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1

Photo-induced growth of DNA-capped silver nanoparticles  

NASA Astrophysics Data System (ADS)

We report the photo-induced nucleation and growth of silver nanoparticles in aqueous solution in the presence of DNA oligomers. An organic dye (Cy5) was used as a photosensitizer to initiate the nanoparticle growth upon illumination with 647 nm light. The formation of nanoparticles and growth kinetics were observed by extinction spectroscopy, dynamic light scattering, and transmission electron microscopy. Irradiation of the precursor solutions with light at the Cy5 absorption maximum triggered the instantaneous formation of spherical particles with a metallic core ˜15 nm in diameter. Remarkably, the particles feature significantly larger effective hydrodynamic diameters (35 nm) in solution, indicative of a DNA ad-layer on the nanoparticle surface. Centrifugation experiments confirmed that DNA was inseparably associated with the nanoparticles and indicated that DNA oligomers adsorb onto the nanoparticle surface during growth, playing the role of a capping agent. The introduced method is a fast and facile way to prepare DNA-capped silver nanoparticles in a single growth step.

Zon, Vera B.; Burley, Glenn A.; Rant, Ulrich

2012-03-01

2

Effect of a thioalkane capping layer on the first hyperpolarizabilities of gold and silver nanoparticles  

NASA Astrophysics Data System (ADS)

We have measured the first hyperpolarizabilities of thioalkane capped silver and gold metallic nanoparticles. The values found are ?AgC 12-10 nm = (2.10 ± 0.23) × 10-26 esu for 10 nm diameter silver nanoparticles and ?AuC 18-18 nm = (3.37 ± 0.08) × 10-26 esu for 18 nm diameter gold nanoparticles at the fundamental wavelength of 784 nm. By comparison to the corresponding values reported for citrate capped silver and gold metallic nanoparticles, after size corrections, decreases by factors of 4.3 and 6.5 respectively are observed. These decreases are tentatively attributed to the bonds formed between the gold and silver surface atoms and the sulfur atoms of the capping layer.

El Harfouch, Yara; Benichou, Emmanuel; Bertorelle, Franck; Russier-Antoine, Isabelle; Jonin, Christian; Lascoux, Noelle; Brevet, Pierre F.

2012-03-01

3

Electrostatic assembly of CTAB-capped silver nanoparticles along predefined ?-DNA template  

NASA Astrophysics Data System (ADS)

Cetyltrimethylammonium bromide (CTAB)-capped positively-charged silver nanoparticles synthesized in water ethanol system was electrostatic assembled on predefined aligned ?-DNA template. Silver nanowire can be obtained by changing the reaction time and the particles concentration. In our work, the length of the silver nanowire obtained is about 10 ?m, and the dimension of the wires is about 20 nm. AFM data reveal that the assembly of CTAB-capped silver nanoparticles on DNA is ordered, but there is space between two particles absorbed on the DNA template. X-ray photoelectron spectroscopy (XPS) was applied to characterize the linear silver clusters, which provides an additional proof that the silver particles were assembled onto DNA template with fine order.

Wei, Gang; Wang, Li; Zhou, Hualan; Liu, Zhiguo; Song, Yonghai; Li, Zhuang

2005-12-01

4

Gellan gum capped silver nanoparticle dispersions and hydrogels: cytotoxicity and in vitro diffusion studies  

NASA Astrophysics Data System (ADS)

The preparation of highly stable water dispersions of silver nanoparticles using the naturally available gellan gum as a reducing and capping agent is reported. Further, exploiting the gel formation characteristic of gellan gum silver nanoparticle incorporated gels have also been prepared. The optical properties, morphology, zeta potential and long-term stability of the synthesized silver nanoparticles were investigated. The superior stability of the gellan gum-silver nanoparticle dispersions against pH variation and electrolyte addition is revealed. Finally, we studied the cytotoxicity of AgNP dispersions in mouse embryonic fibroblast cells (NIH3T3) and also evaluated the in vitro diffusion of AgNP dispersions/gels across rat skin.The preparation of highly stable water dispersions of silver nanoparticles using the naturally available gellan gum as a reducing and capping agent is reported. Further, exploiting the gel formation characteristic of gellan gum silver nanoparticle incorporated gels have also been prepared. The optical properties, morphology, zeta potential and long-term stability of the synthesized silver nanoparticles were investigated. The superior stability of the gellan gum-silver nanoparticle dispersions against pH variation and electrolyte addition is revealed. Finally, we studied the cytotoxicity of AgNP dispersions in mouse embryonic fibroblast cells (NIH3T3) and also evaluated the in vitro diffusion of AgNP dispersions/gels across rat skin. Electronic supplementary information (ESI) available: Time dependent UV-Vis spectral studies revealing the stability of AgNP dispersions and agar plate images displaying the antibacterial activity of AgNPs. See DOI: 10.1039/c1nr10957j

Dhar, S.; Murawala, P.; Shiras, A.; Pokharkar, V.; Prasad, B. L. V.

2012-01-01

5

Sweeter but deadlier: decoupling size, charge and capping effects in carbohydrate coated bactericidal silver nanoparticles.  

PubMed

Silver nanoparticles are widely used due to their biomedical-antibacterial applications. At the same time, the stabilization of these nanoparticles is challenging and may be made using polymeric carbohydrates, based on the practice of avoiding toxic chemicals and undesirable residues. In this study, we synthesized silver nanoparticles (AgNPs) which were stabilized by carbohydrates (potato starch and chitosan) and characterized by UV-Vis spectroscopy, zeta potential and transmission electron microscopy techniques. Bactericidal efficiency of AgNPs capped with different carbohydrates was tested demonstrating that the synthesized materials were able to inhibit the growth of two clinical/medical relevant bacteria strains (Escherichia coil and Staphylococcus aureus). AgNPs stabilized by chitosan presented enhanced bactericidal activity if compared to the ones synthesized in presence of potato starch. This difference is mainly attributed to the known antibacterial properties of chitosan associated to overall positive charge of the nanoparticles capped by this polymer. Those nanoparticles obtained in presence of starch presented minor bactericidal effects since the starch-capping agent is not able to contribute to the avoidance of bacteria growth and confers a quasi-neutral charge to the nanoparticle. PMID:24059081

de Oliveira, Luciane França; Gonçalves, Julianna de Oliveira; Gonçalves, Kaliandra de Almeida; Kobarg, Jörg; Cardoso, Mateus Borba

2013-11-01

6

A new, simple, green, and one-pot four-component synthesis of bare and poly(?,?, L-glutamic acid)-capped silver nanoparticles  

PubMed Central

A simple and green chemical method has been developed to synthesize stable bare and capped silver nanoparticles based on the reduction of silver ions by glucose and capping by poly(?,?,L-glutamic acid) (PGA). The use of ammonia during synthesis was avoided. PGA has had a dual role in the synthesis and was used as a capping agent to make the silver nanoparticle more biocompatible and to protect the nanoparticles from agglomerating in the liquid medium. The synthesized PGA-capped silver nanoparticles in the size range 5–45 nm were stable over long periods of time, without signs of precipitation. Morphological examination has shown that the silver nanoparticles had a nearly spherical, multiply twinned structure. The effects of the reaction temperature and the reaction time during the synthesis were investigated too. The biocompatibility of the PGA-capped silver nano-particles is discussed in terms of in vitro toxicity with human intestinal Caco-2 cells. The samples were characterized by UV–Visible spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and zeta potential measurements.

Savanovic, Igor; Uskokovic, Vuk; Skapin, Sreco D.; Bracko, Ines; Jovanovic, Uros; Uskokovic, Dragan

2013-01-01

7

Enhancement of antibacterial activity of capped silver nanoparticles in combination with antibiotics, on model gram-negative and gram-positive bacteria.  

PubMed

The nanoparticles used in this study were prepared from AgNO3 using NaBH4 in the presence of capping agents such as citrate, sodium dodecyl sulfate, and polyvinylpyrrolidone. The formed nanoparticles were characterized with UV-Vis, TEM, and XRD. The generation of silver nanoparticles was confirmed from the appearance of yellow colour and an absorption maximum between 399 and 404?nm. The produced nanoparticles were found to be spherical in shape and polydisperse. For citrate, SDS, and PVP capped nanoparticles, the average particle sizes were 38.3 ± 13.5, 19.3 ± 6.0, and 16.0 ± 4.8?nm, respectively. The crystallinity of the nanoparticles in FCC structure is confirmed from the SAED and XRD patterns. Also, the combined antibacterial activity of these differently capped nanoparticles with selected antibiotics (streptomycin, ampicillin, and tetracycline) was evaluated on model Gram-negative and Gram-positive bacteria, employing disc diffusion assay. The activity of the tested antibiotics was enhanced in combination with all the stabilized nanoparticles, against both the Gram classes of bacteria. The combined effects of silver nanoparticles and antibiotics were more prominent with PVP capped nanoparticles as compared to citrate and SDS capped ones. The results of this study demonstrate potential therapeutic applications of silver nanoparticles in combination with antibiotics. PMID:23970844

Kora, Aruna Jyothi; Rastogi, Lori

2013-07-18

8

Biopolymer capped silver nanoparticles as fluorophore for ultrasensitive and selective determination of malathion.  

PubMed

This paper describes a novel luminescent sensor for malathion using chitosan capped silver nanoparticles (Chi-AgNPs) as fluorophore. The Chi-AgNPs were synthesized by the wet-chemical method and were characterized by absorption, fluorescence, HR-TEM, XRD and DLS techniques. The Chi-AgNPs show the absorption maximum at 394nm and emission maximum at 536nm. While adding 10µM malathion, yellow color Chi-AgNPs was changed to brown and the absorbance was decreased along with a redshift. The observed spectral and color changes were mainly due to the aggregation of Chi-AgNPs. This was confirmed by zeta potential, DLS and HR-TEM studies. No significant absorption spectral change was observed for Chi-AgNPs in the presence of less than micromolar concentrations of malathion. However, the emission intensity of Chi-AgNPs was decreased and the emission maximum was shifted toward higher wavelength in the presence of picomolar concentration of malathion. Based on the decrease in emission intensity, the concentration of malathion was determined. The Stern-Volmer constant, Gibbs free energy change, association constant, quantum yield and binding constant were calculated and the quenching mechanism was proposed. The Chi-AgNPs show good selectivity toward the determination of 10nM malathion in the presence of 1000-fold higher concentrations of common interferents. A good linearity was observed for the emission intensity against 1×10(-9)-10×10(-12)M malathion and the detection limit was found to be 94fML(-1) (S/N=3). The proposed method was successfully applied to determine malathion in fruits and water samples and the obtained results were validated with HPLC. PMID:24054557

Vasimalai, N; Abraham John, S

2013-04-19

9

Effect of atmospheric exposure on the growth of citrate-capped silver nanoparticles  

NASA Astrophysics Data System (ADS)

Citrate-capped Ag nanoparticles are prepared at 8 oC in aqueous solution by a modified ‘Turkevich’ approach using NaBH4 as reducing agent. Spherical Ag nanoparticles are observed in fresh solution having average size 10-15 nm with a narrow size distribution. UV-vis-NIR spectroscopic result shows a ‘surface plasmon resonance’ induced absorption peak at 389 nm in fresh solution. When the nanoparticles are exposed to atmosphere for 7 days, an enhancement in average size from 10 to 22 nm is observed and corresponding absorption peak is shifted from 389 to 425 nm. When exposure time is increased for a very long duration (17 months), chain formation in Ag nanoparticles is observed. The elemental state of Ag nanoparticles is confirmed with X-ray photoelectron spectroscopic study. The formation and growth mechanism of Ag nanoparticles is explained.

Kumar, Manish; Reddy, G. B.

2010-05-01

10

Nanophotothermolysis of Poly-(vinyl) Alcohol Capped Silver Particles  

NASA Astrophysics Data System (ADS)

Laser-induced thermal fusion and fragmentation of poly-(vinyl) alcohol (PVA)-capped silver nanoparticles in aqueous medium have been reported. PVA-capped silver nanoparticles with an average size of 15 nm were prepared by chemical reduction technique. The laser-induced photo-fragmentation of these particles has been monitored by UV-visible spectroscopy and transmission electron microscopy. The morphological changes induced by thermal and photochemical effects were found to influence the optical properties of these nanoparticles.

Tripathy, Suraj Kumar

2008-04-01

11

Toxicity of Citrate-Capped Silver Nanoparticles in Common Carp (Cyprinus carpio)  

PubMed Central

Juvenile common carp (Cyprinus carpio) were used as a model to investigate acute toxicity and oxidative stress caused by silver nanoparticles (Ag-NPs). The fish were exposed to different concentrations of Ag-NPs for 48 h and 96 h. After exposure, antioxidant enzyme levels were measured, including glutathione-S-transferase (GST), superoxidase dismutase, and catalase (CAT). Other biochemical parameters and histological abnormalities in different tissues (i.e., the liver, gills, and brain) were also examined. The results showed that Ag-NPs agglomerated in freshwater used during the exposure experiments, with particle size remaining <100?nm. Ag-NPs had no lethal effect on fish after 4 days of exposure. Biochemical analysis showed that enzymatic activities in the brain of the fish exposed to 200??g/L of Ag-NPs were significantly reduced. Varied antioxidant enzyme activity was recorded in the liver and gills. Varied antioxidant enzyme activity was recorded for CAT in the liver and GST in the gills of the fish. However, the recovery rate of fish exposed to 200??g/L of Ag-NPs was slower than when lower particle concentrations were used. Other biochemical indices showed no significant difference, except for NH3 and blood urea nitrogen concentrations in fish exposed to 50??g/L of Ag-NPs. This study provides new evidence about the effects of nanoparticles on aquatic organisms.

Lee, Byoungcheun; Duong, Cuong Ngoc; Cho, Jaegu; Lee, Jaewoo; Kim, Kyungtae; Seo, Youngrok; Kim, Pilje; Choi, Kyunghee; Yoon, Junheon

2012-01-01

12

Ultrasensitive fluorescence-quenched chemosensor for Hg(II) in aqueous solution based on mercaptothiadiazole capped silver nanoparticles.  

PubMed

This manuscript describes a highly selective and ultra sensitive determination of Hg(II) in aqueous solution using functionalized mercaptothiadiazole capped silver nanoparticles (AgNPs) by spectrofluorimetry. We have synthesized 2,5-dimercapto-1,3,4-thiadiazole (DMT), 2-mercapto-5-methyl-1,3,4-thiadiazole (MMT) and 2-mercapto-5-amino-1,3,4-thiadiazole (AMT) capped AgNPs by wet chemical method. Among these AgNPs, DMT capped AgNPs (DMT-AgNPs) were more stable and highly fluorescent than the other two AgNPs. DMT-AgNPs show the emission maximum at 677 nm while exciting at 400 nm. After the addition of Hg(II), the emission intensity was decreased at 677 nm. The observed decreased emission intensity was ascribed to the aggregation of AgNPs and it was confirmed by TEM. Based on the decrease in emission intensity, the concentration of Hg(II) was determined. The lowest detection limit (LOD=3S/m) of 1.0 pg L(-1) was achieved for the first time using DMT-AgNPs by spectrofluorimetry. The quantum yield (?(F)), Stern-Volmer constant (K(SV)), Gibbs free energy changes (?G°), association constant (K(f)) were calculated and the quenching mechanism also was discussed. Finally, the proposed method was successfully utilized for the determination of Hg(II) in river water, industrial effluent water and tap water samples. The obtained results were fairly matches with the ICP-AES method. PMID:22342901

Vasimalai, N; Sheeba, G; John, S Abraham

2012-02-02

13

Poly(ethylene) glycol-capped silver and magnetic nanoparticles: Synthesis, characterization, and comparison of bactericidal and cytotoxic effects.  

PubMed

Silver and magnetic (Fe3O4) nanoparticles have attracted wide attention as novel antimicrobial agents due to their unique chemical and physical properties. In order to study the comparative effects on antibacterial and animal cytotoxicity, Staphylococcus aureus and NIH 3T3 fibroblasts were used, respectively. Both nanoparticles were synthesized via a novel matrix-mediated method using poly(ethylene) glycol. Formation of silver nanoparticles was confirmed by fluorescence and ultraviolet-visible spectroscopic techniques. The poly(ethylene) glycol-coated silver and Fe3O4 nanoparticles were characterized by scanning electron microscope, transmission electron microscope, zeta potential, particle size analysis, Fourier-transform infrared, X-ray diffraction, and X-ray photoelectron spectroscopy. The antimicrobial results indicate that both poly(ethylene) glycol-coated silver and Fe3O4 nanoparticles inhibited S. aureus growth at the concentrations of 5 and 10?µg/mL at all time points without showing any significant cytotoxicity on NIH 3T3 fibroblasts. The particle size of both the poly(ethylene) glycol-coated silver and Fe3O4 nanoparticles dominated in the range 10-15?nm, obtained by particle size analyzer. The poly(ethylene) glycol coating on the particles showed less aggregation of nanoparticles, as observed by scanning electron microscope and transmission electron microscope. The overall obtained results indicated that these two nanoparticles were stable and could be used to develop a magnetized antimicrobial scaffolds for biomedical applications. PMID:23959858

Mandal, A; Sekar, S; Chandrasekaran, N; Mukherjee, A; Sastry, Tp

2013-08-19

14

Fabrication of silver nanoparticles ring templated by plasmid DNA  

NASA Astrophysics Data System (ADS)

Silver nanoparticles ring was successfully fabricated by electrostatic assembling 4-aminothiophenol (4-ATP) capped silver nanoparticles on predefined extended circular plasmid pBR322 DNA. The silver nanoparticles ring which was about 1.5 ?m in length, and about 2.2 nm in height can be obtained by adjusting the reaction time. The normal Raman scattering spectra reveal that the 4-ATP has contacted with the silver nanoparticles by forming a strong Ag S bond. The AFM data show that the assembly of 4-ATP capped silver nanoparticles on DNA is ordered.

Sun, Lanlan; Wei, Gang; Song, Yonghai; Liu, Zhiguo; Wang, Li; Li, Zhuang

2006-05-01

15

Formation of hybrid hydrogels consisting of tripeptide and different silver nanoparticle-capped ligands: modulation of the mechanical strength of gel phase materials.  

PubMed

An N-terminally Boc (tert-butyloxycarbonyl) group-protected synthetic tripeptide (Boc-Phe-Phe-Ala-OH) has been found to form a translucent hydrogel in basic aqueous medium. This hydrogel material has been characterized using field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy, differential scanning calorimetric, X-ray diffraction (XRD), and rheological studies. FE-SEM and TEM studies have revealed the formation of a nanofibrillar network structure upon gelation. Thiol (-SH) containing ligands (amino acid/peptide) have been used to stabilize small silver nanoparticles (AgNPs), and these thiol-capped silver nanoparticles have been incorporated into this hydrogel to prepare hybrid hydrogels. Morphological study of silver nanoparticles containing a hybrid hydrogel (using TEM experiments) has indicated the nice fabrication of AgNPs along the gel nanofibers. Fabrication of nanoparticles upon the gel nanofibers is due to noncovalent interactions between the capping ligands of the nanoparticles and the peptide-based hydrogel nanofibers. Rheological investigations of these hybrid hydrogels have shown the weakening of the mechanical strength of the hydrogel after incorporation of AgNPs within the native hydrogel system. Our studies have vividly shown the dependence of the elastic modulus (G') and yield stress (?(y)) on three factors: (a) the nature of the stabilizing ligands used for AgNPs, (b) the size of the AgNPs, and (c) the amount of AgNPs used for the preparation of hybrid hydrogel systems. Modulation of the mechanical strength of the hybrid hydrogel can be successfully achieved by varying these above-mentioned factors. This modulation of the mechanical properties keeps a future promise to make tunable soft materials with interesting properties. PMID:22962848

Nanda, Jayanta; Adhikari, Bimalendu; Basak, Shibaji; Banerjee, Arindam

2012-09-28

16

Chitosan-capped silver nanoparticles as a highly selective colorimetric probe for visual detection of aromatic ortho-trihydroxy phenols.  

PubMed

We reported a new application of silver nanoparticles (NPs) for the visual sensing of aromatic polyphenols, such as gallic acid, pyrogallol and tannic acid, which is based on the intensified plasmon absorbance signals and visual changes from yellow to orange due to hydrogen-bonding recognition and subsequent catalytic oxidation of the target phenols by chitosan-capped Ag NPs (Ch-Ag NPs). The Ch-Ag NPs are generated by the well-known reaction of AgNO3 with NaBH4 and stabilized with chitosan which is a polysaccharide biopolymer with excellent dispersive properties and stability in aqueous media. After optimizing some experimental conditions, a very simple and facile sensing system has been developed for the detection of gallic acid, pyrogallol and tannic acid in water samples. The proposed system promises high selectivity toward gallic acid, pyrogallol and tannic acid, and other phenolic compounds including p-aminobenzoic acid, pentachlorophenol, 2,4,6-trinitrophenol, 2,4-dinitrophenol, p-nitrophenol, 1-naphthol, ?-naphthol, p-aminophenol, catechol, hydroquinone, m-dihydroxybenzene, phloroglucin and phenol could not induce a color change even at 0.1 mM. The outstanding selectivity property of the proposed method for gallic acid, pyrogallol and tannic acid resulted from the Ch-Ag NPs-mediated reduction of Ag(+) by the target phenols. Also, a wide linear response range was obtained for the three targets. The linear response ranges for gallic acid, pyrogallol, and tannic acid were from 1 × 10(-5) to 1 × 10(-3) M, 1 × 10(-5) to 1 × 10(-2) M and 1 × 10(-6) to 1 × 10(-4) M with a respective detection limit (DL) of 1 × 10(-5), 1 × 10(-5), and 1 × 10(-6) M. The proposed method was successfully applied to detect target phenols in environmental water samples. Furthermore, because the color change from yellow to orange is observable by the naked eye, it is easy to realize visual detection of the target phenols without any instrumentation or complicated design. The experimental results reported here open up an innovative application of the catalytic reactivity of Ag NPs. PMID:23457709

Chen, Zhaohui; Zhang, Xiaodan; Cao, Haiyan; Huang, Yuming

2013-04-21

17

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

PubMed

Cadmium sulfide quantum dots capped with cysteamine (Cys-CdS QDs) were demonstrated as a selective fluorescence probe for sensing of free trace silver ions. The fluorescence intensity of the Cys-CdS QDs can be enhanced only in the presence of free Ag(+) and the fluorescence spectrum was slightly red shift from the original spectra. In addition, the fluorescence intensities were linearly increased upon increasing Ag(+) concentration. At the optimized condition for Ag(+) detection, when adding other metal ions to the Cys-CdS QDs solution, fluorescence spectra of Cys-CdS QDs did not change significantly revealing good selectivity of the sensors towards Ag(+). The working linear concentration range was found to be 0.1-1.5µM with LOD of 68nM. The proposed sensor was then applied to detect free Ag(+) in the silver nanoparticles solution. The results showed that the proposed sensor can be efficiently used with good accuracy and precision providing the simple method for detection of free Ag(+) in silver nanoparticles of quality control products. PMID:24054673

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

2013-07-02

18

Effects from filtration, capping agents, and presence/absence of food on the toxicity of silver nanoparticles to Daphnia magna.  

PubMed

Relatively little is known about the behavior and toxicity of nanoparticles in the environment. Objectives of work presented here include establishing the toxicity of a variety of silver nanoparticles (AgNPs) to Daphnia magna neonates, assessing the applicability of a commonly used bioassay for testing AgNPs, and determining the advantages and disadvantages of multiple characterization techniques for AgNPs in simple aquatic systems. Daphnia magna were exposed to a silver nitrate solution and AgNPs suspensions including commercially available AgNPs (uncoated and coated), and laboratory-synthesized AgNPs (coated with coffee or citrate). The nanoparticle suspensions were analyzed for silver concentration (microwave acid digestions), size (dynamic light scattering and electron microscopy), shape (electron microscopy), surface charge (zeta potentiometer), and chemical speciation (X-ray absorption spectroscopy, X-ray diffraction). Toxicities of filtered (100 nm) versus unfiltered suspensions were compared. Additionally, effects from addition of food were examined. Stock suspensions were prepared by adding AgNPs to moderately hard reconstituted water, which were then diluted and used straight or after filtration with 100-nm filters. All nanoparticle exposure suspensions, at every time interval, were digested via microwave digester and analyzed by inductively coupled argon plasma-optical emission spectroscopy or graphite furnace-atomic absorption spectroscopy. Dose-response curves were generated and median lethal concentration (LC50) values calculated. The LC50 values for the unfiltered particles were (in µg/L): 1.1 ± 0.1-AgNO(3) ; 1.0 ± 0.1-coffee coated; 1.1 ± 0.2-citrate coated; 16.7 ± 2.4 Sigma Aldrich Ag-nanoparticles (SA) uncoated; 31.5 ± 8.1 SA coated. LC50 values for the filtered particles were (in µg/L): 0.7 ± 0.1-AgNO(3) ; 1.4 ± 0.1-SA uncoated; 4.4 ± 1.4-SA coated. The LC50 resulting from the addition of food was 176.4 ± 25.5-SA coated. Recommendations presented in this study include AgNP handling methods, effects from sample preparation, and advantages/disadvantages of different nanoparticle characterization techniques. PMID:20890913

Allen, H Joel; Impellitteri, Christopher A; Macke, Dana A; Heckman, J Lee; Poynton, Helen C; Lazorchak, James M; Govindaswamy, Shekar; Roose, Deborah L; Nadagouda, Mallikarjuna N

2010-10-01

19

Thermal decomposition as route for silver nanoparticles  

NASA Astrophysics Data System (ADS)

Single crystalline silver nanoparticles have been synthesized by thermal decomposition of silver oxalate in water and in ethylene glycol. Polyvinyl alcohol (PVA) was employed as a capping agent. The particles were spherical in shape with size below 10 nm. The chemical reduction of silver oxalate by PVA was also observed. Increase of the polymer concentration led to a decrease in the size of Ag particles. Ag nanoparticle was not formed in the absence of PVA. Antibacterial activity of the Ag colloid was studied by disc diffusion method.

Navaladian, S.; Viswanathan, B.; Viswanath, R. P.; Varadarajan, T. K.

2007-01-01

20

Novel switchable sensor for phosphate based on the distance-dependant fluorescence coupling of cysteine-capped cadmium sulfide quantum dots and silver nanoparticles.  

PubMed

A novel switchable sensor was developed for the determination of phosphate based on Ce(3+) induced aggregation and phosphate triggered disaggregation of cysteine (Cys)-capped CdS quantum dots (QDs) and silver nanoparticles (AgNPs). The rare earth metal Ce(3+) could aggregate a mixture of QDs and AgNPs, which induced electron or energy transfer between CdS QDs and AgNPs and serious fluorescence quenching. However, phosphate dissociated the formed aggregation of CdS QDs and AgNPs, restoring the enhanced fluorescence of Cys-capped CdS triggered by AgNPs. Although, CdS QDs alone could also be used to detect phosphate through the aggregation-disaggregation mechanism adjusted by Ce(3+) and phosphate. It was found that the distance-dependent interaction between AgNPs and CdS QDs driven by Ce(3+) and phosphate could lead to enhanced quenching or enhancement of the fluorescence of Cys-capped CdS to form a more sensitive detection system for phosphate. The developed method was applied in the detection of phosphate in real water samples with acceptable and satisfactory results. PMID:23435242

Wang, Guang-Li; Jiao, Huan-Jun; Zhu, Xiao-Ying; Dong, Yu-Ming; Li, Zai-Jun

2013-02-22

21

Green synthesis of silver nanoparticles using Macrotyloma uniflorum.  

PubMed

Green synthesis of noble metal nanoparticles is a vast developing area of research. In this paper we report the green synthesis of silver nanoparticles using aqueous seed extract of Macrotyloma uniflorum. The effect of experimental parameters such as amount of extract, temperature and pH on the formation of silver nanoparticles was studied. The as prepared samples are characterized using XRD, TEM, UV-Visible and FTIR techniques. The formation of silver nanoparticles is evidenced by the appearance of signatory brown colour of the solution and UV-vis spectra. The XRD analysis shows that the silver nanoparticles are of face centered cubic structure. Well-dispersed silver nanoparticles with anisotropic morphology having size ?12 nm are seen in TEM images. FTIR spectrum indicates the presence of different functional groups in capping the nanoparticles. The possible mechanism leading to the formation of silver nanoparticles is suggested. PMID:21920808

Vidhu, V K; Aromal, S Aswathy; Philip, Daizy

2011-08-31

22

Stability of citrate-capped silver nanoparticles in exposure media and their effects on the development of embryonic zebrafish (Danio rerio).  

PubMed

The stability of citrate-capped silver nanoparticles (AgNPs) and the embryonic developmental toxicity were evaluated in the fish test water. Serious aggregation of AgNPs was observed in undiluted fish water (DM-100) in which high concentration of ionic salts exist. However, AgNPs were found to be stable for 7 days in DM-10, prepared by diluting the original fish water (DM-100) with deionized water to 10 %. The normal physiology of zebrafish embryos were evaluated in DM-10 to see if DM-10 can be used as a control vehicle for the embryonic fish toxicity test. As results, DM-10 without AgNPs did not induce any significant adverse effects on embryonic development of zebrafish determined by mortality, hatching, malformations and heart rate. When embryonic toxicity of AgNPs was tested in both DM-10 and in DM-100, AgNPs showed higher toxicity in DM-10 than in DM-100. This means that the big-sized aggregates of AgNPs were low toxic compared to the nano-sized AgNPs. AgNPs induced delayed hatching, decreased heart rate, pericardial edema, and embryo death. Accumulation of AgNPs in the embryo bodies was also observed. Based on this study, citrate-capped AgNPs are not aggregated in DM-10 and it can be used as a control vehicle in the toxicity test of fish embryonic development. PMID:23325492

Park, Kwangsik; Tuttle, George; Sinche, Federico; Harper, Stacey L

2013-01-01

23

Synthesis of Stable, Polyshaped Silver, and Gold Nanoparticles Using Leaf Extract of Lonicera japonica L  

Microsoft Academic Search

Silver nanoparticles and gold nanoparticles of various shapes and sizes have applications in medicine, biosensing, and catalysis. Plant-mediated synthesis is preferred due to ecofriendly nature and enhanced quality of the synthesized nanoparticles. As Lonicera japonica plant has several medicinal properties, we explored it here for the first time in the synthesis of silver nanoparticles and gold nanoparticles. Capping of synthesized

Vineet Kumar; Sudesh Kumar Yadav

2011-01-01

24

Optical and structural studies of silver nanoparticles  

NASA Astrophysics Data System (ADS)

Gamma radiolysis method was used to prepare polyvinyl alcohol (PVA) capped silver nanoparticles by optimizing various conditions like metal ion concentration and polymer (PVA) of different molecular weights. The role of different scavengers was also studied. The decrease in particle size was observed with increase in the molecular weight of capping agent. ?-radiolytic method provides silver nanoparticles in fully reduced and highly pure state. XRD (X-ray diffraction) technique confirmed the zero valent state of silver. Optical studies were done using UV-visible spectrophotometer to see the variation of electronic structure of the metal sol. Transmission Electron Microscopic (TEM) studies reveal the fcc geometry. The TEM show clearly split Debye-Scherrer rings. The d values calculated from the diffraction ring pattern are in perfect agreement with the ASTM data. Ag particles less than 10nm are spherical in shape, whereas the particles above 30nm have structure of pentagonal biprisms or decahedra, referred to as multiply twinned particles.

Temgire, M. K.; Joshi, S. S.

2004-12-01

25

Citrate-capped silver nanoparticles showing good bactericidal effect against both planktonic and sessile bacteria and a low cytotoxicity to osteoblastic cells.  

PubMed

A common problem with implants is that bacteria can form biofilms on their surfaces, which can lead to infection and, eventually, to implant rejection. An interesting strategy to inhibit bacterial colonization is the immobilization of silver (Ag) species on the surface of the devices. The aim of this paper is to investigate the action of citrate-capped silver nanoparticles (AgNPs) on clinically relevant Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria in two different situations: (i) dispersed AgNPs (to assess the effect of AgNPs against planktonic bacteria) and (ii) adsorbed AgNPs on titanium (Ti) substrates, a material widely used for implants (to test their effect against sessile bacteria). In both cases, the number of surviving cells was quantified. The small amount of Ag on the surface of Ti has an antimicrobial effect similar to that of pure Ag surfaces. We have also investigated the capability of AgNPs to kill planktonic bacteria and their cytotoxic effect on UMR-106 osteoblastic cells. The minimum bactericidal concentration found for both strains is much lower than the AgNP concentration that leads to cytotoxicity to osteoblasts. Planktonic P. aeruginosa show a higher susceptibility to Ag than S. aureus, which can be caused by the different wall structures, while for sessile bacteria, similar results are obtained for both strains. This can be explained by the presence of extracellular polymeric substances in the early stages of P. aeruginosa biofilm formation. Our findings can be important to improving the performance of Ti-based implants because a good bactericidal action is obtained with very small quantities of Ag, which are not detrimental to the cells involved in the osseointegration process. PMID:23534883

Flores, Constanza Y; Miñán, Alejandro G; Grillo, Claudia A; Salvarezza, Roberto C; Vericat, Carolina; Schilardi, Patricia L

2013-04-12

26

Shaped gold and silver nanoparticles  

Microsoft Academic Search

Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with\\u000a a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticle shape and its internal crystalline\\u000a structures. According to the relationship, the nanoparticles with well-defined shapes are classified into three categories:\\u000a nanoparticles with single crystallinity, nanoparticles

Yugang Sun; Changhua An

2011-01-01

27

Gold nanoparticles capped by peptides  

Microsoft Academic Search

Two dipeptides (GK and GC) and two 15-aminoacid peptides (GK15 and GC15) were used as capping agents in the preparation of monolayer-protected gold nanoparticles (MPCs). They were characterized by TEM microscopy, UV–vis, NMR and IR spectroscopy.

Francesca Porta; Giovanna Speranza; Željka Krpeti?; Vladimiro Dal Santo; Pierangelo Francescato; Giorgio Scarì

2007-01-01

28

Green synthesis of silver nanoparticles using latex of Jatropha curcas  

Microsoft Academic Search

Silver nanoparticles were successfully synthesized from AgNO3 through a simple green route using the latex of Jatropha curcas as reducing as well as capping agent. Nanoparticles were characterized with the help of HRTEM, X-ray diffraction and UV–vis absorption spectroscopy. X-ray diffraction analysis showed that the nanoparticles were of face centered cubic structure. A comparison of radius of nanoparticles obtained from

Harekrishna Bar; Dipak Kr. Bhui; Gobinda P. Sahoo; Priyanka Sarkar; Sankar P. De; Ajay Misra

2009-01-01

29

A versatile synthesis of highly bactericidal Myramistin® stabilized silver nanoparticles  

NASA Astrophysics Data System (ADS)

Silver nanoparticles stabilized by a well-known antibacterial surfactant benzyldimethyl[3-(myristoylamino)propyl]ammonium chloride (Myramistin®) were produced for the first time by borohydride reduction of silver chloride sol in water. Stable aqueous dispersions of silver nanoparticles without evident precipitation for several months could be obtained. In vitro bactericidal tests showed that Myramistin® capped silver NPs exhibited notable activity against six different microorganisms—gram-positive and gram-negative bacteria, yeasts and fungi. The activity was up to 20 times higher (against E. coli) compared to Myramistin® at the same concentrations and on average 2 times higher if compared with citrate-stabilized NPs.

Vertelov, G. K.; Krutyakov, Yu A.; Efremenkova, O. V.; Olenin, A. Yu; Lisichkin, G. V.

2008-09-01

30

Composition-Controlled Synthesis of Bimetallic Gold-Silver Nanoparticles  

SciTech Connect

This paper reports finding of an investigation of the synthesis of monolayer-capped binary gold-silver bimetallic nanoparticles that is aimed at understanding the control factors governing the formation of the bimetallic compositions. The findings have important implications to the exploration of gold-based bimetallic nanoparticles for biosensing and fuell cell catalytic nanomaterials.

Kariuki, Nancy N.; Luo, Jin; Maye, Mathew M.; Hassan, Syed A.; Menard, Tanya; Naslund, H. R.; Lin, Yuehe; Wang, Chong M.; Engelhard, Mark H.; Zhong, Chuan-Jian

2004-12-07

31

Synthesis, characterization and SERS activity of biosynthesized silver nanoparticles  

NASA Astrophysics Data System (ADS)

Silver nanoparticles were rapidly synthesized using Moringa oleifera flower extract as the reducing agent shows surface plasmon resonance peak at 439 nm. The size and shape of the nanoparticles controlled by varying the concentration of M. oleifera flower extract in the reaction medium. The synthesized silver nanoparticles were well-dispersed spherical nanoparticles with the average size of 14 nm. The retinoic acid present in M. oleifera flower extract used as reducing agent and proteins was responsible for capping of the bioreduced silver nanoparticles. The obtained nanoparticle shows size-dependent SERS activity. The SERS spectrum indicates that the pyridine adsorbed on the silver surface in a stand-on orientation via its nitrogen lone pair electrons.

Bindhu, M. R.; Sathe, V.; Umadevi, M.

2013-11-01

32

Fluorescence From Metallic Silver and Iron Nanoparticles Prepared by Exploding Wire Technique  

Microsoft Academic Search

The observation of intense visible fluorescence from silver and iron nanoparticles in different solution phases and surface\\u000a capping is reported here. Metallic silver and iron nanoparticles were obtained by exploding pure silver and iron wires in\\u000a double distilled water. The adsorption of bovine serum albumin protein on the silver nanoparticles showed enhanced fluorescence.\\u000a The presence of polyvinyl pyrrolidone polymer in

Abdullah Alqudami; S. Annapoorni

2007-01-01

33

Toxicity of silver nanoparticles in zebrafish models  

NASA Astrophysics Data System (ADS)

This study was initiated to enhance our insight on the health and environmental impact of silver nanoparticles (Ag-np). Using starch and bovine serum albumin (BSA) as capping agents, silver nanoparticles were synthesized to study their deleterious effects and distribution pattern in zebrafish embryos (Danio rerio). Toxicological endpoints like mortality, hatching, pericardial edema and heart rate were recorded. A concentration-dependent increase in mortality and hatching delay was observed in Ag-np treated embryos. Additionally, nanoparticle treatments resulted in concentration-dependent toxicity, typified by phenotypes that had abnormal body axes, twisted notochord, slow blood flow, pericardial edema and cardiac arrhythmia. Ag+ ions and stabilizing agents showed no significant defects in developing embryos. Transmission electron microscopy (TEM) of the embryos demonstrated that nanoparticles were distributed in the brain, heart, yolk and blood of embryos as evident from the electron-dispersive x-ray analysis (EDS). Furthermore, the acridine orange staining showed an increased apoptosis in Ag-np treated embryos. These results suggest that silver nanoparticles induce a dose-dependent toxicity in embryos, which hinders normal development.

Asharani, P. V.; Lian Wu, Yi; Gong, Zhiyuan; Valiyaveettil, Suresh

2008-06-01

34

Electrochemical synthesis of silver nanoparticles  

Microsoft Academic Search

Silver polarisation in non-aqueous solution of NaNO3 in ethanol was investigated by means of cyclic voltammetry and chronoamperometry. A deposit consisting of metallic silver nanoparticles has been obtained by both potentiostatic and galvanostatic method. The proposed mechanism assumes that both anodic dissolution of silver and its reduction to metallic state proceed during polarisation in ethanol. The described process is a

Maria Starowicz; Barbara Stypu?a; Jacek Bana?

2006-01-01

35

Synthesis of silver nanoparticles by sophorolipids: Effect of temperature and sophorolipid structure on the size of particles  

Microsoft Academic Search

We report in situ synthesis of silver nanoparticles using biosurfactants called sophorolipids as reducing and capping agents. We further study\\u000a the effect of temperature and the structure of sophorolipid on the size of silver nanoparticles obtained. The silver nanoparticles\\u000a were characterized by UV-visible, transmission electron microscope (TEM) and light scattering (DLS) analysis techniques.

M. B. Kasture; P. Patel; A. A. Prabhune; C. V. Ramana; A. A. Kulkarni; B. L. V. Prasad

2008-01-01

36

Saccharide Sensing Using Gold and Silver Nanoparticles-A Review  

Microsoft Academic Search

We review new methodologies for glucose sensing from our laboratories based on the specific biological interactions between Con A, dextran-coated gold nanoparticles and glucose, and the interactions between dextran, glucose, and boronic-acid capped silver nanoparticles in solution. Our new approaches promise new tunable glucose sensing platforms. Dextran-coated gold nanoparticles were aggregated with the addition of Con A resulting in increase

Kadir Aslan; Jian Zhang; Joseph R. Lakowicz; Chris D. Geddes

2004-01-01

37

Subchronic oral toxicity of silver nanoparticles  

Microsoft Academic Search

BACKGROUND: The antibacterial effect of silver nanoparticles has resulted in their extensive application in health, electronic, consumer, medicinal, pesticide, and home products; however, silver nanoparticles remain a controversial area of research with respect to their toxicity in biological and ecological systems. RESULTS: This study tested the oral toxicity of silver nanoparticles (56 nm) over a period of 13 weeks (90

Yong Soon Kim; Moon Yong Song; Jung Duck Park; Kyung Seuk Song; Hyeon Ryol Ryu; Yong Hyun Chung; Hee Kyung Chang; Ji Hyun Lee; Kyung Hui Oh; Bruce J Kelman; In Koo Hwang; Il Je Yu

2010-01-01

38

Synthesis and characterization of silver nanoparticle\\/polyaniline nanocomposites  

Microsoft Academic Search

Novel dodecanethiol-capped silver nanoparticle (NP)\\/polyaniline (PANI) nanocomposites were prepared via the in situ polymerization of aniline in a metal NP containing medium. Sample PANI\\/Ag-1 was obtained by the polymerization of aniline in an aqueous solution in the presence of powdered NPs, and sample PANI\\/Ag-2 was obtained by a two-phase reaction, in which a toluene solution of silver NPs and aniline

M. M. Oliveira; D. Zanchet; D. Ugarte; A. J. G. Zarbin

39

Evaluation of green synthesized silver nanoparticles against parasites  

Microsoft Academic Search

Green nanoparticle synthesis has been achieved using environmentally acceptable plant extract and eco-friendly reducing and\\u000a capping agents. The present study was based on assessments of the antiparasitic activities to determine the efficacies of\\u000a synthesized silver nanoparticles (AgNPs) using aqueous leaf extract of Mimosa pudica Gaertn (Mimosaceae) against the larvae of malaria vector, Anopheles subpictus Grassi, filariasis vector Culex quinquefasciatus Say

Sampath Marimuthu; Abdul Abdul Rahuman; Govindasamy Rajakumar; Thirunavukkarasu Santhoshkumar; Arivarasan Vishnu Kirthi; Chidambaram Jayaseelan; Asokan Bagavan; Abdul Abduz Zahir; Gandhi Elango; Chinnaperumal Kamaraj

2011-01-01

40

Sulfidation of silver nanoparticles  

NASA Astrophysics Data System (ADS)

Rapid development of nanotechnologies that exploit the properties of silver nanoparticles (Ag-NPs) raises questions concerning the impact of Ag on the environment. Ag-NPs are currently among the most widely used in the nanotechnology industry and the amount released into the environment is expected to increase along with production (1). When present in geochemical systems, Ag-NPs may undergo a variety of changes due to varying redox, pH, and chemical conditions. Expected changes range from surface modification (e.g., oxidation, sulfidation, chloridation etc.) to complete dissolution and re-precipitation. In this context, the focus of our work is on understanding the behavior of synthetic Ag-NPs with different particle sizes under varying conditions relevant to the environment. Sulfidation of Ag-NPs is of particular interest since it among the processes most likely to occur in aqueous systems, in particular under reducing conditions. Three sizes of Ag-NPs coated with polyvinyl pyrrolidone were produced using the polyol process (2) (7 ±1; 20 ±4, and 40 ±9 nm). Batch solutions containing the different Ag-NPs were subsequently reacted with Na2S solutions of different concentrations. The sulfidation process was followed step-wise for 24 hours and the corrosion products formed were characterized by electron microscopy (TEM/SEM), diffraction (XRD), and photo-electron spectroscopy (XPS). Surface charge (pHPZC) of the products formed during this process was also measured, as were changes in solubility and reactivity. Based on experimental observations we infer that the sulfidation process is the result of dissolution-precipitation and find that: (i) acanthite (Ag2S) is formed as a corrosion product; (ii) Ag-NPs aggregation increased with sulfidation rate; (iii) pHPZC increases with the rate of sulfidation; and (iv) the solubility of the corrosion products formed from sulfidation appears lower than that of non-sulfidated Ag-NPs. We observe size-dependent differences in the kinetics of sulfidation and in solubility behavior. The results of this type of fundamental study are important for predicting the behavior and fate of Ag-NPs in natural ecosystems. For example, aggregation caused by sulfidation may limit transport in porous media such as soils. Modification of surface charge during the sulfidation process may have an important impact on electrostatic interactions between Ag-NPs and charged phases such as natural organic matter. Finally, it is well known that Ag+ has a greater toxicity than metallic Ag (3) and the observed decrease in solubility of Ag-NPs after sulfidation may strongly impact the toxicity of silver in the environment. (1) www.nanotechproject.org (2) F. Fievet, J.P. Lagier, B. Blin, B. Beaudoin and M. Figlarz, Solid State Ionics 32/33, 198 (1989) (3) G.A. Sotiriou and S.E. Pratsinis, Environmental Science & Technology 14, 5649 (2010).

Levard, C.; Michel, F. M.; Brown, G. E.

2010-12-01

41

Interaction of Silver Nanoparticles with Plasma Proteins  

NASA Astrophysics Data System (ADS)

Bio-functionalization or surface modification is an important technique to obtain biocompatibility in metal nanoparticles for biomedical applications. In this study, colloidal silver nanoparticles have been prepared by chemical reduction method and characterized by TEM & UV- Vis spectroscopy. We have studied binding of plasma proteins with colloidal silver nanoparticles. Particle characterization, effect on particle size and surface charge has been investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). DLS measurements revealed that average particle hydrodynamic diameter (z-average) increased after incubation of silver nanoparticles with plasma. TEM Images after binding of plasma proteins to the Ag nanoparticles showed protein coating over these nanoparticles.

Kaur, Harmandeep; Tripathi, S. K.

2011-12-01

42

Dithiocarbamate-capped silver nanoparticles as a resonance light scattering probe for simultaneous detection of lead(II) ions and cysteine.  

PubMed

We investigated the suitability of dithiocarbamate (DTC) capped Ag nanoparticles (NPs) as resonance light scattering (RLS) probes for the simultaneous sensing of Pb(2+) and cysteine. The DTC capping ligands are generated by a very simple in situ method through reaction of carbon disulfide with diethanolamine as primary precursor molecules under ultrasonic irradiation. This strategy was based on the fact that Pb(2+) could induce the aggregation of DTC-Ag NPs due to the strong metal affinity of DTC along with an enhanced RLS signal. After optimizing some experimental conditions (including the pH value of the solution, concentration of DTC-Ag NPs, and ion strength), a very simple and facile sensing system has been developed for the detection of Pb(2+) in water based on RLS technology. The proposed system promises excellent selectivity, a wide linear response range and high sensitivity for Pb(2+). The linear response range for Pb(2+) was from 0.01 ?M to 60 ?M. The limit of detection (S/N = 3?) for Pb(2+) was as low as 4 nM. The proposed method was successfully used to detect Pb(2+) in river and tap water samples, indicating the potential of this new, sensitive and selective method in water quality monitoring. Meanwhile, due to the strong binding preference of cysteine toward Pb(2+) by the formation of Pb(2+)-S bonds, Pb(2+) was removed from the surfaces of the DTC-Ag NPs, leading to redispersion of DTC-Ag NPs, along with a decreased RLS signal. The possibility of the proposed system for the sensing of cysteine was also investigated. PMID:23463028

Cao, Haiyan; Wei, Minghong; Chen, Zhaohui; Huang, Yuming

2013-04-21

43

Biosynthesis, characterization and cytotoxic effect of plant mediated silver nanoparticles using Morinda citrifolia root extract.  

PubMed

Silver has been used since time to control bodily infection, prevent food spoilage and heal wounds by preventing infection. The present study aims at an environmental friendly method of synthesizing silver nanoparticles, from the root of Morinda citrifolia; without involving chemical agents associated with environmental toxicity. The obtained nanoparticles were characterized by UV-vis absorption spectroscopy with an intense surface plasmon resonance band at 413 nm clearly reveals the formation of silver nanoparticles. Fourier transmission infra red spectroscopy (FTIR) showed nanopartilces were capped with plant compounds. Field emission-scanning electron microscopy (FE-SEM) and Transmission electron microscopy (TEM) showed that the spherical nature of the silver nanoparticles with a size of 30-55 nm. The X-ray diffraction spectrum XRD pattern clearly indicates that the silver nanoparticles formed in the present synthesis were crystalline in nature. In addition these biologically synthesized nanoparticles were also proved to exhibit excellent cytotoxic effect on HeLa cell. PMID:23434694

Suman, T Y; Radhika Rajasree, S R; Kanchana, A; Elizabeth, S Beena

2013-01-24

44

Coleus aromaticus leaf extract mediated synthesis of silver nanoparticles and its bactericidal activity  

NASA Astrophysics Data System (ADS)

The utilization of various plant resources for the biosynthesis of metallic nanoparticles is called green nanotechnology, and it does not utilize any harmful chemical protocols. The present study reports the plant-mediated synthesis of silver nanoparticles using the plant leaf extract of Coleus aromaticus, which acts as a reducing and capping agent. The silver nanoparticles were characterized by ultraviolet visible spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and the size of the silver nanoparticles is 44 nm. The bactericidal activity of the silver nanoparticles was carried out by disc diffusion method that showed high toxicity against Bacillus subtilis and Klebsiella planticola. Biosynthesis of silver nanoparticles by using plant resources is an eco-friendly, reliable process and suitable for large-scale production. Moreover, it is easy to handle and a rapid process when compared to chemical, physical, and microbe-mediated synthesis process.

Vanaja, Mahendran; Annadurai, Gurusamy

2013-06-01

45

From silver nanoparticles to nanostructures through matrix chemistry  

Microsoft Academic Search

Direct in situ reduction of silver ions by a biopolymer such as agar, without any other reducing nor capping agent is shown\\u000a in this article to lead either to nanoparticles (typically 12(2) nm in an optimized case) or to more complex nanostructures\\u000a depending on the reaction conditions used. This approach takes advantage of the porous polymer lattice acting as a template

Omar Ayyad; David Muñoz-Rojas; Judith Oró-Solé; Pedro Gómez-Romero

2010-01-01

46

Lysozyme Catalyzes the Formation of Antimicrobial Silver Nanoparticles (POSTPRINT).  

National Technical Information Service (NTIS)

Hen egg white lysozyme acted as the sole reducing agent and catalyzed the formation of silver nanoparticles in the presence of light. Stable silver colloids formed after mixing lysozyme and silver acetate in methanol and the resulting nanoparticles were c...

D. M. Eby G. R. Johnson K. E. Farrington N. M. Schaeublin S. M. Hussain

2009-01-01

47

Biosynthesis of iron and silver nanoparticles at room temperature using aqueous sorghum bran extracts.  

PubMed

Iron and silver nanoparticles were synthesized using a rapid, single step, and completely green biosynthetic method employing aqueous sorghum extracts as both the reducing and capping agent. Silver ions were rapidly reduced by the aqueous sorghum bran extracts, leading to the formation of highly crystalline silver nanoparticles with an average diameter of 10 nm. The diffraction peaks were indexed to the face-centered cubic (fcc) phase of silver. The absorption spectra of colloidal silver nanoparticles showed a surface plasmon resonance (SPR) peak centered at a wavelength of 390 nm. Amorphous iron nanoparticles with an average diameter of 50 nm were formed instantaneously under ambient conditions. The reactivity of iron nanoparticles was tested by the H(2)O(2)-catalyzed degradation of bromothymol blue as a model organic contaminant. PMID:21133391

Njagi, Eric C; Huang, Hui; Stafford, Lisa; Genuino, Homer; Galindo, Hugo M; Collins, John B; Hoag, George E; Suib, Steven L

2010-12-06

48

Studies on aggregation behaviour of silver nanoparticles in aqueous matrices: Effect of surface functionalization and matrix composition  

Microsoft Academic Search

The surface stabilizing agents often play a major role in determining colloidal stability of the nanoparticles. In the present study a difference in surface coverage of colloidal silver nanoparticles was deliberately introduced by following two soft synthesis approaches: (a) biological process: using aqueous extract of Citrus limon [partial citrate capping] and (b) chemical process: using tri sodium citrate [complete capping].

T. C. Prathna; N. Chandrasekaran; Amitava Mukherjee

2011-01-01

49

Electron beam induced growth of silver nanoparticles.  

PubMed

An electron beam inducing method for sprouting large quantities of silver nanoparticles on the surface of silver chloride particles is reported. The electron beam driven process was characterized by time-dependent scanning electron microscope (SEM) and energy dispersive spectrum (EDS), allowing for observing several key intermediates in and characteristics of the growth process. Theoretical calculation coupled with experimental observation demonstrated that the growth of silver nanoparticles was mostly related to the current density of electron beam. Decomposition of the silver chloride on the surface of sample was under electron beam irradiation resulted in silver nanoparticles and chlorine. This phenomenon could be useful in developing a novel mechanism for preparation of nanostructures and proposing a reference to avoid image distortion during the characterization of silver compounds under SEM. PMID:22753345

Shi, Guanghua; Bao, Shengxiang; Lai, Weiming; Rao, Zhenzhen; Zhang, Xiaowen; Wang, Zuwen

2012-07-02

50

Silver nanoparticles -- allies or adversaries?  

