticles.

  2. Earthworm coelomocytes as nanoscavenger of ZnO NPs

    PubMed Central

    2014-01-01

    Earthworms can ‘biotransform’ or ‘biodegrade’ chemical contaminants, rendering them harmless in their bodies, and can bioaccumulate them in their tissues. They ‘absorb’ the dissolved chemicals through their moist ‘body wall’ due to the interstitial water and also ingest by ‘mouth’ while soil passes through the gut. Since the advent of the nanotechnology era, the environmental sink has been continuously receiving engineered nanomaterials as well as their derivatives. Our current understanding of the potential impact of nanomaterials and their natural scavenger is limited. In the present investigation, we studied the cellular uptake of ZnO nanoparticles (NPs) by coelomocytes especially by chloragocytes of Eisenia fetida and their role as nanoscavenger. Results from exposure to 100- and 50-nm ZnO NPs indicate that coelomocytes of the earthworm E. fetida show no significant DNA damage at a dose lower than 3 mg/l and have the potential ability to uptake ZnO NPs from the soil ecosystem and transform them into microparticles. PMID:24959107

  3. Size-dependent cytotoxicity of silver nanoparticles in human lung cells: the role of cellular uptake, agglomeration and Ag release

    PubMed Central

    2014-01-01

    Background Silver nanoparticles (AgNPs) are currently one of the most manufactured nanomaterials. A wide range of toxicity studies have been performed on various AgNPs, but these studies report a high variation in toxicity and often lack proper particle characterization. The aim of this study was to investigate size- and coating-dependent toxicity of thoroughly characterized AgNPs following exposure of human lung cells and to explore the mechanisms of toxicity. Methods BEAS-2B cells were exposed to citrate coated AgNPs of different primary particle sizes (10, 40 and 75 nm) as well as to 10 nm PVP coated and 50 nm uncoated AgNPs. The particle agglomeration in cell medium was investigated by photon cross correlation spectroscopy (PCCS); cell viability by LDH and Alamar Blue assay; ROS induction by DCFH-DA assay; genotoxicity by alkaline comet assay and γH2AX foci formation; uptake and intracellular localization by transmission electron microscopy (TEM); and cellular dose as well as Ag release by atomic absorption spectroscopy (AAS). Results The results showed cytotoxicity only of the 10 nm particles independent of surface coating. In contrast, all AgNPs tested caused an increase in overall DNA damage after 24 h assessed by the comet assay, suggesting independent mechanisms for cytotoxicity and DNA damage. However, there was no γH2AX foci formation and no increased production of intracellular reactive oxygen species (ROS). The reasons for the higher toxicity of the 10 nm particles were explored by investigating particle agglomeration in cell medium, cellular uptake, intracellular localization and Ag release. Despite different agglomeration patterns, there was no evident difference in the uptake or intracellular localization of the citrate and PVP coated AgNPs. However, the 10 nm particles released significantly more Ag compared with all other AgNPs (approx. 24 wt% vs. 4–7 wt%) following 24 h in cell medium. The released fraction in cell medium did not induce any

  4. Various types of semiconductor photocatalysts modified by CdTe QDs and Pt NPs for toluene photooxidation in the gas phase under visible light

    NASA Astrophysics Data System (ADS)

    Marchelek, M.; Grabowska, E.; Klimczuk, T.; Lisowski, W.; Zaleska-Medynska, A.

    2017-01-01

    A novel synthesis process was used to prepare TiO2 microspheres, TiO2 P-25, SrTiO3 and KTaO3 decorated by CdTe QDs and/or Pt NPs. The effect of semiconductor matrix, presence of CdTe QDs and/or Pt NPs on the semiconductor surface as well as deposition technique of Pt NPs (photodeposition or radiolysis) on the photocatalytic activity were investigated. The as-prepared samples were characterized by X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) with energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), photoluminescence spectrometry (PL), Fourier transform infrared (FT-IR) and Raman spectra, diffuse reflectance spectroscopy (DRS) and BET surface area analysis. The photocatalytic decomposition of toluene in gas phase, activated by light-emitting diodes (LEDs), with the CdTe/Pt nanoparticles-modified TiO2 microspheres, P25, SrTiO3 and KTaO3 semiconductors was investigated under UV-vis and visible irradiation.The results showed that the photoactivity depends on semiconductor matrix. The highest photoactivity under Vis light was observed for KTaO3/CdTe-Pt(R) sample (56% of toluene was decompose after 30 min of irradiation). The efficiency of the most active sample was 3 times higher than result for P25 and two times higher than for unmodified KTaO3.

  5. Using the M13 Phage as a Biotemplate to Create Mesoporous Structures Decorated with Gold and Platinum Nanoparticles.

    PubMed

    Vera-Robles, L Irais; González-Gracida, Jaqueline; Hernández-Gordillo, Armin; Campero, Antonio

    2015-08-25

    By taking advantage of the physical and chemical properties of the M13 bacteriophage, we have used this virus to synthesize mesoporous silica structures. Major coat protein p8 was chemically modified by attaching thiol groups. As we show, the resulting thiolated phage can be used as a biotemplate able to direct the formation of mesoporous silica materials. Simultaneously, this thiol functionality acts as an anchor for binding metal ions, such as Au(3+) and Pt(4+), forming reactive M13-metal ionic complexes which evolve into metal nanoparticles (NPs) trapped in the mesoporous network. Interestingly, Au(3+) ions are reduced to Au(0) NPs by the protein residues without requiring an external reducing agent. Likewise, silica mesostructures decorated with Au and Pt NPs are prepared in a one-pot synthesis and characterized using different techniques. The obtained results allow us to propose a mechanism of formation. In addition, gold-containing mesoporous structures are tested for the reduction of 4-nitrophenol (4-NP) and methylene blue (MB) in the presence of NaBH4. Although all of the gold-containing catalysts exhibit catalytic activity, those obtained with thiolated phages present a better performance than that obtained with M13 alone. This behavior is ascribed to the position of the Au NPs, which are partially embedded in the wall of the final mesostructures.

  6. Cobalt/copper-decorated carbon nanofibers as novel non-precious electrocatalyst for methanol electrooxidation

    PubMed Central

    2014-01-01

    In this study, Co/Cu-decorated carbon nanofibers are introduced as novel electrocatalyst for methanol oxidation. The introduced nanofibers have been prepared based on graphitization of poly(vinyl alcohol) which has high carbon content compared to many polymer precursors for carbon nanofiber synthesis. Typically, calcination in argon atmosphere of electrospun nanofibers composed of cobalt acetate tetrahydrate, copper acetate monohydrate, and poly(vinyl alcohol) leads to form carbon nanofibers decorated by CoCu nanoparticles. The graphitization of the poly(vinyl alcohol) has been enhanced due to presence of cobalt which acts as effective catalyst. The physicochemical characterization affirmed that the metallic nanoparticles are sheathed by thin crystalline graphite layer. Investigation of the electrocatalytic activity of the introduced nanofibers toward methanol oxidation indicates good performance, as the corresponding onset potential was small compared to many reported materials; 310 mV (vs. Ag/AgCl electrode) and a current density of 12 mA/cm2 was obtained. Moreover, due to the graphite shield, good stability was observed. Overall, the introduced study opens new avenue for cheap and stable transition metals-based nanostructures as non-precious catalysts for fuel cell applications. PMID:24387682

  7. Cobalt/copper-decorated carbon nanofibers as novel non-precious electrocatalyst for methanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Barakat, Nasser A. M.; El-Newehy, Mohamed; Al-Deyab, Salem S.; Kim, Hak Yong

    2014-01-01

    In this study, Co/Cu-decorated carbon nanofibers are introduced as novel electrocatalyst for methanol oxidation. The introduced nanofibers have been prepared based on graphitization of poly(vinyl alcohol) which has high carbon content compared to many polymer precursors for carbon nanofiber synthesis. Typically, calcination in argon atmosphere of electrospun nanofibers composed of cobalt acetate tetrahydrate, copper acetate monohydrate, and poly(vinyl alcohol) leads to form carbon nanofibers decorated by CoCu nanoparticles. The graphitization of the poly(vinyl alcohol) has been enhanced due to presence of cobalt which acts as effective catalyst. The physicochemical characterization affirmed that the metallic nanoparticles are sheathed by thin crystalline graphite layer. Investigation of the electrocatalytic activity of the introduced nanofibers toward methanol oxidation indicates good performance, as the corresponding onset potential was small compared to many reported materials; 310 mV (vs. Ag/AgCl electrode) and a current density of 12 mA/cm2 was obtained. Moreover, due to the graphite shield, good stability was observed. Overall, the introduced study opens new avenue for cheap and stable transition metals-based nanostructures as non-precious catalysts for fuel cell applications.