PubMed

Nanoparticles (NP) are structures with at least one dimension of less than 100 nanometers (nm) and unique properties. Silver nanoparticles (AgNP), due to their bactericidal action, have found practical applications in medicine, cosmetics, textiles, electronics, and other fields. Nevertheless, their less advantageous properties which make AgNP potentially harmful to public health or the environment should also be taken into consideration. These nanoparticles are cyto- and genotoxic and accumulate in the environment, where their antibacterial properties may be disadvantageous for agriculture and waste management. The presented study reviews data concerning the biological effects of AgNP in mammalian cells in vitro: cellular uptake and excretion, localization in cellular compartments, cytotoxicity and genotoxicity. The mechanism of nanoparticle action consists on induction of the oxidative stress resulting in a further ROS generation, DNA damage and activation of signaling leading to various, cell type-specific pathways to inflammation, apoptotic or necrotic death. In order to assure a safe application of AgNP, further detailed studies are needed on the mechanisms of the action of AgNP on mammalian cells at the molecular level. PMID:23540211

Bart?omiejczyk, Teresa; Lankoff, Anna; Kruszewski, Marcin; Szumiel, Irena

2013-01-01

51

Electrospinning method for the preparation of silver chloride nanoparticles in PVP nanofiber  

Microsoft Academic Search

It has been successfully developed by the electrospinning technology that AgCl nanoparticles were incorporated into polymer fiber. In this paper, we chose poly(vinyl pyrrolidone) (PVP) because it was not only a good material for electrospinning but also it was excellent capping reagent of various metal nanoparticles. The silver ions interacted with the carbonyl groups in the PVP molecules. The formation

Jie Bai; Yaoxian Li; Meiye Li; Shugang Wang; Chaoqun Zhang; Qingbiao Yang

2008-01-01

52

Anti-proliferative activity of silver nanoparticles  

Microsoft Academic Search

BACKGROUND: Nanoparticles possess exceptional physical and chemical properties which led to rapid commercialisation. Silver nanoparticles (Ag-np) are among the most commercialised nanoparticles due to their antimicrobial potential. Ag-np based cosmetics, therapeutic agents and household products are in wide use, which raised a public concern regarding their safety associated with human and environmental use. No safety regulations are in practice for

PV AshaRani; M Prakash Hande; Suresh Valiyaveettil

2009-01-01

53

Synthesis and characterization of silver nanoparticles: effect on phytopathogen Colletotrichum gloesporioides  

Microsoft Academic Search

Colloidal silver nanoparticles were synthesized by reducing silver nitrate solutions with glucose, in the presence of gelatin\\u000a as capping agent. The obtained nanoparticles were characterized by means of UV–Vis spectroscopy, transmission electron microscopy\\u000a (TEM), and Fourier transform infrared (FTIR) spectroscopy. The response surface methodology (RSM) was also used to determine\\u000a the influence of the variables on the size of the

Miguel A. Aguilar-MendezEduardo; Eduardo San Martín-Martínez; Lesli Ortega-Arroyo; Georgina Cobián-Portillo; Esther Sánchez-Espíndola

2011-01-01

54

Controllable aggregates of silver nanoparticle induced by methanol for surface-enhanced Raman scattering  

NASA Astrophysics Data System (ADS)

In this work, a series of highly sensitive surface-enhanced Raman scattering substrates have been achieved based on the controllable aggregation of silver nanoparticles. In such system, hexadecylamine-capped silver nanoparticles were ink-jet printed on glass substrates and subsequently dipped into methanol solution. An aggregation was induced due to preferential dissolution of hexadecylamine into methanol and partial removal of the protective layers on silver nanoparticle surfaces, which exhibited stable and controllable Raman enhancement effect. This strategy could be further extended to construct various chemical and biological functional sensors.

Zhang, Zhiliang; Wen, Yongqiang

2012-10-01

55

Nanosecond laser ablation of silver nanoparticle film  

NASA Astrophysics Data System (ADS)

Nanosecond laser ablation of polyvinylpyrrolidone (PVP) protected silver nanoparticle (20 nm diameter) film is studied using a frequency doubled Nd:YAG nanosecond laser (532 nm wavelength, 6 ns full width half maximum pulse width). In the sintered silver nanoparticle film, absorbed light energy conducts well through the sintered porous structure, resulting in ablation craters of a porous dome shape or crown shape depending on the irradiation fluence due to the sudden vaporization of the PVP. In the unsintered silver nanoparticle film, the ablation crater with a clean edge profile is formed and many coalesced nanoparticles of 50 to 100 nm in size are observed inside the ablation crater. These results and an order of magnitude analysis indicate that the absorbed thermal energy is confined within the nanoparticles, causing melting of nanoparticles and their coalescence to larger agglomerates, which are removed following melting and subsequent partial vaporization.

Chung, Jaewon; Han, Sewoon; Lee, Daeho; Ahn, Sanghoon; Grigoropoulos, Costas P.; Moon, Jooho; Ko, Seung H.

2013-02-01

56

Green synthesis of silver nanoparticles using marine macroalga Chaetomorpha linum  

NASA Astrophysics Data System (ADS)

The present investigation demonstrates the formation of silver nanoparticles by the reduction of the aqueous silver metal ions during exposure to the seaweed (Chaetomorpha linum) extract. The silver nanoparticles obtained were characterized by UV-visible spectrum, FTIR and scanning electron microscopy. The characteristic absorption peak at 422 nm in UV-vis spectrum confirmed the formation of silver nanoparticles. The colour intensity at 422 nm increased with duration of incubation. The size of nanoparticles synthesized varied from 3 to 44 nm with average of ~30 nm. The FTIR spectrum of C. linum extract showed peaks at 1,020, 1,112, 1,325, 1,512, 1,535, 1,610, 1,725, 1,862, 2,924, 3,330 cm-1. The vibrational bands corresponding to the bonds such as -C=C (ring), -C-O, -C-O-C and C=C (chain) are derived from water-soluble compounds such as amines, peptides, flavonoids and terpenoids present in C. linum extract. Hence, it may be inferred that these biomolecules are responsible for capping and efficient stabilization. Since no synthetic reagents were used in this investigation, it is environmentally safe and have potential for application in biomedicine and agriculture.

Kannan, R. Ragupathi Raja; Arumugam, R.; Ramya, D.; Manivannan, K.; Anantharaman, P.

2012-05-01

57

Silver nanoparticles in polyvinylpyrrolidone grafted natural rubber  

Microsoft Academic Search

Polyvinylpyrrolidone grafted natural rubber (PVP-g-NR) latex was used as matrix to synthesize silver nanoparticles. The average diameter of the silver nanoparticles is 4.1nm. The modified natural rubber was previously formed via in situ polymerization of N-vinyl-2-pyrrolidone (NVP) in natural rubber latex (NRL) using cumene hydroperoxide (CHP) and tetraethylenepentamine (TEPA) as a redox initiator. The evidence of PVP grafted rubber particles

N. H. H. Abu Bakar; J. Ismail; M. Abu Bakar

2010-01-01

58

Coupled plasmons induce broadband circular dichroism in patternable films of silver nanoparticles with chiral ligands  

NASA Astrophysics Data System (ADS)

This contribution reports the chiro-optic response of as-cast and photopatterned films of silver nanoparticles capped with photothermally-cleavable chiral ligands. We demonstrate broadband circular dichroism in these nanoparticle films, which is not present in dispersions of the nanoparticles capped with the chiral ligands. Long wavelength circular dichroism is derived from coupling of the plasmonic bands of neighbouring silver nanoparticles. Furthermore, the chiral response is preserved in the microstructured film after photopatterning using direct two-photon absorption in the plasmonic band of the silver nanoparticles. Thus, both the as-cast and photopatterned films show circular dichroism from the UV wavelength of intrinsic absorption of the ligand, through the plasmon resonances of both the isolated silver nanoparticles and the interacting nanoparticles, which extend to the near IR. Density functional theory (DFT) calculations of model electronic complexes of a chiral ligand and a small metallic cluster suggest that the new chiral bands at the plasmonic resonances are derived from new chiral hybrid electronic states of the metal nanoparticle-ligand complexes.This contribution reports the chiro-optic response of as-cast and photopatterned films of silver nanoparticles capped with photothermally-cleavable chiral ligands. We demonstrate broadband circular dichroism in these nanoparticle films, which is not present in dispersions of the nanoparticles capped with the chiral ligands. Long wavelength circular dichroism is derived from coupling of the plasmonic bands of neighbouring silver nanoparticles. Furthermore, the chiral response is preserved in the microstructured film after photopatterning using direct two-photon absorption in the plasmonic band of the silver nanoparticles. Thus, both the as-cast and photopatterned films show circular dichroism from the UV wavelength of intrinsic absorption of the ligand, through the plasmon resonances of both the isolated silver nanoparticles and the interacting nanoparticles, which extend to the near IR. Density functional theory (DFT) calculations of model electronic complexes of a chiral ligand and a small metallic cluster suggest that the new chiral bands at the plasmonic resonances are derived from new chiral hybrid electronic states of the metal nanoparticle-ligand complexes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03244b

Vidal, Xavier; Kim, Won Jin; Baev, Alexander; Tokar, Valentyna; Jee, Hongsub; Swihart, Mark. T.; Prasad, Paras N.

2013-10-01

59

Silver Nanoparticles and Mitochondrial Interaction  

PubMed Central

Nanotechnology has gone through a period of rapid growth, thus leading to the constant increase in the application of engineered nanomaterials in daily life. Several different types of nanoparticles have been engineered to be employed in a wide array of applications due to their high surface to volume ratio that leads to unique physical and chemical properties. So far, silver nanoparticles (AgNps) have been used in many more different medical devices than any other nanomaterial, mainly due to their antimicrobial properties. Despite the promising advantages posed by using AgNps in medical applications, the possible health effects associated with the inevitable human exposure to AgNps have raised concerns as to their use since a clear understanding of their specific interaction with biological systems has not been attained yet. In light of such consideration, aim of the present work is the morphological analysis of the intracellular behavior of AgNps with a diameter of 10?nm, with a special attention to their interaction with mitochondria.

Bressan, Eriberto; Ferroni, Letizia; Gardin, Chiara; Rigo, Chiara; Stocchero, Michele; Vindigni, Vincenzo; Cairns, Warren; Zavan, Barbara

2013-01-01

60

Synthesis and applications of silver nanoparticles  

NASA Astrophysics Data System (ADS)

Due to their unique properties, silver nanoparticles are used in a wide range of applications, like electronics, optics, catalysis, biology, etc. The preferred route for their preparation has been, and still is, the reduction of silver salts in solutions. While dedicated reducing agents, solvents, and dispersants are typically used in this approach, in some cases, the same additive (ex: polyols) may play multiple roles. Such dual-function additives are particularly interesting alternatives as they offer the possibility of replacing the undesirable reductants often used in conventional precipitation methods. In the current research, an environmentally friendly route to prepare stable concentrated aqueous dispersions of silver nanoparticles is investigated experimentally. It was found that Arabic gum, a well known stabilizing agent, can also rapidly and completely reduce Ag 2O to metallic silver in alkaline solutions (pH >12.0) and elevated temperature (65 °C). The average size of the silver nanoparticles could be tailored from 13 to 30 nm by varying the experimental conditions. To prepare stable metal colloids by chemical precipitation methods requires in most cases a high concentration of polymeric dispersants. Consequently, the particles are embedded in the organic matrix, which can not be removed without affecting the properties of the particles and/or the dispersion stability. This can have a negative effect in many applications. In this work, an enzymatic hydrolysis method for isolating the silver particles from dispersions containing high concentrations of polymer was identified. In addition, a chemical hydrolysis method yielding dispersed silver nanoparticles with low content of residual polymer for printable electronics applications is investigated. The low sintering temperature of silver nanoparticles and high electrical conductivity make them very attractive for the fabrication of conductive patterns especially for flexible electronic applications. In the final section of this thesis, the silver nanoparticles are deposited using inkjet printing technology with a Dimatix printer DMP -2831. Silver nanoparticles of 13 nm, 80 nm, and mixtures of the two sizes were used to evaluate the effect of particle size and size distribution on the electrical properties of sintered films. The silver layers deposited with a 'drop-on-demand' inkjet printer were heated at temperatures ranging from 125°C to 200°C. The small particles formed less resistive films at 125°C, while the larger ones provided better electrical conductivity above 150°C. The inks containing mixed small and large particles yielded the most conductive silver films over the entire investigated temperature range. A mechanism explaining these results is proposed based on the evolution of film microstructure with temperature.

Balantrapu, Krishna Chaitanya

61

Biofunctionalized silver nanoparticles: advances and prospects.  

PubMed

The unique size-dependent properties of nano scale materials have significantly impacted all spheres of human life making nanotechnology a promising field for biomedical applications. Metal nanoparticles like silver have gained significant interest over the years due to their remarkable optical, electrical and antimicrobial properties. However, the toxic nature and aggregation of these nanoparticles has limited its use in more optimized applications. Rational selection of therapeutically active biomolecules for functionalizing the surface of these particles will certainly increase the biocompatibility and biological applicability. The current review attempts to stress on the application domains of silver nanoparticles and also extends an overview on the current strategies involved in biofunctionalizing these particles for specific applications. This review is divided into three sections. The first section emphasizes the importance of silver nanoparticles and its biomedical applications. The need for functionalization and the various concepts and techniques involved in creating surface modified silver nanoparticles will be described in the second section; and the last section throws light on the various applications of the functionalized silver nanoparticles. PMID:23411404

Ravindran, Aswathy; Chandran, Preethy; Khan, S Sudheer

2012-08-03

62

Biosynthesis of silver nanoparticles from Trichoderma species.  

PubMed

A total of 75 isolates belonging to five different species of Trichoderma viz., T. asperellum, T. harzianum, T. longibrachiatum, T. pseudokoningii and T. virens were screened for the production of silver nanoparticles. Although all the isolates produced nanoparticles, T. virens VN-11 could produce maximum nanoparticles as evident from the UV-Vis study. The highest Plasmon band was observed at 420 nm at every 24 h that attained maximum intensity at 120 h (0.543). The high resolution transmission electron microscopy (HRTEM) further provided the morphology of the nanoparticles. These nanoparticles were found single or aggregated with round and uniform in shape and 8-60 nm in size. The nitrate reductase activity of VN-11 was found to be 150 nmol/h/mL which confirmed the production of silver nanoparticles through reduction of Ag+ to Ag0. PMID:23898553

Devi, T Prameela; Kulanthaivel, S; Kamil, Deeba; Borah, Jyoti Lekha; Prabhakaran, N; Srinivasa, N

2013-07-01

63

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

64

Photochromic silver nanoparticles fabricated by sputter deposition  

SciTech Connect

In this study a simple route to preparing photochromic silver nanoparticles in a TiO{sub 2} matrix is presented, which is based upon sputtering and subsequent annealing. The formation of silver nanoparticles with sizes of some tens of nanometers is confirmed by x-ray diffraction and transmission electron microscopy. The inhomogeneously broadened particle-plasmon resonance of the nanoparticle ensemble leads to a broad optical-absorption band, whose spectral profile can be tuned by varying the silver load and the annealing temperature. Multicolor photochromic behavior of this Ag-TiO{sub 2} system upon irradiation with laser light is demonstrated and discussed in terms of a particle-plasmon-assisted electron transfer from the silver nanoparticles to TiO{sub 2} and subsequent trapping by adsorbed molecular oxygen. The electron depletion in the nanoparticles reduces the light absorption at the wavelength of irradiation. A gradual recovery of the absorption band is observed after irradiation, which is explained with a slow thermal release of electrons from the oxygen trapping centers and subsequent capture into the nanoparticles. The recovery can be accelerated by ultraviolet irradiation; the explanation for this observation is that electrons photoexcited in the TiO{sub 2} are captured into the nanoparticles and restore the absorption band.

Okumu, J.; Dahmen, C.; Sprafke, A.N.; Luysberg, M.; Plessen, G. von; Wuttig, M. [Department of Physics, Kenyatta University, P.O. Box 43844, Nairobi (Kenya); I. Physikalisches Institut (IA), Lehrstuhl fuer Physik neuer Materialien, Rheinisch-Westfaelische Technische Hochschule (RWTH) Aachen, 52056 Aachen (Germany); Institut fuer Festkoerperforschung (IFF)/ Forschungszentrum Juelich, 52428 Juelich (Germany); I. Physikalisches Institut (IA), Lehrstuhl fuer Physik neuer Materialien, Rheinisch-Westfaelische Technische Hochschule (RWTH) Aachen, 52056 Aachen (Germany)

2005-05-01

65

Silver nanoparticles with gelatin nanoshells: photochemical facile green synthesis and their antimicrobial activity  

Microsoft Academic Search

In the current study, a facile green synthesis of silver-gelatin core–shell nanostructures (spherical, spherical\\/cubic hybrid,\\u000a and cubic, DLS diameter: 4.1–6.9 nm) is reported via the wet chemical synthesis procedure. Sunlight-UV as an available reducing\\u000a agent cause mild reduction of silver ions into the silver nanoparticles (Ag-NPs). Gelatin protein, as an effective capping\\/shaping\\u000a agent, was used in the reaction to self-assemble silver

Ali Pourjavadi; Rouhollah Soleyman

66

Circular dichroism study of chiral biomolecules conjugated with silver nanoparticles  

Microsoft Academic Search

Chiral biomolecules conjugated with silver nanoparticles were investigated by circular dichroism (CD) spectroscopy. Silver nanoparticles were prepared by the citrate reduction method and were characterized by UV spectroscopy and TEM. Conjugation of thiol group-containing biomolecules, such as cysteine, glutathione and penicillamine, with silver nanoparticles resulted in the generation of new characteristic CD signals in the region of 240-400 nm, whereas

Taihua Li; Hyun Gyu Park; Hee-Seung Lee; Seong-Ho Choi

2004-01-01

67

In vivo Genotoxicity of Silver Nanoparticles after 90-day Silver Nanoparticle Inhalation Exposure  

PubMed Central

Objectives The antimicrobial activity of silver nanoparticles has resulted in their widespread use in many consumer products. Yet, despite their many advantages, it is also important to determine whether silver nanoparticles may represent a hazard to the environment and human health. Methods Thus, to evaluate the genotoxic potential of silver nanoparticles, in vivo genotoxicity testing (OECD 474, in vivo micronuclei test) was conducted after exposing male and female Sprague-Dawley rats to silver nanoparticles by inhalation for 90 days according to OECD test guideline 413 (Subchronic Inhalation Toxicity: 90 Day Study) with a good laboratory practice system. The rats were exposed to silver nanoparticles (18 nm diameter) at concentrations of 0.7 × 106 particles/cm3 (low dose), 1.4 × 106 particles/cm3 (middle dose), and 2.9 × 106 particles/cm3 (high dose) for 6 hr/day in an inhalation chamber for 90 days. The rats were killed 24 hr after the last administration, then the femurs were removed and the bone marrow collected and evaluated for micronucleus induction. Results There were no statistically significant differences in the micronucleated polychromatic erythrocytes or in the ratio of polychromatic erythrocytes among the total erythrocytes after silver nanoparticle exposure when compared with the control. Conclusion The present results suggest that exposure to silver nanoparticles by inhalation for 90 days does not induce genetic toxicity in male and female rat bone marrow in vivo.

Kim, Jin Sik; Sung, Jae Hyuck; Ji, Jun Ho; Song, Kyung Seuk; Lee, Ji Hyun; Kang, Chang Soo

2011-01-01

68

Chemical synthesis and characterization of silver-protected vasoactive intestinal peptide nanoparticles.  

PubMed

We characterized a method to conjugate functional silver nanoparticles with vasoactive intestinal peptide (VIP), which could be used as a working model for further tailor-made applications based on VIP surface functionality. Despite sustained interest in the therapeutic applications of VIP, and the fact that its drugability could be largely improved by the attachament to functionalized metal nanoparticles, no methods have been described so far to obtain them. Materials & methods: VIP was conjugated to tiopronin-capped silver nanoparticles of a narrow size distribution, by means of proper linkers, to obtain VIP functionalized silver nanoparticles with two different VIP orientations (Ag-tiopronin-PEG-succinic-[His]VIP and Ag-tiopronin-PEG-VIP[His]). VIP intermediate nanoparticles were characterized by transmission-electron microscopy and Fourier transform infrared spectroscopy. VIP functionalized silver nanoparticles cytotoxicity was determined by lactate dehydrogenase release from mixed glial cultures prepared from cerebral cortices of 1-3 days-old C57/Bl mice. Cells were used for lipopolysaccharide stimulation at day 18-22 of culture. Results: Two different types of VIP-functionalized silver nanoparticles were obtained; both expose the C-terminal part of the neuropeptide, but in the first type VIP is attached to silver nanoparticle through its free amine terminus (Ag-tiopronin-PEG-succinic-[His]VIP), while in the second type, VIP N-terminus remains free (Ag-tiopronin-PEG-VIP[His]). VIP-functionalized silver nanoparticles did not compromise cellular viability and inhibited microglia-induced stimulation under inflammatory conditions. Conclusion: The chemical synthesis procedure developed to obtain VIP-functionalized silver nanoparticles rendered functional products, in terms of biological activity. The two alternative orientations designed, reduced the constraints for chemical synthesis that depends on the nanosurface to be functionalized. Our study provides, for the first time, a proof of principle to enhance the therapeutic potential of VIP with the valuable properties of metal nanoparticles for imaging, targeting and drug delivery. PMID:19958228

Fernandez-Montesinos, Rafael; Castillo, Paula M; Klippstein, Rebecca; Gonzalez-Rey, Elena; Mejias, Jose A; Zaderenko, Ana P; Pozo, David

2009-12-01

69

Coupled plasmons induce broadband circular dichroism in patternable films of silver nanoparticles with chiral ligands.  

PubMed

This contribution reports the chiro-optic response of as-cast and photopatterned films of silver nanoparticles capped with photothermally-cleavable chiral ligands. We demonstrate broadband circular dichroism in these nanoparticle films, which is not present in dispersions of the nanoparticles capped with the chiral ligands. Long wavelength circular dichroism is derived from coupling of the plasmonic bands of neighbouring silver nanoparticles. Furthermore, the chiral response is preserved in the microstructured film after photopatterning using direct two-photon absorption in the plasmonic band of the silver nanoparticles. Thus, both the as-cast and photopatterned films show circular dichroism from the UV wavelength of intrinsic absorption of the ligand, through the plasmon resonances of both the isolated silver nanoparticles and the interacting nanoparticles, which extend to the near IR. Density functional theory (DFT) calculations of model electronic complexes of a chiral ligand and a small metallic cluster suggest that the new chiral bands at the plasmonic resonances are derived from new chiral hybrid electronic states of the metal nanoparticle-ligand complexes. PMID:24056891

Vidal, Xavier; Kim, Won Jin; Baev, Alexander; Tokar, Valentyna; Jee, Hongsub; Swihart, Mark T; Prasad, Paras N

2013-09-18

70

Synthesis of antibacterial silver nanoparticles by ?-irradiation  

Microsoft Academic Search

Silver nanoparticles (Ag NPs) were synthesized by ?-irradiation of silver ions in aqueous solutions containing polyvinyl pyrrolidone (PVP). Increasing of ?-irradiation doses from 1 to 5kGy enhanced the concentration of Ag NPs, indicated by UV–vis analysis. The XRD and the TEM measurements showed the production of face-centered cubic (fcc) Ag NPs with a mean size of about 16nm. The produced

N. Sheikh; A. Akhavan; M. Z. Kassaee

2009-01-01

71

Synthesis of antibacterial silver nanoparticles by ?-irradiation  

NASA Astrophysics Data System (ADS)

Silver nanoparticles (Ag NPs) were synthesized by ?-irradiation of silver ions in aqueous solutions containing polyvinyl pyrrolidone (PVP). Increasing of ?-irradiation doses from 1 to 5 kGy enhanced the concentration of Ag NPs, indicated by UV-vis analysis. The XRD and the TEM measurements showed the production of face-centered cubic (fcc) Ag NPs with a mean size of about 16 nm. The produced nanoparticles were effectively stabilized by PVP through interactions, confirmed by the FT-IR. The relatively higher antibacterial activities of Ag NPs, synthesized through ?-irradiation method, against E. coli indicate their potential for practical applications as biocidal materials.

Sheikh, N.; Akhavan, A.; Kassaee, M. Z.

2009-12-01

72

Hyaluronan- and heparin-reduced silver nanoparticles with antimicrobial properties  

PubMed Central

Aims Silver nanoparticles exhibit unique antibacterial properties that make these ideal candidates for biological and medical applications. We utilized a clean method involving a single synthetic step to prepare silver nanoparticles that exhibit antimicrobial activity. Materials & methods These nanoparticles were prepared by reducing silver nitrate with diaminopyridinylated heparin (DAPHP) and hyaluronan (HA) polysaccharides and tested for their efficacy in inhibiting microbial growth. Results & discussion The resulting silver nanoparticles exhibit potent antimicrobial activity against Staphylococcus aureus and modest activity against Escherichia coli. Silver–HA showed greater antimicrobial activity than silver–DAPHP, while silver–glucose nanoparticles exhibited very weak antimicrobial activity. Neither HA nor DAPHP showed activity against S. aureus or E. coli. Conclusion These results suggest that DAPHP and HA silver nanoparticles have potential in antimicrobial therapeutic applications.

Kemp, Melissa M; Kumar, Ashavani; Clement, Dylan; Ajayan, Pulickel; Mousa, Shaker

2009-01-01

73

Extracellular biosynthesis of silver nanoparticles using the fungus Fusarium semitectum  

SciTech Connect

Development of environmental friendly procedures for the synthesis of metal nanoparticles through biological processes is evolving into an important branch of nanobiotechnology. In this paper, we report on the use of fungus 'Fusarium semitectum' for the extracellular synthesis of silver nanoparticles from silver nitrate solution (i.e. through the reduction of Ag{sup +} to Ag{sup 0}). Highly stable and crystalline silver nanoparticles are produced in solution by treating the filtrate of the fungus F. semitectum with the aqueous silver nitrate solution. The formations of nanoparticles are understood from the UV-vis and X-ray diffraction studies. Transmission electron microscopy of the silver particles indicated that they ranged in size from 10 to 60 nm and are mostly spherical in shape. Interestingly the colloidal suspensions of silver nanoparticles are stable for many weeks. Possible medicinal applications of these silver nanoparticles are envisaged.

Basavaraja, S.; Balaji, S.D. [Department of Materials Science, Gulbarga University, Gulbarga 585106, Karnataka (India); Department of Chemistry, Gulbarga University, Gulbarga 585106, Karnataka (India); Lagashetty, Arunkumar [Appa Institute of Engineering and Technology, Gulbarga 585102, Karnataka (India); Rajasab, A.H. [Department of Botany, Gulbarga University, Gulbarga 585106, Karnataka (India); Venkataraman, A. [Department of Materials Science, Gulbarga University, Gulbarga 585106, Karnataka (India); Department of Chemistry, Gulbarga University, Gulbarga 585106, Karnataka (India)], E-mail: raman_chem@rediffmail.com

2008-05-06

74

Novel optical nanobiosensor assembled with silver nanoparticles on gold surface  

Microsoft Academic Search

A novel optical biosensor with gold surface bound silver nanoparticles has been constructed for detection of bio-molecules like antigen, antibody protein and DNA plasmid, which exhibited distinct optical properties of localized surface plasmon resonance (LSPR). The silver colloidal nanoparticles were prepared by using sodium borohydride reduction of silver nitrate and characterized by using UV-vis absorption spectroscopy, transmission electron microscopy (TEM),

Zhong Cao; Meng-Xue Zeng; Ling Zhang; Xi-Xi Huang; Ming-Xing Wang; Fu-Chun Gong; Shu-Zhen Tan

2009-01-01

75

Phytotoxicity, accumulation and transport of silver nanoparticles by Arabidopsis thaliana.  

PubMed

The widespread availability of nano-enabled products in the global market may lead to the release of a substantial amount of engineered nanoparticles in the environment, which frequently display drastically different physiochemical properties than their bulk counterparts. The purpose of the study was to evaluate the impact of citrate-stabilised silver nanoparticles (AgNPs) on the plant Arabidopsis thaliana at three levels, physiological phytotoxicity, cellular accumulation and subcellular transport of AgNPs. The monodisperse AgNPs of three different sizes (20, 40 and 80 nm) aggregated into much larger sizes after mixing with quarter-strength Hoagland solution and became polydisperse. Immersion in AgNP suspension inhibited seedling root elongation and demonstrated a linear dose-response relationship within the tested concentration range. The phytotoxic effect of AgNPs could not be fully explained by the released silver ions. Plants exposed to AgNP suspensions bioaccumulated higher silver content than plants exposed to AgNO3 solutions (Ag(+) representative), indicating AgNP uptake by plants. AgNP toxicity was size and concentration dependent. AgNPs accumulated progressively in this sequence: border cells, root cap, columella and columella initials. AgNPs were apoplastically transported in the cell wall and found aggregated at plasmodesmata. In all the three levels studied, AgNP impacts differed from equivalent dosages of AgNO3. PMID:22263604

Geisler-Lee, Jane; Wang, Qiang; Yao, Ying; Zhang, Wen; Geisler, Matt; Li, Kungang; Huang, Ying; Chen, Yongsheng; Kolmakov, Andrei; Ma, Xingmao

2012-03-06

76

Size-Controlled and Optical Properties of Monodispersed Silver Nanoparticles Synthesized by the Radiolytic Reduction Method  

PubMed Central

Size-controlled and monodispersed silver nanoparticles were synthesized from an aqueous solution containing silver nitrate as a metal precursor, polyvinyl alcohol as a capping agent, isopropyl alcohol as hydrogen and hydroxyl radical scavengers, and deionized water as a solvent with a simple radiolytic method. The average particle size decreased with an increase in dose due to the domination of nucleation over ion association in the formation of the nanoparticles by gamma reduction. The silver nanoparticles exhibit a very sharp and strong absorption spectrum with the absorption maximum ?max blue shifting with an increased dose, owing to a decrease in particle size. The absorption spectra of silver nanoparticles of various particle sizes were also calculated using a quantum physics treatment and an agreement was obtained with the experimental absorption data. The results suggest that the absorption spectrum of silver nanoparticles possibly derived from the intra-band excitations of conduction electrons from the lowest energy state (n = 5, l = 0) to higher energy states (n ? 6; ?l = 0, ±1; ?s = 0, ±1), allowed by the quantum numbers principle. This demonstrates that the absorption phenomenon of metal nanoparticles based on a quantum physics description could be exploited to be added into the fundamentals of metal nanoparticles and the related fields of nanoscience and nanotechnology.

Saion, Elias; Gharibshahi, Elham; Naghavi, Kazem

2013-01-01

77

Subchronic oral toxicity of silver nanoparticles  

PubMed Central

Background The antibacterial effect of silver nanoparticles has resulted in their extensive application in health, electronic, consumer, medicinal, pesticide, and home products; however, silver nanoparticles remain a controversial area of research with respect to their toxicity in biological and ecological systems. Results This study tested the oral toxicity of silver nanoparticles (56 nm) over a period of 13 weeks (90 days) in F344 rats following Organization for Economic Cooperation and Development (OECD) test guideline 408 and Good Laboratory Practices (GLP). Five-week-old rats, weighing about 99 g for the males and 92 g for the females, were divided into four 4 groups (10 rats in each group): vehicle control, low-dose (30 mg/kg), middle-dose (125 mg/kg), and high-dose (500 mg/kg). After 90 days of exposure, clinical chemistry, hematology, histopathology, and silver distribution were studied. There was a significant decrease (P < 0.05) in the body weight of male rats after 4 weeks of exposure, although there were no significant changes in food or water consumption during the study period. Significant dose-dependent changes were found in alkaline phosphatase and cholesterol for the male and female rats, indicating that exposure to more than 125 mg/kg of silver nanoparticles may result in slight liver damage. Histopathologic examination revealed a higher incidence of bile-duct hyperplasia, with or without necrosis, fibrosis, and/or pigmentation, in treated animals. There was also a dose-dependent accumulation of silver in all tissues examined. A gender-related difference in the accumulation of silver was noted in the kidneys, with a twofold increase in female kidneys compared to male kidneys. Conclusions The target organ for the silver nanoparticles was found to be the liver in both the male and female rats. A NOAEL (no observable adverse effect level) of 30 mg/kg and LOAEL (lowest observable adverse effect level) of 125 mg/kg are suggested from the present study.

2010-01-01

78

Preparation and Characterization of Gold Nanoparticles with Different Capping Agents  

Microsoft Academic Search

Biocompatible gold nanoparticles have gained considerable attention in recent years for potential applications in bio-diagnostics, gas sensing, catalysis, and nanomedicine due to their interesting size-dependent properties. In the present work a chemical reduction method is used to produce gold nanoparticles with different capping agents. These nanoparticles were prepared by reducing HAuCl4 using citrate and trialanine phosphine (THPAL) and then capping

S. Vijaya Kumar; S. Ganesan

2011-01-01

79

Inoculation of silicon nanoparticles with silver atoms.  

PubMed

Silicon (Si) nanoparticles were coated inflight with silver (Ag) atoms using a novel method to prepare multicomponent heterostructured metal-semiconductor nanoparticles. Molecular dynamics (MD) computer simulations were employed, supported by high-resolution bright field (BF) transmission electron microscopy (HRTEM) and aberration-corrected scanning transmission electron microscopy (STEM) with a resolution ?0.1?nm in high angle annular dark field (HAADF) mode. These studies revealed that the alloying behavior and phase dynamics during the coating process are more complex than when attaching hetero-atoms to preformed nanoparticles. According to the MD simulations, Ag atoms condense, nucleate and diffuse into the liquid Si nanoparticles in a process that we term "inoculation", and a phase transition begins. Subsequent solidification involves an intermediate alloying stage that enabled us to control the microstructure and crystallinity of the solidified hybrid heterostructured nanoparticles. PMID:24170178

Cassidy, Cathal; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Djurabekova, Flyura; Nordlund, Kai; Sowwan, Mukhles

2013-10-30

80

Inoculation of silicon nanoparticles with silver atoms  

PubMed Central

Silicon (Si) nanoparticles were coated inflight with silver (Ag) atoms using a novel method to prepare multicomponent heterostructured metal-semiconductor nanoparticles. Molecular dynamics (MD) computer simulations were employed, supported by high-resolution bright field (BF) transmission electron microscopy (HRTEM) and aberration-corrected scanning transmission electron microscopy (STEM) with a resolution ?0.1?nm in high angle annular dark field (HAADF) mode. These studies revealed that the alloying behavior and phase dynamics during the coating process are more complex than when attaching hetero-atoms to preformed nanoparticles. According to the MD simulations, Ag atoms condense, nucleate and diffuse into the liquid Si nanoparticles in a process that we term “inoculation”, and a phase transition begins. Subsequent solidification involves an intermediate alloying stage that enabled us to control the microstructure and crystallinity of the solidified hybrid heterostructured nanoparticles.

Cassidy, Cathal; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Djurabekova, Flyura; Nordlund, Kai; Sowwan, Mukhles

2013-01-01

81

Toxicity of various silver nanoparticles compared to silver ions in Daphnia magna  

PubMed Central

Background To better understand the potential ecotoxicological impacts of silver nanoparticles released into freshwater environments, the Daphnia magna 48-hour immobilization test was used. Methods The toxicities of silver nitrate, two types of colloidal silver nanoparticles, and a suspension of silver nanoparticles were assessed and compared using standard OECD guidelines. Also, the swimming behavior and visible uptake of the nanoparticles by Daphnia were investigated and compared. The particle suspension and colloids used in the toxicity tests were well-characterized. Results The results obtained from the exposure studies showed that the toxicity of all the silver species tested was dose and composition dependent. Plus, the silver nanoparticle powders subsequently suspended in the exposure water were much less toxic than the previously prepared silver nanoparticle colloids, whereas the colloidal silver nanoparticles and AgNO3 were almost similar in terms of mortality. The silver nanoparticles were ingested by the Daphnia and accumulated under the carapace, on the external body surface, and connected to the appendages. All the silver species in this study caused abnormal swimming by the D. magna. Conclusion According to the present results, silver nanoparticles should be classified according to GHS (Globally Harmonized System of classification and labeling of chemicals) as "category acute 1" to Daphnia neonates, suggesting that the release of nanosilver into the environment should be carefully considered.

2012-01-01

82

Adhesion of silver nanoparticles on the montmorillonite surface  

Microsoft Academic Search

Adhesion of silver nanoparticles on the montmorillonite substrate was investigated using molecular modeling (force field calculations) and experiment (infrared spectroscopy, high-resolution transmission electron microscopy). Modeling revealed the preferred orientation of silver nanoparticles on the silicate substrate and showed the strong dependence of total energy and stability of nanocomposite structure on two factors: (1) the mutual crystallographic orientation of nanoparticle and

Jonás Tokarský; Pavla ?apková; Volker Klemm; David Rafaja; Jana Kukutschová

2010-01-01

83

Green synthesis of silver nanoparticles using Macrotyloma uniflorum  

Microsoft Academic Search

Green synthesis of noble metal nanoparticles is a vast developing area of research. In this paper we report the green synthesis of silver nanoparticles using aqueous seed extract of Macrotyloma uniflorum. The effect of experimental parameters such as amount of extract, temperature and pH on the formation of silver nanoparticles was studied. The as prepared samples are characterized using XRD,

V. K. Vidhu; S. Aswathy Aromal; Daizy Philip

2011-01-01

84

Printed UHF RFID antennas with high efficiencies using nano-particle silver ink.  

PubMed

One of the most popular targets of conductive ink technology is to print RFID tag antennas. However, the printed RFID antennas, manufactured by conductive silver ink which is generally based on microsized silver particles, have lower conductivity and consequently lower radiation efficiency than those by conventional copper etching method. This work demonstrates nano-particle conductive silver ink that is capable of printing UHF RFID antennas with improved radiation efficiency. Compared with commercial micro-particle silver ink, the solid content of metal is much higher in the proposed nanoparticle silver ink, leading to better electrical properties. Two types of dipole antennas are printed with the proposed nano-particle as well as with commercial micro-particle inks. Also, the same antennas are fabricated by copper etching. With these conductive inks, a straight and a meandered dipole antennas are fabricated and their radiation efficiencies are measured with the Wheeler cap method. Experimental results show that the radiation efficiencies of the antennas based on nanoparticle silver ink are superior to those printed with the micro-particle silver ink, and are comparable to those of popular copper antennas. PMID:22121728

Lee, Yongshik; Kim, Chung Hwan; Shin, Dong-Youn; Kim, Young Gook

2011-07-01

85

Three strategies to stabilise nearly monodispersed silver nanoparticles in aqueous solution  

PubMed Central

Silver nanoparticles are extensively used due to their chemical and physical properties and promising applications in areas such as medicine and electronics. Controlled synthesis of silver nanoparticles remains a major challenge due to the difficulty in producing long-term stable particles of the same size and shape in aqueous solution. To address this problem, we examine three strategies to stabilise aqueous solutions of 15 nm citrate-reduced silver nanoparticles using organic polymeric capping, bimetallic core-shell and bimetallic alloying. Our results show that these strategies drastically improve nanoparticle stability by distinct mechanisms. Additionally, we report a new role of polymer functionalisation in preventing further uncontrolled nanoparticle growth. For bimetallic nanoparticles, we attribute the presence of a higher valence metal on the surface of the nanoparticle as one of the key factors for improving their long-term stability. Stable silver-based nanoparticles, free of organic solvents, will have great potential for accelerating further environmental and nanotoxicity studies. PACS: 81.07.-b; 81.16.Be; 82.70.Dd.

2012-01-01

86

Shell crosslinked nanoparticles carrying silver antimicrobials as therapeutics†  

PubMed Central

Amphiphilic polymer nanoparticles loaded with silver cations or/and N-heterocyclic carbene–silver complexes were assessed as antimicrobial agents against Gram-negative pathogens Escherichia coli and Pseudomonas aeruginosa.

Li, Yali; Hindi, Khadijah; Watts, Kristin M.; Taylor, Jane B.; Zhang, Ke; Li, Zicheng

2010-01-01

87

Silver nanoparticles produced by green production method  

NASA Astrophysics Data System (ADS)

Nanomaterials as novel materials with nanometer sizes are involved in higher performance technology. On this context nanobiotechnology is able to create different nanostructures using living organisms.An attractive research area is the application of microorganisms to synthesize nanoparticles from different metals, one of which is silver, an antimicrobial agent. Green production methods have a considerable interest for environmental protection, often based on plant extracts, organic compounds or microorganisms (bacteria, fungi, algae). Marine plants were used as "real factors" for synthesis of nanoparticles of Au and Ag using different processes of biomineralization. This paper deals with a complete study about obtaining silver nanoparticles from AgNO3 using red algae (Porphyridium purpureum). The red algae contain the red pigment-phycobilins, responsible for red color and for the strong absorption in visible spectrum. The properties and structure of silver nanoparticles have been put into evidence by means of: Fourier transform infrared spectroscopy-FTIR, optical microscopy, X-ray fluorescence spectrometry-EDXRF.

Bunghez, Ioana-Raluca; Ion, Rodica-Mariana; Velea, Sanda; Ilie, Lucia; Fierascu, Radu-Claudiu; Dumitriu, Irina; Dinu, Angela; Troncea, Simona

2010-09-01

88

On the fluorescence of luminol in a silver nanoparticles complex.  

PubMed

The photophysical properties of luminol in a silver nanoparticles complex have been studied by steady-state and time resolved fluorescence spectroscopy. The effect of the serum albumin on the luminol fluorescence in the silver nanoparticles has been also investigated. It was found that the fluorescence quantum yield value of luminol in a silver nanoparticles complex is ? = 0.00407. The decrease of the average fluorescence lifetime value of the luminol in the silver nanoparticles complex was found to be low, = 1.712 ns. The luminol does not bind to the serum albumins in the presence of silver nanoparticles. The formation of a new species of luminol on silver nanoparticles is discussed. The results have influence regarding the use of luminol as an assay for bio-analytical applications. PMID:23463296

Voicescu, Mariana; Ionescu, Sorana

2013-03-06

89

Mode of antiviral action of silver nanoparticles against HIV1  

Microsoft Academic Search

BACKGROUND: Silver nanoparticles have proven to exert antiviral activity against HIV-1 at non-cytotoxic concentrations, but the mechanism underlying their HIV-inhibitory activity has not been not fully elucidated. In this study, silver nanoparticles are evaluated to elucidate their mode of antiviral action against HIV-1 using a panel of different in vitro assays. RESULTS: Our data suggest that silver nanoparticles exert anti-HIV

Humberto H Lara; Nilda V Ayala-Nuñez; Liliana Ixtepan-Turrent; Cristina Rodriguez-Padilla

2010-01-01

90

Silver nanoparticle studded porous polyethylene scaffolds: bacteria struggle to grow on them while mammalian cells thrive.  

PubMed

Silver nanoparticle studded scaffolds were prepared by exploiting the Ag(+) ion reducing activity of sophorolipids--a class of 'glycolipids' that cap the ensuing nanoparticles as well. To achieve this, the porous polyethylene scaffolds are subjected to N(2) + H(2) plasma treatment, in the first step. Subsequently the sophorolipids are covalently attached to the amine groups on the polymer surface through simple amide chemistry to yield sophorolipid grafted polymer scaffolds. These are then exposed to Ag(+) ions under appropriate conditions leading to the formation of silver nanoparticles immobilized on the polymer scaffolds. It has been found that while bacteria do not survive on these silver studded scaffolds, CHO-K1 cells thrive on them making them good candidates for tissue engineering and bio-implant applications. PMID:21643585

D'Britto, Virginia; Kapse, Harsha; Babrekar, Harshada; Prabhune, A A; Bhoraskar, S V; Premnath, V; Prasad, B L V

2011-06-03

91

Immobilization of silver nanoparticles on silica microspheres  

Microsoft Academic Search

The silver nanoparticles (Ag NPs) have been immobilized onto silica microspheres through the adsorption and subsequent reduction\\u000a of Ag+ ions on the surfaces of the silica microspheres. The neat silica microspheres that acted as the core materials were prepared\\u000a through sol–gel processing; their surfaces were then functionalized using 3-mercaptopropyltrimethoxysilane (MPTMS). The major\\u000a aims of this study were to immobilize differently

Chih-Kai Huang; Chia-Yin Chen; Jin-Lin Han; Chii-Chang Chen; Meng-Dan Jiang; Jen-Sung Hsu; Chia-Hua Chan; Kuo-Huang Hsieh

2010-01-01

92

Mechanism of Silver Nanoparticles as a Disinfectant  

Microsoft Academic Search

Using environmentally friendly synthesis techniques, monodispersive silver nanoparticles (AgNPs) were engineered. These particles exhibited bactericidal activity against Escherichia coli under both light and dark conditions. Unlike sodium hypochlorite, which demonstrated almost immediate disinfection, AgNPs required 30 min. In contrast to hypochlorite, however, the minimum dose of AgNPs decreased as the incubation time increased to less than 1 part per million.

Sajid Bashir; Karthik Chamakura; Rafael Perez-Ballestero; Zhiping Luo; Jingbo Liu

2011-01-01

93

Extracellular synthesis of silver nanoparticles by a silver-tolerant yeast strain MKY3  

NASA Astrophysics Data System (ADS)

Silver nanoparticles in the size range of 2-5 nm were synthesized extracellularly by a silver-tolerant yeast strain MKY3, when challenged with 1 mM soluble silver in the log phase of growth. The nanoparticles were separated from dilute suspension by devising a new method based on differential thawing of the sample. Optical absorption, transmission electron microscopy, x-ray diffraction and x-ray photoelectron spectroscopy investigations confirmed that metallic (elemental) silver nanoparticles were formed. Extracellular synthesis of nanoparticles could be highly advantageous from the point of view of synthesis in large quantities and easy downstream processing.

Kowshik, Meenal; Ashtaputre, Shriwas; Kharrazi, Sharmin; Vogel, W.; Urban, J.; Kulkarni, S. K.; Paknikar, K. M.

2003-01-01

94

Extracellular synthesis of silver nanoparticles using living peanut seedling  

NASA Astrophysics Data System (ADS)

Synthesis of nanoparticles by environment friendly method is an important aspect of nanotechnology. In the present study, extracellular reduction of silver ions to silver nanoparticles was carried out using living peanut plant. The electron microscopic analysis shows that the formed nanoparticles were of different shapes and sizes. The formed nanoparticles were polydispersed. The shapes of the nanoparticles were spherical, square, triangle, hexagonal and rod. Most of the particles were spherical and 56 nm in size. EDS analysis confirmed the formed nanoparticles were of silver. The crystalline nature of nanoparticles was confirmed by diffraction. This method opens up an exciting possibility of plant-based synthesis of other inorganic nanomaterials. This study confirms the synthesis of extracellular silver nanoparticles by living plant.

Raju, D.; Paneliya, Nikita; Mehta, Urmil J.

2013-09-01

95

Antimicrobial efficacy and ocular cell toxicity from silver nanoparticles  

PubMed Central

Silver in various forms has long been recognized for antimicrobial properties, both in biomedical devices and in eyes. However, soluble drugs used on the ocular surface are rapidly cleared through tear ducts and eventually ingested, resulting in decreased efficacy of the drug on its target tissue and potential concern for systemic side effects. Silver nanoparticles were studied as a source of anti-microbial silver for possible controlled-release contact lens controlled delivery formulations. Silver ion release over a period of several weeks from nanoparticle sources of various sizes and doses in vitro was evaluated in vitro against Pseudomonas aeruginosa strain PA01. Mammalian cell viability and cytokine expression in response to silver nanoparticle exposure is evaluated using corneal epithelial cells and eye-associated macrophages cultured in vitro in serum-free media. Minimal microcidal and cell toxic effects were observed for several silver nanoparticle suspensions and aqueous extraction times for bulk total silver concentrations commensurate with comparative silver ion (e.g., Ag+(aq)) toxicity. This indicates that (1) silver particles themselves are not microcidal under conditions tested, and (2) insufficient silver ion is generated from these particles at these loadings to produce observable biological effects in these in vitro assays. If dosing allows substantially increased silver particle loading in the lens, the bactericidal efficacy of silver nanoparticles in vitro is one possible approach to limiting bacterial colonization problems associated with extended-wear contact lenses.

Santoro, Colleen M.; Duchsherer, Nicole L.

2009-01-01

96

Green synthesis of silver nanoparticles using white sugar.  

PubMed

Till date several methods of chemical synthesis of silver nanoparticles (AgNps) are known. Most of the protocol dealing with the chemical synthesis of AgNps involves high pressure, temperature, energy and technical skills. Thus, a method with much greener approach is the need of the hour. Accordingly, the authors have developed a method that is cost-effective, energy-efficient and easy method for the synthesis of AgNps. The AgNps were synthesised by using white sugar and sodium hydroxide (NaOH) in the presence of sunlight. These nanoparticles were characterised by visual observation, ultraviolet-visible (UV-vis) spectrophotometry, Fourier transform infrared (FTIR), nanoparticle tracking and analysis (NTA) and transmission electron microscopy (TEM). The effect of NaOH on the rate of AgNps synthesis was also studied. Formation of AgNps was primarily detected by change in colour of reaction mixture from colourless to yellow after treatment with 1 mM silver salt (AgNO3). UV-vis spectroscopy showed peak at 409 nm. NTA revealed the polydispersed nature of nanoparticles, 15-30 nm in diameter. FTIR showed the presence of gluconic acid as capping agent, which increases the stability of AgNps in the colloids. TEM demonstrated the presence of spherical AgfNps in the range of 10-25 nm. The present method confirms the synthesis of AgNps by using white sugar and NaOH. This method is simple, eco-friendly and economically sustainable, making it amenable to large-scale industrial production of AgNps. PMID:23705290

Meshram, Sachin M; Bonde, Shital R; Gupta, Indarchand R; Gade, Aniket K; Rai, Mahendra K

2013-03-01

97

Silver Nanoparticles in Cellulose Acetate Polymers: Rheological and Morphological Properties  

Microsoft Academic Search

Silver nitrate was incorporated in cellulose acetate with different substitution degrees as a dispersion medium. Silver-containing polymer solutions in 2-methoxyethanol were rheologically investigated, both before and after boiling, which permitted a better understanding of the morphological aspects of the corresponding cast films. The different distribution of the obtained silver nanoparticles in the polymer matrix, as well as the influence of

Adina Maria Necula; Iuliana Stoica; Niculae Olaru; Florica Doroftei; Silvia Ioan

2011-01-01

98

Adhesion mechanisms of nanoparticle silver to substrate materials: identification  

Microsoft Academic Search

Nanoparticle silver (NPS) conductors are increasingly being investigated for printed electronics applications. However, the adhesion mechanism of the nanoparticle silver to substrate materials has not been identified yet. In particular, the adhesion of NPS to organic materials such as the widely used polyimide Kapton HN and Kapton FPC dry films is concerned with low adhesion strength because the processed polymer

Sungchul Joo; Daniel F. Baldwin

2010-01-01

99

Optical Properties and Sizes of Silver Nanoparticles in Micellar Solutions  

Microsoft Academic Search

Sizes of silver nanoparticles prepared by the reduction of silver ions in reverse micelles with solvated electron (radiation-chemical synthesis) and natural pigment quercetin (biochemical synthesis) were determined. The sizes were measured by the dynamic light-scattering technique. Histograms of the micelle size distributions were compared with the absorption spectra of the corresponding solutions of nanoparticles. It was shown that the employed

E. M. Egorova; A. A. Revina

2002-01-01

100

Biogenic silver nanoparticles with chlorogenic acid as a bioreducing agent.  

PubMed

We report the synthesis of biogenic silver nanoparticles using chlorogenic acid as a bioreducing agent. Chlorogenic acid is a polyphenol compound abundant in coffee. UV-Vis spectra showed the characteristic surface plasmon resonance band at 415 nm, indicating the successful synthesis of biogenic silver nanoparticles. Spherical and irregular shaped nanoparticles were observed with an average diameter of 19.29 +/- 8.23 nm. The reaction yield from silver ion to silver nanoparticles was observed as 95.43% by using inductively coupled plasma-mass spectrometry. Fourier transform infrared spectra revealed that the -C = O groups of chlorogenic acid may coordinate or complex into silver nanoparticles. Biogenic silver nanoparticles exerted higher antibacterial activity against Gram-negative bacteria than against Gram-positive bacteria. Interestingly, a comparable antibacterial activity to a standard antibiotic was observed against two strains of Pseudomonas aeruginosa (minimum inhibitory concentration of 0.66 microg/mL). The synergistic effect of a combination of silver nanoparticles and chlorogenic acid on antibacterial activity is obvious, leading to approximately 8-fold enhancement in the case of Pseudomonas aeruginosa when compared with chlorogenic acid alone. The present report suggests that a pure compound with a plant origin is capable of being a bioreducing agent for the synthesis of biogenic silver nanoparticles with superior antibacterial activity, opening up many applications in nanomedicine and nanobiotechnology. PMID:23882836

Noh, Hwa Jung; Kim, Hyun-Seok; Jun, Sang Hui; Kang, Young-Hwa; Cho, Seonho; Park, Youmie

2013-08-01

101

Active Silver Nanoparticles for Wound Healing  

PubMed Central

In this preliminary study, the silver nanoparticle (Ag NP)-based dressing, Acticoat™ Flex 3, has been applied to a 3D fibroblast cell culture in vitro and to a real partial thickness burn patient. The in vitro results show that Ag NPs greatly reduce mitochondrial activity, while cellular staining techniques show that nuclear integrity is maintained, with no signs of cell death. For the first time, transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS) analyses were carried out on skin biopsies taken from a single patient during treatment. The results show that Ag NPs are released as aggregates and are localized in the cytoplasm of fibroblasts. No signs of cell death were observed, and the nanoparticles had different distributions within the cells of the upper and lower dermis. Depth profiles of the Ag concentrations were determined along the skin biopsies. In the healed sample, most of the silver remained in the surface layers, whereas in the unhealed sample, the silver penetrated more deeply. The Ag concentrations in the cell cultures were also determined. Clinical observations and experimental data collected here are consistent with previously published articles and support the safety of Ag NP-based dressing in wound treatment.

Rigo, Chiara; Ferroni, Letizia; Tocco, Ilaria; Roman, Marco; Munivrana, Ivan; Gardin, Chiara; Cairns, Warren R. L.; Vindigni, Vincenzo; Azzena, Bruno; Barbante, Carlo; Zavan, Barbara

2013-01-01

102

Polyhexamethylene biguanide functionalized cationic silver nanoparticles for enhanced antimicrobial activity  

PubMed Central

Polyhexamethylene biguanide (PHMB), a broad spectrum disinfectant against many pathogens, was used as a stabilizing ligand for the synthesis of fairly uniform silver nanoparticles. The particles formed were characterized using UV-visible spectroscopy, FTIR, dynamic light scattering, electrophoretic mobility, and TEM to measure their morphology and surface chemistry. PHMB-functionalized silver nanoparticles were then evaluated for their antimicrobial activity against a gram-negative bacterial strain, Escherichia coli. These silver nanoparticles were found to have about 100 times higher bacteriostatic and bactericidal activities, compared to the previous reports, due to the combined antibacterial effect of silver nanoparticles and PHMB. In addition to other applications, PHMB-functionalized silver nanoparticles would be extremely useful in textile industry due to the strong interaction of PHMB with cellulose fabrics.

2012-01-01

103

Silver as antibacterial agent: Metal nanoparticles to nanometallopharmaceuticals: (Silver based antibacterial nanometallopharmaceuticals)  

Microsoft Academic Search

Because of increase in bacterial resistance to common antibiotics, antibacterial nanometallopharmaceuticals have been drawing increasing interest. Recent literature reports encouraging results about the bactericidal activity of silver nanoparticles of either a simple or composite nature. We, for the first time, demonstrated that silver nanoparticles (AgNP) undergo a shape dependant interaction with bacteria. We also developed highly antibacterial porous carbon matrices

Joon Myong Song

2010-01-01

104

Microbial synthesis of silver nanoparticles by Bacillus sp  

Microsoft Academic Search

A silver resistant Bacillus sp. was isolated through exposure of an aqueous AgNO3 solution to the atmosphere. Silver nanoparticles were synthesized using these airborne bacteria (Bacillus sp.). Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analyses confirmed that silver nanoparticles\\u000a of 5–15 nm in size were deposited in the periplasmic space of the bacterial cells; a preferable cell surface location

Nalenthiran Pugazhenthiran; Sambandam Anandan; Govindarajan Kathiravan; Nyayiru Kannaian Udaya Prakash; Simon Crawford; Muthupandian Ashokkumar

2009-01-01

105

Investigating Fluorescence Quenching of ZnS Quantum Dots by Silver Nanoparticles  

Microsoft Academic Search

Water dispersible zinc sulfide quantum dots (ZnS QDs) with an average diameter of 2.9 nm were synthesized in an environment\\u000a friendly method using chitosan as stabilizing agent. These nanocrystals displayed characteristic absorption and emission spectra\\u000a having an absorbance edge at 300 nm and emission maxima (?\\u000a emission) at 427 nm. Citrate-capped silver nanoparticles (Ag NPs) of ca. 37-nm diameter were prepared by modified

Amit Jaiswal; Pallab Sanpui; Arun Chattopadhyay; Siddhartha Sankar Ghosh

2011-01-01

106

Influence of synthetic parameters on the size, structure, and stability of dodecanethiol-stabilized silver nanoparticles  

Microsoft Academic Search

Metal nanoparticles (NP) are very attractive because of their size- and shape-dependent properties. A widely used preparation of ligand-stabilized metal NP is the two-phase liquid–liquid method using dodecanethiol (DT) as ligand. This work presents various procedures to synthesize dodecanethiol-capped silver NPs, all of them based on a two-phase liquid–liquid method. Small alterations in the synthetic parameters lead to dramatic modifications

Marcela M. Oliveira; Daniel Ugarte; Daniela Zanchet; Aldo J. G. Zarbin

2005-01-01

107

Evaluation of green synthesized silver nanoparticles against parasites.  

PubMed

Green nanoparticle synthesis has been achieved using environmentally acceptable plant extract and eco-friendly reducing and capping agents. The present study was based on assessments of the antiparasitic activities to determine the efficacies of synthesized silver nanoparticles (AgNPs) using aqueous leaf extract of Mimosa pudica Gaertn (Mimosaceae) against the larvae of malaria vector, Anopheles subpictus Grassi, filariasis vector Culex quinquefasciatus Say (Diptera: Culicidae), and Rhipicephalus (Boophilus) microplus Canestrini (Acari: Ixodidae). Parasite larvae were exposed to varying concentrations of aqueous extract of M. pudica and synthesized AgNPs for 24 h. AgNPs were rapidly synthesized using the leaf extract of M. pudica and the formation of nanoparticles was observed within 6 h. The results recorded from UV-vis spectrum, Fourier transform infrared, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy support the biosynthesis and characterization of AgNPs. The maximum efficacy was observed in synthesized AgNPs against the larvae of A. subpictus, C. quinquefasciatus, and R. microplus (LC(50)?= 13.90, 11.73, and 8.98 mg/L, r (2)?= 0.411, 0.286, and 0.479), respectively. This is the first report on antiparasitic activity of the plant extract and synthesized AgNPs. PMID:21181192

Marimuthu, Sampath; Rahuman, Abdul Abdul; Rajakumar, Govindasamy; Santhoshkumar, Thirunavukkarasu; Kirthi, Arivarasan Vishnu; Jayaseelan, Chidambaram; Bagavan, Asokan; Zahir, Abdul Abduz; Elango, Gandhi; Kamaraj, Chinnaperumal

2010-12-22

108

Green Synthesis of Silver Nanoparticles Using Pinus eldarica Bark Extract  

PubMed Central

Recently, development of reliable experimental protocols for synthesis of metal nanoparticles with desired morphologies and sizes has become a major focus of researchers. Green synthesis of metal nanoparticles using organisms has emerged as a nontoxic and ecofriendly method for synthesis of metal nanoparticles. The objectives of this study were production of silver nanoparticles using Pinus eldarica bark extract and optimization of the biosynthesis process. The effects of quantity of extract, substrate concentration, temperature, and pH on the formation of silver nanoparticles are studied. TEM images showed that biosynthesized silver nanoparticles (approximately in the range of 10–40?nm) were predominantly spherical in shape. The preparation of nano-structured silver particles using P. eldarica bark extract provides an environmentally friendly option, as compared to currently available chemical and/or physical methods.

Iravani, Siavash; Zolfaghari, Behzad

2013-01-01

109

Toxicity of Silver Nanoparticles at the Air-Liquid Interface  

PubMed Central

Silver nanoparticles are one of the most prevalent nanomaterials in consumer products. Some of these products are likely to be aerosolized, making silver nanoparticles a high priority for inhalation toxicity assessment. To study the inhalation toxicity of silver nanoparticles, we have exposed cultured lung cells to them at the air-liquid interface. Cells were exposed to suspensions of silver or nickel oxide (positive control) nanoparticles at concentrations of 2.6, 6.6, and 13.2??g cm?2 (volume concentrations of 10, 25, and 50??g?ml?1) and to 0.7??g?cm?2 silver or 2.1??g?cm?2 nickel oxide aerosol at the air-liquid interface. Unlike a number of in vitro studies employing suspensions of silver nanoparticles, which have shown strong toxic effects, both suspensions and aerosolized nanoparticles caused negligible cytotoxicity and only a mild inflammatory response, in agreement with animal exposures. Additionally, we have developed a novel method using a differential mobility analyzer to select aerosolized nanoparticles of a single diameter to assess the size-dependent toxicity of silver nanoparticles.

Holder, Amara L.; Marr, Linsey C.

2013-01-01

110

Silver nanoparticle polymer composite based humidity sensor.  

PubMed

Silver nanoparticles were synthesised by a chemical reduction process in order to produce an aqueous colloidal dispersion. The resulting colloids were then characterised by a combination of UV-Vis spectroscopy, dynamic light scattering, X-ray diffraction and transmission electron microscopy and the nanoparticles were found to have an average diameter of 20-22 nm. The Ag/polymer nanocomposites were then applied to platinum interdigital electrodes as sensor coatings and the capability of the resulting sensor as a humidity detector investigated. With the application of 1 V, a current developed which was found to be directly proportional to humidity levels. The sensor gives a reversible, selective and rapid response which is proportional to levels of humidity within the range of 10% RH to 60% RH. An investigation into the mechanism of the sensor's response was conducted and the response was found to correlate well with a second order Langmuir adsorption model. PMID:20514383

Power, Aoife C; Betts, Anthony J; Cassidy, John F

2010-06-01

111

Photocatalytic studies of capped ZnS nanoparticles  

NASA Astrophysics Data System (ADS)

In this work, we report on the synthesis of ZnS semiconductor nanoparticles stabilized with sodium hexa meta phosphate (SHMP). Capped ZnS nanoparticles were synthesized by a chemical route. The as obtained nanoparticles were characterized by X-ray diffraction (XRD), uv-vis absorption spectroscopy, and photoluminescence (PL) spectroscopy. The average particle size was found to be 2-3 nm. UV-Vis optical spectra showed a blue shift with respect to the bulk counterpart. The room temperature photoluminescence spectra of the nanoparticles showed emission peaks in the range of 363 - 446 nm at excitation wavelength of 325 nm for different concentrations of SHMP. Photocatalytic degradation of bromophenol blue dye was done using capped ZnS nanoparticles. It took about 3.5 hours to degrade the dye completely under uv irradiation.

Kaur, Jagdeep; Sharma, Manoj; Pandey, O. P.

2013-06-01

112

Multiutility sophorolipids as nanoparticle capping agents: synthesis of stable and water dispersible Co nanoparticles.  

PubMed

Sophorolipids are a class of glycolipids that can be obtained from fatty acids by simply treating them with yeast cells (Candida bombicola, ATCC 22214) and glucose. In this letter, we demonstrate the application of sophorolipids obtained from oleic acid as a capping agent for Co nanoparticles. Upon capping the nanoparticle surface, the sugar moiety of these sophorolipids is exposed to the solvent environment, making the nanoparticles stable and water-redispersible. PMID:17935370

Kasture, Manasi; Singh, Sanjay; Patel, Pitamber; Joy, P A; Prabhune, A A; Ramana, C V; Prasad, B L V

2007-10-13

113

Silver Nanoparticles and Graphitic Carbon Through Thermal Decomposition of a Silver/Acetylenedicarboxylic Salt  

NASA Astrophysics Data System (ADS)

Spherically shaped silver nanoparticles embedded in a carbon matrix were synthesized by thermal decomposition of a Ag(I)/acetylenedicarboxylic acid salt. The silver nanoparticles, which are formed either by pyrolysis at 300 °C in an autoclave or thermolysis in xylene suspension at reflux temperature, are acting catalytically for the formation of graphite layers. Both reactions proceed through in situ reduction of the silver cations and polymerization of the central acetylene triple bonds and the exact temperature of the reaction can be monitored through DTA analysis. Interestingly, the thermal decomposition of this silver salt in xylene partly leads to a minor fraction of quasicrystalline silver, as established by HR-TEM analysis. The graphitic layers covering the silver nanoparticles are clearly seen in HR-TEM images and, furthermore, established by the presence of sp2 carbon at the Raman spectrum of both samples.

Dallas, Panagiotis; Bourlinos, Athanasios B.; Komninou, Philomela; Karakassides, Michael; Niarchos, Dimitrios

2009-11-01

114

Photoswitchable bactericidal effects from novel silica-coated silver nanoparticles  

Microsoft Academic Search

The enhancement of the electromagnetic field in the surroundings of nanoparticles via surface plasmon resonance offers promising possibilities for biomedical applications. Here we report on the selective triggering of antibacterial activity using a new type of silver nanoparticles coated with silica, Ag@silica, irradiated at their surface plasmon frequency. The nanoparticles are able to bind readily to the surface of bacterial

Gustavo Fuertes; Esteban Pedrueza; Kamal Abderrafi; Rafael Abargues; Orlando Sánchez; Juan Martínez-Pastor; Jesús Salgado; Ernesto Jiménez

2011-01-01

115

Development of nanostructured silver vanadates decorated with silver nanoparticles as a novel antibacterial agent  

NASA Astrophysics Data System (ADS)

In this work we report the synthesis, characterization and application of silver vanadate nanowires decorated with silver nanoparticles as a novel antibacterial agent. These hybrid materials were synthesized by a precipitation reaction of ammonium vanadate and silver nitrate followed by hydrothermal treatment. The silver vanadate nanowires have lengths of the order of microns and diameters around 60 nm. The silver nanoparticles decorating the nanowires present a diameter distribution varying from 1 to 20 nm. The influence of the pH of the reaction medium on the chemical structure and morphology of silver vanadates was studied and we found that synthesis performed at pH 5.5-6.0 led to silver vanadate nanowires with a higher morphological yield. The antimicrobial activity of these materials was evaluated against three strains of Staphylococcus aureus and very promising results were found. The minimum growth inhibiting concentration value against a MRSA strain was found to be ten folds lower than for the antibiotic oxacillin.

Holtz, R. D.; Souza Filho, A. G.; Brocchi, M.; Martins, D.; Durán, N.; Alves, O. L.

2010-05-01

116

Silver nanoparticle toxicity in Drosophila: size does matter  

PubMed Central

Background: Consumer nanotechnology is a growing industry. Silver nanoparticles are the most common nanomaterial added to commercially available products, so understanding the influence that size has on toxicity is integral to the safe use of these new products. This study examined the influence of silver particle size on Drosophila egg development by comparing the toxicity of both nanoscale and conventional-sized silver particles. Methods: The toxicity assays were conducted by exposing Drosophila eggs to particle concentrations ranging from 10 ppm to 100 ppm of silver. Size, chemistry, and agglomeration of the silver particles were evaluated using transmission electron microscopy, X-ray photoelectron spectroscopy, and dynamic light scattering. Results: This analysis confirmed individual silver particle sizes in the ranges of 20–30 nm, 100 nm, and 500–1200 nm, with similar chemistry. Dynamic light scattering and transmission electron microscope data also indicated agglomeration in water, with the transmission electron microscopic images showing individual particles in the correct size range, but the dynamic light scattering z-average sizes of the silver nanoparticles were 782 ± 379 nm for the 20–30 nm silver nanoparticles, 693 ± 114 nm for the 100 nm silver nanoparticles, and 508 ± 32 nm for the 500–1200 nm silver particles. Most importantly, here we show significantly more Drosophila egg toxicity when exposed to larger, nonnanometer silver particles. Upon exposure to silver nanoparticles sized 20–30 nm, Drosophila eggs did not exhibit a statistically significant (P < 0.05) decrease in their likelihood to pupate, but eggs exposed to larger silver particles (500–1200 nm) were 91% ± 18% less likely to pupate. Exposure to silver nanoparticles reduced the percentage of pupae able to emerge as adults. At 10 ppm of silver particle exposure, only 57% ± 48% of the pupae exposed to 20–30 nm silver particles became adults, whereas 89% ± 25% of the control group became adults, and 94% ± 52% and 91% ± 19% of the 500–1200 nm and 100 nm group, respectively, reached adulthood. Conclusion: This research provides evidence that nanoscale silver particles (<100 nm) are less toxic to Drosophila eggs than silver particles of conventional (>100 nm) size.

Gorth, Deborah J; Rand, David M; Webster, Thomas J

2011-01-01

117

Possible protection of silver nanoparticles against salt by using rhamnolipid.  

PubMed

Rhamnolipid (RL) from Pseudomonas aeruginosa was dissolved in distilled water with concentration equivalent to its critical micelle concentration (CMC). Silver nanoparticles (SNP) synthesized in the RL colloid were found to be stable for more than 1 month. Further, after 1 month when the SNP in RL colloid (SNPRL) were exposed to NaCl solution it took about 60 mg/ml as compared to 2 mg NaCl/ml in the case of SNP colloid for degrading silver nanoparticles. The inference suggests that the RL must undergo vesicle formation and to prevent silver nanoparticle exposure to NaCl. PMID:23290768

Saikia, Jyoti Prasad; Bharali, Pranjal; Konwar, Bolin Kumar

2012-11-24

118

Interaction effects and transport properties of Pt capped Co nanoparticles  

NASA Astrophysics Data System (ADS)

We studied the magnetic and transport properties of Co nanoparticles (NPs) being capped with varying amounts of Pt. Beside field and temperature dependent magnetization measurements, we performed ?? measurements to study the magnetic interactions between the Co NPs. We observe a transition from demagnetizing towards magnetizing interactions between the particles for an increasing amount of Pt capping. Resistivity measurements show a crossover from giant magnetoresistance towards anisotropic magnetoresistance.

Ludwig, A.; Agudo, L.; Eggeler, G.; Ludwig, A.; Wieck, A. D.; Petracic, O.

2013-01-01

119

Effect of the capping agents on cobalt nanoparticles  

NASA Astrophysics Data System (ADS)

The achievement of high information density and fast recording rate in memory devices crucially depends on the structure of magnetic domains. In this paper cobalt nanoparticles are synthesised using two capping agents (TOA, ODA) and two different preparation routes: thermal decomposition (TD) and Solvated Metal Atom Dispersion (SMAD). The interaction of capping agents with free metal clusters and their influence on Co nanoparticles size, atomic structure and oxidation state is investigated by means of X-ray diffraction and X-ray absorption spectroscopy.

Sciortino, L.; Longo, A.; Giannici, F.; Martorana, A.

2009-11-01

120

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

PubMed

Poly(ethylene glycol) stabilized colloidal silver nanoparticles were prepared using the reductive potency of the aqueous extract of Thuja occidentalis leaves under ambient conditions. The nanoparticles were well dispersed within a narrow size spectrum (7-14 nm) and displayed characteristic surface plasmon resonance peak at around 420 nm and Bragg's reflection planes of fcc structure. MTT assay revealed the dose-dependent cytocompatibility and toxicity of the nanoparticles with the L929 normal cell line. On the other hand, the antiproliferative action of the nanoparticles was evaluated on HeLa cell (cancerous cells) line. Fluorescence and phase contrast microscopic imaging indicated the appearance of multinucleate stages with aggregation and nuclear membrane disruption of the HeLa cells post treatment with the nanoparticles. The interaction at the prokaryotic level was also assessed via differential antibacterial efficacy against Staphylococcus aureus (MTCC 3160) and Escherichia coli (MTCC 40). Under these perspectives, it is also necessary to observe the environmental impact of the prepared silver nanoparticles. Hence, the dose dependent toxicity of silver nanoparticles was evaluated upon the earthworm species Eisenia fetida. Neither the survival nor the reproduction was affected by the addition of silver nanoparticles up to 1000 ppm. Thus these 'green' silver nanoparticles have promising potential as future materials. PMID:23352940

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

2012-12-26

121

Characterization and antimicrobial activity of silver nanoparticles prepared by a thermal decomposition technique  

NASA Astrophysics Data System (ADS)

Recently, there has been an increasing need of efficient synthetic protocols using eco-friendly conditions including low costs and green chemicals for production of metal nanoparticles. In this work, silver nanoparticles (silver NPs) with average particle size about 10 nm were synthesized by using a thermal decomposition technique. Unlike the colloidal chemistry method, the thermal decomposition method developed has advantages such as the high crystallinity, single-reaction synthesis, and easy dispersion ability of the synthesized NPs in organic solvents. In a modified synthesis process, we used sodium oleate as a capping agent to modify the surface of silver NPs because the oleate has a C18 tail with a double bond in the middle, therefore, forming a kink which is to be effective for aggregative stability. Importantly, the as-synthesized silver NPs have demonstrated strong antimicrobial effects against various bacteria and fungi strains. Electron microscopic studies reveal physical insights into the interaction and bactericidal mechanism between the prepared silver NPs and tested bacteria in question. The observed excellent antibacterial and antifungal activity of the silver NPs make them ideal for disinfection and biomedicine applications.

Tam, Le Thi; Phan, Vu Ngoc; Lan, Hoang; Thuy, Nguyen Thanh; Hien, Tran Minh; Huy, Tran Quang; Quy, Nguyen Van; Chinh, Huynh Dang; Tung, Le Minh; Tuan, Pham Anh; Lam, Vu Dinh; Le, Anh-Tuan

2013-06-01

122

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

123

Antibacterial activity and cell viability of hyaluronan fiber with silver nanoparticles.  

PubMed

Silver has been used since time immemorial in different chemical form to treat burns, wounds and several different infections caused by pathogenic bacteria, advancement of biological process of nanoparticles synthesis is evolving into a key area of nanotechnology. The current study deals with the green synthesis, characterization, and evaluation of the biological activity and cell viability of hyaluronan fibers with incorporated silver nanoparticles (HA-Ag NPs). Hyaluronan fiber was prepared by the dissolving of sodium hyaluronate (HA) in aqueous alkaline solution to prepare a transparent solution, which was used for the preparation of fibers by a wet-spinning technique. Consequently, hyaluronan fiber was used as capping and stabilizing agent for the preparation of fibers with silver nanoparticles. HA-Ag NPs were confirmed by transmission electron microscopy, dynamic light scattering, UV/VIS spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermal analysis, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. HA-Ag NPs showed high antibacterial activity of against Staphylococcus aureus and Escherichia coli. Cell viability tests indicated that hyaluronan, hyaluronan fibers and hyaluronan fibers with silver nanoparticles were non-toxic on the cell growth. Two different particles size of Ag NPs (10, 40 nm) had not any toxicity till the concentration limit. These tests were performed using mouse fibroblast cell line 3T3. PMID:23399144

Abdel-Mohsen, A M; Hrdina, Radim; Burgert, Ladislav; Abdel-Rahman, Rasha M; Hašová, Martina; Šmejkalová, Daniela; Kolá?, Michal; Pekar, M; Aly, A S

2012-09-12

124

Chemotactic assay for biological effects of silver nanoparticles  

Microsoft Academic Search

A method is proposed for assessing the biocidal efficacy of water-dispersed nanoparticles of silver. It is based on negative\\u000a chemotaxis of the plasmodia of the slime mold Physarum polycephalum. Biocidal and repellent effects were compared for silver nanoparticles, Ag+ ions, and AOT in solution and in the agar gel. In such characteristics as increasing the period of auto-oscillations of contractile

N. B. Matveeva; E. M. Egorova; S. I. Beilina; V. V. Lednev

2006-01-01

125

Preparation of silver nanoparticles using tryptophan and its formation mechanism  

Microsoft Academic Search

A non-toxic route was used for the preparation of silver nanoparticles using tryptophan (Trp) as reducing\\/stabilizing agent in the presence of cetyltrimethyl ammonium bromide (CTAB). Role of water soluble neutral polymer poly(vinylpyrrolidone) (PVP) has been studied on the growth of yellow colour silver nanoparticle formation. The synthesized nanostructures were characterized by UV–Visible absorption spectroscopy, transmission electron microscopy (TEM) by observing

Zoya Zaheer; Maqsood Ahmad Malik; F. M. Al-Nowaiser; Zaheer Khan

2010-01-01

126

Obtaining of bactericidal polyethylene terephthalate films modified by silver nanoparticles  

Microsoft Academic Search

The synthesis of stable, concentrated (to 3 g\\/l), and highly dispersive silver aquasols stabilized by cetyltrimethylammonium\\u000a bromide was proposed. The possibility of silver-nanoparticle modification of polyethylene terephthalate preliminarily deformed\\u000a by the crazing mechanism was discussed. Microbiological tests using Pseudomonas aeruginosa bacteria showed that produced nanocomposites feature a pronounced biocide effect.

Yu. A. Krutyakov; E. G. Rukhlya; A. V. Artemov; A. Yu. Olenin; M. N. Ivanov; O. V. Shelyakov

2008-01-01

127

Silver nanoprism enhanced fluorescence in YVO4:Eu(3+) nanoparticles.  

PubMed

Silver nanoprisms of different sizes influence fluorescence enhancement in YVO4:Eu(3+) nanoparticles to various degrees under excitation of green light (532 nm). The local field generated by silver nanoprisms and their dimers is simulated through the FDTD method and a direct correlation with fluorescence enhancement is established. PMID:24013681

Buch, Zubair; Kumar, Vineet; Mamgain, Hitesh; Chawla, Santa

2013-09-06

128

Toxicity of silver nanoparticles in macrophages.  

PubMed

Silver nanoparticles (nanosilver) are broadly used today in textiles, food packaging, household devices and bioapplications, prompting a better understanding of their toxicity and biological interactions. In particular, the cytotoxicity of nanosilver with respect to mammalian cells remains unclear, because such investigations can be biased by the nanosilver coatings and the lack of particle size control. Here, nanosilver of well-defined size (5.7 to 20.4 nm) supported on inert nanostructured silica is produced using flame aerosol technology. The cytotoxicity of the prepared nanosilver with respect to murine macrophages is assessed in vitro because these cells are among the first to confront nanosilver upon its intake by mammals. The silica support facilitates the dispersion and stabilization of the prepared nanosilver in biological suspensions, and no other coating or functionalization is applied that could interfere with the biointeractions of nanosilver. Detailed characterization of the particles by X-ray diffraction and electron microscopy reveals that the size of the nanosilver is well controlled. Smaller nanosilver particles release or leach larger fractions of their mass as Ag? ions upon dispersion in water. This strongly influences the cytotoxicity of the nanosilver when incubated with murine macrophages. The size of the nanosilver dictates its mode of cytotoxicity (Ag? ion-specific and/or particle-specific). The toxicity of small nanosilver (<10 nm) is mostly mediated by the released Ag? ions. The influence of such ions on the toxicity of nanosilver decreases with increasing nanosilver size (>10 nm). Direct silver nanoparticle-macrophage interactions dominate the nanosilver toxicity at sizes larger than 10 nm. PMID:23418027

Pratsinis, Anna; Hervella, Pablo; Leroux, Jean-Christophe; Pratsinis, Sotiris E; Sotiriou, Georgios A

2013-02-18

129

Multiutility sophorolipids as nanoparticle capping agents: Synthesis of stable and water dispersible Co nanoparticles  

Microsoft Academic Search

Sophorolipids are a class of glycolipids that can be obtained from fatty\\u000a acids by simply treating them with yeast cells (Candida bombicola, ATCC\\u000a 22214) and glucose. In this letter, we demonstrate the application of\\u000a sophorolipids obtained from oleic acid as a capping agent for Co\\u000a nanoparticles. Upon capping the nanoparticle surface, the sugar moiety\\u000a of these sophorolipids is exposed to

Manasi Kasture; Sanjay Singh; Pitamber Patel; P. A. Joy; A. A. Prabhune; C. V. Ramana; B. L. V. Prasad

2007-01-01

130

Chemiluminescent Reactions Catalyzed by Nanoparticles of Gold, Silver, and Gold/Silver Alloys  

NASA Astrophysics Data System (ADS)

Chemiluminescence (CL) reactions are catalyzed by metals nanoparticles, which display unique catalytic properties due to an increased surface area. The present study describes the catalytic effects of nanoparticles (NP) of silver, gold, and alloys of Au/Ag nanoparticles on the chemiluminescent reaction taking place between luminol and potassium ferricyanide. It was found that silver nanoparticles and alloy nanoparticles enhance the CL process when their sizes remained in the range of 30 nm to 50 nm. The data show that the intensity and rate of chemiluminescence were influenced by the mole fraction of gold and silver in the alloy. Data to this chemiluminescence reaction are modeled by a double exponential curve, which indicates that two competing processes are occurring.

Abideen, Saqib Ul

131

Cellular oxido-reductive proteins of Chlamydomonas reinhardtii control the biosynthesis of silver nanoparticles  

PubMed Central

Background Elucidation of molecular mechanism of silver nanoparticles (SNPs) biosynthesis is important to control its size, shape and monodispersity. The evaluation of molecular mechanism of biosynthesis of SNPs is of prime importance for the commercialization and methodology development for controlling the shape and size (uniform distribution) of SNPs. The unicellular algae Chlamydomonas reinhardtii was exploited as a model system to elucidate the role of cellular proteins in SNPs biosynthesis. Results The C. reinhardtii cell free extract (in vitro) and in vivo cells mediated synthesis of silver nanoparticles reveals SNPs of size range 5 ± 1 to 15 ± 2 nm and 5 ± 1 to 35 ± 5 nm respectively. In vivo biosynthesized SNPs were localized in the peripheral cytoplasm and at one side of flagella root, the site of pathway of ATP transport and its synthesis related enzymes. This provides an evidence for the involvement of oxidoreductive proteins in biosynthesis and stabilization of SNPs. Alteration in size distribution and decrease of synthesis rate of SNPs in protein-depleted fractions confirmed the involvement of cellular proteins in SNPs biosynthesis. Spectroscopic and SDS-PAGE analysis indicate the association of various proteins on C. reinhardtii mediated in vivo and in vitro biosynthesized SNPs. We have identified various cellular proteins associated with biosynthesized (in vivo and in vitro) SNPs by using MALDI-MS-MS, like ATP synthase, superoxide dismutase, carbonic anhydrase, ferredoxin-NADP+ reductase, histone etc. However, these proteins were not associated on the incubation of pre-synthesized silver nanoparticles in vitro. Conclusion Present study provides the indication of involvement of molecular machinery and various cellular proteins in the biosynthesis of silver nanoparticles. In this report, the study is mainly focused towards understanding the role of diverse cellular protein in the synthesis and capping of silver nanoparticles using C. reinhardtii as a model system.

2011-01-01

132

Anti-proliferative activity of silver nanoparticles  

PubMed Central

Background Nanoparticles possess exceptional physical and chemical properties which led to rapid commercialisation. Silver nanoparticles (Ag-np) are among the most commercialised nanoparticles due to their antimicrobial potential. Ag-np based cosmetics, therapeutic agents and household products are in wide use, which raised a public concern regarding their safety associated with human and environmental use. No safety regulations are in practice for the use of these nanomaterials. The interactions of nanomaterials with cells, uptake mechanisms, distribution, excretion, toxicological endpoints and mechanism of action remain unanswered. Results Normal human lung fibroblasts (IMR-90) and human glioblastoma cells (U251) were exposed to different doses of Ag-nps in vitro. Uptake of Ag-nps occurred mainly through endocytosis (clathrin mediated process and macropinocytosis), accompanied by a time dependent increase in exocytosis rate. The electron micrographs revealed a uniform intracellular distribution of Ag-np both in cytoplasm and nucleus. Ag-np treated cells exhibited chromosome instability and mitotic arrest in human cells. There was efficient recovery from arrest in normal human fibroblasts whereas the cancer cells ceased to proliferate. Toxicity of Ag-np is mediated through intracellular calcium (Ca2+) transients along with significant alterations in cell morphology and spreading and surface ruffling. Down regulation of major actin binding protein, filamin was observed after Ag-np exposure. Ag-np induced stress resulted in the up regulation of metallothionein and heme oxygenase -1 genes. Conclusion Here, we demonstrate that uptake of Ag-np occurs mainly through clathrin mediated endocytosis and macropinocytosis. Our results suggest that cancer cells are susceptible to damage with lack of recovery from Ag-np-induced stress. Ag-np is found to be acting through intracellular calcium transients and chromosomal aberrations, either directly or through activation of catabolic enzymes. The signalling cascades are believed to play key roles in cytoskeleton deformations and ultimately to inhibit cell proliferation.

AshaRani, PV; Hande, M Prakash; Valiyaveettil, Suresh

2009-01-01

133

Green synthesis of silver nanoparticles from Gloriosa superba L. leaf extract and their catalytic activity  

NASA Astrophysics Data System (ADS)

The present work focuses the use of aqueous extract of Gloriosa superba Linn. (Glory Lily) for producing silver nanoparticles (AgNPs) from silver nitrate aqueous solution. Phytochemical analysis of the extract revealed the presence of alkaloid, amino acids, carbohydrates and proteins in the extract and they serve as effective reducing and capping agents for converting silver nitrate to silver nanoparticles. The nanoparticles were characterised by UV (Ultra violet), FT-IR (Fourier Transform Infrared), XRD (X-ray diffraction), TEM (Transmission Electron Microscope) SEM-EDX (Scanning Electron Microscopy-Energy Dispersive X-ray), and PL (Photoluminescence) studies. Moreover, the catalytic activity of synthesized AgNPs in the reduction of methylene blue was studied by UV-vis spectrophotometer. The synthesized AgNPs are observed to have a good catalytic activity on the reduction of methylene blue by G. superba extract which is confirmed by the decrease in absorbance maximum values of methylene blue with respect to time using UV-vis spectrophotometer.

Ashokkumar, S.; Ravi, S.; Velmurugan, S.

2013-11-01

134

A facile approach to synthesize silver nanorods capped with sodium tripolyphosphate  

Microsoft Academic Search

Silver nanorods have been successfully synthesized via a facile route using sodium tripolyphosphate (Na5P3O10) as the capping agent. Silver nitrate and glucose served as the Ag+ source and green reducing agent in aqueous solution, respectively. The products were characterized by X-ray powder diffraction (XRD), UV–visible spectroscopy (UV–vis), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and selected area

Yuli Shi; Liyun Lv; Hong Wang

2009-01-01

135

Polyaniline\\/Silver Nanoparticle-Doped Multiwalled Carbon Nanotube Composites  

Microsoft Academic Search

A simple method was used to synthesize the hybrid nanocomposites consisting of the functionalized multiwalled carbon nanotube composites (MWCNTs) with the polyaniline incorporated silver nanoparticles (a-MWCNT\\/PANI-Ag) through an emulsion polymerization at room temperature in order to enhance the electrical conductivity of polyaniline. The electrical conductivity of the composite with the incorporated Ag nanoparticles was 5% higher than the same weight

Ali Grinou; Hyeonseong Bak; Young Soo Yun; Hyoung-Joon Jin

2012-01-01

136

Polyaniline\\/Silver Nanoparticle-Doped Multiwalled Carbon Nanotube Composites  

Microsoft Academic Search

A simple method was used to synthesize the hybrid nanocomposites consisting of the functionalized MWCNTs with the polyaniline incorporated silver nanoparticles (a-MWCNT\\/PANI-Ag) through an emulsion polymerization at room temperature in order to enhance the electrical conductivity of polyaniline. The electrical conductivity of the composite with the incorporated Ag nanoparticles was 5% higher than the same weight percent for the composite

Ali Grinou; Hyeonseong Bak; Young Soo Yun; Hyoung-Joon Jin

2011-01-01

137

Can silver nanoparticles be useful as potential biological labels?  

Microsoft Academic Search

Silver (Ag) nanoparticles have unique plasmon-resonant optical scattering properties that are finding use in nanomedical applications such as signal enhancers, optical sensors, and biomarkers. In this study, we examined the chemical and biological properties of Ag nanoparticles of similar sizes, but that differed primarily in their surface chemistry (hydrocarbon versus polysaccharide), in neuroblastoma cells for their potential use as biological

Amanda M. Schrand; Laura K. Braydich-Stolle; John J. Schlager; Liming Dai; Saber M. Hussain

2008-01-01

138

Environmental and Human Health Risks of Aerosolized Silver Nanoparticles  

Microsoft Academic Search

Silver nanoparticles (AgNPs) are gaining attention from the academic and regulatory communities, not only because of their antimicrobial effects and subsequent product applications, but also because of their potential health and environmental risks. Whereas AgNPs in the aqueous phase are under intensive study, those in the atmosphere have been largely overlooked, although it is well established that inhalation of nanoparticles

Marina E. Quadros; Linsey C. Marr; Krzysztof Pikon´; Krzysztof Gaska; Lingjuan Wang; Edgar Oviedo-Rondon; John Small; Zifei Liu; Brian Sheldon; Gerald Havenstein; C. Williams; Di Tian; Daniel Cohan; Sergey Napelenok; Michelle Bergin; Yongtao Hu; Michael Chang; Armistead Russell; Ye Xu; Guohe Huang; Xiaosheng Qin; Kuo-Pin Yu; Grace Lee; Guo-Hao Huang; Prabhakar Sharma; Tjalfe Poulsen; William Vizuete; Leiran Biton; Harvey Jeffries; Evan Couzo; Yi-Chi Chien; Chenju Liang; Shou-Heng Liu; Shu-Hua Yang; Maciej Kryza; Malgorzata Werner; Marek Blas; Anthony Dore; Mieczyslaw Sobik; Daniel Olsen; Morgan Kohls; Gregg Arney; Kaushlendra Singh; L. Risse; K. C. Das; John Worley; Sidney Thompson; Bryan Comer; James Corbett; J. Hawker; Karl Korfmacher; Earl Lee; Chris Prokop; James Winebrake

2010-01-01

139

Molecular mechanisms of toxicity of silver nanoparticles in zebrafish embryos.  

PubMed

Silver nanoparticles cause toxicity in exposed organisms and are an environmental health concern. The mechanisms of silver nanoparticle toxicity, however, remain unclear. We examined the effects of exposure to silver in nano-, bulk-, and ionic forms on zebrafish embryos (Danio rerio) using a Next Generation Sequencing approach in an Illumina platform (High-Throughput SuperSAGE). Significant alterations in gene expression were found for all treatments and many of the gene pathways affected, most notably those associated with oxidative phosphorylation and protein synthesis, overlapped strongly between the three treatments indicating similar mechanisms of toxicity for the three forms of silver studied. Changes in oxidative phosphorylation indicated a down-regulation of this pathway at 24 h of exposure, but with a recovery at 48 h. This finding was consistent with a dose-dependent decrease in oxygen consumption at 24 h, but not at 48 h, following exposure to silver ions. Overall, our data provide support for the hypothesis that the toxicity caused by silver nanoparticles is principally associated with bioavailable silver ions in exposed zebrafish embryos. These findings are important in the evaluation of the risk that silver particles may pose to exposed vertebrate organisms. PMID:23758687

van Aerle, Ronny; Lange, Anke; Moorhouse, Alex; Paszkiewicz, Konrad; Ball, Katie; Johnston, Blair D; de-Bastos, Eliane; Booth, Timothy; Tyler, Charles R; Santos, Eduarda M

2013-06-26

140

Plasmonic coupling from silver nanoparticle dimer array mediating surface plasmon resonant enhancement on the thin silver film  

NASA Astrophysics Data System (ADS)

We investigate the optical absorption spectrum of a periodic array of silver nanoparticle dimer on a thin silver film using multiple-scattering formalism. Surface plasmon polariton mediated from silver nanoparticle dimer array is excited and enhanced by about four times compared with that from monomer array. This enhancement results from the coupling between the two nanoparticles' plasmons of symmetry mode and anti-symmetry mode. We also illustrate the distance-dependent nanoparticle plasmonic coupling modes based on the polarized charge distribution in dimer geometry. The proposed silver nanoparticle dimer array can be used to enhance surface spectroscopy.

Chang, Ying; Jiang, Yongyuan; Sun, Xiudong

2013-05-01

141

Size-dependent structure of silver nanoparticles under high pressure  

SciTech Connect

Silver noble metal nanoparticles that are<10 nm often possess multiply twinned grains allowing them to adopt shapes and atomic structures not observed in bulk materials. The properties exhibited by particles with multiply twinned polycrystalline structures are often far different from those of single-crystalline particles and from the bulk. I will present experimental evidence that silver nanoparticles<10 nm undergo a reversible structural transformation under hydrostatic pressures up to 10 GPa. Results for nanoparticles in the intermediate size range of 5 to 10 nm suggest a reversible linear pressure-dependent rhombohedral distortion which has not been previously observed in bulk silver. I propose a mechanism for this transitiion that considers the bond-length distribution in idealized multiply twinned icosahedral particles. Results for nanoparticles of 3.9 nm suggest a reversible linear pressure-dependent orthorhombic distortion. This distortion is interpreted in the context of idealized decahedral particles. In addition, given these size-dependent measurements of silver nanoparticle compression with pressure, we have constructed a pressure calibration curve. Encapsulating these silver nanoparticles in hollow metal oxide nanospheres then allows us to measure the pressure inside a nanoshell using x-ray diffraction. We demonstrate the measurement of pressure gradients across nanoshells and show that these nanoshells have maximum resolved shear strengths on the order of 500 MPa to IGPa.

Koski, Kristie Jo

2008-12-31

142

Agricultural waste Annona squamosa peel extract: biosynthesis of silver nanoparticles.  

PubMed

Development of reliable and eco-friendly process for the synthesis of metallic nanoparticles is an important step in the field of application of nanotechnology. We have developed modern method by using agriculture waste to synthesize silver nanoparticles by employing an aqueous peel extract of Annona squamosa in AgNO(3). Controlled growth of silver nanoparticles was formed in 4h at room temperature (25°C) and 60°C. AgNPs were irregular spherical in shape and the average particle size was about 35±5 nm and it is consistent with particle size obtained by XRD Scherer equation. PMID:22336049

Kumar, Rajendran; Roopan, Selvaraj Mohana; Prabhakarn, Arunachalam; Khanna, Venkatesan Gopiesh; Chakroborty, Subhendu

2012-01-28

143

Synthesis and antibacterial activity of of silver nanoparticles  

NASA Astrophysics Data System (ADS)

Silver nanoparticles have been known to have inhibitory and bactericidal effects but the antimicrobial mechanism have not been clearly revealed. Here, we report on the synthesis of metallic nanoparticles of silver using wild strains of Penicillium isolated from environment. Kinetics of the formation of nanosilver was monitored using the UV-Vis. TEM micrographs showed the formation of silver nanoparticles in the range 10-100 nm. Obtained Ag nanoparticles were evaluated for their antimicrobial activity against the gram-positive and gram-negative bacteria. As results, Bacillus cereus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were effectively inhibited. Nanosilver is a promising candidate for development of future antibacterial therapies because of its wide spectrum of activity.

Maliszewska, I.; Sadowski, Z.

2009-01-01

144

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

NASA Astrophysics Data System (ADS)

Conducting silver paste was prepared by using Ag nanoparticles which were synthesized by e-beam irradiation method (from KAERI); its conductivity was comparatively determined with Ag nanoparticles which were prepared by thermolysis method (commercial). The silver nanoparticles with the diameter of approximately 150 nm size prepared by e-beam irradiation were mixed with glass frit and sintered for 1 h at 500 °C. It is presumably concluded that the wt% of silver nanoparticle, size distribution and homogenous dispersibility of Ag nanoparticles in the pastes are the critical factors for the high conductivity of the paste. Among the various wt% of silver nanoparticle in the conducting silver pastes, silver paste with 90 wt% of silver nanoparticle has the highest conductivity as 1.6×104 S cm-1. This conductivity value is 1.6 times higher than the Ag pastes which were prepared with silver nanoparticles obtained by thermolysis method.

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

2010-11-01

145

Fabrication and characterization of silver nanoparticle and its potential antibacterial activity  

Microsoft Academic Search

In the present research silver nanoparticle was fabricated by chemical reduction of silver salt (Silver nitrate, AgNO3) solution. Sodium citrate was used as a reducer. The formation of silver nanoparticle was observed visually by color change\\u000a (greenish yellow). The surface plasmon resonance peak in absorption spectra of silver nanoparticle showed an absorption maximum\\u000a at 420 nm in UV-VIS spectrometry. The

P. Prema; Rincy Raju

2009-01-01

146

Enhanced Sensitivity of Surface Plasmon Resonance Phase-Interrogation Biosensor by Using Silver Nanoparticles  

Microsoft Academic Search

It is demonstrated that the sensitivity of surface plasmon resonance phase-interrogation biosensor can be enhanced by using\\u000a silver nanoparticles. Silver nanoparticles were fabricated on silver films by using thermal evaporation. Sizes of silver nanoparticles\\u000a on silver thin film can be tuned by controlling the deposition parameters of thermal evaporation. By using surface plasmon\\u000a resonance heterodyne interferometey to measure the phase

Tzu-Cheih Peng; Wen-Chi Lin; Chih-Wei Chen; Din Ping Tsai; Hai-Pang Chiang

2011-01-01

147

The synthesis of chitosan-based silver nanoparticles and their antibacterial activity  

Microsoft Academic Search

Chitosan-based silver nanoparticles were synthesized by reducing silver nitrate salts with nontoxic and biodegradable chitosan. The silver nanoparticles thus obtained showed highly potent antibacterial activity toward both Gram-positive and Gram-negative bacteria, comparable with the highly active precursor silver salts. Silver-impregnated chitosan films were formed from the starting materials composed of silver nitrate and chitosan via thermal treatment. Compared with pure

Dongwei Wei; Wuyong Sun; Weiping Qian; Yongzhong Ye; Xiaoyuan Ma

2009-01-01

148

Synthesis and size control of silver nanoparticles using reverse micelles of sucrose fatty acid esters  

Microsoft Academic Search

Silver nanoparticles were prepared in reverse micelles of sucrose fatty acid esters. The TEM image showed that the obtained\\u000a silver nanoparticles displayed a wide variety of shapes. The size of silver nanoparticles was strongly dependent upon a kind\\u000a of reducing agents and tended to increase with an increase in reaction temperature. Moreover, the size of silver nanoparticles\\u000a was controlled by

Hidetaka Noritomi; Naohiro Igari; Kenji Kagitani; Yoshihiro Umezawa; Yasutaka Muratsubaki; Satoru Kato

2010-01-01

149

Trapping and release of citrate-capped gold nanoparticles  

NASA Astrophysics Data System (ADS)

An electrical method to trap and release charged gold nanoparticles onto and from the surface of gold electrodes modified by an alkanethiol self-assembled monolayer (SAM) is presented. To form electrodes coated with gold nanoparticles (GNPs), amine-terminated SAMs on gold electrodes were immersed in a solution of negatively charged citrate-capped GNPs. Accumulation of GNPs on the electrode surface was monitored by a decrease in the impedance of the SAM-modified electrode and by an increase in the electrochemical activity at the electrode as shown through cyclic voltammetry (CV). Electrostatic interactions between the GNPs and the amine-terminated SAM trap the GNPs on the electrode surface. Application of a subsequent negative bias to the electrode initiated a partial release of the GNPs from the electrode surface. Impedance spectroscopy, cyclic voltammetry, ultraviolet-visible (UV-Vis) spectroscopy and atomic force microscopy (AFM) were used to monitor and confirm the attraction of GNPs to and release from the aminealkanethiolated gold electrodes. This work describes a method of trapping and release for citrate-capped GNPs that could be used for on-demand nanoparticle delivery applications such as in assessing and modeling nanoparticle toxicology, as well as for monitoring the functionalization of gold nanoparticles.

Reyes, Darwin R.; Mijares, Geraldine I.; Nablo, Brian; Briggman, Kimberly A.; Gaitan, Michael

2011-08-01

150

Distribution of silver in rats following 28 days of repeated oral exposure to silver nanoparticles or silver acetate  

PubMed Central

Background The study investigated the distribution of silver after 28 days repeated oral administration of silver nanoparticles (AgNPs) and silver acetate (AgAc) to rats. Oral administration is a relevant route of exposure because of the use of silver nanoparticles in products related to food and food contact materials. Results AgNPs were synthesized with a size distribution of 14 ± 4 nm in diameter (90% of the nanoparticle volume) and stabilized in aqueous suspension by the polymer polyvinylpyrrolidone (PVP). The AgNPs remained stable throughout the duration of the 28-day oral toxicity study in rats. The organ distribution pattern of silver following administration of AgNPs and AgAc was similar. However the absolute silver concentrations in tissues were lower following oral exposure to AgNPs. This was in agreement with an indication of a higher fecal excretion following administration of AgNPs. Besides the intestinal system, the largest silver concentrations were detected in the liver and kidneys. Silver was also found in the lungs and brain. Autometallographic (AMG) staining revealed a similar cellular localization of silver in ileum, liver, and kidney tissue in rats exposed to AgNPs or AgAc. Using transmission electron microscopy (TEM), nanosized granules were detected in the ileum of animals exposed to AgNPs or AgAc and were mainly located in the basal lamina of the ileal epithelium and in lysosomes of macrophages within the lamina propria. Using energy dispersive x-ray spectroscopy it was shown that the granules in lysosomes consisted of silver, selenium, and sulfur for both AgNP and AgAc exposed rats. The diameter of the deposited granules was in the same size range as that of the administered AgNPs. No silver granules were detected by TEM in the liver. Conclusions The results of the present study demonstrate that the organ distribution of silver was similar when AgNPs or AgAc were administered orally to rats. The presence of silver granules containing selenium and sulfur in the intestinal wall of rats exposed to either of the silver forms suggests a common mechanism of their formation. Additional studies however, are needed to gain further insight into the underlying mechanisms of the granule formation, and to clarify whether AgNPs dissolve in the gastrointestinal system and/or become absorbed and translocate as intact nanoparticles to organs and tissues.

2011-01-01

151

Power dependence of size of laser ablated colloidal silver nanoparticles  

NASA Astrophysics Data System (ADS)

Silver nanoparticles have been produced by laser ablation of silver metal in nanopure water without any chemical additives. It has been observed that laser power has a control over the size of the nanoparticles. Increasing laser power shows a clear blue shift in the absorption peak of fabricated nanoparticles indicating that the average size of the particles decreases with increasing laser power. Ablation for longer period reduces the average size of nanoparticles which is attributed to the re-ablation of fabricated nanoparticles. A good correlation has been observed between the peak of the absorption spectrum measured by UV-VIS spectroscopy and the average particle size measured by scanning electron microscope imaging method. The value of the coefficient of correlation is determined to be 0.965.

Talukder, A. I.; Sultana, P.; Haider, A. F. M. Y.; Wahadoszamen, M.; Abedin, K. M.; Farhad, S. F. U.

2010-11-01

152

Photoswitchable bactericidal effects from novel silica-coated silver nanoparticles  

NASA Astrophysics Data System (ADS)

The enhancement of the electromagnetic field in the surroundings of nanoparticles via surface plasmon resonance offers promising possibilities for biomedical applications. Here we report on the selective triggering of antibacterial activity using a new type of silver nanoparticles coated with silica, Ag@silica, irradiated at their surface plasmon frequency. The nanoparticles are able to bind readily to the surface of bacterial cells, although this does not affect bacterial growing since the silica shell largely attenuates the intrinsic toxicity of silver. However, upon simultaneous exposure to light corresponding to the absorption band of the nanoparticles, bacterial death is triggered selectively on the irradiated zone. Because of the low power density used in the treatments, we discard thermal effects as the cause of cell killing. Instead, we propose that the switched toxicity is due to the enhanced electromagnetic field in the proximity of the nanoparticles, which either directly (through membrane perturbation) or indirectly (through induced photochemical reactions) is able to cause cell death.

Fuertes, Gustavo; Pedrueza, Esteban; Abderrafi, Kamal; Abargues, Rafael; Sánchez, Orlando; Martínez-Pastor, Juan; Salgado, Jesús; Jiménez, Ernesto

2011-06-01

153

Plasmonic coupling of SiO{sub 2}-Ag 'post-cap' nanostructures and silver film for surface enhanced Raman scattering  

SciTech Connect

We demonstrate a surface enhanced Raman scattering (SERS) substrate consisting of SiO{sub 2}-Ag''post-cap'' nanostructures with an underlying silver film fabricated by the glancing angle deposition technique. Electromagnetic simulations predict that SERS enhancement is strongly polarization-dependent, consistent with experimental measurements. Optimized coupling between Ag cap nanoparticles and the underlying silver film can be achieved by controlling the thickness of SiO{sub 2} post sandwiched between them to significantly enhance local electric-field intensity and to increase the density of electromagnetic hot spots. A maximum SERS enhancement factor of 2.38x10{sup 9} within the hot spot region is demonstrated, providing sufficient sensitivity for many important applications.

Wu, Hsin-Yu [Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Cunningham, Brian T. [Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

2011-04-11

154

Green biosynthesis of silver nanoparticles using Curcuma longa tuber powder  

PubMed Central

Green synthesis of noble metal nanoparticles is a vastly developing area of research. Metallic nanoparticles have received great attention from chemists, physicists, biologists, and engineers who wish to use them for the development of a new-generation of nanodevices. In this study, silver nanoparticles were biosynthesized from aqueous silver nitrate through a simple and eco-friendly route using Curcuma longa tuber-powder extracts, which acted as a reductant and stabilizer simultaneously. Characterizations of nanoparticles were done using different methods, which included ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray fluorescence spectrometry, and Fourier-transform infrared spectroscopy. The ultraviolet-visible spectrum of the aqueous medium containing silver nanoparticles showed an absorption peak at around 415 nm. Transmission electron microscopy showed that mean diameter and standard deviation for the formation of silver nanoparticles was 6.30 ± 2.64 nm. Powder X-ray diffraction showed that the particles are crystalline in nature, with a face-centered cubic structure. The most needed outcome of this work will be the development of value-added products from C. longa for biomedical and nanotechnology-based industries.

Shameli, Kamyar; Ahmad, Mansor Bin; Zamanian, Ali; Sangpour, Parvanh; Shabanzadeh, Parvaneh; Abdollahi, Yadollah; Zargar, Mohsen

2012-01-01

155

Controlling the Shapes of Silver Nanocrystals with Different Capping Agents  

SciTech Connect

This paper provides direct evidence to support the role of a capping agent in controlling the evolution of Ag seeds into nanocrystals with different shapes. Starting with single-crystal seeds (spherical or cubic in shape), we could selectively obtain Ag octahedrons enclosed by {l_brace}111{r_brace} facets and nanocubes/nanobars enclosed by {l_brace}100{r_brace} facets by adding sodium citrate (Na{sub 3}CA) and poly(vinyl pyrrolidone) (PVP), respectively, as a capping agent while all other parameters were kept the same. This research not only offers new insights into the role played by a capping agent in shape-controlled synthesis but also provides, for the first time, Ag octahedrons as small as 40 nm in edge length for optical and spectroscopic studies.

Zeng, J.; Tao, J.; Zheng, Y.; Rycenga, M.; Li, Z.-Y.; Zhang, Q.A.; Zhu, Y.; Xia, Y.

2010-06-30

156

Rapid tarnishing of silver nanoparticles in ambient laboratory air  

NASA Astrophysics Data System (ADS)

Silver has useful surface-plasmon-resonance properties for many potential applications. However, chemical activity in silver nanoparticles exposed to laboratory air can make interpretation of optical scattering and extinction spectra problematic. We have measured the shift of the plasmon polariton wavelength of arrays of silver nanoparticles with increasing exposure to ambient laboratory air. The resonance peak wavelength shifts 65 nm in 36 h (1.8 nm/h). We show by scanning Auger spectroscopy that the shift is due to contamination from sulfur, most likely chemisorbed on the surface. The rate of corrosion product growth on the nanoparticles is estimated to be 3 nm per day, 7.5 times higher than that of bulk Ag under the same conditions.