  8. Cobalt/copper-decorated carbon nanofibers as novel non-precious electrocatalyst for methanol electrooxidation.

    PubMed

    Barakat, Nasser A M; El-Newehy, Mohamed; Al-Deyab, Salem S; Kim, Hak Yong

    2014-01-03

    In this study, Co/Cu-decorated carbon nanofibers are introduced as novel electrocatalyst for methanol oxidation. The introduced nanofibers have been prepared based on graphitization of poly(vinyl alcohol) which has high carbon content compared to many polymer precursors for carbon nanofiber synthesis. Typically, calcination in argon atmosphere of electrospun nanofibers composed of cobalt acetate tetrahydrate, copper acetate monohydrate, and poly(vinyl alcohol) leads to form carbon nanofibers decorated by CoCu nanoparticles. The graphitization of the poly(vinyl alcohol) has been enhanced due to presence of cobalt which acts as effective catalyst. The physicochemical characterization affirmed that the metallic nanoparticles are sheathed by thin crystalline graphite layer. Investigation of the electrocatalytic activity of the introduced nanofibers toward methanol oxidation indicates good performance, as the corresponding onset potential was small compared to many reported materials; 310 mV (vs. Ag/AgCl electrode) and a current density of 12 mA/cm2 was obtained. Moreover, due to the graphite shield, good stability was observed. Overall, the introduced study opens new avenue for cheap and stable transition metals-based nanostructures as non-precious catalysts for fuel cell applications.

  9. Uptake and translocation of metals and nutrients in tomato grown in soil polluted with metal oxide (CeO₂, Fe₃O₄, SnO₂, TiO₂) or metallic (Ag, Co, Ni) engineered nanoparticles.

    PubMed

    Vittori Antisari, Livia; Carbone, Serena; Gatti, Antonietta; Vianello, Gilmo; Nannipieri, Paolo

    2015-02-01

    The influence of exposure to engineered nanoparticles (NPs) was studied in tomato plants, grown in a soil and peat mixture and irrigated with metal oxides (CeO2, Fe3O4, SnO2, TiO2) and metallic (Ag, Co, Ni) NPs. The morphological parameters of the tomato organs, the amount of component metals taken up by the tomato plants from NPs added to the soil and the nutrient content in different tomato organs were also investigated. The fate, transport and possible toxicity of different NPs and nutrients in tomato tissues from soils were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The tomato yield depended on the NPs: Fe3O4-NPs promoted the root growth, while SnO2-NP exposure reduced it (i.e. +152.6 and -63.1 % of dry matter, respectively). The NP component metal mainly accumulated in the tomato roots; however, plants treated with Ag-, Co- and Ni-NPs showed higher concentration of these elements in both above-ground and below-ground organs with respect to the untreated plants, in addition Ag-NPs also contaminated the fruits. Moreover, an imbalance of K translocation was detected in some plants exposed to Ag-, Co- and Fe3O4-NPs. The component metal concentration of soil rhizosphere polluted with NPs significantly increased compared to controls, and NPs were detected in the tissues of the tomato roots using electron microscopy (ESEM-EDS).

  10. 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%.

  11. Synergistic influence of polyoxometalate surface corona towards enhancing the antibacterial performance of tyrosine-capped Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Daima, Hemant K.; Selvakannan, P. R.; Kandjani, Ahmad E.; Shukla, Ravi; Bhargava, Suresh K.; Bansal, Vipul

    2013-12-01

    We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNPs) by their surface modification with the surface corona of biologically active polyoxometalates (POMs). The stable POM surface corona was achieved by utilising zwitterionic tyrosine amino acid as a pH-switchable reducing and capping agent of AgNPs. The general applicability of this approach was demonstrated by developing surface coronas of phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) around AgNPs. Our investigations on Gram negative bacterium Escherichia coli demonstrate that in conjugation with AgNPs, the surface corona of POMs enhances the physical damage to the bacterial cells due to synergistic antibacterial action of AgNPs and POMs, and the ability of tyrosine-reduced AgNPs (AgNPsY) to act as an excellent carrier and stabiliser for the POMs. The further extension of this study towards Gram positive bacterium Staphylococcus albus showed a similar toxicity pattern, whereas these nanomaterials were found to be biocompatible for PC3 epithelial mammalian cells, suggesting the potential of these materials towards specific antimicrobial targeting for topical wound healing applications. The outcomes of this work show that facile tailorability of nanostructured surfaces may play a considerable role in controlling the biological activities of different nanomaterials.We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNPs) by their surface modification with the surface corona of biologically active polyoxometalates (POMs). The stable POM surface corona was achieved by utilising zwitterionic tyrosine amino acid as a pH-switchable reducing and capping agent of AgNPs. The general applicability of this approach was demonstrated by developing surface coronas of phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) around AgNPs. Our investigations on Gram negative bacterium Escherichia coli demonstrate that in conjugation

  12. Aqueously dispersed silver nanoparticle-decorated boron nitride nanosheets for reusable, thermal oxidation-resistant surface enhanced Raman spectroscopy (SERS) devices.