McMahon, M. D.; Lopez, R.; Meyer, H. M.; Feldman, L. C.; Haglund, R. F.

2005-06-01

157

Synthesis and optical properties of silver nanoparticles in ORMOCER  

NASA Astrophysics Data System (ADS)

Experimental results on synthesis of metal nanoparticles in ORMOCER by ion implantation are presented. Silver ions were implanted into organic/inorganic matrix at an accelerating energy of 30 keV and doses in the range of 0.25?1017 to 0.75?1017 ion/cm2. The silver ions form metal nanoparticles, which demonstrate surface plasmon absorption at the wavelength of 425-580 nm. The nonlinear absorption of new composite materials is measured by Z-scan technique using 150 fs laser pulses at 780 nm wavelength. ORMOCER matrix shows two-photon nonlinear absorption, whereas ORMOCER with silver nanoparticles demonstrates saturated absorption. Some optical applications of these composite materials are discussed.

Stepanov, Andrey L.; Kiyan, Roman; Ovsianikov, Alexander; Nuzhdin, Vladimir I.; Valeev, Valery F.; Osin, Yuri N.; Chichkov, Boris N.

2012-08-01

158

Synthesis of antibacterial silver nanoparticles by gamma-irradiation  

Microsoft Academic Search

Silver nanoparticles (Ag NPs) were synthesized by gamma-irradiation of silver ions in aqueous solutions containing polyvinyl pyrrolidone (PVP). Increasing of gamma-irradiation doses from 1 to 5 kGy enhanced the concentration of Ag NPs, indicated by UV-vis analysis. The XRD and the TEM measurements showed the production of face-centered cubic (fcc) Ag NPs with a mean size of about 16 nm.

N. Sheikh; A. Akhavan; M. Z. Kassaee

2009-01-01

159

[Green synthesis of silver nanoparticles and their application in SERS].  

PubMed

In the present paper, we have successfully synthesized silver nancomparticles by reducing of silver nitrate in alkaline solution via 60 degrees C water bath for 20 minutes with the use of tyrosine, a nontoxic and green macromolecule, as a reducing and stabilizing agent. The formation of silver nanoparticles was observed visually by color change of the solutions (from faint yellow to brown yellow). The morphologies of the Ag NPs were characterized by UV-Vis absorption spectroscopy and transmission electron microscopy (TEM). The UV-Vis absorption peak of silver nanoparticles located at 412 nm. The TEM image of silver nanoparticles indicated that the diameters of nanospheres are mainly in the range 15-25 nm. In order to evaluate the SERS activity of the silver nancomparticles, crystal violet and folic acid were used as the Raman probe molecule. The experimental results indicated that there are two ascendancies, firstly, the approach is convenient and the reaction condition is facile, secondly, tyrosine is a water-soluble, nontoxic and biodegradable macromolecule, which makes this approach provide a green strategy to prepare Ag NPs. Significantly, the synthesized Ag NPs exhibits good surface enhanced Raman scattering (SERS) activity as SERS substrates to detect crystal violet and folic acid in aqueous solution. PMID:24059181

Yang, Bi-Wen; Guo, Zhou-Yi; Liu, Zhi-Ming; Wan, Ming-Ming; Qin, Xiao-Chu; Zhong, Hui-Qing

2013-07-01

160

Formation mechanism of silver nanoparticles stabilized in glassy matrices.  

PubMed

In any given matrix control over the final particle size distribution requires a constitutive understanding of the mechanisms and kinetics of the particle evolution. In this contribution we report on the formation mechanism of silver nanoparticles embedded in a soda-lime silicate glass matrix. For the silver ion-exchanged glass it is shown that at temperatures below 410 °C only molecular clusters (diameter <1 nm) are forming which are most likely silver dimers. These clusters grow to nanoparticles (diameter >1 nm) by annealing above this threshold temperature of 410 °C. It is evidenced that the growth and thus the final silver nanoparticle size are determined by matrix-assisted reduction mechanisms. As a consequence, particle growth proceeds after the initial formation of stable clusters by addition of silver monomers which diffuse from the glass matrix. This is in contrast to the widely accepted concept of particle growth in metal-glass systems, in which it is assumed that the nanoparticle formation is predominantly governed by Ostwald ripening processes. PMID:23098252

Simo, Anne; Polte, Jörg; Pfänder, Norbert; Vainio, Ulla; Emmerling, Franziska; Rademann, Klaus

2012-11-02

161

Biocide silver nanoparticles in two different silica-based coating  

NASA Astrophysics Data System (ADS)

Silica-based coatings containing biocide silver nanoparticles have been synthesized using low temperature sol-gel method. Two different silane based matrices, phenyltriethoxysilane (PhTEOS) and tetraethyl orthosilicate (TEOS), were selected as precursor to prepare silica-based film. The films were analyzed by using UV-visible spectrophotometry, atomic force microscopy (AFM) and scanning electron microscopy (SEM) for their optical, surface morphological as well as structural properties. Optical properties of nanosilver in these two matrices showed that the peak absorption observed at different wavelength, which is due to the fact that optical absorption of nanoparticles is affected by the surrounding medium. It is also found that the silver absorption has higher intensity in PhTEOS than in TEOS matrix, indicating higher concentration of silver nanoparticles being loaded into the coating. To study silver release property, the films were immersed in water for 12 and 20 days. AFM and SEM analyzes present that higher concentration of silver nanoparticles and smaller particle sizes were synthesis in PhTEOS coating and consequently, more particles remains on the surfaces after 20 days which leads to longer antibacterial activity of PhTEOS coating.

Babapour, A.; Yang, B.; Bahang, S.; Cao, W.

2012-09-01

162

Formation of silver nanoparticles by laser ablation of a silver target in NaCl solution  

Microsoft Academic Search

Silver nanoparticles were synthesized by laser (Nd:YAG, ?=1064nm) ablation of a silver target immersed in various concentrations of NaCl solutions as well as in neat water. The concentration dependence of the surface plasmon absorption at around 400nm was examined by analyzing the absorbance and peak shape. Significant changes in the peak intensity and full width at half maximum (FWHM) were

Chang Hyun Bae; Sang Hwan Nam; Seung Min Park

2002-01-01

163

Deposition of silver nanoparticles on titanium surface for antibacterial effect  

PubMed Central

Microbial colonization on implanted devices and biofilm formation is a recurrent complication in implant surgery and may result in loss of implants. The aim of this study was to deposit silver nanoparticles on a titanium surface to obtain antibacterial properties. In the present study, we prepared a silver nanoparticle-modified titanium (Ti-nAg) surface using silanization method. The morphology and chemical components of the Ti-nAg surface were characterized by scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS). Two species of bacteria, Staphylococcus aureus and Escherichia coli, were utilized to test the antibacterial effect of the Ti-nAg treated surface. The SEM examination revealed that a small quantity of silver nanoparticles was sparsely deposited on the titanium surface. The diameter of these nanoparticles ranged from ten to several hundred nm. EDS analyses revealed that there was 4.26% of Ag present on the surface. After a 24-hour incubation, 94% of Staphylococcus aureus and over 95% of Escherichia coli had been killed on the Ti-nAg surface, and the SEM examination of anti-adhesive efficacy test showed that there were less bacteria attached to Ti-nAg surface than to a control surface of untreated Titanium. These data suggest that silver nanoparticle-modified titanium is a promising material with an antibacterial property that may be used as an implantable biomaterial.

Juan, Liao; Zhimin, Zhu; Anchun, Mo; Lei, Li; Jingchao, Zhang

2010-01-01

164

Core shell silver/silver chloride nanoparticles on carbon nanofibre arrays for bio-potential monitoring  

NASA Astrophysics Data System (ADS)

We report a novel electrode material for the detection of human bio-potentials using carbon nanofibre (CNF) arrays functionalized with silver/silver chloride (Ag-AgCl) core-shell nanoparticles. The CNFs are protected against detachment using a thin polymer film, which firmly secures the fibres to the substrate surface. The core-shell Ag-AgCl nanoparticles on the CNF surfaces clearly enhance transduction in ionic media as shown by cyclic voltammetry and impedance spectroscopy. We infer that these functionalized CNF arrays can be utilized as dry electrophysiological sensors for bio-potential monitoring applications.

Watts, Paul C. P.; Henley, Simon J.; Mendoza, Ernest; Silva, S. Ravi P.; Irvine, June K.; McAdams, Eric T.

2007-05-01

165

Antibacterial nano-structured titania coating incorporated with silver nanoparticles  

Microsoft Academic Search

Titanium (Ti) implants are widely used clinically but post-operation infection remains one of the most common and serious complications. A surface boasting long-term antibacterial ability is highly desirable in order to prevent implant associated infection. In this study, titania nanotubes (TiO2-NTs) incorporated with silver (Ag) nanoparticles are fabricated on Ti implants to achieve this purpose. The Ag nanoparticles adhere tightly

Lingzhou Zhao; Hairong Wang; Kaifu Huo; Lingyun Cui; Wenrui Zhang; Hongwei Ni; Yumei Zhang; Zhifen Wu; Paul K. Chu

2011-01-01

166

Antibacterial efficacy of silver nanoparticles against Escherichia coli  

NASA Astrophysics Data System (ADS)

Silver nanoparticles (AgNPs) synthesized by subjecting an aqueous solution of AgNO3 and polyvinyl alcohol to irradiation from an UV lamp has been studied for its antibacterial potential against Gram-negative bacteria (Escherichia coli). The diameter of the zone of inhibition is found to depend on both the irradiation time and the nanoparticle concentration. As the synthesis method adopted uses no toxic reagents, these particles may serve as promising candidates in the search for better antibacterial agents.

Pattabi, Rani M.; Thilipan, G. Arun Kumar; Bhat, Vinayachandra; Sridhar, K. R.; Pattabi, Manjunatha

2013-02-01

167

Colloidal stability of silver nanoparticles in biologically relevant conditions  

Microsoft Academic Search

Understanding the colloidal stability of nanoparticles (NPs) plays a key role in phenomenological interpretation of toxicological\\u000a experiments, particularly if single NPs or their aggregates or agglomerates determine the dominant experimental result. This\\u000a report examines a variety of instrumental techniques for surveying the colloidal stability of aqueous suspensions of silver\\u000a nanoparticles (AgNPs), including atomic force microscopy, dynamic light scattering, and colorimetry.

Robert I. MacCuspie

2011-01-01

168

Uncovering loss mechanisms in silver nanoparticle-blended plasmonic organic solar cells.  

PubMed

There has been much controversy over the incorporation of organic-ligand-encapsulated plasmonic nanoparticles in the active layer of bulk heterojunction organic solar cells, where both enhancement and detraction in performance have been reported. Here through comprehensive transient optical spectroscopy and electrical characterization, we demonstrate evidence of traps responsible for performance degradation in plasmonic organic solar cells fabricated with oleylamine-capped silver nanoparticles blended in the poly (3-hexylthiophene):[6,6]-phenyl-C 61-butyric acid methyl ester active layer. Despite an initial increase in exciton generation promoted by the presence of silver nanoparticles, transient absorption spectroscopy reveals no increase in the later free polaron population-attributed to fast trapping of polarons by nearby nanoparticles. The increased trap-assisted recombination is also reconfirmed by light intensity-dependent electrical measurements. These new insights into the photophysics and charge dynamics of plasmonic organic solar cells would resolve the existing controversy and provide clear guidelines for device design and fabrication. PMID:23759833

Wu, Bo; Wu, Xiangyang; Guan, Cao; Fai Tai, Kong; Yeow, Edwin Kok Lee; Jin Fan, Hong; Mathews, Nripan; Sum, Tze Chien

2013-01-01

169

Enhanced antibacterial activities of leonuri herba extracts containing silver nanoparticles.  

PubMed

We report an efficient and powerful green process to enhance the antibacterial activities of the Leonuri herba extract. Plant sources, especially leaves and herbs, are precious for the generation of gold and silver nanoparticles. Various kinds of polyphenols and hydroxyl groups are capable of processing a reduction reaction to generate metals from its corresponding salts. We have prepared gold and silver nanoparticles with 70% ethanol and water extracts. No other toxic chemicals were utilized and the extracts played dual roles as reducing and stabilizing agents. For the generation of nanoparticles, both oven incubation and autoclaving methods were applied and the reaction conditions were optimized. Surface plasmon resonance band indicated that the formation of nanoparticles was successful. Images of high-resolution transmission electron microscopy revealed mostly spherical nanoparticles ranging from 9.9 to 13.0?nm in size. A water extract containing silver nanoparticles exhibited remarkable (approximately 127-fold) enhancement in antibacterial activities against Pseudomonas aeruginosa, Escherichia coli and Enterobacter cloacae when compared with the water extract alone. In addition, antibacterial activity towards Gram-negative bacteria was greater than that against Gram-positive bacteria. The process reported here has the potential to be a new approach to improve the antibacterial activities of plant extracts. PMID:22170803

Im, A-Rang; Han, Lina; Kim, E Ray; Kim, Jinwoong; Kim, Yeong Shik; Park, Youmie

2011-12-15

170

Synthesis and standardization of biologically synthesized silver nanoparticles  

NASA Astrophysics Data System (ADS)

The biological silver nanoparticle was synthesized extracellularly by using a fungi Aspergillus foetidus. The live cell filtrate of fungi has been used as reducing agent in the process of nanoparticles synthesis. In 50 ml cell filtrate a volume of AgNO3 stock solution was added to make finally the concentration as 1 mM of AgNO3 and allowed to shake in an incubator for several hrs in dark. The changed color was considered as the primary indication of nanoparticles formation and studies of UV-VIS, DLS, FTIR, AFM, TEM, EDS, Zeta pot. and nitrate reductase assay confirmed the same. It was indicated that stable & 20-40 nm roughly spherical shaped silver nanoparticles was formed. To standardize the nanoparticles biosynthesis different physical parameters like Substrate cone. (0-8 mM), PH-(5-12), Temp.-(5-50°C), incubation time (0-120) hrs and salinity (0.1-1.0 %) were investigated and it was observed that 4 mM AgNO3 conc., PH-9, Temp. -30°C, incubation time 72h and 0.2 % salinity were found to be optimum for the synthesis & stability of the silver nanoparticles.

Roy, Swarup; Das, Tapan Kumar

2013-06-01

171

Silver nanoparticle enhanced silver ion stress response in Escherichia coli K12.  

PubMed

This study investigated the dissolution-based toxicity mechanism for silver nanoparticles to Escherichia coli K12. The silver nanoparticles, synthesised in the vapour phase, are effective anti-bacterial agents against the Gram-negative bacterium, E. coli K12. The nanoparticles associate with the bacterial cell wall, appearing to interact with the outer and inner membranes, and then dissolve to release Ag(+) into the cell and affect a transcriptional response. The dissolution of these nanoparticles in a modified LB medium was measured by inductively coupled plasma mass spectrometry (ICP-MS) and has been shown to follow a simple first-order dissolution process proportional to the decreasing surface area of the nanoparticles. However, the resulting solution phase concentration of Ag(+), demonstrated by the ICP-MS data, is not sufficient to cause the observed effects, including inhibition of bacterial growth and the differential expression of Cu(+) stress response genes. These data indicate that dissolution at the cell membrane is the primary mechanism of action of silver nanoparticles, and the Ag(+) concentration released into the bulk solution phase has only limited anti-bacterial efficacy. PMID:22007647

McQuillan, Jonathan S; Infante, Heidi Groenaga; Stokes, Emma; Shaw, Andrew M

2011-10-18

172

Surface enhanced Raman scattering of silver sensitized cobalt nanoparticles in metal-dielectric nanocomposites.  

PubMed

We report the preparation of a new type of nanocomposite containing cobalt and silver nanoparticles organized in parallel layers with a well controlled separation. This arrangement allows the observation of an enhanced low-frequency Raman signal at the vibration frequency of cobalt nanoparticles excited through the surface plasmons of silver nanoparticles. Numerical simulations of the electric field confirm the emergence of hot spots when the separation between silver and cobalt nanoparticles is small enough. PMID:21832555

Margueritat, J; Gonzalo, J; Afonso, C N; Hörmann, U; Van Tendeloo, G; Mlayah, A; Murray, D B; Saviot, L; Zhou, Y; Hong, M H; Luk'yanchuk, B S

2008-08-01

173

Silver nanoparticles are broad-spectrum bactericidal and virucidal compounds  

PubMed Central

The advance in nanotechnology has enabled us to utilize particles in the size of the nanoscale. This has created new therapeutic horizons, and in the case of silver, the currently available data only reveals the surface of the potential benefits and the wide range of applications. Interactions between viral biomolecules and silver nanoparticles suggest that the use of nanosystems may contribute importantly for the enhancement of current prevention of infection and antiviral therapies. Recently, it has been suggested that silver nanoparticles (AgNPs) bind with external membrane of lipid enveloped virus to prevent the infection. Nevertheless, the interaction of AgNPs with viruses is a largely unexplored field. AgNPs has been studied particularly on HIV where it was demonstrated the mechanism of antiviral action of the nanoparticles as well as the inhibition the transmission of HIV-1 infection in human cervix organ culture. This review discusses recent advances in the understanding of the biocidal mechanisms of action of silver Nanoparticles.

2011-01-01

174

Silver nanoparticles are broad-spectrum bactericidal and virucidal compounds.  

PubMed

The advance in nanotechnology has enabled us to utilize particles in the size of the nanoscale. This has created new therapeutic horizons, and in the case of silver, the currently available data only reveals the surface of the potential benefits and the wide range of applications. Interactions between viral biomolecules and silver nanoparticles suggest that the use of nanosystems may contribute importantly for the enhancement of current prevention of infection and antiviral therapies. Recently, it has been suggested that silver nanoparticles (AgNPs) bind with external membrane of lipid enveloped virus to prevent the infection. Nevertheless, the interaction of AgNPs with viruses is a largely unexplored field. AgNPs has been studied particularly on HIV where it was demonstrated the mechanism of antiviral action of the nanoparticles as well as the inhibition the transmission of HIV-1 infection in human cervix organ culture. This review discusses recent advances in the understanding of the biocidal mechanisms of action of silver Nanoparticles. PMID:21812950

Lara, Humberto H; Garza-Treviño, Elsa N; Ixtepan-Turrent, Liliana; Singh, Dinesh K

2011-08-03

175

Light scattering simulation for the characterization of sintered silver nanoparticles  

Microsoft Academic Search

Light scattering is a useful tool in optical particle characterization. It can help to understand the nature of single particles as well as systems or clusters of particles; information about particle sizes, materials or shapes can be gathered. In this paper we investigate the application of light scattering studies to the analysis of a sintering process of silver nanoparticles. For

Jens Hellmers; Norbert Riefler; Thomas Wriedt; Yuri A. Eremin

2008-01-01

176

Silver nanoparticles: the powerful nanoweapon against multidrug-resistant bacteria.  

PubMed

In the present scenario, pharmaceutical and biomedical sectors are facing the challenges of continuous increase in the multidrug-resistant (MDR) human pathogenic microbes. Re-emergence of MDR microbes is facilitated by drug and/or antibiotic resistance, which is acquired way of microbes for their survival and multiplication in uncomfortable environments. MDR bacterial infections lead to significant increase in mortality, morbidity and cost of prolonged treatments. Therefore, development, modification or searching the antimicrobial compounds having bactericidal potential against MDR bacteria is a priority area of research. Silver in the form of various compounds and bhasmas have been used in Ayurveda to treat several bacterial infections since time immemorial. As several pathogenic bacteria are developing antibiotic resistance, silver nanoparticles are the new hope to treat them. This review discusses the bactericidal potential of silver nanoparticles against the MDR bacteria. This multiactional nanoweapon can be used for the treatment and prevention of drug-resistant microbes. PMID:22324439

Rai, M K; Deshmukh, S D; Ingle, A P; Gade, A K

2012-03-28

177

Efficient synthesis and structural characterization of silver nanoparticle/ bis(o-phenolpropyl)silicone composites.  

PubMed

Silver nanoparticle/bis(o-phenolpropyl)silicone composites have been synthesized by the reduction of silver nitrate with bis(o-phenolpropyl)silicone BPPS [(o-phenolpropyl)2(SiMe2O)n, n = 2, 3, 8, 236]. TEM and FE-SEM data clearly show that the silver nanoparticles with the size of < 20 nm are well dispersed throughout the BPPS matrix in the composites. XRD patterns are consistent with those for multicrystalline silver. The size of silver nanoparticles increased with increasing the relative molar concentration of silver salts added. It was found that in the absence of BPPS, most of the silver nanoparticles undergo macroscopic precipitation by agglomeration, indicating that BPPS is essential to stabilize the silver nanoparticles. PMID:21456244

Kim, Myoung-Hee; Woo, Hee-Gweon; Lee, Byeong-Gweon; Kim, Do-Heyoung; Yang, Kap-Seung; Kim, Bo-Hye; Park, Yeong-Joon; Ko, Young Chun; Roh, Sung-Hee; Sohn, Honglae

2011-02-01

178

In Vivo Toxicity of Silver Nanoparticles and Silver Ions in Zebrafish (Danio rerio)  

PubMed Central

The influence of water chemistry on characterised polyvinyl pyrrolidone- (PVP-) coated silver nanoparticles (81?nm) was investigated. NaCl solution series of 100–800?mg L?1 lead to initial and temporal increase in nanoparticles size, but agglomeration was limited. pH variation (5–8) had only minor influence on the hydrodynamic particle size. Acute toxicity of nanosivler to zebrafish (Danio rerio) was investigated in a 48-hour static renewal study and compared with the toxicity of silver ions (AgNO3). The nanosilver and silver ion 48-hour median lethal concentration (LC50) values were 84??g L?1 and 25??g L?1, respectively. To investigate exposure-related stress, the fish behaviour was observed visually after 0, 3, 6, 12, 24, 27, 30, and 48 hours of both nanosilver and ionic silver treatments. These observations revealed increased rate of operculum movement and surface respiration after nanosilver exposure, suggesting respiratory toxicity. The present study demonstrates that silver nanoparticles are lethal to zebrafish.

Bilberg, Katrine; Hovgaard, Mads Bruun; Besenbacher, Flemming; Baatrup, Erik

2012-01-01

179

Chemical assembly of silver nanoparticles on stainless steel for antimicrobial applications  

Microsoft Academic Search

Microbial adhesion on stainless steel is the most common contamination in many applications. In this work, we present a simple method to fabricate stainless steel-based antimicrobial composites by fixing silver nanoparticles onto the surface. Silver nanoparticles were covalently assembled on the surface of stainless steel by using 3-aminopropyltriethoxysilane (APTES) as the coupling agent. After 24h immersion the release of silver

Limei Chen; Lin Zheng; Yaohui Lv; Hong Liu; Guancong Wang; Na Ren; Duo Liu; Jiyang Wang; Robert I. Boughton

2010-01-01

180

The production of graphene nanosheets decorated with silver nanoparticles for use in transparent, conductive films  

Microsoft Academic Search

Aggregation and restacking of graphene nanosheets (GNS) can be efficiently inhibited by decorating the silver nanoparticles on the surface of GNS to form GNS\\/silver (GNS-Ag) composites, which can construct high transparent and electrically conductive thin films. Silver nanoparticles act as a useful nanospacer and conductor, which not only increase the interlayer distance but also improve the electrical conductivity between layers.

Hsi-Wen Tien; Yuan-Li Huang; Shin-Yi Yang; Jen-Yu Wang; Chen-Chi M. Ma

2011-01-01

181

Novel phase-transfer preparation of monodisperse silver and gold nanoparticles at room temperature  

Microsoft Academic Search

In a novel water-cyclohexane two-phase system, the aqueous formaldehyde is transferred to cyclohexane phase via reaction with dodecylamine to form reductive intermediates in cyclohexane; the intermediates are capable of reducing silver or gold ions in aqueous solution to form dodecylamine protected silver and gold nanoparticles in cyclohexane solution at room temperature. The prepared silver and gold nanoparticles are examined by

Yangying Chen; Xinkui Wang

2008-01-01

182

Strain effects on the SERS enhancements for spherical silver nanoparticles.  

PubMed

We demonstrate in the present work through the utilization of classical Mie scattering theory in conjunction with a radiation damping and dynamic depolarization-corrected electrostatic approximation the significant effect that mechanical strain has on the optical properties of spherical silver nanoparticles. Through appropriate modifications of the bulk dielectric functions, we find that the application of tensile strain generates significant enhancements in the local electric field for the silver nanoparticles, leading to large SERS enhancements of more than 300% compared to bulk, unstrained nanoparticles when a 5% tensile strain is applied. While the strain-induced SERS enhancements are found to be strongest for nanoparticle diameters where radiation damping effects are minimized, we find that the surface plasmon resonance wavelengths are relatively unchanged by mechanical strain, and that the various measures of the far field optical efficiencies (absorption, scattering, extinction) can be enhanced by up to 150% through the application of tensile strain. The present findings indicate the opportunity to actively engineer and enhance the optical properties of silver nanoparticles through the application of mechanical deformation. PMID:20699483

Qian, Xiaohu; Park, Harold S

2010-08-11

183

A physiologically based pharmacokinetic model for ionic silver and silver nanoparticles  

PubMed Central

Silver is a strong antibiotic that is increasingly incorporated into consumer products as a bulk, salt, or nanosilver, thus potentially causing side-effects related to human exposure. However, the fate and behavior of (nano)silver in the human body is presently not well understood. In order to aggregate the existing experimental information, a physiologically based pharmacokinetic model (PBPK) was developed in this study for ionic silver and nanosilver. The structure of the model was established on the basis of toxicokinetic data from intravenous studies. The number of calibrated parameters was minimized in order to enhance the predictive capability of the model. We validated the model structure for both silver forms by reproducing exposure conditions (dermal, oral, and inhalation) of in vivo experiments and comparing simulated and experimentally assessed organ concentrations. Therefore, the percutaneous, intestinal, or pulmonary absorption fraction was estimated based on the blood silver concentration of the respective experimental data set. In all of the cases examined, the model could successfully predict the biodistribution of ionic silver and 15–150 nm silver nanoparticles, which were not coated with substances designed to prolong the circulatory time (eg, polyethylene glycol). Furthermore, the results of our model indicate that: (1) within the application domain of our model, the particle size and coating had a minor influence on the biodistribution; (2) in vivo, it is more likely that silver nanoparticles are directly stored as insoluble salt particles than dissolve into Ag+; and (3) compartments of the mononuclear phagocytic system play a minor role in exposure levels that are relevant for human consumers. We also give an example of how the model can be used in exposure and risk assessments based on five different exposure scenarios, namely dietary intake, use of three separate consumer products, and occupational exposure.

Bachler, Gerald; von Goetz, Natalie; Hungerbuhler, Konrad

2013-01-01

184

The effect of substrate material on silver nanoparticle antimicrobial efficacy.  

PubMed

With the advent of nanotechnology, silver nanoparticles increasingly are being used in coatings, especially in medical device applications, to capitalize on their antimicrobial properties. The attractiveness of nanoparticulate silver systems is the expected increased antimicrobial efficacy relative to their bulk counterparts, which may be attributed to an increased silver ion (Ag+) solubility, and hence availability, that arises from capillarity effects in small, nanometer-sized particles. However, a change of the material upon which the antimicrobial nanoparticulate silver is deposited (herein called "substrate") may affect the availability of Ag+ ions and the intended efficacy of the device. We utilize both theory and experiment to determine the effect of substrate on ion release from silver particles in electrochemical environments and find that substrate surface charge, chemical reactivity or affinity of the surface for Ag+ ions, and wettability of the surface all affect availability of Ag+ ions, and hence antimicrobial efficacy. It is also observed that with time of exposure to deionized water, Ag+ ion release increases to a maximum value at 5 min before decreasing to undetectable levels, which is attributed to coarsening of the nanoparticles, and which subsequently reduces the solubility and availability of Ag+ ions. This coarsening phenomenon is also predicted by the theoretical considerations and has been confirmed experimentally by transmission electron microscopy. PMID:21121354

Dair, Benita J; Saylor, David M; Cargal, T Eric; French, Grace R; Kennedy, Kristen M; Casas, Rachel S; Guyer, Jonathan E; Warren, James A; Kim, Chang-Soo; Pollack, Steven K

2010-12-01

185

Biopersistence of silver nanoparticles in tissues from Sprague-Dawley rats.  

PubMed

Silver nanoparticles are known to be distributed in many tissues after oral or inhalation exposure. Thus, understanding the tissue clearance of such distributed nanoparticles is very important to understand the behavior of silver nanoparticles in vivo. For risk assessment purposes, easy clearance indicates a lower overall cumulative toxicity. Accordingly, to investigate the clearance of tissue silver concentrations following oral silver nanoparticle exposure, Sprague-Dawley rats were assigned to 3 groups: control, low dose (100 mg/kg body weight), and high dose (500 mg/kg body weight), and exposed to two different sizes of silver nanoparticles (average diameter 10 and 25 nm) over 28 days. Thereafter, the rats were allowed to recover for 4 months. Regardless of the silver nanoparticle size, the silver content in most tissues gradually decreased during the 4-month recovery period, indicating tissue clearance of the accumulated silver. The exceptions were the silver concentrations in the brain and testes, which did not clear well, even after the 4-month recovery period, indicating an obstruction in transporting the accumulated silver out of these tissues. Therefore, the results showed that the size of the silver nanoparticles did not affect their tissue distribution. Furthermore, biological barriers, such as the blood-brain barrier and blood-testis barrier, seemed to play an important role in the silver clearance from these tissues. PMID:24059869

Lee, Ji Hyun; Kim, Yong Soon; Song, Kyung Seuk; Ryu, Hyun Ryol; Sung, Jae Hyuck; Park, Jung Duck; Park, Hyun Min; Song, Nam Woong; Shin, Beom Soo; Marshak, Daniel; Ahn, Kangho; Lee, Ji Eun; Yu, Il Je

2013-08-01

186

Surface enhanced Raman scattering of silver sensitized cobalt nanoparticles in metal dielectric nanocomposites  

Microsoft Academic Search

We report the preparation of a new type of nanocomposite containing cobalt and silver nanoparticles organized in parallel layers with a well controlled separation. This arrangement allows the observation of an enhanced low-frequency Raman signal at the vibration frequency of cobalt nanoparticles excited through the surface plasmons of silver nanoparticles. Numerical simulations of the electric field confirm the emergence of

J. Margueritat; J. Gonzalo; C. N. Afonso; U. Hörmann; G. Van Tendeloo; A. Mlayah; D. B. Murray; L. Saviot; Y. Zhou; M. H. Hong; B S Luk’yanchuk

2008-01-01

187

Gold and silver nanoparticles for biomolecule immobilization and enzymatic catalysis.  

PubMed

In this work, a simple method for alcohol synthesis with high enantiomeric purity was proposed. For this, colloidal gold and silver surface modifications with 3-mercaptopropanoic acid and cysteamine were used to generate carboxyl and amine functionalized gold and silver nanoparticles of 15 and 45?nm, respectively. Alcohol dehydrogenase from Thermoanaerobium brockii (TbADH) and its cofactor (NADPH) were physical and covalent (through direct adsorption and using cross-linker) immobilized on nanoparticles' surface. In contrast to the physical and covalent immobilizations that led to a loss of 90% of the initial enzyme activity and 98% immobilization, the use of a cross-linker in immobilization process promoted a loss to 30% of the initial enzyme activity and >92% immobilization. The yield of NADPH immobilization was about 80%. The best results in terms of activity were obtained with Ag-citr nanoparticle functionalized with carboxyl groups (Ag-COOH), Au-COOH(CTAB), and Au-citr functionalized with amine groups and stabilized with CTAB (Au-NH2(CTAB)) nanoparticles treated with 0.7% and 1.0% glutaraldehyde. Enzyme conformation upon immobilization was studied using fluorescence and circular dichroism spectroscopies. Shift in ellipticity at 222?nm with about 4 to 7?nm and significant decreasing in fluorescence emission for all bioconjugates were observed by binding of TbADH to silver/gold nanoparticles. Emission redshifting of 5?nm only for Ag-COOH-TbADH bioconjugate demonstrated change in the microenvironment of TbADH. Enzyme immobilization on glutaraldehyde-treated Au-NH2(CTAB) nanoparticles promotes an additional stabilization preserving about 50% of enzyme activity after 15?days storage. Nanoparticles attached-TbADH-NADPH systems were used for enantioselective (ee?>?99%) synthesis of (S)-7-hydroxy-2-tetralol. PMID:22655978

Petkova, Galina A; Záruba, Capital Ka Cyrillicamil; Zvátora, Pavel; Král, Vladimír

2012-06-01

188

Attenuation of allergic airway inflammation and hyperresponsiveness in a murine model of asthma by silver nanoparticles  

PubMed Central

The use of silver in the past demonstrated the certain antimicrobial activity, though this has been replaced by other treatments. However, nanotechnology has provided a way of producing pure silver nanoparticles, and it shows cytoprotective activities and possible pro-healing properties. But, the mechanism of silver nanoparticles remains unknown. This study was aimed to investigate the effects of silver nanoparticles on bronchial inflammation and hyperresponsiveness. We used ovalbumin (OVA)-inhaled female C57BL/6 mice to evaluate the roles of silver nanoparticles and the related molecular mechanisms in allergic airway disease. In this study with an OVA-induced murine model of allergic airway disease, we found that the increased inflammatory cells, airway hyperresponsiveness, increased levels of IL-4, IL-5, and IL-13, and the increased NF-?B levels in lungs after OVA inhalation were significantly reduced by the administration of silver nanoparticles. In addition, we have also found that the increased intracellular reactive oxygen species (ROS) levels in bronchoalveolar lavage fluid after OVA inhalation were decreased by the administration of silver nanoparticles. These results indicate that silver nanoparticles may attenuate antigen-induced airway inflammation and hyperresponsiveness. And antioxidant effect of silver nanoparticles could be one of the molecular bases in the murine model of asthma. These findings may provide a potential molecular mechanism of silver nanoparticles in preventing or treating asthma.

Park, Hee Sun; Kim, Keun Hwa; Jang, Sunhyae; Park, Ji Won; Cha, Hye Rim; Lee, Jeong Eun; Kim, Ju Ock; Kim, Sun Young; Lee, Choong Sik; Kim, Joo Pyung; Jung, Sung Soo

2010-01-01

189

Interaction of silver nanoparticles (SNPs) with bacterial extracellular proteins (ECPs) and its adsorption isotherms and kinetics.  

PubMed

Indiscriminate and increased use of silver nanoparticles (SNPs) in consumer products leads to the release of it into the environment. The fate and transport of SNPs in environment remains unknown. We have studied the interaction of SNPs with extracellular protein (ECP) produced by two environmental bacterial species and the adsorption behavior in aqueous solutions. The effect of pH and salt concentrations on the adsorption was also investigated. The adsorption process was found to be dependent on surface charge (zeta potential). The capping of SNPs by ECP was confirmed by Fourier transform infrared spectroscopy and X-ray diffraction. The adsorption of ECP on SNPs was analyzed by Langmuir and Freundlich models, suggesting that the equilibrium adsorption data fitted well with Freundlich model. The equilibrium adsorption data were modeled using the pseudo-first-order and pseudo-second-order kinetic equations. The results indicated that pseudo-second-order kinetic equation would better describe the adsorption kinetics. The capping was stable at environmental pH and salt concentration. The destabilization of nanoparticles was observed at alkaline pH. The study suggests that the stabilization of nanoparticles in the environment might lead to the accumulation and transport of nanomaterials in the environment, and ultimately destabilizes the functioning of the ecosystem. PMID:21684082

Khan, S Sudheer; Srivatsan, P; Vaishnavi, N; Mukherjee, Amitava; Chandrasekaran, N

2011-06-01

190

Aggregation kinetics and dissolution of coated silver nanoparticles.  

PubMed

Determining the fate of manufactured nanomaterials in the environment is contingent upon understanding how stabilizing agents influence the stability of nanoparticles in aqueous systems. In this study, the aggregation and dissolution tendencies of uncoated silver nanoparticles and the same particles coated with three common coating agents, trisodium citrate, sodium dodecyl sulfate (SDS), and Tween 80 (Tween), were evaluated. Early stage aggregation kinetics of the uncoated and coated silver nanoparticles were assessed by dynamic light scattering over a range of electrolyte types (NaCl, NaNO(3), and CaCl(2)) and concentrations that span those observed in natural waters. Although particle dissolution was observed, aggregation of all particle types was still consistent with classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The aggregation of citrate-coated particles and SDS-coated particles were very similar to that for the uncoated particles, as the critical coagulation concentrations (CCC) of the particles in different electrolytes were all approximately the same (40 mM NaCl, 30 mM NaNO(3), and 2 mM CaCl(2)). The Tween-stabilized particles were significantly more stable than the other particles, however, and in NaNO(3) aggregation was not observed up to an electrolyte concentration of 1 M. Differences in the rate of aggregation under diffusion-limited aggregation conditions at high electrolyte concentrations for the SDS and Tween-coated particles, in combination with the moderation of their electrophoretic mobilities, suggest SDS and Tween imparted steric interactions to the particles. The dissolution of the silver nanoparticles was inhibited by the SDS and Tween coatings, but not by the citrate coating, and in chloride-containing electrolytes a secondary precipitate of AgCl was observed bridging the individual particles. These results indicate that coating agents could significant influence the fate of silver nanoparticles in aquatic systems, and in some cases these stabilizers may completely prevent particle aggregation. PMID:22149007

Li, Xuan; Lenhart, John J; Walker, Harold W

2011-12-22

191

Synthesis of silver nanoparticles in methacrylic acid solution by gamma radiolysis and their application for estimation of dopamine at low concentrations  

NASA Astrophysics Data System (ADS)

Polymethacrylate capped silver nanoparticles have been synthesized in aqueous solution by gamma radiolysis method. The nanoparticle synthesis and polymerization of methacrylic acid occurred simultaneously in situ. Effect of different parameters such as precursor concentration and alkalinity on nanoparticle formation has been studied. These silver nanoparticles were tested for estimation of dopamine (DA) by monitoring surface plasmon band of nanoparticles at various DA concentrations. The result showed the response of spectral change towards DA concentration is linear in the DA concentration in the range of 5.27×10-7 to 1.58×10-5 mol dm-3. Also the interference of ascorbic acid (AA) in estimation of DA has also been studied. AA concentration up to 1.0×10-4 mol dm-3 does not interfere in the estimation of DA in the range of 5.27×10-7 to 1.05×10-5 mol dm-3.

Biswal, Jayashree; Misra, Nilanjal; Borde, Lalit C.; Sabharwal, S.

2013-02-01

192

Preparation and study of polyacryamide-stabilized silver nanoparticles through a one-pot process.  

PubMed

A one-pot route was illustrated to synthesize stable well-dispersed silver colloids stabilized by polyacrylamide on a large scale. Reduction of silver ions and polymerization of acrylamide occurred almost simultaneously in the absence of a commonly used reducing agent and initiator. A possible mechanism for the formation of silver nanoparticles with bimodal size distribution was proposed. The structure and composition of the obtained nanoparticles were characterized carefully. Furthermore, light scattering simulation and UV-vis absorption studies confirmed that the obtained colloids were the mixture of Ag and Ag2O nanoparticles. The presence of silver oxide layers on the nanoparticle surface should be responsible for the broadening of the surface plasmon band of silver nanoparticles. Ag2O layers could be added or removed from Ag nanoparticle surfaces by the addition of HNO3, HAc, or NaCl solution to the as-obtained silver colloids. PMID:16771388

Chen, Meng; Wang, Li-Ying; Han, Jian-Tao; Zhang, Jun-Yan; Li, Zhi-Yuan; Qian, Dong-Jin

2006-06-15

193

Spatially controlled synthesis of silver nanoparticles and nanowires by photosensitized reduction.  

PubMed

The present paper reports on the spatially controlled synthesis of silver nanoparticles (NPs) and silver nanowires by photosensitized reduction. In a first approach, direct photogeneration of silver NPs at the end of an optical fiber was carried out. Control of both size and density of silver NPs was possible by changing the photonic conditions. In a further development, a photochemically assisted procedure allowing silver to be deposited at the surface of a polymer microtip was implemented. Finally, polymer tips terminated by silver nanowires were fabricated by simultaneous photopolymerization and silver photoreduction. The silver NPs were characterized by UV-visible spectroscopy and scanning electron microscopy. PMID:20124664

Jradi, S; Balan, L; Zeng, X H; Plain, J; Lougnot, D J; Royer, P; Bachelot, R; Akil, S; Soppera, O; Vidal, L

2010-02-03

194

Sensitive signal-on fluorescent sensing for copper ions based on the polyethyleneimine-capped silver nanoclusters-cysteine system.  

PubMed

In this work, we present a label-free sensor for copper ions. This sensor is composed of silver nanoclusters and cysteine. The fluorescence of the silver nanoclusters was quenched by cysteine, which was recovered in the presence of copper ions. This binding of silver nanoclusters to cysteine promoted agglomeration of silver nanoclusters to yield larger non-fluorescent silver nanoparticles. The presence of copper ions resulted in the oxidation of cysteine to form a disulfide compound, leading to recovery of fluorescence of the silver nanoclusters. The fluorescence of the silver nanoclusters in the presence of cysteine increased with increasing concentration of copper ions in the range of 10-200 nM. The detection limit of this sensor for copper ions was 2.3 nM. The silver nanoclusters-cysteine sensor provides a simple, cost-effective, and sensitive platform for the detection of copper ions. PMID:23890605

Zhang, Na; Qu, Fei; Luo, Hong Qun; Li, Nian Bing

2013-07-03

195

PEG conjugated citrate-capped magnetite nanoparticles for biomedical applications  

NASA Astrophysics Data System (ADS)

We aim to develop polyethylene glycol decorated, citric acid capped magnetite nanoparticles (MNPs) with proper physicochemical characteristics including particle size distribution, morphology, magnetic property and stability in a biologic medium. MNP of about 10 nm were synthesized by a biocompatible chemical co-precipitation of Fe2+ and Fe3+ in an ammonia solution. A synthetic methodology has been developed to get a well dispersed and homogeneous aqueous suspension of MNPs. The naked MNPs are often insufficient for their stability, hydrophilicity and further functionalization. In order to overcome these limitations, citric acid was used to stabilize the magnetite particle suspension, which was anchored on the surface of freshly prepared MNPs by a direct addition method. Polyethylene glycol was covalently attached to the carboxylic moieties of citric acid anchored MNPs by carbodiimide chemistry. The microstructure and morphology of the nanoparticles were characterized by X-ray diffraction and transmission electron microscopy, and Fourier transform infrared spectroscopy. Also, the magnetic properties were investigated by vibrating sample magnetometry. It was found that the nanoparticles demonstrated superparamagnetic behavior.

Cheraghipour, Elham; Tamaddon, A. M.; Javadpour, S.; Bruce, I. J.

2013-02-01

196

Tuning the electromagnetic field coupling between nanoporous silver and silver nanoparticles connected by hybridized oligonucleotide  

NASA Astrophysics Data System (ADS)

On monolithic nanoporous silver (NPS), via DNA hybridization, we constructed an NPS/DNA-Cy5/silver nanoparticle (Ag NP) sandwich to investigate its SERS effect. In this sandwich, no chemical enhancement contributes to the SERS signal of Cy5. As compared with NPS, the present substrate exhibits particularly strong electromagnetic (EM) field enhancement. At the same Ag NPs surface loading, the SERS intensity decreases exponentially with increasing the length of double-stranded DNA (dsDNA). A larger pore size of NPS leads to weaker EM enhancement within the sandwich, but the relative intensity is not sensitive to the sizes and it is determined by the length of dsDNA.

Zhao, Yin; Yan, Keqian; Huang, Xirong; Zhang, Zhonghua; Qu, Yinbo

2013-01-01

197

Green synthesis of silver nanoparticles using cellulose extracted from an aquatic weed; water hyacinth.  

PubMed

As part of the desire to save the environment through "green" chemistry practices, we herein report an environmentally benign synthesis of silver nanoparticles (Ag-NPs) using cellulose extracted from an environmentally problematic aquatic weed, water hyacinth (WH), as both reducing and capping agent in an aqueous medium. By varying the pH of the solution and reaction time, the temporal evolutions of the optical and morphological properties of the as-synthesised Ag-NPs were investigated. The as-synthesised cellulose capped silver nanoparticles (C-Ag-NPs) were characterised using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The maximum surface plasmon resonance (SPR) peak decreased as the pH increased indicating that an increase in the pH of the solution favoured the formation of smaller particles. In addition, instantaneous change in the colour of the solution from colourless to brown within 5min at pH 11 showed that the rate of reduction is faster at this pH compared to those at lower pH. The TEM micrographs showed that the materials are small, highly monodispersed and spherical in shape. The average particle mean diameters were calculated to be 5.69±5.89nm, 4.53±1.36nm and 2.68±0.69nmnm at pH 4, 8 and 11 respectively. The HRTEM confirmed the crystallinity of the material while the FTIR spectra confirmed the capping of the as-synthesised Ag-NPs by the cellulose. It has been shown therefore that based on this synthetic method, this aquatic plant can be used to the advantage of mankind. PMID:23987347

Mochochoko, Tanki; Oluwafemi, Oluwatobi S; Jumbam, Denis N; Songca, Sandile P

2013-06-06

198

Effect of Inorganic Silver Nanoparticles on Structural and Electrical Properties of Polyaniline\\/PVC Blends  

Microsoft Academic Search

Dodecylbenzenesulfonic acid (DBSA) doped polyaniline (PANDR) has been synthesized by redoping method. Inorganic silver nanoparticles\\u000a were incorporated in THF solution of PANDR (PANDS) and then mixed with PVC solution to prepare PANDS\\/PVC nanocomposites. FTIR\\u000a spectroscopy indicated that silver nanoparticles reside more close to imine nitrogen of PANDS. Transmission electron microscopy\\u000a (TEM) confirmed the formation and dispersion of silver nanoparticles in

Asma B. Afzal; M. Javed Akhtar

2010-01-01

199

Non-functionalized silver nanoparticles for a localized surface plasmon resonance-based glucose sensor  

NASA Astrophysics Data System (ADS)

The optical properties of non-functionalized silver nanoparticles in ethanol solution have been analyzed and a progressive shift of localized surface plasmon resonances caused by the adding of increasing quantities of glucose has been observed. To understand this occurrence, the interaction of glucose molecules with the silver nanoparticle surface has been investigated using Raman spectroscopy. In addition, high resolution transmission electron microscopy shows the presence of superstructures on the silver nanoparticle surface that can be imputed to the presence of glucose.

Serra, A.; Filippo, E.; Re, M.; Palmisano, M.; Vittori-Antisari, M.; Buccolieri, A.; Manno, D.

2009-04-01

200

Can silver nanoparticles be useful as potential biological labels?  

NASA Astrophysics Data System (ADS)

Silver (Ag) nanoparticles have unique plasmon-resonant optical scattering properties that are finding use in nanomedical applications such as signal enhancers, optical sensors, and biomarkers. In this study, we examined the chemical and biological properties of Ag nanoparticles of similar sizes, but that differed primarily in their surface chemistry (hydrocarbon versus polysaccharide), in neuroblastoma cells for their potential use as biological labels. We observed strong optical labeling of the cells in a high illumination light microscopy system after 24 h of incubation due to the excitation of plasmon resonance by both types of Ag nanoparticle. Surface binding of both types of Ag nanoparticle to the plasma membrane of the cells was verified with scanning electron microscopy as well as the internalization and localization of the Ag nanoparticles into intracellular vacuoles in thin cell sections with transmission electron microscopy. However, the induction of reactive oxygen species (ROS), degradation of mitochondrial membrane integrity, disruption of the actin cytoskeleton, and reduction in proliferation after stimulation with nerve growth factor were found after incubation with Ag nanoparticles at concentrations of 25 µg ml-1 or greater, with a more pronounced effect produced by the hydrocarbon-based Ag nanoparticles in most cases. Therefore, the use of Ag nanoparticles as potential biological labels, even if the surface is chemically modified with a biocompatible material, should be approached with caution.

Schrand, Amanda M.; Braydich-Stolle, Laura K.; Schlager, John J.; Dai, Liming; Hussain, Saber M.

2008-06-01

201

Electronic conductivity of alkyne-capped ruthenium nanoparticles  

NASA Astrophysics Data System (ADS)

Ruthenium nanoparticles (2.12 +/- 0.72 nm in diameter) were stabilized by the self-assembly of alkyne molecules (from 1-hexyne to 1-hexadecyne) onto the Ru surface by virtue of the formation of Ru-vinylidene interfacial linkages. Infrared measurements depicted three vibrational bands at 2050 cm-1, 1980 cm-1 and 1950 cm-1, which were ascribed to the vibrational stretches of the terminal triple bonds that were bound onto the nanoparticle surface. Thermogravimetric analysis showed that there were about 65 to 96 alkyne ligands per nanoparticle (depending on the ligand chainlength), corresponding to a molecular footprint of 20 to 15 Å2. This suggests that the ligands likely adopted a head-on configuration on the nanoparticle surface, consistent with a vinylidene bonding linkage due to interfacial tautomeric rearrangements. With this conjugated interfacial bonding interaction, electronic conductivity measurements of the corresponding nanoparticle solid films showed that the nanoparticles all exhibited linear current-potential curves within the potential range of -0.8 V to +0.8 V at varied temperatures (200 to 300 K). The ohmic characters were partly ascribed to the spilling of core electrons into the organic capping layer that facilitated interparticle charge transfer. Furthermore, based on the temperature dependence of the nanoparticle electronic conductivity, the activation energy for interparticle charge transfer was estimated to be in the range of 70 to 90 meV and significantly, the coupling coefficient (?) was found to be 0.31 Å-1 for nanoparticles stabilized by short-chain alkynes (1-hexyne, 1-octyne, and 1-decyne), and 1.44 Å-1 for those with long alkynes such as 1-dodecyne, 1-tetradecyne, and 1-hexadecyne. This may be accounted for by the relative contributions of the conjugated metal-ligand interfacial bonding interactions versus the saturated aliphatic backbones of the alkyne ligands to the control of interparticle charge transfer.Ruthenium nanoparticles (2.12 +/- 0.72 nm in diameter) were stabilized by the self-assembly of alkyne molecules (from 1-hexyne to 1-hexadecyne) onto the Ru surface by virtue of the formation of Ru-vinylidene interfacial linkages. Infrared measurements depicted three vibrational bands at 2050 cm-1, 1980 cm-1 and 1950 cm-1, which were ascribed to the vibrational stretches of the terminal triple bonds that were bound onto the nanoparticle surface. Thermogravimetric analysis showed that there were about 65 to 96 alkyne ligands per nanoparticle (depending on the ligand chainlength), corresponding to a molecular footprint of 20 to 15 Å2. This suggests that the ligands likely adopted a head-on configuration on the nanoparticle surface, consistent with a vinylidene bonding linkage due to interfacial tautomeric rearrangements. With this conjugated interfacial bonding interaction, electronic conductivity measurements of the corresponding nanoparticle solid films showed that the nanoparticles all exhibited linear current-potential curves within the potential range of -0.8 V to +0.8 V at varied temperatures (200 to 300 K). The ohmic characters were partly ascribed to the spilling of core electrons into the organic capping layer that facilitated interparticle charge transfer. Furthermore, based on the temperature dependence of the nanoparticle electronic conductivity, the activation energy for interparticle charge transfer was estimated to be in the range of 70 to 90 meV and significantly, the coupling coefficient (?) was found to be 0.31 Å-1 for nanoparticles stabilized by short-chain alkynes (1-hexyne, 1-octyne, and 1-decyne), and 1.44 Å-1 for those with long alkynes such as 1-dodecyne, 1-tetradecyne, and 1-hexadecyne. This may be accounted for by the relative contributions of the conjugated metal-ligand interfacial bonding interactions versus the saturated aliphatic backbones of the alkyne ligands to the control of interparticle charge transfer. Electronic supplementary information (ESI) available: TEM micrograph, derivative thermogravimetric curves, and UV-vis and fluorescence spectra of the

Kang, Xiongwu; Chen, Shaowei

2012-06-01

202

Time-dependent effect in green synthesis of silver nanoparticles.  

PubMed

The application of "green" chemistry rules to nanoscience and nanotechnology is very important in the preparation of various nanomaterials. In this work, we successfully developed an eco-friendly chemistry method for preparing silver nanoparticles (Ag-NPs) in natural polymeric media. The colloidal Ag-NPs were synthesized in an aqueous solution using silver nitrate, gelatin, and glucose as a silver precursor, stabilizer, and reducing agent, respectively. The properties of synthesized colloidal Ag-NPs were studied at different reaction times. The ultraviolet-visible (UV-vis) spectra were in excellent agreement with the obtained nanostructure studies performed by transmission electron microscopy (TEM) and their size distributions. The prepared samples were also characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The use of eco-friendly reagents, such as gelatin and glucose, provides green and economic attributes to this work. PMID:21556342

Darroudi, Majid; Ahmad, Mansor Bin; Zamiri, Reza; Zak, A K; Abdullah, Abdul Halim; Ibrahim, Nor Azowa

2011-04-05

203

The double effects of silver nanoparticles on the PVDF membrane: Surface hydrophilicity and antifouling performance  

NASA Astrophysics Data System (ADS)

In this study, silver nanoparticles were used to endow poly(vinylidene fluoride) (PVDF) membrane with excellent surface hydrophilicity and outstanding antifouling performance. Silver nanoparticles were successfully immobilized onto PVDF membrane surface under the presence of poly(acrylic acid) (PAA). The double effects of silver nanoparticles on PVDF membrane, i.e., surface hydrophilicity and anti-fouling performance, were systematically investigated. Judging from result of water static contact measurement, silver nanoparticles had provided a significant improvement in PVDF membrane surface hydrophilicity. And the possible explanation on the improvement of PVDF membrane surface hydrophilicity with silver nanoparticles was firstly proposed in this study. Membrane permeation and anti-bacterial tests were carried out to characterize the antifouling performance of PVDF membrane. Flux recovery ratio (FRR) increased about 40% after the presence of silver nanoparticles on the PVDF membrane surface, elucidating the anti-organic fouling performance of PVDF membrane was elevated by silver nanoparticles. Simultaneously, anti-bacterial test confirmed that PVDF membrane showed superior anti-biofouling activity because of silver nanoparticles. The above-mentioned results clarified that silver nanoparticles can endow PVDF membrane with both excellent surface hydrophilicity and outstanding antifouling performance in this study.

Li, Jian-Hua; Shao, Xi-Sheng; Zhou, Qing; Li, Mi-Zi; Zhang, Qi-Qing

2013-01-01

204

Suspended hybrid films assembled from thiol-capped gold nanoparticles  

PubMed Central

In this work, we explored the formation processes of suspended hybrid thin films of thiol-capped Au nanoparticles (AuNPs) inside metal oxide tubular structures. We found that a balance between in-film interactions of the AuNPs and boundary interactions with metal oxides is a key in making these special organic–inorganic thin films. The hybrid films process many processing advantages and flexibilities, such as controllable film thickness, interfacial shape and inter-AuNPs distance, tuning of particle sizes, thiol population, chain lengths, and other new properties by introducing functional groups to thiol chains. Among their many unique features, the assembly-disassembly property may be useful for future on-off or store-release applications.

2012-01-01

205

Self-assembly of cinnamic acid-capped gold nanoparticles  

NASA Astrophysics Data System (ADS)

In this work, a new capping agent, cinnamic acid (CA) was used to synthesize Au nanoparticles (NPs) under ambient conditions. The size of the NPs can be controlled by adjusting the concentration of reductant (in our experiment sodium borohydride was used) or CA. The CA-stabilized Au NPs can self-assemble into 'nanowire-like' or 'pearl-necklace-like' nanostructures by adjusting the molar ratio of CA to HAuCl4 or by tuning the pH value of the Au colloidal solution. The process of Au NPs self-assembly was investigated by UV-vis spectroscopy and transmission electron microscopy. The results reveal that the induced dipole-dipole interaction is the driving force of Au NP linear assemblies.

Wang, Li; Wei, Gang; Sun, Lanlan; Liu, Zhiguo; Song, Yonghai; Yang, Tao; Sun, Yujing; Guo, Cunlan; Li, Zhuang

2006-06-01

206

Silver-based crystalline nanoparticles, microbially fabricated  

PubMed Central

One mechanism of silver resistance in microorganisms is accumulation of the metal ions in the cell. Here, we report on the phenomenon of biosynthesis of silver-based single crystals with well-defined compositions and shapes, such as equilateral triangles and hexagons, in Pseudomonas stutzeri AG259. The crystals were up to 200 nm in size and were often located at the cell poles. Transmission electron microscopy, quantitative energy-dispersive x-ray analysis, and electron diffraction established that the crystals comprise at least three different types, found both in whole cells and thin sections. These Ag-containing crystals are embedded in the organic matrix of the bacteria. Their possible potential as organic-metal composites in thin film and surface coating technology is discussed.

Klaus, Tanja; Joerger, Ralph; Olsson, Eva; Granqvist, Claes-Goran

1999-01-01

207

Characterization by spectroscopic Ellipsometry, the physical properties of silver nanoparticles.  

NASA Astrophysics Data System (ADS)

Physicists are able to change their minds through their experiments. I think it is time to go kick the curse and go further in research if we want a human future. I work in the Nano-Optics and Plasmonics research. I defined with ellipsomètrie the structure of new type of Nano particles of silver. It's same be act quickly to replace the old dirty leaded electronic-connexion chip and by the other hand to find a new way for the heath care of cancer disease by nanoparticles the next killers of bad cells. Silver nanoparticle layers are obtained by Spark Plasma Sintering are investigated as an alternative to lead alloy based material for solder joint in power mechatronics modules. These layers are characterized by mean of conventional techniques that is the dilatometry technique, the resistivity measurement through the van der Pauw method, and the flash laser technique. Furthermore, the nanoparticles of silver layer are deeply studied by UV-Visible spectroscopic ellipsometry. Spectroscopic angles parameters are determined in function of temperature and dielectric constants are deduced and analyzed through an optical model which takes into account a Drude and a Lorentz component within the Bruggeman effective medium approximation (EMA). The relaxation times and the electrical conductivity are plot in function of temperature. The obtained electrical conductivity give significant result in good agreement to those reported by four points electrical measurement method.

Coanga, Jean-Maurice

2013-04-01

208

Spontaneous formation of silver nanoparticles in aminosilica  

Microsoft Academic Search

We report a rapid and spontaneous metallization process associated with sol–gel reaction of aminosilane that can be utilized\\u000a to synthesise silver embedded silica nanocomposite without involving additional reducing agents. The reduction reaction induced\\u000a by bis[3-(trimethoxysilyl)propyl]ethylenediamine (enTMOS) involves amine functional moieties, which drive the reduction reaction\\u000a with presence of water. Cyclic voltammetry was used to investigate the redox potential of enTMOS

Yong-Jae Choi; Uk Huh; Tzy-Jiun M. Luo

2009-01-01

209

Enhanced frequency upconversion in Er3+-doped sodium lead tellurite glass containing silver nanoparticles  

NASA Astrophysics Data System (ADS)

A series of silver nanoparticle embedded in erbium-doped tellurite glasses were synthesized using a one step melt-quenching method. Density and refractive index of glasses were measured. Thermal and optical characterizations were performed and plasmon bands of elliptical nanoparticles were observed. An enhancement of green (525 and 550 nm) and red (632 nm) lines in luminescence spectra of Er3+-doped silver-embedded tellurite glass was recorded and explained by energy transfer mechanism from silver nanoparticles to erbium ion in addition to enhanced local field in vicinity of metallic nanoparticles in the glass. The presence of nanoparticles was confirmed by transmission electron microscopy imaging and reduction of silver ions to silver neutral particles discussed through the redox potential estimation in probable reactions. Silver-erbium co-doped tellurite glass exhibits strong novel optical properties which nominate it as the promising glass for laser, color displays, and photonic applications.

Reza Dousti, M.; Sahar, M. R.; Amjad, Raja J.; Ghoshal, S. K.; Khorramnazari, A.; Dordizadeh Basirabad, A.; Samavati, A.

2012-09-01

210

Effects of ionic surfactants on the morphology of silver nanoparticles using Paan (Piper betel) leaf petiole extract.  

PubMed

Stable silver nanoparticles were synthesized by the reduction of silver ions with a Paan (Piper betel) leaf petiole extract in absence and presence of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS). The reaction process was simple and convenient to handle, and was monitored using ultraviolet-visible spectroscopy. Absorbance of Ag-nanoparticles increases with the concentrations of Paan leaf extract, acts as reducing, stabilizing and capping agents. The polyphenolic groups of petiole extract are responsible to the rapid reduction of Ag(+) ions into metallic Ag(0). The results indicated that the shape of the spectra, number of peaks and its position strongly depend on the concentration of CTAB, which played a shape-controlling role during the formation of silver nanoparticles in the solutions, whereas SDS has no significant effect. The morphology (spherical, truncated triangular polyhedral plate and some irregular nanoparticles) and crystalline phase of the particles were determined from transmission electron microscopy (TEM) and selected area electron diffraction (SAED). PMID:22652360

Khan, Zaheer; Bashir, Ommer; Hussain, Javed Ijaz; Kumar, Sunil; Ahmad, Rabia

2012-04-30

211

Bioactivity and protein attachment onto bioactive glasses containing silver nanoparticles.  

PubMed

There is much interest in silver containing glasses for use in bone replacement owing to the demonstrated antibacterial effect. In this work, 2 and 8 mol % of silver was added during the sol-gel process to the composition of a bioactive glass belonging to CaO-SiO(2 -P(2)O(5) system. The samples were characterized by means of ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques to demonstrate that the silver is embedded into the glass matrix as nanoparticles. Bioactivity test in simulated body fluid proved that the presence of silver in the bioactive glass composition, even in high amount, preserve or even improve the bioactivity of the starting glass, and consequently, leads to the carbonated apatite formation, which is the prerequisite for bioactive materials to bond with living bones. Complementary information proving these findings were delivered by performing X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and XPS measurements. The presence of silver also improves protein binding capability to the bioactive glass surface as demonstrated by cw-electron paramagnetic resonance experiments and XPS measurements. PMID:22345075

Vulpoi, A; Gruian, C; Vanea, E; Baia, L; Simon, S; Steinhoff, H-J; Göller, G; Simon, V

2012-02-18

212

In-situ observation of silver nanoparticle ink at high temperature.  

PubMed

In-situ TEM (transmission electron microscopy) of silver nanoparticle ink at high temperature was carried out. Into a carbon film tube coating the spiral tungsten filament which was attached to the TEM specimen holder, a silver nanoparticle ink was injected. After evaporation, silver nanoparticles with an aggregated structure could be observed. The temperature of the tungsten wire can be controlled by DC current supplied by dry batteries. Fusion of smaller nanoparticles was observed at a higher temperature and some particles were incorporated to larger particles. This technique can be generally used to consider the sintering temperature of such metal nanoparticles. PMID:19458443

Yonezawa, Tetsu

2009-01-01

213

Biosynthesis of silver nanoparticles by a Bacillus sp. of marine origin  

NASA Astrophysics Data System (ADS)

This study was aimed to explore the nanoparticle synthesizing properties of a silver resistant Bacillus sp. isolated from a marine water sample. The 16SrDNA sequence analysis of the isolate proved it as a Bacillus strain. Very interestingly, the isolate was found to have the ability to form intracellular silver nanoparticles at room temperature within 24 hours. This was confirmed by the UV-Vis absorption analysis which showed a peak at 430 nm corresponding to the plasmon absorbance of silver nanoparticles. Further characterization of the nanoparticles was carried out by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analysis. The presence of silver nanoparticles with the size less than 100 nm was confirmed. These particles were found to be extremely stable as confirmed by the TEM analysis after three months of purification. So, the current study is the demonstration of an efficient synthesis of stable silver nanoparticles by a marine Bacillus strain.

Janardhanan, A.; Roshmi, T.; Varghese, Rintu T.; Soniya, E. V.; Mathew, Jyothis; Radhakrishnan, E. K.

2013-04-01

214

Origanum vulgare mediated biosynthesis of silver nanoparticles for its antibacterial and anticancer activity.  

PubMed

In the present study, we achieved silver nanoparticles using the aqueous extract of Origanum vulgare (Oregano) by reducing 1mM silver nitrate (AgNO3) solution. The green synthesized silver nanoparticles were characterized by high throughput techniques like UV-vis spectroscopy, Fourier infrared spectroscopy (FT-IR), field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and dynamic light scattering measurements. Morphologically, the nanoparticles were found to be spherical with an average particle size distribution of 136±10.09nm. FT-IR spectral analysis illustrates the occurrence of possible biomolecules required for the reduction of silver ions. The obtained nanoparticles were stable (-26±0.77mV) at ambient temperature. The biosynthesized nanoparticles were found to be impressive in inhibiting human pathogens. The green synthesized silver nanoparticles showed dose dependent response against human lung cancer A549 cell line (LD50 - 100?g/ml). PMID:23537829

Sankar, Renu; Karthik, Arunachalam; Prabu, Annamalai; Karthik, Selvaraju; Shivashangari, Kanchi Subramanian; Ravikumar, Vilwanathan

2013-03-04

215

Green synthesis of silver nanoparticles for the control of mosquito vectors of malaria, filariasis, and dengue.  

PubMed

A biological method was used to synthesize stable silver nanoparticles that were tested as mosquito larvicides against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. Annona squamosa leaf broth (5%) reduced aqueous 1?mM AgNO? to stable silver nanoparticles with an average size of 450?nm. The structure and percentage of synthesized nanoparticles was characterized by using ultraviolet spectrophotometry, X-Ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy methods. The median lethal concentrations (LC??) of silver nanoparticles that killed fourth instars of Ae. aegypti, Cx. quinquefasciatus, and An. stephensi were 0.30, 0.41, and 2.12 ppm, respectively. Adult longevity (days) in male and female mosquitoes exposed as larvae to 0.1 ppm silver nanoparticles was reduced by ~30% (p<0.05), whereas the number of eggs laid by females exposed as larvae to 0.1 ppm silver nanoparticles decreased by 36% (p<0.05). PMID:22022807

Arjunan, Naresh Kumar; Murugan, Kadarkarai; Rejeeth, Chandrababu; Madhiyazhagan, Pari; Barnard, Donald R

2011-10-24

216

Titania–supported silver nanoparticles: An efficient and reusable catalyst for reduction of 4-nitrophenol  

NASA Astrophysics Data System (ADS)

Supported silver nanoparticles were synthesized via in situ sol–gel followed by reduction method with dextrose as reductant and sodium dodecyl sulfate as stabilizer. The synthesized nanoparticles were characterized by X–ray diffraction, transmission electron microscopy, Fourier transform Infra-Red spectroscopy and UV–visible measurements. The XRD peaks confirm the metallic face-centered cubic silver particles. The formation of silver nanoparticles was confirmed from the appearance of surface plasmon absorption maxima at 412 nm; which shifted to the longer wavelengths after supported on titania host lattice. TEM showed the spherical nanoparticles with size in the range of 18–23 nm. An efficient and simple method was reported for the reduction of 4-nitrophenol using titania-supported silver nanoparticles at room temperature. The reaction was first order with respect to the concentration of 4-nitrophenol with higher efficiency. Titania supported silver nanoparticles are reusable and stable heterogeneous catalyst.

Deshmukh, S. P.; Dhokale, R. K.; Yadav, H. M.; Achary, S. N.; Delekar, S. D.

2013-05-01

217

Enhanced antibacterial activity of bimetallic gold-silver core-shell nanoparticles at low silver concentration  

NASA Astrophysics Data System (ADS)

Herein we report the development of bimetallic Au@Ag core-shell nanoparticles (NPs) where gold nanoparticles (Au NPs) served as the seeds for continuous deposition of silver atoms on its surface. The core-shell structure and morphology were examined by UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD). The core-shell NPs showed antibacterial activity against both Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Enterococcus faecalis and Pediococcus acidilactici) bacteria at low concentration of silver present in the shell, with more efficacy against Gram negative bacteria. TEM and flow cytometric studies showed that the core-shell NPs attached to the bacterial surface and caused membrane damage leading to cell death. The enhanced antibacterial properties of Au@Ag core-shell NPs was possibly due to the more active silver atoms in the shell surrounding gold core due to high surface free energy of the surface Ag atoms owing to shell thinness in the bimetallic NP structure.Herein we report the development of bimetallic Au@Ag core-shell nanoparticles (NPs) where gold nanoparticles (Au NPs) served as the seeds for continuous deposition of silver atoms on its surface. The core-shell structure and morphology were examined by UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD). The core-shell NPs showed antibacterial activity against both Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Enterococcus faecalis and Pediococcus acidilactici) bacteria at low concentration of silver present in the shell, with more efficacy against Gram negative bacteria. TEM and flow cytometric studies showed that the core-shell NPs attached to the bacterial surface and caused membrane damage leading to cell death. The enhanced antibacterial properties of Au@Ag core-shell NPs was possibly due to the more active silver atoms in the shell surrounding gold core due to high surface free energy of the surface Ag atoms owing to shell thinness in the bimetallic NP structure. Electronic supplementary information (ESI) available. See DOI: 10.1039/c1nr10703h

Banerjee, Madhuchanda; Sharma, Shilpa; Chattopadhyay, Arun; Ghosh, Siddhartha Sankar

2011-12-01

218

Silver nanoparticles dispersed in polyaniline matrixes coated on titanium substrate as a novel electrode for electro-oxidation of hydrazine  

Microsoft Academic Search

Silver nanoparticles dispersed in polyaniline matrixes coated on titanium substrate, as a novel electrode, was easily synthesized\\u000a by electro-polymerization of aniline on titanium and then electrodeposited silver nanoparticles on PAni electrode. The electrochemical\\u000a behavior and electro-catalytic activity of silver nanoparticles\\/PAni\\/Ti electrodes were characterized by cyclic voltammetry.\\u000a The morphology of silver nanoparticles on PAni\\/Ti electrodes were characterized by scanning electron microscopy

Mirghasem HosseiniMohamad; Mohamad Mohsen Momeni

2010-01-01

219

Facile chemical synthesis of nano-silver powders for printable electronics applications  

Microsoft Academic Search

In this article, a simple and reproducible technique for the synthesis of silver nanoparticles in organic phase without using external reducing agents is reported. The organic phase contains silver acetate as precursor, oleic acid and oleyl amine as capping molecules and diphenyl ether as solvent. Monodispersed silver nanoparticles with an average size of 5?nm could be easily synthesised at large

P. K. Sahoo; S. S. Kalyan Kamal; B. Shankar; B. Sreedhar; L. Durai

2012-01-01

220

Synthesis of short chain thiol capped gold nanoparticles, their stabilization and immobilization on silicon surface  

Microsoft Academic Search

Tethering between nanoparticles and a supporting substrate, especially in the form of covalent bonding, is a highly useful way of ensuring development of robust systems for various applications. This requires bestowing specific functionalities on nanoparticle surfaces that can also prevent aggregation between nanoparticles. In this work, short chain thiol (4-aminothiophenol)-capped gold nanoparticles functionalized with amine-termination have been synthesized and changes

Raju Kumar Gupta; M. P. Srinivasan; R. Dharmarajan

2011-01-01

221

Homogeneous silver-coated nanoparticle substrates for enhanced fluorescence detection.  

PubMed

A simple method has been developed for the deposition of uniform silver-coated nanoparticles on glass substrates, with a homogeneous distribution shown by scanning electron microscopy (SEM). UV-visible spectroscopy and energy-dispersive X-ray analysis (EDX) have been used to characterize both the optical density and elemental content of the deposited nanoparticles. The fluorescence enhancement was investigated using a monolayer of FITC-conjugated human serum albumin (FITC-HSA) and tested using laser scanning microscopy at 488 nm excitation wavelength. The enhancement factor was calculated from individual spectra recorded with a Fluorolog-Tau-3 spectrofluorometer. We identified the nanoparticle growth regime which led to fluorescence enhancement. Such enhancement is detectable when Au core-Ag shell nanoparticles increased their size to 47 nm, in agreement with theoretical estimates. The origin of this enhancement for appropriate size nanoparticles is attributed to the effect of an increased excitation rate from the local field enhanced by the interaction of incident light with the nanoparticles and/or higher quantum yield from an increase of the intrinsic decay rate of the fluorophore. We thus demonstrated that the Au core-Ag shell nanostructures on glass surfaces are promising substrates for fluorescence enhancement with outstanding macroscopic homogeneity. This important feature will pave the way for the application of our substrates in biotechnology and life sciences such as imaging and sensing of biomolecules in proteomics. PMID:17107148

Xie, Fang; Baker, Mark S; Goldys, Ewa M

2006-11-23

222

Synthesis of silver nanoparticles using Aegle marmelos plant extract and evaluation of their antimicrobial activities and cytotoxicity  

Microsoft Academic Search

This paper describes a simple and efficient procedure based on the green method for the preparation of silver nanoparticles with a relatively narrow distribution in size. Stable silver nanoparticles have been synthesized by using Aegle marmelos (Vilvam) plant extract as both the reducing and stabilizing agents. The amount of silver nanoparticles synthesized and its qualitative characterization was done by UV-Visible

S. Lokina; V. Narayanan

2011-01-01

223

Specific biomolecule corona is associated with ring-shaped organization of silver nanoparticles in cells  

NASA Astrophysics Data System (ADS)

We correlate the localization of silver nanoparticles inside cells with respect to the cellular architecture with the molecular information in the vicinity of the particle surface by combining nanoscale 3D cryo-soft X-ray tomography (cryo-SXT) with surface-enhanced Raman scattering (SERS). The interaction of the silver nanoparticle surface with small molecules and biopolymers was monitored by SERS in vitro over time in living cells. The spectra indicate a stable, time-independent surface composition of silver nanoparticles, despite the changing environment in the endosomal structure. Cryo-SXT reveals a characteristic ring-shaped organization of the silver nanoparticles in endosomes of different cell types. The ring-like structures inside the endosomes suggest a strong association among silver particles and with membrane structures. The comparison of the data with those obtained with gold nanoparticles suggests that the interactions between the nanoparticles and with the endosomal component are influenced by the molecular composition of the corona.We correlate the localization of silver nanoparticles inside cells with respect to the cellular architecture with the molecular information in the vicinity of the particle surface by combining nanoscale 3D cryo-soft X-ray tomography (cryo-SXT) with surface-enhanced Raman scattering (SERS). The interaction of the silver nanoparticle surface with small molecules and biopolymers was monitored by SERS in vitro over time in living cells. The spectra indicate a stable, time-independent surface composition of silver nanoparticles, despite the changing environment in the endosomal structure. Cryo-SXT reveals a characteristic ring-shaped organization of the silver nanoparticles in endosomes of different cell types. The ring-like structures inside the endosomes suggest a strong association among silver particles and with membrane structures. The comparison of the data with those obtained with gold nanoparticles suggests that the interactions between the nanoparticles and with the endosomal component are influenced by the molecular composition of the corona. Electronic supplementary information (ESI) available: Description of additional experiments. Explanation of transmitted intensity and linear absorption coefficient in a cryo-XRT experiment (Fig. S1 and S2). Additional X-ray data (Fig. S3 and Movie S1). Toxicity of silver nanoparticles (Fig. S4). X-ray microscopy and SERS experiments with gold nanoparticles (Fig. S5 and S6). Size, plasmonic properties, and stability of silver and gold nanoparticles (Fig. S7-S9). Distribution of the silver nanoparticles in the cells using SERS mapping (Fig. S10). Tentative band assignments (Table S1). See DOI: 10.1039/c3nr02129g

Drescher, Daniela; Guttmann, Peter; Büchner, Tina; Werner, Stephan; Laube, Gregor; Hornemann, Andrea; Tarek, Basel; Schneider, Gerd; Kneipp, Janina

2013-09-01

224

Development of a hydrophilic polymer membrane containing silver nanoparticles with both organic antifouling and antibacterial properties  

Microsoft Academic Search

To obtain both organic antifouling and antibacterial properties, acrylamide was grafted onto a polyethersulfone (PES) hollow fiber membrane and silver nanoparticles were then formed within the acrylamide layer. The hydrophilicity of the membrane surface was improved by acrylamide grafting, leading to a reduction in membrane fouling by Bovine serum albumin. The silver nanoparticles were detected by X-ray photoelectron spectroscopy and

Isao Sawada; Razi Fachrul; Tatsuya Ito; Yoshikage Ohmukai; Tatsuo Maruyama; Hideto Matsuyama

225

Silver nanoparticles decrease body weight and locomotor activity in adult male rats.  

PubMed

Silver nanoparticles (Ag-NPs) are widely used in FDA regulated products. The physical-chemical properties of Ag-NPs are characterized using various instruments. The dose-dependent activity and body weight alterations are evaluated after rats were exposed to Ag nanoparticles, suggesting a major human health risk, given the wide application of silver nanomaterials. PMID:23335405

Zhang, Yongbin; Ferguson, Sherry A; Watanabe, Fumiya; Jones, Yvonne; Xu, Yang; Biris, Alexandru S; Hussain, Saber; Ali, Syed F

2013-01-20

226

Stability, size and optical properties of colloidal silver nanoparticles prepared by electrical arc discharge in water  

Microsoft Academic Search

We have fabricated and characterised colloidal silver nanoparticles by the electrical arc discharge method in DI water. Size and optical properties of the silver nanoparticles were studied versus different arc currents. Optical absorption indicates a plasmonic peak at 392 nm for 10 A which increases to 398 nm for 20 A arc current. This reveals that by raising the arc

A. A. Ashkarran; A. Iraji Zad; M. M. Ahadian; M. R. Hormozi Nezhad

2009-01-01

227

Polymeric microspheres containing silver nanoparticles as a bactericidal agent for water disinfection  

Microsoft Academic Search

A facile methodology has been developed by anchoring silver nanoparticles on to the macroporous methacrylic acid copolymer beads for disinfection of water in this study. Methacrylic acid copolymer beads are prepared by suspension polymerization technique. Silver nanoparticles formed on these copolymer beads by chemical reduction method are stable and are not washed away by water washing. Their stability is due

D. Gangadharan; Kumar Harshvardan; G. Gnanasekar; Dhara Dixit; Kiritkumar Mangaldas Popat; Pritpal Singh Anand

2010-01-01

228

Weakly bound capping agents on gold nanoparticles in catalysis: Surface poison?  

Microsoft Academic Search

The influence of the concentration and nature of weakly bound capping agents on the catalytic activity and selectivity of gold nanoparticles is explored in the selective liquid phase oxidation of benzyl alcohol with oxygen and complemented with a detailed XPS analysis. Two nitrogen-based capping agents, dodecylamine (DDA) and poly(vinyl-pyrrolidone) (PVP) and different gold catalysts (supported and unsupported gold nanoparticles, a

A. Quintanilla; V. C. L. Butselaar-Orthlieb; C. Kwakernaak; W. G. Sloof; M. T. Kreutzer; F. Kapteijn

2010-01-01

229

Selective photothermal efficiency of citrate capped gold nanoparticles for destruction of cancer cells  

Microsoft Academic Search

Gold nanoparticles are recently having much attention because of their increased applications in biomedical fields. In this paper, we demonstrated the photothermal efficacy of citrate capped gold nanoparticles (AuNPs) for the destruction of A431 cancer cells. Citrate capped AuNPs were synthesized successfully and characterized by UV–visible–NIR spectrophotometry and High Resolution Transmission Electron Microscopy (HR-TEM). Further, AuNPs were conjugated with epidermal

V. Raji; Jatish Kumar; C. S. Rejiya; M. Vibin; Vinesh N. Shenoi; Annie Abraham

2011-01-01

230

Inhibition Effects of Silver Nanoparticles against Powdery Mildews on Cucumber and Pumpkin  

PubMed Central

Powdery mildew is one of the most devastating diseases in cucurbits. Crop yield can decline as the disease severity increases. In this study, we evaluated the effect of silver nanoparticles against powdery mildew under different cultivation conditions in vitro and in vivo . Silver nanoparticles (WA-CV-WA13B) at various concentrations were applied before and after disease outbreak in plants to determine antifungal activities. In the field tests, the application of 100 ppm silver nanoparticles showed the highest inhibition rate for both before and after the outbreak of disease on cucumbers and pumpkins. Also, the application of 100 ppm silver nanoparticles showed maximum inhibition for the growth of fungal hyphae and conidial germination in in vivo tests. Scanning electron microscope results indicated that the silver nanoparticles caused detrimental effects on both mycelial growth and conidial germination.

Lamsal, Kabir; Kim, Sang-Woo; Jung, Jin Hee; Kim, Yun Seok; Kim, Kyoung Su

2011-01-01

231

Optimization for rapid synthesis of silver nanoparticles and its effect on phytopathogenic fungi  

NASA Astrophysics Data System (ADS)

In this present study, silver nanoparticles were synthesized by green chemistry approach using Acalypha indica leaf extract as reducing agents. The reaction medium employed in the synthesis process was optimized to attain better yield, controlled size and stability. Further, the biosynthesized silver nanoparticles were conformed through UV-vis spectrum, XRD and HR-TEM analyses. Different concentration of silver nanoparticles were tested to know the inhibitory effect of fungal plant pathogens namely Alternaria alternata, Sclerotinia sclerotiorum, Macrophomina phaseolina, Rhizoctonia solani, Botrytis cinerea and Curvularia lunata. Interestingly, 15 mg concentration of silver nanoparticles showed excellent inhibitory activity against all the tested pathogens. Thus, the obtained results clearly suggest that silver nanoparticles may have important applications in controlling various plant diseases caused by fungi.

Krishnaraj, C.; Ramachandran, R.; Mohan, K.; Kalaichelvan, P. T.

232

Green Synthesis of Silver Nanoparticles Using Neem Leaf (Azadirachta indica) Extract  

NASA Astrophysics Data System (ADS)

Silver nanoparticles were successfully synthesized using crude neem leaf (Azadirachta indica) extract at room temperature. The formation and crystallinity of synthesized silver nanoparticles was confirmed by X-Ray diffraction (XRD) pattern. The average size of these silver nanoparticles is about 20-50 nm as observed by Transmission electron microscopy (TEM) images. Optical absorption measurements were performed to determine band-edge energy gap of these silver nanoparticles. Photoluminescence (PL) studies were performed to emphasize its emission properties. The synthesized silver nanoparticles could have major applications in the area of nanoscale optoelectronics devices and biomedical engineering. Our synthesis method has advantage over other conventional chemical routes because it is cost effective & environmental compatibility.

Shukla, Vineet Kumar; Pandey, Shipra; Pandey, Avinash C.

2010-10-01

233

Behaviour of silver nanoparticles and silver ions in an in vitro human gastrointestinal digestion model.  

PubMed

Abstract Oral ingestion is an important exposure route for silver nanoparticles (AgNPs), but their fate during gastrointestinal digestion is unknown. This was studied for 60 nm AgNPs and silver ions (AgNO3) using in vitro human digestion model. Samples after saliva, gastric and intestinal digestion were analysed with SP-ICPMS, DLS and SEM-EDX. In presence of proteins, after gastric digestion the number of particles dropped significantly, to rise back to original values after the intestinal digestion. SEM-EDX revealed that reduction in number of particles was caused by their clustering. These clusters were composed of AgNPs and chlorine. During intestinal digestion, these clusters disintegrated back into single 60 nm AgNPs. The authors conclude that these AgNPs under physiological conditions can reach the intestinal wall in their initial size and composition. Importantly, intestinal digestion of AgNO3 in presence of proteins resulted in particle formation. These nanoparticles (of 20-30 nm) were composed of silver, sulphur and chlorine. PMID:22931191

Walczak, Agata P; Fokkink, Remco; Peters, Ruud; Tromp, Peter; Herrera Rivera, Zahira E; Rietjens, Ivonne M C M; Hendriksen, Peter J M; Bouwmeester, Hans

2012-10-01

234

Enhanced antibacterial activity of bimetallic gold-silver core-shell nanoparticles at low silver concentration.  

PubMed

Herein we report the development of bimetallic Au@Ag core-shell nanoparticles (NPs) where gold nanoparticles (Au NPs) served as the seeds for continuous deposition of silver atoms on its surface. The core-shell structure and morphology were examined by UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD). The core-shell NPs showed antibacterial activity against both gram negative (Escherichia coli and Pseudomonas aeruginosa) and gram positive (Enterococcus faecalis and Pediococcus acidilactici) bacteria at low concentration of silver present in the shell, with more efficacy against gram negative bacteria. TEM and flow cytometric studies showed that the core-shell NPs attached to the bacterial surface and caused membrane damage leading to cell death. The enhanced antibacterial properties of Au@Ag core-shell NPs was possibly due to the more active silver atoms in the shell surrounding gold core due to high surface free energy of the surface Ag atoms owing to shell thinness in the bimetallic NP structure. PMID:22057130

Banerjee, Madhuchanda; Sharma, Shilpa; Chattopadhyay, Arun; Ghosh, Siddhartha Sankar

2011-11-04

235

Evaluating cell specific cytotoxicity of differentially charged silver nanoparticles.  

PubMed

Silver nanoparticles (AgNPs) are one of the most commercially viable nanotechnological products, nevertheless; safety issues are raised regarding the use of such nanoparticles due to unintentional health and environmental impacts. In the present study, AgNPs were synthesized by chemically reducing silver nitrate alternatively with sodium borohydride, tannic acid, ascorbic acid and sodium citrate. AgNPs synthesized by reduction with tannic acid (TSNPs) and sodium borohydride (BSNPs) exhibited highest and lowest surface potential respectively. Therefore these two types of AgNPs were selected for their toxicity assessment in cellular environment. We treated skin epithelial A431, lung epithelial A549 and murine macrophages RAW264.7 cells with AgNPs over a range of doses (5-100?g/ml). Toxicity was evaluated by measuring changes in cellular morphology, ROS generation, metabolic activity and expression of various stress markers. Interestingly, TSNPs exhibited a higher negative zeta-potential and also higher toxicity. Higher toxicity of TSNPs was attested by dose-dependent increase in cellular disruption and ROS generation. BSNPs showed cytotoxic effect up to the concentration of 50?g/ml and thereafter the cytotoxic effect attenuated. TSNPs induced a dose dependent increase in the expression of stress markers pp38, TNF-? and HSP-70. Our report proposes that cytotoxicity of AgNPs changes with surface potential of nanoparticles and cells type. PMID:22975145

Kaur, Jasmine; Tikoo, Kulbhushan

2012-08-30

236

Influence of silver nanoparticles on food components in wheat  

NASA Astrophysics Data System (ADS)

During storage, grain might be affected by bacterial and fungal infections. Pathogens diminish the grain quality through contamination with excrements and second metabolites. It is very important to prevent grain from infections. Due to their antimicrobial properties, silver nanoparticles can play the role of an effective protector. The influence of nanoparticles on wheat quality was studied. The gluten parameters and falling number did not change after covering the grain with silver nanoparticles stabilized by sodium citrate. Changes in the structure of starch and gluten were investigated using Fourier-transform infrared spectroscopy. Infrared spectra of the whole meal and starch have shown a slight shift (from 1 000 to 995cm-1) of the band connected with the C-O-H bending. This displacement is probably related to the changes in sample moisture. Significant differences, corresponding to changes in the protein secondary structure, have appeared in the gluten spectra after covering.A decrease of absorbance in the amide and CH and OH regions has been observed regardless of the covering time.

Nawrocka, A.; Cieoela, J.

2013-01-01

237

Retention and transport of silver nanoparticles in a ceramic porous medium used for point-of-use water treatment.  

PubMed

The retention and transport of silver nanoparticles (Ag-NPs) through a ceramic porous medium used for point-of-use drinking water purification is investigated. Two general types of experiments were performed: (i) pulse injections of suspensions of Ag-NPs in aqueous MgSO4 solutions were applied to the ceramic medium, and effluent silver was quantified over time; (ii) Ag-NPs were applied directly to the porous medium during fabrication using a paint-on, dipping, or fire-in method, a synthetic, moderately hard water sample with monovalent and divalent inorganic ions was applied to the ceramic medium, and effluent silver was quantified over time. These latter experiments were performed to approximate real-world use of the filter medium. For experiments with Ag-NPs suspended in the inflow solution, the percentage of applied Ag-NPs retained in the ceramic porous medium ranged from about 13 to 100%. Ag-NP mobility decreased with increasing ionic strength for all cases and to a lesser extent with increasing nanoparticle diameter. Citrate-capped particles were slightly less mobile than proteinate-capped particles. For ceramic disks fabricated with Ag-NPs by the paint-on and dipping methods (where the Ag-NPs are applied to the disks after firing), significant release of nanoparticles into the filter disk effluent was observed relative to the fire-in method (where the nanoparticles are combined with the clay, water, grog, and flour before firing). These results suggest that the fire-in method may be a new and significant improvement to ceramic filter design. PMID:23496137

Ren, Dianjun; Smith, James A

2013-04-01

238

Size-dependent magnetic properties of naked and ligand-capped nickel nanoparticles  

Microsoft Academic Search

Ligand-free naked and oleylamine-capped nickel nanoparticles (Ni NPs) were size-selectively prepared in the size ranges of 5–17nm (naked) and 13–19nm (capped) in diameter through gas- and liquid-phase syntheses, respectively. As for the magnetic properties of both the naked and oleylamine-capped Ni NPs, the blocking temperatures, TB, increase with the size, where TB for the naked Ni NPs are significantly higher

Akinori Sugiyama; Yousuke Taguchi; Shuhei Nagaoka; Atsushi Nakajima

2010-01-01

239

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

PubMed

The antibacterial activity of silver nanoparticles and rhamnolipid are well known individually. In the present research, antibacterial and chemotactic activity due to colloidal silver nanoparticles (SNP), rhamnolipid (RL) and silver nanoparticles/rhamnolipid composite (SNPRL) were evaluated using Staphylococcus aureus (MTCC3160), Escherichia coli (MTCC40), Pseudomonas aeruginosa (MTCC8163) and Bacillus subtilis (MTCC441) as test strains. Further, the SNPRL nanoparticles were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The observation clearly indicates that SNPRL shows prominent antibacterial and chemotactic activity in comparison to all of its individual precursor components. PMID:23850558

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

2013-07-12

240

Study on gelatin-silver nanoparticle composite towards the development of bio-based antimicrobial film.  

PubMed

Nano-scale silver particle stabilized by gelatin protein was prepared through the reduction of aqueous silver nitrate solution by sodium borohydride. Gelatin concentration was varied against a fixed concentration of silver nitrate to optimize the gelatin to metal ratio. Gelatin-protected Ag-nanoparticle was characterized by UV-VIS spectroscopy and transmission electron microscopy (TEM). All the samples exhibited similar yellow color with a characteristic plasmonic band of silver nanoparticles at 412 nm. TEM micrographs also showed the presence of nanoscale silver particles of approximately 3.9 nm. Since silver has strong bactericidal properties and at the same time relatively less toxic to human cell, silver in various forms is ideally suited for a wide range of applications in consumer, industrial and medical products The antimicrobial properties of gelatin-silver nanocomposites were tested by 'cup-plate zone of inhibition' method. The nanocomposites exhibited significant antibacterial and antifungal activity. PMID:22408912

Halder, Dipankar; Mitra, Atanu; Bag, Surajit; Raychaudhuri, Utpal; Chakraborty, Runu

2011-12-01

241

Dispersion and rheology of surfactant-mediated silver nanoparticle suspensions  

NASA Astrophysics Data System (ADS)

Polycrystalline silver (Ag) nanoparticles were dispersed in solvent mixtures consisting of 2-butoxyethyl acetate (BCA) and diethylene glycol monoethyl ether acetate (CA) in a BCA:CA weight ratio of 5:1. Three commercially available polymeric surfactants were used, and the gravitational sedimentation, agglomerate-size distribution, isothermal adsorption, and rheological behavior of the nanoparticle suspensions were examined. One of the surfactants (hereafter termed 9250) was found effective in stabilizing the Ag nanoparticle suspensions. Both the adsorption isotherm and the Fourier transform infrared spectroscopy revealed the preferential adsorption of the 9250 surfactant molecules on the nanoparticle surface, forming a Langmuir-type monolayer adsorption in the given solvents so that a steric stabilization was rendered. An optimal surfactant concentration of 5 wt.% (in terms of the solids weight) was determined experimentally. In addition, the Ag suspensions with a broad range of solids concentration ( ? = 1-16 vol.%) showed a shear-thinning flow character over a shear-rate range from 1 to 4000 s -1, revealing that an attractive interparticle interaction was operative. Relative viscosity ( ?r) of the nanoparticle suspensions deviated from the linearity when ? was greater than ˜10 vol.%; at which, the attractive potential began to dominate the interparticle interactions. This ?r- ? dependence was compared with various existing models and the (viscosity) predictive capability of the models was discussed.

Chen, Chun-Nan; Huang, Chih-Ta; Tseng, Wenjea J.; Wei, Ming-Hsiung

2010-11-01

242

Synthesis and properties of crystalline silver nanoparticles supported in natural zeolite chabazite  

NASA Astrophysics Data System (ADS)

A simple, low-temperature, hydrothermal method for the synthesis of silver nanoparticles supported on the surfaces of the natural zeolite chabazite has been developed. The synthesis method includes two ion exchange processes: the first is a conditioning process to exchange the natural cations included in the chabazite tuff with NH4 ions, and the second exchanges the latter ions with silver. The precipitation of silver nanoparticles is achieved by thermal annealing of the silver-exchanged chabazite at 400 °C for 1 h. The samples were studied with X-ray diffraction, Fourier-transform infrared spectroscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and diffuse reflectance spectroscopy. The results show the presence of both silver cations and nanoparticles in the chabazite matrix, the silver nanoparticles being located at the surface of the chabazite microcrystals. The silver nanoparticles are crystalline with an average size of 8 nm and show cube-truncated shapes. The absorption spectra of the silver nanoparticles display several plasmon resonance transitions due to their geometry. The silver-supporting chabazite powders have bactericide properties against several types of bacteria as was shown by the inhibition of bacteria growth on conventional agar medium.

Flores-López, N. S.; Castro-Rosas, J.; Ramírez-Bon, R.; Mendoza-Córdova, A.; Larios-Rodríguez, E.; Flores-Acosta, M.

2012-11-01

243

The investigation of oxidized silver nanoparticles prepared by thermal evaporation and radio-frequency sputtering of metallic silver under oxygen  

NASA Astrophysics Data System (ADS)

The investigation of oxidized silver nanoparticles by the photoemission (XPS, UPS) and HRTEM methods was performed. The nanoparticles of oxidized silver were obtained in the vacuum chamber by two methods of synthesis: thermal evaporation of silver nanoparticles followed by transferring in convective gas flow and sputtering of oxidized clusters under the action of plasma. Both methods indicated that oxygen interaction with silver nanoparticles depends strongly on its size. It was shown that the chemical bonding of oxygen species stabilized on small particles differs from the oxygen species adsorbed on bulk silver surfaces (monocrystals, foils and large particles). The low charged oxygen with molecular type of bonding stabilizes on particles of size approximately 5 nm and smaller. Increasing particle size leads to the dissociation of molecular oxygen species and the formation of strongly charged oxygen composed of oxide nanoparticles like Ag 2O or AgO type. The presence of extended defects in the microdomain large nanoparticles facilitates the formation of Ag 2O or AgO layers covering metallic nanosilver.

Kibis, L. S.; Stadnichenko, A. I.; Pajetnov, E. M.; Koscheev, S. V.; Zaykovskii, V. I.; Boronin, A. I.

2010-11-01

244

Differently Environment Stable Bio-Silver Nanoparticles: Study on Their Optical Enhancing and Antibacterial Properties  

PubMed Central

Generally, limited research is extended in studying stability and applicational properties of silver nanoparticles (Ag NPs) synthesized by adopting ‘green chemistry’ protocol. In this work, we report on the synthesis of stable Ag NPs using plant-derived materials such as leaf extract of Neem (Azadirachta indica) and biopolymer pectin from apple peel. In addition, the applicational properties of Ag NPs such as surface-enhanced Raman scattering (SERS) and antibacterial efficiencies were also investigated. As-synthesized nanoparticles (NPs) were characterized using various instrumentation techniques. Both the plant materials (leaf extract and biopolymer) favored the synthesis of well-defined NPs capped with biomaterials. The NPs were spherical in shape with an average particle size between 14-27 nm. These bio-NPs exhibited colloidal stability in most of the suspended solutions such as water, electrolyte solutions (NaCl; NaNO3), biological solution (bovine serum albumin), and in different pH solutions (pH 7; 9) for a reasonable time period of 120 hrs. Both the bio-NPs were observed to be SERS active through displaying intrinsic SERS signals of the Raman probe molecule (Nile blue A). The NPs were effective against the Escherichia coli bacterium when tested in nutrient broth and agar medium. Scanning and high-resolution transmission electron microscopy (SEM and HRTEM) images confirmed cellular membrane damage of nanoparticle treated E. coli cells. These environmental friendly template Ag NPs can be used as an antimicrobial agent and also for SERS based analytical applications.

Balachandran, Yekkuni L.; Girija, Shanmugam; Selvakumar, Rajendran; Tongpim, Saowanit; Gutleb, Arno C.; Suriyanarayanan, Sarvajeyakesavalu

2013-01-01

245

Differently environment stable bio-silver nanoparticles: study on their optical enhancing and antibacterial properties.  

PubMed

Generally, limited research is extended in studying stability and applicational properties of silver nanoparticles (Ag NPs) synthesized by adopting 'green chemistry' protocol. In this work, we report on the synthesis of stable Ag NPs using plant-derived materials such as leaf extract of Neem (Azadirachta indica) and biopolymer pectin from apple peel. In addition, the applicational properties of Ag NPs such as surface-enhanced Raman scattering (SERS) and antibacterial efficiencies were also investigated. As-synthesized nanoparticles (NPs) were characterized using various instrumentation techniques. Both the plant materials (leaf extract and biopolymer) favored the synthesis of well-defined NPs capped with biomaterials. The NPs were spherical in shape with an average particle size between 14-27 nm. These bio-NPs exhibited colloidal stability in most of the suspended solutions such as water, electrolyte solutions (NaCl; NaNO3), biological solution (bovine serum albumin), and in different pH solutions (pH 7; 9) for a reasonable time period of 120 hrs. Both the bio-NPs were observed to be SERS active through displaying intrinsic SERS signals of the Raman probe molecule (Nile blue A). The NPs were effective against the Escherichia coli bacterium when tested in nutrient broth and agar medium. Scanning and high-resolution transmission electron microscopy (SEM and HRTEM) images confirmed cellular membrane damage of nanoparticle treated E. coli cells. These environmental friendly template Ag NPs can be used as an antimicrobial agent and also for SERS based analytical applications. PMID:24130832

Balachandran, Yekkuni L; Girija, Shanmugam; Selvakumar, Rajendran; Tongpim, Saowanit; Gutleb, Arno C; Suriyanarayanan, Sarvajeyakesavalu

2013-10-09

246

Biosynthesis of silver and gold nanoparticles by novel sundried Cinnamomum camphora leaf  

NASA Astrophysics Data System (ADS)

The synthesis of nanocrystals is in the limelight in modern nanotechnology. Biosynthesis of nanoparticles by plant extracts is currently under exploitation. Not only could silver nanoparticles ranging from 55 to 80 nm in size be fabricated, but also triangular or spherical shaped gold nanoparticles could be easily modulated by reacting the novel sundried biomass of Cinnamomum camphora leaf with aqueous silver or gold precursors at ambient temperature. The marked difference of shape control between gold and silver nanoparticles was attributed to the comparative advantage of protective biomolecules and reductive biomolecules. The polyol components and the water-soluble heterocyclic components were mainly responsible for the reduction of silver ions or chloroaurate ions and the stabilization of the nanoparticles, respectively. The sundried leaf in this work was very suitable for simple synthesis of nanoparticles.

Huang, Jiale; Li, Qingbiao; Sun, Daohua; Lu, Yinghua; Su, Yuanbo; Yang, Xin; Wang, Huixuan; Wang, Yuanpeng; Shao, Wenyao; He, Ning; Hong, Jinqing; Chen, Cuixue

2007-03-01

247

Control of surface plasmon localization via self-assembly of silver nanoparticles along silver nanowires.  

PubMed

A simple and low-cost method to create metal-metal hybrid nanostructures possessing fairly regularly spaced "hot-spots" of surface plasmon resonances is proposed. The nanohybrid structure was prepared via self-assembly during a simple drop-casting procedure, using chemically synthesized silver nanowires and silver nanoparticles prepared in a single batch of a polyol process. Wide field illumination of these nanohybrids produced hot-spots with spacings of around 500 nm to 1 microm. The intensity of the emission/scattering from the hot-spots fluctuates over time. The proposed structure can be useful for the development of molecular-sensors or as a substrate for surface enhanced Raman/fluorescence spectroscopy. PMID:19049275

Tran, M Linh; Centeno, Silvia P; Hutchison, James A; Engelkamp, Hans; Liang, Duoduo; Van Tendeloo, Gustaaf; Sels, Bert F; Hofkens, Johan; Uji-i, Hiroshi

2008-12-24

248

In-situ investigation of the formation of silver nanoparticles in polyvinyl alcohol through micro-Raman spectroscopy  

NASA Astrophysics Data System (ADS)

A novel investigation of in-situ formation of silver nanoparticles in thin films was carried out through light scattering phenomena. The Raman scattering signal of polyvinyl alcohol which acts as a stabilizing agent for the silver nanoparticles, was found to get enhanced with the formation of the silver nanoparticles. In-situ studies were carried out to record the Raman scattering to monitor the growth of the silver nanoparticles. The formation of the silver nanoparticles was confirmed by monitoring the surface plasmon absorption peak and the micrographs of field emission scanning electron microscope.

Shadak Alee, K.; Kuladeep, R.; Narayana Rao, D.

2013-04-01

249

Magnetic properties of thiol-capped gold nanoparticles  

NASA Astrophysics Data System (ADS)

We present the experimental results of magnetization measurements on thiol-capped gold nanoparticles (Au-SR NPs) synthesized in a two-phase liquid-liquid system. The size of particles ranged from 2.0 to 3.5 nm with an average size of 2.8 nm. The magnetic properties of Au-SR NPs were characterized by a mixture of ferromagnetic, paramagnetic and diamagnetic components. Magnetization curves showed the hysteresis behavior typical of a ferromagnet over the whole temperature ( T) range investigated (2 K to 300 K) whereas M( H) did not saturate, not even at low T, implying the existence of a paramagnetic component. The negative slope of M( H) observed at high T demonstrated that a diamagnetic component was also considerable. From a theoretical fit, we obtained effective values of parameters such as the paramagnetic effective moment, ? p = 5.7 ? B, and the diamagnetic susceptibility, ? d = -1.7 ×10-7 emu/gOe. In addition, the T-dependence of the ferromagnetic component M f ( T) was extracted from the experimental M( T), and its characteristics are discussed in the light of the mean field model.

Yoon, Sungwon; Han, K. H.; Suh, B. J.; Jang, Z. H.; Kim, J. H.; Jung, D.-Y.

2012-04-01

250

Silver nanoparticle toxicity in sea urchin Paracentrotus lividus.  

PubMed

Silver nanoparticles (AgNPS) are an important model system for studying potential environmental risks posed by the use of nanomaterials. So far there is no consensus as to whether toxicity is due to AgNPs themselves or Ag(+) ions leaching from their surfaces. In sea urchin Paracentrotus lividus, AgNPs cause dose dependent developmental defects such as delayed development, bodily asymmetry and shortened or irregular arms, as well as behavioural changes, particularly in swimming patterns, at concentration ?0.3 mg/L AgNPs. It has been observed that AgNPs are more toxic than their equivalent Ag(+) ion dose. PMID:23561841

Siller, Lidija; Lemloh, Marie-Louise; Piticharoenphun, Sunthon; Mendis, Budhika G; Horrocks, Benjamin R; Brümmer, Franz; Medakovi?, Davorin

2013-04-02

251

One-Step Deposition of Nano-Sized Gold onto the Carbon Surface of Encapsulated Silver Nanoparticles  

Microsoft Academic Search

In the present work, we demonstrate the modification of silver nanoparticles encapsulated in the shells of amorphous carbon by nanoparticles of noble metals using galvanic replacement reactions. We show that the treatment of these types of carbon encapsulated silver nanoparticles with HAuCl4 solution is accompanied by the deposition of the gold nanoparticles on the outer surface of the carbon capsules.

Boris B. Bokhonov; Sergei A. Novopashin

2012-01-01

252

Deposition of platinum on the outer surface of carbon-encapsulated silver nanoparticles  

Microsoft Academic Search

Investigations of the morphological and phase characteristics of silver nanoparticles encapsulated in amorphous carbon shell (Ag@C) during heating, acid treatment and galvanic replacement reactions were carried out. It was found that upon heating of Ag@C nanoparticles up to 800°C the silver sublimes resulting in the formation of hollow carbon nanocapsules. Washing of Ag@C nanoparticles with nitric or hydrochloric acid solutions

Boris B. Bokhonov

2011-01-01

253

In situ synthesis of silver chloride nanoparticles into bacterial cellulose membranes  

Microsoft Academic Search

In situ synthesis of silver chloride (AgCl) nanoparticles was carried out under ambient conditions in nanoporous bacterial cellulose (BC) membranes as nanoreactors. The growth of the nanoparticles was readily obtained by alternating dipping of BC membranes in the solution of silver nitrate or sodium chloride followed by a rinse step. X-ray diffraction (XRD) patterns indicated the existence of AgCl nanoparticles

Weili Hu; Shiyan Chen; Xin Li; Shuaike Shi; Wei Shen; Xiang Zhang; Huaping Wang

2009-01-01

254

The anodic stripping voltammetry of nanoparticles: electrochemical evidence for the surface agglomeration of silver nanoparticles.  

PubMed

Analytical expressions for the anodic stripping voltammetry of metallic nanoparticles from an electrode are provided. First, for reversible electron transfer, two limits are studied: that of diffusionally independent nanoparticles and the regime where the diffusion layers originating from each particle overlap strongly. Second, an analytical expression for the voltammetric response under conditions of irreversible electron transfer kinetics is also derived. These equations demonstrate how the peak potential for the stripping process is expected to occur at values negative of the formal potential for the redox process in which the surface immobilised nanoparticles are oxidised to the corresponding metal cation in the solution phase. This work is further developed by considering the surface energies of the nanoparticles and its effect on the formal potential for the oxidation. The change in the formal potential is modelled in accordance with the equations provided by Plieth [J. Phys. Chem., 1982, 86, 3166-3170]. The new analytical expressions are used to investigate the stripping of silver nanoparticles from a glassy carbon electrode. The relative invariance of the stripping peak potential at low surface coverages of silver is shown to be directly related to the surface agglomeration of the nanoparticles. PMID:23624744

Toh, Her Shuang; Batchelor-McAuley, Christopher; Tschulik, Kristina; Uhlemann, Margitta; Crossley, Alison; Compton, Richard G

2013-04-25

255

Thermal analysis of silver nanoparticles for flexible printed antenna fabrication  

NASA Astrophysics Data System (ADS)

In this study, the temperature assisted decomposition/desorption behavior of short-chain single and mixed carboxylic acid encapsulants from the core of silver nanoparticles was investigated using thermogravimetric analysis and differential scanning calorimetry, and these particles were used to fabricate a flexible printed antenna. The decomposition temperatures of the single encapsulant particles increased with increasing chain length of encapsulants, whereas the decomposition temperatures for mixed encapsulant particles are close to the average of the corresponding decomposition temperatures of single encapsulant nanoparticles. These experimentally identified decomposition temperatures were utilized for sintering the printed antenna on a flexible substrate. The printed antenna showed a significantly low return loss of 22 dB. The antenna performance and radiation pattern are similar to a reference prototype antenna made of copper.

Ankireddy, Krishnamraju; Iskander, Mina; Vunnam, Swathi; Anagnostou, Dimitris E.; Kellar, Jon; Cross, William

2013-09-01

256

Memecylon edule leaf extract mediated green synthesis of silver and gold nanoparticles.  