    PubMed

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

    2012-02-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  14. Surface modification of additive manufactured Ti6Al4V alloy with Ag nanoparticles: wettability and surface morphology study

    NASA Astrophysics Data System (ADS)

    Chudinova, E.; Surmeneva, M.; Koptioug, A.; Sharonova, A.; Loza, K.; Surmenev, R.

    2016-02-01

    In this work, the use of electrophoretic deposition to modify the surface of Ti6Al4V alloy fabricated via additive manufacturing technology is reported. Poly(vinylpyrrolidone) (PVP)-stabilized silver nanoparticles (AgNPs) had a spherical shape with a diameter of the metallic core of 100±20 nm and ζ -potential -15 mV. The AgNPs- coated Ti6Al4V alloy was studied in respect with its chemical composition and surface morphology, water contact angle, hysteresis, and surface free energy. The results of SEM microphotography analysis showed that the AgNPs were homogeneously distributed over the surface. Hysteresis and water contact angle measurements revealed the effect of the deposited AgNPs layer, namely an increased water contact angle and decreased contact angle hysteresis. However, the average water contact angle was 125° for PVP-stabilized-AgNPs-coated surface, whereas ethylene glycol gave the average contact angle of 17°. A higher surface energy is observed for AgNPs-coated Ti6Al4V surface (70.17 mN/m) compared with the uncoated surface (49.07 mN/m).

  15. Preparation of carbon microspheres decorated with silver nanoparticles and their ability to remove dyes from aqueous solution.

    PubMed

    Chen, Qingchun; Wu, Qingsheng

    2015-01-01

    Solid, but not hollow or porous, carbon microspheres decorated with silver nanoparticles (AgNP-CMSs) were prepared from silver nitrate and CMSs by a redox reaction at room temperature. The CMSs and AgNP-CMSs were characterized using X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and UV-vis spectrophotometry. Though with non-high specific surface area, the AgNP-CMSs exhibited a high adsorption capacity toward methylene blue (MB) in an aqueous solution. The AgNP-CMSs were able to remove all the MB from a solution of 30 mg/L MB in water within 1 min when the adsorbent concentration was 0.12 g/L. The AgNP-CMSs also exhibited good adsorption and photocatalytic activity in the decomposition of aqueous Rhodamine B as well as MB under visible light. FTIR was used to examine the interaction between AgNP-CMSs and MB, and the spectrum and more extra experiments suggest ionic interactions between cationic dyes and the negatively charged groups can be formed but not the presence of abundant π-π conjugations between dye molecules and the aromatic rings. The origin of the photocatalytic activity of AgNP-CMSs was attributed to a surface plasmon resonance (SPR) effect of the silver nanoparticles on the CMSs.

  16. Synthesis of silver quantum dots decorated TiO2 nanotubes and their incorporation in organic hybrid solar cells

    NASA Astrophysics Data System (ADS)

    Tan, Furui; Qu, Shengchun; Zhang, Xingwang; Liu, Kong; Wang, Zhanguo

    2013-08-01

    Uniform silver quantum dots decorated TiO2 nanotubes (Ag-TiO2 NTs) were synthesized via a simple reduction reaction in ethanol solvent. The size distribution of composite NTs arranges from 3 to 5 nm for Ag quantum dots and about 10 nm for TiO2 NTs in diameter. The composite Ag-TiO2 nanoparticles were incorporated in organic hybrid solar cells through doping into the active layer. Both the optical and electrical properties of the solar cells were improved. The photocurrent and fill factor of the devices were obviously increased after the Ag-TiO2 NTs were introduced, accompanied with a greatly reduced series resistance as well as enlarged shunt resistance. Suppressed recombination due to efficient charge transfer from plasmonic Ag quantum dots to the attached TiO2 NTs made contribution to the charge collection and transportation so that the fill factor was increased. Meanwhile, the enhanced light absorption resulted from effective incident light scattering by the Ag-TiO2 NTs composite played a role in increasing photocurrent. As a result, solar cells with Ag-TiO2 NTs generated an enhanced conversion efficiency up to 20 and 50 % compared to that adopting TiO2 NTs and that without doping, respectively.