PubMed

We used an aqueous leaf extract of Memecylon edule (Melastomataceae) to synthesize silver and gold nanoparticles. To our knowledge, this is the first report where M. edule leaf broth was found to be a suitable plant source for the green synthesis of silver and gold nanoparticles. On treatment of aqueous solutions of silver nitrate and chloroauric acid with M. edule leaf extract, stable silver and gold nanoparticles were rapidly formed. The gold nanoparticles were characterized by UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDAX) and Fourier transform infra-red spectroscopy (FTIR). The kinetics of reduction of aqueous silver and gold ions during reaction with the M. edule leaf broth were easily analyzed by UV-visible spectroscopy. SEM analysis showed that aqueous gold ions, when exposed to M. edule leaf broth, were reduced and resulted in the biosynthesis of gold nanoparticles in the size range 20-50 nm. TEM analysis of gold nanoparticles showed formation of triangular, circular, and hexagonal shapes in the size range 10-45 nm. The resulting silver nanoparticles were predominantly square with uniform size range 50-90 nm. EDAX results confirmed the presence of triangular nanoparticles in the adsorption peak of 2.30 keV. Further FTIR analysis was also done to identify the functional groups in silver and gold nanoparticles. The characterized nanoparticles of M. edule have potential for various medical and industrial applications. Saponin presence in aqueous extract of M. edule is responsible for the mass production of silver and gold nanoparticles. PMID:21753878

Elavazhagan, Tamizhamudu; Arunachalam, Kantha D

2011-06-21

257

Accumulation of silver nanoparticles by cultured primary brain astrocytes  

NASA Astrophysics Data System (ADS)

Silver nanoparticles (AgNP) are components of various food industry products and are frequently used for medical equipment and materials. Although such particles enter the vertebrate brain, little is known on their biocompatibility for brain cells. To study the consequences of an AgNP exposure of brain cells we have treated astrocyte-rich primary cultures with polyvinylpyrrolidone (PVP)-coated AgNP. The incubation of cultured astrocytes with micromolar concentrations of AgNP for up to 24 h resulted in a time- and concentration-dependent accumulation of silver, but did not compromise the cell viability nor lower the cellular glutathione content. In contrast, the incubation of astrocytes for 4 h with identical amounts of silver as AgNO3 already severely compromised the cell viability and completely deprived the cells of glutathione. The accumulation of AgNP by astrocytes was proportional to the concentration of AgNP applied and significantly lowered by about 30% in the presence of the endocytosis inhibitors chloroquine or amiloride. Incubation at 4 °C reduced the accumulation of AgNP by 80% compared to the values obtained for cells that had been exposed to AgNP at 37 °C. These data demonstrate that viable cultured brain astrocytes efficiently accumulate PVP-coated AgNP in a temperature-dependent process that most likely involves endocytotic pathways.

Luther, Eva M.; Koehler, Yvonne; Diendorf, Joerg; Epple, Matthias; Dringen, Ralf

2011-09-01

258

Bacterial flagella as biotemplate for the synthesis of silver nanoparticle impregnated bionanomaterial  

NASA Astrophysics Data System (ADS)

The present study was carried out to synthesize one dimensional silver nanoparticle impregnated flagellar bionanomaterial. Flagella was isolated from Salmonella typhimurium and depolymerised into flagellin monomers. The flagellin monomers were repolymerised again into flagella using suitable technique. The molecular weight of native (NF) and polymerized flagella (PF) was determined using polyacrylamide gel electrophoresis. The NF and PF were used as a template, over which silver nanoparticles were impregnated using in situ chemical reduction process. The synthesized flagellar-silver nanoparticle bionanomaterials were characterized using UV-vis, FT-IR Raman and XRD spectroscopy, and High resolution transmission electron microscopy (HR-TEM). The characterization studies confirmed the attachment of silver nanoparticles over flagella and repolymerised flagella. The size of the silver nanoparticles on the flagella and repolymerised flagella varied and was in the range of 3-11 nm. I-V characteristics of the bionanomaterials were analyzed using Kethley meter which indicated the increase of conductivity after impregnation of silver nanoparticles. The results indicated that flagellar-silver nanoparticle bionanomaterials can be used as a potential one dimensional bionanomaterials for various applications.

Gopinathan, Priya; Ashok, Anuradha M.; Selvakumar, R.

2013-07-01

259

Biosynthesis of silver nanoparticles using lemon leaves extract and its application for antimicrobial finish on fabric  

NASA Astrophysics Data System (ADS)

Preparation of silver nanoparticles have been carried out using aqueous extract of lemon leaves ( Citrus limon) which acts as reducing agent and encapsulating cage for the silver nanoparticles. These silver nanoparticles have been used for durable textile finish on cotton and silk fabrics. Remarkable antifungal activity has been observed in the treated fabrics. The antimicrobial activity of silver nanoparticles derived from lemon leaves showed enhancement in activity due to synergistic effect of silver and essential oil components of lemon leaves. The present investigation shows the extracellular synthesis of highly stable silver nanoparticles by biotransformation using the extract of lemon leaves by controlled reduction of the Ag+ ion to Ag0. Further the silver nanoparticles were used for antifungal treatment of fabrics which was tested by antifungal activity assessment of textile material by Agar diffusion method against Fusarium oxysporum and Alternaria brassicicola. Formation of the metallic nanoparticles was established by FT-IR, UV-Visible spectroscopy, transmission electron microscopy, scanning electron microscopy, atomic force microscopy.

Vankar, Padma S.; Shukla, Dhara

2012-06-01

260

Silver nanoparticles: behaviour and effects in the aquatic environment.  

PubMed

This review summarises and evaluates the present knowledge on the behaviour, the biological effects and the routes of uptake of silver nanoparticles (Ag NPs) to organisms, with considerations on the nanoparticle physicochemistry in the ecotoxicity testing systems used. Different types of Ag NP syntheses, characterisation techniques and predicted current and future concentrations in the environment are also outlined. Rapid progress in this area has been made over the last few years, but there is still a critical lack of understanding of the need for characterisation and synthesis in environmental and ecotoxicological studies. Concentration and form of nanomaterials in the environment are difficult to quantify and methodological progress is needed, although sophisticated exposure models show that predicted environmental concentrations (PECs) for Ag NPs in different environmental compartments are at the range of ng L(-1) to mg kg(-1). The ecotoxicological literature shows that concentrations of Ag NPs below the current and future PECs, as low as just a few ng L(-1), can affect prokaryotes, invertebrates and fish indicating a significant potential, though poorly characterised, risk to the environment. Mechanisms of toxicity are still poorly understood although it seems clear that in some cases nanoscale specific properties may cause biouptake and toxicity over and above that caused by the dissolved Ag ion. This review concludes with a set of recommendations for the advancement of understanding of the role of nanoscale silver in environmental and ecotoxicological research. PMID:21159383

Fabrega, Julia; Luoma, Samuel N; Tyler, Charles R; Galloway, Tamara S; Lead, Jamie R

2010-12-14

261

Low-temperature metallic alloying of copper and silver nanoparticles with gold nanoparticles through digestive ripening.  

PubMed

We describe a remarkable and simple alloying procedure in which noble metal intermetallic nanoparticles are produced in gram quantities via digestive ripening. This process involves mixing of separately prepared colloids of pure Au and pure Ag or Cu particles and then heating in the presence of an alkanethiol under reflux. The result after 1 h is alloy nanoparticles. Particles synthesized according to this procedure were characterized by UV-vis spectroscopy, EDX analysis, and high-resolution electron microscopy, the results of which confirm the formation of alloy particles. The particles of 5.6+/-0.5 nm diameter for Au/Ag and 4.8+/-1.0 nm diameter for Cu/Au undergo facile self-assembly to form 3-D superlattice ordering. It appears that during this digestive ripening process, the organic ligands display an extraordinary chemistry in which atom transfer between atomically pure copper, silver, and gold metal nanoparticles yields monodisperse alloy nanoparticles. PMID:16471798

Smetana, Alexander B; Klabunde, Kenneth J; Sorensen, Christopher M; Ponce, Audaldo A; Mwale, Benny

2006-02-01

262

Development of silver nanoparticle loaded antibacterial polymer mesh using plasma polymerization process.  

PubMed

Plasma polymerized polyacrylic acid (PPAA) was deposited on a polymer substrate, namely polyethylene terephthalate (PET) mesh, for entrapment of silver nanoparticle (Ag-NP) in order to achieve antibacterial property to the material. Carboxylic groups of PPAA act as anchor as well as capping and stabilizing agents for Ag-NPs synthesized by chemical reduction method using NaBH(4) as a reducing agent. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and water contact angle analysis were used to characterize the PPAA coatings. The Ag-NPs loaded polymer samples were characterized by UV-visible spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray, and XPS techniques. XPS analysis showed ~1.0 at.% loading of Ag-NPs on to the PPAA-PET-mesh, which was composed of 79% zero-valent (Ag°) and 21% oxidized nano-Ag (Ag(+) ). The plasma processed PET meshes samples were tested for antibacterial activity against two bacterial strains, namely Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative). Qualitative and quantitative tests showed that silver containing PPAA-PET meshes exhibit excellent antibacterial property against the tested bacteria with percent reduction of bacterial concentration >99%, compared to the untreated PET mesh. PMID:23015534

Kumar, Virendra; Jolivalt, Claude; Pulpytel, Jerome; Jafari, Reza; Arefi-Khonsari, Farzaneh

2012-09-27

263

Green synthesis of gold and silver nanoparticles using Hibiscus rosa sinensis  

Microsoft Academic Search

Biological synthesis of gold and silver nanoparticles of various shapes using the leaf extract of Hibiscus rosa sinensis is reported. This is a simple, cost-effective, stable for long time and reproducible aqueous room temperature synthesis method to obtain a self-assembly of Au and Ag nanoparticles. The size and shape of Au nanoparticles are modulated by varying the ratio of metal

Daizy Philip

2010-01-01

264

Silica coating magnetic nanoparticle-based silver enhancement immunoassay for rapid electrical detection of ricin toxin  

Microsoft Academic Search

We developed a novel silica coating magnetic nanoparticle-based silver enhancement immunoassay (SEIA) for ricin toxin (RT) rapid electrical detection using interdigitated array microelectrodes (IDAMs) as electrodes. This novel system was developed by taking advantage of the separation and enrichment properties of magnetic nanoparticles (MNPs) and the catalytic properties of gold nanoparticles (GNPs). In this system, MNPs labeled with anti-ricin A

Jie Zhuang; Tao Cheng; Lizeng Gao; Yongting Luo; Quan Ren; Di Lu; Fangqiong Tang; Xiangling Ren; Dongling Yang; Jing Feng; Jingdong Zhu; Xiyun Yan

2010-01-01

265

Stability, size and optical properties of colloidal silver nanoparticles prepared by electrical arc discharge in water  

NASA Astrophysics Data System (ADS)

We have fabricated and characterised colloidal silver nanoparticles by the electrical arc discharge method in DI water. Size and optical properties of the silver nanoparticles were studied versus different arc currents. Optical absorption indicates a plasmonic peak at 392 nm for 10 A which increases to 398 nm for 20 A arc current. This reveals that by raising the arc current the size of the nanoparticles increases. Optical absorption of silver nanoparticles after 3 weeks shows precipitation of them in a water medium. The effect of different surfactant and stabilizer concentrations such as cethyl trimethylammonium bromide (CTAB), polyvinyl pyrrolidone (PVP), sodium citrate, sodium dodecyl sulfate (SDS), sodium di-2-ethylsulfosuccinate (AOT) and carboxymethyl cellulose (CMC) on the stability of silver nanoparticles was investigated. The colloidal silver nanoparticles with 100 ?M concentration were stable for more than 3 months at 50 ?M CTAB and 6 months at 10 ?M sodium citrate concentration, respectively. SEM images of the sample prepared at 50 ?M CTAB concentration reveal uniform and fine nanoparticles. The mean size from TEM images is about 14 nm. TEM images of the sample prepared at 10 ?M sodium citrate concentration show a shell of citrate that covers the silver nanoparticles.

Ashkarran, A. A.; Iraji Zad, A.; Ahadian, M. M.; Hormozi Nezhad, M. R.

2009-10-01

266

Silver nanoparticles embedded in zeolite membranes: release of silver ions and mechanism of antibacterial action  

PubMed Central

Background The focus of this study is on the antibacterial properties of silver nanoparticles embedded within a zeolite membrane (AgNP-ZM). Methods and Results These membranes were effective in killing Escherichia coli and were bacteriostatic against methicillin-resistant Staphylococcus aureus. E. coli suspended in Luria Bertani (LB) broth and isolated from physical contact with the membrane were also killed. Elemental analysis indicated slow release of Ag+ from the AgNP-ZM into the LB broth. The E. coli killing efficiency of AgNP-ZM was found to decrease with repeated use, and this was correlated with decreased release of silver ions with each use of the support. Gene expression microarrays revealed upregulation of several antioxidant genes as well as genes coding for metal transport, metal reduction, and ATPase pumps in response to silver ions released from AgNP-ZM. Gene expression of iron transporters was reduced, and increased expression of ferrochelatase was observed. In addition, upregulation of multiple antibiotic resistance genes was demonstrated. The expression levels of multicopper oxidase, glutaredoxin, and thioredoxin decreased with each support use, reflecting the lower amounts of Ag+ released from the membrane. The antibacterial mechanism of AgNP-ZM is proposed to be related to the exhaustion of antioxidant capacity. Conclusion These results indicate that AgNP-ZM provide a novel matrix for gradual release of Ag+.

Nagy, Amber; Harrison, Alistair; Sabbani, Supriya; Munson, Robert S; Dutta, Prabir K; Waldman, W James

2011-01-01

267

Effects of silver nanoparticles and silver nitrate in the earthworm reproduction test.  

PubMed

The widespread use of silver nanoparticles (Ag-NPs), for example, in textiles and cleaning products, means that they are likely to reach the environment via biosolids or the effluent from wastewater treatment plants. The aim of the present study was to determine the ecotoxicity of Ag-NPs in the earthworm reproduction test using Eisenia andrei. In addition to the usual endpoints, the authors also investigated the uptake and accumulation of Ag by adult earthworms and the concentration of free Ag(+) in soil pore water. Silver nanoparticles and Ag nitrate showed similar toxicities in the earthworm reproduction test. The uptake of Ag from Ag-NPs in the earthworm was slightly higher than the uptake of Ag from Ag nitrate. Spiked soils showed a concentration-dependent effect on reproduction, but there was no concentration-dependent increase in the amount of Ag in earthworm tissues. The authors noted a concentration-dependent increase in the levels of free Ag(+) in the soil pore water regardless of the Ag source. The number of juveniles is a more suitable endpoint than biomass or mortality. The uptake of Ag does not appear to inhibit reproduction. Instead, inhibition seems to reflect Ag(+) released into the soil pore water, which affects cocoons and juveniles in the soil. Analysis of transformed Ag-NPs after purification in wastewater treatment plants would provide additional information. PMID:23059754

Schlich, Karsten; Klawonn, Thorsten; Terytze, Konstantin; Hund-Rinke, Kerstin

2012-11-21

268

Confined laser ablation for single-shot nanoparticle deposition of silver  

NASA Astrophysics Data System (ADS)

Spatially confined laser ablation of silver was used to form long-lived dense plasma for single-shot deposition of a nanoparticle film. The expansion of the ablation plume was restricted by placing a glass substrate at 50 ?m from the silver target surface. Time-resolved optical emission spectroscopy showed that the confined plasma is sustained for longer time than for free ablation. A single laser shot is sufficient to produce a layer of silver nanoparticles on the substrate. In absorption the nanoparticle layer displays a surface plasmon resonance which is comparable to films made by conventional pulsed laser deposition in vacuum.

Donnelly, T.; Lunney, J. G.

2013-10-01

269

Development and Antibacterial Activity of Cashew Gum-Based Silver Nanoparticles  

PubMed Central

The present study describes the development of a green synthesis of silver nanoparticles reduced and stabilized by exuded gum from Anacardium occidentale L. and evaluates in vitro their antibacterial and cytotoxic activities. Characterization of cashew gum-based silver nanoparticles (AgNPs) was carried out based on UV–Vis spectroscopy, transmission electron microscopy and dynamic light scattering analysis which revealed that the synthesized silver nanoparticles were spherical in shape, measuring about 4 nm in size with a uniform dispersal. AgNPs presented antibacterial activity, especially against Gram-negative bacteria, in concentrations where no significant cytotoxicity was observed.

Quelemes, Patrick V.; Araruna, Felipe B.; de Faria, Bruna E. F.; Kuckelhaus, Selma A. S.; da Silva, Durcilene A.; Mendonca, Ronaldo Z.; Eiras, Carla; dos S. Soares, Maria Jose; Leite, Jose Roberto S. A.

2013-01-01

270

Silver nanoparticles deposited on porous silicon as a surface-enhanced Raman scattering (SERS) active substrate.  

PubMed

Silver nanoparticles were deposited spontaneously from their aqueous solution on a porous silicon (PS) layer. The PS acts both as a reducing agent and as the substrate on which the nanoparticles nucleate. At higher silver ion concentrations, layers of nanoparticle aggregates were formed on the PS surface. The morphology of the metallic layers and their SERS activity were influenced by the concentrations of the silver ion solutions used for deposition. Raman measurements of rhodamine 6G (R6G) and crystal violet (CV) adsorbed on these surfaces showed remarkable enhancement of up to about 10 orders of magnitude. PMID:22449306

Zeiri, Leila; Rechav, Katya; Porat, Ze'ev; Zeiri, Yehuda

2012-03-01

271

Development and antibacterial activity of cashew gum-based silver nanoparticles.  

PubMed

The present study describes the development of a green synthesis of silver nanoparticles reduced and stabilized by exuded gum from Anacardium occidentale L. and evaluates in vitro their antibacterial and cytotoxic activities. Characterization of cashew gum-based silver nanoparticles (AgNPs) was carried out based on UV-Vis spectroscopy, transmission electron microscopy and dynamic light scattering analysis which revealed that the synthesized silver nanoparticles were spherical in shape, measuring about 4 nm in size with a uniform dispersal. AgNPs presented antibacterial activity, especially against Gram-negative bacteria, in concentrations where no significant cytotoxicity was observed. PMID:23455467

Quelemes, Patrick V; Araruna, Felipe B; de Faria, Bruna E F; Kuckelhaus, Selma A S; da Silva, Durcilene A; Mendonça, Ronaldo Z; Eiras, Carla; Dos S Soares, Maria José; Leite, José Roberto S A

2013-03-01

272

Oxygen-induced enhancement of surface plasmon resonance of silver nanoparticles for silver-coated soda-lime glass  

Microsoft Academic Search

The optical properties of a silver film on soda-lime glass substrate were studied after treatment in different atmospheres at different temperatures. It has been shown that pre-treatment in air (at about 500 °C for 1 h) can induce the enhancement of the surface plasmon resonance (SPR) of silver nanoparticles after subsequent treatment in H2. This enhancement effect decreases with decrease

Jinlian Hu; Weiping Cai; Yue Li; Haibo Zeng

2005-01-01

273

Procedures for the synthesis and capping of metal nanoparticles.  

PubMed

The increasing impact of metallic nanoparticles in life sciences has stimulated the development of new techniques and multiple improvements of the existing methods of manufacturing nanoparticles with tailored properties. Nanoparticles can be synthesized through a variety of physical and chemical methods. The choice of preparation procedure will depend on the physical and chemical characteristics required on the final product, such as size, dispersion, chemical miscibility, optical properties, among others. Here we review basic practical procedures used for the preparation of protected and unprotected metallic nanoparticles and describe a number of experimental procedures based on colloidal chemistry methods. These include gold nanoparticle synthesis by reduction with trisodium citrate, ascorbic acid, or sugars in aqueous phase; nanoparticle passivation with alkanethiols, cetyltrimethylammonium bromide, or bovin serum albumin. We also describe microwave-assisted synthesis, nanoparticle synthesis in ethylene glycol, template-assisted synthesis with dendrimers and briefly describe how to control nanoparticle shape (star-shaped and branched nanoparticles). PMID:22791420

Gutiérrez-Wing, Claudia; Velázquez-Salazar, J Jesús; José-Yacamán, Miguel

2012-01-01

274

Antibacterial nano-structured titania coating incorporated with silver nanoparticles.  

PubMed

Titanium (Ti) implants are widely used clinically but post-operation infection remains one of the most common and serious complications. A surface boasting long-term antibacterial ability is highly desirable in order to prevent implant associated infection. In this study, titania nanotubes (TiO(2)-NTs) incorporated with silver (Ag) nanoparticles are fabricated on Ti implants to achieve this purpose. The Ag nanoparticles adhere tightly to the wall of the TiO(2)-NTs prepared by immersion in a silver nitrate solution followed by ultraviolet light radiation. The amount of Ag introduced to the NTs can be varied by changing processing parameters such as the AgNO(3) concentration and immersion time. The TiO(2)-NTs loaded with Ag nanoparticles (NT-Ag) can kill all the planktonic bacteria in the suspension during the first several days, and the ability of the NT-Ag to prevent bacterial adhesion is maintained without obvious decline for 30 days, which are normally long enough to prevent post-operation infection in the early and intermediate stages and perhaps even late infection around the implant. Although the NT-Ag structure shows some cytotoxicity, it can be reduced by controlling the Ag release rate. The NT-Ag materials are also expected to possess satisfactory osteoconductivity in addition to the good biological performance expected of TiO(2)-NTs. This controllable NT-Ag structure which provides relatively long-term antibacterial ability and good tissue integration has promising applications in orthopedics, dentistry, and other biomedical devices. PMID:21565401

Zhao, Lingzhou; Wang, Hairong; Huo, Kaifu; Cui, Lingyun; Zhang, Wenrui; Ni, Hongwei; Zhang, Yumei; Wu, Zhifen; Chu, Paul K

2011-05-12

275

Spontaneous adsorption of silver nanoparticles on Ti/TiO2 surfaces. Antibacterial effect on Pseudomonas aeruginosa.  

PubMed

Titanium is a corrosion-resistant and biocompatible material widely used in medical and dental implants. Titanium surfaces, however, are prone to bacterial colonization that could lead to infection, inflammation, and finally to implant failure. Silver nanoparticles (AgNPs) have demonstrated an excellent performance as biocides, and thus their integration to titanium surfaces is an attractive strategy to decrease the risk of implant failure. In this work a simple and efficient method is described to modify Ti/TiO(2) surfaces with citrate-capped AgNPs. These nanoparticles spontaneously adsorb on Ti/TiO(2), forming nanometer-sized aggregates consisting of individual AgNPs that homogeneously cover the surface. The modified AgNP-Ti/TiO(2) surface exhibits a good resistance to colonization by Pseudomonas aeruginosa, a model system for biofilm formation. PMID:20656295

Flores, C Y; Diaz, C; Rubert, A; Benítez, G A; Moreno, M S; Fernández Lorenzo de Mele, M A; Salvarezza, R C; Schilardi, P L; Vericat, C

2010-06-25

276

Biosynthesis of Silver Nanoparticles from Desmodium triflorum: A Novel Approach Towards Weed Utilization.  

PubMed

A single-step environmental friendly approach is employed to synthesize silver nanoparticles. The biomolecules found in plants induce the reduction of Ag(+) ions from silver nitrate to silver nanoparticles (AgNPs). UV-visible spectrum of the aqueous medium containing silver ions demonstrated a peak at 425?nm corresponding to the plasmon absorbance of silver nanoparticles. Transmission electron microscopy (TEM) showed the formation of well-dispersed silver nanoparticles in the range of 5-20?nm. X-ray diffraction (XRD) spectrum of the AgNPs exhibited 2? values corresponding to the silver nanocrystal. The process of reduction is extracellular and fast which may lead to the development of easy biosynthesis of silver nanoparticles. Plants during glycolysis produce a large amount of H(+) ions along with NAD which acts as a strong redoxing agent; this seems to be responsible for the formation of AgNPs. Water-soluble antioxidative agents like ascorbic acids further seem to be responsible for the reduction of AgNPs. These AgNPs produced show good antimicrobial activity against common pathogens. PMID:21350660

Ahmad, Naheed; Sharma, Seema; Singh, V N; Shamsi, S F; Fatma, Anjum; Mehta, B R

2010-11-01

277

Biosynthesis of Silver Nanoparticles from Desmodium triflorum: A Novel Approach Towards Weed Utilization  

PubMed Central

A single-step environmental friendly approach is employed to synthesize silver nanoparticles. The biomolecules found in plants induce the reduction of Ag+ ions from silver nitrate to silver nanoparticles (AgNPs). UV-visible spectrum of the aqueous medium containing silver ions demonstrated a peak at 425?nm corresponding to the plasmon absorbance of silver nanoparticles. Transmission electron microscopy (TEM) showed the formation of well-dispersed silver nanoparticles in the range of 5–20?nm. X-ray diffraction (XRD) spectrum of the AgNPs exhibited 2? values corresponding to the silver nanocrystal. The process of reduction is extracellular and fast which may lead to the development of easy biosynthesis of silver nanoparticles. Plants during glycolysis produce a large amount of H+ ions along with NAD which acts as a strong redoxing agent; this seems to be responsible for the formation of AgNPs. Water-soluble antioxidative agents like ascorbic acids further seem to be responsible for the reduction of AgNPs. These AgNPs produced show good antimicrobial activity against common pathogens.

Ahmad, Naheed; Sharma, Seema; Singh, V. N.; Shamsi, S. F.; Fatma, Anjum; Mehta, B. R.

2011-01-01

278

Monodispersed biocompatible silver sulfide nanoparticles: facile extracellular biosynthesis using the ?-proteobacterium, Shewanella oneidensis.  

PubMed

Interest in engineered metal and semiconductor nanocrystallites continues to grow due to their unique size- and shape-dependent optoelectronic, physicochemical and biological properties. Therefore identifying novel non-hazardous nanoparticle synthesis routes that address hydrophilicity, size and shape control and production costs has become a priority. In the present article we report for the first time on the efficient generation of extracellular silver sulfide (Ag?S) nanoparticles by the metal-reducing bacterium Shewanella oneidensis. The particles are reasonably monodispersed and homogeneously shaped. They are produced under ambient temperatures and pressures at high yield, 85% theoretical maximum. UV-visible and Fourier transform infrared spectroscopy, dynamic light scattering, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy measurements confirmed the formation, optical and surface properties, purity and crystallinity of the synthesized particles. Further characterization revealed that the particles consist of spheres with a mean diameter of 9±3.5 nm, and are capped by a detachable protein/peptide surface coat. Toxicity assessments of these biogenic Ag?S nanoparticles on Gram-negative (Escherichia coli and S. oneidensis) and Gram-positive (Bacillus subtilis) bacterial systems, as well as eukaryotic cell lines including mouse lung epithelial (C 10) and macrophage (RAW-264.7) cells, showed that the particles were non-inhibitory and non-cytotoxic to any of these systems. Our results provide a facile, eco-friendly and economical route for the fabrication of technologically important semiconducting Ag?S nanoparticles. These particles are dispersible and biocompatible, thus providing excellent potential for use in optical imaging, electronic devices and solar cell applications. PMID:21798382

Suresh, Anil K; Doktycz, Mitchel J; Wang, Wei; Moon, Ji-Won; Gu, Baohua; Meyer, Harry M; Hensley, Dale K; Allison, David P; Phelps, Tommy J; Pelletier, Dale A

2011-07-14

279

Monodispersed biocompatible silver sulfide nanoparticles: Facile extracellular biosynthesis using the gamma-proteobacterium, Shewanella oneidensis  

SciTech Connect

Interest in engineered metal and semiconductor nanocrystallites continues to grow due to their unique size- and shape-dependent optoelectronic, physicochemical and biological properties. Therefore identifying novel non-hazardous nanoparticle synthesis routes that address hydrophilicity, size and shape control and production costs has become a priority. In the present article we report for the first time on the efficient generation of extracellular silver sulfide (Ag{sub 2}S) nanoparticles by the metal-reducing bacterium Shewanella oneidensis. The particles are reasonably monodispersed and homogeneously shaped. They are produced under ambient temperatures and pressures at high yield, 85% theoretical maximum. UV-visible and Fourier transform infrared spectroscopy, dynamic light scattering, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy measurements confirmed the formation, optical and surface properties, purity and crystallinity of the synthesized particles. Further characterization revealed that the particles consist of spheres with a mean diameter of 9 {+-} 3.5 nm, and are capped by a detachable protein/peptide surface coat. Toxicity assessments of these biogenic Ag{sub 2}S nanoparticles on Gram-negative (Escherichia coli and S. oneidensis) and Gram-positive (Bacillus subtilis) bacterial systems, as well as eukaryotic cell lines including mouse lung epithelial (C 10) and macrophage (RAW-264.7) cells, showed that the particles were non-inhibitory and non-cytotoxic to any of these systems. Our results provide a facile, eco-friendly and economical route for the fabrication of technologically important semiconducting Ag{sub 2}S nanoparticles. These particles are dispersible and biocompatible, thus providing excellent potential for use in optical imaging, electronic devices and solar cell applications.

Doktycz, Mitchel John [ORNL; Moon, Ji Won [ORNL; Meyer III, Harry M [ORNL; Hensley, Dale K [ORNL; Phelps, Tommy Joe [ORNL; Pelletier, Dale A [ORNL

2011-01-01

280

Changes in silver nanoparticles exposed to human synthetic stomach fluid: effects of particle size and surface chemistry.  

PubMed

The significant rise in consumer products and applications utilizing the antibacterial properties of silver nanoparticles (AgNPs) has increased the possibility of human exposure. The mobility and bioavailability of AgNPs through the ingestion pathway will depend, in part, on properties such as particle size and the surface chemistries that will influence their physical and chemical reactivities during transit through the gastrointestinal tract. This study investigates the interactions between synthetic stomach fluid and AgNPs of different sizes and with different capping agents. Changes in morphology, size and chemical composition were determined during a 30 min exposure to synthetic human stomach fluid (SSF) using Absorbance Spectroscopy, High Resolution Transmission Electron and Scanning Electron Microscopy (TEM/SEM), Dynamic Light Scattering (DLS), and Nanoparticle Tracking Analysis (NTA). AgNPs exposed to SSF were found to aggregate significantly and also released ionic silver which physically associated with the particle aggregates as silver chloride. Generally, the smaller sized AgNPs (<10nm) showed higher rates of aggregation and physical transformation than larger particles (75 nm). Polyvinylpyrrolidone (pvp)-stabilized AgNPs prepared in house behaved differently in SSF than particles obtained from a commercial source despite having similar surface coating and size distribution characteristics. PMID:23376520

Mwilu, Samuel K; El Badawy, Amro M; Bradham, Karen; Nelson, Clay; Thomas, David; Scheckel, Kirk G; Tolaymat, Thabet; Ma, Longzhou; Rogers, Kim R

2013-02-01

281

Photo-induced growth of silver nanoparticles using UV sensitivity of cellulose fibers  

NASA Astrophysics Data System (ADS)

A simple method has been demonstrated to grow silver nanoparticles on the surface of cellulose fibers. The preparation is based on photo-activation of surface by ultraviolet (UV) photons, followed by chemical reduction of silver nitrate. It is found that the concentration of silver nitrate in the solution is not a determining factor, while UV intensity affects the rate of initial growth and determines the final concentration of the loaded silver. We explain the phenomena based on a model including the number of reducing sites on the surface of cellulose fibers activated by UV photons, and a release mechanism that causes a slow rate of dissolution of silver back into the solution.

Omrani, A. Alahgholipour; Taghavinia, N.

2012-01-01

282

Green synthesis, characterization and evaluation of biocompatibility of silver nanoparticles  

NASA Astrophysics Data System (ADS)

Although green synthesis of silver nanoparticles (Ag NPs) by various plants and microorganisms has been reported, the potential of plants as biological materials for the synthesis of nanoparticles and their compatibility to biological systems is yet to be fully explored. In this study, we report a simple green method for the synthesis of Ag NPs using garlic clove extract as a reducing and stabilizing agent. In addition to green synthesis, biological response of Ag NPs in human lung epithelial A549 cells was also assessed. Ag NPs were rapidly synthesized using garlic clove extract and the formation of nanoparticles was observed within 30 min. The green synthesized Ag NPs were characterized using UV-vis spectrum, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), X-ray energy-dispersive spectroscopy (EDX) and dynamic light scattering (DLS). Characterization data demonstrated that the particles were crystalline in nature and spherical shaped with an average diameter of 12 nm. Measurements of cell viability, cell membrane integrity and intracellular production of reactive oxygen species have shown that the green synthesized Ag NPs were nontoxic to human lung epithelial A549 cells. This study demonstrated a simple, cost-effective and environmentally benign synthesis of Ag NPs with excellent biocompatibility to human lung epithelial A549 cells. This preliminary in vitro investigation needs to be followed up by future studies with various biological systems.

Ahamed, Maqusood; Majeed Khan, M. A.; Siddiqui, M. K. J.; Alsalhi, Mohamad S.; Alrokayan, Salman A.

2011-04-01

283

Tissue specific responses of oysters, Crassostrea virginica, to silver nanoparticles.  

PubMed

Silver nanoparticle (AgNP) toxicity in eastern oysters, Crassostrea virginica, was investigated in both gill and hepatopancreas tissues, and compared to dissolved Ag exposures. Oysters were exposed to varying concentrations of AgNPs prepared with citrate coatings and dissolved Ag (AgNO?) for 48 h and the effects on a suite of biomarkers of cellular stress were evaluated. Two biomarkers of cellular damage were evaluated-lysosomal destabilization rates of hepatopancreas cells as indicators of lysosomal damage, and lipid peroxidation as an indicator of oxidative damage. Total glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD) assays were used as indicators of impacts on antioxidant capacity. The results indicated that gill tissues were more prone to oxidative damage following dissolved Ag exposures than AgNP exposures, while hepatopancreas tissues were more sensitive to AgNP exposures. Total protein levels increased in hepatopancreas tissues following AgNP exposures, but not dissolved Ag exposures. These tissue specific differences in toxicity and bioreactivity of Ag nanoparticles compared to dissolved metal ions reflect distinct nanoparticle effects. Oysters exposed to dissolved Ag would be more prone to cellular and tissue damage of gills, but oysters exposed to AgNPs could be more prone to hepatopancreas damage contributing to metabolic and reproductive impairment. PMID:23728357

McCarthy, Melissa P; Carroll, David L; Ringwood, Amy H

2013-05-09

284

Carboxylate and amino group coated silver nanoparticles as joining materials for copper-to-copper silver joints.  

PubMed

Organic silver complexes are introduced where silver is linked either with a carboxyl group or with an amino group. Upon heating, nanoparticles are generated if the respective ligands are long enough to act as stabilizing agents in the nanoparticulate regime. With decomposition and volatilization of the organic material, the sintering of silver occurs. The thermal characteristics of the carboxylates silver-n-octanoate, silver-n-decanoate, and AgOOC(CH2OCH2)2CH2OCH3 are compared with silver-n-alkylamines (n = 8, 9, and 12), and their thermal behavior is discussed based on thermogravimetry (TG) measurements. The consecutive stages of a metallization process are addressed based on the properties of AgOOC(CH2OCH2)2CH2OCH3, and the usable effects of the individual phases of this metal organic compound are analyzed by cross-sectional scanning electron microscope (SEM) images of silver joints. Selection criteria are addressed based on the thermal behavior. A mechanism for the joining process is proposed, considering formation and sintering of the nanoparticles. It was found that the bulk material can be used for low-temperature joining processes. Strong adherence to copper as a basic material can be achieved. PMID:23447961

Oestreicher, A; Röhrich, T; Lerch, M

2012-12-01

285

Effect of ionic liquid impurities on the synthesis of silver nanoparticles.  

PubMed

Imidazolium-based ionic liquids have been widely utilized as versatile solvents for metal nanoparticle synthesis; however, reactions to synthesize silver nanoparticles that are performed identically in different commercially obtained lots of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF(4)) give divergent results. This suggests that impurities in these nominally identical solvents play an important role in the resulting silver nanoparticle quality. To test the effect that impurities have on the quality of silver nanoparticles synthesized in BMIM-BF(4), silver nanoparticles were synthesized in carefully prepared and purified BMIM-BF(4) and compared against silver nanoparticles that were synthesized in the purified BMIM-BF(4) that had been spiked with trace amounts of water, chloride, and 1-methylimidazole. It was clearly demonstrated that trace amounts of these common ionic liquid impurities cause significant deviation in size and shape (creating polydisperse and irregularly shaped ensembles of both large and small particles), and also negatively impact the stabilization of the resulting silver nanoparticles. PMID:23092200

Lazarus, Laura L; Riche, Carson T; Malmstadt, Noah; Brutchey, Richard L

2012-11-01

286

Investigation of antibacterial properties silver nanoparticles prepared via green method  

PubMed Central

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

2012-01-01

287

A localized surface plasmon resonance light scattering-based sensing of hydroquinone via the formed silver nanoparticles in system  

Microsoft Academic Search

In this contribution, a simple strategy for the detection of hydroquinone (HQ) is proposed based on the localized surface plasmon resonance light scattering (LSPR-LS) of the silver nanoparticles (AgNPs) formed through the modified silver mirror reaction. The redox reaction between HQ and silver ammonia occurred in the coexistence of sodium hydroxide and ammonia at room temperature, where silver ammonia was

Huiying Wang; Dinglong Chen; Yongju Wei; Longquan Yu; Ping Zhang; Jianlu Zhao

2011-01-01

288

Fluorescent protein capped mesoporous nanoparticles for intracellular drug delivery and imaging.  

PubMed

A multifunctional system for intracellular drug delivery and simultaneous fluorescent imaging was constructed by using histidine-tagged, cyan fluorescent protein (CFP)-capped magnetic mesoporous silica nanoparticles (MMSNs). This protein-capped multifunctional nanostructure is highly biocompatible and does not affect cell viability or proliferation. The CFP acts not only as a capping agent, but also as a fluorescent imaging agent. The nanoassembly was activated by histidine-based replacement, leading to release of drug molecules encapsulated in the nanopores into the bulk solution. The fluorescent imaging functionality would allow noninvasive tracking of the nanoparticles in the body. By combining the drug delivery with cell-imaging capability, these nanoparticles may provide valuable multifunctional nanoplatforms for biomedical applications. PMID:24108691

Yang, Xinjian; Li, Zhenhua; Li, Meng; Ren, Jinsong; Qu, Xiaogang

2013-09-20

289

Silver Nanoparticle-Catalyzed Diels-Alder Cycloadditions of 2?-Hydroxychalcones  

PubMed Central

Metal nanoparticles are currently being employed as catalysts for a number of classical chemical transformations. In contrast, identification of novel reactions of nanoparticles, especially towards the synthesis of complex natural products and derivatives, is highly underdeveloped and represents a bourgeoning area in chemical synthesis. Herein, we report silica-supported silver nanoparticles as solid, recyclable catalysts for Diels-Alder cycloadditions of 2?-hydroxychalcones and dienes in high yield and turnover number. The use of silver nanoparticle catalysts is further demonstrated by the total synthesis of the cytotoxic natural product panduratin A employing a highly electron-rich dienophile and Lewis acid-sensitive diene.

Cong, Huan; Becker, Clinton F.; Elliott, Sean J.; Grinstaff, Mark W.; Porco, John A.

2010-01-01

290

Interaction of silver nanoparticles with biological objects: antimicrobial properties and toxicity for the other living organisms  

NASA Astrophysics Data System (ADS)

This paper presents several examples of the biological effects of small-sized silver nanoparticles (10.5±3.5nm) observed in experiments on bacteria, slim mold, unicellular alga and plant seeds. The nanoparticles were prepared by the biochemical synthesis, based on the reduction of metal ions in reverse vicelles by biological reductants - natural plant pigments (flavonoids). It is found that, except for the plant seeds, silver nanoparticles (SNP) act as a strong toxic agent, both in water solution and as part of liquid-phase material. It is shown also that the biological action of silver nanoparticles can not be reduced to the toxic action of silver ions in equivalent concentrations or to that of the surfactant (the SNP stabilizer) present in the SNP water solution. Possible SNP applications are suggested.

Egorova, E. M.

2011-04-01

291

Facile Synthesis of Silver Nanoparticles Under {gamma}-Irradiation: Effect of Chitosan Concentration  

SciTech Connect

In the present study, a biopolymer, low molecular weight chitosan had been utilized as a 'green' stabilizing agent for the synthesis of silver nanoparticles under {gamma}-irradiation. The as-synthesized silver nanoparticles have particle diameters in the range of 5 nm-30 nm depending on the percentage of chitosan used (0.1 wt%, 0.5 wt%, 1.0 wt% and 2.0 wt%). It was found that the yield of the silver nanoparticles was in accordance with the concentration of chitosan presence in the solution due to the reduction by the chitosan radical during irradiation. The highly stable chitosan encapsulated silver nanoparticles were characterized using transmission electron microscopy (TEM), UV-Visible spectrophotometer (UV-VIS) and X-ray diffraction spectroscopy (XRD)

Huang, N. M.; Radiman, S.; Ahmad, A.; Idris, H. [Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi (Malaysia); Lim, H. N. [Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Khiew, P. S.; Chiu, W. S.; Tan, T. K. [Faculty of Engineering and Computer Science, Nottingham University, 43500 Semenyih (Malaysia)

2009-06-01

292

Acceleration effect of reduced graphene oxide on photoinduced synthesis of silver nanoparticles.  

PubMed

The photoinduced growth reaction of silver nanoparticles was accelerated by reduced graphene oxide (RGO) produced from graphene oxide (GO) during the light irradiation process in aqueous solution. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy demonstrated that RGO was generated in the photoinduced process. The acceleration effect of RGO was investigated through monitoring the extinction spectra of silver nanoparticles during the synthesis process. Moreover, transmission electron microscopy (TEM) was employed to characterize the evolution of morphologies of silver nanoparticles at different irradiation times to demonstrate the effect of RGO. The results indicate that RGO accelerates the photoinduced synthesis of silver nanoparticles. It is proposed that the acceleration effect of RGO on the photoinduced reaction is attributed to the particular property of high electronic conductivity. PMID:23719756

Tang, Bin; Hou, Xueliang; Li, Jingliang; Zhang, Mingwen; Sun, Lu; Wang, Xungai

2013-05-30

293

Facile Synthesis of Silver Nanoparticles Under ?-Irradiation: Effect of Chitosan Concentration  

NASA Astrophysics Data System (ADS)

In the present study, a biopolymer, low molecular weight chitosan had been utilized as a ``green'' stabilizing agent for the synthesis of silver nanoparticles under ?-irradiation. The as-synthesized silver nanoparticles have particle diameters in the range of 5 nm-30 nm depending on the percentage of chitosan used (0.1 wt%, 0.5 wt%, 1.0 wt% & 2.0 wt%). It was found that the yield of the silver nanoparticles was in accordance with the concentration of chitosan presence in the solution due to the reduction by the chitosan radical during irradiation. The highly stable chitosan encapsulated silver nanoparticles were characterized using transmission electron microscopy (TEM), UV-Visible spectrophotometer (UV-VIS) and X-ray diffraction spectroscopy (XRD).

Huang, N. M.; Radiman, S.; Lim, H. N.; Khiew, P. S.; Chiu, W. S.; Tan, T. K.; Ahmad, A.; Idris, H.

2009-06-01

294

Catalysis of Gold and Gold-Silver Alloy Nanoparticles Supported on Mesoporous Silica.  

National Technical Information Service (NTIS)

This is a report on research using amino-functionalized mesoporous silica to confine gold or gold/silver alloy nanoparticles inside the nanochannels of the silica with uniform size distribution of particle sizes.

C. Mou

2009-01-01

295

Generation and properties of antibacterial coatings based on electrostatic attachment of silver nanoparticles to protein-coated polypropylene fibers.  

PubMed

We present a simple method for attaching silver nanoparticles to polypropylene (PP) fibers in a two-step process to impart antibacterial properties. Specifically, PP fibers are pretreated by the adsorption from an aqueous solution of heat-denatured lysozyme (LYS) followed by LYS cross-linking using glutaraldehyde and sodium borohydride. At neutral pH, the surface of the adsorbed LYS layer is enriched with numerous positive charges. Silver nanoparticles (AgNPs) capped with trisodium citrate are subsequently deposited onto the protein-coated PP. Nanoparticle binding is mediated by electrostatic interactions between the positively charged LYS layer and the negatively charged AgNPs. The density of AgNPs deposited on PP depends on the amount of protein adsorbed on the surface. UV-vis spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy are employed to follow all preparation steps and to characterize the resulting functional surfaces. The antibacterial activity of the modified surfaces is tested against gram negative bacteria Escherichia coli (E. coli). Overall, our results show that PP surfaces coated with AgNPs exhibit excellent antibacterial activity with 100% removal efficiency. PMID:23675700

Goli, Kiran K; Gera, Nimish; Liu, Xiaomeng; Rao, Balaji M; Rojas, Orlando J; Genzer, Jan

2013-05-29

296

Silver nanoparticles and total aerosols emitted by nanotechnology-related consumer spray products.  

PubMed

Products containing silver nanoparticles are entering the market rapidly, but little is known about the potential for inhalation exposure to nanosilver. The objectives of this work were to characterize the emissions of airborne particles from consumer products that claim to contain silver nanoparticles or ions, determine the relationship between emissions and the products' liquid characteristics, and assess the potential for inhalation exposure to silver during product use. Three products were investigated: an antiodor spray for hunters, a surface disinfectant, and a throat spray. Products emitted 0.24-56 ng of silver in aerosols per spray action. The plurality of silver was found in aerosols 1-2.5 ?m in diameter for two products. Both the products' liquid characteristics and the bottles' spray mechanisms played roles in determining the size distribution of total aerosols, and the size of silver-containing aerosols emitted by the products was largely independent of the silver size distributions in the liquid phase. Silver was associated with chlorine in most samples. Results demonstrate that the normal use of silver-containing spray products carries the potential for inhalation of silver-containing aerosols. Exposure modeling suggests that up to 70 ng of silver may deposit in the respiratory tract during product use. PMID:22070550

Quadros, Marina E; Marr, Linsey C

2011-11-23

297

Synthesis of antimicrobial silver nanoparticles by callus and leaf extracts from saltmarsh plant, Sesuvium portulacastrum L.  

PubMed

The present work studied the effect of extracts from tissue culture-derived callus and leaf of the saltmarsh plant, Sesuvium portulacastrum L. on synthesis of antimicrobial silver nanoparticles using AgNO(3) as a substrate. The callus extract could be able to produce silver nanoparticles, better than leaf extract. The synthesis of silver nanoparticles was confirmed with X-ray diffraction spectrum which exhibited intense peaks, corresponding to the (1 1 1), (2 0 0), (2 2 0), (3 1 1), and (2 2 2) sets of lattice planes of silver. The extracts incubated with AgNO(3) showed gradual change in color of the extracts to yellowish brown, with intensity increasing during the period of incubation. Control without silver nitrate did not show any change in color. The silver nanoparticles synthesized were generally found to be spherical in shape with variable size ranging from 5 to 20 nm, as evident by Transmission Electron Microscopy. There were prominent peaks in the extracts corresponding to amide I, II and III indicating the presence of the protein, as revealed by Fourier transform infrared (FTIR) spectroscopy measurement. There were also peaks that were corresponding to aromatic rings, geminal methyls and ether linkages, indicating the presence of flavones and terpenoids responsible for the stabilization of the silver nanoparticles. The silver nanoparticles were observed to inhibit clinical strains of bacteria and fungi. The antibacterial activity was more distinct than antifungal activity. The antimicrobial activity was enhanced when polyvinyl alcohol was added as a stabilizing agent. The present work highlighted the possibility of using tissue culture-derived callus extract from the coastal saltmarsh species for the synthesis of antimicrobial silver nanoparticles. PMID:20627485

Nabikhan, Asmathunisha; Kandasamy, Kathiresan; Raj, Anburaj; Alikunhi, Nabeel M

2010-09-01

298

Antibacterial titanium plate deposited by silver nanoparticles exhibits cell compatibility  

PubMed Central

Microbial colonization and biofilm formation on the surface of implant devices may cause peri-implantitis and lead to bone loss. The aim of this study was to develop a novel antibacterial titanium implant surface and to test its biological performance. In a previous study, we demonstrated that titanium plates deposited by nanosilver acquired antibacterial activity to Staphylococcus aureus and Escherichia coli. While antibacterial activity is important, biomaterial surfaces should be modified to achieve excellent cell compatibility as well. In the present study, using the MTT assay, fluorescence microscopy, and scanning electron microscopy, we assessed cell viability, cytoskeletal architecture and cell attachment, respectively, on our silver nanoparticle-modified titanium (Ti-nAg) plate. The results demonstrate that the Ti-nAg do not show any cytotoxicity to the human gingival fibroblasts. Our data indicate that Ti-nAg is a novel material with both good antibacterial properties and uncompromised cytocompatibility, which can be used as an implanted biomaterial.

Liao, Juan; Anchun, Mo; Zhu, Zhimin; Quan, Yuan

2010-01-01

299

Reaction of silver nanoparticles in the disinfection process.  

PubMed

This study investigated the dissolution, aggregation, and reaction kinetics of silver nanoparticles (AgNPs) with the three types of water disinfectants (ultraviolet, sodium hypochlorite, and ozone) under the different conditions of pH, ionic strength, or humic acid (HA). The physicochemical changes of AgNPs were measured by using UV-Vis spectroscopy, transmission electron microscopy, and inductively coupled plasma optical emission spectrometer. The results showed that when AgNPs contacted the disinfectants, oxidative dissolution was the primary reaction. In addition, the reaction kinetics studies revealed that the reaction rate of AgNPs with disinfectants was significantly influenced by different disinfectants along with different pH and the presence of sodium nitrate and HA. Our research demonstrated the potential effect of disinfectants on AgNPs, which will improve our understanding of the fate of AgNPs in the disinfection processes in the water and wastewater treatment plant. PMID:23830116

Yuan, Zhihua; Chen, Yunbin; Li, Tingting; Yu, Chang-Ping

2013-07-02

300

Synthesis and antimicrobial activity of silver-doped hydroxyapatite nanoparticles.  

PubMed

The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications. The aim of this study was the evaluation of Ca(10-x)Ag(x)(PO4)6(OH)2 nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against gram-positive and gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures. PMID:23509801

Ciobanu, Carmen Steluta; Iconaru, Simona Liliana; Chifiriuc, Mariana Carmen; Costescu, Adrian; Le Coustumer, Philippe; Predoi, Daniela

2012-12-30

301

Hysteresis effects of the interaction between serum albumins and silver nanoparticles  

Microsoft Academic Search

The mechanisms and effects about the interaction between serum albumins and silver nanoparticles have been intensively studied\\u000a by means of transmission electron microscopy (TEM), circular dichroism (CD) and ultraviolet-visible (UV-Vis) spectroscopy.\\u000a The adsorption of serum albumins on the surface of silver nanoparticles is observed by TEM. The studies with the surface plasmon\\u000a bands indicate that the electrostatic and hydrophilic interactions

Xingcan Shen; Qi Yuan; Hong Liang; Haigang Yan; Xiwen He

2003-01-01

302

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

Microsoft Academic Search

The aim of this study was to evaluate the effect of silver nanoparticles (SN) against Candida albicans and Candida glabrata adhered cells and biofilms. SN (average diameter 5 nm) were synthesized by silver nitrate reduction with sodium citrate and stabilized with ammonia. Minimal inhibitory concentration (MIC) tests were performed for C. albicans (n = 2) and C. glabrata (n = 2) grown in suspension

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

2011-01-01

303

Synthesis of silver nanoparticle necklaces without explicit addition of reducing or templating agents.  

PubMed

Here we report that silver nanoparticle necklaces can be readily formed by treatment of colloidal silica with ammoniacal silver complex solution followed by washing, deposition and ageing. We investigate the morphology of the produced materials and elucidate the key variables that influence this promising new approach to one-dimensional nanostructuring. PMID:22437651

Hanisch, Mathias; Ma?kovi?, Mirza; Taccardi, Nicola; Spiecker, Erdmann; Klupp Taylor, Robin N

2012-03-22

304

Study of silver nanoparticle-hemoglobin interaction and composite formation.  

PubMed

Nanoscience is now an expanding field of research and finds potential application in biomedical area, but it is limited due to lack of comprehensive knowledge of the interactions operating in nano-bio system. Here, we report the studies on the interaction and formation of nano-bio complex between silver nanoparticle (AgNP) and human blood protein hemoglobin (Hb). We have employed several spectroscopic (absorption, emission, Raman, FTIR, CD, etc.) and electron diffraction techniques (FE-SEM and HR-TEM) to characterize the Hb-AgNP complex system. Our results show the Hb-AgNP interaction is concentration and time dependent. The AgNP particle can attach/come closer to heme, tryptophan, and amide as well aromatic amine residues. As a result, the Hb undergoes conformational change and becomes unfolded through the increment of ?-sheet structure. The AgNP-Hb can form charge-transfers (CT) complex where the Hb-heme along with the AgNP involved in the electron transfer mechanism and form Hb-AgNP assembled structure. The electron transfer mechanism has been found to be dependent on the size of silver particle. The overall study is important in understanding the nano-bio system and in predicting the avenues to design and synthesis of novel nano-biocomposite materials in material science and biomedical area. PMID:21788120

Mahato, Mrityunjoy; Pal, Prabir; Tah, Bidisha; Ghosh, Manash; Talapatra, G B

2011-07-08

305

A simple route to triethanolamine (TEA) and cysteine capped ZnSe nanoparticles.  

PubMed

Water soluble triethanolamine (TEA) and cysteine capped ZnSe nanoparticles have been synthesized via simple solution based route. The method involves the reduction of selenium followed by the addition of the metal salt and capping group. The pH and metal salts were varied to study their effect on the optical properties and morphology of the particles. The as-synthesised ZnSe nanoparticles properties were studied by UV-Vis, photoluminescence, FTIR spectroscopy, powder X-ray diffraction, transmission electron microscopy (TEM) and high resolution TEM. PMID:22755103

Dlamini, N N; Pullabhotla, V S R Rajasekhar; Revaprasadu, N

2012-03-01

306

Development of coated-wire silver ion selective electrodes on paper using conductive films of silver nanoparticles.  

PubMed

Films of silver nanoparticles are used for the first time as an electrical conductor and ion-to-electron transducer to fabricate coated-wire ion selective electrodes (ISEs) on paper. The film of nano silver ink (nano silver film), synthesized from the reduction of AgNO3 by NaBH4, was screen printed on paper. Transmission electron microscopy showed that the synthesized silver nanoparticles (AgNPs) possessed a spherical shape with diameter ca. 5 nm. Energy-dispersive X-ray spectroscopy supported the purity and good stability of the synthesized AgNPs. Nano silver films were sintered at room temperature, 100 °C and 200 °C. Upon increasing the sintering temperature, atomic force microscopy showed that the size of AgNPs of nano silver films increased, but the sheet resistivity decreased. Silver ISEs were then fabricated from nano silver films and o-NPOE-plasticized polymeric membranes containing benzothiazolyl calix[4]arene () as ionophore and KTpClPB as anionic site. The performance of the developed Ag-ISEs was investigated by potentiometric measurements, potentiometric water layer tests, current reversal chronopotentiometry and electrochemical impedance spectroscopy. The coated-wire electrode fabricated from the nano silver film sintering at room temperature showed the best characteristics of Ag-ISEs giving a near Nernstian response slope of 59.7 ± 1.0 mV per decade, 10(-6) to 10(-2) M linear range, detection limit of 4.5 × 10(-7) M, long-term potential stability and good reversibility. PMID:24071789

Janrungroatsakul, Wanwisa; Lertvachirapaiboon, Chutiparn; Ngeontae, Wittaya; Aeungmaitrepirom, Wanlapa; Chailapakul, Orawon; Ekgasit, Sanong; Tuntulani, Thawatchai

2013-10-15

307

Blue orange light emission from biogenic synthesized silver nanoparticles using Trichoderma viride.  

PubMed

Recent advances in nanomaterial have produced a new class of fluorescence labels by conjugating noble metal with biomolecules. The nanometer size metal conjugates are water soluble, biocompatible and provide important advantage over the fluorescence dyes. In this regard we synthesized silver nanoparticles at the size of 2-4 nm using biological route and studied fluorescence property of these nanoparticles. We observe that these silver (Ag(+)) ions when exposed to filtrate of Trichoderma viride are reduced in solution, thereby leading to the formation of an extremely stable silver hydrosol. These silver nanoparticles were characterized by means of UV-vis spectrophotometer, FTIR, HrTEM, EDX, XRD and fluorescence spectroscopy. The nanoparticles exhibit maximum absorbance at 405 nm in UV-vis spectrum. The presence of proteins was identified by FTIR. The HrTEM micrograph revealed the formation of monodispersed spherical nanoparticles and the presence of elemental silver was confirmed by EDX analysis and XRD. These monodispersed silver nanoparticles showed emission in the range of 320-520 nm wavelength. PMID:19783414

Fayaz, Mohammed; Tiwary, C S; Kalaichelvan, P T; Venkatesan, R

2009-08-25

308

Application of Silver Nanoparticles for the Control of Colletotrichum Species In Vitro and Pepper Anthracnose Disease in Field  

PubMed Central

Pepper anthracnose caused by Colletotrichum species is one of the most important limiting factors for pepper production in Korea, its management being strongly dependent on chemicals. The aim of this work was to evaluate the possibilities of using silver nanoparticles instead of commercial fungicides. In this study, we evaluated the effect of silver nanoparticles against pepper anthracnose under different culture conditions. Silver nanoparticles (WA-PR-WB13R) were applied at various concentrations to determine antifungal activities in vitro and in the field. The application of 100 ppm concentration of silver nanoparticles produced maximum inhibition of the growth of fungal hyphae as well as conidial germination in comparison to the control in vitro. In field trials, the inhibition of fungi was significantly high when silver nanoparticles were applied before disease outbreak on the plants. Scanning electron microscopy results indicated that the silver nanoparticles caused a detrimental effect on mycelial growth of Colletotrichum species.

Lamsal, Kabir; Kim, Sang Woo; Jung, Jin Hee; Kim, Yun Seok; Kim, Kyong Su

2011-01-01

309

Application of silver nanoparticles for the control of colletotrichum species in vitro and pepper anthracnose disease in field.  

PubMed

Pepper anthracnose caused by Colletotrichum species is one of the most important limiting factors for pepper production in Korea, its management being strongly dependent on chemicals. The aim of this work was to evaluate the possibilities of using silver nanoparticles instead of commercial fungicides. In this study, we evaluated the effect of silver nanoparticles against pepper anthracnose under different culture conditions. Silver nanoparticles (WA-PR-WB13R) were applied at various concentrations to determine antifungal activities in vitro and in the field. The application of 100 ppm concentration of silver nanoparticles produced maximum inhibition of the growth of fungal hyphae as well as conidial germination in comparison to the control in vitro. In field trials, the inhibition of fungi was significantly high when silver nanoparticles were applied before disease outbreak on the plants. Scanning electron microscopy results indicated that the silver nanoparticles caused a detrimental effect on mycelial growth of Colletotrichum species. PMID:22783103

Lamsal, Kabir; Kim, Sang Woo; Jung, Jin Hee; Kim, Yun Seok; Kim, Kyong Su; Lee, Youn Su

2011-09-27

310

Biological synthesis of very small silver nanoparticles by culture supernatant of Klebsiella pneumonia: The effects of visible-light irradiation and the liquid mixing process  

SciTech Connect

This study has investigated different visible-light irradiation's effect on the formation of silver nanoparticles from silver nitrate using the culture supernatant of Klebsiella pneumonia. Our study shows that visible-light emission can significantly prompt the synthesis of silver nanoparticles. Also, the study experimentally investigated the liquid mixing process effect on silver nanoparticle synthesis by visible-light irradiation. This study successfully synthesized uniformly dispersed silver nanoparticles with a uniform size and shape in the range of 1-6 nm with an average size of 3 nm. Furthermore, the study investigated the mechanism of the reduction of silver ions by culture supernatant of K. pneumonia, and used X-ray diffraction to characterize silver chloride as an intermediate compound. Silver chloride was prepared synthetically and used as a substrate for the synthesis of silver nanoparticles by culture supernatant of K. pneumonia. The silver nanoparticles have been prepared from silver chloride during this investigation for the first time.

Mokhtari, Narges [Department of Pharmaceutical Biotechnology and Biotechnology Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Daneshpajouh, Shahram; Seyedbagheri, Seyedali; Atashdehghan, Reza [Hydrometallurgy Research Unit, Research and Development Center, National Iranian Copper Industries Company, Sarcheshmeh, Rafsanjan (Iran, Islamic Republic of); Abdi, Khosro [Department of Pharmaceutical Biotechnology and Biotechnology Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Sarkar, Saeed [Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Minaian, Sara [Department of Pharmaceutical Biotechnology and Biotechnology Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Shahverdi, Hamid Reza [Department of Material Science, Faculty of Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Shahverdi, Ahmad Reza, E-mail: shahverd@sina.tums.ac.ir [Department of Pharmaceutical Biotechnology and Biotechnology Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of)

2009-06-03

311

Size-dependent magnetic properties of naked and ligand-capped nickel nanoparticles  

NASA Astrophysics Data System (ADS)

Ligand-free naked and oleylamine-capped nickel nanoparticles (Ni NPs) were size-selectively prepared in the size ranges of 5-17 nm (naked) and 13-19 nm (capped) in diameter through gas- and liquid-phase syntheses, respectively. As for the magnetic properties of both the naked and oleylamine-capped Ni NPs, the blocking temperatures, TB, increase with the size, where TB for the naked Ni NPs are significantly higher than that for the capped Ni NPs. The results indicate that the ferromagnetic core region of Ni NPs is reduced by the formation of nonmagnetic layers at the surface of the capped NPs, where their thickness is estimated to be 1-2 nm.

Sugiyama, Akinori; Taguchi, Yousuke; Nagaoka, Shuhei; Nakajima, Atsushi

2010-01-01

312

Synthesis of monodispersed silver nanoparticles using Hibiscus cannabinus leaf extract and its antimicrobial activity  

NASA Astrophysics Data System (ADS)

Synthesis of silver nanoparticles using leaf extract of Hibiscus cannabinus has been investigated. The influences of different concentration of H. cannabinus leaf extract, different metal ion concentration and different reaction time on the above cases on the synthesis of nanoparticles were evaluated. The synthesized nanoparticles were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The prepared silver nanoparticles were monodispersed, spherical in shape with the average particle size of 9 nm and shows surface plasmon peak at 446 nm. The study also reveals that the ascorbic acid present in H. cannabinus leaf extract has been used as reducing agent. The prepared silver nanoparticle shows good antimicrobial activity against Escherichia coli, Proteus mirabilis and Shigella flexneri.

Bindhu, M. R.; Umadevi, M.

2013-01-01

313

Environmental Feedbacks and Engineered Nanoparticles: Mitigation of Silver Nanoparticle Toxicity to Chlamydomonas reinhardtii by Algal-Produced Organic Compounds.  

PubMed

The vast majority of nanotoxicity studies measures the effect of exposure to a toxicant on an organism and ignores the potentially important effects of the organism on the toxicant. We investigated the effect of citrate-coated silver nanoparticles (AgNPs) on populations of the freshwater alga Chlamydomonas reinhardtii at different phases of batch culture growth and show that the AgNPs are most toxic to cultures in the early phases of growth. We offer strong evidence that reduced toxicity occurs because extracellular dissolved organic carbon (DOC) compounds produced by the algal cells themselves mitigate the toxicity of AgNPs. We analyzed this feedback with a dynamic model incorporating algal growth, nanoparticle dissolution, bioaccumulation of silver, DOC production and DOC-mediated inactivation of nanoparticles and ionic silver. Our findings demonstrate how the feedback between aquatic organisms and their environment may impact the toxicity and ecological effects of engineered nanoparticles. PMID:24086348

Stevenson, Louise M; Dickson, Helen; Klanjscek, Tin; Keller, Arturo A; McCauley, Edward; Nisbet, Roger M

2013-09-23

314

Environmental Feedbacks and Engineered Nanoparticles: Mitigation of Silver Nanoparticle Toxicity to Chlamydomonas reinhardtii by Algal-Produced Organic Compounds  

PubMed Central

The vast majority of nanotoxicity studies measures the effect of exposure to a toxicant on an organism and ignores the potentially important effects of the organism on the toxicant. We investigated the effect of citrate-coated silver nanoparticles (AgNPs) on populations of the freshwater alga Chlamydomonas reinhardtii at different phases of batch culture growth and show that the AgNPs are most toxic to cultures in the early phases of growth. We offer strong evidence that reduced toxicity occurs because extracellular dissolved organic carbon (DOC) compounds produced by the algal cells themselves mitigate the toxicity of AgNPs. We analyzed this feedback with a dynamic model incorporating algal growth, nanoparticle dissolution, bioaccumulation of silver, DOC production and DOC-mediated inactivation of nanoparticles and ionic silver. Our findings demonstrate how the feedback between aquatic organisms and their environment may impact the toxicity and ecological effects of engineered nanoparticles.

Stevenson, Louise M.; Dickson, Helen; Klanjscek, Tin; Keller, Arturo A.; McCauley, Edward; Nisbet, Roger M.

2013-01-01

315

Comparison of various organic stabilizers as capping agents for CdS nanoparticles synthesis  

Microsoft Academic Search

Results of the studies on the preparation and characterization of CdS nanoparticles capped with various organic stabilizers\\u000a are presented in this article. Solutions of Cadmium acetate and Sodium sulphide were taken as the precursors. CdS nanoparticles\\u000a were synthesized in an aqueous medium with Mercaptopropionic acid (MPA) as the stabilizer and non-aqueous methods were used\\u000a for the synthesis of Polyvinyl Pyrrolidone

B. Saraswathi Amma; K. Ramakrishna; Manjunatha Pattabi

2007-01-01

316

Electrochemical stability of citrate-capped gold nanoparticles electrostatically assembled on amine-modified glassy carbon  

Microsoft Academic Search

The stability of citrate-capped gold nanoparticles assembled on covalently attached ethylenediamine films on glassy carbon was probed using cyclic voltammetry and scanning electron microscopy. The accessible potential windows in 0.01M HClO4 and phosphate buffer (pH 7.4) were found to be very similar to those for re-constructed polycrystalline bulk gold. At the nanoparticle electrodes, gold is dissolved at high positive potentials

Amy C. Cruickshank; Alison J. Downard

2009-01-01

317

Gelatin–Chitosan composite capped gold nanoparticles: a matrix for the growth of hydroxyapatite  

Microsoft Academic Search

Growth of hydroxyapatite (HA) on gelatin–chitosan composite capped gold nanoparticles is presented for the first time by employing\\u000a wet precipitation methods and we obtained good yields of HA. Fourier transform infrared spectroscopy (FTIR) spectrum has shown\\u000a the characteristic bands of phosphate groups in the HA. Scanning electron microscopy (SEM) pictures have shown spherical nanoparticles\\u000a with the size in the range

S. S. Liji Sobhana; J. Sundaraseelan; S. Sekar; T. P. Sastry; A. B. Mandal

2009-01-01

318

Open-tubular gas chromatography using capillary coated with octadecylamine-capped gold nanoparticles  

Microsoft Academic Search

The octadecylamine-capped gold nanoparticles (ODA-Au-NPs) were prepared and directly used to coat the capillary wall. The hydrophobic coating acted as the stationary phase for open-tubular gas chromatography (OTGC). The ODA-Au-NPs can be adsorbed tightly onto the inner surface of fused silica capillary column via electrostatic interaction and enhanced interaction of van der Waals between gold nanoparticles and the capillary wall.

Qi-Shu Qu; Fei Shen; Ming Shen; Xiao-Ya Hu; Gong-Jun Yang; Cheng-Yin Wang; Chao Yan; Yu-Kui Zhang

2008-01-01

319

The effect of particle size on the toxic action of silver nanoparticles  

NASA Astrophysics Data System (ADS)

Silver nanoparticles in AOT reverse micelles were obtained by means of the biochemical synthesis. Synthesis of nanoparticles was carried out with variation of the three parameters of reverse-micellar systems: concentration of silver ions, concentration of the stabilizer (AOT) and hydration extent w = [H2O]/[AOT]. The combinations of varied parameters have been found, allowing to prepare micellar solutions of spherical silver nanoparticles with average sizes 4.6 and 9.5 nm and narrow size distribution. From micellar solution the nanoparticles were transferred into the water phase; water solutions of the nanoparticles were used for testing their biological activity. Our assay is based on negative chemotaxis, a motile reaction of cells to an unfavorable chemical environment. Plasmodium of the slime mold Physarum polycephalum used as an object is a multinuclear amoeboid cell with unlimited growth and the auto-oscillatory mode of locomotion. In researches of chemotaxis on plasmodium it is learned that silver nanoparticles of smaller size exhibit a higher biological activity (behave as stronger repellent) and this correlates with the literary data obtained in studies of silver nanoparticles interaction with other biological objects.

Sosenkova, L. S.; Egorova, E. M.

2011-04-01

320

Aggregation kinetics of citrate and polyvinylpyrrolidone coated silver nanoparticles in monovalent and divalent electrolyte solutions.  

PubMed

The aggregation kinetics of silver nanoparticles (AgNPs) that were coated with two commonly used capping agents-citrate and polyvinylpyrrolidone (PVP)--were investigated. Time-resolved dynamic light scattering (DLS) was employed to measure the aggregation kinetics of the AgNPs over a range of monovalent and divalent electrolyte concentrations. The aggregation behavior of citrate-coated AgNPs in NaCl was in excellent agreement with the predictions based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, and the Hamaker constant of citrate-coated AgNPs in aqueous solutions was derived to be 3.7 × 10(-20) J. Divalent electrolytes were more efficient in destabilizing the citrate-coated AgNPs, as indicated by the considerably lower critical coagulation concentrations (2.1 mM CaCl(2) and 2.7 mM MgCl(2) vs 47.6 mM NaCl). The PVP-coated AgNPs were significantly more stable than citrate-coated AgNPs in both NaCl and CaCl(2), which is likely due to steric repulsion imparted by the large, noncharged polymers. The addition of humic acid resulted in the adsorption of the macromolecules on both citrate- and PVP-coated AgNPs. The adsorption of humic acid induced additional electrosteric repulsion that elevated the stability of both nanoparticles in suspensions containing NaCl or low concentrations of CaCl(2). Conversely, enhanced aggregation occurred for both nanoparticles at high CaCl(2) concentrations due to interparticle bridging by humic acid aggregates. PMID:21630686

Huynh, Khanh An; Chen, Kai Loon

2011-06-01

321

Aggregation Kinetics of Citrate and Polyvinylpyrrolidone Coated Silver Nanoparticles in Monovalent and Divalent Electrolyte Solutions  

PubMed Central

The aggregation kinetics of silver nanoparticles (AgNPs) that were coated with two commonly used capping agents—citrate and polyvinylpyrrolidone (PVP)—were investigated. Time-resolved dynamic light scattering (DLS) was employed to measure the aggregation kinetics of the AgNPs over a range of monovalent and divalent electrolyte concentrations. The aggregation behavior of citrate-coated AgNPs in NaCl was in excellent agreement with the predictions based on Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, and the Hamaker constant of citrate-coated AgNPs in aqueous solutions was derived to be 3.7 × 10-20 J. Divalent electrolytes were more efficient in destabilizing the citrate-coated AgNPs, as indicated by the considerably lower critical coagulation concentrations (2.1 mM CaCl2 and 2.7 mM MgCl2 vs. 47.6 mM NaCl). The PVP-coated AgNPs were significantly more stable than citrate-coated AgNPs in both NaCl and CaCl2, which is likely due to steric repulsion imparted by the large, non-charged polymers. The addition of humic acid resulted in the adsorption of the macromolecules on both citrate- and PVP-coated AgNPs. The adsorption of humic acid induced additional electrosteric repulsion that elevated the stability of both nanoparticles in suspensions containing NaCl or low concentrations of CaCl2. Conversely, enhanced aggregation occurred for both nanoparticles at high CaCl2 concentrations due to interparticle bridging by humic acid clusters.

Huynh, Khanh An; Chen, Kai Loon

2011-01-01

322

Silver-nanoparticle-embedded antimicrobial paints based on vegetable oil  

NASA Astrophysics Data System (ADS)

Developing bactericidal coatings using simple green chemical methods could be a promising route to potential environmentally friendly applications. Here, we describe an environmentally friendly chemistry approach to synthesize metal-nanoparticle (MNP)-embedded paint, in a single step, from common household paint. The naturally occurring oxidative drying process in oils, involving free-radical exchange, was used as the fundamental mechanism for reducing metal salts and dispersing MNPs in the oil media, without the use of any external reducing or stabilizing agents. These well-dispersed MNP-in-oil dispersions can be used directly, akin to commercially available paints, on nearly all kinds of surface such as wood, glass, steel and different polymers. The surfaces coated with silver-nanoparticle paint showed excellent antimicrobial properties by killing both Gram-positive human pathogens (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). The process we have developed here is quite general and can be applied in the synthesis of a variety of MNP-in-oil systems.

Kumar, Ashavani; Vemula, Praveen Kumar; Ajayan, Pulickel M.; John, George

2008-03-01

323

Hepatocurative activity of biosynthesized silver nanoparticles fabricated using Andrographis paniculata.  

PubMed

The current investigation was aimed to determine the hepatocurative role of silver nanoparticles (AgNPs) synthesized rapidly using Andrographis paniculata. The nanoparticles fabricated at varying temperatures were characterized by UV-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), fourier transform infra-red spectroscopy (FTIR), energy dispersive X-ray (EDX) and inductively coupled plasma optical emission spectroscopy (ICP-OES) alongside zeta potential measurement. UV-vis spectroscopic readings indicated a prominent peak at 423 nm. TEM analysis indicated that the biosynthesized nanospheres were in the size range of 13-27 nm. EDX spectrum indicated strong signal for AgNPs with 90.1% purity. The total concentration of AgNps was 216.7 mg/L after synthesis as by ICP-OES. Zeta potential was -34.3 mV indicating stable AgNPs. In vitro radical scavenging assay proved strong antioxidant effect of the AgNPs compared to 5% aqueous leaf extract. CCl(4) was used to induce hepatic injury in mice model. The biosynthesized AgNPs at three different doses (25, 50, 100mg/kg BW of the animal) were used for treatment. Silymarin was used as a standard. Low dose (25mg/kg BW) was effective in revival of all biological parameters to near normal in all intoxicated groups indicating the curing effects on CCl(4) induced liver injury. PMID:23018020

Suriyakalaa, Udhayaraj; Antony, Jacob Joe; Suganya, Subramanian; Siva, Durairaj; Sukirtha, Raman; Kamalakkannan, Soundarrajan; Pichiah, P B Tirupathi; Achiraman, Shanmugam

2012-08-14

324

Nanoparticles at fluid interfaces: how capping ligands control adsorption, stability and dynamics  

NASA Astrophysics Data System (ADS)

The spontaneous assembly of nanoparticles at fluid-fluid interfaces is exploited in microfluidic encapsulation, fabrication of nanomaterials, oil recovery, and catalysis. Control over the microstructure formed by interfacial nanoparticles is an important goal in these contexts: the ability to reversibly tune the packing fraction enables for nanomaterials with tunable properties, while control over nanoparticle removal and recycling is desirable for green processes. I will discuss how capping ligands can promote interfacial self-assembly by tuning the interfacial energies of the nanoparticles with the fluids. Ligand-mediated particle interactions at the interface then affect the formation of equilibrium and non-equilibrium two-dimensional phases. Important differences with colloidal interactions in a bulk suspension arise due to the discontinuity in solvent properties at the interface, which cause the ligand brushes to rearrange in asymmetric configurations. I will present experimental results for gold nanoparticles capped with short amphiphilic ligands, which spontaneously adsorb at an oil-water interface. Using pendant drop tensiometry, we measured the surface pressure of the nanoparticle monolayer during adsorption and subsequent compression. In contrast to the commonly observed buckling of solid-like films of interfacial particles, upon compression these nanoparticles are mechanically forced out of the interface and into suspension. Area density measurements by a newly developed optical method reveal that ligand-mediated short-range interparticle repulsion enables desorption upon compression. Brownian dynamics simulations corroborate this picture. Therefore, ligand-mediated interactions also determine the fate of nanoparticle monolayers upon out-of-plane deformation.

Garbin, Valeria

2013-03-01

325

Microwave Assisted Rapid and Green Synthesis of Silver Nanoparticles Using a Pigment Produced by Streptomyces coelicolor klmp33  

PubMed Central

Traditional synthesis of silver nanoparticles using chemical methods produces toxic substances. In contrast biological synthesis is regarded as a safe and nontoxic process but the major drawback of biological synthesis is, this process is slow. In the present investigation, we developed a rapid and green synthesis of silver nanoparticles employing a pigment produced by Streptomyces coelicolor klmp33 in just 90?s. The silver nanoparticles were characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The biobased synthesis developed in this method is a safe, rapid, and appropriate way for bulky synthesis of silver nanoparticles.

Lingappa, K.

2013-01-01

326

Structural and thermal studies of silver nanoparticles and electrical transport study of their thin films  

PubMed Central

This work reports the preparation and characterization of silver nanoparticles synthesized through wet chemical solution method and of silver films deposited by dip-coating method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and energy dispersive spectroscopy (EDX) have been used to characterize the prepared silver nanoparticles and thin film. The morphology and crystal structure of silver nanoparticles have been determined by FESEM, HRTEM, and FETEM. The average grain size of silver nanoparticles is found to be 17.5 nm. The peaks in XRD pattern are in good agreement with that of face-centered-cubic form of metallic silver. TGA/DTA results confirmed the weight loss and the exothermic reaction due to desorption of chemisorbed water. The temperature dependence of resistivity of silver thin film, determined in the temperature range of 100-300 K, exhibit semiconducting behavior of the sample. The sample shows the activated variable range hopping in the localized states near the Fermi level.

2011-01-01

327

Structural and thermal studies of silver nanoparticles and electrical transport study of their thin films  

NASA Astrophysics Data System (ADS)

This work reports the preparation and characterization of silver nanoparticles synthesized through wet chemical solution method and of silver films deposited by dip-coating method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and energy dispersive spectroscopy (EDX) have been used to characterize the prepared silver nanoparticles and thin film. The morphology and crystal structure of silver nanoparticles have been determined by FESEM, HRTEM, and FETEM. The average grain size of silver nanoparticles is found to be 17.5 nm. The peaks in XRD pattern are in good agreement with that of face-centered-cubic form of metallic silver. TGA/DTA results confirmed the weight loss and the exothermic reaction due to desorption of chemisorbed water. The temperature dependence of resistivity of silver thin film, determined in the temperature range of 100-300 K, exhibit semiconducting behavior of the sample. The sample shows the activated variable range hopping in the localized states near the Fermi level.

Majeed Khan, Mohd Abdul; Kumar, Sushil; Ahamed, Maqusood; Alrokayan, Salman A.; Alsalhi, Mohammad Saleh

2011-06-01

328

Analysis of Adhesion and Fracture Energy of NanoParticle Silver in Electronics Packaging Applications  

Microsoft Academic Search

Nano-particle silver (NPS) conductors are increasingly being investigated for package level electronics applications. Unlike traditional thick film materials and conductive inks, nano-particle conductors often do not incorporate compounds to promote interfacial adhesion such as binders used in thick films and polymer adhesives used in conductive inks as these adhesion promoters can degrade the electrical performance. The NPS is concerned with

Sung Chul Joo; Daniel F. Baldwin

2010-01-01

329

Extracellular biosynthesis and characterization of silver nanoparticles using Aspergillus flavus NJP08: A mechanism perspective  

NASA Astrophysics Data System (ADS)

The present study demonstrates an eco-friendly and low cost protocol for synthesis of silver nanoparticles using the cell-free filtrate of Aspergillus flavus NJP08 when supplied with aqueous silver (Ag+) ions. Identification of the fungal isolate was based on nuclear ribosomal DNA internal transcribed spacer (ITS) identities. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) revealed the formation of spherical metallic silver nanoparticles. The average particle size calculated using Dynamic Light Scattering measurements (DLS) was found to be 17 +/- 5.9 nm. UV-Visible and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of extracellular proteins. SDS-PAGE profiles of the extracellular proteins showed the presence of two intense bands of 32 and 35 kDa, responsible for the synthesis and stability of silver nanoparticles, respectively. A probable mechanism behind the biosynthesis is discussed, which leads to the possibility of using the present protocol in future ``nano-factories''.

Jain, Navin; Bhargava, Arpit; Majumdar, Sonali; Tarafdar, J. C.; Panwar, Jitendra

2011-02-01

330

Extracellular biosynthesis and characterization of silver nanoparticles using Aspergillus flavus NJP08: a mechanism perspective.  

PubMed

The present study demonstrates an eco-friendly and low cost protocol for synthesis of silver nanoparticles using the cell-free filtrate of Aspergillus flavus NJP08 when supplied with aqueous silver (Ag+) ions. Identification of the fungal isolate was based on nuclear ribosomal DNA internal transcribed spacer (ITS) identities. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) revealed the formation of spherical metallic silver nanoparticles. The average particle size calculated using Dynamic Light Scattering measurements (DLS) was found to be 17±5.9 nm. UV-Visible and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of extracellular proteins. SDS-PAGE profiles of the extracellular proteins showed the presence of two intense bands of 32 and 35 kDa, responsible for the synthesis and stability of silver nanoparticles, respectively. A probable mechanism behind the biosynthesis is discussed, which leads to the possibility of using the present protocol in future "nano-factories". PMID:21088776

Jain, Navin; Bhargava, Arpit; Majumdar, Sonali; Tarafdar, J C; Panwar, Jitendra

2010-11-18

331

Sintering of Inkjet-Printed Silver Nanoparticles at Room Temperature Using Intense Pulsed Light  

NASA Astrophysics Data System (ADS)

Intense pulsed light (IPL) was used to sinter printed silver nanoink patterns consisting of 20-nm to 40-nm silver nanoparticles dispersed in diethylene glycol (DEG). Three consecutive pulses at 50 J/cm2 in less than 30 ms was sufficient to adequately sinter silver nanoink patterns for printed electronics without degradation of the substrates. This is an exceptionally short time compared with that of the conventional thermal sintering process. On the sintered conductive silver patterns, neck-like junctions between nanoparticles were observed using scanning electron microscopy (SEM). The melting temperature, 194.1°C, of silver nanoparticles was found using differential scanning calorimetry (DSC). Also, x-ray diffraction (XRD) was used to find the grain size of the printed silver nanoink patterns. The IPL-sintered silver pattern had a grain size of 86.3 ± 7.2 nm. From this work, it was found that the IPL-sintered silver pattern had a low resistivity of 49 ± 3 n? m, which is low enough to be used for printed electronics.

Kang, J. S.; Ryu, J.; Kim, H. S.; Hahn, H. T.

2011-11-01

332

Visible laser induced fusion and fragmentation of thionicotinamide-capped gold nanoparticles  

Microsoft Academic Search

Thionicotinamide-capped gold nanoparticles undergo fusion as well as fragmentation upon laser pulse excitation (532 nm). The aggregation effect which is induced by thionicotinamide also disappears following laser pulse excitation. The morphological changes induced by thermal and photochemical effects were found to influence the optical properties of these particles.

Hiroaki Fujiwara; Shozo Yanagida; Prashant V. Kamat

1999-01-01

333

Sublethal effects of silver nanoparticles and dissolved silver in freshwater mussels.  

PubMed

The increasing application of silver nanoparticles (nAg) in various consumer products has raised concerns regarding toxicological impacts in the environment. It is unclear at present whether the toxicity of nAg is mainly the result of the release of ionic Ag(+) in mussels. The freshwater mussel Elliptio complanata was exposed to increasing concentrations of 20-nm nAg, 80-nm nAg, and dissolved Ag(+) for 48 h at 15°C. The following biomarkers were used to determine the mode of action of nAg-induced adverse effects: metallothioneins (MT) (ionic Ag(+) release), lipid peroxidation (LPO) (ionic Ag(+) and nanosurface interactions), heat-shock proteins (HSP) (size-related effects), protein-ubiquitin levels (size-related effects), and DNA strand breaks (ionic Ag(+) and size effects). Results revealed that the response pattern of 80 nm nAg was more closely related to ionic Ag(+) than 20 nm nAg, suggesting a more important release of dissolved Ag from 80 nm nAg. Data showed that all forms of Ag were able to increase the levels of MT and LPO, which suggests the presence of ionic Ag(+) leads to oxidative stress. However, nanoparticles were also able to induce changes in protein-ubiquitin and to a lesser extent actinomyosin-ATPase, MT, and DNA strand breaks in the digestive gland in a manner different from Ag(+), which permitted discrimination of the forms of Ag. Moreover, LPO was closely associated with DNA strand breaks in the digestive gland and was not entirely explained by induction of MT, suggesting another type of toxic interaction. It was concluded that the presence of nAg not only increases the toxic loadings of released Ag ions but also generates other and perhaps cumulative effects of nanoparticle-induced toxicity related to size and surface properties. PMID:23721583

Gagné, F; Auclair, J; Turcotte, P; Gagnon, C

2013-01-01

334

A novel green one-step synthesis of silver nanoparticles using chitosan: catalytic activity and antimicrobial studies  

NASA Astrophysics Data System (ADS)

Stable silver nanoparticles were synthesized using chitosan acting as both reducing and stabilizing agent without using any toxic chemicals. This reaction was carried out in an autoclave at a pressure of 15 psi and 120 °C temperature by varying the time. The influence of different parameters such as time, change of concentration of silver nitrate and concentration of chitosan on the formation of silver nanoparticles were studied. The synthesized silver nanoparticles were characterized by UV-visible spectroscopy, Fourier transform infrared, X-ray diffraction and transmission electron microscopy. The results of catalytic reduction of 4-nitrophenol by sodium borohydride in the presence of green synthesized silver nanoparticles were presented. The antimicrobial activity of silver nanoparticles was tested against Escherichia coli and Micrococcus luteus and was found to be possessing inhibiting property.

Venkatesham, Maragoni; Ayodhya, Dasari; Madhusudhan, Alle; Veera Babu, Nagati; Veerabhadram, Guttena

2012-12-01

335

Optical properties of functional composite silver nanoparticles and their potential use in reproductive medicine  

NASA Astrophysics Data System (ADS)

Silver nanoparticles are promising product of nanotechnology with attractive physicochemical and biological properties. The main aim of the study was to investigate optical properties of functional silver nanoparticles with different composite agents: polyvinylpyrrolidone, bovine serum albumin, hyaluronan and to explore their potential using in reproductive medicine. The date obtained in the study showed that surface modification of nanoparticles leads to change of their optical, physicochemical and biological properties. The optical properties of silver nanoparticles display, that AgNPs with PVP and BSA is most stable in PBS than AgNPs with HA. However the absorption curves after 120 hours of storage show, that AgNPs-HA were the most stable in ethanol. Results show, that silver nanoparticles did not effect on sperm viability and motility, but cause a changes of some biochemical parameters of conditioned medium, particular increase the concentration of triglycerides, activity of alkaline phosphatase, lactate dehydrogenase and decrease the activity of aspartate aminotransferase and alanine aminotransferase after 3 h of in vitro cultivation at 37°C. According to our latest data AgNPs with HA have a less toxic effect on biological processes in rabbits sperm compared with AgNPs with PVP and BSA. Nevertheless all functional composites of silver nanoparticles at the concentration of 0.1 ?g/mL have no toxic effect on spermatozoa and can be successfully applied in reproductive medicine at low concentrations as signal enhancers, optical sensors, and biomarkers.

Syrvatka, Vasyl J.; Slyvchuk, Yurij I.; Rozgoni, Ivan I.; Gevkan, Ivan I.; Bilyy, Oleksandr I.

2013-06-01

336

Invertebrate water extracts as biocompatible reducing agents for the green synthesis of gold and silver nanoparticles.  

PubMed

We report the use of water extracts of two invertebrates, snail body and earthworm, as biocompatible reducing agents for the green synthesis of gold and silver nanoparticles. The reaction conditions were optimized by varying the extract concentration, gold ion or silver ion concentration, reaction time, and reaction temperature. The gold and silver nanoparticles exhibited their characteristic surface plasmon resonance bands. Mostly spherical and amorphous shapes of the nanoparticles were synthesized. The average diameters of the gold and silver nanoparticles were 4.56 +/- 1.81 nm and 11.12 +/- 5.25 nm, respectively, when the extract of snail body was used as the reducing agent. The earthworm extracts produced gold and silver nanoparticles with average diameters of 6.70 +/- 2.69 nm and 12.19 +/- 4.28 nm, respectively. This report suggests that the invertebrate natural products have potential as biocompatible reducing agents for the green synthesis of metallic nanoparticles. This utility would open up novel applications of invertebrate natural products as nanocomposites and in nanomedicine. PMID:24079190

Han, Lina; Kim, Yeong Shik; Cho, Seonho; Park, Youmie

2013-08-01

337

Antibacterial potential of silver nanoparticles against isolated urinary tract infectious bacterial pathogens  

NASA Astrophysics Data System (ADS)

The silver nanoparticles were synthesized by chemical reduction method and the nanoparticles were characterized using ultraviolet-visible (UV-Vis) absorption spectroscopy and X-ray diffraction (XRD) studies. The synthesized silver nanoparticles were investigated to evaluate the antibacterial activity against urinary tract infectious (UTIs) bacterial pathogens. Thirty-two bacteria were isolated from mid urine samples of 25 male and 25 female patients from Thondi, Ramanathapuram District, Tamil Nadu, India and identified by conventional methods. Escherichia coli was predominant (47%) followed by Pseudomonas aeruginosa (22%), Klebsiella pneumoniae (19%), Enterobacter sp. (6%), Proteus morganii (3%) and Staphylococcus aureus (3%). The antibacterial activity of silver nanoparticles was evaluated by disc diffusion assay. P. aeruginosa showed maximum sensitivity (11 ± 0.58 mm) followed by Enterobacter sp. (8 ± 0.49 mm) at a concentration of 20 ?g disc-1 and the sensitivity was highly comparable with the positive control kanamycin and tetracycline. K. pneumoniae, E. coli, P. morganii and S. aureus showed no sensitivity against all the tested concentrations of silver nanoparticles. The results provided evidence that, the silver nanoparticles might indeed be the potential sources to treat urinary tract infections caused by P. aeruginosa and Enterobacter sp.

Jacob Inbaneson, Samuel; Ravikumar, Sundaram; Manikandan, Nachiappan

2011-12-01

338

Organic bulk heterojunction photovoltaic devices incorporating 2D arrays of cuboidal silver nanoparticles: Enhanced performance  

NASA Astrophysics Data System (ADS)

We have fabricated large-area arrays of two dimensional cuboidal silver nanoparticles on ITO substrates with good control over the coverage density using the Langmuir Blodgett technique and integrated them in functional plasmonic devices with P3HT and PCBM as photoactive layer. The results demonstrate that for device structures with 13.5% surface coverage of cuboidal silver nanoparticles, IPCE and PCE increased by 20% and ˜18% respectively. We attribute the improvements to enhanced absorption of the photoactive layer and an increase in exciton generation induced by strong local electric-field of the nanoparticles as well as an increased in the conductivity of the devices.

Leonard, Kwati; Takahashi, Yukina; You, Jing; Yonemura, Hiroaki; Kurawaki, Junichi; Yamada, Sunao

2013-10-01

339

A simple two-phase route to silver nanoparticles/polyaniline structures.  

PubMed

Novel silver nanoparticles/polyaniline composites were obtained through a two-phase water/toluene interfacial reaction. We show that by rigorously controlling the reaction time, different structures of the nanocomposites can be obtained, such as a thin sheet of polyaniline around the silver nanoparticles or a polymer mass with nanoparticles homogeneously embedded within it. Samples were characterized by FT-IR, UV-vis-NIR and Raman spectroscopy, X-ray diffraction, cyclic voltammetry, TEM, and HRTEM. Conductivity and current-voltage characteristics of the nanocomposites were measured, and the results indicate that different properties result from the different structures in which the nanocomposites were formed. PMID:16928000

Oliveira, Marcela M; Castro, Eryza G; Canestraro, Carla D; Zanchet, Daniela; Ugarte, Daniel; Roman, Lucimara S; Zarbin, Aldo J G

2006-08-31

340

Surface charge driven size evolution during the formation of self-assembled nanostructures from discrete hydrophilic silver nanoparticles  

NASA Astrophysics Data System (ADS)

We investigate the spontaneous evolution of mercaptosuccinic acid-capped silver nanoparticles (MSA-Ag) of size 2.5 ± 1.0 nm during the formation of assembled nanostructures at the air/water interface. In the phase transfer approach induced by the cationic surfactant cetyltrimethylammonium bromide (CTAB), the fusion among MSA-Ag nanoparticles is notably accelerated owing to the formation of a CTA-MSA bilayer on the particle surface. Provided that the size-selective separation is carried out in advance for these polydisperse MSA-Ag nanoparticles, either a unitary or a binary orderly superlattice composed of evolved nanoparticles is obtained at the air/water interface. For self-corrective equilibrium growth by adjusting the pH value of the bulk solution through the diffusion of HCl vapor, a competition is found between the superlattice formation and the size growth. The possible size evolution mechanism of each method is proposed. This work also shows that controllable evolution is a useful approach to prepare nanostructures with structural diversity.

Yang, Yang; Kimura, Keisaku

2007-11-01

341

Anionic 11-mercaptoundecanoic acid capped ZnO nanoparticles  

NASA Astrophysics Data System (ADS)

The anionic zinc oxide nanoparticles have been prepared at room temperature by a precipitation method using ZnCl2 and NaOH and surface modification with 11-mercaptoundecanoic acid (MUA). Atomic force microscopy (AFM) was used for definition of morphology and size of prepared nanoparticles which was proved by measurements of particle size distribution using Zetasizer. Successful coating with MUA as surfactant was acknowledged by X-ray photoelectron spectroscopy and ATR FT-IR spectroscopy.

Šimšíková, Michaela; Antalík, Marián; Ka?uchová, Mária; Škvarla, Ji?í

2013-10-01

342

Characterization of translocation of silver nanoparticles and effects on whole-genome gene expression using an in vitro intestinal epithelium coculture model.  

PubMed

Applications of nanoparticles in the food sector are eminent. Silver nanoparticles are among the most frequently used, making consumer exposure to silver nanoparticles inevitable. Information about uptake through the intestines and possible toxic effects of silver nanoparticles is therefore very important but still lacking. In the present study, we used an in vitro model for the human intestinal epithelium consisting of Caco-2 and M-cells to study the passage of silver nanoparticles and their ionic equivalents and to assess their effects on whole-genome mRNA expression. This in vitro intestine model was exposed to four sizes of silver nanoparticles for 4 h. Exposure to silver ions was included as a control since 6-17% of the silver nanoparticles were found to be dissociated into silver ions. The amount of silver ions that passed the Caco-2 cell barrier was equal for the silver ion and nanoparticle exposures. The nanoparticles induced clear changes in gene expression in a range of stress responses including oxidative stress, endoplasmatic stress response, and apoptosis. The gene expression response to silver nanoparticles, however, was very similar to that of AgNO(3). Therefore, the observed effects of the silver nanoparticles are likely exerted by the silver ions that are released from the nanoparticles. PMID:21480625

Bouwmeester, Hans; Poortman, Jenneke; Peters, Ruud J; Wijma, Elly; Kramer, Evelien; Makama, Sunday; Puspitaninganindita, Kinarsashanti; Marvin, Hans J P; Peijnenburg, Ad A C M; Hendriksen, Peter J M

2011-04-20

343

Size-Controlled Dissolution of Organic-Coated Silver Nanoparticles  

SciTech Connect

The solubility of Ag NPs can affect their toxicity and persistence in the environment. We measured the solubility of organic-coated silver nanoparticles (Ag NPs) having particle diameters ranging from 5 to 80 nm that were synthesized using various methods, and with different organic polymer coatings including poly(vinylpyrrolidone) and gum arabic. The size and morphology of Ag NPs were characterized by transmission electron microscopy (TEM). X-ray absorption fine structure (XAFS) spectroscopy and synchrotron-based total X-ray scattering and pair distribution function (PDF) analysis were used to determine the local structure around Ag and evaluate changes in crystal lattice parameters and structure as a function of NP size. Ag NP solubility dispersed in 1 mM NaHCO{sub 3} at pH 8 was found to be well correlated with particle size based on the distribution of measured TEM sizes as predicted by the modified Kelvin equation. Solubility of Ag NPs was not affected by the synthesis method and coating as much as by their size. Based on the modified Kelvin equation, the surface tension of Ag NPs was found to be {approx}1 J/m{sup 2}, which is expected for bulk fcc (face centered cubic) silver. Analysis of XAFS, X-ray scattering, and PDFs confirm that the lattice parameter, {alpha}, of the fcc crystal structure of Ag NPs did not change with particle size for Ag NPs as small as 6 nm, indicating the absence of lattice strain. These results are consistent with the finding that Ag NP solubility can be estimated based on TEM-derived particle size using the modified Kelvin equation for particles in the size range of 5-40 nm in diameter.

Ma, Rui; Levard, Clément; Marinakos, Stella M.; Cheng, Yingwen; Liu, Jie; Michel, F. Marc; Brown, Jr., Gordon E.; Lowry, Gregory V. (Duke)

2012-04-02

344

Magnetic-nanoparticle-decorated polypyrrole microvessels: toward encapsulation of mRNA cap analogues.  

PubMed

Many phosphorylated nucleoside derivatives have therapeutic potential, but their application is limited by problems with membrane permeability and with intracellular delivery. Here, we prepared polypyrrole microvessel structures modified with superparamagnetic nanoparticles for use as potential carriers of nucleotides. The microvessels were prepared via the photochemical polymerization of the monomer onto the surface of aqueous ferrofluidic droplets. A complementary physicochemical analysis revealed that a fraction of the nanoparticles was embedded in the microvessel walls, while the other nanoparticles were in the core of the vessel. SQUID (superconducting quantum interference device) measurements indicated that the incorporated nanoparticles retained their superparamagnetic properties; thus, the resulting nanoparticle-modified microvessels can be directed by an external magnetic field. As a result of these features, these microvessels may be useful as drug carriers in biomedical applications. To demonstrate the encapsulation of drug molecules, two labeled mRNA cap analogues, nucleotide-derived potential anticancer agents, were used. It was shown that the cap analogues are located in the aqueous core of the microvessels and can be released to the external solution by spontaneous permeation through the polymer walls. Mass spectrometry analysis confirmed that the cap analogues were preserved during encapsulation, storage, and release. This finding provides a foundation for the future development of anticancer therapies and for the delivery of nucleotide-based therapeutics. PMID:23597098

Kijewska, Krystyna; Jarz?bi?ska, Anita; Kowalska, Joanna; Jemielity, Jacek; K?pi?ska, Daria; Szczytko, Jacek; Pisarek, Marcin; Wiktorska, Katarzyna; Stolarski, Jaros?aw; Krysi?ski, Pawe?; Twardowski, Andrzej; Mazur, Maciej

2013-05-03

345

In situ growth of silver nanoparticles on TEMPO-oxidized jute fibers by microwave heating.  

PubMed

Cellulose fibers deposited with metallic nanoparticles as one kind of renewable, biocompatible and antimicrobial nanomaterials evoke much interest because of their versatility in various applications. Herein, for the first time, a facile, simple and rapid method was developed to fabricate TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) selectively oxidized jute fibers in situ deposited with silver nanoparticles in the absence of reducing reagents. The average size of silver nanoparticles deposited on the fibers is 50.0 ± 2.0 nm by microwave heating for 5 min and 90.0 ± 4.7 nm for 10 min heating sample, respectively. The versatile jute-silver nanoparticles nanocomposites with superior thermal stability and high crystallinity would be particularly useful for applications in the public health care and biomedical fields. PMID:23218337

Cao, Xinwang; Ding, Bin; Yu, Jianyong; Al-Deyab, Salem S

2012-09-04

346

H2-induced copper and silver nanoparticle precipitation inside sol-gel silica optical fiber preforms  

PubMed Central

Ionic copper- or silver-doped dense silica rods have been prepared by sintering sol-gel porous silica xerogels doped with ionic precursors. The precipitation of Cu or Ag nanoparticles was achieved by heat treatment under hydrogen followed by annealing under air atmosphere. The surface plasmon resonance bands of copper and silver nanoparticles have been clearly observed in the absorption spectra. The spectral positions of these bands were found to depend slightly on the particle size, which could be tuned by varying the annealing conditions. Hence, transmission electron microscopy showed the formation of spherical copper nanoparticles with diameters in the range of 3.3 to 5.6 nm. On the other hand, in the case of silver, both spherical nanoparticles with diameters in the range of 3 to 6 nm and nano-rods were obtained.

2012-01-01

347

Immobilizing silver nanoparticles onto the surface of magnetic silica composite to prepare magnetic disinfectant with enhanced stability and antibacterial activity  

Microsoft Academic Search

In this article, silver nanoparticles inlaid Fe3O4–SiO2 magnetic composite (Fe3O4–SiO2–Ag) was successfully synthesized and its potential application as an antibacterial material in water disinfection was investigated. Silver nanoparticles, with diameter of about 10nm, were anchored homogeneously and tightly onto the silica coat of Fe3O4–SiO2 magnetic nanoparticles, which increased the antibacterial abilities by avoiding the aggregation of Ag nanoparticles. The minimum

Xiaole Zhang; Hongyun Niu; Jinping Yan; Yaqi Cai

2011-01-01

348

Cellular internalization of silver nanoparticles in gut epithelia of the estuarine polychaete Nereis diversicolor.  

PubMed

Silver nanoparticles (AgNPs) are widely used which may result in environmental impacts, notably within aquatic ecosystems. As estuarine sediments are sinks for numerous pollutants, but also habitat and food for deposit feeders such as Nereis diversicolor, ingested sediments must be investigated as an important route of uptake for NPs. N. diversicolor were fed sediment spiked with either citrate capped AgNPs (30 ± 5 nm) or aqueous Ag for 10 days. Postexposure AgNPs were observed in the lumen of exposed animals, and three lines of evidence indicated direct internalization of AgNPs into the gut epithelium. With TEM, electron-dense particles resembling AgNPs were observed associated with the apical plasma membrane, in endocytotic pits and in endosomes. Energy dispersive X-ray analysis (EDX) confirmed the presence of Ag in these particles, which were absent in controls. Subcellular fractionation revealed that Ag accumulated from AgNPs was predominantly associated with inorganic granules, organelles, and the heat denatured proteins; whereas dissolved Ag was localized to the metallothionein fraction. Collectively, these results indicate separate routes of cellular internalization and differing in vivo fates of Ag delivered in dissolved and NP form. For AgNPs an endocytotic pathway appears to be a key route of cellular uptake. PMID:21517067

García-Alonso, Javier; Khan, Farhan R; Misra, Superb K; Turmaine, Mark; Smith, Brian D; Rainbow, Philip S; Luoma, Samuel N; Valsami-Jones, Eugenia

2011-04-25

349

Key factors controlling the transport of silver nanoparticles in porous media.  

PubMed

The current study investigated the mobility of four silver nanoparticles (AgNPs) stabilized using different capping agents and represent the common stabilization mechanisms as well as surface charging scenarios in reactive and nonreactive porous media. The AgNPs were (1) uncoated H2-AgNPs (electrostatically stabilized) and (2) citrate coated AgNPs (Citrate-AgNPs) (electrostatically stabilized), (3) polyvinylpyrrolidone coated AgNPs (PVP-AgNPs) (sterically stabilized), and (4) branched polyethyleneimine coated AgNPs (BPEI-AgNPs) (electrosterically stabilized). The porous media were (1) quartz sand (QS), (2) ferrihydrite-coated sand (FcS), and (3) kaolin-coated sand (KcS). The H2-AgNPs and Citrate-AgNPs were readily mobile in QS but significantly retained in FcS and KcS with more deposition achieved in the KcS media. The deposition of the H2-AgNPs and Citrate-AgNPs followed the order of KcS > FcS > QS. The PVP-AgNPs breakthrough occurred more rapid as compared to the H2-AgNPs and Citrate-AgNPs but the deposition of PVP-AgNPs followed the same order of the electrostatically stabilized AgNPs (KcS > FcS > QS). The BPEI-AgNPs were readily mobile regardless of the porous media reactivity. Physicochemical interactions were the dominant filtration mechanism in the majority of the investigated cases but straining played the major role in the deposition of the electrostatically stabilized H2-AgNPs and Citrate-AgNPs in the KcS media. The results highlight the importance of both the stabilization mechanism and capping agent chemistry as key factors governing the transport of AgNPs in the environment. PMID:23521179

El Badawy, Amro M; Hassan, Ashraf Aly; Scheckel, Kirk G; Suidan, Makram T; Tolaymat, Thabet M

2013-04-19

350

Enhancement of antidandruff activity of shampoo by biosynthesized silver nanoparticles from Solanum trilobatum plant leaf  

NASA Astrophysics Data System (ADS)

The present investigation describes simple and effective method for synthesis of silver nanoparticles via green route. Solanum trilobatum Linn extract were prepared by both conventional and homogenization method. We optimized the production of silver nanoparticles under sunlight, microwave and room temperature. The best results were obtained with sunlight irradiation, exhibiting 15-20 nm silver nanoparticles having cubic and hexagonal shape. Biosynthesized nanoparticles were highly toxic to various bacterial strains tested. In this study we report antibacterial activity against various Gram negative (Klebsiella pneumoniae, Vibrio cholerae and Salmonella typhi) and Gram positive (Staphylococcus aureus, Bacillus cereus and Micrococcus luteus) bacterial strains. Screening was also performed for any antifungal properties of the nanoparticles against human pathogenic fungal strains (Candida albicans and Candida parapsilosis). We also demonstrated that these nanoparticles when mixed with shampoo enhance the anti-dandruff effect against dandruff causing fungal pathogens (Pityrosporum ovale and Pityrosporum folliculitis). The present study showed a simple, rapid and economical route to synthesize silver nanoparticles and their applications hence has a great potential in biomedical field.

Pant, Gaurav; Nayak, Nitesh; Gyana Prasuna, R.

2012-11-01

351

Enhancement of antidandruff activity of shampoo by biosynthesized silver nanoparticles from Solanum trilobatum plant leaf  

NASA Astrophysics Data System (ADS)

The present investigation describes simple and effective method for synthesis of silver nanoparticles via green route. Solanum trilobatum Linn extract were prepared by both conventional and homogenization method. We optimized the production of silver nanoparticles under sunlight, microwave and room temperature. The best results were obtained with sunlight irradiation, exhibiting 15-20 nm silver nanoparticles having cubic and hexagonal shape. Biosynthesized nanoparticles were highly toxic to various bacterial strains tested. In this study we report antibacterial activity against various Gram negative ( Klebsiella pneumoniae, Vibrio cholerae and Salmonella typhi) and Gram positive ( Staphylococcus aureus, Bacillus cereus and Micrococcus luteus) bacterial strains. Screening was also performed for any antifungal properties of the nanoparticles against human pathogenic fungal strains ( Candida albicans and Candida parapsilosis). We also demonstrated that these nanoparticles when mixed with shampoo enhance the anti-dandruff effect against dandruff causing fungal pathogens ( Pityrosporum ovale and Pityrosporum folliculitis). The present study showed a simple, rapid and economical route to synthesize silver nanoparticles and their applications hence has a great potential in biomedical field.

Pant, Gaurav; Nayak, Nitesh; Gyana Prasuna, R.

2013-10-01

352

Appropriate In Vitro Methods for Genotoxicity Testing of Silver Nanoparticles  

PubMed Central

Objectives We investigated the genotoxic effects of 40-59 nm silver nanoparticles (Ag-NPs) by bacterial reverse mutation assay (Ames test), in vitro comet assay and micronucleus (MN) assay. In particular, we directly compared the effect of cytochalasin B (cytoB) and rat liver homogenate (S9 mix) in the formation of MN by Ag-NPs. Methods Before testing, we confirmed that Ag-NPs were completely dispersed in the experimental medium by sonication (three times in 1 minute) and filtration (0.2 µm pore size filter), and then we measured their size in a zeta potential analyzer. After that the genotoxicity were measured and especially, S9 mix and with and without cytoB were compared one another in MN assay. Results Ames test using Salmonella typhimurium TA98, TA100, TA1535 and TA1537 strains revealed that Ag-NPs with or without S9 mix did not display a mutagenic effect. The genotoxicity of Ag-NPs was also evaluated in a mammalian cell system using Chinese hamster ovary cells. The results revealed that Ag-NPs stimulated DNA breakage and MN formation with or without S9 mix in a dose-dependent manner (from 0.01 µg/mL to 10 µg/mL). In particular, MN induction was affected by cytoB. Conclusions All of our findings, with the exception of the Ames test results, indicate that Ag-NPs show genotoxic effects in mammalian cell system. In addition, present study suggests the potential error due to use of cytoB in genotoxic test of nanoparticles.