  17. Electrospinning directly synthesized metal nanoparticles decorated on both sidewalls of TiO2 nanotubes and their applications.

    PubMed

    Zhang, Guanhua; Duan, Huigao; Lu, Bingan; Xu, Zhi

    2013-07-07

    The hybrid structure of nanoparticle-decorated nanotubes has the advantage of both large specific surface areas of nanoparticles and anisotropic properties of nanotubes, which is desirable for many applications. In this study, Ag nanoparticles on highly porous TiO2 nanotubes (NTs) on both internal and external sidewalls (Ag@TiO2@Ag NTs) are directly synthesized by emulsion electrospinning and thermal evaporation for the first time. The Ag@TiO2@Ag NT heterostructures, which have large surface-to-volume ratios, improved electrical conductivity, and an excellent material synergetic effect, demonstrate excellent electrochemical properties and superior photocatalytic performance. The new method for the synthesis of Ag@TiO2@Ag NT heterostructures can be applied to fabricate various types of other novel metal nanoparticles (for example Au and Pt) on highly porous nanotubes on both internal and external sidewalls. The possible growth mechanism and reasons for excellent electrochemical properties and superior photocatalytic performance were discussed in detail.

  18. Silver decorated LaMnO3 nanorod/graphene composite electrocatalysts as reversible metal-air battery electrodes

    NASA Astrophysics Data System (ADS)

    Hu, Jie; Liu, Qiunan; Shi, Lina; Shi, Ziwei; Huang, Hao

    2017-04-01

    Perovskite LaMnO3 nanorod/reduced graphene oxides (LMO-NR/RGO) decorated with Ag nanoparticles are studied as a bifunctional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolyte. LMO-NR/RGO composites are synthesized by using cetyltrimethyl ammonium bromide (CTAB) as template via a simple hydrothermal reaction followed by heat treatment; overlaying of Ag nanoparticles is obtained through a traditional silver mirror reaction. Electron microscopy reveals that LMO-NR is embedded between the sheets of RGO, and the material is homogeneously overlaid with Ag nanoparticles. The unique composite morphology of Ag/LMO-NR/RGO not only enhances the electron transport property by increasing conductivity but also facilitates the diffusion of electrolytes and oxygen. As confirmed by electrochemical testing, Ag/LMO-NR/RGO exhibits very strong synergy with Ag nanoparticles, LMO-NR, and RGO, and the catalytic activities of Ag/LMO-NR/RGO during ORR and OER are significantly improved. With the novel catalyst, the homemade zinc-air battery can be reversibly charged and discharged and display a stable cycle performance, indicating the great potential of this composite as an efficient bifunctional electrocatalyst for metal-air batteries.

  19. Diastase induced green synthesis of bilayered reduced graphene oxide and its decoration with gold nanoparticles.

    PubMed

    Maddinedi, Sireesh Babu; Mandal, Badal Kumar; Patil, Sagar Hindurao; Andhalkar, Vaibhav Vilas; Ranjan, Shivendu; Dasgupta, Nandita

    2017-01-01

    In this paper, we report an enzyme dependent, green one-pot deoxygenation cum decoration method to synthesize diastase-conjugated reduced graphene oxide (DRG) nanosheets, DRG/gold nanoparticles (DRG/Au) composite. The DRG synthesis was completed in 7h under heating at 90°C on water bath. Selected area electron diffraction (SAED) and Atomic force microscopy (AFM) study has revealed the formation of bilayered reduced graphene oxide sheets. Transmission electron microscopy (TEM) images of DRG/Au composite have shown the uniform decoration of gold nanoparticles (AuNPs) onto the DRG nanosheet surface. Fourier transform infrared spectroscopy (FTIR) and Raman results additionally have shown the functionalization of enzyme molecules onto the DRG nanosheet surface after reduction making it as an effective platform towards the efficient binding of gold nanoparticles. In vitro cytotoxicity studies by MTT assay on A549 and HCT116 cell lines exhibited that the cytotoxicity of the prepared graphene oxide (GO), DRG and DRG/Au is dose dependant. These results have shown that this synthetic method is effective for the production of large scale graphene in a low cost, simple and green method. Since this process avoids the use of hazardous and toxic substances, the produced DRG/Au composites are likely to offer various potential applications in biology and medicine.

  20. 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