Kim, Ha Ryong; Park, Yong Joo; Shin, Da Young; Oh, Seung Min

2013-01-01

353

Spectroscopy study of silver nanoparticles fabrication using synthetic humic substances and their antimicrobial activity  

NASA Astrophysics Data System (ADS)

In this present study, silver nanoparticles were synthesized using synthetic humic substances (HSs) as reducing and stabilizing agents. Preference of synthetic HSs over natural humic matter is determined by a standardization problem resolution of the product due to the strict control of conditions of the synthetic HSs formation. It allows to receive the silver nanoparticles with the standardized biologically-active protective shell that is very important for their use, mainly in medicine. The concentration of sodium hydroxide, synthetic HSs, silver nitrate and temperature employed in the synthesis process are optimized to attain better yield, controlled size and stability by means of UV-visible technique. In the optimal reaction conditions the concentrated silver colloids (55 mM) with 99.99% yield are obtained which were stable for more than 1 year under ambient conditions. The received silver nanoparticles are characterized by UV-visible spectroscopy, X-ray diffraction (XRD), FT-IR spectroscopy and transmission electron microscopy (TEM). The antimicrobial activity of silver nanoparticles against fungal and bacterial strains is also shown.

Litvin, Valentina A.; Minaev, Boris F.

2013-05-01

354

Biosynthesis of silver nanoparticle from leaf extract of Desmodium gangeticum (L.) DC. and its biomedical potential.  

PubMed

An aqueous leaf extract of Desmodium gangeticum was employed to synthesize silver nano particles. Rapid formation of stable silver nanoparticles were observed on exposure of the aqueous leaf extract with solution of silver nitrate. The silver nanoparticles were characterized by UV-visible spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis and transmission electron microscopy (TEM), and Fourier Transform Infra-Red spectroscopy (FTIR) UV-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), and Fourier Transform Infra-Red spectroscopy (FTIR). UV-visible spectrum of the aqueous medium peaked at 450nm corresponding to the plasmon absorbance of silver nanoparticles. SEM analysis revealed the spherical shape of the particles with sizes ranging from 18 to 39nm and the EDAX spectrum confirmed the presence of silver along with other elements in the plant metabolite. Further, these biologically synthesized nanoparticles were found to be highly toxic against pathogenic bacteria Escherichia coli, thus implying significance of the present study in production of biomedical products. PMID:23973589

Thirunavoukkarasu, M; Balaji, U; Behera, S; Panda, P K; Mishra, B K

2013-08-01

355

Combined repeated-dose toxicity study of silver nanoparticles with the reproduction/developmental toxicity screening test.  

PubMed

Abstract Combined repeated-dose toxicity study of citrate-capped silver nanoparticles (7.9 ± 0.95 nm) with reproduction/developmental toxicity was investigated in rats orally treated with 62.5, 125 and 250 mg/kg, once a day for 42 days for males and up to 52 days for females. The test was performed based on the Organization for Economic Cooperation and Development test guideline 422 and Good Laboratory Practice principles. No death was observed in any of the groups. Alopecia, salivation and yellow discolouration of the lung were observed in a few rats but the symptoms were not dose-dependent. Haematology, serum biochemical investigation and histopathological analysis revealed no statistically significant differences between control group and the treated groups. Toxicity endpoints of reproduction/developmental screening test including mating, fertility, implantation, delivery and foetus were measured. There was no evidence of toxicity. PMID:23432083

Hong, Jeong-Sup; Kim, Suhyon; Lee, Sang Hee; Jo, Eunhye; Lee, Byungcheun; Yoon, Junheon; Eom, Ig-Chun; Kim, Hyun-Mi; Kim, Pilje; Choi, Kyunghee; Lee, Moo Yeol; Seo, Yeong-Rok; Kim, Younghun; Lee, Yeonjin; Choi, Jonghye; Park, Kwangsik

2013-03-19

356

Photoluminescence study of PVP capped CdS nanoparticles embedded in PVA matrix  

SciTech Connect

Photoluminescence properties of polyvinyl pyrrolidone (PVP) capped cadmium sulphide (CdS) nanoparticles embedded in polyvinyl alcohol matrix (PVA) are reported. The PVP-CdS nanoparticles are prepared by non-aqueous method wherein cadmium nitrate is used as the cadmium source and hydrogen sulphide as the sulphur source. The synthesized nanoparticles are dispersed in polyvinyl alcohol (PVA) matrix and cast as self-standing flexible (PVP-CdS)-PVA films. The nanocomposites are characterized by optical absorption spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. XRD and TEM studies show the formation of cubic CdS particles with average size {approx}3-5 nm. Thermal studies, carried out to observe the changes in PVA matrix due to the incorporation of PVP-CdS nanoparticles show strong interaction between the polymer matrix and nanoparticles. The photoluminescence emission spectra of the nanocomposites show two peaks, at 502 and 636 nm, which are attributed to the band edge and surface defects respectively, of CdS nanoparticles. Effective surface capping with optimum concentration of polyvinyl pyrrolidone leads to the quenching of surface defect-related emission.

Pattabi, Manjunatha [Department of Materials Science, Mangalore University, Mangalagangotri 574199 (India)]. E-mail: manjupattabi@yahoo.com; Saraswathi Amma, B. [Department of Materials Science, Mangalore University, Mangalagangotri 574199 (India); Manzoor, K. [Defence Laboratory, Jodhpur 342011 (India)

2007-05-03

357

Green synthesis of silver nanoparticles using Terminalia chebula extract at room temperature and their antimicrobial studies  

NASA Astrophysics Data System (ADS)

A green rapid biogenic synthesis of silver nanoparticles (Ag NPs) using Terminalia chebula (T. chebula) aqueous extract was demonstrated in this present study. The formation of silver nanoparticles was confirmed by Surface Plasmon Resonance (SPR) at 452 nm using UV-visible spectrophotometer. The reduction of silver ions to silver nanoparticles by T. chebula extract was completed within 20 min which was evidenced potentiometrically. Synthesised nanoparticles were characterised using UV-vis spectroscopy, Fourier transformed infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The hydrolysable tannins such as di/tri-galloyl-glucose present in the extract were hydrolyzed to gallic acid and glucose that served as reductant while oxidised polyphenols acted as stabilizers. In addition, it showed good antimicrobial activity towards both Gram-positive bacteria (S. aureus ATCC 25923) and Gram-negative bacteria (E. coli ATCC 25922). Industrially it may be a smart option for the preparation of silver nanoparticles.

Mohan Kumar, Kesarla; Sinha, Madhulika; Mandal, Badal Kumar; Ghosh, Asit Ranjan; Siva Kumar, Koppala; Sreedhara Reddy, Pamanji

2012-06-01

358

Biosynthesis of Silver Nanoparticles by Phytopathogen Xanthomonas oryzae pv. oryzae Strain BXO8.  

PubMed

Extracellular biogenic synthesis of silver nanoparticles with various shapes using the rice bacterial blight bacterium Xanthomonas oryzae pv. oryzae BXO8 is reported. The synthesized silver nanoparticles were characterized by UV-Vis spectroscopy, powder X-ray diffractometry (XRD), scanning electron microscopy, energy dispersive X-ray spectrometry, and highresolution transmission electron microscopy (HR-TEM). Based on the evidence of HR-TEM, the synthesized particles were found to be spherical, with anisotropic structures such as triangles and rods, with an average size of 14.86 nm. The crystalline nature of silver nanoparticles was evident from the bright circular spots in the SAED pattern, clear lattice fringes in the high-resolution TEM images, and peaks in the XRD pattern. The FTIR spectrum showed that biomolecules containing amide and carboxylate groups are involved in the reduction and stabilization of the silver nanoparticles. Using such a biological method for the synthesis of silver nanoparticles is a simple, viable, cost-effective, and environmentally friendly process, which can be used in antimicrobial therapy. PMID:23751558

Narayanan, Kannan Badri; Sakthivel, Natarajan

2013-09-28

359

Bacterial inactivation using silver-coated magnetic nanoparticles as functional antimicrobial agents.  

PubMed

The ability for silver nanoparticles to function as an antibacterial agent while being separable from the target fluids is important for bacterial inactivation in biological fluids. This report describes the analysis of the antimicrobial activities of silver-coated magnetic nanoparticles synthesized by wet chemical methods. The bacterial inactivation of several types of bacteria was analyzed, including Gram-positive bacteria ( Staphylococcus aureus and Bacillus cereus ) and Gram-negative bacteria ( Pseudomonas aeruginosa , Enterobacter cloacae , and Escherichia coli ). The results have demonstrated the viability of the silver-coated magnetic nanoparticles for achieving effective bacterial inactivation efficiency comparable to and better than that of silver nanoparticles conventionally used. The bacteria inactivation efficiency of our silver-coated MnZn ferrite (MZF@Ag) nanoparticles was also determined for blood platelets samples, demonstrating the potential of utilization in inactivating bacterial growth in platelets prior to transfusion to ensure blood product safety, which also has important implications for enabling the capability of effective separation, delivery, and targeting of the antibacterial agents. PMID:21999710

Wang, Lingyan; Luo, Jin; Shan, Shiyao; Crew, Elizabeth; Yin, Jun; Zhong, Chuan-Jian; Wallek, Brandi; Wong, Season S S

2011-10-14

360

Stepwise Embryonic Toxicity of Silver Nanoparticles on Oryzias latipes  

PubMed Central

The developmental toxicity of silver nanoparticles (AgNPs) was investigated following exposure of Oryzias latipes (medaka) embryos to 0.1?1?mg/L of homogeneously dispersed AgNPs for 14?days. During this period, developmental endpoints, including lethality, heart rate, and hatching rate, were evaluated by microscopy for different stages of medaka embryonic development. To compare toxic sensitivity, acute adult toxicity was assessed. There was no difference in acute lethal toxicity between embryo and adult medaka. Interestingly, we found that the increase in stepwise toxicity was dependent on the developmental stage of the embryo. Lethal embryonic toxicity increased from exposure days 1 to 3 and exposure days 5 to 8, whereas there was no change from exposure days 3 to 5. In addition, 7 d exposure to 0.8?mg/L AgNPs resulted in significant heart beat retardation in medaka embryos. AgNPs also caused a dose-dependent decrease in the hatching rate and body length of larvae. These results indicate that AgNP exposure causes severe developmental toxicity to medaka embryos and that toxicity levels are enhanced at certain developmental stages, which should be taken into consideration in assessments of metallic NPs toxicity to embryos.

Cho, Jae-Gu; Kim, Kyung-Tae; Lee, Jae-woo; Kim, Ji-Eun; Kim, Jungkon; Lee, Byoung-Cheun; Jo, Eun-Hye; Yoon, Junheon; Eom, Ig-chun; Choi, Kyunghee; Kim, Pilje

2013-01-01

361

Interaction of multi-functional silver nanoparticles with living cells  

NASA Astrophysics Data System (ADS)

Silver nanoparticles (AgNPs) are widely used in household products and in medicine due to their antibacterial and to wound healing properties. In recent years, there is also an effort for their use in biomedical imaging and photothermal therapy. The primary reason behind the effort for their utility in biomedicine and therapy is their unique plasmonic properties and easy surface chemistry for a variety of functionalizations. In this study, AgNPs modified with glucose, lactose, oligonucleotides and combinations of these ligands are investigated for their cytotoxicity and cellular uptake in living non-cancer (L929) and cancer (A549) cells. It is found that the chemical nature of the ligand strongly influences the toxicity and cellular uptake into the model cells. While the lactose-and glucose-modified AgNPs enter the L929 cells at about the same rate, a significant increase in the rate of lactose-modified AgNPs into the A549 cells is observed. The binding of oligonucleotides along with the carbohydrate on the AgNP surfaces influences the differential uptake rate pattern into the cells. The cytotoxicity study with the modified AgNPs reveals that only naked AgNPs influence the viability of the A549 cells. The findings of this study may provide the key to developing effective applications in medicine such as cancer therapy.

Sur, Ilknur; Cam, Dilek; Kahraman, Mehmet; Baysal, Asli; Culha, Mustafa

2010-04-01

362

Casein hydrolytic peptides mediated green synthesis of antibacterial silver nanoparticles.  

PubMed

A green route based on the casein hydrolytic peptides (CHPs) has been established for the synthesis of highly stable and smaller sized (10±5nm) silver nanoparticles (AgNPs), without producing any type of toxic byproducts. The formation of AgNPs was triggered by the addition of an aqueous NaOH solution due to the catalytic properties of OH(-) and/or hydration of the functional groups of CHPs. The 99% transformation of Ag ions (9mM) in 20mL reaction mixture into identical AgNPs using substantially low concentration of CHPs (0.3%, wt/v), indicates that the present system is suitable for the "low volume high concentration" nanosynthesis. The AgNPs obtained by CHPs showed the minimum inhibitory concentration at 24.5ppm against both gram positive and gram negative bacterial cultures with a 96-well titer plate assay. The AgNPs possibly interact with the cell wall structures of pathogenic bacteria, Escherichia coli, causing changes in the cell morphology and the formation of porous structures, as observed by scanning electron microscopy. This eco-friendly process for the bio-mimetic production of AgNPs is a nontoxic and a competitive alternative to existing physical and chemical methods for the production of nano-scale inorganic materials. PMID:23537832

Ghodake, Gajanan; Lim, Seong-Rin; Lee, Dae Sung

2013-03-14

363

Antibacterial activity and increased freeze-drying stability of sialyllactose-reduced silver nanoparticles using sucrose and trehalose.  

PubMed

The resistance to current antibiotics results in the emergence of health-threatening bacteria. Silver nanoparticles are known to exhibit broad-spectrum antibacterial activities without the development of resistance. Herein, we developed a green synthetic method for the preparation of silver nanoparticles with sialyllactose instead of toxic chemicals as a reducing agent, which would improve its therapeutic applicability and increase its biocompatibility. Oven incubation, autoclaving and microwave irradiation methods were applied to prepare the silver nanoparticles. High resolution-transmission electron microscopy and atomic force microscopy images revealed mostly spherical and amorphous silver nanoparticles with an average diameter of 23.64 nm. Fourier Transform-infrared spectra suggest that the N-H amide of sialyllactose might be involved in the binding of silver nanoparticles. Based on thermogravimetric analyses, 2,3-sialyllactose-reduced silver nanoparticles are composed of 54.3 wt% organic components and 45.7 wt% metallic silver. Enhanced antibacterial activities of silver nanoparticles (approximately 8-fold) were observed against Pseudomonas aeruginosa, Escherichia coli and Salmonella typhimurium (minimum inhibitory concentration 16 microg/mL). Next, we employed the use of carbohydrate stabilizers to increase the stability of silver nanoparticles during a freeze-drying process. It was found that sucrose and trehalose were the most effective stabilizers. In addition, silver nanoparticles possessed excellent salt stability as well as on-the-shelf stability in the presence of these stabilizers. Derivatives of sialic acid are known to be anti-influenza agents; therefore, the newly prepared silver nanoparticles may serve as useful antibacterial and antiviral agents to cope with both pathogenic bacteria and viruses in the near future. PMID:22852321

Noh, Hwa Jung; Im, A-Rang; Kim, Hyun-Seok; Sohng, Jae Kyung; Kim, Chong-Kook; Kim, Yeong Shik; Cho, Seonho; Park, Youmie

2012-05-01

364

Importance of surface coatings and soluble silver in silver nanoparticles toxicity to Daphnia magna.  

PubMed

Silver nanoparticles (AgNPs) are now widely used in antibacterial and personal care products. However, the underlying physicochemical mechanisms leading to the toxicity of AgNPs are still under debate. The present study revealed the different effects of three surface coatings (including lactate, polyvinylpyrrolidone, and sodium dodecylbenzene sulfonate, as AgNPs-L, AgNPs-P and AgNPs-S, respectively) on the acute toxicity of AgNPs to a model freshwater cladoceran Daphnia magna. Significant difference in mortality was observed among these three surface coatings of AgNPs, with the 48-h 50% lethal concentrations (48-h LC50s) of AgNPs-L, AgNPs-P and AgNPs-S being 28.7, 2.0 and 1.1 ?g/L, respectively. In contrast, when the daphnids were exposed to soluble Ag released from AgNPs-L and AgNPs-P, the difference in the 48-h LC50s between the two surface coatings (1.1 ?g/L and 0.57 ?g/L, respectively) decreased significantly. These 48-h LC50s were comparable to that of AgNO? (0.88 ?g/L), indicating that soluble Ag was the primarily cause of the observed toxicity of AgNPs. Indeed, the surface coatings influenced the dissolution of AgNPs into soluble Ag, resulting in the different toxicities of AgNP to the daphnids. Additionally, the 48-h bioaccumulation of AgNPs in daphnids was also dependent on the characteristics of the nanoparticles, such as particle size and surface coating. Our results point to the need to consider the effects of surface coating on the toxicity of AgNPs in environmental risk assessments. PMID:21591875

Zhao, Chun-Mei; Wang, Wen-Xiong

2011-05-18

365

Surface magnetism in amine-capped ZnO nanoparticles  

NASA Astrophysics Data System (ADS)

Magnetic behaviors of pure ZnO nanoparticles have been investigated both experimentally and theoretically. It is found that monodisperse ZnO nanoparticles wrapped with oleylamine with an average particle size of about 9.6 nm prepared by thermal decomposition do show ferromagnetic behavior with a saturation magnetization of about 34 memu g-1 and coercive force of about 22 Oe, whereas ZnO nanoparticles with an average particle size of 5.2 nm prepared by ultrasonic irradiation without solvents show a weak ferromagnetic property with a saturation magnetization of about 0.12 memu g-1 and coercive force of about 150 Oe at ambient temperature. First-principles calculations reveal that the 2p holes on the atoms at the surface (dangling bond of O atoms at ZnO(000\\bar {1} ) or 2p electrons of N atom in NH3 adsorbed on Zn(0001)) could be the source for the magnetic behavior of oxide nanoparticles.

Liu, J. F.; Liu, En-Zuo; Wang, H.; Su, N. H.; Qi, J.; Jiang, J. Z.

2009-04-01

366

Biological synthesis of silver and gold nanoparticles using apiin as reducing agent.  

PubMed

We report a novel strategy for the biological synthesis of anisotropic gold and quasi-spherical silver nanoparticles by using apiin as the reducing and stabilizing agent. The size and shape of the nanoparticles can be controlled by varying the ratio of metal salts to apiin compound in the reaction medium. The resultant nanoparticles were characterized by UV-vis-NIR, transmission electron microscopy (TEM), FT-IR spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The interaction between nanoparticles with carbonyl group of apiin compound was confirmed by using FT-IR analysis. TEM photograph confirming the average size of the gold and silver nanoparticles were found to be at 21 and 39 nm. The NIR absorption of the gold nanotriangles is expected to be of application in hyperthermia of cancer cells and in IR-absorbing optical coatings. PMID:18977643

Kasthuri, J; Veerapandian, S; Rajendiran, N

2008-09-30

367

Biosynthesis of silver nanoparticles from the marine seaweed Sargassum wightii and their antibacterial activity against some human pathogens  

NASA Astrophysics Data System (ADS)

In this paper, we have reported on biological synthesis of nano-sized silver and its antibacterial activity against human pathogens. The nanoparticles of silver were formed by the reduction of silver nitrate to aqueous silver metal ions during exposure to the extract of marine seaweed Sargassum wightii. The optical properties of the obtained silver nanoparticles were characterized using UV-visible absorption and room temperature photoluminescence. The X-ray diffraction results reveal that the synthesized silver nanoparticles are in the cubic phase. The existence of functional groups was identified using Fourier transform infrared spectroscopy. The morphology and size of the synthesized particles were studied with atomic force microscope and high-resolution transmission electron microscope measurements. The synthesized nanoparticles have an effective antibacterial activity against S. aureus, K. pneumoniae, and S. typhi.

Shanmugam, N.; Rajkamal, P.; Cholan, S.; Kannadasan, N.; Sathishkumar, K.; Viruthagiri, G.; Sundaramanickam, A.

2013-09-01

368

Silver nanoparticle-mediated enhancement in growth and antioxidant status of Brassica juncea.  

PubMed

Metal nanoparticles can potentially be used as tools for engineering biological redox reactions. Present study underlines the effect of silver metal nanoparticles (at 0, 25, 50, 100, 200 and 400 ppm) on the growth and antioxidant status of 7-day-old Brassica juncea seedlings. Fresh weight, root and shoot length, and vigor index of seedlings is positively affected by silver nanoparticle treatment. It induced a 326 % increase in root length and 133 % increase in vigor index of the treated seedlings. Improved photosynthetic quantum efficiency and higher chlorophyll contents were recorded in leaves of treated seedlings, as compared to the control seedlings. Levels of malondialdehyde and hydrogen peroxide decreased in the treated seedlings. Nanoparticle treatment induced the activities of specific antioxidant enzymes, resulting in reduced reactive oxygen species levels. Decrease in proline content confirmed the improvement in antioxidant status of the treated seedlings. The observed stimulatory affects of silver nanoparticles are found to be dose dependent, with 50 ppm treatment being optimum for eliciting growth response. Present findings, for the first time indicate that silver nanoparticles promote the growth of B. juncea seedlings by modulating their antioxidant status. PMID:22692847

Sharma, Priyadarshini; Bhatt, Deepesh; Zaidi, M G H; Saradhi, P Pardha; Khanna, P K; Arora, Sandeep

2012-06-13

369

Rapid synthesis of silver nanoparticles using dried medicinal plant of basil.  

PubMed

Plants respond to heavy metal stress by metal complexation process like production of phytochelations or by other metal chelating peptides. In this paper we report the synthesis of silver nanoparticles (AgNPs) from the room dried stem and root of Ocimum sanctum. The broth of the plant is used as a reducing agent for the synthesis of Ag nanoparticles at room temperature. The reaction process was simple and was monitored by ultraviolet-visible spectroscopy (UV-vis). There was formation of highly stable silver nanoparticles in the solution. The morphology and crystalline phase of the NPs were determined from transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD) spectra. Transmission Electron Microscopy studies showed that the silver nanoparticles obtained from roots and stem were of sizes 10+/-2 and 5+/-1.5 nm, respectively. The various phytochemicals present within the ocimum plant result in effective reduction of silver salts to nanoparticles but their chemical framework is also effective at wrapping around the nanoparticles to provide excellent robustness against agglomeration. PMID:20656463

Ahmad, Naheed; Sharma, Seema; Alam, Md K; Singh, V N; Shamsi, S F; Mehta, B R; Fatma, Anjum

2010-07-24

370

Green biosynthesis of silver nanoparticles using Callicarpa maingayi stem bark extraction.  

PubMed

Different biological methods are gaining recognition for the production of silver nanoparticles (Ag-NPs) due to their multiple applications. The use of plants in the green synthesis of nanoparticles emerges as a cost effective and eco-friendly approach. In this study the green biosynthesis of silver nanoparticles using Callicarpa maingayi stem bark extract has been reported. Characterizations of nanoparticles were done using different methods, which include; ultraviolet-visible spectroscopy (UV-Vis), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDXF) spectrometry, zeta potential measurements and Fourier transform infrared (FT-IR) spectroscopy. UV-visible spectrum of the aqueous medium containing silver nanoparticles showed absorption peak at around 456 nm. The TEM study showed that mean diameter and standard deviation for the formation of silver nanoparticles were 12.40 ± 3.27 nm. The XRD study showed that the particles are crystalline in nature, with a face centered cubic (fcc) structure. The most needed outcome of this work will be the development of value added products from Callicarpa maingayi for biomedical and nanotechnology based industries. PMID:22801364

Shameli, Kamyar; Bin Ahmad, Mansor; Jaffar Al-Mulla, Emad A; Ibrahim, Nor Azowa; Shabanzadeh, Parvaneh; Rustaiyan, Abdolhossein; Abdollahi, Yadollah; Bagheri, Samira; Abdolmohammadi, Sanaz; Usman, Muhammad Sani; Zidan, Mohammed

2012-07-16

371

Deposition of Silver Nanoparticles on Multiwalled Carbon Nanotubes Grafted with Hyperbranched Poly(amidoamine) and Their Antimicrobial Effects  

Microsoft Academic Search

A nanohybrid comprising silver nanoparticles within third-generation dendritic poly(amidoamine) (PAMAM) grafted onto multiwalled carbon nanotubes (MWNTs) was applied as an antimicrobial agent in solution. The high abundance of amine groups on the dendrimer-modified MWNTs (d-MWNTs) provided sites for reduction and precipitation of silver nanoparticles from silver acetate aqueous solution, resulting in carbon nanotubes\\/ Ag nanohybrids (d-MWNTs\\/Ag). The content of PAMAM

Wei Yuan; Guohua Jiang; Jianfei Che; Xiaobao Qi; Rong Xu; Matthew W. Chang; Yuan Chen; Su Yin Lim; Jie Dai; Mary B. Chan-Park

2008-01-01

372

Structural distortions in 5-10 nm silver nanoparticles under high pressure  

SciTech Connect

We present experimental evidence that silver nanoparticles in the size range of 5-10 nm undergo a reversible structural transformation under hydrostatic pressures up to 10 GPa. We have used x-ray diffraction with a synchrotron light source to investigate pressure-dependent and size-dependent trends in the crystal structure of silver nanoparticles in a hydrostatic medium compressed in a diamond-anvil cell. Results suggest a reversible linear pressure-dependent rhombohedral distortion which has not been previously observed in bulk silver. We propose a mechanism for this transition that considers the bond-length distribution in idealized multiply twinned icosahedral particles. To further support this hypothesis, we also show that similar measurements of single-crystal platinum nanoparticles reveal no such distortions.

Koski, Kristie J.; Kamp, Noelle M.; Kunz, Martin; Knight, Jason K.; Alivisatos, A.P.; Smith, R.K.

2008-10-13

373

Enhanced electrical conductivity of silver nanoparticles for high frequency electronic applications.  

PubMed

An enhancement in the electrical performance of low temperature screen-printed silver nanoparticles (nAg) has been measured at frequencies up to 220 GHz. We show that for frequencies above 80 GHz the electrical losses in coplanar waveguide structures fabricated using nAg at 350 °C are lower than those found in conventional thick film Ag conductors consisting of micrometer-sized grains and fabricated at 850 °C. The improved electrical performance is attributed to the better packing of the silver nanoparticles resulting in lower surface roughness by a factor of 3. We discuss how the use of silver nanoparticles offers new routes to high frequency applications on temperature sensitive conformal substrates and in sub-THz metamaterials. PMID:23151185

Alshehri, Ali H; Jakubowska, Malgorzata; M?o?niak, Anna; Horaczek, Michal; Rudka, Diana; Free, Charles; Carey, J David

2012-11-26

374

A unique solid-solid transformation of silver nanoparticles on reactive ion-etching-processed silicon  

NASA Astrophysics Data System (ADS)

Processes that combine nanoparticle suspensions with micromechanical or microelectronics platforms can reveal new phenomena unique to nanoscale objects. We report that silver nanoparticles react with silicon wafers that have been patterned by reactive ion etching (RIE) in SF6/O2 plasma. This reaction results in the localized deposition of silver on the patterns. Through the modification of the reaction conditions, the reaction mechanism was explored. Redeposition of the sputtered RIE products is suggested as the key to this transformation. The new silver deposition process was utilized to localize the growth of gold nanoparticles and silicon nanowires on the vertical sidewalls of patterns in silicon, demonstrating a simple route to the fabrication of overhanging nanoscale objects.

Lee, Seung Yong; Rabin, Oded

2012-02-01

375

Ion synthesis of silver nanoparticles in viscous-fluid epoxy resin  

NASA Astrophysics Data System (ADS)

A method is described for the ion synthesis of silver nanoparticles in epoxy resin that is in a viscousfluid state (viscosity 30 Pa s) during irradiation. The viscous-fluid or glassy polymer is implanted by 30-keV silver ions at a current density of 4 ?A/cm2 in the ion beam in the dose range 2.2 × 1016-7.5 × 1016 ions/cm2. The epoxy layers thus synthesized contain silver nanoparticles, which are studied by transmission electron microscopy and optical absorption spectroscopy. The use of the viscous-fluid state increases the diffusion coefficient of the implanted impurity, which stimulates the nucleation and growth of nanoparticles at low implantation doses and allows a high factor of filling of the polymer with the metal to be achieved.

Stepanov, A. L.; Khaibullin, R. I.; Valeev, V. F.; Osin, Yu. N.; Nuzhdin, V. I.; Faizrakhmanov, I. A.

2009-08-01

376

Green synthesis of finely-dispersed highly bactericidal silver nanoparticles via modified Tollens technique  

Microsoft Academic Search

In this article, we represent a versatile and effective technique which using non-toxic chemicals to prepare stable aqueous dispersions of silver nanoparticles (NPs) via modified Tollens process. It was shown that as-prepared silver colloids consisted of finely-dispersed NPs with average diameter about 10nm and a relatively narrow size distribution. Moreover, they could be stored very stable after several months without

Anh-Tuan Le; P. T. Huy; Phuong Dinh Tam; Tran Quang Huy; Phung Dac Cam; A. A. Kudrinskiy; Yu A. Krutyakov

2010-01-01

377

In vitro effects of silver nanoparticles on the mitochondrial respiratory chain  

Microsoft Academic Search

Silver has been used for years in medicine; it has known antimicrobial properties. Additionally, silver has been used in water\\u000a and air filtration to eliminate microorganisms, and, more recently, as a biocide to prevent infections in burns. In contact\\u000a with the human body, nanoparticles can elicit a spectrum of tissue responses such as the generation of reactive oxygen species,\\u000a decreased

Cláudio Sérgio Costa; João Vitor Vieira Ronconi; Juliana Felipe Daufenbach; Cinara Ludvig Gonçalves; Gislaine Tezza Rezin; Emilio Luiz Streck; Marcos Marques da Silva Paula

2010-01-01

378

Fabrication and kinetic studies of a novel silver nanoparticles–glucose oxidase bioconjugate  

Microsoft Academic Search

In this study, a new effective, pH and thermally stable glucose oxidase (GOX)–silver nanoparticles (AgNPs) bioconjugate was designed. AgNPs were synthesized based on the reduction of silver nitrate (AgNO3) by sodium borohydride (NaBH4) using two simple procedures. Periodic acid was used for oxidation of the GOX and emission of Lucifer yellow (LyCH) was monitored by spectrofluorometer for evaluation of the

N. Hashemifard; A. Mohsenifar; B. Ranjbar; A. Allameh; A. S. Lotfi; B. Etemadikia

2010-01-01

379

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

380

Synthesis and direct interactions of silver colloidal nanoparticles with pollutant gases  

Microsoft Academic Search

Silver nanoparticles (NPs) were synthesized in organic solvents. Spontaneous reduction of silver salts takes place in N,N?-dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) at room temperature. The formed colloids are not stable without a\\u000a stabilizing agent, hence rarely used, and inexpensive organic molecules (?-cyclodextrin and cholic acid) were used as surface\\u000a modifiers in DMF. The stabilization was successful; the Ag

Rita Patakfalvi; David Diaz; Donaji Velasco-Arias; Geonel Rodriguez-Gattorno; Patricia Santiago-Jacinto

2008-01-01

381

Synthesis and characterization of magnetic Co nanoparticles: A comparison study of three different capping surfactants  

SciTech Connect

This paper compares the performance of three long-chain acids-oleic and elaidic (both olefinic) and stearic (aliphatic)-as a capping agent in the synthesis of magnetic Co nanoparticles. The particles were formed through thermal decomposition of dicobalt octacarbonyl in toluene in the presence of the long-chain acid, and characterized by TEM, high-resolution TEM, and SQUID measurements. Infrared spectra revealed that some of the added olefinic acid was transformed from cis- to trans-configuration (for oleic acid) or from trans- to cis- (for elaidic acid) to facilitate the formation of a densely packed monolayer on the surface of Co nanoparticles. As compared to aliphatic acids, olefinic acids are advantageous for dense packing on small particles with high surface curvatures due to a bent shape of the cis-isomer. The presence of an olefinic acid is able to control particle growth, stabilize the colloidal suspension, and prevent the final product from oxidation by air. Our results indicate that oleic acid, elaidic acid, and a mixture of oleic/stearic acids or elaidic/stearic acids have roughly the same performance in serving as a capping agent for the synthesis of Co nanoparticles with a spherical shape and narrow size distribution. - Graphical abstract: Magnetic Co nanoparticles were synthesized in the presence of different capping agents and the effect of their molecular structures on the morphology of Co nanoparticles was analyzed. The transformation between cis- and trans-isomers of olefinic acids was critical to the formation of a densely packed monolayer on the surface of small nanoparticles characterized by high curvatures.

Lu Yu [Department of Chemistry, University of Washington, Seattle, WA 98195 (United States); Lu Xianmao [Department of Biomedical Engineering, Washington University, St. Louis, MO 63130 (United States); Mayers, Brian T.; Herricks, Thurston [Department of Chemistry, University of Washington, Seattle, WA 98195 (United States); Xia Younan [Department of Chemistry, University of Washington, Seattle, WA 98195 (United States); Department of Biomedical Engineering, Washington University, St. Louis, MO 63130 (United States)], E-mail: xia@biomed.wustl.edu

2008-07-15

382

Comparison of toxicity of uncoated and coated silver nanoparticles  

NASA Astrophysics Data System (ADS)

This study compares toxic effects of uncoated (20, 40, 60 and 80 nm) and OECD (Organization for Economic Co-operation and Development) standard citrate- and polyvinylpyrrolidone (PVP)-coated (10, 50, and 75 nm) silver nanoparticles (Ag-NPs) in J774A. 1 macrophage and HT29 epithelial cells. The cells were exposed to different concentrations (silver content) of Ag-NPs for 24 h. Analysis showed that uncoated Ag-NPs, at a concentration of 1 ?g/ml, decreased cell viability by 20-40% and that 20 and 40 nm particles were 10% more cytotoxic than the 60 and 80 nm particles. In exposures to coated Ag-NPs, cell viability dropped at 25 ?g/ml or higher concentrations, and the effects were also size-dependent. PVP-coated particles induced greater cytotoxicity than citrate-coated particles. Changes in sub-cellular architecture were observed in J774A. 1 cells upon exposure to test Ag-NPs. Furthermore, uncoated Ag-NPs (1 ?g/mL) decreased the expression of selected cytokines including TNF-?, IL-1?, and IL-12 (p70) in J774A. 1 and IL-8 in HT29 cells. In contrast, both citrate- and PVP-coated Ag-NPs increased the expression of these cytokines at higher concentrations (25 ?g/ml), and PVP-coated particles elevated cytokine levels the most. Moreover, while uncoated Ag-NPs resulted in decreased glutathione (GSH) content and increased superoxide dismutase (SOD) activity in test cells in a size-dependent manner at 1 ?g/ml, coated Ag-NPs caused non-significant changes in GSH and SOD, even at the highest test concentrations. Lastly, uncoated (20 and 40 nm) at 1 ?g/ml and coated Ag-NPs (10 nm PVP) at 50 ?g/ml slightly increased the production of reactive oxygen species (ROS). Our data showed that uncoated Ag-NPs are more toxic than coated Ag-NPs. While uncoated Ag-NPs appear to suppress inflammatory responses and enhance oxidative stress in the test cells, coated Ag-NPs induce toxic effects through up-regulation of cytokines. Our findings support the toxicity of Ag-NPs as being size- and coating- dependent while providing additional insight on the health impact of Ag-NPs.

Nguyen, K. C.; Seligy, V. L.; Massarsky, A.; Moon, T. W.; Rippstein, P.; Tan, J.; Tayabali, A. F.

2013-04-01

383

Self-assembly of polyoxometalate macroanion-capped pd0 nanoparticles in aqueous solution.  

PubMed

The self-assembly behavior of polyoxometalate (POM) macroanion-capped 3-nm-radius Pd (0) nanoparticles in aqueous solution is reported. Pd(0) nanoparticles are synthesized from reducing K(2)PdCl(4) by using Dawson-type V-substituted POM K(9)[H(4)PV (IV)W(17)O(62)] (HPV(IV)) clusters as the reductant and stabilizer simultaneously in acidic aqueous solutions. The starting molar ratio of K(2)PdCl(4) to HPV(IV) (R value) in solution is important to the formation of Pd nanoparticles. When R < 0.6, approximately 20-nm-radius Pd(0) colloidal nanocrystals are formed. When R > or = 0.6, HPV-capped (and therefore negatively charged) 3-nm-radius Pd(0) nanoparticles are formed, which can further self-assemble into stable, hollow, spherical, 30-50-nm-radius supramolecular structures in solution without precipitation, as confirmed by light scattering and transmission electron microscopy studies. This structure resembles the unique supramolecular structure formed by hydrophilic POM macroanions in polar solvents, which we refer to as "blackberry" structures. It is the first evidence that the blackberry formation can occur in hydrophobic nanoparticle systems when the surface of nanoparticles is modified to be partially hydrophilic. Counterions play an important role in the self-assembly of Pd nanoparticles, possibly providing an attractive force for blackberry formation, which is the case for blackberry formation in POM macroanionic solutions. Our results suggest that the blackberry formation is not a specific property of POM macroions but most likely a general phenomenon for nanoparticles with relatively hydrophilic surfaces and suitable sizes and charges in a polar solvent. PMID:18439035

Zhang, Jie; Keita, Bineta; Nadjo, Louis; Mbomekalle, Israel Martyr; Liu, Tianbo

2008-04-26

384

Optical studies of capped CdSe nanoparticles and their photocatalytic activity for degradation of methylene blue dye  

NASA Astrophysics Data System (ADS)

Polyethylene glycol (PEG) and mercaptoethanol (ME)-capped CdSe nanoparticles (NPs) have been successfully prepared and systematic investigation on structural, optical and photocatalytic properties is presented. The intrinsic characteristics of resulting nanoparticles were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible and photoluminescence (PL) spectrophotometer. Cubic phase, nearly uniform size (˜10 nm) and spherical morphology of the synthesized nanoparticles were established through XRD and TEM analysis. Spectroscopic measurements exhibit that capping agent can effectively tune energy band structure. ME-capped CdSe NPs exhibit higher light emission efficiency as compared to PEG capping. Photocatalytic activity of CdSe nanoparticles on methylene blue (MB) dye, a significant enhancement was observed in the photodegradation efficiency. A maximum degradation of MB dye (73.5%) was obtained.

Taheri Otaqsara, Seyed Mohammad; Nemati-Kande, Ebrhim; Barzegar, Ramin

2013-04-01

385

Rapid photogeneration of silver nanoparticles in ethanolic solution: a kinetic study.  

PubMed

Ag nanoparticles have been synthesized via UV irradiation of ethanolic solution of AgNO3 in presence of pluronic F127 surfactant. This study is aimed at developing a rapid, simple and green method to prepare Ag nanoparticles and understanding its generation kinetics. The formation dependency of silver nanoparticles on the concentration of reactants, UV exposure time and temperature has been investigated by using UV-vis spectroscopy. The 2D map technique has been used for the first time to estimate the switching time between the nucleation and growth of Ag nanoparticles. Appropriate kinetic models were used for modelling of both stages. PMID:23123241

Yahyaei, Bahareh; Azizian, Saeid

2012-10-12

386

Multipositional silica-coated silver nanoparticles for high-performance polymer solar cells.  

PubMed

We demonstrate high-performance polymer solar cells using the plasmonic effect of multipositional silica-coated silver nanoparticles. The location of the nanoparticles is critical for increasing light absorption and scattering via enhanced electric field distribution. The device incorporating nanoparticles between the hole transport layer and the active layer achieves a power conversion efficiency of 8.92% with an external quantum efficiency of 81.5%. These device efficiencies are the highest values reported to date for plasmonic polymer solar cells using metal nanoparticles. PMID:23611150

Choi, Hyosung; Lee, Jung-Pil; Ko, Seo-Jin; Jung, Jae-Woo; Park, Hyungmin; Yoo, Seungmin; Park, Okji; Jeong, Jong-Ryul; Park, Soojin; Kim, Jin Young

2013-04-23

387

A simple way to prepare Cupric oleate capped AgI nanoparticles  

SciTech Connect

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

Song Meirong [Laboratory of Special Functional Materials, Henan University, Kaifeng 475001 (China); Zhang Zhijun [Laboratory of Special Functional Materials, Henan University, Kaifeng 475001 (China)]. E-mail: s234soow@henu.edu.cn

2004-12-02

388

Selective growth of silver nanoparticle arrays on nanoimprinted sol-gel silica patterns.  

PubMed

Selective growth of silver nanoparticles on ~100 nm thick silica patterns produced by nanoimprint method has been successfully demonstrated using either (1) thermo-induced reduction or (2) room temperature electroless deposition (ELD) without removing the ~25 nm thick residual layer left by nanoimprint process. This selectivity was achieved by silane additive, (3-mercaptopropyl)trimethoxysilane (3-MTS), which was added to the silica matrix to control nucleation and growth of silver. The presence of silver nanoparticles was confirmed by EDX and UV-vis spectrum, and the density, distribution, and size of silver particles were examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Silica film heat-treated between 400 and 600 °C resulted in silver particles of 100-120 nm diameter with a linear density of 2.63-3.36 ?m(-1), while the film treated by room temperature ELD produced silver particles of 67 nm diameter with a linear density of 5.65 ?m(-1). The selective growth ratio based on particle density on pattern area versus residual layer is 12.92 and 20.31 for high- and room-temperature processes, respectively, whereas the samples without 3-MTS shows low selective growth ratio of 1.22 and 1.04. These results prove that both approaches are fast and effective, suggesting their potential to produce other type of nanoparticle arrays directly on nanoimprinted patterns. PMID:23731276

Chiu, Chi-Kai; Luo, Tzy-Jiun M

2013-06-17

389

Silver bromide nanoparticle/polymer composites: dual action tunable antimicrobial materials.  

PubMed

We present a simple method of fabricating highly potent dual action antibacterial composites consisting of a cationic polymer matrix and embedded silver bromide nanoparticles. A simple and novel technique of on-site precipitation of AgBr was used to synthesize the polymer/nanoparticle composites. The synthesized composites have potent antibacterial activity toward both gram-positive and gram-negative bacteria. The materials form good coatings on surfaces and kill both airborne and waterborne bacteria. Surfaces coated with these composites resist biofilm formation. These composites are different from other silver-containing antibacterial materials both in the ease of synthesis and in the use of a silver salt nanoparticle instead of elemental silver or complex silver compounds. We also demonstrate the ability to tune the release of biocidal Ag(+) ions from these composites by controlling the size of the embedded AgBr nanoparticles. These composites are potentially useful as antimicrobial coatings in a wide variety of biomedical and general use applications. PMID:16866536

Sambhy, Varun; MacBride, Megan M; Peterson, Blake R; Sen, Ayusman

2006-08-01

390

Nanoparticle induced conformational change in DNA and chirality of silver nanoclusters.  

PubMed

Nano-clusters formed on macromolecular templates carry the symmetry information of the template. Templates with broken symmetry thus lead to formation of asymmetric clusters. In response, such clusters induce a compensatory stress on the embedded template. Silver nanoparticles grown on a covalently closed negatively supercoiled plasmid DNA (pUC19) exhibit chiral behavior and as a reciprocal response, one observes alteration in DNA conformation. The inference was drawn using gel mobility-shift studies in which a silver nanoparticle (but not ions) induces a mobility shift implying a drift from supercoiled to relaxed state of the plasmid. Supporting evidences for such structural alterations were obtained from circular dichroism (CD) and Fourier transform infrared spectroscopy (FT-IR). Silver ion and silver nanoparticles induce differential FT-IR signals reflected in the fingerprint regions 1720, 1666, 1611, 1529 cm(-1) that respectively corresponds to binding in GT, ATGC, C, and AC (A, T, G, and C representing the four nucleotides). Existence of CD signal in the silver plasmon region (350-550 nm) suggests formation of a chiral clustering of nanoparticles. The reciprocal effect on the covalently closed circular (CCC) pUC19 DNA, namely the transition to a relaxed state, can be regarded as a mimicry of the topological enzyme acting on such CCC DNA. PMID:20352723

Roy, Sarita; Basak, Soumen; Dasgupta, Anjan Kr

2010-02-01

391

Synthesis, characterization and optical properties of gelatin doped with silver nanoparticles.  

PubMed

In this study, silver nanoparticles were synthesized by chemical reduction of silver salt (AgNO3) solution. Formation of nanoparticles was confirmed by UV-visible spectrometry. The surface plasmon resonance peak is located at 430nm. Doping of silver nanoparticles (Ag NPs) with gelatin biopolymer was studied. The silver content in the polymer matrix was in the range of 0.4-1wt%. The formation of nanoparticles disappeared for silver content higher than 1wt%. The morphology and interaction of gelatin doped with Ag NPs was examined by transmission electron microscopy and FTIR spectroscopy. The content of Ag NPs has a pronounced effect on optical and structural properties of gelatin. Optical parameters such as refractive index, complex dielectric constant were calculated. The dispersion of the refractive index was discussed in terms of the single - oscillator Wemple-DiDomenico model. Color properties of the prepared samples were discussed in the framework of CIE L(*)u(*)v(*) color space. PMID:23978746

Mahmoud, K H; Abbo, M

2013-08-08

392

Pine cone-mediated green synthesis of silver nanoparticles and their antibacterial activity against agricultural pathogens.  

PubMed

The medicinal and physicochemical properties of nanoscale materials are strong functions of the particle size and the materials used in their synthesis. The nanoparticle shape also contributes significantly to their medicinal properties. Several shapes ranging from oval, spherical, rods, to teardrop structures may be obtained by chemical methods. Triangular and hexagonal nanoparticles have been synthesized by using a pine cone extract (PCE). Here, we report the discovery that PCE, when reacted with silver nitrate ions, yields a high percentage of thin, flat, single-crystalline nanohexagonal and nanotriangular silver nanoparticles. The nanohexagonal and nanotriangular nanoparticles appear to grow by a process involving rapid reduction with assembly at room temperature at a high pH. The nanoparticles were characterized by UV–Vis absorption spectroscopy, SEM-EDS, TEM, FTIR, and X-ray diffraction analyses. The anisotropy of the nanoparticle shape results in large near-infrared absorption by the particles. Highly anisotropic particles are applicable in various fields, including agriculture and medicine. The obtained silver nanoparticles (Ag NPs) had significant antibacterial action on both Gram classes of bacteria associated with agriculture. Because the Ag NPs are encapsulated with functional group-rich PCE, they can be easily integrated in various applications. PMID:22290649

Velmurugan, Palanivel; Lee, Sang-Myung; Iydroose, Mahudunan; Lee, Kui-Jae; Oh, Byung-Taek

2013-01-01

393

An investigation into the simultaneous enzymatic and SERRS properties of silver nanoparticles.  

PubMed

Investigation into the use of artificial enzymes has become an increasingly popular area of research due to the numerous advantages offered in comparison to protein enzymes. One particular area of research interest involves the use of metal nanoparticles as artificial enzymes. The peroxidase-like activity of a variety of nanoparticles has recently been shown and their use in a range of assay formats for the detection of various analytes has been explored. Herein the enzyme mimicking activity of silver nanoparticles is investigated using the peroxidase substrate 3,3',5',5'-tetramethylbenzidine (TMB). The peroxidase-like nature of these nanoparticles can be used in combination with surface enhanced resonance Raman scattering (SERRS) to provide a novel spectroscopic method of analysis. Negatively charged silver nanoparticles were investigated in combination with TMB using SERRS and it was found that upon formation of the oxidation intermediate of TMB, small clusters of positively charged nanoparticles were formed. The enzyme like behaviour of silver nanoparticles along with their use as a SERRS substrate is combined to demonstrate a simple and rapid method for the direct detection of hydrogen peroxide with a detection limit of 100 nM. PMID:24022024

McKeating, Kristy S; Sloan-Dennison, Sian; Graham, Duncan; Faulds, Karen

2013-09-30

394

A facile "green" synthesis of ascorbic acid-capped ZnSe nanoparticles.  

PubMed

A simple, green room temperature synthesis of ascorbic acid-capped ZnSe nanoparticles is hereby reported. By varying the pH of the solution, the temporal evolution of the optical properties and shape of the nanocrystals was investigated. The nanoparticles were characterized by UV-vis absorption and photoluminescence spectroscopy (PL), transmission electron microscope (TEM) and infra-red spectroscopy (IR). All the particles exhibited quantum confinement in their optical spectra. An atypical optical spectrum was observed at pH 11 after 5h attributed to digestive ripening and shrinkage of ZnSe core. From the TEM image we inferred that the reaction is kinetically driven at pH 7 producing elongated particles as the reaction times increases, while spherical particles are produced at pH 4 and 11. The IR spectroscopy confirmed the capping of ascorbic acid and its deprotonation to give ascorbate ions. PMID:20417073

Oluwafemi, Oluwatobi S; Revaprasadu, N; Adeyemi, Olufemi O

2010-04-04

395

A new approach causing the patterns fabricated by silver nanoparticles to be conductive without sintering  

NASA Astrophysics Data System (ADS)

Silver nanoparticles (Ag NPs) with a mean size of about 90 nm were synthesized by polyol reduction of silver nitrate with ethylene glycol (EG) in the presence of poly(vinyl pyrrolidone) (PVP). The Ag NPs undergo a spontaneous coalescence in the presence of chloride ions even without a traditional sintering process which occurs at a relatively high temperature. Such behavior can cause a rapid decrease in the resistivity of the patterns fabricated by Ag NPs. Conductive silver lines were successfully fabricated on FR-4 substrate using this method. The resulting conductivity of the silver lines reached about 16% of the bulk silver value, which enables fabrication of conductive patterns on some electronic devices.

Tang, Yao; He, Wei; Zhou, Guoyun; Wang, Shouxu; Yang, Xiaojian; Tao, Zhihua; Zhou, Juncheng

2012-09-01

396

Enhanced localized surface plasmon resonance obtained in two step etched silicon nanowires decorated with silver nanoparticles  

NASA Astrophysics Data System (ADS)

We report on localized surface plasmon resonance (LSPR) of silicon nanowires decorated with silver nanoparticles. Hydrogen peroxide in metal-assisted-etching method degenerates the surface of nanowires and creates oxygen-related defect sites. These defect sites enhance the infrared absorption at higher frequencies and emit visible light by band-to-band radiative recombination. Moreover, an almost 50-fold enhanced LSPR was obtained for 24 nm thick silver deposited 5 ?m long silicon nanowires. This enhancement was attributed to the change in the dielectric constant of effective medium created by defect states. LSPR wavelength could be tuned by changing the silver particle size and nanowire length.

Mulazimoglu, Emre; Nogay, Gizem; Turan, Rasit; Emrah Unalan, Husnu

2013-09-01

397

[Preparation and antibacterial capacity of artificial skin loaded with nanoparticles silver using bacterial cellulose].  

PubMed

In the present paper, in-situ preparation of silver nanoparticles have been conducted in 3D network structure of BC membrane through liquid phase chemical deoxidization method. The characterization of products was investigated using scanning electron microscopy (SEM), infrared spectroscopy (IR), energy dispersion spectrometry (SEM-EDS). The absorbing water capacity and preserving water capacity of substitutes and the antibacterial capacities of antibacterial agent-loaded artificial skin were tested. The results showed the silver nanoparticles were approximately spherical particles with an average diameter of 45nm, and were noted to have excellent sterilizing efficacy the efficiency of against Escherichia coli, yeast and Candida albicans. PMID:19947484

Sun, Dongping; Yang, Jiazhi; Li, Jun; Zhou, Lingli; Yu, Junwei

2009-10-01

398

Electrochemical detection of commercial silver nanoparticles: identification, sizing and detection in environmental media.  

PubMed

The electrochemistry of silver nanoparticles contained in a consumer product has been studied. The redox properties of silver particles in a commercially available disinfectant cleaning spray were investigated via cyclic voltammetry before particle-impact voltammetry was used to detect single particles in both a typical aqueous electrolyte and authentic seawater media. We show that particle-impact voltammetry is a promising method for the detection of nanoparticles that have leached into the environment from consumer products, which is an important development for the determination of risks associated with the incorporation of nanotechnology into everyday products. PMID:24113774

Stuart, E J E; Tschulik, K; Omanovi?, D; Cullen, J T; Jurkschat, K; Crossley, A; Compton, R G

2013-10-10

399

Electrochemical detection of commercial silver nanoparticles: identification, sizing and detection in environmental media  

NASA Astrophysics Data System (ADS)

The electrochemistry of silver nanoparticles contained in a consumer product has been studied. The redox properties of silver particles in a commercially available disinfectant cleaning spray were investigated via cyclic voltammetry before particle-impact voltammetry was used to detect single particles in both a typical aqueous electrolyte and authentic seawater media. We show that particle-impact voltammetry is a promising method for the detection of nanoparticles that have leached into the environment from consumer products, which is an important development for the determination of risks associated with the incorporation of nanotechnology into everyday products.

Stuart, E. J. E.; Tschulik, K.; Omanovi?, D.; Cullen, J. T.; Jurkschat, K.; Crossley, A.; Compton, R. G.

2013-11-01

400

Electrochemical route for the fabrication of alkanethiolate-capped gold nanoparticles  

Microsoft Academic Search

Nearly monodispersed gold nanoparticles (NPs) of a few nanometers were fabricated and immobilized simultaneously on silicon surface by the galvanostatic reduction of HAuCl4 in the presence of dodecanethiol. X-ray absorption spectra at both sulfur K edge and gold L3 edge confirm the existence of the alkanethiolate-protected Au NPs and reveal their structural and bonding characteristics. Alkanethiolate-capped Au NPs were also

P. Zhang; P. S. Kim; T. K. Sham

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